Glass substrate and electronic device

Abstract

To provide a glass substrate in which fine unevenness on a glass substrate surface that causes color unevenness is reduced.SOLUTION: A glass substrate according to the present invention has a first main plane and a second main plane, in which a total value A3-10 of undulation intensity in a wavelength of 3 to 10 mm, measured by discrete Fourier transformation of an uneven wave shape of a surface of the first main plane is 0.50×10-3 μm or more and 1.60×10-3 μm or less, undulation intensity A20 in a wavelength of 20 mm is 0.50×10-3 μm or more and 1.60×10-3 μm or less. The glass substrate according to the present invention reduces fine unevenness on the glass substrate surface that causes color unevenness, so that a glass substrate with suppressed color unevenness can be provided.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a glass substrate, an electronic device, and a method for manufacturing a glass substrate. [Background technology]

[0002] For example, minute irregularities exist on the surface of a glass substrate formed by the float method. Such minute irregularities may cause color unevenness when the glass substrate is used, for example, as a glass substrate for a display. Therefore, attempts have been made to efficiently suppress color unevenness by increasing the amount of polishing when polishing the surface of the glass substrate to remove such minute irregularities, or by selecting a glass substrate with little waviness and improving polishability (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-65529 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, the quality required for glass substrates for displays has been increasing, and color unevenness has sometimes become a problem even when the amount of polishing is increased or when a glass substrate with a specific small waviness is selected and polished as in Patent Document 1. Therefore, it has been necessary to further reduce the minute irregularities on the glass substrate surface that cause color unevenness. An object of the present invention is to provide a glass substrate in which the minute irregularities on the glass substrate surface that cause color unevenness are reduced and color unevenness is suppressed. [Means for solving the problem]

[0005] (1) The glass substrate according to the present invention has a first main surface and a second main surface, and a total value A of waviness intensity at a wavelength of 3 to 10 mm calculated by subjecting the surface unevenness waveform of the first main surface to a discrete Fourier transform. 3~10 is 0.50×10 -3 μm or more 1.60×10 -3 μm or less, and the waviness intensity A at a wavelength of 20 mm 20 is 0.50×10 -3 μm or more 1.60×10 -3 It is characterized by being less than μm. (2) The above-mentioned swell strength A 20 The swell strength A 3~10 The ratio (A 3~10 / A 20 ) is 1.00 or more and 2.00 or less. (3) The glass substrate according to (1) or (2), wherein the glass substrate is float glass. (4) The glass substrate according to any one of (1) to (3), wherein the thickness of the glass substrate is 1 mm or less. (5) The glass substrate according to any one of (1) to (4), wherein the glass substrate has a rectangular shape with at least one side of 2400 mm or more. (6) The glass substrate according to any one of (1) to (5), wherein the first main surface is a polished surface. (7) The glass substrate according to any one of (1) to (6), which is for a display. (8) An electronic device comprising the glass substrate according to any one of (1) to (7).

[0006] (9) The method for manufacturing a glass substrate according to the present invention is characterized by comprising a surface shape measurement step of measuring the uneven waveform of the surface of the first main surface to detect convex portions having a height equal to or greater than a predetermined reference value, a convex portion removal step of applying an etching solution to the convex portions having a height equal to or greater than the predetermined reference value detected in the surface shape measurement step, and a polishing step of polishing the main surface treated in the convex portion removal step. (10) The method for producing a glass substrate according to (9), wherein the etching solution is applied by a spray nozzle, a pen, or a brush. (11) The method for producing a glass substrate according to (9) or (10), wherein the glass substrate is a float glass. (12) The method for producing a glass substrate according to any one of (9) to (11), wherein the glass substrate has a thickness of 1 mm or less. (13) The method for producing a glass substrate according to any one of (9) to (12), wherein the glass substrate has a rectangular shape with at least one side of 2400 mm or more. (14) The method for producing a glass substrate according to any one of (9) to (13), wherein the glass substrate is for a display. [Effects of the Invention]

[0007] By reducing minute irregularities on the surface of the glass substrate that cause color unevenness, it is possible to provide a glass substrate with reduced color unevenness. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a flowchart showing a method for manufacturing a glass substrate according to the present embodiment. [Figure 2] FIG. 10 is a flowchart showing each step in the preparation process. [Figure 3] 10A and 10B are conceptual diagrams showing changes in the surface of a glass substrate during a convex portion removal step. [Figure 4] FIG. 1 is a conceptual diagram showing an apparatus for measuring the surface shape of a glass substrate using a stripe pattern projection method. [Figure 5] FIG. 10 is a flowchart showing a method for measuring the surface shape of a glass substrate by a stripe pattern projection method. [Figure 6] 1 is a graph showing waviness intensity at each wavelength of the glass substrates before polishing in Examples 1 and 4. [Figure 7] 1 is a graph showing waviness intensity at each wavelength of the polished glass substrates of Examples 1 and 4. [Figure 8] 1 is a graph showing waviness intensity at each wavelength of the glass substrates before polishing in Examples 3 and 5. [Figure 9]1 is a graph showing waviness intensity at each wavelength of the polished glass substrates of Examples 3 and 5. [Figure 10] 10 is a graph showing gain at each pitch in filter processing. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the term "pitch" refers to the distance between adjacent convex portions when the concave and convex waveform on the surface of a glass substrate is measured by, for example, the stripe pattern projection method or the non-contact surface shape measurement method using an optical interference method, which will be described later. The wavelength refers to the length of one period of a wave. In this specification, unless otherwise specified, the wavelength refers to the wavelength obtained by subjecting the uneven waveform on the surface of a glass substrate to a discrete Fourier transform. The spatial frequency resolution when performing the discrete Fourier transform is 1 mm. In this specification, the waviness height refers to the height of each point when the uneven waveform of the surface of a glass substrate is measured by, for example, the stripe pattern projection method or non-contact surface shape measurement using an optical interference method, which will be described later. In this specification, the waviness intensity refers to the amplitude at each wavelength calculated by measuring the unevenness waveform on the surface of a glass substrate and subjecting the obtained unevenness profile to a discrete Fourier transform. The unevenness waveform on the surface of a glass substrate can be measured, for example, by a stripe pattern projection method or a non-contact surface shape measurement method using an optical interference method, which will be described later. In this specification, the unevenness profile of the surface of the glass substrate is filtered before the discrete Fourier transform. In this specification, filtering refers to a process in which the amplitude of unevenness having a specific pitch is attenuated using a computer for the obtained unevenness profile. The gain at each pitch in the filtering process is shown in FIG. 10, and the gain at the specific pitch in FIG. 10 is shown in Table 1.

