JP2020089999A - Structural color-variable sheet, production method of the same, and polymer particle used for structural color-variable sheet - Google Patents

Abstract

To provide a new material in which a tone-changing material effectively operates when a stress is applied and shows changes in a tone not irreversibly but reversibly in a structural color when the stress is removed, and a stress state can be easily recognized by changes in visible light.SOLUTION: A structural color-variable sheet is provided, in which polymer particles have a layer containing a first methacrylic polymer and a layer containing a second (meth)acrylic polymer different from the first methacrylic polymer on at least a part of surfaces of the polymer particles. The second (meth)acrylic polymer has a structural unit having a reactive functional group and is crosslinked by a crosslinking agent.SELECTED DRAWING: None

Description

The present invention relates to a structural color variable sheet whose structural color changes by tensile stress, a method for manufacturing the structural color variable sheet, and polymer particles used in the structural color variable sheet.

In recent years, a laminated polymer polymer in which a color tone is changed by laminating two kinds of polymers having different refractive indexes has been proposed and reported (for example, see Non-Patent Documents 1 and 2). This laminated polymer has been attracting attention as a color-tone changing material used for various decorative materials because it has an arbitrary structural color and changes by controlling the type of polymer polymer and the thickness of each layer. There is. However, this proposed structural color change material changes its structural color when tensile stress is applied by causing plastic deformation, but the change is irreversible, and therefore it is possible to return to the initial structural color. It was impossible.

On the other hand, another type of structural color change material other than the above-mentioned laminated material is also known. That is, a material containing colloidal crystals containing a large amount of water filled between particles with a hydrogel, which changes color when a compressive stress is applied, and has been proposed and reported in various academic literatures. (Non-patent documents 3, 4). However, such a hydrogel type structural color change material has a low elastic modulus, and its color tone can be changed by using compressive stress instead of tensile stress. .. Therefore, the conditions under which the structural color changes are limited, which places great restrictions on the places and situations in which it can be used, and naturally limits the usage patterns.

T. C. Wang et al. , Adv. Mater. , Vol. 14, p. 1534 (2002) C. Osuji, Adv. Functional Mater. , Vol. 12, p. 753 (2002) Y. Iwayama et al. , Langmuir vol. 19, p. 977 (2003) S. H. Foulger et al. , Adv. Mater. vol. 15, p. 685 (2003)

In view of such a situation, the present invention has no inconvenience that the change in color tone is irreversible or the use form is restricted in the material design in the color tone change type material, unlike the material according to the above-mentioned prior art. That is, it works effectively when stress is applied in any situation and environment, reversibly elastically deforms, and the structural color changes reversibly against strain, tensile stress or compressive stress, and strain deformation The aim is to provide a new material that can easily recognize various stresses by changing the visible light.

Further, by positively utilizing this unique color tone change phenomenon, it is not limited to merely being used as a decorative material, and for example, it can be visually visually recognized easily without using a particularly expensive measuring instrument. Various functional members such as a new strain sensor that is inexpensive and a completely new type, a fuse element that blocks the propagation of light, a simple weighing scale, and a structural color variable sheet that can be used in various fields such as equipment and various toys. It is to provide. Furthermore, another object of the present invention is to provide a new technique in which this structural color variable sheet is attached to an object, the amount of deformation of the elastic body is measured by spectrum analysis, and thereby the deformation or strain change of the object is detected.

Therefore, the inventors of the present invention have conducted diligent research in order to provide a color-tone-changing material satisfying the above-mentioned purpose, and as a result, monodisperse particles in an elastic body have a periodic structure of about the wavelength of light. It has been found that by regularly arranging, the structural color can reversibly change while causing elastic deformation by the stress applied to the elastic body. The present invention has been made based on this finding, and its configuration is as described below.

The present invention includes [1] a layer containing a first methacrylic polymer and a second (meth)acrylic polymer different from the first methacrylic polymer on at least a part of the surface of the polymer particles. The second (meth)acrylic polymer having a layer is a structural color variable sheet having a structural unit having a reactive functional group and further crosslinked with a crosslinking agent.
Further, the present invention is [2] the structural color variable sheet according to the above [1], wherein the polymer particles are crosslinked polystyrene particles.
Further, the present invention is [3] the structural color variable sheet according to the above [2], wherein the crosslinked polystyrene particles are crosslinked polystyrene containing alkylenediol di(meth)acrylate or divinylbenzene.
The present invention also provides [4] the structural color according to any one of the above [1] to [3], wherein the glass transition point (Tg) of the second (meth)acrylic polymer layer is lower than that of the polymer particles. It is a variable seat.
Further, the present invention is [5] the structural color variable sheet according to any one of the above [1] to [4], wherein the first methacrylic polymer layer contains a methacrylate having an allyl group as a structural unit. ..
[6] The structural color variable sheet according to any one of the above [1] to [5], wherein the average particle diameter of the polymer particles is [150] to 750 nm.
[7] The structural color variable sheet according to any one of the above [1] to [6], wherein the crosslinking agent is a blocked isocyanate.
Further, the present invention is [8] the structural color variable sheet according to any one of the above [1] to [7], which further contains carbon particles.
The present invention is also [9] the structural color variable sheet according to any one of the above [1] to [8], which has an adhesive layer on a part or all of at least one main surface.
The present invention also provides [10] a polymer particle for use in the structural color variable sheet according to any one of the above [1] to [9], wherein at least a part of the surface of the polymer particle is And a layer containing a second (meth)acrylic polymer in at least a part of the layer containing the first methacrylic polymer, wherein the second (meth)acrylic polymer is , A polymer particle used for a structural color variable sheet having a structural unit containing a reactive functional group.
Furthermore, the present invention is [11] a method for manufacturing a structural color variable sheet, which comprises the steps of kneading and molding the polymer particles used in the structural color variable sheet according to the above [10] and a crosslinking agent.

