JP5333615B2 - Polarizing element and transmissive liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which has a desired extinction ratio in a visible light region and has light resistance against strong light, and to provide a liquid crystal projector using the polarizing plate. <P>SOLUTION: The polarizing element 10 comprises: a substrate 11 transparent to visible light; and inorganic fine particle layers 15 made by linearly arranging inorganic fine particles on the substrate 11, the inorganic fine particle layers 15 being disposed on the substrate 11 at predetermined intervals to form a wire grid structure, wherein the inorganic fine particles each have shape anisotropic properties in which a diameter of the inorganic fine particles in the disposed direction is long and a diameter in a direction perpendicular to thereto is short. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a polarizing element having durability against strong light and a liquid crystal projector using the polarizing element.

  In the liquid crystal display device, it is indispensable to dispose a polarizing plate on the surface of the liquid crystal panel from the principle of image formation. The function of the polarizing plate is to absorb one of orthogonal polarization 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 high molecular organic substance is contained in a conventional film is often used.

  As a general method for producing a dichroic polarizing plate, a method of dyeing with a dichroic material such as a polyvinyl alcohol film and iodine, followed by crosslinking using a crosslinking agent and uniaxial stretching is used. Since it is produced by stretching as described above, this type of polarizing plate generally tends to shrink. In addition, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed particularly under humidified conditions. Moreover, since the film is fundamentally used, the mechanical strength as a device is weak. In order to avoid this, a method of adhering a transparent protective film may be used.

  Incidentally, in recent years, liquid crystal display devices have become more sophisticated as their applications have expanded. 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 heat resistance required for the polarizing plate used for these is required. However, since the film-based polarizing plate as described above is an organic substance, there is a limit in raising these characteristics.

  In response to this problem, Corning Corporation in the United States sells a highly heat-resistant inorganic polarizing plate under the name Polarcor. This polarizing plate has a structure in which silver fine particles are diffused in glass, and does not use an organic substance such as a film, and its principle uses plasma resonance of island-like fine particles. That is, light absorption by surface plasma resonance when light is incident on noble metal or transition metal island-like particles is used, and the absorption wavelength is affected by the particle shape and the surrounding dielectric constant. Here, when the shape of the island-shaped fine particles is elliptical, the resonance wavelengths in the major axis direction and the minor axis direction are different, and thereby deflection characteristics are obtained. Specifically, a polarization component parallel to the major axis on the long wavelength side is obtained. A polarization characteristic of absorbing and transmitting a polarization component parallel to the minor axis is obtained. However, in the case of Polarcor, the wavelength range in which the polarization characteristics can be obtained is a region close to the infrared region, and does not cover the visible light range required for a liquid crystal display device. This is due to the physical properties of silver used in the island-shaped fine particles.

  Patent Document 1 discloses a UV polarizing plate obtained by applying the above principle and depositing fine particles in glass by thermal reduction, and it is proposed to use silver as metal fine particles in a specific example. In this case, it is considered that absorption in the minor axis direction is used contrary to the previous Polarcor. As shown in Figure 1, although it functions as a polarizing plate even at around 400 nm, the extinction ratio is small and the band that can be absorbed is very narrow, so even if Polarcor and the technique of Patent Document 1 are combined, the entire visible light range It will not 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-shaped fine particles. According to this document, it is described that aluminum fine particles have a resonance wavelength shorter than that of silver fine particles by about 200 nm, and therefore it is possible to produce a polarizing plate that covers the visible light region by using aluminum fine particles.

  Patent Document 2 discloses several methods for producing a polarizing plate using aluminum fine particles. Among them, it is described that glass based on silicate is not desirable as a substrate because aluminum and glass react with each other, and calcium aluminoborate glass is suitable (paragraphs 0018 and 0019). However, glass using silicate is widely distributed as optical glass, and it is economically undesirable that a highly reliable product can be obtained at a low cost and this is not suitable. In addition, a method for forming island-shaped particles by etching a resist pattern is described (paragraphs 0037 and 0038). Usually, a polarizing plate used in a projector needs to have a size of several centimeters and a high extinction ratio. Therefore, for the purpose of a polarizing plate for visible light, the resist pattern size must be sufficiently shorter than the visible light wavelength, that is, several tens of nanometers, and the pattern must be formed in order to obtain a high extinction ratio. It is necessary to form it with high density. Moreover, when using it for projectors, a large area is required. However, in the method of applying high-density fine pattern formation by lithography as described, it is necessary to use electron beam drawing or the like in order to obtain such a pattern. Electron beam drawing is a method of drawing individual patterns from an electron beam, and is not practical because of poor productivity.

  Further, Patent Document 2 describes that aluminum is removed by chlorine plasma. However, when etching is usually performed, chloride adheres to the side wall of the aluminum pattern. Although it can be removed with a commercially available wet etching solution (for example, SST-A2 from Tokyo Ohka Kogyo Co., Ltd.), such a chemical solution that reacts with aluminum chloride reacts with aluminum even though the etching rate is slow. 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, in order to obtain adhesion between the substrate and aluminum, it is considered that aluminum needs to be deposited on the substrate surface to some extent. However, this means that the shape of the deposited aluminum film is different from prolate spheres including prolate ellipsoids, which are suitable shapes described in paragraph 0015. In addition, paragraph 0047 describes that the overprecipitation integral is removed by anisotropic etching perpendicular to the surface. In order to function as a polarizing plate, the shape anisotropy of aluminum is extremely important. Therefore, it is considered necessary to adjust the amount of aluminum deposited on the resist portion and the substrate surface so that a desired shape can be obtained by etching. However, as described in paragraph 0047, the submicron is 0.05 μm or less. It is considered very difficult to control these by size, and it is doubtful whether it is suitable as a production method with high productivity. In addition, as a characteristic of the polarizing plate, high transmittance is required in the direction of the transmission axis, but when glass is usually used for the substrate, reflection of several percent from the glass interface is unavoidable, and no countermeasure is taken to obtain high transmittance. It is difficult.

  Patent Document 3 describes a polarizing plate by oblique vapor deposition. This method obtains polarization characteristics by fabricating a micro-columnar structure by oblique deposition of a transparent and opaque material with respect to the wavelength of the band used, and unlike Patent Document 1, a fine pattern can be obtained by a simple method. Although it is considered a highly productive method, there are also problems. In other words, the aspect ratio of the micro-columnar structure of the opaque material, the spacing between the individual micro-columnar structures, and the linearity are important factors for obtaining good polarization characteristics, and the reproducibility of the characteristics. From this point of view, this method should be intentionally controlled. However, in this method, the phenomenon that the columnar structure is obtained by the deposition of the next flying vapor particles not depositing in the shadowed part of the initial deposition layer of the vapor deposition particles. Since it is used, it was difficult to control the above items intentionally. As a method for improving this, a method of providing a polishing mark on a substrate by rubbing before vapor deposition is described, but in general, the particle diameter of the vapor deposition 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 submicron pitch by polishing. However, a general polishing sheet or the like has a limit of about submicron, and it is not easy to manufacture such fine polishing marks. In addition, as described above, the resonance wavelength of the Al fine particles greatly depends on the surrounding refractive index, and the combination of transparent and opaque materials in this case is important. However, Patent Document 3 obtains good polarization characteristics in the visible light region. There is no description about the combination. Further, as in Patent Document 1, when glass is used as a normal substrate, several percent of reflection from the glass interface is unavoidable, and no countermeasure has been taken.

  Non-Patent Document 2 describes a polarizing plate for infrared communication called Lamipol. This has a laminated structure of Al and SiO2, 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 that is responsible for Lamipol's light absorption. Moreover, it can be expected that FIG. 3 to Te (tellurium) in the same material can also obtain a high extinction ratio. In this way, Lamipol is an absorptive polarizing plate that provides a high extinction ratio, but it is polarized light for projector applications that requires a size of several cm square because the thickness of the light-absorbing and transmissive materials is the size of the light-receiving surface. Not suitable for boards.

  Patent Document 4 discloses a wire grid type polarizing plate. This is a thin metal wire formed on the substrate at a pitch smaller than the wavelength of the light in the use band, and reflects light of a polarization component parallel to the thin metal wire and transmits a perpendicular polarization component to give a predetermined Appears polarization characteristics.

  In Patent Document 5, a wire grid type polarizing element is formed by forming a dielectric layer / metal layer on a metal grid, and a total of three layers is used, so that light reflected from the metal grid is canceled out by an interference effect, so that reflection is generally performed. A method of using a wire grid as a mold as an absorption mold is disclosed. When using the optical characteristics obtained with such a multilayer structure as an absorption type polarizing plate, the film thickness and optical characteristics of the metal layer formed on the dielectric layer are important factors for obtaining desired characteristics. This is not considered in the patent. That is, in this patent, this point is not described and details are unknown. However, in order to obtain the interference effect as described, it is necessary for light to pass through the upper metal layer. The passage of light means that part of the light is absorbed by the upper metal film in the process. Absorption reduces the transmittance in the direction of the transmission axis, which is not desirable as a characteristic of the polarization transmission axis, and is not preferable particularly in a liquid crystal display device that requires high transmittance in the visible range. That is, a polarizing plate having an absorption effect essentially does not function unless the optical anisotropy of the absorbing layer is controlled, and is practically difficult to apply as a polarizing plate.

