Method for manufacturing tempered glass, and tempered glass

Abstract

A method for manufacturing a reinforced glass, the method including an etching step for etching a plate-like or sheet-like chemically reinforced glass having a compression stress layer on the surface thereof, and also including a step for preparing, as an unetched chemically reinforced glass, a chemically reinforced glass that has a flexible thin part having a thickness t1a in at least a part thereof, in which the thickness t1a is 150 μm or less, the maximum compression stress CSa in the compression stress layer before the etching is 1100 MPa or less and the depth DOLa of the compression stress layer before the etching is less than 15 μm, and the chemically reinforced glass is etched in such a manner that the amount of etching Δt in one surface of the chemically reinforced glass in the etching step can become 0.25 to 3 μm, inclusive.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing tempered glass and tempered glass.

Background Art

[0002] In recent years, chemically strengthened glass with a plate thickness of about 0.4 to 1.0 mm has been widely used as a cover glass for various electronic terminals and display devices. Particularly when used in portable electronic terminals such as smartphones, the strength of the cover glass is important. For example, Patent Document 1 discloses a technique for removing defects on the glass surface and improving the strength by performing an etching process on the glass surface after chemical strengthening.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, devices such as so-called foldable smartphones and tablet PCs that enable the display surface of the display to be folded have been developed. The cover glass used for such devices needs to have a thinner plate thickness than conventional ones so as to be foldable. In addition, since extremely high internal tensile stress acts on the bent portion when the cover glass is folded, the presence of defects or cracks on the surface of the bent portion may cause breakage, and furthermore, the glass is likely to be pulverized when broken. Therefore, the cover glass for such applications needs to further suppress surface defects and internal tensile stress more than conventional ones.

[0005] However, conventional glass such as that of Patent Document 1 above is premised on use in non-foldable (so-called straight type) devices and is not assumed to be applied to foldable smartphone devices. Therefore, even if it is attempted to apply it to such uses, sufficient bending performance cannot be obtained, sufficient bending strength to withstand bending cannot be obtained, and scattering upon breakage cannot be sufficiently suppressed.

[0006] An object of the present invention is to provide a method for manufacturing tempered glass that enables high bending performance, bending strength, and suppression of pulverization upon breakage to coexist, and tempered glass.

Means for Solving the Problems

[0007] The method for manufacturing tempered glass according to the present invention is a method for manufacturing tempered glass including an etching step of etching a plate-shaped or sheet-shaped chemically strengthened glass having a compressive stress layer on the surface, wherein, as the chemically strengthened glass before etching, it has at least a partially bendable thin portion with a thickness t1a, the thickness t1a is 150 μm or less, the maximum compressive stress CSa in the compressive stress layer before etching is 1100 MPa or less, and the depth DOLA of the compressive stress layer before etching is less than 15 μm. A step of preparing a chemically strengthened glass is provided, and in the etching step, the chemically strengthened glass is etched such that the etching amount Δt on one surface of the chemically strengthened glass is 0.25 μm or more and 3 μm or less.

[0008] In the method for manufacturing tempered glass according to the present invention, by etching, the thickness t1b of the thin portion after etching is 149.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after etching is 400 MPa or more and 950 MPa or less, and the depth DOLb of the compressive stress layer after etching is 14.75 μm or less, which is preferable.

[0009] In the method for manufacturing tempered glass according to the present invention, it is preferable that the chemically strengthened glass before etching includes a plurality of thick portions having a thickness t2a larger than the thickness t1a of the thin portion, the thickness t2a is more than 150 μm, and the thin portion extends in a strip shape so as to connect the plurality of thick portions.

[0010] In the method for manufacturing tempered glass according to the present invention, it is preferable that the chemically strengthened glass before etching is entirely composed of thin portions and has a substantially uniform plate thickness.

[0011] In the method for manufacturing tempered glass according to the present invention, it is preferable that the etching is a wet method, and the etching medium is brought into contact with the entire surface of the chemically strengthened glass for etching.

[0012] In the method for manufacturing tempered glass according to the present invention, the etching medium is an aqueous solution containing HF, and the aqueous solution containing HF is an aqueous solution containing only HF with a concentration of 0.1 to 30 mol / L, or an aqueous solution containing HF with a concentration of 0.1 to 30 mol / L and one substance selected from the group consisting of HCl, HNO3, H2SO4, and NH4F with a concentration of 0.1 to 30 mol / L. It is preferable to immerse the chemically strengthened glass in the aqueous solution at a temperature of 10 to 30 °C for 0.1 to 60 minutes for etching.

[0013] In the method for manufacturing tempered glass according to the present invention, it is preferable that the etching medium is an alkaline aqueous solution.

[0014] In the method for manufacturing tempered glass according to the present invention, the alkaline aqueous solution is an aqueous solution containing NaOH or KOH as an alkaline component, and the concentration of the alkaline component is 1 to 20 mol / L. It is preferable to immerse the chemically strengthened glass in the aqueous solution at a temperature of 10 to 130 °C for 0.5 to 120 minutes for etching.

[0015] In the method for manufacturing tempered glass according to the present invention, it is preferable that the main surface of the chemically strengthened glass before etching is a non-polished surface.

[0016] In the method for manufacturing tempered glass according to the present invention, when the thickness of the thin portion after etching is t1b, the maximum compressive stress in the compressive stress layer after etching is CSb, and the depth DOLb of the compressive stress layer after etching, it is preferable that the maximum value CTb of the internal tensile stress of the chemically strengthened glass after etching obtained by the following formula (A) is 120 MPa or more and 450 MPa or less. CTb = CSb × DOLb / (t1b - 2 × DOLb) …(A)

[0017] In the method for manufacturing tempered glass according to the present invention, it is more preferable that the thickness t1a is 70 μm or less, and the maximum compressive stress CSa in the compressive stress layer before etching is 600 MPa or more and 900 MPa or less.

[0018] In the method for manufacturing tempered glass according to the present invention, it is more preferable that the thickness t1b is 69.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after etching is 400 MPa or more and 700 MPa or less, and the depth DOLb of the compressive stress layer after etching is 13 μm or less.

