Reflection type polarization optical element, optical apparatus, display apparatus, and method of manufacturing reflection type polarization optical element

Abstract

To reduce the possibility of deterioration in appearance of a reflection type polarization optical element when a wire grid film is stuck to a curved surface substrate.SOLUTION: The reflective polarizing optical element includes a substrate having a curved surface portion in which a surface forms a curved surface, and when viewed in a plan view in an optical axis direction, the curved surface portion has a shape surrounded by a plurality of arcs each constituting a part of the same circle in a plan view and a line connecting ends of adjacent arcs of the plurality of arcs, and a reflective polarizing film for a polarizing beam splitter having a wire grid structure, in which a shortest diameter among diameters passing through a center point of the circle in a plan view is defined as a short diameter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective polarizing optical element, an optical instrument, a display device, and a method for manufacturing a reflective polarizing optical element. [Background technology]

[0002] In recent years, head-mounted displays have been used in various fields, including virtual reality (VR), augmented reality (AR), and mixed reality (MR). Head-mounted displays have an optical system that focuses the image displayed on the display at the user's eye position. Head-mounted displays achieve a compact, lightweight, and high-quality optical system by folding the optical path of linearly polarized or circularly polarized light using a half mirror. Furthermore, in head-mounted displays, the shape of each optical element is often asymmetrical, with at least one side cut off, rather than an axisymmetric circle like a digital camera, to accommodate the user's nose when worn.

[0003] To provide these optical elements with suitable polarization properties, films with optical properties, such as polarizing films, polarizing beam splitter (PBS) films, and retardation films, are attached to curved substrates. In head-mounted displays, elements obtained in this way make it possible to make them smaller and lighter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-139664 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a reflective polarizing optical element in which a film having a wire grid structure (hereinafter referred to as a wire grid film) is attached as a polarizing beam splitter film to a curved substrate having a shape similar to that of an eyeglass lens. However, it is becoming increasingly recognized that when a wire grid film is attached to a curved substrate, cracks may occur in the wire grid structure or haze may occur in the substrate, deteriorating the appearance of the reflective polarizing optical element.

[0006] The present invention has been made in response to this recognition, and one of its objects is to reduce the possibility of deterioration in the appearance of a reflective polarizing optical element when a wire grid film is attached to a curved substrate. [Means for solving the problem]

[0007] In order to solve the above problems, a reflective polarizing optical element according to one aspect of the present invention comprises: a substrate having a curved surface portion that forms a curved surface, wherein, in a plan view seen in the optical axis direction, when the curved surface portion has a shape surrounded by a plurality of arcs each forming a part of the same circle in the plan view and a line connecting ends of adjacent arcs among the plurality of arcs, the shortest diameter among diameters passing through the center point of the circle in the plan view is defined as the minor diameter, and when the curved surface portion has a shape formed by an outline including a plurality of arcs with different curvatures, the shortest diameter among diameters passing through the centroid point of the outline in the plan view is defined as the minor diameter; The present invention comprises a wire grid film for a polarizing beam splitter having a wire grid structure, the wire grid film being attached to the curved surface portion so that the angle between the extension direction of the wires in the wire grid film and the extension direction of the minor axis of the substrate is within 45°. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to reduce the possibility of deterioration of the appearance of a reflective polarization optical element when a wire grid film is attached to a curved substrate. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the structure of an example of a reflective polarizing optical element according to a first embodiment. [Figure 2] 2A to 2C are schematic diagrams illustrating examples of substrate shapes of the reflective polarization optical element according to the first embodiment. [Figure 3] FIG. 2 is a schematic diagram illustrating a cross-sectional structure of an example of a polarizing beam splitter film used in an embodiment. [Figure 4] 1 is a schematic view showing the structure of an example of a manufacturing apparatus according to a first embodiment. [Figure 5] 10A and 10B are diagrams showing examples of a wire grid film to be attached and associated configurations. [Figure 6] 1A to 1C are diagrams illustrating an example of a method for manufacturing a reflective polarizing optical element. [Figure 7] FIG. 10 is a diagram showing the positional relationship between the wire grid film and the substrate in Example 7. [Figure 8] FIG. 10 is a schematic diagram illustrating an example of an optical device according to a second embodiment. [Figure 9] FIG. 10 is a schematic diagram showing another example of the optical device (display device) according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments and examples will be described in detail below with reference to the drawings. In the following description, common components across multiple drawings are designated by common reference numerals. Therefore, the common components will be described with mutual reference to multiple drawings, and descriptions of components designated by common reference numerals will be omitted as appropriate. Furthermore, the dimensions, materials, shapes, and relative positions of components illustrated in the following embodiments and examples are arbitrary and can be changed depending on the configuration of the device to which the present invention is applied or various conditions.

[0011] [First embodiment] A reflective polarization optical element and a manufacturing method thereof according to a first embodiment of the present invention will be described below with reference to Figures 1 to 6. Figure 1 is a schematic diagram showing an example of a reflective polarization optical element according to this embodiment, where Figure 1(a) is a plan view of a reflective polarization optical element 10 as seen from the direction in which light is incident, and Figure 1(b) is a cross-sectional view of the reflective polarization optical element 10 taken along a wire arrangement direction 12a, which will be described later.

[0012] As shown in FIG. 1 , a reflective polarizing optical element 10 according to this embodiment includes a substrate 11 and a wire grid film 12. The wire arrangement direction 12a and the wire extension direction 12b of the wire grid film 12 will be described later. The illustrated substrate 11 has a curved surface portion 11a, a peripheral edge portion 11b, and a step portion 11e. In a plan view of the surface of the substrate 11 viewed from a direction parallel to the optical axis of the reflective polarizing optical element 10, the curved surface portion 11a has a segmented circular shape with two opposing sides missing. Note that although the two opposing sides are shown as straight lines here, they may also be curved. The peripheral edge portion 11b is formed adjacent to the curved surface portion 11a and surrounding the periphery of the curved surface portion 11a in a plan view. The step portion 11e is arranged to connect the curved surface portion 11a and the peripheral edge portion 11b, and is formed to have a surface parallel to the optical axis direction in this example.

[0013] In the substrate 11 illustrated in FIG. 1, the curved surface portion 11a has a minor axis 11c and a major axis 11d when viewed in plan. The major axis corresponds to the length of the longest axis passing through the center point O calculated from the arc portion of the curved surface portion 11a when viewed in plan, and the minor axis corresponds to the length of the shortest axis passing through the center point O calculated from the arc portion of the curved surface portion 11a. Therefore, as in the case where the shape of the curved surface portion 11a is non-axisymmetric, the major axis and the minor axis do not necessarily need to be orthogonal depending on the shape of the curved surface portion 11a when viewed in plan. Furthermore, multiple major axes and multiple minor axes can be selected depending on the shape. The curved surface portion 11a may have a convex or concave shape, or may have an aspherical shape.

[0014] The peripheral edge portion 11b is an optically ineffective region and is provided, for example, to serve as a mold release margin when manufacturing the substrate 11, particularly when manufactured by injection molding. It may also be provided so that the completed reflective polarizing optical element 10 can be attached to the housing of an optical device such as a head-mounted display. Therefore, its shape may be either curved or flat, and may be either axially symmetric or non-axially symmetric. Furthermore, the peripheral edge portion 11b does not need to be present along the entire periphery of the curved portion 11a; it may be present only partially. Furthermore, the peripheral edge portion 11b may be absent.

[0015] It should be noted that the shape of the substrate when viewed in plan, which is assumed when carrying out the present invention, is not limited to the shape exemplified in Fig. 1. Other examples of the shape of the substrate will be described with reference to Figs. 2(a) to 2(c). Figs. 2(a) to 2(c) are plan views showing other examples of the shape of the substrate when viewed in plan in the optical axis direction of the substrate.

[0016] 2(a), in a plan view, the curved surface portion 11a-2 has a shape similar to that of a segmented circle, with a portion of the circle removed by a straight line. The peripheral edge portion 11b-2 is disposed so as to surround the outer periphery of the curved surface portion 11a-2. In the example of the substrate 11-2, the minor axis 11c is the diameter that passes through the center point O and defines the shortest distance in a plan view, and the major axis 11d is the diameter that passes through the center point O and defines the longest distance in a direction perpendicular to the minor axis 11c.

[0017] In the case of the substrate 11-3 shown in FIG. 2(b), the curved surface portion 11a-3 has a shape obtained by connecting two sides that do not face each other at the center with an arc in a plan view, or a shape obtained by removing two regions of a circle with non-opposing straight lines. This shape can also be defined as a partial circle shape obtained by removing different parts of a circle with two straight lines. Note that the two non-opposing sides or the two straight lines may be formed by curves. Furthermore, the number of parts of the circle that are removed is not limited to two, and a shape in which more than one part is removed may be used.

[0018] The peripheral edge portion 11b-3 is arranged in a similar shape to the curved portion 11a-3 so as to surround the outer periphery of the curved portion 11a-3. In the example of the substrate 11-3, the minor axis 11c is the diameter that passes through the center point O and defines the shortest distance in a plan view, and the major axis 11d is the diameter that passes through the center point O and defines the longest distance regardless of the extension direction of the minor axis 11c. Note that the center point O coincides with the center point of a circle that forms part of the outline of the curved portion 11a-3 in a plan view. In the curved portion 11a-3, the minor axis 11c and the major axis 11d are not perpendicular to each other.

[0019] 1, 2(a), and 2(b), the curved surface portion has two or one straight line in a plan view. However, the number of straight lines constituting the curved surface portion is not limited to two, and the curved surface portion may have three or more straight lines in a plan view of the substrate. In this case, the curved surface portion may have three or more arcs in a plan view, each arc being part of the circumference of the same circle, and two adjacent ends of the straight lines may be connected by an arc.

[0020] 2(c), the curved surface 11a-4 has a shape formed by a plurality of arcs with different curvatures, such as a spectacle lens, in a plan view. As shown in the example, the substrate 11-4 can be configured without a peripheral edge, unlike the substrates shown in FIGS. 1 to 2(b).

[0021] Furthermore, in the illustrated substrate 11-4, since no identical circle exists, it is not possible to determine the center point in a planar view of the substrate 11-4. In such a case, the centroid C of the curved surface portion 11a-4 in a planar view of the substrate 11-4 can be used as a reference point. The minor axis 11c is the shortest diameter passing through the centroid C of the shape of the curved surface portion 11a in a planar view, and the major axis 11d is the longest diameter passing through the centroid C.

[0022] Optical devices using the reflective polarizing optical element 10, particularly head-mounted displays, are expected to be worn on the user's face, particularly around the eyes and nose, which imposes size restrictions on the device. Therefore, in order to provide a nose guard for the user and ensure installation space for electronic devices such as motors and sensors, the shape of the substrate is often not axially symmetric but rather asymmetric, with a minor axis and a major axis. In such cases, the substrate shape shown in FIG. 2(c) is expected, and for such substrates and curved surfaces, the minor axis and major axis can be determined by using the centroid C as the reference point, as described above.

[0023] Here, the curvature of the curved surface portion 11a of the substrate 11 illustrated in Fig. 1 is defined as R (the optimum value obtained by the least squares method in the case of an aspherical surface). In addition, if the length of the major axis 11d of the curved surface portion 11a is L2, the length of the minor axis 11c is L1, and the half opening angle is θ, then Formula sinθ=(L2 / 2) / R holds true.

[0024] The substrate material described above can be either plastic or glass, as long as it is transparent and transmissive to light, such as visible light, targeted by the reflective polarizing optical element 10. When using plastic, it is preferable to use a material that can be formed by injection molding and is used for optical purposes. Examples of materials that can be used include polycarbonate (PC), polyester (PEs), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), and cycloolefin copolymer (COC). When using glass, the material is not particularly limited, but examples include synthetic quartz and the common glass material BK-7.

[0025] Next, details of the wire grid film used as the polarizing beam splitter film in this embodiment will be described with reference to Fig. 3. Fig. 3 shows a schematic cross-sectional structure of the wire grid film cut along the wire arrangement direction.

[0026] The wire grid film 12 includes a base resin film 201 and a metal layer 202. The base resin film 201 has a surface texture formed by providing a sheet 201a made of, for example, triacetyl cellulose (TAC) resin with fine protrusions 201b made of the same resin. The sheet 201a and the protrusions 201b may be made of different materials. The protrusions 201b are provided at a pitch P, have a height H and a width t, and extend in a direction perpendicular to the paper surface. The metal layer 202 is a wire made of a conductive metal deposited on the fine protrusions and recesses of the base resin film 201. The metal layer 202 is formed of a conductive metal such as aluminum and is arranged periodically in a fixed direction along the extension direction of the protrusions 201b. The wire grid film 12 has the optical property of transmitting light polarized parallel to the wire arrangement direction 12a and reflecting light polarized parallel to the wire extension direction 12b due to the electromagnetic interaction between the incident light and the wires consisting of a fine uneven shape (see Figure 1).

[0027] As described above, one of the factors that determine the performance of the wire grid film 12 is the relationship between the pitch P of the convex portions 201b in the base resin film 201 and the wavelength λ of the incident light. When the pitch P is in the range of approximately half to twice the wavelength, the polarization separation performance for light of a specific wavelength is significantly reduced. Furthermore, as the pitch P becomes smaller, good polarization characteristics are exhibited over a wide wavelength range, but processability becomes more difficult. Therefore, in this embodiment, the pitch P is set to 120 nm from the two viewpoints of maintaining the incident light shorter than half the wavelength of 380 nm, which is the short wavelength of visible light, and of facilitating molding processability.

[0028] In the wire grid film 12 used in this embodiment, the metal layer 202 is formed using an oblique deposition method. With this method, the deposition shielding effect of the convex portions 201b of the base resin film 201 can cause the growth direction of the metal layer 202 to be oblique in cross-sectional view, potentially resulting in connection with adjacent metal layers. Such connection between metal layers during the formation of the metal layer 202 reduces parallel transmittance. In particular, if the height H of the convex portions 201b is less than 120 nm when the pitch P is 120 nm, an adequate deposition shielding effect cannot be obtained, potentially increasing the likelihood of connection between metal layers during the formation of the metal layer 202. Therefore, controlling the deposition shielding effect of the convex portions 201b is important. On the other hand, if the height H of the convex portions 201b exceeds 120 nm, the deposition shielding effect of the convex portions 201b becomes excessive, resulting in insufficient growth of the metal layer in the concave portions. This reduces the contact area between the metal layer in the concave portions and the bottom surface of the concave portions, resulting in insufficient rigidity for maintaining the wire grid structure. As a result, the durability of the polarization separation performance is reduced. From the two viewpoints of reducing the possibility of the metal layers being connected and maintaining the configuration of the wire grid structure, in this embodiment, the height H of the convex portions 201b of the base resin film 201 in the wire grid film 12 is set to 120 nm.

[0029] Next, we investigated the convex width t of the convex portions 201b at the H / 2 position. Oblique deposition was performed with a convex pitch of 120 nm and a convex height of 120 nm, with the convex width at the H / 2 position set to less than 32 nm. In this case, metal layers were bonded together during the formation of the metal layer 202, resulting in a decrease in parallel transmittance. On the other hand, when the convex width t of the convex portions 201b at the H / 2 position exceeded 32 nm, the spacing between adjacent convex portions became narrower, hindering deposition. This reduced the contact area between the metal layer in the concave portions and the bottom surface of the concave portions, resulting in insufficient rigidity to maintain the wire grid structure and a decrease in the durability of the polarization separation performance. From the two perspectives of reducing the possibility of metal layer bond and maintaining the wire grid structure, in this embodiment, the convex width t of the convex portions 201b of the base resin film 201 in the wire grid film 12 at the H / 2 position was set to 32 nm.

[0030] For the reasons described above, this embodiment uses a base resin film 201 in which the pitch P of the convex portions 201b is 120 nm, the height H of the convex portions is 120 nm, and the position of H / 2 of the convex portions 201b is 32 nm. This makes it possible to appropriately block the deposition effect of the convex portions 201b when forming the metal layer 202 by oblique deposition, and allows the metal layer 202 to grow in the vertical direction. This gives the metal layer 202 a shape that extends in the vertical direction in cross-section, preventing a decrease in transmittance due to the connection of adjacent metal layers.

