JP6539879B2 - Wire grid type light absorbing polarizing element, transmission type projector, and liquid crystal display device - Google Patents

Description

The present invention relates to a wire grit type light absorbing polarizing element, a transmission type projector, and a liquid crystal display having durability against strong light.

  In the liquid crystal display device, it is essential 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 the orthogonal polarization components (so-called P polarized wave, 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 manufacturing method of a dichroic polarizing plate, after dyeing with a polyvinyl alcohol film and a dichroic material such as iodine, a method of crosslinking using a crosslinking agent and uniaxially stretching is used. Since such a polarizing plate is produced by stretching, this type of polarizing plate generally shrinks easily. In addition, since polyvinyl alcohol films use hydrophilic polymers, they are very easily deformed particularly under humidified conditions. In addition, the mechanical strength of the device is weak because the film is basically used. In order to avoid this, a method of bonding a transparent protective film may be used.

  By the way, in recent years, the applications of liquid crystal display devices have been expanded and their functions have been enhanced. Along with this, 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, excellent heat resistance is required for the polarizing plate used for these. However, since the film-based polarizing plate as described above is an organic substance, there are inherent limitations in enhancing these characteristics.

  To cope with this problem, a highly heat-resistant inorganic polarizing plate is sold under the trade name Polarcor from Corning, USA. This polarizing plate has a structure in which silver fine particles are diffused in glass, and an organic substance such as a film is not used, and the principle is to utilize plasma resonance of island-like fine particles. That is, it utilizes light absorption by surface plasma resonance when light is incident on noble metal or transition metal island particles, and the absorption wavelength is affected by the particle shape and the dielectric constant of the surroundings. Here, if the shape of the island-like fine particles is elliptical, the resonance wavelengths in the major axis direction and the minor axis direction are different, and thus polarization characteristics are obtained. Specifically, polarization components parallel to the major axis on the long wavelength side are A polarization characteristic of absorbing and transmitting a polarization component parallel to the short axis is obtained. However, in the case of Polarcor, the wavelength range in which the polarization characteristics are obtained is a range close to the infrared portion, and does not cover the visible light range required for the liquid crystal display device. This is due to the physical properties of silver used in the island-like particles.

  Patent Document 1 discloses a UV polarizing plate by applying the above principle and depositing fine particles in glass by thermal reduction, and it is suggested that silver is used as metal fine particles in a specific example. In this case, it is considered that the absorption in the minor axis direction is used contrary to the previous Polarcor. Although it functions as a polarizing plate even at around 400 nm as shown in FIG. 1, it has a small extinction ratio and a very narrow absorption band, so even if the technique of Polarcor and Patent Document 1 is combined, the entire visible light is obtained. It can not be a polarizing plate that can cover the

  Further, Non-Patent Document 1 describes theoretical analysis of an inorganic polarizing plate using plasma resonance of metal island-like 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 manufacture a polarizing plate covering a visible light range by using aluminum fine particles.

  In addition, Patent Document 2 shows several methods of producing a polarizing plate using aluminum fine particles. Among them, it is described that calcium aluminoborate glass is not suitable as a substrate because aluminum and glass react with each other in silicate-based glass (paragraph 0018, 0019). However, glass using silicate is widely distributed as optical glass, and reliable products can be obtained inexpensively, and it is economically unpreferable that this is not suitable. There is also described a method of forming island-like particles by etching a resist pattern (paragraphs 0037 and 0038). In general, a polarizing plate used in a projector is required to have a size of about several cm and a high extinction ratio is required. Therefore, when aiming at a polarizing plate for visible light, the resist pattern size needs to be sufficiently shorter than the visible light wavelength, that is, several tens of nanometers in size, and in order to obtain a high extinction ratio, the pattern is It is necessary to form in high density. In addition, when used for a projector, 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 to obtain such a pattern. Electron beam writing is a method of drawing individual patterns from an electron beam, and the productivity is poor and impractical.

  Further, Patent Document 2 describes that aluminum is removed by chlorine plasma, but when etched in such a manner, chloride adheres to the side wall of the aluminum pattern. Although it can be removed by a commercially available wet etching solution (for example, SST-A2 of Tokyo Ohka Kogyo Co., Ltd.), such a chemical solution that reacts with aluminum chloride is described because it reacts with aluminum although its etching rate is slow. It is difficult to realize the desired pattern shape by the conventional method.

  Further, Patent Document 2 describes, as another method, a method of depositing aluminum by oblique film formation on a patterned photoresist and removing the photoresist (paragraphs 0045 and 0047). However, in such a method, it is considered that aluminum needs to be deposited on the substrate surface to some extent in order to obtain adhesion between the substrate and the aluminum. However, this means that the shape of the deposited aluminum film is different from that of a prolate spheroid containing prolate spheroid which is the appropriate shape described in paragraph 0015. Further, paragraph 0047 describes that the oversediment integral is removed by anisotropic etching perpendicular to the surface. The shape anisotropy of aluminum is extremely important to function as a polarizing plate. Therefore, it is considered necessary to adjust the amount of aluminum deposited on the resist portion and the substrate surface so as to obtain a desired shape by etching, but the submicron of 0.05 μm or less as described in paragraph 0047. It is considered very difficult to control these by size, and it is questionable whether it is suitable as a highly productive manufacturing method. In addition, high transmittance is required in the transmission axis direction as a characteristic of the polarizing plate, but when glass is used as a normal substrate, reflection of several% from the glass interface can not be avoided, and measures are not taken to obtain high transmittance. It is difficult.

  Patent Document 3 describes a polarizing plate by oblique deposition. In this method, polarization characteristics are obtained by producing a minute columnar structure by oblique deposition of a transparent and opaque material with respect to the wavelength of the used band, and unlike Patent Document 1, a fine pattern can be obtained by a simple method. It is considered to be a highly productive method, but there are also problems. That is, the aspect ratio of the microcolumnar structure of the opaque substance to the use zone initially formed, the distance between the individual microcolumnar structures, and the linearity are important factors to obtain good polarization characteristics and the reproducibility of the characteristics. This method should be intentionally controlled from the point of view as well, but in this method the phenomenon that a columnar structure can be obtained by not depositing deposition particles that fly next to the shadowed portion of the initial deposition layer of deposition particles It was difficult to control the above items intentionally because it was used. As a method of improving this, a method is described in which a polishing mark is provided on a substrate by rubbing treatment before vapor deposition, but generally, the particle diameter of the vapor deposition film is at most about several tens of nm in size. In order to control the anisotropy of such particles, it was necessary to intentionally produce sub-micron pitches by polishing. However, in the case of general polishing sheets and the like, submicrons are the limit, and it is not easy to produce such fine polishing marks. Also, as described above, the resonance wavelength of the Al fine particle largely depends on the refractive index of the surroundings, and in this case the combination of transparent and opaque substances is important, but in Patent Document 3, good polarization characteristics are obtained in the visible light range. There is no description for the combination. When glass is used as a normal substrate as in Patent Document 1, reflection of several% from the glass interface can not be avoided, and no countermeasure has been taken against this.

Non-Patent Document 2 describes a polarizer for infrared communication called Lamipol. It has a laminated structure of Al and SiO ₂ , and according to this document, it exhibits a very high extinction ratio. In addition, Non-Patent Document 3 states that a high extinction ratio can be realized at a wavelength of 1 μm or less by using Ge instead of Al responsible for light absorption of Lamipol. Also, from Fig. 3 in the same document, it is expected that Te (tellurium) can also obtain a high extinction ratio. As described above, Lamipol is an absorption-type polarizing plate that can obtain a high extinction ratio, but the polarization of a projector application requiring a size of several cm square for the laminated thickness of the light absorbing material and the light transmitting material to be the size of the light receiving surface. It does not go to the board.

  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 working band, and the light of the polarization component parallel to the metal thin wire is reflected, and the orthogonal polarization component is transmitted. Make the polarization characteristic appear.

  Further, in Patent Document 5, a wire grid type polarization element is formed on a metal grid by forming a dielectric layer / metal layer, and the light reflected from the metal grid is generally canceled by interference effect by forming a total of three layers. There is disclosed a method of using a wire grid which is a mold as an absorbing mold. When using as an absorption type polarizing plate by utilizing the optical properties obtained by such a multilayer structure, the film thickness and the optical properties of the metal layer formed on the dielectric layer are important elements to obtain the desired properties. It is believed that the patent does not take it into consideration. That is, although the patent does not describe this point and the details are unclear, it is necessary for light to pass through the upper metal layer to obtain the interference effect as described. The passage of light means that part of the light is absorbed by the upper metal film in the process. The absorption lowers the transmittance in the transmission axis direction, which is not desirable as a property of the polarization transmission axis, and particularly in a liquid crystal display device where high transmittance in the visible range is required. That is, a polarizing plate having an absorption effect essentially does not function unless the optical anisotropy of the absorbing layer is controlled, and it is practically difficult to apply as a polarizing plate.

  Further, Patent Document 6 describes an inorganic polarizing plate in which semiconductor nanorods are dispersed in glass. It is described that good polarization characteristics can be obtained in the visible light range, but since this is manufactured by the same method as Polaringor of Corning Co., a drawing process is required and enlargement is difficult.

