JP6725129B2 - Nano-embossed structure, method for producing nano-embossed structure, and polymerizable material for producing nano-embossed structure - Google Patents

Description

The present invention relates to a nano-embossed structure, a method for manufacturing the nano-embossed structure, and a polymerizable material for manufacturing the nano-embossed structure.

In recent years, nanostructures having a nano-embossed structure composed of a fine uneven structure have a superhydrophobic property, a superhydrophilic property, a structural color, a structural birefringence, a polarization conversion, an antireflection property, an adhesive property, etc. Since such various functions can be exhibited, it has been attracting attention in a wide range of fields such as the fields of electronics, photonics, and medical materials, and various manufacturing methods have been actively studied.

For example, in Japanese Unexamined Patent Publication No. 2006-108635 (Patent Document 1), after forming a thin film made of a resin composition containing a block copolymer or a graft copolymer and forming a microphase-separated structure in a self-organizing manner, the thin film is formed. The method of forming a concavo-convex structure by selectively etching at least one phase of the micro phase separation structure is disclosed. However, in the method for forming a concavo-convex structure as described in Patent Document 1, an etching step is required to selectively remove one phase during the concavo-convex production, and a fine concavo-convex structure can be formed by a simple process. Could not be manufactured.

Further, Japanese Patent Application Laid-Open No. 2011-53496 (Patent Document 2) discloses a method of forming a fine uneven structure with a so-called photoresist, and a method of transferring the uneven structure by pressing the uneven structure on a resin layer. Has been done. However, in Patent Document 2, when manufacturing the uneven structure used as a mold, it is necessary to form a fine uneven structure with a so-called photoresist, and the process is complicated.

As described above, conventionally, an etching process is required to manufacture a fine concavo-convex structure or a mold obtained through a complicated process is required, and an embossed structure having a fine concavo-convex structure can be efficiently formed by a simple process. I couldn't.

JP, 2006-108635, A JP, 2011-53496, A

The present invention has been made in view of the problems of the above-described conventional technology, and without having to perform a complicated etching step or the like, it is possible to form a nanoembossed structure composed of a fine concavo-convex structure, and a nanoembossed structure is obtained. Provided are a method for producing a nano-embossed structure that can be simply and efficiently produced, a polymerizable material for producing a nano-embossed structure used in the production method, and a nano-embossed structure obtained by the production method. The purpose is to do.

The present inventors have conducted extensive studies to achieve the above object, and as a result, at least one polyfunctional acrylic monomer (A) selected from 4 to 8 functional acrylic monomers, and a carbon-carbon dimer. Content of at least one kind of monomer (B) selected from monomers having 1 to 3 functional groups having a heavy bond, and content of the polyfunctional acrylic monomer (A) A step of preparing a polymerizable material in which is 70 mol% or more based on the total amount of the polyfunctional acrylic monomer (A) and the monomer (B), a step of forming a film made of the polymerizable material, and By irradiating the film with light in an oxygen-containing atmosphere to perform photopolymerization, and having a step of forming a nano-embossed structure on the surface of the film in contact with oxygen, it is not necessary to carry out a complicated etching step, etc. We have found that it is possible to form a nano-embossed structure composed of a fine uneven structure by polymerization, which makes it possible to manufacture a nano-embossed structure easily and efficiently, and completed the present invention. ..

That is, the method for producing a nano-embossed structure of the present invention comprises at least one polyfunctional acrylic monomer (A) selected from 4 to 8 functional acrylic monomers, and a functional group having a carbon-carbon double bond. It contains at least one kind of at least one kind of monomer (B) selected from monomers having 1 to 3 groups, and the content of the polyfunctional acrylic monomer (A) is the polyfunctional acrylic. A step of preparing a polymerizable material that is 70 mol% or more based on the total amount of the system monomer (A) and the monomer (B), a step of forming a film made of the polymerizable material, and an oxygen content of 15% by volume or more The method is characterized by comprising a step of self-organizing a nano-embossed structure on the surface of the film in contact with oxygen by irradiating the film with light in an oxygen-containing atmosphere to perform photopolymerization. ..

In the method for producing a nano-embossed structure of the present invention described above, the film thickness of the polymerizable material is preferably 0.1 to 100 μm.

Furthermore, in the method for producing a nano-embossed structure according to the present invention, it is preferable that the nano-embossed structure is a concavo-convex structure in which an average value of the concavo-convex maximum heights at arbitrary 5 points or more is 2 to 1000 nm.

In the method for producing a nano-embossed structure of the present invention, the functional group having the carbon-carbon double bond in the monomer (B) is selected from the group consisting of an acryl group, a methacryl group and a vinyl group. It is preferably at least one kind.

In the method for producing a nano-embossed structure of the present invention, in the step of forming a nano-embossed structure on the surface of the film in contact with oxygen in a self-organizing manner, the presence of the oxygen causes variations in the progress of polymerization in the film. Is preferably generated.

In the method for producing a nano-embossed structure of the present invention, in the step of self-organizing a nano-embossed structure on the surface of the film in contact with oxygen, a direction parallel to the surface of the film in contact with oxygen and the film In both the direction perpendicular to the surface in contact with oxygen, a part where the polymer formed by polymerization accumulates and a part where the unreacted monomer diffuses and flows out are spontaneously generated, and It is preferable to form a nano-embossed structure on the surface in contact with oxygen in a self-organizing manner.

The reason why the above object is achieved by the method for producing a nano-embossed structure of the present invention is not always clear, but the present inventors speculate as follows.

In general, when a film made of various monomers is photopolymerized by irradiating it with light in an oxygen-containing atmosphere, radical polymerization is inhibited in the vicinity of the surface of the film by the effect of oxygen (oxygen inhibition). Therefore, the polymerization is performed efficiently. I can't. Therefore, when photopolymerizing various monomers, it is common to carry out the polymerization in an inert gas atmosphere containing no oxygen. On the other hand, in the present invention, photopolymerization is performed in an oxygen-containing atmosphere. By carrying out photopolymerization in such an environment, the vicinity of the surface that is easily affected by oxygen (these sites differ depending on the polymerizable monomer used, the initiator used during photopolymerization, the light intensity during polymerization, etc. , Which cannot be unconditionally defined, but it is possible to exemplify, for example, a site of about 1 to 100 nm in the depth direction from the surface in contact with oxygen). , It becomes difficult to generate nuclei. Therefore, in the vicinity of the surface, it is difficult to uniformly proceed with the polymerization, and when a polymer molecule is formed in a part, there is a situation that a polymer is likely to be sequentially formed around the core with the part where the polymer is formed as a core. In the vicinity of the surface, in the in-plane direction (direction parallel to the surface of the film in contact with oxygen: in-plane direction), the sites where the polymer is formed are scattered and scattered. As described above, in the vicinity of the surface that is easily affected by oxygen, the polymerization partially proceeds at the position where the polymer as the nucleus is formed, and the progress of the polymerization in the in-plane direction is different. It should be noted that the polymerization tends to proceed more efficiently at the site inside the film (the site that is unlikely to be affected by oxygen) away from the surface in contact with oxygen. Therefore, the degree of progress of polymerization also varies in the out-of-plane direction (direction perpendicular to the surface of the film in contact with oxygen: out-of-plane direction).

Here, in the present invention, a polymerizable material containing 100 mol% of the polyfunctional acrylic monomer (A) with respect to the total amount of the polyfunctional acrylic monomer (A) and the monomer (B) ( Among the monomers (A) and (B), only the monomer (A) is used), or 70 mol% or more of the polyfunctional acrylic monomer (A), and the monomer (B) And a mixture (using both of the above-mentioned monomers (A) and (B)). In such a polymerizable material, at least one polyfunctional acrylic-based monomer selected from a 4- to 8-functional acrylic-based monomer is contained in an amount of 70 mol% or more based on the total amount of the monomers (A) and (B). The monomer (A) has extremely high reactivity, as is clear from the number of its functional groups. Therefore, the polymerizable material containing the polyfunctional acrylic monomer (A) in the above proportion allows the polymerization to proceed more efficiently. As described above, when photopolymerization is started by irradiating light under an oxygen-containing atmosphere, a difference in the degree of progress of polymerization in the in-plane direction is likely to occur, especially in the vicinity of the surface, but the polymerizable material according to the present invention On the other hand, when the photopolymerization is performed in an oxygen-containing atmosphere, the content of the polyfunctional acrylic monomer (A) is less than 70 mol% relative to the total amount of the monomers (A) and (B). However, the difference in the degree of polymerization progress in the in-plane direction tends to be larger at the site near the surface than the above materials. When the polymerizable material according to the present invention is subjected to photopolymerization in an oxygen-containing atmosphere, the amount of the monomer component (the monomer (A) and/or the monomer (B)) decreases in the portion where the polymerization proceeds. Then, a large amount of polymer is formed, but it is considered that the amount of the monomer component (the above-mentioned monomer (A) and/or the above-mentioned monomer (B)) hardly changes in the other portions. In this way, in the vicinity of the surface susceptible to the influence of oxygen, the concentrations of the monomer component and the polymer component greatly differ between the position where the nucleus was not formed due to the initiation of photopolymerization and the position where the nucleus was formed. Then, due to the difference in the in-plane concentration of the monomer component and the polymer, a difference in chemical potential occurs between a portion where the polymerization is sufficiently advanced and a portion where the polymerization is not sufficiently progressed, and the polymerization is performed depending on the difference in the chemical potential. The monomer component diffuses to a more advanced portion (the monomer component moves so as to eliminate the difference in chemical potential (in particular, the difference in concentration of the monomer component)). On the other hand, as described above, the polymerizable material contains at least one polyfunctional acrylic monomer (A) selected from 4- to 8-functional acrylic monomers with respect to the total amount of the monomers (A) and (B). Since it contains 70 mol% or more of the polyfunctional acrylic monomer (A), the polymer formed by the polymerization has a sterically cross-linked structure in various directions. Since the polymer has an appropriately high molecular weight and an appropriately high cross-linking density, the formed polymer has a structure that is less likely to diffuse in the film than the monomer. Therefore, while the monomer components gather at the site where the polymer is formed and the polymerization further proceeds to cause the accumulation of polymer molecules, the formed polymer itself is difficult to diffuse and tends to accumulate. As a result, in both the out-of-plane direction and the in-plane direction, a portion where the polymer accumulates and a portion where the monomer flows out occur. Such variations in the degree of progress of polymerization spontaneously occur when photopolymerization is performed on a film made of the polymerizable material in an oxygen-containing atmosphere. As a result, the present inventors presume that an embossed structure is formed near the surface (note that the presence of oxygen tends to cause accumulation in the in-plane direction rather than out-of-plane direction particularly near the surface. Thought to be). That is, in the present invention, a simple method such as photopolymerization efficiently and spontaneously causes the accumulation of polymer molecules and the outflow of monomer components in the out-of-plane direction and the in-plane direction, and the nano-level embossing near the surface thereof. The present inventors presume that the structure is efficiently formed.

In addition, when the film thickness of the film used at the time of photopolymerization is 0.1 to 100 μm, which is suitable in the present invention, the film is sufficiently thin and the oxygen concentration in the out-of-plane direction when oxygen enters the film is The difference is not so large, and as a result, the difference in the degree of polymerization in the in-plane direction tends to relatively increase. Therefore, when a film having a thickness of 0.1 to 100 μm as described above is used, the difference in the degree of polymerization is further increased in the in-plane direction over the entire film (not only near the surface but also inside the film). The present inventors presume that there is a tendency that the polymer is likely to occur, and that the portion where the polymer accumulates and the portion where the monomer flows out are generated more efficiently, and thereby the formation of the embossed structure can be further promoted.

As described above, in the present invention, a site where photopolymerization efficiently proceeds in a position-selective manner by irradiating light in an oxygen-containing atmosphere to perform photopolymerization (hereinafter, referred to as “polymerization part” in some cases). And a site that is difficult to progress (hereinafter, referred to as “non-polymerized part” in some cases) to efficiently generate a polymer in the polymerized part, and to make a difference in chemical potential between the polymerized part and the non-polymerized part. It causes and causes molecular diffusion, thereby forming a nano-embossed structure. As described above, in the present invention, the presence of oxygen causes spatially non-uniform polymerization to spontaneously and regioselectively cause the accumulation of a polymer (polymer), and the nano-embossed structure causes the polymer film to have a polymer film. The present inventors presume that they are self-organized on the surface.

According to the present invention, it is possible to form a nano-embossed structure composed of a fine uneven structure without performing a complicated etching step and the like, and it is possible to easily and efficiently manufacture a nano-embossed structure. It is possible to provide a method for producing a structure, a polymerizable material for producing a nano-embossed structure used in the production method, and a nano-embossed structure obtained by the production method.

It is a figure (section curve of unevenness) which shows typically a section of an embossing structure. 3 is a scanning probe microscope image (SPM image) of an arbitrary 500 nm long and 500 nm wide region on the surface of the structure obtained in Example 1 on which the embossed structure (fine pattern) is formed. FIG. 3 is a cross-sectional view of an embossed structure (fine pattern) created based on the SPM image shown in FIG. 2.

Hereinafter, the present invention will be described in detail with reference to its preferred embodiments.

[Method for producing nano-embossed structure]
The method for producing a nano-embossed structure of the present invention comprises at least one polyfunctional acrylic monomer (A) selected from 4- to 8-functional acrylic monomers and a functional group having a carbon-carbon double bond. The polyfunctional acrylic monomer contains at least one kind of at least one kind of monomer (B) selected from the monomers whose number is 1 to 3, and the content of the polyfunctional acrylic monomer (A) is the polyfunctional acrylic monomer. A step of preparing a polymerizable material which is 70 mol% or more based on the total amount of (A) and the monomer (B), a step of forming a film made of the polymerizable material, and an oxygen-containing atmosphere in the film. The method is characterized by comprising a step of forming a nano-embossed structure on the surface of the film in contact with oxygen by irradiating light and photopolymerization.

The polymerizable material according to the present invention contains at least one selected from the group consisting of the polyfunctional acrylic monomer (A) and the monomer (B), and contains the polyfunctional acrylic monomer (A). The content is 70 mol% or more based on the total amount of the polyfunctional acrylic monomer (A) and the monomer (B). Thus, the polymerizable material according to the present invention contains the polyfunctional acrylic monomer (A) and/or the monomer (B), and the polyfunctional acrylic monomer (A) and the monomer (B). Among them, when it contains only the polyfunctional acrylic monomer (A) or contains the monomer (B), 70 mol% or more of the polyfunctional acrylic monomer (A) and the monomer (B) And (a mixture of the monomer (A) and the monomer (B)). As described above, the polymerizable material according to the present invention includes only the polyfunctional acrylic monomer (A) among the polyfunctional acrylic monomer (A) and the monomer (B) (the polyfunctional acrylic monomer). When the content of the polyfunctional acrylic monomer (A) is 100 mol% with respect to the total molar amount of (A) and the monomer (B)), the polyfunctional acrylic monomer (A) and the monomer ( B) and the content of the polyfunctional acrylic monomer (A) is 70 mol% or more based on the total molar amount of the polyfunctional acrylic monomer (A) and the monomer (B). It includes cases and cases.

Such a polyfunctional acrylic monomer (A) is at least one monomer selected from acrylic monomers having 4 to 8 functional groups (having 4 to 8 functional groups). The “acrylic monomer” here means that the functional group is an acrylic group (group represented by the formula: CH ₂ ═CH—C(═O): acryloyl group) and/or methacrylic group (formula: CH ₂ ═C). _{(CH 3) -C (= O} ) - , a group represented by: methacryloyl group), compound means a (monomeric), other acrylates and methacrylates, concept including compounds containing both acrylic group and methacrylic group Is.

Thus, the polyfunctional acrylic monomer (A) according to the present invention is selected from monomers having a total of 4 to 8 functional groups consisting of acrylic groups and/or methacrylic groups (4 to 8 functional acrylic monomers). At least one kind. That is, the polyfunctional acrylic monomer (A) is composed of a tetrafunctional acrylic monomer, a pentafunctional acrylic monomer, a hexafunctional acrylic monomer, a hexafunctional acrylic monomer, and an octafunctional acrylic monomer. It is at least one kind selected from Naru. Further, the number of such functional groups (total number of acrylic groups and methacrylic groups) is more preferably 5 to 8, and further preferably 5 to 7. That is, the polyfunctional acrylic monomer (A) is more preferably at least one selected from 5 to 8 functional acrylic monomers, and at least one selected from 5 to 7 functional acrylic monomers. More preferably, If the number of such functional groups (total number of acrylic groups and methacrylic groups) is less than the lower limit, the polymerization does not proceed efficiently even if photopolymerization is performed in an oxygen-containing atmosphere. The film becomes sticky (a film having tackiness), and a film having an embossed structure cannot be obtained. On the other hand, when the number of polymerizable functional groups exceeds the above upper limit, the reactivity of the monomer becomes too high, and the polymerization tends to proceed before the compound diffuses in the plane during the polymerization, and also necessary for molecular diffusion. The amount of such unreacted monomer becomes small, and it tends to be difficult to sufficiently form an embossed structure.

Examples of 4- to 8-functional acrylic monomers used as the polyfunctional acrylic monomer (A) include dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, and pentaerythritol tetraacrylate. , Ethoxylated pentaerythritol tetraacrylate, and the like.

Moreover, as a 4- to 8-functional acrylic monomer used as such a polyfunctional acrylic monomer (A), it exhibits appropriate polymerization reactivity when forming a nano-embossed structure, and the nano-embossed structure can be more efficiently used. It is preferable to use pentaerythritol hexaacrylate and dipentaerythritol pentaacrylate because they can be formed. In addition, as such a polyfunctional acrylic monomer (A), 1 type selected from the said 4 to 8 functional acrylic monomer may be used individually or in mixture of 2 or more types. Further, the method for producing a 4- to 8-functional acrylic monomer used as such a polyfunctional acrylic monomer (A) is not particularly limited, and a known method can be appropriately adopted. Moreover, you may use a commercial item as such a polyfunctional acrylic monomer (A).

Further, the monomer (B) according to the present invention is at least one kind of monomer selected from monomers having 1 to 3 functional groups having a carbon-carbon double bond. The functional group having such a carbon-carbon double bond is not particularly limited, and examples thereof include an acryl group, a methacryl group, and a vinyl group.

As the functional group having a carbon-carbon double bond contained in the monomer used as the monomer (B), from the viewpoint of wide selection range of monomers, easy availability, and polymerization reaction rate in oxygen atmosphere, Acrylic, methacrylic and vinyl groups are particularly preferred. Further, such a monomer (B) may contain only one kind of functional group or may contain different kinds of functional groups.

The number of the functional groups contained in the monomer (monomer containing the functional group having a carbon-carbon double bond) used as the monomer (B) is 1 to 3, more preferably 1 or 2, Particularly preferably, it is 1. When the number of such functional groups exceeds the above upper limit, the polymerization reaction is completed before the unreacted monomer diffuses, and the embossed structure tends to be difficult to be formed.

In addition, the monomer having 1 to 3 functional groups having a carbon-carbon double bond used as such a monomer (B) is, for example, monofunctional or bifunctional, from the viewpoint of availability. The vinyl-based monomer (monomer having a vinyl group) can be preferably used. Examples of such monofunctional or bifunctional vinyl monomers include styrene, 2,4-dimethylstyrene, vinylaniline, vinylbenzoic acid, 2-vinylpyridine, 4-vinylpyridine, 2-vinylquinoline, and 4-vinylquinoline. Vinylquinoline, 2-vinylthiophene, 4-vinylthiophene, vinylnaphthalene, vinylanthracene, divinylbenzene, vinyl acetate, N-vinylpyrrolidone, vinyl chloride, acrylonitrile, α-methylstyrene, N-vinylcarbazole, 1,3-butadiene Etc. can be mentioned.

In addition, the monomer having 1 to 3 functional groups having a carbon-carbon double bond used as such a monomer (B) is, for example, monofunctional or bifunctional, from the viewpoint of availability. It is also possible to use (meth)acrylate (here, “(meth)acrylate” is a concept including both acrylate and methacrylate). Examples of such monofunctional or bifunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl ( (Meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, phenoxyethyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth) Acrylate, 2-hydroxybutyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, Decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, benzyl (meth)acrylate, phenoxy 2-Methylethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate, 2-phenylphenoxyethyl (meth)acrylate, 4-phenylphenoxyethyl (meth)acrylate , 3-(2-phenylphenyl)-2-hydroxypropyl (meth)acrylate, polyoxyethylene nonylphenyl ether (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclo Pentenyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, polyethylene glycol mono (meth)acrylate, polypropylene glycol mono (meth)acrylate, Methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate Crylate, 7-amino-3,7-dimethyloctyl (meth)acrylate, trimethylolpropane di(meth)acrylate, dimethyloltricyclodecane diacrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate , Polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate Etc.

In addition, as the monomer having 1 to 3 functional groups having a carbon-carbon double bond used as such a monomer (B), styrene, 2, 4-dimethylstyrene, vinylaniline, vinylbenzoic acid, 2-vinylpyridine, 4-vinylpyridine, 2-vinylquinoline, 4-vinylquinoline, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, Isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, phenoxyethyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, 2- Hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, Polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate are preferably used, and styrene, 2 , 4-dimethylstyrene, vinylaniline, vinylbenzoic acid, 2-vinylpyridine, 4-vinylpyridine, 2-vinylquinoline, 4-vinylquinoline, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate More preferably, isopropyl (meth)acrylate, butyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate are used. As such a monomer (B), one type of the above-mentioned monomers may be used alone or two or more types may be used in combination. Moreover, you may utilize a commercial item as such a monomer (B).

As described above, the polymerizable material according to the present invention contains at least one polyfunctional acrylic monomer (A) selected from 4- to 8-functional acrylic monomers, and a functional group having a carbon-carbon double bond. It contains at least one kind of at least one kind of monomer (B) selected from monomers having 1 to 3 groups (containing the polyfunctional acrylic monomer (A) and/or the monomer (B). And the content of the polyfunctional acrylic monomer (A) is 70 mol% or more based on the total amount of the polyfunctional acrylic monomer (A) and the monomer (B) (the polyfunctional acrylic monomer (A)). Of the functional acrylic monomer (A) and the monomer (B), it contains only the multifunctional acrylic monomer (A), or the multifunctional acrylic monomer (A) and the monomer (B ), wherein the content of the polyfunctional acrylic monomer (A) is 70 mol% or more). As described above, the polymerizable material contains the polyfunctional acrylic monomer (A) in an amount of 70 mol% or more based on the total amount of the monomers (the total amount of the polyfunctional acrylic monomer (A) and the monomer (B)). To do. In the polymerizable material according to the present invention, the content of the polyfunctional acrylic monomer (A) is 70 to 100 mol% with respect to the total amount of the polyfunctional acrylic monomer (A) and the monomer (B). Is more preferable, 80 to 100 mol% is more preferable, 85 to 100 mol% is still more preferable, 90 to 100 mol% is particularly preferable, and 95 to 100 mol% is particularly preferable. Is most preferred. When the content of the acrylic monomer (A) is less than the lower limit, a polymer which becomes a core of the embossed structure is not sufficiently generated during photopolymerization (a core is not sufficiently formed), and the embossed structure is sufficiently efficiently formed. It tends to be difficult to form. In the present invention, when the content of the monomer (A) becomes less than the lower limit and the content of the monomer (B) increases, the number of functional groups in the monomer (B) is 1 to 3 and the reaction progresses. Since it is a slow monomer, it is difficult to sufficiently generate nuclei near the surface during photopolymerization, and diffusion of the polymerizable material in the out-of-plane direction easily occurs, but the polymerizable material in the in-plane direction It is difficult to cause the diffusion of the polymer, which makes it difficult to form a concavo-convex structure (embossed structure) sufficiently, or the polymerization does not proceed sufficiently in the first place, and the resulting film is tacky. Therefore, it becomes difficult to obtain a sufficiently cured film. As described above, in the present invention, the monomer (A) having a high reactivity among the monomers (A) and (B) is used in an amount of 70 mol% or more with respect to the total amount of the monomers (A) and (B), and thus, in an oxygen-containing atmosphere It is possible to efficiently cause the diffusion of the polymerizable material in the in-plane direction while allowing the polymerization to proceed sufficiently to form an embossed structure.

Further, the polymerizable material according to the present invention may appropriately contain components other than the monomers (A) and (B) within a range not impairing the effects of the present invention. In this case, the film made of the polymerizable material is a film made of a composition (polymerizable composition) of the monomer (A) and/or (B) and other components.

Other components that can be contained in such a polymerizable material include various solvents, other monomers, photopolymerization initiators, viscosity modifiers, plasticizers, polymerization inhibitors, surfactants, and the like. it can. When the polymerizable material contains other components (various additives, etc.) as described above, all compounds other than the solvent in the polymerizable material (when the polymerizable material contains a solvent, a solid content is formed). The total amount of the monomers (A) and (B) relative to the total amount of the compounds (A) and (B) when the polymerizable material does not contain a solvent. Other components are preferably used so that the molar ratio is 70 mol% or more (more preferably 80 mol% or more, further preferably 90 mol% or more, particularly preferably 95 mol% or more). When the total amount (content) of the monomers (A) and (B) in the polymerizable material is less than the lower limit, formation of the embossed structure tends to be insufficient.

In addition, when photopolymerizing the polymerizable material, a photopolymerization initiator is added together with at least one of the monomers (A) and (B) from the viewpoint that the polymerization can be progressed more efficiently. It is preferable to use. Such a photopolymerization initiator is not particularly limited, and a known one can be appropriately used, and a commercially available one (for example, trade name “Irgacure 651” manufactured by BASF) may be used. Further, when using such a photopolymerization initiator, the amount used can be appropriately designed according to the type of components in the polymerizable material used, the absorption wavelength of light, and the like. May be 0.1 to 10% of the total molar amount of the monomers (A) and (B) (for example, the total amount of the monomers (A) and (B) in the polymerizable material is 100 mol). In this case, the photopolymerization initiator may be used in an amount of 0.1 mol to 10 mol). In addition, when the content ratio of such a photopolymerization initiator is less than the lower limit, there is a tendency that the effect of using the photopolymerization initiator cannot be sufficiently obtained. On the other hand, when the content ratio of the photopolymerization initiator exceeds the upper limit, the degree of polymerization of the polymerizable monomer during photopolymerization is increased. Does not increase sufficiently, and the effect of using the photopolymerization initiator tends to be insufficient.

