Chemically strengthened glass, cover glass for image display device, and glass material with antifouling layer

Abstract

To provide a chemically strengthened glass that exhibits superior transparency and allows improvement of peel resistance even when a functional layer such as an antifouling layer is formed.SOLUTION: A chemically strengthened glass having a first main surface and a second main surface, wherein the surface roughness Ra of the first main surface is 5 nm or more and 100 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to chemically strengthened glass, a cover glass for an image display device, and a glass material with an antifouling layer. [Background technology]

[0002] Cover glasses used in image display devices such as mobile terminals are provided with an anti-fouling layer (AFP) to prevent fingerprints and dirt from adhering to the glass. The anti-fouling layer may peel off with repeated use or over time, and various methods for preventing this peeling have been investigated (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-144097 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes a technique that attempts to prevent peeling of an antifouling layer by changing the composition of the antifouling layer-forming composition. If peeling of the antifouling layer can be prevented from viewpoints other than the composition, it will be possible to apply the antifouling layer to antifouling layers of various compositions. Furthermore, if the composition is not limited, the peeling prevention effect can be expected for other functional layers such as antireflection films. On the other hand, the cover glass must have high transparency so as not to impair visibility. An object of the present invention is to provide chemically strengthened glass that is excellent in transparency and peel resistance when a functional layer such as an antifouling layer is provided. [Means for solving the problem]

[0005] The present invention relates to the following chemically strengthened glass. A chemically strengthened glass having a first principal surface and a second principal surface, wherein the first principal surface has a surface roughness Ra of 5 nm or more and 100 nm or less. [Effects of the Invention]

[0006] The present invention provides chemically strengthened glass that exhibits excellent transparency and peel resistance when a functional layer such as an antifouling layer is provided thereon. Furthermore, the present invention also provides a cover glass for an image display device and a glass material with an antifouling layer, each of which includes the chemically strengthened glass. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of a glass plate according to an embodiment of the present invention. [Figure 2] Figure 2 is an SEM image of the precipitated particles. [Figure 3] FIG. 3 shows the results of X-ray diffraction of the precipitated particles. DETAILED DESCRIPTION OF THE INVENTION

[0008] In this specification, unless otherwise specified, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0009] 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 below. "Crystalline glass" is obtained by heat-treating "amorphous glass" to precipitate crystals, and contains crystals. In this specification, "amorphous glass" and "crystallized glass" are sometimes collectively referred to as "glass." Furthermore, amorphous glass that becomes crystallized glass by heat treatment is sometimes referred to as "mother glass of crystallized glass."

[0010] In this specification, powder X-ray diffraction measurement is performed using, for example, CuKα radiation in the 2θ range of 10° to 80°, and if a diffraction peak appears, the precipitated crystals are identified by the Hanawalt method. Furthermore, among the crystals identified by this method, the crystal identified from the peak group containing the peak with the highest integrated intensity is considered to be the main crystal. For example, a Rigaku SmartLab can be used as a measuring device.

[0011] In this specification, "chemically strengthened glass" refers to glass after chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before chemical strengthening treatment. Also, "mother composition of chemically strengthened glass" refers to the glass composition of the glass for chemical strengthening.

[0012] In this specification, unless otherwise specified, glass compositions are expressed in mole percent on an oxide basis, and mole percent is simply represented as "%."

[0013] In this specification, "substantially free" means that the content is below the impurity level contained in raw materials, i.e., it is not intentionally added. Specifically, for example, it is less than 0.1%.

[0014] In this specification, the term "stress profile" refers to a representation of compressive stress values ​​with depth from the glass surface as a variable. In the stress profile, tensile stress is represented as negative compressive stress.

[0015] The "compressive stress value (CS)" can be measured by cutting a cross section of glass into thin slices and analyzing the sliced ​​samples with 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, etc., and one example is the birefringence imaging system Abrio-IM manufactured by CRi.

[0016] Measurements can also be made using scattered light photoelasticity. With this method, light is incident on the glass surface and the polarization of the scattered light is analyzed to measure CS. An example of a stress measuring instrument that uses scattered light photoelasticity is the SLP-2000 scattered light photoelasticity meter manufactured by Orihara Seisakusho.

[0017] In this specification, the "depth of compressive stress (DOL)" is the depth at which the compressive stress value becomes zero. Hereinafter, the surface compressive stress value is referred to as CS0, and the compressive stress value at a depth of 50 μm is referred to as CS 50 Also, "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 of the plate thickness t.

[0018] <Chemically strengthened glass> The chemically strengthened glass according to an embodiment of the present invention (hereinafter also referred to as the present strengthened glass) is typically a plate-shaped glass product, but may be a flat (2D) glass plate without warping, or may be a curved glass plate having a curved surface. Examples of curved glass plates include 2.5D-shaped glass plates and 3D-shaped glass plates. The glass plate may also have portions with different thicknesses, such as a border shape with different peripheral thicknesses. The glass plate may also be a plate whose two main surfaces are not parallel to each other. In the present invention, the term "2.5D shape" refers to a shape having a rounded portion on one surface and a flat surface opposite the rounded portion. The "rounded portion" refers to a portion having a circular or substantially circular arc shape. Alternatively, it may be a polygonal shape close to a circle. In addition, in the present invention, the term "3D shape" refers to a curved shape that is not a flat (2D shape). An example of a 2.5D glass plate is a glass plate having a first main surface with a 2.5D shape. Specifically, as shown in FIG. 1, a glass plate (10) having a first main surface (1) with a rounded portion (R) and a flat second main surface (2) is exemplified. In a shape having rounded portions at the corners of a flat plate as shown in FIG. 1, when a functional layer such as an antifouling layer is formed on the surface having the rounded portion, the antifouling layer is likely to peel off. As described below, the surface roughness Ra of the first main surface of this tempered glass is within a specific range, which prevents peeling of the antifouling layer. Therefore, even if the glass plate has a 2.5D shape, it is possible to provide chemically tempered glass with excellent peel resistance. Even if the glass plate has a 3D shape, chemically strengthened glass with excellent peel resistance can be obtained.

[0019] When the tempered glass is in a plate form, the thickness (t) is preferably 3 mm or less, and more preferably 2 mm or less, 1.6 mm or less, 1.1 mm or less, 0.9 mm or less, 0.8 mm or less, and 0.7 mm or less in the following stepwise order. In addition, the thickness (t) is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.5 mm or more, in order to obtain sufficient strength by chemical strengthening treatment.

[0020] This tempered glass has a first main surface and a second main surface, and the surface roughness Ra of the first main surface is 5 nm or more and 100 nm or less. A surface roughness Ra of 5 nm or more forms appropriate irregularities on the glass surface, creating an anchor effect and making it easier to bond a functional layer such as an anti-fouling layer to the glass surface. The surface roughness Ra is preferably 7 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, and most preferably 30 nm or more. Furthermore, a surface roughness Ra of 100 nm or less ensures the transparency of the glass. The surface roughness Ra is preferably 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, particularly preferably 60 nm or less, and most preferably 50 nm or less. The surface roughness Ra of the second main surface may also be 5 nm or more and 100 nm or less. The surface roughness Ra can be measured by observing the glass surface with a laser microscope.

[0021] As described above, the present tempered glass has a glass surface roughness Ra within a specific range, i.e., has convex and concave portions. In the present tempered glass, the convex and concave shapes are preferably caused by silicon compound particles. Furthermore, the silicon compound particles preferably contain Li2SiO3.

[0022] Silicon compound particles are considered to be substances that are precipitated on the glass surface during the chemical strengthening process. For example, if the silicon compound particles contain Li2SiO3, the following reaction occurs on the glass surface in an alkaline solution, resulting in the formation of SiO3 2- is thought to be liberated on the glass surface. H2SiO3→2H + +SiO3 2- This SiO3 2- It is thought that the Li ions in the salt react with the glass as follows, causing insoluble Li2SiO3 to precipitate on the glass surface. 2Li + +SiO3 2- →Li2SiO3

[0023] It is believed that the areas where Li2SiO3 precipitates form convex portions on the glass surface. Also, free SiO3 2- It is thought that Li2SiO3 is partially bonded to the Si-O network of the glass, and exists in a bonded state to the glass surface. However, because the bonding strength is weaker than that of the Si-O network of the glass, it is thought that when a strong external force is applied, Li2SiO3 will peel off from the surface along with part of the glass. The traces are thought to form depressions on the glass surface. The composition of the silicon compound particles can be identified by measuring the particles precipitated on the glass surface by powder X-ray diffraction.

[0024] The presence or absence of recesses can be confirmed by observing the glass surface with a scanning electron microscope. The average depth of the recesses is preferably 1 μm or more, more preferably 3 μm or more, from the viewpoint of enhancing the anchoring effect, and is preferably 10 μm or less, more preferably 8 μm or less, from the viewpoint of making the glass appearance transparent. The average depth of the recesses can be measured with a scanning electron microscope.

[0025] The presence of silicon compound particles on the glass surface provides an anchoring effect, but large particles with a particle size of more than 300 nm can affect the transparency of the glass and cause concerns about whitish cloudiness. From the viewpoint of glass transparency, silicon compound particles with a particle size of 300 nm or less are 50 μm 2 Preferably, the number of particles per 50 μm of particles having a particle size of 300 nm or less is 100 or less, more preferably 80 or less, and further preferably 70 or less. 2 The number per unit is preferably 1 or more, more preferably 5 or more, and even more preferably 10 or more.

[0026] In addition, from the viewpoint of glass transparency, particles with a particle size of more than 300 nm are filtered out at a density of 50 μm. 2The number of particles per 50 μm of particles having a particle size exceeding 300 nm is preferably 1 or less, more preferably 0.8 or less, and further preferably 0.6 or less. 2 The number per unit is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The particle size and number of silicon compound particles on the glass surface can be measured using a scanning electron microscope.

