JP2011059180A - Optical element, method for manufacturing the same and fine irregularity structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce deformation and breakage of a fine irregularity structure by external force, contact or the like, and to prevent deterioration of optical performance such as reflection preventing effect. <P>SOLUTION: The fine irregularity structure 8 wherein recessed parts 5 are disposed to be enclosed by a ridge line part 3 continued in a net shape formed by top parts 2 of projecting parts 1 is formed along the surface of an optical element. A cross section of the projecting part 1 presents a recessed curve in both width direction so that the width Wh of the projecting part increases in the depth direction from the ridge line part 3 (projecting part 2). Since the projecting parts 1 are continued in a net shape, strength to deformation by external force and contact is high, a flat surface does not exist between recessed parts 5 and a satisfactory reflection preventing effect is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical element, a method for manufacturing the optical element, and a fine uneven structure.

In an optical system composed of optical elements, the reflection of incident light on the optical function surface of each optical element causes a loss of the incident light quantity and a decrease in optical performance due to unexpected scattering of the reflected light. It is not preferable.
Therefore, conventionally, an antireflection coating has been applied to the surface of an optical element such as a lens.

  In recent years, instead of anti-reflection coatings, surface non-reflection structures with various advantages such as the ability to suppress reflection of light in a wide wavelength band and a wide range of incident angles and integration with optical elements have been proposed. Has been.

  This surface non-reflective structure, that is, an antireflection structure is realized by forming fine irregularities having a wavelength equal to or less than the wavelength of incident light on the optical function surface of the optical element.

  For example, in Japanese Patent No. 4197100, a fine concavo-convex shape, which is an antireflection structure, is formed on the surface of a base material, and the peak shape of the convex portion of each isolated convex portion is sharper than the valley shape of the concave portion. Anti-reflection performance is improved by shape.

Japanese Patent No. 4197100

However, the following technical problems remain in the above-described conventional technology.
In other words, in an optical element in which each convex surface is formed on the substrate surface as an antireflection structure, it is deformed so that the fine convex portion of the antireflection structure collapses due to contact with an object or the like. As a result, the optical performance such as the antireflection effect may be deteriorated.

  An object of the present invention is to provide a technique capable of reducing deformation and breakage of a fine concavo-convex structure due to external force, contact, etc., and preventing deterioration of optical performance such as antireflection effect.

  A first aspect of the present invention includes a convex portion whose ridge line is continuous in a mesh shape, and a plurality of concave portions surrounded by the convex portion, in a cross section passing through the central portion of each of the plurality of adjacent concave portions. Provided is an optical element having a fine concavo-convex structure in which the width of the convex portion is curvedly increased in the depth direction of the concave portion.

  According to a second aspect of the present invention, there is provided an optical element manufacturing method for forming a fine concavo-convex structure including a plurality of concave portions surrounded by convex portions having ridge lines continuous in a mesh shape on the surface of the optical element.

  A third aspect of the present invention includes a convex portion whose ridgeline is continuous in a mesh shape and a plurality of concave portions surrounded by the convex portion, in a cross section passing through the central portion of each of the plurality of adjacent concave portions. Provided is a fine concavo-convex structure in which the width of the convex portion is curvilinearly increased in the depth direction of the concave portion.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can reduce the deformation | transformation and damage of the fine concavo-convex structure by external force, a contact, etc., and can prevent deterioration of optical performance, such as an antireflection effect, can be provided.

It is a schematic plan view which shows an example of the structure of the fine concavo-convex structure which is one embodiment of the present invention. It is sectional drawing which shows an example of a structure of the fine concavo-convex structure which is one embodiment of this invention. It is sectional drawing which expanded and illustrated the uneven | corrugated | grooved part of the fine concavo-convex structure which is one embodiment of this invention. It is a conceptual diagram which shows the example of a definition of the shape of the uneven | corrugated | grooved part in the fine concavo-convex structure which is one embodiment of this invention. It is a perspective view which shows an example of the optical element provided with the fine grooving | roughness structure which is one embodiment of this invention. It is a perspective view which shows the structural example of the optical element provided with the fine concavo-convex structure which is other embodiment of this invention. It is a flowchart which shows an example of the manufacturing method of the optical element provided with the fine concavo-convex structure which is one embodiment of this invention. It is a fragmentary sectional view showing the modification of the convex part of the fine concavo-convex structure which is one embodiment of the present invention.

  In the first aspect of the present embodiment, as an example, in an optical element in which a fine concavo-convex shape is formed on the surface of a substrate, a convex portion is continuously formed, and in a cross section passing through the center line of the adjacent concave portion, the concave portion The maximum value of the distance maximum portion adjacent to the central portion is smaller than the visible light wavelength, and the convex-concave structure has a fine concavo-convex structure in which the convex portion width increases in a depth direction.

  In the optical element according to the first aspect, the convex portions are continuously formed, and the maximum value of the adjacent distance maximum portions of the central portions of the concave portions is smaller than the visible light wavelength in a cross section passing through the center line of the adjacent concave portions. In addition, the convex portion width is formed to increase in a curve in the depth direction.

  In an optical element having such a fine concavo-convex structure formed on the surface, the reflectance with respect to incident light can be effectively reduced, and the ridge line of the convex portion is a continuous shape. It is possible to reduce the breakage of the fine concavo-convex structure due to the like.

  According to the second aspect, in the optical element according to the first aspect, in the cross section passing through the center line of the adjacent concave portion, the concave portion width at a position that is ½ of the concave portion depth is a position that is ½ of the convex portion height. Is formed smaller than the width of the convex portion.

  In the optical element according to the second aspect, in the cross section passing through the center line of the adjacent recess, the recess width at the position of 1/2 of the recess depth is the protrusion at the position of 1/2 of the protrusion height. It is formed smaller than the width.

  By forming such a fine concavo-convex structure on the surface, it becomes possible to further uniformly reduce the reflected light on the optical surface with respect to incident light, and further, the structure by contact etc. by improving the strength of the convex part An optical element capable of reducing body breakage is obtained.

According to a third aspect, there is provided an optical element according to the first aspect or the second aspect, wherein the surface shape of the substrate is a curved surface.
In the optical element according to the third aspect, the fine concavo-convex shape is formed on the surface of the curved optical element substrate.

  In this way, in the antireflection optical element having a fine concavo-convex structure formed on the surface, it is possible to reduce reflected light with respect to incident light by forming the fine concavo-convex structure on the surface of the curved optical element substrate. In addition, since the strength of the convex shape is improved, damage to the structure due to contact or the like can be reduced, and the optical element can be applied to optical systems for various applications.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a schematic plan view showing an example of the configuration of a fine relief structure according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an example of the configuration of a fine concavo-convex structure according to an embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view illustrating an uneven portion of a fine uneven structure according to an embodiment of the present invention.
FIG. 4 is a conceptual diagram showing a definition example of the shape of the uneven portion in the fine uneven structure according to the embodiment of the present invention.
FIG. 5 is a perspective view showing an example of an optical element having a fine relief structure according to an embodiment of the present invention.

  In the present embodiment, in each drawing, the X direction, the Y direction, and the Z direction orthogonal to each other are as illustrated.

(Constitution)
FIG. 1 is a top view of a fine concavo-convex structure 8 (fine concavo-convex structure) formed on a substrate, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.
The fine concavo-convex structure 8 according to the present embodiment includes a plurality of concave portions 5 (concave portions) so as to be surrounded by convex portions 1 (convex portions) that are continuous in a mesh shape along the ridge line portions 3 (ridge line portions) connecting the convex top portions 2. ) Are arranged.

  For example, when the optical surface of an optical element such as a prism 20 described later on which the fine concavo-convex structure 8 is arranged and formed is a flat surface, an XY plane parallel to the optical surface is an array surface of the concave portions 5. The depth direction of 5 (that is, the normal direction of the optical surface) is the Z direction.