The method for preparing such a polymerizable material is not particularly limited, and may be prepared by appropriately mixing the various materials so as to satisfy the above-mentioned conditions, and for example, it is used for efficiently preparing a film. From such a viewpoint, a mixed solution may be prepared by adding at least one of the polyfunctional acrylic monomer (A) and the monomer (B) to the solvent.

Further, in the step of forming a film made of such a polymerizable material, the method for preparing the film is not particularly limited, and a known method capable of forming a coating film of a monomer can be appropriately adopted, for example, a solvent. The polyfunctional acrylic monomer (A) and/or the monomer (B) is added therein (if necessary, other components such as a photopolymerization initiator are also added), and the mixture is sufficiently stirred to be uniform. A method of obtaining a coating liquid, and then applying the coating liquid on a substrate (for example, a glass substrate) to form a coating film, and then removing the solvent from the coating film to obtain a film made of a polymerizable material. Can be used.

The solvent used in such a method is not particularly limited, depending on the type of the polymerizable material or photopolymerization initiator used, so that a uniform mixture can be obtained, among known solvents It can be appropriately selected and used, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, cyclopentanone, alcohols such as isopropyl alcohol, n-butanol, butoxyethyl alcohol, hexyloxyethyl. Alcohol, ether alcohols such as methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 2-methoxyethyl acetate, propylene glycol 1-monomethyl ether 2-acetate, esters such as ethyl acetate and ethyl lactate Phenols such as phenol and chlorophenol, amides such as N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, chloroform, dichloromethane, trichloroethylene, tetrachloroethane, tetrachloroethane, tetrachloroethylene, chlorobenzene, dichloroethylene. Chlorobenzene and other halogenated hydrocarbons, tetrahydrofuran, γ-butyrolactone and other heterocycles, benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene and other aromatic hydrocarbons, methyl cellosolve, ethyl cellosolve , Cellosolves such as butyl cellosolve, and mixed systems thereof may be used.

Moreover, when forming such a coating liquid, the total amount (total amount) of the polyfunctional acrylic monomer (A) and the monomer (B) is preferably 1 to 80% by mass, and 2 to 70% by mass. Is more preferable, and it is further preferable that the content is 2 to 60% by mass. When the total amount of the polyfunctional acrylic monomer (A) and the monomer (B) in the coating liquid is less than the lower limit, it tends to be impossible to secure a sufficient film thickness after coating, while when the amount exceeds the upper limit. Since the concentration of the monomer composed of the polyfunctional acrylic monomer (A) and the monomer (B) is high, the film thickness of the film obtained after coating tends to be non-uniform in the plane.

The method of applying such a coating liquid onto the substrate is not particularly limited, and known methods that can be used when forming a coating film of a monomer (eg, dip coating method, spray coating method, spin coating method, etc. (Coating method, bar coating method, etc.) can be appropriately adopted.

The method for removing the solvent from the coating film obtained by applying such a coating liquid is not particularly limited, and a known method can be appropriately used, for example, the polymerization proceeds in the atmosphere. The temperature at which the solvent does not evaporate efficiently (the temperature varies depending on the type of the solvent and the type of the polymerizable material, and cannot be generally stated, but is, for example, 40 to 150°C. It is preferable that the solvent is removed by heating the coating film, or the coating film is removed under reduced pressure at room temperature (25° C.). The pressure reduction condition when adopting such a reduced pressure drying step is preferably 15 kPa or less, and more preferably 0.1 to 10 kPa. Further, the depressurization time is preferably 0.1 to 100 hours. In addition, such a reduced pressure drying step may be performed at once or may be performed in multiple steps. Here, when the reduced pressure drying step is performed a plurality of times, it is possible to appropriately adjust the reduced pressure time by checking the degree of drying each time the reduced pressure drying step is performed.

The form (size, shape, etc.) of the film made of such a polymerizable material is not particularly limited, and the form can be appropriately changed according to the intended design.

The film thickness of the film made of such a polymerizable material is preferably 0.1 to 100 μm, more preferably 0.5 to 80 μm, and further preferably 1 to 60 μm. When the film thickness is less than the lower limit described above, it becomes difficult to make the average value of the maximum unevenness height of the embossed structure to be sufficient, and it is possible to efficiently form the unevenness structure having a sufficient height. On the other hand, if the amount exceeds the upper limit, the change in the degree of polymerization in the out-of-plane direction tends to become larger, whereby the in-plane direction of the polyfunctional acrylic monomer (A ) And/or it is difficult to sufficiently cause the diffusion of the monomer (B), and it tends to be difficult to efficiently and sufficiently form an embossed structure.

The total amount of the monomers (A) and (B) in the film made of such a polymerizable material is the total amount of all the compounds constituting the solid content in the film (when the film is formed using the coating liquid, It is preferably 70 mol% or more (more preferably 80 mol% or more, further preferably 90 mol% or more, particularly preferably 95 mol% or more) in terms of molar ratio to all compounds other than the solvent. When the total amount (content) of the monomers (A) and (B) in the film is less than the lower limit, formation of the embossed structure tends to be insufficient.

Further, in the present invention, after forming the film, the film is irradiated with light in an oxygen-containing atmosphere to perform photopolymerization to form a nano-embossed structure on the surface of the film in contact with oxygen. As described above, in the present invention, it is necessary to irradiate the film made of the polymerizable material with light in an oxygen-containing atmosphere.

Irradiation of such light (X-rays, electron beams, ultraviolet rays, visible rays, infrared rays (heat rays), etc.) is more preferably performed uniformly on the entire surface of the film (all-surface exposure). In this way, by uniformly irradiating the entire surface of the film with light to expose the entire surface (by making the light irradiation area the entire surface of the film), the in-plane polymerization property in the film is increased. It is possible to cause the diffusion of the material more efficiently.

Further, when the polymerizable material is irradiated with light to perform photopolymerization, it is preferable to use ultraviolet rays or visible light because it is possible to proceed the polymerization reaction more efficiently. ) Is particularly preferred. The light source for irradiating such light is not particularly limited, and a known light source that can be used for photopolymerization can be appropriately used. For example, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, an LED A lamp or the like may be used. The irradiation wavelength of light used in such photopolymerization is not particularly limited, and may be determined in consideration of the absorption spectrum of the polymerizable material, the recommended use wavelength of the photopolymerization initiator, and the like.

In the present invention, the “oxygen-containing atmosphere” may be a gas atmosphere containing oxygen, but is preferably a gas atmosphere containing 15% by volume or more of oxygen. When the content of oxygen is less than the lower limit, the influence of oxygen inhibition is reduced, and the polymerization proceeds uniformly in the film, so that it tends to be difficult to efficiently produce an embossed structure. Further, as the atmospheric gas of such an oxygen-containing atmosphere, air is preferable because it is not particularly necessary to prepare the gas. As described above, in the present invention, photopolymerization can be carried out in the atmosphere, and it can be said that the method is simple from this point of view.

Further, in such photopolymerization, the film may be irradiated with light under heating conditions, and the heating temperature depends on the type of monomer in the polymerizable material used, the viscosity of the polymerizable material, and the ease of heating. Although it can be appropriately selected in consideration of the above, it is preferably about 10 to 300°C, more preferably 20 to 250°C, and further preferably 20 to 100°C. When such a heating temperature is less than the lower limit, it becomes difficult to efficiently proceed the polymerization reaction, it is impossible to sufficiently cause the diffusion of the monomer in the polymerizable material in the in-plane direction, the embossed structure efficiently On the other hand, when it exceeds the upper limit, polymerization of the entire film proceeds due to heat before irradiation with light, and it becomes impossible to form an embossed structure or a polymerizable material. There is a high possibility that the monomer therein will be decomposed by heat, and it tends to be difficult to stably form an embossed structure. In addition, such a temperature condition tends to be a higher temperature in order to carry out the polymerization more efficiently, for example, when the irradiation intensity is lowered, but the kind of the polymerizable material, other polymerization conditions, etc. It may be appropriately set according to

Further, it is preferable to irradiate light at an irradiation intensity of 0.1μW ^/ cm ² ~30mW ^/ cm 2 in case of the photopolymerization, light irradiation intensity of 0.5μW ^/ cm ² ~10mW ^/ cm 2 Is more preferably irradiated. When the irradiation intensity of such light is less than the lower limit, the reaction rate becomes slow, it becomes difficult to generate nuclei near the surface in an oxygen-containing atmosphere, and it tends to be difficult to efficiently form an embossed structure. Yes, on the other hand, if the above-mentioned upper limit is exceeded, the rate of the polymerization reaction becomes too fast than the rate at which the polymerizable compound diffuses, so that the diffusion of the compound does not sufficiently occur, and the nano-embossed structure has a sufficient unevenness height. Tends to be difficult to obtain.

In addition, the time for irradiating light in such photopolymerization (total time of light irradiation in the case of irradiating light in multiple stages) is preferably 0.1 to 30 minutes, and 0.2 to 20 minutes. Is more preferable. If the irradiation time of such light is less than the lower limit, the polymerization reaction does not proceed sufficiently, and it becomes difficult to generate nuclei derived from the polymer generated in the vicinity of the surface, which makes it difficult to efficiently form an embossed structure. On the other hand, when the amount exceeds the upper limit, the progress of the polymerization reaction is completed, the unreacted monomer is not further diffused, and the economical efficiency tends to decrease.

