Optical instrument

Abstract

Provided is an optical instrument capable of obtaining desired polarization characteristics. The optical instrument is an optical instrument provided with a light source, an incident-side polarization element, a light modulation element, an exit-side first polarization element, and an exit-side second polarization element. The exit-side first polarization element has a wire grid structure and is provided with a plurality of convex portions arranged separately from each other at a pitch shorter than the wavelength of light of a wavelength band used by the light source on one surface of a transparent substrate. The rotation angle of the transmission axis of the exit-side first polarization element with respect to the transmission axis of the incident-side polarization element is within ±8.5°. The exit-side second polarization element has a wire grid structure and is provided with a plurality of convex portions arranged separately from each other at a pitch shorter than the wavelength of light of a wavelength band used by the light source on one surface of a transparent substrate. The convex portions are lattice-shaped convex portions extending in a predetermined direction. The lattice-shaped convex portions sequentially have a reflection layer, a dielectric layer, and an absorption layer from the transparent substrate side. The rotation angle of the absorption axis of the exit-side second polarization element with respect to the absorption axis of the incident-side polarization element is within ±0.7°.

Description

Technical Field

[0001] This technology relates to optical instruments equipped with polarizing elements. This application claims priority based on Japanese Patent Application No. 2021-041786, filed on March 15, 2021, which is incorporated herein by reference. Background Technology

[0002] A polarizing element is an optical element that absorbs polarized light in one direction and transmits polarized light in a direction orthogonal to that direction. Polarizing elements are theoretically required in liquid crystal display (LCD) devices. Particularly in LCD devices using high-intensity light sources, such as transmissive liquid crystal projectors, the polarizing element receives strong radiation, thus requiring excellent heat or light resistance, a size of several centimeters, and high extinction ratio and controlled reflectivity. A wire-grid type inorganic polarizing element has been proposed to meet these requirements.

[0003] A wire-grid polarizing element has a structure in which a plurality of conductor wires extending in one direction are arranged side by side on a substrate at a spacing (tens of nm to hundreds of nm) narrower than the wavelength of the light used. When light is incident on the polarizing element, polarized light parallel to the extension direction of the wires (TE waves (S waves)) cannot be transmitted, while polarized light perpendicular to the extension direction of the wires (TM waves (P waves)) is transmitted as is.

[0004] Wire grid polarizing elements excel in heat resistance and light resistance, allowing for the fabrication of larger elements and exhibiting a high extinction ratio. Furthermore, by employing a multi-layered structure, reflectivity characteristics can be controlled, reducing image quality degradation caused by ghosting and other issues resulting from the reflection of light already reflected from the surface of the polarizing element within the LCD projector device. Therefore, they are suitable for applications such as LCD projectors.

[0005] In contrast, various polarizers have been proposed as wire grid type polarizers.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 5184624;

[0009] Patent Document 2: Japanese Patent No. 5359128. Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] For example, Patent Document 1 discloses a polarization element having a wire grid layer on a substrate, which is composed of an arrangement of extended metal elements having a length longer than the wavelength of the incident light and a period shorter than half the wavelength of the incident light.

[0012] In addition, Patent Document 2 discloses a polarization element having a diffraction lattice-shaped irregularity on a substrate that is transparent to visible light, and an inorganic microparticle layer on a portion of the irregularity.

[0013] However, while these patent documents describe the grating structure of the polarizing element, they do not describe the specific optical characteristics, nor do they describe the method of use that can fully utilize its performance.

[0014] In recent years, lighting / display light sources have evolved from mercury lamps to LEDs, and then to lasers. In LCD projectors, multiple semiconductor lasers (LDs) are used to achieve high luminous flux and thus high brightness. Consequently, polarization elements are required to withstand even intense light conditions while simultaneously possessing high transmittance characteristics. Therefore, to reduce the burden on the polarization elements on the output side, two elements—a pre-polarization element and a main polarization element—must be used, and their performance must be fully utilized through appropriate methods.

[0015] This technology was proposed in view of such past realities, and provides an optical instrument capable of obtaining the desired polarization characteristics.

[0016] Solution for solving the problem

[0017] This technology relates to an optical instrument comprising a light source, an incident-side polarizing element, a light modulation element, an exit-side first polarizing element, and an exit-side second polarizing element. The aforementioned exit-side first polarizing element has a wire grid structure and, on one side of a transparent substrate, a plurality of protrusions arranged at intervals shorter than the wavelength of light in the operating band of the aforementioned light source. These protrusions are lattice-shaped protrusions extending along a predetermined direction. From the transparent substrate side, each lattice-shaped protrusion sequentially comprises a base shape portion formed such that the width of its cross-section, orthogonal to the predetermined direction, tapers towards the front end, and a portion protruding from the base shape portion and having a polarizing effect relative to the wavelength of light in the operating band. The aforementioned second polarizing element on the emission side has an absorptive protrusion and a wire grid structure. It also has a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of the light used in the light source band. The protrusions are lattice-shaped protrusions extending in a predetermined direction. The lattice-shaped protrusions have a reflective layer, a dielectric layer and an absorption layer in sequence from the transparent substrate side. The rotation angle of the orthogonal axis of the first polarizing element on the emission side relative to the orthogonal axis of the polarizing element on the incident side is within ±8.5°, and the rotation angle of the orthogonal axis of the second polarizing element on the emission side relative to the orthogonal axis of the polarizing element on the incident side is within ±0.7°.

[0018] Furthermore, this technology is a method for manufacturing an optical instrument comprising a light source, an incident-side polarizing element, a light modulation element, an exit-side first polarizing element, and an exit-side second polarizing element. The aforementioned exit-side first polarizing element has a wire grid structure and, on one side of a transparent substrate, has a plurality of protrusions arranged separately at a spacing shorter than the wavelength of light in the operating band of the aforementioned light source. These protrusions are lattice-shaped protrusions extending along a predetermined direction. From the transparent substrate side, each lattice-shaped protrusion sequentially has a base shape portion formed such that the width of its cross-section orthogonal to the predetermined direction tapers towards the front end, and a protrusion extending from the base shape portion and having absorbent properties for the wavelength of light in the operating band. The aforementioned exit-side second polarizing element has a wire grid structure. The optical instrument is manufactured by means of: a plurality of protrusions arranged at a spacing shorter than the wavelength of light used in the aforementioned light source on one side of a transparent substrate; the aforementioned protrusions being lattice-shaped protrusions extending in a predetermined direction; the lattice-shaped protrusions having a reflective layer, a dielectric layer, and an absorption layer sequentially from the transparent substrate side; and a manufacturing method comprising: a step of arranging the aforementioned first polarizing element on the emission side with the rotation angle of the orthogonal axis of the aforementioned first polarizing element on the emission side relative to the orthogonal axis of the aforementioned second polarizing element on the emission side relative to the orthogonal axis of the aforementioned second polarizing element on the emission side with the rotation angle of the aforementioned second polarizing element on the emission side relative to the orthogonal axis of the aforementioned second polarizing element on the emission side within ±0.7°; and a step of arranging the aforementioned second polarizing element on the emission side with the rotation angle of the aforementioned second polarizing element on the emission side relative to the orthogonal axis of the aforementioned second polarizing element on the emission side within ±0.7°.

[0019] Invention Effects

[0020] According to this technology, by optimizing the orthogonal angle offset between the first polarizing element on the emission side and the second polarizing element on the emission side, high P-polarized light transmittance (Tp) and contrast ratio (CR) can be obtained in the entire visible light spectrum, thus achieving the desired polarization characteristics. Attached Figure Description

[0021] Figure 1 This is a perspective view schematically showing an example of the configuration of the optical instrument involved in this embodiment.

[0022] Figure 2 It is a diagram used to illustrate the rotation angle relative to the orthogonal axis of the incident side polarizing element.

[0023] Figure 3 This is a cross-sectional view schematically showing a first configuration example of the first polarizing element on the emission side.

[0024] Figure 4 This is a cross-sectional view schematically showing a second configuration example of the first polarizing element on the emission side.

[0025] Figure 5 This is a cross-sectional view schematically showing an example of the configuration of the second polarizing element on the emission side.

[0026] Figure 6 This is a cross-sectional view schematically showing an example of the structure of an anti-reflective film.

[0027] Figure 7 This is a top view schematically showing a portion of the optical unit of a liquid crystal projector.

[0028] Figure 8 This is a graph showing the change in the transmittance (Tp) of P-polarized light in the green band of the outgoing prepolarizer.

[0029] Figure 9 This is a graph showing the change in S-polarized light transmittance (Ts) in the green band of the outgoing pre-polarizer.

[0030] Figure 10 This is a graph showing the change in contrast ratio (CR) in the green band of the outgoing prepolarizer.

[0031] Figure 11 It is shown Figure 8 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° of orthogonal offset angle.

[0032] Figure 12 This is a graph showing the change in the transmittance (Tp) of P-polarized light in the green band of the exiting main polarizer.

[0033] Figure 13This is a graph showing the change in the transmittance (Ts) of S-polarized light in the green band of the exiting main polarizer.

[0034] Figure 14 This is a graph showing the change in contrast ratio (CR) in the green band of the exiting main polarizer.

[0035] Figure 15 It is shown Figure 14 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0036] Figure 16 This is a graph showing the variation in P-polarized light transmittance (Tp) in the green band of the output pre-polarizer (0-30°) and the output main polarizer (0-30°).

[0037] Figure 17 It is shown Figure 16 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° of orthogonal offset angle.

[0038] Figure 18 This is a graph showing the change in contrast ratio (CR) in the green band of the output pre-polarizer (0-30°) and the output main polarizer (0-30°).

[0039] Figure 19 It is shown Figure 18 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0040] Figure 20 This is a graph showing the change in P-polarized light transmittance (Tp) in the green band of the output pre-polarizer (0°) and the output main polarizer (0-30°).

[0041] Figure 21 It is shown Figure 20 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° of orthogonal offset angle.

[0042] Figure 22 This is a graph showing the change in contrast ratio (CR) in the green band of the output pre-polarizer (0°) and the output main polarizer (0-30°).

[0043] Figure 23 It is shown Figure 22 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0044] Figure 24This is a graph showing the variation in P-polarized light transmittance (Tp) in the green band of the output pre-polarizer (8.5°) and the output main polarizer (0-30°).

[0045] Figure 25 It is shown Figure 24 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° of orthogonal offset angle.

[0046] Figure 26 This is a graph showing the change in contrast ratio (CR) in the green band of the output pre-polarizer (8.5°) and the output main polarizer (0-30°).

[0047] Figure 27 It is shown Figure 26 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0048] Figure 28 This is a cross-sectional schematic diagram of the polarizer in Comparative Experiment Example 1.

[0049] Figure 29 It is a graph showing the average transmittance of the transmission axis in each wavelength band of the polarizers in Experimental Examples 1-1 to 1-4 and Comparative Experimental Example 1.

[0050] Figure 30 This is a graph showing the average transmittance of the transmission axis in each wavelength band of the polarizers in Experimental Examples 2-1 to 2-5.

[0051] Figure 31 This is a graph showing the average transmittance of the transmission axis in each wavelength band of the polarizers in Experimental Examples 3-1 to 3-5.

[0052] Figure 32 This is a graph showing the average transmittance of the transmission axis in each wavelength band of the polarizers in Experimental Examples 4-1 to 4-5.

[0053] Figure 33 This is a graph showing the average transmittance of the transmission axis in each wavelength band of the polarizers in Experimental Examples 5-1 to 5-5.

[0054] Figure 34 This is a graph showing the transmittance along the transmission axis in the optical properties of a polarizer, calculated through simulation.

[0055] Figure 35 This is a graph showing the results of actual measurements of the transmittance along the transmission axis for experimental examples 1 to 3.

[0056] Figure 36This is a graph showing the average transmission axis transmittance for each wavelength band, calculated by simulation for the polarizer.

[0057] Figure 37 This is a graph showing the results of the actual measurements of the average transmission axis transmittance for each wavelength band in Experimental Examples 1 to 3.

[0058] Figure 38 This is a chart comparing the contrast in optical properties based on the actual fabrication of polarizers and their heat resistance evaluation. Detailed Implementation

[0059] Hereinafter, embodiments of the present technology will be described in detail with reference to the accompanying drawings and in the following order.

[0060] 1. Optical instruments

[0061] 2. First Embodiment

[0062] 3. Second Embodiment

[0063] 4. Third embodiment

[0064] <1. Optical Instruments>

[0065] Figure 1 This is a perspective view schematically illustrating an example of the configuration of the optical instrument involved in this embodiment. Figure 1 As shown, the optical instrument 10 according to this embodiment includes a light source 11, an incident-side polarizing element 12, a light modulation element 13, an exit-side first polarizing element 14, and an exit-side second polarizing element 15.

[0066] As will be described later, the first polarizing element 14 on the emission side has a wire grid structure and a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of light in the operating band of the aforementioned light source. The protrusions are lattice-shaped protrusions extending along a predetermined direction. The lattice-shaped protrusions have, from the transparent substrate side, a base shape portion formed in such a way that the width of the cross section orthogonal to the predetermined direction becomes thinner towards the front end side and a protrusion protruding from the base shape portion that has an absorptive effect on the wavelength of light in the operating band.

[0067] Furthermore, as described later, the second polarizing element 15 on the emission side has a wire grid structure and has a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of the light used by the light source. The protrusions are lattice-shaped protrusions extending in a predetermined direction, and the lattice-shaped protrusions have a reflective layer, a dielectric layer and an absorption layer in sequence from the transparent substrate side.

[0068] An optical instrument 10 with such a configuration has a first polarizing element 14 on the emission side disposed in front of the second polarizing element 15 on the emission side. The first polarizing element 14 on the emission side absorbs a portion of the high-intensity light and dissipates heat efficiently, thereby improving the durability of the second polarizing element 15 on the emission side and obtaining the desired polarization characteristics.

[0069] Figure 2 This is a diagram used to illustrate the rotation angle relative to the orthogonal axis of the incident-side polarizing element. For example... Figure 2 As shown, the incident-side polarizing element 12 and the exit-side first polarizing element 14 are configured such that the rotation angle α1 of the orthogonal axis of the exit-side first polarizing element 14 relative to the orthogonal axis of the incident-side polarizing element 12 is within ±8.5°, and the incident-side polarizing element 12 and the exit-side second polarizing element 15 are configured such that the rotation angle α2 of the orthogonal axis of the exit-side second polarizing element 15 relative to the orthogonal axis of the incident-side polarizing element 12 is within ±0.7°.

[0070] When the rotation angle α1 (orthogonal offset angle) of the first polarizing element 14 on the emission side relative to the orthogonal axis of the polarizing element 12 on the incident side is within ±8.5°, the P-polarized light transmittance (Tp) across the entire visible light spectrum is preferably 95% or higher, and the change in P-polarized light transmittance (Tp) across the entire visible light spectrum from the position of 0° (rotation angle α1) is preferably -1% or less (a decrease of 1% or less). Furthermore, when the rotation angle α1 (orthogonal offset angle) of the first polarizing element 14 on the emission side relative to the orthogonal axis of the polarizing element 12 on the incident side is within ±8.5°, the contrast ratio (CR) across the entire visible light spectrum is preferably 2.0 or less, and the change in contrast ratio (CR) across the entire visible light spectrum from the position of 0° (rotation angle α1) is preferably -5% or less (a decrease of 5% or less).

[0071] When the rotation angle α2 (orthogonal offset angle) of the exit-side second polarizing element 15 relative to the orthogonal axis of the incident-side polarizing element 12 is within ±0.7°, it is preferable that the P-polarized light transmittance (Tp) across the entire visible light spectrum is 90% or more, and preferably that the change in P-polarized light transmittance (Tp) across the entire visible light spectrum from the position of 0° (rotation angle α2) is -1% or less (a decrease of 1% or less). Furthermore, when the rotation angle α2 (orthogonal offset angle) of the exit-side second polarizing element 15 relative to the orthogonal axis of the incident-side polarizing element 12 is within ±0.7°, it is preferable that the contrast ratio (CR) across the entire visible light spectrum is 1000 or more, and preferably that the change in contrast ratio (CR) across the entire visible light spectrum from the position of 0° (rotation angle α1) is -20% or less (a decrease of 20% or less).

[0072] Therefore, with the first polarizing element 14 on the emission side and the second polarizing element 15 on the emission side configured, the change in P-polarized light transmittance (Tp) across the entire visible light spectrum from the 0° (rotation angle α1, α2) position is within -1%, and the change in contrast ratio (CR) across the entire visible light spectrum from the 0° (rotation angle α1, α2) position is within -20%.

[0073] Regarding the orthogonal axis of the polarizing element, for example, a spectrophotometer can be used to rotate the sample, simultaneously setting the angular position where the S-polarized light transmittance (Ts) reaches its minimum value as the absorption axis (0°), and the angular position at 90° relative to the absorption axis as the transmission axis. P-polarized light transmittance (Tp) refers to the transmittance of polarized light (TM wave) incident on the transmission axis (X-axis direction) of the polarizer. S-polarized light transmittance (Ts) refers to the transmittance of polarized light (TE wave) incident on the absorption axis (Y-axis direction) of the polarizer.

[0074] The components of the optical instrument 10 will be described in detail below.

[0075] [light source]

[0076] The light source 11 can be a laser (LD), LED, mercury lamp (UHE), etc. In this embodiment, a semiconductor laser that can be configured to have high luminous flux and high brightness by using multiple light sources 11 can be appropriately used. For example, a two-dimensional laser array light source corresponding to various colors of RGB can be used.

[0077] [Incident-side polarizing element]

[0078] The incident-side polarizing element 12 is not particularly limited, but is preferably an inorganic polarizer having a wire grid structure and having a plurality of protrusions arranged apart from each other on one side of the transparent substrate at a spacing shorter than the wavelength of the light used by the light source.

[0079] [Optical modulation element]

[0080] The light modulation element 13 is not particularly limited, but it can be configured to use a transmissive liquid crystal element, a reflective liquid crystal display element, or the like.

[0081] [First polarizing element on the emission side (first configuration example)]

[0082] Figure 3 This is a cross-sectional view schematically showing a first configuration example of the first polarizing element on the exit side. (See diagram below.) Figure 3As shown, the polarizer 20, which is shown as a first configuration example of the first polarizing element 14 on the emission side, has a wire grid structure, includes a transparent substrate 21 and a plurality of protrusions 22. The plurality of protrusions 22 extend on the transparent substrate 21 along a first direction (y direction) and are arranged periodically and separated from each other at a spacing P shorter than the wavelength of the light in the band of use. The protrusions 22 are each composed of the following: a base shape portion 23, which is formed such that the width of the cross section orthogonal to the first direction (y direction) becomes thinner towards the front end; and a protrusion 24, which protrudes from the base shape portion 23 and has absorption properties for the wavelength of the light in the band of use.

[0083] Furthermore, the polarizer 20 is configured such that the rotation angle α1 of the orthogonal axis of the polarizer 20 relative to the orthogonal axis of the incident polarizing element 12 is within ±8.5°. As a result, the P-polarized light transmittance (Tp) across the entire visible light spectrum can be 95% or more, and the change in P-polarized light transmittance (Tp) across the entire visible light spectrum from the position of 0° (rotation angle α1) can be within -1%.

[0084] like Figure 3 As shown, the surface extended from the main surface 21a of the transparent substrate 21 is designated as the xy plane, the direction in which the protrusions 22 extend (the first direction) is designated as the y-direction, and the direction orthogonal to the y-direction and in which the protrusions are arranged is designated as the x-direction. Furthermore, the direction orthogonal to the xy plane is designated as the z-direction. Figure 3 The example shown is that the light incident on the polarizer 20 is incident from the z-direction of the side of the transparent substrate 21 where the protrusion 22 is formed (the grid side), but the light incident on the polarizer 20 can also be incident from the transparent substrate 21 side.

[0085] Polarizer 20 utilizes four effects—transmission, reflection, interference, and selective light absorption of polarized waves due to optical anisotropy—to attenuate polarized waves with an electric field component parallel to the y-direction (TE wave (S wave)) and allow polarized waves with an electric field component parallel to the x-direction (TM wave (P wave)) to transmit. Therefore, in Figure 3 In the diagram, the y-direction is the direction of the absorption axis of the polarizer, and the x-direction is the direction of the transmission axis of the polarizer.

[0086] Light incident from the side of the polarizer 20 with the protrusions 22 (grid side) is partially absorbed and attenuated as it passes through the protrusions 24. The TM wave (P wave) in the light transmitted through the protrusions 24 is transmitted through the transparent substrate 21 with high transmittance. On the other hand, the TE wave (S wave) in the light transmitted through the protrusions 24 is reflected by the transparent substrate 21. The TE wave reflected by the transparent substrate 21 is attenuated by interference as it passes through the protrusions 24. By selectively attenuating the TE wave as described above, the polarizer 20 can obtain the desired polarization characteristics.

[0087] (Transparent substrate)

[0088] Regarding the transparent substrate 21, there are no particular limitations as long as it is transparent to light of the wavelength range used by the polarizer 20, and it can be appropriately selected according to the purpose. "Transparent" means that it is not necessary to transmit 100% of the wavelength range used, as long as it can transmit to a degree that maintains its function as a polarizer. The average thickness of the transparent substrate 20 is preferably 0.3 mm or more and 1 mm or less. For example, visible light with wavelengths of around 380 nm to 810 nm can be cited as examples of light used in the polarizer range.

[0089] As the constituent material of the transparent substrate 21, a material with a refractive index of 1.1 to 2.2 is preferred, such as glass, quartz, and sapphire. From the viewpoint of cost and light transmittance, glass is preferred, especially quartz glass (refractive index 1.46) or soda-lime glass (refractive index 1.51). The composition of the glass material is not particularly limited; for example, inexpensive glass materials such as silicate glass, which are widely used as optical glass, can be used. From the viewpoint of thermal conductivity, quartz or sapphire, which have high thermal conductivity, are preferred. This results in high light resistance to strong light, making it suitable for use as a polarizer in the optical engine of a projector, which generates a lot of heat.

