Method for producing crystallized glass

Abstract

Provided is a method for producing crystallized glass, by which crystallized glass having a low haze is obtained.　Provided is a method for producing crystallized glass in which glass for crystallization having a first crystal growth peak temperature Tp1 measured by a differential thermal scanning calorimeter and a second crystal growth peak temperature Tp2 measured by a differential thermal scanning calorimeter is subjected to a heat treatment that is performed sequentially at a first heat treatment temperature T1, at a second heat treatment temperature T2, and at a third heat treatment temperature T3 in this order, wherein the first crystal growth peak temperature Tp1, the second crystal growth peak temperature Tp2, the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy formula (1) to formula (4). The units of the left side and the right side of formula (1) to formula (4) are °C, and Tg in formula (1) is the glass transition point of the glass for crystallization.　Formula (1): Tg < T1, Formula (2): T1 < T2, Formula (3): T2 ≤ T3 - 100, Formula (4): T1 ≤ Tp1 - 80

Description

Method for manufacturing crystallized glass 【0001】 This invention relates to a method for producing crystallized glass. 【0002】 Crystallized glass is glass containing fine crystals internally and possesses various excellent properties. For example, crystallized glass can exhibit excellent strength and is applied to a variety of uses. Crystallized glass is generally obtained by heat-treating glass of a predetermined composition. Hereinafter, the glass subjected to heat treatment to obtain crystallized glass will also be referred to as "crystallization glass." 【0003】 For example, Patent Document 1 discloses that crystallized glass is obtained by performing a two-step heat treatment on crystallized glass. 【0004】 Japanese Patent Publication No. 2024-109520 【0005】 In the above-mentioned Patent Document 1, crystallized glass is obtained by performing a two-stage heat treatment. However, further improvement in transmittance is required for crystallized glass. In other words, further reduction of haze is required for crystallized glass. When the present inventors obtained crystallized glass by referring to the heat treatment described in Patent Document 1, they found that there is room for improvement in reducing haze. 【0006】 This invention has been made in view of the above problems, and aims to provide a method for producing crystallized glass that yields crystallized glass with low haze. 【0007】 As a result of diligent research into the above-mentioned problems, the inventors of the present invention discovered that by adjusting the heat treatment temperature and performing a three-stage heat treatment, crystallized glass with low haze can be obtained, leading to the completion of the present invention. 【0008】In other words, the inventors have found that the above problem can be solved by the following configuration: [1] A method for manufacturing crystallized glass, wherein a crystallization glass having a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2 measured by a differential thermal scanning calorimeter is subjected to sequential heat treatment at a first heat treatment temperature T1, a second heat treatment temperature T2, and a third heat treatment temperature T3, wherein the first crystal growth peak temperature Tp1, the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy the following formulas (1) to (4). However, the units of the left and right sides of the following formulas (1) to (4) are °C, and Tg in the following formula (1) is the glass transition temperature of the crystallization glass. Equation (1) Tg < T1 Equation (2) T1 < T2 Equation (3) T2 ≤ T3 - 100 Equation (4) T1 ≤ Tp1 - 80 [2] A method for producing crystallized glass according to [1], wherein the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following equation (5). However, the units of the left and right sides of the following equation (5) are °C. Equation (5) T2 < Tp1 [3] A method for producing crystallized glass according to [1] or [2], wherein the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following equation (5-1). However, the units of the left and right sides of the following equation (5-1) are °C. Formula (5-1) T2 ≤ Tp1 - 50 [4] A method for producing crystallized glass according to any one of [1] to [3], wherein the first crystal growth peak temperature Tp1 and the second crystal growth peak temperature Tp2 satisfy the following formula (6). However, the units of the left and right sides of the following formula (6) are °C. Formula (6) Tp2 - Tp1 ≥ 160 [5] A method for producing crystallized glass according to any one of [1] to [4], wherein the first heat treatment temperature T1 and the second heat treatment temperature T2 satisfy the following formula (7). However, the units of the left and right sides of the following formula (7) are °C. Formula (7) T2 - T1 ≤ 50 [6] A method for producing crystallized glass according to any one of [1] to [5], wherein the third heat treatment temperature T3 and the first crystal growth peak temperature Tp1 satisfy the following formula (8). However, the units of the left and right sides of equation (8) below are °C.Formula (8): Tp1 < T3 [7] The method for producing a crystallized glass according to any one of [1] to [6], wherein the third heat treatment temperature T3 and the second crystal growth peak temperature Tp2 satisfy the following formula (9). However, the units of the left and right sides of the following formula (9) are °C. Formula (9): T3 < Tp2 [8] The method for producing a crystallized glass according to any one of [1] to [7], wherein the second heat treatment temperature T2, the third heat treatment temperature T3, the first crystal growth peak temperature Tp1, and the second crystal growth peak temperature Tp2 satisfy the following formula (5), the following formula (8), and the following formula (9). Formula (5): T2 < Tp1 Formula (8): Tp1 < T3 Formula (9): T3 < Tp2 [9] The composition of the glass for crystallization is expressed in mole percentage based on oxides, SiO. ２ is 60.0 to 75.0%, Al ２ O ３ is 2.0 to 6.0%, P ２ O ５ is more than 0.0% and 3.0% or less, Li ２ O is 20.0 to 30.0%, Na ２ O is 0.0 to 5.0%, K ２ O is 0.0 to 1.0%, MgO is 0.0 to 2.0%, CaO is 0.0 to 2.0%, ZrO ２ is 1.0 to 5.0%, SnO ２ is 0.0 to 1.0%, SrO is 0.0 to 1.0% and contains substantially no Y ２ O ３ The method for producing a crystallized glass according to any one of [1] to [8].

[10] The method for producing a crystallized glass according to any one of [1] to [9], wherein the obtained crystallized glass contains Li ２ Si ２ O ５ crystals.

[11] The method for producing a crystallized glass according to any one of [1] to

[10] , wherein the fracture toughness value K ＩＣ of the obtained crystallized glass is 1.3 MPa·m １／２ or more.

