Strengthened crystallized glass and method for producing same

Abstract

Provided are strengthened crystallized glass having excellent optical properties and a method for producing the strengthened crystallized glass.　The method for producing strengthened crystallized glass comprises immersing a portion or the whole of crystallized glass containing an alkali metal component in a mixture for ion exchange to conduct an ion exchange treatment and thereby obtain the strengthened crystallized glass. The mixture for ion exchange comprises a molten salt and either silicic acid or a silicic acid salt as an additive. The average reflectance of the strengthened crystallized glass at wavelengths of 360-780 nm after the ion exchange treatment is lower than that of the crystallized glass at wavelengths of 360-780 nm before the ion exchange treatment.

Description

Tempered crystallized glass and its manufacturing method

[0001] The present invention relates to a crystallized glass and a method for producing the same, and more particularly to a crystallized glass suitable for use as a cover glass for mobile phones, digital cameras, PDAs (personal digital assistants), and touch panel displays, and a method for producing the same.

[0002] Devices such as mobile phones (especially smartphones), digital cameras, PDAs, touch panel displays, large televisions, and contactless power transfer devices are becoming increasingly popular. Chemically strengthened glass that has been ion-exchanged is used for these applications. In recent years, chemically strengthened glass has also been increasingly used for exterior components of digital signage, mice, smartphones, and the like.

[0003] In order to further increase the strength of the cover glass for the above-mentioned applications, a technology has been developed in which glass-ceramics is chemically strengthened by ion exchange to obtain strengthened glass-ceramics (for example, Patent Document 1). Glass-ceramics is glass in which crystals are precipitated inside, i.e., glass containing crystals inside, and is known to have high strength. It is believed that by ion-exchanging glass-ceramics, glass with even higher strength can be obtained.

[0004] International Publication No. 2019 / 230889

[0005] However, conventional tempered crystallized glass has room for improvement in terms of optical properties when used as a cover glass.

[0006] An object of the present invention is to provide a strengthened crystallized glass having excellent optical properties and a manufacturing method for obtaining the same.

[0007] First aspect of the present invention: A method for producing strengthened crystallized glass of the present invention is a method for producing strengthened crystallized glass, which comprises immersing a part or all of crystallized glass containing an alkali metal component in an ion exchange mixture to perform ion exchange treatment to obtain strengthened crystallized glass, wherein the ion exchange mixture contains a molten salt and silicic acid or a silicate as an additive, and the average reflectance of the strengthened crystallized glass in the wavelength range of 360 to 780 nm after the ion exchange treatment is lower than the average reflectance of the glass in the wavelength range of 360 to 780 nm before the ion exchange treatment.

[0008] Second aspect of the present invention: In the method for producing strengthened crystallized glass of the first aspect of the present invention, the molten salt is NaNO ３ The additive is an alkali metal silicate, and the alkali metal silicate is Na ２ SiO ３ , Na ４ SiO ４ , Na ２ Si ２ O ５ , and Na ２ Si ４ O ９ It is preferable that the composition contains at least one selected from the following:

[0009] A third aspect of the present invention: In the method for producing strengthened crystallized glass of the first or second aspect of the present invention, the molten salt has a composition of, in mass %, NaNO ３ 50-100%, KNO ３ +LiNO ３ It is preferable that the content be 0 to 50%, and that the ion exchange treatment lowers the average reflectance in the wavelength range of 360 to 780 nm and forms a compressive stress layer in the crystallized glass.

[0010] Fourth aspect of the present invention: In the method for producing strengthened crystallized glass of any one of the first to third aspects of the present invention, it is preferable that the amount of the additive added is 0.1 to 30 parts by mass when the amount of the molten salt is 100 parts by mass.

[0011] Fifth aspect of the present invention: In the method for producing strengthened crystallized glass of the present invention, in any one of the first to fourth aspects, the crystallized glass contains, as a composition, in mol %, SiO ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O 0-15%, ZrO ２ It is preferable that the content is 1.5 to 10%.

[0012] Sixth aspect of the present invention: In the method for producing strengthened crystallized glass of any one of the first to fifth aspects of the present invention, it is preferable that at least one of lithium disilicate and lithium metasilicate is precipitated.

[0013] Seventh aspect of the present invention: In any one of the first to sixth aspects, the method for manufacturing strengthened crystallized glass of the present invention further comprises a step of reducing the crystallization degree of the surface of the crystallized glass to form a low crystallization layer, and it is preferable that the crystallization degree of the low crystallization layer is smaller than the crystallization degree of a central layer located at the center of the glass thickness direction from the low crystallization layer.

[0014] Eighth aspect of the present invention: In the method for producing strengthened crystallized glass of the present invention, in the seventh aspect, it is preferable that in the ion exchange treatment, a compressive stress layer is formed in the crystallized glass and the low crystallinity layer is also formed.

[0015] Ninth aspect of the present invention: In the method for producing strengthened crystallized glass of the present invention, in the first to eighth aspects, it is preferable to adjust the conditions of the ion exchange treatment so that the temperature of the molten salt is 350 to 450°C and the immersion time is 2 hours or more, so that the depth of the compressive stress layer is 50 μm or more.

[0016] Tenth aspect of the present invention: The strengthened glass-ceramics of the present invention is a strengthened glass-ceramics having a compressive stress layer on the surface, characterized in that the average reflectance at wavelengths of 360 to 780 nm is 9.5% or less.

[0017] Eleventh aspect of the present invention: In the strengthened glass-ceramics of the present invention according to the tenth aspect, it is preferable that the average reflectance in the wavelength range of 360 to 780 nm is 8.5% or less.

[0018] Twelfth aspect of the present invention: In the strengthened glass-ceramics of the present invention according to the tenth or eleventh aspect, at least one of lithium disilicate and lithium metasilicate is preferably precipitated.

[0019] A thirteenth aspect of the present invention: The strengthened glass-ceramics of the present invention, in any one of the tenth to twelfth aspects, comprises, as a composition, in mol %, SiO ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0.2-15%, Li ２ O 1.5-30%, Na ２ O 0-15%, ZrO ２ It is preferable that the content is 1.5 to 10%.

[0020] A fourteenth aspect of the present invention: The strengthened glass-ceramics of the present invention is the same as the thirteenth aspect, and has a composition, in mol %, of SiO ２ 50-80%, Al ２ O ３ 0-4.8%, P ２ O ５ 0.2-15%, Li ２ O 1.5-30%, Na ２ O+K ２ O 0 to less than 3.8%, Na ２ O 0-10%, K ２ O 0 to less than 3.8%, ZrO ２ It is preferable that the content is 1.5 to 10%.

[0021] Fifteenth aspect of the present invention: In any one of the tenth to fourteenth aspects, the strengthened glass-ceramics of the present invention preferably has a plate thickness of 1.5 mm or less and a compressive stress value of the compressive stress layer of 400 MPa or more.

[0022] Sixteenth aspect of the present invention: In any of the tenth to fifteenth aspects, the strengthened crystallized glass of the present invention preferably comprises a central layer located in the center of the thickness direction, in which amorphous and crystalline are mixed, and a low-crystallinity layer located on the surface side of the thickness direction, and having a lower crystallinity than the central layer.

