WO2012055105A1

WO2012055105A1 - Method for manufacturing structural color object

Info

Publication number: WO2012055105A1
Application number: PCT/CN2010/078188
Authority: WO
Inventors: Norimasa Fukazawa; Renhua Jin; Ruiyu Si; Meijuan Liu
Original assignee: Dic Corporation
Priority date: 2010-10-29
Filing date: 2010-10-29
Publication date: 2012-05-03
Also published as: TW201235387A; JP5435171B2; JP2013522420A

Abstract

The present invention relates to a manufacturing method characterized in that, in the manufacture of the structural color object based on the regular arrangement of the polymer particles, the processes of purification and isolation of the polymer particles beforehand are not required and, the low cost continuous manufacturing from the manufacture of the polymer particles to the manufacture of the structural color object can be realized. The present invention also relates a simple method for manufacturing relatively large object also showing the "play of colors? More specifically, the structural color object formed by organic-inorganic composite can be obtained by carrying out the sol-gel reaction having the aqueous dispersion of the copolymer particles obtained by polymerizing the acrylate monomers in water at specific concentration and the metal alkoxides as raw materials.

Description

METHOD FOR MANUFACTURING STRUCTURAL COLOR OBJECT

FIELD OF THE INVENTION

A simple method for manufacturing an object which is relatively large in size and shows structural color is related. More specifically, a method for manufacturing the structural color object is related in which after the manufacture of the monodisperse polymer particles by soap-free emulsion-polymerization, the reaction solution of the polymer particles is used as the aqueous composition formed by mixing with metal alkoxide compounds without special purification process, and by which structural color object of arbitrary shape can be obtained easily through continuous manufacturing process.

DESCRIPTION OF THE PRIOR ART

The common coloring materials contain colorants such as dyes or pigments inside, and the colors of them depend on the light absorption or light reflection based on the molecular structure of colorants. Such coloration derived from colorants is often subjected to color changing or fading because of chemical reactions by absorbed light energy. On the other hand, the coloration derived from the optical effects such as refraction, diffraction, scattering or interference, which based on the physical structure of the materials have advantage on maintaining the colors. This is because the absence of the light energy absorption by the materials. The colors based on the physical structures are kept as long as the structures are maintained. The colors based on the optical effects, such as light diffraction, scattering, and interference, etc., are called as "structural color", as are well known as the coloration phenomenon of the gem opals or the wings of the morpho-butterfly. "Structural colors" are realized and characterized by their vivid coloration with metallic luster. "Structural colors" are also characterized by color shift by changing the relative angles between the light source and materials and/or the observation angels and materials. These anomalous characters of structural colors are considered as the colors of "high designablility". Of all various structural color materials, gem opals have colors of attractive and high designability. On the gem opals, even in the same observation angle, various colors can be observed, which is called as "play of colors". This is because colloidal crystals of hundreds nanometer size of silica particles exist, and they have many different orientations in opals.

In order to realize this structural color materials in industry, the realization of the regular arrangement of the hundreds nanometer size of particles or pores is required. As such method, for example, the method of arranging the particles by the electrostatic repulsion caused by their surface electric charge, and the method of removing solvents from the dispersion of the particles and then drying are proposed. In these methods, structural color materials have not been used for practical articles of high designability, since further research on fixation of the arranged particles is required or the structural color is only demonstrated in transparent vessels.

Besides, the method of constructing regular pores in the object by removing the particles after filling in other materials among these arranged particles to fix them is also provided. However, in this method, since the tiny spaces among the closely packed particles have to be filled by organic or inorganic materials, if once the spaces of the surface region of the object of arranged particles are filled up by these materials, the filling materials can't penetrate in deeper., As a result, there raises the problem that the spaces among the particles are not totally filled up and an uniform periodic structure can not be formed. Furthermore, since the unfilled-in materials will form into un-periodic continuous layers, the object prepared in this method have inhomogeneous structure in which the parts showing periodic structure and parts having no periodic structure are mixed. Also, since the template wherein the particles are contacting each other is used, resultant objects have weak structures in which all the pores are connected at the contact points. And cracks caused by the contraction during the calcination process make it difficult to maintain the template periodic structures and it difficult to prepare structural color objects of large volume.

As one of the methods to solve such inhomogeniety and strength problem, the present inventors had disclosed the following technology

(e.g. referring to patent literature 1): after dispersing the core-shell particles having rigid polymer core and surrounding cross-linked hydrophilic polymer layer as the shell into water or hydrophilic solvent, metal alkoxides are added and preparing the organic-inorganic composite periodic object by sol-gel reaction of the alkoxides. By successive calcination of it, the polymer cores are removed, and the periodic objects of metal oxides having inverse opal structure are obtained. In this technology, since the particle-arranged film is not completely dried and then the cross-linked hydro-gel shell layers of arranged core-shell polymer particles work as the reaction space of the sol-gel reaction, thicker metal oxide layers, which has homogeneous thickness all over the object, can be easily formed among the particles. And compared to the prior methods, robust object of structural colors can be obtained.

Further, as a method to obtain structural color film of large area, the method using the aqueous coating composition comprising monodisperse hollow polymer particles and metal oxides obtained from sol-gel reaction of the metal alkoxides is also disclosed

(e.g. referring to patent literature 2). According to this method, the hollow polymer particles are closely packed and the metal oxide sol cure along them during the formation process of the film, the organic-inorganic composite coating film having internal periodic hollow structure and having semi-sphere periodic surface profile can be formed by simple coating of the aqueous composition on the solid substrate surface. Further since the internal structure of the coating film is not destroyed even after calcination at high temperature and the periodic porous structure can be maintained, the coating films of large area demonstrating structural colors can be obtained.

However, complex and time-consuming purification process is indispensable for obtaining such specific particles, the core-shell particles having special structure and the monodisperse hollow polymer particles which are indispensable raw materials to obtain above mentioned robust structural color object or the structural color films of large area,. For example, in the manufacture of the core-shell particles, homopolymer of the hydro-gel is also formed during the synthetic process of cross-linked hydro-gel shell layer. And then, this homopolymer has to be removed for constructing structural color object. While, in the manufacture of the hollow polymer particles, a part of un-reactive monomers (especially the water-soluble monomers) is remained and the homopolymers polymerized from the water-soluble monomers often exist in the system, since this particle preparation method is utilizing the difference of reactivity between the water-soluble monomers and the water-insoluble monomers. Removing of these impurities is also required. Since the byproduct to be removed also contains polymers of certain molecular weight, the purification can't be achieved by simple filtration process only, and time and cost consuming purification method, such as micro filtration, ion exchange, dialysis, centrifuging etc., has to be done separately or combined. Furthermore, in order to obtain the uniform-sized particles of high dispersity, monomers can't be polymerized at high concentration. As a result, there also exists the problem that enough amount of particles can't be obtained in one batch.

Prior art literature

Patent literature

Patent literature 1 : Japanese published unexamined application No.2006-213534 Patent literature 2: Japanese published unexamined application No.2009- 195794

DISCLOSURE OF THE INVENTION Technical problems to be solved

In view of above problems, the technical solution of the present invention lies in that providing a manufacturing method characterized in that, in the manufacture of the structural color object based on the regular arrangement of the uniform-sized polymer particles, the purification process of the polymer particles is not required, and then the low cost continuous manufacturing process, from the preparation of the uniform-sized polymer particles to the manufacture of the object of structural color object, can be realized. And this invention also provides a simple method for manufacturing relatively large structural color objects which also demonstrates "play of colors".

Technical solution

To solve the above mentioned problems, after comprehensive research, the present inventors have found that the aqueous dispersion of monodisperse copolymer particles of high concentration can be easily obtained by emulsion-polymerization of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent in aqueous solvent at relatively high concentration, and the dispersion can be suitably applied in the aqueous composition to obtain the structural color object even without purification process. Further, the following phenomenon is found and upon which the present application is accomplished: since the periodic structure of the organic-inorganic composite object obtained by curing the aqueous composition won't be destroyed even after calcination at high temperature and the periodic porous structure is formed by removing the organic component, the structural color object shows vivider colors and "play of colors" by calcination. Also according to such method, in addition to two dimensional structural color films, three dimensional structural color objects which is relatively large can be obtained steadily. That is, the present invention provides a method for manufacturing the structural color objects formed by organic-inorganic composite, which is characterized by comprising the following steps:

(1) in aqueous solvent radically polymerizable monomers, the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, are quantitatively polymerized by soap-free polymerization at the concentration in the range of 10-30 mass% (summation of the mass (al) and (a2) against the total mass of the reactive composition) to obtain an aqueous dispersion of copolymer particles (A);

(2) preparing an aqueous composition containing the aqueous dispersion of copolymer particles (A) obtained from step (1), metal alkoxides and/or the partially condensed compounds thereof (B) and acid catalysts (C);

(3) curing the aqueous composition obtained from step (2) on a substrate or in a vessel. Moreover, the present invention also provides a method for manufacturing the structural color object composed of metal oxide as a main constituent, which is characterized by comprising the following steps:

(1) in aqueous solvent, radically polymerizable monomers, the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, are quantitatively polymerized by soap-free polymerization in the range of 10-30 mass% (summation of the mass (al) and (a2) against the total mass of the reactive composition) to obtain an aqueous dispersion of copolymer particles (A);

(2) preparing an aqueous composition containing the aqueous dispersion of copolymer particles (A) obtained from step (1), metal alkoxides and/or the partially condensed compounds thereof (B) and acid catalysts (C); (3) curing the aqueous composition obtained from step (2) on a substrate or in a vessel.

(4) calcination of the cured material obtained from step(3).

The advantages of the invention

The structural color object of the present invention has large volume of arbitrary shape and shows vivid structural color with "play of colors". It can be suitably used in the fields of artistic design and decoration, etc. Also, by forming into a flake or spherical shape, the object can be used in inks or coatings as a structural color pigment. Moreover, it can also be used in the fields of photonic crystals or various sensors which take advantage of the light interference, anti-counterfeiting, the anchoring of biomolecules or catalyst by exploiting their porous structures, dye-sensitized solar cells, fuel cells and heat insulation, soundproof materials, etc.

Brief explanation of the drawings

Fig.1 is the SEM image of the copolymer particles Al obtained in Example 1.

Fig.2 is the appearance image of the object obtained in Example 2 after calcination.

Fig.3 is the specular reflection spectrum of the perpendicular direction of the disc plane of the object obtained in Example 4.

Fig. 4 is the variable-angle specular reflection spectrum of the object obtained in Example 4.

Fig.5 is the solid-state ¹³C-NMR spectrum of the object obtained in Example 4 (calcination at 350 °C).

Fig. 6 is the cross-sectional SEM image of the object obtained in Example 4 (calcination at 350 °C). Fig. 7 is the cross-sectional SEM image of the object obtained in Example 5 (calcination at 600 °C).

Fig. 8 is the solid-state ¹³C-NMR spectrum of the object obtained in Example 5 (calcination at 600 °C).

Fig. 9 is the cross-sectional SEM image of one cross-section of the object obtained in Example 6 (calcination at 500 °C, under nitrogen flow)

Fig.10 is the cross-sectional optical microscope image of the object obtained in Example 6 (calcination at 500 °C, under nitrogen flow)

Fig. 11 is the cross-sectional SEM image that shows the dislocation line (dashed line) of the object obtained in Example 6 (calcination at 500°C, under nitrogen flow).

Fig. 12 is the images that show the "artificial nail" vessels in Example 7 and the appearance of the calcined object (350 ^°C) made by using the artificial nails.

Fig. 13 is the specular reflection spectrum of the perpendicular direction of the positive chamber of the "artificial nail" shape object obtained in Example 7 (after calcination at 350°C)

Fig.14 is images that show the "Silicon Multimat" which is used as the vessel in Example 8 and the appearance of the calcined objects obtained (calcination at 350°C).

Fig.15 is the image of the appearance of the objects manufactured by using vessels of various shapes in Example 9.

Fig. 16 is the stereomicroscope images which show the appearance image of plastic prism array (a) used as the vessel in Example 10, the appearance images of the calcined object (after calcination at 350°C) made by using the array observed from the top (b) and from the lateral direction (c) (after calcination at 350°C).

Fig.17 is the image that shows the appearance of the object (calcination at 350°C) obtained by using PFTE sheet in Example 11.

Fig. 18 is the image that shows the spherical appearance of the object (calcination at 350°C) obtained by using silicone oil in Example 12.

Fig. 19 are the specular reflection spectrums of the perpendicular direction of the objects (calcination at 350 ^°C) obtained by changing the type of the silane coupling agent in Example 20.

Fig. 20 are the cross-sectional SEM images of the objects (calcination at 350 ^°C ) obtained by changing the type of the silane coupling agent in Example 20.

Fig.21 is the image the shows the appearance and the transparency of the obtained in Example 22.