[12] The method for producing a crystallized glass according to any one of [1] to

[11] , wherein the haze of the obtained crystallized glass is 0.17% or less. 【0009】According to the present invention, a method for producing crystallized glass with low haze can be provided. 【0010】 Fracture toughness value K by DCDC method ＩＣ This is an explanatory diagram of the sample used for measurement. Fracture toughness value K by DCDC method. ＩＣ The stress intensity factor K1 (unit: MPa・m) used in the measurement １／２ This figure shows the K1-v curve, which illustrates the relationship between the crack growth rate v (unit: m / s) and the crack propagation rate v. 【0011】 The present invention will now be described in detail. The following descriptions of constituent elements may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, the "~" indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits. 【0012】 In glass composition, "substantially absent" means that, excluding unavoidable impurities contained in the raw materials, etc., it does not mean that the impurities are not intentionally included. Specifically, for components other than those listed in the glass composition, for example, less than 0.1 mol% is preferred, 0.08 mol% or less is more preferred, and 0.05 mol% or less is even more preferred. 【0013】 In this specification, "fracture toughness value K" ＩＣ The stress intensity factor K1 (unit: MPa・m) is measured using the DCDC method [Reference: M. Y. He, M. R. Turner and A. G. Evans, Acta Metal. Mater. 43 (1995) 3453.]. Specifically, using a sample with the shape shown in Figure 1 and a SHIMADZU Autograph AGS-X5KN, the stress intensity factor K1 (unit: MPa・m) is measured as shown in Figure 2. １／２ The K1-v curve, which shows the relationship between the stress intensity factor K1 and the crack propagation rate v (unit: m / s), was measured. The obtained data for Region III was then regression-extrapolated using a linear equation, and the fracture toughness value K1 was set to a stress intensity factor K1 of 0.1 m / s. ＩＣ Let's assume that. 【0014】<Method for Manufacturing Crystallized Glass> The method for manufacturing crystallized glass of the present invention involves sequentially heat-treating a crystallization glass having a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2, as measured by a differential thermal scanning calorimeter, at a first heat treatment temperature T1, a second heat treatment temperature T2, and a third heat treatment temperature T3. Here, the first crystal growth peak temperature Tp1, the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy the following equations (1) to (4). However, the units of the left and right sides of the following equations (1) to (4) are °C, and Tg in the following equation (1) is the glass transition temperature of the crystallization glass. Equation (1) Tg < T1 Equation (2) T1 < T2 Equation (3) T2 ≤ T3 - 100 Equation (4) T1 ≤ Tp1 - 80 【0015】 The mechanism by which the crystallized glass manufacturing method of the present invention yields crystallized glass with low haze is not entirely clear, but the inventors speculate as follows. In the crystallized glass manufacturing method of the present invention, crystallization glass having a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2 is used. Since it can be said that two types of crystals precipitate from such crystallization glass by heat treatment, it is thought that when heat treatment is performed at the first heat treatment temperature T1 and the second heat treatment temperature T2, fine crystals corresponding to the first crystal growth peak temperature Tp1 precipitate in the crystallization glass. Furthermore, when heat treatment is performed at the third heat treatment temperature T3, fine crystals corresponding to the second crystal growth peak temperature Tp2 precipitate based on the crystals corresponding to the first crystal growth peak temperature Tp1, so it is thought that crystallized glass with precipitated fine crystals is obtained. In crystallized glass, the smaller the particle size of the precipitated crystals, the lower the haze tends to be, so according to the crystallized glass manufacturing method of the present invention, crystallized glass with low haze can be obtained. 【0016】The following describes the crystallization glass to be subjected to heat treatment and the heat treatment process. The process of sequentially performing heat treatment at the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 will also be referred to as the "heat treatment process." Furthermore, the obtained crystallized glass may be subjected to a chemical strengthening treatment, as described later, to obtain chemically strengthened glass. 【0017】 [Glass for Crystallization] In the method for manufacturing crystallized glass of the present invention, a heat treatment step described later is performed on crystallized glass having a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2, which are measured by a differential thermal scanning calorimeter. That is, the crystallized glass used in the method for manufacturing crystallized glass of the present invention has a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2. Furthermore, the crystallized glass used in the method for manufacturing crystallized glass of the present invention has a glass transition temperature Tg. 【0018】 The glass transition temperature Tg, the first crystal growth peak temperature Tp1, and the second crystal growth peak temperature Tp2 can be measured using a differential thermal scanning calorimeter (DSC). In this specification, a Bruker DSC3300SA is used as the DSC. The DSC measurement procedure is as follows: First, the crystallization glass is crushed and classified into 150-300 μm particles to obtain crystallization glass powder. The obtained crystallization glass powder is placed in a platinum pan (container) and heated from room temperature to 1050°C for DSC measurement. The heating rate is 5°C / min. 【0019】 The curve obtained by DSC (DSC curve) has temperature on the horizontal axis and heat quantity on the vertical axis. By analyzing the DSC curve, the glass transition temperature Tg, the first crystal growth peak temperature Tp1, and the second crystal growth peak temperature Tp2 can be obtained. When a glass transition occurs in a sample, a baseline shift is observed in the DSC curve. In this specification, the extrapolation glass transition onset temperature is defined as the glass transition temperature Tg. The extrapolation glass transition onset temperature is defined as the temperature at the intersection of a straight line extending from the low-temperature baseline to the high-temperature side and a tangent line drawn at the point where the slope of the curve representing the stepwise change portion of the glass transition is maximum. 【0020】 Furthermore, when crystallization occurs in a sample, an exothermic peak is observed in the DSC curve. In this specification, the temperature at which the exothermic peak takes its maximum value is defined as the crystal growth peak temperature. The crystallization glass used in the method for manufacturing crystallized glass of the present invention shows two or more exothermic peaks in the DSC curve, and the crystal growth peak temperatures are defined as the first crystal growth peak temperature Tp1 and the second crystal growth peak temperature Tp2, respectively, starting from the lower temperature side. 【0021】 The glass transition temperature Tg of the crystallizing glass used in the crystallizing glass manufacturing method of the present invention is preferably 400°C or higher, more preferably 430°C or higher, and even more preferably 450°C or higher. Furthermore, the glass transition temperature Tg is preferably 570°C or lower, more preferably 540°C or lower, and even more preferably 520°C or lower. The first crystal growth peak temperature Tp1 of the crystallizing glass used in the crystallizing glass manufacturing method of the present invention is preferably 520°C or higher, more preferably 550°C or higher, and even more preferably 570°C or higher. Furthermore, the first crystal growth peak temperature Tp1 is preferably 680°C or lower, more preferably 650°C or lower, and even more preferably 630°C or lower. Note that the first crystal growth peak temperature Tp1 is often higher than the glass transition temperature Tg. The second crystal growth peak temperature Tp2 of the crystallizing glass used in the crystallizing glass manufacturing method of the present invention is preferably 700°C or higher, more preferably 730°C or higher, and even more preferably 750°C or higher. Furthermore, the second crystal growth peak temperature Tp2 is preferably 870°C or lower, more preferably 840°C or lower, and even more preferably 820°C or lower. 