Wire grid polarization element, manufacturing method of wire grid polarization element, projection display device and vehicle

Abstract

To improve optical characteristics by inhibiting protrusions of a grid structure from being inclined due to deposition of a functional film.SOLUTION: A wire grid polarization element 1 comprises: a substrate 10; a grid structure 20 obtained by integrally forming a base part 21 and a plurality of protrusions 22; a functional film 30 covering a part of the protrusion 22; and a reinforced film 51. The reinforced film 51 includes inorganic oxide, is interposed between the part of the protrusion 33 covered by the functional film 30 and the functional film 30 to reinforce the protrusion 22. The reinforced film 51 covers and envelopes at least a tip 22a and an upper side of both side faces 22b of the protrusion 22. The functional film 30 covers and envelopes a top of the protrusion 22 via the reinforced film 51 while does not cover a bottom side of the protrusion 22 and the base part 21, and has a coverage factor (Rc) of 30% or more and 70% or less.SELECTED DRAWING: Figure 25

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 Art

[0002] A wire grid polarizing element is used, for example, as a polarizing beam splitter of a head-up display device for a vehicle. The head-up display device is installed on the dashboard inside the vehicle and requires high heat resistance and heat dissipation when used in a high-temperature environment such as in summer. Therefore, the wire grid polarizing element mounted on the head-up display device is also required to have excellent heat resistance and heat dissipation.

[0003] For example, in Patent Document 1, in order to improve the heat resistance and heat dissipation of a wire grid polarizing element, a substrate of the wire grid polarizing element is formed of a transparent inorganic material (for example, glass), and a grid structure provided on the substrate is integrally formed of a transparent organic material (for example, resin). Such a grid structure is integrally formed with a base portion provided on the substrate and a plurality of protruding ridges protruding from the base portion, and the tip portions of the respective protruding ridges are covered with a functional film made of a metal material such as Al, thereby imparting a reflection function to incident light. Further, Patent Document 1 discloses that in order to improve various optical characteristics (transmission axis transmittance (Tp) characteristics, Tp×Rs characteristics, contrast) required for a wire grid polarizing element, the height H of the protruding ridges is increased to 160 nm or more.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the protruding strip portion of the grid structure described in Patent Document 1 is formed of an organic material such as resin, which has lower rigidity and heat resistance than inorganic materials such as glass, and has a tapered shape that becomes thinner toward its tip. Therefore, when the height H of the protruding strip portion is increased as described in Patent Document 1, and a high-temperature functional film is formed to cover the tip of the protruding strip portion by a film-forming method such as sputtering or vapor deposition, the protruding strip portion made of an organic material may tilt to the left or right without being able to maintain a straight upwardly extending tapered shape. Thus, when the protruding strip portion tilts due to the film formation of the functional film covering the protruding strip portion, there has been a problem that various optical characteristics (for example, Tp characteristics, Tp×Rs characteristics, contrast) required for the wire grid polarizing element deteriorate.

[0006] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a wire grid polarizing element, a method for manufacturing a wire grid polarizing element, a projection display device, and a vehicle capable of suppressing the tilting of the protruding strip portion of the grid structure due to the film formation of the functional film and improving the optical characteristics.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventor has found the following. First, the substrate of the wire grid polarizing element is formed of a transparent inorganic material, and the grid structure provided on the substrate is integrally formed of a transparent organic material. Thereby, the wire grid polarizing element can be made into a hybrid type structure composed of an organic material and an inorganic material. As a result, the heat dissipation of the wire grid polarizing element can be significantly improved.

[0008] Furthermore, as the grid structure, a grid structure in which a base portion provided along the surface of the substrate and a plurality of protruding ridges protruding from the base portion are integrally formed is used. As a result, since the grid structure can be formed by a technique such as nanoimprint, the manufacturing cost of the grid structure can be reduced compared to the case of using photolithography technology or etching technology, and mass production is also possible.

[0009] Furthermore, when providing a functional film such as a reflective film that reflects light or an absorption film that absorbs light on the protruding ridges of the grid structure, the covering range and covering form of the protruding ridges by the functional film are preferably adjusted. That is, the tip of the protruding ridge and the upper side of one or both side surfaces are covered so as to be wrapped by the functional film, while the lower side of the side surface of the protruding ridge and the surface of the base portion are left open without being covered by the functional film. And the functional film has a rounded shape and bulges in the width direction of the protruding ridge so as to cover and wrap the tip and the upper side of the side surface of the protruding ridge. Furthermore, the maximum width (m MAX ) of the grid formed by combining the protruding ridge and the functional film covering the protruding ridge is made to be B ) or more of the bottom of the protruding ridge. Furthermore, it is preferable to limit the range in which the functional film covers the side surface of the protruding ridge to a specific range on the upper side of the side surface (for example, a range of 25% or more and 80% or less of the height (H) of the protruding ridge).

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

[0011] Based on the above findings, the inventor of the present invention arrived at the following invention.

[0012] To solve the above problems, according to one aspect of the present invention, a substrate made of an inorganic material, a grid structure integrally formed of an organic material, having a base portion provided on the substrate and a plurality of protruding ridges protruding from the base portion, a functional film made of a metal material and covering a part of the protruding ridges, a reinforcing film made of an inorganic oxide, interposed between a part of the protruding ridges covered by the functional film and the functional film, and reinforcing the protruding ridges, are provided, the protruding ridges have a tapered shape in which the width becomes narrower as they move away from the base portion, the reinforcing film covers at least the tip and the upper sides of both side surfaces of the protruding ridges, the functional film covers the tip and the upper side of at least one side surface of the protruding ridges via the reinforcing film, and does not cover the lower sides of both side surfaces of the protruding ridges and the base portion, when the coverage rate (Rc) of the side surface of the protruding ridges by the functional film is the ratio of the height (Hx) of the portion of the side surface of the protruding ridges covered by the functional film to the height (H) of the protruding ridges, 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 wire grid polarizing element further includes a protective film covering the surfaces of the grid structure and the functional film, the protective film continuously covers the surface of the functional film, the lower sides of both side surfaces of the protruding ridges, and the surface of the base portion, when the thickness of the protective film covering the top of the functional film covering the protruding ridges is Tt and the thickness of the protective film covering the lower sides of both side surfaces of the protruding ridges and the surface of the base portion is Bt, the following formula (10) may be satisfied. Bt / Tt ≥ 0.85 ···(10)

[0015] It may also be configured to satisfy the following formula (11). 0.85 ≤ Bt / Tt ≤ 1.07 ···(11)

[0016] It may also be configured to satisfy the following formula (12). 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 including a first coating layer made of Al2O3 and a second coating 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] It may be a hybrid wire grid polarizing element combining the substrate made of the inorganic material and the grid structure made of the organic material.

[0024] The surface of the functional film covering and enclosing the rib portion has a rounded shape and bulges in the width direction of the rib portion, The maximum width (W MAX ) of the functional film covering and enclosing the rib portion is the width (W BIt may be as described above.

[0025] The cross-sectional shape of the entire convex structure composed of the convex strip portion and the functional film may be such that there is a constricted portion where the width in the width direction of the entire convex structure becomes narrow directly below the lower end portion of the functional film covering the convex strip portion.

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

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

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

[0029] The thickness (Ds) of the functional film covering the side surface of the convex strip 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 strip portion in a cross-section orthogonal to the reflection axis direction of the wire grid polarizing element may be a trapezoid, triangle, bell-shaped, or elliptical shape whose width narrows 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 have a dielectric film.

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

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

[0036] The wire grid polarizing element may be a polarization 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, A method for manufacturing the above-described wire grid polarizing element, A step of forming a grid structure material made of an organic material on a substrate made of an inorganic material, A step of forming a grid structure in which a base portion provided on the substrate and a plurality of ridge portions protruding from the base portion are integrally formed by performing nanoimprint on the grid structure material, A step of forming a reinforcing film that covers at least a part of the ridge portion using an inorganic oxide, A step of forming a functional film that covers at least a part of the ridge portion through the reinforcing film using a metal material, including In the step of forming the grid structure, the ridge portion having a tapered shape whose width becomes narrower as it moves away from the base portion is formed, In the step of forming the functional film, The reinforcing film covers at least the tip and the upper sides of both side surfaces of the rib portion, the functional film covers the tip and the upper sides of both side surfaces of the rib portion via the reinforcing film, and does not cover the lower sides of both side surfaces of the rib portion and the base portion. When the coverage rate (Rc) of the side surface of the rib portion by the functional film is the ratio of the height (Hx) of the portion of the side surface of the rib portion covered by the functional film to the height (H) of the rib portion, a method for manufacturing a wire grid polarizing element is provided in which the coverage rate (Rc) is 30% or more and 70% or less, and the functional film is formed.

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

[0039] In the step of forming the reinforcing film, The reinforcing film may be formed by ALD so as to continuously cover the tip and both side surfaces of the rib portion and the surface of the base portion.

[0040] The method further includes a step of forming a protective film on the surfaces of the grid structure and the functional film, In the step of forming the protective film, The protective film may be formed by ALD so as to continuously cover the surface of the functional film, the lower sides of both side surfaces of the rib portion, and the surface of the base portion.

[0041] The step of forming the protective film is A first step of introducing a precursor gas into a chamber in which the grid structure covered with the functional film is disposed, A second step of exhausting excess precursor gas out of the chamber by introducing an inert gas into the chamber, A third step of introducing an oxidizing gas into the chamber, A fourth step of exhausting excess oxidizing gas out of the chamber by introducing an inert gas into the chamber, including, In the first step, the precursor gas is introduced into and filled in the chamber without exhausting the precursor gas outside the chamber, In the third step, the oxidant gas may be introduced into and filled in the chamber without exhausting the oxidant gas outside the chamber.

[0042] In the step of forming the functional film, film formation may be alternately performed on the convex strip portion from a plurality of directions by sputtering or vapor deposition.

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

[0044] The predetermined range of the incident angle may 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 including the projection display device is provided.

Advantages of the Invention

[0047] According to the present invention, it is possible to suppress the inclination of the protruding strip portion of the grid structure due to the formation of the functional film and improve the optical characteristics.

Brief Description of the Drawings

[0048]

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Embodiments for Carrying Out the Invention

[0049] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. For the sake of convenience of explanation, in the following drawings, the states of the respective members disclosed are schematically represented with scales and shapes different from the actual ones in some cases.

[0050] <1. Outline of Wire Grid Polarizing Element> First, with reference to FIGS. 1 and 2 and the like, the outline of the wire grid polarizing element 1 according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing the wire grid polarizing element 1 according to the present embodiment. FIG. 2 is a plan view schematically showing the wire grid polarizing element 1 according to the present embodiment.

[0051] The wire grid polarizing element 1 according to the present 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, flat or a curved plate. That is, the surface (the surface on which light is incident) of the wire grid polarizing element 1 may be flat or curved. Hereinafter, an example in which the wire grid polarizing element 1 according to the present 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 an arbitrary shape according to its use, function, and the like.

[0052] Incidentally, 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 one direction, or alternatively, as a polarization beam splitter that separates incident light into a first polarization (S polarization) and a second polarization (P polarization). Hereinafter, an example in which the wire grid polarizing element 1 according to the present embodiment is used as a polarization beam splitter will be mainly described.

[0053] As shown in FIGS. 1 and 2, the wire grid polarizing element 1 (hereinafter, may also be abbreviated as "polarizing element 1") includes a transparent substrate 10, a transparent grid structure 20, and an opaque functional film (for example, a reflective film 30).

[0054] In this specification, "transparent" means that the transmittance of light with a wavelength λ belonging to the use band (for example, the visible light band, the infrared light band, or the visible light and infrared light bands, etc.) is high. For example, it means that the transmittance of the light is 70% or more. The wavelength band of visible light is, for example, 360 nm or more and 830 nm or less. The wavelength band of infrared light (infrared rays) is larger than the wavelength band of visible light, for example, 830 nm or more. From the viewpoint of the preferable wavelength range of visible light projected as a display image, the wavelength λ of the use band in the polarizing element 1 according to the present 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 the present embodiment is formed of a material that is transparent to light in the use band, it does not adversely affect the polarization characteristics of the polarizing element 1 and the light transmittance, etc.

[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, for example, an organic resin material such as an ultraviolet-curable resin or a thermosetting resin having excellent heat resistance. The grid structure 20 has a concave-convex structure for realizing the polarization function of the polarizing element 1. Specifically, the grid structure 20 has a base portion 21 provided along the surface of the substrate 10, and a plurality of convex streaks 22 protruding from the base portion 21 in a grid pattern. The base portion 21 and the plurality of convex streaks 22 of the grid structure 20 are integrally formed using the same organic material.

[0057] The base portion 21 is a thin film having a predetermined thickness TB, and is laminated over the entire main surface of the substrate 10 (the XY plane shown in FIGS. 1 and 2). The thickness TB of the base portion 21 is preferably substantially 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 with a certain degree of error from the reference thickness of TB. For example, TB may vary by about ±3 μm from the reference thickness of 6 μm. In this way, the thickness TB of the base portion 21 is determined by allowing for molding errors when molding the base portion 21 by imprinting or the like.

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

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

[0060] The reflective film 30 is a thin film made of a metal material (such as a metal or a metal oxide) such as aluminum or silver, for example. The reflective film 30 is formed so as to cover at least the top of the ridge portion 22. The reflective film 30 may be composed of a metal film that functions as a metal wire of the wire grid. The reflective film 30 has a function of reflecting incident light incident on the grid structure 20.

[0061] The ridge portion 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 plurality of ridge portions 22 in the grid structure 20 (that is, the array pitch of the grid) is set to a pitch (for example, 1 / 2 or less) smaller than the wavelength λ of the incident light (for example, visible light). Thereby, the polarizing element 1 can almost completely reflect the light (S-polarized light) of the electric field vector component vibrating in the direction parallel to the reflective film 30 (conductor line) extending in the Y direction (reflection axis direction: Y direction), and can almost completely transmit the light (P-polarized light) of the electric field vector component vibrating in the direction perpendicular to the reflective film 30 (conductor line) (transmission axis direction: X direction).

[0062] As described above, the wire grid polarizing element 1 according to the present embodiment realizes a polarization function by a combination of a grid structure body 20 having a fine concavo-convex structure and a functional film (for example, a reflective film 30) selectively added to the ridge portions 22 of the grid structure body 20. The substrate 10 of the wire grid polarizing element 1 is made of an inorganic material such as glass having extremely excellent heat resistance, and the grid structure body 20 is made of an organic resin material having heat resistance. Thus, the wire grid polarizing element 1 according to the present embodiment is a hybrid type polarizing element combining an organic material and an inorganic material. Therefore, since heat can be efficiently dissipated from the grid structure body 20 having a small thermal resistance R [m 2 ·K / W] to the substrate 10, it has excellent heat dissipation properties. Therefore, the hybrid type wire grid polarizing element 1 according to the present embodiment is excellent in heat resistance and heat dissipation properties as compared with a conventional film type polarizing element made of only an organic material (heat resistance: about 100° C.), and has heat resistance in a high temperature environment up to about 200° C., for example. Thus, while realizing excellent polarization characteristics, a good heat dissipation effect can be maintained.

[0063] Furthermore, the wire grid polarizing element 1 according to the present embodiment may include a protective film 40 (see FIGS. 7 and 8) that covers the surface of the grid structure body 20. The protective film 40 is made of an inorganic material, for example, a dielectric material such as SiO2. This protective film 40 may be laminated on the entire surface of the wire grid polarizing element 1 so as to cover all the surfaces of the base portion 21, the ridge portions 22, and the reflective film 30 of the grid structure body 20 (see FIG. 7). By providing such a protective film 40, an advantageous effect that the thermal resistance R of the polarizing element 1 can be further reduced is obtained, so that while realizing excellent polarization characteristics, a better heat dissipation effect can be maintained.

[0064] In addition, as described above, since the grid structure 20 in which the base portion 21 and the rib portion 22 are integrally formed can be manufactured using a printing technique such as nanoimprinting, a fine concavo-convex structure can be realized with a simple manufacturing process. Therefore, compared with the case of manufacturing using photolithography technology or etching technology, the cost and labor required for manufacturing the grid structure 20 can be reduced. Thus, the hybrid polarizing element 1 according to the present embodiment has an advantage that the manufacturing cost can be significantly reduced compared to a polarizing element made of only a conventional inorganic material, and the unit price of the wire grid polarizing element 1 can be made inexpensive.

[0065] On the other hand, a conventional film-type organic polarizing plate uses a large amount of organic materials, and since the thickness of the substrate (base film), double-sided tape (OCA: Optically Clear Adhesive), and grid structure becomes large, it is considered that the heat dissipation and heat resistance are inferior compared to the hybrid polarizing element 1 according to the present embodiment.

[0066] In addition, in the wire grid polarizing element 1 according to the present embodiment, the grid composed of the rib portion 22 of the grid structure 20 and the reflection film 30 has a special tree shape as shown in FIG. 1 and the like (details will be described later). Thereby, even when light is incident obliquely from an oblique direction at a wide range of large incident angles θ (for example, 30 to 60°) with respect to the polarizing element 1, the transmittance of the second polarized light (P-polarized light) transmitted through the polarizing element 1 (that is, the transmission axis transmittance Tp) can be suppressed from decreasing depending on the incident angle θ of the obliquely incident light. Therefore, the product of the reflectance of the first polarized light (S-polarized light) reflected by the wire grid polarizing element 1 (that is, the 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 the present embodiment is excellent in the polarization separation characteristics represented by the Tp×Rs, and can preferably separate obliquely incident light into S-polarized light (reflected light) and P-polarized light (transmitted light). Thus, the polarizing element 1 according to the present embodiment can obtain sufficient transmittance and polarization separation characteristics even for obliquely incident light with a large incident angle θ and a wide range.

[0067] As described above, the wire grid polarizing element 1 according to the present embodiment is excellent in heat resistance and heat dissipation, can reduce the manufacturing cost, and is also excellent in permeability and polarization separation characteristics with respect to obliquely incident light with a large incident angle θ in a wide range. Therefore, the wire grid polarizing element 1 according to the present embodiment can be suitably applied as various components of various products. For example, the polarizing element 1 can be applied to a polarizing beam splitter installed in a smart display. Further, the polarizing element 1 can be applied to a polarizing element for countermeasures against heat from sunlight, a polarizing element for countermeasures against heat from an LED light source, a polarizing reflection mirror, etc., installed in a head-up display (HUD). Furthermore, the polarizing element 1 can also be applied to a polarizing beam splitter installed in a headlight such as an adaptive driving beam (ADB). In addition, the polarizing element 1 can also be applied to a lens-integrated retardation element, a lens-integrated polarizing element, etc., installed in various devices for augmented reality (AR) or virtual reality (VR).

[0068] <2. Components of the wire grid polarizing element> Next, with reference to FIGS. 1 and 2 and the like, the components of the wire grid polarizing element 1 according to the present embodiment will be described in detail.

[0069] <2.1. Substrate> As shown in FIG. 1, the wire grid polarizing element 1 according to the present 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] As the material of the substrate 10, from the viewpoint of obtaining more excellent heat dissipation and heat resistance, for example, it is preferably an inorganic material such as various glasses, quartz, crystal, sapphire, etc., more preferably an inorganic material having a thermal conductivity of 1.0 W / m·K or more, and even more preferably an inorganic material having a thermal conductivity of 8.0 W / m·K or more.

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

[0072] <2.2. Grid structure> As shown in FIGS. 1 and 2, the polarizing element 1 according to the present embodiment includes a grid structure 20 having the base portion 21 and the lattice-shaped convex stripe portions 22 on the substrate 10. By providing a reflection film 30 described later on the convex stripe portions 22, the grid structure 20 can obtain desired polarization characteristics.

[0073] When light is incident on the polarizing element 1 from the surface side where the grid structure 20 is formed, a part of the incident light is reflected by the reflection film 30. Among the light incident on the reflection film 30, the light having an electric field component in the direction orthogonal to the longitudinal direction of the convex stripe portion 22 (i.e., the extending direction of the convex stripe portion 22 = the reflection axis direction: Y direction) (i.e., the width direction of the convex stripe portion 22 = the transmission axis direction: X direction) passes through the polarizing element 1 with a high transmittance. On the other hand, most of the light having an electric field component in the direction parallel to the longitudinal direction of the convex stripe portion 22 (i.e., the extending direction of the convex stripe portion 22 = the reflection axis direction: Y direction) among the light incident on the reflection film 30 is reflected by the reflection film 30. Therefore, in the present embodiment, by providing the grid structure 20 partially covered by the reflection film 30, a single polarization can be created. Note that the same polarization effect can also be obtained for the light incident from the back surface side of the substrate 10.

[0074] As shown in FIG. 1, the grid structure 20 has a base portion 21. The base portion 21 is a thin film provided along the surface of the substrate 10 and is a portion for supporting the convex rib portion 22. When the uneven structure (convex rib portion 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 convex rib portion 22 are integrally formed of the same material. Further, since the grid structure 20 has the base portion 21, the strength of the convex rib portion 22 can be increased as compared with the case where the convex rib portion 22 is directly formed on the substrate 10. Therefore, the durability of the grid structure 20 can be enhanced. Furthermore, since the base portion 21 is in close contact with the substrate 10 over the entire surface, the peel resistance of the grid structure 20 can be enhanced.

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

[0076] Further, according to the polarizing element 1 according to the present embodiment, since the base portion 21 and the plurality of convex rib portions 22 of the grid structure 20 are directly formed 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. Note that the temperature difference ΔT is the temperature difference between the temperature T1 [° C.] of the outermost surface (the root portion of the plurality of convex rib portions 22) of the base portion 21 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. Thereby, the heat of the grid structure 20 made of an organic material can be quickly transferred to the substrate 10 made of an inorganic material, efficiently released from the substrate 10 to the outside of the polarizing element 1, and heat can be dissipated. Thus, the temperature difference ΔT can be, for example, 32 °C or less. Further, the thickness TB of the base portion 21 is more preferably 0.09 mm or less, whereby the temperature difference ΔT can be, for example, 20 °C or less. Further, the thickness TB of the base portion 21 is more preferably 0.045 mm or less, whereby the temperature difference ΔT can be, for example, 10 °C or less. Further, the thickness TB of the base portion 21 is particularly preferably 0.02 mm or less, whereby the temperature difference ΔT can be, for example, 5 °C or less. In this way, by reducing the thickness TB of the base portion 21, the heat dissipation property from the grid structure 20 to the outside through the substrate 10 can be improved, so that the heat dissipation property and heat resistance of the polarizing element 1 can be improved.

