Glass-ceramics and tempered glass-ceramics

Abstract

The present invention provides easily processable crystallized glass capable of achieving a high compressive stress value on the surface thereof, and also provides strengthened crystallized glass thereof. [Solution] This is glass-ceramics containing one or more types selected from α-cristobalite and α-cristobalite solid solution as the main crystalline phase, and the glass-ceramics has, in mass % oxide equivalent, an SiO2 component content of 50.0% to 75.0%, a Li2O component content of 3.0% to 10.0%, an Al2O3 component content of 5.0% or more and less than 15.0%, and a B2O3 component content of more than 0% and 10.0% or less.

Description

[Technical Field]

[0001] The present invention relates to glass-ceramics and strengthened glass-ceramics.

[0002] Various types of glass are expected to be used as cover glass and housings to protect the displays of mobile electronic devices such as smartphones and tablet PCs, as protectors to protect the lenses of in-vehicle optical devices, interior bezels and console panels, touch panel materials, smart keys, etc. These devices are required to be used in harsh environments, and there is an increasing demand for glass with higher strength.

[0003] Glass-ceramics, which have increased strength, are glass-ceramics made by precipitating crystals inside the glass, and are known to have superior mechanical strength to amorphous glass.

[0004] Chemical strengthening is a known method for increasing the strength of glass. The alkali components present in the surface layer of the glass are exchanged with alkali components with a larger ionic radius to form a compressive stress layer in the surface layer. A high compressive stress value in the compressive stress layer can suppress crack propagation and increase mechanical strength.

[0005] Patent Document 1 discloses the material composition of a chemically strengthenable crystallized glass substrate for information recording media. It states that the α-cristobalite crystallized glass described in Patent Document 1 can be chemically strengthened and can be used as a high-strength material substrate. However, crystallized glass for information recording media, such as hard disk substrates, was not designed for use in harsh environments.

[0006] Furthermore, as the applications of crystallized glass have expanded, there has been a demand for crystallized glass to be easily produced and further for it to be possible to process the crystallized glass into various three-dimensional shapes. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2008-254984 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide easily processable crystallized glass capable of achieving a high compressive stress value on the surface thereof, and to provide a strengthened crystallized glass thereof.

[0009] The present invention provides the following: (Configuration 1) The glass-ceramics contains, as a main crystalline phase, one or more selected from α-cristobalite and α-cristobalite solid solution, In terms of oxide, mass % SiO2 content is 50.0% to 75.0%. The content of Li2O component is 3.0% to 10.0%. The content of Al2O3 component is 5.0% or more and less than 15.0%. B2O3 content is over 0% and 10.0% or less Glass-ceramics. (Configuration 2) In terms of oxide, mass % The content of ZrO2 component is more than 0% and 10.0% or less, The total content of Al2O3 and ZrO2 components is 10.0% or more 2. The glass-ceramics according to claim 1, wherein (Configuration 3) In terms of oxide, mass % The content of K2O component is 0% to 5.0%. P2O5 content: 0% to 10.0% 3. The glass-ceramics according to claim 1 or 2, wherein (Configuration 4) In terms of oxide, mass % Na2O content is 0% to 4.0%. MgO content: 0% to 4.0% CaO content is 0% to 4.0%. SrO content is 0% to 4.0%. BaO content is 0% to 5.0%. ZnO content: 0% to 10.0% Sb2O3 content: 0% to 3.0% 4. The crystallized glass according to any one of configurations 1 to 3, wherein (Configuration 5) In terms of oxide, mass % Nb2O5 content is 0% to 5.0%. Ta2O5 content is 0% to 6.0%. TiO2 content is 0% or more and less than 1.0% 5. The crystallized glass according to any one of claims 1 to 4, wherein (Configuration 6) 6. The crystallized glass according to any one of claims 1 to 5, having a glass transition temperature (Tg) of 610°C or lower. (Configuration 7) 7. A tempered glass-ceramics obtained by tempering the glass-ceramics according to any one of Configurations 1 to 6, which has a compressive stress layer on its surface. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide easily processable glass-ceramics that can achieve a high compressive stress value on the surface, and to provide strengthened glass-ceramics.

