JP2004334074A - Method for manufacturing optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical member in which an antireflective grating can easily be formed in a central part area and a peripheral area on the optical surface of the optical member. <P>SOLUTION: In the method for manufacturing an optical member 10 by forming an antireflective grating 14 on the optical surface 11, a mold 20 is formed by forming an optical surface formation part 21 matching the optical surface 11 on a mold material 20a, forming a center grating part 24a by forming a resist pattern 30 corresponding to the antireflective grating 14 by photolithography in the central part area 21a on the optical surface formation part 21 and etching the resist pattern 30, and forming a grooved peripheral grating part 24b by cutting the peripheral part area 21b at the optical surface formation part 21. The optical member 10 is molded by using the mold 20 to form the antireflective grating 14 on the nearly entire optical surface 11 of the optical member 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an optical member having an antireflection grating for preventing reflection of incident light, and more particularly to a method for manufacturing an optical member having an antireflection grating on substantially the entire optical surface.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a method of preventing reflection on an optical surface of an optical member such as a lens or a diffraction grating, it is common to form a multilayer antireflection film on the optical surface of the optical member. However, in order to form an antireflection film on an optical member, a dielectric multilayer film having high adhesion at a low temperature must be deposited, and in order to effectively perform antireflection, the refractive index and film thickness of the antireflection film are required. Since the thickness must be strictly controlled, the manufacturing cost of the optical member increases.
[0003]
As an anti-reflection treatment instead of such an anti-reflection film, there is a method of providing an anti-reflection grating on the optical surface of the optical member, in which the grating period (interval) and groove depth are smaller than the wavelength of the incident light. According to such an antireflection grating, diffracted light of incident light does not occur, which has the same effect as gradually lowering the refractive index on the optical surface, thereby preventing reflection of the optical element.
As a method of forming such an antireflection grating, for example, as described in Patent Document 1, a portion corresponding to an optical surface of a mold for molding an optical member is subjected to cutting with a cutting tool or the like. Then, there is a method of forming an antireflection grating on the optical surface of the optical member by forming a concentric lattice portion having concavities and convexities opposite to the antireflection grating and molding the optical member using this mold. Alternatively, there is a method of forming an antireflection grating directly on an optical member.
As another method, there is a method of forming an antireflection grating by etching the surface of an optical member.
[0004]
[Patent Document 1]
JP-A-2000-24801 (FIG. 1)
[0005]
[Problems to be solved by the invention]
However, since the period and the groove depth of the antireflection grating are smaller than those of a normal diffraction grating, when a concentric antireflection grating is formed with respect to a mold or an optical member, the radius of the antireflection grating becomes smaller at the center. In the area, it is difficult to cut the concentric anti-reflection grating.
When an antireflection grating is formed by an etching process, it is necessary to form a resist pattern serving as an etching mask on an optical surface before etching in order to etch only necessary portions. The resist pattern is formed by applying a resist on an optical surface, exposing the resist with an electron beam or the like to form an original pattern, and then developing the resist. Here, when the surface of the optical member is convex or concave, the electron beam does not focus on the entire resist on the optical surface at the time of exposure, so that the resist pattern cannot be formed well on the entire surface. Therefore, it is also difficult to form an antireflection grating having a desired shape by etching.
[0006]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing an optical member that can easily form an antireflection grating in a central region and a peripheral region of an optical surface of an optical member. And
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a method for manufacturing an optical member having an antireflection grating formed on an optical surface having a convex top or a concave bottom in a central region, wherein the mold material is adapted to the optical surface. The first step of forming an optical surface molding portion to be formed, a resist pattern corresponding to the antireflection grating is formed in a central region of the optical surface molding portion by a photolithography method and subjected to etching to form a central lattice portion. A second step of forming, and a third step of forming a groove-shaped peripheral lattice portion by cutting in the peripheral region of the optical surface molding portion, in the order of the first, second, and third steps Alternatively, the mold material is processed in the order of the first, third, and second steps to form a molding die, and the optical member is molded by the molding die, thereby forming an antireflection grating on substantially the entire optical surface of the optical member. Is characterized by forming It has been.
[0008]
Further, the present invention provides a method for manufacturing an optical member, wherein an antireflection grating is formed on an optical surface having a convex top or a concave bottom in a central region, wherein a copying surface having the same shape as the optical surface of the optical member is provided. A first step of forming a model member having, and a second step of forming a resist pattern corresponding to the antireflection grid by photolithography in a central region of the copying surface and performing etching to form a central grid portion And a third step of forming a groove-shaped peripheral lattice portion by cutting in the peripheral area of the copying surface, in the order of the first, second and third steps or the first and third・ Process the model member in the order of the second step to form an optical member model, form an optical member model by performing electroforming on the optical member model, and mold the optical member using the molding die. The optical surface of the optical member It is configured as characterized by forming an antireflection grating over substantially the entire surface.
[0009]
Further, the present invention provides a method for manufacturing an optical member, wherein an antireflection grating is formed on an optical surface having a convex top or a concave bottom in a central region, the first step of forming the optical surface on an optical material. A second step of forming a resist pattern corresponding to the antireflection grating in a central region of the optical surface by photolithography and performing etching to form a central grating portion; and a peripheral portion of the optical surface. Having a third step of forming a groove-shaped peripheral lattice portion by cutting in the area, the optical material in the order of the first, second and third steps or in the order of the first, third and second steps On the other hand, an optical member having an antireflection grating is formed on substantially the entire optical surface by performing processing.
[0010]
Further, the present invention is characterized in that the central grating portion and the peripheral grating portion are formed with a period equal to or less than half the wavelength of the incident light.
[0011]
Further, the present invention is characterized in that the peripheral lattice portion is formed in a substantially concentric groove shape.
[0012]
Further, the present invention is characterized in that the central lattice portion is formed in a convex or concave substantially conical shape.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view of a lens according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the lens according to the embodiment of the present invention.
In this embodiment, a method for manufacturing a lens 10 having one surface that is spherically convex and the other surface that is flat as shown in FIGS. 1 and 2 will be described. The lens 10 is formed of a transparent optical resin, and includes a convex lens surface 11, a flat lens surface 12, and a peripheral portion 13. The convex lens surface 11 is formed in a spherical shape with the central portion as the top. Further, on the convex lens surface 11, an anti-reflection grating 14 for preventing reflection of light on the convex lens surface 11 is formed. In the present embodiment, the period (interval) and groove depth of the antireflection grating 14 of the lens 10 are formed to be equal to or less than half the wavelength λ of the incident light. For example, for incident light of 650 nm band and 780 nm band used for DVD and CD, the period is set to 0.20 μm and the groove depth is set to 0.25 μm. Thereby, the reflectance of the incident light can be suppressed to 2% or less.
[0014]
Here, in the present embodiment, the shape of the antireflection grating 14 is different between the central region 11a and the peripheral region 11b. The anti-reflection grating (hereinafter, referred to as the center grating 14a) in the center region 11a includes a plurality of convex portions formed in a substantially conical shape. On the other hand, the antireflection grating in the peripheral region (hereinafter, referred to as the peripheral grating 14b) includes a plurality of concentric grooves.
The present invention is characterized by the formation of such an antireflection grating 14. Hereinafter, a method for manufacturing such a lens 10 will be described.
[0015]
First, a first embodiment will be described. In the present embodiment, the lens is molded by a mold made of silicon. Hereinafter, a method of forming the mold will be described first. FIG. 3 is a cross-sectional view showing a forming step of the forming die according to the first embodiment of the present invention. First, a lens forming portion for transferring the convex lens surface 11, the flat lens surface 12, and the peripheral portion 13 thereof to an optical material is formed on a mold member made of silicon by cutting or the like. Specifically, the convex lens surface forming portion 21 and the peripheral edge forming portion 23 are formed on one mold member 20a, and the flat lens surface forming portion is formed on the other mold member (not shown) by cutting with a cutting tool or the like (FIG. 3). (A)).
[0016]
On the convex lens surface forming portion 21 of the mold member 20a, a lattice portion 24 including a central lattice portion 24a for transferring the central lattice 14a to the lens 10 and a peripheral lattice portion 24b for transferring the peripheral lattice 14b is formed. I do. In the present embodiment, first, the central lattice portion 24a is formed. The central lattice portion 24a is composed of a plurality of concave portions formed in a shape opposite to that of the central lattice 14a, that is, in a substantially conical shape.
[0017]
Such a central lattice portion 24a is formed by forming a resist pattern 30 on the convex lens surface forming portion 21 by a photolithography method, and performing an etching process on the central portion region 21a using the resist pattern 30 as an etching mask. . Specifically, first, a resist 31 is applied to the convex lens surface forming portion 21, and an electron beam is exposed to draw an original pattern 32, and the original pattern 32 is developed to form a resist pattern 30 (FIG. 3B). ). Here, the resist pattern 30 has such a shape that a portion to be removed when the etching process is performed on the mold member 20a, that is, a portion that forms a substantially conical concave portion in the present embodiment is exposed.
Since the change in the thickness direction is less in the central region 21a of the convex lens surface forming portion 21 than in the peripheral region 21b, the focus of the electron beam exposure can be adjusted to substantially the entire central region 21a. It is possible to form the resist pattern 30 having the shape of FIG.
[0018]
Next, dry etching is performed with an etching gas such as a chlorine-based gas on the mold member 20a on which the etching mask has been formed by the resist pattern 30 (FIG. 3C). As a result, a portion of the convex lens surface forming portion 21 that is not protected by the resist pattern 30 is eroded and removed, and a central lattice portion 24a including a plurality of substantially conical concave portions is formed according to the shape of the resist pattern 30. Is done.
After the formation of the central lattice portion 24a, the resist pattern 30 is removed.
[0019]
With respect to the mold member 20a having the central lattice portion 24a formed in this manner, the peripheral lattice portion 24b is formed in the peripheral region 21b to complete the molding die 20 (FIG. 3D). The peripheral lattice portion 24b is composed of a plurality of concentric grooves having a shape opposite to that of the peripheral lattice 14b. The peripheral grating portion 24b is formed by fixing the mold member 20a to a lathe, rotating the mold member 20a, and cutting the same with a cutting tool, as in the case of forming a normal diffraction grating. In the peripheral region 21b of the convex lens surface forming portion 21, the radius of the groove to be cut is sufficiently larger than the period and the groove depth of the groove, so that the cutting edge of the cutting tool is easily cut into the mold member 20a, and therefore, the cutting can be sufficiently performed. It is.
The lens 10 having the anti-reflection grating 14 on almost the entire surface of the convex lens surface 11 is formed by molding the lens 10 with the molding die 20.
[0020]
In the present embodiment, the central lattice portion 24a is first formed in the central region 21a and then the peripheral lattice portion 24b is formed in the peripheral region 21b with respect to the mold member 20a. However, the order of this step is not particularly limited to this. First, the peripheral lattice portion 24b may be formed in the peripheral region 21b, and then the central lattice portion 24a may be formed in the central region 21a.
[0021]
The first embodiment of the present invention has been described above. In the first embodiment, the mold is formed from silicon. However, a mold made of metal may be required from the viewpoint of durability and ease of cutting. Hereinafter, a second embodiment in which the lens 10 is molded using a mold partially made of metal will be described.
[0022]
FIG. 4 is a view showing a forming step of a mold according to the second embodiment of the present invention. In the present embodiment, first, a lens forming portion for transferring the convex lens surface 11, the flat lens surface 12, and the peripheral portion 13 to the optical material is cut into a metal mold member made of Ni or another alloy or the like. Formed by Specifically, the convex lens surface forming portion 41 and the peripheral edge forming portion 43 are formed on one mold member 40a, and the flat lens surface forming portion is formed on the other mold member (not shown) by cutting with a cutting tool or the like (FIG. 4). (A)).
In addition, the central region 41a of the convex lens surface forming portion 41 is carved with a certain thickness to form a film forming portion 45.
[0023]
A lattice forming film 46 made of silicon is formed on the film forming portion 45. This lattice forming film 46 is formed so as to form the same plane as the convex lens surface forming portion 41. Thereafter, a resist 51 is applied to the convex lens surface forming portion 41 in which the lattice forming film 46 is formed in the central region 41a, and the original pattern 52 is developed by exposing with an electron beam, and developing the original pattern 52. Thus, a resist pattern 50 is formed (FIG. 4B).
Next, dry etching is performed on the mold member 50a on which the etching mask has been applied by the resist pattern 50 to form a central grid portion 44a including a plurality of substantially conical concave portions on the grid forming film 46 (FIG. 4C). )). After the formation of the central lattice portion 44a, the resist pattern 50 is removed.
[0024]
In the peripheral region 41b of the mold member 40a in which the central lattice portion 44a is formed on the lattice forming film 46 in this manner, a peripheral lattice portion 44b composed of a plurality of concentric grooves having a shape opposite to that of the peripheral lattice 14b is formed. And a cutting tool using a cutting tool to complete the molding die 40 (FIG. 4D).
By molding the lens 10 with the molding die 40, the lens 10 having the antireflection grating 14 on almost the entire surface of the convex lens surface 11 is formed.
Note that, as in the first embodiment, the peripheral lattice portion 44b may be formed first, and then the central lattice portion 44a may be formed.
[0025]
As described above, by forming the lattice forming film 46 in the central region 41a, it becomes possible to perform an etching process that cannot be performed with metal, and it is possible to form the central lattice portion 44a by the etching process in the central region 41a. It becomes possible. In addition, since the peripheral region 41b is made of metal, it can be easily cut and has high durability.
[0026]
As above, the second embodiment of the present invention has been described. In the second embodiment, a molding die is formed by cutting a metal mold member or the like. However, it is possible to form a metal mold by other methods. Hereinafter, a third embodiment in which a metal mold is formed by another method and the lens 10 is molded with the mold will be described.
[0027]
In the present embodiment, first, a lens model having the same shape as the lens 10 is formed of silicon. FIG. 5 is a view showing a step of forming a lens model according to the third embodiment of the present invention. Specifically, first, the model member 60a made of silicon is cut or the like, and the convex lens surface 11, the flat lens surface 12, and the convex lens imitation surface 61, the flat lens imitation surface 62 having the same shape as the peripheral portion 13 of the lens 10 are formed. The peripheral copy surface 63 is formed by cutting with a cutting tool or the like (FIG. 5A).
[0028]
With respect to the convex lens imitation surface 61 of the model member 60a, a lattice imitation portion 64 including a central lattice imitation portion 64a having the same shape as the central lattice 14a formed on the lens 10 and a peripheral lattice imitation portion 64b having the same shape as the peripheral lattice 14b. To form In the present embodiment, first, the central lattice copy portion 64a is formed. The forming method is almost the same as that of the first embodiment. First, a resist 71 is applied to the convex lens imitation surface 61, an electron beam is exposed to draw an original pattern 72, and the original pattern 72 is developed to form a resist pattern 70. It is formed (FIG. 5B). Here, in the present embodiment, the resist pattern 70 has a shape such that portions other than the substantially conical convex portion to be formed are exposed. Next, dry etching is performed on the model member 60a on which the etching mask has been applied by the resist pattern 70, thereby forming a central lattice copy portion 64a including a plurality of substantially conical convex portions (FIG. 5C). After the formation of the central lattice copy portion 64a, the resist pattern 70 is removed.
[0029]
In the peripheral region 61b of the model member 60a on which the central lattice copying portion 64a is formed in this way, the peripheral grating copying portion 64b having the same shape as the peripheral grating 14b formed on the lens 10, that is, the concentric circular groove portion is provided with a cutting tool. The lens model 60 is completed by the used cutting process (FIG. 5D).
It is to be noted that, as in the first embodiment, the peripheral grid copying section 64b may be formed first, and then the central grid copying section 64a may be formed.
[0030]
Next, an electroforming process is performed using the lens model 60 as an electroforming master mold to form a metal mold, and the lens 10 is molded with the mold to prevent reflection of almost the entire surface of the convex lens surface 11. A lens 10 having a grating 14 is formed.
[0031]
As described above, first, a lens model 60 having the same shape as the lens 10 is formed, and a metal mold is formed by electroforming using the lens model 60 as an electroforming master mold. Can be formed. Further, according to the electroforming, since the transfer accuracy is high, the surface shape of the lens model 60 is faithfully transferred to the molding die, and therefore, the lens 10 with high accuracy can be molded using this molding die.
[0032]
As above, the third embodiment of the present invention has been described. In the first, second, and third embodiments, the lens 10 is molded using a molding die. However, for example, when the lens 10 is a small lot product, it is conceivable not to use a molding die. In such a case, the lens 10 having the anti-reflection grating 14 may be formed by directly processing an optical material such as glass in the same manner as forming the lens model 60 in the third embodiment. It is possible.
[0033]
Further, in the above embodiment, the case where the one-side convex lens is formed has been described as an example. However, the present invention is not particularly limited to this, and can be applied to various optical members such as a concave lens and a convex or concave diffraction grating.
Further, in the above-described embodiment, a case has been described in which a lens having a substantially conical convex central lattice in the central region is formed. However, the shape of the central lattice is not particularly limited to this, and the shape of the central lattice is substantially Other shapes that function as an anti-reflection grating, such as a concave shape or a substantially concentric groove shape like the peripheral grating, may be used.
[0034]
【The invention's effect】
According to the present invention, the central lattice portion is formed in the central region of the optical surface molding portion by photolithography and etching, and the groove-shaped peripheral lattice portion is formed in the peripheral region of the optical surface molding portion by cutting. By forming an optical member by using the mold, the optical member is molded using the mold. Therefore, even if the optical surface of the optical member to be molded is convex or concave, the optical Since a grating portion corresponding to the anti-reflection grating of the member can be formed, and thus the anti-reflection grating can be formed on substantially the entire optical surface of the optical member, the anti-reflection effect can be enhanced.
[0035]
Further, according to the present invention, a central lattice portion is formed by a photolithography method and an etching process in a central region of a copying surface, and a groove-shaped peripheral grating portion is formed by a cutting process in a peripheral portion of the copying surface. Since a mold is formed by forming a member model and subjecting the optical member model to electroforming, it is possible to form a metal mold having high durability. According to the electroforming, since the transfer accuracy is high, the surface shape of the optical member model is faithfully transferred to the molding die, and therefore, the antireflection grating is almost completely provided on the entire optical surface using this molding die. The optical member can be molded.