In the case of the fine concavo-convex structure 8 of the present embodiment, the ridge curved surface 4 (that is, the inner peripheral surface 7 of the concave portion 5) separated from the ridge line portion 3 of the convex portion 1 is convex to the outside, that is, the concave portion 5 side. The width dimension of the cross section of the convex portion 1 increases in a curved manner in the depth direction of the concave portion 5.
That is, the cross-sectional shape of the concave portion 5 surrounded by the continuous convex portion 1 has, for example, a substantially funnel shape that tapers toward the concave bottom portion 6.

  As described above, the fine concavo-convex structure 8 of the present embodiment is completely different from the structure in which the holes are discretely formed on the XY plane which is the arrangement surface, and is located at the boundary between the adjacent concave portions 5 and the concave portions 5. There is no flat part parallel to the XY plane, and there is a ridged curved surface 4 that falls into the inside of the concave part 5 adjacent to the ridgeline part 3 that is continuous in a mesh shape connecting the convex top parts 2 of the convex part 1. Only. And the ridge curved surface 4 of this convex part 1 is the structure used as the internal peripheral surface 7 of the recessed part 5 simultaneously.

When the optical surface on which the fine concavo-convex structure 8 is arranged is a flat surface, the envelope surface of the ridge line portion 3 of the fine concavo-convex structure 8 is a flat surface, and when the optical surface is a curved surface, the ridge line portion of the fine concavo-convex structure 8 is formed. The envelope surface of 3 is the curved surface.
For this reason, in the fine concavo-convex structure 8 of this Embodiment, the fall of the antireflection effect resulting from a flat part existing between the recessed parts 5 does not arise.

Here, with reference to FIG. 3, an example of various dimensions characterizing the shape of the fine relief structure 8 of the present embodiment will be described.
In FIG. 3, the concave portion depth D and the convex portion height H, which are the reference when measuring and positioning the concave portion width Wd and the convex portion width Wh, are shown.

The distance in the Z direction from the convex top part 2 to the concave bottom part 6 is the convex part height H of the convex part 1 and at the same time the concave part depth D of the concave part 5, both of which are structurally equal.
A line passing through the center of the recess 5 (the exact definition in this embodiment will be described later) and parallel to the Z direction is the center line 5 c of the recess 5.

And the cross section containing the centerline 5c of each adjacent recessed part 5 is a cross section of line AA '.
In the example of FIG. 1, the line AA ′ is a straight line, but the straight line in the XY plane connecting the center lines 5 c of the plurality of recesses 5 may be zigzag.

In the cross section taken along line AA ′, the width at the position of ½ (= H / 2) of the height H of the protrusion is the protrusion width Wh of the protrusion 1.
Similarly, the recess width Wd of the recess 5 is a width at ½ (= D / 2) of the recess depth D.
In the case of the present embodiment, the contour shapes of the convex portion 1 and the concave portion 5 are set and controlled so that the convex portion width Wh> the concave portion width Wd.

Further, the distance between the center lines 5c of the two recesses 5 adjacent to each other with the protrusion 1 in the cross section taken along the line AA ′ is the distance L between the recesses.
A specific example of the dimensions of the above-described parts in the fine concavo-convex structure 8 of the present embodiment is illustrated below.
That is, the average value of the concave portion depth D is 200 nm as an example, and the average value of the convex portion height H is 200 nm as an example.

Moreover, the average value of the convex part width Wh is 60 nm as an example, and the average value of the concave part width Wd is 45 nm as an example.
Moreover, the average value of the distance L between the center parts of the recesses is 105 nm as an example.

  And when the object which implement | achieves reflection prevention by the fine concavo-convex structure 8 of this Embodiment is visible light (wavelength 380 nm-780 nm), for example, the maximum value Lmax of the distance L between recessed part center parts in the fine concavo-convex structure 8 is , Lmax <380 nm.

Here, with reference to FIG. 4, an example of a method for evaluating the size and variation of each part in the fine concavo-convex structure 8 of the present embodiment will be described.
In the example of FIG. 1 described above, the case where the cross-sectional shape of each concave portion 5 in a plane parallel to the XY plane is exemplified as a substantially circular shape. It may be a closed curve.

