JP2005148506A - Polarization converting element, manufacturing method of the polarization converting element and projection type liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization converting element which has high heat resistance and provides superior optical performance in a stable manner. <P>SOLUTION: The polarization converting element is provided with a substrate 11 that is provided with a surface on which a great number of linear groove sections 12 having a prescribed depth H and a prescribed width W is formed with an equal interval in a mutually parallel manner, a foundation layer 13 which is formed at the top region of the surface where the groove sections 12 of the substrate 11 are formed and light shielding layers 15 which are formed in the groove sections 12 with approximately same widths of the sections 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polarization conversion element and the like, and more particularly to a polarization conversion element and the like excellent in heat resistance.

In recent years, with the advancement of an advanced information society, as a device for enlarging and projecting images on a screen, a projection type liquid crystal display device capable of directly projecting electronic data instead of conventional slide projectors and overhead projectors (OHP) Is being used. In such a projection-type liquid crystal display device, since the illuminance of the projected image can be improved, projection in a bright room is possible. However, in order to display a brighter and higher-definition image, the projection lens is improved, a high-intensity lamp Improvement of the above, improvement of the integrator lens for uniformly illuminating the liquid crystal panel, or improvement of the polarization conversion optical system for improving the light utilization efficiency by aligning the polarization direction are being promoted.
Under such circumstances, it is common to use a high-intensity lamp such as an ultra-high pressure mercury lamp as a light source as an effective means for improving the illuminance of the projected image. For such a high-intensity lamp, since it is necessary to increase the heat resistance of optical elements such as lenses and polarization conversion elements, in particular, in the polarization conversion element, a large number of light-transmitting materials are formed on a substrate. A wire grid type polarization conversion element in which a thin metal wire is fixed has been developed.

  Here, FIG. 5 is a diagram for explaining such a wire grid type polarization conversion element. A wire grid type polarization conversion element 200 shown in FIG. 5 includes a substrate 201 made of a light transmitting material, and a metal wire wire grid 202 fixed on the substrate 201. A large number of wire grids 202 having a width of about 100 nm are provided in parallel at intervals of about 100 nm. In the wire grid type polarization conversion element 200, a metal layer such as aluminum is usually formed on the substrate 201 by an evaporation method or a sputtering method, and an etching process is performed on the metal layer, whereby a large number of wire grids 202 are spaced at a certain interval. It is prepared by a method of providing convex portions arranged in parallel. In addition, a method has been reported in which a space between convex portions formed by fine metal wires formed on the substrate 201 is solidified using a material having a refractive index comparable to that of the substrate 201 (see, for example, Patent Document 1 and Patent Document 2). ).

Japanese translation of PCT publication No. 2003-502708 (pages 19-20, FIG. 4) Japanese Patent Laid-Open No. 10-153706 (page 4, FIG. 1)

However, in such a wire grid type polarization conversion element, it is necessary to perform an etching process for each product on a metal layer formed by sputtering or the like in order to form a wire grid of fine metal wires on a substrate which is a support. There are disadvantages in that the manufacturing cost is high and mass production is impossible.
Further, for example, like a wire grid type polarization conversion element described in Patent Document 2, a space between convex portions formed by fine metal wires formed on a substrate is solidified using a material having a refractive index similar to that of the substrate. If the polarization conversion element having the above structure is used at a high temperature for a long time, the wire grid and the substrate may be peeled off, which is problematic in terms of reliability.
Accordingly, the present invention has been made to solve the technical problems as described above, and an object thereof is to provide a polarization conversion element having excellent heat resistance.

For this purpose, the polarization conversion element of the present invention includes a substrate having a surface in which a number of linear grooves having a predetermined depth and width are formed in parallel with each other at equal intervals, and a groove on the substrate. It has a base layer formed in the top region of the formed surface, and a light-shielding layer formed in the groove with a width substantially the same as that of the groove. This makes it possible to stably exhibit excellent optical performance while having high heat resistance.
Here, if the light shielding layer is formed with a thickness equal to or less than the depth of the groove, the light shielding layer can be configured to be embedded in the substrate. Can be suppressed.
Further, if the base layer is formed of a material harder than the light shielding layer, deformation of the light shielding layer that occurs during the manufacture of the polarization conversion element can be suppressed. Further, if the underlayer is formed of SiO ₂ , SiC, or Si ₃ N ₄ , the effect of suppressing the deformation of the light shielding layer is great.
In addition, if the light-shielding layer is formed of aluminum, aluminum alloy, silver, or silver alloy, an efficient light-shielding effect can be obtained and light-shielding can be achieved even when used for a long time at high temperatures. The layer is prevented from peeling from the substrate.

