Glass substrate and manufacturing method thereof

Abstract

To provide a glass substrate excellent in a tactile feeling on a surface or a writing touch with a pen, while excellent in visibility of a displayed image.SOLUTION: A glass substrate 1 is made of alkali-containing silicate glass. A first principal surface 1a of the glass substrate 1 includes an irregularity part 2 and a non-processed part 3 with no processing for disposing the irregularity part 2. In a 74 μm×55 μm region of the irregularity part 2, if a cut-off value of a high-pass filter λc is 14 μm and a cut-off value of a low-pass filter λs is 0.35 μm, an arithmetical average height Sa is 1 to 100 nm. In the glass substrate 1, if a total mass ratio of Na and K in a given range of 100 μm square is regarded as an alkali content, an alkali content of the irregularity part 2 is smaller than an alkali content of the non-processed part 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a glass substrate having an uneven surface and a method for manufacturing the glass substrate. [Background technology]

[0002] In recent years, attempts have been made to improve the feel of the surface and the writing comfort with a pen by imparting irregularities to the surface of glass substrates used for displays, housings, doors, and the like of electronic devices.

[0003] For example, the following Patent Document 1 discloses a glass substrate for a pen input device that is disposed on the front side of a display device in the pen input device. Patent Document 1 describes that the glass substrate for the pen input device has irregularities on at least one main surface, and that the maximum valley depth Rv of the roughness curve on the main surface having irregularities is 10 nm or more and 400 nm or less, and the average length RSm of the roughness curve is 500 nm or more and 2000 nm or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-20942 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when unevenness is imparted to the surface of a glass substrate as in Patent Document 1, while the surface feels better to the touch and is easier to write on with a pen, there is a problem that the linear transmittance of light is likely to decrease due to scattering caused by the unevenness. Therefore, when an image is displayed on such a glass substrate, there is a problem that the visibility of the image decreases.

[0006] An object of the present invention is to provide a glass substrate having a surface that is pleasant to the touch and comfortable to write on with a pen, and that exhibits excellent visibility of images displayed thereon, and a method for manufacturing the glass substrate. [Means for solving the problem]

[0007] Various aspects of a glass substrate and a method for manufacturing the glass substrate that solves the above problems will be described below.

[0008] A glass substrate according to a first aspect of the present invention is a glass substrate made of alkali-containing silicate glass, the surface of the glass substrate having an uneven portion and an unprocessed portion that has not been processed to provide the uneven portion, the uneven portion having an arithmetic mean height Sa of 1 nm or more and 100 nm or less in a 74 μm × 55 μm area when the cutoff value of a high-pass filter λc is 14 μm and the cutoff value of a low-pass filter λs is 0.35 μm, and when the total mass proportion of Na and K in any 100 μm square area is taken as the alkali content, the alkali content of the uneven portion is less than the alkali content of the unprocessed portion.

[0009] In the glass substrate of aspect 2, in accordance with aspect 1, it is preferable that the ratio of the alkali content in the concave-convex portion to the non-processed portion is 0.5 or more and less than 1.0.

[0010] In the glass substrate of aspect 3, in aspect 1 or aspect 2, both the concave-convex portion and the non-processed portion may be provided on one main surface of the glass substrate.

[0011] In the glass substrate of aspect 4, in aspect 3, the glass substrate may have a first main surface and a second main surface opposing each other, the first main surface of the glass substrate may be provided with the uneven portion, and the second main surface of the glass substrate may be provided with the unprocessed portion.

[0012] In the glass substrate of Aspect 5, in any one of Aspects 1 to 4, the alkali-containing silicate glass preferably contains, in mass %, as a glass composition, 30% to 70% of SiO2, 10% to 20% of Al2O3, 0% to 10% of B2O3, 1% to 20% of Na2O, 1% to 20% of K2O, and 0% to 20% of MgO.

[0013] A method for producing a glass substrate according to a sixth aspect of the present invention is a method for producing a glass substrate according to any one of the first to fifth aspects, characterized in that it includes the steps of: preparing an original glass substrate; and performing a wet blasting treatment on at least one main surface of the original glass substrate using a slurry containing abrasive grains and having a pH of 5.0 or more and 9.0 or less.

[0014] In the method for producing a glass substrate of the seventh aspect, in the sixth aspect, the pH of the slurry is preferably 7.0 or more and 8.0 or less.

[0015] In the method for producing a glass substrate of the eighth aspect, in the sixth or seventh aspect, the abrasive grains are preferably alumina grains.

