JP7237057B2 - Polarizing element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polarizing element having durability against strong light.

From the image forming principle of the liquid crystal display device, it is essential to dispose a polarizing plate on the surface of the liquid crystal panel. The function of the polarizing plate is to absorb one of orthogonal polarized components (so-called P-polarized wave and S-polarized wave) and transmit the other. As such a polarizing plate, a dichroic polarizing plate in which an iodine-based or dye-based polymer organic substance is contained in a film has been widely used.

As a general method for producing a dichroic polarizing plate, a polyvinyl alcohol film and a dichroic material such as iodine are dyed, then crosslinked with a crosslinking agent, and uniaxially stretched. Since this type of polarizing plate is produced by stretching in this way, it generally tends to shrink. Moreover, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed especially under humidified conditions. In addition, since a film is fundamentally used, the mechanical strength as a device is weak. To avoid this, a method of adhering a transparent protective film is sometimes used.

By the way, in recent years, the applications of liquid crystal display devices have expanded and their functions have become higher. Accordingly, high reliability and durability are required for individual devices constituting the liquid crystal display device. For example, in the case of a liquid crystal display device using a light source with a large amount of light, such as a transmissive liquid crystal projector, the polarizing plate receives strong radiation. Therefore, the polarizing plates used for these are required to have excellent heat resistance. However, since the film-based polarizing plate as described above is an organic material, there is a limit to improving these properties.

In order to address this problem, Corning Inc. of the United States sells an inorganic polarizing plate with high heat resistance under the trade name of Polarcor. This polarizing plate has a structure in which silver fine particles are diffused in glass, does not use an organic substance such as a film, and is based on the principle of plasma resonance of island-like fine particles. That is, it utilizes light absorption due to surface plasma resonance when light is incident on island-like particles of noble metals or transition metals, and the absorption wavelength is affected by the shape of the particles and the dielectric constant of the surroundings. Here, if the shape of the island-like fine particles is made elliptical, the resonance wavelengths in the major axis direction and the minor axis direction are different, and this provides polarization characteristics. A polarizing characteristic of absorbing and transmitting a polarized component parallel to the short axis is obtained. However, in the case of Polarcor, the wavelength range in which polarization characteristics are obtained is a range near the infrared region, and does not cover the visible light range required for liquid crystal display devices. This is due to the physical properties of silver used for the island-like fine particles.

Patent Literature 1 discloses a UV polarizing plate in which fine particles are deposited in glass by thermal reduction by applying the above principle, and it is proposed to use silver as metal fine particles as a specific example. In this case, it is considered that the absorption in the short axis direction is used contrary to the above Polarcor. As shown in Figure 1, it functions as a polarizing plate around 400 nm, but the extinction ratio is small and the absorption band is very narrow. It cannot be a polarizing plate that can cover

Non-Patent Document 1 describes a theoretical analysis of an inorganic polarizing plate using plasma resonance of metal island-like fine particles. According to this document, the resonance wavelength of fine aluminum particles is about 200 nm shorter than that of silver fine particles, and it is described that there is a possibility that a polarizing plate covering the visible light range can be manufactured by using aluminum fine particles.

Further, Patent Document 2 discloses several methods of producing a polarizing plate using fine aluminum particles. Among them, it is described that glass based on silicate is not preferable as a substrate because aluminum reacts with glass, and calcium aluminoborate glass is suitable (paragraphs 0018 and 0019). However, glass using silicate is widely distributed as optical glass, and a highly reliable product can be obtained at a low cost. Also, a method of forming island-like particles by etching a resist pattern is described (paragraphs 0037 and 0038). A polarizing plate normally used in a projector is required to have a size of several centimeters and a high extinction ratio. Therefore, when a polarizing plate for visible light is intended, the resist pattern size must be sufficiently shorter than the wavelength of visible light, that is, a size of several tens of nanometers. It must be formed in high density. Also, when used for a projector, a large area is required. However, in the method of applying high-density fine patterning by lithography as described, it is necessary to use electron beam writing or the like to obtain such patterns. Electron beam writing is a method of writing individual patterns using an electron beam, and is not practical due to poor productivity.

Further, Patent Document 2 describes that aluminum is removed by chlorine plasma, but normally chloride adheres to the sidewalls of the aluminum pattern when such etching is performed. It can be removed by a commercially available wet etchant (for example, Tokyo Ohka Kogyo SST-A2). It is difficult to realize a desired pattern shape by such a method.

Furthermore, Patent Document 2 describes another method of depositing aluminum on a patterned photoresist by oblique film formation and removing the photoresist (paragraphs 0045 and 0047). However, in such a method, it is considered necessary to deposit aluminum on the substrate surface to some extent in order to obtain adhesion between the substrate and aluminum. However, this means that the shape of the deposited aluminum film is different from prolate spheres, including prolate ellipsoids, which are suitable shapes as described in paragraph 0015. Paragraph 0047 describes removing the overprecipitation by anisotropic etching perpendicular to the surface. The shape anisotropy of aluminum is extremely important for functioning as a polarizing plate. Therefore, it is considered necessary to adjust the amount of aluminum deposited on the resist portion and the substrate surface so that the desired shape can be obtained by etching. It is considered very difficult to control these by size, and it is doubtful whether it is suitable as a highly productive manufacturing method. In addition, high transmittance in the direction of the transmission axis is required as a characteristic of polarizing plates, but when glass is used as a substrate, reflection of several percent from the glass interface cannot be avoided, and no countermeasures have been taken to achieve high transmittance. difficult.

Further, Patent Document 3 describes a polarizing plate formed by oblique vapor deposition. This method obtains polarization characteristics by fabricating a micro-columnar structure by oblique vapor deposition of materials that are transparent and opaque with respect to the wavelength of the band used. Although it is considered to be a highly productive method, there are problems. That is, the aspect ratio of the micro-columnar structure of the opaque substance to the initially formed operating band, the interval between the individual micro-columnar structures, and the linearity are important factors for obtaining good polarization characteristics, and reproducibility of the characteristics. However, in this method, there is a phenomenon that a columnar structure is obtained due to the fact that the deposition particles that come next do not deposit in the shadow of the initial deposition layer of the deposition particles. It was difficult to intentionally control the above items. As a method for improving this, a method of forming polishing marks on the substrate by rubbing treatment before vapor deposition is described, but generally the particle diameter of the vapor deposited film is about several tens of nanometers at maximum. In order to control the anisotropy of such particles, it was necessary to intentionally produce a pitch of submicron or less by polishing. However, with a general abrasive sheet, etc., the submicron level is the limit, and it is not easy to produce such fine polishing marks. In addition, as described above, the resonance wavelength of Al fine particles greatly depends on the refractive index of the surroundings, and in this case, the combination of transparent and opaque substances is important. There is no description of the combination for Further, as in Patent Document 1, when glass is used as a substrate, reflection of several percent from the glass interface is unavoidable, and no countermeasures have been taken.

Non-Patent Document 2 describes a polarizing plate for infrared communication called Lamipol. It has a laminated structure of Al and SiO ₂ and according to this document exhibits a very high extinction ratio. Non-Patent Document 3 describes that a high extinction ratio can be realized at a wavelength of 1 μm or less by using Ge instead of Al responsible for light absorption in Lamipol. Also, from Fig. 3 in the same material, Te (tellurium) can be expected to have a high extinction ratio. As described above, Lamipol is an absorptive polarizing plate that can obtain a high extinction ratio. Not suitable for boards.

Patent Document 4 discloses a wire grid polarizing plate. This is a substrate on which fine metal wires are formed at a pitch smaller than the wavelength of light in the operating band. Make the polarizing properties appear.

In addition, in Patent Document 5, a wire grid type polarizing element is formed by forming a dielectric layer/metal layer on a metal grid, and by forming a total of three layers, the light reflected from the metal grid is canceled by an interference effect. A method of using a wire grid mold as an absorption mold is disclosed. When using the optical properties obtained from such a multilayer structure as an absorptive polarizing plate, the film thickness and optical properties of the metal layer formed on the dielectric layer are important factors for obtaining the desired properties. Although it is thought that it becomes, it is not considered in the said patent. That is, although the patent does not address this point and the details are unclear, light must pass through the upper metal layer in order to obtain the interference effect as described. Passing light means that part of the light is absorbed by the upper metal film in the process. If there is absorption, the transmittance in the direction of the transmission axis decreases, which is not desirable in terms of the characteristics of the polarization transmission axis, particularly in liquid crystal displays that require high transmittance in the visible region. In other words, a polarizing plate having an absorption effect essentially does not function unless the optical anisotropy of the absorbing layer is controlled, and it is practically difficult to apply it as a polarizing plate.

Patent Document 6 describes an inorganic polarizing plate in which semiconductor nanorods are dispersed in glass. It is described that good polarization characteristics can be obtained in the visible light region, but since this is manufactured by the same method as Polarcor manufactured by Corning, it requires a stretching process and is difficult to increase in size.

U.S. Pat. No. 6,772,608 JP-A-2000-147253 Japanese Patent Application Laid-Open No. 2002-372620 U.S. Pat. No. 6,122,103 U.S. Pat. No. 6,813,077 Japanese Patent Application Laid-Open No. 2006-323119

J. Opt. Soc. Am. A Vol. 8, No. 4 619-624 Applied Optics Vol. 25 No. 2 1986 311-314 J. Lightwave Tec. Vol. 15 No. 6 1997 1042-1050 Development of Nanoparticle Optoscience Applied Physics Vol.73 No.7 2004 J. Microelectromechanical Systems Vol. 10 No. 1 2001 33-40

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in the prior art, and provides a polarizing element having a desired extinction ratio in the visible light range and light resistance properties against strong light, and a liquid crystal projector using the polarizing element. intended to

According to the present invention, a substrate that is transparent to visible light, a reflective layer that is made of a metal and has band-shaped thin films that extend in one direction on the substrate and is provided at regular intervals, and a dielectric layer that is formed on the reflective layer. A polarizing element is provided comprising a body layer and an antireflection layer provided between the substrate and the reflective layer.

Further, according to the present invention, a light source, a liquid crystal panel, an incident-side polarizing plate, and an output-side polarizing plate are provided, and either the incident-side polarizing plate or the output-side polarizing plate is transparent to visible light. a reflective layer made of a metal and having strip-shaped thin films extending in one direction on the substrate at regular intervals; a dielectric layer formed on the reflective layer; and the substrate and the reflective layer. and an antireflection layer disposed between.