Further, the polarization conversion element of the present invention includes a substrate formed of a light transmissive material, a linear metal grid embedded in parallel to each other at equal intervals on the surface of the substrate, and a metal grid embedded in parallel. And the metal grid is characterized by having a region in direct contact with the substrate. This makes it possible to stably exhibit excellent optical performance while having high heat resistance.
In addition, the metal grid may be characterized in that the arrangement density is 2.5 to 10 / μm.

The present invention can also be regarded as a method for manufacturing a polarization conversion element. In the method for manufacturing a polarization conversion element of the present invention, a large number of linear grooves having a predetermined depth and width are parallel to each other at equal intervals. A substrate forming step of forming a substrate having the formed surface, a base layer forming step of forming a base layer in a top region on a surface provided with a groove portion of the substrate formed by the substrate forming step, and forming on the substrate A metal layer forming step of forming a metal layer having a predetermined thickness on the surface of the substrate, which is filled in direct contact with the side surface of the groove portion, and polishing the metal layer formed by the metal layer forming step; And a polishing step for removing the metal layer while leaving the metal layer filled in the groove. Accordingly, it is possible to provide a polarization conversion element that has high heat resistance and can stably exhibit excellent optical performance.
Here, if the base layer forming step is characterized in that a base layer made of a hard material is formed by a vapor phase method on the surface of the substrate where the groove is provided, a uniform base layer is formed. Can do. In addition, the metal layer forming step is characterized in that a metal layer made of a light-shielding substance is formed on the surface of the substrate on which the groove is provided by a vapor phase method. it can.

  Furthermore, the present invention can also be regarded as a projection-type liquid crystal display device, and includes a light source, a polarization conversion element that polarizes and separates light from the light source, a liquid crystal display element that transmits or reflects light polarized by the polarization conversion element, And a projection optical system that projects light transmitted or reflected by the liquid crystal display element onto the screen. The polarization conversion element includes a plurality of linear grooves having predetermined depths and widths that are parallel to each other at equal intervals. A substrate having a formed surface, a base layer formed in a top region of the surface of the substrate where the groove portion is formed, and a light shielding layer formed in the groove portion with substantially the same width as the groove portion. It is said. As a result, the polarization conversion element is not damaged by heat even if light irradiation is performed for a long period of time, so that a high-quality projected image can be stably obtained. Here, if the polarization conversion element is characterized in that the base layer is formed of a material harder than the light shielding layer, it is possible to suppress the deformation of the light shielding layer that occurs during the manufacture of the polarization conversion element, and to stably The effect of obtaining a high-quality projection image is great.

  As an effect of the present invention, it is possible to provide a polarization conversion element having excellent heat resistance.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Embodiment 1]
FIG. 1 is a diagram illustrating a transmissive projection type liquid crystal display device to which the present embodiment is applied. A three-plate liquid crystal projector 1 that is a transmissive projection type liquid crystal display device shown in FIG. 1 includes a white light source 30 that is a light source, and integrator lenses 21 and 22 that make white light 31 emitted from the white light source 30 uniform. The polarization conversion element 10 that separates the white light 31 into S-polarized light and P-polarized light, the dichroic mirrors 51 and 52 that separate the white light 31 into light of different wavelengths, and the transmissive liquid crystal panels 61 and 62 that transmit light of different wavelengths, respectively. 63, a dichroic prism 45 that synthesizes the separated light, and a projection lens 70 that is a projection optical system that forms an image on the screen 80 of the light synthesized by the dichroic prism 45. Further, mirrors 41, 42, 43, and 44, relay lenses 23 and 24, and condenser lenses 25, 26, and 27 are provided as optical components. The white light source 30 includes a high-intensity lamp such as an ultra-high pressure mercury lamp and a metal halide lamp, and a reflector (elliptical mirror) that collects light from the high-intensity lamp.

In the three-plate liquid crystal projector 1 according to the present embodiment, white light 31 converted into substantially parallel light by the reflector is emitted from the white light source 30. The emitted white light 31 enters the integrator lens 21. The integrator lens 21 divides the incident white light 31 into a plurality of light beams by a plurality of lens cells arranged in a matrix and efficiently guides the light to pass through the integrator lens 22 and the polarization conversion element 10. Similar to the integrator lens 21, the integrator lens 22 having a plurality of lens cells arranged in a matrix shape changes the shape of the lens cell of the integrator lens 21 corresponding to each of the constituting lens cells to the transmissive liquid crystal panels 61, 62, 63. Project to the side. Then, the projection images of the lens cells of the integrator lens 21 are superimposed on the transmissive liquid crystal panels 61, 62, 63 by the relay lenses 23, 24 and the condenser lenses 25, 26, 27. At that time, since the white light 31 is aligned with linearly polarized light in the same direction by the polarization conversion element 10, it is possible to reduce the light amount loss in the transmissive liquid crystal panels 61, 62, and 63.
In this process, the white light 31 emitted from the white light source 30 is separated by the dichroic mirrors 51 and 52 into the three primary colors of blue light 32, green light 33, and red light 34. , 62, 63 are irradiated. Here, the dichroic mirror 51 has a green-blue reflection red transmission characteristic, and the dichroic mirror 52 has a green reflection blue transmission characteristic.