[0027] The shape of the silicon compound particles is not particularly limited, but in order to facilitate the exertion of the anchoring effect, the average aspect ratio, expressed as the major axis diameter / minor axis diameter, is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less. This is thought to be because the closer the aspect ratio is to 1, i.e., the more the particle shape resembles a sphere, the more uniformly the particles will be caught on the glass surface.

[0028] This tempered glass is expressed as mole percent based on oxides. SiO2 40% or more, Al2O3 5% or more, Li2O 7.5% or more, Contains 0-10% ZrO2, The ratio of ZrO2 content to Al2O3 content is 0.005 to 0.7. The ratio of SiO2 content / (SiO2 content + Al2O3 content + B2O3 content + P2O5 content) is preferably 0.55 to 0.9.

[0029] The above composition refers to the base composition. "Base composition of chemically strengthened glass" refers to the composition of glass before chemical strengthening. This composition will be described later. The composition of this strengthened glass is similar to that of the glass before strengthening overall, 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 the composition of the glass before strengthening, except in cases where extreme ion exchange treatment has been performed.

[0030] The tempered glass of the present invention is glass obtained by chemically strengthening amorphous glass or crystallized glass, and from the viewpoint that high drop strength is preferable, it is preferably glass obtained by chemically strengthening amorphous glass. Chemical strengthening will be described later.

[0031] From the viewpoint of transparency, the tempered glass has a haze value of preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, particularly preferably 0.5% or less, and most preferably 0.1% or less, calculated based on a thickness of 0.7 mm. The smaller the haze value, the better, but it is usually 0.001% or more.

[0032] The present tempered glass preferably has a surface compressive stress (CS0) of 400 MPa or more, since it is less likely to break due to deformation such as bending. CS0 is more preferably 500 MPa or more, and even more preferably 600 MPa or more. The greater the CS0, the higher the strength, but if it is too large, there is a risk of severe shattering if the glass breaks, so the CS0 is preferably 1200 MPa or less, and more preferably 1000 MPa or less.

[0033] The depth of compressive stress layer (DOL) of the present tempered glass is preferably 70 μm or more, since it is less likely to break even if scratches occur on the surface. The DOL is more preferably 80 μm or more, even more preferably 90 μm or more, and particularly preferably 100 μm or more. The larger the DOL, the less likely it is to break even if scratches occur, but in chemically tempered glass, tensile stress occurs internally in response to the compressive stress formed near the surface, so it cannot be made extremely large. When the thickness is t, the DOL is preferably t / 4 or less, and more preferably t / 5 or less. The DOL is preferably 200 μm or less, and more preferably 180 μm or less, in order to shorten the time required for chemical tempering.

[0034] The CT of the present tempered glass is preferably 110 MPa or less, since scattering of fragments when the chemically tempered glass breaks is suppressed. The CT is more preferably 100 MPa or less, and even more preferably 90 MPa or less. On the other hand, if the CT is reduced, the surface compressive stress tends to be reduced, making it difficult to obtain sufficient strength. Therefore, the CT is preferably 50 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more.

[0035] The fracture toughness value (ST value) of this tempered glass is preferably 18,000 MPa μm or more to increase drop strength, more preferably 20,000 MPa μm or more, even more preferably 22,000 MPa μm or more, and most preferably 24,000 MPa μm or more. On the other hand, if the ST value is too high, glass fragments will scatter when shattered, so the ST value is preferably 30,000 MPa μm or less, more preferably 29,000 MPa μm or less, even more preferably 28,000 MPa μm or less, and most preferably 27,000 MPa μm or less.

[0036] Because this tempered glass is transparent and has an anchoring effect for functional layers such as antifouling layers, it is useful as cover glass for displays of mobile devices such as mobile phones and smartphones. It is also useful as cover glass for non-portable displays such as televisions, personal computers, and touch panels, as well as for elevator walls and wall surfaces (full-surface displays) of buildings such as houses and buildings. It is also useful as building materials such as window glass, tabletops, interiors of automobiles and airplanes, and cover glass for these, as well as for curved housings.

[0037] <Method of manufacturing chemically strengthened glass> The tempered glass can be produced by chemically tempering amorphous glass or crystallized glass.

[0038] (amorphous glass) Amorphous glass can be produced by a conventional method. For example, the raw materials for the glass components are mixed and heated and melted in a glass melting furnace. The glass is then homogenized by a known method, formed into a desired shape such as a plate, and slowly cooled.

[0039] Thereafter, the formed glass is ground and polished as necessary to form a glass substrate. When the glass substrate is cut to a predetermined shape and size or when the glass substrate is chamfered, it is preferable to perform the cutting or chamfering of the glass substrate before performing the chemical strengthening treatment described later, because a compressive stress layer is also formed on the end surface by the subsequent chemical strengthening treatment.

[0040] As amorphous glass, the oxide-based mole percentage is: SiO2 40% or more, Al2O3 5% or more, Li2O 7.5% or more, Contains 0-10% ZrO2, The ratio of ZrO2 content / Al2O3 content is 0.1~0.7, The ratio of SiO2 content / (SiO2 content + Al2O3 content + B2O3 content + P2O5 content) is preferably 0.8 to 0.9.

