1. Field of the Invention
The present invention relates to a structured material having a mesostructure that can be used for, for example, optical devices, light-emitting devices, carrier materials, chemical reaction field materials, and sensors.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2001-145831 discloses a method for producing a mesostructured film having a two-dimensional hexagonal structure in which the orientation of cylindrical micelles is controlled by orientation regulation force of a rubbed polyimide layer.
Angew. Chem. Int. Ed., 46, 5364 (2007), Applied Physics Letters, 91, 023104 (2007), and Langmuir, 25, 11221 (2009) teach processes for forming a mesostructured material in which the orientation of cylindrical micelles is controlled in the spaces of microtrenches formed in the surface of a substrate.
These methods, however, have some disadvantages. In the method of Japanese Patent Laid-Open No. 2001-145831 in which the orientation is controlled by using a rubbed polyimide layer, the existence of such an organic interlayer between a mesostructured film and a substrate is liable to decrease the adhesion of the film to the substrate.
In the process using microtrenches described in Angew. Chem. Int. Ed., 46, 5364 (2007), the range of orientation control is limited to the regions within the microtrenches, and it is therefore difficult to form a continuous mesostructure whose orientation is controlled throughout the entire film. Even within the microtrenches, orientation regulation force is applied from three interfaces with two side surfaces and the bottom surface. Accordingly, the structural regularity of the resulting mesostructured material is not sufficient in an out-of-plane direction.
Applied Physics Letters, 91, 023104 (2007) describes a process for controlling the orientation of a mesostructured material using a substrate having a micro-grating structure at the surface thereof. However, this process limits the range of the orientation control to the region within the grating structure as with the case of Angew. Chem. Int. Ed., 46, 5364 (2007). Actually, it is described that when a mesostructured material has been formed to a level higher than the height of the grating structure, the orientation has not been controlled.
As with the case of Angew. Chem. Int. Ed., 46, 5364 (2007), Langmuir, 25, 11221 (2009) describes an orientation control process using microtrenches. In this case, the range of orientation control is limited to the regions within the microtrenches. Also, this document reports a phenomenon in which the mesostructured material is oriented in a direction perpendicular to the longitudinal direction of the microtrenches under specific conditions, and explains that this is because the surface of liquid in the trenches is deformed. Therefore, the process described in Langmuir, 25, 11221 (2009) is not suitable as a method for applying an orientation regulation force to a continuous mesostructured film completely covering the microtrenches.
Accordingly, an embodiment of the present invention provides a structured material including a base member, and a mesostructured member on the surface of the base member, including a wall defining cylindrically shaped portions. The base member has a plurality of grooves periodically formed in the surface thereof. The grooves each have a bottom surface and side surfaces in a shape in which a plane including the bottom surface is perpendicular to planes including the side surfaces. The cylindrically shaped portions in a region opposite to the base member with respect to an imaginary surface of the base member defined by imaginarily filling grooves to form an even surface are oriented at angles within a range of ±10° with respect to a direction perpendicular to the longitudinal direction of the grooves.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Embodiments of the invention will now be described with reference to the drawings.
The structured material of an embodiment is shown in
A structured material of an embodiment includes a base member, and a mesostructured member on the surface of the base member, including a wall defining cylindrically shaped portions. The base member has a plurality of grooves periodically formed in the surface thereof. The grooves each have a bottom surface and a side surface in a shape in which a plane including the bottom surface is perpendicular to a plane including the side surface. The cylindrically shaped portions in a region opposite to the base member with respect to an imaginary surface of the base member defined by imaginarily filling grooves to form an even surface are oriented at angles within a range of ±10° with respect to a direction perpendicular to the longitudinal direction of the grooves.
The structured material 11 of the present embodiment includes a base member 12, a mesostructured member 13 disposed on the surface of the base member 12, and mesostructured members 14 in the grooves. These components will be described in detail with reference to
A technique will be described with reference to
As shown in
The plane including the bottom surface 41 of each groove is perpendicular to the planes including the side surfaces of the groove. More specifically, the angle 43 between the plane including the bottom surface 41 and the plane including a side surface 42 is rectangular (right angle). However, the rectangular angle 43 (right angle) mentioned herein is not necessarily strictly 90°, and may be in a range of angles at which orientation regulation force is produced as intended. More specifically, the angle 43 is preferably in the range of 85° to 100°.
