Glass and method for producing glass

Abstract

The present invention suppresses a decrease in optical characteristics even when forming a curved surface part in glass having a high refractive index. This glass (10): has a refractive index nd of at least 1.77; at a thickness of 10 mm, has an internal transmittance of at least 89% for light having a wavelength of 460 nm; has a curved surface part (13) having a radius of curvature of at most 10,000 mm in at least a portion of a peripheral part; and has a thickness deviation of at most 1% of the maximum thickness.

Description

Glass and method for manufacturing glass

[0001] The present invention relates to glass and a method for manufacturing glass.

[0002] In recent years, there has been a demand for glass with a high refractive index. In particular, for example, in head-mounted displays used in AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc., it is required to achieve a wide viewing angle (FOV). The viewing angle of a head-mounted display depends on the refractive index of the light guide material used in the display portion, and thus a light guide plate with a high refractive index is used.

[0003] Also, in Non-Patent Document 1, it has been proposed that in a light guide plate used in a glasses-type display, by giving a curvature in the image propagation direction, the viewing angle can be increased compared to a flat plate even with the same material. Patent Document 1 describes a method for manufacturing a glass molded body having a curved surface portion by bending molding.

[0004] Japanese Unexamined Patent Application Publication No. 2016-121050

[0005] Anastasiia Kalinina, Andrey Putilin, “Wide-field-of-view augmented reality eyeglasses using curved wedge waveguide” Proc. SPIE 11350, Digital Optics for Immersive Displays II, 1135005 (April 14, 2020), <https: / / doi.org / 10.1117 / 12.<2559320> <​​​The present invention has been made in view of the above-mentioned problems, and aims to provide glass and a method for manufacturing glass that can suppress deterioration in optical properties even when curved surface portions are formed on glass having a high refractive index.

[0008] The glass according to the present disclosure has a refractive index n ｄ The internal transmittance of a 10 mm thick film for light with a wavelength of 460 nm is 89% or more, at least a part of the peripheral portion has a curved surface portion with a radius of curvature of 10,000 mm or less, and the thickness deviation is 1% or less of the maximum thickness.

[0009] The method for producing glass according to the present disclosure is a method for producing glass having a curved surface portion, the method comprising heating a glass substrate and applying an external force to the heated glass substrate to form the curved surface portion having a radius of curvature of 10,000 mm or less in at least a part of the periphery of the glass substrate, and forming a refractive index n ｄ The glass has a transmittance of 1.77 or more, an internal transmittance of 89% or more for light with a wavelength of 460 nm over a thickness of 10 mm, and a thickness deviation of 1% or less of the maximum thickness.

[0010] According to the present invention, even when a curved surface portion is formed on glass having a high refractive index, deterioration of optical characteristics can be suppressed.

[0011] Fig. 1 is a schematic diagram of glass according to this embodiment. Fig. 2 is a schematic diagram showing an example of application of glass to a head-mounted display. Fig. 3 is a schematic plan view of glass according to this embodiment. Fig. 4 is a graph showing viscosity changes with temperature of glass material X and glass material Y used in the examples. Fig. 5 is a diagram illustrating a method for manufacturing glass according to this embodiment.

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that are made by combining the respective embodiments. Furthermore, numerical values ​​include the range of rounding.

[0013] (Glass) FIG. 1 is a schematic diagram of glass according to this embodiment. The glass 10 according to this embodiment is a light-transmitting member that can transmit visible light. The glass 10 according to this embodiment is a plate-shaped member. In this embodiment, the glass 10 is used as a light guide plate. The glass 10 is used as a light guide plate for an AR / MR head-mounted display. A head-mounted display is a display device (wearable device) that is worn on a person's head. However, the use of the glass 10 is arbitrary and is not limited to being used as a light guide plate, nor is it limited to being used in a head-mounted display.

[0014] FIG. 2 is a schematic diagram showing an example of application of the glass 10 to a head-mounted display. The glass 10 is used, for example, in a see-through head-mounted display. The glass 10 is applied to the lens portion of an eyeglass-type device or the visor shield portion of a helmet-type device, and is positioned in front of the wearer's eyes 90. The glass 10 allows the wearer to view a scene within their field of view through the glass 10. In the example of FIG. 2, the glass 10 is provided with an incident portion 21 into which a display image (incident light) is incident from a projection device 91, and an exit portion 22 that emits the display image toward the wearer's eyes 90. The incident portion 21 and the exit portion 22 are, for example, diffraction gratings. The glass 10 propagates the display image from the incident portion 21 toward the exit portion 22 by repeatedly specularly reflecting the incident light inside the glass 10 (between the two main surfaces 11a and 11b). The glass 10 projects the display image toward the wearer's eyes 90 by emitting the display image from the exit portion 22. As a result, the wearer can view the display image superimposed on the view within their field of vision (the view ahead as seen through the glass 10). The configuration shown in Fig. 2 is merely an example, and the glass 10 may be applied to any type of head-mounted display, and the image display method using the glass 10 is not particularly limited. The incident portion 21 and the exit portion 22 may be provided at any position on the glass 10, and the incident portion 21 and the exit portion 22 do not have to be diffraction gratings.

[0015] (Glass Structure) As shown in FIG. 1 , the glass 10 has a pair of main surfaces 11a, 11b and an end face 12. The pair of main surfaces 11a, 11b are the surfaces with the largest area of ​​the glass 10 and face each other in the thickness direction of the glass 10. The end face 12 is a peripheral surface connecting the outer edges of the pair of main surfaces 11a, 11b. The glass 10 has a thickness t. The outer shape of the glass 10 (the shape of the main surfaces 11a, 11b) is not particularly limited and depends on the device to which the glass 10 is applied. For example, when the glass 10 is applied to an eyeglass-type device, the shape of the main surfaces 11a, 11b corresponds to the shape of the lens portion of eyeglasses.

[0016] Hereinafter, the thickness direction of the glass 10 is referred to as the Z direction, a direction perpendicular to the Z direction is referred to as the X direction, and a direction perpendicular to the Z direction and the X direction is referred to as the Y direction. The Z direction may be a direction perpendicular to the main surface of the glass 10 at the center position of the main surface. Here, the X direction refers to the direction in which the radius of curvature of a line formed by the intersection of a plane including the tangential direction and the normal direction with the main surface 11a of the glass 10 is smallest among tangential directions of the main surface 11a at an arbitrary point P on the main surface 11a. In the example of this embodiment, the incident section 21 and the exit section 22 are arranged side by side in the X direction.

[0017] (Curved surface portion) The glass 10 according to this embodiment has a curved surface portion 13 in at least a portion of its periphery. The curved surface portion 13 is bent with the Y axis as the bending axis. The curved surface portion 13 is a region of the glass 10 that is bent with the same radius of curvature R with the Y direction as the bending axis. Note that the same radius of curvature R here does not necessarily mean that the radius of curvature R is strictly the same at each position. The radius of curvature R of the curved surface portion 13 may vary within a predetermined range at each position in the curved surface portion 13, as will be described later.

[0018] In the example of FIG. 1 , the entire glass sheet 10 is uniaxially bent with a center of curvature 15 and a radius of curvature R. Because the entire glass sheet 10 is bent in the X direction with the radius of curvature R, the entire glass sheet 10 is a curved surface portion 13. Therefore, in the example of FIG. 1 , the X direction is uniquely determined regardless of the position P. However, there may be cases where multiple curved surface portions 13 are provided and the bending directions of the respective curved surface portions 13 intersect. In this case, the X direction may be defined for each curved surface portion 13. That is, the X direction of the curved surface portion 13 may be determined in the same manner as for each curved surface portion 13 by taking the direction in which the radius of curvature of the line formed by the intersection of a plane including the tangential direction and the normal direction with the main surface 11 a, among the tangent directions at position P on one curved surface portion 13, is the smallest. In addition, if there are multiple tangential directions in which the radius of curvature of the line formed by the intersection of a plane including the tangential direction and the normal direction with the main surface 11a is the smallest, at least one of these tangential directions may be defined as the X direction.

[0019] In the examples of FIGS. 1 and 2 , the curved surface portion 13 of the glass 10 causes the glass 10 to have a curved shape in the image propagation direction (X direction) connecting the incident portion 21 (see FIG. 2 ) and the exit portion 22 (see FIG. 2 ). This increases the field of view (FOV) at the exit portion 22 compared to a flat plate shape. Note that, in one example, the glass 10 forms a three-dimensional curved surface at the curved surface portion 13. That is, the Gaussian curvature of the curved surface portion 13 may be non-zero. In the example of FIG. 1 , almost the entire glass 10 has the curved surface portion 13, but the curved surface portion 13 may be provided only on a portion of the periphery of the glass 10, with the remaining portion having a flat shape.

[0020] (Radius of Curvature of Curved Surface Portion) In this embodiment, the radius of curvature R of the curved surface portion 13 is 10,000 mm or less. This allows the viewing angle of the head-mounted display to be wider than when the curved surface portion 13 has a flat shape. The radius of curvature R of the curved surface portion 13 is preferably 10 mm or more and 1,000 mm or less, more preferably 50 mm or more and 500 mm or less, and even more preferably 80 mm or more and 200 mm or less. The radius of curvature R of the curved surface portion 13 can be obtained, for example, by acquiring a cross-sectional profile (distribution of the positions (displacements) of the main surfaces 11a and 11b along the cross section) of a region in the vicinity of the curved surface portion 13 and approximating the cross-sectional profile to a circle using the least squares method. The cross-sectional profile can be obtained by measuring the distribution of the positions (displacements) of the main surfaces 11a and 11b along the cross section using a multi-color confocal laser displacement meter (manufactured by Keyence Corporation).

[0021] (Rate of change in radius of curvature) The rate of change of the radius of curvature R of the glass 10 relative to the average value of the radius of curvature R at the curved surface portion 13 (rate of change in radius of curvature) is preferably 200% or less and 70% or more. Here, the rate of change in radius of curvature R refers to the ratio of the measured value of the radius of curvature R at the measurement position to the average value of the radius of curvature R of the entire curved surface portion 13. When the rate of change in radius of curvature R is within this range, high shape accuracy can be achieved, thereby improving image quality and reducing chromatic aberration. The rate of change in radius of curvature R is more preferably 195% or less and 75% or more, and even more preferably 190% or less and 80% or more. To obtain the rate of change in radius of curvature R, first, the cross-sectional profile of the area surrounding the curved surface portion 13 is divided into unit lengths, and positional measurements of multiple measurement points within each division are obtained. The unit length is a predetermined value, for example, 1 mm or more and 10 mm or less (e.g., 5 mm). The pitch of the measurement points within each division is, for example, 25 μm. The radius of curvature R for each section is calculated by approximating the measured values ​​within the section using the least squares method. The rate of change in the radius of curvature R is expressed as a percentage by dividing the radius of curvature R of each section by the average value of the radii of curvature R of all sections.

[0022] (Glass Area) The glass 10 has an area of ​​40 cm on the main surfaces 11 a and 11 b. ２The glass 10 is formed so that each of the main surfaces 11a and 11b falls within this range. Since an excessively large area can cause a decrease in shape precision, the glass 10 having a surface area within this range is suitable for the display unit of a head-mounted display, and can easily ensure uniformity in optical characteristics. The areas of the main surfaces 11a and 11b are 15 cm ２ 35cm or more ２ Less than 10 cm is more preferable. ２ More than 30cm ２ The following is even more preferred:

[0023] (Thickness) The thickness t of the glass 10 according to the present embodiment is preferably 1.5 mm or less. As the thickness t increases, shape errors are more likely to occur, and therefore, glass 10 with a thickness t falling within this range can achieve high shape precision. The thickness t is more preferably 0.3 mm or more and 1.4 mm or less, and even more preferably 0.5 mm or more and 1.2 mm or less.

[0024] The thickness t is measured by obtaining the axial positions of the main surfaces 11a and 11b at a measurement point on the glass 10 using a multicolor confocal laser displacement meter (manufactured by Keyence Corporation) with its optical axis aligned vertically and its measurement direction aligned. The thickness t at the measurement point is obtained as the difference between the position measurement value of the main surface 11a and the position measurement value of the main surface 11b. During measurement, the glass 10 is held so that at least one of the main surfaces 11a and 11b is perpendicular to the optical axis of the sensor.

[0025] (Thickness Deviation) The glass 10 according to this embodiment has a thickness deviation of 1% or less of the maximum thickness. For example, when the thickness t of the glass 10 is 1 mm, the thickness deviation is 10 μm or less (i.e., ±5 μm). Glass 10 having a thickness deviation within this range can achieve high shape uniformity even in the curved surface portion 13, thereby improving image quality and effectively reducing chromatic aberration. The thickness deviation of the glass 10 is more preferably 0.8% or less of the maximum thickness, even more preferably 0.7% or less of the maximum thickness, and even more preferably 0.6% or less of the maximum thickness. The thickness deviation is the difference between the maximum and minimum values ​​of the thickness t at each measurement point on the glass 10. The measurement points are set at a constant pitch along the bending direction of the glass 10 (along the cross section where the main surfaces 11a and 11b are curved). The pitch of the measurement points is, for example, 130 μm.

[0026] (Flat portion) The glass 10 according to this embodiment preferably has one or more flat portions 14 (see FIG. 3 ) on the outer periphery of the main surfaces 11a, 11b. FIG. 3 is a schematic plan view of the glass 10 according to this embodiment. The flat portion 14 is a region whose cross section is a straight line (normal lines at each point are parallel) over a range from one end of the flat portion 14 to the other end. In the example of FIG. 3 , the flat portion 14 is formed at one location on the end face 12 that constitutes the outer periphery of the main surfaces 11a, 11b. The flat portion 14 is formed locally in a predetermined range on the outer periphery of the main surfaces 11a, 11b. The flat portion 14 may be formed in a continuous ring shape over the entire periphery of the main surfaces 11a, 11b.

[0027] The glass 10 having the flat portion 14 on its periphery can have the flat portion 14 function as a reference surface for positioning or a gripping (supporting) surface. Therefore, compared to a glass 10 that does not have the flat portion 14 and has a curved periphery, the positioning accuracy of the glass 10 when holding the glass 10 during processing, inspection, and assembly is improved.

[0028] (End Face) In the glass 10 according to this embodiment, the surface roughness Ra of the end face 12 is preferably 5 nm or more. Having a surface roughness in this range for the end face 12 allows for diffuse reflection of light at the end face 12. As a result, optical noise such as bright lines caused by specular reflection at the end face 12 of light guided through the glass 10 (see FIG. 2 ) can be suppressed, thereby improving image quality. The Ra of the end face 12 is more preferably 10 nm or more, and even more preferably 20 nm or more. Here, the surface roughness Ra is the arithmetic mean roughness defined in JIS B0601 (2001). In this specification, the value is measured over an area of ​​10 μm × 10 μm using a laser microscope.