[0023] Seventeenth aspect of the present invention: In the strengthened glass-ceramics of the present invention, in the sixteenth aspect, the difference in crystallinity between the central layer and the low crystallinity layer is preferably 10% or more.

[0024] Eighteenth aspect of the present invention: In the strengthened glass-ceramics of the present invention according to the sixteenth or seventeenth aspect, it is preferable that the low crystallinity layer contains the constituent components of the central layer.

[0025] Nineteenth aspect of the present invention: In the strengthened glass-ceramics of the present invention according to the sixteenth or seventeenth aspect, it is preferable that the depth of the low crystallinity layer is 0.02 μm or more.

[0026] A twentieth aspect of the present invention: In the method for producing strengthened crystallized glass of the present invention according to the nineteenth aspect, it is preferable that the depth of the low crystallinity layer is smaller than the depth of the compressive stress layer.

[0027] 21st aspect of the present invention: The strengthened crystallized glass of the present invention is a strengthened crystallized glass having a compressive stress layer on the surface, characterized in that it comprises a central layer located in the center of the thickness direction and having a mixture of amorphous and crystalline, and a surface layer located on the surface side of the thickness direction and having a lower crystallinity than the central layer.

[0028] 22nd aspect of the present invention: The method for producing strengthened crystallized glass of the present invention is a method for producing strengthened crystallized glass, which comprises immersing a part or all of crystallized glass containing an alkali metal component in an ion exchange mixture to perform ion exchange treatment to obtain strengthened crystallized glass, and further comprises a step of reducing the crystallinity of the surface of the crystallized glass to form a low crystallization layer, characterized in that the crystallization of the low crystallization layer is smaller than the crystallization of a central layer located at the center of the glass thickness direction from the low crystallization layer.

[0029] A 23rd aspect of the present invention: A manufacturing method of strengthened crystallized glass of the present invention is a manufacturing method of strengthened crystallized glass, which obtains strengthened crystallized glass by immersing a part or all of crystallized glass containing an alkali metal component in an ion exchange mixture to perform ion exchange treatment, characterized in that the ion exchange mixture contains a molten salt and an alkali metal silicate as an additive, and the average reflectance of the strengthened crystallized glass in a wavelength range of 360 to 780 nm after the ion exchange treatment is lowered compared to the average reflectance of the crystallized glass in a wavelength range of 360 to 780 nm before the ion exchange treatment.

[0030] According to the present invention, it is possible to obtain strengthened crystallized glass having superior optical properties compared to conventional techniques.

[0031] 1 is a schematic diagram of the cross-sectional structure of the strengthened crystallized glass of the present invention; 2 is a graph showing the reflectance at each wavelength of the glasses of the examples and comparative examples of the present invention; 3 is an enlarged observation image of the vicinity of the surface of the cross-section of the strengthened crystallized glass of the example of the present invention; 4 is an enlarged observation image of the vicinity of the surface of the cross-section of the strengthened crystallized glass of the comparative example of the present invention;

[0032] In the present invention, the glass that does not necessarily contain crystals before crystallization treatment (at least crystals are not intentionally precipitated) is called crystallizable glass.In addition, in the present invention, the glass that contains crystals obtained by subjecting crystallizable glass to crystallization treatment is called crystallized glass.In addition, in the present invention, the glass that is obtained by subjecting crystallized glass to ion exchange treatment is called strengthened crystallized glass.

[0033] The crystallizable glass, crystallized glass, and tempered crystallized glass of the present invention have a composition, in mol %, of SiO ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O 0-15%, ZrO ２It is preferable that the content of each component is 1.5 to 10%. The reasons for limiting the content of each component as described above are as follows. In the description of the content of each component, % indicates mol% unless otherwise specified. In this specification, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0034] SiO ２ is a component that forms a glass network and is also a component that precipitates crystals such as lithium disilicate and lithium metasilicate. ２ The content of SiO is preferably 50 to 80%, 55 to 75%, 60 to 73%, 60 to 70%, particularly preferably 65 to 70%. ２ If the content of SiO is too small, vitrification becomes difficult, the Young's modulus and weather resistance tend to decrease, and lithium disilicate and lithium metasilicate become difficult to precipitate. ２ If the content is too high, the melting property and moldability are likely to decrease, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material, and the transmittance is likely to decrease due to the precipitation of heterogeneous crystals (unintended crystals).

[0035] Al ２ O ３ is a component that adjusts the precipitated crystals and adjusts the compressive stress. ２ O ３ The upper limit range of Al is preferably 12% or less, 10% or less, 8% or less, 6% or less, 4.8% or less, 4.7% or less, 4.5% or less, 4.4% or less, 4.3% or less, 4.2% or less, 4.0% or less, 3.8% or less, 3.5% or less, 3.3% or less, 3.0% or less, 2.8% or less, 2.5% or less, 2.2% or less, 2.1% or less, particularly 2.0% or less. ２ O ３ If the content of Al is too high, the compressive stress value of the strengthened glass-ceramics may decrease. ２ O ３ If the content of Al is too small, the transmittance and resistance to devitrification may be easily reduced. ２ O ３The lower limit range of the content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.7% or more, 1.0% or more, particularly 1.5% or more.

[0036] P ２ O ５ is a component that promotes phase separation of glass and helps the formation of crystal nuclei. ２ O ５ If a large amount of P is introduced, the glass will undergo excessive phase separation and become cloudy. ２ O ５ The upper limit of the content is preferably 15% or less, 10% or less, 8% or less, 5% or less, particularly 3% or less, and the lower limit is preferably 0% or more, 0.2% or more, 0.3% or more, 0.4% or more, particularly 0.5% or more.

[0037] Li ２ O is a component for precipitating crystals of lithium disilicate, lithium metasilicate, etc., and is also a component for enhancing the ion exchange performance. ２ If the O content is too high, the weather resistance is likely to decrease. ２ The upper limit of O is preferably 30% or less, 29% or less, 28% or less, 26% or less, and particularly 25% or less, and the lower limit is preferably 1.5% or more, 2% or more, 3% or more, 4% or more, 4.5% or more, 5% or more, 5.5% or more, 6% or more, 6.3% or more, 6.5% or more, 6.6% or more, 8% or more, 10% or more, 12% or more, 15% or more, 18% or more, 20% or more, 21% or more, 22% or more, 22.5% or more, 23% or more, 23.5% or more, 24% or more, and particularly 24.5% or more.

[0038] Na ２ O is a component that reduces high-temperature viscosity and significantly improves meltability. It is also a component that contributes to the initial melting of glass raw materials. However, Na ２ If the O content is too high, the crystallite size tends to become coarse and the weather resistance tends to decrease. ２The upper limit of O is preferably 15% or less, 12% or less, 10% or less, 9.8% or less, 9.5% or less, 9.3% or less, 9.1% or less, 9% or less, 8.7% or less, particularly 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, less than 2.4%, 2.2% or less, 2% or less, 1.8% or less, 1.5% or less, when focusing on weather resistance, 1% or less, particularly less than 1%. In particular, in the crystallized glass before ion exchange, 5% or less, 4% or less, less than 3.8% is preferred. The lower limit is preferably 0% or more, 0.1% or more, 0.3% or more, 0.5% or more, 0.8% or more, 1% or more, particularly 2% or more.

