Wire grid type polarizing element and manufacturing method thereof

Abstract

The invention provides a wire grid type polarized light element which has excellent polarization degree and high polarized light transmittance in the vertical direction, and a manufacturing method thereof. A wire grid type polarizing element includes: a base material formed so that a transparent sheet surface has a continuous wave-shaped cross-section; a conductor protruding portion that continuously protrudes in the tip direction in a direction perpendicular to the arrangement direction at the tip portion of the wave-shaped shape; and a conductor layer covering the surface portion other than the tip portion, in which the cycle (a) of the wave shape is 100-400 nm, the average depth (b) of the wave shape from the tip portion of the convex portion to the valley portion of the concave portion is 200-600 nm, and the average depth (b) of the wave shape from the tip portion of the convex portion to the valley portion of the concave portion is 200-600 nm. The average occupancy ([2d / a] * 100) of the conductor layers, which is the ratio of the average width (d) in the arrangement direction of two conductor layers present in one cycle to the cycle (a), is 18%-40%, and the average thickness (h) in the tip direction of the conductor protrusions is 1.5 times or more of the average width (d) of the conductor layers.

Description

Technical Field

[0001] The present invention relates to a wire grid type polarizing element and a method for manufacturing the same, which can be applied to the field of optical products such as displays, cameras, sunglasses, and optical measurement devices that utilize electromagnetic waves such as visible light and near-infrared rays. Background Art

[0002] The wire grid type polarizing element utilizes the following property: a layer in which linear objects made of metal or the like are arranged in stripes at a specific period is included in a substrate, and if this period is sufficiently small compared to the wavelength of the incident electromagnetic wave (light), light with an electric field component parallel to the linear objects is reflected or absorbed, and light with an electric field component perpendicular to the linear objects is transmitted. The wire grid type polarizing element is characterized by excellent optical properties and high durability capable of exhibiting a polarizing function in a wide wavelength range from visible light to near-infrared rays.

[0003] In Patent Document 1 described below, a wire grid type polarizing plate and a method for manufacturing the same are disclosed. In this wire grid type polarizing plate, on a base layer composed of the top of the ridges of a transparent substrate having an uneven structure and a metal oxide layer formed on the entire side surface thereof, a metal thin wire composed of a metal layer is formed on at least the top of the ridges and further on more than 70% of the area of the side surface of the ridges by an inclined evaporation method using a vacuum evaporation method.

[0004] In Patent Document 2 described below, a wire grid polarizing element having excellent polarization characteristics and a method for manufacturing the same are disclosed. This wire grid polarizing element is obtained by the following method: particles are incident from an inclined direction onto the uneven structure surface of a grid structure layer of a transparent substrate having a one-dimensional lattice-like uneven structure by a dry process such as sputtering or vacuum evaporation, and an Al—Si alloy layer having a Si content of 0.05 wt% to 1.5 wt% is formed on the convex portions of the uneven structure.

[0005] In Patent Document 3 described below, an optical functional body and a method for manufacturing the same are disclosed. This optical functional body has a filling layer formed by filling the concave portions of a substrate having a fine uneven pattern with particles having a particle diameter smaller than the width of the concave portions of the uneven pattern by an electroless plating method. Generally, in a wire grid type polarizing plate, it is known that the transmittance is increased by periodically thinning the width of the conductive wire, and the light shielding performance of light with an electric field component parallel to the wire is improved by increasing the thickness of the conductive wire (see Non-Patent Document 1). Therefore, Patent Document 3 shows that if a nanoimprint method is used in the formation of the uneven structure body, it can be manufactured at low cost.

[0006] A polarization separation element composed of a triangular-wave-shaped metal thin film is disclosed in Patent Document 4. In a structure composed of a triangular-wave-shaped metal thin film having periodicity in one of two orthogonal directions, being the same in the other direction, and continuously repeating with a certain period of less than the wavelength in the cross-sectional shape along the one direction, when the period is set as Λ, the depth of the groove in the cross-sectional triangular wave shape is set as h, the thickness of the metal thin film in the depth direction of the groove in the cross-sectional triangular wave shape is set as d, and the minimum wavelength in the used wavelength region is set as λmin, the conditions of Λ / λmin < 0.5, h > 1.5Λ, and d > 0.010 μm are satisfied. That is, regarding the shape of the above metal thin film, the upper limit of the above period Λ, and the lower limits of the depth h of the groove and the thickness d of the metal thin film are disclosed. Prior Art Documents Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5459210 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2009-204894 Patent Document 3: Japanese Patent No. 6042642 Patent Document 4: Japanese Patent No. 4650931 Non-Patent Documents

[0008] Non-Patent Document 1: Low-reflective wire-grid polarizers with an absorptive layer formed by glancing angle deposition, Journal of Imaging Science and Technology, Vol. 65, No. 10, pp. 1440-1445 (2011) Summary of the Invention Problems to be Solved by the Invention

[0009] In the invention disclosed in the above Patent Document 1, when forming metal fine lines composed of a metal layer on the top and side surfaces of the ridges of a substrate by vapor deposition, the crystallization of the metal material inhibits the generation of minute metal particles, and thus a base layer composed of a metal oxide layer is provided to prevent the transmittance of incident light of the polarization element from decreasing. In addition, in order to also form a metal layer on a part of the side surface of the ridge by oblique vapor deposition, there is a limitation that the value of the height of the ridge from the bottom surface of the concave part to the top of the convex part of the uneven shape cannot be increased. For example, in Examples 1 to 11 corresponding to the examples in the specification of Patent Document 1, the height of the ridge is about 100 nm, and accordingly, the thickness of the metal layer formed on the convex top for improving the degree of polarization also increases. Therefore, there are limitations in the uneven structure formed on the base material.

[0010] The problem of the invention disclosed in the above Patent Document 2 is to solve the following problem: When pure aluminum (Al) is used as the metal constituting the wire grid, the pure Al particles on the convex portions formed on the substrate by a dry process are not refined, so that the polarization characteristics as designed cannot be obtained. To solve this problem, an Al-Si alloy with a Si content of 0.05 wt% to 1.5 wt% is used as the metal constituting the wire grid to refine the particles formed on the convex portions and improve the polarization characteristics. However, the situation where the invention disclosed in Patent Document 2 can be applied is limited to the case where an Al-based metal is formed on a substrate by a dry process as the metal constituting the wire grid.

[0011] The degree of polarization of the wire grid polarizer manufactured by the electroless plating method described in the above Patent Document 3 is less than 90%. In order to increase the degree of polarization while maintaining the transmittance, it is necessary to increase the aspect ratio (thickness to width ratio) of the concave portions filled with the conductor. However, in this case, it may cause damage to the mold used to form the concavo-convex shape on the substrate and collapse of the concavo-convex structure body. Therefore, there are practical limitations when increasing this aspect ratio.

[0012] The case where a polarization function is expressed in a structure body using a metal thin film having a triangular wave shape in cross section is disclosed in the above Patent Document 4. However, regarding the determination of the shape of the metal thin film, only the upper limit value of the period with respect to the wavelength region used, the lower limit value of the height of the triangular wave shape with respect to the period, and the lower limit value of the thickness of the metal thin film are disclosed. In the examples of this document Figure 1 、 Figure 3 a metal thin film with a period of 0.12 μm, a height (h) of 0.30 μm, and a thickness (d) in the depth direction of 0.03 μm is disclosed. However, the thickness in the direction perpendicular to the surface of the metal thin film is relatively thin, and the width of the metal thin film in the period direction with respect to the period is also small. Therefore, its polarization characteristics are that in the wavelength region of 0.40 μm to 0.70 μm used, the reflected S-polarized light is about 70% to 75%, and the transmitted P-polarized light is about 60% to 80%. Therefore, further research is required to obtain a structure body with a high degree of polarization. In addition, as a method for manufacturing a metal thin film, a method of laminating a metal thin film on a transparent substrate and a method of removing the transparent substrate from the metal thin film laminated on the transparent substrate to support the metal thin film on a rectangular frame, etc. are disclosed. However, it is not easy to manufacture a thin film with a large amplitude and a triangular wave shape of the thin film, and its top end may be damaged. In addition, removing the substrate from the metal thin film laminated on the substrate may be accompanied by practical difficulties.

