Crystallized glass and three-dimensionally shaped cover glass

Abstract

The present invention pertains to a crystallized glass which has a haze value of 0.4% or less, and an average transmittance of 85% or more (in terms of a thickness of 0.7 mm) with respect to a wavelength of 380-780 nm, and in which the content proportions as indicated in oxide-based mole percentage are 55-75% for SiO2, 0.1-5% for Al2O3, 0.5-5% for P2O5, 0-10% for B2O3, 15-30% for Li2O, 0-5% for Na2O, 0-3% for K2O, 2.1-10% for ZrO2, 0-5% for TiO2, 0-2% for SnO2, 0-5% for Y2O3, and 0-5% for MgO, and the value indicated by formula (1) is 6-500.

Description

Glass-ceramics and three-dimensional cover glass

[0001] The present invention relates to a crystallized glass and a three-dimensional cover glass made of the crystallized glass.

[0002] Thin, high-strength chemically strengthened glass is used as the cover glass for display devices of mobile devices such as mobile phones and smartphones, and for in-vehicle display components such as instrument panels and head-up displays (HUDs). These display devices may require a three-dimensional (curved) cover glass to improve operability and visibility. Three-dimensional cover glass is produced by heating a flat glass plate and bending it using a forming mold (also referred to as three-dimensional bending or three-dimensional forming).

[0003] As a crystalline phase in glass-ceramics applicable to such three-dimensionally shaped cover glasses, lithium disilicate crystals, which have high strength, have attracted attention. For example, Patent Documents 1 and 2 disclose glass-ceramics containing lithium disilicate and petalite crystals. Specifically, Patent Document 1 discloses that by combining three crystalline phases, lithium disilicate, petalite, and β-eucryptite, it is possible to achieve good fracture strength and tensile bending strength of microcrystalline glass. Furthermore, Patent Document 2 discloses that by forming a glass-ceramic composition containing lithium disilicate and petalite crystals, it is possible to achieve high mechanical strength and fracture strength.

[0004] Chinese Patent No. 111018356 International Publication No. 2016 / 057748

[0005] While the lithium disilicate crystalline phase can increase the strength of the glass-ceramics, it tends to become white due to its rapid crystal growth rate. Therefore, in order to achieve high transmittance, Patent Documents 1 and 2 contain petalite crystals to suppress the crystal growth of lithium disilicate and control the average crystal size.

[0006] However, when other crystals are contained in addition to the desired lithium disilicate crystals, the crystallinity is higher than when the desired crystals are contained in a single phase, making it difficult to bend the glass into a three-dimensional shape. Furthermore, when the crystallinity is high and the crystals constituting the crystalline phase are crystals that do not undergo ion exchange with alkali metal ions even after chemical strengthening, the proportion of exchangeable alkali metal ions in the glass-ceramics is low, making it difficult to perform chemical strengthening. Furthermore, when the crystallinity is the same, the strength of glass-ceramics containing the desired crystals and other crystals is lower than that of glass-ceramics containing the desired crystals in a single phase due to the presence of the other crystals.

[0007] Therefore, an object of the present invention is to provide a crystallized glass that achieves high transmittance and low haze while also achieving high strength and high three-dimensional formability and is also excellent in chemical strengthening processability. Another object of the present invention is to provide a three-dimensional shaped cover glass made of the crystallized glass.

[0008] As a result of extensive research into the above-mentioned problems, the present inventors have determined that the composition of the crystallized glass should be within a specific range, and that SiO ２ , Li ２ O and Al ２ O ３ The inventors have found that by making the content ratio of the thickening components satisfy a specific relationship, it is possible to slow down the crystal growth rate of crystals that originally have a fast crystal growth rate, and to make them into fine crystals. As a result, it has been found that it is possible to obtain crystallized glass with high transmittance and low haze value, and this has led to the completion of the present invention.

[0009] That is, the present invention relates to the following [1] to

[11] . [1] A crystallized glass having a crystalline phase, wherein the haze value converted to a thickness of 0.7 mm is 0.4% or less, the average transmittance of light having a wavelength of 380 to 780 nm converted to a thickness of 0.7 mm is 85% or more, and the content expressed as mole percentage based on oxides is: SiO ２ 55 to 75% Al ２ O ３ 0.1 to 5% of P ２O ５ 0.5 to 5%, B ２ O ３ 0 to 10%, Li ２ 15-30% O, Na ２ O 0-5%, K ２ O 0 to 3%, ZrO ２ 2.1 to 10% of TiO ２ 0 to 5%, SnO ２ 0 to 2%, Y ２ O ３ and MgO is 0 to 5%, and the value represented by the following formula (1) is 6 to 500.

[0010]

[0011] (In formula (1), [SiO ２ ], [Li ２ O] and [Al ２ O ３ ] respectively represent SiO ２ , Li ２ O and Al ２ O ３ [LAS] represents the content (mol%) of SiO in the crystallized glass. ２ , Li ２ O and Al ２ O ３ [A] represents the total content (mol%) of the thickening components in the crystallized glass.

[0012] [2] SiO in crystallized glass ２ , Li ２ O and Al ２ O ３ The content ratios of these in mole percentages are expressed as [SiO ２ ], [Li ２ O] and [Al ２ O ３ ], 66≦[{[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２O])}×100) (%)≦77. ２ , Li ２ O and Al ２ O ３ The content ratios of these in mole percentages are expressed as [SiO ２ ], [Li ２ O] and [Al ２ O ３ ], 1≦[{[Al ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ [4] The crystallized glass according to the above [1] or [2], wherein the crystal phase satisfies the relationship of Li x 100] (%)≦5. ２ Si ２ O ５ In the crystalline phase, ２ Si ２ O ５ [5] The crystallized glass according to any one of [1] to [3], wherein the content of the Li crystals in the crystal phase is 50% by volume or more. ２ Si ２ O ５ [6] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions. [7] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions. [8] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions. [9] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions.

[10] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions.

[11] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions.

[12] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions.

[13] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions.

[14] The glass-ceramics according to any one of [1] to [5], which contains Li ions that can be ion-exchanged with Na ions when immersed in a molten salt containing Na ions. [1 ２ The content of O is determined by the ratio of Na to the content of O in the center of the crystallized glass. ２ The glass-ceramics according to any one of the above [1] to [5], wherein the content of O is higher than that of O, and the difference is 1% or more. [8] The glass-ceramics according to the above [7], wherein the surface compressive stress is 500 MPa or more and the compressive stress depth is 70 μm or more. [9] The fracture toughness value is 0.8 MPa m １／２The crystallized glass according to any one of [7] to [8] above, wherein the ST limit value determined by the following test method is 10,000 to 300,000 MPa μm.

[10] The crystallized glass according to any one of [7] to [9] above, wherein the ST limit value determined by the following test method is 10,000 to 300,000 MPa μm. (Test Method) A plurality of test glass plates, each 15 mm square and 0.7 mm thick with a mirror-finished surface, are chemically strengthened under various conditions to prepare different ST values ​​(tensile stress integral). Using a Vickers tester, a diamond indenter with a 90° tip angle is struck into the center of the test glass plate to break the test glass plate, and the number of broken pieces is counted as the number of broken pieces. The test is started with a diamond indenter impact load of 1 kgf. If the test glass plate does not break, the impact load is increased by 1 kgf increments, and the test is repeated until the test glass plate breaks, and the number of broken pieces is counted at the first break. The number of fractures is plotted against the ST value of the test glass plate, and the ST value at which the number of fractures becomes 10 is read and taken as the ST limit.

[11] A three-dimensional shaped cover glass, which is made of the crystallized glass according to any one of [1] to

[10] , and which has a three-dimensional shape with a curved surface portion forming a three-dimensional curved surface.

