JP2005132660A - Manufacturing method of optical element having non-reflective structure and optical element having non-reflective structure manufactured through the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical element whereby a high-precision optical element having a non-reflective structure can be repetitively molded. <P>SOLUTION: A cylindrical Cr mask is formed on the surface of a quartz glass substrate, and the surface of the quartz glass substrate is subjected to dry etching to form a conical non-reflective structure on the surface. An Ir-Rh alloy film for surface protection is formed on the surface, and a master mold for molding the non-reflective structure is prepared. A high-melting-point glass material onto which a mold release agent is applied for mold release is press-molded using the master mold, and the master mold is released from the press-molded high-melting-point glass material without cooling. The mold release agent is removed after the high-melting-point glass material is being cooled, and the Ir-Rh alloy film for surface protection is formed to prepare a replica mold 22 for molding the non-reflective structure. An optical material 11 onto which a mold release agent 16 is applied for mold release is press-molded using the replica mold 22, and the replica mold 22 is released from the optical material 11 without cooling. The mold release agent 16 is removed after the optical material 11 is being cooled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical element having a highly accurate non-reflective structure that does not cause pattern shift over a large area, and an optical element having a non-reflective structure manufactured by the method.

  In order to prevent surface reflection of the optical element, a method of forming a non-reflection structure on the surface of the optical element has been proposed. The proposed non-reflective structure has a very fine uneven shape with a submicron pitch and an aspect ratio of 1 or more. As a method for forming such a fine structure, a fine processing method using dry etching has been proposed.

  On the other hand, as an effective method for manufacturing a high-precision optical element in a large amount and at a low cost, a method of press-molding an optical material (molding material) made of glass or resin has been proposed.

When an optical material made of heat-softened glass or resin is press-molded using a mold, the optical material is difficult to release from the mold, so a special release film may be formed on the surface of the mold. A mold release agent is applied for each molding shot, so that the mold release is facilitated. In particular, when glass is used as the optical material, a very special coating is applied to the surface of the mold. For example, Patent Document 1 discloses a technique in which a cemented carbide or cermet containing WC as a main component is used as a mold material, and a surface of a mold manufactured using the mold material is coated with a noble metal protective film. Has been. By using the mold having such a configuration, it is possible to mass-produce optical elements by press molding. Moreover, in the metal mold | die of patent document 2, the film thickness of 10 nm or less is provided on the optical function surface of the metal mold body made of boron nitride, chromium nitride, chromium carbide, chromium oxide, silicon carbide, carbon, platinum or cemented carbide. By forming a carbon film having the above, release properties from glass are improved.
Japanese Examined Patent Publication No. 62-28091 JP-A-6-305742

  However, in the case of a microfabrication method using dry etching, depending on the optical material to be used, the surface becomes very rough after etching or the etching rate becomes very slow, which limits the usable optical materials. . That is, the optical material that can be used is limited to quartz glass or the like, and it is not possible to use multicomponent glass or resin used in optical devices designed with various optical constants. For this reason, even if an optical element having a non-reflective structure is produced by a fine processing method using dry etching, a desired selectivity cannot be obtained, and an optical element having a non-reflective structure having a large aspect ratio cannot be obtained. . In addition, since the reproducibility of etching is low, there is a problem that the production cost is remarkably increased due to a decrease in yield and a decrease in mass productivity.

  Further, when press-molding an optical element having a non-reflective structure, in the conventional press-molding method, when the heated and softened optical material is cooled in a state of being in contact with the mold (pressed state), the mold and the optical material are Thermal stress is generated due to the difference in coefficient of thermal expansion, and as a result, the accuracy of the pattern transferred to the optical material is lowered. In particular, as the distance from the center of the mold increases toward the outer periphery, the shift of the pattern transferred to the optical material increases, so that a fine uneven pattern cannot be accurately transferred over a large area. For this reason, it is necessary to release the mold from the optical material obtained by press molding without cooling.

  However, as an optical material, a surface of a mold produced by using a cemented carbide or cermet mainly composed of WC described in Patent Document 1 as a mold material is coated with a noble metal-based protective film. When press-molding glass, the mold-to-glass releasability is quite good, but the mold cannot be released from the press-molded glass without cooling, and has an anti-reflective structure. The element cannot be molded precisely. In addition, if a mold having a carbon film described in Patent Document 2 is used, the mold can be released without cooling, but the material of the mold body can be processed into a concavo-convex shape with a non-reflective structure. It is very difficult.

  Furthermore, when an optical element having a non-reflective structure is manufactured by press molding, the press surface of the mold used for molding must have the inverted shape of the optical element, but depending on the shape of the optical element, the inverted shape is formed. It can be very difficult to do. For example, in the case of a microlens array or the like, generally, after forming a cylindrical resist pattern, it is heated and softened, and after forming a lens shape by surface tension, dry etching is performed. The formation of the convex shape is easy, but the formation of the concave shape as a mold is very difficult. Therefore, it is very difficult to produce a microlens array molding mold having a concave shape, and furthermore, a microlens array molding mold having a nonreflective structure by forming a nonreflective structure on the mold. Is more difficult to obtain.

  The present invention has been made to solve the above-described problems in the prior art, and it is possible to repeatedly mold an optical element having a high-precision non-reflective structure that does not cause pattern displacement over a large area. An object of the present invention is to provide a method for manufacturing an optical element having an antireflective structure, and an optical element having an antireflective structure manufactured by the method.

  In order to achieve the above object, the first method of manufacturing an optical element having an antireflection structure according to the present invention is excellent in high temperature strength, heat resistance, and non-reflection on a mold material with less surface roughness due to dry etching. After forming the non-reflective structure on the surface of the mold material by forming a mask corresponding to the structure and performing dry etching, a thin film for surface protection is formed on the surface of the mold material, and non-reflective A master mold for structural molding is produced, and using the non-reflective structural molding master mold, a glass material having higher heat resistance than an optical material coated with a release agent for mold release is press-molded, The non-reflective structure molding master mold is released from the press-molded glass material without cooling, and after the press-molded glass material is cooled, the mold release agent is removed and the surface of the glass material The optical material in which a thin film for surface protection is formed, a replica mold for forming an antireflective structure is manufactured, and a release agent for mold release is applied using the replica mold for forming an antireflective structure Removing the mold release agent after cooling the press-molded optical material, releasing the anti-reflective structure molding replica mold from the press-molded optical material without cooling. Features.

  The second method for manufacturing an optical element having an antireflective structure according to the present invention is a mask corresponding to an antireflective structure in a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching. After forming the nonreflective structure on the surface of the mold material by dry etching, a carbon (C) film or boron nitride is formed on the surface of the mold material as a thin film for mold release. (BN) A film is formed to produce a master mold for forming an anti-reflective structure, and using the master mold for forming an anti-reflective structure, a glass material superior in heat resistance than an optical material is press-molded, The master mold for forming the non-reflective structure is released from the glass material that has been press-molded without cooling, and after the glass material that has been press-molded is cooled, the surface of the glass material that has been press-molded is released for mold release. Thin A carbon (C) film or a boron nitride (BN) film is formed to produce a replica mold for forming an antireflective structure, and the optical material is pressed using the replica mold for forming the antireflective structure The non-reflective structure molding replica mold is molded and released from the press-molded optical material without cooling, and the press-molded optical material is cooled.

The third method for manufacturing an optical element having an antireflective structure according to the present invention is a mask corresponding to an antireflective structure in a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching. And forming the non-reflective structure on the surface of the mold material by dry etching, forming a thin film for surface protection on the surface of the mold material, and forming a master mold for forming the non-reflective structure In an atmosphere in which a mold is prepared and a gas containing a carbon (C) or fluorine (F) in a constituent molecule or a mist-like liquid is mixed in an inert gas using the master mold for forming an antireflective structure Then, the glass material superior in heat resistance than the optical material is press-molded, and the non-reflective structure molding master mold is released from the press-molded glass material without cooling, and the press-molded glass material is cold Then, a thin film for surface protection is formed on the surface of the press-molded glass material to produce a replica mold for forming the non-reflective structure, and the inert mold using the replica mold for forming the non-reflective structure is inactive. For molding the non-reflective structure without press-cooling the optical material in an atmosphere in which a gas containing carbon (C) or fluorine (F) in a constituent molecule or an atomized liquid is mixed in a gas. A replica mold is released from the press-molded optical material,
The press-molded optical material is cooled.

In the first to third manufacturing methods of the optical element having the non-reflective structure according to the present invention, the mold material is made of SiO ₂ film or Si film on quartz glass, silicon, Ni alloy, and cemented carbide. It is preferably one selected from the group consisting of those formed.

  In the first to third manufacturing methods of the optical element having the nonreflective structure of the present invention, the optical material is preferably multicomponent glass or resin.

  In the first to third manufacturing methods of the optical element having the nonreflective structure according to the present invention, the mask material corresponding to the nonreflective structure is selected from the group consisting of Cr, Ni, Au, and C. It is preferable that it is one.

  In the first to third manufacturing methods of the optical element having the non-reflective structure according to the present invention, the mask corresponding to the non-reflective structure is a columnar or polygonal column mask, and has a pitch equal to or less than a use wavelength. It is preferably formed in an array.

  In the first to third methods for manufacturing an optical element having a non-reflective structure according to the present invention, a resist is formed on the mask corresponding to the non-reflective structure, and electron beam lithography, X-ray lithography, or interference exposure is used. The resist is circular or polygonal by photolithography, and is patterned into an array with a pitch equal to or less than the wavelength used, and the mask is cylindrical or polygonal by wet etching or dry etching, It is preferable to form an array with a pitch equal to or shorter than the wavelength used.

  In the first or third method for manufacturing an optical element having a non-reflective structure according to the present invention, the thin film for surface protection is made of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta. It preferably contains at least one metal selected from the group consisting of:

  In the first or third method for manufacturing an optical element having a nonreflective structure according to the present invention, the mask material corresponding to the nonreflective structure is preferably a resist for X-ray lithography. In this case, it is preferable that the surface shape of the non-reflective structure molding die is a curved surface.

  In the first or third method for manufacturing an optical element having a non-reflective structure according to the present invention, the mask corresponding to the non-reflective structure is a conical or polygonal pyramid mask, and is obtained by X-ray lithography. It is preferably formed in an array with a pitch equal to or shorter than the wavelength used. In this case, it is preferable that the surface shape of the non-reflective structure molding die is a curved surface.

  In addition, the configuration of the optical element having the nonreflective structure according to the present invention is manufactured by the first to third manufacturing methods of the optical element having the nonreflective structure of the present invention.

  According to the present invention, it becomes possible to release the non-reflective structure molding master mold from the press-molded glass material without cooling, and press-molding the non-reflective structure molding replica mold without cooling. Because it is possible to release from the optical material, the generation of thermal stress due to the difference in thermal expansion coefficient between the master mold for forming the non-reflective structure and the glass material to be press-molded, and for forming the non-reflective structure Prevents the occurrence of thermal stress due to the difference in thermal expansion coefficient between the replica mold and the optical material to be press-molded. Master mold for non-reflective structure molding → Replica mold for non-reflective structure molding → Optical material It is possible to suppress the deterioration of the accuracy of the pattern transferred in this order. As a result, it is possible to repeatedly mold an optical element having a highly accurate non-reflective structure that does not cause pattern deviation over a large area. Also, according to the present invention, an optical element is manufactured by press molding using a non-reflective structure molding master mold and a non-reflective structure molding replica mold, so that an optical element having a non-reflective structure is reproduced. It can be molded with good performance. As a result, mass productivity is dramatically improved, and production costs can be significantly reduced.

  Furthermore, according to the present invention, it is possible to easily produce a concave replica mold using a convex master mold. As a result, like a microlens array, after forming a cylindrical resist pattern, heating and softening it, forming a lens shape by surface tension, and then performing dry etching to form a convex shape, A mold for forming a microlens array having a concave shape can be easily produced. Therefore, according to the present invention, by forming the non-reflective structure on the master mold, it is possible to easily obtain the microlens array molding mold having the non-reflective structure. Micro lens array can be molded.

  Hereinafter, the present invention will be described more specifically using embodiments.

[First Embodiment]
In the present embodiment, as an optical element having a non-reflective structure of the present invention, a flat plate optical element having a conical microstructure with a pitch of 0.15 μm and a height of 0.15 μm on one side will be described as an example.

  FIG. 1 is a cross-sectional view showing a non-reflective structure molding master mold for producing a press molding mold of an optical element having a non-reflective structure.

  In FIG. 1, 1 is a quartz glass substrate of 20 mm × 20 mm × 5 mm. Quartz glass is a material having excellent high-temperature strength, heat resistance, and less surface roughness due to dry etching. A conical non-reflective structure 2 having a pitch of 0.15 μm and a height of 0.15 μm is formed on the surface (press surface) of the quartz glass substrate 1, and the quartz glass substrate 1 on which the non-reflective structure 2 is formed. Is used as the non-reflective structure forming master mold 3.

Hereinafter, a method for producing the non-reflective structure forming master mold 3 will be described with reference to FIG. As shown in FIG. 2A, first, the surface (press surface) of the quartz glass substrate 1 was processed smoothly (Ra about 2 nm) by high-precision grinding and polishing. Next, as shown in FIG. 2B, a Cr film 25 having a thickness of 0.1 μm was formed on the surface (pressed surface) of the quartz glass substrate 1 processed smoothly using a sputtering method. Next, as shown in FIG. 2C, a PMMA resist 26 having a thickness of 0.1 μm was formed on the surface of the Cr film 25 by spin coating. Next, as shown in FIG. 2D, a cylindrical pattern 27 made of PMMA resist and having a diameter of 0.15 μm was formed at a pitch of 0.15 μm on the surface of the Cr film 25 by using an EB (electron beam) drawing method. . Next, as shown in FIG. 2 (e), the Cr film 25 is wet etched to form a cylindrical pattern made of Cr corresponding to the nonreflective structure 2 on the surface (press surface) of the quartz glass substrate 1 as a mask. (Cr mask 28). This mask is formed in an array at a pitch equal to or shorter than the wavelength used. Next, as shown in FIG. 2 (f), the quartz glass substrate 1 on which the cylindrical Cr mask 28 is formed is placed in an RF dry etching apparatus, and the quartz glass substrate 1 is used by using CHF ₃ + O ₂ gas. The surface of was etched. Thereby, the Cr mask 28 is etched little by little together with the quartz glass substrate 1, and the width is reduced. Then, by etching until the Cr mask 28 disappeared completely, a conical non-reflective structure 2 having a pitch of 0.15 μm and a height of 0.15 μm was formed on the surface (press surface) of the quartz glass substrate 1. Finally, an Ir—Rh alloy film for surface protection is formed to a thickness of 0.05 μm on the surface (press surface) of the quartz glass substrate 1 on which the conical non-reflective structure 2 is formed by using a sputtering method. did. In this way, the master mold 3 for forming the non-reflective structure was obtained.

  Hereinafter, a method for producing a non-reflective structure molding replica mold for press-molding an optical element having a non-reflective structure using the non-reflective structure molding master mold 3 having the above-described configuration will be described. 3 and will be described with reference to FIG. FIG. 3 is a process diagram showing a molding process of a replica mold for forming an antireflective structure, and FIG. 4 is a process chart showing a press molding method of the replica mold for forming an antireflective structure.

As shown in FIG. 3A, first, the above-mentioned non-reflective structure molding master mold 3 is placed on the upper head 5 of the molding machine which is covered with the chamber 15 and into which N ₂ gas is introduced from the atmospheric gas inlet 18. The upper mold 6 was fixed, and the upper mold 6 was heated to a predetermined temperature (here, 750 ° C.) together with the press stage 8. The preheating stage 7 was also heated to 750 ° C. Then, alkali-free glass (transition point (Tg): 625 ° C., yield point (At): 696 ° C.) 20 which is a high melting point glass of 15 mm × 15 mm × 1.0 mm superior in heat resistance to the optical material is used as the lower mold The lower die 10 on which the high melting point glass 20 is placed is put into the molding machine through the mold inlet 12 of the chamber 15 and heated on the preheating stage 7 set at 750 ° C. for 2 minutes. . Here, a boron nitride (BN) fine particle release agent 21 for release is applied to the surface of the alkali-free glass 20 (see FIG. 4A).

  Next, as shown in FIG.3 (b), the lower mold | type 10 with which the alkali free glass 20 was mounted was conveyed from the preheating stage 7 to the press stage 8 similarly set to 750 degreeC. Next, the cylinder 13 was lowered, and the alkali-free glass 20 was pressed for 2 minutes at a pressure of 2000 N by the upper mold 6 that was also set to 750 ° C. and fixed to the upper head 5 (FIG. 4A). (See (b)). Then, by raising the cylinder 13 without cooling (at the same temperature), the upper die 6 is raised together with the upper head 5, and the upper die 6 is released from the press-formed alkali-free glass 20 ( (Refer FIG.4 (b), (c)). Here, the reason why the upper mold 6 can be released from the press-molded alkali-free glass 20 without cooling (while maintaining the high temperature) is because the wettability between the BN particles and the alkali-free glass 20 is poor. It is. That is, it is impossible to release the oxide or metal without cooling (while maintaining high temperature), but the BN particles (or C particles) have very poor wettability with the alkali-free glass 20. Therefore, it is possible to release the mold without cooling (while maintaining the high temperature). When the upper mold 6 is released from the press-molded high-melting glass 20, the press-molded high-melting glass 20 is placed on the lower mold 10.

  Next, as shown in FIG. 3 (c), the lower mold 10 on which the press-melted high melting point glass 20 is placed is conveyed from the press stage 8 to the cooling stage 9 set to 400 ° C., and there for 2 minutes. Cooled down.

  Finally, the high melting point glass 20 press-molded together with the lower mold 10 is taken out from the mold outlet 14 of the chamber 15, the press-molded high melting point glass 20 is removed from the lower mold 10, and then the release agent 21. Then, an Ir—Rh alloy film for surface protection was formed to a thickness of 0.05 μm using a sputtering method. Thereby, a replica mold 22 for forming a non-reflective structure was obtained (see FIG. 4C).

  Hereinafter, a method of manufacturing an optical element having a non-reflective structure using the non-reflective structure molding replica mold 22 and the lower mold 4 having the above-described configuration will be described. FIG. 5 is a cross-sectional view showing a press-molding die for an optical element having an anti-reflection structure, FIG. 6 is a process diagram showing a molding process of the optical element having an anti-reflection structure, and FIG. 7 is an optical element having an anti-reflection structure. It is process drawing which shows a press molding method.

  In FIG. 5, reference numeral 22 denotes a replica mold for forming a non-reflective structure, and the lower mold 4 has the following structure. That is, a recess 4a of 15 mm × 15 mm × 0.5 mm is formed in the central portion of a cemented carbide whose main component is 20 mm × 20 mm × 5 mm WC, and a sputtering method is used on the surface where the recess 4a is formed. Thus, an Ir—Rh alloy film for surface protection is formed with a thickness of 0.5 μm.

As shown in FIG. 6A, first, the above-described non-reflective structure molding replica mold 22 is placed on the upper head 5 of the molding machine which is covered with the chamber 15 and into which N ₂ gas is introduced from the atmospheric gas inlet 18. The upper die 6 was fixed, and the upper die 6 was heated to a predetermined temperature (here, 590 ° C.) together with the press stage 8. The preheating stage 7 was also heated to 590 ° C. Then, using the above lower mold 4 as the lower mold 10, a 15 mm × 15 mm × 1.0 mm crown borosilicate glass (transition point (Tg): 501 ° C., yield point (At): 549 ° C.) An optical material 11 is placed on the lower die 10, and the lower die 10 on which the optical material 11 is placed is introduced into the molding machine through the mold inlet 12 of the chamber 15, and the preheating stage 7 set at 590 ° C. Heated for 3 minutes. Here, a boron nitride (BN) fine particle release agent 16 for release is applied to the surface of the optical material 11 (see FIG. 7A).

  Next, as shown in FIG. 6 (b), the lower mold 10 on which the optical material 11 was placed was conveyed from the preheating stage 7 to the press stage 8 which was also set to 590 ° C. Next, the cylinder 13 was lowered, and the optical material 11 was pressed for 3 minutes at a pressure of 1000 N by the upper mold 6 that was also set to 590 ° C. and fixed to the upper head 5 (FIG. 7A). (See (b)). Then, by raising the cylinder 13 without cooling (at the same temperature), the upper die 6 is raised together with the upper head 5 to release the upper die 6 from the press-molded optical material 11 ( (See FIGS. 7B and 7C). Here, the reason why the upper die 6 can be released from the press-molded optical material 11 without cooling (while maintaining a high temperature) is the same as described above. When the upper mold 6 is released from the press-molded optical material 11, the press-molded optical material 11 is placed on the lower mold 10.

  Next, as shown in FIG. 6C, the lower mold 10 on which the press-molded optical material 11 is placed is conveyed from the press stage 8 to the cooling stage 9 set to 300 ° C., where it is cooled for 3 minutes. did.

  Finally, the optical material 11 press-molded together with the lower mold 10 is taken out from the mold outlet 14 of the chamber 15, and after removing the press-molded optical material 11 from the lower mold 10, the release agent 16 is removed. did. Thereby, an optical element 17 having a non-reflective structure was obtained (see FIG. 7C).

  According to the present embodiment, as described above, it is possible to release the upper mold 6 (the non-reflective structure molding master mold 3) from the press-molded high melting point glass 20 without cooling, Since the upper mold 6 (non-reflective structure molding replica mold 22) can be released from the press-molded optical material 11 without cooling, the upper mold 6 (non-reflective structure molding master mold 3). Of thermal stress due to the difference in thermal expansion coefficient between the refractory glass 20 and the high-melting glass 20 to be press-molded, and the heat between the upper mold 6 (non-reflective structure molding replica mold 22) and the optical material 11 to be press-molded The generation of thermal stress due to the difference in expansion coefficient is prevented, and the accuracy of the pattern transferred in the order of non-reflective structure forming master die 3 → non-reflective structure forming replica die 22 → optical material 11 is improved. Deterioration can be suppressed. As a result, it is possible to repeatedly mold the optical element 17 having a highly accurate non-reflective structure that does not cause pattern deviation over a large area. In addition, according to the present embodiment, the optical element 17 is manufactured by press molding using the non-reflective structure-forming master mold 3 and the non-reflective structure-forming replica mold 22, so that the non-reflective structure is formed. It is possible to mold the optical element 17 having good reproducibility. As a result, mass productivity is dramatically improved, and production costs can be significantly reduced.

In this embodiment, quartz glass is used as a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching. However, the mold material is not necessarily limited to quartz glass. For example, silicon, a Ni alloy, a cemented carbide formed with a SiO ₂ film or a Si film, or the like may be used as a mold material.

  In the present embodiment, a crown-type borosilicate glass is used as the optical material 11, but the optical material is not necessarily limited to the crown-type borosilicate glass. If it is. As multi-component glass, aluminosilicate glass, flint glass, phosphate glass and the like are used in addition to borosilicate glass, and acrylic, Teflon (registered trademark of DuPont), polyethylene, polyolefin and the like are used as resin. Since the non-reflective structure is formed by molding, even if multi-component glass or resin is used as the optical material 11, an optical element having a non-reflective structure with a large aspect ratio can be obtained.

  In this embodiment, an Ir—Rh alloy film is used as a thin film for surface protection, but the thin film for surface protection is not necessarily limited to an Ir—Rh alloy film. The thin film for surface protection should contain at least one metal selected from the group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta. If the release agent 16 is not evenly applied to the surface of the optical material 11, if there is no thin film for protecting the surface, the optical material 11 partially contacts the mold directly and is completely welded. It becomes impossible to release the mold at all. Then, if the mold is forcibly released, the optical material 11 is broken. A thin film for surface protection such as an Ir—Rh alloy film is for preventing this.

  In the present embodiment, a cylindrical Cr mask corresponding to the non-reflective structure 2 is formed on the surface (press surface) of the quartz glass substrate 1, but for example, Ni, Au, C The mask may be formed using a material such as, or a polygonal columnar mask may be formed.

  In this embodiment mode, the resist is patterned into a columnar shape or a polygonal column shape by using electron beam lithography. However, the resist is formed into a circular shape by using X-ray lithography or photolithography using interference exposure. Patterning may be performed in a columnar shape or a polygonal columnar shape.

  In this embodiment mode, the mask is formed in a columnar shape or a polygonal columnar shape by wet etching. However, the mask may be formed in a columnar shape or a polygonal columnar shape by dry etching. .

[Second Embodiment]
In the present embodiment, a non-reflective structure molding master mold for producing a press-molding mold for an optical element having a non-reflective structure is substantially the same as that in the first embodiment. (See FIG. 1). The non-reflective structure molding master mold 3 of the present embodiment is different from the non-reflective structure molding master mold 3 of the first embodiment in the following points. That is, in the present embodiment, when the non-reflective structure-forming master mold 3 is manufactured, the surface protection (press surface) of the quartz glass substrate 1 on which the conical non-reflective structure 2 is formed is subjected to surface protection. Instead of forming an Ir—Rh alloy film, a carbon (C) film for mold release was formed with a thickness of 0.05 μm. Therefore, in the present embodiment, unlike the first embodiment, a mold release agent for mold release is not applied to the surface of the alkali-free glass 20 that is a high-melting glass to be press-formed.

  Further, in the present embodiment, a replica mold for forming the non-reflective structure for press-molding the optical element having the non-reflective structure is the same as that in the first embodiment (FIG. 5). No. 22). The non-reflective structure molding replica mold 22 of the present embodiment is different from the non-reflective structure molding replica mold 22 of the first embodiment in the following points. That is, in the present embodiment, when producing the non-reflective structure forming replica mold 22, a carbon (C) film for mold release is formed on the surface (press surface) of the press-formed alkali-free glass 20. Was formed with a thickness of 0.05 μm. For this reason, in the present embodiment, unlike the first embodiment, a mold release agent for mold release is not applied to the surface of the optical material 11 to be press-molded.

  A method for producing a non-reflective structure molding replica mold for press-molding an optical element having a non-reflective structure using the non-reflective structure molding master mold 3, and a non-reflective structure molding replica mold Since the method of manufacturing the optical element 17 having the non-reflective structure using the lower mold 4 and the lower mold 4 is the same as that in the first embodiment (see FIGS. 3, 4, 6, and 7). The description is omitted here.

  Also in this embodiment, for the same reason as in the first embodiment, the upper mold 6 (the non-reflective structure forming master mold 3) is released from the press-formed alkali-free glass 20 without cooling. In addition, the upper mold 6 (non-reflective structure molding replica mold 22) can be released from the press-molded optical material 11 without cooling, so that a pattern can be formed over a large area. It is possible to repeatedly mold the optical element 17 having a highly accurate non-reflective structure that does not cause a deviation.

  In the present embodiment, when the non-reflective structure molding master mold 3 is manufactured, the surface (press surface) of the quartz glass substrate 1 on which the conical non-reflective structure 2 is formed is used for mold release. A carbon (C) film is formed as a thin film, and when the anti-reflective structure forming replica mold 22 is manufactured, the surface of the refractory glass 20 that has been press-molded (press surface) is separated. A carbon (C) film is formed as a thin film for the mold, but the thin film for mold release is not limited to the carbon (C) film. For example, boron nitride (BN) It may be a membrane.

[Third Embodiment]
In the present embodiment, as the non-reflective structure molding master mold for producing the press molding mold of the optical element having the non-reflective structure, the same one as in the first embodiment is used ( (See FIG. 1).

Further, in the present embodiment, a replica mold for forming the non-reflective structure for press-molding the optical element having the non-reflective structure is the same as that in the first embodiment (FIG. 5). No. 22). The non-reflective structure molding replica mold 22 of the present embodiment is different from the non-reflective structure molding replica mold 22 of the first embodiment in the following points. That is, in the present embodiment, the production (molding) of the non-reflective structure molding replica mold 22 is performed by introducing N ₂ and CO ₂ (10 vol.%) Into the molding machine from the atmospheric gas inlet 18 of the chamber 15. On the other hand, the surface of the alkali-free glass 20 to be press-molded was carried out without applying a release agent for release.

In addition, the molding process of the optical element 17 having a non-reflective structure in the present embodiment is substantially the same as that in the first embodiment. The molding process of the optical element 17 of the present embodiment is different from the molding process of the optical element 17 of the first embodiment in the following points. That is, in the present embodiment, the optical element 17 having the non-reflective structure is molded while introducing N ₂ and CO ₂ (10 vol.%) From the atmospheric gas inlet 18 of the chamber 15 into the molding machine. The surface of the optical material 11 to be molded was carried out without applying a release agent for release.

  In the above atmosphere, production (molding) of the non-reflective structure molding replica mold 22 and molding of the optical element 17 having a non-reflective structure using the non-reflective structure molding replica mold 22 were performed. It was found that even after shot molding, the optical element 17 having a highly accurate non-reflective structure that does not cause pattern displacement can be repeatedly molded over the entire 15 mm × 15 mm region of the optical material 11.

As a comparative example, the non-reflective structure molding replica mold 22 is manufactured (molded) and the non-reflective structure molding replica mold 22 is used under the same conditions while introducing only N ₂ gas into the molding machine. When the optical element 17 having the non-reflective structure was molded, the releasability between the master mold 3 for forming the non-reflective structure and the alkali-free glass 20, and the replica mold 22 for forming the non-reflective structure and the optical material 11 After the alkali-free glass 20 is pressed, the non-reflective structure molding master mold 3 is separated from the alkali-free glass 20 that has been press-molded without being cooled (at the same temperature (750 ° C.)). The optical material 1 can not be molded, and after pressing the optical material 11, the non-reflective structure molding replica mold 22 is press-molded without being cooled (at the same temperature (590 ° C.)). Could not be released from. In this case, when the temperature is lowered to 300 ° C. or lower, the non-reflective structure forming master mold 3 is released from the press-molded alkali-free glass 20, and the non-reflective structure forming replica mold 22 is press-formed optically. Since it came to release from the material 11, after cooling with the cooling stage 9, the optical element 17 which has a non-reflective structure was taken out, and the surface was observed. As a result, an optical element pattern having a non-reflective structure is precisely formed in the center portion, but the pattern shift increases as the distance from the center increases, and the optical element pattern having a non-reflective structure is doubled near the outer periphery. It was. This is because the non-reflective structure molding master mold 3, the non-reflective structure molding replica mold 22 are press-molded alkali-free glass 20, and an optical element that cannot be released unless cooled from the optical material 11. In the method, the difference in coefficient of thermal expansion between the master mold 3 for non-reflective structure molding and the alkali-free glass 20 to be press-molded, and the heat between the replica mold 22 for non-reflective structure molding and the optical material 11 to be press-molded. This is considered to be because thermal stress is generated due to the difference in the expansion coefficient, and the non-reflective structure molding master mold 3 and the non-reflective structure molding replica mold 22 are displaced. Therefore, with such a manufacturing method, it is difficult to repeatedly mold an optical element having a highly accurate non-reflective structure that does not cause pattern deviation over a large area.

On the other hand, when N ₂ and CO ₂ (10 vol.%) Are introduced into the molding machine as in the present embodiment, the non-reflective structure molding master mold remains at the temperature at which press molding is performed. 3. The non-reflective structure forming replica mold 22 can be easily released from the press-molded alkali-free glass 20 and the optical material 11, respectively. Here, without cooling (while still at a high temperature), the non-reflective structure molding master mold 3 and the non-reflective structure molding replica mold 22 are released from the press-molded alkali-free glass 20 and the optical material 11, respectively. This is because the CO ₂ gas is adsorbed on the surface of the mold, and the wettability with the alkali-free glass 20 and the optical material 11 deteriorates. As a result, the difference in thermal expansion coefficient between the non-reflective structure molding master mold 3 and the high-melting glass 20 to be press-molded, and the heat between the non-reflective structure molding replica mold 22 and the optical material 11 to be press-molded. Since the generation of thermal stress due to the difference in expansion coefficient can be prevented and the accuracy of the pattern transferred to the optical material 11 can be increased, as described above, pattern deviation does not occur over a large area. The optical element 17 having a highly accurate non-reflective structure can be repeatedly formed.

In the present embodiment, fabrication (molding) of the non-reflective structure molding replica mold 22 and molding of the optical element 17 having a non-reflective structure using the non-reflective structure molding replica mold 22 are performed. Although N ₂ and CO ₂ (10 vol.%) Are introduced into the molding machine from the atmosphere gas inlet 18 of the chamber 15, the atmosphere is not necessarily limited to this, and nitrogen (N ₂ ) or argon is not necessarily limited thereto. An atmosphere in which an inert gas such as (Ar) is mixed with a gas or mist-like liquid containing carbon (C) or fluorine (F) in a constituent molecule may be used. For example, the optical element 17 having a non-reflective structure is molded while introducing a mixed gas of N ₂ and CF ₄ (10 vol.%) Or a gas obtained by passing N ₂ gas into an ethylene glycol solution into the molding machine. Even if it goes, the effect similar to the above can be acquired.

[Fourth Embodiment]
In the present embodiment, the optical element having a non-reflective structure of the present invention has a conical microstructure with a pitch of 0.15 μm and a height of 0.15 μm, a pitch of 50 μm, a center height of 3 μm, and a radius of curvature of 100 μm. A case where a convex-shaped microlens array is manufactured will be described.

  In the present embodiment, a mold manufactured as follows was used as a master mold for forming an antireflective structure for manufacturing a press mold for an optical element having an antireflective structure. FIG. 8 is a process diagram schematically showing a method for producing a quartz microlens array which is a base of a master mold for forming an antireflective structure used in the fourth embodiment of the present invention, and FIG. 9 is a fourth process of the present invention. It is process drawing which shows typically the preparation methods of the non-reflective structure shaping | molding master metal mold | die used in embodiment.

As shown in FIG. 8A, first, the surface of a quartz glass substrate 29 of 20 mm × 20 mm × 5 mm, which is a master mold for forming an anti-reflection structure, was processed smoothly by high precision grinding and polishing ( Ra about 2 nm). Next, as shown in FIG. 8B, a photoresist 30 having a thickness of 3 μm was formed on the surface of the smooth processed quartz glass substrate 29 by using a spin coating method. Next, as shown in FIG. 8C, the surface of the quartz glass substrate 29 on which the photoresist 30 is formed is irradiated with ultraviolet rays through a photomask on which a circular pattern with a pitch of 50 μm is formed, and then developed. A cylindrical photoresist pattern 31 was formed by removing unexposed portions. Next, as shown in FIG. 8 (d), the entire substrate is heated to a temperature (200 ° C.) at which the photoresist melts, and heating and melting are performed until each cylindrical photoresist has a microlens shape due to surface tension. went. As a result, a hemispherical photoresist pattern 32 was formed on the surface of the quartz glass substrate 29. Next, as shown in FIG. 8E, after cooling the quartz glass substrate 29 on which the hemispherical photoresist pattern 32 is formed, it is put into an RF dry etching apparatus, and CHF ₃ + O ₂ gas is used. Then, the surface of the quartz glass substrate 29 was etched. As a result, a microlens array 33 having a pitch of 50 μm and a height of 3 μm was formed on the surface of the quartz glass substrate 29, and a quartz microlens array 34 was obtained.

  Subsequently, a non-reflective structure was formed on the surface of the quartz microlens array 34 produced as described above by the process of FIG.

As shown in FIG. 9A, first, a PMMA resist 35, which is a resist for X-ray lithography, was formed to a thickness of 0.5 μm on the surface of the quartz microlens array 34 by using a spin coating method. Next, as shown in FIGS. 9A and 9B, the X-ray lithography mask 37 is moved with high accuracy while developing with irradiation of the X-ray 36, thereby developing on the surface of the quartz microlens array 34. As a mask 38 corresponding to the non-reflective structure, a conical pattern made of PMMA resist having a diameter of 0.15 μm and a height of 0.3 μm was formed at a pitch of 0.15 μm. The mask 38 is formed in an array with a pitch equal to or less than the wavelength used. Next, as shown in FIG. 9C, the quartz microlens array 34 on which the mask 38 made of PMMA resist is formed is placed in an RF dry etching apparatus, and a quartz microlens is used using CHF ₃ + O ₂ gas. The surface of the array 34 was etched. As a result, a conical non-reflective structure 39 having a pitch of 0.15 μm and a height of 0.15 μm was formed on the surface of the quartz microlens array 34. Finally, on the surface of the quartz microlens array 34 on which the conical non-reflective structure 39 is formed, an Ir—Rh alloy film for surface protection is formed to a thickness of 0.05 μm through a Cr film by using a sputtering method. Formed with. As described above, the master mold 40 for forming the non-reflective structure was obtained.

  A method for producing a non-reflective structure molding replica mold for press-molding a microlens array as an optical element having a non-reflective structure using the non-reflective structure molding master mold 40, and a non-reflective structure Since the method of manufacturing the microlens array as an optical element having a non-reflective structure using the molding replica mold and the lower mold is the same as that in the first embodiment (FIGS. 3, 4, and 4). (See FIGS. 6 and 7).

  Also in the present embodiment, for the same reason as in the first embodiment, the upper mold 6 (the non-reflective structure molding master mold 40) is released from the press-formed alkali-free glass 20 without cooling. In addition, it is possible to release the upper mold 6 (non-reflective structure molding replica mold) from the press-molded optical material 11 without cooling, so that the pattern shift over a large area. Thus, it is possible to repeatedly mold a microlens array as an optical element having a highly accurate non-reflective structure.

  As described above, according to the present embodiment, it becomes possible to easily produce a mold for forming a microlens array, which is very difficult to produce a mold having a concave shape that is an inverted shape, It becomes very easy to form an antireflection structure on the surface of the microlens array.

  In the present embodiment, a conical mask corresponding to the non-reflective structure is formed on the surface (press surface) of the quartz glass substrate 29. However, the present invention is not necessarily limited to this configuration. For example, a polygonal pyramid-shaped mask may be formed.

Sectional drawing which shows the master metal mold | die for non-reflective structure for producing the metal mold | die for press molding of the optical element which has a non-reflective structure Process drawing showing the manufacturing process of master mold for non-reflective structure molding Process diagram showing the molding process of replica mold for non-reflective structure molding Process diagram showing press molding method of replica mold for non-reflective structure molding Sectional drawing which shows the metal mold | die for press molding of the optical element which has a non-reflective structure Process drawing showing molding process of optical element having non-reflective structure Process drawing showing press molding method of optical element having non-reflective structure Process drawing showing the manufacturing process of a quartz microlens array that is the basis of another non-reflective structure molding master mold Process diagram showing the molding process of another non-reflective structure molding master mold