[0090] Furthermore, when using a transparent substrate composed of optically active crystals such as quartz, it is preferable to arrange the protrusions in a direction parallel or perpendicular to the optical axis of the crystal. This results in excellent optical properties. Here, the optical axis refers to the axis along which the difference in refractive index between the O (normal ray) and E (abnormal ray) of light traveling along the path is minimized.

[0091] (convex part)

[0092] The protrusions 22 extend along the y-direction on the transparent substrate 21 and are periodically arranged and separated from each other along the x-direction at a spacing P shorter than the wavelength of light in the used band. The protrusions 22 are composed of a base shape portion 23, which is formed such that the width of the xz cross section orthogonal to the y-direction tapers towards the front end; and a protrusion 24, which protrudes from the base shape portion 23 and has absorption properties for the wavelength of light in the used band.

[0093] exist Figure 3The spacing (repetition interval in the x-direction) of the protrusions 22 indicated by the symbol P is not particularly limited as long as it is shorter than the wavelength of the light used in the band. From the viewpoint of ease of manufacture and stability, the spacing of the protrusions is preferably, for example, 100 nm to 200 nm. The spacing of the protrusions can be measured by observation using a scanning electron microscope or a transmission electron microscope. For example, the spacing can be measured at any four locations using a scanning electron microscope or a transmission electron microscope, and the arithmetic mean of these measurements can be taken as the spacing of the protrusions. Hereinafter, this measurement method will be referred to as the electron microscopy method.

[0094] (Base shape part)

[0095] The base shape portion 23 is formed such that the width of the xz section orthogonal to the y direction tapers towards the front end. Various designs can be adopted to make the width of the xz section taper towards the front end. The base shape portion 23 can also be approximately triangular in the xz section orthogonal to the y direction. The approximately triangular shape is preferably approximately isosceles. Here, "approximately triangular shape" means that even if it is not strictly triangular, it is acceptable as long as it is approximately triangular within the effective range. For example, it can also be a trapezoidal shape lacking a front end. Furthermore, since the protrusion is a very fine structure, there are cases where the pointed shape has a certain degree of roundness in manufacturing, and this is also included in the aforementioned approximately triangular shape. Additionally, there are also cases where the approximately triangular shape of the protrusion has an inclined surface (…). Figure 3 The case where the symbol 23a) has some curvature is also included in the above-mentioned general triangular shape.

[0096] Here, use Figure 3 The dimensions of the base shape portion 23 in this specification will now be explained. The height of the base shape portion 23 refers to the dimension in the z-direction from the bottom surface 23b (main surface 21a of the transparent substrate 21) to the front end 23c of the base shape portion 23. Figure 3 The dimension is indicated by the symbol 'a'. Furthermore, the width of the base shape portion 23 refers to the dimension in the x-direction of the bottom surface 23b of the base shape portion 23 in the xz section. Figure 3 The dimension is indicated by the symbol b.

[0097] The height a of the substrate shape portion 23 is appropriately set in the range of tens of nm to hundreds of nm. This height of the substrate shape portion 23 can be measured, for example, by the electron microscopy method described above. The height a of the substrate shape portion 23 is preferably in the range of 50 to 130 nm. Regarding the relationship between the height a and the width b of the substrate shape portion 23, from the viewpoint of improving transmittance, it is preferable that (a / b) > 1 / 2, more preferably 13 / 10 ≥ (a / b) ≥ 7 / 10, and even more preferably 13 / 10 ≥ (a / b) ≥ 9 / 10.

[0098] The width b of the substrate shape portion 23 is appropriately set in the range of tens of nm to hundreds of nm. The width of the substrate shape portion 21 can be measured, for example, by the electron microscopy method described above. The width b of the substrate shape portion 23 is preferably in the range of 80 to 120 nm. In terms of the relationship between the width b and the height a of the substrate shape portion 23, from the viewpoint of improving transmittance, it is preferable that (a / b) > 1 / 2, more preferably that 13 / 10 ≥ (a / b) ≥ 7 / 10, and even more preferably that 13 / 10 ≥ (a / b) ≥ 9 / 10.

[0099] The ratio of the width b of the base shape portion 23 to the region "Pb" where the base shape portion 23 is not formed is preferably, for example, 6 / 1 ≥ (b / Pb) ≥ 4 / 3.

[0100] The base shape portion 23 may also be made of the same material as the transparent substrate 21. The base shape portion 23 and the transparent substrate 21 may be integrally formed, or the base shape portion 23 may be formed on the transparent substrate 21 and made of the same material as the transparent substrate 21. In the former case, regarding the base shape portion 23, it is formed on the main surface 21a of the transparent substrate 21 by processing (e.g., selective etching) the main surface of the transparent substrate (let's say the substrate before it is processed into the transparent substrate 21 is called the transparent substrate).

[0101] Alternatively, the substrate shape portion 23 may be made of a dielectric material different from that of the transparent substrate 21. In this case, the film thickness of the dielectric (height a of the substrate shape portion 23) is appropriately set in the range of tens of nm to hundreds of nm. The film thickness of the dielectric can be measured, for example, by the electron microscopy method described above. Regarding the relationship between the film thickness of the dielectric (height a of the substrate shape portion 21) and the width b, from the viewpoint of improving transmittance, it is preferable that (a / b) > 1 / 2, more preferably that 13 / 10 ≥ (a / b) ≥ 7 / 10, and even more preferably that 13 / 10 ≥ (a / b) ≥ 9 / 10.

[0102] Examples of materials constituting the dielectric include Si oxides such as SiO2, metal oxides such as Al2O3, beryllium oxide, and bismuth oxide, MgF2, cryolite, germanium (Ge), titanium dioxide, silicon, magnesium fluoride, boron nitride, boron oxide, tantalum oxide, carbon, or combinations thereof. The dielectric is preferably composed of Si oxides. The refractive index of the dielectric is preferably greater than 1.0 and less than 2.5. The optical properties of the protrusion are affected by the surrounding refractive index; therefore, by selecting the dielectric material, the characteristics of the polarizer can be controlled. The substrate shape portion 23 composed of the dielectric can be formed as a high-density film using methods such as evaporation, sputtering, CVD (Chemical Vapor Deposition), or ALD (Atomic Layer Deposition).

[0103] (Protrusion)

[0104] The protrusion 24 extends from the base shape portion 23 and is absorbent of the wavelength of light used in the band. Its protrusion from the base shape portion 23 means that if used... Figure 3 To illustrate, it is formed by protruding from the inclined surface 23a or the front end (apex) 23c of the base shape portion 23.

[0105] The protrusions 24 can also be microparticles in the xz section, and can be configured to extend along the y direction, which is the absorption axis. In this case, the protrusions 24 form a wire grating structure and function as a wire grating type polarizing mirror, attenuating polarized waves (TE waves (S waves)) with electric field components in a direction parallel to the length direction of the protrusions 24, and transmitting polarized waves (TM waves (P waves)) with electric field components in a direction orthogonal to the length direction of the protrusions 22.

[0106] As the constituent material of the protrusion 24, one or more substances with light absorption properties, such as metallic materials and semiconductor materials, whose extinction constants are not zero, can be listed. The appropriate material can be selected based on the wavelength range of the applicable light. As metallic materials, examples include single elements such as Ta, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, and Sn, or alloys containing one or more of these elements. Furthermore, as semiconductor materials, examples include Si, Ge, Te, ZnO, and silicide materials (β-FeSi2, MgSi2, NiSi2, BaSi2, CrSi2, CoSi2, TaSi, etc.). By using these materials, the polarizer can achieve a high extinction ratio in the applicable visible light region.

[0107] When a semiconductor material is used as the constituent material of the protrusion 24, the band gap energy of the semiconductor interferes with the absorption effect, so it is necessary to make the band gap energy below the operating wavelength. For example, when used in visible light, it is necessary to achieve absorption at wavelengths above 400 nm, that is, to use a material with a band gap of 3.1 eV or less.

[0108] When the protrusion 24 is approximately circular in the xz section, its radius is appropriately set in the range of several nm to several hundred nm. The radius of this protrusion 24 can be measured, for example, by the electron microscopy method described above. For example, the radius of the approximately circular protrusion 24 is preferably in the range of 5 nm to 100 nm.

[0109] The film thickness of the protrusion 24 (the thickness protruding from the substrate shape portion 21) is not particularly limited, but is preferably from 5 nm to 100 nm. The film thickness of the protrusion 24 can be measured, for example, by the electron microscopy method described above.

[0110] The position of the protrusion 24 on the base shape portion 23 is not particularly limited; it can be an inclined surface of the base shape portion 23 or a front end. The position of the protrusion 24 on the base shape portion 23 is preferably within three-quarters of the range from the front end to the bottom surface of the base shape portion 23, and more preferably within one-half of the range. This is because, if it is positioned close to the bottom surface of the base shape portion 23, it may also be positioned on the main surface of the transparent substrate during the manufacturing process.

[0111] The protrusion 24 can be formed using well-known dry methods such as vapor deposition or sputtering. In this case, by performing vapor deposition or sputtering from an oblique direction, the protrusion 24 can also be formed on one inclined surface of the substrate shape portion 23. Alternatively, after forming the protrusion 24 on one inclined surface of the substrate shape portion 23, it can be formed on another inclined surface. In the former case, viewed from the z-direction, the protrusion 24 is formed in an asymmetrical position relative to the substrate shape portion 23. In the latter case, viewed from the z-direction, it can be configured to be formed in a symmetrical position relative to the substrate shape portion 23. Furthermore, the protrusion 23 can also be formed using well-known wet methods. The protrusion 23 can also be composed of two or more layers of different constituent materials.

[0112] [Protective film]

[0113] Furthermore, in this embodiment, the polarizer can also cover the surface of the light incident side with a protective film made of dielectric material, within a range that does not affect changes in optical properties.

[0114] Waterproof membrane

[0115] Furthermore, the polarizer of this embodiment can also have its light-incident surface covered by an organic waterproof film. The organic waterproof film is, for example, composed of fluorinated silane compounds such as perfluorododecyltrichlorosilane (FDTS), and can be formed, for example, using the CVD or ALD methods described above. This improves the polarizer's moisture resistance and other reliability.

[0116] [First polarizing element on the emission side (second configuration example)]

[0117] Figure 4 This is a cross-sectional view schematically showing a second configuration example of the first polarizing element on the emission side. (See diagram below.) Figure 4 As shown, the polarizer 30, which is a second configuration example of the first polarizing element 14 on the emission side, has a wire grid structure, includes a transparent substrate 31 and a plurality of protrusions 32. The plurality of protrusions 32 extend on the transparent substrate 31 along a first direction (y direction) and are arranged periodically and separated from each other at a spacing P shorter than the wavelength of the light in the used band. Each protrusion 32 is composed of the following parts: a base shape portion 33, which is formed such that the width of the cross section orthogonal to the first direction (y direction) becomes thinner towards the front end; and a protrusion 34, which protrudes from the base shape portion 33 and has absorption properties for the wavelength of the light in the used band.

[0118] Furthermore, the polarizer 30 is configured such that the rotation angle α1 of the orthogonal axis of the polarizer 30 relative to the orthogonal axis of the incident polarizing element 12 is within ±8.5°. As a result, the P-polarized light transmittance (Tp) across the entire visible light spectrum can be 95% or more, and the change in P-polarized light transmittance (Tp) across the entire visible light spectrum from the 0° (rotation angle α1) position can be within -1%.

[0119] like Figure 4 As shown, the surface extended from the main surface 31a of the transparent substrate 31 is designated as the xy plane, the direction in which the protrusions 32 extend (the first direction) is designated as the y-direction, and the direction orthogonal to the y-direction and in which the protrusions 32 are arranged is designated as the x-direction. Furthermore, the direction orthogonal to the xy plane is designated as the z-direction. Figure 4 The example shown is that light incident on the polarizer is incident from the z-direction of the side of the transparent substrate 31 where the protrusion 32 is formed (the grid side), but light incident on the polarizer 30 can also be incident from the transparent substrate 31 side.

[0120] The polarizer 30 shown as a second configuration example differs from the first configuration example in the shape of its substrate portion. Specifically, the xz-section of the substrate portion 21 in the first configuration example is triangular, while in contrast, the xz-section of the substrate portion 33 in the second configuration example is trapezoidal. The transparent substrate 31 and the protrusion 34 are the same as those in the first configuration example, and therefore their descriptions are omitted here.

[0121] The base shape 33 can also be approximately trapezoidal in the xz section orthogonal to the y direction. Preferably, the approximately trapezoidal shape is formed by two inclined surfaces 33a connecting the upper surface 33c and the lower surface (bottom) 33b having equal lengths and forming an angle θ with the lower surface 33b. This shape is a trapezoidal symmetrical with respect to an axis parallel to the z-axis.

[0122] Here, "approximate trapezoidal shape" refers to a shape that is approximate, even if not strictly trapezoidal, as long as it serves an effective purpose. Furthermore, since protrusions are very fine structures, there are cases where the pointed shape has a certain degree of roundness in its manufacturing; this is also included in the aforementioned approximate trapezoidal shape. Additionally, there are also cases where the protrusion has an inclined surface in an approximate trapezoidal shape (…). Figure 4 The symbol 33a) has some curvature, which can also be described as roughly trapezoidal in shape.

[0123] use Figure 4 The dimensions of the base shape portion 33 will now be explained. The height of the base shape portion 33 refers to the dimension in the z-direction from the bottom surface 33b (main surface 31a of the transparent substrate 31) to the upper surface 33c of the base shape portion 33. Figure 4 The dimension is indicated by the symbol 'a'. Furthermore, the width of the base shape portion 33 refers to the dimension in the x-direction of the bottom surface 33b of the base shape portion 33 in the xz section. Figure 4 The dimension is indicated by the symbol b.

[0124] The shape and material of the base shape portion 33 can be set to be the same as the shape and material described by the base shape portion 23 in the first configuration example.

[0125] [First polarizing element on the emission side (modified example)]

[0126] In both the first and second configuration examples, the transparent substrate may be a laminate of a first substrate made of a first material and a second substrate made of a second material. In this case, it is preferable that the first substrate is disposed on the substrate shape portion side, and the first material is the same as the material of the substrate shape portion. As the material of the second substrate, the same material described as the material of the transparent substrate can be used.

[0127] Furthermore, in both the first and second configuration examples, a phase difference compensation layer may be formed on the surface of the light incident side. This phase difference compensation layer is, for example, composed of a multilayer film using an inorganic material with optical anisotropy, and can be formed, for example, by evaporation or sputtering from an inclined direction. This allows for the correction of scattering of polarized light after it has passed through the liquid crystal panel.

[0128] [Second polarizing element on the emission side]

[0129] Figure 5 This is a cross-sectional view schematically showing an example of the configuration of the second polarizing element on the emission side. (See diagram below.) Figure 5 As shown, the polarizer 40, which is shown as a first configuration example of the second polarizing element 15 on the emission side, has a wire grid structure and includes a transparent substrate 41, a plurality of protrusions 42, and an anti-reflective layer 43 formed on a second surface 41b opposite to a first surface 41a of the transparent substrate 41. The plurality of protrusions 42 are formed on the first surface 41a of the transparent substrate 41 and extend along a first direction. They are separated from each other and arranged periodically at a spacing shorter than the wavelength of the light in the band of use. The plurality of protrusions 42 have, in sequence from the transparent substrate 41 side, a reflective layer 42A, a dielectric layer 42B made of a first dielectric, and an absorption layer 42C. The surfaces 42a of each of the plurality of protrusions 42 and the surface 43a of the anti-reflective layer 43 are covered by protective films 44A and 44B made of a second dielectric, respectively.

[0130] Furthermore, the polarizer 40 is configured such that the rotation angle α2 of the orthogonal axis of the polarizer 40 relative to the orthogonal axis of the incident polarizing element 12 is within ±0.7°. As a result, the transmittance (Tp) of P-polarized light across the entire visible light spectrum can be 90% or more, and the change in contrast ratio (CR) across the entire visible light spectrum from the 0° (rotation angle α2) position can be within -20%.

[0131] like Figure 5 As shown, the surface extended from the main surface 41a of the transparent substrate 41 is designated as the xy plane, and the direction in which the plurality of protrusions 42 extend (the first direction) is called the Y-axis direction. The direction orthogonal to the Y-axis direction and in which the plurality of protrusions 42 are arranged along the main surface of the transparent substrate 41 is designated as the X-axis direction. The direction orthogonal to both the Y-axis and X-axis directions and perpendicular to the main surface of the transparent substrate is designated as the Z-axis direction. Figure 5 The example shown is that the light incident on the polarizer 40 is incident from the z-direction of the side of the transparent substrate 41 where the protrusion 42 is formed (the grid side), but the light incident on the polarizer 40 can also be incident from the transparent substrate 41 side.

[0132] Light incident from the side of polarizer 40 with multiple protrusions 42 (grid side) is partially absorbed and attenuated as it passes through absorption layer 42C and dielectric layer 42B. Polarized waves (TM waves (P waves)) in the light that have passed through absorption layer 42C and dielectric layer 42B are transmitted through reflective layer 42A with high transmittance. On the other hand, polarized waves (TE waves (S waves)) in the light that have passed through absorption layer 42C and dielectric layer 42B are reflected by reflective layer 42A. The TE waves reflected by reflective layer 42A are partially absorbed and partially reflected back to reflective layer 42A as they pass through absorption layer 42C and dielectric layer 42B. Furthermore, the TE waves reflected by reflective layer 42A are attenuated by interference as they pass through absorption layer 42C and dielectric layer 42B. By selectively attenuating TE waves as described above, polarizer 40 can obtain the desired polarization characteristics.

[0133] exist Figure 5 In the polarizer 40 shown, the height h of the grid is the dimension in the Z-axis direction perpendicular to the main surface of the transparent substrate 41, and represents the height of the plurality of protrusions 42 that have the protective film (height (thickness) h1). The width w represents the dimension in the X-axis direction orthogonal to the height h direction when viewed from the Y-axis direction along the direction in which the plurality of protrusions 42 with the protective film 44A extend. Furthermore, when viewing the polarizer 40 from the Y-axis direction along the direction in which the plurality of protrusions 42 extend, the repeating interval of the plurality of protrusions 42 in the X-axis direction is referred to as the spacing p.

[0134] In the polarizer 40, the spacing p of the plurality of protrusions 42 is not particularly limited as long as it is shorter than the wavelength of the light used in the band of operation. From the viewpoint of ease of manufacture and stability, the spacing p of the plurality of protrusions 42 is preferably, for example, 100 nm to 200 nm. The spacing p of the plurality of protrusions 42 can be measured by observation using a scanning electron microscope or a transmission electron microscope. For example, the spacing p can be measured at any four locations using a scanning electron microscope or a transmission electron microscope, and the arithmetic mean of these measurements can be taken as the spacing p of the plurality of protrusions 42.

[0135] By optimizing the thickness of the protective film 44A covering the front end of the grid and the thickness of the protective film 44B on the anti-reflective layer 43, the polarizer 40 can maintain durability while ensuring good light transmission characteristics in the transmission axis direction.

[0136] (Transparent substrate)

[0137] The transparent substrate 21, which is similar to the example of the first polarizing element on the emission side, will not be described here.

[0138] (Reflective layer)

[0139] A reflective layer 42A is formed on a transparent substrate 41, and a strip of metal film is arranged along the Y-axis, which serves as the absorption axis. The reflective layer 42A functions as a wire-grating polarizing mirror, attenuating polarized waves (TE waves (S-waves)) with an electric field component in a direction parallel to the length direction of the reflective layer 42A, and transmitting polarized waves (TM waves (P-waves)) with an electric field component in a direction orthogonal to the length direction of the reflective layer 42A. The thickness of the reflective layer 42A is not particularly limited, but is preferably, for example, between 100 nm and 300 nm. Furthermore, the thickness of the reflective layer 42A can be measured, for example, by the electron microscopy method described above.

[0140] The constituent material of the reflective layer 42A is not particularly limited as long as it is reflective to light in the operating wavelength range. Examples include individual elements such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, and Te, or alloys containing one or more of these elements. From the perspectives of minimizing absorption loss at the grating in the visible light region and cost considerations, the reflective layer 42A is preferably made of aluminum (Al) or an aluminum alloy. Furthermore, in addition to these metallic materials, it can also be made of inorganic films or resin films other than metals, formed by methods such as coloring to increase surface reflectivity.

[0141] The reflective layer 42A can be formed as a high-density film, for example, by using vapor deposition or sputtering. Alternatively, the reflective layer can be composed of two or more layers of different constituent materials.

[0142] (Dielectric layer)

[0143] A dielectric layer 42B is formed on the reflective layer 42A, and dielectric films extending in a strip shape along the Y-axis, which is the absorption axis, are arranged thereon. The thickness of the dielectric layer 42B is formed within the range where the phase of the polarized light transmitted through the absorption layer 42C and reflected by the reflective layer 42A is offset by half a wavelength relative to the polarized light reflected by the absorption layer 42C. Specifically, the thickness of the dielectric layer 42B is appropriately set within the range of 1 nm to 500 nm, which allows for adjustment of the phase of the polarized light to improve the interference effect. The thickness of the dielectric layer 42B can be measured, for example, by the electron microscopy method described above. In addition, the dielectric layer 42B is also formed as a barrier layer to suppress the interdiffusion of the constituent elements of the reflective layer 42A and the absorption layer 42C (described later).

[0144] As the first dielectric material constituting the dielectric layer 42B, general materials such as Si oxides like SiO2, Al2O3, metal oxides like beryllium oxide and bismuth oxide, MgF2, cryolite, germanium, titanium dioxide, silicon, magnesium fluoride, boron nitride, boron oxide, tantalum oxide, carbon, or combinations thereof can be included. From the viewpoint of transmittance and the function of the barrier layer, the dielectric layer 42B is preferably composed of one or more oxides selected from the group consisting of Si oxides, Ti oxides, Zr oxides, Al oxides, Nb oxides, and Ta oxides.

