JP2004042493A - Mold and optical element - Google Patents

Abstract

An object of the present invention is to release a molded product from a mold with high precision.
A molding die (6) for transferring a fine shape having a desired optical function to a resin material to form an optical element, the first forming surface for transferring the fine shape to the resin material. 8 and a second molding surface provided outside the effective range of the first molding surface and having a concave portion 7 deeper than the depth of the fine shape.
[Selection] Fig. 6

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a molding die for transferring a fine shape having a desired optical function to a surface of a resin material, and an optical element molded by the molding die.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as one of the molding techniques of a diffractive optical element, there is a replica molding technique which is excellent in large-area moldability and high transferability and is suitable for mass production due to its ease of molding technique. In this replica molding technique, a photocurable resin is dropped on a molding surface of a mold having an inverted shape of a desired optical shape, a lens blank is pressed thereon, and the resin is spread out. The molding is performed by irradiating light from a light source to cure the photocurable resin and releasing the cured resin together with the lens blank.
[0003]
In such mold release in replica molding, the cured resin easily adheres or adheres to the mold surface, or the fine shape is deformed or damaged by the stress at the time of mold release. It is difficult to release well.
[0004]
Therefore, in a replica molding method for molding a diffractive optical element having a desired shape, many mold release methods have been proposed for improving the mold release property and obtaining a high-precision molded article excellent in transferability.
[0005]
As a known technique for improving the releasability, application of a release agent to a molding surface or addition of a release agent to a resin material, which is a general technique, is already known. Further, as a more specific method, Japanese Patent Laid-Open No. 5-50442 discloses a method of applying a dense / dense substance to the outside of the optical effective diameter of the mold or forming a predetermined shape that maximizes the stress at the time of mold release. A method of reducing the initial adhesion between the mold and the molded article by providing the mold has been proposed. Further, in Japanese Patent Application Laid-Open No. 4-144718, a crack is generated in the outer peripheral portion by vertically moving one of an inner mold and an outer mold of a molding die composed of an inner mold and an outer mold that can move up and down, Methods for facilitating demolding have been proposed.
[0006]
[Problems to be solved by the invention]
However, the technology disclosed in the above-mentioned publications may not be applicable to replica mold release of a diffractive optical element having a desired fine shape, and when more precise moldability and efficient productivity are required. The following problems occur.
[0007]
In replica release of a diffractive optical element having a fine shape on a flat or curved optical function surface, deformation or loss of the lattice due to stress at the time of release is inevitable to some extent. In replica release, a stress at the time of release, which is distributed in a complicated manner, is applied to a minute shape portion, and a deformation or a defect is given to a minute lattice portion or the like. Needless to say, these deformations and defective portions significantly reduce the optical performance of the optical element.
[0008]
Therefore, as one of the methods for avoiding this obstacle, there is a method of applying a release agent on the mold molding surface to reduce the adhesion between the mold and the cured resin. Due to a difference in film thickness or dripping, the optical fine shape on the molded surface which has been extremely precisely processed is distorted.
[0009]
On the other hand, in the technique of adding a release agent to the resin material itself, effects such as deterioration of the environmental resistance of the resin material and a decrease in the refractive index are observed, which is not preferable as an optical material for forming a diffractive optical element.
[0010]
Further, in the molding die disclosed in JP-A-5-50442 for reducing the initial adhesive force at the time of replica release, even if the initial adhesive force at the time of release can be reduced, the optical fine shape can be reduced. The effect cannot be obtained up to the stress at the time of mold release applied to the part.
[0011]
Further, in the molding die disclosed in Japanese Patent Application Laid-Open No. 4-144718, not only the stress at the time of mold release imposed on the optical fine shape portion cannot be reduced, but also the production tact time due to the mold operation process. This leads to an increase in the production time and the scale of the production apparatus itself, which not only lowers productivity but also significantly increases costs.
