JP2009195794A - Method of preparing structural color membrane, substrate coated with structural color membrane, and structural color membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of preparing a structural color membrane capable of preparing one having a large surface area without defects such as a crack, peeling-off or falling-off and one having an arbitrary intended shape, and a structural color membrane of a large surface area comprised primarily of a metal oxide which membrane is characterized by having a structural color developed by the presence of spherical voids forming a three-dimensional periodic structure. <P>SOLUTION: The method of preparing a structural color membrane comprises applying an aqueous paint composition comprised of a metal oxide obtained by the sol-gel reaction of a metal alkoxide and of hollow polymer particles of a monodispersion type onto a solid substrate having heat resistance at a temperature of 250°C or higher to obtain a coated substrate, and subsequently calcining the resulting coated substrate. The structural color membrane is characterized by having an inverse opal structure comprised of the metal oxide prepared by the sol-gel reaction of a metal alkoxide as its principal constituent with the length of the shortest side of the membrane plane being at least 1,000 times greater relative to the thickness of the membrane. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a structural color film that can easily produce a large-area structural color film free from defects such as cracks, peeling and dropping, and a structural color film having a metallic luster and showing vivid color.

  A general coloring film material contains a dye or a pigment inside as a coloring matter, and is colored by absorption or reflection of light based on the molecular structure of the coloring matter. Coloring with such dyes and pigments often causes a chemical reaction by light energy, causing discoloration and discoloration. On the other hand, color development using light refraction, diffraction, scattering and interference effects based on the physical structure of the material will not cause discoloration or discoloration due to the absence of light energy absorption by the material, and the structure will be broken. As long as it is not, permanent and stable coloring can be given. This color phenomenon due to optical diffraction and interference effect is called “structural color”, and it is a vivid color that shows metallic luster, as is widely known as the color development phenomenon of gem opal and morpho butterfly honey. Furthermore, the interference condition changes depending on the light source and the observation angle with respect to the material that is the object, and the brightness and color change.

  As a structural color coloring material that utilizes the diffraction / interference effect of light, a method using a laminated structure having a periodic structure with a one-dimensional refractive index is known. Color development is achieved by the material to be laminated and its refractive index. (For example, refer nonpatent literature 1.). Special pigments and colorants using this principle have already been developed. For example, inorganic oxides such as silica, titanium oxide, alumina, and iron oxide are simply applied on small flakes such as mica, alumina, silica, and titanium oxide. Layers or multilayers are provided. The size is usually an area of about several microns to several tens of microns and basically does not constitute a structural color film having a large area.

  In addition, it is known that when a so-called "opal" structure in which fine particles having a uniform particle size are regularly arranged is produced, light diffraction and interference occur due to the fine particle arrangement structure, and vivid color development is recognized. The central color of color development can be changed by controlling the particle size of the arranged fine particles, and structural color films using this principle have also been proposed (see, for example, Patent Documents 1 to 4 and Non-Patent Document 2). . However, in the technology for regularly arranging these fine particles, there is basically no strong adhesion between the fine particles and between the base material and the fine particle arrangement film, and the film easily peels off and drops by contact or temperature change, and the film itself There was a problem of poor stability.

  On the other hand, instead of using the fine particle arrangement structure itself, the fine particle arrangement film is used as a template (template), and after filling the voids of the fine particle arrangement film with another substance, the fine particles are removed to form a periodic porous structure. A technique for forming a structural color film has also been proposed. For example, a colloidal crystal is prepared by suction filtration of a dispersion of polystyrene fine particles, and a metal alkoxide solution is dropped from the top to penetrate between the fine particles. A method of forming a body structure and then removing polystyrene to create an inverse opal structure (see, for example, Non-Patent Document 3), colloidal dispersions composed of polymer fine particles are precipitated and arranged by centrifugation, and colloidal crystals After pulverizing this into a powder, a metal alkoxide solution is dropped from above to infiltrate between the fine particles, and this is fired to form a metal oxide continuum structure between the fine particles, A method of creating an inverted opal structure by removing a polymer (see, for example, Non-Patent Document 4), and by means of CVD between fine particles of a colloidal crystal obtained by a precipitation method. A method of filling with rumanium (for example, refer to Non-Patent Document 5), a colloidal crystal body is formed on an electrode substrate, a metal is filled between the particles electrochemically, and heated or acid-treated to reverse. A method of creating an opal structure (see, for example, Patent Document 5) is disclosed.

  However, in the above method, after the production of the colloidal crystal, the space between the closely packed very narrow particles is filled with an organic or inorganic material, so that the surface void is filled with these materials. However, there is a problem that it cannot enter deeper than that, and the voids between the particles are not sufficiently filled, resulting in a non-uniform periodic structure. Furthermore, since the excess inorganic material that has not been filled forms a continuum that does not have a periodic structure, in this case, there is a problem that a non-uniform material in which a portion having a periodic structure and a portion having no periodic structure are mixed is present. there were. In addition, the three-dimensional periodic structure part with an inverse opal structure uses a mold in which particles are in contact with each other, so it becomes a fragile structure where holes are connected at the contact points, and cracks are generated due to shrinkage caused by firing, so the structure is maintained. Hard to do. This problem of non-uniformity and strength becomes more serious as the material becomes larger, so it is basically difficult to produce a structural color film with a large area.

  In order to solve the problem of non-uniformity and strength, the present inventor has already used core-shell particles having fine particles as a core portion and crosslinked hydrophilic organic polymer compounds as shell portions as water or hydrophilicity. A metal-based alkoxide is added to a sol dispersed in a solvent, and an organic-inorganic composite three-dimensional periodic structure is simply produced by a sol-gel reaction of the alkoxide, and the core portion of the structure obtained by firing this is formed. The technique which obtains the inorganic oxide periodic structure which has an inverse opal structure by removing is disclosed (refer patent document 6). In this technique, since the crosslinked hydrogel layer is used as a reaction field for the sol-gel reaction without drying the fine particle arrangement film, a uniform and sufficiently thick inorganic oxide layer can be easily formed between the fine particles. Therefore, it is possible to obtain a large three-dimensional periodic porous structure as compared with the conventional method. However, in this method, a dispersion sol of core-shell type fine particles is applied onto a substrate, and this is immersed in a metal alkoxide, and a sol-gel reaction is caused in the shell layer to fix the fine particle arrangement structure. Therefore, the substrate is required to be a material that is stable with respect to the metal alkoxide. Furthermore, since the entire substrate is immersed, in order to obtain a large structural color film, it is necessary to prepare a large immersion tank according to the size of the substrate, and the usage amount of metal alkoxide increases. There were still challenges. In addition, the three-dimensional periodic structure composed of core-shell type fine particles produced on the substrate by this method itself forms a strong organic-inorganic composite three-dimensional periodic structure by a sol-gel reaction in the shell layer. There is originally no adhesion to a strong substrate based on covalent bonds. Therefore, when trying to obtain a large structural color film, it may peel from the substrate as the sol-gel reaction proceeds, or may peel from the substrate during firing. When the film is peeled off in this way, a local stress is applied, and as a result, the resulting structural color film is warped or rolled, and the film is prone to cracks, resulting in a large structural color film or structural color. It is difficult to obtain a coated substrate.

JP-A-8-234007 JP 2001-206719 A JP 2004-269922 A JP-T-2004-514558 JP 2000-233998 A JP 2006-213534 A Pfaff et al., Chemical Reviews, Vol. 99, 1999, 1963-1981 Raul Maypral and 9 others, Advanced Materials, Vol. 9, 1997, p. 257 Brian T. Holland, et al., “Science”, Vol. 281, 1998, p. 538-540 Rick C.I. Schroden and three others, “Inverse Opal Photonic Crystals Laboratory Guide”, [online], October 30, 2001, University of Minnesota, [September 21, 2004], Internet <URL: http: // / Www. mrsec. umn. edu / ehr / InverseOpal. Guide. pdf> Hernan Miguez, 10 others, “Advanced Materials”, Vol. 13, No. 21, 2001, p. 1634-1637

  In view of the above situation, the problem to be solved by the present invention is a structural color film capable of producing a structural color film in a large area free from defects such as cracks, peeling and dropping, and a structural color film in an arbitrary shape. And a structural color film characterized by having a structural color due to three-dimensional periodic existence of spherical vacancies inside the thin film, and a large-area thin film mainly composed of a metal oxide It is to provide.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found that an aqueous coating composition containing a metal oxide obtained by a sol-gel reaction of a metal alkoxide and monodisperse hollow polymer particles is obtained. When applied to the surface of a solid substrate, the metal oxide sol is cured along the close-packed arrangement of the hollow polymer particles during the film formation process, so that the inside of the coating film has a regular hollow structure. In addition, an organic-inorganic composite coating film having a hemispherical concavo-convex pattern is formed on the surface of the coating film, and the structure inside the coating film does not change even when heated and fired. The present inventors have found that a coating film having a structural color is maintained, and the present invention has been completed.