[0029] The end face 12 of the glass 10 is preferably painted black. Painting the end face 12 black, which has a high light absorption rate, can suppress light reflection at the end face 12. This can suppress optical noise such as bright lines caused by specular reflection of light guided within the glass 10 at the end face 12, thereby improving image quality.

[0030] (Glass Characteristics) Next, the characteristics of the glass 10 will be described.

[0031] (Refractive Index) The glass 10 according to this embodiment has a refractive index n ｄ The refractive index n in this range is 1.77 or more. ｄ By having the refractive index n of the glass 10, the viewing angle of the head-mounted display can be effectively widened. ｄ is preferably 1.80 or more, more preferably 1.85 or more, more preferably 1.88 or more, and even more preferably 1.90 or more. This makes it possible to more effectively widen the viewing angle. ｄ is more preferably 1.94 or more, more preferably 1.97 or more, more preferably 1.99 or more, more preferably 2.00 or more, more preferably 2.05 or more, and even more preferably 2.10 or more. The refractive index can be measured by spectroscopic ellipsometry (JA Woollam Co., Inc.; M-2000 DI).

[0032] (Internal Transmittance) The glass 10 according to this embodiment has an internal transmittance of 89% or more for light with a wavelength of 460 nm at a thickness of 10 mm. Having an internal transmittance of the glass 10 within this range makes it possible to achieve high transmittance for visible light and reduce light loss associated with light guiding, thereby improving image quality. The internal transmittance of the glass 10 in the thickness direction for light with a wavelength of 460 nm is preferably 90% or more, more preferably 91.5% or more, even more preferably 93.0% or more, and even more preferably 95.0% or more.

[0033] The internal transmittance of glass 10 is the transmittance that passes through the interior of the glass 10 being measured. The internal transmittance can be calculated from the measured values ​​of the external transmittance of two types of glass with different thicknesses and the following formula (1). Note that the external transmittance refers to the transmittance including surface reflection loss. In formula (1), X is the internal transmittance of glass with a thickness of 10 mm, T1 and T2 are external transmittances, and Δd mm is the difference in thickness of the sample. The external transmittance can be measured using a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation) for a sample that has been mirror-polished on both sides.

[0034] (Retardation) The glass 10 according to this embodiment preferably has a retardation of 40 nm / cm or less, measured by irradiating the glass with light having a wavelength of 543 nm in the thickness direction. By setting the retardation within this range, image distortion caused by retardation can be suppressed, thereby improving image quality. The retardation is more preferably 20 nm / cm or less, more preferably 18 nm / cm or less, and even more preferably 15 nm / cm or less. The retardation can be measured using a WPA-200 manufactured by Photonic Lattice.

[0035] (Wavefront Aberration) In the glass 10 according to this embodiment, the PV (peak-to-valley) value of the wavefront aberration of the principal surfaces 11a and 11b measured with a laser interferometer is preferably 1.6λ or less. λ represents the wavelength of the laser interferometer laser. Furthermore, the RMS (Root Mean Square) value of the wavefront aberration, which indicates the variation of the principal surfaces 11a and 11b from the reference wavefront, is preferably 0.7λ or less. 0.5λ or less is more preferable, 0.25λ or less is more preferable, and 0.1λ or less is even more preferable. By keeping the wavefront aberration of the principal surfaces 11a and 11b within these ranges, blurring and distortion of the displayed image due to wavefront aberration can be suppressed, thereby improving image quality. Wavefront aberration can be measured using a Verifire manufactured by Zygo.

[0036] (Glass Composition) Next, one embodiment of the composition range of each component that can be contained in glass 10 will be described in detail. In this specification, the content of each component is expressed in mass % based on the oxide, unless otherwise specified. In addition, in this specification, "substantially free" means that no component is contained except for inevitable impurities. In this specification, the content of inevitable impurities is 0.1% or less. Note that the glass is not limited to the composition of the following embodiment as long as it has the above-mentioned properties.

[0037] SiO ２ is a glass-forming component that imparts high strength and crack resistance to glass and improves the stability and chemical durability of glass. ２ The content of SiO may be 0% or more and 44% or less. ２ The content of is preferably 3% or more, more preferably 5% or more, even more preferably 7% or more, still more preferably 9% or more, still more preferably 10% or more, and particularly preferably 11% or more. ２ The content of SiO is 44% or less, and the components for obtaining a high refractive index can be contained in larger amounts. ２ The content is more preferably 38% or less, more preferably 30% or less, even more preferably 20% or less, still more preferably 15% or less, still more preferably 12% or less, and particularly preferably 10% or less.

[0038] Al ２ O ３ is a component that improves chemical durability, ２ O ３ If the amount of Al is too large, the glass is likely to devitrify. ２ O ３ The content of Al may be 0% or more and 5% or less. ２ O ３ The content of Al is more preferably 3% or less, particularly preferably 2% or less. ２ O ３ The content is more preferably 0.3% or more, further preferably 0.5% or more, and particularly preferably 1% or more.

[0039] P ２ O ５ is a component that improves the melting property of glass and enhances manufacturability. ２ O ５ The content of P is preferably greater than 0%, more preferably greater than 2.0%, more preferably greater than 4.0%, even more preferably greater than 6.0%, and even more preferably greater than 8.0%. ２ O ５ The content ratio of P is preferably less than 18.0%, more preferably less than 16.0%, even more preferably less than 14.0%, and even more preferably less than 12.0%. ２ O ５ When the content ratio is less than 18.0%, a high refractive index is obtained, which is preferable.

[0040] B ２ O ３ is a component that lowers Tg, improves mechanical properties such as glass strength and crack resistance, and lowers the devitrification temperature. ２ O ３ If the amount of B is large, the refractive index tends to decrease. ２ O ３ The content of B may be 0% or more and 40% or less. ２ O ３The content of B is more preferably 35% or less, even more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, still more preferably 15% or less, and particularly preferably 10% or less. ２ O ３ The content is more preferably 5% or more, even more preferably 12% or more, still more preferably 18% or more, and particularly preferably 20% or more.

[0041] SiO ２ and B ２ O ３ When the content ratio of SiO is high, the devitrification temperature of the glass decreases, making it easier to manufacture. ２ and B ２ O ３ The content of SiO is preferably 10% or more, more preferably 20% or more, more preferably 25% or more, still more preferably 28% or more, still more preferably 30% or more, and particularly preferably 32% or more. ２ and B ２ O ３ Therefore, when a particularly high refractive index is required, it is possible to improve the refractive index by reducing the content of SiO ２ and B ２ O ３ The content is preferably 70% or less, more preferably 50% or less, even more preferably 40% or less, still more preferably 35% or less, still more preferably 33% or less, and particularly preferably 32% or less.

[0042] Li ２ O is a component that improves strength and crack resistance. ２ The content of O may be 0% or more and 10% or less. ２ The content of O is preferably 0% or more, more preferably 1% or more, more preferably 2% or more, even more preferably 4% or more, and particularly preferably 5% or more. ２ If there is too much O, devitrification will occur easily. ２ The O content is preferably 8% or less, more preferably 6% or less, even more preferably 4% or less, still more preferably 2% or less, and particularly preferably 1% or less.

