Glass material, crystallized glass

Abstract

To provide a glass material that has high fracture toughness and can be chemically strengthened to impart compression stress.SOLUTION: There is provided a glass material that contains 40% or more of SiO2, 10 to 30% of Al2O3, 7.5 to 40% of MgO, 5 to 20% of Li2O, 1 to 7.5% of Na2O, 5% or less of ZrO2, 1% or more of (Y2O3+ZrO2), based on the molar percentage representation of the oxide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a glass material and a glass-ceramic. [Background technology]

[0002] Cover glasses and the like used in mobile terminals are required to have various strengths, such as the strength to withstand the application of external force, i.e., bending strength, and the strength to withstand the glass breaking when the mobile terminal is dropped, i.e., drop strength. One method for increasing the bending strength of glass is to impart compressive stress to the glass surface by chemical strengthening. Furthermore, one method for increasing the drop strength of glass is to increase the fracture toughness of the glass (Patent Document 1). One possible method for increasing fracture toughness is to increase the Young's modulus of the glass. In order to increase the Young's modulus of glass, it has been effective to use a predicted value based on a formula. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6798629 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has been extremely difficult to obtain a glass material that has a Young's modulus that far exceeds the calculated value and that can be given compressive stress by chemical strengthening. An object of the present invention is to provide a glass material that has high fracture toughness and can be given compressive stress by chemical strengthening. [Means for solving the problem]

[0005] The present invention relates to the following glass materials and glass-ceramics.

[0006] In mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Glass material containing 1% or more of (Y2O3+ZrO2).

[0007] The mother glass is expressed as mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Glass-ceramics containing 1% or more of (Y2O3+ZrO2). [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a glass material that has a Young's modulus that greatly exceeds the calculated value, and is therefore expected to have high fracture toughness, and that can be given compressive stress by chemical strengthening. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, unless otherwise specified, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] In this specification, "amorphous glass" refers to glass in which no diffraction peaks indicating crystals are observed by the powder X-ray diffraction method described below. "Crystalline glass" is obtained by heat-treating "amorphous glass" to precipitate crystals, and contains crystals. In this specification, "amorphous glass" and "crystallized glass" are sometimes collectively referred to as "glass." Furthermore, amorphous glass that becomes crystallized glass by heat treatment is sometimes referred to as "mother glass of crystallized glass."

[0011] In this specification, powder X-ray diffraction measurement is performed using, for example, CuKα radiation in the 2θ range of 10° to 80°, and if a diffraction peak appears, the precipitated crystals are identified by the Hanawalt method. Furthermore, among the crystals identified by this method, the crystal identified from the peak group containing the peak with the highest integrated intensity is considered to be the main crystal. For example, a Rigaku SmartLab can be used as a measuring device.

[0012] In this specification, "chemically strengthened glass" refers to glass after chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before chemical strengthening treatment. Also, "mother composition of chemically strengthened glass" refers to the glass composition of the glass for chemical strengthening.

[0013] In this specification, unless otherwise specified, glass compositions are expressed in mole percent on an oxide basis, and mole percent is simply represented as "%."

[0014] In this specification, "substantially free" means that the content is below the impurity level contained in raw materials, i.e., it is not intentionally added. Specifically, for example, it is less than 0.1%.

[0015] In this specification, the term "stress profile" refers to a representation of compressive stress values ​​with depth from the glass surface as a variable. In the stress profile, tensile stress is represented as negative compressive stress.

[0016] The "compressive stress value (CS)" can be measured by cutting a cross section of glass into thin slices and analyzing the sliced ​​samples with a birefringence imaging system. A birefringence imaging system birefringence stress meter is a device that measures the magnitude of retardation caused by stress using a polarizing microscope and a liquid crystal compensator, etc., and one example is the birefringence imaging system Abrio-IM manufactured by CRi.

[0017] Measurements can also be made using scattered light photoelasticity. With this method, light is incident on the glass surface and the polarization of the scattered light is analyzed to measure CS. An example of a stress measuring instrument that uses scattered light photoelasticity is the SLP-2000 scattered light photoelasticity meter manufactured by Orihara Seisakusho.

[0018] In this specification, the "depth of compressive stress (DOL)" is the depth at which the compressive stress value becomes zero. Hereinafter, the surface compressive stress value is referred to as CS0, and the compressive stress value at a depth of 50 μm is referred to as CS 50 Also, "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 of the plate thickness t.

[0019] <Glass materials> The glass material according to an embodiment of the present invention (hereinafter also referred to as the present glass material) is typically a plate-shaped glass article, but may be a flat glass plate without warping, or may be a curved glass plate having a curved surface. It may also have portions with different thicknesses, such as a border shape with different peripheral thicknesses. It may also be a plate whose two main surfaces are not parallel to each other, and one or both of the two main surfaces may be entirely or partially curved.

[0020] When the glass material is in a plate form, the thickness (t) is preferably 3 mm or less, and more preferably 2 mm or less, 1.6 mm or less, 1.1 mm or less, 0.9 mm or less, 0.8 mm or less, and 0.7 mm or less in the following stepwise order. Furthermore, the thickness (t) is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.5 mm or more, in order to obtain sufficient strength by chemical strengthening treatment.

[0021] This glass material is expressed as mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Contains 1% or more of (Y2O3+ZrO2).

[0022] The glass material contains a particularly large amount of Mg ions, at 7.5% or more, which can increase the Young's modulus of the glass. Here, the fracture toughness value of glass is determined by multiplying Young's modulus and surface fracture energy as shown in the following formula (in the formula, K1c is the fracture toughness value, E is Young's modulus, γ is the surface fracture energy, and ν is Poisson's ratio).

[0023]

number

[0024] Therefore, to improve the fracture toughness of glass, it is sufficient to increase either Young's modulus or surface fracture energy. In this study, we focused on Young's modulus. We compared the calculated Young's modulus obtained using the formula described below with the measured Young's modulus and found that the measured Young's modulus was significantly higher than the calculated Young's modulus when the glass contained a large amount of Mg ions. Furthermore, we found that the fracture toughness of glass materials containing a large amount of Mg ions, where the measured Young's modulus was significantly higher than the calculated Young's modulus, was also higher. The reason for these favorable physical properties is thought to be the formation of a network in the glass by Mg ions. When present in small amounts in glass, Mg ions act to break the glass network, whereas when present in large amounts, they form a network. When Mg ions form a network, they strengthen bonds with other atoms, thereby increasing fracture toughness. However, because the calculation formula (1) described below does not take into account the role of Mg ions in network formation, it is thought that the resulting Young's modulus and fracture toughness were higher than expected.

[0025] The method for calculating the calculated Young's modulus of this glass material will now be described. It is known that the Young's modulus of glass can be calculated from composition and density information. The glass composition here refers to the composition of the components contained in the glass converted into metal oxides. More specifically, it corresponds to the value obtained by multiplying the size and bonding strength of the metal oxide ions, dividing the result by the weight of the ions, adding up the values ​​for each metal oxide, and multiplying the sum by 2. Specifically, the calculated Young's modulus Ecal (GPa) is calculated using the following formula (1) (Reference: S. Inaba, S. Fujino, K. Morinaga, "Young's Modulus and Compositional Parameters of Oxide Glasses," J. Am. Ceram. Soc., 82

[12] 3501-3507 (1999)). Ecal=2·Σ{(d·V i X i )·(G i X i ) / (M i X i )}…(1) d: Density (g / cm 3 ) V i (cm 3 / mol): the packing parameter of the metal oxide contained in the glass material G i (kJ / cm 3 ): Dissociation energy of the metal oxide contained in the glass material M i (g / mol): Molecular weight of the metal oxide contained in the glass material X i : The molar ratio (X) of the metal oxide contained in the glass material to the entire glass material i (The unit is dimensionless)

[0026] As shown in equation (1), the calculated Young's modulus Ecal is calculated for each metal oxide contained in the glass {(d V i X i )·(G i X i ) / (M i X i)} for all metal oxides contained in the glass and multiplied by 2. V i is calculated from the following formula (2), and G i is calculated using the following formula (3): V i =6.02 10 23 (4 / 3)π(xr 3 M +y·r 3 O )···(2) G i =d i / M i ·{x·ΔHf(M gas )+y·ΔHf(O gas )-ΔHf(M x O ycrystal )-(x+y)·RT}···(3)

[0027] Metal oxides contained in glass materials are called M x O y M is a metal element, O is an oxygen element, x is the valence of the metal element M, and y is the valence of the oxygen element O. r M is the metal oxide M x O y is the Shannon ionic radius of the metal element M in O is the metal oxide M x O y is the Shannon ionic radius of the oxygen element O in the unit Å. Also, d i is the metal oxide M x O y is the density of the material, expressed in g / cm 3 is. ΔHf(M gas ) is the standard enthalpy of formation of the gaseous metal element M, and ΔHf(O gas ) is the standard enthalpy of formation of gaseous oxygen element O, and ΔHf(M x O ycrystal ) is a metal oxide M x O y where R is the gas constant and T is the absolute temperature. In this specification, these values ​​are used to calculate the calculated Young's modulus Ecal of the glass material.

[0028] Furthermore, the glass material preferably has a measured Young's modulus E of 90 GPa or more, more preferably 92.5 GPa or more, and even more preferably 95 GPa or more. Having a measured Young's modulus within this range can enhance the fracture toughness of the glass material. Furthermore, the glass material may be polished before use. For ease of polishing, the measured Young's modulus is preferably 150 GPa or less, more preferably 140 GPa or less, and even more preferably 130 GPa or less. The actual Young's modulus can be measured by the ultrasonic pulse method (JIS R1602:1995).

[0029] The glass material preferably has a difference (E-Ecal) between the measured Young's modulus E and the calculated Young's modulus Ecal calculated from the above formula (1) of 5 GPa or more. If E-Ecal is 5 GPa or more, the fracture toughness of the glass material can be increased. E-Ecal is more preferably 7.5 GPa or more, and particularly preferably 10 GPa or more.

[0030] The composition of this glass material will be described in detail below. SiO2 is a component that forms the skeleton of the glass network structure. It also increases chemical durability. To obtain sufficient chemical durability, the SiO2 content is 40% or more, preferably 42.5% or more, more preferably 45% or more, even more preferably 47.5% or more, particularly preferably 50% or more, extremely preferably 52.5% or more, and most preferably 55% or more. In order to increase the strength of the glass, the SiO2 content is preferably 70% or less, more preferably 68% or less, even more preferably 66% or less, particularly preferably 64% or less, extremely preferably 62% or less, and most preferably 60% or less.

[0031] Al2O3 is a component that contributes to increasing the strength of glass. To obtain sufficient strength, the Al2O3 content is 10% or more, preferably 11% or more, more preferably 12% or more, even more preferably 13% or more, particularly preferably 13.5% or more, extremely preferably 14% or more, and most preferably 14.5% or more. To improve meltability, the Al2O3 content is 30% or less, preferably 28% or less, more preferably 26% or less, even more preferably 24% or less, particularly preferably 22% or less, extremely preferably 20% or less, and most preferably 18% or less.

[0032] MgO is a component that contributes to the formation of a glass network, and this effect is exerted when a specific amount is included. To form a sufficient network, the MgO content is 7.5% or more, preferably 10% or more, more preferably 11% or more, even more preferably 12% or more, particularly preferably 13% or more, extremely preferably 14% or more, and most preferably 14.5% or more. Furthermore, to increase the depth of the compressive stress layer (DOL) during chemical strengthening, the MgO content is 40% or less, preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 22.5% or less, extremely preferably 20% or less, and most preferably 17.5% or less.

[0033] Li2O is a component that forms surface compressive stress through ion exchange and, together with SiO2 and Al2O3, constitutes lithium aluminosilicate glass. Chemically strengthening lithium aluminosilicate glass can be obtained with a desirable stress profile. The Li2O content is 5% or more to increase the depth of the compressive stress layer (DOL), preferably 6% or more, more preferably 7% or more, even more preferably 7.5% or more, particularly preferably 8% or more, extremely preferably 9% or more, and most preferably 10% or more. Furthermore, in order to suppress the occurrence of devitrification during glass production or bending, the LiO content is 20% or less, preferably 19% or less, more preferably 18% or less, even more preferably 17% or less, particularly preferably 16% or less, extremely preferably 14% or less, and most preferably 12% or less.

[0034] Na2O is a component that forms a surface compressive stress layer by ion exchange using a potassium-containing molten salt and also improves the meltability of glass. The Na2O content is 1% or more, preferably 1.25% or more, more preferably 1.5% or more, even more preferably 1.75% or more, particularly preferably 2.0% or more, extremely preferably 2.25% or more, and most preferably 2.5% or more. The Na2O content is 7.5% or less, preferably 7.25% or less, more preferably 7.0% or less, even more preferably 6.5% or less, particularly preferably 6.0% or less, extremely preferably 5.5% or less, and most preferably 5.0% or less.

[0035] ZrO2 is a component that increases the surface compressive stress due to ion exchange and may be contained. When ZrO2 is contained, the content is preferably 0.5% or more, more preferably 0.6% or more, even more preferably 0.7% or more, particularly preferably 0.8% or more, extremely preferably 0.9% or more, and most preferably 1.0% or more. In addition, to suppress devitrification during melting, the ZrO2 content is 5% or less, preferably 4.5% or less, more preferably 4.0% or less, even more preferably 3.5% or less, particularly preferably 3.0% or less, extremely preferably 2.8% or less, and most preferably 2.5% or less.

[0036] Y2O3 is a component that enhances the meltability of glass and also has the effect of preventing glass fragments from scattering when broken, and may be contained. When Y2O3 is contained, the content is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, particularly preferably 2.0% or more, extremely preferably 2.2% or more, and most preferably 2.5% or more. Furthermore, in order to suppress devitrification during melting, the Y2O3 content is preferably 10% or less, more preferably 9.5% or less, even more preferably 9.0% or less, particularly preferably 8.5% or less, extremely preferably 8.2% or less, and most preferably 8.0% or less.

[0037] From the viewpoint of maintaining the strength of the glass, [Y2O3] + [ZrO2] is 1% or more, preferably 1.25% or more, more preferably 1.5% or more, even more preferably 1.75% or more, particularly preferably 2% or more, extremely preferably 2.25% or more, and most preferably 2.5% or more. From the viewpoint of improving the devitrification characteristics of the glass, [Y2O3] + [ZrO2] is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, particularly preferably 7% or less, extremely preferably 6% or less, and most preferably 5% or less.

[0038] Although K2O is not essential, it may be contained to improve the meltability of the glass and suppress devitrification. When K2O is contained, its content is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.3% or more, extremely preferably 0.4% or more, and most preferably 0.5% or more. Furthermore, in order to increase the compressive stress value due to ion exchange, the K2O content is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, particularly preferably 2% or less, extremely preferably 1.5% or less, and most preferably 1% or less.

[0039] Alkali metal oxides such as Li2O, Na2O, and K2O (sometimes collectively referred to as R2O) are components that lower the melting temperature of glass, and are preferably contained in a total amount of 5% or more. The total content of alkali metal oxides, R2O, is preferably 5% or more, more preferably 7% or more, and even more preferably 8% or more. To maintain the strength of the glass, R2O is preferably 20% or less, more preferably 18% or less.

[0040] Furthermore, the ratio [LiO] / [R2O] of the LiO content [LiO] to the total alkali metal oxide content [R2O] is preferably 0.8 or more, more preferably 0.85 or more, to obtain sufficient strength. [LiO] / [R2O] is 1 or less, and more preferably 0.95 or less to increase solubility.

[0041] Metal oxides such as CaO, SrO, BaO, and ZnO are components that improve the meltability of glass, but tend to reduce ion exchange performance. The total content of CaO, SrO, BaO, and ZnO (CaO + SrO + BaO + ZnO) is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less.

[0042] When CaO is contained, the content is preferably 0.5% or more, more preferably 1% or more, and in order to improve the ion exchange performance, the content is preferably 5% or less, more preferably 3% or less.

[0043] When SrO is contained, the content is preferably 0.5% or more, more preferably 1% or more, and in order to improve the ion exchange performance, the content is preferably 5% or less, more preferably 3% or less.

[0044] When BaO is contained, the content is preferably 0.5% or more, more preferably 1% or more. In order to improve the ion exchange performance, the content is preferably 5% or less, more preferably 1% or less, and even more preferably substantially none.

[0045] ZnO is a component that improves the meltability of glass and may be contained. When ZnO is contained, the content is preferably 0.2% or more, more preferably 0.5% or more. To improve the weather resistance of the glass, the ZnO content is preferably 5% or less, more preferably 3% or less.

[0046] Although B2O3 is not essential, it can be added to improve meltability during glass production, etc. Furthermore, when chemically strengthened glass is produced, the B2O3 content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more in order to reduce the gradient of the stress profile near the surface of the chemically strengthened glass and thereby increase stability.

[0047] B2O3 is a component that makes stress relaxation more likely to occur after chemical strengthening, so in order to increase the surface compressive stress of chemically strengthened glass, the content of B2O3 is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and most preferably 3% or less.

[0048] P2O5 may be contained to improve ion exchange performance. When P2O5 is contained, the content is preferably 0.5% or more, more preferably 1% or more. To improve chemical durability, the content of P2O5 is preferably 5% or less, more preferably 3% or less, and even more preferably 2% or less.

[0049] TiO2 may be contained because it tends to prevent fragments from scattering when the chemically strengthened glass is broken. When TiO2 is contained, the content is preferably 0.1% or more. In order to prevent devitrification during melting, the content of TiO2 is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and particularly preferably substantially none.

[0050] Nb2O5 and Ta2O5 may be contained to suppress fracture of chemically strengthened glass, etc. When these components are contained, the total content is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. Also, the total content is preferably 3% or less, more preferably 2% or less.

[0051] To color the glass, coloring components may be added within a range that does not impede the achievement of the desired chemical strengthening properties. Examples of coloring components include Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, and Nd2O3. These may be used alone or in combination.

[0052] The total content of coloring components is preferably 7% or less. This can prevent devitrification of the glass. The content of coloring components is more preferably 5% or less, even more preferably 3% or less, and particularly preferably 1% or less. If high transparency of the glass is desired, it is preferable that these components are substantially not contained.

[0053] Furthermore, SO3, chlorides, fluorides, etc. may be appropriately contained as fining agents during glass melting. It is preferable that As2O3 is substantially not contained. If Sb2O3 is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably substantially not contained.

[0054] This glass material has a high measured Young's modulus, which results in a high fracture toughness value and excellent drop strength. The fracture toughness value of this glass material is preferably 0.85 MPa m 1 / 2 More preferably, 0.88 MPa·m 1 / 2 More preferably, 0.9 MPa m 1 / 2 If the fracture toughness is 1.5 MPa m or more, a glass material with excellent impact resistance can be obtained. There is no particular upper limit to the fracture toughness of the glass material, but it is typically 1.5 MPa m 1 / 2 The following is the result. The fracture toughness value can be measured by the DCDC method [Reference: MY He, MR Turner and AG Evans, Acta Metall. Mater. 43 (1995) 3453.] Specifically, as described in Japanese Patent No. 7327570 (paragraph 0030), a curve showing the relationship between the stress intensity factor and the crack growth rate is measured using a specific sample, and the obtained data is regressed and extrapolated using a linear equation, and the stress intensity factor at 0.1 m / s is determined as the fracture toughness value.

[0055] The fictive temperature of the present glass material is preferably 650 to 800° C., more preferably 700 to 750° C. The fictive temperature is the temperature at which the liquid structure of molten glass is frozen during cooling, and a fictive temperature within the above range is preferable because it increases the Young's modulus of the glass and results in high-strength glass. The fictive temperature can be measured by measuring the refractive index of the glass.

[0056] The devitrification temperature of the present glass material is preferably 1100 to 1450° C., more preferably 1150 to 1350° C. A devitrification temperature within the above range is preferable because it facilitates mass production of the glass.

[0057] The liquidus temperature of the glass material is preferably 1670° C. or lower, and more preferably 1650° C. or lower. The low liquidus temperature allows production without using special methods such as a containerless method.

[0058] The high-temperature viscosity of the glass material is, for example, log η at 1650°C of 2 or less.

[0059] The softening point of the glass material is preferably 1000°C or lower, and more preferably 950°C or lower. The lower the softening point of the glass, the lower the heat treatment temperature when bending or forming, which reduces energy consumption and the load on the equipment. Glass with a softening point that is too low tends to relax the stress introduced during chemical strengthening treatment and result in low strength, so the softening point is preferably 550°C or higher. It is more preferably 600°C or higher, and even more preferably 650°C or higher. The softening point can be measured by the fiber stretching method described in JIS R3103-1:2001.

[0060] The glass material can be produced by a conventional method. When the glass material is a glass substrate, for example, the raw materials of the glass components are mixed and heated and melted in a glass melting furnace. The glass is then homogenized by a known method, formed into a desired shape such as a plate, and slowly cooled.

[0061] Thereafter, the formed glass is ground and polished as necessary to form a glass substrate. When the glass substrate is cut to a predetermined shape and size or when the glass substrate is chamfered, it is preferable to perform the cutting or chamfering of the glass substrate before performing the chemical strengthening treatment described later, because a compressive stress layer is also formed on the end surface by the subsequent chemical strengthening treatment.

[0062] This glass material has a higher measured Young's modulus than the calculated Young's modulus, resulting in a high fracture toughness and excellent drop strength. Furthermore, because it contains alkali metals, the bending strength of the glass can be increased by chemical strengthening. Therefore, this glass material is useful as a cover glass for mobile devices.

[0063] <Glass-ceramics> The crystallized glass according to the embodiment of the present invention (hereinafter also referred to as the present crystallized glass) is a glass obtained by heat-treating the present glass material. Therefore, the mother glass of the present crystallized glass has the same glass composition as the present glass material. That is, the mother glass of the present crystallized glass has, in mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Contains 1% or more of (Y2O3+ZrO2).

[0064] Like this glass material, this glass-ceramics also contains a large amount of Mg, which is expected to increase the measured Young's modulus higher than the calculated value and the fracture toughness of the glass. Furthermore, crystallization can increase the difference between the measured and calculated Young's modulus values ​​compared to this amorphous glass material, resulting in a glass with superior fracture toughness.

[0065] The composition of the mother glass of the present glass-ceramics is the same as the composition of the present glass material described above, including the preferred embodiments.

[0066] Furthermore, from the viewpoint of improving fracture toughness, the present glass-ceramics may contain forsterite crystals and spinel crystals, or may contain either one of them as the main crystal.

[0067] The Young's modulus E of the present crystallized glass is preferably 90 GPa or more, more preferably 95 GPa or more, and even more preferably 100 GPa or more. The Young's modulus in this range can improve the fracture toughness of the crystallized glass. In addition, the present crystallized glass may be polished before use. In order to facilitate polishing, the Young's modulus is preferably 135 GPa or less, more preferably 130 GPa or less, and even more preferably 125 GPa or less.

[0068] The difference (E-Ecal) between the measured Young's modulus E and the calculated Young's modulus Ecal calculated from the above formula (1) is preferably 5 GPa or more, more preferably 7.5 GPa or more, and particularly preferably 10 GPa or more. If E-Ecal is within this range, the fracture toughness of the crystallized glass can be improved.

[0069] The crystallized glass exhibits diffraction peaks indicative of crystallinity when measured by powder X-ray diffraction using Cu-Kα radiation. The diffraction peaks are preferably located at 2θ=20 to 30° and 2θ=24 to 28°, and more preferably at 2θ=25 to 27°.

[0070] The crystallization rate of the present crystallized glass is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and particularly preferably 20% or more in order to increase mechanical strength. In order to increase transparency, it is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A small crystallization rate is also advantageous in that it is easy to heat and bend. The crystallization rate is determined by crushing a part of the crystallized glass, identifying the precipitated crystals by powder X-ray diffraction, and then using the Rietveld method.

[0071] The average particle size of the precipitated crystals of this crystallized glass is preferably 5 nm or more, particularly preferably 10 nm or more, in order to improve mechanical strength. In order to improve transparency, it is preferably 80 nm or less, more preferably 60 nm or less, even more preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. The average particle size of the precipitated crystals can be determined from a transmission electron microscope (TEM) image or FE-SEM image.

