JP2009119641A - Mold for imprinting, its manufacturing method, and structure formed by using its mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for imprinting having a smooth and uniform surface rugged pattern structure without any step derived from crystalline grains, its manufacturing method and the structure formed by using the mold. <P>SOLUTION: The mold for imprinting is characterized in that it is composed of anodized porous alumina having hole array structure having a micropore size and a uniform micropore depth on the surface obtained by anodizing a surface of a raw material formed of single-crystal aluminum. The mold for imprinting, its manufacturing method, and the structure formed by using its mold are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imprint mold having a fine surface unevenness pattern made of anodized porous alumina, a manufacturing method thereof, and a structure formed using the imprint mold.

  The nanoimprint method can transfer sub-micron to nanometer-scale fine concavo-convex patterns onto the substrate surface at once, so various functional devices such as water and oil repellent films, antireflection films, and cell culture sheets It is expected as a technique for manufacturing. Since the structure obtained by the nanoimprint method corresponds to the surface structure of the mold to be used, the mold production method is important. Normally, molds used for imprinting are manufactured by a combination of various lithography processes, including electron beam lithography, and dry etching processes. However, with existing techniques, a fine pattern is manufactured in a large area. Therefore, the application range of the imprint method is limited.

  In recent years, it has been shown that anodized porous alumina, which is a hole array structure material obtained by anodizing an aluminum material, is useful as a mold material for nanoimprinting (for example, Patent Document 1). Since anodized porous alumina has a regular hole array structure formed by a self-organization process, it has the feature that a large-area structure can be formed. Since the pore period and the pore diameter can be controlled by changing, it is possible to obtain a mold having a fine pattern with a large area, which is difficult to produce by other methods.

  However, the porous alumina formed by anodic oxidation has a slight difference in the film growth rate depending on the crystal orientation of the aluminum ingot used. Therefore, when a polycrystalline aluminum material is used as a starting material, the ingot metal is used. As a result, the film thickness unevenness derived from the crystal orientation of the crystal grains distributed in the film occurs. For this reason, when nanoimprinting is performed using the obtained porous alumina as a mold, there is a problem that a pattern having a distribution of protrusion sizes is formed. In addition, in order to obtain anodized porous alumina in which pores are regularly arranged from the film surface by a self-organization process, after anodizing under appropriate conditions, the oxide film once formed is dissolved and removed, and again Anodization will be performed under the same conditions. However, if the aluminum material used as the starting structure is a polycrystal, the crystal grains on the bare metal surface are derived from the difference in the film growth rate due to the difference in crystal orientation. There is a problem that a step corresponding to the pattern is generated. Therefore, the method for producing regular porous alumina by the self-assembly process has a problem that it is difficult to produce a mold for nanoimprinting that requires accuracy of 1 micron or less. In addition, even when electrolytic polishing or chemical polishing is performed on a polycrystal, a concavo-convex pattern derived from the crystal grains is formed on the material surface. Therefore, even if porous alumina is formed on this surface, the hole array structure It is not easy to obtain a smooth surface with excellent flatness.

For these reasons, when a polycrystalline aluminum material is used as a starting structure and anodized porous alumina is formed on the surface thereof, and this is used as an imprint mold, protrusions with a uniform height are formed on the substrate without steps. For example, when the substrate surface is observed as a light reflecting surface, it is difficult to form the surface on a surface that can be observed as a surface state having a protrusion having a uniform height without a step.
JP 2007-86283 A

  The present invention has been completed as a result of intensive studies on a method for producing a mold used for nanoimprinting, which is expected to be applied to a wide range of fields. The purpose is to have a smooth and uniform surface structure without steps derived from crystal grains and to improve the dimensional accuracy of the surface uneven pattern, a mold for nanoimprint made of anodized porous alumina, a method for producing the mold, and a method therefor The object is to provide a structure formed using an imprint mold.

  In order to solve the above problems, an imprint mold according to the present invention is obtained by anodizing a material surface made of single crystal aluminum, and has a hole array structure with a uniform pore size and pore depth on the surface. It is comprised by the anodized porous alumina which has this. By making the material surface made of single crystal aluminum a starting structure for anodization, the crystal orientation of the material surface before anodization is made uniform and constant, so the difference in film growth rate due to the difference in crystal orientation is It does not occur, and it is prevented that a step corresponding to the crystal grain pattern derived therefrom is generated. As a result, a smooth and uniform surface structure with no steps derived from the crystal grains is obtained, and pore formation by anodization is also progressed uniformly, so that the projections with excellent shape uniformity are regularly arranged A pattern is obtained, and an imprint mold having a target form having a uniform and highly accurate surface structure with improved dimensional accuracy of the surface irregularity pattern is surely obtained.

