JP2014047233A - Composition for structural color expression and structural color expression membrane - Google Patents

Abstract

【Task】
A structural color developing film having a clear structural color and capable of maintaining a clear structural color even when held in a high temperature environment, and a structural color developing film capable of easily forming the structural color developing film Providing a composition.
[Solution]
A composition containing copolymer particles having a core-shell structure, wherein the core part of the copolymer particles contains a resin (b) crosslinked with a conjugated diene, and the resin (b) is derived from a conjugated diene And the number average particle diameter of the copolymer particles is from 0.05 μm to 1 μm, based on the total amount of the resin (b). A composition for expressing a structural color, wherein the refractive index difference between the core part and the shell part in the coalesced particles is 0.01 or more.
[Selection] Figure 1

Description

  The present invention relates to a structural color developing composition and a structural color developing film.

  It is known that a coating film in which particles having a uniform shape and size are regularly arranged in a three-dimensional manner selectively reflects light in a specific wavelength region by Bragg reflection. In particular, when the particle interval is in the wavelength range of visible light, the structural color can be visually confirmed. This structural color has the feature that the hue changes depending on the viewing angle. In addition, structural colors exhibit color effects different from those of pigments and pigments, and because they do not fade, they are expected to be applied to coloring materials, photonic crystals, optical sensors, optical filters, etc. Methods for producing the body and coatings containing it have been studied.

  Patent Document 1 discloses a structural color coating film-forming coating composition containing core-shell fine particles composed of a core part and a shell part, and the coating film obtained by applying the coating composition is deformed and fluidized even when dried and heated. Non-dispersed monodisperse core parts are disclosed to be regularly arranged in the shell part and exhibit a structural color.

JP 2009-249527 A

  However, in the structural color coating film forming coating composition described in Patent Document 1, there is a problem that the structural color is not sufficiently developed or the structural color is not developed due to the expansion of the particle size distribution width or the irregular shape of the core particles. There is a fear.

  The present invention provides a structural color developing film having a clear structural color and capable of maintaining a clear structural color even when kept under heating and pressure conditions, and the structural color developing film. It is an object to provide a composition for forming a structural color that can be formed.

  The present inventors set the core part of the copolymer particles having a core-shell structure to contain a resin crosslinked with a predetermined amount of conjugated diene, and further set the number average particle diameter of the copolymer particles to a predetermined value. It was found that a structural color-expressing film that expresses a clear structural color can be obtained by setting the thickness within the range of.

That is, the present invention is as follows.
[1] A composition containing copolymer particles having a core-shell structure, wherein the core part of the copolymer particles contains a resin (b) crosslinked with a conjugated diene, and the resin (b) The structural unit derived from the conjugated diene is contained in a proportion of 0.01% by mass or more and 50% by mass or less based on the total amount of the resin (b), and the number average particle diameter of the copolymer particles is 0.05 μm. The composition for expressing the structural color, which is 1 μm or less and the difference in refractive index between the core part and the shell part in the copolymer particles is 0.01 or more.
[2] The composition for expressing structural color according to [1], wherein the total amount of the shell part in the copolymer particles is 30% by mass or more and 95% by mass or less based on the total amount of the copolymer particles.
[3] The structural color developing composition according to [1] or [2], further comprising a dispersion medium for dispersing the copolymer particles.
[4] A structural color developing film formed from the structural color developing composition according to any one of [1] to [3].
[5] The structural color developing film according to [4], comprising a matrix material derived from the shell portion and core particles derived from the core portion dispersed in the matrix material.

  According to the present invention, there is provided a structural color developing film having a clear structural color and capable of maintaining a clear structural color even when kept under heating and pressure conditions, and the structural color developing film. A composition for expressing a structural color that can be easily formed can be provided.

1 is a schematic cross-sectional view showing one embodiment of a structural color developing composition and a structural color developing film of the present invention. It is a figure which shows an example of a spherical core particle. It is a figure which shows an example of the deformed core particle.

  A preferred embodiment of the present invention will be described below.

(Copolymer particles)
The copolymer particles according to this embodiment have a core-shell structure. Here, “having a core-shell structure” can be rephrased as “having a core portion and a shell portion covering the core portion”.

  In this embodiment, the core part of the copolymer particles is a resin crosslinked with a conjugated diene (hereinafter, referred to as “resin (b)”. In this specification, the resin includes a so-called rubber component). Containing. Moreover, resin (b) contains the structural unit derived from a conjugated diene in the ratio of 0.01 mass% or more and 50 mass% or less on the basis of the whole quantity of resin (b).