[0013] According to the present invention, a glass-ceramic having a high transmittance and a low haze value, a high strength, and a high three-dimensional formability, and excellent chemical strengthening processability can be obtained. The three-dimensional cover glass obtained by providing a curved surface portion forming a three-dimensional curved surface to this glass-ceramic is suitable as a cover glass for display devices of mobile devices such as mobile phones and smartphones, and for in-vehicle display components such as instrument panels and HUDs.

[0014] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below. Furthermore, in this specification, the term "to" indicating a range of values ​​is used to mean that the values ​​before and after it are included as the lower limit and upper limit.

[0015] <<Ceramics>> The crystallized glass according to this embodiment has a crystalline phase. The oxide-based mole percentage content preferably satisfies the following: SiO ２55 to 75% Al ２ O ３ 0.1 to 5% of P ２ O ５ 0.5 to 5%, B ２ O ３ 0 to 10%, Li ２ 15-30% O, Na ２ O 0-5%, K ２ O 0 to 3%, ZrO ２ 2.1 to 10% of TiO ２ 0 to 5%, SnO ２ 0 to 2%, Y ２ O ３ and MgO 0 to 5%.

[0016] Here, in this specification, the term "crystallized glass having a crystalline phase" refers to glass in which diffraction peaks indicating crystals are observed in the XRD pattern obtained by powder X-ray diffraction (XRD). The crystallized glass is obtained by heating amorphous glass in which no diffraction peaks indicating crystals are observed to precipitate crystals. The XRD measurement is performed using CuKα radiation in the range of 2θ of 10° to 80°, and when a diffraction peak appears, the precipitated crystals can be identified by, for example, the three-strong ray method, thereby identifying the crystalline structure of the crystals constituting the crystalline phase.

[0017] In addition, in this specification, the composition of the crystallized glass can be identified using conventionally known methods. For example, it can be identified by wet chemical analysis or quantitative analysis using a fluorescent X-ray calibration curve. Furthermore, the composition of the amorphous glass before crystallization and the composition of the crystallized glass according to this embodiment in which crystals have been precipitated can be considered to be the same. Furthermore, in this specification, crystallized glass that has been subjected to chemical strengthening is referred to as "chemically strengthened glass." However, the matrix composition of the chemically strengthened glass can be considered to be the same as the composition of the crystallized glass before chemical strengthening. Except in cases where extreme ion exchange treatment has been performed, the composition of the portion deeper than the compressive stress depth (DOL) of the chemically strengthened glass can be considered to be the same as the matrix composition of the chemically strengthened glass. In other words, the composition at the center of the plate thickness of the chemically strengthened glass is the same as the matrix composition of the chemically strengthened glass.

[0018] In addition, the crystallized glass according to this embodiment has SiO ２ , Li ２ O and Al ２ O ３ The content ratio (mol%) of each of [SiO ２ ], [Li ２ O] and [Al ２ O ３ ], and SiO ２ , Li ２ O and Al ２ O ３ When the total content (mol%) of the thickening components is [LAS] and the total content (mol%) of the thickening components is [A], the value represented by the following formula (1) is preferably 6 to 500. Here, the thickening components are ZrO ２ , Y ２ O ３ , TiO ２ , and SnO ２ Therefore, the total content of the thickening components is ZrO ２ , Y ２ O ３ , TiO ２ , and SnO ２ The content ratio (mol%) of each of [ZrO ２ ], [Y ２ O ３ ], [TiO ２ ] and [SnO ２ ], {[ZrO ２ ]+[Y ２ O ３ ]+[TiO ２ ]+[SnO ２ ]} means the total amount of the content ratio represented by the formula:

[0019]

[0020] Considering that the crystallized glass according to this embodiment is intended for use as a cover glass, particularly a three-dimensional cover glass, the haze value, calculated as a 0.7 mm thickness, is preferably 0.4% or less, and the average transmittance, calculated as a 0.7 mm thickness, for light having a wavelength of 380 to 780 nm is preferably 85% or more, and it is more preferable that both the haze value and the average transmittance are satisfied. Here, the haze value is a value determined using a C illuminant in accordance with JIS K3761:2000. The average transmittance for light having a wavelength of 380 to 780 nm means the in-line transmittance.

[0021] The crystallized glass will be described in detail below.

[0022] <Composition and Crystals> The composition of the crystallized glass according to this embodiment preferably satisfies the following: SiO ２ 55 to 75% Al ２ O ３ 0.1 to 5% of P ２ O ５ 0.5 to 5%, B ２ O ３ 0 to 10%, Li ２ 15-30% O, Na ２ O 0-5%, K ２ O 0 to 3%, ZrO ２ 2.1 to 10% of TiO ２ 0 to 5%, SnO ２ 0 to 2%, Y ２ O ３ and MgO 0 to 5%.

[0023] The above composition is generally Li ２ O-Al ２ O ３ -SiO ２ This glass is called a "Li-based" glass, and its composition makes it easy to achieve high strength by chemical strengthening treatment, where Li ions in the glass are exchanged with Na ions in the molten salt. One of the factors that determine the crystal species that make up the crystalline phase in crystallized glass is the Li-based glass. ２ O, Al ２ O ３ and SiO ２ In addition, in this specification, the ratio of SiO２ , Al ２ O ３ , and Li ２ O-containing crystals, SiO ２ and Li ２ O-containing crystals, and SiO ２ and Al ２ O ３ Crystals containing these are sometimes referred to collectively as LAS crystals.

[0024] The above Li ２ O-Al ２ O ３ -SiO ２ The crystal seeds in the crystallized glass obtained from the system are, for example, β-spodumene crystals (LiAlSi ２ O ６ ), lithium disilicate (Li ２ Si ２ O ５ ), petalite (LiAlSi ４ O １０ ), β-quartz (including bergerite) (Li ｘ Al ｘ Si ３－ｘ O ６ ), lithium metasilicate (Li ２ SiO ３ ), eucryptite (LiAlSiO ４ ), mullite (Al ４＋２ｘ Si ２－２ｘ O １０－ｘ , 0.2≦x≦0.5), etc.

[0025] The crystal species in the crystallized glass according to this embodiment may be appropriately selected according to the desired properties. For example, when a crystal phase capable of ion exchange by chemical strengthening treatment is desired, lithium disilicate, β-spodumene crystal, petalite, β-quartz, and lithium metasilicate are preferred, with lithium disilicate, β-spodumene crystal, and lithium metasilicate being more preferred, and lithium disilicate and β-spodumene crystal being even more preferred. When a high-strength crystallized glass is desired, β-spodumene crystal, lithium disilicate, petalite, β-quartz, lithium metasilicate, and mullite are preferred, with lithium disilicate and mullite being more preferred. When a crystallized glass with high transmittance and low haze value is desired, β-quartz and lithium metasilicate are preferred. However, by making the crystallized glass according to this embodiment have a composition that satisfies the above formula (1), it is possible to realize high transmittance and low haze value even for crystal species such as β-spodumene crystal, lithium disilicate, and eucryptite, which have a fast crystal growth rate and have previously been considered difficult to achieve high transmittance and low haze value.

[0026] The crystallinity of the crystallized glass according to this embodiment, i.e., the content of the crystalline phase, is preferably 20 to 90% by volume, more preferably 25 to 85% by volume, even more preferably 30 to 83% by volume, and even more preferably 35 to 80% by volume. From the viewpoint of increasing the mechanical strength of the crystallized glass, the crystallinity is preferably 20% by volume or more, more preferably 25% by volume or more, even more preferably 30% by volume or more, and even more preferably 35% by volume or more. Furthermore, from the viewpoint of maintaining high transmittance and low haze value, and from the viewpoint of three-dimensional formability, the crystallinity is preferably 90% by volume or less, more preferably 85% by volume or less, even more preferably 83% by volume or less, and even more preferably 80% by volume or less. Furthermore, when the crystalline phase contains two or more types of crystals, the total of their contents preferably satisfies the above range. The crystallinity herein can be calculated by the Rietveld method from the diffraction intensity of the XRD pattern obtained by powder X-ray diffraction (XRD) measurement. The Rietveld method is described in "Crystal Analysis Handbook" edited by the editorial committee of the Crystallographic Society of Japan (Kyoritsu Shuppan, 1999, pp. 492-499).

