Glass-ceramics

Abstract

Provided is a crystallized glass which has a high Vickers Hardness value and excellent transparency. This crystallized glass is characterized by containing, in % by mass, 58 to 70% of SiO2, 15 to 30% of Al2O3, 2 to 10% of Li2O, 0 to 10% of Na2O, 0 to 10% of K2O, 0 to 15% of Na2O+K2O, 0 to 15% of MgO+CaO+SrO+BaO+ZnO, 0.1 to 6% of SnO2, 0.5 to 6% of ZrO2, 0 to 4% of TiO2 and 0 to 6% of P2O5, having a crystallization degree of 1 to 95%, a thickness of 0.8 mm, and a visible light average transmittance of 50% or more at a wavelength of 380 to 780 nm, and having a compression stress layer formed on the surface thereof.

Description

[Technical Field]

[0001] The present invention relates to glass-ceramics. [Background technology]

[0002] Mobile phones, digital cameras, PDAs (personal digital assistants), etc. are becoming increasingly popular, and for these applications, cover glass is used to protect the touch panel display (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-083045 Summary of the Invention [Problem to be solved by the invention]

[0004] Cover glass, especially that of smartphones, is often used outdoors, where high-intensity, parallel light makes surface scratches easily noticeable, reducing the visibility of the display. Therefore, improving the scratch resistance of glass is important. Increasing the Vickers hardness is considered an effective way to improve scratch resistance. Increasing the Vickers hardness not only makes the surface less susceptible to scratches, but also reduces the width and depth of hard scratches that do occur.

[0005] Glass ceramics, in which crystals are precipitated in glass, is known as glass having a high Vickers hardness value.

[0006] However, crystallized glass is currently not as transparent as amorphous glass and is therefore not suitable for use as a cover glass.

[0007] An object of the present invention is to provide crystallized glass having a high Vickers hardness value and excellent transparency. [Means for solving the problem]

[0008] The crystallized glass of the present invention contains, by mass%, 58-70% SiO2, 15-30% Al2O3, 2-10% Li2O, 0-10% Na2O, 0-10% K2O, 0-15% Na2O+K2O, 0-15% MgO+CaO+SrO+BaO+ZnO, 0.1-6% SnO2, 0.5-6% ZrO2, 0-4% TiO2, and 50-6% P2O, and is characterized by a degree of crystallization of 1-95%, a thickness of 0.8 mm, an average transmittance of visible light at a wavelength of 380-780 nm of 50% or more, and a compressive stress layer formed on the surface. Here, "Na2O+K2O" means the total amount of Na2O and K2O, and "MgO+CaO+SrO+BaO+ZnO" means the total amount of MgO, CaO, SrO, BaO, and ZnO.

[0009] By subjecting the crystallized glass of the present invention having the above composition to ion exchange treatment, it is possible to form a compressive stress layer on the surface of the crystallized glass, and the Vickers hardness value is likely to be increased.

[0010] The crystallized glass of the present invention preferably contains substantially no As2O3 or PbO.

[0011] The crystallized glass of the present invention preferably contains precipitated crystals of one or more types selected from β-eucryptite solid solution, β-spodumene solid solution, and zirconia.

[0012] The crystallized glass of the present invention preferably has an average crystallite size of 1 μm or less.

[0013] The crystallized glass of the present invention preferably has a Vickers hardness value of at least 540. Here, "Vickers hardness" refers to a value measured in accordance with JIS Z2244-1992 by pressing a Vickers indenter with a Vickers hardness tester under a load of 100 gf, and is the average value of 10 measurements.

[0014] The crystallized glass of the present invention preferably has a bending strength of 100 MPa or more and a drop height of 5 mm or more. Here, the "drop height" refers to the maximum height at which the glass maintains its original shape without breaking when a 50 mm x 50 mm glass plate is placed on a granite surface plate and a 53 g weight with a Vickers indenter attached to the tip is dropped vertically onto the glass from a specific height.

[0015] The crystallized glass of the present invention has a thermal expansion coefficient of 0 to 120×10 at 30 to 380°C. -7 / °C is preferred.

[0016] The crystallized glass of the present invention preferably has a Young's modulus of 80 GPa or more. Here, "Young's modulus" is a value measured by the well-known resonance method.

[0017] The method for producing crystallized glass of the present invention is characterized by comprising the steps of: preparing crystallized glass containing, by mass%, 58-70% SiO2, 15-30% Al2O3, 2-10% Li2O, 0-10% Na2O, 0-10% K2O, 0-15% Na2O+K2O, 0-15% MgO+CaO+SrO+BaO+ZnO, 0.1-6% SnO2, 0.5-6% ZrO2, 0-4% TiO2, and 50-6% P2O, and having a crystallinity of 1-95%; and immersing the crystallized glass in a molten salt at 400°C or higher to obtain crystallized glass having a compressive stress layer on its surface.

