JP2009155710A - Method of manufacturing fine structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a fine structure having prescribed pattern shape and curved surface shape. <P>SOLUTION: When manufacturing an outer lens 14, a photolithography process comprising respective processes of resist coating, exposure and development is performed on a bilayer substrate 23 consisting of a flat surface substrate 21 and a flexible substrate 22, thereby, a dot pattern of a photomask 25 is accurately transferred to a resist layer 24 and a resist fine structure 24a assured of forming accuracy can be manufactured. Thereafter, the flexible substrate 22 is stripped from the flat surface substrate 21 and is attached to the surface of a curved surface structure 27 to constitute a curved surface mother mold M and, by performing electrocasting onto the mother mold M, a metal fine structure 28a is formed. Because the resist fine structure 24a is assured of the forming accuracy, molding accuracy of the metal fine structure 28a manufactured based on the resist fine structure 24a and further optical characteristics of the outer lens 14 manufactured by using the metal fine structure 28a as a mold is also assured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a fine structure.

  Conventionally, for example, as shown in Patent Document 1, light from a light source disposed opposite to an end face of a flat light guide is scattered or reflected by a structure such as fine irregularities provided on the bottom surface of the light guide. A so-called sidelight type backlight is known in which the scattered light or reflected light is emitted from a light emitting surface opposite to the bottom surface. Such a sidelight type backlight has advantages such as light weight and thinness, and is therefore suitable for mounting around a vehicle-mounted switch and various meters, for example, in which mounting space is desired to be saved.

  Here, the light guide described above is manufactured, for example, as follows by applying a manufacturing technique of a semiconductor integrated circuit. That is, as shown in FIG. 5A, first, a resist layer 52 having a predetermined thickness is formed on a substrate 51 by applying, for example, polymethyl methacrylate (PMMA) as an ultraviolet-sensitive photoresist (resist). Application process).

  Next, as shown in FIG. 5B, a photomask 53 having ultraviolet blocking properties and innumerable through holes formed as a predetermined dot pattern is placed on the resist layer 52, and the photomask 53 is interposed therebetween. Then, the resist layer 52 is irradiated with ultraviolet rays (exposure process). Thereby, the dot pattern of the photomask 53 is transferred to the resist layer 52. Precisely, in the resist layer 52, the exposed portion of ultraviolet rays shown by cross-hatching in FIG. 5B is changed into a state in which the molecular chain of PMMA is cut by the ultraviolet rays, the molecular weight is reduced, and it can be dissolved by a predetermined developer.

  Thereafter, by developing with a predetermined developer and removing the exposed portion of the resist layer 52, the pattern shape corresponding to the photomask 53 as shown in FIG. 5C has innumerable recesses or holes. A resist microstructure 52a (residual resist layer 52) is formed (development process).

  Next, as shown in FIG. 5D, electroplating is performed using the substrate 51 and the resist microstructure 52a as a planar master mold (master mold), and a metal such as nickel is deposited on the resist microstructure 52a. A metal layer 54 having a predetermined thickness is formed (electroforming process). Then, by removing the resist fine structure 52a which is an unexposed portion of the resist layer 52 and peeling it from the substrate 51, innumerable protrusions were formed as pattern shapes corresponding to the pattern shape of the resist fine structure 52a. A metal microstructure 54a is created.

And finally, as shown in FIG.5 (e), the plastic resin etc. are shape | molded by using the metal microstructure 54a as a metal mold | die, and the fine resin molded product 55, here the said light guide, is obtained. In other words, by forming, for example, polymethylmethacrylate (PMMA), which is a material for forming the light guide, a planar shape in which innumerable concave portions corresponding to the protrusions of the metal microstructure 54a are formed on one side surface. A light guide is manufactured.
JP 2007-80789 A

