Glass-ceramics and tempered glass-ceramics

Abstract

To obtain a crystallized glass and a reinforced crystallized glass, comprising a novel composition and having a high refractive index and a high hardness.SOLUTION: The crystallized glass contains, in percentages by mass in terms of oxides, 20.0% or more but less than 40.0% of an SiO2 component, over 0% and at most 20.0% of an Rn2O component (provided that Rn is one or more selected from Li, Na, and K), 7.0% to 25.0% of an Al2O3 component, 0% to 25.0% of an MgO component, 0% to 45.0% of a ZnO component, and 0% to 20.0% of a Ta2O5 component, the total amount of the MgO component, the ZnO component, and the Ta2O5 component being 10.0% or greater.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a glass-ceramic and a strengthened glass-ceramic having a compressive stress layer.

[0002] Cover glass is used to protect the displays of mobile electronic devices such as smartphones and tablet PCs. Protectors are also used to protect lenses in automotive optical devices. Furthermore, in recent years, there has been a growing demand for glass to be used in the exterior housings of electronic devices. Therefore, there is a growing demand for materials with high hardness so that these devices can withstand the harsh conditions of use.

[0003] Glass-ceramics, which have increased strength, are glass-ceramics made by precipitating crystals inside the glass, and are known to have superior mechanical strength to amorphous glass.

[0004] Chemical strengthening is also known as a method for increasing the strength of glass. By exchanging alkali components present in the surface layer of glass with alkali components having a larger ionic radius, a compressive stress layer is formed in the surface layer, which suppresses crack propagation and increases mechanical strength.

[0005] Patent Documents 1 and 2 disclose high-strength crystallized glasses and crystallized glasses obtained by chemically strengthening these glasses. However, to further expand the applications of glasses as optical components, there has been a demand for crystallized glasses that have a high refractive index in addition to hardness. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2011-207626 [Patent Document 2] Patent Publication No. 2017-001937 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a glass-ceramic having a novel composition, a high refractive index, and high hardness, and a tempered glass-ceramic.

[0008] The present invention provides the following: (Configuration 1) In terms of oxide, mass % SiO2 content of 20.0% or more and less than 40.0% Rn2O component is more than 0% and 20.0% or less (where Rn is one or more selected from Li, Na, and K), Al2O3 component 7.0% to 25.0%, MgO content: 0% to 25.0% ZnO content: 0% to 45.0% Ta2O5 component 0% to 20.0%, Contains Glass-ceramics in which the total amount of MgO, ZnO and Ta2O5 components is 10.0% or more. (Configuration 2) In terms of oxide, mass % TiO2 content: 0% to 15.0% CaO content: 0% to 15.0% BaO content: 0% to 15.0% 2. The crystallized glass according to claim 1, containing 0% to 10.0% of an SrO component. (Configuration 3) In terms of oxide, mass % ZrO2 content: 0% to 10.0% WO3 component 0% to 10.0%, La2O3 component 0 to 10.0%, Gd2O3 component 0 to 15.0%, Bi2O3 content: 0 to 15.0% P2O5 component 0 to 10.0%, Nb2O5 component 0 to 10.0%, 3. The crystallized glass according to claim 1, which contains 0 to 5.0% of an Sb2O3 component. (Configuration 4) 4. The crystallized glass according to any one of aspects 1 to 3, wherein the total amount of the MgO component, the ZnO component, and the Ta2O5 component is 18.0% or more. (Configuration 5) Refractive index (n d 5. The crystallized glass according to any one of aspects 1 to 4, wherein the value of σ is 1.55 or more. (Configuration 6) 6. The crystallized glass according to any one of aspects 1 to 5, having a specific gravity of 3.0 or more. (Configuration 7) 7. A tempered glass-ceramic having the glass-ceramic according to any one of configurations 1 to 6 as a base material and having a compressive stress layer on the surface. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a high refractive index, high hardness crystallized glass and a tempered crystallized glass having a novel composition.