[0018] The method for producing crystallized glass of the present invention is characterized by comprising the steps of: preparing crystallized glass containing, by mass%, 58-70% SiO2, 15-30% Al2O3, 2-10% Li2O, 0-10% Na2O, 0-10% K2O, 0-15% Na2O+K2O, 0-15% MgO+CaO+SrO+BaO+ZnO, 0.1-6% SnO2, 0.5-6% ZrO2, 0-4% TiO2, and 50-6% P2O, and having a crystallinity of 40-95%; and immersing the crystallized glass in molten salt at 500-1000°C to obtain crystallized glass having a compressive stress layer on its surface.

[0019] The crystallized glass of the present invention is characterized in that zirconia crystals are precipitated, the glass has a thickness of 0.8 mm, and has an average visible light transmittance of 50% or more in the wavelength range of 380 to 780 nm.

[0020] The crystallized glass of the present invention preferably has a compressive stress layer formed on the surface thereof.

[0021] The crystallized glass of the present invention preferably has a crystallinity of less than 40%.

[0022] The crystallized glass of the present invention preferably contains, in mass %, 58-70% SiO2, 15-30% Al2O3, 2-10% Li2O, 0-10% Na2O, 0-10% K2O, 0-15% Na2O+K2O, 0-15% MgO+CaO+SrO+BaO+ZnO, 0.1-6% SnO2, 0.5-6% ZrO2, 0-4% TiO2, and 50-6% P2O. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide crystallized glass having a high Vickers hardness value and excellent transparency. DETAILED DESCRIPTION OF THE INVENTION

[0024] The crystallized glass of the present invention contains, by mass%, 58-70% SiO2, 15-30% Al2O3, 2-10% Li2O, 0-10% Na2O, 0-10% K2O, 0-15% Na2O+K2O, 0-15% MgO+CaO+SrO+BaO+ZnO, 0.1-6% SnO2, 0.5-6% ZrO2, 0-4% TiO2, and 50-6% P2O, has a crystallinity of 1-95%, a thickness of 0.8 mm, an average visible light transmittance of 50% or more at a wavelength of 380-780 nm, and has compressive stress formed on the surface.

[0025] First, the reason for limiting the composition of the crystallized glass as described above will be explained. In the following explanation, "%" means "mass %" unless otherwise specified.

[0026] SiO2 is a component that forms the skeleton of glass. The SiO2 content is 58 to 70%, preferably 60 to 68%, and particularly preferably 64 to 66%. If the SiO2 content is too low, weather resistance tends to deteriorate significantly. On the other hand, if the SiO2 content is too high, the meltability of the glass tends to deteriorate.

[0027] Al2O3 is a component that enhances ion exchange performance. The Al2O3 content is 15 to 30%, preferably 17 to 27%, and particularly preferably 20 to 25%. If the Al2O3 content is too low, coarse crystals are likely to precipitate. Also, crystallization becomes difficult. On the other hand, if the Al2O3 content is too high, the meltability of the glass is likely to deteriorate.

[0028] Li2O is a component that improves the meltability of glass and is also a component that participates in ion exchange treatment. The Li2O content is 2 to 10%, preferably 3 to 8%, and particularly preferably 4 to 6%. If the Li2O content is too low, ion exchange becomes difficult. On the other hand, if the Li2O content is too high, the liquidus temperature tends to rise and the crystallite size tends to become too large.

[0029] Na2O and K2O are components that improve the meltability of glass. The Na2O + K2O content is 0 to 15%, and preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 3%, 0 to 2%, and particularly preferably 0 to 1%. If the Na2O + K2O content is too high, the transmittance of the crystallized glass is likely to decrease. The Na2O content is 0 to 10%, and preferably 0 to 7%, 0 to 5%, 0 to 3%, 0 to 2%, and particularly preferably 0 to 1%, and the K2O content is 0 to 10%, and preferably 0 to 7%, 0 to 5%, 0 to 3%, 0 to 2%, and particularly preferably 0 to 1%.

[0030] MgO, CaO, SrO, BaO, and ZnO are components that improve the meltability of glass. The content of MgO+CaO+SrO+BaO+ZnO is 0 to 15%, preferably 0 to 13%, 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%. If the content of MgO+CaO+SrO+BaO+ZnO is too high, coarse crystals are likely to precipitate. The MgO content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%; the CaO content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%; the SrO content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%; the BaO content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%; and the ZnO content is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0 to 4%, and particularly preferably 0 to 3%.