[0041] SiO2 is a component that forms the glass network. The SiO2 content is more preferably 45% or more, even more preferably 55% or more, particularly preferably 60% or more, extremely preferably 63% or more, and most preferably 65% ​​or more. On the other hand, to improve meltability, the SiO2 content is preferably 75% or less, more preferably 72% or less, even more preferably 70% or less, and particularly preferably 68% or less.

[0042] Al2O3 is a component that allows chemically strengthened glass to have high CS and a large DOL. This is because a particularly large CS is generated when Li ions present near Al2O3 are exchanged for Na ions in the glass. To achieve this effect, the Al2O3 content of the amorphous glass is more preferably 8% or more, even more preferably 9% or more, particularly preferably 10% or more, extremely preferably 11% or more, and most preferably 12% or more. On the other hand, if the Al2O3 content is too high, devitrification tends to occur when the glass is melted, and the viscosity increases, reducing meltability. Therefore, the Al2O3 content of the amorphous glass is preferably 30% or less, more preferably 20% or less, even more preferably 18% or less, and particularly preferably 16% or less.

[0043] Li2O is a component that forms surface compressive stress through ion exchange and improves the meltability of glass. By exchanging the Li ions on the surface of glass containing Li2O for Na ions, and then further exchanging the Na ions for K ions, a large stress profile can be obtained, resulting in both a large surface compressive stress and a large compressive stress layer. In order to achieve a high CS and a large DOL in the present tempered glass, the Li2O content of the amorphous glass is preferably 5% or more, more preferably 7% or more, even more preferably 8% or more, and particularly preferably 9% or more. On the other hand, if the Li2O content is too high, devitrification tends to occur when the glass is melted. Therefore, the Li2O content of the amorphous glass is preferably 20% or less, more preferably 15% or less, even more preferably 13% or less, and particularly preferably 12% or less.

[0044] Although neither Na2O nor K2O is essential, they are components that improve the meltability of the glass and may be added for the purpose of improving the ion exchange performance.

[0045] Na2O is a component that forms a surface compressive stress layer in chemical strengthening treatment using potassium salts and can also improve the meltability of glass. To achieve this effect, the Na2O content of amorphous glass is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, particularly preferably 4% or more, and most preferably 5% or more. On the other hand, in order to avoid a decrease in surface compressive stress (CS) during strengthening treatment with sodium salts, the Na2O content of the amorphous glass is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, and particularly preferably 5% or less.

[0046] K2O may be contained for the purpose of improving ion exchange performance, etc. When K2O is contained in the amorphous glass, the 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 avoid a decrease in surface compressive stress (CS) during strengthening treatment with a potassium salt, when KO is contained in amorphous glass, the content is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less.

[0047] The total content of Na2O and K2O ([Na2O] + [K2O]) in the amorphous glass is preferably 0 to 10%. [Na2O] + [K2O] is more preferably 5% or more, even more preferably 6% or more, and is more preferably 8% or less, even more preferably 7% or less.

[0048] Although MgO, CaO, SrO, and BaO are not essential components, it is preferable that the amorphous glass contain at least one of these components to improve stability. The total content of these components in the amorphous glass ([MgO] + [CaO] + [SrO] + [BaO]) 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, from the viewpoint of improving ion exchange capacity by chemical strengthening, the total content of these components in the amorphous glass is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and even more preferably 8% or less.

[0049] In particular, MgO is preferably contained in the present glass from the viewpoint of increasing meltability while decreasing the crystal growth rate. The MgO content of the amorphous glass is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.3% or more, particularly preferably 0.4% or more, and most preferably 0.5% or more. On the other hand, if the MgO content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment. The MgO content of the amorphous glass is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and particularly preferably 3% or less.

[0050] When the amorphous glass contains MgO and one or more of CaO, SrO, and BaO, the ratio of the MgO content to the total content of CaO, SrO, and BaO ([MgO] / ([CaO]+[SrO]+[BaO])) is preferably 0 or more, more preferably 0.1 or more, even more preferably 0.2 or more, and particularly preferably 0.3 or more, from the viewpoint of reducing the surface reflectance of the glass. This is because CaO, SrO, BaO, and ZnO increase the refractive index compared to MgO. From the viewpoint of reducing the devitrification temperature, [MgO] / ([CaO]+[SrO]+[BaO]) is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0051] CaO is a component that improves melting property and may be contained. When CaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. On the other hand, if the CaO content is excessive, it becomes difficult to increase the compressive stress value during chemical strengthening treatment. The CaO content is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0052] SrO is also a component that improves melting property and may be contained. When SrO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. On the other hand, if the SrO content is excessive, it becomes difficult to increase the compressive stress value during chemical strengthening treatment. The SrO content is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0053] BaO is also a component that improves melting property and may be contained. When BaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. On the other hand, if the BaO content is excessive, it becomes difficult to increase the compressive stress value during chemical strengthening treatment. The BaO content is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0054] ZnO is also a component that improves melting property and may be contained. When ZnO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. On the other hand, if the ZnO content is excessive, it becomes difficult to increase the compressive stress value during chemical strengthening treatment. The ZnO content is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0055] Although ZrO2 does not necessarily have to be contained, it is preferable to contain it from the viewpoint of increasing the surface compressive stress of the present tempered glass obtained by subjecting amorphous glass to chemical strengthening treatment. The ZrO2 content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and typically 1% or more. On the other hand, if the ZrO2 content is too high, it becomes difficult to increase the compressive stress value during chemical strengthening treatment. The ZrO2 content is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, and particularly preferably 1.5% or less.