According to the polarizing element of the present invention, it is possible to provide a polarizing element having a desired extinction ratio in the visible light range and having higher durability than conventional polarizing elements.
Further, according to the liquid crystal projector of the present invention, since the polarizing element has excellent light resistance against strong light, it is possible to realize a highly reliable liquid crystal projector.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure in 1st Embodiment of the polarizing element which concerns on this invention. FIG. 4 is a cross-sectional view of an uneven portion of a substrate; FIG. 4 is a cross-sectional view showing the uneven shape of the surface of the polarizing element according to the present invention; It is the schematic which shows the structure of diagonal sputtering film-forming. FIG. 2 is a schematic diagram showing the configuration of a second embodiment of a polarizing element according to the present invention; 6A and 6B are diagrams for explaining the action of the polarizing element shown in FIG. 5; FIG. 6 is a schematic side cross-sectional view showing a modification of the configuration of the polarizing element shown in FIG. 5; FIG. 6 is a diagram showing an example (1) of countermeasures against output surface stray light of the polarizing element shown in FIG. 5; FIG. 6 is a diagram showing an example (2) of countermeasures against output surface stray light of the polarizing element shown in FIG. 5; FIG. It is a schematic diagram showing a configuration of a variation of the second embodiment of the polarizing element according to the present invention. FIG. 11 is a diagram showing an output surface stray light countermeasure example (1) in the polarizing element having the configuration shown in FIG. 10 ; FIG. 11 is a diagram showing an output surface stray light countermeasure example (2) in the polarizing element having the configuration shown in FIG. 10 ; 3 is a cross-sectional view showing the configuration of the optical engine portion of the liquid crystal projector according to the present invention; FIG. FIG. 2 is an explanatory view of a method of obliquely sputter-depositing Ge on a stationary substrate, and a view showing measurement results of optical constants of the deposited Ge film; FIG. 2 is an explanatory diagram of a method of sputter-depositing Ge onto a rotating substrate (injection from the vertical direction), and a diagram showing measurement results of optical constants of the deposited Ge film; FIG. 4 is a diagram showing measurement results of optical constants of a Si film deposited by sputtering; FIG. 4 is a diagram showing polarized light transmission characteristics of a Ge film having optical anisotropy; FIG. 4 is a schematic diagram showing a sample configuration of Example 2; FIG. 10 is a diagram showing the results of optical properties of Example 2; FIG. 10 is a diagram showing the results of optical properties of Example 3; FIG. 3 is a diagram showing optical constants of an inorganic fine particle layer made of Ag and having optical anisotropy. FIG. 22 is a diagram showing polarized light transmission characteristics of a polarizing element having the inorganic fine particle layer of FIG. 21; FIG. 3 is a diagram showing the surface texture of an inorganic fine particle layer on a flat plate; FIG. 4 is a diagram showing the polarization characteristics of the polarizing element sample having the configuration shown in FIG. 3(c); It is an element distribution mapping diagram of the cross section of the polarizing element sample having the configuration shown in FIG. 3(c). FIG. 4 is a sketch diagram of observation results of an inorganic fine particle layer in the polarizing element sample having the configuration shown in FIG. 3(c). 4 is an electron beam diffraction image of the inorganic fine particle layer in the polarizing element sample having the configuration shown in FIG. 3(c). 6 is a diagram showing polarization characteristics of a polarizing element sample having the configuration shown in FIG. 5. FIG. 6 is a diagram showing the transmission contrast of the polarizing element sample having the configuration shown in FIG. 5; FIG. 6 is a sketch diagram of observation results of an inorganic fine particle layer in the polarizing element sample having the configuration shown in FIG. 5. FIG. 6 is an SEM image of the polarizing element sample having the configuration shown in FIG. 5 viewed from above. It is a figure which shows the relationship between the length|longer_axis of an inorganic fine particle, and a film thickness in oblique sputtering film-forming. FIG. 4 is a diagram showing preconditions of a polarizing element in optical property simulation; FIG. 10 is a diagram showing optical characteristics of a polarizing element in the case where the constituent material of the inorganic fine particle layer is Ge fine particles and a Ge thin film; It is an aspect ratio distribution of Ge fine particles when oblique sputtering film formation is performed on a flat plate by changing the substrate tilt angle θ. FIG. 3B is a diagram showing the polarization characteristics of the polarizing element sample having the configuration shown in FIG. FIG. 11 is an explanatory diagram of an oblique film forming method of Example 7; FIG. 11 is a diagram showing polarization characteristics of a Ge fine particle layer sample of Example 7; 6 is a relational diagram between the height of aluminum as a reflective layer and the contrast in the polarizing element having the configuration shown in FIG. 5. FIG. FIG. 10 is a diagram showing polarization characteristics of a polarizing element sample of Example 8; It is a figure which shows the uneven|corrugated state of the texture structure formed by the rubbing process. It is a figure which shows the transmittance|permeability characteristic of the board|substrate before and behind a rubbing process. FIG. 4 is a diagram showing the surface texture of a Ge fine particle film (antireflection film) provided on a rubbed substrate; FIG. 5 is a diagram showing improvement in polarization characteristics of an antireflection film by rubbing. FIG. 10 is a diagram showing polarization characteristics of a sample of an inorganic fine particle layer made of Si in Example 10; FIG. 10 is a diagram showing polarization characteristics of a sample of an inorganic fine particle layer made of Sn in Example 10;

A polarizing element according to the present invention includes a substrate transparent to visible light, and a linear inorganic fine particle layer in which inorganic fine particles are arranged in series on the substrate in one direction. A polarizing element having a one-dimensional grid-like wire grid structure arranged at regular intervals, wherein the inorganic fine particles have a long diameter in the direction in which the inorganic fine particles are arranged and a short diameter in a direction perpendicular to the arrangement direction. It is characterized by having shape anisotropy. Further, as an optical constant of the inorganic fine particle layer, the optical constant in the direction in which the fine inorganic particles are arranged is larger than the optical constant in the direction orthogonal to the direction in which the fine inorganic particles are arranged. Specifically, the refractive index in the direction in which the inorganic fine particles are arranged is greater than the refractive index in the direction perpendicular to the direction in which the inorganic fine particles are arranged, and the consumption coefficient in the direction in which the inorganic fine particles are arranged is perpendicular to the direction in which the inorganic fine particles are arranged. It is characterized by being larger than the consumption coefficient in the direction of rotation.

The configuration of the polarizing element according to the first embodiment of the present invention will be described below. Although the present invention will be described with reference to the embodiments shown in the drawings, the present invention is not limited to these, and can be modified as appropriate according to the mode of implementation. - As long as it is effective, it is included in the scope of the present invention.

In this embodiment, the polarizing element is made of a material transparent to visible light, and has projections extending in one direction parallel to the main surface of the substrate provided at regular intervals on the substrate. A layer is formed on the top or at least one side wall of the projection.
FIG. 1 shows a configuration example of a polarizing element according to a first embodiment of the present invention. 1(a) is a cross-sectional view of the polarizing element 10, and FIG. 1(b) is a plan view of the polarizing element 10. FIG.

As shown in FIG. 1, the polarizing element 10 is formed by selectively forming an inorganic fine particle layer 15 on one side of a convex portion 14a provided on the surface of a substrate 11 transparent to visible light. The layer 15 has a wire grid structure arranged at regular intervals on the substrate 11 .

Here, the substrate 11 is made of a material that is transparent to light in the working band (visible light range in this embodiment) and has a refractive index of 1.1 to 2.2, such as glass, sapphire, or crystal. there is In this embodiment, it is preferable to use glass, particularly quartz (refractive index 1.46) or soda-lime glass (refractive index 1.51). The composition of the glass material is not particularly limited. For example, an inexpensive glass material such as silicate glass, which is widely distributed as optical glass, can be used, and the manufacturing cost can be reduced. By using a crystal or sapphire substrate with high thermal conductivity as the constituent material of the substrate 11, it can be advantageously used as a polarizing element for an optical engine of a projector that generates a large amount of heat.

Concavo-convex portion 14 is formed on the main surface of substrate 11 so as to extend in one direction (absorption axis Y direction) parallel to the main surface of substrate 11 . It is formed periodically in a direction perpendicular to the Y direction (transmission axis X direction) at a pitch smaller than the wavelength of the visible light region. The uneven portion 14 is provided to form the inorganic fine particle layer 15 , and the wire grid structure of the inorganic fine particle layer 15 is determined by the processing size and pattern shape of the uneven portion 14 , and the desired shape of the polarizing element 10 is obtained. important for obtaining polarizing properties. That is, the processing size and pattern shape of the uneven portion 14 are appropriately set according to the target polarization characteristics (extinction ratio) and the target visible light wavelength region. Specifically, in FIG. 2 , the groove pitch (in the X direction) of the uneven portion 14 is 0.5 μm or less, the line width of the uneven portion 14 (width of formation of the convex portion 14 a ) is 0.25 μm or less, and the uneven portion 14 is formed to a depth of 1 nm or more.

The pitch, line width/pitch, recess depth (projection height), projection length, and top line width/bottom line width of the uneven portions 14 are preferably set within the following ranges.
0.05 μm<pitch<0.8 μm,
0.1<(line width/pitch)<0.9,
0.01 μm<recess depth<0.2 μm,
0.05 μm<protrusion length,
1.0≦(top line width/bottom line width)

The uneven portion 14 may be formed directly on the substrate 11 or may be formed separately. As a method for forming the concave-convex portion 14, there is a method of lapping with a polishing sheet, and a pattern is formed by coating a substrate with a photoresist such as that used in the manufacture of semiconductor devices and exposing the substrate to light using a mask, and then forming the pattern. There are a method of etching the substrate using a photoresist as a mask, a method of transferring the shape of the mold onto the substrate using a mold formed corresponding to the shape and size of the uneven portion 14 (nanoimprint method), and the like, which are adopted as appropriate. do it.

In addition, the shape of the convex portion of the uneven portion 14 can be formed in a rectangular shape such as a quadrangle or a trapezoid, a sawtooth shape, or a triangular shape. FIG. 3(a) shows an example in which the convex portion 14a of the uneven portion 14 has a rectangular cross section, and the inorganic fine particle layer 15 is formed on one side surface portion of the convex portion 14a. FIG. 3(b) shows an example in which the convex portion 16a of the concave/convex portion 16 has a serrated cross-section, and the inorganic fine particle layer 15 is formed on one side portion of the convex portion 16a which is erected in the vertical direction. By forming the cross section of the convex portion in a sawtooth shape, it is possible to avoid adhesion of the film to the top portion of the convex portion. FIG. 3(c) shows an example in which the convex portion 17a of the uneven portion 17 has a triangular cross section and the inorganic fine particle layer 15 is formed on one side surface thereof.

