JP2010066571A - Polarizing element and production method, and liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing element having a wire grid structure, with which desired polarization properties can be obtained in a use bandwidth and which is resistant to external forces and is less likely to become contaminated, and to provide a crystal projector that uses the polarizing element. <P>SOLUTION: The polarizing element includes: a substrate 11 which is transparent to light in the use bandwidth; a reflection layer 12, in which projection reflecting films 12a extended linearly on the substrate 11 are arranged with a pitch smaller than the wavelength of light in the working bandwidth and in which a filling part 12b formed by filling an inorganic material with an index of refraction smaller than the substrate 11 is formed among the projection reflecting films 12a; a dielectric layer 13 formed on the projecting reflection layer 12a; and an inorganic fine particle layer 14, which is formed by arranging inorganic fine particles linearly on the dielectric layer 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing element represented by a polarizing plate, a polarizing filter, and the like, and a manufacturing method thereof. The present invention relates to an inorganic polarizing element used and a manufacturing method thereof, and also relates to a liquid crystal projector using the polarizing element.

  In a liquid crystal display device (particularly, a transmissive liquid crystal display device), it is indispensable to dispose a polarizing plate on the surface of the liquid crystal panel from the principle of image formation. The polarizing plate has a function of absorbing one of the orthogonally polarized components (so-called P-polarized wave and S-polarized wave) and transmitting the other. Conventionally, 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 film is often used.

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

  In recent years, the use of liquid crystal display devices has expanded and their functions have been enhanced. Accordingly, high reliability and durability are required for individual devices constituting the liquid crystal display device. For example, in the case of a liquid crystal display device using a light source with a large amount of light, such as a transmissive liquid crystal projector, the polarizing plate receives strong radiation. Therefore, the heat resistance required for the polarizing plate used for these is required. However, since the film-based polarizing plate as described above is made of an organic material, there is a limit to raising these characteristics.

  On the other hand, there is an inorganic polarizing plate as a polarizing plate having high heat resistance. For example, an inorganic polarizing plate (trade name “Polarcor”) manufactured by Corning, USA has a structure in which silver fine particles are diffused in glass, and organic substances such as films are not used. For the polarization principle of the inorganic polarizing plate, plasma resonance of island-shaped fine particles is used. That is, light absorption by surface plasma resonance when light is incident on noble metal or transition metal island-like particles is used, and the absorption wavelength is affected by the particle shape and the surrounding dielectric constant. When the shape of the metal fine particles is an ellipse, the resonance wavelengths in the major axis direction and the minor axis direction are different, thereby obtaining deflection characteristics. That is, a predetermined polarization characteristic is obtained in which a polarized light component parallel to the long axis on the long wavelength side is absorbed and a polarized light component parallel to the short axis is transmitted. In the case of Polarcor, silver fine particles are used. However, in the case of Polarcor, the wavelength range in which the polarization characteristics can be obtained is a region close to the infrared region, and does not cover the visible light range required for a liquid crystal display device. This is due to the physical properties of silver.

  Patent Document 1 discloses a UV polarizing plate by applying the above principle and depositing fine particles in glass by thermal reduction, and a specific example is the use of silver as metal fine particles. In this case, it is considered that absorption in the minor axis direction is used contrary to the previous Polarcor. As shown in Patent Document 1 (Figure 1), although it functions as a polarizing plate even at around 400 nm, the extinction ratio is small and the band that can be absorbed is very narrow. Even if it is, it will not be a polarizing plate that can cover the entire visible light range.

  Non-Patent Document 1 describes a theoretical analysis of an inorganic polarizing plate using plasma resonance of metal island-shaped fine particles. According to this document, it is described that aluminum fine particles have a resonance wavelength shorter than that of silver fine particles by about 200 nm, and therefore it is possible to produce a polarizing plate that covers the visible light region by using aluminum fine particles.

  Patent Document 2 discloses several methods for producing a polarizing plate using aluminum fine particles. Among them, silicate-based glass is described as being suitable as a substrate because calcium and aluminoborate glass are suitable because aluminum and glass react ([0018], [0019]). However, glass using silicate is widely distributed as optical glass, and it is economically unfavorable that a highly reliable product can be obtained at a low cost and this is not suitable. In addition, a method for forming island-like particles by etching a resist pattern is described ([0037], [0038]).

  Usually, a polarizing plate used in a projector needs to have a size of about several centimeters and a high extinction ratio. Therefore, for the purpose of a polarizing plate for visible light, the resist pattern size must be sufficiently shorter than the visible light wavelength, that is, several tens of nanometers, and the pattern must be formed in order to obtain a high extinction ratio. It is necessary to form it with high density. Moreover, when using it for projectors, a large area is required. However, in the method of applying high-density fine pattern formation by lithography as described, it is necessary to use electron beam drawing or the like in order to obtain such a pattern. Electron beam drawing is a method of drawing individual patterns from an electron beam, and is not practical because of poor productivity. In addition, although it is described that aluminum is removed by chlorine plasma, when etching is usually performed, chloride adheres to the sidewall of the aluminum pattern. Although it can be removed with a commercially available wet etching solution (for example, SST-A2 from Tokyo Ohka Kogyo Co., Ltd.), such a chemical solution that reacts with aluminum chloride reacts with aluminum even though the etching rate is slow. It is difficult to realize a desired pattern shape by such a method.

  Patent Document 2 describes, as yet another method, a method of depositing aluminum on a patterned photoresist by oblique film formation and removing the photoresist ([0045], [0047]). In such a method, it is considered that it is necessary to deposit aluminum on the substrate surface to some extent in order to obtain adhesion between the substrate and aluminum. However, this means that the shape of the deposited aluminum film is different from prolate spheres including prolate ellipsoids, which are suitable shapes described in [0015]. [0047] describes that the overprecipitation integral is removed by anisotropic etching perpendicular to the surface.

  In order to function as a polarizing plate, the shape anisotropy of aluminum is extremely important. Therefore, it is considered necessary to adjust the amount of aluminum deposited on the resist portion and the substrate surface so that a desired shape can be obtained by etching. However, as described in [0047], the submicron is 0.05 μm or less. It is thought that it is very difficult to control these by the size of this, and it is doubtful whether it is suitable as a production method with high productivity. In addition, as a characteristic of the polarizing plate, high transmittance is required in the direction of the transmission axis, but when glass is usually used for the substrate, reflection of several% from the glass interface is unavoidable, and no countermeasure is taken against this to obtain high transmittance. It is difficult.

  Patent Document 3 describes a polarizing plate by oblique vapor deposition. This method obtains polarization characteristics by fabricating a micro-columnar structure by oblique deposition of a transparent and opaque material with respect to the wavelength of the band used. Unlike Patent Document 2, it can be considered a highly productive method because a fine pattern can be obtained by a simple method, but there are also problems. The aspect ratio of the micro-columnar structure, the spacing between individual micro-columnar structures, and the linearity of the material that is opaque to the band to be formed at the beginning are important factors for obtaining good polarization characteristics. It should be controlled intentionally.

  However, this method makes use of the phenomenon that the next flying vapor particles do not accumulate in the shadowed part of the initial layer stack of vapor deposited particles, and thus a columnar structure is obtained. Difficult to control. As a method for improving this, a method of providing a polishing mark on a substrate by rubbing before vapor deposition is described. However, in general, the particle size of the deposited film is about several tens of nanometers at the maximum, and in order to control the anisotropy of such particles, a pitch of submicron or less is intentionally manufactured by polishing. There is a need. However, a general polishing sheet or the like has a limit of about submicron, and it is not easy to manufacture such fine polishing marks. In addition, as described above, the resonance wavelength of the Al fine particles greatly depends on the refractive index of the surroundings, and in this case, the combination of transparent and opaque materials is important. However, there is a description of the combination for obtaining good polarization characteristics in the visible light region. It has not been. Similarly to Patent Document 2, when glass is used for a normal substrate, several percent of reflection from the glass interface is inevitable, and no countermeasure is taken against this.

Non-Patent Document 2 describes a polarizing plate for infrared communication called Lamipol. This has a laminated structure of Al and SiO ₂ and shows a very high extinction ratio according to this document. Non-Patent Document 3 describes that a high extinction ratio can be realized at a wavelength of 1 micron or less by using Ge instead of Al which is responsible for Lamipol's light absorption. Moreover, it can be expected that FIG. 3 to Te (tellurium) in the same material can also obtain a high extinction ratio. In this way, Lamipol is an absorptive polarizing plate that provides a high extinction ratio, but it is polarized light for projector applications that requires a size of several cm square because the thickness of the light-absorbing and transmissive materials is the size of the light-receiving surface Not suitable for boards.