  In recent years, for example, for the purpose of improving the design of the interior of a vehicle, a design surface to be provided with an in-vehicle switch or the like is often curved. In this case, for example, in order to ensure uniform surface emission characteristics, it may be required to form the light guide in a curved shape corresponding to the curvature of the design surface. Moreover, the case where the light guide has to be curved may be assumed from the viewpoints of the location of the on-vehicle switch and the mounting space of the backlight. In addition to the backlight, the light guide as described above is used as a light diffusing member for various lamps, and its application range is wide. It is sufficiently assumed that a light guide having a curved surface shape is required for the purpose of expanding the degree of freedom. Furthermore, since the metal microstructure manufactured through the electroforming process described above can be formed with various pattern shapes depending on the pattern of the photomask 53, the metal microstructure itself is provided as a product. Even in this case, it is conceivable that a curved surface is required for the purpose of expanding applications.

  However, it is difficult to manufacture a microstructure having a predetermined pattern shape and curved surface by the conventional method for manufacturing a microstructure including a light guide or a metal microstructure. That is, since the above-described exposure process uses optical characteristics such as ultraviolet rays, when the concave portions or the holes are to be formed uniformly as the pattern shape of the resist fine structure 52a, the resist layer 52 is planar. Need to be formed. Here, when the resist layer 52 is formed in a curved surface shape, the dot pattern of the photomask 53 is not accurately transferred to the resist layer 52, and as a result, the pattern shape of the resist microstructure 52a is not uniform. There is concern about becoming. As a result, the forming accuracy of the metal microstructure 54a manufactured based on the pattern shape of the resist microstructure 52a and further the optical characteristics of the light guide manufactured using the metal microstructure 54a as a mold are also affected. In addition, there is a high probability that desired surface emission characteristics cannot be obtained. From such an actual state, a fine structure having a predetermined pattern shape and curved surface shape has been strongly desired.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing a fine structure having a predetermined pattern shape and curved surface shape.

  The invention according to claim 1 is a method of manufacturing a microstructure having a predetermined pattern shape and curved surface shape, and a photoresist is applied to a surface of a flexible substrate disposed on a flat substrate, and the photoresist is applied. A photolithography process for forming a resist microstructure having a pattern shape corresponding to the photomask by exposing and developing through a photomask having a predetermined pattern formed thereon, and a flexible provided with the resist microstructure A curved surface corresponding to the surface shape of the curved surface structure is formed by peeling the substrate from the flat substrate and sticking it to the surface of the curved surface structure prepared in advance to bend and hold the flexible substrate and the resist microstructure on the surface. A mother die manufacturing process configured as a curved mother die having a shape, and electricity by metal using the curved mother die And electroforming step of forming a metal microstructures having a pattern shape and a curved shape corresponding to the curved mold by performing granulation, to include as its gist.

  When manufacturing a microstructure having a curved surface, a photolithography process including a resist coating process, an exposure process, and a development process is performed on a flat substrate, more precisely on a flexible substrate disposed on the flat substrate. In particular, since optical characteristics are used for exposure, the pattern of the photomask is accurately transferred to the photoresist by performing the exposure on a plane. For this reason, the formation accuracy of the pattern shape formed in the resist microstructure is ensured. Then, the flexible substrate on which the resist fine structure is formed is peeled off from the flat substrate and attached to the surface of a predetermined curved structure, so that the flexible substrate and the resist fine structure have the surface shape of the curved structure. It is configured as a curved surface matrix having a corresponding curved surface shape. Then, by performing electroforming with a metal using the curved matrix, a metal microstructure having a pattern shape and a curved shape corresponding to the curved matrix is formed. As described above, since the formation accuracy of the pattern shape of the resist microstructure is ensured, the forming accuracy of the metal microstructure manufactured based on the pattern shape of the resist microstructure is also ensured. In this manner, a fine structure (here, a metal fine structure) having a predetermined pattern shape and curved surface shape can be suitably produced by using a semiconductor integrated circuit production technique.