By forming the inorganic fine particle layer 15 on the top portion or at least one side wall portion of the convex portion 14a, the inorganic fine particle layer 15 having shape anisotropy is distributed on the surface of the substrate 11 in a desired fine shape in a striped pattern. It is possible to isolate the inorganic fine particles. In addition, since the inorganic fine particle layer 15 is formed on the irregularities 14 that are mechanically formed in advance, the irregularities 14 can be stably formed, and the shape of the inorganic fine particles layer 15 formed thereon can be improved. Easy to control.

The inorganic fine particle layer 15 is formed by attaching inorganic fine particles to the top or at least one of the side walls of the projections 14a so that the inorganic fine particles are linearly formed in one direction (absorption axis Y direction) parallel to the main surface of the substrate 11. It is arranged. "Inorganic fine particles are linearly arranged" means a continuous belt-like film in which inorganic fine particles are connected to each other, and inorganic fine particles are gathered in an appropriate size to form independent islands, and the islands are unidirectional. It may be in any state of a discontinuous film arranged in parallel, as long as a grain boundary is formed. In addition, by forming the inorganic fine particle layer 15 on each of the plurality of convex portions 14a that are regularly provided at regular intervals, the formation pattern of the inorganic fine particle layer 15 becomes striped (one-dimensional lattice) and forms a wire grid structure. Present.

In the present invention, the inorganic fine particles have shape anisotropy in which the diameter in the direction of arrangement of the fine inorganic particles is long and the diameter in the direction orthogonal to the direction of arrangement is small. In addition, it is desirable that the inorganic fine particles have a size equal to or smaller than the wavelength of the band used, and that each particle is completely isolated.

In the present invention, as the optical constant of the inorganic fine particle layer 15, the optical constant in the absorption axis Y direction (the direction in which the inorganic fine particles are arranged) is greater than the optical constant in the transmission axis X direction (the direction perpendicular to the direction in which the inorganic fine particles are arranged). It is important to be large. Specifically, the refractive index in the direction of the absorption axis Y of the inorganic fine particle layer 15 is larger than the refractive index in the direction of the transmission axis X, and the consumption coefficient in the direction of the absorption axis Y is larger than the consumption coefficient in the direction of the transmission axis X. characterized by In order to obtain this characteristic, the inorganic fine particle layer 15 is formed by oblique sputtering.

FIG. 4 shows the oblique sputtering film formation for forming the inorganic fine particle layer 15 of the present invention. Although an example of ion beam sputtering is shown here, the method is not limited to this, and any method may be used as long as it is a sputtering method.

In FIG. 4, 1 is a stage for supporting a substrate 11, 2 is a target, 3 is a beam source (ion source), and 4 is a control plate. The stage 1 is inclined at a predetermined angle θ with respect to the normal direction of the target 2 , and the substrate 11 is oriented such that the longitudinal direction of the projections 14 a of the uneven portion 14 is orthogonal to the incident direction of the inorganic fine particles from the target 2 . are placed in The angle θ is, for example, 0° to 15°. A target 2 is irradiated with ions extracted from the beam source 3 . The inorganic fine particles ejected from the target 2 by the irradiation of the ion beam are incident obliquely on the surface of the substrate 11 and adhere thereto. At this time, if a flat control plate 4 is placed on the substrate 11 at regular intervals (for example, 50 mm), the direction of the incident particles to the surface of the substrate 11 can be controlled, and the particles can be deposited only on the side walls of the projections 14a. can be done. At this time, the film thickness of the inorganic fine particle layer 15 is preferably 200 nm or less.

As described above, by tilting the substrate 11 with respect to the target 2 during film formation by the sputtering method to limit the incident direction of the inorganic fine particles, the particles are selectively formed and arranged on the top portion or one side portion of the convex portion 14a. Inorganic fine particles having shape anisotropy having a long diameter in the direction and a short diameter in the direction orthogonal to the arrangement direction are linearly arranged, and the optical constant in the direction of the absorption axis Y is greater than the optical constant in the direction of the transmission axis X. A large inorganic fine particle layer 15 can be obtained.

Here, as the material used for the inorganic fine particle layer 15 (material constituting the inorganic fine particles), it is necessary to select an appropriate material for the polarizing element 10 according to the band used. That is, metal materials and semiconductor materials are materials that satisfy this requirement. A simple substance or an alloy containing these can be mentioned. Semiconductor materials include Si, Ge, Te, and ZnO. Furthermore, silicide materials such as FeSi ₂ (especially β-FeSi ₂ ), MgSi ₂ , NiSi ₂ , BaSi ₂ , CrSi ₂ and CoSi ₂ are suitable.

Further, when the material used for the inorganic fine particle layer 15 is a semiconductor material, the bandgap energy of the semiconductor is involved in the absorption action. This is because it absorbs light below this energy. Therefore, when a semiconductor material is used as a polarizing element for visible light, the bandgap energy must be less than or equal to the operating band. For example, when considering the use of visible light, it is necessary to use a material that absorbs at a wavelength of 400 nm or more, that is, has a bandgap of 3.1 eV or less. As described in Non-Patent Document 4, the bandgap energy also depends on the size of the fine particles, and there is a tendency to increase sharply especially when the particle size is several nanometers. thickness must be determined. From this point of view, a semiconductor material having a small bandgap energy in the bulk state is preferable. is a desirable material.

With the above configuration, the polarizing element 10 has a desired extinction ratio in the visible light range and has higher durability than conventional polarizing elements.

If necessary, the front and back surfaces of the substrate may be coated with an antireflection film to prevent reflection at the interface between the air and the substrate, thereby improving the transmission axis transmittance. As the antireflection film, a generally used low refractive index film such as MgF ₂ or a multilayer film composed of a low refractive index film and a high refractive index film may be used. Further, after the structure shown in FIG. 1 is formed, the surface is coated with a material such as SiO ₂ which is transparent in the operating band as a protective film with a film thickness within a range that does not affect the polarization characteristics. Effective in improving reliability. However, since the optical properties of the inorganic fine particles are also affected by the refractive index of the surroundings, the formation of the protective film may cause changes in the polarization properties. In addition, since the reflectance for incident light also changes depending on the optical thickness of the protective film (refractive index x film thickness of the protective film), the protective film material and its film thickness should be selected in consideration of these factors. As a material, a substance having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Such substances include SiO ₂ and Al ₂ O ₃ . These can be formed by a general vacuum film formation method (chemical vapor deposition method, sputtering method, vapor deposition method, etc.), or a sol in which these are dispersed in a liquid, by spin coating method, dipping method, etc. be. Furthermore, a self-assembled film as described in Non-Patent Document 5 can also be used. For the purpose of improving moisture resistance, a water-repellent self-assembled film is preferable. Examples include perfluorodecyltrichlorosilane (FDTS) and octadecanetrichlorosilane (OTS). Since it has water repellency, it is also effective in terms of antifouling measures. From this, it can be purchased from a chemical manufacturer, for example Gelest, USA, and can be formed into a film by dipping. It can also be formed by vapor phase epitaxy, and Applied Microstructures in the United States sells dedicated equipment. In the case of such a silane-based self-assembled film, for the purpose of improving adhesion, the polarizing element may be coated with SiO ₂ as an adhesion layer by the method described above, and then the self-assembled film may be deposited. good.

Next, the configuration of the polarizing element according to the second embodiment of the present invention will be described. In the present embodiment, a reflective layer is provided on the substrate at regular intervals with strip-shaped thin films made of metal and extending in one direction parallel to the main surface of the substrate, and a dielectric is formed on the reflective layer. and the inorganic fine particle layer is formed on the dielectric layer at a position corresponding to the belt-shaped thin film.

FIG. 5 is a schematic diagram showing a configuration example of a polarizing element according to a second embodiment of the present invention. 5A is a cross-sectional view of the polarizing element 20, and FIG. 5B is a plan view of the polarizing element 20. FIG. As shown in FIG. 5, an inorganic fine particle layer 25 is selectively formed on a laminated structure of a dielectric layer 23 and a thin film 22a constituting a reflective layer 22 provided on the surface of a substrate 21 transparent to visible light. Thus, the inorganic fine particle layer 25 has a wire grid structure arranged at regular intervals on the substrate 21 .

Here, the substrate 21 is made of the same material as the substrate 11 in the first embodiment.

The reflective layer 22 is formed by arranging on the substrate 21 thin films 22a that are made of metal and extend in a strip shape in one direction (absorption axis Y direction) parallel to the main surface of the substrate 21 . Various materials can be used as the constituent material of the reflective layer 22. For example, metals or semiconductor materials such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, and Te are used. be able to. In addition to the metal material, for example, it may be composed of an inorganic film other than a metal or a resin film which is formed with a high surface reflectance by coloring or the like.

The thin film 22a is arranged on the surface of the substrate 21 at a pitch smaller than the wavelength of visible light, and is formed by patterning the metal film using photolithography, for example (metal grid). The reflective layer 22 functions as a wire grid polarizer. Among the light incident on the surface of the substrate 21, the polarizing wave having an electric field component in the direction (Y-axis direction) parallel to the longitudinal direction of the wire grid ( TE waves (S waves)) are attenuated, and polarized waves (TM waves (P waves)) having an electric field component in the direction (X-axis direction) perpendicular to the longitudinal direction of the wire grid are transmitted.

The pitch, line width/pitch, thin film height (thickness, grating depth), and thin film length (grating length) of the reflective layer 22 (thin film 22a) are preferably within the following ranges.
0.05 μm < pitch < 0.8 μm
0.1<(line width/pitch)<0.9
0.01 μm < thin film height < 1 μm
0.05 μm <thin film length

The dielectric layer 23 is formed on the surface of the substrate 21 by a general vacuum film forming method such as a sputtering method, a vapor deposition method, or a vapor deposition method, or a sol-gel method (for example, a method in which a sol is coated by a spin coating method and gelled by heat curing). ) is made of an optical material transparent to visible light, such as SiO ₂ film formed by ). The dielectric layer 23 forms a base layer for the inorganic fine particle layer 25, and as will be described later, the polarized light reflected by the inorganic fine particle layer 25 is transmitted through the inorganic fine particle layer 25 and reflected by the reflective layer 22. is formed with a film thickness in which the phase of is shifted by half a wavelength. Specifically, the thickness may be appropriately set within the range of 1 to 500 nm. It is formed for the purpose of adjusting the phase of the polarized light and enhancing the interference effect, and it is desirable to have a film thickness that shifts by half a wavelength. Contrast can be improved even if it is not used, and in practice, it may be determined by balancing the desired polarization characteristics and the actual manufacturing process. A practical film thickness range is 1 to 500 nm.

General materials such as SiO ₂ , Al ₂ O ₃ , and MgF ₂ can be used for the material constituting the dielectric layer 23 . These can be formed into thin films by general vacuum film formation methods such as sputtering, vapor deposition, and vapor deposition, or by coating a substrate with a sol-like substance and thermally curing it. Moreover, the refractive index of the dielectric layer 23 is preferably greater than 1 and less than or equal to 2.5. Since the optical properties of the inorganic fine particle layer 25 are also affected by the surrounding refractive index, it is possible to control the polarizing element properties by the dielectric layer material.

The inorganic fine particles layer 25 is formed by depositing inorganic fine particles on the dielectric layer 23 at a position corresponding to the thin film 22a so that the inorganic fine particles extend in one direction (absorption axis Y direction) parallel to the main surface of the substrate 21. They are arranged linearly. In addition, by forming the inorganic fine particle layer 25 on each of the plurality of thin films 22a that are regularly provided at regular intervals, the formation pattern of the inorganic fine particle layer 25 becomes striped and presents a wire grid structure.

In FIG. 5, the inorganic fine particle layer 25 has an oblong shape having a major axis direction parallel to the longitudinal direction (Y-axis direction) of the thin film 22a and a minor axis direction (X-axis direction) orthogonal to the longitudinal direction. Island-shaped inorganic fine particles 25a are arranged in the Y-axis direction. In addition, it is desirable that the inorganic fine particles 25a have a size equal to or smaller than the wavelength of the used band and that each particle is completely isolated.

In the present invention, as the optical constant of the inorganic fine particle layer 25, the optical constant in the absorption axis Y direction (the direction in which the inorganic fine particles are arranged) is larger than the optical constant in the transmission axis X direction (the direction orthogonal to the direction in which the inorganic fine particles are arranged). It is characterized by Specifically, the refractive index in the direction of the absorption axis Y of the inorganic fine particle layer 25 is higher than the refractive index in the direction of the transmission axis X, and the consumption coefficient in the direction of the absorption axis Y is higher than the consumption coefficient in the direction of the transmission axis X. characterized by In order to obtain this characteristic, the inorganic fine particle layer 25 is formed by an oblique sputtering method. The details are the same as the method shown in the first embodiment. The material used for the inorganic fine particle layer 25 is also the same as the material used for the inorganic fine particle layer 15 in the first embodiment.

In the polarizing element 20 of this embodiment configured as described above, the surface side of the substrate 21, that is, the surface side on which the strip-shaped thin film 22a, the dielectric layer 23 and the inorganic fine particle layer 25 are formed, is the light incident surface. The polarizing element 20 utilizes the four effects of light transmission, reflection, interference, and selective light absorption of polarized waves due to optical anisotropy, so that the electric field component parallel to the longitudinal direction of the wire grid of the reflective layer 22 is Attenuates polarized waves (TE waves (S waves)) with (Y-axis direction) and transmits polarized waves (TM waves (P waves)) with electric field components (X-axis direction) perpendicular to the longitudinal direction of the wire grid Let

That is, as shown in FIG. 6A, the TE wave is attenuated by the selective light absorption of the polarized wave due to the optical anisotropy of the inorganic fine particle layer 25 composed of the inorganic fine particles 25a having shape anisotropy. The thin film 22a functions as a wire grid and reflects the TE wave that has passed through the inorganic fine particle layer 25 and the dielectric layer 23, as shown in FIG. 6(b). At this time, the TE wave reflected by the thin film 22a is reflected by the inorganic fine particle layer 25 by configuring the dielectric layer 23 so that the phase of the TE wave transmitted through the inorganic fine particle layer 25 and reflected by the thin film 22a is shifted by half a wavelength. Attenuated by canceling each other out due to interference with the TE wave. Selective attenuation of the TE wave can be performed as described above. As described above, the film thickness that shifts by half a wavelength is desirable, but since the inorganic fine particle layer has an absorption effect, the contrast can be improved even if the film thickness of the dielectric layer is not optimized. It may be determined from the characteristics and economic efficiency in the actual manufacturing process.

On the other hand, if low reflection is required on the exit side, the light should be incident from the reflective layer side. In this case as well, the selective absorption effect of the inorganic fine particle layer provides the same transmission contrast as above. This is because, as will be described later, the magnitude of the transmission contrast depends on the thickness of the reflective layer. Applying this to actual use, for example, in the optical engine portion (FIG. 13) of the liquid crystal projector of the present invention, which will be described later, the polarizing plate of the present invention is attached to the incident polarizing plate 10A for the purpose of avoiding undesirable reflected light to the liquid crystal panel. When used, the film surface of the polarizing plate (inorganic fine particle layer 25 side in FIG. 6) is arranged to face the liquid crystal panel side. By doing so, undesired reflected light will return to the light source side. When the polarizing plate of the present invention is used as the output polarizing plate 10B or 10C, the film surface of the polarizing plate (inorganic fine particle layer 25 side in FIG. 6) should be directed toward the liquid crystal panel. The incident direction of light to this polarizing plate is reversed when it is used as the incident polarizing plate and the output polarizing plate, but as mentioned above, the same transmission contrast can be obtained regardless of which side the light is incident on, so it is practical. no problem above.

The polarizing element 20 can be manufactured, for example, as follows. That is, after laminating a metal film and a dielectric film on a substrate 21 and forming a lattice pattern of the metal film and the dielectric film by photolithography or the like, the inorganic fine particle layer 25 is formed by an oblique sputtering deposition method. By adjusting the incident angle during the oblique sputtering film formation, it is possible to deposit the fine particles intensively in the vicinity of the vertexes of the convex portions formed by the strip thin film 22a and the dielectric layer 23. FIG.

In addition to the above, it is also possible to apply a method in which a transparent material is formed in a one-dimensional grid pattern on a transparent substrate, and a metal layer, a dielectric layer and an inorganic fine particle layer are sequentially laminated on the convex portions of the grid by oblique film formation. be. Furthermore, a method may be used in which a metal film, a dielectric film, and a fine particle film are successively laminated on a substrate, and then these are collectively etched in a one-dimensional lattice pattern.

Furthermore, as shown in FIG. 7, after forming a reflective layer 22 on the substrate 21 in a one-dimensional grid pattern, a dielectric layer 23 is formed over the entire surface of the substrate 21 . As a result, the dielectric layer 23 has an uneven shape with convex portions directly above the strip-shaped thin films 22a of the reflective layer 22 and concave portions between the strip-shaped thin films 22a. After that, by forming an inorganic fine particle layer 25 on the side surface of the top of the convex portion of the dielectric layer 23 by an oblique sputtering film formation method, it is possible to manufacture a polarizing element having the same effects as in the example of FIG. can. The region where the inorganic fine particle layer 25 is formed is not limited to one side surface of the top of the dielectric layer 23 shown in the figure, and may be both side surfaces.

As the polarizing element of the present invention, a polarizing element having a configuration in which the dielectric layer 23 is omitted in FIG. 5 may be used. That is, by selectively forming the inorganic fine particle layer 25 on the thin film 22a constituting the reflective layer 22 provided on the surface of the substrate 21 transparent to visible light, the inorganic fine particle layer 25 is formed on the substrate 21. The wire grid structure is arranged at regular intervals. Even with this configuration, it is possible to provide a desired extinction ratio (contrast: transmission axis transmittance/absorption axis transmittance) in the visible light region.

Next, an example in which a selective light absorption layer is provided on the rear surface side of the polarizing element 20 as a countermeasure against stray light (ghost countermeasure) in the liquid crystal projector will be described.
FIG. 8 is a side sectional view showing a schematic configuration of the polarizing element 20A. In the figure, the same components as those of the polarizing element 20 described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the polarizing element 20A of this embodiment, a reflective layer 22 having a one-dimensional lattice shape is formed on the surface (one surface) of a substrate 21. On the reflective layer 22, a dielectric layer 23 and an inorganic fine particle layer 25 are formed. are formed sequentially. Then, on the back surface (the other surface) of the substrate 21, an uneven portion 26 made of a dielectric material and a second inorganic fine particle layer 27 formed on the top of the convex portion of the uneven portion 26 or at least on one side surface. A selective light absorption layer 28 for polarized waves is provided due to optical anisotropy.

In the polarizing element 20 without the optically anisotropic selective light absorption layer 28 for polarized waves, the back side of the substrate 21 exhibits a mirror surface due to the reflective layer 22. Light that has been reflected back by other optical elements such as lenses arranged in steps is reflected again by the mirror surface. Such stray light causes degradation of image quality such as ghost in liquid crystal projectors.

In this embodiment, by providing the selective light absorption layer 28 for the polarized wave with the optical anisotropy of the above structure on the back side of the substrate 21 , the stray light is absorbed and the reflection on the reflection layer 22 is prevented. The concave-convex portion 26 constituting the optically anisotropic polarized wave selective light absorption layer 28 is made of the same material as the dielectric layer 23 and extends in the same direction as the strip-shaped thin film 22a of the reflective layer 22 extends. It is formed in a one-dimensional lattice shape formed in The second inorganic fine particle layer 27 is formed by linearly arranging inorganic fine particles on the tops or side surfaces of the projections of the uneven portion 26, and is made of the same material as the inorganic fine particle layer 25 on the surface side of the substrate 21. As a result, a selective light absorption effect of incident light from the rear surface of the substrate 21 is produced.

As a method for forming the concave-convex portion 26, the same as the method for forming the dielectric layer 23, the sputtering method, the sol-gel method, or the like is used. It is preferable to apply the concave-convex shape by patterning using a photolithography technique or press forming by a nanoimprinting method. As a method for forming the second inorganic fine particle layer 27, oblique film formation similar to the method for forming the inorganic fine particle layer 25 on the surface side of the substrate 21 is suitable. The second inorganic fine particle layer 27 is formed on the top portion, one side surface portion, or both side surface portions of the projections of the uneven portion 26 .