That is, the present invention
(1) On a solid substrate (X1) having a heat resistance of 250 ° C. or higher, a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a), monodisperse hollow polymer particles (B), A step of applying a water-based coating composition containing, to obtain a coated substrate,
(2) A step of firing the coated substrate obtained in (1),
The present invention provides a method for producing a structural color film characterized by comprising:

Furthermore, the present invention provides
(1) An aqueous coating composition containing a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a) and monodisperse hollow polymer particles (B) is applied onto a solid substrate (X2). The process of obtaining a coated substrate,
(2) The process of peeling a coating film from the coating base material obtained by (1),
(3) A step of firing the release coating obtained in (2),
The present invention provides a method for producing a structural color film characterized by comprising:

  The present invention also relates to a structural color film-coated substrate in which a solid base material (X1) having a heat resistance of 250 ° C. or higher is coated with a structural color film, wherein the structural color film comprises a metal oxide (A). Provided is a structural color film-coated substrate comprising a matrix having an inverse opal structure as a main constituent, and the length of the shortest side of the film plane with respect to the film thickness being 1,000 times or more To do.

  Furthermore, the present invention comprises a matrix having an inverse opal structure containing the metal oxide (A) as a main constituent, and the length of the shortest side of the film plane with respect to the film thickness is 1,000 times or more. The structural color film is also provided.

  The method for producing a structural color film of the present invention is easy to form a structural color film having a defect and having a three-dimensional periodic porous structure in any shape on various solid substrates such as glass, metal, and metal oxide. In addition to the film on the substrate, it can be obtained as a self-standing thin film. The structural color film or the structural color film-coated substrate of the present invention obtained in this way is free of cracks and chips even in a large area and expresses a uniform and vivid color, and is used in the design crafts and decoration fields. Etc. can be suitably used. In addition, photonic crystals and various sensors that use light interference, anti-counterfeit coatings, immobilization of biomolecules and catalysts using porous structures, dye-sensitized solar cells, fuel cells, superhydrophobic or superhydrophilic surfaces It can be applied in many fields such as construction, heat insulation, and sound insulation materials.

  In the method for producing a structural color film of the present invention, an aqueous coating composition containing a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a) and monodisperse hollow polymer particles (B) is applied. And a first step of obtaining a coated substrate. The coated substrate is obtained by forming an organic-inorganic composite coating film on a solid substrate. Here, the organic-inorganic composite coating film is characterized in that monodisperse hollow polymer particles (B) are combined in a matrix made of a metal oxide (A) while having a three-dimensional periodic structure. The matrix composed of the metal oxide (A) refers to a structure in which a continuous phase of a metal oxide material including an oxide of silica and silicon is constructed over the entire coating film. The hollow polymer particles have a coefficient of variation in particle size of 0.1 or less.

[Organic inorganic composite coating film]
The organic-inorganic composite coating film obtained in the first step of the present invention has a spherical hollow structure inside and an uneven pattern on the surface. The spherical hollow structure referred to in the present invention refers to a structure in which hollow polymer particles are regularly arranged along the cross section of the coating film, which is a continuous phase of a metal oxide, and is particularly dense in a three-dimensional space. A regular porous structure filled is preferable. Further, the uneven pattern on the film surface refers to a hemispherical uneven structure formed by the arrangement of hollow polymer particles over the entire surface of the coating film, and may be a hemispherical uneven pattern by a close-packed array. Preferably, the pattern is most preferably honeycomb. That is, the metal oxide (A) forms a continuous film along the entire three-dimensional array structure of the hollow polymer particles (B), and an organic material composed of the metal oxide (A) and the hollow polymer particles (B). It is a self-organizing coating film in which a compound is integrated.

  In the present invention, the reason why the hollow polymer particles (B) finally induce a regular three-dimensional periodic structure can be estimated as follows. In a sol coating solution containing hollow polymer particles, osmotic pressure is always generated inside and outside the particles. Due to this osmotic pressure, a certain exclusion interaction occurs between the particles, preventing disordered aggregation of the particles. That is, the hollow polymer particles (B) already have a fixed arrangement structure in the sol coating liquid. Therefore, when this coating solution is applied, a three-dimensional particle array is already formed, and phase conversion from sol to gel proceeds as the water and alcohols in the sol solution evaporate. The particles in the array state are closed. The gelation process of the sol proceeds on the outside of the particle or on the outer surface of the particle. At this time, moisture or alcohols from the hollow polymer particle (B) are released with a certain delay. This retarding effect prevents abrupt formation of the gelled binder phase and relaxes the stress of film formation. As a result of such cooperation, it is considered that a stable large-area coating film in which the particle arrangement structure was maintained was formed.

  The thickness of the organic-inorganic composite coating film can be adjusted to 1 to 50 μm depending on the size of the hollow polymer particles (B) described later or the coating amount of the aqueous coating composition. The spherical pore diameter in the cross-sectional structure of the coating film in the thickness direction depends on the size of the hollow polymer particles (B), and is preferably in the range of 40 to 780 nm.

  The surface pattern of the organic-inorganic composite coating film is basically an arrangement pattern on the outermost surface of the hollow polymer particles (B), and irregularities resulting from protrusion of half of the hollow polymer particles (B). It is a pattern structure. Therefore, the hemispherical uneven pattern structure reflects the diameter of the hollow polymer particles, the maximum width of the hemisphere is 50 to 800 nm which is not more than the diameter of the hollow polymer particles (B), and the maximum depth of the unevenness is the hollow polymer particles (B ) Within the range of 25 to 400 nm which is less than the maximum radius.

  The uneven pattern is preferably in the form of a honeycomb, and the structure can be formed over the entire surface of the coating film. The distance between adjacent protruding portions or concave lower portions forming the honeycomb shape becomes wider as the diameter of the hollow polymer particles (B) increases, but is generally controlled to 1.2 to 1.5 times the diameter of the hollow polymer particles (B). it can.

  As content of the metal oxide (A) in an organic inorganic composite coating film, it is preferable that it is the range of 30-90 mass%, and it is more preferable in it being the range of 35-75%. If the amount of the metal oxide (A) is within the above range, a uniform metal oxide matrix can be formed on the entire coating film, and cracking of the organic-inorganic composite coating film is less likely to occur.

[Solid substrate]
As the solid base material (X1) used in the present invention, it is essential that the organic / inorganic composite coating film is formed on the base material and then the base material itself is not changed in the firing step. Specifically, it is necessary to have heat resistance of 250 ° C. or higher. The shape and components of the solid substrate (X1) are not particularly limited, and the metal oxide (A) obtained by the sol-gel reaction of the metal alkoxide (a) and the monodisperse hollow polymer particles (B) The base material which consists of various glass materials, a metal material, an inorganic oxide material, etc. can be used suitably. When such a substrate is used, in the coating film formation process, a covalent bond is formed by a condensation reaction with a hydroxyl group on the substrate surface, and a hydrogen bond is formed with a hydrophilic group or an oxide layer. A strong bond is formed between the substrate and the substrate, and a stable large-area coated substrate can be obtained. In addition, that a solid base material has heat resistance of 250 degreeC or more means that the softening point or melting | fusing point of the said base material is 250 degreeC or more.

As the glass material, soda lime glass, crystal glass, borosilicate glass, quartz glass, and the like can be used, and these glasses may contain a metal, a metal oxide, or the like. Examples of the metal material include gold, silver, platinum, iron, copper, zinc, tungsten, nickel, aluminum, carbon, silicon, and the like, and examples of the inorganic oxide material include alumina. , Titanium oxide, zirconium oxide, zinc oxide, iron oxide, indium oxide, tin oxide and other mixed oxide base materials can be used, and in addition to these compositions, Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO, B ₂ O ₃ , P ₂ O _{5 and the} like may be contained.