[0016] In the method for manufacturing a glass substrate of aspect 9, in any one of aspects 6 to 8, the concentration of the abrasive grains in the slurry is preferably 1 mass % or more and 30 mass % or less.

[0017] In the method for producing a glass substrate of Aspect 10, in any one of Aspects 6 to 9, the spraying pressure of the slurry is preferably 0.1 MPa or more and 3.0 MPa or less. Effect of the Invention

[0018] According to the present invention, it is possible to provide a glass substrate having a surface that is pleasant to the touch and comfortable to write on with a pen, and which exhibits excellent visibility of images displayed thereon, and a method for manufacturing the glass substrate. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view showing a glass substrate according to one embodiment of the present invention. [Diagram 2] FIG. 13 is a schematic cross-sectional view showing a glass substrate of a modified example. [Diagram 3] 13A and 13B are diagrams for explaining measured profile curves in modified examples of concaves and convexes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0021] [Glass substrate] FIG. 1 is a schematic cross-sectional view showing a glass substrate according to one embodiment of the present invention.

[0022] 1, the glass substrate 1 has a rectangular flat plate shape. However, the shape of the glass substrate 1 is not particularly limited, and may be a flat plate shape having a circular or polygonal outline, a flat plate shape that is entirely curved, a spherical or aspherical lens shape, or the like.

[0023] The glass substrate 1 is made of an alkali-containing silicate glass. Any glass containing Li, Na, and K in total at 1% or more as alkali components can be used as the alkali-containing silicate glass, but glass containing Na and K in total at 1% or more as alkali components is preferable. Examples of the alkali-containing silicate glass include alkali aluminosilicate glass and alkali titania silicate glass. The content of the alkali components in the alkali-containing silicate glass may be 2% or more, 5% or more, or 8% or more, or 50% or less, 45% or less, 40% or less, or 30% or less.

[0024] More specifically, the alkali-containing silicate glass may have a glass composition containing, in mass %, 30% to 70% SiO2, 10% to 20% Al2O3, 0% to 10% B2O3, 1% to 20% Na2O, 1% to 20% K2O, and 0% to 20% MgO.

[0025] The glass substrate 1 has a first main surface 1a and a second main surface 1b facing each other. The first main surface 1a and the second main surface 1b are the surfaces of the glass substrate 1. In this embodiment, a concave-convex portion 2 is provided in a part of the first main surface 1a of the glass substrate 1. The first main surface 1a of the glass substrate 1 also has a non-processed portion 3 that is not processed to provide the concave-convex portion 2. In this embodiment, the entire second main surface 1b of the glass substrate 1 is also the non-processed portion 3 that is not processed to provide the concave-convex portion 2. However, in the present invention, the concave-convex portion 2 may also be provided on the second main surface 1b of the glass substrate 1.

[0026] In the present invention, it is sufficient that the uneven portion 2 is provided on at least a part of the first main surface 1a of the glass substrate 1. The uneven portion 2 is preferably provided on 1% or more of the area of ​​the first main surface 1a of the glass substrate 1, more preferably on 30% or more, and further preferably on 50% or more.

[0027] Fig. 2 is a schematic cross-sectional view showing a modified glass substrate. As in the glass substrate 10 shown in Fig. 2, the concave-convex portion 2 may be provided on the entire first main surface 1a of the glass substrate 10. In this case, it is sufficient that the non-processed portion 3 is provided on at least a part of the second main surface 1b of the glass substrate 10. Hereinafter, the modified glass substrates 10 will be collectively referred to as glass substrate 1.

[0028] The thickness of the glass substrate 1 is not particularly limited, and can be, for example, 30 μm or more and 5 mm or less.

[0029] In this embodiment, the uneven portion 2 of the glass substrate 1 has an arithmetic mean height Sa of 1 nm or more and 100 nm or less in an area of ​​74 μm × 55 μm, when the cutoff value of the high-pass filter λc is 14 μm and the cutoff value of the low-pass filter λs is 0.35 μm. Since the arithmetic mean height Sa of the uneven portion 2 of the glass substrate 1 of this embodiment is within the above range, the surface (uneven portion 2) is excellent in feel and writing comfort with a pen.

[0030] The arithmetic mean height Sa of the uneven portion 2 of the glass substrate 1 is preferably 2 nm or more, more preferably 3 nm or more, even more preferably 4 nm or more, even more preferably 5 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, and is preferably 98 nm or less, more preferably 97 nm or less, even more preferably 96 nm or less, even more preferably 95 nm or less, even more preferably 90 nm or less, even more preferably 85 nm or less, and particularly preferably 80 nm or less.