U.S. Patent No. 6772608 Unexamined-Japanese-Patent No. 2000-147253 JP 2002-372620 A U.S. Pat. No. 6,122,103 U.S. Pat. No. 6,813,077 JP, 2006-323119, A

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

  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 characteristics against strong light, and a liquid crystal projector using the polarizing plate. The purpose is to

  According to the present invention, a substrate transparent to visible light, a reflective layer made of metal and provided with a thin strip extending in one direction on the substrate at a constant interval, 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-like thin film on the dielectric at a position corresponding to the strip-like thin film There is provided a polarizing element having a wire grid structure which is formed on a surface and whose longitudinal direction is the same direction as the direction in which the inorganic fine particles are linearly arranged.

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

According to the polarizing element of the present invention, it is possible to provide one having higher durability than the conventional polarizing element while having a desired extinction ratio in the visible light range.
Further, according to the liquid crystal projector of the present invention, since the polarizing element having excellent light resistance characteristics 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 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 diagonal sputter film deposition. 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 example (1) of the output surface stray light countermeasure of the polarizing element shown in FIG. It is a figure which shows the example (2) of the output surface stray light countermeasure 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 a structure shown in FIG. It is a figure which shows the example (2) of the output surface stray light countermeasure in the polarizing element of a structure shown in FIG. It is a sectional view showing the composition of the optical engine part of the liquid crystal projector concerning the present invention. It is a figure which shows the measurement result of the optical constant of explanatory drawing of the method of performing oblique sputter film-forming of Ge with respect to the stationary board | substrate, and Ge film-formed. It is a figure which shows the measurement result of the optical constant of explanatory drawing of the method of performing sputter film deposition (incidence from perpendicular direction) of Ge with respect to the rotating board | substrate, and Ge film formed into a film. It is a figure which shows the measurement result of the optical constant of Si film | membrane which carried out sputter film deposition. It is a figure which shows the polarization | polarized-light transmission characteristic of Ge film | membrane which has optical anisotropy. FIG. 5 is a schematic view showing a sample configuration of Example 2; FIG. 6 is a view showing the results of optical characteristics of Example 2; FIG. 16 is a diagram showing the results of optical characteristics 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 | polarized-light transmission characteristic of the polarizing element which has an inorganic fine particle layer of FIG. It is a figure which shows the surface structure | tissue 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 a structure shown to 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 an observation result of an inorganic particulate layer in a polarizing element sample of composition of being shown in Drawing 3 (c). It is the electron beam diffraction image of the inorganic fine particle layer in the polarizing element sample of a structure shown to FIG.3 (c). It is a figure which shows the polarization characteristic of the polarizing element sample of a structure shown in FIG. It is a figure which shows the transmission contrast of the polarizing element sample of a 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 a structure shown in FIG. It is a figure which shows the relationship of the long diameter of an inorganic fine particle and film thickness in diagonal sputter film deposition. It is a SEM image which looked at the polarizing element sample of a structure shown in FIG. 5 from the top. It is a figure which shows the preconditions of the polarizing element in optical characteristic simulation. It is a figure which shows the optical characteristic of the polarizing element in case the constituent material of an inorganic fine particle layer is Ge fine particle and Ge thin film. It is an aspect-ratio distribution of Ge microparticles | fine-particles at the time of changing a board | substrate inclination-angle (theta) on a flat plate, and forming into a diagonal sputter film. It is a figure which shows the polarization characteristic of the polarizing element sample of a structure shown in FIG.3 (c) at the time of changing into a substrate inclination angle (theta) and forming into a diagonal sputter film. FIG. 18 is an explanatory view of an oblique film forming method of Example 7; It is a figure which shows the polarization | polarized-light characteristic of Ge fine particle layer sample of Example 7. FIG. It is a related figure of the aluminum height and contrast as a reflection layer in a polarization element of composition of being shown in FIG. FIG. 16 is a view showing polarization characteristics of a polarizing element sample of Example 8. It is a figure which shows the uneven state of the texture structure formed of 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 (anti-reflective film) provided on the substrate by which the rubbing process was carried out. It is a figure which shows the improvement of the polarization characteristic of the anti-reflective film by 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 comprises a substrate transparent to visible light, and a linear inorganic particle layer formed by arranging inorganic particles in one direction on the substrate, and the inorganic particle layer is the substrate It is a polarizing element arranged in a fixed interval on top to form a one-dimensional lattice wire grid structure, wherein the inorganic fine particles have a long diameter in the arrangement direction of the inorganic fine particles and a short diameter in the direction orthogonal to the arrangement direction. It is characterized by having shape anisotropy. Further, 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 consumption coefficient in the arrangement direction of the inorganic fine particles is orthogonal to the arrangement direction of the inorganic fine particles It is characterized in that it is larger than the consumption coefficient in the vertical direction.

  The configuration of the first embodiment of the polarizing element according to the present invention will be described below. Although the present invention will be described with reference to the embodiments shown in the drawings, the present invention is not limited thereto, and can be appropriately modified according to the embodiment, and the operation of the present invention is also possible in any of the embodiments. -As long as the effect is exerted, 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 protrusion.
FIG. 1 shows a configuration example of the first embodiment of the polarizing element according to the present invention. FIG. 1A is a cross-sectional view of the polarizing element 10, and FIG. 1B is a plan view of the polarizing element 10.

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

  Here, the substrate 11 is made of a material that is transparent to light in the working band (visible light region in the present embodiment) and has a refractive index of 1.1 to 2.2, for example, glass, sapphire, quartz, etc. There is. In the present embodiment, it is preferable to use glass, in particular, 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. The use of quartz or sapphire having high thermal conductivity as a constituent material of the substrate 11 can be advantageously used as a polarizing element for an optical engine of a projector that generates a large amount of heat.

  The 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 is the absorption axis of the substrate 11. It is formed periodically at a pitch smaller than the wavelength of the visible light region in the direction (transmission axis X direction) orthogonal 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 according to the processing size and pattern shape of the uneven portion 14. It is important to obtain polarization characteristics. That is, the processing size and pattern shape of the concavo-convex portion 14 are appropriately set according to the target polarization characteristic (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, The formation depth of is 1 nm or more.

The pitch, line width / pitch, concave depth (convex height), convex length, and top line width / bottom line width of the concavo-convex portion 14 are preferably 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 <protrusion length,
1.0 ≦ (upper line width / bottom line width)

  The uneven portion 14 may be formed directly on the substrate 11 or may be separately formed. As a method of forming the concavo-convex portion 14, a method of forming by lapping with a polishing sheet, a photoresist as used in the manufacture of a semiconductor device is applied to a substrate, a pattern is formed by exposure using a mask, and the pattern is formed. There is a method of etching the substrate using a photoresist as a mask, a method of transferring the shape of the mold onto the substrate using a mold formed corresponding to the shape and size of the concavo-convex portion 14 (nanoimprinting), etc. do it.

  In addition, the shape of the convex part of the uneven | corrugated | grooved part 14 can be formed in rectangular shape, such as quadrangle | tetragon and a trapezoid, sawtooth shape, and triangle shape. FIG. 3A shows an example in which the convex portion 14a of the concavo-convex portion 14 has a rectangular shape in cross section, and the inorganic fine particle layer 15 is formed on one side surface portion. Further, FIG. 3B shows an example in which the inorganic fine particle layer 15 is formed on one side surface portion of the convex portion 16a of the concavo-convex portion 16 having a sawtooth shape in cross section and standing in the vertical direction. By forming the cross section of the convex portion in a sawtooth shape, it is possible to avoid adhesion of the film to the top of the convex portion. Further, FIG. 3C shows an example in which the convex portion 17a of the concavo-convex portion 17 has a triangular shape in 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 such a convex portion 14a, the inorganic fine particle layer 15 having shape anisotropy is distributed in stripes on the surface of the substrate 11 in a desired fine shape. It is possible to realize the isolation of the inorganic fine particles. Further, since the inorganic particle layer 15 is formed on the uneven portion 14 mechanically formed in advance, the uneven portion 14 can be stably formed, and the shape of the inorganic particle layer 15 formed thereon Control can be easily performed.

  The inorganic fine particle layer 15 has inorganic fine particles in a linear shape in one direction parallel to the main surface of the substrate 11 (the absorption axis Y direction) by attaching the inorganic fine particles to the top or at least one side wall of the convex portion 14a. It is arranged. “Inorganic fine particles are linearly arranged” means a continuous band-like film in which the inorganic fine particles are mutually connected, and the inorganic fine particles form an independent island by collecting them in a suitable size, and the islands are unidirectional. It may be in any state of a discontinuous film lined up, as long as grain boundaries are formed. Further, by forming the inorganic fine particle layer 15 on each of the plurality of convex portions 14a regularly provided at regular intervals, the formation pattern of the inorganic fine particle layer 15 becomes stripes (one-dimensional lattice shape), and the wire grid structure is formed. Take on.

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

  Further, in the present invention, as the optical constant of the inorganic fine particle layer 15, the optical constant in the absorption axis Y direction (arrangement direction of the inorganic fine particles) is greater 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 oblique sputtering.

