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

Abstract

This suppresses the tilting of the convex portions of the grid structure caused by the formation of the functional film, thereby improving optical properties. [Solution] The wire grid polarizing element 1 comprises a substrate 10, a grid structure 20 in which a base portion 21 and a plurality of protrusions 22 are integrally formed, a functional film 30 covering a portion of the protrusions 22, and a reinforcing film 51. The reinforcing film 51 is made of an inorganic oxide and is interposed between a portion of the protrusions 33 covered by the functional film 30 and the functional film 30, reinforcing the protrusions 22. The reinforcing film 51 covers at least the tip 22a and the upper sides of both sides 22b of the protrusions 22. The functional film 30 covers the top of the protrusions 22 via the reinforcing film 51, but does not cover the bottom side of the protrusions 22 or the base portion 21, and its coverage rate (Rc) is 30% or more and 70% or less.

Description

[Technical Field]

[0001] The present invention relates to a wire grid polarizing element, a method for manufacturing a wire grid polarizing element, a projection display device, and a vehicle. [Background technology]

[0002] Wire grid polarizing elements 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 the vehicle and require high heat resistance and heat dissipation when used in high-temperature environments such as during the summer. Therefore, wire grid polarizing elements mounted on head-up display devices also require excellent heat resistance and heat dissipation.

[0003] For example, Patent Document 1 discloses that, in order to improve the heat resistance and heat dissipation of a wire grid polarizing element, the substrate of the wire grid polarizing element 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). In this grid structure, a base portion provided on the substrate and a plurality of protruding portions protruding from the base portion are integrally formed, and the tip of each protruding portion is coated with a functional film made of a metallic material such as Al to provide a reflection function for incident light. Furthermore, Patent Document 1 discloses that, in order to improve various optical properties required for a wire grid polarizing element (transmission axis transmittance (Tp) characteristics, Tp×Rs characteristics, contrast), the height H of the protruding portions is increased to 160 nm or more. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-095826 [Patent Document 2] Japanese Patent Publication No. 2014-085516 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the raised portion of the grid structure described in Patent Document 1 is made of an organic material such as resin, which has lower rigidity and heat resistance than an inorganic material such as glass, and has a tapered shape that becomes thinner towards the tip. Therefore, if the height H of the raised portion is increased as described in Patent Document 1, when a high-temperature functional film is deposited on the tip of the raised portion by a film deposition method such as sputtering or vapor deposition, the raised portion made of organic material may not be able to maintain a straight tapered shape extending upward, and may tilt to the left or right. In this way, when the raised portion tilts due to the deposition of a functional film covering the raised portion, there is a problem that various optical properties required for a wire grid polarizing element (e.g., Tp characteristics, Tp×Rs characteristics, contrast) decrease.

[0006] Therefore, the present invention has been made in view of the above problems, and aims to provide a wire grid polarizing element, a method for manufacturing a wire grid polarizing element, a projection display device, and a vehicle that can suppress the tilting of the convex portion of the grid structure due to the formation of a functional film and improve optical properties. [Means for solving the problem]

[0007] The inventors have conducted extensive research to solve the above problems and have found the following: First, the substrate of the wire grid polarizing element is formed from a transparent inorganic material, and the grid structure provided on the substrate is integrally formed from a transparent organic material. This makes it possible to create a hybrid structure of organic and inorganic materials for the wire grid polarizing element. As a result, the heat dissipation performance of the wire grid polarizing element can be significantly improved.

[0008] Furthermore, the grid structure used is one in which a base portion provided along the surface of the substrate and a plurality of protruding ridges are integrally formed from the base portion. As a result, the grid structure can be formed by technologies such as nanoimprinting, which reduces the manufacturing cost of the grid structure compared to using photolithography or etching technologies, and enables mass production.

[0009] Furthermore, when providing a functional film, such as a reflective film that reflects light or an absorbing film that absorbs light, on the raised portion of the grid structure, the coverage area and form of the raised portion by the functional film are suitably adjusted. Specifically, the tip of the raised portion and the upper side of one or both sides of the raised portion are covered by the functional film, while the lower side of the raised portion and the surface of the base are left open without being covered by the functional film. The functional film is rounded and bulges in the width direction of the raised portion, covering the tip of the raised portion and the upper side of the sides of the raised portion. Furthermore, the maximum width of the grid (m) including the raised portion and the functional film covering the raised portion is... MAX ) but the bottom of the convex part B The shape and size of the protrusions and the functional film are adjusted so that they are greater than or equal to ). Furthermore, it is preferable to limit the area in which the functional film covers the side surface of the protrusions 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 protrusions).

[0010] This prevents the decrease in the transmittance (Tp) of the second polarization (P polarization) in the wire grid polarizer from decreasing depending on the incident angle, even when oblique incident light with a large and wide range of incident angles is incident on the wire grid polarizer. Therefore, the product (Tp × Rs) of the reflectance axis (Rs) of the first polarization (S polarization) and the transmittance axis (Tp) of the second polarization (P polarization) in the wire grid polarizer can be maintained at a high value. Thus, when the wire grid polarizer is used, for example, as a polarizing beam splitter, sufficient transmittance and polarization separation characteristics can be obtained even for oblique incident light with a large incident angle and a wide range of incident angles.

[0011] Based on the above findings, the inventors have come up with the following invention.

[0012] To solve the above problems, according to one aspect of the present invention, A substrate made of inorganic material, A grid structure made of an organic material, comprising a base portion provided on the substrate and a plurality of protruding ridges integrally formed thereon, A functional film made of a metal material that covers a part of the aforementioned protruding portion, A reinforcing film made of an inorganic oxide is interposed between a portion of the protruding portion covered by the functional film and the functional film, and reinforces the protruding portion. Equipped with, The aforementioned protruding portion has a tapered shape, becoming narrower in width as it moves away from the base portion. The reinforcing film covers at least the tip and the upper sides of both sides of the protruding portion. The functional film covers the tip of the protrusion and the upper side of at least one side of the protrusion via the reinforcing film, but does not cover the lower sides of both sides of the protrusion and the base portion. When the coverage rate (Rc) of the side surface of the protrusion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the protrusion covered by the functional film to the height (H) of the protrusion, the coverage rate (Rc) is 30% or more and 70% or less. A wire grid polarizing element is provided.

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

[0014] The grid structure and the protective film further comprise a protective film covering the surface of the functional film, The protective film continuously covers the surface of the functional film, the lower sides of both sides of the protruding portion, and the surface of the base portion. When the thickness of the protective film covering the top of the functional film that encloses the protruding portion is Tt, and the thickness of the protective film covering the lower sides of both sides of the protruding portion and the surface of the base portion is Bt, the following formula (10) may be satisfied. Bt / Tt≧0.85 ···(10)

[0015] The following equation (11) may also be satisfied. 0.85 ≤ Bt / Tt ≤ 1.07 ···(11)

[0016] The following equation (12) may also be satisfied. 1.00 <Bt / Tt≦1.07 ···(12)

[0017] The protective film may be a single-layer structure made of SiO2.

[0018] The protective film may have a laminated structure comprising a first film layer made of Al2O3 and a second film layer made of SiO2.

[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 polarizing element may be a hybrid type that combines the substrate made of the inorganic material and the grid structure made of the organic material.

[0024] The surface of the functional film covering the aforementioned protruding portion is rounded and bulges in the width direction of the protruding portion. The maximum width (W) of the functional film covering the aforementioned protruding portion MAX ) is the width (W) of the protrusion in the portion not covered by the functional film at a position 20% above the height of the protrusion from the bottom of the protrusion. B) or more may be used.

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

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

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

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

[0029] The thickness (Ds) of the functional film covering the side surface of the protruding portion may be 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 portion in the cross section perpendicular to the reflection axis direction of the wire grid polarizing element may be a trapezoid, triangle, bell shape, or ellipse, with the width narrowing as it moves away from the base portion.

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

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

[0034] If θ is between 30° and 60°, The difference between the transmission axis transmittance of incident light at an incident angle of +θ to the wire grid polarizing element (Tp(+)) and the transmission axis transmittance of incident light at an incident angle of -θ (Tp(-)) may be kept within 3%.

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

[0036] The wire grid polarizing element may be a polarizing beam splitter that separates obliquely incident light into a first polarization and a second polarization.

[0037] To solve the above problems, according to another aspect of the present invention, The above-mentioned method for manufacturing a wire grid polarizing element, A process of forming a grid structure material made of organic material on a substrate made of inorganic material, A step of forming a grid structure in which a base portion provided on the substrate and a plurality of protruding portions extending from the base portion are integrally formed by applying nanoimprint to the grid structure material, A step of forming a reinforcing film using an inorganic oxide that covers at least a portion of the raised portion, A step of forming a functional film that covers a portion of the protruding portion via the reinforcing film using a metal material, Includes, In the process of forming the grid structure, the convex portion having a tapered shape that narrows in width as it moves away from the base portion is formed. In the process of forming the functional film, A method for manufacturing a wire grid polarizing element is provided, wherein the reinforcing film covers at least the tip and upper sides of both sides of the protrusion, the functional film covers the tip and upper sides of both sides of the protrusion via the reinforcing film, but does not cover the lower sides of both sides of the protrusion and the base portion, and the functional film is formed such that the coverage rate (Rc) of the sides of the protrusion by the functional film is 30% or more and 70% or less, when the coverage rate (Rc) of the sides of the protrusion is the ratio of the height (Hx) of the portion of the sides of the protrusion covered by the functional film to the height (H) of the protrusion,

[0038] In the step of forming the reinforcing film, The reinforcing film may be formed by vapor deposition such that it covers and encloses the tip and upper sides of both sides of the protruding portion.

[0039] In the step of forming the reinforcing film, The reinforcing film may be formed by the ALD method such that the reinforcing film continuously covers the tip and both sides of the protruding portion and the surface of the base portion.

[0040] The process further includes a step of forming a protective film on the surface of the grid structure and the functional film, In the process of forming the protective film, The protective film may be formed by the ALD method such that it continuously covers the surface of the functional film, the lower sides of both sides of the protruding portion, and the surface of the base portion.

[0041] The step of forming the protective film is as follows: A first step involves introducing a precursor gas into a chamber in which the grid structure coated with the functional membrane is placed, A second step involves introducing an inert gas into the chamber to exhaust excess precursor gas to the outside of the chamber, A third step involves introducing an oxidizing agent gas into the chamber, A fourth step involves introducing an inert gas into the chamber to exhaust excess oxidizing gas to the outside of the chamber, Includes, In the first step, the precursor gas is introduced into the chamber and filled without exhausting the precursor gas to the outside of the chamber. In the third step, the oxidizing gas may be introduced into the chamber and filled with it without exhausting the oxidizing gas to the outside of the chamber.

[0042] In the step of forming the functional film, the film may be deposited alternately from multiple directions on the raised ridges by sputtering or vapor deposition.

[0043] To solve the above problems, according to another aspect of the present invention, Light source and A polarization beam splitter is positioned so that the incident light from the light source is incident at an incident angle within a predetermined range including 45°, and separates the incident light into a first polarization and a second polarization. A reflective liquid crystal display element is arranged such that the first polarization reflected by the polarization beam splitter, or the second polarization transmitted through the polarization beam splitter, is incident on it, and the reflective liquid crystal display element reflects and modulates the incident first polarization or second polarization. A lens is arranged such that the first or second polarization reflected and modulated by the reflective liquid crystal display element is incident on the polarizing beam splitter, Equipped with, The polarizing beam splitter is provided as a projection display device composed of the wire grid polarizing elements.

[0044] The angle of incidence within the predetermined range may be set to be 30° or more and 60° or less.

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

[0046] To solve the above problems, according to another aspect of the present invention, a vehicle equipped with the projection display device is provided. [Effects of the Invention]

[0047] According to the present invention, it is possible to suppress the tilting of the convex portions of the grid structure caused by the formation of a functional film, thereby improving the optical properties. [Brief explanation of the drawing]

[0048] [Figure 1] This is a schematic cross-sectional view showing a wire grid polarizing element according to the first embodiment of the present invention. [Figure 2] This is a schematic plan view showing a wire grid polarizing element according to the same embodiment. [Figure 3] This is a schematic cross-sectional view showing a specific example of the tapered shape of the convex portion of the grid structure according to the same embodiment. [Figure 4] This is a schematic cross-sectional view showing a specific example of the shape of a recess in the grid structure according to the same embodiment. [Figure 5] This is a schematic cross-sectional view showing a wire grid polarizing element according to the same embodiment. [Figure 6] This is a schematic cross-sectional view showing a specific example of the shape of the reflective film according to the same embodiment. [Figure 7] This is a schematic cross-sectional view showing a polarizing element covered with a protective film according to the same embodiment. [Figure 8] This is a schematic cross-sectional view showing an example of a modified polarizing element covered with a protective film according to the same embodiment. [Figure 9] This is a schematic perspective view showing a polarizing element equipped with a heat dissipation member according to the same embodiment. [Figure 10] This is a photograph showing an actual grid structure and reflective film according to the same embodiment. [Figure 11] This is a process diagram showing a method for manufacturing a wire grid polarizing element according to the same embodiment. [Figure 12] This is a process diagram showing a conventional method for manufacturing a wire grid polarizing element. [Figure 13] This is a process diagram showing the manufacturing method of the master disc according to the same embodiment. [Figure 14] This is a schematic diagram showing a head-up display device, which is an example of a projection display device according to the same embodiment. [Figure 15] This is a schematic diagram showing a first specific example of the projection display device according to the same embodiment. [Figure 16] This is a schematic diagram showing a second specific example of the projection display device according to the same embodiment. [Figure 17] This is a schematic diagram showing a third specific example of the projection display device according to the same embodiment. [Figure 18] This is a schematic enlarged cross-sectional view showing a wire grid polarizing element covered with a protective film according to the same embodiment. [Figure 19] This is a schematic diagram showing the film formation process of a protective film by the ALD method according to the same embodiment. [Figure 20] This graph shows the heat resistance test results for Comparative Examples 51 and 52. [Figure 21] This graph shows the heat resistance test results for Comparative Examples 53 and 54. [Figure 22] This graph shows the heat resistance test results for Examples 51, 52, and 53. [Figure 23] This graph shows the results of the lightfastness test for Comparative Example 52. [Figure 24] This graph shows the results of the lightfastness tests for Examples 51, 52, and 53. [Figure 25] This is an enlarged cross-sectional view showing a wire grid polarizing element equipped with a reinforcing film that covers the entire grid structure according to the same embodiment. [Figure 26] This is an enlarged cross-sectional view showing a wire grid polarizing element equipped with a reinforcing film that covers a portion of the convex portion of the grid structure according to a modified example of the same embodiment. [Figure 27] This is a schematic diagram showing a model in which reflective films are deposited alternately from the left and right sides onto the upper part of a raised ridge. [Figure 28] Figure 27 is a schematic diagram showing the simulation results of the deformation behavior of the convex section using the model. [Figure 29] This is a schematic diagram showing the results of a simulation of the deformation behavior in which the convex ridges become thinner during the deposition of a reflective film. [Figure 30]This is an explanatory diagram showing the cross-sectional shape of the wire grid polarizing element according to Example 60 and the results of the optical characteristics test. [Figure 31] This is an explanatory diagram showing the cross-sectional shape of the wire grid polarizing element related to Comparative Example 60 and the results of the optical characteristics test. [Modes for carrying out the invention]

[0049] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant explanations will be omitted. For the sake of convenience of explanation, the states of the components disclosed in the following figures are sometimes schematically represented with a different scale and shape than the actual ones.

[0050] <1. Overview of Wire Grid Polarizers> First, an overview of the wire grid polarizing element 1 according to the first embodiment of the present invention will be described with reference to Figures 1 and 2, etc. Figure 1 is a schematic cross-sectional view showing the wire grid polarizing element 1 according to this embodiment. Figure 2 is a schematic plan view showing the wire grid polarizing element 1 according to this embodiment.

[0051] The wire grid polarizing element 1 according to this embodiment is a reflective polarizing element and a wire grid type polarizing element. The wire grid polarizing element 1 may be, for example, a plate-shaped wire grid polarizing plate. The wire grid polarizing plate is a wire grid type polarizing plate having a plate shape. The wire grid polarizing plate may be, for example, a flat plate or a curved plate. In other words, the surface (the surface to which light is incident) of the wire grid polarizing element 1 may be a flat surface or a curved surface. Below, an example in which the wire grid polarizing element 1 according to this embodiment is a flat wire grid polarizing plate will be described, but the wire grid polarizing element of the present invention is not limited to such an example and can have any shape depending on its application and function.

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

[0053] As shown in Figures 1 and 2, the wire grid polarizing element 1 (hereinafter sometimes abbreviated as "polarizing element 1") comprises 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 with a wavelength λ belonging to the usage band (e.g., the visible light band, the infrared light band, or the visible and infrared light bands) is high, for example, that the transmittance of such 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 is larger than the wavelength band of visible light, for example, 830 nm or more. From the viewpoint of a suitable wavelength range of visible light projected as a display image, the wavelength λ of the usage band in the polarizing element 1 according to this embodiment is preferably, for example, 400 nm or more and 800 nm or less, and more preferably 420 nm or more and 680 nm or less. Since the polarizing element 1 according to this embodiment is formed of a material that is transparent to light in the usage band, it does not adversely affect the polarization characteristics or light transmittance of the polarizing element 1.

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

[0056] The grid structure 20 is made of a transparent organic material, such as an organic resin material such as an ultraviolet-curable resin or thermosetting resin with excellent heat resistance. The grid structure 20 has an uneven structure to realize 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 protruding portions 22 that project in a grid pattern from the base portion 21. The base portion 21 and the plurality of protruding 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 (XY plane shown in Figures 1 and 2) of the substrate 10. Preferably, the thickness TB of the base portion 21 is substantially the same over the entire main surface of the substrate 10, but it does not have to be exactly the same thickness, and may vary to a certain extent with respect to the reference thickness of TB. For example, TB may vary by about ±3 μm from a reference thickness of 6 μm. In this way, the thickness TB of the base portion 21 is determined while allowing for molding errors when forming the base portion 21 by imprinting or the like.

[0058] Multiple protrusions 22 are arranged on the base portion 21 at equal intervals in the X direction with a predetermined pitch P. The pitch P is the spacing between the multiple protrusions 22 arranged in the X direction of the polarizing element 1. The multiple protrusions 22 are arranged in a grid pattern, extending parallel to each other in the Y direction. A predetermined gap is formed between two adjacent protrusions 22 in the X direction. This gap serves as the entry path for incident light. Each protrusion 22 is a wall-like projection that extends elongated 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 multiple protrusions 22 are specified. T , W B These are substantially identical to each other. The longitudinal direction (Y direction) of the convex portion 22 is the direction of the reflection axis of the polarizing element 1, and the width direction (X direction) of the convex portion 22 is the direction of the transmission axis of the polarizing element 1.

[0059] The functional film is a film that imparts a predetermined function to the grid structure 20 of the polarizing element 1. The functional film is made of, for example, an opaque metallic material and is provided so as to cover a part of the raised 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 incident on the polarizing element 1, or an absorbing film (not shown) that has the function of absorbing the incident light, or a film with other functions. In this embodiment, an example in which the functional film is a reflective film 30 is 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 (such as a metal or metal oxide), for example, aluminum or silver. The reflective film 30 is formed to cover at least the top of the raised portion 22. The reflective film 30 may also be composed of a metallic film that functions as a metal fine wire of the wire grid. The reflective film 30 has the function of reflecting incident light that enters the grid structure 20.

[0061] The protruding portions 22 of the grid structure 20 and the reflective film 30 constitute the grid of the wire grid polarizing element 1. The pitch P in the X direction of the multiple protruding portions 22 in the grid structure 20 (i.e., the grid arrangement pitch) is set to a pitch small compared to the wavelength λ of the incident light (e.g., visible light) (e.g., less than half). As a result, the polarizing element 1 can reflect almost all of the light (S-polarized) with an electric field vector component vibrating in a direction parallel to the reflective film 30 (conductor wire) extending in the Y direction (reflection axis direction: Y direction), and transmit almost all of the light (P-polarized) with an electric field vector component vibrating in a direction perpendicular to the reflective film 30 (conductor wire) (transmission axis direction: X direction).

[0062] As described above, the wire grid polarizing element 1 according to this embodiment achieves polarization function by combining a grid structure 20 having a fine uneven structure and a functional film (e.g., a reflective film 30) selectively added to the raised ridges 22 of the grid structure 20. The substrate 10 of the wire grid polarizing element 1 is made of an inorganic material such as glass which has excellent heat resistance, and the grid structure 20 is made of an organic resin material which has heat resistance. Thus, the wire grid polarizing element 1 according to this embodiment is a hybrid polarizing element that combines organic and inorganic materials. Therefore, the thermal resistance R[m 2 Because heat can be efficiently dissipated from the grid structure 20 with a small [K / W] to the substrate 10, it exhibits excellent heat dissipation. Therefore, the hybrid wire grid polarizing element 1 according to this embodiment has superior heat resistance and heat dissipation compared to conventional film-type polarizing elements made only of organic materials (heat resistance: about 100°C), and has heat resistance in high-temperature environments up to about 200°C, for example. Thus, it can achieve excellent polarization characteristics while maintaining a good heat dissipation effect.

[0063] Furthermore, the wire grid polarizing element 1 according to this embodiment may include a protective film 40 (see Figures 7 and 8) covering the surface of the grid structure 20. The protective film 40 is made of an inorganic material, such as a dielectric material such as SiO2. This protective film 40 may be laminated over the entire surface of the wire grid polarizing element 1 so as to cover all surfaces of the base portion 21, the raised portion 22, and the reflective film 30 of the grid structure 20 (see Figure 7). By providing such a protective film 40, the advantageous effect of further reducing the thermal resistance R of the polarizing element 1 can be obtained, 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 raised ridge portion 22 are integrally formed, can be manufactured using printing technology such as nanoimprint, thus enabling the realization of a fine uneven structure with 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 technology. Thus, the hybrid polarizing element 1 according to this embodiment has the advantage of significantly reducing manufacturing costs compared to conventional polarizing elements made only of inorganic materials, and thus enabling a lower unit price for the wire grid polarizing element 1.

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

[0066] Furthermore, the wire grid polarizing element 1 according to this embodiment has a grid consisting of a convex portion 22 of the grid structure 20 and a reflective film 30, which has a special tree shape (details will be described later) as shown in Figure 1, etc. This makes it possible to suppress the decrease in the transmittance of the second polarization (P polarization) transmitted through the polarizing element 1 (i.e., transmission axis transmittance Tp) depending on the incident angle θ of the obliquely incident light, even when light is incident on the polarizing element 1 from an oblique direction at a wide range of large incident angles θ (e.g., 30 to 60°). Therefore, the product (Tp × Rs) of the reflectance of the first polarization (S polarization) reflected by the wire grid polarizing element 1 (i.e., reflection axis reflectance Rs) and the transmission axis transmittance Tp can be maintained at a high value of, for example, 70% or more. Therefore, the polarizing element 1 according to this embodiment has excellent polarization separation characteristics represented by Tp × Rs, and can polarize obliquely incident light and suitably separate it into S polarization (reflected light) and P polarization (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 a wide range of angles.

[0067] As described above, the wire grid polarizing element 1 according to this embodiment has excellent heat resistance and heat dissipation, reduced manufacturing costs, and excellent transmittance and polarization separation characteristics for obliquely incident light with a wide range of large incident angles θ. Therefore, the wire grid polarizing element 1 according to this embodiment can be suitably applied as a variety of components in a variety of products. For example, the polarizing element 1 can be applied to polarizing beam splitters installed in smart displays. The polarizing element 1 can also be applied to polarizing elements that are protected from heat from sunlight, polarizing elements that are protected from heat from LED light sources, and polarizing reflective mirrors installed in head-up displays (HUDs). Furthermore, the polarizing element 1 can be applied to polarizing beam splitters installed in headlights such as adjustable beam distribution headlamps (ADBs). In addition, the polarizing element 1 can be applied to lens-integrated phase difference elements, lens-integrated polarizing elements, etc., installed in various devices for augmented reality (AR) or virtual reality (VR).

[0068] <2. Components of a wire grid polarizer> Next, the components of the wire grid polarizing element 1 according to this embodiment will be described in detail with reference to Figures 1 and 2, etc.

[0069] <2.1. Circuit Board> As shown in Figure 1, the wire grid polarizing element 1 according to this embodiment includes a transparent substrate 10. The substrate 10 is made of an inorganic material that is transparent and has a certain degree of strength.

[0070] From the viewpoint of obtaining better heat dissipation and heat resistance, the material of the substrate 10 is preferably an inorganic material such as various types of glass, quartz, crystal, or sapphire, more preferably an inorganic material with a thermal conductivity of 1.0 W / m·K or higher, and even more preferably an inorganic material with a thermal conductivity of 8.0 W / m·K or higher.

[0071] Furthermore, the shape of the substrate 10 is not particularly limited and can be appropriately selected according to the performance required of the polarizing element 1. For example, it can be configured to be plate-shaped or curved. Also, from the viewpoint of not affecting the polarization characteristics of the polarizing element 1, the surface of the substrate 10 can be flat. In addition, the thickness TS of the substrate 10 is not particularly limited and can be in the range of, for example, 0.02 to 10.0 mm.

[0072] <2.2. Grid Structure> As shown in Figures 1 and 2, the polarizing element 1 according to this embodiment comprises a grid structure 20 having the base portion 21 and a grid-like raised portion 22 on a substrate 10. The grid structure 20 can obtain desired polarization characteristics by providing a reflective film 30, which will be described later, on the raised portion 22.

[0073] When light is incident on the polarizing element 1 from the surface side where 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 with an electric field component in a direction perpendicular to the longitudinal direction of the convex portion 22 (i.e., the extension direction of the convex portion 22 = reflection axis direction: Y direction) (i.e., the width direction of the convex portion 22 = 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 with an electric field component in a direction parallel to the longitudinal direction of the convex portion 22 (i.e., the extension direction of the convex portion 22 = reflection axis direction: Y direction) is mostly reflected by the reflective film 30. Therefore, in this embodiment, by providing a grid structure 20 partially covered with the reflective film 30, single polarization can be produced. A similar polarization effect can also be obtained for light incident on the back side of the substrate 10.

[0074] As shown in Figure 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 is a part that supports the raised ridges 22. When the uneven structure (raised ridges 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 raised ridges 22 are integrally formed from the same material. Furthermore, because the grid structure 20 has a base portion 21, the strength of the raised ridges 22 can be increased compared to when the raised ridges 22 are formed directly on the substrate 10. This can increase the durability of the grid structure 20. In addition, because the base portion 21 is in close contact with the substrate 10 over its entire surface, the peel resistance of the grid structure 20 can be increased.

[0075] The thickness TB of the base portion 21 is not particularly limited, but from the viewpoint of more reliably supporting the raised ridge portion 22 and facilitating imprint molding, it is preferably 1 nm or more, and more preferably 10 nm or more. 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, since the base portion 21 and the multiple protrusions 22 of the grid structure 20 are formed directly on the substrate 10, the thickness TB of the base portion 21 can be reduced. Here, in order to improve the 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 reducing the thickness TB of the base portion 21. The temperature difference ΔT is the temperature difference between the temperature T1 [°C] of the outermost surface of the base portion 21 (the base of the multiple protrusions 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 made of organic material to be quickly transferred to the substrate 10 made of inorganic material, and efficiently dissipated from the substrate 10 to the outside of the polarizing element 1, thereby enabling heat dissipation and 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, which allows the temperature difference ΔT to be, for example, 20°C or less. Furthermore, the thickness TB of the base portion 21 is more preferably 0.045 mm or less, which allows the temperature difference ΔT to be, for example, 10°C or less. Furthermore, the thickness TB of the base portion 21 is particularly preferably 0.02 mm or less, which allows the temperature difference ΔT to be, for example, 5°C or less. In this way, by reducing the thickness TB of the base portion 21, the heat dissipation from the grid structure 20 to the outside via the substrate 10 can be improved, thereby improving the heat dissipation and heat resistance of the polarizing element 1.

[0078] Furthermore, as shown in Figures 1 and 2, the grid structure 20 has a plurality of protruding ridges 22 that extend from the base portion 21. The protruding ridges 22 extend with the reflection axis direction (Y direction) of the polarizing element 1 according to this embodiment as the longitudinal direction. A grid-like uneven structure is formed when the plurality of protruding ridges 22 are arranged at a predetermined pitch in the X direction and at a predetermined interval from each other.

[0079] Here, as shown in Figure 1, in the longitudinal section (XZ section) perpendicular to the reflection axis direction (Y direction) of the polarizing element 1, the pitch P of the convex portion 22 in the transmission axis direction (X direction) must be shorter than the wavelength of light in the usable band. This is to obtain the polarization effect described above. More specifically, the pitch P of the convex portion 22 is preferably 50 to 300 nm, more preferably 100 to 200 nm, and particularly preferably 100 to 150 nm, from the viewpoint of balancing ease of manufacturing of the convex portion 22 with polarization characteristics.

[0080] Furthermore, as shown in Figures 1 and 2, the width W of the bottom of the protruding portion 22 in the longitudinal section (XZ section) is also shown. BAlthough not particularly limited, from the viewpoint of achieving both ease of manufacture and polarization characteristics, it is preferably about 10 to 150 nm, more preferably about 10 to 100 nm. Further, the width W of the top of the convex stripe portion 22 T Although not particularly limited, from the viewpoint of achieving both ease of manufacture and polarization characteristics, it is preferably about 5 to 60 nm, more preferably about 10 to 30 nm.

[0081] Incidentally, the width W of the bottom of the convex stripe portion 22 B and the width W of the top T can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, by observing a cross-section (XZ cross-section) orthogonal to the absorption axis direction or the reflection axis direction of the polarization element 1 using a scanning electron microscope or a transmission electron microscope, for any four convex stripe portions 22, the width of the convex stripe portion 22 at the height position 20% above the height H of the convex stripe portion 22 from the bottom of the convex stripe portion 22 is measured, and the arithmetic mean value thereof can be taken as the width W of the bottom of the convex stripe portion 22 B . Further, for the any four convex stripe portions 22, the width of the convex stripe portion 22 at the height position 20% below the height H of the convex stripe portion 22 from the tip 22a of the convex stripe portion 22 is measured, and the arithmetic mean value thereof can be taken as the width W of the top of the convex stripe portion 22 T .

[0082] Also, as shown in FIG. 1, the height H of the convex stripe portion 22 in the longitudinal cross-section (XZ cross-section) is not particularly limited, but from the viewpoint of achieving both ease of manufacture and polarization characteristics, it is preferably about 50 to 350 nm, more preferably about 100 to 300 nm. Incidentally, the height H of the convex stripe portion 22 can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, by observing a cross-section orthogonal to the absorption axis direction or the reflection axis direction of the polarization element 1 using a scanning electron microscope or a transmission electron microscope, for the convex stripe portions 22 at any four locations, the height of the convex stripe portion 22 at the center position in the width direction of the convex stripe portion 22 is measured, and the arithmetic mean value thereof can be taken as the height H of the convex stripe portion 22.

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

[0084] Figure 3 shows a specific example of the tapered shape of the protruding portion 22 according to this embodiment. As shown in Figure 3, the cross-sectional shape of the protruding portion 22 in the longitudinal section (XZ section) can be a variety of shapes, such as a trapezoid, triangle, bell shape, ellipse, or rounded wedge shape, where the width W narrows as it moves away from the base portion 21, as long as it is the tapered shape described above. For example, the cross-sectional shape of the protruding portion 22A shown in Figure 3 is trapezoidal (tapered), the cross-sectional shape of the protruding portion 22B is triangular, the cross-sectional shape of the protruding portion 22C is bell-shaped, and the cross-sectional shape of the protruding portion 22D is a wedge shape with rounded top and bottom. Thus, the tapered shape of the protruding portion 22 makes it easier to form a reflective film 30 that covers part of the tip 22a and side surface 22b of the protruding portion 22, thereby imparting polarization characteristics to the polarizing element 1. Furthermore, since this tapered shape can also be formed by nanoimprinting, it is advantageous in terms of ease of manufacturing.

[0085] Furthermore, because the protruding portions 22 have tapered or narrowing shapes, the refractive index of the grid structure 20 gradually changes. Therefore, similar to the moth-eye structure, an anti-reflection effect of incident light can be obtained due to the change in the physical refractive index of the grid structure 20. Thus, it can be expected that the reflectivity on the surface of the protruding portions 22 of the grid structure 20 can be reduced, and the transmittance of the grid structure 20 can be improved.

[0086] Figure 4 also shows a specific example of the shape of a recess 24 formed between mutually adjacent protrusions 22, 22. The recess 24 is a groove extending in the longitudinal direction (Y direction) of the protrusions 22. As shown in Figure 4, the cross-sectional shape of the recess 24 in the above longitudinal section (XZ section) can be various shapes as long as the width narrows towards the bottom of the recess 24. For example, the cross-sectional shape of recess 24A shown in Figure 4 is trapezoidal (tapered), the cross-sectional shape of recess 24B is triangular (V-shaped), the cross-sectional shape of recess 24C is a roughly rectangular shape with a flat bottom, and the cross-sectional shape of recess 24D is a U-shape with a rounded bottom. The shape of these recesses 24 can be appropriately selected considering productivity, such as release properties 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 known organic materials can be used. For example, from the standpoint of ensuring transparency and being easy to manufacture, it is preferable to use various thermosetting resins, various UV-curable resins, etc., as the material for the grid structure 20.

[0088] Furthermore, from the standpoint of ease of manufacturing and manufacturing cost, it is preferable to use a different material for the grid structure 20 than for the substrate 10. In addition, if the materials of the grid structure 20 and the substrate 10 are different, their refractive indices will be different. For this reason, if this affects the refractive index of the entire polarizing element 1, 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 constituting the grid structure 20. Epoxy polymerizable compounds are monomers, oligomers, or prepolymers having one or more epoxy groups in their molecules. Examples of epoxy polymerizable compounds include various bisphenol-type epoxy resins (bisphenol A type, F type, etc.), 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 their prepolymers.

[0090] Acrylic polymerizable compounds are monomers, oligomers, or prepolymers having one or more acrylic groups in their molecule. Here, monomers are further classified into monofunctional monomers having one acrylic group in their molecule, difunctional monomers having two acrylic groups in their molecule, and polyfunctional monomers having three or more acrylic groups in their molecule.

[0091] Examples of "monofunctional monomers" include carboxylic acids (such as acrylic acid), hydroxyls (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). Examples include acrylate, N,N-dimethylaminopropylacrylamide, 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, and 2-ethylhexyl acrylate.

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

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

[0094] Furthermore, examples of curing initiators for the curable resins mentioned above include thermosetting initiators and photocuring initiators. The curing initiator may also cure using some energy ray other than heat or light (e.g., an electron beam). If the curing initiator is a thermosetting initiator, the curable resin is a thermosetting resin, and if the curing initiator is a photocuring initiator, the curable resin is a photocurable 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-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, and 2-hydroxy-2-methyl-1-phenylpropane-1-one. Therefore, it is preferable that the curable resin is an ultraviolet curable resin. Furthermore, from the viewpoint of transparency, it is even 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 can form the base portion 21 and the raised portion 22 described above. For example, a method for forming unevenness by photolithography or imprinting can be used. Among these, it is preferable to form the base portion 21 and the raised portion 22 of the grid structure 20 by imprinting, from the viewpoint of being able to form the uneven pattern quickly and easily, and furthermore, to be able to reliably form the base portion 21.

[0097] When forming the base portion 21 and the raised portion 22 of the grid structure 20 by nanoimprint, for example, after applying the material for forming the grid structure 20 (grid structure material) onto the substrate 10, a master plate with the uneven surface is pressed against the grid structure material, and the grid structure material can be cured by irradiating it with ultraviolet light or applying heat in that state. This makes it possible to form a grid structure 20 having the base portion 21 and the raised portion 22.

[0098] <2.3. Reflective Coating (Functional Coating)> As shown in Figures 1 and 2, the polarizing element 1 according to this embodiment includes a reflective film 30 formed on the convex portion 22 of the grid structure 20.

[0099] As shown in Figure 1, the reflective film 30 is formed to cover a portion of the tip 22a and side surface 22b of the protruding portion 22 of the grid structure 20. Furthermore, as shown in Figure 1, the reflective film 30 is formed to extend along the longitudinal direction (Y direction) of the protruding portion 22 of the grid structure 20. As a result, the reflective film 30 can reflect light that has an electric field component in a direction parallel to the longitudinal direction of the protruding portion 22 (reflection axis direction: Y direction) of the light incident on the polarizing element 1.

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

[0101] The reflective film 30 may be a single layer made of the above-mentioned metal, or a multilayer film made of multiple metal films. Furthermore, the reflective film 30 may 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. Common materials such as SiO2, Al2O3, MgF2, and TiO2 can be used for the dielectric film. The refractive index of the dielectric film is preferably greater than 1.0 and 2.5 or less. Since the optical properties of the reflective film 30 are also affected by the surrounding refractive index, the polarization characteristics may be controlled by the material of the dielectric film.

[0102] <2.4. Special shapes of raised sections and reflective films> Here, the special shapes of the convex portion 22 of the grid structure 20 and the reflective film 30 in the polarizing element 1 according to this embodiment will be described in detail.

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

[0104] Here, "the state in which the reflective film 30 covers the tip 22a of the protruding portion 22 of the grid structure 20 and the upper side of at least one side 22b" means, for example, as shown in Figures 1 and 5, a state in which both "the tip 22a of the protruding portion 22" and "the upper side of the side 22b connecting the tip 22a of the protruding portion 22 and the base portion 21" are continuously covered by the reflective film 30, while "the lower side of the side 22b" and "the base portion 21" are left exposed without being covered by the reflective film 30. In this state, the reflective film 30 does not cover the entire side 22b of the protruding portion 22 (all side 22b from the tip 22a of the protruding portion 22 to the base portion 21).

[0105] Furthermore, the surface of the reflective film 30 covering the tip 22a and the upper side of at least one side 22b of the protruding portion 22 (hereinafter sometimes referred to as the "top of the protruding portion 22") has a rounded and curved shape (for example, a vertically elongated, roughly elliptical shape) and bulges in the width direction (X direction) of the protruding portion 22. Thus, 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 covering the top of the protruding portion 22 in this manner. MAX The width W of the bottom of the protruding ridge 22 is B That's all. Furthermore, W MAX is, W B It is preferable that it be larger than this.

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

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

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

[0109] In the following explanation, the convex structure formed by combining the raised ridges 22 and the reflective film 30 will be referred to as a "grid," and the height of this convex structure (i.e., the grid) will be referred to as the "grid height." Furthermore, the maximum width W of the reflective film 30 covering the raised ridges 22 will also be used. MAX "Grid maximum width W MAX This refers to the width W of the bottom of the convex ridge 22. B "Grid bottom width W B It is sometimes referred to as "[...]." Also, the width W of the top of the convex ridge 22. T The width of the top of the convex part W T The width of the central position in the height direction of the protruding ridge 22 is sometimes referred to as the "central width of the protruding ridge."

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

[0111] As described above, in the grid structure 20 according to this embodiment, a tapered protrusion 22 and a reflective film 30 are formed that cover only the tip 22a and the upper side of the side surface 22b of the protrusion 22. The lower side of the side surface 22b of the protrusion 22 is not covered by the reflective film 30 and is left open.

[0112] As a result, the cross-sectional shape of the raised portion 22 covered by 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 raised portion 22 where the reflective film 30 is located (for example, the maximum grid width W) MAX ) is large, and the horizontal width of the portion from the center to the bottom of the exposed protrusion 22 that is not covered by the reflective film 30 (for example, the width W of the bottom of the exposed protrusion 22) B The size of the protrusions is reduced. The cross-sectional shape of the entire convex structure (i.e., the "grid") composed of the protrusions 22 and the reflective film 30 is constricted inward at a position directly below the lower end of the curved reflective film 30, and has a constricted portion where the width in the X direction is narrowed. This special cross-sectional shape of the grid can be likened to the shape of a tree. Specifically, the round, widely spreading leaves of the tree correspond to the part of the reflective film 30 that covers the top of the protrusions 22, the trunk of the tree corresponds to the lower part of the protrusions 22 that is not covered by the reflective film 30, and the ground on which the tree grows corresponds to the base part 21. Therefore, in the following explanation, the special cross-sectional shape of the grid composed of the protrusions 22 and the reflective film 30 of the grid structure 20 described above will be referred to as the "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 described above. As a result, for example, when light incident on the polarizing element 1 from an oblique direction, the effective grid width W A The gap width W becomes smaller. G This becomes larger. Here, the effective grid width W A This is the width of the reflective film 30 in the direction perpendicular to the obliquely incident light. Gap width W G This is the gap between the reflective films 30, 30 of two adjacent grids, and is the width of the gap in a direction perpendicular to the obliquely incident light. Effective grid width W AThe larger the gap width W, the more easily obliquely incident light is reflected by the reflective film 30 and less likely to reach the transparent convex portion 22 or base portion 21. Therefore, the transmittance of obliquely incident light decreases in the polarizing element 1. On the other hand, the gap width W G The larger the angle, the easier it is for obliquely incident light to pass between two adjacent reflective films 30, 30 and reach the transparent convex portion 22 or 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 special tree shape described above, the gap width W for obliquely incident light is G As the aperture becomes larger, obliquely incident light can pass through the gaps between the round reflective films 30, 30 and reach the transparent grid structure 20, where it is easily transmitted. Therefore, the transmission axis transmittance Tp of obliquely incident light is high, resulting in excellent transmittance and polarization separation characteristics (Tp × Rs characteristics) for obliquely incident light. Furthermore, a good balance can be achieved between the reflection function of obliquely incident light by the reflective film 30 and the transmission function of obliquely incident light by the grid structure 20, further improving the polarization separation characteristics for obliquely incident light.

[0115] <2.5. Methods and Specific Examples of Reflective Film Formation> Now, with reference to Figure 5, the method for forming the reflective film 30 will be described.

[0116] As a method for forming the reflective film 30 such that it covers the tip 22a and part of both sides 22b of the protruding portion 22 of the grid structure 20, it is preferable to form the reflective film 30 by alternately sputtering or depositing from an oblique direction (film deposition incidence angle φ) to the protruding portion 22 of the grid structure 20, as shown in Figure 5. This makes it possible to form the reflective film 30 so as to cover and enclose the upper side of the tip 22a and both sides 22b of the protruding portion 22. The film deposition incidence angle φ for forming the reflective film 30 by sputtering or depositing is not particularly limited, but for example, it can be about 5 to 70° with respect to the surface of the substrate 10.

[0117] As described above, in this embodiment, a grid structure 20 made of a transparent material is formed, and then a reflective film 30 made of a metallic material is formed by sputtering or vapor deposition. This makes it easy to change the film formation conditions, materials, and film thickness of the reflective film 30. It also easily accommodates cases where the reflective film 30 is a multilayer film. Therefore, by combining metals, semiconductors, and dielectrics, it becomes possible to design films that utilize interference effects, and there is no need to consider the material composition that can be etched when forming the reflective film 30 by etching, as in conventional technology. This makes it easy to adjust the reflectance of polarized waves parallel to the grid structure 20 and to adjust the transmittance (transmittance amount) of polarized waves perpendicular to the grid. In addition, since the reflective film 30 is formed after the grid structure 20 is formed, there is no need for equipment such as a vacuum dry etching apparatus, and there is no need to prepare complex processes or safety devices such as gases and abatement devices that match the etching materials. Therefore, running costs such as capital investment and maintenance can be reduced, and cost benefits can be obtained.

[0118] The thickness Dt of the reflective film 30 covering the tip 22a of the protruding portion 22 shown in Figure 5, and the thickness Ds of the reflective film 30 covering the side surface 22b of the protruding portion 22, are not particularly limited and can be appropriately changed according to the shape of the protruding portion 22 of the grid structure 20 and the performance required of the reflective film 30. 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 part of the reflective film 30 covering the side surface 22b of the protruding portion 22, as shown in Figure 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 appropriately selected according to the conditions of the apparatus for forming the reflective film 30 and the performance required of the reflective film 30.

[0120] Figure 6 is a schematic cross-sectional view showing a specific example of the shape of the reflective film 30. As shown in Figure 6, the reflective film 30 may have various shapes, as long as it is curved to enclose the top of the convex 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 various cross-sectional shapes of the protruding portions 22A, 22B, and 22C in a rounded manner, and has a roughly elliptical shape that bulges significantly in the width direction of the protruding portion 22. The reflective film 30B has a curved shape that covers the top of the roughly wedge-shaped protruding portion 22D in a rounded manner. The reflective film 30C also has a curved shape that covers the top of the trapezoidal protruding portion 22A in a rounded manner. The coverage rate Rc of one side surface 22b of the protruding portion 22 by these reflective films 30B and 30C is approximately the same as the coverage rate Rc of the other side surface 22b.

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

[0123] <2.6. Preferred range of coverage Rc of the raised portion by the reflective film> Next, a preferred range for the coverage Rc of the side surface 22b of the raised 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 protruding portion 22 covered by the reflective film 30 to the height (H) of the protruding portion 22 shown in Figures 1 and 5. The coverage ratio Rc is expressed by the following formula (1).

[0125] Rc[%]=(Hx / H)×100 ···(1) H: Height of the convex portion 22 in the Z direction Hx: Height in the Z direction of the portion of the side surface 22b of the protruding part 22 that is covered by the reflective film 30.

[0126] Furthermore, the openness 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 by the reflective film 30 to the height (H) of the protruding portion 22 shown in Figures 1 and 5. The openness ratio Rr is expressed by the following equation (2).

[0127] Rr[%]=((H-Hx) / H)×100 ···(2)

[0128] Based on the above definition, Rr = 100 - Rc. Therefore, when the coverage rate Rc of the side surface 22b of the raised portion 22 by the reflective film 30 is 25% or more and 80% or less, the openness rate Rr of the side surface 22b of the raised portion 22 by the reflective film 30 will be 20% or more and 75% or less.

[0129] As described above, in the polarizing element 1 according to this embodiment, it is preferable that the coverage rate Rc of the side surface 22b of the convex portion 22 by the reflective film 30 is 25% or more and 80% or less (i.e., the openness rate Rr is 20% or more and 75% or less). More specifically, in this embodiment, the reflective film 30 is formed to cover the tip 22a and the upper side of both side surfaces 22b of the convex portion 22, but to leave the lower side of both side surfaces 22b open without covering it. The coverage rate 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) transmitted 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 effect of the reflective film 30 described above can be exhibited more reliably, regardless of the incident angle θ. Therefore, high transmittance of transmitted light can be ensured regardless of the incident angle θ of the obliquely incident light, and the polarization separation characteristics can be improved.

[0131] In contrast, as a comparative example, when the reflective film 30 is formed to cover only the tip 22a of the protruding portion 22 of the grid structure 20, or when it is formed to cover the entire tip 22a and one side surface 22b of the protruding portion 22, the variation in transmittance Tp becomes large depending on the incident 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 incident angle θ. Also, as a comparative example, when the reflective film 30 covers the entire tip 22a and both side surfaces 22b of the protruding portion 22 of the grid structure 20 (when the coverage rate Rc is 100%), the transmittance decreases significantly as the incident angle θ of the obliquely incident light increases.

[0132] Therefore, from the viewpoint of improving the transmittance and polarization separation characteristics of transmitted light, regardless of the incident angle θ of obliquely incident light, it is preferable to cover the tip 22a of the convex portion 22 and a part of at least one side surface 22b (the upper side of the side surface 22b) with the reflective film 30, as in the polarizing element 1 according to this embodiment.

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

[0134] If the coverage ratio Rc is less than 25%, the transmission axis transmittance Tp of P-polarized light passing through the polarizing element 1 decreases, causing variations in transmittance Tp depending on the incident angle θ, and a sufficiently high Tp × Rs value cannot be obtained. For this reason, sufficient transmittance of the transmitted light and polarization separation characteristics expressed as Tp × Rs cannot be obtained for obliquely incident light at a large incident angle θ. On the other hand, if the coverage ratio Rc is greater than 80%, similar to the case where the entire tip 22a and both sides 22b of the protruding portion 22 of the grid structure 20 are covered, the transmission axis transmittance Tp decreases as the incident angle θ of the obliquely incident light increases (for example, 45 to 60°), so the variation in transmittance Tp depending on the incident angle θ becomes large.

[0135] Therefore, the coverage Rc of the side surface 22b of the convex portion 22 by the reflective film 30 is preferably 25% or more and 80% or less. This makes it possible to make the transmission axis transmittance Tp of the second polarization (P polarization) transmitted through the polarizing element 1 75% or more when light is incident on the polarizing element 1 from an oblique direction at an incident angle θ of 45°, for example. As a result, Tp × Rs can be made 70% or more. Thus, even when oblique incident light over a wide range is incident at a large incident angle θ, the transmittance of the second polarization (P polarization) 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 oblique incident light into the first polarization (S polarization) and the second polarization (P polarization).

[0136] From a similar viewpoint, it is more preferable that the coverage Rc is 30% or more and 70% or less (i.e., the openness Rr is 30% or more and 70% or less). This allows for a high transmittance Tp of 80% or more and a high Tp×Rs of 72% or more under the above oblique incidence conditions. Furthermore, it is more preferable that the coverage Rc is 30% or more and 60% or less (i.e., the openness Rr is 40% or more and 70% or less). This allows for a high transmittance Tp of 83% or more and a high Tp×Rs of 75% or more under the above oblique incidence conditions. Moreover, it is even more preferable that the coverage Rc is 40% or more and 50% or less (i.e., the openness Rr is 50% or more and 60% or less). This allows for a very high transmittance Tp of 85% or more and a very high Tp×Rs of 77% or more under the above oblique incidence conditions.

[0137] Furthermore, regarding the reflectance axis Rs, it is preferable that the coverage Rc is 20% or more. This allows for a high reflectance Rs of 85% or more under the above-mentioned oblique incidence conditions.

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

[0139] <2.7. Suitable range of Tp × Rs> Next, we will describe a suitable range for "Tp × Rs," which is an index representing the polarization separation characteristics of the wire grid polarizing element 1 according to this embodiment.

[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 serves as an indicator of the polarization separation characteristics of the wire grid polarizing element 1. Tp×Rs[%]=(Tp[%] / 100)×(Rs[%] / 100)×100

[0141] As described above, the transmission axis transmittance (Tp) is the transmittance of a second polarization (P polarization) 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 a first polarization (S polarization) having an electric field component parallel to the reflection axis (Y direction) of the polarizing element 1.

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

[0143] S-polarized light in the direction of the reflection axis is mainly 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 axial reflectance (Rs). The axial reflectance (Rs) represents the proportion of S-polarized light that is reflected by the polarizing element 1 out of the S-polarized light incident on the polarizing element 1. The axial transmittance (Rp) represents the proportion of S-polarized light that is transmitted through the polarizing element 1 out of the S-polarized light that is incident on the polarizing element 1.

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

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

[0146] Here, we will describe a preferred range for the value of Tp×Rs according to this embodiment. Consider the 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). In the case of such oblique incident 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 display device to which the polarizing element is applied will have poor light utilization efficiency, resulting in insufficient brightness of the displayed image and poor visibility. In contrast, if Tp×Rs is 70% or more, the display device to which the polarizing element 1 is applied will have improved light utilization efficiency, ensuring sufficient brightness of the displayed image and improving visibility.

[0148] Furthermore, it is more preferable that Tp×Rs be 72% or higher, even more preferable that it be 75% or higher, and particularly preferable that it be 80% or higher. This further improves the light utilization efficiency as described above, as well as the brightness and visibility of the displayed image.

[0149] <2.8. Preferred range for the height H of the protruding 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 of the convex portion 22 of the grid structure 20 (see Figures 1 and 3, etc.) is preferably 160 nm or more, more preferably 180 nm or more, and particularly preferably 220 nm or more. This results in a high transmission axial transmittance Tp, excellent Tp × Rs characteristics, and high contrast CR of the transmitted light.

[0150] Specifically, regarding transmittance, if the height H of the convex 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 even 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, regarding the Tp×Rs characteristics required for a polarizing beam splitter (PBS), if the height H of the convex portion 22 is 160 nm or more, an excellent Tp×Rs of 70% or more can be obtained. Moreover, if H is 180 nm or more, a Tp×Rs of 75% or more can be obtained, which is even 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, regarding the contrast CR of the transmitted light (CR = Tp / Ts), the height H of the convex portion 22 should be 100 nm or more, but if H is 160 nm or more, an excellent contrast CR of 150 or more can be obtained. Moreover, if H is 180 nm or more, an excellent CR of 250 or more can be obtained, which is even 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, in order to improve the various characteristics of the polarizing element 1 (Tp, Tp×Rs, CR), especially Tp, it is preferable that the height H of the raised portion 22 be larger. The reason for this is thought to be as follows: When the deposition incidence angle φ (see Figure 5) is the same when the reflective film 30 is deposited on the raised portion 22 by sputtering or vapor deposition, the lower the height H of the raised portion 22, the greater the coverage Rc by the reflective film 30. When the coverage Rc is large, the area of ​​the raised portion 22 covered by the reflective film 30 becomes wider, so P-polarized light is less likely to pass through the grid structure 20, and the transmittance Tp decreases. Therefore, under the condition that the deposition incidence angle φ is the same, it is preferable to increase the height H of the raised portion 22 to reduce the coverage Rc and increase the transmittance Tp.

[0154] <2.9. Preferred range for the tip thickness Dt of the 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 tip 22a of the protruding portion 22 of the grid structure 20 (thickness Dt of the tip of the reflective film 30: see Figure 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 reflectance Rs and transmittance Tp of obliquely incident light will be 85% or more, resulting in high transmittance. Furthermore, considering the Tp characteristics and the Tp × Rs characteristics required for a polarizing beam splitter, it is more preferable that Dt be 15 nm or more.

[0156] <2.10. Preferred range for the side thickness Ds of the functional film (reflective film)> Furthermore, the thickness Ds of the reflective film 30 covering the side surface 22b of the protruding portion 22 of the grid structure 20 (side surface thickness Ds of the reflective film 30: see Figure 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 results in a high transmission axial transmittance Tp, excellent Tp × Rs characteristics, and high contrast CR of transmitted light.

[0157] Specifically, regarding transmittance, if 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 will be 80% or more, resulting in high transmittance. Furthermore, if Ds is 12.5 nm or more and 25 nm or less, a Tp of 85% or more can be obtained, which is even more preferable.

[0158] Furthermore, regarding reflectivity, if the side thickness Ds of the reflective film 30 is 10 nm or more, the axial reflectivity Rs of obliquely incident light will be 80% or more, resulting in high reflectivity. Moreover, if Ds is 12.5 nm or more, an Rs of 85% or more can be obtained, which is even more preferable.

[0159] Furthermore, 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. Moreover, if Ds is 15 nm or more and 25 nm or less, a Tp×Rs of 76% or more can be obtained, which is even more preferable.

[0160] Furthermore, regarding the contrast CR of transmitted light (CR = Tp / Ts), the side thickness Ds of the reflective film 30 should 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. Moreover, if Ds is 15 nm or more, a CR of 100 or more can be obtained, which is even more preferable.

[0161] <2.11. Uneven distribution of reflective coatings> Furthermore, in the polarizing element 1 according to this embodiment, the reflective film 30 covering the convex portion 22 may be unevenly distributed to one side of the convex portion 22, resulting in an asymmetrical shape in the width direction (X direction) of the convex portion 22. Specifically, the reflective film 30 may be unevenly distributed to one side 22b of the convex portion 22 by changing the side thickness Ds and coverage ratio Rc of the reflective film 30 between one side 22b and the other side 22b of the convex portion 22. In other words, the reflective film 30 may be thicker and wider covering one side 22b of the convex portion 22, and thinner and narrower covering the other side 22b.

[0162] When the reflective film 30 is distributed unevenly to one side of the protruding portion 22 in this manner, it is preferable that the difference between the transmission axis transmittance Tp(+) of incident light with an incident angle of +θ (+30° to +60°) relative to the polarizing element 1 and the transmission axis transmittance Tp(-) of incident light with an incident angle of -θ (-30° to -60°) is within 3%. It is preferable to adjust the thickness Ds and coverage Rc of the reflective film 30 covering one side 22b and the other side 22b of the protruding portion 22, respectively, so that the difference between Tp(+) and Tp(-) is within 3%, thereby appropriately distributing the reflective film 30 unevenly to one side of the protruding portion 22.

[0163] Note that an incidence angle of +θ means that obliquely incident light is incident on the convex portion 22 from a direction inclined to one side in the X direction (the width direction of the convex portion 22). On the other hand, an incidence angle of -θ means that obliquely incident light is incident on the convex portion 22 from a direction inclined to the other side in the X direction.

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

[0165] Specifically, regarding transmittance, even when the reflective film 30 is unevenly distributed to one side, the transmission axis transmittance Tp of obliquely incident light with incident angles θ of +45° and -45° becomes 85% or more, resulting in high transmittance.

[0166] Furthermore, regarding reflectivity, even when the reflective film 30 is unevenly distributed to one side, the axial reflectivity Rs of obliquely incident light at incident angles θ of +45° and -45° becomes 85% or higher, resulting in high reflectivity.

[0167] Furthermore, regarding 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, resulting in 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 to one side. Moreover, from the viewpoint of improving contrast, it is preferable that the thinner of the thicknesses Ds of the reflective film 30 covering one side 22b and the other side 22b of the convex portion 22 is 5 nm or more (its coverage Rc is 22% or more), and it is more preferable that the thickness Ds of the thinner reflective film 30 is 10 nm or more (its coverage 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, grid structure 20, and reflective film 30 described above.

[0170] For example, as shown in Figure 7, it is preferable that the polarizing element 1 further comprises a protective film 40 formed to cover at least the surface of the reflective film 30. More specifically, as shown in Figure 7, it is more preferable that the protective film 40 covers the entire surface of the grid structure 20. That is, it is more preferable that the protective film 40 is formed to cover the entire surface of the side surface 22b of the raised portion 22 of the grid structure 20 and the base portion 21, as well as the surface of the reflective film 30. By forming such a protective film 40, the scratch resistance, stain resistance, and water resistance of the polarizing element 1 can be further enhanced.

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

[0172] The material constituting the protective film 40 is not particularly limited as long as it can enhance the scratch resistance, stain resistance, and water resistance of the polarizing element 1. Examples of materials constituting the protective film 40 include films made of dielectric materials, and more specifically, inorganic oxides, silane-based water-repellent materials, etc. Examples of inorganic oxides include Si oxides and Hf oxides. The silane-based water-repellent material may contain a fluorine-based silane compound such as perfluorodecyltriethoxysilane (FDTS), or it may contain 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. Including an inorganic oxide in the protective film 40 can further enhance the scratch resistance of the polarizing element, and including a fluorine-based water-repellent material can further enhance the antifouling and waterproofing properties of the polarizing element.

[0174] The protective film 40 only needs to be formed to cover at least the surface of the reflective film 30, but it is more preferable that it be formed to cover the entire surface of the grid structure 20 and the reflective film 30, as shown in Figure 7. In this case, for example, as shown in the upper part of Figure 7, the protective film 40 may cover the end face of the grid structure 20 (the end face of the base portion 21), or as shown in the lower part of Figure 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 Figure 8, the protective film 40 can also be formed 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. By covering the outermost surface of the grid structure 20 or the polarizing element 1 with a protective film 40 made of inorganic oxide in this way, the thermal resistance R of the entire polarizing element 1 can be further reduced, thereby further improving the heat dissipation performance of the polarizing element 1.

[0175] Furthermore, in this embodiment, it is preferable that a heat dissipation member 50 is provided so as to surround the substrate 10, as shown in Figure 9. This heat dissipation member 50 allows for more efficient dissipation of heat transferred from the substrate 10. Here, the heat dissipation member 50 is not particularly limited as long as it is a material with high heat dissipation effect. The heat dissipation member 50 may be, for example, a heat sink, heat spreader, die pad, heat pipe, metal cover, or housing.

[0176] <2.13. Image of the actual grid structure> Next, with reference to Figure 10, an example of actually fabricating the polarizing element 1 according to this embodiment and taking magnified images using a scanning electron microscope (SEM) will be described. Figure 10A is an SEM image of the grid structure 20 before it is covered with the reflective film 30, viewed from an oblique direction. Figure 10B is an SEM image showing a cross-section of the raised portion 22 of the grid structure 20 before it is covered with the reflective film 30. Figure 10C is an SEM image showing a cross-section of the raised portion 22 of the grid structure 20 after it has been covered with the reflective film 30.

[0177] As shown in Figures 10A and 10B, the grid structure 20 has a base portion 21 provided along the surface of the substrate 10 and protruding ridges 22 projecting from the base portion 21. The multiple protruding ridges 22 are arranged at approximately equal pitches P. Each protruding ridge 22 has a tapered shape, becoming narrower in width as it moves away from the base portion 21. The width W of the top of the protruding ridge 22 T The width W of the bottom of the protruding ridge 22 is B It is narrower than that. The pitch P is the width W of the bottom of the protruding part 22. B It is significantly larger than the pitch P. The height H of the convex ridge 22 is greater than the pitch P. In the example in Figure 10, P = 140 nm, W T =10nm, W B The wavelength is 30 nm and H = 220 nm. Also, as shown in Figure 10C, the reflective film 30 is formed so as to cover the tip 22a and both sides 22b of the protruding portion 22. The outer surface of the reflective film 30 is rounded and curved, and bulges in the width direction of the protruding portion 22.

[0178] <3. Method for manufacturing polarizing elements> Next, the manufacturing method of the wire grid polarizing element 1 according to this embodiment will be described with reference to Figure 11. Figure 11 is a process diagram showing the manufacturing method of the wire grid polarizing element 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 consisting of an inorganic material (substrate 10) and an organic material (grid structure 20). The manufacturing method of the hybrid wire grid polarizing element 1 will be described below.

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

[0181] Grid structure material formation process (S10) First, in S10, a grid structure material 23 made of a transparent organic material (e.g., UV-curable resin or thermosetting resin) is laminated onto a substrate 10 made of a transparent inorganic material (e.g., glass) by coating or the like. The inorganic material of the substrate 10 can be any of the materials described above. The organic material of the grid structure 20 can also be any of the materials described above. Furthermore, the film thickness of the grid structure material 23 can be appropriately adjusted according to the dimensions of the base portion 21 and the raised portion 22 of the grid structure 20 formed by nanoimprinting in S20.

[0182] Nanoimprint process (S12) and grid structure formation process (S14) Next, in S12, the grid structure material 23 is subjected to nanoimprinting, thereby forming the grid structure 20 on the substrate 10 in S14. The grid structure 20 is a fine uneven structure in which a base portion 21 provided on the substrate 10 and a plurality of protruding ridges 22 protruding from the base portion 21 are integrally formed. The fine uneven structure is a structure having fine protrusions and recesses, for example, on the order of several nanometers to tens of nanometers.

[0183] In the nanoimprint process of S12, the fine uneven shape of the grid structure material 23 is transferred to the surface of the grid structure material 23 using a master plate 60 on which the inverted shape of the fine uneven shape of the grid structure 20 is formed (S12). As a result, an uneven pattern consisting of the base portion 21, the raised portion 22, and the recessed portion 24 is formed on the grid structure material 23. Furthermore, in the nanoimprint process, along with the transfer of the uneven pattern, the grid structure material 23 is cured by irradiating it with energy rays to form the grid structure 20 (S14). For example, if the grid structure material 23 is made of an ultraviolet-curable resin, the ultraviolet-curable resin on which the uneven pattern has been transferred may be cured by irradiating the grid structure material 23 with ultraviolet light using an ultraviolet irradiation device 66. Alternatively, if the grid structure material 23 is made of a thermosetting resin, the thermosetting resin on which the uneven pattern has been transferred may be cured by heating the grid structure material 23 using a heating device 68 such as a heater.

[0184] In steps S12 and S14 described above, the raised ridges 22 of the grid structure 20 are formed, which have a tapered shape that narrows in width as it moves away from the base portion 21. The raised ridges 22 in the example in Figure 11 are trapezoidal (tapered), but they may be any other tapered shape as shown in Figure 3.

[0185] Thus, in this embodiment, since the tapered ridge portion 22 is imprinted in the nanoimprint process S12, the master plate 60 can be easily peeled off from the grid structure material 23, resulting in excellent release properties. Furthermore, the ridge portion 22 of the grid structure 20 can be accurately molded into the desired shape without deformation.

[0186] Reflective film formation process (S16) Next, in S16, a reflective film 30 is formed using a metallic material such as Al or Ag to cover a portion of the raised ridges 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 metallic film (a grid of thin metallic wires) for reflecting incident light that is incident on the grid structure 20 of the polarizing element 1.

[0187] In this reflective film formation step S16, the reflective film 30 is formed as follows: The reflective film 30 is formed so that it covers the tip 22a and the upper side of at least one side 22b of the protruding portion 22, but does not cover the lower sides of both side 22b of the protruding portion 22 and the base portion 21. Furthermore, the reflective film 30 is formed so that the surface of the reflective film 30 covering the protruding portion 22 is rounded and bulges in the width direction of the protruding portion 22. In addition, the maximum width W of the reflective film 30 covering the protruding portion 22 is also formed. MAX (Maximum grid width W) MAX ) is the width W of the bottom of the aforementioned protruding section. B (Grid bottom width W) B A reflective film 30 is formed so that the value is greater than or equal to ).

[0188] As a method for forming such a reflective film 30, for example, sputtering or vapor deposition can be used, as shown in Figure 5. The reflective film 30 is formed by sputtering or vapor deposition of a metal material alternately from an oblique direction onto the raised ridges 22 of the grid structure 20. This makes it possible to suitably form a reflective film 30 of the desired shape so as to roundly cover the tops of the raised ridges 22.

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

[0190] Furthermore, the manufacturing method of the polarizing element 1 according to this embodiment may, if necessary, include a step of forming a protective film 40 that covers the surface of the polarizing element 1 (protective film formation step) after the reflective film formation step S16 shown in Figure 11. It is preferable that the protective film 40 be formed so as to cover the entire surface 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 method for manufacturing the polarizing element 1 according to this embodiment has been described above. By following the steps described above, it is possible to manufacture a polarizing element 1 with excellent polarization characteristics and heat dissipation without increasing the manufacturing cost or complexity of the polarizing element 1.

[0192] Here, in order to compare with the manufacturing method according to this embodiment, a conventional method for manufacturing a wire grid polarizing element will be briefly described with reference to Figure 12.

[0193] As shown in Figure 12, in the conventional method for manufacturing a wire grid polarizing element, first, a metal film 80 is formed on a substrate 10 to create a convex grid shape (S20). In S20, a reflective film, such as a metal film 80 made of aluminum or other material that reflects light in the operating frequency band, is formed on the substrate 10, which is made of an inorganic material such as glass, using sputtering or vapor deposition.

[0194] Next, a resist mask 70 is patterned onto the metal film 80 using photolithography (S22). Then, the metal film 80 is etched using a vacuum dry etching apparatus or the like to form a convex shape made of the metal film 80 (S24). For example, if the etching selectivity ratio between the resist mask 70 and the metal film 80 cannot be obtained at this time, an oxide film such as SiO2 is further deposited on the metal film 80 by sputtering or the like, and the resist mask 70 is formed on top of this using photolithography. After that, the resist mask 70 is peeled off from the metal film 80 (S26), and a protective film 40 made of an SiO2 film or the like is deposited by CVD or the like, and a water-repellent / oil-repellent coating treatment is also performed as needed (S28).

[0195] In addition, the processes S20 to S28 of the conventional manufacturing method described above show the process for fabricating a reflective wire grid polarizing element with a basic configuration. However, if the metal film 80 is a multilayer film, a more complex process is required. Therefore, it is presumed that conventional wire grid polarizing elements fabricated by the process shown in S20 to S28 of Figure 12 will have high manufacturing costs and require a long manufacturing time. Furthermore, when mass-producing polarizing elements, it is necessary to prepare multiple high-precision, expensive etching or photolithography machines to match the production volume in order to form micro-convex shapes smaller than the wavelength of light, and it is predicted that capital investment will be even higher.

[0196] In contrast, the manufacturing method of the polarizing element 1 according to this embodiment (see Figure 11) uses imprint technology such as nanoimprint to form the grid structure 20, so compared to the conventional manufacturing method described above (see Figure 12), it is possible to significantly reduce manufacturing costs, manufacturing time, and capital investment.

[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 Figure 11), but the conditions for nanoimprinting are not particularly limited. For example, as shown in S12 in Figure 11, a replica master plate (or the original master plate) is used as the master plate 60, and while nanoimprinting is performed, UV irradiation or heating is performed on the grid structure material 23 to harden the grid structure material 23 with the uneven pattern imprinted on it. After that, the master plate 60 is released from the hardened grid structure material 23. As a result, the grid structure 20 with the base portion 21 and the raised portion 22 can be formed by transfer.

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

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

[0200] Subsequently, the master disc 60 is obtained by peeling off the resist mask 70 from the master disc metal film 62 (S36). The master disc 60 has a fine uneven structure consisting of a plurality of protrusions 63 and recesses 65 formed on the master disc substrate 61. The fine uneven structure on the surface of the master disc 60 has an inverted shape of the fine uneven structure on the surface of the grid structure 20 of the polarizing element 1. The recesses 65 of the master disc 60 have an inverted shape of the protrusions 22 of the grid structure 20, and the protrusions 63 of the master disc 60 have an inverted shape of the recesses 24 between the protrusions 22, 22 of the grid structure 20.

[0201] Furthermore, the manufacturing method according to this embodiment may optionally include a step (S38) of forming a release film coating 64 on the surface of the fine uneven structure of the master disc 60. By providing a release film coating 64 on the surface of the master disc 60, the master disc 60 can be easily peeled off from the grid structure material 23 after nanoimprinting is performed on the grid structure material 23 in the nanoimprint step (S12) shown in Figure 11, thereby further improving the release properties.

[0202] <4. Projection display device> Next, with reference to Figure 14, a projection display device to which the wire grid polarizing element 1 according to this embodiment is applied will be described.

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

[0204] Here, a projection display device is a device that projects light toward an object and illuminates the object's display surface (projection surface) with the projected light to display a virtual image such as a picture or video. Examples of projection display devices include head-up display devices (HUDs) and projector devices.

[0205] <4.1. Head-Up Display Devices> First, with reference to Figure 14, a head-up display device 100 equipped with a wire grid polarizing element 1 according to this embodiment will be described. Figure 14 is a schematic diagram showing an example of a head-up display device 100 according to this embodiment.

