Glass and optical member

Abstract

The present invention addresses the problem of appropriately transmitting light. In a glass (10), when: the outer peripheral edge of the largest circle, centered on a center (P0) of the glass (10) and being contained within the range of an outer peripheral edge (10C) of the glass (10), is defined as a reference circumference (A0); a circumference, 5 mm away from the reference circumference (A0) inward in the radial direction, is defined as a first circumference (A1); the circumference of a circle, centered on the center (P0) of the glass (10) and having a radius that is half the distance between the reference circumference (A0) and the center (P0) of the glass (10), is defined as a second circumference (A2); a point on the first circumference (A1) is defined as a first point (P1); and a point having the shortest distance from the first point (P1) among the points on the second circumference (A2) is defined as a second point (P2), the maximum value of retardation is 20 nm or less in a straight line section (S) connecting from the first point (P1) to the second point (P2) in a straight line, the retardation does not monotonically decrease or monotonically increase from the first point (P1) toward the second point (P2), and there is a position where the retardation has an extreme value between the first point (P1) and the second point (P2).

Description

Glass and optical components

[0001] This invention relates to glass and optical components.

[0002] Glass may exhibit different retardations depending on its position in the in-plane direction. For example, Patent Document 1 describes a glass-based article in which the maximum optical delay is 40 nm or less and the optical delay decreases towards the central region.

[0003] Patent No. 7405506

[0004] However, when using glass as an optical component, if the light delay is distributed such that it decreases toward the central region, as in Patent Document 1, uneven retardation may occur at each position, potentially preventing proper light transmission.

[0005] The present invention aims to provide glass and optical components that can appropriately transmit light.

[0006] The glass according to this disclosure is a glass having a first surface and a second surface, and when viewed from the thickness direction on the first surface, the reference circumference is defined as the outer edge of the largest circle that is centered at the center of the glass and falls within the range of the outer edge of the glass, the circumference of a circle 5 mm radially inward from the reference circumference is defined as the first circumference, the circumference of a circle centered at the center of the glass and having a radius of half the distance between the reference circumference and the center of the glass is defined as the second circumference, a point on the first circumference is defined as the first point, and among the points on the second circumference, the point that is closest to the first point is defined as the second point, in a straight line section connecting the first point and the second point, the maximum value of retardation is 20 nm or less, the retardation does not monotonically decrease or monotonically increase from the first point to the second point, and there is a position between the first point and the second point where the retardation reaches an extreme value.

[0007] According to the present invention, light can be transmitted appropriately.

[0008] Figure 1 is a schematic front view of the glass according to this embodiment. Figure 2-1 is a schematic plan view of the glass according to this embodiment. Figure 2-2 is a schematic plan view of glass according to another example. Figure 3 is a graph showing an example of the retardation distribution of the glass according to this embodiment. Figure 4 is a cross-sectional view of the glass according to this embodiment when it is made into a glass plate. Figure 5 is a graph showing the retardation distribution of each example. Figure 6 is a graph showing the retardation distribution of each example. Figure 7 is a graph showing the retardation distribution of each example. Figure 8 is a diagram showing the optical evaluation method.

[0009] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the present invention is not limited to these embodiments, and if there are multiple embodiments, they may be constructed by combining these embodiments. Furthermore, numerical values ​​include a range of rounding. Also, a numerical range represented by "~" means a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively, and the same meaning applies when "~" is used hereafter. Furthermore, the upper and lower limits shown in the numerical range can be combined as appropriate.

[0010] (Glass) Figure 1 is a schematic front view of the glass according to this embodiment, and Figure 2-1 is a schematic plan view of the glass according to this embodiment. As shown in Figure 1, the glass 10 according to this embodiment has a first surface 10A which is one of the main surfaces, and a second surface 10B which is the main surface opposite to the first surface 10A. In this embodiment, the glass 10 is a plate-shaped glass plate and is flat. However, the shape of the glass 10 is not limited to this, and it may be curved, or not limited to a plate shape, but may be arbitrary. Hereafter, the thickness direction of the glass 10 will be referred to as the Z direction. Hereafter, the axial direction will refer to the direction along the central axis passing through the center P0 of the glass 10 as viewed from the Z direction, the radial direction will refer to the radial direction with respect to this central axis, and the circumferential direction will refer to the circumferential direction with respect to this central axis.

[0011] As shown in Figure 2-1, the glass 10 has a wafer shape that is circular when viewed from the Z direction. However, the glass 10 is not limited to a wafer shape and may have any shape when viewed from the Z direction. For example, the glass 10 may have a polygonal shape such as a rectangle or an ellipse when viewed from the Z direction. Also, the glass 10 may have notches formed on its outer edge. Figure 2-2 is a schematic plan view of another example of glass. In the example in Figure 2-2, an example is shown where the glass 10 is rectangular when viewed from the Z direction.

[0012] In this embodiment, the glass 10 is used as an optical element. An optical element may be, for example, an element that transmits light or changes the state of light. In this case, the glass 10 itself may be used as a single optical element, or multiple glass elements may be cut from a single glass 10 and each glass element may be used as an optical element. More specifically, the glass 10 in this embodiment is used as a light guide plate. More specifically, the glass 10 is used as a light guide plate for a 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.

[0013] (Physical properties of glass) The physical properties of glass 10 will be described below.

[0014] (Retardation) Figure 3 is a graph showing an example of the retardation distribution of the glass according to this embodiment. The retardation of the glass 10 described below refers to the retardation value measured by irradiating the first surface 10A with light traveling in the Z direction with a wavelength of 543 nm. The retardation can be measured using a WPA-200 manufactured by Photonic Lattice.

[0015] As shown in Figure 2-1, when viewing the first surface 10A from the Z direction, the largest circle that fits within the range of the outer edge 10C of the glass 10, with the center P0 of the glass 10 as the center (the largest circle that does not extend beyond the outer edge 10C when viewed from the Z direction and is centered at the center P0), is defined as the reference circle, and the circumference of the reference circle (the outer edge of the reference circle) is defined as the reference circumference A0. In this embodiment, since the glass 10 is wafer-shaped (circular), as shown in Figure 2-1, the reference circumference A0 coincides with the outer edge 10C of the glass 10. On the other hand, for example, if the glass 10 is rectangular, as shown in Figure 2-2, the reference circumference A0 is the circumference of the inscribed circle of the rectangular outer edge 10C. Note that if a notch is formed on the periphery of the glass 10, the reference circle and reference circumference A0 may be defined as if there were no notch. Furthermore, when viewing the first surface 10A from the Z direction, the circumference of a circle centered at the center P0 of the glass 10 and located 5 mm radially inward from the reference circumference A0 is defined as the first circumference A1. Also, when viewing the first surface 10A from the Z direction, the circumference of a circle centered at the center P0 of the glass 10 and having a radius equal to half the distance between the reference circumference A0 and the center P0 of the glass 10 is defined as the second circumference. That is, for example, if the glass 10 is a circle with a diameter of 300 mm, the first circumference A1 will be the circumference of a concentric circle with a diameter of 290 mm, and the second circumference A2 will be the circumference of a concentric circle with a diameter of 150 mm.

[0016] Furthermore, let P1 be a point on the first circumference A1 on the first surface 10A. Then, let P2 be a point on the second circumference A2 on the first surface 10A that is the closest point to P1. In other words, when viewing the first surface 10A from the Z direction, P2 is a point between the center P0 and P1 on the straight line connecting the center P0 and P1 (the intersection of the straight line connecting the center P0 and P1 and the second circumference A2). In the example in Figure 2-1, four P1s and four corresponding P2s are shown, but the position of P1 is not limited to these and can be arbitrarily selected from any point on the first circumference A1.

[0017] (Retardation Distribution) Here, if we define the linear section S as the straight line connecting the first point P1 and the second point P2 on the first surface 10A (a straight line starting at the first point P1 and ending at the second point P2), then in the linear section S, the retardation of the glass 10 does not monotonically decrease or increase from the first point P1 to the second point P2 (it neither decreases nor increases monotonically). Also, in the linear section S, there is a position PM between the first point P1 and the second point P2 where the retardation of the glass 10 reaches an extreme value (maximum or minimum value). The retardation of the glass 10 in the linear section S is obtained by measuring the retardation at each position (each measurement point) that is 5 mm apart on the linear section S, radially inward from the first point P1 (towards the second point P2).

[0018] In a straight section S, monotonically decreasing retardation means that the retardation of the glass 10 at each position on the straight section S gradually decreases as you move radially inward (towards the second point P2), while monotonically increasing retardation means that the retardation of the glass 10 at each position on the straight section S gradually increases as you move radially inward. That is, in Figure 3, the horizontal axis is the distance radially inward from the reference circle A0, the vertical axis is the retardation value, and the polyline L is the line connecting the retardation values ​​of the glass 10 at each position on the straight section S. In this case, monotonically decreasing retardation means that the slope of the polyline L over the entire length of the straight section S is always negative from the reference circle A0 radially inward (i.e., there is no section where the slope is positive), while monotonically increasing retardation means that the slope of the polyline L over the entire length of the straight section S is always positive from the reference circle A0 radially inward (i.e., there is no section where the slope is negative). In other words, in this embodiment, the retardation of the glass 10 at each position on the straight section S is neither monotonically increasing nor monotonically decreasing. Therefore, as you move radially inward, it can be said that the retardation includes sections where it decreases (sections where the slope of the polyline L is negative) and sections where it increases (sections where the slope of the polyline L is positive).

[0019] Furthermore, the statement that there is a position PM between the first point P1 and the second point P2 where the retardation of the glass 10 reaches an extreme value means that there is at least one position PM between the first point P1 and the second point P2 on the linear section S where the retardation reaches a maximum or minimum value. The statement that there is a position PM where the retardation reaches a maximum value means that there is a section radially inward where the retardation of the glass 10 increases and then decreases (a section in which the broken line L has a maximum value), and the statement that there is a position PM where the retardation reaches a minimum value means that there is a section radially inward where the retardation of the glass 10 decreases and then increases (a section in which the broken line L has a minimum value). Figure 3 shows an example where there is a position PM where the retardation reaches a maximum value, but the retardation at position PM may also be a minimum value. Also, there may be one position PM where the retardation reaches an extreme value, or there may be multiple positions PM.

[0020] The position PM where retardation reaches its extreme value may be any position between the first point P1 and the second point P2 on the straight section S. For example, if a point on the straight section S located a predetermined distance radially outward (towards the first point P1) from the midpoint of the first point P1 and the second point P2 is designated as the first reference point, and a point on the straight section S located a predetermined distance radially inward (towards the second point P2) from the midpoint is designated as the second reference point, then it is preferable that position PM be located between these two reference points. The predetermined distance here (the distance from the midpoint to the first and second reference points) is preferably 25% or less of the total length of the straight section S, more preferably 15% or less, and even more preferably 5% or less. By having position PM located close to the midpoint in this way, the bias in the retardation distribution in the straight section S can be reduced, allowing light to be transmitted appropriately.

