Polarizing element, method for manufacturing polarizing element, and optical apparatus

Abstract

The invention provides a polarizing element capable of improving transmittance of a transmission axis even if the incident angle deviation of light is large. A polarizing element (10) is provided with: a transparent substrate (11); and grid-shaped protrusions (12) which are arranged on one surface of the transparent substrate (11) at a pitch shorter than that of light waves of a used frequency band and extend in a predetermined direction. The grid-shaped protrusion (12) has a reflective layer (21) and an absorbing layer (22) in this order from the transparent substrate (11) side. The width of the absorbing layer (22) is substantially the same as the width of the reflecting layer (21) on the side facing the absorbing layer (22). In a cross-sectional view in the direction in which the grid-shaped protrusions (12) extend, a central surface (C2) that passes through the center of the absorption layer (22) in the width direction and a central surface (C1) that passes through the center of the reflection layer (21) in the width direction are spaced apart from each other by a predetermined interval.

Description

Technical Field

[0001] The present invention relates to a polarizing element, a method for manufacturing the polarizing element, and an optical device. Background Art

[0002] Polarizers are optical elements that absorb light polarized in a predetermined direction and transmit light polarized in a direction orthogonal to the absorbed polarization. Liquid crystal displays fundamentally require polarizers. In particular, polarizers used in liquid crystal displays (LCD projectors), which utilize high-intensity light sources, are subject to intense radiation and therefore require heat resistance. Furthermore, their dimensions, which are several centimeters, require high extinction ratios and reflectivity. To meet these requirements, wire-grid polarizers have been proposed.

[0003] A wire-grid polarization element comprises a transparent substrate and a grid of protrusions arranged on one surface of the transparent substrate at a pitch shorter than the wavelength of light in the intended frequency band and extending in a predetermined direction (see, for example, Patent Document 1). When light enters the polarization element, s-polarized light (TE waves (s-waves)) with an electric field component parallel to the direction in which the protrusions extend is not transmitted, while p-polarized light (TM waves (p-waves)) with an electric field component perpendicular to the direction in which the protrusions extend is transmitted.

[0004] [Prior art literature] [Patent Document] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-64326 Summary of the Invention

[0005] (Problems to be solved by the invention) However, in a wire-grid polarization element, if the incident angle of light deviates greatly, the transmission axis transmittance may decrease.

[0006] An object of the present invention is to provide a polarizing element capable of improving the transmittance along the transmission axis even when the incident angle of light deviates greatly.

[0007] (Methods for solving problems) (1) A polarizing element comprising: a transparent substrate and grid-like protrusions, wherein the grid-like protrusions are arranged on one surface of the transparent substrate at a pitch shorter than the wavelength of light in a used frequency band and extend in a predetermined direction, wherein the grid-like protrusions have a reflective layer and an absorption layer in sequence from one side of the transparent substrate, wherein the width of the absorption layer is substantially the same as the width of the side of the reflective layer opposite to the absorption layer, and when viewed in a cross-section in the direction in which the grid-like protrusions extend, a central plane passing through the center of the width direction of the absorption layer and a central plane passing through the center of the width direction of the reflective layer are spaced apart by a predetermined distance.

[0008] (2) A polarizing element according to (1), wherein, when viewed in a cross-section in the direction in which the grating-shaped protrusions extend, a width ratio of a region of the absorption layer existing on the other side relative to a central plane passing through the center in the width direction of the reflection layer to a region of the absorption layer existing on one side relative to a central plane passing through the center in the width direction of the reflection layer is greater than 0 and less than 45 / 55.

[0009] (3) The polarization element according to (2), wherein when the light in the used frequency band is blue light, the width ratio is greater than 25 / 75 and less than 40 / 60, when the light in the used frequency band is green light, the width ratio is greater than 0 and less than 45 / 55, when the light in the used frequency band is red light, the width ratio is greater than 35 / 65 and less than 45 / 55, and when the light in the used frequency band is visible light, the width ratio is greater than 25 / 75 and less than 45 / 55.