[0206] As shown in Figure 14, the head-up display device 100 according to this embodiment includes the wire grid polarizing element 1 according to this embodiment described above. By including the polarizing element 1 in the head-up display device 100, the polarization characteristics, heat resistance, and heat dissipation can be improved. Conventional head-up displays incorporating polarizing elements have poor heat dissipation, and therefore, considering long-term use and future increases in brightness and magnification, the heat resistance is considered insufficient.

[0207] As shown in Figure 14, the head-up display device 100 comprises a light source 2, a display element 3 that emits a display image, a reflector 4 that reflects the display image onto the display surface 5, and a cover portion 6 provided in the opening of the 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 Figure 14, the polarizing element 1 can be placed between the display element 3 and the reflector 4.

[0208] Here, the head-up display device 100 may be a vehicle-mounted head-up display device. The vehicle-mounted head-up display device displays images on a semi-transparent panel (corresponding to the "display surface 5") such as the windshield or combiner of the vehicle. The vehicle-mounted head-up display device is, for example, an image display device that is installed on the dashboard of a vehicle and projects image light onto the windshield (display surface 5) to display 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). As a result, sunlight may enter in the opposite direction to the direction of emission of the display image and be incident on the display element 3. In the head-up display device 100 according to this embodiment, a reflector 4 is provided to reflect and enlarge the display image in order to meet the requirements for miniaturization and to enlarge the display image. In such cases, in conventional head-up display devices, sunlight incident on the reflector from the outside would be concentrated near the display element, which could cause deterioration or failure of the display element due to heat.

[0210] In contrast, in the head-up display device 100 according to the present embodiment, for the purpose of preventing the incidence of sunlight on the display element 3, the hybrid polarizing element 1 having excellent heat dissipation and heat resistance as described above is provided. This polarizing element 1 can stably exhibit a polarizing function even at a high temperature of about 200°C. Therefore, for example, even in a high-temperature environment such as inside a car in summer, the sunlight incident on the reflector 4 from the outside can be shielded by the polarizing element 1, preventing it from reaching the display element 3, and thus deterioration and failure of the display element 3 can be suppressed.

[0211] Note that the components of the head-up display device 100 shown in FIG. 14 are examples of basic components, and the components of the projection display device are not limited to the example of FIG. 14, and other components can be appropriately provided according to required performance and the like.

[0212] [[ID=*]] Further, by using the polarizing element 1 as a pre-polarizing plate arranged in front of the display element 3, the polarizing element 1 can suppress the incidence of sunlight on the display element 3 while transmitting the display image emitted from the display element 3. Therefore, the heat resistance and durability of the head-up display device 100 can be further enhanced.

[0213] In addition, the arrangement of the wire grid polarizing element in the projection display device is not limited to the example of the arrangement of the polarizing element 1 in the head-up display device 100 shown in FIG. 14, and can be appropriately selected and changed according to the configuration of the projection display device and required performance. For example, although not shown in the figure, the polarizing element 1 can be arranged between the display element 3 and the light source 2. Also, although not shown in the figure, the polarizing element 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 constituted by the polarizing element 1.

[0214] Furthermore, although not illustrated, a heat dissipation member 50 (see FIG. 9) may be provided around the polarizing element 1 installed in the head-up display device 100. By this heat dissipation member 50, the heat dissipation performance of the polarizing element 1 can be further improved, so that the polarization characteristics and heat resistance of the polarizing element 1 can be further improved.

[0215] <4.2. Projection Display Device with Polarizing Beam Splitter> Next, referring to FIGS. 15 to 17, a projection display device using the reflective wire grid polarizing element 1 according to this embodiment as a polarizing beam splitter 230 will be described. Hereinafter, first, matters common to three specific examples of the projection display devices 200A, 200B, and 200C (hereinafter, may also be collectively referred to as "projection display device 200") shown in FIGS. 15 to 17 will be comprehensively described. Thereafter, each specific example shown in FIGS. 15 to 17 will be individually described.

[0216] [[ID=(9]] As shown in FIGS. 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. Note that a retardation compensation plate (not shown) may be installed between the polarizing beam splitter 230 and the reflective liquid crystal display element 240.

[0217] The light source 210 may be a point light source having one light emitting portion, or may be a light source having a plurality of light emitting portions such as LEDs. Also, the light emitted from the light source 210 may be parallel light or diffused light. Therefore, the light of the light source 210 may be incident on the polarizing beam splitter 230 (reflective wire grid polarizing plate) at an incident angle θ within a predetermined range centered at, for example, 45° (for example, in the range of 45° ± 15°).

[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 P polarization or S polarization.

[0219] The polarizing beam splitter 230 is composed of a reflective wire grid polarizer. The reflective wire grid polarizer is an example of the wire grid polarizing element 1 according to this embodiment. The polarizing beam splitter 230 is positioned so that light from the light source 210 is incident at an incident angle θ within a predetermined range including 45°. This predetermined range of incident angles θ is, for example, 45°±15° as described above, i.e., 30° or more and 60° or less.

[0220] For example, in Figures 15 to 17, the polarizing beam splitter 230 is positioned at a 45° inclination with respect to the direction of incidence of the incident light, so that the incident light from the light source 210 is mainly incident on the polarizing beam splitter 230 at an incident angle θ of 45°. Similarly, the polarizing beam splitter 230 is positioned at a 45° inclination with respect to the reflective liquid crystal display element 240 so that the incident light from the reflective liquid crystal display element 240 is mainly incident on the polarizing beam splitter 230 at an incident angle θ of 45°.

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

[0222] When the polarization beam splitter 230 reflects a desired polarization, the polarization beam splitter 230 is positioned such that light containing the polarization to be reflected is incident on its surface (i.e., the uneven surface on the side where the grid structure 20 of the polarization element 1 is formed). For example, as shown in Figure 15, when the polarization beam splitter 230 reflects S-polarized light incident from the PS converter 220, the surface of the polarization beam splitter 230 should be directed toward the PS converter 220 that emits the S-polarized light. On the other hand, as shown in Figure 16, when the polarization beam splitter 230 reflects S-polarized light incident from the reflective liquid crystal display element 240, the surface of the polarization beam splitter 230 should 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 representing a display image. As shown in Figures 15 and 17, the reflective liquid crystal display element 240 may be arranged so that the first polarization (S polarization) 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 polarization (P polarization) transmitted through the polarizing beam splitter 230 is incident on the surface of the reflective liquid crystal display element 240.

[0224] Furthermore, as shown in Figures 15 and 17, the reflective liquid crystal display element 240 reflects and modulates the incident first polarization (S polarization) to emit a second polarization (P polarization) that represents the display image. However, the invention is not limited to this example, and as shown in Figure 16, the reflective liquid crystal display element 240 may also reflect and modulate the incident second polarization (P polarization) to emit a first polarization (S polarization) 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 positioned so that the light representing the display image emitted from the reflective liquid crystal display element 240 is incident on the lens through the polarizing beam splitter 230. For example, as shown in Figures 15 and 17, the lens 250 may be positioned so that the second polarization (P polarization) reflected and modulated by the reflective liquid crystal display element 240 passes through the polarizing beam splitter 230 and is incident on the lens 250. Alternatively, as shown in Figure 16, the lens 250 may be positioned so that the first polarization (S polarization) reflected and modulated by the reflective liquid crystal display element 240 is reflected by the polarizing beam splitter 230 and is incident on the lens 250.

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

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

[0228] As shown in Figure 15, the projection display device 200A according to the first specific example of this embodiment comprises 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 P-polarized and S-polarized components in equal proportions. Therefore, if the polarizing beam splitter 230, which consists of the polarizing element 1, selectively extracts only one of the polarizations, the amount of light is reduced by approximately half. To address this, the PS converter 220 converts the light emitted from the light source 210 into either a first polarization (S-polarization) or a second polarization (P-polarization). This suppresses the reduction in the amount of polarized light extracted by the polarizing beam splitter 230, thereby improving the light utilization efficiency. For example, the PS converter 220 shown in Figure 15 converts the light from the light source 210 into a first polarization (S-polarization).

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

[0231] The projection display device 200A having the above configuration includes a reflective wire grid polarizer plate consisting of the wire grid polarizing element 1 according to this embodiment as the polarizing beam splitter 230. This improves the polarization separation characteristics of the polarizing beam splitter 230 for incident light from oblique angles and incident light with a wide incident angle θ, and also improves the heat dissipation and heat resistance of the polarizing beam splitter 230 and the projection display device 200A.

[0232] In contrast, conventional projection display devices (not shown) equipped with polarizing elements as polarizing beam splitters have poor heat dissipation properties. Therefore, from the standpoint of long-term use, high brightness, and magnified display, their heat resistance is considered insufficient. Furthermore, the incident angle θ of light incident on the polarizing beam splitter is not limited to 45°, but can be any angle within a predetermined range centered on 45° (for example, approximately 45° ± 15°). Thus, even when oblique incident light with a large and wide range of incident angles θ is incident on the polarizing beam splitter, the polarizing beam splitter is required to have the performance to suitably separate oblique incident light into S-polarized and P-polarized light, regardless of the incident angle θ. However, conventional polarizing beam splitters using polarizing elements have poor polarization separation characteristics for the above-mentioned oblique incident light, resulting in poor light utilization efficiency and adverse effects on the image quality of the displayed image, such as brightness unevenness.

[0233] In this regard, the polarization 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 light utilization efficiency of the projection display device 200A can be improved, and brightness unevenness and other issues can be reduced, thereby improving the image quality of the displayed image.

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

[0235] As shown in Figure 16, the projection display device 200B according to the second specific example of this embodiment comprises 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 the light from the light source 210 into the second polarization (P-polarization). The light converted into P-polarization by the PS converter 220 passes through the polarization beam splitter 230 disposed at an inclination of about 45° and is incident on the reflective liquid crystal display element 240. The reflective liquid crystal display element 240 modulates and reflects the second polarization (P-polarization) to generate the first polarization (S-polarization) representing the display image, and emits the first polarization (S-polarization) toward the polarization beam splitter 230. The polarization beam splitter 230 reflects the first polarization (S-polarization) and emits it toward the lens 250 at an emission angle of 45°. The first polarization (S-polarization) is enlarged by the lens 250 and then projected onto a display surface (not shown), and the display image is displayed.

[0237] The projection display device 200B having the above configuration, similar to the above-described projection display device 200A (see FIG. 15), has excellent polarization separation characteristics for obliquely incident light, can improve the light utilization efficiency, reduce luminance unevenness, etc., and improve the image quality of the display image.

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

[0239] In the projection display device 200C, the non-polarized light emitted from the light source 210 is directly incident on the polarization beam splitter 230 disposed at an inclination of about 45°. The polarization beam splitter 230 reflects the component of the first polarization (S-polarization) in the non-polarized light and emits it toward the reflective liquid crystal display element 240 at an emission angle of 45°. On the other hand, among the non-polarized light incident on the polarization beam splitter 230, the component of the second polarization (P-polarization) passes through the polarization beam splitter 230 and is incident on the light absorber 260. Most of this component of the second polarization (P-polarization) is absorbed by the light absorber 260, so it is possible to suppress the unnecessary second polarization (P-polarization) from being incident on other optical systems in the projection display device 200C.

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

[0241] In the projection display device 200C having the above configuration, since a PS converter 220 is not installed, the second polarization (P polarization) component of the unpolarized light emitted from the light source 210 is absorbed by the light absorber 260 and not used for displaying the display image. As a result, the amount of light in the display image is reduced by about half. However, since 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, the cost of the projection display device 200C can be reduced, and the projection display device 200C can be made smaller, which are advantages.

[0242] The above describes a specific example of a projection display device 200 using a reflective wire grid polarizing element 1 as a polarizing beam splitter 230 according to this embodiment. The projection display device is not limited to the specific example 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. Vehicles> Next, a vehicle equipped with a video display device according to this embodiment will be described.

[0244] The vehicle (not shown) according to this embodiment is equipped with a projection display device having the wire grid polarizing element 1 according to this embodiment described above. The vehicle may be any type of vehicle on which the projection display device can be installed, such as a regular passenger car, a light vehicle, a bus, a truck, a racing car, a construction vehicle, or other large vehicle, or it may be any other type of vehicle such as a motorcycle, a train, a maglev train, or an amusement ride.

[0245] In this embodiment, the vehicle can project a display image onto a display surface (for example, the display surface 5 shown in Figure 14) provided on the vehicle using the polarizing element 1 and the projection display device. The display surface is preferably a semi-transparent plate such as the windshield, side windows, rear windows, or combiner of the vehicle. However, the display surface is not limited to these examples, and may be any surface of an object onto which a display image can be projected, such as the surface of various parts, components, or in-vehicle equipment provided on 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 Figure 14, or the projection display device 200 having a polarizing beam splitter 130 shown in Figures 15 to 17. However, it is not limited to these examples, and the projection display device may be any type of image display device that can project or display an image, such as a projector mounted in a vehicle, a car navigation system, or a terminal device with an image display function.

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

[0248] Similarly, even when the projection display device 200 shown in Figures 15 to 17 is installed in a vehicle, the polarizing element 1 used as a polarizing beam splitter 230 can block sunlight from the outside, thus preventing failure or damage to other components such as the reflective liquid crystal display element 240. Furthermore, it can also prevent damage to the polarizing element 1 itself, which has excellent heat dissipation and heat resistance.

[0249] As described above, the projection display device provided in the vehicle according to this embodiment can obtain excellent polarization characteristics (such as sunlight blocking performance and polarization separation characteristics) with 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 projection display device and polarizing element described above, and other conditions can be set and changed as appropriate according to the performance required of the vehicle.

[0251] <6.Protective film> Next, with reference to Figures 7 and 8, and Figure 18, the protective film 40 covering the grid structure 20 and the reflective film 30 (functional film) of the wire grid polarizing element 1 according to this embodiment will be described in more detail. Figure 18 is an enlarged cross-sectional view showing the wire grid polarizing element 1 covered with the protective film 40 according to this embodiment.

[0252] <6.1. Complex structure of grid structures covered with protective film> As shown in Figures 7 and 8 above, the wire grid polarizing element 1 according to this embodiment includes a protective film 40 that covers the entire surface of the wire grid polarizing element 1. The protective film 40 is made of an inorganic material, for example, a dielectric material such as SiO2 or Al2O3. This protective film 40 is formed to cover the entire surface of the grid structure 20 and the reflective film 30. More specifically, the protective film 40 is formed on the entire surface of the polarizing element 1 so as to continuously cover the surface of the exposed portions of the base portion 21 and the raised portion 22 of the grid structure 20, and the surface of the exposed portion of the reflective film 30 that covers the upper side of the raised portion 22. The protective film 40 is made of an inorganic material, for example, an inorganic oxide. The inorganic oxide may be a dielectric material such as SiO2 or Al2O3, or a metal oxide such as Al2O3. Al2O3 is both a dielectric material and a metal oxide. A dielectric material is a material that constitutes a dielectric. Dielectric materials do not conduct direct current but have the property of being polarized by the electric field of alternating current and accumulating electric charge. The dielectric constant of Al2O3 is, for example, about 9.9, while the dielectric constant of SiO2 is, for example, about 3.9.

[0253] By providing such a protective film 40, the surfaces of the grid structure 20 and the reflective film 30 of the polarizing element 1 can be protected. This improves the scratch resistance, stain resistance, and water resistance of the grid structure 20 and the reflective film 30.

[0254] In particular, since the grid structure 20 is formed from organic materials such as resin, it is more susceptible to degradation from heat, light, water, etc., compared to the substrate 10 which is formed from inorganic materials such as glass. By covering the resin grid structure 20 with a protective film 40 made of inorganic material without any gaps, the grid structure 20 can be protected from external heat, air, water, etc. (barrier effect). This suppresses the alteration and degradation of the resin of the grid structure 20 due to heat, air, water, etc. Furthermore, as shown in Figures 7 and 8, by covering the outermost surface of the polarizing element 1 with a protective film 40 made of inorganic oxide, etc., the thermal resistance R of the entire polarizing element 1 can be further reduced, thereby further improving the heat dissipation performance of the polarizing element 1.

[0255] As mentioned 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 and a grid structure 20 made of an organic material. Furthermore, as shown in Figure 18, the grid 41 of the polarizing element 1 according to this embodiment (the entire convex structure including the convex ridges 22 and the reflective film 30) has the special tree shape described above. As a result, complexly shaped valleys 42 are formed between adjacent grids 41, 41. Consequently, the surface of the grid structure 20 of the polarizing element 1 has a complex uneven structure in which multiple convex parts (grids 41) and multiple concave parts (valleys 42) are intertwined.

[0256] The grid structure 20 having such a complex uneven structure, and the protective film 40 covering the grid structure 20, will be explained in more detail with reference to Figure 18.

[0257] As shown in Figure 18, the grid structure 20 is integrally formed with a base portion 21 provided on the substrate 10 and a plurality of protruding ridges 22 projecting from the base portion 21. The grid structure 20 is made of an organic material such as resin, and the substrate 10 is made of an organic material such as glass. The protruding ridges 22 of the grid structure 20 have a tapered shape in which the width in the X direction narrows as they move away from the base portion 21 in the upward direction (Z direction).

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

[0259] Thus, the surface of the reflective film 30 covering the upper side of the protruding portion 22 is rounded and bulges in the width direction (X direction in Figure 1) of the protruding portion 22. The maximum width (W) of the reflective film 30 covering the protruding portion 22 MAX ) is the width (W) of the lower side of the protruding ridge 22. B ) That is all. As shown in Figure 18, the cross-sectional shape of the entire convex structure (i.e., grid 41) composed of the convex ridges 22 and the reflective film 30 has the special tree shape described above. In this special tree shape, there are constrictions 29, 29 located directly below the lower ends on both the left and right sides of the reflective film 30 that covers the convex ridges 22, and the width in the width direction (X direction) of the entire convex structure (i.e., grid 41) is narrowed at the positions of these constrictions 29, 29.

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

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

[0262] The width in the X direction at the top of the valley 42 is narrow, while the width in the X direction at the bottom of the valley 42 is wide. In other words, at the top of the valley 42, the reflective films 30, 30 on both sides bulge out. As a result, the grids 41, 41 on both sides of the top of the valley 42 are close together, making the width of the top of the valley 42 narrow. On the other hand, at the bottom of the valley 42, the lower sides of the sides 22b, 22b of the convex portions 22, 22 on both sides are not covered by the reflective film 30. As a result, the grids 41, 41 on both sides of the bottom of the valley 42 are further apart due to the absence of the reflective film 30, making the width of the bottom of the valley 42 wider. Thus, the cross-sectional shape (XZ section) of the valley 42 has a vase-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 shape. Therefore, the valleys 42 between adjacent grids 41, 41 also become semi-closed spaces with a complex vase shape. Consequently, the surface of the polarizing element 1 has a complex uneven structure consisting of these plurality of grids 41 and plurality of valleys 42. Therefore, it is difficult to cover the entire surface of this complex uneven structure with a protective film 40 of uniform thickness, and the protective film 40 faces the problems described in detail in the next section.

[0264] <6.2. Challenges of protective films> As shown in Figure 18, the protective film 40 continuously covers the entire surface of the complex uneven structure consisting of the multiple grids 41 and the multiple valleys 42. That is, the protective film 40 continuously covers the surface of the grids 41 (i.e., the surface that combines the surface of the reflective film 30 and both sides 22b of the raised ridges 22 that are not covered by the reflective film 30, and the lower sides of 22b) and the bottom surface of the valleys 42 (i.e., the upper surface of the base portion 21). When the entire surface of the grids 41 and valleys 42 of the grid structure 20 is continuously covered with the protective film 40 in this way, it is ideal to deposit a protective film 40 of uniform thickness over the entire surface.

[0265] However, when depositing a protective film 40 on the surface of the grid 41 and valleys 42, the deposition material tends to adhere to the tips of the grids 41 that protrude upward, but has difficulty penetrating into the complex, vase-shaped valleys 42. Therefore, variations in the amount of deposition material tend to occur between the surface of the tips of the grids 41 and the surface of the bottom of the valleys 42. Consequently, depositing an extremely thin protective film 40, on the order of several nanometers to tens of nanometers, with a uniform film thickness across the entire surface of this complex uneven structure consisting of grids 41 and valleys 42 is extremely difficult with existing deposition methods.

[0266] For example, Patent Document 2 (JP 2014-085516) describes forming a coating layer on the surface of a wire grid polarizing plate by sputtering. However, in the sputtering method, the deposition material has strong straight-line properties during deposition, and the adhesion of the deposition material to the fine uneven structure is poor, resulting in reduced uniformity of the film thickness. In particular, in the case of a complex fine uneven structure consisting of the special tree-shaped grid 41 and vase-shaped valleys 42 as in this embodiment, it is extremely difficult to deposit a protective film 40 with a uniform film thickness using the sputtering method. That is, the adhesion of the deposition material to the lower side walls of the special tree-shaped grid 41 (the lower side of the side surface 22b of the convex portion 22) and the bottom surface of the vase-shaped valleys 42 (the upper surface of the base portion 21) is significantly worsened. For this reason, it is extremely difficult to deposit a protective film 40 with a uniform film thickness.

[0267] As described above, it is ideal for the protective film 40 to have a uniform thickness. However, uniformly depositing an extremely thin protective film 40 over the entire surface of the complex micro-uneven structure according to this embodiment is extremely difficult. Therefore, in reality, the thickness of the protective film 40 deposited using existing deposition methods is not uniform, and variations in thickness inevitably occur in the deposited protective film 40.

[0268] In this regard, stably covering the grid structure 20 and the reflective film 30 with a thick protective film 40 enhances the barrier properties of the grid structure 20 and the like. This suppresses the degradation of the resin constituting the grid structure 20 over time due to external heat, light, water, etc., thereby ensuring the reliability (heat resistance and light resistance) of the grid structure 20. However, if the thickness of the protective film 40 is too thick, there is a problem that the optical properties of the polarizing element 1, in particular the transmittance (Tp characteristics) and polarization separation characteristics (Tp×Rs characteristics) of the grid structure will decrease. On the other hand, if the thickness of the protective film 40 is too thin, there is a problem that the resin of the grid structure 20 will degrade due to heat, light, etc., reducing the reliability (heat resistance and light resistance) of the grid structure 20. Thus, there is a trade-off relationship between the optical properties and reliability of the polarizing element 1, depending on the thickness of the protective film 40.

[0269] Therefore, the inventors of this application have made diligent efforts to determine an acceptable range for thickness variations in the protective film 40 that allows for the maintenance of the optical properties of the polarizing element 1 while suppressing the degradation of the resin of the grid structure 20 and improving reliability, when the surface of the grid structure 20, which has a complex micro-uneven structure as shown in Figure 18, is covered with a thin protective film 40 with a thickness of several nanometers to several tens of nanometers. The inventors then conceived of a polarizing element 1 in which the thickness of the protective film 40 is optimized within this acceptable range.

[0270] <6.3. Optimized protective film thickness> Next, with reference to Figure 18, the optimized thickness (film thickness) of the protective film 40 in the wire grid polarizing element 1 according to this embodiment will be described.

[0271] As shown in Figure 18, the protective film 40 of the polarizing element 1 according to this embodiment continuously covers the surface of the reflective film 30 and both sides 22b of the raised ridge portion 22, the lower side of 22b (i.e., the surface of the grid 41), and the surface of the base portion 21 (i.e., the bottom surface of the valley 42). The protective film 40 may be a thin film with a single-layer structure made of a single coating material, or it may be a thin film with a multi-layer laminated 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] As a method for measuring the thickness (film thickness) of the protective film 40, for example, the following measurement method can be used. After preparing a sample of the polarizing element 1 by depositing the protective film 40 over the entire surface of the grid structure 20 in which the raised ridges 22 are covered with the reflective film 30, the cross-section of the sample is observed using a transmission electron microscope (TEM). Next, the data of the cross-sectional image of the sample obtained from this observation is imported into a length measuring application, and the thickness of the protective film 40 is measured. In this case, the thickness of the protective film 40 is measured on multiple grids 41 (for example, three or more) for each sample, and the average of these measured thicknesses 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 method. For example, the thickness (film thickness) of the protective film 40 may be measured when observing a cross-section of the sample using the transmission electron microscope described above. Furthermore, the above measurement method can also be applied to measuring the thickness Tt and Bt of the protective film 40 in each part of the grid 41 described below.