[0072] The present glass-ceramics can be obtained by heat-treating the present glass material.

[0073] The heat treatment may be a two-stage heat treatment in which the temperature is raised from room temperature to a first treatment temperature and maintained for a certain period of time, and then maintained for a certain period of time at a second treatment temperature higher than the first treatment temperature, or a one-stage heat treatment in which the temperature is maintained at a specific treatment temperature and then cooled to room temperature.

[0074] In the case of two-stage heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate is high in the glass composition, and the second treatment temperature is preferably in a temperature range where the crystal growth rate is high in the glass composition. Also, it is preferable to maintain the first treatment temperature for a long time 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 highly transparent crystallized glass is obtained.

[0075] In the case of a two-stage treatment, for example, the first treatment temperature is held at 450°C to 700°C for 1 to 6 hours, and then the second treatment temperature is held at 600°C to 800°C for 1 to 6 hours. In the case of a one-stage treatment, for example, the temperature is held at 500°C to 800°C for 1 to 6 hours.

[0076] The molten glass may be homogenized and formed into a glass plate of a predetermined thickness, or may be formed into a block, followed by continuous crystallization.

[0077] When heat-treating plate-shaped glass, examples of suitable setter plates include silicon carbide plates, silicon nitride plates, SiN plates, alumina plates, mullite cordierite plates, mullite plates, and crystallized glass plates. Materials with high thermal conductivity are preferred to reduce temperature variations during heat treatment. The thermal conductivity of the setter plate is preferably 2 W / (m·K) or higher, more preferably 20 W / (m·K) or higher, and even more preferably 40 W / (m·K) or higher.

[0078] A release agent can be used to prevent the glass from adhering to the setter plate. Examples of release agents include alumina cloth and glass cloth. Other examples include powdered boron nitride, alumina, and minerals. A powdered release agent may be mixed with a solvent and applied by spraying or the like. When a particulate release agent is used, the average particle size is preferably 80 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

[0079] When heat-treating glass, it may be laminated to improve work efficiency. When laminating, it is preferable to use a release agent between the glass sheets. Also, a setter plate may be placed between the glass sheets.

[0080] The crystallized glass obtained by the above procedure is ground and polished as necessary to form a crystallized glass plate. When the crystallized glass plate is cut to a predetermined shape and size or chamfered, it is preferable to perform the cutting or chamfering before performing the chemical strengthening treatment, because a compressive stress layer is formed on the end surface by the subsequent chemical strengthening treatment.

[0081] <Chemically strengthened glass> Chemically strengthened glass according to an embodiment of the present invention (hereinafter also referred to as the present chemically strengthened glass) is glass obtained by chemically strengthening the present glass material (amorphous glass) or the present glass-ceramics. Chemical strengthening is a process in which glass is brought into contact with a metal salt, for example by immersing it in a molten salt (e.g., a sodium salt or a potassium salt) containing metal ions with a large ionic radius (typically Na ions or K ions), thereby replacing metal ions with a small ionic radius (typically Na ions or Li ions) in the glass with metal ions with a large ionic radius (typically Na ions or K ions for Li ions, and K ions for Na ions).

[0082] Examples of molten salts used in chemical strengthening include nitrates, sulfates, carbonates, and chlorides. Nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used alone or in combination.

[0083] The treatment conditions for the chemical strengthening treatment include time and temperature, taking into consideration the glass composition, 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 final chemically strengthened glass. Can be selected.

[0084] In the present invention, the chemical strengthening treatment may be performed only once, or may be performed multiple times under two or more different conditions (multi-stage strengthening). For example, the first stage of chemical strengthening treatment is performed under conditions that increase the DOL and relatively decrease the CS. If the second stage of chemical strengthening treatment is then performed under conditions that decrease the DOL and relatively increase the CS, the CS of the outermost surface of the chemically strengthened glass can be increased while the internal tensile stress (CT) can be kept low.

[0085] When chemical strengthening is carried out in one step, for example, the glass material or the crystallized glass is immersed in molten salt at a temperature of preferably 350 to 450° C. for about 1 to 6 hours. The above temperature conditions allow compressive stress due to chemical strengthening to be imparted to a sufficient depth, and the above treatment time allows compressive stress due to chemical strengthening to be imparted to a sufficient depth, which is preferable.

[0086] When chemical strengthening is carried out in two stages, for example, the glass material or the glass-ceramics is immersed for about 0.1 to 10 hours in a molten salt (e.g., sodium nitrate) at about 350 to 500° C. This causes ion exchange between Li ions in the glass and Na ions in the metal salt, forming a relatively deep compressive stress layer.

[0087] Next, the substrate is immersed in a metal salt containing K ions (e.g., potassium nitrate) at a temperature of preferably about 350 to 500°C for about 0.1 to 10 hours. This generates a large compressive stress in the compressive stress layer formed in the previous treatment, for example, within a depth of about 10 μm. This two-stage treatment makes it easy to obtain a stress profile with a large surface compressive stress value.