  Patent Document 4 discloses a wire grid type polarizing plate. This is a thin metal wire formed on the substrate at a pitch smaller than the wavelength of the light in the use band, and reflects light of a polarization component parallel to the thin metal wire and transmits a perpendicular polarization component to give a predetermined Appears polarization characteristics. In Patent Document 5, a wire grid type polarizing element is formed by forming a dielectric layer / metal layer on a metal grid, and a total of three layers is used, so that light reflected from the metal grid is canceled out by an interference effect, so that reflection is generally performed. A method of using a wire grid as a mold as an absorption mold is disclosed.

  When using optical characteristics obtained with such a multilayer structure as an absorption-type polarizing plate, the film thickness and optical characteristics of the metal layer formed on the dielectric film are important factors for obtaining desired characteristics. However, this is not considered in the present invention. That is, in this document, this point is not described and details are unknown. However, in order to obtain an interference effect as described, it is necessary for light to pass through the upper metal layer. The passage of light means that part of the light is absorbed by the upper metal film in the process. Absorption reduces the transmission in the direction of the transmission axis, which is undesirable as a property of the polarization transmission axis. In particular, it is not preferable in a liquid crystal display device that requires high transmittance in the visible range. That is, a polarizing plate having an absorption effect essentially does not function unless the optical anisotropy of the absorbing layer is controlled, and is practically difficult to apply as a polarizing plate.

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

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

  The present invention has been made in view of the above-mentioned problems. A polarizing element having a wire grid structure that can obtain desired polarization characteristics in a use band and is resistant to external force and hardly contaminated, a manufacturing method thereof, and a liquid crystal projector using the polarizing element It is an issue to provide.

  By the way, the inventor has proposed an invention of the structure and characteristics of an inorganic polarizing plate having a structure in which a dielectric layer and an inorganic fine particle layer are deposited on a metal lattice in Japanese Patent Application No. 2007-170583, which is separately filed. In this three-layer structure, the inorganic fine particle layer has optical anisotropy. The inorganic fine particle layer is a metal fine particle or a semiconductor fine particle. The absorption principle of the metal fine particles is the plasma resonance of free electrons as described above, but in the case of a semiconductor, the band absorption due to the band gap is related to the contribution of free electrons. What is practically important as a polarizing plate is that there is anisotropy in absorption as described above, and the polarizing plate has excellent polarizing properties. However, the convex portion of the reflective layer is very thin with a width of several tens of nanometers, so that it is weak against external force, and there are gaps between the reflective layers, so that foreign matter is likely to accumulate.

  The inventor has been eagerly studied to improve the concavo-convex structure, because the problem is that the concavo-convex structure in the current diffraction grating in the current diffraction grating is affected by an external force, and foreign matter is easily deposited and easily contaminated.

  That is, the present invention provided to solve the above-described problems includes a substrate transparent to the light in the use band (substrate 11) and a convex reflection film (convex reflection film 12a) extending linearly on the substrate. A reflective layer (reflective layer 12) that is arranged with a pitch smaller than the wavelength of light in the use band and is filled (filled portions 12b and 12c) with an inorganic material having a lower refractive index than the substrate between the convex reflective films. ), A dielectric layer (dielectric layer 13) formed on the convex reflective film, and an inorganic fine particle layer (inorganic fine particle layer 14) in which inorganic fine particles are linearly arranged on the dielectric layer; Are polarizing elements (polarizing elements 10, 10 ′) (FIGS. 2 and 4).

Here, the thickness of the inorganic material in the reflective layer is preferably 5 to 100% of the thickness of the convex reflective film.
The filling rate of the inorganic material between the convex reflective films is preferably 50% or less.
The inorganic material is preferably porous silica.

  Further, the present invention provided to solve the above-described problems is a process of arranging a convex reflection film extending linearly on a substrate transparent to light in the use band at a pitch smaller than the wavelength of the light in the use band. (FIG. 5A), a step of coating an inorganic material having a refractive index lower than that of the substrate between the convex reflective films and on the convex reflective film (FIG. 5B), and etching from the surface Removing at least the inorganic material on the convex reflective film (FIGS. 5C and 5D), forming a dielectric layer on the convex reflective film, and the dielectric layer And a step of forming an inorganic fine particle layer by linearly arranging inorganic fine particles thereon.

  Here, the step of coating the inorganic material is preferably performed by a sol-gel method.

  Moreover, this invention provided in order to solve the said subject includes a lamp, a liquid crystal panel (liquid crystal panel 50), and the polarizing element (polarizing element 10, 10 ') in any one of Claims 1-4. This is a liquid crystal projector (liquid crystal projector 100) provided (FIG. 7).