The structural color variable sheet according to the present invention includes polymer particles spatially and periodically arranged, and elastic bodies of a first methacrylic polymer layer and a second (meth)acrylic polymer layer located around the polymer particles. The elastic body is elastically deformed by the tensile stress, and the array period of the monodisperse particles is deformed at a predetermined rate according to the elastic deformation. As a result, light undergoes Bragg reflection in accordance with the array period of the polymer particles after deformation, so that a structural color change can be exhibited. Since the elastic body is used as the dispersion medium of the polymer particles, the material of the present invention can easily return to the initial state by removing the tensile stress. Therefore, it is possible to provide a material that exhibits a reversible elastic deformation behavior and thereby a color tone reversibly changes.

In the present invention, (meth)acrylic means at least one of acrylic and methacrylic corresponding thereto. The same applies to other similar expressions such as (meth)acrylate.
(Polymer particles)
The polymer particles can be used without limitation as long as they are polymer particles, but it is preferable to use crosslinked polystyrene particles as a main component.
The proportion of the crosslinking agent in the crosslinked polystyrene is preferably 5% by mass to 20% by mass. If it is less than 5% by mass, the crosslinked polystyrene particles may be melted and deformed when heated to form a film, and the color of the structural color is lowered. If it exceeds 20% by mass, the particles are likely to aggregate during synthesis of the particles, or the refractive index of the crosslinked polystyrene particles is lowered, so that the color of the structural color is lowered.
The cross-linking agent can be used as long as it has two or more radically polymerizable functional groups, and includes (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di (Poly)alkylene glycol-based di(meth)acrylate such as (meth)acrylate; 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di( (Meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2,4-diethyl- 1,5-Pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, 3-methyl-1,7-octanediol di(meth)acrylate, 2-methyl-1,8-octanedioldi( Alkanediol-based di(meth)acrylates such as (meth)acrylate; neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolpropane tetra(meth)acrylate, Pentaerythritol tri(meth)acrylate, ethoxylated cyclohexanedimethanol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, propoxylated ethoxylated bisphenol A di(meth) Acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1,1-trishydroxymethylpropane triacrylate and the like can be mentioned. .

In addition, as a product name of a commercial item, NK ester [A-TMPT-6P0, A-TMPT-3E0, A-TMM-3LMN, A-GLY series, A-9300, AD-TMP manufactured by Shin-Nakamura Chemical Co., Ltd. , AD-TMP-4CL, ATM-4E, A-DPH] and the like.
The crosslinking agents may be used alone or in combination of two or more. Among these, it is preferable to use alkylenediol di(meth)acrylate or divinylbenzene from the viewpoint of efficiently increasing the degree of crosslinking.
The average particle size of the crosslinked polystyrene particles is preferably 150 to 750 nm from the viewpoint of the particle size showing the structural color.
In addition, in this specification, an average particle diameter is a volume average particle diameter measured by a laser diffraction scattering particle size distribution measuring device (for example, ELSZ manufactured by Otsuka Electronics Co., Ltd.).

(First methacrylic polymer layer, second (meth)acrylic polymer layer)
The polymer particles have a first methacrylic polymer layer and a second (meth)acrylic polymer layer on the surface thereof. It is preferable that the first layer copolymerize 10% or more of a methacrylic monomer having an allyl group (methacrylate) with a radical-polymerizable methacrylic monomer.
Examples of (meth)acrylic monomers that can be used in the first layer and the second layer include the following.
Methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, stearyl acrylate, 2-Chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, methacryl Examples thereof include (meth)acrylic acid esters such as acid n-octyl, dodecyl methacrylate, lauryl methacrylate, and stearyl methacrylate.
By copolymerizing a monomer having an allyl group in the first layer, it becomes possible to graft the second layer from the surface of the first layer.
The amount of the first methacrylic polymer layer based on the crosslinked polystyrene particles of the polymer particles is preferably 10 to 100% by mass.
The second layer copolymerizes a monomer having a reactive functional group with a (meth)acrylic monomer having one radically polymerizable double bond. As the reactive functional group, a hydroxyl group, a carboxyl group, a glycidyl group, an epoxy group or the like can be used. Among them, copolymerization of a monomer having a hydroxyl group or a carboxyl group has an effect of preventing aggregation of particles during synthesis. Further, by providing a reactive functional group to the second layer (shell), it becomes possible to crosslink in a later step. The amount of the second layer based on the crosslinked polystyrene particles of the polymer particles is preferably 100 to 250% by mass.

The following are mentioned as specific monomers having a carboxyl group.
(1) Carboxyl group-containing polymerizable monomer Unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, maleic acid and fumaric acid, monoalkyl itaconic acid such as monobutyl itaconate (carbon number 1 To 8) esters, monoalkyl maleates (C1-8) esters such as monobutyl maleate, and various carboxyl group-containing monomers such as vinyl group-containing aromatic carboxylic acids such as vinylbenzoic acid and salts thereof. Can be mentioned. In addition, these compounds can be used individually by 1 type or in combination of 2 or more types, and may have counter ion, such as Na, by neutralization.

The following are mentioned as specific monomers having a hydroxyl group.
(2) Hydroxyl group-containing polymerizable monomer Hydroxyl group-containing (meth) such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate