Production method of curved-surface metal mold having fine uneven structure and production method of optical element using this metal mold
A method of easily manufacturing a metal mold able to add an antireflection structure to a lens or the like having a complicated surface shape such as an aspherical lens. The method comprises the steps of forming a silicon dioxide film (SiO2) film (2) on a curved-surface base substrate (1) formed in a specified shape, etching the silicon dioxide film (SiO2) film (2) using a resist mask (3) to form a specified shaped antireflection structure pattern, bonding a metal used for the metal mold (4) onto a silicon dioxide film (SiO2) film (21) on which this antireflection film pattern is formed to transfer the antireflection film pattern onto the metal used for the metal mold (4), and then re-moving the silicon dioxide film (SiO2) film to form a metal mold (4a) having an antireflection structure on the curved surface.
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This invention relates to a method for manufacturing curved-surface metal molds having a fine uneven structure serving as an antireflection structure or the like, a method for manufacturing the curved-surface metal molds having the fine uneven structure by using easily workable materials to form a curved surface, and a method for manufacturing optical elements with the metal mold.
BACKGROUND ARTConventionally, optical elements such as optical pickups and aspherical lenses made of glass, plastic or other light-transmitting materials are subjected to a surface treatment to prevent light reflection on the light incident surface of a substrate. This surface treatment includes a method in which a multilayer film composed of laminated thin dielectric films is formed on a surface of a light-transmitting substrate by vacuum deposition or the like and a method in which fine, dense unevenness are provided on a surface of an optical element.
An antireflection structure of fine, dense uneven shape formed on the surface of the optical element is known to be formed by molding plastic with a metal mold (e.g. Japanese unexamined patent publication No. 62-96902).
The metal mold for forming the optical element having the antireflection structure of fine, dense uneven shape is formed with a substrate made from quartz or silicon. The substrate is subjected to an etching process to form a specified antireflection structure thereon and plated to form the metal mold.
By the way, in order to provide the above-mentioned antireflection structure on a lens, such as a lens for optical pickups, having a specified curvature, a predetermined treatment is required to form a curved surface on the quartz or silicon which will be a substrate.
BRIEF SUMMARY OF THE INVENTION Problems to be SolvedIn the case of a lens having a complex surface shape like an aspherical lens, it is difficult to work on the substrate to form the metal mold. In other words, the quartz or silicon used as a substrate is unworkable and often subjected to fractures and chips in the course of manufacture of the substrate. Therefore, the manufacture of the metal mold is time consuming and expensive.
This invention is made to solve the above-discussed conventional problems and has an object to provide a method for readily manufacturing metal molds to add the fine, dense uneven shape to a lens having complex surface shapes such as an aspherical lens.
In addition, this invention has an object to provide a method for readily manufacturing optical elements, including the lens having complex surface shapes such as an aspherical lens, with the fine, dense uneven shape provided on the surface of the optical elements.
MEANS TO SOLVE THE PROBLEMA production method of the metal mold having the fine uneven structure according to the invention is characterized by: forming a silicon-base film on a curved-surface base substrate formed in a specified shape; etching the silicon-base film with a mask to form a specified shape of a fine uneven pattern; bonding metal used for the metal mold on the silicon-base film with the pattern of the fine uneven structure formed thereon; and removing the silicon-base film after the pattern of the fine uneven structure is transferred to the metal used for the metal mold to form the metal mold with the fine uneven structure on a surface thereof.
The pattern of the fine uneven structure is characterized by being an antireflection pattern.
The mask is made of a photoresist and an antireflective film may be formed between the curved-surface base substrate and silicon-base film.
A mold release material film may be formed between the curved-surface base substrate and silicon-base film.
In addition, the silicon-base film can be a silicon dioxide film formed by a sputtering method.
In addition, a production method of the metal mold having the fine uneven structure according to this invention is characterized by: forming a silicon-base film on a curved-surface base substrate formed in a specified shape; providing a mask on this silicon-base film, the mask having a specified shaped fine uneven pattern on an effective area part of the mask and the uneven pattern changing its volume percent toward the outside; etching the silicon-base film using this mask to form a fine pattern composed of fine unevenness gradually becoming deeper from the outer region to the inner region and having a predetermined depth and shape on the effective area; bonding metal used for the metal mold to the substrate with the uneven pattern formed thereon; and releasing the metal used for the metal mold from the substrate to form a metal mold after the uneven pattern is transferred to the metal used for the metal mold.
In addition, a production method of an optical element, according to this invention, is characterized by: forming a silicon-base film on a curved-surface base substrate formed in a specified shape; etching the silicon-base film using a mask to form a pattern of a specified shaped fine uneven structure; bonding metal used for the metal mold to the silicon-base film with the pattern of fine uneven structure formed thereon; removing the silicon-base film after the pattern of the fine uneven structure is transferred to the metal used for the metal mold to form a metal mold having the fine uneven structure on the curved surface; attaching the metal mold to at least either of a stationary mold or moving mold; and performing an injection molding with the stationary mold and moving mold to manufacture the optical element having the fine uneven structure on at least one of surfaces thereof.
EFFECTS OF THE INVENTIONAs discussed above, according to this invention, a curved-surface base substrate having a specified curved surface shape can be readily formed even if it has a complex shape such as a spherical surface and axisymmetric aspherical surface. Based on the curved surface of this curved-surface base substrate, a metal mold having a specified curved-surface with a fine, dense uneven structure can be formed even if it has a complex shape such as a spherical surface and axisymmetric aspherical surface.
In addition, the provision of the antireflective film allows the resist to be pattered more densely, thereby being able to form the curved-surface metal mold having the antireflection structure of further fine, dense uneven shape.
The use of the mold release material film facilitates the separation between the metal mold side and substrate side.
In addition, the use of the curved-surface metal mold having the antireflection function gradually becoming deeper from the outer region to the inner region and the antireflection structure with the unevenness of conical shape formed at a predetermined pitch on the effective area allows the filled resin to be readily peeled off from the outer region, thereby eliminating the possible breakage of the metal mold (stamper) and molded articles.
BRIEF DESCRIPTION OF THE DRAWINGS
- 1 curved-surface base substrate
- 2 a silicon dioxide film (SiO2) film
- 3 resist film
- 4 metal layer
- 4a,4b metal mold (stamper)
The following is a description of embodiments of this invention with reference to drawings.
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According to the above-described embodiment, the curved-surface base substrate 1 having a specified curved surface, even if the specified curved surface is complicated in shape like a spherical surface and axisymmetric aspherical surface, can be readily formed by the ultra precision microfabrication equipment. By undergoing the above steps B-H along the curved surface of the curved-surface base substrate 1, the curved-surface metal mold 4a having a specified curved surface and an antireflection structure of fine, dense uneven shape can be formed even if the curved surface is complicated in shape like a spherical surface and axisymmetric aspherical surface.
Next description will be made on the second embodiment of this invention with reference to
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In the above-described second embodiment, in addition to the effect of the first embodiment, the antireflective material 11 allows the resist to be patterned more densely, thereby being able to form the curved-surface metal mold 4a having the antireflection structure of finer, denser uneven shape.
Next description will be made on the third embodiment of this invention with reference to
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In the above-described third embodiment, the separation between the mold (stamper) side and base substrate 1 side can be readily achieved.
By the way, when optical elements are formed by filling resin into the above-described metal mold with the antireflection structure of the fine unevenness formed, the resin is filled into the fine pattern having a high aspect. This increases a load upon release of the metal mold from the resin. Especially, adherability significantly increases at the boundary between the non-patterned area and patterned area, and therefore causes breakage of the stamper and molded article. Hence, this fourth embodiment is made for decreasing the load upon the release. For this purpose, the unevenness of the antireflection function are gradually deepened from the outer region of the optical element toward the inner region to gradually increase the load upon the release, thereby readily releasing the filled resin from the outer region. The following description is on the fourth embodiment with reference to
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As discussed above, the curved-surface metal mold 4b, having the antireflection structure with the antireflective function gradually deepening from the outer region toward the inner region in the areas outside the effective area 30a and the conical unevenness formed at a predetermined pitch in the effective area 30a, allows the filled resin to be easily peeled off from the outer region, thereby eliminating the possible breakage of the stamper and molded articles.
A molded article is formed using the metal mold with the antireflection structure formed at a uniform depth as shown in
The structure of this fourth embodiment can provide the same effect even if the structure is applied to the above-discussed second and third embodiments.
Although the silicon dioxide film (SiO2) film is used as a silicon-base film in the above embodiments, a silicon (Si) film, silicon nitride (SiN) film and other films are also available. Further, an SOG film formed by spin-coating organic silane or the like is also available as the silicon-base film.
Next, the manufacture of optical elements using the metal mold according to this invention will be described with reference to
The stationary mold 60 includes a first member 61 in the middle and a second member 62 on the periphery side, and both are made from steel and fixed in a mutually integrated manner. The first member 61 includes a smooth concave molding surface 61a facing the moving mold 70, while the second member 61 includes a molding surface 61b, which is a ring-shaped groove, arranged on the periphery of the molding surface 61a. The molding surface 61a of the first member 61 corresponds to one surface of a lens (not shown) which is a molded article, while the molding surface 62a of the second member 62 corresponds to a flange provided on the periphery of the lens.
The moving mold 70 includes a pushing part 71 which is a molding member in the middle and a main body 72 supporting the pushing part 71 at its periphery. On the end of the pushing part 71, the mold (stamper) 4a manufactured by any one of the above-discussed methods according to the first to fourth embodiments of this invention is attached. The metal mold 4a is formed to have a concave surface corresponding to the other surface of the lens and includes the antireflection structure 40a made of the fine, dense uneven surface on the concave surface. The peripheral molding surface 72a defined by the main body 72 corresponds to the flange on the periphery.
The pushing part 71 is fitted in a hole 72b provided in the main body 72 so as to slide in the axial (X) direction. After mold opening, which means both molds 60 and 70 are disengaged from each other, this pushing part 71 is moved toward the stationary mold 60 with respect to the main body 72, thereby releasing the lens laid on the moving mold 70 side.
Next, lens molding using the molding tool shown in
Next, molten plastic resin is injected into the cavity 80 created between the molds 60 and 70. The molten plastic resin is introduced through the gate 81 to the cavity 80 between molds 60 and 70 to fill up the cavity 80.
Subsequently, the molten plastic resin filled in the cavity 80 dissipates heat and is cooled down. The molten plastic resin injected into the cavity 80 usually has a temperature of 200 to 300 degrees C. and therefore is cooled and cured upon contact with the molding surfaces 40a, 72a, 61a, 61b of the molds 60, 70 which are maintained at generally 100 to 180 degrees C. At this time, the molten plastic resin almost completely penetrates into the fine uneven pattern formed on the molding surface 40a of the pushing part 71.
Next, the molten plastic resin filled in the cavity 80 waits to be completely cured. After all, a lens corresponding to the shape of the cavity 80 is obtained. One surface of the lens is a smooth convex surface corresponding to the molding surface 61a, while the other surface of the lens is a convex surface having the antireflection structure corresponding to the molding surface 40a. In addition, a flange is formed on the periphery of the lens, corresponding to the molding surfaces 61b and 72a.
After that, the mold opening is performed to disengage the moving mold 70 from the stationary mold 60. As a result, the molded article stays on the side of the moving mold 70, but is separated from the stationary mold 60.
Then, the pushing part 71 accommodated in the main body 72 is driven toward the stationary mold 60 by a driving device (not shown). This driving process completely demolds, in other words, separates the lens from the moving mold 71.
Thus obtained lens is applicable to an optical pickup device and so forth. Although the metal mold with the fine uneven pattern is attached to the moving mold 70 in the above embodiment, the metal mold can be attached to the stationary mold 60 and moving mold 70 as appropriate based on the design of the optical element to be manufactured, for example, either of the stationary mold 60 or moving mold 70, or both.