Explanation of symbols

1, 29 Quartz glass substrate 2, 39 Non-reflective structure 3, 40 Master mold for forming non-reflective structure 4 Lower mold 5 Upper head 6 Upper mold 7 Preheating stage 8 Press stage 9 Cooling stage 10 Lower mold 11 Optical material 12 Gold Mold inlet 13 Cylinder 14 Mold outlet 15 Chamber 16 Mold release agent 17 Optical element 18 Atmospheric gas inlet 20 High melting point glass 21 Mold release agent 22 Non-reflection structure replica mold 25 Cr film 26, 35 PMMA resist 27 Cylindrical pattern 28 Cr mask 30 Photoresist 31 Cylindrical photoresist pattern 32 Hemispherical photoresist pattern 33 Microlens array 34 Quartz microlens array 36 X-ray 37 X-ray lithography mask 38 Mask

Claims (13)

A mask corresponding to the non-reflective structure is formed on a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching, and the non-reflective structure is formed on the surface of the mold material by dry etching. After forming, a thin film for surface protection is formed on the surface of the mold material, and a master mold for forming a non-reflective structure is manufactured,
Using the non-reflective structure molding master mold, a glass material having better heat resistance than an optical material coated with a release agent for mold release is press-molded, and the non-reflective structure is molded without cooling. After releasing the master mold from the press-molded glass material and cooling the press-molded glass material, the mold release agent is removed and a thin film for surface protection is formed on the surface of the glass material. Make a non-reflective structure molding replica mold,
Using the non-reflective structure molding replica mold, the optical material coated with a release agent for mold release is press-molded, and the non-reflective structure molding replica mold is press-molded without cooling. Release from optical material,
A method of manufacturing an optical element having a non-reflective structure in which the release agent is removed after the press-molded optical material is cooled. A mask corresponding to the non-reflective structure is formed on a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching, and the non-reflective structure is formed on the surface of the mold material by dry etching. After the formation, a carbon (C) film or a boron nitride (BN) film is formed on the surface of the mold material as a thin film for mold release, and a non-reflective structure molding master mold is manufactured.
From the glass material obtained by press-molding a glass material superior in heat resistance than an optical material using the non-reflective structure molding master mold, and press-molding the non-reflective structure molding master mold without cooling After the mold-released and press-molded glass material is cooled, a carbon (C) film or a boron nitride (BN) film is formed on the surface of the press-molded glass material as a thin film for mold release. , Making replica mold for non-reflective structure molding,
Using the non-reflective structure molding replica mold, the optical material is press-molded, and the non-reflective structure molding replica mold is released from the press-molded optical material without cooling,
A method for producing an optical element having a non-reflective structure for cooling the optical material formed by press molding. A mask corresponding to the non-reflective structure is formed on a mold material having excellent high temperature strength, heat resistance, and less surface roughness due to dry etching, and the non-reflective structure is formed on the surface of the mold material by dry etching. After forming, a thin film for surface protection is formed on the surface of the mold material, and a master mold for forming a non-reflective structure is manufactured,
Using an optical material in an atmosphere in which an inert gas is mixed with a gas or mist-like liquid containing carbon (C) or fluorine (F) in a constituent molecule, using the master mold for forming an antireflective structure The glass material with excellent heat resistance is press-molded, and the non-reflective structure molding master mold is released from the press-molded glass material without cooling, and the press-molded glass material is cooled and then pressed. Forming a thin film for surface protection on the surface of the molded glass material to produce a non-reflective structure molding replica mold,
Using the non-reflective structure molding replica mold, the optical material in an atmosphere in which an inert gas is mixed with a gas or mist-like liquid containing carbon (C) or fluorine (F) in a constituent molecule Press-molding, releasing the non-reflective structure molding replica mold from the optical material that has been press-molded without cooling,
A method for producing an optical element having a non-reflective structure for cooling the optical material formed by press molding. According to the mold material, quartz glass, silicon, Ni alloy, and any one of claims 1 to 3, which is one selected from the group consisting of those forming the SiO ₂ film or Si film on cemented carbide The manufacturing method of the optical element which has a non-reflective structure. The method for producing an optical element having an antireflective structure according to any one of claims 1 to 3, wherein the optical material is multi-component glass or resin. The material of the mask corresponding to the nonreflective structure is one selected from the group consisting of Cr, Ni, Au, and C. Manufacturing of an optical element having a nonreflective structure according to any one of claims 1 to 3. Method. The non-reflective structure according to any one of claims 1 to 3, wherein the mask corresponding to the non-reflective structure is a cylindrical or polygonal mask, and is formed in an array with a pitch equal to or less than a use wavelength. The manufacturing method of the optical element which has. A resist is formed on the mask corresponding to the non-reflective structure, and the resist is formed into a circular shape or a polygonal shape with a pitch equal to or less than a use wavelength by photolithography using electron beam lithography, X-ray lithography, or interference exposure. 4. The method according to claim 1, wherein the mask is formed in an array shape at a pitch of a use wavelength or less, by patterning in an array shape by wet etching or dry etching. A method for manufacturing an optical element having a reflective structure. The antireflective structure according to claim 1 or 3, wherein the thin film for surface protection contains at least one metal selected from the group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta. The manufacturing method of the optical element which has these. The method for producing an optical element having an antireflective structure according to any one of claims 1 to 3, wherein a material of the mask corresponding to the antireflective structure is a resist for X-ray lithography. The mask corresponding to the non-reflective structure is a conical or polygonal pyramid-shaped mask, and is formed in an array shape at a pitch equal to or less than a use wavelength by X-ray lithography. The manufacturing method of the optical element which has the non-reflective structure of description. The method of manufacturing an optical element having an antireflective structure according to claim 10 or 11, wherein a surface shape of the antireflective structure molding die is a curved surface. The optical element which has the non-reflective structure manufactured by the method in any one of Claims 1-12.

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