[0011] The crystallized glass and tempered crystallized glass of the present invention can be used as protective materials for devices, taking advantage of their high strength and processability. They can be used as cover glass or housings for smartphones, components for portable electronic devices such as tablet PCs and wearable devices, and components for protective protectors and head-up display substrates used in transportation vehicles such as cars and airplanes. They can also be used for other electronic devices and machinery, building components, solar panel components, projector components, and cover glass (windshields) for eyeglasses and watches. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following will explain in detail the embodiments and examples of the crystallized glass and strengthened crystallized glass of the present invention, but the present invention is not limited to the following embodiments and examples, and can be carried out by making appropriate modifications within the scope of the object of the present invention.

[0013] The crystallized glass of the present invention is a crystallized glass containing, as a main crystalline phase, one or more types selected from α-cristobalite and α-cristobalite solid solution, In terms of oxide, mass % SiO2 content is 50.0% to 75.0%. The content of Li2O component is 3.0% to 10.0%. The content of Al2O3 component is 5.0% or more and less than 15.0%. The content of B2O3 component is more than 0% and 10.0% or less, is.

[0014] This main crystalline phase and composition lower the glass transition temperature, improve the melting properties of the raw materials, and facilitate manufacturing, and the resulting crystallized glass is easier to process, such as 3D processing. Furthermore, by strengthening this crystallized glass, a strengthened crystallized glass can be obtained in which the compressive stress layer formed on the surface has a high compressive stress value. The Tg is preferably 610°C or lower, more preferably 600°C or lower, and further preferably 590°C or lower.

[0015] The glass-ceramics of the present invention contain at least one crystal phase selected from α-cristobalite and α-cristobalite solid solution as the main crystal phase, and the glass-ceramics in which these crystal phases are precipitated have high mechanical strength. Here, the term "main crystalline phase" in this specification corresponds to the crystalline phase that is most abundant in the glass-ceramics as determined from the peaks in the X-ray diffraction pattern.

[0016] In this specification, the content of each component is expressed in mass% converted to oxide unless otherwise specified. Here, "oxide conversion" refers to the amount of oxide of each component contained in the crystallized glass, expressed in mass%, when the total mass of the oxides is 100 mass%, assuming that all the components constituting the crystallized glass are decomposed and converted to oxides. In this specification, A% to B% means A% or more and B% or less.

[0017] The SiO2 component is an essential component required to form one or more selected from α-cristobalite and α-cristobalite solid solutions. If the SiO2 content exceeds 75.0%, excessive viscosity increase and deterioration of meltability may occur, while if it is less than 50.0%, devitrification resistance may deteriorate. Preferably, the upper limit is 75.0% or less, 74.0% or less, 73.0% or less, 72.0% or less, or 70.0% or less, and preferably the lower limit is 50.0% or more, 55.0% or more, 58.0% or more, or 60.0% or more.

[0018] The Li2O component is a component that improves the meltability of the base glass, but if its content is less than 3.0%, this effect may not be obtained and the base glass may become difficult to melt, while if its content exceeds 10.0%, the formation of lithium disilicate crystals may increase. The Li2O component also contributes to chemical strengthening. Preferably, the lower limit is 3.0% or more, 3.5% or more, 4.0% or more, 4.5% or more, 5.0% or more, or 5.5% or more, and preferably the upper limit is 10.0% or less, 9.0% or less, 8.5% or less, or 8.0% or less.

[0019] The Al2O3 component is a component suitable for improving the mechanical strength of crystallized glass. If the Al2O3 content is 15.0% or more, the melting property and devitrification resistance may be deteriorated, and if it is less than 5.0%, the effect of improving the mechanical strength may be poor. Preferably, the upper limit is less than 15.0%, 14.5% or less, 14.0% or less, 13.5% or less, or 13.0% or less, and the lower limit can be 5.0% or more, 5.5% or more, 5.8% or more, 6.0% or more, 6.5% or more, or 8.0% or more.

[0020] The B2O3 component is a suitable component for lowering the glass transition temperature of the crystallized glass, but if the amount exceeds 10.0%, the chemical durability may be easily reduced. Preferably, the upper limit is 10.0% or less, 8.0% or less, 7.0% or less, 5.0% or less, or 4.0% or less, and preferably the lower limit is more than 0%, 0.001% or more, 0.01% or more, 0.05% or more, 0.10% or more, or 0.30% or more.