[0031] The wire grid film of this embodiment includes a base resin film 201 and wires that are partially covered by the base resin film 201 and comprise a metal layer 202, as shown in FIG. 3 . When attaching the wire grid film 12 to a substrate 11, a force pulling the film in the circumferential direction is often applied, resulting in stretching of the film. The inventors discovered that if this stretching occurs in the wire extension direction 12b, the stretching of the base resin film 201 occurs preferentially over the stretching of the metal layer 202. As the base resin film 201 stretches in the wire extension direction 12b, its thickness at the H / 2 position of the protrusion 201b shown in FIG. 3 gradually decreases. As the thickness decreases, the rigidity of the protrusion 201b supporting the metal layer 202 decreases, potentially causing the wires to collapse. This wire collapse narrows the pitch between adjacent wires. Furthermore, excessive wire collapse causes incident light to scatter on the sidewalls of the collapsed wires, resulting in a deterioration in the device appearance. The inventors have found that the problem in the present invention may arise as a result of such a mechanism.

[0032] The details of the present invention, described below in relation to the embodiments, are based on the above findings and aim to reduce the elongation of the wire grid film 12 in the wire extension direction. This reduction in elongation reduces the possibility of degradation of polarization transmission characteristics and deterioration of the appearance. Specifically, the extension direction of the minor axis 11c and the wire extension direction 12b are arranged to be more nearly parallel to each other. However, depending on the shape of the substrate, it may not be easy to clearly define the minor axis 11c. Therefore, when the wire grid film 12 is attached to the curved surface portion 11a, the extension direction of the wire grid film 12 may not be aligned with the direction in which the wire grid film 12 is most extended. Even in such a case, by setting the angle φ between the extension direction of the minor axis 11c and the wire extension direction 12b to φ≦45°, it is possible to roughly align the region in which the wire grid film has a relatively small amount of extension with the extension direction 12b. Furthermore, if the angle is greater than 45°, there is a high possibility that a region with a large extension amount where deterioration of the wire appearance begins to occur will be included on the curved surface portion 11a. By specifying such conditions, it is possible to reduce the possibility of deterioration of the appearance of the reflective polarization optical element, particularly deterioration occurring at the outer periphery of the element.

[0033] Next, a manufacturing apparatus for a reflective polarization optical element 10 according to this embodiment will be described with reference to Fig. 4. Fig. 4(a) is a cross-sectional view showing a schematic configuration of the manufacturing apparatus and the substrate 11 and other components held therein. Fig. 4(b) is a top view showing the positional relationship between a substrate 41 placed in the manufacturing apparatus and a wire grid film 42 placed thereon, as seen through from above.

[0034] As shown in FIG. 4(a) and other figures, the manufacturing apparatus used in this embodiment includes a first chamber 43, a second chamber 44, and a stage 45. The first chamber 43 and the second chamber 44 can be independently evacuated and depressurized. An opening that can connect to each other is provided at the top of the first chamber 43 and the corresponding bottom of the second chamber 44. Note that, although an example in which these chambers are arranged vertically is shown here, this arrangement is merely an example, and they can also be arranged horizontally or upside down.

[0035] A stage 45 is disposed inside the first chamber 43, which supports the substrate 41 and is movable, for example, up and down, toward the second chamber 44. The substrate 41 has a curved surface portion 41a and a peripheral portion 41b similar to the substrate 11 illustrated in FIG. 1, and the curved surface portion 41a defines a minor axis 41c and a major axis 41d. The substrate 41 is disposed on the stage 45 (see FIG. 4(b)). The wire grid film 42 is disposed between the first chamber 43 and the second chamber 44, which are connected via the opening described above.

[0036] 4(b), in a plan view, the substrate 41, which has a curved surface portion 41a and a peripheral portion 41b, is positioned directly opposite the wire grid film 42 so that the extending direction 42a of the wires coincides with the extending direction of the minor axis 41c of the substrate 41. By bonding the substrate 41 and the wire grid film 42 in this positional relationship, the distance between the curved surface portions 41a in the extending direction 42a of the wires of the wire grid film 42 is shortened when the substrate 41 and the wire grid film 42 are bonded. As a result, the portions of the wire grid film 42 that are significantly stretched and where wire collapse may occur can be located outside the curved surface portion 41a of the substrate 41. This reduces the possibility of the appearance being deteriorated due to collapse of the wires of the wire grid film 42 at the curved surface portion 41a.

[0037] It should be noted that, when manufacturing the reflective polarization optical element 10, other configurations may be added to the wire grid film 42. These configurations will be described with reference to Fig. 5. Figures 5(a) to 5(c) each show a schematic cross section of a wire grid film or the like used in the bonding process.

[0038] As shown in FIG. 5( a), a uniform adhesive layer 55 can be provided on the surface of the wire grid film 42 facing the substrate. Furthermore, a protective film 56 for protecting the surface of the wire grid film 42 can be provided on the surface of the wire grid film 42 facing away from the substrate (the surface opposite the adhesive layer 55). The glass transition temperature of the protective film 56 is required to be lower than the glass transition temperature of the wire grid film 42. This increases the strength of the wire grid film 42, making it less likely to tear when attached to the substrate 41.

[0039] Furthermore, the wire grid film 42 is more expensive than general films. Therefore, from the viewpoint of reducing manufacturing costs, it is not appropriate to use a wire grid film 42 that is much larger than the area of ​​the curved surface portion 41a of the substrate 41. In other words, the wire grid film 42 only needs to be slightly larger than the surface area of ​​the curved surface portion 41a of the substrate 41. Specifically, for example, the wire grid film 42 only needs to have an area that is 1.5 to 2.5 times the area of ​​the curved surface portion 41a in a plan view in the optical axis direction of the substrate 41.

[0040] Here, if the size of the wire grid film 42 is made as small as possible, it is necessary to ensure the size necessary for holding the wire grid film 42 between the first chamber 43 and the second chamber 44. For this reason, as shown in FIG. 5( b), a support film 57 made of a material separate from the wire grid film 42 may be attached to the wire grid film 42. In this case, in order to ensure uniform deflection of the film when heated, it is preferable that the glass transition temperature of the support film 57 be equal to or about 20° C. lower than the glass transition temperature of the wire grid film 42.

[0041] 5(c), a support film 57 may be attached only to the outer periphery of the wire grid film 42. After the wire grid film 42 is attached to the substrate 41, the support film 57 can be peeled off from the wire grid film 42 at an appropriate timing.

[0042] In the process of attaching the wire grid film 42, the wire grid film 42 and other components described above are held between the first chamber 43 and the second chamber 44. In the manufacturing apparatus described in this embodiment, the stage 45 is arranged so that a tangent to the center of the minor axis 41c of the substrate 41 is parallel to the wire grid film 42. As a result, the stretching of the wire grid film 42 along the extension direction of the minor axis 41c of the substrate 41 is symmetrical about the center of the minor axis 41c. This prevents the occurrence of regions with large stretching due to the attachment of the wire grid film 42, and allows the wire grid film 42 to be attached with a reduced maximum stretch ratio. As a result, the possibility of wire-tilted wire grid film 42 occurring on the curved surface 41a of the substrate 41 is further reduced, thereby preventing deterioration of the appearance due to wire tilt.

[0043] Next, with reference to FIGS. 6( a) to 6(d), a process for attaching a wire grid film 42 to a substrate 41 using the manufacturing apparatus described with reference to FIG. 4 will be described. After the substrate 41 and the wire grid film 42 are placed in the manufacturing apparatus as shown in FIG. 6, a vacuum is created inside the first chamber 43 and the second chamber 44 as shown in FIG. 6(a). The wire grid film 42 is then heated, for example, using a heater or the like installed in the second chamber 44. After the wire grid film 42 has been heated to a desired temperature, the stage 45 (see FIG. 4) is raised as shown in FIG. 6(b) to bring the curved surface portion 41a of the substrate 41 into contact with the wire grid film 42. By further raising the stage 45, the wire grid film 42 is attached to the entire surface of the curved surface portion 41a.

[0044] Thereafter, only the second chamber 44 is opened to the atmosphere to increase the pressure, and if necessary, high-pressure gas is introduced to pressurize the wire grid film 42 and press it against the substrate 41. At this time, if necessary, the heating and pressurization of the wire grid film 42 may be continued for a certain period of time.

[0045] Here, the wire grid film 42 is typically heated using an infrared heater that directly heats the film, but there is also the option of heating the entire first chamber 43 and second chamber 44 using a heater or similar. In this case, the substrate 41 is also heated. In particular, if the substrate 41 is made of a plastic material, there is a concern that it may deform due to heat. For this reason, it is important to provide a thermal insulating structure for the stage 45 that supports the substrate 41, or for a pedestal used to support the substrate 41 at an angle. In other words, regardless of the temperature of the wire grid film 42, it is preferable to keep the temperature of the substrate 41 below 120°C.

[0046] Thereafter, as shown in FIG. 6( c), the heating and pressurization of the polarizing beam splitter film 42 are stopped, the second chamber 44 is returned to atmospheric pressure, and the first chamber 43 is also opened to the atmosphere. Then, the substrate 41 with the wire grid film 42 attached thereto is removed. Next, as shown in FIG. 6( d), the unnecessary wire grid film 42 is cut away so that the wire grid film 42 remains only on the curved surface portion 41 a of the substrate 41. The cutting method can be performed by cutting away the unnecessary wire grid film 42 by applying a blade along the outer edge of the curved surface portion 41 a, or by applying laser light along the outer edge of the curved surface portion 41 a. In this manner, a reflective polarizing optical element 40 is manufactured in which the wire grid film 42 is attached to the curved surface portion 41 a of the substrate 41.

[0047] Here, an example in which a reflective polarizing optical element according to this embodiment was actually manufactured will be described below. When evaluating the reflective polarizing optical element described below, the chord arc ratio in the extension direction of the wire is also determined. Here, the chord arc ratio is expressed by the ratio of the shortest distance connecting two specific points on the curved surface of the reflective polarizing optical element to the distance of a straight line connecting these two points. In other words, the chord arc ratio is Chordal arc ratio (%) = (the shortest distance between two specific points that are the end points on the curved surface of the curved portion of the substrate) / (the distance between the two specific points in a straight line) × 100 The chord arc ratio is calculated using the following formula. If the chord arc ratio is large, it is assumed that the wire grid film is stretched to a large extent. Here, a 3D scanner-type coordinate measuring machine (VL-5000, manufactured by Keyence) was used to obtain shape data for the reflective polarizing optical element, and the chord arc ratio was calculated based on cross-sectional shape data in directions perpendicular or parallel to the extension direction of the fine uneven structure. The wire pitch and wire width measurements were obtained using an electron microscope (JSM-F100, manufactured by JEOL).

[0048] Specifically, the reflective polarizing optical elements according to each of the examples described below were visually evaluated for wire width ratio, wire pitch ratio, so-called streak irregularities in transmitted light, and wire tilt. The wire width ratio was determined from the ratio of the width of the metal layer at the center of the element to the width of the metal layer at the edge of the element. The wire pitch ratio was also determined from the ratio of the spacing between the metal layers at the center of the element to the spacing between the metal layers at the edge of the element. Regarding streak irregularities, a light table was used to shine light onto the reflective polarizing optical element, and the presence and condition of streak irregularities in the transmitted light were confirmed. Based on the above evaluations, the condition of the wire grid in the reflective polarizing optical element was evaluated as A (best), B (good), C (fair), and D (poor).

[0049] Example 1 In Example 1, the substrate 41 was made of a plastic material mainly composed of cycloolefin copolymer (COC) and molded by injection molding. The substrate 41 had the shape illustrated in FIG. 4, and was a convex lens having a minor axis 41c of the curved surface portion 41a, a length L1 of 28 mm, a major axis 41d of 50 mm, and a half-opening angle θ of 10°. The wire grid film 42 had a thickness of approximately 100 μm, an adhesive layer 55, and a size of 160 mm × 160 mm. During manufacturing, the substrate 41 was positioned so that the extension direction of the minor axis 41c of the curved surface portion 41a and the extension direction 42a of the wires of the wire grid film 42 were approximately parallel (within ±2°).

[0050] During manufacturing, an infrared heater is used to heat the wire grid film, etc., and after heating to the desired temperature (100°C), the bonding process is carried out. After bonding, only the inside of second chamber 44 is opened to the atmosphere, and compressed air is introduced into second chamber 44 to increase the pressure to 0.3 MPa, pressurizing wire grid film 42 and pressing it against substrate 41 for 10 seconds.

[0051] In the reflective polarizing optical element according to Example 1, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. It was also confirmed that the chordal arc ratio was smaller than 110% and close to 100%. Visual observation confirmed that the wire tilt in the reflective polarizing optical element was minor. The state of streaks in transmitted light was also evaluated using a light table. As a result of the above evaluations, the appearance of the reflective polarizing optical element according to Example 1 was evaluated as best, as shown in Table 1.

[0052] Example 2 In Example 2, the shape (dimensions, etc.) of the substrate 41 used in Example 1 was changed. Specifically, the length L1 of the minor axis 41c of the curved portion 41a of the substrate 41 was 38 mm, the length L2 of the major axis 41d was 50 mm, and the half-open angle θ was 50°. A reflective polarizing optical element was manufactured using the same method as in Example 1, except for these dimensions. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was slightly smaller than 110%. Furthermore, visual observation confirmed that the wire tilt in this reflective polarizing optical element was increased compared to Example 1. The state of streaks in transmitted light was also evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 2 was determined to be good, as shown in Table 1.

[0053] Example 3 In Example 3, the shape (dimensions, etc.) of the substrate 41 used in Example 1 was changed. Specifically, the length L1 of the minor axis 41c of the curved portion 41a of the substrate 41 was 38 mm, the length L2 of the major axis 41d was 40 mm, and the half-open angle θ was 48°. A reflective polarizing optical element was manufactured using the same method as in Example 1, except for these dimensions. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was also confirmed to be slightly greater than 110%. Furthermore, visual observation confirmed that the wire tilt in this reflective polarizing optical element was increased compared to Example 2. The state of streaks in transmitted light was also evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 3 was judged to be acceptable, as shown in Table 1.

[0054] Example 4 In Example 4, the shape (dimensions, etc.) of the substrate 41 used in Example 1 was changed. Specifically, the half-opening angle θ of the curved surface portion 41a of the substrate 41 was set to 20°, forming a concave lens. A reflective polarizing optical element was manufactured in the same manner as in Example 1, except for these dimensions. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was also confirmed to be less than 110% and close to 100%. Furthermore, visual observation confirmed that the wire tilt in this reflective polarizing optical element was slight. The state of streaks in transmitted light was also evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element of Example 4 was determined to be excellent, as shown in Table 1.

[0055] Example 5 In Example 5, the shape of the substrate 41 used in Example 1 was changed to the shape illustrated in FIG. 2(b). Specifically, the substrate 11-2 had a convex lens shape, with the length L1 of the minor axis 11c-2 of the curved surface portion 11a-2 being 28 mm, the length L2 of the major axis 11d-2 being 50 mm, and the half-open angle θ being 17°. A reflective polarizing optical element was manufactured using the same method as in Example 1, except for these dimensions. The appearance of this reflective polarizing optical element was evaluated based on the above-described method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was also confirmed to be less than 110% and close to 100%. Furthermore, visual observation confirmed that the wire tilt was slight. The state of streaks in transmitted light was then evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 5 was determined to be excellent, as shown in Table 1.

[0056] Example 6 In Example 6, the shape of the substrate 41 used in Example 1 was changed to the shape illustrated in FIG. 2(b). Specifically, the substrate 11-2 had a curved portion 11a-2 with a minor axis 11c-2 length L1 of 38 mm, a major axis 11d-2 length L2 of 40 mm, a half-open angle θ of 26°, and a flat peripheral edge portion 11b-2 with a width of 2 mm. Aside from these dimensions, a reflective polarizing optical element was manufactured in the same manner as in Example 1. The appearance of this reflective polarizing optical element was evaluated based on the above-described method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was also confirmed to be slightly less than 110%. The state of streaks in transmitted light was then evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 6 was determined to be good, as shown in Table 1.

[0057] Example 7 In Example 7, the shape (dimensions, etc.) of the substrate 41 used in Example 1 was changed. Specifically, the half-opening angle θ was set to 20°, and the substrate 41 had a flat peripheral portion 41b with a diameter of 56 mm. Furthermore, during manufacturing, the substrate 41 was placed in the first chamber 43 so as to have the positional relationship illustrated in FIG. 7 . Specifically, the substrate 41 was positioned so that the angle between the extension direction of the minor axis 41c of the curved portion 41a of the substrate 41 and the extension direction 42a of the wires of the wire grid film 42 was 45°. A reflective polarizing optical element was manufactured in the same manner as in Example 1, except for the width of the peripheral portion and the positional relationship between the wire grid film and the substrate during manufacturing. The appearance of this reflective polarizing optical element was evaluated based on the above-described method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. It was also confirmed that the chordal arc ratio was slightly less than 110%. The state of streaks in transmitted light was evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 7 was judged to be good as shown in Table 1.

[0058] Example 8 In Example 8, the same substrate and wire grid film as in Example 7 were used, and during manufacturing, the angle between the extension direction of the minor axis 41c of the curved surface portion 41a and the extension direction 42a of the wires of the wire grid film 42 was 30°. Otherwise, a reflective polarizing optical element was manufactured in the same manner as in Example 7. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. Furthermore, it was confirmed that the chordal arc ratio was less than 110% and close to 100%. Furthermore, visual observation confirmed that the wire tilt was slight. Then, the state of streaks in transmitted light was evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element of Example 8 was determined to be excellent, as shown in Table 1.

[0059] Example 9 In Example 9, the shape of the substrate 41 in Example 1 was changed to the shape illustrated in FIG. 2(c). Unlike the substrates described above, the shape illustrated in FIG. 2(c) makes it impossible to determine the center point O. Therefore, the centroid point C of the outline of the curved surface portion 11a-3 in a plan view is used as the reference point. The shortest diameter passing through this reference point is defined as the minor diameter 11c-3, and the longest diameter passing through this reference point is defined as the major diameter 11d-3. In addition, in this example, the substrate 11-3 does not have a peripheral edge. Specifically, the length L1 of the minor diameter 11c of the curved surface portion 11a was 38 mm, the length L2 of the major diameter 11d was 40 mm, and the half-open angle θ was 26°. A reflective polarizing optical element was otherwise manufactured in the same manner as in Example 1. The appearance of this reflective polarizing optical element was evaluated based on the above-described method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was greater than 0.9. The chordal arc ratio was also confirmed to be slightly less than 110%. The state of streaks in the transmitted light was then evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Example 9 was judged to be good, as shown in Table 1.

[0060] (Comparative Example 1) In Comparative Example 1, the shape of the substrate 41 used in Example 1 was changed so that the curved surface had a circular shape in a plan view. In this case, the length L1 of the minor axis of the curved surface of the substrate was 40 mm, the length L2 of the major axis was 40 mm, and the half-open angle θ was 48°. A reflective polarizing optical element was otherwise manufactured in the same manner as in Example 1. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was smaller than 0.9. The chordal arc ratio was also greater than 110% and higher than that of the reflective polarizing optical element of Example 3. Furthermore, visual observation confirmed that the wire tilt was excessive. Then, the state of streaks in transmitted light was evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element of Comparative Example 1 was determined to be poor, as shown in Table 1.

[0061] (Comparative Example 2) In Comparative Example 2, the shape (dimensions, etc.) of the substrate 41 used in Example 1 was changed. Specifically, the substrate 41 had a length L1 of the minor axis 41c of the curved surface portion 41a of 38 mm, a length L2 of the major axis 41d of 50 mm, a half-open angle θ of 50°, and a flat peripheral edge portion 42b of φ56 mm. Furthermore, during manufacturing, the substrate 41 was arranged so that the angle between the extension direction of the minor axis 41c of the curved surface portion 41a of the substrate 41 and the extension direction 52a of the wires of the wire grid film 42 was 50°. A reflective polarizing optical element was manufactured in the same manner as in Example 1. The appearance of this reflective polarizing optical element was evaluated based on the above-mentioned method and criteria. As a result, it was confirmed that the wire width ratio or wire pitch ratio was smaller than 0.9. Furthermore, the chordal arc ratio was greater than 110% and higher than that of the reflective polarizing optical element of Example 3. Furthermore, visual observation confirmed that the wire tilt was excessive. Then, the state of streaks in transmitted light was evaluated using a light table. As a result of the above evaluation, the appearance of the reflective polarizing optical element according to Comparative Example 2 was judged to be poor, as shown in Table 1.

[0062] [Table 1]

[0063] As described above, the evaluation results of the examples and comparative examples support the finding by the inventors that the greater the angle between the direction in which the wire grid film is stretched and the extension direction of the minor axis of the substrate, the greater the possibility of deterioration in appearance due to wire tilt, etc. By implementing the present invention, it is possible to reduce the possibility of deterioration in appearance due to wire tilt, etc. in a reflective polarization optical element made of a curved substrate, and in particular to avoid to some extent deterioration in appearance around the periphery in the direction perpendicular to the wires.

[0064] [Second embodiment] The reflective polarizing optical element according to the first embodiment described above can be applied to various devices and apparatuses such as optical instruments, display devices, and imaging devices. Specifically, it can be used in optical instruments such as head-mounted displays, digital cameras, and video cameras. In this embodiment, optical instruments and display devices will be described as specific application examples of the reflective polarizing optical element according to the first embodiment.

[0065] (optical equipment) Specific application examples of the reflective polarizing optical element according to the first embodiment include lenses constituting optical devices (photography optical systems) for cameras and video cameras, and lenses constituting optical devices (projection optical systems) for liquid crystal projectors. Fig. 8 is a schematic diagram showing an example of a preferred embodiment of an optical device 80 using the reflective polarizing optical element according to the first embodiment. The optical system of the optical device 80 includes a plurality of lenses arranged in a housing 81, and the reflective polarizing optical element 10 according to the first embodiment can be used for at least one of the lenses.

[0066] (display device) 9(a) to 9(c) are schematic diagrams showing the configuration of a head-mounted display (HMD) 90, which is an example of a preferred embodiment of a display device using the reflective polarizing optical element 10 according to the first embodiment. FIG. 9(a) is a side view showing the HMD 90. FIG. 9(b) is a front view showing the HMD 90. FIG. 9(c) is a schematic diagram showing the optical system of the HMD 90.

[0067] 9(a) and 9(b), the HMD 90 has a housing 91, a wearing device 92, and display units 93 for the left and right eyes that are disposed within the housing 91. The HMD 90 is worn on the user's head by the wearing device 92 so that the display units 93 for the left and right eyes are positioned corresponding to the user's left and right eyes, respectively.

[0068] As shown in FIG. 9( c), each display unit 93 includes a display panel 94 and optical elements 10, 95, and 96. The optical system may include, for example, the reflective polarizing optical element 10 according to the first embodiment. The display panel 94 is a display unit including an organic electroluminescence (EL) panel, a liquid crystal panel, or the like, and displays an image for the corresponding left or right eye. The optical elements 10, 95, and 96 focus the image light emitted from the display panel 94 at the position of the user's eye E. Depending on the design of the HMD 90, the optical elements 10, 95, and 96 may include a transmissive optical element such as a convex lens or a concave lens, a reflective optical element such as a concave mirror, a mirror, a light path changing element such as a half mirror, or a phase difference optical element. The reflective polarizing optical element 10 is installed so as to be positioned between the optical element 95, the optical element 96, and the eye E. The reflective polarizing optical element 10, together with optical elements 95 and 96, constitutes an optical system that guides image light, which is light emitted from the display panel 94, to the user's eyes, and functions as at least one of the optical elements, i.e., lenses, in the optical system.

[0069] Although the embodiment using an HMD has been described as a display device to which the reflective polarizing optical element is applied, the display device according to the present embodiment is not limited to this example. For example, the reflective polarizing optical element 10 according to the present embodiment can also be used in a display device such as a projector, as in the above-described example.