【0022】 Furthermore, it is preferable that the first crystal growth peak temperature Tp1 and the second crystal growth peak temperature Tp2 satisfy the relationship shown in equation (6) below. However, the units of the left and right sides of equation (6) below are °C. Equation (6) Tp2 - Tp1 ≥ 160 【0023】 The preferred composition of the crystallization glass used in the method for producing crystallized glass of the present invention (hereinafter also referred to as the "mother glass composition") is described below. The mother glass composition is expressed as a mole percentage based on oxides, and is SiO ２ 60.0-75.0%, Al２ O ３ 2.0-6.0%, P ２ O ５ Li ２ 20.0-30.0% O, Na ２ O at 0.0-5.0%, K ２ O 0.0-1.0%, MgO 0.0-2.0%, CaO 0.0-2.0%, ZrO ２ 1.0-5.0%, SnO ２ It contains 0.0-1.0% of and 0.0-1.0% of SrO, Y ２ O ３ It is preferable that it substantially does not contain [this element]. The following describes each component included in the mother glass composition. 【0024】 SiO ２ It is a component that makes up the network of glass. It is also a component that increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched. 【0025】 SiO ２ The content of is more preferably 61.0% or more, and even more preferably 62.0% or more, in order to improve chemical durability. On the other hand, from the viewpoint of improving meltable properties, SiO ２ The content of is more preferably 72.0% or less, and even more preferably 70.0% or less. 【0026】 Al ２ O ３ It is a component that improves ion exchange performance during chemical strengthening and increases surface compressive stress after chemical strengthening. It also contributes to the formation of crystals containing Al and Li. From the viewpoint of obtaining the above effects, Al ２ O ３ A content of 2.2% or more is more preferable. On the other hand, it is sometimes required that crystal growth is less likely to occur during melting, that devitrification defects are less likely to occur and that the yield tends to be higher, and that the high-temperature viscosity of the glass is reduced to make it easier to melt. From this viewpoint, Al ２ O ３The content of is more preferably 5.0% or less, and even more preferably 4.5% or less, 4.0% or less, and 3.5% or less, in that order. 【0027】 SiO ２ and Al ２ O ３ These are all components that stabilize the structure of glass. To reduce brittleness, SiO ２ and Al ２ O ３ The total content is preferably 62.0% or more, more preferably 64.0% or more, and even more preferably 66.0% or more. Also, SiO ２ and Al ２ O ３ Both tend to increase the melting temperature of the glass. Therefore, in order to make it easier to melt, SiO ２ and Al ２ O ３ The total content is preferably 90.0% or less, more preferably 80.0% or less, and even more preferably 75.0% or less. 【0028】 Li ２ O is a component that can undergo ion exchange and improves the meltability of glass. ２ By including O, Li ions on the glass surface are exchanged with external Na ions and incorporated into the glass, and then these incorporated Na ions are exchanged with external K ions. This method makes it easier to obtain a stress profile with high surface compressive stress and a thick compressive stress layer. In addition, within the above range, Li ２ The presence of O makes it easier to obtain crystallized glass when subjected to specific heat treatments. From the above viewpoint, Li ２ The O content is more preferably 21.0% or more, even more preferably 22.0%, and particularly preferably 24.0% or more. 【0029】 On the other hand, in order to reduce the crystal growth rate during glass molding and to minimize quality degradation due to devitrification, Li ２ The O content is more preferably 29.0% or less, even more preferably 28.0% or less, and particularly preferably 27.0% or less. 【0030】 Na２ O and K ２ O is a component that improves the meltability of glass and reduces the crystal growth rate during glass molding. It is also preferable to include a small amount to improve ion exchange performance. 【0031】 Furthermore, the crystal species that precipitate in the crystallization glass depend on the composition of the crystallization glass. That is, the type and number of crystals that precipitate can be adjusted by the range of the composition of the crystallization glass (preferably the composition of the mother glass). Here, as will be described later, when the crystallization glass is subjected to a predetermined heat treatment to obtain crystallization glass, preferred crystals that precipitate include lithium disilicate (Li ２ Si ２ O ５ Examples of crystals include: SiO ２ 60.0-70.0%, Al ２ O ３ 2.0 to 4.0%, Li ２ Compositions containing 20.0-30.0% oxygen are examples. 【0032】 When two or more types of crystals precipitate from a crystallization glass, the crystallization glass has a crystallization peak temperature corresponding to the precipitation of each crystal. For example, when lithium disilicate crystals precipitate, lithium metasilicate (Li ２ SiO ３ After the crystals precipitate, lithium disilicate crystals precipitate, and crystallization glasses with a composition that precipitates lithium disilicate crystals have crystallization peak temperatures derived from each crystal in this order from lowest to highest temperature. 【0033】 Na ２ O is a component that can undergo ion exchange in chemical strengthening treatment using potassium salts, and is also a component that reduces the viscosity of glass. To obtain the above effect, Na ２ The O content is preferably 0.3% or more, and more preferably 0.5% or more, 0.8% or more, 1.2% or more, 1.6% or more, and 2.0% or more, in that order. On the other hand, from the viewpoint of maintaining the glass network and avoiding a decrease in surface compressive stress (Na_CS) during the strengthening treatment with sodium salt, Na２ The content of O is more preferably 4.0% or less, still more preferably 3.5% or less, and particularly preferably 3.0% or less. 【0034】 K ２ O is a component that suppresses devitrification by suppressing the rise in the devitrification temperature and improves the ion exchange performance. K ２ The content of K O is more preferably 0.05% or more, still more preferably 0.1% or more, and particularly preferably 0.3% or more. On the other hand, from the viewpoint of avoiding a decrease in the surface compressive stress (K_CS) in the strengthening treatment with a sodium salt, the content of K ２ O is preferably 0.9% or less, more preferably 0.8% or less, and still more preferably 0.7% or less. Note that K ２ O may not be substantially contained. 【0035】 Li ２ The content of O, Na ２ The content of O and K ２ R, which is the sum of the contents of O, is preferably 21.0 to 35.0%, still more preferably 25.0 to 32.0%, and particularly preferably 27.0 to 31.0% from the viewpoint of suppressing the rise in the devitrification temperature and reducing the crystal growth rate. 【0036】 The ratio of the content of Li O to the above R ([Li O] / ([Li O] + [Na O] + [K O]), hereinafter also referred to as "Li O / R O") is more preferably 0.80 or more, still more preferably 0.85 or more from the viewpoint of further improving the deep layer stress in the chemical strengthening characteristics. Li ２ O / RO ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter, "Li ２ O / RO ２ O") is more preferably 0.99 or less, still more preferably 0.98 or less, and particularly preferably 0.95 or less from the viewpoint of further enhancing the chemical resistance. ２ O / RO ２ O is more preferably 0.99 or less, still more preferably 0.98 or less, and particularly preferably 0.95 or less from the viewpoint of further enhancing the chemical resistance. 【0037】 The ratio of the content of Na O to the above R ([Na O] / ([Li O] + [Na O] + [K O]) ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O])２ O]), hereinafter, "Na ２ O / R ２ O" (also described as such) is preferably more than 0.00, more preferably 0.01 or more, still more preferably 0.02 or more, particularly preferably 0.05 or more, and most preferably 0.06 or more, from the viewpoint of further improving the stress in the deep part in chemical strengthening characteristics. Na ２ O / R ２ O is preferably 0.40 or less, more preferably 0.30 or less, still more preferably 0.20 or less, and particularly preferably 0.10 or less, from the viewpoint of further enhancing chemical resistance. 