[0027] The average particle size (crystallite size) of the crystals that constitute the crystalline phase of the crystallized glass according to this embodiment is preferably 300nm or less, more preferably 200nm or less, even more preferably 150nm or less, and even more preferably 100nm or less, from the viewpoint of realizing higher transmittance and low haze value.In addition, the crystallite size of the crystal in this specification can be calculated by Rietveld method from the diffraction intensity of the XRD pattern obtained by XRD measurement.

[0028] The crystalline phase of the crystallized glass according to this embodiment is, for example, lithium disilicate (Li) from the viewpoint of being able to obtain a crystallized glass with high strength while overcoming the conventional problems such as high transparency and low haze value. ２ Si ２ O ５) crystals. In this case, the content of lithium disilicate crystals in the crystalline phase is preferably 50% by volume or more, more preferably 50 to 100% by volume, even more preferably 60 to 100% by volume, even more preferably 70 to 100% by volume, even more preferably 80 to 100% by volume, and particularly preferably 90 to 100% by volume. Here, from the viewpoint of further increasing the strength of the crystallized glass, the content is preferably 50% by volume or more, more preferably 60% by volume or more, even more preferably 70% by volume or more, even more preferably 80% by volume or more, and particularly preferably 90% by volume or more, and may be 100% by volume, i.e., the crystalline phase may be a single phase of lithium disilicate crystals.

[0029] However, this does not exclude the crystalline phase in this embodiment from including crystals other than lithium disilicate crystals. When the crystalline phase in this embodiment includes crystals other than lithium disilicate crystals, the content of lithium disilicate crystals may be, for example, 99 vol% or less, 95 vol% or less, 90 vol% or less, or 80 vol% or less.

[0030] That is, when the crystalline phase of the crystallized glass according to this embodiment contains lithium disilicate crystals, the total content of other crystals other than lithium disilicate is preferably 50% by volume or less, more preferably 20% by volume or less, even more preferably 0 to 20% by volume, and even more preferably 0 to 10% by volume. Here, from the viewpoint of more preferably obtaining the effect of lithium disilicate, the total content of the other crystals is preferably 50% by volume or less, more preferably 20% by volume or less, even more preferably 10% by volume or less, and may be 0% by volume, i.e., a single phase of lithium disilicate. However, when it is desired to obtain the effect of other crystals, the total content of the other crystals may be 1% by volume or more, 5% by volume or more, 10% by volume or more, or 20% by volume or more.

[0031] The other crystals may be LAS crystals other than lithium disilicate, or may be crystals other than LAS crystals. Examples of crystals other than LAS crystals include lithium phosphate, SiO ２ etc.

[0032] The composition of the crystallized glass according to this embodiment may be any composition that can produce the desired crystals as described above, and each component will be specifically described below.

[0033] SiO ２ is a component that constitutes the glass network and is also a component that constitutes the LAS crystals. ２ The content is preferably 55 to 75%, more preferably 57 to 73%, and even more preferably 59 to 71%. From the viewpoint of facilitating the formation of lithium disilicate crystals, the content is preferably 55% or more, more preferably 57% or more, even more preferably 58% or more, even more preferably 59% or more, and particularly preferably 61% or more. From the viewpoint of improving the meltability of the glass, the content is preferably 75% or less, more preferably 73% or less, and even more preferably 71% or less.

[0034] Al ２ O ３ Al is not only a constituent of the LAS crystal, but also a component that improves the ion exchangeability during chemical strengthening treatment and increases the surface compressive stress after chemical strengthening treatment. ２ O ３ The content is preferably 0.1 to 5%, more preferably 0.5 to 4.5%, and even more preferably 1 to 4%. From the viewpoint of performing chemical strengthening treatment appropriately, the content is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 1% or more, and even more preferably 2% or more. Furthermore, from the viewpoint of facilitating the formation of lithium disilicate crystals, the content is preferably 5% or less, more preferably 4.5% or less, and even more preferably 4% or less.

[0035] P ２ O ５ is a component that promotes crystallization. ２ O ５The content of is preferably 0.5 to 5%, more preferably 0.8 to 4.5%, and even more preferably 1 to 4%. From the viewpoint of facilitating crystallization, the content is preferably 0.5% or more, more preferably 0.8% or more, even more preferably 1% or more, and even more preferably 2% or more. Furthermore, from the viewpoint of suppressing phase separation during melting and a decrease in acid resistance, the content is preferably 5% or less, more preferably 4.5% or less, even more preferably 4% or less, and even more preferably 2% or less.

[0036] B ２ O ３ is a component that improves chipping resistance and melting properties. ２ O ３ The content of B is preferably 0 to 10%, more preferably 0.1 to 9%, and even more preferably 0.2 to 8%. ２ O ３ Although it is not necessary to contain it, if it is contained, from the viewpoint of obtaining good chipping resistance and melting property, the content ratio is preferably 0.1% or more, more preferably 0.2% or more. Furthermore, from the viewpoint of suppressing the occurrence of striae and phase separation during melting and maintaining the quality of the crystallized glass, the content ratio is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less.

[0037] Li ２ O is a component that forms compressive stress near the surface of the glass by being ion-exchanged with Na ions, and is also a component of lithium disilicate crystals. ２ The O content is preferably 15 to 30%, more preferably 17 to 27%, and even more preferably 20 to 25%. From the viewpoint of increasing compressive stress, the O content is preferably 15% or more, more preferably 17% or more, and even more preferably 20% or more. From the viewpoint of chemical durability of the glass, the O content is preferably 30% or less, more preferably 27% or less, and even more preferably 25% or less.

[0038] Na ２ O is a component that forms compressive stress by being ion-exchanged with K ions, and the inclusion of a small amount of O can increase the stability of the glass. ２The content of O is preferably 0 to 5%, more preferably 0.5 to 4.5%, even more preferably 1 to 4%, and even more preferably 1.5 to 3.5%. ２ When O is contained, from the viewpoint of increasing compressive stress and improving stability, the content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more. From the viewpoint of maintaining chemical durability, the content is preferably 5% or less, more preferably 4.5% or less, even more preferably 4% or less, and even more preferably 3.5% or less.

[0039] K ２ O is a component that enhances chemical strengthening properties and suppresses phase separation. ２ The content of O is preferably 0 to 3%, more preferably 0.1 to 2%, and even more preferably 0.3 to 1%. ２ When O is contained, the content is preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more from the viewpoint of enhancing the stability of the glass, and is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less from the viewpoint of maintaining chemical durability.

[0040] ZrO ２ is a thickening component that increases the viscosity when melted, and at the same time, is a component that increases the surface compressive stress due to ion exchange. ２ The content ratio is preferably 2.1 to 10%, more preferably 2.5 to 9%, and even more preferably 3 to 8%. Here, in order to realize high transmittance and low haze value of glass-ceramics by acting as a thickening component and slowing down the growth rate of crystals that become crystalline phases and forming fine crystals, the content ratio is preferably 2.1% or more, more preferably 2.5% or more, and even more preferably 3% or more. Furthermore, in order to suppress devitrification during melting, the content ratio is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less.

