JP2006003447A - Polarized light separating element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarized light separating element capable of relatively easily forming a large-area diffraction grating with a simple step without requiring a high-level technology such as high-precision mask alignment, and to provide a manufacturing method of the polarized light separating element. <P>SOLUTION: The polarized light separating element is constituted such that a rugged pattern 2 constituting the diffraction grating is formed on the surface of a base material 1 made of material having light transmissivity in the usage wavelength range and at least two or more surfaces of protruded parts 3 of the rugged pattern 2 are covered with a film 4 made of material comprising a metal or a metal compound. Therein, the large-area diffraction grating can be simply and precisely formed according to oblique vapor deposition in twice. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarization separation element formed by producing a metal diffraction grating (Wire Grid) and a method for manufacturing the same, and for example, a wire grid polarizer (Wire Grid Polarizer) on a plastic film substrate has a relatively large area. The present invention relates to a polarization separation element and a method for manufacturing the polarization separation element that can provide an inexpensive polarization separation element.

As the polarization separation element, a device utilizing the Brewster reflection angle of a thin film is often used, but this requires a laminated film in which thin films are laminated in multiple layers, and also requires accuracy of the incident angle. The manufacturing process is complicated and it is difficult to reduce the cost, and when it is incorporated in an optical device, it is necessary to accurately place the incident angle at the set angle, and the alignment adjustment greatly affects the polarization separation characteristics, so assembly accuracy is required. There is a problem that.
In contrast to such a conventional polarization separation element, a wire grid type polarization separation element that performs polarization separation by arranging diffraction gratings (wire grids) made of metal at intervals smaller than the wavelength of light has been proposed.

As such a wire grid polarization separation element, there is a polarization separation element in which a diffraction grating made of a metal film is formed on a glass substrate by mask patterning and dry etching by electron beam lithography or interference exposure on a glass substrate. Known (for example, see Patent Documents 1 and 2).
This polarization separation element forms a diffraction grating by forming a 90 nm-width Al wire (pitch 144 nm, height 100 to 200 nm) on a glass substrate. There has also been proposed a polarization separation element in which a diffraction grating made of a metal or a metal compound is formed on a quartz substrate (see, for example, Patent Document 3).
Attempts have also been made to produce nano-sized metal wires (nanowires) by oblique vapor deposition. For example, a nano-sized line on the side wall is realized by vapor deposition on a stepped portion of a glass substrate (see Non-Patent Document 1, for example), or a nanowire such as Pd or Au is formed on an InP substrate by oblique vapor deposition. There is also a report of an example of forming (see Non-Patent Document 2, for example).
In addition, a polarization separation element using a multilayer film has been commercialized (for example, see DBEF: trade name, Non-Patent Document 3 manufactured by 3M USA).

US Pat. No. 6,122,103 US Pat. No. 6,243,199 JP 2004-45672 A D.E.Prober et al, “Fabrication of 300-Å metal lines with substrate-step techniques.”, Applied.Physics.Letters, .Vol.37 (1), (1980) pp.94-96 J. Jorritsma, “General technique for reducing large arrays of nanowires.”, Nanotechnology, Vol. 7, No. 3, (1996) pp.263-265 USA 3M company homepage [2004 date search], Internet <URL: http://www.mmm.co.jp/display/dbef/>

The conventional polarization separation element has a problem in terms of providing a large-area, inexpensive, and lightweight device. In any case, a heavy substrate is used, and there is a problem in terms of weight when used as a polarization separation element for improving luminance used in a large area display (for example, a liquid crystal display). Weight reduction becomes difficult.
In the case of the polarization separation element using the above-mentioned multilayer film, it is excellent in terms of light weight and large area, but it becomes very expensive due to the multilayer structure of several hundred layers, and this polarization separation element There is a problem of incurring high costs for optical devices and display devices incorporating the above.

By the way, as described in Patent Documents 1 and 2, it is known that the characteristics of the wire grid polarization separation element vary greatly depending on the height and pitch of the metal diffraction grating. Therefore, accurate patterning is required by lithography or metal film dry etching. It is difficult to perform these processes in a large area in terms of cost and technology. For example, patterning a metal film on a plastic film by dry etching is much more technically difficult than forming it on a glass or quartz substrate.
In addition, the attempt to manufacture by oblique vapor deposition disclosed in Non-Patent Documents 1 and 2 described above has realized that a nano-sized wire is manufactured, but a method of forming a completed nanowire shape with good controllability. Is currently not being considered.

  In view of the above-described problems, the present invention is a polarization capable of forming a diffraction grating over a large area relatively easily without requiring an advanced technique such as mask alignment accuracy in a simple process by technical ingenuity. An object of the present invention is to provide a separation conversion element and a method for manufacturing the same.

In order to solve the above problems, the polarization separation element according to the present invention is provided with a concavo-convex pattern constituting a diffraction grating on the surface of a base material made of a light-transmitting material in the operating wavelength range. It is characterized in that at least two surfaces of the part are covered with a material film made of a metal or a metal compound.
Further, according to the present invention, in the polarization separation element described above, the material film has a multilayer structure, and is oxidized on the outermost surface as compared with the thickest metal layer or metal compound layer provided in the multilayer structure. A difficult metal or metal compound is formed into a film.

In the method for manufacturing a polarization separation element according to the present invention, a concavo-convex pattern constituting a diffraction grating is formed on the surface of a base material made of a light-transmitting material in a used wavelength range, and at least convex portions of the concavo-convex pattern are formed. A material layer made of a metal or metal compound film is formed on two or more surfaces by an oblique incidence vapor deposition method.
Furthermore, the present invention is characterized in that, in the above-described method for manufacturing a polarization separation element, the uneven pattern on the substrate is formed by an imprint method.

According to the above-described polarization separation element of the present invention, two or more surfaces on the convex portions of the concavo-convex pattern constituting the diffraction grating are coated with a material film made of a metal or a metal compound, thereby reducing the cost and weight. It is possible to provide a practical polarization separation element that can be increased in area.
In addition, by forming a material film as a multilayer structure and forming a metal or metal compound that is relatively difficult to oxidize on the outermost surface, it is possible to prevent the metal diffraction grating from being oxidized and to prolong the life. it can.

In addition, according to the method for manufacturing a polarization separation element of the present invention, the shape of the diffraction grating, such as the width and pitch, can be produced on a substrate such as a large-area plastic film with good controllability. Productivity can be improved and costs can be reduced.
Furthermore, in the method for manufacturing a polarization separation element of the present invention, a diffraction grating having a desired interval can be easily and accurately formed by forming a concavo-convex pattern by an imprint method, and has a desired polarization separation function. A polarization separation element can be easily manufactured.

Hereinafter, an example of the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1A is a schematic cross-sectional view of an essential part of an example of a polarization beam splitting element according to the present invention, and FIG. 1B is a schematic perspective view of an essential part of an example of a polarization beam splitting element according to the present invention.
As shown in FIGS. 1A and 1B, the polarization separation element according to the present invention is provided with a concavo-convex pattern 2 constituting a diffraction grating 10 on a base material 1 such as a plastic film having light transmittance in a used wavelength range. The material film 4 made of a metal or a metal compound is formed on two or more surfaces of the convex portion 3 of the concave / convex pattern 2.

In this way, by forming a concavo-convex pattern constituting a diffraction grating on a base material such as a plastic film, and providing a diffraction grating in which two or more surfaces on the convex portion are coated with a metal film, for example, visible When the diffraction grating 10 having a shorter period than the wavelength of light is provided, it functions as a polarization separation element for visible light incident from above the substrate 1.
In the present invention, it is also possible to use a plastic as a base material, and by configuring the diffraction grating with a metal film, it becomes easier to control the shape of the diffraction grating, resulting in a periodic structure of the diffraction grating, etc. Can be manufactured with high accuracy.
In addition, it is possible to manufacture a polarization separation element that is technically easy and inexpensive in comparison with a conventional method in which a metal film is etched by a dry etching method to produce a diffraction grating.

2A to 2C show a manufacturing process of an example of a method for manufacturing a polarization beam splitting element according to the present invention.
On the surface of the base material 1 made of a plastic film or the like, for example, a concavo-convex pattern 2 constituting a diffraction grating having a period shorter than the wavelength of visible light is formed. For the production of the concave / convex pattern 2, it is preferable to use an imprint method. When the imprint method is applied, diffraction gratings having a desired interval can be easily formed from nano size to micron size. In this example, an example in which an uneven pattern having a rectangular cross section is formed is shown.
Next, as shown in FIG. 2B, a material film 4 made of a metal or a metal compound is formed on the convex portion 3 of the concave / convex pattern 2 from an oblique direction as shown by an arrow S1 by a vacuum deposition method. The vapor deposition direction S1 at this time is a direction that forms a predetermined angle with the normal direction with respect to the surface of the substrate 1 indicated by the alternate long and short dash line v.
Subsequently, as shown in FIG. 2C, similarly, a normal angle v is formed with respect to the surface of the substrate 1, and a direction symmetrical to the direction indicated by the arrow S1 (left side in the illustrated example). Thus, as shown by the arrow S2, the material film 4 is formed by vapor deposition.
Each of these deposition directions is a direction in which the incident surface of the metal particles of the material film 4 intersects substantially perpendicularly with respect to a straight line formed by the ridge line of the convex portion 3, that is, a direction orthogonal to the paper surface of FIG. By selecting this, it is possible to avoid deposition on the concave portions between the convex portions 3.
Through the above manufacturing process, the upper surface of the convex portion of the diffraction grating and the three surfaces on the left and right sides are covered with the metal film. As a result, a polarization separation element having a polarization separation function can be obtained for visible light incident from above the diffraction grating of the substrate 1.

FIG. 3 shows a schematic cross-sectional view of a main part of an example of the polarization separation element according to the present invention in which the diffraction grating has a triangular cross section. In FIG. 3, parts corresponding to those in FIG.
In this case, the imprint method can be applied with high accuracy as a method for producing a concavo-convex pattern having a triangular cross-sectional shape on the surface of the substrate 1. For example, as a mold used for imprinting, by using a mold having a triangular cross section obtained by performing anisotropic wet etching on Si, the interval between diffraction gratings can be accurately controlled.
And the convex part of the uneven | corrugated pattern 2 which comprises a diffraction grating similarly to the example demonstrated in above-mentioned FIG.2A-C with respect to the base material 1 which consists of a plastic film etc. which formed the uneven | corrugated pattern of triangular cross section in this way By obliquely depositing the material film 4 made of a metal or a metal compound from both the left and right directions with respect to the ridgeline 3, a polarization separation element having a desired polarization separation function can be obtained.
Thus, if processing to a substrate such as a plastic film is possible, it is not limited to the rectangular shape shown in FIG. 1, and a diffraction grating having another polygonal cross section, a curved cross section, or the like is configured. You can also.

Hereinafter, specific examples of the present invention will be described.
(1) Example 1
First, an example in which a diffraction grating having a rectangular cross section is formed on a plastic film will be described. In this example,
It was manufactured in the same manufacturing process as the example described in FIG. That is, the uneven | corrugated pattern 2 which has the convex part 3 with a width of 60 nm and a height of 100 nm was produced with the pitch of 200 nm on the surface of the base material 1 which consists of a 120-micrometer-thick PMMA (polymethylmethacrylate) film by the imprint method. The unevenness can also be produced by a dry etching method.

Next, from the direction that is 60 ° with respect to the height direction of the convex portion 3 (that is, the normal direction to the surface of the substrate 1) and that is substantially perpendicular to the direction in which the concave and convex pattern 2 extends, the Al metal The material film 4 was formed by flying particles by a vacuum deposition method. In this example, the material film 4 was formed on the side wall of the convex portion 3 so that the film thickness was about 30 nm.
In this case, the angle of the vapor deposition direction with respect to the normal direction was selected so that the material film 4 did not adhere to the concave portions of the concave / convex pattern 2. Further, the incident direction of the material film 4 was set to a direction substantially perpendicular to the ridge line direction of the convex portion 3.

  Subsequently, 60 ° is formed on the opposite side of the first vapor deposition direction with respect to the height direction of the convex portion 3, and the Al particles are similarly vacuumed from a direction substantially orthogonal to the extending direction of the concave / convex pattern 2. The material film 4 was formed by skipping by vapor deposition. The film thickness of the material film 4 at this time was also formed so that the film thickness of the material film 4 was about 30 nm on the side wall opposite to the convex portion.

Through the above manufacturing process, a structure in which the material film made of Al was coated on the upper part and both side walls of the diffraction grating convex portion on the surface of the PMMA film could be manufactured, and a polarization separating element having a wire grid type configuration could be obtained. In this example, of the light incident on the PMMA film, the S-polarized component parallel to the ridge line of the convex portion was reflected and the vertical P-polarized component was transmitted. The reflectance of S-polarized light was 95% or more in the visible light range, and the transmittance of P-polarized light was 80% or more in the visible light range.
As described above, in the manufacturing method of the present invention, it is possible to easily form a wire grid type polarization separation element using a plastic film that can be processed into any shape by forming a material film by oblique vapor deposition. It was. This makes it possible to realize a polarization splitting element that is large, lightweight, and inexpensive.