  In this embodiment, the number average particle diameter of the copolymer particles is 0.05 μm or more and 1 μm or less, and the difference in refractive index between the core portion and the shell portion in the copolymer particles is 0.01 or more.

  In addition, the core part of the copolymer particle may be formed so as to cover the seed particle. That is, the copolymer particles may have seed particles, a core portion that covers the seed particles, and a shell portion that covers the core portion. At this time, the core particles described later are formed from sheet particles and a core part.

<Particle size, coefficient of variation>
In the present specification, the number average particle diameter is a number average particle diameter measured by a dynamic light scattering method, and can be measured by, for example, MICROTRAC UPA-150 manufactured by Nikkiso Co., Ltd.

  As described above, the number average particle diameter of the copolymer particles is 0.05 μm or more and 1 μm or less. In the structural color developing film formed of such copolymer particles, the light reflected by the regularly arranged core portions interferes and diffracts in accordance with the black reflection conditions, and a clear structural color is expressed. . The structural color developed in the structural color developing film changes depending on the number average particle diameter of the copolymer particles. That is, the structural color expressed in the structural color developing film can be adjusted by adjusting the number average particle diameter of the copolymer particles.

  The Cv value (coefficient of variation) expressed as a percentage of the particle diameter standard deviation with respect to the number average particle diameter is preferably 30% or less. The Cv value is a value obtained by Cv [%] = (σ / D) × 100 (σ: standard deviation, D: average particle diameter), and the smaller this value, the more uniform the particle size. When the Cv value is 30% or less, a coating film in which the shell portion is closely packed can be formed, and a structural color developing film in which the core portion is more regularly arranged can be obtained.

<Refractive index>
The difference in refractive index between the core part and the shell part is the difference between the refractive index value of the resin component constituting the core part and the refractive index value of the resin component constituting the shell part. The refractive index value is measured with an Abbe refractometer. it can. When the difference in refractive index between the core portion and the shell portion is 0.01 or more, light transmission is suppressed in the structural color developing film, and sufficient visible light reflection occurs so that the structural color can be visually confirmed.

  The upper limit of the refractive index difference is not particularly limited, but generally the upper limit of the optical refractive index of the polymer resin is about 1.82, and the refractive index of air (or vacuum) is 1.0. The upper limit of the rate difference is considered to be 0.82. It is known that the relational expression of Gladstone / Dale represented by the following formula (1) holds for the refractive index n of the copolymer.

Wherein (1), ν _i denotes the volume fraction with respect to the entire copolymer polymer of the homopolymer of each monomer, n _i is the refractive index of the homopolymer of each monomer. In the present embodiment, it is possible to select a monomer used for manufacturing the resin constituting the core part and the shell part so that the difference in refractive index calculated by the formula (1) is 0.01 or more. it can.

  The difference in refractive index between the core part and the shell part is preferably 0.02 or more, more preferably 0.03 or more.

  As a technique for achieving the above refractive index difference, for example, a resin component that constitutes the core portion is a resin obtained from 50 to 99.9% by mass of a styrene monomer and 0.1 to 50% by mass of a conjugated diene. And a method in which the resin component constituting the shell part is a resin obtained from 100% by mass of an acrylic monomer having a lower refractive index than a styrene monomer. Moreover, the resin component which comprises a core part is made into resin obtained from 50-99.9 mass% of acryl-type monomers, and 0.1-50 mass% of conjugated dienes, The resin component which comprises a shell part is made into acryl. The above-described difference in refractive index can also be achieved by using a resin obtained from 100% by mass of a styrene monomer having a higher homopolymer refractive index than that of the monomer.

<Core part>
The core part of the copolymer particles contains a resin (b) crosslinked with a conjugated diene, and the resin (b) contains 0.01% by mass of structural units derived from the conjugated diene based on the total amount of the resin (b). More than 50 mass% is included. When the core part contains the resin (b), the deformation of the core particles and the expansion of the particle size distribution range are sufficiently suppressed.

  Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and chloroprene. Among these, 1,3-butadiene is preferable.

  The content of the structural unit derived from the conjugated diene in the resin (b) is 0.01% by mass or more and 50% by mass or less, preferably 0.05% by mass or more and 30% by mass or less, more preferably 0.8% by mass. It is 1 mass% or more and 25 mass% or less.

  That is, the amount of the conjugated diene used in the production of the resin (b) is 0.01% by mass or more and 50% by mass or less, preferably 0.05% by mass or more and 30% by mass or less, based on the total amount of monomers. More preferably, it is 0.1 mass% or more and 25 mass% or less.

  By adjusting the content of the structural unit derived from the conjugated diene as described above, the core particles in the structural color developing film are not easily affected by pressure or heating (for example, shape change due to pressure / heating). That is, it is presumed that the shape change of the core particles due to pressure, heating, etc. can be sufficiently suppressed by adjusting the content of the conjugated diene as described above. In addition, the core particles maintain a true spherical shape and are regularly arranged and fixed, and the shape is maintained even after fixation, so the structural color has good heat resistance and a beautiful structural color It is considered that an expression membrane can be obtained.

  The resin component which comprises a core part may have components other than resin (b). For example, the resin component may contain a resin crosslinked with a crosslinkable monomer having two or more double bonds that are non-conjugated to each other in one molecule, and a resin having no crosslinked structure, that is, You may contain resin obtained from monomers other than a crosslinking agent (conjugated diene and a crosslinkable monomer) among the monomers illustrated in this specification.

  The content of the resin (b) is preferably 10% by mass or more, and more preferably 20% by mass or more, based on the total amount of the resin components constituting the core part. Moreover, the core part may be comprised from resin (b) (namely, content of resin (b) may be 100 mass%).

  The number average particle size of the core part is preferably 0.03 μm or more and 0.8 μm or less, and more preferably 0.05 μm or more and 0.7 μm or less. According to the core portion having such an average particle diameter, a better structural color is expressed.

  The Cv value (coefficient of variation) of the number average particle diameter of the core part is preferably 80% or less. When the Cv value of the core part is 80% or less, a better structural color is expressed.

<Shell part>
The shell part of the copolymer particles contains a resin obtained from a resin-forming monomer to be described later (hereinafter sometimes referred to as “resin (a)”).

  The resin component constituting the shell part may contain components other than the resin (a), but the resin (a) content is 70% by mass or more based on the total amount of the resin component constituting the shell part. It is preferable that it is 90% by mass or more. Moreover, the shell part may be comprised from resin (a) (namely, content of resin (a) may be 100 mass%).

<Core shell ratio>
The amount of the resin component constituting the shell part is preferably 30% by mass or more and 95% by mass or less, and preferably 40% by mass or more and 85% by mass or less, based on the total amount of the resin component constituting the copolymer particles. Is more preferable.

  When the amount of the resin component constituting the shell part is 30% by mass or more, the gap between the core parts regularly arranged at the time of manufacturing the structural color developing film can be easily filled and the core parts can be easily fixed. The structural color developing film can be formed without disturbing the above. Further, when the amount of the resin component constituting the shell part is 95% by mass or less, the core part can be arranged at an appropriate interval during the production of the structural color developing film. The incident light can be sufficiently reflected, and a beautiful structural color can be visually confirmed.

<Tg of core and shell>
The Tg (glass transition temperature) of the resin component constituting the core portion and the resin component constituting the shell portion is not particularly limited, but the Tg of the resin component constituting the shell portion is more than the Tg of the resin component constituting the core portion. Preferably it is low.

  For example, if the Tg of the resin component constituting the core part is a high Tg of 50 ° C. or more and the Tg of the resin component constituting the shell part is a low Tg of 40 ° C. or less, deformation or flow of the core part is caused. Since the shell part can be made to flow without being fixed, the core part can be fixed while the shape of the core part is maintained.

<Core part and shell part forming monomer>
The monomer for obtaining the resin constituting the core part and the shell part (hereinafter referred to as “resin-forming monomer”) is not particularly limited except for the conjugated diene for the resin (b) described above, It can select suitably so that the refractive index difference of a core part and a shell part may be 0.01 or more.

  One resin-forming monomer may be used alone, or two or more resin-forming monomers may be used in combination. Examples of the resin-forming monomer include a styrene monomer, an ethylenically unsaturated carboxylic acid monomer, an unsaturated carboxylic acid ester monomer, an unsaturated monomer having a hydroxyalkyl group, and a vinyl cyanide monomer. A monomer is mentioned.

  Examples of the styrenic monomer include styrene, α-methyl styrene, vinyl toluene, t-butyl styrene and the like. These may be used alone or in combination of two or more. Of these, styrene is preferred.

  Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and anhydrides thereof can also be used. These may be used alone or in combination of two or more. Among these, methacrylic acid is preferable.