  A state of oblique sputtering film formation for forming the inorganic fine particle layer 15 of the present invention is shown in FIG. 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 a substrate 11, 2 is a target, 3 is a beam source (ion source), and 4 is a control plate. The stage 1 is inclined at a predetermined angle θ with respect to the normal direction of the target 2, and in the substrate 11, the longitudinal direction of the convex portion 14 a of the uneven portion 14 is orthogonal to the incident direction of the inorganic fine particles from the target 2 Is located in The angle θ is, for example, 0 ° to 15 °. The ions extracted from the beam source 3 are irradiated to the target 2. The inorganic fine particles knocked out of the target 2 by the irradiation of the ion beam are incident on the surface of the substrate 11 from an oblique direction and adhere. At this time, if the flat control plate 4 is disposed on the substrate 11 at a constant interval (for example, 50 mm), the direction of incident particles on the surface of the substrate 11 is controlled to deposit particles only on the side wall of the convex portion 14a. Can. 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 inclined with respect to the target 2 at the time of film formation by sputtering to restrict the incident direction of the inorganic fine particles, thereby selectively forming the array on the top or one side of the convex portion 14a. Inorganic particles having shape anisotropy in which the diameter in the direction is long and the diameter in the direction orthogonal to the arrangement direction is short are linearly arranged, and the optical constant in the absorption axis Y direction is greater than the optical constant in the transmission axis X direction The inorganic fine particle layer 15 which becomes large can be obtained.

Here, as a material (material which comprises inorganic fine particles) used for inorganic fine particle layer 15, it is necessary to choose a suitable material according to a use zone as polarizing element 10. That is, a metal material or a semiconductor material is a material that satisfies this, and specifically, as a metal material, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn There may be mentioned elemental metals or alloys containing these. In addition, examples of the semiconductor material include Si, Ge, Te, and ZnO. Furthermore, silicide-based materials such as FeSi ₂ (especially β-FeSi ₂ ), MgSi ₂ , NiSi ₂ , BaSi ₂ , CrSi ₂ , CoSi _{2 and the} like 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. Because, it absorbs light less than this energy. Therefore, when the semiconductor material is used as a polarizing element for visible light, the band gap energy needs to be less than the use band. For example, when using visible light, absorption at a wavelength of 400 nm or more, that is, a material having a band gap of 3.1 eV or less needs to be used. As described in Non-Patent Document 4, the band gap energy also depends on the size of the fine particle, and tends to increase rapidly especially when it becomes several nm. It is necessary to determine the thickness. From such a viewpoint, a semiconductor material having a small band gap energy in the bulk state is preferable. For example, since Ge has a small band gap energy in the bulk state of 0.67 eV (wavelength of about 1.85 μm), a polarizing element for visible light Is a desirable material.

  By adopting the above configuration, the polarizing element 10 has a desired extinction ratio in the visible light range, and is more durable than the conventional polarizing element.

In addition, by coating an antireflective film on the front surface and the back surface of the substrate as necessary, it is possible to prevent reflection at the interface between air and the substrate and to improve the transmission axis transmittance. The antireflective film may be a low refractive index film such as MgF ₂ generally used, or a multilayer film composed of a low refractive index film and a high refractive index film. Also, after the configuration shown in FIG. 1, it is possible to coat the surface with a transparent substance such as SiO ₂ as a protective film with a film thickness in a range that does not affect the polarization characteristics, such as improvement of moisture resistance, etc. It is effective for improving reliability. However, since the optical properties of the inorganic fine particles are also affected by the refractive index of the surroundings, the formation of the protective film may cause changes in the polarization properties. In addition, since the reflectance for incident light also changes depending on the optical thickness of the protective film (refractive index × protective film thickness), 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 SiO ₂ , Al ₂ O ₃ and the like. These can be deposited by spin coating, dipping, etc., using a general vacuum deposition method (chemical vapor deposition, sputtering, evaporation, etc.), or sol in the state where they are dispersed in a liquid. is there. Furthermore, a self-assembled film as described in Non-Patent Document 5 can also be used. A water-repellent self-assembled film is preferred for the purpose of improving the moisture resistance. Perfluorodecyltrichlorosilane (FDTS), Octadecainetrichlorosilane (OTS), etc. are examples thereof. Since it has water repellency, it is also effective in terms of antifouling measures. From this, it can be purchased from a chemical maker, for example, Gelest, USA, and can be deposited by dipping. Moreover, film formation is also possible by vapor deposition, and a dedicated apparatus is also sold by Applied Microstructures, Inc. in the United States. 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 the adhesive layer on the polarizing element by the above method. Good.

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

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

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

  The reflective layer 22 is formed by arranging thin films 22 a made of metal and extending in a band shape in one direction (the 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, metals such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Ge, Te, or semiconductor materials are used. be able to. In addition to the metal material, for example, an inorganic film or resin film other than a metal having a high surface reflectance due to coloring or the like may be used.

  The thin film 22a is arranged on the surface of the substrate 21 at a pitch smaller than the wavelength of the visible light region, and is formed by, for example, patterning of the metal film using a photolithography technique (metal grating). The reflective layer 22 has a function as a wire grid type polarizer, and among 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) TE waves (S waves) are attenuated, and polarized waves (TM waves (P waves)) having electric field components in the direction (X-axis direction) orthogonal to the longitudinal direction of the wire grid are transmitted.

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

The dielectric layer 23 is formed by coating the surface of the substrate 21 with a general vacuum film forming method such as sputtering method, vapor phase growth method, vapor deposition method or sol gel method (for example, spin coating method and gelation by heat curing) The optical material is transparent to visible light such as SiO ₂ formed by The dielectric layer 23 forms a base layer of the inorganic fine particle layer 25 and, as described later, the polarized light reflected by the inorganic fine particle layer 25 passes through the inorganic fine particle layer 25 and is reflected by the reflective layer 22. The film thickness is formed such that the phase of the phase shift by half wavelength. Specifically, it is preferable to set appropriately in the range of 1 to 500 nm. The film thickness is preferably formed for the purpose of adjusting the phase of the polarization and enhancing the interference effect, and a half wavelength shift is desirable. However, since the inorganic fine particle layer has an absorption effect, it can absorb reflected light and the film thickness is optimized. Even if it is not used, improvement in contrast can be realized, and in practice, it may be determined in consideration of the desired polarization characteristics and the actual fabrication process. The practical film thickness range is 1 to 500 nm.

The material constituting the dielectric layer 23 _may be formed of commonly available materials, such as _{SiO 2, Al 2 O 3,} MgF 2. These films can be thinned by applying a general vacuum film forming method such as sputtering, vapor phase growth, vapor deposition or the like, or coating a sol-like substance on a substrate and thermally curing it. The refractive index of the dielectric layer 23 is preferably greater than 1 and 2.5 or less. Since the optical properties of the inorganic fine particle layer 25 are also influenced by the refractive index of the surroundings, it is also possible to control the polarization element properties by the dielectric layer material.

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

  In FIG. 5, the inorganic fine particle layer 25 has a long oval shape having a long axis direction parallel to the longitudinal direction (Y axis direction) of the thin film 22a and a short axis direction in the direction (X axis direction) orthogonal to the longitudinal direction. The island-shaped inorganic fine particles 25a are arranged in the Y-axis direction. In addition, it is desirable that the inorganic fine particles 25a have a size equal to or less than the wavelength of the use band, and that the individual particles be 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 oblique sputtering. The details are the same as the method shown in the first embodiment. Further, 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 side on which the strip-like thin film 22a, the dielectric layer 23, and the inorganic fine particle layer 25 are formed is the light incident surface. The polarizing element 20 utilizes the four effects of light transmission, reflection, interference, and selective light absorption of polarized waves by optical anisotropy to make the electric field component parallel to the wire grid longitudinal direction of the reflective layer 22 Attenuates polarized waves (TE waves (S waves)) with (Y axis direction) and transmits polarized waves (TM waves (P waves)) with 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 function of the polarized wave due to the optical anisotropy of the inorganic fine particle layer 25 made of the inorganic fine particle 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. 6 (b). At this time, the TE wave reflected by the thin film 22 a was 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 22 a is shifted by half. It cancels and attenuates by TE wave and interference. As described above, the TE wave can be selectively attenuated. As described above, it is desirable that the film thickness is shifted by a half wavelength, but since the inorganic fine particle layer has an absorption effect, improvement in contrast can be realized even if the film thickness of the dielectric layer is not optimized. It may be determined from the polarization characteristics and the economic efficiency in the actual preparation process.

  In addition, when low reflection is required on the exit side, light may be incident from the side of the reflective layer. 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. As described later, the magnitude of the transmission contrast depends on the reflective layer thickness. If 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 used as the incident polarizing plate 10A for the purpose of avoiding unwanted reflected light to the liquid crystal panel. When used, the film surface of the present polarizing plate (the inorganic fine particle layer 25 side in FIG. 6) is disposed so as to face the liquid crystal panel. By doing so, unwanted reflected light will return to the light source side. When the polarizing plate of the present invention is used as the output polarizing plate 10B or 10C, the film surface (the inorganic fine particle layer 25 side in FIG. 6) of the polarizing plate may be similarly directed to the liquid crystal panel side. The incident direction of the light to this polarizing plate is opposite between the case of using for the incident polarizing plate and the case of using the outgoing polarizing plate, but the same transmission contrast can be obtained even if the light is incident from either side as described above. Above no problem.