  Patent Document 6 describes an inorganic polarizing plate in which semiconductor nanorods are dispersed in glass. Although it is described that good polarization characteristics can be obtained in the visible light region, this is manufactured by a method similar to the above-mentioned Corning's Polarcor, so that a stretching process is required and it is difficult to increase the size.

US Pat. No. 6,772,608 JP 2000-147253 A JP 2002-372620 A US Pat. No. 6,122,103 US Pat. No. 6813077 JP 2006-323119 A

J. et al. Opt. Soc. Am. A Vol. 8, no. 4 619-624 Applied Optics Vol. 25 No. 2 1986 311-314 J. et al. 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

  The present invention has been made in view of the above problems in the prior art, and provides a polarizing plate having a desired extinction ratio in the visible light region and having light resistance to strong light, and a liquid crystal projector using the polarizing plate. The purpose is to do.

  According to the present invention, a substrate transparent to visible light, a reflective layer made of metal and extending in one direction on the substrate and having a strip-like thin film provided at regular intervals, and a dielectric formed on the reflective layer A body layer and an inorganic fine particle layer in which inorganic fine particles are linearly arranged, and the inorganic fine particle layer is located on both sides of the top of the strip thin film on the dielectric at a position corresponding to the strip thin film. A polarizing element is provided which has a wire grid structure formed on the surface portion and having the same direction as the direction in which the inorganic fine particles are linearly arranged in the longitudinal direction.

  Moreover, according to this invention, it has a light source, a liquid crystal panel, an incident side polarizing plate, and an output side polarizing plate, and either the said incident side polarizing plate or the said output side polarizing plate is transparent with respect to visible light. A substrate, a reflective layer in which strip-like thin films made of metal and extending in one direction on the substrate are provided at regular intervals, a dielectric layer formed on the reflective layer, and inorganic fine particles arranged linearly The inorganic fine particle layer is formed on both sides of the top of the strip thin film on the dielectric layer at a position corresponding to the strip thin film, and the inorganic fine particles are linearly formed. There is provided a transmissive liquid crystal projector that is a polarizing element having a wire grid structure whose longitudinal direction is the same direction as the arranged direction.

According to the polarizing element of the present invention, it is possible to provide an element having higher durability than the conventional polarizing element while having a desired extinction ratio in the visible light region.
Moreover, according to the liquid crystal projector of the present invention, since the polarizing element having excellent light resistance against strong light is provided, a highly reliable liquid crystal projector can be realized.

It is the schematic which shows the structure in 1st Embodiment of the polarizing element which concerns on this invention. It is sectional drawing of the uneven | corrugated | grooved part of a board | substrate. It is sectional drawing which shows the uneven | corrugated shape of the polarizing element surface which concerns on this invention. It is the schematic which shows the structure of oblique sputtering film-forming. It is the schematic which shows the structure in 2nd Embodiment of the polarizing element which concerns on this invention. It is a figure explaining the effect | action of the polarizing element shown in FIG. It is a schematic sectional side view which shows the modification of a structure of the polarizing element shown in FIG. It is a figure which shows the output surface stray light countermeasure example (1) of the polarizing element shown in FIG. It is a figure which shows the output surface stray light countermeasure example (2) of the polarizing element shown in FIG. It is the schematic which shows the structure of the variation of 2nd Embodiment of the polarizing element which concerns on this invention. It is a figure which shows the output surface stray light countermeasure example (1) in the polarizing element of the structure shown in FIG. It is a figure which shows the output surface stray light countermeasure example (2) in the polarizing element of the structure shown in FIG. It is sectional drawing which shows the structure of the optical engine part of the liquid crystal projector which concerns on this invention. It is explanatory drawing of the method of performing the oblique sputtering film-forming of Ge with respect to a stationary board | substrate, and the figure which shows the measurement result of the optical constant of the formed Ge film. It is explanatory drawing of the method of performing the sputter film-forming (injection from the orthogonal | vertical direction) of Ge with respect to the rotating board | substrate, and a figure which shows the measurement result of the optical constant of the formed Ge film. It is a figure which shows the measurement result of the optical constant of Si film | membrane formed into a film by sputtering. It is a figure which shows the polarization transmission characteristic of Ge film | membrane which has optical anisotropy. 6 is a schematic diagram illustrating a sample configuration of Example 2. FIG. It is a figure which shows the result of the optical characteristic of Example 2. FIG. It is a figure which shows the result of the optical characteristic of Example 3. It is a figure which shows the optical constant of the inorganic fine particle layer which consists of Ag and has optical anisotropy. It is a figure which shows the polarization transmission characteristic of the polarizing element which has an inorganic fine particle layer of FIG. It is a figure which shows the surface structure of the inorganic fine particle layer on a flat plate. It is a figure which shows the polarization characteristic of the polarizing element sample of the structure shown in FIG.3 (c). It is an element distribution mapping figure of the polarizing element sample cross section of the structure shown in FIG.3 (c). It is a sketch figure of the observation result of the inorganic particulate layer in the polarizing element sample of the composition shown in Drawing 3 (c). It is an electron beam diffraction image of the inorganic fine particle layer in the polarizing element sample of the structure shown in FIG.3 (c). It is a figure which shows the polarization characteristic of the polarizing element sample of the structure shown in FIG. It is a figure which shows the transmission contrast of the polarizing element sample of the structure shown in FIG. It is a sketch figure of the observation result of the inorganic fine particle layer in the polarizing element sample of composition shown in FIG. It is a figure which shows the relationship between the long diameter of an inorganic fine particle and film thickness in oblique sputtering film-forming. It is the SEM image which looked at the polarizing element sample of the structure shown in FIG. 5 from the top. It is a figure which shows the precondition of the polarizing element in an optical characteristic simulation. It is a figure which shows the optical characteristic of a polarizing element in case the constituent material of an inorganic fine particle layer is Ge fine particle and Ge thin film. This is an aspect ratio distribution of Ge fine particles when oblique sputtering film formation is performed by changing the substrate inclination angle θ on a flat plate. It is a figure which shows the polarization characteristic of the polarizing element sample of the structure shown in FIG.3 (c) at the time of changing a board | substrate inclination-angle (theta) and carrying out oblique sputtering film-forming. 10 is an explanatory diagram of an oblique film formation method of Example 7. FIG. It is a figure which shows the polarization characteristic of Ge fine particle layer sample of Example 7. FIG. 6 is a relationship diagram between the height of aluminum as a reflective layer and contrast in the polarizing element having the configuration shown in FIG. 5. It is a figure which shows the polarization characteristic of the 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. It is a figure which shows the surface structure | tissue of Ge fine particle film (antireflection film) provided on the board | substrate by which the rubbing process was carried out. It is a figure which shows the improvement of the polarization characteristic of the antireflection film by a rubbing process. It is a figure which shows the polarization characteristic of the sample of the inorganic fine particle layer which consists of Si of Example 10. FIG. It is a figure which shows the polarization characteristic of the sample of the inorganic fine particle layer which consists of Sn of Example 10. FIG.

  The 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 one direction on the substrate, and the inorganic fine particle layer is the substrate. A polarizing element having a one-dimensional lattice-like wire grid structure arranged at regular intervals above, wherein the inorganic fine particles have a long diameter in the arrangement direction of the inorganic fine particles and a short diameter in a direction perpendicular to the arrangement direction. It has a shape anisotropy. In addition, as an optical constant of the inorganic fine particle layer, an optical constant in the arrangement direction of the inorganic fine particles is larger than an optical constant in a direction orthogonal to the arrangement direction of the inorganic fine particles. Specifically, the refractive index in the arrangement direction of the inorganic fine particles is larger than the refractive index in the direction orthogonal to the arrangement direction of the inorganic fine particles, and the wear coefficient in the arrangement direction of the inorganic fine particles is orthogonal to the arrangement direction of the inorganic fine particles. It is characterized by being larger than the wear coefficient in the direction of the movement.

  The configuration of the polarizing element according to the first embodiment of the present invention will be described below. The present invention will be described with reference to the embodiment shown in the drawings, but the present invention is not limited to this, and can be appropriately changed according to the embodiment. -As long as an effect is produced, it is included in the scope of the present invention.

In the present embodiment, the polarizing element is made of a material transparent to visible light, and convex portions extending in one direction parallel to the main surface of the substrate are provided on the substrate at regular intervals. The layer is formed on the top or at least one side wall of the convex portion.
FIG. 1 shows a configuration example of the polarizing element according to the first embodiment of the present invention. FIG. 1A is a sectional view of the polarizing element 10, and FIG. 1B is a plan view of the polarizing element 10.

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

  Here, the substrate 11 is made of a material having a refractive index of 1.1 to 2.2, for example, glass, sapphire, crystal, etc., with respect to light in the use band (visible light region in the present embodiment). Yes. In the present embodiment, it is preferable to use glass, particularly quartz (refractive index 1.46) or soda lime glass (refractive index 1.51). The component composition of the glass material is not particularly limited. For example, an inexpensive glass material such as silicate glass widely distributed as optical glass can be used, and the manufacturing cost can be reduced. By using a quartz 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.

