Method for producing crystallized glass

Abstract

Provided is a method for producing crystallized glass, in which cracks are less likely to be generated in crystallized glass obtained by peeling when a stack in which glass sheets for crystallization are stacked in a state where the glass sheets are in contact with each other is subjected to a heat treatment.　This method for producing crystallized glass involves obtaining glass for crystallization, the glass for crystallization having an altered layer formed on at least one surface of the glass for crystallization, stacking the glass for crystallization having the altered layer to obtain a glass stack for crystallization in which the altered layer is disposed between adjacent sheets of the glass for crystallization, and subjecting the glass stack for crystallization to a heat treatment involving heating at a crystal growth temperature, wherein the altered layer has a layer thickness of 20 nm or more.

Description

Method for manufacturing crystallized glass

[0001] This invention relates to a method for producing crystallized glass.

[0002] Crystallized glass is a type of glass with various excellent properties. For example, crystallized glass can exhibit excellent strength and is used in a variety of applications. Generally, crystallized glass is obtained by heat-treating glass of a predetermined composition. The glass subjected to heat treatment to obtain crystallized glass (hereinafter also referred to as "crystallization glass") may be subjected to heat treatment in a laminated state for efficiency.

[0003] For example, Patent Document 1 discloses a method of placing a setter having a predetermined range of heat capacity and a predetermined density between crystallization glasses and performing heat treatment.

[0004] International Publication No. 2020 / 018290

[0005] While Patent Document 1 uses a setter, the inventors investigated a method that does not use a setter in order to improve productivity. Specifically, they investigated a method in which crystallization glass is laminated in contact with each other and then heat-treated. When the inventors investigated a method in which crystallization glass is laminated in contact with each other, heat-treated, and then peeled off the crystallization glass after heat treatment, they found that cracks sometimes occur in the crystallized glass obtained by peeling, and that improvement is necessary.

[0006] The present invention has been made in view of the above problems, and aims to provide a method for manufacturing crystallized glass in which cracks are less likely to occur in the crystallized glass obtained by delamination when crystallized glass is laminated in a state where the crystallized glass is in contact with each other and then heat-treated.

[0007] As a result of diligent research into the above-mentioned problems, the present inventors discovered that when crystallization glass with a modified layer formed on its surface is laminated and heat-treated, cracks are less likely to occur in the crystallization glass obtained by peeling after heat treatment, leading to the present invention.

[0008] In other words, the inventors have found that the above problems can be solved by the following configurations: [1] A method for producing crystallized glass, comprising: obtaining crystallized glass with a modified layer formed on at least one surface of crystallized glass; stacking the crystallized glass with the modified layer to obtain a crystallized glass laminate in which the modified layer is arranged between adjacent crystallized glass pieces; and performing a heat treatment on the crystallized glass laminate, including heating at the crystal growth temperature, wherein the thickness of the modified layer is 20 nm or more. [2] The method for producing crystallized glass according to [1], comprising supplying a modification agent to at least one surface of the crystallized glass to obtain crystallized glass with a modified layer formed on at least one surface. [3] The method for producing crystallized glass according to [2], wherein the modification agent is a silicon removal agent. [4] The method for producing crystallized glass according to [3], wherein the silicon removal agent contains a fluorine-containing compound. [5] When obtaining the above-mentioned crystallized glass with altered layer, the process index I is calculated by the following formula (1). Ｐ A method for producing crystallized glass according to [3] or [4], wherein the value of is 100 or more. Formula (1) I Ｐ= T × t × c / logη In equation (1), T is the temperature of the crystallization glass when supplying the fluid containing the Si removal agent. The unit of T is °C. t is the time for supplying the fluid containing the Si removal agent. The unit of t is seconds. c is the content of the Si removal agent in the fluid containing the Si removal agent. The unit of c is volume percent. logη is the common logarithm of the viscosity of the crystallization glass when supplying the fluid containing the Si removal agent. The unit of viscosity is Pa·s. [6] A method for producing crystallization glass according to any one of [1] to [5], wherein the maximum value of the ratio of F content to Si content in the altered layer is 0.05 or more. [7] A method for producing crystallization glass according to any one of [1] to [6], wherein the thickness of the altered layer is 50 nm or more. [8] A method for producing crystallized glass according to any one of [1] to [7], wherein the crystal growth temperature is 700 to 1100°C. [9] A method for producing crystallized glass according to any one of [1] to [8], wherein the thickness of the crystallized glass is 1.5 mm or less.

[10] The composition of the crystallized glass is expressed as a molar percentage based on oxides, SiO ２ 60-75%, Al ２ O ３ 2-20%, Li ２ A method for producing crystallized glass according to any one of [1] to [9], wherein the crystallized glass obtained by the method for producing crystallized glass according to any one of [1] to

[10] contains 5 to 30% O.

[11] A method for producing crystallized glass, wherein the crystallized glass obtained by the method for producing crystallized glass according to any one of [1] to

[10] contains one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

[12] A method for producing crystallized glass, wherein the crystallized glass obtained by the method for producing crystallized glass according to any one of [1] to

[11] contains one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, and petalite crystals.

[13] A method for producing crystallized glass according to any one of [1] to

[12] , wherein the crystallized glass obtained by peeling off the heat-treated crystallized glass from the heat-treated crystallized glass laminate.

[0009] According to the present invention, it is possible to provide a method for manufacturing crystallized glass in which cracks are less likely to occur in the crystallized glass obtained when the laminated crystallized glass, which is in contact with each other, is heat-treated.

[0010] This is a schematic cross-sectional view showing one embodiment of the crystallization glass in the manufacturing method of the present invention. This is a schematic cross-sectional view showing one embodiment of the state in which the crystallization glass is laminated. This is a schematic cross-sectional view showing one embodiment of the laminate subjected to heat treatment of the present invention.

[0011] The present invention will now be described in detail. The following descriptions of constituent elements may be based on typical 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 values ​​described before and after it are included as the lower and upper limits. In the glass composition, "substantially absent" means that it is not present except for unavoidable impurities contained in the raw materials, etc., that is, it is not intentionally included. Specifically, for components other than those described as part of the glass composition, for example, less than 0.1 mol%, more preferably 0.08 mol% or less, and even more preferably 0.05 mol% or less.