[0041] TiO ２ is a thickening component that increases the viscosity when melted, and at the same time, is a component that increases UV resistance. ２The content of TiO is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. ２ When containing, it acts as a thickening component, slows down the growth rate of the crystal that becomes crystalline phase, and makes it into minute crystals, so that the high transmittance and low haze value of the crystallized glass are realized, so that the content ratio is preferably 0.1% or more, more preferably 0.5% or more.In addition, from the viewpoint of suppressing the decrease in haze value due to coloring, the content ratio is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0042] SnO ２ is a thickening component that increases the viscosity when melted, and at the same time, is a component that generates crystal nuclei. ２ The content of SnO is preferably 0 to 2%, more preferably 0.1 to 1.5%, and even more preferably 0.5 to 1%. ２ When containing, it acts as thickening component, slows down the growth rate of the crystal that becomes crystalline phase, and makes it into minute crystal, so that the high transmittance and low haze value of crystallized glass are realized, so that the content ratio is preferably 0.1% or more, more preferably 0.5% or more.In addition, from the viewpoint of suppressing the defects caused by unmelted matter, the content ratio is preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less.

[0043] Y ２ O ３ Y is a thickening component that increases the viscosity when melted, and at the same time, it is a component that prevents glass fragments from scattering when broken. It is also a component that increases the refractive index. ２ O ３ The content of Y is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. ２ O ３ When containing, it acts as thickening component, slows down the crystal growth rate of crystalline phase, makes it into minute crystal, so that realizes high transmittance and low haze value of crystallized glass, the content ratio is preferably 0.1% or more, more preferably 0.5% or more.In addition, from the viewpoint of suppressing mismatch during melting, the content ratio is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0044] The above ZrO ２ , TiO ２ , SnO ２ and Y ２ O ３ are all thickening components. ２ , TiO ２ , SnO ２ and Y ２ O ３ The total content ratio of (hereinafter sometimes referred to as [A]) is preferably 2.1 to 10%, more preferably 3 to 9%, and even more preferably 4 to 8%. Here, from the viewpoint of realizing high transmittance and low haze value of glass-ceramics by acting as a thickening component and slowing down the growth rate of crystals that become crystalline phases and forming fine crystals, the content ratio is preferably 2.1% or more, more preferably 2.5% or more, even more preferably 3% or more, and even more preferably 4% or more. Furthermore, from the viewpoint of solubility, the content ratio is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less.

[0045] MgO is a component that improves the meltability of glass. The MgO content is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. When MgO is contained, from the viewpoint of increasing the strength of the glass, the content is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0046] CaO, SrO, and BaO, which are alkaline earth metals other than MgO, are also components that, like MgO, improve the meltability of glass. The total content of MgO, CaO, SrO, and BaO is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. When alkaline earth metals are contained, from the viewpoint of increasing the strength of the glass, the total content is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the total content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0047] The respective contents of CaO, SrO, and BaO are preferably 0 to 4%, more preferably 0.1 to 3%, even more preferably 0.5 to 3%, even more preferably 1 to 2.5%, and particularly preferably 1 to 2%. When CaO, SrO, and BaO are contained, from the viewpoint of enhancing the stability of the glass, the respective contents are preferably 0.1% or more, more preferably 0.5% or more, and even more preferably 1% or more. From the viewpoint of maintaining good ion exchange performance, the respective contents are preferably 4% or less, more preferably 3% or less, even more preferably 2.5% or less, and even more preferably 2% or less.

[0048] La ２ O ３ , Nb ２ O ５ and Ta ２ O ５ Is Y ２ O ３ Similarly to La, it has the effect of suppressing scattering of fragments when the glass is broken, and may be contained to increase the refractive index. ２ O ３ , Nb ２ O ５ and Ta ２ O ５ The total content of these components is preferably 0 to 3%, more preferably 0.5 to 2%. These components do not necessarily have to be contained, but if they are contained, the total content is preferably 0.5% or more from the viewpoint of increasing the refractive index. Furthermore, the total content is preferably 3% or less, more preferably 2% or less from the viewpoint of suppressing devitrification of the glass during melting.

[0049] CeO ２ has the effect of oxidizing the glass, and the glass-ceramic becomes SnO ２ When the content is large, SnO ２ may be reduced to SnO, which is a coloring component, thereby suppressing coloration. ２ The content of CeO is preferably 0 to 1.5%, more preferably 0.03 to 1.5%, even more preferably 0.05 to 1%, and even more preferably 0.07 to 1%. ２However, if it is contained, the content is preferably 0.03% or more, more preferably 0.05% or more, and even more preferably 0.07% or more, from the viewpoint of suppressing coloration due to SnO. ２ From the viewpoint of suppressing coloration of the glass due to the presence of arsenic, the content is preferably 1.5% or less, and more preferably 1% or less.

[0050] Furthermore, a coloring component may be added to the glass-ceramic to the extent that it does not impede the achievement of the desired properties. ３ O ４ , MnO ２ , Fe ２ O ３ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ , SeO ２ , Er ２ O ３ , Nd ２ O ３ etc. The content ratio of the above coloring components is preferably in the range of 1% or less in total. Furthermore, if it is desired to increase the light transmittance of the crystallized glass, it is preferable that these components are not substantially contained. In this specification, "substantially not contained" means that the content is below the impurity level contained in raw materials, etc., that is, it is not intentionally added. In this specification, when it is stated that a certain component is not substantially contained, the content ratio of the component is specifically, for example, less than 0.03%.

[0051] In addition, SO is used as a fining agent when melting glass. ３ , chloride, fluoride, etc. may be contained as appropriate. ２ O ３ It is preferable that Sb is not contained. ２ O ３ When it is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably it is not contained substantially.

[0052] Among the above components, SiO ２ , Li ２O and Al ２ O ３ , and ZrO, a thickening component ２ , TiO ２ , SnO ２ and Y ２ O ３ The total content ratio of the following formula (1) preferably satisfies the value of 6 to 500. In formula (1), [SiO ２ ], [Li ２ O] and [Al ２ O ３ ] respectively represent SiO ２ , Li ２ O and Al ２ O ３ [LAS] represents the content (mol%) of SiO in the crystallized glass. ２ , Li ２ O and Al ２ O ３ [A] represents the total content (mol %) of the thickening components in the crystallized glass, i.e., ZrO ２ , TiO ２ , SnO ２ and Y ２ O ３ represents the total content ratio of the above.

[0053]

[0054] The value represented by the above formula (1) is preferably 6 to 500, more preferably 6.2 to 450, even more preferably 6.5 to 400, and even more preferably 6.7 to 350. Here, the first term of the above formula (1),

[0055]

[0056] The value of [A] in the first term indicates the ease of precipitation of lithium disilicate crystals, and the second term [A] indicates the total content of the viscosity-increasing components. Therefore, the value represented by the above formula (1) indicates the ease of precipitation of lithium disilicate with a small particle size, and the larger the value represented by formula (1), the easier it is to obtain lithium disilicate with a small particle size. Note that 66.7 and 33.3 in the denominator of the first term indicate the amounts of lithium disilicate (Li２ Si ２ O ５ ) SiO ２ and Li ２ The numerator of the first term, 500, is an optimal value arrived at as a result of the inventors' investigations into obtaining lithium disilicate crystals, in order to achieve a balance with the total content ratio of the viscosity-increasing components represented by [A].

[0057] In view of the above, from the viewpoint of lithium disilicate crystal precipitation, the value represented by the above formula (1) is preferably 6 or more, more preferably 6.2 or more, even more preferably 6.5 or more, and even more preferably 6.7 or more. Furthermore, if the composition is too close to that of lithium disilicate crystals, crystal growth will be rapid, causing haze deterioration. Therefore, the value represented by the above formula (1) is preferably 500 or less, more preferably 450 or less, even more preferably 400 or less, even more preferably 350 or less, or may be 300 or less, 250 or less, 200 or less, 150 or less, 100 or less, or 50 or less.

[0058] SiO ２ , Li ２ O and Al ２ O ３ Using the content ratio expressed in mole percentage, [{[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100] (%), i.e., {([SiO ２ ] / [LAS])×100} (%) is preferably 66 to 77%, more preferably 68 to 75%, and even more preferably 70 to 73%. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 66% or more, more preferably 68% or more, and even more preferably 70% or more. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 77% or less, more preferably 75% or less, and even more preferably 73% or less.

