Wire grid polarizing element, method for manufacturing wire grid polarizing element, projection display device, and vehicle

Abstract

A wire grid polarizing element 1 comprises: a substrate 10; a grid structure 20 in which a base 21 and a plurality of projections 22 are integrally formed; a functional film 30 that covers a portion of the projections 22; and a reinforcement film 51. The reinforcement film 51 is made of an inorganic oxide, is interposed between the functional film 30 and a portion of the projections 33 covered with the functional film 30, and reinforces the projections 22. The reinforcement film 51 envelopes at least tips 22a and the upper sides of both side-surfaces 22b of the projections 22. The functional film 30 envelopes the tops of the projections 22 with the reinforcement film 51 therebetween while not covering the bottom sides of the projections 22 and the base 21, and the coverage (Rc) thereof is 30-70%.

Description

Wire grid polarizer, method for manufacturing wire grid polarizer, projection display device and vehicle

[0001] The present invention relates to a wire grid polarizer, a method for manufacturing a wire grid polarizer, a projection display device, and a vehicle. This application claims the benefit of priority from Japanese Patent Application No. 2023-216488 filed on December 22, 2023, and Japanese Patent Application No. 2024-225992 filed on December 23, 2024, the contents of which are incorporated herein by reference.

[0002] Wire grid polarizers are used, for example, as polarizing beam splitters in head-up display devices for vehicles. Head-up display devices are installed on the dashboard inside a vehicle and are required to have high heat resistance and heat dissipation properties when used in high-temperature environments such as summer. Therefore, wire grid polarizers mounted in head-up display devices are also required to have excellent heat resistance and heat dissipation properties.

[0003] For example, Patent Document 1 discloses that, in order to improve the heat resistance and heat dissipation of a wire-grid polarizer, the substrate of the wire-grid polarizer is formed from a transparent inorganic material (e.g., glass) and the grid structure provided on the substrate is integrally formed from a transparent organic material (e.g., resin). This grid structure is integrally formed with a base portion provided on the substrate and a plurality of ridge portions protruding from the base portion, and the tips of each ridge portion are coated with a functional film made of a metal material such as Al to impart a reflecting function to incident light. Patent Document 1 also discloses that the height H of the ridge portions is increased to 160 nm or more in order to improve various optical characteristics required of the wire-grid polarizer (e.g., transmission axis transmittance (Tp) characteristics, Tp×Rs characteristics, contrast).

[0004] JP 2023-095826 A JP 2014-085516 A

[0005] However, the ridges of the grid structure described in Patent Document 1 are formed of an organic material, such as a resin, which has lower rigidity and heat resistance than inorganic materials, such as glass, and have a tapered shape that narrows toward the tip. Therefore, if the height H of the ridges is increased as described in Patent Document 1, when a high-temperature functional film is formed to cover the tip of the ridges by a film formation method, such as a sputtering method or a vapor deposition method, the ridges made of an organic material may not maintain their tapered shape extending straight upward and may tilt to the left or right. If the ridges tilt due to the formation of the functional film covering the ridges, various optical characteristics (e.g., Tp characteristics, Tp×Rs characteristics, and contrast) required for the wire-grid polarization element are reduced.

[0006] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a wire-grid polarization element, a manufacturing method for a wire-grid polarization element, a projection display device, and a vehicle that can suppress tilting of the convex ridge portions of the grid structure due to the formation of a functional film and improve optical characteristics.

[0007] The inventors of the present invention conducted extensive research to solve the above-mentioned problems and discovered the following. First, the substrate of a wire-grid polarizer is formed from a transparent inorganic material, and the grid structure provided on the substrate is integrally formed from a transparent organic material. This allows the wire-grid polarizer to have a hybrid structure made of organic and inorganic materials. As a result, the heat dissipation properties of the wire-grid polarizer can be significantly improved.

[0008] Furthermore, the grid structure used has a base portion provided along the surface of the substrate and a plurality of ridge portions protruding from the base portion, which are integrally formed. This allows the grid structure to be formed by a technique such as nanoimprinting, which reduces the manufacturing cost of the grid structure compared to when photolithography or etching is used, and also enables mass production.

[0009] Furthermore, when a functional film such as a reflective film that reflects light or an absorbing film that absorbs light is provided on the convex ribs of the grid structure, the coverage area and coverage form of the convex ribs with the functional film are suitably adjusted. That is, the tips of the convex ribs and the upper sides of one or both side surfaces are covered by the functional film so as to envelop them, while the lower sides of the side surfaces of the convex ribs and the surface of the base are left open without being covered by the functional film. The functional film is then rounded and shaped to bulge in the width direction of the convex ribs, enveloping the tips and upper sides of the side surfaces of the convex ribs. Furthermore, the maximum width (m) of the grid, which is the sum of the convex ribs and the functional film enveloping the convex ribs, is adjusted. ＭＡＸ ) is the bottom of the ridge Ｂ The shape and size of the ridges and the functional film are adjusted so that the height (H) of the ridges is at least 100%. Furthermore, it is preferable to limit the area where the functional film covers the side surface of the ridges to a specific area on the upper side of the side surface (for example, a range of 25% to 80% of the height (H) of the ridges).

[0010] As a result, even when obliquely incident light having a large and wide range of incident angles is incident on the wire-grid polarization element, the transmittance (Tp) of the second polarized light (P-polarized light) through the wire-grid polarization element can be prevented from decreasing depending on the incident angle. Therefore, the product (Tp × Rs) of the reflection axis reflectance (Rs) of the first polarized light (S-polarized light) and the transmission axis transmittance (Tp) of the second polarized light (P-polarized light) through the wire-grid polarization element can be maintained at a high value. Therefore, when the wire-grid polarization element is used as, for example, a polarizing beam splitter, sufficient transmittance and polarization separation characteristics can be obtained even for obliquely incident light having a large and wide range of incident angles.

[0011] Based on the above findings, the present inventors have conceived the following invention.

[0012] In order to solve the above problems, according to one aspect of the present invention, there is provided a substrate made of an inorganic material; a grid structure made of an organic material, the grid structure having a base portion provided on the substrate and a plurality of convex ridge portions protruding from the base portion integrally formed therewith; a functional film made of a metal material and covering a portion of the convex ridge portions; and a reinforcing film made of an inorganic oxide and interposed between the functional film and the portion of the convex ridge portions covered by the functional film, the convex ridge portions having a tapered shape whose width narrows as it moves away from the base portion, the reinforcing film covering at least the tip and upper sides of both side surfaces of the convex ridge portions, the functional film covering the tip and the upper side of at least one side surface of the convex ridge portions via the reinforcing film, and not covering the lower sides of both side surfaces of the convex ridge portions or the base portion, The wire grid polarization element is provided, wherein when the coverage rate (Rc) of the side surface of the convex rib portion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the convex rib portion that is covered by the functional film to the height (H) of the convex rib portion, the coverage rate (Rc) is 30% or more and 70% or less.

[0013] The reinforcing film may have a thickness of 0.5 nm or more and 8 nm or less.

[0014] The grid structure may further include a protective film covering the surfaces of the functional film, the protective film continuously covering the surface of the functional film, the lower sides of both sides of the ridge portion, and the surface of the base portion, and the thickness of the protective film covering the top of the functional film that encases the ridge portion may be Tt, and the thickness of the protective film covering the lower sides of both sides of the ridge portion and the surface of the base portion may be Bt, so as to satisfy the following formula (10): Bt / Tt≧0.85 (10)

[0015] The following formula (11) may be satisfied: 0.85≦Bt / Tt≦1.07 (11)

[0016] The following formula (12) may be satisfied: 1.00<Bt / Tt≦1.07 (12)

[0017] The protective film is made of SiO ２Alternatively, the insulating film may have a single layer structure.

[0018] The protective film is made of Al ２ O ３ a first coating layer consisting of SiO ２ and a second coating layer consisting of:

[0019] The thickness (TB) of the base portion may be 0.15 mm or less.

[0020] The thickness (TB) of the base portion may be 0.09 mm or less.

[0021] The thickness (TB) of the base portion may be 0.045 mm or less.

[0022] The thickness (TB) of the base portion may be 0.02 mm or less.

[0023] The wire grid polarizer may be a hybrid type that combines the substrate made of the inorganic material with the grid structure made of the organic material.

[0024] The surface of the functional film that encases the convex ridge portion is rounded and bulges out in the width direction of the convex ridge portion, and the maximum width (W ＭＡＸ ) is the width (W) of the part of the ridge that is not covered with the functional film at a position 20% above the bottom of the ridge. Ｂ ) or more.

[0025] The cross-sectional shape of the entire convex structure composed of the convex streak portion and the functional film may have a constricted portion in which the width of the entire convex structure in the width direction is narrowed directly below the lower end of the functional film that covers the convex streak portion.

[0026] The product (Tp×Rs) of the transmission axis transmittance (Tp) and the reflection axis reflectance (Rs) of light incident on the wire grid polarizer at an incident angle of 45° may be 70% or more.

[0027] The height (H) of the ridge portion may be 160 nm or more.

[0028] The thickness (Dt) of the functional film covering the tip of the ridge portion may be 5 nm or more.

[0029] The thickness (Ds) of the functional film covering the side surface of the protruding ridge may be set to 10 nm or more and 30 nm or less.

[0030] The thickness (TB) of the base portion may be 1 nm or more.

[0031] The cross-sectional shape of the convex ridges in a cross section perpendicular to the reflection axis direction of the wire grid polarizer may be a trapezoid, a triangle, a bell shape, or an ellipse whose width narrows with increasing distance from the base portion.

[0032] The protective coating may include a water-repellent or oil-repellent coating.

[0033] The functional film may further include a dielectric film.

[0034] When θ is 30° or more and 60° or less, the difference between the transmission axis transmittance (Tp(+)) of incident light having an incident angle of +θ to the wire-grid polarizer and the transmission axis transmittance (Tp(-)) of incident light having an incident angle of −θ may be within 3%.

[0035] The functional film may be a reflective film that reflects incident light.

[0036] The wire grid polarizer may be a polarizing beam splitter that splits obliquely incident light into a first polarized light and a second polarized light.

[0037] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for manufacturing the above-mentioned wire grid polarizer, comprising the steps of: forming a grid structure material made of an organic material on a substrate made of an inorganic material; forming a grid structure having a base portion provided on the substrate and a plurality of ridge portions protruding from the base portion by nanoimprinting the grid structure material; forming a reinforcing film using an inorganic oxide that covers at least a portion of the ridge portions; and forming a functional film using a metal material that covers a portion of the ridge portions via the reinforcing film, wherein in the step of forming the grid structure, the ridge portions are formed to have a tapered shape that narrows in width as they move away from the base portion, and in the step of forming the functional film, The present invention provides a method for manufacturing a wire grid polarization element, wherein the reinforcing film covers at least the tip and upper sides of both side surfaces of the convex rib portion, the functional film covers the tip and upper sides of both side surfaces of the convex rib portion via the reinforcing film, and does not cover the lower sides of both side surfaces of the convex rib portion or the base portion, and the functional film is formed so that, when the coverage rate (Rc) of the side surfaces of the convex rib portion by the functional film is the ratio of the height (Hx) of the part of the side surface of the convex rib portion covered by the functional film to the height (H) of the convex rib portion, the coverage rate (Rc) is 30% or more and 70% or less.

[0038] In the step of forming the reinforcing film, the reinforcing film may be formed by vapor deposition so as to cover the tip and upper sides of both side surfaces of the protruding ridge portion.

[0039] In the step of forming the reinforcing film, the reinforcing film may be formed by an ALD method so that the reinforcing film continuously covers the tip and both side surfaces of the protrusion portion and the surface of the base portion.

[0040] The method may further include a step of forming a protective film on the surfaces of the grid structure and the functional film, and in the step of forming the protective film, the protective film may be formed by an ALD method so that the protective film continuously covers the surface of the functional film, the lower sides of both side surfaces of the convex rib portion, and the surface of the base portion.

[0041] The process of forming the protective film includes: a first process of introducing a precursor gas into a chamber in which the grid structure coated with the functional film is placed; a second process of exhausting excess precursor gas to the outside of the chamber by introducing an inert gas into the chamber; a third process of introducing an oxidizer gas into the chamber; and a fourth process of exhausting excess oxidizer gas to the outside of the chamber by introducing an inert gas into the chamber, wherein in the first process, the precursor gas may be introduced into the chamber to fill it without being exhausted to the outside of the chamber, and in the third process, the oxidizer gas may be introduced into the chamber to fill it without being exhausted to the outside of the chamber.

[0042] In the step of forming the functional film, films may be formed alternately from a plurality of directions on the ridge portion by sputtering or vapor deposition.

[0043] In order to solve the above problem, according to another aspect of the present invention, there is provided a projection display device comprising: a light source; a polarizing beam splitter arranged so that incident light from the light source is incident at an incident angle within a predetermined range including 45°, and separating the incident light into a first polarized light and a second polarized light; a reflective liquid crystal display element arranged so that the first polarized light reflected by the polarizing beam splitter or the second polarized light transmitted through the polarizing beam splitter is incident, and reflecting and modulating the incident first polarized light or the second polarized light; and a lens arranged so that the first polarized light or the second polarized light reflected and modulated by the reflective liquid crystal display element is incident through the polarizing beam splitter, wherein the polarizing beam splitter is constituted by the wire grid polarizer.

[0044] The predetermined range of incident angles may be equal to or greater than 30° and equal to or less than 60°.

[0045] A heat dissipation member may be provided around the wire grid polarizer.

[0046] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a vehicle equipped with the projection display device.

[0047] According to the present invention, it is possible to prevent the protruding stripes of the grid structure from tilting due to the formation of the functional film, thereby improving the optical characteristics.

[0048] FIG. 1 is a cross-sectional view schematically showing a wire-grid polarization element according to a first embodiment of the present invention. FIG. 2 is a plan view schematically showing the wire-grid polarization element according to the same embodiment. FIG. 3 is a cross-sectional view schematically showing a specific example of a tapered shape of a convex portion of a grid structure according to the same embodiment. FIG. 4 is a cross-sectional view schematically showing a specific example of a shape of a concave portion of a grid structure according to the same embodiment. FIG. 5 is a cross-sectional view schematically showing a wire-grid polarization element according to the same embodiment. FIG. 6 is a cross-sectional view schematically showing a specific example of a shape of a reflective film according to the same embodiment. FIG. 7 is a cross-sectional view schematically showing a polarization element covered with a protective film according to the same embodiment. FIG. 8 is a cross-sectional view schematically showing a modified example of a polarization element covered with a protective film according to the same embodiment. FIG. 9 is a perspective view schematically showing a polarization element including a heat dissipation member according to the same embodiment. FIG. 10 is a photograph showing an actual grid structure and a reflective film according to the same embodiment. FIG. 11 is a process chart showing a method for manufacturing the wire-grid polarization element according to the same embodiment. FIG. 12 is a process chart showing a method for manufacturing a conventional wire-grid polarization element. FIG. 13 is a process chart showing a method for manufacturing a master according to the same embodiment. FIG. 14 is a schematic diagram showing a head-up display device as an example of a projection display device according to the embodiment. FIG. 15 is a schematic diagram showing a first specific example of the projection display device according to the embodiment. FIG. 16 is a schematic diagram showing a second specific example of the projection display device according to the embodiment. FIG. 17 is a schematic diagram showing a third specific example of the projection display device according to the embodiment. FIG. 18 is an enlarged cross-sectional view showing a wire-grid polarizer covered with a protective film according to the embodiment. FIG. 19 is a schematic diagram showing a process of forming a protective film by an ALD method according to the embodiment. FIG. 20 is a graph showing heat resistance test results for Comparative Examples 51 and 52. FIG. 21 is a graph showing heat resistance test results for Comparative Examples 53 and 54. FIG. 22 is a graph showing heat resistance test results for Examples 51, 52, and 53. FIG. 23 is a graph showing light resistance test results for Comparative Example 52. FIG. 24 is a graph showing light resistance test results for Examples 51, 52, and 53. FIG. 25 is an enlarged cross-sectional view showing a wire-grid polarizer including a reinforcing film that covers the entire grid structure according to the same embodiment.Fig. 26 is an enlarged cross-sectional view showing a wire-grid polarizer including a reinforcing film covering a portion of the convex streak of the grid structure according to a modified example of the embodiment. Fig. 27 is a schematic diagram showing a model in which a reflective film is vapor-deposited alternately from the left and right onto the upper portion of the convex streak. Fig. 28 is a schematic diagram showing the results of a simulation of the deformation behavior of the convex streak using the model of Fig. 27. Fig. 29 is a schematic diagram showing the results of a simulation of the deformation behavior in which the convex streak becomes thinner during vapor deposition of a reflective film. Fig. 30 is an explanatory diagram showing the cross-sectional shape of a wire-grid polarizer according to Example 60 and the results of an optical property test. Fig. 31 is an explanatory diagram showing the cross-sectional shape of a wire-grid polarizer according to Comparative Example 60 and the results of an optical property test.

[0049] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted. For ease of explanation, the states of the components disclosed in the following drawings may be represented schematically at different scales and shapes from the actual state.

[0050] 1. Overview of Wire-Grid Polarizer First, an overview of a wire-grid polarizer 1 according to a first embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a cross-sectional view schematically showing the wire-grid polarizer 1 according to this embodiment. Fig. 2 is a plan view schematically showing the wire-grid polarizer 1 according to this embodiment.

[0051] The wire-grid polarizer 1 according to this embodiment is a reflective polarizer and a wire-grid polarizer. The wire-grid polarizer 1 may be, for example, a plate-shaped wire-grid polarizer. The wire-grid polarizer is a plate-shaped wire-grid polarizer. The wire-grid polarizer may be, for example, a flat plate-shaped or curved plate-shaped. In other words, the surface of the wire-grid polarizer 1 (the surface onto which light is incident) may be either flat or curved. An example in which the wire-grid polarizer 1 according to this embodiment is a flat wire-grid polarizer will be described below. However, the wire-grid polarizer of the present invention is not limited to this example and may have any shape depending on its application, function, etc.

[0052] The wire grid polarization element of the present invention may be used, for example, as a polarizer that transmits only light vibrating in one specific direction, or as a polarization beam splitter that separates incident light into a first polarization (S polarization) and a second polarization (P polarization). The following mainly describes an example in which the wire grid polarization element 1 according to this embodiment is used as a polarization beam splitter.

[0053] As shown in Figures 1 and 2, the wire-grid polarizer 1 (hereinafter sometimes abbreviated as "polarizer 1") includes a transparent substrate 10, a transparent grid structure 20, and an opaque functional film (e.g., a reflective film 30).

[0054] In this specification, "transparent" means that the transmittance of light of wavelength λ belonging to a used band (e.g., the visible light band, the infrared light band, or the visible and infrared light bands) is high, for example, the transmittance of the light is 70% or more. The wavelength band of visible light is, for example, 360 nm or more and 830 nm or less. The wavelength band of infrared light (infrared light) is wider than the wavelength band of visible light, for example, 830 nm or more. From the viewpoint of the suitable wavelength range of visible light projected as a display image, the wavelength λ of the used band in the polarizing element 1 according to this embodiment is, for example, preferably 400 nm or more and 800 nm or less, and more preferably 420 nm or more and 680 nm or less. The polarizing element 1 according to this embodiment is formed of a material transparent to light in the used band, and therefore does not adversely affect the polarization characteristics, light transmittance, etc. of the polarizing element 1.

[0055] The substrate 10 is made of a transparent inorganic material such as glass, etc. The substrate 10 is a flat substrate having a predetermined thickness TS.

[0056] The grid structure 20 is made of a transparent organic material, for example, an organic resin material such as an ultraviolet-curable resin or a thermosetting resin that has excellent heat resistance. The grid structure 20 has a concavo-convex structure for realizing the polarization function of the polarizing element 1. Specifically, the grid structure 20 has a base portion 21 provided along the surface of the substrate 10, and a plurality of ridge portions 22 that protrude in a grid pattern from the base portion 21. The base portion 21 and the plurality of ridge portions 22 of the grid structure 20 are integrally formed using the same organic material.

[0057] The base portion 21 is a thin film having a predetermined thickness TB, and is laminated over the entire main surface of the substrate 10 (the XY plane shown in FIGS. 1 and 2 ). The thickness TB of the base portion 21 is preferably substantially uniform over the entire main surface of the substrate 10, but it does not have to be exactly uniform and may vary with a certain degree of error from the reference thickness of TB. For example, TB may vary by approximately ±3 μm from the reference thickness of 6 μm. In this way, the thickness TB of the base portion 21 is determined, allowing for molding errors when molding the base portion 21 by imprinting or the like.

[0058] The plurality of convex ridges 22 are arranged on the base portion 21 at equal intervals in the X direction at a predetermined pitch P. The pitch P is the spacing between the plurality of convex ridges 22 arranged in the X direction of the polarizing element 1. The plurality of convex ridges 22 are arranged in a lattice pattern so as to extend parallel to each other in the Y direction. A predetermined gap is formed between two convex ridges 22 adjacent to each other in the X direction. This gap serves as a path for incident light to enter. Each convex ridge 22 is a wall-like convex portion formed to protrude and extend elongatedly in a predetermined direction (the Y direction shown in Figures 1 and 2). The height (H) in the Z direction and the width (W) in the X direction of the plurality of convex ridges 22 are Ｔ , W Ｂ ) are substantially identical to each other. The longitudinal direction (Y direction) of the ridge portion 22 is the direction of the reflection axis of the polarizing element 1, and the width direction (X direction) of the ridge portion 22 is the direction of the transmission axis of the polarizing element 1.

[0059] The functional film is a film for imparting a predetermined function to the grid structure 20 of the polarizing element 1. The functional film is made of, for example, an opaque metal material and is provided so as to cover a portion of the ridge portion 22 of the grid structure 20. The functional film may be, for example, a reflective film 30 that has the function of reflecting incident light that is incident on the polarizing element 1, or an absorbing film (not shown) that has the function of absorbing the incident light, or a film having other functions. In this embodiment, an example in which the functional film is a reflective film 30 will be described, but the functional film of the present invention is not limited to the example of a reflective film 30.

[0060] The reflective film 30 is a thin film made of a metallic material (metal or metal oxide, etc.) such as aluminum or silver. The reflective film 30 is formed so as to cover at least the tops of the protruding stripes 22. The reflective film 30 may be made of a metal film that functions as the thin metallic wires of the wire grid. The reflective film 30 has the function of reflecting incident light that is incident on the grid structure 20.

[0061] The convex ridges 22 of the grid structure 20 and the reflective film 30 constitute the grid of the wire-grid polarizer 1. The pitch P in the X direction of the multiple convex ridges 22 in the grid structure 20 (i.e., the grid arrangement pitch) is set to a pitch smaller than (e.g., equal to or smaller than half) the wavelength λ of incident light (e.g., visible light). This allows the polarizer 1 to reflect most of the light (S-polarized light) whose electric field vector component oscillates in a direction parallel to the reflective film 30 (conductor wire) extending in the Y direction (reflection axis direction: Y direction), and to transmit most of the light (P-polarized light) whose electric field vector component oscillates in a direction perpendicular to the reflective film 30 (conductor wire) (transmission axis direction: X direction).

[0062] As described above, the wire grid polarizer 1 according to this embodiment achieves polarization function by combining the grid structure 20 having a fine concave-convex structure with a functional film (e.g., reflective film 30) selectively added to the ridge portions 22 of the grid structure 20. The substrate 10 of the wire grid polarizer 1 is made of an inorganic material such as glass that has excellent heat resistance, and the grid structure 20 is made of an organic resin material that is also heat resistant. In this way, the wire grid polarizer 1 according to this embodiment is a hybrid polarizer that combines organic and inorganic materials. Therefore, the thermal resistance R [m ２ Heat can be efficiently dissipated from the grid structure 20, which has a small [K / W] ratio, to the substrate 10, resulting in excellent heat dissipation. Therefore, the hybrid wire-grid polarizer 1 according to this embodiment has excellent heat resistance and heat dissipation properties compared to conventional film-type polarizers made only of organic materials (heat resistance: approximately 100°C), and is heat resistant in high-temperature environments up to, for example, approximately 200°C. Therefore, excellent polarization characteristics can be achieved while maintaining a good heat dissipation effect.

[0063] Furthermore, the wire grid polarizer 1 according to this embodiment may include a protective film 40 (see FIGS. 7 and 8) that covers the surface of the grid structure 20. The protective film 40 is made of an inorganic material, for example, SiO ２The protective film 40 may be laminated over the entire surface of the wire-grid polarizer 1 so as to cover the entire surfaces of the base portion 21, the ridge portions 22, and the reflective film 30 of the grid structure 20 (see FIG. 7 ). Providing such a protective film 40 has the advantageous effect of further reducing the thermal resistance R of the polarizer 1, thereby achieving excellent polarization characteristics while maintaining a better heat dissipation effect.

[0064] Furthermore, as described above, the grid structure 20, in which the base portion 21 and the ridge portions 22 are integrally configured, can be manufactured using a printing technique such as nanoimprinting, thereby achieving a fine uneven structure through a simple manufacturing process. Therefore, the cost and effort required to manufacture the grid structure 20 can be reduced compared to manufacturing using photolithography or etching techniques. Therefore, the hybrid polarizing element 1 according to this embodiment has the advantage of being able to significantly reduce manufacturing costs and lower the unit price of the wire-grid polarizing element 1 compared to conventional polarizing elements made only of inorganic materials.

[0065] On the other hand, conventional film-type organic polarizing plates use a large amount of organic materials, and the thickness of the substrate (base film), double-sided tape (OCA: Optically Clear Adhesive), and grid structure are large, so they are thought to have inferior heat dissipation and heat resistance compared to the hybrid-type polarizing element 1 according to this embodiment.

[0066] Furthermore, in the wire-grid polarization element 1 according to this embodiment, the grid, which is made up of the convex streak portions 22 of the grid structure 20 and the reflective film 30, has a special tree-like shape (details of which will be described later) as shown in FIG. 1 and other figures. This prevents the transmittance (i.e., transmission axis transmittance Tp) of the second polarized light (P-polarized light) passing through the polarization element 1 from decreasing depending on the incident angle θ of the obliquely incident light, even when light is incident on the polarization element 1 at a wide range of large incident angles θ (e.g., 30 to 60°). Therefore, the product (Tp × Rs) of the reflectance (i.e., reflection axis reflectance Rs) of the first polarized light (S-polarized light) reflected by the wire-grid polarization element 1 and the transmission axis transmittance Tp can be maintained at a high value, e.g., 70% or more. Therefore, the polarization element 1 according to this embodiment has excellent polarization separation characteristics expressed by Tp × Rs, and can polarize obliquely incident light and effectively separate it into S-polarized light (reflected light) and P-polarized light (transmitted light). Therefore, the polarizing element 1 according to this embodiment can obtain sufficient transmittance and polarization separation characteristics even for obliquely incident light with a large incident angle θ and over a wide range.

[0067] As described above, the wire-grid polarizer 1 according to this embodiment has excellent heat resistance and heat dissipation properties, can reduce manufacturing costs, and exhibits excellent transmittance and polarization separation characteristics for obliquely incident light with a wide range of large incident angles θ. Therefore, the wire-grid polarizer 1 according to this embodiment can be suitably used as a variety of components in a variety of products. For example, the polarizer 1 can be used as a polarizing beam splitter installed in a smart display. The polarizer 1 can also be used as a polarizing element installed in a head-up display (HUD) that is resistant to heat from sunlight, a polarizing element installed in a head-up display (HUD) that is resistant to heat from an LED light source, a polarizing reflective mirror, and the like. The polarizer 1 can also be used as a polarizing beam splitter installed in a headlight such as an adaptive beam distribution headlamp (ADB). The polarizer 1 can also be used as a lens-integrated retardation element or lens-integrated polarizing element installed in various devices for augmented reality (AR) or virtual reality (VR).

[0068] 2. Components of Wire-Grid Polarizer> Next, the components of the wire-grid polarizer 1 according to this embodiment will be described in detail with reference to FIGS. 1 and 2.

[0069] 1, the wire-grid polarizer 1 according to this embodiment includes a transparent substrate 10. The substrate 10 is transparent and made of an inorganic material having a certain degree of strength.

[0070] As the material for the substrate 10, from the viewpoint of obtaining better heat dissipation and heat resistance, it is preferable to use an inorganic material such as various types of glass, quartz, crystal, sapphire, etc., more preferably an inorganic material having a thermal conductivity of 1.0 W / m·K or more, and even more preferably an inorganic material having a thermal conductivity of 8.0 W / m·K or more.

[0071] The shape of the substrate 10 is not particularly limited and can be selected appropriately depending on the performance required of the polarizing element 1. For example, it can be configured to have a plate shape or a curved surface. In order not to affect the polarization characteristics of the polarizing element 1, the surface of the substrate 10 can be made flat. Furthermore, the thickness TS of the substrate 10 is not particularly limited either and can be in the range of 0.02 to 10.0 mm, for example.

[0072] 1 and 2 , the polarizing element 1 according to this embodiment includes a grid structure 20 having the above-described base portion 21 and a grid-like ridge portion 22 on a substrate 10. The grid structure 20 can obtain desired polarization characteristics by providing a reflective film 30 (described later) on the ridge portion 22.

[0073] When light is incident on the polarizing element 1 from the front surface on which the grid structure 20 is formed, a portion of the incident light is reflected by the reflective film 30. Of the light incident on the reflective film 30, light having an electric field component in a direction perpendicular to the longitudinal direction of the ridges 22 (i.e., the extension direction of the ridges 22 = the reflection axis direction: Y direction) (i.e., the width direction of the ridges 22 = the transmission axis direction: X direction) is transmitted through the polarizing element 1 with high transmittance. On the other hand, of the light incident on the reflective film 30, light having an electric field component in a direction parallel to the longitudinal direction of the ridges 22 (i.e., the extension direction of the ridges 22 = the reflection axis direction: Y direction) is mostly reflected by the reflective film 30. Therefore, in this embodiment, a single polarization can be produced by providing the grid structure 20 partially covered with the reflective film 30. A similar polarization effect can also be achieved for light incident on the back surface of the substrate 10.

[0074] As shown in FIG. 1 , the grid structure 20 has a base portion 21. The base portion 21 is a thin film provided along the surface of the substrate 10 and serves to support the ridge portions 22. When the uneven structure (ridge portions 22) of the grid structure 20 is formed by nanoimprinting or the like, the base portion 21 is inevitably formed. The base portion 21 and the ridge portions 22 are integrally formed from the same material. Furthermore, since the grid structure 20 has the base portion 21, the strength of the ridge portions 22 can be increased compared to when the ridge portions 22 are formed directly on the substrate 10. This increases the durability of the grid structure 20. Furthermore, since the base portion 21 is in close contact with the substrate 10 over the entire surface, the peel resistance of the grid structure 20 can be improved.

[0075] The thickness TB of the base portion 21 is not particularly limited, but is preferably 1 nm or more, and more preferably 10 nm or more, from the viewpoint of more reliably supporting the ridge portion 22 and facilitating imprint molding. Furthermore, from the viewpoint of ensuring good heat dissipation, the thickness TB of the base portion 21 is preferably 50 μm or less, and more preferably 30 μm or less.

[0076] Furthermore, according to the polarizing element 1 of this embodiment, the base portion 21 and the multiple ridge portions 22 of the grid structure 20 are formed directly on the substrate 10, so that the thickness TB of the base portion 21 can be made thin. Here, in order to improve heat dissipation from the grid structure 20 to the substrate 10, it is preferable to reduce the temperature difference ΔT [°C] between the front and back surfaces of the base portion 21 by making the thickness TB of the base portion 21 thin. The temperature difference ΔT is the temperature difference between the temperature T1 [°C] of the outermost surface of the base portion 21 (the roots of the multiple ridge portions 22) and the temperature T2 [°C] of the base portion 21 at the interface between the base portion 21 and the substrate 10 (ΔT = T1 - T2).

[0077] Therefore, the thickness TB of the base portion 21 is preferably 0.15 mm or less. This allows heat from the grid structure 20, which is made of an organic material, to be quickly transferred to the substrate 10, which is made of an inorganic material, and efficiently dissipates heat from the substrate 10 to the outside of the polarizing element 1, thereby reducing the temperature difference ΔT to, for example, 32°C or less. Furthermore, the thickness TB of the base portion 21 is more preferably 0.09 mm or less, thereby reducing the temperature difference ΔT to, for example, 20°C or less. Furthermore, the thickness TB of the base portion 21 is more preferably 0.045 mm or less, thereby reducing the temperature difference ΔT to, for example, 10°C or less. Furthermore, the thickness TB of the base portion 21 is particularly preferably 0.02 mm or less, thereby reducing the temperature difference ΔT to, for example, 5°C or less. In this way, reducing the thickness TB of the base portion 21 improves heat dissipation from the grid structure 20 to the outside via the substrate 10, thereby improving the heat dissipation and heat resistance of the polarizing element 1.

[0078] 1 and 2, the grid structure 20 further has a plurality of ridges 22 protruding from the base 21. The ridges 22 extend longitudinally in the direction of the reflection axis (Y direction) of the polarizing element 1 according to this embodiment. The plurality of ridges 22 are arranged at a predetermined pitch in the X direction and at predetermined intervals from one another, thereby forming a grid-like uneven structure.

[0079] 1, in a longitudinal section (XZ section) perpendicular to the reflection axis direction (Y direction) of the polarizing element 1, the pitch P of the ridge portions 22 in the transmission axis direction (X direction) must be shorter than the wavelength of light in the band of light used. The reason for this is to obtain the polarization effect described above. More specifically, from the viewpoint of achieving both ease of manufacture of the ridge portions 22 and polarization properties, the pitch P of the ridge portions 22 is preferably 50 to 300 nm, more preferably 100 to 200 nm, and particularly preferably 100 to 150 nm.

[0080] 1 and 2, the width W of the bottom of the convex rib portion 22 in the longitudinal section (XZ section) is Ｂ is not particularly limited, but is preferably about 10 to 150 nm, more preferably about 10 to 100 nm, from the viewpoint of achieving both ease of manufacturing and polarization characteristics. Ｔ is not particularly limited, but is preferably about 5 to 60 nm, more preferably about 10 to 30 nm, from the viewpoint of achieving both ease of manufacture and polarization characteristics.

[0081] The width W of the bottom of the ridge portion 22 Ｂ and the width of the top W Ｔ can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, a cross section (XZ cross section) perpendicular to the absorption axis direction or the reflection axis direction of the polarizing element 1 is observed using a scanning electron microscope or a transmission electron microscope, and the width of the convex rib portion 22 at any four positions is measured at a height position 20% above the height H of the convex rib portion 22 from the bottom of the convex rib portion 22, and the arithmetic average value of the widths is defined as the width W of the bottom of the convex rib portion 22. Ｂ Furthermore, for the four convex rib portions 22, the widths of the convex rib portions 22 are measured at a height position 20% below the height H of the convex rib portions 22 from the tip 22a of the convex rib portion 22, and the arithmetic mean value of the widths is defined as the width W of the top of the convex rib portion 22. Ｔ It can be said that:

[0082] 1 , the height H of the ridge portions 22 in the longitudinal cross section (XZ cross section) is not particularly limited, but is preferably about 50 to 350 nm, more preferably about 100 to 300 nm, from the viewpoint of achieving both ease of manufacture and polarization characteristics. The height H of the ridge portions 22 can be measured by observation with a scanning electron microscope or a transmission electron microscope. For example, a cross section perpendicular to the absorption axis direction or the reflection axis direction of the polarizing element 1 is observed using a scanning electron microscope or a transmission electron microscope, and the heights of the ridge portions 22 at the center positions in the width direction of the ridge portions 22 at any four positions are measured, and the arithmetic average value of these measurements can be used as the height H of the ridge portions 22.

[0083] The shape of the ridges 22 of the grid structure 20 is preferably tapered in order to obtain good polarization separation characteristics for obliquely incident light. Here, the tapered shape is a shape in which the width W (width in the X direction in the XZ cross section) of the ridges 22 gradually narrows with increasing distance from the base 21, in other words, a shape in which the width W of the ridges 22 gradually narrows from the bottom to the top of the ridges 22. Therefore, when the ridges 22 have a tapered shape, the width W of the top of the ridges 22 is Ｔ is the width W of the bottom of the ridge portion 22 Ｂ becomes smaller (W Ｔ <W Ｂ ).

[0084] 3 shows a specific example of the tapered shape of the ridge portion 22 according to this embodiment. As shown in FIG. 3, the cross-sectional shape of the ridge portion 22 in the longitudinal section (XZ section) may be various shapes, such as a trapezoid, a triangle, a bell shape, an ellipse, or a rounded wedge shape, in which the width W narrows with increasing distance from the base portion 21, as long as it is the above-mentioned tapered shape. For example, the cross-sectional shape of the ridge portion 22A shown in FIG. 3 is a trapezoid (tapered shape), the cross-sectional shape of the ridge portion 22B is a triangle, the cross-sectional shape of the ridge portion 22C is a bell shape, and the cross-sectional shape of the ridge portion 22D is a wedge shape with rounded top and bottom. In this way, since the convex rib portion 22 has a tapered shape, it is easy to form a reflective film 30 that covers the tip 22a and part of the side surface 22b of the convex rib portion 22, thereby imparting polarization properties to the polarizing element 1.In addition, since the tapered shape can also be formed by nanoimprinting, it is also advantageous in terms of ease of manufacturing.

[0085] Furthermore, since the ridge portions 22 have a tapered shape, such as a tapered shape, the refractive index of the grid structure 20 gradually changes. Therefore, similar to the moth-eye structure, an anti-reflection effect of incident light due to a change in the physical refractive index of the grid structure 20 is obtained. Therefore, it is possible to reduce the reflectance on the surface of the ridge portions 22 of the grid structure 20, and it is also expected that the transmittance of the grid structure 20 can be improved.

[0086] FIG. 4 also shows a specific example of the shape of the recess 24 formed between adjacent ridge portions 22, 22. The recess 24 is a groove extending in the longitudinal direction (Y direction) of the ridge portion 22. As shown in FIG. 4, the cross-sectional shape of the recess 24 in the longitudinal section (XZ section) may be various shapes as long as the width narrows toward the bottom of the recess 24. For example, the cross-sectional shape of the recess 24A shown in FIG. 4 is a trapezoid (tapered shape), the cross-sectional shape of the recess 24B is a triangle (V-shape), the cross-sectional shape of the recess 24C is a substantially rectangular shape with a flat bottom, and the cross-sectional shape of the recess 24D is a U-shape with a rounded bottom. The optimal shape of these recesses 24 can be selected appropriately taking into account productivity, such as mold releasability during nanoimprint formation.

[0087] Furthermore, the material constituting the grid structure 20 is not particularly limited as long as it is a transparent organic material, and any known organic material can be used. For example, from the viewpoints of ensuring transparency and excellent ease of manufacture, it is preferable to use various thermosetting resins, various ultraviolet curing resins, etc. as the material for the grid structure 20.

[0088] Furthermore, from the viewpoints of ease of manufacturing and manufacturing costs, it is preferable that the material constituting the grid structure 20 is different from that of the substrate 10. In addition, if the grid structure 20 and the substrate 10 are made of different materials, the refractive indexes of the two will be different. For this reason, if the refractive index of the entire polarizing element 1 is affected, a refractive index adjustment layer may be provided between the grid structure 20 and the substrate 10 as appropriate.

[0089] For example, curable resins such as epoxy polymerizable compounds and acrylic polymerizable compounds can be used as materials for forming the grid structure 20. Epoxy polymerizable compounds are monomers, oligomers, or prepolymers having one or more epoxy groups in the molecule. Examples of epoxy polymerizable compounds include various bisphenol-type epoxy resins (such as bisphenol A and F), novolac-type epoxy resins, various modified epoxy resins such as rubber and urethane, naphthalene-type epoxy resins, biphenyl-type epoxy resins, phenol novolac-type epoxy resins, stilbene-type epoxy resins, triphenolmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenylmethane-type epoxy resins, and prepolymers thereof.

[0090] The acrylic polymerizable compound is a monomer, oligomer, or prepolymer having one or more acrylic groups in the molecule. Here, the monomer is further classified into a monofunctional monomer having one acrylic group in the molecule, a bifunctional monomer having two acrylic groups in the molecule, and a polyfunctional monomer having three or more acrylic groups in the molecule.

[0091] Examples of "monofunctional monomers" include carboxylic acids (acrylic acid, etc.), hydroxyl groups (2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate), alkyl or alicyclic monomers (isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate), and other functional monomers (2-methoxyethyl acrylate, methoxyethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, N,N-dimethylaminoethyl acrylate, methyl ... perfluorooctyl acrylate, N,N-dimethylaminopropyl acrylamide, N,N-dimethylacrylamide, acryloylmorpholine, N-isopropylacrylamide, N,N-diethylacrylamide, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate), 2,4,6-tribromophenol acrylate, 2,4,6-tribromophenol methacrylate, 2-(2,4,6-tribromophenoxy)ethyl acrylate), 2-ethylhexyl acrylate, and the like.

[0092] Examples of "bifunctional monomers" include tri(propylene glycol) diacrylate, trimethylolpropane diallyl ether, urethane diacrylate, etc. Examples of "polyfunctional monomers" include trimethylolpropane triacrylate, dipentaerythritol penta- and hexaacrylate, ditrimethylolpropane tetraacrylate, etc.

[0093] Examples of the acrylic polymerizable compounds other than those listed above include acrylic morpholine, glycerol acrylate, polyether acrylate, N-vinylformamide, N-vinylcaprolactam, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, polyethylene glycol acrylate, EO-modified trimethylolpropane triacrylate, EO-modified bisphenol A diacrylate, aliphatic urethane oligomer, and polyester oligomer.

[0094] Furthermore, examples of the curing initiator for the curable resin include a heat-curing initiator and a photo-curing initiator. The curing initiator may be one that is cured by heat, some kind of energy ray other than light (e.g., electron beam), or the like. When the curing initiator is a heat-curing initiator, the curable resin is a thermosetting resin, and when the curing initiator is a photo-curing initiator, the curable resin is a photo-curable resin.

[0095] Among these, it is preferable to use an ultraviolet curing initiator as the curing initiator. An ultraviolet curing initiator is a type of photocuring initiator. Examples of ultraviolet curing initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenylpropan-1-one. Therefore, it is preferable that the curable resin is an ultraviolet curable resin. Furthermore, from the viewpoint of transparency, it is more preferable that the curable resin is an ultraviolet curable acrylic resin.

[0096] The method for forming the grid structure 20 is not particularly limited as long as it is a method that can form the above-described base portion 21 and ridge portions 22. For example, a concavo-convex forming method such as photolithography or imprinting can be used. Among these, it is preferable to form the base portion 21 and ridge portions 22 of the grid structure 20 by imprinting, from the viewpoints that the concavo-convex pattern can be formed easily in a short time and that the base portion 21 can be reliably formed.

[0097] When the base portion 21 and the ridge portions 22 of the grid structure 20 are formed by nanoimprinting, for example, a material for forming the grid structure 20 (grid structure material) is applied to the substrate 10, and then a master having projections and recesses formed thereon is pressed against the grid structure material, and in this state, ultraviolet light is irradiated or heat is applied to harden the grid structure material. In this way, the grid structure 20 having the base portion 21 and the ridge portions 22 can be formed.

[0098] 2.3. Reflective Film (Functional Film) As shown in FIGS. 1 and 2, the polarizing element 1 according to this embodiment includes a reflective film 30 formed on the ridge portions 22 of the grid structure 20.

[0099] 1, the reflective film 30 is formed so as to cover the tips 22a and parts of the side surfaces 22b of the ridge portions 22 of the grid structure 20. As shown in Fig. 1, the reflective film 30 is formed so as to extend along the longitudinal direction (Y direction) of the ridge portions 22 of the grid structure 20. This allows the reflective film 30 to reflect light that has entered the polarizing element 1 and that has an electric field component in a direction parallel to the longitudinal direction of the ridge portions 22 (reflection axis direction: Y direction).

[0100] The material constituting the reflective film 30 is not particularly limited as long as it is a material that is reflective to light in the used band, and examples thereof include metal materials such as simple metal elements such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, and Te, and alloys containing one or more of these elements.

[0101] The reflective film 30 may be a single layer film made of the above metal, or may be a multi-layer film made of multiple metal films. The reflective film 30 may also include other layers, such as a dielectric film, as needed, as long as it has a reflective function. The dielectric film is a thin film made of a dielectric material. The material of the dielectric film is SiO ２ , Al ２ O ３ , MgF ２ , TiO ２Common materials such as the above can be used. The refractive index of the dielectric film is preferably greater than 1.0 and equal to or less than 2.5. Since the optical characteristics of the reflective film 30 are also affected by the refractive index of the surroundings, the polarization characteristics may be controlled by the material of the dielectric film.

[0102] 2.4. Special Shapes of the Convex Strips and Reflective Film The special shapes of the convex strips 22 of the grid structure 20 and the reflective film 30 in the polarizing element 1 according to this embodiment will now be described in detail.

[0103] 1 and 5, in the polarizing element 1 according to this embodiment, the reflective film 30 is formed so as to cover the tips 22a and the upper side of at least one of the side surfaces 22b of the convex rib portions 22 of the grid structure 20, but not to cover the lower sides of both side surfaces 22b of the convex rib portions 22 or the base portion 21. In the example shown in Fig. 1 and 5, the reflective film 30 covers the upper sides of both side surfaces 22b of the convex rib portions 22, but it may also cover the upper side of only one of the side surfaces 22b of the convex rib portions 22.

[0104] 1 and 5, the phrase "a state in which the reflective film 30 covers the tip 22a of the convex rib portion 22 and the upper side of at least one of the side surfaces 22b" means a state in which the reflective film 30 continuously covers both the "tip 22a of the convex rib portion 22" and the "upper side of the side surface 22b connecting the tip 22a of the convex rib portion 22 and the base portion 21," while leaving the "lower side of the side surface 22b" and the "base portion 21" exposed and not covered by the reflective film 30. In this state, the reflective film 30 does not cover the entire side surface 22b of the convex rib portion 22 (all of the side surfaces 22b from the tip 22a of the convex rib portion 22 to the base portion 21).

[0105] Furthermore, the surface of the reflective film 30 that covers the tip 22a and the upper side of at least one of the side surfaces 22b of the convex rib portion 22 (hereinafter, sometimes referred to as the "top of the convex rib portion 22") has a rounded, curved shape (for example, a vertically elongated, approximately elliptical shape) and bulges out in the width direction (X direction) of the convex rib portion 22. In this way, the surface of the reflective film 30 has a rounded, smoothly curved shape and does not have sharp corners or steps. The maximum width W of the reflective film 30 that covers the top of the convex rib portion 22 in this way is ＭＡＸis the width W of the bottom of the ridge portion 22 Ｂ That's all. Furthermore, W ＭＡＸ Is W Ｂ It is preferable that it is greater than .

[0106] Here, the maximum width W of the reflective film 30 that covers the ridge portion 22 ＭＡＸ is the maximum horizontal width of the horizontal widths of the outermost surfaces of both sides of the reflective film 30 in the width direction (X direction) of the ridge portion 22. As shown in Figures 1 and 5, the horizontal widths (width in the X direction) of the outermost surfaces of both sides of the reflective film 30 that cover the ridge portion 22 vary depending on the height position (height in the Z direction) of the reflective film 30, but the maximum value of these horizontal widths is the maximum width W ＭＡＸ In other words, the maximum width W ＭＡＸ is the maximum value of the total width of the thickness Ds×2 of the reflective film 30 on both sides and the horizontal width W of the ridge portion 22. For example, when light is incident on the grid structure 20 from the front direction (Z direction) (when the incident angle θ is 0°), W ＭＡＸ corresponds to the effective grid width of the reflective film 30.

[0107] Width W of the bottom of the ridge portion 22 Ｂ 1 and 3, is the horizontal width (width in the X direction) of the convex rib portion 22 at a height position (height in the Z direction) 20% above the height H of the convex rib portion 22 from the lowest part of the convex rib portion 22 (the upper surface of the base portion 21). In other words, the width W of the bottom of the convex rib portion 22 Ｂ is the horizontal width of the ridge portion 22 at a height of 0.2×H above the top surface of the base portion 21.

[0108] The width W of the top of the ridge portion 22 Ｔ 1 and 3, is the horizontal width (width in the X direction) of the ridge portion 22 at a height position (height in the Z direction) 20% below the height H of the ridge portion 22 from the tip 22a of the ridge portion 22. In other words, the width W of the top of the ridge portion 22 Ｔ is the horizontal width of the ridge portion 22 at a position 0.8×H above the top surface of the base portion 21 (i.e., a position 0.2×H below the tip 22a of the ridge portion 22).

[0109] In the following description, the convex structure formed by combining the convex streak portion 22 and the reflective film 30 will be referred to as a "grid," and the height of the convex structure formed by combining the convex streak portion 22 and the reflective film 30 (i.e., the grid) will be referred to as a "grid height." ＭＡＸ "Grid maximum width W ＭＡＸ ", and the width W of the bottom of the ridge portion 22 Ｂ "Grid bottom width W Ｂ The width W of the top of the ridge portion 22 is also called Ｔ The width of the top of the ridge W Ｔ The width of the ridge portion 22 at the center position in the height direction is sometimes referred to as the "ridge portion center width."

[0110] In this manner, in this embodiment, the width W of the bottom of the ridge portion 22 Ｂ The horizontal width of the ridge portion 22 at a height position 20% above the lowest part (bottom) of the ridge portion 22 is used as the width W of the top of the ridge portion 22. Ｔ The horizontal width of the ridge portion 22 at a height position 20% below the tip 22 a of the ridge portion 22 is used as the horizontal width of the ridge portion 22. The reason for this is that the width of the bottom of the ridge portion 22 on the upper surface of the base portion 21 and the width of the tip 22 a of the ridge portion 22 vary greatly depending on the manufacturing conditions of the grid structure 20, and it is difficult to measure these widths precisely.

[0111] As described above, the grid structure 20 according to this embodiment is formed with tapered ridge portions 22 and a reflective film 30 that covers only the tips 22 a and the upper sides of the side surfaces 22 b of the ridge portions 22. The lower sides of the side surfaces 22 b of the ridge portions 22 are not covered with the reflective film 30 and are open.

[0112] As a result, the cross-sectional shape of the convex streak portion 22 covered with the curved reflective film 30 (i.e., the cross-sectional shape of the grid) has the following special cross-sectional shape. That is, as shown in Figures 1 and 5, the horizontal width of the upper part of the convex streak portion 22 where the reflective film 30 is present (for example, the maximum grid width W ＭＡＸ ) is large, and the horizontal width of the part from the center to the bottom side of the exposed ridge portion 22 that is not covered with the reflective film 30 (for example, the width W Ｂ) is smaller. The cross-sectional shape of the entire convex structure (i.e., "grid") composed of the convex rib portions 22 and the reflective film 30 is constricted inward at a position directly below the lower end of the curved reflective film 30, with the constricted portion having a narrower width in the X direction. Such a special cross-sectional shape of the grid can be likened to the shape of a tree. Specifically, the large, rounded leaves of the tree correspond to the portion of the reflective film 30 that covers the top of the convex rib portions 22, the trunk of the tree corresponds to the lower portion of the convex rib portions 22 that is not covered by the reflective film 30, and the ground on which the tree grows corresponds to the base portion 21. Therefore, in the following description, the special cross-sectional shape of the grid composed of the convex rib portions 22 and the reflective film 30 of the grid structure 20 described above will be referred to as a "special tree shape."

[0113] The grid of the grid structure 20 of the polarizing element 1 according to this embodiment has the special tree shape as described above. As a result, for example, when incident light is incident on the polarizing element 1 from an oblique direction, the effective grid width W Ａ becomes smaller, and the gap width W Ｇ Here, the effective grid width W Ａ is the width of the reflective film 30 in the direction perpendicular to the obliquely incident light. Ｇ is the gap between the reflective films 30 of two adjacent grids, and is the width of the gap in the direction perpendicular to the obliquely incident light. Ａ As the gap width W is larger, the obliquely incident light is more likely to be reflected by the reflective film 30 and less likely to reach the transparent ridge portion 22 or the base portion 21. Therefore, the transmittance of the obliquely incident light in the polarizing element 1 decreases. Ｇ The larger the value of , the more easily the obliquely incident light can pass between the two adjacent reflective films 30, 30 and reach the transparent ridge portion 22 and the base portion 21. Therefore, the transmittance for obliquely incident light can be increased.

[0114] Therefore, since the grid of the polarizing element 1 according to this embodiment has the above-mentioned special tree shape, the gap width W Ｇbecomes larger, and the obliquely incident light passes through the gaps between the round reflective films 30, 30, reaches the transparent grid structure 20, and is easily transmitted. Therefore, the transmission axis transmittance Tp of the obliquely incident light is high, and the transmittance and polarization separation characteristics (Tp×Rs characteristics) for the obliquely incident light are very excellent. Furthermore, a good balance can be achieved between the function of reflecting the obliquely incident light by the reflective film 30 and the function of transmitting the obliquely incident light by the grid structure 20, and the polarization separation characteristics for the obliquely incident light can be further improved.

[0115] 2.5. Method of forming reflective film and specific example Here, a method of forming the reflective film 30 will be described with reference to FIG.

[0116] As a method for forming the reflective film 30 so that it covers the tips 22 a and parts of both side surfaces 22 b of the ridge portions 22 of the grid structure 20, it is preferable to form the reflective film 30 by alternately sputtering or vapor deposition from an oblique direction (film deposition incident angle φ) relative to the ridge portions 22 of the grid structure 20, as shown in Fig. 5. This allows the reflective film 30 to be formed so as to cover the tips 22 a and the upper sides of both side surfaces 22 b of the ridge portions 22. The film deposition incident angle φ for forming the reflective film 30 by sputtering or vapor deposition is not particularly limited, but can be, for example, about 5 to 70° with respect to the surface of the substrate 10.

[0117] As described above, in this embodiment, after forming the grid structure 20 made of a transparent material, the reflective film 30 made of a metal material is formed by sputtering or vapor deposition. This allows for easy adjustment of the deposition conditions, material, and film thickness of the reflective film 30. Furthermore, it is also easy to accommodate a multilayer reflective film 30. Therefore, by combining metals, semiconductors, and dielectrics, it is possible to design a film that utilizes interference effects. Therefore, when forming the reflective film 30 by etching, as in the prior art, it is not necessary to consider the composition of materials that can be etched. This makes it easy to adjust the reflectance of polarized light parallel to the grid structure 20 and the transmittance (transmission amount) of polarized light perpendicular to the grid. In addition, by forming the reflective film 30 after forming the grid structure 20, there is no need for equipment such as a vacuum dry etching device, and there is no need to prepare safety devices such as gases and abatement devices tailored to complex processes and etching materials. This reduces running costs, such as capital investment and maintenance, and provides cost benefits.

[0118] The thickness Dt of the reflective film 30 covering the tips 22a of the ridge portions 22 shown in FIG. 5 and the thickness Ds of the reflective film 30 covering the side surfaces 22b of the ridge portions 22 are not particularly limited and can be changed appropriately depending on the shape of the ridge portions 22 of the grid structure 20, the performance required of the reflective film 30, and the like. For example, from the viewpoint of obtaining better reflective performance, the thicknesses Dt and Ds of the reflective film 30 are preferably 2 to 200 nm, more preferably 5 to 150 nm, even more preferably 10 to 100 nm, and particularly preferably 15 to 80 nm. The thickness Ds of the reflective film 30 is the thickness of the thickest portion of the reflective film 30 covering the side surfaces 22b of the ridge portions 22, as shown in FIG. 5.

[0119] Furthermore, the shape of the reflective film 30 is not particularly limited as long as it is a shape that can form the special tree shape described above, and can be selected appropriately depending on the conditions of the equipment used to form the reflective film 30 and the performance required of the reflective film 30.

[0120] Fig. 6 is a cross-sectional view schematically showing a specific example of the shape of the reflective film 30. As shown in Fig. 6, the reflective film 30 may have various shapes as long as it is curved so as to enclose the top of the protruding ridge portion 22 (the tip 22a and the upper side of the side surface 22b).

[0121] For example, the reflective film 30A shown in Figure 6 covers the tops of the ridges 22A, 22B, and 22C of various cross-sectional shapes in a rounded manner, and has a generally elliptical shape that bulges significantly in the width direction of the ridges 22. The reflective film 30B has a curved shape that covers the top of the generally wedge-shaped ridge 22D. The reflective film 30C has a curved shape that covers the top of the trapezoidal ridge 22A. The coverage rate Rc of one side surface 22b of the ridge 22 by these reflective films 30B and 30C is generally the same as the coverage rate Rc of the other side surface 22b.

[0122] Furthermore, the reflective film 30D envelops and covers the top of the approximately wedge-shaped ridge portion 22D, but is unevenly distributed on one side surface 22b of the ridge portion 22 (the left side surface 22b shown in FIG. 6 ). Specifically, the reflective film 30D covers a wide area of ​​the left side surface 22b of the ridge portion 22, with a coverage rate Rc of approximately 80%. On the other hand, the reflective film 30D only covers a narrow area on the upper side of the right side surface 22b, with a coverage rate Rc of approximately 25%. In this way, the coverage rate Rc of the reflective film 30D may differ between one side surface 22b and the other side surface 22b of the ridge portion 22.

[0123] 2.6. Suitable Range of Coverage Rc of the Convex Strip Portion by the Reflective Film Next, a suitable range of the coverage Rc of the side surface 22b of the convex strip portion 22 by the reflective film 30 according to this embodiment will be described.

[0124] The coverage ratio Rc is preferably 25% or more and 80% or less. Here, the coverage ratio Rc is the ratio of the height (Hx) of the portion of the side surface 22b of the protrusion 22 that is covered by the reflective film 30 to the height (H) of the protrusion 22 shown in Figures 1 and 5. The coverage ratio Rc is expressed by the following formula (1).

[0125] Rc [%] = (Hx / H) x 100 (1) H: height of the ridge portion 22 in the Z direction Hx: height of the portion of the side surface 22b of the ridge portion 22 covered with the reflective film 30 in the Z direction

[0126] The open area ratio Rr is the ratio of the height (H-Hx) of the portion of the side surface 22b of the protruding portion 22 that is not covered with the reflective film 30 to the height (H) of the protruding portion 22 shown in Figures 1 and 5. The open area ratio Rr is expressed by the following formula (2).

[0127] Rr[%]=((H-Hx) / H)×100...(2)

[0128] According to the above definition, Rr = 100 - Rc. Therefore, when the coverage rate Rc of the side surface 22b of the convex ridge portion 22 by the reflective film 30 is 25% or more and 80% or less, the open area rate Rr of the side surface 22b of the convex ridge portion 22 by the reflective film 30 is 20% or more and 75% or less.

[0129] As described above, in the polarizing element 1 according to this embodiment, the coverage Rc of the side surfaces 22b of the ridge portions 22 by the reflective film 30 is preferably 25% or more and 80% or less (i.e., the open area ratio Rr is 20% or more and 75% or less). In particular, in this embodiment, the reflective film 30 is formed so as to cover the tips 22a and the upper sides of both side surfaces 22b of the ridge portions 22, and to leave the lower sides of both side surfaces 22b uncovered and open. The coverage Rc is preferably 25% or more and 80% or less, more preferably 30% or more and 70% or less, and even more preferably 40% or more and 50% or less.

[0130] With this configuration, the polarizing element 1 according to this embodiment can exhibit sufficient transmittance even for obliquely incident light with a large incident angle θ (e.g., 45 to 60°). For example, when the polarizing element 1 separates obliquely incident light into S-polarized light (reflected light) and P-polarized light (transmitted light), the transmittance Tp of the P-polarized light (transmitted light) passing through the polarizing element 1 can be maintained at a high value, regardless of the incident angle θ of the obliquely incident light. Furthermore, by setting the coverage Rc to 25% or more and 80% or less, the contrast (CR = Tp / Ts), which is the ratio of the transmission axis transmittance (Tp) to the transmission axis reflectance (Ts), can be maintained at a good level, and the reflective action of the reflective film 30 can be more reliably exhibited, regardless of the incident angle θ of the obliquely incident light. Therefore, high transmittance of transmitted light can be ensured, and polarization separation characteristics can be improved, regardless of the incident angle θ of the obliquely incident light.