[0010] In the filtering process, amplitudes with short pitches are attenuated to eliminate the effects of measurement noise. Also, since the longer the pitch of irregularities, the smaller the effect on color unevenness tends to be, the longer the pitch of the irregularities is, the more the amplitude is attenuated. Note that gain refers to the value obtained by dividing the amplitude after filtering by the amplitude before filtering. That is, the waviness intensity at a wavelength of 20 mm on the glass substrate surface means the amplitude at a wavelength of 20 mm calculated by filtering the unevenness profile obtained by measuring the unevenness waveform on the glass substrate surface with the gain shown in Figure 10 and then performing a discrete Fourier transform.

[0011] Hereinafter, preferred embodiments of the glass substrate and the method for manufacturing the glass substrate according to the present invention will be described. The embodiments described below are merely examples, and the present invention should not be construed as being limited to these embodiments.

[0012] For example, minute irregularities exist on the surface of a glass substrate formed by a float method. When the glass substrate is used as a glass substrate for a display, for example, these minute irregularities may cause color unevenness. Furthermore, in recent years, the quality required for glass substrates for displays has been increasing, so it has been necessary to further reduce the minute irregularities on the surface of the glass substrate that cause color unevenness.

[0013] As a result of investigating the irregularities that cause color unevenness, the inventors found that when the irregular waveform on the surface of a glass substrate manufactured by the float method was subjected to a discrete Fourier transform, the waviness intensity at a wavelength of 20 mm was large, and that this 20 mm wavelength component was the cause of color unevenness. Therefore, it is important to reduce the waviness intensity at a wavelength of 20 mm on the glass substrate surface.

[0014] However, glass substrates manufactured by the float method, for example, have minute irregularities such as distortion and corrugation, making it difficult to eliminate the irregularities present on the glass substrate. When the waveform of the irregularities on the surface of such a glass substrate is subjected to a discrete Fourier transform, a component with a wavelength of 20 mm is present.

[0015] Furthermore, the inventors have found that the 20 mm wavelength component is difficult to remove by polishing and therefore tends to remain even when a large amount of polishing is performed, i.e., the waviness intensity at a wavelength of 20 mm is difficult to reduce by polishing. Therefore, it is difficult to sufficiently reduce the waviness intensity at a wavelength of 20 mm by polishing the surface of a glass substrate produced by the float method.

[0016] The inventors have found that removing the convex portions present on the surface of the glass substrate before the polishing step S50 described below reduces the waviness strength at a wavelength of 20 mm and results in a glass substrate with reduced color unevenness. This is thought to be because, as shown in FIG. 3, removing the convex portions present on the surface of the glass substrate changes the long-pitch corrugated surface of the glass substrate into multiple corrugated surfaces with short pitches. In this way, by removing the convex portions present on the surface of the glass substrate, a glass substrate with reduced waviness strength at a wavelength of 20 mm can be obtained before polishing. Because the waviness strength at a wavelength of 20 mm, which is difficult to remove by polishing, is reduced in the glass substrate before polishing, a glass substrate with reduced waviness strength at a wavelength of 20 mm can be obtained even after polishing.

[0017] However, the inventors discovered that color unevenness can be a problem even when the waviness intensity at a wavelength of 20 mm is reduced. Through extensive research, the inventors discovered that when the unevenness waveform on the surface of a glass substrate is subjected to a discrete Fourier transform, color unevenness occurs when the total value of waviness intensity at wavelengths of 3 mm or more and 10 mm or less (hereinafter also referred to as "wavelengths of 3 to 10 mm") is high. Components with wavelengths of less than 3 mm are extremely easily removed by polishing, so it is thought that components with wavelengths of less than 3 mm are unlikely to affect color unevenness. Here, the total value of undulation intensity at wavelengths of 3 to 10 mm refers to the total value of undulation intensity at wavelengths of N mm (N=3, 4, . . . , 9, 10, ie, N is a natural number between 3 and 10).

[0018] As mentioned above, components with long wavelengths are difficult to remove by polishing, but components with short wavelengths are easy to remove by polishing. In other words, when the surface of a glass substrate is polished, the waviness intensity at wavelengths of 3 to 10 mm is more likely to be reduced than the waviness intensity at a wavelength of 20 mm. Therefore, when a glass substrate manufactured by the float method is polished, the waviness intensity at wavelengths of 3 to 10 mm is reduced before the waviness intensity at a wavelength of 20 mm, so there is no color unevenness caused by components with wavelengths of 20 mm or less, but color unevenness caused by components with wavelengths of 3 to 10 mm or less does not occur.

[0019] However, when a glass substrate having reduced waviness intensity at a wavelength of 20 mm is polished by removing convex portions present on the glass substrate surface before the polishing step S50, the total value of waviness intensity at wavelengths of 3 to 10 mm may be high when the polished glass substrate is observed, even if the waviness intensity at a wavelength of 20 mm is sufficiently reduced. The inventors have found that in such cases, color unevenness occurs. Therefore, in order to obtain a glass substrate with reduced color unevenness, when the uneven waveform on the glass substrate surface is subjected to a discrete Fourier transform, it is important not only to reduce the waviness intensity at a wavelength of 20 mm, but also to reduce the total value of the waviness intensity at wavelengths of 3 to 10 mm.

[0020] <Glass substrate> In the present embodiment, the glass substrate is preferably manufactured by a float method from the viewpoint of manufacturing efficiency. Furthermore, glass substrates manufactured by the float method are likely to have color unevenness due to minute irregularities caused by distortion or corrugation, and therefore the effects of the present invention are significant.

[0021] The composition of the glass substrate is not particularly limited. Examples include soda-lime glass, aluminosilicate glass, borosilicate glass, and alkali-free glass. For the glass substrate of this embodiment, alkali-free glass that is substantially free of alkali metal components is preferably used when the glass substrate is used as a substrate for an electronic device such as a liquid crystal display.

[0022] Here, "substantially free of alkali metal components" means that the total content of alkali metal oxides is 0.1% by mass or less. The content of alkali metal oxides is more preferably 10 ppm by mass or more, in order to reduce the viscosity of the glass during melting and facilitate the production of the glass.

[0023] When used as a substrate for an electronic device, the glass composition preferably contains, in mass % on an oxide basis, 35 to 73% SiO2, 5 to 35% Al2O3, 0 to 30% B2O3, 0 to 20% MgO, 0 to 30% CaO, 0 to 30% SrO, 0 to 40% BaO, and 1 to 55% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal oxides.

[0024] For applications as substrates for electronic devices, when the glass has a high strain point and solubility is a consideration, it is more preferable that the glass composition contains, in mass % on an oxide basis, 58 to 66% SiO2, 15 to 22% Al2O3, 5 to 12% B2O3, 0 to 8% MgO, 0 to 9% CaO, 3 to 12.5% ​​SrO, 0 to 2% BaO, and 9 to 18% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal oxides.