【0038】 The ratio of the content of K ２ O to R ([K ２ O] / ([Li ２ O]+[Na ２ O]+[K ２ O]), hereinafter, also described as "K ２ O / R ２ O") is preferably 0.001 or more, more preferably 0.004 or more, and still more preferably 0.01 or more, from the viewpoint of further increasing the electrical resistance of the glass. K ２ O / R ２ O is preferably 0.40 or less, more preferably 0.30 or less, still more preferably 0.20 or less, and particularly preferably 0.10 or less, from the viewpoint of increasing the compressive stress near the surface in chemical strengthening characteristics. Note that K ２ O / R ２ O may be 0. 【0039】 Also, Li ２ O / R ２ O, Na ２ O / R ２ O, and K ２ O / R ２ O, the product of them is preferably 0.00005 or more, more preferably 0.0001 or more, and still more preferably 0.001 or more, from the viewpoint of suppressing the increase in devitrification temperature and reducing the crystal growth rate. Also, the above product is more preferably 0.020 or less. Note that the above product may be 0. 【0040】 The ratio of the content of Al ２ O ３ to R ([Al ２O ３ ] / ([Li ２ O] + [Na] ２ O] + [K ２ O]), hereinafter referred to as “Al ２ O ３ / R ２ Al (also written as "O") is preferably 0.02 or higher, more preferably 0.04 or higher, even more preferably 0.06 or higher, and particularly preferably 0.07 or higher. ２ O ３ / R ２ O is preferably 1.00 or less, more preferably 0.50 or less, even more preferably 0.20 or less, and particularly preferably 0.15 or less. 【0041】 [Al ２ O ３ ]-[Na ２ O] - [K ２ O] + [Li ２ The value represented by [O] is preferably 15.0% or more, and more preferably 20.0% or more. Furthermore, the above value is preferably 35.0% or less, and more preferably 30.0% or less. 【0042】 MgO may be included to reduce viscosity during dissolution, etc. The MgO content is more preferably 0.05% or more, and even more preferably 0.08% or more. On the other hand, in order to easily increase the compressive stress layer during chemical strengthening treatment, the MgO content is more preferably 1.5% or less, and even more preferably 1.0% or less, and 0.5% or less, in that order. MgO may be substantially absent. 【0043】 CaO is a component that improves the meltability of the glass and may be included. The CaO content is more preferably 0.005% or more, and even more preferably 0.01% or more. On the other hand, in terms of easily increasing the compressive stress value during chemical strengthening treatment, the CaO content is more preferably 1.8% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less. CaO may be substantially omitted. 【0044】To enhance the stability of the glass, it is more preferable to include at least one of MgO and CaO, and even more preferable to include MgO. The total content of MgO and CaO is preferably 0.01% or more, more preferably more than 0.05%, even more preferably 0.1% or more, and particularly preferably 0.2% or more. In terms of further improving the chemical strengthening properties, the total content of MgO and CaO is preferably 3.5% or less, and more preferably 3.0% or less, 2.0% or less, and 1.0% or less, in that order. It is also acceptable for MgO and CaO to be substantially absent. 【0045】 SrO is a component that improves the meltability of the glass and may be included. The SrO content is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In terms of making it easier to increase the compressive stress value during chemical strengthening treatment, the SrO content is more preferably 1.8% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO may be substantially absent. 【0046】 BaO is a component that improves the meltability of the glass and may be included. When BaO is included, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. In terms of making it easier to increase the compressive stress value during chemical strengthening treatment, the BaO content is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO may be substantially omitted. 【0047】 ZnO is a component that improves the meltability of glass. The ZnO content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. In terms of making it easier to increase the compressive stress value during chemical strengthening treatment, the ZnO content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. ZnO may be substantially absent. 【0048】 TiO ２ TiO is a component that is highly effective in suppressing glass solarization and is a material that forms crystal nuclei, so it may be included. ２ When containing, the content is preferably 0.03% or more, more preferably 0.05% or more, and even more preferably 0.08% or more. On the other hand, TiO ２ Because it has light-absorbing properties, TiO ２ The content is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. ２ It does not necessarily have to be included in practice. 【0049】 ZrO ２ ZrO is a component that makes it easier to increase the surface compressive stress of chemically strengthened crystallized glass. Also, because it is a material that forms crystal nuclei, ２ It may contain ZrO ２ The content of is more preferably 1.2% or more, and even more preferably 1.5% or more, and 1.7% or more, in that order. ZrO ２ The content of is more preferably 4.0% or less, and even more preferably 3.0% or less, and 2.5% or less, in that order. 【0050】 In the composition of the mother glass, Y ２ O ３ It is preferable that it is substantially not included. ２ O ３ The content is preferably less than 0.1%, more preferably 0.08 mol% or less, and even more preferably 0.05 mol% or less. 【0051】 P ２ O ５ This makes it easier to increase the compressive stress layer during chemical strengthening. Furthermore, during the heat treatment at the first heat treatment temperature T1 in the heat treatment process, crystals containing P are more likely to precipitate. ２ O ５The content of is more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, from the viewpoint of increasing acid resistance, P ２ O ５ The content of is more preferably 2.5% or less, and even more preferably 2.0% or less. 【0052】 B ２ O ３ This reduces the brittleness of the glass and improves its crack resistance, or improves its meltability. ２ O ３ The content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2.0% or more. On the other hand, in terms of maintaining good acid resistance, B ２ O ３ The content of is preferably 8.0% or less. ２ O ３ The content is more preferably 6.0% or less, even more preferably 4.0% or less, and particularly preferably 2.0% or less. From the viewpoint of preventing striation formation during melting, it is also preferable that it be substantially absent. 【0053】 La ２ O ３ This component increases the surface compressive stress of chemically strengthened crystallized glass while simultaneously reducing the crystal growth rate. ２ O ３ The amount is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 0.8% or more. On the other hand, if there is too much, it becomes difficult to increase the compressive stress layer during the chemical strengthening treatment, so La ２ O ３ The amount is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. ２ O ３ It is also preferable that it is not included in any meaningful sense. 【0054】 Nb ２ O ５、 Ta ２ O ５ , Gd ２ O ３ , CEO ２These components have the effect of suppressing glass solarization and improving meltability, and may be included. When these components are included, the content of each is preferably 0.03% or more, more preferably 0.1% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, it is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less. 【0055】 Fe ２ O ３ Since it absorbs heat rays, it has the effect of improving the solubility of glass, and it is preferable to include it when mass-producing glass using a large melting furnace. In that case, the content is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.007% or more, and particularly preferably 0.01% or more, expressed in mass percent based on oxide. On the other hand, Fe ２ O ３ Since excessive amounts of this substance cause discoloration, its content is preferably 0.3% or less, more preferably 0.04% or less, even more preferably 0.025% or less, and particularly preferably 0.015% or less, in terms of mass percentage based on oxides, from the viewpoint of improving the transparency of the glass. 【0056】 Furthermore, other coloring components may be added, to the extent that they do not hinder the achievement of desired chemical strengthening properties, etc. Examples of other coloring components include Co ３ O ４ MnO ２ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ SeO ２ Er ２ O ３ , Nd ２ O ３ These are some examples of suitable options. 