[0059] SiO ２ , Li ２ O and Al ２ O３ Using the content ratio expressed in mole percentage, [{[Al ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100] (%), i.e., {([Al ２ O ３ ] / [LAS])×100} (%) is preferably 1 to 5%, more preferably 1.5 to 4.5%, and even more preferably 2 to 4%. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 1% or more, more preferably 1.5% or more, and even more preferably 2% or more. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 5% or less, more preferably 4.5% or less, and even more preferably 4% or less.

[0060] SiO ２ , Li ２ O and Al ２ O ３ Using the content ratio expressed in mole percentage, [{[Li ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100] (%), i.e., {([Li ２ The value represented by {([0] / [LAS]) × 100} (%) is preferably 20 to 30%, more preferably 21 to 29%, and even more preferably 22 to 28%. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 20% or more, more preferably 21% or more, and even more preferably 22% or more. From the viewpoint of precipitating lithium disilicate crystals, the value is preferably 30% or less, more preferably 29% or less, and even more preferably 28% or less.

[0061] The crystallized glass according to this embodiment preferably contains Li ions that can be ion-exchanged with the Na ions in the molten salt when immersed in a molten salt containing Na ions. This means that the crystallized glass is a glass that can be chemically strengthened. The Li ions mentioned above include Li in the glass phase of the crystallized glass, and also Li in the crystalline phase depending on the crystal species. Examples of crystal species containing exchangeable Li ions include LAS crystals such as lithium disilicate, β-spodumene crystals, lithium metasilicate, petalite, and β-quartz, with lithium disilicate, β-spodumene crystals, and lithium metasilicate being preferred.

[0062] In addition to the above, the glass-ceramics may be further immersed in a molten salt containing K ions to further exchange the Na ions contained in the glass-ceramics by the ion exchange with K ions. Furthermore, when the glass-ceramics before chemical strengthening treatment is immersed in a molten salt containing K ions, it may contain Na ions that can be ion-exchanged with K ions in the molten salt.

[0063] <Physical Properties> The crystallized glass according to this embodiment includes both glass before and after chemical strengthening treatment. Furthermore, no significant changes are observed in the overall composition, crystallinity, and physical properties other than strength of the crystallized glass before and after chemical strengthening treatment, and they can be considered to be the same. However, the composition, crystalline structure, and crystallinity near the surface of the crystallized glass may differ. Examples of the strength-related physical properties include surface compressive stress (CS), compressive stress depth (DOL), internal tensile stress (CT), ST limit, fracture toughness value, Young's modulus, Vickers hardness, etc. Examples of physical properties other than strength include haze value, average transmittance, and average thermal expansion coefficient. Furthermore, when the crystallized glass is bent into a three-dimensional shape to form a three-dimensional cover glass, no significant changes are observed in the overall composition, crystallinity, and physical properties of the crystallized glass, and they can be considered to be the same as the flat crystallized glass before three-dimensional forming.

[0064] The crystallized glass according to the present embodiment that has been subjected to chemical strengthening treatment may have, for example, Na on the surface of the crystallized glass. ２The content of O is Na in the center of the crystallized glass. ２ The content of Li in the glass-ceramics is preferably higher than that of O, and the difference is more preferably 1% or more. The above is an example of chemically strengthened glass-ceramics after ion-exchanging the Li ions in the glass-ceramics with Na ions in the molten salt. The difference is more preferably 5% or more, and even more preferably 10% or more. In addition, the Na ２ The upper limit of the difference in the O content is not particularly limited, but is, for example, 30% or less.

[0065] The surface compressive stress (CS) of the chemically strengthened glass-ceramics according to this embodiment is preferably 500 MPa or more, more preferably 600 MPa or more, and even more preferably 700 MPa or more, from the viewpoint of preventing cracking due to deformation such as bending. The upper limit of the surface compressive stress is not particularly limited, but is, for example, 800 MPa or less. The value of the surface compressive stress can be adjusted, for example, by the Na concentration in the molten salt or the Li concentration in the glass composition. Note that, in this specification, the surface compressive stress (CS) can be measured by slicing a cross section of the glass-ceramics and analyzing the sliced ​​sample with a birefringence imaging system. An example of a birefringence imaging system is the Abrio-IM birefringence imaging system manufactured by Tokyo Instruments Inc. Surface compressive stress can also be measured using scattered light photoelasticity. In this method, light is incident on the surface of the glass-ceramics, and the polarization of the scattered light is analyzed to measure CS. An example of a stress measuring instrument that utilizes scattered light photoelasticity is the scattered light photoelastic stress meter SLP-1000 manufactured by Orihara Seisakusho.

[0066] The compressive stress depth (DOL) of the crystallized glass according to this embodiment that has been subjected to chemical strengthening treatment is preferably 70 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more, from the viewpoint of preventing cracks when scratches occur on the surface of the crystallized glass. The upper limit of the compressive stress depth is not particularly limited, but is, for example, 200 μm or less. The value of the compressive stress depth can be adjusted by the chemical strengthening time. In this specification, the compressive stress layer depth (DOL) is the depth at which the surface compressive stress (CS) becomes zero.

[0067] The chemically strengthened crystallized glass according to this embodiment more preferably has a surface compressive stress of 500 MPa or more and a compressive stress layer depth of 70 μm or more.

[0068] The internal tensile stress (CT) of the crystallized glass according to this embodiment that has been subjected to chemical strengthening treatment is preferably 50 to 110 MPa, more preferably 55 to 100 MPa, and even more preferably 60 to 90 MPa. From the viewpoint of preventing scattering of fragments when the crystallized glass is broken, the internal tensile stress is preferably 110 MPa or less, more preferably 100 MPa or less, and even more preferably 90 MPa or less. Furthermore, from the viewpoint of obtaining sufficient surface compressive stress, the internal tensile stress is preferably 50 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more. In this specification, the internal tensile stress (CT) refers to the tensile stress value at a depth of 1 / 2 (t × 1 / 2 depth) in a crystallized glass having a plate thickness t.

[0069] The ST limit value of the crystallized glass according to this embodiment that has been subjected to chemical strengthening treatment is preferably 10,000 to 300,000 MPa μm, more preferably 15,000 to 300,000 MPa μm, and even more preferably 20,000 to 300,000 MPa μm. From the viewpoint of increasing drop strength through chemical strengthening treatment, the ST limit value is preferably 10,000 MPa μm or more, more preferably 15,000 MPa μm or more, and even more preferably 20,000 MPa μm or more, with the higher the value, the better. The upper limit of the ST limit value is not particularly limited, but is, for example, 300,000 MPa μm or less. The ST limit value can be adjusted by the crystal species, degree of crystallization, and glass composition.

[0070] In this specification, the tensile stress integral value (ST value) refers to the area integral of the tensile stress (negative compressive stress) with respect to the sample depth from the DOL to a depth of 1 / 2 of the plate thickness t. In crystallized glass that has been subjected to chemical strengthening treatment, when the ST value in the crystallized glass exceeds a certain threshold, the number of fractures increases rapidly when it is broken. This threshold is called the "ST limit".

[0071] The ST limit value is specifically determined by the following test method. (Test Method) A plurality of test glass plates, each 15 mm square and 0.7 mm thick with a mirror-finished surface, are chemically strengthened under various conditions to prepare test glass plates with different ST values, which are tensile stress integral values. Using a Vickers testing machine, a diamond indenter with a 90° tip angle is driven into the center of the test glass plate to break the test glass plate, and the number of fragments is recorded as the number of fragments. The test is started with a diamond indenter driving load of 1 kgf. If the test glass plate does not break, the driving load is increased by 1 kgf increments, and the test is repeated until the test glass plate breaks, and the number of fragments at the first break is counted. The number of fragments is plotted against the ST value of the test glass plate, and the ST value at which the number of fragments reaches 10 is read and recorded as the ST limit.