  Further, in FIG. 4, for convenience of illustration, the contour of the concave portion 5 is illustrated by a circular solid line, but actually, the inner peripheral surface 7 as a curved surface continuous from the ridge line portion 3 to the concave bottom portion 6 of the surrounding convex portion 1. The recess 5 is formed by the (ridged curved surface 4).

In this embodiment, as an example, as illustrated in FIG. 4, the center of the concave portion 5 having an arbitrary shape has all the ridge line intersections 3 a intersecting with the ridge line portion 3 of the convex portion 1 surrounding the concave portion 5. It is defined as the center of gravity 5b (center portion) of the polygon 5a as the vertex.
The center line 5c is a line segment passing through the center of gravity 5b and parallel to the Z direction.

  Further, the distance L between the center portions of the recesses is a distance between the centroids 5b of the adjacent recesses 5 regardless of whether the arrangement surface of the fine concavo-convex structure 8 is a flat surface or a curved surface.

  Further, when the concave portions 5 having the same shape and the same size are regularly arranged, it may not be possible to obtain a uniform antireflection effect on the entire optical surface.

  Thus, in the present embodiment, the size and shape of the concave portion 5 (in this case, the size and shape of the polygon 5a, and the positional relationship of the concave portion 5, etc.) are varied as necessary, so that the fine uneven structure 8 should be arranged evenly.

  In this embodiment, as an index for evaluating variations in the size and shape of the concave portions 5 in the fine concavo-convex structure 8 in this case, the arrangement positional relationship, and the like, as an example, the variation in the distance 5d between the ridge line intersections of the polygon 5a described above is used. Use.

  In the case of the present embodiment, by controlling the standard deviation of the distance 5d between the ridge line intersections to be in the range of 2 to 14, for example, the concave portions 5 of the fine concavo-convex structure 8 are arranged evenly, and the entire optical surface A uniform anti-reflection effect is realized.

  Further, as in the present embodiment, by providing variation in the size and shape of the concave portion 5 in the fine concavo-convex structure 8, the anisotropy of the antireflection effect in the light incident direction can be eliminated.

FIG. 5 illustrates a prism 20 as an example of the optical element K1 including the fine concavo-convex structure 8 of the present embodiment.
In this prism 20, a reflective coating forming surface 21, an incident surface 22, and an output surface 23 are disposed on each of the three side surfaces of the triangular prism.
The reflective coat forming surface 21 is a reflective surface made of, for example, an aluminum coating layer.

Then, as illustrated in the optical path 31 of the light 30, the light 30 incident from the incident surface 22 is reflected by the reflective coating forming surface 21 and is emitted from the emission surface 23.
The fine concavo-convex structure 8 described above is formed on each of the incident surface 22 and the exit surface 23.

  In this case, the planes of the entrance surface 22 and the exit surface 23 are XY planes in the fine concavo-convex structure 8 described above, and the normal direction is a positional relationship in the Z direction.

(Function)
According to the prism 20 which is the optical element K1 provided with the fine concavo-convex structure 8 of the present embodiment, the convex portion 1 surrounding the concave portion 5 in the fine concavo-convex structure 8 formed on the surfaces such as the entrance surface 22 and the exit surface 23. However, since the ridge line portion 3 connecting the convex top portions 2 is continuously formed so as to be continuous in a mesh shape, the convex portion 1 is compared with a shape in which the convex portions are formed independently. The strength against external force is greatly improved.

Furthermore, since the convex part width of the cross-sectional shape of the convex part 1 is a shape that increases in a convex manner on both sides in the depth direction, the strength of the convex part 1 against an external force is further increased.
As a result, it is possible to reduce the collapse or breakage of the convex portion 1 due to the contact of the fine concavo-convex structure 8 with an external object or the action of external force, and the antireflection effect by the fine concavo-convex structure 8 can be stably maintained.

  Further, in a cross section passing through the center line 5c of the adjacent recesses 5, the maximum value Lmax of the adjacent distance maximum portions (that is, the distance L between the recess center portions) is smaller than the visible light wavelength. Since the part width Wh is increased in a curve in the depth direction, the antireflection performance and the light transmittance are improved with respect to the visible light wavelength, and the strength against the external force of the convex part 1 is further maintained.

