KR20220159902A - Glass substrate, electronic device, and method for manufacturing glass substrate - Google Patents

Abstract

The purpose of the present invention is to provide a glass substrate in which fine unevenness on a glass substrate surface that causes color unevenness is reduced. A glass substrate according to the present invention has a first main plane and a second main plane, in which a total value A_(3-10) 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 x 10^(-3) ㎛ or more and 1.60 x 10^(-3) ㎛ or less, undulation intensity A_(20) in a wavelength of 20 mm is 0.50 X 10^(-3) ㎛ or more and 1.60 x 10^(-3) ㎛ 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.

Description

Glass substrate, electronic device, and manufacturing method of glass substrate {GLASS SUBSTRATE, ELECTRONIC DEVICE, AND METHOD FOR MANUFACTURING GLASS SUBSTRATE}

The present invention relates to glass substrates, electronic devices, and methods of manufacturing glass substrates.

For example, minute irregularities exist on the surface of a glass substrate formed by a float method. Such minute unevenness may cause color nonuniformity, for example, when used as a glass substrate for a display. Therefore, when polishing the surface of a glass substrate, by increasing the amount of polishing, these minute irregularities are removed to suppress color unevenness, or to suppress color unevenness efficiently by selecting a glass substrate with small waviness and improving polishability. (Patent Document 1).

Japanese Unexamined Patent Publication No. 3-65529

However, in recent years, since the quality required for glass substrates for displays has become high, the amount of polishing is increased, or even when a glass substrate having a small specific waviness is selected and polished as in Patent Document 1, when color unevenness becomes a problem there was Therefore, it was necessary to further reduce minute irregularities on the surface of the glass substrate that cause color nonuniformity. An object of the present invention is to reduce minute irregularities on the surface of the glass substrate that cause color nonuniformity, and to provide a glass substrate in which color nonuniformity is suppressed.

(1) The glass substrate according to the present invention has a first main surface and a second main surface, and the waviness intensity at a wavelength of 3 to 10 mm calculated by discrete Fourier transform of the uneven waveform on the surface of the first main surface The sum value A _{3 to 10} is 0.50 × 10 ^-3 µm or more and 1.60 × 10 ^-3 µm or less, and the waviness intensity A ₂₀ at a wavelength of 20 mm is 0.50 × 10 ^-3 µm or more and 1.60 × 10 ^-3 µm or less to be characterized

(2) The glass substrate as described in (1) whose ratio ( _A3-10 / _A20 ) of the said waviness intensity|strength _A3-10 with respect to _the said waviness intensity|strength A20 is 1.00 or more and 2.00 or less.

(3) The glass substrate as described in (1) or (2) whose said glass substrate is float glass.

(4) The glass substrate as described in any one of (1)-(3) whose thickness of the said 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 surface after polishing.

(7) The glass substrate according to any one of (1) to (6), wherein the glass substrate is for a display.

(8) An electronic device provided with the glass substrate described in any one of (1) to (7).

(9) In the method for manufacturing a glass substrate according to the present invention, the surface shape measuring step of measuring the uneven waveform on the surface of the first principal surface and detecting convex portions having a height equal to or greater than a predetermined reference value, and the surface shape measuring step It is characterized by having a convex portion removal step of applying an etchant to the detected convex portion having a height equal to or greater than a predetermined reference value, and a polishing step of polishing the main surface treated in the convex portion removal step.

(10) The manufacturing method of the glass substrate as described in (9) which applies the said etchant with a spray nozzle, a pen, or a brush.

(11) The manufacturing method of the glass substrate as described in (9) or (10) whose said glass substrate is float glass.

(12) The manufacturing method of the glass substrate in any one of (9)-(11) whose thickness of the said glass substrate is 1 mm or less.

(13) The manufacturing method of the glass substrate in any one of (9)-(12) whose at least 1 side|side is a rectangular shape of 2400 mm or more of the said glass substrate.

(14) The method for manufacturing a glass substrate according to any one of (9) to (13), wherein the glass substrate is for a display.

The glass substrate in which color nonuniformity was suppressed can be provided by reducing the micro unevenness of the glass substrate surface which causes color nonuniformity.

1 is a flowchart showing a manufacturing method of a glass substrate in this embodiment.
2 is a flowchart showing each process in the preparation process.
3 is a conceptual diagram showing changes in the surface of a glass substrate in a convex portion removal process.
4 is a conceptual diagram illustrating a device for measuring the surface shape of a glass substrate using a stripe pattern projection method.
5 is a flowchart illustrating a method of measuring the surface shape of a glass substrate by a stripe pattern projection method.
6 is a graph showing waviness intensity at each wavelength of the glass substrates before polishing in Examples 1 and 4. FIG.
7 is a graph showing the waviness intensity in each wavelength of the glass substrate after polishing in Examples 1 and 4.
8 is a graph showing the waviness intensity in each wavelength of the glass substrates before polishing in Examples 3 and 5. FIG.
Fig. 9 is a graph showing waviness intensity at each wavelength of glass substrates after polishing in Examples 3 and 5.
Fig. 10 is a graph showing the gain at each pitch in the filter process.

In this specification, the pitch refers to the distance between adjacent convex portions when the uneven waveform on the surface of a glass substrate is measured by, for example, a stripe pattern projection method described later or non-contact surface shape measurement using an optical interference method.

In addition, a wavelength refers to the length of one cycle of a wave. In this specification, a wavelength means a wavelength when discrete Fourier transform is performed on the concavo-convex waveform on the surface of the glass substrate unless otherwise specified. The spatial frequency resolution at the time of discrete Fourier transform is 1 mm.

In this specification, the waviness height refers to the height of each point when a concavo-convex waveform on the surface of a glass substrate is measured, for example, by non-contact surface shape measurement using a stripe pattern projection method or an optical interference method described later.

In addition, in this specification, waviness intensity means the amplitude in each wavelength calculated by measuring the uneven|corrugated waveform of the surface of a glass substrate, and discrete Fourier transforming the obtained uneven|corrugated profile. The uneven waveform on the surface of the glass substrate can be measured, for example, by non-contact surface shape measurement using a stripe pattern projection method or an optical interference method, which will be described later.

In addition, in this specification, the concavo-convex profile of the surface of the glass substrate is filtered before discrete Fourier transform. In this specification, filter processing refers to a process of attenuating the amplitude of irregularities having a specific pitch using a computer with respect to the obtained irregularities profile. The gain at each pitch in the filter process is shown in FIG. 10, and the gain at a specific pitch in FIG. 10 is shown in Table 1.

In the filter process, amplitudes with short pitches are attenuated in order to eliminate the influence of measurement noise. In addition, the longer the pitch of the irregularities, the smaller the effect on color non-uniformity, so the longer the pitch of the irregularities, the more the amplitude is attenuated. In addition, a gain refers to the numerical 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 surface of the glass substrate is calculated by discrete Fourier transform after filtering the concavo-convex profile obtained by measuring the concavo-convex waveform on the surface of the glass substrate with the gain shown in FIG. It means the amplitude in a wavelength of 20 mm.