[0012] <Method for Manufacturing Crystallized Glass> The method for manufacturing crystallized glass of the present invention involves obtaining crystallized glass with an altered layer formed on at least one surface of crystallized glass, stacking the crystallized glass with the altered layer to obtain a crystallized glass laminate in which the altered layer is placed between adjacent crystallized glass pieces, and then performing a heat treatment on the crystallized glass laminate, including heating at the crystal growth temperature. Here, the thickness of the altered layer is 20 nm or more. Hereinafter, the step of obtaining crystallized glass with an altered layer formed on at least one surface of crystallized glass will also be referred to as the "altered layer formation step". Hereinafter, the step of stacking crystallized glass with an altered layer to obtain a crystallized glass laminate in which the altered layer is placed between adjacent crystallized glass pieces will also be referred to as the "stacking step". Hereinafter, the step of performing a heat treatment on the crystallized glass laminate, including heating at the crystal growth temperature will also be referred to as the "heat treatment step". Furthermore, in the method for manufacturing crystallized glass of the present invention, crystallized glass may be obtained by peeling off the heat-treated crystallized glass from the heat-treated crystallized glass laminate. Hereinafter, the step of obtaining crystallized glass by peeling off the heat-treated crystallized glass from the heat-treated crystallized glass laminate will also be referred to as the "peeling step." Below, each step included in the method for manufacturing crystallized glass of the present invention, and steps that may be included in the method for manufacturing crystallized glass of the present invention, will be described in detail.

[0013] [Process for Forming an Altered Layer] The process for forming an altered layer is a process for obtaining crystallization glass with an altered layer formed on at least one surface of the crystallization glass. That is, the obtained crystallization glass with an altered layer has an altered layer formed on at least one surface of the crystallization glass. In this specification, "altered layer" refers to a layer composed of a material with a different composition from the crystallization glass, and can be formed, for example, by the method described later. The above-mentioned material with a different composition refers to a material in which one or more components are increased or decreased by 5 mol% or more compared to the composition of the crystallization glass, or a material in which one or more components not included in the composition of the crystallization glass are increased by 5 mol% or more. The embodiments of crystallization glass with an altered layer in the manufacturing method of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a schematic cross-sectional view showing one aspect of the crystallization glass with a modified layer in the manufacturing method of the present invention. The crystallization glass 10 with a modified layer shown in FIG. 1 is a plate-shaped glass. In the crystallization glass 10 with a modified layer shown in FIG. 1, a modified layer 14 is formed on one surface of the crystallization glass 12. In the aspect shown in FIG. 1, the modified layer 14 is formed only on one surface of the crystallization glass 12, but the modified layer 14 may also be formed on the other surface of the crystallization glass 12.

[0015] The method for obtaining the crystallization glass with a modified layer is not particularly limited. For example, a method of supplying a modifying agent to the surface of the crystallization glass, modifying the surface of the crystallization glass to form a modified layer, and obtaining the crystallization glass with a modified layer can be mentioned. Hereinafter, as an example of the modified layer forming step, a method of contacting a Si-removing agent with the crystallization glass to form a modified layer on the surface of the crystallization glass and obtaining the crystallization glass with a modified layer will be described. That is, an example in which the above-mentioned modifying agent is a Si-removing agent will be described. In the manufacturing method of the crystallization glass of the present invention, the method for obtaining the crystallization glass with a modified layer is not limited to the above method.

[0016] In an example of the modified layer forming step, first, the crystallization glass is prepared. The crystallization glass is preferably a plate-shaped glass. When the crystallization glass is a plate-shaped glass, the plate thickness of the crystallization glass is not particularly limited, but examples include 0.1 mm or more, and preferably 0.5 mm or more. Also, when the crystallization glass is a plate-shaped glass, the plate thickness of the crystallization glass is often 2.0 mm or less, more preferably 1.5 mm or less, and most preferably 1.0 mm or less. Further, when the crystallization glass is a plate-shaped glass, the area of the main surface (the surface having the largest area) is not particularly limited, but for example, 0.01 m ２ or more can be mentioned, and 0.1 m ２ or more is preferable. Also, the above area is 0.5 m ２The following is often the case. Furthermore, the crystallization glass may be float glass manufactured by the float process, or glass manufactured by the roll-out process. Also, the crystallization glass may be glass manufactured by other methods. The preferred composition of the crystallization glass (hereinafter also referred to as the "mother glass composition") is described below. The preferred composition of the crystallization glass (mother glass composition) is expressed as a molar percentage based on oxides, and is SiO ２ 60-75%, Al ２ O ３ 2-20%, P ２ O ５ 0-5%, Li ２ It is preferable that the content of oxygen be 5 to 30%.

[0017] In particular, the composition of the mother glass is expressed as a mole percentage based on oxides, SiO ２ 60-75%, Al ２ O ３ 2-20%, P ２ O ５ 0-5%, Li ２ 5-28% O, Na ２ O 0-4%, K ２ O 0-5%, MgO 0-10%, CaO 0-5%, ZrO ２ It is preferable that it contains 0 to 5% of [the specified element]. The following describes each component included in the mother glass composition.

[0018] 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.

[0019] SiO ２ The content of is more preferably 63% or more, and even more preferably 65% ​​or more, in order to improve chemical durability. On the other hand, from the viewpoint of improving melting properties, SiO ２ The content of is more preferably 74.0% or less, and even more preferably 72.0% or less.

[0020] Al ２ O ３It is a component that improves ion exchange performance during chemical strengthening and increases the surface compressive stress after 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 The content of is more preferably 2.5% or more, and even more preferably 3.0% or more, and 3.5% or more, in that order. On the other hand, it is sometimes required that crystal growth is difficult 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 ３ The content of is more preferably 18.0% or less, and even more preferably 17.0% or less, 16.0% or less, and 15.0% or less, in that order.

[0021] 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 64.0% or more, more preferably 68.0% or more, even more preferably 72.0% or more, and particularly preferably 76.0% 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 88.0% or less, and even more preferably 86.0% or less.

[0022] Li ２ O is a component that can undergo ion exchange and improves the meltability of glass. ２By 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. Also, 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 7.0% or more, and even more preferably 9.0% or more.

[0023] 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 27.0% or less, even more preferably 25.0% or less, particularly preferably 23.0% or less, most preferably 21.0% or less, and may also be 20.0% or less.