【0057】 SO4 is used as a clarifying agent during glass melting, etc. ３ It may contain chlorides, fluorides, etc. as appropriate. ２ O ３It is preferable that it does not contain Sb. ２ O ３ If it is present, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not present. From the viewpoint of clarifying bubbles in the glass, SnO ２ The content of is more preferably 0.05% or more, and even more preferably 0.08% or more. Also, SnO ２ The content of is preferably 1.5% or less, more preferably 1.2% or less, and even more preferably 0.5% or less, in order to suppress the occurrence of defects. 【0058】 The crystallization glass described above has a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2. 【0059】 [Heat Treatment Process] In the heat treatment process, the crystallization glass is subjected to heat treatment in order at a first heat treatment temperature T1, a second heat treatment temperature T2, and a third heat treatment temperature T3. Here, as described above, the first crystal growth peak temperature Tp1, the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy the following equations (1) to (4). However, the units of the left and right sides of the following equations (1) to (4) are °C, and Tg in equation (1) is the glass transition temperature of the crystallization glass. Equation (1) Tg < T1 Equation (2) T1 < T2 Equation (3) T2 ≤ T3 - 100 Equation (4) T1 ≤ Tp1 - 80 【0060】 In other words, the heat treatment process is performed in the following order: a first heat treatment at a first heat treatment temperature T1 that satisfies predetermined requirements, a second heat treatment at a second heat treatment temperature T2 that satisfies predetermined requirements, and a third heat treatment at a third heat treatment temperature T3 that satisfies predetermined requirements. 【0061】 It is also preferable that the first heat treatment temperature T1 and the glass transition temperature Tg of the crystallization glass satisfy the following equation (1-1). However, the units of the left and right sides of the following equation (1-1) are °C. Equation (1-1) T1 - Tg ≤ 80 【0062】It is also preferable that the first heat treatment temperature T1 and the glass transition temperature Tg of the crystallization glass satisfy the following equation (1-2). However, the units of the left and right sides of the following equation (1-2) are °C. Equation (1-2) T1 - Tg ≥ 10 【0063】 Furthermore, it is preferable that the first heat treatment temperature T1 and the second heat treatment temperature T2 satisfy the following equation (7). However, the units of the left and right sides of the following equation (7) are °C. Equation (7) T2 - T1 ≤ 50 【0064】 It is also preferable that the first heat treatment temperature T1 and the second heat treatment temperature T2 satisfy the following equation (7-1). However, the units of the left and right sides of the following equation (7-1) are °C. Equation (7-1) T2 - T1 ≤ 30 【0065】 It is also preferable that the first heat treatment temperature T1 and the second heat treatment temperature T2 satisfy the following equation (7-2). However, the units of the left and right sides of the following equation (7-2) are °C. Equation (7-2) T2 - T1 ≥ 10 【0066】 It is also preferable that the second heat treatment temperature T2 and the third heat treatment temperature T3 satisfy the following equation (3-1). However, the units of the left and right sides of the following equation (3-1) are °C. Equation (3-1) T2 ≤ T3 - 150 【0067】 It is also preferable that the second heat treatment temperature T2 and the third heat treatment temperature T3 satisfy the following equation (3-2). However, the units of the left and right sides of the following equation (3-2) are °C. Equation (3-2) T2 ≥ T3 - 300 【0068】 Furthermore, it is preferable that the first heat treatment temperature T1 and the first crystal growth peak temperature Tp1 satisfy the following equation (4-1). However, the units of the left and right sides of the following equation (4-1) are °C. Equation (4-1) Tp1 - T1 ≤ 110 【0069】 It is also preferable that the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following equation (5). However, the units of the left and right sides of equation (5) are °C. Equation (5) T2 < Tp1 【0070】It is also preferable that the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following equation (5-1). However, the units of the left and right sides of the following equation (5-1) are °C. Equation (5-1) T2 ≤ Tp1 - 50 【0071】 Furthermore, it is preferable that the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following equation (5-2). However, the units of the left and right sides of the following equation (5-2) are °C. Equation (5-2) Tp1 - T2 ≤ 80 【0072】 Furthermore, it is preferable that the third heat treatment temperature T3 and the first crystal growth peak temperature Tp1 satisfy the following equation (8). However, the units of the left and right sides of equation (8) are °C. Equation (8) Tp1 < T3 【0073】 It is also preferable that the third heat treatment temperature T3 and the first crystal growth peak temperature Tp1 satisfy the following equation (8-1). However, the units of the left and right sides of the following equation (8-1) are °C. Equation (8-1) T3 - Tp1 ≥ 80 【0074】 It is also preferable that the third heat treatment temperature T3 and the second crystal growth peak temperature Tp2 satisfy the following equation (9). However, the units of the left and right sides of equation (9) are °C. Equation (9) T3 < Tp2 【0075】 Furthermore, it is preferable that the third heat treatment temperature T3 and the second crystal growth peak temperature Tp2 satisfy the following equation (10). However, the units of the left and right sides of the following equation (10) are °C. Equation (10) Tp2 - T3 ≥ 20 【0076】 It is also preferable that the third heat treatment temperature T3 and the second crystal growth peak temperature Tp2 satisfy the following equation (10-1). However, the units of the left and right sides of the following equation (10-1) are °C. Equation (10-1) Tp2 - T3 ≤ 120 【0077】Furthermore, it is also preferable that the second heat treatment temperature T2, the third heat treatment temperature T3, the first crystal growth peak temperature Tp1, and the second crystal growth peak temperature Tp2 satisfy the above equations (5), (8), and (9). That is, it is also preferable that the relationship Tg < T1 < T2 < Tp1 < T3 < Tp2 is satisfied in the heat treatment process. 【0078】 The first heat treatment temperature T1 for the first heat treatment is not particularly limited as long as it satisfies formulas (1), (2), and (4) above, but is preferably 400°C or higher, more preferably 430°C or higher, even more preferably 460°C or higher, and particularly preferably 480°C or higher. Furthermore, the first heat treatment temperature T1 is preferably 750°C or lower, more preferably 650°C or lower, even more preferably 550°C or lower, and particularly preferably 530°C or lower. In terms of obtaining crystallized glass with lower haze, it is also preferable to select a temperature for the first heat treatment temperature T1 at which the nucleation rate is greater than the nucleation growth rate. 【0079】 The second heat treatment temperature T2 is not particularly limited as long as it satisfies formulas (2) and (3) above, but is preferably 430°C or higher, more preferably 460°C or higher, even more preferably 490°C or higher, and particularly preferably 510°C or higher. Furthermore, the second heat treatment temperature T2 is preferably 800°C or lower, more preferably 700°C or lower, even more preferably 600°C or lower, particularly preferably 560°C or lower, and most preferably 540°C or lower. In terms of obtaining crystallized glass with lower haze, it is also preferable to select a temperature for the second heat treatment temperature T2 at which the nucleation growth rate is greater than the nucleation rate. 【0080】 The third heat treatment temperature T3 is not particularly limited as long as it satisfies the above formula (3), but is preferably 600°C or higher, more preferably 630°C or higher, even more preferably 660°C or higher, and particularly preferably 690°C or higher. Furthermore, the third heat treatment temperature T3 is preferably 950°C or lower, more preferably 850°C or lower, even more preferably 800°C or lower, and particularly preferably 760°C or lower. 【0081】The above-mentioned first heat treatment is carried out by holding the material at the first heat treatment temperature T1 for a certain period of time. The duration of the first heat treatment can be 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. The duration of the first heat treatment can be 24 hours or less, preferably 12 hours or less, and more preferably 8 hours or less. The first heat treatment often causes nucleation of crystals that precipitate at the first crystal growth peak temperature Tp1. 