Glass substrate

Abstract

The glass substrate is a circular glass substrate having a first main surface and a second main surface facing each other, and an end portion between the two main surfaces, and having a notch in a portion of the end portion, the glass substrate having a specific gravity of 3.00 or more, a radius r of 75 mm or more, and a refractive index nd of 1.800 or more, the ratio (Tf / Tg) of the virtual temperature Tf (DEG C) to the glass transition temperature Tg (DEG C) is 1.00 or more, and in terms of 10 mm thickness, the relationship of internal transmittance with respect to wavelength, where lambda 70 is the lowest wavelength at which the internal transmittance is 70%, the lambda 70 is 440 nm or less, and in plan view, the wavelength is 440 nm or less. The ratio (g / r) of the offset (g) (mm) of the center of gravity (G) of the glass substrate with respect to the center (P) of the glass substrate to the radius (r) is in the range of 0.05-1.2%.

Description

Technical Field

[0001] The invention relates to a glass substrate, in particular to a glass substrate with high refractive index and high internal transmittance. Background Art

[0002] As the next generation of wearable displays, AR glasses are attracting much attention. In addition, it has been proposed to use a glass substrate in the lens portion of AR glasses.

[0003] Such a glass substrate for AR glasses is required to have a high refractive index as a light guide member and a high internal transmittance with respect to visible light.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 082616 Summary of the invention

[0007] Generally, it is known that a glass substrate with a high refractive index is weaker in strength than a glass substrate with a low refractive index, and is more likely to break even when a small stress is applied. Therefore, a glass substrate tends to become more brittle as the specific gravity of the glass increases. This is because the high density makes it less likely to cause plastic deformation when an object contacts the glass substrate.

[0008] In particular, in glass substrates for AR glasses with a high refractive index, notches are often formed at the ends for the purpose of position confirmation when handling the glass substrate in the production of optical components and position adjustment (alignment adjustment) of the wafer. However, such notches are likely to become the starting point of stress concentration, so the glass substrates for AR glasses have the problem of being easily damaged during the process flow and when handling the glass substrate.

[0009] In view of such a situation, a glass substrate that is not easily broken is required as a member for AR glasses.

[0010] It should be noted that the above-mentioned problem is not limited to glass substrates for AR glasses, but the same problem may occur in the entire glass substrate having a high refractive index and internal transmittance and a stress concentration portion such as a notch.

[0011] The present invention has been made in view of the above background, and an object of the present invention is to provide a notched glass substrate that is less likely to be broken.

[0012] The present invention provides a glass substrate.

[0013] The invention is a circular glass substrate having a first main surface and a second main surface facing each other and an end portion between the two main surfaces, and a notch in a part of the end portion.

[0014] The specific gravity of the glass substrate is 3.00 or more.

[0015] The radius r is 75 mm or more,

[0016] Refractive index n d is 1.800 or above,

[0017] The ratio (Tf / Tg) of the virtual temperature Tf (°C) to the glass transition temperature Tg (°C) is 1.00 or more,

[0018] In the relationship between internal transmittance and wavelength, the minimum wavelength when the internal transmittance is 70% is set to λ. 70 When 70 Below 440nm,

[0019] In a plan view, a ratio (g / r) of an offset g (mm) of the center of gravity G of the glass substrate relative to the center P of the glass substrate to a radius r is in a range of 0.05% to 1.2%.

[0020] The present invention can provide a glass substrate with a notch which is less prone to breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a virtual diagram schematically showing the relationship between the wavelength and the internal transmittance (value converted to a thickness of 10 mm) of two types of transparent members.

[0022] Figure 2 It is a top view schematically showing an example of a glass substrate according to one embodiment of the present invention.

[0023] Figure 3 This is a side view schematically showing the state of the end portion of the glass substrate according to one embodiment of the present invention.

[0024] Figure 4 This is a side view schematically showing the state of a first chamfered surface at the end of a glass substrate according to one embodiment of the present invention.

[0025] Figure 5 This is an enlarged view schematically showing a notch provided on a glass substrate according to one embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, one embodiment of the present invention will be described.

[0027] One embodiment of the present invention provides a glass substrate.

[0028] The invention is a circular glass substrate having a first main surface and a second main surface facing each other and an end portion between the two main surfaces, and a notch in a part of the end portion.

[0029] The specific gravity of the glass substrate is 3.00 or more.

[0030] The radius r is 75 mm or more,

[0031] Refractive index n d is 1.800 or above,

[0032] The ratio (Tf / Tg) of the virtual temperature Tf (°C) to the glass transition temperature Tg (°C) is 1.00 or more,

[0033] In the relationship between internal transmittance and wavelength, the minimum wavelength when the internal transmittance is 70% is set to λ. 70 When 70 Below 440nm,

[0034] In a plan view, a ratio (g / r) of an offset g (mm) of the center of gravity G of the glass substrate relative to the center P of the glass substrate to a radius r is in a range of 0.05% to 1.2%.

