Optical element and glass paste

Abstract

To provide a technique capable of reducing the pigment concentration and film thickness of a light shielding film for obtaining desired transmittance.SOLUTION: The optical element includes a transparent glass body and a light shielding film provided inside the transparent glass body. At least a part of the light-shielding film includes a glass substrate and a pigment dispersed in the glass substrate. The pigments have a mean particle size of 150nm or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an optical element and a glass paste. [Background technology]

[0002] The optical unit described in Patent Document 1 includes a transparent first substrate, a transparent second substrate, and an aperture formed of black resin that fills the area around the convex portion between the first and second substrates. The first and second substrates are transparent glass substrates or transparent resin substrates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 176704 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, an optical element is constructed using a transparent resin substrate and black resin, or a transparent glass substrate and black resin. If the substrate is a resin substrate, the optical properties change significantly with temperature changes. Therefore, it is preferable that the substrate is a glass substrate. However, when an optical element is constructed using a glass substrate and black resin, the absolute value of the difference in average linear expansion coefficient between the glass and the resin is large, and the durability of the optical element against temperature changes is low.

[0005] The optical element preferably comprises a transparent glass body and a glass light-shielding film disposed inside the transparent glass body. By including glass in the light-shielding film, the difference in the average linear expansion coefficient between the transparent glass body and the light-shielding film can be reduced, improving the durability of the optical element against temperature changes. The light-shielding film may be composed of only black glass, or may be composed of transparent glass and a pigment. The pigment is dispersed in the transparent glass.

[0006] When a light-shielding film is made only of black glass, the coloring components are contained in the glass as metal ions. Unlike pigments, metal ions dissolve in glass. There is an upper limit to their solubility. Therefore, in order to reduce the parallel light transmittance of a light-shielding film made only of black glass, the film thickness must be increased. If the film thickness is too large, the transmitted wavefront aberration will increase.

[0007] When the light-blocking film is made of black glass only, the size of the metal ions that make up the coloring component is sufficiently small compared to the wavelength of light. Furthermore, unlike pigments, the metal ions are dissolved in the glass, and there are no discontinuous refractive index surfaces inside the black glass. Therefore, there is almost no scattering of light in the black glass.

[0008] When the light-shielding film is composed of transparent glass and a pigment, the transparent glass and the pigment exist separately, so the pigment concentration can be increased within the range that allows the glass powder to be fired. However, if the pigment concentration is too high, the bonding strength between the light-shielding film and the transparent glass will be weak, and the shear strength of the optical element will be weakened.

[0009] The pigment used is an inorganic oxide, such as a composite oxide of copper and chromium. There is a large difference in refractive index between inorganic oxides and glass. Therefore, when a light-shielding film is made of transparent glass and a pigment, light scattering occurs at the interface of discontinuity in refractive index, unlike when the light-shielding film is made of only black glass.

[0010] One embodiment of the present disclosure provides a technique that can reduce the pigment concentration and film thickness of a light-shielding film in order to obtain a desired parallel light transmittance. [Means for solving the problem]

[0011] An optical element according to an embodiment of the present disclosure includes a transparent glass body and a light-shielding film disposed inside the transparent glass body. At least a portion of the light-shielding film includes a glass substrate and a pigment dispersed in the glass substrate. The pigment has an average particle size of 150 nm or greater. [Effects of the Invention]

[0012] According to one embodiment of the present disclosure, the pigment concentration and film thickness of the light-shielding film can be reduced to obtain a desired parallel light transmittance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1A is a plan view of an optical element according to an embodiment, and FIG. 1B is a cross-sectional view of the optical element according to an embodiment. [Figure 2] FIG. 2(A) is a cross-sectional view showing an example of a tapered portion, and FIG. 2(B) shows an example of a change in parallel light transmittance in the tapered portion. [Figure 3] FIG. 3 is a diagram showing an example of the relationship between Tt, Tp, and Td. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between the thickness of the light-shielding film and the transmitted wavefront aberration. [Figure 5] FIG. 5 is a flowchart illustrating a manufacturing method according to one embodiment. [Figure 6] FIG. 6(A) is a cross-sectional view showing an example of S101, FIG. 6(B) is a cross-sectional view showing an example of S102, FIG. 6(C) is a cross-sectional view showing an example of S104, and FIG. 6(D) is a cross-sectional view showing an example of S105. [Figure 7] FIG. 7 is a diagram showing an example of a shear strength measuring device. [Figure 8] FIG. 8 is a diagram showing the wavelength dependence of haze of the optical elements according to Examples 5 to 7. In FIG. [Figure 9] FIG. 9 is a diagram showing the wavelength dependence of Tp of the optical elements according to Examples 5 to 7. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or similar components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits. The numerical range includes the range rounded up or down.

[0015] An optical element 10 according to one embodiment will be described with reference to FIG. 1. In FIG. 1(B), the arrow direction indicates the transmission direction of light LB. The transmission direction of light LB coincides with a predetermined direction perpendicular to the plane 30a of the light-shielding film 30 (hereinafter also referred to as the "first axis direction"), but may also be oblique to the first axis direction. In this embodiment, the light LB is visible light, but may also be infrared light. The optical element 10 is used, for example, in the optical system of an imaging device.

[0016] As shown in Fig. 1A, when viewed from the first axis direction, optical element 10 includes a transmissive region A1 that transmits a portion of light LB and a light-shielding region A2 that blocks another portion of light LB. Optical element 10 adjusts the shape of light LB using light-shielding region A2. In Fig. 1A, A3 is the boundary between transmissive region A1 and light-shielding region A2 when viewed from the first axis direction.

[0017] In this embodiment, the shape of the light-shielding region A2 when viewed from the first axis direction is a rectangular frame as shown in FIG. 1A, but is not limited to a rectangular frame. The shape of the light-shielding region A2 when viewed from the first axis direction may be annular, U-shaped, or the like. Furthermore, when viewed from the first axis direction, the light-shielding region A2 is disposed outside the transmission region A1 as shown in FIG. 1A in this embodiment, but may also be disposed inside the transmission region A1.

[0018] As shown in FIG. 1(B), the optical element 10 includes a transparent glass body 20 and a light-shielding film 30. The light-shielding film 30 forms a light-shielding region A2 inside the transparent glass body 20. The light-shielding region A2 is an area where the light-shielding film 30 is provided. The transparent glass body 20 is provided on both the upstream and downstream sides of the light-shielding film 30 in the transmission direction of light LB. The transparent glass body 20 includes a first transparent substrate 21 and a second transparent substrate 22. The first transparent substrate 21 and the second transparent substrate 22 are provided in the first axial direction with the light-shielding film 30 sandwiched therebetween and are continuously adjacent in the transmission region A1. In the transmission region A1, nothing need be present between the first transparent substrate 21 and the second transparent substrate 22.

[0019] The first transparent substrate 21 and the second transparent substrate 22 have bonding surfaces 21a and 22a, respectively, that face each other. The bonding surfaces 21a and 22a have flat surfaces. The flat surfaces of the bonding surfaces 21a and 22a are provided in the transmissive region A1. If the bonding surfaces 21a and 22a have flat surfaces, the first transparent substrate 21 and the second transparent substrate 22 can be uniformly pressed against each other and bonded together in the transmissive region A1. In the transmissive region A1, the bonding surfaces 21a and 22a may be perpendicular to the first axis direction.

[0020] The first transparent substrate 21 and the second transparent substrate 22 have opposite surfaces 21b and 22b facing opposite to the bonding surfaces 21a and 22a. In this embodiment, both of the opposite surfaces 21b and 22b have flat surfaces, but at least one of them may have a curved surface. The curved surface may be a lens surface, and the optical element 10 may function as a lens. The lens may be any of a plano-convex lens, a biconvex lens, a plano-concave lens, and a biconcave lens.

[0021] The opposite surfaces 21b and 22b may each be a flat surface, a convex curved surface, or a concave curved surface. Any combination of these may be used. For example, one of the opposite surfaces 21b and 22b may be a flat surface and the other may be a convex curved surface or a concave curved surface. Alternatively, one of the opposite surfaces 21b and 22b may be a convex curved surface and the other may be a concave curved surface.

[0022] The transparent glass body 20 has a recess (also referred to as a cavity) 23 on at least one bonding surface (bonding surface 21a in this embodiment) between the first transparent substrate 21 and the second transparent substrate 22. A light-shielding film 30 is embedded in the recess 23. In this embodiment, the recess 23 is formed before the first transparent substrate 21 and the second transparent substrate 22 are bonded together, but it may also be formed by thermal deformation of the bonding surface when the first transparent substrate 21 and the second transparent substrate 22 are bonded together.

[0023] The first transparent substrate 21 and the second transparent substrate 22 preferably include the same first glass. Generally, glass exhibits smaller changes in optical properties (e.g., refractive index and extinction coefficient) due to temperature changes than resin. The first glass is not particularly limited, but may be, for example, soda-lime glass, alkali-free glass, chemically strengthened glass, borosilicate glass, or lanthanum borate glass.

[0024] The light-shielding film 30 contains a second glass. The content of the second glass in the light-shielding film 30 is 50% by volume or more. When the light-shielding film 30 mainly contains the second glass, the difference in linear expansion coefficient between the transparent glass body 20 and the light-shielding film 30 can be made smaller than when the light-shielding film 30 mainly contains a resin. The light-shielding film 30 may be partially crystallized.

[0025] To suppress reflection at the interface between the transparent glass body 20 and the light-shielding film 30, it is preferable to select the second glass with a refractive index close to that of the first glass. Therefore, it is preferable that the second glass be as transparent as the first glass. It is particularly preferable that the first glass and the second glass have the same composition.

[0026] When the second glass is transparent, the light-shielding film 30 contains a pigment dispersed in the second glass. The composition of the glass is measured by SEM-EDX. The light-shielding film 30 may contain a pigment dispersed in black glass. In either case, when the light-shielding film 30 contains a pigment dispersed in glass, the composition of the glass is measured while avoiding the pigment.

[0027] The second glass is, for example, a glass containing SiO2 as its main component, a bismuth-based glass, or a vanadium-based glass. Bismuth-based glass contains Bi2O3. Vanadium-based glass contains V2O5. Glass containing SiO2 as its main component tends to have a lower refractive index than bismuth-based glass and vanadium-based glass. Lanthanum borate glass may also be used as the second glass. In this specification, the term "main component" refers to the component that is contained in the largest amount among the components, preferably 50 mass % or more.

[0028] The light-shielding film 30 is obtained by firing a glass paste containing, for example, glass powder and a pigment. The glass powder is also called glass frit. The glass paste may contain additives other than the glass powder and the pigment, such as a resin binder. The resin binder is removed before firing the glass paste.

[0029] The light-shielding film 30 preferably has a tapered portion 31 near a boundary line A3 between the light-shielding region A2 and the transmission region A1. A tip 31a of the tapered portion 31 contacts the boundary line A3. The tip 31a of the tapered portion 31 may be provided at the interface between the bonding surface 21a of the first transparent base material 21 and the bonding surface 22a of the second transparent base material 22.

[0030] As shown in Fig. 2(A), when the light-shielding film 30 is viewed in the first axis direction (the up-down direction in Fig. 2(A)), the thickness of the tapered portion 31 in the first axis direction increases as the distance L from the boundary line A3 increases. As a result, as shown in Fig. 2(B) in the tapered portion 31, the parallel light transmittance Tp of the light LB decreases as the distance L from the boundary line A3 increases. Compared to when the parallel light transmittance Tp of the light LB changes discontinuously at the boundary line A3, diffraction of the light LB can be suppressed, and the generation of stray light can be suppressed.

[0031] When the light-shielding film 30 is viewed from the first axis direction, the tapered portion 31 is provided on at least a part of the boundary line A3, and preferably on the entire boundary line A3. The light-shielding film 30 has a constant thickness portion 32 in addition to the tapered portion 31. The constant thickness portion 32 forms a plane 30a. The constant thickness portion 32 has a constant thickness regardless of the distance L from the boundary line A3. The constant thickness portion 32 is positioned farther from the boundary line A3 than the tapered portion 31.

[0032] The parallel light transmittance Tp of the light LB at the position where the thickness of the light-shielding film 30 is at its maximum value T0, i.e., at the constant thickness portion 32, is preferably 0.1% or less. This can sufficiently suppress the transmission of the light LB in the light-shielding region A2, and can sufficiently shape the light LB. The maximum thickness T0 of the light-shielding film 30 is set according to the extinction coefficient k of the light-shielding film 30.

[0033] When the extinction coefficient k of the light-shielding film 30 is about 0.01, the maximum value T0 of the thickness T of the light-shielding film 30 is, for example, 20 μm to 50 μm. When the extinction coefficient k of the light-shielding film 30 is about 0.001, the maximum value T0 of the thickness T of the light-shielding film 30 is, for example, 200 μm to 500 μm. When the extinction coefficient k of the light-shielding film 30 is about 0.0003, the maximum value T0 of the thickness T of the light-shielding film 30 is, for example, 800 μm to 1300 μm.

[0034] The extinction coefficient k can also be calculated using the following equation (1) by exposing the object (e.g., the light-shielding film 30) by polishing or the like, measuring the thickness t0 of the object and the parallel light transmittance Tp of the object. The thickness t0 of the object is measured, for example, with a micrometer. The parallel light transmittance Tp of the object is measured, for example, with a spectrophotometer.

[0035] k=α×λ / 4π (1) In formula (1), α is the absorption coefficient of the object, and λ is the wavelength of the light used to measure the parallel light transmittance Tp. The absorption coefficient α is calculated using formula (2) below.

[0036] I = I0 × exp(-α × t0) (2) In equation (2), I0 is the intensity of light immediately after it enters the object from the air, and I is the intensity of light immediately before it leaves the object and enters the air.

[0037] The transparent glass body 20 may further include a third transparent substrate (not shown) in addition to the first transparent substrate 21 and the second transparent substrate 22. The first transparent substrate 21, the second transparent substrate 22, and the third transparent substrate are laminated in this order. In this case, the optical element 10 may further include a light-shielding film (not shown) between the second transparent substrate 22 and the third transparent substrate. The light-shielding film (not shown) is formed in the same manner as the light-shielding film 30.

[0038] An example of the relationship between Tt, Tp, and Td will be described with reference to FIG. 3. Tt is the total light transmittance, which is the transmittance of light rays that pass through the light-shielding film 30 and includes both parallel and diffuse components. Td is the diffuse light transmittance, which is the transmittance of diffuse components excluding parallel components of light rays that pass through the light-shielding film 30. The diffuse component is a component that deviates from the incident light by 2.5° or more due to forward scattering. The percentage of Td to Tt (Td / Tt×100) is the haze. Haze is measured in accordance with JIS K7136:2000. Tp is the parallel light transmittance. The sum of Tp and Td is Tt.

[0039] 3, at least a portion of the light-shielding film 30 (preferably at least the constant thickness portion 32) includes a glass substrate 33 and a pigment 34 dispersed in the glass substrate 33. The pigment 34 is, for example, a black pigment. The pigment 34 has an average particle size of 150 nm or more. The average particle size is determined by cutting the optical element 10 so that the cross section of the light-shielding film 30 can be observed, and measuring the average value of the area-equivalent diameter of the pigment 34 through SEM observation of the cut surface.

[0040] If the average particle size of the pigment 34 is 150 nm or more, the pigment 34 easily scatters the light LB. The scattered light LB changes its traveling direction. Therefore, the pigment concentration and film thickness of the light-shielding film 30 can be reduced to obtain the desired parallel light transmittance Tp.

[0041] The average particle size of the pigment 34 is preferably equal to or greater than the wavelength of the light LB. When the light LB is visible light, the average particle size of the pigment 34 is preferably equal to or greater than 400 nm, more preferably equal to or greater than 550 nm, even more preferably equal to or greater than 650 nm, particularly preferably equal to or greater than 750 nm, and even more particularly preferably equal to or greater than 850 nm. The larger the average particle size of the pigment 34, the more easily the pigment 34 scatters the light LB.

[0042] However, a smaller average particle size of the pigment 34 is preferable from the viewpoint of dispersibility of the pigment 34 in the light-shielding film 30. The average particle size of the pigment 34 is preferably 3000 nm or less, more preferably 2000 nm or less, and even more preferably 1500 nm or less.