  Further, in the present embodiment, as an example, the average value of the distance L between the recesses is 105 nm which is equal to or less than the visible light wavelength, and in the cross section passing through the center line of the adjacent recess 5, the recess depth D = 1 / nm of 200 nm. 2 has a recess width Wd at the 100 nm position of 45 nm and a protrusion height H = 200 nm, and the protrusion width Wh at the 100 nm position of 60 nm is 60 nm. Remarkably expressed and the strength of the convex portion 1 with respect to the external force becomes more remarkable.

  Further, if necessary, the anisotropy of the antireflection effect can be eliminated by setting the standard deviation of the variation of the distance 5d between the ridge line intersections, which is an index of the geometric randomness in the fine concavo-convex structure 8, to 2-14. The performance of the antireflection effect by the fine concavo-convex structure 8 can be improved.

(effect)
As a result, the strength against the external force of the convex portion 1 of the fine concavo-convex structure 8 is maintained, and it is possible to realize an optical element K1 that suppresses the occurrence of collapse and damage of the structure due to contact and improves the optical performance such as the antireflection effect. .

  That is, it is possible to provide the optical element K1 that can reduce deformation and breakage of the fine concavo-convex structure 8 due to external force, contact, etc., and can prevent deterioration of optical performance such as antireflection effect.

  In addition, since the fine concavo-convex structure 8 has a high strength and is not easily deformed by gripping or contact, the optical element K1 can be easily handled, and workability when the optical element K1 is incorporated into an arbitrary optical system is improved.

(Embodiment 2)
Another embodiment of the optical element of the present invention will be described with reference to FIG.

(Constitution)
FIG. 6 is a perspective view showing a configuration example of an optical element having a fine relief structure according to another embodiment of the present invention.
As shown in FIG. 6, the optical element K2 of the present embodiment includes a convex optical surface 41 that is a spherical surface having an effective diameter D0 of 5.4 mm and a curvature radius R0 of 3.5 mm as a first surface, and a flat surface as a second surface. This is a plano-convex lens 40 having an optical surface 42.

The fine concavo-convex structure 8 illustrated in FIGS. 1 to 4 is formed on the convex optical surface 41 that is the first surface.
If necessary, the fine concavo-convex structure 8 may be formed also on the flat optical surface 42.
The fine concavo-convex structure 8 formed on the convex optical surface 41 of the plano-convex lens 40 has the same shape as that of the first embodiment.

  In this case, since the convex optical surface 41 on which the fine concavo-convex structure 8 is formed is a curved surface, the Z direction (the direction of the center line 5c of the concave portion 5) is the normal direction of the convex optical surface 41. The fine uneven structure 8 is formed.

  In this case, the size of the concave portion 5 is adjusted in accordance with the design shape of the convex optical surface 41 so that an antireflection effect can be obtained uniformly over the entire surface of the convex convex optical surface 41 and without causing anisotropy. And the array state is determined. That is, parameters such as the above-described distance L between the center portions of the recesses 5 and the standard deviation of the distance 5d between the ridge line intersections are set.

(Function)
According to the optical element K2 of the second embodiment, the fine concavo-convex structure 8 in which the ridge line portion 3 connecting the convex top portions 2 of the convex portions 1 is continuously formed on the convex optical surface 41 of the plano-convex lens 40 is formed. As a result, the strength of the convex portion 1 with respect to the external force is increased as compared with a shape in which the convex portion is formed independently.

  Further, in the cross section passing through the center line 5c of the adjacent recesses 5, the maximum value of the adjacent distance maximum part of the recess center part, that is, the maximum value Lmax of the distance L between the recess center parts is smaller than the visible light wavelength, and Since the convex portion width Wh increases in a curve in the depth direction, the antireflection performance and the light transmittance with respect to the visible light wavelength are improved, and the strength of the convex portion 1 against the external force is further increased.