The images on the transmissive liquid crystal panels 61, 62, 63 are color-combined by the dichroic prism 45, and further projected onto the screen 80 by the projection lens 70, so that a large screen image can be obtained.
The relay lenses 23 and 24 compensate for the fact that the optical path length from the white light source 30 of the transmissive liquid crystal panel 61 to the liquid crystal panel surface is longer than that of the transmissive liquid crystal panels 62 and 63. Further, the condenser lenses 25, 26, and 27 suppress the spread of light rays that have passed through the transmissive liquid crystal panels 61, 62, and 63, respectively, and the projection lens 70 realizes efficient projection.

  Next, the polarization conversion element 10 of the present embodiment will be described. FIG. 2 is a diagram illustrating the polarization conversion element 10 to which this exemplary embodiment is applied. As shown in FIG. 2, the polarization conversion element 10 of the present embodiment includes a substrate 11 in which a large number of linear groove portions 12 that are parallel to each other and arranged at equal intervals are formed on one surface, and a groove portion of the substrate 11. The base layer 13 formed in the top region on the surface on which the surface 12 is formed, the base layer 14 formed in the bottom region, the light shielding layer 15 filled in the groove 12 of the substrate 11, and the surface on which the groove 12 is formed. It is comprised by the anti-reflective film 16 formed in the surface on the opposite side.

The material for forming the substrate 11 is not particularly limited as long as it is a light transmissive material. For example, polycarbonate resin, acrylic resin, methacrylic resin, polystyrene resin, vinyl chloride resin, epoxy resin, polyester resin, polyimide, Synthetic resins such as polyetherimide, polyether sulfone, phenol resin, norbornene-based amorphous polyolefin resin, and glass such as blue plate glass, white plate glass, and sapphire glass can be used. Among these, polycarbonate resins, norbornene amorphous polyolefins, polyimides, and the like are preferable in terms of good heat resistance. Furthermore, the polycarbonate-based resin is particularly preferable in that it has high light transmittance.
Moreover, the thickness of the board | substrate 11 is 0.1-2.0 mm normally, Preferably it is 0.7-1.1 mm. The shape and outer dimensions of the substrate 11 are appropriately selected according to the mode to be used, and are not particularly limited. In general, a rectangle or a square having a side of 10 to 100 mm, and a circle or an ellipse having a diameter of 5 to 100 mm. Etc. are used.

The groove 12 formed on one surface of the substrate 11 has, for example, a linear shape with a groove width (W) of 50 to 120 nm and a groove depth (H) of 30 to 120 nm. Moreover, the groove pitch (P) of the groove part 12 is provided at equal intervals in parallel with each other at an interval of 50 to 180 nm, and the density thereof is 2.5 to 10 / μm.
The material of the underlayer 13 and the underlayer 14 formed in the top region and the bottom region on the surface of the substrate 11 where the groove 12 is provided is not particularly limited, but the processing speed by polishing or etching treatment is limited to the light shielding layer 15. It is desirable to use a material that is lower than the light shielding material that forms the film. The material of the underlayers 13 and 14 is preferably a light transmissive material. However, if the thickness of the underlayers 13 and 14 is made thin enough to obtain a sufficient light transmittance, a non-light transmissive material is used. There may be. In particular, SiO ₂ , SiC, Si ₃ N _{4 and the} like have a sufficiently low processing speed by polishing or etching treatment as compared with aluminum, an aluminum alloy or the like that is usually used as a light shielding material. Since the deformation | transformation of the board | substrate pattern shape which arises can be suppressed, a favorable polarization conversion characteristic can be acquired.
As the underlayer, in order to suppress the deformation of the substrate pattern shape that occurs during the manufacture of the polarization conversion element 10, it is sufficient to form the underlayer 13 in the top region on the surface of the substrate 11 where the groove 12 is provided. The underlayer 14 formed in the bottom region is not a necessary condition.

The light shielding material for forming the light shielding layer 15 is not particularly limited as long as it is a substance that blocks light, but usually a metal, a semiconductor material, or the like is used. For example, aluminum, silver, an aluminum alloy, a silver alloy, and the like are preferable because they have a large refractive index and a large light absorption. Among them, since aluminum has a high thermal conductivity, when aluminum is used as a light-shielding substance, the polarization conversion element 10 is particularly excellent in heat resistance, for example, even after being left at 400 ° C. for 1 hour, There is no change in performance or performance. In addition, when such a polarization conversion element 10 is incorporated in a projection type liquid crystal display device such as the three-plate liquid crystal projector 1 of the present embodiment, the polarization conversion element 10 has a temperature atmosphere of about 150 to 200 ° C. However, when aluminum or the like is used as a light-shielding substance, it can exhibit better heat resistance than when a normal heat-resistant resin is used. Contributes to stable performance.
Further, when a metal is used as the light shielding material, it is preferable to form an oxide layer as a self-protecting film on the metal surface. Examples of the compound that forms such an oxide layer include silicon oxide, silicon nitride, and aluminum oxide. The oxide layer is formed so as to reduce the reflectance in a desired wavelength range by adjusting the refractive index and the thickness according to the film forming conditions.