[0031] SnO2 is a component that acts as a fining agent. It is also a component necessary for efficient crystal precipitation during the crystallization process. However, if contained in large amounts, it significantly intensifies the coloring of the glass. The SnO2 content is 0.1 to 6%, preferably 1 to 5%, and particularly 1.5 to 4%. If the SnO2 content is too low, it becomes difficult to refine the glass, which tends to reduce productivity. Furthermore, crystal nuclei may not be sufficiently formed, resulting in the precipitation of coarse crystals, which may cause the glass to become cloudy or break. On the other hand, if the SnO2 content is too high, the coloring of the crystallized glass may become strong. Furthermore, the amount of SnO2 evaporation during production increases, which tends to increase the environmental impact.

[0032] ZrO2 is a nucleation component for precipitating crystals in the crystallization process. The ZrO2 content is 0.5 to 6%, preferably 1 to 4%, and particularly preferably 1.5 to 3%. If the ZrO2 content is too low, crystal nuclei are not sufficiently formed, and coarse crystals may precipitate, causing the crystallized glass to become cloudy or break. On the other hand, if the ZrO2 content is too high, coarse ZrO2 crystals may precipitate, making the glass more susceptible to devitrification and breakage.

[0033] The SnO2+ZrO2 content is preferably 1.5 to 12%, 2 to 9%, and particularly preferably 3 to 7%. If the SnO2+ZrO2 content is too low, crystal nuclei are less likely to precipitate, making crystallization more difficult. On the other hand, if the SnO2+ZrO2 content is too high, the crystal nuclei become larger, making the crystallized glass more likely to become cloudy.

[0034] SnO2 has the effect of promoting phase separation of ZrO2. To efficiently cause phase separation while keeping the liquidus temperature low (reducing the risk of devitrification due to primary phase precipitation) and to rapidly carry out nucleation and crystal growth in the subsequent steps, the mass ratio of SnO2 / (SnO2+ZrO2) is preferably 0.3 to 0.7, 0.35 to 0.65, and particularly preferably 0.4 to 0.6.

[0035] TiO2 is a nucleation component for crystallization during the crystallization process. However, excessive TiO2 content significantly intensifies the coloration of glass. Zirconia titanate crystals, particularly those containing ZrO2 and TiO2, act as crystal nuclei, but electrons undergo a LMCT transition from the valence band of the oxygen ligand to the conduction band of the central metals, zirconia and titanium, resulting in the coloration of the crystallized glass. Furthermore, if titanium remains in the residual glass phase, an LMCT transition can occur from the valence band of the SiO2 skeleton to the conduction band of the tetravalent titanium in the residual glass phase. Furthermore, trivalent titanium in the residual glass phase undergoes a dd transition, contributing to the coloration of the crystallized glass. Furthermore, the coexistence of titanium and iron results in an ilmenite (FeTiO3)-like coloration. Furthermore, the coexistence of titanium and tin is known to intensify the yellow color. For this reason, the TiO2 content is generally 0-4%, preferably 0-3%, 0-2%, or 0-1%, with 0-0.1% being particularly preferred. However, because TiO2 is easily mixed in as an impurity, attempting to completely remove TiO2 tends to increase the cost of the raw material batch and the manufacturing cost. In order to suppress the increase in manufacturing cost, the lower limit of the TiO2 content is preferably 0.0003% or more, 0.001% or more, 0.01% or more, and particularly preferably 0.02% or more.

[0036] P2O5 is a component that suppresses the precipitation of coarse ZrO2 crystals. The P2O5 content is 0 to 6%, preferably 0 to 5%, 0.1 to 5%, 0.5 to 4%, and particularly preferably 1 to 3%. If the P2O5 content is too high, the thermal expansion coefficient tends to be high.

[0037] The crystallized glass of the present invention may contain the following components in addition to the above components in its glass composition.

[0038] B2O3 is a component that reduces the viscosity of glass and improves the meltability and formability of glass. It is also a component that can affect the likelihood of phase separation during crystal nucleation. The B2O3 content is preferably 0 to 3%, 0 to 2%, 0 to 1%, and particularly preferably 0 to 0.1%. If the B2O3 content is too high, the amount of B2O3 evaporated during melting increases, increasing the environmental impact.

[0039] CeO2 not only improves solubility but also acts as an oxidizing agent, reducing the Fe content of the total Fe impurity. 2+ It is a component that suppresses the increase in CeO2 and improves the transparency of the glass-ceramic. The CeO2 content is preferably 0 to 0.5%, 0 to 0.5%, and particularly preferably 0 to 0.3%. If the CeO2 content is too high, Ce 4+ The coloring due to the addition of the fluorine-containing compound may become too strong, causing the crystallized glass to turn brown.

[0040] SO3 can be introduced from Glauber's salt. SO3 is a component that improves the melting point of raw glass. It also acts as an oxidizing agent like CeO2, and its effect becomes more pronounced when it coexists with CeO2. The SO3 content is preferably 0-0.5%, 0.02-0.5%, and particularly 0.05-0.3%. If the SO3 content is too high, foreign crystals may precipitate, deteriorating the surface quality of the crystallized glass.

