Chemically strengthened glass made from crystallized glass and method for manufacturing the same

Abstract

The present invention relates to a chemically-strengthened glass having a first main surface and a second main surface that face each other, comprising a crystallized glass that contains crystals and residual glass, and having a CS0 of 450 MPa or greater and a CS50 of 150 MPa or greater. The chemically-strengthened glass has, on the first main surface and the second main surface, a plurality of non-through holes having a diameter average value of 5-50 nm, the depth average value of the non-through holes measured by using a cross-section SEM image of the first main surface and second main surface is 5-50 nm, and the total area ratio of the non-through holes with respect to the whole visual field area in a surface SEM image of the first main surface and second main surface is 1-40%.

Description

[Technical Field]

[0001] This invention relates to chemically strengthened crystallized glass and a method for producing the same. [Background technology]

[0002] Chemically strengthened glass is used for the cover glass of mobile devices, etc. Chemically strengthened glass is made by, for example, contacting glass with a molten salt containing alkali metal ions, causing ion exchange between the alkali metal ions in the glass and the alkali metal ions in the molten salt, and forming a compressive stress layer on the glass surface.

[0003] Amorphous glass containing Li2O or crystallized glass containing Li2O are particularly excellent as base materials for such chemically strengthened glass. This is because ion exchange between lithium ions in the base material and sodium ions in the strengthening salt easily forms compressive stress deep within the chemically strengthened glass. Since lithium ions and sodium ions have relatively small ionic radii, the diffusion coefficient due to ion exchange is large. In addition, amorphous glass and crystallized glass containing Li2O tend to have relatively high fracture toughness and are less prone to cracking.

[0004] Crystallized glass is made by precipitating crystals within the glass, making it harder and more scratch-resistant than amorphous glass, which does not contain crystals. Furthermore, chemically strengthened crystallized glass can be made stronger while preventing shattering compared to amorphous glass. However, crystallized glass often has less transparency than amorphous glass.

[0005] Patent documents 1 and 2 describe examples of chemically strengthening crystallized glass by ion exchange treatment. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2019 / 022035 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0017398 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Although the chemically strengthened glass made from crystallized glass described in Patent Documents 1 and 2 has excellent transparency and chemical strengthening properties, its transparency may be insufficient in some cases.

[0008] Therefore, the present invention aims to provide a chemically strengthened glass made of crystallized glass that is excellent in transparency and chemical strengthening properties. [Means for solving the problem]

[0009] As a result of examining the above problems, the inventors of the present invention have found that chemically strengthened glass made of crystallized glass, having a plurality of non-penetrating holes on both main surfaces, and in which the average diameter, average depth, and total area ratio of the non-penetrating holes are within a specific range, exhibits excellent transparency and chemical strengthening properties, and have completed the present invention.

[0010] The present invention relates to a chemically strengthened glass having opposing first and second main surfaces, comprising crystallized glass containing crystals and residual glass, having a surface compressive stress value (CS0) of 450 MPa or more, and a compressive stress value (CS0) at a depth of 50 μm from the surface. 50 The present invention relates to a chemically strengthened glass having a pressure of 150 MPa or more, having a plurality of non-through holes with an average diameter of 5 to 50 nm on the first main surface and the second main surface, having an average depth of 5 to 50 nm on the cross-sectional SEM images of the first main surface and the second main surface, and having a total area ratio of the non-through holes to the total field of view of the surface SEM images on the first main surface and the second main surface of 1 to 40%.

[0011] In this chemically strengthened glass, when the etching rate of the residual glass is defined as Eg and the etching rate of the crystal is defined as Ec, it is preferable that Eg / Ec is 0.1 to 0.0001.

[0012] It is preferable that this chemically strengthened glass contains 40 to 70% of SiO2, 5 to 35% of Li2O, and 1 to 20% of Al2O3 in terms of mol% based on the oxide-based mother composition.

[0013] It is preferable that the crystallization rate of this chemically strengthened glass is 10 to 90% by mass.

[0014] It is preferable that the reflectance of this chemically strengthened glass on the first main surface and the second main surface is 10% or less.

[0015] It is preferable that the light transmittance of this chemically strengthened glass in terms of a thickness of 700 μm before chemical strengthening is 90% or more.

[0016] It is preferable that the plate thickness of this chemically strengthened glass is 300 to 3000 μm.

[0017] The present invention also relates to a method for manufacturing a chemically strengthened glass, which includes chemically strengthening a crystallized glass containing crystals and residual glass, and after the chemical strengthening, cleaning the surface of the crystallized glass using a cleaning liquid with a pH of 2 to 12. The chemically strengthened glass has opposite first and second main surfaces, a surface compressive stress value (CS0) of 450 MPa or more, and a compressive stress value (CS 50 ) of 150 MPa or more at a depth of 50 μm from the surface, has a plurality of non-penetrating holes with an average diameter of 5 to 50 nm on the first main surface and the second main surface, the average depth of the non-penetrating holes measured by a cross-sectional SEM image of the first main surface and the second main surface is 5 to 50 nm, and the total area ratio of the non-penetrating holes to the total viewing area of the surface SEM image on the first main surface and the second main surface is 1 to 40%.

[0018] In the method for manufacturing chemically strengthened glass, when the etching rate of the residual glass is Eg and the etching rate of the crystal is Ec, it is preferable that Eg / Ec is 0.1 to 0.0001.

[0019] In the method for producing this chemically strengthened glass, it is preferable that the crystallized glass has a matrix composition expressed in mole percent based on oxides, containing 40-70% SiO2, 5-35% Li2O, and 1-20% Al2O3. [Effects of the Invention]

[0020] The chemically strengthened glass of the present invention has multiple non-penetrating holes on both main surfaces, and is a crystallized glass in which the average diameter, average depth, and total area ratio of these non-penetrating holes are within a specific range. As a result, reflectivity is suppressed, exhibiting excellent transparency and achieving high chemical strengthening properties. [Brief explanation of the drawing]

[0021] [Figure 1] Figures 1(a) to (c) show examples of surface SEM images. (a) shows an example of the chemically strengthened glass of the present invention, and (b) shows an example of conventional chemically strengthened glass. (c) is a magnified view of the area enclosed by the dotted line in (a). [Figure 2] Figure 2 is a conceptual partial cross-sectional view showing the surface layer of one of the main surfaces in one embodiment of the present invention. [Figure 3] Figures 3(a) and 3(b) show examples of cross-sectional SEM images of the chemically strengthened glass of the present invention. [Modes for carrying out the invention]

[0022] In this specification, the "~" indicating a numerical range means, unless otherwise specified, that the numbers before and after it are included as the lower and upper limits, respectively.

[0023] In this specification, "amorphous glass" refers to glass in which no diffraction peaks indicating crystals are observed by the powder X-ray diffraction method described later. "Crystallized glass" is obtained by heat-treating "amorphous glass" to precipitate crystals, and therefore contains crystals. In this specification, "amorphous glass" and "crystallized glass" are sometimes collectively referred to as "glass." Furthermore, amorphous glass that becomes crystallized glass through heat treatment is sometimes referred to as "the mother glass of crystallized glass."

