Glass plate and display device

Abstract

To provide a glass plate capable of reducing surface crystallization of crystallized glass.SOLUTION: Provided is a glass plate having a first main surface and a second main surface opposite to the first main surface, wherein the thickness is from 0.30 to 1.00 mm; a β-OH value at the thickness center is from 0.20 to 0.50 / mm; a β-OH value at at least the first main surface is 0.02 to 0.10 / mm lower than the β-OH value at the thickness center; and a crystallized glass plate, which is formed by crystallizing the glass plate, has an arithmetic average roughness Ra of the first main surface of 200 nm or less. The β-OH value is measured by FT-IR-ATR (Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a glass plate and a display device.

Background Art

[0002] For protective members of display devices such as cover glasses of mobile terminals and cover glasses of in-vehicle car navigation systems, high transparency is often required to improve the visibility of the display and the like.

[0003] Devitrified glass is obtained by precipitating crystals in glass, and is harder and less likely to be damaged than non-crystalline glass that does not contain crystals. And devitrified glass capable of chemical strengthening treatment can achieve high strength while preventing crushing as compared with non-crystalline glass.

[0004] Due to the above-described characteristics, devitrified glass is suitably used as a protective member of a display device. For example, Patent Document 1 describes devitrified glass suitable as a protective member for portable electronic devices and optical devices.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Devitrified glass has a problem that when it crystallizes, surface crystallization occurs and the flatness of the surface deteriorates. When the flatness of the surface deteriorates, transparency and strength decrease, and also, man-hours for improving the flatness of the surface such as polishing are required in the manufacturing process, leading to a decrease in production efficiency.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a glass plate capable of suppressing surface crystallization of crystallized glass.

Means for Solving the Problems

[0008] The inventors of the present invention have found that by reducing the β-OH concentration on the glass surface, surface crystallization of crystallized glass can be suppressed, and the present invention has been completed.

[0009] That is, the present invention is as follows. 1. A glass plate having a first main surface and a second main surface facing the first main surface, having a thickness of 0.30 to 1.00 mm, having a β-OH value at the center of the plate thickness of 0.20 to 0.50 / mm, wherein at least the β-OH value on the first main surface is 0.02 to 0.10 / mm smaller than the β-OH value at the center of the plate thickness, and the crystallized glass plate obtained by crystallizing the glass plate has an arithmetic mean roughness Ra of 200 nm or less on the first main surface, the glass plate. However, the β-OH value is measured by the FT-IR-ATR method (Fourier transform infrared spectroscopy with total reflection). 2. The glass plate according to 1 above, wherein the base composition is expressed in terms of mass percentage based on oxides, containing 60 to 75% of SiO2, 7.0 to 23% of Al2O3, and 4.5 to 13.0% of Li2O. 3. The glass plate according to 1 or 2 above, wherein the base composition is expressed in terms of mass percentage based on oxides, containing 60 to 75% of SiO2, 7.0 to 23% of Al2O3, 4.5 to 13.0% of Li2O, 0 to 1.5% of Na2O, 0.10 to 2.5% of SnO2, 1.0 to 6.0% of ZrO2, 1.0 to 9.0% of Y2O3, and 0 to 5.0% of P2O5 The glass plate according to 1 or 2 above. 4. The glass sheet according to any one of 1 to 3 above, which is float glass. 5. The glass sheet according to any one of 1 to 4 above, wherein the visible light transmittance when converted to a thickness of 0.7 mm is 91.0% or more. 6. A glass sheet which is a crystallized glass obtained by crystallizing the glass sheet according to any one of 1 to 5 above. 7. The glass sheet according to any one of 1 to 6 above, which is chemically strengthened glass. 8. A display device including the glass sheet according to any one of 1 to 7 above.

Advantages of the Invention

[0010] The glass sheet of the present invention is a crystallized glass sheet in which the glass sheet is crystallized, and the β-OH value at the center of the plate thickness of the glass sheet is in a specific range, and is lower than the β-OH value at the center of the plate thickness, and the difference is in a specific range, whereby the surface crystallization of the crystallized glass sheet is suppressed and excellent surface flatness is exhibited.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the crystallized glass sheet of the present invention will be described in detail based on embodiments. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0013] The crystallized glass is obtained by subjecting an amorphous glass to a heat treatment for crystallization. The glass composition of the crystallized glass is the same as the composition of the amorphous glass before crystallization. In this specification, "chemically strengthened glass" refers to the glass after being subjected to a chemical strengthening treatment. Also, "glass for chemical strengthening" refers to the glass before being subjected to a chemical strengthening treatment. In chemically strengthened glass, usually, a compressive stress layer is formed on the glass surface portion by ion exchange, so the glass composition of the portion where ion exchange has not occurred coincides with the parent composition of the chemically strengthened glass in terms of molar percentage based on oxides. Also, the concentration of components other than alkali metal oxides basically does not change even in the ion-exchanged portion. Note that, as will be described later, the glass composition in this specification is shown in terms of mass percentage based on oxides, but the change in the glass components before and after ion exchange is based on the molar percentage based on oxides.

[0014] In this specification, the glass composition of the glass before crystallization or before crystallization and chemical strengthening treatment may be referred to as the parent composition of the crystallized glass. The parent composition of the crystallized glass is equivalent to the composition at the center of the plate thickness.