[0035] The glass substrate according to one embodiment of the present invention has a refractive index n of 1.800 or more. d . Refractive index n d For example, it may be 1.820 or more, or 1.850 or more, or 1.900 or more, or 1.940 or more, or 1.960 or more, or 2.000 or more.

[0036] It should be noted that in this application, the refractive index n d It represents the refractive index of helium at d-ray (wavelength 587.6nm).

[0037] The specific gravity of the first glass substrate is 3.00 or more, for example, in the range of 3.10 to 6.50. The specific gravity of the first glass substrate is preferably in the range of 3.40 to 6.60, more preferably in the range of 3.50 to 6.40, further preferably in the range of 3.60 to 6.30, further preferably in the range of 4.00 to 6.22, and most preferably in the range of 4.30 to 6.15.

[0038] In addition, the glass substrate according to one embodiment of the present invention has a wavelength λ specified as described above. 70 The characteristic is that the wavelength is below 440nm.

[0039] Below, refer to Figure 1 This feature will be described.

[0040] Figure 1 This is a virtual diagram schematically showing the relationship between the wavelength and the internal transmittance (value converted to a thickness of 10 mm) of two types of transparent members (a and b). Figure 1 In FIG. 1 , curve (a) is the internal transmittance profile of the first transparent component, and curve (b) is the internal transmittance profile of the second component.

[0041] like Figure 1 As shown in (b), the internal transmittance of the second transparent member to visible light, especially blue light, cannot be said to be too high. Figure 1 As shown in (a), the first transparent member has a higher internal transmittance to blue light and a higher transmittance to the entire visible light than the second transparent member.

[0042] Here, if Figure 1 The wavelength λ when the internal transmittance of the first transparent member is 70% is calculated. 70 (a) and the wavelength when the internal transmittance of the second transparent member is 70%, that is, λ 70 (b), then λ 70 (a)≤440nm and λ 70 (b)>440nm.

[0043] It can be seen that, depending on whether λ is satisfied 70 ≤440nm, can judge the quality of the component's internal transmittance to visible light.

[0044] The glass substrate according to one embodiment of the present invention satisfies λ 70 ≤440nm. Therefore, it can be said that the internal transmittance to visible light is high.

[0045] According to the above-mentioned features, the glass substrate of one embodiment of the present invention can be used as a glass substrate requiring a high refractive index n. d And components with high internal visible light transmittance, such as glass substrates for AR glasses.

[0046] As described above, the conventional notched glass substrate for AR glasses has a problem that stress is easily concentrated on the notch and the notch is easily broken during handling.

[0047] In contrast, a glass substrate according to one embodiment of the present invention further has the following characteristics:

[0048] (i) the ratio of the virtual temperature Tf (°C) to the glass transition temperature Tg (°C) (Tf / Tg) is 1.00 or more,

[0049] (ii) In a plan view, a ratio (g / r) of an offset g (mm) of the center of gravity G of the glass substrate relative to the center P of the glass substrate to a radius r is in a range of 0.05% to 1.2%.

[0050] Here, the virtual temperature Tf of glass is an index indicating the quasi-thermal equilibrium state (stable structure) at which the glass structure corresponds to a certain temperature. Since the stable structure of glass changes according to the cooling rate from the molten state, the virtual temperature Tf of the obtained glass can be changed by changing the cooling rate.

[0051] In addition, relatively speaking, the higher the virtual temperature Tf of glass is, the smaller the specific gravity is, and the brittleness of the glass tends to be suppressed.

[0052] Therefore, as in one embodiment of the present invention, when the ratio (Tf / Tg) is set to 1.00 or more, the brittleness of the glass substrate can be improved.

[0053] In the glass substrate according to one embodiment of the present invention, the ratio (g / r) of the offset amount g (mm) of the center of gravity G with respect to the center P to the radius r is suppressed within the range of 0.05% to 1.2%.

[0054] Therefore, in one embodiment of the present invention, when the glass substrate is rotated or spun, the centrifugal force generated by the deviation of the center of gravity G from the center P can significantly suppress the problem of breakage of the glass substrate.

[0055] According to the above effects, one embodiment of the present invention can provide a d In addition, the glass substrate of one embodiment of the present invention can also be applied to the lens part of AR glasses.

[0056] (Glass substrate according to one embodiment of the present invention)

[0057] Next, refer to Figure 2 , the structure and characteristics of the glass substrate according to one embodiment of the present invention are described in more detail.