[0019] The method for manufacturing tempered glass according to the present invention is a method for manufacturing tempered glass including an etching step of etching a plate-shaped or sheet-shaped chemically strengthened glass having a compressive stress layer on the surface, the chemically strengthened glass having a bendable thin portion, and in the etching step, the etching amount Δt on one surface of the chemically strengthened glass is 0.25 μm or more and 3 μm or less, and by etching, the thickness t1b of the thin portion after etching is 149.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after etching is 950 MPa or less, and the depth DOLb of the compressive stress layer after etching is 14.75 μm or less.

[0020] In the method for manufacturing the tempered glass of the present invention, the chemically strengthened glass is entirely composed of a bendable thin portion with a thickness of 70 μm or less. In the etching process, the etching amount Δt on one surface of the chemically strengthened glass is set to 0.5 μm or more and 3 μm or less. By etching, the thickness t1b of the thin portion after etching is set to 69.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after etching is set to 400 MPa or more and 700 MPa or less, and the depth DOLb of the compressive stress layer after etching is preferably set to 13 μm or less.

[0021] The tempered glass according to the present invention is a plate-like or sheet-like tempered glass having a compressive stress layer on the surface, and at least partially has a bendable thin portion with a thickness t1b, the thickness t1b is 149.5 μm or less, the maximum compressive stress CSb in the compressive stress layer is 950 MPa or less, the depth DOLb of the compressive stress layer is 14.75 μm or less, and at least the surface of the thin portion is composed of an etched surface.

[0022] The tempered glass according to the present invention preferably has the entire surface composed of an etched surface, the thickness t1b is 20 μm or more and 149.5 μm or less, the maximum compressive stress CSb in the compressive stress layer is 400 MPa or more and 850 MPa or less, and the depth DOLb of the compressive stress layer is 3 μm or more and 13 μm or less.

[0023] The tempered glass according to the present invention preferably includes a plurality of thick portions having a thickness t2b larger than the thickness t1b of the thin portion, the thickness t2b is 150 μm or more and 300 μm or less, and the thin portion extends in a strip shape so as to connect the plurality of thick portions.

[0024] The tempered glass according to the present invention preferably has a strip width of the thin portion of 3 mm or more.

[0025] The tempered glass according to the present invention is preferably entirely composed of a thin portion and has a substantially uniform thickness.

[0026] For the tempered glass according to the present invention, when the thickness of the thin portion after etching is t1b, the maximum compressive stress in the compressive stress layer after etching is CSb, and the depth of the compressive stress layer after etching is DOLb, the maximum value CTb of the internal tensile stress of the tempered glass after etching obtained by the following formula (B) is preferably 120 MPa or more and 450 MPa or less. CTb = CSb × DOLb / (t1b - 2 × DOLb) …(B)

[0027] The tempered glass according to the present invention preferably contains, as a glass composition, 50 to 80% by mass of SiO2, 5 to 25% by mass of Al2O3, 0 to 15% by mass of B2O3, 1 to 20% by mass of Na2O, and 0 to 10% by mass of K2O.

[0028] For the tempered glass according to the present invention, the flexural strength at two points in the thin portion is preferably 1500 MPa or more, and it is preferably not broken in a continuous bending test in which the thin portion is repeatedly bent 200,000 times so that the bending radius is 1.5 mm.

[0029] For the tempered glass according to the present invention, it is more preferable that the thickness t1b is 69.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after etching is 400 MPa or more and 700 MPa or less, and the depth DOLb of the compressive stress layer after etching is 13 μm or less.

Effect of the Invention

[0030] According to the present invention, compared with the prior art, tempered glass with high flexural performance, flexural strength, and suppression of pulverization at the time of breakage can be obtained.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0032] (First Embodiment) Hereinafter, a method for manufacturing tempered glass according to the first embodiment of the present invention and the tempered glass will be described.

[0033] <Method for Manufacturing Tempered Glass> The tempered glass 1b according to the first embodiment of the present invention is obtained by subjecting the chemically strengthened glass 1a for etching to an etching treatment.

[0034] First, the chemically strengthened glass 1a for etching is prepared. FIG. 1 is a schematic plan view of the chemically strengthened glass 1a for etching before etching and the tempered glass 1b after etching according to the first embodiment of the present invention, viewed in the thickness direction. FIG. 2 is a schematic cross-sectional view taken along line AA of FIG. 1. In the present invention, the tempered glass 1b is obtained by etching the chemically strengthened glass 1a for etching. However, since the etching amount is extremely small compared to the glass dimensions, the schematic shape of the glass viewed from above does not change significantly before and after etching. Therefore, in FIGS. 1 and 2, for the chemically strengthened glass 1a for etching and the tempered glass 1b, the schematic shapes of both glasses are shown on the same drawing by attaching the reference numerals of the corresponding parts in parentheses.

[0035] As shown in FIG. 1, the chemically strengthened glass 1a for etching is a plate-shaped or sheet-shaped chemically strengthened glass. In the present embodiment, as shown in FIG. 1, the case where the chemically strengthened glass 1a for etching and the strengthened glass 1b are rectangular having a long side and a short side in plan view is exemplified. The length of the long side of the chemically strengthened glass 1a for etching is, for example, 50 mm or more and 500 mm or less, preferably 60 mm or more and 450 mm or less, more preferably 65 mm or more and 400 mm or less, still more preferably 70 mm or more and 300 mm or less, 75 mm or more and 200 mm or less, 80 mm or more and 160 mm or less. The length of the short side is, for example, 40 mm or more and 400 mm or less, preferably 45 mm or more and 350 mm or less, more preferably 50 mm or more and 300 mm or less, still more preferably 55 mm or more and 120 mm or less, 60 mm or more and 80 mm or less.

[0036] The chemically strengthened glass 1a for etching has at least a part of a bendable thin portion 11a. In the present invention, being bendable means having flexibility such that the minimum bending radius is 10 mm or less without being damaged during bending.

[0037] The chemically strengthened glass 1a for etching includes a thick portion 12a having a relatively larger thickness than the thin portion 11a. The chemically strengthened glass 1a for etching includes a plurality of thick portions 12a.