According to the polarizing element of the present invention, by filling a predetermined inorganic material between the convex reflection films, the adhesion strength of the convex reflection film constituting the diffraction grating can be increased, and foreign matter can be prevented from entering. The antifouling effect of the polarizing element can be improved while maintaining high polarization characteristics.
According to the method for manufacturing a polarizing element of the present invention, a desired inorganic material can be reliably filled between the convex reflective films, and a polarizing element having an antifouling effect can be easily manufactured.
According to the liquid crystal projector of the present invention, it is possible to provide a highly reliable liquid crystal projector by using a polarizing element that is easy to handle when assembling the liquid crystal projector into a set body.

FIG. 1 shows a wire grid structure of a polarizing element which is a premise of the present invention.
The polarizing element 90 includes a reflective layer 92 in which convex thin films 12 a extending linearly on the substrate 11 are arranged at a constant pitch, a dielectric layer 13 formed on the reflective layer 92, and the dielectric layer 13. An inorganic fine particle layer 14 formed thereon and a protective layer 15 formed on the inorganic fine particle layer 14 are configured.

  Here, in the polarizing element 90, the pitch of the convex thin film 12a is made smaller than the wavelength of light in the use band in order to improve the polarization characteristics. Considering that the polarizing element 90 is used for visible light, since the blue region is in the vicinity of a wavelength of 400 nm, the pitch of the convex thin film 12a is set to, for example, 150 nm. At this time, if the line / slit ratio (L / S) = 1 in the reflective layer 12, the width of the convex thin film 12a is very narrow, 75 nm.

  Since the diffraction grating of the polarizing element 90 has such a fine concavo-convex structure, it is difficult to remove foreign matter (dust) attached on or between the gratings. In addition, there is a problem that the diffraction grating itself is destroyed when trying to remove foreign matter with a cotton swab. Note that the diffraction grating in the present invention means a grating formed by convex portions up to the convex reflective film 12a on the substrate 11, the dielectric layer 13, and the inorganic fine particle layer 14, or a convex portion obtained by adding a protective layer 15 thereto. A lattice formed by

  In order to solve such problems, the inventor increases the adhesion strength of the convex reflective film 12a constituting the diffraction grating with the substrate or the adhesion strength between the layers of the diffraction grating, and prevents the entry of foreign matter. In the present invention, the inventors of the present invention have been intensively studied based on the idea of filling the concave portions of the diffraction grating with a material that does not affect the polarization characteristics, and have achieved the present invention.

  Below, the polarizing element which concerns on this invention, its manufacturing method, and a liquid crystal display are demonstrated. The present invention will be described with reference to the embodiment shown in the drawings, but the present invention is not limited to this, and can be appropriately changed according to the embodiment. -As long as an effect is produced, it is included in the scope of the present invention.

FIG. 2 shows a configuration of the polarizing element according to the first embodiment of the present invention.
As shown in FIG. 2, the polarizing element 10 includes a substrate 11 transparent to light in the use band and a convex reflection film 12a extending linearly on the substrate 11 at a pitch smaller than the wavelength of the light in the use band. A reflective layer 12 formed by forming a filling portion 12b arranged and filled with an inorganic material having a refractive index lower than that of the substrate 11 between the convex reflection films 12a, and a dielectric layer formed on the convex reflection film 12a 13, an inorganic fine particle layer 14 in which inorganic fine particles are linearly arranged at positions corresponding to the convex reflective film 12 a on the dielectric layer 13, and a position corresponding to the convex reflective film 12 a on the inorganic fine particle layer 14. And a protective layer 15 formed on.

  The substrate 11 is made of a material that is transparent with respect to light in the use band (visible light region in the present embodiment), such as glass, sapphire, and quartz. In this embodiment, glass, particularly quartz (refractive index 1.46) or soda lime glass (refractive index 1.51) is used. The component composition of the glass material is not particularly limited. For example, an inexpensive glass material such as silicate glass widely distributed as optical glass can be used, and the manufacturing cost can be reduced.

  By using a quartz or sapphire substrate with high thermal conductivity as the constituent material of the substrate 11, it can be advantageously used as a polarizing element for an optical engine of a projector that generates a large amount of heat.