Next, an example of obtaining a polarization separation element having a diffraction grating having a triangular cross section will be described.
(2) Example 2
In this example, the polarization separation element having the structure described with reference to FIG. 3 was manufactured. In this case, a concavo-convex pattern of a diffraction grating having an isosceles triangular cross section with an apex angle of 70 ° was formed on the surface of the substrate 1 made of a PMMA film having a thickness of 120 μm by an imprint method. The mold used for imprint transfer is manufactured using anisotropic wet etching of the Si (100) surface. The difference in height between the peaks and valleys in this cross section was 150 nm. The pitch of the diffraction grating was 215 nm.

Next, a material film 4 made of Al is formed by an oblique deposition method from a direction that is approximately 60 ° from the normal to the surface of the base material 1 and that is substantially orthogonal to the ridge line in which the vertex of the isosceles triangle extends. . Thereafter, in the same manner as in Example 1, an Al material film was similarly formed from a direction symmetric with respect to the normal direction with respect to the first deposition direction. These film thicknesses were set to be approximately 35 nm. As a result, it was possible to obtain a polarization separating element having a wire grid type configuration in which a diffraction grating was configured by depositing metal on the left and right sides of the ridge line of the concavo-convex pattern having a substantially isosceles cross section. In this example, the reflectance of S-polarized light was 85% or more in the visible light range, and the transmittance of P-polarized light was 70% or more in the visible light range.

A diffraction grating having a triangular cross section has a manufacturing advantage because the performance as a polarization separating element is inferior to that of a rectangular cross section, but imprinting on a film is much easier than in the case of a rectangular cross section. This is because in the case of a triangular cross section, the indentation pressure is low and the mold release is easy.
As described above, according to the manufacturing method of the present invention, it is possible to configure the polarization separation element in a shape that is easier to manufacture, thereby improving the productivity of a large-area and lightweight polarization separation element and reducing the cost. Further reduction can be achieved.

  The present invention is not limited to the examples described above, and the dimensions, materials, process conditions, and the like of each part can be changed without departing from the gist of the present invention. For example, in the above-described example, an example in which a plastic film such as PMMA is used as the base material has been described. However, any other material having a desired light transmission property in the use wavelength range such as PET (polyethylene terephthalate) can be used. In addition, the material is not necessarily flexible, and various materials can be used.

Furthermore, the material film is not limited to Al, and various other metals or metal compounds such as TiN, TaN, TiSi ₂ can be used. In particular, in the case of using a material film such as Al that is easily oxidized, in order to protect this, for example, by laminating a metal thin film such as Au or Pt that is difficult to oxidize on the Al film, the optical characteristics of the material film are improved. It is possible to suppress deterioration and prolong the service life. In addition, it goes without saying that various modifications and changes can be made without departing from the configuration of the present invention, such as the provision of a base layer below the material film made of Al or the like.

It is a schematic sectional drawing of the principal part of an example of the polarization splitting element by this invention. FIG. 4A is a process diagram of an example of a method for manufacturing a polarization separation element according to the present invention. FIG. 4B is a process diagram of an example of a method of manufacturing a polarization separation element according to the present invention. C is a process diagram of an example of a method of manufacturing a polarization beam splitting element according to the present invention. FIG. It is a schematic sectional drawing of the principal part of an example of the polarization splitting element by this invention.

Explanation of symbols

1. Base material, 2. 2. Uneven pattern; Convex part, 4. Material film, 10. Diffraction grating

Claims (4)

A concave / convex pattern constituting a diffraction grating is provided on the surface of a base material made of a material having light permeability in the wavelength range used,
A polarization separation element, wherein at least two surfaces of the convex portions of the concave / convex pattern are covered with a material film made of a metal or a metal compound. The material film has a multi-layer structure, and a metal or metal compound that is difficult to oxidize is formed on the outermost surface of the material film as compared to the thickest metal or metal compound layer provided in the multi-layer structure. The polarization separation element according to claim 1, wherein the polarization separation element is formed. On the surface of the base material made of a material having optical transparency in the wavelength range used, an uneven pattern constituting the diffraction grating is formed,
A method for manufacturing a polarized light separating element, wherein a material layer made of a metal or a metal compound film is formed on at least two surfaces of convex portions of the concave / convex pattern by an oblique incidence vapor deposition method. 4. The method for manufacturing a polarization separation element according to claim 3, wherein the uneven pattern on the substrate is formed by an imprint method.

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