[0039] ZrO ２ is a component for generating crystal nuclei. ２ If a large amount of ZrO is introduced, the glass is likely to devitrify, and since the introduced raw materials are hardly soluble, there is a risk that unmelted foreign matter will be mixed into the glass. ２ The upper limit range is preferably 10% or less, 9% or less, 8% or less, 7% or less, 6.5% or less, particularly 6% or less, and the lower limit range is preferably 1.5% or more, 1.7% or more, 1.9% or more, 2% or more, 2.1% or more, 2.3% or more, 2.5% or more, 2.7% or more, 3% or more, 3.3% or more, 3.5% or more, particularly 4% or more.

[0040] Molar ratio of Al ２ O ３ / SiO ２ is preferably 0.07 or less, 0.06 or less, 0.05 or less, 0.045 or less, 0.043 or less, 0.04 or less, 0.038 or less, 0.035 or less, 0.033 or less, 0.03 or less, 0.028 or less, particularly 0 to 0.025. ２ O ３ / SiO ２ If the value of "Al" is too large, vitrification may be difficult, or the compressive stress value of the strengthened glass-ceramics may decrease. ２ O ３ / SiO ２ " is Al ２ O ３ The content of SiO ２ The value is divided by the content of

[0041] Molar ratio of Al２ O ３ / Li ２ O is preferably 0.2 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, particularly 0 to 0.065. ２ O ３ / Li ２ If the O content is too large, it may be difficult for crystals such as lithium disilicate and lithium metasilicate to precipitate, or it may be easy for crystals such as petalite to precipitate, and the compressive stress value of the strengthened glass-ceramics may decrease. ２ O ３ / Li ２ "O" is Al ２ O ３ The content of Li ２ This is the value divided by the O content.

[0042] Molar ratio of Al ２ O ３ / (SiO ２ +Li ２ O) is preferably 0.06 or less, 0.055 or less, 0.05 or less, 0.047 or less, 0.045 or less, 0.043 or less, 0.04 or less, 0.038 or less, 0.035 or less, 0.033 or less, particularly 0 to 0.03. ２ O ３ / (SiO ２ +Li ２ If the "Al O" is too large, crystals such as lithium disilicate and lithium metasilicate may be difficult to precipitate, crystals such as petalite may be easily precipitated, and the compressive stress value of the strengthened glass-ceramics may be reduced. ２ O ３ / (SiO ２ +Li ２ O) is Al ２ O ３ The content of SiO ２ and Li ２ This is the value divided by the total amount of O.

[0043] In addition to the above components, other components may be incorporated as optional components.

[0044] K ２O is a component that enhances ion exchange performance, and also reduces high-temperature viscosity and improves melting properties. ２ If the O content is too high, the crystallite size tends to become coarse. ２ The O content is preferably 0 to 7%, 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1.5%, 0 to 1.2%, or 0 to less than 1%, particularly preferably 0 to 0.8%.

[0045] Na ２ O and K ２ The total amount of Na and O ２ O+K ２ The content of O in the crystallizable glass before crystallization is preferably 0 to 8%, 0 to 7%, 0 to 5%, 0 to less than 3.8%, 0 to 3.5%, 0 to 3%, 0 to 2.5%, and particularly preferably 0 to 2%. ２ O+K ２ If the O content is too high, the crystallite size tends to become coarse.

[0046] Molar ratio (Na ２ O+K ２ O) / (Li ２ O + Na ２ O+K ２ O) is preferably less than 1.50, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, 1.00 or less, 0.05 to 0.90, particularly 0.10 to 0.80. ２ O+K ２ O) / (Li ２ O + Na ２ O+K ２ O) is too large, NaNO ３ The ion exchange performance of the molten salt is reduced, and it becomes difficult to form a portion in the strengthened crystallized glass where the Na ion concentration decreases from the surface side to the inside of the glass, i.e., a compressive stress layer based on Na ions. ２ O+K ２ O) / (Li ２ O + Na ２ O+K ２ O) is Na ２ O and K ２ The total amount of O is Li ２ O, Na ２ O and K ２ This is the value divided by the total amount of O.

[0047] B ２ O ３ is a component that improves melting property and devitrification resistance. ２ O ３ If the content of B is too high, the weather resistance is likely to decrease. ２ O ３ The content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 3%, particularly preferably 0 to less than 1%.

[0048] MgO is a component that increases Young's modulus and ion exchange performance, as well as lowering high-temperature viscosity and improving meltability. However, if the MgO content is too high, the glass is prone to devitrification during molding. Therefore, the MgO content is preferably 0 to 10%, 0 to 7%, 0 to 4%, 0 to 2%, 0 to 1%, and particularly preferably 0 to 0.1%.

[0049] CaO is a component that reduces high-temperature viscosity and improves meltability. Furthermore, among alkaline earth metal oxides, CaO is a component that reduces batch costs because the raw material used is relatively inexpensive. However, if the CaO content is too high, the glass is prone to devitrification during molding. Therefore, the CaO content is preferably 0 to 5%, 0 to 3%, 0 to 1%, and particularly 0 to 0.5%.

[0050] SrO is a component that suppresses phase separation and also suppresses coarsening of crystallite size, but if its content is too high, it becomes difficult to precipitate crystals by heat treatment. Therefore, the SrO content is preferably 0 to 5%, 0 to 3%, 0 to 2%, particularly 0 to 1%.

[0051] BaO is a component that suppresses coarsening of crystallite size, but if its content is too high, it becomes difficult to precipitate crystals by heat treatment. Therefore, the BaO content is preferably 0 to 5%, 0 to 3%, 0 to 2%, particularly preferably 0 to 1%.

[0052] ZnO is a component that reduces high-temperature viscosity and significantly improves meltability, as well as suppresses coarsening of crystallite size. However, if the ZnO content is too high, the glass is prone to devitrification during molding. Therefore, the ZnO content is preferably 0 to 5%, 0 to 3%, 0 to 2%, and particularly preferably 0 to 1%.

[0053] TiO ２ is a component for generating crystal nuclei and also a component for improving weather resistance. ２ If a large amount of TiO is introduced, the glass becomes colored and the transmittance tends to decrease. ２ The content is preferably 0 to 5%, 0 to 3%, and particularly preferably 0 to less than 1%.

[0054] SnO ２ is a component that enhances ion exchange performance, but if its content is too high, devitrification resistance is likely to decrease. ２ The content is preferably 0 to 3%, 0.01 to 3%, 0.05 to 3%, 0.1 to 3%, particularly preferably 0.2 to 3%.

[0055] Depending on the high temperature viscosity, effective fining agents can be added. ３ , CeO ２ , Sb ２ O ３ (preferably Cl, SO ３ One or more selected from the group consisting of (a) and (b) may be added in an amount of 0.001 to 1%.

