JP2007219340A - Compound wire grid polarizer, compound optical element and polarized light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wire grid polarizer with which downsizing and weight reduction of a polarized light source for displaying an image are attained. <P>SOLUTION: A plurality of metallic grids 3a which are long in an X-axis direction and have width w1 and thickness h1 are arranged in parallel to the X-axis direction in a cycle p1 on a main surface of a light translucent substrate 2 on its almost upper half in a Z-axis direction to form a 1st wire grid polarizer 1a. A plurality of metallic grids 3b which are long in the Z-axis direction and have width w2 and thickness h2 are arranged in parallel to the Z-axis direction in a cycle p2 on the same surface as the 1st wire grid polarizer 1a on its almost lower half in the Z-axis direction while perpendicularly crossing the cycle p1 direction of the 1st wire grid polarizer 1a to form a 2nd wire grid polarizer 1b. Thus a compound wire grid polarizer 1 having two wire grid polarizers 1a, 1b which are orthogonally crossed on the main surface of the light translucent substrate 2 is constituted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wire grid polarizer and a polarized light source, and particularly to a composite wire grid polarizer (composite polarizer) in which wire grid polarizers orthogonal to each other are formed on the same substrate, and a part of the back surface of the composite polarizer. The present invention relates to a composite optical element having structural birefringence and a polarized light source for image display using the same.

  Recently, various optical devices have been developed and put into practical use as the demand for large-screen image display devices rapidly expands. FIG. 4 (a) is a diagram schematically showing a conventional projection type liquid crystal display device disclosed in Patent Document 1, in which a light source 10, a quarter wavelength plate 11, a polarization beam splitter 12, and light incidence. The liquid crystal display panel 14, the projection lens 15, and the screen 16 are sandwiched between the polarizing plates 13 a and 13 b on the side and the emission side. FIG. 4B is an enlarged view of the light source unit. The light source 10 includes a lamp 10a such as an ultrahigh pressure mercury lamp or a xenon lamp and a reflecting mirror 10b, for example, a parabolic reflecting mirror. Becomes substantially parallel to the optical axis of the parabolic reflecting mirror 10b. The light emitted from the light source 10 is regarded as natural light (random light), that is, light that uniformly includes polarized light in all states, and is expressed as a sum of two orthogonal linearly polarized lights having equal intensities.

  As shown in FIG. 4B, the polarizing beam splitter 12 disposed between the light source 10 and the liquid crystal display panel 14 includes three prisms 12a and 12b in which a multilayer film is applied to the slope (joint surface) of the prism. 12c, and has the effect of transmitting the P-polarized component light (P-polarized light) in the irradiated light and reflecting the S-polarized component light (S-polarized light). Further, a quarter-wave plate for rotating the transmitted light by 45 ° is disposed between the light source 10 and the polarizing beam splitter 12, and the optical axis thereof is aligned with the direction of 45 ° with respect to the vibration direction of the S-polarized light.

  Random light emitted from the light source 10 enters the polarization beam splitter 12 through the quarter-wave plate 11. While passing through the quarter-wave plate 11, it undergoes an optical rotation action but remains random light. The random light incident on the polarizing beam splitter 12 is separated into P-polarized light and S-polarized light by the polarizing beam splitter 12, and the P-polarized light passes through the polarizing beam splitter 12 and enters the liquid crystal display panel. The S-polarized light is reflected twice by the multilayer film on the boundary surface of the polarizing beam splitter 12 and travels toward the light source 10 side.

  The S-polarized light reflected by the polarizing beam splitter 12 toward the light source 10 is subjected to an optical rotation action when passing through the quarter-wave plate 11 and becomes circularly polarized light. This circularly polarized light is reflected by the parabolic mirror 10b and is incident on the quarter-wave plate again. This circularly polarized light is rotated by 45 ° by the optical rotatory action of the ¼ wavelength plate to become P-polarized light and enters the polarization beam splitter 12. Since the light incident on the polarizing beam splitter 12 is P-polarized light, it passes through the polarizing beam splitter 12 and enters the liquid crystal panel 14. Since almost all of the random light can be irradiated onto the liquid crystal panel in this way, a high-luminance image is displayed, and the projection image enlarged and projected on the screen 16 by the projection lens 15 is a bright image with high contrast. Can do.