PREFERRED EMBODIMENT OF THE INVENTION

The method for manufacturing the structural color object of the present invention can obtain the object formed by organic-inorganic composite and is characterized by comprising the following steps:

(1) in aqueous solvent, radically polymerizable monomers, the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, are quantitatively polymerized by soap-free polymerization at the concentration in the range of 10-30 mass% (summation of the mass (al) and (a2) against the total mass of the reactive composition) to obtain an aqueous dispersion of copolymer particles (A);

(3) curing the aqueous composition obtained from step (2) on a substrate or in a vessel. The term "quantitatively polymerized by soap-free emulsion-polymerization" used herein means a state of soap-free emulsion-polymerization reaction in which the surfactant of any kind is not used, and the theoretical yield calculated from the amount of the monomers used in this reaction is consistent with the actual yield of particles obtained after the reaction in the range of the determination variation (about ±3%), and the existence of the monomers are not confirmed in the aqueous solvent after the reaction according to the NMR spectroscopy.

Moreover, by the calcination process of the above obtained object, removing partially or all of the internal organic components is achieved, and the structural color object comprising metal oxide as a main constituent can be obtained.

The organic-inorganic composite object obtained by the above mentioned process shows the structural colors by the regular arrangement of the monodisperse-sized copolymer particles (A) consisted of the copolymers of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent in the matrix of metal oxides formed by sol-gel reaction (hydrolysis-condensation reaction) of the metal alkoxides and/or the partially condensed compounds thereof (B). Moreover, the arrangement of the particles is achieved even in three dimensional (colloidal crystal), and in a part of the three dimensional arrangement linear or planar dislocation is exist, and thus objects also show the "play of colors". Furthermore, the matrix of the metal oxides means the structure constructed by the continuous phase of the metal oxide materials containing mainly silica or silicon oxide in the whole object. Moreover, the "monodiseprse-sized particles" means the variation coefficient of the diameter of copolymer particles (A) determined in the aqueous solvent by dynamic light scattering method or the diameter obtained by observing the particles using scanning electron microscope (SEM) after drying is below 0.2. Also, if the object formed by the organic-inorganic composite is calcined, the porous object of metal oxides, which are generated by the sol-gel reaction (hydrolysis-condensation reaction) of the metal alkoxides and/or the partially condensed compounds thereof (B) as a main constituent, can be obtained since the internal copolymer particles (A) are removed partially or all of them by thermal decomposition. At this time, in the case that the metal alkoxides and/or the partially condensed compounds thereof (B) is not completely reacted (hydrolysis-condensation reaction) and some of the alkoxyl groups are left in the object, these alkoxyl groups are decomposed and partially or totally removed. The porous objects obtained thereby show structural colors, since the pores of the calcined object maintain the regular arrangement as same as before calcination. Also, the pores are arranged even in three dimension and in a part of the three dimensional arrangement of the pores, linear or planar dislocation is exist, and thus the objects show the "play of colors".

[Step 1 : the synthesis of the copolymer particles (A)]

The first step of the present method is to prepare the monodisperse-sized copolymer particles (A), more specifically, is to quantitatively polymerize the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent in the aqueous solvent at the concentration in the range of 10-30 mass% (summation of the mass (al) and (a2) against the total mass of the reactive composition) by soap-free emulsion polymerization. The solvent used here is preferably water alone, but may also contain organic solvents, like methanol etc. which can be mixed with water by any ratio.

Although in the patent literature [2], the same monomers are used for emulsion-polymerization in order to obtain the hollow polymer particles, the difference with the present invention lies in that, the total mass of the monomers in the aqueous solvent is set at as high as 10~30mass%. That is, as in the manufacture of the hollow polymer particles, the spontaneous formation of hollow structure is required. To achieve this, the polymerization of a part of water-soluble monomers is conducted to obtain homopolymers of certain molecular weight, and the polymerization of the water-insoluble monomers is initiated from the reactive ends of these homopolymers to obtain molecular chains which function as a polymer surfactant. And by the function of this polymer chains, vesicle-like bi-layer particles formed. In order to manufacture the monodisperse-sized particles, which won't cause aggregation and have high stability of dispersion by utilizing above mechanism, the monomer concentration in the aqueous solvents shouldn't be increased. More specifically, the manufacture should be carried out at about lmass% ~ at most 5mass%. Also, there exists the problem that water-soluble monomers are remained in the system or the homopolymers of the water-soluble monomers are polymerized as a by-product.

On the other hand, in the present invention, the copolymerizaion reaction of the water-soluble monomers (al) and water-insoluble monomers (a2) is carried out by setting the concentration of the monomers in the aqueous composition at 10~30mass %, preferably at 10~20mass%. In such a copolymerizaion reaction system, the reaction rates of the water-soluble monomers and the water-insoluble monomers, that is the consuming rates of the monomers, have great difference. The consuming rate of the water-insoluble monomers is faster than that of the water-soluble monomers. This difference results in the decrease of the transformation rate form monomer to polymer of the water-soluble monomers, and even the transformation rate of the water-soluble monomers is increased, they grow as homopolymers rather than the constituent of the particles, and thus the manufacture efficiency of the particles is decreased. In order to prevent these unfavorable problems and to polymerize quantitatively, the method that the monomers are added successively along with the progress of the polymerization rather than adding all the amount of monomers at a time is preferred. By adding the monomers successively, the water-soluble monomers (al) are consumed quantitatively and the remaining of the monomers and the formation of the homopolymers of water soluble monomers are prevented, that is, the formation of the polymers that don't constitute the particles is prevented. The method of successive adding includes for example, the method of continuous adding the total amount of the monomers containing the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent dropwise by small amount, the method of dividing the monomers into several fractions and adding with time intervals, and also the method of dissolving the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent into aqueous solvent beforehand and adding the total amount of the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent dropwise by small amount each time, the method of dissolving the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent into aqueous solvents beforehand, dividing the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent into several fractions and adding with time intervals. Wherein the method of dissolving the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent beforehand, dividing the radically polymerizable water-insoluble monomers (a2) including the (meth)acrylate as a main constituent into several parts and adding with time intervals is more preferred. Moreover, at in the case of dividing the monomer groups into several fractions, adding by small amount successively rather than all at a time is preferred. In the case that the monomers are divided into several fractions and added separately, all through the adding times can be selected properly depending on the type of the monomers and reaction time, from the practical viewpoint, the adding times can be 2—10 times, preferably 2-5 times. In the case that abovementioned successive emulsion-polymerization is used, that "the concentration of the monomers in aqueous solvents is 10~30mass%" means the ratio of the total mass of monomers added is 10-30 mass % against to the total mass of the aqueous composition. Furthermore that "the reaction is taking place quantitatively and there is no remaining monomers in the system after the reaction is over" can be confirmed from the experimental data such that the particle concentration of the resultant particle dispersion is almost equal to the concentration of the monomers used, and can also be confirmed by NMR spectroscopy of the aqueous solvent used in the reaction.

The preferable ratio of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrytlate as a main constituent, which is indicated by the mole ratio (a2)/ (al), is in the range of 3.5-12, since the copolymer particles (A) can be obtained at high yield. A more preferable range indicated by the mole ratio (a2)/ (al) is 3.5-7.

Since the particles (A) obtained by the present invention are polymerized in the aqueous solvent, the hydrophobic parts are spontaneously tend to gather inside the particles by the hydrophobic interaction of the structure derived from the water-insoluble monomers (a2) and the molecular chains of hydrophilic parts mainly exist in the outside of the particles which is in contact with the aqueous solvent. That is, the copolymer particles (A) are particles that the inside of which is mainly hydrophobic and the outside of which is mainly hydrophilic. Also, this is the method of emulsion polymerization of the water-soluble monomers (al) and the water-insoluble monomers (a2) in the aqueous solvent, and the monodisperse-sized particles are obtained by the spontaneous formation of the particles. The aggregation of these particles can be prevented even at high concentration, since the hydrophilic chains stay among the adjacent particles. Further, since the polymer chains derived mainly from the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent locate outside of the particles, they can function as the a site for concentration and hydrolysis-condensation reaction of the metal alkoxides and/or the partially condensed compounds thereof (B). From this, the regular arrangement of the particles is realized as discussed below.

As to the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent, the "water soluble" means the (al) monomers can dissolve in distilled water more than 1.0mass% at 25 ^°C and more preferably (al) monomers are able to be mixed with water by any ratio. Also, "have...as a main constituent" means the content of (meth)acrylamide in the radically polymerizable water-soluble monomers (al) is more than 60 mole%, preferably more than 80mole%, and most preferably more than 95mole%.

The above mentioned (meth)acrylamide, includes for example, acrylamide, N-substituted (meth)acrylamide or N-disubstituted (meth)acrylamide such as N-ethyl acrylamide, N-ethyl metacrylamide, N-isopropyl acrylamide, N-isopropyl metacrylamide, N-n-propyl acrylamide, N-n-propyl metacrylamide, N-cyclopropyl acrylamide, N-cyclopropyl metacrylyamide, Ν,Ν-dimethyl acrylamide, Ν,Ν-diethyl acrylamide, Ν,Ν-dimethylaminopropyl acrylamide, N-methyl-N-ethyl acrylamide, N-methyl-N-isoprpyl acrylamide, N-methyl-N-n-propyl acrylamide, and also N-hydroxy ethyl acrylamide, acryloyl morpholine, N-vinyl pyrolidone, diacetone acrylamide, Ν,Ν'-methylene bisacrylamide, etc. These (meth)acrylamide can be used separately or by mixing more than two of them.

Moreover, water-soluble monomers are able to be added into (meth)acrylamide and be used without special limitation as the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent, as long as they are radically polymerizable and water-soluble. Those having for example, amino group, oxyalkylene chain, cyano group, acid anhydride group etc., those having for example carboxyl group, hydroxyl group, sulfonic acid group, phosphoric acid group etc., and those having the alkaline metal salts and ammonium salts thereof in their structure can be used. More specifically, the water-soluble monomers having amino group include for example, allyl amine, N, N-dimethyl amino ethyl acrylate, dimethyl amino ethyl methacrylate, etc. can be used preferably. Also, the water-soluble monomers having carboxyl group include, for example, acrylic acid, methacrylic acid, maleic acid, etc. And the water-soluble monomers having hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 1 ,4-cyclohexane dimethanol monoacrylate, methoxy polyethyleneglycol acrylate, etc. Water-soluble monomers having sulfonic acid group include styrene sulfonic acid, styrene sulfonic acid sodium salt, styrene sulfonic acid lithium salt, styrene sulfonic acid ammonium salt, styrene sulfonic acid ethyl ester, styrene sulfonic acid cyclohexyl ester, 2-acrylamide-2-methyl propane sulfonic acid, etc. Further, quaternarizd monomers obtained by quaternarizing the monomers formed by reacting vinyl pyridine or glycidyl methacrylate with organic amine can also be used. Single or more than two of these water-soluble non-(meth)acrylamide monomers can be mixed into (meth)acrylamide to use.

As the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, various acrylate monomers or methacrylate monomers can be used as long as they have the group that is able to copolymerize with the water-soluble monomers (al) including (meth)acrylamide as a main constituent. The term "water-insoluble" used herein means that the solubility of the monomers (a2) into distilled water is less than 0.5mass% at 25 ^°C .

The acrylate monomer includes for example, butyl acrylate, lauryl acrylate, cyclohexyl acrylate, phenyl acrylate, isobornyl acrylate, glycidyl acrylate, tert-butyl-a-trifluoromethyl acylate, 1-adamantyl-a-trifluoromethyl acrylate, (3-methyl-3-oxetanyl)methyl acrylate, acryloylpropyl trimethoxysilane, acryloylpropyl triethoxysilane, methyl acrylate, ethyl acrylate, etc.

Also, the methacrylate monomer includes, for example, 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, metacryloyl propyl trimethoxy silane, metacryloyl propyl triethoxy silane, etc.

These radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent can be used separately or by mixing more than two of them. The (meth)acrylate used herein afterward, unless noted otherwise, means the general term including acrylate alone, methacrylate alone and the mixture thereof.

In the above-mentioned radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, the monomer having cyclic ester structure such as the glycidyl (meth)acrylate, oxetane (meth)acrylate etc., can be used preferably, since this type of monomer is considered to be able to form intra-chain or inter-chain cross-linking during or after the formation of the copolymer with the radically polymerizable water-soluble monomers (a2), and this cross-linking improves the strength and stability of the obtained copolymer particles (A ).

the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, include bifunctional di(meth)acrylate for example, polyethylene di(meth)acrylates such as ethylene di(meth)acrylate, diethylene di(meth)acrylate, triethylene di(meth)acrylate etc., polypropylene di(meth)acrylate such as propylene di(meth)acrylate, dipropylene di(meth)acrylate, tripropylene di(meth)acrylate etc., and glycerole di(meth)acrylate. These monomers can be used separately or by combining more than two of them. In the case that these di(meth)acrylates are used, they are preferably used with mono-functional (meth)acrylate to prevent the aggregation of the obtained copolymer particles, and it is especially preferred that the usage ratio of di(meth)acrylates to mono -functional (meth)acrylate indicated by mole ratio in radically polymerizable monomers (a2) including (meth)acrylate as a main constituent is over 0.7.

