1. Field of the Invention
The present invention relates to an optical component such as a lens or a diffraction grating, and more particularly, to an optical component having a fine concave-convex shaped antireflection structure formed on the light incident surface thereof and a method of manufacturing the optical component.
2. Description of the Related Art
Various optical components such as lenses or diffraction gratings have antireflection structures arranged on the light incident surfaces. As examples of the antireflection structure, there are a structure formed by stacking a plurality of thin films having different refractive indices on the incident surface and a structure in which fine prominences and depressions are formed on the incident surface as disclosed in Japanese Unexamined Patent Application Publication No. 2003-222701, Japanese Unexamined Patent Application Publication No. 2005-181740, and Japanese Unexamined Patent Application Publication No. 2006-039450.
The above-described structure in which fine prominences and depressions are formed as the antireflection structure has advantages over the structure formed by stacking a plurality of thin films that the wavelength band of light that can be prevented from being reflected can be formed to be broad and light transmittance is high.
According to a method of manufacturing an antireflection structure having a fine concave-convex pattern on the incident surface of the optical component, a resist layer is formed on the surface of a mold, and the resist layer is partially exposed so as to be developed in accordance with the concave-convex pattern, so that a part of the resist layer remains. Then, the incident surface of the optical component is etched or milled in a portion in which the resist layer is eliminated, and thereby a transfer pattern having fine prominences and depressions on the surface of the mold is formed. When the optical component is formed by using the mold, the transfer pattern is transferred to the incident surface of the optical component, and thereby the antireflection structure is formed.
Since the pitch of the prominences and the depressions of the antireflection structure is fine, commonly, exposure is performed by scanning the surface of the resist layer using electron beams. In such a case, since the area of the range in which exposure can be performed using the electron beams is limited, it is necessary that the surface of the resist layer is divided into a plurality of areas, and the resist layer is exposed by scanning each area using the electron beams.
However, when the scanning range of the electron beams is changed from an area for which scanning is completed to an adjacent area, occurrence of an error in the relative transmission distance between the electron beam emitting unit and the mold cannot be avoided. Exposure areas between areas adjacent to each other overlap with each other due to the error, and a defective portion of the resist layer may be easily formed in the boundary portion of the areas adjacent to each other. When the defective portion is formed in the boundary portion of the areas, a problem of decreasing reflectance of light on the incident surface and the like may easily occur.
An advantage of some aspects of the invention is to provide an optical component capable of consistently maintaining high reflectance of light on the incident surface by preventing formation of a defective portion or the like in the boundary portion of a plurality of divided areas when the antireflection structure is formed on the light incident surface and a method of manufacturing the optical component.
According to an embodiment of the present invention, there is provided an optical component in which an antireflection structure is formed on a light incident surface or a light outgoing surface. The surface of the antireflection structure is divided into a plurality of areas, a plurality of protruded portions and a plurality of groove portions that linearly extend to be parallel to one another are formed on each of the areas by being alternately repeated, and in the areas that are adjacent to each other, the directions in which the protruded portions and the groove portions extend are different from each other by 90 degrees.
In the above-described optical component, the antireflection structure may include a portion in which the protruded portions extending in the directions different from each other by 90 degrees are connected together in a boundary portion of the areas that are adjacent to each other and a portion in which the groove portions extending in the directions different from each other by 90 degrees are connected together in the boundary portion of the areas that are adjacent to each other.
For example, each of the areas is a quadrilateral.
According to another embodiment of the present invention, there is provided a method of manufacturing an optical component including the steps of: forming a concave-convex transfer pattern on a surface of a mold; and forming an antireflection structure of a concave-convex shape by transferring the transfer pattern to a light incident surface of the optical component when the optical component is formed by using the mold. The antireflection structure to which the transfer pattern is transferred is divided into a plurality of areas, a plurality of protruded portions and a plurality of groove portions that linearly extend to be parallel to one another are formed on each of the areas by being alternately repeated, and in the areas that are adjacent to each other, the directions in which the protruded portions and the groove portions extend are different from each other by 90 degrees.
In the above-described method of manufacturing an optical component, the transfer pattern may be formed by forming a resist layer on a surface of the mold, allowing a part of the resist layer to remain by exposing the resist layer using electron beams so as to be developed, and eliminating the surface of the mold in a portion in which the resist layer does not exist.
For example, in the above-described method of manufacturing an optical component, the resist layer is exposed in units of areas by emitting the electron beams to the resist layer in units of the areas.
In the above-described method of manufacturing an optical component, the optical component may be formed by pressing an optical material using the mold, or the optical component may be formed by supplying a melted optical material to the inside of the mold and cooling the optical material.
According to an optical component according of an embodiment of the present invention, a light incident surface of a light outgoing surface is divided into a plurality of quadrilaterals, and more preferably, into a plurality of squares, protruded portions and groove portions are linearly formed to be parallel to each other in each area, and the directions of the protruded portions and the groove portions are orthogonal to each other in the adjacent areas. Accordingly, even when a slight error in the arrangement pitch of the areas occurs, formation of a defective portion having a large width in the boundary portion of the adjacent areas and the like can be prevented.
In addition, according to an optical component of an embodiment of the present invention, the directions of the protruded portions and the groove portions of the areas adjacent to each other are different by 90 degrees. Accordingly, a stable antireflection effect can be consistently exhibited regardless of the polarization direction of light that is incident to the incident surface or outgoing from the outgoing surface. In addition, since a large defective portion or the like cannot be formed on the boundary face of the areas adjacent to each other, a decrease in the antireflection efficiency due to a defective arrangement pitch of the areas can be suppressed.