[0021] The glass 10 of this embodiment has such a retardation distribution, which reduces the bias in retardation in the linear section S and allows light to be transmitted appropriately. This suppresses, for example, image blurring when used as a light guide plate. The method for achieving the retardation distribution as in this embodiment is arbitrary, but it can be achieved, for example, by performing an annealing process during the manufacturing of the glass 10. That is, for example, when obtaining glass 10 by cooling molten glass, if it is simply cooled, the glass cools from the outside in, so the retardation distribution tends to increase or decrease monotonically. In contrast, by performing an annealing process, a retardation distribution like that of this embodiment can be achieved. The conditions for the annealing process in this case can be adjusted as appropriate.

[0022] (Retardation Value) The maximum retardation value of the glass 10 in the linear section S is 20 nm or less, preferably 0 nm to 15 nm, more preferably 0.1 nm to 13 nm, even more preferably 0.2 nm to 10 nm, still more preferably 0.3 nm to 5 nm, and most preferably 0.4 nm to 3 nm. When the maximum retardation value in the linear section S is within the above range, and the retardation distribution in the linear section S is as described above, the retardation in the linear section S can be made small and the bias can be reduced, so that light can be transmitted appropriately.

[0023] In the linear section S, the position where retardation is maximum can be any position, but it is preferably between the first point P1 and the second point P2, and more preferably between the first reference point and the second reference point. Furthermore, it is preferable that the position where retardation is maximum in the linear section S coincides with the position PM where the extreme value occurs; in other words, it is preferable that the retardation at position PM is the maximum value of retardation in the linear section S. By having the retardation maximum at such a position, the bias in the retardation distribution in the linear section S is reduced, and light can be transmitted appropriately.

[0024] The difference between the maximum retardation of the glass 10 in the straight section S and the minimum retardation of the glass 10 in the straight section S is preferably 10 nm or less, more preferably 0 nm to 7.0 nm, more preferably 0.1 nm to 5.0 nm, more preferably 0.2 nm to 3.0 nm, and even more preferably 0.3 nm to 2.0 nm. By having the difference between the maximum and minimum retardation values ​​within this range, the bias in the retardation distribution in the straight section S is reduced, allowing light to be transmitted appropriately. The position where retardation is minimized in the straight section S may be any position, for example, it may be the first point P1 or the second point P2.

[0025] Furthermore, within the linear section S, the section from a point 5 mm away from position PM along the linear section S toward the first point P1, to a point 5 mm away from position PM along the linear section S toward the second point P2, is defined as the extreme value section. In this case, the difference between the maximum retardation of the glass 10 in the extreme value section and the minimum retardation of the glass 10 in the extreme value section is preferably 10 nm or less, more preferably 0 nm to 7.0 nm, more preferably 0.1 nm to 5.0 nm, more preferably 0.2 nm to 3.0 nm, and even more preferably 0.3 nm to 2.0 nm. By having such a small bias in retardation near position PM where the extreme value occurs, light can be transmitted appropriately.

[0026] (Transmittance τ ４５０ ) Transmittance τ of glass 10 ４５０ The transmittance τ is preferably 85% or more, more preferably 90% or more, even more preferably 91% to 99%, and even more preferably 92% to 98%. ４５０ When it falls within this range, visible light can be transmitted appropriately. Note that the transmittance τ ４５０ This represents the internal transmittance for light with a wavelength of 450 nm at a thickness of 10 mm (converted to a thickness of 10 mm).

[0027] Incidentally, the internal transmittance is the transmittance through the interior of the glass 10. The internal transmittance can be obtained from the measured values of the external transmittances of two types with different plate thicknesses and the following formula (A). Note that the external transmittance means the transmittance including the surface reflection loss. In formula (A), τ is the internal transmittance of the glass when converted to a thickness of 10 mm, T1 and T2 are the external transmittances, and Δd is the difference in the thickness of the sample. The external transmittance can be measured using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation: U-4100) for a sample with both sides mirror-polished to a plate thickness of 10 mm.

[0028]

[0029] (Refractive index n ｄ ) The refractive index n of the glass 10 ｄ is preferably 1.80 or more, more preferably 1.85 or more and 2.20 or less, still more preferably 1.90 or more and 2.15 or less, and even more preferably 1.95 or more and 2.12 or less. When the refractive index n ｄ is within this range, it has a high refractive index for visible light and can impart appropriate optical properties to the glass 10. Incidentally, the refractive index n ｄ refers to the refractive index at the d-line of helium (wavelength 587.6 nm). The refractive index n ｄ can be measured by the V-block method.

[0030] (Specific gravity Sg) The specific gravity Sg of the glass 10 is preferably 6.3 g / cm ３ or less, more preferably 2.5 g / cm ３ or more and 5.6 g / cm ３ or less, still more preferably 3.0 g / cm ３ or more and 5.3 g / cm ３ or less, and even more preferably 3.5 g / cm ３ or more and 5.1 g / cm ３ or less. When the specific gravity is thus low, it becomes easier to handle the glass 10. Incidentally, the specific gravity Sg can be measured by the Archimedes method.

[0031] (Young's Modulus E) The Young's modulus E of the glass 10 is preferably 60 GPa or higher, more preferably 65 GPa or higher and 140 GPa or lower, and even more preferably 90 GPa or higher and 136 GPa or lower. Such a high Young's modulus allows for appropriate suppression of glass 10 breakage. The Young's modulus can be measured based on ultrasonic wave propagation using an OLYMPUS 38DL PLUS.

[0032] (Glass transition temperature Tg) The glass transition temperature Tg of glass 10 is preferably 400°C or more and 900°C or less, more preferably 400°C or more and 850°C or less, even more preferably 400°C or more and 800°C or less, and still more preferably 400°C or more and 750°C or less. The glass transition temperature can be measured according to the method specified in JIS R3103-3:2001 "Viscosity and viscosity fixed points of glass - Part 3: Method for measuring transition temperature by thermal expansion".

[0033] (Linear thermal expansion coefficient) The average thermal expansion coefficient CTE of the glass 10 at 100°C to 300°C is preferably 1.0 ppm / °C or more and 25 ppm / °C or less, more preferably 2.0 ppm / °C or more and 20 ppm / °C or less, more preferably 3.0 ppm / °C or more and 15 ppm / °C or less, and even more preferably 4.0 ppm / °C or more and 10 ppm / °C or less. By having the average thermal expansion coefficient CTE within this range, the glass 10 can be made to have low thermal expansion, thereby suppressing breakage. The average thermal expansion coefficient CTE can be measured in accordance with the standard for measuring thermal expansion, DIN-51045-1. Specifically, the sample may be measured using a NETZSCH dilatometer (DIL 402 Expedis) in the range of 30°C to 300°C, and the average thermal expansion coefficient in the range of 100°C to 300°C may be used as the average thermal expansion coefficient CTE.

[0034] (Glass Form) The glass 10 according to this embodiment is preferably optical glass, and preferably a glass plate with a thickness of 0.01 mm or more and 2.0 mm or less. If the thickness is 0.01 mm or more, breakage during handling and processing of the glass 10 can be suppressed. Also, deflection due to the weight of the glass 10 can be suppressed. This thickness is more preferably 0.1 mm or more, even more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. On the other hand, if the thickness is 2.0 mm or less, the optical element using the glass 10 can be made lighter. This thickness is more preferably 1.5 mm or less, even more preferably 1.0 mm or less, and even more preferably 0.8 mm or less. Note that the upper and lower limits in this embodiment can be combined as appropriate. The thickness here refers to the length in the Z direction between the first surface 10A and the second surface 10B.

[0035] The diameter of the glass 10 as viewed from the Z direction is preferably 4 inches or more (101.6 mm or more), more preferably 6 inches or more and 12 inches or less (152.4 mm or more and 304.8 mm or less), and even more preferably 8 inches or more and 10 inches or less (203.2 mm or more and 254.0 mm or less). By setting the retardation of the relatively large glass 10 within the above range, even when multiple glass components are cut from the glass 10 to form optical components, light can be appropriately transmitted to each optical component. Note that if the glass 10 is circular (wafer shape), the diameter of the glass 10 refers to the diameter of the glass 10 itself. On the other hand, if the glass 10 is not circular, the diameter of a circle with the same area as the area of ​​the glass 10 as viewed from the Z direction may be used as the diameter of the glass 10.

[0036] In the case where the glass 10 in this embodiment is a glass plate, the area of ​​the main surface is 8 cm². ２ The above is preferable. ２ If the area is larger than this, a large number of optical elements can be arranged, improving productivity. This area is more preferably 30 cm². ２ The above, and more preferably 170 cm ２ The above, and more preferably 300 cm ２The above is true, and is particularly preferably 1000 cm ２ That's all. On the other hand, the area is 6500 cm². ２ The following conditions make handling the glass plate easier and reduce breakage during handling and processing. This area is more preferably 4500 cm². ２ The following, and more preferably 4000 cm ２ The following, and more preferably 3000 cm ２ The following, and particularly preferably 2000 cm ２ The following applies:

[0037] Furthermore, the Total Thickness Variation (TTV) of the glass 10 is preferably 1 μm or less, more preferably 0 μm or more and 0.8 μm or less, and even more preferably 0.1 μm or more and 0.6 μm or less. When the thickness variation TTV is within this range, the thickness of the glass 10 becomes nearly uniform, and light can be transmitted appropriately. Note that the TTV variation refers to the thickness variation for each position (coordinate) on a plane along the first surface 10A of the glass 10. For example, the thickness at each position (coordinate) on the plane along the first surface 10A can be calculated, and the difference between the maximum and minimum values ​​of the thickness at each position may be used as the TTV variation.

[0038] In the case where the glass 10 according to this embodiment is a glass plate, the main surface is 25 cm ２ The LTV (Local Thickness Variation) in this material is preferably 1 μm or less. Having a flatness within this range allows for the formation of nanostructures of a desired shape on the main surface using imprint technology, etc., and enables the acquisition of desired light-guiding characteristics. In particular, it prevents ghosting and distortion caused by differences in optical path length in the light guide. The LTV is more preferably 0.8 μm or less, even more preferably 0.6 μm or less, and particularly preferably 0.5 μm or less.

[0039] When the glass 10 according to this embodiment is a circular glass plate with a diameter of 8 inches, the curvature is preferably 50 μm or less. If the curvature of this glass 10 is 50 μm or less, a nanostructure of the desired shape can be formed on the main surface using imprint technology or the like, and the desired light-guiding properties can be obtained. When trying to obtain multiple light guides, stable quality can be obtained. The curvature of this glass 10 is more preferably 40 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less.

[0040] Furthermore, when the glass 10 according to this embodiment is a circular glass plate with a diameter of 6 inches, the curvature is preferably 30 μm or less. If the curvature of this glass 10 is 30 μm or less, a nanostructure of the desired shape can be formed on the main surface using imprint technology or the like, and the desired light-guiding properties can be obtained. When trying to obtain multiple light guides, stable quality can be obtained. The curvature of this glass 10 is more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less.

[0041] Furthermore, when the glass 10 according to this embodiment is a square glass plate with sides of 6 inches, the warp is preferably 100 μm or less. If the warp of this glass 10 is 100 μm or less, a nanostructure of the desired shape can be formed on the main surface using imprint technology or the like, and the desired light-guiding properties can be obtained. When trying to obtain multiple light guides, stable quality can be obtained. The warp of this glass 10 is more preferably 70 μm or less, even more preferably 50 μm or less, even more preferably 35 μm or less, and particularly preferably 20 μm or less.

[0042] Figure 4 is a cross-sectional view of the glass according to this embodiment when it is a glass plate. "Warping" is the difference C between the maximum value B and the minimum value A of the vertical distance between the reference line G1D of the glass plate G1 and the center line G1C of the glass plate G1, in any cross section that passes through the center of the main surface G1F of the glass plate G1 and is perpendicular to the main surface G1F of the glass plate G1.

[0043] The intersection line between the aforementioned orthogonal cross-sections and the main surface G1F of the glass plate G1 is defined as the bottom line G1A. The intersection line between the aforementioned orthogonal cross-sections and another main surface G1G of the glass plate G1 is defined as the top line G1B. Here, the center line G1C is the line connecting the centers of the glass plate G1 in the thickness direction. The center line G1C is calculated by finding the midpoint between the bottom line G1A and the top line G1B with respect to the laser irradiation direction, which will be described later.

[0044] The reference line G1D is determined as follows: First, the base line G1A is calculated using a measurement method that cancels out the effect of the self-weight. From this base line G1A, a straight line is determined by the least squares method. The determined straight line is the reference line G1D. A known method is used as the measurement method that cancels out the effect of the self-weight.

[0045] For example, the main surface G1F of a glass plate G1 is supported at three points, and a laser is shone onto the glass plate G1 using a laser displacement meter to measure the height of the main surface G1F and the other main surfaces G1G of the glass plate G1 from an arbitrary reference plane.

[0046] Next, the glass plate G1 is inverted, and three points on the other main surface G1G opposite to the three points supporting one main surface G1F are supported. The heights of the main surface G1F and the other main surface G1G of the glass plate G1 are then measured from an arbitrary reference plane. The effect of self-weight is canceled out by calculating the average of the heights of each measurement point before and after inversion. For example, before inversion, the height of the main surface G1F is measured as described above. After inverting the glass plate G1, the height of the other main surface G1G is measured at the positions corresponding to the measurement points of the main surface G1F. Similarly, before inversion, the height of the other main surface G1G is measured. After inverting the glass plate G1, the height of the main surface G1F is measured at the positions corresponding to the measurement points of the other main surface G1G. Warpage is measured, for example, by a laser displacement meter.

[0047] Furthermore, in the glass 10 according to this embodiment, the arithmetic mean roughness Ra of at least one (preferably both) of the first surface 10A and the second surface 10B is preferably 2.0 nm or less. Having Ra in this range allows for the formation of nanostructures of a desired shape on the main surface using imprint technology or the like, and enables the acquisition of desired light-guiding properties. In particular, diffuse reflection at the interface is suppressed in the light guide, preventing ghosting and distortion. This Ra is more preferably 1.7 nm or less, even more preferably 1.4 nm or less, even more preferably 1.2 nm or less, and particularly preferably 1.0 nm or less. Here, the arithmetic mean roughness Ra is the arithmetic mean roughness as defined in JIS B0601 (2001). In this specification, it is the value measured using an atomic force microscope (AFM) over a 10 μm × 10 μm area.

[0048] (Composition) The composition of glass 10 may be arbitrary, but preferred compositions for glass 10 will be described below.

[0049] Glass 10 is Bi based on oxides. ２ O ３ TeO ２ Nb ２ O ５ La ２ O ３ , TiO ２ It is preferable to include at least one selected from the group. This allows for a high refractive index while appropriately transmitting visible light.

[0050] Glass 10 is Cr on an oxide basis ２ O ３ NiO, Fe ２ O ３ , and HfO ２ The total content of Pt is preferably 0.1% or less by mass, more preferably 0.07% or less, even more preferably 0.05% or less, and still more preferably 0.03% or less. This allows for appropriate transmission of visible light.

[0051] (SiO ２ ) Glass 10 is SiO ２ It is preferable that it contains SiO. The glass 10 is expressed in mol% based on oxides. ２The content of is preferably 0% to 60%, more preferably 0.4% to 30%, and even more preferably 8.0% to 23%. ２ By having the content within this range, the transmittance to visible light can be increased.

[0052] (B ２ O ３ ) Glass 10 is B ２ O ３ It is preferable that it contains. Glass 10 is expressed in mol% based on oxide, B ２ O ３ The content of is preferably 0% to 30%, more preferably 1.0% to 25%, and even more preferably 3.0% to 20%. ２ O ３ By keeping the content within this range, a high refractive index can be appropriately achieved.

[0053] (Al ２ O ３ ) Glass 10 is Al ２ O ３ It may contain, but does not have to contain (i.e., the content may be 0%). Glass 10 is expressed in molar percentage on an oxide basis, Al ２ O ３ The content of is preferably 0% to 20%, more preferably 0% to 10%, and even more preferably 0% to 5.0%. ２ O ３ By having the content within this range, the transmittance to visible light can be increased.

[0054] (P ２ O ５ ) Glass 10 is P ２ O ５ It is preferable that it contains P. Glass 10 is expressed in mol% based on oxides. ２ O ５ The content is preferably 0% to 30%, more preferably 0.5% to 28%, and even more preferably 15% to 26%. ２ O ５ By having the content within this range, the transmittance to visible light can be increased.

[0055] (CaO) Glass 10 preferably contains CaO. The CaO content of glass 10, expressed in molar percentage based on oxides, is preferably 0% to 15%, more preferably 0.1% to 8.0%, and even more preferably 1.0% to 4.0%. A CaO content within this range helps to suppress a decrease in refractive index.

[0056] (SrO) Glass 10 preferably contains SrO. The SrO content of glass 10, expressed in molar percentage based on oxides, is preferably 0% to 15%, more preferably 0.1% to 8.0%, and even more preferably 1.0% to 4.0%. This range of SrO content helps to suppress a decrease in refractive index.

[0057] (BaO) Glass 10 preferably contains BaO. The BaO content of glass 10, expressed in molar percentage based on oxide, is preferably 0% to 20%, more preferably 0.1% to 15%, and even more preferably 1.0% to 13%. A BaO content within this range helps to suppress a decrease in refractive index.

[0058] (ZrO ２ ) Glass 10 is ZrO ２ It is preferable that it contains ZrO ２ The content of ZrO is preferably 0% to 15%, more preferably 0.1% to 10%, and even more preferably 1.0% to 8.0%. ２ By having the content within this range, the transmittance to visible light can be increased.

[0059] (Nb ２ O ５ ) Glass 10 is Nb ２ O ５ It is preferable that it contains Nb. Glass 10 is expressed in mole percent based on oxide. ２ O ５ The content of Nb is preferably 0% to 35%, more preferably 1.0% to 30%, and even more preferably 2.5% to 20%. ２ O ５By having the content within this range, it is possible to suppress a decrease in the refractive index.

[0060] (Li ２ O) Glass 10 preferably contains Li ２ O. In terms of mol% based on oxides, the content of Li ２ O is preferably 0% or more and 20% or less, more preferably 0.1% or more and 10% or less, and even more preferably 1.0% or more and 5.0% or less. By having the content of Li ２ O within this range, it is possible to suppress a decrease in the refractive index.

[0061] (Na ２ O) Glass 10 preferably contains Na ２ O. In terms of mol% based on oxides, the content of Na ２ O is preferably 0% or more and 15% or less, more preferably 0.1% or more and 8.0% or less, and even more preferably 1.0% or more and 6.0% or less. By having the content of Na ２ O within this range, it is possible to suppress a decrease in the refractive index.

[0062] (K ２ O) Glass 10 preferably contains K ２ O. In terms of mol% based on oxides, the content of K ２ O is preferably 0% or more and 15% or less, more preferably 0.1% or more and 10% or less, and even more preferably 1.0% or more and 5.0% or less. By having the content of K ２ O within this range, it is possible to suppress a decrease in the refractive index.

[0063] (La ２ O ３ ) Glass 10 preferably contains La ２ O ３ . In terms of mol% based on oxides, the content of La ２ O ３ is preferably 0% or more and 30% or less, more preferably 5.0% or more and 27% or less, and even more preferably 9.0 or more and 25% or less. By having the content of La<000010>'O<'000'0101> within this range, it is possible to suppress a decrease in the refractive index.

[0064] (TiO ２ ) Glass 10 is TiO ２ It is preferable that it contains TiO. ２ The content of TiO is preferably 0% to 45%, more preferably 12% to 40%, and even more preferably 20% to 35%. ２ By keeping the content within this range, the decrease in refractive index can be suppressed.

[0065] (WO ３ ) Glass 10 is WO ３ It is preferable that it contains. Glass 10 is expressed in molar percentage based on oxide, WO ３ The content is preferably 0% to 20%, more preferably 0.01% to 10%, and even more preferably 0.10% to 5.0%. ３ By keeping the content within this range, the decrease in refractive index can be suppressed.

[0066] (ZnO) Glass 10 preferably contains ZnO. The ZnO content of glass 10, expressed in mole percent based on oxide, is preferably 0% to 25%, more preferably 0.2% to 10%, and even more preferably 1.0% to 5.0%. A ZnO content within this range helps to suppress a decrease in refractive index.

[0067] (Method for manufacturing glass) Glass 10 may be manufactured by any method, but for example, it may be manufactured by the following method. First, raw materials such as silica sand and soda ash, which are the raw materials for the compounds contained in glass 10, are heated to a predetermined temperature (for example, 1500°C to 1600°C) and melted. Then, after clarifying the molten raw material (glass), a molding process is carried out to form it into a plate shape. Then, a slow cooling process is carried out on the glass formed in the molding process to manufacture glass 10. It is also preferable to perform the annealing treatment described above between the molding process and the slow cooling process. The method for manufacturing glass 10 is not limited to the above and may be arbitrary. For example, the slow cooling process is not essential. Furthermore, various methods can be used for the molding process when manufacturing glass 10, such as the molten casting method, the down-draw method (for example, the overflow down-draw method, the slot-down method and the redraw method), the float method, the roll-out method and the press method.

[0068] (Effects) As described above, the glass 10 according to the first aspect of this disclosure has a first surface 10A and a second surface 10B. When viewed from the thickness direction (Z direction) on the first surface 10A, the outer circumference of the largest circle that is centered at the center P0 of the glass 10 and fits within the range of the outer circumference 10C of the glass 10 is defined as the reference circumference A0, the circumference of the first circumference A1 is 5 mm radially inward from the reference circumference A0, and the radius is half the distance between the reference circumference A0 and the center P0 of the glass 10, with the center P0 of the glass 10 as the center. When the circumference of a circle is defined as the second circumference A2, a point on the first circumference A1 is defined as the first point P1, and the point on the second circumference A2 that is closest to the first point P1 is defined as the second point P2, in the straight-line section S connecting the first point P1 to the second point P2, the maximum retardation is 20 nm or less, the retardation does not monotonically decrease or increase from the first point P1 to the second point P2, and there is a position between the first point P1 and the second point P2 where the retardation reaches an extreme value. According to this disclosure, the retardation distribution in the straight-line section S is as described above, and the maximum retardation in the straight-line section S is small as described above, so that the retardation in the straight-line section S is small and the bias can be reduced, so that light can be transmitted appropriately.