[0015] In this specification, the glass composition is shown in terms of mass percentage based on oxides, and mass % may be simply described as %. Also, "~" indicating a numerical range is used in the sense of including the numerical values described before and after it as the lower limit value and the upper limit value.

[0016] <Glass plate> The glass plate according to this embodiment is a glass plate having a first main surface and a second main surface facing the first main surface, having a thickness of 0.30 to 1.00 mm, a β-OH value at the center of the plate thickness of 0.20 to 0.50 / mm, at least the β-OH value on the first main surface being 0.02 to 0.10 / mm smaller than the β-OH value at the center of the plate thickness, and the crystallized glass plate obtained by crystallizing the glass plate having an arithmetic mean roughness Ra of 200 nm or less on the first main surface, and is characterized by being such a glass plate. However, the β-OH value is measured by the FT-IR-ATR method (Fourier transform infrared spectroscopy with attenuated total reflection).

[0017] The glass plate according to this embodiment is preferably a glass (float glass) plate manufactured by the float process. The float glass plate has a bottom surface that contacts the molten metal during forming and a top surface that faces the bottom surface. In this embodiment, when the glass plate is a float glass plate, it is preferable that the first main surface is the top surface and the second main surface is the bottom surface.

[0018] (β-OH concentration) The glass plate according to this embodiment has a β-OH value at the center of the plate thickness of 0.20 to 0.50 / mm, and at least the β-OH value on the first main surface is 0.02 to 0.10 / mm smaller than the β-OH value at the center of the plate thickness. Thereby, the surface crystallization of the crystallized glass plate is suppressed, and excellent surface flatness is exhibited. The β-OH value is measured by the FT-IR-ATR method (Fourier transform infrared spectroscopy with attenuated total reflection).

[0019] The relationship between the depth from the first main surface of the glass plate according to one embodiment and the β-OH concentration is shown in FIG. 1. In FIG. 1, t represents the plate thickness, and t / 2 represents the center of the plate thickness. As shown in FIG. 1, the glass plate in one embodiment has a gradually increasing β-OH concentration up to the β-OH concentration at the center of the plate thickness as the depth from the first main surface increases in the region from the first main surface to a depth x1.

[0020] The glass plate according to this embodiment has a β-OH value at the center of the plate thickness that is preferably 0.21 / mm or more, more preferably 0.23 / mm or more, still more preferably 0.25 / mm or more, and is preferably 0.40 / mm or less, more preferably 0.37 / mm or less, still more preferably 0.35 / mm or less.

[0021] The glass plate according to this embodiment has a β-OH value at least on the first main surface that is 0.02 to 0.10 / mm smaller than the β-OH value at the center of the plate thickness, preferably 0.02 to 0.09 / mm smaller, more preferably 0.02 to 0.08 / mm smaller, and still more preferably 0.03 to 0.07 / mm smaller.

[0022] The β-OH concentration distribution of the glass plate can be adjusted by, for example, the rare speed, the hydrogen concentration in the air, the temperature of the molten metal bath, the dealcoholization treatment, and the glass composition (for example, the content of SnO2) during the production of the glass plate as described below, such as during forming by the float method.

[0023] (Arithmetic mean roughness Ra of the crystallized glass plate) For the glass plate according to the present embodiment, the arithmetic mean roughness Ra of the first main surface of the crystallized glass plate obtained by crystallizing the glass plate is 200 nm or less, more preferably 150 nm or less, still more preferably 100 nm or less, particularly preferably 60 nm or less, and most preferably 40 nm or less. When the arithmetic mean roughness Ra of the first main surface is 200 nm or less, the flatness of the surface is excellent and the production efficiency can be improved. The lower limit of the arithmetic mean roughness Ra of the first main surface is not particularly limited, but is, for example, 20 nm or more.

[0024] The arithmetic mean roughness Ra can be measured by a method according to JIS B0601:1994. Note that for the glass plate according to the present embodiment, it is preferable that the arithmetic mean roughness Ra of the first main surface of the crystallized glass plate in the unpolished state obtained by crystallizing the glass plate is 200 nm or less.

[0025] As the crystallization treatment for obtaining the crystallized glass plate showing the arithmetic mean roughness Ra, it is possible to perform treatment at a first treatment temperature for a certain period of time and then perform treatment at a second treatment temperature for a certain period of time. As the conditions of the crystallization treatment, it is preferable that the second treatment temperature is higher than the first treatment temperature. Specifically, the following conditions can be mentioned. Conditions: The first treatment temperature is 550°C to 800°C, the second treatment temperature is 750°C to 1000°C, hold at the first treatment temperature for 1 hour to 10 hours, and then hold at the second treatment temperature for 10 minutes to 10 hours. The heating rate and the cooling rate in each stage of the heat treatment are 5 to 120°C / min.

[0026] (Composition) Hereinafter, the composition of the glass plate according to this embodiment will be described. The composition of the glass plate is described in terms of the base composition. The base composition is equivalent to the composition at the center of the plate thickness. In this specification, the glass composition is indicated in terms of mass percentage based on oxides, and the notation “%” indicates mass %.

[0027] The glass plate according to this embodiment preferably contains 60 to 75% of SiO2, 7.0 to 23% of Al2O3, and 4.5 to 13.0% of Li2O.

[0028] More preferably, the composition of the glass plate according to this embodiment specifically includes, for example, a composition containing 60 to 75% of SiO2, 7.0 to 23% of Al2O3, 4.5 to 13.0% of Li2O, 0 to 1.5% of Na2O, 0.10 to 2.5% of SnO2, 1.0 to 6.0% of ZrO2, 1.0 to 9.0% of Y2O3, and 0 to 5.0% of P2O5.