[0070] As described above, a reflective polarizing optical element according to one embodiment of the present invention includes a substrate and a reflective polarizing film having a wire grid structure, such as the wire grid film 12. For example, the substrate 11 has a curved surface portion 11a whose surface forms a curved surface. The curved surface portion can have a shape surrounded by multiple arcs, each of which forms part of the same circle, and lines connecting the ends of adjacent arcs in a planar view in the optical axis direction, as in the substrates 11-2 and 11-3 illustrated in FIG. 2(a) or 2(b). In such a case, the shortest diameter passing through the center of the circle in a planar view is defined as the minor diameter. Furthermore, the curved surface portion can have a shape formed by an outline including multiple arcs with different curvatures in a planar view in the optical axis direction, as in the substrate 11-4 illustrated in FIG. 2(c). In such a case, the shortest diameter passing through the centroid of the outline in a planar view is defined as the minor diameter. The reflective polarizing film is attached to the curved surface so that the angle between the extension direction of the wires in the wire grid and the extension direction of the minor axis of the substrate is within 45°. By arranging the extension direction of the minor axis of the substrate and the wire arrangement direction in this positional relationship, excessive stretching of the base resin film in the wire grid film 12 can be avoided. As a result, it is possible to reduce the possibility of deterioration in polarized light transmission characteristics and deterioration of the appearance of the wires.

[0071] To obtain the effects of the present invention, it is more preferable that the angle between the extending direction of the wire and the extending direction of the minor axis of the substrate be within 30°. By making the extending direction of the wire and the extending direction of the minor axis closer to parallel, partial deterioration of appearance due to wire collapse and the like can be more effectively reduced.

[0072] The wire grid film 12 described above can include a base resin film 201, which is an example of a substrate, and a metal layer (wires) 202 made of a conductive metal such as aluminum. The substrate (201) can have a flat sheet 201a and protrusions 201b arranged on the sheet 201a at a predetermined pitch and extending in a specific direction. The wires (202) can be arranged so as to be concentrated on one side of the protrusions.

[0073] The protrusions 201b may have a substantially rectangular cross-sectional shape in a cross-sectional view perpendicular to their extension direction. In this case, the pitch P, which is the distance between two adjacent protrusions, and the height H of the protrusions 201b may be approximately equal, and the cross-sectional width of the protrusions 201b at a first height position (height 1 / H) from the surface of the sheet 201a may be approximately 1 / 4 of the pitch P. The height H is defined as the difference from the surface of the sheet 201a to the highest point of the protrusion 201b. The surface of the sheet 201a when defining the height H may also be defined as the bottom surface of a recess between two adjacent protrusions, depending on the shape of the protrusions. In this embodiment, taking into account the wavelength of 380 nm of short-wavelength visible light, the pitch P is set to 120 nm, the height H is set to 120 nm, and the protrusion width in a direction parallel to the surface of the sheet at the first height position in a cross-sectional view of the wire grid film is set to 32 nm. In this case, metal layer 202 extends from the surface of sheet 201a to the highest part of protrusion 201b, and at least a part of metal layer 202 can be provided above the highest part of protrusion 201b. Note that pitch P, height H, and width of the protrusion at the first position are determined in consideration of the wavelength of light to be transmitted and the characteristics of the oblique vapor deposition method for forming the metal layer, but may be changed as appropriate depending on the wavelength of light to be transmitted, the method for forming the metal layer, and the cross-sectional shape of the protrusion.

[0074] Furthermore, the metal layer 202 attached to the convex portion 201b can be provided above the top of the convex portion 201b in the cross-sectional view illustrated in FIG. 2, for example, and can be provided so as to be disposed on only one side surface of one convex portion 201b. Furthermore, the metal layer 202 can be provided so that its thickness in a direction parallel to the surface of the sheet 201a increases from the top to the bottom of the convex portion 201b in the cross-sectional view. More specifically, the thickness in a direction parallel to the sheet surface at a position 1 / 10H high from the sheet surface can be provided thicker than the thickness in a direction parallel to the sheet surface at a position 9 / 10H high from the sheet surface. Furthermore, the thickness in a direction parallel to the sheet surface at the highest portion of the metal layer 202 can be provided thinner than the thickness in a direction parallel to the sheet surface at the highest portion of the convex portion 201b. By providing the metal layer 202 on the base resin film 201 in this manner, improved adhesion of the metal layer 202 to the base resin film 201 can be expected. Furthermore, there are many options for the method of forming the metal layer that can be adopted.

[0075] Furthermore, it can be inferred that the reflective polarizing optical element according to one aspect of the present invention has reduced deterioration in appearance by satisfying all the evaluation criteria described in the examples except for the criteria related to visual observation of wire tilt, etc. Specifically, when the chordal arc ratio, wire width ratio, wire pitch ratio, etc. satisfy desired conditions, the reflective polarizing optical element can be said to be capable of solving the problems of the present invention.

[0076] For example, the chord arc ratio may be such that the curved shape in the direction in which the wires (202) of the wire grid film 12 extend is greater than 100% and less than 110% in a cross-sectional view perpendicular to the extension direction of the convex portions 201b. In this case, the chord arc ratio (%) can be calculated by dividing the shortest distance on the curved shape between two specific end points on the curved substrate by the distance between the two specific points and a straight line, and multiplying the result by 100. The specific two points can be defined as, for example, both ends in a direction parallel to the extension direction of the wires, and can be defined as the points on the curved shape at both ends that give the largest chord arc ratio according to the above formula.

[0077] Regarding the wire width, when the maximum wire width after the wire grid film 12 is attached to the substrate 11 is defined as t1 and the minimum wire width is defined as t2, the width ratio t2 / t1 > 0.9 should be satisfied. The wire width ratio can be calculated, for example, from the ratio of the width of the metal layer at the center of the element to the width of the metal layer at the edge of the element. More specifically, the wire width t1 can be defined as the maximum wire width in the curved direction in which the wires located on the curved surface identified by the calculation of the chord arc ratio extend. In this case, the wire width t2 corresponding to the wire width t1 can be defined as the wire width at either of two specific points on the end of the curved surface of the wire located on the curved surface identified by the calculation of the chord arc ratio. While the wire widths t1 and t2 are defined as above, the method for determining them is not limited to this example. For example, the wire widths can also be measured in the wire arrangement direction and the wire widths at each position on the entire curved surface can be determined to determine the conditions.

[0078] Regarding the wire pitch, when the maximum wire pitch after the wire grid film 12 is attached to the substrate 11 is defined as p1 and the minimum wire pitch is defined as p2, the relationship p2 / p1 > 0.9 should be satisfied. The wire pitch ratio can be calculated, for example, from the ratio between the spacing between the metal layers at the center of the element and the spacing between the metal layers at the edge of the element. More specifically, the wire pitch p1 can be defined as the maximum wire pitch between a wire located on a curved surface specified by the calculation of the chordal arc ratio and an adjacent wire in the direction in which the wire located on the curved surface extends. In this case, the wire pitch p2, corresponding to the wire pitch p1, can be defined as the wire pitch between a wire located on the curved surface specified by the calculation of the chordal arc ratio and an adjacent wire, and can be defined as the wire pitch at either of the two specified points. While the wire pitches p1 and p2 are defined as above, the method for determining them is not limited to the example given here. For example, the wire pitch can also be measured in the wire arrangement direction, and the wire pitch at each position on the entire curved surface can be determined to determine the conditions.

[0079] In the present invention, for example, the substrate 11 can have a peripheral portion 11b provided on the periphery of the curved portion 11a, as illustrated in Fig. 1. By having such a peripheral portion 11b, it is possible to obtain effects such as improving the degree of freedom when fixing the reflective polarizing optical element to an optical device. Furthermore, as illustrated in Fig. 5, the wire grid film can be attached to the curved portion via an adhesive layer 55. This can reduce material constraints that may arise when heating the reflective polarizing film.

[0080] The present invention can also provide an optical device (80, 90) including a housing (81, 91) and an optical system disposed within the housing and having at least one optical element including, for example, the above-described reflective polarization optical element 10. Furthermore, the present invention can provide a display device including a housing 91, an optical system (10, 95, 96) disposed within the housing and having at least one optical element, and a display unit (94) that emits light guided by the optical system.