The bottom surfaces 41 of the grooves 31 are desirably flat, but may have a small surface roughness of less than 5 nm in height at the surface thereof in the process for forming the grooves. Such a small surface roughness hardly affects the orientation control in the present embodiment and is negligible. The word “flat” mentioned herein implies that the bottom surfaces 41 are approximated by straight lines in the sectional view of
In the structure shown in
When the bottom surface 41 and the each side surface 42 intersect at the right angle, as shown in
It is thought that the presence of grooves in the surface of the base member having such a shape in section allows orientation regulation force to act to orient cylindrical micelles at angles within a range of ±10° with respect to a direction perpendicular to the longitudinal direction of the grooves in the stage of forming the mesostructured member on the surface of the base member.
The dimensions of the grooves required for producing orientation regulation force will now be described with reference to
The grooves 31 of the base member 12 each have a depth Td and a width Tw. The depth Td and the width Tw desirably satisfy the following relationship:
2≧Tw/Td≧0.5
where 10 nm<Tw<1 μm and 10 nm<Td<1 μm
The reason is as below. When Tw/Td is less than 0.5, the width of the grooves is too small relative to the depth of the grooves. In this case, in the structure shown in
When Tw/Td is larger than 2, the width of the grooves is too large relative to the depth of the grooves. In this case, in the structure shown in
The width Tw and the depth Td of the grooves are each desirably less than 1 μm. When either is 1 μm or more, in the structure shown in
The distance Tp between adjacent grooves (intervals of the grooves) is desirably 2 μm or less. If the distance Tp is larger than 2 μm, the orientation of the cylindrically shaped portions 15 of the mesostructured member 13 on the surface of the base member, shown in
Portions between Grooves
The shape of the portions between the grooves is not particularly limited as long as the shape of the grooves in section has the above-described features.
The base member having the grooves periodically formed in the surface thereof will now be described with reference to
The base member 12 may be composed of a single layer as shown in
In the case of the structure shown in
The base member 12 may have any shape, as long as grooves are periodically formed in the surface thereof and a mesostructured member can be formed on the surface thereof. For example, the shape of the base member 12 may be plate-like, curved, or lens-like.
The periodically arranged grooves can be formed by known processes including, for example, a patterning process using photolithography or electron beam drawing and an etching process.
The orientation-controlled mesostructured member of the present embodiment will now be described with reference to
The cylindrically shaped portions 15 are oriented at angles within a range of ±10° with respect to a direction perpendicular to the longitudinal direction 61 of the grooves.
As long as the cylindrically shaped portions 15 are oriented at angles within a range of ±10° with respect to a direction perpendicular to the longitudinal direction 61 of the grooves, the plurality of grooves may be in any form. For example, a plurality of straight grooves may be arranged in the same direction throughout the entire main surface of the base member 12, as shown in
Alternatively, as shown in
The orientation-controlled portion of the mesostructured member may be limited to a region with a finite thickness near the surface of the base member, or may cover the entirety of the mesostructured member from the position near the surface of the base member to the boundary between the mesostructured member and the atmosphere.
In the structured material shown in
When a diblock copolymer having a PEO-PPO structure is used, the number of repetitions of polyethylene oxide and the number of repetitions of polypropylene oxide are each preferably in the range of 10 to 500. Examples of such a PEO-PPO diblock copolymer include PEO68-PPO60 and PEO98-PPO60. When a triblock copolymer having a PEO-PPO-PEO structure is used, the number of repetitions of polyethylene oxide and the number of repetitions of polypropylene oxide are each preferably in the range of 10 to 200. Examples of such a PEO-PPO-PEO triblock copolymer include PEO20-PPO70-PEO20 and PEO106-PPO70-PEO106.