[0088] <Cover Glass and Electronic Devices> The glass material, the glass-ceramics, and the chemically strengthened glass are particularly useful as cover glass for mobile electronic devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet devices. They are also useful as cover glass for non-portable electronic devices such as televisions (TVs), personal computers (PCs), and touch panels. They are also useful as building materials such as window glass, tabletops, and interiors of automobiles and airplanes, as well as their cover glass.

[0089] As described above, the present specification discloses the following glass materials and glass-ceramics. [1] Mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Glass material containing 1% or more of (Y2O3+ZrO2). [2] The glass material according to [1], wherein the difference (E-Ecal) between the Young's modulus E of the glass material and the calculated Young's modulus Ecal expressed by the following formula (1) is 5 GPa or more. Ecal=2·Σ{(d·V i X i )·(G i X i ) / (M i X i )}…(1) d: Density (g / cm 3 ) V i (cm 3 / mol): the packing parameter of the metal oxide contained in the glass material G i (kJ / cm 3 ): Dissociation energy of the metal oxide contained in the glass material M i (g / mol): Molecular weight of the metal oxide contained in the glass material X i: Molar ratio of metal oxide contained in the glass material to the entire glass material [3] The glass material according to [1] or [2], having a fictive temperature of 500°C or higher and 800°C or lower. [4] The glass material according to any one of [1] to [3], wherein the content of Al2O3 is 11% or more. [5] The glass material according to any one of [1] to [4], wherein the content of MgO is 10% or more. [6] The glass material according to any one of [1] to [5], wherein the content of ZrO2 is 4.5% or less. [7] The mother glass is, in terms of mole percentage based on oxides, SiO2 40% or more, Al2O3 10-30%, MgO 7.5 to 40%, Li2O 5-20%, Na2O 1-7.5%, ZrO2 5% or less, Glass-ceramics containing 1% or more of (Y2O3+ZrO2). [8] In the mother glass, in terms of mole percentage based on oxides, TiO2 content is 5% or less, The crystallized glass according to [7], having a P2O5 content of 5% or less. [9] The crystallized glass according to [7] or [8], wherein the content of Al2O3 is 11% or more.

[10] The crystallized glass according to any one of [7] to [9], wherein the content of MgO is 10% or more.

[11] The crystallized glass according to any one of [7] to

[10] , having a ZrO2 content of 4.5% or less. [Example]

[0090] The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0091] <Example 1 to Example 27> Glass raw materials were mixed to obtain the compositions shown in Tables 1 to 3 in terms of oxide-based mole percentages, and weighed out to give 400 g of glass. The mixed raw materials were then placed in a platinum crucible and placed in an electric furnace at 1500 to 1700°C, where they were melted for about 3 hours, degassed, and homogenized. The resulting molten glass was poured into a metal mold and held at a temperature approximately 50°C higher than the glass transition point for 1 hour, then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The resulting glass block was cut and ground, and finally both sides were mirror-polished to obtain a glass plate with a thickness of 0.7 mm.

[0092] <Example 28> A glass plate manufactured with the same composition as in Example 5 was subjected to heat treatment at 700° C. for 4 hours to obtain a glass plate of crystallized glass.

[0093] <Density (d)> The density was measured based on the liquid weighing method (JIS Z 8807:2012, Methods for measuring density and specific gravity of solids). The unit is g / cm 3 is.

[0094] <Young's modulus (E)> The Young's modulus (E) (unit: GPa) of the glass before chemical strengthening was measured by the ultrasonic pulse method (JIS R1602:1995).

[0095] <Calculated Young's modulus (Ecal)> For the glass before chemical strengthening, the calculated Young's modulus (Ecal) (unit: GPa) was calculated using the following formula. Ecal=2·Σ{(d·V i X i )·(G i X i ) / (M i X i )}

[0096] <Devitrification temperature> Crushed glass particles were placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled at a constant temperature. After heat treatment, the glass was observed under a polarizing microscope, and the devitrification temperature was estimated using an evaluation method to determine whether or not devitrification occurred. For example, if the table shows "1050-1078°C," this means that devitrification occurred when heat-treated at 1050°C, but not when heat-treated at 1078°C. In this case, the devitrification temperature is between 1050°C and 1078°C.

[0097] <Virtual Temperature> The "refractive index nd" of each glass plate was measured by the V-block method using a refractive index measuring device KPR-3000 (manufactured by Shimadzu Corporation). The "fictive temperature Tf" was calculated as follows. First, the glass plate (for example, glass plate 1) was cut into pieces measuring 20 mm × 20 mm × 1 mm to prepare glass pieces. Next, the glass pieces were heated to a predetermined heat treatment temperature in a reducing atmosphere, held for 2 hours, and then rapidly cooled to room temperature. This heat treatment was carried out at different heat treatment temperatures to produce four glass pieces (evaluation samples) with different thermal histories. The refractive index nd of each evaluation sample was measured in the same manner as for the glass plate. Furthermore, a relational expression between the heat treatment temperature and the refractive index nd was determined from the four evaluation samples. Using the obtained relational expression, the corresponding heat treatment temperature was determined from the refractive index nd measured for the glass plate 1, and this was designated as the fictive temperature Tf. The fictive temperatures Tf of the other glass plates were also determined in the same manner.