  The material surface made of single crystal aluminum to be anodized can be formed as a flat surface, can be formed into a curved shape, or formed into any other shape. You can also. In particular, if surface treatment with curvature is applied to the surface of a single crystal aluminum material in advance, porous alumina with uniform pore depth and pore size can be formed on the surface of aluminum material of various shapes. Is possible. By using the porous alumina after anodization as an imprint mold, it is possible to form a structure in which protrusions having excellent size uniformity are regularly arranged on a surface having a curvature. If a lens shape such as a convex lens, a concave lens, an aspherical lens, or a Fresnel lens is formed as a shape having a curvature, various lenses can be obtained by imprint processing using a mold obtained by anodization. It is possible to form a concavo-convex pattern having a uniform projection height and projection size on the surface.

  In this way, when a single crystal aluminum material is used, anodization proceeds at a uniform film growth rate over the entire surface of the material, so that even when anodization is performed for a long time, a step is generated on the surface of the aluminum material. There is nothing. However, in aluminum materials that have been subjected to curved surface processing such as lens shapes, for example, even if the (100) surface is exposed on the outermost surface of the single crystal aluminum material before processing, it is exposed on the outermost surface within the processed curved surface. As for the crystal orientation of the aluminum material, a surface different from (100) is exposed. Therefore, when anodization is performed for a long time on a single crystal aluminum material subjected to curved surface processing, a difference occurs in the growth rate of the film within the curved surface. As a result, the surface shape of the bare metal has an error compared to the surface shape immediately after processing. For example, in order to manufacture a high-performance lens, in-plane curvature accuracy is important, and thus a shape error caused by anodization for a long time leads to deterioration of lens performance. Since the growth rate of the film in each crystal orientation of the aluminum material can be estimated in advance, the single crystal aluminum material can be shaped into a shape that allows for an error in the shape change of the aluminum material due to long-term anodization. For example, it is considered that an imprint mold having a target shape can be produced after a predetermined long-term anodic oxidation. Therefore, it is preferable that the shape having the curvature of the surface of the material made of single crystal aluminum is formed in a shape that allows for a shape change error due to anodization before anodization.

  Various shapes can be imparted to the surface of the single crystal aluminum material, but as a method of imparting a predetermined shape, in addition to a method of shaping by machining, a mold having a desired shape (for example, A technique for controlling the shape by pressing the mold) is effective.

  In the present invention, anodized porous alumina having pores whose pore diameters are continuously changed by repeatedly performing anodization and pore diameter expansion treatment can be used as an imprint mold. By using anodized porous alumina having pores with continuously changing pore diameters produced by combining such anodization and pore diameter expansion treatment as a mold, a mold from an imprint object during imprinting is used. It is possible not only to improve the peeling characteristics of the film, but also to form a concavo-convex pattern with a continuously changing projection diameter on the surface of the imprint object. The surface on which the protrusions with continuously changing protrusion diameters are regularly arranged has a very effective structure as a water repellent / hydrophilic surface or an antireflection surface.

  The anodized porous alumina for constituting the imprint mold according to the present invention can be produced by various methods. For example, anodized porous alumina prepared using oxalic acid as an electrolyte and an anodizing voltage of 30 to 60 V, or anodized porous alumina prepared using sulfuric acid as an electrolyte and an anodizing voltage of 10 to 30 V, or phosphorus An imprint mold having a hole array structure having higher regularity can be obtained by using an acid as an electrolytic solution and using anodized porous alumina produced at a conversion voltage of 180 V to 200 V.

  Furthermore, after anodizing at a constant voltage for a long time, once the oxide film is removed and anodizing is performed again under the same conditions, anodized porous alumina with high pore arrangement regularity is imprinted from the surface. It can be produced as a mold for use.

  In addition, a negative mold obtained by dissolving and removing the ingot aluminum and the porous alumina layer after filling the pores of the anodized porous alumina obtained as described above and the surface thereof with a substance is used. For example, it is possible to obtain an imprint mold having a hole array pattern in which pores having a uniform size and depth are regularly arranged on the surface.

  By using the imprint mold configured as described above and transferring the surface structure, protrusions with a uniform height and pores with a uniform depth are arranged on the surface consisting of a flat surface and a curved surface. A structure having a target uneven pattern can be obtained. Since such a fine and uniform surface uneven pattern is a particularly useful structure as an antireflection structure, it is suitable as a means for uniformly forming an antireflection layer evenly on the surface of a lens, for example.

  The method for producing an imprint mold according to the present invention comprises anodizing a porous alumina having a hole array structure having a uniform pore size and pore depth on the surface by anodizing a material surface made of single crystal aluminum. The method is characterized in that an imprint mold having an uneven pattern on the surface is formed using the anodized porous alumina.

  The surface of the material made of the single crystal aluminum can be formed on a flat surface or a shape having a curvature. As a shape having a curvature, for example, it can be formed into a lens shape as described above.

  Further, when the material surface made of single crystal aluminum is formed in a shape having a curvature, it is preferably formed in a shape that allows for a shape change error due to anodization before anodization.

  As a method for forming the surface of the material made of single crystal aluminum into a predetermined shape, the surface shape to be anodized can be controlled by pressing a forming die in addition to machining.

  In the produced anodized porous alumina, pores whose pore diameters are continuously changed can be formed by repeatedly performing anodization and pore diameter expansion treatment.

  Anodized porous alumina uses, for example, oxalic acid as an electrolytic solution as described above, sulfuric acid as an electrolytic solution at a formation voltage of 30 to 60 V, phosphoric acid as an electrolytic solution at an formation voltage of 10 to 30 V, and a conversion voltage of 180 V. It can be produced at ˜200V.

  The anodized porous alumina can also be produced by anodizing at a constant voltage, once dissolving and removing the oxide film, and again anodizing under the same conditions.

  Furthermore, after filling the material into the pores of the anodized porous alumina prepared as described above, the mold for the imprint having a negative structure can be formed by removing the template of the anodized porous alumina. .

  As described above, according to the imprint mold and the method for manufacturing the same according to the present invention, it has a smooth and uniform surface structure free from steps derived from crystal grains, and improves the dimensional accuracy of the surface uneven pattern. An anodized porous alumina nanoimprint mold can be obtained efficiently. By using this imprint mold, a structure having a desired surface irregularity pattern can be reliably obtained.

Below, the production form of the mold for imprints using the single crystal aluminum material which concerns on this invention is demonstrated in detail, referring drawings.
FIG. 1 shows a process in which anodized porous alumina 2 is formed on the surface of a single crystal aluminum material 1 and used as an imprint mold 3 to transfer the structure onto the surface of, for example, a resin substrate 4 as an imprint object. Is shown. By anodizing the single crystal aluminum material 1 in an acid bath, anodized porous alumina 2 having pores 5 of uniform size and uniform depth formed on the surface. By using this as the imprint mold 3 and transferring the structure onto the surface of the resin base material 4, it is possible to obtain a concavo-convex pattern in which the projections 6 of uniform size are uniformly arranged.

  As described above, the growth rate of the anodized porous alumina depends on the crystal orientation of the aluminum material surface. In order to form porous alumina with regularly arranged pores, it is necessary to perform anodization for a long time. However, if anodization is performed for a long time using a polycrystalline aluminum material, it depends on the crystal orientation. Thus, not only the thickness of the porous alumina is different, but also the surface of the bare aluminum material is uneven due to the difference in the progress rate of the anodic oxidation. By using the single crystal aluminum material 1 as in the present invention, anodization proceeds at a uniform film growth rate over the entire surface of the material, so that even when anodization is performed for a long time, crystal grains are present on the surface of the aluminum material. Therefore, the surface structure of a desired uniform concavo-convex pattern is obtained.

  FIG. 2 shows a projection 16 having a uniform size by depositing nickel 14 in the pores 13 and on the surface of anodized porous alumina 12 formed using a single crystal aluminum material 11 and dissolving and removing the mold 15. 4 shows a process for producing an imprint mold 17 made of a structure regularly arranged. By using this imprint mold 17 and transferring the structure to, for example, a resin base material 18 as an imprint object, a concavo-convex pattern in which uniform-sized pores 19 are uniformly arranged can be obtained.

  FIG. 3 shows a case where the surface of the single crystal aluminum material 21 is processed with a curved surface 22 such as a lens shape before anodizing, and the curved surface 22 is formed into a curved surface shape that allows for a shape change error due to anodization. Is done. For example, as shown in FIG. 3, even if the (100) plane is exposed on the outermost surface of the single crystal aluminum material 21 before processing, the crystal orientation of the aluminum material exposed on the outermost surface in the processed curved surface Will expose a different surface than (100). For this reason, when the long-term anodic oxidation is performed on the single crystal aluminum material 21 that has been subjected to the curved surface processing, a difference occurs in the growth rate of the film within the curved surface 22. As a result, the surface shape of the bare metal is different from the surface shape immediately after processing. In order to fabricate a high-performance lens, in-plane curvature accuracy is important, and thus an error in shape caused by anodization for a long time leads to deterioration of lens performance. Therefore, since the growth rate of the film in each crystal orientation of the aluminum material can be estimated in advance, the single crystal aluminum material is shaped into a shape that allows for an error in the shape change of the aluminum material due to long-term anodic oxidation. As a result, it is possible to form the target curved surface shape as the surface curved surface shape of the formed layer of the anodized porous alumina 23, and the imprint mold 24 having a desired lens shape can be obtained.

  In FIG. 4, a lens-shaped mold 32 is pressed against the surface of the single crystal aluminum material 31 to perform shaping, and then the shaped article 33 is anodized to form a layer of anodized porous alumina 34 on the surface. A process for producing an imprint mold 35 for forming a nano-pattern having a shape is shown. For example, a resin 36 is filled in the uneven surface pattern of the imprint mold 35, and the resin substrate 37 of the same kind is pressed on the surface to transfer the structure of the uneven surface pattern of the imprint mold 35. The structure 38 in which the nano pattern is formed can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this Example.
Example 1 [Comparison of Porous Alumina Formed Using Single Crystal Aluminum Material and Polycrystalline Aluminum Material]
A single crystal aluminum plate and a polycrystalline aluminum plate having a purity of 99.99% were subjected to electropolishing treatment in a mixed solution of perchloric acid and ethanol (volume ratio 1: 4). The result of comparing the appearance of the mirror-finished aluminum plate was anodized in an aqueous oxalic acid solution adjusted to a concentration of 0.3 M for 15 hours at a bath temperature of 17 ° C and a direct current of 40 V. 5 (A) (single crystal), (B) (polycrystal). Both of the aluminum materials before anodizing had a smooth surface with no steps because they were mechanically polished. However, looking at samples that had been anodized for a long time, a polycrystalline aluminum plate was used. Only the anodized porous alumina 42 was found to have a pattern derived from crystal grains, and in the anodized porous alumina 41 using a single crystal aluminum plate, no pattern (step) derived from the crystal grains was generated. This is caused by the fact that the film growth rate of anodized porous alumina varies depending on the crystal orientation.

Example 2 [Imprint with Mold Formed Using Single Crystal Aluminum Material]
A single crystal aluminum plate having a purity of 99.99% was subjected to electropolishing treatment in a mixed solution of perchloric acid and ethanol (volume ratio 1: 4). The mirror-finished aluminum plate was anodized in an oxalic acid aqueous solution adjusted to a concentration of 0.3 M at a bath temperature of 17 ° C. under a direct current of 40 V for 15 hours. After the formed film was once dissolved and removed in the chromic acid phosphoric acid mixed solution, anodization was again performed for 1 minute under the same conditions to form porous alumina. After the surface of the formed porous alumina was modified with a fluorine-based surface treatment agent, the structure was transferred to a photocurable resin. FIG. 6A (plan view) and FIG. 6B (perspective view) show the results of observing the resin sheet after imprinting and the surface thereof by SEM.

Example 3 [Production of lens-shaped mold using single crystal aluminum and application to imprint]
A single crystal aluminum plate having a purity of 99.99% was annealed at 400 ° C. for 1 hour. The annealed single crystal aluminum plate was electropolished in a perchloric acid / ethanol mixed solution (volume ratio 1: 4). The surface of the aluminum plate was formed into a lens shape by pressing a microlens array-shaped Ni mold against the base metal. Anodization was carried out for 3 hours under conditions of 40 V DC at a bath temperature of 17 ° C. in an aqueous oxalic acid solution prepared by adjusting an aluminum plate having a lens shape on the surface to a concentration of 0.3 M. Thereafter, the formed film was once dissolved and removed in a chromic acid phosphoric acid mixed solution, and anodization was again performed for 1 minute under the same conditions to form porous alumina. The sample after anodization was immersed in a 5 wt% phosphoric acid aqueous solution for 20 minutes, and the pore diameter was enlarged. After the surface of the formed porous alumina was modified with a fluorine-based surface treatment agent, the structure was transferred to a photocurable resin. FIG. 7A (plan view), (B) (plan view), and (C) (perspective view) show the results of observing the resin sheet after imprinting and its surface with an SEM.

  The imprint mold according to the present invention can be applied to any imprint that requires the formation of a fine and uniform surface irregularity pattern, and is suitable for forming an antireflection layer such as a lens structure.