  The concavo-convex portion 14 is a convex portion 14 a having a rectangular cross-sectional shape formed on the main surface of the substrate 11 so as to extend in one direction (absorption axis Y direction) parallel to the main surface of the substrate 11, and the absorption axis of the substrate 11. It is formed periodically at a pitch smaller than the wavelength in the visible light region in a direction (transmission axis X direction) perpendicular to the Y direction. 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 polarizing element 10 is expected. This is important for obtaining polarization characteristics. That is, the processing size and pattern shape of the concavo-convex 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 pitch (in the X direction) of the grooves of the concavo-convex portion 14 is 0.5 μm or less, the line width of the concavo-convex portion 14 (formation width of the convex portion 14 a) is 0.25 μm or less, and the concavo-convex portion 14. The formation depth of is 1 nm or more.

In addition, it is preferable that the pitch, the line width / pitch, the concave portion depth (the convex portion height), the convex portion length, and the top line width / bottom portion line width of the concavo-convex portions 14 are in the following ranges, respectively.
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 <projection 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 concavo-convex portion 14, a pattern is formed by applying a photoresist as used in semiconductor device fabrication to a substrate by lapping with a polishing sheet, and by using a mask to produce a pattern. There are a method of etching a substrate using a photoresist as a mask, a method of transferring a mold shape onto a substrate (a nanoimprint method) using a mold formed corresponding to the shape and size of the concavo-convex portion 14, and so on. do it.

  In addition, the shape of the convex part of the uneven | corrugated | grooved part 14 can be formed in rectangular shapes, such as a rectangle and a trapezoid, or a sawtooth shape and a triangular shape. FIG. 3A shows an example in which the convex portion 14a of the concave and convex portion 14 has a rectangular cross section, and the inorganic fine particle layer 15 is formed on one side surface portion thereof. FIG. 3B shows an example in which the convex part 16a of the concave-convex part 16 has a sawtooth cross-sectional shape, and the inorganic fine particle layer 15 is formed on one side face standing in the vertical direction. By forming the cross section of the convex portion in a sawtooth shape, adhesion of the film to the top of the convex portion can be avoided. FIG. 3C shows an example in which the convex portion 17a of the concave-convex 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 or at least one side wall of the convex portion 14a, the inorganic fine particle layer 15 having shape anisotropy is distributed in a striped pattern on the surface of the substrate 11 in a desired fine shape. And isolation of inorganic fine particles can be realized. In addition, since the inorganic fine particle layer 15 is formed on the concavo-convex portion 14 mechanically formed in advance, the concavo-convex portion 14 can be stably formed, and the shape of the inorganic fine particle layer 15 formed thereon is formed. Control can be easily performed.

  The inorganic fine particle layer 15 is linearly formed in one direction (absorption axis Y direction) parallel to the main surface of the substrate 11 by adhering inorganic fine particles to the top portion or at least one side wall portion of the convex portion 14a. It is arranged. “Inorganic fine particles are arranged in a line” means a continuous band-like film in which inorganic fine particles are connected to each other, and the inorganic fine particles are gathered in an appropriate size to form independent islands. Any of the discontinuous films arranged in a row may be used 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 regularly provided at a constant interval, the formation pattern of the inorganic fine particle layer 15 becomes striped (one-dimensional lattice shape), and the wire grid structure is formed. Present.

  In the present invention, the inorganic fine particles have shape anisotropy having a long diameter in the arrangement direction of the inorganic fine particles and a short diameter in the direction orthogonal to the arrangement direction. In addition, it is desirable that the inorganic fine particles have a size equal to or smaller than the wavelength in the use band, and the individual particles are completely isolated.

  In the present invention, the optical constant of the inorganic fine particle layer 15 is such that the optical constant in the absorption axis Y direction (arrangement direction of the inorganic fine particles) is larger than the optical constant in the transmission axis X direction (direction orthogonal to the arrangement direction of the inorganic fine particles). It is important to be large. Specifically, the refractive index in the absorption axis Y direction of the inorganic fine particle layer 15 is larger than the refractive index in the transmission axis X direction, and the consumption coefficient in the absorption axis Y direction is larger than the consumption coefficient in the transmission axis X direction. It is characterized by. In order to obtain this characteristic, the inorganic fine particle layer 15 is formed by an oblique sputtering method.

  FIG. 4 shows a state of 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 present invention 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 the 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 so that the longitudinal direction of the convex portion 14 a of the concave and convex portion 14 is orthogonal to the incident direction of the inorganic fine particles from the target 2. Is arranged. The angle θ is, for example, 0 ° to 15 °. Ions extracted from the beam source 3 are irradiated to the target 2. The inorganic fine particles knocked out from the target 2 by the irradiation of the ion beam are incident on and adhered to the surface of the substrate 11 from an oblique direction. At this time, if the flat control plate 4 is arranged on the substrate 11 at a constant interval (for example, 50 mm), the direction of the incident particles on the surface of the substrate 11 is controlled, and the particles are deposited only on the side wall portion of the convex portion 14a. Can do. The film thickness of the inorganic fine particle layer 15 at this time is preferably 200 nm or less.

  As described above, the substrate 11 is tilted with respect to the target 2 at the time of film formation by the sputtering method to limit the incident direction of the inorganic fine particles, thereby being selectively formed on the top portion or one side surface portion of the convex portion 14a. Inorganic fine particles having a shape anisotropy having a long direction diameter and a short diameter in the direction orthogonal to the arrangement direction are linearly arranged, and the optical constant in the absorption axis Y direction is larger than the optical constant in the transmission axis X direction. 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 use band. That is, a metal material or a semiconductor material is a material satisfying this, and specifically, as a metal material, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn A simple substance or an alloy containing these may be used. Moreover, Si, Ge, Te, ZnO is mentioned as a semiconductor material. Further, silicide-based materials such as FeSi2 (particularly β-FeSi2), MgSi2, NiSi2, BaSi2, CrSi2, CoSi2 are suitable.

  When the material used for the inorganic fine particle layer 15 is a semiconductor material, the band gap energy of the semiconductor is involved in the absorption action. This is because light below this energy is absorbed. Therefore, when the semiconductor material is a polarizing element for visible light, the band gap energy needs to be equal to or lower than the use band. For example, considering the use of visible light, it is necessary to use a material having an absorption at a wavelength of 400 nm or more, that is, a band gap of 3.1 eV or less. As described in Non-Patent Document 4, the band gap energy also depends on the size of the fine particles, and particularly tends to increase rapidly when it reaches several nanometers. It is necessary to determine the thickness. From this point of view, a semiconductor material having a small band gap energy in the bulk state is preferable. For example, Ge has a small band gap energy in the bulk state of 0.67 eV (wavelength of about 1.85 μm). Is a desirable material.

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

  In addition, if necessary, an antireflection film is coated on the front surface and the back surface of the substrate, so that reflection at the interface between air and the substrate can be prevented and the transmission axis transmittance can be improved. The antireflection film may be a generally used low refractive index film such as MgF2, or a multilayer film composed of a low refractive index film and a high refractive index film. In addition, after the structure shown in FIG. 1 is applied, the surface is coated with a transparent material in a use band such as SiO2 as a protective film so as not to affect the polarization characteristics. It is effective for improving the performance. However, since the optical characteristics of the inorganic fine particles are also affected by the refractive index of the surroundings, the polarization characteristics may change due to the formation of the protective film. Moreover, since the reflectance with respect to incident light changes also with the optical thickness (refractive index x protective film thickness) of the protective film, the protective film material and the film thickness should be selected in consideration of these. As a material, a material having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Such materials include SiO2, Al2O3 and the like. These can be formed by a general vacuum film-forming method (chemical vapor deposition, sputtering, vapor deposition, etc.) or a sol in which these are dispersed in a liquid by spin coating or dipping. is there. 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 are perfluorodecyltrichlorosilane (FDTS) and Octadecanetrichlorosilane (OTS). Since it has water repellency, it is also effective in terms of antifouling measures. From now on, it can be purchased from a chemical manufacturer, for example, Gelest, USA, and can be formed by dipping. Films can also be formed by vapor deposition, and dedicated equipment is also sold by Applied Microstructures, USA. In the case of such a silane-based self-assembled film, for the purpose of improving adhesion, the self-assembled film may be deposited after coating SiO 2 as an adhesion layer on the polarizing element by the above method. .

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 in which a strip-like thin film made of metal and extending in one direction parallel to the main surface of the substrate is provided on the substrate, and a dielectric formed on the reflective layer And the inorganic fine particle layer is formed on the dielectric layer at a position corresponding to the strip-shaped thin film.

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

  Here, the board | substrate 21 is comprised from the same material as the board | substrate 11 in 1st Embodiment.

  The reflective layer 22 is made of metal, and is formed by arranging thin films 22 a extending in a strip shape in one direction (absorption axis Y direction) parallel to the main surface of the substrate 21 on the substrate 21. Various materials can be used as the constituent material of the reflective layer 22, for example, a metal such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, Te, or a semiconductor material is used. be able to. In addition to the metal material, for example, it may be composed of an inorganic film or a resin film other than a metal formed with 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 in the visible light region, and is formed by, for example, pattern processing of the metal film using a photolithography technique (metal lattice). The reflective layer 22 has a function as a wire grid polarizer, and of the light incident on the surface of the substrate 21, a polarized wave having an electric field component in the direction parallel to the longitudinal direction of the wire grid (Y-axis direction) ( The TE wave (S wave) is attenuated, and a polarized wave (TM wave (P wave)) having an electric field component in a direction (X-axis direction) orthogonal to the longitudinal direction of the wire grid is transmitted.