  And as described in Claim 2, the resin which has the pattern shape and curved-surface shape corresponding to the said metal microstructure by passing through the shaping | molding process which shape | molds a synthetic resin material by using the said metal microstructure as a metal mold | die. A fine structure can be formed. As described above, since the resin microstructure is manufactured using the metal microstructure having the formation accuracy as a mold, the formation accuracy of the resin microstructure is also ensured.

  Further, as described in claim 3, the method for manufacturing a fine structure according to claim 2 can be applied to the manufacture of an optical component as a resin fine structure. As this optical component, for example, a light guide as described in claim 4 is assumed. This light guide has two surfaces located on opposite sides, and reflects the light introduced inside using a predetermined pattern shape formed on one of the two surfaces. The light is emitted from the other surface which is the surface opposite to the one surface. In this case, since the formation accuracy of the predetermined pattern shape that reflects light is ensured, the optical characteristics of the light guide are also ensured.

  According to the present invention, it is possible to manufacture a fine structure having a predetermined pattern shape and curved surface shape.

<First Embodiment>
Hereinafter, an embodiment in which the present invention is embodied in an outer lens of a side turn lamp provided on a door mirror cover of a vehicle will be described with reference to FIGS. 1 and 2.

<Schematic configuration of side turn lamp>
As shown in FIG. 1, the door mirror cover 11 is provided with a side turn lamp 12 that blinks when turning right or left to inform the surroundings of the traveling direction of the host vehicle. As shown in FIG. 2, the side turn lamp 12 includes an outer lens 14 that is attached so as to cover a window portion 13 that is formed so as to wrap around from the front surface of the door mirror cover 11 to the outer surface. The outer lens 14 is formed in a belt shape that curves along the surface of the door mirror cover 11 with a transparent resin material such as polymethyl methacrylate (PMMA). One end of the outer lens 14 enters the inside of the door mirror cover 11, and the other end opposite to the one end is open to the outside of the door mirror cover 11. A light source 15 such as an LED (light emitting diode) is disposed inside the door mirror cover 11 so as to face the inner end face of the outer lens 14.

  As shown in FIG. 3, the inner surface of the outer lens 14 is a light reflecting surface 14a, and the outer surface is a light emitting surface 14b. Innumerable dot-like recesses (fine concave dots in units of μm) 16 are formed on the entire reflecting surface 14a. The recess 16 is formed in a truncated cone shape having a tapered surface that converges from the reflecting surface 14a toward the emitting surface 14b. Therefore, the light from the light source 15 incident from the inner end surface of the outer lens 14 serving as the light incident portion propagates through the outer lens 14 while being totally reflected by the difference in refractive index between the outer lens 14 and air. During the propagation of this light, a part of the light is totally reflected to the exit surface 14b side by the innumerable concave portions 16 (exactly their taper surfaces) provided on the reflection surface 14a of the outer lens 14, and the exit. The light exits from the entire surface 14b. Thus, the exit surface 14b of the outer lens 14 acts as a light emitting surface. Further, part of the light incident on the outer lens 14 proceeds toward the outer end portion of the outer lens 14 while repeating total reflection, and is emitted to the outside from the outer end surface.

<Manufacturing method of outer lens>
Next, a method of manufacturing the outer lens configured as described above will be described with reference to FIGS. 4 (a) to 4 (g). In the present embodiment, the outer lens 14 is manufactured using a so-called LIGA process, which is a microfabrication technique for forming a very fine structure by applying a manufacturing technique of a semiconductor integrated circuit. “LIGA” is an acronym for “Lithographie”, “Galvanoformung”, “Abformung” in German, and means lithography, electroforming, and molding (molding), respectively. The LIGA process includes lithography using synchrotron radiation (such as X-rays and ultraviolet rays), creation of a microstructure by electroforming such as nickel or copper, and further plastics using the microstructure as a fine mold or This is a method for creating a fine three-dimensional structure by injection molding of powder. In the present embodiment, ultraviolet rays are used as synchrotron radiation, nickel is used as a metal used for electroforming, and PMMA which is a material for forming the outer lens 14 is used as an injection molding material.

<Resist application process>
When the outer lens 14 is manufactured, as shown in FIG. 4A, a two-layer substrate 23 in which a flat substrate 21 and a flexible flexible substrate 22 are bonded together is prepared in advance. deep. Here, as the planar substrate 21, a metal substrate such as copper or a silicon substrate on which a metal such as titanium is deposited can be employed. Moreover, as the flexible substrate 22, a film substrate formed in a film shape from a synthetic resin material such as polyimide and polyethylene terephthalate (PET) can be employed. Then, a resist layer 24 having a predetermined thickness is formed by applying an ultraviolet-sensitive photoresist on the upper surface of the flexible substrate 22. As the material of the resist layer 24, a positive resist material such as polymethyl methacrylate (PMMA) is used. Note that a positive resist material means a material whose solubility with respect to a developer increases when exposed to light and an exposed portion is removed.

<Exposure process>
Next, as shown in FIG. 4B, a photomask 25 having a predetermined pattern is placed on the resist layer 24 at a predetermined interval, and the resist layer 24 is irradiated with ultraviolet rays through the photomask 25. As a result, the pattern of the photomask 25 is transferred to the resist layer 24. Precisely, in the resist layer 24, the exposed portion of ultraviolet rays shown by cross-hatching in the figure is changed to a state in which the molecular chain of PMMA is cut by the ultraviolet rays and the molecular weight is reduced, so that it can be dissolved by a predetermined developer. Here, as the pattern of the photomask 25, a dot pattern composed of innumerable circular through holes 25a is employed.

  As described above, since the photomask 25 is disposed at a predetermined distance from the resist layer 24, a part of the ultraviolet rays does not travel straight, but passes through the side surface of the photomask 25 on the resist layer 24 side. It goes around outside the hole 25a. That is, the resist layer 24 is denatured by the ultraviolet light that has passed through the through hole 25a of the photomask 25 and the diffracted light. The diffracted light has a longer wavelength than the straight light and has a low intensity. In other words, the irradiation amount of the diffracted light to the resist layer 24 is smaller than the irradiation amount of the straight light to the resist layer 24. For this reason, the modified depth of the resist layer 24 by diffracted light is shallower than the modified depth of the resist layer 24 by straight light. Therefore, as shown by cross-hatching in FIG. 4B, the width (diameter) of the altered portion of the resist layer 24 that has been altered by exposure becomes larger toward the upper surface of the resist layer 24. In the present embodiment, since the pattern of the photomask 25 includes circular through holes 25a, the altered portion of the resist layer 24 has a truncated cone shape.

<Development process>
Next, the exposed resist layer 24 is developed with a predetermined developer to remove the altered portion due to ultraviolet rays. Then, as shown in FIG. 4C, innumerable recesses 26 having an inner shape corresponding to the outer shape of the altered portion are formed in the resist layer 24 as a predetermined pattern shape corresponding to the photomask 25. The As described above, since the altered portion of the resist layer 24 has a truncated cone shape, the concave portion 26 formed by removing the altered portion has a truncated cone shape whose diameter increases toward the upper side. In this manner, a resist microstructure 24a (residual resist layer 24) having innumerable recesses 26 as pattern shapes corresponding to the photomask 25 is formed. The resist coating process, the exposure process, and the development process described above constitute a photolithography process.

<Matrix fabrication process>
Next, as shown in FIG. 4D, the planar substrate 21 is peeled from the flexible substrate 22 provided with the resist microstructures 24a (peeling step). Then, as shown in FIG. 4 (e), the flexible substrate 22 from which the planar substrate 21 is peeled off is closely attached to the surface of the curved structure 27 (attaching step). Since the surface of the curved structure 27 is formed to include a curved surface having a predetermined curvature, the flexible substrate 22 is held in a curved state according to the surface shape of the curved structure 27. That is, the flexible substrate 22 and the resist fine structure 24 a that are curved and held on the surface of the curved structure 27 are a curved matrix (curved master mold) M having a curved shape corresponding to the surface shape of the curved structure 27. Configured as The curved surface structure 27 is prepared in advance according to the product to be manufactured, and the surface shape of the curved surface structure 27 is set according to the shape of the product to be manufactured. In the present embodiment, the surface shape of the curved structure 27 is formed to correspond to the shape of the emission surface 14 b of the outer lens 14. In addition, the peeling process and sticking process mentioned above comprise the mother die preparation process which produces a curved surface mother die.

<Electroforming process>
Next, as shown in FIG. 4 (f), nickel electroplating is applied to the curved matrix M composed of the flexible substrate 22 and the resist microstructure 24 a that are curved and held on the surface of the curved structure 27. Then, nickel is deposited on the resist microstructure 24a to form a metal layer 28 having a predetermined thickness. Then, as shown in the figure, a pattern corresponding to the curved matrix M is obtained by removing the resist microstructure 24a which is an unexposed portion of the resist layer 24 and peeling the metal layer 28 from the flexible substrate 22. A metal microstructure 28a having a shape and a curved shape is created. That is, in the electroforming process, metal is deposited in a region including the infinite number of recesses 26 of the resist microstructure 24a, so that the metal microstructure 28a has an inner shape of the recess 26 of the resist microstructure 24a. Innumerable frustoconical protrusions 29 having corresponding outer shapes are formed as pattern shapes corresponding to the resist microstructures 24a.

<Molding process>
Finally, as shown in FIG. 4G, the metal microstructure 28a created as described above is mounted on a molding machine (not shown) as a mold, and a predetermined molding material is injected to form a mold. As a result, a microstructure of the molding material having a pattern shape and a curved surface shape corresponding to the metal microstructure 28a is obtained. In the present embodiment, a resin microstructure (PMMA microstructure) 30 as a microstructure of the molding material is formed by adopting PMMA which is a material for forming the outer lens 14 as the molding material. Here, the outer lens 14 having a curved shape in which innumerable concave portions 16 corresponding to the protrusions 29 of the metal microstructure 28a are formed on one side surface is manufactured.

<Effect of Embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) When manufacturing the outer lens 14, a photolithography process including a resist coating process, an exposure process, and a development process is performed on the planar two-layer substrate 23. In particular, since the exposure process utilizes optical characteristics such as ultraviolet rays, the dot pattern of the photomask 25 can be accurately transferred to the resist layer 24 by performing the process on a plane. For this reason, the formation accuracy (uniformity etc.) of the pattern shape of the resist fine structure 24a is ensured. Then, after forming the resist microstructure 24a, the flexible substrate 22 is peeled off from the flat substrate 21 and attached to the surface of a predetermined curved structure 27, whereby the flexible substrate 22 and the resist microstructure 24a are fixed. The metal microstructure 28a is formed by electroforming with a metal as the curved matrix M having a curved shape. As described above, since the formation accuracy of the pattern shape of the resist microstructure 24a is ensured, the forming accuracy of the metal microstructure 28a manufactured based on the pattern shape of the resist microstructure 24a, and further Optical characteristics such as surface emission characteristics of the outer lens 14 manufactured using the metal microstructure 28a as a mold are also ensured. As described above, the outer lens 14 having a predetermined pattern shape and curved surface shape can be suitably manufactured by using the LIGA process which is a manufacturing technology of a semiconductor integrated circuit.

  (2) Also, by preparing the curved structure 27 corresponding to the desired product shape, it is possible to manufacture fine structures having various curved shapes. For this reason, the freedom degree in the design of the attachment object of the said fine structure, or expansion of an installation freedom degree is achieved.

<Other embodiments>
In addition, you may implement this Embodiment as follows.
-The manufacturing method of the outer lens 14 of this Embodiment can also be applied to manufacture of the light guide used for the backlight which performs illumination, such as a vehicle-mounted switch and instruments. Moreover, it is applicable also to manufacture of the light guide used for the backlight of liquid crystal screens, such as a personal computer and various portable terminals. As the backlight, there are a sidelight method in which light is incident from the side of the light guide and a direct type in which light is incident from the back surface (back surface) of the light guide.

-The manufacturing method of the outer lens 14 of this Embodiment may be applied to manufacture of the light-diffusion member of various lamps, such as a tail lamp.
It is also possible to manufacture a metal microstructure or a resin microstructure having, for example, innumerable protrusions as a predetermined pattern shape using a negative photoresist. In contrast to the positive type described above, the negative resist material refers to a resist material whose solubility in a developing solution is reduced when exposed and an exposed portion remains after development.

  Since the metal microstructure manufactured through the electroforming process can be formed with various pattern shapes depending on the pattern of the photomask 25, the metal microstructure itself is provided as a product. Also good. Although it is sufficiently assumed that a metal microstructure having a predetermined pattern shape and curved surface shape is required for the purpose of expanding applications, such a requirement can be suitably met.

<Other technical ideas>
Next, the technical idea that can be grasped from the embodiment will be described below.
-Having two surfaces located on opposite sides of each other, and reflecting the light introduced into the inside of the two surfaces by utilizing innumerable concave portions formed as reflection patterns on one surface of the two surfaces; A light guide that emits light from the other surface on the opposite side, wherein the one surface has a curved surface at least in part. According to this configuration, the application range of the light guide can be expanded.

The perspective view from the door mirror which shows the aspect of attachment of an outer lens. FIG. 1 is a sectional view taken along line 1-1 of FIG. The longitudinal cross-sectional view of an outer lens. (A)-(g) is the schematic which shows the manufacturing process of an outer lens. (A)-(e) is schematic which shows the manufacturing process of the conventional light guide.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 14 ... Outer lens (Optical component, light guide body, resin fine structure), 14a ... Reflecting surface (one side), 14b ... Outgoing surface (other side), 16 ... Concave part (predetermined pattern shape), 21 ... Planar substrate , 22 ... Flexible substrate, 24 ... Resist layer (photoresist), 24a ... Resist fine structure, 25 ... Photomask, 27 ... Curved structure, 28a ... Metal fine structure, 29 ... Projection (predetermined pattern shape) 30: Resin microstructure, M: Curved matrix.

Claims (4)

A method for producing a microstructure having a predetermined pattern shape and curved surface shape,
The photoresist has a pattern shape corresponding to the photomask by applying a photoresist on the surface of the flexible substrate disposed on the flat substrate, exposing the photoresist through a photomask on which a predetermined pattern is formed, and developing the photoresist. A photolithography process for forming a resist microstructure;
The flexible substrate on which the resist fine structure is provided is peeled off from the flat substrate and attached to the surface of the curved structure prepared in advance, and the flexible substrate and the resist fine structure which are held curvedly on the surface are provided. A mother mold manufacturing process configured as a curved mother mold having a curved shape corresponding to the surface shape of the curved structure;
Forming a metal microstructure having a pattern shape and a curved surface shape corresponding to the curved surface mold by performing electrocasting with a metal using the curved surface mold, and a manufacturing method of the microstructure . In the manufacturing method of the fine structure according to claim 1,
A microstructure further comprising a molding step of forming a resin microstructure having a pattern shape and a curved shape corresponding to the metal microstructure by molding the synthetic resin material using the metal microstructure as a mold. Manufacturing method. In the manufacturing method of the fine structure according to claim 2,
The resin microstructure is a method of manufacturing a microstructure that is an optical component. In the manufacturing method of the fine structure according to claim 3,
The optical component has two surfaces located on opposite sides of each other, and reflects the light introduced inside by utilizing a predetermined pattern shape formed on one surface of the two surfaces. The manufacturing method of the microstructure which is a light guide made to radiate | emit from the other surface which is a surface on the opposite side to a direction.

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