Further, in such photopolymerization, a known method of photopolymerization can be appropriately used depending on the material used, the irradiation conditions of light, and the like. For example, light irradiation for a certain period of time can be performed once. A method of performing photopolymerization (single-step irradiation) may be adopted, or a method of performing photopolymerization by performing a step of irradiating light with a desired irradiation intensity for a predetermined time multiple times (multistep irradiation: irradiation The irradiation intensity may be changed appropriately for each step).

As a method for photopolymerization by multistage irradiation, irradiation of ^{10μW / cm 2 ~100mW / cm 2} 0.1~20 minutes light irradiation intensity (more preferably ^{100μW / cm 2 ~70mW / cm 2} ) after (first stage of the light ^{irradiation), 10μW / cm 2 ~100mW /} cm 2 ( more preferably ^{100μW / cm 2 ~70mW / cm 2} ) irradiation (two steps from 0.1 to 10 minutes light irradiation intensity of It is preferable to employ a method of irradiating light to the eyes) (a method of photopolymerization by gradually changing the irradiation intensity of light). By adopting such a method, first, the photopolymerization of the monomer in the polymerizable material is started at the time of the first irradiation of light, and the nucleus for the growth of the embossed structure near the surface under the influence of oxygen inhibition. Since it becomes possible to produce a polymer that becomes, the embossed structure can be produced more efficiently, and the embossed structure formed after the embossed structure is sufficiently formed during the second stage light irradiation. It is also possible to sufficiently fix the structure, and it is possible to efficiently manufacture the embossed structure that is sufficiently fixed. Further, in such a method, when the irradiation intensity of light in the first-stage light irradiation is less than the lower limit, the reaction rate becomes slow, and it becomes difficult to generate nuclei near the surface in an oxygen-containing atmosphere, forming an embossed structure. It tends to be difficult to do, on the other hand, the polymerization reaction rate is too fast than the rate at which the polymerizable compound diffuses above the upper limit, the diffusion of the compound does not occur sufficiently, nanoembossed structure There is a tendency that the body cannot be obtained efficiently. Further, the irradiation intensity of light in the second stage of light irradiation tends to be unable to sufficiently fix the formed nano-embossed structure at less than the lower limit, while, if it exceeds the upper limit, the polymerization reaction proceeds too rapidly. As a result, cracks may occur, and it tends to be difficult to efficiently obtain a nano-embossed structure having a desired shape.

In addition, in such photopolymerization, the integrated irradiation amount of light ([irradiation intensity (illuminance)]×[time (seconds)]) is preferably 100 mJ/cm ^{2 to} 10 J/cm ² , and 200 mJ/cm ² More preferably, it is cm ^{2 to} 8 J/cm ² . If the cumulative irradiation amount of light (cumulative light amount) is less than the lower limit, the reaction rate becomes slow, it becomes difficult to generate nuclei near the surface in an oxygen-containing atmosphere, and an embossed structure can be efficiently formed. On the other hand, if the above upper limit is exceeded, the polymerization reaction rate becomes too fast compared to the rate at which the polymerizable compound (monomer, etc.) diffuses, so that diffusion of the compound does not sufficiently occur, and nanoembossing It tends to be difficult to efficiently form the structure.

As described above, in the present invention, by using the film made of the polymerizable material and irradiating the film with light in an oxygen-containing atmosphere to perform photopolymerization, the surface of the film in contact with oxygen (preferably Form a nano-embossed structure on the light irradiation surface) to obtain a nano-embossed structure.

The nano-embossed structure thus formed is a site where photopolymerization efficiently proceeds in a position-selective manner and a site where it is difficult to proceed by performing photopolymerization by irradiating light in an oxygen-containing atmosphere in the present invention. To form a polymer efficiently at the site where photopolymerization proceeds efficiently, and cause a difference in chemical potential between the site where the polymerization proceeds efficiently and the site where the polymerization hardly proceeds. By causing the more easily movable monomer molecules to be diffused, and due to this is a method of forming a nano-embossed structure, the characteristics of the uneven structure are appropriately changed according to the polymerization rate or the conditions of the polymerization. It is possible.

Further, the nano-embossed structure thus formed can be confirmed by obtaining an SPM image using a scanning probe microscope (for example, atomic force microscope (AFM)). That is, such a nano-embossed structure is measured using, for example, a trade name “Cypher” manufactured by Asylum Research Co., Ltd. as an atomic force microscope (AFM) and a standard silicon cantilever “Olympus OMCL-AC160TS-C3” as a cantilever. This can be confirmed by setting the mode to the AC mode (dynamic mode) and obtaining an SPM image of an arbitrary region (for example, a square region having a length of 500 nm and a width of 500 nm) on the surface of the cured film.

Further, as such a nano-embossed structure, the average value of the maximum unevenness heights at arbitrary 5 points or more is preferably 2 to 1000 nm, more preferably 2.5 to 800 nm, and 3.0 to More preferably, it is 800 nm. Further, the upper limit value of a suitable numerical range of the average value of the maximum unevenness heights of 5 or more points is preferably 600 nm, more preferably 500 nm, and further preferably 400 nm. preferable. If the average value of the maximum unevenness heights of 5 or more arbitrary points is less than the lower limit, it tends to be impossible to impart a specific function to surface characteristics such as optical properties, hydrophilicity and hydrophobicity of the surface. If the upper limit is exceeded, the uneven shape tends to have a steep high-aspect shape with respect to the horizontal pitch, which tends to lower the mechanical strength.

The following method is adopted as a method of measuring such an "average value of the maximum heights of irregularities". That is, first, a trade name "Cypher" manufactured by Asylum Research Co., Ltd. is used as an atomic force microscope (AFM), a standard silicon cantilever "Olympus OMCL-AC160TS-C3" is used as a cantilever, and a measurement mode is an AC mode (dynamic mode). Then, a scanning probe microscope image (SPM image) is obtained for an arbitrary region on the surface of the embossed structure (for example, the measurement region may be a square or rectangular region having a length of 500 nm or more and a width of 500 nm or more). .. After that, a sectional view of irregularities at arbitrary 5 points or more is obtained from the SPM image. Although a cross-sectional curve can be obtained from such a cross-sectional view, it is preferable that the reference length of the cross-sectional curve is the same as the longer one of the vertical and horizontal lengths of the measurement region of the SPM image. Here, for reference, FIG. 1 schematically shows a cross-sectional view of an embossed structure (a cross-sectional view in a direction perpendicular to a horizontal plane) obtained based on an SPM image of a square measurement region having a length of 500 nm and a width of 500 nm. To indicate. Here, FIG. 1 is a sectional curve with a reference length (scan length) L of 500 nm, and schematically shows a state of a fine concavo-convex structure formed by accumulation of resin. Then, after obtaining a cross-sectional view of such a reference length at positions of arbitrary 5 points or more, in each cross-sectional view (each cross-sectional curve), the maximum height of the convex portion and the minimum height of the concave portion (here, " The "height" means the height in the vertical direction from the horizontal plane. In addition, the maximum height D of the unevenness is obtained from the difference from the vertical direction (out-of-plane direction) from the horizontal plane in FIG. Then, by calculating the average value, it is possible to calculate the average value of the maximum unevenness heights of arbitrary 5 points or more. It should be noted that, with reference to FIG. 1, a vertex P1 of the convex portion at the highest position among the convex portions in FIG. 1 and a point (lowermost point) P2 at the lowest position of the concave portion are formed. The vertical distance between them (the maximum vertical distance between the convex portion having the maximum height and the concave portion having the minimum height) is the maximum height D of the unevenness in the cross-sectional view shown in FIG.

Further, as such a nano-embossed structure, the maximum height of the unevenness at any 5 points or more (the convex portion of the maximum height and the minimum height is the same as in the above-mentioned “average value of the maximum height of the unevenness”) is measured. In the case of measuring the maximum distance in the vertical direction between the height and the concave portion, it is more preferable that the distribution of the maximum unevenness heights of arbitrary 5 points or more is in the range of 1.0 to 2000 nm. More preferably, it is in the range of 0 to 1000 nm. When the distribution of the maximum unevenness heights of 5 or more arbitrary points is out of the above range, first, if the distribution is less than the lower limit, a function peculiar to the surface characteristics such as optical property, hydrophilicity and hydrophobicity of the surface, etc. On the other hand, if the upper limit is exceeded, the concavo-convex shape becomes a steep high aspect shape with respect to the horizontal pitch, and mechanical strength tends to be insufficient. In addition, such a distribution of the maximum unevenness heights of 5 or more points is 1.0 to 600 nm from the viewpoint that a nano-embossed structure having such characteristics can be prepared more efficiently. Is preferably in the range of 1.0 to 500 nm, more preferably in the range of 1.5 to 400 nm.

