Chemically strengthened glass comprising microcrystalline glass and methods of making the same

Abstract

The present invention relates to a chemically strengthened glass having opposite first and second main faces, wherein the chemically strengthened glass comprises a glass-ceramic containing crystals and residual glass, the CS0 of the chemically strengthened glass is 450 MPa or more, and the CS150 of the chemically strengthened glass is 150 MPa or more, the first and second main faces have a plurality of non-through holes having an average diameter of 5 nm to 50 nm, the average depth of the non-through holes is 5 nm to 50 nm as determined from cross-sectional SEM images of the first and second main faces, and the total area ratio of the non-through holes relative to the total field area of the surface SEM images is 1% to 40% in the first and second main faces. 50 The present invention relates to a chemically strengthened glass having opposite first and second main faces, wherein the chemically strengthened glass comprises a glass-ceramic containing crystals and residual glass, the CS0 of the chemically strengthened glass is 450 MPa or more, and the CS150 of the chemically strengthened glass is 150 MPa or more, the first and second main faces have a plurality of non-through holes having an average diameter of 5 nm to 50 nm, the average depth of the non-through holes is 5 nm to 50 nm as determined from cross-sectional SEM images of the first and second main faces, and the total area ratio of the non-through holes relative to the total field area of the surface SEM images is 1% to 40% in the first and second main faces.

Description

TECHNICAL FIELD

[0001] The present application relates to a chemically strengthened glass-ceramic and a method for producing the same. BACKGROUND

[0002] Chemically strengthened glass is used in a protective glass of a portable terminal or the like. The chemically strengthened glass is, for example, a glass in which an ion exchange between alkali metal ions in the glass and alkali metal ions in a molten salt is caused by bringing the glass into contact with the molten salt containing the alkali metal ions, whereby a compressive stress layer is formed on the surface of the glass.

[0003] As a base material of such a chemically strengthened glass, an amorphous glass containing Li2O or a glass-ceramic containing Li2O is particularly excellent. As a reason therefor, a compressive stress is easily formed to a deep portion in the chemically strengthened glass by ion exchange between lithium ions contained in the base material and sodium ions contained in the strengthening salt. The lithium ions and the sodium ions have a relatively small ionic radius, and thus a diffusion coefficient caused by ion exchange is large. In addition, the amorphous glass containing Li2O or the glass-ceramic has a relatively large fracture toughness value, and has a tendency to be difficult to break.

[0004] The glass-ceramic is a glass in which crystals are precipitated in a glass, and is harder and less scratchable than an amorphous glass not containing the crystals. In addition, the chemically strengthened glass-ceramic can achieve high strength while preventing breakage, as compared with the amorphous glass. However, the glass-ceramic tends to have insufficient transparency, as compared with the amorphous glass.

[0005] Examples of ion exchange treatment of a glass-ceramic to perform chemical strengthening are described in Patent Literature 1 and Patent Literature 2.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: International Publication No. 2019 / 022035

[0009] Patent Literature 2: U.S. Patent Application Publication No. 2020 / 0017398 Specification SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The chemically strengthened glass containing the glass-ceramic described in Patent Literatures 1 and 2 is excellent in transparency and chemical strengthening properties, but sometimes has insufficient transparency.

[0012] Therefore, an object of the present application is to provide a chemically strengthened glass containing a glass-ceramic, which is excellent in transparency and chemical strengthening properties.

[0013] MEANS FOR SOLVING THE PROBLEMS

[0014] The present inventors have conducted studies on the above problem, and as a result, have found that a chemically strengthened glass containing a glass-ceramic, having a plurality of non-through holes in both main surfaces, and having an average diameter, an average depth, and a total area ratio of the non-through holes within specific ranges, is excellent in transparency and chemical strengthening properties, thereby completing the present invention.

[0015] The present invention relates to a chemically strengthened glass having opposite first and second main surfaces, wherein the chemically strengthened glass contains a glass-ceramic containing crystals and residual glass, a surface compressive stress value (CS0) of the chemically strengthened glass is 450 MPa or greater, and a compressive stress value (CS50) at a depth of 50 μm from the surface of the chemically strengthened glass is 150 MPa or greater, has a plurality of non-through holes having an average diameter of 5 nm to 50 nm in the first and second main surfaces, an average depth of the non-through holes measured using a cross-sectional SEM image of the first and second main surfaces is 5 nm to 50 nm, and a total area ratio of the non-through holes with respect to a total field area of a surface SEM image is 1% to 40% in the first and second main surfaces. 50

[0016] When the etching rate of the residual glass in the present chemically strengthened glass is set as Eg, and the etching rate of the crystals in the chemically strengthened glass is set as Ec, it is preferable that Eg / Ec is 0.1 to 0.0001.

[0017] In the present chemically strengthened glass, it is preferable that the basic composition of the chemically strengthened glass contains 40% to 70% of SiO2, 5% to 35% of Li2O, and 1% to 20% of Al2O3, in terms of mol% on an oxide basis.

[0018] It is preferable that the crystallization rate of the present chemically strengthened glass is 10 mass% to 90 mass%.

[0019] It is preferable that the reflectance of the first and second main surfaces of the present chemically strengthened glass is 10% or less.

[0020] It is preferable that the light transmittance of the present chemically strengthened glass before chemical strengthening is 90% or greater, in terms of thickness of 700 μm.

[0021] It is preferable that the plate thickness of the present chemically strengthened glass is 300 μm to 3000 μm.

[0022] ​The present application also relates to a method for producing a chemically strengthened glass, the method comprising: chemically strengthening a glass-ceramic containing crystals and residual glass; and after the chemical strengthening, cleaning the surface of the glass-ceramic using a cleaning solution having a pH of 2 to 12, the chemically strengthened glass having opposite first and second main faces, a surface compressive stress value (CS0) of the chemically strengthened glass being 450 MPa or greater, and a compressive stress value (CS50) at a depth of 50 μm from the surface of the chemically strengthened glass being 150 MPa or greater, the first and second main faces having a plurality of non-through holes having an average diameter of 5 to 50 nm, the average depth of the non-through holes being 5 to 50 nm as determined from a cross-sectional SEM image of the first and second main faces, and the total area ratio of the non-through holes relative to the total field area of a surface SEM image being 1 to 40% in the first and second main faces. 50 ) of 150 MPa or greater at a depth of 50 μm from the surface of the chemically strengthened glass, the first and second main faces having a plurality of non-through holes having an average diameter of 5 to 50 nm, the average depth of the non-through holes being 5 to 50 nm as determined from a cross-sectional SEM image of the first and second main faces, and the total area ratio of the non-through holes relative to the total field area of a surface SEM image being 1 to 40% in the first and second main faces.

[0023] In the method for producing a chemically strengthened glass, when the etching rate of the residual glass is set as Eg and the etching rate of the crystals is set as Ec, it is preferable that Eg / Ec be 0.1 to 0.0001.

[0024] In the method for producing a chemically strengthened glass, the base composition of the glass-ceramic preferably contains, in terms of mol% on an oxide basis, 40 to 70% of SiO2, 5 to 35% of Li2O, and 1 to 20% of Al2O3.

[0025] Effects of the Invention

[0026] The chemically strengthened glass of the present application is a glass-ceramic having a plurality of non-through holes in both main faces, and the average diameter, average depth, and total area ratio of the non-through holes are within specific ranges, and thus the reflectance is suppressed, excellent transparency is exhibited, and high chemical strengthening properties can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 (a) to (c) of FIG. 1 are diagrams showing one example of a surface SEM image. Figure 1 (a) of FIG. 2 is a diagram showing one example of a chemically strengthened glass of the present application, Figure 1 (b) of FIG. 2 is a diagram showing one example of a conventional chemically strengthened glass. Figure 1 (c) of FIG. 2 is Figure 1 (a) of FIG. 3 is an enlarged view of the portion enclosed by the broken line of (a) of FIG. 3.