Alternatively, as another method of manufacturing the polarizing element 20A, the polarizing element 10 shown in FIG. 1 and the polarizing element 20 shown in FIG. It may be the element 20A. In this case, it is preferable that the inorganic fine particles of the inorganic fine particle layers 15 and 25 are arranged in the same direction.

Next, an example in which an antireflection layer is provided between the substrate 21 and the reflective layer 22 as another countermeasure against ghosts in the liquid crystal projector will be described.
FIG. 9 is a side sectional view showing a schematic configuration of the polarizing element 20B. In the figure, the same components as those of the polarizing element 20 described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The polarizing element 20B of this embodiment is configured for the same purpose as the polarizing element 20A described above. That is, the polarizing element 20B of this embodiment has the antireflection layer 29 formed between the substrate 21 and the reflective layer 22 . By providing the anti-reflection layer 29 immediately below the one-dimensional lattice-like reflective layer 22 in this way, reflection of incident light from the rear surface of the substrate 21 is prevented.

The antireflection layer 29 is preferably a black layer such as a carbon black film. Thereby, incident light from the back surface of the substrate 21 can be efficiently absorbed. In addition to carbon, an oxygen-deficient silicon oxide layer and a low-reflection material layer having a lower reflectance than the reflection layer 22 can be applied. Alternatively, the same material as the inorganic fine particle layer 25 may be used as the antireflection layer 29 . In the illustrated example, the dielectric layer 2a is provided for the purpose of reducing the reflectance by obtaining an interference effect between the reflective layer 22 and the antireflection layer 29. FIG. The processing of the dielectric layer 2a and the antireflection layer 29 into the lattice shape can be performed at the same time, for example, by the pattern processing of the reflective layer 22. FIG.

Furthermore, there is the following method as another ghost countermeasure in liquid crystal projectors. That is, the surface of the substrate 21 is subjected to a rubbing treatment, and fine streaks are aligned in one direction so as to correspond to the arrangement direction of the inorganic fine particles 25a of the inorganic fine particle layer 25 to be formed on the surface. A textured structure is formed, and then a thin film (antireflection layer) made of inorganic fine particles having shape anisotropy is formed on the surface after the rubbing treatment by the oblique sputtering method described above so as to correspond to the arrangement direction of the inorganic fine particles 25a. do it. The texture structure improves the orientation of the inorganic fine particles so that the long axis direction of the inorganic fine particles becomes the longitudinal direction of the streaks, thereby improving the polarizing properties of the thin film and increasing the ghost countermeasure effect. At the same time, an increase in transmission contrast characteristics as a polarizing element can be expected.

As a variation of the second embodiment of the present invention, a multi-layer structure in which one or a plurality of dielectric layer 23/inorganic fine particle layer 25 laminate structures may be stacked on the inorganic fine particle layer 25 . FIG. 10 shows an example of the configuration.

In FIG. 10, the polarizing element 30 has a strip-shaped thin film 22a constituting a reflective layer 22, a dielectric layer 23, and an inorganic fine particle layer 25 laminated in this order on a substrate 21. On the inorganic fine particle layer 25, a dielectric The layer 23/inorganic fine particle layer 25 laminate structure 26a is further stacked to form a wire grid structure. Further, another laminated structure 26a may be stacked on top of this laminated structure 26a. As a result, the interference effect between each layer can be enhanced to increase the transmission axis direction contrast at a desired wavelength, and at the same time, the reflection component from the polarizing element, which is undesirable in the transmissive liquid crystal display device, can be reduced over a wide range. High contrast and low reflection can be achieved with a thinner film thickness than the polarizing element 20 having the configuration of FIG.

There are, for example, the following three methods for manufacturing the polarizing element 30 of the present invention. That is, as the first method, a reflective layer material (metal lattice material) and a dielectric film are laminated on the substrate 21, a one-dimensional lattice pattern is formed or etched by a technique such as nanoimprinting or photolithography, and then oblique sputtering is performed. Fine particles are formed into a film by a film method. According to this, by adjusting the incident angle during the oblique sputtering film formation, it is possible to deposit the inorganic fine particles intensively near the top of the dielectric layer 23 which is a convex portion. In the second method, a transparent material is used on a transparent substrate to form a one-dimensional lattice-shaped uneven portion, and the reflective layer material, the dielectric layer material, and the inorganic fine particle material are sequentially laminated by oblique film formation for the number of laminated layers. It is something to do. A third method is to sequentially laminate the laminated structure of (dielectric film/inorganic fine particle thin film) on the thin film (metal lattice film) of the reflective layer by the number of laminated layers, and then etch the laminated structure. It should be noted that the inorganic fine particle material does not need to have a perfect island shape, and it is sufficient that grain boundaries are formed. Alternatively, the dielectric layer 23 and the inorganic fine particle layer 25 may be manufactured by combining a formation method by sputtering film formation and etching and a formation method by oblique sputtering film formation. Although there is no limitation on the type of substrate material in carrying out the above manufacturing process, crystal or sapphire substrates with high thermal conductivity are suitable for application to projectors that generate a large amount of heat.

By the way, with the polarizing element 30 having the structure described so far, the light output surface (reflecting layer 22) is made of metal, so the reflectance increases when there is return light. Therefore, also in the present embodiment, it is preferable to take measures against the stray light on the exit surface as described above.
FIG. 11 and FIG. 12 show an example of countermeasures against exit surface stray light in this embodiment.

FIG. 11 shows an example in which the configuration of FIG. 8 is applied to this embodiment.
The polarizing element 30A has an uneven portion 26 made of a dielectric material on the surface (back surface) of the substrate 21 opposite to the surface of the substrate 21 on which the reflective layer 22 is formed. A selective light absorption layer 28 for polarized waves due to optical anisotropy, which is composed of the formed second inorganic fine particle layer 27, is provided.

FIG. 12 shows an example in which the configuration of FIG. 9 is applied to this embodiment.
In the polarizing element 30B, the polarizing element 30B is provided with an antireflection layer 29 immediately below the one-dimensional lattice-like reflective layer 22, and furthermore, a dielectric layer 29 is formed between the reflective layer 22 and the antireflection layer 29 for the purpose of obtaining an interference effect. A layer 2a is provided. 12, the dielectric layer 2a under the reflective layer 22 may be omitted, and the antireflection layer 29 may simply be formed under the reflective layer 22. FIG. If the antireflection layer 29 is the same as the inorganic fine particle layer 25, it contributes to the improvement of contrast. As the layer 29, a layer having a lower reflectance than the reflective layer 22 (low reflective layer) is preferably provided. If the reflectance is lower than that of the reflective layer 22, it is effective as a low-reflection material, and it is possible to use an oxide film such as carbon or oxygen-deficient SiOx, or use metal or semiconductor fine particles.

When the antireflection layer 29 and the dielectric layer 2a are added under the reflective layer 22, or when the antireflection layer 29 is formed directly under the reflective layer 22, these films are formed before the film for the reflective layer is formed. If these layers are formed only directly under the belt-like thin film 22a of the reflective layer 22 by etching simultaneously with the etching for forming the reflective layer 22, it is possible not to affect the transmission characteristics.

Also in the second embodiment, if necessary, the front and back surfaces of the substrate are coated with an antireflection film to prevent reflection at the interface between the air and the substrate, thereby improving the transmission axis transmittance. . As the antireflection film, a generally used low refractive index film such as MgF ₂ or a multilayer film composed of a low refractive index film and a high refractive index film may be used. After the configuration shown in FIG. 5 or FIG. 7, it is possible to coat the surface with a material such as SiO ₂ which is transparent in the operating band as a protective film with a thickness within a range that does not affect the polarization characteristics. It is effective for improving reliability such as improvement of However, since the optical properties of the inorganic fine particles are also affected by the refractive index of the surroundings, the formation of the protective film may cause changes in the polarization properties. In addition, since the reflectance for incident light also changes depending on the optical thickness of the protective film (refractive index x film thickness of the protective film), the protective film material and its film thickness should be selected in consideration of these factors. As a material, a substance having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Such substances include SiO ₂ and Al ₂ O ₃ . These can be formed by a general vacuum film formation method (chemical vapor deposition method, sputtering method, vapor deposition method, etc.), or a sol in which these are dispersed in a liquid, by spin coating method, dipping method, etc. be. Furthermore, a self-assembled film as described in Non-Patent Document 5 can also be used. For the purpose of improving moisture resistance, a water-repellent self-assembled film is preferable. Examples include perfluorodecyltrichlorosilane (FDTS) and octadecanetrichlorosilane (OTS). Since it has water repellency, it is also effective in terms of antifouling measures. From this, it can be purchased from a chemical manufacturer, for example Gelest, USA, and can be formed into a film by dipping. It can also be formed by vapor phase epitaxy, and Applied Microstructures in the United States sells dedicated equipment. In the case of such a silane-based self-assembled film, for the purpose of improving adhesion, the polarizing element may be coated with SiO ₂ as an adhesion layer by the method described above, and then the self-assembled film may be deposited. good.

Next, a liquid crystal projector according to the present invention will be explained.
The liquid crystal projector of the present invention includes a lamp serving as a light source, a liquid crystal panel, and any one of the polarizing elements 10, 20, 20A, 20B, 30, 30A, and 30B of the present invention described above.

FIG. 13 shows a configuration example of the optical engine portion of the liquid crystal projector according to the present invention. The optical engine portion of the liquid crystal projector 100 includes an incident side polarizing element 10A, a liquid crystal panel 50, an output pre-polarizing element 10B, and an output main polarizing element 10C for the red light LR, and an incident side polarizing element 10A, the liquid crystal panel 50, for the green light LG. Output pre-polarization element 10B, output main polarization element 10C, incident side polarization element 10A for blue light LB, liquid crystal panel 50, output pre-polarization element 10B, output main polarization element 10C, and output from each output main polarization element 10C A cross dichroic prism 60 is provided for synthesizing incoming light and emitting it to a projection lens. Here, the polarizing elements 10, 20, and 30 of the present invention are applied to the incident side polarizing element 10A, the output pre-polarizing element 10B, and the output main polarizing element 10C, respectively.

