JP2005062241A - Polarization conversion element, method for manufacturing polarization conversion element, and projection type liquid crystal display device - Google Patents

Abstract

A polarization conversion element having excellent heat resistance, a method for manufacturing the same, and a projection type liquid crystal display device including such a polarization conversion element.
A line having a groove width (W) of 50 to 120 nm and a groove depth (H) of 30 to 120 nm is formed on the surface of a rectangular glass substrate 11 having a thickness of 0.1 to 2 mm and a side of 10 to 100 mm. The groove portion 12 is provided with a stripe-shaped groove portion 12 having a groove pitch (P) of 50 to 180 nm, parallel to each other and equally spaced, and having a density of 8 to 20 lines / μm. A polarization conversion element 10 filled with aluminum as a functional substance.
[Selection] Figure 2

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
In recent years, a projection type liquid crystal display device that directly projects electronic data has been used in place of a slide projector and an overhead projector (OHP) that have been conventionally used as a device for enlarging and projecting onto a screen against the background of an advanced information society. Projection-type liquid crystal display devices improve the projection lens, improve the high-intensity lamp, and the liquid crystal panel in order to display particularly bright and high-definition images because the illuminance of the projected image is improved and projection is possible even in a bright room Improvement of an integrator lens for uniformly illuminating the light, or improvement of a polarization conversion optical system for improving the light utilization efficiency by aligning the polarization direction is being promoted.
[0003]
Among them, a high-intensity lamp such as an ultra-high pressure mercury lamp is used to improve the illuminance of the projected image, but this requires the heat resistance of optical elements such as lenses and polarization conversion elements to be increased. As a polarization conversion element, a wire grid type polarization conversion element in which a large number of fine metal wires are fixed on a substrate of a light transmitting material has been developed.
[0004]
FIG. 4 is a diagram for explaining such a wire grid type polarization conversion element. The wire grid type polarization conversion element 90 shown in FIG. 4 includes a substrate 91 made of a light transmissive material, and a fine metal wire grid 92 fixed on the substrate 91. A large number of wire grids 92 having a width of about 100 nm are provided in parallel at intervals of about 100 nm. The wire grid type polarization conversion element 90 is formed by forming a metal layer such as aluminum on the substrate 91 by an evaporation method or a sputtering method, and performing an etching process on the metal layer. 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 a substrate is hardened using a material having a refractive index comparable to that of the substrate (see, for example, Patent Document 1 and Patent Document 2).
[0005]
[Patent Document 1]
JP-T-2003-502708 [Patent Document 2]
Japanese Patent Laid-Open No. 10-153706 [0006]
[Problems to be solved by the invention]
However, in such a wire grid type polarization conversion element, in order to form a fine metal wire grid on a substrate as a support, it is necessary to perform an etching process for each metal layer formed by sputtering or the like. There is a problem that the manufacturing cost is high and mass production is impossible.
[0007]
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 comparable 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 causes a problem in reliability.
[0008]
As described above, the present invention has been made to solve the problem which has been highlighted when developing a projection type liquid crystal display device using a wire grid type polarization conversion element.
That is, an object of the present invention is to provide a polarization conversion element having excellent heat resistance.
Another object of the present invention is to provide a method for producing a polarization conversion element having excellent heat resistance.
Furthermore, another object of the present invention is to provide a projection type liquid crystal display device provided with a polarization conversion element having excellent heat resistance.
[0009]
[Means for Solving the Problems]
In order to solve this problem, the present invention adopts a configuration in which a light-transmitting substrate provided with a number of stripe-shaped grooves in advance is integrally formed and a metal wire is embedded in the grooves. That is, the polarization conversion element of the present invention includes a substrate having a surface on which a plurality of linear grooves having a predetermined depth and width are formed in parallel with each other at equal intervals, and the grooves provided in this way. And a light-shielding substance to be filled.
[0010]
If the thickness of the light-shielding material filling the groove is equal to or less than the depth of the groove, the thickness of the light-shielding substance is caused by damage to the metal wire grid as in the conventional wire grid type polarization conversion element. The problem of performance degradation is solved.
[0011]
Further, if the substrate on which the groove portion is provided in advance is formed from a heat-resistant synthetic resin or glass, it is possible to prevent the performance of the polarization conversion element from being deteriorated even when used for a long time at a high temperature.