In addition, according to a method of manufacturing an optical component of an embodiment of the present invention, the protruded portions and the groove portions having a fine pitch can be formed with high precision by using electron beams. Furthermore, an optical component capable of suppressing a decrease in the antireflection efficiency of the incident surface or the outgoing surface even in a case where there is a defect in the pitch of the areas can be manufactured.
The antireflection structure 1 shown in
For example, the optical component is formed by pressing heated glass with a mold. In such a case, a transfer pattern having fine prominences and depressions formed on the surface of the mold is transferred to the incident surface or the outgoing surface of the optical component, and thereby the above-described antireflection structure 1 is formed. Alternatively, the optical component may be formed by injecting an organic optical material into the inside of a melted mold. In such a case, a transfer pattern having fine prominences and depressions formed on the surface of the mold is transferred to the incident surface or the outgoing surface of the optical component, and thereby the above-described antireflection structure 1 is formed.
As shown in
In
As shown in
Both the width dimension of the protruded portions 11x and 11y and the width dimension of the groove portions 12x and 12y are in the range of about 100 nm to 500 nm. In addition, the depth dimension of the groove portions 12x and 12y and the width dimension of the protruded portions 11x and 11y are in the range of the same degree. The length dimension of one side of the first areas 2A and 2B is in the range of about 200 to 400 μm.
Next, a method of forming the above-described antireflection structure 1 in the optical component will be described.
Among molds that form the optical component, on the surface of a mold that transfers the incident surface or the outgoing surface, a resist layer is formed, and the resist layer is partially exposed by using an electron beam exposure device.
As shown in
As shown in
After exposure of the partition area 21 corresponding to the first area 2 and the partition area 31 corresponding to the second area 3 is completed in the almost entire area of the surface to which the incident surface of the mold is transferred, the process proceeds to a development process. When the resist layer is for the positive use, the resist layer of the photosensitive portion 24x is eliminated, and the resist layer of the non-photosensitive portion 25x remains. Then, the surface of the mold is etched or milled in the portion in which the resist layer is eliminated so as to eliminate the surface of the mold from the band-shaped area. Thereafter, by eliminating the remaining resist layer, a transfer pattern having fine prominences and depressions is formed on the surface of the mold.
By performing press molding of an optical material or injection molding of an optical material by using the above-described mold, the optical component is formed, and the antireflection structure 1 shown in
An antireflection structure 101 of a comparative example shown in
In the area 103, the protruded portion 111y and the groove portion 112y are alternately formed in the X direction. However, in the comparative example, in all the areas 103, the protruded portion 111y and the groove portion 112y linearly extend in the Y direction and are formed to be parallel to each other.
The antireflection structure of the comparative example is formed by using the same manufacturing method as that of the above-described embodiment. In other words, a resist layer is formed on the surface of the mold, and electron beams are emitted to the partition areas that are divided on the surface of the resist layer, whereby a photosensitive portion and a non-photosensitive portion are formed so as to extend in the Y direction. Then, after the photosensitive portions and the non-photosensitive portions are formed in all the partition areas that are adjacent to each other by moving the X-Y table and additionally performing exposure, the resist layer is developed. Then, fine prominences and depressions are formed on the surface of the mold by an etching or milling process, and by transferring the surface of the mold to the incident surface of the optical component, the antireflection structure 101 shown in
When the antireflection structure 1 of the embodiment of the present invention that is shown in
However, in a practical sense, generation of a defect in the arrangement pitch of the partition areas adjacent to each other cannot be avoided when the X-Y table is moved, and an adjacent partition area is exposed after completion of exposure of one partition area using electron beams.
As shown in
As a result, as shown in
For example, as shown in
In other words, in areas adjacent to each other, by mixing a portion in which protruded portions extending in the directions orthogonal to each other are connected and a portion in which groove portions extending in the directions orthogonal to each other, a large defect can be prevented from being formed in the boundary portion of the areas.
In both the antireflection structure 1 of the embodiment and the antireflection structure 101 of the comparative example, all the partitions 2, 3, and 103 have a square shape of 300 μm×300 μm. In addition, in both the embodiment and the comparative example, the width dimension of the protruded portion is 300 nm, the width dimension of the bottom of the groove portion is 200 nm, and the depth dimension of the groove portion is 300 nm.
Each antireflection structure was formed on the surface of a Si wafer, ultraviolet rays were vertically emitted to the antireflection structure, and reflectance was measured at a reflection direction of five degrees with respect to the emission direction by using a reflectometer.
In both the embodiment and the comparative example, ultraviolet rays of linearly polarized light were used. The wavelength was in the range of 400 nm to 700 nm. In
In the comparative example shown in
When the measurement results shown in
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims of the equivalents thereof.
Number | Date | Country | Kind |
---|---|---|---|
2008-176135 | Jul 2008 | JP | national |
This application is a Continuation of International Application No. PCT/JP2009/061441 filed on Jun. 24, 2009, which claims benefit of Japanese Patent Application No. 2008-176135 filed on Jul. 4, 2008. The entire contents of each application noted above are hereby incorporated by reference.
Number | Date | Country | |
---|---|---|---|
Parent | PCT/JP2009/061441 | Jun 2009 | US |
Child | 12972076 | US |