  As the shape of the substrate, in addition to the plate-like substrate, various shapes such as a rod shape, a spherical shape, a hemispherical shape and a pyramid shape can be used, and the coated surface is a flat shape. It is not limited, What has a curved surface can also be used suitably. Therefore, commercially available glasses, teacups, dishes, tiles, and the like can be used as the base material.

  In addition, when it is difficult to apply the base material, a base coating called a primer may be applied on the base material in advance.

  Further, the solid substrate (X2) used when the structural color film of the present invention is produced as a self-standing thin film (self-supporting film) does not require heat resistance like the solid substrate (X1) described above, Especially if it is a base material which can apply | coat the aqueous coating composition containing the metal oxide (A) obtained by the sol-gel reaction of a metal alkoxide (a) and a monodisperse hollow polymer particle (B), it will be restrict | limited. It can be used without any limitation and can be selected according to the purpose. In particular, if it is a base material such as polyethylene or polyvinyl chloride having a low adhesive strength to a general aqueous composition, it is preferably used since the peeling step after obtaining the organic-inorganic composite coating film is easy. Can do.

  For example, when the water-based coating composition is applied to a polyethylene or polyvinyl chloride substrate, when the organic-inorganic composite coating film is formed upon drying, a part or the entire surface thereof peels off from the surface. By peeling it off after drying, an independent organic-inorganic composite coating film can be obtained. Thereafter, a thin structural color film can be obtained by a method described later.

[Metal oxide (A)]
The metal oxide (A) in the organic-inorganic composite coating film is obtained by a sol-gel reaction of the metal alkoxide (a). Metal alkoxides having trivalent or higher alkoxide groups that can be hydrolyzed are capable of forming a metal oxide network containing oxides of silica or silicon by hydrolysis / condensation reaction and obtaining a strong coating film. It is preferable to use it. In particular, when a tetravalent or higher-valent metal alkoxide such as tetraalkoxysilane is used, the hardness of the resulting coating film can be increased, which is preferable. In the case of using a metal alkoxide having a large number of functional groups for the purpose of increasing the coating film hardness, it is preferable that the content of tetravalent or higher metal alkoxide in the total metal alkoxide (a) is 30% by mass or higher. 50% by mass or more is more preferable.

  Examples of the metal species of the metal alkoxide (a) include silicon, titanium, zirconium, aluminum, boron, germanium, and zinc. Among these, sol-gel reaction is easy, and silicon, titanium, zirconium, Aluminum is preferable, and silicon is particularly preferable from the viewpoint of industrial availability.

  Examples of the metal alkoxide having silicon as a metal species include an alkoxysilane which may have a reactive functional group. In the present invention, unless otherwise specified, alkoxysilanes include those oligomerized by a hydrolysis reaction. The oligomerized product may be used in a silica sol state converted to silanol. As the oligomerized alkoxysilane, those having an average degree of polymerization of 2 to 20 can be suitably used. As the catalyst used for the hydrolysis reaction in this case, various acids and alkalis can be used.

  Examples of the alkoxysilane include dialkoxysilanes such as dimethyldimethoxysilane, diethyldimethoxysilane, methylethyldimethoxysilane, diphenyldimethoxysilane, and phenylmethyldimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, Trialkoxy such as phenyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloylpropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, methyltriethoxysilane, phenyltriethoxysilane Silane, tetramethoxysilane, tetraethoxysilane, tetra (2-ethanol) orthosilicate, tetra (n-propoxy) silane, tetra (isopropyl) Epoxy) tetraalkoxysilane such as silane.

  Furthermore, examples of the alkoxysilane having a functional group include chlorosilanes such as tetrachlorosilane and methyltrichlorosilane as halogen-containing silanes.

  Examples of the metal alkoxide having titanium as a metal species include alkoxytitanium such as tetraisopropoxytitanium, tetraethoxytitanium, tetrabutoxytitanium, and tetrapropoxytitanium, and titanium acetylacetonate, titanium octylene glycol, and titanium. Various titanium chelates prepared from a metal alkoxide of titanium such as tetraacetylacetonate and titanium ethyl acetate may be used. Examples of the metal alkoxide having aluminum as a metal species include alkoxyaluminum such as triethoxyaluminum.

  These metal alkoxides (a) may be used singly or in combination of two or more, but in order to increase the hardness of the resulting composite coating film, divalent or lower valent alkoxysilane, alkoxy titanium, The proportion of metal alkoxide having a metal species other than silane such as alkoxyaluminum is preferably 10% by mass or less in the total metal alkoxide (a).

[Hollow polymer particles]
The hollow polymer particles (B) used in the organic / inorganic composite coating film can be combined with the metal oxide (A) described above and may be monodisperse, but the surface thereof is hydrophilic and the aqueous medium Among these, those that are stably dispersed are preferred. In addition, it is preferable that the hollow polymer particles have a thin shell wall from the viewpoint of color formation of the intended structural color film because the porous structure inside the resulting organic-inorganic composite coating film and the uneven structure on the surface can be easily formed. From the point that such hollow polymer particles can be easily obtained, the hollow polymer particles (B) used in the present invention comprise a radical polymerizable water-soluble monomer (b1) and a radical polymerizable water-insoluble monomer (b2). Most preferably, it is obtained by carrying out a pseudo-emulsion type radical polymerization reaction in an aqueous medium.

  When the monomer group containing the radically polymerizable water-soluble monomer (b1) and the radically polymerizable water-insoluble monomer (b2) is copolymerized in an aqueous medium, the water-soluble monomer (b1) is not Compared to the water-soluble monomer (b2), its molar concentration is very low. When the polymerization is carried out using a water-soluble initiator, the water-soluble monomer (b1) is preferentially polymerized to form a hydrophilic segment derived from the monomer (b1). However, when the hydrophilic segment of the terminal radical grows to a certain size, a depletion interaction is strongly induced between the water-insoluble monomer droplets due to factors such as an increase in the degree of polymerization. A phenomenon occurs in which the growing hydrophilic segment is concentrated on the droplet surface. In other words, the periphery of the growth end of the hydrophilic segment is filled with the water-insoluble monomer (b2). Accordingly, the addition reaction of the water-insoluble monomer (b2) starts at the radical growth terminal of the hydrophilic segment, and the polymerization of the water-insoluble monomer (b2) proceeds rapidly. The copolymer which has is produced | generated. The copolymer having the hydrophobic segment and the hydrophilic segment thus produced acts as a so-called polymer surfactant, and during the polymerization reaction, the copolymer spontaneously sandwiches the hydrophobic segment. Aggregates into bilayer polymer aggregate particles (polymer vesicles). As a result, a large amount of the remaining water-insoluble monomer (b2) is polymerized while being taken into the film of the aggregated particles, and finally the inner and outer surfaces similar to the polymer vesicle structure are hydrophilic, and the shell wall Thin hollow polymer particles are provided. In the present invention, the above polymerization process is defined as pseudoemulsion polymerization.

  The average particle diameter and the shell wall thickness of the hollow polymer particles thus obtained can be adjusted according to the purpose. In the organic-inorganic composite coating film, the hollow polymer particles (B) are used for developing the strength of the entire coating film while maintaining the hollow structure inside the coating film and increasing the strength of the target structural color film. The shell wall thickness is preferably 10 nm to 20 nm and the average particle size is 50 nm to less than 150 nm, or the shell wall thickness is 10 nm to 80 nm and the average particle size is 150 nm to 800 nm.

  The radically polymerizable water-soluble monomer (b1) is not particularly limited, but is preferably one that dissolves 1.0% by mass or more with respect to 25 ° C. distilled water. More preferable are those that are miscible with, for example, an amide group, an amino group, an oxyalkylene chain, a cyano group, an acid anhydride group, etc. Those having a phosphate group and the like, and those having an alkali metal salt or an ammonium salt thereof can be used. Specifically, examples of the water-soluble monomer having an amide group include acrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, Nn-propylacrylamide, Nn. -Propylmethacrylamide, N-cyclopropylacrylamide, N-cyclopropylmethacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropylacrylamide, N-methyl-N-ethylacrylamide, N-substituted (meth) acrylamide such as N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N-disubstituted (meth) acrylamide, N-hydroxyethylacrylamide , Acryloyl morpholine, N- vinylpyrrolidone, diacetone acrylamide, N, N'-methylene bis-acrylamide. Examples of the water-soluble monomer having an amino group include allylamine, N, N-dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and the like. Examples of the water-soluble monomer having a carboxy group include acrylic acid, methacrylic acid, and maleic acid. Examples of the water-soluble monomer having a hydroxy group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxy Examples thereof include ethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 1,4-cyclohexanedimethanol monoacrylate and the like. Examples of water-soluble monomers having a sulfonic acid group include styrene sulfonic acid, sodium styrene sulfonate, lithium styrene sulfonate, ammonium styrene sulfonate, ethyl styrene sulfonate, cyclohexyl styrene ester, 2-acrylamido-2-methylpropane A sulfonic acid etc. are mentioned. Furthermore, a quaternized monomer obtained by quaternizing a monomer synthesized by reacting vinyl pyridine or glycidyl methacrylate with an organic amine may be used.

  Among these water-soluble monomers (b1), those having an amide group, amino group, carboxy group or salt thereof, sulfonic acid group or salt thereof in the structure are industrially available, water-soluble, and easily radically polymerized. From the viewpoint of excellent properties and the like, it is preferable.

  Furthermore, N-substituted acrylamide and N, N-disubstituted acrylamide are considered to have a surface-active action from the viewpoint of having a hydrophobic group and a hydrophilic group in one molecule, and the homopolymers thereof are: It has a unique property that the degree of water solubility varies depending on the degree of polymerization and the temperature of the aqueous medium. By these properties, the reaction mechanism described above can be easily achieved, and the hollow polymer particles (B) used in the present invention can be more easily produced.

  As the radical polymerizable water-insoluble monomer (b2), various monomers can be used as long as they have a group copolymerizable with the water-soluble monomer (b1). It is preferable that the solubility in distilled water is 0.5% by mass or less, particularly acrylate and methacrylate from the viewpoint of excellent reactivity with the water-soluble monomer (b1) and easy industrial availability. It is preferable.

  Examples of the acrylate include butyl acrylate, lauryl acrylate, cyclohexyl acrylate, phenyl acrylate, isobornyl acrylate, glycidyl acrylate, tert-butyl-α-trifluoromethyl acrylate, 1-adamantyl-α-trifluoromethyl. Examples thereof include acrylate, (3-methyl-3-oxetanyl) methyl acrylate, acryloylpropyltrimethoxysilane, acryloylpropyltriethoxysilane, methyl acrylate, and ethyl acrylate.

  Examples of the methacrylate include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, stearyl methacrylate, glycidyl methacrylate, allyl methacrylate, 2 2,2-trifluoroethyl methacrylate, (3-methyl-3-oxetanyl) methyl methacrylate, methacryloylpropyltrimethoxysilane, methacryloylpropyltriethoxysilane, and the like. These radically polymerizable water-insoluble monomers (b1) can be used alone or in admixture of two or more. Hereinafter, (meth) acrylate used in the text is used as a general term for acrylate alone, methacrylate alone and mixtures thereof unless otherwise specified.

  Among the radical polymerizable water-insoluble monomers (b2), those having a cyclic ether structure such as glycidyl (meth) acrylate and oxetane (meth) acrylate are co-polymerized with the radical polymerizable water-soluble monomer (b1). During the formation of the polymer, or after becoming a copolymer, it is possible to carry out a crosslinking reaction within the molecule of the copolymer or between the molecules. Since it is thought that it contributes to increasing the strength of the copolymer forming the part and enhancing the stability of the hollow polymer particles, it can be used particularly suitably.

  As the radical polymerizable water-insoluble monomer (b2), bifunctional di (meth) acrylate, for example, polyethylene di (meth) acrylate such as ethylene di (meth) acrylate, diethylene (meth) acrylate, triethylene di (meth) acrylate, etc. , Polypropylene di (meth) acrylates such as propylene di (meth) acrylate, dipropylene di (meth) acrylate, tripropylene di (meth) acrylate, glycerol di (meth) acrylate, etc. alone or in combination of two or more Can be used. When these di (meth) acrylates are used, they are preferably used in combination with the monofunctional (meth) acrylate for the purpose of preventing aggregation of the resulting hollow particles, and in particular, radically polymerizable water-insoluble monomers (b2 ) Is preferably 0.7 or more in terms of molar ratio.

  As the radical polymerizable water-insoluble monomer (b2), for example, a styrene compound, vinyl ester, vinyl ether, bisvinyl compound, etc. other than (meth) acrylate may be used alone or in combination of two or more. Can do. At this time, it is preferable to use in combination with (meth) acrylate from the viewpoint of easily obtaining the hollow polymer particles (B) used in the present invention, and in particular, (meth) in the radical polymerizable water-insoluble monomer (b2). It is preferable that the use ratio of the acrylate is 0.5 or more in terms of molar ratio.

  The styrenic compound is a compound having a styryl group. For example, styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-, m-, p-chlorostyrene, p-ethylstyrene, p- tert-butoxystyrene, m-tert-butoxystyrene, p-acetoxystyrene, p- (1-ethoxyethoxy) styrene, p-methoxystyrene, styryltrimethoxysilane, styryltriethoxysilane, vinylnaphthalene, vinylbiphenyl, vinylanthracene And vinylpyrene.

  Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl monochloroacetate, vinyl pivalate, and vinyl butyrate.

  Examples of the vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, allyl vinyl ether, cyclohexane dimethanol monovinyl ether, Examples include 1,4-butanediol divinyl ether, nonanediol divinyl ether, cyclohexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylpropane trivinyl ether, pentaerythritol tetravinyl ether, and phenyl vinyl ether.

  Examples of the bisvinyl compound include divinylbenzene and the like, and a cross-linked structure is generated in the shell of the resulting hollow polymer particle (B), which is preferable from the viewpoint that stable hollow particles can be produced. is there.

  The use ratio of the radical polymerizable water-soluble monomer (b1) and the radical polymerizable water-insoluble monomer (b2) is selected depending on the average particle diameter of the intended hollow polymer particles, the thickness of the shell wall, and the like. However, since a hollow polymer particle that can exist stably in an aqueous medium is obtained and the hollow structure is also stable, the radically polymerizable water-soluble monomer (b1) and the radically polymerizable water-insoluble monomer The molar ratio (b2) / (b1) to (b2) is preferably 3.5 to 12, and particularly preferably 3.5 to 10. Instead of adding the monomers all at once, the polymerization proceeds to some extent, and after the formation of the hollow polymer particles, the radically polymerizable water-insoluble monomer (b2) is added and the average particle size of the hollow polymer particles or When controlling the thickness of the shell wall, stable hollow polymer particles can be obtained even when the ratio exceeds 12.

  As an aqueous medium used for the pseudo-emulsion polymerization, in addition to using water alone, lower alcohols such as methanol, ethanol, and isopropanol, polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, and triethylene glycol are used. Mention may be made of ketones such as acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran alone or a mixed solvent in which a plurality of them are mixed.

  The mixing ratio when using the mixed solvent is such that the water-soluble polymerization initiator and radical-polymerizable water-soluble monomer (b1) described later are soluble, and the radical-polymerizable water-insoluble monomer (b2). In the range of 0.5% by mass or less, and can be appropriately selected according to the purpose, but in order to keep the polymerization initiation efficiency by the water-soluble polymerization initiator high, the proportion of water is 50% by mass. As mentioned above, it is preferable to make it 80 mass% or more especially.

  The water-soluble polymerization initiator is not particularly limited, and various types can be used, but it is preferable to use a persulfate or an amino group-containing azo compound. For example, potassium persulfate (KPS) ), Ammonium persulfate (APS), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2, 2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [N- (2-carboxyethyl) 2-methylpropionamide], 2, 2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] pro Dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2 , 2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis (2-methylbutanamidooxime) dihydrochloride tetra Hydrate, etc. are mentioned.

  The use ratio of these water-soluble polymerization initiators is 0.1 to 5 mass with respect to 100 mass parts in total of the radical polymerizable water-soluble monomer (b1) and the radical polymerizable water-insoluble monomer (b2). However, it is more preferable to select in the range of 0.5 to 3 parts by mass for the purpose of increasing the efficiency of the polymerization reaction and suppressing the aggregation of the hollow polymer particles.