[0043] Na ２ O is a component that suppresses devitrification and lowers Tg. ２ The content of O may be 0% or more and 10% or less. ２ When O is contained, an excellent effect of suppressing devitrification can be obtained. ２ When O is contained, the content is preferably 0% or more, more preferably 1% or more, still more preferably 2% or more, still more preferably 3% or more, and particularly preferably 4% or more. ２ Too much O tends to reduce strength and crack resistance. ２ The O content is preferably 7% or less, more preferably 4% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0044] K ２ O is a component that suppresses devitrification and lowers Tg. ２ The content of O may be 0% or more and 10% or less. ２ The content of O is preferably 0% or more, more preferably 1% or more, still more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more. ２ If there is too much O, the strength and crack resistance tend to decrease. ２ The O content is preferably 7% or less, more preferably 4% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0045] ZrO ２ is a component that increases the refractive index of the glass and enhances the chemical durability of the glass. ２ The content of ZrO may be 0% or more and 20% or less. ２ The content of ZrO is preferably 1% or more, more preferably 3% or more, even more preferably 5% or more, still more preferably 6% or more, and particularly preferably 6.5% or more. ２ If the amount is too large, devitrification tends to occur. ２ The content is more preferably 15% or less, even more preferably 10% or less, still more preferably 8% or less, and particularly preferably 7% or less.

[0046] Furthermore, the glass contains Sb２ O ３ and SnO ２ At least one of the following may be contained. These are not essential components, but can be added for the purposes of adjusting refractive index characteristics, improving meltability, suppressing coloration, improving transmittance, clarifying, and improving chemical durability. When these components are contained, the total content is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, and particularly preferably 1% or less.

[0047] Y ２ O ３ is a component that increases the refractive index of glass. ２ O ３ The content of Y may be 0% or more and 10% or less. ２ O ３ The content of Y is preferably 1% or more, more preferably 1.5% or more, even more preferably 2% or more, still more preferably 2.5% or more, still more preferably 3% or more, still more preferably 3.5% or more, still more preferably 4% or more, and particularly preferably 5% or more. ２ O ３ If the amount is too large, devitrification occurs easily. Therefore, for applications requiring a lower surface roughness Ra, ２ O ３ The content is preferably 10% or less, more preferably 7% or less, more preferably 5% or less, still more preferably 4% or less, even more preferably 3.5% or less, and particularly preferably 3% or less.

[0048] Alkali metal component (Li ２ O + Na ２ O+K ２ When the total amount of alkali metal components (MgO + CaO + SrO + BaO) and alkaline earth metal components (MgO + CaO + SrO + BaO) increases, the Tg of the glass tends to decrease. Therefore, the content ratio of the alkali metal components and alkaline earth metal components can be 50% or less. The content ratio is more preferably 40% or less, even more preferably 30% or less, even more preferably 16% or less, even more preferably 12% or less, even more preferably 10% or less, even more preferably 5% or less, and particularly preferably 2% or less.

[0049] TiO ２is a component that increases the refractive index of the glass and increases the dispersion of the glass. ２ The content of TiO may be 0% or more and 50% or less. ２ When TiO is contained, its content is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, still more preferably 15% or more, still more preferably 20% or more, still more preferably 25% or more, still more preferably 28% or more, still more preferably 30% or more, and particularly preferably 32% or more. ２ If the amount is too large, the film is likely to be colored and the transmittance is reduced. Therefore, when transmittance is particularly required, it is preferable to use a TiO ２ The content is preferably 50% or less, more preferably 40% or less, even more preferably 35% or less, still more preferably 30% or less, still more preferably 25% or less, still more preferably 20% or less, and particularly preferably 15% or less.

[0050] WO ３ The addition of WO suppresses devitrification of the glass, but if the amount added is too large, the glass becomes more susceptible to devitrification. ３ The content of WO may be 0% or more and 10% or less. ３ The content of WO is more preferably 6% or less, even more preferably 2% or less, even more preferably 1.5% or less, even more preferably 1.0% or less, still more preferably 0.5% or less, and particularly preferably 0.3% or less. ３ The refractive index of the glass can be improved by adding WO. ３ The content is more preferably 0.1% or more, even more preferably 0.2% or more, still more preferably 0.3% or more, and particularly preferably 0.4% or more.

[0051] La ２ O ３ is a component that improves the refractive index of the glass. ２ O ３ The content of La may be 0% or more and 55% or less. ２ O ３When La is contained, the content is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, still more preferably 25% or more, still more preferably 30% or more, and particularly preferably 40% or more. ２ O ３ If the amount of La is too large, the mechanical properties will be reduced and the devitrification temperature will be increased. Therefore, when the mechanical properties and manufacturing properties are important, ２ O ３ The content is preferably 53% or less, more preferably 50% or less, still more preferably 45% or less, and particularly preferably 42% or less.

[0052] Nb ２ O ５ increases the refractive index of the glass and also increases the Abbe number (v ｄ ) is a component that reduces ２ O ５ The content of Nb may be 0% or more and 35% or less. ２ O ５ The content of Nb is preferably 2% or more, more preferably 4% or more, even more preferably 5% or more, still more preferably 6% or more, still more preferably 7% or more, still more preferably 8% or more, and particularly preferably 10% or more. ２ O ５ If the content is too high, devitrification tends to occur. Therefore, for applications requiring a lower surface roughness Ra, the content is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, still more preferably 8% or less, and particularly preferably 7% or less.

[0053] (Method for Manufacturing Glass) The glass 10 according to the present embodiment may be manufactured by any method, and one example of the manufacturing method will be described below.

[0054] (Preparation of Raw Materials) Raw materials used to manufacture the glass 10 are weighed out from the above composition range so as to obtain a desired glass composition, and then mixed uniformly.

[0055] (Preparation of Glass Mother Plate) Glass raw material is turned into a glass state by any glass melting and forming method such as float, fusion, ingot forming, etc., and if necessary, mechanical processing such as slicing, to prepare a glass mother plate 30 (see FIG. 5) of a desired composition. Alternatively, molten glass can be formed into a block shape and then made into the glass mother plate 30 by a redraw method or the like. The glass mother plate 30 is a plate-shaped glass that serves as the base material for the glass 10. The glass mother plate 30 has a refractive index n ｄ is 1.77 or more, and the internal transmittance for light with a wavelength of 460 nm at a thickness of 10 mm is 89% or more.

[0056] In the present embodiment, the glass substrate 30 preferably has a temperature difference between the glass transition point Tg and the softening point of 150° C. or less. The glass substrate 30 having a temperature difference between the glass transition point Tg and the softening point in this range has a high refractive index n suitable for widening the viewing angle of a head-mounted display. ｄ The temperature difference between the glass transition point Tg and the softening point is more preferably 120°C or less, and even more preferably 100°C or less. The glass transition point Tg can be measured, for example, by a thermal expansion method. The softening point can be measured by the fiber stretching method described in JIS R3103-1:2001.

[0057] 4 is a graph showing the viscosity change with temperature of glass material X and glass material Y used in the examples described later. The vertical axis of the graph represents viscosity log η (dPa·s), and the horizontal axis represents temperature (°C). The refractive index n of glass material X ｄ is the refractive index n of the glass material Y ｄ is higher than the refractive index n. In the glass material Y, the viscosity log η changes from about 13.5 (dPa·s) to about 7.65 (dPa·s) in the temperature range (temperature difference of about 250°C) from the glass transition point Tg (about 532°C) to the softening point (about 782°C). In contrast, in the glass material X, the viscosity log η changes from about 13.2 (dPa·s) to about 5.8 (dPa·s) in the temperature range (temperature difference of about 95°C) from the glass transition point Tg (about 705°C) to the softening point (about 800°C). In this way, the glass materials that are the raw materials for glass 10 have a refractive index n ｄWhen the refractive index n of each of the glass materials A, B, and C used in the examples described later is increased, the temperature difference between the glass transition point Tg and the softening point becomes smaller, and the change in viscosity with respect to the temperature change near the molding temperature tends to become larger. ｄ is the refractive index n of glass material Y ｄ (See Table 3.) Therefore, glass materials A, B, and C have a larger change in viscosity with respect to the temperature change from the glass transition point Tg to the softening point than glass material Y.

[0058] In glass materials whose viscosity changes significantly with temperature, variations in the temperature distribution of the glass substrate 30 during molding cause large variations in viscosity, which has a significant impact on molding variations (variations in thickness t, surface roughness Ra, retardation, wavefront aberration, etc.). Therefore, in the production of glass 10 with a high refractive index, it is important to make the temperature distribution of the glass substrate 30 uniform during molding.

[0059] (Bending of Glass Mother Sheet) Fig. 5 is a diagram illustrating a manufacturing method of glass 10 according to this embodiment. The manufacturing method of glass 10 according to this embodiment includes heating glass mother sheet 30 (step S10), applying an external force to the heated glass mother sheet 30, and forming a curved surface portion 13 with a curvature radius of 10,000 mm or less on at least a part of the periphery of the glass mother sheet 30 (step S14), thereby obtaining glass 10. That is, the manufacturing method of glass 10 according to this embodiment includes a reheat-forming step (reheat-bending step) of the glass mother sheet 30.

[0060] In the reheat bending process, the heating and bending are preferably performed in a batch process using a batch-type forming device 50. This allows precise control of the forming temperature for each shot, and high shape accuracy can be achieved. For example, in an eyeglass-type head-mounted display, a pair of glasses 10 for the left and right eyes are used as light guide plates, so batch processing may be performed to form multiple sheets (for example, two sheets) in one shot, or one sheet in one shot.

[0061] In FIG. 5, a batch molding apparatus 50 includes a mold 51 and a heater 55 .

[0062] The forming mold 51 includes a first mold 52 and a second mold 53 into which the first mold 52 fits. In FIG. 5 , the first mold 52 is the upper mold, and the second mold 53 is the lower mold. The first mold 52 has a forming surface 52a and a peripheral wall 52b surrounding the outer periphery of the forming surface 52a. The forming surface 52a is a convex curved surface corresponding to the main surface 11a of the glass 10 (see FIG. 1). The second mold 53 has a forming surface 53a and a peripheral side surface 53b. The forming surface 53a is a concave curved surface corresponding to the main surface 11b of the glass 10 (see FIG. 1). In other words, the forming surface 52a and the forming surface 53a include curved portions for forming the curved surface portion 13 in at least a portion of the periphery of the glass mother sheet 30.

[0063] The peripheral wall 52b of the first die 52 forms an opening corresponding to the outer shape of the second die 53. The peripheral side surface 53b of the second die 53 forms the outer shape of the second die 53 and fits into the inner periphery of the peripheral wall 52b. Both the first die 52 and the second die 53 have sensor holding holes, to which temperature sensors 54a and 54b are attached, respectively. The first die 52 and the second die 53 are held so as to be relatively movable toward and away from each other. For example, the first die 52, which is the upper die, and the second die 53, which is the lower die, can each be moved up and down by a drive source (e.g., a cylinder or a motor) not shown.

[0064] The heater 55 heats the glass mother sheet 30 together with the forming mold 51 by radiant heating. The heater 55 is, for example, an infrared lamp heater, and various known heaters such as a carbon lamp and a halogen lamp can be used. The heater 55 is provided so as to surround the periphery of the forming mold 51. A plurality of heaters 55 can be arranged in the height direction of the forming mold 51 to uniformly heat the forming mold 51. In the step S10 of heating the glass mother sheet 30, the heater 55 heats the glass mother sheet 30 until it reaches a set temperature.

[0065] (Step of Heating the Glass Mother Sheet) In this embodiment, in step S10 of heating the glass mother sheet 30, it is preferable to heat the glass mother sheet 30 together with the forming mold 51 by radiant heating from a heater 55 arranged around the forming mold 51 while the glass mother sheet 30 is placed in the forming mold 51. This allows the entire forming mold 51 to be uniformly heated by radiation, effectively reducing temperature variations in the glass mother sheet 30 and the forming mold 51. In FIG. 5, the radiant heat is indicated by arrows extending from the heater 55. The difference between the set temperature of the heater 55 and the temperature of the forming mold 51 measured by the temperature sensors 54a and 54b is preferably ±3°C or less, more preferably ±2°C or less, and even more preferably ±1°C or less.

[0066] Furthermore, in this embodiment, when heating the glass substrate 30 (step S10), it is preferable to heat it at a temperature increase rate of 50°C / min or less. That is, it is preferable that the temperature increase per unit time (minute) be within this range throughout the entire period from the start of heating to the end of heating. By keeping the temperature increase rate within this range, temperature variations in the forming mold 51 and the glass substrate 30 therein can be suppressed. In particular, in the forming mold 51 having a fitting structure as shown in Figure 5, the first mold 52 is more likely to increase in temperature than the second mold 53, which is partially covered by the peripheral wall 52b. Therefore, the temperature difference can be reduced by lowering the temperature increase rate. The temperature increase rate is more preferably 45°C / min or less, even more preferably 40°C / min or less, and even more preferably 35°C / min or less. The lower the temperature increase rate, the more the temperature variations can be reduced.

[0067] (Step of Stopping Heating) In this embodiment, it is preferable to monitor the temperature of the forming mold 51 and stop heating when the temperature reaches the set temperature (step S12). That is, based on the temperature values ​​detected by the temperature sensors 54a and 54b, heating is stopped when both detected temperatures reach the set temperature. This ensures that the temperature of the forming mold 51 is set to the set temperature, effectively suppressing temperature variations in the forming mold 51 and the glass mother plate 30 therein. The set temperature is, for example, equal to or higher than the glass transition point Tg and equal to or lower than the softening point, and is set to an appropriate value depending on the glass composition.

[0068] When heating is stopped (step S12), the temperature difference between the first mold 52 and the second mold 53 when the set temperature is reached is preferably 60° C. or less. By setting the temperature difference between the first mold 52 and the second mold 53 within this range, temperature variation in the glass mother plate 30 can be more effectively suppressed. The temperature difference between the first mold 52 and the second mold 53 when the set temperature is reached is more preferably 55° C. or less, and even more preferably 50° C. or less.

[0069] (Process for forming curved surface portion) In process S14 for forming the curved surface portion 13, press molding is performed by pressing the heated glass mother sheet 30 with the pressing mold 51. That is, the first mold 52 is moved relatively toward the second mold 53 in a direction approaching the second mold 53, and the glass mother sheet 30 placed between the first mold 52 and the second mold 53 is pressed. In FIG. 5 , the convex molding surface 52a of the first mold 52 presses the glass mother sheet 30 downward, deforming the glass mother sheet 30. The molding mold 51 deforms the glass mother sheet 30 by pressing it, and both surfaces of the glass mother sheet 30 are brought into close contact with the molding surface 52a of the first mold 52 and the molding surface 53a of the second mold 53, respectively. As a result, the curved shape of the molding surface 52a is transferred to one surface of the glass mother sheet 30, forming the main surface 11a. The curved shape of the molding surface 53a is transferred to the other surface of the glass mother sheet 30, forming the main surface 11b. The forming surfaces 52a and 53a approach each other to a distance corresponding to the thickness t of the glass 10. As a result, the glass 10 having the curved surface portion 13 and the thickness t is formed.

[0070] Step S14 of forming the curved surface portion 13 ends when a predetermined time has elapsed after the applied pressure reaches a predetermined set value. The predetermined time is, for example, 30 seconds. When step S14 of forming the curved surface portion 13 is completed, the first mold 52 and the second mold 53 are moved relatively away from each other to a retracted position, and the forming mold 51 is separated. Thereafter, the glass 10 held in the second mold 53 is cooled.