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

  The dielectric layer 23 is formed by coating the surface of the substrate 21 with a general vacuum film forming method such as a sputtering method, a vapor phase growth method, or an evaporation method, or a sol-gel method (for example, a method of coating a sol by a spin coating method and gelling it by thermosetting. ) Formed by an optical material transparent to visible light such as SiO2. The dielectric layer 23 forms an underlayer of the inorganic fine particle layer 25 and, as will be described later, the polarized light reflected by the inorganic fine particle layer 25 and reflected by the reflective layer 22 with respect to the polarized light reflected by the inorganic fine particle layer 25. Is formed with a film thickness that is shifted by a half wavelength. Specifically, it may be set appropriately within a range of 1 to 500 nm. It is formed to increase the interference effect by adjusting the phase of the polarized light, and a film thickness shifted by half wavelength is desirable. However, since the inorganic fine particle layer has an absorption effect, the reflected light can be absorbed and the film thickness is optimized. Even if it is not, improvement in contrast can be realized, and in practice, it may be determined based on a balance between desired polarization characteristics and an actual manufacturing process. The practical film thickness range is 1 to 500 nm.

  As a material constituting the dielectric layer 23, a general material such as SiO2, Al2O3, MgF2 can be used. These can be thinned by coating a substrate with a general vacuum film-forming method such as sputtering, vapor phase epitaxy, or vapor deposition, or a sol-like substance and thermally curing it. The refractive index of the dielectric layer 23 is preferably greater than 1 and not greater than 2.5. Since the optical characteristics of the inorganic fine particle layer 25 are also influenced by the surrounding refractive index, it is also possible to control the polarizing element characteristics by the dielectric layer material.

  The inorganic fine particle layer 25 is located at a position corresponding to the thin film 22a and adheres to the dielectric layer 23 so that the inorganic fine particles are in one direction parallel to the main surface of the substrate 21 (absorption axis Y direction). It is arranged in a line. In addition, by forming the inorganic fine particle layer 25 on each of the plurality of thin films 22a regularly provided at a constant interval, the formation pattern of the inorganic fine particle layer 25 becomes striped and exhibits a wire grid structure.

  In FIG. 5, the inorganic fine particle layer 25 has a long elliptical shape having a major axis direction parallel to the longitudinal direction (Y-axis direction) of the thin film 22a and a minor axis direction perpendicular to the longitudinal direction (X-axis direction). The island-shaped inorganic fine particles 25a are arranged in the Y-axis direction. Further, it is desirable that the inorganic fine particles 25a have a size equal to or smaller than the wavelength of the use band, and the individual particles are 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 (arrangement direction of the inorganic fine particles) is larger than the optical constant in the transmission axis X direction (direction orthogonal to the arrangement direction of the inorganic fine particles). It is characterized by being. Specifically, the refractive index in the absorption axis Y direction of the inorganic fine particle layer 25 is larger than the refractive index in the transmission axis X direction, and the consumption coefficient in the absorption axis Y direction is larger than the consumption coefficient in the transmission axis X direction. It is 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 the present embodiment configured as described above, the surface side of the substrate 21, that is, the formation surface side of the band-shaped thin film 22a, the dielectric layer 23, and the inorganic fine particle layer 25 is the light incident surface. The polarizing element 20 uses four functions of light transmission, reflection, interference, and selective light absorption of polarized waves due to optical anisotropy, so that an electric field component parallel to the longitudinal direction of the wire grid of the reflective layer 22 is obtained. Attenuates a polarized wave (TE wave (S wave)) having (Y-axis direction) and transmits a polarized wave (TM wave (P wave)) having an electric field component (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 action 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 TE waves transmitted through the inorganic fine particle layer 25 and the dielectric layer 23, as shown in FIG. 6B. 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 a half wavelength. Attenuated by TE wave and interference. The TE wave can be selectively attenuated as described above. As described above, a film thickness shifted by half a wavelength is desirable. However, since the inorganic fine particle layer has an absorption effect, an improvement in contrast can be realized 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 fabrication process.

  On the contrary, when low reflection is required on the emission side, light may be incident on the reflection layer side. Also in this case, the transmission contrast equivalent to the above can be obtained by the selective absorption effect of the inorganic fine particle layer. This is because the size of the transmission contrast depends on the thickness of the reflective layer as will be described later. When this is applied to actual use, for example, in the optical engine portion (FIG. 13) of the liquid crystal projector of the present invention described later, the polarizing plate of the present invention is applied to the incident polarizing plate 10A for the purpose of avoiding unwanted reflected light to the liquid crystal panel. When used, the polarizing plate is disposed so that the film surface (the inorganic fine particle layer 25 side in FIG. 6) faces the liquid crystal panel. By doing so, undesirable reflected light returns to the light source side. Similarly, 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 (the inorganic fine particle layer 25 side in FIG. 6) is preferably directed to the liquid crystal panel side. Although the incident direction of light to the polarizing plate is reversed when used for the incident polarizing plate and the outgoing polarizing plate, the same transmission contrast can be obtained regardless of which side the light is incident as described above. No problem.

  The polarizing element 20 can be manufactured as follows, for example. That is, after laminating a metal film and a dielectric film on the 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 film forming method. By adjusting the incident angle at the time of oblique sputtering film formation, fine particles can be concentrated in the vicinity of the apex of the convex portion formed of the strip-shaped thin film 22a and the dielectric layer 23.

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

  Further, as shown in FIG. 7, after the reflective layer 22 is formed on the substrate 21 in a one-dimensional lattice shape, the dielectric layer 23 is formed over the entire surface of the substrate 21. As a result, the dielectric layer 23 has a concavo-convex shape in which a convex portion is formed immediately above the strip-shaped thin film 22a of the reflective layer 22 and a concave portion is formed between the strip-shaped thin films 22a. Thereafter, by forming the inorganic fine particle layer 25 on the side surface portion of the top of the convex portion of the dielectric layer 23 by an oblique sputtering film forming method, a polarizing element having the same function and effect as the example of FIG. 5 can be manufactured. it can. The formation region of the inorganic fine particle layer 25 is not limited to one side surface portion of the top portion of the dielectric layer 23 shown in the drawing, and may be both side surface portions.

  The polarizing element of the present invention may be a polarizing element having a configuration in which the dielectric layer 23 is omitted in FIG. That is, the inorganic fine particle layer 25 is selectively formed on the substrate 21 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 wire grid structure is arranged at regular intervals. Even with this configuration, a desired extinction ratio (contrast: transmission axis transmittance / absorption axis transmittance) can be provided in the visible light range.

Next, an example in which a selective light absorption layer is provided on the back side of the polarizing element 20 will be described as a countermeasure against stray light on the emission surface (ghost countermeasure) in the liquid crystal projector.
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 is omitted.

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

  In the polarizing element 20 in which the selective light absorption layer 28 for the polarized wave due to the optical anisotropy is not provided, the back surface side of the substrate 21 exhibits a mirror surface by the reflecting layer 22, so that it passes through the polarizing element and follows the polarizing element. The light reflected and returned by another optical element such as a lens arranged in a step is reflected again by the mirror surface. Such stray light causes image quality deterioration such as ghost in the liquid crystal projector.

  In the present embodiment, by providing the selective light absorption layer 28 of the polarized wave due to the optical anisotropy having the above configuration on the back surface side of the substrate 21, the stray light is absorbed and reflection on the reflection layer 22 is prevented. The concavo-convex part 26 constituting the selective light absorption layer 28 of the polarized wave due to optical anisotropy is made of the same material as the dielectric layer 23 and extends in the same direction as the direction in which the strip-like thin film 22a of the reflective layer 22 extends. Are formed in a one-dimensional lattice shape. The second inorganic fine particle layer 27 is formed by linearly arranging inorganic fine particles on the top or side surface of the convex portion of the concavo-convex portion 26 and is composed 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 back surface of the substrate 21 appears.

  As a method for forming the concavo-convex portion 26, it is formed by a sputtering method, a sol-gel method, or the like, similarly to the method for forming the dielectric layer 23. For imparting the uneven shape, pattern processing using a photolithography technique or press formation by a nanoimprint method is suitable. As a method for forming the second inorganic fine particle layer 27, an 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 convex portion of the uneven portion 26.

  Alternatively, as another manufacturing method of the polarizing element 20A, the polarizing element 10 shown in FIG. 1 and the polarizing element 20 shown in FIG. 5 are used, and the back surfaces of the substrates 11 and 21 are bonded to each other with a transparent adhesive. The element 20A may be used. In this case, the arrangement direction of the inorganic fine particles in the inorganic fine particle layers 15 and 25 is preferably aligned.

Next, an example in which an antireflection layer is provided between the substrate 21 and the reflection layer 22 will be described as another ghost countermeasure in the liquid crystal projector.
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 is omitted.

  The polarizing element 20B of the present embodiment is configured for the same purpose as the polarizing element 20A described above. That is, in the polarizing element 20 </ b> B of this embodiment, the antireflection layer 29 is formed between the substrate 21 and the reflection layer 22. In this way, by providing the antireflection layer 29 immediately below the one-dimensional lattice-like reflection layer 22, reflection of incident light from the back surface of the substrate 21 is prevented.