[0098] <Chemical strengthening and stress measurement> Each glass plate was chemically strengthened using 100% sodium nitrate at 450°C for 4 hours, and the compressive stress value of the surface layer (CS0) and the depth of compressive stress (DOL) were measured using a scattered light photoelastic stress meter SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.

[0099] <Powder X-ray diffraction> Powder X-ray diffraction was measured under the following conditions to identify the precipitated crystals. Measurement equipment: Rigaku Smart Lab X-ray used: CuKα ray Measurement range: 2θ=10°~80° Speed: 1° / min Step: 0.01°

[0100] When the above measurement was carried out on the glass-ceramics obtained in Example 28, spinel crystals and forsterite crystals were detected.

[0101] The measurement results of each physical property are shown in Tables 1 to 3. Examples 1 to 24 and 28 are working examples, and Examples 25 to 27 are comparative examples.

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] The above results indicate that the measured Young's modulus values ​​for the glasses in Examples 1 to 24 and 28, which contained 7.5% or more Mg, were 5 GPa or more higher than the calculated values. Since the difference between the measured and calculated Young's modulus was 5 GPa or more, higher fracture toughness values ​​than expected were expected. The reason for these favorable physical properties is thought to be the contribution of Mg ions to network formation. It has been suggested that Mg ions, when present in small amounts in glass, have the effect of breaking the glass network, whereas when present in large amounts, they form a network. When Mg ions form a network, they strengthen bonds with other atoms, increasing fracture toughness values. However, the formula (1) used to calculate the calculated Young's modulus Ecal does not take into account the network formation of Mg ions, which is likely why the Young's modulus is higher than expected.

[0106] In the glass of Example 28, crystals were precipitated by heat treatment, and as a result, the discrepancy between the measured value and the calculated value of Young's modulus was larger than that of the glass of Example 5 (not heat treated) with the same composition.

[0107] On the other hand, in the glasses of Examples 25 and 26, in which the Mg content in the glass was less than 7.5%, the difference between the measured and calculated Young's modulus was less than 5 GPa, and therefore it is expected that the fracture toughness value would not be high.

[0108] Furthermore, the glasses of Examples 1 to 24 and 28 are given a compressive stress of 50 MPa or more by chemical strengthening, which allows the glass to be strengthened.

[0109] On the other hand, since the glasses of Examples 25 and 27 did not contain Li, compressive stress could not be imparted by chemical strengthening using a Na salt as the molten salt, and the strength of the glass could not be increased.

Claims

1. In mole percentage based on oxides, SiO ２ More than 40% Al ２ O ３ を10~30%、 MgO 7.5 to 40%, Li ２ Oを5~20%、 Na ２ Oを1~7.5%、 ZrO ２ 5% or less, (Y ２ O ３ + ZrO ２ ) glass material containing 1% or more.

2. 2. The glass material according to claim 1, wherein the difference (E−Ecal) between the Young's modulus E of the glass material and the calculated Young's modulus Ecal expressed by the following formula (1) is 5 GPa or more. Ecal=2・Σ{(d・V ｉ ・X ｉ )・(G ｉ ・X ｉ ) / (M ｉ ・X ｉ )}…(1) d: density (g / cm ３ ) V ｉ (cm ３ / mol): packing parameter of the metal oxide contained in the glass material G ｉ (kJ / cm ３ ): Dissociation energy of the metal oxide contained in the glass material M ｉ (g / mol): molecular weight of metal oxide contained in the glass material X ｉ : Molar ratio of metal oxide contained in the glass material to the entire glass material

3. 3. The glass material according to claim 1, wherein the fictive temperature is 500°C or higher and 800°C or lower.

4. Al ２ O ３ The glass material according to claim 1 or 2, wherein the content of

5. 3. The glass material according to claim 1, wherein the content of MgO is 10% or more.

6. ZrO ２ 3. The glass material according to claim 1, wherein the content of is 4.5% or less.

7. The mother glass is expressed as mole percentage based on oxides, SiO ２ More than 40% Al ２ O ３ を10~30%、 MgO 7.5 to 40%, Li ２ Oを5~20%、 Na ２ Oを1~7.5%、 ZrO ２ 5% or less, (Y ２ O ３ + ZrO ２ ) containing 1% or more of glass-ceramics.

8. In the mother glass, in terms of mole percentage based on oxides, TiO ２ The content is 5% or less, P ２ O ５ The crystallized glass according to claim 7, wherein the content of is 5% or less.

9. Al ２ O ３ The crystallized glass according to claim 7 or 8, wherein the content of is 11% or more.

10. 9. The crystallized glass according to claim 7, wherein the content of MgO is 10% or more.

11. ZrO ２ The crystallized glass according to claim 7 or 8, wherein the content of is 4.5% or less.

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