  Moreover, you may use various dispersion stabilizers suitably as needed at the time of the said superposition | polymerization. Examples of the dispersion stabilizer include an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and an organic suspension protective agent. Among them, a hollow polymer is obtained. From the viewpoint of excellent dispersion stability of the particles, it is preferable to use an anionic surfactant or a cationic surfactant.

  Examples of the anionic surfactant include rosin salts such as potassium rosinate and sodium rosinate, sodium oleate, potassium laurate, sodium laurate, sodium laurate, sodium stearate, potassium stearate, and the like. Examples thereof include salts, sulfate esters of aliphatic alcohols such as sodium lauryl sulfate, and alkylallyl sulfonic acids such as sodium dodecylbenzene sulfonate.

  Examples of nonionic surfactants include polyethylene glycol alkyl esters, alkyl ethers, alkylphenyl ethers, and the like.

  Examples of the cationic surfactant include alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl dimethyl benzyl ammonium salts, and amine salt surfactants.

  Examples of amphoteric surfactants include alkylamino fatty acid salts, alkylbetaines, and alkylamine oxides.

  These dispersion stabilizers can be used alone or in combination of two or more as required. In using a dispersion stabilizer, an ionic surfactant or nonionic surfactant having the same charge as the surface electrification imparted to the particles by a water-soluble polymerization initiator in order to prevent aggregation of the resulting hollow polymer particles Is preferably used.

  The amount of the dispersion stabilizer used may be appropriately selected as necessary. However, when the concentration at the initial stage of the reaction is too high, normal emulsion polymerization proceeds and the particles are less likely to exhibit a hollow structure. Therefore, the amount used may be reduced in the initial stage, and may be added later as the particles are formed.

  The reaction temperature of the pseudo-emulsion polymerization may be appropriately set in the range of 35 to 90 ° C. according to the polymerization start temperature of the water-soluble polymerization initiator to be used. And it is preferable to set in the range of 40-85 degreeC from the point which prevents evaporation of an aqueous medium and suppresses destabilization of a reaction system, and it is more preferable to set in the range of 60-80 degreeC.

  When the concentration of the monomer during the pseudo-emulsion polymerization is too low, the synthesis efficiency of the hollow polymer particles is poor, and when it is too high, aggregation is likely to occur. Therefore, depending on the purpose in the range of 0.5 to 20% by mass. It is preferable to select appropriately, and it is preferable to select the concentration from the range of 1 to 10% by mass from the viewpoint of efficiently obtaining more stable hollow polymer particles.

  In the pseudo-emulsion polymerization, the raw materials are charged in a state where the radical polymerizable water-soluble monomer (b1) and the radical polymerizable water-insoluble monomer (b2) are added in advance in an aqueous medium. A conventional one-pot manufacturing method of radical polymerization in which polymerization is performed using a water-soluble polymerization initiator can be employed.

  In addition, polymerization is performed using a water-soluble polymerization initiator in a state where a radical polymerizable water-soluble monomer (b1) and a radical polymerizable water-insoluble monomer (b2) are added in advance in an aqueous medium. It can also be synthesized by a one-pot production method in which a radically polymerizable water-insoluble monomer (b2) that is the same as or different from that used at the beginning is added while the reaction has progressed. When the post-addition method is used, the thickness of the hollow shell wall can be increased.

[Water-based paint composition]
In the structural color film production method of the present invention, the aqueous coating composition used in the first step of obtaining a coated substrate can easily give the aforementioned organic-inorganic composite coating film, and comprises a metal alkoxide (a). Containing a metal oxide (A) obtained by the sol-gel reaction and an aqueous dispersion of hollow polymer particles (B).

  In the method for producing a structural color film of the present invention, a preferred embodiment of the aqueous coating composition used in the first step is a hydrolyzable that can give the hollow polymer particles (B) and the metal oxide (A). It contains a metal alkoxide having a trivalent or higher functional group and an acid catalyst.

  In the aqueous coating composition, a metal oxide sol is formed by hydrolysis and condensation reaction of the metal alkoxide (a), and a part of the sol is concentrated on the outer surface of the hollow polymer particle (B). Thus, a structure is formed in which the outer surface of the hollow polymer particles (B) is already hybridized with the sol of the metal oxide (A) in the coating composition. Therefore, in the water-based coating composition, the sol of the metal oxide (A) and the hollow polymer particles (B) whose outer surface is covered with the sol are present. After coating it on the substrate, the volatile components are volatilized, so that the hollow polymer particles (B) covered with the metal oxide (A) sol form a close-packed three-dimensional array structure. The structure is solidified with the sol of the metal oxide (A), and as a result, a coating film having a spherical cavity inside and a hemispherical uneven pattern on the outer surface is formed.

  As the hollow polymer particles (B) and the metal alkoxide (a) of the aqueous coating composition, the aforementioned hollow polymer particles (B) and metal alkoxide (a) can be preferably used. Further, the outermost surface of the hollow polymer particle (B) from the point that the sol of the metal oxide (A) is easily concentrated on the outer surface of the hollow polymer particle (B) and the structural color film of the present invention can be easily obtained. Is preferably hydrophilic.

  In particular, the outer surface of the hollow polymer particles is preferably composed of segments having a high density of structures derived from (meth) acrylamide, (meth) acrylic acid, or amino group-containing (meth) acrylic ester. In the case of having a structure derived from an amino group-containing (meth) acrylic ester, when it is protonated, the hollow polymer particle has a high effect of stabilizing the sol of the metal oxide (A). The amino group (B) is preferably partially protonated or fully protonated.

  The aqueous medium used in the aqueous coating composition is water or a mixed solvent of water and a water-soluble solvent. Examples of the water-soluble solvent include alcohols such as methanol, ethanol and isopropanol, and ketones such as acetone. , Pyridine, dimethylformamide and the like can be used. When using the mixed solvent of water and a water-soluble solvent, it is preferable that the quantity of a water-soluble solvent is less than 40 mass% with respect to the quantity of the water to be used.

  Although the order of mixing is not particularly limited, a method of adding an aqueous solution of an acid catalyst, a solution of metal alkoxide (a) to an aqueous dispersion of hollow polymer particles (B), or an acid to an aqueous solution of metal alkoxide (a) After adding a catalyst and conducting preliminary hydrolysis of the metal alkoxide (a), a coating solution can be prepared by a method of adding an aqueous dispersion of hollow polymer particles (B).

  Examples of the acid catalyst include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and boric acid, acetic acid, phthalic acid, fumaric acid, maleic acid, malic acid, acrylic acid, methacrylic acid, and trifluoromethylsulfonic acid. Organic acids such as ethyl sulfonic acid can be used. These acids may be used alone or in combination of two or more. Among these, unsaturated organic acids such as maleic acid and acrylic acid are preferred because pH adjustment is easy, the storage stability of the resulting aqueous coating composition is good, and the water resistance of the resulting organic-inorganic composite coating film is excellent. It is preferable to use an acid. The pH of the aqueous coating composition is preferably adjusted to 1.5 to 6.5 from the viewpoint of the stability of the aqueous coating composition and the good coating formation (curing) after application to the substrate. .

  In the metal alkoxide (a), the ratio (B) / (a) of the mass of the hollow polymer particles (B) to be used and the mass of the metal alkoxide (a) is generally in the range of 70/30 to 5/95. May be adjusted as appropriate, preferably in the range of 40/60 to 15/85, more preferably in the range of 35/65 to 25/75. If the ratio (B) / (a) is 5/95 or more, cracks of the obtained coating film can be reduced, and if it is 70/30 or less, the water resistance of the coating film is improved.

  The amount of the aqueous medium to be used is preferably about 0.2 to 50 times the amount of the metal alkoxide (a) to be used.

  In the aqueous coating composition, various organic solvents such as ethyl cellosolve, propylene glycol monobutyl ether, propylene glycol dibutyl ether, diethylene glycol monopropyl ether may be added, as long as the effects of the present invention are not impaired. Various additives such as a smoothing agent and a wetting agent can also be added.

  Moreover, various hardening | curing agents, for example, water-soluble polyglycidyl ether, etc. can also be added to the aqueous coating material composition used at the 1st process of this invention in the range which does not impair the effect of this invention.

  The aqueous coating composition can be easily cured at room temperature or by heat treatment after application on the above-mentioned various substrates to form an organic-inorganic composite coating film. In the case of curing by heating, the heating temperature can be selected in the range of 60 to 250 ° C, and it is preferable to treat at about 100 ° C for 30 minutes.