[0012]
Further, if the light-shielding material filling the groove is aluminum, aluminum alloy, silver or silver alloy, an efficient light-shielding effect can be obtained, and the light-shielding material can be used after being used at a high temperature for a long time. Is prevented from peeling from the substrate.
[0013]
Furthermore, if the polarization conversion element of the present invention further includes an antireflection film formed on the surface opposite to the surface provided with the stripe-shaped groove portion, the polarization efficiency of incident light can be increased. Can do.
[0014]
On the other hand, a polarization conversion element to which the present invention is applied has a substrate formed of a light-transmitting material and a large number of linear metal wires embedded in parallel at equal intervals on the surface of the substrate. The density of the metal wires on the surface of such a substrate is characterized by being 8-20 wires / μm, and by having a structure in which the metal wires are embedded in the substrate, the heat resistance is excellent, Stable polarization performance can be obtained.
[0015]
Next, in the method for manufacturing a polarization conversion element to which the present invention is applied, a substrate having a surface in which a large number of linear grooves having a predetermined depth and width are formed in parallel with each other at equal intervals is formed. A substrate forming step, and a metal layer forming step of filling a groove portion with a light-shielding substance and forming a metal layer having a predetermined thickness on the surface of the substrate thus formed with the groove portion; A polishing step of polishing the metal layer formed on the metal layer, leaving a light-shielding substance filling the groove, and removing the other metal layer portions.
[0016]
In particular, if the metal layer forming step in the method for manufacturing a polarization conversion element 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 is uniform. A metal layer can be formed.
[0017]
The present invention also provides a light source lamp, a polarization conversion element that polarizes and separates light from the light source lamp, a liquid crystal panel that transmits light polarized by the polarization conversion element, and light that has passed through the liquid crystal panel. A polarization conversion element provided in the projection lens, and a light shielding material filled in a large number of stripe-shaped grooves provided on a substrate made of a light-transmitting material. With this feature, the contrast and brightness of the projected image can be improved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining a projection type liquid crystal display device to which the present embodiment is applied. A three-plate liquid crystal projector 100 that is a projection type liquid crystal display device shown in FIG. 1 includes a white light source 30 of a light source lamp, integrator lenses 21 and 22, and a polarization conversion element 10 that separates white light 31 into S-polarized light and P-polarized light. The dichroic mirrors 51 and 52 for separating the white light 31 into three light beams having different wavelengths, the three liquid crystal panels 61, 62 and 63 through which the three light beams respectively transmit, and the dichroic for synthesizing the separated light beams. A prism 45 and a projection lens 70 are provided. Furthermore, it has mirrors 41, 42, 43 and 44 and relay lenses 23 and 24 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 an elliptical mirror that collects light from the high-intensity lamp.
[0019]
Next, the polarization conversion element 10 will be described. FIG. 2 is a diagram for explaining a polarization conversion element to which the present embodiment is applied. A polarization conversion element 10 shown in FIG. 1 includes a substrate 11 having a large number of grooves 12 formed thereon, and these grooves 12 are filled with a light-shielding substance. The material for forming the substrate 11 is not particularly limited as long as it is a light-transmitting material. For example, polycarbonate resin, acrylic resin, methacrylic resin, polystyrene resin, vinyl chloride resin, epoxy resin, polyester resin, polyimide, poly Synthetic resins such as ether imide, polyether sulfone, phenol resin, norbornene amorphous polyolefin resin; and glass such as blue plate glass, white plate glass, and sapphire glass. Among these, polycarbonate resin, norbornene amorphous polyolefin resin, polyimide, and the like are preferable because of good heat resistance. Polycarbonate resins are preferred because of their high light transmittance.
[0020]
The thickness of the board | substrate 11 is 0.1-2 mm normally, Preferably, it is 0.7-1.1 mm. The shape and external dimensions of the substrate 11 are appropriately selected according to the mode to be used, and are not particularly limited. Usually, a rectangle or a square having a side of 10 to 100 mm, a circle or an ellipse having a diameter of 5 to 100 mm, and the like can be given. It is done.