[0029] SiO2 is a component that forms the network structure of the glass. It is also a component that improves chemical durability and can also be a constituent component of precipitated crystals. The content of SiO2 is preferably 60% or more, more preferably 62% or more, still more preferably 64% or more, particularly preferably 66% or more, and most preferably 67% or more. On the other hand, in order to improve the meltability, the content of SiO2 is preferably 75% or less, more preferably 73% or less, still more preferably 71% or less, particularly preferably 70% or less, and most preferably 69% or less.

[0030] Al2O3 is a component that increases the surface compressive stress by chemical strengthening. The content of Al2O3 is preferably 7.0% or more, more preferably 8.0% or more, still more preferably 8.5% or more, particularly preferably 9.0% or more, and most preferably 9.5% or more. On the other hand, from the viewpoint of suppressing the devitrification temperature of the glass from becoming too high, the content of Al2O3 is preferably 23% or less, more preferably 21% or less, still more preferably 20% or less, particularly preferably 19% or less, and most preferably 18% or less.

[0031] Li2O is a component that forms surface compressive stress through ion exchange and can also be a constituent of the precipitated crystals. The content of Li2O is preferably 4.5% or more, more preferably 5.0% or more, still more preferably 5.5% or more, particularly preferably 6.0% or more, and most preferably 6.5% or more. On the other hand, in order to stabilize the glass, the content of Li2O is preferably 13.0% or less, more preferably 12.0% or less, still more preferably 11.0% or less, particularly preferably 10.5% or less, and most preferably 10.0% or less.

[0032] Na2O is a component that improves the meltability of the glass. When containing the content of Na2O, the content is preferably 0.2% or more, more preferably 0.5% or more, particularly preferably 0.7% or more, and most preferably 0.9% or more. If there is too much Na2O, it becomes difficult for crystals to precipitate or the chemical strengthening characteristics deteriorate. Therefore, it is preferably 1.5% or less, more preferably 1.3% or less, still more preferably 1.2% or less, particularly preferably 1.1% or less, and most preferably 1.0% or less.

[0033] K2O, like Na2O, is a component that lowers the melting temperature of the glass and may be contained. When containing K2O, the content is preferably 0.1% or more, more preferably 0.2% or more, still more preferably 0.3% or more, particularly preferably 0.4% or more, and most preferably 0.5% or more. If there is too much K2O, the chemical strengthening characteristics deteriorate or the chemical durability deteriorates. Therefore, it is preferably 1.5% or less, more preferably 1.3% or less, still more preferably 1.2% or less, particularly preferably 1.1% or less, and most preferably 1.0% or less.

[0034] For the glass sheet according to this embodiment, the total content of Na₂O and K₂O, Na₂O + K₂O, is preferably 0% or more and 3.0% or less. From the viewpoint of improving the meltability of the glass, Na₂O + K₂O is more preferably 0.2% or more, still more preferably 0.4% or more, even more preferably 0.6% or more, particularly preferably 0.7% or more, and most preferably 0.8% or more. Further, if Na₂O + K₂O is too high, the chemical strengthening characteristics will deteriorate or the chemical durability will deteriorate. Therefore, 2.7% or less is more preferable, still more preferably 2.5% or less, even more preferably 2.3% or less, particularly preferably 2.2% or less, and most preferably 2.1% or less.

[0035] For the glass sheet according to this embodiment, taking the total content of Li₂O, Na₂O and K₂O, Li₂O + Na₂O + K₂O, as R₂O, R₂O is preferably 4.5% or more and 16% or less. From the viewpoint of improving the meltability of the glass, R₂O is more preferably 5.0% or more, still more preferably 6.0% or more, particularly preferably 6.5% or more, and most preferably 7.0% or more. Further, from the viewpoint of enhancing the chemical strengthening characteristics and chemical durability, R₂O is more preferably 15% or less, still more preferably 14% or less, particularly preferably 13% or less, and most preferably 12% or less.

[0036] For the glass sheet according to this embodiment, from the viewpoint of enhancing the chemical strengthening characteristics and chemical durability, K₂O / R₂O is preferably 0.20 or less, more preferably 0.15 or less, still more preferably 0.13 or less, particularly preferably 0.12 or less, and most preferably 0.11 or less. The lower limit of K₂O / R₂O is not particularly limited, but is, for example, 0.003 or more.

[0037] From the perspective of controlling the generation of crystal nuclei, the SnO2 content of the glass plate according to this embodiment is preferably 0.10% or more, more preferably 0.15% or more, 0.20% or more, 0.25% or more, 0.30% or more in this order, still more preferably 0.35% or more, particularly preferably 0.40% or more, and most preferably 0.45% or more. From the perspective of further suppressing devitrification and coloring, the SnO2 content is preferably 2.5% or less, still more preferably 2.0% or less, particularly preferably 2.2% or less, and most preferably 2.0% or less. Although Sn can take divalent and tetravalent forms, the concentration is expressed based on SnO2 in this specification.