Hereinafter, preferred embodiments of the glass substrate and the method for manufacturing the glass substrate according to the present invention will be described. Embodiment described below is an example, and this invention is limited to these embodiment and is not interpreted.

For example, minute irregularities exist on the surface of a glass substrate formed by a float method. Such minute unevenness may cause color nonuniformity, for example, when used as a glass substrate for a display. Moreover, since the quality demanded of the glass substrate for a display in recent years has become high, it was necessary to further reduce the fine unevenness of the glass substrate surface which causes color nonuniformity.

As a result of investigating the irregularities that cause color unevenness, the inventors found that when discrete Fourier transform was performed on the uneven waveform on the surface of a glass substrate produced by the float method, the waviness intensity at a wavelength of 20 mm was large, and at this wavelength of 20 mm It was found that the component of was the cause of color non-uniformity. Therefore, it is important to reduce the waviness intensity on the surface of the glass substrate at a wavelength of 20 mm.

However, since fine irregularities such as distortion and corrugation exist in a glass substrate produced, for example, by a float method, it is difficult to eliminate the irregularities present in the glass substrate. When discrete Fourier transform is performed on the uneven waveform on the surface of the glass substrate at this time, a component with a wavelength of 20 mm exists.

In addition, the inventors found that since this component with a wavelength of 20 mm is difficult to remove by polishing, it is easy to remain even when the amount of polishing is increased, that is, the waviness intensity at a wavelength of 20 mm is not reduced by polishing I found it difficult. Therefore, it is difficult to sufficiently reduce the waviness intensity in a wavelength of 20 mm by polishing the glass substrate surface produced by the float method.

The inventors found that by removing the convex portion present on the surface of the glass substrate before the polishing step (S50) described later, the waviness intensity in a wavelength of 20 mm was reduced, and a glass substrate with color unevenness suppressed was obtained. . This is considered to be because, as shown in FIG. 3 , by removing the convex portions present on the surface of the glass substrate, the concave-convex waveform with a long pitch existing on the surface of the glass substrate becomes a plurality of concave-convex and convex waveforms with a short pitch. Thus, before polishing, by removing the convex part which exists on the surface of a glass substrate, the glass substrate in which the waviness intensity|strength in wavelength 20mm was reduced can be obtained. In the glass substrate before polishing, since the waviness intensity at a wavelength of 20 mm, which is difficult to remove by polishing, is reduced, a glass substrate having a reduced waviness intensity at a wavelength of 20 mm is obtained even after polishing.

However, the inventors have found that even when the waviness intensity at a wavelength of 20 mm is reduced, there are cases where color unevenness becomes a problem. As a result of diligent research by the inventors, when discrete Fourier transform was performed on the uneven waveform on the surface of the glass substrate, the total value of waviness intensity in a wavelength of 3 mm or more and 10 mm or less (hereinafter also referred to as "wavelength 3 to 10 mm"). It was found that color non-uniformity occurs when the is high. Since components with a wavelength of less than 3 mm are very easily removed by polishing, it is considered that components with a wavelength of less than 3 mm hardly affect color unevenness.

Here, the sum of waviness intensities at a wavelength of 3 to 10 mm is the waviness at a wavelength N mm (N = 3, 4, ..., 9, 10, ie, N is a natural number of 3 or more and 10 or less). represents the sum of the strengths.

As described above, a component having a long wavelength is difficult to remove by polishing, but a component having a short wavelength is easy to remove by polishing. That is, when the surface of a glass substrate is polished, the waviness intensity in a wavelength of 3 to 10 mm is more likely to be reduced than the waviness intensity in a wavelength of 20 mm. Therefore, when polishing a glass substrate produced by the float method, since the waviness intensity in a wavelength of 3 to 10 mm decreases earlier than the waviness intensity in a wavelength of 20 mm, Although there was no color unevenness, it was not possible to say that color unevenness caused by a component with a wavelength of 3 to 10 mm occurred.

However, for example, in the case of polishing a glass substrate having reduced waviness intensity at a wavelength of 20 mm by removing convex portions present on the surface of the glass substrate before the polishing step (S50), the glass substrate after polishing may have been observed. At this time, even when the waviness intensity at a wavelength of 20 mm is sufficiently reduced, there may be cases where the total value of the waviness intensity at a wavelength of 3 to 10 mm is high. The inventors have found that in such a case, color non-uniformity occurs.

Therefore, in order to obtain a glass substrate in which color non-uniformity is suppressed, when discrete Fourier transform is performed on the uneven waveform on the surface of the glass substrate, not only the waviness intensity in a wavelength of 20 mm is reduced, but also the waviness in a wavelength of 3 to 10 mm is reduced. It is important to also reduce the total value of the island intensity.

<Glass Substrate>

In this embodiment, the manufacturing method of a glass substrate is a float method from a viewpoint of manufacturing efficiency. In addition, since there is a possibility that color non-uniformity due to minute irregularities caused by distortion or corrugation may occur in a glass substrate produced by the float method, the effect according to the present invention is remarkable.

The composition of the glass substrate is not particularly limited. For example, soda lime glass, aluminosilicate glass, borosilicate glass, alkali free glass, etc. are mentioned. It is preferable that the glass substrate of this embodiment uses the alkali-free glass which does not contain an alkali metal component substantially in the board|substrate use for electronic devices like a liquid crystal display.

Here, substantially not containing an alkali metal component means that the total content of an alkali metal oxide is 0.1% by mass or less. In addition, the content of the alkali metal oxide is more preferably 10 mass ppm or more from the viewpoint of lowering the viscosity during glass melting and facilitating glass production.

In the case of use as a substrate for electronic devices, the glass composition is SiO ₂ : 35 to 73%, Al ₂ O ₃ : 5 to 35%, B ₂ O ₃ : 0 to 30%, MgO: 0 to 20%, CaO: 0 to 30%, SrO: 0 to 30%, BaO: 0 to 40%, and the total of MgO, CaO, SrO, and BaO: 1 to 55%, further comprising an alkali metal oxide It is preferable to not contain substantially.

In the case of substrate use for electronic devices, the composition of the glass is SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O in terms of oxide-based mass% when the strain point is high and solubility is taken into consideration. ₃ : 5 to 12%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 3 to 12.5%, BaO: 0 to 2%, and the sum of MgO, CaO, SrO, and BaO: 9 to 18 It is more preferable to include % and not substantially contain an alkali metal oxide.

When the strain point is high and solubility is taken into consideration, the glass composition is more preferably SiO ₂ : 56 to 62%, Al ₂ O ₃ : 15 to 20%, B ₂ O ₃ : 6 in terms of oxide-based mass%. to 10% MgO: 2 to 5%, CaO: 3 to 7%, SrO: 4 to 10%, BaO: 0 to 1%, and the sum of MgO, CaO, SrO, and BaO: 12 to 17% and substantially free of alkali metal-containing substances. It is more preferable to substantially not contain BaO.