[0021]
The groove 12 formed in the upper part of the substrate 11 usually has a linear shape with a groove width (W) of 50 to 120 nm and a groove depth (H) of 30 to 120 nm. On the substrate 11, a large number of groove portions 12 are usually provided at equal intervals in parallel with each other at intervals of a groove pitch (P) of 50 to 180 nm, and the density thereof is 8 to 20 lines / μm. is there.
[0022]
The light-shielding substance that fills the groove 12 formed on the upper portion of the substrate 11 is not particularly limited as long as it is a substance that shields light, and usually includes metals, semiconductor materials, and the like. Among these, aluminum, silver, an aluminum alloy, a silver alloy, and the like are particularly preferable because they have a large refractive index and large light absorption. In particular, since aluminum has a high thermal conductivity, the polarization conversion element 10 using aluminum as a light-shielding substance has excellent heat resistance. For example, after standing at 400 ° C. for 1 hour, appearance and performance change. can not see. Further, when such a polarization conversion element 10 is incorporated in the three-plate liquid crystal projector 100, the polarization conversion element 10 is placed in a temperature atmosphere of about 150 to 200 ° C., and therefore when a normal heat resistant resin is used. Better heat resistance.
[0023]
Moreover, when using a metal as a light-shielding substance, 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 that the refractive index and thickness are adjusted according to the film forming conditions, and the reflectance is reduced in a desired wavelength range.
[0024]
In the polarization conversion element 10 to which this exemplary embodiment is applied, it is preferable to provide an antireflection film on the surface of the substrate 11 opposite to the surface on which the groove 12 is formed. As a material for forming the antireflection film, a compound selected from metals, metal oxides and metal fluorides is usually mentioned. 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.
[0025]
The polarization conversion element 10 to which this exemplary embodiment is applied has a structure in which a light shielding material is filled in a groove portion 12 formed integrally with a substrate 11, so that, like a conventional wire grid type polarization conversion element, The problem of performance degradation due to breakage of the metal wire grid is eliminated. Further, since the groove portion 12 is integrally formed with the substrate 11, the light shielding material filled in the groove portion 12 does not peel off from the substrate 11 even when used for a long time at high temperature, and has high heat resistance.
[0026]
Next, a method for manufacturing the polarization conversion element 10 will be described. FIG. 3 is a diagram for explaining a method of manufacturing the polarization conversion element 10. As shown in FIG. 3A, a substrate 11 having a large number of grooves 12 formed thereon 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.
[0027]
Next, as shown in FIG. 3B, a metal layer 13 is formed so as to cover the groove 12 of the substrate 11 formed in this way. For example, the metal layer 13 is formed by depositing a metal such as Al, Al alloy, Ag, or Ag alloy on the surface of the substrate 11 on which the groove 12 is provided by a vapor phase method such as a vacuum evaporation method or a sputtering method.
[0028]
Subsequently, as shown in FIG. 3C, the surface of the metal layer 13 formed so as to cover the groove 12 of the substrate 11 is removed by polishing or chemical etching, and the groove 12 is filled with a metal light-shielding substance. The manufactured polarization conversion element 10 is manufactured. The method of polishing is not particularly limited, and examples thereof include a method of using a sheet for polishing optical components and performing polishing by applying a uniform load from the back surface of the substrate 11. At this time, it is preferable to use a polishing aid such as a slurry.
[0029]
Next, the operation of the three-plate liquid crystal projector 100 will be described. Since the white light 31 from the white light source 30 is condensed by the elliptical mirror, the brightness is uneven, and this is made uniform by dividing and synthesizing the luminous flux of the white light 31 using the integrator lenses 21 and 22. . The white light 31 having a uniform luminous flux is further aligned with linearly polarized light in the same direction by the polarization conversion element 10. Thereby, the loss of the liquid crystal panels 61, 62, 63 can be reduced. The white light 31 that has passed through the polarization conversion element 10 and turned back through the optical path by the mirror 41 is divided by the dichroic mirrors 51 and 52 into three parts of blue light 32, green light 33, and red light 34. The optical path is turned back by 43 and 44, and the liquid crystal panels 61, 62 and 63 are irradiated with these three lights. The three lights transmitted through the liquid crystal panels 61, 62, and 63 are combined again by the dichroic prism 45 and projected onto the screen 80 via the projection lens 70.
[0030]
【Example】
Hereinafter, this embodiment will be specifically described based on examples. The present embodiment is not limited to the examples.
[0031]
(Example 1)
On a glass substrate having a thickness of 1.0 mm, a groove portion having a groove width of 100 nm and a groove depth of 50 nm is formed with a preformat in which a groove pitch is 170 nm and provided in parallel at equal intervals. An antireflection film in which two layers of Ta ₂ O ₅ / SiO ₂ were laminated was formed on the opposite surface. Next, an Al film having a thickness of 70 nm was formed on the surface of the glass substrate provided with the groove by sputtering so as to fill the groove and further 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 100 shown in FIG. 1, and a 1000 hour projection experiment was performed. 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.
[0032]
(Example 2)
A 200 nm pitch line-and-space pattern was previously formed on the Cr 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.
[0033]
In addition, an antireflection film was formed with two layers of Ta ₂ O ₅ / SiO ₂ on the surface opposite to the groove. Thereafter, an Al film having a thickness of 70 nm was formed on the substrate preformat, and then only the Al metal embedded in the groove portion of the substrate was left, and the excess portion was removed by polishing. For polishing, a sheet for polishing optical parts was used, and the load was applied uniformly from the back surface of the substrate.
[0034]
The polarization conversion element thus prepared was attached to the three-plate liquid crystal projector 100 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.
[0035]
【The invention's effect】
Thus, according to the present invention, a polarization conversion element and the like excellent in heat resistance are provided.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a projection-type liquid crystal display device.
FIG. 2 is a diagram for explaining a polarization conversion element;
FIG. 3 is a diagram for explaining a method of manufacturing a polarization conversion element.
FIG. 4 is a diagram for explaining a conventional wire grid type polarization conversion element;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Polarization conversion element 11, 91 ... Board | substrate, 12 ... Groove part, 13 ... Metal layer, 21, 22 ... Integrator lens, 23, 24 ... Relay lens, 30 ... White light source, 31 ... White light, 32 ... Blue light, 33 ... Green light, 34 ... Red light, 41, 42, 43, 44 ... Mirror, 45 ... Dichroic prism, 51, 52 ... Dichroic mirror, 61, 62, 63 ... Liquid crystal panel, 70 ... Projection lens, 80 ... Screen, 90 ... Wire grid type polarization conversion element, 92 ... Wire grid

Claims (9)

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;
A light-shielding substance filling the groove,
A polarization conversion element comprising: The polarization conversion element according to claim 1, wherein a thickness of the light shielding material is equal to or less than a depth of the groove. The polarization conversion element according to claim 1, wherein the substrate is made of a heat-resistant synthetic resin or glass. The polarization conversion element according to claim 1, wherein the light-shielding substance is aluminum, an aluminum alloy, silver, or a silver alloy. The polarization conversion element according to claim 1, further comprising an antireflection film formed on a surface of the substrate opposite to the surface on which the groove is formed. A substrate formed of a light transmissive material;
A number of linear metal wires embedded in parallel to each other at equal intervals on the surface of the substrate,
The polarization conversion element, wherein the density of the metal wires on the surface of the substrate is 8 to 20 wires / μm. A substrate forming step of forming a substrate having a surface in which a number of linear grooves having a predetermined depth and width are parallel to each other and formed at equal intervals;
A metal layer forming step of filling the groove portion with a light-shielding material and forming a metal layer having a predetermined thickness on the surface of the substrate formed by the substrate forming step;
Polishing the metal layer formed by the metal layer forming step, leaving the light-shielding substance filling the groove, and removing the metal layer;
A method for producing a polarization conversion element comprising: 8. The polarization conversion element according to claim 7, wherein in the metal layer forming step, the metal layer made of a light shielding material is formed by a vapor phase method on a surface of the substrate on which the groove is provided. Production method. A light source lamp,
A polarization conversion element for polarizing and separating light from the light source lamp;
A liquid crystal panel that transmits light polarized by the polarization conversion element;
A projection lens that projects light transmitted through the liquid crystal panel onto a screen;
The projection type liquid crystal display device, wherein the polarization conversion element is formed by filling a plurality of stripe-shaped grooves provided on a substrate made of a light transmitting material with a light shielding material.

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