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

  Further, as another ghost countermeasure in the liquid crystal projector, there is the following method. That is, the surface of the substrate 21 is composed of irregularities in which 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 subsequently formed on the surface by rubbing the surface. A texture 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 above-described oblique sputtering method so as to correspond to the arrangement direction of the inorganic fine particles 25a. Good. Due to the texture structure, the alignment of the inorganic fine particles is improved so that the long axis direction of the inorganic fine particles becomes the longitudinal direction of the stripes, the polarization characteristics of the thin film are improved, and the ghost countermeasure effect can be enhanced. 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 multilayer structure in which one or a plurality of the above-described multilayer structure of the dielectric layer 23 / inorganic fine particle layer 25 are stacked on the inorganic fine particle layer 25 may be used. FIG. 10 shows an example of the configuration.

  In FIG. 10, the polarizing element 30 is formed by laminating a strip-like thin film 22 a constituting a reflective layer 22, a dielectric layer 23, and an inorganic fine particle layer 25 in this order on a substrate 21, and a dielectric material on the inorganic fine particle layer 25. The layered structure 26a of the layer 23 / inorganic fine particle layer 25 is further stacked to form a wire grid structure. Further, the laminated structure 26a may be further stacked on the laminated structure 26a. As a result, the interference effect between the respective layers can be enhanced to increase the contrast in the transmission axis direction at a desired wavelength, and at the same time, the reflection component from the polarizing element that is not preferable in the transmissive liquid crystal display device can be reduced over a wide range, High contrast and low reflection can be realized with a thinner film thickness than the polarizing element 20 having the configuration of FIG.

  For example, there are the following three methods for manufacturing the polarizing element 30 of the present invention. That is, as a first method, a reflective layer material (metal lattice material) and a dielectric film are laminated on the substrate 21, and a one-dimensional lattice pattern is formed or etched by a technique such as nanoimprint or photolithography, and then oblique sputtering is performed. Fine particles are formed by a film method. According to this, by adjusting the incident angle at the time of oblique sputtering film formation, inorganic fine particles can be concentrated in the vicinity of the apex of the dielectric layer 23 that has become a convex portion. As a second method, a transparent material is used to form a one-dimensional lattice-shaped concavo-convex portion on a transparent substrate, and a reflective layer material, a dielectric layer material, and an inorganic fine particle material are sequentially stacked by the number of layers. To do. As a third method, a stacked structure of (dielectric film / inorganic fine particle thin film) is sequentially stacked on the thin film (metal lattice film) of the reflective layer by the number of stacked layers and then etched. In addition, the inorganic fine particle material does not need to be a complete island shape, and it is sufficient that a grain boundary is formed. 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. In executing the above manufacturing process, the type of substrate material is not limited, but a quartz or sapphire substrate with high thermal conductivity is suitable for application to a projector with a large amount of heat generation.

By the way, if the polarizing element 30 having the structure described so far is used, the light exit surface (reflective layer 22) is made of metal, and therefore the reflectance is high when there is return light. Therefore, it is preferable to take the above-described countermeasure against stray light on the exit surface also in this embodiment.
FIG. 11 and FIG. 12 show examples of the exit surface stray light countermeasure in this embodiment.

FIG. 11 shows an example in which the configuration of FIG. 8 is applied to this embodiment.
The polarizing element 30A includes a concavo-convex portion 26 made of a dielectric material on a surface (back surface) opposite to the surface on which the reflective layer 22 is formed of the substrate 21, and a top portion or at least one side surface portion of the convex portion of the concavo-convex portion 26. A selective light absorption layer 28 for a polarized wave due to optical anisotropy, which is formed 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 anti-reflection layer 29 is provided immediately below the one-dimensional lattice-like reflecting layer 22 in the polarizing element 30, and a dielectric is provided for the purpose of obtaining an interference effect between the reflecting layer 22 and the anti-reflection layer 29. Layer 2a is provided. In FIG. 12, the dielectric layer 2 a below the reflective layer 22 may be omitted, and the antireflection layer 29 may be simply formed below the reflective layer 22. Further, when the antireflection layer 29 is the same as the inorganic fine particle layer 25, it contributes to the improvement of contrast. However, for the purpose of simply preventing the reflection of the return light, the antireflection layer 22 is provided under the reflection layer 22. As the layer 29, a layer having a lower reflectance than the reflective layer 22 (a low reflective layer) may be provided. The low reflection material is effective when the reflectance is lower than that of the reflection layer 22, and an oxide film such as carbon or oxygen deficient SiOx, or metal or semiconductor fine particles can be used.

  When the antireflection layer 29 and the dielectric layer 2a are added under the reflection layer 22, or when the antireflection layer 29 is formed directly under the reflection layer 22, these films are formed before forming the film for the reflection layer. When the film is formed and etched simultaneously to form the reflective layer 22, these layers can be formed only immediately below the strip-like thin film 22a of the reflective layer 22, so that the transmission characteristics can be unaffected.

  Also in the second embodiment, if necessary, an antireflection film can be coated on the front surface and back surface of the substrate to prevent reflection at the interface between the air and the substrate and improve the transmission axis transmittance. . The antireflection film may be a generally used low refractive index film such as MgF2, or a multilayer film composed of a low refractive index film and a high refractive index film. In addition, after the structure shown in FIG. 5 or FIG. 7 is applied, the surface is coated with a transparent material in a use band such as SiO2 as a protective film in a thickness range that does not affect the polarization characteristics. It is effective for improving reliability such as improvement. However, since the optical characteristics of the inorganic fine particles are also affected by the refractive index of the surroundings, the polarization characteristics may change due to the formation of the protective film. Moreover, since the reflectance with respect to incident light changes also with the optical thickness (refractive index x protective film thickness) of the protective film, the protective film material and the film thickness should be selected in consideration of these. As a material, a material having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Such materials include SiO2, Al2O3 and the like. These can be formed by a general vacuum film-forming method (chemical vapor deposition, sputtering, vapor deposition, etc.) or a sol in which these are dispersed in a liquid by spin coating or dipping. is there. 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 are perfluorodecyltrichlorosilane (FDTS) and Octadecanetrichlorosilane (OTS). Since it has water repellency, it is also effective in terms of antifouling measures. From now on, it can be purchased from a chemical manufacturer, for example, Gelest, USA, and can be formed by dipping. Films can also be formed by vapor deposition, and dedicated equipment is also sold by Applied Microstructures, USA. In the case of such a silane-based self-assembled film, for the purpose of improving adhesion, the self-assembled film may be deposited after coating SiO 2 as an adhesion layer on the polarizing element by the above method. .

Next, a liquid crystal projector according to the present invention will be described.
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 for the red light LR, a liquid crystal panel 50, an outgoing pre-polarizing element 10B, an outgoing main polarizing element 10C, and an incident side polarizing element 10A for the green light LG, the liquid crystal panel 50, Outgoing pre-polarizing element 10B, outgoing main polarizing element 10C, incident side polarizing element 10A for blue light LB, liquid crystal panel 50, outgoing pre-polarizing element 10B, outgoing main polarizing element 10C, and outgoing main polarizing element 10C And a cross dichroic prism 60 for synthesizing the incoming light and emitting it to the projection lens. Here, the polarizing elements 10, 20, and 30 of the present invention are applied to the incident side polarizing element 10A, the outgoing pre-polarizing element 10B, and the outgoing 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), and incident sides corresponding to the respective lights. 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 emitted, and the outgoing pre-polarizing element 10B and the outgoing main polarizing element 10C are output. After passing, it is composed by the cross dichroic prism 60 and projected from a projection lens (not shown). Even if the light source lamp has a high output, since the polarizing elements 10, 20, and 30 of the present invention having excellent light resistance against strong light are used, a highly reliable liquid crystal projector can be realized. it can.

  The polarizing element of the present invention is not limited to application to the liquid crystal projector, but is suitable as a polarizing element that receives heat as a use environment. For example, the present invention can be applied as a polarizing element for a car navigation system of an automobile or a liquid crystal display of 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 characteristics of the inorganic fine particle layer formed by the oblique sputtering film formation of FIG. 4 were verified.
FIG. 14 shows the experimental results of the optical anisotropy enhancement effect by such oblique ion beam sputtering. As shown in FIG. 14A, a Ge particle film 44 was produced by allowing Ge sputtered particles to be incident and deposited in a 10 ° direction with respect to the surface of the glass substrate 41 in a stationary state by ion beam sputtering. FIG. 14B shows the measurement results of the optical constants (refractive index, extinction constant) of the manufactured Ge particle film 44. The measurement was performed with a spectroscopic ellipsometer. The film thickness at this time is 10 nm. In this experiment, due to the occurrence of optical anisotropy, the optical constant, that is, the refractive index n and the extinction constant k were different in the plane. For comparison, when Ge sputtered particles were formed while rotating the substrate 41 from the direction perpendicular to the substrate 41 as shown in FIG. 15A, the optical constant of the obtained Ge particle film 44 is shown in FIG. 15B. Thus, the optical anisotropy of the refractive index n and the extinction constant k did not occur, and each optical constant was a value close to the literature value.