Although the antireflection structure is cited as an example use of the fine, dense uneven shape in the above embodiment, the present invention can be applied to any cases to manufacture the optical-element pattern structure having the other functions as long as the optical elements require the fine, dense uneven shape. For example, the present invention is applicable to manufacture fine patterns included in wave plates and diffraction gratings.
It should be understood that the embodiments disclosed herein are to be taken as examples and are not limited. The scope of the present invention is defined not by the above described embodiments but by the following claims. All changes that fall within meets and bounds of the claims, or equivalence of such meets and bounds are intended to be embraced by the claims.
INDUSTRIAL APPLICABILITYThis invention is applicable to the method for manufacturing diffraction gratings for optical pickup, wave plates for optical pickups, lenses for optical pickups, display covers for cellular phones and other optical elements to provide the antireflection structure on surfaces of these elements.
Claims
1. A production method of a curved-surface metal mold having a fine uneven structure characterized by comprising:
- forming a silicon-base film on a curved-surface base substrate formed in a specified shape;
- etching the silicon-base film with a mask to form a specified shaped fine uneven structure pattern;
- bonding a metal used for the metal mold on the silicon-base film with the fine uneven structure pattern formed thereon; and
- removing the silicon-base film after the fine uneven structure pattern is transferred to the metal used for the metal mold to form the metal mold having the fine uneven structure on the curved surface thereof.
2. The production method of the curved-surface metal mold having the fine uneven structure according to claim 1 characterized in that said fine uneven structure pattern is an antireflection pattern.
3. The production method of the curved-surface metal mold having the fine uneven structure according to claim 1 or 2 characterized in that said mask is made from a photoresist, and an antireflective film is formed between said curved-surface base substrate and silicon-base film.
4. The production method of the curved-surface metal mold having the fine uneven structure according to claim 1 or 2 characterized in that a mold release material film is formed between said curved-surface base substrate and silicon-base film.
5. The production method of the curved-surface metal mold having the fine uneven structure according to claim 1 or 2 characterized in that said silicon-base film is a silicon dioxide film formed by a sputtering method.
6. A production method of a metal mold having a fine uneven structure characterized by comprising:
- forming a silicon-base film on a curved-surface base substrate formed in a specified shape;
- providing a mask on the silicon-base film, the mask having a specified shaped fine uneven pattern on an effective area part of the mask, and the uneven pattern changing its volume percent toward the outside of the mask;
- etching the silicon-base film using the mask to form a fine pattern composed of fine unevenness gradually becoming deeper from the outer region to the inner region and having a predetermined depth and shape on the effective area;
- bonding metal used for the metal mold to the substrate with the uneven pattern formed thereon; and
- releasing the metal used for the metal mold from the substrate to form a metal mold after the uneven pattern is transferred to the metal used for the metal mold.
7. A production method of an optical element characterized by:
- forming a silicon-base film on a curved-surface base substrate formed in a specified shape;
- etching the silicon-base film using a mask to form a pattern of a specified shaped fine uneven structure;
- bonding metal used for the metal mold to the silicon-base film with the pattern of fine uneven structure formed thereon;
- removing the silicon-base film after the pattern of the fine uneven structure is transferred to the metal used for the metal mold to form a metal mold having the fine uneven structure on the curved surface of the metal mold;
- attaching the metal mold to at least either of a stationary mold or moving mold; and
- performing an injection molding with the stationary mold and moving mold to manufacture the optical element having the fine uneven structure on at least one of surfaces thereof.
Type: Application
Filed: Mar 18, 2005
Publication Date: Jun 28, 2007
Applicant: SANYO ELECTRIC CO., LTD. (MORIGUCHI-SHI)
Inventors: Shinji Kobayashi (Gifu), Atsushi Yamaguchi (Gifu), Satoshi Sumi (Gifu), Masahiro Higuchi (Gifu), Yoshiaki Maeno (Gifu)
Application Number: 10/594,154
International Classification: B22C 3/00 (20060101);