[0145] The refractive index of the dielectric layer 42B is preferably greater than 1.0 and less than 2.5. The optical properties of the reflective layer 42A are also affected by the surrounding refractive index; therefore, by selecting the material of the dielectric layer 42B, the optical properties of the polarizer can be controlled. Furthermore, by appropriately adjusting the film thickness and refractive index of the dielectric layer 42B, a portion of the TE wave reflected by the reflective layer 42A can be reflected back to the reflective layer 42A when transmitted through the absorption layer 42C. Interference can be used to attenuate the light that has passed through the absorption layer 42C. In this way, by selectively attenuating the TE wave, the desired polarization characteristics can be obtained.

[0146] The dielectric layer 42B can be formed as a high-density film using methods such as vapor deposition, sputtering, CVD, or ALD. Alternatively, the dielectric layer can be composed of two or more layers of different constituent materials.

[0147] (Absorbing layer)

[0148] The absorption layer 42C, which absorbs the wavelength of light in the band of use, is formed on the dielectric layer 42B and extends in a strip-like pattern along the Y-axis, which serves as the absorption axis. The thickness of the absorption layer 42C is not particularly limited, but is preferably from 5 nm to 50 nm. The thickness of this absorption layer 42C can be measured, for example, by the electron microscopy method described above.

[0149] The absorption layer 42C is preferably composed of one or more materials selected from the group consisting of metals, alloys, and semiconductors. The constituent materials of the absorption layer 42C can be appropriately selected according to the wavelength range of the applicable light. Examples of metal materials include individual elements such as Ta, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, and Sn, or alloys containing one or more of these elements. Examples of semiconductor materials include Si, Ge, Te, ZnO, and silicide materials (β-FeSi2, MgSi2, NiSi2, BaSi2, CrSi2, CoSi2, TaSi, etc.). By using these materials, the polarizer can achieve a high extinction ratio in the applicable visible light region. The absorption layer 42C is preferably composed of Fe or Ta and also contains Si.

[0150] When a semiconductor material is used as the absorption layer 42C, the bandgap energy of the semiconductor interferes with the absorption effect, so it is necessary to make the bandgap energy below the operating wavelength. For example, when used in visible light, it is necessary to achieve absorption at wavelengths above 400 nm, that is, to use a material with a bandgap of 3.1 eV or less.

[0151] The absorber layer 42C can be formed as a high-density film, for example, by using vapor deposition or sputtering. Alternatively, the absorber layer 42C can also be composed of two or more layers of different constituent materials.

[0152] (Anti-reflective layer)

[0153] An anti-reflective layer 43 is formed on the second surface 41b of the transparent substrate 41. The anti-reflective layer 43 can be configured to be made of a well-known anti-reflective material, for example, the material constituting the dielectric layer 42B can be a material composed of at least two or more multilayer films.

[0154] Figure 6 This is a cross-sectional view schematically illustrating an example of the structure of an anti-reflective film. (As shown...) Figure 6 As shown, the antireflective film 43, by alternately stacking low-refractive-index layers 43A and high-refractive-index layers 43B with different refractive indices, can utilize interference to attenuate light reflected from the interface. The thickness of the antireflective layer 43 is not particularly limited, and each dielectric layer constituting the dielectric layer 42B is appropriately set in the range of 1 nm to 500 nm. The thickness of this antireflective layer 43 can be measured, for example, by the electron microscopy method described above.

[0155] The low-refractive-index layer 43A is a layer whose main component is SiO2 (an oxide of Si). The refractive index of the low-refractive-index layer is preferably 1.20 to 1.60, and more preferably 1.30 to 1.50.

[0156] The refractive index of the high refractive index layer 43B is preferably 2.00 to 2.60, more preferably 2.10 to 2.45. Examples of such high refractive index dielectrics include niobium pentoxide (Nb₂O₅, refractive index 2.33), titanium oxide (TiO₂, refractive index 2.33 to 2.55), tungsten oxide (WO₃, refractive index 2.2), cerium oxide (CeO₂, refractive index 2.2), tantalum pentoxide (Ta₂O₅, refractive index 2.16), zinc oxide (ZnO, refractive index 2.1), and indium tin oxide (ITO, refractive index 2.06).

[0157] The antireflective layer 43 can be formed as a high-density film using the same film-forming method as the dielectric layer 42B described above. Preferably, ion beam assisted deposition (IAD) or ion beam sputtering (IBS) methods, which are capable of forming films with higher density, are preferred.

[0158] (Protective film)

[0159] The surfaces of the multiple protrusions 42 and the surface 43a of the antireflective layer 43 are respectively covered by protective films 44A and 44B made of dielectric material. Protective film 44A covers the top surface and sides of the protrusions 42, and may also cover the surface of the transparent substrate 41 between the protrusions 42 if needed. By using protective films 44A and 44B for covering, the durability of the polarizer can be improved.

[0160] When forming the protective films 44A and 44B, the ALD method, which provides dense, uniform film thickness control, is preferred. Furthermore, similar to the dielectric layer 42B described above, it can also be composed of two or more layers of different constituent materials.

[0161] Alternatively, the protective film 44A can be completely embedded between the protrusions 42. In this case, in addition to the method for forming the dielectric layer 42B described above, the SOG (Spin-on Glass) method can also be used. According to SOG, planarization can be achieved without an air layer.

[0162] As the dielectric constituting the protective films 44A and 44B, the same dielectric as the first dielectric constituting the dielectric film 22 can be used. From the viewpoint of heat resistance, Al2O3 is particularly preferred.

[0163] The thickness of at least one of the protective films 44A and 44B can be set to 2.5 nm or less. From the viewpoint of maintaining durability, it is preferable to have a thickness of 1 nm or more, more preferably 1.5 nm or more, and even more preferably 2.0 nm or more. This maintains the durability of the polarizer while simultaneously improving its light transmission characteristics, and in particular, prevents a significant decline in optical properties.

[0164] Furthermore, the thickness of at least one of the protective films 44A and 44B can be set to 2.5 nm or more, and from the viewpoint of improving light transmission characteristics, it is preferably 10 nm or less, more preferably 7.5 nm or less, and even more preferably 5.0 nm or less. In this case, the durability of the polarizer is maintained, and the light transmission characteristics are improved at the same time, and in particular, high heat resistance can be maintained.

[0165] (Waterproof membrane)

[0166] Furthermore, the polarizer 40 can also be covered by an organic waterproof membrane, which can be used to cover at least one of the protective films 44A and 44B. The organic waterproof membrane is, for example, composed of fluorinated silane compounds such as perfluorododecyltrichlorosilane (FDTS), and can be formed, for example, using the CVD or ALD methods described above. This improves the polarizer's moisture resistance and other reliability.

[0167] [LCD Projector]

[0168] The optical instrument 10 described above can be appropriately used in applications requiring heat resistance, such as liquid crystal projectors and head-up displays. Hereinafter, a liquid crystal projector will be used as a specific example for illustration.

[0169] Figure 7 This is a top view schematically showing a portion of the optical unit of a transmissive 3LCD type liquid crystal projector. The optical engine portion of the liquid crystal projector 50 includes: for red light L R The incident polarizing element 51R, the liquid crystal panel 52R, the exit pre-polarizing element 53R, and the exit main polarizing element 54R; for green light L G The incident side polarizing element 51G, liquid crystal panel 52G, exit pre-polarizing element 53G, and exit main polarizing element 54G; for blue light L B The optical instrument 10 includes an incident polarizing element 51B, a liquid crystal panel 52B, an exit pre-polarizing element 53B, and an exit main polarizing element 54B; and a cross-shaped dichroic prism 55 that combines the light emitted from each of the exit main polarizing elements 54R, 54G, and 54B and projects it onto the projection lens. Here, the incident polarizing elements 51R, 51G, 51B, the liquid crystal panels 52R, 52G, 52B, the exit pre-polarizing elements 53R, 53G, 53B, and the exit main polarizing elements 54R, 54G, and 54B correspond to the incident polarizing element 12, the light modulation element 13, the exit first polarizing element 14, and the exit second polarizing element 15, respectively, of the aforementioned optical instrument 10.

[0170] In the liquid crystal projector 50 to which this technology is applied, each liquid crystal panel 52R, 52G, and 52B projects the incident red light L... R Green light L G Blue light L B The light corresponding to the incident-side polarizing elements 51R, 51G, and 51B, and the light L polarized by the incident-side polarizing elements 51R, 51G, and 51B. R L G L BSpatially modulated and emitted, the light passes through exiting pre-polarization elements 53R, 53G, 53B and exiting main polarization elements 54R, 54G, 54B, and is then combined by a cross-shaped dichroic prism 55 and projected through a projection lens (not shown). Red light L R Green light L G Blue light L B It can also be light separated from the light emitted from the light source by a dichroic mirror, but because this technology has excellent light resistance to strong light, it can use high-output light from a two-dimensional laser array light source corresponding to various colors.

[0171] Based on the optical instrument involved in this technology, by optimizing the rotation angle (orthogonal offset angle) of the orthogonal axis of the first polarizing element 14 on the output side relative to the orthogonal axis of the polarizing element 12 on the incident side and the rotation angle (orthogonal offset angle) of the orthogonal axis of the second polarizing element 15 on the output side relative to the orthogonal axis of the polarizing element 12 on the incident side, high P-polarized light transmittance (Tp) and contrast ratio (CR) can be obtained across the entire visible light spectrum. Therefore, when projected by a projector, a bright and well-defined image quality can be obtained.

[0172] Furthermore, while the present technology has been described based on the accompanying drawings and embodiments, it should be noted that the present technology is not limited to the above-described embodiments. Those skilled in the art can easily make various modifications or variations based on this disclosure. Therefore, it should be understood that such modifications or variations are included within the scope of the present technology. Additionally, the drawings are schematic, and the ratios of various dimensions may sometimes differ from actual ratios. Specific dimensions should be determined with reference to the above description. Of course, the drawings also include portions where the dimensions or ratios differ from each other.

[0173] Example

[0174] <2. First Embodiment>

[0175] In the first embodiment, the angular dependence of the exit pre-polarizer and the exit main polarizer was measured. Furthermore, this technology is not limited to these embodiments; variations and modifications that achieve the effects of this technology are also included within its scope.

[0176] [Outgoing pre-polarizer]

[0177] Made with Figure 3 The polarizer shown is constructed in the same way as the first example. The transparent substrate 21 is made of sapphire, the base shape portion 23 is made of SiO2, and the protrusion portion 24 is made of Ge. The shape of the base shape portion 23 is such that the xz cross section is approximately triangular, and the shape of the protrusion portion 24 is such that the cross section is approximately circular. The protrusion portion 24 is configured to contact the inclined surface 23a.