  In the polarization conversion element 10 to which this exemplary embodiment is applied, an antireflection film 16 is provided on the surface of the substrate 11 opposite to the surface on which the groove 12 is formed in order to increase the polarization efficiency of incident light. It is preferable. As a material for forming the antireflection film 16, a compound selected from metals, metal oxides, and metal fluorides is usually used. Specifically, silver etc. are mentioned as a metal, for example. Examples of the metal oxide include silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, yttrium oxide, and zirconium oxide. Examples of the metal fluoride include magnesium fluoride. The antireflection film may be a single layer or a multilayer. The thickness of the antireflection film and the thickness of each layer in the case of a multilayer are appropriately selected depending on the number of layers, the refractive index of the substance used for each layer, and the like.

In the polarization conversion element 10 to which this exemplary embodiment is applied, the light shielding layer 15 has a structure in which a light shielding material is filled in a groove portion 12 formed integrally with the substrate 11. Therefore, unlike a structure in which a metal wire grid portion protrudes on a substrate like a conventional wire grid type polarization conversion element, it is possible to solve the problem of performance degradation due to breakage of the wire grid portion. Further, since the groove portion 12 is integrally formed with the substrate 11, the light shielding material filled in the groove portion 12 constituting the light shielding layer 15 does not peel from the substrate 11 even when used for a long time in a high temperature environment. High heat resistance can also be realized.
In particular, in the polarization conversion element 10 according to the present embodiment, the substrate 11 and the light shielding material constituting the light shielding layer 15 are coupled to each other on the side surface of the groove portion 12 by direct contact. That is, a light shielding layer 15 having a width substantially the same as the width of the groove 12 is formed in the groove 12. Since the resin material constituting the substrate 11 and the light-shielding substance such as metal can be firmly attached, the light-shielding layer 15 can be fixed sufficiently strongly to the substrate 11. As will be described later, the base layer 13 and the base layer 14 are respectively formed in the top region and the bottom region on the surface of the substrate 11 where the groove 12 is provided, and are not formed on the side surface of the groove 12 or may be formed. Very little. Therefore, the light shielding substance can directly contact the resin material constituting the substrate 11 on the side surface of the groove 12.

Next, a method for manufacturing the polarization conversion element 10 to which this exemplary embodiment is applied will be described. FIG. 3 is a diagram illustrating a method for manufacturing the polarization conversion element 10. As shown in FIG. 3A, first, a substrate 11 having a large number of grooves 12 on one surface is formed using a light transmissive material. When a heat resistant synthetic resin such as polycarbonate is used as the material of the substrate 11, for example, a plurality of linear groove portions 12 having a predetermined groove width and groove depth and having a predetermined groove pitch are equally spaced. Using a mold (stamper) in which a preformat is formed so as to be arranged in parallel, a single substrate 11 having the groove 12 can be produced in large quantities by an injection molding method. It is also possible to use the 2P method.
By forming the groove portion 12 directly on the substrate 11 by such a method, the groove portion 12 can be formed into a desired groove shape with high accuracy, so that the polarization characteristics of the polarization conversion element 10 can be improved. Can be planned

Next, as shown in FIG. 3B, a base layer 13 and a base layer 14 are formed in the top region and the bottom region of the substrate 11 formed in this way, respectively. The underlayer 13 and the underlayer 14 are formed by, for example, a material such as SiO ₂ , SiC, or Si ₃ N _{4 on} the surface of the substrate 11 provided with the groove 12 by a vapor phase method such as a vacuum evaporation method or a sputtering method. To form. The layer thickness of the foundation layer 13 and the foundation layer 14 is preferably such that the shape of the groove 12 is not significantly changed, and is usually formed to be 10 to 50 nm.
Here, in the vapor phase method, film formation proceeds exclusively on a plane parallel to the surface of the substrate 11. Therefore, as a cross-sectional shape of the groove portion 12 formed in the substrate 11, a trapezoidal shape in which an angle θ (see FIG. 2) formed by the side surface of the groove portion 12 and the surface (top region) of the substrate 11 is 55 to 90 °, By forming a rectangular shape, sufficient film formation can be performed in the top region and the bottom region of the substrate 11, and almost no film can be formed on the side surface of the groove 12, or no film can be formed at all. By setting the cross-sectional shape of the groove 12 in this manner, the base layer 13 and the base layer 14 are formed in the top region and the bottom region of the substrate 11, respectively.
Note that the underlayer 14 formed in the bottom region is not a necessary condition as described above, and may be set so that no film is formed in the bottom region.

Next, as shown in FIG. 3C, a metal film 17 is formed so as to cover the groove 12 of the substrate 11 thus formed. In that case, since the base layer is hardly formed on the side surface of the groove portion 12 or not formed at all, the metal film which becomes the light shielding layer 15 having the same width as the groove portion 12 in the groove portion 12. 17 is filled. Here, the metal film 17 is formed of a metal such as aluminum, silver, an aluminum alloy, or a silver alloy on the surface of the substrate 11 on which the groove portion 12 is provided by a vapor phase method such as a vacuum evaporation method or a sputtering method. To do. The thickness of the metal film 17 is not particularly limited, but is usually formed with a thickness of about 100 to 500 nm.
Subsequently, as shown in FIG. 3D, the surface of the metal film 17 formed so as to cover the groove 12 of the substrate 11 is removed by polishing or chemical etching, and only the groove 12 is filled with metal. A light shielding layer 15 having a depth of 12 or less is formed. The polishing method is not particularly limited. For example, the polishing liquid (pad) is disposed between the pad 11 and the substrate 11 while the substrate 11 is placed on the polishing cloth (pad) so that the surface of the substrate 11 is applied, and the substrate 11 is uniformly loaded from the back surface. There is a method of polishing while supplying the slurry.

In this polishing step, SiO ₂ , SiC, Si ₃ N _4, etc., which form the base layer 13 in the top region, are processed at a processing speed by polishing or etching, and are usually used as a light shielding material for the light shielding layer 15. Since it is sufficiently lower than an alloy or the like, deformation of the pattern shape of the light shielding layer 15 can be suppressed. That is, during polishing, the base layer 13 in the top region serves as a stopper against the progress of polishing, and therefore, the metal film 17 and the substrate 11 are prevented from being etched deeper than the base layer 13 in the top region of the substrate 11. For this reason, it is possible to prevent the light shielding layer 15 from having a non-uniform thickness due to partial progress of polishing more than necessary. Further, since the shading of the central portion of the light shielding layer 15 is not increased and the light shielding layer 15 does not have a curved shape, the surface of the light shielding layer 15 can be formed stably and smoothly.

Thus, according to the method for manufacturing the polarization conversion element 10 of the present embodiment, the groove 12 is formed on one surface of the substrate 11, and the top region and the bottom region of the surface on which the groove 12 is formed, A base layer 13 and a base layer 14 are formed respectively. As a result, the light shielding layer 15 can be accurately formed in a desired shape, and a smooth surface can be stably formed, so that excellent optical performance can be stably obtained in the polarization conversion element 10. It becomes possible.
In particular, since a metal such as aluminum can be used as the light shielding substance constituting the light shielding layer 15 and the shape can be formed with high accuracy, the polarization conversion element 10 is particularly excellent in heat resistance in addition to stable optical performance. In addition, since the light shielding layer 15 can be firmly fixed to the substrate, the occurrence of breakage hardly occurs.

Hereinafter, based on an Example, the polarization conversion element 10 of this Embodiment is demonstrated concretely. In addition, the polarization conversion element 10 of this Embodiment is not limited to an Example.
(Example 1)
On a heat-resistant polymer substrate having a thickness of 1.1 mm, a preformat is formed in which groove portions having a groove width of 100 nm and a groove depth of 50 nm are provided in parallel at equal intervals with a groove pitch of 170 nm. An antireflection film in which two layers of Ta ₂ O ₅ / SiO ₂ were laminated was formed on the surface of the molecular substrate opposite to the groove. Next, a SiO ₂ film having a thickness of 20 nm was formed by sputtering on the surface of the heat-resistant polymer substrate provided with the groove. Further, an aluminum (Al) film having a thickness of 200 nm was formed so as to fill the groove portion of the substrate from above the SiO ₂ layer and to cover the groove. Subsequently, this Al film was polished to prepare a polarization conversion element in which Al metal was filled in the groove portion of the substrate. The polarization conversion element thus prepared was attached to the three-plate liquid crystal projector shown in FIG. 1, and a 1000-hour projection experiment was conducted. As a result of the experiment, no damage was observed in the appearance of the polarization conversion element. Also, no deterioration in display quality was observed for the projected image.

(Example 2)
A 200 nm pitch line-and-space pattern was previously formed on a chromium mask using an electron beam. A resist was applied on the silicon wafer, mask exposure was performed, and patterning was performed. Thereafter, the photosensitive portion of the resist was removed, and anisotropic etching of silicon was performed to obtain a groove depth of 110 nm. An electroless plating was performed on the silicon substrate on which the groove was formed, and a metal mold required for substrate formation was obtained by peeling the plated portion from the silicon. Using this mold, a glass substrate having a preformat in which a number of grooves having a groove width of 100 nm and a groove depth of 90 nm were formed in parallel with each other at a groove pitch of 170 nm was obtained by the glass 2P method.
Further, an antireflection film was formed with two layers of Ta ₂ O ₅ / SiO ₂ on the surface opposite to the groove. Thereafter, SiC having a thickness of 15 nm was formed on the substrate preformat. Further, an Al film having a thickness of 200 nm was formed. Subsequently, only the Al metal embedded in the groove portion of the substrate was left, and the excess portion was removed by polishing.
The polarization conversion element thus prepared was attached to the three-plate liquid crystal projector shown in FIG. 1, and a projection experiment was performed. After projecting for 1000 hours, the polarization conversion element was taken out and visually observed, but no damage was observed. Also, no deterioration in display quality was observed for the projected image.

As described above, in the polarization conversion element 10 of the present embodiment, the groove 12 is formed on one surface of the substrate 11, and the base layer is formed in each of the top region and the bottom region of the surface on which the groove 12 is formed. 13 and the underlayer 14 are formed. Therefore, the light shielding layer 15 formed by filling the groove portion 12 with a light shielding substance such as a metal can be formed in a predetermined shape with high accuracy in close contact with the groove portion 12, and can be formed with a smoother surface shape. Thereby, it is possible to stably exhibit excellent optical performance in the polarization conversion element 10.
In particular, since a metal such as aluminum can be used as the light shielding material constituting the light shielding layer 15, the polarization conversion element 10 can realize a particularly excellent characteristic in heat resistance. At this time, since the light shielding layer 15 has a structure in which the groove portion 12 formed integrally with the substrate 11 is filled with a light shielding material, the light shielding layer 15 is hardly damaged and has excellent optical performance over a long period of time. Can be realized. Further, since the groove portion 12 is integrally formed with the substrate 11 and the light shielding layer 15 is fixed sufficiently strongly with respect to the side surface of the groove portion 12, the light shielding material filled in the groove portion 12 constituting the light shielding layer 15 is in a high temperature environment. Since it does not peel off from the substrate 11 even if it is used for a long time under this, high heat resistance is also realized from that point.
Due to the characteristics of the polarization conversion element 10 according to the present embodiment, the polarization conversion element 10 can be applied to a projection-type liquid crystal display device such as the three-plate liquid crystal projector 1 to perform light irradiation over a long period of time. Since excellent optical performance can be stably maintained without being damaged by heat, a high-quality projection image can be obtained.

[Embodiment 2]
In the first embodiment, the three-plate liquid crystal projector 1 that is a transmissive projection type liquid crystal display device has been described. In the second embodiment, a liquid crystal projector 2 that is a projection type liquid crystal display device will be described. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

  FIG. 4 is a diagram illustrating a reflection type projection type liquid crystal display device to which the present embodiment is applied. A liquid crystal projector 2 which is a reflection type projection type liquid crystal display device shown in FIG. 4 includes a white light source 30 which is a light source, a polarization conversion element 90 which converts white light emitted from the white light source 30 into S-polarized light, and white light. A dichroic mirror 53 that separates light of different wavelengths, three reflective liquid crystal panels 64, 65, and 66 that reflect three lights of different wavelengths, and polarizers 91, 93, 95, and 96, polarization rotation elements 92, 94, 97, and 98 that rotate the polarization direction by 90 °, polarization beam splitters 101, 102, and 103 that selectively transmit and reflect the polarization components of each light, and the combined light on the screen 80. A projection lens 70 is provided as a projection optical system that forms an image on the top.

The white light source 30 emits white light converted into substantially parallel light by a reflector (elliptical mirror) provided in the white light source 30. White light consists of three primary colors of blue light (B), green light (G), and red light (R), and is converted into S-polarized light by the polarization conversion element 90.
The R S-polarized light and B S-polarized light incident on the dichroic mirror 53 having green reflection red-blue transmission characteristics are transmitted through the polarizer 91 after passing through the dichroic surface of the dichroic mirror 53, and the P-polarized component is cut almost completely. R-polarized light and B-polarized light. Note that the reason why the polarizer 91 is disposed at this position is that the polarization rectification by the polarization conversion element 90 is not sufficient, and the incident light at the time of passing through the polarization conversion element 90 partially includes P-polarized light. In order to degrade the contrast of the image, a higher image contrast can be obtained by aligning the polarization by the polarizer 91. The R S-polarized light and the B S-polarized light are incident on the polarization rotation element 92 that rotates the polarization of the B light, the R S-polarized light does not change, and the B S-polarized light is rotated by the rotation of the B-polarized light. Become.

  The R S-polarized light incident on the polarization beam splitter 101 corresponding to the first prism is reflected by the dielectric multilayer film 101a which is the splitter surface, and is incident on the reflective liquid crystal panel 64 as R S-polarized light. Here, light to be displayed brightly by the reflective liquid crystal panel 64 is reflected as R P-polarized light, and light to be displayed dark is reflected as R S-polarized light. The P-polarized light of R, which is light to be displayed brightly, is incident on the polarization beam splitter 101 again, and is transmitted through the splitter surface 101a because it is now P-polarized light.

  On the other hand, the B P-polarized light that has passed through the polarization rotating element 92 that rotates the B-polarized light enters the polarization beam splitter 101, passes through the dielectric multilayer film 101a that is the splitter surface, and is reflected as B P-polarized light. Is incident on the liquid crystal panel 65. Here, light to be displayed brightly by the B reflection type liquid crystal panel 65 is reflected as S-polarized light of B, and light to be displayed dark is reflected as B P-polarized light. The S-polarized light of B, which is the light to be displayed brightly, is incident again on the polarization beam splitter 101 and is now S-polarized light. Of P-polarized light.

The R P-polarized light and the B S-polarized light synthesized by the polarization beam splitter 101 are incident on the polarization rotation element 94 that rotates the polarization of the B light, and the R P-polarized light does not change and becomes the R P-polarized light. The polarization of B S-polarized light is rotated to become B P-polarized light. The light that has become P-polarized in both R and B is then incident on a polarizer 93 that is arranged to pass P-polarized light, and unnecessary S-polarized stray light is cut, so that P-polarized light of R having high contrast is obtained. And B P-polarized light.
The R P-polarized light and the B P-polarized light enter the polarization beam splitter 102 corresponding to the second prism, pass through the splitter surface 102a, and become R P-polarized light and B P-polarized light.

As for the G light, the G light emitted from the white light source 30 is converted into G S-polarized light by the polarization conversion element 90 and then reflected by the dichroic mirror 53 having green reflection red-blue transmission characteristics. The S-polarized light enters the polarizer 95.
When the G S-polarized light reflected by the dichroic mirror 53 is incident on the polarizer 95, the P-polarized component is almost completely cut to become the S-polarized G light and enters the polarizing beam splitter 103 corresponding to the third prism.
The G S-polarized light incident on the polarization beam splitter 103 is reflected by the dielectric multilayer film 103 a that is the splitter surface to become G S-polarized light, and is incident on the G reflective liquid crystal panel 66. The light to be displayed brightly is reflected as P-polarized light of G and enters the polarization beam splitter 103 again. Since it is now P-polarized light, it passes through the dielectric multilayer film 103a which is the splitter surface.

Here, the G P-polarized light passes through the polarizer 96 arranged to transmit the P-polarized light, and then enters the polarization rotating element 97 to rotate the polarized light to become G S-polarized light.
The G S-polarized light enters the polarization beam splitter 102, is reflected by the splitter surface 102a, and is combined with the R P-polarized light and the B P-polarized light.
Then, the R P-polarized light, the G S-polarized light, and the B P-polarized light enter the polarization rotating element 98 that rotates the polarized light of the R light and the B light, and the S polarized light of the G does not change, The polarization of the B P-polarized light is rotated to become the S-polarized light of R and the S-polarized light of B. Accordingly, the image light synthesized by the polarization beam splitter 102 has R, G, and B components that are all S-polarized components, and is enlarged and projected onto the screen 80 by the projection lens 70. By making all the polarization planes emitted from the projection lens 70 the same S-polarized light, it is possible to cope with a polarizing screen or a rear projection screen in which light of a predetermined polarization direction is specified. .

Here, also in the polarization conversion element 90 and the polarizers 91, 93, 95, and 96 of the present embodiment, the groove portion 12 is formed on one surface of the substrate 11 as in the polarization conversion element 10 of the first embodiment. The base layer 13 and the base layer 14 are formed in each of the top region and the bottom region of the surface on which the groove 12 is formed. Therefore, the light shielding layer 15 formed by filling the groove portion 12 with a light shielding substance such as a metal can be formed in a predetermined shape with high accuracy in close contact with the groove portion 12, and can be formed with a smoother surface shape. Thereby, it is possible to stably exhibit excellent optical performance in the polarization conversion element 10.
In particular, since a metal such as aluminum can be used as the light shielding material constituting the light shielding layer 15, the polarization conversion element 10 can realize a particularly excellent characteristic in heat resistance. At this time, since the light shielding layer 15 has a structure in which the groove portion 12 formed integrally with the substrate 11 is filled with a light shielding material, the light shielding layer 15 is hardly damaged and has excellent optical performance over a long period of time. Can be realized. Further, since the groove portion 12 is integrally formed with the substrate 11 and the light shielding layer 15 is fixed sufficiently strongly with respect to the side surface of the groove portion 12, the light shielding material filled in the groove portion 12 constituting the light shielding layer 15 is in a high temperature environment. Since it does not peel off from the substrate 11 even if it is used for a long time under this, high heat resistance is also realized from that point.
Due to the characteristics of the polarization conversion element 90 and the polarizers 91, 93, 95, and 96 according to the present embodiment, by applying these to the liquid crystal projector 2, even if light irradiation is performed for a long time, damage due to heat is caused. In addition, since stable and excellent optical performance can be maintained, a high-quality projected image can be obtained.

  Examples of utilization of the present invention include various optical devices such as an optical transmission device and an optical amplification device, and a projection type liquid crystal display device of a transmission type or a reflection type.

It is a figure explaining a transmissive projection type liquid crystal display device. It is sectional drawing explaining the structure of a polarization conversion element. It is a figure explaining the manufacturing method of a polarization conversion element. It is a figure explaining a reflection type projection type liquid crystal display device. It is a figure for demonstrating the conventional wire grid type | mold polarization conversion element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,90 ... Polarization conversion element, 11 ... Board | substrate, 12 ... Groove part, 13 ... Underlayer (top area), 14 ... Underlayer (bottom area), 15 ... Light shielding layer, 16 ... Antireflection film, 17 ... Metal film, 21, 22 ... Integrator lens, 23, 24 ... Relay lens, 25, 26, 27 ... Condenser lens, 30 ... White light source, 91, 93, 95, 96 ... Polarizer, 41, 42, 43, 44 ... Mirror, 45 ... Dichroic prism, 51, 52, 53 ... Dichroic mirror, 61, 62, 63 ... Transmission type liquid crystal panel, 64, 65, 66 ... Reflection type liquid crystal panel, 70 ... Projection lens, 80 ... Screen, 92, 94, 97, 98: Polarization rotating element, 101, 102, 103 ... Polarizing beam splitter

Claims (12)

A substrate having a surface in which a plurality of linear grooves having a predetermined depth and width are formed in parallel with each other at equal intervals;
An underlayer formed in a top region of the surface of the substrate where the groove is formed;
A light shielding layer formed in the groove with a width substantially the same as the groove,
A polarization conversion element comprising:   The polarization conversion element according to claim 1, wherein the light shielding layer has a thickness equal to or less than a depth of the groove.   The polarization conversion element according to claim 1, wherein the base layer is made of a material harder than the light shielding layer. The polarization conversion element according to claim 1, wherein the underlayer is made of SiO ₂ , SiC, or Si ₃ N ₄ .   The polarization conversion element according to claim 1, wherein the light shielding layer is formed of aluminum, an aluminum alloy, silver, or a silver alloy. A substrate formed of a light transmissive material;
Linear metal grids embedded parallel to each other at equal intervals on the surface of the substrate;
A hard layer formed between the metal grids embedded in parallel,
The polarization conversion element, wherein the metal grid has a region in direct contact with the substrate.   The polarization conversion element according to claim 6, wherein the metal grid has an arrangement density of 2.5 to 10 lines / μm. A substrate forming step of forming a substrate having a surface in which a plurality of linear grooves having a predetermined depth and width are parallel to each other and formed at equal intervals;
An underlayer forming step of forming an underlayer in a top region on the surface of the substrate provided with the groove portion formed by the substrate forming step;
A metal layer forming step of forming a metal layer that is filled in direct contact with the side surface of the groove formed in the substrate and has a predetermined thickness on the surface of the substrate;
Polishing the metal layer formed in the metal layer forming step, and removing the metal layer while leaving the metal layer filled in the groove portion. .   The said base layer formation process forms the said base layer which consists of hard materials with a vapor phase method on the surface in which the said groove part of the said board | substrate was provided, The manufacture of the polarization converting element of Claim 8 characterized by the above-mentioned. Method.   The said metal layer formation process forms the said metal layer which consists of a light-shielding substance by a vapor phase method on the surface in which the said groove part of the said board | substrate was provided, The manufacture of the polarization conversion element of Claim 8 characterized by the above-mentioned. Method. A light source;
A polarization conversion element that polarizes and separates light from the light source;
A liquid crystal display element that transmits or reflects light polarized by the polarization conversion element;
A projection optical system that projects light transmitted or reflected by the liquid crystal display element onto a screen;
The polarization conversion element is:
A substrate having a surface in which a plurality of linear grooves having a predetermined depth and width are formed in parallel with each other at equal intervals;
An underlayer formed in a top region of the surface of the substrate where the groove is formed;
A light shielding layer formed in the groove with a width substantially the same as the groove,
A projection type liquid crystal display device comprising:   12. The projection type liquid crystal display device according to claim 11, wherein the polarization conversion element is formed of a material whose base layer is harder than the light shielding layer.

Images