Further, in such a nano-embossed structure, the average pitch of the irregularities is more preferably 10 to 1000 nm, further preferably 20 to 900 nm, and particularly preferably 30 to 800 nm. The upper limit of the preferable numerical range of the average pitch of such irregularities is preferably 500 nm, more preferably 400 nm, and further preferably 250 nm. If the average pitch of such unevenness is less than the lower limit, the uneven shape becomes too fine, and the desired optical properties and surface characteristics tend not to be exhibited, while if it exceeds the upper limit, the uneven shape becomes close to the micron order. , Optical properties and surface properties tend to be insufficient. The average pitch of the irregularities adopts the value measured as follows. That is, first, an SPM image is obtained in the same manner as the method adopted in the method of obtaining the average maximum unevenness height, and then a cross-sectional view of any five or more points (cross-sectional curve of the reference length) from the SPM image. Note that it is preferable that the reference length of the cross-sectional curve is the same as the longer one of the vertical and horizontal lengths of the measurement region of the SPM image, where the reference length is 500 nm in FIG. ). After that, in each cross-sectional view (each cross-section curve), a convex portion having a vertex (vertex P1 in FIG. 1) at the highest position in the vertical direction is obtained, and two adjacent concave portions (figure sandwiching) surrounding the convex portion (FIG. In 1, the distance in the horizontal direction (direction perpendicular to the arrow A in FIG. 1) between the lowest points of the two concave portions adjacent to the convex portion having the apex P1 is calculated, and the average value thereof is calculated. The value obtained by (the average value of the distances between the recesses respectively obtained from the cross-section curves of 5 points or more) is adopted as the average pitch of the irregularities.

The nano-embossed structure thus obtained is made of a polymer of the above-mentioned polymerizable material, and has a film thickness of 0.1 to 100 μm (more preferably 0.5 to 80 μm, further preferably 1 It is preferably in the form of a film having a thickness of 60 μm). The nano-embossed structure thus obtained may be finally peeled off from the base material when the film used for photopolymerization is laminated on the base material, or, It may be used as it is as a laminate with a substrate.

The method for producing a nano-embossed structure of the present invention, as described above, by irradiating the film made of the polymerizable material with light under an oxygen-containing atmosphere, a spatially non-uniform light is generated in the film. By advancing the polymerization and causing the accumulation of the polymer spontaneously and regioselectively, a range of a nanoscale embossed structure (for example, 1.0 to 2000 nm (in some cases, 500 to 1000 nm depending on the type of polymer)). Is a method capable of forming an uneven structure having an arbitrary maximum unevenness distribution of 5 points or more) on the surface of the polymer film (the surface in contact with oxygen), and irradiating with light in an oxygen-containing atmosphere. It is a method capable of spontaneously forming a nanoscale embossed structure by a simple method such as. Further, the nano-embossed structure thus obtained has a super water repellency, a super hydrophilic property, a structural color, a structural birefringence, a polarization conversion property, an antireflection property, due to the embossed structure (uneven structure). Since it can exhibit various functions such as adhesiveness, it can be used in a wide range of fields from electronics to photonics and medical materials. Therefore, the method for producing a nano-embossed structure of the present invention is particularly useful as a method for forming a concavo-convex structure used in the fields of electronics, photonics, medical materials and the like. In the method for producing a nano-embossed structure of the present invention, the characteristics of the nano-embossed structure can be changed by appropriately changing the polymerization conditions according to the application of the nano-embossed structure to be formed.

The method for producing the nano-embossed structure of the present invention has been described above. Hereinafter, the polymerizable material and the nano-embossed structure for producing the nano-embossed structure of the present invention will be described.

[Polymerizable Material for Manufacturing Nano-embossed Structure and Nano-embossed Structure]
The polymerizable material for producing a nano-embossed structure of the present invention has at least one polyfunctional acrylic monomer (A) selected from 4 to 8 functional acrylic monomers, and a carbon-carbon double bond. At least one kind of at least one kind of monomer (B) selected from monomers having 1 to 3 functional groups (at least one kind of the polyfunctional acrylic monomer (A) and the monomer (B)) ), and the content of the polyfunctional acrylic monomer (A) is 70 mol% or more based on the total amount of the polyfunctional acrylic monomer (A) and the monomer (B). To do.

Such a polymerizable material for producing a nano-embossed structure is the same as the “polymerizable material” described in the method for producing a nano-embossed structure of the present invention (the preferred ones are also the same). .. As described above, the 4- to 8-functional polyfunctional acrylic monomer (A), the monomer (B), the content thereof, and the like relating to the polymerizable material for producing the nano-embossed structure are all the same as those of the nano-embossed structure of the present invention. It is similar to that described in the manufacturing method.

Further, the nano-embossed structure of the present invention has at least one polyfunctional acrylic monomer (A) selected from 4 to 8 functional acrylic monomers, and the number of functional groups having a carbon-carbon double bond. Contains at least one kind of at least one kind of monomer (B) selected from the monomers of 1 to 3, and the content of the polyfunctional acrylic monomer (A) is the polyfunctional acrylic monomer ( It is composed of a polymer of a polymerizable material in an amount of 70 mol% or more based on the total amount of A) and the monomer (B), and has a nano-embossed structure formed on at least part of the surface. ..

Further, the nano-embossed structure of the present invention is composed of a polymer of the above-mentioned polymerizable material (as long as it contains the polymer of the above-mentioned polymerizable material), and the nano-embossed structure is present on at least a part of the surface. It is formed. The "polymerizable material" here is also the same as the "polymerizable material" described in the method for producing a nano-embossed structure of the present invention (the preferred ones are also the same). Further, the “nano-embossed structure” formed in the nano-embossed structure of the present invention is preferably the same as the nano-embossed structure formed by the method for producing a nano-embossed structure of the present invention ( The preferred conditions are also preferably the same). Therefore, the nano-embossed structure of the present invention is preferably obtained by adopting the above-mentioned method for producing a nano-embossed structure of the present invention. The nano-embossed structure of the present invention may be made of a polymer of the above-mentioned polymerizable material, and therefore may be used together with the polymer of the polyfunctional acrylic monomer (A) and/or the monomer (B). It may also include the components of.

In addition, such a nano-embossed structure of the present invention has a super-hydrophobic property, a super-hydrophilic property, a structural color, a structural birefringence, a polarization conversion property, an antireflection property, an adhesive property, etc. due to its uneven structure. It is possible to express various functions. Therefore, the nano-embossed structure of the present invention can be applied to a wide range of fields from electronics to photonics and medical materials due to its uneven structure.

Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

(Example 1)
<Coating liquid preparation process (A)>
In a brown sample tube, the following general formula (1):

5.79 g of dipentaerythritol hexaacrylate (DPHA: manufactured by Tokyo Kasei Kogyo Co., Ltd., 6-functional acrylate) and 0.13 g of a photopolymerization initiator (trade name "IRGACURE 651" manufactured by BASF) are added. To give a mixture. The molar ratio of the 6-functional acrylate to the photopolymerization initiator in the mixture ([6-functional acrylate]:[photopolymerization initiator]) was 100:5. Next, the whole amount of the mixture thus obtained was added to and dissolved in 9.14 mL (8.87 g) of propylene glycol monomethyl ether acetate (PGMEA) as a solvent, followed by stirring for 30 minutes, A coating liquid having a content of the hexafunctional acrylate (DPHA) of 40% by mass was obtained.

<Glass substrate preparation process>
Prepare a glass substrate (length: 50 mm, width: 50 mm, thickness: 1.3 mm (manufactured by Muto Kagaku Co., Ltd., product name: slide glass, model number: 1201 (water drain), As One product code: 1-6723-01)), and prepare such glass. The substrate was subjected to ultrasonic cleaning using an ultrasonic cleaning machine (trade name "US-205" manufactured by SND Co., Ltd.). In addition, in such ultrasonic cleaning, as a cleaning liquid, a neutral detergent (an aqueous solution (concentration: 1% by mass) of trade name "Shika Clean LX-II" manufactured by Kanto Chemical Co., Inc.), distilled water, isopropyl alcohol (IPA) is used. The ultrasonic cleaning was performed three times for each cleaning solution, and each time, ultrasonic cleaning was performed for 30 minutes at a frequency of 38 kHz. After drying at room temperature (25° C.), ozone treatment was performed for 10 minutes using an ozone treatment machine (“UV ozone cleaner (draw-out type, NL-UV42)” manufactured by Takeda Rika Kogyo Co., Ltd.). Then, a glass substrate (glass substrate after ozone treatment) for coating liquid coating was prepared.

<Membrane preparation process>
On the ozone-treated glass substrate obtained as described above, 5 drops of the coating liquid were dropped using a Pasteur pipette. Then, the dropped coating solution was spread on the entire glass substrate using the side surface of the Pasteur pipette, and then spin-coated using a spin coater at a rotation speed of 400 rpm for 5 seconds and then at a rotation speed of 1200 rpm for 30 seconds. Then, a coating film was obtained on the glass substrate. Then, the glass substrate on which the coating film is formed is left to stand on a hot plate heated to 120° C., and the solvent is removed from the coating film by keeping the glass substrate at 120° C. for 5 minutes in the air, and then the glass substrate is placed on the glass substrate. Then, a film made of a mixture of the above-mentioned 6-functional acrylate and a photopolymerization initiator (a film made of a polymerizable material (6-functional acrylate): length 50 mm, width 50 mm, thickness: 1.3 μm) was formed.