[0071] (Post-processing step) Thereafter, post-processing may be performed on the glass 10. Specifically, a flat portion 14 may be formed on a portion of the outer periphery of the glass 10. A polishing process, for example, may be used to form the flat portion 14. A roughening process may be performed to set the surface roughness Ra of the end face 12 of the glass 10 to a set value of 5 nm or more. A blasting process such as sandblasting may be used as a roughening process. Furthermore, the roughened end face 12 may be painted black. In addition, a surface coating may be formed on the main surfaces 11a and 11b of the glass 10.

[0072] As described above, in the method for manufacturing the glass 10 according to this embodiment, the refractive index n ｄ The glass 10 is manufactured in which the internal transmittance for light with a wavelength of 460 nm is 89% or more and the thickness deviation is 1% or less of the maximum thickness.

[0073] (Effects) As described above, the glass 10 according to the first aspect of the present disclosure has a refractive index n ｄ The glass 10 has a refractive index of 1.77 or greater, an internal transmittance of 89% or greater for light with a wavelength of 460 nm at a thickness of 10 mm, a curved surface 13 with a radius of curvature of 10,000 mm or less in at least a portion of the periphery, and a thickness deviation of 1% or less of the maximum thickness. According to the present disclosure, a glass 10 is obtained that has a high refractive index suitable for widening the viewing angle in a head-mounted display and a high transmittance that achieves low light loss suitable for image display. Furthermore, by keeping the thickness deviation to 1% or less of the maximum thickness, it is possible to suppress variations in thickness distribution. As a result, even when a curved surface 13 is formed on glass 10 with a high refractive index, degradation of optical properties can be suppressed.

[0074] The glass 10 according to the second aspect of the present disclosure is the glass 10 according to the first aspect, except that the refractive index n ｄ According to the present disclosure, it is preferable that the refractive index n be 1.90 or more, which is high enough to effectively widen the viewing angle when applied to an optical system such as a head-mounted display. ｄ A glass 10 having the formula:

[0075] Glass 10 according to a third aspect of the present disclosure is glass 10 according to the first or second aspect, and preferably has a retardation of 40 nm / cm or less as measured by irradiating light with a wavelength of 543 nm in the thickness direction. According to the present disclosure, when glass 10 is applied to an optical system such as a head-mounted display, distortion of the displayed image due to retardation can be suppressed.

[0076] Glass 10 according to a fourth aspect of the present disclosure is glass 10 according to any of the first to third aspects, and preferably has an RMS value of wavefront aberration of the main surface measured with a laser interferometer of 0.7λ or less. According to the present disclosure, when glass 10 is applied to an optical system such as a head-mounted display, blurring and distortion of the displayed image caused by wavefront aberration can be suppressed.

[0077] Glass 10 according to a fifth aspect of the present disclosure is glass 10 according to any one of the first to fourth aspects, and preferably has one or more flat portions 14 on the periphery of the main surface. According to the present disclosure, the flat portions 14 can function as a reference surface for positioning or a gripping surface. This improves the positioning accuracy of glass 10 when holding glass 10 during processing, inspection, and assembly of glass 10, compared to, for example, a case in which no flat portions 14 are present and the entire periphery is a curved surface.

[0078] Glass 10 according to a sixth aspect of the present disclosure is glass 10 according to any of the first to fifth aspects, wherein the surface roughness Ra of the end face 12 is preferably 5 nm or greater. According to the present disclosure, light can be diffused at the end face 12. As a result, when glass 10 is used as a light guide plate, optical noise such as bright lines caused by light guided within glass 10 being specularly reflected at the end face 12 can be suppressed.

[0079] Glass 10 according to a seventh aspect of the present disclosure is glass 10 according to any one of the first to sixth aspects, wherein the end face 12 is preferably painted black. According to the present disclosure, by increasing the light absorptance of the end face 12, it is possible to suppress light reflection at the end face 12. As a result, when glass 10 is used as a light guide plate, it is possible to suppress optical noise such as bright lines caused by specular reflection at the end face 12 of light guided within glass 10.

[0080] Glass 10 according to an eighth aspect of the present disclosure is glass 10 according to any one of the first to seventh aspects, wherein the areas of main surfaces 11a, 11b are 40 cm ２ According to the present disclosure, it is possible to obtain glass 10 of a size suitable for application to a head-mounted display. Furthermore, since the area of ​​glass 10 does not become excessively large, variation in the shape of glass 10 can be easily and effectively suppressed.

[0081] Glass 10 according to a ninth aspect of the present disclosure is glass 10 according to any one of the first to eighth aspects, and preferably has a thickness t of 1.5 mm or less. According to the present disclosure, the greater the thickness t, the more likely shape errors are to occur, and therefore, by setting the thickness t within this range, glass 10 with high shape precision can be obtained.

[0082] Glass 10 according to a tenth aspect of the present disclosure is glass 10 according to any of the first to ninth aspects, and preferably has a rate of change of 200% or less and 70% or more relative to the average value of the radius of curvature R in curved portion 13. According to the present disclosure, high shape accuracy can be obtained, and therefore the optical properties of glass 10 can be effectively improved.

[0083] The glass manufacturing method according to the eleventh aspect of the present disclosure is a method for manufacturing glass 10 having a curved surface portion 13, which includes heating a glass substrate 30 (step S10), applying an external force to the heated glass substrate 30 to form a curved surface portion 13 having a curvature radius of 10,000 mm or less in at least a part of the periphery of the glass substrate 30 (step S14), and forming a refractive index n ｄThe present disclosure provides glass 10 having a refractive index of 1.77 or greater, an internal transmittance of 89% or greater for light with a wavelength of 460 nm at a thickness of 10 mm, and a thickness deviation of 1% or less of the maximum thickness. According to the present disclosure, glass 10 is obtained that has a high refractive index suitable for widening the viewing angle in head-mounted displays and a high transmittance that achieves low light loss suitable for image display. Furthermore, by keeping the thickness deviation to 1% or less of the maximum thickness, it is possible to suppress variations in thickness distribution. As a result, even when curved surface portions 13 are formed on glass 10 with a high refractive index, it is possible to suppress degradation of optical properties.

[0084] A method for manufacturing glass 10 according to a twelfth aspect of the present disclosure is the method for manufacturing glass 10 according to the eleventh aspect, wherein the temperature difference between the glass transition point Tg and the softening point of the glass mother plate 30 is preferably 150° C. or less. ｄ On the other hand, if the viscosity changes greatly with temperature, it becomes difficult to obtain shape accuracy. However, by suppressing the thickness deviation to 1% or less of the maximum thickness, it is possible to obtain a high refractive index n ｄ Even from this glass mother plate 30, glass 10 having high shape precision and uniformity that can suppress deterioration of optical properties can be obtained.

[0085] A manufacturing method of glass 10 according to a thirteenth aspect of the present disclosure is the manufacturing method of glass 10 according to the eleventh or twelfth aspect, and preferably, when heating the glass mother sheet 30 (step S10), the glass mother sheet 30 is placed in the forming mold 51 and the glass mother sheet 30 is heated together with the forming mold 51 by radiant heating from a heater 55 arranged around the forming mold 51. According to the present disclosure, compared to heating by contact heat transfer, radiant heating can improve the temperature uniformity of the forming mold 51, thereby effectively reducing temperature variations in the glass mother sheet 30 and the forming mold 51. As a result of the reduced temperature variations, viscosity variations in the glass mother sheet 30 are reduced, and therefore the shape precision and uniformity of the glass 10 can be effectively improved.