  As a constituent material of the convex reflective film 12a in the reflective layer 12, a normal wire grid polarizer lattice material can be used. In this example, Al or an Al-Si alloy is preferably used. Alternatively, a simple substance or an alloy of a metal or a semiconductor material such as silver, gold, copper, molybdenum, chromium, titanium, nickel, tungsten, iron, silicon, germanium, or tellurium can be used. In addition to the metal material, for example, it may be composed of an inorganic film or a resin film other than a metal formed with high surface reflectance by coloring or the like.

  The thickness of the convex reflective film 12a is 10 nm to 1 μm, more preferably 10 to 300 nm, and is usually about 200 nm.

  The convex reflection films 12a are arranged in a diffraction grating (one-dimensional grating) on the surface of the substrate 11 at a pitch smaller than the wavelength in the visible light region. For example, it is formed by pattern processing of the metal film using a photolithography technique.

  The filling portion 12b is formed by filling an inorganic material between the convex reflection films 12a, and is for increasing the adhesion strength of the convex reflection film 12a constituting the diffraction grating and preventing the intrusion of foreign matters. is there. In the present embodiment, the thickness of the filling portion 12b is 5 to 100% of the thickness of the convex reflective film 12a. In FIG. 2, the thickness of the filling portion 12b is 100% of the thickness of the convex reflective film 12a (the same thickness).

The inorganic material to be filled is preferably a low refractive index material whose refractive index is as close as possible to the refractive index of air = 1 so as not to deteriorate the polarization characteristics of the polarizing element 10. For example, a porous ceramic material formed by dispersing fine pores in ceramics is preferable, and examples include porous silica (SiO ₂ ), porous magnesium fluoride (MgF), and porous alumina (Al ₂ O ₃ ). It is done. The degree of these low refractive indexes is determined by the number and size (porosity) of the holes in the ceramic. Among these, in particular, when the substrate 11 is made of silica crystal or glass whose main component is silica, porous silica (n = 1.2-1.26) is preferable because the refractive index is smaller than that of the substrate 11.

  The reflective layer 12 thus configured has a function as a wire grid polarizer, and of the light incident on the surface of the substrate 11, an electric field component in a direction parallel to the grating (lattice axis direction, Y axis direction). Is attenuated, and a polarized wave (TM wave (P wave)) having an electric field component in a direction perpendicular to the grating (lattice perpendicular direction, X-axis direction) is transmitted.

Note that the pitch, line width / pitch, grating depth, and grating length of the metal grating (the diffraction grating (one-dimensional grating) pattern of the convex reflecting film 12a) constituting the reflecting layer 12 are in the following ranges, respectively. Is preferred.
50 nm <pitch <800 nm
0.1 <(line width / pitch) <0.9
10 nm <lattice depth <1 μm
50 nm <lattice length

  Further, in order to reduce the reflection of the substrate surface at the filling portion 12b of the reflective layer 12, a non-reflective coating is applied to the surface of the substrate 11 in advance, and then the reflective film 12, the dielectric layer 13, and the inorganic fine particle layer 14 are formed. You may make it perform. The non-reflective coating can be composed of a general laminated film of a high refractive index film and a low refractive index film. By applying the same non-reflective coating to the back surface of the substrate 11, reflection on the substrate surface can be reduced.

The dielectric layer 13 is formed of an optical material transparent to visible light such as SiO ₂ formed on the convex reflective film 12a by sputtering. The dielectric layer 13 forms a base layer of the inorganic fine particle layer 14 and adjusts the phase of the polarized light that is transmitted through the inorganic fine particle layer 14 and reflected by the reflective layer 12 with respect to the polarized light reflected by the inorganic fine particle layer 14. A film thickness that is formed for the purpose of enhancing the interference effect and is shifted by half a wavelength is desirable. However, since the inorganic fine particle layer 14 has an absorption effect, the reflected light can be absorbed, and the contrast can be improved even if the film thickness is not optimized. Improvements can be realized. In practical use, it may be determined based on a balance between desired polarization characteristics and an actual manufacturing process. The practical film thickness range is 1 to 500 nm, more preferably 300 nm or less.

A general material such as SiO ₂ , Al ₂ O ₃ , or MgF ₂ can be used as the material constituting the dielectric layer 13. These can be thinned by a general vacuum film formation such as sputtering, vapor phase growth, and vapor deposition. The refractive index of the dielectric layer 13 is preferably greater than 1 and not greater than 2.5. Further, since the optical characteristics of the inorganic fine particle layer 14 are also affected by the refractive index of the surroundings, it is possible to control the polarizing element characteristics by the dielectric layer material.