In the case of substrate use for electronic devices, the glass composition, when considering the high strain point, is SiO ₂ : 54 to 73%, Al ₂ O ₃ : 10.5 to 22.5%, B ₂ O ₃ in terms of oxide-based mass%. : 0 to 7%, MgO: 0 to 10%, CaO: 0 to 10%, SrO: 0 to 16%, BaO: 0 to 10%, and the sum of MgO, CaO, SrO, and BaO: 8 to 26% It is more preferable that it contains and does not contain alkali metal oxide substantially.

In the substrate application for electronic devices, the glass composition, in terms of oxide-based mass%, is SiO ₂ : 54 to 73%, Al ₂ O ₃ : 10.5 to 22.5%, B ₂ when considering the further high strain point. O ₃ : 0 to 5.5%, MgO: 0 to 10%, CaO: 0 to 10%, SrO: 0 to 10%, BaO: 0 to 10%, and the sum of MgO, CaO, SrO, and BaO: 8 to It is more preferable that it contains 20% and does not contain alkali metal oxide substantially.

In substrate applications for electronic devices, the glass composition, when considering electrical properties such as low dielectric constant and low dielectric loss tangent, is SiO ₂ : 54 to 73%, Al ₂ O ₃ : 5 to 5%, expressed as mass% based on oxide. 22.5%, B ₂ O ₃ : 15-30%, MgO: 0-10%, CaO: 0-9%, SrO: 0-16%, BaO: 0-20%, and MgO, CaO, SrO and BaO It is more preferable to include 1 to 26% of the total of: and to substantially not contain an alkali metal oxide.

In substrate applications for electronic devices, the glass composition improves the controllability of the expansion rate and, in particular, when obtaining a substrate with a high expansion rate, SiO ₂ : 40 to 73%, Al ₂ O in terms of mass% based on oxide ₃ : 5 to 23%, B ₂ O ₃ : 0 to 15%, MgO: 0 to 20%, CaO: 0 to 20%, SrO: 0 to 20%, BaO: 0 to 40%, and MgO, CaO , the total of SrO and BaO: 10 to 55%, and it is more preferable to contain substantially no alkali metal oxide.

It is preferable that the thickness of a glass substrate is 1 mm or less. Weight reduction can be achieved by thinning the glass substrate. The glass substrate thickness of the present invention is more preferably 0.65 mm or less, more preferably 0.55 mm or less, particularly preferably 0.45 mm or less, and most preferably 0.4 mm or less. It is also possible to make the thickness 0.1 mm or less or 0.05 mm or less. However, from the viewpoint of preventing dead weight deflection, the thickness is preferably 0.1 mm or more, and more preferably 0.2 mm or more.

The size of the glass substrate is G3 (550 × 650 mm), G4 (680 × 880 mm), G5 (1000 × 1200 mm), G6 (1500 × 1800 mm), G7 (1900 × 2200 mm), G8 (2200 × 2400 mm), G9 (2400 x 2800 mm), G10 (2800 x 3000 mm), or G11 (3000 x 3300 mm) may be used.

Moreover, the size of a glass substrate is suitable for the glass substrate of 2400 mm or more of at least 1 side, as a specific example, the glass substrate of 2400 mm or more of a long side and 2000 mm or more of a short side, for example. Since the area of the main surface of the glass substrate increases as the size of the glass substrate increases, the possibility of occurrence of color unevenness within the surface of the glass substrate also increases. In addition, since the degree of difficulty of polishing increases as the size of the glass substrate increases, the possibility of color nonuniformity occurring within the surface of the glass substrate also increases. Therefore, a more remarkable effect is acquired in the case of a glass substrate whose at least one side is 2400 mm or more.

<Wavness strength A ₂₀ at a wavelength of 20 mm>

The glass substrate according to the present invention has a first main surface and a second main surface, and the waviness intensity A 20 at a wavelength of 20 mm, calculated by discrete Fourier transform of the concavo-convex waveform on the _surface of the first main surface, is 1.60 × 10 ^-3 μm or less.

When the waviness intensity A ₂₀ at a wavelength of 20 mm is 1.60 × 10 ^-3 µm or less, color unevenness due to components with a wavelength of 20 mm can be suppressed. The waviness intensity A ₂₀ at a wavelength of 20 mm is preferably 1.40 × 10 ^-3 µm or less, more preferably 1.20 × 10 ^-3 µm or less, and still more preferably 1.00 × 10 ^-3 µm or less. The lower limit of the waviness strength A ₂₀ is not particularly limited, but is, for example, 0.50×10 ⁻³ μm or more.

In addition, in the case of a glass substrate in which the first main surface is not polished, the waviness intensity A ₂₀ at a wavelength of 20 mm calculated by discrete Fourier transform of the uneven waveform on the surface of the first main surface of the glass substrate is 2.00 × 10 ^- It is preferable that it is ³ micrometers or less. Although it is difficult to reduce the waviness intensity A ₂₀ at a wavelength of 20 mm in the polishing step (S50), the waviness intensity A 20 at a wavelength of 20 mm is 2.00 × ₁₀ in a glass substrate in which the first main surface is not polished. By setting it as ^-3 micrometer or less, color nonuniformity can be suppressed also in the glass substrate after polishing. The glass substrate after polishing is a glass substrate after a polishing step (S50) described later.

In the glass substrate in which the first principal surface is not polished, the waviness intensity A ₂₀ of the first principal surface at a wavelength of 20 mm is more preferably 1.70 × 10 ^-3 µm or less, and 1.40 × 10 ^-3 µm or less. More preferably, it is particularly preferable that it is 1.20 × 10 ^-3 μm or less. In addition, in the glass substrate in which the first principal surface is not polished, the lower limit of the waviness strength A ₂₀ of the first principal surface is not particularly limited, but is, for example, 0.50×10 ^-3 μm or more.

In the glass substrate before polishing, the waviness intensity A ₂₀ at a wavelength of 20 mm can be adjusted by the height of the reference value H2 in the surface shape measuring step (S20) described later. As the reference value H2 is increased, in the convex part removal step (S30) described later, the convex part to be removed decreases, and it becomes difficult to reduce the waviness intensity at a wavelength of 20 mm. Further, even if the reference value H2 is too low, it becomes difficult to reduce the waviness intensity at a wavelength of 20 mm. The glass substrate before polishing is a glass substrate after the cleaning step (S40) described later and before the polishing step (S50).

In the glass substrate after polishing, the waviness intensity A ₂₀ at a wavelength of 20 mm is influenced by the waviness intensity A ₂₀ at a wavelength of 20 mm in the glass substrate before polishing. The value of waviness intensity A ₂₀ in a wavelength of 20 mm also increases in the glass substrate after polishing, so that the value of the waviness intensity A ₂₀ in the glass substrate wavelength 20 mm before polishing is large.