[0031] When the arithmetic mean height Sa of the uneven portion 2 of the glass substrate 1 is equal to or greater than the above lower limit, the feel of the surface of the glass substrate 1 to the touch and the feel of writing with a pen can be further improved. When the arithmetic mean height Sa of the uneven portion 2 of the glass substrate 1 is equal to or less than the above upper limit, the visibility of an image displayed on the glass substrate 1 can be further improved. In this case, the uneven portion 2 of the glass substrate 1 is not too rough, and the feel of the surface of the glass substrate 1 to the touch and the feel of writing with a pen can be further improved.

[0032] The "arithmetic mean height Sa" is a parameter defined by ISO 25178, which is a parameter obtained by expanding a measured cross-sectional curve showing the cross-sectional shape of the unevenness to a surface. Specifically, the arithmetic mean height Sa can be calculated from the average of the absolute values ​​of the heights Zn of each point relative to the average plane of the surface in a predetermined three-dimensional region (Sa=(Σ|Zn|) / n). In the present invention, the uneven portion 2 is measured in an area of ​​74 μm×55 μm, and the arithmetic mean height Sa is calculated by setting the cutoff value of the high-pass filter λc to 14 μm and the cutoff value of the low-pass filter λs to 0.35 μm.

[0033] In addition, in the glass substrate 1 of this embodiment, when the total mass ratio of Na and K in any 100 μm square region is defined as the alkali content, the alkali content in the concave-convex portion 2 is lower than the alkali content in the unprocessed portion 3.

[0034] The total mass ratio of Na and K in any 100 μm square region can be determined by performing elemental analysis on any 100 μm square region, for example, by scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX). It is preferable to perform elemental analysis on any 100 μm square region at multiple measurement points and determine the mass ratio of each component from the average value. In the examples described below, elemental analysis is performed on a 100 μm square region at five arbitrary points on each of the uneven portion (processed portion) and the non-processed portion, and the average value is used as the mass ratio of each component.

[0035] Since the glass substrate 1 of the present embodiment has the above-mentioned configuration, the surface of the glass substrate 1 is pleasant to touch and pleasant to write on with a pen, and the visibility of the displayed image can be improved.

[0036] Conventionally, when a glass substrate has a surface with irregularities, the touch feeling with a finger or the writing feeling with a pen is improved, but there is a problem that the linear transmittance of light is likely to decrease due to scattering caused by the irregularities. Therefore, when an image is displayed on such a glass substrate, the visibility of the image may decrease.

[0037] In contrast, in the glass substrate 1 of the present embodiment, the alkali content in the concave-convex portion 2 is less than the alkali content in the non-processed portion 3, and therefore the refractive index of the concave-convex portion 2 is lower than the refractive index of the non-processed portion 3, and the reflectance of the concave-convex portion 2 is reduced, thereby increasing the linear transmittance of light in the concave-convex portion 2. As a result, the glass substrate 1 can improve the visibility of the displayed image.

[0038] Therefore, in glass substrate 1, by making the arithmetic mean height Sa of uneven portion 2 1 nm or more and 100 nm or less, the feel of the surface to the touch and the feel of writing with a pen can be improved, while at the same time, by making the alkali content of uneven portion 2 less than the alkali content of non-processed portion 3, the visibility of the displayed image can be improved.

[0039] In this embodiment, the alkali content ratio of the uneven portion 2 to the non-processed portion 3 (uneven portion 2 / non-processed portion 3) is preferably 0.5 or more, more preferably 0.55 or more, even more preferably 0.6 or more, and is preferably less than 1.0, more preferably 0.99 or less, even more preferably 0.98 or less, even more preferably 0.97 or less, even more preferably 0.96 or less, even more preferably 0.95 or less, and even more preferably 0.94 or less.

[0040] When the alkali content ratio of the concave-convex portion 2 to the non-processed portion 3 is within the above range, the visibility of the image displayed on the glass substrate 1 can be further improved.

[0041] The alkali content ratio of the uneven portion 2 to the non-processed portion 3 can be determined from the ratio of the total mass proportion of Na and K in any 100 μm square area of ​​the uneven portion 2 to the total mass proportion of Na and K in any 100 μm square area of ​​the non-processed portion 3.

[0042] The total mass proportion of Na and K in any 100 μm square area of ​​the uneven portion 2 is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 5 mass% or more, and preferably 50 mass% or less, more preferably 45 mass% or less, even more preferably 40 mass% or less.