[0028] Figure 2 is a partial cross-sectional view schematically showing a surface layer of one main face in one embodiment of the present application.

[0029] Figure 3(a) and (b) of FIG. 1 are examples of cross-sectional SEM images of the chemically strengthened glass of the present application. DETAILED DESCRIPTION

[0030] In the present specification, unless particularly specified, "~" indicating a numerical range is used in the meaning that the numerical values recited before and after it are included as lower limit values and upper limit values.

[0031] In the present specification, "amorphous glass" means a glass in which no diffraction peak indicating a crystal is observed by the powder X-ray diffraction method described later. "Microcrystalline glass" is a glass in which a crystal is precipitated by heat treatment of "amorphous glass", and contains a crystal. In the present specification, "amorphous glass" and "microcrystalline glass" are sometimes collectively referred to as "glass". In addition, amorphous glass which becomes a microcrystalline glass by heat treatment is sometimes referred to as "matrix glass of microcrystalline glass".

[0032] In the present specification, in powder X-ray diffraction measurement, for example, CuKα rays are used to measure a range of 10° to 80° in 2θ, and in the case where a diffraction peak appears, a crystal is identified by the Hanawalt method. In addition, a crystal identified by this method is identified as a main crystal from a group of peaks including the peak with the highest integrated intensity. As a measurement device, for example, Smart Lab manufactured by Rigaku Corporation can be used.

[0033] In the present specification, "residual glass" means an amorphous portion which is not crystallized in a microcrystalline glass.

[0034] In the present specification, the diameter of a non-through-hole in a chemically strengthened glass is obtained by the following method. The surface of a non-through-hole of a chemically strengthened glass is observed from directly above each of the first main surface and the second main surface by SEM (scanning electron microscope), and a surface SEM image at 100,000 times is obtained. From the obtained surface SEM image, a non-through-hole and a matrix portion (a portion in which a non-through-hole is not formed) are discriminated, the major axis of each non-through-hole is obtained as a diameter, and a diameter average as an average thereof is calculated.

[0035] Specifically, for example, in Figure 1 In (a) of FIG. 1, the gray portion is a matrix portion in which a non-through-hole is not formed, and the black portion is a non-through-hole. Figure 1 (c) of FIG. 1 is Figure 1 The enlarged view of the portion surrounded by a broken line in (a) is a portion indicated by white double-headed arrows, and the length of the portion is an example of the diameter of a non-through-hole.

[0036] In the present specification, the total area ratio of non-through holes in the chemically strengthened glass is obtained by the following method. The surface of the chemically strengthened glass is observed in plan view using an SEM, thereby obtaining a surface SEM image at a magnification of 100,000 times. The non-through holes and the matrix portion are discriminated from the obtained surface SEM image, the proportion of the total area of the non-through holes with respect to the total field area of the surface SEM image is obtained, and this is taken as the total area ratio of the non-through holes.

[0037] In the present specification, the depth of the non-through hole is obtained by the following method. A cross-sectional SEM image at a magnification of 300,000 times is obtained on a cut surface of the chemically strengthened glass. The non-through holes and the matrix portion are discriminated from the obtained cross-sectional SEM image, the depth of each non-through hole is obtained, and the depth average, which is the average value thereof, is calculated. Specifically, in the case of the cross-sectional SEM image shown in (a) of FIG. 6, the length of the portion indicated by the black double-headed arrow is an example of the depth of the non-through hole. Figure 3

[0038] In the present specification, the "etching rate" (unit: nm / min) is obtained by measuring the weight reduction (nm) per unit time (1 minute) caused by the etching treatment. As the conditions for measuring the etching rate ratio, there is no particular limitation as long as the desired etching rate ratio can be obtained, and specifically, for example, conditions generally set to pH 2 to 12, room temperature (15°C) to 100°C can be cited. In addition, the etching solution used in the etching treatment is not particularly limited, and specifically, for example, NaOH, HC1 can be cited.

[0039] Hereinafter, the "chemically strengthened glass" refers to a glass after the chemical strengthening treatment is performed, and the "glass for chemical strengthening" refers to a glass before the chemical strengthening treatment is performed.

[0040] In the present specification, the glass composition is expressed in terms of mol% on an oxide basis, and the mol% is simply denoted as "%", unless otherwise specified.

[0041] In addition, in the present specification, "substantially free of" means at a level of impurities contained in raw materials and the like, that is, not intentionally added. Specifically, for example, less than 0.1%.

[0042] In the present specification, the "stress profile" refers to a graph in which the depth from the surface of the glass is taken as a variable to represent the compressive stress value. In the stress profile, a negative compressive stress indicates a tensile stress.

[0043] The "compressive stress value (CS)" can be measured by thinning a cross section of the glass and analyzing the thinned sample using a birefringence imaging system. The birefringence imaging system birefringence stress meter is a device that measures the magnitude of the retardation generated by stress using a polarizing microscope and a liquid crystal compensator, and the like, and is, for example, a birefringence imaging system Abrio-IM manufactured by CRi, Inc. ​

[0044] In addition, sometimes it is also possible to measure using scattered light photoelasticity. In this method, light is incident from the surface of the glass, and the polarization of the scattered light is analyzed, whereby it is possible to measure CS. As a stress measuring device using scattered light photoelasticity, for example, there is scattered light photoelasticity stress meter SLP-2000 manufactured by Shikoku Engineering Corporation.

[0045] In the present specification, the "depth of compressive stress layer (DOL)" is the depth at which the compressive stress value is zero. Hereinafter, sometimes the surface compressive stress value is denoted as CS0, and the compressive stress value at a depth of 50 μm is denoted as CS50. 50 In addition, the "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 of the plate thickness t, and in the present specification, is equivalent to "CS t / 2 ".

[0046] In the present specification, the "light transmittance" refers to the average transmittance of light having a wavelength of 380 nm to 780 nm. In addition, the "haze value" is measured using a halogen lamp C light source in accordance with JIS K7136:2000.

[0047] In the present specification, the "reflectance" is based on the provisions of JIS Z8701 (1999). Note that, as the light source, a D65 light source is used.

[0048] In the present specification, the "fracture toughness value" is the value obtained according to the IF method prescribed in JIS R1607:2015.

[0049] In the present specification, the "drop strength" is measured by the following method.

[0050] A glass sample of 120 mm x 60 mm x 0.6 mm t was embedded in a structure body in which the mass and rigidity were adjusted to the size of a general smartphone, whereby a simulated smartphone was prepared, and then was allowed to freely fall onto #180 SiC sandpaper. With respect to the drop height, in the case where it was not broken when dropped from a height of 5 cm, the operation of increasing the drop height by 5 cm and allowing it to fall again was repeated until it was broken, and the average value of the height at which 10 glass samples were first broken was measured.

[0051] <Chemically Strengthened Glass>

[0052] The chemically strengthened glass of the present application (hereinafter, also simply referred to as the present chemically strengthened glass.) is typically a glass article in the form of a plate, and can be in the form of a flat plate or in the form of a curved surface. In addition, it can also have portions having different thicknesses.

[0053] The thickness (t) of the present chemically strengthened glass is preferably 3000 μm or less, more preferably 2000 μm or less, 1600 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, or 700 μm or less in the case of a plate shape. In addition, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and further preferably 500 μm or more in order to obtain sufficient strength resulting from the chemical strengthening treatment.

[0054] When the surface compressive stress value (CS0) of the present chemically strengthened glass is 450 MPa or more, it is less likely to be broken by deformation such as warping, and thus is preferable. CS0 is more preferably 500 MPa or more, and further preferably 600 MPa or more. The greater CS0 is, the higher the strength is, but when CS0 is excessively large, violent shattering can occur in the case of breakage, and thus CS0 is preferably 1100 MPa or less, and more preferably 900 MPa or less.