Further, the waviness strength A ₂₀ of the glass substrate after polishing at a wavelength of 20 mm is also affected by polishing conditions. For example, as the polishing time is lengthened, the waviness intensity A ₂₀ at a wavelength of 20 mm is reduced. However, since it is difficult to reduce the waviness intensity A ₂₀ at a wavelength of 20 mm by polishing, in a glass substrate produced by a float method, the value of the waviness intensity A ₂₀ at a wavelength of 20 mm is reduced by 1.60 × only by polishing. It is difficult to set it as 10 ^-3 micrometer or less. When a glass substrate manufactured by the float method is polished, for example, even when the polishing amount is increased by increasing the polishing time, the waviness strength A ₂₀ at a wavelength of 20 mm is usually greater than 1.60 × 10 ^-3 μm. do.

<Waveness strength A 3 _{to 10} at a wavelength of 3 to 10 mm>

The glass substrate according to the present invention has a first main surface and a second main surface, and the total value A of waviness intensities at a wavelength of 3 to 10 mm, calculated by discrete Fourier transform of the uneven waveform on the surface of the first main surface. _{3 to 10} is 1.60 × 10 ^-3 µm or less. When A _{3 to 10} is 1.60 × 10 ⁻³ μm or less, color unevenness caused by components having a wavelength of 3 to 10 mm can be suppressed.

The sum of waviness intensities A 3 _to 10 at a wavelength of 3 to 10 mm is preferably 1.40 × 10 ^-3 µm or less, more preferably 1.30 × 10 ^-3 µm or less, and 1.20 × 10 ^-3 µm or less is more preferable In addition, the lower limit of the total value A _{3 to 10} of the waviness strength is not particularly limited, but is, for example, 0.50×10 ⁻³ μm or more.

In addition, in the case of a glass substrate in which the first principal surface is not polished, the total value of the waviness intensity at a wavelength of 3 to 10 mm calculated by discrete Fourier transform of the uneven waveform on the surface of the first principal surface of the glass substrate A _{3 -10} is preferably 7.00 × 10 ^-3 µm or less. When the total value A 3 _{to 10} of the waviness intensity at a wavelength of 3 to 10 mm is large, it is necessary to increase the polishing amount in order to suppress color unevenness caused by components at a wavelength of 3 to 10 mm. However, if the total value A _{3 to 10} of the waviness intensity at a wavelength of 3 to 10 mm is small, color unevenness can be suppressed without increasing the amount of polishing in the polishing step (S50), so productivity is improved. can be expected

It is more preferable that the total value A _3-10 of the waviness intensity in the wavelength 3-10 mm in the glass substrate whose 1st main surface is not polished is 6.00x10 ^-3 micrometer or less, and it is 5.50x10 ^-3 It is more preferably ㎛ or less, and it is particularly preferable that it is 5.00 × 10 ^-3 ㎛ or less.

In addition, in the glass substrate in which the first main surface is not polished, the lower limit of the total value A _{3 to 10} of the waviness strength is preferably 4.00 × 10 ^-3 µm or more, and more preferably 4.20 × 10 ^-3 µm or more. , more preferably 4.50×10 ^-3 μm or more. In the glass substrate in which the first main surface is not polished, the sum of the waviness intensities A _{3 to 10} is equal to or greater than the lower limit, as shown in FIG. There is a high possibility that a plurality of pitches are short concave-convex waveforms by the convex portion removal step (S30) described later.

The total value A 3 _{to 10} of the waviness intensity in the wavelength range of 3 to 10 mm in the glass substrate before polishing can be adjusted by the height of the reference value H2 in the surface shape measuring step (S20) described later. The higher the reference value H2 is, the fewer the convex portions are removed in the convex portion removal step (S30) described later. As shown in FIG. 3 , the total value A _{3 to 10} of the waviness intensity at a wavelength of 3 to 10 mm is a concavo-convex waveform with a long pitch that exists on the surface of the glass substrate in the convex portion removal step (S30). , increases as a plurality of pitches become a short concave-convex waveform. Therefore, if the convex part removed in the convex part removal process (S30) decreases, the total value A _3-10 of the waviness intensity in a wavelength of 3-10 mm will also become small. In addition, even if the reference value H2 is too low, the total values A _{3 to 10} of the waviness intensities become small.

In the glass substrate after polishing, the total value A 3 to ₁₀ of the waviness intensity at a wavelength of 3 to 10 mm is affected by the total value A _{3 to 10} of the waviness intensity of the glass substrate before polishing. The larger the total value A _{3 to 10} of the waviness strength of the glass substrate before polishing, the larger the A _{3 to 10} tends to be in the glass substrate after polishing.

In addition, in the glass substrate after polishing, the total value A 3 _{to 10} of the waviness intensity at a wavelength of 3 to 10 mm is also influenced by the polishing conditions. For example, the total value _A3-10 of waviness intensity in a wavelength of 3-10 mm becomes small, so that polishing time is lengthened and the amount of polishing is increased.

<Ratio (A 3 to 10 /A ₂₀ ) of the total value A 3 to 10 of the waviness intensity at a wavelength of 3 to ₁₀ mm to the waviness intensity A ₂₀ at a _wavelength of 20 mm>

The ratio (A 3 to ₁₀ /A 20 ) of the total value A 3 _to 10 of the waviness intensity at a wavelength of 3 _to 10 mm to the waviness intensity A ₂₀ at a wavelength of 20 mm changes before and after polishing. , especially affected by changes in A _{3 to 10} . This is attributed to the fact that in the polishing step (S50), components with a short wavelength are easily reduced, and components with a long wavelength are difficult to be reduced. That is, before and after the polishing step (S50), A 3 to 10, _{which is the total value of the waviness intensity in the waviness wavelength of 3 to 10 mm, is liable to change, but the waviness intensity A 20 in} the waviness wavelength of 20 mm is hard to change Therefore, before and after polishing, the ratio (A _{3 to 10} /A ₂₀ ) is greatly affected by the change in the sum of the waviness intensities A 3 _{to 10} at a wavelength of 3 to 10 mm.

In the glass substrate after polishing, the ratio (A _{3 to 10} /A ₂₀ ) is preferably 1.00 or more, more preferably 1.05 or more, and still more preferably 1.10 or more. The larger the ratio (A _{3 to 10} /A ₂₀ ), the smaller the amount of polishing. By polishing the glass substrate so that the ratio (A _{3 to 10} /A ₂₀ ) is equal to or greater than the lower limit, an improvement in productivity can be expected.

Moreover, in the glass substrate after polishing, the ratio (A _{3 to 10} /A ₂₀ ) is preferably 2.00 or less, more preferably 1.70 or less, and still more preferably 1.50 or less. The ratio (A _{3 to 10} /A ₂₀ ) below the upper limit means that the glass substrate is sufficiently polished.

Here, about the glass substrate produced by the float method, when polishing is carried out without carrying out the convex part removal process (S30) mentioned later, the waviness intensity|strength _A20 in a wavelength of 20 mm is normal in wavelengths 3-10 mm Since it is larger than the sum of the waviness strengths A _{3 to 10} , the ratio (A _{3 to 10} /A ₂₀ ) is less than 1.00.