  However, a polarization light source using a polarizing beam splitter has a problem that it is difficult to form a multilayer film under optimum conditions when forming the multilayer film of the polarizing beam splitter, and there is a difficulty in miniaturization due to the shape of the prism. There was also a problem that it was expensive. As an improvement, a wire grid polarizer has been proposed and put into practical use. A wire grid polarizer (wire grid polarization separation element) is disclosed in Patent Document 2 and the like. As shown in FIG. 5, the wire grid polarizer 20 is obtained by forming a parallel metal lattice 22 of a metal such as aluminum on a glass substrate 21. The width of the metal grating 22 is b, the thickness thereof is h, and the arrangement period (pitch) is d. When the metal grating 22 is configured with a sufficiently small period d of about 1/5 or less with respect to the wavelength of the incident light A, the light of the electric field component that oscillates perpendicularly to the grid period direction 23 is reflected and the electric field component that oscillates in parallel is reflected. Light is transmitted and can be polarized and separated efficiently.

  In Patent Document 3, a metal film 32 is formed on a transparent and flexible polymer film substrate 31 as shown in FIG. 6A, and the substrate 31 and the metal film 32 are stretched in the X-axis direction. As shown in FIG. 6 (b), metal cracks occur in the Y-axis direction perpendicular to the direction, and the metal-attached portions and the exposed portions of the base material are alternately arranged in stripes. A structure having a rectangular shape is formed. By making the short axis of the structure smaller than the wavelength of light and the long axis longer than the wavelength of light, the wire grid type polarizer 30 can be obtained. Linearly polarized light whose electric field component oscillates in the X-axis direction is transmitted, and linearly polarized light whose electric field oscillates in the Y-axis direction orthogonal to the stretching direction is reflected.

  It is disclosed that the light use efficiency of the light source can be increased by arranging the polarizer 30 and the scattering reflector 33 shown in FIG. 6B as shown in FIG. Of light having an intensity of 100 emitted from a light source (not shown), light having an intensity of 50 (linearly polarized light) is transmitted through the polarizer 30, and the remaining linearly polarized light having an intensity of 50 is reflected in the direction of the reflector 33. This linearly polarized light is scattered by the scattering reflector 33, the polarization state is disturbed, and some of the natural light is incident on the polarizer 30 again and includes linearly polarized light that passes through the polarizer 30. By configuring as shown in FIG. 7, the efficiency of light from the light source can be increased.

  Further, by arranging the polarizer 30, the quarter wavelength plate 34, and the reflection plate 35 shown in FIG. 6B as shown in FIG. 8, the light use efficiency of the light source can be increased. Is disclosed. Of natural light having an intensity of 100 emitted from a light source (not shown), linearly polarized light having an intensity of 50 in which the electric field component vibrates in the X-axis direction is transmitted through the polarizer 30 and the remaining intensity of 50 in which the electric field component vibrates in the Y-axis direction. Linearly polarized light is reflected. The reflected linearly polarized light is converted into, for example, clockwise circularly polarized light when passing through the quarter-wave plate 34. The clockwise circularly polarized light becomes counterclockwise circularly polarized light when reflected by the reflecting plate 35, enters the quarter wavelength plate 34 again, and becomes linearly polarized light whose electric vector vibrates in the X-axis direction. The child 30 can be transmitted. By configuring as shown in FIG. 8, the efficiency of light from the light source can be increased.

  Patent Document 4 discloses a polarizer (reflective polarizer) in which a wire grid polarizing film is formed on both surfaces of an optical glass substrate, and each wire grid polarizing film has a parallel Nicol relationship. As shown in FIG. 9, wire grid polarizing films 42 and 43 are formed on both main surface portions of the optical glass substrate 41, respectively. The wire grid polarizing films 42 and 43 are parallel Nicols, that is, wire grid polarizing films 42 and 43, respectively. The polarization directions of the light speed reflected at each of these are parallel to each other. When natural light is incident on the polarizer 40 on one wire grid polarizing film 42, the S-polarized component contained in the incident light is reflected by the wire grid polarizing film 42. Then, the P-polarized component of the incident light is transmitted through the reflecting surface 42, transmitted through the substrate 41, and further transmitted through the wire grid polarizing film 43 on the other main surface.

In this polarizer 40, the polarized light component transmitted through the wire grid polarizing films 42 and 43 of the incident light is birefringent due to stress (strain) in the substrate 41 regardless of which main surface side of the substrate 41 is incident. The influence is cut off when it passes through the wire grid polarizing films 42 and 43 on the main surface to be emitted.
Japanese Patent No. 2720730 JP 2002-311382 A JP 2001-74935 A JP-A-2005-106940

However, the conventional wire grid polarizer as shown in FIG. 5 has a problem that a large number of optical components are required when configuring a polarized light source for image display. Moreover, the wire grid polarizer formed in the polymer film substrate form shown in FIG. 6 has a problem in durability with respect to an environmental test, and the problem of the number of optical components has not been solved. In addition, the wire grid polarizer shown in FIG. 9 generates stress (strain) inside, and even if it is affected by the birefringence caused thereby, the component affected by the birefringence is blocked in the emitted light. Although having the characteristics, there is a problem that the number of optical components cannot be reduced when a polarized light source is configured.
The composite polarizer of the present invention is thin, and it is an object of the present invention to provide a composite wire grid polarizer that can reduce the number of optical components when forming a polarized light source for image display.

  In the composite polarizer and composite optical element according to the present invention, in order to reduce the size and weight of the polarized light source for image display, a plurality of first metal gratings are provided on a substantially upper half of the main surface of the light-transmitting substrate at a predetermined period. A first wire grid polarizer arranged, and a second wire in which a plurality of second metal gratings are arranged at a predetermined cycle on the lower half of the substrate perpendicular to the periodic direction of the first wire grid polarizer A composite wire grid polarizer comprising a grid polarizer. By using such a composite wire grid polarizer for a polarized light source, the number of optical components can be reduced, and the polarized light source can be reduced in size and weight.

  The composite wire grid polarizer is configured using quartz, optical glass, or polymer film on the light transmissive substrate. By using either crystal, optical glass, or polymer film according to the application of the polarized light source, it is possible to realize a polarized light source that focuses on any of the downsizing, weight reduction, and cost reduction required by the application. is there.

  A first wire grid polarizer in which a plurality of first metal gratings are arranged on a substantially upper half of one main surface of the light-transmitting substrate at a predetermined period; and the same surface as the first wire grid polarizer and In the lower half, a second wire grid polarizer in which a plurality of second metal gratings are arranged with a predetermined period orthogonal to the periodic direction of the first wire grid polarizer, and the other main surface half of the substrate And a structural birefringence in which a first medium having a first refractive index and a second medium having a second refractive index are formed with a predetermined period. By using such a composite optical element for a polarized light source, the number of optical components can be reduced, and the polarized light source can be reduced in size and weight.

  A polarized light source comprising a light emitting light source, the composite wire grid polarizer, and a half-wave plate, wherein a part of the light flux from the light emitting light source passes through the first wire grid polarizer, The other part is reflected by the first wire grid polarizer, and the reflected light is incident on and transmitted to the second wire grid polarizer by the reflecting mirror provided in the light emitting light source. A polarized light source converted into the same polarized light by being converted by a half-wave plate arranged behind the child is configured. By configuring the image display polarized light source in this manner, the number of optical components can be reduced, and the image display polarized light source can be reduced in size, weight, and cost.