[0056] Furthermore, the content of Al2O3 relative to the content of ZrO2 in the amorphous glass, i.e., the ratio of ZrO2 / Al2O3, is preferably 0.0001 or more, more preferably 0.0002 or more, even more preferably 0.0003 or more, and particularly preferably 0.0005 or more, from the viewpoint of preventing excessive unevenness from being formed, and is preferably 0.7 or less, more preferably 0.1 or less, even more preferably 0.05 or less, and particularly preferably 0.02 or less, from the viewpoint of being able to form unevenness to a certain extent.

[0057] TiO2 is a component that suppresses solarization and may be contained. When TiO2 is contained, the content is preferably 0.02% or more, more preferably 0.05% or more, even more preferably 0.1% or more, particularly preferably 0.12% or more, and typically 0.15% or more. On the other hand, if the TiO2 content exceeds 1%, devitrification is likely to occur. The TiO2 content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less.

[0058] Y2O3 is a component that increases the surface compressive stress of the present tempered glass obtained by chemically strengthening amorphous glass while decreasing the crystal growth rate, and may be contained. The Y2O3 content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and typically 1% or more. On the other hand, if the Y2O3 content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening. The Y2O3 content is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1.5% or less.

[0059] Although B2O3 is not essential, it may be contained for the purposes of reducing brittleness and improving crack resistance, and for the purposes of improving meltability. When B2O3 is contained, the content is preferably 0.5% or more, preferably 1% or more, and more preferably 2% or more. On the other hand, if the B2O3 content is too high, acid resistance tends to deteriorate, so when B2O3 is contained, the content is preferably 10% or less, more preferably 6% or less, even more preferably 4% or less, and typically 2% or less. From the viewpoint of preventing the formation of striae during melting, it is more preferable that B2O3 is substantially not contained.

[0060] Although P2O5 is not essential, it may be contained for the purpose of increasing the compressive stress layer of the present tempered glass obtained by chemically strengthening amorphous glass. When P2O5 is contained, the content is preferably 0.5% or more, preferably 1% or more, and more preferably 2% or more. On the other hand, from the viewpoint of improving acid resistance, the content of P2O5 is preferably 6% or less, more preferably 4% or less, and even more preferably 2% or less. From the viewpoint of preventing the formation of striae during melting, it is more preferable that P2O5 is substantially not contained.

[0061] The total content of B2O3 and P2O5 is preferably 0 to 10%, with the lower limit being more preferably 1% or more, and even more preferably 2% or more. The total content of B2O3 and P2O5 is more preferably 6% or less, and even more preferably 4% or less.

[0062] Furthermore, in the amorphous glass, the ratio of the SiO2 content to the total content of SiO2, Al2O3, B2O3, and P2O5, i.e., the ratio of SiO2 / (SiO2+Al2O3+B2O3+P2O5), is preferably 0.55 to 0.95, with the lower limit being more preferably 0.6 or more, and even more preferably 0.7 or more, and the upper limit being more preferably 0.9 or less, and even more preferably 0.8 or less. By keeping the ratio within this range, the amount of particulate precipitates can be controlled within an appropriate range.

[0063] La2O3, Nb2O 5、Ta2O5 and Gd2O3 are components that reduce the crystal growth rate and improve melting properties, and may be included. When these components are included, their respective contents are preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and typically 1% or more. On the other hand, if their contents are too high, it becomes difficult to increase the compressive stress value during chemical strengthening treatment, so they are preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0064] Fe2O3 absorbs heat rays and has the effect of improving meltability, so it may be added. When Fe2O3 is added to amorphous glass, the content is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.007% or more, and particularly preferably 0.01% or more. On the other hand, since excessive Fe2O3 content causes coloration, when Fe2O3 is added to amorphous glass, from the viewpoint of improving the transparency of the glass, the content is preferably 0.3% or less, more preferably 0.04% or less, even more preferably 0.025% or less, and particularly preferably 0.015% or less. Although all iron oxides in glass have been described as Fe2O3, in reality, a mixture of oxidized Fe(III) and reduced Fe(II) is usually present. Of these, Fe(III) produces a yellow color, while Fe(II) produces a blue color, and the balance between the two produces a green color in the glass.

[0065] Furthermore, other components may be added as long as they do not impede the achievement of the desired chemical strengthening properties. For example, coloring components may be added. Suitable coloring components include Co3O4, MnO2, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, and Nd2O3. The total content of the coloring components, expressed as mole percentage based on oxides, is preferably 5% or less. If it exceeds 5%, the glass may be prone to devitrification. The content of the coloring components is preferably 3% or less, more preferably 1% or less. If high transmittance is desired, it is preferable that these components are substantially not contained. In addition, SO3, chlorides, fluorides, etc. may be added as appropriate as fining agents when melting the glass. It is preferable that As2O3 is not contained. If Sb2O3 is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably zero.

[0066] Amorphous glass preferably has a high fracture toughness value in order to obtain high-strength glass.

[0067] (chemical strengthening treatment) Chemical strengthening is a process in which glass is brought into contact with a metal salt, for example by immersing it in a molten salt (e.g., a sodium salt or a potassium salt) containing metal ions with a large ionic radius (typically Na ions or K ions), thereby replacing metal ions with a small ionic radius (typically Na ions or Li ions) in the glass with metal ions with a large ionic radius (typically Na ions or K ions for Li ions, and K ions for Na ions).

[0068] Examples of molten salts used in chemical strengthening include nitrates, sulfates, carbonates, and chlorides. Nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used alone or in combination.

[0069] From the viewpoint of facilitating the appropriate precipitation of silicon compound particles on the glass surface, it is preferable to use a combination of multiple molten salts, and it is preferable to include a small amount of molten salt containing metal ions with a small ionic radius (typically Na ions or Li ions) in the glass. For example, a molten salt containing 50 mass % or more of a sodium salt or a molten salt containing 50 mass % or more of a potassium salt preferably contains 100 to 3000 mass ppm, more preferably 500 to 1000 mass ppm, of a lithium salt. When chemical strengthening is carried out in two stages as described below, a combination of multiple types of molten salts may be used in either one of the chemical strengthening stages or in both stages.

[0070] The conditions for the chemical strengthening treatment, such as time and temperature, can be selected taking into consideration the glass composition, the type of molten salt, the chemical strengthening characteristics desired for the final chemically strengthened glass, such as the surface compressive stress and depth of the compressive stress layer, and the surface roughness Ra. The time for the chemical strengthening treatment is preferably 0.5 to 6 hours, more preferably 1 to 4 hours, from the viewpoint of forming a compressive stress layer with high strength. The temperature of the molten salt is preferably 350°C or higher, more preferably 380°C or higher, from the viewpoint of forming a deep compressive stress layer, and is preferably 450°C or lower, more preferably 430°C or lower, from the viewpoint of not reducing the compressive stress layer due to excessive ion exchange.

[0071] In the present invention, the chemical strengthening treatment may be performed only once, or may be performed multiple times under two or more different conditions (multi-stage strengthening). For example, the first stage of chemical strengthening treatment is performed under conditions that increase the DOL and relatively decrease the CS. If the second stage of chemical strengthening treatment is then performed under conditions that decrease the DOL and relatively increase the CS, the CS of the outermost surface of the chemically strengthened glass can be increased while the internal tensile stress (CT) can be kept low.

[0072] When chemical strengthening is performed in one step, for example, amorphous glass or crystallized glass is immersed in a molten salt (e.g., sodium nitrate and lithium nitrate) at a temperature of preferably 350 to 500°C for approximately 0.1 to 10 hours. The above temperature conditions and treatment time allow ion exchange between Li ions in the glass and Na ions in the metal salt, which is preferable because it allows the formation of a relatively deep compressive stress layer. Furthermore, silicon compound particles (Li2SiO3) are appropriately precipitated on the glass surface, which is preferable because it provides the desired surface roughness.

[0073] When chemical strengthening is performed in two stages, for example, amorphous glass or the present crystallized glass is immersed in a molten salt (e.g., sodium nitrate and lithium nitrate) at about 350 to 500°C for about 0.1 to 10 hours. This causes ion exchange between Li ions in the glass and Na ions in the metal salt, forming a relatively deep compressive stress layer. Furthermore, silicon compound particles (Li2SiO3) are appropriately precipitated on the glass surface, imparting the desired surface roughness, which is preferable. Next, the glass is immersed in a molten salt (e.g., potassium nitrate and lithium nitrate) at a temperature of preferably about 350 to 500°C for about 0.1 to 10 hours. This generates a large compressive stress in the compressive stress layer formed in the previous treatment, for example, within a depth of about 10 μm. This two-stage treatment tends to produce a stress profile with a large surface compressive stress value. Furthermore, silicon compound particles (Li2SiO3) are appropriately precipitated on the glass surface, which is preferable as it imparts the desired surface roughness.

[0074] <Glass material with anti-fouling layer> A glass material with an anti-fouling layer according to an embodiment of the present invention comprises the tempered glass and an anti-fouling layer provided on the first principal surface of the chemically strengthened glass. The first principal surface has a predetermined surface roughness Ra, which provides an anchoring effect for the anti-fouling layer, allowing it to be firmly bonded to the glass surface. The anchoring effect of the tempered glass is exerted regardless of the composition of the anti-fouling layer, and therefore an anti-fouling layer of any composition can be provided. The anti-fouling layer can be formed, for example, by vacuum-depositing a fluorine-containing composition onto the glass surface. The thickness of the antifouling layer is usually preferably 5 to 20 nm.

[0075] As described above, this specification discloses the following chemically strengthened glass and the like. [1] Chemically strengthened glass having a first principal surface and a second principal surface, wherein the surface roughness Ra of the first principal surface is 5 nm or more and 100 nm or less. [2] The chemically strengthened glass according to [1], wherein silicon compound particles are present on the surface on the first principal surface side. [3] The chemically strengthened glass according to [1] or [2], wherein the first main surface has a 2.5D shape. [4] The chemically strengthened glass according to any one of [1] to [3], which is an amorphous glass. [5] The chemically strengthened glass according to any one of [1] to [4], wherein the surface on the first main surface side has a recess. [6] The chemically strengthened glass according to [5], wherein the average depth of the recesses is 1 μm or more and 10 μm or less. [7] The chemically strengthened glass according to [2], wherein the silicon compound particles contain Li2SiO3. [8] Among the silicon compound particles on the surface on the first main surface side, particles having a particle size of 300 nm or less are 50 μm 2 The chemically strengthened glass according to [2], wherein the number of particles per one particle is 100 or less. [9] The base composition of the chemically strengthened glass is In mole percent based on oxides, SiO2 40% or more, Al2O3 5% or more, Li2O 7.5% or more, Contains 0-10% ZrO2, ZrO2 / Al2O3 ratio is 0.005~0.7, The chemically strengthened glass according to any one of [1] to [8], wherein the ratio of SiO2 / (SiO2+Al2O3+B2O3+P2O5) is 0.55 to 0.9.

[10] The chemically strengthened glass according to [2], wherein the silicon compound particles have an average aspect ratio, expressed as the major axis diameter / minor axis diameter, of 1.5 or less.

[11] The chemically strengthened glass according to any one of [1] to

[10] , which is used as a cover glass for an image display device.

[12] A cover glass for an image display device, comprising the chemically strengthened glass according to any one of [1] to

[11] .

[13] A glass material with an antifouling layer, comprising the chemically strengthened glass according to any one of [1] to

[11] and an antifouling layer provided on a first main surface side of the chemically strengthened glass. [Example]

[0076] The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0077] <Example 1 to Example 28> Glass raw materials were mixed to obtain the composition shown in Table 1 in terms of oxide-based mole percentage, and weighed out to give 400 g of glass. The mixed raw materials were then placed in a platinum crucible and placed in an electric furnace at 1500 to 1700°C, where they were melted for about 3 hours, degassed, and homogenized. The resulting molten glass was poured into a metal mold and held at a temperature approximately 50°C higher than the glass transition point for 1 hour, then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The resulting glass block was cut and ground, and finally both sides were mirror-polished to obtain a glass plate with a thickness of 0.7 mm.

[0078] <Chemical strengthening treatment> Each glass plate obtained above was subjected to a two-stage chemical strengthening treatment under the conditions shown in Tables 2 and 3 using molten salts prepared by mixing lithium nitrate, sodium nitrate, and potassium nitrate in the ratios shown in Tables 2 and 3. The molten salt for the first chemical strengthening treatment was prepared by adding lithium nitrate to sodium nitrate at the concentrations (ppm by mass) shown in Tables 2 and 3. The molten salt for the second chemical strengthening treatment was prepared by adding lithium nitrate to potassium nitrate:sodium nitrate = 90:10 (mass ratio) at the concentrations (ppm by mass) shown in Tables 2 and 3.

[0079] <Measurement of surface roughness Ra> The surface roughness Ra of one main surface (first main surface) of each of the chemically strengthened glass plates obtained above was measured by observing the glass surface with a 50x lens using a Keyence VK-200 laser microscope.

[0080] <Observation of surface precipitated particles and uneven shape> The presence of precipitated particles on the glass surface of one of the main surfaces (first main surface) of each of the chemically strengthened glass plates obtained above and the uneven shape of the glass surface were observed using an SEM. The particle diameter and particle density per unit area were calculated from the SEM images. The particle diameter represents the average particle size when 50 particles were measured. In addition, the presence or absence of depressions on the glass surface was observed from the SEM images, and if depressions were observed, their average depth was calculated.

[0081] <Identification of surface precipitated particles> The precipitated particles on the glass surface of one main surface (first main surface) of each of the chemically strengthened glass plates obtained above were identified by powder X-ray diffraction measurement under the following conditions. Measurement equipment: Rigaku Smart Lab X-ray used: CuKα ray Measurement range: 2θ=10°~80° Speed: 1° / min Step: 0.01° Figure 3 shows the results of X-ray diffraction of the chemically strengthened glass plate of Example 2. As shown in Figure 3, a crystalline peak derived from Li2SiO3 was observed. Note that similar crystalline peaks were also observed in the glass plates of Examples 2 to 13 and 15 to 28.

[0082] <Formation of anti-fouling layer> The water-washed chemically strengthened glass plate was further plasma cleaned, and then a fluorine-containing organic compound (UD-509 manufactured by Daikin Corporation) was deposited on one of the main surfaces (first main surface) of the glass plate using a vacuum deposition method with resistance heating. The pressure in the vacuum chamber during film formation was 3.0 × 10 -3 Pa, and the deposition output was 318.45 kA / m 2 The deposition was carried out for 300 seconds, and the thickness of the resulting antifouling layer was 15 nm.

[0083] <Eraser friction and abrasion test of anti-fouling layer (water contact angle measurement)> Using a flat surface abrasion tester (triple type) (manufactured by Daiei Scientific Instruments Manufacturing Co., Ltd., device name: PA-300A), the surface of the antifouling layer was rubbed and abraded 7,500 times with a 6 mm diameter eraser (Woojin Co., Ltd. pink pencil) under conditions of a load of 1 kgf, a stroke width of 40 mm, a speed of 40 rpm, 25°C, and 50% RH. After the abrasion test, a droplet of about 1 μL of pure water was placed on the surface of the antifouling layer, and the contact angle (degrees) of the water was measured using a contact angle meter. Judgment criteria (A or B is pass): A Contact angle of 90 degrees or more B: Contact angle between 60 degrees and 90 degrees C Contact angle less than 60 degrees

[0084] <Haze> Using a haze meter (HZ-V3 manufactured by Suga Test Instruments), the haze value (unit: %) of each chemically strengthened glass sheet was measured using a halogen lamp C light source. A haze of 1.0% or less was considered acceptable.

[0085] The composition of each glass is shown in Table 1. The measurement results of each physical property are shown in Tables 2 and 3. Examples 2 to 13 and 15 to 28 are working examples, and Examples 1 and 14 are comparative examples.

[0086] [Table 1]

[0087] [Table 2]

[0088] [Table 3]

[0089] The chemically strengthened glasses of Examples 2 to 13 and 15 to 28 have a surface roughness Ra within a specific range, and therefore maintain a high water contact angle even after the abrasion test, and the haze value is also kept low. In the chemically strengthened glasses of Examples 2 to 13 and 15 to 28, particles with a particle size of 300 nm or less are 50 μm in diameter. 2 The number of particles per square meter indicates that particles are moderately precipitated on the glass surface after chemical strengthening.

[0090] On the other hand, the glass of Example 14 had a large number of precipitated lithium metasilicate particles, a surface roughness Ra of more than 100 nm, and maintained a high water contact angle after the abrasion test, but had a high haze of 8.7% and insufficient transparency. Furthermore, the glass of Example 1 has low haze and transparency due to the small amount of lithium metasilicate particles precipitated, but the water contact angle after the abrasion test is low, suggesting peeling of the antifouling layer. [Explanation of symbols]

[0091] 10 Glass Plate 1 First main surface RR section 2 Second main surface

Claims

1. Chemically strengthened glass having a first main surface and a second main surface, wherein the surface roughness Ra of the first main surface is 5 nm or more and 100 nm or less.

2. The chemically strengthened glass according to claim 1, wherein silicon compound particles are present on a surface of the first main surface side.

3. The chemically strengthened glass according to claim 1, wherein the first main surface has a 2.5D shape.

4. The chemically strengthened glass according to claim 1, which is amorphous glass.

5. The chemically strengthened glass according to claim 1 , wherein the surface on the first main surface side has a recess.

6. The chemically strengthened glass according to claim 5, wherein the average depth of the recesses is 1 μm or more and 10 μm or less.

7. The silicon compound particles are Li ２ SiO ３ The chemically strengthened glass according to claim 2, comprising:

8. Among the silicon compound particles on the surface on the first main surface side, particles having a particle size of 300 nm or less are 50 μm ２ The chemically strengthened glass according to claim 2, wherein the number of particles per one particle is 100 or less.

9. The base composition of the chemically strengthened glass is In mole percent based on oxides, SiO ２ More than 40% Al ２ O ３ 5% or more, Li ２ O 7.5% or more, ZrO ２ Contains 0 to 10% of ZrO ２ / Al ２ O ３ The ratio is 0.005 to 0.7, SiO ２ / (SiO ２ +Al ２ O ３ +B ２ O ３ +P ２ O ５ 2. The chemically strengthened glass according to claim 1, wherein the ratio of SiO 2 to SiO 2 is 0.55 to 0.

9.

10. The chemically strengthened glass according to claim 2, wherein the silicon compound particles have an average aspect ratio represented by major axis diameter / minor axis diameter of 1.5 or less.

11. The chemically strengthened glass according to claim 1, which is used as a cover glass for an image display device.

12. A cover glass for an image display device comprising the chemically strengthened glass according to any one of claims 1 to 11.

13. A glass material with an antifouling layer, comprising: the chemically strengthened glass according to any one of claims 1 to 11; and an antifouling layer provided on a first main surface side of the chemically strengthened glass.

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