[0086] A manufacturing method of glass 10 according to a fourteenth aspect of the present disclosure is the manufacturing method of glass 10 according to the thirteenth aspect, and preferably monitors the temperature of forming mold 51 and stops heating when the temperature reaches a set temperature (step S12). According to the present disclosure, the temperature of forming mold 51 can be reliably set to the set temperature, thereby effectively suppressing temperature variations in forming mold 51 and the glass mother sheet 30 therein.

[0087] A manufacturing method of glass 10 according to a fifteenth aspect of the present disclosure is the manufacturing method of glass 10 according to the fourteenth aspect, wherein the forming mold 51 includes a first mold 52 and a second mold 53 into which the first mold 52 fits, and when heating is stopped (step S12), it is preferable that the temperature difference between the first mold 52 and the second mold 53 when the set temperature is reached is 60° C. or less. According to the present disclosure, by reducing the temperature difference between the first mold 52 and the second mold 53, it is possible to more effectively suppress temperature variation in the glass mother sheet 30.

[0088] A method for manufacturing glass 10 according to a sixteenth aspect of the present disclosure is the method for manufacturing glass 10 according to any one of the eleventh to fifteenth aspects, in which the glass mother sheet 30 is preferably heated at a temperature rise rate of 60° C. / min or less when heating the glass mother sheet 30 (step S10). According to the present disclosure, by lowering the temperature rise rate, it is possible to effectively suppress temperature variations in the forming die 51 and the glass mother sheet 30 therein.

[0089] A manufacturing method of glass 10 according to a seventeenth aspect of the present disclosure is a manufacturing method of glass 10 according to any one of the eleventh to sixteenth aspects, in which the reheat bending of the glass mother sheet 30 is preferably performed as a batch process using a batch-type forming device. According to the present disclosure, precise control of the forming temperature for each shot is possible, and high shape accuracy can be obtained.

[0090] A manufacturing method of glass 10 according to an eighteenth embodiment of the present disclosure is the manufacturing method of glass 10 according to the seventeenth embodiment, wherein the batch-type molding device includes a forming die 51 and a heater 55, temperature sensors (54a, 54b) are inserted in the forming die 51, and the temperature difference of the forming die 51 relative to the set temperature of the heater 55 during press molding is preferably ±3 degrees or less. According to the present disclosure, temperature variations in the forming die 51 and the glass mother sheet 30 can be suppressed more effectively.

[0091] Examples Next, examples will be described. Note that the embodiment may be modified as long as the effects of the invention are achieved. Table 1 shows the composition and physical properties of the glass substrate used in producing the glass of each example.

[0092]

[0093] Example 1 In Example 1, a glass substrate was prepared using the composition shown in "Glass Material X" in Table 1. The glass substrate had a flat plate shape with a thickness of 1.0 mm, a width of 34 mm, and a length of 65 mm.

[0094] A convex mold (first mold) and a concave mold (second mold) made of carbon were prepared, designed to be able to mold glass into a design shape having a uniaxially bent surface in the long side direction with a curvature radius of 150 mm and a bending depth of 5 mm, and a chamfered glass substrate was placed near the center of the molding surface of the concave mold.

[0095] The glass mother plate was heated, deformed, and cooled while the concave and convex molds on which the glass mother plate was placed were fixed to the lower and upper shafts, respectively, of a molding device (Shibaura Machine (formerly Toshiba Machine) Co., Ltd., glass element molding device: GMP-315V).

[0096] In the heating step, the set temperature was set to 710°C, and heating was stopped when the set temperature was reached for both the convex and concave molds. The temperature was raised from the starting temperature (25°C) to the set temperature (710°C) over 20 minutes. The temperature rise rate was controlled to a range of 50°C / min or less.

[0097] The concave mold was moved upward, and the convex mold was pressed with a maximum pressure of 0.5 kN. 30 seconds after the pressure reached the set value (0.5 kN), the pressure application was stopped. During this time, nitrogen gas was blown in at 20 L / min through the through-holes in the convex mold to ensure uniform molding of the glass sheet.

[0098] Next, it was gradually cooled to 100° C. over 28 minutes. Next, the concave mold was lowered and removed, and the glass mother plate was allowed to cool to room temperature, thereby obtaining a glass.

[0099] Example 2 In Example 2, the same glass substrate (glass material X) as in Example 1 was formed using a different forming method. In Example 2, glass was obtained by bending using a continuous forming apparatus (JM2000 manufactured by SHENZHEN HUANQIUTONGCHUANG MACHINERY CO., LTD.). The continuous forming apparatus had a rod heater built into each of the movable upper mold plate that held the upper surface of the convex mold (upper mold) and the lower mold plate that held the lower surface of the concave mold (lower mold). The heated upper and lower mold plates heated the convex and concave molds, respectively, by contact heat transfer. The glass substrate placed in the concave mold was heated by contact heat transfer through the contact points with the heated concave mold. The structures of the convex mold (upper mold) and the concave mold (lower mold) were the same as in Example 1.

[0100] The continuous molding apparatus is equipped with a chamber, and inside the chamber, from the inlet to the outlet, there are first to sixth preheating zones, first to third heating zones, first to third slow-cooling zones, and first to fourth water-cooling zones. Each zone is equipped with a stage that supports a convex mold (upper mold) and a concave mold (lower mold). The rod heater temperature and pressurizing pressure in each zone, as well as the total residence time in the chamber, are shown in Table 2 below.

[0101]

[0102] The upper heaters in the first to sixth preheating zones, the first to third heating zones, the first to third annealing zones, and the first to fourth water-cooling zones are configured to be raised and lowered by piston shafts, allowing the pressing mold to be pressed from above. In preparation for press molding, the chamber's lower and upper heaters are turned on to heat each zone and create an inert atmosphere. A conveying mechanism (not shown) then transports the pressing mold with the glass mother sheet set into the chamber and positions it in each zone for a predetermined time. First, the pressing mold is preheated in the first to sixth preheating zones to soften the glass mother sheet to a temperature suitable for press molding. Then, in the first to third heating zones, the pressure is increased to form the glass mother sheet into the desired shape. Then, in the first to third annealing zones, the pressing mold and the formed glass are annealed. Finally, in the first to fourth water-cooling zones, the glass is cooled to room temperature and removed from the chamber.

[0103] (Examples 3 and 4) In Example 3, glass was obtained in the same manner as in Example 1 except for the composition conditions of the glass mother plate and the molding temperature. In Example 3, the molding temperature was set to 610°C in accordance with the difference in the composition of the glass mother plate. The composition of the glass mother plate in Example 3 is shown in "Glass Material Y" in Table 1. The glass mother plate in Example 3 (Glass Material Y) has a refractive index n ｄ In Example 4, the same glass mother plate (glass material Y) as in Example 3 was molded at a molding temperature of 680° C. in the same manner as in Example 2 except for the molding temperature to obtain a glass.

[0104] (Examples 5 and 6) In Example 5, glass was obtained in the same manner as in Example 1 except for the composition conditions of the glass mother plate and the molding temperature. In Example 5, the molding temperature was set to 643°C in accordance with the difference in the composition of the glass mother plate. The composition of the glass mother plate in Example 5 is shown in "Glass Material A" in Table 1. The glass mother plate in Example 5 (Glass Material A) has a refractive index n ｄ Although the value was low, it was higher than that of the glass mother plate (glass material Y) of Example 3. In Example 6, the same glass mother plate (glass material A) as in Example 5 was molded at a molding temperature of 770° C. in the same manner as in Example 2 except for the molding temperature to obtain a glass.