In the structured material shown in
The cylindrically shaped portions 15 are desirably arranged so as to form a two-dimensional hexagonal structure in the mesostructured member 13 on the surface of the base material 12. The two-dimensional hexagonal structure mentioned herein is such that when a section of the mesostructured member 13 is taken along a plane perpendicular to the orientation direction 62 of the cylindrically shaped portions, the circular sections of the cylindrically shaped portions 15 are arranged in a hexagonal close-packed manner in the matrix or the wall 18. Such a two-dimensional hexagonal structure leads to a highly regular arrangement of the cylindrically shaped portions in the mesostructured member 13 on the surface of the base 12. The cylindrically shaped portions 15 are arranged preferably with a structural period of 5 nm or more in an out-of-plane direction, more preferably 9 nm or more, and most preferably 15 nm or more. The out-of-plane direction mentioned herein refers to a direction perpendicular to the main surface of the base member.
A process will now be described for forming the mesostructured member 13 having orientation-controlled cylindrically shaped portions on the surface of the base member 12 having a plurality of grooves periodically formed therein.
The mesostructured member 13 on the surface of the base member 12 may be formed through the following steps:
A material having a plurality of grooves periodically formed in the surface thereof is used as the base member. In the present embodiment, the width of each groove is preferably 10 nm or more. A solution containing amphiphilic molecules, an inorganic oxide precursor and a catalyst is applied onto the surface of such a base member.
Any amphiphilic compound may be used as the amphiphilic molecules without particular limitation, as long as its aggregate can be used as a template for forming the mesostructured member. The amphiphilic compound is appropriately selected from the compounds that can form cylindrical micelles having dimensions according to the structural period of the desired mesostructured member.
Desirably, an amphiphilic compound is selected whose molecule includes a hydrophilic group and a hydrophobic group with a relatively small hydrophilic/hydrophobic contrast. A preferred amphiphilic compound may be a PEO-PPO diblock copolymer or a PEO-PPO-PEO triblock copolymer as mentioned above.
The solution containing amphiphilic molecules, an inorganic oxide precursor and a catalyst may further contain an additive for adjusting the structural period. The additive for adjusting the structural period may be a hydrophobic material. Examples of the hydrophobic material include alkanes, and aromatic compounds not containing a hydrophilic group. More specifically, octane, trimethylbenzene or the like may be used as the hydrophobic material.
Examples of the inorganic oxide precursor include alkoxides and halides of silicon or a metal. Examples of the alkoxide include methoxide, ethoxide, propoxide, and compounds in which part of alkoxide is substituted with an alkyl group. More specifically, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, or the like may be used. As the halide, for example, a chloride may be used. Alternatively, a precursor that can introduce an organic group to an inorganic oxide skeleton may be used to form an organic-inorganic hybrid wall.
The application of the solution containing amphiphilic molecules, an inorganic oxide precursor, and a catalyst may be performed by coating, such as spin coating, dip coating, a cast method, or spray coating.
Among these coating techniques, suitable are dip coating performed at a withdrawal speed of less than 100 μm/s or a cast method. By forming the mesostructured member in a process taking a long time, orientation regulation force from the base member having the grooves periodically formed in the surface thereof acts to help the uniaxial orientation of the cylindrical micelles, thereby enabling a highly in-plane oriented structure to be reproducibly formed in the mesostructured member on the surface of the base member.
In a structured material of a second embodiment, the cylindrically shaped portions of the mesostructured member may be hollow, or hollow with inner walls chemically modified with an organic material or the like. The second embodiment is the same as the first embodiment except for this feature.
The structured material of the present embodiment can be formed by a process including, for example, steps (i) and (ii) of forming the structured material of the first embodiment, and, in addition, step (iii) of removing the amphiphilic molecules by firing, extraction, or any other technique, and optional step (iv) of chemically modifying the inner walls of the cylindrically shaped hollow portions. The chemical modification may be performed by treating the surface of the wall with a silane coupling agent having an organic group according to the function to be given, such as alkyl, alkylfluoro, mercapto, or carboxy.
A silica layer was formed by thermally oxidizing the surface of a silicon base, and a pattern of grooves was formed in the silica layer. The grooves had a depth Td and a width Tw of 500 nm each and were arranged at intervals (distances) Tp of 500 nm.
A solution containing tetraethoxysilane, a triblock copolymer having a PEO20-PPO70-PEO20 structure, ethanol, hydrochloric acid, and water was applied to the above-prepared base member by dip coating to form a mesostructured silica film acting as a mesostructured member. For dip coating, the base member was withdrawn at a speed of 20 μm/s.