  Further, in the second embodiment, the distance L between the center portions of the recesses is set to 105 nm which is equal to or less than the visible light wavelength, and the position of 100 nm which is 1/2 of the recess depth D = 200 nm in the cross section passing through the center line of the adjacent recesses 5. The concave width Wd is 45 nm, and the convex width Wh is 60 nm at the position of 100 nm, which is 1/2 of the convex height H = 200 nm. In addition, the strength of the convex portion 1 with respect to the external force is significantly increased.

(effect)
It is possible to provide an optical element K2 that can reduce deformation or breakage of the fine concavo-convex structure 8 due to external force or contact, and can prevent deterioration of optical performance such as antireflection effect.

  That is, since the fine concavo-convex structure 8 is formed on the convex optical surface 41 of the plano-convex lens 40 as the optical element K2, the strength against the external force of the convex portion 1 is maintained, and reflection is prevented with respect to the visible light wavelength. The optical element K2 having an effect and high light transmittance can be provided, and incident light can be efficiently condensed.

  As described above, the plano-convex lens 40 having the fine concavo-convex structure 8 can be applied to various optical systems by efficiently collecting incident light.

  In the optical system, in particular, the optical element K1 or the optical element K2 of the present embodiment is disposed at a position where light such as the first surface on the incident side is incident, thereby preventing reflection more effectively in the optical surface. Since an effect can be obtained, it becomes possible to construct an optical system having high antireflection performance.

  In the first and second embodiments described above, the depth of the concave portion 5 between the convex portion 1 and the convex portion 1 may be different within a range in which an effect such as an antireflection effect and strength can be realized. Even in such a case, it can be regarded as the convex part 1 formed continuously so that the convex top part 2 forms the ridge line part 3.

In the second embodiment, the optical element K2 is exemplified by the plano-convex lens 40, one of which is a convex optical surface 41 and the other is a flat optical surface 42. However, both surfaces may be curved surfaces. Any curved surface such as a spherical surface or a free-form surface may be used.
The optical surface on which the fine concavo-convex structure 8 is formed may be a concave lens having a concave surface.

  In the second embodiment, the direction in which the fine concavo-convex structure 8 is formed on the convex optical surface 41 (in this case, the direction of the center line 5c of the recess 5 or the Z direction) is the effect of the present invention such as antireflection effect and strength. As long as the optical axis 43 of the plano-convex lens 40 is maintained, it may be formed so as to deviate from the normal direction of the convex optical surface 41, such as the same direction or an inclined direction.

Here, a method of forming the fine concavo-convex structure 8 having an antireflection effect provided in the optical element K1 or the optical element K2 in each of the above-described embodiments of the present invention will be described.
In the optical element of the present embodiment, the fine uneven structure 8 may be formed on the optical element substrate and the optical element curved surface by any method.

  As a method for forming the fine concavo-convex structure 8, a method for forming the fine concavo-convex structure 8 on the curved surface of the optical element at the same time as forming an optical element using a mold having a concavo-convex shape opposite to the fine concavo-convex structure 8 to be formed. Can be used.

Alternatively, after the curable material is formed on the surface of the optical element, the shape of the fine concavo-convex structure 8 is transferred to the curable material using a mold having a concavo-convex shape opposite to the fine concavo-convex structure 8 to be formed and cured. A method of curing the functional material can be used.
Alternatively, a method of directly drawing an electron beam on the optical element curved surface can be used.

Moreover, you may use combining these methods arbitrarily.
It should be noted that any method may be used for manufacturing a mold having an uneven shape opposite to the fine uneven structure 8 to be formed.

  For example, a method of forming a mold by forming a microstructure having a shape opposite to the microstructure to be formed on the mold base using lithography techniques such as electron beam lithography and ion etching in a semiconductor process may be used. it can.

Alternatively, a method of forming an inverted mold by electroforming using a metal such as nickel (Ni) after the target fine concavo-convex structure 8 is formed on the mold substrate can be used.
Next, an example of a method for manufacturing an optical element in the present embodiment will be described with reference to the flowchart of FIG.

FIG. 7 is a flowchart showing an example of a method for manufacturing an optical element having a fine relief structure according to an embodiment of the present invention.
First, the shape of the optical surface (in this case, the entrance surface 22 of the prism 20, the exit surface 23, or the convex optical surface 41 of the plano-convex lens 40) is determined according to the required specification of the optical function for the optical element K1 and the optical element K2. (Step 101).

  Next, the size and layout of the convex portions 1 and the concave portions 5 in the fine concavo-convex structure 8, that is, the distance L between the central portions of the concave portions and the above-described ridge lines so that a uniform antireflection effect can be realized over the entire optical surface. Variations such as the distance 5d between the intersections are set (step 102).

  In addition, although the incident surface 22 and the output surface 23 which are the formation regions of the fine concavo-convex structure 8 in the prism 20 as the optical element K1 are flat, an antireflection effect can be obtained by appropriately varying the distance 5d between the ridge lines. The anisotropy of is eliminated.

  Further, when the fine concavo-convex structure 8 is formed on the convex optical surface 41 as in the optical element K2, the distance L between the central portions of the concave portions, the above-mentioned distance 5d between the ridge line intersections, etc. according to the shape of the convex optical surface 41 By setting the variation in the above, the antireflection effect is uniformly realized on the entire surface without impairing the design shape of the convex optical surface 41.

  Then, depending on whether or not a mold is used to form the fine concavo-convex structure 8 in the optical element K1, the method for forming the fine concavo-convex structure 8 is divided as follows (step 103).

  That is, when a mold is used to form the fine concavo-convex structure 8, a mold having a surface shape in which the concavo-convex structure 8 and the concavo-convex are reversed is created (step 104), and the shape of the mold is changed to the optical element K1. Transfer to the surface (step 105).

In the case of forming the fine concavo-convex structure 8 by transfer, the fine concavo-convex structure 8 may be formed at the same time as the base material of the optical element K1, or the fine concavo-convex structure 8 is formed on the resin layer deposited on the surface of the base material. It may be formed by transfer.
Or the method of sticking the transparent sheet | seat in which the fine uneven structure 8 was transcribe | transferred on the surface of the base material of the optical element K1 may be used.

  On the other hand, when the fine uneven structure 8 is directly formed on the optical surface of the optical element K1 without using a mold (step 106), for example, the optical surface of the optical element K1 is directly processed to form the fine uneven structure. 8 is formed.

  As described above, according to the method for manufacturing an optical element of each embodiment of the present invention, deformation or breakage of the fine concavo-convex structure 8 due to external force or contact is reduced, and deterioration of optical performance such as antireflection effect is prevented. In addition, it is possible to provide an optical element having a uniform antireflection effect without unevenness of the antireflection effect according to the shape of the optical surface on which the fine concavo-convex structure 8 is formed.

  As described above, according to the optical element of each embodiment of the present invention, in the antireflection optical element having a fine concavo-convex structure formed on the surface, the ridge line of the convex part is continuously formed and the convex part width is deep. By adopting a structure that increases in a curve in the direction, it is possible to reduce the collapse and breakage of the fine concavo-convex structure due to external force or contact, and by optimizing the shape of this convex part and concave part, antireflection performance etc. An optical element capable of improving the optical performance can be provided.

  Needless to say, the present invention is not limited to the configuration exemplified in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, as illustrated in FIG. 8, the contour of the ridge curved surface 4 in the cross-sectional shape of the convex portion 1 in the fine concavo-convex structure 8 includes a linear ridge surface 4 a in the vicinity of the ridge line portion 3 (convex apex portion 2), It is good also as a structure which consists of the ridge curved surface 4b smoothly continued to the ridge surface 4a.

(Appendix 1)
In an optical element in which a fine uneven shape is formed on the surface of a base material, a convex portion is continuously formed, and in the cross section passing through the center line of the adjacent concave portion, the maximum of the adjacent maximum distance portion (L) of the central portion of the concave portion An optical element having a fine concavo-convex structure, wherein the value (Lmax) is smaller than the visible light wavelength, and the width of the convex portion increases in a curve in the depth direction.

(Appendix 2)
Supplementary note 1 characterized in that, in a cross section passing through the center line of the adjacent concave portion, the concave portion width at a half of the concave portion depth is smaller than the convex portion width at a half of the convex portion height. An optical element having the fine concavo-convex structure described.

(Appendix 3)
The optical element having a fine concavo-convex structure according to Supplementary Note 1 or Supplementary Note 2, wherein a shape of a substrate surface is a curved surface.

DESCRIPTION OF SYMBOLS 1 Convex part 2 Convex apex part 3 Edge line part 3a Edge line intersection 4 Edge curved surface 4a Edge surface 4b Edge curved surface 5 Concave part 5a Polygon 5b Center of gravity 5c Center line 5d Distance between edge line intersection 6 Concave bottom part 7 Inner peripheral surface 8 Fine uneven structure 20 Prism 21 Reflective coat forming surface 22 Incident surface 22a Antireflection structure forming surface 23 Output surface 23a Antireflection structure forming surface 30 Light 31 Optical path 40 Plano-convex lens 41 Convex optical surface 42 Plane optical surface 43 Optical axis D Concave depth H Convex height Wd Concave part width Wh Convex part width K1 Optical element K2 Optical element L Distance between central parts of concave part

Claims (13)

  The ridge line portion includes a convex portion having a mesh shape and a plurality of concave portions surrounded by the convex portion, and the width of the convex portion in a cross section passing through the central portion of each of the plurality of adjacent concave portions is the width of the concave portion. An optical element having a fine concavo-convex structure increasing in a curve in the depth direction. The optical element according to claim 1, wherein
In the cross section of the fine concavo-convex structure, the convex portion of the convex portion at a position where the concave portion width of the concave portion at a half of the concave portion depth of the concave portion is half the convex portion height of the convex portion. An optical element characterized by being smaller than the width. The optical element according to claim 1 or 2,
An optical element, wherein a maximum value of a distance between the central portions of adjacent concave portions in the fine concavo-convex structure is smaller than a visible light wavelength. The optical element according to any one of claims 1 to 3,
The fine concavo-convex structure is formed such that at least one of the shape and size of the concave portion is random.   A method for producing an optical element, comprising: forming a fine concavo-convex structure including a plurality of concave parts surrounded by convex parts whose ridge lines are continuous in a mesh pattern on the surface of the optical element. In the manufacturing method of the optical element according to claim 5,
An optical element characterized in that the fine concavo-convex structure is formed such that the width of the convex portion in a cross section passing through the central portion of each of the plurality of adjacent concave portions is increased in a curve in the depth direction of the concave portion. Production method. In the manufacturing method of the optical element according to claim 6,
In the cross section, the concave portion width of the concave portion at a position that is ½ of the concave portion depth of the concave portion is made smaller than the convex portion width of the convex portion at a position that is ½ of the convex height of the convex portion. A method for manufacturing an optical element. In the manufacturing method of the optical element of Claim 6 or Claim 7,
The method of manufacturing an optical element, wherein a maximum value of a distance between the central portions of adjacent concave portions in the fine concavo-convex structure is smaller than a desired wavelength of light. In the manufacturing method of the optical element of any one of Claims 5-8,
A method of manufacturing an optical element, wherein at least one of the shape and size of the recess in the fine concavo-convex structure is random.   The ridge line portion includes a convex portion having a mesh shape and a plurality of concave portions surrounded by the convex portion, and the width of the convex portion in a cross section passing through the central portion of each of the plurality of adjacent concave portions is the width of the concave portion. A fine concavo-convex structure characterized by increasing in a curve in the depth direction. The fine concavo-convex structure according to claim 10,
In the cross section, the recess width of the recess at a position that is 1/2 the recess depth of the recess is smaller than the protrusion width of the protrusion at a position that is 1/2 of the height of the protrusion. A fine concavo-convex structure characterized by In the fine concavo-convex structure according to claim 10 or 11,
A fine concavo-convex structure, wherein a maximum value of a distance between the central portions of adjacent concave portions is smaller than a desired wavelength of light. In the fine concavo-convex structure according to any one of claims 10 to 12,
A fine concavo-convex structure, wherein at least one of the shape and size of the concave portion is random.

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