[0038] The thin portion 11a is provided so as to partition and connect two thick portions 12a to each other. In other words, the thin portion 11a extends in a strip shape from one end to the other end of the strengthened glass 1. More specifically, the thin portion 11a is provided parallel to the short side so as to cross the main surface of the chemically strengthened glass 1a for etching from the central portion of one long side to the central portion of the other long side.

[0039] The thickness t1a of the thin portion 11a is 150 μm or less, preferably 20 μm or more and 150 μm or less, more preferably 20 μm or more and 120 μm or less, still more preferably 25 μm or more and 100 μm or less. Note that it is preferable that the thickness of the thin portion 11a is constant. However, when the thickness is not constant, the thickness of the thinnest part in the thin portion 11a can be determined as t1a.

[0040] The width W of the thin portion 11a is, for example, 3 mm or more and 50 mm or less, preferably 5 mm or more and 30 mm or less. It is preferable that the width of the thin portion 11a is constant.

[0041] The thickness t2a of the thick portion 12a is, for example, more than 150 μm, preferably more than 150 μm and 300 μm or less, more preferably 160 μm or more and 270 μm or less, still more preferably 170 μm or more and 250 μm or less. It is preferable that the thickness t2a of the thick portion 12a is constant.

[0042] By previously configuring the chemical strengthening glass 1a for etching with the above dimensions, the strengthened glass 1b described later can be obtained with a minute etching amount Δt, that is, with high productivity.

[0043] The chemical strengthening glass 1a for etching is provided with a compressive stress layer on the surface. The maximum compressive stress CSa in the compressive stress layer (the compressive stress layer before etching) of the chemical strengthening glass 1a for etching is 1100 MPa or less, preferably 550 MPa or more and 1000 MPa or less, more preferably 580 MPa or more and 950 MPa or less, still more preferably 600 MPa or more and 900 MPa or less, still more preferably 650 MPa or more and 880 MPa or less.

[0044] The depth DOLa of the compressive stress layer (the compressive stress layer before etching) of the chemical strengthening glass 1a for etching is less than 15 μm, preferably 5 μm or more and 14 μm or less, more preferably 6 μm or more and 13.5 μm or less, more preferably 8 μm or more and 13 μm or less.

[0045] By setting the stress characteristics of the chemically strengthened glass 1a for etching before etching within the above range, the maximum compressive stress CSb and the depth of the compressive stress layer DOLb after etching can be maintained at high levels.

[0046] Note that numerical values related to stress such as the maximum compressive stress and the depth of the compressive stress layer in the present invention can be measured, for example, by measuring devices such as the FSM-6000 or SLP-1000 manufactured by Orihara Manufacturing Co., Ltd.

[0047] The chemically strengthened glass 1a for etching is obtained by subjecting the chemically strengthened glass to ion exchange treatment after shaping and processing it into the above-described shape.

[0048] The chemically strengthened glass is obtained, for example, by cutting and processing a plate-shaped or sheet-shaped mother glass obtained by a forming method such as the overflow down-draw method, slot down-draw method, float method, or redraw method into small pieces of glass. In order to obtain a smooth surface, it is preferable to use the overflow down-draw method as the forming method. The cut small pieces of glass are processed to form concave grooves in order to form thin portions 11a. The concave grooves are formed by processing such as etching or grinding.

[0049] The end faces of the chemically strengthened glass are preferably subjected to chamfering or strength improvement treatment by polishing, heat treatment, etching, etc. The main surfaces of the chemically strengthened glass may be polished, but for example, when the main surfaces are pre-formed smoothly by the overflow down-draw method or when the thickness is formed uniformly and accurately, the main surfaces do not need to be polished and can be non-polished surfaces. When formed by the overflow down-draw method and not polished, the main surfaces of the chemically strengthened glass become flame-polished surfaces. The chemically strengthened glass may further be subjected to slimming treatment to reduce the thickness by etching. Note that in the present invention, the main surfaces refer to the front and back surfaces of the plate-shaped or sheet-shaped glass surface excluding the end faces.

[0050] As the glass for chemical strengthening, any glass composition can be adopted as long as it contains ion-exchangeable components. The glass for chemical strengthening is, for example, an alkali aluminosilicate glass. For example, as the glass composition, it contains, by mass%, 50 to 80% of SiO2, 5 to 25% of Al2O3, 0 to 15% of B2O3, 5 to 20% of Na2O, and 0 to 10% of K2O. In the case of this composition, it may be substantially free of Li2O. In the present invention, being substantially free of means that the content is less than 0.1% by mass.

[0051] As another example of the glass composition, the glass for chemical strengthening may have a glass composition containing, by mass%, 40% to 70% of SiO2, 10% to 30% of Al2O3, 0% to 3% of B2O3, 5% to 25% of Na2O, 0% to 5.5% of K2O, 0.1% to 10% of Li2O, 0% to 5.5% of MgO, and 2% to 10% of P2O5.

[0052] Na2O is an ion-exchange component and is also a component that reduces the high-temperature viscosity and improves the meltability and formability. In addition, Na2O is also a component that improves the devitrification resistance and the reaction devitrification resistance with the shaped refractory, especially the alumina refractory. If the content of Na2O is too small, the meltability will decrease, the thermal expansion coefficient will decrease too much, and the ion-exchange rate will be likely to decrease. Therefore, the preferred lower limit range of Na2O is 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, particularly 12.5% or more by mass%. On the other hand, if the content of Na2O is too large, the viscosity at which phase separation occurs is likely to decrease. In addition, the acid resistance may decrease, the component balance of the glass composition may be lacking, and instead, the devitrification resistance may decrease. Therefore, the preferred upper limit range of Na2O is 25% or less, 22% 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, particularly 15% or less.

[0053] K2O is a component that reduces the high-temperature viscosity, enhances the fusibility and formability. It is also a component that improves the devitrification resistance and increases the Vickers hardness. However, if the content of K2O is too high, the viscosity at which phase separation occurs tends to decrease. Also, the acid resistance decreases, the component balance of the glass composition is lacking, and conversely, the devitrification resistance tends to decrease. Therefore, the preferable lower limit range of K2O 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, particularly 3.5% or more in mass%, and the preferable upper limit range is 10% or less, 5.5% or less, 5% or less, particularly less than 4.5%.