Whether or not the glass substrate is polished can be judged by observing the surface of the glass substrate. In the polishing step (S50), since the surface of the glass substrate is usually polished using an abrasive grain, the relevant main surface has polished stripes. The presence or absence of polishing streaks can be determined by surface observation by AFM (Atomic Force Microscopy; atomic force microscope). Specifically, when one or more polishing stripes having a length of 0.5 μm or more exist in a 1 μm × 1 μm area, it can be said that the surface has polishing stripes.

In particular, whether or not the bottom surface of the glass substrate produced by the float method is polished can be judged also by irradiating the glass substrate with ultraviolet rays of 300 nm or less. In the state before polishing, tin adhering to the bottom surface of the glass substrate emits fluorescence when irradiated with ultraviolet rays. On the other hand, when the bottom surface of the glass substrate is polished, such fluorescence is not seen.

<Method of measuring waviness strength>

The waviness intensity at each wavelength is calculated by discrete Fourier transform of the concavo-convex waveform on the surface of the glass substrate. The concavo-convex waveform on the surface of the glass substrate is measured, for example, by a stripe pattern projection method or non-contact surface shape measurement using an optical interference method.

<Surface shape measurement by stripe pattern projection>

Fig. 4 shows an apparatus for measuring the uneven waveform on the surface of a glass substrate. The apparatus shown in FIG. 4 includes a stripe pattern 1 for irradiating a stripe pattern on the surface of a glass substrate, a glass substrate 10 on which the stripe pattern 1 is irradiated, and the glass substrate of the stripe pattern 1. It has a line sensor camera 2 that captures a reflected image by (10).

The line sensor camera 2 and the stripe pattern ( 1) is installed. At this time, the angle θ is preferably 45°.

Fig. 5 is a flow chart showing a flow in the case of measuring the first main surface 10a of the glass substrate by the stripe pattern projection method. The surface shape measurement by the stripe pattern projection method includes a step of irradiating the stripe pattern (S21), a step of capturing a reflected image of the stripe pattern reflected on the glass substrate (S22), and a first main surface of the glass substrate from the reflected image ( The step of detecting only the reflected image in 10a) (S23), the step of calculating the slope of the first main surface 10a of the glass substrate from the detected shift in light and shade of the stripe pattern (S24), and integrating the slope It has a process (S25) of obtaining the surface shape of the 1st main surface 10a of a glass substrate.

In step S23, when the stripe pattern is irradiated onto the glass substrate from the stripe pattern, the reflected image is the stripe pattern reflected from the first main surface 10a of the glass substrate and the opposite direction to the first main surface 10a. A stripe pattern reflected from the second main surface 10b exists. Therefore, only the stripe pattern reflected on the first main surface 10a is detected from the captured image.

Next, from the obtained image, the slope of the concavo-convex waveform of the first main surface 10a is calculated based on the deviation of the light-dark cycle caused by the concavo-convex waveform of the first main surface 10a. Then, the concavo-convex profile of the first main surface of the glass substrate is obtained by integrating the slope of the concavo-convex waveform.

After filtering the obtained concavo-convex profile, the waviness intensity at each wavelength can be calculated by discrete Fourier transform.

<Measurement of concavo-convex waveform by optical interference method non-contact surface shape measurement>

In addition, you may measure the uneven|corrugated waveform of the surface of a glass substrate by non-contact surface shape measurement of an optical interference method. The non-contact surface shape measurement of the optical interference method irradiates and reflects coherent light to the surface of the glass substrate, and observes the difference in height of the glass substrate surface as a phase shift of the reflected light. The non-contact surface shape measurement of the optical interference method is not particularly limited, but, for example, Micromap, Vertscan2.0, Vertscan3.0 (manufactured by Ryoka Systems Co., Ltd.), etc. are used.

For example, by measuring the concavo-convex waveform on the surface of the glass substrate with Vertscan 2.0 (lens magnification: 5 times), filtering the obtained concavo-convex profile, and then calculating the waviness intensity at each wavelength by discrete Fourier transform. can do.

<Method for manufacturing glass substrate>

1 shows a schematic flowchart for explaining a method for manufacturing a glass substrate according to an embodiment of the present invention.

In the same figure, the manufacturing method of the glass substrate of the present invention includes a preparation step (S10) of preparing a glass substrate, a surface shape measuring step (S20) of measuring a concavo-convex waveform on the surface of the glass substrate, and It has a convex part removal process (S30) which removes a convex part with an etchant, a cleaning process (S40) which removes the etchant existing on the glass substrate surface, and a polishing process (S50) which polishes the glass substrate surface.

<Preparation process (S10)>

The preparation step (S10) includes a melting process (S12) of melting glass raw materials, a molding process (S14) of forming the molten glass, an annealing process (S16) of annealing the molded glass ribbon, and a glass substrate. It has a cutting process (S18) to cut into a predetermined size. In melting processing (S12), molten glass is produced by melting glass raw materials. In the molding process (S14), the molten glass present in the float bath is continuously supplied onto the surface of the 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 while moving from the upstream side of the float bath to the downstream side. In the annealing treatment (S16), the glass ribbon molded into a strip shape in the molding treatment (S14) is annealed. Next, in the cutting process (S18), the annealed glass ribbon is cut into a predetermined size with a cutter to obtain a glass substrate. In this preparatory step (S10), minute irregularities are generated on the surface of the glass substrate under the influence of distortion or corrugation, for example.

<Surface shape measurement process (S20)>

The surface shape measurement step (S20) is a step of measuring the uneven waveform on 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, when polishing the first main surface of the glass substrate with the bottom surface of the glass substrate (the surface in contact with the molten metal in the molding process (S14)) as the first main surface, at least the first main surface is measured do.

The concavo-convex waveform on the surface of the glass substrate is measured, for example, by the non-contact surface shape measurement using the above-mentioned stripe pattern projection method or optical interference method. The concavo-convex profile obtained by measuring the measured concavo-convex waveform is stored in a recording medium such as a computer. Next, a filter process is performed with respect to the obtained concavo-convex profile.

Next, a region having a height equal to or higher than a predetermined reference value H2 set in advance (hereinafter, also referred to as "removal region 14") is calculated. The removal region 14 is a region removed in the convex portion removal step (S30). By removing the removal region 14 in the next convex part removal step (S30), the waviness intensity A ₂₀ at a wavelength of 20 mm can be reduced, and as the A ₂₀ decreases, the wavelengths 3 to 10 The total value A _{3 to 10} of waviness strength in mm increases.

The reference value H2 is determined based on the average value H1 of the waviness height and the arithmetic average height Sa of the surface of the glass substrate. The arithmetic mean height Sa is a parameter obtained by extending the arithmetic mean height Ra of the line into a plane, and represents the average of the absolute value of the difference between the average value H1 of the waviness height on the glass substrate surface and the waviness height of each point on the glass substrate surface. Generally, it is a parameter used when evaluating surface roughness.

The reference value H2 is preferably set within a range that satisfies the following two equations when the average of the waviness heights on the surface of the glass substrate is H1.

(H1-1.5×Sa)≤H2... (One)

H2≤(H1+0.5×Sa) . (2)

In addition, H1 and Sa are calculated using the concavo-convex profile before filter treatment.