Further, the composition of the target 2 was changed from Ge to Si, an Si particle film was formed on the glass substrate 41 under the same conditions as in the Ge sputtering film formation, and the optical constants were measured. The result is shown in FIG.
Also in the case of Si, when the oblique sputtering film formation is performed in the direction of 10 ° with respect to the surface of the glass substrate 41 (FIG. 16A), optical anisotropy occurs, so that the optical constant, that is, the refractive index n and A difference was observed in the extinction constant k. Further, when the sputter film was formed while rotating the substrate 41 from the vertical direction of the substrate 41 (FIG. 16B), the optical anisotropy of the refractive index n and the extinction constant k did not occur.

  Next, the polarization transmittance in the case where a 20 nm-thick Ge particle film 44 is formed on the glass substrate 41 under the conditions of FIG. 14A was obtained by simulation calculation. The result is shown in FIG. Here, an optical constant in the X-axis direction is used for light whose electric field is oscillating parallel to the X-axis direction, and polarization is performed using an optical constant in the Y-axis direction for light whose electric field is oscillating in the Y-axis direction. The transmittance is calculated. According to the result, the transmittance varies depending on the polarization direction due to the optical anisotropic characteristics. That is, by using a film having such an optical anisotropy as a material for a polarizing element, an improvement in the characteristics of the polarizing element can be expected.

(Example 2)
Next, the influence of the optical anisotropy of the inorganic fine particle layer on the polarizing element was examined. Specifically, on the premise of the configuration of the polarizing element of FIG. 1 and FIG. 5, the polarization characteristics were obtained by wavelength rigorous coupled wave analysis (RCWA). Here, as shown in FIG. 18, the inorganic fine particle layer 45 made of Ge having a wire grid structure is provided on a glass substrate 41, and each dimension of the inorganic fine particle layer 45 is set to a pitch of 150 nm and a line width (Ge lattice direction). Width): 37.5 nm, thickness calculated when the inorganic fine particle layer 45 has optical anisotropy (method of FIG. 14A) is 100 nm, and thickness without optical anisotropy (method of FIG. 15A) is 10 nm. Went. The result is shown in FIG.

  In FIG. 19, there is no optical anisotropy in the visible region of 550 nm or less (that is, green or blue region), which is important for optical engine applications such as projectors (data indicated by a dotted line described as “bulk”). Compared with the data indicated by the solid line), the absorption axis transmittance is high and the reflectance is high even though the film thickness is small. On the other hand, those with optical anisotropy have low absorption axis transmittance and low reflectance. Therefore, it is a characteristic preferable as an absorption type. Regarding the film thickness, in this calculation, no optical anisotropy is 10 nm. Increasing the thickness reduces the absorption axis transmittance, but at the same time increases the reflectance. Therefore, characteristics preferable as a polarizing element having optical anisotropy cannot be obtained by film thickness manipulation.

(Example 3)
FIG. 19 shows an example in which the inorganic fine particle layer is a single layer, but this is also true for the polarizing element having the multilayer structure of the inorganic fine particle layer shown in FIG.
Here, in the polarizing element having a multilayer structure, when the inorganic fine particle layer made of Ge has optical anisotropy by the method shown in FIG. 14A and when there is no optical anisotropy by the method shown in FIG. 15A The polarization characteristics were calculated by wavelength rigorous coupled wave analysis (RCWA). The multilayer structure used here is a multilayer structure of Ge (15 nm) / reflective layer; Al (240 nm) / dielectric layer; SiO2 (205 nm) / inorganic fine particle layer; Ge (90 nm) (surface side) from the substrate side. (The thickness in parentheses is the thickness of each layer), and the dimensions of the inorganic fine particle layer were set to pitch: 150 nm, line width (Ge lattice direction width): 37.5 nm. Note that a Ge layer is provided on the substrate side of the reflective layer in order to suppress the influence of stray light due to re-reflection of the return light to the output surface of the polarizing element. The result of the calculation is 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), there is optical anisotropy in a visible region of 550 nm or less (described as anisotropic). As a result, the reflectance of the absorption axis is higher and the transmittance of the transmission axis is lower than the data indicated by the solid line. Therefore, it is not preferable as an absorption type 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, the use of the inorganic fine particle layer having optical anisotropy for the polarizing element can improve the polarization characteristics. Preferably, the optical constant of the inorganic fine particle layer is (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 important that the relationship of (coefficient) <(absorption coefficient in the absorption axis direction) is satisfied. Examples showing this are shown in FIGS.
FIG. 21 shows the optical constants of the Ag film (inorganic fine particle layer 25) when Ag is formed as the inorganic fine particle layer 25 by the oblique sputtering film forming method in the polarizing element having the structure of FIG. Also in this case, it can be seen that it has optical anisotropy like Ge. However, the magnitudes of the refractive indexes in the X and Y directions are inverted near the wavelength of 550 nm, and the extinction coefficients in the X and Y directions are inverted near the wavelength of 440 nm.
FIG. 22 shows the result of calculating the polarization transmittance when the Ag film thickness is 20 nm based on the optical constants of the Ag film (inorganic fine particle layer 25) shown in FIG. The polarization transmittance decreases as the wavelength decreases, and the transmittance in the x and y directions is reversed around the wavelength of 450 nm. This is due to the inversion of the optical constant in FIG. 21. When applied to a polarizing element, having such inversion characteristics is not preferable because it means a decrease in the polarization transmittance. Further, if the extinction coefficient is large on the absorption axis, the absorptance is large. On the transmission axis, it is desirable that light incident from the air layer is transmitted without being attenuated or reflected. (Because refractive index = 1). Therefore, as the optical constant of the desired inorganic fine particle layer, there is no inversion of the optical constant in the use band, and (transmission axis direction optical constant) <(absorption axis direction optical constant), that is, (transmission axis direction refractive index) <(absorption That is, the relationship of “axial refractive index” and (transmission axis direction extinction coefficient) <(absorption axis direction extinction coefficient) is satisfied.

(Example 5)
Next, the relationship between the optical anisotropy expression and the inorganic fine particles in the polarizing element of the present invention was investigated.
(1) Inorganic fine particle layer on flat plate First, using a substrate having a smooth surface with a SiO2 film of 10 nm on the surface of a single crystal Si substrate, the same conditions as in Example 1 (oblique sputtering film formation, with respect to the substrate surface) A Ge particle film was formed by sputtering from the vertical direction), and the shape of Ge fine particles in the Ge fine particle film was observed by AFM (atomic force microscope). The result is shown in FIG.
In the oblique sputter deposition sample shown in FIG. 23A, individual fine particles are clearly observed, and the fine particles are anisotropic in shape having a diameter that is long in the direction perpendicular to the Ge incident direction and short in the Ge incident direction. Sex was occurring. On the other hand, in the sample sputter-deposited from the direction perpendicular to the substrate surface shown in FIG. 23 (b), the particle size is very small at the same magnification, and the surface is very flat. The shape could not be observed.

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

  When the element distribution by TEM was analyzed from the cross section of this polarizing element sample, as shown in the element distribution mapping of FIG. 25, the inorganic particle layer made of Ge from the top part to the side wall of each convex part 17a of the Si-based substrate. It was found that 15 was formed. Based on this result, the inorganic fine particle layer 15 in the polarizing element sample was observed in detail. The result is shown in FIG. FIG. 26A is a sketch when observed from a cross section, and takes into account the element distribution result of FIG. FIG. 26B is a sketch when observed from above.

  As shown in FIG. 26 (b), the inorganic fine particle layer 15 is formed in a mode along the longitudinal direction of the convex portion 17a from the top portion to the side wall portion of each convex portion 17a in the primary lattice shape, and the inorganic fine particle layer 15 is formed. Was observed as a line or band composed of a series of inorganic fine particles 15a having shape anisotropy. In addition, individual particles of the inorganic fine particles 15a were clearly observed, and a state in which the major axis direction of the inorganic fine particles was the arrangement direction and the minor axis direction was a direction orthogonal to the arrangement direction was observed.

  Further, when an electron diffraction image of the Ge portion in FIG. 25 was examined, no clear emission line was observed as shown in FIG. 27. Therefore, the crystal structure of the Ge fine particles 15a constituting the inorganic fine particle layer 15 was amorphous. I found out. Being amorphous means that the deposited Ge microparticles have no crystallographic orientation. In general, it is known that the structure of Ge film formed at low temperature tends to be in an amorphous state (DUBEY M, MCLANE GF, JONES KA, LAREAU RT, ECKART DW, HAN WY, ROBERTS C, DUNKEL J, WEST. LC, Mat. Res. Soc. Symp. Proc. Vol. 340. 411-416 (1994)).

(3) Polarizing element 20
Next, a sample of a polarizing element having the configuration shown in FIG. 5 was produced. Here, an aluminum grating having a pitch of 150 nm and a grating depth of 200 nm is formed on the substrate 21 made of glass (Corning 1737) as the reflective layer 22, and SiO 2 of 30 nm is formed thereon as the dielectric layer 23. As shown in FIG. 5, oblique sputtering film formation is performed under the same conditions as in the polarizing element 10 of the example, and a Ge fine particle layer is deposited as an inorganic fine particle layer 25 with a thickness of 30 nm. 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. FIG. 29 shows the transmittance ratio in this case as contrast. The transmission contrast is 3000 or more in the green region centered on the 550 nm region, and 1500 or more in the entire visible light region including the blue region near 450 nm. As a result, it showed 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), the primary lattice-like reflective layer 22 and dielectric layer 23 provided on the substrate 21 were respectively covered with Ge from the top to the side wall. It turned out that the inorganic particle layer 25 which consists of is formed.

Moreover, the result of having observed this polarizing element sample from the top in FIG.30 (b) and FIG.31 is shown. FIG. 30B is a sketch, and FIG. 31 is an SEM image as a basis.
The inorganic fine particle layer 25 is formed in a mode along the longitudinal direction of the dielectric layer 23 from the top portion to the side wall portion of each of the primary lattice-like dielectric layers 23, and the inorganic fine particle layer 25 is an inorganic material having shape anisotropy. The fine particles 25a were observed as a line or a band composed of a continuous array. Further, in the inorganic fine particles 25a, it was observed that the long axis direction of the inorganic fine particles was the arrangement direction, and the short axis direction was the direction orthogonal to the arrangement direction.

  From the above results, the inorganic fine particles in the polarizing element of the present invention have shape anisotropy by oblique sputtering film formation, and when the inorganic fine particles are arranged in a one-dimensional lattice, the long axis direction is a one-dimensional lattice. Are aligned in the lattice direction. It is in an amorphous state. In the present invention, these are considered to influence the expression of optical anisotropy. Fine particles with shape anisotropy are formed by oblique deposition, and this shape anisotropy is called the 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 particles (FIG. 32A), it has optical anisotropy in two directions (X and Y directions) on the substrate surface, and the direction of the major axis a is the absorption axis. It becomes. On the other hand, when the film thickness b of the inorganic fine particles is larger than the major axis a of the particles (FIG. 32B), it has optical anisotropy in the thickness direction of the inorganic fine particles and the in-plane axial direction. Becomes the absorption axis, the direction of optical anisotropy is substantially reversed in FIGS. 32A and 32B. In the polarizing elements 10 and 20 of the present invention, since the grating direction is used as the absorption axis, a thick film means that the polarization characteristics deteriorate. Therefore, as shown in FIG. 32A, it is desirable to use in a region where the relationship (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 reflectivity in the absorption axis direction can be improved by optimizing the film thickness. Suppression is possible. However, in this case, since the interference effect is dominant in the suppression, there is a problem that the transmission band transmittance decreases because the wavelength band is narrow and there is absorption in the transmission axis direction. Furthermore, since the interference effect is sensitive to the film thickness, in order to obtain desired characteristics, it is necessary to strictly control the film thickness of the dielectric layer 23 and the film thickness of the germanium thin film. On the other hand, in the present invention, germanium fine particles having optical anisotropy are used, so that the design range is wide and the manufacture is easy.

Therefore, a difference in optical characteristics between the case where the inorganic fine particle layer 25 in the polarizing element 20 is a thin film and the case of fine particles was simulated by a wavelength strict coupling wave analysis (RCWA) method. Here, the reflection layer 22 has a film thickness (aluminum thickness): 200 nm, a lattice pitch: 150 nm, and an aluminum width: 45 nm, and the dielectric layer 23 has a film thickness (SiO2): 30 nm. The dependence of absorption axis reflectance, transmission axis transmittance, and transmission contrast at a wavelength of 450 nm was calculated. In addition, the optical constant of the Ge thin film uses the value of FIG. 15B, and the optical constant of the Ge fine particle takes into account the increase in anisotropy when it is formed on the lattice. The calculation was performed on the assumption that fine particles sufficiently smaller than the wavelength were distributed in the dielectric layer with the axial direction aligned. Further, the volume ratio of Ge in the dielectric layer 23 was calculated as 0.4 and the aspect ratio was 20.
The result is shown in FIG. FIG. 34A shows the absorption axis reflectance, FIG. 34B shows the transmission axis transmittance, and FIG. 34C shows the transmission contrast. It can be seen that the Ge fine particles have the same contrast, higher transmittance, and wider film thickness range in which the reflectance can be reduced than the Ge thin film.

(Example 6)
Next, the relationship between the aspect ratio of the inorganic fine particles and the contrast in the polarizing element was examined.
(1) Diagonal sputtering film formation on a flat plate First, using the ion beam sputtering apparatus of FIG. 4, the substrate inclination angle θ is changed to 20 and 10 °, and a Ge fine particle layer having a film thickness of 30 nm is formed on a flat Si substrate. The sample obtained is observed with an 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. To obtain the aspect ratio.
FIG. 35 shows the result as an aspect ratio histogram. As for the distribution of the histogram, the distribution shifts toward a larger aspect ratio in FIG. 35B (substrate tilt angle θ = 10 °) than in FIG. 35A (substrate tilt angle θ = 20 °). There was a trend. Further, the average value of the major axis length of the Ge fine particles at this time is 30 nm when the substrate tilt angle θ = 20 °, and 63 nm when the substrate tilt angle θ = 10 °, and the average value of the aspect ratio is It was 3.2 when the substrate tilt angle θ = 20 °, and 4.0 when the substrate tilt angle θ = 10 °.

  Further, the transmittance of a sample in which a Ge fine particle layer having a thickness of 10 nm is formed on a flat glass substrate (Corning 1737) by changing the substrate inclination angle θ = 20, 10 ° using the ion beam sputtering apparatus of FIG. Was measured, and the ratio of transmittance at a wavelength of 550 nm was determined as contrast. The x direction and the y direction have the relationship shown in FIG. 14A. The results are shown in Table 1. When the substrate tilt angle θ was decreased, the aspect ratio of the Ge fine particles increased and the contrast tended to increase.

(2) Polarizing element 10
Regarding the polarizing element 10 of Example 5, the substrate inclination angle θ = 10, 20 ° out of the oblique sputtering film forming conditions at the time of forming the inorganic fine particle layer 15, and the other conditions are the same as those of the polarizing element 10 of Example 5. A polarizing element sample was prepared. The transmittance of the transmission axis and absorption axis of this sample was measured, and the ratio of the transmittance at a wavelength of 550 nm was determined as contrast. The results are shown in FIG. Also in the polarizing element of the present invention, when the substrate tilt angle θ is decreased, the contrast tends to increase.

  As described above, inorganic fine particles having shape anisotropy can be formed on the substrate surface by oblique sputter film formation, but the aspect ratio, which is the ratio of the long axis to the short axis of the inorganic fine particles, is incident on the inorganic particles. Depending on the angle (substrate tilt angle θ in FIG. 4), the smaller the angle, the larger the aspect ratio. In addition, the transmission contrast increases as the aspect ratio increases. In this way, by using the steering effect by oblique sputtering film formation, a polarizing element having good characteristics can be realized.

(Example 7)
By changing the type of film forming method (dry process), a Ge fine particle layer was obliquely formed on a substrate provided with a reflective layer 22 made of Al in a one-dimensional lattice shape (pitch 150 nm). Here, the following three types of dry processes were used.
(A) Electron beam evaporation (FIG. 37 (a))
A substrate tilted by 10 degrees with respect to the normal direction of the evaporation source equipped with Ge was set 80 cm away from the evaporation source, and electron beam evaporation was performed at a deposition rate of 0.3 nm / sec.
(B) Magnetron sputtering (FIG. 37 (b))
A substrate tilted 10 degrees in the normal direction of the Ge target was set 40 cm away from the target, and magnetron sputter deposition was performed at a deposition rate of 0.1 nm / sec.
(C) Ion beam sputtering (FIG. 37 (c))
It is the sputter film-forming method shown in FIG. 4 illustrated by this invention. Here, the substrate was set at θ = 45 degrees, and was 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 substrate used was the same substrate 11 as in the polarizing element 10 of Example 5, and was set so that the Ge incident direction was a direction (y direction) perpendicular to the lattice longitudinal direction (x direction), as in FIG. 14A. . In addition, the film thickness of each Ge fine particle layer was 10 nm.

The transmittance of the obtained sample was measured. The result is shown in FIG.
Among the three samples, the film forming method by ion beam sputtering has a high transmittance, and the difference in the transmittance in the x direction and the y direction is large. Therefore, it can be seen that the film forming method of the polarizing element of the present invention is the most preferable.

(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 of this, FIG. 39 shows a strict coupled wave analysis (RCWA) of the reflection layer thickness (aluminum height) and transmission contrast when the pitch is 150 nm and the aluminum width is 37.5 nm as the primary lattice-like reflection layer 22 made of Al. The calculation result by is shown.

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

From the obtained results, for example, when it is desired to reduce the absorption axis reflectivity, the film thickness of the dielectric layer 23 may be set in the range of 19 to 37 nm. In addition, when used in applications where the influence of reflection is small, the film thickness of the dielectric layer 13 can be set to zero. This means a reduction in the production process and leads to an improvement in productivity. In addition, it achieves high contrast at a wavelength of 450 to 650 nm, and is suitable for projector applications with a wide operating wavelength range.
On the other hand, the transmittance is as high as 70% or higher at a wavelength of 450 nm and 80% or higher at wavelengths of 550 and 650 nm. The transmittance can be further improved by narrowing the pitch of the grating.
The contrast can be adjusted by the height of the metal grid. If higher contrast is required, the aluminum grid should be raised, and lower if desired.

  Next, FIG. 40 shows the polarization characteristics when the aluminum height is 30 nm with the same structure as the polarizing element 20 of the fifth embodiment. In this case, since the thickness of the reflective layer is thin (the aluminum height is low), the contrast is about 3 in the blue region. Similar to FIG. 28, the reflectance is suppressed to 2% or less by the effect of the Ge fine particles. It has been. In the case of a polarizing element having such a performance, Ge fine particles are deposited on the side wall of the convex portion made of a reflective layer / dielectric layer as shown in the SEM image of FIG. It has a nice shape. This also applies to 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 layer 14a in FIG. 2, the reflective 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) In combination with the ratio, arrangement, etc., a fine particle shape suitable as an absorption polarizing element can be realized.

