JP2005037868A - Method for forming antireflection face, method for manufacturing mold for forming antireflection member, mold, antireflection member, and method for manufacturing master member for manufacturing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection member for decreasing the manufacture cost by forming minute projections to constitute a wavelength grating without using deposition of fine particles or a semiconductor process, and provide a method for forming an antireflection face, a method for manufacturing a master member for the manufacture of the mold, and a method for manufacturing the mold, and the mold. <P>SOLUTION: In the process of forming an antireflection face of an optical element, many V-grooves 52, 53 are vertically and horizontally formed on the surface 51 of an optical element material 5 or the like by a cutting process using a cutting tool 6 or the like. Thereby, minute pyramid-like projections 3 constituting a wavelength grating for antireflection are formed in the region surrounded by the V-grooves 52, 53. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antireflection member having a wavelength grating formed by a large number of pyramidal microprojections, a method of forming an antireflection surface of the antireflection member, a method of manufacturing a mold for forming an antireflection member, a mold, The present invention relates to a method for manufacturing a master member for manufacturing a mold.

  In an optical element used in various optical devices, an antireflection multilayer film is often formed on the surface in order to reduce energy loss and stray light due to light reflection. In such a multilayer film, reflection is prevented by interference between the layers due to interference.

  However, when a multilayer film is used for antireflection, substances having an optimum refractive index as the multilayer film are limited, and therefore there may be no optimum combination of substances depending on the material and incident wavelength. Further, there may be a problem that heat resistance and durability are low due to physical, chemical, and thermal mismatch due to the difference in the material of each layer. Furthermore, since the multilayer film is formed by vapor deposition, there is a problem that the cost of the vapor deposition material is required.

  In place of such a multilayer film, reflection may be prevented by forming a wavelength grating composed of minute protrusions having a period shorter than the wavelength of light on the surface of the optical element. A wavelength grating composed of minute protrusions having a period shorter than the wavelength of light is equivalent to a medium having a certain refractive index, and an antireflection effect similar to that of a thin film can be obtained. Furthermore, when the shape of the microprotrusions is a conical shape or a pyramid shape, the volume occupancy gradually changes from the root of the microprotrusions to the tip side. Then, since the equivalent refractive index on the surface gradually changes, the antireflection characteristic is improved. In addition to this, a configuration has also been proposed in which irregularities are randomly formed on the surface to achieve similar antireflection characteristics (see, for example, Patent Document 1).

  As a method of forming such a wavelength grating, there are conventionally a method of forming fine protrusions by depositing fine particles on the surface of the base and a method of forming irregularities by etching the base. Here, if the base is a material for forming an optical element, an optical element having an antireflection surface is directly manufactured. On the other hand, if the base is a mold material or a material of a master member for manufacturing a mold, injection molding or press molding is performed using the manufactured mold.

JP 2002-286906 A

  However, a method that uses a semiconductor process such as deposition of fine particles or etching to produce a wavelength grating has problems of low productivity and high material cost. In particular, in the method using etching, an exposure mask is required in the photolithography process. Therefore, it is necessary to prepare a new mask each time the pitch of minute projections constituting the wavelength grating is changed, which increases the manufacturing cost. There is a problem.

  In view of the above problems, an object of the present invention is to reduce the manufacturing cost by forming minute protrusions for forming a wavelength grating without using the deposition of fine particles or a semiconductor process. An object of the present invention is to provide an antireflection member, a method of forming an antireflection surface of the antireflection member, a method of manufacturing a mold for forming an antireflection member, a mold, and a method of manufacturing a master member for manufacturing a mold.

  In order to solve the above problems, in the present invention, a large number of V-shaped grooves are formed vertically and horizontally on the surface of the material by cutting, and each of the portions surrounded by the V-shaped grooves has a pyramidal shape. A microprotrusion is formed, and an antireflection surface is formed using the large number of pyramidal microprotrusions.