[0024] Na ２ 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.

[0025] 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 and 0.8% 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, Na ２ The O content is more preferably 3.0% or less, even more preferably 2.5% or less, and particularly preferably 2.3% or less.

[0026] K ２ O is a component that suppresses devitrification by inhibiting the rise in devitrification temperature, and also improves ion exchange performance. ２The O content is more preferably 0.03% or more, even more preferably 0.05% or more, and particularly preferably 0.1% or more. On the other hand, from the viewpoint of avoiding a decrease in surface compressive stress (K_CS) during the strengthening treatment with sodium salt, K ２ The O content is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. ２ O does not necessarily need to be included.

[0027] Li ２ O content, Na ２ O content and K ２ The total oxygen content, R, is preferably 8.0 to 30.0%, more preferably 9.0 to 28.0%, and particularly preferably 10.0 to 25.0%, from the viewpoint of suppressing the rise in devitrification temperature and reducing the crystal growth rate.

[0028] Li for the above R ２ Ratio of O content ([Li ２ O] / ([Li ２ O] + [Na] ２ O] + [K ２ O]), hereinafter referred to as “Li ２ O / R ２ Li (also written as "O") is more preferably 0.80 or higher, and even more preferably 0.85 or higher, from the viewpoint of further improving the deep stress in the chemical strengthening properties. ２ O / R ２ From the viewpoint of further improving chemical resistance, O is more preferably 0.99 or less, even more preferably 0.98 or less, and particularly preferably 0.95 or less.

[0029] Na for the above ２ Ratio of O content ([Na ２ O] / ([Li ２ O] + [Na] ２ O] + [K ２ O]), hereinafter referred to as “Na ２ O / R ２ Na (also written as "O") is preferably greater than 0.00, more preferably 0.01 or higher, even more preferably 0.02 or higher, particularly preferably 0.05 or higher, and most preferably 0.06 or higher, from the viewpoint of further improving the deep stress in chemical strengthening properties. ２O / R ２ From the perspective of further enhancing the drug resistance, 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.

[0030] The K to the above R ２ The ratio of the content of O ([K ２ O] / ([Li ２ O]+[Na ２ O]+[K ２ O]), hereinafter, also referred to 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 perspective of further increasing the electrical resistance of the glass. K ２ O / R ２ O is preferably 0.50 or less, more preferably 0.40 or less, still more preferably 0.30 or less, and particularly preferably 0.20 or less from the perspective of increasing the compressive stress near the surface in the chemical strengthening characteristics. Incidentally, K ２ O / R ２ O may be 0.

[0031] Also, the product of Li[[ID=�1]] ２ O / R ２ O, Na ２ O / R ２ O, and K ２ O / R ２ O is preferably 0.00005 or more, more preferably 0.0001 or more, and still more preferably 0.001 or more from the perspective of suppressing the increase in the devitrification temperature and reducing the crystal growth rate. Also, the above product is more preferably 0.020 or less. Incidentally, the above product may be 0.

[0032] The ratio of the content of Al ２ O ３ to the above R ([Al ２ O ３ / ([Li ２ O]+[Na ２ O]+[K ２ O]), hereinafter, also referred to as "Al ２ O ３ / R ２Al (also written as "O") is preferably 0.10 or higher, more preferably 0.20 or higher, even more preferably 0.50 or higher, and particularly preferably 0.80 or higher. ２ O ３ / R ２ O is preferably 3.00 or less, more preferably 2.00 or less, even more preferably 1.50 or less, and particularly preferably 1.30 or less.

[0033] [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.

[0034] 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 terms of making it easier to increase the compressive stress layer during chemical strengthening treatment, the MgO content is more preferably 9.0% or less, and even more preferably 7.0% or less, 5.0% or less, and 3.0% or less, in that order.

[0035] Furthermore, the inclusion of MgO can suppress the phase transition of the crystalline phase from β-quartz solid solution to β-spodumene, thereby suppressing the precipitation of β-spodumene crystals. From the above viewpoint, it is also preferable to contain more than 0.5% and 7.0% or less of MgO. MgO may be substantially absent.

[0036] 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 2.0% 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.

[0037] 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 10.0% or less, and more preferably 8.0% or less, 7.0% or less, 6.0% or less, 3.0% or less, and 1.0% or less, in that order.

[0038] 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 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO may be substantially absent.

[0039] 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 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO may be substantially omitted.

[0040] ZnO is a component that improves the meltability of glass. The ZnO 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 ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. ZnO may be substantially absent.

[0041] lnW is a parameter that represents the degree of oxide mixing, calculated from the content of alkali metal oxides, alkaline earth metal oxides, and zinc oxide in the glass. lnW is expressed by the following formula: lnW = ln(([Li ２ O] + [Na] ２ O] + [K ２ O] + [MgO] + [CaO] + [SrO] + [BaO] + [ZnO])! / ([Li ２ O]! ×[Na ２ O]! × [K ２ O]! ×[MgO]! ×[CaO]! ×[SrO]! ×[BaO]! ×[ZnO]! ))...Equation (W1) In Equation (W1), [Li ２ O] [Na ２ O], [K ２ [O], [MgO], [CaO], [SrO], [BaO], and [ZnO] are each Li ２ O, Na ２ O, K ２ This represents the content of each component, O, MgO, CaO, SrO, BaO, and ZnO, expressed as a molar percentage based on their oxides. The ! symbol indicates raising a positive integer to a factorial. For example, [XO]! means taking the molar percentage content of component XO based on its oxides, truncating the decimal part to an integer, and then raising that integer to a factorial. For example, Na ２ If O is 4.8 mol%, the calculation is the factorial of "4", i.e., 4 × 3 × 2 × 1. A larger value for lnW indicates a higher degree of mixing of the above metal oxide, and the devitrification of the glass can be suppressed accordingly. From the above viewpoint, lnW is preferably 10 or more, more preferably 12 or more, even more preferably 13 or more, and particularly preferably 14 or more. lnW is preferably 20 or less, more preferably 18 or less, and even more preferably 17 or less.

[0042] 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, TiO２ 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.

[0043] 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 more than 0%, and even more preferably 0.5% or more, 1% or more, and 1.5% or more, in that order. ZrO ２ The content of is more preferably 4% or less.