As the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, besides (meth)acrylate, one or more than two of the monomers of styrene compound, for example, vinyl ester, vinyl ether, bisvinyl compound etc., can be used by mixed into (meth)acrylate. At this time, from the viewpoint of facile preparation of the copolymer particles of the present invention, it is especially preferred that the usage ratio of styrene compound indicated by mole ratio in the radically polymerizable water-insoluble monomers (a2) is less than 0.4 and more preferably less than 0.2.

The styrene compound is a compound that has styryl group, including for example, styrene, a-methyl styrene, vinyl toluene, a-chloro styrene, o-, m-, p-chlorostyrene, p-ethyl styrene, p-tert-butoxy styrene, m-tert-butoxy styrene, p-acetoxy styrene, p-(l-ethoxyethoxy) styrene, p-methoxy styrene, styryl trimethoxy silane, styryl triethoxy silane, vinyl naphthalene, vinyl biphenyl, vinyl anthracene, vinyl pyrene, etc.

The vinyl ester includes for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl mono-chloroacetate, vinyl pivalate, vinyl butylate, etc.

The vinyl ether includes for example, 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, cyclohexanedimethanol monovinyl ether, 1, 4-butanediol divinyl ether, nonanediol divinyl ether, cyclohexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylpropane trivinyl ether, pentaerythritol tetravinyl ether, phenyl vinyl ether, etc.

As the aqueous solvent used in the emulsion-polymerization, besides using water alone, mixed solvents formed by adding one or more than two of lower alcohols such as methanol, ethanol, isopropanol etc., polyhydric alcohols such as ethylene glycol, propylene glycol, butane diol, diethylene glycol, triethylene glycol etc., ketones such as acetone, methyl ethyl ketone etc., ethers such as tetrahydrofuran etc., into water can also be used.

When a mixed solvent is used, any mixing ratio can be used as long as the water-soluble polymerization initiator discussed below and the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent are soluble in the solvent and the solubility of the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent is less than 0.5mass%. While the mixing ratio can be selected properly according to the purpose, the ratio of water is preferably over 50mass% and especially preferred over 80mass% in order to achieve the high initiating efficiency of polymerization.

The emulsion-polymerization is preferably carried out by using water-soluble polymerization initiator, and persulfate or azo-compound having amino group is especially preferred, including for example, potassium persulfate (KPS), ammonium persulfate (APS), 2,2'-azobis(2-amidino propane) dihydrochloride,

2,2'-azobis[2-(2-imidazoline-2-yl)propane]dihydrochloride,

2,2'-azobis[2-(2-imidazoline-2-yl)propane]disulfate dihydrate, 2,2'-azobis[N-(2-carboxyethyl)2-methyl propionamide] , 2,2'-azobis( 1 -imino- 1 - pyrrolidino-2-methylpropane)dihydrochloride,

2,2'-azobis {2-[ 1 -(2-hydroxyethyl)-2-imidazoline-2-yl]propane} dihydrochloride ,

2,2'-azobis[2-2(imidazoline-2-yl)propane],

2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide, 2,2'-azobis {2-methyl-N-[ 1 , 1 -di(hydroxymethyl)-2-hydroxyethyl]propionamide} , 2,2'-azobis(2-methylbutane amide oxime)dihydrochloride tetrahydrate, sodium metabisulfite, etc. These water-soluble polymerization initiators can be used separately or by mixing more than two of them.

The usage ratio of these water-soluble initiators can be selected from the range of 0.05~5mass% of the total mass of monomers (sum of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent). However, to improve the efficiency of the polymerization and to prevent the aggregation of the copolymer particles (A), it is more preferred that the ratio is selected from the range of 0.1~3 mass%.

The copolymer particles (A) of the present invention can be synthesized efficiently by soap-free emulsion-polymerization without using dispersion stabilizer. However, various appropriate dispersion stabilizers can also be used simultaneously without hindering the formation of the polymer particles. That is, the emulsion-polymerization using dispersion stabilizer can also be carried out. The dispersion stabilizer includes for example, anionic surfactant, non-ionic surfactant, cationic surfactant, zwitterionic-surfactant, organic suspension protectant, etc. And from the viewpoint of preparing the highly stable dispersion of the copolymer particles (A), the anionic surfactant or the cationic surfactant is more preferable.

The anionic surfactant includes for example, salts of the rhodinic acid, such as rhodinic acid potassium salt, rhodinic acid sodium salt etc., sodium salt or potassium salt of fatty acid such as potassium oleate, potassium laurate, sodium laurate, sodium stearate, potassium stearate etc., salt of sulphate of the fatty alcohol such as lauryl sodium sulphate, salts of alkyl aryl sulfonic acid such as dodecyl benzene sulfonic acid sodium salt, etc.. The non-ionic surfactant includes for example, alkyl ester of polyethylene glycol, alkyl ether, alkyl phenyl ether, etc.

The cationic surfactant includes, for example, the surfactants of alkyl trimethyl ammonium salt, dialkyl dimethyl ammonium salt, alkyl dimethyl benzyl ammonium salt, amine salt.

The zwitter ionic surfactant includes, for example, alkyl amino fatty acid salt, alkyl betaine, alkyl amine oxide, etc.

These dispersion stabilizers can be used separately or by combining more than two of them depending on the requirement. In the use of the dispersion stabilizer, in order to prevent the aggregation of the obtained copolymer particles (A), usage of ionic-surfactant or non-ionic surfactant that has the same electric charge as the surface electric charge of the particles which are given by the water-soluble polymerization initiator is preferred.

The usage amount of the dispersion stabilizer can be determined properly depending on the requirement. If the amount is too much, the purification procedure to remove the excessive dispersion stabilizer is required and thereby controlling of the usage amount is preferable.

The reaction temperature of the emulsion-polymerization should be adjusted to the polymerization initiating temperature of the water-soluble polymerization initiator and can be set properly in the range of 35-90 ^°C . And in view of increasing the initiating efficiency of the water-soluble polymerization initiator, preventing the evaporation of the aqueous solvent to stabilize the system, it is preferred that the temperature is set in the range of 40-85 ^°C and more preferred 60-80 ^°C .

The average particle size of the resultant copolymer particles (A) thereby can be adjusted depending on the purpose. For example, the increase of average particle size can be achieved by reducing the usage amount of the water-soluble polymerization initiator or by increasing the mixing ratio a2/al of (al) the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent. In the obtained structural color object of the present invention, in order to demonstrate satisfactory coloration and the efficiency of the light reflection and diffraction, the particles have an average particle size of 40~780nm can be properly used for improving the efficiency of the light reflection and diffraction, and in order to form a structural color object demonstrating vivid coloration, the average particle size of 100~400nm is more preferable.

[Step 2: the preparation of the aqueous composition]

In the method of the present invention, the step (2) is a step of preparing an aqueous composition containing the resultant aqueous dispersion of the copolymer particles (A) from step (1), metal alkoxides and/or the partially condensed compounds thereof (B) and acid catalysts (C). And in the present invention, the resultant solution in which copolymer particles are polymerized obtained in step (1) can be used in the step (2) directly without being subjected to separation or purification process, etc. At this time, the resultant solution in which copolymer particles are polymerized can be concentrated and used depends on the case.

In the above mentioned aqueous composition, the hydrolysis and condensation reaction of the metal alkoxides and/or the partially condensed compounds thereof (B) are carried out to generate a sol of metal oxides by the catalytic action of the acid catalysts (C). And a part of the sol is concentrated at the surface of the copolymer particles (A) in which the hydrophilic segment derived from the (meth)acrylamide exists and the surface of the copolymer particles (A) hybridized with the metal oxide sol in the aqueous composition. Thereby, the metal oxide sol and the copolymer particles (A) whose surface is covered by the sol are present in the aqueous composition. And by the gelation of the aqueous composition, the copolymer particles (A) covered by the metal oxide sol form a three dimensional periodic structures and are fixed.

When preparing the aqueous composition, the resultant dispersion of the previous step can be used directly as an aqueous dispersion of the copolymer particles (A). The concentration of the copolymer particles (A) is 10~30mass % since it is almost the same as the ratio of the amount of the monomers. In the metal alkoxides and/or the partially condensed compounds thereof (B), medium, such as alcohols, or alcohols generated from the hydrolysis reaction of a part of them by the acid catalysts as mentioned above, exist in some case. Thus, if the resultant aqueous dispersion of the copolymer particles (A) from the previous step is used directly, since the non-volatile constituent in the prepared aqueous composition is low, either it takes quite long time in the following drying process or it is difficult to obtain the thicker object. Thereby, the resultant aqueous dispersion of the copolymer particles (A) obtained from the previous step can be concentrated depends on the purpose. The concentration can be readily carried out by vacuum distillation that are the common methods for removing solvent or centrifuge, etc.. While any concentration can be achieved, if the non-volatile constituent is set to more than 35mass%, the working performance in the preparing and drying process of the aqueous composition is satisfactory. While the concentration has no special upper limitation, less than 60mass% is preferable in view of preventing the aggregation of the copolymer particles (A).

Also, in the above aqueous composition, particles of different kinds can also be used together with the copolymer particles (A) as long as the average particle size of the particles is the same as the copolymer particles (A) and no aggregation is caused by the particles added. For example, the core-shell particles shown in the patent literature [1] having cross-linked hydrophilic organic polymer as the shell or the hollow particles described in the patent literature [2] can be contained. Furthermore, the polymer particles such as polystyrene, poly(methyl methacrylate) etc., synthesized by various methods can also be used. The content of these particles besides the copolymer particles (A) is preferably less than 20mass% based on the total amount of particles and in view that vivid structural coloration is demonstrated in the obtained object, less than lOmass % is more preferable.

As the metal alkoxides and/or the partially condensed compounds thereof (B) that forms the above mentioned aqueous composition, the metal alkoxides and/or the partially condensed compounds thereof (B) having hydrolysable group of over trivalent is preferred in view of being able to form a metal oxide network by hydrolysis and obtain a robust object. Especially when the metal alkoxides of over tetravalent such as tetra alkoxy silane etc. is used, the hardness of the obtained object can be improved. When the metal alkoxides having multiple functional groups are used to improve the hardness of the object , it is preferred that the concentration of the metal alkoxides of over tetravalent is more than 20mass% based on the total amount of the metal alkoxides, and more preferred more than 40mass%.

The metal of the metal alkoxides and/or the partially condensed compounds thereof (B) includes for example, silicon, titanium, zirconium, aluminum, boron, germanium, zinc, etc. In view of making the sol-gel reaction readily to occur, silicon, titanium, zirconium and aluminum are preferred and in view of the availability in industry, silicon is especially preferred.

The metal alkoxides having silicon as the metal includes the alkoxy silane that can also have reactive functional groups, etc. Here, the term "the partially condensed compounds" used herein means alkoxides that is oligomerized by hydrolysis. When the metal is silicon, the oligomerized alkoxides can also be used in the form of silica sol that has become the silanol. As the partially condensed compounds, the compounds having an average polymerization degree of 2-20 can be used. Various acids and alkalis can be used as the catalyst used in the hydrolysis under this situation. The alkoxy silane includes for example, dialkoxy silane such as dimethyl dimethoxy silane, diethyl dimethoxy silane, methyl ethyl dimethoxy silane, diphenyl dimethoxy silane, phenyl methyl dimethoxy silane etc., trialkoxy silane such as methyl trimethoxy silane, ethyl trimethoxy silane, propyl trimethoxy silane, phenyl trimethoxy silane, γ-glycidoxy propyl trimethoxy silane, γ-methacryloyl propyl trimethoxy silane, Y-(2-aminoethyl)aminopropyl trimethoxy silane, methyl triethoxy silane, phenyl triethoxy silane etc., tetraalkoxy silane such as tetramethoxy silane, tetraethoxy silane, tetra(2-ethanol) orthosilicate, tetra(n-propoxy) silane, tetra(isopropoxy) silane, etc.

Further, the alkoxy silane having functional groups includes for example, as the silane having halogen, tetrachlorosilane, methyl trichlorosilane, etc.

The metal alkoxide having titanium as the metal, includes for example, alkoxy titanium such as tetraisopropoxy titanium, tetraethoxy titanium, tetrabutoxy titanium, etc. Also various titanium chelate formed from the metal alkoxide salt of titanium such as titanium acetyl acetonate, octylene glycol titanium, titanium tetraacetyl acetonate, titanium ethyl acetate. As the metal alkoxide having aluminum as the metal, for example the alkoxy aluminum such as triethoxy aluminum can be used.

These metal alkoxides and/or the partially condensed compounds thereof (B) can be used separately or by combining more than two of them. In order to impart sufficient strength and structural coloration to the obtained structural color object , it is preferred that the usage ratio of alkoxy silane of less than divalence or metal alkoxide that has other metals besides silicone such as alkoxy titianium, alkoxy aluminum etc., is less than 30mass% based on the total amount of the metal alkoxide.