[0055] When the compressive stress value (CS50) at a depth of 50 μm from the surface of the present chemically strengthened glass is 150 MPa or more, it is easy to suppress breakage of the present chemically strengthened glass when a portable terminal or the like having the present chemically strengthened glass as a protective glass is dropped, and thus is preferable. CS50 is more preferably 180 MPa or more, and further preferably 200 MPa or more. The greater CS50 is, the higher the strength is, but when CS50 is excessively large, violent shattering can occur in the case of breakage, and thus CS50 is preferably 300 MPa or less, and more preferably 270 MPa or less. 50 ) of the present chemically strengthened glass is 150 MPa or more, it is easy to suppress breakage of the present chemically strengthened glass when a portable terminal or the like having the present chemically strengthened glass as a protective glass is dropped, and thus is preferable. CS 50 is more preferably 180 MPa or more, and further preferably 200 MPa or more. The greater CS 50 is, the higher the strength is, but when CS 50 is excessively large, violent shattering can occur in the case of breakage, and thus CS 50 is preferably 300 MPa or less, and more preferably 270 MPa or less.

[0056] When the DOL of the present chemically strengthened glass is 90 μm or more, it is less likely to be broken even when a scratch is generated on the surface, and thus is preferable. The DOL is more preferably 95 μm or more, further preferably 100 μm or more, and particularly preferably 110 μm or more. The greater the DOL is, the less likely it is to be broken even when a scratch is generated, but in the chemically strengthened glass, a tensile stress is generated in the inside due to the compressive stress formed in the vicinity of the surface, and thus the DOL cannot be extremely large. In the case where the thickness is t, the DOL is preferably t / 4 or less, and more preferably t / 5 or less. In order to shorten the time required for the chemical strengthening, the DOL is preferably 200 μm or less, and more preferably 180 μm or less.

[0057] In the case where the plate thickness is t, the compressive stress value CS t / 2 at a depth of t / 2 from the surface of the present chemically strengthened glass is preferably -120 MPa or more, more preferably -115 MPa or more, and further preferably -110 MPa or more. By making CSt / 2 With a pressure of -120MPa or higher, it can prevent explosive breakage when glass is damaged. Additionally, it is effective against CS. t / 2 There is no particular upper limit, but in order to maintain sufficient compressive stress, it is preferred to be below -80 MPa, for example.

[0058] When observing the first and second main surfaces of this chemically strengthened glass directly from above using the above method, multiple non-through holes were observed. Figure 2 The image shows a partial sectional view, schematically representing an example of a main face. (See image.) Figure 2 As shown, the chemically strengthened glass 24 has non-through holes 22, thus forming an uneven surface on the surface of the chemically strengthened glass containing microcrystalline glass. Through this uneven surface, the area ratio of the residual glass on the main surface of the chemically strengthened glass is increased, the refractive index is reduced, thereby suppressing reflection at the surface of the chemically strengthened glass, and thus increasing the transmittance.

[0059] The average diameter of the non-through-hole is preferably 5 nm to 50 nm, more preferably 8 nm to 40 nm, and even more preferably 10 nm to 30 nm. That is, the average diameter of the non-through-hole is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more. In addition, the average diameter of the non-through-hole 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 5 nm or more for the non-through-hole, the reflectivity at the main surface can be reduced, thereby improving transparency. In addition, when the average diameter of the non-through-hole is greater than 50 nm, the depth of the hole is close to the wavelength of light, the scattering increases, and the transmittance decreases.

[0060] In the first and second main surfaces of this chemically strengthened glass, the average depth of the non-through-hole, measured using cross-sectional SEM images, is 5 nm to 50 nm, preferably 8 nm to 40 nm, and more preferably 10 nm to 30 nm. That is, the average depth of the non-through-hole 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 the non-through-hole 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, thereby reducing reflectivity and improving transparency. On the other hand, when the average depth is greater than 50 nm, the average depth of the non-through-hole approaches the wavelength of light, resulting in increased scattering and reduced transmittance. The shape of the non-through-hole observed by cross-sectional SEM images is not particularly limited; for example, circular, semi-circular, and rectangular shapes can be included.

[0061] The total area ratio of the non-through holes with respect to the total field area of the surface SEM image is preferably 1 to 40%, more preferably 1 to 30%, and even more preferably 2 to 20%. That is, the total area ratio of the non-through holes is preferably 1% or more, and more preferably 2% or more. In addition, the total area ratio of the non-through holes is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. By the total area ratio of the non-through holes being 1% or more, the area ratio of the glass of the glass main surface can be increased, the reflectance can be reduced, and the transparency can be improved. When the total area ratio of the non-through holes is greater than 40%, the scattering of the surface becomes large, and the transmittance decreases.

[0062] The distribution of the non-through holes of the first main surface and the second main surface of the present chemically strengthened glass is not particularly limited, but is preferably uniform from the viewpoint of improving transparency.

[0063] The reflectance of the first main surface and the second main surface of the present chemically strengthened glass is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less. By the reflectance of the first main surface and the second main surface being 10% or less, excellent transparency is exhibited. The lower limit of the reflectance is not particularly limited, but is typically 5% or more.

[0064] The haze value of the present 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, in the case where the thickness is 700 μm. The haze value is more preferably smaller, but is typically 0.01% or more.

[0065] The drop strength of the present chemically strengthened glass, which is measured by the above method, is preferably 160 cm or more, more preferably 170 cm or more, and even more preferably 180 cm or more. By the drop strength being 160 cm or more, the breakage of the present chemically strengthened glass when a portable terminal or the like having the present chemically strengthened glass as a protective glass is dropped can be easily suppressed. The upper limit of the drop strength is not particularly limited, but is typically 300 cm or less.

[0066] <Composition>

[0067] The basic composition of the present chemically strengthened glass preferably contains SiO2, Li2O, and Al2O3. The basic composition of the present chemically strengthened glass preferably contains, in terms of mol% on an oxide basis:

[0068] 40 to 70% of SiO2,

[0069] 5 to 35% of Li2O, and

[0070] 1 to 20% of Al2O3.

[0071] Further, the base composition of the present chemically strengthened glass is further preferably composed of:

[0072] 50 to 70% of Si02,

[0073] 10 to 30% of Li20,

[0074] 1 to 15% of Al203,

[0075] 0 to 5% of P205,

[0076] 0 to 8% of Zr02,

[0077] 0 to 10% of MgO,

[0078] 0 to 5% of Y203,

[0079] 0 to 10% of B203,

[0080] 0 to 5% of Na20,

[0081] 0 to 5% of K20, and

[0082] 0 to 2% of Sn02.

[0083] Here, the "base composition of the chemically strengthened glass" refers to the composition of the glass-ceramic before the chemical strengthening. Regarding the composition, it will be described later. The present chemically strengthened glass has, as a whole, a similar composition to the glass-ceramic before the strengthening except for the case where the extreme ion exchange treatment is performed. In particular, except for the case where the extreme ion exchange treatment is performed, the composition of the deepest portion from the surface of the glass is the same as that of the glass-ceramic before the strengthening.

[0084] < USE >

[0085] The present chemically strengthened glass is also useful as a protective glass used in electronic devices such as mobile devices, smartphones, and the like. In addition, it is also useful as a protective glass for electronic devices such as televisions, personal computers, and touch panels, which are not intended to be carried, a wall surface of an elevator, a wall surface (full screen display) of a building such as a house or a building, and the like. Further, it is also useful as a building material such as a window glass, a table top, an interior material of an automobile or an airplane, and the like, a protective glass thereof, and in applications such as a case having a curved shape.

[0086] < GLASS-CERAMIC >

[0087] The present chemically strengthened glass is a glass-ceramic containing crystals and residual glass (hereinafter, also referred to as the present glass-ceramic). By the present chemically strengthened glass being a glass-ceramic containing crystals and residual glass, the crystals in the surface layer portion are dissolved by the cleaning treatment described later, and become non-through holes.

[0088] When the etching rate of the residual glass is set as Eg and the etching rate of the crystal is set as Ec, the Eg / Ec of the present glass-ceramics is preferably 0.1 to 0.0001, more preferably 0.05 to 0.0005, and further preferably 0.01 to 0.001. That is, the Eg / Ec is preferably 0.0001 or more, more preferably 0.0005 or more, and further preferably 0.001 or more. In addition, the Eg / Ec is preferably 0.1 or less, more preferably 0.05 or less, and further preferably 0.01 or less. By setting the Eg / Ec to 0.1 to 0.0001, the crystal existing on the surface of the glass-ceramics dissolves, non-through holes are easily generated, and the transparency can be improved.

[0089] The present glass-ceramics preferably contains at least one crystal selected from the group consisting of Li3PO4crystal, LiAlSi4O 10 Li2Si2O5crystal, and Li4SiO4crystal, and more preferably contains at least one crystal selected from the group consisting of Li3PO4crystal, LiAlSi4O 10 Li2Si2O5crystal. The present glass-ceramics can contain a solid solution crystal of these. The etching rate of these crystals is large, and thus by the cleaning treatment described later, the crystal existing on the surface of the glass-ceramics dissolves, non-through holes are easily generated, and the transparency can be improved.

[0090] The crystal structure of Li3PO4crystal and Li4SiO4crystal is similar, and thus it is sometimes difficult to distinguish by powder X-ray diffraction measurement. That is, when the powder X-ray diffraction is measured, diffraction peaks appear near 2θ = 16.9°, 22.3°, 23.1°, and 33.9°. Since there are cases where the amount of crystal is small and the orientation is performed, the peak of low intensity and the peak of a specific crystal plane cannot be confirmed sometimes. In addition, in the case where the two kinds of crystals are solid-solved, the 2θ peak position is sometimes shifted by about 1°.

[0091] When the X-ray diffraction is measured in the range of 2θ = 10° to 80°, the most intense diffraction peak of the present glass-ceramics preferably appears at 22.3° ± 0.2° or 23.1° ± 0.2°.

[0092] In order to improve the mechanical strength, the crystallization rate of the present glass-ceramics is preferably 10 mass% or more, more preferably 15 mass% or more, and further preferably 20 mass% or more. In order to improve the transparency, the crystallization rate is preferably 90 mass% or less, more preferably 70 mass% or less, further preferably 60 mass% or less, and particularly preferably 50 mass% or less. The point that the crystallization rate is small is also excellent in terms of easy bending formation by heating and the like.

[0093] To improve the strength, the average particle size of the precipitated crystals of the present glass-ceramics is preferably 5 nm or more, and particularly preferably 10 nm or more. To improve the transparency, the average particle size is preferably 80 nm or less, more preferably 60 nm or less, further preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. The average particle size of the precipitated crystals can be calculated from a transmission electron microscope (TEM) image.

[0094] The thickness (t) of the present glass-ceramics in the case of a plate shape is preferably 3000 μm or less, more preferably 2000 μm or less, 1600 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, 700 μm or less in this order. In addition, to obtain sufficient strength by chemical strengthening treatment, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and further preferably 500 μm or more.

[0095] In the case of a thickness of 700 μm, the light transmittance of the present glass-ceramics before chemical strengthening is 85% or more, and thus, in the case of a protective glass for a portable display, the screen of the display is easily seen, and thus, it is satisfactory. The light transmittance is more preferably 88% or more, further preferably 90% or more, and particularly preferably 92% or more. The higher the light transmittance is, the more preferable it is, but it is usually 95% or less. In the case of a thickness of 700 μm, a light transmittance of 90% is equivalent to that of a general non-crystalline glass.

[0096] In the case of a thickness of 700 μm, the light transmittance of the present glass-ceramics after chemical strengthening is 88% or more, and thus, in the case of a protective glass for a portable display, the screen of the display is easily seen, and thus, it is satisfactory. The light transmittance is more preferably 90% or more, further preferably 91% or more, and particularly preferably 92% or more. The higher the light transmittance is, the more preferable it is, but it is usually 95% or less. In the case of a thickness of 700 μm, a light transmittance of 90% is equivalent to that of a general non-crystalline glass.

[0097] Note that, in the case of an actual thickness other than 700 μm, the light transmittance in the case of 700 μm can be calculated from the measured value based on the Lambert-Beer law.

[0098] In the case where the total light visible light transmittance of the present glass in a plate thickness t [μm] is 100 x T [%], and the surface reflectance of one side is 100 x R [%], by citing the Lambert-Beer law, using the constant a, there is a relationship of T = (1 - R) x exp(-at). 2 ​

[0099] Here, if α is represented by R, T, t, and t = 700 μm, R does not change with the thickness of the plate, and thus the total light visible light transmittance T when converted to 700 μm is 0.7 0.7 = 100 x T 0.7 / t / (1-R)^(1.4 / t-2) [%]. Here, X^Y means X Y .

[0100] The surface reflectance can be calculated from the refractive index or can be actually measured. In addition, in the case where the thickness t of the plate is greater than 700 μm, the visible light transmittance can be measured after adjusting the thickness of the plate to 700 μm by polishing, etching, or the like.

[0101] In addition, in the case where the thickness is 700 μm, the haze value of the present glass-ceramic before chemical strengthening is preferably 0.5% or less, more preferably 0.4% or less, further preferably 0.3% or less, particularly preferably 0.2% or less, and most preferably 0.15% or less. The smaller the haze value, the more preferable, but it is usually 0.01% or more. In the case where the thickness is 700 μm, a haze value of 0.02% is equivalent to that of a general non-crystalline glass.

[0102] Note that, in the case where the total light visible light transmittance of the glass-ceramic having a thickness t [μm] is 100 x T [%] and the haze value is 100 x H [%], dH / dt ∝ exp(-αt) x (1-H) is obtained by citing the Lambert-Beer law using the above constant α.

[0103] That is, it is considered that the haze value increases by an amount proportional to the internal straight-line transmittance as the thickness of the plate increases, and thus the haze value H 0.7 is obtained by the following formula. Here, "X^Y" means "X Y ".

[0104] H 0.7 = 100 x [1-(1-H)^( (1-R 2 -T 0.7 ) / (1-R 2 -T) ] [%]

[0105] In addition, in the case where the thickness t of the plate is greater than 700 μm, the haze value can be measured after adjusting the thickness of the plate to 700 μm by polishing, etching, or the like.

[0106] The fracture toughness value of the present glass-ceramic is high, and even if a large compressive stress is formed by chemical strengthening, violent fracture is not likely to occur. When the fracture toughness value of the present glass-ceramic is preferably 0.81 MPa-m 1 / 2 or more, and more preferably 0.84 MPa-m​1 / 2 Further preferably, the above is 0.87 MPa • m 1 / 2 When the above, a glass having high impact resistance can be obtained. The upper limit of the fracture toughness value of the present glass-ceramics is not particularly limited, and is typically 1.5 MPa • m 1 / 2 The following.

[0107] In order to be able to suppress warping at the time of chemical strengthening treatment, the Young's modulus of the present glass-ceramics is preferably 80 GPa or more, more preferably 85 GPa or more, further preferably 90 GPa or more, and particularly preferably 95 GPa or more. The present glass-ceramics is sometimes used after polishing. In order to facilitate polishing, the Young's modulus is preferably 130 GPa or less, more preferably 120 GPa or less, and further preferably 110 GPa or less.

[0108] The present glass-ceramics is obtained by subjecting an amorphous glass described later to heat treatment and crystallization.

[0109] Composition of the Glass-Ceramics

[0110] The present glass-ceramics preferably contains SiO2, Li2O, and Al2O3. The present glass-ceramics more preferably contains, in terms of mol% on an oxide basis:

[0111] 40% to 70% of SiO2,

[0112] 5% to 35% of Li2O, and

[0113] 1% to 20% of Al2O3.