[0275] In this embodiment, the ratio of the thicknesses of the protective film 40, "Bt / Tt", preferably 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 surrounds the raised portion 22. Bt: Thickness of the protective film 40 covering both sides 22b of the raised portion 22, the lower side of 22b, and the surface of the base portion 21. Bt1: Thickness of the protective film 40 covering both sides 22b of the raised portion 22 and the lower side of 22b. Bt2: Thickness of the protective film 40 covering the surface of the base portion 21

[0277] As shown in Figure 18, Tt is the thickness of the protective film 40 that covers the top 30a of the reflective film 30 that covers the tip 22a of the protruding ridge 22 at the tip of the grid 41. In other words, Tt is the thickness of the protective film 40 that covers the metallic material portion (the top 30a of the reflective film 30 made of a metallic material such as Al) at the tip of the grid 41.

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

[0279] Here, Bt is preferably the average value of Bt1 and Bt2 shown in Figure 18. Bt1 is the thickness of the protective film 40 covering the lower side of the side surface 22b of the protruding 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 of forming the protective film 40, Bt1 and Bt2 are considered to be approximately the same thickness (Bt ≈ Bt1 ≈ Bt2). However, in reality, there may be slight differences between Bt1 and Bt2. In this case, it is preferable to take the average value of the measured Bt1 and Bt2 and use that as Bt (Bt = Average(Bt1, Bt2)). By using the average value, the thickness Bt of the protective film 40 covering the exposed resin portion of the grid structure 20 at the bottom of the valley 42 can be determined more accurately. Note that the method for calculating Bt is not limited to the example above; for example, Bt = Bt1 or Bt = Bt2 may also be used.

[0280] In equation (10) above, "Bt / Tt" is the ratio of Bt to Tt. If the value of "Bt / Tt" is 1, then Bt and Tt are the same value, meaning that the thickness Tt of the protective film 40 covering the leading edge of the grid 41 and the thickness Bt of the protective film 40 covering the bottom of the valleys 42 are perfectly uniform. On the other hand, the further the value of "Bt / Tt" is from 1, the larger the difference between Bt and Tt becomes, meaning that there is thickness variation between the thickness Tt of the protective film 40 covering the leading edge of the grid 41 and the thickness Bt of the protective film 40 covering the bottom of the valleys 42.

[0281] By satisfying equation (10) above, the degradation of the resin portion of the grid structure 20 can be suppressed while maintaining the optical properties required for the polarizing element 1 (for example, high Tp characteristics and high Tp×Rs characteristics), thereby improving the reliability (heat resistance, 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 thinner, reducing the barrier properties and thus lowering 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 time or longer, it is preferable that "Bt / Tt" be 0.85 or higher.

[0283] Furthermore, the ratio of the thicknesses of the protective film 40 according to this embodiment, "Bt / Tt", is more preferably satisfied by the following formula (11).

[0284] 0.85 ≤ Bt / Tt ≤ 1.07 ···(11)

[0285] If "Bt / Tt" is greater than 1.07, the thickness Bt of the protective film 40 covering the valleys 42 is too thick, which may cause the valleys 42 to be filled with the protective film 40, potentially degrading the optical properties. Therefore, in order to suppress the filling of the valleys 42 with the protective film 40 and maintain the required optical properties, it is preferable that "Bt / Tt" be 1.07 or less.

[0286] Furthermore, the ratio of the thicknesses of the protective film 40 according to this embodiment, "Bt / Tt", is more preferably satisfied by 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 by the reflective film 30 is protected by the protective film 40, thereby suppressing the deterioration of the organic material portion and further improving the reliability (heat resistance, light resistance) of the grid structure 20.

[0289] As described above, the thickness of the protective film 40 of the polarizing element 1 according to this embodiment preferably satisfies formula (10), more preferably satisfies formula (11), and even more preferably satisfies formula (12). This allows the grid 41 and valleys 42 of the grid structure 20 to be appropriately covered with the protective film 40 when a grid structure 20 having a complex uneven structure as shown in Figure 18 is covered with a thin protective film 40, within the allowable range of thickness unevenness of the protective film 40 necessary to achieve both the optical properties and reliability of the polarizing element 1. This makes it possible to improve the reliability (heat resistance, light resistance) of the polarizing element 1 by suppressing the deterioration of the resin portion of the grid structure 20 while maintaining the required optical properties (Tp characteristics, Tp×Rs characteristics) of the polarizing element 1 when the polarizing element 1 is used, for example, as a polarizing beam splitter.

[0290] Furthermore, since it is not necessary to deposit the protective film 40 with a perfectly uniform thickness, it becomes practically possible to deposit the protective film 40 with thickness variations within the acceptable range using, for example, the ALD method described later.

[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, heat resistance). Examples of materials for the protective film 40 include dielectric materials, inorganic oxides such as metal oxides, silane-based water-repellent materials, and fluorine-based water-repellent materials. Dielectric materials include, for example, Si oxide and Hf oxide. Metal oxides include, for example, Al oxide. Including inorganic oxides in the protective film 40 can further improve the scratch resistance of the polarizing element 1 and the barrier properties that protect the grid structure 20 from heat, light, water, etc. Including water-repellent materials such as fluorine-based water-repellent materials in the protective film 40 can further improve the antifouling and waterproofing properties of the polarizing element 1.

[0293] In particular, the protective film 40 is preferably a single-layer structure made of SiO2. By using SiO2 as the material for the protective film 40, it is possible to coat the surface with a protective film 40 that has high transmittance over a wide wavelength range.

[0294] Furthermore, it is preferable that the protective film 40 has a laminated structure comprising a first layer made of Al2O3 and a second layer made of SiO2. This allows the protective film 40 to combine the high barrier properties of Al2O3 with the high transmittance of SiO2.

[0295] The protective film 40 is not limited to the above examples and may be formed from other inorganic oxides or metal oxides other than SiO2 and Al2O3, or it 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 enhance the antifouling and waterproofing properties of the polarizing element 1.

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

[0297] As described above, the method for manufacturing the wire grid polarizing element 1 according to this embodiment includes a grid structure material formation step (S10) shown in Figure 11, a nanoimprint step (S12), a grid structure formation step (S14), and a reflective film formation step (S16), and may further include a protective film formation step (S18).

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

[0299] In the film formation process (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 technique that utilizes a continuous chemical reaction in the gas phase. The ALD method involves repeatedly introducing and evacuating two or more gas-phase raw materials (precursors) alternately into a reaction chamber, and reacting the raw material molecules adsorbed on the surface of the object to be filmed (the surface to be coated) to form a film. In the ALD method, unlike the CVD method, different types of precursors do not enter the reaction chamber at the same time; instead, the precursors are introduced (pulsed) and discharged (purged) as independent steps. In each pulse, the precursor molecules behave self-regulatingly on the surface to be coated, and the reaction ends when there are no more sites on the surface where adsorption is possible.

[0300] This ALD method has the advantage of enabling extremely thin and uniform film formation compared to the CVD method, as it allows for precise control of film thickness and material at the atomic layer level. Therefore, in the film formation step (S18) according to this embodiment, when forming a protective film 40 over the entire surface of the complex micro-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 micro-uneven structure.

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

[0302] First, the configuration of the chamber 300 used in the film deposition process (S18) of the protective film 40 by the ALD method according to this embodiment will be described. As shown in Figure 19, the chamber 300 forms a processing space for performing the film deposition process by the ALD method described above. A grid structure 20 is arranged 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 gaseous raw materials (e.g., precursors, oxidizers) into the chamber 300. The gas inlet 310 is provided, for example, at the top of the chamber 300. Gases are introduced through the gas inlet 310 by switching between valves (not shown) for the precursor gas, oxidizer gas, and inert gas.

[0304] The jig 320 holds the grid structure 20 in the chamber 300 in a state where the raised ridges 22 are covered with the reflective film 30 (the state before the protective film 40 is formed). As shown in Figure 19, one jig 320 may hold the grid structure. To improve the efficiency of the film formation process, one jig 320 may hold multiple grid structures 20.

[0305] The gas exhaust port 330 is an opening for discharging the gas inside the chamber 300 to the outside of the chamber 300. The gas exhaust port 330 is provided, for example, at the bottom of the chamber 300. An exhaust valve (not shown) is provided at the gas exhaust port 330. The exhaust valve opens or closes the gas exhaust port 330. A vacuum pump 340 is also provided at the gas exhaust port 330. By operating the vacuum pump 340, the gas inside the chamber 300 can be discharged (purged) to the outside through the gas exhaust port 330.

[0306] Next, the film formation process (S18) of 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 Figure 19, the grid structure 20 in a state where the raised ridges 22 are covered with the reflective film 30 (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 gaseous raw material gases for forming the protective film 40 (hereinafter referred to as "precursor gas" and "oxidizing gas," respectively) 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 from the gas inlet 310 (S181: first step). As a result, the introduced precursor gas is adsorbed onto the surface (coating surface) of the grid structure 20 and undergoes a chemical reaction, generating a first atomic layer on the coating surface.

[0310] Next, an inert gas is introduced into the chamber 300 from the gas inlet 310 (S182: second step). This flushes out any excess precursor gas (residual gas) in the chamber 300 with the inert gas, causing the excess precursor gas to be 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 oxidizing agent gas (second precursor gas) is introduced into the chamber 300 from the gas inlet 310 (S183: third step). This causes a chemical reaction between the precursor of the first atomic layer deposited on the coating surface of the grid structure 20 and the introduced oxidizing agent gas, thereby bonding oxygen to the precursor and generating a second atomic layer on top of the first atomic layer.

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

[0313] Subsequently, the process of alternately introducing and exhausting the precursor gas and oxidizing gas into the chamber 300 (S181-S184: steps 1-4) is repeated. This alternately stacks the first and second atomic layers on the surface of the grid structure 20 to be coated, thereby forming a protective film 40 of the desired material.

[0314] For example, when forming a single-layer protective film 40 made of SiO2, alkylaminosilylamine and ozone are used as two types of gas-phase raw materials (precursors and oxidizing agents). Also, when forming a single-layer protective film 40 made of Al2O3, trimethylaluminum (TMA) and water are used as two types of gas-phase raw materials (precursors). Furthermore, when forming a laminated protective film 40 containing a first film layer made of Al2O3 and a second film layer made of SiO2, the first film layer made of Al2O3 is formed first, and then the second film layer made of SiO2 is laminated on top of the first film layer.

[0315] Furthermore, according to the special ALD method for film formation (S18) in this embodiment, the precursor gas introduction step (S181) and the oxidizing gas introduction step (S183) are characterized in that the precursor gas and oxidizing gas are introduced into and filled into the chamber without exhausting them from the chamber 300 to the outside.

[0316] In this regard, in the conventional ALD method for film deposition, the precursor gas and oxidizer gas are introduced into the chamber 300 during the precursor gas and oxidizer gas introduction steps (S181, S183) while the precursor gas and oxidizer gas in the chamber 300 are evacuated.

[0317] In contrast, in the special ALD method film formation process (S18) according to this embodiment, in the precursor gas and oxidizer gas introduction process (S181, S183: first and third processes), the precursor gas and oxidizer gas in the chamber 300 are not exhausted from the gas exhaust port 330, but are continuously introduced into the chamber 300. Specifically, in the precursor gas introduction process (S181: first process), with the exhaust valve of the gas exhaust port 330 closed to seal the chamber 300, the precursor gas is introduced into the chamber 300 from the gas inlet 310, and the precursor gas in the chamber 300 is not exhausted from the gas exhaust port 330. Similarly, in the oxidizer gas introduction process (S183: third process), with the exhaust valve of the gas exhaust port 330 closed to seal the chamber 300, the oxidizer gas is introduced into the chamber 300 from the gas inlet 310, and the oxidizer gas in the chamber 300 is not 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 come into sufficient contact with the surface of the grid structure 20 to be coated. Therefore, the precursor gas and oxidizer gas can be sufficiently introduced into the deepest parts of the vase-shaped vase 42 on the surface of the complex micro-undulation structure consisting of the grid 41 and vase 42 shown in Figure 18, allowing for the proper deposition of the first and second atomic layers of the required thickness. Thus, a protective film 40 of the desired thickness can be deposited not only on the surface of the tip of the grid 41, but also on the surface of the vase-shaped vase 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 30a of the reflective film 30) and the thickness Bt of the protective film 40 covering the bottom of the valley 42 (i.e., the resin portion of the grid structure 20) can be made approximately the same, and a protective film 40 that satisfies the above formula (10) can be formed. As a result, the uniformity of the thickness of the protective film 40 formed by the ALD method according to this embodiment can be further improved compared to the conventional ALD method. Thus, a protective film 40 with even greater uniformity can be formed within the allowable range of thickness unevenness defined by the above formula (10).

[0320] The above describes in detail the film formation process (S18) of the protective film 40 by 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 film formation method for the protective film 40, and the film formation conditions (conditions related to the introduction and discharge of precursor gas and oxidizer gas) in the precursor gas and oxidizer gas introduction process (S181, S183) by the ALD method can be optimized to match the complex fine uneven structure of the grid structure 20.

[0321] This makes it possible to deposit an extremely thin protective film 40, on the order of several nanometers to tens of nanometers, very uniformly across the entire surface of the complex micro-rough structure. Therefore, it becomes possible to deposit an extremely uniform, thin protective film 40 within the allowable range of thickness variation of the protective film 40 as defined by formula (10) above. As a result, the grid structure 20 can be robustly protected by the protective film 40, and the reliability (heat resistance and light resistance) of the polarizing element 1 equipped with the protective film 40 can be improved while maintaining the optical properties of the polarizing element 1.

[0322] In this regard, conventional film deposition methods such as sputtering, vacuum deposition, and CVD make it difficult to properly deposit a protective film on the surface of a complex micro-uneven structure as in this embodiment. For example, in the sputtering method, as mentioned above, the deposition material has high linearity, so the deposition material does not adhere well to parts of the complex micro-uneven structure that are in shadow relative to the direction of the deposition material's movement, making it difficult to deposit a uniform protective film 40. Similarly, in the vacuum deposition method, the deposition material does not adhere well, making it difficult to deposit a uniform protective film 40. Furthermore, in the CVD method, although the deposition material adheres well, the deposition temperature is high, several hundred degrees Celsius or more, causing the resin of the grid structure 20 to soften and destroy the micro-uneven structure.

[0323] In contrast, according to this embodiment, by using the ALD method as the film deposition method, the deposition material adheres well to the fine uneven structure, so the uniformity of the protective film 40 can be greatly improved compared to conventional sputtering and vacuum deposition methods. Furthermore, according to the ALD method of this embodiment, the protective film 40 can be deposited at a low film deposition temperature (e.g., 190°C or less) that is below the heat resistance temperature (e.g., 200°C) of the resin of the grid structure 20. As a result, the resin of the grid structure 20 is less likely to soften during the deposition of the protective film 40, so the fine uneven structure of the grid structure 20 can be maintained. Furthermore, the reliability (heat resistance and light resistance) of the grid structure 20 coated with the protective film 40 can also be greatly improved compared to conventional film deposition methods.

[0324] The conditions for film deposition 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 deposition temperature, whether or not exhaust is used, and the state of the grid structure 20 placed inside the chamber 300. These conditions can be appropriately set to optimal values ​​to satisfy the desired film deposition conditions.

[0325] <7. Reinforcement film> Next, with reference to Figures 25 and 26, the reinforcing film 51 provided between the grid structure 20 and the reflective film 30 (functional film) of the wire grid polarizing element 1 according to this embodiment will be described. Figure 25 is an enlarged cross-sectional view showing the wire grid polarizing element 1 equipped with a reinforcing film 51 that covers the entire grid structure 20 according to this embodiment. Figure 26 is an enlarged cross-sectional view showing the wire grid polarizing element 1 equipped with a reinforcing film 51 that covers a part of the convex portion 22 of the grid structure 20 according to a modified example of this embodiment.

[0326] <7.1. Overview of Reinforcement Films> As described above, the height H of the protruding portion 22 of the grid structure 20 according to this embodiment (see Figures 1, 3, etc.) is preferably as high as possible, for example, preferably 160 nm or more. By increasing the height H of the protruding portion 22, various optical properties required of the wire grid polarizing element 1 (for example, Tp characteristics, Tp×Rs characteristics, contrast (CR)) can be improved.

[0327] However, the ridges 22 of the grid structure 20 according to this embodiment are made of organic materials (such as resin), which have lower strength and heat resistance than inorganic materials (such as glass). Furthermore, the ridges 22 have a tapered shape that becomes narrower towards their tips. For this reason, the ridges 22 made of organic materials have lower rigidity and heat resistance compared to those made of inorganic materials. Consequently, 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 deposited to cover the tip of the ridges 22 by a film deposition method such as vapor deposition or sputtering, the ridges 22 made of organic materials will soften due to the heat and force applied during the deposition of the reflective film 30. For this reason, the ridges 22 may not be able to maintain a tapered shape that extends straight upward (Z direction) and may tilt in the left-right direction (X direction) (see Figure 31). Thus, if the convex portion 22 tilts due to the formation of the reflective film 30 (functional film) covering the convex portion 22, there is a problem that various optical properties required of the wire grid polarizing element 1 (for example, Tp characteristics, Tp×Rs characteristics, CR) will decrease.

[0328] To solve this problem, in the wire grid polarizing element 1 according to this embodiment, as shown in Figures 25 and 26, a reinforcing film 51 is provided between the upper part of the raised portion 22 of the grid structure 20 and the reflective film 30 (functional film), and the upper part of the raised portion 22 is reinforced by the reinforcing film 51. The reinforcing film 51 is made of an inorganic oxide such as a dielectric material and has better rigidity and heat resistance than the resin of the raised portion 22. The reinforcing film 51 is formed to cover at least the upper part of the raised portion 22 and is interposed between the upper part of the resin raised portion 22 and the metallic reflective film 30 such as Al.

[0329] By reinforcing the upper part of the protrusion 22 with the reinforcing film 51, when the reflective film 30 is formed on the upper part of the protrusion 22, it is possible to suppress the tilting of the protrusion 22 in the left-right direction (X direction) due to heat and force acting on the protrusion 22. Therefore, the protrusion 22 can maintain the desired shape extending straight upward (Z direction), and the reflective film 30 supported by the protrusion 22 does not tilt, and the reflective film 30 does not block incident light contrary to the design intent. Thus, the transmission and reflection characteristics of incident light to the wire grid polarizing element 1 can be realized as intended, and the optical properties of the wire grid polarizing element 1 (e.g., Tp characteristics, Tp×Rs characteristics, CR) can be improved.

[0330] Here, referring to Figures 27 to 29, we will explain the principle by which, when the reinforcing film 51 is not provided, the convex portions 22 of the grid structure 20 become tilted or narrowed due to the formation of the reflective film 30.

[0331] As a result of diligent investigation by the inventors of the present invention, it was found that when a reflective film 30 is deposited on the upper part of the raised ridges 22 of the grid structure 20 by vapor deposition or the like, the raised ridges 22 tilt in the left-right direction (X direction) (see Figure 31). One reason for this is thought to be that the raised ridges 22 soften due to the heat generated during the deposition of the reflective film 30. Another reason is thought to be that, because the high-temperature metallic material (such as Al) of the reflective film 30 is deposited on the raised ridges 22 from diagonally above and alternately from left to right (see Figure 5), the accumulation of stress (strain) due to the thermal contraction of the deposited metal film (reflective film 30) acts as a force that tilts the raised ridges 22 towards the deposited side.

[0332] Figures 27 and 28 show the results of a simulation of the deformation behavior of the convex portions 22 of the grid structure 20 and the reflective film 30 during the deposition of the reflective film 30, using models of the convex portions 22 and the reflective film 30. Figure 27 is a schematic diagram showing a model in which the reflective film 30 is deposited alternately from the left and right sides onto the upper part of the convex portions 22. Figure 28 is a schematic diagram showing the simulation results of the deformation behavior of the convex portions 22 using the above model. The shades in Figure 28 indicate the degree of displacement of the convex portions 22 and the reflective film 30 during deposition.

[0333] In the model shown in Figure 27, high-temperature Al is deposited alternately from both the left and right sides onto the upper part of the raised ridge 22. As a result, the reflective film 30 (Al film) is formed so that it covers and encases the upper part of the raised ridge 22 from both sides. In the model shown in Figure 27, for example, 600°C Al is deposited alternately twice on each side in the order of S1 to S4 onto the upper part of the raised ridge 22 (a total of 4 deposition steps).

[0334] As a result of simulating the deformation behavior of the convex portion 22 using this model, it was found that, as shown in Figure 28, stress accumulates due to the thermal contraction of the deposited Al film (reflective film 30), causing the convex portion 22 to deform and tilt toward the deposited side. Specifically, in the first deposition (S1), high-temperature Al was deposited on the right side of the convex portion 22, causing the convex portion 22 to tilt toward the right side where the Al was deposited. Next, in the second deposition (S2), high-temperature Al was deposited on the left side of the convex portion 22, causing the convex portion 22 to return to its straight position. Furthermore, in the third deposition (S3), high-temperature Al was again deposited on the right side of the convex portion 22, causing the convex portion 22 to tilt toward the right again. Subsequently, in the fourth deposition (S4), high-temperature Al was again deposited on the left side of the convex portion 22, causing the convex portion 22 to return to its straight position once more. In the simulation results shown in Figure 28, the raised section 22 returned to its straight shape after the fourth deposition (S4). However, in the actual sample of the product in which an Al film was deposited on the raised section 22, the tilt of the raised section 22 did not return to normal.

[0335] As described above, when Al is deposited onto the raised ridge portion 22 from an oblique upward direction, alternating between left and right, the deposited Al film (reflective film 30) alternates between a high temperature state immediately after deposition and a temperature decrease state during waiting. At this time, the difference in thermal expansion coefficients between the resin of the raised ridge portion 22 and the Al of the reflective film 30 inhibits the contraction of the Al film (reflective film 30), leaving residual stress inside and around the Al film. This residual stress is thought to be one of the causes of the raised ridge portion 22 tilting. In other words, the resin of the raised ridge portion 22 becomes softened by the deposition of high-temperature Al, and when the above-mentioned residual stress is applied to this softened raised ridge portion 22, it is thought that the raised ridge portion 22 tilts so as to curve in either the left or right direction (deposition direction).

[0336] Therefore, conventionally, there has been a need for a technology to improve the optical properties of the polarizing element 1 by solving the problem of the convex portion 22 of the grid structure 20 tilting due to the deposition of such an Al film (reflective film 30).

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

[0338] As described above, when depositing the Al film (reflective film 30), if Al is deposited alternately from the left and right sides from an oblique upward angle onto the protruding portion 22, the deposited Al film (reflective film 30) alternately repeats between a high temperature state immediately after deposition and a temperature decrease state during waiting. At that time, due to the difference in thermal expansion coefficients between the resin of the protruding portion 22 and the Al of the reflective film 30, the contraction of the Al film (reflective film 30) is inhibited, and residual stress remains inside and around the Al film. Let's consider the case when the polarizing element 1 having the reflective film 30 and protruding portion 22 in this state of residual stress is placed in a high-temperature environment. In this case, it was found that due to the softening of the resin of the protruding portion 22 due to the high-temperature environment and the release of residual stress in the Al film, the reflective films 30 on both the left and right sides of the protruding portion 22 deform to close inward, and the protruding portion 22 is sandwiched between the reflective films 30 on both sides, becoming thinner.

