JP2019061218A - Polarizing element, method of manufacturing the same, and optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing element capable of suppressing the absorption axis reflectance to a low value with respect to both incident light from a grid surface side on which a grid-like convex portion is formed and incident light from a substrate surface side, and a method for manufacturing the same. In addition, an optical device including the polarizing element is provided. SOLUTION: This is a polarizing element 1 having a wire grid structure, in which a transparent substrate 10 is arranged on the transparent substrate 10 at a pitch shorter than the wavelength of light in the band used, and a grid-like convex portion extending in a predetermined direction. The first absorption layer 13, the first dielectric layer 14, the reflection layer 15, the second dielectric layer 16, and the second are in order from the transparent substrate 10 side. It is a polarizing element 1 having an absorption layer 17. [Selection diagram] Fig. 1

Description

  The present invention relates to a polarizing element, a method of manufacturing the same, and an optical apparatus.

  The polarizing element is an optical element that absorbs polarized light in one direction and transmits polarized light in a direction orthogonal to the polarized light. In principle, a liquid crystal display device requires a polarizing element. In particular, in a liquid crystal display device using a light source with a large amount of light, such as a transmissive liquid crystal projector, the polarizing element receives strong radiation, and in addition to the need for excellent heat resistance, the size is about several centimeters. , High extinction ratio is required. In order to meet these requirements, wire grid type inorganic polarization elements have been proposed.

  In the wire grid type polarization element, a large number of conductor wires (reflecting layer) extending in one direction are arranged side by side on a transparent substrate at a pitch (several tens of nm to several hundreds of nm) shorter than the wavelength of light in the working band It has the following structure. When light enters this polarizing element, polarized light (TE wave (S wave)) parallel to the extending direction of the wire can not be transmitted, and polarized light (TM wave (P wave) perpendicular to the extending direction of the wire ) Is transparent as it is. The wire grid type polarizing element is excellent in heat resistance, can produce a relatively large element, and has a high extinction ratio, and thus is suitable for applications such as liquid crystal projectors.

  Heretofore, polarization elements of various structures have been proposed as wire grid type polarization elements.

For example, Patent Document 1 includes a substrate and grid-like convex portions arranged on the substrate at a pitch shorter than the wavelength of light in the working band, and the grid-like convex portions are wire grids in order from the substrate side A polarizing element is disclosed comprising a layer, a dielectric layer, an absorbing layer and a dielectric layer.
Further, Patent Document 2 includes a transparent substrate and lattice-like convex portions arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band, and the lattice-like convex portions are arranged in order from the transparent substrate side A polarizing element is disclosed having a reflective layer, a dielectric layer, and an absorbing layer.

Patent No. 5184624 gazette Patent No. 5960319 gazette

  By the way, when using a wire grid type polarization element for a liquid crystal projector, it is common to arrange the grid side in which a lattice-like convex part was formed toward the liquid crystal panel side. Therefore, in the polarizing element disposed on the exit side of the liquid crystal panel, light is incident from the grid surface side on which the grid-like convex portions are formed. According to the conventional polarizing elements described in Patent Documents 1 and 2, it is possible to suppress the absorption axis reflectance to a low level with respect to light incident from the grid surface side on which the grid-like convex portions are formed.

  However, in the liquid crystal projector, light transmitted through the polarization element on the output side may be reflected by another optical element or the like and be incident on the polarization element as return light. In this case, in the conventional polarizing elements described in Patent Documents 1 and 2, the absorption axis reflectance can not be suppressed low, and the light is reflected at a high ratio. When such reflection of return light is repeated, there is a possibility that the image quality may be deteriorated due to a ghost or the like.

  The present invention has been made in view of the above, and the purpose thereof is to reflect the absorption axis with respect to both incident light from the grid surface side on which the grid-like convex portions are formed and incident light from the substrate surface side. It is an object of the present invention to provide a polarizing element capable of suppressing the temperature of the light source, a method of manufacturing the same, and an optical apparatus including the polarizing element.

  In order to achieve the above object, the present invention is a polarizing element having a wire grid structure, and is provided on a transparent substrate (for example, a transparent substrate 10 described later) and the transparent substrate at a pitch shorter than the wavelength of light in a working band. And a grid-like convex part (for example, grid-like convex part 11 described later) which extends in a predetermined direction, and the grid-like convex part is arranged in order from the transparent substrate side to a first absorption layer (for example, The first absorption layer 13 described later, the first dielectric layer (for example, the first dielectric layer 14 described later), the reflection layer (for example the reflection layer 15 described later), and the second dielectric layer A polarizing element (e.g., a polarizing element 1 described below) including a second dielectric layer 16 described later and a second absorption layer (e.g., second absorption layer 17 described below) is provided.

  The lattice-like convex portion has a pedestal (for example, pedestal 12 described later) between the transparent substrate and the first absorption layer, and the pedestal has a trapezoidal shape when viewed from the predetermined direction It may be

  The pedestal may be made of Si oxide that is transparent to the wavelength of light in the use band.

  The first absorption layer and the second absorption layer may be made of the same material.

  The first dielectric layer and the second dielectric layer may be made of the same material.

  The film thickness of the first absorption layer and the film thickness of the second absorption layer are substantially the same, and the film thickness of the first dielectric layer and the film thickness of the second dielectric layer are substantially the same. It may be.

  The transparent substrate may be transparent to the wavelength of light in the working band, and may be made of glass, quartz or sapphire.

  The reflective layer may be made of aluminum or an aluminum alloy.

  The first dielectric layer and the second dielectric layer may be made of Si oxide.

  The first absorption layer and the second absorption layer may contain Fe or Ta and may contain Si.

  The surface on the grid-like convex portion side of the polarizing element may be covered with a protective film made of a dielectric.

  The surface on the grid-like convex portion side of the polarizing element may be covered with an organic water repellent film.

  A tapered shape in which the side surface of the grid tip (for example, grid tip 19 described later) formed at the tip of the grid-like convex portion is inclined in a direction in which the width narrows toward the tip when viewed from the predetermined direction May be included.

  The reflective layer is a metal layer (for example, a metal layer 151 described later), and an oxide layer made of an oxide of a metal that covers the side surface of the metal layer when viewed from the predetermined direction. (For example, an oxide layer 152 described later).

  The width of the reflective layer may be smaller than the widths of the first dielectric layer and the second dielectric layer.

  The present invention is also a method of manufacturing a polarizing element having a wire grid structure, comprising: on a transparent substrate, a first absorption layer, a first dielectric layer, a reflective layer, a second dielectric layer, and A step of forming a laminate having the two absorption layers in this order from the transparent substrate side, and selectively etching the laminate to form the laminate on the transparent substrate at a pitch shorter than the wavelength of light in the working band. And forming a grid-like convex portion arranged in the following manner.

  Further, the present invention provides an optical apparatus comprising the polarizing element.

  According to the present invention, a polarizing element capable of suppressing the absorption axis reflectance to a low level both for incident light from the grid surface side on which the grid-like convex portions are formed and incident light from the substrate surface side It is possible to provide a manufacturing method and an optical apparatus provided with the polarizing element.

It is a cross-sectional schematic diagram which shows an example of the optical element which concerns on this embodiment. It is a cross-sectional schematic diagram which shows the optical element which concerns on the modification 1 of this embodiment. It is a cross-sectional schematic diagram which shows the optical element which concerns on the modification 2 of this embodiment. It is a cross-sectional schematic diagram which shows the optical element which concerns on the modification 3 of this embodiment. It is a cross-sectional schematic diagram which shows an example of an optical element which does not have a 1st absorption layer and a 1st dielectric material layer. It is a graph which shows the result of having verified the absorption axis reflectance to the incidence light from the grid side by simulation about the polarizing element of the structure shown in FIG. 1, and the polarizing element of the structure shown in FIG. It is a graph which shows the result of having verified the absorption axis reflectance to the incidence light from the substrate surface side by simulation about the polarizing element of the structure shown in Drawing 1, and the polarizing element of the structure shown in Drawing 5. It is a graph which shows the result of having produced the polarizing element of the structure shown in FIG. 1 actually, and having verified transmission axis transmittance, absorption axis transmittance, transmission axis reflectance, and absorption axis reflectance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Polarizer]
The polarizing element according to the present embodiment is a polarizing element having a wire grid structure, and is arranged on the transparent substrate at a pitch (period) shorter than the wavelength of the light of the used band and extends in a predetermined direction. And a grid-like convex part. Further, the lattice-like convex portion has a first absorption layer, a first dielectric layer, a reflection layer, a second dielectric layer, and a second absorption layer in order from the transparent substrate side.

  FIG. 1 is a schematic cross-sectional view showing an example of a polarizing element 1 according to the present embodiment. As shown in FIG. 1, the polarizing element 1 has a transparent substrate 10 transparent to light in the use band, and a lattice array arranged on one surface of the transparent substrate 10 at a pitch P shorter than the wavelength of light in the use band. And a convex portion 11. The grid-like convex portion 11 is formed, in order from the transparent substrate 10 side, as a pedestal 12, a first absorption layer 13, a first dielectric layer 14, a reflective layer 15, and a second dielectric layer, as necessary. 16 and a second absorption layer 17. That is, in the polarizing element 1 shown in FIG. 1, the pedestal 12, the first absorption layer 13, the first dielectric layer 14, the reflection layer 15, the second dielectric layer 16, and the second absorption layer 17 are from the transparent substrate 10 side. The grid-like convex portions 11 formed by being stacked in this order have a wire grid structure arranged on the transparent substrate 10 in a one-dimensional grid shape.

  In the present specification, as shown in FIG. 1, the extending direction (predetermined direction) of the grid-like convex portion 11 is referred to as a Y-axis direction. Further, a direction orthogonal to the Y-axis direction and in which the grid-like convex portions 11 are arranged along the main surface of the transparent substrate 10 is referred to as an X-axis direction. In this case, the light incident on the polarizing element 1 is preferably from the direction orthogonal to the X-axis direction and the Y-axis direction on the side (grid surface side) on which the grid-like convex portion 11 of the transparent substrate 10 is formed. It will be incident.

  The polarizing element 1 has a polarization (TE wave (S wave (S wave (S wave) having an electric field component parallel to the Y-axis direction by utilizing four effects of transmission, reflection, interference, and selective light absorption of polarized wave by optical anisotropy) Wave)) and transmits polarized light (TM wave (P wave)) having an electric field component parallel to the X-axis direction. Therefore, the Y-axis direction is the direction of the absorption axis of the polarizing element 1, and the X-axis direction is the direction of the transmission axis of the polarizing element 1.

  The light incident from the side (grid surface side) on which the grid-like convex portions 11 of the polarizing element 1 are formed is partially absorbed and attenuated when passing through the second absorption layer 17 and the second dielectric layer 16 . Of the light transmitted through the second absorption layer 17 and the second dielectric layer 16, the TM wave (P wave) transmits the reflection layer 15, the first dielectric layer 14, and the first absorption layer 13 with high transmittance. . On the other hand, in the light transmitted through the second absorption layer 17 and the second dielectric layer 16, the TE wave (S wave) is reflected by the reflection layer 15. The TE wave reflected by the reflection layer 15 is partially absorbed when passing through the second dielectric layer 16 and the second absorption layer 17, and is partially reflected back to the reflection layer 15. Further, the TE wave reflected by the reflective layer 15 interferes and attenuates when passing through the second dielectric layer 16 and the second absorption layer 17.

  On the other hand, light incident from the transparent substrate 10 side (substrate surface side) of the polarizing element 1 is partially absorbed and attenuated when passing through the first absorption layer 13 and the first dielectric layer 14. Of the light transmitted through the first absorption layer 13 and the first dielectric layer 14, the TM wave (P wave) transmits the reflection layer 15, the second dielectric layer 16, and the second absorption layer 17 with high transmittance. . On the other hand, of the light transmitted through the first absorption layer 13 and the first dielectric layer 14, the TE wave (S wave) is reflected by the reflection layer 15. The TE wave reflected by the reflection layer 15 is partially absorbed when passing through the first dielectric layer 14 and the first absorption layer 13, and is partially reflected back to the reflection layer 15. Also, the TE wave reflected by the reflective layer 15 interferes and attenuates when passing through the first dielectric layer 14 and the first absorption layer 13.

  As described above, according to the polarizing element 1 according to the present embodiment, the absorption axis reflectivity for both incident light from the grid surface side on which the grid-like convex portions are formed and incident light from the substrate surface side Can be kept low.

  The transparent substrate 10 is not particularly limited as long as it is a substrate that exhibits transparency to light in the use band, and can be appropriately selected according to the purpose. The term "shows translucency to light in the use band" does not mean that the transmittance of light in the use band is 100%, but means that the light transmissivity capable of maintaining the function as a polarizing element Just show it. Examples of light in the use band include visible light having a wavelength of about 380 nm to 810 nm.

  The main surface shape of the transparent substrate 10 is not particularly limited, and a shape (for example, a rectangular shape) according to the purpose is appropriately selected. The average thickness of the transparent substrate 10 is preferably, for example, 0.3 mm to 1 mm.

  As a constituent material of the transparent substrate 10, a material having a refractive index of 1.1 to 2.2 is preferable, and glass, quartz, sapphire and the like can be mentioned. From the viewpoint of cost and light transmittance, it is preferable to use glass, particularly quartz glass (refractive index 1.46) or soda lime glass (refractive index 1.51). The component composition of the glass material is not particularly limited. For example, inexpensive glass materials such as silicate glass widely distributed as optical glass can be used.

  Further, from the viewpoint of thermal conductivity, it is preferable to use quartz or sapphire having high thermal conductivity. As a result, high light resistance to strong light can be obtained, and it is preferably used as a polarizing element for an optical engine of a projector that generates a large amount of heat.

  In the case of using a transparent substrate made of an optically active crystal such as quartz, it is preferable to dispose the grid-like convex portion 11 in the parallel direction or the vertical direction with respect to the optical axis of the crystal. Thereby, excellent optical characteristics can be obtained. Here, the optical axis is a direction axis in which the difference in refractive index between light O (ordinary ray) and light E (abnormal ray) traveling in that direction is minimized.

  The grid-like convex portions 11 are arranged on the transparent substrate at a pitch P shorter than the wavelength of light in the working band. The pitch P of the grid-like convex portions 11 is not particularly limited as long as it is shorter than the wavelength of the light of the working band. The pitch P of the grid-like convex portions 11 is preferably, for example, 100 nm to 200 nm from the viewpoint of ease of preparation and stability. The pitch P of the grid-like convex portions 11 can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, the pitch can be measured at any four places using a scanning electron microscope or a transmission electron microscope, and the arithmetic mean value can be used as the pitch of the grid-like convex portions 11. Hereinafter, this measurement method is referred to as electron microscopy.

  The width W of the grid-like convex portions 11 is not particularly limited, but is preferably smaller than the width of the recesses between the grid-like convex portions 11. Specifically, the width W of the grid-like convex portion 11 is preferably, for example, 35 nm to 45 nm. The width W of the grid-like convex part 11 can be measured by the above-mentioned electron microscopy at the central position of the height of the grid-like convex part 11.

  The pedestal 12 has a trapezoidal shape when viewed from the extending direction (predetermined direction) of the grid-like convex portion 11 as shown in FIG. 1, that is, in a cross-sectional view orthogonal to the predetermined direction. More specifically, the pedestal 12 has an equilateral trapezoidal shape in which the side surface is inclined such that the width decreases from the transparent substrate 10 toward the first absorbent layer 13 when viewed from the predetermined direction.

  The film thickness of the pedestal 12 is not particularly limited, and, for example, 10 nm to 100 nm is preferable. The film thickness of the pedestal 12 can be measured, for example, by the above-mentioned electron microscope method.

The pedestal 12 is formed by arranging, on the transparent substrate 10, dielectric films extending in a band shape in the Y-axis direction which is an absorption axis. The material of the pedestal 12 is preferably a material that is transparent to light in the working band and has a smaller refractive index than the transparent substrate 10, and in particular, a Si oxide such as SiO ₂ is preferable.

  For example, the pedestal 12 changes the balance between isotropic etching and anisotropic etching by dry etching in a stepwise manner with respect to the base layer 18 made of the above-described dielectric formed on the transparent substrate 10, for example. It can be formed. In this case, as shown in FIG. 1, the pedestal 12 is disposed on the base layer 18 formed on the transparent substrate 10. By forming the pedestal 12 in a trapezoidal shape, an effect equivalent to that of a moth-eye structure in which the refractive index changes gradually can be obtained, reflection of light can be prevented, and high transmittance characteristics can be obtained.

  However, as described above, the pedestal 12 is not an essential component in the present embodiment, and the polarizing element 1 may not have the pedestal 12. In this case, the grid-like convex portions 11 can be disposed directly on the underlayer 18.

The first absorption layer 13 is formed on the pedestal 12 and extends in a band shape in the Y axis direction, which is an absorption axis, and is arranged. As a constituent material of the first absorption layer 13, one or more kinds of substances having a light absorbing action such as metal materials, semiconductor materials, etc. whose extinction constants of optical constants are not zero may be mentioned, depending on the wavelength range of applied light It is selected appropriately. Examples of the metal material include elemental elements such as Ta, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Sn, etc., and alloys containing one or more of these elements. As the semiconductor material, Si, Ge, Te, ZnO, suicide material _{(β-FeSi 2, MgSi 2} , NiSi 2, BaSi 2, CrSi 2, CoSi 2, TaSi , etc.). By using these materials, the polarizing element 1 can obtain a high extinction ratio to the applied visible light region. Among them, it is preferable that the first absorption layer 13 contains Fe or Ta and is configured to contain Si.

  When a semiconductor material is used as the first absorption layer 13, the band gap energy of the semiconductor needs to be equal to or less than the use band because the band gap energy of the semiconductor is involved in the absorption function. For example, in the case of use in visible light, it is necessary to use a material having an absorption at a wavelength of 400 nm or more, that is, a band gap of 3.1 eV or less.

The film thickness of the first absorption layer 13 is not particularly limited, and for example, 10 nm to 100 nm is preferable. The film thickness of the first absorption layer 13 can be measured, for example, by the above-mentioned electron microscopy.
The first absorption layer 13 can be formed as a high density film by vapor deposition, sputtering or the like. Moreover, the 1st absorption layer 13 may be comprised from two or more layers from which a constituent material differs.

  The first dielectric layer 14 is formed on the first absorption layer 13 and is formed by arranging dielectric films extending in a band shape in the Y-axis direction which is an absorption axis. The first dielectric layer 14 is a film in which the phase of the polarized light transmitted through the first absorbing layer 13 and reflected by the reflecting layer 15 is shifted by a half wavelength with respect to the polarized light incident from the substrate surface side and reflected by the first absorbing layer 13 It is formed of thickness. Specifically, the film thickness of the first dielectric layer 14 is appropriately set in the range of 1 nm to 500 nm in which the phase of polarized light can be adjusted to enhance the interference effect. The film thickness of the first dielectric layer 14 can be measured, for example, by the above-mentioned electron microscopy.

The material constituting the first dielectric layer 14 includes Si oxides such as SiO ₂ , Al ₂ O ₃ , metal oxides such as Al ₂ O ₃ , beryllium oxide, bismuth oxide, MgF ₂ , cryolite, germanium, titanium dioxide, silicon General materials such as magnesium fluoride, boron nitride, boron oxide, tantalum oxide, carbon, or a combination thereof. Among them, the first dielectric layer 14 is preferably made of Si oxide.

The refractive index of the first dielectric layer 14 is preferably greater than 1.0 and 2.5 or less. The optical properties of the reflective layer 15 are also affected by the refractive index of the surroundings, so the properties of the polarizing element 1 can be controlled by selecting the material of the first dielectric layer 14.
Further, by appropriately adjusting the film thickness and the refractive index of the first dielectric layer 14, a part of the TE wave incident from the substrate surface side and reflected by the reflective layer 15 is transmitted when passing through the first absorption layer 13. The light can be reflected back to the reflective layer 15, and the light passing through the first absorption layer 13 can be attenuated by interference. Thus, desired polarization characteristics can be obtained by selectively attenuating the TE wave among the light incident from the substrate surface side.

  The reflective layer 15 is formed on the first dielectric layer 14 and is formed by arranging metal films extending in a band shape in the Y axis direction which is an absorption axis. The reflective layer 15 has a function as a wire grid type polarizer, and attenuates a polarized wave (TE wave (S wave)) having an electric field component in a direction parallel to the longitudinal direction of the reflective layer 15. The polarized wave (TM wave (P wave)) having an electric field component in the direction orthogonal to the longitudinal direction of (1) is transmitted.

  The constituent material of the reflective layer 15 is not particularly limited as long as it is a material having reflectivity to light in the use band, and, for example, Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si And elemental alloys such as Ge and Te, and alloys containing one or more of these elements. Among them, the reflective layer 15 is preferably made of aluminum or an aluminum alloy. In addition, you may comprise the reflection layer 15 by inorganic films other than the metal in which the reflectance of the surface was formed high, for example by coloring etc., or resin films other than these metal materials.

  The film thickness of the reflective layer 15 is not particularly limited, and is preferably, for example, 100 nm to 300 nm. The film thickness of the reflective layer 15 can be measured, for example, by the above-mentioned electron microscope.

  The second dielectric layer 16 is formed on the reflective layer 15, and is formed by arranging dielectric films extending in a band shape in the Y axis direction which is an absorption axis. The second dielectric layer 16 is a film in which the phase of the polarized light transmitted through the second absorbing layer 17 and reflected by the reflecting layer 15 is shifted by a half wavelength with respect to the polarized light incident from the grid surface side and reflected by the second absorbing layer 17 It is formed of thickness. Specifically, the film thickness of the second dielectric layer 16 is appropriately set in the range of 1 nm to 500 nm in which the interference effect can be enhanced by adjusting the phase of polarized light. The film thickness of the second dielectric layer 16 can be measured, for example, by the above-mentioned electron microscopy.

  As a material which comprises the 2nd dielectric material layer 16, the material similar to the 1st dielectric material layer 14 is mentioned. Among them, the second dielectric layer 16 is preferably made of the same material as the first dielectric layer 14. By forming the first dielectric layer 14 and the second dielectric layer 16 with the same material, the etching conditions and the like at the time of manufacture become the same, and the manufacture becomes easy. It is also possible to combine the performance of the first dielectric layer 14 and the performance of the second dielectric layer 16.

The refractive index of the second dielectric layer 16 is preferably greater than 1.0 and 2.5 or less. The optical properties of the reflective layer 15 are also affected by the refractive index of the surroundings, so the properties of the polarizing element 1 can be controlled by selecting the material of the second dielectric layer 14.
Further, by appropriately adjusting the film thickness and the refractive index of the second dielectric layer 16, a part of the TE wave which is incident from the grid surface side and reflected by the reflective layer 15 is transmitted when passing through the second absorption layer 17. The light can be reflected back to the reflective layer 15, and the light passing through the second absorption layer 17 can be attenuated by interference. Thus, desired polarization characteristics can be obtained by selectively attenuating the TE wave in the light incident from the grid surface side.

  The second absorption layer 17 is formed on the second dielectric layer 16 and extends in a band shape in the Y axis direction which is the absorption axis. As a constituent material of the 2nd absorption layer 17, the material similar to the 1st absorption layer 13 is mentioned. Among them, the second absorption layer 17 is preferably made of the same material as the first absorption layer 13. By making the first absorption layer 13 and the second absorption layer 17 of the same material, the etching conditions and the like at the time of manufacture become the same, and the manufacture becomes easy. It is also possible to combine the performance of the first absorption layer 13 and the performance of the second absorption layer 17.

The film thickness of the second absorption layer 17 is not particularly limited, and for example, 10 nm to 100 nm is preferable. The film thickness of the second absorption layer 17 can be measured, for example, by the above-mentioned electron microscopy.
The second absorption layer 17 can be formed as a high density film by a vapor deposition method, a sputtering method, or the like. Moreover, the 2nd absorption layer 17 may be comprised from two or more layers from which a constituent material differs.

In the polarizing element 1 according to the present embodiment, the thickness of the first absorption layer 13 and the thickness of the second absorption layer 17 are substantially the same, and the thickness of the first dielectric layer 14 and the thickness of the first absorption layer It is preferable that the film thickness of the second dielectric layer 16 be substantially the same. Specifically, when the thickness of the first absorption layer 13 is t ₁ (nm), the thickness of the second absorption layer 17 is 0.90 t ₁ (nm) to 1.10 t ₁ (nm). Is preferable, and 0.95 t ₁ (nm) to 1.05 t ₁ (nm) is more preferable. When the film thickness of the first dielectric layer 14 is t ₂ (nm), the film thickness of the second dielectric layer 16 is 0.90 t ₂ (nm) to 1.10 t ₂ (nm). Preferably, 0.95 t ₂ (nm) to 1.05 t ₂ (nm) is more preferable. By thus matching the film thickness, it is possible to match the wavelength at the minimum point of the absorption axis reflectance for the incident light from the grid surface side and the incident light from the substrate surface side.

  The polarizing element 1 according to the present embodiment having the above-described configuration is provided between the first absorption layer 13 and the first dielectric layer 14 and between the second dielectric layer 16 and the second absorption layer 17. It may have a diffusion barrier layer. That is, in this case, the lattice-like convex portion 11 includes, in order from the transparent substrate 10 side, the pedestal 12, the first absorption layer 13, the diffusion barrier layer, the first dielectric layer 14, the reflective layer 15, and A second dielectric layer 16, a diffusion barrier layer, and a second absorption layer 17 are provided. By including the diffusion barrier layer, diffusion of light in the first absorption layer 13 and the second absorption layer 17 is prevented. The diffusion barrier layer is formed of a metal film such as Ta, W, Nb, Ti or the like.

  In addition, in the polarizing element 1 according to the present embodiment, the surface on the grid surface side may be covered with a protective film made of a dielectric in a range not affecting the change of the optical characteristics. The protective film is formed of a dielectric film, and can be formed on the surface on the grid surface side by using a CVD method (chemical vapor deposition method), an ALD method (atomic layer deposition method) or the like. Thereby, it is possible to suppress the oxidation reaction more than necessary to the metal film.

  Furthermore, in the polarizing element 1 according to the present embodiment, the surface on the grid surface side may be covered with an organic water repellent film. The organic water repellent film is made of, for example, a fluorine-based silane compound such as perfluorodecyl triethoxysilane (FDTS) or the like, and can be formed by using the above-mentioned CVD method, ALD method or the like. Thereby, the reliability such as the moisture resistance of the polarizing element 1 can be improved.

[Method of Manufacturing Polarizing Element]
The method of manufacturing a polarizing element according to the present embodiment is a method of manufacturing a polarizing element having a wire grid structure, and includes a first absorption layer, a first dielectric layer, a reflective layer, and a second layer on a transparent substrate. A step of forming a laminate having the dielectric layer and the second absorption layer in this order from the transparent substrate side, and selectively etching this laminate to obtain a pitch shorter than the wavelength of light in the working band And forming a grid-like convex portion arranged on the transparent substrate.

  Hereinafter, a method of manufacturing the polarizing element 1 shown in FIG. 1 will be described as an example.

  First, on the transparent substrate 10, the base layer, the first absorption layer, the first dielectric layer, the reflection layer, the second dielectric layer, and the second absorption layer in this order from the transparent substrate 10 side. To form a laminate. A sputtering method, a vapor deposition method, etc. are mentioned as a formation method of these each layer.

  Next, a one-dimensional grid-like mask pattern is formed on the second absorption layer by photolithography, nanoimprinting, or the like. Then, the laminated body is selectively etched to form the grid-like convex portions 11 arranged on the transparent substrate 10 at a pitch shorter than the wavelength of the light of the working band. As an etching method, for example, a dry etching method using an etching gas corresponding to an etching target can be mentioned.

  In particular, when manufacturing the polarizing element 1 shown in FIG. 1, the pedestal 12 having a trapezoidal shape when viewed from the extending direction of the grid-like convex portion 11 is formed by optimizing the etching conditions of the underlayer. Do. Thus, the polarizing element 1 shown in FIG. 1 is manufactured.

  In addition, the manufacturing method of the polarizing element which concerns on this embodiment may further have the process of coat | covering the surface by the side of a grid surface with a protective film. Moreover, the manufacturing method of the polarizing element which concerns on this embodiment may further have the process of coat | covering the surface by the side of a grid surface with an organic type water repellent film.

[Optical equipment]
The optical apparatus according to the present embodiment includes the polarizing element according to the above-described present embodiment. Examples of the optical device include a liquid crystal projector, a head-up display, and a digital camera. The polarizing element according to the present embodiment is an inorganic polarizing element that is excellent in heat resistance as compared to an organic polarizing element, and thus is suitable for applications such as a liquid crystal projector and a head-up display that require heat resistance.

  When the optical device according to the present embodiment includes a plurality of polarizing elements, at least one of the plurality of polarizing elements may be the polarizing element according to the present embodiment. For example, when the optical device according to the present embodiment is a liquid crystal projector, at least one of the polarizing elements disposed on the incident side and the output side of the liquid crystal panel may be the polarizing element according to the present embodiment. From the viewpoint of further reducing deterioration in image quality due to ghosts and the like, it is preferable that at least the output-side polarizing element be the polarizing element according to the present embodiment, and both the incident-side and the output-side polarizing elements be the present It is more preferable that it is a polarizing element.

  According to the polarizing element 1 described above, the method of manufacturing the same, and the optical device, the following effects can be obtained.

  In the polarizing element 1 according to the present embodiment, the first absorption layer 13, the first dielectric layer 14, the reflective layer 15, the second dielectric layer 16, and the second absorption layer 17 are stacked in this order from the transparent substrate 10 side. Since the grid-like convex portions 11 are formed, it is possible to suppress the absorption axis reflectance to be low for both the incident light from the grid surface side and the incident light from the substrate surface side. Therefore, even when the polarizing element 1 according to the present embodiment is used as the polarizing element of the liquid crystal panel on the output side of the liquid crystal projector, it is possible to reduce the deterioration of the image quality due to a ghost or the like.

  In addition, this invention is not limited to embodiment mentioned above, The deformation | transformation and improvement in the range which can achieve the objective of this invention are included in this invention.