  As unsaturated carboxylic acid ester monomers, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, glycidyl (meth) acrylate, dimethyl fumarate, diethyl fumarate Dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like. These may be used alone or in combination of two or more. Among these, methyl methacrylate, 2-ethylhexyl acrylate, n-butyl acrylate, and glycidyl methacrylate are preferable.

  Examples of unsaturated monomers having a hydroxyalkyl group include 2-hydroxymethyl acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxy Examples thereof include propyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate and the like. These may be used alone or in combination of two or more. Among these, 2-hydroxyethyl acrylate is preferable.

  Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like. These may be used alone or in combination of two or more. Of these, acrylonitrile is preferred.

  In addition to the above, unsaturated carboxylic acid amide monomers such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylacrylamide; fatty acid vinyl such as vinyl acetate and vinyl propionate Esters; basic monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine; vinyl chloride; vinylidene chloride; Can be used.

  The same monomer may be used for the core part and the shell part as long as the refractive index difference between the core part and the shell part is 0.01 or more. Among the above monomers, from the viewpoint of design, the resin-forming monomer used for the core part contains styrene, methyl methacrylate and 1,3-butadiene, and the resin-forming monomer used for the shell part is It is preferable to contain n-butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate and methacrylic acid. For example, the compounding ratio of the resin-forming monomer for forming the core part is 1 to 39% by mass of styrene, 1 to 30% by mass of methyl methacrylate, 0.13 butadiene of 1,3-butadiene based on the total amount of the copolymer particles. 1 to 15% by mass, other monomer copolymerizable with these is preferably 0.1 to 10% by mass, and the compounding ratio of the resin-forming monomer for forming the shell portion is a copolymer. N-butyl acrylate 5 to 20% by mass, methyl methacrylate 1 to 20% by mass, 2-hydroxyethyl acrylate 1 to 10% by mass, methacrylic acid 1 to 10% by mass, and other copolymerizable with these, based on the total amount of particles It is preferable to set it as 5-15 mass% of monomers. The (meth) acrylate means acrylate or methacrylate.

<Polymerization method and average particle size>
The copolymer particles can be prepared by, for example, emulsion polymerization using the resin-forming monomer or multistage polymerization of soap-free emulsion polymerization. Also, suitable seed particles can be used during emulsion polymerization. Ordinary emulsion polymerization can be used for the polymerization of the seed particles. For example, the average particle size of the copolymer particles can be adjusted to a uniform and appropriate coefficient of variation by appropriately selecting the type and size of seed particles, the type of emulsifier, and the type of initiator and using appropriate amounts. Here, the average particle diameter is the number average particle diameter.

(Method for producing copolymer particles)
Hereinafter, a method for producing copolymer particles will be described.
The copolymer particles can be produced by emulsion polymerization of the above-described resin-forming monomer (including a crosslinking agent). Appropriate seed particles can be used during the polymerization, and the seed particles can also be produced by a known emulsion polymerization. In addition, a known method can be employed for emulsion polymerization, and it can be carried out in an aqueous medium by appropriately using a molecular weight adjusting agent in addition to an emulsifier and a polymerization initiator.

<Emulsifier>
Examples of emulsifiers used include sodium dodecyl sulfate, sodium dodecyl benzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium dodecyl benzene sulfonate, sodium dodecyl diphenyl ether sulfonate, sodium laurate, dihexyl Sodium sulfosuccinate, potassium stearate, calcium oleate, dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, hexadecyl trimethyl ammonium bromide, dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, lauryl poly Oxyethylene ether Etc. The. These may be used alone or in combination of two or more. The amount of the emulsifier used is appropriately determined by a technique known to those skilled in the art according to the target particle size.

<Polymerization initiator>
Polymerization initiators include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate; oil-soluble polymerization initiators such as benzoyl peroxide and lauryl peroxide; redox polymerization initiators in combination with reducing agents, etc. Can be mentioned. These can be used alone or in combination.

<Molecular weight regulator>
Adhesiveness to an object to be coated can be improved by adding a molecular weight adjusting agent as needed during the shell part polymerization of the copolymer particles to reduce the molecular weight. Examples of the molecular weight modifier include 3-chlorobenzenethiol, carbon tetrachloride, t-dodecyl mercaptan, n-hexyl mercaptan, octyl thioglycolate, α-methylstyrene dimer, and the like. Among these, t-dodecyl mercaptan is particularly preferable. The amount of the molecular weight modifier used is preferably 0 to 3 parts by mass with respect to the total amount of single monomers forming the copolymer particles from the viewpoint of film formability.