  Therefore, in the present invention, since the pyramid-shaped microprotrusions for forming the wavelength grating are formed without using a semiconductor process such as deposition of fine particles or etching, and using cutting, the productivity is high. In addition, material costs can be reduced. In addition, since it is a cutting process, it is easy to change the pitch and height of the minute protrusions constituting the wavelength grating. Therefore, the manufacturing cost can be reduced.

  Specifically, as described below, the present invention relates to a mold used for forming a pyramid-shaped microprotrusion directly on the antireflection surface of the antireflection member, or to mold the antireflection member, and the mold. It can be used to form pyramid-shaped microprotrusions on a master member for manufacturing a mold.

  That is, in the present invention, a large number of V-shaped grooves are formed vertically and horizontally by cutting the surface of the material of the antireflection member, and each of the portions surrounded by the V-shaped grooves has an antireflection wavelength. A pyramidal minute protrusion constituting the lattice is formed.

In another embodiment of the present invention, the antireflection member forming mold is manufactured by the following two methods. That is, a large number of V-shaped grooves are formed vertically and horizontally by cutting directly on the surface of the material of the mold for forming the anti-reflective member, and each of the portions surrounded by the V-shaped grooves has a pyramidal shape. First, in the same manner as in the first method, cutting is performed on the material surface of the first method for forming the microprojections and the surface of the master member for manufacturing the mold for manufacturing the mold for forming the antireflection member. A plurality of V-shaped grooves are formed vertically and horizontally to form pyramidal microprojections in each of the portions surrounded by the V-shaped grooves, and then the microprojections formed on the master member are formed. The shape can be transferred to a mold material and manufactured by a second method for forming an antireflection surface molding surface of the mold. With the antireflection member forming mold manufactured by the second method, the antireflection surface of the antireflection member formed by injection molding or press molding has a pyramidal shape that constitutes the antireflection wavelength grating. A microprotrusion is formed.
On the other hand, a pyramidal minute hole is formed on the antireflection surface of the antireflection member formed by injection molding or press molding by the antireflection member forming mold manufactured by the first method. However, this minute hole can provide the same antireflection effect as the minute protrusion. As for the shape of the micropores, the volume content gradually changes from the root of the micropores to the tip side by adopting a pyramid shape like the microprojections, so the equivalent refractive index on the surface gradually changes, preventing reflection. The characteristics are improved.

In the present invention, cutting is used to form the pyramid-shaped microprotrusions for forming the wavelength grating, so that the productivity is high and the material cost can be reduced. In addition, since it is a cutting process, it is easy to change the pitch and height of the minute protrusions constituting the wavelength grating. Therefore, it is possible to reduce the manufacturing cost of the antireflection member and the mold.

  In the following, referring to the drawings, an optical element (antireflection member) having a wavelength grating for preventing reflection on the surface and a minute projection for forming a pyramidal minute protrusion constituting the wavelength grating. The protrusion forming method will be described.

(Configuration of optical element)
1A and 1B are a perspective view showing an optical element to which the present invention is applied, and an explanatory diagram of a refractive index distribution on the surface of the optical element.

  The optical element 1 shown in FIG. 1A constitutes a common optical system in an optical apparatus such as an optical pickup device that uses a laser beam to reproduce different types of optical recording disks such as CDs and DVDs. A diffraction grating, an objective lens, and the like, and a wavelength grating 2 for preventing reflection are provided on the surface.