[0339] Figure 29 shows the simulation results performed to elucidate the behavior of the convex ridge 22 as it narrows. The shading of the reflective film 30 (Al film) in the upper part of Figure 29 indicates the temperature distribution of the reflective film 30. The shading of the lower part of Figure 29 indicates the amount of deformation of the reflective film 30 (Al film) and the convex ridge 22 in the left-right direction.

[0340] As shown in the upper diagram of Figure 29, a model of the convex portion 22 and the reflective film 30 was prepared. In this model, the inner portion 30 of the deposited Al film (reflective film 30) in This is the portion formed by the first deposition, and the said portion 30 in Assume that the temperature of the film has decreased to room temperature. On the other hand, the outer part 30 of the deposited Al film (reflective film 30) out This is the part formed by the third and subsequent depositions. In other words, the low-temperature part 30 in Outer side of part 30 outAssume that high-temperature Al is deposited. Then, this outer part 30 out When the temperature drops to room temperature, the outer part 30 out It contracts, and consequently the inner part 30 in A contractile force also acts on this inner part 30 in Further inside, the resin of the protruding ridge 22 (with a low coefficient of thermal expansion) causes the inner part 30 in Because the contraction of the Al film (high coefficient of thermal expansion) is hindered, the inner part 30 in Residual stress remains in the direction of contraction.

[0341] Consequently, when the polarizing element 1, which has an Al film (reflective film 30) and a raised portion 22 with residual stress remaining inside as described above, is placed in a high-temperature environment, the resin raised portion 22 softens, and the inner part 30 in The residual stress in the Al film is released, causing the Al film to contract and close inward in the left-right direction. As a result, as shown in the lower diagram of Figure 29, the Al films (reflective film 30) on both sides of the protruding portion 22 deform to close inward in the left-right direction, causing the softened protruding portion 22 to become about 4 nm thinner.

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

[0343] Therefore, there has been a desire to improve the optical properties of the polarizing element 1 by solving the problem of the convex ridges 22 of the grid structure 20 becoming thinner due to residual stress during the deposition of such an Al film (reflective film 30).

[0344] Therefore, in order to solve the problem of the raised ridge portion 22 tilting or becoming thinner as described above, the polarizing element 1 according to this embodiment is newly provided with a reinforcing film 51 that covers the upper part of the raised ridge portion 22, and the raised ridge portion 22 is reinforced by the reinforcing film 51. That is, as shown in Figures 25 and 26, the polarizing element 1 according to this embodiment is provided with a reinforcing film 51 interposed between the upper part of the raised ridge portion 22 of the grid structure 20 and the reflective film 30 (functional film). This reinforcing film 51 covers and reinforces the upper part of the raised ridge portion 22. The reinforcing film 51 is made of an inorganic oxide such as a dielectric material and has superior rigidity and heat resistance compared to the resin raised ridge portion 22. The softening point of the resin of the raised ridge portion 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 raised ridge portion 22 softens due to the deposition of the reflective film 30 at a high temperature, the inorganic oxide of the reinforcing film 51 does not soften.

[0345] Therefore, according to this embodiment, when a reflective film 30 (such as an Al film) is deposited around the upper part of the protruding portion 22 by vapor deposition or the like, the resin protruding portion 22, which is easily softened by heat, is reinforced by a heat-resistant reinforcing film 51, and the protruding portion 22 does not come into direct contact with the hot reflective film 30 that has been deposited. Therefore, even if the protruding portion 22 softens during the deposition of the hot reflective film 30, the reinforcing film 51, which has excellent rigidity and heat resistance, reinforces the protruding portion 22, thus preventing the protruding portion 22 from tilting in the left-right direction (X direction).

[0346] Furthermore, we consider the case where, due to the inhibition of thermal shrinkage of the reflective film 30 during the above-mentioned film formation, residual stress remains within the reflective film 30, and the polarizing element 1 is used in a high-temperature environment, causing the convex portion 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 convex portion 22 and the reflective film 30. Therefore, as shown in Figure 29, even if the reflective film 30 on both the left and right sides of the convex portion 22 tries to deform to close inward in the left-right direction due to residual stress within the reflective film 30, the highly rigid reinforcing film 51 can suppress this deformation. Thus, the problem of the convex portion 22 becoming thinner due to residual stress during the formation of the reflective film 30 can be resolved.

[0347] <7.2. Structure of the reinforcing film> Next, the configuration of the reinforcing film 51 according to this embodiment will be described in more detail with reference to Figures 25 and 26.

[0348] As shown in Figures 25 and 26, the wire grid polarizing element 1 according to this embodiment includes a protective film 40 that covers the entire grid structure 20 and the reflective film 30 (functional film), as well as a reinforcing film 51 that covers the raised portion 22 inside the protective film 40 and the reflective film 30. The reinforcing film 51 is a film for reinforcing the raised portion 22 which is made of an organic material. For this reason, the reinforcing film 51 is made of an inorganic oxide that has higher rigidity than the organic material of the raised portion 22. The reinforcing film 51 is interposed at least between the raised portion 22 covered by the reflective film 30 and the reflective film 30. The reinforcing film 51 covers at least the tip 22a and both sides 22b and the upper side of 22b of the raised portion 22 of the grid structure 20 (hereinafter sometimes referred to as "the upper part of the raised portion 22"). The reflective film 30 (functional film) covers the upper part of the raised portion 22 via the reinforcing film 51, but does not cover both sides 22b of the raised portion 22, the lower side of 22b, or the upper surface of the base portion 21. On the other hand, the protective film 40 covers the entire surface 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 tip 22a and both sides 22b, 22b of the protruding portion 22, and the upper surface of the base portion 21). Therefore, the reinforcing film 51 shown in Figure 25 is interposed between the upper part of the protruding portion 22 and the reflective film 30, as well as between the lower part of the protruding portion 22 and the base portion 21 and the protective film 40. Consequently, the reflective film 30 indirectly covers the upper part of the protruding portion 22 via the reinforcing film 51 and does not directly contact the upper part of the protruding portion 22. Similarly, the protective film 40 indirectly covers the lower part of the protruding portion 22 and the upper surface of the base portion 21 via the reinforcing film 51 and does not directly contact the lower part of the protruding portion 22 and the upper surface of the base portion 21.

[0350] On the other hand, the reinforcing film 51 shown in Figure 26 covers only the upper part of the raised section 22 of the grid structure 20 (the tip 22a and both sides 22b, and the upper side of 22b), and does not cover both sides 22b of the raised section 22, the lower side of 22b, or the upper surface of the base section 21. The coverage area of ​​the upper part of the raised section 22 by the reinforcing film 51 shown in Figure 26 is wider than the coverage area of ​​the upper part of the raised section 22 by the reflective film 30. For this reason, the reinforcing film 51 shown in Figure 26 is interposed between the upper part of the raised section 22 and the reflective film 30. Consequently, the reflective film 30 indirectly covers the upper part of the raised section 22 via the reinforcing film 51 and does not directly contact the upper part of the raised section 22. Furthermore, the reinforcing film 51 shown in Figure 26 is not interposed between both sides 22b of the raised section 22, the lower ends of 22b, and between the base section 21 and the protective film 40. Therefore, the protective film 40 directly contacts and covers both sides 22b of the raised ridge portion 22, the lower ends of the 22b, and the base portion 21.

[0351] As shown in Figures 25 and 26, the reinforcing film 51 only needs to be interposed in the portion of the grid structure 20 between the upper part of the raised ridge portion 22 covered by the reflective film 30 (functional film) and the reflective film 30. In other words, the reinforcing film 51 only needs to cover the upper part of the raised ridge portion 22 covered by the reflective film 30 of the grid structure 20, and may cover other parts of the grid structure 20 (the lower part of the raised ridge portion 22 or the base portion 21) (see Figure 25), or it may not need to cover them at all (see Figure 26).

[0352] By interposing the reinforcing film 51 between the upper part of the protruding portion 22 and the reflective film 30, the upper part of the protruding portion 22 and the reflective film 30 do not come into direct contact. Furthermore, by covering the upper part of the protruding portion 22, which is made of an organic material such as resin, with the reinforcing film 51 made of an inorganic oxide, the reinforcing film 51, which has high rigidity and heat resistance, reinforces the upper part of the protruding portion 22.

[0353] Therefore, when forming the reflective film 30 on the outside of the reinforcing film 51 that covers the upper part of the protruding portion 22, it is possible to suppress the tilting of the upper part of the protruding portion 22, which is covered and reinforced by the reinforcing film 51, in the left-right direction (X direction) due to the heat and stress acting during the film formation. Thus, when forming the reflective film 30, the protruding portion 22 can maintain a tapered shape that extends straight upward (Z direction). Consequently, it is possible to suppress the tilting of the grid 41 of the polarizing element 1 (the entire convex structure combining the protruding portion 22, the reinforcing film 51, and the reflective film 30), and thus suppress the decrease in the Tp characteristics and contrast of the polarizing element 1. As a result, the optical characteristics of the polarizing element 1 (e.g., Tp characteristics, Tp×Rs characteristics, CR) can be improved compared to when the reinforcing film 51 is not provided.

[0354] Furthermore, the reinforcing film 51 shown in Figure 25 covers the entire resin grid structure 20. This allows the reinforcing film 51 to protect the lower part of the raised ridge portion 22 and the upper resin portion of the base portion 21 of the grid structure 20. This also enhances the scratch resistance, stain resistance, and water resistance of the grid structure 20.

[0355] In particular, since the grid structure 20 is formed from organic materials such as resin, it is more susceptible to degradation from heat, light, water, etc., compared to the substrate 10 which is formed from inorganic materials such as glass. By completely 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, etc. (barrier properties). This suppresses the alteration and degradation of the resin of the grid structure 20 due to heat, air, water, etc. Furthermore, as shown in Figure 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 performance of the polarizing element 1.

[0356] <7.3. Material and layer structure of the 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 protruding portion 22 made of organic material. For this reason, the reinforcing film 51 is made of an inorganic oxide that has higher rigidity than the organic material of the protruding portion 22. Preferably, the reinforcing film 51 is made of a dielectric material such as SiO2 or Al2O3. This allows the protruding portion 22 to be suitably reinforced by the reinforcing film 51 made of a dielectric material. When the reinforcing film 51 is formed of a dielectric material, the reinforcing film 51 is made of a thin film made of the dielectric material (for example, an SiO2 thin film or an Al2O3 thin film). However, the reinforcing film 51 may also 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 materials and film formation methods.

[0359] The material of the reinforcing film 51 is not particularly limited as long as it is an inorganic oxide that can reinforce the raised ridges 22 and maintain the optical properties of the polarizing element 1, but it is preferable that it contains a dielectric material or a metal oxide. Dielectric materials include, for example, Si oxide and Hf oxide. Metal oxides include, for example, Al oxide. By including an inorganic oxide in the reinforcing film 51, the scratch resistance of the polarizing element 1 and the barrier properties that protect the grid structure 20 from heat, light, water, etc. can be further enhanced. In addition to the inorganic oxide, the reinforcing film 51 may also contain, for example, a silane-based water-repellent material or a fluorine-based water-repellent material. By including a water-repellent material in the reinforcing film 51, the antifouling and waterproofing properties of the polarizing element 1 can be further enhanced.

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

[0361] For example, the reinforcing film 51 may be a single-layer structure made of SiO2. By using SiO2 as the material for the reinforcing film 51, the raised portions 22 of the grid structure 20 can be covered with a reinforcing film 51 that has high transmittance over a wide wavelength range. Alternatively, the reinforcing film 51 may be a single-layer structure made of Al2O3. By using Al2O3 as the material for the reinforcing film 51, the raised portions 22 of the grid structure 20 can be covered with a reinforcing film 51 that has high barrier properties that protect the grid structure 20 from external heat, air, water, etc.

[0362] Furthermore, the reinforcing film 51 may have a laminated structure including a first layer made of Al2O3 and a second layer made of SiO2. This allows the reinforcing film 51 to combine the high barrier properties of Al2O3 with the high permeability of SiO2.

[0363] The reinforcing film 51 is not limited to the above examples and may be formed from other inorganic oxides or metal oxides other than SiO2 and Al2O3, 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 enhance the antifouling and waterproofing 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 the reinforcing film> Next, with reference to Figures 25 and 26, the thickness Rt (film thickness) of the reinforcing film 51 in the wire grid polarizing element 1 according to this embodiment will be described.

[0365] If the thickness Rt of the reinforcing film 51 is too large, the reflective film 30 covering the reinforcing film 51 will become too thick, which may degrade the optical properties (especially the Tp properties) of the polarizing element 1, and is therefore undesirable. On the other hand, if the thickness Rt of the reinforcing film 51 is too small, the reinforcing performance of the convex portion 22 by the reinforcing film 51 may decrease, which is also undesirable.

[0366] Therefore, the thickness Rt of the reinforcing film 51 is not particularly limited as long as it can ensure the optical characteristics of the polarizing element 1 and the reinforcing performance of the convex rib portion 22. For example, it is preferably 0.5 nm or more and 8 nm or less. Thereby, while ensuring suitable optical characteristics (particularly, Tp characteristics) of the polarizing element 1, suitable reinforcing performance of the convex rib portion 22 can also be ensured.

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

[0368] Also, the reinforcing film 51 shown in FIG. 25 continuously covers the upper part of the convex rib portion 22 (that is, 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 (that is, the lower sides of both side surfaces 22b, 22b of the convex rib portion 22), and the surface of the base portion 21 (that is, 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. Such a reinforcing film 51 and protective film 40 exhibit a barrier property for protecting the resin-made 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 only needs to be a thickness capable of suppressing at least the inclination of the convex rib portion 22, and does not need to be excessively large. On the other hand, in order to ensure the barrier property of reliably protecting the entire grid 41 and valley 42 of the polarizing element 1 by the protective film 40, the thickness Bt of the protective film 40 is preferably a thickness of a predetermined value or more capable of exhibiting the barrier property. Therefore, the thickness Bt of the protective film 40 is preferably 2 times or more the thickness Rt of the reinforcing film 51 (2 × Rt ≤ Bt), and more preferably 5 times or more (5 × Rt ≤ Bt).

[0370] Furthermore, if the combined thickness (Rt+Bt) of the reinforcing film 51 (Rt) and the protective film 40 (Bt) shown in Figure 25 is too thick, the valleys 42 between the grids 41, 41 of the complex micro-uneven structure may be filled with the resin of the reinforcing film 51 and the protective film 40, which may degrade the optical properties of the polarizing element 1, and is therefore undesirable. Accordingly, the combined thickness (Rt+Bt) of the reinforcing film 51 and the protective film 40 is preferably 20 nm or less (Rt+Bt < 20 nm), and more preferably 15 nm or less (Rt+Bt < 15 nm). This ensures that the combined thickness (Rt+Bt) of the reinforcing film 51 and the protective film 40 is sufficient to maintain barrier properties while appropriately securing the optical properties of the polarizing element 1, particularly the Tp properties. Also, from a similar viewpoint, the thickness Bt of the protective film 40 is preferably 5 nm or more and 12 nm or less, and more preferably 5 nm or more and 10 nm or less.

[0371] For example, the following measurement method can be used to measure the thickness Rt (film thickness) of the reinforcing film 51. After forming the reinforcing film 51 on the raised ridge portion 22 and forming the reflective film 30 on the outside of the reinforcing film 51, a sample of the polarizing element 1 is prepared, and the cross-section of the sample is observed using a transmission electron microscope (TEM). Next, the data of the cross-sectional image of the sample obtained from this observation is imported into a length measuring application, and the thickness of the reinforcing film 51 is measured. In this case, the thickness of the reinforcing film 51 is measured on multiple grids 41 (for example, three or more) for each sample, and the average of these measured thicknesses is taken as the thickness Rt of the reinforcing film 51. Note that the method for measuring the thickness Rt of the reinforcing film 51 is not limited to the above measurement method, and 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 of the reinforcing film 51 in the portion interposed between the reflective film 30 and the raised ridge portion 22 as the thickness Rt of the reinforcing film 51, but other parts 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, which has a complex fine uneven structure as shown in Figure 25, to be suitably covered with a 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 protruding portions 22. As a result, when the polarizing element 1 is used, for example, as a polarizing beam splitter, the required optical properties of the polarizing element 1 (Tp characteristics, Tp×Rs characteristics, CR) can be maintained while suppressing the deterioration of the resin portion of the grid structure 20, improving the reliability of the polarizing element 1 (heat resistance, light resistance), and suitably reinforcing the protruding portions 22 with the reinforcing film 51. Furthermore, it is not necessary to deposit the reinforcing film 51 and the protective film 40 with perfectly uniform thicknesses, so it becomes practically possible to deposit the reinforcing film 51 and the protective film 40 with thickness variations within an acceptable range using, for example, the special ALD method described above.

[0373] <7.5. Relationship between the complex uneven grid structure 20 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 and 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 ridges 22, reinforcing film 51, and reflective film 30) has the special tree shape described above. As a result, complexly shaped valleys 42 are formed between adjacent grids 41, 41. Consequently, the surface of the grid structure 20 of the polarizing element 1 has a complex uneven structure in which multiple convex parts (grids 41) and multiple concave parts (valleys 42) are intertwined.

[0374] The raised ridges 22 of the grid structure 20 have a tapered shape, with the width in the X direction narrowing as they move upward (Z direction) from the base portion 21. The reflective film 30 (functional film) is a metal film (Al film) made of a metallic material such as Al, and covers the upper part of the raised ridges 22 (the tip 22a and both sides 22b, the upper side of 22b), but does not cover both sides 22b of the raised ridges 22, the lower side of 22b, or the surface of the base portion 21. The coverage rate (Rc) of both sides 22b, 22b of the raised ridges 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 protruding portion 22. The reinforcing film 51 covers at least the upper part of the protruding portion 22 that is covered by the reflective film 30. As shown in Figure 25, the reinforcing film 51 covers not only the upper part of the protruding portion 22 that is covered by the reflective film 30, but also the lower part of the protruding portion 22 and the upper surface of the base portion 21.

[0376] The reflective film 30 indirectly covers the upper part of the protruding portion 22 via the reinforcing film 51. The surface of the reflective film 30 is rounded and bulges in the width direction (X direction in Figure 25) of the protruding portion 22. The maximum width (W) of the reflective film 30 covering the protruding portion 22 is MAX ) is the width (W) of the lower side of the protruding ridge 22. B ) That is all. As shown in Figures 25 and 26, the cross-sectional shape of the entire convex structure (i.e., grid 41) composed of the convex ridges 22, the reinforcing film 51, and the reflective film 30 has the special tree shape described above. In this special tree shape, there are constrictions 29, 29 located directly below the lower ends on both the left and right sides of the reflective film 30 that covers the convex ridges 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 these constrictions 29, 29.

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

[0378] Furthermore, between adjacent grids 41, 41 in the X direction, a complexly shaped valley 42 is formed. The valley 42 is a recess formed between adjacent grids 41, 41. The upper part of the valley 42 is a space sandwiched between the reflective films 30, 30 on both the left and right sides, and is open upwards. The bottom of the valley 42 is a semi-closed space surrounded on three sides by the convex portions 22, 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 section) of the valley 42 has a vase-like shape, with a narrow entrance on the upper side and a wider semi-closed space on the bottom side.

[0379] 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 shape. Therefore, the valleys 42 between adjacent protrusions 22, 22 and the valleys 42 between grids 41, 41 also form semi-closed spaces with a complex vase shape. Consequently, the surface of the polarizing element 1 has a complex uneven structure consisting of these plurality of grids 41 and plurality of 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 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 the upper part of at least the protruding portions 22 of the grid structure 20. When forming the reinforcing film 51, the semi-closed space between adjacent protruding portions 22, 22 in the X direction is not a vase shape narrowed by the reflective films 30, 30 on both sides, and the upper entrance is wide. Therefore, forming the reinforcing film 51 before forming the reflective film 30 is easier than forming the protective film 40 after forming the reflective film 30. However, the reinforcing film 51 is an even thinner film than the protective film 40. Therefore, as shown in Figure 25, in order to form a 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 makes it possible to suitably form a reinforcing film 51 of a thin and uniform thickness.

[0381] <7.6. Method for forming reinforcing films> Next, the method for forming the reinforcing film 51 in the manufacturing method of the polarizing element 1 according to this embodiment will be described in detail.

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

[0383] The reinforcing film deposition process (S15) is performed between the grid structure formation process (S14) and the reflective film formation process (S16) shown in Figure 11. The reinforcing film deposition process (S15) is a process in which an inorganic oxide is used to deposit a reinforcing film 51 that covers at least the upper surface of the raised ridges 22 of the grid structure 20 formed in S14.

[0384] Here, there are two types of deposition areas for the reinforcing film 51, as shown in Figures 25 and 26. In the example of Figure 25, the reinforcing film 51 is deposited over the entire surface of the grid structure 20. That is, the reinforcing film 51 is deposited so as to continuously cover the entire tip 22a and both sides 22b, 22b of the protruding portion 22, and the surface of the base portion 21. In the case of the deposition area of ​​the reinforcing film 51 in the example of Figure 25, it is preferable to deposit the reinforcing film 51 over the entire surface of the grid structure 20 with as uniform a thickness as possible, for example, by the ALD method. By using the ALD method as the overall deposition method for the reinforcing film 51, it is possible to reduce the unevenness of the thickness Rt of the reinforcing film 51 deposited over the entire surface of the grid structure 20, and to deposit a reinforcing film 51 with a very uniform thickness Rt.

[0385] On the other hand, in the example shown in Figure 26, the reinforcing film 51 is deposited only on the upper part of the protruding portion 22 of the grid structure 20. That is, the reinforcing film 51 is deposited so as to partially cover only the upper part of the protruding portion 22 (the tip 22a and both sides 22b, and the upper side of 22b). In the case of the deposition range of the reinforcing film 51 in the example shown in Figure 26, it is preferable to partially deposit the protective film 40 on the upper part of the protruding portion 22 of the grid structure 20 by vapor deposition, for example. By using vapor deposition as the method for depositing the partial reinforcing film 51, the reinforcing film 51 can be easily deposited using a relatively simple deposition apparatus. Alternatively, the reinforcing film 51 may be partially deposited on the upper part of the protruding portion 22 by sputtering instead of vapor deposition.

[0386] After the film formation process of the reinforcing film 51 as described above (S15), a reflective film formation process (S16) is performed. In the reflective film formation process (S16), the reflective film 30 (functional film) is formed so that it covers and encloses the upper part of the protruding portion 22 (the tip 22a and both sides 22b of the protruding portion 31, and the upper side of 22b) via the reinforcing film 51. For example, sputtering or vapor deposition can be used to form the reflective film 30.

[0387] Subsequently, a protective film deposition process (S18) is performed. The protective film deposition process (S18) is a process of depositing a protective film 40 that covers the entire surface of the polarizing element 1 (the entire surface of the grid structure 20 and the reflective film 30).

[0388] In the example shown in Figure 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 peripheral portion above the raised ridges 22). In this case, during the film formation process of the protective film 40 (S18), the protective film 40 is formed so as to continuously cover the surface of the reflective film 30 and the reinforcing film 51 that covers both sides 22b of the raised ridges 22, and the lower side of 22b (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 surface of the valleys 42).

[0389] On the other hand, in the example shown in Figure 26, the reinforcing film 51 covers only the upper part of the raised ridge portion 22, and does not cover the lower part of the raised ridge portion 22 or the upper surface of the base portion 21. In this case, during the film formation process of the protective film 40 (S18), the protective film 40 is formed so as to continuously cover the surface of the reflective film 30, the exposed portion of the reinforcing film 51 below it, both sides 22b of the raised ridge portion 22, the lower side of 22b (i.e., the entire surface of the grid 41), and the surface of the base portion 21 (i.e., the bottom surface of the valleys 42).