[0072] The fracture toughness value of the chemically strengthened glass-ceramics according to this embodiment is set to 0.8 MPa m from the viewpoint of preventing scattering of fragments when the glass-ceramics is broken. １／２ More than 1 MPa m １／２ The upper limit of the fracture toughness value is not particularly limited, but for example, it is 2.0 MPa m １／２ The fracture toughness value can be adjusted by the crystal species, degree of crystallization, and glass composition. In this specification, the fracture toughness value means a value measured by the single-edge-precracked-beam method (SEPB method) specified in JIS R1607:2015.

[0073] The Young's modulus of the crystallized glass according to this embodiment that has been subjected to chemical strengthening treatment is preferably 80 GPa or more, more preferably 86 GPa or more, more preferably 90 GPa or more, and even more preferably 100 GPa or more, from the viewpoint of preventing scattering of fragments when the crystallized glass is broken. The upper limit of the Young's modulus is not particularly limited, but is, for example, 150 GPa or less. In this specification, the Young's modulus refers to a value obtained by an ultrasonic method.

[0074] The Vickers hardness of the crystallized glass according to this embodiment that has been subjected to chemical strengthening treatment is preferably 680 GPa or more, more preferably 720 GPa or more, and even more preferably 750 GPa or more, from the viewpoint of scratch resistance. The higher the Vickers hardness, the better, but it is usually 1200 GPa or less. In this specification, the Vickers hardness refers to the Vickers hardness (HV0.1) specified in JIS R1610:2003.

[0075] The haze value of the crystallized glass according to this embodiment, calculated as a thickness of 0.7 mm, is preferably 0.4% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and even more preferably 0.15% or less, from the viewpoint of visibility when the crystallized glass is used as a cover glass, particularly a three-dimensionally shaped cover glass. The smaller the haze value, the better, but it is usually 0.01% or more. The haze value of typical amorphous glass without a crystalline phase is usually about 0.02%. The haze value can be adjusted by the crystal species, degree of crystallization, and glass composition. The haze value in this specification refers to a value measured using a C illuminant in accordance with JIS K3761:2000. If the actual thickness of the crystallized glass is not 0.7 mm, the measured value can be converted to a haze value calculated as a thickness of 0.7 mm using the Lambert-Beer law. Furthermore, when the plate thickness t is greater than 0.7 mm, the plate thickness of the crystallized glass may be adjusted to 0.7 mm by polishing, etching, or the like before measurement.

[0076] The average transmittance of the crystallized glass according to this embodiment for light having a wavelength of 380 to 780 nm, calculated as a thickness of 0.7 mm, is preferably 85% or more, more preferably 87% or more, and even more preferably 90% or more, from the viewpoint of visibility when the crystallized glass is used as a cover glass, particularly a three-dimensionally shaped cover glass. The higher the average transmittance, the better, but it is typically 92% or less. A light transmittance of 90% calculated as a thickness of 0.7 mm can be said to be equivalent to that of general amorphous glass. The average transmittance value can be adjusted by the crystal species, degree of crystallization, and glass composition. In this specification, average transmittance refers to the average linear transmittance of light having a wavelength of 380 to 780 nm. Furthermore, if the actual thickness of the crystallized glass is not 0.7 mm, the measured value can be converted to a transmittance calculated as a thickness of 0.7 mm using the Lambert-Beer law. Furthermore, when the plate thickness t is greater than 0.7 mm, the plate thickness of the crystallized glass may be adjusted to 0.7 mm by polishing, etching, or the like before measurement.

[0077] When the crystallized glass according to this embodiment is flat, its thickness (t) is preferably 0.1 to 3 mm, more preferably 0.2 to 2 mm, even more preferably 0.3 to 1.6 mm, even more preferably 0.35 to 1.1 mm, even more preferably 0.4 to 0.9 mm, and particularly preferably 0.5 to 0.7 mm. From the viewpoint of obtaining sufficient strength, the thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.3 mm or more, even more preferably 0.35 mm or more, even more preferably 0.4 mm or more, and particularly preferably 0.5 mm or more. From the viewpoint of weight and haze value, the thickness is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1.6 mm or less, even more preferably 1.1 mm or less, even more preferably 0.9 mm, and particularly preferably 0.7 mm or less. The crystallized glass according to this embodiment does not need to have a constant thickness, and may include a configuration in which the thickness varies partially.

[0078] <Applications> The crystallized glass according to this embodiment is useful as a cover glass for electronic devices such as mobile devices such as mobile phones and smartphones. It is also useful as a cover glass for non-portable electronic devices such as televisions, personal computers, and touch panels, as well as elevator walls and wall surfaces (full-surface displays) of buildings such as houses and buildings. It is also useful as building materials such as window glass, tabletops, interiors of automobiles and airplanes, and cover glass for these, as well as for curved housings.

[0079] The crystallized glass according to this embodiment can also be suitably used for the above-mentioned applications after being subjected to a chemical strengthening treatment to form crystallized glass.

[0080] Furthermore, the crystallized glass according to this embodiment is also suitable for use as a three-dimensional cover glass having a three-dimensional curved surface, and a crystallized glass that has been subjected to chemical strengthening treatment is also suitable for use as the three-dimensional cover glass. These three-dimensional cover glasses are also used for the above-mentioned applications.

[0081] <Three-dimensionally shaped cover glass> The three-dimensionally shaped cover glass according to this embodiment can have a conventionally known three-dimensional shape. Here, the three-dimensional shape refers to a shape obtained by bending a flat plate. Note that the three-dimensional shape is not limited to a shape with a uniform thickness overall, and may also have a shape with portions of different thicknesses.

[0082] The three-dimensional shape may be, for example, a shape in which the central portion is flat and the end portions are concave or convex. Alternatively, the central portion may not be flat, and the entire crystallized glass may be curved, or may be a shape consisting of multiple R shapes.

[0083] <<Method for Producing Crystallized Glass>> The crystallized glass according to this embodiment can be produced by heat-treating and crystallizing amorphous glass. That is, the method for producing crystallized glass according to this embodiment includes the following steps: Step 1: A step for producing amorphous glass; Step 2: A step for crystallizing the amorphous glass obtained in Step 1 to obtain crystallized glass; Step 3: Optionally, a step for chemically strengthening the crystallized glass obtained in Step 2.

[0084] The three-dimensionally shaped cover glass according to this embodiment can be obtained by a manufacturing method including the following step 4 in addition to the above steps 1 to 3. Step 4: A step of providing a three-dimensionally curved surface to the crystallized glass obtained in step 2 or 3 to obtain a three-dimensionally shaped cover glass.

[0085] Each step will be described below.

[0086] <Step 1> Step 1 is a step of producing amorphous glass, and the specific method can be a conventionally known method. That is, when obtaining a plate-shaped amorphous glass, for example, glass raw materials are mixed to obtain a desired composition, and heated and melted in a glass melting furnace. Thereafter, the molten glass is homogenized by bubbling, stirring, adding a clarifier, etc., and formed into a glass plate of a predetermined thickness by a known forming method, and then slowly cooled. Alternatively, the molten glass may be formed into a block shape, and then slowly cooled and cut into a plate shape. Examples of the forming method of plate-shaped glass include a float method, a press method, a fusion method, and a down-draw method.