[0013] In any of the above patent documents or the like, a wire-grid polarizing element having a high transmittance and excellent polarization degree by disposing a conductor layer made of various conductive materials on a substrate having a shape that can be stably manufactured, and a method for manufacturing the same are unknown. The present invention has been completed in view of this, and an object thereof is to provide a wire-grid polarizing element that exhibits a high polarization degree and a relatively high single transmittance (visual transmittance of polarized light in a direction perpendicular to incident light) and can be manufactured inexpensively and stably, and a method for manufacturing the same. Solution for Solving Technical Problems

[0014] In view of the above prior art, the inventors have found the following situation and completed the present invention: On the surface of a substrate formed by making the surface of a transparent sheet into a waveform shape in which the cross-sectional shape along the arrangement direction of the concavo-convex pattern is continuous, and the period and the depth from the top of the convex portion to the bottom of the concave portion in the concavo-convex pattern are within a specific range, a conductor layer covering the surface portion other than the top of the convex portion of the concavo-convex pattern is formed such that the ratio of the width in the above arrangement direction of two conductor layers existing in one period, that is, the occupancy rate of the conductor layer, is within a specific range, and the average thickness of the conductor protrusion provided at the top of the convex portion of the concavo-convex pattern is a certain multiple or more with respect to the width in the arrangement direction of the conductor layer. The wire-grid polarizing element thus formed maintains excellent polarization degree and high light transmittance. In addition, the above wire-grid polarizing element can be manufactured relatively easily without a process of removing local conductors even when using a general conductor forming method. That is, the gist of the present invention lies in the inventions described in the following (1) to (8).

[0015] (1) A wire-grid polarizing element, comprising: a substrate having a periodic concavo-convex pattern formed on the surface of a transparent sheet, the concavo-convex pattern being a waveform shape in which the cross-sectional shape along its arrangement direction is continuous; and a conductor protrusion formed by further protruding from the top of each convex portion extending in the longitudinal direction in the concavo-convex pattern toward the top direction, and a conductor layer covering the surface portion other than the top of the convex portion, wherein the wire-grid polarizing element is characterized in that the period (a) of the concavo-convex pattern on the substrate surface is 100 nm to 400 nm, the average depth (b) from the top of the convex portion to the bottom of the concave portion of the concavo-convex pattern on the substrate surface is 200 nm to 600 nm, The average occupancy of the conductor layer ([2d / a]×100), as indicated by the ratio of the average width (d) in the arrangement direction of the two conductor layers within each period to the period (a), is 18% to 40%. The average thickness (h) in the top direction of the conductor protrusion provided at the top of the convex portion of the concavo-convex pattern is 1.5 times or more the average width (d) in the arrangement direction of the conductor layer.

[0016] (2) The wire grid polarizing element according to (1) above, wherein the average thickness (h) in the top direction of the conductor protrusion provided at the top of the convex portion of the concavo-convex pattern provided on the surface of the substrate is 1.5 times or more and 5 times or less the average width (d) in the arrangement direction of the conductor layer. (3) The wire grid polarizing element according to (1) or (2) above, wherein the average width (d) in the arrangement direction of the conductor layer of the surface portion of the concavo-convex pattern provided on the surface of the substrate other than the top of the convex portion is 14 nm to 70 nm. (4) The wire grid polarizing element according to any one of (1) to (3) above, wherein the continuous waveform shape in the cross-sectional shape along the arrangement direction formed on the surface of the substrate is a triangular waveform shape composed of continuous substantially isosceles triangle shapes.

[0017] (5) The wire grid polarizing element according to any one of (1) to (4) above, wherein the cross-sectional shape in the arrangement direction of the conductor protrusion protruding in the top direction at the top of the convex portion of the concavo-convex pattern provided on the surface of the substrate is a substantially rectangular shape, a top-tapering shape, a top-thickening shape, or a substantially longitudinal elliptical shape. (6) The wire grid polarizing element according to any one of (1) to (5) above, wherein the conductor material forming the conductor protrusion and the conductor layer is one or more selected from aluminum, gold, silver, copper, platinum, molybdenum, nickel, chromium, titanium, tungsten, tantalum, zirconium, iron, niobium, hafnium, cobalt, palladium, bismuth, and neodymium, or an alloy composed of two or more of them.

[0018] (7) A method for manufacturing a wire grid polarizing element, comprising forming, on the surface of a substrate, a conductor protrusion that further protrudes in the top direction at the top of each convex portion formed by extending along the length direction in a concavo-convex pattern, and a conductor layer that covers the surface portion other than the top of the convex portion, wherein the substrate has the periodic concavo-convex pattern formed on the surface of a transparent sheet, and the concavo-convex pattern is a continuous waveform shape in the cross-sectional shape along its arrangement direction, and the method for manufacturing the wire grid polarizing element is characterized in that On the surface of a substrate where the period (a) of the concavo-convex pattern on the substrate surface is 100 nm to 400 nm and the average depth (b) from the top of the convex portion to the bottom of the concave portion of the concavo-convex pattern on the substrate surface is 200 nm to 600 nm, by physical vapor deposition of introducing a vapor deposition material from above in a direction perpendicular to the substrate surface, or by a chemical plating method in which catalyst imparting and activation are performed using a liquid containing tin ions (Sn 2+ ), and a liquid containing palladium ions (Pd 2+ ) and then chemical plating is performed, a conductor layer is formed such that the average occupancy rate ([2d / a]×100) of the conductor layer, which is shown by the ratio of the average width (d) in the arrangement direction of the two conductor layers existing in one period to the period (a), is 18% to 40%, and a conductor protrusion is provided at the top of the convex portion of the concavo-convex pattern, and the average thickness (h) in the top direction of the conductor protrusion is 1.5 times or more the average width (d) in the arrangement direction of the conductor layer. (8) According to the method for manufacturing a wire grid polarizing element as described in (7) above, the physical vapor deposition method is any one of a vacuum vapor deposition method, an electron beam vapor deposition method, or a sputtering method. Advantages of the Invention

[0019] In the wire grid polarizing element of the present invention, regarding the substrate, the period (a) of the concavo-convex pattern in the waveform shape on its surface and the average depth (b) from the top of the convex portion to the bottom of the concave portion are set to a certain shape, Regarding the conductor disposed on the substrate surface, by setting the ratio (2d / a) of the period (a) and the average width (d) of the conductor layer except at the top of the convex portion to a certain range, the degree of polarization can be improved. And by setting the ratio (h / d) of the thickness (h) in the top direction of the conductor protrusion provided at the top of the convex portion to a certain value with respect to the average width (d) of the conductor layer, the degree of polarization can be further improved, and the necessary light transmittance can be maintained. In addition, compared with a structure having a rectangular cross-sectional shape of the concavo-convex structure, in the polarizing element having a waveform shape as the concavo-convex structure of the present invention, even for a structure having the same depth (thickness), the width gradually changes in the thickness direction. Therefore, structural failure due to peeling of the conductor layer is less likely to occur, and by selecting the material used in the substrate sheet, a wire grid polarizing element excellent in environmental resistance, flexibility, and stretchability can be easily obtained.