[0021] The ZrO2 component is a component that can improve the mechanical strength, but if the amount exceeds 10.0%, there is a risk that the meltability will deteriorate. The upper limit is preferably 10.0% or less, 9.0% or less, 8.5% or less, or 8.0% or less, and the lower limit can be more than 0%, 1.0% or more, 1.5% or more, or 2.0% or more.

[0022] If the sum of the contents of the Al2O3 component and the ZrO2 component, [Al2O3 + ZrO2], is high, the compressive stress on the surface increases when strengthened. Preferably, the lower limit of [Al2O3 + ZrO2] is set to 10.0% or more, 11.0% or more, 12.0% or more, or 13.0% or more. On the other hand, if it is contained in excess, the meltability may be deteriorated. Therefore, the upper limit of [Al2O3 + ZrO2] is preferably set to 22.0% or less, 21.0% or less, 20.0% or less, or 19.0% or less.

[0023] The lower limit of the total content of the SiO2 component, Li2O component, Al2O3 component, and B2O3 component can be preferably set to 75.0% or more, 80.0% or more, 83.0% or more, or 85.0% or more.

[0024] The P2O5 component is an optional component that can be added to act as a crystal nucleating agent for glass, but if the amount exceeds 10.0%, there is a risk that devitrification resistance will deteriorate and glass phase separation will be more likely to occur. Preferably, the upper limit is 10.0% or less, 8.0% or less, 6.0% or less, 5.0% or less, or 4.0% or less, and the lower limit can be 0% or more, 0.5% or more, 1.0% or more, or 1.5% or more.

[0025] The K2O component is an optional component that contributes to chemical strengthening. The lower limit can be set to 0% or more, 0.1% or more, 0.3% or more, or 0.5% or more. Moreover, if it is contained in excess, crystal precipitation may become difficult in some cases. Therefore, the upper limit can be preferably set to 5.0% or less, 4.0% or less, 3.5% or less, or 3.0% or less.

[0026] The Na2O component is an optional component involved in chemical strengthening. If it is contained in excess, it may be difficult to obtain the desired crystal phase. The upper limit can be set to preferably 4.0% or less, 3.5% or less, more preferably 3.0% or less, and even more preferably 2.5% or less.

[0027] The MgO, CaO, SrO, BaO, and ZnO components are optional components that improve low-temperature melting properties and can be included within a range that does not impair the effects of the present invention. Therefore, the upper limit of the MgO component can be preferably set to 4.0% or less, 3.5% or less, 3.0% or less, or 2.5% or less. The lower limit of the MgO component can be preferably set to 0% or more, more than 0%, 0.3% or more, or 0.4% or more. The upper limit of the CaO component can be preferably set to 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less. The upper limit of the SrO component can be preferably set to 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less. The upper limit of the BaO component can be preferably set to 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less. The upper limit of the ZnO component can be preferably set to 10.0% or less, 9.0% or less, 8.5% or less, 8.0% or less, or 7.5% or less, and the lower limit of the ZnO component can be preferably set to 0% or more, more than 0%, 0.5% or more, or 1.0% or more.

[0028] The crystallized glass may or may not contain Nb2O5, Ta2O5, and TiO2 components, as long as the effects of the present invention are not impaired. The Nb2O5 component is an optional component that improves the mechanical strength of the crystallized glass when contained in an amount greater than 0%. The upper limit can be preferably 5.0%, 4.0%, 3.5%, or 3.0%. The Ta2O5 component is an optional component that improves the mechanical strength of the crystallized glass when contained in an amount greater than 0%. The upper limit can be preferably 6.0%, 5.5%, 5.0%, or 4.0%. The TiO2 component is an optional component that improves the chemical durability of the crystallized glass when contained in an amount greater than 0%. The upper limit can be preferably less than 1.0%, 0.8%, 0.5%, or 0.1%.

[0029] The glass-ceramics may or may not contain La2O3, Gd2O3, Y2O3, WO3, TeO2, and Bi2O3 components, as long as the effects of the present invention are not impaired. The blending amount of each component can be 0% to 2.0%, 0% to less than 2.0%, or 0% to 1.0%.

[0030] Furthermore, the crystallized glass may or may not contain other components not mentioned above, as long as the properties of the crystallized glass of the present invention are not impaired. For example, metal components such as Yb, Lu, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo (including oxides of these metals) may be included.