[0036]
According to the present invention, the central lattice portion is formed by photolithography and etching in the central region of the optical surface, and the groove-shaped peripheral lattice portion is formed by cutting in the peripheral region of the optical surface. Since the optical member having the antireflection grating is formed on almost the entire optical surface, it is possible to form the optical member having the antireflection grating on almost the entire convex or concave optical surface even without forming a mold. The antireflection effect can be enhanced.
[0037]
Further, according to the present invention, since the central grating portion and the peripheral grating portion are formed with a period equal to or less than half the wavelength of the incident light, the reflectance of the optical surface for the incident light can be kept low.
[0038]
Further, according to the present invention, since the peripheral grating portion is formed in a substantially concentric groove shape, it can be formed in the same manner as a normal diffraction grating, and thus the peripheral grating portion can be easily formed.
[0039]
Further, according to the present invention, since the central lattice portion is formed in a convex or concave substantially conical shape, it can be easily formed by etching, and the reflection of incident light in the central region can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is a front view of a lens according to an embodiment of the present invention.
FIG. 2 is a sectional view of a lens according to the embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a step of forming a molding die according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating a step of forming a molding die according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating a step of forming a lens model according to a third embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 Lens 11 Convex lens surface 11a Central region 11b Peripheral region 14 Anti-reflection grating 14a Central lattice 14b Peripheral lattice 20 Mold 21 Convex lens surface molding 21a Central region 21b Peripheral region 23 Peripheral molding 24 Grid 24a Central lattice 24b Peripheral lattice part 30 Resist pattern 40 Mold 41 Convex lens surface molded part 41a Central part 41b Peripheral part 44 Lattice part 44a Central lattice part 44b Peripheral lattice part 45 Film formation part 46 Grid formation film 50 Resist pattern 60 Lens model 61 Convex lens Copying surface 61a Central region 61b Peripheral region 64 Grid copying portion 64a Central grid copying portion 64b Peripheral grid copying portion 70 Resist pattern

Claims (6)

In a method for manufacturing an optical member having an antireflection grating formed on an optical surface having a convex top or a concave bottom in a central region,
A first step of forming an optical surface molding portion that matches the optical surface in the mold material,
A second step of forming a resist pattern corresponding to the antireflection grating by photolithography in the central region of the optical surface forming portion and performing etching to form a central grating portion,
A third step of forming a groove-shaped peripheral grid portion by cutting in a peripheral region of the optical surface forming portion,
By processing the mold material in the order of the first, second, and third steps or in the order of the first, third, and second steps to form a molding die, and molding the optical member with the molding die. A method for manufacturing an optical member, comprising forming an antireflection grating on substantially the entire optical surface of the optical member. In a method for manufacturing an optical member having an antireflection grating formed on an optical surface having a convex top or a concave bottom in a central region,
A first step of forming a model member having a replication surface of the same shape as the optical surface of the optical member,
A second step of forming a resist pattern corresponding to the antireflection grid by photolithography in the central area of the copying surface and performing etching to form a central grid portion,
A third step of forming a groove-shaped peripheral grid portion by cutting in a peripheral region of the copying surface,
The optical member model is formed by processing the model member in the order of the first, second, and third steps or in the order of the first, third, and second steps, and electroforming the optical member model. And forming an antireflection grating on substantially the entire optical surface of the optical member by forming the optical member with the forming die. In a method for manufacturing an optical member having an antireflection grating formed on an optical surface having a convex top or a concave bottom in a central region,
A first step of forming the optical surface on an optical material,
A second step of forming a resist pattern corresponding to the antireflection grating by photolithography in the central region of the optical surface and performing etching to form a central grating portion,
A third step of forming a groove-shaped peripheral lattice portion by cutting in the peripheral region of the optical surface,
By processing the optical material in the order of the first, second, and third steps or in the order of the first, third, and second steps, an optical member having an antireflection grating is formed on substantially the entire optical surface. A method for manufacturing an optical member, comprising: The method for manufacturing an optical member according to any one of claims 1 to 3, wherein the central grating portion and the peripheral grating portion are formed with a period equal to or less than half the wavelength of the incident light. The method according to any one of claims 1 to 4, wherein the peripheral grating portion is formed in a substantially concentric groove shape. The method for manufacturing an optical member according to claim 1, wherein the central lattice portion is formed in a convex or concave substantially conical shape.

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