  As shown in FIG. 3, the inorganic fine particle layer 14 has a major axis direction parallel to the longitudinal direction (one-dimensional lattice direction, Y-axis direction) of the convex reflection film 12a of the reflection layer 12, and the convex reflection film 12a. The elliptical island-shaped inorganic fine particles 14a having a short axis direction in the short direction (direction perpendicular to the lattice direction, X-axis direction) are straight in one direction (one-dimensional lattice direction) parallel to the main surface of the substrate 11. It is arranged in a shape. The inorganic fine particle layer 14 is provided on the dielectric layer 13 above the metal lattice (convex reflective film 12 a) constituting the reflective layer 12. Therefore, the inorganic fine particle layer 14 has a wire grid structure with the same pattern as the convex reflective film 12a of the reflective layer 12 on the substrate 11.

  Further, if the inorganic fine particles 14a constituting the inorganic fine particle layer 14 have a shape anisotropy between the X-axis direction and the Y-axis direction, the optical constants may be different between the major axis direction and the minor axis direction. it can. As a result, it is possible to obtain a predetermined polarization characteristic of absorbing a polarization component parallel to the major axis and transmitting a polarization component parallel to the minor axis. In addition, when the inorganic fine particles 14a do not have shape anisotropy (for example, circular shape), TM wave absorption is also generated in the TE wave absorption band, which is not preferable.

  In order to control the shape anisotropy of the inorganic fine particle layer 14, the arrangement pitch of the convex reflective films 12 a constituting the reflective layer 12 is reduced so that the inorganic fine particles 14 a are deposited only on the top of the dielectric layer 13. Is effective. As a result, the metal fine particles 14a can be isolated. Further, as the film formation method of the metal fine particles 14a, oblique sputtering film formation, for example, an ion beam sputtering method for forming a film in an oblique direction with respect to the surface of the substrate 11 is effective. The metal fine particles 14a do not have to be formed in a perfect island shape, and it is sufficient that a grain boundary is formed.

The protective layer 15 is formed on the inorganic fine particle layer 14 as a thin film with a film thickness that does not affect the polarization characteristics of the transparent material in the use band corresponding to the position of the convex reflective film 12a. It is. As this material, a material having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Examples of such a substance include SiO ₂ and Al ₂ O ₃ . These may be formed by a general vacuum film formation method (vapor phase film formation method, sputtering method, vapor deposition method, etc.). The protective layer 15 improves moisture resistance and antifouling properties and contributes to improving the reliability of the polarizing element 10.

FIG. 4 shows the configuration of the polarizing element according to the second embodiment of the present invention.
Compared with the configuration of the polarizing element 10, the polarizing element 10 ′ is different from the polarizing element 10 only in the filling portion 12 c in the reflective layer 12 ′, and is otherwise the same in configuration as the polarizing element 10.

  That is, the filling portion 12c is formed by filling the same inorganic material as the filling portion 12b between the convex reflective films 12a. In the present embodiment, the filling portion 12c is recessed as it is away from the convex reflection film 12a, and is thinnest at the midpoint between the adjacent convex reflection films 12a. Thereby, the filling rate of the inorganic material between the convex reflective films 12a is 50% or less. FIG. 4 shows a case where the thickness of the filling portion 12c at the midpoint between the adjacent convex reflective films 12a is approximately 0 μm.

As described above, in the polarizing elements 10 and 10 ′ of the present invention, the filling portions 12b and 12c are provided between the convex reflection films 12a, thereby increasing the adhesion strength of the convex reflection films 12a constituting the diffraction grating. At the same time, it is possible to prevent foreign substances from entering, and to improve the antifouling effect of the polarizing elements 10 and 10 ′ while maintaining high polarization characteristics. Note that it is not necessary that the concave portions of the diffraction grating are simply filled with the inorganic material of the filling portions 12b and 12c. If the inorganic material is filled between the dielectric layers 13 and between the inorganic fine particle layers 14, the polarization characteristics are also obtained. Is not preferable because it deteriorates. In addition, since the polarization characteristic is improved when the refractive index in the region between the convex reflective films 12a is smaller, the shape of the filling portion is preferably the polarizing element 10 ′.
In addition, this facilitates handling when assembling the liquid crystal projector into the set main body, and improves the assembling efficiency.

Next, a method for manufacturing a polarizing element according to the present invention will be described.
FIG. 5 is a schematic view showing the main part of the manufacturing process of the polarizing element according to the present invention.
(S11) On the substrate 11 transparent to the light in the use band, the convex reflection films 12a extending linearly are arranged at a pitch smaller than the wavelength of the light in the use band (FIG. 5A). The predetermined metal film described above may be formed on the entire surface of the substrate 11, and then the convex reflective film 12a may be formed by patterning the metal film using a photolithography technique.