[0178] [Outgoing main polarizer]

[0179] Made with Figure 5 The polarizer shown is constructed using the same configuration as the example shown. A transparent substrate 41 is made of glass, a reflective layer 42A of the protrusion 42 is made of Al, a dielectric layer 42B is made of SiO2, and an absorption layer 42C is made of FeSi. Anti-reflective layers 43 are sequentially and alternately stacked from the side closest to the transparent substrate 41 as a first layer (SiO2), a second layer (TiO2), a third layer (SiO2), a fourth layer (TiO2), a fifth layer (SiO2), a sixth layer (TiO2), a seventh layer (SiO2), an eighth layer (TiO2), and a ninth layer (SiO2). Additionally, protective films 44A and 44B are made of Al2O3.

[0180] [Measurement of optical properties]

[0181] As the measuring instrument, a Hitachi U-4100 spectrophotometer is used. The polarizer sample is rotated, and the angle at which the S-polarized light transmittance (Ts) reaches its minimum value is set to 0°. From this point, the angle is changed and measured.

[0182] [Optical properties and changes in optical properties of the exit prepolarizer]

[0183] Table 1 shows the optical properties and their variations of the exit pre-polarizer. By rotating the orthogonal axis of the exit pre-polarizer, the S-polarized transmittance (Ts) and P-polarized transmittance (Tp) were measured across the entire visible light spectrum (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm), and the contrast ratio (CR) was calculated. Furthermore, the percentage changes in S-polarized transmittance (Ts), P-polarized transmittance (Tp), and contrast ratio (CR) from the 0° position were calculated.

[0184] [Table 1]

[0185]

[0186] Figure 8 This is a graph showing the change in the transmittance (Tp) of P-polarized light in the green band of the output pre-polarizer. Figure 9 This is a graph showing the change in S-polarized light transmittance (Ts) in the green band of the output pre-polarizer. Figure 10 This is a graph showing the change in contrast ratio (CR) in the green band of the output prepolarizer. Figure 11 It is shown Figure 8 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° of orthogonal offset angle.

[0187] As shown in Table 1 and Figures 8 to 11 As shown, the output pre-polarizer exhibits over 90% P-polarized light transmittance (Tp) across the entire visible light spectrum within an orthogonal offset angle of ±20°. Furthermore, with an orthogonal offset angle of ±8.5°, the P-polarized light transmittance (Tp) for the blue, green, and red bands are 95.1%, 96.7%, and 97.7%, respectively, and the changes in P-polarized light transmittance (Tp) from the 0° position for the blue, green, and red bands are -1.1%, -1.1%, and -0.8%, respectively. Furthermore, when the contrast ratio (CR) of the output prepolarizer is 2.0 or less and the orthogonal offset angle of the output prepolarizer is ±8.5°, the change in contrast ratio (CR) from the 0° position is -5% or less in the entire visible light region. When the orthogonal offset angle of the output prepolarizer is ±20°, the change in contrast ratio (CR) from the 0° position is also -20% or less in the entire visible light region.

[0188] [Optical properties and changes in optical properties of the output primary polarizer]

[0189] Table 2 shows the optical characteristics and changes in optical characteristics of the exiting main polarizer. By rotating the orthogonal axis of the exiting main polarizer, the transmittance of S-polarized light (Ts) and the transmittance of P-polarized light (Tp) were measured across the entire visible light spectrum (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm), and the contrast ratio (CR) was calculated. Furthermore, the changes (%) of S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) from the 0° position were calculated.

[0190] [Table 2]

[0191]

[0192] Figure 12 This is a graph showing the change in the transmittance (Tp) of P-polarized light in the green band of the output main polarizer. Figure 13 This is a graph showing the change in the transmittance (Ts) of S-polarized light in the green band of the output main polarizer. Figure 14 This is a graph showing the change in contrast ratio (CR) in the green band of the output primary polarizer. Figure 15 It is shown Figure 14 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0193] As shown in Table 2 and Figures 12 to 15As shown, the output main polarizer exhibits a P-polarized light transmittance (Tp) of over 90% across the entire visible light spectrum within a cross-offset angle of ±0.7°. Furthermore, with the output main polarizer at a cross-offset angle of ±0.7°, the change in P-polarized light transmittance (Tp) from 0° is less than -1% across the entire visible light spectrum. Additionally, with the output main polarizer at a cross-offset angle of ±0.7°, it exhibits a contrast ratio (CR) of over 1000 across the entire visible light spectrum. Furthermore, with the output main polarizer at a cross-offset angle of ±0.7°, the change in contrast ratio (CR) from 0° is less than -20% across the entire visible light spectrum.

[0194] [Optical properties and changes in optical properties of the exit pre-polarizer (0-30°) and the exit main polarizer (0-30°)]

[0195] Table 3 shows the optical properties and their changes when the orthogonal axes of the exit pre-polarizer and the exit main polarizer are rotated simultaneously. Based on the optical properties of the exit pre-polarizer shown in Table 2 and the optical properties of the exit main polarizer shown in Table 3, the S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) were calculated for the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm). Furthermore, the changes (%) of the S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) from the position where the orthogonal axes of the exit pre-polarizer and the exit main polarizer are at 0° were calculated.

[0196] [Table 3]

[0197]

[0198] Figure 16 This is a graph showing the change in P-polarized light transmittance (Tp) in the green band of the output pre-polarizer (0-30°) and the output main polarizer (0-30°). Figure 17 It is shown Figure 16 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° from the orthogonal offset angle. Figure 18 This is a graph showing the change in contrast ratio (CR) in the green band for the output pre-polarizer (0-30°) and the output main polarizer (0-30°). Figure 19 It is shown Figure 18 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0199] As shown in Table 3 and Figures 16 to 19 As shown, with the orthogonal offset angle between the exit pre-polarizer and the exit main polarizer at 0°, the P-polarized light transmittance (Tp) in the blue, green, and red bands are 87.9%, 91.7%, and 92.0%, respectively. Furthermore, with an orthogonal offset angle of ±0.7°, the change in contrast ratio (CR) from the 0° position is approximately -20% across the entire visible light spectrum.

[0200] [Optical properties and changes in optical properties of the exit pre-polarizer (0°) and the exit main polarizer (0-30°)]

[0201] Table 4 shows the optical characteristics and their changes when the orthogonal axis of the exit pre-polarizer is positioned at 0° and the orthogonal axis of the exit main polarizer is rotated. Based on the optical characteristics of the exit pre-polarizer shown in Table 2 and the optical characteristics of the exit main polarizer shown in Table 3, the S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) were calculated for the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm). Furthermore, the percentage changes in S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) from the position where the orthogonal axis of the exit pre-polarizer and exit main polarizer is at 0° were calculated.

[0202] [Table 4]

[0203]

[0204] Figure 20 This is a graph showing the change in P-polarized light transmittance (Tp) in the green band between the exit pre-polarizer (0°) and the exit main polarizer (0-30°). Figure 21 It is shown Figure 20 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° from the orthogonal offset angle. Figure 22 This is a graph showing the change in contrast ratio (CR) in the green band for the output pre-polarizer (0°) and the output main polarizer (0-30°). Figure 23 It is shown Figure 22 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0205] As shown in Table 4 and Figures 20 to 23As shown, when the orthogonal axis of the exit pre-polarizer is positioned at 0° and the orthogonal offset angle of the exit main polarizer is ±0.7°, the change in P-polarized light transmittance (Tp) from the position of 0° orthogonal offset angle of the exit main polarizer is within -1% in the entire visible light region, and the change in contrast ratio (CR) is about -20% in the entire visible light region.

[0206] [Optical properties and changes in optical properties of the exit pre-polarizer (8.5°) and the exit main polarizer (0-30°)]

[0207] Table 5 shows the optical properties and their changes when the orthogonal axis of the exit pre-polarizer is positioned at 8.5° and the orthogonal axis of the exit main polarizer is rotated. Based on the optical properties of the exit pre-polarizer shown in Table 2 and the optical properties of the exit main polarizer shown in Table 3, the S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) were calculated for the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm). Furthermore, the percentage changes in S-polarized light transmittance (Ts), P-polarized light transmittance (Tp), and contrast ratio (CR) were calculated from the point where the orthogonal axis of the exit pre-polarizer was positioned at 8.5° and the orthogonal axis of the exit main polarizer was at 0°.

[0208] [Table 5]

[0209]

[0210] Figure 24 This is a graph showing the change in P-polarized light transmittance (Tp) in the green band of the output pre-polarizer (8.5°) and the output main polarizer (0-30°). Figure 25 It is shown Figure 24 The graph shows the variation in P-polarized light transmittance (Tp) over a range of ±10° from the orthogonal offset angle. Figure 26 This is a graph showing the change in contrast ratio (CR) in the green band for the output pre-polarizer (8.5°) and the output main polarizer (0-30°). Figure 27 It is shown Figure 26 The graph shows the variation in contrast ratio (CR) within the range of ±1° of the orthogonal offset angle.

[0211] As shown in Table 5 and Figures 24 to 27As shown, when the orthogonal axis of the exit pre-polarizer is positioned at 8.5° and the orthogonal offset angle of the exit main polarizer is ±0°, the P-polarized light transmittance (Tp) of the blue, green, and red bands are 86.9%, 90.7%, and 91.2%, respectively.

[0212] Furthermore, when the orthogonal axis of the exit pre-polarizer is positioned at 8.5° and the orthogonal offset angle of the exit main polarizer is ±0.7°, the change in P-polarized light transmittance (Tp) from the position where the orthogonal offset angle of the exit main polarizer is 0° is within -1% in the entire visible light region, and the change in contrast ratio (CR) is approximately -20% in the entire visible light region.

[0213] According to the first embodiment, by setting the orthogonal offset angle of the exiting pre-polarizer to within 8.5° and the orthogonal offset angle of the exiting main polarizer to within ±0.7°, high P-polarized light transmittance (Tp) and contrast ratio (CR) can be obtained across the entire visible light spectrum. Therefore, when projected by a projector, a bright and well-defined image quality can be obtained.

[0214] <3. First Experiment Example>

[0215] In the first experimental example, the optical properties of the pre-polarizer on the outgoing side were verified.

[0216] The effectiveness of the pre-polarizer on the output side was verified through simulation. More specifically, the optical properties of the polarizer were verified through electromagnetic field simulation using the RCWA (Rigorous Coupled Wave Analysis) method. The simulation employed Gsolver, a grating simulator from Grating Solver Development.

[0217] [Experimental Examples 1-1 to 1-4]

[0218] The polarizer in Experiment Example 1-1 has the following shape: Figure 3 As shown, the shapes of the polarizers in Experiment Examples 1-2 to 1-4 are as follows: Figure 4As shown. Regarding the materials of the polarizers in Experimental Examples 1-1 to 1-4, the transparent substrates 21 and 31 and the base-shaped portions 23 and 33 are all made of quartz, while the protrusions 24 and 34 are made of Ge. The base-shaped portions 23 and 33 in Experimental Examples 1-1 to 1-4 all have a height a of 70 nm, a width b of 100 nm, a spacing P of 141 nm, and tilt angles θ of 54°, 63°, 72°, and 81°, respectively. With the height a and width b fixed, the xz-section of Experimental Example 1-1 (θ = 54°) is triangular, while the xz-sections of Experimental Examples 1-2 (θ = 63°), 1-3 (θ = 72°), and 1-4 (θ = 81°) are trapezoidal. Furthermore, the protrusions 24 in Experimental Examples 1-1 to 1-4 all have a circular cross-section with a radius of 15 nm. Regarding the positions of the protrusions 24 and 34 at the base shape portions 23 and 33, such as Figure 3 and Figure 4 As shown, the outermost periphery of the circular shape is set to be the same as the height a and in contact with the inclined surface 21a.

[0219] [Comparative Experiment Example 1]

[0220] The shape of the xz section of the polarizer in Comparative Experiment Example 1 is as follows: Figure 28 As shown. Regarding the materials of the polarizer 100 in Comparative Experiment Example 1, the transparent substrate 101 and the base shape portion 103 are both made of quartz, and the protrusion portion 104 is made of Ge, which is the same as in Experiment Examples 1-1 to 1-4, but the xz cross section is rectangular, which is different from Experiment Examples 1-1 to 1-4.

[0221] The base shape 103 in Comparative Experiment Example 1 has a height a of 70 nm, a width b of 100 nm, a spacing P of 141 nm, and a tilt angle θ of 90°. Furthermore, the protrusion 104 in Comparative Experiment Example 1 has a circular cross-section with a radius of 15 nm. Regarding the position of the protrusion 104 within the base shape 103, as... Figure 28 As shown, the outermost periphery of the circle is set to be the same as the height a and in contact with the inclined surface 103a.

[0222] Figure 29 This is a graph showing the average transmittance along the transmission axis for each wavelength band in the polarizers of Experimental Examples 1-1 to 1-4 and Comparative Experimental Example 1. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance along the transmission axis Tp (%). Here, the transmittance along the transmission axis Tp means the transmittance of the polarized wave (TM wave) incident on the polarizer along the transmission axis direction (X direction).

[0223] like Figure 29As shown, the polarizer involved in this technology reduces the tilt angle θ compared to the polarizer in Comparative Experiment Example 1, thereby improving the transmittance of the transmission axis in the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm).

[0224] When height a and width b are the same, it can be seen that, regarding the base shape 121, the pointed shape has better optical properties than the rectangular shape. Furthermore, when height a and width b are the same, it can be seen that the triangular shape of the xz section has better optical properties than the trapezoidal shape. Additionally, when height a and width b are the same and the xz section is trapezoidal, the shape with a smaller tilt angle θ has better optical properties.

[0225] [Experimental Examples 2-1 to 2-5]

[0226] The shapes of the polarizers in Experiment Examples 2-1 to 2-5 are as follows: Figure 3 As shown. Regarding the materials of the polarizers in Experimental Examples 2-1 to 2-5, the transparent substrate 21 and the base-shaped portion 23 are both made of quartz, and the protrusion 24 is made of Ge.

[0227] The polarizers in Experimental Examples 2-1 to 2-5 all share the same shape: a width b of 100 nm and a spacing P of 141 nm, but their heights a are 50 nm, 70 nm, 90 nm, 110 nm, and 130 nm, respectively (resulting in tilt angles θ of 54°, 45°, 61°, 66°, and 69°, respectively). Furthermore, the protrusions 24 in Experimental Examples 1-1 to 1-4 all have a circular cross-section with a radius of 15 nm. Regarding the position of the protrusions 24 at the base shape portion 23, as... Figure 3 As shown, the outermost periphery of the circle is set to be the same as the height a and in contact with the inclined surface 23a.

[0228] Figure 30 This is a graph showing the average transmittance along the transmission axis for each wavelength band in the polarizers of Experimental Examples 2-1 to 2-5. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance along the transmission axis Tp (%). (Based on...) Figure 30 If the ratio of height a to width b (a / b) is preferably greater than 1 / 2, more preferably 7 / 10 or more, and 9 / 10, 11 / 10 and 13 / 10 are more preferred than 7 / 10.

[0229] [Experiment Examples 3-1 to 3-5]

[0230] The shapes of the polarizers in Experiment Examples 3-1 to 3-5 are as follows: Figure 3As shown. Regarding the materials of the polarizers in Experimental Examples 3-1 to 3-5, the transparent substrate 21 and the base shape portion 23 are both made of sapphire, and the protrusion portion 24 is made of Ge.

[0231] The polarizers in Experimental Examples 3-1 to 3-5 all share the same shape: a width b of 100 nm and a spacing P of 141 nm, but their heights a are 50 nm, 70 nm, 90 nm, 110 nm, and 130 nm, respectively (resulting in tilt angles θ of 54°, 45°, 61°, 66°, and 69°, respectively). Furthermore, the protrusions 24 in Experimental Examples 3-1 to 3-5 all have a circular cross-section with a radius of 15 nm. Regarding the position of the protrusions 24 at the base shape portion 23, as... Figure 3 As shown, the outermost periphery of the circle is set to be the same as the height a and in contact with the inclined surface 23a.

[0232] Figure 31 This is a graph showing the average transmittance along the transmission axis for each wavelength band in the polarizers of Experimental Examples 3-1 to 3-5. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance along the transmission axis Tp (%). (Based on...) Figure 31 In this case, the ratio of height a to width b (a / b) is preferably greater than 1 / 2, more preferably 7 / 10 or more, and 9 / 10, 11 / 10 and 13 / 10 are more preferred than 7 / 10. This is similar to the polarizers in experimental examples 2-1 to 2-5, showing that even if the material of the transparent substrate and the base shape portion is changed from quartz to sapphire, the relevant characteristics will not change.

[0233] [Experiment Examples 4-1 to 4-5]

[0234] The polarizers in Experiment Examples 4-1 to 4-5 have the following shapes: Figure 3 As shown. Regarding the materials of the polarizers in Experimental Examples 4-1 to 4-5, the transparent substrate 21 is made of sapphire, the substrate-shaped portion 23 is made of SiO2, and the protrusion portion 24 is made of Ge.

[0235] The polarizers in Experimental Examples 4-1 to 4-5 all share the same shape: a width b of 100 nm and a spacing P of 141 nm, but their heights a are 50 nm, 70 nm, 90 nm, 110 nm, and 130 nm, respectively (resulting in tilt angles θ of 54°, 45°, 61°, 66°, and 69°, respectively). Furthermore, the protrusions 24 in Experimental Examples 4-1 to 4-5 all have a circular cross-section with a radius of 15 nm. Regarding the position of the protrusions 24 at the base shape portion 23, as... Figure 3 As shown, the outermost periphery of the circle is set to be the same as the height a and in contact with the inclined surface 23a.

[0236] Figure 32This is a graph showing the average transmittance along the transmission axis for each wavelength band in the polarizers of Experimental Examples 4-1 to 4-5. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance along the transmission axis Tp (%). (Based on...) Figure 32 For the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm), a shape in which the ratio of height a to width b (a / b) exceeds 1 / 2 is preferred as it improves the transmittance along the transmission axis. Furthermore, for the entire visible light region, a shape in which a / b is 7 / 10 or higher improves the transmittance along the transmission axis is even more preferred. Additionally, for the entire visible light region, a shape with an a / b ratio of 9 / 10 or 11 / 10 and a shape with a ratio of 7 / 10 is even more preferred. Furthermore, for the green band (wavelength λ = 520 nm to 590 nm) and the blue band (λ = 430 nm to 510 nm), a shape in which a / b ratio of 13 / 10 and a shape with a ratio of 7 / 10 is even more preferred.

[0237] [Experiment Examples 5-1 to 5-5]

[0238] Regarding the shape of the polarizer in Experiment Examples 5-1 to 5-3, instead of... Figure 3 The transparent substrate 21 shown is a laminated plate consisting of a first substrate made of SiO2 and a second substrate made of sapphire. The substrate shape portion 23 is made of SiO2, and the protrusion portion 24 is made of Ge. In addition, regarding the polarizers of experimental examples 5-1 to 5-3, the thickness d1 of the first substrate is 35 nm, 70 nm, and 105 nm, respectively, and the thickness d2 of the second substrate is 0.7 mm.

[0239] In addition, the shape of the polarizer in Experiment Example 5-4 is as follows: Figure 3 As shown, the transparent substrate 21 is made of sapphire, the base-shaped portion 23 is made of SiO2, and the protrusion portion 24 is made of Ge. The thickness of the transparent substrate 21 is 0.7 mm.

[0240] In addition, the shape of the polarizer in Experiment Example 5-5 is as follows: Figure 3 As shown, the transparent substrate 21 and the base shape portion 23 are both made of sapphire, while the protrusion portion 24 is made of Ge. The thickness of the transparent substrate 21 is 0.7 mm.

[0241] Furthermore, in experimental examples 5-1 to 5-5, the protrusions 24 are all circular in cross-section with a radius of 15 nm. Regarding the position of the protrusions 24 at the base shape portion 23, as... Figure 3 As shown, the outermost periphery of the circle is set to be the same as the height a and in contact with the inclined surface 23a.

[0242] The simulation was conducted for the case where the incident light is incident from the substrate side.

[0243] Figure 33 This is a graph showing the average transmittance along the transmission axis for each wavelength band in the polarizers of Experimental Examples 5-1 to 5-5. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance along the transmission axis Tp (%). (Based on...) Figure 33 In Experimental Examples 5-1 to 5-2, where the transparent substrate is a two-layer laminate and the first substrate on the substrate-shaped portion side is made of the same material as the substrate-shaped portion, the polarizers exhibit improved transmission axis transmittance across the entire visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm) compared to the polarizers in Experimental Examples 5-4 and 5-5, where the transparent substrate is a single layer. Furthermore, the polarizer in Experimental Example 5-3 also exhibits improved transmission axis transmittance in the green and blue bands compared to the polarizers in Experimental Examples 5-4 and 5-5, where the transparent substrate is a single layer. Therefore, from the viewpoint of improving transmission axis transmittance, it is preferable to use a transparent substrate that is a two-layer laminate and where the first substrate on the substrate-shaped portion side is made of the same material as the substrate-shaped portion.

[0244] <4. Example of the second experiment>

[0245] In the second experimental example, the optical properties of the output-side main polarizer were verified.

[0246] [simulation]

[0247] As the polarizer involved in this technology, Figure 5 The polarizers shown were used as models for simulation. More specifically, the optical properties of these polarizers were verified by electromagnetic field simulations based on the RCWA (Rigorous Coupled Wave Analysis) method.

[0248] Figure 34 It shows that Figure 5 The graph shown is a distribution of the beam pattern of transmission axis transmittance in the visible light region (red band: wavelength λ = 600 to 680 nm; green band: wavelength λ = 520 nm to 590 nm; blue band: λ = 430 nm to 510 nm) obtained by simulating the polarizer as a model. The horizontal axis represents wavelength λ (nm), and the vertical axis represents transmission axis transmittance (%). Here, transmission axis transmittance means the transmittance of polarized light (TM wave) incident on the transmission axis (X-axis direction) of the polarizer.

[0249] In the polarizer model, the following parameters and materials are used.