[0044] P ２ O ５ This makes it easier to increase the compressive stress layer during chemical strengthening. ２ O ５ The content of is more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 1.5% or more. On the other hand, from the viewpoint of increasing acid resistance, P ２ O ５ The content of is more preferably 3.0% or less. From the viewpoint of preventing striations from forming during melting, it is also preferable that it be substantially absent.

[0045] 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 ３The 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.

[0046] Y 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 content of is preferably more than 0%, and more preferably 0.1% or more, 0.2% or more, 0.5% or more, and 0.8% or more, in that order. On the other hand, Y is suitable because it is easy to increase the compressive stress layer during chemical strengthening treatment. ２ O ３ The content is more preferably 2.0% or less, and even more preferably 1.5% or less. ２ O ３ It does not necessarily have to be included in practice.

[0047] From the viewpoint of improving initial solubility, ZrO ２ and Y ２ O ３ The total content of ZrO is more preferably 5.0% or less. ２ and Y ２ O ３ There is no particular lower limit to the total content of the elements, but from the viewpoint of increasing the strength of the glass, it is more preferable to have 0.5% or more, and even more preferable to have 1.0% or more and 1.5% or more, in that order.

[0048] ZrO ２ and Y ２ O ３ ZrO ２ Ratio of content [ZrO ２ ] / ([ZrO ２ ] + [Y ２ O ３ [ZrO] is more preferably 0.50 or higher, even more preferably 1.00 or higher, and particularly preferably 2.00 or higher. ２ ] / ([ZrO ２ ] + [Y ２ O ３The coefficient of the

[0049] ZrO ２ and Y ２ O ３ While ZrO is known as a nucleating agent when added alone, ２ and Y ２ O ３ By co-adding with ZrO ２ and Y ２ O ３ Since a eutectic is formed, the devitrification temperature, crystal growth rate, and crystallization start temperature can be controlled. Furthermore, [ZrO ２ ] / ([ZrO ２ ] + [Y ２ O ３ By setting [ZrO] to the above range, the diffusion of ions in the glass is suppressed, which reduces the rise in the devitrification temperature and suppresses devitrification. ２ ] / ([ZrO ２ ] + [Y ２ O ３ By setting [ZrO] to the above range, the glass is stabilized, and furthermore, the temperature range in which nucleation occurs and the temperature range in which crystal growth occurs are separated without overlapping, thereby suppressing an increase in the crystal growth rate and thus suppressing the occurrence of defects. ２ ] / ([ZrO ２ ] + [Y ２ O ３ By setting the temperature range to the above range, the temperature range in which nucleation occurs shifts to the lower temperature side, suppressing the decrease in the crystallization initiation temperature and improving manufacturing characteristics.

[0050] La ２ O ３ It is not required, but Y ２ O ３ It can be contained for the same reasons. La 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 ３The 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.

[0051] Nb ２ O ５、 Ta ２ O ５ , Gd ２ O ３ , CEO ２ These 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.

[0052] 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.

[0053] 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 O５ , Bi ２ O ３ SeO ２ Er ２ O ３ , Nd ２ O ３ These are some examples of suitable options.

[0054] SO4 is used as a clarifying agent when melting glass. ３ It may also contain chlorides, fluorides, etc., as appropriate. ２ O ３ It 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 0.1% or more, even more preferably 0.2% or more, and particularly preferably 0.3% or more. Also, SnO ２ The content of this substance is preferably 1.5% or less, and more preferably 1.2% or less, in order to suppress the occurrence of defects.

[0055] In one example of the altered layer formation process, a silicon removal agent is brought into contact with the prepared crystallization glass. In this specification, the silicon removal agent is a substance that removes SiO2 from the crystallization glass that has been brought into contact with it. ２ This refers to a compound that changes a component into a state that makes it easier to remove. Examples of silicon-removing agents include fluorine-containing compounds and alkali metal salts, with fluorine-containing compounds being preferred. Examples of fluorine-containing compounds include hydrogen fluoride (HF), fluorocarbons (e.g., chlorofluorocarbons, fluorocarbons (carbon tetrafluoride), hydrochlorofluorocarbons, hydrofluorocarbons, halons), and fluorine gas (F ２ Examples include trifluoroacetic acid, silicon tetrafluoride, phosphorus pentafluoride, phosphorus trifluoride, boron trifluoride, nitrogen trifluoride, and chlorine trifluoride, with hydrogen fluoride being preferred.

[0056] In one example of the altered layer formation process, the method of contacting the crystallization glass with the desilicon agent is not particularly limited, but one example is a method of spraying a fluid containing the desilicon agent onto the surface of the crystallization glass. In the fluid containing the desilicon agent, water (H) ２ It is also preferable to include O). The fluid containing the silicon removal agent may be a gas or a liquid. If the fluid containing the silicon removal agent is a liquid, it may be supplied to the surface of the crystallization glass by a method such as spray coating while still in liquid form. Alternatively, if the fluid containing the silicon removal agent is a liquid, the liquid may be vaporized and the vaporized silicon removal agent may be supplied to the surface of the crystallization glass. The fluid containing the silicon removal agent may contain a carrier gas. Examples of carrier gases include nitrogen gas, helium gas, argon gas, and carbon dioxide gas. When using a fluid containing gaseous water as the silicon removal agent, for example, the carrier gas may be supplied by bubbling into a device containing water, and the carrier gas supplied into the device may be supplied to the crystallization glass together with the silicon removal agent. Alternatively, water vapor may be supplied directly to the crystallization glass together with the silicon removal agent.

[0057] The content of the silicon removal agent in a fluid containing the silicon removal agent is preferably 1 volume% or more, more preferably 3 volume% or more, even more preferably 5 volume% or more, and particularly preferably 7 volume% or more, relative to the total volume of the fluid containing the silicon removal agent. Furthermore, the content of the silicon removal agent in a fluid containing the silicon removal agent is preferably 30 volume% or less, more preferably 20 volume% or less, and even more preferably 15 volume% or less, relative to the total volume of the fluid containing the silicon removal agent. In the above preferred content of the silicon removal agent, it is also preferable that the silicon removal agent is hydrogen fluoride.

[0058] The temperature of the crystallization glass when supplying the fluid containing the silicon removal agent is preferably 100°C or higher, more preferably 200°C or higher, and even more preferably 300°C or higher, as this facilitates the formation of the altered layer. The temperature of the crystallization glass when supplying the fluid containing the silicon removal agent is preferably 1000°C or lower, more preferably 800°C or lower, even more preferably 700°C or lower, and particularly preferably 500°C or lower.