[0078] Furthermore, as shown in FIGS. 1 and 2, the grid structure 20 has a plurality of protruding ridges 22 protruding from the base portion 21. The protruding ridges 22 extend in the longitudinal direction along the reflection axis direction (Y direction) of the polarizing element 1 according to the present embodiment. By arranging the plurality of protruding ridges 22 at a predetermined pitch in the X direction and arranging them at a predetermined interval from each other, a lattice-like uneven structure is formed.

[0079] Here, as shown in FIG. 1, in the longitudinal cross section (XZ cross section) orthogonal to the reflection axis direction (Y direction) of the polarizing element 1, it is necessary that the pitch P in the transmission axis direction (X direction) of the protruding ridge 22 is shorter than the wavelength of the light in the used band. The reason for this is to obtain the polarization effect described above. More specifically, the pitch P of the protruding ridges 22 is preferably 50 to 300 nm, more preferably 100 to 200 nm, and particularly preferably 100 to 150 nm from the viewpoint of achieving both the ease of manufacturing the protruding ridges 22 and the polarization characteristics.

[0080] Also, as shown in FIGS. 1 and 2, the width W of the bottom of the protruding ridge 22 in the above longitudinal cross section (XZ cross section) BAlthough not particularly limited, from the viewpoint of achieving both ease of manufacturing 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 portion of the convex strip portion 22 T Although not particularly limited, from the viewpoint of achieving both ease of manufacturing 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 portion of the convex strip portion 22 B and the width W of the top portion 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 strip portions 22, the width of the convex strip portion 22 at a height position 20% above the height H of the convex strip portion 22 from the bottom of the convex strip portion 22 is measured, and the arithmetic mean value thereof is taken as the width W of the bottom portion of the convex strip portion 22 B can be obtained. Further, for the above-mentioned any four convex strip portions 22, the width of the convex strip portion 22 at a height position 20% below the height H of the convex strip portion 22 from the tip 22a of the convex strip portion 22 is measured, and the arithmetic mean value thereof is taken as the width W of the top portion of the convex strip portion 22 T can be obtained.

[0082] Also, as shown in FIG. 1, the height H of the convex strip portion 22 in the longitudinal cross section (XZ cross section) is not particularly limited, but from the viewpoint of achieving both ease of manufacturing 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 strip 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 strip portion 22 at any four positions, the height of the convex strip portion 22 at the center position in the width direction of the convex strip portion 22 is measured, and the arithmetic mean value thereof can be taken as the height H of the convex strip portion 22.

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

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

[0085] In addition, since the rib portion 22 has a tapered shape such as a tapered shape, the refractive index of the grid structure 20 gradually changes. Therefore, similar to the moth-eye structure, an antireflection effect of incident light due to a physical change in the refractive index of the grid structure 20 can be obtained. Thus, it is possible to expect an effect of reducing the reflectance on the surface of the rib portion 22 of the grid structure 20 and improving the transmittance of the grid structure 20.

[0086] Further, FIG. 4 shows a specific example of the shape of the recess 24 formed between the adjacent ridge portions 22, 22. The recess 24 is a groove extending in the longitudinal direction (Y direction) of the ridge portion 22. As shown in FIG. 4, the cross-sectional shape of the recess 24 in the longitudinal cross-section (XZ cross-section) may be various shapes as long as the width becomes narrower toward the bottom of the recess 24. For example, the cross-sectional shape of the recess 24A shown in FIG. 4 is trapezoidal (tapered shape), the cross-sectional shape of the recess 24B is triangular (V-shaped), the cross-sectional shape of the recess 24C is a substantially rectangular shape with a flat bottom, and the cross-sectional shape of the recess 24D is a U-shaped with a rounded bottom. As the shape of these recesses 24, an appropriate optimal shape can be selected in consideration of productivity such as mold release property during nanoimprint formation.

[0087] Moreover, 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 viewpoint of ensuring transparency and excellent manufacturability, it is preferable to use various thermosetting resins, various ultraviolet curable resins, etc. as the material of the grid structure 20.

[0088] Furthermore, from the viewpoints of ease of manufacture and manufacturing cost, it is preferable to use a material different from that of the substrate 10 for the material constituting the grid structure 20. In addition, when the materials of the grid structure 20 and the substrate 10 are different, their refractive indices will be different. Therefore, when there is an influence on the refractive index of the entire polarization element 1, a refractive index adjustment layer may be provided between the grid structure 20 and the substrate 10 as appropriate.

[0089] For example, as the material constituting the grid structure 20, curable resins such as epoxy polymerizable compounds and acrylic polymerizable compounds can be used. The epoxy polymerizable compound is a monomer, oligomer, or prepolymer having one or more epoxy groups in the molecule. Examples of the epoxy polymerizable compound include various bisphenol type epoxy resins (bisphenol A type, F type, etc.), novolak type epoxy resins, various modified epoxy resins such as rubber and urethane, naphthalene type epoxy resins, biphenyl type epoxy resins, phenol novolak type epoxy resins, stilbene type epoxy resins, triphenol methane type epoxy resins, dicyclopentadiene type epoxy resins, triphenyl methane type epoxy resins, and prepolymers thereof.

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

[0091] Examples of the "monofunctional monomer" include carboxylic acids (such as acrylic acid), hydroxy compounds (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), 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, N,N-dimethylaminopropyl acrylamide, N,N-dimethylacrylamide, acryloylmorpholine, N-isopropylacrylamide, N,N-diethylacrylamide, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate), 2,4,6-tribromophenol acrylate, 2,4,6-tribromophenol methacrylate, 2-(2,4,6-tribromophenoxy)ethyl acrylate), 2-ethylhexyl acrylate, and the like.

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

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

[0094] In addition, examples of the curing initiator of the curable resin described above include a thermal curing initiator, a photo-curing initiator, and the like. The curing initiator may be cured by some energy ray (for example, electron beam) other than heat and light. When the curing initiator is a thermal curing initiator, the curable resin is a thermosetting resin, and when the curing initiator is a photo-curing initiator, the curable resin is a photo-curing resin.

[0095] Among these, it is preferable to use an ultraviolet curing initiator as the curing initiator. The ultraviolet curing initiator is a kind of photo-curing initiator. Examples of the ultraviolet curing initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and the like. Therefore, the curable resin is preferably an ultraviolet curable resin. Further, from the viewpoint of transparency, the curable resin is more preferably an ultraviolet curable acrylic resin.

[0096] Note that the method for forming the grid structure 20 is not particularly limited as long as it can form the base portion 21 and the rib portion 22 described above. For example, a method for forming unevenness such as photolithography or imprint can be used. Among these, from the viewpoint of being able to form an uneven pattern in a short time and easily, and further being able to surely form the base portion 21, it is preferable to form the base portion 21 and the rib portion 22 of the grid structure 20 by imprint.

[0097] When forming the base portion 21 and the ridge portion 22 of the grid structure 20 by nanoimprinting, for example, after applying a material (grid structure material) for forming the grid structure 20 on the substrate 10, a master disk with unevenness is pressed against the grid structure material, and in this state, ultraviolet light is irradiated or heat is applied to cure the grid structure material. Thereby, the grid structure 20 having the base portion 21 and the ridge portion 22 can be formed.

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

[0099] As shown in FIG. 1, the reflective film 30 is formed so as to cover and wrap the tip 22a and a part of the side surface 22b of the ridge portion 22 of the grid structure 20. And as shown in FIG. 1, the reflective film 30 is formed so as to extend along the longitudinal direction (Y direction) of the ridge portion 22 of the grid structure 20. Thereby, the reflective film 30 can reflect light having an electric field component in a direction parallel to the longitudinal direction of the ridge portion 22 (reflection axis direction: Y direction) among 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 having reflectivity with respect to light in the used band. For example, single metal elements such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, Te, and metal materials such as alloys containing one or more of these elements can be mentioned.

[0101] Note that the reflective film 30 may be a single-layer film made of the above metal or a multi-layer film made of a plurality of metal films. Further, as long as the reflective film 30 has a reflective function, it can also include other layers such as a dielectric film as necessary. The dielectric film is a thin film made of a dielectric. As the material of the dielectric film, general materials such as SiO2, Al2O3, MgF2, and TiO2 can be used. Further, the refractive index of the dielectric film is preferably greater than 1.0 and not more than 2.5. Note that since the optical characteristics of the reflective film 30 are also affected by the refractive index of the surroundings, the polarization characteristics may be controlled by the material of the dielectric film.

[0102] <2.4. Special Shapes of the Ridge Portions and the Reflective Film> Here, the special shapes of the ridge portions 22 of the grid structure 20 and the reflective film 30 in the polarization element 1 according to the present embodiment will be described in detail.

[0103] In the polarization element 1 according to the present embodiment, as shown in FIGS. 1 and 5, the reflective film 30 covers the tip 22a of the ridge portion 22 of the grid structure 20 and the upper side of at least one side surface 22b, and is formed so as not to cover the lower side of both side surfaces 22b of the ridge portion 22 and the base portion 21. In the examples of FIGS. 1 and 5, the reflective film 30 covers the upper sides of both side surfaces 22b of the ridge portion 22, but may cover only the upper side of one side surface 22b of the ridge portion 22.

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

[0105] Furthermore, the surface of the reflective film 30 that covers and wraps the tip 22a of the rib portion 22 and the upper side of at least one side surface 22b (hereinafter, may also be referred to as the "top of the rib portion 22") has a rounded and curved shape (for example, a vertically long substantially elliptical shape) and bulges in the width direction (X direction) of the rib portion 22. In this way, the surface of the reflective film 30 has a rounded and smooth curved surface shape and does not have angular corner portions or stepped portions. The maximum width W of the reflective film 30 that covers and wraps the top of the rib portion 22 in this way MAX is the width W at the bottom of the rib portion 22 B as described above. Furthermore, W MAX is preferably larger than W B .

[0106] Here, the maximum width W of the reflective film 30 that covers and wraps the rib portion 22 MAX 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 rib portion 22. As shown in FIGS. 1 and 5 and the like, the horizontal widths (widths in the X direction) of the outermost surfaces on both sides of the reflective film 30 that covers and wraps the rib portion 22 vary 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 is the maximum value of the total width of twice the thickness Ds on both sides of the reflective film 30 and the horizontal width W of the rib portion 22. For example, when light is incident on the grid structure 20 from the front direction (Z direction) (when the incident angle θ = 0°), W MAX corresponds to the effective grid width of the reflective film 30.

[0107] The width W at the bottom of the rib portion 22 B is, as shown in FIGS. 1 and 3, the horizontal width (width in the X direction) of the rib portion 22 at a height position (height in the Z direction) 20% above the height H of the rib portion 22 from the lowermost part (upper surface of the base portion 21) of the rib portion 22. That is, the width W at the bottom of the rib portion 22 B is the horizontal width of the rib portion 22 at a position 0.2×H above the upper surface of the base portion 21.

[0108] Also, the width W at the top of the rib portion 22 TAs shown in FIGS. 1 and 3, it is the horizontal width (width in the X direction) of the rib portion 22 at the height position 20% below the height H of the rib portion 22 from the tip 22a of the rib portion 22. That is, the width W at the top of the rib portion 22 T is the horizontal width of the rib portion 22 at a position 0.8×H above the upper surface of the base portion 21 (that is, at a position 0.2×H below the tip 22a of the rib portion 22).

[0109] In the following description, the convex structure formed by combining the rib portion 22 and the reflective film 30 may be referred to as a "grid", and the height of the convex structure (that is, the grid) formed by combining the rib portion 22 and the reflective film 30 may be referred to as the "grid height". Also, the maximum width W of the reflective film 30 covering the rib portion 22 MAX is referred to as the "grid maximum width W MAX ", and the width W at the bottom of the rib portion 22 B may be referred to as the "grid bottom width W B ". Also, the width W at the top of the rib portion 22 T may be referred to as the "rib top width W T ", and the width at the central position in the height direction of the rib portion 22 may be referred to as the "rib central width".

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

[0111] As described above, in the grid structure 20 according to the present embodiment, a tapered rib portion 22 and a reflective film 30 that covers only the tip 22a and the upper side of the side surface 22b of the rib portion 22 are formed. And the lower side of the side surface 22b of the rib portion 22 is not covered with the reflective film 30 and is open.

[0112] As a result, the cross-sectional shape of the rib portion 22 covered with the curved reflective film 30 (that is, the cross-sectional shape of the grid) has the following special cross-sectional shape. That is, as shown in FIGS. 1 and 5, etc., the horizontal width of the upper side portion of the rib portion 22 where the reflective film 30 exists (for example, the maximum grid width W MAX ) is large, and the horizontal width of the portion from the central portion to the bottom side of the rib portion 22 that is not covered with the reflective film 30 and is exposed (for example, the width W B ) of the bottom of the exposed rib portion 22 is small. And the cross-sectional shape of the entire convex structure (that is, the "grid") composed of the rib portion 22 and the reflective film 30 has a constricted portion that constricts inward and has a narrow width in the X direction at a position directly below the lower end of the curved reflective film 30. Such a special cross-sectional shape of the grid can be likened to the shape of a tree. Specifically, the round and widely spreading leaf portion of the tree corresponds to the portion of the reflective film 30 that covers the top of the rib portion 22, the trunk portion of the tree corresponds to the lower side portion of the rib portion 22 that is not covered with the reflective film 30, and the portion of the ground where the tree grows corresponds to the base portion 21. Therefore, in the following description, the special cross-sectional shape of the grid composed of the rib portion 22 and the reflective film 30 of the grid structure 20 as described above is referred to as the "special tree shape".

[0113] The grid of the grid structure 20 of the polarizing element 1 according to the present embodiment has the above-described special tree shape. Thereby, for example, when incident light is incident on the polarizing element 1 from an oblique direction, the effective grid width W A becomes small, and the gap width W G becomes large. Here, the effective grid width W A is the width of the reflective film 30 in the direction perpendicular to the obliquely incident light. The gap width W G is the gap between two adjacent reflective films 30, 30 of the grid, and is the width of the gap in the direction perpendicular to the obliquely incident light. The effective grid width W AThe larger it is, the more likely the obliquely incident light is to be reflected by the reflection film 30 and the less likely it is to reach the transparent convex strip portion 22 and the base portion 21. Therefore, the transmittance of the obliquely incident light in the polarization element 1 decreases. On the other hand, the larger the gap width W G is, the more likely the obliquely incident light is to pass through between two adjacent reflection films 30, 30 and reach the transparent convex strip portion 22 and the base portion 21. Therefore, the transmittance for the obliquely incident light can be increased.

[0114] Therefore, since the grid of the polarization element 1 according to the present embodiment has the above special tree shape, the gap width W for the obliquely incident light G becomes large, and the obliquely incident light passes through the gaps between the round reflection films 30, 30 and reaches the transparent grid structure 20 and is likely to transmit. Therefore, since the transmission axis transmittance Tp of the obliquely incident light is high, the transmittance for the obliquely incident light and the polarization separation characteristic (Tp×Rs characteristic) are very excellent. Furthermore, the reflection function of the obliquely incident light by the reflection film 30 and the transmission function of the obliquely incident light by the grid structure 20 can be realized in a well-balanced manner, and the polarization separation characteristic for the obliquely incident light can be further improved.

[0115] <2.5. Method for Forming Reflection Film and Specific Example> Here, with reference to FIG. 5, a method for forming the reflection film 30 will be described.

[0116] As a method for forming the reflection film 30 so that the reflection film 30 covers the tip 22a and a part of both side surfaces 22b of the convex strip portion 22 of the grid structure 20, as shown in FIG. 5, it is preferable to form the reflection film 30 by alternately performing sputtering or vapor deposition in an oblique direction (film formation incident angle φ) with respect to the convex strip portion 22 of the grid structure 20. Thereby, the reflection film 30 can be formed so as to cover and wrap the tip 22a and the upper side of both side surfaces 22b of the convex strip portion 22. The film formation incident angle φ for forming the reflection film 30 by sputtering or vapor deposition is not particularly limited, but can be, for example, about 5 to 70° with respect to the surface of the substrate 10.

[0117] Thus, in this embodiment, after forming the grid structure 20 made of a transparent material, the reflective film 30 made of a metal material is formed by sputtering or vapor deposition. Thereby, the film formation conditions, material, and film thickness of the reflective film 30 can be easily changed. Also, even when the reflective film 30 is composed of a multilayer film, it can be easily dealt with. For this reason, film design utilizing the interference effect becomes possible by combining metals, semiconductors, and dielectrics, and when forming the reflective film 30 by etching as in the prior art, it is not necessary to consider the material configuration that can be etched. Thereby, it also becomes easy to adjust the reflectance of the polarized light wave parallel to the grid structure 20 and to adjust the transmittance (transmission amount) of the polarized light in the direction perpendicular to the grid. In addition, after forming the grid structure 20, forming the reflective film 30 requires no equipment such as a vacuum dry etching apparatus, and there is no need to prepare complicated processes, gases corresponding to etching materials, and safety devices such as decontamination devices. Therefore, running costs such as equipment investment and maintenance can be reduced, and cost merits can also be obtained.

[0118] Note that the thickness Dt of the reflective film 30 covering the tip 22a of the ridge portion 22 shown in FIG. 5 and the thickness Ds of the reflective film 30 covering the side surface 22b of the ridge portion 22 are not particularly limited and can be appropriately changed according to the shape of the ridge portion 22 of the grid structure 20, the performance required for the reflective film 30, and the like. For example, from the viewpoint of obtaining more excellent reflection performance, it is preferable that the thicknesses Dt and Ds of the reflective film 30 be 2 to 200 nm, more preferably 5 to 150 nm, still more preferably 10 to 100 nm, and particularly preferably 15 to 80 nm. Note that the thickness Ds of the reflective film 30 is the thickness of the thickest portion among the reflective films 30 covering the side surface 22b of the ridge portion 22 as shown in FIG. 5.

[0119] Also, the shape of the reflective film 30 is not particularly limited as long as it can form the above-described special tree shape, and can be appropriately selected according to the conditions of the apparatus for forming the reflective film 30 and the performance required for the reflective film 30.

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

[0121] For example, the reflective film 30A shown in FIG. 6 covers the tops of the rib portions 22A, 22B, and 22C having various cross-sectional shapes so as to wrap them roundly, and has a substantially elliptical shape that bulges greatly in the width direction of the rib portion 22. Further, the reflective film 30B has a curved shape that covers the top of the substantially wedge-shaped rib portion 22D so as to wrap it. Further, the reflective film 30C has a curved shape that covers the top of the trapezoidal rib portion 22A so as to wrap it. The coverage rate Rc of one side surface 22b of the rib portion 22 by these reflective films 30B and 30C and the coverage rate Rc of the other side surface 22b are substantially the same.

[0122] Further, the reflective film 30D covers the top of the substantially wedge-shaped rib portion 22D so as to wrap it, but is unevenly distributed on one side surface 22b (the left side surface 22b shown in FIG. 6) side of the rib portion 22. Specifically, the reflective film 30D covers a wide range of the left side surface 22b of the rib portion 22, and its coverage rate Rc is about 80%. On the other hand, the reflective film 30D covers only a narrow range of the upper side of the right side surface 22b, and its coverage rate Rc is about 25%. Thus, the coverage rate Rc by the reflective film 30D may differ between one side surface 22b and the other side surface 22b of the rib portion 22.

[0123] <2.6. Preferred range of coverage rate Rc of rib portion by reflective film> Next, the preferred range of the coverage rate Rc of the side surface 22b of the rib portion 22 by the reflective film 30 according to the present embodiment will be described.

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

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

[0126] Also, the opening rate Rr is the ratio of the height (H - Hx) of the portion of the side surface 22b of the rib portion 22 not covered by the reflective film 30 to the height (H) of the rib portion 22 shown in FIGS. 1 and 5. The opening rate Rr is represented by the following formula (2).

[0127] Rr [%] = ((H - Hx) / H) × 100 ···(2)

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

[0129] As described above, in the polarizing element 1 according to the present embodiment, it is preferable that the coverage rate Rc of the side surface 22b of the rib portion 22 by the reflective film 30 is 25% or more and 80% or less (that is, the opening rate Rr is 20% or more and 75% or less). Specifically, in the present embodiment, the reflective film 30 is formed so as to cover the tip 22a and the upper sides of both side surfaces 22b of the rib portion 22 and to be open without covering the lower sides of both side surfaces 22b. And 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 such a configuration, the polarizing element 1 according to the present embodiment can exhibit sufficient transmittance even for obliquely incident light with a large incident angle θ (for example, 45 to 60°). For example, when the obliquely incident light is separated into S-polarized light (reflected light) and P-polarized light (transmitted light) by the polarizing element 1, 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. Further, by setting the coverage ratio Rc to 25% or more and 80% or less, while maintaining the contrast (CR = Tp / Ts), which is the ratio of the transmittance Tp of the transmission axis to the reflectance Ts of the transmission axis, at a good level, the reflection action by the above-described reflection film 30 can be more surely exhibited without depending on the incident angle θ. Therefore, regardless of the incident angle θ of the obliquely incident light, high transmittance of the transmitted light can be ensured, and the polarization separation characteristics can be improved.

[0131] On the other hand, as a comparative example, when the reflection film 30 is formed so as to cover only the tip 22a of the ridge portion 22 of the grid structure 20, or when it is formed so as to cover the entire tip 22a and one side surface 22b of the ridge portion 22, the variation in the 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. Further, as a comparative example, when the reflection film 30 covers all of the tip 22a and both side surfaces 22b of the ridge portion 22 of the grid structure 20 (when the coverage ratio Rc is 100%), the transmittance significantly decreases 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 the transmitted light without depending on the incident angle θ of the obliquely incident light, it is preferable to cover the tip 22a of the ridge portion 22 and a part of at least one side surface 22b (the upper side of the side surface 22b) with the reflection film 30 as in the polarizing element 1 according to the present embodiment.