[0038] ZrO2 can be a component that can form crystal nuclei during the crystallization process and may be contained. The ZrO2 content is preferably 1.0% or more, more preferably 1.5% or more, still more preferably 2.0% or more, particularly preferably 2.5% or more, and most preferably 3.0% or more. On the other hand, in order to suppress devitrification during melting, the ZrO2 content is preferably 6.0% or less, more preferably 5.5% or less, still more preferably 5.0% or less, particularly preferably 4.5% or less, and most preferably 4.2% or less.

[0039] Also, taking the total content of Li2O, Na2O, and K2O, Li2O + Na2O + K2O, as R2O, ZrO2 / R2O is preferably 0.1 or more, more preferably 0.2 or more, from the perspective of enhancing chemical durability. From the perspective of enhancing transparency after crystallization, ZrO2 / R2O is preferably 0.8 or less, more preferably 0.6 or less.

[0040] Y2O3 is a component that makes it difficult for fragments to scatter when the chemically strengthened glass breaks, and it may be contained. The content of Y2O3 is preferably 1.0% or more, more preferably 1.3% or more, still more preferably 1.6% or more, particularly preferably 1.9% or more, and most preferably 2.1% or more. On the other hand, in order to suppress devitrification during melting, the content of Y2O3 is preferably 9.0% or less, more preferably 8.0% or less, still more preferably 7.0% or less, particularly preferably 6.0% or less, and most preferably 5.0% or less.

[0041] P2O5 is not essential, but it has the effect of promoting phase separation of the glass and thus promoting crystallization, and it may be contained. When containing P2O5, the content is preferably 0.2% or more, more preferably 0.4% or more, still more preferably 0.6% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, if the content of P2O5 is too high, it is likely to phase separate during melting, and the acid resistance will be significantly reduced. The content of P2O5 is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, particularly preferably 3.7% or less, and most preferably 3.5% or less.

[0042] TiO2 is a component that can form crystal nuclei during the crystallization treatment, and it may be contained. TiO2 is not essential, but when contained, it is preferably 0.05% or more and 1.0% or less. The content of TiO2 is more preferably 0.08% or more, still more preferably 0.10% or more, particularly preferably 0.15% or more, and most preferably 0.20% or more. On the other hand, in order to suppress devitrification during melting and to impart coloration to the glass, the content of TiO2 is more preferably 0.8% or less, still more preferably 0.6% or less, particularly preferably 0.5% or less, and most preferably 0.4% or less.

[0043] SnO2 can facilitate the formation of crystal nuclei and may be contained. SnO2 is not essential, but when contained, it is preferably 0.1% or more and 2.5% or less. The content of SnO2 is more preferably 0.2% or more, still more preferably 0.3% or more, particularly preferably 0.4% or more, and most preferably 0.5% or more. On the other hand, in order to suppress devitrification during melting, the content of SnO2 is more preferably 2.5% or less, still more preferably 2.2% or less, particularly preferably 2.0% or less, and most preferably 1.8% or less.

[0044] B2O3 is not essential, but it is a component that can improve the chipping resistance of chemically strengthened glass or chemically strengthened glass and also improve the meltability, and may be contained. When B2O3 is contained, the content is preferably 0% or more and 3.0% or less. From the perspective of further improving the meltability, the content of B2O3 is more preferably 0.2% or more, still more preferably 0.4% or more, particularly preferably 0.6% or more, and most preferably 0.8% or more. On the other hand, in order to suppress the occurrence of veining during melting and prevent phase separation and deterioration of the quality of chemically strengthened glass, the content of B2O3 is more preferably 2.0% or less, still more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.8% or less.

[0045] BaO, SrO, MgO, CaO, and ZnO are components that can improve the meltability of the glass and may be contained. When these components are contained, the total content of BaO, SrO, MgO, CaO, and ZnO, BaO + SrO + MgO + CaO + ZnO, is preferably more than 0% and 3.0% or less. From the perspective of further improving the meltability of the glass, BaO + SrO + MgO + CaO + ZnO is more preferably 0.1% or more, still more preferably 0.2% or more, particularly preferably 0.3% or more, and most preferably 0.5% or more. On the other hand, from the perspective of suppressing the decrease in the ion exchange rate, BaO + SrO + MgO + CaO + ZnO is more preferably 2.5% or less, still more preferably 2.0% or less, particularly preferably 1.8% or less, and most preferably 1.5% or less.

[0046] Among the above components, BaO, SrO, and ZnO may be contained to improve the refractive index of the residual glass and approach the precipitated crystal phase, thereby improving the light transmittance of the crystallized glass and reducing the haze value. In that case, the total content of BaO + SrO + ZnO is preferably 0% or more and 1.0% or less. BaO + SrO + ZnO is more preferably 0.05% or more, still more preferably 0.1% or more, particularly preferably 0.2% or more, and most preferably 0.3% or more. On the other hand, these components may reduce the ion exchange rate. From the viewpoint of improving the chemical strengthening characteristics, BaO + SrO + ZnO is more preferably 0.8% or less, still more preferably 0.6% or less, particularly preferably 0.5% or less, and most preferably 0.4% or less.

[0047] CeO2 has the effect of oxidizing the glass and may suppress coloring, and may be contained. When CeO2 is contained, the content is preferably 0% or more and 1.0% or less. The content of CeO2 is more preferably 0.1% or more, still more preferably 0.2% or more, particularly preferably 0.3% or more, and most preferably 0.4% or more. When CeO2 is used as an oxidizing agent, the content of CeO2 is more preferably 0.8% or less, still more preferably 0.7% or less, particularly preferably 0.6% or less, and most preferably 0.5% or less in order to enhance transparency.