[0024] In this specification, powder X-ray diffraction measurements are performed using, for example, CuKα rays in the range of 2θ from 10° to 80°. If diffraction peaks appear, precipitated crystals are identified by the Hanawalt method. The crystal identified from the group of peaks containing the highest integrated intensity among the crystals identified by this method is designated as the principal crystal. As a measurement device, for example, a SmartLab manufactured by Rigaku Corporation can be used.

[0025] In this specification, "residual glass" refers to the amorphous portion of crystallized glass that has not crystallized.

[0026] In this specification, the diameter of non-through holes in chemically strengthened glass is determined by the following method: Non-through holes on the surface of the chemically strengthened glass are observed in a plan view from directly above the first and second principal surfaces using a scanning electron microscope (SEM), and surface SEM images at 100,000x magnification are obtained. From the obtained surface SEM images, non-through holes and matrix portions (parts without non-through holes) are distinguished, the major axis of each non-through hole is determined as the diameter, and the average diameter is calculated.

[0027] Specifically, for example, in Figure 1(a), the gray areas represent matrix portions without through-holes, while the black areas represent non-through-holes. Figure 1(c) is a magnified view of the area enclosed by the dotted line in (a), and the length of the area indicated by the white double arrow is an example of the diameter of a non-through-hole.

[0028] In this specification, the total area ratio of non-penetrating holes in chemically strengthened glass is determined by the following method: The surface of the chemically strengthened glass is observed using a SEM in a planar view, and a surface SEM image at 100,000x magnification is obtained. From the obtained surface SEM image, non-penetrating holes and matrix portions are distinguished, and the ratio of the total area of ​​non-penetrating holes to the total field of view area of ​​the surface SEM image is determined and defined as the total area ratio of non-penetrating holes.

[0029] In this specification, the depth of a non-through hole is determined by the following method: A cross-sectional SEM image at 300,000x magnification is obtained on the fracture surface of the chemically strengthened glass. In the obtained cross-sectional SEM image, the non-through holes and the matrix portion are distinguished, the depth of each non-through hole is determined, and the average depth is calculated as the average value. Specifically, in Figure 3(a), the length of the portion indicated by the black double arrow is an example of the depth of a non-through hole.

[0030] In this specification, the "etching rate" (unit: nm / min) is determined by measuring the weight loss (nm) per minute (1 minute) due to the etching process. The conditions for measuring the etching rate ratio are not particularly limited, as long as the desired etching rate ratio can be obtained, but specifically, for example, conditions such as pH 2 to 12 and room temperature (15°C) to 100°C are usually used. Furthermore, the etching solution used in the etching process is not particularly limited, but specifically, for example, NaOH and HCl are used.

[0031] In the following, "chemically strengthened glass" refers to glass that has undergone chemical strengthening treatment, and "glass for chemical strengthening" refers to glass that has not undergone chemical strengthening treatment.

[0032] In this specification, glass composition is expressed in mole percent based on oxides unless otherwise specified, and mole percent is simply denoted as "%".

[0033] Furthermore, in this specification, "substantially absent" means that the amount is below the level of impurities present in the raw materials, etc., that is, not intentionally added. Specifically, for example, it means less than 0.1%.

[0034] In this specification, "stress profile" refers to a representation of compressive stress values ​​with respect to the depth from the glass surface. In the stress profile, tensile stress is represented as negative compressive stress.

[0035] The compressive stress value (CS) can be measured by thinning a cross-section of glass and analyzing the thinned sample using a birefringence imaging system. A birefringence imaging system birefringence stress meter is a device that measures the magnitude of retardation caused by stress using a polarizing microscope and a liquid crystal compensator, for example, the Abrio-IM birefringence imaging system manufactured by CRi.

[0036] Furthermore, measurements can sometimes be performed using scattered light photoelasticity. In this method, light is incident on the surface of the glass, and the polarization of the scattered light is analyzed to measure CS. An example of a stress measuring instrument that utilizes scattered light photoelasticity is the scattered light photoelasticity stress meter SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.

[0037] In this specification, "DOL (Depth of Compressive Stress)" is the depth at which the compressive stress value becomes zero. Below, the surface compressive stress value is CS0, and the compressive stress value at a depth of 50 μm is CS 50 It is sometimes written as, "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 the plate thickness t, and in this specification, "CS t / 2 This is equivalent to "[...]."

[0038] In this specification, "light transmittance" refers to the average transmittance for light with wavelengths of 380 nm to 780 nm. Furthermore, "haze value" is measured using a halogen lamp C light source in accordance with JIS K7136:2000.

[0039] In this specification, "reflectance" is defined in accordance with JIS Z8701 (1999). A D65 light source is used as the light source.

[0040] In this specification, the "fracture toughness value" is the value obtained by the IF method as defined in JIS R1607:2015.

[0041] In this specification, "drop strength" shall be measured by the following method. A 120 x 60 x 0.6 mm thick glass sample is fitted into a structure whose mass and rigidity are adjusted to match the size of a typical smartphone, creating a simulated smartphone. This simulated smartphone is then free-dropped onto #180 SiC sandpaper. The drop height is set to 5 cm. If the sample does not break, the height is increased by 5 cm and the drop is repeated until it breaks. The average of the heights at which the sample first broke (10 samples) is measured.

[0042] <Chemically strengthened glass> The chemically strengthened glass of the present invention (hereinafter also referred to as "this chemically strengthened glass") is typically a plate-shaped glass article, which may be flat or curved. It may also have portions with different thicknesses.

[0043] When the chemically strengthened glass is in plate form, its thickness (t) is preferably 3000 μm or less, and more preferably, in stages, 2000 μm or less, 1600 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, and 700 μm or less. Furthermore, in order to obtain sufficient strength through the chemical strengthening treatment, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and even more preferably 500 μm or more.

[0044] This chemically strengthened glass is preferable if its surface compressive stress (CS0) is 450 MPa or higher, as this makes it less prone to cracking due to deformation such as bending. A CS0 of 500 MPa or higher is more preferable, and 600 MPa or higher is even more preferable. While a higher CS0 increases strength, if it is too high, severe shattering may occur if it breaks, so a CS0 of 1100 MPa or lower is preferable, and 900 MPa or lower is more preferable.

[0045] This chemically strengthened glass has a compressive stress value (CS) at a depth of 50 μm from the surface. 50 A pressure of 150 MPa or higher is preferable because it helps to suppress the cracking of the chemically strengthened glass when a mobile device or the like equipped with this chemically strengthened glass as a cover glass is dropped.50 is preferably 180 MPa or more, more preferably 200 MPa or more. CS 50 The larger it is, the higher the strength, but if it is too large, there is a risk of intense crushing when it cracks, so 300 MPa or less is preferable, and 270 MPa or less is more preferable.