[0043] The refractive index difference Δn (Δn = |n1 - n2|) between the glass substrate 33 and the pigment 34 at a wavelength of 550 nm is preferably 0.30 or more. n1 is the refractive index of the glass substrate 33, and n2 is the refractive index of the pigment 34. n1 may be determined by measuring the components of the glass substrate 33 using SEM-EDX and referencing literature values ​​from the components of the glass substrate 33. n2 may be calculated from the volume concentration of the pigment 34 in the light-shielding film 30, the reflectance at the interface between the transparent glass body 20 and the light-shielding film 30, and n1. The reflectance at the interface between the transparent glass body 20 and the light-shielding film 30 may be measured using a microspectrometer (USPM-WB, manufactured by Olympus).

[0044] When the pigment 34 contains multiple types of components, the sum of the products of the refractive index and volume percentage of each component is n2. The volume of the pigment is determined by measuring the length of the pigment using an image observed with an SEM. When performing component analysis and length measurement using SEM-EDX, for example, the cross section of the light-shielding film 30 is observed at 50,000 magnification, and component analysis and length measurement are performed for all pigments within the field of view.

[0045] Meanwhile, reflection of light LB occurs at a surface where the refractive index is discontinuous. The greater the difference in refractive index, the greater the reflection of light LB. If Δn is 0.30 or more, the pigment 34 is likely to scatter light LB. Δn is preferably 0.30 or more, more preferably 0.40 or more, and even more preferably 0.50 or more.

[0046] From the viewpoint of scattering of light LB, a larger Δn is preferable. However, from the viewpoint of selecting the materials for the glass substrate 33 and the pigment 34, Δn is preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.60 or less.

[0047] The pigment 34 preferably contains a metal or a metal compound. The metal or metal compound preferably contains at least one element selected from Fe, Cr, Mn, Co, Ni, Ti, and Cu. Specific examples of metal oxides or metals include those listed in Table 1. In Table 1, the refractive index is the refractive index at a wavelength of 550 nm.

[0048] [Table 1]

[0049] As shown in Figure 4, the smaller the film thickness of the light-shielding film 30, the smaller the variation in internal stress of the light-shielding film 30 and the smaller the transmitted wavefront aberration of the light-shielding film 30. Therefore, it is preferable that the maximum film thickness of the portion of the light-shielding film 30 that is made up of the glass substrate 33 and the pigment 34 is 90 µm or less. If the maximum film thickness is 90 µm or less, the transmitted wavefront aberration will be 100 nm or less. The transmitted wavefront aberration is a value at a wavelength of 632 nm.

[0050] The maximum film thickness of the portion of the light-shielding film 30 that is made up of the glass substrate 33 and the pigment 34 is preferably 70 μm or less, and more preferably 50 μm or less, from the viewpoint of transmitted wavefront aberration. The maximum film thickness is preferably 5.0 μm or more, and more preferably 10.0 μm or more, from the viewpoint of parallel ray transmittance Tp of the light LB.

[0051] The pigment concentration in the portion of the light-shielding film 30 that is composed of the glass substrate 33 and the pigment 34 is preferably 35 vol% or less. If the pigment concentration is 35 vol% or less, the bonding strength between the light-shielding film 30 and the transparent glass body 20 is high, and the shear strength of the optical element 10 is high. The pigment concentration is determined by converting the area occupancy calculated from a cross-sectional photograph of the light-shielding film 30 by image analysis or the like into a volume occupancy (vol%).

[0052] The lower the pigment concentration, the higher the bonding strength between the light-shielding film 30 and the transparent glass body 20, and the higher the shear strength of the optical element 10. From the viewpoint of the shear strength of the optical element 10, the pigment concentration is more preferably 30 vol% or less. From the viewpoint of the parallel light transmittance of the light LB, the pigment concentration is preferably 3.0 vol% or more, and more preferably 5.0 vol% or more.

[0053] A method for manufacturing an optical element 10 according to one embodiment will be described with reference to Figures 5 and 6. As shown in Figure 5, the manufacturing method includes, for example, steps S101 to S105. Note that the manufacturing method does not necessarily include all of steps S101 to S105. For example, when manufacturing optical elements 10 one by one, step S105 may be omitted. The manufacturing method may include steps other than steps S101 to S105.

[0054] Step S101 includes preparing a first transparent substrate 21 and a second transparent substrate 22, as shown in Fig. 6(A), for example. At least one bonding surface (bonding surface 21a in Fig. 6(A)) of the first transparent substrate 21 and the second transparent substrate 22 is provided with recesses 23 onto which glass paste 30A, which is the material of the light-shielding film 30, is applied. The recesses 23 are provided in the bonding surface 21a, for example, in a grid pattern.

[0055] Step S102 includes applying a glass paste 30A, for example, as shown in FIG. 6(B). The glass paste 30A includes, for example, glass powder and a pigment. The glass paste 30A is filled into the recess 23. The application and drying of the glass paste 30A may be repeated. The glass paste 30A may include a resin binder in addition to the glass powder and the pigment.

[0056] Step S103 involves removing the resin binder contained in the glass paste 30A (so-called degreasing). The degreasing temperature is set to a temperature equal to or higher than the thermal decomposition temperature of the resin binder. To promote the thermal decomposition of the resin binder, step S103 is performed in an air atmosphere or a nitrogen atmosphere. The degreasing temperature is preferably 400°C or lower.

[0057] Step S104 includes, for example, as shown in FIG. 6(C), firing the glass paste 30A to form the light-shielding film 30. The firing temperature is set to a temperature higher than the degreasing temperature and equal to or higher than the softening point Ts2 of the light-shielding film 30. The softening point Ts2 of the light-shielding film 30 is approximately equal to the softening point of the glass powder that constitutes the light-shielding film 30. The firing temperature is preferably 600°C or higher.

[0058] If the difference ΔTs (ΔTs = |Ts1 - Ts2|) between the softening point Ts1 of the transparent glass body 20 and the softening point Ts2 of the light-shielding film 30 is small, the transparent glass body 20 may deform in step S104. By designing the shape and dimensions of the transparent glass body 20 in anticipation of shape changes during firing, the target shape and dimensions can be finally obtained. Alternatively, by firing the glass paste 30A while the transparent glass body 20 is fitted into a mold, deformation of the transparent glass body 20 can be suppressed. Alternatively, if a heating method using light such as infrared light is used, the glass paste 30A containing the pigment has a higher light absorption rate than the transparent glass body 20, so the glass paste 30A can be selectively heated, and the glass paste 30A can be fired while suppressing deformation of the transparent glass body 20.

[0059] Step S104 preferably includes bonding the first transparent substrate 21 and the second transparent substrate 22 when firing the glass paste 30A. With the glass paste 30A sandwiched between the flat bonding surface 21a of the first transparent substrate 21 and the flat bonding surface 22a of the second transparent substrate 22, the bonding surfaces 21a, 22a of the first transparent substrate 21 and the second transparent substrate 22 are fused together. The fusion temperature is set to a temperature equal to or higher than the glass transition temperature Tg1 of the transparent glass body 20.

[0060] During welding, the glass bodies may be pressed together. In addition to thermocompression bonding between the first transparent substrate 21 and the second transparent substrate 22, thermocompression bonding between the first transparent substrate 21 and the light-shielding film 30 and thermocompression bonding between the second transparent substrate 22 and the light-shielding film 30 are also possible. The welding temperature may be +100°C or lower based on the softening point Ts1 of the transparent glass body 20.

[0061] In this embodiment, the firing of the glass paste 30A and the bonding of the first transparent substrate 21 and the second transparent substrate 22 are performed simultaneously, but they do not have to be performed simultaneously. The bonding of the first transparent substrate 21 and the second transparent substrate 22 may be performed after the firing of the glass paste 30A. After the firing of the glass paste 30A and before the bonding of the first transparent substrate 21 and the second transparent substrate 22, the light-shielding film 30 may be flattened by grinding or the like.

[0062] Step S105 includes cutting the bonded body obtained in step S104 into a plurality of optical elements 10, as shown in Fig. 6(D), for example. Cutting includes, for example, blade processing or laser processing.

[0063] The heat treatments in steps S103 and S104 may change the refractive index of the glass or may generate internal stress, resulting in birefringence. Therefore, after step S104, the bonded body obtained in step S104 may be heated and slowly cooled (so-called annealing). Annealing restores the refractive index of the glass to a desired value and also removes internal stress and birefringence. Annealing may be performed before or after S105. However, because annealing may cause dimensional changes, annealing before S105 stabilizes the dimensions after cutting.

[0064] [Example] The experimental data will be explained below. In Examples 1 to 7, optical elements 10 were manufactured with the same configuration except for the configuration of the light-shielding film 30 shown in Table 2. The manufacturing method was as described above, so a description thereof will be omitted. In Examples 1 to 7, optical elements 10 were manufactured in which the light-shielding film 30 was configured only with the constant-thickness portion 32, and had only the light-shielding region A2 when viewed from the first axis direction, but no transmission region A1. In Example 1, a block of black glass was used as the light-shielding film 30. Examples 2 to 4 and Examples 6 and 7 are working examples, and Examples 1 and 5 are comparative examples.

[0065] [Table 2]

[0066] The refractive index n1 listed in Table 2 was a value obtained by measuring the glass used for the glass substrate 33 with a Kalnew precision refractometer (Shimadzu Corporation KPR-3000). The value of n2 was calculated from the volume concentration of the pigment 34 in the light-shielding film 30, the reflectance at the interface between the transparent glass body 20 and the light-shielding film 30, and n1. The reflectance at the interface between the transparent glass body 20 and the light-shielding film 30 was measured by microspectrometer (Olympus USPM-WB).

[0067] The transmitted wavefront aberrations shown in Table 2 were measured using an interferometer (Zygo Verifire manufactured by Zygo Corp.) The film thicknesses of the light-shielding film 30 and the transmitted wavefront aberrations of Examples 1 and 2 are shown in FIG.

[0068] The shear strengths listed in Table 2 were measured using a measuring apparatus 100 shown in FIG. 7. The measuring apparatus 100 has a stage 101, a pair of fixed blocks 102 and 103, and a movable block 104. The stage 101 has a horizontal upper surface. The second transparent substrate 22 is in contact with the upper surface of the stage 101 so that the light-shielding film 30 is parallel to the upper surface of the stage 101. The pair of fixed blocks 102 and 103 are fixed below the light-shielding film 30, sandwiching the second transparent substrate 22 between them. The movable block 104 is above the light-shielding film 30 and pushes the first transparent substrate 21 laterally. The pushing direction is from one fixed block 102 toward the other fixed block 103.

[0069] 8 and 9 show that when the average particle size of the pigment is 150 nm or more, the haze increases, resulting in a smaller Tp. In other words, when the average particle size of the pigment is 150 nm or more, the pigment concentration and film thickness can be reduced to obtain the desired parallel light transmittance Tp. Comparing Example 1 and Example 2 in Table 1, it can be seen that when the maximum film thickness of the light-shielding film 30 is 90 μm or less, the transmitted wavefront aberration is 100 nm or less. Comparing Example 3 and Example 4 in Table 1, it can be seen that when the pigment concentration is 35 vol% or less, the shear strength is high.

[0070] The optical element and glass paste according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0071] 10 Optical Elements 20 Transparent glass body 30 Light-shielding film 33 Glass substrate 34 Pigments

Claims

1. An optical element comprising a transparent glass body and a light-shielding film provided inside the transparent glass body, At least a portion of the light-shielding film includes a glass substrate and a pigment dispersed in the glass substrate, The pigment has an average particle size of 150 nm or more.

2. 2. The optical element according to claim 1, wherein the difference in refractive index between the glass substrate and the pigment at a wavelength of 550 nm is 0.3 or more.

3. 2. The optical element according to claim 1, wherein the pigment contains a metal or a metal compound, and the metal or the metal compound contains at least one element selected from Fe, Cr, Mn, Co, Ni, Ti, and Cu.

4. 2. The optical element according to claim 1, wherein the maximum film thickness of the portion of the light-shielding film that is formed by the glass substrate and the pigment is 90 [mu]m or less.

5. 2. The optical element according to claim 1, wherein a concentration of the pigment in a portion of the light-shielding film that is formed by the glass substrate and the pigment is 35 vol % or less.

6. A glass paste comprising a glass powder and a pigment having an average particle size of 150 nm or more.

Images