[0131] In contrast, as a comparative example, when the reflective film 30 is formed so as to cover only the tips 22 a of the protruding rib portions 22 of the grid structure 20, or when the reflective film 30 is formed so as to cover the entire tips 22 a and one side surface 22 b of the protruding rib portions 22, the variation in transmittance Tp becomes large depending on the incidence angle θ of the obliquely incident light, and it is considered that sufficient transmittance cannot be obtained even for obliquely incident light with a large incidence angle θ. Also, as a comparative example, when the reflective film 30 covers the entire tips 22 a and both side surfaces 22 b of the protruding rib portions 22 of the grid structure 20 (when the coverage rate Rc is 100%), the transmittance decreases significantly as the incidence angle θ of the obliquely incident light increases.

[0132] Therefore, from the viewpoint of improving the transmittance and polarization separation characteristics of transmitted light without depending on the incident angle θ of obliquely incident light, it is preferable to cover the tip 22a of the convex rib portion 22 and at least a portion of one of the side surfaces 22b (the upper side of the side surface 22b) with a reflective film 30, as in the polarizing element 1 of this embodiment.

[0133] Furthermore, from the viewpoint of the Tp×Rs characteristics required for a polarizing beam splitter (PBS), in the polarizing element 1 of this embodiment, it is preferable that the coverage rate Rc of the side surface 22b of the convex streak portion 22 by the reflective film 30 is 25% or more and 80% or less.

[0134] If the coverage Rc is less than 25%, the transmission axis transmittance Tp of P-polarized light passing through the polarizing element 1 decreases, the transmittance Tp varies depending on the incident angle θ, and a sufficiently high Tp × Rs value cannot be obtained. Therefore, for obliquely incident light with a large incident angle θ, sufficient transmittance of the transmitted light and the polarization separation characteristics expressed by Tp × Rs cannot be obtained. On the other hand, if the coverage Rc is greater than 80%, the transmission axis transmittance Tp decreases as the incident angle θ of the obliquely incident light increases (e.g., 45 to 60°), as in the case where the tip 22a and both side surfaces 22b of the protrusion 22 of the grid structure 20 are entirely covered, resulting in a large variation in the transmittance Tp depending on the incident angle θ.

[0135] Therefore, the coverage Rc of the side surface 22b of the ridge portion 22 by the reflective film 30 is preferably 25% or more and 80% or less. As a result, when light is incident on the polarizing element 1 from an oblique direction, for example, at an incident angle θ of 45°, the transmission axis transmittance Tp of the second polarized light (P polarized light) passing through the polarizing element 1 can be 75% or more. As a result, Tp × Rs can be 70% or more. Therefore, even when a wide range of obliquely incident light is incident at a large incident angle θ, the transmittance of the second polarized light (P polarized light) in the transmission axis direction of the polarizing element 1 can be increased, improving the polarization separation characteristics of the polarizing element 1 and allowing the polarizing element 1 to suitably separate the obliquely incident light into the first polarized light (S polarized light) and the second polarized light (P polarized light).

[0136] From the same viewpoint, it is more preferable that the coverage Rc is 30% or more and 70% or less (i.e., the open area Rr is 30% or more and 70% or less). As a result, under the above-mentioned oblique incidence conditions, a high transmittance Tp of 80% or more can be obtained, and a high Tp×Rs of 72% or more can be obtained. Furthermore, it is more preferable that the coverage Rc is 30% or more and 60% or less (i.e., the open area Rr is 40% or more and 70% or less). As a result, under the above-mentioned oblique incidence conditions, a high transmittance Tp of 83% or more can be obtained, and a high Tp×Rs of 75% or more can be obtained. Furthermore, it is even more preferable that the coverage Rc is 40% or more and 50% or less (i.e., the open area Rr is 50% or more and 60% or less). As a result, under the above-mentioned oblique incidence conditions, an extremely high transmittance Tp of 85% or more can be obtained, and a very high Tp×Rs of 77% or more can be obtained.

[0137] Furthermore, with regard to the reflection axis reflectance Rs, it is preferable that the coverage Rc is 20% or more, which makes it possible to obtain a high reflectance Rs of 85% or more under the above-mentioned oblique incidence conditions.

[0138] Furthermore, with regard to the contrast CR of transmitted light (CR=Tp / Ts), a sufficient contrast CR can be obtained if the coverage Rc is 20% or more. The higher the coverage Rc, the higher the contrast CR can be obtained.

[0139] 2.7. Preferred Range of Tp×Rs Next, a preferred range of “Tp×Rs,” which is an index representing the polarization separation characteristics of the wire-grid polarizer 1 according to this embodiment, will be described.

[0140] Tp×Rs [%] is the product of the transmission axis transmittance (Tp) and the reflection axis reflectance (Rs) expressed as a percentage. This Tp×Rs is an index representing the polarization separation characteristics of the wire grid polarizer 1. Tp×Rs [%] = (Tp [%] / 100) × (Rs [%] / 100) × 100

[0141] As described above, the transmission axis transmittance (Tp) is the transmittance of the second polarized light (P-polarized light) having an electric field component parallel to the transmission axis (X-direction) of the polarizing element 1. The reflection axis reflectance (Rs) is the reflectance of the first polarized light (S-polarized light) having an electric field component parallel to the reflection axis (Y-direction) of the polarizing element 1.

[0142] When the wire grid polarization element 1 according to this embodiment is used as a polarization beam splitter to separate incident light into S-polarized light and P-polarized light (see FIGS. 15 to 17 ), the polarization element 1 is positioned at a predetermined angle (e.g., 45°) with respect to the incident light from the light source. For example, when the incident light from the light source is incident on the polarization element 1 at an incident angle θ of approximately 45°, the incident light is separated by the polarization element 1 into a first polarization (S-polarized light: reflected light) and a second polarization (P-polarized light: transmitted light). The S-polarized light is incident light having an electric field component parallel to the longitudinal direction of the ridges 22 of the grid structure 20 (the reflection axis direction: Y direction shown in FIG. 2 ). On the other hand, the P-polarized light is incident light having an electric field component parallel to the width direction of the ridges 22 of the grid structure 20 (the transmission axis direction: X direction shown in FIG. 2 ).

[0143] The S-polarized light in the reflection axis direction mainly becomes reflected light reflected by the reflective film 30 of the polarizing element 1. The reflectance [%] of the S-polarized light at this time is the reflection axis reflectance (Rs). The reflection axis reflectance (Rs) represents the proportion of S-polarized light that is reflected by the polarizing element 1 out of the S-polarized light that enters the polarizing element 1. The reflection axis transmittance (Rp) represents the proportion of S-polarized light that is transmitted through the polarizing element 1 out of the S-polarized light that enters the polarizing element 1.

[0144] On the other hand, P-polarized light in the transmission axis direction mainly becomes transmitted light that passes through the transparent grid structure 20 and substrate 10 of the polarizing element 1. The transmittance [%] of the P-polarized light at this time is the transmission axis transmittance (Tp). The transmission axis transmittance (Tp) represents the proportion of P-polarized light that is transmitted through the polarizing element 1 out of the P-polarized light that is incident on the polarizing element 1. The transmission axis reflectance (Ts) represents the proportion of P-polarized light that is reflected by the polarizing element 1 out of the P-polarized light that is incident on the polarizing element 1.

[0145] Therefore, a higher transmission axis transmittance Tp means that P-polarized light in the transmission axis direction can be transmitted more efficiently. Also, a higher reflection axis reflectance Rs means that S-polarized light in the reflection axis direction can be reflected more efficiently. Therefore, the higher the Tp×Rs value, which is the product of Tp and Rs, the higher the transmittance of P-polarized light (transmitted light) and the reflectance of S-polarized light (reflected light), resulting in excellent polarization separation characteristics as a polarizing beam splitter.

[0146] Here, a preferred range of the value of Tp×Rs according to this embodiment will be described. Consider a case in which light of a predetermined wavelength range (e.g., 430 to 680 nm) is incident on the polarizing element 1 according to this embodiment from an oblique direction at a predetermined incident angle θ (e.g., 45°), and is separated into P-polarized light (transmitted light) and S-polarized light (reflected light). Under such oblique incidence conditions, from the viewpoint of good polarization separation characteristics of the polarizing element 1, it is preferable that Tp×Rs be 70% or more.

[0147] If Tp×Rs is less than 70%, the light utilization efficiency is poor in a display device to which the polarizing element is applied, the brightness of the displayed image is insufficient, and visibility is poor. In contrast, if Tp×Rs is 70% or more, the light utilization efficiency in a display device to which the polarizing element 1 is applied can be increased, sufficient brightness of the displayed image can be ensured, and visibility can be improved.

[0148] Furthermore, Tp×Rs is more preferably 72% or more, even more preferably 75% or more, and particularly preferably 80% or more, which can further improve the light utilization efficiency and the brightness and visibility of the displayed image.

[0149] <2.8. Preferred Range of Height H of Convex Rib Portion> When incident light is incident on the polarizing element 1 according to this embodiment at a relatively large incident angle θ (for example, 45°), the height H (see FIGS. 1, 3, etc.) of the convex rib portion 22 of the grid structure 20 is preferably 160 nm or more, more preferably 180 nm or more, and particularly preferably 220 nm or more. This makes it possible to obtain a high transmission axis transmittance Tp, excellent Tp×Rs characteristics, and a high contrast CR of transmitted light.

[0150] Specifically, with regard to transmittance, if the height H of the ridge portion 22 is 160 nm or more, the transmission axis transmittance Tp of obliquely incident light becomes 80% or more, resulting in high transmittance. Furthermore, if H is 180 nm or more, a Tp of 85% or more can be obtained, which is more preferable. In addition, if H is 220 nm or more, a Tp of 87% or more can be obtained, which is particularly preferable.

[0151] Furthermore, with regard to the Tp×Rs characteristics required for a polarization beam splitter (PBS), if the height H of the ridge portion 22 is 160 nm or more, an excellent Tp×Rs of 70% or more can be obtained. Furthermore, if H is 180 nm or more, a Tp×Rs of 75% or more can be obtained, which is more preferable. In addition, if H is 220 nm or more, a Tp×Rs of 77% or more can be obtained, which is particularly preferable.

[0152] Furthermore, with regard to the contrast CR (CR = Tp / Ts) of transmitted light, the height H of the ridge portion 22 needs to be 100 nm or more, but if H is 160 nm or more, an excellent contrast CR of 150 or more can be obtained. Furthermore, if H is 180 nm or more, an excellent CR of 250 or more can be obtained, which is more preferable. In addition, if H is 220 nm or more, an excellent CR of 500 or more can be obtained, which is particularly preferable.

[0153] As described above, it can be seen that a larger height H of the ridge portions 22 is preferable for improving various characteristics (Tp, Tp×Rs, CR) of the polarizing element 1, particularly Tp. The reason for this is believed to be as follows. That is, when the deposition incident angle φ (see FIG. 5 ) is the same when the reflective film 30 is deposited on the ridge portions 22 by sputtering, vapor deposition, or the like, the lower the height H of the ridge portions 22, the greater the coverage Rc of the reflective film 30. As the coverage Rc increases, the area of ​​the ridge portions 22 covered by the reflective film 30 becomes wider, making it more difficult for P-polarized light to pass through the grid structure 20, and thus reducing the transmittance Tp. Therefore, under the condition that the deposition incident angle φ is the same, it is preferable to increase the height H of the ridge portions 22 to reduce the coverage Rc and increase the transmittance Tp.

[0154] <2.9. Preferred Range of Tip Thickness Dt of Functional Film (Reflective Film)> When incident light is incident on the polarizing element 1 according to this embodiment at a relatively large incident angle θ (for example, 45°), the thickness Dt of the reflective film 30 covering the tips 22 a of the protruding stripes 22 of the grid structure 20 (tip thickness Dt of the reflective film 30: see FIG. 5 ) is preferably 5 nm or more, and more preferably 15 nm or more.

[0155] If the tip thickness Dt of the reflective film 30 is 5 nm or more, both the reflection axis reflectance Rs and the transmission axis transmittance Tp of obliquely incident light will be 85% or more, resulting in high transmittance. Furthermore, when the Tp characteristics and the Tp×Rs characteristics required for a polarizing beam splitter are taken into consideration, it is more preferable that Dt be 15 nm or more.

[0156] <2.10. Suitable range of side thickness Ds of functional film (reflective film)> Furthermore, the thickness Ds of the reflective film 30 covering the side surfaces 22b of the protruding stripes 22 of the grid structure 20 (side surface thickness Ds of the reflective film 30: see FIG. 5) is preferably 10 nm or more and 30 nm or less, more preferably 12.5 nm or more and 25 nm or less, and particularly preferably 15 nm or more and 25 nm or less. This makes it possible to obtain a high transmission axis transmittance Tp, excellent Tp×Rs characteristics, and a high contrast CR of transmitted light.

[0157] Specifically, when the side thickness Ds of the reflective film 30 is 10 nm or more and 30 nm or less, the transmission axis transmittance Tp of obliquely incident light becomes 80% or more, and high transmittance is obtained. Furthermore, when Ds is 12.5 nm or more and 25 nm or less, Tp of 85% or more can be obtained, which is more preferable.

[0158] Regarding reflectivity, if the side thickness Ds of the reflective film 30 is 10 nm or more, the reflection axis reflectivity Rs of obliquely incident light becomes 80% or more, and high reflectivity is obtained. Furthermore, if Ds is 12.5 nm or more, Rs of 85% or more can be obtained, which is more preferable.

[0159] Regarding the Tp×Rs characteristics required for a polarizing beam splitter (PBS), an excellent Tp×Rs of 70% or more can be obtained if the side thickness Ds of the reflective film 30 is 12.5 nm or more and 30 nm or less. Furthermore, if Ds is 15 nm or more and 25 nm or less, a Tp×Rs of 76% or more can be obtained, which is more preferable.

[0160] Regarding the contrast CR (CR=Tp / Ts) of transmitted light, the side thickness Ds of the reflective film 30 needs to be 10 nm or more, but if Ds is 12.5 nm or more, an excellent contrast CR of 50 or more can be obtained. Furthermore, if Ds is 15 nm or more, a CR of 100 or more can be obtained, which is more preferable.

[0161] 2.11. Uneven Distribution of Reflective Film In addition, in the polarizing element 1 according to this embodiment, the reflective film 30 covering the ridge portions 22 may be unevenly distributed on one side of the ridge portions 22, to form an asymmetric shape in the width direction (X direction) of the ridge portions 22. Specifically, the side thickness Ds or coverage Rc of the reflective film 30 may be changed between one side surface 22b and the other side surface 22b of the ridge portions 22, to cause the reflective film 30 to be unevenly distributed on one side surface 22b of the ridge portions 22. In other words, the reflective film 30 may be thick and widely covering one side surface 22b of the ridge portions 22, and thin and narrowly covering the other side surface 22b.

[0162] When the reflective film 30 is unevenly distributed on one side of the ridge portion 22 in this way, it is preferable that the difference between the transmission axis transmittance Tp(+) of incident light whose incident angle with respect to the polarizing element 1 is +θ (+30° to +60°) and the transmission axis transmittance Tp(-) of incident light whose incident angle is -θ (-30° to -60°) be within 3%. Then, it is preferable to appropriately unevenly distribute the reflective film 30 on one side of the ridge portion 22 by adjusting the thickness Ds and coverage Rc of the reflective film 30 that covers one side 22b and the other side 22b of the ridge portion 22 so that the difference between Tp(+) and Tp(-) is within 3%.

[0163] An incident angle of +θ means that oblique incident light is incident on the ridge portion 22 from a direction tilted toward one side of the X direction (the width direction of the ridge portion 22). On the other hand, an incident angle of −θ means that oblique incident light is incident on the ridge portion 22 from a direction tilted toward the other side of the X direction.

[0164] As described above, when the reflective film 30 is unevenly distributed on one side of the ridge portion 22, it is preferable to keep the difference between Tp(+) and Tp(-) within 3%. This makes it possible to obtain a high transmission axis transmittance Tp, excellent Tp×Rs characteristics, and a high contrast CR of transmitted light, even when the reflective film 30 is unevenly distributed on one side of the ridge portion 22.

[0165] Specifically, with regard to transmittance, even when the reflective film 30 is biased to one side, the transmission axis transmittance Tp of obliquely incident light with an incident angle θ of +45° and −45° is 85% or more, thereby achieving high transmittance.

[0166] Furthermore, with regard to reflectivity, even when the reflective film 30 is unevenly distributed on one side, the reflection axis reflectivity Rs of obliquely incident light with an incident angle θ of +45° and −45° is 85% or more, and high reflectivity is obtained.

[0167] Furthermore, with regard to the Tp×Rs characteristics required for a polarizing beam splitter (PBS), even when the reflective film 30 is biased to one side, the Tp×Rs of obliquely incident light with an incident angle θ of 45° is 75% or more, thereby achieving excellent Tp×Rs characteristics.

[0168] Furthermore, regarding the contrast CR of transmitted light (CR=Tp / Ts), excellent contrast CR can be obtained even when the reflective film 30 is unevenly distributed on one side. Furthermore, from the viewpoint of improving contrast, of the thicknesses Ds of the reflective films 30 covering the one side surface 22b and the other side surface 22b of the convex ridge portion 22, the thinner thickness Ds is preferably 5 nm or more (its coverage rate Rc is 22% or more), and more preferably the thinner thickness Ds of the reflective film 30 is 10 nm or more (its coverage rate Rc is 33% or more).

[0169] <2.12. Other Components> The polarizing element 1 according to this embodiment may further include components other than the substrate 10, the grid structure 20, and the reflective film 30 described above.

[0170] For example, as shown in Fig. 7, the polarizing element 1 preferably further includes a protective film 40 formed so as to cover at least the surface of the reflective film 30. In particular, as shown in Fig. 7, the protective film 40 more preferably covers the entire surface of the grid structure 20. That is, the protective film 40 is more preferably formed so as to cover all of the side surfaces 22b of the ridge portions 22 of the grid structure 20, the surface of the base portion 21, and the surface of the reflective film 30. By forming such a protective film 40, the scratch resistance, stain resistance, and waterproof properties of the polarizing element 1 can be further improved.

[0171] Furthermore, it is more preferable that the protective film 40 further includes a water-repellent coating or an oil-repellent coating, which can further improve the stain-proof and waterproof properties of the polarizing element 1.

[0172] The material constituting the protective film 40 is not particularly limited as long as it can improve the scratch resistance, stain resistance, and waterproof properties of the polarizing element 1. Examples of materials constituting the protective film 40 include films made of dielectric materials, more specifically, inorganic oxides and silane-based water-repellent materials. Examples of inorganic oxides include silicon oxide and halide oxide. The silane-based water-repellent material may contain a fluorine-based silane compound such as perfluorodecyltriethoxysilane (FDTS), or a non-fluorine-based silane compound such as octadecyltrichlorosilane (OTS).

[0173] Among these materials, it is more preferable that the protective film 40 contains at least one of an inorganic oxide and a fluorine-based water-repellent material. When the protective film 40 contains an inorganic oxide, the scratch resistance of the polarizing element can be further improved, and when the protective film 40 contains a fluorine-based water-repellent material, the stain resistance and waterproofing properties of the polarizing element can be further improved.

[0174] The protective film 40 may be formed so as to cover at least the surface of the reflective film 30. However, as shown in Fig. 7, it is more preferable that the protective film 40 be formed so as to cover the entire surfaces of the grid structure 20 and the reflective film 30. In this case, for example, as shown in the upper diagram of Fig. 7, the protective film 40 may cover the end face of the grid structure 20 (the end face of the base portion 21). Alternatively, as shown in the lower diagram of Fig. 7, the protective film 40 may not cover the end face of the grid structure 20 (the end face of the base portion 21). Furthermore, as shown in Fig. 8, the protective film 40 may be formed so as to cover the entire polarizing element 1, including the surface of the substrate 10 in addition to the surfaces of the grid structure 20 and the reflective film 30. In this way, by covering the outermost surface of the grid structure 20 or the polarizing element 1 with the protective film 40 made of an inorganic oxide, the thermal resistance R of the entire polarizing element 1 can be further reduced, thereby further improving the heat dissipation properties of the polarizing element 1.

[0175] Furthermore, the polarizing element 1 according to this embodiment preferably includes a heat dissipation member 50 surrounding the periphery of the substrate 10, as shown in Fig. 9. The heat dissipation member 50 can more efficiently dissipate heat transferred from the substrate 10. Here, the heat dissipation member 50 is not particularly limited as long as it has a high heat dissipation effect. The heat dissipation member 50 may be, for example, a heat sink, a heat spreader, a die pad, a heat pipe, a metal cover, a housing, or the like.

[0176] 2.13. Actual Image of Grid Structure Next, with reference to Fig. 10 , an example of an actual fabricated polarizing element 1 according to this embodiment, and an enlarged image thereof taken using a scanning electron microscope (SEM), will be described. Fig. 10A is an SEM image of the grid structure 20 before being coated with the reflective film 30, viewed from an oblique direction. Fig. 10B is an SEM image showing a cross section of the ridge portions 22 of the grid structure 20 before being coated with the reflective film 30. Fig. 10C is an SEM image showing a cross section of the ridge portions 22 of the grid structure 20 coated with the reflective film 30.

[0177] 10A and 10B, the grid structure 20 has a base portion 21 provided along the surface of the substrate 10 and protruding ridge portions 22 protruding from the base portion 21. The plurality of protruding ridge portions 22 are arranged at a substantially equal pitch P. Each protruding ridge portion 22 has a tapered shape that narrows in width as it moves away from the base portion 21. The width W of the top of the protruding ridge portion 22 is Ｔ is the width W of the bottom of the ridge portion 22 Ｂ The pitch P is narrower than the width W of the bottom of the ridge portion 22. Ｂ The height H of the ridge portion 22 is greater than the pitch P. In the example of FIG. 10, P=140 nm, W Ｔ = 10 nm, W Ｂ 10C, a reflective film 30 is formed to cover the tip 22a and both side surfaces 22b of the protruding ridge portion 22. The outer surface of the reflective film 30 is curved and rounded, and bulges out in the width direction of the protruding ridge portion 22.

[0178] 3. Method for Manufacturing Polarizing Element Next, a method for manufacturing the wire grid polarizer 1 according to this embodiment will be described with reference to Fig. 11. Fig. 11 is a process chart showing the method for manufacturing the wire grid polarizer 1 according to this embodiment.

[0179] As described above, the polarizing element 1 according to this embodiment is a hybrid wire-grid polarizing element 1 made of an inorganic material (substrate 10) and an organic material (grid structure 20). A method for manufacturing this hybrid wire-grid polarizing element 1 will be described below.

[0180] As shown in FIG. 11, the method for manufacturing the wire-grid polarizer 1 according to this embodiment includes a grid structure material formation step (S10), a nanoimprinting step (S12), a grid structure formation step (S14), and a reflective film formation step (S16).

[0181] Grid Structure Material Formation Step (S10) First, in S10, a grid structure material 23 made of a transparent organic material (e.g., an ultraviolet-curable resin or a thermosetting resin) is laminated by coating or the like on a substrate 10 made of a transparent inorganic material (e.g., glass). The various materials described above can be used as the inorganic material for the substrate 10. The various materials described above can be used as the organic material for the grid structure 20. Furthermore, the film thickness of the grid structure material 23 can be adjusted appropriately depending on the dimensions of the base portion 21 and the ridge portions 22 of the grid structure 20 formed by nanoimprinting in S20.

[0182] Nanoimprinting Step (S12) and Grid Structure Forming Step (S14) Next, in S12, nanoimprinting is performed on the grid structure material 23, and in S14, a grid structure 20 is formed on the substrate 10. The grid structure 20 is a micro-relief structure in which a base portion 21 provided on the substrate 10 and a plurality of protruding ridge portions 22 protruding from the base portion 21 are integrally formed. The micro-relief structure is a structure having minute protrusions and recesses on the order of, for example, several nanometers to several tens of nanometers.

[0183] In the nanoimprinting step of S12, a master 60 on which a reversed shape of the fine concave-convex shape of the grid structure 20 is formed is used to transfer the fine concave-convex shape of the master 60 to the surface of the grid structure material 23 (S12). As a result, a concave-convex pattern consisting of the base portion 21, the ridge portions 22, and the recesses 24 is formed in the grid structure material 23. Furthermore, in the nanoimprinting step, in addition to the transfer of the concave-convex pattern, the grid structure material 23 is irradiated with energy rays to harden the grid structure material 23 to which the concave-convex pattern has been transferred, thereby forming the grid structure 20 (S14). For example, when the grid structure material 23 is made of an ultraviolet curable resin, ultraviolet rays may be irradiated onto the grid structure material 23 using an ultraviolet irradiation device 66 to harden the ultraviolet curable resin to which the concave-convex pattern has been transferred. Alternatively, when the grid structure material 23 is made of a thermosetting resin, a heating device 68 such as a heater may be used to heat the grid structure material 23 to harden the thermosetting resin to which the concave-convex pattern has been transferred.

[0184] In the above steps S12 and S14, the convex rib portions 22 of the grid structure 20 are formed to have a tapered shape whose width narrows with increasing distance from the base portion 21. The convex rib portions 22 in the example of Fig. 11 are trapezoidal (tapered) in shape, but may have various other tapered shapes as shown in Fig. 3.

[0185] As described above, in this embodiment, the tapered convex ridges 22 are imprinted in the nanoimprinting step S12, so that the master 60 can be easily peeled off from the grid structure material 23, resulting in excellent mold-removal properties. Furthermore, the convex ridges 22 of the grid structure 20 can be accurately molded into a desired shape without losing their shape.

[0186] Reflective Film Forming Step (S16) Next, in S16, a metallic material such as Al or Ag is used to form a reflective film 30 that covers part of the protruding stripes 22 of the grid structure 20. The reflective film 30 is an example of a functional film that imparts a predetermined function to the polarizing element 1. The reflective film 30 is a thin metal film (a grid of thin metal wires) that reflects incident light that is incident on the grid structure 20 of the polarizing element 1.

[0187] In this reflective film forming step S16, the reflective film 30 is formed as follows. That is, the reflective film 30 is formed so that it covers the tip 22a and the upper side of at least one side surface 22b of the convex rib portion 22, but does not cover the lower sides of both side surfaces 22b of the convex rib portion 22 or the base portion 21. Furthermore, the reflective film 30 is formed so that the surface of the reflective film 30 that covers the convex rib portion 22 is rounded and bulges in the width direction of the convex rib portion 22. In addition, the maximum width W of the reflective film 30 that covers the convex rib portion 22 is ＭＡＸ (Maximum grid width W ＭＡＸ ) is the width W of the bottom of the convex ridge portion mentioned above Ｂ (Grid bottom width W Ｂ The reflective film 30 is formed so that the reflectance is equal to or greater than 100 .mu.m.

[0188] 5, for example, sputtering or vapor deposition can be used to form such a reflective film 30. The reflective film 30 is formed by sputtering or vapor depositing a metal material alternately from oblique directions relative to the ridge portions 22 of the grid structure 20. This makes it possible to suitably form the reflective film 30 in a desired shape so as to surround the tops of the ridge portions 22 in a round shape.

[0189] By forming the reflective film 30 in this manner, the convex streak portions 22 of the grid structure 20 and the reflective film 30 have the special tree-like shape described above. As a result, as described above, even when light is incident on the polarizing element 1 from an oblique direction at a relatively large and wide range of incident angles θ (e.g., 30 to 60°), the transmission axis transmittance Tp of P-polarized light contained in the obliquely incident light can be maintained at a high value, and the transmittance of P-polarized light (transmitted light) can be ensured. Therefore, the value of Tp×Rs can be maintained at a high value (e.g., 70% or more), thereby improving the polarization separation characteristics of the polarizing element 1 for obliquely incident light.

[0190] The manufacturing method for the polarizing element 1 according to this embodiment may include, as necessary, a step of forming a protective film 40 that covers the surface of the polarizing element 1 (protective film forming step) after the reflective film forming step S16 shown in Fig. 11. The protective film 40 is preferably formed so as to cover the entire surfaces of the grid structure 20 and the reflective film 30. The various materials described above can be used as the material for the protective film 40.

[0191] The above describes the method for manufacturing the polarizing element 1 according to this embodiment. By going through the above-described steps, it is possible to manufacture a polarizing element 1 that has excellent polarization properties and heat dissipation properties without increasing the manufacturing cost of the polarizing element 1 or making the manufacturing process complicated.

[0192] Here, for comparison with the manufacturing method according to this embodiment, a conventional method for manufacturing a wire grid polarizer will be briefly described with reference to FIG.

[0193] 12, in a conventional method for manufacturing a wire-grid polarizer, first, in order to create a convex grid pattern, a metal film 80 is formed on a substrate 10 (S20). In S20, a reflective film made of a material that reflects light in the used band, such as a metal film 80 made of aluminum, is formed on the substrate 10 made of an inorganic material such as glass by sputtering or vapor deposition.

[0194] Next, a resist mask 70 is patterned on the metal film 80 using photolithography (S22). After that, the metal film 80 is etched using a vacuum dry etching device or the like to form a convex shape made of the metal film 80 (S24). For example, if the etching selectivity between the resist mask 70 and the metal film 80 cannot be obtained at this time, a SiO ２ Then, a resist mask 70 is formed on the metal film 80 by photolithography (S26). ２ A protective film 40 made of a film or the like is formed by CVD or the like, and a water-repellent and oil-repellent coating process is also performed as needed (S28).

[0195] While steps S20 to S28 of the conventional manufacturing method described above show the process for producing a reflective wire-grid polarization element with a basic configuration, a more complex process is required when metal film 80 is a multilayer film. Therefore, it is expected that conventional wire-grid polarization elements produced by the process shown in S20 to S28 of Figure 12 will be expensive to manufacture and will take a long time to manufacture. Furthermore, when mass-producing polarization elements, in order to form minute convex shapes smaller than the wavelength of light, it will be necessary to prepare multiple high-precision, expensive etching devices and photolithography devices according to the production volume, and this is expected to result in even higher capital investment.

[0196] In contrast, the manufacturing method of the polarizing element 1 according to this embodiment (see FIG. 11 ) uses an imprinting technique such as nanoimprinting to form the grid structure 20, and therefore can significantly reduce manufacturing costs, manufacturing time, and capital investment compared to the conventional manufacturing method (see FIG. 12 ).