[0056] Fe ２ O ３ The preferred content of Fe is less than 1000 ppm (less than 0.1%), less than 800 ppm, less than 600 ppm, less than 400 ppm, particularly less than 300 ppm. ２ O ３ The content of SnO is limited to the above range, and the molar ratio ２ / (Fe ２ O ３ + SnO ２ ) is preferably 0.8 or more, 0.9 or more, particularly 0.95 or more. In this way, the total light transmittance in the wavelength range of 400 to 770 nm is easily improved.

[0057] Y ２ O ３ is a component that increases the strength of glass. ２ O ３ The raw material itself is expensive, and when added in a large amount, the devitrification resistance is likely to decrease.２ O ３ The content is preferably 0 to 15%, 0 to 12%, 0 to 10%, particularly preferably 0.1 to 1%.

[0058] Gd ２ O ３ , Nb ２ O ５ , La ２ O ３ , Ta ２ O ５ , HfO ２ is a component that increases the strength of glass. ２ O ３ , Nb ２ O ５ , La ２ O ３ , Ta ２ O ５ , HfO ２ The raw material itself is expensive, and when added in a large amount, the devitrification resistance tends to decrease. ２ O ３ , Nb ２ O ５ , La ２ O ３ , Ta ２ O ５ , HfO ２ The total amount and individual contents of are preferably 0 to 15%, 0 to 10%, 0 to 5%, particularly preferably 0 to 3%.

[0059] The strengthened glass-ceramics of the present invention is made of a composition substantially containing As, from an environmental consideration. ２ O ３ It is preferable that the alloy does not contain Bi, PbO, F, etc. ２ O ３ The phrase "substantially free of ..." means that the specified component is not actively added as a glass component, but the addition of an impurity level is permitted, and specifically refers to the case where the content of the specified component is less than 0.05%.

[0060] In the crystallizable glass, crystallized glass, and strengthened crystallized glass of the present invention, it is possible to obtain a suitable composition range by appropriately combining the suitable content ranges of each component, but among these, the following composition ranges (1) to (3) are suitable because they can simultaneously achieve high levels of strength, transmittance, and impact resistance: (1) SiO in mol % ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O+K ２ O 0 to less than 3.8%, Na ２ O 0 to less than 3.8%, K ２ O 0 to less than 3.8%, ZrO ２ (2) SiO in mole percent ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O+K ２ O 0-3.5%, Na ２ O 0-2%, K ２ O 0-1.2%, ZrO ２ (3) SiO in mole percent ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O+K ２ O 0 to less than 3.8%, Na ２ O 0 to less than 3.8%, K ２ O 0 to less than 3.8%, ZrO ２ 1.5 to 10%, and the molar ratio (Na ２ O+K ２ O) / (Li ２ O + Na ２ O+K ２ O) is 1.20 or less.

[0061] The crystallized glass and strengthened crystallized glass of the present invention preferably have the following properties.

[0062] In the crystallized glass and strengthened crystallized glass of the present invention, in order to increase transmittance, it is preferable that any one of lithium disilicate, lithium metasilicate, β-quartz, β-spodumene, trilithium phosphate, and petalite is precipitated, and it is particularly preferable that any one of lithium disilicate, lithium metasilicate, and trilithium phosphate is precipitated. Furthermore, it is preferable that lithium disilicate or lithium metasilicate is precipitated as the main crystal (crystal with the largest amount of precipitation).

[0063] The full width at half maximum (FWHM) at the maximum peak of the X-ray diffraction spectrum is preferably 0.120° or more, 0.121° or more, 0.122° or more, 0.123° or more, 0.125° or more, 0.130° or more, 0.135° or more, 0.140° or more, and particularly preferably 0.150° or more. If the full width at half maximum (FWHM) at the maximum peak of the X-ray diffraction spectrum is too small, the transmittance is likely to decrease.

[0064] Fracture toughness K of glass-ceramics before ion exchange treatment １Ｃ is preferably 0.7 MPa m ０．５ Above, 0.8MPa・m ０．５ Above, 1.0MPa・m ０．５ Above, 1.2MPa・m ０．５ Above 1.5 to 3.5 MPa m ０．５ Fracture toughness K １Ｃ If is too small, the strength is likely to be low. １Ｃ " was measured using the Single-Edge-Precracked-Beam (SEPB) method based on JIS R1607 "Fracture Toughness Testing Method for Fine Ceramics." The SEPB method measures the maximum load until the test piece breaks in a three-point bending test of a precracked test piece, and calculates the plane strain fracture toughness K from the maximum load, precrack length, test piece dimensions, and the distance between bending supports. １Ｃ This is a method to determine the fracture toughness K １Ｃ The measured value is the average value of five measurements.

[0065] The Young's modulus of the crystallized glass before ion exchange treatment is preferably 70 GPa or more, 72 GPa or more, 73 GPa or more, 74 GPa or more, 75 GPa or more, 76 GPa or more, 77 GPa or more, 78 GPa or more, 79 GPa or more, 80 GPa or more, 83 GPa or more, 85 GPa or more, 87 GPa or more, 90 GPa or more, particularly 100 to 150 GPa. If the Young's modulus is low, the crystallized glass will be easily bent when the plate thickness is thin. The "Young's modulus" can be measured by a well-known resonance method.

[0066] The Vickers hardness of the crystallized glass before ion exchange treatment is preferably 500 or more, 550 or more, or 580 or more, particularly 600 to 2500. If the Vickers hardness is too low, the glass is easily scratched. The "Vickers hardness" is a value measured by pressing a Vickers indenter with a Vickers hardness tester under a load of 100 gf.

[0067] The transmittance of the crystallized glass in the thickness direction at a wavelength of 550 nm is preferably 75% or more, 76% or more, 77% or more, 78% or more, 79% or more, 81% or more, 83% or more, 85% or more, 88% or more, particularly 89% or more. In the present invention, the "transmittance" at a predetermined wavelength is measured using a spectrophotometer (V-670 manufactured by JASCO Corporation) at the wavelength in the thickness direction.

[0068] The strengthened glass-ceramics of the present invention preferably has the following properties.

[0069] The average reflectance of the tempered crystallized glass of the present invention in the wavelength range of 360 to 780 nm is 9.5% or less. The average reflectance of the tempered crystallized glass in the wavelength range of 360 to 780 nm is more preferably 9.4% or less, 9.3% or less, 9.2% or less, 9.1% or less, 9.0% or less, 8.9% or less, 8.8% or less, 8.7% or less, 8.6% or less, 8.5% or less, 8.4% or less, 8.3% or less, 8.2% or less, or 8.1% or less. If the average reflectance in this wavelength range, i.e., the reflectance in the visible light wavelength range, is too high, for example, when the tempered crystallized glass is used as a cover glass for a display device, it is likely to reflect external light, reducing the visibility of the display. While the lower limit of the average reflectance in this wavelength range is not particularly specified, from the viewpoint of productivity, it is preferably 3% or more, more preferably 3.5% or more. The average reflectance in the wavelength range of 360 to 780 nm can be determined by measurement and calculation using a spectrophotometer. Alternatively, the average reflectance can be measured and calculated based on JIS R 3106.