[0012]
Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to enable a molded product to be released from a mold with high accuracy.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, a molding die according to the present invention is a molding die for transferring a fine shape having a desired optical function to a resin material and molding an optical element. A first molding surface for transferring the fine shape to the resin material; and a first molding surface provided outside the effective range of the first molding surface, the concave shape portion having a depth greater than the depth of the fine shape. 2 molding surface.
[0014]
In the molding die according to the present invention, the fine shape has a light diffraction function as the optical function.
[0015]
Further, in the molding die according to the present invention, the fine shape is constituted by concentric unevenness.
[0016]
Further, in the molding die according to the present invention, the concave portion is formed concentrically with the fine shape outside the effective diameter of the fine shape.
[0017]
Further, in the molding die according to the present invention, the concave portion is formed of a groove having a rectangular cross section.
[0018]
Further, in the molding die according to the present invention, the concave portion has a trapezoidal groove in cross section.
[0019]
Further, in the molding die according to the present invention, the concave portion is formed of a V-shaped groove in cross section.
[0020]
Further, the optical element according to the present invention includes an optical function surface on which a fine shape is formed, and a convex portion which is arranged outside the effective range of the optical function surface and has a height higher than the fine shape. It is characterized by.
[0021]
Further, in the optical element according to the present invention, the fine shape has a light diffraction function as an optical function.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0023]
First, an outline of the present embodiment will be described.
[0024]
In this embodiment, a photocurable resin is dropped on a mold surface having an optically desired fine shape, and the photocurable resin is pressed with a flat or curved glass substrate, and irradiated with light to form a diffractive optical element. In a molding die to be molded, a groove or opening shape sufficiently deeper than a fine shape depth on a desired optical function surface is provided on a molding surface outside the optically effective portion of the molding die.
[0025]
In addition, the inverted shape of the concentric or vertical stripe fine shape of the desired diffractive optical element is processed on the molding surface, and the molding of the fine surface of the molding surface with the photocurable resin is performed by the molding die. The molding surface is configured so that it is performed simultaneously with the shape molding with a photocurable resin having a groove or opening shape that is sufficiently deep compared to the fine shape depth in the desired optical function surface provided outside the optical effective surface. I have.
[0026]
Further, the diffractive optical element of the present embodiment is a molded diffractive optical element formed by so-called replica molding in a molding die, and outside the optically effective portion thereof, compared with a fine shape height on a desired optical functional surface. Also, a sufficiently high convex shape is formed.
[0027]
By using the above configuration, the following effects can be obtained. FIG. 1 is a schematic view showing a mold release process of replica molding. A process of applying an external force F and releasing the resin 3 after the resin 3 pressed by the lens blank 1 and the molding die 2 is cured is shown.
[0028]
FIG. 2 shows a stress state at the time of mold release at the left end of the mold in the initial stage of mold release. The component force of the releasing force f applied to the first lattice at the left end by the external force F can be divided into a centripetal force f2 due to the warpage of the lens blank 1 and the resin 3, and a force f1 in the tangential direction of the warped curved surface. These stresses at the time of releasing are continuously applied to each lattice as the releasing proceeds.
[0029]
The stress that causes deformation or loss of the lattice in the replica release is f1 in the drawing, and the present embodiment shows a configuration in which the stress f1 during release is reduced or dispersed by an easy method.
[0030]
FIG. 3 is a schematic diagram illustrating a mold release process of replica molding according to the configuration of the present embodiment.
[0031]
The external force F after the resin 3 pressed by the molding die 5 provided with a groove or opening shape 4 which is sufficiently deeper than the fine shape depth on the optical function surface on the molding surface outside the optically effective portion is cured. 3 shows a demolding process.
[0032]
FIG. 4 shows a stress state at the time of mold release at the left end of the mold 5 in the initial stage of mold release of the mold 5.
[0033]
The component force of the releasing force f3 applied to the left end groove shape portion by the external force F can be divided into a centripetal force f5 due to the warpage of the lens blank 1 and the resin 3, and a force f4 in the tangential direction of the warped curved surface. Further, at this time, the stress f1 ′ that causes deformation or loss of the grating is also applied to the leftmost first grating portion, which is the optical function surface, at all. However, warping due to the releasing force F of the lens blank 1 or the resin 3 is also reduced by stress concentration on the groove-shaped portion 4 or stress dispersion on the optical function surface, and the releasing stress F1 ′ is not deformed or damaged. It can be sufficiently suppressed to a slight force. The stress f1 ′ at the time of mold release is continuously applied to each lattice at the same time as the mold release proceeds, but the height of the groove-shaped portion 4 is sufficiently higher than the lattice height of the optical function surface. Accordingly, the release of the optical function surface can be completed before the release of the groove-shaped portion 4, and the stress at the time of release can be concentrated on the groove-shaped portion 4.
[0034]
Therefore, the deformation or loss of the optical function surface lattice due to the stress at the time of mold release is reduced, the productivity in replica molding of the diffractive optical element having a fine shape is improved, the cost is reduced, and the sufficient optical function is satisfied. A replica molded product having a desired shape can be obtained.
[0035]
(1st Embodiment)
FIG. 5 is a diagram showing a schematic configuration of a replica molding apparatus according to the first embodiment of the present invention.
[0036]
In FIG. 5, reference numeral 6 denotes a molding die provided with an inverted shape 8 of a desired optical function shape and a groove-shaped portion 7 on its molding surface. The molding die 6 is fixed, and a lens blank 10 is placed on a ring-shaped lens blank holding member 9 in which the molding die 6 is fitted, and the center axis of the lens blank 10 and the molding surface of the molding die 6 are formed. The alignment with the center axis is realized by fitting the lens blank 10 into the fitting portion of the lens blank holding member 9. The lens blank 10 is made of glass or plastic material, and has a flat or curved optical surface.
[0037]
The ring-shaped lens blank holding member 9 is held movably up and down. A photo-curable resin 11 is supplied onto the molding surface of the molding die 6 by a dispenser (not shown), and an ultraviolet irradiation lamp 12 is provided above the lens blank 10 so that ultraviolet rays are perpendicular to the optical function surface of the molding die. It is set to be incident.
[0038]
As the UV-curable resin 11, an optical resin such as an acrylate-based, methacrylate-based, or epoxy resin whose polymerization starts at a wavelength of around 365 nm is used. As the UV irradiation lamp 12, a high-pressure mercury lamp or an ultra-high-pressure mercury lamp is used. A light source such as a lamp having an oscillation peak near a wavelength of 365 nm is used.
[0039]
FIG. 6 is a top view and a side view of the molding die 6 in the present embodiment.
[0040]
The fine shape forming the optical function surface 8 has a blazed diffraction grating having a grating height of 5 to 20 μm and a grating width of 0.1 to 10 mm on a plane within an optical effective diameter range of 20 mm, and is shown in a top view. And concentrically arranged in a convex shape toward the center. On the mold forming surface outside the optical effective diameter, groove-shaped portions 7 having a groove depth of 80 to 200 μm and a groove width of 0.5 to 1 mm, which are sufficiently deeper than the lattice height of the optical function surface, are arranged concentrically. As shown in FIG. 13, the shape and size of the groove-shaped portion 7 are selected in consideration of the material and shape of the lens blank, the characteristics of the molding resin, and the optical function surface shape of the molding die. . Specifically, the cross-sectional shape of the groove-shaped portion 7 may be a trapezoid or a V-shape as shown in FIG.
[0041]
FIG. 7 is a diagram showing a diffractive optical element molded by the molding die shown in FIG.
[0042]
The optical function surface 8 ′ of the resin layer formed on the lens blank 10 is formed concentrically as a concave shape toward the center of the blazed diffraction grating, that is, an inverted shape of the above-mentioned mold. Outside the optical effective diameter of the diffractive optical element, a block portion 7 ', which is the inverted shape of the groove-shaped portion 7 on the mold forming surface, is formed concentrically.
[0043]
Hereinafter, the molding process in the present embodiment will be described with reference to FIGS.
[0044]
First, an appropriate amount of the ultraviolet curable resin 11 is supplied by a dispenser (not shown) to the vicinity of the center of the molding surface of the molding die 6, and the lens blank 10 which has been subjected to a coupling treatment for increasing the adhesive force with the resin on one surface in advance is prepared. Then, it is fitted into the ring-shaped lens blank holding member 9 with the coupling processing surface facing down. At this time, a mechanism for holding the lens blank 10 such as a centering chuck or the like may be provided. Thereafter, the ring-shaped lens blank holding member 9 is lowered, the mold 6 and the lens blank 10 are relatively approached to each other, and the ultraviolet curable resin 11 has a desired thickness and a groove-shaped portion 7 outside the optical effective diameter. Fill so as to fill up to the outer circumference. At this time, the liquid contact speed must be adjusted in consideration of the viscosity of the resin and the wettability of the molding surface in order to prevent air bubbles from entering the resin 11 and to prevent the resin from being filled into the molded shape. Thereafter, ultraviolet rays are applied to the resin layer by an ultraviolet irradiation lamp 12. After the polymerization and curing are completed, the diffractive optical element including the cured resin 11 and the lens blank 10 is separated from the mold 6 by raising the ring-shaped lens blank holding member 9.
[0045]
As described above, in this mold in which the blazed grating is arranged concentrically in a convex shape toward the center, it is most effective that the mold releasing direction proceeds from the outer periphery of the mold toward the center of the mold. is there. However, the release force applied to the outer peripheral portion of the lens blank 10 due to the elevation of the ring-shaped lens blank holding member 9 must be applied to this outer peripheral portion as uniformly as possible. Therefore, the upper surface of the mold 6 and the upper surface of the ring-shaped lens blank holding member 9 are arranged so as to be as parallel as possible with high precision.
[0046]
In addition, a pressing member 13 as shown in FIG. 9 may be provided on the lens blank 10 in order to make the mold release proceeding from the outer periphery of the mold end at the center of the mold. The pressing member 13 is vertically movably held on the optical axis of the mold by a device (not shown), and presses the lens blank 10 with an appropriate force at the time of releasing the mold. Therefore, the force by which the pressing member 13 presses the center of the molding die through the lens blank 10 and the resin layer 11 causes the stress at the time of releasing, which is applied to the outer peripheral portion of the lens blank 10, to progress toward the center of the die.
[0047]
Further, it is preferable that the ascending speed of the ring-shaped lens blank holding member 9 by the driving mechanism is set to a continuous and gentle speed using a motor or the like as much as possible in consideration of production tact. In addition, a more uniform releasing force can be applied by simultaneously raising the lower surface of the ring-shaped lens blank holding member 9 to the same pressure at three or more application points by using a hydraulic drive mechanism.
[0048]
However, in the configuration of the present embodiment, the replica release can be performed with high precision by reducing or dispersing the release stress applied to the optical fine shape portion during release. Therefore, a diffractive optical element having a desired shape that satisfies a sufficient optical function can be obtained, and at the same time, productivity in replica molding of the diffractive optical element can be improved and cost can be reduced.
[0049]
(Second embodiment)
FIG. 10 is a top view and a side view of the molding die 14 in the second embodiment.
[0050]
The fine shape forming the optical function surface 8 has a blazed diffraction grating having a grating height of 5 to 20 μm and a grating width of 0.1 to 10 mm on a plane within an optical effective diameter range of 20 mm, and is shown in a top view. So that they are arranged concentrically with a concave shape toward the center. On the mold forming surface outside the optical effective diameter, a groove portion 7 having a groove depth of 80 to 200 μm and a groove width of 0.5 to 1 mm, which is sufficiently deeper than the lattice height of the optical function surface, is arranged concentrically.
[0051]
FIG. 11 is a diagram showing a diffractive optical element manufactured by this mold. The optically functional surface 8 'of the resin layer formed on the lens blank 10 is formed concentrically as a convex shape toward the center of the blazed diffraction grating, that is, an inverted shape of the molding die. Outside the optical effective diameter of the diffractive optical element, a block portion 7 ', which is the inverted shape of the groove-shaped portion 7 on the mold forming surface, is formed concentrically.
[0052]
FIG. 12 shows a stress state at the time of mold release at the end of the mold at the initial stage of mold release of the mold 14, and the reference numerals in the figure are the same as those in FIG. 4. In the first embodiment, the release stress f1 ′ is applied to the vertical side surface of the lattice, but in the present embodiment, the stress f1 ′ is applied to the lattice slope. Therefore, the stress f1 ′ at the time of release in the present embodiment is further reduced, and the deformation or loss of the optical function surface lattice can be further prevented.
[0053]
This embodiment is different from the first embodiment in the shape of the molding die and the shape of the diffractive optical element to be manufactured, and the other configuration is the same.
[0054]
As described above, according to the above-described embodiment, a groove or an opening that is sufficiently deep compared to the fine shape depth of the desired optical function surface is provided on the molding surface outside the optically effective portion of the replica molding die. An easy method can reduce or disperse the stress at the time of release applied to the optical fine shape portion at the time of release, and perform replica release with high accuracy. As a result, it is possible to improve productivity in replica molding of the diffractive optical element, reduce costs, and obtain a diffractive optical element having a desired shape that satisfies a sufficient optical function.
[0055]
【The invention's effect】
As described above, according to the present invention, a molded product can be released from a mold with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a conventional mold release method.
FIG. 2 is a diagram illustrating a conventional mold release method and its operation.
FIG. 3 is an explanatory diagram of a mold and a method of releasing the mold according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a mold release method according to the first embodiment of the present invention and its operation.
FIG. 5 is a cross-sectional view of a forming die and a forming apparatus according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view and a top view of a molding die according to the first embodiment of the present invention.
FIG. 7 is a sectional view and a top view of the optical element according to the first embodiment of the present invention.
FIG. 8 is a sectional view of a molding die and a molding apparatus according to the first embodiment of the present invention.
FIG. 9 is a sectional view of a molding die and a molding device according to the first embodiment of the present invention.
FIG. 10 is a cross-sectional view and a top view of a molding die according to a second embodiment of the present invention.
FIG. 11 is a sectional view and a top view of an optical element according to a second embodiment of the present invention.
FIG. 12 is a diagram illustrating a mold release method according to a second embodiment of the present invention and its operation.
FIG. 13 is a view showing a modification of the groove portion.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 lens blank 2 molding die 3 photocurable resin 4 grooved portion 5 molding die 6 molding die 7 grooved portion 7 ′ grooved portion of optical element 8 optical function surface 8 ′ of molding die optical element Optical function surface 9 Lens blank holding member 10 Lens blank 11 Photocurable resin 12 Ultraviolet irradiation lamp 13 Pressing member 14 Mold

Claims (9)

A molding die for molding an optical element by transferring a fine shape having a desired optical function to a resin material,
A first molding surface for transferring the fine shape to the resin material;
A second molding surface provided outside the effective range of the first molding surface and having a concave portion deeper than the depth of the fine shape. The molding die according to claim 1, wherein the fine shape has an optical diffraction function as the optical function. The molding die according to claim 1, wherein the fine shape is formed of concentric concave and convex. The molding die according to claim 3, wherein the concave portion is formed concentrically with the fine shape outside the effective diameter of the fine shape. The molding die according to claim 1, wherein the concave portion has a rectangular cross section. The molding die according to claim 1, wherein the concave portion has a trapezoidal groove in cross section. The molding die according to claim 1, wherein the concave portion has a V-shaped groove in cross section. An optical function surface on which a fine shape is formed,
An optical element comprising: a convex portion that is arranged outside an effective range of the optical function surface and that is higher than the fine shape. The optical element according to claim 8, wherein the fine shape has a light diffraction function as an optical function.

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