[0010] The crystallized glass or tempered crystallized glass of the present invention can be used as optical components (lenses, substrates, etc.) for smartphones, tablets, PC cover glass, housings, filters, cameras, etc. Specific examples include automotive lenses, lenses for short-focus projectors, wearable devices, decorative items (vehicles, buildings, smart keys, etc.), touch panels, and dielectric filters. The high refractive index facilitates compactness, while the high strength facilitates thin film and lightweight design. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments and examples of the present invention will be described in detail, but the present invention is not limited to the following embodiments and examples in any way, and can be practiced with appropriate modifications within the scope of the object of the present invention.

[0012] In this specification, the content of each component is expressed in mass% converted to oxide unless otherwise specified. Here, "oxide conversion" refers to the amount of oxide of each component contained in the crystallized glass, expressed in mass%, when the total mass of the oxides is 100 mass%, assuming that all the components constituting the crystallized glass are decomposed and converted to oxides. In this specification, A to B% means A% or more and B% or less. Also, 0% in 0% to C% means that the content is 0%.

[0013] The crystallized glass of the present invention is SiO2 content of 20.0% or more and less than 40.0% Rn2O component is more than 0% and 20.0% or less (where Rn is one or more selected from Li, Na, and K), Al2O3 component 7.0% to 25.0%, MgO content: 0% to 25.0% ZnO content: 0% to 45.0% Ta2O5 component 0% to 20.0%, Contains The total amount of the MgO component, the ZnO component, and the Ta2O5 component is 10.0% or more.

[0014] Generally, when the amount of SiO2, a glass-forming component, is small and the amount of crystal-forming components such as ZnO is large, vitrification tends to become difficult. However, according to the present invention, crystallized glass can be obtained with the above composition. Furthermore, the crystallized glass of the present invention has a high refractive index because it contains predetermined amounts of components that increase the refractive index, such as ZnO, MgO, and Ta2O5. That is, the above composition makes it possible to obtain a hard crystallized glass having a high refractive index. Furthermore, chemical strengthening can be performed to further increase hardness.

[0015] Glass-ceramics, also known as glass ceramics, are materials in which crystals are precipitated inside the glass by heat-treating the glass. Glass-ceramics are materials that have both crystalline and glass phases, and are distinct from amorphous solids. The crystalline phase of glass-ceramics is generally determined by the angle of the peaks that appear in the X-ray diffraction pattern of X-ray diffraction analysis.

[0016] The crystallized glass of the present invention may contain, for example, ZnAl2O4, Zn2Ti3O8, Zn2SiO4, ZnTiO3, Mg2SiO4, Mg2Al4Si5O as the main crystalline phase. 18 , NaAlSiO4, Na2Zn3SiO4, Na4Al2Si2O9, LaTiO3 and solid solutions thereof. In this specification, the "main crystalline phase" corresponds to the crystalline phase that is most abundant in the glass-ceramics, as determined from the peaks in the X-ray diffraction pattern.

[0017] The SiO2 component is an essential glass-forming component that forms the network structure of glass. However, if the SiO2 component is insufficient, the resulting glass will have poor chemical durability and poor resistance to devitrification. Therefore, the upper limit of the SiO2 content can be less than 40.0%, 39.0% or less, 37.0% or less, or 35.0% or less, and the lower limit of the SiO2 content can be 20.0% or more, 23.0% or more, 25.0% or more, or 30.0% or more.

[0018] The RnO component (Rn is one or more selected from Li, Na, and K) is a component that participates in ion exchange during chemical strengthening, but if contained in excess, it is a component that deteriorates chemical durability and devitrification resistance. Therefore, the upper limit of the RnO content can be 20.0% or less, 18.0% or less, 15.0% or less, or 14.0% or less, and the lower limit of the RnO content can be more than 0%, 2.0% or more, 4.0% or more, or 6.0% or more.

[0019] In particular, the NaO component is a potassium component (K +ions) and the sodium component with a small ionic radius in the substrate (Na + As an exchange reaction with silicon ions proceeds, compressive stress is formed on the surface of the substrate, so it is preferable that silicon ions be included as an essential component. Therefore, the upper limit of the Na2O content can be 20.0% or less, 18.0% or less, 15.0% or less, or 14.0% or less, and the lower limit of the Na2O content can be more than 0%, 2.0% or more, 4.0% or more, or 6.0% or more.

