Crystallized glass, glass, and method for producing crystallized glass

Abstract

The present invention relates to crystallized glass having a crystal phase. The crystallized glass contains SiO2, Li2O, and Al2O3 in a base composition. In the base composition, the total content ratio of SiO2, Al2O3, and Li2O, in terms of mol% based on oxides, is 90-98%. In a curve obtained through differential scanning calorimetry (DSC) of glass having the aforementioned base composition, there is only one local peak indicating an exothermic reaction within the range of 700-900°C.

Description

Crystallized glass, glass, and method for producing crystallized glass

[0001] The present invention relates to a crystallized glass, a glass, and a method for producing the crystallized glass.

[0002] Thin, high-strength chemically strengthened glass is used as cover glass for displays of electronic devices such as mobile devices such as mobile phones and smartphones. Chemically strengthened glass is produced by bringing glass into contact with a molten salt composition such as sodium nitrate to cause ion exchange between alkali metal ions contained in the glass and alkali metal ions with a larger ionic radius contained in the molten salt composition, thereby forming a compressive stress layer from the surface to the interior of the glass.

[0003] Drop strength is an important strength characteristic of materials for mobile devices such as cover glass, and in order to achieve high drop strength, the fracture toughness value K ＩＣ Furthermore, the strength of a vehicle such as an automobile is important in terms of its strength characteristics, and the fracture toughness value K ＩＣ It is important to improve this.

[0004] Therefore, a high fracture toughness value K ＩＣ Glass-ceramics have been attracting attention as a glass having the above properties. In particular, Li-based glass-ceramics containing lithium may be used as the cover glass, taking into consideration the fact that chemical strengthening treatment is also performed.

[0005] Generally, glass-ceramics can achieve higher strength by increasing the degree of crystallization, but the strength characteristics change depending on the crystal species that make up the crystalline phase and their content.

[0006] Therefore, among the crystals constituting the crystalline phase in the high-strength Li-based crystallized glass, those having a higher fracture toughness value K ＩＣ As a crystal that realizes this, lithium disilicate (Li ２ Si ２ O ５ For example, Patent Document 1 discloses a SiO ２ Ingredients, Al ２ O ３ Ingredients, Li ２ O component, ZrO２ Ingredients, and P ２ O ５ Crystallized glass articles are disclosed that contain lithium silicate crystalline phases (one or both of lithium metasilicate and lithium disilicate) with component proportions within specified ranges.

[0007] Japanese Patent Application Publication No. 2023-506666

[0008] However, the inventors have found that increasing the crystallinity of the crystallized glass to achieve higher strength tends to decrease the transparency, and in particular, ２ Si ２ O ５ The crystals were found to be white and prone to becoming cloudy.

[0009] In fact, it has been found that the crystallized glass product disclosed in Patent Document 1 exhibits a decrease in transparency when the degree of crystallization is increased, and the desired transparency cannot be achieved.

[0010] Therefore, the present invention aims to provide a new crystallized glass that maintains the desired transparency while also having high strength, and a method for producing the same. Another aim is to provide a new glass that can be turned into the above-mentioned crystallized glass by crystallization treatment.

[0011] To solve the above problems, the inventors have conceived that crystallized glass that can solve the above problems can be obtained by crystallizing a mother glass of a specific composition that has only one local peak showing an exothermic reaction in a specific temperature range in a curve obtained by differential scanning calorimetry (DSC) measurement.

[0012] That is, the gist of this embodiment relates to the following: [1] A crystallized glass having a crystalline phase, wherein the composition of the crystallized glass is expressed in mole percentage based on oxides, and ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２A glass-ceramic having a total content of 90 to 98% of SiO, and a curve obtained by differential scanning calorimetry (DSC) measurement of glass having the matrix composition of the glass-ceramic has only one local peak showing an exothermic reaction in the range of 700 to 900°C. [2] The composition is expressed in mole percentage based on oxides and is: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５ 0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２ The crystallized glass according to claim 1, wherein the composition satisfies the following: 0 to 1% of SiO. ２ , Al ２ O ３ , and Li ２ Using the content ratio of O expressed as mole percentage, {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ [4] The glass-ceramics according to the above [1] or [2], wherein the ratio represented by Li x 100 is 21.0 to 28.5%. ２ Si ２ O ５[5] The crystallized glass according to any one of [1] to [3], wherein the peak is derived from a crystal. ２ Si ２ O ５ The glass-ceramics according to any one of [1] to [4], having a crystalline content of 40% by mass or more. [6] The glass-ceramics according to any one of [1] to [5], wherein a curve obtained by differential scanning calorimetry (DSC) measurement of the glass having the matrix composition has only one local peak showing an exothermic reaction in the range of 550°C to less than 700°C. [7] The glass-ceramics according to [6], wherein a value expressed by {W_Tp2 / W_Tp1} is 0.5 to 1 when the difference from the baseline of the local peak showing an exothermic reaction in the range of 550°C to less than 700°C in the curve obtained by differential scanning calorimetry (DSC) measurement of the glass having the matrix composition is W_Tp1 (mcal / s), and the difference from the baseline of the local peak showing an exothermic reaction in the range of 700 to 900°C in the curve is W_Tp2 (mcal / s). [8] The glass-ceramics according to [6], having a fracture toughness value K ＩＣ is 1.3 MPa m １／２ The glass-ceramics according to any one of [1] to [7], wherein the Young's modulus is 107 GPa or more. [9] The glass-ceramics according to any one of [1] to [8], wherein the Young's modulus is 107 GPa or more.

[10] The glass-ceramics according to any one of [1] to [9], wherein the average crystallite size of the crystals constituting the crystalline phase is 20 to 200 nm.

[11] The glass-ceramics according to any one of [1] to

[10] , wherein the transmittance of light with a wavelength of 600 nm is 85% or more when converted into a thickness of 0.6 mm.

[12] The glass-ceramics according to any one of [1] to

[11] , wherein the surface layer has a compressive stress layer formed by ion exchange.

[13] The glass-ceramics according to

[12] , wherein the compressive stress layer depth DOL is 50 μm or more.

[14] The crystallized glass according to

[12] or

[13] , wherein the compressive stress layer depth DOL is {t × 0.13} μm or more, where t is the thickness of the glass (μm).

[15] The compressive stress value CS at the outermost surface ０ The crystallized glass according to any one of

[12] to

[14] , wherein the compressive strength is 300 MPa or more.

[0013]

[16] The composition is expressed in mole percentage based on oxides, and is SiO ２ , Al ２ O ３ , and Li ２ Contains O and SiO ２ , Al ２ O ３ , and Li ２ A glass having a total content of SiO of 90 to 98%, and having only one local peak indicating an exothermic reaction in a range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement.

[17] The composition is expressed in mole percentage based on oxides and is: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５ 0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２

[18] The glass according to the above

[16] , wherein the composition satisfies 0 to 1% of SiO ２ , Al ２ O ３ , and Li ２ Using the content ratio of O expressed as mole percentage, {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li２

[0022] The glass-ceramics according to any one of

[16] to

[17] , wherein the ratio expressed by {W_Tp1 / W_Tp2} × 100 is 21.0 to 28.5%.

[19] The glass-ceramics according to any one of

[16] to

[18] , wherein the curve obtained by differential scanning calorimetry (DSC) measurement has only one local peak showing an exothermic reaction in the range of 550°C or higher and lower than 700°C.

[20] The glass-ceramics according to

[19] , wherein the value expressed by {W_Tp2 / W_Tp1} is 0.5 to 1, where W_Tp1 (mcal / s) is the difference from the baseline of the local peak showing an exothermic reaction in the range of 550°C or higher and lower than 700°C in the curve obtained by differential scanning calorimetry (DSC) measurement, and W_Tp2 (mcal / s) is the difference from the baseline of the local peak showing an exothermic reaction in the range of 700 to 900°C in the curve.

[0014]

[21] A method for producing crystallized glass having a crystalline phase, comprising: producing glass; and crystallizing the glass to obtain crystallized glass, wherein the glass has only one local peak indicating an exothermic reaction in a range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement, the crystallization treatment is carried out by a three-stage heat treatment, and the composition of the crystallized glass, expressed in mole percentage on an oxide basis, is SiO ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２

[22] A method for producing crystallized glass according to

[21] above, wherein, in a curve obtained by differential scanning calorimetry (DSC), Tp1 is the temperature of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C, and Tp2 is the temperature of a local peak showing an exothermic reaction observed in the range of 700 to 900°C, the three-stage heat treatment includes a first heat treatment in which a first treatment temperature T1 satisfies the relationship {Tp1 - T1} ≦ 140°C, a second heat treatment in which a second treatment temperature T2 satisfies the relationship {T2 - T1} ≧ 10°C, and a third heat treatment in which a third treatment temperature T3 satisfies the relationship {Tp2 - T3} ≦ 120°C.

[0015] According to the present invention, a new glass-ceramic can be obtained that maintains a desired transparency while also having high strength. Furthermore, a glass that can be turned into the above-described glass-ceramic can be obtained by a crystallization treatment.

[0016] Fig. 1 is a graph showing the results of DSC measurement of glass material A, in which (a) of Fig. 1 is a DSC curve in the temperature range of 450 to 920°C, and (b) of Fig. 1 is a graph showing a profile obtained by first differentiating the DSC curve of (a) of Fig. 1 and processing it through a Gaussian filter under the conditions of σ = 30 and a kernel size of 501. Fig. 2 is a graph showing the results of DSC measurement of glass material B, in which (a) of Fig. 2 is a DSC curve in the temperature range of 450 to 920°C, and (b) of Fig. 2 is a graph showing a profile obtained by first differentiating the DSC curve of (a) of Fig. 2 and processing it through a Gaussian filter under the conditions of σ = 30 and a kernel size of 501. Fig. 3 is a graph showing the results of DSC measurement of glass material C, in which Fig. 3(a) is a DSC curve in the temperature range of 450 to 920°C, Fig. 3(b) is a graph showing a profile obtained by first differentiating the DSC curve of Fig. 3(a) and processing it through a Gaussian filter under conditions of σ = 30 and a kernel size of 501, and Fig. 3(c) is a graph showing a profile in which the vertical scale is enlarged relative to Fig. 3(b). Fig. 4 is a graph showing the results of DSC measurement of glass material D, in which Fig. 4(a) is a DSC curve in the temperature range of 450 to 920°C, and Fig. 4(b) is a graph showing a profile obtained by first differentiating the DSC curve of Fig. 4(a) and processing it through a Gaussian filter under conditions of σ = 30 and a kernel size of 501.