[0250] Transparent substrate: Material (alkali-free glass), thickness (0.7mm);

[0251] Reflective layer: material (Al), thickness (250nm), width (35nm);

[0252] Dielectric layer: material (SiO2), thickness (5nm), width (35nm);

[0253] Absorber layer: Material (FeSi), thickness (25nm), width (35nm);

[0254] Anti-reflective layer: The material (alternating layers of TiO2 / SiO2), thickness (641.15 nm), and width (35 nm) are shown in Table 6. The first to ninth layers are arranged sequentially from the side closest to the transparent substrate to the side furthest from the transparent substrate.

[0255] Grid: Height h (280 + protective film thickness) nm, Width w (35 + protective film thickness × 2) nm, Spacing p (141 nm).

[0256] [Table 6]

[0257] Constituent materials Film thickness(nm) First layer <![CDATA[SiO2]]> 170.99 Second floor <![CDATA[TiO2]]> 12.76 Third layer <![CDATA[SiO2]]> 33.72 Fourth floor <![CDATA[TiO2]]> 121.52 Fifth floor <![CDATA[SiO2]]> 36.77 Sixth floor <![CDATA[TiO2]]> 25.13 Seventh floor <![CDATA[SiO2]]> 39.09 Eighth floor <![CDATA[TiO2]]> 114.39 Ninth floor <![CDATA[SiO2]]> 86.78 total 641.15

[0258] Additionally, in the polarizer model, regarding the protective film ( Figure 5 Using symbols 44A and 44B, the material was set to Al2O3, and the film thickness was set to 1 nm, 2.5 nm, 5 nm, 7.5 nm, and 10 nm. Additionally, as a comparative experimental example, simulations were also performed without a protective film. Figure 34 As shown in the image.

[0259] Protective films can improve the durability of polarizers, but from... Figure 34 It can be seen that as the film thickness increases, the overall transmittance of the transmission axis decreases in the visible light region, especially the drop on the short wavelength side becomes larger.

[0260] [Experimental Examples 1 to 3, Comparative Experimental Examples]

[0261] The protective film was set to 2.5 nm (Experimental Example 1), 5 nm (Experimental Example 2), and 7.5 nm (Experimental Example 3). Other parameters used in the above simulations were employed to actually fabricate polarizers, and the transmittance along the transmission axis was measured. Figure 35 The results are shown in the figure. Additionally, for polarizers without a protective film (comparative experimental example), the transmittance along the transmission axis was also measured, and... Figure 35 The results are shown in the figure. It can be seen that... Figure 34 The simulation results shown reflect the optical characteristics of the actual polarizer quite well.

[0262] If based on Figure 34 and Figure 35 As a result, when it is required that the transmission axis transmittance be 80% or more across the entire wavelength range of 400 nm to 700 nm, the thickness of the protective film is set to 5 nm or less. Furthermore, when it is required that the transmission axis transmittance be 80% or more across the entire wavelength range of 430 nm to 700 nm, the thickness of the protective film is set to 10 nm or less.

[0263] Figure 36 This is a graph showing the average transmittance of the transmission axis for each wavelength band obtained from simulations. Figure 37 This is a graph showing the average transmittance of the transmission axis for each wavelength band, which was actually measured for the polarizers of Experimental Examples 1 to 3 and the Comparative Experimental Examples. Figure 37 As shown in the chart, Figure 36 The simulation results shown reflect the optical characteristics of the actual polarizer quite well.

[0264] If based on Figure 36 and Figure 37 If the average transmission axis transmittance is required to be 86% or higher across the entire red, green, and blue bands, the thickness of the protective film should be 5 nm or less. Alternatively, if the average transmission axis transmittance is required to be 90% or higher across the entire red, green, and blue bands, the thickness of the protective film should be 2.5 nm or less.

[0265] The polarizer described in this technology was used as an example, and the heat resistance of an actual fabricated polarizer was evaluated. Furthermore, the heat resistance evaluation was conducted at 300°C in a cleanroom oven. The contrast ratio, as an optical characteristic of the polarizer, was evaluated as the rate of change from its initial characteristics, i.e., from when it was placed in the cleanroom oven. Contrast ratio is a value that can be calculated as the transmittance along the transmission axis / the transmittance along the absorption axis. The transmittance along the absorption axis means the transmittance of polarized light (TE wave) incident on the polarizer along the absorption axis direction (Y-axis). The rate of change in contrast ratio is suitable for capturing the effect on the heat resistance of the polarizer.

[0266] Figure 38 This is a chart comparing the contrast in optical properties through actual fabrication and heat resistance evaluation. The horizontal axis shows the test time (time already configured in a cleanroom oven), and the vertical axis shows the rate of change in contrast, using incident light in the green band of the visible light region (wavelength = 520 nm to 590 nm) as an example. Figure 38 The results are also shown in the case of not having a protective film.

[0267] like Figure 38 As shown, as the protective film thickens, the rate of change in contrast decreases, thus improving the durability of the polarizer. Furthermore, while an example is given using green wavelength light, the same effect can be achieved even with red wavelength light (wavelength = 600 to 680 nm) or blue wavelength light (wavelength = 430 nm to 510 nm), as long as the value of the rate of change in contrast varies slightly. Figure 38 The results show that if the thickness of the protective film is set to 2.5 nm or more, high heat resistance can be maintained.

[0268] The results above show that the polarizer of this technology, which has protective films on the surfaces of the protrusions and the anti-reflective layer, maintains durability while simultaneously improving light transmission characteristics. Specifically, a film thickness of 2.5 nm or less is ideal as it does not significantly degrade optical properties, while a film thickness of 2.5 nm or more is ideal as it maintains high heat resistance. Furthermore, when forming the protective film, it is preferable to design both the protective film and the anti-reflective layer considering not only their effects on the multiple protrusions but also their effects on the anti-reflective layer.

[0269] Symbol Explanation

[0270] 10 Optical instrument, 11 Light source, 12 Incident-side polarizing element, 13 Light modulation element, 14 Outgoing-side first polarizing element, 15 Outgoing-side second polarizing element, 20 Polarizer, 21 Transparent substrate, 21a Main surface, 22 Protrusion, 23 Base-shaped portion, 24 Protrusion, 30 Polarizer, 31 Transparent substrate, 31a Main surface, 32 Protrusion, 33 Base-shaped portion, 34 Protrusion, 40 Polarizer, 41 Transparent substrate, 41a First surface, 41b Second surface, 42 Protrusion 42A Reflective layer, 42B Dielectric layer, 42C Absorbing layer, 43 Anti-reflective layer, 44A, 44B Protective film, 50 Liquid crystal projector, 51R, 51G, 51B Incident side polarizing element, 52R, 52G, 52B Liquid crystal panel, 53R, 53G, 53B Outgoing pre-polarizing element, 54R, 54G, 54B Outgoing main polarizing element, 100 Polarizing film, 101 Transparent substrate, 102 Protrusion, 103 Base shape part, 104 Protrusion.

Claims

1. An optical instrument comprising a light source, an incident-side polarizing element, a light modulation element, an exit-side first polarizing element, and an exit-side second polarizing element, wherein, The first polarizing element on the emission side has a wire grid structure and a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of light used in the light source band. The protrusions are lattice-shaped protrusions extending along a predetermined direction. Starting from the transparent substrate side, the lattice-shaped protrusions sequentially have a base shape portion formed in such a way that the width of the cross section orthogonal to the predetermined direction becomes thinner towards the front end, and a protrusion portion protruding from the base shape portion and having absorbent properties for the wavelength of light used in the band. The second polarizing element on the emission side has a wire grid structure and a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of light used in the light source band. The protrusions are lattice-shaped protrusions extending in a predetermined direction, and the lattice-shaped protrusions sequentially have a reflective layer, a dielectric layer, and an absorption layer from the transparent substrate side. The rotation angle of the orthogonal axis of the first polarizing element on the output side relative to the orthogonal axis of the polarizing element on the incident side is within ±8.5°. The rotation angle of the orthogonal axis of the second polarizing element on the outgoing side relative to the orthogonal axis of the polarizing element on the incoming side is within ±0.7°.

2. The optical instrument according to claim 1, wherein, When the rotation angle of the first polarizing element on the output side relative to the orthogonal axis of the polarizing element on the incident side is within ±8.5°, the P-polarized light transmittance in the entire visible light region is above 95%, and the change in P-polarized light transmittance in the entire visible light region from the position of 0° rotation angle is below -1%.

3. The optical instrument according to claim 1, wherein, When the rotation angle of the second polarizing element on the output side relative to the orthogonal axis of the polarizing element on the incident side is within ±0.7°, the contrast ratio of the entire visible light region is greater than 1000, and the change in the contrast ratio of the entire visible light region from the position of 0° rotation angle is less than -20%.

4. The optical instrument according to claim 1 or 2, wherein, The second polarizing element on the emission side also has an anti-reflective layer on the other side of the transparent substrate.

5. The optical instrument according to claim 4, wherein, The surface of the protrusion in the second polarizing element on the emission side and the surface of the antireflective layer are covered by a protective film made of dielectric material.

6. The optical instrument according to claim 5, wherein, The thickness of the protective film in the second polarizing element on the emission side is less than 10 nm.

7. The optical instrument according to any one of claims 1 to 6, wherein, The base shape portion of the first polarizing element on the emission side is approximately triangular in a cross section orthogonal to the predetermined direction.

8. The optical instrument according to any one of claims 1 to 7, wherein, The first polarization element on the emission side is provided with a phase difference compensation element on the other side of the transparent substrate.

9. The optical instrument according to any one of claims 1 to 8, wherein, The protrusion in the first polarizing element on the output side is made of a material selected from the group consisting of metals, alloys and semiconductors that is absorbent for the wavelength of light used in the band of light.

10. A method for manufacturing an optical instrument, comprising a light source, an incident-side polarizing element, a light modulation element, an exit-side first polarizing element, and an exit-side second polarizing element, wherein, The first polarizing element on the emission side has a wire grid structure and a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of light used in the light source band. The protrusions are lattice-shaped protrusions extending along a predetermined direction. Starting from the transparent substrate side, the lattice-shaped protrusions sequentially have a base shape portion formed in such a way that the width of the cross section orthogonal to the predetermined direction becomes thinner towards the front end, and a protrusion portion protruding from the base shape portion and having absorbent properties for the wavelength of light used in the band. The second polarizing element on the emission side has a wire grid structure and a plurality of protrusions arranged separately on one side of the transparent substrate at a spacing shorter than the wavelength of light used in the light source band. The protrusions are lattice-shaped protrusions extending in a predetermined direction, and the lattice-shaped protrusions sequentially have a reflective layer, a dielectric layer, and an absorption layer from the transparent substrate side. The method for manufacturing the optical instrument includes: The process of arranging the first polarizing element on the exit side such that the rotation angle of the orthogonal axis of the first polarizing element on the exit side relative to the orthogonal axis of the first polarizing element on the incident side is within ±8.5°; and The process of arranging the second polarizing element on the emission side such that the rotation angle of the orthogonal axis of the second polarizing element on the emission side relative to the orthogonal axis of the polarizing element on the incident side is within ±0.7°.

11. The optical instrument according to any one of claims 1 to 9, wherein, The optical instrument is a transmissive liquid crystal projector.

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