[0114] The present glass-ceramics further preferably contains, in terms of mol% on an oxide basis:

[0115] 50% to 70% of SiO2,

[0116] 10% to 30% of Li2O,

[0117] 1% to 15% of Al2O3,

[0118] 0 to 5% of P2O5,

[0119] 0% to 8% of ZrO2,

[0120] 0% to 10% of MgO,

[0121] 0% to 5% of Y2O3,

[0122] 0% to 10% of B2O3,

[0123] 0% to 5% of Na2O,

[0124] 0% to 5% of K2O, and

[0125] 0 to 2% of Sn02.

[0126] In addition, the total amount of Si02, Al203, P205, and B203in the present glass-ceramics, in terms of mol% on an oxide basis, is preferably 60 to 80%. Si02, Al203, P205, and B203are network-forming components (hereinafter, also referred to as NWF) of the glass. By having a large total amount of these NWFs, the strength of the glass is improved. The fracture toughness value of the glass-ceramics is thereby increased, and thus the total amount of the NWFs is preferably 60% or more, more preferably 63% or more, and particularly preferably 65% or more. However, a glass having too much NWFs is difficult to manufacture because the melting temperature is high, and thus the total amount of the NWFs is preferably 85% or less, more preferably 80% or less, and more preferably 75% or less.

[0127] The total amount of Li20, Na20, and K20 in the present glass-ceramics is preferably 0.20 to 0.60 with respect to the total amount of NWFs, i.e., Si02, Al203, P205, and B203.

[0128] Li20, Na20, and K20 are network-modifying components, and by reducing the ratio thereof with respect to the NWFs, the gaps in the network are increased, and thus the impact resistance is improved. Thus, the total amount of Li20, Na20, and K20 is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less with respect to the NWFs. On the other hand, since these are components that are essential in chemical strengthening, in order to improve the chemical strengthening characteristics, the total amount of Li20, Na20, and K20 is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.30 or more with respect to the NWFs.

[0129] Hereinafter, the composition of the present glass-ceramics will be described.

[0130] In the present glass-ceramics, Si02is a component that forms the network structure of the glass. In addition, Si02is a component that reduces the etching rate of the residual glass. The content of Si02is preferably 40% or more. The content of Si02is more preferably 48% or more, further preferably 50% or more, particularly preferably 52% or more, and extremely preferably 54% or more. On the other hand, in order to improve the melting property, the content of Si02is preferably 70% or less, more preferably 68% or less, further preferably 66% or less, and particularly preferably 64% or less.

[0131] Li2O is a component for forming surface compressive stress by ion exchange, and is a constituent component of the main crystal, and thus is essential. The content of Li2O is preferably 5% or more, more preferably 10% or more, further preferably 15% or more, still further 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 content of Li2O is preferably 35% or less, more preferably 32% or less, further preferably 30% or less, particularly preferably 28% or less, and most preferably 26% or less.

[0132] Al2O3 is a component for increasing surface compressive stress generated by chemical strengthening and reducing etching rate of residual glass, and is essential. The content of Al2O3 is preferably 1% or more, more preferably 2% or more, further 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, in order that devitrification temperature of the glass does not become excessively high, the content of Al2O3 is preferably 20% or less, more preferably 15% or less, further preferably 12% or less, particularly preferably 10% or less, and most preferably 9% or less.

[0133] P2O5 is not essential, but is essential in the case where a glass-ceramic containing Li3PO4 crystal is desired to be obtained, since it is a constituent component of Li3PO4 crystal. In order to promote crystallization, the content of P2O5 is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, when the content of P2O5 is excessively large, phase separation is easily caused at the time of melting, and further, acid resistance is significantly reduced, and thus the content of P2O5 is preferably 5% or less, more preferably 4.8% or less, further preferably 4.5% or less, particularly preferably 4.2% or less.

[0134] ZrO2 is a component for improving mechanical strength and reducing etching rate of residual glass, and is preferably contained in order to significantly improve CS. The content of ZrO2 is preferably 0.5% or more, more preferably 1% or more, further 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 at the time of melting, ZrO2 is preferably 8% or less, more preferably 5% or less, further preferably 4% or less, still further preferably 3.5% or less, and particularly preferably 3% or less. When the content of ZrO2 is excessively large, viscosity is reduced due to an increase in devitrification temperature. In order to suppress this reduction in viscosity to thereby improve formability, the content of ZrO2 is preferably 5% or less, more preferably 4.5% or less, and further preferably 3.5% or less, in the case where the forming viscosity is low.

[0135] MgO is a component for stabilizing the glass, and is also a component for improving mechanical strength and chemical resistance, and thus is preferably contained in cases where the Al2O3 content is relatively small or the like. The content of MgO is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and particularly preferably 4% or more. On the other hand, when MgO is excessively added, the viscosity of the glass decreases, and devitrification or phase separation is easily caused, and thus the content of MgO is preferably 10% or less, more preferably 9% or less, further preferably 8% or less, and particularly preferably 7% or less.

[0136] Y2O3 is a component having an effect of making the fragments less likely to scatter at the time of fracture of a chemically strengthened glass, and Y2O3 can be contained. The content of Y2O3 is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, particularly preferably 2.5% or more, and extremely preferably 3% or more. On the other hand, in order to suppress devitrification at the time of melting, the content of Y2O3 is preferably 5% or less, and more preferably 4% or less.

[0137] B2O3 is a component for improving the edge chipping resistance of a glass for chemical strengthening or a chemically strengthened glass and for improving the melting property, and B2O3 can be contained. In order to improve the melting property, the content of B2O3 is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more, in the case where B2O3 is contained. On the other hand, when the content of B2O3 is excessively large, a moiré is generated at the time of melting or phase separation is easily caused, and the quality of the glass for chemical strengthening easily decreases, and thus the content of B2O3 is preferably 10% or less. The content of B2O3 is more preferably 8% or less, further preferably 6% or less, and particularly preferably 4% or less.

[0138] Na2O is a component for improving the melting property of the glass. Na2O is not essential, but in the case where Na2O is contained, the content of Na2O is preferably 0.5% or more, more preferably 1% or more, and particularly preferably 2% or more. When Na2O is excessively large, it is difficult to precipitate crystals such as Li3PO4 as a main crystal, or the chemical strengthening characteristics decrease, and thus the content of Na2O is preferably 5% or less, more preferably 4.5% or less, further preferably 4% or less, and particularly preferably 3.5% or less.

[0139] K2O is also a component for lowering the melting temperature of the glass, and K2O can be contained. In the case where K2O is contained, the content of K2O is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. When K2O is excessively large, the chemical strengthening characteristics decrease, or in order to suppress an increase in the etching rate of the residual glass, the content of K2O is preferably 5% or less, more preferably 4% or less, further preferably 3.5% or less, particularly preferably 3% or less, and most preferably 2.5% or less.

[0140] In order to improve the melting property of the glass raw material, the content of the total of Na2O and K2O, Na2O + K2O, is preferably 1% or more, more preferably 2% or more.

[0141] In addition, when the ratio K2O / R2O of the content of K2O with respect to the total of the contents of Li2O, Na2O, and K2O (hereinafter, referred to as R2O) is 0.2 or less, the chemical strengthening property can be improved and the etching rate of the residual glass can be reduced, and thus is preferable. The K2O / R2O is more preferably 0.15 or less, and further preferably 0.10 or less.

[0142] Note that R2O is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. In addition, R2O is preferably 29% or less, and more preferably 26% or less.

[0143] In addition, in order to reduce the etching rate of the residual glass, ZrO2 / R2O is preferably 0.02 or more, more preferably 0.03 or more, further preferably 0.04 or more, particularly preferably 0.1 or more, and most preferably 0.15 or more. In order to improve the transparency after crystallization, ZrO2 / R2O is preferably 0.6 or less, more preferably 0.5 or less, further preferably 0.4 or less, and particularly preferably 0.3 or less.

[0144] SnO2 has an effect of promoting the generation of crystal nuclei, and SnO2 can be contained. SnO2 is not essential, but in the case where SnO2 is contained, the content of SnO2 is preferably 0.5% or more, more preferably 0.7% or more, further preferably 1% or more, and particularly preferably 1.5% or more. On the other hand, in order to suppress devitrification at the time of melting, the content of SnO2 is preferably 3% or less, more preferably 2.5% or less, and further preferably 2% or less.

[0145] TiO2 is a component that can promote crystallization, and TiO2 can be contained. TiO2 is not essential, but in the case where TiO2 is contained, the content of TiO2 is preferably 0.2% or more, and more preferably 0.5% or more. On the other hand, in order to suppress devitrification at the time of melting, the content of TiO2 is preferably 4% or less, more preferably 2% or less, and further preferably 1% or less.

[0146] BaO, SrO, MgO, CaO and ZnO are components which improve the melting property of the glass, and these components can be contained. In the case where these components are contained, 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, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, since the ion exchange rate decreases, BaO + SrO + MgO + CaO + ZnO is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, and particularly preferably 4% or less.

[0147] BaO, SrO and ZnO among them increase the refractive index of the residual glass to approach the precipitated crystal phase, thereby improving the light transmittance of the glass-ceramics and reducing the haze value, and therefore BaO, SrO and ZnO can be contained. In this case, the total content of BaO, SrO and ZnO (hereinafter referred to as BaO + SrO + ZnO) is preferably 0.3% or more, more preferably 0.5% or more, further preferably 0.7% or more, and particularly preferably 1% or more. On the other hand, these components sometimes decrease the ion exchange rate. In order to improve the chemical strengthening properties, BaO + SrO + ZnO is preferably 2.5% or less, more preferably 2% or less, further preferably 1.7% or less, and particularly preferably 1.5% or less.

[0148] La2O3, Nb2O5 and Ta2O5 are components which make the fragments less likely to scatter at the time of breakage of the chemically strengthened glass, and La2O3, Nb2O5 and Ta2O5 can be contained in order to increase the refractive index. In the case where these substances are contained, 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, further preferably 1.5% or more, and particularly preferably 2% or more. In addition, in order to make the glass less likely to devitrify at the time of melting, La2O3 + Nb2O5 + Ta2O5 is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

[0149] In addition, CeO2 can be contained. CeO2 sometimes suppresses coloring by oxidizing the glass. In the case where CeO2 is contained, the content of CeO2 is preferably 0.03% or more, more preferably 0.05% or more, and further preferably 0.07% or more. In order to improve the transparency, the content of CeO2 is preferably 1.5% or less, and more preferably 1.0% or less.

[0150] When the present chemically strengthened glass is used by being colored, coloring components can be added within a range not to hinder achievement of desired chemical strengthening properties. As the coloring components, for example, Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3 can be listed.

[0151] The content of the coloring components is preferably within a range of 1% or less in total. In a case where it is desired to make the visible light transmittance of the glass higher, it is preferable that these components are not contained substantially.

[0152] In addition, SO3, chloride, and fluoride can be appropriately contained as a fining agent or the like at the time of melting the glass. It is preferable that As2O3 is not contained. In a case where Sb2O3 is contained, the content of Sb2O3 is preferably 0.3% or less, more preferably 0.1% or less, and most preferably Sb2O3 is not contained.

[0153] <Method for manufacturing chemically strengthened glass>

[0154] The method for manufacturing the chemically strengthened glass of the present application includes a chemical strengthening treatment of a glass-ceramic containing crystals and residual glass and a cleaning treatment of the glass-ceramic. The method preferably includes: chemically strengthening the glass-ceramic containing crystals and residual glass; and cleaning the surface of the glass-ceramic after the chemical strengthening using a cleaning solution having a pH of 2 to 12. The glass-ceramic is manufactured by a method of crystallizing an amorphous glass of the same composition by a heat treatment.

[0155] <Manufacture of amorphous glass>

[0156] The amorphous glass can be manufactured, for example, by the following method. Note that the following described manufacturing method is an example of a case of manufacturing a plate-shaped chemically strengthened glass.

[0157] The glass raw materials are prepared in a manner to obtain a glass of a desired composition, and are heated and melted in a glass melting furnace. Then, the molten glass is homogenized by bubbling, stirring, addition of a fining agent, or the like, is formed into a glass sheet of a prescribed thickness by a publicly known forming method, and is then slowly cooled. Alternatively, it can be formed into a plate shape by a method of forming the molten glass into a block and slowly cooling, and then cutting.

[0158] <Crystallization treatment>

[0159] The amorphous glass obtained by the above described operation steps is subjected to a heat treatment, whereby a glass-ceramic can be obtained.

[0160] The heat treatment can be two-step heat treatment of warming from room temperature to a first treatment temperature and holding for a certain time, and then holding for a certain time at a second treatment temperature which is higher than the first treatment temperature. Alternatively, one-step heat treatment of holding at a certain treatment temperature and then cooling to room temperature can be performed.

[0161] In the case of two-step heat treatment, the first treatment temperature is preferably a temperature range in which the nucleation rate increases for the glass composition, and the second treatment temperature is preferably a temperature range in which the crystal growth rate increases for the glass composition. In addition, with respect to the holding time at the first treatment temperature, long-time holding is preferable so that a sufficient number of crystal nuclei are generated. By generating a large number of crystal nuclei, the size of each crystal becomes small, and thus a glass-ceramic with high transparency can be obtained.

[0162] In the case of two-step treatment, for example, holding at a first treatment temperature of 450°C to 700°C for 1 hour to 6 hours, and then holding at a second treatment temperature of, for example, 600°C to 800°C for 1 hour to 6 hours can be exemplified. In the case of one-step treatment, for example, holding at 500°C to 800°C for 1 hour to 6 hours can be exemplified.

[0163] The glass-ceramic obtained by the above operation steps is subjected to grinding and polishing treatment as necessary, and thus a glass-ceramic plate is formed. In the case where the glass-ceramic plate is cut into a prescribed shape and size or subjected to chamfering processing, it is preferable to perform cutting, chamfering processing before performing chemical strengthening treatment, because a compressive stress layer is formed on the end surface by the subsequent chemical strengthening treatment.

[0164] <<Chemical Strengthening Treatment>>

[0165] The chemical strengthening treatment is a treatment in which a metal ion with a small ionic radius (typically, Na ion or Li ion) in the glass is replaced with a metal ion with a large ionic radius (typically, Na ion or K ion with respect to Li ion, or K ion with respect to Na ion) by bringing the glass into contact with a metal salt (for example, potassium nitrate) containing a metal ion with a large ionic radius (typically, Na ion or K ion) by immersion in a molten salt or the like.

[0166] In order to accelerate the speed of the chemical strengthening treatment, "Li-Na exchange" in which Li ion in the glass is exchanged with Na ion is preferable. In addition, in order to form a large compressive stress by ion exchange, "Na-K exchange" in which Na ion in the glass is exchanged with K ion is preferable.

[0167] As the molten salt used for the chemical strengthening treatment, for example, nitrates, sulfates, carbonates, chlorides, and the like can be listed. Among them, as the nitrates, for example, lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate, and the like can be listed. As the sulfates, for example, lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate, and the like can be listed. As the carbonates, for example, lithium carbonate, sodium carbonate, potassium carbonate, and the like can be listed. As the chlorides, for example, lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, and the like can be listed. These molten salts can be used alone or in combination of a plurality of kinds.