[0054] Li2O is an ion-exchange component and also a component that reduces the high-temperature viscosity, enhances the fusibility and formability. It is also a component that increases the Young's modulus. Also, Li2O is a component that elutes during the ion-exchange treatment and deteriorates the ion-exchange solution. Therefore, Li2O may be in a form that is not substantially contained as the glass composition as described above, but when contained, the preferable lower limit range of Li2O is 0.1% or more, 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, particularly 2.5% or more in mass%, and the preferable upper limit range is 10% or less, 8% or less, 5% or less, 4.5% or less, 4.0% or less, particularly less than 3.5%.

[0055] The chemically strengthened glass obtained as described above is subjected to an ion-exchange treatment. Specifically, the chemically strengthened glass is immersed in a molten salt for ion-exchange treatment and processed.

[0056] The molten salt is a salt containing components that can be ion-exchanged with the components in the chemically strengthened glass, and is typically an alkali nitrate. Examples of the alkali nitrate include NaNO3, KNO3, LiNO3, etc., and these can be used alone or in a mixture of multiple types. The mixing ratio of the alkali nitrate can be arbitrarily determined. For example, it can be 5 to 95% of NaNO3, 5 to 95% of KNO3 in mass%, preferably 30 to 80% of NaNO3, 20 to 70% of KNO3, more preferably 50 to 70% of NaNO3, 30 to 50% of KNO3.

[0057] The conditions such as the temperature of the molten salt and the immersion time in the ion exchange treatment may be set according to the composition and the like within the range where the above stress characteristics can be obtained. The temperature of the molten salt is, for example, 350°C to 500°C, preferably 360°C to 470°C, 360°C to 450°C, 360°C to 430°C, 360°C to 410°C. The immersion time is, for example, 3 to 300 minutes, preferably 5 to 120 minutes, more preferably 7 to 100 minutes.

[0058] In addition, the shape, dimensions, and characteristics of the chemically strengthened glass 1a for etching may be determined inversely considering the shape, dimensions, and characteristics of the target strengthened glass 1b and the influence of etching within the range that does not impair the features of the present invention described above. For example, the dimensional shape of the chemically strengthened glass 1a for etching may be designed to have a thickness and dimensions slightly larger than those of the strengthened glass 1b by an amount corresponding to the etching amount in the etching process. Also, considering the decrease in thickness due to etching, the ion exchange conditions and the like may be adjusted so that the CSa and DOLa are slightly larger than those of the strengthened glass 1b.

[0059] The chemically strengthened glass 1a for etching obtained by the above ion exchange treatment is subjected to an etching treatment after being washed and dried.

[0060] Note that the chemically strengthened glass 1a for etching may be further polished after the ion exchange treatment and before the etching. When the dimensions, shape, and surface state of the chemically strengthened glass 1a for etching vary due to the ion exchange treatment, these can be corrected by performing a polishing treatment. On the other hand, since it is also conceivable that unnecessary microcracks increase due to the polishing treatment, when there is an unpolished product of the chemically strengthened glass formed by the overflow down-draw method or the like as described above, and the main surface of the chemically strengthened glass 1a for etching after the ion exchange treatment is also a smooth non-polished surface (fire-polished surface), it is preferable to perform the etching without performing the polishing treatment.

[0061] In this embodiment, the above-described chemically strengthened glass 1a for etching is etched by wet etching. Specifically, the entire chemically strengthened glass 1a for etching is immersed in a liquid etching medium, and the entire surface of the chemically strengthened glass 1a for etching is etched. According to such a process, since the entire glass can be etched uniformly, the occurrence of thickness variation due to the etching process can be suppressed.

[0062] As the etching medium, an acidic or alkaline aqueous solution capable of etching glass can be used.

[0063] As the acidic etching medium, for example, an acidic aqueous solution containing HF can be used. When an aqueous solution containing HF is used, the etching rate for glass is high, and the strengthened glass 1 can be produced with high productivity.

[0064] The aqueous solution containing HF is, for example, an aqueous solution containing only HF, or a combination of HF and HCl, HF and HNO3, HF and H2SO4, HF and NH4F, respectively. The concentration of each compound of HF, HCL, HNO3, H2SO4, and NH4F is preferably 0.1 to 30 mol / L. In the etching using an aqueous solution containing HF, fluorides containing glass components are generated as by-products, which can cause a decrease in the etching rate and defects. However, by using a mixed acid with other acids such as HCL, HNO3, or H2SO4 as described above, the by-products can be decomposed to suppress the decrease in productivity. When etching is performed using an acidic aqueous solution, the temperature of the acidic aqueous solution is, for example, 10 to 30 °C, and the time for immersing the chemically strengthened glass 1a for etching is preferably, for example, 0.1 to 60 minutes.

[0065] As the alkaline etching medium, an alkaline aqueous solution containing NaOH or KOH can be used. Since the alkaline aqueous solution has a relatively small etching rate for glass compared to the above-described etching medium containing HF, it has the advantage of being easy to precisely control the etching amount. In particular, it is suitable when it is necessary to control the thickness of the glass, DOLb, etc. in units of several micrometers as in the present invention.

[0066] In an aqueous solution containing NaOH or KOH, the concentration of the alkaline component is preferably 1 to 20 mol / L. When etching is performed using an alkaline aqueous solution, the temperature of the alkaline aqueous solution is, for example, 10 to 130°C, and the immersion time of the chemically strengthened glass 1a for etching is preferably, for example, 0.5 to 120 minutes. When increasing the etching rate to improve productivity, it is preferable to heat the alkaline aqueous solution to 80°C or higher. Conversely, when it is desired to control the etching amount with higher accuracy, it is preferable to limit the temperature of the alkaline aqueous solution to 70°C or lower. Also, when paying more attention to the magnitude of the etching rate, it is preferable to use an aqueous solution of NaOH.