  The polarizing element 20 can be manufactured, for example, as follows. That is, a metal film and a dielectric film are laminated on the substrate 21 and a lattice pattern of the metal film and the dielectric film is formed by photolithography or the like, and then the inorganic fine particle layer 25 is formed by the oblique sputtering film forming method. By adjusting the incident angle at the time of oblique sputtering film formation, it is possible to deposit fine particles intensively in the vicinity of the apex of the convex portion composed of the thin film strip 22 a 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 in a one-dimensional lattice shape on a transparent substrate, and a metal layer, a dielectric layer and an inorganic fine particle layer are sequentially laminated by oblique film formation on convex portions of this lattice. is there. Furthermore, a metal film, a dielectric film, and a fine particle film may be sequentially stacked on a substrate, and then these may be collectively etched in a one-dimensional lattice.

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

  In addition, as a polarizing element of this invention, it is good also as a polarizing element of the structure which abbreviate | omitted the dielectric material layer 23 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 22 a 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 in this configuration, it is possible to provide a desired extinction ratio (contrast: transmission axis transmittance / absorption axis transmittance) in the visible light range.

Next, an example in which a selective light absorbing layer is provided on the back surface side of the polarizing element 20 will be described as a countermeasure against stray light at the output surface (a countermeasure against ghost) 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 the detailed description thereof is omitted.

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

  In the polarizing element 20 in which the selective light absorbing layer 28 of the polarized light wave due to this optical anisotropy is not provided, the back surface side of the substrate 21 exhibits a mirror surface by the reflective layer 22. The light reflected back by the other optical element such as the lens disposed in the step will be reflected again by the mirror surface. Such stray light causes degradation of image quality such as ghost in a liquid crystal projector.

  In the present embodiment, the stray light is absorbed by providing the selective light absorbing layer 28 of the polarized light with the optical anisotropy of the above configuration on the back surface side of the substrate 21, and the reflection in the reflective layer 22 is prevented. The concavo-convex portion 26 constituting the selective light absorption layer 28 of polarized light by optical anisotropy is made of the same material as the dielectric layer 23, and extends in the same direction as the strip thin film 22a of the reflection layer 22 extends. Are formed in a one-dimensional grid shape. The second inorganic fine particle layer 27 is formed by arranging the inorganic fine particles in a line at the top or side of the convex portion of the concavo-convex portion 26, and is made of the same material as the inorganic fine particle layer 25 on the surface side of the substrate 21. As a result, the selective light absorption effect of the incident light from the back surface of the substrate 21 is exhibited.

  The method for forming the concavo-convex portion 26 is the same as the method for forming the dielectric layer 23, and is formed by a sputtering method, a sol-gel method, or the like. The provision of the uneven shape is preferably pattern processing using a photolithography technique or press formation using a nanoimprint method. As the method of forming the second inorganic fine particle layer 27, oblique film formation similar to the method of forming the inorganic fine particle layer 25 on the surface side of the substrate 21 is preferable. The second inorganic fine particle layer 27 is formed on the top or one side or both sides of the convex portion of the uneven portion 26.

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

Next, an example in which an anti-reflection layer is provided between the substrate 21 and the reflective 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 the 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 20B of the present embodiment, the anti-reflection layer 29 is formed between the substrate 21 and the reflective layer 22. As described above, the reflection preventing layer 29 is provided immediately below the one-dimensional lattice-like reflecting layer 22 so that 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, for example. Thereby, the incident light from the back surface of the substrate 21 can be efficiently absorbed. In addition to carbon, a silicon oxide layer lacking oxygen, or a low reflection material layer having a reflectance lower than that of the reflection layer 22 is applicable. Alternatively, the same material as the inorganic fine particle layer 25 may be used as the antireflective layer 29. In the illustrated example, the dielectric layer 2a is provided for the purpose of reducing the reflectance by obtaining an interference effect between the reflective layer 22 and the antireflective layer 29. The processing of the dielectric layer 2 a and the antireflective layer 29 into the lattice shape can be performed simultaneously, for example, by patterning of the reflective layer 22.

  Furthermore, there are the following methods as another ghost countermeasure in the liquid crystal projector. That is, the surface of the substrate 21 is subjected to rubbing treatment, and the fine lines are arranged in one direction so as to correspond to the arrangement direction of the inorganic fine particles 25a of the inorganic fine particle layer 25 formed later on 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 process by the oblique sputtering method described above so as to correspond to the arrangement direction of the inorganic fine particles 25a. It is good to do. The alignment property of the inorganic fine particles is improved by the texture structure so that the long axis direction of the inorganic fine particles becomes the longitudinal direction of the streaks, the polarization characteristic of the thin film is improved, and the ghost countermeasure effect can be enhanced. At the same time, an increase in transmission contrast characteristics as a polarizing element can also be expected.

  As a variation of the second embodiment of the present invention, a multilayer structure in which one or more of the laminated structure of the dielectric layer 23 / the inorganic fine particle layer 25 described above is stacked on the inorganic fine particle layer 25 may be used. FIG. 10 shows an example of the configuration.

  In FIG. 10, in the polarizing element 30, the strip-like thin film 22a constituting the reflective layer 22, the dielectric layer 23, and the inorganic fine particle layer 25 are laminated in this order on the substrate 21, and the dielectric is formed on the inorganic fine particle layer 25. A layered structure 26a of the layer 23 / the inorganic fine particle layer 25 is further stacked to form a wire grid structure. Further, the stacked structure 26a may be further stacked on the stacked structure 26a. As a result, the interference effect between the 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 which is undesirable in the transmissive liquid crystal display can be reduced over a wide range. High contrast and low reflection can be realized with a film thickness thinner than that of the polarizing element 20 having the configuration of FIG.

  There are, for example, the following three methods for producing 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 method such as nanoimprinting or photolithography, and then oblique sputtering is performed. The fine particles are formed by the film method. According to this, it is possible to concentrate the inorganic fine particles in the vicinity of the top of the dielectric layer 23 which has become the convex portion by adjusting the incident angle at the time of oblique sputtering film formation. As a second method, a transparent material is used to form a one-dimensional lattice-shaped uneven portion on a transparent substrate, and a reflective layer material, a dielectric layer material, and an inorganic fine particle material are sequentially stacked by oblique deposition for the number of stacked layers. It is As a third method, a laminated structure of (dielectric film / inorganic fine particle thin film) is sequentially laminated on the thin film (metal lattice film) of the reflective layer by the number of laminated layers and then etching is performed. The inorganic fine particle material does not have to be completely island-like, as long as grain boundaries are formed. The dielectric layer 23 and the inorganic fine particle layer 25 may be manufactured by combining the formation method by sputtering deposition and etching and the formation method by oblique sputtering deposition. There is no limitation on the type of substrate material in carrying out the above manufacturing process, but when applied to a projector with a large amount of heat generation, a quartz or sapphire substrate with high thermal conductivity is suitable.

By the way, with the polarizing element 30 having the above-described structure as it is, since the light emission surface (reflection layer 22) is made of metal, the reflectance is high when there is return light. Therefore, it is preferable to take measures against the output surface stray light also in the present embodiment.
FIGS. 11 and 12 show an example of a countermeasure against stray light at the exit surface in the present embodiment.

FIG. 11 shows an example in which the configuration of FIG. 8 is applied to the present embodiment.
In the polarizing element 30A, the polarizing element 30A has the convex / concave portion 26 made of a dielectric material on the surface (back surface) opposite to the surface of the substrate 21 on which the reflective layer 22 is formed, A selective light absorbing layer 28 of polarized light according to optical anisotropy, which is formed of the second inorganic fine particle layer 27 formed, is provided.

FIG. 12 shows an example in which the configuration of FIG. 9 is applied to the present embodiment.
In the polarizing element 30B, in the polarizing element 30, the antireflective layer 29 is provided immediately below the reflection layer 22 in the form of a one-dimensional lattice, and a dielectric is additionally provided for the purpose of obtaining an interference effect between the reflective layer 22 and the antireflective layer 29. Layer 2a is provided. In FIG. 12, the dielectric layer 2 a below the reflective layer 22 may not be present, and the antireflective layer 29 may be formed simply below the reflective layer 22. In addition, when the antireflective layer 29 is the same as the inorganic fine particle layer 25, it also contributes to the improvement of the contrast, but for the purpose of simply preventing the return light from being reflected, the antireflective layer under the reflective layer 22 is prevented. It is preferable to provide a layer (low reflective layer) having a lower reflectance than the reflective layer 22 as the layer 29. As the low reflection material, it is effective if the reflectance is lower than that of the reflection layer 22. It is also possible to use an oxide film such as carbon or oxygen deficient SiOx, or to use metal or semiconductor fine particles.

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

Moreover, also in the second embodiment, by coating an antireflective film on the front surface and the back surface of the substrate as necessary, reflection at the interface between air and the substrate can be prevented, and the transmission axis transmittance can be improved. . The antireflective film may be a low refractive index film such as MgF ₂ generally used, or a multilayer film composed of a low refractive index film and a high refractive index film. After the configuration shown in FIG. 5 or FIG. 7, it is possible to coat the surface with a transparent substance such as SiO ₂ as a protective film with a film thickness in a range that does not affect the polarization characteristics. It is effective to improve the reliability by improving the However, since the optical properties of the inorganic fine particles are also affected by the refractive index of the surroundings, the formation of the protective film may cause changes in the polarization properties. In addition, since the reflectance for incident light also changes depending on the optical thickness of the protective film (refractive index × protective film thickness), 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 SiO ₂ , Al ₂ O ₃ and the like. These can be deposited by spin coating, dipping, etc., using a general vacuum deposition method (chemical vapor deposition, sputtering, evaporation, etc.), or sol in the state where they are dispersed in a liquid. is there. Furthermore, a self-assembled film as described in Non-Patent Document 5 can also be used. A water-repellent self-assembled film is preferred for the purpose of improving the moisture resistance. Perfluorodecyltrichlorosilane (FDTS), Octadecainetrichlorosilane (OTS), etc. are examples thereof. Since it has water repellency, it is also effective in terms of antifouling measures. From this, it can be purchased from a chemical maker, for example, Gelest, USA, and can be deposited by dipping. Moreover, film formation is also possible by vapor deposition, and a dedicated apparatus is also sold by Applied Microstructures, Inc. in the United States. 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 the adhesive layer on the polarizing element by the above method. Good.

Next, a liquid crystal projector according to the present invention will be described.
The liquid crystal projector of the present invention includes a lamp 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 an optical engine portion of a 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 red light LR, a liquid crystal panel 50, an outgoing pre-polarizing element 10B, an outgoing main polarizing element 10C, an incident side polarizing element 10A for green light LG, a liquid crystal panel 50, Emitting 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 from outgoing main polarizing element 10C It has a cross dichroic prism 60 which combines incoming light and emits it to a projection lens. Here, the polarizing elements 10, 20, and 30 of the present invention are applied to the incident side polarizing element 10A, the outgoing pre-polarizing element 10B, and the outgoing main polarizing element 10C.

  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 the incident side corresponding to each light The light LR, LG, and LB polarized by the respective incident-side polarization elements 10A after being incident on the polarization element 10A are spatially modulated by the liquid crystal panel 50 and emitted, and the emission pre-polarization element 10B and the emission main polarization element 10C are After passing, they are combined by the cross dichroic prism 60 and projected from a projection lens (not shown). Even though the light source lamp has a high output, since the polarizing elements 10, 20, and 30 of the present invention having excellent light resistance characteristics against strong light are used, it is possible to realize a highly reliable liquid crystal projector. it can.

  In addition, the polarizing element of this invention is not necessarily limited to the application to the said liquid-crystal projector, It is suitable as a polarizing element which receives heat as a use environment. For example, it can be applied as a polarizing element of a car navigation system of an automobile or a liquid crystal display of an instrument panel.

Hereinafter, results of verification of polarization characteristics of the polarizing element according to the present invention will be 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, Ge sputtered particles are allowed to enter and deposit on the surface of the glass substrate 41 at 10 ° with respect to the surface of the glass substrate 41 by ion beam sputtering, thereby forming a Ge particle film 44. FIG. 14B shows the measurement results of the optical constants (refractive index, extinction constant) of the Ge particle film 44 produced. The measurement was performed by a spectroscopic ellipsometer. The film thickness at this time is 10 nm. In this experiment, due to the occurrence of optical anisotropy, there is a difference in the optical constant, that is, the refractive index n and the extinction constant k in the plane. For comparison, as shown in FIG. 15A, when Ge sputtered particles were deposited while rotating the substrate 41 from the vertical direction of the substrate 41, the optical constant of the obtained Ge particle film 44 is shown in FIG. 15B. Thus, optical anisotropy of refractive index n and extinction constant k did not occur, and each optical constant had a value close to the literature value.

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

  Next, the polarization transmittance in the case where the Ge particle film 44 with a film thickness of 20 nm is formed on the glass substrate 41 under the conditions of FIG. 14A was determined by simulation calculation. The results are shown in FIG. Here, polarization is performed using optical constants in the X-axis direction for light whose electric field is oscillating parallel to the X-axis direction, and using optical constants in the Y-axis direction for light whose electric field is oscillating in the Y-axis direction. Calculation of transmittance is performed. According to the result, the transmittance is different in the polarization direction by having the optical anisotropy characteristic. That is, by using a film having such optical anisotropy as a material of the polarizing element, improvement in the characteristics of the polarizing element can be expected.

(Example 2)
Next, the influence of the presence or absence 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 shown in FIG. 1 and FIG. 5, its polarization characteristic was determined by wavelength coupled wave analysis (RCWA). Here, as shown in FIG. 18, each size of the inorganic fine particle layer 45 has a pitch of 150 nm and a line width (Ge lattice direction, as a structure having the inorganic fine particle layer 45 of wire grid structure Ge on a glass substrate 41. Width): 37.5 nm, the thickness of the inorganic fine particle layer 45 with optical anisotropy (method in FIG. 14A) is 100 nm, and the thickness without optical anisotropy (method in FIG. 15A) is 10 nm. Did. The results are shown in FIG.

  In FIG. 19, there is optical anisotropy (diagonal indicated by a dotted line indicated as bulk) in the visible region 550 nm or less (that is, green and blue regions) important for an optical engine application such as a projector (that is, green and blue regions). Compared to the data shown by the solid line in the description, the absorption axis transmittance is high and the reflectance is high despite the thin film thickness. On the other hand, in the presence of optical anisotropy, the absorption axis transmittance is low and the reflectance is also low. Therefore, it is a desirable characteristic as an absorption type. With respect to the film thickness, in this calculation, no optical anisotropy is 10 nm. If this is made thicker, the absorption axis transmittance decreases, but at the same time the reflectance also increases. Therefore, properties preferable as a polarizing element as in the case of having optical anisotropy can not be obtained by film thickness control.

(Example 3)
FIG. 19 shows an example in which the inorganic fine particle layer is a single layer, but the same can be said for the polarizing element having a multilayer structure of the inorganic fine particle layer shown in FIG.
Here, in the case where the inorganic fine particle layer made of Ge is made to have optical anisotropy by the method shown in FIG. 14A in the polarizing element of the multilayer structure and no optical anisotropy is made by the method shown in FIG. The polarization properties of the light were calculated by wavelength exact coupled wave analysis (RCWA). Moreover, the multilayer structure used here is a multilayer of Ge (15 nm) / reflection layer; Al (240 nm) / dielectric layer; SiO ₂ (205 nm) / inorganic fine particle layer; Ge (90 nm) (surface side) from the substrate side The structure (the thickness in parentheses is the film thickness of each layer), the dimensions of the inorganic fine particle layer were 150 nm in pitch, and 37.5 nm in line width (Ge lattice direction width). In addition, in order to suppress the influence of the stray light due to the rereflection of the return light to the polarization element exit surface, the Ge layer is provided on the substrate side of the reflective layer. 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 dotted lines described with isotropy), when there is an optical anisotropy in the visible region of 550 nm or less (anisotropic as described The result is that the reflectance of the absorption axis is higher than that of the data shown by the solid line) and the transmittance of the transmission axis is lower. Therefore, it is not preferable as an absorption type polarizing element. As described above, the effect of the optical anisotropy on the polarization characteristics of the polarizing element is large.

(Example 4)
As described above, by using the inorganic fine particle layer having optical anisotropy for the polarizing element, it is possible to improve the polarization characteristic. And 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 to satisfy the relationship of coefficient) <(absorption axial extinction coefficient). Examples showing this are shown in FIG. 21 and FIG.
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 among the polarizing elements of the structure of FIG. Also in this case, it can be seen that it has optical anisotropy like Ge. However, the magnitude of the refractive index in the X and Y directions is inverted around a wavelength of 550 nm, and the extinction coefficients in the X and Y directions are reversed around a wavelength of 440 nm.
FIG. 22 shows the result of calculating the polarization transmittance in the case where the Ag film thickness is 20 nm, using the optical constant of the Ag film (inorganic fine particle layer 25) shown in FIG. 21 in the same manner as FIG. As the wavelength becomes lower, the polarized light transmittance decreases, and in the vicinity of the wavelength of 450 nm, the magnitudes of the x- and y-direction transmittances are reversed. This is due to the inversion of the optical constant in FIG. 21. In the case of application to a polarizing element, having such an inversion characteristic is not preferable because it means a decrease in polarized light transmittance. In the absorption axis, the extinction coefficient is large if the extinction coefficient is large, and it is desirable that the light incident from the air layer is transmitted without being attenuated or reflected in the transmission axis, that is, it is desirable that the refractive index is small (air Because the refractive index = 1). Therefore, there is no reversal of the optical constant in the used band as the optical constant of the desirable inorganic particle layer, and (transmission axis direction optical constant) <(absorption axis direction optical constant), that is, (transmission axis direction refractive index) <(absorption The relationship between axial refractive index) and (transmission axial extinction coefficient) <(absorption axial extinction coefficient) is satisfied.