[0020] The Al2O3 component is a component suitable for improving mechanical strength, but if contained in excess, it deteriorates meltability and devitrification resistance. Therefore, the upper limit of the Al2O3 content can be 25.0% or less, 23.0% or less, 22.0% or less, or 20.0% or less, and the lower limit of the Al2O3 content can be 7.0% or more, 9.0% or more, 10.0% or more, or 11.0% or more.

[0021] The MgO component increases the refractive index and contributes to mechanical strength, but if contained in excess, it deteriorates resistance to devitrification. Therefore, the upper limit of the MgO content can be 25.0% or less, 22.0% or less, 20.0% or less, 18.0% or less, or 15.0% or less, and the lower limit of the MgO content can be 0% or more, 1.0% or more, 1.5% or more, or 2.0% or more.

[0022] ZnO is a component that not only increases the refractive index and contributes to mechanical strength, but is also effective in lowering the viscosity of the glass, but if contained in excess, it deteriorates the devitrification resistance. Therefore, the upper limit of the ZnO content can be 45.0% or less, 40.0% or less, 38.0% or less, or 25.0% or less, and the lower limit of the ZnO content can be 0% or more, 2.0% or more, 5.0% or more, 8.0% or more, or 10.0% or more.

[0023] The Ta2O5 component is a component that increases the refractive index, but when contained in excess, it also deteriorates the resistance to devitrification. Therefore, the upper limit of the content of the Ta2O5 component can be set to 20.0% or less, 19.0% or less, 17.0% or less, or 15.0% or less. The lower limit of the Ta2O5 content can be 0% or more, 1.0% or more, 3.0% or more, or 5.0% or more. Furthermore, the lower limit of the Ta2O5 content can be more than 5.0 mol% or 5.5 mol% or more.

[0024] A high refractive index can be obtained by adjusting the total amount of the MgO component, ZnO component, and Ta2O5 component, but if they are contained in excess, the devitrification resistance of the glass deteriorates. Therefore, the lower limit of the total amount of MgO, ZnO, and Ta2O5 components can be preferably 10.0% or more, 15.0% or more, 18.0% or more, or 20.0% or more, and the upper limit of the total amount of MgO, ZnO, and Ta2O5 components can be preferably 45.0% or less, 40.0% or less, or 38.0% or less.

[0025] A high refractive index can be obtained by adjusting the total amount of ZnO and Ta2O5 components, but if they are contained in excess, the devitrification resistance of the glass deteriorates. Therefore, the lower limit of the total amount of the ZnO component and the Ta2O5 component can be preferably 5.0% or more, 8.0% or more, or 10.0% or more, and the upper limit of the total amount of the ZnO component and the Ta2O5 component can be preferably 35.0% or less, 30.0% or less, or 28.0% or less.

[0026] The TiO2 component is a nucleating agent for crystallization and a component that contributes to increasing the refractive index. Therefore, the content of the TiO2 component can be preferably set to 0% to 15.0%, more preferably 1.0% to 13.0%, and even more preferably 2.0% to 10.0%.

[0027] The CaO component, the BaO component, and the SrO component are components that contribute to improving the refractive index and stabilizing the glass. Therefore, the content of the CaO component can be preferably set to 0% to 15.0%, more preferably 0.1% to 13.0%, and even more preferably 0.5% to 10.0%. The content of the BaO component can be set to preferably 0% to 15.0%, more preferably 0% to 13.0%, and even more preferably 0% to 12.0%. The content of the SrO component can be set to preferably 0% to 10.0%, more preferably 0% to 8.0%, and even more preferably 0% to 7.0%.

[0028] The glass-ceramics may or may not contain ZrO2, WO3, La2O3, P2O5, or Nb2O5 components. The content of each component can be 0 to 10.0%, 0 to 8.0%, or 0 to 7.0%.

[0029] The crystallized glass may or may not contain a Gd2O3 component and a Bi2O3 component, and the content of each component can be 0 to 15.0%, 0 to 13.0%, or 0 to 10.0%.

[0030] The glass-ceramics may or may not contain B2O3, Y2O3, and TeO2 components. The content of each component can be 0% to 2.0%, 0% or more and less than 2.0%, or 0% to 1.0%.