[0168] The treatment conditions of the chemical strengthening treatment can be selected in terms of time and temperature and the like, taking into consideration the glass composition, the kind of the molten salt, and the like. For example, the chemical strengthening treatment can be listed, in which the present glass-ceramics is preferably immersed in a molten salt at 450°C or lower for preferably 1 hour or less. Specifically, for example, a treatment in which the present glass-ceramics is preferably immersed in a molten salt containing 0.3 mass% of Li and 99.7 mass% of Na (for example, a mixed salt of lithium nitrate and sodium nitrate) at 450°C for preferably about 0.5 hour can be listed.

[0169] The chemical strengthening treatment can be performed, for example, by two-step ion exchange. First, the present glass-ceramics is immersed in a metal salt containing Na ions (for example, sodium nitrate) at preferably about 350°C to about 500°C for preferably about 0.1 hour to about 10 hours. By this, ion exchange of Li ions in the glass-ceramics with Na ions in the metal salt occurs, and a relatively deep compressive stress layer can be formed.

[0170] Next, the present glass-ceramics is immersed in a metal salt containing K ions (for example, potassium nitrate) at preferably about 350°C to about 500°C for preferably about 0.1 hour to about 10 hours. By this, a large compressive stress is generated in a portion of the compressive stress layer formed in the previous treatment, for example, within about 10 μm in depth. According to such two-step treatment, a stress profile in which the surface compressive stress value is large is easily obtained.

[0171] < Cleaning Treatment >

[0172] By subjecting the chemical strengthened glass obtained by the chemical strengthening treatment to a cleaning treatment, a plurality of non-through holes are formed in both main surfaces of the chemical strengthened glass. The cleaning treatment is performed by immersing the chemical strengthened glass in a cleaning solution. The pH of the cleaning solution is preferably, for example, 2 to 12, more preferably 2.5 to 11, and further preferably 3 to 10. The cleaning treatment time can be appropriately adjusted in consideration of the pH and the composition of the cleaning solution, the etching rate of the glass-ceramics, and the like, so that the average value of the diameters, the average value of the depths, and the total area ratio of the non-through holes formed are within a desired range, but is generally preferably 5 minutes to 48 hours, more preferably 10 minutes to 36 hours, and further preferably 30 minutes to 24 hours.

[0173] The temperature of the cleaning liquid is not particularly limited, and it is used at room temperature (15°C) to 100°C. In the case of greater than 100°C, the water in the cleaning liquid can boil, which is inconvenient in terms of the cleaning operation, and is not preferred. Drying can be performed after cleaning. As the drying method, a method of blowing hot air, a method of blowing compressed air, and the like can be cited.

[0174] As the cleaning liquid, an acidic or basic cleaning liquid can be cited. The acidic cleaning liquid preferably contains an organic acid and an inorganic acid. As the organic acid contained in the acidic cleaning liquid, for example, an organic carboxylic acid such as citric acid, ascorbic acid, and the like, an organic phosphonic acid, and the like can be cited, and citric acid is preferred. As the inorganic acid contained in the acidic cleaning liquid, for example, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and the like can be cited, and hydrochloric acid is preferred. In addition, in the case of using the above inorganic acid, in order to suppress the variation in pH, a salt of the acid can be added together with the inorganic acid. As the preferred combination of the organic acid and the inorganic acid, for example, citric acid and hydrochloric acid can be cited.

[0175] The basic cleaning liquid contains a base, and in addition to the base, a surfactant, a chelating agent can be contained. As the base contained in the basic cleaning liquid, for example, an alkali metal compound such as an alkali metal hydroxide, an alkali metal carbonate, and the like, an amine, a quaternary ammonium hydroxide, and the like can be cited. As the base, an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide, and the like is preferred. As the surfactant, a nonionic surfactant is preferred.

[0176] Example

[0177] Hereinafter, the present application will be described by way of examples, but the present application is not limited thereto.

[0178] <Manufacture and Evaluation of Amorphous Glass>

[0179] The glass raw material was weighed in such a manner as to become the glass composition in Table 1 in terms of mol% on an oxide basis, in such a manner as to obtain 800 g of glass. Next, the mixed glass raw material was put into a platinum crucible and was put into an electric furnace at 1600°C, was melted for about 5 hours, and was subjected to deaeration and homogenization.

[0180] The obtained molten glass was poured into a mold, was held at the glass transition temperature for 1 hour, and was then cooled to room temperature at a rate of 0.5°C / minute, whereby a glass block was obtained. Using a part of the obtained block, the glass transition temperature, the specific gravity, the Young's modulus, and the fracture toughness value of the amorphous glass were evaluated, and the results of the evaluation are shown in Table 1.

[0181] R2O in the table indicates the total of the contents of Li2O, Na2O, and K2O, and NWF indicates the total of the contents of SiO2, Al2O3, P2O5, and B2O3.

[0182] (Specific gravity p)

[0183] Specific gravity p was measured by the Archimedes method.

[0184] (Glass transition temperature Tg)

[0185] The glass was crushed using an agate mortar, about 80 mg of the powder was put in a platinum cell, the temperature increase rate was set to 10 / minute, and the DSC curve was measured using a differential scanning calorimeter (manufactured by BRUKER; DSC3300SA) while increasing the temperature from room temperature to 1100°C, whereby the glass transition temperature Tg was obtained.

[0186] Alternatively, based on JIS R1618:2002, a thermal dilatometer (manufactured by BRUKER AXS; TD5000SA) was used, the temperature increase rate was set to 10°C / minute, whereby the thermal dilatation curve was obtained, and the glass transition temperature Tg [unit: °C] was obtained from the obtained thermal dilatation curve.

[0187] (Haze value)

[0188] The haze value under a halogen lamp C light source [unit: %] was measured using a haze meter (manufactured by SUGA TEST MACHINE CO., LTD.; HZ-V3).

[0189] (Young's modulus E)

[0190] Young's modulus E was measured by the ultrasonic wave method.

[0191] (Fracture toughness value Kc)

[0192] The fracture toughness value Kc was measured by the IF method according to JIS R1607:2015.

[0193] Table 1

[0194] G1 G2 SiO2 61 70.9 Al2O3 5 4.2 P2O5 2 0.9 Li2O 21 21.7 Na2O 2 0.1 [K2O] 0 0.1 MgO 5 0 ZrO2 3 2 [Y2O3] 1 0 SnO2 0 0.2 [R2O] 23 21.9 NWF 68 76 ρ (g / cm 3 )]]> 2.56 2.41 Tg (°C) 513 481 Haze (%) 0.02 0.05 E (GPa) 90 84 [Kc (MPa-m 1 / 2 )]]> 0.98 1.01

[0195] <Crystallization treatment and evaluation of glass-ceramics>

[0196] The obtained glass block was processed to 50 mm x 50 mm x 1.5 mm, and then heat-treated under the conditions described in Table 2, whereby glass-ceramics were obtained. In the crystallization condition column of the table, the upper row is the nucleation treatment condition, and the lower row is the crystal growth treatment condition, for example, in the case where 550°C for 2 hours is described in the upper row and 750°C for 2 hours is described in the lower row, it means that 2 hours at 550°C is followed by 2 hours at 750°C.

[0197] The obtained glass-ceramics was processed and mirror-polished, thereby obtaining a glass-ceramic plate having a thickness t of 700 μm. In addition, a bar-shaped sample for measuring the coefficient of thermal expansion was prepared. A part of the remaining glass-ceramics was pulverized and used for analysis of precipitated crystals. The evaluation results of the glass-ceramics are shown in Table 2.

[0198] (X-ray diffraction: precipitated crystals)

[0199] The precipitated crystals were identified by powder X-ray diffraction under the following conditions.

[0200] Measurement device: Smart Lab manufactured by Japan Rigaku Manufacturing Co., Ltd.

[0201] X-ray used: Cu Kα ray

[0202] Measurement range: 2θ = 10° to 80°

[0203] Speed: 1° / minute

[0204] Step pitch: 0.01°

[0205] The main crystals detected are shown in the crystal column of Table 2. Li3PO4 and Li4SiO4 are difficult to distinguish by powder X-ray diffraction, and thus both are described.