(Structural color expression composition)
The structural color developing composition according to this embodiment contains the copolymer particles.

  The structural color developing composition may further contain a dispersion medium in which the copolymer particles are dispersed. That is, the structural color developing composition may be a composition containing a dispersion medium and copolymer particles dispersed in the dispersion medium. The dispersion medium is preferably an aqueous solvent. For example, water or an aqueous solvent obtained by adding a hydrophilic solvent such as ethanol to water can be suitably used. The composition for expressing a structural color in which copolymer particles are dispersed in an aqueous solvent can also be referred to as latex.

  The structural color developing composition further contains a preservative, a surfactant, a film-forming aid, a thickener, a pH adjuster, a chelating agent, an ultraviolet absorber, an antioxidant, an emulsifier, and the like as necessary. It may be.

  The content of the copolymer particles in the structural color developing composition is preferably 90% by mass or more, more preferably 92% by mass or more, and 95% by mass or more based on the total amount of the solid content. More preferably.

  Further, the solid content in the structural color developing composition can be appropriately adjusted according to the type of the object to be coated, the desired thickness of the structural color developing film, and the like. For example, the solid content can be 5 to 65% by mass based on the total amount of the structural color developing composition, and can also be 30 to 60% by mass.

(Structural color expression film)
FIG. 1B is a schematic view showing one embodiment of a structural color developing film according to this embodiment. The structural color expression coating film 200 is a coating film obtained by using the copolymer particles 100 shown in FIG. 1A, and includes a matrix material 11 and core particles 21 dispersed in the matrix material 11. To do.

  The matrix material 11 is formed by deforming (for example, melting and flowing) the shell portion 10 of the copolymer particle 100. The matrix material 11 is made of a resin component constituting the shell portion 10 and holds regularly arranged core particles 21. The core particles 21 are particles derived from the core portion 20 of the structural color developing resin 100, and are regularly arranged in the matrix material 11.

  The thickness of the structural color developing film is not particularly limited, but is preferably 10 μm to 1000 μm.

  The structural color developing film can be formed by, for example, applying a structural color developing composition to an object to be coated and then performing a treatment such as heating as necessary to deform the shell portion of the copolymer particles. it can. When the structural color developing composition contains a dispersion medium, for example, after applying to the object to be coated, drying and heating can be performed to deform, melt or flow the shell portion to obtain a structural color developing film. . In addition, when the glass transition temperature of the shell part of the copolymer particles is room temperature or lower, heating is not necessarily required, and the dispersion medium is dried at room temperature after applying the structural color developing composition to the object to be coated. It can also be removed to obtain a structural color developing film.

  The structural color developing composition can form a coating film by various commonly used coating methods such as bar coater coating, spin coating, dip coating, applicator coating, and spray coating.

  For example, in the case of applicator coating, the composition for expressing the structural color is concentrated to a solid content of 40% by mass or more (preferably 40 to 65% by mass), applied to the object to be coated, and dried under appropriate conditions (necessary) Accordingly, a structural color developing film can be obtained by drying and heating. In the case of spray coating, the composition for expressing the structural color is applied to the object to be coated with a solid content of 20 to 60% by mass, and dried under appropriate conditions (drying and heating as necessary) to express the structural color. A membrane can be obtained.

  Conditions for drying and heating the coating film of the structural color developing composition can be appropriately selected according to the solid content concentration of the structural color developing composition, the coating method of the structural color developing composition, and the like.

Drying and heating can be performed separately or simultaneously. The heating conditions may be any conditions as long as the resin component constituting the shell portion can be melted to fill the gaps between the copolymer particles. For example, the heating temperature is preferably equal to or higher than the glass transition temperature of the resin component constituting the shell portion (hereinafter sometimes referred to as “T ₁ ”). In addition, the heating temperature is preferably T ₁ + 150 ° C. or less, and more preferably T ₁ + 130 ° C. or less, from the viewpoint of sufficiently suppressing the shape change of the core part.

<To be painted>
The article to be coated on which the structural color developing composition is applied is not limited. For example, paper, a SUS board, an acrylic board, and an electrodeposition board are mentioned. In particular, if the object to be coated is painted black in advance, extra scattered light that occurs when light is incident can be excluded, and only reflected light can be received, so that the structural color looks clearer.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  Hereinafter, the contents of the present invention will be specifically described with reference to examples. In addition, all the mass parts were made into the solid content conversion value.