[0031] The Sb2O3 component may be contained as a fining agent for glass. However, excessive Sb2O3 content may result in poor transmittance in the short wavelength region of the visible light spectrum. Therefore, the upper limit of Sb2O3 content is preferably set to 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.6% or less.

[0032] Furthermore, as a fining agent for glass, in addition to the Sb2O3 component, the glass may or may not contain one or more elements selected from the group consisting of SnO2, CeO2, As2O3, and F, NOx, and SOx. However, the upper limit of the content of the fining agent can be set to preferably 2.0% or less, more preferably 1.0% or less, and most preferably 0.6% or less.

[0033] On the other hand, since there has been a recent trend to refrain from using Pb, Th, Tl, Os, Be, Cl and Se as harmful chemical substances, it is preferable that these components are substantially not contained.

[0034] The crystallized glass of the present invention can form a compressive stress layer on its surface. The compressive stress CS (MPa) of the compressive stress layer is preferably 650 MPa or more, more preferably 680 MPa or more, and even more preferably 700 MPa or more. The upper limit is, for example, 1400 MPa or less, 1300 MPa or less, 1200 MPa or less, or 1100 MPa or less. By having such a compressive stress value, it is possible to suppress the development of cracks and increase mechanical strength.

[0035] The thickness DOLzero (μm) of the compressive stress layer is not limited because it depends on the thickness of the crystallized glass, but for example, when the thickness of the crystallized glass substrate is 0.70 mm, the lower limit of the thickness of the compressive stress layer can be 70 μm or more, or 100 μm or more, and the upper limit is, for example, 180 μm or less, or 150 μm or less.

[0036] When using crystallized glass as the substrate, the lower limit of the thickness of the substrate is preferably 0.10 mm or more, more preferably 0.30 mm or more, more preferably 0.40 mm or more, and even more preferably 0.50 mm or more, and the upper limit of the thickness of the crystallized glass is preferably 2.00 mm or less, more preferably 1.50 mm or less, more preferably 1.10 mm or less, more preferably 1.00 mm or less, more preferably 0.90 mm or less, and even more preferably 0.80 mm or less.

[0037] Crystallized glass can be produced by the following method: raw materials are mixed uniformly so that each component falls within a predetermined content range, and then melt-molded to produce base glass. This base glass is then crystallized to produce crystallized glass.

[0038] The heat treatment for crystallization may be carried out in one stage or at two temperatures. In the two-stage heat treatment, a nucleation step is first performed by heat treatment at a first temperature, and after this nucleation step, a crystal growth step is performed by heat treatment at a second temperature higher than that of the nucleation step. The first temperature of the two-stage heat treatment is preferably 450° C. to 750° C., more preferably 500° C. to 720° C., and even more preferably 550° C. to 680° C. The holding time at the first temperature is preferably 30 minutes to 2000 minutes, and more preferably 180 minutes to 1440 minutes. The second temperature of the two-stage heat treatment is preferably 550° C. to 850° C., more preferably 600° C. to 800° C. The holding time at the second temperature is preferably 30 minutes to 600 minutes, more preferably 60 minutes to 400 minutes.

[0039] In one-stage heat treatment, the nucleation process and the crystal growth process are carried out consecutively at a single temperature. Typically, the temperature is raised to a predetermined heat treatment temperature, and after reaching that temperature, the temperature is maintained for a certain period of time, and then the temperature is lowered. In the case of one-stage heat treatment, the heat treatment temperature is preferably 600 to 800° C., more preferably 630 to 770° C. The holding time at the heat treatment temperature is preferably 30 to 500 minutes, more preferably 60 to 400 minutes.

[0040] Methods for forming a compressive stress layer in strengthened crystallized glass include chemical strengthening, in which an alkali component present in the surface layer of the crystallized glass is subjected to an exchange reaction with an alkali component having a larger ionic radius to form a compressive stress layer in the surface layer, thermal strengthening, in which the crystallized glass is heated and then rapidly cooled, and ion implantation, in which ions are implanted into the surface layer of the crystallized glass.

[0041] Chemical strengthening can be carried out, for example, by the following steps: Crystallized glass is brought into contact with or immersed in a molten salt of a salt containing potassium or sodium, such as potassium nitrate (KNO3), sodium nitrate (NaNO3), or a mixed or composite salt thereof. This treatment of contacting or immersing in a molten salt (chemical strengthening treatment) may be carried out in one step or two steps.

[0042] For example, in the case of a two-stage chemical strengthening treatment, first, the steel is contacted with or immersed in sodium salt or a mixed salt of potassium and sodium heated at 350°C to 550°C for 1 to 1440 minutes, preferably 30 to 500 minutes, followed by second, the steel is contacted with or immersed in potassium salt or a mixed salt of potassium and sodium heated at 350°C to 550°C for 1 to 1440 minutes, preferably 60 to 600 minutes. In the case of one-stage chemical strengthening treatment, the material is brought into contact with or immersed in a salt containing potassium or sodium, or a mixed salt thereof, heated at 350°C to 550°C for 1 to 1,440 minutes.

[0043] The chemical strengthening of the crystallized glass of the present invention may be carried out in one step or in multiple steps. However, in order to efficiently increase the surface compressive stress and the thickness of the compressive stress layer, a two-step strengthening process is preferred, in which first, strengthening is carried out with a molten salt of sodium alone or a mixture of sodium and potassium, and then, second, strengthening is carried out with a molten salt of potassium alone.

[0044] The thermal strengthening method is not particularly limited, but for example, by heating crystallized glass to 300°C to 600°C and then rapidly cooling it by water cooling and / or air cooling, a compressive stress layer can be formed due to the temperature difference between the surface and the interior of the glass. Note that by combining this with the above-mentioned chemical treatment method, the compressive stress layer can be formed more effectively.

[0045] The ion implantation method is not particularly limited, but for example, ions are implanted into the surface of the crystallized glass by bombarding the surface with an acceleration energy and acceleration voltage that are not enough to destroy the surface. By subsequently performing a heat treatment as necessary, a compressive stress layer can be formed on the surface in the same way as with other methods. [Example]

[0046] Examples 1 to 25, Reference Example 1, Comparative Examples 1 and 2 As raw materials for each component of the crystallized glass, raw materials such as oxides, hydroxides, carbonates, nitrates, fluorides, chlorides, metaphosphate compounds, etc. were selected, and these raw materials were weighed and uniformly mixed to obtain the compositions shown in Tables 1 to 4.

[0047] Next, the mixed raw materials were placed in a platinum crucible and melted in an electric furnace at 1300°C to 1600°C for 2 to 24 hours, depending on the melting difficulty of the glass composition. The molten glass was then stirred to homogenize it, and the temperature was lowered to 1000°C to 1450°C before being poured into a mold and slowly cooled to produce base glass. The obtained base glass was heated under the crystallization conditions shown in Tables 1 to 4 to produce crystallized glass.

[0048] The crystalline phase of the glass-ceramics was determined from the angles of peaks appearing in X-ray diffraction patterns obtained using an X-ray diffraction analyzer (D8Discover, manufactured by Bruker). When the X-ray diffraction patterns of the glass-ceramics of Examples 1 to 25, Reference Example 1, and Comparative Examples 1 and 2 were examined, a main peak (the peak with the highest intensity and largest peak area) was observed at a position corresponding to the peak pattern of α-cristobalite and / or α-cristobalite solid solution, indicating that α-cristobalite and / or α-cristobalite solid solution had precipitated as the main crystalline phase in all cases.

[0049] The glass transition temperatures (Tg) of the crystallized glasses of Examples 1 to 25, Comparative Examples 1 and 2, and Reference Example 1 were measured in accordance with the Japan Optical Glass Industry Association standard JOGIS08-2019, "Method for measuring thermal expansion of optical glass." The results are shown in Tables 1 to 4. Tables 1 to 4 show that the crystallized glasses of the Examples have lower Tg than the Reference Example.

[0050] In Examples 2 to 4, 6 to 12 and Comparative Examples 1 and 2, the produced crystallized glass was cut and ground, and then polished parallel to each other to obtain a crystallized glass substrate with the thickness shown in Table 5. In the Examples, the crystallized glass substrate was used as a base material and subjected to two-stage strengthening to obtain a chemically strengthened crystallized glass substrate. Specifically, the glass substrate was immersed in molten NaNO3 at the temperature and for the time shown in Table 5 (first stage), and then in molten KNO3 at the temperature and for the time shown in Table 5 (second stage).

[0051] The substrates obtained in Comparative Examples 1 and 2 were strengthened by one step by immersing them in KNO molten salt at the temperature and for the time shown in Table 5. Comparative Examples 1 and 2 are chemically strengthened crystallized glass substrates corresponding to Examples 25 and 27 described in Patent Document 1.