Also organic compounds that can react with the functional groups of the used metal alkoxides and/or the partially condensed compounds thereof (B) can be mixed into the metal alkoxides and/or the partially condensed compounds thereof (B) depending on the requirement. For example, polydimethyl siloxane having reactive end of monoamine modified, diamine modified, amino modified, epoxy modified, alicyclic epoxy modified, carbinol modified, mercapto modified, carboxyl modified, methacryl modified, phenol modified, silanol modified etc., can be used. Also, for example, when a silane coupling agent having glycidyl group is used, multi-functional thiol compounds such as l,4-bis(3 -mercapto butyloxy)butane, l,3,5-tris(3-mercapto butyloxy ethyl)-l,3,5-triazine-2,4,6(lH,3H,5H)-trione, pentaerythritol tetrakis(3 -mercapto butylate), etc. can be combined. Thereby, if the compound that can react with the metal alkoxides and/or the partially condensed compounds thereof (B) is used, flexibility can be imparted to the object.

As the content of the organic compound that can react with the functional groups of the used metal alkoxides and/or the partially condensed compounds thereof (B), the mole amount equal to the number of the reactable functional groups can be used in the concentration range that no separation occurs in the aqueous composition.

The aqueous solvent used in the aqueous composition is water or mixed solvent formed by mixing water and water-soluble solvent. As the water-soluble solvent, for example, alcohols such as methanol, ethanol, isopropanol etc., ketones such as acetone, pyridine, dimethyl formamide can be used. When the mixed solvent formed by mixing water and water-soluble solvent is used, it is preferred that the content of the water-soluble solvent is less than 40mass% based on the amount of water used.

As the acid catalysts (C), inorganic acid such as chloro-hydric acid, nitric acid, sulphuric acid, phosphoric acid, boric acid etc., or organic acid such as acetic acid, phthalic acid, fumaric acid, maleic acid, malic acid, acrylic acid, methacrylic acid, trifluoromethyl sulfonic acid, ethyl sulfonic acid etc., can be used. These acids can be used separately or by combining more than two of them. Among these acids, in view of being easy to adjust the pH, making the obtained aqueous composition excellent in storage stability and making the obtained object excellent in water resistance, it is preferred that unsaturated organic acids such as maleic acid, acrylic acid etc., is used. Here, in view of making the stability of the aqueous composition and drying process (curing) that forms the object to be excellent, it is preferred that the pH of the aqueous composition is adjusted to 1.5-6.5.

There is no limitation on the order of the mixing when the preparation of the aqueous composition is carried out and the preparation can be conducted by the methods of: adding the water solution of acid catalysts (C) and the solution of the metal alkoxides and/or the partially condensed compounds thereof (B) into the aqueous dispersion of the copolymer particles (A); or adding the aqueous dispersion of the copolymer particles (A) after adding the acid catalysts into the aqueous solution of the metal alkoxides and/or the partially condensed compounds thereof (B) to pre-hydrolyzed metal alkoxides and/or the partially condensed compounds thereof (B);or others.

The mass ratio of the aqueous dispersion of the copolymer particles (A) and the metal alkoxides and/or the partially condensed compounds thereof (B) represented by the mass ratio (A)/ (Β') in which (Β') is the mass of completely hydrolyzed (B), can be adjusted in the range of 70/30-5/95, preferred in the range of 60/40-15/85, more preferred in the range of 55/45-25/75. If the above mentioned (A)/ (Β') is over 5/95, the cracks of the resultant object can be reduced.

Also, it is preferred that the amount of the aqueous solvent used is 0.2-50 mass times of the used metal alkoxides and/or the partially condensed compounds thereof (B).

As long as the effect of the present invention is not damaged, various organic solvents such as ethylene glycol, ethyl cellosolve, propylene glycol, propylene glycol monobutyl ether, propylene glycol dibutyl ether, diethylene glycol, diethylene glycol monopropyl ether can be added. Additives such as smoother, wetting agent and various curing agents such as water-soluble polyglycidyl ether etc., can also be added into the aqueous composition. Also, as long as the effect of the present invention is not damaged, colorants soluble in above mentioned aqueous solvent can also be added into the aqueous composition. Such colorants include mainly the water-soluble dyes and various natural or synthesized organic dyes can be properly selected depending on the requirement. For example, azo dye, anthraquinone dye, indigo dye, sulphur dye, diphenyl methane dye, triphenyl methane dye, acridine dye, xanthene dye, azine dye, oxazine dye, thiazine dye, azomethine dye, nitro dye, nitroso dye, thiazole dye, methine dye, polymethine dye, cyanine dye, porphyrin dye, phthalocyanine dye etc., can be used. The water-soluble compound by forming the sulfonic acid or salt of sulfonic acid, such as naphthalene sulfonic acid, naphthalene sulfonic acid sodium, pyrene sulfonic acid sodium, can also be properly used. These water-soluble dyes can be used separately or by combining more than two of them.

Also, small amount of oil-soluble dyes which are soluble in water-soluble solvent of the aqueous solvent or the metal alkoxides and/or the partially condensed compounds thereof (B) can be used as colorants and monoazo, bisazo, anthraquinone dye or condensed poly-cyclic pigments such as perylene, quinophthalone, anthrapyridone etc., can be used. Further, photochromic dyes: condensed poly-cyclic aromatic compounds and derivatives thereof such as naphthalene, anthracene, tetracene, pentacene, phenanthrene, chrysene, triphenylene, pyrene etc., oligophenylene and derivatives thereof such as biphenyl, terphenyl etc., azobenzene, spiropyran, spirooxazine, fulgide, diaryl ethene and derivatives thereof can also be suitably used. These oil-soluble dyes can be used separately or by combining more than two of them. The term "colorants" used herein contains not only the materials that are able to color by having absorption band in the wavelength region of the visible lights, but also the materials that emit light in the visible light region by light absorption or the materials that are originally colorless and become able to color by the absorption of the visible light or the emission of light through the change of chemical structure that is caused by the absorption of light energy or heat energy.

By adding these dyes, the penetration of the scattered light and the stray light into the structural color object can be prevented and the structural colors originated from the internal three dimensional periodic porous structure of the object can be emphasized. Especially the black dyes such as water-soluble chlorazol black E, chlorazol black LF, chlorazol black BH, oil-soluble disperse black, etc., can be suitably used. By using the fluorescent colorants, for example, xanthene dyes represented by rhodamine dyes and derivatives thereof, or condensed multi-cyclic aromatic compounds and derivatives thereof such as naphthalene, anthracene, tetracene, pentacene, phenanthrene, chrysene, triphenylene, pyrene etc., the color of fluorescent coloration can also be added besides structural coloration and the structural color object having higher designability can be manufactured.

If the added amount of such colorants is too high, the light absorption becomes too strong, and the light diffraction effect can not be obtained adequately and the structural coloration is inhibited. Thus the total amount of such colorants is generally less than 10mass% in relation to the total amount of the polymer particles (A) and metal alkoxides and/or the partially condensed compounds thereof (B) in the aqueous composition, and preferably less than 5%, more preferably less than 2%.

[Step 3 : the curing of the aqueous composition]

The step 3 of the method for manufacturing the structural color object of the present invention is a step in which the solvent is removed from the aqueous composition obtained from the step 2, the sol-gel reaction of the metal alkoxides and/or the partially condensed compounds thereof (B) is carried out and the copolymer particles (A) are fixed in the matrix of metal oxide. This step is conducted on a substrate or in a vessel.

The aqueous composition can be easily cured by coating onto various substrates described bellow or in various vessels at room temperature or by heating, and a film-type object or a three-dimensional object is formed. In the case that it is heated to cure, the heating temperature can be selected in the range of 30-60 ^°C . The curing time can be adjusted by the concentration of the aqueous composition, the size of the object being manufactured and the heating temperature. As to the curing of the film on the substrate, it is preferred that, curing time of 5~30min is set and regarding object having a thickness of over 500μιη, especially over 1mm, the curing time of about l~10days is set. When an object having a thickness of more than 1mm is being manufactured, it is preferred that there is a drying period of about l~10days after the curing for preventing the cracks.

Also, annealing after the drying is effective to prevent the cracks getting into the object. The annealing is carried out properly in the range of 60-250^°C , considering the pyro lysis temperature of the copolymer particles(A) that are used and the heat-resisting temperature of the substrate in case of coated substrate.

When making a film on the substrate to obtain a coated substrate, the coating method of the aqueous composition is not specially limited, for example, various methods such as brush coating, dip-coat method, spray-coat method, roll-coat method, bar-coat method and air knife-coat method can be used. Further, these methods can be combined to use.

Also, when the aqueous composition is cured in a vessel of any shape, the method of transporting the aqueous composition into the vessel is without special limit as long as it can transport the required amount of the aqueous composition into the vessel, the injection or flow by the pipette dispenser or injector, or the method of immersing the vessel into the aqueous composition and lifting-up can be used.

(Solid substrate)

The shape and the constituent of the solid substrate that can be used in the present invention have no special limitation, as long as it can be coated by the aqueous composition which contains the monodisperse copolymer particles (A) and the metal oxides obtained from the sol-gel reaction of the metal alkoxides and/or the partially condensed compounds thereof (B) and as long as the substrate has no change itself between before and after the coating and drying the aqueous composition on the substrate. Various substrates formed by plastic materials, glass materials, metal materials, or metal oxide materials can be used.

For example, the plastic materials include vinyl chloride, acrylic resin such as polymethacrylate, bakelite, phenol resin, ABS resin, fluorine resin such as PTFE etc., polycarbonate, polypropylene, polyethylene, polystyrene, etc.

As the glass materials, soda-lime glass, crystal glass, borosilicate glass, quartz glass, etc., can be used and these glasses can also contain metal, metal oxide, etc. Furthermore, the metal materials include gold, silver, platinum, iron, copper, zinc, tungsten, nickel, aluminum, carbon, silicon, etc. Moreover as the metal oxide materials, for example, the substrate made by one or more of alumina, titanium oxide, zirconium oxide, zinc oxide, iron oxide, indium oxide, tin oxide etc. can be used. Also Li₂0, Na₂0, K₂0, MgO, CaO, SrO, BaO, B₂0₃, P₂0₅ etc. can further be contained in their composition.

When the object is calcined with the substrate according to the step 4 described below, the substrate to which no change will be made by the calcination is required. More specifically, heat resistance of more than 250 ^°C is required and the various substrates made by glass materials, metal materials, metal oxide materials etc. discussed before can be suitably used. Here, that the solid substrate has heat-resistance of more than 250 ^°C means that the softening point or the melting point of the substrate is over 250 ^°C .

As to the shape of the substrates, besides plate shape, various shapes such as rod-shape, ball-shape, semi-ball shape, pyramid-shape etc., can be used. The surface to be coated is not necessarily limited to plane-shape and a curved surface can also be suitably used. Thus, commercially available glasses, bowls, plates, tiles etc., can be used as a substrate.

Also, when the coating onto the substrate is difficult to conduct, base-coat agent called as "primer" can be coated to the substrate in advance.

(Vessel)

The material of the vessel used in the curing step of the aqueous composition described before is not specially limited. Vessels of any material can be used depending on the requirement, and glass, metal, metal oxide, rubber, plastic etc. can be suitably used. As the glass material, soda-lime glass, crystal glass, borosilicate glass, quartz glass etc., can be used. And metal or metal oxide etc., can also be contained in these glasses. Also, the metal materials may include gold, silver, platinum, iron, copper, zinc, tungsten, nickel, aluminum, carbon, silicon, etc. And as the metal oxide material, for example, the substrate made by one or more of alumina, titanium oxide, zirconium oxide, zinc oxide, iron oxide, indium oxide, tin oxide etc., can be used. Also, Li₂0, Na₂0, K₂0, MgO, CaO, SrO, BaO, B₂0₃, P₂0₅ etc, can further be contained in their composition. Furthermore, the rubber materials may include nitrile rubber, fluorine rubber, perfluropolyether rubber, silicone rubber such as flurosilicone rubber, methylsilicone, vinyl methylsilicone, phenyl methylsilicone, epichlorohydrin rubber such as epichlorohydrin, epichlorohydrin -ethylene oxide etc., acrylic rubber, ethylene-propylene rubber, chloroprene rubber, styrene -butadiene rubber, butyl rubber, natural rubber, urethane rubber, etc. Moreover, the plastic may include vinyl chloride, acrylic resin such as polymethacrylate, bakelite, phenol resin, ABS resin, fluorine resin such as PTFE, polycarbonate, polypropylene, polyethylene, polystyrene, etc.