Example 9
In the polarizing element 20 shown in FIG. 5, as a countermeasure against the stray light on the exit surface (ghost countermeasure), the surface of the substrate 21 is aligned in one direction so as to correspond to the arrangement direction of the inorganic fine particles 25a to be formed later. A rubbing process is performed so as to have a certain texture structure, and a thin film made of inorganic fine particles having shape anisotropy corresponding to the arrangement direction of the inorganic fine particles 25a on the surface after the rubbing process (a thin film to be the antireflection layer 29 (hereinafter referred to as an antireflection layer 29) An antireflection film)) may be formed. Specifically, a texture structure is mechanically formed on the surface of the substrate 21 with an abrasive such as an abrasive tape, and then an antireflection film made of inorganic fine particles is formed on the lattice by an oblique sputtering film formation method. Since the inorganic fine particles having shape anisotropy due to the steering effect can be formed in the same manner as the inorganic fine particle layer 25 to be formed, the polarization effect of the inorganic fine particles is enhanced, and as a result, the ghost suppressing effect can be enhanced. Hereinafter, a specific example will be described.

  Here, the effect was verified using Nippon Micro Coating D20000 as an abrasive. Corning 1737 glass was used as the substrate, and the texture was formed by rubbing the surface in one direction with D2000. FIG. 41 shows the result of measuring 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 surface irregularities. The average pitch of the irregularities on the substrate surface was 160 nm. Further, when the transmittance of the substrate before and after the texture formation was examined, it was found that the transmittance did not change before and after the texture formation (before and after polishing) as shown in FIG. That is, according to this method, it is possible to easily perform nano-level precision processing without deteriorating the transmission characteristics of the substrate.

  Next, a 10 nm-thick antireflection film made of Ge fine particles was formed on the textured substrate by oblique sputtering deposition with the substrate tilt angle θ = 5 ° by the ion beam sputtering apparatus of FIG. At this time, as for the relationship between the Ge incident direction and the substrate, sputtering was performed by arranging the substrate so that the y direction in FIG. 14A is the texture longitudinal direction. With respect to the obtained sample, the shape of Ge fine particles in the antireflection film was observed with an AFM (atomic force microscope). As a result, as shown in FIG. 43, the Ge fine particles were aligned along the texture. It was.

FIG. 44 shows the transmission characteristics of this sample. For comparison, transmission characteristics were also examined for a sample in which an antireflection film was formed under the same conditions using a 1737 glass substrate on which the substrate was not rubbed. In FIG. 44, the sample of this example is described as “texture substrate”, and the comparative sample as “substrate as it is”. As a result, both showed polarization characteristics due to the steering effect. However, the texture formation had higher transmittance in the x direction and a larger difference from the transmittance in the y direction, indicating good polarization characteristics. .
In the present invention, the layer structure of the polarizing element 20 in FIG. 5 is formed on the sample of this embodiment (an antireflection film formed on a substrate having a texture structure). At the same time that the body layer 23 is patterned, the antireflection film is also processed into a lattice shape to form an antireflection layer 29. Thereby, the ghost countermeasure effect can be enhanced, and at the same time, an increase in transmission contrast characteristics as a polarizing element can be expected.

(Example 10)
In the above embodiments, Ge has been shown as an example in most cases, but inorganic fine particles having shape anisotropy can be formed using other materials. Therefore, it is possible to obtain a polarizing element having a target wavelength by selecting a material.
45 and 46 show the polarization characteristics in the case where the inorganic fine particles having a film thickness of 30 nm are manufactured using Si and Sn, respectively, with the configuration of the polarizing element 10 in FIG. Note that an antireflection film on the back surface is not formed. In the case of these materials, the reflectance is slightly higher than that of Ge, but the transmission axis polarization characteristics in the blue region are high, and depending on the purpose, it can be used as a polarizing element.

DESCRIPTION OF SYMBOLS 1 ... Stage, 2 ... Target, 3 ... Beam source, 4 ... Control board 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 ... belt-like thin film, 23, 2a ... dielectric layer, 25a ... inorganic fine particles, 26 ... irregularities, 27 ... inorganic fine particle layer (selection of polarized wave by optical anisotropy) Light absorption layer), 28 ... selective light absorption layer of polarized wave due to optical anisotropy, 29 ... antireflection layer, 44 ... Ge particle film, 50 ... liquid crystal panel, 60 ...・ Cross dichroic prism, 100 ... LCD projector

Claims (18)

A substrate transparent to visible light;
A reflective layer made of metal and provided with a strip-like thin film extending in one direction on the substrate at regular intervals;
A dielectric layer formed on the reflective layer;
An inorganic fine particle layer in which inorganic fine particles are linearly arranged;
With
The inorganic fine particle layer is formed on both sides of the top of the strip thin film on the dielectric at a position corresponding to the strip thin film,
A polarizing element having a wire grid structure in which the same direction as the direction in which the inorganic fine particles are linearly arranged is a longitudinal direction.   The polarizing element according to claim 1, wherein the polarizing element has one or a plurality of laminated structures of the dielectric layer and the inorganic fine particle layer on the inorganic fine particle layer.   The polarizing element according to claim 1, wherein the inorganic fine particles are made of a semiconductor material having a band gap energy of 3.1 eV or less.   The polarizing element according to claim 1, wherein the inorganic fine particle layer has a thickness of 200 nm or less.   The polarizing element according to claim 1, further comprising an antireflection layer between the substrate and the reflective layer. An uneven part is formed on the substrate, the pitch of the uneven part is 0.05 to 0.8 μm, and the value obtained by dividing the line width of the uneven part by the pitch is 0.1 to 0.9, The concave / convex depth of the concave / convex portion is 0.01 to 0.2 μm, the convex portion length of the concave / convex portion is smaller than 0.05 μm, and the value obtained by dividing the top line width of the concave / convex portion by the bottom line width is 1.0. Ri der above,
The convex and concave portions formed on the surface of the substrate so as to extend in one direction parallel to the surface of the substrate have a wavelength of visible light in a direction perpendicular to the one direction of the substrate. Is formed periodically with a small pitch,
Top of the convex portion, one side surface or the both sides face the inorganic fine particle layer is Ru is formed, the polarization element according to any one of claims 1 to 5. Wherein the outermost surface of the polarizing element, a transparent polarizing element protective layer to light in the usable band is formed, the polarization element according to any one of claims 1-6.   The polarizing element according to claim 7, wherein the polarizing element protective layer is formed of SiO 2.   The inorganic fine particles are made of a single substance of Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn or a material containing them. The polarizing element according to item. The substrate is formed of glass, sapphire, or quartz,
An uneven portion having a pitch of 0.5 μm or less, a line width of 0.25 μm or less, and a depth of 1 nm or more is formed on the substrate ,
The convex and concave portions formed on the surface of the substrate so as to extend in one direction parallel to the surface of the substrate have a wavelength of visible light in a direction perpendicular to the one direction of the substrate. Is formed periodically with a small pitch,
Top of the convex portion, Ru the inorganic particle layer on one side surface or both side surfaces is formed, the polarization element according to any one of claims 1 to 9.   The polarizing element according to claim 1, wherein a refractive index in the transmission axis direction of the inorganic fine particle layer is smaller than a refractive index in the absorption axis direction, and a transmission axis direction extinction coefficient is smaller than the absorption axis direction extinction coefficient. .   The polarizing element according to claim 1, wherein the inorganic fine particles are made of Si, Ge, Te, or ZnO, or FeSi 2, MgSi 2, NiSi 2, BaSi 2, CrSi 2, or CoSi 2. A light source, a liquid crystal panel, an incident side polarizing plate, an outgoing side polarizing plate,
With
Either the incident side polarizing plate or the outgoing side polarizing plate is:
A substrate transparent to visible light, a reflective layer made of metal and extending in one direction on the substrate and provided at regular intervals, a dielectric layer formed on the reflective layer, and inorganic fine particles Have an inorganic fine particle layer arranged linearly,
The inorganic fine particle layer is formed on both sides of the top of the strip thin film on the dielectric layer at a position corresponding to the strip thin film,
A polarizing element having a wire grid structure in which the same direction as the direction in which the inorganic fine particles are linearly arranged is a longitudinal direction,
A transmissive LCD projector.   The transmissive liquid crystal projector according to claim 13, wherein the output-side polarizing plate is a polarizing element in which the inorganic fine particle layer is disposed on the liquid crystal panel side with respect to the substrate.   The transmissive liquid crystal projector according to claim 13, wherein the incident-side polarizing plate is a polarizing element in which the inorganic fine particle layer is disposed closer to the liquid crystal panel than the substrate.   The transmissive liquid crystal projector according to claim 13, wherein the reflective layer is a metal layer.   The transmissive liquid crystal projector according to claim 13, wherein the inorganic fine particles are made of a semiconductor material having a band gap energy of 3.1 eV or less. The transmissive liquid crystal projector according to claim 13, wherein the inorganic fine particle layer has a thickness of 200 nm or less.