[0105] (Examples 7 and 8) In Example 7, glass was obtained in the same manner as in Example 1 except for the composition conditions of the glass mother plate and the molding temperature. In Example 7, the molding temperature was set to 613°C in accordance with the difference in the composition of the glass mother plate. The composition of the glass mother plate in Example 7 is shown in "Glass Material B" in Table 1. The glass mother plate in Example 5 (Glass Material B) has a refractive index n ｄ Although the value was low, it was higher than that of the glass mother plate (glass material Y) of Example 3. In Example 8, the same glass mother plate (glass material B) as in Example 7 was molded at a molding temperature of 680° C. in the same manner as in Example 2 except for the molding temperature to obtain a glass.

[0106] (Examples 9 and 10) In Example 9, glass was obtained in the same manner as in Example 1 except for the composition conditions of the glass mother plate and the molding temperature. In Example 9, the molding temperature was set to 675°C in accordance with the difference in the composition of the glass mother plate. The composition of the glass mother plate in Example 9 is shown in "Glass Material C" in Table 1. The glass mother plate in Example 9 (Glass Material C) has a refractive index n ｄ Although the value was low, it was higher than that of the glass mother plate (glass material Y) of Example 3. In Example 10, the same glass mother plate (glass material C) as in Example 9 was molded at a molding temperature of 770° C. in the same manner as in Example 2 except for the molding temperature to obtain a glass.

[0107] (Measurement Items) Table 3 shows the molding conditions and measurement results for each measurement item for each example. For each of the glasses obtained in Examples 1 to 10, measurements of each measurement item shown in Table 3 were carried out as follows.

[0108] The thickness deviation of the glass was measured using a multicolor confocal laser displacement meter (CL-P030 manufactured by Keyence Corporation) by the method described in this embodiment. The rate of change in the radius of curvature R of the glass was measured using a multicolor confocal laser displacement meter (CL-P030 manufactured by Keyence Corporation) by the method described in this embodiment. The retardation of the glass was measured by irradiating light with a wavelength of 543 nm in the thickness direction using a WPA-200 manufactured by Photonic Lattice. The refractive index n of the glass ｄwas measured by spectroscopic ellipsometry (JA Woollam Co., Inc.; M-2000 DI). The wavefront aberration of the glass was measured by a laser interferometer (Zygo Verifire). The laser used was a He-Ne laser with a wavelength of 633 nm.

[0109]

[0110] (Measurement Results) The measurement results for each measurement item are shown in Table 3. The refractive index n ｄ The refractive index n of the glass (glass material Y) in Examples 3 and 4 was 1.96. ｄ The refractive index n of the glass (glass material A) in Examples 5 and 6 was 1.52. ｄ The refractive index n of the glass (glass material B) in Examples 7 and 8 was 1.9. ｄ The refractive index n of the glass (glass material C) of Examples 9 and 10 was 1.85. ｄ The value was 1.8. In Table 3, for the rate of change of the radius of curvature R, the ratio of the maximum measured value to the average value is shown under the heading (R > average value), and the ratio of the minimum measured value to the average value is shown under the heading (R < average value). The internal transmittance (wavelength 460 nm) of each of the glasses of Examples 1 to 10 was 89% or more when converted into a glass with a thickness of 10 mm.

[0111] (Evaluation) In Examples 1, 5, 7, and 9, the refractive index n ｄ Even when a curved surface portion with a radius of curvature of 10,000 mm or less is formed on glass having a refractive index of 1.77 or more and an internal transmittance of 89% or more, the thickness deviation is kept to 1% or less of the maximum thickness, so that even when a curved surface portion is formed on glass material X having a high refractive index, deterioration in optical properties can be suppressed. On the other hand, in Example 2, even when a curved surface portion is formed on glass material X having a high refractive index, the thickness deviation exceeds 1% of the maximum thickness, so deterioration in optical properties cannot be suppressed. A comparison of Example 2 with Examples 4, 6, 8, and 10 reveals that the refractive index n ｄIt can be seen that this has a significant effect on shape accuracy such as thickness deviation. Furthermore, a comparison of Example 1 with Examples 3, 5, 7, and 9 shows that shape accuracy such as thickness deviation is maintained despite the difference in high refractive index, and therefore the manufacturing method of the glass of this embodiment is suitable for glass materials with high refractive index. Note that in Examples 3 and 4, although the thickness deviation is kept to 1% or less of the maximum thickness, the refractive index n ｄ Since the refractive index is less than 1.77, desired optical properties cannot be obtained.

[0112] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0113] 10 Glass 11a, 11b Main surface 12 End surface 13 Curved surface portion 14 Flat portion 51 Forming mold 52 First mold 53 Second mold 55 Heater

Claims

1. Refractive index n ｄ A glass having an internal transmittance of 89% or more for light with a wavelength of 460 nm at a thickness of 10 mm, a curved portion having a radius of curvature of 10,000 mm or less in at least a part of a peripheral portion, and a thickness deviation of 1% or less of a maximum thickness.

2. Refractive index n ｄ 2. The glass of claim 1 , wherein the MnO sigma is 1.80 or greater.

3. The glass according to claim 1, which has a retardation of 40 nm / cm or less as measured by irradiating light with a wavelength of 543 nm in the thickness direction.

4. The glass according to claim 1, wherein the RMS value of the wavefront aberration of the main surface as measured by a laser interferometer is 0.7 λ or less.

5. The glass of claim 1, having one or more flat portions on the periphery of the main surface.

6. The glass according to any one of claims 1 to 5, wherein the surface roughness Ra of the end face is 5 nm or more.

7. The glass according to any one of claims 1 to 5, wherein the end faces are painted black.

8. The area of ​​the main surface is 40 cm ２ 6. The glass according to claim 1, wherein:

9. The glass according to any one of claims 1 to 5, having a thickness of 1.5 mm or less.

10. The glass according to any one of claims 1 to 5, wherein the rate of change of the radius of curvature at the curved surface portion with respect to the average value is 200% or less and 70% or more.

11. A method for manufacturing glass having a curved surface, comprising: heating a glass mother plate; applying an external force to the heated glass mother plate to form the curved surface having a radius of curvature of 10,000 mm or less on at least a part of the periphery of the glass mother plate; and ｄ a thickness deviation of 1% or less of the maximum thickness is obtained, the glass having a thickness of 10 mm and an internal transmittance of 89% or more for light with a wavelength of 460 nm.

12. The method for manufacturing glass according to claim 11, wherein the temperature difference between the glass transition point and the softening point of the glass substrate is 150° C. or less.

13. The method for producing glass according to claim 11, wherein, when the glass mother plate is heated, the glass mother plate is placed in a forming mold and the glass mother plate is heated together with the forming mold by radiant heating from a heater arranged around the forming mold.

14. The method for producing glass according to claim 13, further comprising monitoring the temperature of the mold and stopping heating based on the temperature reaching a set temperature.

15. The method for manufacturing glass according to claim 14, wherein the forming mold includes a first mold and a second mold into which the first mold fits, and when heating is stopped, the temperature difference between the first mold and the second mold when the set temperature is reached is 60°C or less.

16. The method for producing glass according to any one of claims 11 to 15, wherein the glass mother plate is heated at a temperature increase rate of 60°C / min or less.

17. The method for producing glass according to claim 11, wherein the glass mother sheet is formed by a batch-type forming device.

18. The method for producing glass according to claim 17, characterized in that the batch-type molding device includes a mold and a heater, a temperature sensor is inserted into the mold, and the temperature difference of the mold relative to the set temperature of the heater during press molding is within ±3 degrees.