[0041] Since As2O3 and PbO are harmful, it is preferable that they are substantially not contained. Here, "substantially not contained" means that these components are not intentionally added to the glass, but does not mean that unavoidable impurities are completely excluded. More objectively, it means that the content of these components, including impurities, is 1000 ppm or less.

[0042] The crystallized glass of the present invention preferably contains one or more crystals selected from β-eucryptite solid solution, β-spodumene solid solution, and zirconia. Precipitating any one crystal selected from β-eucryptite solid solution, β-spodumene solid solution, and zirconia increases the Vickers hardness and chemical durability of the crystallized glass. Note that the present invention does not exclude the precipitation of crystals other than β-eucryptite solid solution, β-spodumene solid solution, and zirconia. Furthermore, although β-eucryptite solid solution, β-spodumene solid solution, and zirconia are preferably the main crystals, they are not necessarily required to be the main crystals.

[0043] Furthermore, in the crystallized glass of the present invention, particularly when the degree of crystallization is low, less than 40%, it is preferable that zirconia is precipitated, and it is particularly preferable that zirconia is the main crystal. When zirconia is the main crystal, there is an advantage that a large amount of glass phase remains due to its small crystal grain size, making ion exchange more likely to occur. Ion exchange becomes more likely to occur, and by introducing strong surface stress, mechanical properties such as Vickers hardness and strength can be easily improved. In addition, since a large amount of glass phase remains, it is easier to create a smooth surface, which has the advantage of mainly increasing bending strength.

[0044] The crystallized glass of the present invention has a crystallinity of 1 to 95%, preferably 1 to 50%, 2 to 40%, 3 to 35%, 4 to 30%, and particularly preferably 5 to 20%. If the crystallinity is too low, the Vickers hardness and Young's modulus tend to decrease. On the other hand, if the crystallinity is too high, the transmittance tends to decrease. In addition, when ion-exchanging, the proportion of the glass phase that is the target of the ion-exchanging treatment is small, so it is difficult to form a high compressive stress layer by the ion-exchanging treatment unless special conditions as described below are adopted.

[0045] On the other hand, for crystallized glass with a high degree of crystallization, a high compressive stress layer can be formed by using a molten salt with a high boiling point, such as a sulfate, carbonate, or chloride salt, and performing ion exchange at 500° C. or higher. If a high compressive stress layer can be formed in this way, the crystallization degree is preferably 40% or higher, 50% or higher, 60% or higher, 70% or higher, 75% or higher, 78% or higher, 80% or higher, 81% or higher, 83% or higher, 85% or higher, 87% or higher, 90% or higher, 92% or higher, and particularly preferably 93% or higher, which makes it easy to achieve both a high compressive stress layer and a high Young's modulus.

[0046] The crystallite size of the crystallized glass of the present invention is preferably 1 μm or less, 0.5 μm or less, particularly 0.3 μm or less. If the crystallite size is too large, the transmittance tends to decrease. Although the lower limit of the crystallite size is not particularly limited, it is practically 1 nm or more.

[0047] The crystallized glass of the present invention has a thickness of 0.8 mm and an average visible light transmittance at a wavelength of 380 to 780 nm of 50% or more, preferably 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, and particularly preferably 91% or more. If the transmittance is too low, it will be difficult to use as a cover glass for a smartphone.

[0048] The crystallized glass of the present invention has a whiteness L *The value is preferably 50 or less, 40 or less, and particularly preferably 30 or less. If the whiteness is too high, the transmittance is likely to decrease. * The values ​​are as defined in JIS Z 8730.

[0049] The crystallized glass of the present invention preferably has a Vickers hardness value of 540 or more, 550 or more, particularly 560 or more. If the Vickers hardness value is too low, the glass surface is easily scratched. Although the upper limit of the Vickers hardness value is not particularly limited, it is practically 1000 or less.

[0050] The Young's modulus of the crystallized glass of the present invention is preferably 70GPa or more, 74GPa or more, 75GPa or more, 80GPa or more, 85GPa or more, 87GPa or more, 89GPa or more, 90GPa or more, 93GPa or more, particularly 95GPa or more.If the Young's modulus is too low, when the plate thickness is thin, the cover glass is easily bent.In addition, the upper limit is not particularly limited, but in reality it is 200GPa or less, 150GPa or less, 120GPa or less, particularly 110GPa or less.

[0051] The crystallized glass of the present invention preferably has a compressive stress value (CS) of 50 MPa or more, 70 MPa or more, 80 MPa or more, 90 MPa or more, 100 MPa or more, 120 MPa or more, 150 MPa or more, 180 MPa or more, 200 MPa or more, 230 MPa or more, 250 MPa or more, 260 MPa or more, 280 MPa or more, particularly 300 MPa or more. If the compressive stress value is too small, there is a risk that the Vickers hardness and bending strength will be low.