[0046] This chemically strengthened glass is preferably such that when DOL is 90 μm or more, even if scratches occur on the surface, it is difficult to crack. DOL is more preferably 95 μm or more, still more preferably 100 μm or more, and particularly preferably 110 μm or more. The larger DOL is, the more difficult it is to crack even if scratches occur, but in chemically strengthened glass, since tensile stress is generated inside according to the compressive stress formed near the surface, it cannot be extremely large. DOL is preferably t / 4 or less, more preferably t / 5 or less in the case of thickness t. DOL is preferably 200 μm or less, more preferably 180 μm or less in order to shorten the time required for chemical strengthening.

[0047] In this chemically strengthened glass, when the plate thickness is t, the compressive stress value CS at a depth of t / 2 from the surface t / 2 is preferably -120 MPa or more, more preferably -115 MPa or more, still more preferably -110 MPa or more. CS t / 2 When CS is -120 MPa or more, explosive cracking when the glass is damaged can be prevented. Also, CS t / 2 The upper limit of is not particularly limited, but in order to maintain sufficient compressive stress, for example, it is preferably -80 MPa or less.

[0048] When this chemically strengthened glass observes the first main surface and the second main surface from directly above by the above method, a plurality of non-through holes are recognized. A partial cross-sectional view conceptually showing an example of one main surface is shown in FIG. 2. As shown in FIG. 2, since the chemically strengthened glass 24 has non-through holes 22, irregularities are formed on the surface of the chemically strengthened glass made of crystallized glass, and due to the irregularities, the area ratio of the residual glass on the main surface of the chemically strengthened glass increases, and the refractive index decreases, so reflection on the surface of the chemically strengthened glass is suppressed, and the transmittance is improved.

[0049] The average diameter of non-through holes is preferably 5 to 50 nm, more preferably 8 to 40 nm, and even more preferably 10 to 30 nm. That is, the average diameter of non-through holes is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more. Furthermore, the average diameter of non-through holes is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. By having an average diameter of non-through holes of 5 nm or more, the reflectance on the main surface can be reduced and transparency can be improved. However, if the average diameter of non-through holes exceeds 50 nm, the depth of the holes approaches the wavelength of light, scattering increases and transmittance decreases.

[0050] In this chemically strengthened glass, the average depth of non-penetrating holes measured by cross-sectional SEM images on the first and second main surfaces is 5 to 50 nm, preferably 8 to 40 nm, and more preferably 10 to 30 nm. That is, the average depth of non-penetrating holes is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more. Furthermore, the average depth of non-penetrating holes is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. The deeper the average depth is than 5 nm, the more effectively the refractive index near the glass surface decreases, which can reduce reflectivity and improve transparency. On the other hand, if the average depth exceeds 50 nm, the average depth of non-penetrating holes approaches the wavelength of light, increasing scattering and reducing transmittance. The shape of the non-penetrating holes observed by cross-sectional SEM images is not particularly limited, and examples include circular, semicircular, rectangular, etc.

[0051] The total area ratio of non-through holes to the total field of view in the surface SEM image is 1 to 40%, preferably 1 to 30%, and more preferably 2 to 20%. That is, the total area ratio of non-through holes is preferably 1% or more, and more preferably 2% or more. Furthermore, the total area ratio of non-through holes is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. By having a total area ratio of non-through holes of 1% or more, the area ratio of glass on the main surface of the glass can be increased, reducing reflectivity and improving transparency. If the total area ratio of non-through holes exceeds 40%, surface scattering increases, and transmittance decreases.

[0052] The distribution of non-penetrating holes on the first and second main surfaces of this chemically strengthened glass is not particularly limited, but it is preferable that it be uniform from the viewpoint of improving transparency.

[0053] The chemically strengthened glass preferably has a reflectance of 10% or less on the first and second main surfaces, more preferably 9% or less, and even more preferably 8% or less. A reflectance of 10% or less on the first and second main surfaces results in excellent transparency. While there is no particular lower limit to the reflectance, it is typically 5% or higher.

[0054] The haze value of this chemically strengthened glass is preferably 1.0% or less, more preferably 0.8% or less, even more preferably 0.6% or less, particularly preferably 0.4% or less, and most preferably 0.2% or less, when the thickness is 700 μm. A smaller haze value is preferable, but it is usually 0.01% or more.

[0055] The chemically strengthened glass preferably has a drop strength of 160 cm or more, more preferably 170 cm or more, and even more preferably 180 cm or more, as measured by the method described above. A drop strength of 160 cm or more makes it easier to suppress the cracking of the chemically strengthened glass when a mobile device or the like equipped with this chemically strengthened glass as a cover glass is dropped. There is no particular upper limit to the drop strength, but it is typically 300 cm or less.

[0056] <<Composition>> The matrix composition of this chemically strengthened glass preferably contains SiO2, Li2O, and Al2O3. The matrix composition of this chemically strengthened glass is expressed in molar percentage based on oxides. SiO2 at 40-70%, Li2O 5-35%, It is more preferable to contain 1-20% Al2O3.

[0057] Also, SiO2 is 50-70%, Li2O at 10-30%, Al2O3 in a concentration of 1-15%, P2O5 at 0-5%, ZrO2 0-8%, MgO 0-10%, Y2O3 0-5% B2O3 at 0-10%, Na2O at 0-5%, K2O 0-5%, It is even more preferable to contain 0-2% SnO2.

[0058] Here, "matrix composition of chemically strengthened glass" refers to the composition of crystallized glass before chemical strengthening. This composition will be described later. The composition of this chemically strengthened glass is generally similar to that of crystallized glass before strengthening, except in cases where extreme ion exchange treatment has been performed. In particular, the composition of the deepest part from the glass surface is the same as that of crystallized glass before strengthening, except in cases where extreme ion exchange treatment has been performed.

[0059] <<Application>> This chemically strengthened glass is also useful as cover glass for electronic devices such as mobile phones and smartphones. Furthermore, it is useful as cover glass for electronic devices not intended for portability, such as televisions, personal computers, and touch panels, as well as for elevator walls and the walls (full-surface displays) of buildings such as houses and office buildings. It is also useful as building materials such as window glass, tabletops, interiors of automobiles and airplanes, and as cover glass for these, as well as for enclosures with curved shapes.

[0060] <Crystallized glass> This chemically strengthened glass is a crystallized glass containing crystals and residual glass (hereinafter also referred to as this crystallized glass). Because it is a crystallized glass containing crystals and residual glass, the crystals in the glass surface layer are dissolved by the cleaning process described later, resulting in a non-penetrating hole.