  FIG. 2 is a schematic cross-sectional view showing a polarizing element 1A according to a modification 1 of the embodiment. In this polarizing element 1A, the width of the grid tip 19 formed at the tip of the grid convex 11A becomes narrower toward the tip when viewed from the extending direction (predetermined direction) of the grid convex 11A. It has a tapered shape whose side faces are inclined in the direction. More specifically, the grid tip 19 of the polarizing element 1A according to the first modification has an equal leg trapezoidal shape. The grid tip 19 is constituted by a part of the reflective layer 15A, the second dielectric layer 16A, and the second absorbing layer 17A.

  As shown in FIG. 2, by making the grid tip 19 into a tapered shape, the transmittance of polarized light (TM wave) in the transmission axis direction (X-axis direction) can be increased. The reason why the transmittance of the TM wave is increased as described above is considered to be that, by making the grid tip 19 into a tapered shape, it has an effect of suppressing scattering of light incident with angular variation. .

  Although in FIG. 2 the grid tip portion 19 includes a part of the reflective layer 15A, the present invention is not limited to this structure. For example, only the second dielectric layer 16A and the second absorbing layer 17A may be used to form the grid tip. The unit 19 may be configured.

  FIG. 3 is a schematic cross-sectional view showing a polarizing element 1B according to a modification 2 of the present embodiment. In the polarizing element 1B, the reflective layer 15B covers the side surface of the metal layer 151 when viewed from the metal layer 151 and the extending direction (predetermined direction) of the grid-like convex portion 11B, and constitutes the metal layer 151. And an oxide layer 152 formed of a metal oxide.

  The constituent material of the metal layer 151 is not particularly limited as long as it is a material having reflectivity to light in the use band, and, for example, Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si And elemental alloys such as Ge and Te, and alloys containing one or more of these elements. Among them, the metal layer 151 is preferably made of aluminum or an aluminum alloy.

The oxide layer 152 is made of an oxide of a metal forming the metal layer 151. For example, when the metal layer 151 is made of Al, the oxide layer 152 is made of Al ₂ O ₃ . The oxide layer 152 is formed by an oxidation reaction or the like by heat treatment of the metal layer.

  As shown in FIG. 3, by forming the reflective layer 15B with the metal layer 151 and the oxide layer 152, the area of the reflective layer 15B viewed from the incident direction of light is polarized and the light reflected by the reflective layer 15B Amount of change. Therefore, light transmission characteristics equivalent to the case of narrowing the grid width can be obtained without narrowing the grid width.

  In the polarizing element 1B according to the second modification, as in the polarizing element 1A according to the first modification, the grid tip may be formed at the tip of the grid-like convex portion 11B.

  FIG. 4 is a schematic cross-sectional view showing a polarizing element 1C according to Modification 3 of the present embodiment. In the grid-like convex portion 11C of the polarizing element 1C, the width of the reflective layer 15C is smaller than the widths of the first dielectric layer 14 and the second dielectric layer 16.

  As shown in FIG. 4, by making the width of the reflective layer 15C smaller than the widths of the first dielectric layer 14 and the second dielectric layer 16, the area of the reflective layer 15C viewed from the light incident direction is changed. The amount of light reflected by the reflective layer 15C changes. Therefore, by controlling the width of the reflective layer 15C, the light transmission characteristic of the polarizing element 1C can be controlled.

  Also in the polarizing element 1C according to the third modification, as in the polarizing element 1A according to the first modification, the grid tip may be formed at the tip of the grid-like convex portion 11C.

  Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 and Comparative Example 1
In Example 1, the polarizing element 1 having the structure shown in FIG. 1 was subjected to simulation. Moreover, in the comparative example 1, the polarizing element 100 of the structure shown in FIG. 5 was used for simulation. More specifically, the optical characteristics of these polarizing elements were verified by electromagnetic field simulation by RCWA (Rigorous Coupled Wave Analysis) method. For the simulation, a grating simulator Gsolver from Grating Solver Development was used. The polarizing element 1 of Example 1 and the polarizing element 100 of Comparative Example 1 are designed to be optimized for light in the color band (wavelength λ = 520 nm to 590 nm (predetermined wavelength)). .

  FIG. 5 is a schematic cross-sectional view showing the structure of the polarizing element 100 of Comparative Example 1. As shown in FIG. In FIG. 5, the same reference numerals as in the polarizing element 1 shown in FIG. The grating convex portion 101 of the polarizing element 100 has the same configuration as the grating convex portion 11 of the polarizing element 1 shown in FIG. 1 except that the first absorbing layer 13 and the first dielectric layer 14 are not provided.

  FIG. 6 is a graph showing the result of simulation verification of absorption axis reflectance with respect to incident light from the grid surface side for the polarizing element 1 having the structure shown in FIG. 1 and the polarizing element 100 having the structure shown in FIG. In FIG. 6, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the absorption axis reflectance (%). Here, the absorption axis reflectance means the reflectance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing element.

  As shown in FIG. 6, when light is incident from the grid surface side, absorption is caused by the function of the second dielectric layer 16 and the second absorption layer 17 in any of the structures of FIG. 1 and FIG. The axial reflectivity was kept low.

  FIG. 7 is a graph showing the result of simulation verification of the absorption axis reflectance with respect to incident light from the substrate surface side for the polarizing element 1 having the structure shown in FIG. 1 and the polarizing element 100 having the structure shown in FIG. In FIG. 7, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the absorption axis reflectance (%).