In the curing step, when the object is adhered to the wall, it is preferred to be done the liquid-repellent treatment of the internal surface in advance, since there is a possibility that cracks in object may occur. Also, the liquid-repellent treatment can reduce the drying time. The method of liquid-repellent treatment is not specially limited and various water-repellent and oil-repellent agents can be used in the surface treatment. For example, by coating hydrocarbon and fluorine wax, or the silicone oil, the manufacture of the object can be easily carried out. Also, the silane coupling agent can be used to carry out the surface treatment. As the silane coupling agent that can be used for this aim, besides methyl trimethoxy silane, methyl triethoxy silane, dimethyl dimethoxy silane, dimethyl diethoxy silane, trimethyl methoxy silane, trimethyl ethoxy silane, ethyl trimethoxy silane, ethyl triethoxy silane, n-propyl trimethoxy silane, n-propyl triethoxy silane, diisopropyl dimethoxy silane, diisopropyl diethyoxy silane, isobutyl trimethoxy silane, isobutyl triethoxy silane, diisobutyl dimethoxy silane, diisobutyl diethoxy silane, n-hexyl trimethoxy silane, n-hexyl triethoxy silane, cyclohexyl methyl trimethoxy silane, cyclohexyl methyl triethoxy silane, n-octyl trimethoxy silane, n-octyl triethoxy silane, n-decyl trimethoxy silane, n-decyl triethoxy silane, phenyl trimethoxy silane, phenyl triethoxy silane, trifluoropropyl trimethoxy silane, tridecafluorooctyl triethoxy silane, heptafluoroisopropoxypropyl treimethoxy silane and chloro silane such as heptadecafluorodecyl trichloro silane, tetrachloro silane, methyl trichlorosilane, the Dynasilane F8263 _* F8815 of EVONIC Corporation, KP-801M _^

X-24-7890 of ShinEtsu Chemical Co., Ltd, DURASURF DS-l lOO_^ DS-1600_^ DS-5400_^

DS-140( DS-2100 of HAREVES Corporation can be used as fluorine surface treatment agent. Also, fluorine coating agent such as Defenser series, TR-220K_^ 220E^ 230I 301E^

3 ^ 330 FH-800ME etc. of DIC Co., Ltd, can be used to carry out the liquid-repellent treatment of the surface.

The vessel used in the curing step is not necessarily a vessel that has limited space by shape. The aqueous composition containing copolymer particles (A) and metal oxide obtained from the sol-gel reaction of the metal alkoxides and/or the partially condensed compounds thereof (B) can be cured as drop on the substrate whereupon the aqueous composition can not be adhered or the liquid- repellent substrate such as the substrate made from tetrafluoroethylene. The composition can also be dropped into a liquid that can not be mixed with the aqueous composition to be cured. Silicone oil and fluorine oil can be used for this purpose. The silicone oil to be used can be selected without special limitation as long as it won't react or mix with the aqueous composition. For example, straight silicone oil such as dimethyl silicone, methyl phenyl silicone oil, methyl hydrogen silicone oil etc. or silicone oil modified at side chain or at the end by organic group can be used. The type of the modified silicone oil can be amino modified, epoxy modified, alicylic epoxy modified, carbinol modified, methacrylic modified, polyether modified, mercapto modified, carboxyl modified, phenol modified, silanol modified, polyether modified, polyether modified-methoxy modified. And especially the non-reactive modified silicone oil such as polyether modified silicone and polyether modified-methoxy modified silicone can be suitably used. When the liquid-repellent substrate or the oils are used, object of semi-spherical or spherical xternal shape can be formed.

[Step 4: calcination]

In the method for manufacturing the structural color object of the present invention, the structural color object having metal oxide as a main constituent can be obtained by calcination of the object formed by the organic-inorganic composite constructed from the previous steps. If the amount of the organic constituent of the object obtained from step 3 is changed by the calcination, the average refractive index of the object is changed and a structural color of different tone is demonstrated. Also, if the calcination is carried out at higher temperature, the internal copolymer particles (A) decomposed. Through removing them partially or totally, a porous object having metal oxide formed by the sol-gel reaction (hydrolysis-condensation reaction) of metal alkoxides and/or the partially condensed compounds thereof (B) as a main constituent can be obtained. The porous objects obtained in this way show structural colors, since the pores of the object maintain the regular arrangement same as before the calcination. In the case that the copolymer particles (A) are decomposed and partially removed by calcination of the object formed by organic-inorganic composite obtained from the previous step3, the copolymer particles (A) can be decomposed and removed uniformly in the whole object or the regions where the decomposition and removing were carried out can have distribution in the object. For example, by heating from the one direction of the object, to impart a internal temperature gradient to the object, it is possible to demonstrate the graded structure in which the copolymer particles (A) are removed almost completely near the heated surface and on the other hand, the copolymer particles are remained to the inside of the object because the decomposition hardly took place at inside.

The calcination temperature can be selected properly from the range of 250~1300^°C depending on the purpose. For example, when calcination of the object formed by organic-inorganic composite on a substrate is achieved, the calcination temperature should be under the heat-resisting temperature of the solid substrate. For example, when soda glass that has a low melting point is used as the substrate, the calcination is carried out preferably in the range of 250-500 ^°C , when the quartz glass having a high melting point is used as the substrate, the calcination can be carried out in the range of 250~1000^°C . Further, when ceramics having high heat-resistance such as alumina are used, the calcination can be carried out in the range of 250~1300^°C . On the other hand, when calcination of the self- standing object formed by organic-inorganic composite without substrate, the calcination temperature can be properly selected from the range of 250~1300^°C without any special limitation. Here, "having metal oxide as a main constituent" means that the object is formed by the metal oxide, except the cases by the calcination condition described below, in the state that the internal organic component is changed by thermal oxidization etc., which is known as "yellowing", or when part of the organic compound or the carbonized compounds of them are remained in the object after the calcination, or no third component is added on purpose. There also include the situation that the internal organic constituent has a larger mass than that of the metal oxide, in the mass ratio of the organic constituent remained inside and the metal oxide, depending on the calcination condition and calcination method. Under this situation, the basic structure of the object is formed by the matrix of the metal oxide.

By selecting the calcination temperature, organic constituent can be remained in the object comprising of metal oxides as a main constituent, objects formed by the same organic-inorganic composite that show different structural colors can be obtained. For example, if the calcination is carried out under the condition that the organic constituent in the formed organic-inorganic composite is not completely decomposed and disappeared, the structural colors based on the three dimensional periodic porous internal structure of the object can be emphasized, since some yellow-brown colored constituents are remained in the object after calcination and they impart the color and prevent the penetration of the scattered light and/or the stray light inside the object. The origin of the yellow-brown colorations depend on the calcination temperature, the copolymer particles (A) that are used, the type of the metal alkoxides and/or the partially condensed compounds thereof (B). Though their chemical structures are not clear, but this is the phenomenon that is caused by thermal oxidation etc., and is called as "yellowing". The condition under which the organic constituent is not completely decomposed and removed can be set by using thermogravimetric analysis to measure the pyrolysis behavior in advance.

Furthermore, by changing the atmosphere of the calcination from air to nitrogen, and to argon etc., the organic constituent of the organic-inorganic composite can be carbonized so that the object contains carbonized compounds derived from the metal alkoxides and/or the partially condensed compounds thereof (B) and/or the copolymer particles (A). At this situation, since the black carbonized compounds are added to the object comprising of metal oxide as a main constituent, the penetration of the internal scattered light and the stray light can be restrained, so that the structural colorations based on the internal three dimensional periodic porous structure can be emphasized and the object demonstrating deeper coloration can be obtained. The switching of the atmosphere can be carried out completely before the calcination or during the heating period depending on the purpose.

Besides the well known furnace such as muffle furnace, atmosphere furnace and infrared furnace, the method of heating by microwave furnace and the method of firing by burner can also be used.

Also, it is possible to emphasize the structural colors by further adding of colorants to the calcined object. The adding method of colorants-to the object includes the method of immersing the object into a solution of dyes to adsorb the dyes on the outer surface of the object and on the surface of internal pores of the object. As the colorants used for this purpose, the abovementioned dyes that can be added to the aqueous composition can be suitably used, especially, if the black pigment, for example, the chlorazol black E, chlorazol black LF or chlorazol black BH is used, the effect of emphasizing the coloration is quite obvious.

In the method for manufacturing the structural color object of the second embodiment of the present invention, the structural color object formed by organic-inorganic composite can be obtained in step 4 by calcination of the object obtained through stepl~3. However, instead of calcination, the removal by dissolution of the internal copolymer particles (A) can also be realized by selecting the proper solvent. As to the removal of the internal copolymer particles (A), a complete removal is not necessarily required. For example, the structural color can be emphasized even if 2% are removed.

The organic solvent used for this purpose is not specially limited as long as the internal copolymer particles (A) have enough solubility in it and it can be selected properly depending on the purpose. For example, benzene, toluene, chlorobenzene, dichlorobenzene, acetone, ethyl acetate, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, dichloromethane, dichloroethane, trichloroethane, tetracholoethane, chloroform, dimethyl acetamide and dimethyl formamide can be used.

[Structural color object]

The structural color object obtained from step 1~3 is formed by several domains of colloid crystal composed by combining the monodisperse copolymer particles (A) having three-dimensional periodic structure, which are obtained by the copolymerization of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, in the matrix formed by metal oxide. The term "three dimensional periodic structure" used herein means a structure formed by the regular arrangement of the copolymer particles (A) along any random cross-section of the continuous phase of the metal oxide, the regular structure having close packed particles (A) in the three dimensional space is especially preferred. Also, the "domain of colloid crystal" means a piece of the spatial unit of regular arranging of the copolymer particles (A) with three dimensional periodicity. The object formed by organic-inorganic composite according to the present invention is in a state that the several adjacent colloid crystal domains are combined under the condition that the arrangement of the colloid particles is dislocated linearly or planarly, which is called as "linear defect" or "planar defect" in the crystallography field. Thereby, as to the structural color object obtained in the present invention, since the monodisperse copolymer particles (A) having three dimensional periodic structure are combined in the matrix formed by metal oxide, the periodic distribution of refractive index is formed, which causes the diffraction effect of light, and thereby the structure coloration is demonstrated. As described before, since the periodic distribution of the refractive index based on the three dimensional periodic structure which is formed in matrix of metal oxide makes the structural color to demonstrate, in the case that the difference in refractive indexes between the matrix of metal oxide and the copolymer particles (A) formed by the copolymerization of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monoers (a2) including (meth)acrylate as a main constituent is small, the object of the present invention is almost transparent and has both transparency and structural colors. For example, if phenyl trimethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxy silane or glycidoxy propyl trimethoxy silane etc., which has a refractive index of about 1.4-1.5 is used among the silane coupling agents that constitute the aqueous composition to manufacture the object that has silica as a main constituent, transparent object at the first sight can be obtained. Vivid structural color can be recognized by changing the incident angle and the strength of the light that is irradiated upon the object.

Also, the structural color object obtained from the stepl~4 is formed by several domains of inverse opal structure which are formed by the pores with three dimensional periodic structure, in the matrix of the metal oxide. The three dimensional structure is the same as the structure described before which is formed by the regular arrangement of the pores along any random cross-section of the continuous phase of the metal oxide, and the regular structure having close packed pores in the three dimensional space is specially preferred. Here, the domain of the inverse opal structure means a piece of the spatial unit of a regular arranging of the pores with three-dimensional periodicity. The several adjacent inverse opal structure domains are in the state of being combined under the condition that the arrangement of the pores is dislocated linearly or planarly which is called as the "lineal defect" or "planar defect" in the crystallography field. Thereby, since the structural color object obtained in the present invention is formed by the pores with three-dimensional periodic structure in the matrix of metal oxide, the periodic distribution of the refractive index is formed, which causes the diffraction effect of light, and thereby the structural color is demonstrated.

The shape of the pores can be different depending on the condition of the calcination, and they can be true sphere pores that originated from the copolymer particles (A) or can be non-true sphere pores formed by removing a part of the copolymer particles (A). The average pore size of the pores can be made into the range of 20~780nm and to form the object that shows vivid coloration, the average pore size of 50~400nm is more preferred.

As described before, since the structural color object of the present invention show structural colors by the periodic distribution of refractive index originated from the pores formed three-dimensionally in the matrix of metal oxide, under the condition that the difference of refractive index becomes small as a result of immersing the present object in liquid or filling the pores with some materials, it can be recognized as an object that is almost transparent and has transparency and structural colors. For example, by immersing the object into the liquid having a refractive index of about 1.4-1.5, for example halogen solvents such as chloroform, dichloromethane etc., aromatic solvents such as benzene, toluene etc., cyclohexanone, dimethyl acetamide (DMA), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and various methacrylate monomers or styrene monomers etc., to make the object soaked by the liquid, the object comprising silica as a main constituent of metal oxide can be recognized as object that is almost transparent. On the other hand, by changing the direction and strength of the light, the diffraction of the light can be emphasized and vivid structural colors can be recognized.

Further as described above, as to the structural color object obtained from step 1-4, by changing the calcination condition such as temperature or atmosphere, either organic components are remained in the matrix of the metal oxide to emphasize the coloration or the variation of the tone is imparted. The residual amount of the organic constituent is not specially limited and can be selected properly depending on the purpose. If the calcination is conducted over 250 ^°C , the weight changes because of the gradual decomposition or the carbonization of organic components. When the organic constituent are remained inside for the purpose of emphasizing the structural coloration, it is preferred that 10~95mass% of the organic constituent in the object are removed, more preferred 15~90mass%. If the removed amount is too low, the object show approximately the same structural coloration as the object obtained from step 3 and if the removed amount is too much, the scattered light inside the object increases and structural color object of intense white color is obtained. The removed amount of the organic constituent can be controlled by the calcination temperature, and can be measured quantitatively by the thermogravimetry (TG).