[0061] In this crystallized glass, when the etching rate of the residual glass is Eg and the etching rate of the crystals is Ec, the Eg / Ec ratio is preferably 0.1 to 0.0001, more preferably 0.05 to 0.0005, and even more preferably 0.01 to 0.001. That is, an Eg / Ec ratio of 0.0001 or higher is preferred, 0.0005 or higher is more preferred, and 0.001 or higher is even more preferred. Furthermore, an Eg / Ec ratio of 0.1 or lower is preferred, 0.05 or lower is more preferred, and 0.01 or lower is even more preferred. When the Eg / Ec ratio is 0.1 to 0.0001, the crystals present on the surface of the crystallized glass dissolve easily, creating non-penetrating holes and improving transparency.

[0062] This crystallized glass is made of Li3PO4 crystal and LiAlSi4O 10 Preferably, it contains at least one selected from Li3PO4 crystals, LiAlSi4O crystals, and Li3PO4 crystals, LiAlSi4O 10 It is more preferable to contain at least one selected from crystals and Li2Si2O5 crystals. This crystallized glass may contain these solid solution crystals. Since these crystals have a relatively large etching rate, the crystals present on the surface of the crystallized glass are easily dissolved by the cleaning treatment described later, which can create non-through holes and improve transparency.

[0063] Li3PO4 and Li4SiO4 crystals have similar crystal structures, making them difficult to distinguish by powder X-ray diffraction. Specifically, both crystals exhibit diffraction peaks around 2θ = 16.9°, 22.3°, 23.1°, and 33.9°. However, due to the small amount of crystals present or their orientation, low-intensity peaks or peaks on specific crystal planes may not be visible. Furthermore, if both crystals are in solid solution, the peak position may shift by approximately 1° at 2θ.

[0064] When X-ray diffraction is measured in the range of 2θ = 10 to 80°, it is preferable that the strongest diffraction peak of this crystallized glass appears at 22.3°±0.2 or 23.1°±0.2.

[0065] The crystallinity of this crystallized glass is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, in order to increase its mechanical strength. In order to increase its transparency, the crystallinity is preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. A low crystallinity is also advantageous in that it is easy to heat and bend or shape.

[0066] To increase the strength of the crystallized glass, the average grain size of the precipitated crystals is preferably 5 nm or more, and particularly preferably 10 nm or more. To improve transparency, it is preferably 80 nm or less, more preferably 60 nm or less, even more preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. The average grain size of the precipitated crystals is determined from transmission electron microscope (TEM) images.

[0067] When the crystallized glass is in plate form, its thickness (t) is preferably 3000 μm or less, and more preferably, in stages, 2000 μm or less, 1600 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, and 700 μm or less. Furthermore, in order to obtain sufficient strength through chemical strengthening treatment, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and even more preferably 500 μm or more.

[0068] The light transmittance of this crystallized glass before chemical strengthening is preferably 85% or higher when the thickness is 700 μm, as this makes the display screen easier to see when used as cover glass for mobile phone displays. A light transmittance of 88% or higher is more preferable, 90% or higher is even more preferable, and 92% or higher is particularly preferable. A higher light transmittance is preferable, but it is usually 95% or lower. A light transmittance of 90% when the thickness is 700 μm is equivalent to that of ordinary amorphous glass.

[0069] The light transmittance of this crystallized glass after chemical strengthening is preferably 88% or higher when the thickness is 700 μm, as this makes the display screen easier to see when used as cover glass for mobile phone displays. A light transmittance of 90% or higher is more preferable, 91% or higher is even more preferable, and 92% or higher is particularly preferable. A higher light transmittance is preferable, but it is usually 95% or lower. A light transmittance of 90% when the thickness is 700 μm is equivalent to that of ordinary amorphous glass.

[0070] If the actual thickness is not 700 μm, the light transmittance for a 700 μm thickness can be calculated based on the measured value using the Lambert-Beer law. If a glass plate with thickness t [μm] has a total visible light transmittance of 100 × T [%] and a surface reflectance of 100 × R [%] on one side, then by applying the Lambert-Beer law, using a constant α, T = (1 - R) 2 There is a relationship of ×exp(-αt). From here, we can express α in terms of R, T, and t, and if we set t = 700 μm, then R does not change with plate thickness, so the total visible light transmittance T converted to 700 μm is... 0.7 is T 0.7 = 100 × T 0.7 / t It can be calculated as / (1-R)^(1.4 / t-2)[%], where X^Y is X Y It represents. Surface reflectance can be calculated from the refractive index or measured directly. Furthermore, if the plate thickness t is greater than 700 μm, the plate thickness may be adjusted to 700 μm by polishing or etching, and then the visible light transmittance may be measured.

[0071] Furthermore, the haze value of this crystallized glass before chemical strengthening is preferably 0.5% or less, more preferably 0.4% or less, even more preferably 0.3% or less, particularly preferably 0.2% or less, and most preferably 0.15% or less, when the thickness is 700 μm. A smaller haze value is preferable, but it is usually 0.01% or more. A haze value of 0.02% when the thickness is 700 μm is equivalent to that of ordinary amorphous glass.

[0072] Furthermore, if a crystallized glass plate with thickness t [μm] has a total visible light transmittance of 100 × T [%] and a haze value of 100 × H [%], then by applying the Lambert-Beer law, and using the constant α mentioned above, dH / dt ∝ exp(-αt) × (1-H). In other words, the haze value can be considered to increase proportionally to the internal linear transmittance as the plate thickness increases, so the haze value H for 700 μm is... 0.7 It can be calculated using the following formula. However, "X^Y" is "X Y This represents ". H 0.7 =100 × [1-(1-H)^{((1-R) 2 -T 0.7 ) / ((1-R) 2 -T)}][%] Furthermore, if the plate thickness t is greater than 700 μm, the plate thickness may be adjusted to 700 μm by polishing or etching before measuring the haze value.

[0073] This crystallized glass has high fracture toughness, and even when large compressive stresses are formed by chemical strengthening, severe fracture is unlikely to occur. The fracture toughness of this crystallized glass is preferably 0.81 MPa·m 1 / 2 More preferably 0.84 MPa·m 1 / 2 More preferably 0.87 MPa·m 1 / 2If the above conditions are met, a highly impact-resistant glass can be obtained. There is no particular upper limit to the fracture toughness value of this crystallized glass, but it is typically 1.5 MPa·m. 1 / 2 The following applies:

[0074] The Young's modulus of this crystallized glass is preferably 80 GPa or higher, more preferably 85 GPa or higher, even more preferably 90 GPa or higher, and particularly preferably 95 GPa or higher, in order to suppress warping during chemical strengthening treatment. This crystallized glass may be used after polishing. For ease of polishing, the Young's modulus is preferably 130 GPa or lower, more preferably 120 GPa or lower, and even more preferably 110 GPa or lower.

[0075] This crystallized glass is obtained by heating and crystallizing amorphous glass, which will be explained later.

[0076] <<Composition of crystallized glass>> This crystallized glass preferably contains SiO2, Li2O, and Al2O3. This crystallized glass is expressed in molar percentage based on oxides. SiO2 at 40-70%, Li2O 5-35%, It is more preferable to contain 1-20% Al2O3.