[0197] In the manufacturing method of the polarizing element 1 according to this embodiment, nanoimprinting is performed on the grid structure material 23 (S12 in FIG. 11 ), but the conditions for nanoimprinting are not particularly limited. For example, as shown in S12 in FIG. 11 , a replica master (which may also be a main mold master) is used as the master 60, and while nanoimprinting is performed, the grid structure material 23 is irradiated with UV light or heated, etc., so that the grid structure material 23 is cured in a state in which the concave-convex pattern is imprinted. Thereafter, the master 60 is released from the cured grid structure material 23. In this way, the grid structure 20 having the base portion 21 and the ridge portions 22 formed thereon can be molded by transfer.

[0198] The master 60 used in the nanoimprint step S12 (FIG. 11) in the manufacturing method for the polarizing element 1 according to this embodiment can be manufactured by photolithography, for example, as shown in Fig. 13. Fig. 13 is a process chart showing the manufacturing method for the master 60 according to this embodiment.

[0199] 13, first, a master metal film 62 is formed on a master substrate 61 (S30), and then a resist mask 70 is formed on the master metal film 62 (S32). Next, the master metal film 62 is etched using the resist mask 70, and grooves 65 corresponding to the ridge portions 22 of the grid structure 20 are formed in the etched master metal film 62 (S34).

[0200] Thereafter, the resist mask 70 is peeled off from the master metal film 62 to obtain the master 60 (S36). The master 60 has a fine uneven structure consisting of a plurality of convex portions 63 and concave grooves 65 formed on the master substrate 61. The fine uneven structure on the surface of the master 60 has an inverted shape of the fine uneven structure on the surface of the grid structure 20 of the polarizing element 1. The concave grooves 65 of the master 60 have an inverted shape of the convex streak portions 22 of the grid structure 20, and the convex portions 63 of the master 60 have an inverted shape of the concave portions 24 between the convex streak portions 22, 22 of the grid structure 20.

[0201] Furthermore, the manufacturing method according to this embodiment may include, as necessary, a step (S38) of forming a release film coat 64 on the surface of the fine concave-convex structure of the master 60. By providing the release film coat 64 on the surface of the master 60, after nanoimprinting is performed on the grid structure material 23 in the nanoimprinting step (S12) shown in Fig. 11, the master 60 can be easily peeled off from the grid structure material 23, and the releasability can be further improved.

[0202] 4. Projection Display Device Next, a projection display device to which the wire-grid polarizer 1 according to this embodiment is applied will be described with reference to FIG.

[0203] The projection display device according to this embodiment includes the above-described wire-grid polarizer 1 according to this embodiment. By including the polarizer 1 in the projection display device according to this embodiment, excellent polarization characteristics, as well as the heat resistance and heat dissipation properties of the polarizer 1 can be achieved.

[0204] Here, a projection display device is a device that projects light toward an object and irradiates the projected light (projection light) onto a display surface (projection surface) of the object, thereby displaying a virtual image such as an image or video. Examples of types of projection display devices include a head-up display device (HUD) and a projector device.

[0205] <4.1. Head-up display device> First, a head-up display device 100 including a wire-grid polarizer 1 according to this embodiment will be described with reference to Fig. 14. Fig. 14 is a schematic diagram showing an example of the head-up display device 100 according to this embodiment.

[0206] 14, the head-up display device 100 according to this embodiment includes the wire-grid polarizer 1 according to this embodiment described above. By including the polarizer 1 in the head-up display device 100, it is possible to improve polarization characteristics, heat resistance, and heat dissipation. Head-up displays incorporating conventional polarizers have poor heat dissipation properties, and are therefore considered to have insufficient heat resistance when considering long-term use and future trends toward higher brightness and larger displays.

[0207] 14 , the head-up display device 100 includes a light source 2, a display element 3 that emits a display image, a reflector 4 that reflects the display image onto a display surface 5, and a cover portion 6 that is provided at an opening of a housing 7. In the head-up display device 100, the arrangement of the polarizing element 1 is not particularly limited. For example, as shown in FIG. 14 , the polarizing element 1 can be arranged between the display element 3 and the reflector 4.

[0208] Here, the head-up display device 100 may be a vehicle head-up display device provided in a vehicle. The vehicle head-up display device displays an image on a semi-transparent plate (corresponding to the "display surface 5") such as a windshield or a combiner of the vehicle. The vehicle head-up display device is, for example, an image display device disposed on the dashboard of the vehicle, projects image light onto the windshield (display surface 5), and displays driving information as a virtual image.

[0209] The head-up display device 100 is configured to emit a display image from below toward the windshield surface (display surface 5). Therefore, sunlight may enter in a direction opposite to the emission direction of the display image and be incident on the display element 3. The head-up display device 100 according to this embodiment is provided with a reflector 4 for reflecting and enlarging the display image in order to meet the demand for compactness and to enlarge the display image. In such cases, in conventional head-up display devices, sunlight incident on the reflector from outside is concentrated near the display element, which may cause heat to deteriorate or malfunction the display element.

[0210] In contrast, the head-up display device 100 according to this embodiment is provided with the hybrid polarizing element 1, which has excellent heat dissipation and heat resistance properties as described above, in order to prevent sunlight from entering the display element 3. This polarizing element 1 can stably exhibit its polarization function even at high temperatures, for example, around 200°C. Therefore, even in a high-temperature environment, such as the inside of a car in summer, sunlight that has entered the reflector 4 from the outside can be blocked by the polarizing element 1, preventing it from reaching the display element 3, thereby suppressing deterioration and failure of the display element 3.

[0211] Note that the components of the head-up display device 100 shown in Figure 14 are examples of basic components, and the components of the projection display device are not limited to the example in Figure 14, and other components may be included as appropriate depending on the required performance, etc.

[0212] Furthermore, by using the polarizing element 1 as a pre-polarizing plate disposed in front of the display element 3, the polarizing element 1 can transmit the display image emitted from the display element 3 while suppressing the incidence of sunlight on the display element 3. Therefore, the heat resistance and durability of the head-up display device 100 can be further improved.

[0213] In addition, the arrangement of the wire grid polarizer in the projection display device is not limited to the example of the arrangement of the polarizer 1 in the head-up display device 100 shown in Fig. 14, and can be appropriately selected and changed depending on the configuration of the projection display device, the required performance, etc. For example, although not shown, the polarizer 1 can be arranged between the display element 3 and the light source 2. Also, although not shown, the polarizer 1 can be incorporated into the reflector 4. Furthermore, the cover portion 6 provided in the head-up display device 100 shown in Fig. 14 can also be composed of the polarizer 1.

[0214] Although not shown, a heat dissipation member 50 (see FIG. 9 ) may be provided around the polarizing element 1 installed in the head-up display device 100. The heat dissipation member 50 can further improve the heat dissipation properties of the polarizing element 1, thereby further improving the polarization characteristics and heat resistance of the polarizing element 1.

[0215] 15 to 17, a projection display device that uses the reflective wire-grid polarizer 1 according to this embodiment as a polarization beam splitter 230 will be described. Below, we will first comprehensively describe matters common to the three specific examples of projection display devices 200A, 200B, and 200C (hereinafter sometimes collectively referred to as "projection display device 200") shown in FIGS. 15 to 17. Then, we will individually describe each of the specific examples shown in FIGS. 15 to 17.

[0216] 15 to 17, the projection display device 200 includes a light source 210, a PS converter 220, a polarizing beam splitter 230, a reflective liquid crystal display element 240, and a lens 250. A phase difference compensator (not shown) may be installed between the polarizing beam splitter 230 and the reflective liquid crystal display element 240.

[0217] Light source 210 may be a point light source having one light-emitting element, or may be a light source having multiple light-emitting elements such as LEDs. Furthermore, the light emitted from light source 210 may be parallel light or diffused light. Therefore, the light from light source 210 may be incident on polarizing beam splitter 230 (reflective wire-grid polarizer) at an incident angle θ within a predetermined range (e.g., a range of 45°±15°) centered around 45°.

[0218] The PS converter 220 is a polarization conversion element for converting the light from the light source 210 into a specific polarization (for example, P polarization or S polarization). The PS converter 220 may convert the light from the light source 210 into either P polarization or S polarization.

[0219] Polarizing beam splitter 230 is configured with a reflective wire-grid polarizer. A reflective wire-grid polarizer is an example of the wire-grid polarizer 1 according to this embodiment. Polarizing beam splitter 230 is disposed so that light from light source 210 is incident at an incident angle θ within a predetermined range including 45°. This predetermined range of incident angle θ is, for example, the above-mentioned 45°±15°, i.e., not less than 30° and not more than 60°.

[0220] 15 to 17, for example, the polarizing beam splitter 230 is disposed at an angle of 45° with respect to the incident direction of the incident light so that the incident light from the light source 210 is incident on the polarizing beam splitter 230 mainly at an incident angle θ of 45°. Also, the polarizing beam splitter 230 is disposed at an angle of 45° with respect to the reflective liquid crystal display element 240 so that the incident light from the reflective liquid crystal display element 240 is incident on the polarizing beam splitter 230 mainly at an incident angle θ of 45°.

[0221] The polarizing beam splitter 230 separates the incident light into a first polarized light (S polarized light) and a second polarized light (P polarized light). For example, the polarizing beam splitter 230 may separate the S polarized light and the P polarized light by reflecting the first polarized light (S polarized light) of the incident light and transmitting the second polarized light (P polarized light). Conversely, the polarizing beam splitter 230 may separate the S polarized light and the P polarized light by reflecting the second polarized light (P polarized light) of the incident light and transmitting the first polarized light (S polarized light).

[0222] When the polarizing beam splitter 230 is to reflect a desired polarized light, the polarizing beam splitter 230 is disposed so that light containing the polarized light to be reflected is incident on the surface of the polarizing beam splitter 230 (i.e., the uneven surface on the side of the polarizing element 1 on which the grid structure 20 is formed). For example, as shown in FIG. 15 , when the polarizing beam splitter 230 is to reflect S-polarized light incident from the PS converter 220, the surface of the polarizing beam splitter 230 can be directed toward the PS converter 220 that emits the S-polarized light. On the other hand, as shown in FIG. 16 , when the polarizing beam splitter 230 is to reflect S-polarized light incident from the reflective liquid crystal display element 240, the surface of the polarizing beam splitter 230 can be directed toward the reflective liquid crystal display element 240 that emits the S-polarized light.

[0223] The reflective liquid crystal display element 240 is a display element that reflects incident light and emits light that represents a display image. As shown in Figures 15 and 17, the reflective liquid crystal display element 240 may be arranged so that the first polarized light (S-polarized light) reflected by the polarizing beam splitter 230 is incident on the surface of the reflective liquid crystal display element 240. Alternatively, as shown in Figure 16, the reflective liquid crystal display element 240 may be arranged so that the second polarized light (P-polarized light) transmitted through the polarizing beam splitter 230 is incident on the surface of the reflective liquid crystal display element 240.

[0224] 15 and 17, the reflective liquid crystal display element 240 reflects and modulates the incident first polarized light (S polarized light) and emits the second polarized light (P polarized light) that represents the display image. However, without being limited to such an example, as shown in FIG. 16, the reflective liquid crystal display element 240 may reflect and modulate the incident second polarized light (P polarized light) and emit the first polarized light (S polarized light) that represents the display image.

[0225] The lens 250 magnifies the light representing the display image emitted from the reflective liquid crystal display element 240 and outputs it to the outside. The lens 250 is arranged so that the light representing the display image emitted from the reflective liquid crystal display element 240 is incident through the polarizing beam splitter 230. For example, as shown in FIGS. 15 and 17 , the lens 250 may be arranged so that the second polarized light (P polarized light) reflected and modulated by the reflective liquid crystal display element 240 passes through the polarizing beam splitter 230 and enters the lens 250. Alternatively, as shown in FIG. 16 , the lens 250 may be arranged so that the first polarized light (S polarized light) reflected and modulated by the reflective liquid crystal display element 240 is reflected by the polarizing beam splitter 230 and enters the lens 250.

[0226] As described above, the projection display device 200 according to this embodiment uses the wire-grid polarizer 1 according to this embodiment described above as the polarizing beam splitter 230. Therefore, the polarizing beam splitter 230 has excellent reflectivity for S-polarized light, excellent transmittance for P-polarized light, and excellent Tp×Rs characteristics for obliquely incident light with a relatively large and wide range of incident angles θ (for example, 30 to 60°), and is excellent in the ability to separate obliquely incident light into P-polarized light and S-polarized light.

[0227] Next, specific examples of the projection display devices 200A, 200B, and 200C shown in FIGS. 15 to 17 will be described individually.

[0228] As shown in FIG. 15, a projection display device 200A according to a first specific example of this embodiment includes a light source 210, a PS converter 220, a polarizing beam splitter 230, a reflective liquid crystal display element 240, and a lens 250.

[0229] The light emitted from the light source 210 is unpolarized and contains equal proportions of P-polarized and S-polarized components. Therefore, if the polarizing beam splitter 230, which is made of the polarizing element 1, selects and extracts only one polarized light, the amount of light will be reduced by approximately half. Therefore, the PS converter 220 converts the light emitted from the light source 210 into either a first polarized light (S-polarized) or a second polarized light (P-polarized). This suppresses the reduction in the amount of polarized light extracted by the polarizing beam splitter 230, thereby improving light utilization efficiency. For example, the PS converter 220 shown in FIG. 15 converts the light from the light source 210 into a first polarized light (S-polarized).

[0230] The light converted into S-polarized light by PS converter 220 is incident on polarizing beam splitter 230, which is tilted at an angle of approximately 45°. Polarizing beam splitter 230 reflects the first polarized light (S-polarized light) and emits it toward reflective liquid crystal display element 240 at an emission angle of 45°. Reflective liquid crystal display element 240 modulates and reflects the first polarized light (S-polarized light) to generate second polarized light (P-polarized light) that represents a display image, and emits this second polarized light (P-polarized light) toward polarizing beam splitter 230. This second polarized light (P-polarized light) passes through polarizing beam splitter 230 and is magnified by lens 250, after which it is projected onto a display surface (not shown), and the display image is displayed.

[0231] The projection display device 200A having the above configuration includes a reflective wire-grid polarizer made of the wire-grid polarizer 1 according to this embodiment as the polarization beam splitter 230. This improves the polarization separation characteristics of the polarization beam splitter 230 for obliquely incident light and light incident at a wide incidence angle θ, and also improves the heat dissipation and heat resistance of the polarization beam splitter 230 and the projection display device 200A.

[0232] In contrast, projection display devices (not shown) that use conventional polarizing elements as polarizing beam splitters have poor heat dissipation properties. Therefore, their heat resistance is considered insufficient from the standpoints of long-term use, high brightness, and enlarged display. Furthermore, the incident angle θ of light entering a polarizing beam splitter is not limited to 45°, but can be any angle within a predetermined range (e.g., approximately 45°±15°) centered on 45°. Even when obliquely incident light with a large and wide range of incident angles θ is incident on a polarizing beam splitter, the polarizing beam splitter must be able to effectively separate the obliquely incident light into S-polarized and P-polarized light regardless of the incident angle θ. However, polarizing beam splitters using conventional polarizing elements have poor polarization separation characteristics for the obliquely incident light, resulting in poor light utilization efficiency and adverse effects on the image quality of the displayed image, such as uneven brightness.

[0233] In this regard, the polarizing beam splitter 230 of the projection display device 200A according to the first specific example of this embodiment has excellent polarization separation characteristics for obliquely incident light with a large and wide range of incident angles θ, as described above. Therefore, the projection display device 200A can improve the light utilization efficiency and reduce brightness unevenness, thereby improving the quality of the displayed image.

[0234] Furthermore, the projection display device is not limited to the example of the projection display device 200A shown in Figure 15 above, and the components and arrangement of the projection display device can be changed as appropriate, for example, to the projection display device 200B shown in Figure 16 or the projection display device 200C shown in Figure 17.

[0235] As shown in FIG. 16, a projection display device 200B according to a second specific example of this embodiment includes a light source 210, a PS converter 220, a polarizing beam splitter 230, a reflective liquid crystal display element 240, and a lens 250.

[0236] In the projection display device 200B, the PS converter 220 converts light from the light source 210 into second polarized light (P polarized light). The light converted into P polarized light by the PS converter 220 passes through a polarizing beam splitter 230 tilted at an angle of approximately 45° and enters a reflective liquid crystal display element 240. The reflective liquid crystal display element 240 modulates and reflects the second polarized light (P polarized light) to generate first polarized light (S polarized light) that represents a display image, and emits the first polarized light (S polarized light) toward the polarizing beam splitter 230. The polarizing beam splitter 230 reflects the first polarized light (S polarized light) and emits it toward the lens 250 at an emission angle of 45°. The first polarized light (S polarized light) is magnified by the lens 250 and then projected onto a display surface (not shown), whereupon the display image is displayed.

[0237] The projection display device 200B having the above configuration, like the projection display device 200A described above (see Figure 15), has excellent polarization separation characteristics for obliquely incident light, and can improve the light utilization efficiency and reduce brightness unevenness, thereby improving the image quality of the displayed image.

[0238] Also, as shown in Figure 17, a projection display device 200C according to a third specific example of this embodiment includes a light source 210, a polarizing beam splitter 230, a reflective liquid crystal display element 240, a lens 250, and a light absorber 260, but does not include the above-mentioned PS converter 220.

[0239] In the projection display device 200C, unpolarized light emitted from the light source 210 is directly incident on the polarizing beam splitter 230, which is tilted at an angle of approximately 45°. The polarizing beam splitter 230 reflects the first polarized light (S-polarized) component of the unpolarized light and emits it toward the reflective liquid crystal display element 240 at an emission angle of 45°. On the other hand, the second polarized light (P-polarized) component of the unpolarized light incident on the polarizing beam splitter 230 passes through the polarizing beam splitter 230 and is incident on the light absorber 260. Most of this second polarized light (P-polarized) component is absorbed by the light absorber 260, thereby preventing unwanted second polarized light (P-polarized) from being incident on other optical systems within the projection display device 200C.

[0240] The reflective liquid crystal display element 240 modulates and reflects the component of the first polarized light (S polarized light) incident from the polarizing beam splitter 230 to generate a second polarized light (P polarized light) that represents a display image, and emits the second polarized light (P polarized light) toward the polarizing beam splitter 230. The second polarized light (P polarized light) passes through the polarizing beam splitter 230 and is magnified by the lens 250, and then projected onto a display surface (not shown), whereby the display image is displayed.

[0241] In the projection display device 200C having the above configuration, the PS converter 220 is not installed, and therefore the second polarized light (P polarized light) component of the unpolarized light emitted from the light source 210 is absorbed by the light absorber 260 and is not used to display the display image. This reduces the amount of light in the display image by approximately half. However, this has the advantage that the cost and installation space required for the PS converter 220 can be reduced and the number of parts in the projection display device 200C can be reduced, thereby reducing the cost of the projection display device 200C and making the projection display device 200C more compact.

[0242] The foregoing has described a specific example of the projection display device 200 that uses the reflective wire-grid polarizer 1 according to this embodiment as the polarizing beam splitter 230. Note that the projection display device is not limited to the specific examples of the projection display device 200 shown in Figures 15 to 17, and the components and arrangement of the projection display device may be changed as appropriate, or other components may be provided as appropriate, depending on the required performance, etc.

[0243] 5. Vehicle Next, a vehicle equipped with the image display device according to this embodiment will be described.

[0244] A vehicle (not shown) according to this embodiment is equipped with a projection display device having the wire-grid polarizer 1 according to this embodiment described above. The vehicle may be any of a variety of automobiles, such as passenger cars, light vehicles, buses, trucks, racing cars, construction vehicles, and other large vehicles, as long as it is capable of installing a projection display device. In addition, the vehicle may also be any of a variety of vehicles, such as motorcycles, trains, linear motor cars, and attraction vehicles.

[0245] The vehicle according to this embodiment can project and display a display image on a display surface (for example, the display surface 5 shown in FIG. 14 ) provided in the vehicle using the polarizing element 1 and the projection display device. The display surface is preferably a semi-transparent plate such as the vehicle's windshield, side window, rear window, or combiner. However, the display surface is not limited to this example and may be the surface of any object onto which a display image can be projected, such as various parts, components, or on-board equipment provided in the vehicle.

[0246] The projection display device provided in the vehicle according to this embodiment is, for example, the head-up display device 100 shown in Fig. 14 or the projection display device 200 having the polarizing beam splitter 130 shown in Figs. 15 to 17. However, the projection display device is not limited to these examples, and may be any of various image display devices, such as a projector mounted on a vehicle, a car navigation device, or a terminal device with an image display function, as long as it is a device capable of projecting or displaying an image.

[0247] As described above, in the head-up display device 100, as shown in FIG. 14 , sunlight may enter the head-up display device 100 from outside the vehicle through the windshield (display surface 5). The heat of this sunlight may cause deterioration or failure of the display element 3. Therefore, in order to prevent sunlight from entering the display element 3, the hybrid wire-grid polarizer 1 described above is provided in the head-up display device 100. This polarizer 1 has a hybrid structure with high thermal conductivity, and therefore has excellent heat dissipation and heat resistance. Therefore, the polarizer 1 can block sunlight entering the head-up display device 100 from outside, preventing it from reaching the display element 3, thereby preventing failure or damage to the display element 3. Furthermore, the polarizer 1 has excellent heat dissipation and heat resistance, and therefore can prevent damage to the polarizer 1 itself.

[0248] 15 to 17 is installed in a vehicle, the polarizing element 1 used as the polarizing beam splitter 230 can block sunlight from outside, thereby preventing breakdowns and damage to other components such as the reflective liquid crystal display element 240. Furthermore, damage to the polarizing element 1 itself, which has excellent heat dissipation and heat resistance, can also be prevented.

[0249] As described above, the projection display device installed in the vehicle of this embodiment can obtain excellent polarization characteristics (such as sunlight blocking performance and polarization separation characteristics) due to the polarizing element 1, and can also achieve excellent heat resistance and durability of the projection display device.

[0250] The vehicle is not particularly limited as long as it is equipped with the above-mentioned projection display device and polarizing element, and other conditions can be set and changed as appropriate depending on the performance required of the vehicle.

[0251] 7 and 8, and Fig. 18, the protective film 40 that covers the surfaces of the grid structure 20 and the reflective film 30 (functional film) of the wire-grid polarizer 1 according to this embodiment will be described in more detail. Fig. 18 is an enlarged cross-sectional view showing the wire-grid polarizer 1 covered with the protective film 40 according to this embodiment.

[0252] 7 and 8, the wire grid polarizer 1 according to this embodiment includes a protective film 40 that covers the entire surface of the wire grid polarizer 1. The protective film 40 is made of an inorganic material, for example, SiO ２ , Al ２ O ３ The protective film 40 is made of a dielectric material such as SiO. The protective film 40 is formed so as to cover the entire surfaces of the grid structure 20 and the reflective film 30. More specifically, the protective film 40 is formed over the entire surface of the polarizing element 1 so as to continuously cover the surfaces of the base portion 21 and exposed portions of the ridge portions 22 of the grid structure 20, and the exposed portions of the reflective film 30 that encase the upper sides of the ridge portions 22. The protective film 40 is made of an inorganic material such as an inorganic oxide. The inorganic oxide may be, for example, SiO ２ , Al ２ O ３or may be a dielectric material such as Al ２ O ３ The metal oxide may be Al. ２ O ３ Al is both a dielectric material and a metal oxide. Dielectric materials are materials that make up dielectrics. Dielectrics do not pass direct current, but they polarize in the electric field of alternating current and store electricity. ２ O ３ The dielectric constant of SiO is, for example, about 9.9. ２ The dielectric constant of the film is, for example, about 3.9.

[0253] By providing such a protective film 40, it is possible to protect the surfaces of the grid structure 20 and the reflective film 30 of the polarizing element 1. This makes it possible to improve the scratch resistance, stain resistance, and waterproof properties of the grid structure 20 and the reflective film 30.

[0254] In particular, since the grid structure 20 is made of an organic material such as resin, it is more susceptible to deterioration due to heat, light, water, etc. than the substrate 10, which is made of an inorganic material such as glass. By tightly covering the resin grid structure 20 with a protective film 40 made of an inorganic material, the grid structure 20 can be protected from external heat, air, water, etc. (barrier properties). This prevents the resin of the grid structure 20 from being altered or deteriorated due to heat, air, water, etc. Furthermore, as shown in FIGS. 7 and 8 , covering the outermost surface of the polarizing element 1 with a protective film 40 made of an inorganic oxide or the like further reduces the thermal resistance R of the entire polarizing element 1, thereby further improving the heat dissipation of the polarizing element 1.

[0255] As described above, the polarizing element 1 according to this embodiment is a hybrid wire-grid polarizing element that combines a substrate 10 made of an inorganic material with a grid structure 20 made of an organic material. Furthermore, as shown in FIG. 18 , the grid 41 (the entire convex structure including the convex stripes 22 and the reflective film 30) of the polarizing element 1 according to this embodiment has the unique tree-like shape described above. Therefore, complexly shaped valleys 42 are formed between adjacent grids 41. As a result, the surface of the grid structure 20 of the polarizing element 1 has a complex uneven structure with multiple convex portions (grids 41) and multiple concave portions (valleys 42) intertwined.

[0256] The grid structure 20 having such a complex uneven structure and the protective film 40 covering the grid structure 20 will be described in detail again with reference to FIG.

[0257] 18 , the grid structure 20 is formed integrally with a base portion 21 provided on a substrate 10 and a plurality of ridge portions 22 protruding from the base portion 21. The grid structure 20 is formed of an organic material such as resin, and the substrate 10 is formed of an organic material such as glass. The ridge portions 22 of the grid structure 20 have a tapered shape in which the width in the X direction narrows as the distance from the base portion 21 increases upward (in the Z direction).

[0258] The reflective film 30 (functional film) is made of a metal material such as Al, and covers only the tip side of the ridge portion 22. In detail, the reflective film 30 covers the tip 22a and the upper sides of both side surfaces 22b, 22b of the ridge portion 22, but does not cover the lower sides of both side surfaces 22b, 22b of the ridge portion 22 or the surface of the base portion 21. The coverage rate (Rc) of both side surfaces 22b, 22b of the ridge portion 22 by the reflective film 30 is 30% or more and 70% or less.

[0259] In this way, the surface of the reflective film 30 that covers the upper side of the ridge portion 22 is rounded and bulges out in the width direction of the ridge portion 22 (the X direction in FIG. 1). ＭＡＸ ) is the width (W Ｂ18 , the cross-sectional shape of the entire convex structure (i.e., grid 41) composed of the convex streak portions 22 and the reflective film 30 has the special tree-like shape described above. In this special tree-like shape, constricted portions 29, 29 are provided immediately below the lower end portions on both the left and right sides of the reflective film 30 that encases the convex streak portions 22, and the width of the entire convex structure (i.e., grid 41) in the width direction (X direction) is narrowed at the positions of the constricted portions 29, 29.

[0260] As described above, the grid 41 of the grid structure 20 according to this embodiment has the reflective film 30 that bulges out in a rounded shape in the X direction above the ridges 22, the constricted portions 29, 29 that are recessed inward in the X direction at the lower end of the reflective film 30, and the lower side of the ridges 22 that is not covered with the reflective film 30. Therefore, the grid 41 has a complex cross-sectional shape like a tree. The grid 41 having such a special tree shape can improve the polarization separation characteristics (Tp×Rs characteristics) for obliquely incident light, as described above.

[0261] A complexly shaped valley 42 is formed between adjacent grids 41 in the X direction. The valley 42 is a recess formed between adjacent grids 41. The upper part of the valley 42 is a space sandwiched between the reflective films 30 on both the left and right sides, and is open upward. The bottom of the valley 42 is a semi-closed space surrounded on three sides by the convex ridges 22 on both the left and right sides and the base portion 21 on the bottom side.

[0262] The width of the top of the valley 42 in the X direction is narrow, while the width of the bottom of the valley 42 in the X direction is wide. That is, at the top of the valley 42, the reflective films 30, 30 on both sides bulge out. Therefore, the grids 41, 41 on both sides of the top of the valley 42 are close to each other, resulting in a narrower width at the top of the valley 42. On the other hand, at the bottom of the valley 42, the lower sides of the side surfaces 22b, 22b of the convex ridge portions 22, 22 on both sides are not covered by the reflective film 30. Therefore, the grids 41, 41 on both sides of the bottom of the valley 42 are spaced apart by the amount corresponding to the absence of the reflective film 30, resulting in a wider width at the bottom of the valley 42. In this way, the cross-sectional shape (XZ cross section) of the valley 42 has a pot-like shape with a narrow entrance at the top and a wider semi-closed space at the bottom.

[0263] As described above, in the polarizing element 1 according to this embodiment, the plurality of grids 41 have a complex structure with a special tree-like shape. Therefore, the valleys 42 between adjacent grids 41, 41 also form semi-closed spaces with complex pot-like shapes. Therefore, the surface of the polarizing element 1 has a complex uneven structure made up of the plurality of grids 41 and the plurality of valleys 42. Therefore, it is difficult to cover the entire surface of this complex uneven structure with a protective film 40 of a uniform thickness, and therefore the protective film 40 presents problems as will be described in detail in the next section.

[0264] 18 , the protective film 40 continuously covers the entire surface of the complex uneven structure made up of the plurality of grids 41 and the plurality of valleys 42. That is, the protective film 40 continuously covers the surface of the grid 41 (i.e., the surface formed by combining the surface of the reflective film 30 and the lower sides of both side surfaces 22 b, 22 b of the protruding ridge portion 22 that are not covered by the reflective film 30) and the bottom surfaces of the valleys 42 (i.e., the upper surface of the base portion 21). When the protective film 40 continuously covers the entire surface of the grids 41 and valleys 42 of the grid structure 20 in this way, it is ideal to form the protective film 40 to a uniform thickness over the entire surface.

[0265] However, when the protective film 40 is formed on the surfaces of the grid 41 and the valleys 42, the film material easily adheres to the upwardly protruding tip of the grid 41, but has difficulty penetrating into the complex pot-shaped interior of the valleys 42. This tends to result in variations in the amount of film material adhered between the surface at the tip of the grid 41 and the surface on the bottom side of the valleys 42. Therefore, it is extremely difficult to form an extremely thin protective film 40, on the order of several nanometers to several tens of nanometers, with a uniform thickness over the entire surface of the complex uneven structure formed by the grid 41 and the valleys 42, using existing film formation methods.

[0266] For example, the aforementioned Patent Document 2 (JP 2014-085516 A) describes forming a coating layer on the surface of a wire-grid polarizer by sputtering. However, with sputtering, the film-forming material tends to travel in a straight line during film formation, resulting in poor adhesion of the film-forming material to the fine unevenness structure, resulting in reduced film thickness uniformity. In particular, with a complex fine unevenness structure, such as the present embodiment, consisting of the special tree-shaped grid 41 and the pot-shaped valleys 42, it is extremely difficult to form a protective film 40 with a uniform thickness using sputtering. That is, the adhesion of the film-forming material to the lower sidewall of the special tree-shaped grid 41 (the lower side of the side surface 22b of the ridge portion 22) and the bottom surface of the pot-shaped valleys 42 (the upper surface of the base portion 21) is significantly impaired. This makes it extremely difficult to form a protective film 40 with a uniform thickness.

[0267] As described above, it is ideal for the protective film 40 to have a uniform thickness, but it is extremely difficult to uniformly form an extremely thin protective film 40 over the entire surface of the complex fine concave-convex structure according to this embodiment. For this reason, in reality, the thickness of the protective film 40 formed by existing film formation methods is not uniform, and thickness unevenness inevitably occurs in the formed protective film 40.

[0268] In this regard, if the grid structure 20 and the reflective film 30 are stably covered with a thick protective film 40, the barrier properties of the grid structure 20 and the like are enhanced by the thick protective film 40. This prevents the resin constituting the grid structure 20 from deteriorating over time due to external heat, light, water, and the like, thereby ensuring the reliability (heat resistance and light resistance) of the grid structure 20. However, if the protective film 40 is too thick, the optical characteristics of the polarizing element 1, particularly the transmittance (Tp characteristics) and polarization separation characteristics (Tp×Rs characteristics) of the grid structure 20, are likely to be reduced. On the other hand, if the protective film 40 is too thin, the resin of the grid structure 20 is likely to be degraded due to heat, light, and the like, resulting in a reduction in the reliability (heat resistance and light resistance) of the grid structure 20. Thus, there is a trade-off between the optical characteristics and reliability of the polarizing element 1 depending on the thickness of the protective film 40.

[0269] Therefore, the inventors of the present application have made extensive efforts to clarify the allowable range of uneven thickness of the protective film 40 that can suppress deterioration of the resin of the grid structure 20 and improve reliability while maintaining the optical characteristics of the polarizing element 1 when the surface of the grid structure 20 having a complex fine uneven structure as shown in Fig. 18 is covered with a thin protective film 40 having a thickness of about several nanometers to several tens of nanometers. They have then come up with a polarizing element 1 in which the thickness of the protective film 40 is optimized within this allowable range.

[0270] 6.3. Optimized Thickness of Protective Film Next, with reference to FIG. 18, the optimized thickness (film thickness) of the protective film 40 in the wire-grid polarizer 1 according to this embodiment will be described.

[0271] 18 , the protective film 40 of the polarizing element 1 according to this embodiment continuously covers the surface of the reflective film 30, the lower sides of both side surfaces 22 b, 22 b of the convex ridge portion 22 (i.e., the surface of the grid 41), and the surface of the base portion 21 (i.e., the bottom surfaces of the valleys 42). The protective film 40 may be a thin film with a single layer structure made of a single coating material, or may be a thin film with a multi-layer laminate structure made of multiple types of coating materials.

[0272] The thickness (film thickness) of the protective film 40 is preferably 6 to 10 nm.

[0273] The thickness (film thickness) of the protective film 40 can be measured, for example, by the following measurement method. After forming the protective film 40 over the entire surface of the grid structure 20, whose protruding ridges 22 are covered with the reflective film 30, to prepare a sample of the polarizing element 1, the cross section of the sample is observed using a transmission electron microscope (TEM). Next, data on the cross section image of the sample obtained by the observation is imported into a length measurement application, and the thickness of the protective film 40 is measured. At this time, the thickness of the protective film 40 is measured on multiple (e.g., three or more) grids 41 per sample, and the average of these measured thickness values ​​is taken as the thickness (film thickness) of the protective film 40.

[0274] The method for measuring the thickness (film thickness) of the protective film 40 is not limited to the above measurement method, and for example, the thickness (film thickness) of the protective film 40 may be measured when observing the cross section of a sample using the above-mentioned transmission electron microscope. The above measurement method can also be applied to measuring the thicknesses Tt and Bt of the protective film 40 at each part of the grid 41, which will be described below.

[0275] It is preferable that the thickness ratio "Bt / Tt" of the protective film 40 according to this embodiment satisfies the following formula (10).

[0276] Bt / Tt≧0.85 (10) Tt: thickness of the protective film 40 covering the top 30a of the reflective film 30 that envelops the protruding ridge portion 22 Bt: thickness of the protective film 40 covering both side surfaces 22b of the protruding ridge portion 22, the lower sides of the 22b, and the surface of the base portion 21 Bt1: thickness of the protective film 40 covering both side surfaces 22b of the protruding ridge portion 22, the lower sides of the 22b Bt2: thickness of the protective film 40 covering the surface of the base portion 21

[0277] 18 , Tt is the thickness of the protective film 40 that covers the tops 30a of the reflective film 30 that cover the tips 22a of the protruding stripes 22 at the tip of the grid 41. In other words, Tt is the thickness of the protective film 40 that covers the metal material portion at the tip of the grid 41 (the tops 30a of the reflective film 30 made of a metal material such as Al).

[0278] On the other hand, Bt is the thickness of the protective film 40 that covers the resin portion on the lower side of the grid structure 20 (portions of the resin ridge portions 22 and base portion 21 that are not covered with the reflective film 30 and where the resin is exposed) of the grid structure 20. In other words, Bt is the thickness of the protective film 40 that covers the surface of the approximately cup-shaped portion where the resin of the grid structure 20 is exposed (the lower sides of the side surfaces 22 b, 22 b of the two opposing ridge portions 22, 22 and the surface of the base portion 21) at the bottom of the valley 42 between adjacent grids 41, 41.

[0279] Here, Bt is preferably the average value of Bt1 and Bt2 shown in FIG. 18 . Bt1 is the thickness of the protective film 40 covering the lower side of the side surface 22b of the ridge portion 22. Bt2 is the thickness of the protective film 40 covering the surface of the base portion 21 (the bottom surface of the valley 42). Both Bt1 and Bt2 are the thicknesses of the protective film 40 formed on the bottom of the valley 42. Therefore, regardless of the method for forming the protective film 40, Bt1 and Bt2 are considered to be approximately the same thickness (Bt ≒ Bt1 ≒ Bt2). However, in reality, Bt1 and Bt2 may differ slightly. In this case, it is preferable to calculate the average value of the measured Bt1 and Bt2 and use this as Bt (Bt = Average (Bt1, Bt2)). By using the average value, it is possible to more accurately determine the thickness Bt of the protective film 40 that covers the exposed resin portion of the grid structure 20 at the bottom of the valley 42. Note that the method of calculating Bt is not limited to this example, and for example, Bt = Bt1 or Bt = Bt2 may also be used.

[0280] In the above formula (10), "Bt / Tt" is the ratio of Bt to Tt. When the value of "Bt / Tt" is 1, Bt and Tt are the same value, which means that the thickness Tt of the protective film 40 covering the tips of the grid 41 and the thickness Bt of the protective film 40 covering the bottoms of the valleys 42 are completely uniform. On the other hand, the farther the value of "Bt / Tt" is from 1, the greater the difference between Bt and Tt, which means that thickness unevenness occurs between the thickness Tt of the protective film 40 covering the tips of the grid 41 and the thickness Bt of the protective film 40 covering the bottoms of the valleys 42.

[0281] By making "Bt / Tt" satisfy the above formula (10), the optical characteristics required of the polarizing element 1 (e.g., high Tp characteristics and high Tp×Rs characteristics) can be maintained while suppressing deterioration of the resin portion of the grid structure 20, thereby improving the reliability (heat resistance and light resistance) of the polarizing element 1.

[0282] If "Bt / Tt" is less than 0.85, the thickness Bt of the protective film 40 covering the bottom of the valleys 42 becomes thin, and the barrier properties are reduced, resulting in a decrease in the reliability (heat resistance, light resistance) of the grid structure 20. Therefore, in order to ensure the reliability (heat resistance, light resistance) of the grid structure 20 when used for a predetermined period of time or longer, it is preferable that "Bt / Tt" be 0.85 or more.

[0283] Furthermore, it is more preferable that the thickness ratio "Bt / Tt" of the protective film 40 according to this embodiment satisfies the following formula (11).

[0284] 0.85≦Bt / Tt≦1.07 (11)

[0285] If "Bt / Tt" exceeds 1.07, the thickness Bt of the protective film 40 covering the valleys 42 will be too thick, which may result in the valleys 42 being filled with the protective film 40 and deteriorating the optical characteristics. Therefore, in order to prevent the valleys 42 from being filled with the protective film 40 and maintain the required optical characteristics, it is preferable that "Bt / Tt" be 1.07 or less.

[0286] Furthermore, it is more preferable that the thickness ratio "Bt / Tt" of the protective film 40 according to this embodiment satisfies the following formula (12).

[0287] 1.00<Bt / Tt≦1.07 (12)

[0288] If "Bt / Tt" is greater than 1.00, it can be said that the organic material portion of the grid structure 20 that is not covered with the reflective film 30 is protected by the protective film 40, and therefore deterioration of the organic material portion can be suppressed, and the reliability (heat resistance and light resistance) of the grid structure 20 can be further improved.

[0289] As described above, the thickness of the protective film 40 of the polarizing element 1 according to this embodiment preferably satisfies Expression (10), more preferably Expression (11), and even more preferably Expression (12). As a result, when a grid structure 20 having a complex concavo-convex structure such as that shown in FIG. 18 is covered with a thin protective film 40, the grids 41 and valleys 42 of the grid structure 20 can be appropriately covered with the protective film 40 within the allowable range of thickness variation of the protective film 40 necessary to achieve both the optical properties and reliability of the polarizing element 1. As a result, when the polarizing element 1 is used as, for example, a polarizing beam splitter, the required optical properties (Tp characteristics, Tp×Rs characteristics) of the polarizing element 1 can be maintained while suppressing deterioration of the resin portion of the grid structure 20, thereby improving the reliability (heat resistance and light resistance) of the polarizing element 1.

[0290] Furthermore, since it is not necessary to deposit the protective film 40 with a completely uniform thickness, it is actually possible to deposit the protective film 40 with thickness variations within the above-mentioned allowable range, for example, by using the ALD method described below.

[0291] 6.4. Material and Layer Structure of Protective Film Next, the material and layer structure of the protective film 40 according to this embodiment will be described.

[0292] The material of the protective film 40 is not particularly limited as long as it can maintain the optical properties of the polarizing element 1 and improve reliability (e.g., light resistance and heat resistance). Examples of the material of the protective film 40 include dielectric materials, inorganic oxides such as metal oxides, silane-based water-repellent materials, and fluorine-based water-repellent materials. Examples of dielectric materials include silicon oxide and hafnium oxide. Examples of metal oxides include aluminum oxide. When the protective film 40 contains an inorganic oxide, it is possible to further improve the scratch resistance of the polarizing element 1 and the barrier properties that protect the grid structure 20 from heat, light, water, and the like. When the protective film 40 contains a water-repellent material such as a fluorine-based water-repellent material, it is possible to further improve the stain resistance and waterproof properties of the polarizing element 1.

[0293] In particular, the protective film 40 is made of SiO ２ It is preferable that the protective film 40 has a single layer structure made of SiO. ２By using this, it is possible to cover with a protective film 40 that has high transmittance over a wide wavelength range.

[0294] The protective film 40 is made of Al ２ O ３ a first layer consisting of SiO ２ It is preferable that the protective film 40 has a laminated structure including a second layer made of Al. ２ O ３ High barrier properties and SiO ２ It is possible to combine high transmittance.

[0295] The protective film 40 is not limited to the above example, and may be formed of SiO ２ , Al ２ O ３ The protective film 40 may be formed of an inorganic oxide or a metal oxide other than the above, or may have a laminated structure of three or more layers. For example, the protective film 40 may further include a water-repellent coating or an oil-repellent coating. This can further improve the stain-resistant and waterproof properties of the polarizing element 1.

[0296] 6.5. Method for Forming Protective Film Next, a method for forming the protective film 40 in the method for manufacturing the polarizing element 1 according to this embodiment will be described in detail.

[0297] As described above, the method for manufacturing the wire-grid polarizer 1 according to this embodiment includes the grid structure material formation step (S10), the nanoimprinting step (S12), the grid structure formation step (S14), and the reflective film formation step (S16) shown in FIG. 11 , and may further include the protective film 40 deposition step (S18).

[0298] The protective film 40 deposition step (S18) is a step of depositing the protective film 40 to cover the entire surface (the entire surfaces of the grid structure 20 and the reflective film 30) of the polarizing element 1. In this deposition step (S18), as shown in Fig. 18 , the protective film 40 is deposited so as to continuously cover the surface of the reflective film 30 and the lower sides of both side surfaces 22b, 22b of the convex streak portion 22 (i.e., the entire surface of the grid 41), and the surface of the base portion 21 (i.e., the bottom surfaces of the valleys 42).

[0299] In the film formation step (S18) of the protective film 40 according to this embodiment, atomic layer deposition (ALD) is used as the film formation method. The ALD method is a thin film formation technology that utilizes continuous chemical reactions in the gas phase. The ALD method involves repeatedly alternately introducing and exhausting two or more types of gaseous precursors (precursors) into a reaction chamber, causing precursor molecules adsorbed on the surface of the target object to react and form a film. Unlike the CVD method, the ALD method does not involve simultaneously introducing different types of precursors into the reaction chamber. Instead, precursors are introduced (pulsed) and purged (purged) in independent steps. During each pulse, the precursor molecules behave self-limitingly on the target surface, and the reaction ends when there are no more adsorption sites on the surface.

[0300] The ALD method has the advantage that it can precisely control the film thickness and material at the atomic layer level, and therefore can form an extremely thin and uniform film compared to the CVD method. Therefore, in the film formation step (S18) according to this embodiment, when forming the protective film 40 over the entire surface of the complex fine uneven structure of the grid structure 20, it is preferable to form the protective film 40 by the ALD method. This makes it possible to form the protective film 40 almost uniformly over the entire surface of the complex fine uneven structure.

[0301] Here, the step of forming the protective film 40 by the ALD method (S18) according to this embodiment will be described in detail with reference to Fig. 19. Fig. 19 is a schematic diagram showing the step of forming the protective film 40 by the ALD method (S18) according to this embodiment.

[0302] First, the configuration of the chamber 300 used in the film formation step (S18) of the protective film 40 by the ALD method according to this embodiment will be described. As shown in Fig. 19, the chamber 300 forms a processing space for performing the film formation process by the ALD method. A grid structure 20 is disposed inside the chamber 300. The chamber 300 includes a gas inlet 310, a jig 320, a gas exhaust port 330, and a vacuum pump 340.

[0303] The gas inlet 310 is an opening for introducing (pulsing) gases such as vapor-phase raw materials (e.g., precursors, oxidizers) into the chamber 300. The gas inlet 310 is provided, for example, in the upper part of the chamber 300. Gases are introduced from the gas inlet 310 by switching valves (not shown) for the precursor gas, oxidizer gas, and inert gas, respectively.

[0304] The jig 320 holds the grid structure 20 in a state where the protruding ridges 22 are covered with the reflective film 30 (before the protective film 40 is formed) in the chamber 300. As shown in Fig. 19, the grid structure may be held by one jig 320. In order to improve the efficiency of the film forming process, a plurality of grid structures 20 may be held by one jig 320.

[0305] The gas exhaust port 330 is an opening for exhausting gas inside the chamber 300 to the outside of the chamber 300. The gas exhaust port 330 is provided, for example, in the lower part of the chamber 300. An exhaust valve (not shown) is provided in the gas exhaust port 330. The exhaust valve opens or closes the gas exhaust port 330. In addition, a vacuum pump 340 is provided in the gas exhaust port 330. By operating the vacuum pump 340, the gas inside the chamber 300 can be exhausted (purged) to the outside through the gas exhaust port 330.

[0306] Next, the process (S18) of forming the protective film 40 by the ALD method according to this embodiment using the chamber 300 will be described.

[0307] In the film formation process (S18) according to this embodiment, first, as shown in FIG. 19 , the grid structure 20 in a state where the convex streak portion 22 is covered with the reflective film 30 (the state before the protective film 40 is formed) is placed in the chamber 300 (S180).

[0308] Next, the first to fourth steps (S181 to S184) are repeated, in which two types of vapor-phase raw material gases (hereinafter referred to as "precursor gas" and "oxidizer gas", respectively) for forming the protective film 40 are alternately introduced (pulsed) and exhausted (purged) into the chamber 300.

[0309] Specifically, first, a precursor gas (first precursor gas) is introduced into the chamber 300 through the gas inlet 310 (S181: first step). As a result, the introduced precursor gas is adsorbed onto the surface (the surface to be coated) of the grid structure 20 and undergoes a chemical reaction, thereby generating a first atomic layer on the surface to be coated.

[0310] Next, an inert gas is introduced into the chamber 300 through the gas inlet 310 (S182: second step). As a result, excess precursor gas (residual gas) in the chamber 300 is flushed with the inert gas, and the excess precursor gas is exhausted to the outside through the gas exhaust port 330. As a result, excess precursor components are removed from the chamber 300.

[0311] Furthermore, an oxidizer gas (second precursor gas) is introduced into the chamber 300 through the gas inlet 310 (S183: third step). This causes a chemical reaction between the precursor of the first atomic layer deposited on the surface to be coated of the grid structure 20 and the introduced oxidizer gas, bonding oxygen to the precursor, and thereby generating a second atomic layer on the first atomic layer.

[0312] Next, an inert gas is introduced into the chamber 300 through the gas inlet 310 (S184: fourth step). As a result, excess oxidant gas (residual gas) in the chamber 300 is flushed with the inert gas, and the excess oxidant gas is exhausted to the outside through the gas exhaust port 330. As a result, excess oxidant components are removed from the chamber 300.

[0313] Thereafter, the precursor gas and the oxidizer gas are alternately introduced into and exhausted from the chamber 300 (S181 to S184: first to fourth steps) as described above, whereby the first atomic layer and the second atomic layer are alternately stacked on the surface to be coated of the grid structure 20, thereby forming the protective film 40 of the desired material.

[0314] For example, SiO ２ When forming a protective film 40 having a single layer structure made of Al, alkylaminosilylamine and ozone are used as two types of gaseous raw materials (precursor, oxidizing agent). ２ O ３When forming a protective film 40 having a single layer structure made of Al, trimethylaluminum (TMA) and water are used as two kinds of vapor phase raw materials (precursors). ２ O ３ a first coating layer consisting of SiO ２ When forming the protective film 40 having a laminated structure including the second coating layer made of Al ２ O ３ After forming a first coating layer having a single layer structure consisting of ２ Then, a second coating layer having a single layer structure consisting of the above may be laminated.

[0315] Furthermore, the film formation process (S18) using the special ALD method according to this embodiment is characterized in that in the precursor gas introduction process (S181) and the oxidizer gas introduction process (S183), the precursor gas and the oxidizer gas are introduced into the chamber 300 and filled therewith, without being exhausted to the outside.

[0316] In this regard, in a conventional film formation process using the ALD method, in the precursor gas and oxidizer gas introduction process (S181, S183), the precursor gas and oxidizer gas are introduced into chamber 300 while being exhausted from chamber 300.

[0317] In contrast, in the film formation process (S18) using the special ALD method according to this embodiment, in the precursor gas and oxidant gas introduction processes (S181, S183: first and third processes), the precursor gas and oxidant gas are continuously introduced into the chamber 300 without being exhausted from the gas exhaust port 330. Specifically, in the precursor gas introduction process (S181: first process), the exhaust valve of the gas exhaust port 330 is closed to seal the chamber 300, and the precursor gas is introduced into the chamber 300 from the gas inlet 310, without being exhausted from the gas exhaust port 330. Similarly, in the oxidant gas introduction process (S183: third process), the exhaust valve of the gas exhaust port 330 is closed to seal the chamber 300, and the oxidant gas is introduced into the chamber 300 from the gas inlet 310, without being exhausted from the gas exhaust port 330.

[0318] As a result, in each introduction step (S181 and S183), the precursor gas and oxidizer gas introduced into the chamber 300 can be sufficiently filled and retained within the chamber 300, allowing them to fully contact the surface to be coated of the grid structure 20. Therefore, the precursor gas and oxidizer gas can be sufficiently introduced deep into the pot-shaped valleys 42 of the complex micro-relief structure surface formed by the grid 41 and the valleys 42 shown in FIG. 18 , allowing the first and second atomic layers to be appropriately formed with the required thicknesses. Therefore, the protective film 40 with the desired thickness can be formed not only on the surface of the tip of the grid 41 but also on the surface of the pot-shaped valleys 42.

[0319] Therefore, the thickness Tt of the protective film 40 covering the tip of the grid 41 (i.e., the metal portion of the top 30 a of the reflective film 30) and the thickness Bt of the protective film 40 covering the surface of the bottom of the valley 42 (i.e., the resin portion of the grid structure 20) can be made approximately equal, and a protective film 40 that satisfies the above formula (10) can be formed. As a result, the thickness uniformity of the protective film 40 formed by the ALD method according to this embodiment can be further improved compared to that of a conventional ALD method. Therefore, a protective film 40 with even better uniformity can be formed within the allowable range of thickness unevenness defined by the above formula (10).

[0320] The above has described in detail the step (S18) of forming the protective film 40 by the ALD method in the manufacturing method of the polarizing element 1 according to this embodiment. According to this embodiment, the ALD method is used as the method of forming the protective film 40, and the film formation conditions (conditions related to the introduction and discharge of the precursor gas and the oxidant gas) in the steps (S181, S183) of introducing the precursor gas and the oxidant gas by the ALD method can be optimized to suit the complex fine uneven structure of the grid structure 20.

[0321] This allows an extremely thin protective film 40, on the order of several nanometers to several tens of nanometers, to be formed very uniformly over the entire surface of the complex microrelief structure. Therefore, it becomes possible to form an extremely uniform thin protective film 40 within the allowable range of thickness unevenness of the protective film 40 defined by the above formula (10). This allows the grid structure 20 to be robustly protected by the protective film 40, thereby improving the reliability (heat resistance and light resistance) of the polarizing element 1 while maintaining the optical properties of the polarizing element 1 equipped with the protective film 40.

[0322] In this regard, when using conventional film formation methods such as sputtering, vacuum deposition, and CVD, it is difficult to properly form a protective film on the surface of a complex fine uneven structure as in this embodiment. For example, as described above, with sputtering, the film formation material has a high linearity, so the film formation material adheres poorly to parts of the complex fine uneven structure that are shaded relative to the direction of travel of the film formation material, making it difficult to form a uniform protective film 40. Furthermore, with vacuum deposition, the film formation material also adheres poorly, making it difficult to form a uniform protective film 40. Furthermore, with CVD, the film formation material adheres well, but the film formation temperature is high, at several hundred degrees Celsius or more, so the resin of the grid structure 20 softens and the fine uneven structure is destroyed.

[0323] In contrast, according to the present embodiment, the ALD method is used as the film formation method, which allows for good adhesion of the film formation material to the fine unevenness structure, thereby significantly improving the uniformity of the protective film 40 compared to conventional sputtering or vacuum deposition methods. Furthermore, the ALD method according to the present embodiment allows the protective film 40 to be formed at a low film formation temperature (e.g., 190°C or lower) that is lower than the heat-resistant temperature (e.g., 200°C) of the resin of the grid structure 20. This makes it difficult for the resin of the grid structure 20 to soften during the formation of the protective film 40, thereby allowing the fine unevenness of the grid structure 20 to be maintained. Furthermore, the reliability (heat resistance and light resistance) of the grid structure 20 coated with the protective film 40 can also be significantly improved compared to conventional film formation methods.

[0324] Conditions for film formation by the ALD method according to this embodiment include the capacity of the chamber 300, the type of gas used, the flow rate of the gas, the film formation temperature, whether or not exhaust is performed, and the state of the grid structure 20 disposed in the chamber 300. These conditions can be set to optimal values ​​as appropriate to satisfy desired film formation conditions.

[0325] 25 and 26 , the reinforcing film 51 provided between the grid structure 20 and the reflective film 30 (functional film) of the wire-grid polarizer 1 according to this embodiment will be described. Fig. 25 is an enlarged cross-sectional view showing the wire-grid polarizer 1 including the reinforcing film 51 that covers the entire grid structure 20 according to this embodiment. Fig. 26 is an enlarged cross-sectional view showing the wire-grid polarizer 1 including the reinforcing film 51 that covers part of the protruding stripes 22 of the grid structure 20 according to a modified example of this embodiment.

[0326] 7.1. Overview of the Reinforcing Film As described above, the higher the height H of the ridge portions 22 of the grid structure 20 according to this embodiment (see FIGS. 1 and 3, etc.), the better, and for example, it is preferably 160 nm or more. Increasing the height H of the ridge portions 22 can improve various optical characteristics required of the wire-grid polarization element 1 (for example, Tp characteristics, Tp×Rs characteristics, and contrast (CR)).

[0327] However, the ridges 22 of the grid structure 20 according to this embodiment are formed of an organic material (e.g., resin), which has lower strength and heat resistance than inorganic materials (e.g., glass). Furthermore, the ridges 22 have a tapered shape that narrows toward their tips. Therefore, ridges 22 formed of an organic material have lower rigidity and heat resistance than ridges formed of an inorganic material. Therefore, if the height H of the ridges 22 is increased as described above, when a high-temperature reflective film 30 (a functional film made of a metal such as Al) is formed to cover the tips of the ridges 22 by a deposition method such as vapor deposition or sputtering, the organic ridges 22 will soften due to the heat and force applied during the formation of the reflective film 30. Therefore, the ridges 22 may not maintain their tapered shape extending straight upward (in the Z direction) and may tilt left and right (in the X direction) (see FIG. 31 ). In this way, if the convex streak portion 22 tilts due to the formation of the reflective film 30 (functional film) covering the convex streak portion 22, there is a problem in that the various optical characteristics required of the wire grid polarization element 1 (e.g., Tp characteristics, Tp×Rs characteristics, CR) are reduced.

[0328] 25 and 26 , in order to solve this problem, in the wire-grid polarizer 1 according to this embodiment, a reinforcing film 51 is provided between the upper parts of the protruding streaks 22 of the grid structure 20 and the reflective film 30 (functional film), and the reinforcing film 51 reinforces the upper parts of the protruding streaks 22. The reinforcing film 51 is made of an inorganic oxide such as a dielectric material, and is more rigid and heat-resistant than the resin of the protruding streaks 22. The reinforcing film 51 is formed so as to cover at least the upper parts of the protruding streaks 22, and is interposed between the upper parts of the resin protruding streaks 22 and the reflective film 30 made of a metal such as Al.

[0329] By reinforcing the upper portions of the ridge portions 22 with the reinforcing film 51, tilting of the ridge portions 22 in the left-right direction (X direction) due to heat or force acting on the ridge portions 22 when forming the reflective film 30 on the upper portions of the ridge portions 22 can be suppressed. Therefore, the ridge portions 22 can maintain the desired shape extending straight upward (Z direction), so that the reflective film 30 supported by the ridge portions 22 also does not tilt, and the reflective film 30 does not block incident light contrary to the design intent. Therefore, the transmission characteristics and reflection characteristics of incident light on the wire-grid polarization element 1 can be achieved as intended, and the optical characteristics (e.g., Tp characteristics, Tp×Rs characteristics, CR) of the wire-grid polarization element 1 can be improved.

[0330] Here, with reference to Figures 27 to 29, the principle behind why the convex stripes 22 of the grid structure 20 become tilted or thin due to the formation of the reflective film 30 when the reinforcing film 51 is not provided will be described.

[0331] As a result of extensive research, the inventors of the present application have found that when a reflective film 30 is formed on the top of the protruding streaks 22 of the grid structure 20 by vapor deposition or the like, the protruding streaks 22 tilt in the left-right direction (X direction) (see FIG. 31 ). One reason for this is thought to be that the heat generated during vapor deposition of the reflective film 30 softens the protruding streaks 22. Another reason is thought to be that the high-temperature metal material (e.g., Al) of the reflective film 30 is vapor-deposited alternately left and right onto the protruding streaks 22 from diagonally above (see FIG. 5 ). This causes stress (distortion) to accumulate due to thermal contraction of the vapor-deposited metal film (reflective film 30), which acts as a force that tilts the protruding streaks 22 toward the vapor-deposited side.

[0332] 27 and 28 show the results of a simulation of the deformation behavior of the protruding streak portion 22 tilting during vapor deposition of the reflective film 30, using a model of the protruding streak portion 22 and reflective film 30 of the grid structure 20. Fig. 27 is a schematic diagram showing a model in which the reflective film 30 is vapor-deposited alternately from the left and right onto the top of the protruding streak portion 22. Fig. 28 is a schematic diagram showing the results of a simulation of the deformation behavior of the protruding streak portion 22 using the above model. Note that the shading in Fig. 28 indicates the degree of displacement of the protruding streak portion 22 and the reflective film 30 during vapor deposition.

[0333] 27, high-temperature Al is deposited alternately from the left and right sides onto the upper part of the protruding rib portion 22, thereby forming the reflective film 30 (Al film) so that it covers the upper part of the protruding rib portion 22 from both the left and right sides. In the model shown in Fig. 27, for example, Al at 600°C is deposited alternately from the left and right twice on each side onto the upper part of the protruding rib portion 22 in the order of S1 to S4 (a total of four deposition steps).

[0334] A simulation of the deformation behavior of the ridge portion 22 using this model revealed that, as shown in Fig. 28, stress accumulates due to thermal contraction of the evaporated Al film (reflective film 30), causing the ridge portion 22 to deform and tilt toward the evaporated side. Specifically, in the first evaporation (S1), high-temperature Al was evaporated on the right side of the ridge portion 22, causing the ridge portion 22 to tilt toward the evaporated side. Next, in the second evaporation (S2), high-temperature Al was evaporated on the left side of the ridge portion 22, causing the ridge portion 22 to return to a straight state. Furthermore, in the third evaporation (S3), high-temperature Al was evaporated again on the right side of the ridge portion 22, causing the ridge portion 22 to tilt toward the right again. Then, in the fourth evaporation (S4), high-temperature Al was evaporated again on the left side of the ridge portion 22, causing the ridge portion 22 to return to a straight state. In the simulation results of Figure 28, after the fourth vapor deposition (S4), the convex rib portion 22 returned to a straight state, but in the actual sample in which an Al film was vapor-deposited on the convex rib portion 22, the inclination of the convex rib portion 22 did not return to its original state.

[0335] When Al is vapor-deposited diagonally from above onto the ridges 22, alternating left and right, the vapor-deposited Al film (reflective film 30) alternates between a high temperature immediately after vapor deposition and a reduced temperature during standby. During this process, the difference in thermal expansion coefficient between the resin of the ridges 22 and the Al of the reflective film 30 inhibits the Al film (reflective film 30) from shrinking, leaving residual stress inside and around the Al film. This residual stress is thought to be one of the causes of the tilt of the ridges 22. Specifically, the vapor deposition of high-temperature Al softens the resin of the ridges 22, and the residual stress applied to the softened ridges 22 causes the ridges 22 to tilt and curve in either the left or right direction (the vapor deposition direction).

[0336] For this reason, there has been a demand for a technology that can solve the problem of the protruding streak portion 22 of the grid structure 20 tilting due to the formation of such an Al film (reflective film 30) and improve the optical characteristics of the polarizing element 1.

[0337] Next, the reason why the convex streak portions 22 become thinner due to vapor deposition of the reflective film 30 will be described with reference to Fig. 29. Fig. 29 is a schematic diagram showing the results of a simulation of the deformation behavior of the convex streak portions 22 becoming thinner during vapor deposition of the reflective film 30, using a model of the convex streak portions 22 of the grid structure 20 and the reflective film 30.

[0338] As described above, when depositing the Al film (reflective film 30), Al is deposited alternately on the left and right sides of the ridge portions 22 from diagonally above. The deposited Al film (reflective film 30) alternates between a high temperature immediately after deposition and a reduced temperature state during standby. During this process, the difference in thermal expansion coefficient between the resin of the ridge portions 22 and the Al of the reflective film 30 inhibits the Al film (reflective film 30) from shrinking, leaving residual stress inside and around the Al film. Assume that a polarizing element 1 having the reflective film 30 and the ridge portions 22 with this residual stress remaining is placed in a high-temperature environment. In this case, the softening of the resin of the ridge portions 22 due to the high-temperature environment and the release of the residual stress in the Al film cause the reflective films 30 on both the left and right sides of the ridge portions 22 to deform inward, resulting in the ridge portions 22 being sandwiched between the reflective films 30 on both the left and right sides and becoming thinner.

[0339] Figure 29 shows the results of a simulation conducted to clarify the behavior of the ridge portion 22 becoming thinner. The shading of the reflective film 30 (Al film) in the upper diagram of Figure 29 indicates the temperature distribution of the reflective film 30. The shading in the lower diagram of Figure 29 indicates the amount of deformation of the reflective film 30 (Al film) and the ridge portion 22 in the left-right direction.

[0340] As shown in the upper diagram of Fig. 29, a model of the ridge portion 22 and the reflective film 30 was prepared. In this model, the inner portion 30 of the evaporated Al film (reflective film 30) ｉｎ is a portion formed by the first vapor deposition, and the portion 30 ｉｎ On the other hand, the temperature of the outer portion 30 of the evaporated Al film (reflective film 30) is assumed to have dropped to room temperature. ｏｕｔThe low temperature portion 30 is a portion formed by the third or subsequent deposition. ｉｎ Outside of the part 30 ｏｕｔ After that, the outer portion 30 ｏｕｔ When the temperature of the outer portion 30 drops to room temperature, ｏｕｔ contracts, and the inner part 30 ｉｎ However, a contracting force acts on this inner part 30 ｉｎ The resin (low thermal expansion coefficient) of the ridge portion 22 located further inside the inner portion 30 ｉｎ Since the contraction of the Al film (which has a high thermal expansion coefficient) is prevented, the inner portion 30 ｉｎ Residual stress in the shrinkage direction remains.

[0341] If the polarizing element 1 having the Al film (reflective film 30) and the ridge portion 22 with residual stress remaining therein as described above is placed in a high temperature environment, the resin ridge portion 22 will soften and the inner portion 30 ｉｎ The residual stress in the Al film is released, causing the Al film to shrink and close inward in the left-right direction. As a result, as shown in the lower diagram of Figure 29, the Al film (reflective film 30) on both the left and right sides of the protruding ridge portion 22 deforms and closes inward in the left-right direction, causing the softened protruding ridge portion 22 to become thinner by about 4 nm.

[0342] As described above, if the phenomenon of the ridge portions 22 becoming thinner due to residual stress occurs when the polarizing element 1 is placed in a high-temperature environment, there is a risk that the polarizing element 1 will not be able to exhibit the desired optical properties. For example, if the polarizing element 1 is mounted in a head-up display device of a vehicle, when the head-up display device becomes hot due to direct sunlight in the summer, the ridge portions 22 of the polarizing element 1 will become thinner and deform, which may deteriorate the optical properties of the polarizing element 1.

[0343] For this reason, it has been desired to solve the problem of the protruding streak portion 22 of the grid structure 20 becoming thinner due to residual stress during the deposition of such an Al film (reflective film 30) and to improve the optical characteristics of the polarizing element 1.

[0344] Therefore, in order to solve the above-described problem of the ridges 22 being tilted or thinned, the polarizing element 1 according to this embodiment newly provides a reinforcing film 51 that covers the upper portions of the ridges 22, thereby reinforcing the ridges 22. That is, as shown in FIGS. 25 and 26 , the polarizing element 1 according to this embodiment includes a reinforcing film 51 interposed between the upper portions of the ridges 22 of the grid structure 20 and the reflective film 30 (functional film). This reinforcing film 51 envelops and covers the upper portions of the ridges 22 to reinforce them. The reinforcing film 51 is made of an inorganic oxide, such as a dielectric material, and is more rigid and heat-resistant than the resin ridges 22. The softening point of the resin of the ridges 22 is, for example, 120°C, and the softening point of the inorganic oxide of the reinforcing film 51 is higher than the softening point of the resin. Therefore, even if the resin of the ridges 22 softens due to, for example, the deposition of the high-temperature reflective film 30, the inorganic oxide of the reinforcing film 51 does not soften.

[0345] Therefore, according to this embodiment, when the reflective film 30 (such as an Al film) is formed around the upper periphery of the ridge portion 22 by vapor deposition or the like, the ridge portion 22 made of resin, which is easily softened by heat, is reinforced by the reinforcing film 51 having excellent heat resistance, and the ridge portion 22 does not come into direct contact with the vapor-deposited high-temperature reflective film 30. Therefore, even if the ridge portion 22 softens during the formation of the high-temperature reflective film 30, the ridge portion 22 is reinforced by the reinforcing film 51 having excellent rigidity and heat resistance, and therefore, tilting of the ridge portion 22 in the left-right direction (X direction) can be suppressed.

[0346] Furthermore, suppose that the polarizing element 1 is used in a high-temperature environment while residual stress remains in the reflective film 30 due to the inhibition of thermal contraction of the reflective film 30 during film formation, causing the ridge portions 22 of the grid structure 20 to soften. Even in this case, according to this embodiment, a reinforcing film 51 with excellent rigidity and heat resistance is interposed between the softened ridge portions 22 and the reflective film 30. Therefore, even if the reflective film 30 on both sides of the ridge portions 22 deforms inward in the left-right direction due to residual stress in the reflective film 30 as shown in FIG. 29 , the highly rigid reinforcing film 51 can suppress such deformation. This solves the problem of the ridge portions 22 becoming thinner due to residual stress during film formation of the reflective film 30.

[0347] 7.2. Configuration of Reinforcing Film Next, the configuration of the reinforcing film 51 according to this embodiment will be described in more detail with reference to FIGS. 25 and 26. FIG.

[0348] 25 and 26 , the wire-grid polarizer 1 according to this embodiment includes a protective film 40 that entirely covers the grid structure 20 and the reflective film 30 (functional film), as well as a reinforcing film 51 that covers the ridges 22 inside the protective film 40 and the reflective film 30. The reinforcing film 51 is a film for reinforcing the ridges 22 made of an organic material. For this reason, the reinforcing film 51 is made of an inorganic oxide that is more rigid than the organic material of the ridges 22. The reinforcing film 51 is interposed at least between the ridges 22 covered by the reflective film 30 and the reflective film 30. The reinforcing film 51 covers and envelops at least the tips 22 a and the upper sides of both side surfaces 22 b, 22 b of the ridges 22 of the grid structure 20 (hereinafter, sometimes referred to as “upper parts of the ridges 22”). The reflective film 30 (functional film) covers the upper part of the convex rib portion 22 via the reinforcing film 51, but does not cover both side surfaces 22 b of the convex rib portion 22, the lower sides of the 22 b, or the upper surface of the base portion 21. On the other hand, the protective film 40 covers the entire surfaces of the grid structure 20, the reinforcing film 51, and the reflective film 30.

[0349] The reinforcing film 51 shown in Figure 25 covers the entire grid structure 20 (i.e., the tips 22a and both side surfaces 22b, 22b of the ridge portions 22, and the upper surface of the base portion 21). Therefore, the reinforcing film 51 shown in Figure 25 is interposed between the upper portions of the ridge portions 22 and the reflective film 30, and is also interposed between the lower portions of the ridge portions 22 and between the base portion 21 and the protective film 40. Therefore, the reflective film 30 indirectly covers the upper portions of the ridge portions 22 via the reinforcing film 51, and is not in direct contact with the upper portions of the ridge portions 22. Furthermore, the protective film 40 indirectly covers the lower portions of the ridge portions 22 and the upper surface of the base portion 21 via the reinforcing film 51, and is not in direct contact with the lower portions of the ridge portions 22 and the upper surface of the base portion 21.

[0350] On the other hand, the reinforcing film 51 shown in FIG. 26 covers only the upper portions of the ridge portions 22 of the grid structure 20 (the tips 22 a and the upper sides 22 b and 22 b of the ridge portions 22), and does not cover the lower sides 22 b and 22 b of the ridge portions 22 or the upper surface of the base portion 21. The coverage area of ​​the upper portions of the ridge portions 22 by the reinforcing film 51 shown in FIG. 26 is wider than the coverage area of ​​the upper portions of the ridge portions 22 by the reflective film 30. Therefore, the reinforcing film 51 shown in FIG. 26 is interposed between the upper portions of the ridge portions 22 and the reflective film 30. Therefore, the reflective film 30 indirectly covers the upper portions of the ridge portions 22 via the reinforcing film 51 and does not directly contact the upper portions of the ridge portions 22. Furthermore, the reinforcing film 51 shown in FIG. 26 is not interposed between the lower ends of the lower sides 22 b and 22 b of the ridge portions 22 and the base portion 21 and the protective film 40. Therefore, the protective film 40 is in direct contact with and covers both side surfaces 22 b of the ridge portion 22 , the lower end of 22 b and the base portion 21 .

[0351] 25 and 26 , the reinforcing film 51 may be present in at least the portion of the grid structure 20 between the upper portions of the protruding streaks 22 that are covered with the reflective film 30 (functional film) and the reflective film 30. In other words, the reinforcing film 51 may cover at least the upper portions of the protruding streaks 22 that are covered with the reflective film 30, and may cover other portions of the grid structure 20 (the lower portions of the protruding streaks 22 and the base portion 21) (see FIG. 25 ), or may not cover them (see FIG. 26 ).

[0352] By interposing the reinforcing film 51 between the upper part of the ridge portion 22 and the reflective film 30, the upper part of the ridge portion 22 and the reflective film 30 are prevented from coming into direct contact with each other. The upper part of the ridge portion 22 made of an organic material such as resin is covered and coated with the reinforcing film 51 made of an inorganic oxide, so that the reinforcing film 51, which has high rigidity and heat resistance, reinforces the upper part of the ridge portion 22.

[0353] Therefore, when the reflective film 30 is formed outside the reinforcing film 51 covering the upper portion of the ridge portion 22, the upper portion of the ridge portion 22, which is covered and reinforced by the reinforcing film 51, can be prevented from tilting in the left-right direction (X direction) due to heat and stress acting during the film formation. Therefore, when the reflective film 30 is formed, the ridge portion 22 can maintain a tapered shape extending straight upward (Z direction). This prevents the grid 41 of the polarizing element 1 (the entire convex structure including the ridge portion 22, the reinforcing film 51, and the reflective film 30) from tilting, thereby preventing a decrease in the Tp characteristics and contrast of the polarizing element 1. As a result, the optical characteristics (e.g., Tp characteristics, Tp×Rs characteristics, CR) of the polarizing element 1 can be improved compared to when the reinforcing film 51 is not provided.

[0354] 25 covers the entire resin grid structure 20. This allows the reinforcing film 51 to protect the resin portions of the grid structure 20, namely, the lower portions of the ridge portions 22 and the upper surface of the base portion 21. This also improves the scratch resistance, stain resistance, and waterproof properties of the grid structure 20.

[0355] In particular, since the grid structure 20 is made of an organic material such as resin, it is more susceptible to deterioration due to heat, light, water, and the like than the substrate 10 made of an inorganic material such as glass. By tightly covering the resin grid structure 20 with a reinforcing film 51 and a protective film 40 made of inorganic oxide, the grid structure 20 can be protected from external heat, air, water, and the like (barrier properties). This prevents the resin of the grid structure 20 from being altered or deteriorated due to heat, air, water, and the like. Furthermore, as shown in FIG. 25 , by covering the entire surface of the polarizing element 1 with both the reinforcing film 51 and the protective film 40 made of inorganic oxide, the thermal resistance R of the entire polarizing element 1 can be further reduced, thereby further improving the heat dissipation of the polarizing element 1.

[0356] 7.3. Material and Layer Structure of Reinforcing Film Next, the material and layer structure of the reinforcing film 51 according to this embodiment will be described.

[0357] The reinforcing film 51 is a film for reinforcing the ridge portions 22 made of an organic material. Therefore, the reinforcing film 51 is made of an inorganic oxide having higher rigidity than the organic material of the ridge portions 22. The reinforcing film 51 is made of, for example, SiO ２ , Al ２ O ３ It is preferable that the reinforcing film 51 is made of a dielectric material such as SiO 2 . This allows the reinforcing film 51 made of a dielectric material to suitably reinforce the ridge portion 22. When the reinforcing film 51 is made of a dielectric material, the reinforcing film 51 is preferably made of a thin film made of a dielectric material (for example, SiO 2 ). ２ thin film, Al ２ O ３ However, the reinforcing film 51 may be made of a thin film made of an inorganic oxide such as a metal oxide other than a dielectric material.

[0358] Furthermore, the material of the reinforcing film 51 may be the same as or different from the material of the protective film 40. If the material of the reinforcing film 51 is the same as the material of the protective film 40, both the reinforcing film 51 and the protective film 40 can be formed relatively easily using the same material and film formation method.

[0359] The material of the reinforcing film 51 is not particularly limited as long as it is an inorganic oxide that can reinforce the ridge portion 22 and maintain the optical properties of the polarizing element 1, but preferably contains a dielectric material or a metal oxide. Examples of the dielectric material include silicon oxide and hafnium oxide. Examples of the metal oxide include aluminum oxide. When the reinforcing film 51 contains an inorganic oxide, the scratch resistance of the polarizing element 1 and the barrier properties that protect the grid structure 20 from heat, light, water, and the like can be further improved. Furthermore, the reinforcing film 51 may contain, in addition to the inorganic oxide, a silane-based water-repellent material, a fluorine-based water-repellent material, or the like. When the reinforcing film 51 contains a water-repellent material, the stain resistance and waterproof properties of the polarizing element 1 can be further improved.

[0360] Furthermore, the reinforcing film 51 may be a thin film with a single layer structure made of one type of inorganic oxide (e.g., one type of dielectric material), or may be a thin film with a layered structure made of multiple types of inorganic oxides (e.g., multiple types of dielectric materials).

[0361] For example, the reinforcing film 51 is made of SiO ２The reinforcing film 51 may have a single layer structure made of SiO. ２ By using Al, the convex stripes 22 of the grid structure 20 can be covered with the reinforcing film 51 having high transmittance in a wide wavelength range. ２ O ３ The reinforcing film 51 may have a single layer structure made of Al. ２ O ３ By using this, the convex stripes 22 of the grid structure 20 can be covered with the reinforcing film 51 that has high barrier properties to protect the grid structure 20 from external heat, air, water, etc.

[0362] The reinforcing film 51 is made of Al ２ O ３ a first layer consisting of SiO ２ The reinforcing film 51 may have a laminated structure including a second layer made of Al. ２ O ３ High barrier properties and SiO ２ It is possible to combine high transmittance.

[0363] The reinforcing film 51 is not limited to the above example, and may be formed of SiO ２ , Al ２ O ３ The reinforcing film 51 may be formed of an inorganic oxide or a metal oxide other than the above, or may contain other materials. For example, the reinforcing film 51 may further include a water-repellent coating or an oil-repellent coating. This can further improve the stain resistance and waterproof properties of the polarizing element 1. The reinforcing film 51 may also have a laminated structure of three or more layers made of the same or different types of inorganic oxides.

[0364] 7.4. Thickness of Reinforcing Film Next, with reference to FIGS. 25 and 26, the thickness Rt (film thickness) of the reinforcing film 51 in the wire-grid polarizer 1 according to this embodiment will be described. FIG.

[0365] If the thickness Rt of the reinforcing film 51 is too large, the reflective film 30 covering the reinforcing film 51 becomes too thick, which is undesirable because it may deteriorate the optical characteristics (particularly the Tp characteristics) of the polarizing element 1. On the other hand, if the thickness Rt of the reinforcing film 51 is too small, it is undesirable because it may deteriorate the reinforcing performance of the reinforcing film 51 for the ridge portions 22.

[0366] For this reason, the thickness Rt of the reinforcing film 51 is not particularly limited as long as it is a thickness that can ensure the optical characteristics of the polarizing element 1 and the reinforcing performance of the ridge portions 22, but is preferably, for example, 0.5 nm or more and 8 nm or less. This makes it possible to ensure the suitable optical characteristics (particularly the Tp characteristics) of the polarizing element 1 while also ensuring the suitable reinforcing performance of the ridge portions 22.

[0367] Furthermore, from the viewpoint of more suitably achieving both the optical properties of the polarizing element 1 and the reinforcing performance of the ridge portions 22, the thickness Rt of the reinforcing film 51 is more preferably 1 nm or more and 5 nm or less.

[0368] 25 continuously covers the upper part of the convex rib portion 22 (i.e., the tip 22a of the convex rib portion 22 and the upper sides of both side surfaces 22b, 22b), the lower part of the convex rib portion 22 (i.e., the lower sides of both side surfaces 22b, 22b of the convex rib portion 22), and the surface of the base portion 21 (i.e., the bottom surface of the valley 42). The protective film 40 continuously covers the surface of the reinforcing film 51 (excluding the surface of the portion covered by the reflective film 30) and the surface of the reflective film 30. The reinforcing film 51 and the protective film 40 exhibit barrier properties that protect the resin grid structure 20.

[0369] Here, the thickness Rt of the reinforcing film 51 is preferably smaller than the thickness Bt of the protective film 40 (Rt<Bt). The thickness Rt of the reinforcing film 51 need only be thick enough to suppress the inclination of the ridge portions 22, and does not need to be excessively thick. On the other hand, in order to ensure that the protective film 40 has barrier properties that reliably protect the entire grid 41 and valleys 42 of the polarizing element 1, the thickness Bt of the protective film 40 is preferably at least a predetermined thickness that can exhibit barrier properties. Therefore, the thickness Bt of the protective film 40 is preferably at least twice the thickness Rt of the reinforcing film 51 (2×Rt≦Bt), and more preferably at least five times the thickness Rt (5×Rt≦Bt).

[0370] Furthermore, if the total thickness (Rt + Bt) of the reinforcing film 51 thickness Rt and the protective film 40 thickness Bt shown in FIG. 25 is too thick, the valleys 42 between the grids 41, 41 with a complex micro-relief structure may be filled with the resin of the reinforcing film 51 or the protective film 40, which may degrade the optical characteristics of the polarizing element 1, which is undesirable. Therefore, the total thickness (Rt + Bt) of the reinforcing film 51 and the protective film 40 is preferably 20 nm or less (Rt + Bt < 20 nm), more preferably 15 nm or less (Rt + Bt < 15 nm). This ensures that the total thickness (Rt + Bt) of the reinforcing film 51 and the protective film 40 is thick enough to ensure barrier properties, while also ensuring the optical characteristics, particularly the Tp characteristics, of the polarizing element 1. From a similar perspective, the thickness Bt of the protective film 40 is preferably 5 nm or more and 12 nm or less, more preferably 5 nm or more and 10 nm or less.

[0371] The thickness Rt (film thickness) of the reinforcing film 51 can be measured using, for example, the following measurement method. After forming the reinforcing film 51 on the ridge portion 22 and then forming the reflective film 30 on the outer surface of the reinforcing film 51 to create a sample of the polarizing element 1, the cross-section of the sample is observed using a transmission electron microscope (TEM). Next, the cross-sectional image data of the sample obtained by the observation is imported into a length measurement application to measure the thickness of the reinforcing film 51. At this time, the thickness of the reinforcing film 51 is measured on multiple (e.g., three or more) grids 41 per sample, and the average of these thickness measurements is defined as the thickness Rt of the reinforcing film 51. The measurement method for the thickness Rt of the reinforcing film 51 is not limited to this measurement method. For example, the thickness Rt of the reinforcing film 51 may be measured when observing the cross-section of the sample using the above-mentioned transmission electron microscope. Furthermore, it is preferable to measure the thickness Rt of the reinforcing film 51 at the portion of the reinforcing film 51 between the reflective film 30 and the ridge portion 22, but other portions of the reinforcing film 51 may also be measured.

[0372] As described above, it is preferable to adjust the thickness Rt of the reinforcing film 51 and the thickness Bt of the protective film 40 to appropriate thicknesses. This allows the grid structure 20, having a complex micro-relief structure as shown in FIG. 25, to be suitably coated with the thin reinforcing film 51 and protective film 40, thereby ensuring the optical properties of the polarizing element 1, the barrier properties of the grid structure 20, and the reinforcement performance of the ridge portions 22. This allows the polarizing element 1, for example, to be used as a polarizing beam splitter, to maintain the required optical properties (Tp characteristics, Tp×Rs characteristics, CR) of the polarizing element 1 while suppressing deterioration of the resin portion of the grid structure 20, improving the reliability (heat resistance, light resistance) of the polarizing element 1, and allowing the reinforcing film 51 to suitably reinforce the ridge portions 22. Furthermore, since the reinforcing film 51 and the protective film 40 do not need to be formed to completely uniform thicknesses, it is practically possible to form the reinforcing film 51 and the protective film 40 with thickness variations within an acceptable range, for example, using the special ALD method described above.

[0373] 7.5. Relationship between the grid structure 20 with a complex concavo-convex structure and the reinforcing film 51 As shown in Figures 25 and 26, the polarizing element 1 according to this embodiment is a hybrid wire-grid polarizing element that combines a substrate 10 made of an inorganic material such as glass with a grid structure 20 made of an organic material such as resin. The grid 41 of the polarizing element 1 (the entire convex structure including the convex stripes 22, the reinforcing film 51, and the reflective film 30) has the unique tree-like shape described above. Therefore, complexly shaped valleys 42 are formed between adjacent grids 41. As a result, the surface of the grid structure 20 of the polarizing element 1 has a complex concavo-convex structure with multiple convex portions (grids 41) and multiple concave portions (valleys 42) intertwined.

[0374] The convex streak portions 22 of the grid structure 20 have a tapered shape in which the width in the X direction narrows as the distance from the base portion 21 increases in the upward direction (Z direction). The reflective film 30 (functional film) is a metal film (Al film) made of a metal material such as Al, and covers the upper portions of the convex streak portions 22 (the tips 22a and the upper sides of both side surfaces 22b and 22b of the convex streak portions 22) but does not cover the lower sides of both side surfaces 22b and 22b of the convex streak portions 22 or the surface of the base portion 21. The coverage rate (Rc) of both side surfaces 22b and 22b of the convex streak portions 22 by the reflective film 30 is 30% or more and 70% or less.

[0375] Furthermore, a reinforcing film 51 is interposed between the reflective film 30 and the upper part of the ridge portion 22. The reinforcing film 51 covers at least the upper part of the ridge portion 22 that is covered with the reflective film 30. The reinforcing film 51 shown in Figure 25 covers not only the upper part of the ridge portion 22 that is covered with the reflective film 30, but also the lower part of the ridge portion 22 and the upper surface of the base portion 21.

[0376] The reflective film 30 indirectly covers the upper part of the ridge portion 22 via the reinforcing film 51. The surface of the reflective film 30 is rounded and bulges out in the width direction of the ridge portion 22 (the X direction in FIG. 25). The maximum width (W ＭＡＸ ) is the width (W Ｂ 25 and 26 , the cross-sectional shape of the entire convex structure (i.e., grid 41) composed of the convex streak portions 22, the reinforcing film 51, and the reflective film 30 has the special tree-like shape described above. In this special tree-like shape, constricted portions 29, 29 are provided immediately below the lower end portions on both the left and right sides of the reflective film 30 that encases the convex streak portions 22, and the width of the entire convex structure (i.e., grid 41) in the width direction (X direction) is narrowed at the positions of the constricted portions 29, 29.

[0377] As described above, the grid 41 of the grid structure 20 according to this embodiment has the reflective film 30 that bulges out in a rounded shape in the X direction above the ridges 22, the constricted portions 29, 29 that are recessed inward in the X direction at the lower end of the reflective film 30, and the lower side of the ridges 22 that is not covered with the reflective film 30. Therefore, the grid 41 has a complex cross-sectional shape like a tree. The grid 41 having such a special tree shape can improve the polarization separation characteristics (Tp×Rs characteristics) for obliquely incident light, as described above.

[0378] A complexly shaped valley 42 is formed between adjacent grids 41 in the X direction. The valley 42 is a recess formed between adjacent grids 41. The upper part of the valley 42 is a space sandwiched between the reflective films 30 on both the left and right sides and is open upward. The bottom part of the valley 42 is a semi-closed space surrounded on three sides by the convex rib portions 22 on both the left and right sides and the base portion 21 on the bottom side. The width of the upper part of the valley 42 in the X direction is narrow, and the width of the bottom part of the valley 42 in the X direction is wide. Thus, the cross-sectional shape (XZ cross section) of the valley 42 has a pot-like shape with a narrow entrance on the upper side and a wide semi-closed space on the bottom side.

[0379] As described above, in the polarizing element 1 according to this embodiment, the grids 41 have a complex structure with a special tree-like shape. Therefore, the valleys 42 between adjacent ridges 22, 22, as well as the valleys 42 between the grids 41, 41, form semi-closed spaces with complex pot-like shapes. Therefore, the surface of the polarizing element 1 has a complex uneven structure consisting of the grids 41 and the valleys 42. Therefore, after forming the reflective film 30, it is difficult to cover the entire surface of this complex uneven structure with a protective film 40 of a uniform thickness. For this reason, it is preferable to form the protective film 40 using the special ALD method described above.

[0380] On the other hand, the reinforcing film 51 is formed before the reflective film 30 is formed so as to cover at least the upper portions of the ridge portions 22 of the grid structure 20. When the reinforcing film 51 is formed, the semi-closed space between the ridge portions 22, 22 adjacent in the X direction is not narrowed by the reflective films 30, 30 on both sides, and the entrance on the upper side is wider. Therefore, the formation of the reinforcing film 51 is easier than the formation of the protective film 40 after the formation of the reflective film 30, or the formation of the reinforcing film 51 before the reflective film 30. However, the reinforcing film 51 is even thinner than the protective film 40. Therefore, as shown in FIG. 25 , in order to form the thin reinforcing film 51 with a uniform thickness over the entire grid structure 20, it is preferable to form the reinforcing film 51 using the special ALD method described above, similar to the formation of the protective film 40. This allows the reinforcing film 51 to be formed with a thin and uniform thickness.

[0381] 7.6. Reinforcing Film Forming Method Next, a method for forming the reinforcing film 51 in the method for manufacturing the polarizing element 1 according to this embodiment will be described in detail.

[0382] As described above, the method for manufacturing the wire grid polarizer 1 according to this embodiment includes the grid structure material formation step (S10), the nanoimprinting step (S12), the grid structure formation step (S14), and the reflective film formation step (S16) shown in FIG. 11 , and may further include the reinforcing film 51 deposition step (S15) and the protective film 40 deposition step (S18).

[0383] The reinforcing film 51 forming step (S15) is a step performed between the grid structure forming step (S14) and the reflective film forming step (S16) shown in Fig. 11. The reinforcing film 51 forming step (S15) is a step of forming, using an inorganic oxide, the reinforcing film 51 that covers at least the upper surface of the ridge portion 22 of the surface of the grid structure 20 formed in S14.

[0384] Here, there are two types of deposition ranges for the reinforcing film 51, as shown in, for example, FIGS. 25 and 26 . In the example of FIG. 25 , the reinforcing film 51 is deposited on the entire surface of the grid structure 20. That is, the reinforcing film 51 is deposited so as to continuously cover the entire tip 22 a and both side surfaces 22 b, 22 b of the ridge portion 22, as well as the surface of the base portion 21. In the case of the deposition range of the reinforcing film 51 in the example of FIG. 25 , it is preferable to deposit the reinforcing film 51 as widely as possible with a uniform thickness over the entire surface of the grid structure 20 by, for example, the ALD method. By using the ALD method as the deposition method for the overall reinforcing film 51, unevenness in the thickness Rt of the reinforcing film 51 deposited over the entire surface of the grid structure 20 can be reduced, and the reinforcing film 51 can be deposited with a very uniform thickness Rt.

