Optical element

Abstract

To provide a technique for improving the durability of an optical element against a temperature change.SOLUTION: An optical element includes a transmission region that transmits part of light and a light shielding region that shields another part of the light when viewed from a transmission direction of the light. The optical element includes a transparent glass body and a light shielding film made of glass that forms the light shielding region inside the transparent glass body. A difference ΔTg (ΔTg=|Tg1-Tg2|) between a glass transition point Tg1 of the transparent glass body and a glass transition point Tg2 of the light shielding film is 100°C or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical elements. [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] One aspect of the present disclosure provides a technique for improving the durability of an optical element against temperature changes. [Means for solving the problem]

[0006] An optical element according to one aspect of the present disclosure includes, as viewed from the light transmission direction, a transmission region that transmits a portion of the light and a light-shielding region that blocks another portion of the light. The optical element includes a transparent glass body and a glass light-shielding film that forms the light-shielding region inside the transparent glass body. The difference ΔTg between the glass transition temperature Tg1 of the transparent glass body and the glass transition temperature Tg2 of the light-shielding film (ΔTg = |Tg1 - Tg2|) is 100°C or less. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the light-shielding film is made of glass, so the absolute value of the difference in the average linear expansion coefficient between the transparent glass body and the light-shielding film can be reduced, thereby improving the durability of the optical element against temperature changes. [Brief explanation of the drawings]

[0008] [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 diagram showing an example of the relationship between the stress generated at the boundary between the transmissive region and the light-shielding region and the difference in the average linear expansion coefficient, and FIG. 2(B) is a diagram showing another example. [Figure 3] FIG. 3 is a flowchart showing a method for manufacturing an optical element according to an embodiment. [Figure 4] FIG. 4(A) is a cross-sectional view showing an example of S101, FIG. 4(B) is a cross-sectional view showing an example of S102, FIG. 4(C) is a cross-sectional view showing an example of S103, FIG. 4(D) is a cross-sectional view showing an example of S104, FIG. 4(E) is a cross-sectional view showing an example of S105, and FIG. 4(F) is a cross-sectional view showing an example of S106. [Figure 5] Figure 5(A) is a plan view showing a first modified shape of the light-shielding area, Figure 5(B) is a plan view showing a second modified shape of the light-shielding area, Figure 5(C) is a plan view showing a third modified shape of the light-shielding area, and Figure 5(D) is a plan view showing a fourth modified shape of the light-shielding area. [Figure 6]Figure 6(A) is a cross-sectional view showing a first modified example of the cross-sectional shape of the light-shielding film, Figure 6(B) is a cross-sectional view showing a second modified example of the cross-sectional shape of the light-shielding film, Figure 6(C) is a cross-sectional view showing a third modified example of the cross-sectional shape of the light-shielding film, Figure 6(D) is a cross-sectional view showing a fourth modified example of the cross-sectional shape of the light-shielding film, Figure 6(E) is a cross-sectional view showing a fifth modified example of the cross-sectional shape of the light-shielding film, and Figure 6(F) is a cross-sectional view showing a sixth modified example of the cross-sectional shape of the light-shielding film. [Figure 7] Figure 7(A) is a cross-sectional view showing an example of an optical element having multiple light-shielding films spaced apart in the light transmission direction, and Figure 7(B) is a diagram showing an example of an optical element in which the light-shielding films are embedded in grooves on the surface of a transparent glass body. [Figure 8] FIG. 8 is a diagram showing an example of the relationship between the cross-sectional shape of a light-shielding film and the internal transmittance of light in the light-shielding film. [Figure 9] FIG. 9(A) is a diagram showing a first example of the light intensity distribution on the light projection surface, and FIG. 9(B) is a diagram showing a second example of the light intensity distribution on the light projection surface. [Figure 10] FIG. 10 is a diagram showing an example of the relationship between ΔI, W, and RT. [Figure 11] FIG. 11 is a diagram showing an example of the relationship between RV, W, and RT. [Figure 12] FIG. 12 is a diagram showing functions (1) to (3) that represent the change in thickness of the tapered portion. [Figure 13] FIG. 13 is a diagram showing an example of the relationship between the functions (1) to (3) and the internal transmittance of light in the light-shielding film. [Figure 14] FIG. 14 is a diagram showing an example of the relationship between the functions (1) to (3) and ΔI. [Figure 15] FIG. 15 is a cross-sectional view showing an example of the first region and the second region in the tapered portion. [Figure 16] FIG. 16(A) is a diagram showing an example of the relationship between W1 and ΔI, and FIG. 16(B) is a diagram showing an example of the relationship between W2 and ΔI. [Figure 17] FIG. 17 is a diagram showing an example of the relationship between the functions (1) to (3) and LW. [Figure 18]FIG. 18 is a diagram showing an example of the relationship between W2 and LW when ΔI is 15% or less. [Figure 19] FIG. 19(A) is a diagram showing an example of the relationship between functions (1) to (3), the distance from the light-shielding film to the projection surface, and ΔI, and FIG. 19(B) is a diagram showing another example of the relationship between functions (1) to (3), the distance from the light-shielding film to the projection surface, and ΔI. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] 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 may be opposite to the direction of the arrow. In this embodiment, the transmission direction of light LB is perpendicular to the main surface of the glass substrate, but may be oblique to the glass substrate. In this embodiment, light LB is visible light, but may be ultraviolet light or infrared light. The optical element 10 is used in, for example, the optical system of an imaging device.

[0011] As shown in Fig. 1(A), when viewed from the transmission direction of light LB, optical element 10 has a transmission region A1 that transmits a part of light LB and a light-shielding region A2 that blocks another part of light LB, thereby adjusting the shape of light LB. In Fig. 1(A), A3 is the boundary between transmission region A1 and light-shielding region A2 when viewed from the transmission direction of light LB.

[0012] 1(B), optical element 10 includes transparent glass body 11 and light-shielding film 15. Light-shielding film 15 forms light-shielding region A2 inside transparent glass body 11. Light-shielding region A2 is an area where light-shielding film 15 is provided. Transparent glass body 11 is provided on both the upstream and downstream sides of light-shielding film 15 in the transmission direction of light LB.

[0013] In this embodiment, the light-shielding film 15 is made of glass. If the light-shielding film 15 is made of glass, the absolute value of the difference Δα between the average linear expansion coefficients of the transparent glass body 11 and the light-shielding film 15 can be reduced, thereby improving the durability of the optical element 10 against temperature changes. Δα is the value obtained by subtracting the average linear expansion coefficient of the transparent glass body 11 from the average linear expansion coefficient of the light-shielding film 15.

[0014] The difference Δα between the average linear expansion coefficients of the transparent glass body 11 and the light-shielding film 15 is measured, for example, in accordance with JIS R3102:1995. The measurement temperature range is, for example, -40°C to 85°C. FIG. 2(A) shows an example of the relationship between the stress generated at the boundary A3 between the transmission region A1 and the light-shielding region A2 and the difference Δα between the average linear expansion coefficients of the transparent glass body 11 and the light-shielding film 15 when the temperature of the optical element 10 is 85°C. FIG. 2(B) shows an example of the relationship between the stress generated at the boundary A3 between the transmission region A1 and the light-shielding region A2 and the difference Δα between the average linear expansion coefficients of the transparent glass body 11 and the light-shielding film 15 when the temperature of the optical element 10 is -40°C.

[0015] The analysis conditions for Figures 2(A) and 2(B) were as follows: Thermal stress analysis software: Solidworks Simulation by Dassault Systemes SolidWorks Corporation, Average linear expansion coefficient of transparent glass B1: 7.2 x 10 -6 / ℃, Young's modulus of transparent glass B1: 70 GPa, Average linear expansion coefficient of black glass B2: 0.5 x 10 -6 / ℃~100×10 -6 / ℃, Young's modulus of black glass B2: 70 GPa, Average linear expansion coefficient of black resin B3: 100 x 10 -6 / ℃, Young's modulus of black resin B3: 3 GPa.

[0016] 2(A) and 2(B), the black circles indicate the case where the transparent glass body 11 is made of the above-mentioned transparent glass B1 and the light-shielding film 15 is made of the above-mentioned black glass B2, that is, when Δα is −6.7×10 -6 / ℃~92.8×10 -6 / °C. In addition, in Fig. 2(A) and Fig. 2(B), the white circles indicate the stress generated when the transparent glass body 11 is made of the transparent glass B1 and the light-shielding film 15 is made of the black resin B3, that is, when Δα is 92.8 × 10 -6 / °C.

[0017] When the transparent glass body 11 was made of the transparent glass B1 and the light-shielding film 15 was made of the black resin B3 (see the open circles in FIG. 2(A)), the transparent glass body 11 cracked when the temperature of the optical element 10 was increased from 20°C to 85°C. On the other hand, when the transparent glass body 11 was made of the transparent glass B1 and the light-shielding film 15 was made of the black glass B2 (average linear expansion coefficient: 8.6×10 -6 / °C), the transparent glass body 11 did not break even when the temperature of the optical element 10 was increased from 20°C to 85°C. Furthermore, when the transparent glass body 11 was made of the transparent glass B1 and the light-shielding film 15 was made of the black resin B3 (see the open circles in Figure 2(B)), a heat cycle test was conducted in which the temperature was repeatedly increased and decreased between -40°C and 85°C, and the transparent glass body 11 broke. On the other hand, when the transparent glass body 11 was made of the transparent glass B1 and the light-shielding film 15 was made of the black glass B2 (average linear expansion coefficient: 8.6 x 10 -6 / °C), the transparent glass body 11 did not break even when subjected to the heat cycle test.

[0018] 2(A) and 2(B), the dashed lines indicate a stress of 50 MPa. From FIGS. 2(A) and 2(B) and the results of the heat cycle test described above, it is believed that breakage of the transparent glass body 11 can be suppressed if the stress generated at the boundary A3 between the transmissive region A1 and the light-shielding region A2 is 50 MPa or less. Therefore, the absolute value of the difference Δα between the average linear expansion coefficients of the transparent glass body 11 and the light-shielding film 15 is preferably 10×10 -6 / °C or less, and more preferably 5 × 10 -6 / °C or less, and more preferably 1 × 10 -6 / ℃ or less. The smaller the absolute value of Δα, the better. -6 / ℃ or higher is sufficient.

[0019] As shown in FIG. 1(B), the transparent glass body 11 may have a first transparent glass layer 12 and a second transparent glass layer 13. The first transparent glass layer 12 and the second transparent glass layer 13 are disposed in the transmission direction of light LB with a light-shielding film 15 sandwiched therebetween, and are continuously adjacent to each other in the transmissive region A1. In the transmissive region A1, there may be nothing between the first transparent glass layer 12 and the second transparent glass layer 13. The first transparent glass layer 12 and the second transparent glass layer 13 are bonded together.

[0020] The first transparent glass layer 12 and the second transparent glass layer 13 are each a glass substrate. The glass of the glass substrate is not particularly limited, but may be, for example, soda-lime glass, alkali-free glass, chemically strengthened glass, borosilicate glass, or lanthanum borate glass. The first transparent glass layer 12 and the second transparent glass layer 13 may be made of different glasses, but from the viewpoint of durability of the optical element 10 against temperature changes, they are preferably made of the same glass.

[0021] The first transparent glass layer 12 and the second transparent glass layer 13 have bonding surfaces 12a and 13a facing each other, respectively. The bonding surfaces 12a and 13a are preferably flat. The flat surfaces of the bonding surfaces 12a and 13a are provided in the transmissive region A1. If the bonding surfaces 12a and 13a are flat, the first transparent glass layer 12 and the second transparent glass layer 13 can be uniformly pressed against each other and bonded together in the transmissive region A1.

[0022] The first transparent glass layer 12 and the second transparent glass layer 13 have opposite surfaces 12b and 13b facing opposite to the bonding surfaces 12a and 13a. In this embodiment, both of the opposite surfaces 12b and 13b have flat surfaces, but at least one of them may have a curved surface. The curved surface may constitute 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.

[0023] The first transparent glass layer 12 and the second transparent glass layer 13 may have a recess (also referred to as a cavity) 14 on at least one of the bonding surfaces 12a, 13a. In this embodiment, the recess 14 is formed on the bonding surface 12a of the first transparent glass layer 12, but it may also be formed on the bonding surface 13a of the second transparent glass layer 13, or on both bonding surfaces 12a, 13a. A light-shielding film 15 is embedded in the recess 14.

[0024] In this embodiment, transparent glass body 11 is formed by bonding first transparent glass layer 12 and second transparent glass layer 13 together, but they may not be bonded together. As will be described in detail later, optical element 10 can also be manufactured by forming grooves on the surface of transparent glass body 11 and embedding light-shielding film 15 in the grooves.

[0025] The light-shielding film 15 contains an amorphous inorganic oxide, that is, glass, as a main component. The glass content in the light-shielding film 15 is 50% by volume or more. The light-shielding film 15 may be partially crystallized. The light-shielding film 15 is made of so-called black glass. The black glass may be a common type. In this embodiment, the black glass is a sintered body obtained by firing a paste containing transparent glass powder and a black pigment. The sintered body contains the black pigment dispersed in the transparent glass. Note that the black glass may also be a block obtained by molding black molten glass. That is, although the black glass is transparent in this embodiment, the glass itself may be black.

[0026] The light-shielding film 15 may be made of glass containing bismuth-based glass or vanadium-based glass, in addition to glass containing SiO2 as its main component. 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 or vanadium-based glass. In order to suppress reflection at the interface between the transparent glass body 11 (described below) and the light-shielding film 15, it is preferable to select a material for the light-shielding film 15 that has a refractive index close to that of the transparent glass body 11. In this specification, the term "main component" refers to the component that is contained in the largest amount among the components, preferably at 50 wt% or more.

[0027] Table 1 shows the relationship between the refractive index difference Δn (Δn = |n1-n2|) between the transparent glass body 11 and the light-shielding film 15, the extinction coefficient k of the light-shielding film 15, and the reflectance R of light LB at the interface between the transparent glass body 11 and the light-shielding film 15.

[0028] [Table 1]

[0029] The reflectance R was calculated using the following formula (1). (1)R=((n1-n2) 2 +k 2 ) / ((n1+n2) 2 +k 2 ) The reflectance R varies mainly depending on the refractive index difference Δn and the extinction coefficient k. Note that n1 is the refractive index of the transparent glass body 11, and n2 is the refractive index of the light-shielding film 15. In Table 1, n1 is 1.52 (constant). n1, n2, and k are measured at the same wavelength as the light LB. The refractive index n1 of the transparent glass body 11 is measured, for example, by the V-block method. The refractive index n2 and extinction coefficient k of the light-shielding film 15 are measured, for example, by an ellipsometer.

[0030] The extinction coefficient k of the light-shielding film 15 can also be calculated using the following formula (2) by exposing the light-shielding film 15 by polishing or the like, measuring the thickness and transmittance of the light-shielding film 15, and then using the following formula (2). The thickness of the exposed light-shielding film 15 is measured with, for example, a micrometer. The transmittance of the light-shielding film 15 is measured with, for example, a spectrophotometer. (2)k=αλ / 4π In equation (2), α is the absorption coefficient and λ is the wavelength of the light used to measure the transmittance. The absorption coefficient α is calculated using equation (3) below. (3) I = I0 exp(-αt) In equation (3), t is the thickness of the light-shielding film 15, I 0 is the intensity of light before it passes through the light-shielding film 15, and I is the intensity of light after it passes through the light-shielding film 15.

[0031] The reflectance R of the light LB at the interface between the transparent glass body 11 and the light-shielding film 15 may be measured, for example, by a microspectrometer.

[0032] It is preferable that the refractive index difference Δn is 0.10 or less and the extinction coefficient k is 0.05 or less. If the refractive index difference Δn is 0.10 or less and the extinction coefficient k is 0.05 or less, the reflectance R is 0.15% or less. If the reflectance R is 0.15% or less, stray light can be suppressed. The reflectance R is preferably 0.15% or less, and more preferably 0.10% or less.

[0033] The smaller the refractive index difference Δn, the smaller the reflectance R. The refractive index difference Δn is preferably 0.10 or less, more preferably 0.08 or less, and even more preferably 0.05 or less. Furthermore, the smaller the extinction coefficient k, the smaller the reflectance R. The extinction coefficient k is preferably 0.05 or less, and more preferably 0.01 or less. However, if the extinction coefficient k is too small, sufficient light blocking properties cannot be obtained. The extinction coefficient k is preferably 0.0001 or more.

[0034] The reflectance R also depends on the surface roughness Ra of the interface between the transparent glass body 11 and the light-shielding film 15. The surface roughness Ra is the arithmetic mean roughness as defined in JIS B0601:2013. The larger the surface roughness Ra, the smaller the reflectance R. If the surface roughness Ra is 100 nm or more, the reflectance R can be reduced to half or less compared to when the surface roughness Ra is 0 nm.

[0035] In Table 1, the surface roughness Ra is 0 nm. From the viewpoint of reflectance R, the surface roughness Ra is preferably 100 nm or more, and more preferably 120 nm or more. The surface roughness Ra is preferably 6400 nm or less.

[0036] The refractive index n1 of the transparent glass body 11 is preferably 1.58 or more, more preferably 1.65 or more. The higher the refractive index n1 of the transparent glass body 11, the longer the optical path length (distance × refractive index), which may allow the optical element 10 to be made more compact. As mentioned above, the smaller the refractive index difference Δn (Δn = |n1 - n2|) between the transparent glass body 11 and the light-shielding film 15, the more preferable it is. Generally, glass can have a higher refractive index than resin. By making the light-shielding film 15 out of glass rather than resin, the refractive index n2 of the light-shielding film 15 can be increased. The refractive index is a value evaluated at a wavelength of 588 nm (d-line).

[0037] When black glass is a sintered body obtained by firing a paste containing a transparent glass powder and a black pigment, the black pigment contains, for example, a metal or metal compound containing at least one element selected from Fe, Cr, Mn, Co, Ni, Ti, and Cu. The metal compound is, for example, an oxide.

[0038] The paste may contain additives other than the transparent glass powder and the black pigment, such as ceramic powder.

[0039] The firing temperature of the paste is set to a temperature equal to or higher than the softening point of the glass that constitutes the paste. The glass that constitutes the paste is the same as the glass that constitutes the light-shielding film 15. If the difference ΔTs (ΔTs = |Ts1 - Ts2|) between the softening point Ts1 of the transparent glass body 11 and the softening point Ts2 of the light-shielding film 15 is small, the transparent glass body 11 may deform during firing of the paste. By designing the shape and dimensions of the transparent glass body 11 in anticipation of shape changes during firing, the final target shape and dimensions can be achieved. Alternatively, by firing the paste while the transparent glass body 11 is fitted into a mold, deformation of the transparent glass body 11 can be suppressed. Alternatively, if a heating method using light such as infrared light is used, the paste containing the pigment has a higher light absorption rate than the transparent glass body 11, so the paste can be selectively heated, and firing of the paste with reduced deformation of the transparent glass body 11 is possible. Ts1, Ts2, Tg1, and Tg2 are measured, for example, using a differential thermal analyzer. Tg1 is the glass transition temperature of the transparent glass body 11, and Tg2 is the glass transition temperature of the light-shielding film 15.

[0040] The light-shielding film 15 may contain a black pigment dispersed in transparent glass. In this case, the glass constituting the light-shielding film 15 preferably has the same composition as that of the transparent glass body 11. The composition of the glass is measured by SEM-EDX. When the light-shielding film 15 contains a black pigment dispersed in transparent glass, the composition of the glass is measured while avoiding the pigment.

[0041] When black glass is a block obtained by molding black molten glass, that is, when the glass itself is colored black, it contains at least one element selected from, for example, Fe, Cr, Mn, Co, Ni, Ti, V, and Cu as a coloring component.

[0042] When the glass itself is colored black, black glass may contain, for example, in mass % oxide content, 50% to 75% SiO2, 0% to 20% Al2O3, 0% to 20% Na2O, 0% to 20% K2O, 0% to 15% MgO, 0% to 20% CaO, 10% to 20% B2O3, 0% to 20% ΣRO (where R is Mg, Ca, Sr, Ba, or Zn), 0% to 5% ZrO2, 1.0% to 14% Fe2O3, 0% to 2% CoO or Co3O4, and 0% to 0.5% SO3. ΣRO is the total content of MgO, CaO, SrO, BaO, and ZnO.

[0043] When the glass itself is colored black, the black glass may contain at least one selected from V2O5, CrO, MnO, CuO, MoO3, and CeO2 to the extent that the coloring is not impaired. The total content of V2O5, CrO, MnO, CuO, MoO3, and CeO2, expressed in mass % on an oxide basis, is preferably 0% to 3%, and more preferably 0% to 1%.

[0044] When the glass itself is colored black, the black glass may contain at least one fining agent selected from SO3, Sb2O3, SnO, Cl, and F, to the extent that the coloring is not impaired. The total content of SO3, Sb2O3, SnO, Cl, and F is preferably 0% to 1%, and more preferably 0% to 0.5%.

[0045] The ratio (T0 / width) of the maximum value T0 of the thickness T in the transmission direction of light LB of the light-shielding film 15 to the width in the direction perpendicular to the transmission direction of light LB is preferably 1 to 1 / 500, more preferably 1 / 2 to 1 / 500, and even more preferably 1 / 4 to 1 / 250.

[0046] The light-shielding film 15 may have a tapered portion 16 at the boundary line A3 between the light-shielding region A2 and the transmission region A1, in which the thickness T in the transmission direction of light LB decreases from the light-shielding region A2 toward the transmission region A1. When viewed in the transmission direction of light LB, the thickness T of the tapered portion 16 increases the farther it is from the boundary line A3. The tapered portion 16 is in contact with the boundary line A3. The tapered portion 16 is provided on at least a part of the boundary line A3, and preferably on the entire boundary line A3.

[0047] The tapered portion 16 can continuously change the internal transmittance of the light LB at and near the boundary line A3. The tapered portion 16 is in contact with the boundary line A3 in the light-shielding region A2, and continuously increases the internal transmittance of the light LB as the distance from the boundary line A3 increases. The internal transmittance is the transmittance excluding losses due to surface reflection. Compared to when the internal transmittance of the light LB changes discontinuously at the boundary line A3, the diffraction of the light LB can be suppressed, and the generation of stray light can be suppressed. The change in the internal transmittance of the light LB at and near the boundary line A3 will be described later. The internal transmittance of the light-shielding film 15 can be calculated from the absorption coefficient α described above, and can be calculated from exp(-αt), where t is the thickness of the light-shielding film 15.

[0048] The light-shielding film 15 has a constant-thickness portion 17, which has a constant thickness T in the transmission direction of light LB, in a region farther from the boundary line A3 than the tapered portion 16. The constant-thickness portion 17 is formed continuously with the tapered portion 16. The thickness T of the constant-thickness portion 17 is the same as the maximum value T0 of the thickness T of the tapered portion 16. Note that the light-shielding film 15 does not necessarily have to have the constant-thickness portion 17, and may have only the tapered portion 16.

[0049] A method for manufacturing an optical element 10 according to one embodiment will be described with reference to Figures 3 and 4. As shown in Figure 3, the manufacturing method includes, for example, steps S101 to S106. Note that the manufacturing method does not necessarily include all of steps S101 to S106. For example, when manufacturing optical elements 10 one by one, step S106 may be omitted. Furthermore, the manufacturing method may include steps other than steps S101 to S106.

[0050] Step S101 includes preparing a first transparent glass layer 12, as shown in FIG. 4A, for example. The first transparent glass layer 12 has recesses 14 on its bonding surface 12a. The recesses 14 are formed, for example, in a rectangular lattice pattern. The groove width of the recesses 14 is, for example, 1 mm to 5 mm. The maximum depth of the recesses 14 is determined based on the maximum value T0 of the thickness T of the light-shielding film 15 and the amount of change in the depth of the recesses 14 in the subsequent steps. If the depth of the recesses 14 changes in steps S103 and S104, which will be described later, the depth of the recesses 14 is determined so that the maximum value T of the thickness T of the light-shielding film 15 after step S104 is completed becomes T0. Note that T0 is set according to the extinction coefficient of the light-shielding film 15. When the extinction coefficient of the light-shielding film 15 is about 0.01, the maximum value T0 of the thickness T of the light-shielding film 15 is, for example, 20 μm to 50 μm. When the extinction coefficient of the light-shielding film 15 is about 0.001, the maximum value T0 of the thickness T of the light-shielding film 15 is, for example, 200 μm to 500 μm. When the extinction coefficient of the light-shielding film 15 is about 0.0003, the maximum value T0 of the thickness T of the light-shielding film 15 is, for example, 800 μm to 1300 μm. In this embodiment, the recesses 14 are formed on the bonding surface 12a of the first transparent glass layer 12, but they may also be formed on the bonding surface 13a of the second transparent glass layer 13, or on both bonding surfaces 12a, 13a. Glass processing includes, for example, wet etching, mechanical processing, and thermoforming.

[0051] Step S102 includes applying paste 15A, for example, as shown in FIG. 4B. The paste 15A is applied, for example, to the entire joining surface 12a on which the recesses 14 are formed, to a thickness greater than the depth of the recesses 14. An applicator for applying the paste 15A includes, for example, a screen printer or a dispenser. Note that the paste 15A only needs to fill at least the recesses 14, and may be applied only to the recesses 14.

[0052] Step S103 includes firing the paste 15A, as shown in FIG. 4(C), for example. The glass powder and black pigment constituting the paste 15A are sintered to obtain the light-shielding film 15. The firing temperature of the paste 15A is set to a temperature equal to or higher than the softening point of the glass constituting the paste 15A. The glass constituting the paste 15A is the same as the glass constituting the light-shielding film 15. As mentioned above, if the difference ΔTs (ΔTs = |Ts1 - Ts2|) between the softening point Ts1 of the transparent glass body 11 and the softening point Ts2 of the light-shielding film 15 is small, the transparent glass body 11 may deform when the paste 15A is fired. By designing the shape and dimensions of the transparent glass body 11 in anticipation of shape changes during firing, the target shape and dimensions can be finally obtained. Alternatively, the deformation of the transparent glass body 11 can be suppressed by firing the paste 15A while the transparent glass body 11 is fitted into a mold. Alternatively, if a heating method using light such as infrared light is used, the pigment-containing paste 15A has a higher light absorption rate than the transparent glass body 11, so the paste 15A can be selectively heated, and the paste 15A can be fired while suppressing deformation of the transparent glass body 11.

[0053] Step S104 includes planarizing the light-shielding film 15, as shown in FIG. 4(D), for example. Planarizing the light-shielding film 15 includes at least one of lapping and polishing. Planarizing the light-shielding film 15 may further include wet etching. Planarizing the light-shielding film 15 is performed until the first transparent glass layer 12 is exposed. By planarizing the light-shielding film 15, for example, it is formed into a square lattice shape.

[0054] 4(E), for example, the first transparent glass layer 12 and the second transparent glass layer 13 are bonded together by hydrogen bonds between OH groups provided on the glass surfaces, covalent bonds formed by dehydration condensation after the formation of hydrogen bonds, or van der Waals forces between the glass surfaces.

[0055] For example, step S105 includes, in this order, modifying the surfaces of the glass substrates by plasma treatment, adding OH groups to the modified surfaces, stacking the glass substrates with the surfaces to which OH groups have been added facing each other, and heat-treating the stacked glass substrates. The addition of OH groups is performed by supplying pure water or water vapor.

[0056] Alternatively, step S105 may include, in this order, treating the surfaces of the glass substrates with an alkaline detergent, washing the surfaces treated with the alkaline detergent with pure water, stacking the glass substrates with the surfaces washed with pure water facing each other, and heat-treating the stacked glass substrates. Here, treating the surfaces of the glass substrates with an alkaline detergent can be omitted.

[0057] Step S105 may include welding the glass substrates together. The welding temperature is set to a temperature equal to or higher than the glass transition point of the glass substrates. During welding, the glass substrates may be pressed together.

[0058] Step S106 includes cutting the bonded body obtained in step S105 into a plurality of optical elements 10, as shown in Fig. 4(F), for example. Cutting includes, for example, blade processing or laser processing.

[0059] When glass is heated (e.g., by firing a paste or welding), the refractive index of the glass may change and birefringence may occur due to internal stress. The refractive index of the glass can then be returned to the desired value by heating the glass and slowly cooling it, while eliminating the internal stress and the resulting birefringence. However, if the thermal properties of the transparent glass body 11 and the light-shielding film 15 differ significantly, cracks may occur during the heating or slow cooling process. Table 2 lists Tg1, Tg2, Ts1, Ts2, ΔTg, and ΔTs, as well as the presence or absence of cracks during heating or slow cooling. In Table 2, Examples 1 and 2 are comparative examples, and Examples 3 to 5 are working examples.

[0060] [Table 2]

[0061] In Table 2, the conditions for heating and slow cooling are as follows: The heating time from room temperature to T1 in the table was 4 hours, the temperature was then held at T1 for 6 hours, and the rate of slow cooling from T1 to T2 was 10°C per hour. The subsequent cooling from T2 to room temperature was natural cooling. T1 was set to a temperature above the strain point and below the glass transition point of the transparent glass body 11, and T2 was set to a temperature at least 50°C lower than T1. The presence or absence of cracks was determined by visually inspecting the transparent glass body 11 after heating and slow cooling.

[0062] As shown in Table 2, cracks occurred when ΔTg exceeded 100° C. No cracks occurred when ΔTg was 100° C. or less. ΔTg is preferably 100° C. or less, more preferably 70° C. or less, and even more preferably 40° C. or less.

[0063] Furthermore, as shown in Table 2, the ΔTs of the substrates that did not develop cracks was 50°C or less.

[0064] Example 5 shows the results when glass materials of the same composition are used for the glass that constitutes the transparent glass body 11 and the light-shielding film 15. If the glass materials that constitute the transparent glass body 11 and the light-shielding film 15 are of the same composition, it is possible to select the materials without worrying about differences in thermal properties.

[0065] In addition, in Example 5, the birefringence of light (n e -n o ) was 0.000030, whereas the birefringence of light in the transmission region A1 after heating and slow cooling was 0.000002 or less. The birefringence was measured using a rotating analyzer method. The measurement wavelength was 520 nm. e is the refractive index of the extraordinary ray, and n ois the refractive index of ordinary light. Light that passes through an optical element with birefringence generates a phase difference depending on the polarization direction, causing a shift in the image position, so a small birefringence is preferable. The birefringence is preferably 0.000010 or less, and more preferably 0.000005 or less. Since a small birefringence is preferable, it is sufficient if it is 0.000000 or more.

[0066] When glass is processed at a temperature above its glass transition point and then rapidly cooled, its volume increases and its refractive index decreases compared to its state before the thermal processing. If the rapidly cooled glass is then reheated and slowly cooled, its volume decreases and its refractive index increases compared to its state after the thermal processing (before the heating). During thermal processing (e.g., firing or welding of paste), the heating temperature is set to a temperature higher than both the glass transition point Tg1 of the transparent glass body 11 and the glass transition point Tg2 of the glass light-shielding film 15. During thermal processing, glass materials with low glass transition points experience greater volumetric expansion upon rapid cooling than glass materials with high glass transition points. Therefore, glass materials with low glass transition points experience greater volumetric contraction upon subsequent heating and slow cooling than glass materials with high glass transition points. When the difference ΔTg between the glass transition points Tg1 and Tg2 is large, the difference in volumetric contraction upon heating and slow cooling is large, resulting in cracks. If the difference ΔTg between the glass transition points Tg1 and Tg2 is small, the difference in volumetric shrinkage due to heating and slow cooling is small, and cracks do not occur. Generally, when the temperature of glass exceeds the glass transition point, the linear expansion coefficient of the glass increases significantly. Even if the difference ΔTg between the glass transition points Tg1 and Tg2 is small, if the difference ΔTs between the softening points Ts1 and Ts2 is large, the rate of increase in the linear expansion coefficient will differ significantly, resulting in a large difference in the amount of volumetric expansion when heating is complete. Therefore, it is preferable that the difference ΔTs between the softening points Ts1 and Ts2 is small.

[0067] Referring to FIG. 5, first to fourth modified examples of the shape of the light-shielding region A2 as viewed from the transmission direction of light LB will be described. In the above embodiment, the shape of the light-shielding region A2 as viewed from the transmission direction of light LB is a rectangular frame as shown in FIG. 1(A), but is not limited to a rectangular frame. The shape of the light-shielding region A2 may be a shape in which two rectangles are arranged parallel to each other with a gap therebetween as shown in FIG. 5(A), a U-shape as shown in FIG. 5(B), a ring shape as shown in FIG. 5(C), or a circle shape as shown in FIG. 5(D). The light-shielding region A2 may be disposed outside the transmitting region A1 as shown in FIGS. 1(A), 5(A), 5(B), and 5(C), or may be disposed inside the transmitting region A1 as shown in FIG. 5(D).

[0068] Referring to Fig. 6, first to sixth modified examples of the cross-sectional shape of the light-shielding film 15 taken perpendicularly to the boundary line A3 as viewed from the transmission direction of the light LB will be described. In the above embodiment, the cross-sectional shape of the light-shielding film 15 is a rectangle with one corner cut out by a quadrant as shown in Fig. 1(B), but is not limited to this shape. The cross-sectional shape of the light-shielding film 15 may be a rectangle as shown in Fig. 6(A), a shape combining a rectangle and a semicircle as shown in Fig. 6(B), a shape combining a rectangle and an isosceles triangle as shown in Fig. 6(C), a shape combining a rectangle and an isosceles trapezoid as shown in Fig. 6(D), a rectangle with two rounded corners as shown in Fig. 6(E), or a wave-shaped shape as shown in Fig. 6(F).

[0069] As shown in Fig. 7(A), a plurality of light-shielding films 15 may be provided at intervals in the transmission direction of light LB. Alternatively, as shown in Fig. 7(B), optical element 10 can be manufactured by forming grooves on the surface of transparent glass body 11 and embedding light-shielding films 15 in the grooves.

[0070] Referring to Fig. 8, an example of the relationship between the cross-sectional shape of the light-shielding film 15 cut perpendicular to the boundary line A3 as viewed from the transmission direction of the light LB and the internal transmittance of the light LB in the light-shielding film 15 will be described. In Fig. 8, for convenience of the drawing, the cross-sectional shape of the light-shielding film 15 is shown compressed in the transmission direction of the light LB (downward in Fig. 8). In Fig. 8, the maximum value T0 of the thickness T of the tapered portion 16 is 0.100 mm, and the width W of the tapered portion 16 is 0.100 mm.

[0071] In Fig. 8, L indicates the distance from the boundary line A3. A positive L indicates a position shifted from the boundary line A3 to the light-shielding region A2. A negative L indicates a position shifted from the boundary line A3 to the light-transmitting region A1.

[0072] Also, in Figure 8, R T R denotes the ratio (T1 / T0) of the thickness T1 corresponding to an internal transmittance of 0.1% of the light LB to the maximum value T0 of the thickness T of the tapered portion 16. T represents the black density of the light-shielding film 15. T can be adjusted by the content of the black pigment in the light-shielding film 15. The smaller the content of the black pigment, the lower the black density of the light-shielding film 15, and the T is large.

[0073] The tapered portion 16 preferably has an internal transmittance of 0.1% or less for the light LB at the position where the thickness T reaches the maximum value T0. If the internal transmittance of the light LB at the position where the thickness T reaches the maximum value T0 is 0.1% or less, the transmission of the light LB at the position where the thickness T reaches the maximum value T0 can be sufficiently suppressed, and the shape of the light LB can be sufficiently adjusted.

[0074] Also, R T (R T = T1 / T0), the larger the better. As shown in Figure 8, R T As R increases, the change in the internal transmittance of the light LB can be made gentler at and near the boundary line A3. As a result, as shown in FIG. T The larger the value of T, the smaller the ΔI. Note that when the internal transmittance of the light LB at the position where the thickness T is the maximum value T0 is 0.1% or less, T =T1 / T0" equation, R T is less than or equal to 1.00.

[0075] In FIG. 9, I is the light intensity (relative value) on the projection surface, and ΔI is the fluctuation range of the light intensity at the position where boundary line A3 is projected onto the projection surface. In FIGS. 9 to 11, the distance from light-shielding film 15 to the projection surface is 0.5 mm. The intensity I of light that has passed through a position in transmission region A1 that is sufficiently far from boundary line A3 is taken as the reference value (1.0). The average value of the light intensity I in transmission region A1 may also be taken as the reference value (1.0). ΔI is expressed as a percentage (%) of the reference value. The smaller ΔI is, the weaker the diffraction of light LB is.

[0076] Figure 10 shows ΔI, W, and R T As shown in Figure 10, ΔI is T and depends on W. If W is greater than 0.000 and constant, R T The larger is, the smaller is ΔI. However, when W is 0.000, ΔI is R T It does not depend on R T If is constant, the larger W is, the smaller ΔI is.

[0077] As shown in Figure 10, the reduction effect of ΔI is T When W is 1.00, the reduction in ΔI when W changes from 0.000 mm to ΔW is V0. T When W changes from 0.000 mm to ΔW while is constant, the ratio R of the reduction amount V of ΔI V Expressed in (%). R V is expressed by the following formula (4): (4) Rv = V / V0 × 100 ΔW is an arbitrary value.

[0078] Figure 11 shows the R V and W and R T An example of the relationship between R T If is 0.50 or more, in the range of W 0.040 mm or more, R V It can be seen that R T is preferably 0.50 or more, more preferably 0.75 or more. T The larger the better, but T=T1 / T0" equation, R T is less than or equal to 1.00.

[0079] Next, functions (1) to (3) will be described with reference to FIG. 12. Functions (1) to (3) represent changes in the thickness of tapered portion 16. In functions (1) to (3), x is the distance L (mm) from boundary line A3 and is equal to or greater than 0 and equal to (1 / a). Here, constant a is the reciprocal of width W. The larger the width W, the smaller the constant a. In functions (1) to (3), y is relative thickness Ta. Relative thickness Ta is the thickness T divided by maximum value T0 (T / T0), and is equal to or greater than 0 and equal to 1.

[0080] In function (1), the constant b represents the change in slope. The slope is the ratio (ΔT / ΔL) of the increase in T, ΔT, to the increase in L, ΔL. The slope is calculated by differentiating function (1) once. When b is greater than or equal to 0 and less than 1, function (1) is an upward convex curve, and the larger L is, the smaller the slope. When b is 1, function (1) is a straight line, and the slope remains constant even when L is large. Furthermore, when b is greater than 1, function (1) is a downward convex curve, and the larger L is, the larger the slope is.

[0081] Note that function (2) is an upward convex curve that protrudes upward compared to function (1) (b=1 / 2). The larger L is, the smaller the slope of function (2). On the other hand, function (3) is a downward convex curve that protrudes downward compared to function (1) (b=2). The larger L is, the larger the slope of function (3).

[0082] Fig. 13 shows an example of the relationship between the functions (1) to (3) and the internal transmittance of light in the light-shielding film 15. In Fig. 13, the constant b of the function (1) is 1 / 2, 2 / 3, 1, 3 / 2, or 2. From Fig. 13, it can be seen that when b exceeds 1 in the function (1) and when the function (3) is used, that is, when the slope increases as L increases, the change in the internal transmittance can be made more gradual than in other cases.

[0083] In FIG. 13, the internal transmittance at the position where the thickness T of the tapered portion 16 is at its maximum value T0 is 0.01%, and R T 14 and 16 to 19 described later, the internal transmittance is 0.01% at the position where the thickness T of the tapered portion 16 reaches the maximum value T0, and R T is 0.75.

[0084] 14 and 16 to 18, the distance from the light-shielding film 15 to the projection surface is 5 mm. Fig. 19, which will be described in detail later, shows an example of the relationship between the distance from the light-shielding film 15 to the projection surface and ΔI.

[0085] Fig. 14 shows an example of the relationship between functions (1) to (3) and ΔI. In Fig. 14, the constant b of function (1) is 1 / 2, 2 / 3, 1, 3 / 2, or 2. Fig. 14 also shows the internal transmittance when the cross-sectional shape of light-shielding film 15 is rectangular, that is, when only constant thickness portion 17 is present and tapered portion 16 is not present.

[0086] From FIG. 14, when the constant a is constant in functions (1) to (3), the following trends (A) to (C) are observed. (A) Function (1) has a smaller ΔI than function (2). (B) Function (3) has a smaller ΔI than function (1). (C) In function (1), the larger the constant b, the smaller the ΔI.

[0087] 14, when the constant b is constant in the function (1), the smaller the constant a, the smaller ΔI becomes. Note that when the function (2) or (3) is used, the smaller the constant a, the smaller ΔI becomes. This is because the smaller the constant a, the larger the width W of the tapered portion 16, and the more gradual the change in the internal transmittance becomes.

[0088] The change in thickness T of the tapered portion 16 can be expressed by at least one (preferably both) of the width W1 of the first region 16A and the width W2 of the second region 16B shown in Fig. 15, instead of the functions (1) to (3). The widths W1 and W2 are measured in a direction perpendicular to the boundary line A3 when the light-shielding film 15 is viewed from the transmission direction of the light LB.

[0089] The first region 16A is a region where the internal transmittance of the light-shielding film 15 is 50.0% to 99.9%. The width W1 of the first region 16A represents the slope (ΔT / ΔL) when the thickness T is small. Note that regions where the internal transmittance of the light-shielding film 15 is greater than 99.9% are not included in the first region 16A because the internal transmittance of the light LB is too high.

[0090] The second region 16B is a region where the internal transmittance of the light-shielding film 15 is 1.0% to 99.9%. The width W2 of the second region 16B represents the slope (ΔT / ΔL) when the thickness T is large. The second region 16B includes the first region 16A. Note that regions where the internal transmittance of the light-shielding film 15 is greater than 99.9% are not included in the second region 16B because the internal transmittance of the light LB is too high.

[0091] FIG. 16(A) shows an example of the relationship between W1 and ΔI, and FIG. 16(B) shows an example of the relationship between W2 and ΔI. In FIGS. 16(A) and 16(B), ΔI was calculated by repeatedly changing the constant a in functions (1) to (3) and the constant b in function (1). From FIG. 16(A), a clear correlation is observed between W1 and ΔI. From FIG. 16(B), no clear correlation is observed between W2 and ΔI.

[0092] As shown in Figure 16(A), the larger W1 is, the smaller ΔI is. W1 is preferably 0.020 mm (20 μm) or more, and more preferably 0.050 mm (50 μm) or more. If W1 is 20 μm or more, ΔI is 15% or less. Also, if W1 is 50 μm or more, ΔI is 5% or less.

[0093] The larger W1 is, the smaller ΔI is. However, W1 is preferably less than 400 μm, and more preferably less than 200 μm. By setting W1 to less than 400 μm, it is possible to set W2 to 400 μm or less. Furthermore, by setting W1 to less than 200 μm, it is possible to set W2 to 200 μm or less.

[0094] From the viewpoint of suppressing leakage light, it is preferable that W2 is as small as possible. Leakage light is light that is irradiated outside the intended target range, and becomes stray light, similar to diffracted light. Note that the intensity of leakage light is weaker than that of diffracted light. Therefore, suppressing leakage light has a lower priority than suppressing diffracted light. The impact of leakage light is expressed by the size of the leakage light width LW shown in Figure 9.

[0095] 9, the leakage light width LW is the amount of change in the distance L when I continuously decreases from 1 to 0.001. The larger the leakage light width LW, the stronger the intensity of the leakage light and the more likely stray light is to occur.

[0096] Fig. 17 shows an example of the relationship between functions (1) to (3) and LW. In Fig. 17, the constant b of function (1) is 1 / 2, 2 / 3, 1, 3 / 2, or 2. Fig. 17 also shows the leakage light width LW (LW = 0.292 µm) when the cross-sectional shape of light-shielding film 15 is rectangular, that is, when only constant thickness portion 17 is present and tapered portion 16 is not present.

[0097] 17, when b exceeds 1 in function (1) and when function (3) is used, that is, when the slope increases as L increases, the larger the constant a, the narrower the leaked light width LW. This is because the larger the constant a, the smaller the width W of the tapered portion 16, making it less likely that leaked light will occur.

[0098] Fig. 18 shows an example of the relationship between W2 and LW when ΔI is 15% or less. In Fig. 18, LW was calculated by repeatedly changing the constant a in functions (1) to (3) and the constant b in function (1). Fig. 18 also shows LW (LW = 0.292 µm) when the cross-sectional shape of light-shielding film 15 is rectangular, that is, when only constant-thickness portion 17 is present and tapered portion 16 is not present.

[0099] As shown in Figure 18, when ΔI is 15% or less, a clear correlation is observed between W2 and LW. As shown in Figure 18, the smaller W2 is, the smaller LW is. W2 is preferably 0.330 mm (330 μm) or less, and more preferably 0.160 mm (160 μm) or less. If W2 is 330 μm or less, LW is less than 0.292 μm. Furthermore, if W2 is 160 μm or less, LW is half of 0.292 μm or less.

[0100] The smaller W2 is, the smaller LW is. However, W2 is preferably greater than 20 μm, and more preferably greater than 50 μm. By setting W2 to greater than 20 μm, it is possible to set W1 to 20 μm or more. Furthermore, by setting W2 to greater than 50 μm, it is possible to set W1 to 50 μm or more.

[0101] 19(A) and 19(B) show an example of the relationship between functions (1) to (3), the distance from light-shielding film 15 to the projection surface, and ΔI. In FIG. 19(A), the constant a is 1, and in FIG. 19(B), the constant a is 2. FIGS. 19(A) and 19(B) also show the relationship between the distance from light-shielding film 15 to the projection surface and ΔI when the cross-sectional shape of light-shielding film 15 is rectangular, that is, when only constant-thickness portion 17 is present and tapered portion 16 is not present.

[0102] 19(A) and 19(B) show that the greater the distance from light-shielding film 15 to the projection surface, the greater ΔI. Also, from Figures 19(A) and 19(B), it can be seen that when b exceeds 1 in function (1) and when function (3) is used, that is, when the slope increases as L increases, the increase in ΔI due to an increase in the distance from light-shielding film 15 to the projection surface can be suppressed compared to other cases.

[0103] The optical element according to the present disclosure has 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]

[0104] 10 optical elements 11 transparent ガラス body 15 shading film A1 Transmission Area A2 light-shielding area LB Light

Claims

1. An optical element comprising: a transmission region that transmits a part of the light when viewed from a light transmission direction; and a light-shielding region that blocks another part of the light, A transparent glass body; a glass light-shielding film that forms the light-shielding region inside the transparent glass body; Equipped with An optical element in which the difference ΔTg between the glass transition point Tg1 of the transparent glass body and the glass transition point Tg2 of the light-shielding film (ΔTg=|Tg1−Tg2|) is 100° C. or less.

2. 2. The optical element according to claim 1, wherein a difference ΔTs between the softening point Ts1 of said transparent glass body and the softening point Ts2 of said light-shielding film (ΔTs=|Ts1-Ts2|) is 50° C. or less.

3. the light-shielding film contains a black pigment dispersed in transparent glass, 3. The optical element according to claim 1, wherein the transparent glass body and the glass constituting the light-shielding film have the same composition.

4. 3. The optical element according to claim 1, wherein the birefringence of the light in the transmission region is 0.000010 or less.

5. the light-shielding film has a tapered portion whose thickness in the light-transmitting direction increases as the distance from the boundary line between the light-shielding region and the light-transmitting region increases when the light-shielding film is viewed from the light-transmitting direction, The optical element according to claim 1 , wherein the tapered portion is in contact with the boundary line.

6. The light-shielding film has an internal transmittance of 0.1% or less at a position where the thickness of the tapered portion is at its maximum value, and a ratio R of the thickness T1 corresponding to an internal transmittance of 0.1% of the light to the maximum thickness T0 Ｔ (R Ｔ 6. The optical element according to claim 5, wherein T1 / T0) is 0.5 or more.

7. The optical element of claim 6, wherein, when viewed from the light transmission direction, the tapered portion has a first region in which the internal transmittance of the light is 50.0% to 99.9%, and when the light-shielding film is viewed from the light transmission direction, the width of the first region in a direction perpendicular to the boundary line is 20 μm or more.

8. The optical element of claim 7, wherein the tapered portion has a second region in which the internal transmittance of the light is 1.0% to 99.9%, and when the light-shielding film is viewed from the light transmission direction, the width of the second region in a direction perpendicular to the boundary line is 330 μm or less.

9. the transparent glass body has a first transparent glass layer and a second transparent glass layer; The optical element according to claim 1 , wherein the first transparent glass layer and the second transparent glass layer are disposed in the light transmission direction with the light-shielding film sandwiched therebetween, and are continuously in contact with each other in the transmission region.

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