Crystalline glass

Abstract

The present invention provides a crystallized glass having high Vickers hardness and excellent transparency. The crystallized glass is characterized by containing, in mass%, SiO2 58 to 70%, Al2O3 15 to 30%, Li2O 2 to 10%, Na2O 0 to 10%, K2O 0 to 10%, Na2O+K2O 0 to 15%, MgO+CaO+SrO+BaO+ZnO 0 to 15%, SnO2 0.1 to 6%, ZrO2 0.5 to 6%, TiO2 0 to 4%, P2O5 0 to 6%, and having a crystallinity of 1 to 95%, an average transmittance of visible light of 50% or more at a thickness of 0.8 mm and a wavelength of 380 to 780 nm, and a compressive stress layer formed on the surface of the crystallized glass.

Description

Technical Field

[0001] This invention relates to crystallizing glass. Background Technology

[0002] Mobile phones, digital cameras, and PDAs (mobile terminals) are becoming increasingly popular. For these applications, protective glass is used to protect the touch panel display (see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-083045 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] Protective glass, especially for smartphones, is mostly used outdoors. High illuminance and parallelism of light make surface damage easily visible and reduce display visibility. Therefore, improving the damage resistance of glass is important. Increasing the Vickers hardness value is considered a useful method to improve damage resistance. Increasing the Vickers hardness value makes surface damage less likely, and even with hard scratches, it can reduce the width and depth of the damage.

[0008] As a type of glass with a high Vickers hardness, crystalline glass is known to precipitate crystals within the glass.

[0009] However, the current situation is that crystal glass does not reach the level of transparency of amorphous glass and is not suitable for protective glass.

[0010] The purpose of this invention is to provide a crystal glass with high Vickers hardness and excellent transparency.

[0011] Technical means for solving problems

[0012] The crystal glass of the present invention is characterized by 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 0-6% P2O5; having a crystallinity of 1-95%; having an average visible light transmittance of 50% or more at a thickness of 0.8 mm and a wavelength of 380-780 nm; and having a compressive stress layer formed on the surface of the crystal glass. Here, "Na2O+K2O" refers to the total amount of Na2O and K2O, and "MgO+CaO+SrO+BaO+ZnO" refers to the total amount of MgO, CaO, SrO, BaO, and ZnO.

[0013] The crystal glass of the present invention, by performing ion exchange treatment on the crystal glass having the above composition, can form a compressive stress layer on the surface of the crystal glass, thereby easily increasing the Vickers hardness value.

[0014] The crystal glass of the present invention preferably does not contain substantially As2O3 or PbO.

[0015] The crystal glass of the present invention preferably precipitates one or more crystals selected from β-nepheline solid solution, β-spodumene solid solution and zirconium oxide.

[0016] The average crystallite size of the crystal glass of the present invention is preferably less than 1 μm.

[0017] The Vickers hardness value of the crystal glass of the present invention is preferably 540 or higher. Here, "Vickers hardness" refers to the value measured according to JIS Z2244-1992 and by pressing a Vickers indenter with a load of 100 gf using a Vickers hardness tester, and is the average value of 10 measurements.

[0018] The crystal glass of the present invention preferably has a bending strength of 100 MPa or more, and a drop height preferably of 5 mm or more. Here, "drop height" refers to the maximum height at which a 50 mm × 50 mm × 0.7 mm thick glass plate is placed on a granite platform, and a 53 g weight with a Vickers indenter at the front end is dropped vertically onto the glass from a specific height without breaking the glass plate and maintaining its original shape.

[0019] The crystal glass of the present invention preferably has a coefficient of thermal expansion of 0 to 120 × 10⁻⁶ at 30–380°C. -7 / ℃.

[0020] The crystal glass of the present invention preferably has a Young's modulus of 80 GPa or higher. Here, "Young's modulus" is a value measured by a known resonance method.

[0021] The method for preparing the crystal glass of the present invention is characterized by comprising: a step of preparing crystal glass, wherein the crystal glass contains, by mass %: SiO2 58-70%, Al2O3 15-30%, Li2O 2-10%, Na2O 0-10%, K2O 0-10%, Na2O+K2O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO2 0.1-6%, ZrO2 0.5-6%, TiO2 0-4%, P2O5 0-6% and has a crystallinity of 1-95%; and a step of immersing the crystal glass in a molten salt at a temperature of 400°C or higher to obtain crystal glass with a compressive stress layer on its surface.

[0022] The method for preparing the crystal glass of the present invention is characterized by comprising: a step of preparing crystal glass, wherein the crystal glass contains, by mass %: SiO2 58-70%, Al2O3 15-30%, Li2O 2-10%, Na2O 0-10%, K2O 0-10%, Na2O+K2O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO2 0.1-6%, ZrO2 0.5-6%, TiO2 0-4%, P2O5 0-6% and has a crystallinity of 40-95%; and a step of immersing the crystal glass in a molten salt at 500-1000°C to obtain crystal glass with a compressive stress layer on its surface.