[0067] Etching is performed using the above-described etching medium such that the etching amount Δt (reduction in thickness due to etching) on one surface of the chemically strengthened glass 1a for etching is 0.25 μm or more and 3 μm or less. The etching amount Δt of the chemically strengthened glass 1a for etching is preferably 0.4 μm or more and 2.7 μm or less, more preferably 0.5 μm or more and 2.6 μm or less, still more preferably 0.6 μm or more and 2.5 μm or less, and even more preferably 0.8 μm or more and 2.3 μm or less. By setting the etching reduction amount within such a range, the variation amount of the maximum compressive stress and the compressive stress depth before and after etching can be reduced and it becomes easier to control.

[0068] After the above etching, the strengthened glass 1b is washed and dried, and a protective film is attached for protection. It is preferable to use a self-adhesive type protective film or a protective film provided with a slightly adhesive adhesive so that there is no adhesive residue and a high surface cleanliness can be obtained after peeling of the protective film.

[0069] <Toughened glass> The toughened glass 1b according to the first embodiment of the present invention obtained as described above has the following characteristics.

[0070] The toughened glass 1b is provided with a compressive stress layer on its surface. The maximum compressive stress CSb in the compressive stress layer (compressive stress layer after etching) of the toughened glass 1b is 950 MPa or less, preferably 500 MPa or more and 900 MPa or less, more preferably 520 MPa or more and 850 MPa or less, still more preferably 530 MPa or more and 800 MPa or less, 550 MPa or more and 700 MPa or less.

[0071] The depth DOLb of the compressive stress layer (compressive stress layer after etching) of the toughened glass 1b is less than 14.75 μm, preferably 4 μm or more and less than 14 μm, more preferably 5 μm or more and 13 μm or less, 7 μm or more and 12.5 μm or less.

[0072] Note that the theoretical value of the depth DOLb of the compressive stress layer after etching can also be obtained by the following formula (1) based on the depth DOLa of the compressive stress layer before etching and the etching amount Δt. DOLb = DOLa - Δt (1)

[0073] The toughened glass 1b is provided with at least a part of a thin-walled portion 11b that can be bent. The surface of the thin-walled portion 11b is composed of an etched surface. In the present embodiment, the entire surface of the toughened glass 1b, that is, both the front and back main surfaces and the end surfaces including the thin-walled portion 11b are all composed of etched surfaces. In this way, since the entire surface of the toughened glass 1b is etched, defects are reduced over the entire surface and it has high strength.

[0074] The toughened glass 1b further includes a thick-walled portion 12b that is relatively thicker than the thin-walled portion 11b. The toughened glass 1b includes a plurality of thick-walled portions 12b. In the present embodiment, the surface of the thick-walled portion 12b is also constituted by an etched surface.

[0075] The thin portion 11b is provided so as to partition and connect the two thick portions 12b to each other. In other words, the thin portion 11b extends in a strip shape from one end to the other end of the tempered glass 1. More specifically, the thin portion 11b is provided parallel to the short side so as to cross the main surface of the tempered glass 1b from the central portion of one long side to the central portion of the other long side.

[0076] The two thick portions 12b preferably have a shape that is line-symmetric with respect to each other with the thin portion 11b as a reference. According to such a configuration, the tempered glass 1b can be bent so that the two thick portions 12b overlap, which is suitable for applications such as foldable devices.

[0077] The thickness t1b of the thin portion 11b is 149.5 μm or less, preferably 20 μm or more and 149 μm or less, preferably 20 μm or more and 120 μm or less, more preferably 25 μm or more and 100 μm or less, still more preferably 28 μm or more and 69.5 μm or less. Note that the thickness of the thin portion 11b is preferably constant, but when the thickness is not constant, the thickness of the thinnest part in the thin portion 11b can be taken as t1b.

[0078] Note that the theoretical value of the thickness t1b of the thin portion 11b after etching can also be obtained by the following formula (2) based on the thickness t1a of the thin portion 11a before etching and the etching amount Δt. t1b = t1a - 2×Δt (2)

[0079] The width W of the thin portion 11b is, for example, 3 mm or more and 50 mm or less, preferably 5 mm or more and 30 mm or less. The width of the thin portion 11b is preferably constant. By setting the width W within such a range, a sufficient movable range required for bending can be ensured.

[0080] The thickness t2b of the thick portion 12b is, for example, 150 μm or more and 300 μm or less, preferably 160 μm or more and 270 μm or less, and more preferably 170 μm or more and 250 μm or less. The thickness t2b of the thick portion 12b is preferably constant. By setting the thickness t2b of the thick portion 12b within such a range, the deformability of the thick portion 12b can be appropriately suppressed, and the workability during the assembly and manufacture of the device can be improved.

[0081] In addition, the theoretical value of the thickness t2b of the thick portion 12b after etching can also be obtained by the following formula (3) based on the thickness t2a of the thick portion 12a before etching and the etching amount Δt. t2b = t2a - 2×Δt (3)

[0082] The planar dimensions of the strengthened glass 1b are about the same as those of the chemical strengthened glass 1a for etching before etching. The length of the long side is, for example, 50 mm or more and 500 mm or less, preferably 60 mm or more and 450 mm or less, more preferably 65 mm or more and 400 mm or less, still more preferably 70 mm or more and 300 mm or less, 75 mm or more and 200 mm or less, 80 mm or more and 160 mm or less. The length of the short side is, for example, 40 mm or more and 400 mm or less, preferably 45 mm or more and 350 mm or less, more preferably 50 mm or more and 300 mm or less, still more preferably 55 mm or more and 120 mm or less, 60 mm or more and 80 mm or less.

[0083] In this embodiment, the thin portion 11b forms a concave groove portion on one main surface side of the strengthened glass 1b and is constituted by the remaining portion on the other main surface side. The strengthened glass 1b can be bent, for example, in the direction in which the concave groove portion side faces outward (arrow R direction in FIG. 2). By being bendable in such a direction, the flat surface without the concave groove portion can be used as the touch surface of the foldable device, and the touch surface can be protected when the foldable device is folded.

[0084] According to the tempered glass 1b and its manufacturing method described above, by suitably controlling its stress characteristics and thickness dimensions, and further reducing surface defects by etching, high flexural performance, bending strength, and suppression of pulverization during breakage can be achieved simultaneously.