<Preparation of composition for expression of structural color>
In an eggplant flask, 100 parts by mass of the latex (solid content: 18 ± 2% by mass) obtained in Examples and Comparative Examples was added, 0.45 parts by mass of an emulsifier was added, and 0.7 parts by mass of potassium hydroxide was added while stirring. Added to adjust pH 6-8. Next, 0.06 parts by mass of an antifoaming agent was added, and then concentrated to a solid content of 43 ± 2% by mass using a rotary evaporator to obtain a structural color developing composition.

<Coating method: applicator coating>
The concentrate adjusted to a solid content of 43 ± 2% by mass by the above-described method was applied to an about 0.2 mm film using an applicator on a black-coated electrodeposition plate. After coating, a structural color developing film was obtained by heating and drying at 55 ° C. and RH 75% for 40 minutes.

(Evaluation method)
<Measurement of refractive index>
The refractive index difference was defined as a difference in refractive index value measured by an Abbe refractometer after separately polymerizing the resins constituting the core portion and the shell portion.

<Method of measuring reflected light>
The reflectance and color of the structural color developing film were measured using a Macbeth colorimeter (CE-741GL) manufactured by Sakata Inx. The light receiving angle was 45 °, the incident angle was −30 °, and the wavelength range was 360 to 750 nm. The color is a color obtained by converting the reflection peak wavelength obtained by measurement into a color system.

<Evaluation of color>
The impression of color development of the structural color developing film was evaluated according to the following evaluation criteria.
A: The color is beautiful and the color is strong B: The color can be clearly identified C: The color can be identified relatively D: The paint film is pure white or transparent and the hue cannot be confirmed

<Evaluation of film formability>
The film formability of the structural color developing film was evaluated by visual observation and scratching with a nail. The evaluation criteria are as follows.
A: A uniform coating film is formed, and even if scratched with a nail, the coating film does not peel off B: A uniform coating film is formed, but when scratched with a nail, the coating film peels off C: Partially cracked Yes, the film peels off when scratched with a nail D: There are many fine cracks in the whole, and the film peels off just by touching

<Ratio of spherical core particles>
In order to evaluate the ratio of particles that maintain a true spherical shape with respect to the core particles in the latex, individual particles when observed at a magnification of 10,000 using a scanning electron microscope (SEM) The total number of each particle was counted in distinction from the particles, and the ratio was calculated. The evaluation criteria were as follows.
A: The proportion of true spherical particles is 90% or more of the whole B: The proportion of true spherical particles is 80% or more and less than 90% of the whole C: The proportion of true spherical particles is 70% or more and less than 80% of the whole D: True spherical particles Less than 70% of the total

Example 1
A reactor is charged with 300 parts by weight of water, 0.01 parts by weight of sodium dodecyl diphenyl ether sulfonate, 0.01 parts by weight of sodium dihexyl sulfosuccinate, and 0.28 parts by weight of seed particles (polystyrene particles having a particle diameter of 35 nm). The mixture was heated to about 80 ° C. with mixing and stirring. To this solution, a mixed liquid 1 consisting of 35 parts by mass of styrene, 12 parts by mass of methyl methacrylate, and 3 parts by mass of 1,3-butadiene was added over 120 minutes. At the same time, 100 parts by mass of water and 0.1 parts by mass of sodium hydroxide were added. A mixed liquid 2 consisting of 0.01 parts by mass of sodium dihexylsulfosuccinate and 0.7 parts by mass of sodium persulfate was added over 300 minutes. When 30 minutes had elapsed after the addition of the mixed liquid 1, a small amount of the formed resin particles were collected, and the particle diameter was measured.

  When 60 minutes have passed after the addition of liquid mixture 1, 20 parts by mass of methyl methacrylate, 6 parts by mass of 2-hydroxyethyl acrylate, 15 parts by mass of butyl acrylate, 6 parts by mass of methacrylic acid, 3 parts by mass of glycidyl methacrylate, t -The liquid mixture 3 which consists of 0.2 mass part of dodecyl mercaptan was added over 100 minutes.

  After the addition of the mixed liquid 2, the temperature was raised to 95 ° C. over 30 minutes with stirring, held for 1 hour, and then cooled to room temperature to obtain a latex containing copolymer particles. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass.

  The resulting copolymer particles had a particle size of 233 nm and a coefficient of variation of 12%. The particle size of only the core part was 181 nm. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The coating film had a strong purple color and a beautiful purple-blue structural color, and was formed with a uniform surface. FIG. 2 shows a typical observation result (observation result by SEM) of the core particle in which the true spherical shape is maintained. In Example 1, the same observation results as in FIG. 2 were obtained.