[0052] The crystallized glass of the present invention preferably has a depth of compressive stress (DOC) of 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, 100 μm or more, 110 μm or more, particularly 120 μm or more. If the depth of compressive stress is too small, the drop height may be low.

[0053] The flexural strength of the crystallized glass of the present invention is preferably 100 MPa or more, 105 MPa or more, 110 MPa or more, particularly 120 MPa or more. If the flexural strength is too low, it becomes prone to breakage. The upper limit of the flexural strength is not particularly limited, but in reality it is 2000 MPa or less.

[0054] The crystallized glass of the present invention preferably has a scratched four-point bending strength of 150 MPa or more, 160 MPa or more, 165 MPa or more, 170 MPa or more, 180 MPa or more, 190 MPa or more, 210 MPa or more, 220 MPa or more, 230 MPa or more, 235 MPa or more, 240 MPa or more, 245 MPa or more, particularly 250 MPa or more.If the scratched four-point bending strength is too low, when used as a cover glass of a smartphone, it is likely to break when dropped.In addition, the upper limit of the scratched four-point bending strength is not particularly limited, but in reality it is 1500 MPa or less.

[0055] The crystallized glass of the present invention is preferably dropped from a height of 5 mm or more, 7 mm or more, and particularly 10 mm or more. If the drop height is too low, the glass is prone to breakage.

[0056] The crystallized glass of the present invention preferably has a strain point of 500° C. or higher, particularly preferably 530° C. or higher. If the strain point is too low, there is a risk that the glass will deform during the crystallization step.

[0057] The crystallized glass of the present invention has a thermal expansion coefficient of 0 to 120×10 at 30 to 380°C. -7 / ℃, 10~110×10 -7 / ℃, especially 20~100×10 -7 / °C. If the thermal expansion coefficient is too low, it becomes difficult to match the thermal expansion coefficient with that of surrounding members. On the other hand, if the thermal expansion coefficient is too high, the thermal shock resistance is likely to decrease.

[0058] Next, the method for producing the crystallized glass of the present invention will be described.

[0059] First, glass raw materials are mixed to obtain the desired composition. Next, the mixed raw material batch is melted at 1400 to 1600°C for 8 to 16 hours and formed into a predetermined shape to obtain a crystallizable glass body. For forming, well-known forming methods such as the float method, overflow method, downdraw method, roll-out method, and mold press method can be used. If necessary, bending or other processing may be performed.

[0060] Next, to achieve the desired crystallinity, the crystallizable glass body is heat-treated at 700 to 840°C for 0.1 to 15 hours to precipitate one or more crystals selected from β-eucryptite solid solution, β-spodumene solid solution, and zirconia, thereby obtaining transparent crystallized glass. It is acceptable for crystals other than these two to precipitate. Heat treatment may be performed at a specific temperature only, or may be performed stepwise by maintaining two or more temperatures, or by heating while applying a temperature gradient. Crystallization may also be promoted by applying or irradiating ultrasonic waves or electromagnetic waves.

[0061] When there is a risk that warpage occurs due to the crystallization of thin crystallizable glass, the crystallized glass can be polished to obtain the crystallized glass of desired thickness. Note that, from the viewpoint of manufacturing cost, after the crystallization of the crystallizable glass of desired thickness, polishing may not be performed.

[0062] The crystallized glass is then subjected to ion exchange to further increase the Vickers hardness. Ion exchange involves contacting the crystallized glass body with molten salt at 400°C or higher, replacing alkali ions (e.g., Li ions) in the surface glass phase with alkali ions (e.g., Na ions, K ions) with larger ionic radii. In this way, a compressive stress layer with a compressive stress value of 50 MPa or more and a compressive stress depth of 50 μm or more can be formed on the surface of the crystallized glass. The "compressive stress value" and "depth of the compressive stress layer" refer to values ​​measured using microscopic laser Raman spectroscopy.

[0063] The molten salt may be a nitrate (potassium nitrate, sodium nitrate, lithium nitrate, etc.), a carbonate (potassium carbonate, sodium carbonate, lithium carbonate, etc.), a sulfate (potassium sulfate, sodium sulfate, lithium sulfate, etc.), a chloride (potassium chloride, sodium chloride, lithium chloride, etc.), or a combination thereof.

[0064] When the crystallinity is low, less than 40%, it is preferable to use a nitrate or the like with a low melting point as the molten salt, and it is particularly preferable to use sodium nitrate. The ion exchange temperature is preferably 330 to 550°C, 350 to 500°C, and particularly 390 to 450°C, and the ion exchange time is preferably 30 minutes to 12 hours, 45 minutes to 10 hours, 1 hour to 8 hours, 1 hour to 6 hours, and particularly 1 hour to 4 hours.