[0059] Furthermore, the time for supplying the fluid containing the silicon removal agent is preferably 5 seconds or more, more preferably 10 seconds or more, and even more preferably 20 seconds or more, in that it facilitates the formation of the altered layer. The time for supplying the fluid containing the silicon removal agent is often 180 seconds or less, preferably 120 seconds or less, more preferably 60 seconds or less, and most preferably 30 seconds or less.

[0060] The above-mentioned altered layer formation step is sufficient to obtain crystallization glass with an altered layer, and may be performed in the process of manufacturing the crystallization glass. The following describes the case in which the crystallization glass is manufactured by the float method. In the float method, molten glass is supplied to the surface of molten metal (e.g., molten tin) contained in a float bath, a glass ribbon is formed, and the glass ribbon is slowly cooled in an annealing furnace to obtain plate-shaped crystallization glass. For example, a fluid containing the above-mentioned silicon removal agent may be supplied to the slowly cooling glass ribbon to form an altered layer on the surface of the crystallization glass. The preferred temperature of the glass ribbon when supplying the fluid containing the above-mentioned silicon removal agent is preferably within the temperature range described above. Furthermore, the viscosity of the glass ribbon when supplying the fluid containing the above-mentioned silicon removal agent is 1.0 × 10⁻⁶. ９ Pa·s or higher is preferred, and 1.0 × 10 １０ Pa·s or higher is more preferable, and 1.0 × 10 １１ Pa·s or higher is even more preferable, and 1.0 × 10 １２ Pa·s or higher is particularly preferred, and 1.0 × 10 １３ A viscosity of Pa·s or higher is most preferable. The apparatus for supplying the fluid containing the above-mentioned silicon removal agent to the glass ribbon is not particularly limited, and known apparatus can be used. Furthermore, it is also preferable to supply the fluid containing the above-mentioned silicon removal agent at the above viscosity in a form other than a glass ribbon. The viscosity of the glass can be measured by known methods.

[0061] Here, in the altered layer formation process, the process index I is calculated using the following formula (1) with respect to the temperature T (unit: °C) of the crystallization glass when supplying the fluid containing the silicon removal agent, the time t (unit: seconds) for supplying the fluid containing the silicon removal agent (hereinafter also referred to as "processing time"), the content c (unit: volume%) of the silicon removal agent (more preferably HF) in the fluid containing the silicon removal agent (hereinafter also referred to as "silicon removal agent concentration"), and the common logarithm logη of the viscosity (unit: Pa·s) of the crystallization glass when supplying the fluid containing the silicon removal agent. Ｐ Calculate the process index I. Ｐ The process index I is preferably 100 or more, more preferably 200 or more, and even more preferably 250 or more. Ｐ It is usually 20,000 or less, and preferably 15,000 or less. Formula (1) I Ｐ = T × t × c / logη Note that the common logarithm is a logarithm with base 10. Also, the values ​​substituted into equation (1) should be those with the units mentioned above.

[0062] As described above, when the desilicon agent is brought into contact with the crystallization glass, SiO is released from the surface of the crystallization glass. ２ A layer (altered layer) is formed from which the altered layer has been removed, and a crystallization glass with an altered layer is obtained. Note that in the method described above, SiO ２A modified layer is obtained in which the content of is low relative to the composition of the crystallization glass. In the method for manufacturing crystallization glass of the present invention, the thickness of the modified layer is 20 nm or more, preferably 50 nm or more, and more preferably 100 nm or more, as described above. The thickness of the modified layer is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less, in that the modified layer is easier to remove in a later step. The thickness of the modified layer can be measured by a scanning electron microscope (SEM). Specifically, first, the crystallization glass is cut and a measurement sample is prepared in which the cross section perpendicular to the surface of the crystallization glass is exposed. The cross section of the measurement sample is observed with an SEM and the thickness of the modified layer is measured. The thickness of the modified layer is the arithmetic mean of the thicknesses measured at any 10 points. Furthermore, when cross-sectional observation is performed using SEM, a difference in contrast or morphology is often observed between the altered layer and the non-altered layer, and the interface between the altered layer and the non-altered layer can often be identified.

[0063] Furthermore, when forming a modified layer using a silicon removal agent, the SiO in the composition of the crystallization glass ２ The SiO content of the altered layer ２ The ratio of the content is preferably 0.95 or less, more preferably 0.90 or less, even more preferably 0.80 or less, particularly preferably 0.70 or less, and most preferably 0.60 or less. Also, the above ratio is often 0.10 or more, and preferably 0.20 or more. SiO in the composition of crystallization glass ２ The content of, and the SiO of the altered layer ２ The content can be measured by secondary ion mass spectrometry (SIMS). The above ratio is determined by the ratio of the Si ion detection intensity at the center of the thickness of the altered layer to the Si ion detection intensity at the center of the thickness of the chemically strengthened glass plate. In this specification, SIMS measurements are performed using an ULVAC-PHIE ADEPT1010 under the following conditions: Primary ion species: Cs ＋Primary ion accelerating voltage: 5 kV; Primary ion current: 500 nA; Primary ion incidence angle: 60° relative to the normal to the sample surface; Primary ion raster size: 300 × 300 μm ２ Secondary ion polarity: Negative Secondary ion detection area: 60 × 60 μm ２ (4% of the raster size of the primary ions) ESA Input Lens: 0 Use of neutralizing gun: Yes In addition, the sputtering rate by primary ions is measured in advance and the sputtering time is converted to depth. Specifically, the depth of the analytical crater is measured using a stylus-type surface profile analyzer (Veeco Dektak 150) and the sputtering rate of primary ions is determined.

[0064] Furthermore, when a compound containing fluorine (preferably hydrogen fluoride) is used as a silicon removal agent, the altered layer often contains fluorine. Here, the maximum value of the ratio of F content to Si content in the altered layer is preferably 0.01 or higher, more preferably 0.05 or higher, and even more preferably 0.1 or higher. Also, the maximum value of the above ratio is often 2.0 or lower, and preferably 1.0 or lower. The maximum value of the ratio of F content to Si content in the altered layer can be measured by SIMS. Specifically, when crystallization glass with an altered layer is analyzed in the thickness direction by SIMS, the ratio of the detected intensity of F to the detected intensity of Si is calculated at each depth, and a chart of the F / Si ratio in the depth direction is created. In the above chart, the maximum value of the F / Si ratio is taken as the maximum value of the above ratio.