Regarding the reference value H2, by setting the formulas (1) and (2) to be satisfied, it is possible to remove convexities present on the surface of the glass substrate, and as a result, the waviness intensity A ₂₀ at a wavelength of 20 mm can be reduced. have.

When reference value H2 does not satisfy Formula (1), the area|region (removal area 14) of height more than reference value H2 increases on the surface of a glass substrate. As a result, there is a possibility that the waviness intensity at a wavelength of 20 mm cannot be efficiently reduced because a large number of convex portions are newly generated by removing the convex portions using the etchant. Further, when the reference value H2 does not satisfy Expression (2), the area of the height equal to or higher than the reference value H2 decreases. As a result, there exists a possibility that the convex part on the surface of a glass substrate cannot be removed and the waviness intensity in wavelength 20mm cannot be reduced efficiently.

<Convex part removal process (S30)>

The convex portion removal step (S30) is a step of removing a region having a height equal to or higher than the predetermined reference value H2 calculated by the arithmetic processing means in the surface shape measuring step (S20). In this embodiment, the said convex part is removed by apply|coating etching liquid to the said convex part in the convex part removal process (S30).

3 : is a schematic diagram which shows the change of the glass substrate surface in the convex part removal process (S30) of this embodiment. In addition, in FIG. 3, the uneven waveform of the surface of a glass substrate is shown exaggeratedly for the sake of understanding.

Figure 3 (a) is a conceptual diagram showing the surface of the glass substrate before coating the etching solution on the convex portion of the surface of the glass substrate. In (a) of FIG. 3, H1 shown by the solid line is the average value of the waviness height of the surface of a glass substrate. In addition, H2 indicated by a solid line is a reference value. In (a) of Fig. 3, the reference value H2 is set at a position that satisfies Expressions (1) and (2). The shaded area in (a) of FIG. 3 indicates an area (removal area 14) having a height equal to or higher than the reference value H2.

(b) of FIG. 3 shows a case where the removal region 14 is removed by applying an etchant to the removal region 14 . By applying an etchant to the removal area 14, the removal area 14 is removed.

When the removal area 14 is removed with an etchant, the convex portion that was the removal area 14 is not removed along the reference value H2, but a concave portion is formed in the portion that was the convex portion before processing, as shown in (b) of FIG. 3 . removed as much as possible. At this time, as shown in Fig. 3(b), the vicinity of the end point 12 where the reference value H2 and the removal region 14 intersect becomes steep. This is considered to be because, assuming that the surface of the removal region 14 is etched by the same depth, the vicinity of the end point tends to be equal to or less than the reference value H2.

Comparing FIG. 3(a) with FIG. 3(b) before and after removal of the removal region 14, the surface of the glass substrate in FIG. 3(a) before the convex portion removal step has a concavo-convex waveform with a long pitch. On the other hand, the surface of the glass substrate of Fig. 3(b) after the convex portion removal step (S30) becomes a concave-convex waveform with a short pitch.

As a result, after the projection removal step (S30), compared to before the projection removal step (S30), when the discrete Fourier transform of the concavo-convex waveform on the surface of the glass substrate is performed, the waviness intensity at a relatively long wavelength of about 20 mm is reduced. In addition, the intensity of waviness with a relatively short wavelength of 10 mm or less increases.

Here, when trying to remove the convex part of the removal area 14 using an etching gas, it is difficult to remove the convex part. Further, even if the convex portion can be removed, since it is difficult for the concave portion to be formed in the portion that was the convex portion, the waviness intensity at a wavelength of 10 mm or less is difficult to increase.

As the etching solution, for example, a mixture of fluoride and inorganic acid may be used. As the fluoride, for example, a salt selected from ammonium fluoride, ammonium hydrogen fluoride, sodium fluoride, sodium hydrogen fluoride, potassium fluoride, potassium hydrogen fluoride, and similar salts, or combinations thereof can be used. The inorganic acid may be, for example, one of hydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and similar acids, or combinations thereof. Although the etching solution is not particularly limited, for example, a solution containing a fluorine content of 1% by mass to 20% by mass and an inorganic acid of 5% by mass to 60% by mass can be used.

The depth of the newly generated concave portion in the convex portion removal step (S30) can be adjusted by the concentration of the etchant and the etching time. In the case where a region having a height equal to or higher than the reference value H2 before the convex portion removal step (S30) still remains due to insufficient etching amount, it can be adjusted by increasing the concentration of the etchant or lengthening the etching time. Since the amount of etching of the convex portion is too large, when excessively deep concavities occur in the convex portion that was the removal area 14 before the convex portion removal step (S30), it can be adjusted by lowering the concentration of the etchant or shortening the etching time. can

Here, the excessively deep concave portion means, for example, that the waviness height is (H1-4×Sa) or less using the average H1 and arithmetic average height Sa of the waviness height of the glass substrate surface before the convex portion removal step (S30). It refers to the concave area where the area to be is present. If it is 4 × Sa (nm) or more lower than the average H1 of the waviness height on the surface of the glass substrate before the convex part removal step (S30), the polishing required to remove the concave part generated in the convex part removal step (S30) using an etchant There is a risk of increasing the amount.

The method of applying the etching solution is not particularly limited as long as the etching solution can be applied only to the removal area 14 . The liquid extraction part may be applied with a brush containing a fiber bundle, the liquid extraction part may be applied with a pen containing synthetic resin such as felt, or may be applied with a spray nozzle. Applying using a spray nozzle is preferable because the application amount of the etchant can be adjusted and the etchant can be uniformly applied to the removal area 14 . In addition, when applying with a brush or pen, it is preferable because the handling property is excellent.

In the case of using a spray nozzle, a spray nozzle is disposed above the removal area 14, and an etching liquid is ejected from the spray nozzle toward the removal area, and at the same time, the end point where the reference value H2 and the removal area 14 intersect ( Air is ejected toward the end point 12 from an air nozzle disposed above 12). Thereby, the etchant ejected from the spray nozzle is applied only to the removal area 14 . In addition, the applied etchant does not flow into the concave portion and can remain in the removal area 14 .

When the liquid outlet applies the etchant with a pen or brush shape, the etchant can be applied only to the removal area 14 even when there is no air nozzle. In addition, the etchant stays in the removal area 14 due to the surface tension acting on the surface of the liquid depending on the application amount of the etchant, but when the etchant flows from the removal area 14 to the concave portion because the application amount is large, the end point You may make it stay in the removal area|region 14 by blowing air toward the said end point 12 from the air nozzle arrange|positioned above 12.

<Cleaning process (S40)>

The cleaning step (S40) is a step of removing the etchant applied to the surface of the glass substrate in the convex portion removal step (S30). In the cleaning step (S40), the surface of the glass substrate is cleaned with, for example, pure water to remove the etchant applied to the surface of the glass substrate.

<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 is, for example, one containing cerium oxide, zirconium oxide, manganese oxide, lanthanum oxide or bengala as polishing abrasive grains. In particular, it is preferable to use cerium oxide.