[0081] A method for manufacturing a reflective polarizing optical element according to one embodiment of the present invention includes attaching a wire grid film for a polarizing beam splitter having a wire grid structure to a substrate having a curved surface portion that forms a curved surface. In this case, when viewed in a plan view along the optical axis, if the curved surface portion has a shape as exemplified in FIG. 2(a) or 2(b), the shortest diameter among the diameters passing through the center point of a single circle that forms multiple arcs in the plan view can be defined as the minor diameter. Furthermore, if the curved surface portion has a shape as exemplified in FIG. 2(c), the shortest diameter among the diameters passing through the centroid point in the plan view of an outline including multiple arcs with different curvatures can be defined as the minor diameter. The wire grid film is attached to the curved surface such that the angle between the extension direction of the wires and the extension direction of the minor diameter of the substrate is within 45°. Furthermore, for example, if the curved surface portion has a convex shape, the extension direction of the minor diameter can also be defined as the extension direction in a plan view of a line connecting the point on the curved surface where the wire grid film first contacts and the point on the circumference of the curved surface where the wire grid film first reaches. Furthermore, when the curved surface portion is concave, the extension direction of the minor axis can also be defined as the direction that forms the shortest distance between the point on the circumference of the curved surface that the reflective polarizing film first comes into contact with when attached, and a point on the curved surface at the time attachment is completed, such as the centroid of the curved surface portion.

[0082] When attaching the reflective polarizing film to a curved surface, the effects of the present invention can be more effectively achieved by setting the angle between the wire arrangement direction and the extension direction of the minor axis of the substrate to 30° or less. The reflective polarizing film can be attached to the curved surface by pressing the reflective polarizing film against the substrate. The reflective polarizing film can also be attached to the curved surface in a heated state.

[0083] As described above, according to the present invention, by suppressing the increase in elongation in the wire extension direction that occurs when attaching a wire grid film to a substrate, it is possible to reduce wire collapse and scattering of incident light, thereby making it possible to suppress deterioration of the appearance of the reflective polarization optical element.

[0084] The above-mentioned invention includes the following configurations and methods. (Configuration 1) a substrate having a curved surface portion that forms a curved surface, wherein, in a plan view seen in the optical axis direction, when the curved surface portion has a shape surrounded by a plurality of arcs each forming a part of the same circle in the plan view and a line connecting ends of adjacent arcs among the plurality of arcs, the shortest diameter among diameters passing through the center point of the circle in the plan view is defined as the minor diameter, and when the curved surface portion has a shape formed by an outline including a plurality of arcs with different curvatures, the shortest diameter among diameters passing through the centroid point of the outline in the plan view is defined as the minor diameter; A reflective polarizing optical element comprising: a wire grid film for a polarizing beam splitter having a wire grid structure, the wire grid film being attached to the curved surface portion so that the angle between the extension direction of the wires in the wire grid film and the extension direction of the minor axis of the substrate is within 45°. (Configuration 2) 2. The reflective polarizing optical element according to configuration 1, wherein the angle formed between the extending direction of the wire and the extending direction of the minor axis of the substrate is 30° or less. (Configuration 3) The wire grid film includes a substrate having a flat sheet and convex portions provided on the sheet so as to be aligned at a predetermined pitch and extend in a specific direction, and a metal layer made of a conductive metal provided so as to be unevenly distributed on one side surface of the convex portions, In a cross-sectional view perpendicular to the extension direction of the protrusions, the cross-sectional shape of the protrusions is approximately rectangular, the pitch P that is the distance between two adjacent protrusions is 120 nm, and the height H that is the difference in height from the highest part of the protrusions to the sheet surface is 120 nm, and when a position H / 2 from the sheet surface is set to a first height position, the width of the protrusions in a direction parallel to the sheet surface at the first height position in the cross-sectional view is 32 nm, 3. The reflective polarizing optical element according to claim 1, wherein the metal layer extends from the surface of the sheet to the highest part of the convex portion, and at least a portion of the metal layer is provided above the highest part of the convex portion. (Configuration 4) In a cross-sectional view, the thickness of the metal layer in a direction parallel to the sheet surface at a position 1 / 10H of the height H from the sheet surface is thicker than the thickness of the metal layer in a direction parallel to the sheet surface at a position 9 / 10H of the height H from the sheet surface, 4. The reflective polarizing optical element according to configuration 3, wherein the thickness of the metal layer at the highest point in a direction parallel to the sheet surface is thinner than the thickness of the convex portions at the highest point in a direction parallel to the sheet surface. (Configuration 5) In a cross-sectional view taken along a direction perpendicular to the extending direction of the protrusions, the curved shape of the wire grid film in the extending direction of the wires is: Chordal arc ratio (%) = (the shortest distance between two specific points that are the end points on the curved substrate) / (the distance between the two specific points in a straight line) × 100 5. The reflective polarizing optical element according to configuration 3 or 4, wherein the chordal arc ratio calculated by the following formula is greater than 100% and less than 110%. (Configuration 6) The reflective polarizing optical element according to configuration 5, wherein t2 / t1>0.9 is satisfied when t1 is the maximum wire width after the wire grid film is attached to the substrate and t2 is the minimum wire width. (Configuration 7) The reflective polarized optical element of configuration 6, wherein the maximum wire width t1 is the maximum wire width in a curve in the direction in which the wire located on the curved surface identified by the calculation of the chord arc ratio extends, and the minimum wire width t2 is the wire width at either of the two specific points on the end of the curved surface of the wire located on the curved surface identified by the calculation of the chord arc ratio. (Configuration 8) 8. The reflective polarizing optical element according to any one of configurations 5 to 7, wherein p2 / p1>0.9 is satisfied when p1 is the maximum wire pitch after the wire grid film is attached to the substrate and p2 is the minimum wire pitch. (Configuration 9) A reflective polarized optical element according to configuration 8, wherein the maximum wire pitch p1 is the maximum wire pitch between a wire located on a curve in the direction in which the wire located on the curved surface identified by the calculation of the chord arc ratio extends and an adjacent wire, and the minimum wire pitch p2 is the wire pitch between a wire located on the curved surface identified by the calculation of the chord arc ratio and the adjacent wire, and is the wire pitch at either of the two specified points. (Configuration 10) 10. The reflective polarizing optical element according to any one of configurations 1 to 9, wherein the substrate has a peripheral portion provided on the periphery of the curved surface portion. (Configuration 11) 11. The reflective polarizing optical element according to any one of configurations 1 to 10, wherein the wire grid film is attached to the curved surface portion via an adhesive layer. (Configuration 12) The housing and an optical system having at least one optical element disposed within the housing; 12. An optical device, wherein the optical element includes the reflective polarizing optical element according to any one of configurations 1 to 11. (Configuration 13) The housing and an optical system having at least one optical element disposed within the housing; a display unit that emits light guided by the optical system, 12. A display device, wherein the optical element includes the reflective polarizing optical element according to any one of configurations 1 to 11. (Method 1) In a substrate having a curved surface portion whose surface forms a curved surface, when the curved surface portion has a shape surrounded by a plurality of arcs each forming a part of the same circle in the planar view as seen in the optical axis direction and a line connecting ends of adjacent arcs among the plurality of arcs, the shortest diameter among diameters passing through the center point of the circle in the planar view is defined as the minor diameter, and when the curved surface portion has a shape formed by an outline including a plurality of arcs with different curvatures, the shortest diameter among diameters passing through the centroid point of the outline in the planar view is defined as the minor diameter; a wire grid film for a polarization beam splitter having a wire grid structure is attached to the curved surface portion so that the angle between the extending direction of the wires in the wire grid film and the extending direction of the minor axis of the substrate is within 45°; A method for manufacturing a reflective polarizing optical element, comprising: (Method 2) The method for manufacturing a reflective polarizing optical element according to Method 1, wherein, when the wire grid film is attached to the curved surface portion, the substrate is positioned so that a tangent to the center point of the minor axis of the curved surface portion is parallel to the wire grid film. (Method 3) 3. The method for manufacturing a reflective polarizing optical element according to Method 1 or 2, wherein when the wire grid film is attached to the curved surface portion, the angle between the arrangement direction of the wires and the extension direction of the minor axis of the substrate is within 30°. (Method 4) 4. The method for manufacturing a reflective polarizing optical element according to any one of Methods 1 to 3, further comprising: pressing the wire grid film against the substrate to attach the wire grid film to the curved surface portion. (Method 5) 5. The method for manufacturing a reflective polarizing optical element according to any one of methods 1 to 4, wherein the wire grid film is attached to the curved surface portion in a heated state. (Method 6) The method includes attaching a wire grid film for a polarization beam splitter having a wire grid structure to a substrate having a curved surface portion that forms a curved surface, a straight line connecting a point on the curved surface where the wire grid film first comes into contact with the curved surface and a point on the circumference of the curved surface where the wire grid film first arrives, the straight line extending in a plan view of the substrate in the optical axis direction, and the angle formed by the straight line and the direction of extension of the wires in the wire grid structure are 45° when the substrate is attached.