[0085] In addition, in the above first embodiment, the thin portion 11a is constituted by the remaining portion on the other main surface side where the concave groove portion is formed on one main surface side of the tempered glass 1. The thin portion 11a may be constituted by forming concave grooves on both main surfaces so that the central portion of the cross section of the tempered glass 1 remains. According to such a configuration, it is possible to make it difficult to break even when bent to either the front side or the back side.

[0086] (Second Embodiment) In the above first embodiment, the case where the tempered glass 1b includes the thin portion 11b and the thick portion 12b has been exemplified. However, the tempered glass may be entirely constituted by the thin portion. Regarding the configuration and processing not specifically described in the second embodiment shown below, the same configuration and processing as those in the first embodiment can be applied, and detailed description is omitted.

[0087] FIG. 3 is a schematic cross-sectional view of the tempered glass 2b according to the second embodiment of the present invention. The planar shape and dimensions of the tempered glass 2b are the same as the planar dimensions (FIG. 1) of the tempered glass 1b according to the first embodiment. FIG. 3 is a view showing a cross section along the long side of the tempered glass 2b. Also in FIG. 3, similar to FIG. 2, the schematic shapes of the glass before and after etching are shown on the same drawing by attaching reference numerals to the corresponding parts in parentheses.

[0088] As shown in FIG. 3, the tempered glass 2b after etching according to the second embodiment is entirely constituted by the thin portion 21b and has a substantially uniform thickness. In the present invention, having a substantially uniform thickness means that the deviation of the glass thickness is ±10% or less. The thickness of the tempered glass 2b is the same as the thickness t1b of the thin portion 11b after etching according to the above first embodiment. The stress characteristics (CS, DOL, etc.) of the tempered glass 2b can be configured in the same manner as the tempered glass 1b according to the first embodiment.

[0089] The tempered glass 2b according to the second embodiment is obtained by subjecting the chemically strengthened glass 2a for etching to an etching treatment.

[0090] First, prepare the chemically strengthened glass 2a for etching. The strengthened glass 2a is entirely composed of a thin portion 21a and has a substantially uniform thickness. The thickness of the chemically strengthened glass 2a for etching is the same as the thickness t1a of the thin portion 11a before etching according to the above-described first embodiment. The stress characteristics (CS, DOL, etc.) of the chemically strengthened glass 2a for etching can be configured in the same manner as the chemically strengthened glass 1a for etching according to the first embodiment.

[0091] The chemically strengthened glass 2a for etching is obtained by subjecting a chemically strengthened glass having the same dimensional shape to the same ion exchange treatment as in the first embodiment.

[0092] The etching conditions of the chemically strengthened glass 2a for etching can be the same as those in the first embodiment.

[0093] According to the tempered glass 2b according to the second embodiment, since the entire surface is composed of the thin portion 21b, it can be bent at an arbitrary position, and the degree of freedom in device design can be improved. Further, there is no need to form a concave groove, and a tempered glass having both high flexibility and strength with high productivity can be obtained. (Modification example)

[0094] In each of the above embodiments, an example is shown in which an etching treatment is performed on the entire surface of the tempered glass and the entire surface is composed of an etched surface. However, only the thin portion of the tempered glass may be subjected to the etching treatment. That is, only the surface of the thin portion may be composed of an etched surface, and the surfaces of other regions may be composed of non-etched surfaces. For example, such a configuration can be achieved by performing etching in a state where the portions other than the thin portion are masked in advance with a resin or the like. According to such a configuration, a decrease in the compressive stress CS due to etching can be suppressed in the region that becomes the main display surface.

[0095] In the tempered glass of the present invention, from the viewpoint of further suppressing pulverization at the time of breakage, the maximum compressive stresses CSa and CSb in the compressive stress layer may be further limited to be lower than the above-described ranges. By suppressing the maximum compressive stress, the internal tensile stress can be suppressed, and pulverization at the time of breakage can be further suppressed. Specifically, the upper limits of the maximum compressive stresses CSa and CSb may be 500 MPa or less, preferably 400 MPa or less, more preferably 300 MPa or less, still more preferably 200 MPa or less, and 150 MPa or less, and the lower limits may be 50 MPa or more and 100 MPa or more.

[0096] In the tempered glass of the present invention, from the viewpoint of further suppressing pulverization at the time of breakage, the maximum value CTb of the internal tensile stress calculated by the following formula (4) from the maximum compressive stress CSb, the depth DOLb of the compressive stress layer, and the thickness t1b in the compressive stress layer after the entire surface of the tempered glass has been subjected to an etching treatment is preferably 120 MPa or more and 450 MPa or less, more preferably 150 MPa or more, and still more preferably 200 MPa or more. CTb = CSb × DOLb / (t1b - 2 × DOLb) (4) If CTb is too large, the energy remaining inside the glass after strengthening increases, making it difficult to suppress pulverization at the time of breakage. On the other hand, if DOLb or CSb is made too small in order to reduce CTb, it becomes difficult to obtain sufficient flexural strength or repeated flexural strength for applications such as foldable devices.

[0097] The tempered glass of the present invention may be subjected to three-dimensional bending processing as necessary. Specifically, by subjecting the chemically strengthened glass to three-dimensional bending processing in whole or in part in advance, a three-dimensional bent shape can be imparted to the tempered glass after ion exchange treatment and etching treatment.

[0098] In each of the above embodiments, the chemically strengthened glass for etching before etching was exemplified as being one that had undergone a single ion exchange treatment. However, the chemically strengthened glass for etching may have undergone two or more ion exchange treatments. Further, heat treatment may be performed before and after the ion exchange. By performing heat treatment, stress relaxation and the depth of the compressive stress layer can be controlled.

[0099] Although an example of immersion in an etching solution was shown, the etching solution may be adhered to the glass surface by a shower method or a spray method, or the etching solution may be applied only to necessary portions for etching. Further, the etching may be performed not only by wet etching but also by using a known dry etching method.

[0100] The glass according to each of the above embodiments can be laminated via an adhesive or the like with an arbitrary plate-shaped or sheet-shaped resin material or metal material and used as a laminate.

Example

[0101] Hereinafter, a method for manufacturing the strengthened glass and an ion exchange mixture according to the present invention will be described based on examples. Note that the following examples are merely illustrative, and the present invention is not limited to the following examples at all.