[0065] In the procedure described above, a method was described in which a modified layer is formed on the surface of the crystallized glass by bringing the desilicon removal agent into contact with the crystallization glass. However, the modified layer formation process is not limited to the above method. For example, an acidic compound (e.g., nitric acid (HNO)) can be used as the modified agent. ３ ) and sulfuric acid (H ２ SO ４Methods using acids such as 0.575 and their salts, and basic compounds (for example, sodium hydroxide (NaOH) and potassium hydroxide (KOH)) are also mentioned. When using an acidic or basic compound as a degrading agent, a method of contacting the crystallization glass with a solution of the degrading agent (preferably an aqueous solution) is mentioned. The method of contact is not particularly limited and includes, for example, immersing the crystallization glass in the above-mentioned solution of the degrading agent, and supplying the solution of the degrading agent to the surface of the crystallization glass. The time and temperature of contact between the degrading agent solution and the crystallization glass can be adjusted as appropriate, and the composition and thickness of the degraded layer can be controlled by the time and temperature.

[0066] [Lamination Process] The lamination process is a process of laminating crystallization glass with altered layers to produce a crystallization glass laminate in which the altered layer is positioned between adjacent crystallization glass pieces. In other words, in the lamination process, crystallization glass with altered layers is laminated so that the altered layer is positioned between the crystallization glass pieces. The state in which the crystallization glass with altered layers is laminated will be explained with reference to the drawings.

[0067] Figure 2 is a schematic cross-sectional view showing one embodiment of a state in which crystallization glass with an altered layer is laminated. The crystallization glass laminate 20 shown in Figure 2 is made up of three layers of crystallization glass 10 with an altered layer obtained in the altered layer formation process. In the crystallization glass laminate 20, an altered layer 14 is placed between each of the three crystallization glass 12. In the embodiment shown in Figure 2, one layer of altered layer 14 is placed between the crystallization glass 12, but two or more layers of altered layer 14 may be placed between the crystallization glass 12. Also, in the embodiment shown in Figure 2, the surface of the crystallization glass 10 placed at the bottom of the paper does not have an altered layer 14, but an altered layer 14 may be placed there.

[0068] In the embodiment shown in Figure 2, the number of layers of the altered layer crystallization glass 10 is three, but this can be changed as appropriate. The number of layers of the altered layer crystallization glass 10 may be, for example, two, four or more, five or more, or ten or more. Furthermore, there is no particular upper limit to the number of layers, but it is preferable to adjust the number of layers so that the total mass of the stacked crystallization glass 10 is 30 kg or less. If the total mass of the stacked crystallization glass 18 is 30 kg or less, the crystallization glass 18 placed at the bottom becomes less likely to break.

[0069] The method for carrying out the lamination process is not particularly limited. For example, one method is to stack the crystallization glass with the altered layer obtained in the altered layer formation process in order, with the side with the altered layer facing upwards. Alternatively, the lamination position of the upper glass may be offset from the lower glass during lamination to serve as a gripping portion during delamination.

[0070] [Heat Treatment Process] In the heat treatment process, the crystallization glass laminate is subjected to heat treatment including heating at the crystal growth temperature to obtain crystallized glass. Note that the heat treatment process only needs to include heating at the crystal growth temperature (hereinafter also referred to as "crystal growth treatment"), and the heat treatment process may also include heating at the nucleation temperature (hereinafter also referred to as "nucleation treatment"). The heat treatment process can be carried out, for example, by heating the laminate as shown in Figure 3.

[0071] Figure 3 is a schematic cross-sectional view showing one embodiment of a laminate used in a heat treatment process. The laminate 30 shown in Figure 3 comprises a first setter plate 22, a crystallization glass laminate 20, a second setter plate 24, and a support 26 in that order. Note that the crystallization glass laminate 20 is the same as the crystallization glass laminate described in Figure 2, so its description is omitted. The support 26 supports the crystallization glass laminate 20 and facilitates transport and other operations. Furthermore, arranging the first setter plate 22 and the second setter plate 24 makes it less likely for the crystallization glass 12 in the crystallization glass laminate 20 to shift position.

[0072] In the embodiment shown in Figure 3, one or more of the first setter plate 22, the second setter plate 24, and the support 26 may be omitted. Preferably, the first setter plate 22, the second setter plate 24, and the support 26 are formed from known heat-resistant materials.

[0073] In the heat treatment process, heating at the crystal growth temperature (crystal growth treatment) is performed. The heating temperature in the crystal growth treatment can be appropriately adjusted depending on the type of crystal to be precipitated in the crystallization glass. For example, the heating temperature in the crystal growth treatment is preferably 600°C or higher, more preferably 700°C or higher, even more preferably 800°C or higher, and may also be 900°C or higher. The heating temperature in the crystal growth treatment is usually 1100°C or lower. The heating time for the crystal growth treatment is, for example, 0.2 hours or more, preferably 0.5 hours or more, more preferably 1.0 hour or more, and even more preferably 1.5 hours or more. The heating time for the high-temperature heat treatment is 12 hours or less, preferably 6 hours or less, and even more preferably 4 hours or less.

[0074] Furthermore, the heat treatment process may include a heating process at the nucleation temperature (nucleation treatment), as described above. It is preferable to perform the nucleation treatment before the crystal growth treatment. More specifically, it is preferable to perform the crystal growth treatment after performing the nucleation treatment on the crystallization glass. It is also preferable to perform the nucleation treatment at a temperature lower than the temperature at which the crystal growth treatment is performed. Nucleation treatment generates crystal nuclei in the crystallization glass, and when the crystal growth treatment is performed, the crystal nuclei grow more easily. The heating temperature in the nucleation treatment can be appropriately adjusted, for example, depending on the type of crystal to be precipitated in the crystallization glass. For example, the heating temperature in the nucleation treatment can be 500°C or higher, preferably 600°C or higher, and more preferably 700°C or higher. It is also preferable that the heating temperature in the nucleation treatment be less than 800°C, and more preferably 795°C or lower. The heating time for the nucleation treatment can be 0.5 hours or more, preferably 1 hour or more, and more preferably 2 hours or more. Furthermore, the heating time for the nucleation treatment is 12 hours or less, preferably 8 hours or less, and more preferably 6 hours or less.