[0052] The compressive stress (CS) of the outermost surface was measured using a glass surface stress meter FSM-6000LE series manufactured by Orihara Manufacturing Co., Ltd. A light source with a wavelength of 596 nm was used as the light source for the measuring instrument.

[0053] The refractive index used in the CS measurements was the value at 596 nm, calculated using a second-order approximation formula from the measured refractive index values ​​at the wavelengths of the C-line, d-line, F-line, and g-line in accordance with the V-block method specified in JIS B 7071-2:2018.

[0054] The photoelastic constant used in the CS measurement was the value of the photoelastic constant at 596 nm. The photoelastic constant can be calculated using a quadratic approximation formula from the measured values ​​of the photoelastic constant at wavelengths of 435.8 nm, 546.1 nm, and 643.9 nm. In the examples, a representative value of 29.6 was used as the photoelastic constant.

[0055] The photoelastic constant (β) was determined by polishing the specimen on both sides to form a disk with a diameter of 25 mm and a thickness of 8 mm, applying a compressive load in a specified direction, measuring the optical path difference at the center of the glass, and using the relational expression δ = β d F. In this relational expression, the optical path difference is expressed as δ (nm), the glass thickness as d (mm), and the stress as F (MPa).

[0056] The depth DOLzero (μm) when the compressive stress of the compressive stress layer was 0 MPa was measured using a scattered light photoelastic stress meter SLP-1000. A light source with a wavelength of 640 nm was used as the measurement light source. The refractive index at a wavelength of 640 nm was calculated using a second-order approximation formula from the measured refractive index values ​​at the wavelengths of C-line, d-line, F-line, and g-line in accordance with the V-block method specified in JIS B 7071-2:2018.

[0057] The photoelastic constant at a wavelength of 640 nm used in DOLzero measurements can be calculated using a quadratic approximation formula from the measured photoelastic constants at wavelengths of 435.8 nm, 546.1 nm, and 643.9 nm. In this example, 29.2 was used as a representative value.

[0058] Comparative Examples 1 and 2 were measured using the same method as Comparative Examples 1 and 2 of PCT / JP2020 / 9459.

[0059] The results are shown in Table 5. Table 5 shows that the strengthened glass-ceramics of the present invention has a deep compressive stress layer with high CS on the surface and is therefore strong.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4]

[0064] [Table 5]

Claims

1. The glass-ceramics contains, as a main crystalline phase, one or more selected from α-cristobalite and α-cristobalite solid solution, In terms of oxide, mass % SiO ２ The content of the ingredients is 50.0% to 75.0%. Li ２ The content of O component is 3.0% to 10.0%. Al ２ O ３ The content of the ingredient is 10.1% or more but less than 15.0%; B ２ O ３ The content of the ingredient is more than 0% and 10.0% or less Glass-ceramics.

2. In terms of oxide, mass % ZrO ２ The content of the ingredient is more than 0% and 10.0% or less, Al ２ O ３ Ingredients and ZrO ２ The total content of ingredients is 10.0% or more 2. The crystallized glass according to claim 1, wherein

3. In terms of oxide, mass % K ２ The content of O component is 0% to 5.0%. P ２ O ５ Ingredient content: 0% to 10.0% 3. The crystallized glass according to claim 1, wherein:

4. In terms of oxide, mass % Na ２ O content is 0% to 4.0%; The content of MgO component is 0% to 4.0%. The content of CaO component is 0% to 4.0%. The content of SrO component is 0% to 4.0%. The content of BaO component is 0% to 5.0%; ZnO content is 0% to 10.0%; Sb ２ O ３ Ingredient content: 0% to 3.0% 4. The crystallized glass according to claim 1, wherein:

5. In terms of oxide, mass % Nb ２ O ５ Ingredient content: 0% to 5.0% Ta ２ O ５ Ingredient content: 0% to 6.0% TiO ２ Ingredient content is 0% or more but less than 1.0% 5. The crystallized glass according to claim 1, wherein:

6. 6. The crystallized glass according to claim 1, which has a glass transition temperature (Tg) of 610° C. or lower.

7. 7. A strengthened glass-ceramics obtained by strengthening the glass-ceramics according to claim 1, which has a compressive stress layer on its surface.

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