[Structural color film production process]
(Application of water-based paint composition)
In the first step of the method for producing the structural color film of the present invention, the application method of the water-based coating composition when producing an organic-inorganic composite coating film on a substrate to obtain a coated substrate is not particularly limited. Various methods such as brush coating, dip coating method, spray coating method, roll coating method, bar coating method and air knife coating method can be used, and these can also be used in combination.

(Baking process of organic-inorganic composite coating film)
The first method for producing a structural color film of the present invention is a method for obtaining a structural color film-coated substrate by baking the coated substrate obtained in the above-mentioned step, and this baking temperature is determined by solid substrate (X1). ) Can be appropriately selected from a temperature range of 250 to 1300 ° C. The firing temperature needs to be selected at a temperature lower than the heat resistant temperature of the solid substrate. For example, when a low-melting soda glass is used as the substrate, firing is performed in the range of 250 to 500 ° C. Preferably, when a high melting point quartz glass is used as the substrate, it can be fired in the range of 250 to 1000 ° C. Further, when a high heat-resistant ceramic such as alumina is used, firing is possible in the range of 250 to 1300 ° C.

  The 2nd preparation method of the structural color film of this invention is a method of obtaining the self-supporting structural color film by baking the organic inorganic composite coating film peeled from the coating base material. The firing temperature can be appropriately selected from a temperature range of 250 to 1300 ° C. depending on the purpose. When the peeled organic-inorganic composite coating film is fired, it may be fired by sandwiching it between two heat-resistant planar substrates in order to suppress warping and cracking of the coating film. In this case, the heat resistant substrate can be appropriately selected from the materials of the solid substrate (X1).

  Further, by selecting the baking temperature, it is possible to leave the organic component in the structural color film and obtain a structural color film exhibiting different color from the same coated substrate. For example, when baking is performed under conditions where the organic components in the formed organic-inorganic composite coating are not completely decomposed and lost, in addition to the color derived from the three-dimensional periodic porous structure inside the structural color film, a slight yellow to brown color is added. A structural color film having a different color can be obtained. The conditions under which the organic components in the film are not completely decomposed and lost can be set by measuring the thermal decomposition behavior of the coating film in advance using, for example, thermogravimetric analysis.

  Furthermore, the organic component in the organic-inorganic composite film is carbonized by changing the atmosphere during firing of the coated substrate from the presence of air to under nitrogen, under argon, etc., and the metal alkoxide (a) and The carbide (C) derived from the hollow polymer particles (B) can be contained. In this case, in addition to the coloration derived from the three-dimensional periodic porous structure inside the structural color film, the black color of the carbide (C) is added, and a deeper structural color film showing different color development is obtained from the same coated substrate. be able to. Depending on the purpose, the atmosphere may be changed by completely exchanging the atmosphere before heating and baking, or by changing the atmosphere in the heating stage.

  For the firing, a microwave oven or the like can be used in addition to various known firing furnaces such as a muffle furnace, an atmospheric furnace, and an infrared furnace.

[Structural color film]
In the structural color film of the present invention, a film composed of a matrix having an inverse opal structure containing the metal oxide (A) as a main component is formed on the solid substrate (X1), or independent of the above. It is a film made of a matrix having an inverse opal structure containing a metal oxide (A) as a main constituent. As described above, the “opposite opal structure” refers to the “opal structure” in which particles are periodically arranged in a three-dimensional manner. A structure having pores.

  The thickness of the structural color film of the present invention and the spherical pore diameter of the film cross section in the thickness direction substantially maintain the thickness of the organic-inorganic composite coating film produced in the first step of production, as described above. Further, the thickness is 1 to 50 μm, and the inner spherical pore diameter is generally in the range of 40 to 780 nm.

  In the method for producing a structural color film of the present invention, a film having such a thickness is applied to a substrate having a size of at least 1 cm square, and a large-area structural color film free from defects such as cracks can be obtained. Is possible. Accordingly, the length of the shortest side of the film plane with respect to the thickness of the film is at least 1,000 times or more, and 10,000 or more times can be easily produced. In the present invention, the length of the shortest side of the film plane refers to the shortest side length in the plane direction of a film having no defects such as cracks and tears in the structural color film having an inverse opal structure.

  A structural color film of an inverse opal structure composed of an inorganic oxide that has been proposed in the past is a method of injecting an organic oxide precursor between fine particles of an opal structure in which fine particles are arranged, and then heating and firing the organic component. It is obtained by advancing the condensation reaction of the inorganic oxide while removing. Therefore, as the whole material shrinks with heating and baking, the inverted opal structure cannot be maintained on the substrate coated with the film, and a large-area structural color film is produced because many cracks are likely to occur. It is difficult. On the other hand, in the method for producing a structural color film of the present invention, an organic-inorganic composite coating film is produced on a substrate in the first step. As described above, this organic-inorganic composite coating film is characterized in that monodisperse hollow polymer particles are composited in a matrix made of a metal oxide while having a three-dimensional periodic structure. The matrix consisting of is a structure in which a continuous phase of a metal oxide material is constructed over the entire coating. The continuous phase made of the metal oxide material as the matrix is hardly reduced even by the subsequent heating and firing step, and only the organic component can be removed while being applied onto the substrate. This is clear from the fact that the structural color film of the present invention substantially maintains the internal structure of the organic-inorganic composite coating film produced in the first step. Accordingly, the average diameter of the uniform diameter spherical voids of the inverse opal structure inside the structural color film can be prepared depending on the purpose, but in order to sufficiently diffract and interfere the light in the visible light region. The average diameter of the uniform spherical pores is preferably 100 nm to 600 nm, more preferably 200 nm to 500 nm.

  As one form of the structural color film of the present invention, a structural color film containing a metal alkoxide (a) and / or a carbide (C) derived from hollow polymer particles (B) in the structural color film can be produced. When the metal oxide (A) is made of a material having a relatively high light transmittance such as silica or a material having a high reflectance such as titanium oxide, light diffraction or light scattering is caused by transmission or scattering of light from the periphery. It may be difficult to see the structural color due to interference. At this time, it is possible to develop a more vivid structural color by containing the carbide (C) exhibiting a black color and exhibiting a shielding effect. Further, since the ratio of transmitted light, scattered light, diffraction, and interference light is changed by controlling the remaining amount of the carbide (C), it is also possible to produce a structural color film having a different color tone.

  As described above, the remaining amount of the carbide (C) can be controlled by controlling the firing temperature and the firing atmosphere in the firing process of the organic-inorganic composite coating film in the second step of producing the structural color film. The remaining amount of the carbide (C) varies depending on the type of the hollow polymer particles (B) used and the composition of the aqueous coating composition used, but it is left at a ratio of 1 to 60% by mass in the structural color film after firing. Preferably, it is in the range of 1 to 40% by mass.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” represents “mass%”.

Measuring instrument A VE-9800 scanning electron microscope (SEM) manufactured by Keyence Corporation was used for observation of the shape and hollowness of the fine particles.

  A VE-9800 scanning electron microscope (SEM) manufactured by Keyence Corporation and an SPI4000 atomic force microscope (AFM) manufactured by SII Corporation were used for observing the surface of the structural color film and the cross-sectional shape. For measurement of the UV-Vis reflection spectrum of the structural color film, a three-dimensional variable angle spectrocolor measurement system GCMS-11 manufactured by Murakami Optical Co., Ltd. was used.

  For thermogravimetric analysis of the structural color film, a differential thermothermogravimetric simultaneous measurement apparatus (EXSTAR6000 TG / DTA) manufactured by SII Nano Technology Co., Ltd. was used.

  A Raman laser microscope manufactured by Renishaw was used for the residual component analysis of the organic components in the structural color film after firing.