The resulting mesostructured silica film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles to form cylindrically shaped portions were oriented in a direction perpendicular to the longitudinal direction of the grooves with a structural period d of 9 nm in an out-of-plane direction and in a manner of a two-dimensional hexagonal structure. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more. These results will be described below using the scanning electron micrographs (hereinafter refers to SEM images).
A mesoporous silica film was formed from the mesostructured film produced in Example 1 by removing the triblock copolymer by solvent extraction at 80° C. using ethanol.
It was confirmed that the resulting mesoporous silica film had the same characteristics observed in Example 1 except that hollow cylindrically shaped portions were formed in the film by the removal of the triblock copolymer.
A mesostructured silica film was formed in the same manner as in Example 1, except that the grooves of the groove pattern had a depth Td and a width Tw of 250 nm each and were arranged at intervals (distances) Tp of 250 nm.
The resulting mesostructured silica film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles were oriented in a direction perpendicular to the longitudinal direction of the grooves with a structural period d of 9 nm in the out-of-plane direction and in a manner of a two-dimensional hexagonal structure as in Example 1. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more. As a representative of the results, an SEM image of a section of the film taken along a plane perpendicular to the longitudinal direction of the grooves is shown in
A silica layer was formed by thermally oxidizing the surface of a silicon base, and a pattern of grooves was formed in the silica layer. The grooves had a depth Td and a width Tw of 250 nm each and were arranged at intervals (distances) Tp of 250 nm.
A solution containing tetraethoxysilane, a diblock copolymer having a PEO98-PPO60 structure, ethanol, hydrochloric acid, and water was applied to the above-prepared base member by dip coating to form a mesostructured silica film acting as a mesostructured member. For dip coating, the base member was withdrawn at a speed of 20 μm/s.
The resulting mesostructured silica film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles were oriented in a direction perpendicular to the longitudinal direction of the grooves with a structural period d of 16 nm in the out-of-plane direction and in a manner of a two-dimensional hexagonal structure. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more. As a representative of the results, an SEM image of a section of the film taken along a plane perpendicular to the longitudinal direction of the grooves is shown in
A mesostructured silica film was formed in the same manner as in Example 4, except that the diblock copolymer had a PEO68-PPO60 structure.
The resulting mesostructured silica film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles were oriented in a direction substantially perpendicular to the longitudinal direction of the grooves with a structural period d of 14 nm in the out-of-plane direction and in a manner of a two-dimensional hexagonal structure. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more.
A silica layer was formed by thermally oxidizing the surface of a silicon base, and a pattern of grooves was formed in the silica layer. The grooves had a depth Td and a width Tw of 500 nm each and were arranged at intervals (distances) Tp of 500 nm.
A solution containing tetraisopropyl titanate, a triblock copolymer having a PEO20-PPO70-PEO20 structure, 1-butanol, hydrochloric acid, and water was applied to the above-prepared base member by dip coating to form an oriented mesostructured titania film. For dip coating, the base member was withdrawn at a speed of 20 μm/s.
The resulting mesostructured titania film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles were oriented in a direction substantially perpendicular to the longitudinal direction of the grooves with a structural period d of 9 nm in the out-of-plane direction and in a manner of a two-dimensional hexagonal structure. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more.
A mesostructured silica film was formed in the same manner as in Example 1, except that the base member having the pattern of grooves described in Example 1 in the surface thereof was treated for 333 seconds to deform the portions between the grooves by plasma etching using Ar gas. Consequently, the highest surfaces between the grooves continue to the side surfaces through slants.
The resulting mesostructured silica film was subjected to X-ray diffraction analysis. As a result, it was confirmed that cylindrical micelles were oriented in a direction perpendicular to the longitudinal direction of the grooves with a structural period d of 9 nm in the out-of-plane direction and in a manner of a two-dimensional hexagonal structure as in Example 1. This orientation-controlled two-dimensional hexagonal structure was kept in the thickness direction throughout the region from the highest surface of the base member between the grooves to a height of 500 nm or more. As a representative of the results,
The embodiments of the present invention can achieve oriented mesostructured materials having high structural regularity and a large structural period without decreasing their adhesion to the substrate.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2013-073650 filed Mar. 29, 2013, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2013-073650 | Mar 2013 | JP | national |