【0082】 The second heat treatment described above is carried out by holding the material at the second heat treatment temperature T2 for a certain period of time. The duration of the second heat treatment can be 0.2 hours or more, preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 1.5 hours or more. The duration of the second heat treatment can be 12 hours or less, preferably 6 hours or less, more preferably 4 hours or less, and even more preferably 3 hours or less. The second heat treatment often results in the growth of crystals that precipitate at the first crystal growth peak temperature Tp1. 【0083】 The above third heat treatment is carried out by holding the temperature at the third heat treatment temperature T3 for a certain period of time. The duration of the third heat treatment can be 0.2 hours or more, preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 1.5 hours or more. The duration of the third heat treatment can be 12 hours or less, preferably 6 hours or less, more preferably 4 hours or less, and even more preferably 3 hours or less. In many cases, the third heat treatment causes crystals to precipitate and grow at the first crystal growth peak temperature Tp1, and then crystals to precipitate at the second crystal growth peak temperature Tp2 grow from these crystals. 【0084】 In this specification, when controlling and holding the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 for a certain period of time, the temperature of the atmosphere in which the crystallization glass is heat-treated is controlled. For example, the heat treatment process can be carried out in a known heat treatment furnace, and the temperature inside the heat treatment furnace can be monitored by a thermocouple or the like installed near the crystallization glass, and the output of the heat treatment furnace can be adjusted to reach a predetermined temperature. The type of heat treatment furnace is not particularly limited and may be a batch type or a continuous type. The heating method of the heat treatment furnace is also not particularly limited and may be a combustion heating method or an electric heating method. 【0085】 Preferred crystals precipitated during the first and second heat treatments include lithium metasilicate (Li ２ SiO ３ Examples include ) crystals and β-quartz solid solutions, with lithium metasilicate crystals being preferred. In addition, preferred crystals precipitated in the third heat treatment include lithium disilicate (Li ２ Si ２ O ５ Examples include lithium metasilicate crystals and β-spodumene crystals, with lithium disilicate crystals being preferred. Furthermore, a configuration in which lithium metasilicate crystals precipitate in the first and second heat treatments, and lithium disilicate crystals precipitate in the third heat treatment is more preferred. In the above configuration, the first crystal growth peak temperature Tp1 is the temperature at which nucleation and growth of lithium metasilicate crystals occur, and the second crystal growth peak temperature Tp2 is the temperature at which nucleation and growth of lithium disilicate crystals occur. 【0086】 Furthermore, the heat treatment process typically includes a first heating treatment to raise the temperature from room temperature to a first heat treatment temperature T1, a second heating treatment to raise the temperature from the first heat treatment temperature T1 to a second heat treatment temperature T2, and a third heating treatment to raise the temperature from the second heat treatment temperature T2 to a third heat treatment temperature T3. The heating rate in the first heating treatment is not particularly limited, but for example, it is 0.5°C / min or more, preferably 1°C / min or more, and more preferably 5°C / min or more. Also, the heating rate in the first heating treatment is 100°C / min or less, preferably 50°C / min or less, and more preferably 30°C / min or less. The heating rate in the second heating treatment is not particularly limited, but for example, it is 0.5°C / min or more, preferably 1°C / min or more, and more preferably 5°C / min or more. Furthermore, the heating rate in the second heating treatment is 100°C / min or less, preferably 50°C / min or less, and more preferably 30°C / min or less. The heating rate in the third heating treatment is not particularly limited, but for example, it is 0.5°C / min or more, preferably 1°C / min or more, and more preferably 5°C / min or more. Furthermore, the heating rate in the third heating treatment is 100°C / min or less, preferably 50°C / min or less, and more preferably 30°C / min or less. 【0087】Furthermore, in the heat treatment process, after the third heat treatment is completed, a cooling treatment is usually performed to lower the temperature to room temperature. The cooling rate in the cooling treatment is preferably 0.1°C / min or more, more preferably 0.5°C / min or more, and even more preferably 1°C / min or more. In addition, the cooling rate in the cooling treatment is preferably 300°C / min or less, more preferably 100°C / min or less, and even more preferably 50°C / min or less. 【0088】 The atmosphere during the heat treatment process is not particularly limited, but it may be an inert atmosphere or an atmospheric atmosphere. 【0089】 <Characteristics of Crystallized Glass> The crystallized glass obtained by the crystallized glass manufacturing method of the present invention will be described below. Hereinafter, the crystallized glass obtained by the crystallized glass manufacturing method of the present invention will also be simply referred to as "crystallized glass". 【0090】 Crystallized glass is lithium disilicate (Li ２ Si ２ O ５ It is preferable that the crystals are included. Crystallized glass containing lithium disilicate crystals tends to have a high fracture toughness value and thus tends to have a high strength. It is also preferable that the crystallized glass contains only lithium disilicate crystals as the crystals. From the viewpoint of increasing strength, the crystallization rate in crystallized glass is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more. In addition, to increase transparency, it is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A low crystallization rate is also advantageous in that it is easy to heat and bend or shape. 【0091】 The crystallized glass may contain crystals other than lithium disilicate crystals. The crystallization rate mentioned above refers to the total proportion of crystals if the crystalline phase contains two or more types of crystals. Examples of the other crystals mentioned above include β-spodumene (LiAlSi ２ O ６ ) Crystal, petalite (LiAlSi ４ O １０ ) crystals, β-quartz (including burgellite) crystals, (Li ｘ Al ｘ Si３－ｘ O ６ ) Crystals, Lithium Metasilicate (Li ２ SiO ３ ) Crystal, eucryptite (LiAlSiO ４ ) Crystal, mullite (Al ４＋２ｘ Si ２－２ｘ O １０－ｘ , 0.2 ≤ x ≤ 0.5) crystal, and lithium phosphate (Li ３ PO ４ Examples include crystals, etc. However, the material is not limited to these, and can be appropriately selected according to the desired properties. 【0092】 For example, if you want to obtain a crystalline phase that can undergo ion exchange by chemical strengthening, in addition to lithium disilicate crystals, at least one crystal selected from the group consisting of β-spodumene crystals, petalite crystals, β-quartz crystals, and lithium metasilicate crystals may be included. Also, if you want to obtain a crystallized glass with higher strength, in addition to lithium disilicate crystals, at least one crystal selected from the group consisting of β-spodumene crystals, petalite crystals, β-quartz crystals, lithium metasilicate crystals, and mullite crystals may be included. If you want to achieve higher transparency, in addition to lithium disilicate crystals, at least one crystal selected from the group consisting of β-quartz crystals, lithium metasilicate crystals, and lithium phosphate crystals may be included. 【0093】 The crystallization rate can be calculated from the X-ray diffraction intensity using the Rietveld method. The Rietveld method is described in the "Crystal Analysis Handbook" edited by the editorial committee of the Crystallographic Society of Japan (Kyōritsu Shuppan, 1999, pp. 492-499). In addition, X-ray diffraction measurements can be used to identify the crystal species contained in crystallized glass. 