[0020] In the manufacturing method of the wire grid type polarization element with a corrugated cross-sectional shape according to the present invention, when forming the substrate, molding methods such as film insert molding, casting molding, and injection molding can also be used. Therefore, a three-dimensional curved surface molded product capable of extracting a specific polarization component can also be realized. In addition, when disposing a conductor on a substrate having a corrugated structure on the surface, general film forming apparatuses such as vacuum evaporation, electron beam evaporation, and sputtering, which are ordinary physical vapor deposition methods, and electroless plating can be used. Therefore, by combining these processes, commercial production becomes relatively easy, and an expansion of the market for applications to optical members and the like can be expected. In addition, this is a manufacturing method in which void-like defects are rarely generated even in post-treatment processes such as hard coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a conceptual diagram for explaining an example of the wire grid type polarization element of the present invention. (1) is a perspective view, (2) is a cross-sectional view, and (3) is an enlarged view of part A in the above-mentioned figure (2). Figure 2 It is a conceptual diagram for explaining the conductor occupancy rate in three cross-sections of the wire grid type polarization element of the present invention. (1) is a longitudinal cross-sectional view showing the positions of the three cross-sections, (2) is a cross-sectional view taken along line B-B, (3) is a cross-sectional view taken along line C-C, and (4) is a cross-sectional view taken along line D-D. Figure 3 It is a conceptual diagram of a cross-section showing another example of the wire grid type polarization element of the present invention. Figure 4 It is a conceptual diagram of a cross-section showing another example of the wire grid type polarization element of the present invention. Figure 5 It is a conceptual diagram of a cross-section showing an example in which a base layer is provided in the wire grid type polarization element of the present invention. Figure 6 It is a conceptual diagram of a cross-section showing an example in which a coating layer is provided in the wire grid type polarization element of the present invention. Figure 7 It is a cross-sectional view schematically showing examples of the manufacturing processes (1) to (4) of the wire grid type polarization element of the present invention. Figure 8 It is an image (SEM image) obtained by observing a cross-section of the mold produced in Example 1 with a scanning electron microscope (SEM). Figure 9 It is an SEM image of a cross-section of the polarization element test piece of the present invention produced in Example 1-1. Figure 10 It is an SEM image of a cross-section of the polarization element test piece of the present invention produced in Example 3. Figure 11 It is an SEM image of a cross-section of the polarization element test piece of the present invention produced in Example 4-2. Figure 12 In Reference Example 1 and Reference Example 2, they are cross-sectional views of models of polarization elements with (1) a rectangular shape, (2) a trapezoidal shape, and (3) a triangular wave shape, which are referred to in the numerical calculation of optical properties. Figure 13 It is a graph showing the numerical calculation results of the optical properties of the polarization element of Reference Example 1. Figure 14 They are model diagrams used in the numerical calculation of the optical properties of each of the triangular wave-shaped polarization elements (1), (2), and (3) in Reference Example 3. Figure 15 It is an SEM image of the cross-section of the mold fabricated in Comparative Example 1. Figure 16 It is an SEM image of the cross-section of the polarization element test piece fabricated in Comparative Example 1. Detailed implementation manners

[0022] Hereinafter, the present invention will be described by dividing it into (1) a wire grid type polarization element and (2) a manufacturing method of the wire grid type polarization element. (1) Wire grid type polarization element Each element and structure constituting the wire grid type polarization element of the present invention will be described. In addition, in the wire grid type polarization element of the present invention, the shape of the conductor is not the so-called "linear shape", but in this technical field, the term "wire grid type polarization element" is also used when the metal reflector is not linear, so the term wire grid type polarization element is used.

[0023] Hereinafter, embodiments of the wire grid type polarization element of the present invention will be described with reference to the drawings. Figure 1 (1) is a perspective view showing an example of the wire grid type polarization element 11 of the present invention, on the surface of which a conductor layer 25 and conductor protrusions 26 are formed, Figure 1 (2) is a cross-sectional view along the arrangement direction of the concavo-convex pattern, Figure 1 (3) is Figure 1 (2) is a partial enlarged view of part A in Figure 1 (2) and Figure 1The period (a) of the concavo-convex pattern in the base material 21, the depth (b) from the top of the convex portion 22 to the bottom of the concave portion 23, the average thickness (c) in the direction perpendicular to the surface of the conductor layer 25 in the wire grid polarizing element 11, the average width (d) in the arrangement direction of the conductor layer 25, the average width (e) of the conductor protrusion 26 provided at the top of the convex portion 22, and the average thickness (h) in the top direction of the conductor protrusion 26 shown in (3) are also commonly used in other embodiments.

[0024] [Base material] The base material 21 constituting the wire grid polarizing element of the present invention is formed as Figure 1 shown, so that the surface of the transparent sheet becomes a continuous wave shape in a cross section along the arrangement direction of the periodic concavo-convex pattern. The period (a) of the concavo-convex pattern of the wave shape on the surface of the base material 21 is 100 nm to 400 nm, and the average depth (b) of the concavo-convex pattern from the top of the convex portion 22 to the bottom of the concave portion 23 is 200 nm to 600 nm.

[0025] As Figure 1 shown in (1) of Figure 1 and (2) of Figure 1 shown, a convex top portion 22 and a concave portion 23 are provided on the surface side of the base material 21. In such a wave shape, a slope shape is formed with respect to the direction of light incident from above in a direction perpendicular to the base material surface. Therefore, when a conductive material layer is formed on the surface of the base material having such a shape as described later, an improvement in polarization degree can be expected. As a specific example of the wave shape, as shown in (2) of Figure 1 , it is preferably a triangular wave shape in which the wave shape portion of the base material 21 is composed of continuous substantially isosceles triangles. On the other hand, even in the case of a shell shape, a sine wave shape, as shown in the base material 41 in Figure 3 , and a shape in which the wave shape portion of the base material, as shown in the base material 42 in Figure 4 , is a part of the concavo-convex structure and has a portion parallel to the depth direction, such as a countersunk thread shape without thread teeth, etc., the effects of the present invention can also be expected to be exerted. In addition, the cross-sectional shapes of the two inclined surfaces between the convex portion and the concave portion existing within one period may not be the same, and may be a cross-sectional shape in which one is a triangular wave shape and the other is a sine wave shape.

[0026] The average period (a) of the concavo-convex pattern formed on the surface of the above base material is usually not more than the wavelength of the incident electromagnetic wave as the object. Therefore, when mainly targeting the visible light region, the average period (a) of the polarizing element in the present invention is selected from the range of 100 nm to 400 nm, preferably 100 nm to 200 nm. The depth (b) of the concavo-convex pattern on the substrate surface, that is, the depth (b) from the top end portion 22 of the convex portion to the valley portion of the concave portion 23 as shown in (2) of Figure 1 also depends on the physical property values of the material of the conductor, but from the viewpoints of ease of production, durability, etc. of the substrate, it suffices to be 0.1 times or more of the wavelength of the electromagnetic wave as the object, preferably about 0.5 times to 1 time. However, considering the improvement of the degree of polarization, the depth (b) of the concavo-convex pattern is selected from the range of 200 nm to 600 nm. In addition, in Reference Example 2 described later, taking the shape model of (1) of Figure 12 as the object, using numerical calculation based on the rigorous coupled-wave analysis method, the changes in the optical properties (degree of polarization and monomer transmittance (visual transmittance of polarized light in the direction perpendicular to the incident light)) when the depth (b) of the concavo-convex structure increases in the range of 200 nm to 1000 nm are calculated. As a result, as shown in Table 4, it is also confirmed by numerical calculation that the degree of polarization increases as the depth (b) increases. In addition, from the viewpoints of formability when manufacturing the substrate, mechanical strength as a polarization element, etc., the depth (b) is preferably 600 nm or less.

[0027] The substrate 21 used in the wire grid type polarization element of the present invention may be any material that is transparent to electromagnetic waves having wavelengths such as in the visible light region and the infrared region. For example, amorphous thermoplastic resins such as polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin polymer resin, crosslinked polyethylene resin, polyvinyl chloride resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polyethersulfone resin, polysulfone resin, polyether ketone resin; crystalline thermoplastic resins such as polyethylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal resin, polyamide resin; ultraviolet curable resins and thermosetting resins such as acrylic, epoxy, and polyurethane systems; organic substrates such as triacetate resin; inorganic substrates such as glass, silicon, quartz, and ceramic materials. In addition, considering stretching processes such as bending processing, such a substrate is preferably a single layer, but may also be a multilayer.

[0028] [Wire grid type polarization element] As Figure 1As shown, in the wire grid type polarization element 11 of the present invention, on the surface of the base material 21 having a waveform shape in the above cross-section, there are provided: a conductor protrusion 26 formed by further protruding from the top end portion 22 of each convex portion formed by extending along the length direction in the concavo-convex pattern toward the top end direction; and a conductor layer 25 covering the surface portion except the top end portion of the convex portion. The average occupancy rate ([2d / a]×100) of the conductor layer 25, shown by the ratio of the average width (d) in the arrangement direction of the two conductor layers 25 existing within one period to the period (a), is 18% to 40%. The average thickness (h) in the top end direction of the conductor protrusion 26 provided at the top end portion 22 of the convex portion is 1.5 times or more the average width (d) in the period direction of the conductor layer.