In the liquid crystal projector 100 of the present invention, light emitted from a light source lamp (not shown) is separated into red light LR, green light LG, and blue light LB by a dichroic mirror (not shown). The lights LR, LG, and LB that are incident on the polarizing element 10A and then polarized by the respective incident-side polarizing elements 10A are spatially modulated by the liquid crystal panel 50 and output, and pass through the output pre-polarizing element 10B and the output main polarizing element 10C. After passing through, they are synthesized by the cross dichroic prism 60 and projected from a projection lens (not shown). Even if the light source lamp has a high output, the polarizing elements 10, 20, and 30 of the present invention, which have excellent light resistance against strong light, are used, so that a highly reliable liquid crystal projector can be realized. can.

In addition, the polarizing element of the present invention is not limited to application to the liquid crystal projector, and is suitable as a polarizing element that receives heat as a usage environment. For example, it can be applied as a polarizing element for a car navigation system or a liquid crystal display for an instrument panel.

Below, the result of having verified the polarization characteristic in the polarizing element which concerns on this invention is shown.
(Example 1)
First, the optical properties of the inorganic fine particle layer formed by the oblique sputtering film formation shown in FIG. 4 were verified.
FIG. 14 shows experimental results of the effect of enhancing optical anisotropy by such oblique ion beam sputtering. As shown in FIG. 14A, a Ge particle film 44 was formed by ion beam sputtering by depositing Ge sputter particles on the glass substrate 41 while the substrate 41 was stationary at an angle of 10° to the surface of the glass substrate 41 . FIG. 14B shows measurement results of optical constants (refractive index, extinction constant) of the fabricated Ge particle film 44 . Measurements were made with a spectroscopic ellipsometer. The film thickness at this time is 10 nm. In this experiment, due to the occurrence of optical anisotropy, there was a difference in the optical constants, that is, the refractive index n and the extinction constant k within the plane. For comparison, a film of Ge sputtered particles was formed while the substrate 41 was rotated from the vertical direction as shown in FIG. 15A. Optical anisotropy of the refractive index n and the extinction constant k did not occur, and each optical constant was close to the literature value.

Also, the composition of the target 2 was changed from Ge to Si, a Si particle film was formed on the glass substrate 41 under the same conditions as in the Ge sputtering film formation, and its optical constant was measured. The results are shown in FIG.
In the case of Si as well, when the film is formed by oblique sputtering at an angle of 10° to the surface of the glass substrate 41 (FIG. 16A), optical anisotropy occurs, resulting in an in-plane optical constant, that is, the refractive index n and A difference was observed in the extinction constant k. Further, when the film was formed by sputtering while rotating the substrate 41 from the vertical direction (FIG. 16B), optical anisotropy of the refractive index n and the extinction constant k did not occur.

Next, the polarization transmittance in the case where the Ge particle film 44 with a film thickness of 20 nm is formed on the glass substrate 41 under the conditions of FIG. 14A was obtained by simulation calculation. The results are shown in FIG. Here, the optical constant in the X-axis direction is used for light whose electric field oscillates parallel to the X-axis direction, and the optical constant in the Y-axis direction is used for light whose electric field oscillates in the Y-axis direction. Calculating transmittance. According to the results, the transmittance differs depending on the polarization direction due to the optically anisotropic property. That is, by using such a film having optical anisotropy as a material for the polarizing element, it is expected that the characteristics of the polarizing element will be improved.

(Example 2)
Next, the influence of the presence or absence of optical anisotropy in the inorganic fine particle layer on the polarizing element was investigated. Specifically, on the premise of the configuration of the polarizing element shown in FIGS. 1 and 5, the polarization characteristics thereof were determined by wavelength rigorous coupled wave analysis (RCWA). Here, as shown in FIG. 18, assuming a configuration having an inorganic fine particle layer 45 made of Ge in a wire grid structure on a glass substrate 41, each dimension of the inorganic fine particle layer 45 is set to a pitch of 150 nm and a line width (in the direction of the Ge lattice). Width): 37.5 nm, the thickness is 100 nm when the inorganic fine particle layer 45 has optical anisotropy (method of FIG. 14A), and the thickness is 10 nm when there is no optical anisotropy (method of FIG. 15A). did The results are shown in FIG.

In FIG. 19, there is no optical anisotropy in the visible region of 550 nm or less (that is, the green and blue regions), which is important for optical engine applications such as projectors (data indicated by the dotted line labeled Bulk). ), the absorption axis transmittance is high and the reflectance is high even though the film thickness is thin. On the other hand, the one with optical anisotropy has a low absorption axis transmittance and a low reflectance. Therefore, it has desirable characteristics as an absorption type. Regarding the film thickness, this calculation assumes that the thickness is 10 nm without optical anisotropy. If the film is thickened, the absorption axis transmittance decreases, but the reflectance also increases at the same time. Therefore, properties desirable as a polarizing element such as those having optical anisotropy cannot be obtained by controlling the film thickness.

(Example 3)
Although FIG. 19 shows an example in which the inorganic fine particle layer is a single layer, the same applies to the polarizing element having a multi-layer structure of the inorganic fine particle layer shown in FIG.
Here, in the polarizing element with a multilayer structure, the polarization characteristics when the inorganic fine particle layer made of Ge is made optically anisotropic by the method shown in FIG. 14A and when it is made optically anisotropic by the method shown in FIG. 15A was calculated by wavelength rigorous coupled wave analysis (RCWA). The multilayer structure used here is composed of Ge (15 nm)/reflective layer; Al (240 nm)/dielectric layer; SiO ₂ (205 nm)/inorganic fine particle layer; Ge (90 nm) (surface side) from the substrate side. The structure (film thickness of each layer is shown in parentheses), and the dimensions of the inorganic fine particle layer were pitch: 150 nm and line width (Ge lattice direction width): 37.5 nm. In addition, in order to suppress the influence of stray light due to re-reflection of return light to the exit surface of the polarizing element, a Ge layer is provided on the substrate side of the reflective layer. The calculation results are shown in FIG. As in the case of a single layer (FIG. 19), when there is no optical anisotropy (data indicated by a dotted line described as isotropic), when there is optical anisotropy in the visible range of 550 nm or less (data indicated as anisotropic) The result is that the reflectance on the absorption axis is higher and the transmittance on the transmission axis is lower than the data indicated by the solid line). Therefore, it is not preferable as an absorptive polarizing element. As described above, the optical anisotropy has a great effect on the polarization characteristics of the polarizing element.

(Example 4)
As described above, by using an inorganic fine particle layer having optical anisotropy in a polarizing element, it is possible to improve the polarizing characteristics. Preferably, the optical constants of the inorganic fine particle layer are (transmission axis direction optical constant) < (absorption axis direction optical constant), that is, (transmission axis direction refractive index) < (absorption axis direction refractive index) and (transmission axis direction extinction It is essential that the relation of (absorption axial direction extinction coefficient) is satisfied. An embodiment showing this is shown in FIGS. 21 and 22. FIG.
FIG. 21 shows the optical constants of the Ag film (inorganic fine particle layer 25) in the polarizing element having the structure shown in FIG. It can be seen that this case also has optical anisotropy like Ge. However, the magnitudes of the refractive indices in the X and Y directions are inverted around a wavelength of 550 nm, and the extinction coefficients in the X and Y directions are inverted around a wavelength of 440 nm.
FIG. 22 shows the result of calculating the polarized light transmittance when the Ag film thickness is 20 nm using the optical constants of the Ag film (inorganic fine particle layer 25) shown in FIG. 21 in the same manner as in FIG. As the wavelength region becomes lower, the polarized light transmittance decreases, and the magnitude of the transmittance in the x and y directions is reversed near the wavelength of 450 nm. This is due to the inversion of the optical constants shown in FIG. 21. In the case of application to a polarizing element, having such an inversion characteristic means a decrease in polarized light transmittance, which is not preferable. On the absorption axis, a large extinction coefficient indicates a large absorptance, and on the transmission axis, it is desirable that the light incident from the air layer is transmitted without being attenuated or reflected. (due to refractive index = 1). Therefore, the desired optical constants of the inorganic fine particle layer are such that there is no inversion of the optical constants in the operating band, and (optical constant in the transmission axis direction)<(optical constant in the absorption axis direction), that is, (refractive index in the transmission axis direction)<(absorption (Axial refractive index) and (Axial transmission extinction coefficient) < (Absorption axial extinction coefficient).

(Example 5)
Next, the relationship between the manifestation of optical anisotropy and inorganic fine particles in the polarizing element of the present invention was investigated.
(1) Inorganic fine particle layer on a flat plate First, a substrate having a smooth surface obtained by forming a 10 nm SiO ₂ film on the surface of a single crystal Si substrate was used under the same conditions as in Example 1 (oblique sputtering film formation, relative to the substrate surface). A Ge particle film was formed by sputtering film formation from a vertical direction), and the shape of Ge particles in the Ge particle film was observed by an AFM (atomic force microscope). The results are shown in FIG.
In the sample formed by oblique sputtering shown in FIG. 23( a ), individual fine particles are clearly observed, and the fine particles have an anisotropic shape with a long diameter in the direction perpendicular to the Ge incident direction and a short diameter in the Ge incident direction. sex was occurring. On the other hand, in the sample formed by sputtering from the direction perpendicular to the substrate surface shown in FIG. No shape could be observed.

(2) Polarizing element 10
Next, a sample of the polarizing element having the configuration shown in FIG. 3(c) was produced. Here, first, a polymer layer (mr-I 8010E manufactured by Micro Resist Technology Co., Ltd.) applied to a quartz substrate is subjected to a thermal nanoimprint method using a mold with a primary lattice pattern (pitch 150 nm, line/space ratio = 0.7, depth 150 nm). to transfer the mold pattern to the polymer layer, and then etching the crystal substrate with CF4 gas + Ar gas using the polymer layer as a resist mask to obtain a substrate on which convex portions 17a extending in one direction are provided at regular intervals. 11. Then, using the ion beam sputtering apparatus shown in FIG. 4, oblique sputtering was performed on the substrate 11 at room temperature with the substrate tilt angle θ=5° as in Example 1 to form an inorganic fine particle layer 15 made of Ge and having a thickness of 30 nm. , and SiO ₂ with a film thickness of 15 nm was formed as a sample by vapor deposition. A multilayer film of SiO ₂ /Ta ₂ O ₅ was formed as an antireflection film on the back side of the substrate 11 by sputtering. The polarization characteristics of the obtained polarizing element samples were investigated. As a result, as shown in FIG. 24, optical anisotropy was exhibited in which the transmittance along the absorption axis was lower than the transmittance along the transmission axis.