  A polarized light source including a light emitting light source and the above-described composite optical element, wherein a part of a light beam from the light emitting light source transmits a first wire grid polarizer of the composite optical element and the other part Is reflected by the first wire grid polarizer, and the reflected light is incident on and transmitted through the second wire grid polarizer by the reflecting mirror provided in the light emitting light source, and faces the second wire grid polarizer. The polarized light source is converted into the same polarized light by being converted by the structural birefringence. By configuring the polarization light source for image display using the above-described composite optical element, the number of optical components can be reduced, and the polarization light source for image display can be reduced in size, weight, and cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a configuration of a composite wire grid polarizer (composite polarizer) 1 according to the present invention. A plurality of metal gratings 3a having a width w1 and a thickness h1 that are long in the direction are arranged in parallel with the X-axis direction at a period p1 to form a first wire grid polarizer 1a. Then, on the same plane as the first wire grid polarizer 1a, a width w2 that is long in the Z-axis direction, orthogonal to the period p1 direction of the first wire grid polarizer 1a, substantially in the lower half of the Z-axis direction, A plurality of metal gratings 3b having a thickness h2 are arranged in parallel with the Z-axis direction at a period p2 to form a second wire grid polarizer 1b, and two orthogonal to each other on the main surface of the light-transmitting substrate 2 A composite wire grid polarizer 1 including wire grid polarizers 1a and 1b is configured.

As the light-transmitting substrate 2, optical glass, crystal, polymer film such as polycarbonate, polyethylene, polyethylene terephthalate, polyvinyl chloride and the like can be used. Various metals are used as the material of the metal grid. For example, aluminum is often used because it is inexpensive and has good light reflection efficiency. As a method for forming the metal grid, a metal film having a predetermined thickness can be formed on the substrate using a vacuum deposition method, a sputtering method, or the like, and can be formed using a photolithography technique and an etching technique. . In addition, a submicron fine metal lattice forms an aluminum base of several nm on a substrate, and creates a resist pattern by electron beam drawing. Then, aluminum having a predetermined thickness is vapor-deposited, and unnecessary aluminum is selectively removed by lift-off to form a metal lattice. Further, the remaining base film other than the metal lattice is removed by etching.
Recently, a technology called nanoimprint has been developed that presses the mold against the resist film, transfers the pattern of the mold, removes the remaining resist film, and forms a metal film on it to form a metal lattice. Has been.

  As is well known, when the metal grid is formed with a sufficiently small period of about 1/5 or less with respect to the wavelength of the incident light, the action of the wire grid polarizer reflects the light of the electric field component that oscillates perpendicularly to the grid period direction. However, there is a characteristic that light of an electric field component that vibrates in parallel is transmitted. Therefore, as shown in FIG. 1, in the composite wire grid polarizer in which two wire grid polarizers 1a and 1b whose period directions are orthogonal to each other are formed on the same substrate, transmission and reflection polarization are performed in the upper half and the lower half. The light will be different from each other. When the composite wire grid polarizer 1 shown in FIG. 1 is used, the widths w1, w2, thicknesses h1, h2, and periods p1, p2 of the metal grids of the wire grid polarizers 1a, 1b are substantially equal. Is generally used.

  FIG. 2 is a schematic diagram showing the configuration of a polarized light source for image display using the composite wire grid polarizer 1 according to the present invention. The polarized light source for image display is a polarized light source including a light emitting light source 4, a composite wire grid polarizer 1, and a half-wave plate 7. The light emitting light source 4 includes a lamp 5 such as an ultra-high pressure mercury lamp or a xenon lamp and a reflecting mirror 6, for example, a parabolic reflecting mirror, and light emitted from the lamp 5 is substantially parallel to the optical axis of the parabolic reflecting mirror 6. It becomes light. The light emitted from the lamp 5 is natural light (random light), and can be represented by the sum of two orthogonal linearly polarized light (P-polarized light and S-polarized light) having the same intensity.

  The composite wire grid polarizer 1 shown in FIG. 2 is configured as shown in FIG. First, consider a case where a parallel light beam from the light source 4 is incident on the upper half of the composite wire grid polarizer 1. Of the parallel light flux, S-polarized light passes through the wire grid polarizer 1 a of the composite wire grid polarizer 1 and enters the liquid crystal panel 8. Of the parallel light flux, the P-polarized light is reflected by the wire grid polarizer 1 a, returns to the direction of the light emitting light source 4, is reflected twice by the parabolic reflector 6, and enters the lower half of the composite wire grid polarizer 1. The wire grid polarizer 1b formed in the lower half of the composite wire grid polarizer 1 transmits P-polarized light because the periodic directions are perpendicular to the wire grid polarizer 1a formed in the upper half. Then, it is rotated 90 ° by the half-wave plate 7 arranged behind the composite wire grid polarizer 1, converted into S-polarized light, and incident on the liquid crystal panel 8.

Next, consider the case where the parallel light beam from the light source 4 is incident on the lower half of the composite wire grid polarizer 1. Of the parallel light flux, the P-polarized light passes through the wire grid polarizer 1 b of the composite wire grid polarizer 1 and enters the liquid crystal panel 8. Then, the light is converted into S-polarized light by a half-wave plate disposed at the rear and is incident on the liquid crystal panel 8.
Of the parallel light flux, the S-polarized light is reflected by the wire grid polarizer 1 b, returns to the direction of the light emitting light source 4, is reflected twice by the parabolic reflector 6, and enters the upper half of the composite wire grid polarizer 1. The wire grid polarizer 1 a formed in the upper half of the composite wire grid polarizer 1 transmits S-polarized light and enters the liquid crystal panel 8.

  In the composite wire grid polarizer according to the present invention, wire grid polarizers whose periodic directions are orthogonal to each other are formed on the same substrate, so that it is possible to reduce the number of optical components when configuring a polarized light source for image display. It is also effective in reducing the size and thickness.

FIG. 3A is a cross-sectional view of a planar composite optical element 10 according to the present invention, and a wire grid polarizer 11 orthogonal to each other as shown in FIG. 12 are formed in the lower half of the main surface on the right side of the figure, as shown in FIG. 3C. The optical wave plate using the structural birefringence of the dielectric includes a first medium 1 (first refractive index n ₁ ) and a second medium 2 (second refractive index n ₂ ) having different refractive indexes. The first medium 1 and the second medium 2 form a refractive index periodic structure in which the boundary surface A changes periodically. In a region where the wavelength λ is sufficiently smaller than the pitch p, the refractive index na for polarized light parallel to the periodic structure groove (boundary surface A) and the refractive index nb in the direction perpendicular to the groove have different values. The periodic structure functions as a birefringent crystal. The refractive indexes na and nb are given by the following equations using the refractive indexes n ₁ and n ₂ of the media 1 and ₂ .
na = {n ₁ ² + n ₂ ² (1-q)} ^1/2 (1)
nb = {(1 / n ₁ ) ² q + (1 / n ₂ ) ² (1-q)} ^−1/2 (2)
Here, q is w / p. The birefringence magnitude Δn is given by the following equation.
Δn = | na−nb | (3)
Further, the phase difference (delay amount) Re between the light whose polarization direction is parallel to the grooves of the periodic structure and the light perpendicular thereto is d, where the depth of the periodic structure is d
Re = dΔn (4)
It becomes. The half-wave plate functions as a half-wave plate not only when the phase difference is ½ of the wavelength, but also when it is an odd multiple of ½ wavelength.