[0043] When the total mass ratio of Na and K in any 100 μm square area of ​​the concave-convex portion 2 is within the above range, the visibility of the image displayed on the glass substrate 1 can be further improved.

[0044] In this embodiment, the average length RSm of the roughness curve element in the uneven portion 2 of the glass substrate 1 is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 50 nm or more, even more preferably 100 nm or more, even more preferably 200 nm or more, even more preferably 500 nm or more, and preferably 10,000 nm or less, more preferably 8,000 nm or less, even more preferably 5,000 nm or less, even more preferably 3,000 nm or less, and even more preferably 2,000 nm or less. When the average length RSm in the uneven portion 2 of the glass substrate 1 is the above-mentioned lower limit value or more, the touch feeling of the surface of the glass substrate 1 and the writing feeling with a pen can be more effectively improved. Also, when the average length RSm in the uneven portion 2 of the glass substrate 1 is the above-mentioned upper limit value or less, the visibility of the image displayed on the glass substrate 1 can be more effectively improved.

[0045] In this embodiment, the maximum valley depth Rv in the uneven portion 2 of the glass substrate 1 is preferably 0.3 nm or more, more preferably 1 nm or more, even more preferably 10 nm or more, particularly preferably 50 nm or more, and is preferably 10,000 nm or less, more preferably 8,000 nm or less, even more preferably 5,000 nm or less, even more preferably 3,000 nm or less, and particularly preferably 1,000 nm or less. When the maximum valley depth Rv in the uneven portion 2 of the glass substrate 1 is equal to or greater than the above lower limit, the touch feeling of the surface of the glass substrate 1 and the writing feeling with a pen can be improved more effectively. Also, when the maximum valley depth Rv in the uneven portion 2 of the glass substrate 1 is equal to or less than the above upper limit, the visibility of the image displayed on the glass substrate 1 can be improved more.

[0046] When the average length RSm of the roughness curve element and the maximum valley depth Rv in the uneven portion 2 of the glass substrate 1 are within the above ranges, the resolution can be further increased when the glass substrate 1 is used in a display, and the writing comfort with a pen can be further effectively improved. In this case, the uneven portion 2 formed can more reliably suppress the occurrence of glare called sparkling caused by interference of scattered light.

[0047] The "average length RSm of the roughness curve element" and the "maximum valley depth Rv" are values ​​obtained when the cutoff value of the high-pass filter λc for cutting off long wavelength components from the contour curve showing the cross-sectional shape of the uneven portion 2 of the glass substrate 1 is set to 14 μm, and the cutoff value of the low-pass filter λs for cutting off short wavelength components from the contour curve showing the cross-sectional shape of the uneven portion 2 is set to 0.35 μm.

[0048] The "average length RSm of roughness curve elements" is a parameter defined by JIS B0601:2001, and is a parameter that represents the average pitch between adjacent concave and convex portions in a contour curve that shows the cross-sectional shape of the concave-convex portion 2. Hereinafter, the "average length RSm of roughness curve elements" may be referred to as the "average length RSm".

[0049] Furthermore, "maximum valley depth Rv" is a parameter defined by JIS B0601:2001, and represents the depth of the deepest valley with respect to the average line in the contour curve showing the cross-sectional shape of the uneven portion 2. The above "average line" is a line obtained by replacing the curve showing the long wavelength components blocked by the high-pass filter λc with a straight line using the least squares method.

[0050] In addition, when the unevenness having the above-mentioned average length RSm is defined as the first unevenness, the uneven portion 2 of the glass substrate 1 may further have a second unevenness having a larger average length RSm of roughness curve elements than the first unevenness. More specifically, as shown in Fig. 3, the measured cross-sectional curve of the uneven portion 2 may have the first unevenness which is a minute unevenness and the second unevenness which is a large unevenness.

[0051] The average length RSm2 of the roughness curve elements of the second irregularity is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 100 μm or more, and preferably 10,000 μm or less, more preferably 8,000 μm or less, even more preferably 5,000 μm or less, even more preferably 1,000 μm or less, and particularly preferably 500 μm or less.

[0052] The "average length RSm2 of the roughness curve element" is a value obtained when the cutoff value of the high-pass filter λc for cutting off long wavelength components from the contour curve showing the cross-sectional shape of the uneven portion 2 is set to a value four times the average length RSm of the roughness curve element of the second unevenness, and the cutoff value of the low-pass filter λs for cutting off short wavelength components from the contour curve showing the cross-sectional shape of the uneven portion 2 is set to 0.35 μm. The cutoff value of the high-pass filter λc of the second unevenness can be four times the value of the provisional average length RSm of the roughness curve element obtained when provisionally measuring without a filter. The "average length RSm2 of the roughness curve element" can be measured in accordance with JIS B0601:2001, similar to the average length RSm of the roughness curve element of the first unevenness. The "average length RSm2 of the roughness curve element" is the average of each periodic length Xs of the unevenness in a predetermined reference length.

[0053] The haze of the glass substrate 1 is not particularly limited, but in the wavelength range of 380 nm to 780 nm, is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, even more preferably 2% or more, and is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. When the haze of the glass substrate 1 is within the above range, the visibility of the image displayed on the glass substrate 1 can be further improved.

[0054] The linear transmittance of light with a wavelength of 550 nm through the uneven portion 2 of the glass substrate 1 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and is preferably 99% or less, more preferably 98% or less, even more preferably 97% or less. When the linear transmittance through the uneven portion 2 of the glass substrate 1 is within the above range, the visibility of the image displayed on the glass substrate 1 can be further improved.

[0055] Furthermore, the linear transmittance of light with a wavelength of 550 nm in the non-processed portion 3 of the glass substrate 1 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and is preferably 99% or less, more preferably 98% or less, even more preferably 97% or less. When the linear transmittance of the non-processed portion 3 of the glass substrate 1 is within the above range, the visibility of the image displayed on the glass substrate 1 can be further improved.

[0056] The linear transmittance of the glass substrate 1 can be measured, for example, by using a transmittance measuring device. In this embodiment, the linear transmittance of the glass substrate 1 is measured by making light incident on the first main surface 1a including the concave-convex portion 2 and making light exit from the second main surface 1b including the non-processed portion 3.

[0057] The non-processed portion 3 of the glass substrate 1 may not be subjected to any surface treatment at all, or may be subjected to a surface treatment different from that of the uneven portion 2. Examples of surface treatment different from that of the uneven portion 2 include blast treatment performed under conditions different from those of the uneven portion 2, coating with a component containing a SiO2 component, coating with a component containing fluorine, and surface treatment by HF etching. The non-processed portion 3 may be subjected to multiple surface treatments different from those of the uneven portion 2.

[0058] The first and second principal surfaces 1a and 1b of the glass substrate 1 may each be provided with an anti-reflection film, an anti-soiling film, a decorative film, a decorative coating, or the like.

[0059] The anti-reflection film may be, for example, a dielectric multilayer film in which a low refractive index film and a high refractive index film are alternately laminated. The anti-reflection film may be formed by sputtering, CVD, or the like.

[0060] When the uneven portion 2 of the glass substrate 1 has an anti-reflection film, the unevenness of the surface of the anti-reflection film is formed so as to correspond to the unevenness of the uneven portion 2.

[0061] The antifouling film is a film for preventing fingerprints from adhering and imparting water repellency and oil repellency. The antifouling film preferably contains a fluorine-containing polymer containing silicon in the main chain. As the fluorine-containing polymer, for example, a polymer having a -Si-O-Si- unit in the main chain and a water-repellent functional group containing fluorine in the side chain can be used. The fluorine-containing polymer can be synthesized, for example, by dehydration condensation of silanol.

[0062] Examples of decorative films and decorative coatings include resins such as polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polypropylene (PP), polyethylene terephthalate (PET), acrylic, urethane, and fluorine-based resins, metal foils, and laminates thereof.

[0063] The glass substrate 1 of this embodiment can be suitably used for displays, housings, doors, etc. of electronic devices. In particular, it can be suitably used as a cover member provided on the front of a display device such as a liquid crystal display. In this case, the glass substrate 1 may be used for a pen input device that allows input operations (pointing operations) of characters, figures, etc. to be performed using input means such as an input pen or a fingertip.

[0064] [Glass substrate manufacturing method] Next, an example of a method for manufacturing the glass substrate 1 will be described.

[0065] The concave-convex portion 2 of the glass substrate 1 can be formed, for example, by subjecting the surface of the original glass substrate to a surface treatment such as wet blasting.

[0066] Wet blasting is a process in which abrasive grains composed of solid particles such as alumina and liquid such as water are uniformly mixed to form a slurry, which is then sprayed at high speed from a spray nozzle using compressed air onto a workpiece made of an original glass substrate, thereby forming fine irregularities on the workpiece.

[0067] In wet blasting, when the slurry is sprayed at high speed and collides with the workpiece, the abrasive particles in the slurry scrape, hit, and rub the surface of the workpiece, forming fine irregularities on the surface of the workpiece.

[0068] In this case, the abrasive grains sprayed onto the workpiece and the pieces of the workpiece scraped off by the abrasive grains are washed away by the liquid sprayed onto the workpiece, so that fewer particles remain on the workpiece.

[0069] In wet blasting, when the slurry is sprayed onto the workpiece, the liquid carries the abrasive grains to the workpiece, making it easier to use finer abrasive grains than in dry sandblasting, and reducing the impact when the abrasive grains collide with the workpiece, making it possible to perform precise machining.

[0070] In the wet blasting process, the scanning pitch of the nozzle can be, for example, 50 μm or more and 10,000 μm or less. The number of times the nozzle scans (the number of times the same location is scanned) can be, for example, 1 time or more and 5 times or less. The moving speed of the nozzle (processing speed) can be, for example, 1 mm / s or more and 300 mm / s or less.

[0071] The arithmetic mean height Sa and maximum valley depth Rv of the uneven portion 2 of the glass substrate 1 can be increased by increasing the grain size of the abrasive grains in the wet blasting process, increasing the processing pressure, slowing down the nozzle movement speed, or increasing the number of nozzle scans.

[0072] In addition, the average length RSm of the roughness curve elements in the uneven portion 2 of the glass substrate 1 can be reduced by reducing the grain size of the abrasive grains in the wet blasting process, reducing the processing pressure, or increasing the nozzle scanning speed.

[0073] In the manufacturing method of this embodiment, a slurry having a pH of 5.0 or more and 9.0 or less is used to perform a wet blasting treatment on at least one main surface of the original glass substrate. This causes alkali to elute in the uneven portion 2 (the processed portion subjected to the wet blasting treatment), thereby reducing the alkali content in the uneven portion 2. Therefore, the alkali content in the uneven portion 2 can be made smaller than the mass ratio of the alkali component in the non-processed portion 3, and the visibility of the image displayed on the obtained glass substrate 1 can be improved.

[0074] The pH of the slurry is preferably 6.0 or more, more preferably 6.5 or more, even more preferably 7.0 or more, and is preferably 8.5 or less, more preferably 8.0 or less.

[0075] When the pH of the slurry is equal to or higher than the above lower limit, the alkali content in the uneven portion 2 of the glass substrate 1 can be further reduced, and the visibility of the image displayed on the glass substrate 1 can be further improved. When the pH of the slurry is equal to or lower than the above upper limit, the mechanical strength of the glass substrate 1 can be further increased, and the transparency of the glass substrate 1 can be further improved.

[0076] The electrical conductivity of the water used in the slurry of this embodiment is not particularly limited, but is, for example, 0.01 mS / m or more and 20 mS / m or less. If the electrical conductivity of the water is higher than 20 mS / m, there are many impurities, so that it may take a long time for alkaline elution. On the other hand, if the electrical conductivity of the water is lower than 0.01 mS / m, it may be difficult to obtain water by a general method. The electrical conductivity of the water is preferably 0.02 mS / m or more, more preferably 0.03 mS / m or more, even more preferably 0.04 mS / m or more, and preferably 10 mS / m or less, more preferably 8 mS / m or less, and even more preferably 7 mS / m or less.

[0077] In addition, either an inorganic acid or an organic acid may be used to adjust the pH of the slurry. For example, when adjusting to pH≦7, examples of inorganic and organic acids include hydroxy acids such as sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, oxalic acid, lactic acid, citric acid, malic acid, tartaric acid, and glyceric acid. When adjusting to pH≧7, the pH can be adjusted with an alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, aqueous ammonia, ammonium carbonate, and amines such as ethylamine, methylamine, triethylamine, and tetramethylamine.

[0078] The alkali content in the uneven portion 2 of the glass substrate 1 can be adjusted by the pH of the slurry, the concentration of abrasive grains in the slurry, the type of abrasive grains, the spray pressure of the slurry (treatment pressure), the nozzle movement speed (treatment speed), etc.

[0079] The concentration of the abrasive grains in the slurry is preferably 1 mass % or more, more preferably 2 mass % or more, and even more preferably 2.5 mass % or more, and is preferably 30 mass % or less, more preferably 27 mass % or less, and even more preferably 25 mass % or less. When the concentration of the abrasive grains in the slurry is within the above range, the alkali content in the uneven portion 2 can be further reduced, and the visibility of the image displayed on the glass substrate 1 can be further improved.