[0077] This crystallized glass is expressed in mole percent based on oxides. SiO2 at 50-70%, Li2O at 10-30%, Al2O3 in a concentration of 1-15%, P2O5 at 0-5%, ZrO2 0-8%, MgO 0-10%, Y2O3 0-5% B2O3 at 0-10%, Na2O at 0-5%, K2O 0-5%, It is even more preferable to contain 0-2% SnO2.

[0078] Furthermore, the crystallized glass preferably contains 60-80% total amounts of SiO2, Al2O3, P2O5, and B2O3, expressed in molar percentages based on oxides. SiO2, Al2O3, P2O5, and B2O3 are the network-forming components of the glass (hereinafter also abbreviated as NWF). A higher total amount of NWF increases the strength of the glass. This increases the fracture toughness of the crystallized glass, so the total amount of NWF is preferably 60% or more, more preferably 63% or more, and particularly preferably 65% ​​or more. However, glass with too much NWF becomes difficult to manufacture due to its high melting temperature, so it is preferably 85% or less, more preferably 80%, and more preferably 75% or less.

[0079] In this crystallized glass, it is preferable that the ratio of the total amount of Li2O, Na2O, and K2O to the total amount of SiO2, Al2O3, P2O5, and B2O3 (NWF) is 0.20 to 0.60.

[0080] Li2O, Na2O, and K2O are network modification components, and reducing their ratio to NWF increases the gaps in the network, thereby improving impact resistance. For this reason, NWF is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less. On the other hand, since these are components necessary for chemical strengthening, in order to improve chemical strengthening properties, NWF is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.30 or more. The composition of this crystallized glass is described below.

[0081] In this crystallized glass, SiO2 is a component that forms the network structure of the glass. It is also a component that reduces the etching rate of the residual glass. The SiO2 content is preferably 40% or more. More preferably 48% or more, even more preferably 50% or more, particularly preferably 52% or more, and most preferably 54% or more. On the other hand, in order to improve meltability, the SiO2 content is preferably 70% or less, more preferably 68% or less, even more preferably 66% or less, and particularly preferably 64% or less.

[0082] Li2O is an essential component as it is a constituent of the main crystal and is a component that forms surface compressive stress through ion exchange. The Li2O content is preferably 5% or more, more preferably 10% or more, more preferably 15% or more, even more preferably 18% or more, particularly preferably 20% or more, and most preferably 22% or more. On the other hand, in order to stabilize the glass, the Li2O content is preferably 35% or less, more preferably 32% or less, even more preferably 30% or less, particularly preferably 28% or less, and most preferably 26% or less.

[0083] Al2O3 is an essential component that increases the surface compressive stress due to chemical strengthening and reduces the etching rate of residual glass. The Al2O3 content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, 5% or more, 5.5% or more, 6% or more, particularly preferably 6.5% or more, and most preferably 7% or more. On the other hand, the Al2O3 content is preferably 20% or less, more preferably 15% or less, even more preferably 12% or less, particularly preferably 10% or less, and most preferably 9% or less, in order to prevent the devitrification temperature of the glass from becoming too high.

[0084] Although P2O5 is not essential, it is a component of Li3PO4 crystals and is therefore essential when obtaining crystallized glass containing Li3PO4 crystals. The P2O5 content is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more, in order to promote crystallization. On the other hand, if the P2O5 content is too high, phase separation becomes more likely during melting, and the acid resistance is significantly reduced, so the P2O5 content is preferably 5% or less, more preferably 4.8% or less, even more preferably 4.5% or less, and particularly preferably 4.2% or less.

[0085] ZrO2 is a component that increases mechanical strength and reduces the etching rate of residual glass, and it is preferable to include it because it significantly improves CS. The ZrO2 content is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, in order to suppress devitrification during melting, the ZrO2 content is preferably 8% or less, more preferably 5% or less, even more preferably 4% or less, even more preferably 3.5% or less, and particularly preferably 3% or less. If the ZrO2 content is too high, the viscosity decreases due to an increase in the devitrification temperature. In order to suppress the deterioration of moldability due to such a decrease in viscosity, when the molding viscosity is low, the ZrO2 content is preferably 5% or less, more preferably 4.5% or less, and even more preferably 3.5% or less.

[0086] MgO is a component that stabilizes glass and also enhances its mechanical strength and chemical resistance, so its inclusion is preferable when the Al2O3 content is relatively low. The MgO content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more. On the other hand, adding too much MgO lowers the viscosity of the glass and makes devitrification or phase separation more likely, so the MgO content is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, and particularly preferably 7% or less.

[0087] Y2O3 is a component that helps prevent fragments from scattering when chemically strengthened glass breaks, and may be included. The Y2O3 content is preferably 1% or more, more preferably 1.5% or more, even more preferably 2% or more, particularly preferably 2.5% or more, and most preferably 3% or more. On the other hand, in order to suppress devitrification during melting, the Y2O3 content is preferably 5% or less, and more preferably 4% or less.

[0088] B2O3 is a component that improves the chipping resistance and meltability of chemically strengthened glass or chemically strengthened glass, and may be included. When B2O3 is included, the content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more, in order to improve meltability. On the other hand, if the B2O3 content is too high, striations may occur during melting, or phase separation may occur easily, which can degrade the quality of the chemically strengthened glass, so 10% or less is preferable. The B2O3 content is more preferably 8% or less, even more preferably 6% or less, and particularly preferably 4% or less.

[0089] Na2O is a component that improves the meltability of glass. Na2O is not essential, but if it is included, it is preferably 0.5% or more, more preferably 1% or more, and particularly preferably 2% or more. If there is too much Na2O, it becomes difficult for crystals such as Li3PO4, which are the main crystals, to precipitate, or the chemical strengthening properties decrease, so the Na2O content is preferably 5% or less, more preferably 4.5% or less, even more preferably 4% or less, and particularly preferably 3.5% or less.

[0090] K2O, like Na2O, is a component that lowers the melting temperature of glass and may be included. If K2O is included, the content is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. Too much K2O reduces the chemical strengthening properties or suppresses the increase in the etching rate of residual glass, so the content is preferably 5% or less, more preferably 4% or less, even more preferably 3.5% or less, particularly preferably 3% or less, and most preferably 2.5% or less.

[0091] The total content of Na2O and K2O (Na2O + K2O) is preferably 1% or more, and more preferably 2% or more, in order to improve the meltability of the glass raw material.

[0092] Furthermore, a ratio of K2O content to the total content of Li2O, Na2O, and K2O (hereinafter referred to as R2O), K2O / R2O, is preferable because it can enhance chemical strengthening properties and reduce the etching rate of residual glass. A K2O / R2O ratio of 0.15 or less is more preferable, and 0.10 or less is even more preferable.

[0093] Furthermore, the R2O content is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. In addition, the R2O content is preferably 29% or less, and more preferably 26% or less.