[0087] The viscosity of the molten glass in the second stage of the crystallization heat treatment (crystal growth step) is 1×10 ４ ~1 x 10 １２ dPa·s is preferred, and 1×10 ５ ~1 x 10 １１ dPa·s is more preferable, and 1×10 ６ ~1 x 10 １０ Here, in the crystallization treatment in the subsequent step 2, the crystal growth rate of the crystals constituting the crystalline phase is suppressed, and the average particle size (crystallite size) of the crystals is kept small, so that high transmittance and low haze value can be achieved. ４ dPa·s or more is preferable, and 1×10 ５ dPa s or more is more preferable, and 1×10 ６ From the viewpoint of precipitating a crystalline phase, the viscosity is more preferably 1×10 １２ dPa s or less is preferable, and 1×10 １１ dPa s or less is more preferable, and 1×10 １０The viscosity is more preferably 500 dPa·s or less. ２ , Y ２ O ３ , TiO ２ , and SnO ２ The content can be adjusted by the ratio of

[0088] The desired composition is the same as the preferred embodiment described in the above section "Ceramics." For example, it is preferable that the content ratio expressed as mole percentage based on oxides satisfies the following: SiO ２ 55 to 75% Al ２ O ３ 0.1 to 5% of P ２ O ５ 0.5 to 5%, B ２ O ３ 0 to 10%, Li ２ 15-30% O, Na ２ O 0-5%, K ２ O 0 to 3%, ZrO ２ 2.1 to 10% of TiO ２ 0 to 5%, SnO ２ 0 to 2%, Y ２ O ３ and MgO 0 to 5%.

[0089] In addition to the above, the value represented by the following formula (1) is more preferably 6 to 500. In formula (1), [SiO ２ ], [Li ２ O] and [Al ２ O ３ ] respectively represent SiO ２ , Li ２ O and Al ２ O ３ [LAS] represents the content (mol%) of SiO in the crystallized glass. ２ , Li ２ O and Al ２ O ３ [A] represents the total content (mol %) of the thickening components in the crystallized glass.

[0090]

[0091] <Step 2> Step 2 is a step of crystallizing the amorphous glass obtained in step 1 to obtain crystallized glass. The heat treatment for crystallization is not particularly limited as long as it can obtain the desired crystals, but for example, it can 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 at a second treatment temperature higher than the first treatment temperature for a certain period of time. After the two-stage heat treatment, a three-stage heat treatment can be performed in which the temperature is maintained at a third treatment temperature for a certain period of time. Alternatively, it can be a one-stage heat treatment in which the temperature is maintained at a specific treatment temperature and then cooled to room temperature.

[0092] In the case of a two-stage heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate is high for the glass composition, and the second treatment temperature is preferably in a temperature range where the crystal growth rate is high for the glass composition.

[0093] In the case of a three-stage heat treatment, it is preferable that the first and second treatment temperatures are temperatures at which the crystal nucleation rate increases, and the third treatment temperature is a temperature at which the crystal growth rate increases. Alternatively, the first treatment temperature may be a temperature at which the crystal nucleation rate increases, and the second and third treatment temperatures may be temperatures at which the crystal growth rate increases.

[0094] In the two-stage heat treatment and the three-stage heat treatment, the holding time at the first treatment temperature is preferably long enough to generate a sufficient number of crystal nuclei. The generation of a large number of crystal nuclei reduces the size of each crystal, resulting in a highly transparent crystallized glass.

[0095] More specifically, in the case of a two-stage treatment, for example, the first treatment temperature is held at 500°C to 700°C for 1 hour to 6 hours, and then the second treatment temperature is held at 600°C to 800°C for 1 hour to 6 hours.

[0096] More specifically, in the case of a three-stage treatment, for example, after holding at a first treatment temperature of 500°C to 600°C for 1 hour to 6 hours, for example, at a second treatment temperature of 550°C to 650°C for 1 hour to 6 hours, and further, for example, at a third treatment temperature of 600°C to 800°C for 1 hour to 6 hours.

[0097] More specifically, in the case of a one-stage treatment, the temperature may be maintained at 500° C. to 800° C. for 1 hour to 6 hours.

[0098] The crystallized glass obtained in step 2 may be ground and polished as necessary. Furthermore, when the crystallized glass obtained 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 in the next step 3. This allows a compressive stress layer to be formed on the end surfaces, such as the cut surface and the chamfered surface, by the subsequent chemical strengthening treatment.

[0099] <Step 3> Step 3 is an optional step of chemically strengthening the crystallized glass obtained in step 2. Chemical strengthening is a process in which glass is brought into contact with a metal salt (e.g., potassium nitrate) containing a metal ion with a large ionic radius (typically, Na ion or K ion) by, for example, immersing the glass in a melt of the metal salt, thereby replacing the metal ion with a small ionic radius (typically, Li ion or Na ion) in the glass with a metal ion with a large ionic radius (typically, Na ion or K ion for Li ion, and K ion for Na ion).

[0100] To increase the speed of chemical strengthening, it is preferable to use "Li-Na exchange," in which Li ions in the glass are exchanged with Na ions. Also, to create a large compressive stress by ion exchange, it is preferable to use "Na-K exchange," in which Na ions in the glass are exchanged with K ions.

[0101] Examples of molten salts for chemical strengthening include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used alone or in combination.

[0102] The conditions for the chemical strengthening treatment, such as time and temperature, can be selected taking into consideration the glass composition, the type of molten salt, etc. For example, the present crystallized glass can be chemically strengthened at preferably 500°C or less for preferably 20 hours or less. Also, two or more stages of chemical strengthening treatment may be performed.

[0103] <Step 4> Step 4 is a step of providing the obtained crystallized glass with a three-dimensional curved surface to obtain a three-dimensionally shaped cover glass.

[0104] To provide a curved surface, a conventionally known bending method can be used. Examples of the bending method include gravity forming, vacuum forming, and press forming. Two or more bending methods may also be used in combination.

[0105] Gravity forming method is a method of placing crystallized glass on a forming mold, then heating the crystallized glass, and making it conform to the forming mold by gravity, and bending it into a predetermined shape.Vacuum forming method is a method of placing crystallized glass on a forming mold, sealing the periphery of the crystallized glass, then reducing the pressure in the space between the forming mold and the crystallized glass, and applying a pressure difference between the front and back sides of the crystallized glass to bend it.At this time, the upper side of the crystallized glass can be additionally pressurized.Press forming method is a method of placing crystallized glass between forming molds (lower mold and upper mold), heating the crystallized glass, and applying a press load between the upper and lower molds to bend it into a predetermined shape.In any forming method, crystallized glass is deformed by applying force while heated.

[0106] The bending (hot bending) temperature is, for example, 700°C to 1100°C, and preferably 750°C to 1050°C.

[0107] Furthermore, the difference between the maximum temperature of the crystallization treatment in step 2 and the heat bending temperature in step 4 is preferably 10 to 120°C, more preferably 10 to 100°C, even more preferably 30 to 90°C, and even more preferably 30 to 60°C. Here, if the heat bending temperature is higher than the maximum temperature of the crystallization treatment in step 2, thermal deformation easily occurs, so from the viewpoint of achieving high dimensional accuracy, the difference between the maximum temperature of the crystallization treatment and the heat bending temperature is preferably 10°C or more, more preferably 30°C or more. Furthermore, from the viewpoint of suppressing a decrease in light transmittance due to bending, the temperature difference is preferably 120°C or less, more preferably 100°C or less, even more preferably 90°C or less, and even more preferably 60°C or less.

[0108] The decrease in the average transmittance of the crystallized glass for light with wavelengths of 380 to 780 nm due to bending is preferably 3% or less, more preferably 2% or less, even more preferably 1.5% or less, and even more preferably 1% or less, and the smaller the decrease the better.

[0109] Alternatively, the crystallized glass obtained in step 2 may be subjected to chemical strengthening treatment in step 3 after a three-dimensionally shaped cover glass is obtained in step 4 .

[0110] The present invention will be described below with reference to examples, but the present invention is not limited thereto. Examples 1 to 15 are examples.