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

[0134] When the coverage ratio Rc is less than 25%, the transmission axis transmittance Tp of the P-polarized light transmitted through the polarizing element 1 decreases, and variations occur in the transmittance Tp depending on the incident angle θ, and a sufficiently high value of Tp×Rs cannot be obtained. For this reason, sufficient transmittance of the transmitted light and polarization separation characteristics represented by Tp×Rs cannot be obtained for obliquely incident light with a large incident angle θ. On the other hand, when the coverage ratio Rc is more than 80%, similar to the case where all of the tip 22a and both side surfaces 22b of the ridge portion 22 of the grid structure 20 are covered, as the incident angle θ of the obliquely incident light increases (for example, 45 to 60°), the transmission axis transmittance Tp decreases, so variations in the transmittance Tp become large depending on the incident angle θ.

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

[0136] From the same perspective, it is more preferable that the coverage ratio Rc is 30% or more and 70% or less (that is, the opening ratio Rr is 30% or more and 70% or less). Thereby, in the case of the above-mentioned oblique incidence condition, a high transmittance Tp of 80% or more can be obtained, and a high Tp×Rs of 72% or more can be obtained. Further, it is more preferable that the coverage ratio Rc is 30% or more and 60% or less (that is, the opening ratio Rr is 40% or more and 70% or less). Thereby, in the case of the above-mentioned oblique incidence condition, a high transmittance Tp of 83% or more can be obtained, and a high Tp×Rs of 75% or more can be obtained. Furthermore, it is even more preferable that the coverage ratio Rc is 40% or more and 50% or less (that is, the opening ratio Rr is 50% or more and 60% or less). Thereby, in the case of the above-mentioned oblique incidence condition, a very high transmittance Tp of 85% or more can be obtained, and a very high Tp×Rs of 77% or more can be obtained.

[0137] Regarding the reflectance Rs of the reflection axis, it is preferable that the coverage ratio Rc is 20% or more. Thereby, in the case of the above-mentioned oblique incidence condition, a high reflectance Rs of 85% or more can be obtained.

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

[0139] <2.7. Preferred range of Tp×Rs> Next, the preferred range of "Tp×Rs", which is an index representing the polarization separation characteristics of the wire grid polarizing element 1 according to the present embodiment, will be described.

[0140] Tp×Rs [%] represents the product of the transmittance of the transmission axis (Tp) and the reflectance of the reflection axis (Rs) as a percentage. This Tp×Rs serves as an index representing 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 the second polarization (P-polarization) having an electric field component parallel to the transmission axis (X direction) of the polarization element 1. The reflection axis reflectance (Rs) is the reflectance of the first polarization (S-polarization) having an electric field component parallel to the reflection axis (Y direction) of the polarization element 1.

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

[0143] The S-polarized light in the reflection axis direction mainly becomes reflected light reflected by the reflection film 30 of the polarization element 1. The reflectance [%] of the S-polarized light at this time is the reflection axis reflectance (Rs). The reflection axis reflectance (Rs) represents the ratio of the S-polarized light reflected by the polarization element 1 among the S-polarized light incident on the polarization element 1. Note that the reflection axis transmittance (Rp) represents the ratio of the S-polarized light transmitted through the polarization element 1 among the S-polarized light incident on the polarization element 1.

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

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

[0146] Here, the preferred range of the value of Tp×Rs according to this embodiment will be described. For the polarization element 1 according to this embodiment, consider the case where light with a wavelength in a predetermined range (for example, 430 to 680 nm) is incident obliquely from an oblique direction at a predetermined incident angle θ (for example, 45°) and separated into P-polarized light (transmitted light) and S-polarized light (reflected light). In the case of such an oblique incidence condition, from the viewpoint of good polarization separation characteristics of the polarization element 1, Tp×Rs is preferably 70% or more.

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

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

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

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

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

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

[0153] As described above, it can be understood that in order to improve various characteristics (Tp, Tp×Rs, CR) of the polarizing element 1, particularly Tp, it is preferable that the height H of the ridge portion 22 is larger. The reason is considered as follows. That is, when the film formation incident angle φ (see Fig. 5) when forming the reflective film 30 on the ridge portion 22 by sputtering, evaporation, or the like is the same, the lower the height H of the ridge portion 22, the larger the coverage rate Rc by the reflective film 30. When the coverage rate Rc increases, the range of the ridge portion 22 covered by the reflective film 30 becomes wider, so that P-polarized light is less likely to pass through the grid structure 20, and the transmittance Tp decreases. Therefore, under the condition that the film formation incident angle φ is the same, it can be said that it is preferable to increase the height H of the ridge portion 22 to reduce the coverage rate Rc and increase the transmittance Tp.

[0154] <2.9. Preferred Range of Tip Thickness Dt of Functional Film (Reflective Film)> When incident light is incident on the polarizing element 1 according to the present 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 ridge portion 22 of the grid structure 20 (the tip thickness Dt of the reflective film 30: see Fig. 5) is preferably 5 nm or more, and more preferably 15 nm or more.

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

[0156] <2.10. Preferred Range of Side Thickness Ds of Functional Film (Reflective Film)> Also, the thickness Ds of the reflective film 30 covering the side surface 22b of the rib portion 22 of the grid structure 20 (the side thickness Ds of the reflective film 30: see Fig. 5) is preferably 10 nm or more and 30 nm or less, more preferably 12.5 nm or more and 25 nm or less, and particularly preferably 15 nm or more and 25 nm or less. Thereby, a high transmission axis transmittance Tp, excellent Tp×Rs characteristics, and a high contrast CR of transmitted light can be obtained.

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

[0158] Also, regarding the reflectance, when the side thickness Ds of the reflective film 30 is 10 nm or more, the reflectance Rs of the reflection axis of obliquely incident light becomes 80% or more, and a high reflectance can be obtained. Further, when Ds is 12.5 nm or more, Rs of 85% or more can be obtained, which is more preferable.

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

[0160] Also, regarding the contrast CR of transmitted light (CR = Tp / Ts), the side thickness Ds of the reflective film 30 may be 10 nm or more, but when Ds is 12.5 nm or more, excellent contrast CR of 50 or more can be obtained. Further, when Ds is 15 nm or more, CR of 100 or more can be obtained, which is more preferable.

[0161] <2.11. Non-uniformity of Reflective Film> In addition, in the polarizing element 1 according to the present embodiment, the reflective film 30 covering the convex stripe portion 22 may be unevenly distributed on one side of the convex stripe portion 22 to have an asymmetrical shape in the width direction (X direction) of the convex stripe portion 22. Specifically, between one side surface 22b and the other side surface 22b of the convex stripe portion 22, the side surface thickness Ds, the coverage rate Rc, etc. of the reflective film 30 may be changed to unevenly distribute the reflective film 30 on one side surface 22b of the convex stripe portion 22. That is, the reflective film 30 may be made to cover one side surface 22b of the convex stripe portion 22 thickly and widely, and the other side surface 22b thinly and narrowly.

[0162] When the reflective film 30 is unevenly distributed on one side of the convex stripe portion 22 in this way, it is preferable that the difference between the transmission axis transmittance Tp(+) of incident light with an incident angle of +θ (+30° to +60°) with respect 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%. Then, it is preferable to adjust the thickness Ds and the coverage rate Rc of the reflective film 30 covering one side surface 22b and the other side surface 22b of the convex stripe portion 22 so that the difference between Tp(+) and Tp(-) is within 3%, and appropriately unevenly distribute the reflective film 30 on one side of the convex stripe portion 22.

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

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

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

[0166] Also, regarding the reflectance, even when the reflective film 30 is unevenly distributed on one side, the axial reflectance Rs of the obliquely incident light with the incident angle θ of +45° and -45° is 85% or more, and a high reflectance can be obtained.

[0167] Also, regarding the Tp×Rs characteristics required for a polarizing beam splitter (PBS), even when the reflective film 30 is unevenly distributed on one side, the Tp×Rs of the obliquely incident light with the incident angle θ of 45° is 75% or more, and excellent Tp×Rs characteristics can be obtained.

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

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

[0170] For example, as shown in FIG. 7, the polarizing element 1 preferably further includes a protective film 40 formed so as to cover at least the surface of the reflective film 30. Specifically, as shown in FIG. 7, the protective film 40 more preferably covers the entire surface of the grid structure 20. That is, the protective film 40 is more preferably formed so as to cover the side surface 22b of the ridge portion 22 and the surface of the base portion 21 of the grid structure 20 and the surface of the reflective film 30. By forming such a protective film 40, the scratch resistance, antifouling property, and waterproof property 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. Thereby, the antifouling property and the waterproof property of the polarizing element 1 can be further enhanced.

[0172] The material constituting the protective film 40 is not particularly limited as long as it can enhance the scratch resistance, antifouling property, and waterproof property of the polarizing element 1. Examples of the material constituting the protective film 40 include a film made of a dielectric material. More specifically, inorganic oxides, silane-based water-repellent materials, and the like can be mentioned. Examples of the inorganic oxide include Si oxide, Hf oxide, and the like. The silane-based water-repellent material may contain a fluorine-based silane compound such as perfluorodecyltriethoxysilane (FDTS), or may contain a non-fluorine-based silane compound such as octadecyltrichlorosilane (OTS).

[0173] Among these materials, it is more preferable to include at least one of an inorganic oxide and a fluorine-based water-repellent material. By including an inorganic oxide in the protective film 40, the scratch resistance of the polarizing element can be further enhanced, and by including a fluorine-based water-repellent material, the antifouling property and the waterproof property of the polarizing element can be further enhanced.

[0174] Note that the protective film 40 only needs to be formed so as to cover at least the surface of the reflective film 30. However, as shown in FIG. 7, it is more preferable that the protective film 40 is formed so as to cover the entire surfaces of the grid structure 20 and the reflective film 30. In this case, for example, as shown in the upper figure of FIG. 7, the protective film 40 may cover the end face (the end face of the base portion 21) of the grid structure 20, or, as shown in the lower figure of FIG. 7, the protective film 40 does not have to cover the end face (the end face of the base portion 21) of the grid structure 20. Further, as shown in FIG. 8, the protective film 40 can also be formed so as to cover the entire polarizing element 1 including the surface of the substrate 10 in addition to the surfaces of the grid structure 20 and the reflective film 30. In this way, by covering the outermost surface of the grid structure 20 or the polarizing element 1 with the protective film 40 made of an inorganic oxide, the thermal resistance R of the entire polarizing element 1 can be further reduced, and thus the heat dissipation property of the polarizing element 1 is further improved.

[0175] Furthermore, as shown in FIG. 9, it is preferable that a heat radiating member 50 is provided around the substrate 10 so as to surround the polarizing element 1 according to the present embodiment. By this heat radiating member 50, the heat transmitted from the substrate 10 can be released more efficiently. Here, the heat radiating member 50 is not particularly limited as long as it is a member having a high heat radiating effect. The heat radiating member 50 may be, for example, a radiator, a heat sink, a heat spreader, a die pad, a heat pipe, a metal cover, a housing, or the like.

[0176] <2.13. Image of the actual grid structure> Next, with reference to FIG. 10, an example in which the polarizing element 1 according to the present embodiment is actually manufactured and magnified photographed using a scanning electron microscope (SEM) will be described. FIG. 10A is an SEM image of the grid structure 20 before being covered with the reflective film 30, viewed from an oblique direction. FIG. 10B is an SEM image showing a cross section of the ridge portion 22 of the grid structure 20 before being covered with the reflective film 30. FIG. 10C is an SEM image showing a cross section of the ridge portion 22 of the grid structure 20 covered with the reflective film 30.

[0177] As shown in FIGS. 10A and 10B, the grid structure 20 is formed with a base portion 21 provided along the surface of the substrate 10 and a ridge portion 22 protruding from the base portion 21. The plurality of ridge portions 22 are arranged at substantially equal pitches P. Each ridge portion 22 has a tapered shape in which the width becomes narrower as it moves away from the base portion 21. The width W of the top of the ridge portion 22 T is narrower than the width W of the bottom of the ridge portion 22 B The pitch P is sufficiently larger than the width W of the bottom of the ridge portion 22 B The height H of the ridge portion 22 is larger than the pitch P. In the example of FIG. 10, P = 140 nm, W T = 10 nm, W B = 30 nm, and H = 220 nm. Further, as shown in FIG. 10C, the reflective film 30 is formed so as to cover and wrap the tip 22a and both side surfaces 22b of the ridge portion 22. The outer surface of the reflective film 30 is rounded and curved, and bulges in the width direction of the ridge portion 22.

[0178] <3. Method for manufacturing polarizing element> Next, with reference to FIG. 11, a method for manufacturing the wire grid polarizing element 1 according to the present embodiment will be described. FIG. 11 is a process diagram showing the method for manufacturing the wire grid polarizing element 1 according to the present embodiment.

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

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

[0181] Grid structure material forming step (S10) First, in S10, a grid structure material 23 made of a transparent organic material (for example, an ultraviolet curable resin or a thermosetting resin) is laminated on a substrate 10 made of a transparent inorganic material (for example, glass) by coating or the like. As the inorganic material of the substrate 10, various materials described above can be used. Also, as the organic material of the grid structure 20, various materials described above can be used. Further, the film thickness of the grid structure material 23 may be appropriately adjusted according to the dimensions of the base portion 21 and the ridge portion 22 of the grid structure 20 formed by the nanoimprint in S20.

[0182] Nanoimprint step (S12) and grid structure forming step (S14) Next, in S12, by performing nanoimprint on the grid structure material 23, in S14, a grid structure 20 is formed on the substrate 10. The grid structure 20 is a fine concavo-convex structure in which a base portion 21 provided on the substrate 10 and a plurality of protruding ridge portions 22 protruding from the base portion 21 are integrally formed. The fine concavo-convex structure is, for example, a structure having fine convex and concave portions on the order of several nm to several tens of nm.

[0183] In the nanoimprint process of S12, using a master disk 60 on which an inverted shape of the fine concavo-convex shape of the grid structure 20 is formed, the fine concavo-convex shape of the master disk 60 is transferred to the surface of the grid structure material 23 (S12). Thereby, an uneven pattern composed of the base portion 21, the ridge portion 22, and the concave portion 24 is formed on the grid structure material 23. Further, in the nanoimprint process, together with the transfer of the uneven pattern, by irradiating the grid structure material 23 with energy rays, the grid structure material 23 on which the uneven pattern is transferred is cured to form the grid structure 20 (S14). For example, when the grid structure material 23 is made of an ultraviolet curable resin, the ultraviolet curable resin on which the uneven pattern is transferred may be cured by irradiating the grid structure material 23 with ultraviolet rays using an ultraviolet irradiation device 66. Alternatively, when the grid structure material 23 is made of a thermosetting resin, the thermosetting resin on which the uneven pattern is transferred may be cured by heating the grid structure material 23 using a heating device 68 such as a heater.

[0184] In the above steps S12 and S14, as the ridge portion 22 of the grid structure 20, a ridge portion 22 having a tapered shape in which the width becomes narrower as it moves away from the base portion 21 is formed. The ridge portion 22 in the example of FIG. 11 is trapezoidal (tapered), but may have various other tapered shapes as shown in FIG. 3.

[0185] Thus, in this embodiment, in the nanoimprinting step S12, since the rib portion 22 having a tapered shape is imprinted, the master disk 60 can be easily peeled off from the grid structure material 23, and the mold release property is excellent. Further, the rib portion 22 of the grid structure 20 can be accurately formed into a desired shape without collapsing the mold.

[0186] Reflective film forming step (S16) Next, in S16, a reflective film 30 that covers a part of the rib portion 22 of the grid structure 20 is formed using a metal material such as Al or Ag. The reflective film 30 is an example of a functional film that imparts a predetermined function to the polarization element 1. The reflective film 30 is a metal thin film (a grid of metal fine wires) for reflecting incident light incident on the grid structure 20 of the polarization element 1.

[0187] In this reflective film forming step S16, the reflective film 30 is formed as follows. That is, the reflective film 30 is formed so as to cover and wrap the tip 22a and at least the upper side of one side surface 22b of the rib portion 22, and not to cover the lower sides of both side surfaces 22b of the rib portion 22 and the base portion 21. Further, the surface of the reflective film 30 that covers and wraps the rib portion 22 is formed to have a rounded shape and bulge in the width direction of the rib portion 22. In addition, the maximum width W MAX (grid maximum width W MAX ) of the reflective film 30 that covers and wraps the rib portion 22 is made to be equal to or greater than the width W B (grid bottom width W B ) of the bottom of the aforementioned rib portion, and the reflective film 30 is formed.

[0188] As a method for forming such a reflective film 30, for example, as shown in FIG. 5, sputtering or vapor deposition can be used. The metal material is alternately sputtered or vapor deposited on the rib portion 22 of the grid structure 20 from an oblique direction to form the reflective film 30. Thereby, the reflective film 30 having a desired shape can be suitably formed so as to cover and wrap the top of the rib portion 22 in a rounded manner.

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

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

[0191] As described above, the manufacturing method of the polarization element 1 according to the present embodiment has been described. By going through the above-described steps, a polarization element 1 excellent in polarization characteristics and heat dissipation can be manufactured without causing an increase in the manufacturing cost and complexity of the manufacturing of the polarization element 1.

[0192] Here, in order to compare with the manufacturing method according to the present embodiment, with reference to FIG. 12, the manufacturing method of a conventional wire grid polarization element will be briefly described.

[0193] As shown in FIG. 12, in the manufacturing method of a conventional wire grid polarization element, first, in order to form a convex grid shape, a metal film 80 is formed on a substrate 10 (S20). In this S20, on a substrate 10 made of an inorganic material such as glass, a reflective film made of a material that reflects light in the used band, for example, a metal film 80 such as aluminum, is formed using sputtering or evaporation.

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

[0195] In the steps S20 to S28 of the above conventional manufacturing method, a process for manufacturing a reflective wire grid polarizing element having a basic configuration is shown. However, considering the case where the metal film 80 is a multilayer film, a more complicated process is required. Therefore, it is presumed that the conventional wire grid polarizing element manufactured by the process shown in S20 to S28 of FIG. 12 has a high manufacturing cost and a long manufacturing time. Further, when mass-producing the polarizing element, in order to form a fine convex shape smaller than the wavelength of light, it is necessary to prepare a plurality of high-precision and expensive etching apparatuses and photolithography apparatuses according to the production volume, and the facility investment is also predicted to be higher.

[0196] On the other hand, the manufacturing method of the polarizing element 1 according to the present embodiment (see FIG. 11) uses an imprint technology such as nanoimprint to form the grid structure 20. Therefore, compared with the above conventional manufacturing method (see FIG. 12), the manufacturing cost, manufacturing time, and facility investment can be significantly reduced.

[0197] In the manufacturing method of the polarization element 1 according to this embodiment, nanoimprinting is performed on the grid structure material 23 (S12 in FIG. 11), but the nanoimprinting conditions are not particularly limited. For example, as shown in S12 of FIG. 11, a replica master (or a mold master) is used as the master disk 60, and while performing nanoimprinting, UV irradiation, heating, etc. are performed on the grid structure material 23, and the grid structure material 23 is cured in a state where the concavo-convex pattern is imprinted. Then, the master disk 60 is demolded from the cured grid structure material 23. Thereby, the grid structure 20 having the base portion 21 and the rib portion 22 can be formed by transfer.

[0198] Note that the master disk 60 used in the nanoimprinting step S12 (FIG. 11) in the manufacturing method of the polarization element 1 according to this embodiment can be manufactured, for example, by photolithography technology as shown in FIG. 13. FIG. 13 is a process diagram showing the manufacturing method of the master disk 60 according to this embodiment.

[0199] As shown in FIG. 13, first, after forming the master disk metal film 62 on the master disk base material 61 (S30), a resist mask 70 is formed on the master disk metal film 62 (S32). Next, the master disk metal film 62 is etched using the resist mask 70, and a concave groove 65 corresponding to the rib portion 22 of the grid structure 20 is formed in the etched master disk metal film 62 (S34).

[0200] Thereafter, the master disk 60 is obtained by peeling the resist mask 70 from the master disk metal film 62 (S36). The master disk 60 has a fine concavo-convex structure composed of a plurality of convex portions 63 and concave grooves 65 formed on the master disk base material 61. The fine concavo-convex structure on the surface of the master disk 60 has an inverted shape of the fine concavo-convex structure on the surface of the grid structure 20 of the polarization element 1. The concave groove 65 of the master disk 60 has an inverted shape of the rib portion 22 of the grid structure 20, and the convex portion 63 of the master disk 60 has an inverted shape of the concave portion 24 between the rib portions 22, 22 of the grid structure 20.

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

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

[0203] The projection display device according to the present embodiment includes the wire grid polarizing element 1 according to the present embodiment described above. By providing the projection display device according to the present embodiment with the polarizing element 1, excellent polarization characteristics, heat resistance, heat dissipation, etc. of the polarizing element 1 can be realized.

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

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

[0206] As shown in FIG. 14, the head-up display device 100 according to the present embodiment includes the wire grid polarizing element 1 according to the present 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. A conventional head-up display incorporating a polarizing element is considered to have insufficient heat resistance in view of long-term use and the need to cope with future increases in brightness and enlarged displays because of its poor heat dissipation.

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

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

[0209] The head-up display device 100 is configured to emit a display image from below toward the front glass surface (display surface 5). For this reason, sunlight may enter in the direction opposite to the emission direction of the display image and be incident on the display element 3. In the head-up display device 100 according to the present embodiment, a reflector 4 for reflecting and enlarging the display image is provided for the purpose of miniaturization and enlargement of the display image. In such a case, in a conventional head-up display device, sunlight incident on the reflector from the outside is condensed in the vicinity of the display element, which may 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 the 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 to prevent it from reaching the display element 3, so that 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 the required performance and the like.

[0212] Further, by using the polarizing element 1 as a pre-polarizing plate disposed 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 the required performance. For example, although not shown, the polarizing element 1 can be disposed between the display element 3 and the light source 2. Also, although not shown, 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] Further, although not shown in the drawings, 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 including a polarizing beam splitter> Next, with reference to FIGS. 15 to 17, a projection display device using the reflective wire grid polarizing element 1 according to the present 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] 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 provided 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. Further, 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 on, 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 arranged such that the light from the light source 210 is incident at an incident angle θ within a predetermined range including 45°. This predetermined range of the incident angle θ is, for example, 45° ± 15° described above, that is, 30° or more and 60° or less.