When the elemental distribution of this polarizing element sample was analyzed by TEM from the cross section, as shown in the elemental distribution mapping of FIG. 15 was found to be formed. Based on this result, the inorganic fine particle layer 15 in the polarizing element sample was observed in detail. The results are shown in FIG. FIG. 26(a) is a sketch when observed from the cross section, with the element distribution result of FIG. 25 added. Also, FIG. 26(b) is a sketch when observed from above.

As shown in FIG. 26(b), the inorganic fine particle layer 15 is formed along the longitudinal direction of the primary grid-shaped protrusions 17a from the top to the side wall of each protrusion 17a. was observed as a line or band formed by continuously arranging the inorganic fine particles 15a having shape anisotropy. In addition, individual particles of the inorganic fine particles 15a were clearly observed, and it was observed that the long axis direction of the inorganic fine particles was the alignment direction and the short axis direction was the direction perpendicular to the alignment direction.

Further, when the electron beam diffraction image of the Ge portion in FIG. 25 was examined, no clear bright line was observed as shown in FIG. It turns out there is. Being amorphous means that the deposited Ge particles have no crystallographic orientation. In general, it is known that the structure of a Ge film formed at a low temperature tends to be amorphous (DUBEY M, MCLANE G F, JONES K A, LAREAU R T, ECKART D W, HAN W Y, ROBERTS C, DUNKEL J, WEST L C, Mat. Res. Soc. Symp. Proc. Vol. 340. 411-416 (1994)).

(3) Polarizing element 20
Next, a sample of the polarizing element having the configuration shown in FIG. 5 was produced. Here, an aluminum grating with a pitch of 150 nm and a grating depth of 200 nm was formed as a reflective layer 22 on a substrate 21 made of glass (Corning 1737), and a dielectric layer 23 of 30 nm thick SiO2 was formed thereon. Oblique sputtering film formation was performed under the same conditions as the polarizing element 10 of the example to laminate a Ge fine particle layer of 30 nm as the inorganic fine particle layer 25, and SiO2 having a thickness of 30 nm was formed as the outermost layer as a protective film, as shown in FIG. A polarizing element sample was produced. FIG. 28 shows the polarization characteristics of the polarizing element sample. The transmittance of the absorption axis is almost zero, and the reflectance is also low. Also, FIG. 29 shows the transmittance ratio in this case as a contrast, and the transmission contrast is 3000 or more in the green region centered on the 550 nm region, and 1500 or more in the visible light region including the blue region around 450 nm. and exhibited good characteristics as a polarizing element.

When this polarizing element sample was observed from the cross section, as shown in the sketch of FIG. 30(a), Ge It was found that an inorganic particle layer 25 consisting of was formed.

30(b) and 31 show the results of observing this polarizing element sample from above. FIG. 30(b) is a sketch, and FIG. 31 is an SEM image on which it is based.
An inorganic fine particle layer 25 is formed along the longitudinal direction of the dielectric layer 23 from the top to the side wall of each of the primary lattice-like dielectric layers 23, and the inorganic fine particle layer 25 has shape anisotropy. It was observed as a line or band in which fine particles 25a were arranged in a row. It was also observed that the inorganic fine particles 25a were aligned in the long axis direction and in the direction orthogonal to the short axis direction.

From the above results, the inorganic fine particles in the polarizing element of the present invention have shape anisotropy due to the oblique sputtering film formation, and when the inorganic fine particles are arranged in a one-dimensional lattice, the long axis direction is the one-dimensional lattice. are aligned in the lattice direction. It is also in an amorphous state. In the present invention, these factors are considered to affect the expression of optical anisotropy. Fine particles having shape anisotropy are formed as a film by oblique deposition, and exhibiting this shape anisotropy is called a steering effect (Jikeun Seo, S.-M. Kwon, H.-Y. Kim and J.-S. Kim Phys. Rev. B67 121402 (2003)).

In the oblique sputtering film formation, as shown in FIG. 32, the shape of the film formation particles changes with the film thickness (thickness in the growth direction of the inorganic fine particles), which affects the optical anisotropy. That is, when the film thickness b of the inorganic fine particles is smaller than the major axis a of the particle (FIG. 32A), it has optical anisotropy in two directions (X and Y directions) on the substrate surface, and the direction of the particle major axis a is the absorption axis. becomes. On the other hand, when the film thickness b of the inorganic fine particles is larger than the major diameter a of the particles (FIG. 32B), the inorganic fine particles have optical anisotropy in the thickness direction and in-plane axial direction. is the absorption axis, the directions of optical anisotropy are substantially reversed between FIG. 32A and FIG. 32B. In the polarizers 10 and 20 of the present invention, since the lattice direction is used as the absorption axis, a thicker film means a lower polarization characteristic. Therefore, as shown in FIG. 32A, it is desirable to use it in a region where the relationship of (particle long diameter a)>(particle film thickness b) is satisfied.

By the way, even if a thin film having no optical anisotropy (for example, a germanium thin film) is formed on the dielectric layer 23 instead of the inorganic fine particle layer 25, the reflectance in the direction of the absorption axis can be improved by optimizing the film thickness. Suppression is possible. However, in this case, since the suppression is dominated by the interference effect, there is a problem that the wavelength band is narrow and the transmission axis transmittance is reduced due to absorption in the transmission axis direction. Furthermore, since the interference effect is sensitive to film thickness, it is necessary to strictly control the film thickness of the dielectric layer 23 and the film thickness of the germanium thin film in order to obtain desired characteristics. In contrast, the present invention uses germanium fine particles having optical anisotropy, so that the design range is wide and the production is easy.

Therefore, the difference in optical characteristics between when the inorganic fine particle layer 25 in the polarizing element 20 is a thin film and when it is a fine particle was simulated by the wavelength rigorous coupled wave analysis (RCWA) method. Here, the film thickness (aluminum thickness) of the reflective layer 22 is 200 nm, the grating pitch is 150 nm, the aluminum width is 45 nm, and the dielectric layer 23 is 30 nm thick (SiO ₂ ). Dependence of absorption axis reflectance, transmission axis transmittance, and transmission contrast at a wavelength of 450 nm was calculated. The optical constants of the Ge thin film are the values shown in FIG. It was obtained by calculation assuming that fine particles sufficiently smaller than the wavelength are distributed in the dielectric layer in the same axial direction. Further, the volume fraction of Ge in the dielectric layer 23 was 0.4 and the aspect ratio was 20 for calculation.
The results are shown in FIG. FIG. 34(a) shows the absorption axis reflectance, FIG. 34(b) shows the transmission axis transmittance, and FIG. 34(c) shows the transmission contrast. It can be seen that in the case of the Ge fine particles, the contrast is about the same as in the case of the Ge thin film, the transmittance is higher, and the film thickness range in which the reflectance can be reduced is wider.

(Example 6)
Next, the relationship between the aspect ratio of the inorganic fine particles and the contrast in the polarizing element was investigated.
(1) Oblique sputtering film formation on a flat plate First, using the ion beam sputtering apparatus shown in FIG. is formed, the resulting sample is observed with SEM, 40 arbitrary Ge fine particles in the SEM image are extracted, and the size (major axis (major axis length), minor axis (minor axis length)) is measured Then, the aspect ratio was obtained.
FIG. 35 shows the results as a histogram of aspect ratios. As the distribution of the histogram, the distribution shifts to a larger aspect ratio in FIG. 35(b) (substrate tilt angle θ=10°) than in FIG. 35(a) (substrate tilt angle θ=20°). A trend was seen. In this case, the average length of the long axis of the Ge particles was 30 nm when the substrate tilt angle θ was 20°, and 63 nm when the substrate tilt angle θ was 10°. It was 3.2 when the substrate tilt angle θ was 20°, and 4.0 when the substrate tilt angle θ was 10°.

In addition, using the ion beam sputtering apparatus in FIG. 4, the transmittance of a sample in which a Ge fine particle layer with a thickness of 10 nm was formed on a flat glass substrate (Corning 1737) by changing the substrate tilt angle θ=20, 10° was measured, and the transmittance ratio at a wavelength of 550 nm was obtained as the contrast. Note that the x direction and the y direction have the relationship shown in FIG. 14A. Table 1 shows the results. When the substrate tilt angle θ is decreased, the aspect ratio of the Ge particles tends to increase and the contrast tends to increase.

(2) Polarizing element 10
Regarding the polarizing element 10 of Example 5, among the oblique sputtering deposition conditions when forming the inorganic fine particle layer 15, two levels of the substrate tilt angle θ = 10 and 20° were used, and the other conditions were the same as those of the polarizing element 10 of Example 5. A polarizing element sample was produced by The transmittance of this sample along the transmission axis and the absorption axis was measured, and the ratio of the transmittances at a wavelength of 550 nm was obtained as the contrast. The results are shown in FIG. 36 and Table 2. In the polarizing element of the present invention as well, there was a tendency for the contrast to increase as the substrate tilt angle θ decreased.

As described above, inorganic fine particles having shape anisotropy can be formed in the substrate plane by oblique sputtering. It depends on the angle (substrate tilt angle θ in FIG. 4), and the smaller the angle, the larger the aspect ratio. Further, as the aspect ratio increases, the transmission contrast also increases. By utilizing the steering effect of oblique sputtering film formation in this manner, a polarizing element having good characteristics can be realized.

(Example 7)
By changing the type of film formation method (dry process), a Ge fine particle layer was obliquely formed on a substrate on which a reflective layer 22 made of Al was provided in a one-dimensional lattice pattern (pitch: 150 nm). Here, the following three types of dry processes were used.
(a) electron beam deposition (Fig. 37(a))
A substrate on which Ge was mounted was tilted by 10 degrees with respect to the normal direction of the evaporation source, and was set at a distance of 80 cm from the evaporation source, and electron beam evaporation was performed at a film formation rate of 0.3 nm/sec.
(b) Magnetron sputtering (Fig. 37(b))
A substrate tilted 10 degrees to the normal direction of the Ge target was set at a distance of 40 cm from the target, and film formation was performed by magnetron sputtering at a film formation rate of 0.1 nm/sec.
(c) ion beam sputtering (Fig. 37(c))
It is a sputtering film forming method shown in FIG. 4 exemplified in the present invention. Here, the substrate was set at θ=45 degrees, separated from the Ge target by 15 cm, and ion beam sputtering film formation was performed at a film formation rate of 0.2 nm/sec.
The same substrate 11 as in the case of the polarizing element 10 of Example 5 was used as the substrate, and the Ge incident direction was set so as to be perpendicular to the longitudinal direction of the grating (x direction) (y direction), as in FIG. 14A. . In addition, the film thickness of the Ge fine particle layer was set to 10 nm.