[0080] The abrasive grains are not particularly limited, and for example, particles of aluminum oxide (alumina), aluminum nitride, aluminum carbide, aluminum silicate, zirconium oxide, yttria-stabilized zirconia, zircon, silicon oxide, silicon nitride, silicon carbide, or the like can be used. Among them, it is preferable to use alumina particles as the abrasive grains. In this case, the pH of the slurry can be easily adjusted, and the alkali content of the uneven portion 2 can be more reliably reduced.

[0081] The purity of the abrasive grains can be, for example, 90% or more and 100% or less. 50 can be 0.1 μm or more and 10 μm or less.

[0082] The spray pressure of the slurry is preferably 0.1 MPa or more, more preferably 0.15 MPa or more, and even more preferably 0.2 MPa or more, and is preferably 3.0 MPa or less, more preferably 2.5 MPa or less, and even more preferably 2.0 MPa or less. When the spray pressure of the slurry is within the above range, the alkali content of the uneven portion 2 can be further reduced, and the visibility of the image displayed on the glass substrate 1 can be further improved.

[0083] The nozzle movement speed (treatment speed) is preferably 1 mm / s or more, more preferably 5 mm / s or more, and even more preferably 10 mm / s or more, and is preferably 300 mm / s or less, more preferably 250 mm / s or less, and even more preferably 200 mm / s or less. When the nozzle movement speed (treatment speed) is equal to or more than the above lower limit, the alkali content of the uneven portion 2 can be further reduced. On the other hand, when the time of the wet blasting treatment is equal to or less than the above upper limit, the mechanical strength of the glass substrate 1 can be further increased.

[0084] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be modified as appropriate within the scope of the present invention.

[0085] (Examples 1 to 8) First, an alkali aluminosilicate glass plate was prepared as the original glass substrate. The glass composition (mass %) of the alkali aluminosilicate glass plate was SiO2 62.0%, Al2O3 16.0%, B2O3 2.0%, Na2O 15.0%, MgO 2.0%, and K2O 3.0% (thickness: 0.5 mm, linear transmittance of light at a wavelength of 550 nm: 95%, 50 mm square).

[0086] Next, a wet blasting process was performed on one main surface of the prepared original glass substrate to form a concave-convex portion. The wet blasting process was performed by using a slurry prepared by uniformly mixing abrasive grains and water, and spraying the slurry from a nozzle using air to scan the processing stage on which the glass plate was placed while moving the nozzle at a speed of 20 mm / s (scanning pitch: 0.5 mm).

[0087] The water used for the slurry was pure water with a pH of 7 and an electric conductivity of 0.05 mS / m.

[0088] In the wet blasting treatment in Examples 1 to 8, the spray pressure of the slurry as the treatment pressure was set to 0.30 MPa. 50 Pure water was used, and hydrochloric acid or potassium hydroxide was added to adjust the pH of the slurry to the pH shown in Tables 1 and 2 below. The concentration of abrasive grains in the slurry is as shown in Tables 1 and 2 below.

[0089] In Examples 1 to 8, the original glass substrate after the wet blasting treatment was washed with pure water, and then the original glass substrate was subjected to a heat treatment at 120° C. for 30 minutes to obtain a glass substrate.

[0090] Comparative Example 1 One main surface of an original glass substrate prepared in the same manner as in Example 1 was subjected to dry sandblasting treatment using the same abrasive grains as in Example 1 at a low pressure set by a regulator to obtain a glass substrate.

[0091] Comparative Example 2 The other main surface of the glass substrate obtained in Comparative Example 1 was subjected to alkaline etching to obtain a glass substrate.

[0092] Comparative Example 3 A glass substrate was obtained in the same manner as in Example 1, except that the pH of the slurry and the concentration of the abrasive grains in the slurry were adjusted as shown in Table 2 below.

[0093] [Evaluation method] (Evaluation of surface roughness of glass substrate) The arithmetic mean height Sa of the uneven portion (processed portion) of the glass substrates obtained in Examples 1 to 8 and Comparative Examples 1 to 3 was measured.

[0094] The arithmetic mean height Sa was measured using a white light interference microscope manufactured by Zygo (product name: NewView7300).

[0095] The measurement conditions were a 50x objective lens and a 2x zoom lens, and the arithmetic mean height Sa was measured over a measurement area of ​​74 μm × 55 μm, with a camera pixel count of 640 × 480 and an accumulation count of 10. The cutoff value of the high-pass filter λc when measuring the arithmetic mean height Sa of the uneven portion (surface) was set to 14 μm, and the cutoff value of the low-pass filter λs was set to 0.35 μm.