Since the internal structure of the structural color object obtained in the present invention are formed respectively by combining the several colloid crystal domains or inverse opal structure domains, any cross-section of the object show the optical phenomenon called as "play of colors" and multiple reflected colors can be recognized even when observed from the same direction. The presence of the colloid crystal domains or the inverse opal structure domains can be confirmed by that when any cross-section of the object is observed under optical microscope, polychromic pseudo-polygon mosaic patterns can be recognized. As to the size of each domain, one of the diagonals of each mosaic of the any cross-section observed under optical microscope is about ΙΟμΓη-Ιιητη, mainly 40μιη~500μιη. When the object is of a film shape, the size of the domains is restrained in the thickness direction and the size of the film plane direction is approximately same as described before.

The structural color object of the present invention is formed by combining plural domains as described above, the boundary among every domain is in a state that the arrangement of the particles or the pores are present under the condition that they are dislocated linearly or planarly, which is called as "linear defect" or "planar defect" in the crystallography field and the matrix of the metal oxide are of robust structure which forms continuous layer in the whole object. Thus, even through the structural color object is irradiated by ultrasonic waves etc., none of the domain will disintegrate or collapse.

In the method for manufacturing the organic-inorganic composite having large volume and the metal oxide object proposed before, such as the method of patent the literature [1] or [2], respectively, there is a shell that can be actually solvated in the aqueous solvent on the surface of the polymer particles. And this shell functions as the reaction site of the sol-gel reaction and the growing site of the metal oxide. Thereby, since these techniques are to form an organic-inorganic composite wherein the colloid crystal is present in the whole firm uniformly, further to form an object of metal oxide by calcination, the coloration is uniform in the whole object and the phenomenon of "play of colors" can't be confirm in its cross-sections.

The shape and size of the structural color object obtained in the present invention can be determined by the shape and size of the vessel used in the coating or curing process. Any shape or size of any thickness depending on the position can be properly selected by the application purpose, such as rod, plane, scale, ball, ellipsoid, spindle, cylinder, cone, pyramid, etc.

For example, the thickness of the film shape object formed on the substrate is 1~50μιη. This won't change even calcination. In the manufacture method of the present invention, film of such thickness is coated on the substrate of at least 1cm ^x 1cm square so that a structural color film of large area without defects such as cracks can be obtained. Thereby, the length of the shortest side of the film is at least more than 1 ,000 times of the thickness of the film and film wherein the length of the shortest side of the film is at least more than 10,000 times of the thickness of the film can be easily made. The shortest side of the film of the present invention means the shortest side of the surface direction of the film having no defect such as cracks or fracture in the structural color film.

Also, one embodiment of the structural color object obtained in the present invention is self-standing object of arbitrary shape, for example, when used as structural color pigment, it is preferred that the object has flake shape and a thickness of 3~50μιη, preferably 3~30μιη, and preferably the minor axis and the major axis of the scale plane is 50μιη ~500μιη. In the case of being spherical shape, the diameter is 3~50μιη, preferably 3~10μιη. When the object itself is used as decoration article or handcraft article, the object wherein the minimal diameter of the cross-section demonstrating the largest area of the object of arbitrary shape is at least 3mm, more preferably 5mm, can be provided depending on the purpose.

Also, the object obtained in the present invention can further be imparted with structures of smaller shape at the surface thereof, along with any one of the above mentioned shape or size. For example, structures such as "prism array" of μιη ~ several mm or "microlens array" formed by aligning semi-spherical shape bumps, latticed grating, grid and so on, which are used for reflection plate etc., can be imparted. As the reflection and diffraction effect of the light is enhanced by such structures, structural color object of higher designability can be formed.

Example

Thereinafter, the examples are referred to explain the present invention further in detail; however the present invention is not necessarily limited to these examples. Unless noted otherwise, "%" means "mass%".

Devices for measurement

VE-9800 electron scanning microscope of Keyence Corporation is used to observe the shape of the copolymer particles. Using the "particle size distribution analysis software" Mac- View (Mountech Co. Ltd), the particle size is measured by image-analysis of the image of the particles obtained by the above device. The "Fiber-Optics Particle Analyzer" (FPAR-1000) of Otsuka Electronics Co., Ltd is used to measure the particle size by dynamic light scattering method.

SZ60 stereomicroscope of Olympus Corporation, BX-60 metal microscope of Olympus Corporation and VE-9800 electron scanning microscope (SEM) of the Keyence Corporation are used to observe the surface and cross-section shape of the structural color object.

The three-dimensional variable-angle spectrophotometric colorimetry system GCMS-11 of Murakami Optics Corporation is used to measure the UV-VIS variable-angle reflection spectrum of the structural color object surface. The Fiber-multichannel spectroscope USB4000 of the Ocean Photonics Corporation is used to measure the specular reflection spectra of the perpendicular direction. The differential thermal-thermogravimetric analyzer (EXSTAR6000 TG/DTA) is used to carry out the thermogravimetric analysis of the structural color object.

Raman laser microscope of Renishaw Corporation is used to analyze the remained organic component in the structural color object after calcination.

Example 1

17g of N-isopropyl acrylamide (Kohjin Co., Ltd, thereinafter referred to as "NIPAM") was dissolved into 677g of water and then 30g of glycidyl methacrylate (Wako Pure Chemical Industries, Ltd., thereinafter referred to as "GMA") was added. The system was stirred at 80 ^°C under nitrogen flow. 10ml of aqueous solution in which 0.4g of potassium persulfate (KPS, Wako Pure Chemical Industries, Ltd.) had been dissolved was added as water-soluble polymerization initiator. Then 10 min after 30g of GMA was added and another 10 min after 43g of GMA was added. (Monomer concentration^ 5.4%, GMA/NIPAM=5mol/mol). Particle dispersion having solid content 15% was obtained by stirring for 2h at the same temperature. NMR measurement was conducted to the upper clear supernatant liquid which was obtained by precipitating the particles through centrifuge using part of the dispersion. As no peak assigned to the monomer was observed, it was confirmed that no monomer was remained. The shape of the obtained particles was observed by SEM and the particles were monodisperse spherical particles having an average size of 320nm (Fig . l).

The copolymer particles were precipitated from the obtained 15% water dispersion of the copolymer particles by centrifuge. The particles were re-dispersed by adding water thereinto and the resultant dispersion was concentrated to a particle concentration of 40%. The existence of the remained NIPAM monomers and homopolymers of the polyNIPAM in the upper clear supernatant liquid couldn't be confirmed.

100 parts of the water dispersion of the copolymer particles which had been concentrated to 40%, 20 parts of 10% maleic acid water solution and 80 parts of the 2-propanol (66%) solution of silane oligomer MS-51 (Colcoat Co. Ltd.) were mixed and stirred in 40 ^°C water bath for 2h to obtain a milky white aqueous composition that was homogeneously dispersed.

2g of the prepared aqueous composition was put into No.5 screw tube made by Maruemu Co.Ltd., and capped. The tube was put into an incubator set at 30 ^°C . The "play of colors" is recognized at the surface of the liquid after 3h and the liquid cured after 1 day. Hereafter the tube was left still for 3 weeks. A free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained after spontaneous peeling from the glass. The object was milky white solid that showed the "play of colors". It was confirmed by the thermogravimetric analysis that 70% of the object was organic constituent mainly comprised copolymer particles and 30% of object mainly comprised by silica.

Example 2

DURASURF DS-1100 of HARVES Corporation was put into No.5 screw tube and the tube was kept still for lh. After taking it out, the inside of the tube was subjected to liquid-repellent treatment by putting it into an environment of 65 ^°C , over 85% humidity. 2g of the aqueous composition obtained in Example 1 was put into the liquid-repellent No.5 screw tube and capped. Then the tube was left in the incubator set at 30 ^°C . After 3h, the "play of colors" was recognized on the surface of the liquid and the liquid cured 1 day after. Hereafter, the tube was left still for 10 days. A free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained after spontaneous peeling from the glass. The object was milky white solid that showed "play of colors". It was confirmed by the thermogravimetric analysis that 70% of the object was organic constituent mainly comprised copolymer particles and 30% of object comprised silica. Then the structural color object formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and a structural color object having metal oxide as a main constituent which showed vivid coloration with red-orange luster when observed from the perpendicular direction of the disc plane was obtained, without defects such as crack (Fig. 2). Moreover the cross-sections of the object showed vivid polychromic "play of colors".

Example 3

The water was removed by rotary evaporator of 60 ^°C from the 15% water dispersion of the copolymer particles Al obtained in Example 1 and the dispersion was concentrated to 40%). And satisfactory dispersion of particles wherein no aggregation was caused by concentration was obtained. The aqueous composition containing copolymer particles Al was obtained the same way as Example 1 except for using evaporator to remove the solvent in order to concentrate the composition instead of centrifuge. The aqueous composition was put into the liquid-repellent No.5 screw tube as Example 2 and capped. Then the tube was left in the incubator set at 30 ^°C . Same as the Example 2, a free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which is formed by organic-inorganic composite was obtained. The object is milky white solid that shows "play of colors". It is confirmed that 70% of the object was organic constituent mainly composed copolymer particles and 30% of the object composed silica. Then the structural color object formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and a structural color object having metal oxide as a main constituent which showed vivid coloration with red-orange luster when observed from the perpendicular direction of the disc plane was obtained, without defects such as cracks. Moreover the cross-sections of the object showed vivid polychromic "play of colors".

Comparative example 1

60 parts of water wherein no copolymer particles had been blended, 20 parts of 10% water solution of maleic acid and 80 parts of 2-propanol (66%) of silane oligomer MS-51 were mixed and stirred in 40 ^°C water bath for 2h. Then the composition was put in the No.5 screw tube and capped. Then the tube was left in the incubator set at 30^°C . The liquid cured in one week. It was recognized that longer curing time was required compared with using particle dispersion.

Comparative example 2

<The synthesis of the hollow polymer particles formed by PNIPAM- co -PGMA> 23.6g of GMA was added into 290ml water solution in which 3.6g of NIPAM had been dissolved. The system was stirred at 70 ^°C under nitrogen flow. 10ml of water solution in which 0.15g of KPS had been dissolved was added as water-soluble polymerization initiator (monomer concentration=9%, GMA/NIPAM=5.2mol/mol). The system was stirred at the same temperature and in lOmin after the water-soluble initiator had been added, fierce aggregation occurred and massive flocculating solid was formed in the reaction solution. Even after the reaction had carried out for lh, separation of oily constituent from the reaction solution could be observed and the smell of the monomers could be confirmed. Also, needle-like NIPAM crystals were precipitated by drying the reaction solution. The flocculating solid was subjected to SEM observation and it was recognized that it was blocks formed by the aggregation of particles almost uniform in size. This aggregation couldn't be re-dispersed even being stirred or irradiated by ultrasonic waves and couldn't form into aqueous composition used for the manufacture of the structural color object.

Comparative example 3

Except for reducing the added amount of NIPAM and GMA (monomer concentration=4.5%, GMA/NIPAM=5.2mol/mol) to the half, the same operation was carried out as Comparative example 2. Polymer particle dispersion having solid content 4.2% was obtained by stirring the system for lh at 70 ^°C after the KPS had been added. The shape of the polymer particles was observed by SEM and the particles were monodisperse-sized true spherical particles having an average particle size of 250nm. Then the particles were crashed to observe the structure. And it could be confirmed that the particles were hollow polymer particles that the center of which was cavity. The precipitation of particles as well as transparent film-like solid and needle-like crystals could be observed when the dispersion of the particles had been dried up. And according to the NMR, IR measurement, it was confirmed that they were homopolymers of poly(NIPAM) and unreacted NIPAM.

Water was removed from the 4.2% dispersion of the hollow polymer particles obtained thereby using an evaporator of 60 ^°C . When the solid content was reached to about 10%, the particle dispersion gelled and the particles aggregated, by the influence of poly (NIPAM) existing in the system. The aggregation couldn't be re-dispersed by mixing or ultrasonic wave irradiation and can't form into the aqueous composition that is used for the manufacture of structural color object.

Comparative example 4

The 4.2% dispersion of hollow polymer was obtained the same way as comparative example 2 and the copolymer particles were precipitated by centrifuge. The existence of remained NIPAM monomers and homopolymers of poly(NIPAM) in the upper supernatant liquid was conformed. The remained NIPAM monomers and the homopolymers of poly(NIPAM) could be removed from the system by repeating the centrifuge of 3 times. Water was added thereinto to re-disperse the particles and the resultant dispersion was concentrated to a particle concentration of 40%.