[0102] Samples were prepared as follows. First, ion-exchange glass containing, by mass%, 61.5% SiO2, 18.0% Al2O3, 0.5% B2O3, 2.0% K2O, 14.5% Na2O, 0.1% Li2O, 3.0% MgO, and 0.4% SnO2 was prepared as the glass composition.

[0103] Specifically, glass raw materials were formulated to have the above composition and melted at 1600°C for 21 hours using a platinum pot. Thereafter, the obtained molten glass was formed by flowing down from a refractory forming body using the overflow down-draw method and formed and processed into the dimensional shapes shown in Tables 1 and 2 to obtain strengthened glass.

[0104] In Tables 1 and 2, the glass with the thickness dimension of the thick portion indicated is a glass having a thick portion and a thin portion, similar to the first embodiment described above. For the glass having a thick portion and a thin portion, first, a plate-shaped sample with a uniform thickness of the thick portion was prepared, and then the thin portion was formed by etching so that the bandwidth W was 20 mm and was the same as the shape in FIG. 2. Note that the glass indicated as having no thick portion in Tables 1 and 2 is a glass in which the entire glass is composed of a thin portion, similar to the second embodiment described above. In addition, two types of samples with a plan view dimension of 50 × 150 mm used for the two-point bending test described later and samples with a plan view dimension of 50 × 50 mm used for the pendulum drop test were each prepared.

[0105] Next, the strengthening glass was immersed in a molten salt, and ion exchange treatment was performed under the conditions described in the same table so as to obtain the stress characteristics shown in Tables 1 and 2, and chemically strengthened glass for etching was obtained. Next, the chemically strengthened glass for etching was etched under the conditions shown in Tables 1 and 2 to obtain strengthened glass.

[0106] In Tables 1 and 2, Nos. 1 to 9 are examples of the present invention, and Nos. 10 and 11 are comparative examples.

[0107] The maximum compressive stress (CSa, CSb) and the depth of compressive stress (DOLa, DOLb) in Tables 1 and 2 are values measured using a surface stress meter FSM-6000LE manufactured by Orihara Seisakusho Co., Ltd. The etching amount was obtained from the difference value of the thickness of the glass before and after.

[0108]

Table 1

[0109]

Table 2

[0110] For each of the samples obtained as described above, a two-point bending test, a continuous bending test, and a pendulum drop test were performed in the following manner, and their strengths were evaluated.

[0111] In the two-point bending test, under the conditions of an ambient temperature of 25°C and a humidity of 50%, stress was applied to gradually increase, causing the glass sample to undergo bending deformation at the center of the long side, and the stress at the time when the glass sample broke was measured as the breaking stress. For the glass with a thick part, it was bent and tested in the R direction shown in Figure 2.

[0112] In the continuous bending test, the glass sample was attached onto a bendable plate with a notch at the center, and under the conditions of an ambient temperature of 25°C and a humidity of 50%, after bending and deforming the glass sample at the thin part of the center of the long side so that the final radius became 1.5 mm and then returning it to the flat state, it was confirmed whether the glass sample broke during continuously repeating the bending operation 200,000 times. In the table, if no damage was found at the bent part after the continuous bending test, it is indicated by ○, and if damage was confirmed, it is indicated by ×.

[0113] The results of the two-point bending test and the continuous bending test are shown in Figure 4, Table 3, and Table 4. Figure 4 shows the results of the two-point bending test in a box-and-whisker plot, and Table 3 and Table 4 are the reading values thereof. Figure 4, Table 3, and Table 4 extracted the evaluation results for 30 samples broken by in-plane origin cracks and showed their distributions.

[0114]

Table 3

[0115]

Table 4

[0116] In the pendulum drop test, a glass sample was placed without adhesion on top of a 3-mm-thick stainless steel (SUS) sheet, and the tip of a ballpoint pen with a ball diameter of 0.5 mm and a mass of 12.5 g was dropped vertically onto the center of the glass sample to conduct the test. The dropping height of the ballpoint pen was gradually increased until the glass sample broke, and the number of fragments of the broken glass was counted. Since it was difficult to count microfragments, the counting target was limited to those with a maximum outer diameter of 0.1 mm or more. The test was conducted with a sample number of 5 for each sample, and the average value was calculated. For a glass sample having a thick part and a thin part, it was placed so that the flat surface was downward (the concave groove part was upward), and the test was conducted by dropping the pen tip onto the thin part.

[0117] The evaluation results of the pendulum drop test are shown in Tables 5 and 6.

[0118] [Table 5]

[0119] [Table 6]

[0120] According to the results of the above two-point bending test, it was confirmed that the examples had higher bending strength than the comparative examples by maintaining a higher maximum surface compressive stress than the comparative examples. For glass for foldable applications, it is preferable that the value of the first quartile shown in Tables 3 and 4 is 1500 MPa or more.

[0121] According to the results of the above pendulum drop test, it was confirmed that the number of glass fragments at the time of breakage was suppressed after etching compared to before etching, and pulverization was suppressed. Also, in the examples, since the internal tensile stress was suppressed by setting the compressive stress layer relatively shallow, it was confirmed that the number of fragments at the time of breakage was less than that of the comparative examples, and pulverization could be suppressed.

[0122] The above embodiments are examples. As other embodiments of the present invention, ion-exchange glass containing, by mass%, 66.0% of SiO2, 14.0% of Al2O3, 2.5% of B2O3, 0.6% of K2O, 13.4% of Na2O, 0.1% of Li2O, 3.0% of MgO, and 0.4% of SnO2 may be used. By using ion-exchange glass having such a composition, chemical durability can be improved while having the same level of strength as the above embodiments.

Industrial Applicability

[0123] The tempered glass and its manufacturing method of the present invention can be used, for example, in tempered glass used in smartphones, mobile phones, tablet computers, personal computers, digital cameras, touch panel displays, cover glasses of other display devices, in-vehicle display devices, in-vehicle panels, particularly devices equipped with foldable or rollable displays, devices equipped with curved displays, etc., and can be utilized in the manufacture thereof.