[0070] The transmittance of the strengthened crystallized glass in the thickness direction at a wavelength of 550 nm is preferably 75% or more, 76% or more, 77% or more, 78% or more, 79% or more, 81% or more, 83% or more, 85% or more, 88% or more, particularly 89% or more. Although there is no particular upper limit for the transmittance in the thickness direction at a wavelength of 550 nm, from the viewpoint of productivity, etc., it is preferably 99.5% or less, more preferably 99.0% or less.

[0071] The strengthened crystallized glass of the present invention preferably has a portion where the Na ion concentration decreases from the surface side of the glass toward the inside, in other words, a portion where the Na ion concentration increases from the inside side of the glass toward the surface side. This increases the resistance to crack penetration from the glass surface and tends to increase the impact resistance. ３ When an ion exchange treatment is performed using a molten salt to introduce Na ions into glass, the Na ion concentration at the glass surface becomes relatively high, and it becomes possible to form a portion in which the Na ion concentration decreases from the surface side toward the interior of the glass. ３When Na ions in the molten salt are exchanged with Li ions in the glass, the strengthened crystallized glass has a portion where the Li ion concentration increases from the surface side to the interior of the glass, i.e., a portion where the Li ion concentration decreases from the interior side to the surface of the glass, in contrast to the above-mentioned Na ion concentration. The "Na ion concentration" can be confirmed, for example, by measuring the cross section of the sample with SEM-EDX. In this way, strengthened crystallized glass with high transmittance and high impact resistance can be obtained.

[0072] 1 is a schematic diagram of the cross-sectional structure of a strengthened crystallized glass 1 of the present invention. The strengthened crystallized glass 1 has a compressive stress layer 11 formed by ion exchange on the surface and a tensile stress layer 12 at the center of the compressive stress layer 11 in the thickness direction.

[0073] The maximum compressive stress value (CS) of the compressive stress layer 11 is preferably 200 MPa or more, 250 MPa or more, 300 MPa or more, 400 MPa or more, 500 MPa or more, 520 MPa or more, 530 MPa or more, particularly 550 MPa or more. If the compressive stress value is low, resistance to crack penetration is reduced and impact resistance is likely to be reduced. However, if the compressive stress value is too high, the tensile stress value at the center becomes excessive, resulting in a large number of fragments upon breakage, which is dangerous. Therefore, the compressive stress value is preferably 1500 MPa or less, 1400 MPa or less, 1300 MPa or less, or 1200 MPa or less.

[0074] The stress depth (DOC) of the compressive stress layer 11 is preferably 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 85 μm or more, 90 μm or more, 95 μm or more, or 100 μm or more. The stress depth of the compressive stress layer is preferably 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 17.5% or more, 18% or more, 18.5% or more, particularly 19% or more of the plate thickness. If the stress depth is small, resistance to crack penetration will be low and impact resistance will likely be low.

[0075] The maximum tensile stress value of the internal tensile stress layer 12 is preferably 180 MPa or less, 150 PMa or less, 120 MPa or less, particularly 110 MPa or less. If the internal tensile stress value is too high, the tempered crystallized glass is prone to self-destruction due to hard scratches. On the other hand, if the internal tensile stress value is too low, it becomes difficult to ensure the strength of the tempered crystallized glass. The internal tensile stress value is preferably 35 MPa or more, 45 MPa or more, 55 MPa or more, particularly 70 MPa or more. The internal tensile stress value can be measured, for example, using a scattered light photoelastic stress meter SLP-2000 from Orihara Seisakusho.

[0076] The P180 scratch strength is an index of impact resistance and is preferably 250 MPa or more, 270 MPa or more, 290 MPa or more, particularly 300 MPa or more. The upper limit of the P180 scratch strength is not particularly limited, but in reality it is 800 MPa or less. The P180 scratch strength can be measured by the method described below.

[0077] The strengthened crystallized glass of the present invention is preferably in a plate shape, and the plate thickness is preferably 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, particularly 0.9 mm or less. The smaller the plate thickness, the lighter the strengthened crystallized glass can be. On the other hand, if the plate thickness is too thin, it is difficult to obtain the desired strength. Therefore, the plate thickness is preferably 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, particularly 0.7 mm or more.

[0078] 1, the strengthened crystallized glass 1 of the present invention has a low crystallinity layer 21 on the surface and a central layer 22 located on the inner side (center side) of the low crystallinity layer 21 in the thickness direction of the glass. The central layer 22 contains a mixture of amorphous and crystalline materials.

[0079] The low-crystalline layer 21 is a surface layer with a lower degree of crystallization than the central layer 22. By providing the low-crystalline layer 21, the strengthened crystallized glass 1 of the present invention can achieve the effects of reducing reflectivity, improving scratch resistance, improving crack resistance, and improving ion exchangeability. To appropriately achieve these effects, the depth of the low-crystalline layer 21 is preferably 0.02 μm or more. The depth of the low-crystalline layer 21 is more preferably 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.8 μm or more, 1.0 μm or more, 1.5 μm or more, or 2.0 μm or more. However, in order to obtain sufficient strength, the depth of the low crystalline layer 21 is preferably 150 μm or less, 120 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, or 30 μm or less. The depth of the low crystalline layer 21 can be confirmed from a transmission electron microscope (TEM) image or an electron diffraction pattern of a cross section of the strengthened crystallized glass.

[0080] The low crystallinity layer 21 is preferably formed not by subsequent film formation but by modifying the surface of glass of the same quality as the amorphous portion of the central layer 22. As a result, the constituents of the low crystallinity layer 21 preferably have the same constituents as those of the central layer 22. More preferably, the low crystallinity layer 21 has SiO ２ , Al ２ O ３ , Li ２ O, Na ２ O.P. ２ O ５ , ZrO ２ , and the like. The constituent components of the surface layer can be measured by energy dispersive X-ray spectroscopy (EDX) or the like. More specifically, it is preferable that the glass composition of the amorphous portion contained in the low crystallinity layer 21 and the glass composition of the amorphous portion contained in the central layer 22 are substantially the same glass composition. It is also preferable that the crystals contained in the low crystallinity layer 21 and the crystals contained in the central layer 22 are substantially the same type of crystal. With this configuration, the low crystallinity layer 21 can be formed integrally with the central layer 22 by a modification treatment, thereby reducing the risk of delamination compared to when the optical film layer is formed afterwards.

[0081] The low-crystalline layer 21 of the strengthened crystallized glass 1 of the present invention may be a layer containing a mixture of amorphous and crystalline materials. The crystallinity of the low-crystalline layer 21 is preferably 60% or less. More preferably, it is 58% or less, 55% or less, 53% or less, 50% or less, 48% or less, 45% or less, 43% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less. The lower the crystallinity of the low-crystalline layer 21, the easier it is to achieve effects such as reduced reflectance. Furthermore, the crystallinity of the low-crystalline layer 21 of the strengthened crystallized glass 1 of the present invention is preferably 1% or more, 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 30% or more. Allowing the low-crystalline layer 21 to contain a small amount of crystals can improve productivity. The crystallinity of the low-crystalline layer 21 may be 0%. The degree of crystallinity of the low crystalline layer 21 can be measured by in-plane measurement using an X-ray diffraction device.

[0082] The crystallinity of the central layer 22 of the strengthened crystallized glass 1 of the present invention is preferably 3% or more, 5% or more, 10% or more, 13% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. Furthermore, the difference between the crystallinity of the central layer 22 and the crystallinity of the low crystallinity layer 21 of the strengthened crystallized glass of the present invention is preferably 1% or more, 2% or more, 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, 30% or more, 40% or more, or 50% or more. The greater the difference between the crystallinity of the central layer 22 and the crystallinity of the low crystallinity layer 21, the easier it is to obtain effects such as a reduction in reflectance.

[0083] The technical concepts of the low crystallinity layer 21 and the central layer 22 and the technical concepts of the compressive stress layer 11 and the tensile stress layer 12 are independent of each other, and these concepts can coexist in each depth direction region of the strengthened crystallized glass 1. For example, the region indicated by diagonal hatching in FIG. 1 is both the low crystallinity layer 21 and part of the compressive stress layer 11. The region indicated by dotted hatching in FIG. 1 is both the central layer 22 and part of the compressive stress layer 11. The non-hatched region in FIG. 1 is both the central layer 22 and the tensile stress layer 12. Although FIG. 1 illustrates an example in which the depth of the compressive stress layer 11 is greater than the depth of the low crystallinity layer 21, the strengthened crystallized glass of the present invention may also be configured such that the depth of the compressive stress layer 11 is less than the depth of the low crystallinity layer 21. The depth of the compressive stress layer 11 can be changed by adjusting the ion exchange treatment time, etc.

[0084] <Method for manufacturing strengthened crystallized glass> The method for manufacturing strengthened crystallized glass of the present invention will be described. The method for manufacturing strengthened crystallized glass of the present invention includes a step of preparing crystallized glass and a step of chemically strengthening the crystallized glass by ion exchange treatment.

[0085] The method for preparing the crystallized glass may be any method as long as the crystallized glass having the above-mentioned properties is available. When the crystallized glass is produced from glass raw materials, it can be prepared by the following procedure.

[0086] Glass raw materials prepared to have a glass composition within the above-mentioned composition range are fed into a continuous melting furnace, heated and melted at 1200 to 1700°C, and refined. The molten glass is then fed into a forming device, formed into a plate shape, and cooled to obtain crystallizable glass. After forming into a plate shape, known methods can be used to cut the glass into predetermined dimensions.

[0087] As a method for forming molten glass into a sheet shape, any forming method can be used, such as an overflow downdraw method, a float method, a slot downdraw method, a redraw method, a roll-out method, or a press method.

[0088] <Crystallization Treatment> Next, the crystallizable glass is heat-treated to obtain a crystallized glass plate. The heat treatment process preferably includes a phase separation formation process in which phase separation occurs in the glass matrix, a crystal nucleation process in which crystal nuclei are generated, and a crystal growth process in which the generated crystal nuclei are grown. The heat treatment temperature in the phase separation formation process is 400 to 600°C, particularly 480 to 580°C, and the heat treatment time is 10 minutes to 24 hours, particularly 30 minutes to 12 hours. The heat treatment temperature in the crystal nucleation process is 500 to 700°C, particularly 520 to 650°C, and the heat treatment time is 10 minutes to 24 hours, particularly 30 minutes to 12 hours. By appropriately adjusting the temperature, the phase separation formation process and the crystal nucleation process may be performed simultaneously. The heat treatment temperature in the crystal growth process is preferably 690 to 920°C, particularly 700 to 830°C, and the heat treatment time is 10 minutes to 5 hours, particularly 30 minutes to 3 hours. The temperature rise rate is preferably 1° C. / min to 30° C. / min, particularly preferably 1° C. / min to 10° C. / min. If the heat treatment temperature, heat treatment time, and temperature rise rate are outside the above ranges, the crystallite size may become coarse and the degree of crystallinity may decrease.

[0089] <Ion exchange treatment> The crystallized glass plate prepared as described above is subjected to ion exchange treatment to obtain tempered crystallized glass having a compressive stress layer on the surface due to ion exchange. By performing ion exchange treatment, a compressive stress layer is formed on the surface, thereby increasing the strength.

[0090] In the present invention, an ion exchange treatment is carried out using a mixture for ion exchange. The mixture for ion exchange is a treatment agent that comes into contact with the crystallized glass to perform ion exchange with components in the crystallized glass. The mixture for ion exchange contains a molten salt and an additive.

[0091] The molten salt is a salt containing a component that can be ion-exchanged with the component in the crystallized glass, and is typically an alkali nitrate. The alkali nitrate includes at least NaNO ３ Other examples of alkali nitrates include KNO ３ , LiNO ３ These are NaNO ３ The molten salt can be used by mixing it with NaNO. ３50-100%, KNO ３ +LiNO ３ It is preferable that the content is 0 to 50%. ３ (100%) is used as an example.

[0092] The additive is silicic acid or silicate, typically an alkali metal silicate. By using silicic acid or silicate, particularly an alkali metal silicate, it is possible to suppress the reflectance of the strengthened crystallized glass before and after ion exchange. In this embodiment, the additive is preferably sodium silicate. Specifically, the alkali metal silicate is Na ２ SiO ３ , Na ４ SiO ４ , Na ２ Si ２ O ５ , and Na ２ Si ４ O ９ It is preferable that the sodium silicate contains at least one selected from the following: The sodium silicate is preferably an anhydrous form, but may also be a hydrate.

[0093] The silicic acid or silicate used as an additive is preferably a crystalline substance. Furthermore, the silicic acid or silicate is preferably a powdered crystalline silicic acid or silicate. The silicic acid or silicate crystalline substance is preferably in a powdered form when added to the molten salt, but may also be powdered by being crushed in the molten salt after addition to the molten salt. The average particle size D50 of the powder is preferably 10 to 1,000 μm. To improve ion exchangeability with alkali metal components eluted from the ion-exchange glass, the average particle size D50 of the powder is more preferably 900 μm or less, 800 μm or less, 700 μm or less, 500 μm or less, or 450 μm or less. To prevent dust before addition, the average particle size D50 of the powder is more preferably 20 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, 200 μm or more, or 250 μm or more.

[0094] The amount of additive added to the molten salt, i.e., the amount of silicic acid or silicate, is preferably measured and added so that the amount of silicic acid or silicate is 0.1 to 30 parts by mass, based on 100 parts by mass of the molten salt. The amount of silicic acid or silicate added is more preferably 1 to 30 parts by mass, 2 to 25 parts by mass, 3 to 20 parts by mass, or 4 to 15 parts by mass. If the amount of additive added is too small, the reflectance suppression effect and sufficient ion adjustment effect cannot be obtained, and if the amount added is too excessive, there is a concern that the cost of the additive will increase.

[0095] The additive is preferably an alkali metal silicate. The alkali metal silicate as the additive is preferably a metal salt containing an alkali metal component that is ion-exchangeable with the alkali metal component eluted from the crystallized glass into the molten salt during the ion exchange process, and containing a monovalent metal component different from the eluted ion. In particular, it is preferable to use an alkali metal silicate containing an alkali metal component with an ionic radius larger than that of the alkali metal component eluted from the crystallized glass into the molten salt. This configuration can suppress deterioration of the molten salt. For example, if the alkali metal component eluted into the molten salt is Li ions, using sodium silicate as the additive can ion-exchange the Li ions eluted into the molten salt with Na ions contained in the alkali metal silicate, thereby suppressing an increase in the concentration of Li ions in the molten salt.

[0096] The conditions for the ion exchange treatment, such as the temperature of the molten salt and the immersion time, may be determined arbitrarily, but the temperature of the molten salt is, for example, 350° C. to 500° C., preferably 360° C. to 480° C., 370° C. to 450° C., or 380° C. to 440° C. The immersion time is, for example, 0.1 to 30 hours, preferably 0.2 to 20 hours, 0.3 to 15 hours, 0.5 to 10 hours, 1 to 9 hours, 2 to 9 hours, and particularly 3.5 to 8 hours.

[0097] Strengthened crystallized glass is obtained by immersing part or all of the crystallized glass in the above-mentioned ion exchange mixture and performing an ion exchange treatment. This treatment amorphousizes part of the surface layer of the crystallized glass before the ion exchange treatment, creating a low-crystallinity layer 21, which reduces the refractive index and thereby reduces the average reflectance of the strengthened crystallized glass after the ion exchange treatment in the wavelength range of 360 to 780 nm. Furthermore, improved surface plasticity improves scratch resistance and crack resistance, and reduced density improves ion exchange performance.

[0098] When performing ion exchange treatment, for example, a plurality of crystallized glass sheets are held in a jig as one lot and immersed in molten salt. When the ion exchange treatment of one lot is completed, the next lot of crystallized glass is subjected to ion exchange treatment, and the ion exchange treatment is repeated until the ion exchange of a predetermined number of lots is completed. During this lot cycle, the optical properties (reflectance and transmittance) and stress properties (surface compressive stress, compressive stress depth) of the strengthened crystallized glass are measured, and if the properties are outside the desired range, an alkali metal silicate can be added as an additive to the molten salt.

[0099] It is preferable to stir the molten salt after adding the additive to the molten salt. Stirring can be performed manually using a stick, paddle, or the like, or automatically by a machine. After stirring, the ion exchange treatment of the next lot may be performed in a state in which the additive is dispersed in the molten salt, or the process may wait until the additive precipitates at the inner bottom of the tank containing the molten salt.

[0100] In the present invention, by performing ion exchange treatment using an ion exchange mixture containing silicic acid or silicate as an additive as described above, amorphization progresses from the surface, forming a surface layer with a lower crystallinity than the central layer, thereby obtaining tempered crystallized glass with an appropriately suppressed reflectance.

[0101] The present invention will be described below based on examples. Note that the following examples are merely illustrative and the present invention is not limited to the following examples in any way.

[0102] In Table 1, Samples Nos. 1, 4, 7, 10, and 11 are examples, and Samples Nos. 2, 3, 5, 6, 8, 9, 12, 13, 14, and 15 are comparative examples.

[0103]

[0104]

[0105]

[0106] First, glass raw materials were prepared to obtain the glass compositions shown in Tables 1 to 3, and melted in a platinum pot at 1500°C for 8 hours. The resulting molten glass was then poured onto a carbon plate and formed into a flat plate to obtain a glass plate. The surface of the obtained glass plate was optically polished to a plate thickness of 1000 μm (1.0 mm) or 600 μm (0.6 mm).

[0107] Next, the obtained glass samples Nos. 1 to 13 were heat-treated in an electric furnace under the heat-treatment conditions shown in Tables 1 to 3 to precipitate and grow crystals in the glass matrix. They were then cooled to room temperature to obtain crystallized glass plates. The amorphous glass plates (samples Nos. 14 and 15) were not subjected to any particular heat treatment. The obtained glass plates were evaluated for the following properties.

[0108] The primary crystals were evaluated by powder X-ray diffraction using an X-ray diffractometer (Aeris manufactured by Malvern Panalytical). The measurement range was 2θ = 10 to 60°. The crystallinity of the central layer was calculated from the ratio of the area excluding the background to the area excluding the amorphous portion (halo peak) from the obtained X-ray diffraction spectrum. The full width at half maximum (FWHM) was derived by peak fitting at the peak with the maximum intensity, excluding the background and the amorphous portion (halo peak).

[0109] Next, samples Nos. 1, 2, 4, 5, 7, 8, 10, 11, 12, 14, and 15 were subjected to ion exchange treatment under the conditions shown in Tables 1 to 3 to form a compressive stress layer on the surface, thereby obtaining strengthened crystallized glass (Nos. 1, 2, 4, 5, 7, 8, 10, 11, and 12) and strengthened amorphous glass (Nos. 14 and 15). Samples Nos. 1, 4, 7, 10, 11, and 14 were subjected to ion exchange treatment using an ion exchange mixture containing silicic acid or an alkali metal silicate as an additive. Samples Nos. 2, 5, 8, 12, and 15 were subjected to ion exchange treatment using a molten salt containing no additive. The amounts of additives shown in Tables 1 to 3 are expressed in parts by mass as the amount of alkali metal silicate added per 100 parts by mass of molten salt.

[0110] The surface compressive stress value and compressive stress depth were measured using a scattered light photoelastic stress meter SLP-2000 manufactured by Orihara Manufacturing Co., Ltd. For the measurement, the photoelastic constant of Nos. 1, 2, 4, 5, 7, 8, 10, 11, and 12 was 27.0, the refractive index was 1.55, and the photoelastic constant of Nos. 14 and 15 was 30.5, and the refractive index was 1.51.

[0111] The 550 nm transmittance indicates a value obtained by measuring the transmittance at a wavelength of 550 nm in the thickness direction of the glass using a spectrophotometer (V-670 manufactured by JASCO Corporation).

[0112] The reflectance was measured and calculated as the average reflectance at wavelengths from 360 to 780 nm. The reflectance at each wavelength was measured using a spectrophotometer (using an integrating sphere, manufactured by JASCO Corporation, Model V-670). Figure 2 shows the measurement results of the reflectance at each wavelength for Samples No. 1 to 3. In Figure 2, the horizontal axis represents wavelength, and the vertical axis represents reflectance at each wavelength.

[0113] The crystallinity of the low-crystalline layer was evaluated by in-plane measurement using a parallel beam method using an X-ray diffractometer (SmarLab manufactured by Rigaku). The X-ray incident angle was θ = 0.5°, and the measurement range was 2θ = 5 to 60°. From the obtained X-ray diffraction spectrum, the crystallinity of the low-crystalline layer was calculated from the ratio of the area excluding the background to the area excluding the amorphous portion (halo peak).

[0114] As is clear from Tables 1 and 3, Sample No. 1, an example, is a strengthened glass-ceramic, and therefore has a higher fracture toughness value and superior impact resistance than Comparative Samples Nos. 14 and 15. In addition, Sample No. 1 uses an ion exchange mixture containing sodium metasilicate as an additive in the ion exchange treatment, and thus exhibits a more favorable suppression of reflectance than Comparative Samples Nos. 2 and 3. Note that Sample No. 1, an example, corresponds to the strengthened glass-ceramic of Comparative Sample No. 3 after ion exchange treatment, and its average reflectance in the wavelength range of 360 to 780 nm is lower than that before ion exchange treatment.