(Example 5)
Next, the relationship between the expression of optical anisotropy 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 the substrate having a smooth surface in which 10 nm of SiO 2 is formed into a film on the surface of a single crystal Si substrate, the same conditions as Example 1 (oblique sputter deposition, with respect to the substrate surface A Ge particle film was formed by sputtering film formation from the vertical direction, and the shape of Ge particles in the Ge particle film was observed by AFM (atomic force microscope). The results are shown in FIG.
In the obliquely sputtered film formation sample shown in FIG. 23A, individual fine particles are clearly observed, and in the fine particles, the shape anisotropy is such that the diameter is long in the direction perpendicular to the Ge incident direction and the diameter is short in the Ge incident direction. Sex was occurring. On the other hand, in the sample shown in FIG. 23 (b) sputter-deposited from the direction perpendicular to the substrate surface, the particle size is very small and the film surface is very flat at the same magnification. The shape could not be observed.

(2) Polarizer 10
Next, a sample of the polarizing element having the configuration shown in FIG. 3C was produced. Here, first, a thermal nanoimprint method is performed using a polymer layer (mr-I 8010E manufactured by Micro Resist Technology) coated on a quartz substrate with a mold of primary grating pattern (pitch 150 nm, line / space ratio = 0.7, depth 150 nm) By press molding to transfer the mold pattern to the polymer layer, and then using the polymer layer as a resist mask to etch the quartz substrate with CF 4 gas + Ar gas to provide projections 17 a extending in one direction at regular intervals. It was eleven. Then, after performing the oblique sputtering film formation of Example 1 with the substrate inclination angle θ = 5 ° on the substrate 11 at normal temperature by the ion beam sputtering apparatus of FIG. 4 to form the inorganic fine particle layer 15 of 30 nm thickness of Ge. A polarizing element protective layer having a film thickness of 15 nm made of SiO ₂ was formed into a sample by vapor deposition. A multilayer film of SiO 2 / Ta 2 O 5 was formed on the back surface side of the substrate 11 by sputtering as an antireflective film. The polarization properties of the obtained polarizing element sample were investigated. As a result, as shown in FIG. 24, the transmittance of the absorption axis showed lower optical anisotropy than the transmittance of the transmission axis.

  The element distribution of this polarizing element sample was analyzed by TEM from the cross-section, and as shown in the element distribution mapping of FIG. 25, the inorganic fine particle layer of Ge from the top to the side wall of each of the convex portions 17 a of the main component Si It turned out that 15 is formed. Based on this result, the inorganic fine particle layer 15 in the polarizing element sample was observed in detail. The results are shown in FIG. FIG. 26 (a) is a sketch when observed from the cross section, in which the element distribution result of FIG. 25 is taken into consideration. FIG. 26 (b) is a sketch when observed from above.

  As shown in FIG. 26 (b), the inorganic fine particle layer 15 is formed along the longitudinal direction of the convex portion 17a from the top to the side wall portion of each of the primary grid convex portions 17a, and the inorganic fine particle layer 15 is also formed. Were observed as lines or bands formed by arranging inorganic fine particles 15a having shape anisotropy in series. Further, individual particles of the inorganic fine particles 15a were clearly observed, and the state in which the long axis direction of the inorganic fine particles was the alignment direction and the short axis direction was the direction orthogonal to the alignment direction was observed.

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

(3) Polarizing element 20
Next, a sample of the polarizing element having the configuration shown in FIG. 5 was produced. Here, an aluminum lattice with a pitch of 150 nm and a lattice depth of 200 nm is produced as a reflective layer 22 on a substrate 21 made of glass (Corning 1737), and 30 nm of SiO ₂ is formed as a dielectric layer 23 thereon. The oblique sputtering film formation is performed under the same conditions as the polarizing element 10 of the present embodiment to stack a Ge fine particle layer of 30 nm as the inorganic fine particle layer 25 and form SiO ₂ with a film thickness of 30 nm as a protective film on the outermost layer. The polarizing element sample shown to 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 a low value. Further, FIG. 29 shows the ratio of transmittance in this case as a contrast, but 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. It showed good characteristics as a polarizing element.

  When this polarizing element sample is observed from the cross section, as shown by the sketch in FIG. 30A, Ge on the top and side walls of the primary grid-like reflective layer 22 and the dielectric layer 23 provided on the substrate 21 It was found that the inorganic fine particle layer 25 consisting of

Moreover, the result of having observed this polarizing element sample from the top in FIG.30 (b) and FIG. 31 is shown. FIG. 30 (b) is a sketch, and FIG. 31 is an SEM image on which it is based.
The inorganic fine particle layer 25 is formed in a mode along the longitudinal direction of the dielectric layer 23 from the top to the side wall of each of the primary lattice dielectric layers 23, and the inorganic fine particle layer 25 is an inorganic material having shape anisotropy. The particles 25a were observed as a line or a band formed by arranging in series. In the inorganic fine particles 25a, it was observed that the long axis direction of the inorganic fine particles was the alignment direction, and the short axis direction was the direction orthogonal to the alignment 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 major axis direction is one-dimensional lattice It is formed in the state aligned in the grid direction of. It is also in an amorphous state. In the present invention, these are considered to affect the expression of optical anisotropy. In addition, although fine particles having shape anisotropy are formed into a film by oblique deposition, exhibiting such shape anisotropy is called a steering effect (Jikeun Seo, S.-M. Kwon, H.-Y. Kim and J.-S. Kim Phys. Rev. B67 121402 (2003)).

  In the oblique sputtering film formation, as shown in FIG. 32, the shape of the film formation particles changes with the film thickness (the 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 long diameter a of the particles (FIG. 32A), the substrate has optical anisotropy in two directions (X and Y directions) on the substrate surface, and the direction of the particle long diameter a is the absorption axis It becomes. On the other hand, when the film thickness b of the inorganic fine particle is larger than the major diameter a of the particle (FIG. 32B), the direction of the particle film thickness b has optical anisotropy in the thickness direction and the in-plane axial direction of the inorganic fine particle Is the absorption axis, the direction of the 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, it means that the polarization characteristics are degraded when the film thickness is large. Therefore, as shown in FIG. 32A, it is desirable to use in a region in which (particle major diameter a)> (particle film thickness b).

  Incidentally, even if a thin film having no optical anisotropy (for example, a germanium thin film) is formed on the dielectric layer 23 instead of the inorganic fine particle layer 25, the reflectance in the absorption axis direction is optimized by optimizing the film thickness. Suppression is possible. However, in this case, since the interference effect is dominant in the suppression, the wavelength band is narrow, and there is a problem that the transmission axis transmittance decreases due to the absorption in the transmission axis direction. Furthermore, since the interference effect is sensitive to the film thickness, strict control of the film thickness of the dielectric layer 23 and the film thickness of the germanium thin film is necessary to obtain desired characteristics. On the other hand, in the present invention, since germanium fine particles having optical anisotropy are used, the design range is wide and the manufacture is easy.

Therefore, the 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 where it is a fine particle was simulated by the wavelength strict coupled wave analysis (RCWA) method. Here, the film thickness (aluminum thickness): 200 nm, lattice pitch: 150 nm, aluminum width: 45 nm for the reflective layer 22 and the film thickness (SiO ₂ ): 30 nm for the dielectric layer 23 The dependence of the absorption axis reflectance, the transmission axis transmittance, and the transmission contrast at a wavelength of 450 nm with respect to is calculated. The optical constant of the Ge thin film uses the value shown in FIG. 15B, and the optical constant of the Ge fine particle takes into consideration the increase in anisotropy when the film is formed on the lattice. It was calculated by assuming that fine particles sufficiently smaller than the wavelength are distributed in the dielectric layer in the same axial direction. Furthermore, the volume ratio of Ge in the dielectric layer 23 was calculated as 0.4 and the aspect ratio as 20.
The results are shown in FIG. FIG. 34 (a) shows the absorption axis reflectance, FIG. 34 (b) shows the transmission axis transmittance, and FIG. 34 (c) shows the transmission contrast. It can be seen that the contrast in the case of Ge fine particles is the same as in the case of the Ge thin film, the transmittance is higher, and the film thickness range in which the reflectance can be reduced is wider.

(Example 6)
Next, the relationship between the aspect ratio of the inorganic fine particles and the contrast in the polarizing element was examined.
(1) Oblique sputter deposition on a flat plate First, using the ion beam sputtering apparatus shown in FIG. 4, the substrate tilt angle θ is changed to 20, 10 °, and a Ge particulate layer of 30 nm thickness on a flat Si substrate The sample obtained is observed by SEM, and 40 arbitrary Ge fine particles in the SEM image are extracted, and their sizes (long diameter (long axis length), short diameter (short axis length)) are measured The aspect ratio was determined.
The result is shown as a histogram of the aspect ratio in FIG. As the distribution of the histogram, the distribution shifts to the one in which the aspect ratio is larger in FIG. 35 (b) (substrate tilt angle θ = 10 °) than in FIG. 35 (a) (substrate tilt angle θ = 20 °) A trend was seen. Further, the average value of the major axis lengths of Ge fine particles at this time is 30 nm when the substrate inclination angle θ = 20 ° and 63 nm when the substrate inclination angle θ = 10 °, and the average value of the aspect ratio is When the substrate inclination angle θ = 20 °, it was 3.2, and when the substrate inclination angle θ = 10 °, it was 4.0.