  The wavelength grating 2 is a two-dimensional array of a large number of quadrangular pyramidal microprojections 3, and each quadrangular pyramidal microprojection 3 has coordinate axes orthogonal to each other as shown in FIG. Are formed in a matrix by a V-shaped groove 52 parallel to the X-axis and a V-shaped groove 53 parallel to the Y-axis. From the portion) toward the tip 32 in the Z-axis direction with a height h. For this reason, the volume occupancy of the surrounding medium and the quadrangular pyramidal microprojections 3 gradually changes from the bottom 31 to the tip 32 of the microprojections 3. For this reason, as shown in FIG. 1 (B), between the height h from the bottom 31 of the wavelength grating 2 to the tip 32, the refractive index n2 of the surrounding medium (air) determines the quadrangular pyramid-shaped microprojections 3. It gradually changes to the refractive index n1. Further, the periods Px and Py of the bottom 31 in the X-axis and Y-axis directions are shorter than the wavelength λ of the incident light 4 incident on the optical element 1. Accordingly, in the optical element 1, the change in the refractive index with respect to the incident light 4 is moderate due to the wavelength grating 2, so that the reflection of the incident light 4 can be prevented.

(Manufacturing method 1 of the optical element 1)
2A, 2 </ b> B, and 2 </ b> C are explanatory views showing a method of forming the quadrangular pyramid-shaped microprojections 3 constituting the wavelength grating 2 of the optical element shown in FIG. 1.

  In this embodiment, the surface 51 of the optical element material 5 is cut with a cutting tool 6 as shown in FIGS. The cutting tool 6 is a single-crystal diamond cutting tool having a V-shaped cutting edge 61. A V-shaped groove 52 extending in the X-axis direction is formed by cutting on the surface 51, and each time one piece is cut, the cutting tool 61 moves in the Y-axis direction. The next V-shaped groove 52 is formed on the surface 51 by cutting. By such a cutting process, first V-shaped grooves 52 arranged in the Y-axis direction are formed on the surface of the optical element material 5. The processing pitch of the first V-shaped groove 52 is equal to or less than the wavelength λ of the incident light 4.

  Next, as shown in FIG. 2C, the direction of the cutting tool 6 is changed by 90 °, and the second V-shaped groove 53 extending in the Y-axis direction perpendicular to the first V-shaped groove 52 is cut into the surface 51. To form. Further, every time one second V-shaped groove 53 is cut, the cutting tool 6 is moved in the X-axis direction to form the next V-shaped groove 53 by cutting. Here, the processing pitch of the second V-shaped groove 53 is also equal to or less than the wavelength λ of the incident light 4.

  By such a cutting process, the quadrangular pyramid-shaped microprotrusions 3 are formed on the surface 51 at portions partitioned by the first V-shaped groove 52 and the second V-shaped groove 53. The cutting of the second V-shaped groove 53 can be performed by rotating the optical element material 5 by 90 ° relative to the cutting tool 6 instead of changing the orientation of the cutting tool 6 by 90 ° with respect to the optical element material 5. .

  Thus, in this embodiment, the quadrangular pyramid-shaped microprojections 3 are formed by machining using the cutting tool 6. Therefore, compared to the case where etching, photolithography, electron beam lithography, or the like is used, material costs can be reduced and productivity is high. Moreover, since it is machining, it is easy to change the pitch and height of the microprojections 3 while the degree of freedom of the machining shape is high. Therefore, the manufacturing cost of the optical element 1 provided with the antireflection surface can be reduced.

(Manufacturing method 2 of the optical element 1)
FIGS. 3A, 3B, and 3C are explanatory views showing another mode of forming the quadrangular pyramid-shaped microprotrusions 3 that constitute the wavelength grating 2 of the optical element shown in FIG.

  In manufacturing method 1, a V-shaped groove was formed by linearly moving a diamond tool having a V-shaped cutting edge. However, as shown in FIGS. 3 (A), (B), and (C), a V-shaped groove is formed at the tip of the shank 71. The V-grooves 52 and 53 are formed on the surface 51 of the optical element material 5 by a fly-cut method in which the diamond blade portion 72 is formed and the shank 71 is rotated around the axis at a high speed. You may form the square protrusion-shaped microprotrusion 3 which comprises.