[0048] When the glass is used after being colored, a coloring component may be added within a range that does not inhibit the achievement of the desired chemical strengthening characteristics. Examples of suitable coloring components include Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3. The total content of the coloring components is preferably in the range of 1% or less. When it is desired to increase the visible light transmittance of the glass, it is preferably substantially free of these components.

[0049] When melting glass, it may appropriately contain SO3, chlorides, fluorides, etc. as fining agents. It is preferably free of As2O3. When containing As2O3, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not contained.

[0050] The glass composition is not particularly limited, but specifically, for example, the following glass compositions can be mentioned. (1) Glass containing 60 - 66% of SiO2, 18.0 - 23% of Al2O3, 4.5 - 9.0% of Li2O, and 1.50 - 2.5% of SnO2 in terms of mass% based on oxides (2) Glass containing 60 - 66% of SiO2, 7.0 - 18% of Al2O3, 7 - 11.0% of Li2O, and 1.00 - 2.5% of SnO2 in terms of mass% based on oxides (3) Glass containing 65 - 75% of SiO2, 8.0 - 13% of Al2O3, 7 - 11.0% of Li2O, and 1.50 - 2.5% of SnO2 in terms of mass% based on oxides (4) Glass containing 65 - 75% of SiO2, 18.0 - 23% of Al2O3, 4.5 - 9.0% of Li2O, and 0.10 - 2.5% of SnO2 in terms of mass% based on oxides (5) Glass containing 60 - 66% of SiO2, 12.0 - 18% of Al2O3, 4.5 - 9.0% of Li2O, and 0.50 - 1.5% of SnO2 in terms of mass% based on oxides

[0051] (Visible light transmittance) The glass plate according to this embodiment has a visible light transmittance of preferably 91.0% or more when converted to a thickness of 0.7 mm. When used as a protective member of a display device (for example, the cover glass of a portable display), the display screen is easy to see. The visible light transmittance is more preferably 91.2% or more, and even more preferably 91.4% or more. The higher the visible light transmittance, the better, but it is usually 92% or less. The visible light transmittance of ordinary amorphous glass is about 90%. The visible light transmittance can be measured by a method conforming to JIS R3106 (2019).

[0052] (Haze value) The glass plate according to this embodiment preferably has a haze value of 0.50% or less, more preferably 0.30% or less, still more preferably 0.20% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less when converted to a thickness of 0.7 mm. The smaller the haze value, the more preferable. The haze value is a value measured in accordance with JIS K7136 (2000).

[0053] When the total light visible light transmittance of the glass with a plate thickness t [mm] is T [%] and the surface reflectance on one side is R [%], by applying the Lambert-Beer law, using the constant α, T / 100 = (1 - R / 100) 2 ×exp(-αt) holds a relationship. From this, expressing α in terms of R, T, and t, and setting t = 0.7 mm, since R does not change depending on the plate thickness, the total light visible light transmittance T 0.7 / 100 is T 0.7 / 100 = T / 100 0.7 / t / (1 - R / 100)^(1.4 / t - 2) [%] can be calculated. However, X^Y represents X Y .

[0054] (Thickness) The thickness of the glass plate according to this embodiment is 0.30 to 1.00 mm. The thickness is preferably 0.90 mm or less, more preferably 0.80 mm or less, still more preferably 0.70 mm or less, particularly preferably 0.65 mm or less, and most preferably 0.60 mm or less. Also, from the viewpoint of enhancing strength more, the thickness is preferably 0.35 mm or more, more preferably 0.40 mm or more, still more preferably 0.45 mm or more, and particularly preferably 0.50 mm or more.

[0055] The shape of the glass plate according to this embodiment may be a shape other than plate-like, depending on the product to which it is applied, the intended use, etc. Further, the glass plate may have a beveled shape with different thicknesses at the outer periphery. Also, the form of the glass plate is not limited to this. For example, the two main surfaces may not be parallel to each other, and all or part of one or both of the two main surfaces may be a curved surface. More specifically, the glass plate may be, for example, a flat glass plate without warping, or a curved glass plate having a curved surface.

[0056] <<Devitrified glass>> The glass plate according to this embodiment is preferably devitrified glass obtained by crystallizing the above-described glass plate. Devitrified glass is obtained by heat-treating amorphous glass to crystallize it. The glass composition of the devitrified glass is the same as the composition of the amorphous glass before crystallization. The base composition of the devitrified glass is the same as the composition of the glass plate according to the above-described present embodiment, and the preferable composition range is also the same.

[0057] In this specification, "devitrified glass" refers to glass in which diffraction peaks indicating crystals are recognized by X-ray diffraction method (XRD: X-ray Diffraction). X-ray diffraction measurement can be performed, for example, by measuring the range of 2θ from 10° to 80° using CuKα rays. Examples of the crystals include β-spodumene-based crystals, lithium disilicate-based crystals, β-quartz-based crystals, lithium metasilicate crystals, and lithium phosphate crystals in the case of crystals containing lithium. These crystals form solid solutions and may dissolve various elements. Particularly, the elements that can dissolve are alkali metals (Na, K) and alkaline earth metals (Mg, Ca, Sr, Ba), but this is not necessarily the case. Also, examples of crystals that do not contain lithium include ZrO2 and its solid solution crystals. Examples of the elements that can dissolve include Y, Sn, etc., but this is not necessarily the case.