<Preparation process of embossed structure>
The film side (glass substrate) was applied to the film on the glass substrate obtained as described above by using a UV light irradiation device (trade name “UVLED irradiation device (LHPUV365/2501)” manufactured by Iwasaki Electric Co., Ltd.). By irradiating with ultraviolet light with a uniform irradiation intensity from the outer surface side of the film (not from the side) to the entire surface of the film (by exposing the entire surface), the polymerizable material in the film The (6-functional acrylate) was photopolymerized to form a cured film. In addition, as conditions for such irradiation of ultraviolet light, atmospheric gas: air, pressure: atmospheric pressure (1 atm), temperature (temperature during polymerization): room temperature (25° C.), wavelength: After irradiation with 365 nm ultraviolet light at an irradiation intensity (illuminance) of 2.6 mW/cm ² for 10 minutes, the irradiation intensity was 14.8 mW/cm ² for 5 minutes. An embossed structure was formed on the surface of the cured film thus obtained (light irradiation surface: surface in contact with air).

The surface state of the cured film thus obtained was measured with an atomic force microscope (AFM). In addition, in such a measurement, a trade name "Cypher" manufactured by Asylum Research Co., Ltd. is used as an atomic force microscope (AFM), a standard silicon cantilever "Olympus OMCL-AC160TS-C3" is used as a cantilever, and a measurement mode is AC. As a mode (dynamic mode), an SPM image of an area of arbitrary 500 nm in length and 500 nm in width was obtained on the surface of the cured film. The obtained SPM image is shown in FIG. Further, FIG. 3 shows a sectional view of an arbitrary portion of the SPM image. The position of 0.00 nm of the height in FIG. 3 is the average position of the maximum convex portion and the minimum concave portion in the depth direction when the cross section is cut off by 500 nm in the horizontal direction. The region having a scan length of 0 to 500 nm in the cross-sectional view shown in FIG. 3 is the region where the SPM image, which is the basis of the cross-sectional view, was measured.

As is clear from FIGS. 2 and 3, it was confirmed that the cured film obtained in Example 1 had an embossed structure having a fine uneven structure on the surface of the film. Further, based on the SPM image (FIG. 2 ), five arbitrary uneven sectional views (section curves with a reference length of 500 nm) were obtained for a range of 500 nm in length, and the maximum height of the convex portion in each sectional view was obtained. From the average value of the difference between (the height of the highest point from the glass substrate) and the maximum depth of the recess (the minimum height from the glass substrate), the average value of the uneven maximum heights was measured. The average value of the maximum heights of the unevenness at 5 points was 10.5 nm. Furthermore, when the distribution of the maximum unevenness heights is obtained from an arbitrary five-point unevenness cross-sectional view (cross-sectional curve having a reference length of 500 nm), the maximum unevenness height distribution is in the range of 8.3 to 13.1 nm. I found out. In addition, based on the SPM image (Fig. 2), five arbitrary concave-convex sectional views with a length of 500 nm (a sectional curve with a reference length of 500 nm) were obtained, and the maximum height of irregularities in each sectional view was obtained. In the horizontal direction between the lowest points of two concave portions (two adjacent concave portions sandwiching the convex portion) surrounding the convex portion (convex portion having the highest vertex) of the concave portion (in the direction parallel to the glass substrate). The average pitch of the concavities and convexities was 41.9 nm when the average pitch of the concavities and convexities was determined by measuring the respective distances and calculating the average value of the distances (the average value of the distances of the five points). The total number of convex portions observed when obtaining the average pitch of the irregularities was 5). The results obtained are shown in Table 1.

(Example 2)
Instead of using the coating liquid obtained in the coating liquid preparing step (A), the coating liquid obtained in the following coating liquid preparing step (B) is used, and the ultraviolet ray irradiation in the embossing structure preparing step is performed. Under the conditions (environment) of atmospheric gas: air, pressure: atmospheric pressure, temperature (temperature during polymerization): 70° C., irradiation intensity (illuminance): 0.32 mW/cm of ultraviolet light of wavelength: 365 nm ^A cured film was obtained in the same manner as in Example 1 except that the irradiation condition was changed to ² for 40 minutes.

<Coating liquid preparation process (B)>
First, in a brown sample tube, 5.21 g of dipentaerythritol hexaacrylate (DPHA: manufactured by Tokyo Chemical Industry Co., Ltd., 6-functional acrylate) represented by the general formula (1) and styrene (C ₆ H ₅ − CH = CH _2: carbon - and number one monomer (monofunctional monomer)) 0.10 g of functional groups having a carbon-carbon double bond, a photopolymerization initiator (BASF Co., Ltd. under the trade name "Irgacure 651") 0 0.13 g was added to obtain a mixture. The total molar amount of monomers (total molar amount of hexafunctional acrylate and monofunctional monomer) and the molar ratio of photopolymerization initiator ([total molar amount of monomers]:[photoinitiator]) in the mixture are It was 100:5 and the molar ratio of dipentaerythritol hexaacrylate to styrene in the mixture ([dipentaerythritol hexaacrylate]:[styrene]) was 90:10. Then, the whole amount of the mixture thus obtained was added to and dissolved in 8.41 mL (8.16 g) of propylene glycol monomethyl ether acetate (PGMEA) as a solvent, followed by stirring for 30 minutes, A coating liquid having a content (total amount) of the monomers of 40% by mass was obtained.

An SPM image of an area of arbitrary length 500 nm and width 500 nm on the surface (light irradiation surface: surface in contact with air) of the cured film obtained in Example 2 was obtained, and unevenness was obtained in the same manner as in Example 1. When the average value of the maximum height, the distribution, and the average pitch of the unevenness were determined, the average value of the maximum unevenness was 4.0 nm, and the distribution of the maximum unevenness was in the range of 3.0 to 5.6 nm. The average pitch of the irregularities was 32.5 nm (note that the total number of convex portions observed when determining the average pitch of the irregularities was 5). The results obtained are shown in Table 1.

(Comparative Example 1)
Instead of using the coating liquid obtained in the coating liquid preparing step (A), the coating liquid obtained by carrying out the following coating liquid preparing step (C) is used, and the ultraviolet light in the step of preparing the embossed structure is used. Under the conditions (environment) of atmospheric gas: air, pressure: atmospheric pressure, temperature (temperature at the time of polymerization): room temperature (25° C.), the irradiation intensity of light is an irradiation intensity (illuminance) of ultraviolet light having a wavelength of 365 nm. : An attempt was made to form a cured film in the same manner as in Example 1 except that the irradiation condition was changed to 5 mW/cm ² for 60 minutes.

<Coating liquid preparation step (C)>
First, in a brown sample tube, the following general formula (2):

2.56 g of 1,6-hexanediol dimethacrylate (HDDMA: bifunctional methacrylate manufactured by Tokyo Kasei Kogyo Co., Ltd.) and a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF Co.) 13 g was added to obtain a mixture. The molar ratio of the 6-functional acrylate to the photopolymerization initiator in the mixture ([6-functional acrylate]:[photopolymerization initiator]) was 100:5. Then, the whole amount of the mixture thus obtained was added to 4.13 mL (4.01 g) of propylene glycol monomethyl ether acetate (PGMEA) as a solvent and dissolved, followed by stirring for 30 minutes, A coating liquid having a content of the bifunctional acrylate of 40% by mass was obtained.

In Comparative Example 1 as described above, although the film was irradiated with light at a sufficient irradiation intensity for a sufficiently long time, the photopolymerization did not proceed sufficiently, and the film was sticky. A cured film could not be formed, and an uneven structure (emboss structure) could not be formed.

(Comparative example 2)
Instead of using the coating liquid obtained in the coating liquid preparing step (A), the coating liquid obtained by carrying out the following coating liquid preparing step (D) is used, and the ultraviolet light in the embossing structure preparing step is used. Under the conditions (environment) of atmospheric gas: air, pressure: atmospheric pressure, temperature (temperature at the time of polymerization): room temperature (25° C.), the irradiation intensity of light is an irradiation intensity (illuminance) of ultraviolet light having a wavelength of 365 nm. A cured film was obtained in the same manner as in Example 1 except that the irradiation conditions were changed to 15.5 mW/cm ² for 15 minutes.

<Coating liquid preparation process (D)>
First, in a brown sample tube, styrene _{(C 6 H 5 -CH = CH} 2: 1 functional monomer) 1.04 g and a photopolymerization initiator (BASF Co., Ltd. under the trade name "Irgacure 651") 0. 13 g was added to obtain a mixture. The molar ratio of the styrene to the photopolymerization initiator in the mixture ([styrene]:[photopolymerization initiator]) was 100:5. Next, the total amount of the mixture thus obtained was added to 1.81 mL (1.75 g) of propylene glycol monomethyl ether acetate (PGMEA) as a solvent and dissolved, followed by stirring for 30 minutes, A coating liquid having a styrene content of 40 mass% was obtained.