[0058] Figure 2 An example of a plan view of a glass substrate according to an embodiment of the present invention is schematically shown.

[0059] like Figure 2 As shown, a glass substrate (hereinafter referred to as a "first glass substrate") 100 according to one embodiment of the present invention has a substantially circular shape.

[0060] In addition, the first glass substrate 100 has a substantially circular first main surface 110 and a substantially circular second main surface 120 (from the Figure 1 ) and an end 130 between the two main surfaces 110 and 120.

[0061] A notch 180 is formed at a portion of the end portion 130 of the first glass substrate 100 .

[0062] The radius r of the first glass substrate 100 is 75 mm or more, for example, in the range of 75 mm to 160 mm. The radius r is preferably in the range of 85 mm to 135 mm, and more preferably in the range of 98 mm to 120 mm.

[0063] The first glass substrate 100 has a refractive index n greater than 1.800. d In addition, the specific gravity of the first glass substrate 100 is greater than or equal to 3.00.

[0064] In addition, as described above, the first glass substrate 100 has the following characteristics: when converted to a thickness of 10 mm, in the relationship between the internal transmittance and the wavelength, the minimum wavelength λ at which the internal transmittance is 70% is 70 Therefore, the first glass substrate 100 has a high internal transmittance for visible light.

[0065] like Figure 2 As shown, the first glass substrate 100 has a center P and a center of gravity G. The distance between the center P and the center of gravity G (also referred to as "offset g") is selected so that the value of (offset g / radius r) is in the range of 0.05% to 1.2%. g / r is preferably in the range of 0.1% to 1.0%.

[0066] Furthermore, in the first glass substrate 100 , the ratio (Tf / Tg) of the virtual temperature Tf (° C.) to the glass transition temperature Tg (° C.) is 1.00 or more. Therefore, the brittleness of the first glass substrate 100 is significantly suppressed.

[0067] In addition, the virtual temperature Tf (° C.) of the glass substrate can be adjusted by controlling the cooling rate in the process from the molten state to the solidification of the glass.

[0068] In particular, the ratio (Tf / Tg) is preferably 1.02 or more, more preferably 1.03 or more, further preferably 1.04 or more, and most preferably 1.05 or more.

[0069] The first glass substrate 100 having such characteristics can be used as a substrate requiring a high refractive index n. d And glass substrates for AR glasses with high internal transmittance for visible light.

[0070] (Other Features of Glass Substrate According to One Embodiment of the Present Invention)

[0071] Next, other features of the glass substrate according to one embodiment of the present invention will be described.

[0072] It should be noted that, for the sake of clarity, the first glass substrate 100 is assumed to be a glass substrate of one embodiment of the present invention, and its features are described. Figure 2 Reference symbols shown.

[0073] (composition)

[0074] The composition of the first glass substrate 100 is not particularly limited.

[0075] The first glass substrate 100 may be, for example, silica glass, phosphate glass, borate glass, or tellurite glass. Silica glass preferably contains 20 mol % or more of SiO 2 The phosphate-based glass preferably contains 20 mol % or more of P. 2 O 5 For example, the boric acid glass preferably contains 10 mol % or more of B. 2 O 3 The tellurite glass preferably contains 10 mol % or more of TeO. 2 .

[0076] The first glass substrate 100 may be, for example, silica-based glass, phosphate-based glass, borate-based glass, or tellurite-based glass.

[0077] The first glass substrate 100 may include a material selected from TiO 2 , Nb 2 O 5 、Bi 2 O 3 ,La 2 O 3 and Gd 2 O 3 At least one of them is used as a high refractive index component.

[0078] TiO 2 , Nb 2 O 5 、Bi 2 O 3 ,La 2 O 3 and Gd 2 O 3 The total amount is, for example, in the range of 1 mol% to 80 mol%. From the viewpoint of high refractive index, strength characteristics and manufacturing characteristics, their total amount is preferably in the range of 5 mol% to 75 mol%, more preferably in the range of 10 mol% to 70 mol%, and further preferably in the range of 15 mol% to 65 mol%.

[0079] The total amount of iron, chromium, and nickel in the first glass substrate 100 is preferably less than 8 ppm by mass, more preferably less than 6 ppm by mass, and further preferably less than 4 ppm by mass.

[0080] By making the total amount of iron, chromium, and nickel, which are coloring transition metals, less than 8 ppm by mass ratio, it is possible to significantly suppress a decrease in the internal transmittance of visible light of the first glass substrate 100 .

[0081] In addition, from the viewpoint of environmental load, the first glass substrate 100 preferably does not substantially contain arsenic, lead, and antimony.

[0082] (End shape)

[0083] The first glass substrate 100 has an end portion 130 in which a notch 180 is formed.