[0017] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below. In this specification, the term "to" indicating a range of values ​​is used to mean that the values ​​before and after it are included as the lower and upper limits. Furthermore, in this specification, mass % and weight %, and parts by mass and parts by weight have the same meaning.

[0018] The crystallized glass according to this embodiment has a crystalline phase. The composition of the crystallized glass is expressed in mole percentage based on oxides as follows: SiO ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２The total content of O is 90 to 98%. In addition, in a curve obtained by differential scanning calorimetry (DSC) measurement of glass having the matrix composition of the glass-ceramics according to this embodiment, there is only one local peak showing an exothermic reaction within the range of 700 to 900°C.

[0019] In this specification, the composition of the crystallized glass is the same as the composition (mother composition) of the amorphous glass (mother glass) before crystallization. In other words, glass having the mother composition of the crystallized glass means the glass before crystallization of the crystallized glass, i.e., the mother glass. In addition, the composition of the amorphous phase in the crystallized glass can be determined from the composition of the crystallized glass and the composition and content of the crystalline phase of the crystallized glass. Furthermore, when the crystallized glass is chemically strengthened to obtain chemically strengthened glass, the composition (bulk composition) of the center in the thickness direction of the chemically strengthened glass can be considered to be the same as the composition of the crystallized glass, except when ion exchange treatment is performed under extreme conditions.

[0020] The composition of the crystallized glass can be identified by a conventionally known method, for example, by wet chemical analysis or quantitative analysis using a fluorescent X-ray calibration curve.

[0021] Glass-ceramics can be determined to have a crystalline phase by observing diffraction peaks indicating crystals in an XRD pattern obtained by powder X-ray diffraction (XRD). The glass-ceramics have a crystalline phase in which crystals are precipitated by heat-treating amorphous glass (mother glass) in which no diffraction peaks indicating crystals are observed. The XRD measurement is performed using CuKα radiation in the 2θ range of 10° to 80°.

[0022] The composition and content of the crystalline phase in the crystallized glass can be determined by Rietveld analysis from the XRD pattern and diffraction intensity. The Rietveld method is described in "Crystal Analysis Handbook" edited by the Editorial Committee of the Crystallographic Society of Japan (Kyoritsu Shuppan, 1999, pp. 492-499). When the crystalline phase is composed of one type of crystal, the content of that crystal is the crystallinity, and when multiple crystals are present, the total content of those crystals is the crystallinity.

[0023] <Thermal properties of the mother glass> The glass having the mother composition of the crystallized glass according to this embodiment, i.e., the mother glass of the crystallized glass according to this embodiment, has only one local peak indicating an exothermic reaction within the range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement.

[0024] Here, the DSC measurement is performed under the following conditions. Measurement conditions: The mother glass of the glass-ceramics is crushed and classified to 150 to 300 μm to obtain a mother glass powder. The obtained mother glass powder is placed in a platinum pan (container), and the temperature is raised from room temperature to 1050°C to perform the DSC measurement. The temperature rise rate is 5°C / min. The mother glass of the glass-ceramics may be any glass having the same composition as the glass-ceramics. Therefore, the measurement may be performed on a newly produced glass that has the same composition as the glass-ceramics, or on an amorphous glass obtained by crushing and melting the glass-ceramics.

[0025] In this specification, a local peak is defined as a profile that indicates an exothermic reaction in which the DSC temperature profile (DSC curve) obtained by DSC measurement changes from a value of 0.005 mcal / (s·°C) or more to a value of −0.005 mcal / (s·°C) or less, with respect to the profile that is obtained by first differentiating the DSC temperature profile (DSC curve) obtained by DSC measurement and processing the profile through a Gaussian filter under conditions of σ = 30 and kernel size: 501. Furthermore, the temperature at which the local peak shows the highest intensity is the temperature of the local peak that indicates an exothermic reaction.

[0026] The glass-ceramics according to this embodiment has a base glass having only one local peak indicating the exothermic reaction within the range of 700 to 900° C. This means that, of the crystals constituting the crystalline phase of the glass-ceramics, there is only one type of crystal whose crystallization temperature is between 700 and 900° C.

[0027] The inventors' investigations have revealed that by using a glass having only one local peak indicating an exothermic reaction in the above range as the base glass, Li ２ Si ２ O ５ (Lithium disilicate) crystals are selectively precipitated in large quantities, and the fracture toughness value KＩＣ The inventors have come to the conclusion that a highly effective glass-ceramic can be obtained.

[0028] The local peaks indicating the exothermic reaction observed in the range of 700 to 900°C of the mother glass are Li ２ Si ２ O ５ It is preferable that the peak is derived from a crystal. ２ Si ２ O ５ The peak derived from the crystal is observed in the range of 700 to 900° C., and in particular, the temperature Tp2 of the local peak indicating an exothermic reaction observed in the range of 700 to 900° C. is preferably observed in the range of 720 to 870° C. The observed temperature may be 700° C. or higher, preferably 720° C. or higher, more preferably 750° C. or higher, and even more preferably 800° C. or higher, and may be 900° C. or lower, preferably 870° C. or lower, and more preferably 840° C. or lower.

[0029] In addition to the above, the crystallized glass according to this embodiment preferably has only one local peak showing an exothermic reaction within the range of 550°C or more and less than 700°C in the curve obtained when the glass having the matrix composition is subjected to differential scanning calorimetry (DSC) measurement.

[0030] The local peaks indicating the exothermic reaction observed in the range of 550°C or more and less than 700°C of the mother glass are due to lithium phosphate (Li ３ P.O. ４ When such a mother glass is subjected to a crystallization treatment to obtain a crystallized glass, the peak derived from the Li crystal is preferably a peak derived from the Li crystal. ３ P.O. ４ The crystals become nuclei and Li ２ Si ２ O ５ Crystals are more likely to precipitate.

[0031] Li ３ P.O. ４The peak derived from the crystal is observed in the range of 550° C. or higher and lower than 700° C., and the temperature Tp1 of the local peak indicating an exothermic reaction observed in the range of 550° C. or higher and lower than 700° C. is preferably observed in the range of 580 to 680° C. The observed temperature may be 550° C. or higher, preferably 580° C. or higher, more preferably 600° C. or higher, or may be lower than 700° C., preferably 680° C. or lower, more preferably 650° C. or lower.

[0032] In a DSC curve of a glass having the matrix composition, it is preferable that there is only one local peak (referred to as "Peak 1") showing an exothermic reaction in the range of 550° C. or higher but lower than 700° C., and there is only one local peak (referred to as "Peak 2") showing an exothermic reaction in the range of 700° C. or higher but lower than 900° C. In this case, when the difference from the baseline in the heat quantity at the peak top of Peak 1 (local peak temperature Tp1) is defined as W_Tp1 (mcal / s) and the difference from the baseline in the heat quantity at the peak top of Peak 2 (local peak temperature Tp2) is defined as W_Tp2 (mcal / s), the value represented by {W_Tp2 / W_Tp1} is preferably 0.5 to 1.

[0033] The baseline is created for each peak using the method described below. First, the DSC curve is first differentiated, and the profile is subjected to Gaussian filter processing (first-order differential GF processing) under the conditions of σ = 30 and kernel size: 501. The profile is then differentiated again with respect to temperature to create a profile obtained by second-order differentiation of the DSC temperature profile. Here, when the value of the second-order differential profile is 1 × 10 －５ From smaller values ​​to 1 x 10 －５ Among the temperatures at which the second derivative profile is equal to or greater than the peak temperature, the temperature at which the gradient of the second derivative profile is positive in the range of ±1.0°C around the peak temperature, and which is lower than the peak temperature and closest to the peak temperature is defined as the "starting point 1 temperature." －５ From the larger value to 1 x 10 －５Among the temperatures below, the temperature at which the slope of the second-order differentiated profile is negative in the range of ±1.0°C around that temperature, and which is higher than the peak temperature and closest to the peak temperature, is defined as the "origin 2 temperature." When the value of the DSC curve at the "origin 1 temperature" is defined as "origin 1," and the value of the DSC curve at the "origin 2 temperature" is defined as "origin 2," the straight line connecting origin 1 and origin 2 is defined as the baseline.

[0034] The value expressed by {W_Tp2 / W_Tp1} above is Li ２ Si ２ O ５ From the viewpoint of forming more crystals, the ratio is preferably 0.50 or more, more preferably 0.53 or more, and even more preferably 0.57 or more. There is no upper limit, but generally, the ratio is preferably 1.00 or less, more preferably 0.90 or less, and even more preferably 0.80 or less.

[0035] <Composition of Crystallized Glass> As described above, the composition of the crystallized glass according to this embodiment is expressed in mole percentage based on oxides, and is: SiO ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２ The total content of O is 90 to 98%.

[0036] The crystallized glass according to this embodiment is ２ , Al ２ O ３ , and Li ２ In addition to the total content of O, it is more preferable to satisfy the following composition: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２ 0 to 1%.

[0037] The crystallized glass according to this embodiment is ２ , Al ２ O ３ , and Li ２ In addition to the total content of O, SiO ２ , Al ２ O ３ , and Li ２ It is more preferable that the content of O expressed in mole percentage satisfies the following composition: {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 21.0 to 28.5%.

[0038] Furthermore, the crystallized glass according to this embodiment contains the above-mentioned SiO ２ , Al ２ O ３ , and Li ２ In addition to the total content of O, it is more preferable to satisfy the following composition: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５0.0~3.0%, MgO 0.0~2.0%, CaO 0.0~2.0%, SnO ２ 0-1%, {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 = 21.0 to 28.5%.

[0039] As mentioned above, the composition of the glass-ceramics is the same as the composition of the mother glass before crystallization, and can also be considered to be the same as the composition of the center portion in the thickness direction of the chemically strengthened glass obtained by strengthening the glass-ceramics.

[0040] SiO ２ is a component that constitutes the glass network, and Li ２ Si ２ O ５ It is also a component that forms crystals. SiO in crystallized glass ２ The content of Li is preferably 60 to 75%, more preferably 62 to 72%, and even more preferably 64 to 70%. ２ Si ２ O ５ From the viewpoint of facilitating crystal formation, the content is preferably 60% or more, more preferably 62% or more, even more preferably 64% or more, and even more preferably 66% or more. ２ Si ２ O ５From the viewpoint of facilitating crystal formation and enhancing the meltability of the glass, the content is preferably 75% or less, more preferably 72% or less, even more preferably 70% or less, still more preferably 68% or less, and particularly preferably 67% or less.