  As shown in FIG. 7, when light enters from the substrate surface side, in the polarizing element 1 having the structure shown in FIG. 1, the absorption axis reflectance is low due to the functions of the first absorption layer 13 and the first dielectric layer 14 It was suppressed. On the other hand, in the polarizing element 100 having the structure shown in FIG. 5, since the first absorption layer 13 and the first dielectric layer 14 are not provided, the absorption axis reflectance is significantly increased.

Example 2
In Example 2, the polarizing element 1 having the structure shown in FIG. 1 was actually produced, and its optical characteristics were verified. FIG. 8 is a graph showing the results of verification of transmission axis transmittance, absorption axis transmittance, transmission axis reflectance, and absorption axis reflectance for the polarizing element 1 having the structure shown in FIG. In FIG. 8, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the transmittance or the reflectance (%). Here, the transmission axis transmittance means the transmittance of polarized light (TM wave) in the transmission axis direction (X-axis direction) incident on the polarizing element, and the transmission axis reflectance refers to the transmission axis incident on the polarizing element It means the reflectance of polarized light (TM wave) in the direction (X-axis direction). In addition, the absorption axis transmittance means the transmittance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing element.
With regard to the absorption axis reflectance, both incident light from the grid surface side and incident light from the substrate surface side were verified, and with respect to the other optical characteristics, incident light from the grid surface side was verified.

  As shown in FIG. 8, in the polarizing element 1 having the structure shown in FIG. 1, the absorption axis reflectance can be suppressed to a low value for both incident light from the grid surface side and incident light from the substrate surface side, There were no adverse effects on other optical properties.

  1, 1A, 1B, 1C Polarizing element, 10 Transparent substrate, 11, 11A, 11B, 11C Lattice-like convex part, 12 pedestal, 13 first absorption layer, 14 first dielectric layer, 15, 15A, 15B, 15C reflection Layer 16, 16A second dielectric layer 17, 17A second absorbing layer 18 underlayer, 19 grid tip, 100 polarizing element, 101 lattice-like convex portion, 151 metal layer, 152 oxide layer

Claims (17)

A polarization element having a wire grid structure,
A transparent substrate,
And a grid-like convex portion arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band and extending in a predetermined direction,
A polarizing element having a first absorption layer, a first dielectric layer, a reflective layer, a second dielectric layer, and a second absorption layer, in order from the transparent substrate side. The grid-like convex portion has a pedestal between the transparent substrate and the first absorption layer,
The polarizing element according to claim 1, wherein the pedestal has a trapezoidal shape when viewed from the predetermined direction.   The polarizing element according to claim 1 or 2, wherein the pedestal is made of Si oxide which is transparent to the wavelength of light in a working band.   The polarizing element according to any one of claims 1 to 3, wherein the first absorption layer and the second absorption layer are made of the same material.   The polarization element according to any one of claims 1 to 4, wherein the first dielectric layer and the second dielectric layer are made of the same material.   The film thickness of the first absorption layer and the film thickness of the second absorption layer are substantially the same, and the film thickness of the first dielectric layer and the film thickness of the second dielectric layer are substantially the same. The polarization element according to any one of claims 1 to 5.   The polarizing element according to any one of claims 1 to 6, wherein the transparent substrate is transparent to the wavelength of light in a working band, and is made of glass, quartz or sapphire.   The polarizing element according to any one of claims 1 to 7, wherein the reflective layer is made of aluminum or an aluminum alloy.   The polarizing element according to any one of claims 1 to 8, wherein the first dielectric layer and the second dielectric layer are made of Si oxide.   The polarizing element according to any one of claims 1 to 9, wherein the first absorption layer and the second absorption layer contain Fe or Ta and contain Si.   The polarizing element according to any one of claims 1 to 10, wherein a surface of the polarizing element on the side of the lattice convex portion is covered with a protective film made of a dielectric.   The polarizing element according to any one of claims 1 to 11, wherein the surface of the polarizing element on the side of the lattice-like convex portion is covered with an organic water repellent film.   13. The grid tip portion formed at the tip end of the grid-like convex portion has a tapered shape in which the side surface is inclined in a direction in which the width becomes narrower toward the tip end side when viewed from the predetermined direction. The polarizing element as described in.   14. The method according to claim 1, wherein the reflective layer includes a metal layer, and an oxide layer formed of an oxide of a metal that covers the side surface of the metal layer when viewed from the predetermined direction. The polarizing element as described in any one of.   The polarizing element according to any one of claims 1 to 14, wherein the width of the reflective layer is smaller than the widths of the first dielectric layer and the second dielectric layer. A method of manufacturing a polarizing element having a wire grid structure, comprising:
A laminate having a first absorption layer, a first dielectric layer, a reflection layer, a second dielectric layer, and a second absorption layer is formed on a transparent substrate in this order from the transparent substrate side. Process,
And forming a grid-like convex portion arranged on the transparent substrate at a pitch shorter than the wavelength of light in a working band by selectively etching the laminate.   An optical apparatus comprising the polarizing element according to any one of claims 1 to 15.

Images