【0094】 The average grain size of the precipitated crystals in the crystallized glass is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less, in order to achieve high transparency. The average grain size of the precipitated crystals can be determined from transmission electron microscope (TEM) images. It can also be estimated from scanning electron microscope (SEM) images. 【0095】 Fracture toughness value K of crystallized glass ＩＣ It is 0.8 MPa·m １／２ The above is preferable, and 1.0 MPa·m １／２ The above is more preferable, 1.3 MPa·m １／２ The above is even more preferable. Fracture toughness value K of crystallized glass ＩＣ There is no particular upper limit, but it is typically 2.0 MPa·m. １／２ The following are listed: 【0096】 The Young's modulus of crystallized glass is preferably 80 GPa or higher, more preferably 90 GPa or higher, and even more preferably 95 GPa or higher. The Young's modulus of crystallized glass is often 140 GPa or lower. The Young's modulus of crystallized glass is determined by measuring the value obtained by ultrasonic pulse method at the center of the crystallized glass plane in accordance with JIS R 1602. 【0097】 As described above, the haze of the crystallized glass obtained by the crystallized glass manufacturing method of the present invention is low, preferably 0.17% or less, more preferably 0.16% or less, and even more preferably 0.15% or less. The lower limit of the haze of the crystallized glass is not particularly limited, but for example, it can be 0.01% or more. The haze of the crystallized glass described above refers to the value calculated for a crystallized glass plate thickness of 0.6 mm, measured using a C light source in accordance with JIS K3761:2000. If the plate thickness of the crystallized glass to be measured is not 0.6 mm, the haze value can be converted to a 0.6 mm thickness equivalent based on the measured value using the Lambert-Beer law. If the plate thickness is greater than 0.6 mm, the plate thickness of the crystallized glass may be adjusted to 0.6 mm by polishing and etching or the like before measurement. 【0098】[Other steps] The method for manufacturing crystallized glass of the present invention may include steps other than those described above. For example, it may include a cutting step for cutting the obtained crystallized glass to a desired size and thickness. It may also include a chamfering step for chamfering the cut crystallized glass. It may also include a forming step for bending the obtained crystallized glass. It may also include a polishing step for polishing the surface of the obtained crystallized glass. 【0099】 The cutting method in the cutting process is not particularly limited and can be cut using known methods. The size to which the crystallized glass is cut is also not particularly limited and can be cut to any desired size. 【0100】 Furthermore, the crystallized glass obtained by the method for producing crystallized glass of the present invention may be subjected to a chemical strengthening treatment. That is, the method for producing crystallized glass of the present invention may include a chemical strengthening treatment step in which the obtained crystallized glass is subjected to a chemical strengthening treatment. The chemical strengthening treatment step can be carried out by known methods. The chemical strengthening treatment is carried out, for example, by contacting the crystallized glass with a molten salt of a metal salt (e.g., potassium nitrate or sodium nitrate) containing metal ions with a large ionic radius (typically K ions or Na ions). Contact between the crystallized glass and the molten salt of the metal salt is carried out, for example, by immersing the crystallized glass in the molten salt of the metal salt. By contacting the crystallized glass and the metal salt, metal ions with a small ionic radius (typically Na ions or Li ions) in the crystallized glass are replaced with metal ions with a large ionic radius (typically K ions for Na ions, and Na ions or K ions for Li ions). Examples of the molten salt include a molten salt containing at least one of sodium nitrate and potassium nitrate. The chemical strengthening treatment may be carried out in two or more stages. 【0101】<Applications> The crystallized glass obtained by the crystallized glass manufacturing method of the present invention can be applied to a variety of uses. In particular, the obtained crystallized glass is useful as cover glass. The above cover glass can be suitably used for surface protection of displays and solar cell modules, etc. In particular, chemically strengthened crystallized glass is useful as cover glass used in mobile devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet devices. Furthermore, it is also useful as cover glass for display devices such as televisions (TVs), personal computers (PCs), and touch panels that are not intended to be portable, as cover glass provided on the surface of solar cell modules, building materials such as elevator walls, walls of buildings such as houses and office buildings (full-surface displays), and window glass, as well as for tabletops, interiors of automobiles and airplanes, etc. It is also useful as cover glass for the above articles. Furthermore, by bending, it can be applied to applications such as housings with curved shapes. 【0102】 The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. Examples 1, 3, and 4 described later are examples, and Examples 2 and 5 described later are comparative examples. 【0103】<Example 1> First, glass raw materials were mixed to obtain glass material A, which was then melted in a platinum crucible to obtain glass material A. More specifically, oxides, hydroxides, carbonates, or nitrates used as glass raw materials were appropriately selected from commonly used glass raw materials and weighed to obtain 1,000 g of glass. The glass transition temperature Tg, first crystal growth peak temperature Tp1, and second crystal growth peak temperature Tp2 of glass material A were also measured using the method described above and are shown in Table 1. The first crystal growth peak temperature Tp1 of glass material A was the temperature originating from the nucleation and growth of lithium metasilicate crystals, and the second crystal growth peak temperature Tp2 was the temperature originating from the nucleation and growth of lithium disilicate crystals. 【0104】 【0105】 Next, the mixed raw materials were placed in a platinum crucible and melted in a resistance-heated electric furnace at 1,500 to 1,700°C for about 3 hours. After degassing and homogenization, molten glass was obtained. The obtained molten glass was poured into a mold, held at a temperature 50°C above the glass transition point for 1 hour, and then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The obtained glass block was cut and ground to form glass plates. The thickness of the glass plates was 0.7 mm. 【0106】 Furthermore, after forming glass material A into a glass plate, the following heat treatment (heat treatment process) was performed: the temperature was raised to 510°C at a rate of 5°C / min and held for 4 hours, then raised to 530°C at a rate of 5°C / min and held for 2 hours, and finally raised to 740°C at a rate of 5°C / min and held for 2 hours. The heat treatment atmosphere was an atmospheric atmosphere. That is, in Example 1, the heat treatment process was performed with the first heat treatment temperature T1 set to 510°C, the second heat treatment temperature T2 set to 530°C, and the third heat treatment temperature T3 set to 740°C. The first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy the relationship shown in equations (1) to (4) above. Crystallized glass of Example 1 was obtained by following the above procedure. 【0107】<Example 2> After the glass material A was made into a glass plate, the temperature was raised to 530°C at a rate of 5°C / min and held for 2 hours, and then the temperature was raised to 740°C at a rate of 5°C / min and held for 2 hours to perform heat treatment (heat treatment process). Except for the above, the procedure was the same as in Example 1 to obtain the crystallized glass of Example 2. Note that in the procedure for obtaining the crystallized glass of Example 2, heat treatment was performed in only two stages and therefore does not satisfy the above equations (1) to (4). 