[0041] Al ２ O ３ is a component that improves ion exchangeability during chemical strengthening treatment and increases the surface compressive stress after chemical strengthening treatment. ２ O ３ The content ratio of Li is preferably 1.2 to 4%, more preferably 1.5 to 3.8%, and even more preferably 2.0 to 3.6%. Here, from the viewpoint of performing chemical strengthening treatment appropriately, the content ratio is preferably 1.2% or more, more preferably 1.5% or more, and even more preferably 1.6% or more, and may be 2.0% or more, 2.2% or more, 2.3% or more, or 2.4% or more. ２ Si ２ O ５ From the viewpoint of facilitating crystal formation, the content is preferably 4% or less, more preferably 3.8% or less, even more preferably 3.6% or less, even more preferably 3.4% or less, particularly preferably 3.0% or less, and may be 2.6% or less.

[0042] Li ２ O is Li ２ Si ２ O ５ It is a component of crystals and is also a component that forms compressive stress near the surface of crystallized glass by ion exchange with Na ions. ２ The content of O is preferably 20 to 30%, more preferably 22 to 28%, and even more preferably 24 to 27%. ２ Si ２ O ５ From the viewpoint of facilitating crystal formation and increasing compressive stress, the content is preferably 20% or more, more preferably 22% or more, even more preferably 24% or more, may be 25% or more, or may be 26% or more. ２ Si ２ O ５From the viewpoint of facilitating crystal formation and chemical durability of the glass, the content is preferably 30% or less, may be 28% or less, or may be 27% or less.

[0043] In the crystallized glass according to this embodiment, SiO ２ , Al ２ O ３ , and Li ２ The total content of O is 90 to 98%, preferably 91 to 97%, more preferably 92 to 96%, and even more preferably 93 to 95%. ２ Si ２ O ５ From the viewpoint of facilitating crystal formation, the total content is 90% or more, preferably 91% or more, more preferably 92% or more, even more preferably 93% or more, and even more preferably 94% or more. Also, from the viewpoint of improving ion exchangeability during chemical strengthening treatment, the total content is 98% or less, preferably 97% or less, more preferably 96% or less, and even more preferably 95% or less.

[0044] Na ２ O is a component that forms compressive stress by ion-exchanging with K ions, and the inclusion of a small amount can increase the stability of the glass. ２ The content of O is preferably 0 to 5%, more preferably 0.1 to 5%, even more preferably 0.5 to 4.5%, even more preferably 1.0 to 4%, and particularly preferably 1.5 to 3.5%. ２ The content of O is 0%, that is, it may not be contained, but Na ２ When O is contained, from the viewpoint of increasing compressive stress and improving stability, the content is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more. Also, from the viewpoint of maintaining chemical durability, the content is preferably 5% or less, more preferably 4.5% or less, even more preferably 4% or less, even more preferably 3.5% or less, or may be 3% or less, 2.5% or less, or 2% or less.

[0045] K ２O is a component that enhances chemical strengthening properties and suppresses phase separation. ２ The content of O is preferably 0 to 3%, more preferably 0.1 to 3%, and even more preferably 0.2 to 2.5%. ２ The content of O is 0%, that is, it may not be contained, but K ２ When O is contained, from the viewpoint of enhancing the stability of the glass, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.4% or more, and even more preferably 0.6% or more. From the viewpoint of maintaining chemical durability, the content is preferably 3% or less, more preferably 2.5% or less.

[0046] ZrO ２ is a thickening component that increases the viscosity when melted, and at the same time, is a component that increases the surface compressive stress due to ion exchange. ２ It has been found that by adding an appropriate amount of ZrO, it is possible to suitably control phase separation so that crystallization is facilitated while maintaining high transparency. As a result, when the glass is made into a crystallized glass, the crystallization degree can be increased while maintaining high transparency, and higher strength can be achieved. ２ The content ratio is preferably 1.5 to 3.4%, more preferably 1.5 to 3.0%, and even more preferably 1.5 to 2.5%. Here, from the viewpoint of controlling phase separation and acting as a thickening component to slow the growth rate of crystals that become crystalline phases and form fine crystals, thereby realizing higher transparency of the crystallized glass, the content ratio is preferably 1.5% or more, more preferably 1.6% or more, and even more preferably 1.7% or more. Furthermore, from the viewpoint of suppressing devitrification during melting, the content ratio is preferably 3.4% or less, and may be 3.0% or less, 2.5% or less, 2.3% or less, 2.2% or less, 2.1% or less, or 2.0% or less.

[0047] Furthermore, ZrO in the crystallized glass according to this embodiment ２The content ratio is preferably 1 to 6 mass% when expressed as a mass percentage based on oxides. Here, from the viewpoint of controlling phase separation and acting as a thickening component to slow the growth rate of crystals that become crystalline phases and form fine crystals, thereby realizing higher transparency of the crystallized glass, the content ratio is preferably 1 mass% or more, more preferably 2.5 mass% or more, even more preferably 3.2 mass% or more, and even more preferably 3.7 mass% or more. Furthermore, from the viewpoint of suppressing devitrification during melting, the content ratio is preferably 6 mass% or less, more preferably less than 5 mass%, even more preferably 4.8 mass% or less, and may be 4.5 mass% or less, or may be 4.4 mass% or less.

[0048] P ２ O ５ is a component that promotes crystallization. ２ O ５ The content of P is preferably 0.0 to 3.0%, more preferably 0.3 to 2.5%, and even more preferably 0.5 to 2.0%. ２ O ５ The content ratio of P may not be included, ２ O ５ In the case where the crystalline silicon dioxide contains α-methyl-2-pyrrolidone, the content is preferably 0.3% or more, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.2% or more from the viewpoint of facilitating crystallization. In addition, in the case where the crystalline silicon dioxide contains α-methyl-2-pyrrolidone, the content is preferably 3.0% or less, more preferably 2.5% or less, or may be 2.0% or less or 1.5% or less from the viewpoint of suppressing phase separation during melting and a decrease in acid resistance.

[0049] The alkaline earth metals BaO, MgO, CaO, and SrO are components that enhance the meltability of glass. The total content of MgO, CaO, SrO, and BaO is preferably 0.0 to 5.0%, more preferably 0.1 to 4.0%, and even more preferably 0.5 to 3.0%. Although alkaline earth metals are not required, if they are contained, from the viewpoints of meltability and strength, the total content is preferably 0.1% or more, more preferably 0.5% or more, and may be 1.0% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the total content is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and may be 1.0% or less.

[0050] The MgO content is preferably 0.0 to 2.0%, more preferably 0.1 to 1.5%, and even more preferably 0.2 to 1.0%. Although MgO need not be contained, if it is contained, from the viewpoint of enhancing the stability of the glass, the content is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.5% or more. From the viewpoint of maintaining good ion exchange performance, the content is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less.

[0051] The CaO content is preferably 0.0 to 2.0%, more preferably 0.1 to 1.5%, and even more preferably 0.2 to 1.0%. CaO does not necessarily have to be contained, but if it is contained, from the viewpoint of enhancing the stability of the glass, the content is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.5% or more. From the viewpoint of maintaining good ion exchange performance, the content is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less.

[0052] The respective contents of BaO and SrO are preferably 0.0 to 2.0%, more preferably 0.1 to 1.5%, and even more preferably 0.2 to 1.0%. BaO and SrO do not necessarily have to be contained, but if they are contained, from the viewpoint of enhancing the stability of the glass, the respective contents are preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.5% or more. From the viewpoint of maintaining good ion exchange performance, the respective contents are preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less.

[0053] SnO ２ is a fining agent during melting and also a component that generates crystal nuclei. ２ It has been found that the inclusion of SnO in the glass-ceramics can improve chemical resistance such as acid resistance and alkali resistance. ２ The content of SnO is preferably 0 to 1%, more preferably 0.1 to 0.8%, and even more preferably 0.2 to 0.5%. ２ Although it is not necessary to contain, when it is contained, it acts as a component that generates the nucleus of crystal, and by forming minute crystals, from the viewpoint of realizing high transparency of crystallized glass and from the viewpoint of chemical resistance, the content ratio can be 0.1% or more, can be 0.2% or more, can be 0.5% or more.In addition, from the viewpoint of suppressing the defects caused by unmelted matter, the content ratio is preferably 1% or less, more preferably 0.8% or less, can be 0.5% or less, can be 0.3% or less, can be less than 0.1%.

[0054] ZnO is a component that improves the meltability of glass. The ZnO content in the crystallized glass is preferably 0.0 to 2.0%, more preferably 0.1 to 1.5%, and even more preferably 0.2 to 1.0%. While ZnO need not be contained, if it is contained, from the viewpoint of obtaining good meltability, the content is preferably 0.1% or more, may be 0.2% or more, or may be 0.5% or more. Furthermore, from the viewpoint of improving weather resistance, the content is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, may be 0.5% or less, or may be 0.2% or less.

[0055] B ２ O ３ is a component that improves chipping resistance and melting property. ２ O ３ The content of B is preferably 0 to 10.0%, more preferably 0.1 to 5.0%, and even more preferably 0.2 to 2.0%. ２ O ３ Although it is not necessary to contain it, if it is contained, from the viewpoint of obtaining good chipping resistance and melting property, the content ratio is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.5% or more. Furthermore, from the viewpoint of suppressing the occurrence of striae and phase separation during melting and maintaining the quality of crystallized glass, the content ratio is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 2.0% or less, and even more preferably 1.0% or less.

[0056] Y ２ O ３ Y is a thickening component that increases the viscosity during melting, and at the same time, it is a component that increases the mechanical strength of the glass. It is also a component that increases the refractive index. ２ O ３ The content of Y is preferably 0 to 5.0%, more preferably 0.1 to 4.0%, and even more preferably 0.3 to 3.0%. ２ O ３ Although it is not necessary to contain, when it is contained, it acts as a thickening component, slows down the growth rate of the crystal of crystalline phase, and makes it into minute crystal, so that the high transparency of crystallized glass is realized, so that the content ratio is preferably 0.1% or more, more preferably 0.3% or more.In addition, from the viewpoint of suppressing the mismatch during melting, the content ratio is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, can be 2.0% or less, can be 1.0% or less.