[0010] (4) The polarizing element according to any one of (1) to (3), wherein the transparent substrate includes glass, crystal, quartz, or sapphire.

[0011] (5) The polarization element according to any one of (1) to (4), wherein the absorption layer includes a metal material or a semiconductor material.

[0012] (6) The polarizing element according to any one of (1) to (5), further comprising an antireflection layer on the other surface of the transparent substrate.

[0013] (7) The polarizing element according to any one of (1) to (6), wherein at least a portion of the surface is covered with a protective film containing Si oxide, Ti oxide, Zr oxide, Al oxide, Nb oxide, or Ta oxide.

[0014] (8) The polarizing element according to any one of (1) to (7), wherein at least a portion of the surface is covered with an organic hydrophobic film.

[0015] (9) A method for manufacturing a polarizing element, wherein the polarizing element according to any one of (1) to (8) is manufactured, comprising: a process of forming a reflective layer on one surface of the transparent substrate; a process of forming a precursor of the grid-shaped protrusions by selectively etching the reflective layer; a process of patterning a resist in an area of ​​the one surface of the transparent substrate where the precursor of the grid-shaped protrusions is not formed; a process of forming an absorption layer on the surface of the precursor of the grid-shaped protrusions and the resist; and a process of forming the grid-shaped protrusions by selectively etching the absorption layer.

[0016] (10) The method for manufacturing a polarizing element according to (9) further includes a step of forming an antireflection layer on the other surface of the transparent substrate.

[0017] (11) The method for manufacturing a polarizing element according to (9) or (10) further includes a step of covering at least a portion of the surface with a protective film, wherein the protective film comprises Si oxide, Ti oxide, Zr oxide, Al oxide, Nb oxide or Ta oxide.

[0018] (12) The method for manufacturing a polarizing element according to any one of (9) to (11), further comprising: a step of covering at least a portion of the surface with an organic hydrophobic film.

[0019] (13) An optical device comprising the polarizing element according to any one of (1) to (8).

[0020] (Effects of the Invention) According to the present invention, it is possible to provide a polarizing element capable of improving the transmittance along the transmission axis even when the incident angle of light varies greatly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic perspective view showing a polarization element according to one embodiment of the present invention. Figure 2 It shows Figure 1 Schematic cross-sectional view of a polarization element. Figure 3 It shows Figure 1 A schematic cross-sectional view of a modified example of a polarizing element. Figure 4 It shows Figure 1 A schematic cross-sectional view of a modified example of a polarizing element. Figure 5 It is an explanation Figure 1 A cross-sectional schematic diagram of a method for manufacturing a polarizing element. Figure 6 It is an explanation Figure 1 A cross-sectional schematic diagram of a method for manufacturing a polarizing element. Figure 7 It is an explanation Figure 1 A cross-sectional schematic diagram of a method for manufacturing a polarizing element. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0023] [Polarizing element] Figure 1 and Figure 2 A polarization element according to one embodiment of the present invention is shown.

[0024] The polarizing element 10 includes a transparent substrate 11 and lattice-shaped protrusions 12 arranged on one surface of the transparent substrate 11 at a pitch p shorter than the wavelength of light in the used band and extending along the Y-axis direction. The lattice-shaped protrusions 12 have a width w and a height h.

[0025] Here, if Figure 1 and Figure 2 As shown, the direction in which the grid-like protrusions 12 extend is referred to as the Y-axis direction. Furthermore, the direction perpendicular to the Y-axis direction and in which the grid-like protrusions 12 are arranged at a pitch p along the principal surface of the transparent substrate 11 is referred to as the X-axis direction. Furthermore, the direction perpendicular to the Y-axis and X-axis directions, that is, the direction perpendicular to the principal surface of the transparent substrate 11, is referred to as the Z-axis direction. It should be noted that the direction in which light enters the polarizing element 10 is the Z-axis direction, but light preferably enters from the side of the polarizing element 10 where the grid-like protrusions 12 are formed.

[0026] The polarizing element 10 utilizes four functions: transmission, reflection, interference, and selective absorption of polarized light due to optical anisotropy. This attenuates s-polarized light (TE waves (s-waves)) with an electric field component parallel to the Y-axis, while transmitting p-polarized light (TM waves (p-waves)) with an electric field component parallel to the X-axis. Therefore, the Y-axis is the absorption axis of the polarizing element 10, and the X-axis is the transmission axis.

[0027] Here, the height h of the lattice-shaped protrusions 12 refers to the dimension in the Z-axis direction perpendicular to the main surface of the transparent substrate 11. Furthermore, the width w of the lattice-shaped protrusions 12 refers to the dimension in the X-axis direction of the lattice-shaped protrusions 12. Furthermore, the pitch p of the lattice-shaped protrusions 12 refers to the repetitive spacing in the X-axis direction of the polarizing element 10.

[0028] The pitch p of the grid-like protrusions 12 is not particularly limited as long as it is shorter than the wavelength of light in the used frequency band. However, from the perspective of ease of manufacture and stability of the polarizing element 10, it is preferably greater than 100 nm and less than 200 nm. It should be noted that the pitch p of the grid-like protrusions 12 can be measured by observation using a scanning electron microscope or a transmission electron microscope. The pitch p of the grid-like protrusions 12 can be, for example, the arithmetic mean of the values ​​measured at any four locations. Hereinafter, this measurement method will be referred to as electron microscopy.

[0029] like Figure 2As shown, the grid-like protrusion 12 has a reflective layer 21 and an absorption layer 22 in this order from the transparent substrate 11 side. Here, the grid-like protrusion 12 has a wire grid structure arranged in a one-dimensional grid shape. In addition, the cross-sectional shape of the reflective layer 21 and the absorption layer 22 are both rectangular, and the width of the absorption layer 22 is approximately the same as the width of the side of the reflective layer 21 opposite to the absorption layer 22. Furthermore, when viewed in a cross-section along the direction in which the grid-like protrusion 12 extends, the central plane C2 passing through the center of the width direction of the absorption layer 22 and the central plane C1 passing through the center of the width direction of the reflective layer 21 are separated by a predetermined interval. Therefore, even when the deviation of the incident angle θ of light is large, the transmission axis transmittance is improved. In this case, the ratio (w1 / w2) of the width w1 of the region of the absorption layer 22 located on the other side (left side in the figure) relative to the central plane C1 passing through the center of the width direction of the reflective layer 21 to the width w2 of the region located on one side (right side in the figure) relative to the central plane C1 passing through the center of the width direction of the reflective layer 21 is preferably 0 or more and 45 / 55 or less. When w1 / w2 is 0 or more and 45 / 55 or less, the transmission axis transmittance is further improved even when the incident angle θ of light varies greatly.

[0030] For example, when the light band used is blue light, w1 / w2 is preferably 25 / 75 or more and 40 / 60 or less, with 25 / 75 being particularly preferred. Furthermore, when the light band used is green light, w1 / w2 is preferably 0 or more and 45 / 55 or less, with 25 / 75 being more preferred. Furthermore, when the light band used is red light, w1 / w2 is preferably 35 / 65 or more and 45 / 55 or less, with 35 / 65 being particularly preferred. Furthermore, when the light band used is visible light, w1 / w2 is preferably 25 / 75 or more and 45 / 55 or less, with 25 / 75 being particularly preferred.

[0031] Light incident from the side of the transparent substrate 11 where the grid-shaped protrusions 12 are formed is partially absorbed when passing through the absorption layer 22, thereby attenuating. Of the light that passes through the absorption layer 22, p-polarized light (TM wave (p wave)) passes through the reflective layer 21 with a relatively high transmittance. On the other hand, of the light that passes through the absorption layer 22, s-polarized light (TE wave (s wave)) is reflected by the reflective layer 21. The s-polarized light reflected by the reflective layer 21 is partially absorbed when passing through the absorption layer 22, but a portion returns to the reflective layer 21 after reflection. In addition, the s-polarized light reflected by the reflective layer 21 is attenuated due to interference when passing through the absorption layer 22. As described above, the s-polarized light is selectively attenuated, thereby enabling the polarization element 10 to obtain the desired polarization characteristics.

[0032] (Transparent substrate) The material constituting the transparent substrate 11 is not particularly limited as long as it is transparent to light in the used band and can be appropriately selected according to the purpose. Examples of the light in the used band include visible light having a wavelength of 400 nm to 700 nm.

[0033] It should be noted that “transparent to light of the used band” means that the light transmittance can maintain the function as a polarizing element, and does not mean that the transmittance of light of the used band is 100%.

[0034] The transparent substrate 11 is preferably made of a material with a refractive index of 1.1 to 2.2. The material having a refractive index of 1.1 to 2.2 is not particularly limited, and examples thereof include glass, crystal, quartz, and sapphire. Quartz and glass are preferred from the perspectives of cost and light transmittance, with quartz having a refractive index of 1.46 and soda-lime glass having a refractive index of 1.51 being particularly preferred. Furthermore, crystal and sapphire are preferred from the perspective of thermal conductivity. This improves the heat resistance of the transparent substrate 11, making it possible to use the transparent substrate 11 in a liquid crystal projector.

[0035] When an optically active crystal such as quartz crystal or sapphire is used as the material for transparent substrate 11, it is preferable to arrange the lattice-shaped projections 12 in a direction parallel or perpendicular to the optical axis of the crystal. This allows for excellent optical properties. The optical axis is the axis in which the difference in refractive index between the ordinary ray O and the extraordinary ray E of light propagating in that direction is minimized.

[0036] The average thickness of the transparent substrate 11 is not particularly limited, and is, for example, 0.3 mm to 1 mm. The shape of the main surface of the transparent substrate 11 is not particularly limited, and examples thereof include a rectangular shape.

[0037] (Reflective layer) The reflective layer 21 is formed on one surface of the transparent substrate 11 and forms a grid-like protrusion 12 extending in the Y-axis direction. The reflective layer 21 attenuates s-polarized light (TE waves (s-waves)) having an electric field component in the Y-axis direction, while transmitting p-polarized light (TM waves (p-waves)) having an electric field component in the X-axis direction.

[0038] The thickness of the reflective layer 21 is not particularly limited, and is, for example, 100 nm to 300 nm inclusive. The thickness of the reflective layer 21 is measured, for example, by electron microscopy.

[0039] The material constituting the reflective layer 21 is not particularly limited as long as it reflects light in the intended frequency band. Examples include simple elements such as Al, Ag, Cu, Mo, Cr, Ti, Nd, Ni, W, Fe, Si, Ge, and Te, as well as alloys containing one or more of these elements. Among these, aluminum or aluminum alloys are preferred. The reflective layer 21 may be, for example, a non-metallic inorganic film or resin film whose surface reflectivity is increased by coloring.

[0040] The film-forming method of the reflective layer 21 is not particularly limited, and examples thereof include a vapor deposition method and a sputtering method.

[0041] In addition, the reflective layer 21 may be a laminated body in which layers formed of different constituent materials are laminated.

[0042] (Absorbent layer) The absorption layer 22 is formed on the surface of the reflection layer 21 and forms lattice-shaped protrusions 12 extending in the Y-axis direction.

[0043] The thickness of the absorption layer 22 is not particularly limited, and is, for example, 5 nm to 50 nm. The thickness of the absorption layer 22 can be measured, for example, using an electron microscope.

[0044] The material constituting the absorption layer 22 is not particularly limited as long as it can absorb light in the desired frequency band. Examples include metal materials and semiconductor materials. Examples of metal materials include simple elements such as Ta, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, and Sn, as well as alloys containing one or more of these elements. Examples of semiconductor materials include Si, Ge, Te, ZnO, and silicide materials (such as β-FeSi2, MgSi2, NiSi2, BaSi2, CrSi2, CoSi2, and TaSi). Among these, materials containing Fe or Ta and Si are preferred.