[0094] Furthermore, to reduce the etching rate of residual glass, the ZrO2 / R2O is preferably 0.02 or higher, more preferably 0.03 or higher, even more preferably 0.04 or higher, particularly preferably 0.1 or higher, and most preferably 0.15 or higher. To increase transparency after crystallization, the ZrO2 / R2O is preferably 0.6 or lower, more preferably 0.5 or lower, even more preferably 0.4 or lower, and particularly preferably 0.3 or lower.

[0095] SnO2 has the effect of promoting the formation of crystal nuclei and may be included. SnO2 is not essential, but if included, it is preferably 0.5% or more, more preferably 0.7% or more, even more preferably 1% or more, and particularly preferably 1.5% or more. On the other hand, in order to suppress devitrification during melting, the SnO2 content is preferably 3% or less, more preferably 2.5% or less, and even more preferably 2% or less.

[0096] TiO2 is a component that can promote crystallization and may be included. TiO2 is not essential, but if included, it is preferably 0.2% or more, and more preferably 0.5% or more. On the other hand, in order to suppress devitrification during melting, the TiO2 content is preferably 4% or less, more preferably 2% or less, and even more preferably 1% or less.

[0097] BaO, SrO, MgO, CaO, and ZnO are all components that improve the meltability of the glass and may be included. When these components are included, the total content of BaO, SrO, MgO, CaO, and ZnO (hereinafter referred to as BaO+SrO+MgO+CaO+ZnO) is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, because the ion exchange rate decreases, BaO+SrO+MgO+CaO+ZnO is preferably 8% or less, more preferably 6% or less, even more preferably 5% or less, and particularly preferably 4% or less.

[0098] Of these, BaO, SrO, and ZnO may be included to improve the light transmittance of the crystallized glass and lower the haze value by increasing the refractive index of the residual glass and bringing it closer to the precipitated crystalline phase. In that case, the total content of BaO, SrO, and ZnO (hereinafter, BaO + SrO + ZnO) is preferably 0.3% or more, more preferably 0.5% or more, even more preferably 0.7% or more, and particularly preferably 1% or more. On the other hand, these components may reduce the ion exchange rate. To improve the chemical strengthening properties, BaO + SrO + ZnO is preferably 2.5% or less, more preferably 2% or less, even more preferably 1.7% or less, and particularly preferably 1.5% or less.

[0099] La2O3, Nb2O5, and Ta2O5 are all components that make it difficult for fragments to scatter when chemically strengthened glass breaks, and they may be included to increase the refractive index. When these are included, the total content of La2O3, Nb2O5, and Ta2O5 (hereinafter referred to as La2O3+Nb2O5+Ta2O5) is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. Furthermore, in order to prevent devitrification of the glass during melting, La2O3+Nb2O5+Ta2O5 is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0100] Furthermore, CeO2 may be included. CeO2 may suppress discoloration by oxidizing the glass. If CeO2 is included, the content is preferably 0.03% or more, more preferably 0.05% or more, and even more preferably 0.07% or more. To ensure high transparency, the CeO2 content is preferably 1.5% or less, and more preferably 1.0% or less.

[0101] When using this chemically strengthened glass with color, coloring components may be added to the extent that they do not hinder the achievement of the desired chemical strengthening properties. Examples of coloring components include Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3.

[0102] The total content of coloring components is preferably 1% or less. If a higher visible light transmittance of the glass is desired, it is preferable that these components are substantially absent.

[0103] Furthermore, SO3, chlorides, and fluorides may be appropriately included as clarifying agents during glass melting. It is preferable that As2O3 is not included. If Sb2O3 is included, it is preferable that it be 0.3% or less, more preferably 0.1% or less, and most preferably not included.

[0104] <Method for manufacturing chemically strengthened glass> The present invention relates to a method for producing chemically strengthened glass, comprising chemically strengthening crystallized glass containing crystals and residual glass, and cleaning the crystallized glass. Preferably, such a method includes chemically strengthening crystallized glass containing crystals and residual glass, and, after the chemical strengthening, cleaning the surface of the crystallized glass with a cleaning solution having a pH of 2 to 12. The crystallized glass is produced by a method of crystallizing amorphous glass of the same composition by heat treatment.

[0105] <<Manufacturing of Amorphous Glass>> Amorphous glass can be manufactured, for example, by the following method. Note that the manufacturing method described below is an example for producing sheet-shaped chemically strengthened glass.

[0106] Glass raw materials are mixed to obtain glass of a desirable composition and heated and melted in a glass melting furnace. The molten glass is then homogenized by bubbling, stirring, adding fining agents, etc., and formed into glass sheets of a predetermined thickness using a known molding method, followed by slow cooling. Alternatively, the molten glass may be formed into blocks, slowly cooled, and then cut to form sheets.

[0107] <<Crystalling Treatment>> Crystallized glass can be obtained by heat-treating the amorphous glass obtained using the above procedure.

[0108] The heat treatment may be carried out in two stages: raising the temperature from room temperature to a first treatment temperature and holding it for a certain period of time, and then holding it at a second treatment temperature, which is higher than the first treatment temperature, for a certain period of time. Alternatively, it may be carried out in one stage: holding it at a specific treatment temperature and then cooling it to room temperature.

[0109] In a two-stage heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate is high for that glass composition, and the second treatment temperature is preferably in a temperature range where the crystal growth rate is high for that glass composition. Furthermore, it is preferable to hold the glass at the first treatment temperature for a long time so that a sufficient number of crystal nuclei are generated. The generation of numerous crystal nuclei reduces the size of each crystal, resulting in a crystallized glass with high transparency.

[0110] In the case of a two-stage process, for example, the first processing temperature may be 450°C to 700°C and held for 1 to 6 hours, followed by a second processing temperature of 600°C to 800°C and held for 1 to 6 hours. In the case of a one-stage process, for example, the temperature may be 500°C to 800°C and held for 1 to 6 hours.

[0111] The crystallized glass obtained by the above procedure is ground and polished as needed to form a crystallized glass plate. When cutting the crystallized glass plate to a predetermined shape and size, or when chamfering it, it is preferable to perform the cutting and chamfering before applying the chemical strengthening treatment, because this will allow a compressive stress layer to be formed on the edge surface during the subsequent chemical strengthening treatment.

[0112] <<Chemical Strengthening Treatment>> Chemical strengthening is a process in which glass is brought into contact with a metal salt (e.g., potassium nitrate) containing metal ions with a large ionic radius (typically Na ions or Li ions) by methods such as immersion in a molten metal salt containing metal ions with a large ionic radius (typically Na ions or Li ions), thereby replacing metal ions with a large ionic radius (typically Na ions or K ions for Li ions, and K ions for Na ions).

[0113] To increase the speed of the chemical strengthening process, it is preferable to use "Li-Na exchange," which involves exchanging Li ions for Na ions in the glass. Furthermore, to create a large compressive stress through ion exchange, it is preferable to use "Na-K exchange," which involves exchanging Na ions for K ions in the glass.