[0096] (Observation of the surface of a glass substrate) The mass proportions of Na and K in a 100 μm square area were determined at five arbitrary locations on the uneven portions (processed portions) and non-processed portions of the glass substrates obtained in Examples 1 to 8 and Comparative Examples 1 to 3 using a scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX, Hitachi High-Tech Corporation, product number "S3400"), and the average value was taken as the alkali content in the uneven portions and non-processed portions. The alkali content ratio was then calculated from the ratio of the alkali content in the uneven portions to the alkali content in the non-processed portions (uneven portions / non-processed portions). The results are shown in Tables 1 and 2 below.

[0097] (Linear transmittance) The linear transmittance of light at a wavelength of 550 nm was determined for the uneven portions (processed portions) of the glass substrates of Examples 1 to 8 and Comparative Examples 1 to 3. The linear transmittance of the glass substrate was measured using a transmittance measuring device (manufactured by JASCO, product number "V670"). The linear transmittance of the glass substrate was measured by illuminating light from one main surface including the uneven portions and emitting light from the other main surface including the non-processed portions. The results are shown in Tables 1 and 2 below.

[0098] [Table 1]

[0099] [Table 2]

[0100] In the glass substrates of Examples 1 to 8, the arithmetic mean height Sa of the uneven portion was 1 nm or more and 100 nm or less, and it was confirmed by sensory evaluation that the surface was excellent in terms of touch feeling and writing comfort with a pen. In addition, as shown in Tables 1 and 2, in the glass substrates of Examples 1 to 8, the alkali content ratio was less than 1, and the linear transmittance was increased, so it was confirmed that the visibility of the displayed image was also excellent. On the other hand, in the glass substrates of Comparative Examples 1 and 2, the alkali content ratio was 1 or more, and the linear transmittance was low, so the visibility of the displayed image was also insufficient. In addition, in the glass substrate of Comparative Example 3, the arithmetic mean height Sa of the uneven portion was large at 2000 nm, and as a result, the linear transmittance was significantly reduced, so the visibility of the displayed image was also insufficient. [Explanation of symbols]

[0101] 1,10...Glass substrate 1a...First main surface 1b…Second main surface 2...Uneven part 3…Unprocessed part

Claims

1. A glass substrate made of alkali-containing silicate glass, the surface of the glass substrate has an uneven portion and a non-processed portion that has not been processed to provide the uneven portion, the concave-convex portion has an arithmetic mean height Sa of 1 nm or more and 100 nm or less in a 74 μm×55 μm region when the cutoff value of the high-pass filter λc is 14 μm and the cutoff value of the low-pass filter λs is 0.35 μm; A glass substrate, wherein when the total mass ratio of Na and K in any 100 μm square region is defined as the alkali content, the alkali content in the concave-convex portion is lower than the alkali content in the non-processed portion.

2. 2. The glass substrate according to claim 1, wherein the ratio of an alkali content in the concave-convex portion to that in the non-processed portion is 0.5 or more and less than 1.

0.

3. The glass substrate according to claim 1 , wherein both the concave-convex portion and the non-processed portion are provided on one main surface of the glass substrate.

4. the glass substrate has a first main surface and a second main surface opposed to each other; The uneven portion is provided on the first main surface of the glass substrate, The glass substrate according to claim 3 , wherein the unprocessed portion is provided on the second main surface of the glass substrate.

5. The alkali-containing silicate glass has a glass composition, in mass %, of SiO ２ 30%~70%, Al ２ O ３ 10% to 20%, B ２ O ３ 0% to 10%, Na ２ O 1% to 20%, K ２ 3. The glass substrate according to claim 1, comprising 1% to 20% O and 0% to 20% MgO.

6. A method for producing a glass substrate according to claim 1 or 2, comprising the steps of: preparing an original glass substrate; a step of subjecting at least one principal surface of the original glass substrate to a wet blasting treatment using a slurry containing abrasive grains and having a pH of 5.0 or more and 9.0 or less; A method for manufacturing a glass substrate comprising the steps of:

7. The method for producing a glass substrate according to claim 6 , wherein the pH of the slurry is 7.0 or more and 8.0 or less.

8. The method for producing a glass substrate according to claim 6 , wherein the abrasive grains are alumina grains.

9. The method for producing a glass substrate according to claim 6 , wherein a concentration of the abrasive grains in the slurry is 1 mass % or more and 30 mass % or less.

10. The method for manufacturing a glass substrate according to claim 6 , wherein a spraying pressure of the slurry is 0.1 MPa or more and 3.0 MPa or less.

Images