[0065] When the crystallinity is as high as 40% or more, it is preferable to use a molten salt with a high boiling point such as a sulfate, carbonate or chloride, the ion exchange temperature is preferably 500 to 1000°C, 600 to 980°C, and particularly preferably 700 to 950°C, and the ion exchange time is preferably 1 to 12 hours, 2 to 10 hours, and particularly preferably 4 to 8 hours.

[0066] When the crystallinity is as high as 40% or more, it is preferable to use a jig made of a material with high heat resistance and chemical durability, such as titanium, molybdenum, Hastelloy C22, SUS440C, Inconel, Incoloy, or alumina, as a jig for setting the glass when immersing the glass in high-temperature molten salt. Alternatively, a material that has been thermally sprayed to improve heat resistance and chemical durability, such as conical spraying or zirconia spraying, may be used as the jig.

[0067] If necessary, surface treatment such as film formation, or machining such as cutting or drilling may be carried out before or after ion exchange. [Example]

[0068] The present invention will be described in detail below based on examples. Table 1 shows Examples 1 to 4 and Comparative Examples 5 and 6.

[0069] [Table 1]

[0070] The crystallized glasses of Examples 1 to 4 and Comparative Examples 5 and 6 were prepared as follows.

[0071] First, the batch raw materials prepared to obtain the composition shown in the table were placed in a melting furnace and melted at 1500-1600 ° C., and then the molten glass material was rolled and slowly cooled to produce crystallizable glass of 900 × 1200 × 7 mm. This crystallizable glass was heat-treated at the temperature and time shown in the table to obtain crystallized glass. Note that, for Comparative Example 6, no heat treatment was performed and no crystallization was performed.

[0072] Next, for Examples 1 to 4 and Comparative Example 5, the crystallized glass was subjected to an ion exchange treatment by immersing it in a NaNO3 molten salt maintained at 430°C for 4 hours to obtain chemically strengthened crystallized glass. Note that, for Comparative Example 6, no ion exchange treatment was performed.

[0073] The thus prepared samples were evaluated for crystallinity, average crystallite size, precipitated crystals, transmittance, Vickers hardness, flexural strength, drop height, and thermal expansion coefficient. The results are shown in Table 1.

[0074] Crystallinity, average crystallite size, and precipitated crystals were evaluated using an X-ray diffractometer (Rigaku Smart Lab, fully automated multipurpose horizontal X-ray diffractometer). The scan mode was 2θ / θ measurement, the scan type was continuous scan, the scattering and divergence slit widths were 1°, the receiving slit width was 0.2°, the measurement range was 10–60°, the measurement step was 0.1°, and the scan rate was 5° / min. The precipitated crystals were evaluated using the analysis software installed in the instrument package. The average crystallite size of the precipitated crystals was calculated using the measured X-ray diffraction peaks according to the Debye-Scherrer method. The scan rate for the measurement used to calculate the average crystallite size was 1° / min. The crystallinity was calculated based on the X-ray diffraction profile obtained using the above method as follows: (integrated intensity of the crystalline X-ray diffraction peak) / (total integrated intensity of the measured X-ray diffraction) × 100 [%].

[0075] The average transmittance of visible light in the wavelength range of 380 to 780 nm was measured using a crystallized glass plate with a thickness of 0.8 mm and optically polished on both sides, using a spectrophotometer, model V-670 manufactured by JASCO Corporation.

[0076] The Vickers hardness value conforms to JIS Z2244-1992 and is measured by pressing a Vickers indenter with a load of 100 gf using a Vickers hardness tester, and is the average value of 10 measurements.

[0077] The bending strength was measured using the three-point load method according to ASTM C880-78.

[0078] The drop height was determined by a drop test in which a 50mm x 50mm x 0.7mm thick crystallized glass plate was placed on a granite surface plate, and a 53g weight with a Vickers indenter attached to the tip was dropped vertically onto the glass from a specific height. The maximum height at which the glass retained its original shape without breaking was taken as the drop height.

[0079] The thermal expansion coefficient was measured using a crystallized glass sample processed to 20 mm×3.8 mmφ in a temperature range of 30 to 380° C. A Dilatometer manufactured by NETZSCH was used for the measurement.

[0080] Examples 1 to 4 of the present invention were crystallized glasses with a degree of crystallinity of 10 to 25%, and had high transmittances of 86% or more and high Vickers hardness values ​​of 720 or more. On the other hand, Comparative Example 5 was amorphous glass, and therefore had a low Vickers hardness value of 500. Comparative Example 6 was not ion-exchanged, and therefore had a low Vickers hardness value of 530. [Example]

[0081] Tables 2 to 9 show Examples A to AK of the present invention.

[0082] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9]

[0083] The crystallized glasses of Examples A to AK were prepared as follows.

[0084] First, the batch raw materials prepared to obtain the composition shown in the table were placed in a melting furnace and melted at 1500-1600°C. The molten glass material was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7mm. This crystallizable glass was then heat-treated at the temperature and time shown in the table to obtain crystallized glass.