Synthesis example 1
<Synthesis of Hollow Polymer Particle B-1 Consisting of PNIPAM-co-PGMA>
11.8 g of glycidyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter referred to as GMA) is added to 290 ml of an aqueous solution in which 1.8 g of N-isopropylacrylamide (manufactured by Kojin Co., Ltd., hereinafter referred to as NIPAM) is dissolved. The mixture was stirred while flowing nitrogen at 70 ° C. (GMA / NIPAM = 5.2 mol / mol). As a water-soluble polymerization initiator, 10 ml of an aqueous solution in which 0.15 g of 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved was added. A particle dispersion was obtained by stirring at the same temperature for 1 hour. After the dispersion was washed by centrifugation, the shape of the fine particles was observed with an SEM. As a result, the particles were monodisperse spherical particles having an average particle diameter of 225 nm (FIG. 1). When the fine particles were crushed and the morphology was observed, it was confirmed that the center of the particles was a hollow polymer particle having a hollow (FIG. 2). The thickness of the shell wall of this particle was approximately 10 nm. Hereinafter, this hollow polymer particle is referred to as B-1.

Synthesis example 2
<Synthesis of Hollow Polymer Particle B-2 Consisting of PACMO-co-PGMA>
GMA (13.5 g) was added to 290 ml of an aqueous solution in which 1.8 g of acryloylmorpholine (manufactured by Kojin Co., Ltd., hereinafter referred to as ACMO) was dissolved, and the mixture was stirred at 70 ° C. with nitrogen flow (GMA / ACMO = 4.8 mol). / Mol) As a water-soluble polymerization initiator, 10 ml of an aqueous solution in which 0.15 g of V-50 was dissolved was added. A particle dispersion was obtained by stirring at the same temperature for 1 hour. After the dispersion was washed by centrifugation, the shape of the fine particles was observed with an SEM. As a result, the particles were monodisperse spherical particles having an average particle diameter of 270 nm (FIG. 3). When the fine particles were crushed and the morphology was observed, it was confirmed that the center of the particles was hollow polymer particles (FIG. 4). The thickness of the shell wall of this particle was approximately 10 nm. Hereinafter, this hollow polymer particle is referred to as B-2.

Example 1
<Water-based paint composition containing B-1>
100 parts of an aqueous dispersion in which the concentration of the hollow polymer particles B-1 obtained in Synthesis Example 1 is 20%, 20 parts of an aqueous 10% maleic acid solution, and an isopropanol solution of silane oligomer MS-51 (manufactured by Colcoat Co., Ltd.) (50 %) 100 parts were mixed and stirred in a bath at 20 ° C. for 2 hours to obtain a milky white aqueous coating composition in a uniform dispersion state.

  A composite coating film obtained by applying the aqueous coating composition prepared in Example 1 to a glass substrate having a size of 2.5 cm × 7 cm with a bar coater (No. 30) was used at 25, 80, 130, and 180 ° C. When cured at each temperature for 30 minutes, a good organic-inorganic composite coating film free from cracks was obtained. SEM observation of the surface of the composite coating cured at 25 and 80 ° C. confirmed a surface morphology in which fine particles were closely packed and regularly arranged (FIGS. 5 and 6). As a result of SEM observation of the cross section of this film, a regular porous structure was confirmed (FIG. 7).

  When the coating substrate of the organic-inorganic composite coating film obtained above was baked at 500 ° C. for 1 hour in the presence of air using an electric furnace, there were no defects such as cracks over the entire surface, and the film surface was When observed from the vertical direction, a structural color film made of silica showing a bright blue color was obtained. This film had an average film thickness of about 2.5 μm, and the ratio L / D of the length (L) of the shortest side of the film plane to the film thickness (D) was 10,000.

Example 2
The aqueous coating composition used in Example 1 was applied on a glass plate with a painting brush to draw a picture. When the obtained organic / inorganic composite coating film-coated substrate of the pattern was baked for 0.5 hours at a temperature of 500 ° C. in the presence of air, a structural color film made of silica showing a vivid blue color was obtained.

Example 3
The water-based coating composition used in Example 1 was applied on a 15 cm square black tile using a bar coater (# 30). When the obtained coated substrate was baked for 0.5 hours at a temperature of 500 ° C. in the presence of air, a structural color film made of silica showing vivid blue color was obtained.

Example 4
A glass substrate having a size of 2.5 cm × 7 cm was applied to the water-based coating composition used in Example 1 by dipping and pulling up to form a composite coating film on the glass surface. When the obtained composite coating substrate is baked at 500 ° C. for 1 hour in the presence of air, the entire surface is free from defects such as cracks, and a bright blue color is observed when observed from the direction perpendicular to the film surface. A structural color film made of the indicated silica was obtained. This film had an average film thickness of about 2 μm, and the ratio L / D of the length (L) of the shortest side of the film plane to the film thickness (D) was 12,500.

Example 5
The aqueous coating composition used in Example 1 was applied to a 5 cm square polyethylene plate to form a composite coating film on the polyethylene plate. A part of this composite coating film was peeled off from the substrate with drying. This part was grasped with tweezers and peeled off to obtain an independent organic-inorganic composite film. When the obtained film was heated to 800 ° C. in the presence of air, a structural color film made of transparent silica free from defects and showing a bright blue color was obtained. When this cross section was observed with an SEM, an internal structure maintaining a structure in which the particles were closely packed was confirmed (FIG. 8).

Example 6
<Aqueous paint composition containing B-2>
100 parts of an aqueous dispersion in which the concentration of the hollow polymer particles B-2 obtained in Synthesis Example 2 is 25%, 20 parts of a 10% maleic acid aqueous solution, and 100 parts of an isopropanol solution (50%) of the silane oligomer MS-51 are mixed. The mixture was stirred in a bath at 20 ° C. for 2 hours to obtain a milky white aqueous coating composition in a uniform dispersion state.

  A composite coating film obtained by applying the coating composition prepared above on a 2.5 cm × 7.5 cm glass substrate with a bar coater (No. 30) at temperatures of 25, 80, 130, and 180 ° C. for 30 minutes. When cured, a good film free of cracks was obtained. From the SEM observation of the composite coating film surface and cross section obtained at a curing temperature of 25 ° C., a regular arrangement pattern of fine particles was confirmed (FIGS. 9 and 10). Moreover, in the AFM observation of this coating film, the uneven | corrugated pattern by surface particle arrangement appeared clearly (FIG. 11), and the valley distance was 370-400 nm (FIG. 12).

  When the coating substrate of the organic-inorganic composite coating film obtained above was baked at 500 ° C. for 1 hour in the presence of air using an electric furnace, there were no defects such as cracks over the entire surface, and the film surface When observed from the vertical direction, a structural color film made of silica showing a bright green color was obtained. When the observation direction was tilted, a color shift from green to red was observed.

Example 7
A composite coating film coated substrate obtained by applying the aqueous coating composition prepared in Example 6 to a 10 cm × 10 cm glass substrate with a bar coater (No. 30) was used in an electric furnace in the presence of air. When calcination was carried out at 1 ° C. for 1 hour, a structural color film made of silica was obtained which had no defects such as cracks over the entire surface and showed a vivid green color when observed from a direction perpendicular to the film surface. When the observation direction was tilted, a color shift from green to red was observed. This film had an average film thickness of about 10 μm, and the ratio L / D of the length (L) of the shortest side of the film plane to the film thickness (D) was 10,000.

Example 8
100 parts of an aqueous dispersion containing hollow polymer particles (Table 1) synthesized in the same manner as in Synthesis Example 1 and Synthesis Example 2 were treated in the same manner as in Example 1 and Example 6, 20 parts of a 10% aqueous maleic acid solution. 100 parts of an isopropanol solution (50%) of silane oligomer MS-51 was mixed and stirred in a bath at 20 ° C. for 2 hours to obtain a milky white aqueous coating composition in a uniform dispersion state. A composite coating obtained by applying this aqueous coating composition to a 2.5 cm × 7.5 cm glass substrate with a bar coater (No. 30) was cured at 130 ° C. for 30 minutes. A membrane was obtained.

Footnotes in Table 1:
AIBN: 2,2′-azobis (2-amidinopropane) dihydrochloride KPS: potassium persulfate

  When the obtained coated substrate was baked at 500 ° C. for 1 hour in the presence of air, a structural color film made of silica showing a clear and vivid color without cracks and other defects was obtained over the entire surface. It was. These films appeared to change in observation color when the light irradiation direction and the observation direction were changed. Table 2 shows the reflection peak wavelengths obtained by the variable angle spectroscopic measurement of the structural color film. When SEM observation of the structural color film produced using 300 nm particles was performed, a regular porous structure was observed on the surface of the structural color film (FIG. 13).