  Note that the steps performed in this embodiment have the same basic configuration as the method described with reference to FIG. 2, so the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

(Manufacturing method 3 of the optical element 1)
In both manufacturing methods 1 and 2, the V-shaped grooves 52 and 53 are directly formed on the surface 51 of the optical element material 5, and the optical element 1 including the antireflection surface on which the quadrangular pyramid-shaped microprojections 3 are formed is directly applied. In the same manner as described with reference to FIG. 2 and FIG. 3, on the surface of the material for manufacturing the mold for forming the antireflection member or the master member for manufacturing the mold. On the other hand, by manufacturing a mold or a master member in which a large number of V-shaped grooves are formed vertically and horizontally by cutting, and each of the portions surrounded by the V-shaped grooves is formed with pyramidal microprojections. Also good.

When manufacturing a master member for manufacturing a mold to form an antireflection member, the shape of the minute projections formed on the master member is transferred to the mold material, An antireflection surface molding surface is formed. Therefore, by the antireflection surface molding surface of this mold, the pyramid-shaped minute projections constituting the wavelength grating for antireflection are formed on the antireflection surface of the antireflection member formed by injection molding or press molding. The

  On the other hand, in the case of directly manufacturing a reflection member mold by forming a large number of V-shaped grooves vertically and horizontally on the surface of the mold for forming the antireflection member, this mold is used. With the antireflection surface molding surface, pyramid-shaped micropores are formed on the antireflection surface of the antireflection member formed by injection molding or press molding. This microhole also has the same antireflection effect as the microprojection, and the volume content gradually changes from the root part to the tip side of the microhole by making the microhole shape into a pyramid shape. The refractive index changes gradually, and the antireflection characteristics are improved.

  Even in such a form, since the quadrangular pyramidal microprotrusions are formed by cutting, the material cost can be reduced and the processing time can be reduced compared to the case of forming by etching, photolithography, electron beam drawing method, etc. Therefore, the mold for forming the master member for manufacturing the mold and the antireflection member can be manufactured at a low cost. In addition, since machining is performed, the degree of freedom of the machining shape can be improved, and the pitch and height of the minute protrusions can be easily changed. Therefore, the manufacturing cost of the optical element having the antireflection surface can be reduced.

(A), (B) is a perspective view which shows the optical element to which this invention is applied, and explanatory drawing of the refractive index distribution in the optical element surface. (A), (B), (C) is explanatory drawing which shows the method of forming the square pyramid-shaped microprotrusion which comprises the wavelength grating of the optical element shown in FIG. (A), (B), (C) is explanatory drawing which shows another method of forming the square pyramid-shaped microprotrusion which comprises the wavelength grating of the optical element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical element 2 Wavelength grating 3 A pyramidal microprotrusion 4 Incident light 5 Optical element material 6 Bit 31 Tip 32 Bottom 51 Surface 52, 53 V-shaped groove 61 Cutting edge 71 Shank 72 Blade

Claims (6)

  A large number of V-shaped grooves are formed vertically and horizontally by cutting on the surface of the material, and each of the portions surrounded by the V-shaped grooves has a pyramidal minute projection that constitutes an antireflection wavelength grating. A method of forming an antireflection surface, characterized in that:   A large number of V-shaped grooves are formed vertically and horizontally by cutting on the surface of the mold material for forming the antireflection member, and each of the portions surrounded by the V-shaped grooves has a pyramidal minute projection. The manufacturing method of the metal mold | die for anti-reflective member formation characterized by manufacturing the metal mold | die with which was formed.   A mold manufactured by the method defined in claim 2.   Formed by injection molding or press molding using a metal mold as defined in claim 3, the surface formed by the antireflection surface molding surface has pyramidal micropores constituting an antireflection wavelength grating. An antireflective member characterized by being formed.   An antireflection member having an antireflection surface formed by the method defined in claim 1. A large number of V-shaped grooves are formed vertically and horizontally by cutting on the surface of a material for manufacturing a master member for mold manufacture, and each portion surrounded by the V-shaped grooves has a pyramidal shape. A method for producing a master member for producing a mold, comprising producing a master member on which fine protrusions are formed.

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