If 100 parts of 40%> dispersion of hollow polymer particles obtained such way, 20 parts of 10% maleic acid water solution and 80 parts of 2-propanol solution of silane oligomer MS-51 were mixed and stirred in 40 ^°C water bath, the particles aggregated and homogeneous aqueous composition couldn't be obtained, by the influence of poly(NIPAM) which was on the surface of the hollow particles,.

Comparative example 5

100 parts of 40%> water dispersion of the hollow polymer particles, 20 parts of the 10%> water solution of maleic acid, 80 parts of the 2-propanol solution (66%) of the silane oligomer MS-51 were mixed and stirred for 2h in the same way as Comparative example 4 except that the stirring temperature had been changed from 40 ^°C to 20 ^°C , to obtain a milky white aqueous composition that was uniformly dispersed. 20g of the above aqueous composition was put into the No.5 screw tube and capped. Then the tube was left in the incubator set at 30 ^°C for 3 weeks. A free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained after spontaneous peeling from the glass. However, this object didn't show the "play of colors" and was a milky white solid show blue reflection when observed from the top.

Also, the object formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and although a disc-shape object was obtained without defects such as cracks, the phenomenon of "play of colors" couldn't be confirmed.

Comparative example 6

0.5g of NIPAM and 3.5g of styrene were added into 100ml of water to prepare the core particles at 70^°Cunder nitrogen flow and using KPS as initiator. Further, 0.7g of NIPAM and

0.07g of Ν,Ν'-methylene bisacrylamide (monomer concentration=4.8%) were added to form the shell using KPS as initiator. The core-shell particles (particles' concentration about 3.5%) were prepared having polystyrene as the core and cross-linked poly(N-isopropyl acrylamide) as the shell. The dynamic light scattering method was used to measure the average particle size and the particles were monodisperse-sized particles having a shell thickness of about 20nm when dispersed in water and an average core size of 310nm. It was recognized that gel-like poly(NIPAM) was contained after precipitating the particles from the particles' dispersion by centrifuge and concentrating the upper supernatant liquid by evaporator.

When the 3.5% dispersion of the monodisperse-sized core-shell particles obtained this way had been heated to over 35 ^°C , by the effect of the shell and the poly(NIPAM) present in the system, the particles aggregated and gelled. Thus they couldn't be concentrated by evaporator.

Comparative example 7

The core-shell particles were precipitated from the 3.5% dispersion of the monodisperse core-shell particles obtained the same way as Comparative example 6 by centrifuge. The presence of poly(NIPAM) in the upper supernatant liquid was confirmed and the poly(NIPAM) homopolymers could be removed by repeating the centrifuge 3 times. The particles were re-dispersed by adding water and concentrated to a particle concentration of 20%. 100 parts of the 20%> water dispersion of the monodisperse core-shell polymer particles obtained this way, 20 parts of the 10% water solution of maleic aicd and 80 parts of the 2-propanol solution(66%) of the silane oligomer MS-51 were mixed and the system was immersed into 40 ^°C water bath, and because of the effect of the poly(NIPAM) of the particle's shell, the particles aggregated and homogeneous aqueous composition couldn't be obtained.

Comparative example 8

100 parts of the 20% water dispersion of the monodisperse core-shell polymer particles obtained the same way as the Comparative example 7, 20 parts of the 10% water solution of maleic acid and 80 parts of the 2-propanol solution (66%) of the silane oligomer MS-51 were mixed and stirred for 2h at 20 ^°C to obtain a milky white aqueous composition that was homogeneously dispersed. 2g of prepared aqueous composition was put into the No.5 screw tube and capped. Then the tube was left in the incubator set at 30 ^°C for 3 weeks. A free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 1.3mm which was formed by organic-inorganic composite was obtained after spontaneous peeling from the glass. This object was white solid that didn't show the "play of colors".

The object formed by organic-inorganic composite was calsined using electronic furnace under aerated condition at 350 ^°C for 30min and a brown object having metal oxides as a main constituent was obtained. The object didn't demonstrate the "play of colors" and the structural colors also couldn't be confirmed.

Example 4 The DURASURF DS-1100 of the HARVES Corporation was put into a laboratory glass-made flat dish having a diameter of 6cm and left for lh. After taking it out, the internal wall of the dish was subjected to liquid-repellent treatment by leaving it into an environment of 65 ^°Cand over 80% humidity for lh. 4g of aqueous composition obtained in Example 1 was put into the liquid-repellent dish and capped. Then the dish was left in the incubator set at 30 ^°C . The surface of the liquid showed the "play of colors" after 3h and the liquid cured one day after. Then the dish was left for another 10 days. A free-standing disc-shape structural color object having a diameter of 3cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained after spontaneous peeling from the glass. The object was milky white solid that showed the "play of colors". It is confirmed by the thermogravimetric analysis that 70% of the object was organic constituent mainly comprised copolymer particles and 30%> of object comprised silica.

The object formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 350 ^°C for 30 min and a structural color object without defects such as cracks, which showed "play of colors" with red-orange luster when observed from the perpendicular direction of the disc plane was obtained. The specular reflection spectrum of the perpendicular direction of the disc plane was measured and a spectrum that had a peak at 650nm was observed (Fig. 3). And when the incident angle of light was increased, the color of the object was changed from green to blue. When the specular reflection spectrum was measured every 10° while the incident angle of light was changing from 10°~60°, peak shift of the sepecular reflection spectrum from 650nm to 440nm was observed, which was in conformity with the color change observed by naked eyes (Fig.4). According to the thermogravimetric analysis, the object after calcined at 350 ^°C was mainly consisted of 60% organic component formed by the remained constituent of the modified copolymer particles and 40%> of object formed by silica. The peaks at 21.7, 45.1, 65.0, 175.6ppm could be observed in the solid-state ¹³C-NMR measurement and it was confirmed that a lot of copolymer particle's constituent were remained even after the calcination at 350 ^°C (Fig 5). Also, it was confirmed by the cross-sectional SEM image of the object that the object has a porous structure formed by the periodic arrangement of the uniform-sized pores (Fig. 6).

Example 5

The object obtained from Example 4 formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 600 ^°C for 30min and a structural color object which showed blue-white coloration with luster when observed from the perpendicular direction of disc plane was obtained. The specular reflection spectrum of the perpendicular direction of the disc plane was measured and a spectrum that show peak at 450nm was observed. It was confirmed by the cross-sectional SEM image of the object that the porous structure formed by the periodic arrangement of the uniform-sized pores was maintained even after the calcination at 600 ^°C (Fig.7). It was recognized by the solid-state ¹³C-NMR measurement that only the peak belonging to sp² carbon near 120-130ppm was observed (Fig.8), and carbon constituent different from that of the copolymer particles was remained in the object calcined at 600 ^°C and the structural color was emphasized.

The object was immersed into 0.5% water solution of black dye-chlorazol black E (Tokyo Kasei) and lifted up. The chlorazol black E was adsorbed upon the internal and external surface of the object and vivid coloration of deep blue to deep green was shown.

Example 6

The object obtained from Example 4 formed by organic-inorganic composite was calcined using electronic furnace with nitrogen flow at 500 ^°C for 30min and a structural color object which showed vivid coloration with green luster when observed from the perpendicular direction of the disc plane was obtained. And when the observing angle was increased, the color of the object was changed from green to blue-violet. It was confirmed by the cross-sectional SEM image of the object that the object was a porous structure formed by the periodic arrangement of uniform-sized pores (Fig 9). On the other hand, poly chromic vivid mosaic patterns could be observed when the cross-section of the object was subjected to the optical microscope observation (Fig.10) and the dislocation line of the porous inverse opal structure was confirmed by the cross-sectional SEM image of the object (Fig.11). Thus, it was confirmed that the object was a combination of several inverse opal structures. By the Raman spectrum measurement of the object, the peak assigned to carbon (near 1354, 1548cm^"1) were observed and the existence of hybridized carbon could be confirmed.

Example 7

5 of artificial nails made of acrylic resin were set into a laboratory glass-made flat dish having an internal diameter of 6cm in a way that the positive chambers were facing downward and they were used as the drying vessels of the aqueous composition obtained in Example 1. The dish was capped after filling in the aqueous composition. The dish was left in the incubator set at 30 ^°C . The surface of the liquid showed the "play of colors" after 3h and the liquid cured one day after. And then the dish was left for 3 days. Free-standing nail-shape structural color object which were formed by organic-inorganic composite were obtained after spontaneous peeling from the plastic wall (Fig 12). The objects were white objects that showed pearl luster. The objects were calcined using electronic furnace under aerated condition at 350 ^°C for 30min and structural color object which demonstrated vivid color with luster of green to blue when observed from the perpendicular direction of nail-shape camber, were obtained without defects such as cracks. The specular reflection spectrum of the positive chamber of the nail-shape object with 2mm irradiation diameter was measured and a reflection spectrum that had peaks at 430nm and 500nm was obtained. Example 8

The "Multimat (Daiso-sangyo Co. Ltd)" made by silicone resin having square pores of 4mm length and 2mm depth arranged thereupon as grid was used as the vessel. The "Multimat" was set into a laboratory glass-made dish and the dish was capped after filling in the aqueous composition obtained from Example 1. The dish was left in theincubator set at 30 ^°C . After 3h the surface of the liquid showed the "play of colors" and the liquid cured 2 days after. Then the dish was left still for another 8 days. Many free-standing square plate-shape structural color objects of 2mm square and 1mm thickness which were formed by the organic-inorganic composite were obtained (Fig. 14). The objects were white objects that showed pearl luster. The objects were calcined with using electronic furnace at 350 ^°C under aerated condition for 30 min and structural color objects which showed vivid colors with blue-green luster when observed from the perpendicular direction of the camber of the square plate, were obtained without defects such as cracks.

Example 9

Cups and molds of various shapes made by silicone resin were used as vessels. And after filling in aqueous composition obtained from Example 1, each vessel was put into a plastic case and capped. Then the case was left in the incubator set at 30 ^°C . The surface of the liquid showed the "play of colors" in one day and the liquid cured 2 days after. Then the case was left still for another 9 days. The structural color objects formed by organic-inorganic composite that have the shape of the vessel were obtained after the spontaneous peeling from the silicone resin walls. The objects were white objects that showed opal-like luster. Then the objects were calcined under aerated condition at 350 ^°C using electronic furnace for 30min and the structural color objects which showed vivid coloration, were obtained without defects such as cracks (Fig.15).

Example 10 The back part of the commercially available light reflector was removed and the plastic prism array of it was used as the bottom plane of the vessel for the manufacture of the object. The vessel was put into a laboratory glass-made dish after filling in the aqueous composition obtained from Example 1 and capped. Then the dish was left in the incubator set at 30^°C . The surface of the liquid showed the "play of colors" in one day and after 6 days, the structural color object formed by organic-inorganic composite which reflects the shape of the prism array and had prism array structure at the surface was obtained (Fig. 16) after spontaneous peeling from the vessel. The object was white object that showed opal-like luster. Then the object was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and structural color object which showed vivid coloration, without defects such as cracks was obtained. The reflected light was emphasized by the prism array and blue -violet color of the object observed from the top was shifted green, red and gold when the observing angle was increased.

Example 11

The aqueous composition obtained from Example 1 was added dropwise onto PTFE sheet (Nafuron sheet, AS ONE Co. Ltd.) and the drop amount was adjusted so that the drops had a diameter of 4mm when observed from the perpendicular direction. The aqueous composition was a semi-spherical shape drop when observed laterally and showed the "play of colors" in 10 min after dropping. The sheet was put in to a plastic case and capped, and then left in the incubator set at 30^°C . The drops became a thin disc having a convex upper part along with the drying. And a structural color objects of 2mm diameter formed by organic-inorganic composite which had the opal-like luster were obtained 6 days after. Then the objects was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and a structural color objects which showed vivid coloration, was obtained without defects such as cracks (Fig. 17). The structural color objects were in a shape of the thickness thinning from center of the plate to the periphery and showed vivid coloration that was gold in the center of the plate and green at the periphery when observed from the top.

Example 12

Silicone oil (GE Toshiba Silicone Corporation) was poured into the beaker made of PTFE. 7μ1 of aqueous composition obtained from Example 1 was added dropwise using mircro-pipette and the aqueous composition became spherical-shape drops. The drops showed the "play of colors" in lOmin after dropping. The beaker was left in the incubator set at 30 ^°C for 7 days and then taken out and washed by hexane. Spherical shape structural color objects formed by organic-inorganic composite which had opal-like luster were obtained. Then the objects were calcined using electronic furnace under aerated condition at 350 ^°C for 30min and structural color objects which showed vivid coloration, were obtained without defects such as cracks. The objects showed a vivid coloration of red in center and green at periphery when observed from the top.