[0385] On the other hand, in the example of FIG. 26 , the reinforcing film 51 is formed only on the upper portions of the convex streak portions 22 of the grid structure 20. That is, the reinforcing film 51 is formed so as to partially cover only the upper portions of the convex streak portions 22 (the tips 22 a and both side surfaces 22 b, upper sides of 22 b of the convex streak portions 22). In the case of the formation range of the reinforcing film 51 in the example of FIG. 26 , it is preferable to form the protective film 40 partially on the upper portions of the convex streak portions 22 of the grid structure 20 by, for example, a vapor deposition method. By using the vapor deposition method as a method for forming the partial reinforcing film 51, the reinforcing film 51 can be easily formed using a relatively simple film formation device. Note that instead of the vapor deposition method, the reinforcing film 51 may be partially formed on the upper portions of the convex streak portions 22 by a sputtering method.

[0386] After the above-described film formation step (S15) of the reinforcing film 51, a reflective film formation step (S16) is performed. In the reflective film formation step (S16), the reflective film 30 (functional film) is formed so as to cover the upper part of the convex rib portion 22 (the tip 22 a and both side surfaces 22 b, upper sides of 22 b of the convex rib portion 31) via the reinforcing film 51. The reflective film 30 can be formed by, for example, sputtering or vapor deposition.

[0387] Thereafter, a step (S18) of forming the protective film 40 is performed. The step (S18) of forming the protective film 40 is a step of forming the protective film 40 that covers the entire surface of the polarizing element 1 (the entire surfaces of the grid structure 20 and the reflective film 30).

[0388] 25 , the reinforcing film 51 covers the entire surface of the grid structure 20, and the reflective film 30 covers a portion of the reinforcing film 510 (the upper peripheral portion of the convex rib portion 22). In this case, in the step (S18) of depositing the protective film 40, the protective film 40 is deposited so as to continuously cover the reinforcing film 51 that covers the surface of the reflective film 30 and the lower sides of both side surfaces 22 b, 22 b of the convex rib portion 22 (i.e., the entire surface of the grid 41), and the surface of the reinforcing film 51 that covers the base portion 21 (i.e., the bottom surfaces of the valleys 42).

[0389] 26 , the reinforcing film 51 covers only the upper portions of the convex rib portions 22, and does not cover the lower portions of the convex rib portions 22 or the upper surface of the base portion 21. In this case, in the step (S18) of depositing the protective film 40, the protective film 40 is deposited so as to continuously cover the surface of the reflective film 30, the exposed portions of the reinforcing film 51 below it, the lower sides of both side surfaces 22 b, 22 b of the convex rib portions 22 (i.e., the entire surface of the grid 41), and the surface of the base portion 21 (i.e., the bottom surfaces of the valleys 42).

[0390] The protective film 40 is preferably formed by ALD, particularly the special ALD method described above (see FIG. 19 ), which makes it possible to form the protective film 40 almost uniformly over the entire surface of the grid structure 20 having the complex fine concave-convex structure.

[0391] Next, a more detailed description will be given of a special ALD method used to form the entire reinforcing film 51 shown in FIG. 25 in the above-described reinforcing film 51 forming step (S15).

[0392] The ALD method has the advantage of being able to precisely control the film thickness and material at the atomic layer level, and therefore is able to form extremely thin and uniform films compared to the CVD method. Therefore, in the reinforcing film 51 formation step (S15) according to this embodiment, when the reinforcing film 51 is to be formed over the entire surface of the complex fine uneven structure of the grid structure 20, it is preferable to form the reinforcing film 51 by the ALD method. This makes it possible to form the reinforcing film 51 almost uniformly over the entire surfaces of the ridge portions 22 and base portion 21 of the grid structure 20.

[0393] Furthermore, in this embodiment, the above-described special ALD method (see FIG. 19 ) is used when forming the overall reinforcing film 51 shown in FIG. 25 , as in the case of forming the protective film 40. In this special ALD method, for example, the chamber 300 shown in FIG. 19 may be used. The configuration of the chamber 300 is as described above, and therefore a detailed description thereof will be omitted. A method for forming the overall reinforcing film 51 shown in FIG. 25 using the special ALD method according to this embodiment will be described below.

[0394] In the overall reinforcing film 51 forming step (S15) shown in FIG. 25, first, as shown in FIG. 19, the grid structure 20 in a state before the reflective film 30 is formed is placed in the chamber 300 (S150).

[0395] Next, first to fourth steps (S151 to S154) are repeated to alternately introduce (pulse) and exhaust (purge) two types of vapor-phase source gases (hereinafter referred to as "precursor gas" and "oxidizer gas") for forming the reinforcing film 51 into the chamber 300. Here, the precursor gas introduction step (S151: first step), inert gas introduction step (S152: second step), oxidizer gas introduction step (S153: third step), and inert gas introduction step (S154: fourth step) are the same as the respective steps (S181 to S184) of the above-described process (S18) for forming the protective film 40, and therefore detailed description thereof will be omitted.

[0396] Furthermore, according to the film formation process (S15) of the reinforcing film 51 using the special ALD method of this embodiment, in the precursor gas introduction process (S151) and the oxidizer gas introduction process (S153), the precursor gas and the oxidizer gas are introduced into the chamber 300 and filled therewith, without being exhausted to the outside.

[0397] In this regard, in a conventional film formation process using the ALD method, in the precursor gas and oxidizer gas introduction process (S151, S153), the precursor gas and oxidizer gas are introduced into the chamber 300 while being exhausted from the chamber 300.

[0398] In contrast, in the film formation step (S15) of the reinforcing film 51 using the special ALD method according to this embodiment, in the precursor gas and oxidant gas introduction steps (S151, S153: first and third steps), the precursor gas and oxidant gas are continuously introduced into the chamber 300 without being exhausted from the gas exhaust port 330 within the chamber 300. Specifically, in the precursor gas introduction step (S151: first step), the exhaust valve of the gas exhaust port 330 is closed to seal the chamber 300, and the precursor gas is introduced into the chamber 300 from the gas inlet 310, without being exhausted from the gas exhaust port 330 within the chamber 300. Similarly, in the oxidant gas introduction process (S153: third process), the exhaust valve of the gas exhaust port 330 is closed to seal the chamber 300, and the oxidant gas is introduced into the chamber 300 from the gas inlet 310, without exhausting the oxidant gas from the chamber 300 through the gas exhaust port 330.

[0399] As a result, in each introduction step (S151 and S153), the precursor gas and oxidizer gas introduced into the chamber 300 can be sufficiently filled and retained within the chamber 300, allowing them to be in sufficient contact with the surface to be coated of the grid structure 20. Therefore, the precursor gas and oxidizer gas can be sufficiently introduced deep into the valleys 42 between adjacent ridge portions 22, 22 on the surface of the complex fine uneven structure of the grid structure 20 shown in FIG. 25, and the first and second atomic layers can be appropriately formed to the required layer thicknesses. Therefore, the reinforcing film 51 can be suitably formed to the desired thickness Rt not only on the upper surface of the ridge portion 22, but also on the lower surface of the ridge portion 22 and the surface of the base portion 21.

[0400] Therefore, the thickness of the reinforcing film 51 covering the tip 22 a of the ridge portion 22 and the thickness of the reinforcing film 51 covering the surface of the base portion 21 can be made approximately the same. As a result, the uniformity of the thickness of the reinforcing film 51 formed by the special ALD method according to this embodiment can be further improved compared to that of the conventional general ALD method. Therefore, the reinforcing film 51 can be formed with even better uniformity within a predetermined tolerance range for thickness unevenness.

[0401] 25 has been described in detail above. According to this embodiment, the ALD method is used as the method for forming the overall reinforcing film 51 shown in Fig. 25. In addition, the ALD method is used as the method for forming the reinforcing film 51, and the film formation conditions (conditions related to the introduction and discharge of the precursor gas and the oxidant gas) in the ALD precursor gas and oxidant gas introduction steps (S151, S153) can be optimized to suit the fine uneven structure of the grid structure 20.

[0402] This allows an extremely thin reinforcing film 51, on the order of several nanometers to several tens of nanometers, to be formed very uniformly over the entire surface of the fine unevenness of the grid structure 20. This makes it possible to form an extremely uniform, thin reinforcing film 51 within a predetermined tolerance for thickness variation. This reinforcing film 51 reinforces the upper portions of the ridges 22, thereby preventing the ridges 22 from tilting or becoming thinner due to the formation of the reflective film 30. Furthermore, as shown in FIG. 25 , the reinforcing film 51, which covers the entire grid structure 20, together with the protective film 40 on its outer side, can more robustly protect the grid structure 20. Therefore, the optical properties of the polarizing element 1 equipped with this reinforcing film 51 can be maintained while improving the reliability (heat resistance and light resistance) of the polarizing element 1.

[0403] Furthermore, according to this embodiment, the use of the ALD method as a film formation method allows for good adhesion of the film formation material to the fine unevenness structure, thereby significantly improving the uniformity of the reinforcing film 51 compared to conventional sputtering or vacuum deposition methods. Furthermore, the ALD method according to this embodiment allows the reinforcing film 51 to be formed at a low film formation temperature (e.g., 190°C or lower) that is lower than the heat-resistant temperature (e.g., 200°C) of the resin of the grid structure 20. This makes it difficult for the resin of the grid structure 20 to soften during the formation of the reinforcing film 51 (S15), allowing the shape of the ridge portions 22 of the grid structure 20 to be maintained. Furthermore, the reliability (heat resistance and light resistance) of the grid structure 20 coated with the reinforcing film 51 can also be significantly improved compared to conventional film formation methods.

[0404] Conditions for forming the reinforcing film 51 by the ALD method according to this embodiment include the capacity of the chamber 300, the type of gas used, the flow rate of the gas, the film formation temperature, whether or not exhaust is performed, and the state of the grid structure 20 disposed in the chamber 300. These conditions can be set to optimal values ​​as appropriate to satisfy the desired film formation conditions.

[0405] Note that the above has described in detail an example in which a special ALD method is used as a method for forming the overall reinforcing film 51 shown in Fig. 25. On the other hand, as a method for forming the partial reinforcing film 51 shown in Fig. 26, for example, a general vapor deposition method or sputtering method may be used to deposit the material of the reinforcing film 51 onto the upper and central parts of the convex ridge portion 22, and the reinforcing film 51 may be formed so as to cover the upper and central parts of the convex ridge portion 22.

[0406] Next, examples of the present invention will be described. However, the examples described below are specific examples provided to illustrate the configuration and effects of the polarizing element 1 according to the above-described embodiment, and the present invention is not limited to the following examples.

[0407] <1. Verification Results of Protective Film Thickness> As an example of the present invention, a sample of the wire-grid polarizer 1 satisfying the formula (10) regarding the thickness of the protective film 40 according to the present embodiment described above was fabricated, and tests were conducted to evaluate the optical characteristics, heat resistance, and light resistance of the sample. Furthermore, for comparison with the example of the present invention (satisfying the formula (10)), a sample of the wire-grid polarizer 1 according to a comparative example (not satisfying the formula (10)) was also fabricated and similarly tested and evaluated. Note that, for ease of explanation, the reference symbols representing the components of the polarizer 1 (such as the substrate 10, the grid structure 20, the base 21, the ridges 22, the reflective film 30, and the protective film 40) and the symbols representing the various dimensions of these components are denoted by the same reference symbols and symbols in both the example and the comparative example.

[0408] The symbols used in the following description to represent various dimensions of the polarizing element 1 are as follows: P: pitch of the ridges 22 W: Ｔ　　 W: width of the top of the ridge portion 22 (ridge portion top width) Ｍ　　W: width of the central position of the ridge portion 22 in the height direction (central width of the ridge portion) Ｂ　　 W: Width of the bottom of the ridge portion 22 (grid bottom width) ＭＡＸ : maximum width of the reflective film 30 that covers the convex rib portion 22 (maximum grid width) H: height of the convex rib portion 22 Hx: height of the portion of the side surface 22b of the convex rib portion 22 that is covered by the reflective film 30 Dt: thickness of the reflective film 30 that covers the tip 22a of the convex rib portion 22 (tip thickness of the reflective film 30) Ds: thickness of the reflective film 30 that covers the side surface 22b of the convex rib portion 22 (side surface thickness of the reflective film 30) Rc: coverage rate of the side surface 22b of the convex rib portion 22 by the reflective film 30 Rr: opening rate of the side surface 22b of the convex rib portion 22 by the reflective film 30 Tt: thickness of the protective film 40 that covers the top portion 30a of the reflective film 30 that covers the convex rib portion 22 (i.e., thickness of the protective film 40 at the tip of the grid 41) Bt: thickness of the protective film 40 covering both side surfaces 22b of the protruding rib portion 22, the lower sides of the 22b, and the surface of the base portion 21 (i.e., the thickness of the protective film 40 at the bottom of the valley 42); Bt1: thickness of the protective film 40 covering both side surfaces 22b of the protruding rib portion 22, the lower sides of the 22b; Bt2: thickness of the protective film 40 covering the surface of the base portion 21; θ: angle of incidence of incident light; λ: wavelength of incident light;

[0409] <1.1. Test conditions> (1) Method for preparing samples of polarizing element 1 In Examples 51 to 53 and Comparative Examples 51 to 54 of the present invention, samples of polarizing element 1 were prepared in which the entire surface of the polarizing element 1 was covered with a protective film 40 as described below.

[0410] Fifty-First Embodiment First, a fifty-first embodiment of the present invention will be described with reference to FIG.

[0411] A sample of polarizing element 1 according to Example 51 was fabricated using the manufacturing method of polarizing element 1 according to the present embodiment described above. As shown in Fig. 18 , polarizing element 1 according to Example 51 includes a glass substrate 10 and a grid structure 20 made of ultraviolet-curable resin (acrylic resin). Grid structure 20 has a base portion 21 provided along the surface of substrate 10 and a plurality of ridge portions 22 formed in a grid pattern and protruding from base portion 21. The cross-sectional shape of ridge portion 22 is a vertically elongated trapezoid, tapering toward tip 22a of ridge portion 22.

[0412] The reflective film 30 covering the ridge portion 22 in Example 51 is an Al film. The reflective film 30 is formed to cover the tip 22a of the ridge portion 22 and the upper sides of both side surfaces 22b, 22b. However, the reflective film 30 does not cover the lower sides of both side surfaces 22b, 22b of the ridge portion 22 or the base portion 21. The coverage rate Rc of both side surfaces 22b, 22b of the ridge portion 22 by the reflective film 30 is 38%. In this way, the reflective film 30 of Example 51 roundly covers the top of the ridge portion 22 (the tip 22a and the upper sides of both side surfaces 22b, 22b). The surface of the reflective film 30 is approximately elliptical with a rounded shape that bulges outward, and bulges in the width direction of the ridge portion 22.

[0413] As a result, as shown in Fig. 18, the grid 41 (a structure combining the ridges 22 and the reflective film 30) according to Example 51 has the above-mentioned special tree shape. ＭＡＸ (the width of the grid at the most bulging portion of the reflective film 30) is the width W of the bottom of the ridge portion 22 Ｂ (the width of the protruding portion 22 at a height position 20% above the bottom of the protruding portion 22) or more. In addition, the cross-sectional shape (XZ cross section) of the valley 42 between adjacent grids 41, 41 has a pot-like shape with a narrow entrance on the upper side and a wide semi-closed space on the bottom side.

[0414] Furthermore, in Example 51, a protective film 40 was formed by the film formation step (S18: see FIG. 19) using the ALD method according to the present embodiment described above, covering the entire surfaces of the grid structure 20 and the reflective film 30. The material of the protective film 40 was SiO ２ The target thickness of the protective film 40 to be formed was set to 10 nm.

[0415] In the deposition of Example 51, a deposition method was employed in which, in the precursor gas and oxidant gas introduction steps (S181 and S183: first and third steps) described above, the precursor gas and oxidant gas were not exhausted from the gas exhaust port 330 within the chamber 300, but instead the precursor gas and oxidant gas were introduced into the chamber 300 to fill it. As a result, as will be described later, the thickness Tt of the protective film 40 covering the tip of the grid 41 (i.e., the metal portion of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 covering the surface of the bottom of the valley 42 (i.e., the resin portion of the grid structure 20) could be made to be approximately the same, and a protective film 40 satisfying the above formula (10) could be deposited (see Table 1).

[0416] The thicknesses Bt and Tt of the protective film 40 were measured for the sample of the polarizing element 1 according to Example 51 prepared as described above. At this time, Bt1, Bt2, and Tt were measured for each of the grids 41 of the sample of the polarizing element 1 according to Example 51, and the average values ​​thereof were calculated.

[0417] More specifically, after preparing a sample of the polarizing element 1 according to Example 51, the cross section of the sample was observed using a transmission electron microscope. Next, the data of the cross-sectional image of the sample obtained by the observation was imported into a length measurement application, and the thicknesses Bt1, Bt2, and Tt of the protective film 40 on the outermost layer of the grid 41 were measured. At this time, the thicknesses Bt1, Bt2, and Tt of the protective film 40 on three or more grids 41 per sample were measured. Then, the average value Bt1 (ave.) of the multiple measured values ​​of Bt1 and the average value Bt2 (ave.) of the multiple measured values ​​of Bt2 were calculated, and this was defined as Bt. The average value Tt (ave.) of the multiple measured values ​​of Tt was also calculated, and this was defined as Tt.

[0418] Next, a fifty-second embodiment of the present invention will be described. In the fifty-second embodiment, the material of the protective film 40 is SiO ２The protective film 40 had a single-layer structure of 6 nm, and the target thickness of the protective film 40 to be formed was 6 nm. Except for these points, a sample of the polarizing element 1 according to Example 52 was produced in the same manner as in Example 51. The method for measuring Bt and Tt in Example 52 was also the same as in Example 51. In Example 52, as in Example 51, it was possible to make Tt and Bt approximately the same thickness, and to form a protective film 40 that satisfied the above formula (10).

[0419] Example 53 Next, Example 53 of the present invention will be described. In Example 53, the material of the protective film 40 is Al ２ O ３ A first coating layer (target thickness: 1 nm) consisting of SiO ２ A laminated structure was formed with a second coating layer (target thickness: 5 nm) consisting of: A sample of the polarizing element 1 according to Example 53 was fabricated in the same manner as in Example 51 except for these points. Furthermore, the measurement method for Bt and Tt in Example 53 was also the same as in Example 51. In Example 53, as in Example 51, it was possible to make Tt and Bt approximately the same thickness, and to form a protective film 40 that satisfied the above formula (10).

[0420] Comparative Examples 51 and 52 Next, comparative examples 51 and 52 will be described. In both comparative examples 51 and 52, the material of the protective film 40 was SiO ２ The protective film 40 had a single-layer structure, and the target thickness of the protective film 40 to be formed was 10 nm. In Comparative Examples 51 and 52, the protective film 40 was formed by a conventional ALD method, which differs from the special ALD methods used in Examples 51 to 53. That is, in Comparative Examples 51 and 52, when the protective film 40 was formed by the ALD method, a conventional ALD method was used in the precursor gas and oxidizer gas introduction steps (S181, S183: first and third steps). More specifically, in Comparative Examples 51 and 52, a conventional ALD method was used in which the precursor gas and oxidizer gas were introduced into the chamber 300 while the precursor gas and oxidizer gas were exhausted from the gas exhaust port 330. As a result, as described below, in Comparative Examples 51 and 52, Bt was significantly smaller than Tt, resulting in thickness unevenness between Tt and Bt, and the ratio of Tt to Bt (Bt / Tt) did not satisfy the above formula (10).

[0421] Comparative Examples 53 and 54 Next, comparative examples 53 and 54 will be described. In both comparative examples 52 and 54, the material of the protective film 40 was SiO ２ The target thicknesses of the formed protective film 40 were 10 nm and 20 nm, respectively. In Comparative Examples 53 and 54, the protective film 40 was formed by a conventional vapor deposition method. As a result, as will be described later, in Comparative Examples 53 and 54, Bt was significantly smaller than Tt, resulting in thickness unevenness between Tt and Bt, and the ratio of Tt to Bt (Bt / Tt) did not satisfy the above formula (10).

[0422] (2) Dimensional Conditions of Each Part of Polarizing Element 1 The dimensions and shapes of each part of the samples of polarizing elements 1 according to Examples 51 to 53 and Comparative Examples 51 to 54 are as follows: P: 151 nm W Ｔ　　 : 20 nm W Ｂ　　 : 43 nm W ＭＡＸ : 72 nm H: 265 nm Hx: 101 nm Dt: 37 nm Ds: 27 nm (maximum value) Rc: 38% Rr: 62% Tt: See Table 1 below Bt: See Table 1 below θ: 45° λ: 400 to 700 nm

[0423] Table 1 also shows the measurement results of the thicknesses Tt and Bt of the protective film 40 of the samples of the polarizing elements 1 according to Examples 51 to 53 and Comparative Examples 51 to 54, which were prepared as described above. Table 1 also shows the results of (1) an optical property test, (2) a 150°C heat resistance test, and (3) a light resistance test, which were performed on Examples 51 to 53 and Comparative Examples 51 to 54.

[0424]

[0425] (3) Thickness ratio (Bt / Tt) of protective film 40 As shown in Table 1, in Comparative Examples 51 and 52, the Bt / Tt values ​​are 0.59 and 0.71, respectively, which are significantly smaller than the lower limit of 0.85 in the above formula (10). This means that in Comparative Examples 51 and 52, Bt is significantly smaller than Tt, and the thickness unevenness between Bt and Tt is large. As a result, Comparative Examples 51 and 52 do not satisfy the condition of formula (10). Bt / Tt≧0.85 (10)

[0426] The reason for this is thought to be that in Comparative Examples 51 and 52, the protective film 40 was formed by the conventional ALD method, but the conditions for forming the protective film 40 by the ALD method were not appropriate.

[0427] That is, in Comparative Examples 51 and 52, the introduction steps (S181 and S183: first and third steps) were performed using a deposition method similar to the conventional ALD method described above, in which precursor gases and oxidizer gases were introduced into chamber 300 while being exhausted from gas exhaust port 330. For this reason, in Comparative Examples 51 and 52, the precursor gases and oxidizer gases could not be filled or retained in chamber 300. Therefore, a sufficient amount of precursor gas and oxidizer gas could not be supplied to the bottom of the pot-shaped valleys 42 on the surface of the complex micro-relief structure formed by grid 41 and valleys 42 shown in FIG. 18 . Therefore, the thickness Bt of the protective film 40 formed on the bottom of valleys 42 (the resin portion of grid structure 20) was significantly smaller than the thickness Tt of the protective film 40 formed on the tip of grid 41 (the metal portion of top 30a of reflective film 30). As a result, it is believed that the ratio of Tt to Bt (Bt / Tt) in Comparative Examples 51 and 52 did not satisfy the condition of the above formula (10).

[0428] Furthermore, as shown in Table 1, in Comparative Examples 53 and 54, the Bt / Tt values ​​were 0.31 and 0.29, respectively, which are significantly smaller than the lower limit of 0.85 in the above formula (10). This means that in Comparative Examples 53 and 54, Bt was significantly smaller than Tt, and the thickness variation between Bt and Tt was significantly large. As a result, Comparative Examples 53 and 54 did not satisfy the condition of formula (10).

[0429] The reason for this is believed to be that in Comparative Examples 53 and 54, the protective film 40 was formed by a conventional vapor deposition method. That is, in Comparative Examples 53 and 54, an extremely thin protective film 40 of approximately 10 nm or 20 nm was formed by vapor deposition on the surface of the complex micro-relief structure consisting of the grid 41 and the valleys 42 shown in FIG. 18 . Therefore, the protective film 40 was formed at the tip of the grid 41 (the metal portion of the top 30 a of the reflective film 30) to a thickness close to the target thickness, but the protective film 40 was formed at the pot-shaped valleys 42 to a thickness less than half that of the tip of the grid 41. Furthermore, almost no protective film 40 was formed on the sidewalls of the grid 41. This made it difficult to form a uniform film over the entire grid structure 20.

[0430] Specifically, in Comparative Example 53 (target thickness of protective film 40: 10 nm), a 10 nm protective film 40 is formed on the tip of the grid 41, but only a 3.3 nm protective film 40 is formed in the valleys 42 of the grid 41, resulting in a significantly low Bt / Tt of 0.31. Also, in Comparative Example 54 (target thickness of protective film 40: 20 nm), a 16.8 nm protective film 40 is formed on the tip of the grid 41, but only a 4.9 nm protective film 40 is formed in the valleys 42 of the grid 41, resulting in a significantly low Bt / Tt of 0.29, even when the target thickness is large as in Comparative Example 54. As a result, in Comparative Examples 53 and 54, as will be described later, the change ΔTp in the Tp characteristics during the heat resistance test was ２ It was confirmed that the heat resistance was low.

[0431] In contrast, in Examples 51 to 53, the Bt / Tt values ​​were 0.85 to 1.07. This means that in Examples 51 to 53, Bt was approximately the same as Tt, and the thickness variation between Bt and Tt was very small. As a result, in all of Examples 51 to 53, a protective film 40 that satisfied the condition of formula (10) above could be formed.

[0432] The reason for this is thought to be that in Examples 51 to 53, the protective film 40 was formed by the special ALD method according to the present embodiment described above, and the film formation conditions for the protective film 40 by this special ALD method were appropriate.

[0433] That is, in Examples 51 to 53, the precursor gas introduction step (S181) and the oxidizer gas introduction step (S183) each used a special ALD method in which the precursor gas and the oxidizer gas were introduced into the chamber 300 and filled therewith without being exhausted to the outside. As a result, in each introduction step (S181 and S183), the precursor gas and the oxidizer gas introduced into the chamber 300 were sufficiently filled and retained within the chamber 300, allowing them to fully contact the surface of the grid structure 20 to be coated. Therefore, among the complex micro-relief structure surface formed by the grid 41 and the valleys 42 shown in FIG. 18 , the precursor gas and the oxidizer gas were sufficiently introduced deep into the pot-shaped valleys 42, allowing the first and second atomic layers to be appropriately deposited with the required thicknesses. Therefore, the protective film 40 with the target thickness was formed substantially uniformly not only on the surface of the tip of the grid 41 but also on the surface of the pot-shaped valleys 42. Therefore, it was possible to make the thickness Tt of the protective film 40 formed on the tip of the grid 41 (the metal portion of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 formed on the bottom of the valley 42 (the resin portion of the grid structure 20) almost the same. As a result, it is considered that the ratio of Tt to Bt (Bt / Tt) in Examples 51 to 53 satisfied the condition of the above formula (10).

[0434] From the above results, it has been demonstrated that by depositing the protective film 40 using the special ALD method according to the present embodiment described above, it is possible to deposit the protective film 40 with a substantially uniform thickness over the entire surface of the grid structure 20 having a complex fine uneven structure, and that it is possible to deposit the protective film 40 that satisfies the above formula (10).

[0435] (4) Optical Property Test Next, with reference to Table 1, the conditions and evaluation results of the optical property test will be described.

[0436] As shown in Table 1, in the optical property test, the change in the optical properties (Tp characteristics) of the polarizing element 1 samples relating to Examples 51 to 53 and Comparative Examples 51 to 54 was measured before and after the formation of the protective film 40, and the effect of the protective film 40 on the optical properties of the polarizing element 1 was evaluated.

[0437] In the optical property test, the transmission axis transmittance (Tp) was measured for each of the samples of polarizing element 1 according to Examples 51 to 53 and Comparative Examples 51 to 54 before and after forming the protective film 40. In measuring Tp, incident light was irradiated onto the surface of each sample at an incident angle θ = 45°, and Tp was measured at each wavelength λ while varying the wavelength λ of the incident light within a range of 400 to 700 nm, and the average of the measured Tp values ​​from 430 to 680 nm was calculated.

[0438] The change in Tp before and after the formation of the protective film 40 shown in Table 1, ΔTp １ The amount of change ΔTp was calculated. １ is the average value Tp of the measured values ​​of Tp before the protective film 40 is formed. １Ｂ and the average value Tp of the measured values ​​of Tp after the protective film 40 is formed. １Ａ is the difference between (ΔTp １ = Tp １Ａ -Tp １Ｂ ). The amount of change ΔTp １ The larger the absolute value of ΔTp, the greater the change in the optical characteristics (Tp characteristics) of the polarizing element 1 before and after the formation of the protective film 40. １ The smaller the absolute value of ΔTp, the less the optical characteristics (Tp characteristics) of the polarizing element 1 are degraded by the effect of forming the protective film 40, and the more the desired optical characteristics (Tp characteristics) required for the polarizing element 1 can be maintained. １ It is preferable that the absolute value of is small.

[0439] According to the results of the optical property test, as shown in Table 1, in Comparative Examples 51 and 52, ΔTp １ The absolute value of ΔTp is 0.3 to 0.9%, which is smaller than the reference value of 1.0%, which indicates that the optical characteristics of the polarizing element 1 are not deteriorated. １ The absolute value of is 0.3 to 0.7%, which is smaller than the reference value of 1.0%, which indicates that the optical characteristics of the polarizing element 1 are not deteriorated.

[0440] In contrast, in Examples 51 to 53, ΔTp １The absolute value of is 0.4 to 0.7%, which is significantly smaller than the reference value of 1.0% and is even smaller than the cases of Comparative Examples 51 and 52. Therefore, it can be seen that in Examples 51 to 53, even when the protective film 40 is provided, the desired optical characteristics (Tp characteristics) can be sufficiently maintained, just as in the case where the protective film 40 is not provided.

[0441] The results of the above optical property tests demonstrated that the desired optical properties (Tp properties) required for the polarizing element 1 can be maintained by forming a protective film 40 that satisfies the above formula (10) on the entire surface of the complex fine uneven structure of the grid structure 20.

[0442] (5) Heat Resistance Test Next, the conditions and evaluation results of the heat resistance test will be described with reference to Table 1, Fig. 20, and Fig. 22. Fig. 20 is a graph showing the results of the heat resistance test for Comparative Examples 51 and 52. Fig. 21 is a graph showing the results of the heat resistance test for Comparative Examples 53 and 54. Fig. 22 is a graph showing the results of the heat resistance test for Examples 51 to 53.