[0085] Although the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Inventions modified within the scope of the present invention and inventions equivalent to the present invention are also included in the present disclosure. Furthermore, the above-described examples can be combined as appropriate within the scope of the present invention. [Explanation of symbols]

[0086] 10 40 Reflective polarizing optical element 11 41 board 11a 41a Curved section 11b 41b Periphery 11c 41c Minor diameter 11d 41d major axis 12 42 Wire grid film 12a 42a Wire extension direction 43 First Chamber 44 Second Chamber 55 Adhesive layer 56 Protective Film 57 Support Film 80 Head-Mounted Display (HMD) 81 HMD housing 82 HMD wearing equipment 83 HMD display unit 84 HMD display panel 85 86 Optical elements of HMD E User's Eyes 201 Base resin film 202 Metal layer

Claims

1. a substrate having a curved surface portion that forms a curved surface, wherein, in a plan view seen in the optical axis direction, when the curved surface portion has a shape surrounded by a plurality of arcs each forming a part of the same circle in the plan view and a line connecting ends of adjacent arcs among the plurality of arcs, the shortest diameter among diameters passing through the center point of the circle in the plan view is defined as the minor diameter, and when the curved surface portion has a shape formed by an outline including a plurality of arcs with different curvatures, the shortest diameter among diameters passing through the centroid point of the outline in the plan view is defined as the minor diameter; a wire grid film for a polarizing beam splitter having a wire grid structure, the wire grid film being attached to the curved surface portion so that the angle between the extension direction of the wires in the wire grid film and the extension direction of the minor axis of the substrate is within 45°;

2. 2. The reflective polarizing optical element according to claim 1, wherein the angle formed between the extending direction of the wire and the extending direction of the minor axis of the substrate is within 30 degrees.

3. The wire grid film includes a substrate having a flat sheet and convex portions provided on the sheet so as to be aligned at a predetermined pitch and extend in a specific direction, and a metal layer made of a conductive metal provided so as to be unevenly distributed on one side surface of the convex portions, In a cross-sectional view perpendicular to the extension direction of the protrusions, the cross-sectional shape of the protrusions is approximately rectangular, the pitch P that is the distance between two adjacent protrusions is 120 nm, and the height H that is the difference in height from the highest part of the protrusions to the sheet surface is 120 nm, and when a position of H / 2 from the sheet surface is set to a first height position, the width of the protrusions in a direction parallel to the sheet surface at the first height position in the cross-sectional view is 32 nm, 2. The reflective polarizing optical element according to claim 1, wherein the metal layer extends from the surface of the sheet to the highest part of the convex portion, and at least a part of the metal layer is provided above the highest part of the convex portion.

4. In a cross-sectional view, the thickness of the metal layer in a direction parallel to the sheet surface at a position 1 / 10H of the height H from the sheet surface is thicker than the thickness of the metal layer in a direction parallel to the sheet surface at a position 9 / 10H of the height H from the sheet surface, 4. The reflective polarizing optical element according to claim 3, wherein the thickness of the metal layer at the highest point in a direction parallel to the sheet surface is thinner than the thickness of the convex portions at the highest point in a direction parallel to the sheet surface.

5. In a cross-sectional view taken along a direction perpendicular to the extending direction of the protrusions, the curved shape of the wire grid film in the extending direction of the wires is: Chordal arc ratio (%) = (the shortest distance on the curved surface between two specific points that are the end points on the curved surface of the curved surface portion) / (the distance between the two specific points in a straight line) × 100 4. The reflective polarizing optical element according to claim 3, wherein the chordal arc ratio calculated by the following formula is greater than 100% and less than 110%.

6. 6. The reflective polarizing optical element according to claim 5, wherein t2 / t1 > 0.9 is satisfied when t1 is the maximum wire width after the wire grid film is attached to the substrate and t2 is the minimum wire width.

7. 7. The reflective polarized optical element according to claim 6, wherein the maximum wire width t1 is the maximum wire width in a curve in the direction in which a wire located on the curved surface identified by the calculation of the chord arc ratio extends, and the minimum wire width t2 is the wire width at one of the two specific points on the end of the curved surface identified by the calculation of the chord arc ratio.

8. 6. The reflective polarizing optical element according to claim 5, wherein p2 / p1>0.9 is satisfied, where p1 is the maximum wire pitch after the wire grid film is attached to the substrate, and p2 is the minimum wire pitch.

9. 9. The reflective polarized optical element according to claim 8, wherein the maximum wire pitch p1 is the maximum wire pitch between a wire located on a curve in a direction in which the wire located on the curved surface identified by the calculation of the chord arc ratio extends and an adjacent wire, and the minimum wire pitch p2 is the wire pitch between the wire located on the curved surface identified by the calculation of the chord arc ratio and the adjacent wire, and is the wire pitch at either of the two specified points.

10. The reflective polarizing optical element according to claim 1 , wherein the substrate has a peripheral edge portion provided on a peripheral edge of the curved surface portion.

11. The reflective polarizing optical element according to claim 1 , wherein the wire grid film is attached to the curved surface portion via an adhesive layer.

12. The housing and an optical system having at least one optical element disposed within the housing; An optical instrument, wherein the optical element comprises the reflective polarizing optical element according to claim 1 .

13. The housing and an optical system having at least one optical element disposed within the housing; a display unit that emits light guided by the optical system, A display device, wherein the optical element comprises the reflective polarizing optical element according to claim 1 .

14. In a substrate having a curved surface portion whose surface forms a curved surface, when the curved surface portion has a shape surrounded by a plurality of arcs each forming a part of the same circle in the plan view as seen in the optical axis direction and a line connecting ends of adjacent arcs among the plurality of arcs, the shortest diameter among diameters passing through the center point of the circle in the plan view is defined as the minor diameter, and when the curved surface portion has a shape formed by an outline including a plurality of arcs with different curvatures, the shortest diameter among diameters passing through the centroid point of the outline in the plan view is defined as the minor diameter; attaching a wire grid film for a polarization beam splitter having a wire grid structure to the curved surface portion such that the angle between the extending direction of wires in the wire grid film and the extending direction of the minor axis of the substrate is within 45°; A method for manufacturing a reflective polarizing optical element, comprising:

15. 15. The method for manufacturing a reflective polarizing optical element according to claim 14, wherein, when the wire grid film is attached to the curved surface portion, the substrate is positioned so that a tangent to the center point of the minor axis of the curved surface portion is parallel to the wire grid film.

16. 15. The method for manufacturing a reflective polarizing optical element according to claim 14, wherein when the wire grid film is attached to the curved surface portion, the angle between the arrangement direction of the wires and the extension direction of the minor axis of the substrate is within 30°.

17. The method for manufacturing a reflective polarizing optical element according to claim 14 , further comprising: pressing the wire grid film against the substrate to attach the wire grid film to the curved surface portion.

18. The method for manufacturing a reflective polarizing optical element according to claim 14 , wherein the wire grid film is attached to the curved surface portion in a heated state.

19. The method includes attaching a wire grid film for a polarization beam splitter having a wire grid structure to a substrate having a curved surface portion that forms a curved surface, a straight line connecting a point on the curved surface where the wire grid film first comes into contact with the curved surface and a point on the circumference of the curved surface where the wire grid film first arrives, the straight line extending in a plan view of the substrate in the optical axis direction, and the angle formed by the straight line and the extending direction of the wires in the wire grid structure is 45° when the substrate is attached.

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