(S12) Next, an inorganic material film 12z made of an inorganic material having a refractive index lower than that of the substrate 11 is formed by coating between the convex reflective films 12a and on the convex reflective film 12a (FIG. 5B). . Even if an attempt is made to fill the space between the convex reflective films 12a with an inorganic material by a normal film formation method such as sputtering or CVD, it is difficult to completely fill the convex portions (the convex reflective films 12a) for shadowing. In the present invention, a sol-gel method (for example, a method in which a sol is coated by spin coating and gelled by thermal curing) is applied, and a predetermined ceramic paint is applied between the convex reflective films 12a and the convex reflective films 12a. An inorganic material film 12z is formed thereon. For example, a siloxane solution using colloidal silica is applied to the surface on which the convex reflection film 12a is formed by spin coating, and then fired at a predetermined temperature (for example, 400 ° C.) to form an inorganic material film 12z made of porous silica ( (1) Japanese Journal of Applied Physics Vol. 47, No.1 2008, pp.538-540, (2) Japanese Journal of Applied Physics V0l.44, No.8, 2005, pp. 5982-5986) . As the siloxane solution, ULVAC's ULKS solution or SOG-ISM solution may be used.

(S13) Next, at least the inorganic material on the convex reflective film 12a is removed by etching from the surface of the inorganic material film 12z (FIGS. 5C and 5D). The etching process at this time is performed by oxygen plasma or CF ₄ fluorine plasma. FIG. 5C shows a configuration when the process is completed when the unnecessary inorganic material on the convex reflection film 12a is removed, and the filling portion 12b is completely formed between the convex reflection films 12a by the inorganic material. It is in a state filled with.

  When the plasma etching is further continued, the center of the filling portion 12c is recessed as shown in FIG. When an aluminum-based substance (Al, Al-Si, etc.) is used for the convex reflective film 12a, these materials have a very low etching rate with respect to oxygen plasma or fluorine plasma, so that the shape of FIG. realizable. Further, the refractive index of the filling portion 12c can be adjusted by the removal amount of the inorganic material at this time, and the refractive index can be lowered as the removal amount increases.

(S14) The dielectric layer 13 is formed on the convex reflective film 12a by a general vacuum film formation such as sputtering, vapor phase growth, or vapor deposition.

(S15) Further, inorganic fine particles 14 are formed by linearly arranging inorganic fine particles at positions corresponding to the convex reflective film 12a on the dielectric layer 13.
The state of oblique sputtering film formation for forming the inorganic fine particle layer 14 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. 6, 1 is a stage for supporting the substrate 11, 2 is a target, 3 is a beam source (ion source), and 4 is a control plate. The stage 1 is inclined at a predetermined angle θ with respect to the normal direction of the target 2, and the substrate 11 is arranged in a direction in which the longitudinal direction of the convex reflective film 12 a is orthogonal to the incident direction of the inorganic fine particles from the target 2. Has been. The angle θ is, for example, 0 ° to 20 °. Ions extracted from the beam source 3 are irradiated to the target 2. The inorganic fine particles knocked out from the target 2 by the irradiation of the ion beam are incident on and adhered to the surface of the substrate 11 from an oblique direction. At this time, if the flat control plate 4 is arranged on the substrate 11 at a constant interval (for example, 50 mm), the direction of the incident particles on the surface of the substrate 11 is controlled and corresponds to the convex reflective film 12a on the dielectric layer 13. It is possible to deposit particles only at the positions where they do. The film thickness of the inorganic fine particle layer 14 at this time is preferably 200 nm or less.

(S16) Finally, the protective layer 15 is formed to obtain the polarizing element of the present invention. The thing of the state of the filling part 12b of FIG.5 (c) to which the process of step S14 to S16 was performed becomes the polarizing element 10 (FIG. 2). Further, the polarizing element 10 '(FIG. 4) is obtained by performing the processing of steps S14 to S16 on the state of the filling portion 12c in FIG. 5D.

  Note that the step of forming the inorganic material layer 12z in step S12 and the step of performing the etching process in step S13 may be performed after the formation of the inorganic fine particle layer 15 in step S15.

Next, a liquid crystal projector using the polarizing element according to the present invention will be described.
The liquid crystal projector of the present invention includes a lamp serving as a light source, a liquid crystal panel, and the polarizing element 10 (or 10 ′) of the present invention described above.