(Example 2)
A latex containing copolymer particles is obtained in the same manner as in Example 1 except that the composition of the liquid mixture 1 of Example 1 is 26 parts by mass of styrene, 5 parts by mass of methyl methacrylate, and 19 parts by mass of 1,3-butadiene. It was. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass.

  The resulting copolymer particles had a particle size of 234 nm and a coefficient of variation of 14%. The particle size of only the core part was 188 nm. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The coating film showed a purple-blue structural color with a weak color and was formed with a uniform surface.

(Example 3)
The copolymer particles were prepared in the same manner as in Example 1 except that the composition of the liquid mixture 1 of Example 1 was 35 parts by mass of styrene, 14.9 parts by mass of methyl methacrylate, and 0.1 parts by mass of 1,3-butadiene. A latex containing was obtained. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass.

  The resulting copolymer particles had a particle size of 235 nm and a coefficient of variation of 12%. The particle size of only the core part was 184 nm. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The coating film showed a purple-blue structural color with a weak color and was formed with a uniform surface.

Example 4
The seed amount of Example 1 is 0.16 parts by mass, the composition of the liquid mixture 1 is 2.6 parts by mass of styrene, 1.2 parts by mass of methyl methacrylate, and 0.2 parts by mass of 1,3-butadiene. Composition of methyl methacrylate 24.8 parts by mass, 2-hydroxyethyl acrylate 15.6 parts by mass, butyl acrylate 38.6 parts by mass, methacrylic acid 11.6 parts by mass, glycidyl methacrylate 5 parts by mass, t-dodecyl mercaptan 0. A latex containing copolymer particles was obtained in the same manner as in Example 1 except that the amount was 4 parts by mass. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 96% by mass.

  The resulting copolymer particles had a particle size of 338 nm and a coefficient of variation of 12%. The particle size of only the core part was 125 nm. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The coating film showed a green structural color with a weak color and was formed with a uniform surface.

(Example 5)
The composition of the liquid mixture 1 of Example 1 was 49.6 parts by mass of styrene, 17.4 parts by mass of methyl methacrylate, and 4 parts by mass of 1,3-butadiene, and the composition of the liquid mixture 3 was 7.5 parts by mass of methyl methacrylate, 2 Example 1 except that 4.7 parts by weight of hydroxyethyl acrylate, 11.6 parts by weight of butyl acrylate, 3.5 parts by weight of methacrylic acid, 1.5 parts by weight of glycidyl methacrylate, and 0.2 parts by weight of t-dodecyl mercaptan In the same manner as above, a latex containing copolymer particles was obtained. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 29% by mass.

  The resulting copolymer particles had a particle size of 347 nm and a coefficient of variation of 13%. The particle size of only the core part was 303 nm. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The paint film showed a strong reddish orange structural color with a strong tint, was formed in a partially cracked state, and peeled off when scratched with a nail.

(Comparative Example 1)
The composition of the liquid mixture 1 of Example 1 is 19 parts by mass of styrene, 5 parts by mass of methyl methacrylate, and 26 parts by mass of 1,3-butadiene, and the composition of the liquid mixture 3 is 19 parts by mass of methyl methacrylate and 6 parts by mass of 2-hydroxyethyl acrylate. Part, butyl acrylate 15.5 parts by weight, methacrylic acid 6 parts by weight, acrylonitrile 2.8 parts by weight, acrylic acid 0.5 parts by weight, t-dodecyl mercaptan 0.2 parts by weight Thus, a latex containing copolymer particles was obtained. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass. In addition, in FIG. 3, the observation result (observation result by SEM) of the deformed core particle which does not express a structural color is shown. In Comparative Example 1, the same observation results as in FIG. 3 were obtained.

  The resulting copolymer particles had a particle size of 238 nm and a coefficient of variation of 15%. The particle size of only the core part was 185 nm. The refractive index was 1.56 for the core and 1.49 for the shell, and the difference was 0.07. The coating film was white and the structural color could not be confirmed, and it was partially cracked and peeled off when scratched with a nail.