A composite optical component in which two mutually orthogonal wire grid polarizers are formed on one surface of a parallel flat optical glass as shown in FIG. 3 and a half-wave plate using structural birefringence is formed on the other half. By using this, the polarized light source can be reduced in size.
As described above, when a composite optical element in which two wire grid polarizers orthogonal to each other are formed on one surface and a half-wave plate having a structural birefringence is formed on the other half, polarization for image display is used. In constructing the light source, it is possible to reduce the number of optical components, and it is effective for miniaturization and thinning.

Schematic which showed the structure of the composite wire grid polarizer which concerns on this invention. Schematic which showed the structure of the polarized light source for image displays which concerns on this invention. (A) is sectional drawing of the composite optical component which concerns on this invention, (b) is a top view of one surface, (c) is detailed sectional drawing of the other surface. (A) is a side view of a liquid crystal display device, (b) is an enlarged view of a light source part. Schematic which showed the structure of the wire grid polarizer. (A) is a figure before extending | stretching a polarizer, (b) is a figure which shows a polarizer. The figure which shows the polarized light source which consists of a polarizer, a light source, and a diffusive reflecting plate. The figure which shows the polarized light source which consists of a polarizer, a light source, and a phase difference plate. The side view which shows the structure of a polarizer.

Explanation of symbols

  1 Composite wire grid polarizer, 1a, 1b, 11, 12 Wire grid polarizer, 2 Substrate, 3a, 3b Metal grid, w1, w2 Metal grid width, h1, h2 Metal grid thickness, p1, p2, Metal Period of grating, 4 light source, 5 lamp, 6 reflector, 7 1/2 wavelength plate, 8 liquid crystal panel, 9a, 9b polarizing plate, 10 composite optical component, 13 structure birefringence, p structure birefringence period, w medium 1 width, n1 medium 1 refractive index, n2 medium 2 refractive index

Claims (7)

A first wire grid polarizer comprising a plurality of first metal gratings arranged in a predetermined period within a substantially upper half of the main surface of the light transmissive substrate;
A second wire grid comprising a plurality of second metal gratings arranged in a predetermined cycle in a state orthogonal to the periodic direction of the first wire grid polarizer within a range of substantially the lower half of the light transmissive substrate. A polarizer,
A composite wire grid polarizer characterized by comprising:   The composite wire grid polarizer according to claim 1, wherein quartz is used as a material of the light transmissive substrate.   The composite wire grid polarizer according to claim 1, wherein optical glass is used as a material of the light transmissive substrate.   The composite wire grid polarizer according to claim 1, wherein a polymer film is used as the light transmissive substrate. A first wire grid polarizer comprising a plurality of first metal gratings arranged in a predetermined cycle within a substantially upper half of one main surface of the light transmissive substrate;
A plurality of second arrays arranged at a predetermined cycle in a state orthogonal to the periodic direction of the first wire grid polarizer, in the same plane as the first wire grid polarizer and in a substantially lower half range thereof. A second wire grid polarizer comprising a metal grid;
A first medium having a first refractive index and a second medium having a second refractive index are within a predetermined period within a range approximately half of the other main surface of the light transmissive substrate. The formed structural birefringence,
A composite optical element comprising: A polarized light source comprising a light emitting source, the composite wire grid polarizer according to claim 1, and a half-wave plate,
A part of the light flux from the light emitting light source is transmitted through the first wire grid polarizer, and the other part is reflected by the first wire grid polarizer, and the reflected light is reflected by the light emitting light source. A polarized light source characterized in that it is incident on and transmitted through a second wire grid polarizer by a mirror and converted by a half-wave plate disposed behind the second wire grid polarizer to be the same polarized light. . A polarized light source comprising: a light emitting source; and the composite optical element according to claim 5,
A part of the light flux from the light emitting light source passes through the first wire grid polarizer of the composite optical element, the other part is reflected by the first wire grid polarizer, and the reflected light is transmitted to the light emitting light source. It is characterized in that it is incident on and transmitted through the second wire grid polarizer by the reflecting mirror provided and converted by the structural birefringence provided on the surface facing the second wire grid polarizer to be the same polarized light. A polarized light source.

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