[0069] The glass 10 according to the second aspect of this disclosure is the same as the glass 10 according to the first aspect, wherein the difference between the maximum and minimum retardation values ​​in a straight section S is 10 nm or less. This reduces the bias in retardation in the straight section S, allowing light to be transmitted appropriately.

[0070] The glass 10 according to the third aspect of this disclosure is the glass 10 according to the first or second aspect, and has a thickness of 1 mm or less. According to this disclosure, light can be transmitted appropriately.

[0071] The glass 10 according to the fourth aspect of this disclosure is the glass 10 according to any of the first to third aspects, wherein the retardation at position PM where the retardation reaches an extreme value in the straight section S is the maximum value of the retardation in the straight section S. According to this disclosure, the bias in retardation in the straight section S can be reduced, so that light can be transmitted appropriately.

[0072] The glass 10 according to the fifth aspect of this disclosure is the glass 10 according to any of the first to fourth aspects, wherein in a linear section S, the difference between the maximum and minimum values ​​of retardation is 10 nm or less in the section from a position 5 mm away from the position PM where retardation reaches its extreme value toward the first point P1 along the linear section S to a position 5 mm away from the position PM where retardation reaches its extreme value toward the second point P2 along the linear section S. According to this disclosure, the bias of retardation near position PM can be reduced, so that light can be transmitted appropriately.

[0073] The glass 10 according to the sixth aspect of this disclosure is the glass 10 according to any of the first to fifth aspects, wherein the glass 10 is wafer-shaped and has a diameter of 4 inches or more. According to this disclosure, the retardation bias in the linear section S can be reduced, so that light can be transmitted appropriately.

[0074] The glass 10 according to the seventh aspect of this disclosure is the glass 10 according to any of the first to sixth aspects, wherein the plate thickness deviation TTV is 1 μm or less. According to this disclosure, by making the retardation distribution as described above, the bias in the stress distribution can be reduced, and the non-uniformity of the polishing rate can be suppressed, so as a result the plate thickness deviation TTV can be reduced. This allows light to be transmitted appropriately.

[0075] The glass 10 according to the eighth aspect of this disclosure is the glass 10 according to any of the first to seventh aspects, wherein the arithmetic mean roughness Ra of at least one of the first surface 10A and the second surface 10B is 2.0 nm or less. According to this disclosure, light can be transmitted appropriately.

[0076] The glass 10 according to the ninth aspect of this disclosure is the glass 10 according to any of the first to eighth aspects, and has a refractive index of 1.80 or higher. This allows it to be used appropriately as an optical component.

[0077] The glass 10 according to the tenth aspect of this disclosure is the glass 10 according to any of the first to ninth aspects, and has a Young's modulus of 60 GPa or more. This makes it possible to suppress breakage of the glass 10.

[0078] The glass 10 according to the eleventh aspect of this disclosure is the glass 10 according to any of the first to tenth aspects, wherein the internal transmittance for light with a wavelength of 450 nm at a thickness of 10 mm is 90% or more. This makes it suitable for use as an optical component.

[0079] The glass 10 according to the twelfth aspect of this disclosure is the glass 10 according to any of the first to eleventh aspects, wherein the glass transition temperature Tg is 400°C or more and 900°C or less, and the average thermal expansion coefficient CTE at 100°C to 300°C is 1.0 ppm / °C or more and 25 ppm / °C or less. This makes it suitable for use as an optical component.

[0080] The glass 10 according to the 13th aspect of this disclosure is the glass 10 according to any of the 1st to 12th aspects, wherein the oxide-based mol% expression is SiO ２ : 0% to 60%, B ２ O ３:0%~30%, Al ２ O ３ : 0% to 20%, P ２ O ５ :0%~30% CaO:0%~15%, SrO:0%~15% BaO:0%~20% ZrO ２ : 0% to 15% Nb ２ O ５ : 0% to 35% Li ２ O: 0% to 20% Na ２ O: 0% to 15% K ２ O: 0% to 15%, La ２ O ３ :0%~30% TiO ２ : 0% to 45% WO ３ It contains 0% to 20% of ZnO and 0% to 25% of ZnO. This allows it to be used appropriately as an optical component.

[0081] An optical member according to a fourteenth aspect of this disclosure has a glass 10 according to any of the first to thirteenth aspects. According to this disclosure, light can be transmitted appropriately.

[0082] (Examples) Next, examples will be described. Table 1 is a table showing the composition of the glass, and Table 2 is a table showing the retardation distribution of the glass in each example. Figures 5 to 7 are graphs showing the retardation distribution of each example. The embodiments may be modified as long as the effects of the invention are achieved.

[0083]

[0084] Glass materials A, B, and C with the compositions shown in Table 1 were prepared. The specific gravity and refractive index n of each glass material were also determined. ｄ , Young's modulus, internal transmittance (transmittance τ ４５０ The glass transition temperature was measured, and the values ​​are shown in Table 1. Each physical property was measured using the method described in this embodiment.

[0085] (Example 1) In Example 1, when manufacturing glass material A, the glass was heated to the glass transition temperature + 15°C at a rate of approximately 10°C / min, then maintained at that temperature for approximately 2 hours, and then cooled to room temperature at a rate of approximately -0.8°C / min. Annealing treatment was performed under these conditions, and both sides were polished to obtain a circular piece of glass with a diameter of 300 mm and a thickness of 0.5 mm. For the glass of Example 1, retardation was measured at each position at 5 mm intervals along a straight section from the first point P1 to the second point P2, 5 mm radially inward from the outer edge (reference circumference A0), using the method described in this embodiment. The retardation value at each position, the maximum retardation value in the straight section, the minimum retardation value in the straight section, and the difference between the maximum and minimum retardation values ​​in the straight section are shown in Table 1. Also, as shown in Table 1, the glass thickness deviation TTV was measured using the method described in this embodiment. The retardation distribution at each position is shown in Figure 5.

[0086] (Examples 2-13) In Examples 2-13, circular glass pieces of the size shown in Table 1 were obtained using the glass materials shown in Table 2. In Examples 2-13, retardation and plate thickness deviation TTV were also measured. The measurement results are shown in Table 2. The retardation distribution at each position is shown in Figures 5-7. The annealing conditions in Example 2-12 were almost the same as in Example 1, and in Example 13, the annealing treatment was performed by heating the glass to its glass transition temperature at a rate of approximately 10°C / min, maintaining the temperature for approximately 1 hour, and then cooling it to room temperature at a rate of approximately -1°C / min.

[0087] (Evaluation) Figure 8 shows the optical evaluation method. Optical evaluation was performed on the glass of each example. As shown in Figure 8, for the optical evaluation, prisms T1 and T2 were placed on the surface of the glass 10, and a stripe-shaped image was incident on the glass 10 using prism T1 at an arbitrary location. The stripe shape was then observed using prism T2 at a position 20 mm away from the incident position. Prisms T1 and T2 are triangular prism-shaped glass members. When observing the stripe shape from prism T2, if no deformation of the image was recognized, it was marked as ○ (pass), and if distortion of the image was recognized, it was marked as × (fail). Examples 1 to 12, which are embodiments, did not show any deformation of the observed stripe-shaped image, so the optical evaluation was passed, indicating that light can be transmitted appropriately. On the other hand, in the comparative example Example 13, the observed stripe-shaped image was distorted, so the optical evaluation was failed, indicating that light cannot be transmitted appropriately.

[0088] Although embodiments of the present invention have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned 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 embodiments described above.

[0089] 10 Glass 10A First surface 10B Second surface A0 Reference circumference A1 First circumference A2 Second circumference P0 Center P1 First point P2 Second point

Claims

1. A glass having a first surface and a second surface, wherein, when viewed from the thickness direction on the first surface, the reference circumference is defined as the outer edge of the largest circle centered at the center of the glass and contained within the range of the outer edge of the glass, the circumference of a circle 5 mm radially inward from the reference circumference is defined as the first circumference, the circumference of a circle centered at the center of the glass and having a radius of half the distance between the reference circumference and the center of the glass is defined as the second circumference, a point on the first circumference is defined as the first point, and among the points on the second circumference, the point closest to the first point is defined as the second point, and in the straight-line section connecting the first point and the second point, the maximum value of retardation is 20 nm or less, the retardation does not monotonically decrease or monotonically increase from the first point to the second point, and there is a position between the first point and the second point where the retardation reaches an extreme value.

2. The glass according to claim 1, wherein in the straight section, the difference between the maximum and minimum values ​​of retardation is 10 nm or less.

3. The glass according to claim 1, wherein the thickness is 1 mm or less.

4. The glass according to claim 1, wherein the retardation at the position where the retardation reaches an extreme value in the straight section is the maximum value of the retardation in the straight section.

5. The glass according to claim 1, wherein in the linear section, the difference between the maximum and minimum values ​​of retardation is 10 nm or less in the section from a position 5 mm away from the position where retardation reaches its extreme value toward the first point along the linear section, to a position 5 mm away from the position where retardation reaches its extreme value toward the second point along the linear section.

6. The glass according to claim 1, wherein the glass is wafer-shaped and has a diameter of 4 inches or more.

7. The glass according to claim 1, wherein the plate thickness deviation TTV is 1 μm or less.

8. The glass according to claim 1, wherein the arithmetic mean roughness Ra of at least one of the first surface and the second surface is 2.0 nm or less.

9. The glass according to claim 1, wherein the refractive index is 1.80 or higher.

10. The glass according to claim 1, wherein the Young's modulus is 60 GPa or higher.

11. The glass according to claim 1, wherein the internal transmittance for light with a wavelength of 450 nm at a thickness of 10 mm is 90% or more.

12. The glass according to claim 1, wherein the glass transition temperature Tg is 400°C or higher and 900°C or lower, and the average thermal expansion coefficient CTE at 100°C to 300°C is 1.0 ppm / °C or higher and 25 ppm / °C or lower.

13. In terms of molar percentage based on oxides, SiO ２ , ５ , ２ , ３ , ２ , ２ , ３ , ２ , ３ , ２ , ２ , ５ , ２ : 0% to 60%, B ２ O ３ : 0% to 30%, Al ２ O ３ : 0% to 20%, P ２ O ５ : 0% to 30% CaO: 0% to 15%, SrO: 0% to 15% BaO: 0% to 20% ZrO ２ : 0% to 15%, Nb ２ O ５ : 0% to 35%, Li ２ O: 0% to 20%, Na ２ O: 0% to 15%, K ２ O: 0% to 15%, La ２ O ３ : 0% to 30%, TiO ２ : 0% to 45%, WO ３ : 0% to 20%, ZnO: 0% to 25%, the glass according to claim 1.

14. An optical member having the glass according to any one of claims 1 to 13.

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