It is a schematic block diagram which shows preparation of the imprint mold which concerns on one embodiment of this invention, and the imprint process using the same. It is a schematic block diagram which shows preparation of the imprint mold which concerns on another embodiment of this invention, and an imprint process using the same. It is a schematic block diagram which shows preparation of the mold for imprint which concerns on another embodiment of this invention. It is a schematic block diagram which shows preparation of the imprint mold which concerns on another embodiment of this invention, and the imprint process using the same. It is a figure which shows the result of having observed the surface of the anodic porous alumina obtained in Example 1, (A) shows the result using a single crystal aluminum material, (B) shows the result using a polycrystalline aluminum material. ing. It is a figure which shows the result of having observed the surface of the resin sheet after the imprint in Example 2 by SEM. It is a figure which shows the result of having observed the surface of the resin sheet after the imprint in Example 3 by SEM.

Explanation of symbols

1, 11, 21, 31 Single crystal aluminum material 2, 12, 23, 34 Anodized porous alumina 3, 17, 24, 35 Imprint mold 4, 18 Resin substrate 5, 13 Pore 6 Projection 14 Nickel 15 Mold 16 Protrusion 19 Pore 22 Curved surface 32 Mold 33 Shaped product 36 Resin 37 Resin substrate 38 Structure 41 Anodized porous alumina 42 using single crystal aluminum plate Anodized porous alumina using polycrystalline aluminum plate

Claims (20)

  Imprint characterized by comprising anodized porous alumina having a hole array structure with uniform pore size and pore depth obtained by anodizing the surface of a material made of single crystal aluminum Mold.   The imprint mold according to claim 1, wherein the material surface made of the single crystal aluminum is formed in a shape having a curvature.   The imprint mold according to claim 2, wherein the shape having the curvature is a lens shape.   The imprint mold according to claim 2 or 3, wherein the shape having a curvature of the surface of the material made of single crystal aluminum is formed into a shape that allows for a shape change error due to anodization before anodization.   The imprint mold according to any one of claims 1 to 4, wherein a shape of a surface of the material made of the single crystal aluminum is controlled by pressing a forming die.   The mold for imprinting according to any one of claims 1 to 5, which has pores whose pore diameter is continuously changed by repeatedly performing anodization and pore diameter expansion treatment.   The imprint mold according to any one of claims 1 to 6, wherein the anodized porous alumina is made of oxalic acid as an electrolytic solution and formed at a conversion voltage of 30V to 60V.   The anodized porous alumina comprises anodized porous alumina obtained by anodizing at a constant voltage, once dissolving and removing the oxide film, and again anodizing under the same conditions. The imprint mold according to any one of the above.   An imprint mold having a negative structure obtained by filling the pores of the anodized porous alumina according to any one of claims 1 to 8 and then removing the anodized porous alumina mold.   The structure which has an uneven | corrugated pattern on the surface by which the surface structure of the imprint mold in any one of Claims 1-9 was transcribe | transferred.   The structure according to claim 10, wherein the layer having an uneven pattern on the surface is configured as an antireflection layer.   By anodizing the surface of the material made of single crystal aluminum, anodized porous alumina having a hole array structure with a uniform pore size and pore depth is produced on the surface, and the anodized porous alumina is used on the surface. A method for producing an imprint mold, comprising forming an imprint mold having an uneven pattern.   The manufacturing method of the mold for imprint of Claim 12 which forms the raw material surface which consists of the said single crystal aluminum in the shape which has a curvature.   The method for manufacturing an imprint mold according to claim 13, wherein the shape having the curvature is formed into a lens shape.   The method for producing an imprint mold according to claim 13 or 14, wherein the shape having the curvature of the material surface made of single crystal aluminum is formed into a shape that allows for a shape change error due to anodization before anodization.   The method for manufacturing an imprint mold according to any one of claims 12 to 15, wherein a molding die is pressed against a surface of the single crystal aluminum material to control a surface shape to be anodized.   The method for producing an imprint mold according to any one of claims 12 to 16, wherein pores whose pore diameters are continuously changed are formed by repeatedly performing anodization and pore diameter expansion treatment.   The method for producing an imprint mold according to any one of claims 12 to 17, wherein the anodized porous alumina is produced at an formation voltage of 30 to 60 V using oxalic acid as an electrolyte.   The anodized porous alumina is produced by anodizing at a constant voltage, once dissolving and removing the oxide film, and again anodizing under the same conditions. A method for producing an imprint mold.   After filling the substance into the pores of the anodized porous alumina according to any one of claims 12 to 19, an anodized porous alumina mold is removed to form an imprint mold having a negative structure. A method for producing an imprint mold.

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