Example 9
When the same organic-inorganic composite coating film coated substrate as used in Example 8 was baked at various firing temperatures under a nitrogen stream, there was no defect such as cracks over the entire surface, and an opaque and vivid coloration was exhibited. A structural color film made of silica was obtained. These films appeared to change in observation color when the light irradiation direction and the observation direction were changed, and showed a color development different from that obtained by baking in the presence of air. Table 3 shows the respective reflection conditions and the reflection peak wavelengths obtained by the variable angle spectroscopic measurement of the structural color film.

When the Raman spectrum of these structural color films was measured, peaks appeared at 1354 and 1548 cm ⁻¹ , and the presence of carbides in the films could be confirmed. According to the TG-DTA measurement, the abundance of the carbides after firing at 400, 450, and 500 ° C. was approximately 15%, 20%, and 33%, respectively. When SEM observation of the structural color film produced using 300 nm particles was performed, a regular porous structure was observed on the surface of the structural color film (FIG. 14).

Example 10
100 parts of an aqueous dispersion containing hollow polymer particles (Table 1) synthesized in the same manner as in Synthesis Examples 1 and 2 were mixed with 20 parts of a 10% maleic acid aqueous solution, silane oligomer MS-51 and glycidoxypropyltrimethoxy. Silane (GPTMS) mixed silica source (mass ratio MS-51 / GPTMS = 2) 100 parts of an isopropanol solution (50%) is mixed and stirred in a bath at 20 ° C. for 2 hours to give a milky white aqueous solution in a uniform dispersion state. A coating composition was obtained. A composite coating obtained by applying this aqueous coating composition to a 2.5 cm × 7.5 cm glass substrate with a bar coater (No. 30) was cured at 130 ° C. for 30 minutes. A membrane was obtained.

  When the obtained coated substrate is baked for 1 hour at various calcination temperatures in the presence of air or in a nitrogen stream, the structure is made of silica and has no defects such as cracks over the entire surface and shows vivid color development A color film was obtained. These films appeared to change in observation color when the light irradiation direction and the observation direction were changed. The reflection peak wavelengths obtained by the variable angle spectroscopic measurement of the structural color film are shown in Table 4 (firing in the presence of air) and Table 5 (under a nitrogen stream).

Comparative Example 1
A coating liquid having the same composition as in Example 1 was prepared except that the hollow polymer particles were not used, and a composite coating film was obtained by applying the coating liquid to a glass substrate with a bar coater (No. 30). When dried at 25 and 80 ° C., many cracks were generated in the film, and the film was detached from the substrate.

Comparative Example 2
Spin a 20% by weight dispersion of core-shell fine particles with a non-hollow core of polystyrene with a diameter of 250 nm and a cross-linked poly (N-isopropylacrylamide) shell layer with a thickness of 50 nm on a 2.5 cm square glass substrate. The film was spin-coated for 10 seconds at a coater rotation speed of 1000 rpm to obtain a film in which fine particles were three-dimensionally arranged. This film is immersed in a petri dish with a diameter of 5 cm containing tetraethoxysilane for 12 hours, and the sol-gel reaction in the shell layer proceeds to solidify the three-dimensional periodic structure of fine particles on the entire surface of the glass substrate. Film was obtained. When this film was heated and baked at 500 ° C., a structural color film showing a vivid iris color was obtained, but cracks occurred on the film surface, and strip-like peeling with a width of several mm occurred.

Comparative Example 2
A 20% by weight dispersion of core-shell type fine particles having a non-hollow core of polystyrene having a diameter of 250 nm and a crosslinked poly (N-isopropylacrylamide) shell layer having a thickness of 50 nm is applied to a 5 cm square glass substrate with a bar coater ( No. 30) to obtain a film in which fine particles are three-dimensionally periodically arranged. When this film is immersed in a petri dish with a diameter of 10 cm containing tetraethoxysilane for 12 hours and the sol-gel reaction is allowed to proceed in the shell layer, the film peels off in a strip shape with a width of several mm from the surface of the glass substrate. did.

3 is an SEM observation image showing the form of hollow polymer particles obtained in Synthesis Example 1. It is a SEM observation image showing the hollow form observed by crushing the hollow polymer particle obtained in Synthesis Example 1. 4 is an SEM observation image showing the form of hollow polymer particles obtained in Synthesis Example 2. It is a SEM observation image showing the hollow form observed by crushing the hollow polymer particles obtained in Synthesis Example 2. 2 is an SEM observation image showing the form of a 25 ° C. cured composite coating surface obtained in Example 1. FIG. 2 is an SEM observation image showing the form of the 80 ° C. cured composite coating film surface obtained in Example 1. FIG. 2 is an SEM observation image showing a form of a cross section of a 25 ° C. cured composite coating film obtained in Example 1. FIG. 6 is an SEM observation image showing a form of a cross section of an 800 ° C. fired structural color film obtained in Example 5. FIG. It is a SEM observation image showing the form of the 25 degreeC hardening composite coating film surface obtained in Example 6. FIG. It is a SEM observation image showing the form of a 25 ° C hardening compound coat section obtained in Example 6. 7 is an AFM observation image of the surface of a 25 ° C. cured composite coating obtained in Example 6. FIG. 7 is an AFM observation cross-sectional profile of a 25 ° C. cured composite coating film obtained in Example 6. In Example 8, it is a SEM observation image showing the form of the surface of the structural color film produced using the particle | grains with a particle size of 300 nm. In Example 9, it is a SEM observation image showing the form of the surface of the structural color film produced using the particle | grains with a particle size of 300 nm.

Claims (14)

(1) On a solid substrate (X1) having a heat resistance of 250 ° C. or higher, a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a), monodisperse hollow polymer particles (B), A step of applying a water-based coating composition containing, to obtain a coated substrate,
(2) A step of firing the coated substrate obtained in (1),
A method for producing a structural color film, comprising: The method for producing a structural color film according to claim 1, wherein the solid substrate (X1) is glass, metal or inorganic oxide. The method for producing a structural color film according to claim 1 or 2, wherein the metal alkoxide (a) is a metal alkoxide having a trivalent or higher hydrolyzable functional group. An aqueous coating composition is used in which the use ratio of the hollow polymer particles (B) and the metal alkoxide (a) is in the range of 70/30 to 5/95 by mass ratio represented by (B) / (a). The manufacturing method of the structural color film in any one of Claims 1-3. (1) An aqueous coating composition containing a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a) and monodisperse hollow polymer particles (B) on a solid substrate (X2). Applying a coating to obtain a coated substrate,
(2) The process of peeling a coating film from the coating base material obtained by (1),
(3) A step of firing the release coating obtained in (2),
A method for producing a structural color film, comprising: 6. The method for producing a structural color film according to claim 5, wherein the solid substrate (X2) is polyethylene or polyvinyl chloride. The method for producing a structural color film according to claim 5 or 6, wherein the metal alkoxide (a) is a metal alkoxide having a trivalent or higher hydrolyzable functional group. An aqueous coating composition is used in which the use ratio of the hollow polymer particles (B) and the metal alkoxide (a) is in the range of 70/30 to 5/95 by mass ratio represented by (B) / (a). The manufacturing method of the structural color film in any one of Claims 5-7. A structural color film-coated substrate obtained by coating a solid substrate (X1) having a heat resistance of 250 ° C. or higher with a structural color film, the structural color film having a metal oxide (A) as a main constituent component A structural color film-coated substrate, comprising a matrix having an inverse opal structure, wherein the length of the shortest side of the film plane with respect to the film thickness is 1,000 times or more. A coating film obtained by applying an aqueous coating composition in which the structural color film contains a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a) and monodisperse hollow polymer particles (B) The structural color film-coated substrate according to claim 9, which is fired. The structural color film-coated substrate according to claim 10, further comprising a metal alkoxide (a) and / or a carbide (C) derived from the hollow polymer particles (B) in the structural color film. A structural color film comprising a matrix having an inverse opal structure containing a metal oxide (A) as a main constituent, and having a length of the shortest side of the film plane with respect to the film thickness being 1,000 times or more. A coating film obtained by applying an aqueous coating composition in which the structural color film contains a metal oxide (A) obtained by a sol-gel reaction of a metal alkoxide (a) and monodisperse hollow polymer particles (B) The structural color film according to claim 12, which is fired after being peeled from the substrate. The structural color film according to claim 13, wherein the structural color film further contains a metal alkoxide (a) and / or a carbide (C) derived from the hollow polymer particles (B).