[0058] The crystallization rate of the crystallized glass is preferably 60% or more, more preferably 65% or more, still more preferably 70% or more, and particularly preferably 75% or more in order to increase the mechanical strength. Also, in order to enhance transparency, it is preferably 90% or less, more preferably 85% or less, and particularly preferably 80% or less. A small crystallization rate is also excellent in terms of being easy to heat and bend-mold.

[0059] The crystallization rate can be calculated by the Rietveld method from the X-ray diffraction intensity. Regarding the Rietveld method, it is described in the "Crystallographic Analysis Handbook" (published by Kyoritsu Shuppan in 1999, p492 - 499), edited by the editorial committee of the Crystallographic Society of Japan.

[0060] The average particle size of the precipitated crystals in the crystallized glass is preferably 150 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less, and particularly preferably 20 nm or less in order to enhance transparency. The average particle size of the precipitated crystals is determined from a transmission electron microscope (TEM) image. It can also be estimated from a scanning electron microscope (SEM) image.

[0061] [[Chemical Strengthened Glass]] The glass plate according to the present embodiment is preferably chemically strengthened glass. The chemically strengthened glass according to the present embodiment is obtained by chemically strengthening the glass plate according to the above-described present embodiment. That is, the base composition of the chemically strengthened glass according to the present embodiment is the same as the compositions of the glass plate and the crystallized glass according to the above-described present embodiment, and the preferable composition ranges are also the same.

[0062] When the chemically strengthened glass is in a plate shape, the content ratio of the alkali metal element differs between the surface layer and the center in the thickness direction. On the other hand, except for the case where an extreme ion exchange treatment is performed, the glass composition at the deepest part from the surface of the chemically strengthened glass is the same as the base composition of the chemically strengthened glass. When the chemically strengthened glass is in a plate shape, the deepest part from the glass surface is, for example, the depth of 1 / 2 of the plate thickness t.

[0063] (Stress Characteristics) In this specification, the "depth of the compression stress layer (DOL)" is the depth at which the compression stress value CS becomes zero. The surface compression stress value CS0 and the depth of the compression stress layer DOL can be measured using a surface stress meter [for example, the surface stress meter (FSM-6000) manufactured by Orihara Seisakusho]. The preferred plate thickness (t) and the preferred shape of the chemically strengthened glass according to this embodiment are the same as the preferred plate thickness (t) and the shape of the glass plate according to the above-described embodiment.

[0064] The chemically strengthened glass according to this embodiment preferably has a surface compression stress value CS0 of 300 MPa or more, more preferably 350 MPa or more, even more preferably 400 MPa or more, and still more preferably 450 MPa or more. The upper limit value of the surface compression stress value CS0 is not particularly limited, but the surface compression stress value CS0 may be, for example, 1400 MPa or less.

[0065] If the depth of the compression stress layer DOL of the chemically strengthened glass according to this embodiment is too large with respect to the thickness t (mm), CT may become too large. Therefore, it is preferably 0.30t or less, and more preferably 0.20t or more. Also, from the viewpoint of improving the strength, DOL is preferably 0.10t or more, and more preferably 0.15t or more.

[0066] <Use> The glass plate according to this embodiment can be used as a cover glass for mobile electronic devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet terminals. It is also useful for cover glasses of electronic devices that are not for the purpose of portability, such as televisions (TVs), personal computers (PCs), and touch panels. It is also useful as building materials such as window glass, table tops, interior decorations of automobiles and airplanes, etc., and their cover glasses (for example, in-vehicle cover glasses).

[0067] Since the glass plate according to this embodiment can be bent or formed into a shape other than a flat plate shape before or after chemical strengthening, it is also useful for applications such as a housing having a curved surface shape.

[0068] <<Method for manufacturing a glass plate>> The manufacturing method of the glass plate according to this embodiment preferably includes at least the following step (1), more preferably includes at least one of the following steps (2) and (3) in addition to step (1), and even more preferably includes the following steps (1) to (3). (1) Step of producing amorphous glass (2) Step of heat-treating the glass to obtain crystallized glass (3) Step of ion-exchanging the glass to obtain chemically strengthened glass Hereinafter, each step will be described.

[0069] (1) Step of producing amorphous glass The amorphous glass can be produced, for example, by the following method. Glass raw materials are prepared so as to obtain glass having a preferable composition, and are heated and melted in a glass melting furnace. Thereafter, the molten glass is homogenized by bubbling, stirring, addition of a fining agent, etc., formed into a glass plate having a predetermined thickness by a known forming method, and gradually cooled.

[0070] As the forming method, the float method is preferable. The float method refers to a method of flowing molten glass onto a molten metal bath and forming it into a plate shape. In this specification, the upstream side of the molten metal bath refers to the side into which the molten glass flows, and the downstream side refers to the side from which the ribbon-shaped formed glass is carried out.

[0071] Fig. 2 shows a schematic diagram of an apparatus for manufacturing glass by the float method. As shown in Fig. 2, the apparatus for manufacturing glass by the float method includes a melting furnace 10, a float bath 20, and a lehr (annealing furnace) 30. In the manufacture of glass by the float method, first, glass raw materials are melted in the melting furnace 10 to obtain molten glass. The melting furnace 10 has a melting kiln 11, and in the melting kiln 11, the charged glass raw materials 1 are melted to obtain molten glass 2. More specifically, the melting kiln 11 includes a melting tank 12 on the upstream side and a cooling tank 13 on the downstream side, and these are connected by a neck 14 (or throat), and the glass raw materials 1 are melted into molten glass 2 on the upstream side (i.e., the melting tank), and the temperature of the molten glass 2 is adjusted on the downstream side.