[0045] When a semiconductor material is used as the material constituting the absorption layer 22, it is necessary to use a semiconductor material having a band gap energy that is less than or equal to the energy of light in the frequency band used. For example, when the light in the frequency band used is visible light, it is necessary to use a semiconductor material having a band gap energy that is equal to or less than the energy of light with a wavelength of 400 nm, that is, a band gap energy of 3.1 eV or less.

[0046] The film-forming method of the absorption layer 22 is not particularly limited, and examples thereof include a vapor deposition method and a sputtering method.

[0047] It should be noted that the absorption layer 22 may be a laminate in which layers composed of different materials are laminated.

[0048] (Anti-reflection layer) The polarizing element 10 may include an antireflection layer on the other surface of the transparent substrate 11. The antireflection layer is, for example, a laminate in which low-refractive-index layers and high-refractive-index layers having different refractive indices are alternately laminated.

[0049] The material constituting the antireflection layer is not particularly limited, and examples thereof include Si oxide, Ti oxide, Zr oxide, Al oxide, Nb oxide, and Ta oxide.

[0050] The thickness of the antireflection layer is not particularly limited, and is, for example, 1 nm to 500 nm. The thickness of the antireflection layer can be measured, for example, using an electron microscope.

[0051] The method for forming the antireflection layer is not particularly limited, and examples thereof include vapor deposition, sputtering, chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among them, ion beam assisted deposition (IAD) and ion beam sputtering (IBS) are preferred.

[0052] (Protective film) At least a portion of the surface of the polarizing element 10 may be covered with a protective film, thereby improving the durability of the polarizing element 10 .

[0053] The material constituting the protective film is the same as the material constituting the antireflection layer.

[0054] The method for forming the protective film is not particularly limited, and examples thereof include CVD and ALD.

[0055] In addition, the protective film may be a laminated body in which layers composed of different materials are laminated.

[0056] (Organic hydrophobic membrane) At least a portion of the surface of the polarizing element 10 may be covered with an organic hydrophobic film, thereby improving the moisture resistance of the polarizing element 10 .

[0057] The material constituting the organic hydrophobic film is not particularly limited, and examples thereof include fluorine-based silane coupling agents such as tridecafluorooctyltrichlorosilane (FOTS).

[0058] The method for forming the organic hydrophobic film is not particularly limited, and examples thereof include CVD, ALD, and coating methods.

[0059] (simulation) The simulation verified that even if the incident angle θ of light varies greatly, the transmission axis transmittance of the polarizing element 10 will increase. Specifically, the simulation was performed using Gsolver (manufactured by Grating Solver Development) under the following conditions. Next, the average value of the transmission axis transmittance when the light incident angles were -45°, -30°, -15°, 0°, 15°, 30°, and 45° was calculated. The refractive index of the transparent substrate 11 is: 1.5 Width of the reflective layer 21 and the absorption layer 22: 28 nm Height of the reflective layer 21: 250 nm Material constituting the reflective layer 21: Al Height of the absorption layer 22: 35 nm Materials constituting the absorption layer 22: FeSi w1 / w2: 50 / 50, 45 / 55, 40 / 60, 35 / 65, 25 / 75, 0 Blue light wavelength range: 430~510nm Green light wavelength range: 520~590nm Red light wavelength range: 600~680nm Visible light wavelength range: 400-700nm Angle of incident light: -45°, -30°, -15°, 0°, 15°, 30°, 45°

[0060] Table 1 shows the evaluation results of the average values ​​of the transmission axis transmittance.

[0061] [Table 1]

[0062] As can be seen from Table 1, when the incident angle of visible light is 0°±45°, the transmission axis transmittance is improved when w1 / w2 is 25 / 75 or more and 45 / 55 or less, compared to the case where w1 / w2 is 50 / 50. In addition, when the incident angle of blue light is 0°±45°, the transmission axis transmittance is improved when w1 / w2 is 25 / 75 or more and 40 / 60 or less, compared to the case where w1 / w2 is 50 / 50. Furthermore, when the incident angle of green light is 0°±45°, the transmission axis transmittance is improved when w1 / w2 is 0 or more and 45 / 55 or less, compared to the case where w1 / w2 is 50 / 50. In addition, when the incident angle of red light is 0°±45°, the transmission axis transmittance is improved when w1 / w2 is 35 / 65 or more and 45 / 55 or less, compared to the case where w1 / w2 is 50 / 50.

[0063] It should be noted that the cross-sectional shape of the reflective layer 21 is not particularly limited, as long as the width of the side of the reflective layer 21 facing the absorption layer 22 is substantially the same as the width of the absorption layer 22. The cross-sectional shape of the reflective layer 21 can be, for example, a trapezoidal shape with a continuously increasing or decreasing width (see FIG. Figure 3 (a) Figure 3 (b)), or a hexagonal shape with a continuously decreasing and then increasing width (see Figure 3 (c)).

[0064] In addition, the lattice-shaped convex portion 12 is not particularly limited as long as it has a reflective layer 21 and an absorption layer 22 in order from the transparent substrate 11 side. The lattice-shaped convex portion 12 may also include, for example, an absorption layer 22 between the transparent substrate 11 and the reflective layer 21 (see Figure 4 (a)). In this case, the absorption layers 22 disposed on both sides of the reflective layer 21 are arranged in line symmetry with respect to a central plane C3 passing through the center of the height direction of the reflective layer 21. In this case, the grid-shaped convex portion 12 may further include an intermediate layer 41 between the reflective layer 21 and the absorption layer 22 (see Figure 4 (b)). In this case, the intermediate layers 41 disposed on both sides of the reflective layer 21 are arranged line-symmetrically with respect to a central plane C3 passing through the height center of the reflective layer 21. Furthermore, the spacing between the central plane passing through the width center of the intermediate layer 41 and the central plane passing through the width center of the reflective layer 21 is substantially the same as the spacing between the central plane passing through the width center of the absorbent layer 22 and the central plane passing through the width center of the reflective layer 21. However, the absorbent layer 22 and the intermediate layer 41 are disposed on opposite sides of the width direction relative to the central plane C1 passing through the width center of the reflective layer 21. The intermediate layer 41 is not particularly limited, and examples thereof include an absorbent layer, a reflective layer, and an anti-reflection layer.

[0065] [Method for Manufacturing Polarizing Element] use Figures 5 to 7 , a method for manufacturing the polarization element 10 is described.

[0066] First, a reflective layer 21 is formed on one surface of the transparent substrate 11 (see Figure 5 (a)), and then a resist R1 is patterned on the surface of the reflective layer 21 (refer to Figure 5 (b)). Next, after selectively etching the reflective layer 21 (see Figure 5 (c)), the resist R1 is removed to form a precursor 12A of a grid-like protrusion (see Figure 6 (a)). Next, a resist R2 is patterned on a region of one surface of the transparent substrate 11 where the precursor 12A of the grid-shaped protrusions is not formed (see Figure 6 (b)) an absorption layer 22 is formed on the surface of the precursor 12A of the grid-shaped protrusion and the resist R2 (see Figure 6 (c)). Next, after patterning the resist R3 on the surface of the absorption layer 22 (see Figure 7 (a)), selectively etching the absorption layer 22 (refer to Figure 7 (b)). Finally, the resists R2 and R3 are removed to form the grid-like protrusions 12, and the polarization element 10 is obtained (see Figure 7 (c)).

[0067] The resist patterning method is not particularly limited, and examples thereof include photolithography and nanoimprinting. The etching method is not particularly limited, and examples thereof include dry etching using an etching gas suitable for the etching target.

[0068] It should be noted that an antireflection layer may be formed on the other surface of the transparent substrate 11. In addition, at least a portion of the surface may be covered with a protective film, or at least a portion of the surface may be covered with an organic hydrophobic film.

[0069] [Optical equipment] The polarizing element 10 can be applied to optical devices such as liquid crystal displays, liquid crystal projectors, head-up displays, and automobile headlights. Among them, considering the heat resistance of the polarizing element 10, a liquid crystal projector is preferable.