[0390] As a method for depositing the protective film 40, it is preferable to use the ALD method, particularly the special ALD method described above (see Figure 19). This makes it possible to deposit the protective film 40 almost uniformly over the entire surface of the complex micro-roughness structure of the grid structure 20.

[0391] Next, we will explain in more detail the special ALD method used to form the overall reinforcing film 51 shown in Figure 25 during the film formation process (S15) of the reinforcing film 51 described above.

[0392] The ALD method has the advantage of enabling extremely thin and uniform film formation compared to the CVD method, as it allows for precise control of film thickness and material at the atomic layer level. Therefore, in the film formation step (S15) of the reinforcing film 51 according to this embodiment, it is preferable to form the reinforcing film 51 by the ALD method when forming the reinforcing film 51 over the entire surface of the complex micro-rough structure of the grid structure 20. This makes it possible to form the reinforcing film 51 almost uniformly over the entire surface of the protruding portions 22 and the base portion 21 of the grid structure 20.

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

[0394] In the overall reinforcing film deposition process (S15) shown in Figure 25, first, as shown in Figure 19, the grid structure 20 in its state before deposition of the reflective film 30 is placed inside the chamber 300 (S150).

[0395] Next, the first to fourth steps (S151 to S154) are repeated in which two types of gaseous raw material gases for forming the reinforcing film 51 (hereinafter referred to as "precursor gas" and "oxidizing gas," respectively) are alternately introduced (pulsed) and exhausted (purged) into the chamber 300. Here, the introduction of the precursor gas (S151: first step), the introduction of the inert gas (S152: second step), the introduction of the oxidizing gas (S153: third step), and the introduction of the inert gas (S154: fourth step) are the same as the steps (S181 to S184) of the protective film formation process (S18) described above, so a detailed explanation is omitted.

[0396] Furthermore, according to the special ALD method for forming the reinforcing film 51 (S15) in this embodiment, the precursor gas introduction step (S151) and the oxidizing gas introduction step (S153) are characterized in that the precursor gas and oxidizing gas are introduced into and filled into the chamber without exhausting them from the chamber 300 to the outside.

[0397] In this regard, in the conventional ALD method for film deposition, the precursor gas and oxidizer gas are introduced into the chamber 300 during the precursor gas and oxidizer gas introduction steps (S151, S153) while the precursor gas and oxidizer gas in the chamber 300 are evacuated.

[0398] In contrast, in the film formation process (S15) of the reinforcement film 51 by the special ALD method according to this embodiment, in the precursor gas and oxidizer gas introduction processes (S151, S153: first and third processes), the precursor gas and oxidizer gas in the chamber 300 are not exhausted from the gas exhaust port 330, but are continuously introduced into the chamber 300. Specifically, in the precursor gas introduction process (S151: first process), with the exhaust valve of the gas exhaust port 330 closed to seal the chamber 300, the precursor gas is introduced into the chamber 300 from the gas inlet 310, and the precursor gas in the chamber 300 is not exhausted from the gas exhaust port 330. Similarly, in the oxidizer gas introduction process (S153: third process), with the exhaust valve of the gas exhaust port 330 closed to seal the chamber 300, the oxidizer gas is introduced into the chamber 300 from the gas inlet 310, and the oxidizer gas in the chamber 300 is not exhausted from 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 come into sufficient contact with the surface of the grid structure 20 to be coated. Therefore, the precursor gas and oxidizer gas can be sufficiently introduced into the deepest parts of the valleys 42 between adjacent raised ridges 22, 22 on the surface of the complex fine uneven structure of the grid structure 20 shown in Figure 25, allowing for the proper deposition of the first and second atomic layers of the required thickness. Thus, a reinforcing film 51 of the desired thickness Rt can be suitably deposited not only on the upper surface of the raised ridges 22, but also on the lower surface of the raised ridges 22 and the surface of the base portion 21.

[0400] Therefore, the thickness of the reinforcing film 51 covering the tip 22a of the protruding 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 the conventional general ALD method. Thus, a reinforcing film 51 with even greater uniformity can be formed within a predetermined tolerance range for thickness unevenness.

[0401] The above describes in detail the process (S15) for forming the overall reinforcing film 51 shown in Figure 25 using the special ALD method according to this embodiment. According to this embodiment, 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 precursor gas and oxidizer gas) in the precursor gas and oxidizer gas introduction steps (S151, S153) by the ALD method can be optimized to match the fine uneven structure of the grid structure 20.

[0402] This allows for the formation of an extremely thin reinforcing film 51, on the order of several nanometers to tens of nanometers, very uniformly across the entire surface of the fine uneven structure of the grid structure 20. Therefore, it becomes possible to form an extremely uniform thin reinforcing film 51 within a predetermined tolerance range for thickness variation. Since the upper part of the raised ridges 22 can be reinforced by this reinforcing film 51, it is possible to suppress tilting or thinning of the raised ridges 22 caused by the formation of the reflective film 30. Furthermore, as shown in Figure 25, the reinforcing film 51 that covers the entire grid structure 20, together with the protective film 40 on the outside, can provide more robust protection for the grid structure 20. Therefore, it is possible to improve the reliability (heat resistance and light resistance) of the polarizing element 1 equipped with the reinforcing film 51 while maintaining its optical properties.

[0403] Furthermore, according to this embodiment, by using the ALD method as the film deposition method, the deposition material adheres well to the fine uneven structure, so the uniformity of the reinforcing film 51 can be significantly improved compared to conventional sputtering and vacuum deposition methods. Moreover, according to the ALD method of this embodiment, the reinforcing film 51 can be deposited at a low film deposition temperature (e.g., 190° or less) that is below the heat resistance temperature (e.g., 200°) of the resin of the grid structure 20. As a result, the resin of the grid structure 20 is less likely to soften during the deposition of the reinforcing film 51 (S15), so the shape of the protruding parts 22 of the grid structure 20 can 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 deposition methods.

[0404] The 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 used, and the state of the grid structure 20 placed inside the chamber 300. These conditions can be appropriately set to optimal values ​​to satisfy the desired film formation conditions.

[0405] In the above, we have described in detail an example of using a special ALD method as a method for forming the overall reinforcing film 51 shown in Figure 25. On the other hand, as a method for forming a partial reinforcing film 51 as shown in Figure 26, for example, a general vapor deposition method or sputtering method can be used to attach the material for the reinforcing film 51 to the upper and central parts of the protruding ridges 22, thereby forming the reinforcing film 51 so as to cover and encase the upper and central parts of the protruding ridges 22. [Examples]

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

[0407] <1. Verification results of the protective film thickness> As an embodiment of the present invention, a sample of a wire grid polarizing element 1 satisfying formula (10) for the thickness of the protective film 40 according to the above embodiment was prepared, and tests were conducted to evaluate the optical properties, heat resistance, and light resistance of the sample. In addition, for comparison with the embodiment of the present invention (satisfying formula (10)), a sample of a wire grid polarizing element 1 according to a comparative example (not satisfying formula (10)) was also prepared and similarly tested and evaluated. For the sake of explanation, in the following, both the embodiment and the comparative example use the same reference numerals and symbols to represent the components of the polarizing element 1 (substrate 10, grid structure 20, base portion 21, raised portion 22, reflective film 30, protective film 40, etc.) and the symbols to represent the various dimensions of these components.

[0408] The symbols used in the following explanation to represent the various dimensions of polarizing element 1 are as follows: P: Pitch of the convex portion 22 W T : Width of the top of the convex part 22 (width of the top of the convex part) W M : The width of the central position in the height direction of the protruding ridge 22 (width of the central part of the protruding ridge) W B : Width of the bottom of the convex section 22 (grid bottom width) WMAX : Maximum width of the reflective film 30 covering the convex portion 22 (maximum grid width) H: Height of the protruding part 22 Hx: Height of the portion of the side surface 22b of the protruding part 22 that is covered by the reflective film 30. Dt: Thickness of the reflective film 30 covering the tip 22a of the protruding portion 22 (thickness of the tip of the reflective film 30) Ds: Thickness of the reflective film 30 covering the side surface 22b of the protruding portion 22 (side surface thickness of the reflective film 30) Rc: Coverage rate of the side surface 22b of the raised portion 22 by the reflective film 30 Rr: Openness ratio of the side surface 22b of the convex portion 22 due to the reflective film 30 Tt: The thickness of the protective film 40 covering the top 30a of the reflective film 30 that surrounds the raised portion 22 (i.e., the thickness of the protective film 40 at the tip of the grid 41) Bt: The thickness of the protective film 40 covering both sides 22b of the protruding portion 22, the lower side of 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 sides 22b of the raised portion 22 and the lower side of 22b. Bt2: Thickness of the protective film 40 covering the surface of the base portion 21 θ: Incident angle of the incident light λ: Wavelength of incident light

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

[0410] (Example 51) First, with reference to Figure 18, Example 51 of the present invention will be described.

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

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

[0413] As a result, as shown in Figure 18, the grid 41 (a structure combining the raised ridge portion 22 and the reflective film 30) according to Example 51 has the special tree shape described above. The maximum width W of the grid with this special tree shape MAX (The width of the grid at the most bulging part of the reflective film 30) is the width W at the bottom of the convex portion 22. B The width of the protruding ridge 22 at a height position 20% above the bottom of the protruding ridge 22 is greater than or equal to the width of the protruding ridge 22 at a height position 20% above the bottom of the protruding ridge 22. In addition, the cross-sectional shape (XZ section) of the valley 42 between adjacent grids 41, 41 has a vase-like shape in which the entrance on the upper side is narrow and the semi-closed space on the lower side is wide.

[0414] Furthermore, in Example 51, a protective film 40 covering the entire surface of the grid structure 20 and the reflective film 30 was formed by the ALD method according to the present embodiment described above (S18: see Figure 19). The material of the protective film 40 was a single layer structure of SiO2, and the target thickness of the formed protective film 40 was set to 10 nm.

[0415] In Example 51, during the film formation process, the precursor gas and oxidizer gas introduction steps (S181, S183: first and third steps) described above were not exhausted from the gas exhaust port 330, but rather the precursor gas and oxidizer gas in the chamber 300 were introduced and filled into the chamber 300. As a result, as 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 bottom of the valleys 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 formed (see Table 1).

[0416] In the sample of polarizing element 1 according to Example 51 prepared as described above, the thicknesses Bt and Tt of the protective film 40 were measured. At this time, Bt1, Bt2, and Tt were measured for multiple grids 41 of the sample of polarizing element 1 according to Example 51, and their average values ​​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 from this observation was imported into a length measuring application, and the thicknesses Bt1, Bt2, and Tt of the protective film 40 on the outermost layer of the grid 41 were measured. In this process, the thicknesses Bt1, Bt2, and Tt of the protective film 40 were measured for at least three grids 41 per sample. The average value Bt1(ave.) of multiple measurements of Bt1 and the average value Bt2(ave.) of multiple measurements of Bt2 were then calculated. Furthermore, the average of the average value Bt1(ave.) and the average value Bt2(ave.) of Bt2 was calculated and defined as Bt. In addition, the average value Tt(ave.) of multiple measurements of Tt was calculated and defined as Tt.

[0418] (Example 52) Next, Example 52 of the present invention will be described. In Example 52, the material of the protective film 40 was a single-layer structure of SiO2, and the target thickness of the protective film 40 to be deposited was set to 6 nm. In all other respects, a sample of the polarizing element 1 according to Example 52 was prepared 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 a protective film 40 satisfying the above formula (10) could be deposited.

[0419] (Example 53) Next, Example 53 of the present invention will be described. In Example 53, the protective film 40 was made of a laminated structure consisting of a first film layer made of Al2O3 (target thickness: 1 nm) and a second film layer made of SiO2 (target thickness: 5 nm). In all other respects, a sample of the polarizing element 1 according to Example 53 was prepared in the same manner as in Example 51. The method for measuring 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 a protective film 40 satisfying the above formula (10) could be formed.

[0420] (Comparative Examples 51, 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 a single-layer structure of SiO2, and the target thickness of the protective film 40 to be deposited was set to 10 nm. In Comparative Examples 51 and 52, the protective film 40 was deposited using a conventional ALD method, which differs from the special ALD method used in Examples 51 to 53 above. That is, in Comparative Examples 51 and 52, when depositing the protective film 40 by the ALD method, a conventional ALD method was used in the introduction steps of the precursor gas and oxidizer gas (S181, S183: first and third steps). Specifically, in Comparative Examples 51 and 52, as a conventional ALD method, a method was used in which the precursor gas and oxidizer gas in the chamber 300 were introduced into the chamber 300 while the precursor gas and oxidizer gas in the chamber 300 were exhausted from the gas exhaust port 330. As a result, as will be described later, in Comparative Examples 51 and 52, Bt became significantly smaller than Tt, and thickness variations occurred between Tt and Bt, so the ratio of Tt to Bt (Bt / Tt) did not satisfy the above equation (10).

[0421] (Comparative Examples 53, 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 a single-layer structure of SiO2, and the target thickness of the deposited protective film 40 was set to 10 nm and 20 nm, respectively. In Comparative Examples 53 and 54, the protective film 40 was deposited by a conventional vapor deposition method. As a result, as will be described later, in Comparative Examples 53 and 54, Bt became significantly smaller than Tt, and thickness variations occurred between Tt and Bt, so the ratio of Tt to Bt (Bt / Tt) did not satisfy the above formula (10).

[0422] (2) Dimensional conditions of each part of the polarizing element 1 The dimensions and shapes of each part of the polarizing element 1 samples in Examples 51-53 and Comparative Examples 51-54 described above are as follows. P: 151nm W T :20nm W B :43nm W MAX :72nm H: 265nm Hx: 101nm Dt: 37nm Ds: 27nm (maximum value) Rc: 38% Rr: 62% Tt: As shown in Table 1 below Bt: As shown in Table 1 below θ: 45° λ: 400~700nm

[0423] Table 1 also shows the measurement results of the thickness Tt and Bt of the protective film 40 in the polarizing element 1 samples from Examples 51-53 and Comparative Examples 51-54, which were prepared as described above. Furthermore, Table 1 also shows the results of (1) optical properties tests, (2) 150°C heat resistance tests, and (3) light resistance tests performed on Examples 51-53 and Comparative Examples 51-54.

[0424] [Table 1]

[0425] (3) The ratio of the thickness of the protective film 40 (Bt / Tt) 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 equation (10). This means that in Comparative Examples 51 and 52, Bt is significantly smaller than Tt, and there is a large variation in thickness between Bt and Tt. As a result, Comparative Examples 51 and 52 do not satisfy the conditions of equation (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 using the conventional ALD method, but the film formation conditions for the protective film 40 using the ALD method were not appropriate.

[0427] Specifically, in Comparative Examples 51 and 52, in the introduction step (S181, S183: first and third steps), a film deposition method was used in which the precursor gas and oxidizer gas in the chamber 300 were introduced into the chamber 300 while being exhausted from the gas exhaust port 330, as described above for the conventional ALD method. As a result, in Comparative Examples 51 and 52, it was not possible to fill and retain the precursor gas and oxidizer gas in the chamber 300. Consequently, a sufficient amount of precursor gas and oxidizer gas could not be supplied to the bottom of the vase-shaped vase 42 on the surface of the complex micro-undulation structure consisting of grid 41 and vase 42 shown in Figure 18. Therefore, the thickness Bt of the protective film 40 deposited on the bottom of the vase 42 (the resin portion of the grid structure 20) was significantly smaller than the thickness Tt of the protective film 40 deposited on the tip of grid 41 (the metal portion of the top 30a of the reflective film 30). As a result, it is considered that the ratio of Tt to Bt (Bt / Tt) in Comparative Examples 51 and 52 did not satisfy the conditions of equation (10) above.

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

[0429] The reason for this is thought to be that in Comparative Examples 53 and 54, the protective film 40 was deposited using a conventional vapor deposition method. Specifically, in Comparative Examples 53 and 54, an extremely thin protective film 40 of about 10 nm and 20 nm was deposited on the surface of the complex micro-uneven structure consisting of grids 41 and valleys 42 shown in Figure 18 using the vapor deposition method. As a result, a protective film 40 with a thickness close to the target thickness was deposited on the tip of the grid 41 (the metal portion of the top 30a of the reflective film 30), but the protective film 40 was deposited in the vase-shaped valleys 42 with a thickness of less than half that of the tip of the grid 41, and furthermore, the protective film 40 was hardly deposited on the side walls of the grid 41. Therefore, it was difficult to uniformly deposit the 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 was deposited on the leading edge of the grid 41, but only a 3.3 nm protective film 40 was deposited in the valleys 42 of the grid 41, resulting in a remarkably low Bt / Tt of 0.31. Similarly, in Comparative Example 54 (target thickness of protective film 40: 20 nm), a 16.8 nm protective film 40 was deposited on the leading edge of the grid 41, but only a 4.9 nm protective film 40 was deposited in the valleys 42 of the grid 41. Even with a thicker target thickness as in Comparative Example 54, the Bt / Tt was remarkably low at 0.29. As a result, as will be described later, in Comparative Examples 53 and 54, the change in Tp characteristics ΔTp2 in the heat resistance test was large, confirming low heat resistance.

[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 equal to 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 satisfying the conditions of the above formula (10) was formed.

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

[0433] Specifically, in Examples 51-53, in the precursor gas introduction step (S181) and the oxidizing gas introduction step (S183), a special ALD method was used in which the precursor gas and oxidizing gas were introduced into the chamber 300 and filled with the gas without exhausting the gas from the chamber 300 to the outside. As a result, in each introduction step (S181 and S183), the precursor gas and oxidizing gas introduced into the chamber 300 were sufficiently filled and retained within the chamber 300, allowing them to make sufficient contact with the target surface of the grid structure 20. Therefore, the precursor gas and oxidizing gas were sufficiently introduced into the deepest parts of the vase-shaped vase 42 on the surface of the complex micro-undulation structure consisting of the grid 41 and vase 42 shown in Figure 18, allowing for the proper deposition of the first and second atomic layers with the required thickness. Thus, a protective film 40 with the target thickness was deposited almost uniformly not only on the surface of the tip of the grid 41 but also on the surface of the vase-shaped vase 42. Therefore, the thickness Tt of the protective film 40 deposited 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 deposited on the bottom of the valleys 42 (the resin portion of the grid structure 20) could be made to be approximately the same. As a result, the ratio of Tt to Bt (Bt / Tt) in Examples 51 to 53 is considered to satisfy the conditions of the above formula (10).

[0434] From the above results, it has been demonstrated that by forming the protective film 40 using the special ALD method according to the present embodiment described above, a protective film 40 with a nearly uniform thickness can be formed over the entire surface of the complex micro-uneven structure of the grid structure 20, and a protective film 40 that satisfies formula (10) can be formed.

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

[0436] As shown in Table 1, in the optical properties test, the change in optical properties (Tp properties) before and after the deposition of the protective film 40 was measured for samples of polarizing element 1 according to Examples 51-53 and Comparative Examples 51-54, and the influence of the protective film 40 on the optical properties of polarizing element 1 was evaluated.

[0437] In the optical properties test, the transmission axis transmittance (Tp) was measured before and after the deposition of the protective film 40 for samples of polarizing element 1 according to Examples 51-53 and Comparative Examples 51-54. For Tp measurement, incident light was incident on the surface of each sample at an incident angle θ = 45°, and the Tp was measured at each wavelength λ while varying the wavelength λ of the incident light in the range of 400-700 nm. The average value of the measured Tp values ​​in the 430-680 nm range was calculated.

[0438] Then, the change in Tp ΔTp1 before and after the deposition of the protective film 40, as shown in Table 1, was calculated. The change in ΔTp1 is the average value of the measured Tp values ​​before the deposition of the protective film 40. 1B And the average value of the Tp measured after the formation of the protective film 40 Tp 1A This is the difference between (ΔTp1=Tp 1A -Tp 1B ). The larger the absolute value of the change amount ΔTp1, the greater the change in the optical properties (Tp characteristics) of the polarizing element 1 before and after the deposition of the protective film 40. Therefore, the smaller the absolute value of ΔTp1, the more the optical properties (Tp characteristics) of the polarizing element 1 are maintained without being reduced due to the deposition of the protective film 40, and the desired optical properties (Tp characteristics) required for the polarizing element 1 are maintained. Therefore, from the viewpoint of maintaining the optical properties (Tp characteristics) of the polarizing element 1, it is preferable to have a small absolute value of ΔTp1.

[0439] According to the results of these optical property tests, as shown in Table 1, in Comparative Examples 51 and 52, the absolute value of ΔTp1 was 0.3 to 0.9%, which is smaller than the reference value of 1.0%, indicating that the optical properties of polarizing element 1 have not deteriorated. Similarly, in Comparative Examples 53 and 54, the absolute value of ΔTp1 was 0.3 to 0.7%, which is also smaller than the reference value of 1.0%, indicating that the optical properties of polarizing element 1 have not deteriorated.

[0440] In contrast, in Examples 51-53, the absolute value of ΔTp1 was 0.4-0.7%, which is significantly smaller than the reference value of 1.0% and even smaller than in Comparative Examples 51 and 52. Therefore, it can be seen that in Examples 51-53, even when the protective film 40 is provided, the desired optical properties (Tp properties) can be sufficiently maintained, just as in the case where the protective film 40 is not provided.

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

[0442] (5) Heat resistance test Next, the conditions and evaluation results of the heat resistance test will be explained with reference to Table 1, Figure 20, and Figure 22. Figure 20 is a graph showing the results of the heat resistance test for Comparative Examples 51 and 52. Figure 21 is a graph showing the results of the heat resistance test for Comparative Examples 53 and 54. Figure 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 20-22, in the heat resistance test, samples of polarizing element 1 according to Examples 51-53 and Comparative Examples 51-54 were continuously heated to 150°C for a predetermined time t (t = 500 hours, 1000 hours). The change in Tp ΔTp2 before and after heating was measured, and the influence of the protective film 40 on the heat resistance of the polarizing element 1 was evaluated based on the magnitude of this change ΔTp2 (i.e., the degree of Tp degradation).

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

[0445] Then, the change in Tp before and after heating, ΔTp2, was calculated as shown in Table 1. The change in ΔTp2 is the average value of the Tp measurements taken before heating the sample (before the start of the test). 2B The average value of Tp measured after heating the sample at 150°C for 1000 hours (1000 hours after the start of the test) is Tp 2A This is the difference between (ΔTp² = Tp 2A -Tp 2B ). The larger the absolute value of the change amount ΔTp2, the more the Tp characteristics of the sample deteriorate due to prolonged heating, resulting in lower heat resistance. Therefore, the smaller the absolute value of ΔTp2, the less the optical properties (Tp characteristics) of the polarizing element 1 deteriorate due to the effects of heat, and the higher the heat resistance of the polarizing element 1. Thus, from the viewpoint of improving the heat resistance (reliability against heat) of the polarizing element 1, it is preferable to have a small absolute value of ΔTp2.

[0446] According to the results of the heat resistance test, as shown in Figure 20, in Comparative Examples 51 and 52, Tp decreased as the heating time increased, and the decrease in Tp was particularly significant in the low wavelength range of 500 nm or less. As a result, as shown in Table 1, the absolute value of ΔTp2 in Comparative Examples 51 and 52 was 3.3 to 5.2%, which is significantly larger than the standard value of 3.0%, which indicates that the heat resistance of the polarizing element 1 has not deteriorated. Therefore, in Comparative Examples 51 and 52, the Tp characteristics of the polarizing element 1 deteriorated due to prolonged heating at high temperatures, indicating that 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 was small, and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 was thin, so the thin protective film 40 could not adequately protect the resin portion, and the resin portion deteriorated due to the heat.