[0023] The crystal glass of the present invention is characterized in that it contains precipitated zirconium oxide crystals and has an average visible light transmittance of more than 50% at a thickness of 0.8 mm and a wavelength of 380-780 nm.

[0024] The crystal glass of the present invention preferably has a compressive stress layer formed on its surface.

[0025] The crystal glass of the present invention preferably has a crystallinity of less than 40%.

[0026] The crystal glass of the present invention preferably contains, by mass percent: SiO2 58-70%, Al2O3 15-30%, Li2O 2-10%, Na2O 0-10%, K2O 0-10%, Na2O+K2O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO2 0.1-6%, ZrO2 0.5-6%, TiO2 0-4%, and P2O5 0-6%.

[0027] Invention Effects

[0028] According to the present invention, a crystal glass with high Vickers hardness and excellent transparency can be provided. Detailed Implementation

[0029] The crystal glass of the present invention contains, by mass percent: SiO2 58-70%, Al2O3 15-30%, Li2O 2-10%, Na2O 0-10%, K2O 0-10%, Na2O+K2O 0-15%, MgO+CaO+SrO+BaO+ZnO 0-15%, SnO2 0.1-6%, ZrO2 0.5-6%, TiO2 0-4%, P2O 50-6%. The crystallinity of the crystal glass is 1-95%. The average transmittance of visible light at a thickness of 0.8 mm and a wavelength of 380-780 nm is more than 50%. A compressive stress layer is formed on the surface of the crystal glass.

[0030] First, the reasons for limiting the composition of the crystal glass to the above-described manner will be explained. It should be noted that, unless otherwise specified, "%" in the following description refers to mass percentage.

[0031] SiO2 is a component that forms the glass framework. The SiO2 content is 58-70%, preferably 60-68%, and particularly preferably 64-66%. If the SiO2 content is too low, the 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.

[0032] Al₂O₃ is a component that improves ion exchange performance. The Al₂O₃ content is 15–30%, preferably 17–27%, and particularly preferably 20–25%. If the Al₂O₃ content is too low, coarse crystals are easily precipitated, and crystallization becomes difficult. On the other hand, if the Al₂O₃ content is too high, the meltability of the glass tends to deteriorate.

[0033] Li₂O is a component that improves the melting point of glass and participates in ion exchange treatment. The content of Li₂O is 2-10%, preferably 3-8%, and particularly preferably 4-6%. If the content of Li₂O is too low, ion exchange is difficult to carry out. On the other hand, if the content of Li₂O is too high, the liquidus temperature tends to rise, and there is a tendency for the crystallite size to become too large.

[0034] Na₂O and K₂O are components that improve the melting properties of glass. The Na₂O + K₂O content is 0–15%, 0–10%, 0–7%, 0–5%, 0–3%, 0–2%, and particularly preferably 0–1%. If there is too much Na₂O + K₂O, the transmittance of the crystal glass will easily decrease. It should be noted that the Na₂O content is 0–10%, preferably 0–7%, 0–5%, 0–3%, 0–2%, and particularly preferably 0–1%, and the K₂O content is 0–10%, preferably 0–7%, 0–5%, 0–3%, 0–2%, and particularly preferably 0–1%.

[0035] MgO, CaO, SrO, BaO, and ZnO are components that improve the melting properties of glass. The concentration of MgO+CaO+SrO+BaO+ZnO is 0–15%, preferably 0–13%, 0–10%, 0–7%, 0–5%, 0–4%, and particularly preferably 0–3%. If there is too much MgO+CaO+SrO+BaO+ZnO, coarse crystals are more likely to precipitate. In addition, the content of MgO is preferably 0-10%, 0-7%, 0-5%, 0-4%, and particularly preferably 0-3%; the content of CaO is preferably 0-10%, 0-7%, 0-5%, 0-4%, and particularly preferably 0-3%; the content of SrO is preferably 0-10%, 0-7%, 0-5%, 0-4%, and particularly preferably 0-3%; the content of BaO is preferably 0-10%, 0-7%, 0-5%, 0-4%, and particularly preferably 0-3%; and the content of ZnO is 0-10%, 0-7%, 0-5%, 0-4%, and particularly preferably 0-3%.

[0036] SnO2 acts as a clarifying agent. It is also essential for efficient crystallization during the crystallization process. Furthermore, a high concentration of SnO2 significantly enhances glass coloration. The SnO2 content is typically 0.1–6%, preferably 1–5%, and particularly preferably 1.5–4%. Insufficient SnO2 content makes glass clarification difficult, leading to reduced productivity. Furthermore, inadequate crystal nucleation results in coarse crystal precipitation, potentially causing the glass to become cloudy or break. Conversely, excessive SnO2 content may result in stronger coloration of the crystallized glass. Additionally, increased SnO2 evaporation during manufacturing tends to increase environmental impact.