[0085] Next, the obtained crystallized glass was polished to 0.615 mm, and then subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass.

[0086] The samples thus prepared were evaluated for crystallinity, precipitated crystals, transmittance, Young's modulus, compressive stress (CS), and depth of compressive stress (DOC). The results are shown in Table 2.

[0087] The Young's modulus was calculated according to JIS R1602-1995 "Testing method for elastic modulus of fine ceramics."

[0088] The compressive stress value (CS) and compressive stress depth (DOC) were measured using a scattered light photoelastic stress meter SLP-1000 (Orihara Manufacturing Co., Ltd.) and a surface stress meter FSM-6000 (Orihara Manufacturing Co., Ltd.) In calculating the stress characteristics, the refractive index of each measurement sample was set to 1.52 and the optical elastic constant was set to 25.1 [(nm / cm) / MPa].

[0089] Examples A to AK of the present invention were crystallized glasses with a degree of crystallization of 40% or more, high transmittance of 50% or more, and high Young's modulus of 92 to 93 GPa. In addition, they were sufficiently chemically strengthened by undergoing ion exchange treatment with high-temperature molten salt. [Example]

[0090] Tables 10 to 16 show Examples 7 to 48.

[0091] [Table 10] [Table 11] [Table 12] [Table 13] [Table 14] [Table 15] [Table 16]

[0092] The crystallized glasses of Examples 7 to 48 were prepared as follows.

[0093] First, the batch raw materials prepared to obtain the composition shown in the table were placed in a melting furnace and melted at 1500-1600°C. The molten glass material was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7mm. This crystallizable glass was then heat-treated at the temperature and time shown in the table to obtain crystallized glass.

[0094] Next, the obtained crystallized glass was polished to the thickness shown in the table, and then the crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass.

[0095] The samples thus prepared were evaluated for crystallinity, precipitated crystals, transmittance, Young's modulus, scratched four-point bending strength, Vickers hardness, and thermal expansion coefficient. The results are shown in Tables 10 to 16.

[0096] The scratching four-point bending strength test was performed using the following procedure. First, the glass was scratched using the following procedure. A 50 mm x 50 mm crystallized glass plate processed to the thicknesses listed in Tables 9 to 15 was fixed vertically to a 1.5 mm thick SUS plate, and the tip of a pendulum-shaped arm was struck against it through P180 grit sandpaper, causing scratching. The tip of the arm was a φ5 mm iron cylinder, and the arm weighed 550 g. The arm was swung down 5 mm from the point of impact. Next, a four-point bending test was performed on the scratched sample, and the strength was measured.

[0097] Examples 7 to 48 of the present invention were made of crystallized glass, and had high transmittance of 90% or more and high strength in a scratched four-point bending test. [Example]

[0098] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was heat-treated at the temperatures and times listed in the table to obtain crystallized glass. It was then cut into individual pieces of the desired size, such as 50 mm x 50 mm, and cut to a thickness close to the target thickness using a wire saw. It was then ground and polished to obtain crystallized glass. The crystallized glass was subjected to ion exchange treatment under the conditions listed in the table to obtain chemically strengthened crystallized glass. [Example]

[0099] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then roll-formed and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was then cut into pieces of the desired size, such as 50 mm x 50 mm, and cut to a thickness close to the target thickness using a wire saw, followed by grinding and polishing. The desired crystallized glass was then obtained by heat treatment at the temperature and time shown in the table. The crystallized glass was then subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0100] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was then cut into pieces of the desired size, such as 50 mm x 50 mm, and heat-treated at the temperature and time shown in the table to obtain the desired crystallized glass. The crystallized glass was then cut to a thickness close to the target thickness using a wire saw, followed by grinding and polishing to obtain the desired sample. The crystallized glass was then subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0101] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then roll-formed and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was polished to the thickness shown in the table and then heat-treated at the temperature and time shown in the table to obtain the desired crystallized glass. The desired sample was then obtained by cutting into pieces of the desired size, such as 50 mm x 50 mm. The crystallized glass was then subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0102] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was polished to a thickness greater than that shown in the table, and then heat-treated at the temperature and time shown in the table to obtain the desired crystallized glass. The crystallized glass was then polished to the thickness shown in the table and cut into individual pieces to obtain the desired sample. The crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0103] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then roll-formed and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was polished to the thickness shown in the table and then cut into pieces of the desired size, such as 50 mm x 50 mm. The desired crystallized glass was then obtained by heat treatment at the temperature and time shown in the table. The crystallized glass was then subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0104] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then roll-formed and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 7 mm. This crystallizable glass was polished to a thickness greater than that shown in the table, and then sliced ​​into pieces of the desired size, such as 50 mm x 50 mm. This was then heat-treated at the temperature and time shown in the table to obtain crystallized glass. The crystallized glass was then polished to the thickness shown in the table. The crystallized glass was then subjected to ion-exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0105] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then rolled and slowly cooled to produce crystallizable glass measuring 900 x 1200 x 1.1 mm. This crystallizable glass was then cut into pieces of the desired size, such as 50 mm x 50 mm, and heat-treated at the temperature and time shown in the table to obtain crystallized glass. The crystallized glass was then polished to the thickness shown in the table. The crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0106] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then rolled and slowly cooled to produce crystallizable glass of 900 x 1200 x 1.1 mm. This crystallizable glass was heat-treated at the temperature and time shown in the table to obtain crystallized glass, which was then sliced ​​into pieces of the desired size, such as 50 mm x 50 mm. The crystallized glass was then polished to the thickness shown in the table. The crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0107] Batch raw materials prepared to give the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then down-draw molded and slowly cooled to produce 900 x 1200 crystallizable glass. The thickness was as shown in the table. This crystallizable glass was cut into individual pieces of the desired size, such as 50mm x 50mm, and then heat-treated at the temperature and time shown in the table to obtain crystallized glass. The crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Example]