The transmittance of the obtained sample was measured. The results are shown in FIG.
Among the three samples, the film formation method using ion beam sputtering has a high transmittance and a large difference in transmittance between the x and y directions.

(Example 8)
Among the polarizing elements according to the present invention, in the polarizing element 20 having the configuration shown in FIG. 5, the transmission contrast can be easily controlled by changing the height (film thickness) of the reflective layer 22 . As an example, FIG. 39 shows wavelength rigorous coupled wave analysis (RCWA) of the reflective layer thickness (aluminum height) and transmission contrast when the pitch of the primary lattice-shaped reflective layer 22 made of Al is 150 nm and the aluminum width is 37.5 nm. Calculation results are shown by

Further, in the polarizing element 20 having the structure shown in FIG. 5, the optical characteristics can be easily controlled by changing the height (film thickness) of the dielectric layer 23 . Here, on a substrate 21 made of glass (Corning 1737), a primary lattice-shaped reflective layer 22 made of Al is formed with a film thickness (aluminum height) of 200 nm, a pitch of 150 nm, and a lattice width of 50 nm. The film thickness of the dielectric layer 23 made of SiO2 was changed to 0, 19, 37, 56, and 74 nm, and the thickness of the inorganic fine particle layer 25 made of Ge fine particles was set to 30 nm. , and the relationship between the thickness of the dielectric layer and the transmission axis transmittance, contrast, and absorption axis reflectance of the obtained samples at wavelengths of 450, 550 and 650 nm was determined. Table 3 shows the results.

Based on the obtained results, the film thickness of the dielectric layer 23 should be in the range of 19 to 37 nm, for example, in order to reduce the absorption axis reflectance. In addition, the film thickness of the dielectric layer 13 can be set to 0 when the device is used for applications where the influence of reflection is small. This means a reduction in manufacturing steps, leading to an increase in productivity. In addition, high contrast is achieved at wavelengths of 450 to 650 nm, making it suitable for projector applications that use a wide range of wavelengths.
On the other hand, the transmittance is 70% or higher at a wavelength of 450 nm and 80% or higher at wavelengths of 550 and 650 nm. It is possible to further improve the transmittance by narrowing the pitch of the grating.
Also, the contrast can be adjusted by adjusting the height of the metal grid. If you want higher contrast, you can raise the aluminum grid, and if you want it lower, you can lower it.

Next, FIG. 40 shows the polarization characteristics in the case of having the same structure as the polarizing element 20 of Example 5 but with an aluminum height of 30 nm. In this case, since the film thickness of the reflective layer is thin (the aluminum height is low), the contrast is about 3 in the blue region, but the reflectance is suppressed to 2% or less by the effect of the Ge fine particles, as in FIG. It is In the case of the polarizing element having such performance, as shown in the SEM image of FIG. It has a nice shape. The same can be said for the polarizing element 10 shown in FIGS.

In the polarizing element of the present invention, the lattice shape (the shape and height of the convex portion 14a in FIG. 2 and the reflection layer 22/dielectric layer 23 in FIG. 5, the pitch of the primary lattice, etc.) and the steering effect (size of inorganic fine particles, aspect ratio, etc.) ratio, alignment, etc.), it is possible to realize a fine particle shape suitable for an absorbing polarizing element.

(Example 9)
In the polarizing element 20 shown in FIG. 5, as a countermeasure against stray light on the output surface (a countermeasure against ghost), the surface of the substrate 21 is formed with fine streaks aligned in one direction so as to correspond to the arrangement direction of the inorganic fine particles 25a to be formed later. Rubbing treatment is performed so as to have a certain texture structure, and a thin film of inorganic fine particles having shape anisotropy corresponding to the arrangement direction of the inorganic fine particles 25a (a thin film to be the antireflection layer 29 (hereinafter referred to as hereinafter) is formed on the surface after the rubbing treatment. , an antireflection film)). Specifically, a textured structure is mechanically formed on the surface of the substrate 21 using an abrasive material such as a polishing tape, and then an antireflection film made of inorganic fine particles is formed by an oblique sputtering deposition method, thereby forming a lattice structure. As with the inorganic fine particle layer 25 to be formed, the inorganic fine particles can have shape anisotropy due to the steering effect, so that the polarizing effect of the inorganic fine particles is enhanced, and as a result, the ghost suppressing effect can be enhanced. A specific implementation example will be described below.

Here, D20000 manufactured by Nippon Micro Coating was used as an abrasive to verify the effect. Corning 1737 glass was used for the substrate, and the texture was formed by rubbing the surface in one direction with D2000. FIG. 41 shows the results of measurement of the substrate surface after texture formation by AFM (atomic force microscope). The horizontal axis is the position on the substrate, and the vertical axis is the height of the unevenness on the surface. The average pitch of the unevenness on the substrate surface was 160 nm. When the transmittance of the substrate before and after texture formation was examined, it was found that the transmittance did not change before and after texture formation (before and after polishing), as shown in FIG. That is, according to this method, nano-level precision processing can be easily performed without deteriorating the transmission characteristics of the substrate.

Next, on the substrate after the texture formation, an antireflection film with a thickness of 10 nm made of Ge fine particles was formed by oblique sputtering with the ion beam sputtering apparatus shown in FIG. At this time, the relationship between the Ge incident direction and the substrate was set such that the y direction was the longitudinal direction of the texture in FIG. When the shape of the Ge microparticles in the antireflection film of the obtained sample was observed with an AFM (atomic force microscope), it was observed that the Ge microparticles were aligned along the texture as shown in FIG. rice field.

FIG. 44 shows the transmission characteristics of this sample. For comparison, a 1737 glass substrate, which was not subjected to rubbing treatment, was used, and a sample having an antireflection film formed thereon under the same conditions was also examined for transmission characteristics. In FIG. 44, the sample of this embodiment is indicated as "textured substrate", and the comparative sample is indicated as "as substrate". As a result, polarization characteristics were observed in both cases due to the steering effect, but texture formation showed higher transmittance in the x direction and a greater difference from the transmittance in the y direction, indicating better polarization characteristics. .
In the present invention, the sample of this example (a substrate having a textured structure on which an antireflection film is formed) is used, and the layer structure of the polarizing element 20 shown in FIG. 5 is formed thereon. An antireflection layer 29 is formed by patterning the body layer 23 and at the same time processing the antireflection film into a grid pattern. As a result, it is possible to enhance the anti-ghost effect, and at the same time, an increase in transmission contrast characteristics as a polarizing element can be expected.

(Example 10)
In most of the above examples, examples of polarizing elements have been shown using Ge as an example, but inorganic fine particles having shape anisotropy can also be formed from other materials. Therefore, by selecting a material, it is possible to obtain a polarizing element with a desired wavelength.
FIGS. 45 and 46 show the polarization characteristics of inorganic fine particles having a film thickness of 30 nm using Si and Sn, respectively, and having the structure of the polarizing element 10 shown in FIG. 3(c). An antireflection film was not formed on the back surface. Although these materials have a slightly higher reflectance than Ge, they have high transmission axis polarization characteristics in the blue region, and can be used as polarizing elements depending on the purpose.

DESCRIPTION OF SYMBOLS 1... Stage, 2... Target, 3... Beam source, 4... Control plate, 10, 10A, 10B, 10C, 20, 20A, 20B, 30, 30A, 30B... Polarizing element , 11, 21, 41 ... substrate, 14, 16, 17 ... uneven portion, 14a, 16a, 17a ... convex portion, 15, 25, 45 ... inorganic fine particle layer, 22 ... reflection Layer 22a... Strip thin film 23, 2a... Dielectric layer 25a... Inorganic fine particles 26... Uneven portion 27... Inorganic fine particle layer (Selection of polarized wave by optical anisotropy selective light absorption layer), 28: Selective light absorption layer for polarized waves due to optical anisotropy, 29: Antireflection layer, 44: Ge particle film, 50: Liquid crystal panel, 60:・Cross dichroic prism, 100・・・Liquid crystal projector

Claims (4)

a substrate transparent to visible light;
a reflective layer made of a metal and having strip-shaped thin films extending in one direction on the substrate provided at regular intervals;
a dielectric layer formed on the reflective layer;
an antireflection layer provided between the substrate and the reflective layer;
An uneven portion is formed on the substrate, the pitch of the uneven portion is 0.05 to 0.8 μm, the value obtained by dividing the line width of the uneven portion by the pitch is 0.1 to 0.9, and the The recess depth of the uneven portion is 0.01 to 0.2 μm, the length of the convex portion of the uneven portion is less than 0.05 μm, and the value obtained by dividing the line width of the top portion of the uneven portion by the line width of the bottom portion is 1.0. and
The uneven portion is for forming a wire grid structure, and the convex portion formed on the surface of the substrate so as to extend in one direction parallel to the surface of the substrate is formed on the one side of the substrate. periodically formed at a pitch smaller than the wavelength of the visible light region in a direction orthogonal to the direction,
Inorganic fine particles arranged on the substrate and having shape anisotropy having a long diameter in the arrangement direction and a short diameter in a direction orthogonal to the arrangement direction are arranged on the top of the protrusion, one side surface, or Inorganic fine particle layers arranged linearly on both side surfaces are formed.
Polarizing element. 2. The polarizing element according to claim 1, wherein a polarizing element protective layer transparent to light in the used band is formed on the outermost surface of the polarizing element. 3. The polarizing element according to claim 2, wherein the polarizing element protective layer is made of _SiO2 . The substrate is made of glass, sapphire, or quartz,
The uneven portion is formed on the substrate with a pitch of 0.05 to 0.5 μm, a line width of 0.25 μm or less, and a recess depth of 0.01 to 0.2 μm ,
The uneven portion is for forming a wire grid structure, and the convex portion formed on the surface of the substrate so as to extend in one direction parallel to the surface of the substrate is formed on the one side of the substrate. periodically formed at a pitch smaller than the wavelength of the visible light region in a direction orthogonal to the direction,
The polarizing element according to any one of claims 1 to 3.

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