Of the first main surface or the second main surface of the glass substrate, at least the main surface processed in the convex portion removal step (S30) is polished to finish the glass substrate with high smoothness. For example, when the bottom surface of a glass substrate is made into a 1st main surface and the convex part removal process (S30) is performed with respect to the surface of the said 1st main surface, at least a bottom surface is polished. The polishing conditions may be appropriately adjusted and are not particularly limited. For example, in the case of polishing using a polishing pad, the polishing pressure is preferably 0.05 to 0.5 MPa, and the polishing pad rotation speed (revolution number) is preferably 30 to 1000 rpm. do. Further, the polishing pad may be rotated while rotating the polishing pad. In this case, the number of rotations of the polishing pad is preferably 10 to 300 rpm. The number of times of polishing in the examples described later is not particularly limited, but considering the load of the polishing step (S50), it is preferably 1 to 10 times, more preferably 3 to 8 times, and most preferably 3 to 6 times. desirable. Further, the surface of the glass substrate may be polished using a belt polishing machine using an endless strip-shaped polishing belt instead of a polishing pad.

<Electronic Device>

The glass substrate according to the present embodiment is preferably used as a substrate for electronic devices, more preferably used as a substrate for a display among them, and still more preferably used as a substrate for a liquid crystal display, a-Si ( It is most preferable to use it as a substrate for Amorphous Silicon) TFT.

Moreover, it is more preferable to use as a carrier substrate for flexible display manufacture or a carrier substrate for semiconductor packaging. Especially, it is more preferable to use as a carrier substrate for flexible display manufacture. Moreover, the electronic device concerning this embodiment is provided with the said glass substrate, For example, such a glass substrate can be suitably applied also to the large-sized electronic device whose at least one side is 2400 mm or more rectangular shape.

[Example]

Although the present invention will be specifically described below with reference to test examples, the present invention is not limited thereto. In addition, Examples 1 and 2 are Examples, and Examples 3 to 6 are Comparative Examples.

<Example 1>

A glass substrate containing substantially no alkali metal having a size of 2500 × 2200 mm and a thickness of 0.5 mm was produced in the melting furnace A. In Example 1, in the glass substrate produced by the float method, assume that the bottom surface in contact with molten tin in the molding process is the first main surface, and the main surface in the opposite direction to the first main surface is the second main surface. The composition of the produced glass substrate was as follows in mass % concentration notation.

SiO ₂ : 60%

Al ₂ O ₃ : 17%

B ₂ O ₃ : 8%

MgO: 3%

CaO: 4%

SrO: 8%

BaO: 0%

Others: less than 0.1%.

Next, the surface of the first main surface of the glass substrate produced in the surface shape measurement step was measured using a stripe pattern projection method, and the surface shape of the first main surface of the glass substrate was measured. Next, after filtering the concavo-convex profile obtained by the measurement, the waviness intensity of each wavelength was calculated by discrete Fourier transform.

Then, using the concavo-convex profile of the first main surface of the glass substrate before the filter treatment, the average value H1 of the waviness height and the arithmetic average height Sa were calculated, and the reference value H2 was set. The reference value H2 was set to be “H2=H1-Sa”.

Next, with respect to the 1st main surface of the glass substrate, the convex part was removed in the convex part removal process. In the convex portion removal step, a region (removed region) having a height equal to or higher than the reference value H2 was calculated, and an etchant was applied to the removed region using a spray nozzle to remove the removed region. After that, 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. The step of polishing for about 15 seconds at a rotational speed of the polishing pad at 100 rpm, a rotational speed of the polishing pad at 33 rpm, and a polishing pressure of 0.08 MPa was counted as one polishing step, and polishing was performed six times.

Next, the surface shape of the first main surface of the polished glass substrate is measured again using the stripe pattern projection method, and the obtained concavo-convex profile is subjected to a filter treatment, followed by discrete Fourier transform to form wave patterns at each wavelength of the polished glass substrate. The strength was also calculated. The gain at each pitch in the filter process is shown in FIG. 10, and the gain at a specific pitch in FIG. 10 is shown in Table 1. After that, color unevenness was evaluated by the method described later.

<Example 2>

A glass substrate was obtained in the same manner as in Example 1 except that a melting furnace B different from Example 1 was used, the thickness of the glass substrate was 0.4 mm, and the number of times of polishing was 8 times.

<Example 3>

A glass substrate was obtained in the same manner as in Example 2, except that the number of times of polishing was 4 times.

<Example 4>

A glass substrate was obtained in the same manner as in Example 1 except that the convex portion removal step of removing the convex portion of the first main surface of the glass substrate with an etchant was not performed.

<Example 5>

A glass substrate was obtained in the same manner as in Example 3, except that the convex portion removal step of removing the convex portion of the first main surface of the glass substrate with an etchant was not performed.

<Example 6>

A glass substrate was obtained in the same manner as in Example 1, except that the convex portion removal step of removing the convex portion of the first main surface of the glass substrate with an etchant was not performed, and the number of times of polishing was 9 times.

<Evaluation method>

(Measurement of waviness intensity at each wavelength)

The surface shape of the entire surface of the first main surface was measured by the stripe pattern projection method. Then, after filtering the obtained concavo-convex profile, the waviness intensity at each wavelength was calculated by discrete Fourier transform.

At this time, it was installed so that the optical axis of the line sensor camera and the normal of the plane on which the stripe pattern exists would each become 45 degrees from the normal direction of the surface of the glass substrate.

<Evaluation of color unevenness>

A VA mode type liquid crystal panel was started using the glass substrates of Examples 1 to 6, and color unevenness of the glass substrate was evaluated according to the following criterion in the visual inspection.

A: No color unevenness was seen at all, and there was no problem at all.

B: Although color unevenness was hardly seen, color unevenness sometimes became a problem in the case of ultra-high definition, such as 4K and 8K.

C: Color nonuniformity was seen, which was a problem.

The total value of the waviness intensity in the glass substrate wavelength 3-10mm before polishing A _3-10 and the waviness intensity A ₂₀ in the wavelength 20mm, and the waviness in the wavelength 3-10mm of the glass substrate after polishing Table 2 shows the total values A _{3 to 10} of wave strength and the wavy intensity A ₂₀ at a wavelength of 20 mm.

Fig. 6 shows a graph of waviness intensity at each wavelength of the glass substrate before polishing in Examples 1 and 4. Fig. 7 shows a graph of waviness intensity at each wavelength of the glass substrate after polishing in Examples 1 and 4. Fig. 8 shows a graph of waviness intensity at each wavelength of the glass substrate before polishing in Examples 3 and 5.

In the graphs of Figs. 6 to 8, the waviness intensity at a wavelength of less than 3.0 mm has a large influence of noise, and for a portion with a wavelength of less than 3.0 mm, components with a short wavelength are very easily polished. Since it is considered that it is not necessary to take into account that it is removed, the waviness intensity in wavelengths less than 3.0 mm is cut.

In Examples 1 to 6 after polishing, the sum of waviness intensities A 3 to 10 at a wavelength of ₃ to 10 mm is 1.60 × 10 ^-3 μm or less, and the waviness intensity A ₂₀ at a wavelength of 20 mm is When it is 1.60×10 ⁻³ μm or less, it can be seen that color unevenness is evaluated as A.

Fig. 6 shows the waviness intensity at each wavelength in the glass substrates before polishing in Examples 1 and 4. Here, in Example 1, in the convex part removal process, the convex part of the 1st main surface of a glass substrate is removed with an etchant, whereas Example 4 is different in that it does not have a convex part removal process in the manufacturing process.

In the glass substrate of Example 1, compared to the glass substrate of Example 4, it can be seen that the waviness intensity at a wavelength of 20 mm is significantly reduced, and the total value of the waviness intensity at a wavelength of 3 to 10 mm is increased. have. This is because, in the convex portion removal step, a region (removal region) having a height equal to or higher than the reference value H2 is removed with an etchant, and as shown in FIG. I think it's because it became a waveform.

8 shows the waviness intensity in each wavelength of the glass substrate before polishing of Example 3 and Example 5. As shown in FIG. Example 3 differs from Example 5 in that it does not have a convex removal process in the manufacturing process, whereas the convex part of the 1st main surface of a glass substrate is removed with an etchant in the convex part removal process. 8, the glass substrate having the convex part removal step in the manufacturing process significantly reduced the waviness intensity at a wavelength of 20 mm and increased the total value of the waviness intensity at a wavelength of 3 to 10 mm. Able to know.

Fig. 7 shows the waviness intensity at each wavelength in the glass substrates after polishing in Examples 1 and 4. Even after polishing from this, it turns out that the glass substrate of Example 1 produced by the manufacturing method with a convex part removal process has smaller waviness intensity _A20 at a wavelength of 20 mm than the glass substrate of Example 4.

The glass substrate of Example 6 had the highest number of polishing times, with 9 times. However, after polishing, the waviness intensity at a wavelength of 20 mm is greater than that of the glass substrate of Example 1 in which the number of times of polishing is 6 times. This is because, in Example 6, the irregularities on the first principal surface are removed only by polishing, but it is difficult to reduce the waviness strength at a wavelength of 20 mm by polishing. Therefore, in the glass substrate of Example 6, the waviness intensity in a wavelength of 20 mm became more than 1.60, and evaluation of color unevenness was B.

Comparing Examples 2 and 3, they differ in that the number of polishing is 8 and 4, respectively. Regarding the glass substrates before polishing of Examples 2 and 3, (A _{3 to 10} /A ₂₀ ) is the same value for both, but (A _{3 to 10} /A ₂₀ ) in the glass substrate after polishing is the number of times of polishing. You can see that Example 2 is smaller. This is because it is difficult to reduce the waviness intensity A ₂₀ at a wavelength of 20 mm by polishing, but the total value A 3 _to 10 of the waviness intensity at a wavelength of 3 to 10 mm is easily reduced as the number of polishing is increased. It is considered that (A _{3 to 10} /A ₂₀ ) in the glass substrate of Example 2 with many times is small.

That is, the larger the (A _{3 to 10} /A ₂₀ ) after polishing, the shorter the polishing time of the glass substrate, and the smaller the (A _{3 to 10} /A ₂₀ ) after polishing, the higher the productivity.

When A ₂₀ in the glass substrate of Example 3 whose color nonuniformity is a C evaluation and A ₂₀ in the glass substrate of Example 6 whose color nonuniformity is a B evaluation are compared, the glass substrate of Example 3 is smaller. Therefore, from the point of view of A ₂₀ , it can be considered that Example 3 evaluates color unevenness better than Example 6, but Example 3 is actually worse than Example 6. The fact that Example 3 had a poorer evaluation of color unevenness than Example 6 suggests that color unevenness is not limited to the effect of the waviness intensity at a wavelength of 20 mm, and that the color unevenness of Example ₃ was rated C indicates that I think it is because of the large value.

Next, Example 1 in which the number of polishing was 6 times was compared with Example 6 in which the number of polishing was 9 times. Looking at the evaluation of color non-uniformity, the glass substrate of Example 1 was rated A, whereas the glass substrate of Example 6 was rated B, even though the number of times of polishing was greater than that of the glass substrate of Example 1. That is, comparing the glass substrates of Examples 1 and 6 before polishing, the glass substrate of Example 1 is a glass substrate in which color nonuniformity is suppressed with fewer polishing cycles than the glass substrate of Example 6. It means that a glass substrate is obtained.

This is an effect by setting A ₂₀ , which is difficult to reduce by polishing, to 2.00 × 10 ^-3 µm or less in the glass substrate before polishing in Example 1. Further, in the glass substrate before polishing in Example 1, since A _{3 to 10} is also 7.00 × 10 ^-3 µm or less, components having a wavelength of 10 mm or less do not cause color unevenness after polishing.

10: glass substrate
12: end point
14: Elimination area

Claims (14)

A glass substrate having a first main surface and a second main surface,
The sum value A 3 to 10 of waviness intensities at a wavelength of 3 to 10 mm, calculated by discrete Fourier transform of the uneven waveform on the surface of the first principal surface, is _0.50 × 10 ^-3 μm or more and 1.60 × 10 ^-3 μm or less ego,
A glass substrate characterized in that the waviness intensity A ₂₀ at 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 claim 1, wherein a ratio (A _{3 to 10} /A 20 ) of the waviness intensity A ₃ to ₁₀ to the waviness intensity A ₂₀ is 1.00 or more and 2.00 or less. The glass substrate according to claim 1 or 2, wherein the glass substrate is float glass. The glass substrate according to any one of claims 1 to 3, wherein the glass substrate has a thickness of 1 mm or less. The glass substrate according to any one of claims 1 to 4, wherein at least one side of the glass substrate has a rectangular shape of 2400 mm or more. The glass substrate according to any one of claims 1 to 5, wherein the first main surface is a surface after polishing. The glass substrate according to any one of claims 1 to 6, wherein the glass substrate is for a display. An electronic device provided with the glass substrate according to any one of claims 1 to 7. A method for manufacturing a glass substrate having a first main surface and a second main surface,
A surface shape measuring step of measuring a concavo-convex waveform on the surface of the first principal surface and detecting convex portions having a height equal to or greater than a predetermined reference value;
A convex part removal step of applying an etchant to the convex part having a height equal to or greater than a predetermined reference value detected in the surface shape measurement step;
A polishing step of polishing the main surface treated in the convex portion removal step
Method for producing a glass substrate, characterized in that having a. 10. The method of claim 9, wherein the etching solution is applied using a spray nozzle, a pen, or a brush. The manufacturing method of the glass substrate of Claim 9 or 10 whose said glass substrate is float glass. The manufacturing method of the glass substrate of any one of Claims 9-11 whose thickness of the said glass substrate is 1 mm or less. The glass substrate manufacturing method according to any one of claims 9 to 12, wherein at least one side of the glass substrate has a rectangular shape of 2400 mm or more. The method of manufacturing a glass substrate according to any one of claims 9 to 13, wherein the glass substrate is for a display.

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