[0206] (Haze value)

[0207] The haze value under halogen lamp C light source [unit: %] was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.; HZ-V3).

[0208] Table 2

[0209]

[0210] <Chemical strengthening treatment and cleaning treatment>

[0211] The glass-ceramics CG1 and CG2 were subjected to chemical strengthening and ion exchange treatment under the conditions shown in Table 3, and the obtained chemically strengthened glasses were respectively designated as glass A, glass B, and glass X. The obtained chemically strengthened glasses were immersed in a cleaning solution having a pH of 8.9 at room temperature for 24 hours, thereby subjected to cleaning treatment, and the chemically strengthened glasses of Examples 1 to 4 were obtained and 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.

[0212] (Stress distribution)

[0213] The stress distribution was measured using a scattered light photoelastic stress meter SLP-2000 manufactured by Horiba Ltd.

[0214] (etching rate)

[0215] The weight reduction per unit time was measured by NaOH treatment (95°C, pH 10) and calculated.

[0216] (crystallinity, average crystal size)

[0217] The powder X-ray diffraction was measured under the following conditions, and the crystallinity [unit: %] and the average crystal size (crystal size) [unit: nm] were calculated using the Rietveld method.

[0218] Measurement device: Smart Lab, manufactured by Japan Rigaku Corporation

[0219] X-ray used: Cu Kα ray

[0220] Measurement range: 2θ = 10° to 80°

[0221] Speed: 10° / minute

[0222] Step pitch: 0.02°

[0223] (diameter average of non-through holes, total area ratio)

[0224] The diameter average of non-through holes and the total area ratio of non-through holes were calculated as follows. The chemically strengthened glass was observed from directly above with a SEM, and thereby a surface SEM image at 100,000 times was obtained. The non-through holes and the matrix portion were discriminated from the obtained surface SEM image, the length diameter of each non-through hole was calculated as the diameter, and the diameter average as the average thereof was calculated. In addition, for the total area ratio of non-through holes, the total area of non-through holes was calculated with respect to the total field area of the surface SEM image.

[0225] (depth average of non-through holes)

[0226] In the present specification, the depth of non-through holes was calculated as follows. A cross-sectional SEM image at 300,000 times was obtained in a cut cross section of the chemically strengthened glass. The non-through holes and the matrix portion were discriminated from the obtained cross-sectional SEM image, the depth of each non-through hole was calculated, and the depth average as the average thereof was calculated.

[0227] (drop strength)

[0228] In the drop test, the obtained glass sample of 120 mm x 60 mm x 0.6 mm t was embedded in a structure body adjusted in mass and rigidity to the size of a general smartphone currently in use, thereby preparing a simulated smartphone, and then dropped freely onto #180 SiC sandpaper. For the drop height, in the case where the sample was not broken when dropped from a height of 5 cm, the operation of increasing the drop height by 5 cm and dropping it again was repeated until it was broken, and the average value of the heights at which 10 glass samples were first broken was calculated.

[0229] (transmittance)

[0230] As the transmittance, the average transmittance of light of wavelengths of 380 nm to 780 nm was measured.

[0231] Table 3

[0232]

[0233] Table 4

[0234] Example 1 Example 2 Example 3 Example 4 chemically strengthened glass Glass A Glass B Glass A Glass X t [pm] 700 700 700 700 [MPa] CS0 540 530 540 340 CS 50 [MPa]]]> 220 240 220 100 CS t / 2 [MPa]]]> -100 -105 -100 -110 DOL [pm] 90 128 90 180 Ec [nm / min] 1 1 1 0.01 Eg / Ec 0.007 0.008 0.007 1.5 crystallinity [%] 20 20 20 88 average crystal size [nm] 15 15 15 35 cleaning treatment yes yes no no average diameter of non-through holes [nm] 25 22 0 0 total area ratio of non-through holes [%] 5.3 4.1 0 0 average depth of non-through holes [nm] 22.00 25.00 0 0 drop strength [cm] 180 190 180 130 transmittance [%] 92.5 92.4 91.1 90.2

[0235] As shown in Table 4, the transparency and strength of Examples 1 and 2, which are chemically strengthened glasses of the present application, were superior compared to Examples 3 and 4, which are comparative examples.

[0236] Although the present application has been described in detail and with reference to specific embodiments, it will be apparent to one skilled in the art that various changes and modifications can be applied thereto without departing from the spirit and scope of the present application. This application is based on Japanese Patent Application (Japanese Patent Application No. 2021-065435) filed on April 7, 2021, the contents of which are incorporated herein by reference.

[0237] Explanation of Reference Signs

[0238] 24 chemically strengthened glass

[0239] 22 non-through hole

Claims

1. A chemically strengthened glass having opposite first and second main faces, wherein the chemically strengthened glass comprises a glass-ceramic containing crystals and residual glass, the glass-ceramic contains crystals and residual glass, The surface compressive stress value CS0 of the chemically strengthened glass is 450 MPa or greater, and the compressive stress value CS at a depth of 50 μm from the surface of the chemically strengthened glass is 150 MPa or greater 50 150 MPa or greater, a plurality of non-through holes having an average diameter of 5 nm to 50 nm are present in the first and second main faces, an average depth of the non-through holes measured from cross-sectional SEM images of the first and second main faces is 5 nm to 50 nm, and a total area ratio of the non-through holes relative to a total field area of a surface SEM image is 1% to 40% in the first and second main faces.

2. The chemically strengthened glass of claim 1, wherein, when an etching rate of the residual glass in the glass-ceramic is set as Eg and an etching rate of the crystals in the glass-ceramic is set as Ec, Eg / Ec is 0.1 to 0.0001.

3. The chemically strengthened glass of claim 1, wherein, the base composition of the chemically strengthened glass contains 40% to 70% of Si02, 5% to 35% of Li20, and 1% to 20% of Al203 in terms of mol% on an oxide basis.

4. The chemically strengthened glass of any of claims 1-3, wherein, the crystallization rate of the chemically strengthened glass is 10 mass% to 90 mass%.

5. The chemically strengthened glass of any of claims 1-3, wherein, the reflectivity of the first and second main faces is 10% or less.

6. The chemically strengthened glass of any of claims 1-3, wherein, the light transmittance of the chemically strengthened glass before chemical strengthening is 90% or more at a thickness of 700 μm.

7. The chemically strengthened glass of any of claims 1-3, wherein, the chemically strengthened glass has a plate thickness of 300 μm to 3000 μm.

8. A method of manufacturing chemically strengthened glass, wherein, the method for producing the chemically strengthened glass comprises: chemically strengthening a glass-ceramic containing crystals and residual glass; and after the chemical strengthening, cleaning a surface of the glass-ceramic using a cleaning solution having a pH of 2 to 12, The chemically strengthened glass has opposite first and second main faces, a surface compressive stress value CS0 of the chemically strengthened glass is 450 MPa or greater, and a compressive stress value CS 50 is 150 MPa or greater, a plurality of non-through holes having an average diameter of 5 nm to 50 nm are present in the first and second main faces, an average depth of the non-through holes measured from cross-sectional SEM images of the first and second main faces is 5 nm to 50 nm, and a total area ratio of the non-through holes relative to a total field area of a surface SEM image is 1% to 40% in the first and second main faces.

9. The method of producing chemically strengthened glass according to claim 8, wherein, when an etching rate of the residual glass is set as Eg and an etching rate of the crystals is set as Ec, Eg / Ec is 0.1 to 0.0001.

10. The method of producing a chemically strengthened glass according to claim 8 or 9, wherein, the base composition of the glass-ceramic contains 40% to 70% of Si02, 5% to 35% of Li20, and 1% to 20% of Al203 in terms of mol% on an oxide basis.

Images