[0072] Next, molten glass 2 is continuously supplied to the surface of the molten metal bath 21 stored in the float bath 20 from the upstream side to form a glass ribbon 3. Then, the formed glass ribbon 3 is drawn out from the downstream end of the float bath 20 and introduced into a lehr (rare) 30 for slow cooling to produce a plate-shaped glass. The glass ribbon 3 introduced into the lehr 30 is slowly cooled while being conveyed by a conveying means such as a roller conveyor to a lehr (not shown). Since the molten glass 2 on the molten metal bath 21 and the glass ribbon 3 in the lehr 30 are continuous, the conveying speed (lehr speed) in the lehr 30 depends on the speed at which the molten glass 2 flows from the upstream to the downstream on the molten metal bath 21. Although the glass ribbon 3 in the lehr 30 is solidified, since the molten glass 2 is flowing, the speed of the molten glass 2 is slower than the lehr speed, and the speed of the molten glass 2 on the molten metal bath 21 tends to be faster toward the downstream. The type of molten metal is not particularly limited, but generally molten tin is used.

[0073] As described above, in the present embodiment, the SnO2 concentration distribution in the glass plate can be adjusted by 1) the lehr speed, 2) the hydrogen concentration in the air, 3) the temperature of the molten metal bath, and 4) the glass composition (for example, the content of SnO2), etc. during the forming by the float method. Each item will be described below.

[0074] 1) The lehr speed during float forming The lehr speed is preferably 20 m / h or more, more preferably 100 m / h or more, still more preferably 200 m / h or more, particularly preferably 300 m / h or more, and most preferably 400 m / h or more. If the lehr speed is too high, the quality of the glass is likely to deteriorate, so 1200 m / h or less is preferable, more preferably 1000 m / h or less, still more preferably 900 m / h or less, particularly preferably 850 m / h or less, and most preferably 800 m / h or less.

[0075] 2) The hydrogen concentration in the atmosphere during float forming The hydrogen concentration in the atmosphere during float forming can be adjusted by the concentration of gases such as reducing gases and oxidizing gases supplied to the glass during float forming, the spraying amount, the main surface to be sprayed, the processing temperature and time, etc. Examples of the supply of such gases include supply from holes in the ceiling arranged at an interval from the molten metal bath 21, and spraying of gas onto the glass plate in the lehr.

[0076] Examples of the reducing gas include nitrogen gas, hydrogen gas, carbon monoxide gas, or a mixed gas thereof. The reducing gas may contain an inert gas such as air, nitrogen, or argon as a carrier gas. The reducing gas can be supplied, for example, from holes in the ceiling arranged at an interval from the molten metal bath 21. Specific examples of the processing conditions of the reducing gas include conditions such as setting the mixed gas to 0.1 to 100 cc / min and the processing temperature to 600 to 1200 °C. The mixed gas is, for example, a mixed gas of nitrogen gas and hydrogen gas, and contains 80 to 99.5 vol% of nitrogen gas and 0.5 to 20 vol% of hydrogen gas.

[0077] Examples of the oxidizing gas include sulfurous acid gas (SO2 gas), hydrofluoric acid gas, oxygen gas, or a mixed gas thereof. The oxidizing gas may contain an inert gas such as air, nitrogen, or argon as a carrier gas. The oxidizing gas may further contain water vapor. The oxidizing gas is sprayed, for example, onto the main surface of the glass plate (preferably at least the top surface, specifically, for example, only the first main surface or both the first main surface and the second main surface) in the lehr. Specific examples of the processing conditions of the oxidizing gas include conditions such as setting the mixed gas to 0.1 to 100 cc / min and the processing temperature to 600 to 1200 °C. The mixed gas may vary, for example, in the oxygen content in the range of 0.5 to 10 vol% or higher. In some embodiments, the mixed gas may be oxygen gas with a maximum of 100 vol%.

[0078] 3) Temperature of the molten metal bath during float forming The temperature of the molten metal bath is preferably 700 °C or higher, more preferably 800 °C or higher, still more preferably 850 °C or higher, and particularly preferably 900 °C or higher. From the viewpoint of volatilization of metallic tin, it is preferably 1300 °C or lower, more preferably 1250 °C or lower, still more preferably 1200 °C or lower, and particularly preferably 1150 °C or lower.

[0079] 4) Glass composition The SnO2 concentration distribution in the glass plate can also be adjusted by adjusting the SnO2 concentration of the base composition. The preferable range of the SnO2 concentration of the base composition is the same as the range described above in the section of <Glass plate> (composition).

[0080] (2) Step of heat-treating the glass to obtain a crystallized glass A crystallized glass can be obtained by heat-treating (heat treatment) the amorphous glass obtained by the above procedure. In that case, the heat treatment includes a multi-step heat treatment of two or more steps. The multi-step heat treatment refers to a heat treatment in which holding at a predetermined temperature range for a predetermined time is performed a plurality of times while changing the temperature range and the like. Specifically, as an example of the multi-step heat treatment, there is a two-step heat treatment in which the temperature is raised from room temperature to a first treatment temperature and held for a certain time, and then held at a second treatment temperature higher than the first treatment temperature for a certain time.