【0108】 <Example 3> Crystallized glass of Example 3 was obtained in the same manner as in Example 1, except that the temperature in the heat treatment process was adjusted as shown in the table below. That is, in Example 3, the heat treatment process was carried out with a first heat treatment temperature T1 of 510°C, a second heat treatment temperature T2 of 550°C, and a third heat treatment temperature T3 of 740°C. The above first heat treatment temperature T1, second heat treatment temperature T2, and third heat treatment temperature T3 satisfy the relationship given by equations (1) to (4). 【0109】 <Example 4> Crystallized glass of Example 4 was obtained in the same manner as in Example 1, except that the temperature in the heat treatment process was adjusted as shown in the table below. That is, in Example 4, the heat treatment process was carried out with a first heat treatment temperature T1 of 510°C, a second heat treatment temperature T2 of 570°C, and a third heat treatment temperature T3 of 740°C. The above first heat treatment temperature T1, second heat treatment temperature T2, and third heat treatment temperature T3 satisfy the relationship given by equations (1) to (4). 【0110】 <Example 5> Crystallized glass of Example 5 was obtained in the same manner as in Example 1, except that the temperature in the heat treatment process was adjusted as shown in the table below. That is, in Example 5, the heat treatment process was carried out with a first heat treatment temperature T1 of 510°C, a second heat treatment temperature T2 of 650°C, and a third heat treatment temperature T3 of 740°C. The above first heat treatment temperature T1, second heat treatment temperature T2, and third heat treatment temperature T3 satisfy the relationships of equations (1), (2), and (4) above, but do not satisfy the relationship of equation (3). 【0111】 <Measurements> The following measurements were performed on each example of crystallized glass obtained. 【0112】[X-ray Diffraction] Powder X-ray diffraction measurements were performed on each example of crystallized glass obtained under the following conditions to identify the crystals precipitated in the crystallized glass and to calculate the crystallization rate. The results are shown in Table 2 below. • Measurement device: Rigaku SmartLab • X-rays used: CuKα rays • Measurement range: 2θ = 10 to 80° • Scan speed: 10° / min • Scan step: 0.02° 【0113】 [Fracture toughness value K] ＩＣ For each example of crystallized glass obtained, the fracture toughness value K was determined using the method described above. ＩＣ The following measurements were taken. The results are shown in Table 2 below. 【0114】 [Young's Modulus] The Young's modulus of each crystallized glass obtained was measured using the method described above. The results are shown in Table 2 below. 【0115】 [Haze] For each example of crystallized glass obtained, the haze at a thickness of 0.6 mm was measured using a HZ-V3 haze meter manufactured by Suga Test Instruments, with a C light source. The haze measurement results are shown in Table 2 below. In practical terms, a haze of 0.17% or less is preferable, 0.16% or less is more preferable, and 0.15% or less is even more preferable. 【0116】 <Results> The heat treatment conditions for obtaining crystallized glass in each example and the measurement results are shown in Table 2. In Table 2, the column for "Equation (1)" is written as "A" if the relationship of Equation (1) is satisfied, and as "B" if the relationship of Equation (1) is not satisfied. The same applies to the columns for "Equation (2)", "Equation (3)", "Equation (4)", "Equation (5-1)", and "Equation (7-1)". 【0117】 【0118】The results shown in Table 2 confirm that when heat treatment satisfying the requirements of formulas (1) to (4) is performed, the resulting crystallized glass exhibits reduced haze (Examples 1, 3, and 4). On the other hand, when the heat treatment is performed in two stages and does not satisfy the requirements of formulas (1) to (4), the resulting crystallized glass exhibits no reduction in haze (Examples 2 and 5). Furthermore, a comparison between Examples 1 and 3 and Example 4 confirms that when the requirements of formula (5-1) are met, the resulting crystallized glass exhibits even lower haze. Additionally, a comparison between Example 1 and Example 3 confirms that when the requirements of formula (7-1) are met, the resulting crystallized glass exhibits even lower haze. 【0119】 Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-218857, filed on December 13, 2024, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A method for manufacturing crystallized glass, comprising sequentially heat-treating a crystallization glass having a first crystal growth peak temperature Tp1 and a second crystal growth peak temperature Tp2, as measured by a differential thermal scanning calorimeter, at a first heat treatment temperature T1, a second heat treatment temperature T2, and a third heat treatment temperature T3, wherein the first crystal growth peak temperature Tp1, the first heat treatment temperature T1, the second heat treatment temperature T2, and the third heat treatment temperature T3 satisfy the following equations (1) to (4). However, the units of the left and right sides of the following equations (1) to (4) are °C, and Tg in the following equation (1) is the glass transition temperature of the crystallization glass. Equation (1) Tg < T1 Equation (2) T1 < T2 Equation (3) T2 ≤ T3 - 100 Equation (4) T1 ≤ Tp1 - 80 2. The method for producing crystallized glass according to claim 1, wherein the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following formula (5). However, the units of the left and right sides of the following formula (5) are °C. Formula (5) T2 < Tp1 3. A method for producing crystallized glass according to claim 1 or 2, wherein the second heat treatment temperature T2 and the first crystal growth peak temperature Tp1 satisfy the following formula (5-1). However, the units of the left and right sides of the following formula (5-1) are °C. Formula (5-1) T2 ≤ Tp1 - 50 4. A method for producing crystallized glass according to claim 1 or 2, wherein the first crystal growth peak temperature Tp1 and the second crystal growth peak temperature Tp2 satisfy the following formula (6). However, the units of the left and right sides of the following formula (6) are °C. Formula (6) Tp2 - Tp1 ≥ 160 5. A method for producing crystallized glass according to claim 1 or 2, wherein the first heat treatment temperature T1 and the second heat treatment temperature T2 satisfy the following formula (7). However, the units of the left and right sides of the following formula (7) are °C. Formula (7) T2 - T1 ≤ 50 6. A method for producing crystallized glass according to claim 1 or 2, wherein the third heat treatment temperature T3 and the first crystal growth peak temperature Tp1 satisfy the following formula (8). However, the units of the left and right sides of the following formula (8) are °C. Formula (8) Tp1 < T3 7. A method for producing crystallized glass according to claim 1 or 2, wherein the third heat treatment temperature T3 and the second crystal growth peak temperature Tp2 satisfy the following formula (9). However, the units of the left and right sides of the following formula (9) are °C. Formula (9) T3 < Tp2 8. A method for producing crystallized glass according to claim 1 or 2, wherein the second heat treatment temperature T2, the third heat treatment temperature T3, the first crystal growth peak temperature Tp1, and the second crystal growth peak temperature Tp2 satisfy the following formulas (5), (8), and (9). However, the units on the left and right sides of formula (5), formula (8), and formula (9) are °C. Formula (5) T2 < Tp1 Formula (8) Tp1 < T3 Formula (9) T3 < Tp2 9. The composition of the glass for crystallization, expressed in mole percentage based on oxides, contains 60.0 to 75.0% of SiO ２ O ３ 2.0 to 6.0% of Al ２ O ５ more than 0.0% and at most 3.0% of P ２ 20.0 to 30.0% of Li ２ O 0.0 to 5.0% of Na ２ O 0.0 to 1.0% of K ２ 1.0 to 5.0% of ZrO ２ 0.0 to 1.0% of SnO ２ 0.0 to 1.0% of SrO, and substantially does not contain Y ３ O. The method for producing the crystallized glass according to claim 1 or 2.​ 10. The resulting crystallized glass is Li ２ Si ２ O ５ A method for producing crystallized glass according to claim 1 or 2, comprising crystals.

11. Fracture toughness value K of the obtained crystallized glass. ＩＣ However, 1.3 MPa·m １／２ The method for producing crystallized glass according to claim 1 or 2.

12. A method for producing crystallized glass according to claim 1 or 2, wherein the haze of the resulting crystallized glass is 0.17% or less.

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