[0220] For example, in FIGS. 15 to 17, the polarizing beam splitter 230 is arranged to be inclined at 45° with respect to the incident direction 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°. Also, the polarizing beam splitter 230 is arranged to be inclined at 45° with respect to the reflective liquid crystal display element 240 so that the incident light from the reflective liquid crystal display element 240 is 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 the S polarization and the 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 the S polarization and the P polarization by reflecting the second polarization (P polarization) of the incident light and transmitting the first polarization (S polarization).

[0222] When reflecting the desired polarization by the polarization beam splitter 230, the polarization beam splitter 230 is arranged such that light including the polarization to be reflected is incident on the surface of the polarization beam splitter 230 (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 FIG. 15, when reflecting the S polarization incident from the PS converter 220 by the polarization beam splitter 230, the surface of the polarization beam splitter 230 may be directed toward the PS converter 220 side that emits the S polarization. On the other hand, as shown in FIG. 16, when reflecting the S polarization incident from the reflective liquid crystal display element 240 by the polarization beam splitter 230, the surface of the polarization beam splitter 230 may be directed toward the reflective liquid crystal display element 240 side that emits the S polarization.

[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 FIGS. 15 and 17, the reflective liquid crystal display element 240 may be arranged such that the first polarization (S polarization) reflected by the polarization beam splitter 230 is incident on the surface of the reflective liquid crystal display element 240. Alternatively, as shown in FIG. 16, the reflective liquid crystal display element 240 may be arranged such that the second polarization (P polarization) transmitted through the polarization beam splitter 230 is incident on the surface of the reflective liquid crystal display element 240.

[0224] Also, as shown in FIGS. 15 and 17, the reflective liquid crystal display element 240 reflects and modulates the incident first polarization (S polarization) and emits a second polarization (P polarization) representing a display image. However, it is not limited to such an example. As shown in FIG. 16, the reflective liquid crystal display element 240 may reflect and modulate the incident second polarization (P polarization) and emit a first polarization (S polarization) representing a display image.

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

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

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

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

[0229] The light emitted from the light source 210 is non-polarized and contains P-polarized components and S-polarized components in the same ratio. Therefore, if only one polarization is selected and extracted by the polarization beam splitter 230 composed of the polarization element 1, the light quantity will decrease by about half. Thus, the PS converter 220 converts the light emitted from the light source 210 into either the first polarization (S-polarization) or the second polarization (P-polarization). Thereby, it is possible to suppress the decrease in the light quantity of the polarized light extracted by the polarization beam splitter 230 and improve the light utilization efficiency. For example, the PS converter 220 shown in FIG. 15 converts the light from the light source 210 into the first polarization (S-polarization).

[0230] The light converted to S-polarization by the PS converter 220 is incident on the polarization beam splitter 230 disposed obliquely at about 45°. The polarization 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) representing the display image, and emits the second polarization (P-polarization) toward the polarization beam splitter 230. The second polarization (P-polarization) passes through the polarization beam splitter 230, is enlarged by the lens 250, and then is projected onto a display surface (not shown) to display the display image.

[0231] The projection display device 200A having the above configuration includes, as the polarization beam splitter 230, a reflective wire grid polarizing plate composed of the wire grid polarizing element 1 according to the present embodiment. Thereby, the polarization separation characteristics of the polarization beam splitter 230 can be improved with respect to obliquely incident light and incident light with a wide incident angle θ, and the heat dissipation and heat resistance of the polarization beam splitter 230 and the projection display device 200A can be improved.

[0232] On the other hand, a projection display device (not shown) equipped with a conventional polarization element as a polarization beam splitter has poor heat dissipation of the polarization element. For this reason, from the viewpoints of long-term use, increased brightness, and enlarged display, it is considered that the heat resistance is not sufficient. Further, the incident angle θ of the light incident on the polarization beam splitter is not only 45°, but also any angle within a predetermined range centered on 45° (for example, about 45° ± 15°). Thus, even when obliquely incident light with a large and wide range of incident angles θ is incident on the polarization beam splitter, the polarization beam splitter is required to have a performance capable of preferably separating the obliquely incident light into S-polarized light and P-polarized light regardless of the incident angle θ. However, in a polarization beam splitter using a conventional polarization element, the polarization separation characteristics with respect to the above obliquely incident light are poor, so that the light utilization efficiency deteriorates, and adverse effects on the image quality of a display image such as brightness unevenness have been a problem.

[0233] In this regard, the polarization beam splitter 230 of the projection display device 200A according to the first specific example of the present embodiment is excellent in polarization separation characteristics with respect to obliquely incident light having a large and wide range of incident angles θ as described above. Therefore, in the projection display device 200A, the light utilization efficiency can be improved, and brightness unevenness and the like can be reduced to improve the image quality of the display image.

[0234] Further, the projection display device is not limited to the example of the projection display device 200A shown in FIG. 15 above. For example, like the projection display device 200B shown in FIG. 16 or the projection display device 200C shown in FIG. 17, the components and arrangements of the projection display device can be appropriately changed.

[0235] As shown in FIG. 16, the projection display device 200B according to the second specific example of the present embodiment includes a light source 210, a PS converter 220, a polarization 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 obliquely at 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] Similar to the above-described projection display device 200A (see FIG. 15), the projection display device 200B having the above configuration 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] Further, 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 obliquely at 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 the component of the second polarization (P polarization) is absorbed by the light absorber 260, so it is possible to suppress 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 polarized light (S polarized light) incident from the polarization beam splitter 230 to generate a second polarized light (P polarized light) representing a display image, and emits the second polarized light (P polarized light) toward the polarization beam splitter 230. The second polarized light (P polarized light) passes through the polarization beam splitter 230, is enlarged by the lens 250, and then is projected onto a display surface (not shown), and the display image is displayed.

[0241] In the projection display device 200C having the above configuration, since the PS converter 220 is not installed, among the non-polarized light emitted from the light source 210, the component of the second polarized light (P polarized light) is absorbed by the light absorber 260 and not used for displaying the display image. For this reason, the amount of light of the display image is reduced to about half. However, since the cost and installation space required for the PS converter 220 can be reduced, and the number of components of the projection display device 200C can be reduced, there is an advantage that the cost of the projection display device 200C can be reduced and the projection display device 200C can be miniaturized.

[0242] As described above, a specific example of the projection display device 200 using the reflective wire grid polarizing element 1 according to the present embodiment as the polarization beam splitter 230 has been described. Note that the projection display device is not limited to the specific examples of the projection display device 200 shown in FIGS. 15 to 17, and the components and arrangements of the projection display device may be appropriately changed according to required performance and the like, or other components may be appropriately provided.

[0243] <5. Vehicle> Next, a vehicle equipped with the video display device according to the present embodiment will be described.

[0244] The vehicle according to this embodiment (not shown) includes a projection display device having the wire grid polarizing element 1 according to the above-described embodiment. The vehicle may be various automobiles such as a passenger car, a light automobile, a bus, a truck, a racing car, a construction vehicle, and other large vehicles as long as it is a vehicle on which the projection display device can be installed. In addition to these, various vehicles such as a motorcycle, a train, a linear motor car, and an attraction vehicle may also be used.

[0245] The vehicle according to this embodiment can project and display a display image on a display surface provided on the vehicle (for example, the display surface 5 shown in FIG. 14) by the polarizing element 1 and the projection display device. The display surface is preferably a semi-transmissive plate such as the front glass, side glass, rear glass, or combiner of the vehicle. However, the display surface is not limited to such an example, and may be the surface of various parts, members, in-vehicle devices, etc. provided on the vehicle as long as it is the surface of an object on which the display image can be projected.

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

[0247] As described above, in the head-up display device 100, as shown in FIG. 14, sunlight may enter the head-up display device 100 through the windshield (display surface 5) from the outside of the vehicle. The heat of this sunlight may cause deterioration or failure of the display element 3. Therefore, for the purpose of preventing the incidence of sunlight on the display element 3, the above-described hybrid wire grid polarizing element 1 is provided in the head-up display device 100. Since this polarizing element 1 has a hybrid structure with high thermal conductivity, it is excellent in heat dissipation and heat resistance. Therefore, the polarizing element 1 can shield the sunlight incident from the outside into the head-up display device 100 and prevent it from reaching the display element 3, so that failures and damages of the display element 3 can be prevented. Furthermore, since the polarizing element 1 is excellent in 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 FIGS. 15 to 17 is installed in a vehicle, the polarizing element 1 used as the polarizing beam splitter 230 can block sunlight from the outside, so that failures and damages of other components such as the reflective liquid crystal display element 240 can be prevented. Furthermore, damage to the polarizing element 1 itself, which is excellent in heat dissipation and heat resistance, can also be prevented.

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

[0250] Note that the vehicle is not particularly limited as long as it includes the above-described projection display device and polarizing element, and other conditions can be appropriately set and changed according to the performance required for the vehicle.

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

[0252] <6.1. Complex Structure of Grid Structure Covered with Protective Film> As shown in FIGS. 7 and 8 described above, the wire grid polarizing element 1 according to the present 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 so as to cover the entire surfaces of the grid structure 20 and the reflective film 30. More specifically, the protective film 40 is formed on the entire surface of the polarizing element 1 so as to continuously cover the surfaces of the base portion 21 and the exposed portions of the ridge portions 22 of the grid structure 20, and the surfaces of the exposed portions of the reflective film 30 that cover and wrap the upper sides of the ridge portions 22. The protective film 40 is made of an inorganic material such as an inorganic oxide, for example. The inorganic oxide may be a dielectric material such as SiO2 or Al2O3, or may be 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. A dielectric has the property of not allowing direct current to pass through but polarizing in an alternating current electric field and storing electricity. The dielectric constant of Al2O3 is, for example, about 9.9, and 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. Thereby, the scratch resistance, antifouling property, and waterproof property of the grid structure 20 and the reflective film 30 can be enhanced.

[0254] In particular, since the grid structure 20 is formed of an organic material such as resin, it is more likely to deteriorate due to heat, light, water, etc. compared to the substrate 10 formed of an inorganic material such as glass. By covering such a resin-made grid structure 20 with a protective film 40 made of an inorganic material without any gaps, the grid structure 20 can be protected from external heat, air, water, etc. (barrier property). Thereby, it is possible to suppress the resin of the grid structure 20 from being altered or deteriorated due to heat, air, water, etc. Further, as shown in FIGS. 7 and 8, by covering the outermost surface of the polarizing element 1 with a protective film 40 made of an inorganic oxide or the like, the thermal resistance R of the entire polarizing element 1 can be further reduced, so that the heat dissipation property of the polarizing element 1 can be further improved.

[0255] By the way, as described above, the polarizing element 1 according to the present embodiment is a hybrid type wire grid polarizing element that combines a substrate 10 made of an inorganic material and a grid structure 20 made of an organic material. Further, as shown in FIG. 18, the grid 41 (the entire convex structure combining the convex strip portion 22 and the reflection film 30) of the polarizing element 1 according to the present embodiment has the above-described special tree shape. For this reason, valleys 42 having a complicated shape are formed between adjacent grids 41, 41. As a result, the surface of the grid structure 20 of the polarizing element 1 has a complicated uneven structure in which a plurality of convex portions (grids 41) and a plurality of concave portions (valleys 42) are intertwined.

[0256] The grid structure 20 having such a complicated uneven structure and the protective film 40 covering the grid structure 20 will be described in detail again with reference to FIG. 18.

[0257] As shown in FIG. 18, the grid structure 20 is integrally formed with a base portion 21 provided on the substrate 10 and a plurality of convex strip portions 22 protruding from the base portion 21. The grid structure 20 is formed of an organic material such as resin, and the substrate 10 is formed of an organic material such as glass. The convex strip portion 22 of the grid structure 20 has a tapered shape in which the width in the X direction becomes narrower as it separates upward (Z direction) from the base portion 21.

[0258] The reflective film 30 (functional film) is made of a metal material such as Al and covers only the tip side of the rib portion 22. Specifically, the reflective film 30 covers the tip 22a of the rib portion 22 and the upper sides of both side surfaces 22b, 22b, and does not cover the lower sides of both side surfaces 22b, 22b of the rib portion 22 and the surface of 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 30% or more and 70% or less.

[0259] Thus, the surface of the reflective film 30 that wraps around the upper side of the rib portion 22 has a rounded shape and bulges in the width direction (X direction in FIG. 1) of the rib portion 22. The maximum width (W MAX ) of the reflective film 30 that wraps around the rib portion 22 is equal to or greater than the width (W B ) of the lower side of the rib portion 22. And as shown in FIG. 18, the cross-sectional shape of the entire convex structure (i.e., the grid 41) composed of the rib portion 22 and the reflective film 30 has the above-described special tree shape. In this special tree shape, constrictions 29, 29 are provided at positions directly below the lower ends on both the left and right sides of the reflective film 30 that wraps around the rib portion 22, and at the positions of the constrictions 29, 29, the width in the width direction (X direction) of the entire convex structure (i.e., the grid 41) becomes narrower.

[0260] As described above, the grid 41 of the grid structure 20 according to the present embodiment has a reflective film 30 that bulges roundly in the X direction on the upper side of the rib portion 22, constrictions 29, 29 that are recessed inward in the X direction at the lower end positions of the reflective film 30, and a lower side of the rib portion 22 that is not covered by the reflective film 30. Therefore, the grid 41 has a complex cross-sectional shape like that of a single tree. With the grid 41 having such a special tree shape, as described above, the polarization separation characteristics (Tp×Rs characteristics) with respect to obliquely incident light can be improved.

[0261] Between adjacent grids 41 in the X direction, valleys 42 with a complex shape are formed. The valleys 42 are recesses formed between adjacent grids 41. The upper part of the valleys 42 is a space sandwiched between the reflection films 30 on the left and right sides and is open upward. The bottom of the valleys 42 is a semi-closed space surrounded in three directions by the ridge portions 22 on the left and right sides and the base portion 21 on the bottom side.

[0262] The width of the upper part of the valleys 42 in the X direction is narrow, and the width of the bottom of the valleys 42 in the X direction is wide. That is, at the upper part of the valleys 42, the reflection films 30 on both sides bulge. For this reason, since the grids 41 on both sides of the upper part of the valleys 42 are approaching, the width of the upper part of the valleys 42 is narrow. On the other hand, at the bottom of the valleys 42, the lower sides of the side surfaces 22b of the ridge portions 22 on both sides are not covered by the reflection film 30. For this reason, the grids 41 on both sides of the bottom of the valleys 42 are separated by the amount where the reflection film 30 does not exist, so the width of the bottom of the valleys 42 is wide. Thus, the cross-sectional shape (XZ cross-section) of the valleys 42 has a bowl shape in which the upper side entrance is narrow and the semi-closed space on the bottom side is wide.

[0263] As described above, in the polarization element 1 according to the present embodiment, the plurality of grids 41 have a complex structure with a special tree shape. For this reason, the valleys 42 between adjacent grids 41 also become semi-closed spaces having a complex bowl shape. Therefore, the surface of the polarization element 1 has a complex uneven structure composed of these plurality of grids 41 and plurality of valleys 42. Therefore, since it is difficult to cover the entire surface of the complex uneven structure with the protective film 40 having a uniform film thickness, the protective film 40 has problems as described in detail in the next section.

[0264] <6.2. Problems of the protective film> As shown in FIG. 18, the protective film 40 continuously covers the entire surface of the complex uneven structure composed of the plurality of grids 41 and the plurality of valleys 42. That is, the protective film 40 continuously covers the surface of the grid 41 (that is, the combined surface of the surface of the reflective film 30 and the lower sides of the both side surfaces 22b, 22b of the protruding strip portion 22 not covered by the reflective film 30) and the bottom surface of the valley 42 (that is, the upper surface of the base portion 21). When continuously covering the entire surface of the grid 41 and the valley 42 of the grid structure 20 with the protective film 40 in this way, it is ideal to form a protective film 40 with a uniform thickness on the entire surface.

[0265] However, when forming the protective film 40 on the surfaces of the grid 41 and the valley 42, the film-forming material easily adheres to the tip portions of the grid 41 protruding upward, but it is difficult to enter the inside of the valley 42 having a complex concave shape. Therefore, variations in the amount of the film-forming material adhered are likely to occur between the surface of the tip portion of the grid 41 and the surface on the bottom side of the valley 42. Therefore, it is very difficult to form a very thin protective film 40 with a uniform film thickness on the entire surface of the complex uneven structure composed of these grid 41 and valley 42 by the existing film-forming methods.

[0266] For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-085516) describes forming a coating layer on the surface of a wire grid polarizer by a sputtering method. However, in the sputtering method, the straightness of the film-forming material is strong during film formation, and the surrounding of the film-forming material with respect to the fine uneven structure is poor, so the film thickness uniformity decreases. In particular, in the case of the complex fine uneven structure composed of the above special tree-shaped grid 41 and the concave-shaped valley 42 as in the present embodiment, it is extremely difficult to form the protective film 40 with a uniform film thickness by the sputtering method. That is, the surrounding of the film-forming material with respect to the lower side wall of the above special tree-shaped grid 41 (the lower side of the side surface 22b of the protruding strip portion 22) and the bottom surface of the concave-shaped valley 42 (the upper surface of the base portion 21) deteriorates significantly. For this reason, it is extremely difficult to form the protective film 40 with a uniform film thickness.

[0267] As described above, it is ideal for the thickness of the protective film 40 to be uniform. However, it is very difficult to uniformly form an extremely thin protective film 40 over the entire surface of the complex fine concavo-convex structure according to this embodiment. Therefore, in reality, the thickness of the protective film 40 formed by the existing film-forming method is not uniform, and thickness unevenness inevitably occurs in the formed protective film 40.

[0268] In this regard, if the grid structure 20 and the reflective film 30 are stably coated with a thick protective film 40, the barrier property of the thick protective film 40 for the grid structure 20 and the like is enhanced. As a result, the resin constituting the grid structure 20 is suppressed from deteriorating over time due to heat, light, water, etc. from the outside, and the reliability (heat resistance and light resistance) of the grid structure 20 can be ensured. However, if the thickness of the protective film 40 is too thick, there is a problem that the optical characteristics of the polarization element 1, particularly the transmittance (Tp characteristic) of the grid structure and the polarization separation characteristic (Tp×Rs characteristic) 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 deteriorates due to heat, light, etc., and the reliability (heat resistance and light resistance) of the grid structure 20 decreases. Thus, depending on the thickness of the protective film 40, the optical characteristics and the reliability of the polarization element 1 are in a trade-off relationship.

[0269] Therefore, the inventor of the present application diligently studied and, when covering the surface of the grid structure 20 having a complex fine concavo-convex structure as shown in FIG. 18 with a thin protective film 40 having a thickness of about several nm to several tens of nm, clarified the allowable range of thickness unevenness of the protective film 40 that can suppress the deterioration of the resin of the grid structure 20 and improve the reliability while maintaining the optical characteristics of the polarization element 1. Then, the inventor conceived of a polarization element 1 in which the thickness of the protective film 40 was optimized within the allowable range.

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

[0271] As shown in FIG. 18, the protective film 40 of the polarization element 1 according to the present embodiment continuously covers the surface of the reflection film 30, the lower sides (i.e., the surfaces of the grids 41) of both side surfaces 22b, 22b of the ridge portion 22, 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 having a single-layer structure made of a single coating material, or may be a thin film having a multilayer laminated structure made of a plurality of 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 forming the protective film 40 on the entire surface of the grid structure 20 in which the ridge portion 22 is covered with the reflection film 30 to create a sample of the polarization element 1, 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 by the observation is imported into a length measurement application, and the thickness of the protective film 40 is measured. At this time, the thickness of the protective film 40 in a plurality of (for example, three or more) grids 41 per sample is measured, and the average value of these measured thickness values is taken as the thickness (film thickness) of the protective film 40.

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

[0275] The ratio "Bt / Tt" of the thickness of the protective film 40 according to the present embodiment preferably satisfies the following formula (10).

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

[0277] As shown in FIG. 18, Tt is the thickness of the protective film 40 covering the top portion 30a of the reflective film 30 that covers the tip 22a of the rib portion 22 at the tip of the grid 41. In other words, Tt is the thickness of the protective film 40 covering the metal material portion (the top portion 30a of the reflective film 30 made of a metal 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 covering the resin portion on the lower side of the grid structure 20 (the portion of the rib portion 22 and the base portion 21 made of resin 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 covering the surface of the substantially cup-shaped portion where the resin of the grid structure 20 is exposed at the bottom of the valley 42 between adjacent grids 41, 41 (the lower sides of the side surfaces 22b, 22b of the two opposing rib portions 22, 22 and the surface of the base portion 21).

[0279] Here, Bt is preferably the average value of Bt1 and Bt2 shown in FIG. 18. Bt1 is the thickness of the protective film 40 covering the lower side of the side surface 22b of the rib portion 22. Bt2 is the thickness of the protective film 40 covering the surface of the base portion 21 (the bottom surface of the groove 42). Both Bt1 and Bt2 are the thicknesses of the protective film 40 formed on the bottom of the groove 42. Therefore, regardless of the film formation method of the protective film 40, it is considered that Bt1 and Bt2 have substantially the same thickness (Bt≈Bt1≈Bt2). However, in reality, Bt1 and Bt2 may slightly differ. In this case, it is preferable to obtain the average value of the measured Bt1 and Bt2 and set it as Bt (Bt = Average(Bt1, Bt2)). By using the average value, the thickness Bt of the protective film 40 covering the exposed portion of the resin of the grid structure 20 at the bottom of the groove 42 can be obtained more accurately. Note that the calculation method of Bt is not limited to such an example. For example, Bt = Bt1 may be used, or Bt = Bt2 may be used.

[0280] "Bt / Tt" in the above formula (10) is the ratio of Bt to Tt. If the value of "Bt / Tt" is 1, it means that Bt and Tt have the same value, and the thickness Tt of the protective film 40 covering the tip of the grid 41 and the thickness Bt of the protective film 40 covering the bottom of the groove 42 are completely uniform. On the other hand, the farther the value of "Bt / Tt" is from 1, the greater the difference between Bt and Tt, which means that thickness unevenness occurs between the thickness Tt of the protective film 40 covering the tip of the grid 41 and the thickness Bt of the protective film 40 covering the bottom of the groove 42.

[0281] By satisfying the above formula (10) for "Bt / Tt", while maintaining the optical characteristics required for the polarizing element 1 (for example, high Tp characteristics and high Tp×Rs characteristics), deterioration of the resin portion of the grid structure 20 can be suppressed, so the reliability (heat resistance, light resistance) of the polarizing element 1 can be improved.

[0282] If "Bt / Tt" is less than 0.85, the thickness Bt of the protective film 40 covering the bottom of the valley 42 becomes thin, and the barrier property deteriorates, so the reliability (heat resistance, light resistance) of the grid structure 20 decreases. Therefore, in order to ensure the reliability (heat resistance, light resistance) of the grid structure 20 when used for a predetermined time or more, "Bt / Tt" is preferably 0.85 or more.

[0283] Furthermore, the ratio "Bt / Tt" of the thickness of the protective film 40 according to the present embodiment more preferably satisfies the following formula (11).

[0284] 0.85 ≦ Bt / Tt ≦ 1.07 ···(11)

[0285] If "Bt / Tt" exceeds 1.07, the thickness Bt of the protective film 40 covering the valley 42 is too thick, so the valley 42 may be filled with the protective film 40, and the optical characteristics may deteriorate. Therefore, in order to suppress the filling of the valley 42 with the protective film 40 and maintain the required optical characteristics, "Bt / Tt" is preferably 1.07 or less.

[0286] Furthermore, the ratio "Bt / Tt" of the thickness of the protective film 40 according to the present embodiment more preferably satisfies the following formula (12).

[0287] 1.00 < Bt / Tt ≦ 1.07 ···(12)

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

[0289] As described above, the thickness of the protective film 40 of the polarizing element 1 according to the present embodiment preferably satisfies the formula (10), more preferably satisfies the formula (11), and even more preferably satisfies the formula (12). Thereby, when the grid structure 20 having a complicated concavo-convex structure as shown in FIG. 18 is covered with the thin protective film 40, within the allowable range of the thickness unevenness of the protective film 40 necessary for achieving both the optical characteristics and reliability of the polarizing element 1, the grid 41 and the valleys 42 of the grid structure 20 can be appropriately covered with the protective film 40. Thereby, when the polarizing element 1 is used as, for example, a polarizing beam splitter, while maintaining the required optical characteristics (Tp characteristics, Tp×Rs characteristics) of the polarizing element 1, deterioration of the resin portion of the grid structure 20 is suppressed, and the reliability (heat resistance, light resistance) of the polarizing element 1 can be improved.

[0290] In addition, since it is not necessary to form the protective film 40 with a completely uniform thickness, it is realistically possible to form the protective film 40 with thickness unevenness within the above allowable range by 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 the present embodiment will be described.

[0292] The material of the protective film 40 is not particularly limited as long as it can maintain the optical characteristics of the polarizing element 1 and can enhance the reliability (for example, light resistance, heat resistance). Examples of the material of the protective film 40 include dielectric materials, inorganic oxides such as metal oxides, silane-based water-repellent materials, and fluorine-based water-repellent materials. The dielectric material is, for example, Si oxide, Hf oxide, etc. The metal oxide is, for example, Al oxide, etc. By including an inorganic oxide in the protective film 40, the scratch resistance of the polarizing element 1 and the barrier property for protecting the grid structure 20 from heat, light, water, etc. can be further enhanced. By including a water-repellent material such as a fluorine-based water-repellent material in the protective film 40, the antifouling property and waterproof property of the polarizing element 1 can be further enhanced.

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

[0294] Further, the protective film 40 preferably has a laminated structure including a first layer made of Al2O3 and a second layer made of SiO2. Thereby, the protective film 40 can have both the high barrier property of Al2O3 and the high transmittance of SiO2.

[0295] Note that the present invention is not limited to the above examples, and the protective film 40 may be formed of other inorganic oxides or metal oxides other than SiO2 and Al2O3, or may have a laminated structure of three or more layers. For example, the protective film 40 may further include a water-repellent coating or an oil-repellent coating. Thereby, the antifouling property and waterproof property of the polarizing element 1 can be further enhanced.

[0296] <6.5. Film formation method of protective film> Next, the film formation method of the protective film 40 in the manufacturing method of the polarizing element 1 according to the present embodiment will be described in detail.

[0297] As described above, the manufacturing method of the wire grid polarizing element 1 according to the present embodiment includes a grid structure body material forming step (S10), a nanoimprint step (S12), a grid structure body forming step (S14), and a reflective film forming step (S16) shown in FIG. 11, and may further include a film formation step (S18) of the protective film 40.

[0298] The film formation step (S18) of the protective film 40 is a step of forming the protective film 40 that covers the entire surface of the polarizing element 1 (the entire surfaces of the grid structure body 20 and the reflective film 30). In this film formation step (S18), as shown in FIG. 18, the protective film 40 is formed so as to continuously cover the surface of the reflective film 30, the lower sides of both side surfaces 22b, 22b of the ridge portion 22 (that is, the entire surface of the grid 41), and the surface of the base portion 21 (that is, the bottom surface of the valley 42).

[0299] In the film formation step (S18) of the protective film 40 according to the present embodiment, an atomic layer deposition (ALD) method is used as the film formation method. The ALD method is a thin film formation technology that utilizes continuous chemical reactions in the gas phase. The ALD method repeatedly introduces and evacuates two or more types of gas phase raw materials (precursors, also referred to as precursors) into the reaction chamber alternately, and reacts the raw material molecules adsorbed on the surface (coating target surface) of the film formation target to form a film. In the ALD method, unlike the CVD method, different types of precursors do not enter the reaction chamber simultaneously, and as independent steps, the precursors are introduced (pulsed) and exhausted (purged). In each pulse, the precursor molecules behave self - controllably on the coating target surface, and the reaction ends when there are no more adsorbable sites on the surface.

[0300] Such an ALD method has the advantage that the film thickness and material can be precisely controlled at the atomic layer level, so that extremely thin and uniform film formation is possible compared to the CVD method. Therefore, in the film formation step (S18) according to the present embodiment, when forming the protective film 40 on 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. Thereby, it becomes possible to form the protective film 40 almost uniformly on the entire surface of the complex micro - uneven structure.

[0301] Here, referring to FIG. 19, the film formation step (S18) of the protective film 40 by the ALD method according to the present embodiment will be described in detail. FIG. 19 is a schematic diagram showing the film formation step (S18) of the protective film 40 by the ALD method according to the present embodiment.

[0302] First, the configuration of the chamber 300 used in the film formation step (S18) of the protective film 40 by the ALD method according to the present embodiment will be described. As shown in FIG. 19, the chamber 300 forms a processing space for performing the film formation process by the above - mentioned ALD method. Inside the chamber 300, the grid structure 20 is disposed. 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) gas such as a vapor-phase raw material (e.g., a precursor, an oxidizing agent) into the chamber 300. The gas inlet 310 is provided, for example, at the upper part of the chamber 300. The valves (not shown) for the precursor gas, the oxidizing agent gas, and the inert gas are switched to introduce gas from the gas inlet 310.

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

[0305] The gas exhaust port 330 is an opening for discharging the gas in the chamber 300 to the outside of the chamber 300. The gas exhaust port 330 is provided, for example, at the lower part 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. Further, a vacuum pump 340 is provided at the gas exhaust port 330. By operating the vacuum pump 340, the gas in the chamber 300 can be discharged (purged) to the outside through the gas exhaust port 330.

[0306] Next, the film formation step (S18) of the protective film 40 by the ALD method according to the present embodiment using the above chamber 300 will be described.

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

[0308] Next, the first to fourth steps (S181 to S184) of alternately introducing (pulsing) and exhausting (purging) two types of vapor-phase raw material gases (hereinafter, referred to as "precursor gas" and "oxidizing agent gas", respectively) for forming the protective film 40 into the chamber 300 are repeated.

[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 on the surface (coating target surface) of the grid structure 20 and chemically reacts, thereby generating a first atomic layer on the coating target surface.

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

[0311] Furthermore, an oxidant gas (second precursor gas) is introduced into the chamber 300 from the gas inlet 310 (S183: third step). As a result, the precursor of the first atomic layer deposited on the coating target surface of the grid structure 20 and the introduced oxidant gas are chemically reacted to bond oxygen to the precursor, thereby generating a second atomic layer on the first atomic layer.

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

[0313] Thereafter, the introduction and exhaust of the precursor gas and the oxidant gas into the chamber 300 alternately as described above (S181 to S184: first to fourth steps) are repeated. As a result, the first atomic layer and the second atomic layer are alternately laminated on the coating target surface of the grid structure 20, and a protective film 40 made of a desired material can be formed.

[0314] For example, when forming a protective film 40 with a single-layer structure made of SiO2, an alkylaminosilylamine and ozone are used as two types of gas-phase raw materials (precursor, oxidizing agent). Also, when forming a protective film 40 with a single-layer structure made of Al2O3, trimethylaluminum (TMA) and water are used as two types of gas-phase raw materials (precursor). Further, when forming a protective film 40 with a laminated structure including a first coating layer made of Al2O3 and a second coating layer made of SiO2, after forming the first coating layer with a single-layer structure made of Al2O3, a second coating layer with a single-layer structure made of SiO2 may be laminated on the first coating layer.

[0315] Furthermore, according to the film formation process (S18) by the special ALD method according to the present embodiment, in the precursor gas introduction process (S181) and the oxidizing agent gas introduction process (S183), the precursor gas and the oxidizing agent gas are introduced into the chamber and filled without exhausting the precursor gas and the oxidizing agent gas from the chamber 300 to the outside.

[0316] In this regard, in the conventional film formation process by the general ALD method, in the precursor gas introduction process (S181, S183) and the oxidizing agent gas introduction process (S183), the precursor gas and the oxidizing agent gas are introduced into the chamber 300 while exhausting the precursor gas and the oxidizing agent gas in the chamber 300.

[0317] In contrast, in the film formation step (S18) by the special ALD method according to the present embodiment, in the steps of introducing the precursor gas and the oxidant gas (S181, S183: the first and third steps), the precursor gas and the oxidant gas in the chamber 300 are continuously introduced into the chamber 300 without exhausting them from the gas exhaust port 330. Specifically, in the step of introducing the precursor gas (S181: the first step), with the exhaust valve of the gas exhaust port 330 closed and the chamber 300 in a sealed state, 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 step of introducing the oxidant gas (S183: the third step), with the exhaust valve of the gas exhaust port 330 closed and the chamber 300 in a sealed state, the oxidant gas is introduced into the chamber 300 from the gas inlet 310, and the oxidant 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 the oxidant gas introduced into the chamber 300 can be sufficiently filled and retained in the chamber 300 and brought into sufficient contact with the surface to be coated of the grid structure 20. Therefore, among the surfaces of the complex fine concavo-convex structure composed of the grid 41 and the valleys 42 shown in FIG. 18, the precursor gas and the oxidant gas can be sufficiently introduced to the depth of the trough-shaped valleys 42, and the first and second atomic layers with the required layer thickness can be appropriately formed. Thus, a protective film 40 with a desired film thickness can be formed not only on the surface of the tip of the grid 41 but also on the surface of the trough-shaped valleys 42.

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

[0320] As described above, in the manufacturing method of the polarizing element 1 according to this embodiment, the film formation process (S18) of the protective film 40 by the ALD method has been described in detail. According to this embodiment, while using the ALD method as the film formation method of the protective film 40, the film formation conditions (conditions related to the introduction and discharge of the precursor gas and the oxidizing agent gas) in the introduction steps (S181, S183) of the precursor gas and the oxidizing agent gas by the ALD method can be optimized according to the complex fine concavo-convex structure of the grid structure 20.

[0321] Thereby, an extremely thin protective film 40 on the order of several nm to several tens of nm can be formed very uniformly over the entire surface of the complex fine concavo-convex structure. Therefore, within the allowable range of thickness unevenness of the protective film 40 defined by the above formula (10), it becomes possible to form an extremely uniform thin protective film 40. Thereby, since the grid structure 20 can be firmly protected by the protective film 40, the reliability (heat resistance and light resistance) of the polarizing element 1 can be improved while maintaining the optical characteristics of the polarizing element 1 provided with the protective film 40.

[0322] In this regard, when using the sputtering method, vacuum evaporation method, or CVD method, which are conventional film-forming methods, it is difficult to appropriately form a protective film on the surface of a complex fine concavo-convex structure as in the present embodiment. For example, in the sputtering method, as described above, since the straightness of the film-forming material is high, among the complex fine concavo-convex structures, the surrounding of the film-forming material is poor with respect to the portion that becomes a shadow with respect to the traveling direction of the film-forming material, and it is difficult to form a uniform protective film 40. Also, in the vacuum evaporation method, the surrounding of the film-forming material is poor, and it is difficult to form a uniform protective film 40. Further, in the CVD method, although the surrounding of the film-forming material is good, since the film-forming temperature is as high as several hundred degrees Celsius or more, the resin of the grid structure 20 softens and the fine concavo-convex structure is destroyed.

[0323] On the other hand, according to the present embodiment, by using the ALD method as the film-forming method, the surrounding of the film-forming material with respect to the fine concavo-convex structure is good, so the uniformity of the protective film 40 can be significantly improved compared to the conventional sputtering method and vacuum evaporation method. Further, according to the ALD method according to the present embodiment, the protective film 40 can be formed at a low film-forming temperature (for example, 190° or less) that is lower than the heat-resistant temperature of the resin of the grid structure 20 (for example, 200°). Thereby, since the resin of the grid structure 20 is difficult to soften during the formation of the protective film 40, the fine concavo-convex structure of the grid structure 20 can be maintained. Further, the reliability (heat resistance and light resistance) of the grid structure 20 covered with the protective film 40 can also be significantly improved compared to the conventional film-forming method.

[0324] Note that, as conditions for film formation by the ALD method according to the present embodiment, there are the capacity of the chamber 300, the type of gas used, the flow rate of the gas, the film-forming temperature, the presence or absence of exhaust, the state of the grid structure 20 disposed in the chamber 300, and the like. These conditions can be appropriately set to optimal values so as to satisfy the desired film-forming conditions.

[0325] <7. Reinforcing film> Next, with reference to FIGS. 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 the present embodiment will be described. FIG. 25 is an enlarged cross-sectional view showing the wire grid polarizing element 1 including the reinforcing film 51 covering the entire grid structure 20 according to the present embodiment. FIG. 26 is an enlarged cross-sectional view showing the wire grid polarizing element 1 including the reinforcing film 51 covering a part of the ridge portion 22 of the grid structure 20 according to a modified example of the present embodiment.

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

[0327] However, the ridge portion 22 of the grid structure 20 according to the present embodiment is formed of an organic material (such as resin) having lower strength and heat resistance than an inorganic material (such as glass). Further, the ridge portion 22 has a tapered shape that becomes thinner toward its tip. For this reason, the ridge portion 22 formed of an organic material has lower rigidity and heat resistance than when formed of an inorganic material. Therefore, when the height H of the ridge portion 22 is increased as described above, when the high-temperature reflective film 30 (functional film made of a metal such as Al) is formed so as to cover the tip portion of the ridge portion 22 by a film-forming method such as a vapor deposition method or a sputtering method, the ridge portion 22 made of an organic material may soften due to the heat and force applied during the film formation of the reflective film 30. For this reason, the ridge portion 22 may not be able to maintain the tapered shape extending straight upward (Z direction) and may tilt in the left-right direction (X direction) (see FIG. 31). Thus, when the ridge portion 22 tilts due to the film formation of the reflective film 30 (functional film) covering the ridge portion 22, there has been a problem that various optical characteristics (for example, Tp characteristics, Tp×Rs characteristics, CR) required for the wire grid polarizing element 1 deteriorate.

[0328] Therefore, in order to solve such problems, in the wire grid polarizing element 1 according to the present embodiment, as shown in FIGS. 25 and 26, a reinforcing film 51 is provided between the upper portion of the ridge portion 22 of the grid structure 20 and the reflective film 30 (functional film), and the upper portion of the ridge 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 is superior in rigidity and heat resistance to the resin of the ridge portion 22. The reinforcing film 51 is formed so as to cover at least the upper portion of the ridge portion 22, and is interposed between the upper portion of the resin ridge portion 22 and the reflective film 30 made of a metal such as Al.

[0329] By reinforcing the upper portion of the ridge portion 22 with such a reinforcing film 51, when the reflective film 30 is formed on the upper portion of the ridge portion 22, it is possible to suppress the ridge portion 22 from tilting in the left - right direction (X direction) due to the heat and force acting on the ridge portion 22. Therefore, the ridge portion 22 can maintain a desired shape extending straight upward (Z direction), so that the reflective film 30 supported by the ridge portion 22 does not tilt either, and the reflective film 30 does not block the incident light contrary to the design intention. Thus, the transmission characteristics and reflection characteristics of the incident light with respect to the wire grid polarizing element 1 can be realized as designed, and the optical characteristics (for example, Tp characteristics, Tp×Rs characteristics, CR) of the wire grid polarizing element 1 can be improved.

[0330] Here, with reference to FIGS. 27 to 29, the principle by which the ridge portion 22 of the grid structure 20 tilts or becomes thinner due to the formation of the reflective film 30 when the reinforcing film 51 is not provided will be described.

[0331] As a result of intensive studies by the inventors of the present application, it has been found that when the reflective film 30 is formed on the upper part of the rib portion 22 of the grid structure 20 by vapor deposition or the like, the rib portion 22 tilts in the left - right direction (X direction) (see Fig. 31). One of the reasons is considered to be that the rib portion 22 softens due to the heat during the vapor deposition of the reflective film 30. Another reason is that the high - temperature metal material (such as Al) of the reflective film 30 is vapor - deposited alternately from the upper left and right diagonally onto the rib portion 22 (see Fig. 5). Therefore, due to the accumulation of stress (strain) caused by the thermal contraction of the vapor - deposited metal film (reflective film 30), a force that tilts the rib portion 22 acts on the vapor - deposited side.

[0332] Figs. 27 and 28 show the results of simulating the deformation behavior in which the rib portion 22 tilts during the vapor deposition of the reflective film 30 using a model of the rib portion 22 and the reflective film 30 of the grid structure 20. Fig. 27 is a schematic diagram showing a model in which the reflective film 30 is vapor - deposited alternately from the left and right on the upper part of the rib portion 22. Fig. 28 is a schematic diagram showing the simulation results of the deformation behavior of the rib portion 22 using the above - mentioned model. The shading in Fig. 28 indicates the degree of displacement of the rib portion 22 and the reflective film 30 during vapor deposition.

[0333] In the model shown in Fig. 27, high - temperature Al is vapor - deposited alternately from both the left and right sides on the upper part of the rib portion 22. As a result, the reflective film 30 (Al film) covers the upper part of the rib portion 22 from both the left and right sides, and the reflective film 30 is formed. In the model shown in Fig. 27, for example, Al at 600°C is vapor - deposited alternately twice on the left and right in the order of S1 to S4 on the upper part of the rib portion 22 (vapor deposition in a total of 4 steps).

[0334] As a result of simulating the deformation behavior of the rib portion 22 in this model, as shown in FIG. 28, it was found that stress was accumulated due to the thermal contraction of the deposited Al film (reflective film 30), and the rib portion 22 was deformed so as to incline toward the deposited side. Specifically, first, in the first deposition (S1), since high-temperature Al was deposited on the right side of the rib portion 22, the rib portion 22 inclined toward the right side where Al was deposited. Next, in the second deposition (S2), since high-temperature Al was deposited on the left side of the rib portion 22, the rib portion 22 returned straight. Furthermore, in the third deposition (S3), since high-temperature Al was deposited again on the right side of the rib portion 22, the rib portion 22 inclined to the right side again. After that, in the fourth deposition (S4), since high-temperature Al was deposited again on the left side of the rib portion 22, the rib portion 22 returned straight again. In addition, in the simulation result of FIG. 28, after the fourth deposition (S4), the rib portion 22 returned straight, but in the sample of the actual product in which the Al film was deposited on the rib portion 22, the inclination of the rib portion 22 did not return.

[0335] Thus, when Al is alternately deposited on the rib portion 22 from diagonally above to the left and right, the deposited Al film (reflective film 30) alternately repeats the high-temperature state immediately after deposition and the temperature decrease state during standby. At that time, due to the difference in the coefficient of thermal expansion between the resin of the rib 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. It is considered that this residual stress is one of the causes of the inclination of the rib portion 22. That is, the resin of the rib portion 22 is softened by the deposition of high-temperature Al, and when the above residual stress is applied to the softened rib portion 22, the rib portion 22 is considered to incline so as to curve in either the left-right direction (deposition direction).

[0336] For this reason, conventionally, there has been a demand for a technique for solving the problem that the rib portion 22 of the grid structure 20 inclines due to the formation of such an Al film (reflective film 30) and improving the optical characteristics of the polarizing element 1.

[0337] Next, with reference to FIG. 29, the reason why the ridge portion 22 becomes thinner due to the deposition of the reflective film 30 will be described. FIG. 29 is a schematic diagram showing the result of simulating the deformation behavior in which the ridge portion 22 becomes thinner during the deposition of the reflective film 30, using a model of the ridge portion 22 of the grid structure 20 and the reflective film 30.

[0338] As described above, when Al is deposited alternately from the upper left and right diagonally above the ridge portion 22 during the film formation of the Al film (reflective film 30), the deposited Al film (reflective film 30) alternately repeats the high-temperature state immediately after deposition and the temperature decrease state during standby. At this time, due to the difference in the coefficient of thermal expansion between the resin of the ridge portion 22 and the Al of the reflective film 30, the shrinkage of the Al film (reflective film 30) is inhibited, and residual stress remains inside and around the Al film. Assume a case where the polarizing element 1 having the reflective film 30 and the ridge portion 22 with the residual stress remaining is placed in a high-temperature environment. In this case, it was found that due to the softening of the resin of the ridge portion 22 due to the high-temperature environment and the release of the residual stress of the Al film, the reflective films 30 on both the left and right sides of the ridge portion 22 are deformed so as to close inward, and the ridge portion 22 is sandwiched by the reflective films 30 on both the left and right sides and becomes thinner.

[0339] FIG. 29 shows the simulation results performed to clarify the behavior in which the ridge portion 22 becomes thinner in this way. The shading of the reflective film 30 (Al film) in the upper figure of FIG. 29 indicates the temperature distribution of the reflective film 30. The shading in the lower figure of FIG. 29 indicates the amount of deformation in the left-right direction of the reflective film 30 (Al film) and the ridge portion 22.

[0340] As shown in the upper figure of FIG. 29, a model of the ridge portion 22 and the reflective film 30 was prepared. In this model, the inner part 30 of the deposited Al film (reflective film 30) in is the portion formed by the first deposition, and it is assumed that the temperature of the portion 30 in has dropped to room temperature. On the other hand, the outer part 30 of the deposited Al film (reflective film 30) out is the portion formed by the deposition after the third time. That is, with respect to the outside of the low-temperature portion 30 in , the portion 30 outAssume that high-temperature Al is deposited. Then, when the temperature of the outer part 30 out drops to room temperature, the outer part 30 out contracts, and accordingly, a contracting force acts on the inner part 30 in as well. However, due to the resin (low coefficient of thermal expansion) of the rib portion 22 further inside the inner part 30 in , the contraction of the Al film (high coefficient of thermal expansion) of the inner part 30 in is hindered, so residual stress in the contraction direction remains in the inner part 30 in .

[0341] Then, when the polarizing element 1 having the Al film (reflective film 30) and the rib portion 22 with residual stress remaining inside as described above is placed in a high-temperature environment, the resin rib portion 22 softens, and the residual stress of the Al film in the inner part 30 in is released, and the Al film contracts so as to close inward in the left-right direction. As a result, as shown in the lower figure of FIG. 29, the Al films (reflective films 30) on both the left and right sides of the rib portion 22 are deformed so as to close inward in the left-right direction, and the softened rib portion 22 becomes thinner by about 4 nm.

[0342] As described above, when the polarizing element 1 is placed in a high-temperature environment and the phenomenon occurs that the rib portion 22 becomes thinner due to residual stress, there is a risk that the polarizing element 1 cannot exhibit the desired optical characteristics. For example, when the polarizing element 1 is mounted on a head-up display device of a vehicle, when the head-up display device becomes hot due to direct sunlight in summer, the rib portion 22 of the polarizing element 1 may be deformed to become thinner, and the optical characteristics of the polarizing element 1 may deteriorate.

[0343] Therefore, conventionally, there has also been a demand to solve the problem that the rib portion 22 of the grid structure 20 becomes thinner due to the residual stress during the formation of such an Al film (reflective film 30) and to improve the optical characteristics of the polarizing element 1.

[0344] Therefore, in order to solve the problems that the rib portion 22 inclines or becomes thinner as described above, the polarizing element 1 according to the present embodiment newly provides a reinforcing film 51 that covers the upper portion of the rib portion 22, and reinforces the rib portion 22 with the reinforcing film 51. That is, as shown in FIGS. 25 and 26, the polarizing element 1 according to the present embodiment includes a reinforcing film 51 interposed between the upper portion of the rib portion 22 of the grid structure 20 and the reflective film 30 (functional film). This reinforcing film 51 covers and reinforces the upper portion of the rib portion 22 so as to wrap it. The reinforcing film 51 is made of an inorganic oxide such as a dielectric material, and is superior in rigidity and heat resistance to the resin-made rib portion 22. The softening point of the resin of the rib portion 22 is, for example, 120° C., and the softening point of the inorganic oxide of the reinforcing film 51 is higher than the temperature of the softening point of the resin. Therefore, even when the resin of the rib portion 22 softens due to vapor deposition or the like of the high-temperature reflective film 30, the inorganic oxide of the reinforcing film 51 does not soften.

[0345] Therefore, according to the present embodiment, when forming the reflective film 30 (such as an Al film) by vapor deposition or the like around the upper portion of the rib portion 22, the resin-made rib portion 22 that is easily softened by heat is reinforced by the reinforcing film 51 having excellent heat resistance, and the rib portion 22 does not directly contact the vapor-deposited high-temperature reflective film 30. Therefore, even if the rib portion 22 softens during the film formation of the high-temperature reflective film 30, the rib portion 22 is reinforced by the reinforcing film 51 having excellent rigidity and heat resistance, so that the rib portion 22 can be prevented from inclining in the left-right direction (X direction).

[0346] In addition, assume a case where the rib portion 22 of the grid structure 20 softens because the polarizing element 1 is used in a high-temperature environment with residual stress remaining in the reflective film 30 due to inhibition of thermal shrinkage of the reflective film 30 during the film formation. Even in this case, according to the present embodiment, a reinforcing film 51 having excellent rigidity and heat resistance is interposed between the softened rib portion 22 and the reflective film 30. Therefore, as shown in FIG. 29, even if the reflective films 30 on both the left and right sides of the rib portion 22 tend to deform inward in the left-right direction due to the residual stress in the reflective film 30, the high-rigidity reinforcing film 51 can suppress the deformation. Thus, the problem that the rib portion 22 becomes thinner due to the residual stress during the film formation of the reflective film 30 can be solved.

[0347] <7.2. Structure of Reinforcement Film> Next, with reference to FIGS. 25 and 26, the structure of the reinforcement film 51 according to the present embodiment will be described in more detail.

[0348] As shown in FIGS. 25 and 26, the wire grid polarizing element 1 according to the present embodiment includes a reinforcement film 51 that covers the ridge portion 22 inside the protective film 40 and the reflective film 30 (functional film) in addition to the protective film 40 that covers the entire grid structure 20 and the reflective film 30. The reinforcement film 51 is a film for reinforcing the ridge portion 22 made of an organic material. For this reason, the reinforcement film 51 is made of an inorganic oxide having higher rigidity than the organic material of the ridge portion 22. The reinforcement film 51 is interposed at least between the ridge portion 22 covered by the reflective film 30 and the reflective film 30. The reinforcement film 51 covers at least the tip 22a and both side surfaces 22b, 22b of the ridge portion 22 of the grid structure 20 on the upper side (hereinafter, may also be referred to as "the upper part of the ridge portion 22"). The reflective film 30 (functional film) covers the upper part of the ridge portion 22 via the reinforcement film 51, and does not cover the lower sides of both side surfaces 22b, 22b of the ridge portion 22 and 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 reinforcement film 51, and the reflective film 30.

[0349] The reinforcement film 51 shown in FIG. 25 covers the entire grid structure 20 (that is, the tip 22a and both side surfaces 22b, 22b of the ridge portion 22 and the upper surface of the base portion 21). For this reason, the reinforcement film 51 shown in FIG. 25 is interposed between the upper part of the ridge portion 22 and the reflective film 30, and is also interposed between the lower part of the ridge portion 22 and the base portion 21 and the protective film 40. Therefore, the reflective film 30 indirectly covers the upper part of the ridge portion 22 via the reinforcement film 51 and does not directly contact the upper part of the ridge portion 22. Further, the protective film 40 indirectly covers the lower part of the ridge portion 22 and the upper surface of the base portion 21 via the reinforcement film 51 and does not directly contact the lower part of the ridge portion 22 and the upper surface of the base portion 21.

[0350] On the one hand, the reinforcing film 51 shown in FIG. 26 covers only 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) of the grid structure 20, and does not cover the lower sides of both side surfaces 22b, 22b of the rib portion 22 and the upper surface of the base portion 21. The covering range of the upper part of the rib portion 22 by the reinforcing film 51 shown in FIG. 26 is wider than the covering range of the upper part of the rib portion 22 by the reflective film 30. Therefore, the reinforcing film 51 shown in FIG. 26 is interposed between the upper part of the rib portion 22 and the reflective film 30. Accordingly, the reflective film 30 indirectly covers the upper part of the rib portion 22 via the reinforcing film 51 and does not directly contact the upper part of the rib portion 22. Further, the reinforcing film 51 shown in FIG. 26 is not interposed between the lower ends of both side surfaces 22b, 22b of the rib portion 22 and the base portion 21 and the protective film 40. Therefore, the protective film 40 directly contacts and covers the lower ends of both side surfaces 22b, 22b of the rib portion 22 and the base portion 21.

[0351] As shown in FIGS. 25 and 26, the reinforcing film 51 may be interposed at least between the upper part of the rib portion 22 covered by the reflective film 30 (functional film) of the grid structure 20 and the portion between the reflective film 30. That is, the reinforcing film 51 only needs to cover at least the upper part of the rib portion 22 covered by the reflective film 30 of the grid structure 20, and may (see FIG. 25) or may not (see FIG. 26) cover other parts of the grid structure 20 (the lower part of the rib portion 22 or the base portion 21).

[0352] By interposing such a reinforcing film 51 between the upper part of the rib portion 22 and the reflective film 30, the upper part of the rib portion 22 and the reflective film 30 are prevented from directly contacting each other. Then, by covering the upper part of the rib portion 22 made of an organic material such as resin with the reinforcing film 51 made of an inorganic oxide so as to wrap it, the reinforcing film 51 having high rigidity and heat resistance reinforces the upper part of the rib 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 rib portion 22, it is possible to suppress the upper part of the rib portion 22 covered and reinforced by the reinforcing film 51 from tilting 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 rib portion 22 can maintain a tapered shape that extends straight upward (Z direction). Therefore, tilting of the grid 41 (the entire convex structure including the rib portion 22, the reinforcing film 51, and the reflective film 30) of the polarizing element 1 can be suppressed, so that a decrease in the Tp characteristics and contrast of the polarizing element 1 can be suppressed. As a result, the optical characteristics (for example, Tp characteristics, Tp×Rs characteristics, CR) of the polarizing element 1 can be improved compared to the case where the reinforcing film 51 is not provided.

[0354] Further, the reinforcing film 51 shown in FIG. 25 covers the entire resin-made grid structure 20. Thereby, the reinforcing film 51 can protect the lower part of the rib portion 22 and the resin portion on the upper surface of the base portion 21 in the grid structure 20. Thereby, the scratch resistance, antifouling property, and waterproof property of the grid structure 20 can also be enhanced.

[0355] In particular, since the grid structure 20 is formed of an organic material such as resin, it is more likely to deteriorate by heat, light, water, etc. compared to the substrate 10 formed of an inorganic material such as glass. By covering such a resin-made grid structure 20 without a gap with the reinforcing film 51 and the protective film 40 made of an inorganic oxide, the grid structure 20 can be protected from external heat, air, water, etc. (barrier property). Thereby, it is possible to suppress the resin of the grid structure 20 from being altered and deteriorated due to heat, air, water, etc. Further, as shown in FIG. 25, by covering the entire surface of the polarizing element 1 with both the reinforcing film 51 and the protective film 40 made of an inorganic oxide, the thermal resistance R of the entire polarizing element 1 can be further reduced, so that the heat dissipation property of the polarizing element 1 can be further improved.

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

[0357] The reinforcing film 51 is a film for reinforcing the rib portion 22 made of an organic material. Therefore, the reinforcing film 51 is made of an inorganic oxide having higher rigidity than the organic material of the rib portion 22. The reinforcing film 51 is preferably made of a dielectric material such as SiO2, Al2O3, etc. Thereby, the rib portion 22 can 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 composed of a thin film made of a dielectric material (for example, a SiO2 thin film, an Al2O3 thin film). However, the reinforcing film 51 may be composed of a thin film made of an inorganic oxide such as a metal oxide other than the dielectric material.

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

[0359] The material of the reinforcing film 51 is not particularly limited as long as it is an inorganic oxide that can reinforce the rib portion 22 and maintain the optical properties of the polarizing element 1, but it preferably contains a dielectric material or a metal oxide. The dielectric material is, for example, Si oxide, Hf oxide, etc. The metal oxide is, for example, Al oxide, etc. By the reinforcing film 51 containing an inorganic oxide, the scratch resistance of the polarizing element 1 and the barrier property of protecting the grid structure 20 from heat, light, water, etc. can be further enhanced. Also, the reinforcing film 51 may contain, in addition to the inorganic oxide, for example, a silane-based water repellent material, a fluorine-based water repellent material, etc. By the reinforcing film 51 containing a water repellent material, the antifouling property and waterproof property of the polarizing element 1 can be further enhanced.

[0360] Also, the reinforcing film 51 may be a thin film having a single-layer structure made of one type of inorganic oxide (for example, one type of dielectric material), or a thin film having a laminated structure made of a plurality of types of inorganic oxides (for example, a plurality of types of dielectric materials).

[0361] For example, the reinforcing film 51 may have a single-layer structure made of SiO2. By using SiO2 as the material of the reinforcing film 51, the reinforcing film 51 with high transmittance in a wide wavelength range can cover the convex strip portion 22 of the grid structure 20. Also, the reinforcing film 51 may have a single-layer structure made of Al2O3. By using Al2O3 as the material of the reinforcing film 51, the convex strip portion 22 of the grid structure 20 can be covered with the reinforcing film 51 having high barrier properties for protecting the grid structure 20 from external heat, air, water, etc.

[0362] Also, the reinforcing film 51 may have a laminated structure including a first layer made of Al2O3 and a second layer made of SiO2. Thereby, the reinforcing film 51 can have both the high barrier properties of Al2O3 and the high transmittance of SiO2.

[0363] Note that the present invention is not limited to the above examples, and the reinforcing film 51 may be formed of 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. Thereby, the antifouling property and waterproof property of the polarizing element 1 can be further enhanced. Also, the reinforcing film 51 may 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 FIGS. 25 and 26, the thickness Rt (film thickness) of the reinforcing film 51 in the wire grid polarizing element 1 according to the present 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 thick, and the optical characteristics (particularly, Tp characteristics) of the polarizing element 1 may deteriorate, which is not preferable. On the other hand, if the thickness Rt of the reinforcing film 51 is too small, the reinforcing performance of the convex strip portion 22 by the reinforcing film 51 may deteriorate, which is not preferable.

[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 preferably 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 portion 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 portion 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 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 equal to or more than a predetermined value 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] Also, if the total thickness (Rt + Bt) of the reinforcing film 51 and the protective film 40 shown in FIG. 25 is too thick, the valleys 42 between the grids 41, 41 of the complex fine uneven structure may be filled with the resin of the reinforcing film 51 or the protective film 40, which may deteriorate the optical characteristics of the polarizing element 1, which is not preferable. Therefore, the total thickness (Rt + Bt) of the reinforcing film 51 and the protective film 40 is preferably 20 nm or less (Rt + Bt < 20 nm), and more preferably 15 nm or less (Rt + Bt < 15 nm). Thereby, as the total thickness (Rt + Bt) of the reinforcing film 51 and the protective film 40, while ensuring the thickness necessary for ensuring the barrier property, the optical characteristics of the polarizing element 1, particularly the Tp characteristics, can be appropriately ensured. Also, from the same 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] Note that, as a method for measuring the thickness Rt (film thickness) of the reinforcing film 51, for example, the following measuring method can be used. After forming the reinforcing film 51 on the ridge portion 22, a reflective film 30 is formed outside the reinforcing film 51 to create a sample of the polarizing element 1. Then, 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 by the observation is imported into a length measurement application to measure the thickness of the reinforcing film 51. At this time, for each sample, the thicknesses of the reinforcing film 51 in a plurality of (for example, three or more) grids 41 are measured, and the average value of these measured thickness values is taken as the thickness Rt of the reinforcing film 51. Note that the measuring method of the thickness Rt of the reinforcing film 51 is not limited to such a measuring method. For example, when observing the cross-section of the sample using the above transmission electron microscope, the thickness Rt of the reinforcing film 51 may be measured. Also, as the thickness Rt of the reinforcing film 51, it is preferable to measure the thickness of the reinforcing film 51 in the portion intervening between the reflective film 30 and the ridge portion 22, but other portions of the reinforcing film 51 may 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. As a result, the grid structure 20 having a complex fine concavo-convex structure as shown in FIG. 25 can be suitably covered with the thin reinforcing film 51 and the protective film 40, so that both the optical characteristics of the polarizing element 1, the barrier property of the grid structure 20, and the reinforcing performance of the rib portion 22 can be ensured. Thereby, when the polarizing element 1 is used as, for example, a polarizing beam splitter, while maintaining the required optical characteristics (Tp characteristics, Tp×Rs characteristics, CR) of the polarizing element 1, deterioration of the resin portion of the grid structure 20 is suppressed, and the reliability (heat resistance, light resistance) of the polarizing element 1 can be improved, and the rib portion 22 can be suitably reinforced by the reinforcing film 51. Further, since each of the reinforcing film 51 and the protective film 40 does not have to be formed with a completely uniform thickness, it is realistically possible to form the reinforcing film 51 and the protective film 40 with thickness unevenness within an allowable range, for example, by using the above-described special ALD method.

[0373] <7.5. Relationship between the grid structure 20 with a complex concavo-convex structure and the reinforcing film 51> As shown in FIGS. 25 and 26, the polarizing element 1 according to the present 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 (the entire convex structure including the rib portion 22, the reinforcing film 51, and the reflective film 30) of the polarizing element 1 has the above-described special tree shape. For this reason, valleys 42 having a complex shape are formed between adjacent grids 41, 41. As a result, the surface of the grid structure 20 of the polarizing element 1 has a complex concavo-convex structure in which a plurality of convex portions (grids 41) and a plurality of concave portions (valleys 42) are intertwined.

[0374] The rib portion 22 of the grid structure 20 has a tapered shape in which the width in the X direction becomes narrower as it moves away from the base portion 21 in the upward direction (Z direction). The reflective film 30 (functional film) is a metal film (Al film) made of a metal material such as Al, which covers 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), and does not cover the lower sides of both side surfaces 22b, 22b of the rib portion 22 and the surface of 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 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 rib portion 22. The reinforcing film 51 covers at least the upper part of the rib portion 22 covered by the reflective film 30. The reinforcing film 51 shown in FIG. 25 covers not only the upper part of the rib portion 22 covered by the reflective film 30 but also the lower part of the rib portion 22 and the upper surface of the base portion 21.

[0376] The reflective film 30 indirectly covers and wraps the upper part of the rib portion 22 via such a reinforcing film 51. The surface of the reflective film 30 has a rounded shape and bulges in the width direction (X direction in FIG. 25) of the rib portion 22. The maximum width (W MAX ) of the reflective film 30 covering and wrapping the rib portion 22 is equal to or greater than the width (W B ) on the lower side of the rib portion 22. Then, as shown in FIGS. 25 and 26, the cross-sectional shape of the entire convex structure (i.e., the grid 41) composed of the rib portion 22, the reinforcing film 51, and the reflective film 30 has the above-described special tree shape. In this special tree shape, constrictions 29, 29 are provided at positions directly below the lower ends on both the left and right sides of the reflective film 30 covering and wrapping the rib portion 22, and at the positions of the constrictions 29, 29, the width in the width direction (X direction) of the entire convex structure (i.e., the grid 41) becomes narrower.

[0377] As described above, the grid 41 of the grid structure 20 according to the present embodiment has a reflective film 30 that bulges roundly in the X direction on the upper side of the convex strip portion 22, constriction 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 strip portion 22 not covered by the reflective film 30. Therefore, the grid 41 has a complex cross-sectional shape like that of a single tree. With the grid 41 having such a special tree shape, as described above, the polarization separation characteristics (Tp×Rs characteristics) with respect to obliquely incident light can be improved.

[0378] And, between the grids 41, 41 adjacent to each other in the X direction, valleys 42 with a complex shape are formed. The valley 42 is a recess formed between the 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 upward. The bottom of the valley 42 is a semi-closed space surrounded in three directions by the convex strip portions 22, 22 on both the left and right sides and the base portion 21 on the bottom side. The width in the X direction of the upper part of the valley 42 is narrow, and the width in the X direction of the bottom of the valley 42 is wide. Thus, the cross-sectional shape (XZ cross-section) of the valley 42 has a bowl shape in which the entrance on the upper side is narrow and the semi-closed space on the bottom side is wide.

[0379] As described above, in the polarization element 1 according to the present embodiment, the plurality of grids 41 have a complex structure with a special tree shape. Therefore, the valley 42 between the adjacent convex strip portions 22, 22 and the valley 42 between the grids 41, 41 also become semi-closed spaces with a complex bowl shape. Therefore, the surface of the polarization element 1 has a complex uneven structure composed 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 the complex uneven structure with a protective film 40 having a uniform film thickness. For this reason, it is preferable to form the protective film 40 using the above-described special ALD method.

[0380] On the other hand, for the reinforcing film 51, the reinforcing film 51 is formed so as to cover at least the upper part of the ridge portion 22 of the grid structure 20 before forming the reflective film 30. When the reinforcing film 51 is formed, the semi-closed space between the ridge portions 22 and 22 adjacent in the X direction does not have a pot shape narrowed by the reflective films 30 and 30 on both sides, and the upper inlet is wide. Therefore, it is easier to form the reinforcing film 51 before forming the reflective film 30 and to form the protective film 40 after forming the reflective film 30. However, the reinforcing film 51 is a thinner film than the protective film 40. Therefore, as shown in FIG. 25, in order to form the thin reinforcing film 51 with a uniform film thickness over the entire grid structure 20, it is preferable to form the reinforcing film 51 using the above-described special ALD method as in the case of forming the protective film 40. Thereby, the reinforcing film 51 having a thin and uniform thickness can be suitably formed.

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

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

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

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

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

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

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

[0388] In the example shown in FIG. 25, the reinforcing film 51 covers the entire surface of the grid structure 20, and the reflective film 30 covers a part of the reinforcing film 510 (the peripheral portion above the convex strip portion 22). In this case, in the film formation process (S18) of the protective film 40, the protective film 40 continuously covers the surface of the reflective film 30, the lower sides of both side surfaces 22b, 22b of the convex strip portion 22 (that is, the entire surface of the grid 41), and the surface of the reinforcing film 51 that covers the base portion 21 (that is, the bottom surface of the valley 42). Thus, the protective film 40 is formed.

[0389] On the other hand, in the example shown in FIG. 26, the reinforcing film 51 covers only the upper part of the convex strip portion 22 and does not cover the lower part of the convex strip portion 22 or the upper surface of the base portion 21. In this case, in the film formation process (S18) of the protective film 40, the protective film 40 continuously covers the surface of the reflective film 30, the exposed portion of the reinforcing film 51 below it, the lower sides of both side surfaces 22b, 22b of the convex strip portion 22 (that is, the entire surface of the grid 41), and the surface of the base portion 21 (that is, the bottom surface of the valley 42). Thus, the protective film 40 is formed.

[0390] As a method for forming the protective film 40, it is preferable to use the ALD method, particularly the special ALD method described above (see FIG. 19). Thereby, it becomes possible to form the protective film 40 substantially uniformly on the entire surface of the complex fine concavo-convex structure of the grid structure 20.

[0391] Next, in the film formation process (S15) of the reinforcing film 51 described above, a special ALD method used for forming the overall reinforcing film 51 shown in FIG. 25 will be described in more detail.

[0392] Since the ALD method can precisely control the film thickness and material at the atomic layer level, it has the advantage of enabling extremely thin and uniform film formation compared to the CVD method. Therefore, in the film formation step (S15) of the reinforcing film 51 according to the present embodiment, when forming the reinforcing film 51 on the entire surface of the complex fine concavo-convex structure of the grid structure 20, it is preferable to form the reinforcing film 51 by the ALD method. Thereby, it becomes possible to form the reinforcing film 51 almost uniformly on the entire surfaces of the rib portions 22 and the base portion 21 of the grid structure 20.

[0393] Furthermore, in the present embodiment, when forming the overall reinforcing film 51 shown in FIG. 25 as well, the above-described special ALD method (see FIG. 19) is used in the same manner as when forming the protective film 40. In this special ALD method, for example, the chamber 300 shown in FIG. 19 described above may be used. Since the configuration of the chamber 300 is as described above, its detailed description is omitted. A method for forming the overall reinforcing film 51 shown in FIG. 25 by the special ALD method according to the present embodiment will be described below.

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

[0395] Next, the first to fourth steps (S151 to S154) of alternately introducing (pulsing) and exhausting (purging) two types of gaseous raw material gases (hereinafter, referred to as “precursor gas” and “oxidant gas” respectively) for forming the reinforcing film 51 into the chamber 300 are repeated. Here, the precursor gas introduction step (S151: first step), the inert gas introduction step (S152: second step), the oxidant gas introduction step (S153: third step), and the inert gas introduction step (S154: fourth step) are the same as the respective steps (S181 to S184) of the film formation step (S18) of the protective film 40 described above, and thus their detailed description is omitted.

[0396] Furthermore, according to the film formation process (S15) of the reinforcing film 51 by the special ALD method according to this embodiment, in the precursor gas introduction step (S151) and the oxidant gas introduction step (S153), the precursor gas and the oxidant gas are introduced into the chamber without exhausting the precursor gas and the oxidant gas from the chamber 300 to the outside and filling the chamber.

[0397] In this regard, in the conventional film formation process by the general ALD method, in the precursor gas introduction step and the oxidant gas introduction step (S151, S153), while exhausting the precursor gas and the oxidant gas in the chamber 300, the precursor gas and the oxidant gas are introduced into the chamber 300.

[0398] On the contrary, in the film formation process (S15) of the reinforcing film 51 by the special ALD method according to this embodiment, in the precursor gas introduction step and the oxidant gas introduction step (S151, S153: the first and the third steps), without exhausting the precursor gas and the oxidant gas in the chamber 300 from the gas exhaust port 330, the precursor gas and the oxidant gas are continuously introduced into the chamber 300. Specifically, in the precursor gas introduction step (S151: the first step), with the exhaust valve of the gas exhaust port 330 closed and the chamber 300 in a sealed state, 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 oxidant gas introduction step (S153: the third step), with the exhaust valve of the gas exhaust port 330 closed and the chamber 300 in a sealed state, the oxidant gas is introduced into the chamber 300 from the gas inlet 310, and the oxidant 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 the oxidant gas introduced into the chamber 300 can be sufficiently filled and retained in the chamber 300 and brought into sufficient contact with the surface to be coated of the grid structure 20. Therefore, among the surfaces of the complex fine concavo-convex structure of the grid structure 20 shown in FIG. 25, the precursor gas and the oxidant gas can be sufficiently introduced even to the depth of the valley 42 between the adjacent ridge portions 22, 22, and the first and second atomic layers with the required layer thickness can be appropriately formed. Thus, the reinforcing film 51 with a desired thickness Rt can be preferably formed not only on the upper surface of the ridge portion 22 but also on the lower surface of the ridge portion 22 and the surface of the base portion 21.

[0400] Therefore, the thickness of the reinforcing film 51 covering the tip 22a of the ridge portion 22 and the thickness of the reinforcing film 51 covering the surface of the base portion 21 can be made substantially the same. As a result, the uniformity of the thickness of the reinforcing film 51 formed by the special ALD method according to the present embodiment can be further improved as compared with the case of the conventional general ALD method. Thus, a reinforcing film 51 having further excellent uniformity can be formed within the allowable range of a predetermined thickness unevenness.

[0401] As described above in detail, the process (S15) of forming the overall reinforcing film 51 shown in FIG. 25 using the special ALD method according to the present embodiment has been described. According to the present 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 the precursor gas and the oxidant gas) in the introduction steps (S151, S153) of the precursor gas and the oxidant gas by the ALD method can be optimized according to the fine concavo-convex structure of the grid structure 20.

[0402] As a result, an extremely thin reinforcing film 51 on the order of several nm to a dozen or so nm can be formed very uniformly over the entire surface of the fine uneven structure of the grid structure 20. Thus, it becomes possible to form an extremely uniform thin reinforcing film 51 within the allowable range of a predetermined thickness unevenness. Since the upper part of the ridge portion 22 can be reinforced by this reinforcing film 51, it is possible to suppress the ridge portion 22 from tilting or becoming thinner due to the formation of the reflective film 30. Further, as shown in FIG. 25, the reinforcing film 51 covering the entire grid structure 20 can more firmly protect the grid structure 20 together with the protective film 40 on the outside thereof. Therefore, it is possible to improve the reliability (heat resistance and light resistance) of the polarizing element 1 while maintaining the optical characteristics of the polarizing element 1 provided with the reinforcing film 51.

[0403] Furthermore, according to the present embodiment, by using the ALD method as the film forming method, since the surrounding of the film forming material with respect to the fine uneven structure is good, the uniformity of the reinforcing film 51 can be significantly improved as compared with the conventional sputtering method and vacuum evaporation method. Further, according to the ALD method according to the present embodiment, the reinforcing film 51 can be formed at a low film forming temperature (for example, 190° or less) that is lower than the heat resistant temperature (for example, 200°) of the resin of the grid structure 20. As a result, since the resin of the grid structure 20 is difficult to soften during the formation of the reinforcing film 51 (S15), the shape of the ridge portion 22 of the grid structure 20 can be maintained. Further, the reliability (heat resistance and light resistance) of the grid structure 20 covered with the reinforcing film 51 can also be significantly improved as compared with the conventional film forming method.

[0404] Note that, as conditions for forming the reinforcing film 51 by the ALD method according to the present embodiment, there are the capacity of the chamber 300, the type of gas used, the flow rate of the gas, the film forming temperature, the presence or absence of exhaust, the state of the grid structure 20 disposed in the chamber 300, and the like. These conditions can be appropriately set to optimal values so as to satisfy the desired film forming conditions.

[0405] Incidentally, in the above, as a method for forming the overall reinforcing film 51 shown in FIG. 25, an example using a special ALD method has been described in detail. On the other hand, as a method for forming the partial reinforcing film 51 shown in FIG. 26, for example, a general vapor deposition method or sputtering method may be used to deposit the material of the reinforcing film 51 on the upper part and the central part of the convex strip portion 22, and the reinforcing film 51 may be formed so as to cover the upper part and the central part of the convex strip portion 22.

Example

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

[0407] <1. Verification Results of the Thickness of the Protective Film> As an example of the present invention, a sample of the wire grid polarizing element 1 that satisfies the formula (10) regarding the thickness of the protective film 40 according to the above-described embodiment was manufactured, and tests were conducted to evaluate the optical characteristics, heat resistance, and light resistance of the sample. Further, in order to compare with the example of the present invention (satisfies the formula (10)), a sample of the wire grid polarizing element 1 according to the comparative example (does not satisfy the formula (10)) was also manufactured and tested and evaluated in the same manner. Incidentally, hereinafter, for convenience of explanation, in both the example and the comparative example, reference numerals representing the components of the polarizing element 1 (substrate 10, grid structure 20, base portion 21, convex strip portion 22, reflection film 30, protective film 40, etc.) and symbols representing various dimensions of these components are given the same reference numerals and symbols.

[0408] Incidentally, symbols representing various dimensions, etc. of the polarizing element 1 used in the following description will be explained as follows. P: Pitch of the convex strip portion 22 W T : Width of the top of the convex strip portion 22 (width of the top of the convex strip) W M : Width at the central position in the height direction of the convex strip portion 22 (central width of the convex strip) W B : Width of the bottom of the convex strip portion 22 (width of the grid bottom) WMAX : Maximum width of the reflective film 30 covering the rib portion 22 (maximum grid width) H: Height of the rib portion 22 Hx: Height of the portion of the side surface 22b of the rib portion 22 covered by the reflective film 30 Dt: Thickness of the reflective film 30 covering the tip 22a of the rib portion 22 (tip thickness of the reflective film 30) Ds: Thickness of the reflective film 30 covering the side surface 22b of the rib portion 22 (side surface thickness of the reflective film 30) Rc: Coverage rate of the side surface 22b of the rib portion 22 by the reflective film 30 Rr: Opening rate of the side surface 22b of the rib portion 22 by the reflective film 30 Tt: Thickness of the protective film 40 covering the top 30a of the reflective film 30 covering the rib portion 22 (i.e., thickness of the protective film 40 at the tip of the grid 41) Bt: Thickness of the protective film 40 covering the lower sides of both side surfaces 22b, 22b of the rib portion 22 and the surface of the base portion 21 (i.e., thickness of the protective film 40 at the bottom of the valley 42) Bt1: Thickness of the protective film 40 covering the lower sides of both side surfaces 22b, 22b of the rib portion 22 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 the incident light

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

[0410] (Example 51) First, referring to FIG. 18, Example 51 of the present invention will be described.

[0411] By the manufacturing method of the polarizing element 1 according to the above-described embodiment, a sample of the polarizing element 1 according to Example 51 was produced. As shown in FIG. 18, the polarizing element 1 according to Example 51 includes a glass substrate 10 and a grid structure 20 made of an 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 ridge portions 22 protruding from the base portion 21 in a lattice shape. The cross-sectional shape of the ridge portion 22 is a vertically long trapezoid, and is a tapered shape that becomes thinner toward the tip 22a of the ridge portion 22.

[0412] The reflective film 30 covering the ridge portion 22 according to Example 51 is an Al film. The reflective film 30 is formed so as to cover the tip 22a of the ridge portion 22 and the upper sides of both side surfaces 22b, 22b. However, the reflective film 30 does not cover the lower sides of both side surfaces 22b, 22b of the ridge portion 22 and the base portion 21. The coverage rate Rc of both side surfaces 22b, 22b of the ridge portion 22 by the reflective film 30 is 38%. Thus, the reflective film 30 of Example 51 roundly covers and wraps the top of the ridge portion 22 (the tip 22a and the upper sides of both side surfaces 22b, 22b). The surface of the reflective film 30 has a substantially elliptical shape with a bulge outward, and bulges in the width direction of the ridge portion 22.

[0413] As a result, as shown in FIG. 18, the grid 41 (the structure combining the ridge portion 22 and the reflective film 30) according to Example 51 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 having the special tree shape is equal to or greater than the width W B (the width of the ridge portion 22 at a height position 20% above the bottom of the ridge portion 22) of the ridge portion 22. Further, the cross-sectional shape (XZ cross-section) of the valley 42 between adjacent grids 41, 41 has a bowl shape in which the upper side inlet is narrow and the bottom side semi-closed space is wide.

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

[0415] During the film formation in Example 51, in the step of introducing the above-described precursor gas and oxidant gas (S181, S183: the first and third steps), a film formation method was adopted in which the precursor gas and oxidant gas in the chamber 300 were introduced into the chamber 300 and filled without exhausting the precursor gas and oxidant gas in the chamber 300 from the gas exhaust port 330. As a result, as will be described later, the thickness Tt of the protective film 40 covering the tip of the grid 41 (i.e., the metal portion of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 covering the surface of the bottom of the valley 42 (i.e., the resin portion of the grid structure 20) could be made substantially the same, and the protective film 40 satisfying the above formula (10) was formed (see Table 1).

[0416] In the sample of the polarizing element 1 according to Example 51 produced as described above, the thicknesses Bt and Tt of the protective film 40 were measured. At this time, for a plurality of grids 41 of the sample of the polarizing element 1 according to Example 51, Bt1, Bt2, and Tt were measured respectively, and their average values were obtained.

[0417] More specifically, after producing a sample of the polarizing element 1 according to Example 51, the cross section of the sample was observed using a transmission electron microscope. Next, the data of the cross-sectional image of the sample obtained by the observation was imported into a length measurement application, and the thicknesses Bt1, Bt2, and Tt of the protective film 40 on the outermost layer of the grid 41 were measured respectively. At this time, the thicknesses Bt1, Bt2, and Tt of the protective film 40 in three or more grids 41 per sample were measured. Then, the average value Bt1(ave.) of the plurality of measured values of Bt1 and the average value Bt2(ave.) of the plurality of measured values of Bt2 were obtained. Furthermore, the average value of the average value Bt1(ave.) of the Bt1 and the average value Bt2(ave.) of the Bt2 was obtained and used as Bt. Also, the average value Tt(ave.) of the plurality of measured values of Tt was obtained and used 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 formed was 6 nm. Except for these points, in the same manner as in Example 51, a sample of the polarization element 1 according to Example 52 was produced. Also, the measurement methods of Bt and Tt in Example 52 were the same as those in Example 51. In Example 52 as well, in the same manner as in Example 51, Tt and Bt could be made to have substantially the same thickness, and a protective film 40 satisfying the above formula (10) could be formed.

[0419] (Example 53) Next, Example 53 of the present invention will be described. In Example 53, the material of the protective film 40 had a laminated structure of a first coating layer made of Al2O3 (target thickness: 1 nm) and a second coating layer made of SiO2 (target thickness: 5 nm). Except for these points, in the same manner as in Example 51, a sample of the polarization element 1 according to Example 53 was produced. Also, the measurement methods of Bt and Tt in Example 53 were the same as those in Example 51. In Example 53 as well, in the same manner as in Example 51, Tt and Bt could be made to have substantially 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 formed was 10 nm. In Comparative Examples 51 and 52, the protective film 40 was formed by a conventional general ALD method different from the special ALD method of Examples 51 to 53 above. That is, in Comparative Examples 51 and 52, when forming the protective film 40 by the ALD method, a film formation method by a conventional general ALD method was used in the steps of introducing the precursor gas and the oxidant gas (S181, S183: the first and third steps). Specifically, in Comparative Examples 51 and 52, as a conventional general ALD method, a film formation method of introducing the precursor gas and the oxidant gas into the chamber 300 while exhausting the precursor gas and the oxidant gas in the chamber 300 from the gas exhaust port 330 was used. As a result, as will be described later, in Comparative Examples 51 and 52, Bt became significantly smaller than Tt, and thickness unevenness occurred between Tt and Bt. Therefore, the ratio of Bt to Tt (Bt / Tt) did not satisfy the above formula (10).

[0421] (Comparative Examples 53 and 54) Next, Comparative Examples 53 and 54 will be described. In both Comparative Examples 52 and 54, the material of the protective film 40 was a single-layer structure of SiO2, and the target thicknesses of the protective film 40 to be formed were 10 nm and 20 nm, respectively. In Comparative Examples 53 and 54, the protective film 40 was formed by a conventional general 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 unevenness occurred between Tt and Bt. Therefore, the ratio of Bt to Tt (Bt / Tt) did not satisfy the above formula (10).

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

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

[0424]

Table 1

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

[0426] This is presumably because in Comparative Examples 51 and 52, the protective film 40 was formed by the conventionally common ALD method, but the film formation conditions of the protective film 40 by the ALD method were not appropriate.

[0427] That is, in Comparative Examples 51 and 52, in the introduction steps (S181, S183: the first and third steps), as the above-described conventional general ALD method, a film formation method was used in which a precursor gas and an oxidizing agent gas in the chamber 300 were introduced into the chamber 300 while exhausting the precursor gas and the oxidizing agent gas from the gas exhaust port 330. Therefore, in Comparative Examples 51 and 52, it was not possible to fill and retain the precursor gas and the oxidizing agent gas in the chamber 300. Therefore, a sufficient amount of the precursor gas and the oxidizing agent gas could not be supplied to the bottom of the trough-shaped valley 42 among the surfaces of the complex fine concavo-convex structure composed of the grid 41 and the valley 42 shown in FIG. 18. Thus, the thickness Bt of the protective film 40 formed on the bottom of the valley 42 (the resin portion of the grid structure 20) was significantly smaller than the thickness Tt of the protective film 40 formed on the tip of the grid 41 (the metal portion of the top 30a of the reflective film 30). As a result, it is considered that the ratio (Bt / Tt) of Tt and Bt according to Comparative Examples 51 and 52 did not satisfy the condition of the above formula (10).

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

[0429] This is considered to be because in Comparative Examples 53 and 54, the protective film 40 was formed by a conventionally general vapor deposition method. That is, in Comparative Examples 53 and 54, an extremely thin protective film 40 of about 10 nm or 20 nm was formed on the surface of the complex fine concavo-convex structure composed of the grid 41 and the valley 42 shown in FIG. 18 by vapor deposition. For this reason, a protective film 40 having a film thickness close to the target thickness is formed at the tip of the grid 41 (the metal portion of the top 30a of the reflective film 30), but the protective film 40 is formed in the trough-shaped valley 42 with a film thickness of less than half compared to the tip of the grid 41, and furthermore, almost no protective film 40 was formed on the side wall portion of the grid 41. Therefore, it was difficult to form a film uniformly over the entire grid structure 20.

[0430] Specifically, in Comparative Example 53 (target thickness of protective film 40: 10 nm), a 10-nm protective film 40 is formed at the tip of grid 41, but only a 3.3-nm protective film 40 is formed in the valley 42 of grid 41, and Bt / Tt is significantly low at 0.31. Also, in Comparative Example 54 (target thickness of protective film 40: 20 nm), a 16.8-nm protective film 40 is formed at the tip of grid 41, but only a 4.9-nm protective film 40 is formed in the valley 42 of grid 41. Even when the target thickness is large as in Comparative Example 54, Bt / Tt is significantly low at 0.29. As a result of these, in Comparative Examples 53 and 54, as will be described later, the change amount ΔTp2 of the Tp characteristic in the heat resistance test is large, and it is confirmed that the heat resistance is low.

[0431] In contrast, in Examples 51 to 53, the value of Bt / Tt is 0.85 to 1.07. This means that in Examples 51 to 53, Bt is about the same as Tt, and the thickness unevenness between Bt and Tt is very small. As a result, in each of Examples 51 to 53, a protective film 40 satisfying the conditions of the above formula (10) could be formed.

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

[0433] That is, in Examples 51 to 53, in the precursor gas introduction step (S181) and the oxidant gas introduction step (S183), respectively, as the special ALD method, a film formation method was used in which the precursor gas and the oxidant gas were introduced into the chamber 300 and filled without exhausting the precursor gas and the oxidant gas from the chamber 300 to the outside. As a result, in each introduction step (S181 and S183), the precursor gas and the oxidant gas introduced into the chamber 300 were sufficiently filled and retained in the chamber 300, and could be sufficiently brought into contact with the surface to be coated of the grid structure 20. Therefore, among the surfaces of the complex fine concavo-convex structure composed of the grid 41 and the valleys 42 shown in FIG. 18, the precursor gas and the oxidant gas were sufficiently introduced to the depth of the trough-shaped valleys 42, and the first and second atomic layers with the required layer thickness could be appropriately formed. Thus, the protective film 40 with the target film thickness could be formed almost uniformly not only on the surface of the tip of the grid 41 but also on the surface of the trough-shaped valleys 42. Therefore, the thickness Tt of the protective film 40 formed on the tip of the grid 41 (the metal part of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 formed on the bottom of the valleys 42 (the resin part of the grid structure 20) could be made substantially the same. As a result, it is considered that the ratio (Bt / Tt) of Tt and Bt according to Examples 51 to 53 satisfied the conditions of the above formula (10).

[0434] From the above results, by forming the protective film 40 by the special ALD method according to the above-described embodiment, it was demonstrated that a protective film 40 with a substantially uniform film thickness could be formed over the entire surface of the complex fine concavo-convex structure of the grid structure 20, and a protective film 40 satisfying the above formula (10) could be formed.

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

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

[0437] In the optical property test, for the samples of the polarizing element 1 according to Examples 51 to 53 and Comparative Examples 51 to 54, the transmission axis transmittance (Tp) was measured before and after forming the protective film 40, respectively. 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.

[0438] And the change amount ΔTp1 of Tp before and after forming the protective film 40 shown in Table 1 was calculated. The change amount ΔTp1 is the average value Tp 1B of the measured values of Tp before forming the protective film 40 and the average value Tp 1A of the measured values of Tp after forming the protective film 40, and the difference therebetween (ΔTp1 = Tp 1A - Tp 1B ). The larger the absolute value of such change amount ΔTp1, the more the optical properties (Tp properties) of the polarizing element 1 change greatly before and after forming the protective film 40. Therefore, the smaller the absolute value of ΔTp1, the more the optical properties (Tp properties) of the polarizing element 1 can maintain the desired optical properties (Tp properties) required for the polarizing element 1 without being degraded by the influence of forming the protective film 40. Therefore, from the viewpoint of maintaining the optical properties (Tp properties) of the polarizing element 1, it is preferable that the absolute value of ΔTp1 is small.

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

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

[0441] From the results of the above optical characteristics tests, it was demonstrated that by forming the protective film 40 satisfying the above formula (10) on the entire surface of the complex fine concavo-convex structure of the grid structure 20, the desired optical characteristics (Tp characteristics) required for the polarizing element 1 can be maintained.

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

[0443] As shown in Table 1 and FIGS. 20 to 22, in the heat resistance test, samples of the polarizing element 1 according to Examples 51 to 53 and Comparative Examples 51 to 54 were continuously heated to 150° C. for a predetermined time t (t = 500 hours, 1000 hours). Then, the change amount ΔTp2 of Tp before and after heating was measured, and based on the magnitude of the change amount ΔTp2 (i.e., the degree of deterioration of Tp), the influence of the protective film 40 on the heat resistance of the polarizing element 1 was evaluated.

[0444] In the heat resistance test, for samples of the polarizing element 1 according to Examples 51 to 53 and Comparative Examples 51 to 54, Tp before and after heating (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.

[0445] Then, the change amount ΔTp2 of Tp before and after heating shown in Table 1 was calculated. The change amount ΔTp2 is the average value Tp of the measured values of Tp before heating the sample (before the start of the test) 2B and the average value Tp of the measured values of Tp after heating the sample at 150 °C for 1000 hours (1000 hours after the start of the test). 2A It is the difference between them (ΔTp2 = Tp 2A - Tp 2B ). The larger the absolute value of such a change amount ΔTp2, the more the Tp characteristics of the sample deteriorate due to long-term heating, meaning that the heat resistance is low. Therefore, the smaller the absolute value of ΔTp2, the less the optical characteristics (Tp characteristics) of the polarizing element 1 decrease due to the influence of heat, and the higher the heat resistance of the polarizing element 1. Therefore, from the viewpoint of enhancing the heat resistance (reliability against heat) of the polarizing element 1, it is preferable that the absolute value of ΔTp2 is small.

[0446] According to the results of such a heat resistance test, as shown in Fig. 20, in Comparative Examples 51 and 52, the longer the heating time, the lower the Tp, and particularly, the decrease in Tp in the low wavelength region of 500 nm or less is remarkable. As a result, as shown in Table 1, in Comparative Examples 51 and 52, the absolute value of ΔTp2 is 3.3 to 5.2%, which is significantly larger than the reference value of 3.0% indicating that the heat resistance of the polarizing element 1 has not deteriorated. Therefore, it can be seen that in Comparative Examples 51 and 52, the Tp characteristics of the polarizing element 1 deteriorate due to long-term high-temperature heating, and the heat resistance of the polarizing element 1 is low. The reason for this is considered to be that in Comparative Examples 51 and 52, Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so the resin portion cannot be sufficiently protected by the thin protective film 40, and the resin portion deteriorates due to heat.

[0447] Also, as shown in Fig. 21, in Comparative Examples 53 and 54 as well, the longer the heating time, the lower the Tp. In particular, the decrease in Tp in the low wavelength region of 500 nm or less is significant. As a result, as shown in Table 1, in Comparative Examples 53 and 54, the absolute value of ΔTp2 is 3.8 - 3.9%, which is significantly larger than the reference value of 3.0% indicating that the heat resistance of the polarizing element 1 has not deteriorated. Therefore, it can be seen that in Comparative Examples 53 and 54 as well, the Tp characteristics of the polarizing element 1 deteriorate due to long-term high-temperature heating, and the heat resistance of the polarizing element 1 is low. This reason is considered to be that in Comparative Examples 53 and 54, Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so the resin portion cannot be sufficiently protected by the thin protective film 40 and the resin portion deteriorates due to heat.

[0448] On the other hand, in Examples 51 to 53, as shown in Fig. 22, there is almost no difference in Tp characteristics depending on the length of the heating time, and the Tp characteristics show almost the same tendency regardless of the length of the heating time. As a result, as shown in Table 1, the absolute value of ΔTp2 is 0.1 - 0.2%, which is significantly smaller than the above reference value of 3.0%. Therefore, it can be seen that in Examples 51 to 53, the Tp characteristics of the polarizing element 1 do not deteriorate even due to long-term high-temperature heating, and the heat resistance of the polarizing element 1 is high. This reason is considered to be that in Examples 51 to 53, Bt / Tt satisfies the formula (10) and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is sufficiently thick, so the resin portion is appropriately protected by the thick protective film 40 and the resin portion does not deteriorate due to heat.

[0449] From the results of the above heat resistance test, it was demonstrated that the heat resistance of the polarizing element 1 can be improved by forming the protective film 40 satisfying the above formula (10) on the entire surface of the complex fine uneven structure of the grid structure 20.

[0450] (6) Light resistance test Next, with reference 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, the light from a laser light source was incident on a dichroic mirror, for example, and blue light among the visible light 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 and the difference therebetween (ΔTp3 = Tp 3A -Tp 3B)。The larger the absolute value of such a change amount ΔTp3, the more the Tp characteristics of the sample deteriorate due to long-term light irradiation, which means that the light resistance is low. Therefore, the smaller the absolute value of ΔTp3, the less the optical characteristics (Tp characteristics) of the polarizing element 1 deteriorate due to the influence of light, and the higher the light resistance of the polarizing element 1. Therefore, from the viewpoint of enhancing the light resistance (reliability against light) of the polarizing element 1, it is preferable that the absolute value of ΔTp3 is small.

[0454] According to the results of such a light resistance test, as shown in FIG. 23, in Comparative Example 52, as the light irradiation time becomes longer, Tp increases, and in particular, the increase in Tp in the high wavelength region of 600 nm or more is remarkable. As a result, as shown in Table 1, in Comparative Example 52, the absolute value of ΔTp3 is 1.6%, which is significantly larger than 1.0%, which is a reference value indicating that the light resistance of the polarizing element 1 has not deteriorated. Therefore, in Comparative Example 52, it can be seen that the Tp characteristics of the polarizing element 1 deteriorate due to light irradiation, and the light resistance of the polarizing element 1 is low. The reason for this is considered to be that in Comparative Example 52, Bt / Tt is small and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is thin, so the resin portion cannot be sufficiently protected by the thin protective film 40, and the resin portion deteriorates (for example, discolors to yellow) due to light.

[0455] On the other hand, in Examples 51 to 53, as shown in FIG. 24, there is almost no difference in Tp characteristics depending on the length of the light irradiation time, and regardless of the length of the light irradiation time, the Tp characteristics show almost the same tendency. As a result, as shown in Table 1, the absolute value of ΔTp3 is 0.2 to 0.8%, which is sufficiently smaller than the above reference value of 1.0%. Therefore, in Examples 51 to 53, it can be seen that the Tp characteristics of the polarizing element 1 do not deteriorate even due to long-term light irradiation, and the light resistance of the polarizing element 1 is high. The reason for this is considered to be that in Examples 51 to 53, Bt / Tt satisfies the formula (10) and the thickness Bt of the protective film 40 covering the resin portion of the grid structure 20 is sufficiently thick, so the resin portion is appropriately protected by the thick protective film 40 and the resin portion does not deteriorate due to light.

[0456] From the results of the above light resistance test, it was demonstrated that the light resistance of the polarizing element 1 can be improved by forming the protective film 40 satisfying the above formula (10) on the entire surface of the complex fine concavo-convex structure of the grid structure 20.

[0457] <2. Verification Results of the Reinforcement Function of the Ridge Portion by the Reinforcement Film> Next, as an example of the present invention, a sample of the wire grid polarizing element 1 provided with the reinforcement film 51 according to the above-described embodiment was manufactured, and a test for evaluating the optical characteristics of the sample was conducted. Further, in order to compare with the example of the present invention (in which the ridge portion 22 is covered with the reinforcement film 51), a sample of the wire grid polarizing element 1 according to the comparative example (in which the ridge portion 22 is not covered with the reinforcement film 51) was also manufactured and tested and evaluated in the same manner. In the following, for the sake of convenience of explanation, in both the example and the comparative example, the reference signs representing the components of the polarizing element 1 (substrate 10, grid structure 20, base portion 21, ridge portion 22, reflection film 30, protective film 40, reinforcement film 51, etc.) and the symbols representing various dimensions of these components are given the same reference signs and symbols.

[0458] The symbols representing various dimensions and the like of the polarizing element 1 used in the following description will be explained as follows. P: Pitch of the ridge portion 22 W T : Width of the top of the ridge portion 22 (ridge top width) W M : Width at the central position in the height direction of the ridge portion 22 (ridge central width) W B : Width of the bottom of the ridge portion 22 (grid bottom width) W MAX : Maximum width of the reflection film 30 covering the ridge portion 22 (grid maximum width) H: Height of the ridge portion 22 Hx: Height of the portion of the side surface 22b of the ridge portion 22 covered by the reflection film 30 Dt: Thickness of the reflection film 30 covering the tip 22a of the ridge portion 22 (tip thickness of the reflection film 30) Ds: Thickness of the reflection film 30 covering the side surface 22b of the ridge portion 22 (side surface thickness of the reflection film 30) Rc: Coverage rate of the side surface 22b of the ridge portion 22 by the reflective film 30 Rr: Opening rate of the side surface 22b of the ridge portion 22 by the reflective film 30 Tt: Thickness of the protective film 40 covering the top portion 30a of the reflective film 30 that covers and wraps the ridge portion 22 (i.e., the thickness of the protective film 40 at the tip of the grid 41) Bt: Thickness of the protective film 40 covering the lower sides of both side surfaces 22b, 22b of the ridge portion 22 and the surface of the base portion 21 (i.e., the thickness of the protective film 40 at the bottom of the valley 42) Rt: Thickness of the reinforcing film 51 θ: Incident angle of the incident light λ: Wavelength of the incident light

[0459] (1) Method for manufacturing a sample of the polarization element 1 In Example 60 and Comparative Example 60 of the present invention, samples of the polarization element 1 were manufactured by the manufacturing method described below. In the sample of the polarization element 1 according to Example 60, as shown in FIG. 30, a reinforcing film 51 covering the entire ridge portion 22 and the base portion 21 of the grid structure 20 was provided. On the other hand, in the sample of the polarization element 1 according to Comparative Example 60, as shown in FIG. 31, the reinforcing film 51 was not provided.

[0460] (Example 60) First, referring to FIG. 30, Example 60 of the present invention will be described.

[0461] By the manufacturing method of the polarization element 1 according to the above-described embodiment, a sample of the polarization element 1 according to Example 60 was manufactured. The polarization element 1 according to Example 60 includes a glass substrate 10 and a grid structure 20 made of an ultraviolet curable resin (acrylic resin), as shown in FIG. 30. The grid structure 20 has a base portion 21 provided along the surface of the substrate 10 and a plurality of ridge portions 22 protruding from the base portion 21 in a lattice shape. The cross-sectional shape of the ridge portion 22 is a convex shape with roundness, and is a tapered shape that becomes thinner toward the tip 22a of the ridge portion 22.

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

[0463] Next, the film formation step (S15) of the reinforcing film described above was executed, and a reinforcing film 51 that continuously covers the entire surface of the grid structure 20 (the tip 22a and both side surfaces 22b, 22b of the ridge portion 22 and the surface of the base portion 21) was formed using the special ALD method (see FIG. 19) described above. 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] When forming the reinforcing film 51 by such a special ALD method (S15), in the introduction steps (S151, S153: the first and third steps) of the precursor gas and the oxidant gas described above, a film formation method was adopted in which the precursor gas and the oxidant gas in the chamber 300 were introduced into the chamber 300 and filled without exhausting them from the gas exhaust port 330. As a result, the thickness of the reinforcing film 51 covering the tip 22a of the ridge portion 22 of the grid structure 20 and the thickness of the reinforcing film 51 covering the upper surface of the base portion 21 could be made substantially the same thickness Rt (about 2 nm).

[0465] Next, the reflective film formation step (S16) described above was executed, and a reflective film 30 (functional film) that covers and wraps the tip portion of the ridge portion 22 was formed from above the reinforcing film 51 covering the grid structure 20. At this time, using a vapor deposition method, Al, which is the material of the reflective film 30, was vapor-deposited on the upper part of the ridge portion 22 alternately from the upper left and right obliquely to form the reflective film 30.

[0466] The reflective film 30 formed in this way is made of an Al film, and as shown in FIG. 30, it is formed so as to cover the upper part of the convex rib portion 22 (the tip 22a of the convex 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 convex rib portion 22 and the base portion 21. The coverage rate Rc of both side surfaces 22b, 22b of the convex rib portion 22 by the reflective film 30 is 38%. Thus, the reflective film 30 of Example 60 roundly covers and wraps the top of the convex 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 convex rib portion 22.

[0467] As a result, as shown in FIG. 30, the grid 41 (the structure formed by combining the convex 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 convex rib portion 22 at a height position 20% above the bottom of the convex rib portion 22) of the convex rib portion 22. Also, the cross-sectional shape (XZ cross-section) of the valley 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 covering 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] When forming the protective film 40 by such a special ALD method (S18), in the steps of introducing the above-described precursor gas and oxidant gas (S181, S183: the first and third steps), the precursor gas and oxidant gas in the chamber 300 are not exhausted from the gas exhaust port 330, but a film forming method is adopted in which the precursor gas and oxidant gas are introduced into the chamber 300 and filled. As a result, the thickness Tt of the protective film 40 covering the tip of the grid 41 (i.e., the metal part of the top 30a of the reflective film 30) and the thickness Bt of the protective film 40 covering the surface of the bottom of the valley 42 (i.e., the resin part of the grid structure 20) can be made to be approximately the same thickness (about 7 nm), and the protective film 40 satisfying the above formula (10) could be formed.

[0470] (Comparative Example 60) Next, Comparative Example 60 will be described. As shown in FIG. 31, in the sample of the polarizing element 1 according to Comparative Example 60, the reinforcing film 51 as in Example 60 was not provided. In Comparative Example 60, a sample of the polarizing element 1 according to Comparative Example 60 was produced by the same manufacturing method (S10, S12, S14, S16, S18) as in Example 60, except that the film forming step (S15) of the reinforcing film was not performed.

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

[0472] (3) Observation results of the presence or absence of the inclination of the rib portion 22 Regarding the samples of the polarizing element 1 according to Example 60 and Comparative Example 60 produced by the above manufacturing method, the cross section of the sample was observed using a transmission electron microscope (TEM). Schematic diagrams of the cross-sectional shapes of the samples of the polarizing element 1 observed from this TEM image are shown in FIGS. 30 and 31.

[0473] As shown in FIG. 30, in the sample according to Example 60, the rib portion 22 of the grid structure 20 was not inclined and extended straight upward, and the desired grid shape could be maintained. On the other hand, in the sample according to Comparative Example 60, the rib portion 22 of the grid structure 20 was inclined about 10° to the left. In particular, the upper part of the rib portion 22 on which the reflective film 30 was deposited was inclined so as to curve to the left, and the desired grid shape could not be maintained.

[0474] The reason why the rib portion 22 of Comparative Example 60 was inclined is considered to be that in Comparative Example 60, since the rib portion 22 was not reinforced by the reinforcing film 51, when the reflective film 30 (Al film) was formed, the high-temperature Al material was deposited on the rib portion 22, causing the resin of the rib portion 22 to soften. Further, in the manufacturing method of the polarizing element 1 described above, the Al material is deposited alternately left and right from the obliquely upper side of the rib portion 22 by a plurality of deposition processes (see FIG. 27). For this reason, the stress due to the thermal contraction accompanying the temperature drop of the Al film deposited on one side of the rib portion 22 accumulates around the Al film, and it is considered that the softened rib portion 22 is inclined to the side on which the Al film is deposited due to the accumulated stress (see FIG. 28).

[0475] According to the above results, by covering the rib portion 22 with the reinforcing film 51 as in Example 60, the rigidity and heat resistance of the rib portion 22 can be increased, so it was demonstrated that the inclination of the rib portion 22 due to the formation of the reflective film 30 can be preferably suppressed.

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

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

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

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

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

[0481] In Comparative Example 60, as shown in FIG. 30, since the rib portion 22 is inclined, the transmission of obliquely incident light is blocked by the reflection film 30 supported by the inclined rib portion 22, so that the transmittance (Tp) of the obliquely incident light decreases. In contrast, in Example 60, as shown in FIG. 31, the rib portion 22 is not inclined and extends straight, so that the reflection film 30 does not unnecessarily block the obliquely incident light. Therefore, in Example 60, it is considered that the transmittance (Tp) of the obliquely incident light and the contrast (CR = Tp / Ts) can be significantly improved compared with Comparative Example 60.

[0482] Thus, in Example 60, since the rib portion 22 is not inclined, it is significantly superior to Comparative Example 60 in terms of Tp characteristics, Tp×Rs characteristics, and CR. In particular, when the polarization element 1 is used as a polarization beam splitter (PBS), the ability to achieve both high Tp×Rs characteristics and high CR is very beneficial for the polarization beam splitter. Also, even when evaluated by CR alone, Example 60 realizes a significantly superior CR compared to Comparative Example 60, and since the CR performance of the polarization beam splitter can be significantly improved, it is beneficial.

[0483] From the results of the above optical property tests, by providing the reinforcing film 51 between the convex rib portion 22 and the reflective film 30 as in Example 60 to impart rigidity and heat resistance to the convex rib portion 22, it is possible to suppress the inclination of the convex rib portion 22. Therefore, it has been demonstrated that 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] As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims. Naturally, these are also understood to belong to the technical scope of the present invention.

Industrial Applicability

[0485] According to the present embodiment, it is possible to provide a polarizing element having good polarization characteristics, not causing deterioration of heat dissipation and cost during manufacturing, and excellent in permeability to light at a wide range of incident angles, and a method for manufacturing the polarizing element. F...

Claims

1. A substrate made of an inorganic material, a grid structure integrally formed of an organic material, having a base portion provided on the substrate and a plurality of protruding ridges protruding from the base portion, a functional film made of a metal material, covering a part of the protruding ridges, a reinforcing film made of an inorganic oxide, interposed between a part of the protruding ridges covered by the functional film and the functional film, and reinforcing the protruding ridges, comprising: the protruding ridges have a tapered shape in which the width becomes narrower as they move away from the base portion, the reinforcing film covers at least the tip and the upper sides of both side surfaces of the protruding ridges, the functional film covers and wraps the tip and the upper sides of both side surfaces of the protruding ridges via the reinforcing film, and does not cover the lower sides of both side surfaces of the protruding ridges and the base portion, when the coverage rate (Rc) of the side surface of the protruding ridge by the functional film is the ratio of the height (Hx) of the portion of the side surface of the protruding ridge covered by the functional film to the height (H) of the protruding ridge, the coverage rate (Rc) is 30% or more and 70% or less, a wire grid polarizing element.

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

3. further comprising a protective film covering the surfaces of the grid structure and the functional film, the protective film continuously covers the surface of the functional film, the lower sides of both side surfaces of the protruding ridges, and the surface of the base portion, when the thickness of the protective film covering the top of the functional film covering and wrapping the protruding ridges is Tt and the thickness of the protective film covering the lower sides of both side surfaces of the protruding ridges and the surface of the base portion is Bt, the following formula (10) is satisfied, The wire grid polarizing element according to claim 1. Bt / Tt ≧ 0.85... (10)

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

5. The 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 SiO ２ The wire grid polarizing element according to claim 3, which has a single-layer structure composed of

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

8. The cross-sectional shape of the entire convex structure composed of the protruding ridges and the functional film has a constricted portion where the width in the width direction of the entire convex structure becomes narrower at a position directly below the lower end of the functional film covering and wrapping the protruding ridges. The wire grid polarizing element according to claim 1.

9. A method for manufacturing a wire grid polarizing element according to any one of claims 1 to 8, comprising: forming a grid structure material made of an organic material on a substrate made of an inorganic material; forming a grid structure in which a base portion provided on the substrate and a plurality of ridge portions protruding from the base portion are integrally formed by subjecting the grid structure material to nanoimprinting; forming a reinforcing film that covers at least a part of the ridge portions using an inorganic oxide; forming a functional film that covers a part of the ridge portions through the reinforcing film using a metal material; wherein in the step of forming the grid structure, the ridge portions having a tapered shape that becomes narrower as the distance from the base portion increases are formed; in the step of forming the functional film, the reinforcing film covers at least the tips and the upper sides of both side surfaces of the ridge portions, the functional film covers the tips and the upper sides of both side surfaces of the ridge portions through the reinforcing film, and does not cover the lower sides of both side surfaces of the ridge portions and the base portion, and when the coverage rate (Rc) of the side surfaces of the ridge portions by the functional film is the ratio of the height (Hx) of the portion of the side surfaces of the ridge portions covered by the functional film to the height (H) of the ridge portions, the functional film is formed such that 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, the reinforcing film is formed by vapor deposition so as to cover the tips and the upper sides of both side surfaces of the ridge portions. The method for manufacturing a wire grid polarizing element according to claim 9.

11. In the step of forming the reinforcing film, the reinforcing film is formed by ALD so as to continuously cover the tips and both side surfaces of the ridge portions and the surface of the base portion. The method for manufacturing a wire grid polarizing element according to claim 9.

12. further comprising a step of forming a protective film on the surfaces of the grid structure and the functional film, in the step of forming the protective film, the protective film is formed by ALD so as to continuously cover the surface of the functional film, the lower sides of both side surfaces of the ridge portions, and the surface of the base portion. The method for manufacturing a wire grid polarizing element according to claim 9.

13. The step of forming the protective film is A first step of introducing a precursor gas into a chamber in which the grid structure coated with the functional film is disposed; A second step of exhausting excess precursor gas out of the chamber by introducing an inert gas into the chamber; A third step of introducing an oxidant gas into the chamber; A fourth step of exhausting excess oxidant gas out of the chamber by introducing an inert gas into the chamber; comprising: In the first step, the precursor gas is introduced into and filled in the chamber without exhausting the precursor gas out of the chamber. In the third step, the oxidant gas is introduced into and filled in the chamber without exhausting the oxidant gas out of the chamber. A method for manufacturing a wire grid polarizing element according to claim 12.

14. A light source; A polarizing beam splitter arranged such that incident light from the light source is incident at an incident angle of 30° or more and 60° or less, and separating the incident light into a first polarization and a second polarization; A reflective liquid crystal display element arranged such that the first polarization reflected by the polarizing beam splitter or the second polarization transmitted through the polarizing beam splitter is incident, and reflecting and modulating the incident first polarization or second polarization; A lens arranged such that the first polarization or the second polarization reflected and modulated by the reflective liquid crystal display element is incident through the polarizing beam splitter; comprising: The polarizing beam splitter is composed of the wire grid polarizing element according to any one of claims 1 to 8, a projection display device.

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

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