[0031] The crystallized glass may contain, as a fining agent, one or more selected from the group consisting of Sb2O3, SnO2 and CeO2 components in an amount of 0% to 5.0%, preferably 0.03% to 2.0%, and more preferably 0.05% to 1.0%.

[0032] The above blending amounts can be combined as appropriate.

[0033] By adjusting the total content of SiO2, Rn2O, Al2O3, MgO, ZnO, and Ta2O5, it is possible to obtain glass that contains one or more crystal phases selected from RAl2O4 and R2SiO4 (where R is one or more selected from Zn and Mg), while also enabling chemical strengthening by ion exchange. At the same time, it is possible to obtain glass that has excellent mechanical strength and a high refractive index. Therefore, the lower limit of the mass sum of SiO2+Rn2O+Al2O3+MgO+ZnO+Ta2O5 can be set to 70.0% or more, 75.0% or more, 80.0% or more, or 85.0% or more.

[0034] The crystallized glass of the present invention has a high refractive index (n d Preferably, the lower limit of the refractive index is 1.55 or more, 1.58 or more, 1.60 or more, or 1.61 or more. Usually, the upper limit of the refractive index is 1.65 or less.

[0035] The crystallized glass of the present invention has a high Vickers hardness. Usually, the lower limit of the Vickers hardness is 500 or more, preferably 600 or more, and more preferably 700 or more. Usually, the upper limit of the Vickers hardness is 800 or less. Furthermore, crystallized glass strengthened by chemical strengthening or the like has an even higher hardness, with some having a hardness of 800 to 900.

[0036] The crystallized glass of the present invention usually has a high specific gravity, with the lower limit of the specific gravity being 2.95 or more, or 3.00 or more, and the upper limit of the specific gravity being 3.40 or less.

[0037] The crystallized glass of the present invention can be produced by the following method. That is, raw materials are uniformly mixed and melt-molded to produce a base glass. This base glass is then crystallized to produce a crystallized glass. Furthermore, the crystallized glass may be used as a base material to form a compressive stress layer and be strengthened.

[0038] The raw glass is heat-treated to precipitate crystals inside the glass. This heat treatment can be performed at one temperature or two temperatures. In the two-stage heat treatment, a nucleation step is first performed by heat treatment at a first temperature, and after this nucleation step, a crystal growth step is performed by heat treatment at a second temperature higher than that of the nucleation step. In one-stage heat treatment, the nucleation process and the crystal growth process are carried out consecutively at a single temperature. Typically, the temperature is raised to a predetermined heat treatment temperature, and after reaching that temperature, the temperature is maintained for a certain period of time, and then the temperature is lowered. The first temperature of the two-stage heat treatment is preferably 600° C. to 750° C. The holding time at the first temperature is preferably 30 minutes to 2000 minutes, more preferably 180 minutes to 1440 minutes. The second temperature of the two-stage heat treatment is preferably 650° C. to 850° C. The holding time at the second temperature is preferably 30 minutes to 600 minutes, more preferably 60 minutes to 300 minutes. When heat treatment is performed at one temperature step, the heat treatment temperature is preferably 600 to 800° C., more preferably 630 to 770° C. The holding time at the heat treatment temperature is preferably 30 to 500 minutes, more preferably 60 to 300 minutes.

[0039] When chemically strengthening a substrate, typically, a thin plate of crystallized glass is produced from the crystallized glass by, for example, grinding and polishing, and then a compressive stress layer is formed on the crystallized glass substrate by ion exchange using a chemical strengthening method.

[0040] Methods for forming a compressive stress layer include a chemical strengthening method in which an alkali component present in the surface layer of crystallized glass is subjected to an exchange reaction with an alkali component having a larger ionic radius to form a compressive stress layer in the surface layer, a thermal strengthening method in which crystallized glass is heated and then rapidly cooled, and an ion implantation method in which ions are implanted into the surface layer of crystallized glass.