[0057] TiO ２ is a thickening component that increases the viscosity when melted, and at the same time, is a component that increases UV resistance. ２ The content of TiO is preferably 0 to 5.0%, more preferably 0.1 to 4.0%, and even more preferably 0.5 to 3.0%. ２Although it is not necessary to contain, when it is contained, it acts as a thickening component, slows down the growth rate of the crystals that become crystalline phase, and makes them into minute crystals, so that the high transparency of the crystallized glass can be realized, so that the content ratio is preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more.In addition, from the viewpoint of suppressing the decrease in Haze value due to coloring, the content ratio is preferably 5.0% or less, more preferably 4.0% or less, and even more preferably 3.0% or less.

[0058] La ２ O ３ , Nb ２ O ５ and Ta ２ O ５ Is Y ２ O ３ Similarly to La, it has the effect of increasing the mechanical strength of the glass and may be contained to increase the refractive index. ２ O ３ , Nb ２ O ５ and Ta ２ O ５ The total content ratio of these components is preferably 0.0 to 3.0%, and more preferably 0.5 to 2.0%. These components do not necessarily need to be contained, but if they are contained, the total content ratio may be 0.5% or more from the viewpoint of increasing the refractive index. Furthermore, from the viewpoint of suppressing devitrification of the glass during melting, the total content ratio is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and may be 0.5% or less.

[0059] CeO ２ has the effect of oxidizing the glass, and the glass-ceramic becomes SnO ２ When the content is large, SnO ２ The reduction of CeO in the glass-ceramics to SnO, which is a coloring component, can be suppressed, thereby suppressing coloration. ２ The content of CeO is preferably 0.0 to 1.5%, more preferably 0.1 to 1.0%, and even more preferably 0.2 to 0.5%. ２However, if it is contained, the content is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more, from the viewpoint of suppressing coloration due to SnO. ２ From the viewpoint of suppressing coloration of the glass due to Cr, the content is preferably 1.5% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

[0060] Furthermore, a coloring component may be contained in the glass-ceramics to the extent that it does not hinder the achievement of the desired properties. ３ O ４ , MnO ２ , Fe ２ O ３ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ , SeO ２ , Er ２ O ３ , Nd ２ O ３ etc. The content ratio of the above coloring components in the crystallized glass is preferably in the range of 1.0% or less in total. Furthermore, if it is desired to increase the light transmittance of the crystallized glass, it is preferable that these components are not substantially contained. In this specification, "substantially not contained" means that the content is below the impurity level contained in raw materials, etc., that is, it is not intentionally added. In this specification, when it is stated that a certain component is not substantially contained, the content ratio of the component is specifically, for example, less than 0.03%.

[0061] In addition, SO is used as a fining agent when melting glass. ３ , chloride, fluoride, As ２ O ３ , Sb ２ O ３ The content of each fining agent is preferably 0.3% or less, more preferably 0.1% or less, and most preferably substantially no fining agent is contained.

[0062] The composition of the crystallized glass according to this embodiment is SiO２ , Al ２ O ３ , and Li ２ The values ​​expressed by the following formulas using the content ratio of O expressed in mole percentage are within the respective predetermined ranges: {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 21.0 to 28.5%.

[0063] Each of the above formulas represents SiO ２ , Al ２ O ３ , and Li ２ SiO relative to the total content of O ２ , Al ２ O ３ , or Li ２ The content ratio of each component, such as O.

[0064] SiO ２ , Al ２ O ３ , and Li ２ The total content of O means the total content ratio of components that easily form crystals in the crystallized glass. ２ 68.5 to 76.0%, Al ２ O ３ 2.2 to 5.0%, and Li ２ By containing 21.0 to 28.5% of O, Li ２ Si ２ O ５It was found that the crystals precipitate selectively, easily forming a crystallized glass with a high crystal content, and as a result, it is possible to achieve higher strength while maintaining the desired transparency.

[0065] SiO relative to the total content ２ The content ratio of is 68.5 to 76.0%, preferably 69.0 to 74.5%. Here, the content ratio is 68.5% or more, and Li ２ Si ２ O ５ From the viewpoint of facilitating crystal formation, the content is preferably 69.0% or more, more preferably 69.5% or more, and even more preferably 70.0% or more. ２ Si ２ O ５ From the viewpoint of facilitating crystal formation and enhancing the meltability of the glass, the content is preferably 74.5% or less, more preferably 72.0% or less, and even more preferably 70.0% or less.

[0066] Al content relative to the total content ２ O ３ The content of is 2.2 to 5.0%, preferably 2.3 to 4.7%. Here, the content is 2.2% or more, and from the viewpoint of suppressing phase separation during the production of amorphous glass and improving ion exchangeability during chemical strengthening treatment, it is preferably 2.3% or more, more preferably 2.4% or more, and even more preferably 2.5% or more. Furthermore, the content is 5.0% or less, and SiO ２ , Al ２ O ３ , Li ２ From the viewpoint of suppressing the precipitation of crystals composed of O, the content is preferably 4.7% or less, more preferably 4.4% or less, even more preferably 4.0% or less, and even more preferably 3.8% or less.

[0067] Li relative to the total content ２ The content of O is 21.0 to 28.5%, preferably 23.0 to 28.3%. Here, the content is 21.0% or more, and Li ２ Si ２ O ５From the viewpoint of facilitating crystal formation, the content is preferably 23.0% or more, more preferably 25.0% or more, even more preferably 27.0% or more, and even more preferably 28.0% or more. In addition, the content is 28.5% or less, and after the crystallization treatment, Li ２ SiO ３ From the viewpoint of suppressing residual crystals, the content is preferably 28.3% or less, more preferably 28.2% or less, and even more preferably 28.1% or less.

[0068] <Crystalline Phase> The crystallized glass according to this embodiment has a crystalline phase, and the crystals constituting the crystalline phase are Li. ２ Si ２ O ５ Having crystals leads to a higher fracture toughness value K ＩＣ This is preferable from the viewpoint of realizing the above. ２ Si ２ O ５ The content of crystals is preferably 40 mass % or more, more preferably 40 to 85 mass %. ＩＣ From the viewpoint of realizing the above, the content is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and even more preferably 60% by mass or more. In addition, although the upper limit is not particularly limited, from the viewpoint of maintaining higher transparency and three-dimensional moldability, it is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0069] In this embodiment, the crystalline phase is Li ２ Si ２ O ５ It is preferable that the crystalline structure contains β-spodumene (LiAlSi ２ O ６ ) crystals, petalite (LiAlSi ４ O １０ ) crystal, β-quartz (including bergerite) (Li ｘ Al ｘ Si ３－ｘ O ６ ), 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, lithium phosphate (Li ３ P.O. ４ However, the material is not limited to these and may be selected appropriately according to the desired properties.

[0070] For example, when it is desired to obtain a crystalline phase that can be ion-exchanged by chemical strengthening treatment, the crystals that constitute the crystalline phase in the crystallized glass are Li. ２ Si ２ O ５ It may be composed of crystals only, but may also contain β-spodumene crystals, petalite crystals, β-quartz, lithium metasilicate crystals, and the like.

[0071] When it is desired to obtain a crystallized glass having a higher strength, the crystals constituting the above crystal phase are Li ２ Si ２ O ５ It may be composed of crystals only, but may also contain β-spodumene crystals, petalite crystals, β-quartz, lithium metasilicate crystals, mullite crystals, and the like.

[0072] When it is desired to achieve higher transparency, the crystals constituting the above crystalline phase are Li ２ Si ２ O ５ The material may be composed of crystals only, but may also contain β-quartz, lithium metasilicate crystals, lithium phosphate crystals, etc.

[0073] In addition, the fracture toughness value K ＩＣ From the viewpoint of increasing the content of petalite crystals in the crystallized glass, the content of petalite crystals is preferably 50 mass % or less, more preferably 40 mass % or less, and even more preferably 20 mass % or less, and may be 0 mass %, i.e., no petalite crystals may be contained.

[0074] In the crystalline phase of this embodiment, the Li ２ Si ２ O ５ The total content of crystals other than crystals is preferably 95 mass % or less, more preferably 0 to 70 mass %.ＩＣ From the viewpoint of efficiently improving the Li ２ Si ２ O ５ The total content of the crystals other than the crystals is preferably 95% by mass or less, more preferably 70% by mass or less, even more preferably 68% by mass or less, even more preferably 65% ​​by mass or less, and particularly preferably 63% by mass or less. The lower limit is not particularly limited, and it is 0% by mass, that is, the total amount of the crystal phase is Li ２ Si ２ O ５ It may be a crystal, and when it contains other crystals, it may be 1% by mass or more, 10% by mass or more, 25% by mass or more, 50% by mass or more, or 55% by mass or more.

[0075] The content ratio of the crystalline phase in the crystallized glass according to this embodiment, i.e., the degree of crystallization, is a factor that contributes to a higher fracture toughness value K ＩＣ From the viewpoint of realizing this, 40 to 85 mass % is preferable. Here, from the viewpoint of increasing the Young's modulus, the crystallinity is preferably 40 mass % or more, more preferably 50 mass % or more, even more preferably 55 mass % or more, and even more preferably 60 mass % or more. Furthermore, since the haze is reduced by the presence of an amorphous phase in the crystallized glass, the crystallinity may be 85 mass % or less, 80 mass % or less, or 75 mass % or less. Note that, when Li is present in the crystalline phase, ２ Si ２ O ５ When other crystals than Li are included, ２ Si ２ O ５ The sum of the content rate of the crystal and the total content rate of the other crystals is the degree of crystallinity.

[0076] The crystallized glass according to this embodiment contains Li as a crystalline phase. ２ Si ２ O ５ When the crystal is contained, in the powder X-ray diffraction pattern (XRD pattern) using Cu-Kα radiation, Li is present in the range of 2θ=23.5 to 25.5°. ２ Si ２ O ５It is preferable that a peak derived from crystals is observed, and the half-value width of the peak in the above range is preferably 0.1 to 0.4. The half-value width is related to the crystallinity and the average crystallite size, and the higher the crystallinity, the narrower the half-value width. Also, the smaller the average crystallite size, the narrower the half-value width. In light of this tendency, the half-value width is preferably 0.4 or less, more preferably 0.3 or less, even more preferably 0.25 or less, and preferably 0.1 or more.