[0075] The type of crystals contained in the resulting crystallized glass is not particularly limited, but for example, one or more crystals selected from the group consisting of lithium silicate crystals, lithium aluminosilicate crystals, and lithium phosphate crystals are preferred, and one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals are more preferred. As for lithium silicate crystals, lithium metasilicate (Li ２ SiO ３ ) crystals, lithium disilicate crystals (Li ２ Si ２ O ５ ) etc. are preferred. As lithium phosphate crystals, ortholithium phosphate crystals (Li ３ PO ４ ) etc. are preferred. As lithium aluminosilicate crystals, β-spodumene crystals (LiAlSi ２ O ６ ), petalite crystal (LiAlSi ４ O １０ ) etc. are preferred. The resulting crystallized glass may also preferably contain one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, and petalite crystals. Furthermore, examples of crystals contained in the resulting crystallized glass include β-quartz solid solution, magnesium-containing crystals, and zirconium-containing crystals.

[0076] The crystallinity of the resulting 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 terms of improving mechanical strength. Furthermore, to increase transparency, it is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A low crystallinity is also advantageous in that it is easier to heat and bend or shape. The crystallinity can be calculated from the X-ray diffraction intensity using the Rietveld method. The Rietveld method is described in "Crystal Analysis Handbook" (Kyoritsu Shuppan, 1999, pp. 492-499), edited by the editorial committee of the Crystallographic Society of Japan.

[0077] The average grain size of the precipitated crystals in the resulting 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.

[0078] In the heat treatment process, the rate of heating when changing the temperature can be adjusted as appropriate, but for example, it can be 1°C / min or more, and preferably 3°C / min or more. Alternatively, the rate of heating can be 10°C / min or less. Furthermore, the atmosphere in the heat treatment process is not particularly limited and may be an inert gas atmosphere or an atmospheric atmosphere.

[0079] The heat treatment process can be carried out in a known heat treatment furnace or the like. The type of heat treatment furnace is not particularly limited and may be batch type or continuous type. Furthermore, the heating method of the heat treatment furnace is not particularly limited and may be combustion heating or electric heating.

[0080] [Peeling Step] In the method for manufacturing crystallized glass of the present invention, a peeling step may be performed. In the peeling step, the heat-treated crystallized glass is peeled off from the heat-treated crystallized glass laminate to obtain crystallized glass. As described above, in the manufacturing of crystallized glass of the present invention, since the altered layer is arranged between the crystallized glass, the crystallized crystallized glass can be easily peeled off from each other even after heat treatment. When the peeling step is performed, crystallized glass is obtained by crystallizing the crystallized glass. The peeling step can be performed by known methods, but for example, one method is to pull the crystallized glass of the heat-treated crystallized glass laminate in a direction substantially parallel to the lamination direction and peel off the crystallized crystallized glass.

[0081] [Cutting Step] The method for producing crystallized glass of the present invention may include a step of cutting the obtained crystallized glass to a desired size. That is, the obtained crystallized glass may be cut. The cutting method is not particularly limited and can be done by known methods. The size to which the crystallized glass is cut is also not particularly limited and can be cut to a desired size.

[0082] [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 chamfering step in which the cut crystallized glass is chamfered. It may also include a forming step in which the obtained crystallized glass is bent. It may also include a polishing step in which the surface of the obtained crystallized glass is polished. In the polishing step, it is also preferable that the altered layer formed on the surface of the crystallized glass is removed.

[0083] 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.

[0084] <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, sensors, 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 various centers that are not intended to be portable, as cover glass for display devices such as televisions (TVs), personal computers (PCs), and touch panels, as cover glass provided on the surface of solar cell modules, as 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.

[0085] The present invention will be described in more detail below based on the following 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 following examples. Examples 1 to 4 described below are examples, and Examples 5 to 7 described below are comparative examples.

[0086] <Example 1> First, glass raw materials were mixed and melted to obtain a 0.6 mm thick glass plate by the float method, resulting in each glass composition expressed as a molar percentage based on oxides as shown in Table 1. The obtained glass plate was cut to a size of 50 mm x 50 mm to be used as crystallization glass. The oxides, hydroxides, carbonates, or nitrates used in the above glass raw materials were appropriately selected from commonly used glass raw materials.

[0087] [Glass composition] SiO ２ : 70.00% Al ２ O ３ : 14.15% P ２ O ５: 1.50% Li ２ O: 10.05% Na ２ O: 1.00% K ２ O: 0.50% MgO: 0.10% CaO: 0.10% TiO ２ : 0.10% ZrO ２ : 1.50% SnO ２ : 1.00%

[0088] Next, the resulting crystallization glass plate was heated to 400°C, and a gas containing hydrogen fluoride (a fluid containing a silicon removal agent) was supplied to one surface of the crystallization glass to obtain a crystallization glass with an altered layer. As a result of the above treatment, the SiO on the surface of the crystallization glass ２ Some components were removed, and a modified layer was formed. The fluid containing the above-mentioned Si removal agent was a mixture of nitrogen gas and hydrogen fluoride gas, with the hydrogen fluoride gas content being 10% by volume relative to the total volume of the mixture. The details of the above treatment conditions are described in the table below. Furthermore, the crystallization glass with the modified layer obtained was analyzed using the method described above to obtain parameters related to the modified layer. Specifically, the thickness of the modified layer, the F / Si ratio, the viscosity of the crystallization glass, and the process index I were obtained. Ｐ The values ​​obtained are shown in the table below.

[0089] Next, ten of the obtained crystallization glass with altered layers were stacked in sequence with the altered layer facing upwards to obtain a crystallization glass laminate. The obtained crystallization glass laminate was then placed on an alumina plate, which served as a support, to obtain another laminate, and this laminate was introduced into a heat treatment furnace (MBK furnace manufactured by Tokyo Motoyama Shoji Co., Ltd.).