[0084] Figure 3 A configuration example of the side surface of the end portion 130 of the first glass substrate 100 is schematically shown.

[0085] like Figure 3 As shown, the end portion 130 has a side region 135 , a first chamfered surface 138 and a second chamfered surface 139 .

[0086] It should be noted that, in the present application, the “side region” refers to the entire portion of the end portion 130 that is closer to the outer end than the first chamfered surface 138 and the second chamfered surface 139 .

[0087] The end portion 130 preferably has the following configuration.

[0088] The side region 135 has a boundary O with the first chamfered surface 138. In other words, the first chamfered surface 138 joins the side region 135 at the boundary O. In addition, the first chamfered surface 138 has a boundary S with the first major surface 110. In other words, the first chamfered surface 138 joins the first major surface 110 at the boundary S.

[0089] Likewise, the second chamfered surface 139 also joins with the side region 135 at the boundary O2. In addition, the second chamfered surface 139 joins with the second major surface 120 at the boundary S2.

[0090] Figure 4 An enlarged view of the first chamfered surface 138 is shown.

[0091] Figure 4 When a bisector L passing through the center of the thickness t of the first glass substrate 100 is drawn, the shape of the first glass substrate 100 above the bisector L in a side view is schematically shown.

[0092] like Figure 4As shown in the figure, in a plan view, a direction extending along the first main surface 110 of the first glass substrate 100 and perpendicular to the end 130 of the first glass substrate 100 is set as the X axis. In addition, the thickness direction of the first glass substrate 100 is set as the Y axis. Furthermore, the boundary O between the first chamfered surface 138 and the side area 135 is set as the origin O of the X axis and the Y axis.

[0093] In addition, the Y-axis value of the boundary S (also referred to as “intersection S”) between the first chamfered surface 138 and the first main surface 110 is denoted by C (μm).

[0094] In this case, the end portion 130 of the first glass substrate 100 is configured such that C satisfies (t / 5)≤C≤(t / 3).

[0095] In addition, the first chamfered surface 138 is preferably configured to be included in the region Q.

[0096] Here, the region Q represents a region surrounded by the straight line LL1 connecting the origin O and the intersection S′, the straight line y=C, and the straight line LL2 connecting the origin O and the intersection S.

[0097] Among them, the straight line LL1 is

[0098] y=(C / 20)·x (1)

[0099] express,

[0100] Line LL2 is

[0101] y=(C / 458)·x (2)

[0102] express.

[0103] In addition, the intersection point S' is the intersection point of the straight line LL1 and the straight line y=C, and its coordinates are represented by (X1, C). On the other hand, the intersection point S is the intersection point of the straight line LL2 and the straight line y=C, and its coordinates are represented by (X2, C). Among them, 5<X1<50, 350<X2<500.

[0104] Furthermore, the first chamfered surface 138 is preferably configured to have a profile in which the value of the Y axis increases monotonically from the origin O to the intersection S in the region Q.

[0105] When the first chamfered surface 138 is configured in this way, the stress concentration on the end 130 can be significantly reduced during the handling of the first glass substrate 100. Therefore, the possibility of the first glass substrate being broken starting from a portion other than the notch 180 can be significantly reduced.

[0106] It should be noted that, in the above description, a preferred shape of the first chamfered surface 138 is described. However, alternatively or additionally, the second chamfered surface 139 may also have such a shape.

[0107] In this case, in a plan view, the direction extending perpendicularly to the end portion 130 of the first glass substrate 100 and along the second main surface 120 of the first glass substrate 100 is set as the X axis. In addition, the thickness direction of the first glass substrate 100 is set as the Y axis. Furthermore, the boundary O2 between the second chamfered surface 139 and the side region 135 is set as the origin of the X axis and the Y axis.

[0108] Furthermore, when the Y-axis value of the intersection S2 of the second chamfered surface 139 and the second main surface 120 is defined as C2 (μm), the second chamfered surface 139 is configured such that C2 satisfies (t / 5)≤C2≤(t / 3).

[0109] In addition, the second chamfered surface 139 is preferably configured to be included in the region Q2.

[0110] Here, the region Q2 indicates a region surrounded by the straight line LR1 connecting the origin O2 and the intersection S2 ′, the straight line y=C2 , and the straight line LR2 connecting the origin O2 and the intersection S2 .

[0111] Among them, the straight line LR1 is

[0112] y=(C2 / 20)·x (3)

[0113] express,

[0114] Line LR2 is

[0115] y=(C2 / 458)·x (4)

[0116] express.