[0037] ZrO2 is a nucleating component used to induce crystal precipitation during the crystallization process. The ZrO2 content is 0.5–6%, preferably 1–4%, and particularly preferably 1.5–3%. If the ZrO2 content is too low, crystal nuclei will not form sufficiently, resulting in coarse crystals that may precipitate, potentially causing the crystal glass to become cloudy or break. On the other hand, if the ZrO2 content is too high, coarse ZrO2 crystals will precipitate, making the glass prone to devitrification and breakage.

[0038] The preferred concentrations of SnO2+ZrO2 are 1.5–12%, 2–9%, and particularly preferably 3–7%. If there is too little SnO2+ZrO2, crystal nuclei are difficult to precipitate, making crystallization difficult. Conversely, if there is too much SnO2+ZrO2, the crystal nuclei become larger, and the crystallized glass easily becomes cloudy.

[0039] SnO2 promotes the phase separation of ZrO2. In order to efficiently generate phase separation while keeping the liquid phase temperature low (suppressing the risk of devitrification caused by the precipitation of the initial phase), and to rapidly carry out nucleation and crystal growth in subsequent processes, the SnO2 / (SnO2+ZrO2) ratio is preferably 0.3 to 0.7, 0.35 to 0.65, and particularly preferably 0.4 to 0.6 by mass ratio.

[0040] TiO2 is a nucleating component used to induce crystal precipitation during the crystallization process. Furthermore, a high TiO2 content significantly enhances the coloration of the glass. In particular, zirconium titanate crystals containing both ZrO2 and TiO2 act as nuclei, but electrons undergo LMCT transitions (transitions from the valence band of oxygen as a ligand to the conduction band of zirconium oxide and titanium as the central metals), contributing to the coloration of the crystalline glass. Additionally, when titanium remains in the residual glass phase, LMCT migration occurs from the valence band of the SiO2 framework to the conduction band of tetravalent titanium in the residual glass phase. Furthermore, dd transitions occur in trivalent titanium in the residual glass phase, contributing to the coloration of the crystalline glass. Moreover, when titanium and iron coexist, an ilmenite (FeTiO3)-like coloration is observed. It is also known that the yellow color is enhanced when titanium and tin coexist. Therefore, the TiO2 content is 0–4%, preferably 0–3%, 0–2%, or 0–1%. Particularly preferred is 0–0.1%. However, TiO2 is easily mixed in as an impurity, so if TiO2 is to be completely removed, the raw material batch becomes expensive, which tends to increase manufacturing costs. In order to suppress the increase in manufacturing costs, the lower limit of TiO2 content is preferably 0.0003% or more, 0.001% or more, 0.01% or more, and particularly preferably 0.02% or more.

[0041] P2O5 is a component that inhibits the precipitation of coarse ZrO2 crystals. The P2O5 content is 0-6%, preferably 0-5%, 0.1-5%, 0.5-4%, and particularly preferably 1-3%. If the P2O5 content is too high, there is a tendency for the coefficient of thermal expansion to increase.

[0042] In addition to the above-mentioned components, the crystal glass of the present invention may also contain the following components in its glass composition.

[0043] B2O3 is a component that reduces the viscosity of glass, thereby improving its meltability and formability. It also affects the ease with which phase separation occurs during crystal nucleation. The preferred B2O3 content is 0–3%, 0–2%, 0–1%, and particularly preferably 0–0.1%. Excessive B2O3 content leads to increased evaporation during melting, resulting in a higher environmental impact.

[0044] CeO2 not only improves solubility but also acts as an oxidizing agent, suppressing Fe2+ as an impurity in all Fe. 2+A component that increases and improves the transparency of crystal glass. The CeO2 content is preferably 0-0.5%, particularly preferably 0-0.3%. If the CeO2 content is too high, Ce... 4+ The resulting coloration becomes too strong, which may cause the crystal glass to appear brown.

[0045] SO3 can be introduced from sodium sulfate. The effect of SO3 is to improve the solubility of the original glass. In addition, it acts as an oxidizing agent, similar to CeO2, and its effect is significantly enhanced when coexisting with CeO2. The SO3 content is preferably 0–0.5%, 0.02–0.5%, and particularly preferably 0.05–0.3%. If there is too much SO3, heterogeneous crystals will precipitate, potentially deteriorating the surface quality of the crystallized glass.

[0046] As₂O₃ and PbO are harmful, so it is preferable that they are substantially absent. Here, "substantially absent" means that these components are not intentionally added to the glass, not that unavoidable impurities are completely eliminated. More objectively, it means that the content of these components, which contain impurities, is below 1000 ppm.

[0047] The crystalline glass of the present invention preferably contains one or more crystals selected from β-nepheline solid solution, β-spodumene solid solution, and zirconium oxide. The Vickers hardness and chemical durability of the crystalline glass are improved by precipitating any one of the crystals selected from β-nepheline solid solution, β-spodumene solid solution, and zirconium oxide. It should be noted that the precipitation of crystals other than β-nepheline solid solution, β-spodumene solid solution, and zirconium oxide is not excluded in the present invention. Furthermore, β-nepheline solid solution, β-spodumene solid solution, and zirconium oxide are preferably the main crystals, but are not necessarily required to be the main crystals.

[0048] Furthermore, in the crystalline glass of the present invention, especially when the crystallinity is less than 40%, it is preferable to precipitate zirconium oxide, and particularly preferable to have zirconium oxide as the main crystal. When zirconium oxide is the main crystal, its small crystal grain size and relatively large amount of residual glass phase provide an advantage in easily inducing ion exchange. This ease of ion exchange introduces strong surface stress, thereby easily improving mechanical properties such as Vickers hardness and strength. Additionally, the large amount of residual glass phase makes it easy to produce a smooth surface, thus primarily improving flexural strength.

[0049] The crystallinity of the crystal glass of the present invention is 1-95%, preferably 1-50%, 2-40%, 3-35%, 4-30%, and particularly preferably 5-20%. If the crystallinity is too low, there is a tendency for the Vickers hardness and Young's modulus to decrease. On the other hand, if the crystallinity is too high, the transmittance tends to decrease. In addition, when ion exchange is performed, the proportion of the glass phase that is subject to ion exchange treatment is small, so it is difficult to form a high compressive stress layer by ion exchange treatment without adopting the special conditions described later.

[0050] On the other hand, for highly crystalline glass, ion exchange can be performed at temperatures above 500°C using molten salts with high boiling points, such as sulfates, carbonates, and chlorides, thereby forming a high compressive stress layer. In this way, if a high compressive stress layer can be formed, the crystallinity 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. In this case, it is easy to achieve both a high compressive stress layer and a high Young's modulus.

[0051] The crystallite size of the crystal glass of the present invention is preferably 1 μm or less, 0.5 μm or less, and particularly preferably 0.3 μm or less. If the crystallite size is too large, the transmittance is easily reduced. It should be noted that the lower limit of the crystallite size is not particularly limited, but in practice it is above 1 nm.

[0052] The crystalline glass of the present invention has an average visible light transmittance of 50% or more at a thickness of 0.8 mm and a wavelength of 380-780 nm, 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, or 90% or more, and particularly preferably 91% or more. If the transmittance is too low, it is difficult to use as a protective glass for smartphones.

[0053] The whiteness L* value of the crystal glass of the present invention is 50 or less, 40 or less, and particularly preferably 30 or less. If the whiteness is too high, the transmittance is likely to decrease. It should be noted that the whiteness L* value refers to the value defined in JIS Z 8730.

[0054] The Vickers hardness value of the crystal glass of the present invention is preferably 540 or higher, 550 or higher, and particularly preferably 560 or higher. If the Vickers hardness value is too low, the glass surface is easily damaged. It should be noted that there is no particular upper limit to the Vickers hardness value, and in practice it is below 1000.

[0055] The Young's modulus of the crystal glass of the present invention is preferably 70 GPa or higher, 74 GPa or higher, 75 GPa or higher, 80 GPa or higher, 85 GPa or higher, 87 GPa or higher, 89 GPa or higher, 90 GPa or higher, or 93 GPa or higher, and particularly preferably 95 GPa or higher. If the Young's modulus is too low, the protective glass becomes easily flexed when the plate thickness is relatively thin. It should be noted that there is no particular upper limit, but in practice it is 200 GPa or lower, 150 GPa or lower, 120 GPa or lower, and particularly 110 GPa or lower.

[0056] The compressive stress (CS) of the crystal glass of the present invention is preferably 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, and particularly preferably 300 MPa or more. If the compressive stress is too low, the Vickers hardness and flexural strength may become lower.

[0057] The compressive stress depth (DOC) of the crystal glass of the present invention is preferably 10 μm or more, 20 μm or more, 30 μm or more, 40 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, and particularly preferably 120 μm or more. If the compressive stress depth is too small, the drop height may be lower.

[0058] The flexural strength of the crystal glass of the present invention is preferably 100 MPa or more, 105 MPa or more, 110 MPa or more, and particularly preferably 120 MPa or more. If the flexural strength is too low, it is prone to breakage. It should be noted that there is no particular upper limit to the flexural strength, and in practice it is below 2000 MPa.

[0059] The crystal glass of the present invention preferably has a 4-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, and particularly preferably 250 MPa or more. If the 4-point bending strength is too low, it is prone to breakage upon drop when used as a protective glass for smartphones. It should be noted that there is no particular upper limit to the 4-point bending strength; in practice, it is below 1500 MPa.

[0060] The crystal glass of this invention is preferably dropped from a height of 5 mm or more, 7 mm or more, and particularly preferably 10 mm or more. If the drop height is too low, it is prone to breakage.

[0061] The strain point of the crystallizing glass of the present invention is preferably 500°C or higher, and particularly preferably 530°C or higher. If the strain point is too low, the glass may deform during the crystallization process.

[0062] The crystal glass of the present invention preferably has a coefficient of thermal expansion of 0 to 120 × 10⁻⁶ at 30–380°C. -7 / ℃, 10~110×10 -7 / ℃, preferably 20~100×10 -7 / ℃. If the coefficient of thermal expansion is too low, it will be difficult to match the coefficient of thermal expansion with the surrounding components. On the other hand, if the coefficient of thermal expansion is too high, the thermal shock resistance will easily decrease.

[0063] Next, the method for manufacturing the crystal glass of the present invention will be described.

[0064] First, glass raw materials are prepared in a manner that achieves the desired composition. Then, the prepared batch of raw materials is melted at 1400–1600°C for 8–16 hours and shaped into a predetermined form to obtain a crystalline glass. It should be noted that the forming process can employ well-known methods such as float glass, overflow glass, pull glass, rolling glass, and molding glass. Additionally, bending or other processing can be performed as needed.

[0065] Next, to achieve the desired crystallinity of the crystalline glass, heat treatment at 700–840°C for 0.1–15 hours is performed to precipitate one or more of the following: β-nepheline solid solution, β-spodumene solid solution, and zirconium oxide, resulting in a transparent crystalline glass. Alternatively, crystals other than these two types may also precipitate. It should be noted that the heat treatment can be performed at a specific temperature, in stages at two temperatures above a certain level, or while simultaneously applying a temperature gradient. Furthermore, crystallization can be promoted by applying or irradiating sound waves or electromagnetic waves.

[0066] In cases where warping may occur due to the crystallization of thin crystalline glass, grinding the crystalline glass can produce crystalline glass of the desired thickness. It should be noted that, from a manufacturing cost perspective, grinding may not be necessary after crystallizing the crystalline glass to the desired thickness.

[0067] Subsequently, to further improve the Vickers hardness value, ion exchange was performed on the crystalline glass. Ion exchange involves contacting the crystalline glass with a molten salt at a temperature above 400°C, thereby replacing alkali ions (e.g., Li ions) in the glass phase on the surface with alkali ions (e.g., Na ions, K ions) with larger ionic radii. This allows the formation of a compressive stress layer on the surface of the crystalline glass with a compressive stress value of 50 MPa or higher and a compressive stress depth of 50 μm or higher. It should be noted that "compressive stress value" and "compressive stress depth" refer to values ​​measured using microscopic laser Raman spectroscopy.

[0068] In addition, nitrates (potassium nitrate, sodium nitrate, lithium nitrate, etc.), carbonates (potassium carbonate, sodium carbonate, lithium carbonate, etc.), sulfates (potassium sulfate, sodium sulfate, lithium sulfate, etc.), chlorides (potassium chloride, sodium chloride, lithium chloride, etc.) or combinations thereof can be used as molten salts.

[0069] When the crystallinity is low to less than 40%, nitrates with low melting points are preferably used as molten salts, and sodium nitrate is particularly preferred. The ion exchange temperature is preferably 330–550°C, 350–500°C, and particularly preferably 390–450°C, and the ion exchange time is preferably 30 minutes–12 hours, 45 minutes–10 hours, 1 hour–8 hours, 1 hour–6 hours, and particularly preferably 1 hour–4 hours.

[0070] When the crystallinity is high to 40% or more, sulfates, carbonates, chlorides, etc. with high boiling points are preferably used as molten salts. The preferred temperature for ion exchange is 500-1000℃, 600-980℃, and particularly preferably 700-950℃. The preferred time for ion exchange is 1-12 hours, 2-10 hours, and particularly preferably 4-8 hours.

[0071] When the crystallinity is high (above 40%), the fixtures used for assembling the glass in high-temperature molten salt are preferably made of raw materials with high heat resistance and chemical durability, such as titanium, molybdenum, Hastelloy C22, SUS440C, Inconel, Incolloy, and alumina. Alternatively, fixtures made from materials that have undergone conical spraying or zirconium oxide spraying to improve heat resistance and chemical durability can also be used.

[0072] It should be noted that surface processing such as coating, cutting, and drilling can also be performed before or after ion exchange as needed.

[0073] Example 1

[0074] The present invention will now be described in detail based on the embodiments. Table 1 shows Examples 1 to 4 and Comparative Examples 5 and 6.

[0075] [Table 1]

[0076]

[0077] The crystal glasses of Examples 1-4 and Comparative Examples 5 and 6 were prepared as follows.

[0078] First, the batch of raw materials prepared in the manner shown in the table was fed into a melting furnace and melted at 1500–1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass measuring 900 × 1200 × 7 mm. Crystalline glass was obtained by heat-treating the crystalline glass at the temperature and time specified in the table. It should be noted that Comparative Example 5 did not undergo heat treatment and therefore did not crystallize.

[0079] Next, for Examples 1-4 and Comparative Example 5, ion exchange treatment was performed by immersion in molten NaNO3 salt at 430°C for 4 hours, and chemical enhancement was also carried out. However, for Comparative Example 6, no ion exchange treatment was performed.

[0080] For the samples prepared in this way, the crystallinity, average crystallite size, precipitation crystals, transmittance, Vickers hardness, flexural strength, drop height, and coefficient of thermal expansion were evaluated. The results are shown in Table 1.

[0081] Crystallinity, average crystallite size, and precipitated crystals were evaluated using an X-ray diffraction apparatus (Rigaku Smart Lab, a fully automated multi-object horizontal X-ray diffraction apparatus). The scanning mode was 2θ / θ measurement, the scanning type was continuous scanning, the scattering and diverging slit width was 1°, the receiving slit width was 0.2°, the measurement range was 10–60°, the measurement step was 0.1°, and the scanning speed was 5° / min. The analysis software included in the apparatus package was used to evaluate the precipitated crystals. The average crystallite size was calculated using the Debye-Scherrer method based on the measured X-ray diffraction peaks. It should be noted that the scanning speed was set to 1° / min in the measurement used to calculate the average crystallite size. Crystallinity was calculated based on the X-ray diffraction pattern obtained by the above method, by (integrated intensity of the crystallized X-ray diffraction peaks) / (total integrated intensity of the measured X-ray diffraction) × 100 [%).

[0082] The average transmittance of visible light in the wavelength range of 380–780 nm was measured using a spectrophotometer on a 0.8 mm thick crystalline glass plate that had undergone double-sided optical polishing. A Japanese V-670 spectrophotometer was used in the measurements.

[0083] The Vickers hardness value is based on JIS Z2244-1992 and is measured by pressing a Vickers indenter with a load of 100gf using a Vickers hardness tester. It is the average value of 10 measurements.

[0084] Bending strength was determined using the three-point load method based on ASTM C880-78.

[0085] The drop height was determined through a drop test. A 50mm × 50mm × 0.7mm thick crystal glass plate was placed on a granite platform, and a 53g weight with a Vickers indenter at the front end was dropped vertically onto the glass from a specific height. The maximum height at which the glass maintained its original shape without breaking was taken as the drop height.

[0086] The coefficient of thermal expansion was determined using a crystalline glass sample machined to a diameter of 20 mm × 3.8 mm φ, within a temperature range of 30–380 °C. A NETZSCH dilatometer was used in the determination.

[0087] Examples 1-4 of the present invention are crystalline glasses with a crystallinity of 10-25%, a transmittance of up to 86% or higher, and a Vickers hardness of up to 720 or higher. On the other hand, Comparative Example 5 is an amorphous glass, and therefore has a Vickers hardness as low as 500. Comparative Example 6, because it did not undergo ion exchange, has a Vickers hardness as low as 530.

[0088] Example 2

[0089] Tables 2 to 9 represent embodiments A to AK of the present invention.

[0090] [Table 2]

[0091]

[0092] [Table 3]

[0093]

[0094] [Table 4]

[0095]

[0096] [Table 5]

[0097]

[0098] [Table 6]

[0099]

[0100] [Table 7]

[0101]

[0102] [Table 8]

[0103]

[0104] [Table 9]

[0105]

[0106] The crystal glass of Examples A to AK was prepared as follows.

[0107] First, the batch of raw materials, prepared as shown in the table, is fed into a melting furnace and melted at 1500–1600°C. The molten glass blank is then rolled into shape and slowly cooled to produce crystalline glass measuring 900 × 1200 × 7 mm. Crystalline glass is then obtained by heat-treating the crystalline glass at the temperature and time specified in the table.

[0108] Next, the obtained crystal glass was ground to 0.615 mm and then subjected to ion exchange treatment under the conditions recorded in the table to obtain chemically strengthened crystal glass.

[0109] For the samples prepared in this way, the crystallinity, precipitation crystallization, transmittance, Young's modulus, compressive stress (CS), and depth of compressive stress (DOC) were evaluated. The results are shown in Table 2.

[0110] Young's modulus was calculated according to the method in JIS R1602-1995 "Test method for elastic modulus of fine ceramics".

[0111] The compressive stress (CS) and compressive stress depth (DOC) were measured using a scattered light photoelastic stress meter SLP-1000 (manufactured by Orihara Corporation) and a surface stress meter FSM-6000 (manufactured by Orihara Corporation). It should be noted that in the calculation of stress characteristics, the refractive index of each measured sample was set to 1.52, and the optical elastic constant was set to 25.1 [(nm / cm) / MPa].

[0112] Examples A to AK of the present invention are crystalline glasses with a crystallinity of 40% or higher, a transmittance of 50% or higher, and a Young's modulus of 92 to 93 GPa. Furthermore, they are sufficiently chemically strengthened due to ion exchange treatment using high-temperature molten salt.

[0113] Example 3

[0114] Tables 10-16 represent Examples 7-48.

[0115] [Table 10]

[0116]

[0117] [Table 11]

[0118]

[0119] [Table 12]

[0120]

[0121] [Table 13]

[0122]

[0123] [Table 14]

[0124]

[0125] [Table 15]

[0126]

[0127] [Table 16]

[0128]

[0129] The crystal glass of Examples 7-48 was prepared as follows.

[0130] First, the batch of raw materials, prepared as shown in the table, is fed into a melting furnace and melted at 1500–1600°C. The molten glass blank is then rolled into shape and slowly cooled to produce crystalline glass measuring 900 × 1200 × 7 mm. Crystalline glass is then obtained by heat-treating the crystalline glass at the temperature and time specified in the table.

[0131] Next, the obtained crystal glass is ground to the thickness recorded in the table, and then subjected to ion exchange treatment under the conditions recorded in the table to obtain chemically strengthened crystal glass.

[0132] For the samples prepared in this way, the crystallinity, precipitation crystals, transmittance, Young's modulus, 4-point flexural strength at damage, Vickers hardness, and coefficient of thermal expansion were evaluated. The results are shown in Tables 10-16.

[0133] The four-point bending strength of the damaged glass was measured in the following order. First, the glass was damaged in the following order: A 50mm × 50mm crystal glass plate, processed to the thicknesses listed in Tables 10-16, was fixed vertically to a 1.5mm thick SUS plate. A pendulum-shaped arm was used to impact the plate through P180 grit sandpaper, causing damage. The arm's tip was a φ5mm iron cylinder, and the arm weighed 550g. The arm was thrown 5mm from the point of impact. Next, a four-point bending test was performed on the damaged sample to determine its strength.

[0134] Examples 7 to 48 of the present invention are crystalline glasses with a transmittance of over 90% and high strength when bent at four points of damage.

[0135] Example 4

[0136] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass blank was then rolled into shape and slowly cooled to produce crystalline glass with dimensions of 900×1200×7mm. The crystalline glass was then heat-treated at the temperatures and times specified in the table to obtain crystalline glass. Subsequently, it was cut into single sheets of desired dimensions such as 50mm×50mm, and after being formed into plates with a thickness approximately close to the target wall thickness using a wire saw, it was ground and polished to obtain crystalline glass. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0137] Example 5

[0138] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×7mm. This crystalline glass was then sheeted into desired dimensions such as 50mm×50mm, and after being formed into plates with a thickness approximately close to the target wall thickness using a wire saw, it was ground and polished. Then, it was heat-treated at the temperature and time specified in the table to obtain the desired crystalline glass. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0139] Example 6

[0140] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×7mm. This crystalline glass was then cut into sheets of desired dimensions such as 50mm×50mm and heat-treated at the temperatures and times specified in the table to obtain the desired crystalline glass. The crystalline glass was then cut into plates approximately close to the target wall thickness using a wire saw, and then ground and polished to obtain the desired sample. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0141] Example 7

[0142] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×7mm. This crystalline glass was ground to the thickness specified in the table and then heat-treated at the temperature and time specified in the table to obtain the desired crystalline glass. Then, it was sheet-cut into desired sizes such as 50mm×50mm to obtain the desired samples. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0143] Example 8

[0144] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass with dimensions of 900×1200×7mm. This crystalline glass was ground to a thickness greater than that listed in the table and then heat-treated at the temperature and time specified in the table to obtain the desired crystalline glass. The crystalline glass was then ground to the thickness listed in the table and monolithically processed to obtain the desired sample. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0145] Example 9

[0146] The batch raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×7mm. This crystalline glass was ground to the thicknesses listed in the table and then sheet-cut into desired sizes such as 50mm×50mm. It was then heat-treated at the temperatures and times listed in the table to obtain the desired crystalline glass. The crystalline glass was then subjected to ion exchange treatment under the conditions listed in the table to obtain chemically strengthened crystalline glass.

[0147] Example 10

[0148] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×7mm. This crystalline glass was ground to a thickness greater than the thickness listed in the table and then sheeted into desired sizes such as 50mm×50mm. It was then heat-treated at the temperature and time listed in the table to obtain crystalline glass. The crystalline glass was then ground to the thickness listed in the table. The crystalline glass was then subjected to ion exchange treatment under the conditions listed in the table to obtain chemically strengthened crystalline glass.