  Further, using the ion beam sputtering apparatus shown in FIG. 4, the transmittance was changed for a sample in which a Ge particle layer of 10 nm in film thickness was formed on a flat glass substrate (Corning 1737) by changing the substrate inclination angle θ = 20, 10 °. The ratio of transmittance at a wavelength of 550 nm was determined as the contrast. The x direction and the y direction are as shown in FIG. 14A. The results are shown in Table 1. When the substrate inclination angle θ was reduced, the aspect ratio of the Ge particles tended to increase and the contrast tended to increase.

(2) Polarizer 10
Among the oblique sputter deposition conditions for forming the inorganic fine particle layer 15 in the polarization element 10 of the fifth embodiment, the substrate inclination angle θ is 10, 20 degrees, and the other conditions are the same as the polarization element 10 of the fifth embodiment. The polarizing element sample was produced by The transmittance of the transmission axis and the absorption axis of this sample was measured, and the ratio of the transmittance at a wavelength of 550 nm was determined as the contrast. The results are shown in FIG. 36 and Table 2. Also in the polarizing element of the present invention, when the substrate tilt angle θ was decreased, the contrast tended to increase.

  As described above, it is possible to deposit inorganic fine particles having shape anisotropy in the substrate surface by oblique sputtering deposition, but the aspect ratio which is the ratio of the major diameter to the minor diameter of the inorganic fine particles is the incidence of the inorganic fine particles Depending on the angle (the substrate inclination angle θ in FIG. 4), the smaller the angle, the larger the aspect ratio. At the same time as the aspect ratio increases, the transmission contrast also increases. As described above, by utilizing the steering effect by the oblique sputtering film formation, it is possible to realize a polarizing element having good characteristics.

(Example 7)
The Ge fine particle layer was obliquely formed on the substrate provided with the reflective layer 22 made of Al in a one-dimensional lattice shape (pitch 150 nm) by changing the type of the film forming method (dry process). Here, the following three types of dry processes were used.
(A) Electron beam evaporation (Fig. 37 (a))
A substrate tilted at 10 degrees with respect to the normal direction of the evaporation source mounted 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 inclined 10 degrees in the normal direction of the Ge target was set 40 cm away from the target, and a magnetron sputtering film was formed at a film forming speed of 0.1 nm / sec.
(C) Ion beam sputtering (FIG. 37 (c))
It is a sputtering film-forming method shown in FIG. 4 illustrated by this invention. Here, the substrate was set at θ = 45 °, and separated from the Ge target by 15 cm, ion beam sputter deposition was performed at a deposition rate of 0.2 nm / sec.
The substrate used was the same substrate 11 as in the case of the polarizing element 10 of Example 5, and was set so that the Ge incident direction was a direction (y direction) orthogonal to the lattice longitudinal direction (x direction) as in FIG. 14A. . Moreover, the film thickness of Ge fine particle layer was 10 nm in all.

The transmittance was measured for the obtained sample. The results are shown in FIG.
Among the three samples, the film forming method by ion beam sputtering is found to be the most preferable as the film forming method of the polarizing element of the present invention because the transmittance is also high and the difference in transmittance in the x direction and y direction is large.

(Example 8)
Of the polarizing element 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, as shown in FIG. 39, the wavelength 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 grating reflection layer 22 made of Al. Shows the calculation result by

Further, in the polarizing element 20 configured as shown in FIG. 5, the optical characteristics can be easily controlled by changing the height (film thickness) of the dielectric layer 23. Here, on a substrate 21 made of glass (Corning 1737), the thickness (aluminum height) is 200 nm, the pitch is 150 nm, and the grating width is 50 nm as a primary grating-like reflective layer 22 made of Al. The polarizing element of the present invention is formed by changing the film thickness to 0, 19, 37, 56, 74 nm as the dielectric layer 23 made of SiO ₂ by film formation, and setting the film thickness to 30 nm as the inorganic fine particle layer 25 made of Ge fine particles. Twenty samples were prepared, and the relationship between the thickness of the dielectric layer at wavelengths 450, 550, and 650 nm, transmission axis transmittance, contrast, and absorption axis reflectance of the obtained samples was determined. The results are shown in Table 3.

From the obtained result, for example, in order to reduce the absorption axis reflectance, the film thickness of the dielectric layer 23 may be in the range of 19 to 37 nm. Moreover, when using for the use with little influence of reflection, it is also possible to use the film thickness of the dielectric material layer 13 as zero. This means a reduction in the number of manufacturing steps, which leads to an improvement in productivity. In addition, high contrast is realized at a wavelength of 450 to 650 nm, which is suitable for a projector application having a wide use wavelength range.
On the other hand, as for the transmittance, a high transmittance of 70% or more at a wavelength of 450 nm and 80% or more at wavelengths of 550 and 650 nm is shown. It is possible to further improve the transmittance by narrowing the pitch of the grating.
Further, the contrast can be adjusted by the height of the metal grid. If you need higher contrast, you can raise the aluminum grid and lower it if you want to lower it.

  Next, FIG. 40 shows polarization characteristics in the case where the aluminum height is set to 30 nm, in the same structure as the polarizing element 20 of the fifth embodiment. In this case, the contrast is about 3 in the blue region because the film thickness of the reflective layer is thin (the aluminum height is low), but the reflectance is suppressed to 2% or less by the effect of Ge fine particles as in FIG. It is done. In the case of a polarizing element having such performance, Ge fine particles are deposited on the side walls of the convex portion consisting of the reflective layer / dielectric layer as shown in the SEM image of FIG. 31, and are good as an anisotropic optical absorption element It has a shape. The same applies to the polarizing element 10 shown in FIGS. 1 and 3.

  In the polarizing element of the present invention, the lattice shape (the shape and height of the convex portion 14a in FIG. 2 and the reflective layer 22 / dielectric layer 23 in FIG. 5, the pitch of the primary grating, etc.) and the steering effect (size and aspect of inorganic fine particles) By combining the ratio, the arrangement, and the like), it is possible to realize a fine particle shape suitable as an absorption type polarizing element.

(Example 9)
In the polarizing element 20 shown in FIG. 5, as a measure against stray light at the exit surface (a measure against ghosts), the fine stripes in the substrate 21 correspond to the arrangement direction of the inorganic fine particles 25a to be formed later. A rubbing process is performed so as to form a certain texture structure, and a thin film made of inorganic fine particles having shape anisotropy on the surface after the rubbing process so as to correspond to the arrangement direction of the inorganic fine particles 25a , Antireflective film)). 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 antireflective film made of inorganic fine particles is formed by oblique sputtering deposition to form a lattice on the lattice. Similar to the inorganic fine particle layer 25 to be formed, inorganic fine particles having shape anisotropy due to the steering effect can be obtained, so that the polarization effect of the inorganic fine particles is enhanced, and as a result, the ghost suppressing effect can be enhanced. Hereinafter, an example implemented specifically will be described.

  Here, the effect was verified using D20000 manufactured by Japan Micro Coating as an abrasive. Corning 1737 glass was used as a substrate, and a texture was formed by rubbing the surface in one direction at D2000. The result of having measured the substrate surface after texture formation by AFM (atomic force microscope) in FIG. 41 is shown. The horizontal axis is the position on the substrate, and the vertical axis is the height of irregularities on the surface. The average pitch of the irregularities on the substrate surface was 160 nm. In addition, when the transmittance of the substrate before and after texture formation was examined, it was found that the transmittance did not change before and after texture formation (before and after polishing), as shown in FIG. That is, according to this method, it is possible to easily perform nano-level precision processing without deteriorating the transmission characteristics of the substrate.