[0117] In addition, the intersection point S2' is the intersection point of the straight line LR1 and the straight line y=C2, and its coordinates are represented by (X3, C2). On the other hand, the intersection point S2 is the intersection point of the straight line LR2 and the straight line y=C2, and its coordinates are represented by (X4, C2). Among them, 5<X3<50, 350<X4<500.

[0118] In addition, the second chamfered surface 139 is configured to have a profile in which the value of the Y axis monotonically increases from the origin O2 to the intersection S2 within the region Q2.

[0119] When the second chamfered surface 139 is configured in this manner, the possibility that the first glass substrate is broken starting from a portion other than the notch 180 can be significantly reduced.

[0120] (Notch 180)

[0121] The first glass substrate 100 has a recess 180 .

[0122] Figure 5A schematic enlarged view of the recess 180 is shown.

[0123] like Figure 5 As shown, the notch 180 has a notch front end 182. The radius of the notch front end 182 (hereinafter referred to as "notch front end radius R") is, for example, in the range of 0.7 mm to 3.0 mm.

[0124] The notch 180 has an opening angle A. The opening angle A is, for example, in the range of 60° to 120°, or may be in the range of 70° to 110°, preferably in the range of 75° to 105°, more preferably in the range of 80° to 100°, and most preferably in the range of 85° to 98°.

[0125] (Other Features)

[0126] The first glass substrate 100 may have a specific elastic modulus in the range of 8 MNm / kg to 35 MNm / kg, preferably in the range of 10 MNm / kg to 30 MNm / kg, and more preferably in the range of 11 MNm / kg to 28 MNm / kg.

[0127] In addition, the thickness t of the first glass substrate 100 may be in the range of 0.1 mm to 1.0 mm.

[0128] In addition, the first major surface 110 and / or the second major surface 120 of the first glass substrate 100 may have a surface roughness (arithmetic mean roughness Ra) of 10 nm or less.

[0129] In addition, the first glass substrate 100 may have a TTV (Total Thickness Variation) of 10 μm or less. TTV refers to the difference between the maximum height and the minimum height from the back surface of the sample measured when the back surface of the sample is adsorbed on a flat chuck surface.

[0130] In addition, the first glass substrate 100 may have a BOW (height of the center plane of the substrate) of less than 100 μm, preferably less than 50 μm. BOW represents the height of the center plane of the sample in a free state (unfixed state) relative to the reference plane. The reference plane is the center point in the standard application area, and is measured as the distance between the center point and the center plane of the sample.

[0131] The warpage of the first glass substrate 100 calculated from a root mean square surface is 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, and most preferably 30 μm or less.

[0132] Example

[0133] Hereinafter, examples of the present invention will be described. It should be noted that in the following description, Examples 1 to 15 are examples, and Examples 21 to 23 are comparative examples.

[0134] (Example 1)

[0135] The glass substrate was manufactured by the following method.

[0136] Glass raw materials weighed to obtain a desired glass composition are put into a melting furnace to obtain a molten glass. The obtained molten glass is stirred and homogenized.

[0137] Next, the molten glass is molded in a molding mold in such a way that the desired glass block is obtained. The molding mold is made of stainless steel. Then, the molded glass is conveyed by rollers and slowly cooled in a slow cooling furnace. In the slow cooling furnace, in order to prevent the glass plate from breaking, the slow cooling speed is controlled by adjusting the slow cooling temperature and its conveying speed. The virtual temperature Tf of the glass is determined by the slow cooling conditions here.

[0138] The obtained glass block is processed into a disc shape and then sliced. After the slicing, it is lapping to a specified thickness, and then the end surface of the glass plate is processed using a CNC (Computerized Numerical Control) diamond grinding wheel for grinding. Then, the diamond grinding wheel is replaced with a notch grinding wheel, and the portion corresponding to the notch is processed to form a notch.

[0139] Then, the main surface of the glass was polished to obtain a glass substrate having a diameter of 150 mm and a thickness of 0.5 mm.

[0140] Hereinafter, the manufactured glass substrate is referred to as a “glass substrate 1 ”.

[0141] (Example 2~Example 15)

[0142] By the same method as in Example 1, a glass substrate was produced.

[0143] However, in Examples 2 to 15, the raw material composition, cooling conditions, etc. were changed compared with the case of Example 1 to produce glass substrates.

[0144] Hereinafter, the manufactured glass substrates are referred to as “glass substrate 2 ” to “glass substrate 15 ”, respectively.

[0145] (Example 21)

[0146] By the same method as in Example 1, a glass substrate was produced.

[0147] However, in Example 21, the raw material composition, cooling conditions, etc. were changed compared with the case of Example 1, and the glass substrate was manufactured.

[0148] Hereinafter, the manufactured glass substrate is referred to as a “glass substrate 21 ”.

[0149] (Example 22~Example 23)

[0150] A glass substrate was manufactured by the same method as in Example 21.

[0151] However, in Examples 22 and 23, the raw material composition, cooling conditions, etc. were changed compared with the case of Example 21, and the glass substrate was manufactured.

[0152] The manufactured glass substrates are referred to as “glass substrate 22 ” to “glass substrate 23 ”, respectively.

[0153] The compositions of the glass substrates are summarized in Table 1 below.

[0154] [Table 1]

[0155]

[0156] (evaluate)

[0157] The evaluation results of the various properties were shown in Table 2 using the produced glass substrates.

[0158] [Table 2]

[0159]

[0160] Table 2 summarizes the "refractive index n" of each glass substrate. d ”, “Specific gravity”, “Glass transition temperature Tg”, “Virtual temperature Tf”, “Tf / Tg”, “λ 70 ”, “Offset g / radius r”, “Shape of the first chamfered surface”, “Shape of the second chamfered surface”, “Opening angle A of the notch”, “Notch front end radius R”, “Specific elastic modulus”, “Surface roughness Ra”, “TTV”, “BOW”, “Warping”, “Young’s modulus E” and “Handling operability”, etc.

[0161] In each glass substrate, the refractive index n d ” Measured by V-block method using KPR-4000.

[0162] The "virtual temperature Tf" is calculated as follows.

[0163] First, the glass substrate (eg, glass substrate 1) is cut into a size of 20 mm×20 mm×1 mm to produce a glass sheet. Next, the glass sheet is heated to a predetermined heat treatment temperature in a reducing atmosphere, maintained for 2 hours, and then rapidly cooled to room temperature.

[0164] The heat treatment was carried out by changing the heat treatment temperature to prepare four glass pieces (evaluation samples) having different thermal histories.

[0165] The refractive index n was measured for each evaluation sample. d In addition, the heat treatment temperature and the refractive index n were calculated from the four evaluation samples. d Using the obtained relationship, according to the refractive index n measured for the glass substrate 1 d The corresponding heat treatment temperature is obtained and is taken as the virtual temperature Tf.

[0166] The virtual temperature Tf is also obtained for other glass substrates by the same method.

[0167] “λ 70 "Evaluated using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation: U-4100).

[0168] “Offset g / radius r” is calculated by setting the distance between the center P and the center of gravity G of the glass substrate as the offset g and dividing the offset g by the radius r of the glass substrate.

[0169] In addition, "deviation g / radius r" was judged by circles (○×). That is, when the value of the deviation g / radius r was within the range of 0.05% to 1.2%, it was judged as "○", and other values ​​were judged as "×".

[0170] In addition, the "shape of the first chamfered surface" and the "shape of the second chamfered surface" are judged by circles and crosses (○×). That is, the shape of the first chamfered surface is judged as "○" when it is included in the area Q specified as described above and has a monotonically increasing contour from the origin O to the intersection S, and "×" when it is otherwise. The same is true for the "shape of the second chamfered surface".

[0171] The “specific elastic modulus” of each glass substrate was calculated by dividing the Young's modulus evaluated by the ultrasonic pulse method by the specific gravity (density) obtained by the Archimedean method.

[0172] In addition, "surface roughness Ra" means the arithmetic mean roughness Ra measured on the first surface of each glass substrate. "Surface roughness Ra" is defined by JIS B0601 (2001). In the present application, the surface roughness Ra is measured in a 10 μm×10 μm area of ​​the glass substrate using an atomic force microscope (AFM).

[0173] "TTV" refers to the difference between the maximum plate thickness and the minimum plate thickness in the entire area of ​​the glass substrate. "TTV" is measured using a laser displacement meter or an optical interferometer.

[0174] "BOW" refers to the height of the center of the glass substrate from the reference plane. "BOW" is measured using an optical interferometer.

[0175] The "warp" of the glass substrate is measured using a laser displacement meter or an optical interferometer.

[0176] The “Young's modulus” of the glass substrate was measured using an ultrasonic pulse method.

[0177] In addition, "handling workability" was judged by circles (○×). That is, the case where cracks or breaks occurred during the handling and process flow of the glass substrate was judged as "×", and the case where it was intact was judged as "○".

[0178] According to the evaluation results, it can be seen that glass substrates 1 to 15 satisfy all of the following characteristics:

[0179] (1) Specific gravity is 3.00 or more,

[0180] (2) Refractive index n d is 1.800 or above,

[0181] (3) The ratio Tf / Tg is 1.00 or more

[0182] (4)λ 70 Below 440nm,

[0183] (5) The ratio g / r is in the range of 0.05% to 1.2%.

[0184] On the other hand, it is found that the glass substrates 21 to 23 do not satisfy at least one of the above-mentioned (1) to (5).