FIG. 7 shows a configuration example of the optical engine portion of the liquid crystal projector according to the present invention.
Optical engine portion of the liquid crystal projector 100, incident-side polarization element 10A with respect to the red light _{L R,} the liquid crystal panel 50, the emission pre-polarizing element 10B, outgoing main polarizing element 10C and the incident side polarizing element 10A with respect to the green light _{L G,} a liquid crystal panel 50, outgoing pre-polarizing element 10B, and the outgoing main polarizing element 10C, the incident side polarizing element 10A with respect to the blue light _{L B,} the liquid crystal panel 50, the emission pre-polarizing element 10B, and the outgoing main polarizing element 10C, each of the outgoing main polarizing element 10C And a cross dichroic prism 60 that synthesizes light emitted from the light and emits the light to a projection lens. Here, the polarizing element 10 (or 10 ′) of the present invention is applied to the outgoing main polarizing element 10C.

In the liquid crystal projector 100 of the present invention, to separate the light emitted from the light source lamp (not shown) the red light L _R by the dichroic mirror (not _shown), the green light L _G, the blue light L _B, respectively corresponding to the light The light L _R , L _G , and L _{B that} is incident on the incident-side polarizing element 10A and then polarized by the respective incident-side polarizing elements 10A is spatially modulated and emitted by the liquid crystal panel 50, and is then emitted to the outgoing pre-polarizing element 10B. After passing through the outgoing main polarizing element 10C, it is synthesized by the cross dichroic prism 60 and projected from a projection lens (not shown). Since the light source lamp uses the polarizing element 10 of the present invention that has excellent light resistance against strong light and has a uniform in-plane spectral characteristic distribution even if it has a high output, a highly reliable liquid crystal projector Can be realized.

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

It is sectional drawing which shows the wire grid structure of the polarizing element used as the premise of this invention. It is sectional drawing which shows the structure in 1st Embodiment of the polarizing element which concerns on this invention. It is the figure which looked at the polarizing element which concerns on this invention from the top. It is sectional drawing which shows the structure in 2nd Embodiment of the polarizing element which concerns on this invention. It is the schematic which shows the principal part process in the manufacturing process of the polarizing element which concerns on this invention. It is the schematic which shows the structure of oblique sputtering film-forming. It is sectional drawing which shows the structure of the optical engine part of the liquid-crystal projector which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Stage, 2 ... Target, 3 ... Beam source, 4 ... Control board 10, 10 ', 10A, 10B, 10C, 90 ... Polarizing element, 11 ... Substrate, 12, 92 ... Reflective layer, 12a ... convex reflective film, 12b, 12c ... filler, 12z ... inorganic material film, 13 ... dielectric layer, 14 ... inorganic fine particle layer, 14a ... inorganic fine particle, 15 ... Protective layer, 50 ... liquid crystal panel, 60 ... cross dichroic prism, 100 ... liquid crystal projector

Claims (7)

A substrate transparent to the light in the use band,
The convex reflection films extending linearly on the substrate are arranged at a pitch smaller than the wavelength of light in the use band, and an inorganic material having a lower refractive index than the substrate is filled between the convex reflection films. A reflective layer,
A dielectric layer formed on the convex reflective film;
A polarizing element comprising: an inorganic fine particle layer in which inorganic fine particles are linearly arranged on the dielectric layer.   The polarizing element according to claim 1, wherein the thickness of the inorganic material in the reflective layer is 5 to 100% of the thickness of the convex reflective film.   The polarizing element according to claim 1, wherein a filling factor of the inorganic material between the convex reflection films is 50% or less.   The polarizing element according to claim 1, wherein the inorganic material is porous silica. Arranging a convex reflection film extending linearly at a pitch smaller than the wavelength of light in the use band on a substrate transparent to the light in the use band; and
Coating an inorganic material having a refractive index lower than that of the substrate between the convex reflective films and on the convex reflective films;
Etching from the surface to remove at least the inorganic material on the convex reflective film;
Forming a dielectric layer on the convex reflective film;
And a step of forming inorganic fine particle layers by linearly arranging inorganic fine particles on the dielectric layer.   The method for manufacturing a polarizing element according to claim 5, wherein the step of coating the inorganic material is performed by a sol-gel method.   A liquid crystal projector provided with a lamp | ramp, a liquid crystal panel, and the polarizing element in any one of Claims 1-4.

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