[0029] In Reference Example 1 described later, referring to Figure 12 (1) to Figure 12 the shape model of the polarization element shown in (3) of, numerical calculations based on the rigorous coupled wave analysis method were performed on the change in optical characteristics when the shape variation (s) becomes large. However, in Figure 12 the case where the cross-section shown in (1) of is rectangular, the displacement (s) becomes 0 nm. If the displacement (s) is increased, then Figure 12 the cross-section shown in (2) of becomes trapezoidal. If the displacement (s) is further increased, then Figure 12 the cross-section shown in (3) of becomes triangular wave-shaped and the displacement (s) becomes 70 nm. As shown in Table 3, it was confirmed by numerical calculation that if the amount of displacement (s) is increased, the monomer transmittance increases. Except for the top end portion 22 of the convex portion of the concavo-convex pattern, the conductor layer 25 provided to cover the surface of the base material is preferably formed to have a substantially uniform thickness, but it may also be formed to be thicker on the side of the top end portion 22 of the convex portion than on the side of the concave portion 23, or may be formed to be thinner on the side of the top end portion 22 of the convex portion than on the side of the concave portion 23, and there may be some deviation in the film thickness.

[0030] In each layer in the traveling direction of the electromagnetic wave, that is, in the direction from the top end portion 22 of the convex portion of the concavo-convex structure toward the concave portion 23, Figure 1 the average width (d) in the arrangement direction of the conductor layer 25 shown in (3) of, or the average thickness (c) in the direction perpendicular to the surface, can be selected from the range of about 0.005 times to 0.4 times the period (a). However, in the case where the incident light is in the visible light or near-infrared wavelength band, considering the improvement of the degree of polarization, the average width (d) in the arrangement direction of the conductor layer 25 is preferably selected from the range of 14 nm to 70 nm. The structure of the above wire grid type polarization element can be used in the electromagnetic waves in the wavelength regions of non-visible light regions such as the ultraviolet region, near-infrared region, infrared region, terahertz region, and microwave region as long as it is within the same magnification range.

[0031] In the wire grid polarizing element of the present invention, within one period of the corrugated concavo-convex pattern, there are two conductor layers in the region shown in (3) of Figure 2 , but considering the improvement of the degree of polarization, the average occupancy rate ([2d / a]×100) of the conductor layer, as indicated by the ratio of the average width (d) in the arrangement direction of the two conductor layers to the period (a) of the corrugated concavo-convex pattern, is selected from the range of 18% to 40%. In addition, in Reference Example 1 described later, taking the Figure 12 shape model of (1) as an object, when calculating the change in optical characteristics in the case of an increase in the average thickness (c) in the direction perpendicular to the surface of the conductor layer 25 by numerical calculation based on the rigorous coupled-wave analysis method, as shown in Table 3, it was confirmed that when the average thickness (c) increased from 5 nm to 10 nm and 15 nm, the degree of polarization tended to increase.

[0032] The wire grid polarizing element of the present invention is characterized in that a substrate formed in a continuous corrugated shape in a cross section along the arrangement direction of the concavo-convex pattern is provided with: a conductor layer 25 covering the surface portion 24 of the substrate except for the top portions of the convex portions of the concavo-convex pattern; and a conductor protrusion 26 continuously protruding in the top direction along the direction perpendicular to the arrangement direction at the top portions 22 of the convex portions of the concavo-convex pattern. There is no particular limitation on the shape of such a conductor protrusion 26, and as the cross-sectional shape in the above arrangement direction, a substantially rectangular shape, a top-tapering shape, a top-thickening shape, or a substantially longitudinal elliptical shape can be cited, and a substantially rectangular shape is preferred. In addition, considering the improvement of the degree of polarization, the average thickness (h) in the top direction of the conductor protrusion 26 provided at the top portions 22 of the convex portions of the concavo-convex pattern provided on the substrate 21 is 1.5 times or more, preferably 1.5 times to 5.0 times, the average width (d) in the arrangement direction of the conductor 25. In Reference Example 3 described later, taking the Figure 14 shape model of (1) to Figure 14 shape model of (3) as an object, the rigorous coupled-wave analysis method was used to perform numerical calculation on the change in optical characteristics in the case of an increase in the average thickness (h) in the top direction of the conductor protrusion 26. As a result, as shown in Table 5, it was confirmed by numerical calculation that there is a tendency for the degree of polarization to increase as the ratio (h / d) of the average thickness (h) in the top direction of the conductor protrusion 26 to the average width (d) increases from 1 to 10. In addition, the average width (e) of the conductor protrusion 26 is preferably 0.005 times to 0.4 times the period (a).

[0033] The material of the conductor used in the present invention may be any material that functions as a conductor in the wavelength region utilized. Specifically, one or more selected from aluminum, gold, silver, copper, platinum, molybdenum, nickel, chromium, titanium, tungsten, tantalum, zirconium, iron, niobium, hafnium, cobalt, palladium, bismuth, and neodymium, or an alloy formed of two or more of these metals may be used. Not only metals but also semiconductors may be used. In addition, when forming a conductor on the substrate 21, as Figure 5 shown, a base layer 27 composed of metal oxides such as silicon oxide, titanium oxide, hafnium oxide, and aluminum oxide can be formed in advance. Further, after forming the conductor layer 25 and the conductor protrusion 26 on the substrate 21, as Figure 6 shown, a coating 28 composed of a transparent body of an organic material or an inorganic material can be formed. In this case, the concave portion of the concavo-convex pattern may or may not be filled with the coating 28.

[0034] Since the wire grid type polarization element 11 of the present invention has a conductor layer 25 formed along the concavo-convex pattern of the waveform shape on the surface 21 of the substrate, high adhesion to the substrate can be obtained. Therefore, the conductor is not easily peeled off due to expansion and contraction caused by temperature changes, etc., and has excellent heat resistance and excellent bending resistance. Thus, it is expected to be applied not only to optical systems of various optical products such as displays and cameras, and optical systems for optical measurement, but also to polarized sunglasses, smart glasses, etc.

[0035] (2) Manufacturing method of wire grid type polarization element A manufacturing method of a wire grid type polarization element of the present invention, in which a conductor protrusion formed by further protruding the top end portion of each convex portion extending in the length direction in the concavo-convex pattern and a conductor layer covering the surface portion except the top end portion of the convex portion are formed on the surface of a substrate, the substrate has the periodic concavo-convex pattern formed on the surface of a transparent sheet, and the concavo-convex pattern is a waveform shape with a continuous cross-sectional shape in the arrangement direction thereof, the manufacturing method of the wire grid type polarization element is characterized in that On the surface of a substrate where the period (a) of the concavo-convex pattern on the substrate surface is 100 nm to 400 nm and the average depth (b) from the top of the convex portion to the bottom of the concave portion of the concavo-convex pattern on the substrate surface is 200 nm to 600 nm, by physical vapor deposition of introducing a vapor deposition material from above in a direction perpendicular to the substrate surface, or by electroless plating in which a catalyst application treatment using stannous chloride and palladium chloride is performed as a pretreatment, a conductor layer is formed such that the average occupancy rate ([2d / a]×100) of the conductor layer, as shown by the ratio of the average width (d) in the arrangement direction of the two conductor layers present in one period to the period (a), is 18% to 40%, and a conductor protrusion provided at the top of the convex portion of the concavo-convex pattern, with an average thickness (h) in the top direction of the conductor protrusion being 1.5 times or more the average width (d) in the arrangement direction of the conductor layer.

[0036] Use Figure 7 of (1) to Figure 7 (4) illustrates an example of a method for manufacturing a wire grid polarizing element of the present invention, but the manufacturing method of the present invention is not limited to the following manufacturing examples. As an example of the manufacturing method, in order to form the substrate 21, a process including the following steps can be cited: preparing a mold 31 having a convex portion 32 of the mold and a concave portion 33 of the mold, with a waveform cross-section (first step: Figure 7 of (1)); performing thermal nanoimprinting (hot embossing) or photo nanoimprinting on the transparent sheet using the mold 31 (second step: Figure 7 of (2)); forming a substrate 21 having a waveform cross-section including a convex top portion 22 and a concave portion 23 (third step: Figure 7 of (3)); and forming a conductor layer 25 and a conductor protrusion 26 on the surface of the substrate 21 having the convex top portion 22 and the concave portion 23 with a waveform cross-section (fourth step: Figure 7 of (4)). In the manufacturing method of the present invention, basically, a wire grid polarizing element with a waveform cross-section of the present invention can be obtained in the above third and fourth steps, and the method for forming the substrate 21 with a waveform cross-section in the first and second steps is not particularly limited. In addition, Figure 7 the display of the period (a') and the average depth (b') of the waveform structure of the mold 31 in

[0037] In the first step, fabricate Figure 7The method of the mold 31 shown in (1) having a concave portion 33 of the mold corresponding to the top portion 22 of the convex portion and the concave portion 23 of the substrate 21, and a convex portion 32 of the mold, and having a period (a') and a depth (b') from the top of the convex portion 32 of the mold to the valley portion of the concave portion 33 of the mold preferably uses exposure techniques such as electron beam lithography, focused ion beam, interference exposure, self-organization techniques using nanoparticles, etc., and preferably uses dry etching or wet etching. In addition, it can also be produced by transfer from a master mold produced by using these methods. The mold 31 is not limited to forming an uneven shape in a plane section, etc., and can also be formed with a structure including a waveform shape in a curved surface section. The material of the mold 31 is preferably silicon, but can also be glass such as quartz, ceramics such as alumina, silicon carbide, metals such as nickel, stainless steel, etc., and can also be a multi-layer material with a metal, semiconductor, or dielectric deposited thereon. In addition, in order to improve the demoldability in nanoimprinting and injection molding, it is preferable to form a fluorine-based release agent or a low-friction inorganic film on the surface of the mold 31. However, depending on the mold material used and the resin material to be molded, a silicon-based release agent can also be used. The second process is as Figure 7 shown in (2), and it is preferably transferred by thermal nanoimprinting (hot embossing) or photo nanoimprinting. On the other hand, molding methods such as injection molding and casting molding can also be used. Considering operability, quality stability, and economy, injection molding is more preferably used.

[0038] In the third process, Figure 7 the substrate 21 shown in (3) including the top portion 22 of the convex portion and the concave portion 23 and having a waveform shape in the cross section is preferably produced through the first process and the second process. However, the substrate 21 can also be produced using exposure techniques such as direct electron beam lithography, focused ion beam, interference exposure, self-organization techniques using nanoparticles, etching techniques, etc. In addition, such a substrate 21 is not limited to a single layer and can also be a multi-layer, and the waveform structure portion can also use a material different from that of the substrate 21. In the fourth process, as Figure 7 the method of forming a conductor on the substrate 21 shown in (4), physical vapor deposition methods such as vacuum evaporation, electron beam evaporation method, sputtering, chemical vapor deposition method, atomic layer deposition method, or a method combining them, or electroless plating method can be used. As the above vapor deposition method, a physical vapor deposition method (front vapor deposition method) in which the vapor deposition material is introduced from above in a direction perpendicular to the substrate surface is preferably used. In addition, as a specific example of the electroless plating method described above, it is preferable that (i) degreasing and cleaning using a surfactant and an alkaline aqueous solution are performed to remove surface dirt, (ii) etching is performed using an aqueous solution of an inorganic acid such as chromic acid, sulfuric acid, or hydrochloric acid to improve adhesion, followed by a neutralization treatment, and (iii) then, as a pretreatment for activating the electroless plating reaction, it is immersed in a liquid containing tin ions (Sn 2+ ) and a liquid containing palladium ions (Pd 2+ ). Specifically, examples include the sensitizer-activator process in which the surface of the substrate to be electroless plated is immersed in a liquid containing tin ions (Sn 2+ ) and then immersed one or two times in a liquid containing palladium ions (Pd 2+ ), or the catalyser-accelerator process in which a palladium colloid solution is prepared by mixing a liquid containing tin ions (Sn 2+ ) and palladium ions (Pd 2+ ), the substrate surface is immersed therein, and then immersed in a hydrochloric acid solution to promote the electroless plating reaction. (iv) Then, electroless plating is performed using an electroless plating solution.

[0039] In the above physical vapor deposition method, when forming a conductor layer 25 that covers the surface portion 24 of the uneven pattern except for the top portion 22 of the convex portion and a conductor protruding portion 26 that protrudes in the top direction (direction perpendicular to the arrangement direction) at the top portion 22 of the convex portion of the uneven pattern on the surface of the substrate 21 formed in a continuous wave shape in a cross section along the arrangement direction of the uneven pattern, the average width (d) in the arrangement direction of the conductor layer and the thickness (h) of the conductor protruding portion 26 in the top direction can be controlled by the irradiation time, voltage, degree of vacuum, distance between the target and the substrate surface, etc. In addition, in the electroless plating method, it can be controlled by the plating treatment time, temperature of the plating solution, component concentration of the plating solution, stirring control of the plating solution, etc.

[0040] In addition, after forming the conductor layer 25 and the conductor protruding portion 26 on the substrate 21, the shape of the conductor can be controlled by dry etching or wet etching using an Ar ion beam or the like. When forming the above conductor on the substrate 21, as Figure 5 shown, a base layer 27 composed of a metal oxide such as silicon oxide, titanium oxide, hafnium oxide, or aluminum oxide can be formed in advance. Furthermore, after forming the conductor layer 25 and the conductor protruding portion 26 on the substrate 21, as Figure 6As shown, a coating 28 is formed. In this case, as the coating material, it is not limited to a colorless transparent material, and a transparent material with a hue containing pigments such as dyes can also be used. The concave portions of the concavo-convex pattern may or may not be filled with the coating 28.

[0041] In the forming process of the above-mentioned substrate, the description of "setting the period (a) of the corrugated concavo-convex pattern to 100 nm to 400 nm and setting the average depth (b) from the top of the convex portion to the bottom of the concave portion of the concavo-convex pattern to 200 nm to 600 nm", and in the process of forming a conductor on the substrate, the description of "setting the average occupancy rate ([2d / a]×100) of the conductor layer, as shown by the ratio of the average width (d) in the arrangement direction of the two conductor layers existing in one period to the period (a), to 18% to 40%, and setting the average thickness (h) in the top direction of the conductor protrusion protruding in the top direction from the top of the convex portion of the concavo-convex pattern to more than 1.5 times the average width (d) in the arrangement direction of the conductor layer" is as described in the description of the above wire grid type polarizing element, so the description here is omitted. Examples

[0042] The present invention will be specifically described in the following examples, comparative examples, and reference examples. In addition, the present invention is not limited to the following examples. The measurement of the degree of polarization and the light transmittance of the test pieces produced was carried out using the following device. A spectrophotometer (model: SolidSpec-3700) manufactured by Shimadzu Corporation was used. In the polarizing element whose cross-section along the arrangement direction of the concavo-convex pattern is a corrugated shape produced in the examples and the like, when observed from this cross-section, the incident light of the electric field component vibrating in the direction parallel and perpendicular to the depth direction was taken as the measurement object. Regarding the polarization characteristics, an evaluation based on the degree of polarization was carried out. When the visual transmittance in the case of polarized light in the direction parallel to the arrangement direction of the concavo-convex pattern is set to Tp and the visual transmittance (monomer transmittance) in the case of polarized light in the vertical direction is set to Tv, the degree of polarization V is represented by the following formula. V(%) = [(Tv - Tp) / (Tv + Tp)] 1 / 2 ×100 The visual transmittance in each polarized light can be obtained from the respective transmittances (transmission spectra) in the case of wavelengths from 380 nm to 780 nm (1 nm scale) and the visual sensitivity curve. Similarly, when the transmittance in the case of polarized light in the parallel direction is set to Tp0 and the transmittance in the case of polarized light in the vertical direction is set to Tv0, the degree of polarization V0 at a certain wavelength is as follows. V0(%) = [(Tv0 - Tp0) / (Tv0 + Tp0)] 1 / 2 × 100

[0043] (Example 1, Comparative Example 1) In Example 2-1, Example 2, and Comparative Example 1, on the surface of a transparent sheet made of a thermoplastic resin, a mold was used, and a concavo-convex pattern with a corrugated shape was transferred onto the surface by thermal nanoimprinting to produce a substrate. Then, an aluminum layer was formed on the surface of the substrate having the concavo-convex pattern by vacuum evaporation to produce a polarizing element test piece. The polarization characteristics of the produced test piece were evaluated. (1) Production of the substrate As the transparent sheet, a polycarbonate sheet (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: FE-2000, thickness: 300 μm) was used. The mold used was fabricated by microfabricating a 4-inch silicon wafer. The concavo-convex cross-sectional shape of the fine structure of the mold used had a triangular wave shape composed of a substantially isosceles triangle with a period (a') as the wavelength of the wave of 140 nm, an average depth (b') of the wave of 426 nm, and the corrugated shape part being continuous. Figure 8 Fig. shows an image (SEM image) obtained by photographing a rough cross-section of the fabricated mold with a scanning electron microscope (SEM). Using the above mold, a substrate was produced by transferring a concavo-convex structure with a corrugated cross-section in the alignment direction onto the sheet surface by thermal nanoimprinting.

[0044] (2) Production of the polarizing element test piece based on vacuum evaporation Next, using an electron beam vacuum evaporation apparatus, with the surface of the substrate facing the front, it was fixed to the workbench (a fixing method by normal evaporation method, not an inclined evaporation method), and while rotating the workbench, an aluminum layer was evaporated on the surface other than the top of the convex part of the concavo-convex pattern, and on the top of the convex part, aluminum was evaporated in such a way that the average thickness (h) in the direction of the top of the conductive protrusion was 41 nm, 80 nm, and 24 nm in Example 1-1, Example 1-2, and Comparative Example 1, respectively, to produce three types of polarizing element test pieces. The shapes, etc. of the produced substrate and polarizing element test pieces are summarized in Table 1. In addition, Figure 9 an SEM image of the cross-section of the polarizing element test piece produced in Example 1-1 is shown.

[0045] (3) Evaluation results For the obtained polarization element test piece, the degree of polarization and the monomer transmittance were measured. These results are summarized in Table 1. In Example 1-1 and Example 2, excellent results were obtained for both the degree of polarization and the monomer transmittance. In Example 1-2, based on the average width (d) of 26 nm in the arrangement direction of the aluminum layer and the average thickness (h) of 80 nm in the top direction of the conductor protrusion, the ratio (h / d) of the average thickness (h) to the average width (d) of the protrusion was approximately 3.1. Additionally, based on the period of 140 nm, the average occupancy (2d / a) of the conductor layer was 37.1%. In Example 1-2, the optical properties were a degree of polarization of 99% and a monomer transmittance of 37%. Furthermore, in Comparative Example 1, the average width (d) in the arrangement direction of the conductor layer was 10 nm, so the average occupancy (2d / a) of the conductor layer was 14.3%, and the degree of polarization was a low value of 45%.

[0046] (Example 2) In Example 2, a substrate was produced in the same manner as in Example 1. Subsequently, a chromium layer was formed on the surface of the substrate having the concavo-convex pattern by vacuum evaporation to produce a polarization element test piece, and the polarization characteristics were evaluated. (1) Production of polarization element test piece Using the same sheet material and mold as those used in Example 1, a substrate was produced by thermally nanoimprinting a concavo-convex pattern with a waveform cross-section in the arrangement direction on the sheet surface. Then, in the same manner as in Example 1, an electron beam vacuum evaporation apparatus was used, and a chromium layer was formed on the surface of the substrate by the same method as described in Example 1 to produce a polarization element test piece. The shapes, etc. of the produced substrate and polarization element test piece are summarized in Table 1.

[0047] (2) Evaluation results The average width (d) in the arrangement direction of the chromium layer formed on the surface side of the substrate was 25 nm, and the average thickness (h) in the top direction of the conductor protrusion was 61 nm. Based on these values, the ratio (h / d) of the average thickness (h) to the average width (d) of the protrusion was 2.44, and the average occupancy (2d / a) of the conductor layer was 35.7%. For the obtained polarization element test piece, the degree of polarization and the monomer transmittance were measured. As a result, the degree of polarization was 99% and the monomer transmittance was 33%, and good results were obtained for both the degree of polarization and the monomer transmittance.

[0048] (Example 3) In Example 3, a substrate was produced in the same manner as in Example 1. Subsequently, a nickel layer was formed on the surface of the substrate having the concavo-convex pattern by electroless plating to produce a polarization element test piece, and the polarization characteristics were evaluated. (1) Fabrication of the substrate Using the same sheet and mold as those used in Example 1, an uneven pattern with a waveform cross-section in the transfer alignment direction is transferred onto the surface of the sheet by thermal nanoimprinting to fabricate the substrate.

[0049] (2) Formation of the conductor based on electroless nickel plating Using an electroless nickel-boron plating solution (trade name: TopChemialloy66-LF) manufactured by Okuno Pharmaceutical Co., Ltd., electroless plating is performed on the surface of the substrate. In addition, as a pretreatment, the surface of the substrate to be electroless plated is degreased and cleaned using a surfactant and an alkaline aqueous solution in advance. Then, after etching with an aqueous solution of inorganic acid, a neutralization treatment is performed. Then, as an activation pretreatment for the electroless plating reaction, a treatment to promote the electroless plating reaction (sensitizer activator method) is performed using a liquid containing tin ions (Sn 2+ ) and a liquid containing palladium ions (Pd 2+ ) (both manufactured by Okuno Pharmaceutical Co., Ltd.). Plating treatment is performed for 80 seconds using a plating solution at room temperature (23°C), followed by washing with water and drying to fabricate a polarization element test piece. The shapes and the like of the fabricated substrate and polarization element test piece are summarized in Table 1.

[0050] (3) Evaluation results The optical properties of the obtained test piece are a polarization degree of 99% and a monomer transmittance of 20%. In Example 3, Figure 10 shows an SEM image obtained by observing the fabricated polarization element with a waveform cross-section from a rough cross-section. From this figure, it can be confirmed that a conductor with a substantially uniform thickness is formed on the surface portion with a triangular wave cross-section. The depth from the top of the convex portion of the formed triangular wave shape to the bottom of the concave portion is approximately 387 nm, the average width (d) in the alignment direction of the conductor layer is 14 nm. The average thickness (h) of the conductor protrusion is 21 nm, and the ratio (h / d) of the thickness (h) to the average width (d) of the conductor layer is approximately 1.5. At this time, the average occupancy rate of the conductor in each layer from the top of the convex portion of the triangular wave shape to the bottom of the concave portion is approximately 20%, and the occupancy rates of the conductor in the top and bottom surface layers are also both 30% or less. Thus, it is confirmed that the polarization element with a waveform cross-section fabricated by the electroless plating method has the necessary light transmittance at a high polarization degree.

[0051] [Table 1]

[0052] (Example 4, Comparative Example 2, Comparative Example 3) In Example 4, a substrate was produced in the same manner as in Example 1. Subsequently, an aluminum layer, silicon oxide, and an aluminum layer were formed on the surface of the substrate by sputtering to produce a polarization element test piece. (1) Fabrication of the polarization element test piece Using the same sheet and mold as those used in Example 1, a substrate was fabricated by thermally nanoimprinting a concavo-convex pattern with a waveform cross-section in the alignment direction on the surface of the sheet.

[0053] Then, in Comparative Example 2 and Examples 4-1 to 4-2, using a sputtering apparatus, the substrate was fixed to the worktable with the surface of the substrate facing the front of the aluminum target, and while rotating the worktable, an aluminum layer was formed on the surface of the substrate such that the average width (d) in the alignment direction became the thickness shown in Table 2, to fabricate three types of polarization element test pieces. In addition, in Comparative Example 3 and Examples 4-3 to 4-4, in the same manner as in Examples 4-1 to 4-2 above, using a sputtering apparatus, the substrate was fixed to the worktable with the surface of the substrate facing the front of the aluminum target, and while rotating the worktable, a silicon oxide (SiO2) layer was first formed such that the average thickness (f) in the direction perpendicular to the surface became 10 nm, and then an aluminum layer was further formed on the surface of the silicon oxide such that the average width (d) in the alignment direction was the width shown in Table 2, to fabricate three types of polarization element test pieces. The shapes and the like of the fabricated substrates and polarization element test pieces are summarized in Table 2.

[0054] (2) Evaluation results For the polarization element test pieces obtained in Examples 4-1 to 4-4, Comparative Example 2, and Comparative Example 3 respectively, the degree of polarization and the monomer transmittance were measured. The measurement results are summarized in Table 2. In any of the polarization element test pieces fabricated in Examples 4-1 to 4-4, good results were obtained for both the degree of polarization and the monomer transmittance. In the polarization element test piece fabricated in Example 4-2, the average thickness (h) of the conductor protrusions was approximately 72 nm, the average width (d) in the alignment direction of the conductor layer was approximately 21 nm, and the ratio (h / d) of the average thickness (h) of the conductor protrusions to the average width (d) in the alignment direction of the conductor layer was approximately 3.4. In Figure 11 shows an SEM image of the cross-section of the polarization element test piece fabricated in Example 4-2. In addition, in Comparative Example 2 and Comparative Example 3, the average width (d) in the alignment direction of the conductor layer was 11 nm in both cases, so the average conductor occupancy was 15.7%, and as a result, the degree of polarization was a low value of 89% in both cases.

[0055] (Comparative Example 4) On the surface of a thermoplastic resin sheet, a fine concave structure in the shape of a shell with a substantially continuous uneven shape is formed by thermal nanoimprinting using a mold. Then, a nickel layer is formed on the surface including the concave portion by electroless plating to fabricate a polarization element test piece. (1) Formation of a fine concave structure on the sheet surface The same sheet as used in Example 1 is used. The mold used is obtained by microfabricating a 4-inch silicon wafer. The convex portion forming the concave portion on the substrate surface has an average width of 54 nm, an average width of the space of 86 nm (pitch 140 nm), an average depth of 586 nm, and a tip portion in the shape of a shell that gradually becomes thinner toward the tip. The bottom surface of the concave portion is flat. Using this mold, the fine concave structure is transferred onto the sheet surface by thermal nanoimprinting. In Figure 15 shows a SEM image obtained by observing the cross-section of the mold used in Comparative Example 4 from a substantially front view. (2) Formation of a conductor based on electroless nickel plating The same plating solution as used in Example 3 is used to perform electroless plating on the sheet having the fine concave structure formed thereon. In addition, the same pretreatment as used in Example 3 is also used, and treatment is performed for 120 seconds with a plating solution at room temperature (23°C), followed by washing with water and drying to fabricate a polarization element test piece. The shapes, etc. of the fabricated substrate and polarization element test piece are summarized in Table 2. In Figure 16 shows a SEM image of the cross-section of the fabricated polarization element test piece.

[0056] (3) Evaluation results The optical characteristics of the fabricated polarization element test piece are as shown in Table 2. The degree of polarization is 99%, and the monomer transmittance is 9.1%. Figure 16 In, a nickel plating film with a thickness of approximately 17 nm was uniformly formed on the substrate surface. However, the occupancy rate of the conductor in each layer of the uneven structure body was approximately 84% in the top layer of the convex portion, approximately 24% in the middle layer, and 12% - 24% in the bottom layer of the concave portion. Comparing the results of Comparative Example 4 with the test piece fabricated in Example 3, it can be seen that the degree of polarization reached 99% in both cases. However, the monomer transmittance of the test piece fabricated in Comparative Example 4 decreased to 1 / 2 or less. Therefore, it can be confirmed that the monomer transmittance of the wire grid type polarization element having a waveform shape in the cross-section in the arrangement direction of the present invention is improved.

[0057] [Table 2]

[0058] (Reference Example 1) (1) Outline In the same manner as in Example 1, using a mold, an uneven shape with a waveform cross-section in the arrangement direction was formed on the surface of the sheet. Then, assuming a polarization element of the shape model shown in (1) of Figure 12 to Figure 12 and (3) of the optical characteristics were evaluated by numerical calculation based on the rigorous coupled-wave analysis method. Figure 12 When the displacement (s) of the shape of the conductor is used as a parameter, when the cross-section is a rectangular uneven shape as shown in (1) of Figure 12 the displacement (s) is 0 nm. If the displacement (s) is increased from this point, it becomes an uneven shape with a trapezoidal cross-section as shown in (2) of Figure 12 If the displacement (s) is further increased, it becomes an uneven shape with a triangular wave cross-section as shown in (3) of Figure 12 and the displacement (s) is 70 nm. Referring to Figure 12 the shape models shown in (1) to (3) of

[0059] numerical calculation of the optical characteristics with respect to the displacement (s) was performed when the average thickness (c) of the conductor layer was used as a parameter. The numerical calculation was performed using DiffractMOD of Synopsys K.K. (former RSoft) in Japan, based on Figure 12 the shape models shown in (1) to Figure 12 and (3) of Figure 12 The substrates 43, 44, and 45 shown in (1) to Figure 12 and (3) of are assumed to be polycarbonate, and the refractive index is defined as 1.58. The conductor layer 25 is assumed to be nickel, and the refractive index is the value disclosed in A.D. Rakic et al., “Optical properties of metallic films for vertical-cavity optoelectronic devices,” Appl. Opt. 37, 5271 (1998). Figure 12 in (2) orFigure 12 In the case of a structure with inclination as in (3), the layers with an approximately given refractive index distribution are separated at a certain interval for calculation. This interval in this calculation is one-tenth of the depth (b) of the concavo-convex structure of the waveform.

[0060] (3) Calculation results (i) When the average thickness (c) of the conductor layer is 10 nm Respectively in Figure 13 (1) of Figure 13 (2) of (2), the transmission spectra showing the calculation results of the polarization light transmittance (Tp) in the parallel direction and the polarization light transmittance (Tv) in the vertical direction at each wavelength are shown. Compared with the case where the conductor is uniformly formed in a rectangular concavo-convex shape with a displacement (s) of 0 nm, as the displacement (s) increases, the transmission spectrum of the polarization light transmittance (Tp) in the parallel direction shows almost no change, but in the transmission spectrum of the polarization light transmittance (monomer transmittance, Tv) in the vertical direction, a tendency for the transmittance to gradually increase can be confirmed. As shown in Table 3, when the displacement (s) is 0 nm, the degree of polarization is 99% and the monomer transmittance is 12%. In contrast, when the displacement is 70 nm, the degree of polarization increases to 99% and the monomer transmittance increases to 28%.

[0061] (ii) When the average thickness (c) of the conductor layer is 5 nm When the displacement (s) is 0 nm, the degree of polarization is 96% and the monomer transmittance is 24%. In contrast, when the displacement is 70 nm, the degree of polarization increases to 97% and the monomer transmittance increases to 39%. (iii) When the average thickness (c) of the conductor layer is 15 nm When the displacement (s) is 0 nm, the degree of polarization is 99% and the monomer transmittance is 6%. In contrast, when the displacement is 70 nm, the degree of polarization is 99% and the monomer transmittance increases to 19%. Therefore, through the numerical calculation assuming the shape models shown in Figure 12 (1) to Figure 12 (3) of Figure 12 , when the cross-sectional shape is changed from a rectangular shape to a waveform shape and the displacement (s) is increased, a result of an increase in the monomer transmittance is obtained. Therefore, it is proved by numerical calculation that the wire grid type polarization element with a wavy cross-sectional shape according to the present invention is much more helpful for increasing the monomer transmittance compared with the conventional wire grid type polarization element with a rectangular cross-sectional shape.

[0062] [Table 3]

[0063] (Reference Example 2) The same as that used in Reference Example 1 Figure 12 shape model was used to perform numerical calculations based on the rigorous coupled-wave analysis method, and the relationship between the depth (b) from the top of the convex part to the bottom of the concave part of the concave-convex shape and the optical properties was studied. (1) Numerical calculation of optical properties when the depth (b) from the top of the convex part to the bottom of the concave part of the concave-convex shape is used as a parameter Using the same software as that used in Reference Example 1, numerical calculations were performed based on the Figure 12 shape model of (1). The substrate 43 was assumed to be polycarbonate, and the refractive index was defined as 1.58. The conductor layer 25 was assumed to be nickel, and the refractive index was used as the value described in the literature A.D. Rakic et al., “Optical properties of metallic films for vertical-cavity optoelectronic devices,” Appl. Opt. 37, 5271 (1998). The period (a) of the concave-convex structure was set to 140 nm, the width (w) of the concave part when the displacement (s) was 0 nm was set to 70 nm, and the average thickness (c) in the direction perpendicular to the surface of the conductor layer 25 was set to 10 nm. The degree of polarization and the monomer transmittance were calculated when the above depth (b) was set to 200 nm, 300 nm, 400 nm, 600 nm, and 1000 nm.

[0064] (2) Calculation results The degree of polarization and the monomer transmittance were calculated from the calculated values. These results are summarized in Table 4. The degree of polarization when the above depth (b) was 200 nm was 96.6%, and the degree of polarization reached 99.4% when the above depth (b) was 300 nm. At this time, the monomer transmittance showed a high value of 28%. Based on these results, it was proved by numerical calculation that the greater the depth (b) from the top of the convex part to the bottom of the concave part of the concave-convex shape, the higher the degree of polarization that can be obtained.

[0065] [Table 4]

[0066] (Reference Example 3) Similar to Example 1, an uneven shape with a waveform arrangement direction was formed on the sheet surface by hot nanoimprinting using a mold. Then, assuming a polarization element obtained by evaporation or sputtering, in Figure 14 of (1) to Figure 14In the shape model shown in (3), the average width (d) in the arrangement direction of the conductor layer 25 is set to 5 nm and 10 nm, and numerical calculations based on the rigorous coupled-wave analysis method are performed when the average thickness (h) of the conductor protrusion 26 is expressed as the ratio (h / d) to the average width (d) in the arrangement direction of the conductor layer 25. Taking the ratio (h / d) of the average thickness (h) of the conductor protrusion in the direction toward the tip to the average width (d) in the arrangement direction of the conductor layer as a parameter, when (h / d) is 1, the cross-sectional shape is as shown in Figure 14 (1), when h / d is 3, the cross-sectional shape is as shown in Figure 14 (2), and when h / d is 5, the cross-sectional shape is as shown in Figure 14 (3) and calculations are performed.

[0067] (1) Numerical calculations of the optical properties when the ratio (h / d) of the above average thickness (h) to the average width (d) in the arrangement direction of the conductor layer is used as a parameter The numerical calculations are performed using DiffractMOD of Synopsys K.K. (former RSoft) in Japan, based on the shape models in Figure 14 (1) to Figure 14 (3). The substrate 21 is assumed to be polycarbonate, and the refractive index is defined as 1.58. The conductor layer 25 is assumed to be nickel and aluminum, and the refractive indices are respectively the values described in A.D. Rakic et al., “Optical properties of metallic films for vertical-cavity optoelectronic devices,” Appl. Opt. 37, 5271 (1998). The period (a) of the uneven shape of the waveform is set to 140 nm, and the depth (b) of the uneven shape is set to 400 nm. In the case of nickel, the degree of polarization and the single-pass transmittance are calculated when the above average width (d) of the conductor layer is 5 nm and 10 nm, and in the case of aluminum, the degree of polarization and the single-pass transmittance are calculated when the above average width (d) of the conductor layer is 5 nm. In addition, in the rigorous coupled-wave analysis method, a refractive index distribution is assigned to each layer of the calculation model for calculation, but in the case of a structure with an inclination such as Figure 14 (1) to Figure 14 (3), the layers with an approximately assigned refractive index distribution are separated at a certain interval for calculation. This interval in this calculation is one-tenth of the depth (b) of the uneven structure of the waveform.

[0068] (2) Calculation results The calculation results are summarized in Table 5. Reference Example 3-1 shows the degree of polarization and the monomer transmittance when the average width (d) of the nickel conductor layer 25 is 5 nm, Reference Example 3-2 shows the degree of polarization and the monomer transmittance when the average width (d) of the nickel conductor layer 25 is 10 nm, and Reference Example 3-3 shows the degree of polarization and the monomer transmittance when the average width (d) of the aluminum conductor layer 25 is 5 nm. It was confirmed from Table 5 that, compared with the case where the ratio (h / d) of the average thickness (h) of the conductor protrusion in the direction toward the tip to the average width (d) in the arrangement direction of the conductor layers is 1, as h / d increases to 2, 3, 5, and 10, the degree of polarization increases while maintaining a high monomer transmittance. For example, when the average width (d) of the nickel conductor layer is 10 nm, the degree of polarization is 99.6% when h / d is 1, whereas the degree of polarization reaches 99.9% when h / d is 10. It was demonstrated by numerical calculation that by using the high polarization structure of the present invention, an increase in the degree of polarization can be achieved while maintaining a high transmittance.

[0069] [Table 5] Industrial application fields

[0070] The wire grid polarizing element of the present invention can be applied to fields of optical articles such as displays, cameras, sunglasses, and optical measuring devices that utilize electromagnetic waves such as visible light and near-infrared light. In addition, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2022-135199 filed on August 26, 2022 are hereby incorporated by reference and made a part of the disclosure of the present invention. Explanation of reference numerals

[0071] 11: wire grid polarizing element; 21: substrate; 22: tip portion of protrusion; 23: recess; 24: substrate surface portion; 25: conductor layer; 26: conductor protrusion; 27: base layer; 28: coating; 31: mold; 32: protrusion of mold; 33: recess of mold; 41: substrate; 42: substrate; 43: substrate; 44: substrate; 45: substrate.

Claims

1. A wire-grid polarizing element, comprising: a substrate having a periodic uneven pattern formed on the surface of a transparent sheet, the uneven pattern being a waveform shape with a continuous cross-sectional shape along its arrangement direction; and a conductor protrusion formed by further protruding toward the top direction from the top end portions of the respective convex portions formed by extending along the length direction in the uneven pattern, and a conductor layer covering the surface portion except for the top end portions of the convex portions, wherein the wire-grid polarizing element is characterized in that the period (a) of the uneven pattern on the substrate surface is 100 nm to 400 nm, the average depth (b) from the top end portion of the convex portion to the bottom of the concave portion of the uneven pattern on the substrate surface is 200 nm to 600 nm, the average occupancy rate ([2d / a]×100) of the conductor layer, indicated by the ratio of the average width (d) in the arrangement direction of the two conductor layers existing in each period to the period (a), is 18% to 40%, the average thickness (h) in the top direction of the conductor protrusion provided at the top end portion of the convex portion of the uneven pattern is 1.5 times or more the average width (d) in the arrangement direction of the conductor layer.

2. The wire-grid polarizing element according to claim 1, wherein the average thickness (h) in the top direction of the conductor protrusion provided at the top end portion of the convex portion of the uneven pattern on the substrate surface is 1.5 times or more and 5 times or less the average width (d) in the arrangement direction of the conductor layer.

3. The wire-grid polarizing element according to claim 1, wherein the average width (d) in the arrangement direction of the conductor layer covering the surface portion except for the top end portion of the convex portion of the uneven pattern disposed on the substrate surface is 14 nm to 70 nm.

4. The wire-grid polarizing element according to claim 1, wherein the continuous waveform shape in the cross-sectional shape along the arrangement direction formed on the substrate surface is a triangular waveform shape composed of continuous substantially isosceles triangle shapes.

5. The wire-grid polarizing element according to claim 1, wherein the cross-sectional shape in the arrangement direction of the conductor protrusion protruding toward the top direction provided at the top end portion of the convex portion of the uneven pattern disposed on the substrate surface is a substantially rectangular shape, a tip-tapering shape, a tip-widening shape, or a substantially longitudinal elliptical shape.

6. The wire-grid polarizing element according to claim 1, wherein the conductor material forming the conductor protrusion and the conductor layer is one or more selected from aluminum, gold, silver, copper, platinum, molybdenum, nickel, chromium, titanium, tungsten, tantalum, zirconium, iron, niobium, hafnium, cobalt, palladium, bismuth, and neodymium, or an alloy composed of two or more of them.

7. A manufacturing method of a wire-grid polarizing element, comprising forming a conductor protrusion on the surface of a substrate, the conductor protrusion being formed at the top of each convex portion that extends in the length direction in a concavo-convex pattern and further protrudes toward the top direction, and forming a conductor layer that covers the surface portion except for the top of the convex portion. The substrate has a periodic concavo-convex pattern formed on the surface of a transparent sheet, and the concavo-convex pattern has a waveform shape with a continuous cross-sectional shape along its arrangement direction. The manufacturing method of the wire-grid polarizing element is characterized in that On the surface of a substrate where the period (a) of the concavo-convex pattern on the substrate surface is 100 nm to 400 nm and the average depth (b) from the top of the convex portion to the bottom of the concave portion of the concavo-convex pattern on the substrate surface is 200 nm to 600 nm, by physical vapor deposition of introducing a vapor deposition material from above in a direction perpendicular to the substrate surface, or by a chemical plating method of performing a catalyst imparting and activation using a liquid containing tin ions (Sn 2+ ) and a liquid containing palladium ions (Pd 2+ ) as a pretreatment and then performing chemical plating, a conductor layer is formed such that the average occupancy rate of the conductor layer ([2d / a]×100), indicated by the ratio of the average width (d) in the arrangement direction of two conductor layers existing within one period to the period (a), is 18% to 40%, and a conductor protrusion is formed at the top of the convex portion of the concavo-convex pattern, and the average thickness (h) in the top direction of the conductor protrusion is 1.5 times or more the average width (d) in the arrangement direction of the conductor layer.

8. The manufacturing method of the wire-grid polarizing element according to claim 7, wherein, the physical vapor deposition method is any one of vacuum evaporation, electron beam evaporation, or sputtering.

Images