[0185] In addition, in the glass substrates 21 to 23 , cracks are generated in the glass substrates during the processing operation, but in the glass substrates 1 to 15 , such breakage is not generated after the processing operation.

[0186] From the above results, it was confirmed that the glass substrates 1 to 15 are unlikely to be cracked or broken during handling despite having high refractive indices and high internal transmittances.

[0187] (One embodiment of the present invention)

[0188] The present invention can have the following aspects.

[0189] (Method 1)

[0190] A glass substrate is a circular glass substrate having a first main surface and a second main surface facing each other and an end portion between the two main surfaces, and a notch in a part of the end portion.

[0191] The specific gravity of the glass substrate is greater than 3.00,

[0192] The radius r is 75 mm or more,

[0193] Refractive index n d is 1.800 or above,

[0194] The ratio (Tf / Tg) of the virtual temperature Tf (°C) to the glass transition temperature Tg (°C) is 1.00 or more,

[0195] In the relationship between internal transmittance and wavelength, the minimum wavelength when the internal transmittance is 70% is set to λ. 70 When 70 Below 440nm,

[0196] In a plan view, a ratio (g / r) of an offset g (mm) of the center of gravity G of the glass substrate relative to the center P of the glass substrate to a radius r is in a range of 0.05% to 1.2%.

[0197] (Method 2)

[0198] The glass substrate according to the first aspect, wherein when a bisector passing through the center of the thickness t of the glass substrate is drawn, the end portion has a contour including a side region and a first chamfered surface above the bisector in a side view of the glass substrate,

[0199] In a plan view of the glass substrate, a direction extending along the first main surface and perpendicularly to the end of the glass substrate as a target is set as an X-axis, the thickness direction of the glass substrate is set as a Y-axis, the boundary between the side area and the first chamfered surface is set as an origin O of the X-axis and the Y-axis, the boundary between the first chamfered surface and the first main surface is set as an intersection S, and the Y-axis value of the intersection S is set as C (μm), (t / 5)≤C≤(t / 3),

[0200] The first chamfered surface is contained in a region Q surrounded by a straight line 1 connecting the origin O and the intersection S', a straight line y=C, and a straight line 2 connecting the origin O and the intersection S.

[0201] The above straight line 1 is

[0202] y=(C / 20)·x (1)

[0203] express,

[0204] The above straight line 2 is

[0205] y=(C / 458)·x (2)

[0206] express,

[0207] The intersection point S' is the intersection point of the straight line 1 and the straight line y=C. The coordinates of the intersection point S' are represented by (X1, C). Here, 5<X1<50.

[0208] The intersection point S is the intersection point of the straight line 2 and the straight line y=C. The coordinates of the intersection point S are represented by (X2, C). Here, 350<X2<500.

[0209] The first chamfered surface has a profile in which the value of the Y axis increases monotonically from the origin O to the intersection S in the region Q.

[0210] (Method 3)

[0211] The glass substrate according to aspect 1 or 2, wherein an opening angle A of the notch is in a range of 60° to 120°, and a notch tip radius R is in a range of 0.7 mm to 3.0 mm.

[0212] (Method 4)

[0213] The glass substrate according to any one of aspects 1 to 3, wherein the glass substrate comprises a 2 , Nb 2 O 5 、Bi 2 O 3 ,La 2 O 3 and Gd 2 O 3 At least one of .

[0214] (Method 5)

[0215] The glass substrate according to embodiment 4, wherein TiO 2 , Nb 2 O 5 、Bi 2 O 3 ,La 2 O 3 and Gd 2 O 3 The total amount is in the range of 1 mol% to 80 mol%.

[0216] (Method 6)

[0217] The glass substrate according to any one of aspects 1 to 5, wherein the glass substrate has a specific elastic modulus in a range of 8 MNm / kg to 35 MNm / kg.

[0218] (Method 7)

[0219] The glass substrate according to any one of aspects 1 to 6, wherein the glass substrate has a thickness of 0.1 mm to 1.0 mm.

[0220] (Method 8)

[0221] The glass substrate according to any one of aspects 1 to 7, wherein the first main surface has a surface roughness (Ra) of 10 nm or less.

[0222] (Method 9)

[0223] The glass substrate according to any one of aspects 1 to 8, wherein the glass substrate has a TTV of 10 μm or less.

[0224] (Method 10)

[0225] The glass substrate according to any one of aspects 1 to 9, wherein the glass substrate has a BOW of 100 μm or less.

[0226] (Method 11)

[0227] The glass substrate according to any one of aspects 1 to 10, wherein a warpage obtained from a root mean square surface is 100 μm or less.