(Comparative Example 2)
The composition of the liquid mixture 1 of Example 1 is 35 parts by mass of styrene, 21 parts by mass of methyl methacrylate, and 1 part by mass of acrylic acid, and the composition of the liquid mixture 3 is 7.5 parts by mass of 1,3-butadiene and methyl methacrylate 11. The same as in Example 1 except that 3 parts by mass, 7 parts by mass of 2-hydroxyethyl acrylate, 10 parts by mass of butyl acrylate, 5 parts by mass of methacrylic acid, 2 parts by mass of glycidyl methacrylate, and 0.2 parts by mass of t-dodecyl mercaptan were used. Thus, a latex containing copolymer particles was obtained. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 43% by mass.

  The resulting copolymer particles had a particle size of 237 nm and a coefficient of variation of 13%. The particle size of only the core part was 185 nm. The refractive index was 1.57 for the core and 1.49 for the shell, and the difference was 0.08. The coating film was transparent and the structural color could not be confirmed. The coating film was partially cracked and peeled off when scratched with a nail.

(Comparative Example 3)
Latex containing copolymer particles by forming 810 nm particles with the same composition as the liquid mixture 1 of Example 1 by soap-free polymerization and using the same as the core to polymerize the shell with the same composition as the liquid mixture 3 of Example 1. Got. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass.

  The resulting copolymer particles had a particle size of 1003 nm and a coefficient of variation of 14%. The refractive index was 1.56 for the core and 1.48 for the shell, and the difference was 0.08. The coating film was white and the structural color could not be confirmed, and it was partially cracked and peeled off when scratched with a nail.

(Comparative Example 4)
The composition of the mixed liquid 1 of Example 1 is 24 parts by mass of styrene, 6 parts by mass of methyl methacrylate, 2 parts by mass of 1,3-butadiene, 6 parts by mass of 2-hydroxyethyl acrylate, 6 parts by mass of butyl acrylate, and 3 parts by mass of methacrylic acid. And 2.8 parts by mass of glycidyl methacrylate, and a copolymer as in Example 1 except that the composition of the mixed solution 3 was changed to the composition of the mixed solution 1 by adding 0.2 parts by mass of t-dodecyl mercaptan. A latex containing particles was obtained. The mass% of the shell part with respect to the total mass of the monomers forming the copolymer particles is 50% by mass.

  The resulting copolymer particles had a particle size of 237 nm and a coefficient of variation of 13%. The particle size of only the core part was 183 nm. The refractive index was 1.55 for the core and 1.55 for the shell, and the difference between them was 0. The coating film was transparent and the structural color could not be confirmed, and there were many fine cracks, and it peeled off when scratched with a nail.

  In the structural color developing composition of the present embodiment, the core particles are regularly arranged in the shell portion because the shape of the core particle sphere is maintained by keeping the amount of the cross-linking agent in the core portion within a certain range. To do. As a result, a structural color with clear color and high designability can be obtained. In the conventional method, it is necessary to adjust the structural color developing body by using another fixing agent to arrange the spherical particles or by alternately laminating two or more kinds of polymers. Compared with these, the structural color expression composition of the present embodiment can be directly applied to an object to be coated in various shapes with one liquid without disturbing the arrangement of the core part without using other fixing agents. There is an advantage that it is possible. In addition, unlike a coloring material such as a dye that absorbs light, it has a characteristic that it is difficult to fade because it is a physical color. From the above, the structural color expression composition of the present embodiment can be used as a color material having a high design property for painting on buildings and outer walls, exteriors of automobiles, and the like.

  DESCRIPTION OF SYMBOLS 10 ... Shell part, 11 ... Matrix material, 20 ... Core part, 21 ... Core particle, 100 ... Copolymer particle, 200 ... Structural color expression film | membrane.

Claims (5)

A composition containing copolymer particles having a core-shell structure,
The core part of the copolymer particles contains a resin (b) crosslinked with a conjugated diene,
The resin (b) includes a structural unit derived from the conjugated diene in a proportion of 0.01% by mass or more and 50% by mass or less based on the total amount of the resin (b).
The number average particle diameter of the copolymer particles is 0.05 μm or more and 1 μm or less,
The composition for structural color expression whose refractive index difference of the core part and shell part in the said copolymer particle is 0.01 or more.   The composition for expressing a structural color according to claim 1, wherein the total amount of the shell portion in the copolymer particles is 30% by mass or more and 95% by mass or less based on the total amount of the copolymer particles.   The composition for expressing a structural color according to claim 1 or 2, further comprising a dispersion medium for dispersing the copolymer particles.   The structural color expression film | membrane formed from the composition for structural color expression as described in any one of Claims 1-3.   The structural color expression film according to claim 4, comprising a matrix material derived from the shell part and core particles derived from the core part dispersed in the matrix material.