[0070] When the optical device includes multiple polarizing elements, at least one of the multiple polarizing elements may be the polarizing element 10. For example, in a liquid crystal projector, at least one of the polarizing elements disposed on the incident and exiting sides of the liquid crystal panel may be the polarizing element 10.

[0071] As mentioned above, although embodiment of this invention was demonstrated, this invention is not limited to the said embodiment, The said embodiment can be modified suitably within the range of the summary of this invention.

[0072] (Description of labels) 10: Polarized light element 11: Transparent substrate 12: Grid-like convex part 12A: Precursor of grid-like protrusions 21: Reflection layer 22: Absorption layer 41: Middle layer C1, C2, C3: Central plane R1, R2, R3: resist.

Claims

1. A polarizing element comprising: A transparent substrate and lattice-shaped protrusions, wherein the lattice-shaped protrusions are arranged on one surface of the transparent substrate at a pitch shorter than the wavelength of light in a used frequency band and extend in a predetermined direction, The grid-like protrusion has a reflective layer and an absorption layer in sequence from one side of the transparent substrate. The width of the absorption layer is substantially the same as the width of the side of the reflection layer opposite to the absorption layer. When viewed in a cross section in a direction in which the lattice-shaped protrusions extend, a central plane passing through the center of the absorption layer in the width direction and a central plane passing through the center of the reflection layer in the width direction are separated by a predetermined distance.

2. The polarization element according to claim 1, wherein When viewed in a cross-section in the direction in which the grating-like protrusion extends, the width ratio of the area of ​​the absorption layer existing on the other side relative to the central plane passing through the center of the width direction of the reflection layer to the area of ​​the absorption layer existing on one side relative to the central plane passing through the center of the width direction of the reflection layer is greater than 0 and less than 45 / 55.

3. The polarization element according to claim 2, wherein When the light in the used frequency band is blue light, the width ratio is greater than or equal to 25 / 75 and less than or equal to 40 / 60. When the light of the used frequency band is green light, the width ratio is greater than or equal to 0 and less than or equal to 45 / 55. When the light of the used frequency band is red light, the width ratio is 35 / 65 or more and 45 / 55 or less. When the light in the used frequency band is visible light, the width ratio is 25 / 75 or more and 45 / 55 or less.

4. The polarizing element according to any one of claims 1 to 3, wherein The transparent substrate comprises glass, crystal, quartz or sapphire.

5. The polarizing element according to any one of claims 1 to 3, wherein The absorption layer includes a metal material or a semiconductor material.

6. The polarizing element according to any one of claims 1 to 3, wherein An antireflection layer is provided on the other surface of the transparent substrate.

7. The polarizing element according to any one of claims 1 to 3, wherein At least a portion of the surface is covered with a protective film containing Si oxide, Ti oxide, Zr oxide, Al oxide, Nb oxide, or Ta oxide.

8. The polarizing element according to any one of claims 1 to 3, wherein At least a portion of the surface is covered by an organic hydrophobic film.

9. A method for manufacturing a polarizing element, comprising: forming a reflective layer on one surface of the transparent substrate; a step of forming a precursor of the grid-shaped protrusions by selectively etching the reflective layer; The steps of patterning a resist in a region of one surface of the transparent substrate where the precursor of the grid-shaped protrusions is not formed; forming an absorption layer on the surface of the precursor of the grid-shaped protrusions and the resist; and A step of forming the grid-like protrusions by selectively etching the absorption layer.

10. The method for manufacturing a polarizing element according to claim 9, further comprising: forming an antireflection layer on the other surface of the transparent substrate.

11. The method for manufacturing a polarizing element according to claim 9, further comprising: a step of covering at least a portion of the surface with a protective film, The protective film includes Si oxide, Ti oxide, Zr oxide, Al oxide, Nb oxide, or Ta oxide.

12. The method for manufacturing a polarizing element according to claim 9, further comprising: The step of covering at least a portion of a surface with an organic hydrophobic film. 13 . An optical device comprising the polarization element according to claim 1 .

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