[0149] Example 11

[0150] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass of 900×1200×1.1 mm. This crystalline glass was then sheeted into desired sizes such as 50 mm × 50 mm and heat-treated at the temperatures and times specified in the table to obtain crystalline glass. The crystalline glass was then ground to the thickness specified in the table. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0151] Example 12

[0152] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then rolled and slowly cooled to produce crystalline glass with dimensions of 900×1200×1.1 mm. The crystalline glass was then heat-treated at the temperatures and times specified in the table to obtain crystalline glass, which was then sheet-cut into desired sizes such as 50 mm × 50 mm. The crystalline glass was then ground to the thickness specified in the table. The crystalline glass was then subjected to ion exchange treatment under the conditions specified in the table to obtain chemically strengthened crystalline glass.

[0153] Example 13

[0154] The batch of raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then drawn into shape and slowly cooled to produce 900×1200mm crystalline glass. The thickness was as described in the table. This crystalline glass was then sheeted into desired sizes such as 50mm×50mm and heat-treated at the temperature and time described in the table to obtain crystalline glass. The crystalline glass was then subjected to ion exchange treatment under the conditions described in the table to obtain chemically strengthened crystalline glass.

[0155] Example 14

[0156] The batch raw materials prepared according to the compositions of Examples 7-48 were fed into a melting furnace and melted at 1500-1600°C. The molten glass preform was then drawn into shape and slowly cooled to produce 900×1200mm crystalline glass. The thickness is as described in the table. The crystalline glass was heat-treated at the temperature and time described in the table to obtain crystalline glass, which was then single-sheeted into desired sizes such as 50mm×50mm. The crystalline glass was then subjected to ion exchange treatment under the conditions described in the table to obtain chemically strengthened crystalline glass.

[0157] Industrial practicality

[0158] The crystal glass of the present invention is suitable as a protective glass for touch panel displays in mobile phones, digital cameras, PDAs (portable devices), etc. In addition to these applications, the crystal glass of the present invention is also expected to be used in applications requiring high Vickers hardness and transparency, such as window glass, disk substrates, flat panel display substrates, protective glass for solar cells, and protective glass for solid-state imaging elements.

Claims

1. A crystal glass, characterized in that, By mass%, it contains: SiO2 58~70%, Al2O3 15~30%, Li2O 2~10%, Na2O 0~10%, K2O 0~10%, Na2O+K2O 0~15%, MgO+CaO+SrO+BaO+ZnO 0~15%, SnO2 0.1~6%, ZrO2 0.5~6%, TiO2 0~4%, P2O5 0~6%. The crystalline glass precipitates zirconium oxide crystals as the main crystals. The crystallinity of the crystallized glass is less than 40%. The crystalline glass has an average visible light transmittance of over 50% when the thickness is 0.8 mm and the wavelength is 380~780 nm. The crystalline glass has a compressive stress layer formed on its surface.

2. The crystal glass according to claim 1, characterized in that, The crystal glass does not actually contain As2O3 or PbO.

3. The crystal glass according to claim 1, characterized in that, The crystalline glass also contains one or more crystals selected from β-nepheline solid solution and β-spodumene solid solution.

4. The crystal glass according to claim 2, characterized in that, The crystalline glass also contains one or more crystals selected from β-nepheline solid solution and β-spodumene solid solution.

5. The crystal glass according to any one of claims 1 to 4, characterized in that, The average crystallite size of the crystallized glass is less than 1 μm.

6. The crystal glass according to any one of claims 1 to 4, characterized in that, The Vickers hardness value of the crystal glass is 540 or higher.

7. The crystal glass according to any one of claims 1 to 4, characterized in that, The flexural strength of the crystal glass is above 100 MPa, and the drop height is above 5 mm.

8. The crystal glass according to any one of claims 1 to 4, characterized in that, The coefficient of thermal expansion of the crystal glass at 30~380℃ is 0~120×10⁻⁶. -7 / ℃.

9. The crystal glass according to any one of claims 1 to 4, characterized in that, The Young's modulus of the crystal glass is above 80 GPa.

10. A method for preparing a crystal glass, characterized in that, include: The process of preparing crystallized glass, wherein the crystallized glass contains, by mass percent: SiO2 58~70%, Al2O3 15~30%, Li2O2~10%, Na2O 0~10%, K2O 0~10%, Na2O+K2O 0~15%, MgO+CaO+SrO+BaO+ZnO 0~15%, SnO2 0.1~6%, ZrO2 0.5~6%, TiO2 0~4%, P2O5 0~6%, and precipitates zirconium oxide crystals as the main crystals, with a crystallinity of less than 40%; and The process of immersing the crystal glass in molten salt at a temperature above 400°C to obtain crystal glass with a compressive stress layer on its surface.

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