An SPM image of an area of arbitrary length 500 nm and width 500 nm on the surface (light irradiation surface: surface in contact with air) of the cured film obtained in Comparative Example 2 was obtained, and unevenness was obtained in the same manner as in Example 1. When the average value of the maximum heights, the distribution and the average pitch of the unevenness were determined, the average value of the maximum unevennesses was 0.5 nm, and the distribution of the maximum unevenness was in the range of 0.2 to 2.0 nm. The average pitch of the irregularities was 20.5 nm (note that the total number of convex portions observed when determining the average pitch of the irregularities was 5). The results obtained are shown in Table 1.

(Comparative example 3)
Instead of using the coating liquid obtained in the coating liquid preparing step (A), the coating liquid obtained by carrying out the following coating liquid preparing step (E) is used, and the ultraviolet ray in the step of preparing the embossed structure is used. Under the conditions (environment) of atmospheric gas: air, pressure: atmospheric pressure, temperature (temperature at the time of polymerization): room temperature (25° C.), the irradiation intensity of light is an irradiation intensity (illuminance) of ultraviolet light having a wavelength of 365 nm. A cured film was obtained in the same manner as in Example 1 except that the irradiation conditions were changed to 15.5 mW/cm ² for 15 minutes.

<Coating liquid preparation process (E)>
First, in a brown sample tube, 2.89 g of dipentaerythritol hexaacrylate (DPHA: a 6-functional acrylate manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the above general formula (1) and styrene (C ₆ H ₅ -). CH = _CH 2: to give 1 and functional monomer) 0.52 g, photoinitiator (BASF Corporation under the trade name "Irgacure 651") mixture were added to 0.13 g. The total molar amount of the monomers (total molar amount of the hexafunctional acrylate and monofunctional monomer) to the molar ratio of the photopolymerization initiator ([total molar amount of monomers]:[photoinitiator]) in the mixture is It was 100:5, and the molar ratio of dipentaerythritol hexaacrylate to styrene in the mixture ([dipentaerythritol hexaacrylate]:[styrene]) was 50:50. Next, the total amount of the mixture thus obtained was added to 5.48 mL (5.31 g) of propylene glycol monomethyl ether acetate (PGMEA) as a solvent and dissolved, and then stirred for 30 minutes, A coating liquid having a content (total amount) of the monomers of 40% by mass was obtained.

An SPM image of an area of arbitrary length 500 nm and width 500 nm on the surface (light-irradiated surface: surface in contact with air) of the cured film obtained in Comparative Example 3 was obtained, and unevenness was obtained in the same manner as in Example 1. When the average value of the maximum heights, the distribution and the average pitch of the unevenness were obtained, the average value of the maximum unevennesses was 1.4 nm, and the distribution of the maximum unevenness was in the range of 0.8 to 2.8 nm. The average pitch of the irregularities was 22.7 nm (the total number of convex portions observed when obtaining the average pitch of the irregularities was 5). The results obtained are shown in Table 1.

As is clear from the results shown in Table 1, in Example 1 and Comparative Examples 2 to 3, the total polymerization time (total light irradiation time) was 15 minutes, but it was obtained in Example 1. In the embossed structure, the embossed structure has a sufficient unevenness height such that the average value of the unevenness maximum height is 10.5 nm and the distribution of the unevenness maximum height is in the range of 8.3 to 13.1 nm. On the other hand, in Comparative Examples 2 to 3 in which the integrated irradiation amount of light (irradiation intensity×time) is larger than that in Example 1, the average maximum unevenness height is 1.4 nm or less. The average value of the maximum unevenness height is not 2.0 nm or more, and the distribution of the maximum unevenness height is in the range of 0.2 to 2.8 nm (Comparative Example 2: 0.2 to 2.0 nm, comparison (Example 3: 0.8 to 2.8 nm), the distribution of the maximum height of the unevenness is not in the range of 1.0 nm or more, and it is not always possible to form an embossed structure having a sufficient unevenness height. could not. As described above, from the results shown in Table 1, according to the method for producing a nano-embossed structure of the present invention (Example 1) in which a 4- to 8-functional polyfunctional acrylic monomer is used as a polymerizable material, a simple method is provided. Then, it was found that the nano-embossed structure having a sufficient height of irregularities can be efficiently formed.

Further, in Example 2 (method for producing a nano-embossed structure of the present invention) using a film made of a polymerizable material containing 70 mol% or more of a 4- to 8-functional polyfunctional acrylic monomer, the maximum unevenness height was set. While an embossed structure having a sufficient unevenness height is formed such that the average value of is 4.0 nm and the maximum unevenness height distribution is in the range of 3.0 to 5.6 nm. In Comparative Example 3 using a film made of a polymerizable material having a content of the 4- to 8-functional polyfunctional acrylic monomer of 50 mol %, the average maximum unevenness height was 1.4 nm, and the maximum unevenness was The height distribution was in the range of 0.8 to 2.8 nm, and it was not always possible to form an embossed structure having a sufficient unevenness height.

In addition, Comparative Example 1 is an example in which a bifunctional acrylic monomer is used as the polymerizable material, but as is clear from the above results, the cumulative irradiation amount of ultraviolet light (irradiation intensity×time) was changed to another value. Despite the maximum compared to the Examples and Comparative Examples, the polymerization did not proceed sufficiently in the oxygen-containing atmosphere, and the film obtained after the polymerization had tackiness.

From the results of Examples 1 to 2 and Comparative Examples 1 to 3 as described above, it is possible to use a polymerizable material containing 70 mol% or more of a polyfunctional acrylic monomer having 4 to 8 functionalities in an oxygen-containing atmosphere. It was found that it is possible to efficiently manufacture a nano-embossed structure having a sufficient height of irregularities.

As described above, according to the present invention, it is possible to form a nano-embossed structure composed of a fine uneven structure without performing a complicated etching step or the like, and to easily and efficiently manufacture a nano-embossed structure. It is possible to provide a method for producing a nano-embossed structure capable of achieving the above, a polymerizable material for producing a nano-embossed structure used in the production method, and a nano-embossed structure obtained by the production method.

As described above, the method for producing a nano-embossed structure of the present invention can easily and efficiently produce a nano-embossed structure, and the obtained embossed structure (concavo-convex structure) can be produced according to the structure. For example, various functions such as superhydrophobicity, superhydrophilicity, structural color, structural birefringence, polarization conversion property, antireflection property, adhesive property, etc. can be exhibited, so that from electronics to photonics and medical materials. It is particularly useful for a method for forming a concavo-convex structure used in such fields.

L: reference length of the concave-convex curve (scan length), D: maximum height of the concave-convex, A: direction perpendicular to the horizontal plane (out-of-plane direction), P1: vertex having the maximum height of the convex portion, P2: vertex having the maximum depth of the recess (vertex having the minimum height from the horizontal plane).

Claims (6)

At least one polyfunctional acrylic monomer (A) selected from 4- to 8-functional acrylic monomers, and at least a monomer having 1 to 3 carbon-carbon double bond-containing functional groups. At least one of the one type of monomer (B) is contained, and the content of the polyfunctional acrylic monomer (A) is the total amount of the polyfunctional acrylic monomer (A) and the monomer (B). On the other hand, a step of preparing a polymerizable material having a content of 70 mol% or more, a step of forming a film made of the polymerizable material, and irradiating the film with light in an oxygen-containing atmosphere containing 15% by volume or more of oxygen. A method for producing a nano-embossed structure, comprising a step of self-organizing a nano-embossed structure on a surface of the film in contact with oxygen by photopolymerization. The method for producing a nano-embossed structure according to claim 1, wherein the film made of the polymerizable material has a thickness of 0.1 to 100 μm. The method for producing a nano-embossed structure according to claim 1 or 2, wherein the nano-embossed structure is a concavo-convex structure in which an average value of the concavo-convex maximum heights at arbitrary 5 points or more is 2 to 1000 nm. The functional group having a carbon-carbon double bond in the monomer (B) is at least one selected from the group consisting of an acryl group, a methacryl group and a vinyl group. The method for producing a nano-embossed structure according to any one of the above. The process of forming a nano-embossed structure on the surface of the film in contact with oxygen in a self-organizing manner causes the progress of polymerization to vary within the film due to the presence of the oxygen. The method for producing a nano-embossed structure according to any one of the above. In the step of self-organizing a nano-embossed structure on the surface of the film in contact with oxygen, both directions parallel to the surface of the film in contact with oxygen and the direction perpendicular to the surface of the film in contact with oxygen. In addition, by spontaneously generating a part where the polymer formed by the polymerization accumulates and a part where the unreacted monomer diffuses and flows out, a nano-embossed structure is self-organized on the surface of the film in contact with oxygen. The method for producing a nano-embossed structure according to any one of claims 1 to 5, wherein: