JP2011059264A - Optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance optical performance such as a reflection preventing function while preventing breakage caused by interference to a fine irregularity part formed on a substrate surface. <P>SOLUTION: The fine irregularity part 16 having many recessed parts 17 and projecting parts 18 is formed on the substrate surface of an optical element 10 and the projecting parts 18 are formed to be continuously connected. When the irregularity part 16 is cut in the irregularity direction by a linear line passing through a center between adjacent recessed parts 17 in plan view, the maximum value of a distance a between recess centers of the adjacent recessed parts 17 is shorter than a wavelength of visible light and a width b in a 1/2 position of the depth d of the recessed part is smaller than the minimum value of the width c in a 1/2 position of the width d of the recessed part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical element having a fine concavo-convex portion for preventing reflection of incident light on the surface of a substrate.

  In an optical system configured using an optical element such as a lens, the reflection of incident light on the optical functional surface of each optical element causes a loss of incident light quantity or a decrease in optical performance due to scattering of the reflected light. . Therefore, conventionally, an antireflection film is coated on the surface of the optical element. In recent years, instead of coating with an antireflection film, a surface non-reflective structure having various advantages such as being capable of suppressing reflection of light in a wide wavelength band and a wide range of incident angles and being capable of being integrated with an optical element has been developed. Proposed.

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 patent document 1, the fine uneven | corrugated shape which is an antireflection structure is formed in the base-material surface. And the peak shape of the most convex part of the convex part which became independent of each is made sharper than the valley shape of the most concave part, and the antireflection performance is improved.

Japanese Patent No. 4197100

  However, in patent document 1, the convex part which became independent respectively on the base-material surface as an antireflection structure is formed. For this reason, there is a possibility that the optical performance such as the antireflection effect is deteriorated when the convex portion falls down or is damaged due to interference with other members.

  The present invention has been made in order to solve such a problem, and an optical element capable of improving optical performance such as an antireflection function while preventing damage due to interference or the like with respect to fine irregularities formed on the surface of a substrate. The purpose is to provide.

  In order to achieve the above object, an optical element according to the present invention is an optical element in which fine irregularities having a large number of depressions and projections are formed on the surface of a substrate, and the projections are continuously formed, When the fine uneven portion is cut in the uneven direction by a straight line passing through the center of the recessed portion adjacent in plan view, the maximum distance in the width direction perpendicular to the uneven direction between the centers of the adjacent recessed portions is visible light. The distance in the width direction of the convex portion at a position that is smaller than the wavelength and is ½ of the depth in the concave-convex direction of the concave portion is the half-depth of the concave portion in the concave-convex direction. It is smaller than the minimum value of the distance of the said recessed part in the said width direction.

  Further, the optical element according to the present invention is the optical element of the present invention, wherein the optical element has a convex contact formed at a portion surrounded by the plurality of concave portions adjacent in plan view, and the distance between the adjacent convex contacts The standard deviation may be greater than 2 nm.

  In the optical element according to the present invention, in the optical element according to the invention, a depth of the concave portion in the concave-convex direction is greater than a maximum value in the width direction connecting the centers of the tips of the adjacent convex portions. May be.

  In the optical element according to the present invention, the substrate surface may be a curved surface in the optical element of the invention.

  ADVANTAGE OF THE INVENTION According to this invention, the optical element which can aim at the improvement of optical performance, such as an antireflection function, can be provided, preventing the damage by interference etc. with respect to the fine unevenness | corrugation part formed in the base-material surface.

3 is a plan view of a fine uneven portion of the optical element according to Embodiment 1. FIG. It is sectional drawing which follows the A-A 'line same as the above. It is an enlarged plan view of a fine uneven part. 6 is an external view of an optical element according to Embodiment 2. FIG. FIG. It is a top view of a fine uneven part. It is sectional drawing which follows the B-B 'line same as the above.

[Embodiment 1]
1 is a plan view of the fine uneven portion 16 of the optical element 10, FIG. 2 is a cross-sectional view taken along the line AA ′, and FIG. 3 is an enlarged plan view of the fine uneven portion 16.

1 and 2, the optical element 10 is an optical flat plate in which the surface of a base material 12 is a flat surface, and fine uneven portions 16 are formed on the surface of the base material 12.
The fine uneven portion 16 has a large number of fine concave portions 17 and convex portions 18. The convex portion 18 is continuously formed. That is, the convex portion 18 of the present embodiment is not a single convex projection on the surface of the substrate 12 but is continuously connected in a honeycomb shape as a wall structure surrounding the concave portion 17. This is a characteristic feature.

  Moreover, the size of the large number of recesses 17 is not necessarily the same. Some are big and some are small. Furthermore, the shape of the recess 17 is not limited to a circle in plan view, and may be a distorted circle, a polygon such as a triangle or a rectangle, or an ellipse.

  In the present embodiment, as shown in FIG. 1, the fine uneven portion 16 is formed in the uneven direction along a straight line AA ′ passing through the centers C 1, C 2, C 3, C 4,. When cut in the direction of the arrow ZZ in FIG. 2, the width direction perpendicular to the concavo-convex direction between the centers C <b> 1, C <b> 2 of the adjacent recesses 17, 17 (arrow XX direction in FIG. 2). The maximum value of the distance a (a1, a2,...) (Hereinafter referred to as “concave center distance a”) is smaller than the visible light wavelength (400 nm to 780 nm).

  And the distance b (hereinafter referred to as “convex width b”) in the width direction of the convex portion 18 at a half position of the depth of the concave portion 17 in the concave and convex direction (hereinafter referred to as “concave portion depth d”), The distance c in the width direction of the concave portion 17 at the same position is smaller than the minimum value (hereinafter referred to as “recess width c”).

In addition, the center of the recessed part 17 means the geometric center of the recessed part 17 in planar view in the case of a perfect circle, a regular polygon, or the like. In the case of a circular shape or a polygonal shape whose plane shape is distorted, it is the centroid.
Further, the reason why the distance a between the recess centers is smaller than the visible light wavelength is as follows.

  That is, even if there is a spatial distribution in the refractive index of the base material 12 and air with respect to the incident light reaching the fine uneven portion 16, it is a distribution below the assumed wavelength, so the distribution is directly as it is. Does not act on the light, it acts as an average. Therefore, if the refractive index after averaging is distributed so as to continuously change as the light advances, reflection of light can be prevented.

  In the present embodiment, the large number of recesses 17 are not randomly arranged according to a certain rule like a matrix or the like, but are randomly arranged. This is because by arranging them randomly, the anisotropy of the antireflection effect can be eliminated and the performance of the antireflection effect can be improved.

  Moreover, in this Embodiment, the cross-sectional shape of the convex part 18 has comprised the substantially isosceles triangle. However, the hypotenuse of the triangle may not be a straight line, and may be inclined gently like a quadratic curve, a cubic curve, or a sine curve.

  Further, as shown in FIG. 3, the fine uneven portion 16 has a convex contact 19 formed in a portion surrounded by a plurality of (for example, three) concave portions 17 that are adjacent in plan view. The standard deviation of the distance between the protrusion 19 and the convex contact 19 (hereinafter referred to as “distance between the convex contacts e”) is larger than 2 nm.

  By setting the standard deviation of the distance e between the convex contact points to be larger than 2 nm, the concave opening diameter f and the concave opening shape are random, and the reflected light on the optical surface with respect to the incident light is further reduced to improve the antireflection performance. To do.

In addition, the recessed part opening diameter f means the distance of the width direction (XX direction) which ties the center of the front-end | tip of the adjacent convex parts 18 and 18 in FIG.
In the optical element 10 of the present embodiment, the average value of the distance e between the convex contact points was 51 nm, and the standard deviation thereof was 14 nm. The average value of the recess opening diameter f of the recess 17 was 67 nm.

Here, the standard deviation is a standard indicating variation and is expressed by the following equation.
σ = √ (Σ (e _i −μ) ² / n)
However, sigma is the standard deviation, e _i is the distance between the convex portions contacts 19 and 19, the average value of the distance e between the μ protrusion contacts 19 and 19, n is the number of combinations of the convex portion contacts 19 adjacent .

In the present embodiment, the average value of the recess center distance a is 105 nm, the average value of the protrusion width b is 33 nm, and the average value of the recess depth d is 270 nm.
In the present embodiment, the recess depth d is larger than the maximum value of the recess opening diameter f.

  That is, as shown in FIG. 2, the recess depth d is larger than the maximum value of the recess opening diameter f. For example, the recess depth d is 1 to 10 times the recess opening diameter f. However, it is not limited to 1 to 10 times, and may be 10 times or more, for example.

By doing in this way, the reflected light with respect to incident light can further be reduced.
In addition, the cross-sectional shape of the convex part 18 is the range in which the antireflection effect and strength are maintained, and the convex part width b is in the width direction from the distal end (protruding end) of the convex part 18 toward the base end side (root side). It may be a shape that expands greatly.

Even if it is such a shape, if the convex part width b is smaller than the minimum value of the concave part opening diameter f, the antireflection effect is maintained.
In the present embodiment, the concave depth d between the convex contact 19 and the convex contact 19 may be different within a range in which the effects such as the antireflection effect and the strength are maintained. Even in such a case, it can be regarded as the convex part 18 formed continuously.

Next, a method for forming the fine uneven portion 16 will be described.
Basically, the fine irregularities 16 may be formed on the base material 12 and the base material curved surface by any method.

  For example, the fine irregularities 16 may be transferred to the surface of the substrate 12 at the same time as the optical element is molded using a mold having a surface shape obtained by inverting the shape of the fine irregularities 16. Moreover, after forming a curable material on the surface of the base material 12, the shape is transferred to the curable material using a mold having a surface shape obtained by inverting the shape of the fine uneven portion 16 to be formed. May be cured. Furthermore, you may draw the fine uneven | corrugated | grooved part 16 on the surface of the base material 12 with an electron beam directly.

  In order to produce a mold having a surface shape obtained by inverting the shape of the fine concavo-convex portion 16, for example, the fine concavo-convex portion 16 is formed on the die using a lithography technique such as electron beam drawing or ion etching in a semiconductor process. A mold may be manufactured by forming a microstructure having a shape obtained by inverting the shape. Further, after forming the fine irregularities 16 on the mold, an inversion mold may be produced by electroforming using a metal such as nickel (Ni).

  According to the present embodiment, since the convex portions 18 of the fine concavo-convex portions 16 are continuously formed, the mechanical strength against the external force of the convex portions 18 is greater than when a large number of the convex portions 18 are formed alone. Can be secured.

  Further, since the maximum value of the recess center distance a (a1, a2,...) Is smaller than the visible light wavelength (400 nm to 780 nm) and the protrusion width b is smaller than the maximum value of the recess opening diameter f, Antireflection performance and light transmittance can be improved with respect to visible light wavelengths.

  In addition, since the standard deviation of the distance e between the convex contacts is 2 nm or more, the concave opening diameter f and the concave opening shape are random, and the reflected light on the optical surface with respect to incident light is further reduced to improve the antireflection performance. be able to.

  Furthermore, since the recess depth d is larger than the maximum value of the recess opening diameter f, the antireflection performance and the light transmittance can be further improved. In addition, the antireflection effect within the optical element surface can be kept uniform. On the other hand, when the recess depth d is not more than 1 times the maximum value of the recess opening diameter f, a high antireflection effect cannot be expected.

  In addition, according to the present embodiment, the distance a between the recess centers is 105 nm which is not more than the visible light wavelength (400 nm to 780 nm), the protrusion width b is about ½ of the recess opening diameter f, and the recess depth d is the recess opening. Since the standard deviation of the distance e between the convex contact points is about 4 times the diameter f and the distance e between the convex contact points is 14 nm, the antireflection effect of the fine uneven portion 16 can be realized more remarkably.

  Thus, according to the present embodiment, the mechanical strength against the external force of the convex portion 18 of the fine concavo-convex portion 16 is maintained, the occurrence of collapse or damage of the fine concavo-convex portion 16 due to contact, etc., and the antireflection effect, etc. The optical performance can be improved.

[Embodiment 2]
4 is an external view of the optical element 20 of the present embodiment, FIG. 5 is a cross-sectional view thereof, FIG. 6 is a plan view of the fine uneven portion 26, and FIG. 7 is a BB ′ line thereof. FIG.

  The optical element 20 is a plano-convex lens. The optical element 20 has a first optical functional surface 23 having a convex curved surface on the surface of the base material 22 and a second optical functional surface 24 having a flat shape on the back surface of the base material 22. In the present embodiment, the first optical function surface 23 is described as a convex spherical shape, but the present invention is not limited to this. For example, the first optical function surface 23 may be a convex aspheric surface or a convex free-form surface.

On the first optical function surface 23, a fine uneven portion 26 for preventing reflection is formed. The fine uneven portion 26 has the same shape as that described in the first embodiment.
In this Embodiment, the average value of the distance e between convex contact was 51 nm, and the standard deviation was 14 nm. Further, the average value of the recess opening diameter f is 67 nm, the average value of the recess center distance a is 105 nm, the average value of the protrusion width b is 33 nm, and the average value of the recess depth d is 270 nm.

Note that the definitions of the distance e between convex contact points, the convex contact point 29, and the like described above are used in the same meaning as described in the first embodiment, and thus the description thereof is omitted here.
In the present embodiment, the convex portions 28 of the fine concave and convex portions 26 on the surface of the optical element 20 are continuously formed, and the maximum value of the maximum portion of the concave portion center distance a (a1, a2,...) Is visible light. The wavelength is smaller than the wavelength (400 nm to 780 nm), and the convex portion width b is smaller than the minimum value of the concave portion width c.

  In addition, the standard deviation of the distance e between the convex contacts is 2 nm or more, and the concave depth d is larger than the maximum value of the concave opening diameter f. For this reason, the mechanical strength with respect to the external force of the convex part 28 of the fine uneven part 26 of the surface of the optical element 20 is maintained. Moreover, it can have an antireflection effect and high light transmittance with respect to visible light wavelengths, and can exhibit high optical performance.

  In the present embodiment, the cross-sectional shape of the convex portion 28 is a convex portion from the distal end (protruding end) of the convex portion 28 toward the base end side (root side) as long as the antireflection effect and strength are maintained. The width b may be a shape that greatly expands in the width direction.

Even if it is such a shape, if the convex part width b is smaller than the minimum value of the concave part opening diameter f, the antireflection effect is maintained.
In the present embodiment, the depth d of the concave portion between the convex contact 29 and the convex contact 29 may be different within a range in which the effects such as the antireflection effect and the strength are maintained. Even in such a case, it can be regarded as the convex part 28 formed continuously.

  In the present embodiment, a plano-convex lens has been described as an example of the optical element 20, but both optical functional surfaces may be curved surfaces, and the curved surface shapes may be curved surfaces such as spherical surfaces, aspheric surfaces, and free curved surfaces. May be.

  According to the present embodiment, since the fine uneven portion 26 is formed on the optical element 20 whose substrate surface is a curved surface, the mechanical strength against the external force of the convex portion 28 can be maintained. Moreover, it can have an antireflection effect and high light transmittance with respect to visible light wavelength, and can exhibit high optical performance. As described above, high optical performance can be exhibited, so that adaptation to various optical systems is possible.

  In the optical system, the optical element 20 of the present embodiment is arranged at a position where light such as the incident-side first surface is incident, so that an antireflection effect with a small reflectance distribution in the optical element plane is obtained. be able to. In this way, an optical system having an antireflection function can be obtained.

DESCRIPTION OF SYMBOLS 10 Optical element 12 Base material 16 Fine uneven | corrugated part 17 Concave part 18 Convex part 19 Convex part contact 20 Optical element 22 Base material 23 1st optical function surface 24 2nd optical function surface 26 Fine uneven part 27 Concave part 28 Convex part 29 Convex Part contact a Center distance between recesses b Width of projection part c Width of recess part d Depth depth e Distance between contact points of convex part f Concave opening diameter C1, C2,.

Claims (4)

In the optical element in which a fine uneven portion having a large number of concave portions and convex portions is formed on the substrate surface,
The convex portions are continuously formed,
When the fine uneven portion is cut in the uneven direction by a straight line passing through the center of the recessed portion adjacent in plan view,
The maximum value of the distance in the width direction perpendicular to the concave-convex direction between the centers of the adjacent concave portions is smaller than the visible light wavelength,
And the distance in the width direction of the convex portion at the half position of the depth in the concave and convex direction of the concave portion is the width direction of the concave portion in the half position of the concave portion in the concave and convex direction. An optical element characterized by being smaller than the minimum value of the distance. It has a convex part contact formed in a part surrounded by a plurality of the above-mentioned concave parts adjoining in plan view, and the standard deviation of the distance between the adjacent convex part contacts is larger than 2 nm. The optical element described. The optical element according to claim 1, wherein a depth of the concave portion in the concave-convex direction is larger than a maximum value of the distance in the width direction connecting the centers of the tips of the adjacent convex portions. The optical element according to claim 1, wherein the substrate surface is a curved surface.

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