Example 13-15

<The synthesis of the copolymer particles A2-A4 formed by PNIPAM-co-PGMA> The copolymer particles formed by PNIPAM-co-PGMA were synthesized in the same way as Example 1 (GMA/NIPAM=5mol/mol), except that the added amount of the NIPAM and GMA and the adding times of the monomers were changed according to the following table. The forth addition of GMA in Example 14, 15 were carried out lOmin after the third addition. The concentration of the polymer particle dispersion was almost the same as the concentration of the monomers. NMR measurement was conducted to the upper clear supernatant liquid formed by precipitating the polymer particles through centrifuge using part of the dispersion. It was confirmed that no remained monomer exists since no peak assigned to the monomer was observed. Also, it was confirmed after the SEM observation of the shape of the obtained particles that they were all of spherical monodisperse-sized particles having an average particle size of 320nm.

Table 1

100 parts of the aqueous dispersion, which had been prepared using these particles and had been concentrated to 40% in the same way as Example 1, were used to prepare the aqueous composition. And the aqueous composition was cured and dried in the liquid-repellent screw tube in the same way as Example 2. And a free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained. The object was milky white solid that showed an opal-like "play of colors". Same as Example 1 and 2, the 70% of the object was mainly organic constituent comprised copolymer particles and 30% of object comprised silica. Then the object was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and same as Example 2, a structural color object which showed vivid coloration with red-orange luster when observed in the perpendicular direction of the disc plane, was obtained without defects such as cracks.

Example 16-18

<The synthesis of the copolymer particles A5-A7 formed by PNIPAM-co-PGMA> The copolymer particles having a monomer concentration of 15%, formed by PNIPAM-co-PGMA was synthesized the same way as Example 1 except that the added amount of NIPAM and GMA and the ratio of GMA/NIPAM were changed. The concentration of the obtained polymer particle dispersion was almost the same as that of the monomers. NMR measurement was conducted to the upper clear supernatant liquid formed by precipitate the particles through centrifuge using part of the dispersion. It was confirmed that no remained monomer existed since no peak assigned to the monomer was observed. Also, it was confirmed after the SEM observation of the shape of the obtained particles that they were all spherical monodisperse-sized particles. And the average particle size of the particles obtained in Example 16-18 was 350nm, 390nm and 440nm respectively.

Table 2

The same operation was carried out as Example 1 except for using polymer particles A5-A7. 100 parts of water dispersion that had been concentrated to 40% were used to prepare the aqueous composition. The aqueous composition was cured and dried in the liquid-repellent screw tube in the same way as Example 2. And free-standing disc-shape structural color objects having a diameter of 1.8cm and a thickness of 3mm formed by organic-inorganic composite were obtained. The objects were milky white solid that showed opal-like "play of colors". Same as Example 1 and 2, the 70% of the object was mainly organic constituent formed by copolymer particles and 30% of objects formed by silica. Then the objects were calcined using electronic furnace under aerated condition at 350 ^°C for 30 min and same as Example 2, 3, structural color objects which showed vivid coloration with luster, were obtained without defects such as cracks. The coloration when observed from the perpendicular direction of the disc plane was red for A5 particles, reddish-gold for A6 particles and gold for A7 particles, respectively.

Example 19 <The synthesis of the copolymer particles formed by PNIPAM-co-PGMA> The synthesis of the copolymer particles A8 were carried out under the same condition as Example 1 except that the water-soluble initiator was changed to 2,2'-azobis (2-amidinopropane) dihydrochloride (Wako Pure Chemical Industries, Ltd.) and the reaction temperature was changed to 65 ^°C . A particle dispersion having solid content 15% was obtained. NMR measurement was conducted to the upper clear supernatant liquid formed by precipitating the particles through centrifuge using part of the dispersion. It was confirmed that no remained monomer existed since no peak assigned to the monomer was observed. And it was confirmed by the SEM observation of the shape of the obtained particles that they were all spherical monodisperse-sized particles having an average particle size of 300nm.

As same as Example 1, 100 parts of water dispersion which had been concentrated to 40% were used to prepare the aqueous composition except for using copolymer particles A8 obtained above. And as same as Example 2, the aqueous composition was cured and dried in liquid-repellent screw tube and a free-standing disc-shape structural color object having a diameter of 1.8cm and a thickness of 3mm which was formed by organic-inorganic composite was obtained. The object was milky white solid that showed an opal-like "play of colors". And as same as Example 1 and 2, the 70% of the object was mainly comprised organic constituent formed by copolymer particles and 30% of object comprised silica. Then the object was calcined using electronic furnace under aerated condition at 350 ^°C for 30min and as same as Example 2 and 3, a structural color object which showed vivid coloration with luster, was obtained without defects such as cracks. The coloration observed from the perpendicular direction of the disc plane was green.

Example 20

<The aqueous composition containing Al> 100 parts of water dispersion of copolymer particles Al obtained from Example 1, 20 parts of 10% maleic acid water solution and 80 parts of isopropanol solution (50%>) of mixed silica source formed by mixing silane coupling agent into the silane oligomer MS-51 by the ratio of the following table (mass ratio) were mixed and stirred for 2h in 40 ^°C water bath. And a milky white aqueous composition that was homogeneously dispersed was obtained.

Table 3

The same operation was carried out as same as Example 2 except for using the prepared aqueous composition. The aqueous composition was cured and dried in the liquid-repellent screw tube and free-standing disc-shape structural color objects which were formed by organic-inorganic composite were obtained. The objects were milky white solid that showed an opal-like "play of colors". Then the objects were calcined at 350 ^°C for 30 min using electronic furnace and as same as Example 2 and 3, structural color objects which showed vivid coloration with luster were obtained. And coloration changed from green to red depending on the used silane coupling agent. The specular reflection spectrums of the objects were measured and different reflection peaks (Fig. 19) were demonstrated depending on the different coloration. It was confirmed by the cross-sectional SEM image of the object that they all had periodic porous structure (Fig. 20).

Example 21

A milky white aqueous composition which was homogeneously dispersed was obtained as same as Example 20 except for changing the mixing ratio of the mixed dimethyl dimethoxy silane to that shown in the following table.

Table 4

The same operation same as Example 2 was carried out except for using the prepared aqueous composition. The aqueous composition was cured and dried in the liquid-repellent screw tube and free-standing plate-shape structural color objects which were formed by organic-inorganic composite were obtained. The objects were milky white solid that showed an opal-like phenomenon of "play of colors". Then the objects were calcined using electronic furnace under aerated condition at 350 ^°C for 30 min and the as same as Example 2 and 3, structural color objects which showed vivid coloration with luster, were obtained without defects such as cracks. The objects showed different coloration as the following table according to the amount of the silane coupling agent mixed.

Table 5

Example22

A milky- white aqueous composition that was homogeneously dispersed was obtained as same as Example 20-2 except that the mixing ratio of the mixed phenyl trimethoxy silane was changed to that shown in the following table.

Table 6

The same operation as Example 2 was carried out except for using the prepared aqueous composition. The aqueous composition was cured and dried in the liquid-repellent screw tube and free-standing disc-shape structural color objects having a diameter of 1.3cm and a thickness of 3mm which were formed by organic-inorganic composite were obtained. The objects were transparent and when put upon the printed paper, the words below were able to be clearly red (Fig.21). Also, when under intense light, the inside of the object showed vivid coloration shining with iridescent luster. Then the objects were calcined using electronic furnace under aerated condition at 350 ^°C for 30min and structural color objects that showed vivid coloration with blue-green luster when observed from the perpendicular direction of the disc plane were obtained without defects such as cracks.

Example 23

The aqueous composition prepared in Example 1 was coated on a glass substrate of 2.5cmx7cm using coating rod (number 30) and the resultant film was cured at 25 ^°C , 80 ^°C ,

130 ^°C , 180 ^°C for 30min respectively. A film formed by organic-inorganic composite without cracks was obtained. Then the film was calcined using electronic furnace under aerated condition at 350 ^°C for lh. A red to green structural color film which showed vivid coloration with the "play of colors" when observed from the perpendicular direction of the film was obtained without defects such as cracks. The average thickness of the film was about 3.5μιη.

Example 24

The film obtained in the same way as Example 23 which was formed by organic-inorganic composite was calcined using electronic furnace under aerated condition at 500 ^°C for lh. And a blue structural color film which showed vivid coloration with the "play of colors" when observed from the perpendicular direction of the film was obtained without defects such as cracks in the whole plane.

Example 25 The film obtained in the same way as Example 23 which was formed by organic-inorganic composite was calcined using electronic furnace with nitrogen flow at 500 °C for lh. And a red to orange structural color film which showed vivid coloration with the "play of colors" when observed from the perpendicular direction of the film was obtained without defects such as cracks in the whole plane.

Example 26

100 parts of 40% water dispersion of the copolymer particles obtained in Example 1, 20 parts of maleic acid water solution, 80 parts of isopropanol solution of mixed metal oxide sources formed by mixing organic titanium compound (isopropanol solution) into silane oligomer MS-51 by the ratio shown in the following table (mass ratio) were mixed and stirred for 2h in 40 ^°C water bath. And milky white aqueous compositions that were homogeneously dispersed were obtained.

Table 7

The same operation as Example 2 was carried out except for using the prepared aqueous compositions. The aqueous composition was cured and dried in the liquid-repellent screw tube and free-standing disc-shape structural color objects which were formed by organic-inorganic composite were obtained. The object was milky white solid that showed an opal-like "play of colors". Then the objects were calcined using electronic furnace under aerated condition at 450 ^°C for 30 min and as same as Example 3, objects which showed vivid coloration with luster depending on the metal oxide source used were obtained without defects such as cracks. The coloration of the objects was blue (26-1), blue-green (26-2) and blue (26-3) respectively.

Claims

What is claimed is:

1. A method for manufacturing a structural color object formed by organic-inorganic composite, characterized by comprising the following steps:

(1) in aqueous solvent, radically polymerizable monomers, the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, are quantitatively polymerized by soap-free emulsion polymerization at the concentration in the range of 10-30 mass (summation of the mass (al) and (a2) against the total mass of the reactive composition) to obtain an aqueous dispersion of copolymer particles (A);

(2) preparing an aqueous composition containing the aqueous dispersion of copolymer particles (A) obtained from step (1), metal alkoxides and/or the partially condensed compounds thereof (B) and acid catalysts(C);

(3) curing the aqueous composition obtained from step (2) on a substrate or in a vessel.

2. A method for manufacturing a structural color object composed of metal oxides as a main constituent, characterized by comprising the following steps:

1) in aqueous solvent, radically polymerizable monomers, the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent, are quantitatively polymerized by soap-free emulsion polymerization at the concentration in the range of 10-30 mass (summation of the mass (al) and (a2) against the total mass of the reactive composition) to obtain an aqueous dispersion of copolymer particles (A);

(3) curing the aqueous composition obtained from step (2) on a substrate or in a vessel;

(4) calcination of the cured material obtained from step(3).

3. The method for manufacturing the structural color object of Claim 1 or 2, wherein, the aqueous dispersion of the copolymer particles (A) obtained from step (1) is concentrated to more than 40mass of solid content and then provided for step (2).

4. The method for manufacturing the structural color object of any one of Claims 1-3, wherein, the ratio of the radically polymerizable water-soluble monomers (al) including (meth)acrylamide as a main

constituent and the radically polymerizable water-insoluble monomers (a2) including (meth)acrytlate as a main constituent, indicated by the mole ratio (al)/(a2), is in the range of 3.5-12

5. The method for manufacturing the structural color object of any one of Claims 1-4, wherein, the soap-free emulsion-polymerization is achieved by multi step polymerization wherein the monomers (al) and/or the monomers (a2) are divided into several fractions and then added.

6. The method for manufacturing the structural color object of any one of Claims 1-5, wherein, the radically polymerizable water-insoluble monomers (a2) including (meth)acrylate as a main constituent contains glycidyl (meth)acrylate or oxetane (meth)acrylate.

7. The method for manufacturing the structural color object of any one of Claims 1-6, wherein, the average particle size of the copolymer particles (A) determined from the observation images of scanning electron microscope is in the range of 100~400nm.

8. The method for manufacturing the structural color object of any one of Claims 1-7, wherein, the metal alkoxides and/or the partially condensed compounds thereof (B) contains silicon alkoxides having a hydrolysable group of over trivalent.

9. The method for manufacturing the structural color object of any one of Claims 1-8, wherein, the pH of the aqueous composition is in the range of 1.5-6.5.

10. The method for manufacturing the structural color object of any one of Claims 1-9, characterized in that, the mass ratio of the aqueous dispersion of the copolymer particles (A) and the metal alkoxides and/or the partially condensed compounds thereof (B) in the aqueous composition, represented by the mass ratio (Α)/(Β') in which the (Β') is the mass of completely hydrolyzed (B), is in the range of 60/40-15/85.

11. The method for manufacturing the structural color object of any one of Claims 1-10, wherein, the substrate or the vessel used in step (3) is subjected to liquid- repellent treatment beforehand.

12. The method for manufacturing the structural color object of any one of Claims 2-11, wherein, the calcination process of step (4) is carried out under nitrogen or argon atmosphere, and the calcined materials contain carbonized compounds of the copolymer particles (A), and/or the metal alkoxides and/or the partially condensed compounds thereof (B).