[0090] The heat treatment in the heat treatment furnace consisted of a heat treatment including heating at 790°C for 4 hours (corresponding to the nucleation treatment described above), followed by a heat treatment including heating at 920°C for 3 hours (corresponding to the crystal growth treatment described above). The heating rate and cooling rate were controlled to 5°C / min. The atmosphere during the heat treatment in the heat treatment furnace was air.

[0091] From the glass laminate for crystallization that underwent the above heat treatment, the crystallized glass was peeled off one sheet at a time to obtain crystallized glass. In the crystallized glass, β-spodumene (LiAlSi ２ O ６ Crystals were precipitated, and the crystallization rate was 70%. In the above procedure, the crystallized glass could be peeled off one sheet at a time. The table below shows the number of crystallized glass sheets that developed cracks among those obtained in the above procedure. For practical purposes, it is preferable that the number of crystallized glass sheets with cracks be one or less, and more preferably zero. The type of crystals precipitated in the crystallized glass and the calculation of the crystallization rate were performed by powder X-ray diffraction measurement under the following conditions: Measurement device: Rigaku SmartLab X-rays used: CuKα rays Measurement range: 2θ = 10 to 80° Scan speed: 10° / min Scan step: 0.02°

[0092] <Examples 2 to 4> Except for the conditions for forming the altered layer in the procedure of Example 1 above, which are shown in the table below, the altered layer-equipped crystallization glass was laminated in the same manner as in Example 1, and heat treatment was performed to obtain the crystallized glasses of Examples 2 to 4. In addition, parameters related to the altered layer formed under the conditions of Examples 2 to 4 were obtained in the same manner as in Example 1. The obtained values ​​are shown in the table below. In the crystallized glasses of Examples 2 to 4, the same crystals as in Example 1 precipitated, and the crystallization rate was also the same. The table below shows the number of crystallized glasses in which cracks occurred among the crystallized glasses of Examples 2 to 4 obtained by the above procedure.

[0093] <Examples 5 to 7> Crystallized glass of Examples 5 to 7 was obtained by laminating the crystallization glass in the same manner as in Example 1, except that the conditions for forming the altered layer were changed to those shown in the table below, and then heat-treating it. Note that no altered layer was formed under the conditions of Example 5, so parameters related to the altered layer were not obtained. Note that the crystallized glass of Examples 5 to 7 also precipitated the same crystals as in Example 1, and the crystallization rate was also the same. The table below shows the number of crystallized glass sheets in which cracks occurred among the crystallized glass of Examples 5 to 7 obtained by the above procedure.

[0094] <Results> Table 1 shows the conditions for forming the altered layer, the parameters related to the altered layer, and the number of crystallized glass pieces in which cracks occurred in each of the examples from Example 1 to Example 7. In Table 1, in the notation of the viscosity η of the crystallization glass during the altered layer formation process, for example, the notation "10^15" means 10 １５ (That is, it represents 10 to the power of 15.)

[0095]

[0096] From a comparison of Examples 1 to 4 and Examples 5 to 7 shown in Table 1, it was confirmed that when a crystallization glass with a modified layer is obtained by forming a modified layer on at least one surface, the thickness of the modified layer is 20 nm or more, and a crystallization glass laminate is fabricated by stacking the crystallization glass with the modified layer placed between adjacent crystallization glass, and when the crystallization glass laminate is subjected to heat treatment including heating at the crystal growth temperature, cracks are less likely to occur in the crystallized glass obtained by delamination. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-163789, filed on September 20, 2024, are incorporated herein by reference as disclosure of the present invention.

[0097] 10 Crystallization glass with altered layer 12 Crystallization glass 14 Altered layer 20 Crystallization glass laminate 22 First setter plate 24 Second setter plate 26 Support 30 Laminate

Claims

1. A method for producing crystallized glass, comprising: obtaining crystallized glass with an altered layer formed on at least one surface of crystallized glass; stacking the crystallized glass with altered layers to obtain a crystallized glass laminate in which the altered layer is placed between adjacent crystallized glass pieces; and performing a heat treatment on the crystallized glass laminate, including heating at the crystal growth temperature, wherein the thickness of the altered layer is 20 nm or more.

2. The method for producing crystallized glass according to claim 1, comprising supplying a modification agent to at least one surface of the crystallized glass to obtain the crystallized glass with the modified layer formed on at least one surface.

3. The method for producing crystallized glass according to claim 2, wherein the altering agent is a silicon removal agent.

4. The method for producing crystallized glass according to claim 3, wherein the silicon removal agent contains a fluorine-containing compound.

5. When obtaining the crystallized glass with the altered layer, the process index I is calculated using the following formula (1). Ｐ A method for producing crystallized glass according to claim 3, wherein the value of is 100 or more. Formula (1) I Ｐ = T × t × c / logη In equation (1), T is the temperature of the crystallization glass when supplying the fluid containing the silicon removal agent. The unit of T is °C. t is the time for supplying the fluid containing the silicon removal agent. The unit of t is seconds. c is the content of the silicon removal agent in the fluid containing the silicon removal agent. The unit of c is volume percent. logη is the common logarithm of the viscosity of the crystallization glass when supplying the fluid containing the silicon removal agent. The unit of viscosity is Pa·s.

6. The method for producing crystallized glass according to any one of claims 1 to 5, wherein the maximum value of the ratio of F content to Si content in the altered layer is 0.05 or more.

7. The method for producing crystallized glass according to any one of claims 1 to 5, wherein the thickness of the altered layer is 50 nm or more.

8. A method for producing crystallized glass according to any one of claims 1 to 5, wherein the crystal growth temperature is 700 to 1100°C.

9. The method for manufacturing crystallized glass according to any one of claims 1 to 5, wherein the thickness of the crystallized glass plate is 1.5 mm or less.

10. The composition of the crystallization glass is expressed as a mole percentage based on oxides, SiO ２ 60-75%, Al ２ O ３ 2-20%, Li ２ A method for producing crystallized glass according to any one of claims 1 to 5, comprising 5 to 30% oxygen.

11. A method for producing crystallized glass according to any one of claims 1 to 5, wherein the crystallized glass obtained by this method comprises one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

12. A method for producing crystallized glass according to any one of claims 1 to 5, wherein the crystallized glass obtained by this method comprises one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, and petalite crystals.

13. A method for producing crystallized glass according to any one of claims 1 to 5, comprising peeling off the heat-treated crystallized glass from the heat-treated crystallized glass laminate to obtain crystallized glass.

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