[0077] In this embodiment, the average crystallite size of the crystals constituting the crystalline phase is preferably 20 to 200 nm. From the viewpoint of achieving higher strength, the average crystallite size is preferably 20 nm or more, more preferably 30 nm or more, even more preferably 40 nm or more, and even more preferably 45 nm or more. From the viewpoint of achieving higher transparency, the average crystallite size is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. The average crystallite size is determined by performing Rietveld analysis on the diffraction pattern obtained by powder X-ray diffraction (XRD) measurement, creating a Williamson-Hall plot from the 2θ value and half-width of each peak obtained, and then determining the intercept. The average crystallite size can also be adjusted by adjusting the heat treatment conditions for crystallization.

[0078] <Characteristics and Physical Properties> Fracture toughness value K of the crystallized glass according to this embodiment ＩＣ is 1.30 MPa m １／２ or more is preferable, and 1.30 to 2.00 MPa m １／２ Here, from the viewpoint of high strength, the fracture toughness value K ＩＣ is 1.30 MPa m １／２ More than 1.40 MPa m １／２ More preferably, 1.45 MPa m １／２ The upper limit is not particularly limited, but is, for example, 2.00 MPa m １／２ The fracture toughness value K ＩＣ is the type of crystal that constitutes the crystalline phase, Li ２ Si ２ O ５The fracture toughness value K ＩＣ can be measured by the pre-crack introduction fracture test method (SEPB method: Single-Edge-Precracked-Beam method) specified in JIS R1607:2015.

[0079] The Young's modulus of the crystallized glass according to this embodiment is preferably 107 GPa or more, and may be 110 to 120 GPa. From the viewpoint of high strength, the Young's modulus is preferably 107 GPa or more, more preferably 110 GPa or more, and even more preferably 115 GPa or more. From the viewpoint of high strength, the higher the Young's modulus, the more preferable it is, but is not particularly limited, and may be, for example, 120 GPa or less. The Young's modulus in this specification can be measured by an ultrasonic method.

[0080] The haze value of the crystallized glass according to this embodiment is preferably 0.05 to 0.20%, and may be 0.10 to 0.18%. From the viewpoint of visibility when the crystallized glass is used as a cover glass, particularly a three-dimensionally shaped cover glass, the haze value is preferably 0.20% or less, more preferably 0.18% or less, even more preferably 0.15% or less, and most preferably 0.10% or less. The smaller the haze value, the better, but it may be, for example, 0.05% or more, or 0.10% or more. The haze value can be adjusted by the crystal species, degree of crystallization, and glass composition. The haze value in this specification refers to the value measured using a C illuminant in accordance with JIS K 7136:2000, converted into a 0.6 mm thickness of the crystallized glass. Furthermore, when the actual thickness of the crystallized glass is not 0.6 mm, the haze value can be converted into a 0.6 mm thickness equivalent value based on the measured value using the Lambert-Beer law. Furthermore, when the plate thickness t is greater than 0.6 mm, the plate thickness of the crystallized glass may be adjusted to 0.6 mm by polishing, etching, or the like, before measurement.

[0081] The average transmittance of the crystallized glass according to this embodiment, when converted into a thickness of 0.6 mm, for light with a wavelength of 600 nm is preferably 85% or more, and may be 85 to 95%. From the viewpoint of achieving higher transparency, the average transmittance is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. There is no particular upper limit to the average transmittance, and the higher the better, but it is usually 95% or less.

[0082] <Chemically strengthened glass> The crystallized glass according to this embodiment may have a compressive stress layer formed by ion exchange on the surface layer. Such crystallized glass may be referred to as "chemically strengthened glass according to this embodiment" hereinafter. The matrix composition of chemically strengthened glass is the composition of the crystallized glass before chemical strengthening treatment (ion exchange treatment), and except in cases where extreme ion exchange treatment has been performed, the composition of the chemically strengthened glass deeper than the compressive stress layer depth (DOL) can be considered to be the same as the matrix composition of the chemically strengthened glass. In other words, the composition of the center of the plate thickness of the chemically strengthened glass coincides with the matrix composition of the chemically strengthened glass and can be considered to be the same as the composition of the crystallized glass.

[0083] The chemically strengthened glass according to this embodiment is preferably a chemically strengthened glass in which Li ions in the surface layer of the crystallized glass are ion-exchanged with Na ions. ２ The content of O is determined based on the composition of the glass-ceramics before chemical strengthening, i.e., the Na content in the base composition of the chemically strengthened glass. ２ The content of Na is preferably higher than that of O, and the difference is more preferably 1 mol % or more, further preferably 5 mol % or more, and even more preferably 10 mol % or more. ２ The upper limit of the difference in the O content is not particularly limited, but is, for example, 30 mol % or less.

[0084] From the viewpoint of improving the falling ball strength and the drop strength, the chemically strengthened glass according to this embodiment preferably has a compressive stress layer in which Na ions are ion-exchanged with K ions in addition to the ion exchange of Li ions and Na ions. In this case, a surface compressive stress is imparted to a portion close to the surface of the glass due to the ion exchange of Na ions with K ions, and a deep compressive stress is imparted to a portion deeper than that due to the ion exchange of Li ions with Na ions.

[0085] The chemically strengthened glass according to this embodiment does not show any significant changes in the overall composition and crystallinity of the glass, as well as its characteristics and physical properties (other than strength), compared to the crystallized glass before chemical strengthening, and can be considered to be the same. However, the peak position in the powder X-ray diffraction (XRD) pattern of the surface of the crystallized glass shifts from before the chemical strengthening treatment. In addition, the surface layer of the chemically strengthened glass may have different composition, crystal structure, and crystallinity.

[0086] Regarding the above XRD pattern, in the X-ray diffraction pattern of the surface using Cu-Kα radiation, Li ２ Si ２ O ５ The peak position derived from the crystal may shift before and after ion exchange, or may shift to a lower angle. The peak shift means that the ions in the crystal are also exchanged. The XRD measurement is performed on the surface of the crystallized glass before and after chemical strengthening treatment using CuKα radiation in the 2θ range of 10° to 80°. Specifically, the Li of the chemically strengthened glass ２ Si ２ O ５ Of the peaks derived from the crystals, the peak shift from the peak before ion exchange is preferably 0.02° or more, more preferably 0.02 to 0.10°. Here, the peak shift is preferably 0.02° or more, more preferably 0.03° or more. Furthermore, from the viewpoint of maintaining the crystal structure, the peak shift is preferably 0.10° or less, more preferably 0.08° or less.

[0087] The chemically strengthened glass according to this embodiment may have different physical properties related to strength compared to the crystallized glass before chemical strengthening. Examples of the physical properties include compressive stress (CS), compressive stress layer depth (DOL), internal tensile stress (CT), ST limit, fracture toughness, Young's modulus, Vickers hardness, etc. On the other hand, no significant changes are observed in physical properties other than strength, such as haze value, average transmittance, and average thermal expansion coefficient, before and after chemical strengthening.

[0088] In this specification, stress profiles such as compressive stress and tensile stress can be measured using, for example, a scattered light photoelastic stress meter (SLP) or a glass surface stress meter (FSM; Film Stress Measurement). In a method using a scattered light photoelastic stress meter (SLP), compressive stress derived from Li-Na exchange can be measured inside the glass, which is a region several tens of μm or more deep from the glass surface. On the other hand, in a method using a glass surface stress meter (FSM), compressive stress derived from Na-K exchange can be measured in the glass surface layer, which is a shallow region several tens of μm or less from the glass surface (see, for example, WO 2018 / 056121 and WO 2017 / 115811).

[0089] Furthermore, when measuring compressive stress on the outermost surface, an optical waveguide surface stress meter may be used. An optical waveguide surface stress meter can accurately measure the stress of glass in a short time. However, in principle, an optical waveguide surface stress meter can only measure stress when the refractive index decreases from the sample surface toward the inside. In contrast, if the outermost surface of chemically strengthened crystallized glass is a layer obtained by substituting sodium ions inside the glass with potassium ions from the outside, the refractive index decreases from the sample surface toward the inside, and therefore stress can be measured with an optical waveguide surface stress meter. When measuring compressive stress using an optical waveguide surface stress meter, the measurement is performed, for example, under the following conditions: - Measuring device: FSM-6000 (manufactured by Orihara Manufacturing Co., Ltd.) - Measurement wavelength: 365 nm

[0090] The compressive stress value (CS ０From the viewpoint of preventing cracks due to deformation such as bending, the compressive stress value (CS) at the outermost surface is preferably 300 MPa or more, more preferably 400 MPa or more, and even more preferably 500 MPa or more. ０ The upper limit of the compressive stress value (CS) at the outermost surface is not particularly limited, but is, for example, 1200 MPa or less. ０ ) can be adjusted, for example, by the Na concentration in the molten salt used in the chemical strengthening treatment, the chemical strengthening treatment conditions, the Li concentration in the glass composition, etc.

[0091] The compressive stress value (CS) at a depth of 50 μm from the outermost surface of the chemically strengthened glass according to this embodiment ５０ ) is preferably 30 to 200 MPa. ５０ is preferably 30 MPa or more, more preferably 50 MPa or more, and even more preferably 70 MPa or more. ５０ is preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 120 MPa or less.

[0092] The compressive stress layer depth (DOL) of the chemically strengthened glass according to this embodiment is preferably 50 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more, from the viewpoint of preventing cracking when scratches occur on the surface of the chemically strengthened glass. The upper limit of the compressive stress layer depth is not particularly limited, but is, for example, 200 μm or less. The value of the compressive stress layer depth can be adjusted, for example, by the molten salt, temperature, time, etc. used in the chemical strengthening treatment. In this specification, the compressive stress layer depth (DOL) is the depth at which the compressive stress value (CS) becomes zero.

[0093] The compressive stress layer depth (DOL) of the chemically strengthened glass according to this embodiment is preferably {t × 0.13} μm or more relative to the plate thickness t (μm), and more preferably {t × 0.13 + 10} μm or more and {t × 0.13 + 70} μm or less. Here, from the viewpoint of preventing cracks when scratches occur on the surface of the chemically strengthened glass, the compressive stress layer depth DOL is preferably {t × 0.13} μm or more, more preferably {t × 0.13 + 10} μm or more, even more preferably {t × 0.13 + 15} μm or more, and even more preferably {t × 0.13 + 20} μm or more. Further, from the viewpoint of improving the productivity of the strengthening process, the compressive stress layer depth DOL is preferably {t × 0.13 + 70} μm or less, more preferably {t × 0.13 + 50} μm or less, and even more preferably {t × 0.13 + 30} μm or less.

[0094] The chemically strengthened glass according to this embodiment has a compressive stress value (CS ０ ) is 300 MPa or more, and the compressive stress layer depth (DOL) is 50 μm or more and the plate thickness t (μm) is {t × 0.13} μm or more. It is more preferable that it satisfies at least one of these.

[0095] The maximum value of the tensile stress of the chemically strengthened glass according to this embodiment (CT ｍａｘ ) is preferably 100 MPa or less, and may be 30 to 95 MPa. Here, from the viewpoint of realizing a higher drop strength, the maximum value of the tensile stress CT ｍａｘ is preferably 100 MPa or less, more preferably 95 MPa or less, even more preferably 80 MPa or less, and even more preferably 60 MPa or less. Although the lower limit is not particularly limited, from the viewpoint of obtaining a certain or higher compressive stress value, the maximum value CT of the tensile stress is ｍａｘ may be 30 MPa or more, 40 MPa or more, or 50 MPa or more.

[0096] <Applications> The crystallized glass according to this embodiment is useful as a cover glass for electronic devices such as mobile devices such as mobile phones and smartphones. It is also useful as a cover glass for non-portable electronic devices such as televisions, personal computers, and touch panels, as well as elevator walls and wall surfaces (full-surface displays) of buildings such as houses and buildings. It is also useful as building materials such as window glass, tabletops, interiors of automobiles and airplanes, and their cover glass, as well as for curved housings. Furthermore, the crystallized glass according to this embodiment becomes extremely useful for the above applications by undergoing a chemical strengthening treatment.

[0097] <<Glass>> The glass according to this embodiment has a composition expressed in mole percentage based on oxides of SiO ２ , Al ２ O ３ , and Li ２ Contains O and SiO ２ , Al ２ O ３ , and Li ２ The total content of O is 90 to 98%. In addition to the above, the glass according to this embodiment has only one local peak indicating an exothermic reaction in the range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement.

[0098] The glass according to this embodiment can be crystallized to become the crystallized glass described in the above "Crystalline Glass" by crystallization treatment. That is, the glass according to this embodiment can be the mother glass of the crystallized glass described in the above "Crystalline Glass".

[0099] Therefore, the composition of the glass according to this embodiment is the same as the composition of the glass-ceramics in the above-mentioned "Glass-ceramics", including preferred embodiments. In addition, the thermal properties of the glass according to this embodiment in terms of DSC measurement are the same as the thermal properties of the mother glass in the above-mentioned "Glass-ceramics", including preferred embodiments.

[0100] Here, in the development of the composition of crystallized glass, it has been common practice to perform heat treatment (crystallization treatment) on glass, produce crystallized glass, and then confirm the crystalline phase by powder X-ray diffraction measurement or the like. In contrast, in this embodiment, before producing crystallized glass, DSC measurement is performed on the glass before heat treatment that is a candidate for mother glass, so that it is possible to know in advance the possibility of obtaining crystallized glass that selectively contains preferred crystals. As a result, this leads to a reduction in development time, and is also effective as a method for searching for crystallized glass.

[0101] Specifically, as shown in the section "Thermal Properties of Mother Glass" in "Ceramics" above, a glass having only one local peak (Peak 2) indicating an exothermic reaction within the range of 700 to 900°C in the curve obtained by differential scanning calorimetry (DSC) measurement can be effectively used to produce crystallized glass by heat treatment. Furthermore, the curve preferably has only one local peak (Peak 1) indicating an exothermic reaction within the range of 550°C or higher and lower than 700°C. When only one Peak 1 and one Peak 2 are present, the difference from the baseline in the calorific value of the peak top of Peak 1 is defined as W_Tp1 (mcal / s), and the difference from the baseline in the calorific value of the peak top of Peak 2 is defined as W_Tp2 (mcal / s), and the value represented by {W_Tp2 / W_Tp1} is preferably 0.5 to 1.

[0102] A preferred specific aspect of the composition of the glass according to this embodiment is, for example, one that satisfies the following in terms of mole percentage based on oxides: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５ 0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２ 0 to 1%.

[0103] In addition, the glass according to this embodiment contains SiO ２ , Al ２ O ３ , and Li ２ It is preferable that the following ratio using the content ratio of O expressed in mole percentage satisfies the following: {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 21.0 to 28.5%.

[0104] <<Method for Producing Glass / Ceramics>> The methods for producing the glass and crystallized glass according to the present embodiment are not particularly limited, but for example, the method for producing the glass includes the following step 1, and the method for producing the crystallized glass includes the following steps 1 and 2. Furthermore, when crystallized glass is made into chemically strengthened glass by chemical strengthening treatment, the manufacturing method preferably includes the following step 3 in addition to step 1 and step 2.

[0105] Step 1: A step of producing glass. Step 2: A step of crystallizing the glass obtained in step 1 to obtain crystallized glass. Step 3: A step of chemically strengthening the crystallized glass obtained in step 2 to obtain chemically strengthened glass.

[0106] That is, one aspect of the method for producing crystallized glass having a crystalline phase according to this embodiment includes a step of producing glass (step 1) and a step of crystallizing the glass to obtain crystallized glass (step 2). Here, the glass has only one local peak indicating an exothermic reaction within the range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC). The composition of the obtained crystallized glass, expressed in mole percentage based on oxides, is: SiO ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２ The total content of O is 90 to 98%.

[0107] In addition to the above, one aspect of the method for producing chemically strengthened glass according to this embodiment further includes a step (step 3) of chemically strengthening the obtained crystallized glass to obtain chemically strengthened glass.

[0108] The crystallization treatment in step 2 is preferably carried out by a three-stage heat treatment. In this case, the first heat treatment, the second heat treatment, and the third heat treatment more preferably satisfy the following relationships, where Tp1 is the temperature of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C in a curve obtained by differential scanning calorimetry (DSC) measurement of the glass obtained in step 1, and Tp2 is the temperature of a local peak showing an exothermic reaction observed in the range of 700 to 900°C. First heat treatment: The first treatment temperature T1 satisfies the relationship {Tp1 - T1} ≦ 140°C. Second heat treatment: The second treatment temperature T2 satisfies the relationship {T2 - T1} ≧ 10°C. Third heat treatment: The third treatment temperature T3 satisfies the relationship {Tp2 - T3} ≦ 120°C. It is more preferable to satisfy one or more of the above three relationships, even more preferably to satisfy two or more, and even more preferably to satisfy all three.

[0109] Each step will be described below.

[0110] <Step 1> Step 1 is a step of producing glass, and a conventionally known method can be used as the specific method. That is, to obtain glass, for example, glass raw materials are mixed to have a desired composition, and then heated and melted in a glass melting furnace. Here, the desired composition is, for example, SiO ２ , Al ２ O ３ , and Li ２ Contains O and SiO ２ , Al ２ O ３ , and Li ２ The total content of O is 90 to 98%.

[0111] After the above-mentioned heating and melting, the molten glass is homogenized by bubbling, stirring, adding a fining agent, etc., and then formed into a desired shape by a known forming method and slowly cooled. Alternatively, the molten glass may be formed into a block, slowly cooled, and then cut and processed into a desired shape. In this way, amorphous glass is obtained.

[0112] Examples of glass forming methods include the float method, the press method, the fusion method, and the down-draw method.

[0113] The slow cooling method may be, for example, a method of cooling to room temperature at a rate of 0.1 to 2°C / min. The slow cooling may be performed by holding the material at a specific temperature for a specific period of time and then cooling to room temperature. Specifically, for example, the material may be held at 420 to 550°C for 10 to 180 minutes and then cooled to room temperature at a rate of 0.1 to 2°C / min.

[0114] By making the glass obtained in this step into a glass that has only one local peak showing an exothermic reaction in the range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement, the crystallized glass obtained through step 2, or the crystallized glass obtained through steps 2 and 3, can be made to have high strength while maintaining the desired transparency.

[0115] <Step 2> Step 2 is a step of obtaining crystallized glass by crystallizing the glass obtained in step 1. This results in crystallized glass having a crystalline phase and desired composition and properties.

[0116] The heat treatment for crystallization is not particularly limited as long as it produces the desired crystals, but may be, for example, a two-stage heat treatment in which the temperature is raised from room temperature to a first treatment temperature and maintained for a certain period of time, and then maintained at a second treatment temperature higher than the first treatment temperature for a certain period of time. After the two-stage heat treatment, a three-stage heat treatment may be performed in which the temperature is maintained at a third treatment temperature for a certain period of time. Alternatively, a one-stage heat treatment in which the temperature is maintained at a specific treatment temperature and then cooled to room temperature may be performed.

[0117] In the case of a two-stage heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate is high for the glass composition, and the second treatment temperature is preferably in a temperature range where the crystal growth rate is high for the glass composition.

[0118] When crystallization treatment is carried out by two-stage heat treatment, it is more preferable that the following relationships be satisfied, where Tp1 is the temperature of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C in the curve obtained by differential scanning calorimetry (DSC) measurement of the glass obtained in step 1, and Tp2 is the temperature of a local peak showing an exothermic reaction observed in the range of 700 to 900°C. First heat treatment: The first treatment temperature T1 satisfies the relationship {Tp1 - T1} ≦ 140°C. Second heat treatment: The second treatment temperature T2 satisfies the relationship {Tp2 - T2} ≦ 120°C. It is more preferable that one or more of the above two relationships be satisfied, and it is even more preferable that both of them be satisfied.

[0119] When crystallization treatment is performed by two-stage heat treatment, the value represented by {Tp1-T1} using the first treatment temperature T1 in the first heat treatment is preferably 140°C or less, more preferably 90 to 140°C. From the viewpoint of nucleation, the value is preferably 140°C or less, more preferably 130°C or less, and even more preferably 120°C or less. Furthermore, from the viewpoint of haze reduction, the value is preferably 90°C or more, more preferably 100°C or more, and even more preferably 110°C or more.

[0120] When the crystallization treatment is carried out by two-stage heat treatment, the value represented by {Tp2-T2} using the second treatment temperature T2 in the second heat treatment is preferably 120°C or less, more preferably 20 to 120°C. ２ Si ２ O ５ From the viewpoint of increasing the content of crystals, the above value is preferably 120° C. or less, more preferably 100° C. or less, and even more preferably 80° C. or less. There is no particular lower limit to the above value, but the above value may be 20° C. or more, 30° C. or more, or 40° C. or more.

[0121] In the case of a three-stage heat treatment, it is preferable that the first and second treatment temperatures are temperatures at which the crystal nucleation rate increases, and the third treatment temperature is a temperature at which the crystal growth rate increases. Alternatively, the first treatment temperature may be a temperature at which the crystal nucleation rate increases, and the second and third treatment temperatures may be temperatures at which the crystal growth rate increases.

[0122] When crystallization treatment is performed by three-stage heat treatment, it is more preferable that the following relationships be satisfied, where Tp1 is the temperature of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C in the curve obtained by differential scanning calorimetry (DSC) measurement of the glass obtained in step 1, and Tp2 is the temperature of a local peak showing an exothermic reaction observed in the range of 700 to 900°C. First heat treatment: The first treatment temperature T1 satisfies the relationship {Tp1 - T1} ≦ 140°C. Second heat treatment: The second treatment temperature T2 satisfies the relationship {T2 - T1} ≧ 10°C. Third heat treatment: The third treatment temperature T3 satisfies the relationship {Tp2 - T3} ≦ 120°C. It is more preferable that one or more of the above two relationships be satisfied, even more preferable that two or more be satisfied, and even more preferable that all three be satisfied.

[0123] When crystallization treatment is performed by three-stage heat treatment, the value represented by {Tp1-T1} using the first treatment temperature T1 in the first heat treatment is preferably 140°C or less, more preferably 90 to 140°C. From the viewpoint of nucleation, the value is preferably 140°C or less, more preferably 130°C or less, and even more preferably 120°C or less. Furthermore, from the viewpoint of reducing haze, the value is preferably 90°C or more, more preferably 100°C or more, and even more preferably 110°C or more.

[0124] When crystallization treatment is performed by a three-stage heat treatment, the value represented by {T2-T1}, where T1 is the first treatment temperature in the first heat treatment and T2 is the second treatment temperature in the second heat treatment, is preferably 10° C. or higher, more preferably 10 to 50° C. From the viewpoint of nucleus growth, the value is preferably 10° C. or higher, more preferably 15° C. or higher, and even more preferably 20° C. or higher. From the viewpoint of reducing haze, the value is preferably 50° C. or lower, more preferably 40° C. or lower, and even more preferably 30° C. or lower.

[0125] When the crystallization treatment is carried out by three-stage heat treatment, the value represented by {Tp2-T3} using the third treatment temperature T3 in the third heat treatment is preferably 120°C or less, more preferably 20 to 120°C. ２ Si ２ O ５ From the viewpoint of increasing the content of crystals, the above value is preferably 120° C. or less, more preferably 100° C. or less, and even more preferably 80° C. or less. There is no particular lower limit to the above value, but the above value may be 20° C. or more, 30° C. or more, or 40° C. or more.

[0126] In the two-stage heat treatment and the three-stage heat treatment, the holding time at the first treatment temperature is preferably long enough to generate a sufficient number of crystal nuclei. The generation of a large number of crystal nuclei reduces the size of each crystal, resulting in a highly transparent crystallized glass.

[0127] More specifically, in the case of a two-stage treatment, for example, the treatment is carried out by holding the material at a first treatment temperature (T1) of 500°C to 700°C for 1 hour to 6 hours, and then holding the material at a second treatment temperature (T2) of 600°C to 800°C for 1 hour to 6 hours.

[0128] More specifically, in the case of a three-stage treatment, for example, the treatment is performed by holding the material at a first treatment temperature (T1) of 450°C to 600°C for 1 to 6 hours, then holding the material at a second treatment temperature (T2) of 500°C to 650°C for 1 to 6 hours, and then holding the material at a third treatment temperature (T3) of 600°C to 800°C for 1 to 6 hours.

[0129] More specifically, in the case of a one-stage treatment, the temperature may be maintained at 500° C. to 800° C. for 1 hour to 6 hours.

[0130] The crystallized glass obtained in step 2 may be ground and polished as necessary. When the crystallized glass obtained is cut to a predetermined shape and size or chamfered, it is preferable to perform the cutting or chamfering before performing the chemical strengthening treatment in the next step 3. This allows a compressive stress layer to be formed on the cut surface or the chamfered surface by the subsequent chemical strengthening treatment.

[0131] <Step 3> Step 3 is a step of chemically strengthening the crystallized glass obtained in step 2 to obtain chemically strengthened glass having a compressive stress layer formed on its surface by ion exchange. The chemical strengthening treatment is a process in which the glass is brought into contact with a metal salt (e.g., potassium nitrate) containing a metal ion with a large ionic radius (typically, Na ion or K ion) by, for example, immersing the glass in a melt of the metal salt, thereby replacing the metal ion with a small ionic radius (typically, Li ion or Na ion) with a metal ion with a large ionic radius (typically, Na ion or K ion for Li ion, and K ion for Na ion).

[0132] To increase the speed of chemical strengthening, it is preferable to use "Li-Na exchange," which exchanges Li ions in the glass with Na ions. Here, the crystallized glass in this embodiment contains a crystalline phase, but a compressive stress layer is formed not only in the amorphous phase but also when Li constituting the crystalline phase is converted to Na.

[0133] In order to form a larger compressive stress by ion exchange, it is preferable to use "Na-K exchange" in which Na ions in the glass are exchanged with K ions.

[0134] Examples of molten salts for chemical strengthening include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used alone or in combination.

[0135] When both the Li—Na exchange and the Na—K exchange are carried out, for example, a mixed molten salt of lithium nitrate, sodium nitrate, and potassium nitrate may be used. In this case, the mixing ratio of lithium nitrate, sodium nitrate, and potassium nitrate is not particularly limited, but for example, the lithium nitrate is preferably 0.002 to 0.5 parts by mass, the sodium nitrate is preferably 20 to 70 parts by mass, and the potassium nitrate is preferably 30 to 80 parts by mass, per 100 parts by mass of the total of lithium nitrate, sodium nitrate, and potassium nitrate.

[0136] The conditions for the chemical strengthening treatment, such as time and temperature, can be selected taking into consideration the glass composition, the type of molten salt, etc. For example, the crystallized glass obtained in step 2 can be chemically strengthened at preferably 500°C or less for preferably 20 hours or less. Alternatively, two or more stages of chemical strengthening treatment may be performed.

[0137] The present invention will be described below with reference to test examples, but the present invention is not limited thereto. Examples 1 and 2 are working examples, and Examples 3 and 4 are comparative examples.

[0138] Examples 1 to 4 Glass raw materials were mixed to obtain the glass compositions shown in Table 1, and weighed out to obtain 600 g of glass. The mixed glass raw materials were then placed in a platinum crucible and placed in an electric furnace at 1,550°C, where they were melted for approximately 5 hours, degassed, and homogenized. The resulting molten glass was poured into a mold, held at 470°C for 1 hour, and then cooled to room temperature at a rate of 0.5°C / min to obtain glass blocks of glass materials A to D. Note that blanks in Table 1 indicate that no material was added.

[0139] The obtained glass blocks were each processed into plates of 50 mm x 50 mm x 0.6 mm, and crystallized by three-stage heat treatment at the temperatures and holding times listed in the "Crystallization Conditions" in Table 2. They were then cooled to room temperature to obtain crystallized glass. It was confirmed that none of the obtained crystallized glass exhibited cloudiness due to enlargement of the crystal grain size, and maintained the desired transparency.

[0140] <Evaluation> <Composition: Crystallized Glass> The composition of the crystallized glass obtained was analyzed, and it was confirmed that there was no significant change from the glass composition before crystallization (composition of the mother glass), and that the glass composition was the same as the glass composition shown in Table 1.

[0141] <Crystalline Phase> The obtained crystallized glass was pulverized and subjected to powder X-ray diffraction measurement under the following conditions. The crystallinity was determined by Rietveld analysis, and the precipitated crystals were identified. In addition, a Williamson-Hall plot was created from the 2θ value and half-width of each peak in the obtained diffraction pattern, and the average crystallite size of the crystals was determined from the intercept. The results are shown in "Crystalline Phase" in Table 2. The crystallinity is shown in "Crystallinity (mass%)" and the Li in the crystalline phase is shown in "Crystallinity (mass%)". ２ Si ２ O ５ The content ratio of LD crystals in the crystalline phase is referred to as "content ratio of LD crystals in the crystalline phase (mass%)", and the content ratio of Li in the crystalline phase is referred to as "content ratio of LD crystals in the crystalline phase (mass%)". ２ Si ２ O ５The crystal species other than the LD crystals are shown in "crystal species other than the LD crystals in the crystalline phase", and the average crystallite size of the crystals is shown in "average crystallite size (nm)". For example, in Example 3, the crystallinity is 80 mass%, of which Li ２ Si ２ O ５ Since the crystal is 55% by mass, the Li in the crystallized glass ２ Si ２ O ５ The content of the crystals is 80 × 0.55 = 44 mass%. ２ Si ２ O ５ As a crystal species other than LiAlSi ２ O ６ (β-spodumene) crystals, LiAlSi in crystallized glass ２ O ６ The content of "crystals" is 80 x (1 - 0.55) = 36 mass %.

[0142] XRD measurement conditions: Measurement device: SmartLab manufactured by Rigaku Corporation; X-ray used: Cu-Kα ray; Measurement range: 2θ = 10° to 80°; Speed: 10° / min; Step: 0.02°

[0143] <Transmittance> The transmittance of light with a wavelength of 600 nm (converted to a thickness of 0.6 mm) of the obtained crystallized glass was measured using a spectrophotometer (product name U-4100) manufactured by Hitachi High-Technologies Corporation. The results are shown in "Transmittance @ 600 nm (%)" under "Characteristics and physical properties" in Table 2.

[0144] <Young's modulus> The Young's modulus of the obtained crystallized glass was measured by an ultrasonic method using an ultrasonic thickness gauge (manufactured by Olympus Corporation, product name 38DL). The results are shown in Table 2 under "Characteristics and physical properties" as "Young's modulus (GPa)".

[0145] Strength: Fracture toughness value K ＩＣ > Fracture toughness value K of the obtained crystallized glass ＩＣThe fracture toughness was measured using a strength testing machine (Shimadzu Corporation, Autograph AGS-X) according to the SEPB method (Single-Edge-Precracked-Beam method) specified in JIS R1607:2015. The results are shown in the "Fracture toughness value K" column in the "Characteristics and physical properties" section of Table 2. ＩＣ (MPa m １／２ ) shown below.