[0025] When the strain point is high and solubility is a consideration, the glass composition more preferably contains, in mass % on an oxide basis, 56 to 62% SiO2, 15 to 20% Al2O3, 6 to 10% B2O3, 2 to 5% MgO, 3 to 7% CaO, 4 to 10% SrO, 0 to 1% BaO, and 12 to 17% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal components. It is even more preferable that the glass be substantially free of BaO.

[0026] When used as a substrate for an electronic device, the glass composition, taking into consideration a high strain point, more preferably contains, in mass % on an oxide basis, 54 to 73% SiO2, 10.5 to 22.5% Al2O3, 0 to 7% B2O3, 0 to 10% MgO, 0 to 10% CaO, 0 to 16% SrO, 0 to 10% BaO, and 8 to 26% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal oxides.

[0027] In applications for electronic device substrates, when an even higher strain point is taken into consideration, the glass composition preferably contains, in mass % on an oxide basis, 54 to 73% SiO2, 10.5 to 22.5% Al2O3, 0 to 5.5% B2O3, 0 to 10% MgO, 0 to 10% CaO, 0 to 10% SrO, 0 to 10% BaO, and 8 to 20% MgO, CaO, SrO, and BaO in total, and is substantially free of alkali metal oxides.

[0028] When the glass is used as a substrate for an electronic device, and in consideration of electrical properties such as a low dielectric constant and a low dielectric loss tangent, it is more preferable that the glass composition contains, in mass % on an oxide basis, 54 to 73% SiO2, 5 to 22.5% Al2O3, 15 to 30% B2O3, 0 to 10% MgO, 0 to 9% CaO, 0 to 16% SrO, 0 to 20% BaO, and 1 to 26% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal oxides.

[0029] In applications for electronic device substrates, when improving the controllability of the expansion coefficient and particularly when attempting to obtain a substrate with a high expansion coefficient, the glass composition preferably contains, in mass % on an oxide basis, 40 to 73% SiO2, 5 to 23% Al2O3, 0 to 15% B2O3, 0 to 20% MgO, 0 to 20% CaO, 0 to 20% SrO, 0 to 20% BaO, and 10 to 55% total of MgO, CaO, SrO, and BaO, and is substantially free of alkali metal oxides.

[0030] The thickness of the glass substrate is preferably 1 mm or less. By making the glass substrate thinner, weight reduction can be achieved. The thickness of the glass substrate of the present invention is more preferably 0.65 mm or less, even more preferably 0.55 mm or less, particularly preferably 0.45 mm or less, and most preferably 0.4 mm or less. The thickness can also be 0.1 mm or less, or 0.05 mm or less. However, from the viewpoint of preventing deflection due to its own weight, the thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more.

[0031] The size of the glass substrate can be any of the following: G3 (550 x 650 mm), G4 (680 x 880 mm), G5 (1000 x 1200 mm), G6 (1500 x 1.500 mm), G7 (1900 x 2200 mm), G8 (2200 x 2400 mm), G9 (2400 x 2800 mm), G10 (2800 x 3000 mm), and G11 (3000 x 3300 mm). Furthermore, the size of the glass substrate is preferably, for example, a glass substrate with at least one side of 2400 mm or more, specifically, a glass substrate with a long side of 2400 mm or more and a short side of 2000 mm or more. The larger the glass substrate, the larger the area of ​​the main surface of the glass substrate, and therefore the greater the possibility of color unevenness occurring within the surface of the glass substrate. Furthermore, the larger the glass substrate, the greater the difficulty of polishing, and therefore the greater the possibility of color unevenness occurring within the surface of the glass substrate. Therefore, a more significant effect can be obtained when the glass substrate has at least one side of 2400 mm or more.

[0032] <Waviness intensity A at wavelength 20 mm 20 > The glass substrate according to the present invention has a first main surface and a second main surface, and has a waviness intensity A at a wavelength of 20 mm calculated by subjecting the surface unevenness waveform of the first main surface to a discrete Fourier transform. 20 is 1.60 x 10 -3 μm or less. Swell intensity A at wavelength 20 mm 20 is 1.60 x 10 -3 By keeping the wavelength below 20 mm, color unevenness caused by components with a wavelength of 20 mm can be suppressed.20 is 1.40 x 10 -3 μm or less is preferable, and 1.20 × 10 -3 μm or less is more preferable, and 1.00×10 -3 It is more preferable that the waviness strength A 20 The lower limit of is not particularly limited, but for example, 0.50 × 10 -3 μm or more.

[0033] In addition, for glass substrates whose first main surface is not polished, the waviness intensity A at a wavelength of 20 mm was calculated by performing a discrete Fourier transform on the uneven waveform of the surface of the first main surface of the glass substrate. 20 is 2.00 x 10 -3 It is preferable that the waviness intensity A at a wavelength of 20 mm is less than 1 μm. 20 is difficult to reduce in the polishing step S50, but the waviness intensity A at a wavelength of 20 mm in a glass substrate whose first main surface is not polished 20 to 2.00 x 10 -3 By making the thickness of the glass substrate 10 μm or less, color unevenness can be suppressed even on the glass substrate 10 after polishing. The glass substrate 10 after polishing is the glass substrate 10 after polishing step S50, which will be described later. In a glass substrate in which the first main surface is not polished, the waviness intensity A of the first main surface at a wavelength of 20 mm is 20 is 1.70 x 10 -3 It is more preferable that the thickness is 1.40 × 10 μm or less. -3 It is more preferable that the thickness is 1.20 × 10 μm or less. -3 In a glass substrate having an unpolished first main surface, the waviness strength A of the first main surface is particularly preferably 1 μm or less. 20 The lower limit of is not particularly limited, but for example, 0.50 × 10 -3 μm or more.

[0034] On a glass substrate before polishing, waviness intensity A at a wavelength of 20 mm 20can be adjusted by adjusting the height of the reference value H2 in the surface shape measurement step S20, which will be described later. The higher the reference value H2, the fewer convexes are removed in the convexity removal step S30, which will be described later, making it more difficult to reduce the waviness intensity at a wavelength of 20 mm. Also, if the reference value H2 is set too low, it becomes more difficult to reduce the waviness intensity at a wavelength of 20 mm. The glass substrate before polishing is the glass substrate that has been subjected to the cleaning step S40, which will be described later, but before the polishing step S50.

[0035] Waviness intensity A at a wavelength of 20 mm on a polished glass substrate 20 is the waviness intensity A at a wavelength of 20 mm on the glass substrate before polishing 20 The waviness intensity A of the glass substrate before polishing at a wavelength of 20 mm 20 The larger the value of , the greater the waviness intensity A at a wavelength of 20 mm even on the polished glass substrate. 20 The value of becomes larger.