[0081] In the case of a two-step heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate becomes large in the glass composition, and the second treatment temperature is preferably in a temperature range where the crystal growth rate becomes large in the glass composition. Also, the holding time at the first treatment temperature is preferably long so that a sufficient number of crystal nuclei are generated. By generating a large number of crystal nuclei, the size of each crystal becomes small, and a highly transparent crystallized glass can be obtained.

[0082] In the case of a two-step heat treatment, the first treatment temperature is, for example, 550 °C to 800 °C, the second treatment temperature is, for example, 850 °C to 1000 °C, and after holding at the first treatment temperature for 2 hours to 10 hours, it is held at the second treatment temperature for 2 hours to 10 hours.

[0083] The heating rate and the cooling rate in each heat treatment stage are preferably 5 to 120 °C / min. Since the heating rate and the cooling rate of 5 °C / min or more can follow the crystal growth rate in the material, it is preferable. On the other hand, since the heating rate and the cooling rate of 120 °C / min or less can suppress the deformation of the material, it is preferable.

[0084] The molten glass may be homogenized and formed into a glass plate with a predetermined thickness, or the molten glass may be formed into a block shape, and subsequently, a crystallization treatment may be continuously performed. The crystallized glass obtained by the above procedure is ground and polished as necessary to form a crystallized glass plate.

[0085] (3) Step of obtaining chemically strengthened glass by ion-exchanging glass In this embodiment, the chemical strengthening treatment (ion-exchange treatment) is performed, for example, by immersing a glass plate in a molten salt such as potassium nitrate heated to 360 to 600 °C for 0.1 to 500 hours. The heating temperature of the molten salt is preferably 375 to 500 °C, and the immersion time of the glass plate in the molten salt is preferably 0.3 to 200 hours.

[0086] Examples of the molten salt for performing the chemical strengthening treatment include nitrates, sulfates, carbonates, chlorides, etc. Among these, examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate, etc. Examples of sulfates include lithium nitrosulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate, etc. Examples of carbonates include lithium nitrocarbonate, sodium carbonate, potassium carbonate, etc. Examples of chlorides include lithium nitrosyl chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, etc. These molten salts may be used alone or in combination of multiple types.

[0087] In this embodiment, the treatment conditions for chemical strengthening treatment may be appropriately selected in consideration of the characteristics and composition of the glass for chemical strengthening, the type of molten salt, and chemical strengthening characteristics such as the surface compressive stress and the depth of the compressive stress layer desired for the finally obtained chemically strengthened glass.

[0088] In particular, it is preferable to perform chemical strengthening treatment on an amorphous glass or a crystallized glass having a large fracture toughness value for a long time. When the ion exchange reaction proceeds due to the long-time chemical strengthening treatment, a large compressive stress is generated in the surface layer portion, and at the same time, due to structural relaxation, a decrease in the compressive stress mainly occurs near the surface, and the compressive stress balance of this embodiment is easily obtained.

[0089] Also, in this embodiment, the chemical strengthening treatment may be performed only once, or the chemical strengthening treatment (multi-stage strengthening) may be performed a plurality of times under two or more different conditions.

[0090] <Display device> The display device according to this embodiment includes the glass plate according to the above-described embodiment. Examples of the display device in this embodiment include a display device such as an in-vehicle car navigation system and a portable display device such as a smartphone.

Explanation of reference numerals

[0091] 1 Glass raw material; 2 Molten glass; 3 Glass ribbon; 10 Melting furnace; 11 Melting kiln; 12 Melting tank; 13 Cooling tank; 14 Neck; 20 Float bath; 21 Molten metal bath; 22 Top roll; 23 Restrictor; 30 Slow cooling furnace (rearer)

Claims

1. A glass plate having a first main surface and a second main surface facing the first main surface, with a thickness of 0.30 to 1.00 mm, the β-OH value at the center of the plate thickness being 0.20 to 0.50 / mm, at least the β-OH value on the first main surface being 0.02 to 0.10 / mm smaller than the β-OH value at the center of the plate thickness, and the crystallized glass plate obtained by crystallizing the glass plate having an arithmetic mean roughness Ra of 200 nm or less on the first main surface. However, the β-OH value is measured by the FT-IR-ATR method (Fourier transform infrared spectroscopy with attenuated total reflection).

2. The base composition is expressed in mass percentage based on oxides, SiO ２ being 60 to 75%, Al ２ O ３ being 7.0 to 23%, Li ２ O containing 4.5 to 13.0%, the glass plate according to claim 1.

3. The base composition is expressed in mass percentage based on oxides, SiO ２ being 60 to 75%, Al ２ O ３ being 7.0 to 23%, Li ２ O being 4.5 to 13.0%, Na ２ O being 0 to 1.5%, SnO ２ being 0.10 to 2.5%, ZrO ２ being 1.0 to 6.0%, Y ２ O ３ being 1.0 to 9.0%, P ２ O ５ being 0 to 5.0% containing, the glass plate according to claim 2.

4. The glass sheet according to claim 1, which is float glass.

5. The glass sheet according to claim 1, having a visible light transmittance of 91.0% or more when converted to a thickness of 0.7 mm.

6. A glass sheet which is a devitrified glass obtained by devitrifying the glass sheet according to claim 1.

7. The glass sheet according to claim 1, which is chemically strengthened glass.

8. A display device including the glass sheet according to any one of claims 1 to 7.

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