[0115] The tempered glass-ceramics of Samples 10 and 12 were sliced ​​by the focused ion beam method and observed using a transmission electron microscope (TEM). Figure 3 shows a TEM image of Sample No. 10 (Example), and Figure 4 shows a TEM image of Sample No. 12 (Comparative Example). Sample No. 12, the comparative example, was composed of relatively homogeneous, highly crystallized glass-ceramics filled with black dots from the glass surface 1a to the interior of the glass. On the other hand, Sample No. 10, the Example, had few black dots from the glass surface 1a to a depth of about 2 μm (the dotted line in Figure 3), revealing the presence of a low-crystallinity layer 21 on the glass surface. The image of Sample No. 10 shown in Figure 3 reveals that the central layer 22, deeper than 2 μm from the surface, contained many black dots and had a relatively higher crystallinity than the low-crystallinity layer 21 on the surface.

[0116] In sample No. 10, by using the ion exchange mixture containing sodium metasilicate as an additive in the ion exchange process, this low crystallinity layer is formed on the surface, the refractive index of the surface is reduced, and the reflectance is suitably suppressed.The principle of the formation of this low crystallinity layer is not clear, but when the same sample is measured by energy dispersive X-ray spectroscopy (EDX), ions such as Si, Al, P, Zr, Na are detected, so it is estimated that the crystalline part of the crystallized glass is changed to amorphous by the ion exchange process.

[0117] REFERENCE SIGNS LIST 1 Tempered crystallized glass 11 Compressive stress layer 12 Tensile stress layer 21 Low crystallinity layer 22 Center layer

Claims

1. A method for producing strengthened crystallized glass, comprising immersing a part or all of a crystallized glass containing an alkali metal component in an ion exchange mixture to obtain strengthened crystallized glass, the ion exchange mixture containing a molten salt and silicic acid or a silicate as an additive, and wherein the average reflectance of the strengthened crystallized glass at wavelengths of 360 to 780 nm after the ion exchange treatment is lower than the average reflectance of the strengthened crystallized glass at wavelengths of 360 to 780 nm before the ion exchange treatment.

2. The molten salt is NaNO ３ The additive is an alkali metal silicate, and the alkali metal silicate is Na ２ SiO ３ , Na ４ SiO ４ , Na ２ S ２ O ５ , and Na ２ S ４ O ９ The method for producing strengthened crystallized glass according to claim 1, wherein the glass contains at least one selected from the group consisting of:

3. The molten salt has a composition, in mass%, of NaNO ３ 50-100%, KNO ３ +LiNO ３ 3. The method for producing strengthened crystallized glass according to claim 2, wherein the ion exchange treatment reduces an average reflectance in the wavelength range of 360 to 780 nm and forms a compressive stress layer in the crystallized glass.

4. The method for producing strengthened crystallized glass according to claim 1 or 2, wherein the amount of said additive is 0.1 to 30 parts by mass per 100 parts by mass of said molten salt.

5. The crystallized glass has a composition, in mol%, of SiO ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O 0-15%, ZrO ２ The method for producing strengthened crystallized glass according to claim 1 or 2, wherein the content is 1.5 to 10%.

6. The method for producing strengthened crystallized glass according to claim 1 or 2, wherein at least one of lithium disilicate and lithium metasilicate is precipitated.

7. A method for producing strengthened crystallized glass according to claim 1 or 2, further comprising a step of reducing the crystallization degree of the surface of the crystallized glass to form a low crystallization layer, the crystallization degree of the low crystallization layer being smaller than the crystallization degree of a central layer located in the center of the thickness direction of the glass from the low crystallization layer.

8. The method for producing strengthened crystallized glass according to claim 7, wherein in the ion exchange treatment, a compressive stress layer is formed in the crystallized glass while the low crystallization layer is formed.

9. Reinforced crystallized glass having a compressive stress layer on its surface, the average reflectance of which in the wavelength range of 360 to 780 nm is 9.5% or less.

10. The strengthened crystallized glass according to claim 9, which has an average reflectance of 8.5% or less in the wavelength range of 360 to 780 nm.

11. The strengthened crystallized glass according to claim 9 or 10, in which at least one of lithium disilicate and lithium metasilicate is precipitated.

12. Composition, in mole percent, is SiO ２ 50-80%, Al ２ O ３ 0-12%, P ２ O ５ 0-15%, Li ２ O 1.5-30%, Na ２ O 0-15%, ZrO ２ The strengthened crystallized glass according to claim 9 or 10, containing 1.5 to 10%.

13. Composition: SiO ２ 50-80%, Al ２ O ３ 0-4.8%, P ２ O ５ 0.2-15%, Li ２ O 1.5-30%, Na ２ O+K ２ O 0 to less than 3.8%, Na ２ O 0-10, K ２ O 0 to less than 3.8%, ZrO ２ The strengthened crystallized glass according to claim 12, containing 1.5 to 10%.

14. The strengthened crystallized glass according to claim 9 or 10, wherein the plate thickness is 1.5 mm or less, and the compressive stress value of the compressive stress layer is 400 MPa or more.

15. The strengthened crystallized glass according to claim 9 or 10, comprising: a central layer located in the center in the thickness direction and having a mixture of amorphous and crystalline materials; and a low-crystallinity layer located on the surface side in the thickness direction and having a lower degree of crystallinity than the central layer.

16. The strengthened crystallized glass according to claim 15, wherein the difference between the crystallinity of the central layer and the crystallinity of the low crystallinity layer is 10% or more.

17. The strengthened crystallized glass according to claim 15, characterized in that the low crystallinity layer contains components of the central layer.

18. The strengthened crystallized glass according to claim 15, characterized in that the depth of the low crystallinity layer is 0.02 μm or more.

19. The strengthened crystallized glass according to claim 18, wherein the depth of the low crystallinity layer is smaller than the depth of the compressive stress layer.

20. Reinforced crystallized glass having a compressive stress layer on its surface, comprising: a central layer located in the center in the thickness direction and consisting of a mixture of amorphous and crystalline materials; and a surface layer located on the surface side in the thickness direction and having a lower degree of crystallinity than the central layer.

21. A method for producing reinforced crystallized glass, comprising immersing a part or all of crystallized glass containing an alkali metal component in an ion exchange mixture to perform ion exchange treatment to obtain reinforced crystallized glass, the method further comprising a step of reducing the crystallinity of the surface of the crystallized glass to form a low crystallinity layer, the crystallinity of the low crystallinity layer being lower than the crystallinity of a central layer located more centrally in the thickness direction of the glass than the low crystallinity layer.

22. A method for producing reinforced crystallized glass, comprising immersing a part or all of crystallized glass containing an alkali metal component in an ion exchange mixture to obtain reinforced crystallized glass, the ion exchange mixture containing a molten salt and an alkali metal silicate as an additive, and reducing the average reflectance of the reinforced crystallized glass at wavelengths of 360 to 780 nm after the ion exchange treatment to be lower than the average reflectance of the crystallized glass at wavelengths of 360 to 780 nm before the ion exchange treatment.