  Next, on the substrate after the texture formation, oblique sputtering film formation was performed with the substrate inclination angle θ = 5 ° by the ion beam sputtering apparatus of FIG. 4 to form a 10 nm thick antireflective film of Ge fine particles. At this time, the substrate was disposed such that the relationship between the incident direction of Ge and the substrate was such that the y direction was the texture longitudinal direction in FIG. About the obtained sample, when the shape of Ge particles in the antireflective film was observed by AFM (atomic force microscope), as shown in FIG. 43, the state where Ge particles were aligned along the texture was observed. The

FIG. 44 shows the transmission characteristics of this sample. As a comparison, the transmission characteristics were examined also for a sample in which an antireflection film was formed under the same conditions except that a 1737 glass substrate in which the substrate was not subjected to rubbing treatment was used. In FIG. 44, the sample of the present example is described as "texture substrate" and the comparative sample is as "substrate as it is". As a result, in both cases, polarization characteristics are observed due to the steering effect, but when texture is formed, the transmittance in the x direction is higher, and the difference from the transmittance in the y direction is large, indicating good polarization characteristics. .
In the present invention, the layer structure of the polarizing element 20 in FIG. 5 is formed thereon using the sample of this example (having the antireflective film formed on the substrate having the texture structure). At the same time as patterning of the body layer 23, the above-mentioned antireflective film is also processed into a lattice shape to form an antireflective layer 29. As a result, the anti-ghosting 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, the examples of the polarizing element have been shown taking Ge as an example in most cases, but inorganic fine particles having shape anisotropy can be formed with other materials. Therefore, by selecting the material, it is possible to obtain a polarizing element of the target wavelength.
FIG. 45 and FIG. 46 show polarization characteristics in the case of using the configuration of the polarizing element 10 of FIG. 3C as inorganic fine particles with a film thickness of 30 nm using Si and Sn, respectively. In addition, the anti-reflective film of the back surface is not formed. In the case of these materials, although the reflectance is slightly higher than that of Ge, the transmission axis polarization characteristic in the blue region is high, and depending on the purpose, it can be used as a polarizing element.

DESCRIPTION OF SYMBOLS 1 ... Stage 2, 2 ... target, 3 ... beam source, 4 ... control board, 10, 10A, 10B, 10C, 20, 20A, 20B, 30, 30A, 30B ... polarization element 11, 21, 41 ··· Substrates 14, 16, 17 ··· Irregularities 14 a, 16 a, 17 a ··· Projections 15, 25, 45 · Inorganic fine particle layer 22 ··· Reflection Layer 22a: band-like thin film 23, 2a: dielectric layer 25a: inorganic fine particle 26: uneven portion 27: inorganic fine particle layer (selection of polarized wave by optical anisotropy Selective light absorbing layer), 28: selective light absorbing layer of polarized wave by optical anisotropy, 29: anti-reflection layer, 44: Ge particle film, 50: liquid crystal panel, 60.・ Cross dichroic prism, 100 ... liquid crystal projector

Claims (33)

A transparent substrate for visible light,
A reflective layer formed of a metal, and a band-shaped thin film made of metal and extending in one direction parallel to the main surface of the substrate being provided on the substrate at regular intervals;
A dielectric layer formed on the reflective layer,
An inorganic fine particle layer formed on the dielectric layer at a position corresponding to the band-like thin film;
Equipped with
The crystal structure of the particles constituting the inorganic particle layer is amorphous,
Irregularities are periodically formed on the substrate in a direction orthogonal to the one direction, and the pitch of the irregularities is more than 0.05 μm and less than 0.8 μm, and the line width of the irregularities is divided by the pitch Is greater than 0.1 and less than 0.9, the recess depth of the uneven portion is greater than 0.01 μm and less than 0.2 μm, the length of the protrusion of the uneven portion is greater than 0.05 μm, and the upper portion of the uneven portion A wire grit type light absorbing polarizing element having a line width divided by a bottom line width of 1.0 or more.   The wire grit type light absorbing polarizing element according to claim 1, having one or more laminated structures of the dielectric layer and the inorganic fine particle layer on the inorganic fine particle layer.   The wire grit type light absorbing polarizing element according to claim 1 or 2, wherein the film thickness of the inorganic fine particle layer is 200 nm or less.   The wire grid type light absorbing polarizing element according to any one of claims 1 to 3, further comprising an antireflective layer between the substrate and the reflective layer. The wire grit type light absorbing polarizing element according to any one of claims 1 to 4, wherein the dielectric layer is made of SiO ₂ , Al ₂ O ₃ or MgF ₂ .   The wire grit type light absorption type according to any one of claims 1 to 5, wherein a protective film transparent to light in a use band is formed on the outermost surface of the wire grit type light absorption type polarizing element. Polarizing element.   The wire grit type light absorbing polarizing element according to claim 6, wherein the protective film is a self-assembled film.   The wire grit-type light-absorbing polarizing element according to claim 7, wherein the self-assembled film is Perfluorodecyltrichlorosilane (FDTS) or Octadecaine Trichlorosilane (OTS).   The wire grit type light absorbing polarizing element according to claim 7, wherein the self-assembled film is a silane type.   The wire grit type light absorbing polarizing element according to claim 7, wherein the self-assembled film has water repellency.   The wire grid type light absorbing polarizing element according to claim 7, wherein the wire grid type light absorbing polarizing element further includes an adhesive layer, and the self-assembled film is formed on the adhesive layer. The wire grit type light absorbing polarizing element according to claim 11, wherein the adhesion layer is formed of SiO ₂ .   The wire grid-type light-absorbing polarizing element according to any one of claims 1 to 12, wherein the substrate is glass, sapphire or quartz.   The wire grit type light absorbing polarizing element according to any one of claims 1 to 13, wherein the wire grit type light absorbing polarizing element is used for any one of the light incident side and the light emitting side of the liquid crystal panel. .   The wire grit type light absorbing polarizing element according to any one of claims 1 to 14, wherein the wire grit type light absorbing polarizing element is used for a transmissive liquid crystal projector. A light source, a liquid crystal panel, an incident side polarizing plate, and an emission side polarizing plate,
At least one of the incident side polarization plate and the emission side polarization plate is
A transparent substrate for visible light,
A reflective layer formed of a metal, and a band-shaped thin film made of metal and extending in one direction parallel to the main surface of the substrate being provided on the substrate at regular intervals;
A dielectric layer formed on the reflective layer,
An inorganic fine particle layer formed on the dielectric layer at a position corresponding to the band-like thin film;
Wire grit type light absorbing polarizing element comprising
The crystal structure of the particles constituting the inorganic particle layer is amorphous,
Irregularities are periodically formed on the substrate in a direction orthogonal to the one direction, and the pitch of the irregularities is more than 0.05 μm and less than 0.8 μm, and the line width of the irregularities is divided by the pitch Is greater than 0.1 and less than 0.9, the recess depth of the uneven portion is greater than 0.01 μm and less than 0.2 μm, the length of the protrusion of the uneven portion is greater than 0.05 μm, and the upper portion of the uneven portion A transmissive projector in which the line width divided by the bottom line width is 1.0 or more.   The transmissive projector according to claim 16, wherein a protective film transparent to light in a use band is formed on the outermost surface of the wire grid type light absorbing polarizing element.   The transmissive projector according to claim 17, wherein the protective film is a self-assembled film.   The transmissive projector according to claim 18, wherein the self-assembled film is Perfluorodecyltrichlorosilane (FDTS) or Octadecainetrichlorosilane (OTS).   The transmissive projector according to claim 18, wherein the self-assembled film is silane-based.   The transmissive projector according to claim 18, wherein the self-assembled film has water repellency.   The transmission type projector according to claim 18, wherein the wire grid type light absorbing polarizing element further includes an adhesive layer, and the self-assembled film is formed on the adhesive layer. The transmissive projector according to claim 22, wherein the adhesion layer is formed of SiO ₂ .   The transmissive projector according to claim 16, wherein the exit-side polarizing plate is the wire grid-type light absorbing polarizing element. A light source, a liquid crystal panel, an incident side polarizing plate, and an emission side polarizing plate,
At least one of the incident side polarization plate and the emission side polarization plate is
A transparent substrate for visible light,
A reflective layer formed of a metal, and a band-shaped thin film made of metal and extending in one direction parallel to the main surface of the substrate being provided on the substrate at regular intervals;
A dielectric layer formed on the reflective layer,
An inorganic fine particle layer formed on the dielectric layer at a position corresponding to the band-like thin film;
Wire grit type light absorbing polarizing element comprising
The crystal structure of the particles constituting the inorganic particle layer is amorphous,
Irregularities are periodically formed on the substrate in a direction orthogonal to the one direction, and the pitch of the irregularities is more than 0.05 μm and less than 0.8 μm, and the line width of the irregularities is divided by the pitch Is greater than 0.1 and less than 0.9, the recess depth of the uneven portion is greater than 0.01 μm and less than 0.2 μm, the length of the protrusion of the uneven portion is greater than 0.05 μm, and the upper portion of the uneven portion The liquid crystal display device, wherein a value obtained by dividing the line width by the bottom line width is 1.0 or more.   26. The liquid crystal display device according to claim 25, wherein a protective film transparent to light in a use band is formed on the outermost surface of the wire grit type light absorbing polarizing element.   The liquid crystal display of claim 26, wherein the protective film is a self-assembled film.   The liquid crystal display according to claim 27, wherein the self-assembled film is Perfluorodecyltrichlorosilane (FDTS) or Octadecainetrichlorosilane (OTS).   The liquid crystal display device according to claim 27, wherein the self-assembled film is a silane type.   The liquid crystal display device according to claim 27, wherein the self-assembled film has water repellency.   28. The liquid crystal display device according to claim 27, wherein the wire grid type light absorbing polarization device further comprises an adhesive layer, and the self-assembled film is formed on the adhesive layer. The adhesion layer is formed by SiO _2, a liquid crystal display device according to claim 31.   26. The liquid crystal display device according to claim 25, wherein the output side polarizing plate is the wire grid type light absorbing type polarizing element.