[0114] Examples of molten salts used for chemical strengthening treatment include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used individually or in combination.

[0115] The processing conditions for chemical strengthening can be selected based on the glass composition, the type of molten salt, and other factors, including time and temperature. For example, a chemical strengthening treatment of the crystallized glass is preferably performed at 450°C or below for 1 hour or less. Specifically, for example, a treatment is performed by immersing the glass in a molten salt containing 0.3% by mass of Li and 99.7% by mass of Na (for example, a mixed salt of lithium nitrate and sodium nitrate) at 450°C for about 0.5 hours.

[0116] The chemical strengthening treatment may also be carried out by a two-step ion exchange, for example, as follows: First, the crystallized glass is immersed in a metal salt containing Na ions (e.g., sodium nitrate) at a temperature of preferably 350 to 500°C for preferably 0.1 to 10 hours. This causes ion exchange between Li ions in the crystallized glass and Na ions in the metal salt, allowing a relatively deep compressive stress layer to be formed.

[0117] Next, the material is preferably immersed in a metal salt containing K ions (e.g., potassium nitrate) at a temperature of approximately 350 to 500°C for about 0.1 to 10 hours. This generates a large compressive stress in the portion of the compressive stress layer formed in the previous treatment, for example, within a depth of about 10 μm. This two-step treatment makes it easier to obtain a stress profile with a large surface compressive stress value.

[0118] <<Cleaning Process>> By subjecting chemically strengthened glass obtained through chemical strengthening treatment to a cleaning treatment, multiple non-penetrating holes are formed on both main surfaces of the chemically strengthened glass. The cleaning treatment is performed by immersing the chemically strengthened glass in a cleaning solution. The pH of the cleaning solution is preferably 2 to 12, more preferably 2.5 to 11, and even more preferably 3 to 10. The cleaning treatment time can be appropriately adjusted, taking into consideration the pH and composition of the cleaning solution, the etching rate of the crystallized glass, etc., so that the average diameter, average depth, and total area ratio of the formed non-penetrating holes are within the desired range, but is usually preferably 5 minutes to 48 hours, more preferably 10 minutes to 36 hours, and even more preferably 30 minutes to 24 hours.

[0119] The temperature of the cleaning solution is not particularly limited and can be used at room temperature (15°C) to 100°C. Temperatures exceeding 100°C may cause the water in the cleaning solution to boil, which is inconvenient and undesirable during the cleaning process. After cleaning, drying may be performed. Drying methods include blowing warm air or blowing compressed air.

[0120] Examples of cleaning solutions include acidic or alkaline cleaning solutions. Acidic cleaning solutions preferably contain organic acids and inorganic acids. Examples of organic acids contained in acidic cleaning solutions include organic carboxylic acids such as citric acid and ascorbic acid, and organic phosphonic acids, with citric acid being preferred. Examples of inorganic acids contained in acidic cleaning solutions include hydrochloric acid, sulfuric acid phosphoric acid, nitric acid, and hydrofluoric acid, with hydrochloric acid being preferred. Furthermore, when using the inorganic acids, salts of these acids may be added together with the inorganic acids to suppress pH fluctuations. A preferred combination of organic and inorganic acids is, for example, citric acid and hydrochloric acid.

[0121] Alkaline cleaning solutions contain a base and may also contain surfactants and chelating agents. Examples of bases contained in alkaline cleaning solutions include alkali metal compounds such as alkali metal hydroxides and alkali metal carbonates, amines, and quaternary ammonium hydroxides. Alkali metal hydroxides such as potassium hydroxide and sodium hydroxide are preferred as bases. Nonionic surfactants are preferred as surfactants. [Examples]

[0122] The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0123] <Fabrication and Evaluation of Amorphous Glass> The glass raw materials were mixed to achieve the glass composition shown in Table 1, expressed in mole percent based on oxides, and weighed to obtain 800 g of glass. The mixed glass raw materials were then placed in a platinum crucible and melted in an electric furnace at 1600°C for about 5 hours, after which they were degassed and homogenized.

[0124] The obtained molten glass was poured into a mold, held at the glass transition temperature for 1 hour, and then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The glass transition temperature, specific gravity, Young's modulus, and fracture toughness values ​​of amorphous glass were evaluated using a portion of the obtained block, and the results are shown in Table 1.

[0125] In the table, R2O represents the total content of Li2O, Na2O, and K2O, and NWF represents the total content of SiO2, Al2O3, P2O5, and B2O3.

[0126] (specific gravity ρ) The measurement was performed using the Archimedes method.

[0127] (Glass transition temperature Tg) Glass was crushed using an agate mortar, and approximately 80 mg of the powder was placed in a platinum cell. While heating from room temperature to 1100°C at a heating rate of 10 / min, the DSC curve was measured using a differential scanning calorimeter (Bruker; DSC3300SA) to determine the glass transition point Tg. Alternatively, in accordance with JIS R1618:2002, a thermal expansion curve was obtained using a thermal expansion meter (Bruker AXS; TD5000SA) with a heating rate of 10°C / min, and the glass transition point Tg [unit: °C] was determined from the obtained thermal expansion curve.

[0128] (Haze value) The haze value [unit: %] was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.; HZ-V3) with a halogen lamp C light source.

[0129] (Young's modulus E) The measurement was performed using ultrasound.

[0130] (Fracture toughness value Kc) Measurements were taken using the IF method in accordance with JIS R1607:2015.

[0131] [Table 1]

[0132] <Evaluation of crystallization treatment and crystallized glass> The obtained glass blocks were processed to 50mm x 50mm x 1.5mm, and then heat-treated under the conditions described in Table 2 to obtain crystallized glass. In the crystallization conditions column of the table, the upper row shows the nucleation treatment conditions, and the lower row shows the crystal growth treatment conditions. For example, if the upper row is listed as 550°C for 2h and the lower row as 750°C for 2h, it means that the glass was held at 550°C for 2 hours, followed by being held at 750°C for 2 hours.

[0133] The obtained crystallized glass was processed and mirror-polished to obtain a crystallized glass plate with a thickness t of 700 μm. A rod-shaped sample was also prepared for measuring the coefficient of thermal expansion. A portion of the remaining crystallized glass was crushed and used for the analysis of precipitated crystals. The evaluation results of the crystallized glass are shown in Table 2.

[0134] (X-ray diffraction: precipitated crystals) Powder X-ray diffraction was measured under the following conditions to identify the precipitated crystals. Measurement device: Smart Lab manufactured by Rigaku Corporation X-ray used: CuKα ray Measurement range: 2θ = 10° to 80° Speed: 1° / min Step: 0.01°

[0135] The detected primary crystal is shown in the "Crystal" column of Table 2. Since it is difficult to distinguish between Li3PO4 and Li4SiO4 by powder X-ray diffraction, both are listed together.

[0136] (Haze value) The haze value [unit: %] was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.; HZ-V3) with a halogen lamp C light source.