[0108] Batch raw materials prepared to achieve the compositions of Examples 7 to 48 were placed in a melting furnace and melted at 1500 to 1600°C. The molten glass was then down-draw molded and slowly cooled to produce crystallizable glass of 900 x 1200 mm. The thickness was as shown in the table. This crystallizable glass was heat-treated at the temperature and time shown in the table to obtain crystallized glass, which was then sliced ​​into pieces of the desired size, such as 50 mm x 50 mm. The crystallized glass was subjected to ion exchange treatment under the conditions shown in the table to obtain chemically strengthened crystallized glass. [Industrial Applicability]

[0109] The crystallized glass of the present invention is suitable as a cover glass for touch panel displays of mobile phones, digital cameras, PDAs (personal digital assistants), etc. In addition to these uses, the crystallized glass of the present invention is also expected to be used in applications requiring high Vickers hardness and transparency, such as window glass, magnetic disk substrates, flat panel display substrates, solar cell cover glass, and solid-state imaging device cover glass.

Claims

1. In mass%, SiO ２ 58-70%, Al ２ O ３ 15-30%, Li ２ O 2-10%, Na ２ O 0-10%, K ２ O 0-10%, Na ２ O+K ２ O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO ２ 0.1-6%, ZrO ２ 0.5-6%, TiO ２ 0-4%, P ２ O ５ The glass-ceramics is characterized by containing 0 to 6% of zirconia, having zirconia crystals precipitated therein, a crystallinity of 1 to 95%, a thickness of 0.8 mm, an average visible light transmittance of 50% or more at wavelengths of 380 to 780 nm, and a compressive stress layer formed on the surface.

2. Substantially As ２ O ３ 2. The crystallized glass according to claim 1, which does not contain PbO.

3. 3. The crystallized glass according to claim 1, further comprising one or more crystals selected from the group consisting of β-eucryptite solid solution and β-spodumene solid solution.

4. 4. The crystallized glass according to claim 1, wherein the average crystallite size is 1 μm or less.

5. 5. The crystallized glass according to claim 1, wherein the Vickers hardness value is 540 or more.

6. 6. The crystallized glass according to claim 1, wherein the bending strength is 100 MPa or more and the drop height is 5 mm or more.

7. Thermal expansion coefficient at 30 to 380°C is 0 to 120 x 10 －７ 7. The crystallized glass according to claim 1, wherein the temperature is 100°C.

8. 8. The crystallized glass according to claim 1, wherein the Young's modulus is 80 GPa or more.

9. In mass%, SiO ２ 58-70%, Al ２ O ３ 15-30%, Li ２ O 2-10%, Na ２ O 0-10%, K ２ O 0-10%, Na ２ O+K ２ O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO ２ 0.1-6%, ZrO ２ 0.5-6%, TiO ２ 0-4%, P ２ O ５ A method for producing crystallized glass, comprising the steps of: preparing crystallized glass containing 0-6% zirconia, in which zirconia crystals are precipitated, and having a crystallinity of 1-95%; and immersing the crystallized glass in molten salt at 400°C or higher to obtain crystallized glass having a compressive stress layer on its surface.

10. In mass%, SiO ２ 58-70%, Al ２ O ３ 15-30%, Li ２ O 2-10%, Na ２ O 0-10%, K ２ O 0-10%, Na ２ O+K ２ O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO ２ 0.1-6%, ZrO ２ 0.5-6%, TiO ２ 0-4%, P ２ O ５ A method for producing crystallized glass, comprising the steps of: preparing crystallized glass containing 0-6% zirconia, in which zirconia crystals are precipitated, and having a crystallinity of 40-95%; and immersing the crystallized glass in molten salt at 500-1000°C to obtain crystallized glass having a compressive stress layer on its surface.

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