[0036] In addition, the waviness intensity A of the polished glass substrate at a wavelength of 20 mm 20 is also affected by the polishing conditions. For example, the longer the polishing time, the greater the waviness intensity A at a wavelength of 20 mm. 20 However, the waviness intensity A at a wavelength of 20 mm is 20 is difficult to reduce by polishing, so in glass substrates manufactured by the float method, the waviness intensity A at a wavelength of 20 mm can be reduced by polishing alone. 20 The value of 1.60×10 -3 When polishing a glass substrate manufactured by the float method, even if the polishing amount is increased by extending the polishing time, the waviness intensity A at a wavelength of 20 mm is 20 is usually 1.60 x 10 -3 It exceeds μm.

[0037] <Waviness intensity A at wavelengths of 3 to 10 mm 3~10 > The glass substrate according to the present invention has a first main surface and a second main surface, and a total value A of waviness intensity at wavelengths of 3 to 10 mm calculated by subjecting the surface unevenness waveform of the first main surface to a discrete Fourier transform.3~10 is 1.60 x 10 -3 μm or less. A 3~10 is 1.60 x 10 -3 By keeping the wavelength below 1 μm, color unevenness caused by components with wavelengths of 3 to 10 mm can be suppressed.

[0038] Total waviness intensity at wavelengths of 3 to 10 mm A 3~10 is 1.40 x 10 -3 μm or less is preferable, and 1.30 × 10 -3 μm or less is more preferable, and 1.20 × 10 -3 It is more preferable that the total waviness intensity A 3~10 The lower limit of is not particularly limited, but for example, 0.50 × 10 -3 μm or more.

[0039] In addition, for a glass substrate whose first main surface is not polished, the sum A of the waviness intensity at wavelengths of 3 to 10 mm calculated by discrete Fourier transform of the uneven waveform on the surface of the first main surface of the glass substrate is 3~10 is 7.00 x 10 -3 The sum of the waviness intensities at wavelengths of 3 to 10 mm is A 3~10 When the total waviness intensity A in the wavelength range of 3 to 10 mm is large, it is necessary to increase the amount of polishing in order to suppress color unevenness caused by the component with a wavelength of 3 to 10 mm. 3~10 If the polishing amount is small, color unevenness can be suppressed without increasing the polishing amount in the polishing step S50, and therefore improvement in productivity can be expected. The sum of waviness intensities A at wavelengths of 3 to 10 mm for a glass substrate with an unpolished first principal surface 3~10 is 6.00 x 10 -3 μm or less is more preferable, and 5.50×10 -3 It is more preferable that the thickness is 5.00×10 μm or less. -3 It is particularly preferable that the thickness is 1 μm or less. In addition, for glass substrates whose first main surface is not polished, the total waviness strength A 3~10 The lower limit is 4.00 × 10 -3 μm or more is preferable, and 4.20 × 10-3 μm or more is more preferable, and 4.50 × 10 -3 In a glass substrate having an unpolished first main surface, the total waviness strength A 3~10 is equal to or greater than the lower limit, it is highly likely that the long-pitch corrugated surface of the first main surface of the glass substrate as shown in FIG. 3 has been converted into a plurality of short-pitch corrugated surfaces by the convex portion removing step S30 described later.

[0040] The total waviness intensity A at wavelengths of 3 to 10 mm on a glass substrate before polishing 3~10 can be adjusted by adjusting the height of the reference value H2 in the surface shape measurement step S20, which will be described later. The higher the reference value H2, the fewer convex portions are removed in the convex portion removal step S30, which will be described later. As shown in FIG. 3, the sum A of the waviness intensities at wavelengths of 3 to 10 mm 3~10 increases as the long-pitch corrugations present on the glass substrate surface become multiple short-pitch corrugations in the convex portion removal step S30. Therefore, when fewer convex portions are removed in the convex portion removal step S30, the total value A of the waviness intensity at wavelengths of 3 to 10 mm 3~10 Also, even if the reference value H2 is set too low, the total value A of the swell strength 3~10 becomes smaller.

[0041] The total waviness intensity A at wavelengths of 3 to 10 mm on a polished glass substrate 3~10 is the total waviness strength of the glass substrate before polishing, A 3~10 The total waviness strength of the glass substrate before polishing, A 3~10 The larger the value, the greater the A 3~10 tends to become large.

[0042] In addition, the total waviness intensity A at wavelengths of 3 to 10 mm on the polished glass substrate 3~10 is also affected by the polishing conditions. For example, the longer the polishing time and the greater the polishing amount, the greater the total waviness intensity A at wavelengths of 3 to 10 mm. 3~10 becomes smaller.

[0043] <Waviness intensity A at wavelength 20 mm 20 The total value A of the waviness intensity at wavelengths of 3 to 10 mm 3~10 The ratio (A 3~10 / A 20 )> Swell intensity A at wavelength 20 mm 20 The total value A of the waviness intensity at wavelengths of 3 to 10 mm 3~10 The ratio (A 3~10 / A 20 ) changes before and after polishing, especially A 3~10 This is because in the polishing step S50, components with short wavelengths are easily reduced, but components with long wavelengths are difficult to reduce. That is, before and after the polishing step S50, the total value of waviness intensity at waviness wavelengths of 3 to 10 mm, A 3~10 is easily changed, but the swell intensity A at a swell wavelength of 20 mm 20 Therefore, the ratio (A 3~10 / A 20 ) is the total value of waviness intensity at wavelengths of 3 to 10 mm A 3~10 The impact of changes in

[0044] In the polished glass substrate, the ratio (A 3~10 / A 20 The ratio (A) is preferably 1.00 or more, more preferably 1.05 or more, and even more preferably 1.10 or more. 3~10 / A 20 The larger the ratio (A 3~10 / A 20 By polishing the glass substrate so that the surface roughness (ratio of surface roughness) is equal to or greater than the lower limit, productivity can be expected to improve.

[0045] In addition, in the polished glass substrate, the ratio (A 3~10 / A 20 The ratio (A) is preferably 2.00 or less, more preferably 1.70 or less, and even more preferably 1.50 or less. 3~10 / A 20 ) being equal to or less than the upper limit means that the glass substrate is sufficiently polished. Here, when a glass substrate manufactured by the float method is polished without carrying out the convex portion removal step S30 described later, the waviness intensity A at a normal wavelength of 20 mm is 20 is the total value of waviness intensity at wavelengths of 3 to 10 mm, A 3~10 Since it is larger than the ratio (A 3~10 / A 20 ) will be less than 1.00.

[0046] Whether or not a glass substrate has been polished can be determined by observing the surface of the glass substrate. In the polishing step S50, the surface of the glass substrate is usually ground using abrasive grains, and therefore the main surface has polishing streaks. The presence or absence of polishing streaks can be determined by observing the surface using an AFM (Atomic Force Microscopy). Specifically, when there is one or more polishing streaks of 0.5 μm or more in length within a 1 μm × 1 μm area, it can be said that the surface has polishing streaks. Whether the bottom surface of a glass substrate, especially one made by the float method, has been polished or not can be determined by irradiating the glass substrate with ultraviolet light of 300 nm or less. Before polishing, tin adhering to the bottom surface of the glass substrate emits fluorescence when irradiated with ultraviolet light. However, if the bottom surface of the glass substrate has been polished, no such fluorescence is observed.

[0047] <Waviness strength measurement method> The waviness intensity at each wavelength is calculated by performing a discrete Fourier transform on the uneven waveform of the surface of the glass substrate, which is measured by, for example, a stripe pattern projection method or a non-contact surface shape measurement method using optical interference.

[0048] <Surface shape measurement using stripe pattern projection method> An apparatus for measuring the uneven waveform of the surface of a glass substrate is shown in Fig. 4. The apparatus shown in Fig. 4 has a stripe pattern 1 for projecting a stripe pattern onto the surface of the glass substrate, a glass substrate 10 onto which the stripe pattern 1 is projected, and a line sensor camera 2 for capturing an image of the stripe pattern 1 reflected by the glass substrate 10. The line sensor camera 2 and the stripe pattern 1 are installed so that the optical axis of the line sensor camera 2 and the normal to the plane on which the stripe pattern 1 exists form the same angle θ with respect to the normal direction to the surface of the glass substrate 10. In this case, the angle θ is preferably 45°.

[0049] 5 is a flowchart showing the steps for measuring the first main surface 10a of a glass substrate using the stripe pattern projection method. Surface shape measurement using the stripe pattern projection method includes step S21 of irradiating a stripe pattern, step S22 of capturing an image of the stripe pattern reflected by the glass substrate, step S23 of detecting only the image reflected by the first main surface 10a of the glass substrate from the reflected image, step S24 of calculating the inclination of the first main surface 10a of the glass substrate from the detected difference in brightness of the stripe pattern, and step S25 of obtaining the surface shape of the first main surface 10a of the glass substrate by integrating the inclination. In step S23, when the stripe pattern is irradiated onto the glass substrate, the reflected image contains a stripe pattern reflected by the first main surface 10a of the glass substrate and a stripe pattern reflected by the second main surface 10b facing opposite to the first main surface 10a. Therefore, only the stripe pattern reflected by the first main surface 10a is detected from the captured image. Next, the slope of the unevenness waveform of the first main surface 10a is calculated based on the shift in the light-dark cycle caused by the unevenness waveform of the first main surface 10a from the obtained image, and the slope of the unevenness waveform is integrated to obtain the unevenness profile of the first main surface of the glass substrate. The obtained unevenness profile is filtered and then subjected to a discrete Fourier transform, thereby allowing the waviness intensity at each wavelength to be calculated.

[0050] <Measurement of unevenness waveforms using non-contact surface shape measurement using optical interference> The uneven waveform of the glass substrate surface may also be measured by non-contact surface profile measurement using optical interference. Non-contact surface profile measurement using optical interference irradiates the glass substrate surface with coherent light, causing it to reflect, and observes the difference in height of the glass substrate surface as a phase shift of the reflected light. Examples of non-contact surface profile measurement using optical interference include, but are not limited to, Micromap, Vertscan 2.0, and Vertscan 3.0 (manufactured by Ryoka Systems Co., Ltd.). For example, the waviness intensity at each wavelength can be calculated by measuring the unevenness waveform of the glass substrate surface using Vertscan 2.0 (lens magnification 5x), filtering the obtained unevenness profile, and then performing a discrete Fourier transform.

[0051] <Glass substrate manufacturing method> FIG. 1 is a schematic flow chart illustrating a method for manufacturing a glass substrate according to an embodiment of the present invention. In the figure, the method for manufacturing a glass substrate of the present invention includes a preparation step S10 of preparing a glass substrate, a surface shape measurement step S20 of measuring the uneven waveform of the glass substrate surface, a convexity removal step S30 of removing convexities on the glass substrate surface with an etching solution, a cleaning step S40 of removing the etching solution present on the glass substrate surface, and a polishing step S50 of polishing the glass substrate surface.

[0052] <Preparation process S10> The preparation process S10 includes a melting process S12 for melting glass raw materials, a forming process S14 for shaping the molten glass, an annealing process S16 for annealing the formed glass ribbon, and a cutting process S18 for cutting glass substrates to a predetermined size. In the melting process S12, glass raw materials are melted to produce molten glass. In the forming process S14, the molten glass present in the float bath is continuously supplied onto the surface of molten metal, and the molten glass is formed into a strip-shaped glass ribbon using the liquid surface of the molten metal. The glass ribbon gradually solidifies as it moves from the upstream side to the downstream side of the float bath. In the annealing process S16, the glass ribbon formed into a strip shape in the forming process S14 is annealed. Next, in the cutting process S18, the annealed glass ribbon is cut to a predetermined size using a cutter to obtain glass substrates. In this preparation process S10, minute irregularities may occur on the surface of the glass substrate due to, for example, distortion or corrugation.

[0053] <Surface shape measurement process S20> The surface shape measuring step S20 is a step of measuring the uneven waveform of the surface of the glass substrate prepared in the preparation step S10. In the surface shape measuring step S20, at least the polished surface of the glass substrate is measured. That is, for example, if the bottom surface of the glass substrate (the surface that was in contact with the molten metal in the shaping process S14) is set as the first main surface and the first main surface of the glass substrate is polished, at least the first main surface is measured. The unevenness waveform of the glass substrate surface is measured, for example, by the above-mentioned stripe pattern projection method or non-contact surface shape measurement using optical interference. The unevenness profile obtained by measuring the unevenness waveform is stored in a recording medium such as a computer. Next, the obtained unevenness profile is subjected to filtering.

[0054] Next, a region having a height equal to or greater than a predetermined reference value H2 (hereinafter also referred to as a "removal region 14") is calculated. The removal region 14 is the region to be removed in the convex portion removal step S30. By removing the removal region 14 in the next convex portion removal step S30, the waviness intensity A at a wavelength of 20 mm is reduced. 20 can be reduced and A 20As a result of the decrease in 3~10 increases.

[0055] The reference value H2 is determined based on the average waviness height H1 and the arithmetic mean height Sa of the glass substrate surface. The arithmetic mean height Sa is a parameter obtained by extending the arithmetic mean height Ra of a line to a surface, and represents the average of the absolute values ​​of the differences between the average waviness height H1 of the glass substrate surface and the waviness height at each point on the glass substrate surface. This parameter is generally used when evaluating surface roughness.

[0056] When the average waviness height of the glass substrate surface is taken as H1, the reference value H2 is preferably set within a range that satisfies the following two formulas: (H1-1.5×Sa)≦H2 (1) H2≦(H1+0.5×Sa) (2) H1 and Sa are calculated using the unevenness profile before filtering. By setting the reference value H2 so that it satisfies formula (1) and formula (2), it is possible to remove the convex parts present on the glass substrate surface, and as a result, the waviness intensity A at a wavelength of 20 mm can be reduced. 20 can be reduced. If the reference value H2 does not satisfy formula (1), the number of regions (removed regions 14) on the glass substrate surface whose height is equal to or greater than the reference value H2 increases. As a result, many new convex portions are generated by removing the convex portions using an etching solution, and there is a risk that the waviness strength at a wavelength of 20 mm cannot be efficiently reduced. Furthermore, if the reference value H2 does not satisfy formula (2), there is a risk that the number of regions whose height is equal to or greater than the reference value H2 decreases. As a result, it is not possible to remove the convex portions on the glass substrate surface, and there is a risk that the waviness strength at a wavelength of 20 mm cannot be efficiently reduced.

[0057] <Protrusion Removal Step S30> The convex portion removing step S30 is a step of removing regions having a height equal to or greater than a predetermined reference value H2, which is calculated by the arithmetic processing means in the surface shape measuring step S20. In this embodiment, in the convex portion removing step S30, the convex portions are removed by applying an etching solution to the convex portions.

[0058] 3 is a schematic diagram showing changes in the surface of the glass substrate in the convex portion removing step S30 of this embodiment. For ease of understanding, FIG. 3 shows the concave and convex waveforms on the surface of the glass substrate exaggerated.

[0059] FIG. 3(a) is a conceptual diagram showing the surface of a glass substrate before an etching solution is applied to the convex portions on the surface of the glass substrate. In FIG. 3(a), H1, shown by a solid line, is the average waviness height on the surface of the glass substrate. H2, also shown by a solid line, is the reference value. In FIG. 3(a), the reference value H2 is set at a position that satisfies equations (1) and (2). The shaded area in FIG. 3(a) indicates an area (removal area 14) with a height equal to or greater than the reference value H2.

[0060] 3(b) shows a state where the removal region 14 is removed by applying an etching solution to the removal region 14. By applying the etching solution to the removal region 14, the removal region 14 is removed.

[0061] When removal region 14 is removed with an etching solution, the convex portions that were removal region 14 are not removed along reference value H2, but are removed so that concave portions are formed in the portions that were convex before processing, as shown in Figure 3(b). In this case, as shown in Figure 3(b), the vicinity of endpoint 12 where reference value H2 and removal region 14 intersect becomes a steep shape. This is thought to be because, assuming that removal region 14 is etched to the same depth from the surface, the vicinity of the endpoint is likely to be below reference value H2.

[0062] Comparing Figures 3(a) and 3(b), which show the state before and after removal of the removal area 14, the surface of the glass substrate in Figure 3(a) before the convex portion removal step has a long-pitch uneven waveform, whereas the surface of the glass substrate in Figure 3(b) after the convex portion removal step S30 has a short-pitch uneven waveform. As a result, after the convex portion removal process S30, when the uneven waveform on the glass substrate surface is subjected to a discrete Fourier transform, the waviness intensity with a relatively long wavelength of about 20 mm is reduced, and the waviness intensity with a relatively short wavelength of 10 mm or less is increased, compared to before the convex portion removal process S30. Here, if an attempt is made to remove the convex portions that are the removal regions 14 using an etching gas, it is difficult to remove the convex portions. Moreover, even if the convex portions can be removed, it is difficult to form concave portions in the areas where the convex portions were, and therefore it is difficult to increase the waviness strength with a wavelength of 10 mm or less.

[0063] The etching solution can be, for example, a mixture of fluoride and an inorganic acid. The fluoride can be, for example, ammonium fluoride, ammonium hydrogen fluoride, sodium fluoride, sodium hydrogen fluoride, potassium fluoride, potassium hydrogen fluoride, and similar salts, or a salt selected from a combination thereof. The inorganic acid can be, for example, hydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and similar acids, or a combination thereof. The etching solution is not particularly limited, but can be, for example, a solution containing 1% to 20% by mass of fluorine and 5% to 60% by mass of inorganic acid.

[0064] The depth of the recesses newly formed in the convex portion removal step S30 can be adjusted by adjusting the concentration of the etching solution and the etching time. If an area with a height equal to or greater than the reference value H2 before the convex portion removal step S30 still remains due to an insufficient amount of etching, the depth can be adjusted by increasing the concentration of the etching solution or lengthening the etching time. If an excessive amount of etching of the convex portion results in an excessively deep recess in the convex portion that was the removal area 14 before the convex portion removal step S30, the depth can be adjusted by decreasing the concentration of the etching solution or shortening the etching time.

[0065] Here, an excessively deep recess refers to a recess in which there is an area where the waviness height is equal to or less than (H1-4×Sa), where H1 is the average waviness height on the glass substrate surface before the convex portion removal step S30 and Sa is the arithmetic mean height. If the waviness height is lower than the average waviness height H1 on the glass substrate surface before the convex portion removal step S30 by 4×Sa (nm) or more, there is a risk that the amount of polishing required to remove the recesses generated in the convex portion removal step S30 using an etching solution will be large.

[0066] The method for applying the etching solution is not particularly limited as long as it can be applied only to the removal region 14. The etching solution may be applied using a brush with a fiber bundle as the liquid outlet, a pen with a synthetic resin such as felt as the liquid outlet, or a spray nozzle. Application using a spray nozzle is preferred because it allows adjustment of the amount of etching solution to be applied and allows the etching solution to be applied uniformly to the removal region 14. Application using a brush or pen is also preferred because it is easy to handle. When a spray nozzle is used, the spray nozzle is placed above the removal area 14, and the etching solution is sprayed from the spray nozzle toward the removal area, and at the same time, air is sprayed from an air nozzle placed above an end point 12 where the reference value H2 and the removal area 14 intersect toward the end point 12. This ensures that the etching solution sprayed from the spray nozzle is applied only to the removal area 14. Furthermore, the applied etching solution can be confined to the removal area 14 without flowing into the recesses. When the etching solution is applied using a pen- or brush-shaped liquid outlet, it is possible to apply the etching solution only to the removal area 14 even without an air nozzle. Depending on the amount of etching solution applied, the etching solution will remain in the removal area 14 due to the surface tension acting on the surface of the liquid. However, if the amount applied is too large and the etching solution flows from the removal area 14 into the recess, the etching solution may be kept in the removal area 14 by spraying air toward the end point 12 from an air nozzle located above the end point 12.

[0067] <Cleaning process S40> The cleaning step S40 is a step of removing the etching solution applied to the surface of the glass substrate in the convex portion removing step S30. In the cleaning step S40, the surface of the glass substrate is washed with, for example, pure water to remove the etching solution applied to the surface of the glass substrate.

[0068] <Polishing process S50> The polishing step S50 is a step of removing irregularities present on the surface of the glass substrate. In the polishing step S50, the main surface of the glass substrate is polished using a polishing slurry. The polishing slurry contains, for example, cerium oxide, zirconium oxide, manganese oxide, lanthanum, or red iron oxide as abrasive grains. It is particularly preferable to use cerium oxide.

[0069] Of the first or second main surface of the glass substrate, at least the main surface treated in the convex portion removing step S30 is polished to produce a highly smooth glass substrate. For example, if the bottom surface of the glass substrate is the first main surface and the convex portion removing step S30 is performed on the surface of the first main surface, at least the bottom surface is polished. The polishing conditions can be adjusted appropriately and are not particularly limited. For example, when polishing is performed using a polishing pad, the polishing pressure is preferably 0.05 to 0.5 MPa, and the polishing pad rotation speed (revolutions) is preferably 30 to 1,000 rpm. The polishing pad may also be rotated while revolving. In this case, the rotation speed of the polishing pad is preferably 10 to 300 rpm. The number of polishing cycles in the examples described below is not particularly limited. However, considering the load in the polishing step S50, 1 to 10 cycles is preferred, 3 to 8 cycles is more preferred, and 3 to 6 cycles is most preferred. The surface of the glass substrate may also be polished using a belt polisher using an endless belt-shaped polishing belt instead of a polishing pad.

[0070] <Electronic Devices> The glass substrate according to this embodiment is preferably used as a substrate for an electronic device, more preferably as a substrate for a display, even more preferably as a substrate for a liquid crystal display, and most preferably as a substrate for an a-Si (amorphous silicon) TFT. It is also more preferable to use it as a carrier substrate for manufacturing flexible displays or a carrier substrate for semiconductor packaging. Of these, it is even more preferable to use it as a carrier substrate for manufacturing flexible displays. Furthermore, the electronic device according to this embodiment includes the glass substrate, and such a glass substrate can be suitably applied to a large electronic device, for example, a rectangular device having at least one side of 2400 mm or more. [Example]

[0071] The present invention will be specifically explained below with reference to test examples, but the present invention is not limited to these. Examples 1 and 2 are working examples, and Examples 3 to 6 are comparative examples.

[0072] <Example 1> Glass substrates substantially free of alkali metals, measuring 2500 × 2200 mm and 0.5 mm thick, were produced in melting furnace A. In Example 1, the bottom surface of the glass substrate produced by the float method, which had been in contact with the molten tin during the forming process, was referred to as the first main surface, and the main surface facing opposite to the first main surface was referred to as the second main surface. The composition of the produced glass substrate, expressed in mass %, was as follows: SiO2:60% Al2O3:17% B2O3:8% MgO:3% CaO: 4% SrO:8% BaO: 0% Others: Less than 0.1%.

[0073] Next, the surface of the first main surface of the glass substrate prepared in the surface shape measurement process was measured using a stripe pattern projection method to measure the surface shape of the first main surface of the glass substrate. Next, the unevenness profile obtained by the measurement was filtered and then subjected to a discrete Fourier transform to calculate the waviness intensity for each wavelength. Next, the average waviness height H1 and the arithmetic mean height Sa were calculated using the unevenness profile of the first main surface of the glass substrate before filtering, and a reference value H2 was set so that "H2 = H1 - Sa". Next, the convex portions were removed from the first main surface of the glass substrate in a convex portion removing process. In the convex portion removing process, a region (removal region) having a height equal to or greater than the reference value H2 was calculated, and an etching solution was applied to the removal region using a spray nozzle to remove the removal region. Thereafter, the etching solution was removed by washing with pure water. Next, the first main surface of the glass substrate was polished using a polishing pad while supplying cerium oxide as a polishing slurry. Polishing was performed six times, with one polishing step counted as one polishing step, where the polishing pad revolution speed was 100 rpm, the polishing pad rotation speed was 33 rpm, and the polishing pressure was 0.08 MPa. Next, the surface shape of the first main surface of the polished glass substrate was measured again using the stripe pattern projection method, and the obtained unevenness profile was filtered and then subjected to a discrete Fourier transform to calculate the waviness intensity of the polished glass substrate at each wavelength. The gain at each pitch in the filter processing is shown in Figure 10, and the gain at a specific pitch in Figure 10 is shown in Table 1. Then, color unevenness was evaluated using the method described below.

[0074] [Table 1]

[0075] <Example 2> A glass substrate was obtained in the same manner as in Example 1, except that a melting furnace B different from that in Example 1 was used, the thickness of the glass substrate was set to 0.4 mm, and the number of polishing cycles was set to 8.

[0076] <Example 3> A glass substrate was obtained in the same manner as in Example 2, except that the polishing was performed four times.

[0077] <Example 4> A glass substrate was obtained in the same manner as in Example 1, except that the convex portion removing step of removing the convex portions on the first main surface of the glass substrate with an etching solution was not carried out.

[0078] <Example 5> A glass substrate was obtained in the same manner as in Example 3, except that the convex portion removing step of removing the convex portions on the first main surface of the glass substrate with an etching solution was not carried out.

[0079] <Example 6> A glass substrate was obtained in the same manner as in Example 1, except that the convex portion removing step of removing the convex portions on the first main surface of the glass substrate with an etching solution was not performed and the polishing was carried out nine times.

[0080] <Evaluation method> (Measurement of waviness intensity at each wavelength) The surface shape of the entire first principal surface was measured using the stripe pattern projection method. The obtained unevenness profile was then filtered and subjected to a discrete Fourier transform to calculate the waviness intensity at each wavelength. At this time, the line sensor camera was set so that the optical axis of the line sensor camera and the normal to the plane on which the stripe pattern was present were both at an angle of 45° from the normal direction to the surface of the glass substrate.

[0081] <Evaluation of color unevenness> VA mode liquid crystal panels were produced as prototypes using the glass substrates of Examples 1 to 6, and the color unevenness of the glass substrates was evaluated by visual inspection according to the following criteria. A: There was absolutely no unevenness in color and no problems whatsoever. B: There is almost no color unevenness, but color unevenness can sometimes be a problem in ultra-high definition images such as 4K and 8K. C: Color unevenness was observed, which was problematic.

[0082] The total waviness intensity A of the glass substrate before polishing at wavelengths of 3 to 10 mm 3~10 and swell intensity A at wavelength 20 mm 20 , and the total value A of the waviness intensity of the polished glass substrate at wavelengths of 3 to 10 mm 3~10and swell intensity A at wavelength 20 mm 20 is shown in Table 2. A graph of the waviness intensity at each wavelength for the glass substrates of Examples 1 and 4 before polishing is shown in Figure 6. A graph of the waviness intensity at each wavelength for the glass substrates of Examples 1 and 4 after polishing is shown in Figure 7. A graph of the waviness intensity at each wavelength for the glass substrates of Examples 3 and 5 before polishing is shown in Figure 8. In the graphs of Figures 6 to 8, the waviness intensity at wavelengths of less than 3.0 mm is largely affected by noise, and since components with short wavelengths less than 3.0 mm are very easily removed by polishing, it is not considered necessary to take this into consideration, so the waviness intensity at wavelengths of less than 3.0 mm has been cut.

[0083] [Table 2]

[0084] In Examples 1 to 6 after polishing, the total waviness intensity A at wavelengths of 3 to 10 mm 3~10 is 1.60 x 10 -3 μm or less and swell intensity A at a wavelength of 20 mm 20 is 1.60 x 10 -3 It can be seen that when the thickness is less than μm, the evaluation of color unevenness is A.

[0085] 6 shows the waviness intensity at each wavelength for the glass substrate before polishing in Examples 1 and 4. Here, Example 1 differs in that the convex portions on the first main surface of the glass substrate are removed with an etching solution in the convex portion removal step, whereas Example 4 does not include a convex portion removal step in its manufacturing process. It can be seen that the glass substrate of Example 1 has a significantly reduced waviness intensity at a wavelength of 20 mm and an increased total value of waviness intensity at wavelengths of 3 to 10 mm compared to the glass substrate of Example 4. This is thought to be because, in the convex portion removal process, the areas (removal areas) with heights equal to or greater than the reference value H2 were removed with an etching solution, changing the long-pitch corrugated surface of the glass substrate to a corrugated surface with multiple short pitches, as shown in Figure 3. Fig. 8 shows the waviness intensity at each wavelength of the glass substrate before polishing in Examples 3 and 5. Example 3 differs in that the convex portions on the first main surface of the glass substrate are removed with an etching solution in the convex portion removal step, whereas Example 5 does not have a convex portion removal step in its manufacturing process. Fig. 8 also shows that the glass substrate having the convex portion removal step in its manufacturing process has a significantly reduced waviness intensity at a wavelength of 20 mm and an increased total value of waviness intensity at wavelengths of 3 to 10 mm.

[0086] FIG. 7 shows the waviness intensity at each wavelength for the polished glass substrates of Examples 1 and 4. From this, it can be seen that even after polishing, the glass substrate of Example 1, which was produced by a manufacturing method including a convex portion removal step, had a waviness intensity A at a wavelength of 20 mm higher than the glass substrate of Example 4. 20 It can be seen that is small.

[0087] The glass substrate of Example 6 was polished nine times, the most. However, after polishing, it had a higher waviness intensity at a wavelength of 20 mm than the glass substrate of Example 1, which was polished six times. This is because, in Example 6, the irregularities on the first main surface were removed only by polishing, but it is difficult to reduce the waviness intensity at a wavelength of 20 mm by polishing. Therefore, the glass substrate of Example 6 had a waviness intensity at a wavelength of 20 mm of more than 1.60, and the color unevenness evaluation was B.

[0088] Comparing Example 2 and Example 3, they differ in that the number of polishing times is 8 and 4, respectively. Regarding the glass substrates before polishing in Example 2 and Example 3, (A 3~10 / A 20 ) are the same value in both cases, but the (A 3~10 / A 20 ) is smaller in Example 2, which has been polished many times. This is because the waviness intensity A 20 is difficult to reduce by polishing, but the total value A of the waviness intensity at wavelengths of 3 to 10 mm 3~10 The more times the polishing is performed, the easier it is to reduce (A 3~10 / A 20 ) is thought to be smaller. That is, after polishing (A 3~10 / A 20 The larger the polishing time of the glass substrate, the shorter the polishing time. 3~10 / A 20 The smaller the glass substrate, the higher the productivity.

[0089] A for the glass substrate of Example 3, which is rated C for color unevenness 20 and A in the glass substrate of Example 6, which was rated B in color unevenness. 20 In comparison, the glass substrate in Example 3 is smaller. 20 From this point of view, it would be expected that Example 3 would receive a better evaluation of color unevenness than Example 6, but in reality, Example 3 is worse than Example 6. The reason that Example 3 receives a worse evaluation of color unevenness than Example 6 suggests that color unevenness is not only influenced by the 20 mm wavelength undulation strength, and the reason that Example 3 received a C evaluation of color unevenness is because 3~10 This is probably because the value of is large.

[0090] Next, Example 1, which was polished 6 times, is compared with Example 6, which was polished 9 times. Looking at the evaluation of color unevenness, the glass substrate of Example 1 was rated A, while the glass substrate of Example 6 was rated B, even though it was polished more times than the glass substrate of Example 1. In other words, when the glass substrates of Examples 1 and 6 before polishing are compared, this means that the glass substrate of Example 1 can be polished fewer times to obtain a glass substrate with reduced color unevenness than the glass substrate of Example 6. This is because the glass substrate before polishing in Example 1 has a A 20 to 2.00 x 10 -3 This is the effect of the glass substrate before polishing in Example 1 being A 3~10 Also 7.00 x 10 -3 Because it is less than μm, components with wavelengths of 10 mm or less will not cause color unevenness after polishing. [Explanation of symbols]

[0091] 10...glass substrate, 12...edge point, 14...removal area

Claims

1. A glass substrate having a first main surface and a second main surface, The uneven waveform of the surface of the first main surface is measured, and the resulting uneven profile is subjected to a discrete Fourier transform to calculate a total value A of waviness intensity at wavelengths of 3 to 10 mm. ３～１０ is 0.50 x 10 －３ μm or more 1.60×10 －３ μm or less, Swell strength A at wavelength 20 mm ２０ is 0.50 x 10 －３ μm or more 1.60×10 －３ A glass substrate characterized by a thickness of 1 μm or less.

2. The waviness strength A ２０ The swell strength A ３～１０ The ratio (A ３～１０ / A ２０ 2. The glass substrate according to claim 1, wherein the value of (a) is 1.00 or more and 2.00 or less.

3. The glass substrate according to claim 1 or 2, wherein the glass substrate is a float glass.

4. 4. The glass substrate according to claim 1, wherein the thickness of the glass substrate is 1 mm or less.

5. 5. The glass substrate according to claim 1, wherein the glass substrate has a rectangular shape with at least one side of 2400 mm or more.

6. 6. The glass substrate according to claim 1, wherein the first main surface is a polished surface.

7. 7. The glass substrate according to claim 1, which is used for a display.

8. An electronic device comprising the glass substrate according to any one of claims 1 to 7.

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