[0447] Furthermore, as shown in Figure 21, in Comparative Examples 53 and 54, Tp decreased as the heating time increased, and the decrease in Tp was particularly pronounced in the low wavelength range below 500 nm. As a result, as shown in Table 1, the absolute value of ΔTp2 in Comparative Examples 53 and 54 was 3.8-3.9%, which is significantly larger than the standard value of 3.0%, which indicates that the heat resistance of the polarizing element 1 has not deteriorated. Therefore, in Comparative Examples 53 and 54, the Tp characteristics of the polarizing element 1 deteriorated due to prolonged heating at high temperatures, indicating that the heat resistance of the polarizing element 1 is low. The reason for this is thought to be that in Comparative Examples 53 and 54, Bt / Tt was small, and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 was thin, so the thin protective film 40 could not adequately protect the resin portion, and the resin portion deteriorated due to heat.

[0448] In contrast, in Examples 51-53, as shown in Figure 22, there was almost no difference in Tp characteristics due to the length of heating time, and the Tp characteristics showed almost the same trend regardless of the length of heating time. As a result, as shown in Table 1, the absolute value of ΔTp2 was 0.1-0.2%, which is significantly smaller than the above standard value of 3.0%. Therefore, in Examples 51-53, the Tp characteristics of the polarizing element 1 did not deteriorate even with prolonged heating at high temperatures, indicating that the polarizing element 1 has high heat resistance. The reason for this is thought to be that in Examples 51-53, Bt / Tt satisfies equation (10), and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 was sufficiently thick, so the resin portion was properly protected by the thick protective film 40 and did not deteriorate due to heat.

[0449] The results of the above heat resistance tests demonstrate 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 micro-uneven structure of the grid structure 20.

[0450] (6) Lightfastness test Next, referring to Table 1, FIGS. 23 and 24, the conditions and evaluation results of the light resistance test will be described. FIG. 23 is a graph showing the results of the light resistance test according to Comparative Example 52. FIG. 24 is a graph showing the results of the light resistance test according to Examples 51 to 53.

[0451] As shown in Table 1, FIGS. 23 and 24, in the light resistance test, test light was continuously irradiated for a predetermined time t (t = 500 hours, 1000 hours, 2000 hours) from a direction perpendicular to the surface of the sample of the polarizing element 1 according to Examples 51 to 53 and Comparative Example 52. As the test light, for example, the light from a laser light source was incident on a dichroic mirror, and blue light among the visible lights transmitted through the mirror was used. Then, the change amount ΔTp3 of Tp before and after light irradiation was measured, and based on the magnitude of the change amount ΔTp3 (that is, 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, for the samples of the polarizing element 1 according to Examples 51 to 53 and Comparative Example 52, Tp before and after light irradiation (before and after the start of the test) was measured. In the measurement of Tp, incident light was incident on the surface of each sample at an incident angle θ = 45°, and while changing the wavelength λ of the incident light in the range of 400 to 700 nm, Tp at each wavelength λ was measured, and the average value of the measured values of Tp in the range of 430 to 680 nm was calculated.

[0453] Then, the change amount ΔTp3 of Tp before and after light irradiation shown in Table 1 was calculated. The change amount ΔTp3 is the average value Tp of the measured values of Tp before irradiating the sample with light (before the start of the test) 3B and the average value 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 The difference between them (ΔTp3 = Tp 3A -Tp 3B). The larger the absolute value of the change amount ΔTp3, the more the Tp characteristics of the sample deteriorate due to prolonged light irradiation, resulting in lower light resistance. Therefore, the smaller the absolute value of ΔTp3, the less the optical properties (Tp characteristics) of the polarizing element 1 deteriorate due to the effects of light, and the higher the light resistance of the polarizing element 1. Thus, from the viewpoint of improving the light resistance (reliability against light) of the polarizing element 1, a small absolute value of ΔTp3 is preferable.

[0454] According to the results of the light resistance test, as shown in Figure 23, in Comparative Example 52, Tp increased as the light irradiation time increased, and the increase in Tp was particularly significant in the high wavelength range of 600 nm or higher. As a result, as shown in Table 1, the absolute value of ΔTp3 in Comparative Example 52 was 1.6%, which is significantly larger than the standard value of 1.0%, which indicates that the light resistance of the polarizing element 1 has not deteriorated. Therefore, in Comparative Example 52, the Tp characteristics of the polarizing element 1 deteriorated due to light irradiation, indicating that 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 was small, and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 was thin, so the thin protective film 40 could not adequately protect the resin portion, and the resin portion deteriorated due to light (for example, it turned yellow).

[0455] In contrast, in Examples 51-53, as shown in Figure 24, there was almost no difference in Tp characteristics depending on the length of light irradiation time, and the Tp characteristics showed almost the same trend regardless of the length of light irradiation time. As a result, as shown in Table 1, the absolute value of ΔTp3 was 0.2-0.8%, which is sufficiently smaller than the above standard value of 1.0%. Therefore, in Examples 51-53, the Tp characteristics of the polarizing element 1 did not deteriorate even with prolonged light irradiation, indicating that the polarizing element 1 has high light resistance. The reason for this is thought to be that in Examples 51-53, Bt / Tt satisfies equation (10), and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 was sufficiently thick, so the resin portion was adequately protected by the thick protective film 40 and did not deteriorate due to light.

[0456] The results of the above light resistance tests demonstrate 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 micro-uneven structure of the grid structure 20.

[0457] <2. Verification results of the reinforcing function of the reinforcing film on the raised sections> Next, as an embodiment of the present invention, a sample of a wire grid polarizing element 1 equipped with the reinforcing film 51 according to the present embodiment described above was prepared, and a test was conducted to evaluate the optical properties of the sample. In addition, in order to compare with the embodiment of the present invention (where the raised portion 22 is covered with the reinforcing film 51), a sample of a wire grid polarizing element 1 according to a comparative example (where the raised portion 22 is not covered with the reinforcing film 51) was also prepared and similarly tested and evaluated. For the sake of convenience of explanation, in the following, both the embodiment and the comparative example use the same reference numerals and symbols to represent the components of the polarizing element 1 (substrate 10, grid structure 20, base portion 21, raised portion 22, reflective film 30, protective film 40, reinforcing film 51, etc.) and symbols to represent the various dimensions of these components.

[0458] The symbols used in the following explanation to represent the various dimensions of polarizing element 1 are as follows: P: Pitch of the convex portion 22 W T : Width of the top of the convex part 22 (width of the top of the convex part) W M : The width of the central position in the height direction of the protruding ridge 22 (width of the central part of the protruding ridge) W B : Width of the bottom of the convex section 22 (grid bottom width) W MAX : Maximum width of the reflective film 30 covering the convex portion 22 (maximum grid width) H: Height of the protruding part 22 Hx: Height of the portion of the side surface 22b of the protruding part 22 that is covered by the reflective film 30. Dt: Thickness of the reflective film 30 covering the tip 22a of the protruding portion 22 (thickness of the tip of the reflective film 30) Ds: Thickness of the reflective film 30 covering the side surface 22b of the protruding portion 22 (side surface thickness of the reflective film 30) Rc: Coverage rate of the side surface 22b of the raised portion 22 by the reflective film 30 Rr: Openness ratio of the side surface 22b of the convex portion 22 due to the reflective film 30 Tt: The thickness of the protective film 40 covering the top 30a of the reflective film 30 that surrounds the raised portion 22 (i.e., the thickness of the protective film 40 at the tip of the grid 41) Bt: The thickness of the protective film 40 covering both sides 22b of the protruding portion 22, the lower side of 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 reinforcing film 51 θ: Incident angle of the incident light λ: Wavelength of incident light

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

[0460] (Example 60) First, with reference to Figure 30, an embodiment 60 of the present invention will be described.

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

[0462] In Example 60, first, the grid structure material formation step (S10), nanoimprint step (S12), and grid structure formation step (S14) in the manufacturing method of the polarizing element 1 according to the present embodiment described above were performed to create the grid structure 20 shown in Figure 30.

[0463] Next, the reinforcing film deposition process (S15) described above was performed, and a reinforcing film 51 was deposited using the special ALD method described above (see Figure 19) to continuously cover the entire surface of the grid structure 20 (the tip 22a and both sides 22b, 22b of the protruding ridges 22, and the surface of the base portion 21). The material of the reinforcing film 51 was a single layer structure of SiO2, and the target thickness of the reinforcing film 51 was set to 2 nm.

[0464] During the deposition of the reinforcing film 51 by this special ALD method (S15), in the precursor gas and oxidizer gas introduction steps (S151, S153: first and third steps) described above, the precursor gas and oxidizer gas in the chamber 300 were not exhausted from the gas exhaust port 330, but instead introduced and filled into the chamber 300. This made it possible to make the thickness of the reinforcing film 51 covering the tip 22a of the protruding portion 22 of the grid structure 20 and the thickness of the reinforcing film 51 covering the upper surface of the base portion 21 approximately the same thickness Rt (about 2 nm).

[0465] Next, the reflective film formation process (S16) described above was performed to form a reflective film 30 (functional film) that covers the leading edge of the protruding portion 22 on top of the reinforcing film 51 that covers the grid structure 20. At this time, using a vapor deposition method, Al, which is the material for the reflective film 30, was deposited onto the upper part of the protruding portion 22 alternately from the left and right from an oblique upward angle to form the reflective film 30.

[0466] The reflective film 30 formed in this manner is made of an Al film, and as shown in FIG. 30, it is formed so as to cover the upper part of the rib portion 22 (the tip 22a of the rib portion 22 and the upper sides of both side surfaces 22b, 22b) via the reinforcing film 51. However, the reflective film 30 does not cover the lower sides of both side surfaces 22b, 22b of the rib portion 22 and the base portion 21. The coverage rate Rc of both side surfaces 22b, 22b of the rib portion 22 by the reflective film 30 is 38%. Thus, the reflective film 30 of Example 60 roundly covers and encloses the top of the rib portion 22 (the tip 22a and the upper sides of both side surfaces 22b, 22b). The surface of the reflective film 30 has a substantially elliptical shape with a bulge outward, and bulges in the width direction of the rib portion 22.

[0467] As a result, as shown in FIG. 30, the grid 41 (the structure formed by combining the rib portion 22, the reinforcing film 51, and the reflective film 30) according to Example 60 has the above-described special tree shape. The maximum width W MAX (the width of the grid at the portion where the reflective film 30 bulges the most) of the grid of the special tree shape is equal to or greater than the width W B (the width of the rib portion 22 at the height position 20% above the bottom of the rib portion 22) of the rib portion 22. Also, the cross-sectional shape (XZ cross-section) of the groove 42 between adjacent grids 41, 41 has a bowl shape in which the upper-side entrance is narrow and the bottom-side semi-closed space is wide.

[0468] Thereafter, the above-described protective film forming step (S18) was executed, and a protective film 40 that covers the entire surfaces of the reinforcing film 51 and the reflective film 30 of the grid structure 20 was formed using the above-described special ALD method (see FIG. 19). The material of the protective film 40 has a single-layer structure of SiO2, and 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 precursor gas and oxidizer gas introduction steps (S181, S183: first and third steps) described above, the precursor gas and oxidizer gas in the chamber 300 were not exhausted from the gas exhaust port 330, but instead introduced and filled into the chamber 300. This allowed 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 bottom of the valleys 42 (i.e., the resin portion of the grid structure 20) to be approximately the same (about 7 nm), and a protective film 40 satisfying the above formula (10) could be deposited.

[0470] (Comparative Example 60) Next, Comparative Example 60 will be described. As shown in Figure 31, the polarizing element 1 sample according to Comparative Example 60 did not have the reinforcing film 51 as in Example 60. In Comparative Example 60, the polarizing element 1 sample according to Comparative Example 60 was prepared using the same manufacturing method (S10, S12, S14, S16, S18) as in Example 60, except that the reinforcing film deposition step (S15) was not performed.

[0471] (2) Dimensional conditions of each part of the polarizing element 1 The dimensions and shapes of each part of the polarizing element 1 samples for Example 60 and Comparative Example 60, which were manufactured using the above method, are as follows. P: 151nm W T :20nm W B :43nm 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: 430~680nm

[0472] (3) Observation results regarding the presence or absence of inclination of the convex portion 22 The cross-sections of the polarizing element 1 samples from Example 60 and Comparative Example 60, which were prepared using the above manufacturing method, were observed using a transmission electron microscope (TEM). Schematic diagrams of the cross-sectional shape of the polarizing element 1 samples observed by these TEM images are shown in Figures 30 and 31.

[0473] As shown in Figure 30, in the sample according to Example 60, the protruding portions 22 of the grid structure 20 were not tilted but extended straight upwards, maintaining the desired grid shape. In contrast, in the sample according to Comparative Example 60, the protruding portions 22 of the grid structure 20 were tilted to the left by about 10°. In particular, the upper part of the protruding portions 22 on which the reflective film 30 was deposited was tilted to the left in a curved manner, making it impossible to maintain the desired grid shape.

[0474] The reason why the raised ridge portion 22 in Comparative Example 60 tilted is thought to be that, in Comparative Example 60, the raised ridge portion 22 was not reinforced by the reinforcing film 51, and therefore, when the reflective film 30 (Al film) was deposited on the raised ridge portion 22 at a high temperature, the resin of the raised ridge portion 22 softened. Furthermore, in the manufacturing method of the polarizing element 1 described above, the Al material is deposited alternately from the left and right sides from diagonally above the raised ridge portion 22 through multiple deposition processes (see Figure 27). As a result, stress due to thermal shrinkage caused by the temperature decrease of the Al film deposited on one side of the raised ridge portion 22 accumulated around the Al film, and it is thought that this accumulated stress caused the softened raised ridge portion 22 to tilt towards the side on which the Al film was deposited (see Figure 28).

[0475] Based on the above results, it has been demonstrated that by covering the raised portion 22 with the reinforcing film 51 as in Example 60, the rigidity and heat resistance of the raised portion 22 can be increased, thereby effectively suppressing the tilting of the raised portion 22 caused by the formation of the reflective film 30.

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

[0477] In the optical properties test, the optical properties (Tp properties, Ts properties, Rp properties, Rs properties, contrast, Tp×Rs properties) of the polarizing element 1 samples from 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 properties test, simulations were performed on samples of polarizing element 1 according to Example 60 and Comparative Example 60 by changing 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°. The values ​​of Tp, Rs, Ts, and Rp were calculated by changing the wavelength λ of the obliquely incident light in the range of 430 to 680 nm, and the average values ​​of multiple Tp, Ts, Rp, and Rs values ​​calculated for incident light at each wavelength λ were used. The contrast (CR) of the transmitted light was also calculated by dividing Tp by Ts (CR = Tp / Ts).

[0479] The relationship between Tp, Rs, Ts, Rp, CR, Tp×Rs calculated as described above and λ is shown in the tables in Figures 30 and 31.

[0480] According to the results of these optical property tests, as shown in Figures 30 and 31, the Ts characteristics, Rp characteristics, and Rs characteristics are similar between Example 60 and Comparative Example 60. In contrast, Example 60 is superior to Comparative Example 60 in 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%). Consequently, 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 than the average CR value of Comparative Example 60 (570), by more than 1.9 times.

[0481] In Comparative Example 60, as shown in Figure 30, the convex portion 22 is inclined, and the reflective film 30 supported by the inclined convex portion 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 Figure 31, the convex portion 22 is not inclined and extends straight, so the reflective film 30 does not unnecessarily block obliquely incident light. Therefore, it is considered 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, since the convex portion 22 is not tilted, it is significantly superior in Tp characteristics, Tp×Rs characteristics, and CR compared to Comparative Example 60, in which the convex portion 22 is tilted. In particular, when the polarizing element 1 is used as a polarizing beam splitter (PBS), the ability to achieve both high Tp×Rs characteristics and high CR is extremely beneficial for the polarizing beam splitter. Furthermore, even when CR is evaluated alone, Example 60 achieves significantly better CR than Comparative Example 60, and is beneficial because it can greatly improve the CR performance of the polarizing beam splitter.

[0483] From the results of the optical properties tests described above, it has been demonstrated that by providing a reinforcing film 51 between the convex portion 22 and the reflective film 30, as in Example 60, and thereby imparting rigidity and heat resistance to the convex portion 22, the tilting of the convex portion 22 can be suppressed, and 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 preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Industrial applicability]

[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 characteristics, do not cause deterioration in heat dissipation or manufacturing costs, and have excellent transmittance to light over a wide range of incident angles. Furthermore, according to this embodiment, it is possible to provide a projection display device with excellent polarization characteristics and heat resistance, and a vehicle equipped with the projection display device. Furthermore, according to this embodiment, it is possible to provide a photocurable acrylic resin for imprinting that has a low viscosity in the uncured resin composition and excellent heat resistance in the cured resin composition. [Explanation of symbols]

[0486] 1 Wire grid polarizer 2 light source 3 Display element 4 reflector 5 Display surface 6. Cover section 10 circuit boards 20 Grid Structures 21 Base section 22 Convex part 22b Side 23 Grid Structure Materials 24 recesses 29 Waist area 30 Reflective film 30a top 40 Protective film 41 grid 42 Valley 50 Heat dissipation components 51 Reinforcement film 60 Original recording 61 Substrate for Master Disc 62 Metal film for master disc 63 Convex part 64 Release film coating 65 grooves 70 Resist Masks 80 Metal film 100 Head-Up Display Devices 200 Projection display device 210 Light source 220 PS Converter 230 Polarizing Beam Splitter 240 Reflective Liquid Crystal Display Elements 250 lenses 260 Light absorber 300 Chambers 310 Gas inlet 320 jigs 330 Gas exhaust port 340 Vacuum pump TS substrate thickness TB base thickness Pitch of the protruding part Height of the H-shaped protrusion Hx Height range where the reflective film covers the sides of the convex portion Ds side thickness of the reflective film Dt reflective film tip thickness W MAX The maximum width of the reflective film covering the raised grooves (maximum grid width) W B Width of the bottom of the raised section (grid bottom width) W T Width of the top of the convex part (width of the top of the convex part) W A Effective grid width W G Gap width Rc coverage Tt The thickness of the protective film covering the top of the reflective film that encloses the raised ridges. Bt: Thickness of the protective film covering the lower side of both sides of the raised section and the surface of the base section. Rt Reinforcement film thickness

Claims

1. A substrate made of inorganic material, A grid structure made of an organic material, comprising a base portion provided on the substrate and a plurality of protruding ridges integrally formed thereon, A functional film made of a metal material that covers a part of the aforementioned protruding portion, A reinforcing film made of an inorganic oxide is interposed between a portion of the protruding portion covered by the functional film and the functional film, and reinforces the protruding portion. Equipped with, The aforementioned protruding portion has a tapered shape, becoming narrower in width as it moves away from the base portion. The reinforcing film covers at least the tip and the upper sides of both sides of the protruding portion. The functional film covers the tip and upper sides of both sides of the protrusion via the reinforcing film, but does not cover the lower sides of both sides of the protrusion and the base portion. When the coverage rate (Rc) of the side surface of the protrusion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the protrusion covered by the functional film to the height (H) of the protrusion, the coverage rate (Rc) is 30% or more and 70% or less. Wire grid polarizer.

2. The wire grid polarizing 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 grid structure and the protective film further comprise a protective film covering the surface of the functional film, The protective film continuously covers the surface of the functional film, the lower sides of both sides of the protruding portion, and the surface of the base portion. When the thickness of the protective film covering the top of the functional film that encloses the protruding portion is Tt, and the thickness of the protective film covering the lower sides of both sides of the protruding portion and the surface of the base portion is Bt, the following equation (10) is satisfied: The wire grid polarizing element according to claim 1. Bt / Tt≧0.85 (10)

4. A wire grid polarizing element according to claim 3, satisfying the following formula (11). 0.85 ≤ Bt / Tt ≤ 1.07 ... (11)

5. A wire grid polarizing element according to claim 3, satisfying the following formula (12). 1.00<Bt / Tt≦1.07 (12)

6. The protective film is made of SiO ２ A wire grid polarizing element according to claim 3, which has a single-layer structure consisting of the above.

7. The aforementioned protective film is made of Al ２ O ３ A first coating layer consisting of and SiO ２ The wire grid polarizing element according to claim 3, which has a laminated structure including a second coating layer made of the same material.

8. The wire grid polarizing element according to claim 1, wherein the cross-sectional shape of the entire convex structure composed of the convex portion and the functional film has a constricted portion in the width direction of the entire convex structure, located directly below the lower end of the functional film covering the convex portion, where the width of the entire convex structure is narrowed.

9. A method for manufacturing a wire grid polarizing element according to any one of claims 1 to 8, A process of forming a grid structure material made of organic material on a substrate made of inorganic material, A step of forming a grid structure in which a base portion provided on the substrate and a plurality of protruding portions extending from the base portion are integrally formed by applying nanoimprint to the grid structure material, A step of forming a reinforcing film using an inorganic oxide that covers at least a portion of the raised portion, A step of forming a functional film that covers a portion of the protruding portion via the reinforcing film using a metal material, Includes, In the process of forming the grid structure, the convex portion having a tapered shape that narrows in width as it moves away from the base portion is formed. In the process of forming the functional film, The reinforcing film covers at least the tip and upper sides of both sides of the protrusion, and the functional film covers the tip and upper sides of both sides of the protrusion via the reinforcing film, but does not cover the lower sides of both sides of the protrusion and the base portion. The functional film is formed such that the coverage rate (Rc) of the sides of the protrusion by the functional film is the ratio of the height (Hx) of the portion of the sides of the protrusion covered by the functional film to the height (H) of the protrusion, and the coverage rate (Rc) is 30% or more and 70% or less. A method for manufacturing a wire grid polarizing element.

10. In the step of forming the reinforcing film, A method for manufacturing a wire grid polarizing element according to claim 9, wherein the reinforcing film is formed by vapor deposition such that the reinforcing film covers the tip and upper sides of both sides of the protruding portion.

11. In the step of forming the reinforcing film, A method for manufacturing a wire grid polarizing element according to claim 9, wherein the reinforcing film is formed by the ALD method such that the reinforcing film continuously covers the tip and both sides of the protruding portion and the surface of the base portion.

12. The process further includes a step of forming a protective film on the surface of the grid structure and the functional film, In the process of forming the protective film, A method for manufacturing a wire grid polarizing element according to claim 9, wherein the protective film is formed by the ALD method such that the protective film continuously covers the surface of the functional film, the lower sides of both sides of the protruding portion, and the surface of the base portion.

13. The step of forming the protective film is as follows: The first step involves introducing a precursor gas into a chamber in which the grid structure coated with the functional membrane is placed, A second step involves introducing an inert gas into the chamber to exhaust excess precursor gas to the outside of the chamber, A third step involves introducing an oxidizing agent gas into the chamber, A fourth step involves introducing an inert gas into the chamber to exhaust excess oxidizing gas to the outside of the chamber, Includes, In the first step, the precursor gas is introduced into the chamber and filled without exhausting the precursor gas to the outside of the chamber. In the third step, the oxidizing gas is introduced into the chamber and filled without exhausting the oxidizing gas to the outside of the chamber. A method for manufacturing a wire grid polarizing element according to claim 12.

14. Light source and A polarization beam splitter is positioned so that the incident light from the light source is incident at an incident angle of 30° or more and 60° or less, and separates the incident light into a first polarization and a second polarization. A reflective liquid crystal display element is arranged such that the first polarization reflected by the polarization beam splitter, or the second polarization transmitted through the polarization beam splitter, is incident on it, and the reflective liquid crystal display element reflects and modulates the incident first polarization or second polarization. A lens is arranged such that the first or second polarization reflected and modulated by the reflective liquid crystal display element is incident on the polarizing beam splitter, Equipped with, The polarization beam splitter is composed of a wire grid polarizing element as described in any one of claims 1 to 8, in a projection display device.

15. A vehicle comprising the projection display device described in claim 14.

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