[0111] Examples 1 to 15 Glass raw materials were mixed to obtain the glass compositions shown in Table 1 in terms of oxide-based mole percent, and weighed out to obtain 400 g of glass. The mixed glass raw materials were then placed in a platinum crucible and placed in an electric furnace at 1500°C, where they were melted for approximately 5 hours, degassed, and homogenized. The resulting molten glass was poured into a mold, held at 500°C for 2 hours, and then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block.

[0112] The obtained glass blocks were each processed into a plate of 50 mm × 50 mm × 1.5 mm, and subjected to a two-stage crystallization treatment. Specifically, the first treatment and the second treatment were performed at the temperature and holding time shown in the "Crystallization Conditions" in Table 1. Then, the blocks were cooled to room temperature to obtain crystallized glass.

[0113] In Example 5, the obtained crystallized glass was immersed in molten sodium nitrate (100%) at 450° C. for 4 hours to perform chemical strengthening treatment. ２ The content of O is determined by the ratio of Na in the center of the crystallized glass. ２ It was confirmed that the surface compressive stress (CS) of the glass-ceramics subjected to this chemical strengthening treatment was 540 MPa, the depth of the compressive stress layer (DOL) was 119 μm, and the ST limit value was 27,000 MPa μm. Furthermore, the fracture toughness values ​​of the glass-ceramics of Example 5 and Example 6 before the chemical strengthening treatment were both 1.3 MPa μm. １／２ It was.

[0114]

[0115] <Evaluation> <X-ray Diffraction: Precipitated Crystals> Powder X-ray diffraction was measured for the crystallized glass under the following conditions, and precipitated crystals were identified by Rietveld analysis. Measuring device: SmartLab manufactured by Rigaku Corporation X-ray used: CuKα ray Measurement range: 2θ = 10° to 80° Speed: 10° / min Step: 0.02°

[0116] The results are shown in Table 1. All of Examples 1 to 15 were glass-ceramics containing lithium disilicate (LD) crystals. The content of LD crystals in the crystal phase was 80% by volume or more, and crystals other than LD crystals were also confirmed, but their specific crystal structures could not be identified. The crystallinity of the glass-ceramics was 20% by volume or more and 50% by volume or less.

[0117] <Young's Modulus> The Young's modulus of the crystallized glass was measured by an ultrasonic method using an ultrasonic thickness gauge (manufactured by Olympus Corporation, product name 38DL). The results are shown in Table 1.

[0118] <Haze Value> The haze value of the crystallized glass was measured using a haze meter (HZ-V3 manufactured by Suga Test Instruments) under Illuminant C, and converted into a haze value at a thickness of 0.7 mm. The results are shown in Table 1.

[0119] <Average transmittance> A spectrophotometer (manufactured by PerkinElmer; LAMBDA950) was fitted with an integrating sphere unit (150 mm InGaAs Int. Sptere) as a detector, and the glass was tightly attached to the integrating sphere to measure the transmittance of the crystallized glass at wavelengths of 380 to 780 nm. The arithmetic mean value of the transmittances at each wavelength obtained was taken as the average transmittance, and this was converted to the average transmittance for a thickness of 0.7 mm. The results are shown in Table 1.

[0120] From the above results, the crystallized glass according to this embodiment can achieve both a high average transmittance and a low haze value by appropriately controlling the total content ratio of the thickening components, even without actively incorporating crystals other than LD crystals. Furthermore, because the crystallized glass according to this embodiment has a low content ratio of crystals other than LD crystals, a high Young's modulus can be achieved, resulting in a high-strength crystallized glass. In addition, by reducing the content ratio of crystals other than LD crystals, high three-dimensional formability can also be achieved. Furthermore, although the crystallized glass of Examples 1 to 15 above was not chemically strengthened, the LD crystal is a crystal capable of ion exchange between Li ions in the crystal and Na ions in the molten salt through chemical strengthening. Therefore, it can be said to have excellent chemical strengthening processability, and further strength can be achieved through ion exchange.

[0121] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-221645) filed on December 27, 2023, the contents of which are incorporated herein by reference.

Claims

1. A crystallized glass having a crystalline phase, the haze value calculated based on a thickness of 0.7 mm is 0.4% or less, the average transmittance of light having a wavelength of 380 to 780 nm calculated based on a thickness of 0.7 mm is 85% or more, and the content expressed as a mole percentage based on oxides is: SiO ２ 55 to 75% Al ２ O ３ 0.1 to 5% P ２ O ５ 0.5 to 5%, B ２ O ３ 0 to 10%, Li ２ 15-30% O, Na ２ O 0 to 5%, K ２ O 0 to 3%, ZrO ２ 2.1 to 10% TiO ２ 0 to 5% SnO ２ 0 to 2%, Y ２ O ３ and MgO is 0 to 5%, and the value represented by the following formula (1) is 6 to 500. (In formula (1), [SiO ２ ], [Li ２ O] and [Al ２ O ３ ] are the SiO ２ , Li ２ O and Al ２ O ３ [LAS] represents the content (mol%) of SiO in the crystallized glass. ２ , Li ２ O and Al ２ O ３ represents the total content (mol%) of the thickening components in the crystallized glass, and [A] represents the total content (mol%) of the thickening components in the crystallized glass.

2. The SiO in the crystallized glass ２ , Li ２ O and Al ２ O ３ When the content ratios in terms of mole percentages are respectively [SiO ２ , [Li ２ O] and [Al ２ O ３ , the crystallized glass according to claim 1, which satisfies the relationship of 66 ≤ {([SiO ２ / ([SiO ２ + [Al ２ O ３ + [Li ２ O])} × 100 (%) ≤ 77.

3. The SiO in the crystallized glass ２ , Li ２ O and Al ２ O ３ The content ratios in terms of mole percentages are respectively [SiO ２ , [Li ２ O] and [Al ２ O ３ . When the relationship 1 ≤ {{[Al ２ O ３ / ([SiO ２ + [Al ２ O ３ + [Li ２ O])} × 100] (%) ≤ 5 is satisfied, the crystallized glass according to claim 1.

4. The crystalline phase contains Li ２ Si ２ O ５ crystals, and in the crystalline phase, the content ratio of the ２ Li ２ Si ５ O crystals is 50% by volume or more. The devitrified glass according to claim 1.

5. In the crystalline phase, the content ratio of crystals other than the Li ２ Si ２ O ５ is 20% by volume or less. The devitrified glass according to claim 4.

6. The crystallized glass according to claim 1, which contains Li ions capable of ion-exchanging with the Na ions when immersed in a molten salt containing Na ions.

7. The content ratio of Na ２ O on the surface of the crystallized glass in terms of the molar percentage based on the oxide is higher than the content ratio of Na ２ O at the center of the crystallized glass, and the difference is 1% or more. The crystallized glass according to claim 1.

8. The crystallized glass according to claim 7, wherein the surface compressive stress is 500 MPa or more and the depth of the compressive stress is 70 μm or more.

9. The fracture toughness value is 0.8 MPa·m １／２ or more, and the crystallized glass according to claim 7.

10. The crystallized glass according to claim 7, wherein the value of the ST limit obtained by the following test method is 10,000 to 300,000 MPa·μm. (Test method) Prepare a plurality of test glass plates with different ST values, which are 15 mm square, 0.7 mm thick, and have a mirror-finished surface, and are chemically strengthened under various conditions. Using a Vickers tester, drive a diamond indenter with a tip angle of 90° into the central part of the test glass plate to break the test glass plate, and take the number of fragments as the number of fragments. The indentation load of the diamond indenter starts from 1 kgf. If the test glass plate does not crack, increase the indentation load by 1 kgf each time and repeat the test until the test glass plate cracks, and count the number of fragments at the first crack. Plot the number of fragments against the ST value of the test glass plate, and read the ST value when the number of fragments is 10 as the ST limit.

11. A three-dimensional shape cover glass made of the crystallized glass according to any one of claims 1 to 10, wherein the crystallized glass has a curved surface portion forming a three-dimensional curved surface.

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