[0146] <Thermal Properties: Exothermic Peak in DSC Curve> Differential scanning calorimetry (DSC) was performed on the glass before crystallization as the glass having the mother composition of the obtained glass-ceramics. Specifically, the glass was crushed and classified into 150-300 μm particles to obtain glass powder. This glass powder was placed in a platinum pan (container) and heated from room temperature to 1050°C at a heating rate of 5°C / min, followed by DSC measurement. The temperature profile of the obtained DSC curve was first differentiated, and the profile was subjected to Gaussian filtering (first-derivative GF processing) under conditions of σ = 30 and kernel size: 501. The profile showing an exothermic reaction that changed from a value of 0.005 mcal / (s °C) or more to a value of -0.005 mcal / (s °C) or less was determined as a local peak, and the temperature at which the local peak showed the highest intensity was determined as the temperature of the local peak showing the exothermic reaction. Of the DSC measurement results obtained for glass materials A to D, the DSC curves in the temperature range of 450 to 920°C are shown as (a) in Figures 1 to 4, respectively. The profiles subjected to the first-derivative GF treatment are shown as (b) in Figures 1 to 4 and (c) in Figure 3, respectively. Note that in (c) in Figure 3, the upper and lower limits of the profile subjected to the first-derivative GF treatment are outside the scale of the vertical axis, but the profile in (c) in Figure 3 is enlarged so that the change from values ​​of 0.005 mcal / (s °C) or more to values ​​of -0.005 mcal / (s °C) or less can be seen. Glass material C, which corresponds to (a) to (c) in Figures 3, contains Li. ２ Si ２ O ５ In addition to the crystals, Virgilite crystals (LiAlSi ２ O ６ It is thought that the value of the calorific value is larger than that of glass material A (see FIG. 1) and glass material B (see FIG. 2) because a large amount of crystals is formed.

[0147] The number of local peaks observed in the temperature range of 500°C or higher and lower than 700°C and the number of local peaks in the temperature range of 700 to 900°C, which were obtained from the above results, are shown in "@500°C or higher and lower than 700°C" and "@700 to 900°C," respectively, under "Number of exothermic peaks of mother glass" in "Characteristics and physical properties" in Table 2. Note that for Examples 1 and 2, the temperature (Tp1) of the local peak indicating an exothermic reaction observed at a temperature of 500°C or higher and lower than 700°C and the temperature (Tp2) of the local peak indicating an exothermic reaction observed at a temperature of 700 to 900°C are also shown. Furthermore, for Examples 1 and 2, a baseline was drawn for the DSC curve by the method described above, and the difference from the baseline in the heat quantity at the peak top of a local peak (Peak 1) that exhibits an exothermic reaction in the range of 700 to 900°C was defined as W_Tp1 (mcal / s), and the difference from the baseline in the heat quantity at the peak top of a local peak (Peak 2) that exhibits an exothermic reaction in the range of 550°C or higher and lower than 700°C was defined as W_Tp2 (mcal / s). The value expressed as {W_Tp2 / W_Tp1} was also determined and shown as "{W_Tp2 / W_Tp1}" in Example 2.

[0148] <Chemically strengthened glass> The obtained crystallized glass was immersed in a 450 ° C. mixed molten salt of potassium nitrate: sodium nitrate: lithium nitrate = 60:39.97:0.03 (mass ratio, Examples 1 to 3), or potassium nitrate: sodium nitrate: lithium nitrate = 60:39.99:0.01 (mass ratio, Example 4) for 300 minutes (Example 1, Example 2), 240 minutes (Example 3), or 180 minutes (Example 4), followed by washing and drying to obtain chemically strengthened glass. The depth direction stress profile of the obtained chemically strengthened glass was measured using a measuring instrument SLP-2000 manufactured by Orihara Seisakusho Co., Ltd. Based on the above stress profile, the compressive stress value CS of the outermost surface of the glass was calculated. ０ (MPa), compressive stress value CS at a depth of 50 μm from the outermost surface ５０ (MPa), compressive stress layer depth DOL (μm), and maximum tensile stress CT ｍａｘ The results are shown in the "chemically strengthened glass" section of Table 2.

[0149]

[0150]

[0151] From the above results, the crystallized glass according to this embodiment satisfies a specific composition range, and in the DSC curve of the glass having the base composition, there is only one local peak indicating an exothermic reaction within the range of 700 to 900 ° C., and therefore has good transparency and a high fracture toughness value K Ｉｃ Furthermore, the crystallized glass according to this embodiment also achieved an improvement in strength due to the formation of a compressive stress layer by chemical strengthening treatment.

[0152] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese patent applications filed on June 7, 2024 (Patent Application No. 2024-092882), December 13, 2024 (Patent Application No. 2024-218857), and March 31, 2025 (Patent Application No. 2025-058531), the contents of which are incorporated herein by reference.

Claims

1. A crystallized glass having a crystalline phase, wherein the composition of the crystallized glass is expressed in mole percentage based on oxides, and ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２ A glass-ceramic having a total O content of 90 to 98%, wherein a curve obtained by differential scanning calorimetry (DSC) measurement of glass having the matrix composition of the glass-ceramic has only one local peak showing an exothermic reaction within a range of 700 to 900°C.

2. The composition is expressed in mole percentage based on oxides, and is: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５ 0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２ 2. The crystallized glass according to claim 1, wherein the content of the crystallized glass satisfies 0 to 1%.

3. The composition is SiO ２ , Al ２ O ３ , and Li ２ Using the content ratio of O expressed as mole percentage, {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ 3. The crystallized glass according to claim 1, wherein the ratio expressed as ##EQU1## is 21.0 to 28.5%.

4. The local peak is Li ２ Si ２ O ５ The crystallized glass according to claim 1 or 2, wherein the peak is derived from crystals.

5. Li in the crystallized glass ２ Si ２ O ５ 3. The crystallized glass according to claim 1, wherein the crystal content is 40% by mass or more.

6. The crystallized glass according to claim 1 or 2, wherein the curve obtained when a glass having the above matrix composition is subjected to differential scanning calorimetry (DSC) measurement has only one local peak indicating an exothermic reaction within the range of 550°C or higher but lower than 700°C.

7. The crystallized glass according to claim 6, wherein, in a curve obtained by differential scanning calorimetry (DSC) measurement of glass having the matrix composition, the difference from the baseline of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C is defined as W_Tp1 (mcal / s), and the difference from the baseline of a local peak showing an exothermic reaction in the range of 700 to 900°C is defined as W_Tp2 (mcal / s), and the value represented by {W_Tp2 / W_Tp1} is 0.5 to 1.

8. Fracture toughness value K ＩＣ is 1.3 MPa m １／２ The crystallized glass according to claim 1 or 2, wherein 9. The crystallized glass according to claim 1 or 2, having a Young's modulus of 107 GPa or more.

10. The crystallized glass according to claim 1 or 2, wherein the crystals constituting the crystalline phase have an average crystallite size of 20 to 200 nm.

11. The crystallized glass according to claim 1 or 2, which has a transmittance of 85% or more for light with a wavelength of 600 nm when converted into a glass with a thickness of 0.6 mm.

12. The crystallized glass according to claim 1 or 2, which has a compressive stress layer formed on its surface by ion exchange.

13. The crystallized glass according to claim 12, wherein the compressive stress layer depth DOL is 50 μm or more.

14. The crystallized glass according to claim 12, wherein the compressive stress layer depth DOL is equal to or greater than {t×0.13} μm, where t (μm) is the thickness of the glass.

15. Compressive stress value CS at the outermost surface ０ The crystallized glass according to claim 12, wherein the strain is 300 MPa or more.

16. The composition is expressed as mole percentage based on oxides, and is SiO ２ , Al ２ O ３ , and Li ２ Contains O and SiO ２ , Al ２ O ３ , and Li ２ A glass having a total O content of 90 to 98%, and having only one local peak showing an exothermic reaction in a range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement.

17. The composition is expressed in mole percentage on an oxide basis: SiO ２ 60-75%, Al ２ O ３ 1.2 to 4%, Li ２ O 20-30%, Na ２ O 0-5%, K ２ O 0-1%, ZrO ２ 1.5-3.4%, P ２ O ５ 0.0 to 3.0%, MgO 0.0 to 2.0%, CaO 0.0 to 2.0%, and SnO ２ 17. The glass of claim 16, wherein the glass satisfies the following: 0 to 1%.

18. The composition is SiO ２ , Al ２ O ３ , and Li ２ Using the content ratio of O expressed as mole percentage, {[SiO ２ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 68.5 to 76.0%, ２ O ３ ] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ O])} × 100 is 2.2 to 5.0%, and ２ O] / ([SiO ２ ]+[Al ２ O ３ ]+[Li ２ 18. The crystallized glass according to claim 16, wherein the ratio expressed as 100% by mass of the crystals is 21.0 to 28.5%.

19. The glass according to claim 16 or 17, wherein a curve obtained by differential scanning calorimetry (DSC) measurement has only one local peak indicating an exothermic reaction within a range of 550°C or higher and lower than 700°C.

20. The glass according to claim 19, wherein, in a curve obtained by said differential scanning calorimetry (DSC) measurement, the difference from the baseline of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C is defined as W_Tp1 (mcal / s), and the difference from the baseline of a local peak in said curve showing an exothermic reaction in the range of 700 to 900°C is defined as W_Tp2 (mcal / s), and the value represented by {W_Tp2 / W_Tp1} is 0.5 to 1.

21. A method for producing crystallized glass having a crystalline phase, comprising: producing glass; and crystallizing the glass to obtain crystallized glass, wherein the glass has only one local peak indicating an exothermic reaction within a range of 700 to 900°C in a curve obtained by differential scanning calorimetry (DSC) measurement; the crystallization is carried out by a three-stage heat treatment; and the composition of the crystallized glass, expressed in mole percentage on an oxide basis, is SiO ２ , Li ２ O and Al ２ O ３ and SiO ２ , Al ２ O ３ , and Li ２ A method for producing crystallized glass, wherein the total content of O is 90 to 98%.

22. The method for producing crystallized glass according to claim 21, wherein, in the curve obtained by said differential scanning calorimetry (DSC) measurement, Tp1 is the temperature of a local peak showing an exothermic reaction in the range of 550°C or higher but lower than 700°C, and Tp2 is the temperature of a local peak showing an exothermic reaction observed in the range of 700 to 900°C, said three-stage heat treatment comprises a first heat treatment in which a first treatment temperature T1 satisfies the relationship {Tp1 - T1} ≦ 140°C, a second heat treatment in which a second treatment temperature T2 satisfies the relationship {T2 - T1} ≧ 10°C, and a third heat treatment in which a third treatment temperature T3 satisfies the relationship {Tp2 - T3} ≦ 120°C.

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