[0443] As shown in Table 1 and Figures 20 to 22, in the heat resistance test, samples of the polarizing elements 1 according to Examples 51 to 53 and Comparative Examples 51 to 54 were continuously heated to 150°C for a predetermined time t (t = 500 hours, 1000 hours). ２ The change ΔTp ２ Based on the magnitude of Tp (i.e., the degree of deterioration of Tp), the influence of the protective film 40 on the heat resistance of the polarizing element 1 was evaluated.

[0444] In the heat resistance test, Tp was measured before and after heating (before and after the start of the test) for the samples of polarizing element 1 according to Examples 51 to 53 and Comparative Examples 51 to 54. In measuring Tp, incident light was irradiated onto the surface of each sample at an incident angle θ = 45°, and Tp was measured at each wavelength λ while varying the wavelength λ of the incident light within a range of 400 to 700 nm, and the average of the measured Tp values ​​from 430 to 680 nm was calculated.

[0445] The change in Tp before and after heating, ΔTp, shown in Table 1 ２ The amount of change ΔTp was calculated. ２is the average Tp value measured before heating the sample (before the test started). ２Ｂ and the average Tp of the measured values ​​of Tp after heating the sample at 150°C for 1000 hours (1000 hours after the start of the test). ２Ａ is the difference between (ΔTp ２ = Tp ２Ａ -Tp ２Ｂ ). The amount of change ΔTp ２ The larger the absolute value of ΔTp, the more the Tp characteristic of the sample deteriorates due to heating for a long time, and the lower the heat resistance. ２ The smaller the absolute value of ΔTp, the less the optical characteristics (Tp characteristics) of the polarizing element 1 are degraded by the influence of heat, and the higher the heat resistance of the polarizing element 1. ２ It is preferable that the absolute value of is small.

[0446] According to the results of the heat resistance test, as shown in Figure 20, in Comparative Examples 51 and 52, the longer the heating time, the lower the Tp, and the lowering of Tp is particularly noticeable in the short wavelength range of 500 nm or less. As a result, as shown in Table 1, in Comparative Examples 51 and 52, ΔTp ２ is 3.3 to 5.2%, which is significantly larger than the reference value of 3.0%, which indicates that the heat resistance of the polarizing element 1 is not deteriorated. Therefore, it is clear that in Comparative Examples 51 and 52, the Tp characteristics of the polarizing element 1 deteriorate due to heating at high temperatures for a long period of time, and the heat resistance of the polarizing element 1 is low. The reason for this is thought to be that in Comparative Examples 51 and 52, Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so that the thin protective film 40 cannot fully protect the resin portion, and the resin portion deteriorates due to heat.

[0447] 21, in Comparative Examples 53 and 54, the longer the heating time, the lower the Tp, and the lowering of Tp is particularly noticeable in the short wavelength range of 500 nm or less. As a result, as shown in Table 1, in Comparative Examples 53 and 54, ΔTp ２is 3.8 to 3.9%, which is significantly larger than the reference value of 3.0%, which indicates that the heat resistance of the polarizing element 1 is not deteriorated. Therefore, it can be seen that the Tp characteristics of the polarizing element 1 deteriorate and the heat resistance of the polarizing element 1 is low in Comparative Examples 53 and 54 as well due to prolonged high-temperature heating. The reason for this is thought to be that in Comparative Examples 53 and 54, the Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so that the thin protective film 40 cannot fully protect the resin portion, and the resin portion deteriorates due to heat.

[0448] In contrast, in Examples 51 to 53, as shown in Figure 22, there is almost no difference in the Tp characteristics depending on the length of the heating time, and the Tp characteristics show almost the same tendency regardless of the length of the heating time. ２ is 0.1 to 0.2%, which is significantly smaller than the reference value of 3.0%. Therefore, in Examples 51 to 53, the Tp characteristics of the polarizing element 1 do not deteriorate even when heated at high temperatures for a long period of time, and it is clear that the heat resistance of the polarizing element 1 is high. The reason for this is thought to be that in Examples 51 to 53, Bt / Tt satisfies formula (10), and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is sufficiently thick, so that the thick protective film 40 adequately protects the resin portion, and the resin portion does not deteriorate due to heat.

[0449] The results of the above heat resistance tests demonstrated that the heat resistance of the polarizing element 1 can be improved by forming a protective film 40 that satisfies the above formula (10) on the entire surface of the complex fine uneven structure of the grid structure 20.

[0450] (6) Lightfastness Test Next, the conditions and evaluation results of the lightfastness test will be described with reference to Table 1, Fig. 23, and Fig. 24. Fig. 23 is a graph showing the results of the lightfastness test for Comparative Example 52. Fig. 24 is a graph showing the results of the lightfastness test for Examples 51 to 53.

[0451] As shown in Table 1, Figures 23 and 24, in the light resistance test, test light was continuously irradiated from the direction perpendicular to the surface of the samples of polarizing element 1 according to Examples 51 to 53 and Comparative Example 52 for a predetermined time t (t = 500 hours, 1000 hours, 2000 hours). The test light was, for example, light from a laser light source incident on a dichroic mirror, and blue light from the visible light transmitted through the mirror. The change in Tp before and after light irradiation, ΔTp ３ The change ΔTp ３ Based on the magnitude of Tp (i.e., the degree of deterioration of Tp), the influence of the protective film 40 on the light resistance of the polarizing element 1 was evaluated.

[0452] In the light resistance test, Tp was measured before and after light irradiation (before and after the start of the test) for the samples of polarizing element 1 according to Examples 51 to 53 and Comparative Example 52. In measuring Tp, incident light was made incident on the surface of each sample at an incident angle θ = 45°, and Tp was measured at each wavelength λ while changing the wavelength λ of the incident light in the range of 400 to 700 nm, and the average value of the measured Tp values ​​in the range of 430 to 680 nm was calculated.

[0453] The change in Tp before and after light irradiation ΔTp shown in Table 1 ３ The amount of change ΔTp was calculated. ３ is the average Tp value measured before the sample is irradiated with light (before the test begins) ３Ｂ and the average Tp of the measured values ​​of Tp after irradiating the sample with light for 2000 hours (2000 hours after the start of the test). ３Ａ is the difference between (ΔTp ３ = Tp ３Ａ -Tp ３Ｂ ). The amount of change ΔTp ３ The larger the absolute value of ΔTp, the more the Tp characteristic of the sample deteriorates due to long-term light irradiation, and the lower the light resistance. ３ The smaller the absolute value of ΔTp, the less the optical characteristics (Tp characteristics) of the polarizing element 1 are degraded by the influence of light, and the higher the light resistance of the polarizing element 1. ３ It is preferable that the absolute value of is small.

[0454] According to the results of the light resistance test, as shown in Figure 23, in Comparative Example 52, the longer the light irradiation time, the higher the Tp, and the increase in Tp is particularly remarkable in the long wavelength region of 600 nm or more. As a result, as shown in Table 1, in Comparative Example 52, ΔTp ３ The absolute value of is 1.6%, which is significantly larger than the reference value of 1.0%, which indicates that the light resistance of the polarizing element 1 is not deteriorated. Therefore, it is clear that in Comparative Example 52, the Tp characteristic of the polarizing element 1 deteriorates due to light irradiation, and the light resistance of the polarizing element 1 is low. The reason for this is thought to be that in Comparative Example 52, Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so that the thin protective film 40 cannot fully protect the resin portion, and the resin portion deteriorates due to light (for example, turns yellow).

[0455] In contrast, in Examples 51 to 53, as shown in Figure 24, there is almost no difference in the Tp characteristics depending on the length of the light irradiation time, and the Tp characteristics show almost the same tendency regardless of the length of the light irradiation time. ３ is 0.2 to 0.8%, which is sufficiently smaller than the reference value of 1.0%. Therefore, in Examples 51 to 53, the Tp characteristics of the polarizing element 1 do not deteriorate even when exposed to light for a long period of time, and it can be seen that the light resistance of the polarizing element 1 is high. The reason for this is thought to be that in Examples 51 to 53, Bt / Tt satisfies formula (10), and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is sufficiently thick, so that the thick protective film 40 adequately protects the resin portion, and the resin portion does not deteriorate due to light.

[0456] The results of the above light resistance test demonstrated that the light resistance of the polarizing element 1 can be improved by forming a protective film 40 that satisfies the above formula (10) on the entire surface of the complex fine uneven structure of the grid structure 20.

[0457] 2. Verification Results of the Reinforcement Function of the Reinforcement Film for the Convex Ribs Next, as an example of the present invention, a sample of the wire-grid polarizer 1 including the reinforcing film 51 according to the present embodiment described above was prepared, and a test was conducted to evaluate the optical characteristics of the sample. Furthermore, for comparison with the example of the present invention (in which the convex ribs 22 are covered with the reinforcing film 51), a sample of the wire-grid polarizer 1 according to a comparative example (in which the convex ribs 22 are not covered with the reinforcing film 51) was also prepared and similarly tested and evaluated. Note that, for ease of explanation, the following reference numerals representing the components of the polarizer 1 (such as the substrate 10, the grid structure 20, the base 21, the convex ribs 22, the reflective film 30, the protective film 40, and the reinforcing film 51) and the symbols representing the various dimensions of these components are assigned the same reference numerals and symbols in both the example and the comparative example.

[0458] The symbols used in the following description to represent various dimensions of the polarizing element 1 are as follows: P: pitch of the ridges 22 W: Ｔ　　 W: width of the top of the ridge portion 22 (ridge portion top width) Ｍ　　 W: width of the central position of the ridge portion 22 in the height direction (central width of the ridge portion) Ｂ　　 W: Width of the bottom of the ridge portion 22 (grid bottom width) ＭＡＸ : maximum width of the reflective film 30 that covers the convex rib portion 22 (maximum grid width) H: height of the convex rib portion 22 Hx: height of the portion of the side surface 22b of the convex rib portion 22 that is covered by the reflective film 30 Dt: thickness of the reflective film 30 that covers the tip 22a of the convex rib portion 22 (tip thickness of the reflective film 30) Ds: thickness of the reflective film 30 that covers the side surface 22b of the convex rib portion 22 (side surface thickness of the reflective film 30) Rc: coverage rate of the side surface 22b of the convex rib portion 22 by the reflective film 30 Rr: opening rate of the side surface 22b of the convex rib portion 22 by the reflective film 30 Tt: thickness of the protective film 40 that covers the top portion 30a of the reflective film 30 that covers the convex rib portion 22 (i.e., thickness of the protective film 40 at the tip of the grid 41) Bt: thickness of the protective film 40 covering both side surfaces 22b of the ridge portion 22, the lower sides of the 22b, and the surface of the base portion 21 (i.e., the thickness of the protective film 40 at the bottom of the valley 42); Rt: thickness of the reinforcing film 51; θ: angle of incidence of incident light; λ: wavelength of incident light;

[0459] (1) Method for Producing Samples of Polarizing Element 1 In Example 60 of the present invention and Comparative Example 60, samples of polarizing element 1 were produced by the manufacturing method described below. In the sample of polarizing element 1 according to Example 60, a reinforcing film 51 was provided to cover the entire ridge portion 22 and base portion 21 of the grid structure 20, as shown in Fig. 30. In contrast, in the sample of polarizing element 1 according to Comparative Example 60, the reinforcing film 51 was not provided, as shown in Fig. 31.

[0460] Sixtieth Embodiment First, a sixtieth embodiment of the present invention will be described with reference to FIG.

[0461] A sample of polarizing element 1 according to Example 60 was fabricated using the manufacturing method of polarizing element 1 according to the present embodiment described above. As shown in Fig. 30 , polarizing element 1 according to Example 60 includes a glass substrate 10 and a grid structure 20 made of ultraviolet-curable resin (acrylic resin). Grid structure 20 has a base portion 21 provided along the surface of substrate 10 and a plurality of ridge portions 22 formed in a grid pattern and protruding from base portion 21. The cross-sectional shape of ridge portions 22 is a rounded convex shape, and is tapered toward tips 22a of ridge portions 22.

[0462] In Example 60, first, the grid structure material formation step (S10), the nanoimprint step (S12), and the grid structure formation step (S14) in the manufacturing method of the polarizing element 1 according to the present embodiment described above were carried out to create the grid structure 20 shown in FIG.

[0463] Next, the above-mentioned reinforcing film forming step (S15) was carried out, and the above-mentioned special ALD method (see FIG. 19) was used to form a reinforcing film 51 that continuously covers the entire surface of the grid structure 20 (the tip 22a and both side surfaces 22b, 22b of the ridge portion 22, and the surface of the base portion 21). ２ The target thickness of the reinforcing film 51 was set to 2 nm.

[0464] When forming the reinforcing film 51 by this special ALD method (S15), a film formation method was adopted in which the precursor gas and the oxidant gas were introduced into the chamber 300 to fill it, without exhausting the precursor gas and the oxidant gas in the chamber 300 from the gas exhaust port 330 in the above-mentioned precursor gas and oxidant gas introduction steps (S151, S153: first and third steps). As a result, the thickness of the reinforcing film 51 covering the tips 22a of the protruding ridge portions 22 of the grid structure 20 and the thickness of the reinforcing film 51 covering the upper surface of the base portion 21 could be made to be approximately the same thickness Rt (approximately 2 nm).

[0465] Next, the above-described reflective film forming step (S16) was carried out, and a reflective film 30 (functional film) was formed on the reinforcing film 51 covering the grid structure 20, covering the tips of the ridge portions 22. At this time, Al, the material of the reflective film 30, was deposited by vapor deposition onto the tops of the ridge portions 22 from diagonally above, alternately on the left and right, to form the reflective film 30.

[0466] The reflective film 30 thus formed is made of an Al film and, as shown in FIG. 30 , is formed to cover the top of the ridge portion 22 (the tip 22 a and the upper sides of both side surfaces 22 b, 22 b of the ridge portion 22) via the reinforcing film 51. However, the reflective film 30 does not cover the lower sides of both side surfaces 22 b, 22 b of the ridge portion 22 or the base portion 21. The coverage rate Rc of both side surfaces 22 b, 22 b of the ridge portion 22 by the reflective film 30 is 38%. In this way, the reflective film 30 of Example 60 roundly covers the top of the ridge portion 22 (the tip 22 a and the upper sides of both side surfaces 22 b, 22 b). The surface of the reflective film 30 is approximately elliptical, with a rounded shape that bulges outward, and bulges in the width direction of the ridge portion 22.

[0467] As a result, as shown in Fig. 30, the grid 41 according to Example 60 (a structure combining the ridges 22, the reinforcing film 51, and the reflective film 30) has the above-mentioned special tree shape. ＭＡＸ (the width of the grid at the most bulging portion of the reflective film 30) is the width W of the bottom of the ridge portion 22 Ｂ(the width of the protruding portion 22 at a height position 20% above the bottom of the protruding portion 22) or more. In addition, the cross-sectional shape (XZ cross section) of the valley 42 between adjacent grids 41, 41 has a pot-like shape with a narrow entrance on the upper side and a wide semi-closed space on the bottom side.

[0468] Thereafter, the above-described protective film forming step (S18) was carried out, and the protective film 40 was formed by using the above-described special ALD method (see FIG. 19) to cover the entire surface of the reinforcing film 51 and the reflective film 30 of the grid structure 20. The material of the protective film 40 was SiO ２ The target thickness of the protective film 40 to be formed was set to 7 nm.

[0469] During the deposition of the protective film 40 by this special ALD method (S18), in the above-described precursor gas and oxidant gas introduction steps (S181, S183: first and third steps), the precursor gas and oxidant gas are not exhausted from the gas exhaust port 330, but are instead introduced into the chamber 300 to fill it. This allows the thickness Tt of the protective film 40 covering the tip of the grid 41 (i.e., the metal portion of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 covering the surface of the bottom of the valley 42 (i.e., the resin portion of the grid structure 20) to be approximately the same thickness (approximately 7 nm), and the protective film 40 satisfying the above formula (10) can be deposited.

[0470] (Comparative Example 60) Next, a description will be given of Comparative Example 60. As shown in Fig. 31 , a sample of polarizing element 1 according to Comparative Example 60 did not have a reinforcing film 51 like that of Example 60. In Comparative Example 60, a sample of polarizing element 1 according to Comparative Example 60 was produced using the same manufacturing method (S10, S12, S14, S16, S18) as Example 60, except that the reinforcing film formation step (S15) was not performed.

[0471] (2) Dimensional Conditions of Each Part of Polarizing Element 1 The dimensions and shapes of each part of the polarizing element 1 samples according to Example 60 and Comparative Example 60, which were produced by the above-described manufacturing method, are as follows: P: 151 nm W Ｔ　　 : 20 nm W Ｂ　　 : 43 nm W ＭＡＸ: 72nm H : 265nm Hx : 101nm Dt : 37nm Ds : 27nm (maximum value) Rc : 38% Rr : 62% Tt : 7nm Bt : 7nm Rt : 2nm θ : 45° λ : 430 to 680nm

[0472] (3) Observation Results for Presence or Absence of Inclination of the Convex Rib Portion 22 The cross sections of the polarizing element 1 samples according to Example 60 and Comparative Example 60, which were produced by the above-described manufacturing method, were observed using a transmission electron microscope (TEM). Schematic diagrams of the cross-sectional shapes of the polarizing element 1 samples observed using the TEM images are shown in Figs. 30 and 31.

[0473] 30 , in the sample according to Example 60, the convex streaks 22 of the grid structure 20 were not tilted but extended straight upward, and the desired grid shape was maintained. In contrast, in the sample according to Comparative Example 60, the convex streaks 22 of the grid structure 20 were tilted to the left by about 10°. In particular, the upper part of the convex streaks 22 on which the reflective film 30 was vapor-deposited was tilted so as to curve to the left, and the desired grid shape could not be maintained.

[0474] The reason why the ridge portions 22 in Comparative Example 60 were tilted is thought to be that, since the ridge portions 22 in Comparative Example 60 were not reinforced by the reinforcing film 51, the resin of the ridge portions 22 softened due to the vapor deposition of high-temperature Al material onto the ridge portions 22 during the formation of the reflective film 30 (Al film). Furthermore, in the manufacturing method of the polarizing element 1 described above, the Al material is vapor deposited alternately on the left and right sides of the ridge portions 22 from diagonally above the ridge portions 22 through multiple vapor deposition processes (see FIG. 27 ). Therefore, stress due to thermal contraction caused by a temperature drop in the vapor-deposited Al film on one side of the ridge portions 22 accumulates around the Al film, and this accumulated stress is thought to have tilted the softened ridge portions 22 toward the side where the Al film was vapor-deposited (see FIG. 28 ).

[0475] According to the above results, it has been demonstrated that by covering the convex rib portion 22 with the reinforcing film 51 as in Example 60, the rigidity and heat resistance of the convex rib portion 22 can be increased, and therefore tilting of the convex rib portion 22 due to the formation of the reflective film 30 can be effectively suppressed.

[0476] (4) Optical Property Test Next, the conditions and evaluation results of the optical property test will be described with reference to Fig. 30 and Fig. 31. The tables in Fig. 30 and Fig. 31 show the results of the optical property test performed on the samples of the polarizing element 1 according to Example 60 and Comparative Example 60.

[0477] In the optical property test, the optical properties (Tp characteristics, Ts characteristics, Rp characteristics, Rs characteristics, contrast, Tp×Rs characteristics) of the polarizing element 1 samples according to Example 60 and Comparative Example 60 were measured, and the effect of the reinforcing film 51 on the optical properties of the polarizing element 1 was evaluated.

[0478] In the optical property test, a simulation was performed on the samples of polarizing element 1 according to Example 60 and Comparative Example 60, varying the wavelength λ of obliquely incident light, and the transmission axis transmittance (Tp), transmission axis reflectance (Ts), reflection axis transmittance (Rp), reflection axis reflectance (Rs), contrast (CR), and Tp × Rs were calculated. The incident angle θ of the obliquely incident light was set to +45°. Note that the wavelength λ of the obliquely incident light was varied in the range of 430 to 680 nm, and the average values ​​of multiple Tp, Ts, Rp, and Rs calculated for incident light of each wavelength λ were used to calculate the transmitted light contrast (CR) by dividing Tp by Ts (CR = Tp / Ts).

[0479] The relationships between Tp, Rs, Ts, Rp, CR, Tp×Rs calculated as above and λ are shown in the tables of FIG. 30 and FIG. 31.

[0480] According to the results of the optical property test, as shown in FIGS. 30 and 31 , the Ts characteristics, Rp characteristics, and Rs characteristics are comparable between Example 60 and Comparative Example 60. In contrast, it can be seen that Example 60 is superior to Comparative Example 60 in terms of Tp characteristics, Tp×Rs characteristics, and CR. Specifically, the average Tp value of Example 60 is 84.6%, which is 4.7% higher than the average Tp value of Comparative Example 60 (80.9%). Therefore, the average Tp×Rs value of Example 60 is 75.1%, which is 4.1% higher than the average Tp×Rs value of Comparative Example 60 (71%). Furthermore, the average CR value of Example 60 is 1104, which is significantly higher by more than 1.9 times than the average CR value of Comparative Example 60 (570).

[0481] In Comparative Example 60, as shown in Fig. 30, the ridges 22 are inclined, and the reflective film 30 supported by the inclined ridges 22 blocks the transmission of obliquely incident light, resulting in a decrease in the transmittance (Tp) of obliquely incident light. In contrast, in Example 60, as shown in Fig. 31, the ridges 22 are not inclined but extend straight, and the reflective film 30 does not block obliquely incident light unnecessarily. Therefore, it is believed that Example 60 can significantly improve the transmittance (Tp) and contrast (CR = Tp / Ts) of obliquely incident light compared to Comparative Example 60.

[0482] Thus, in Example 60, the ridge portions 22 are not tilted, and therefore the Tp characteristics, Tp×Rs characteristics, and CR are significantly superior to those of Comparative Example 60, in which the ridge portions 22 are tilted. In particular, when the polarizing element 1 is used as a polarizing beam splitter (PBS), being able to achieve both high Tp×Rs characteristics and high CR is extremely beneficial for the polarizing beam splitter. Furthermore, even when CR alone is evaluated, Example 60 achieves significantly better CR than Comparative Example 60, and is therefore beneficial because it can significantly improve the CR performance of the polarizing beam splitter.

[0483] From the results of the above optical property tests, it was demonstrated that by providing a reinforcing film 51 between the convex rib portion 22 and the reflective film 30 as in Example 60, and thereby imparting rigidity and heat resistance to the convex rib portion 22, tilting of the convex rib portion 22 can be suppressed, and therefore the optical properties required for the polarizing element 1 (high Tp, excellent Tp×Rs characteristics, and high contrast CR of transmitted light) can be obtained.

[0484] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0485] According to this embodiment, it is possible to provide a polarizing element and a method for manufacturing a polarizing element that have good polarization properties, do not deteriorate heat dissipation properties, and are excellent in transmittance for light over a wide range of incident angles without incurring deterioration in production costs. Furthermore, according to this embodiment, it is possible to provide a projection display device and a vehicle equipped with the projection display device that have excellent polarization properties and heat resistance. Furthermore, according to this embodiment, it is possible to provide a photocurable acrylic resin for imprinting that has a low viscosity of the uncured resin composition and has excellent heat resistance of the cured resin composition.

[0486] REFERENCE SIGNS LIST 1 wire grid polarizer 2 light source 3 display element 4 reflector 5 display surface 6 cover portion 10 substrate 20 grid structure 21 base portion 22 convex ridge portion 22b side surface 23 grid structure material 24 concave portion 29 constriction portion 30 reflective film 30a top portion 40 protective film 41 grid 42 valley 50 heat dissipation member 51 reinforcing film 60 master 61 master substrate 62 master metal film 63 convex portion 64 release film coat 65 groove 70 resist mask 80 metal film 100 head-up display device 200 projection display device 210 light source 220 PS converter 230 polarizing beam splitter 240 reflective liquid crystal display element 250 lens 260 light absorber 300 Chamber 310 Gas inlet 320 Jig 330 Gas outlet 340 Vacuum pump TS Thickness of substrate TB Thickness of base P Pitch of ridges H Height of ridges Hx Height range where reflective film covers the side surface of ridge Ds Side thickness of reflective film Dt Tip thickness of reflective film W ＭＡＸ Maximum width of the reflective film that covers the convex stripe (maximum grid width) W Ｂ Width of the bottom of the ridge (width of the grid bottom) W Ｔ Width of the top of the ridge (width of the top of the ridge) W Ａ Effective grid width W ＧGap width Rc Coverage rate Tt Thickness of the protective film covering the top of the reflective film that envelops the ridge portion Bt Thickness of the protective film covering the lower side of both sides of the ridge portion and the surface of the base portion Rt Thickness of the reinforcing film

Claims

1. A substrate made of an inorganic material; a grid structure made of an organic material, the grid structure having a base portion provided on the substrate and a plurality of ridges protruding from the base portion integrally formed therewith; a functional film made of a metallic material covering a portion of the ridges; and a reinforcing film made of an inorganic oxide interposed between the functional film and the portion of the ridges covered by the functional film and reinforcing the ridges, the ridges having a tapered shape that narrows in width as it moves away from the base portion, the reinforcing film covering at least the tip and upper sides of both side surfaces of the ridges, the functional film covering the tip and upper sides of both side surfaces of the ridges via the reinforcing film, and not covering the lower sides of both side surfaces of the ridges or the base portion, A wire grid polarization element, wherein the coverage rate (Rc) of the side surface of the convex streak portion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the convex streak portion covered by the functional film to the height (H) of the convex streak portion, and the coverage rate (Rc) is 30% or more and 70% or less.

2. The wire grid polarization element according to claim 1, wherein the thickness of the reinforcing film is 0.5 nm or more and 8 nm or less.

3. The wire grid polarizer according to claim 1, further comprising a protective film covering the surfaces of the grid structure and the functional film, the protective film continuously covering the surface of the functional film, the lower sides of both sides of the convex streak portion, and the surface of the base portion, the thickness of the protective film covering the top of the functional film that envelops the convex streak portion being Tt, and the thickness of the protective film covering the lower sides of both sides of the convex streak portion and the surface of the base portion being Bt, satisfying the following formula (10): Bt / Tt≧0.85...(10) 4. The wire grid polarizer according to claim 3, which satisfies the following formula (11): 0.85≦Bt / Tt≦1.07 (11) 5. The wire grid polarizer according to claim 3, which satisfies the following formula (12): 1.00<Bt / Tt≦1.07 (12) 6. The protective film is made of SiO ２ 4. The wire grid polarizer according to claim 3, which has a single layer structure consisting of:

7. The protective film is Al ２ O ３ A first coating layer consisting of SiO ２ 4. The wire grid polarizer according to claim 3, which has a laminate structure including a second coating layer consisting of:

8. A wire grid polarization element as described in claim 1, wherein the cross-sectional shape of the entire convex structure composed of the convex streak portion and the functional film has a constricted portion where the width in the width direction of the entire convex structure is narrowed directly below the lower end of the functional film that covers the convex streak portion.

9. A method for manufacturing a wire grid polarizer according to any one of claims 1 to 8, comprising the steps of: forming a grid structure material made of an organic material on a substrate made of an inorganic material; forming a grid structure having a base portion provided on the substrate and a plurality of ridge portions protruding from the base portion by nanoimprinting the grid structure material; forming a reinforcing film using an inorganic oxide that covers at least a portion of the ridge portions; and forming a functional film using a metal material that covers a portion of the ridge portions via the reinforcing film, wherein in the step of forming the grid structure, the ridge portions are formed to have a tapered shape that narrows in width as it moves away from the base portion, and in the step of forming the functional film, a reinforcing film covering at least the tip and upper sides of both sides of the convex rib portion, the functional film covering the tip and upper sides of both sides of the convex rib portion via the reinforcing film, but not covering the lower sides of both sides of the convex rib portion or the base portion, and the functional film is formed such that, when the coverage rate (Rc) of the side surface of the convex rib portion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the convex rib portion covered by the functional film to the height (H) of the convex rib portion, the coverage rate (Rc) is 30% or more and 70% or less.

10. A method for manufacturing a wire grid polarization element as described in claim 9, wherein in the step of forming the reinforcing film, the reinforcing film is deposited by a vapor deposition method so that the reinforcing film covers and envelops the tip and upper sides of both side surfaces of the convex rib portion.

11. A method for manufacturing a wire grid polarization element as described in claim 9, wherein in the step of forming the reinforcing film, the reinforcing film is deposited by an ALD method so that the reinforcing film continuously covers the tip and both side surfaces of the convex rib portion and the surface of the base portion.

12. A method for manufacturing a wire grid polarization element as described in claim 9, further comprising a step of forming a protective film on surfaces of the grid structure and the functional film, wherein in the step of forming the protective film, the protective film is formed by an ALD method so that the protective film continuously covers the surface of the functional film, the lower sides of both side surfaces of the convex rib portion, and the surface of the base portion.

13. The method for manufacturing a wire grid polarization element as described in claim 12, wherein the process for forming the protective film includes a first process of introducing a precursor gas into a chamber in which the grid structure coated with the functional film is placed, a second process of exhausting excess precursor gas to the outside of the chamber by introducing an inert gas into the chamber, a third process of introducing an oxidizer gas into the chamber, and a fourth process of exhausting excess oxidizer gas to the outside of the chamber by introducing an inert gas into the chamber, wherein in the first process, the precursor gas is introduced into the chamber to fill it without exhausting it to the outside of the chamber, and in the third process, the oxidizer gas is introduced into the chamber to fill it without exhausting it to the outside of the chamber.

14. A projection display device comprising: a light source; a polarizing beam splitter arranged so that light from the light source is incident at an angle of incidence of 30° or more and 60° or less, and separating the incident light into a first polarized light and a second polarized light; a reflective liquid crystal display element arranged so that the first polarized light reflected by the polarizing beam splitter or the second polarized light transmitted through the polarizing beam splitter is incident, and reflects and modulates the incident first polarized light or the second polarized light; and a lens arranged so that the first polarized light or the second polarized light reflected and modulated by the reflective liquid crystal display element is incident through the polarizing beam splitter, wherein the polarizing beam splitter is constituted by a wire grid polarization element described in any one of claims 1 to 8.

15. A vehicle equipped with the projection display device according to claim 14.

Images