[0137] [Table 2]

[0138] <Chemical strengthening treatment and cleaning treatment> Crystallized glasses CG1 and CG2 were chemically strengthened under the conditions shown in Table 3 and subjected to ion exchange treatment. The resulting chemically strengthened glasses were designated Glass A, Glass B, and Glass X, respectively. The obtained chemically strengthened glasses were immersed in a pH 8.9 washing solution at room temperature for 24 hours to obtain the chemically strengthened glasses of Examples 1 to 4, which were then analyzed. The evaluation results of the chemically strengthened glasses are shown in Table 4. In Table 4, Examples 1 and 2 are examples, and Examples 3 and 4 are comparative examples.

[0139] (Stress Profile) The stress profile was measured using a scattered light photoelastic stress meter SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.

[0140] (Etching rate) The weight loss per unit time due to NaOH treatment (95°C, pH 10) was measured to determine the result.

[0141] (Crystallinity, crystal average grain size) Powder X-ray diffraction was measured under the following conditions, and the degree of crystallinity [unit: %] and average grain size (crystal size) [unit: nm] were calculated using the Rietveld method. Measurement equipment: Manufactured by Rigaku Corporation, Smart Lab X-ray used: CuKα ray Measurement range: 2θ = 10° to 80° Speed: 10° / min Step: 0.02°

[0142] (Average diameter of non-through holes, ratio of total area) The average diameter and total area ratio of non-through holes were determined as follows: Chemically strengthened glass was observed from directly above using a SEM, and a surface SEM image at 100,000x magnification was obtained. From the obtained surface SEM image, non-through holes and matrix portions were distinguished, and the major axis of each non-through hole was determined as the diameter, and the average diameter was calculated. The total area ratio of non-through holes was calculated by determining the ratio of the total area of ​​non-through holes to the total field of view area of ​​the surface SEM image.

[0143] (Average depth of non-through holes) In this specification, the depth of non-penetrating holes was determined as follows: A cross-sectional SEM image at 300,000x magnification was obtained from the fractured surface of chemically strengthened glass. In the obtained cross-sectional SEM image, non-penetrating holes and matrix portions were distinguished, the depth of each non-penetrating hole was determined, and the average depth was calculated.

[0144] (Drop strength) In the drop test, the obtained 120×60×0.6mmt glass sample was fitted into a structure whose mass and rigidity were adjusted to match the size of a typical smartphone currently in use, creating a simulated smartphone. This simulated smartphone was then free-dropped onto #180 SiC sandpaper. The drop height was set to 5cm. If the sample did not break, the height was increased by 5cm and the drop was repeated until it broke. The average of the heights at which the sample first broke (10 samples) was calculated.

[0145] (transmittance) The transmittance was measured as the average transmittance for light with wavelengths from 380 nm to 780 nm.

[0146] [Table 3]

[0147] [Table 4]

[0148] As shown in Table 4, Examples 1 and 2, which are chemically strengthened glasses of the present invention, exhibit superior transparency and strength compared to comparative examples 3 and 4.

[0149] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2021-065435, filed on April 7, 2021, the contents of which are incorporated herein by reference. [Explanation of Symbols]

[0150] 24 Chemically strengthened glass 22 Non-through holes

Claims

1. A chemically strengthened glass having opposing first main surface and second main surface, It consists of crystallized glass containing crystals and residual glass, The crystallized glass contains at least one selected from Li3PO4 crystals, LiAlSi4O10 crystals, Li2Si2O5 crystals, and Li4SiO4 crystals. Surface compressive stress value (CS ０ ) is 450 MPa or more, and the compressive stress value (CS) at a depth of 50 μm from the surface ５０ ) is 150 MPa or more, The first main surface and the second main surface have a plurality of non-through holes with an average diameter of 5 to 50 nm. The average depth of the non-through hole, as measured by the cross-sectional SEM images of the first main surface and the second main surface, is 5 to 50 nm, and Chemically strengthened glass in which the total area ratio of the non-through holes to the total field of view of the surface SEM images on the first main surface and the second main surface is 1 to 40%.

2. The crystallized glass has an etching rate of Eg to Ec of 0.1 to 0.0001, where Eg is the etching rate of the residual glass when NaOH is used as the etching solution, and Ec is the etching rate of the crystal when NaOH is used as the etching solution. The chemically strengthened glass according to claim 1, wherein the base composition contains 40-70% SiO₂, 5-35% Li₂O, and 1-20% Al₂O₃, expressed in mole percent on an oxide basis.

3. The base composition is expressed in mole percent based on oxides, SiO ２ 40-70%, Li ２ 5-35% O, Al ２ O ３ A chemically strengthened glass according to claim 1, containing 1 to 20% of the above.

4. A chemically strengthened glass according to any one of claims 1 to 3, wherein the crystallinity is 10 to 90% by mass.

5. The chemically strengthened glass according to any one of claims 1 to 4, wherein the reflectance of the first main surface and the second main surface is 10% or less.

6. A chemically strengthened glass according to any one of claims 1 to 5, wherein the light transmittance calculated based on a thickness of 700 μm before chemical strengthening is 90% or more.

7. A chemically strengthened glass according to any one of claims 1 to 6, wherein the plate thickness is 300 to 3000 μm.

8. A method for manufacturing chemically strengthened glass, Chemical strengthening of crystallized glass containing crystals and residual glass, The process includes cleaning the surface of the crystallized glass with a cleaning solution having a pH of 2 to 12 after the chemical strengthening, The crystallized glass contains at least one selected from Li3PO4 crystals, LiAlSi4O10 crystals, Li2Si2O5 crystals, and Li4SiO4 crystals. The chemically strengthened glass has opposing first main surfaces and second main surfaces, and the surface compressive stress value (CS ０ ) is 450 MPa or more, and the compressive stress value (CS) at a depth of 50 μm from the surface ５０ ) is 150 MPa or more, The first main surface and the second main surface have a plurality of non-through holes with an average diameter of 5 to 50 nm. The average depth of the non-through hole, as measured by the cross-sectional SEM images of the first main surface and the second main surface, is 5 to 50 nm, and A method for manufacturing chemically strengthened glass, wherein the total area ratio of the non-through holes to the total field of view of the surface SEM images on the first main surface and the second main surface is 1 to 40%.

9. When the etching rate of the residual glass when NaOH is used as the etching solution is Eg, and the etching rate of the crystal when NaOH is used as the etching solution is Ec, Eg / Ec is 0.1 to 0.0001. A method for producing chemically strengthened glass according to claim 8, wherein the base composition contains 40-70% SiO₂, 5-35% Li₂O, and 1-20% Al₂O₃, expressed in mole percent on an oxide basis.

10. The crystallization glass has a mother composition expressed in mol% based on oxides, with SiO ２ being 40 to 70%, Li ２ O being 5 to 35%, and Al ２ O ３ being contained at 1 to 20%. The method for manufacturing chemically strengthened glass according to claim 8.

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