[0041] The chemical strengthening method can be carried out, for example, by the following steps: The crystallized glass base material is brought into contact with or immersed in a molten salt of a salt containing potassium or sodium, such as potassium nitrate (KNO3), sodium nitrate (NaNO3), or a mixed or composite salt thereof. This treatment of contacting or immersing in the molten salt (chemical strengthening treatment) may be carried out in one step or two steps.

[0042] For example, in the case of a two-stage chemical strengthening treatment, first, the steel is contacted with or immersed in sodium salt or a mixed salt of potassium and sodium heated at 350°C to 550°C for 1 to 1440 minutes, preferably 90 to 800 minutes, followed by second, the steel is contacted with or immersed in potassium salt or a mixed salt of potassium and sodium heated at 350°C to 550°C for 1 to 1440 minutes, preferably 60 to 800 minutes. In the case of one-stage chemical strengthening treatment, the material is contacted with or immersed in a salt containing potassium or sodium or a mixed salt thereof heated at 350°C to 550°C for 1 to 1440 minutes, preferably 60 to 800 minutes.

[0043] The thermal strengthening method is not particularly limited, but for example, by heating a crystallized glass base material to 300°C to 600°C and then rapidly cooling it by water cooling and / or air cooling, a compressive stress layer can be formed due to the temperature difference between the surface and the interior of the glass substrate. Note that by combining this with the above-mentioned chemical treatment method, the compressive stress layer can be formed more effectively.

[0044] The ion implantation method is not particularly limited, but for example, ions are implanted into the surface of the crystallized glass base material by bombarding the surface of the base material with an acceleration energy and acceleration voltage that are not enough to destroy the surface of the base material. By subsequently performing heat treatment as necessary, a compressive stress layer can be formed on the surface as with other methods. [Example]

[0045] Examples 1 to 35 1. Manufacturing of crystallized glass As raw materials for each component of the crystallized glass, raw materials such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, chlorides, metaphosphate compounds, etc. were selected, and these raw materials were weighed out to obtain the compositions (mass%) shown in Tables 1 to 4 and mixed uniformly.

[0046] Next, the mixed raw materials were placed in a platinum crucible and melted in an electric furnace at 1300-1600°C for 2-24 hours depending on the melting difficulty of the glass composition. The molten glass was then stirred to homogenize it, and the temperature was lowered to 1000-1450°C before being poured into a mold and slowly cooled to produce base glass. The resulting base glass was then heated to 730°C to crystallize it.

[0047] The glass-ceramics thus prepared were cut and ground, and then polished parallel to each other to a thickness of 1 mm to obtain a glass-ceramics substrate. The glass-ceramics substrate was then immersed in a molten salt of KNO3 at 420°C for 500 minutes to obtain a tempered glass-ceramics substrate.

[0048] 2. Evaluation of glass-ceramics The obtained crystallized glass and strengthened crystallized glass were measured for the following physical properties. The results are shown in Tables 1 to 4.

[0049] (1) Refractive index (n d ) Refractive index (n d ) is shown as a measurement value for the d-line (587.56 nm) of a helium lamp in accordance with the V-block method specified in JIS B 7071-2:2018.

[0050] (2) Specific gravity (d) Measurement was performed by the Archimedes method.

[0051] (3) Vickers hardness (Hv) A 136° diamond pyramidal indenter was pressed with a load of 980.7 mN for 10 seconds, and the surface area (mm ) was calculated from the length of the indentation. 2 The hardness was measured using a micro Vickers hardness tester HMV-G manufactured by Shimadzu Corporation.

[0052] (4) Stress measurement For the tempered crystallized glasses of Examples 3, 5, 6, 13, and 20, the surface compressive stress value (CS) and the thickness of the compressive stress layer (stress depth DOLzero) were measured using a glass surface stress meter FSM-6000LE series manufactured by Orihara Manufacturing Co., Ltd. The light source used in the CS measurement was a light source with a wavelength of 596 nm. The refractive index used in the CS measurement was the refractive index value at 596 nm. The refractive index value at a wavelength of 596 nm was calculated using a quadratic approximation formula from the measured refractive index values ​​at the wavelengths of C-line, d-line, F-line, and g-line in accordance with the V-block method specified in JIS B 7071-2:2018. The central compressive stress value (CT) was determined by curve analysis.

[0053] (4) Photoelastic constant (β) The photoelastic constant β (nm / cm / 10 5 The values ​​of the photoelastic constant (Pa) used were those shown in Tables 1 to 4. The photoelastic constant at 596 nm was used for the CS measurement. The photoelastic constant was measured by polishing the specimen on both sides to form a disk with a diameter of 25 mm and a thickness of 8 mm, applying a compressive load of 0 to approximately 100 kgf to the side, measuring the optical path difference at the center of the glass, and calculating it using the relational expression δ = β d F. In the above expression, the optical path difference is expressed as δ (nm), the glass thickness as d (cm), and the stress as F (MPa).

[0054] In addition, the refractive index of Examples 11, 14, 23, 24, 26 to 30 could not be measured because they were devitrified due to the high crystallization temperature. As shown in Tables 1 to 4, the Vickers hardness increased due to chemical strengthening, so a compressive stress layer was formed. Example 29 broke into pieces in the salt bath and could not be chemically strengthened.

[0055] Example 36 Crystallized glass was produced in the same manner as in Example 24, except that the crystallization temperature was set to 680°C. The refractive index was measured without devitrification. The refractive index was 1.63, the specific gravity was 3.16, and the Vickers hardness was 755.

[0056] Example 37 Glass-ceramics were produced in the same manner as in Example 26, except that the crystallization temperature was set to 700°C. The refractive index was measured without devitrification. The refractive index was 1.63 and the specific gravity was 3.18.

[0057] Example 38 Except for the crystallization temperature being 760°C, crystallized glass and strengthened crystallized glass were prepared in the same manner as in Example 2. The refractive index of the crystallized glass was 1.60, the specific gravity was 3.05, and the Vickers hardness was 682, and the Vickers hardness of the strengthened crystallized glass was 803.

[0058] Example 39 Except for the crystallization temperature being 760° C., crystallized glass and strengthened crystallized glass were prepared in the same manner as in Examples 7 and 8. The specific gravities of the crystallized glass were 3.17 and 3.15, respectively, and the Vickers hardness of the strengthened crystallized glass was 815 and 834, respectively.

[0059] Comparative Example 1 As Comparative Example 1, the crystallized glass of Example 26 of Patent Document 2 was used and evaluated in the same manner as in the Examples. The results are shown in Table 4.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4]

Claims

1. In terms of oxide, mass % SiO ２ Ingredients: 20.0% or more but less than 40.0% Rn ２ O component is 6% or more and 20.0% or less (wherein Rn is one or more selected from Li, Na, and K), Al ２ O ３ Ingredients: 7.0% to 25.0%, MgO component: 0% to 25.0% ZnO component: 0% to 45.0% Ta ２ O ５ Ingredients: 0% to 20.0%, Na ２ O component 6% to 20.0%, Contains MgO component, ZnO component and Ta ２ O ５ The total amount of the components is 10.0% or more, The refractive index (nd) is 1.55 or more, A crystallized glass having a Vickers hardness of 500 or more.

2. In terms of oxide, mass % TiO ２ Ingredients: 0% to 15.0%, CaO content: 0% to 15.0% BaO component: 0% to 15.0% 2. The crystallized glass according to claim 1, containing 0 to 10.0% of an SrO component.

3. In terms of oxide, mass % ZrO ２ Ingredients: 0% to 10.0%, WO ３ Ingredients: 0% to 10.0%, La ２ O ３ Ingredients: 0-10.0%, Gd ２ O ３ Ingredients: 0-15.0%, Bi ２ O ３ Ingredients: 0-15.0%, P ２ O ５ Ingredients: 0-10.0%, Nb ２ O ５ Ingredients: 0-10.0%, Sb ２ O ３ 3. The crystallized glass according to claim 1, containing 0 to 5.0% of the component.

4. The MgO component, the ZnO component, and the Ta ２ O ５ 4. The crystallized glass according to claim 1, wherein the total amount of the components is 18.0% or more.

5. 5. The crystallized glass according to claim 1, which has a specific gravity of 3.0 or more.

6. 6. A strengthened glass-ceramic having the glass-ceramic of claim 1 as a base material and having a compressive stress layer on the surface.

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