[0228] (Method 12)

[0229] The glass substrate according to any one of aspects 1 to 11, wherein the glass substrate does not substantially contain arsenic, lead, and antimony.

[0230] (Method 13)

[0231] The glass substrate according to any one of aspects 1 to 12, wherein the total amount of iron, chromium, and nickel in the glass substrate is less than 8 ppm by mass ratio.

[0232] This application claims the benefit of priority based on Japanese Patent Application No. 2022-127385 filed on August 9, 2022, the entire contents of which are incorporated herein by reference.

[0233] Explanation of symbols

[0234] 100 First Glass Substrate

[0235] 110 first main surface

[0236] 120 second main surface

[0237] 130 end

[0238] 135 Side Area

[0239] 138 First chamfer surface

[0240] 139 Second chamfer surface

[0241] 180 Notch

[0242] 182 Notch front

Claims

1. A glass substrate having a first main surface and a second main surface facing each other and an end portion between the two main surfaces, wherein a portion of the end portion has a circular glass substrate having a notch, The specific gravity of the glass substrate is greater than 3.00, The radius r is 75mm or more, Refractive index n d is 1.800 or above, The ratio of the virtual temperature Tf to the glass transition temperature Tg, that is, Tf / Tg, is greater than 1.00, wherein the units of Tf and Tg are °C. In the relationship between internal transmittance and wavelength, the minimum wavelength when the internal transmittance is 70% is set to λ. 70 When 70 Below 440nm, In a plan view, a ratio of an offset g of the center of gravity G of the glass substrate relative to the center P of the glass substrate to a radius r, that is, g / r, is in a range of 0.05% to 1.2%, and the unit of the offset g is mm.

2. The glass substrate according to claim 1, wherein When a bisector passing through the center of the thickness t of the glass substrate is drawn, the end portion has a contour including a side area and a first chamfered surface above the bisector in a side view of the glass substrate. In a top view of the glass substrate, a direction extending along the first main surface and perpendicularly to the end of the glass substrate as an object is set as an X-axis, the thickness direction of the glass substrate is set as a Y-axis, the boundary between the side area and the first chamfered surface is set as an origin O of the X-axis and the Y-axis, the boundary between the first chamfered surface and the first main surface is set as an intersection S, and the Y-axis value of the intersection S is set as C, (t / 5)≤C≤(t / 3), and the unit of C is μm, The first chamfered surface is contained in a region Q surrounded by a straight line 1 connecting the origin O and the intersection S', a straight line y=C, and a straight line 2 connecting the origin O and the intersection S. The straight line 1 is represented by the following formula (1): y=(C / 20)·x (1) The straight line 2 is represented by the following formula (2): y=(C / 458)·x (2) The intersection point S' is the intersection point of the straight line 1 and the straight line y=C. The coordinates of the intersection point S' are represented by (X1, C). Here, 5<X1<50. The intersection point S is the intersection point of the straight line 2 and the straight line y=C. The coordinates of the intersection point S are represented by (X2, C). Here, 350<X2<500. The first chamfered surface has a profile in the region Q in which the value of the Y axis increases monotonically from the origin O to the intersection S.

3. The glass substrate according to claim 1 or 2, wherein: The opening angle A of the notch is in the range of 60° to 120°, and the front end radius R is in the range of 0.7 mm to 3.0 mm.

4. The glass substrate according to claim 1 or 2, wherein: The glass substrate contains at least one of TiO2, Nb2O5, Bi2O3, La2O3 and Gd2O3.

5. The glass substrate according to claim 4, wherein: The total amount of TiO2, Nb2O5, Bi2O3, La2O3 and Gd2O3 is in the range of 1 mol% to 80 mol%.

6. The glass substrate according to claim 1 or 2, wherein: The glass substrate has a specific elastic modulus in a range of 8 MNm / kg to 35 MNm / kg.

7. The glass substrate according to claim 1 or 2, wherein: The glass substrate has a thickness of 0.1 mm to 1.0 mm.

8. The glass substrate according to claim 1 or 2, wherein: The first main surface has a surface roughness Ra of 10 nm or less.

9. The glass substrate according to claim 1 or 2, wherein: The glass substrate has a TTV of 10 μm or less.

10. The glass substrate according to claim 1 or 2, wherein: The glass substrate has a BOW of 100 μm or less.

11. The glass substrate according to claim 1 or 2, wherein: The warpage calculated from the root mean square surface is 100 μm or less.

12. The glass substrate according to claim 1 or 2, wherein: The glass substrate is substantially free of arsenic, lead and antimony.

13. The glass substrate according to claim 1 or 2, wherein: The total amount of iron, chromium, and nickel in the glass substrate is less than 8 ppm by mass.

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