Explanation of Signs

[0124] 1a, 2a Chemically strengthened glass for etching (before etching) 1b, 2b Tempered glass (after etching) 11a, 21a Thin part (before etching) 11b, 21b Thin part (after etching) 12a Thick part (before etching) 12b Thick part (after etching)

Claims

1. A method for manufacturing tempered glass, comprising an etching step of etching a plate-shaped or sheet-shaped chemically strengthened glass having a compressive stress layer on its surface, wherein, as the chemically strengthened glass before the etching, it has at least a partially bendable thin portion with a thickness t1a, the thickness t1a is 70 μm or less, the maximum compressive stress CSA in the compressive stress layer before the etching is 1100 MPa or less, a step of preparing a chemically strengthened glass having a depth DOLA of the compressive stress layer before the etching of less than 15 μm is provided, in the etching step, an etching medium containing HF with a concentration of 0.1 to 30 mol / L and HCl with a concentration of 0.1 to 30 mol / L is brought into contact with the surface of the chemically strengthened glass for 0.1 to 60 minutes for etching, A method for manufacturing tempered glass, wherein in the etching step, the chemically strengthened glass is etched so that the etching amount Δt on one surface of the chemically strengthened glass is 0.25 μm or more and 3 μm or less.

2. By the etching, the thickness t1b of the thin portion after the etching is 69.5 μm or less, the maximum compressive stress CSb in the compressive stress layer after the etching is 400 MPa or more and 950 MPa or less, The method for manufacturing tempered glass according to claim 1, wherein the depth DOLb of the compressive stress layer after the etching is 14.75 μm or less.

3. The chemically strengthened glass before the etching includes a plurality of thick portions having a thickness t2a greater than the thickness t1a of the thin portion, the thickness t2a is more than 150 μm, The method for manufacturing tempered glass according to claim 1 or 2, wherein the thin portion extends in a strip shape so as to connect the plurality of thick portions.

4. The chemically strengthened glass before the etching is entirely composed of the thin portion and has a substantially uniform plate thickness. The method for manufacturing tempered glass according to claim 1 or 2.

5. The method for manufacturing tempered glass according to any one of claims 1 to 4, wherein the etching medium is brought into contact with the entire surface of the chemically strengthened glass for etching.

6. The method for manufacturing tempered glass according to claim 5, wherein the chemically strengthened glass is immersed in the etching medium at a temperature of 10 to 30 °C for 0.1 to 60 minutes for etching.

7. The method for manufacturing tempered glass according to any one of claims 1 to 6, wherein the main surface of the chemically strengthened glass before the etching is a non-polished surface.

8. When the thickness of the thin portion after the etching is t1b, the maximum compressive stress in the compressive stress layer after the etching is CSb, and the depth DOLb of the compressive stress layer after the etching are used, the maximum value CTb of the internal tensile stress of the chemically strengthened glass after the etching obtained by the following formula (A) is set to 150 MPa or more and 450 MPa or less. The method for manufacturing a strengthened glass according to any one of claims 1 to 7. CTb = CSb × DOLb / (t1b - 2 × DOLb) …(A)

9. A method for manufacturing a strengthened glass including an etching step of performing etching on a plate-shaped or sheet-shaped chemically strengthened glass having a compressive stress layer on the surface, The chemically strengthened glass includes a bendable thin portion, In the etching step, An etching medium containing HF with a concentration of 0.1 to 30 mol / L and HCl with a concentration of 0.1 to 30 mol / L is brought into contact with the surface of the chemically strengthened glass for 0.1 to 60 minutes for etching, The etching amount Δt on one surface of the chemically strengthened glass is set to 0.25 μm or more and 3 μm or less, By the etching, The thickness t1b of the thin portion after the etching is set to 69.5 μm or less, The maximum compressive stress CSb in the compressive stress layer after the etching is set to 950 MPa or less, The depth DOLb of the compressive stress layer after the etching is set to 14.75 μm or less, The method for manufacturing a strengthened glass, wherein the maximum value CTb of the internal tensile stress obtained by the following formula (B) after the etching is 150 MPa or more. CTb = CSb × DOLb / (t1b - 2 × DOLb) …(B)

10. A plate-shaped or sheet-shaped strengthened glass having a compressive stress layer on the surface, It has at least a part of a bendable thin portion with a thickness t1b, The thickness t1b is 69.5 μm or less, The maximum compressive stress CSb in the compressive stress layer is 950 MPa or less, The depth DOLb of the compressive stress layer is 14.75 μm or less, At least the surface of the thin portion is composed of an etched surface, A strengthened glass, wherein the maximum value CTb of the internal tensile stress obtained by the following formula (C) is 150 MPa or more. CTb = CSb × DOLb / (t1b - 2 × DOLb) …(C)

11. The entire surface is composed of an etched surface, The thickness t1b is 20 μm or more and 69.5 μm or less, The maximum compressive stress CSb in the compressive stress layer is 400 MPa or more and 850 MPa or less, The tempered glass according to claim 10, wherein the depth DOLb of the compressive stress layer is 3 μm or more and 13 μm or less.

12. comprising a plurality of thick portions having a thickness t2b greater than the thickness t1b of the thin portion, wherein the thickness t2b is 150 μm or more and 300 μm or less, The tempered glass according to claim 10 or 11, wherein the thin portion extends in a strip shape so as to connect the plurality of thick portions.

13. The tempered glass according to claim 12, wherein the bandwidth of the thin portion is 3 mm or more.

14. The tempered glass according to claim 10 or 11, which is entirely composed of the thin portion and has a substantially uniform plate thickness.

15. The tempered glass according to any one of claims 10 to 14, wherein the maximum value CTb of the internal tensile stress is 150 MPa or more and 450 MPa or less.

16. As a glass composition, in mass %, SiO ２ 50 to 80%, Al ２ O ３ 5 to 25%, B ２ O ３ 0 to 15%, Na ２ O 1 to 20%, K ２ The tempered glass according to any one of claims 10 to 15, containing 0 to 10%.

17. the flexural strength at two points in the thin portion is 1500 MPa or more, The tempered glass according to any one of claims 10 to 16, which does not break in a continuous bending test in which the thin portion is repeatedly bent 200,000 times so that the bending radius is 1.5 mm.

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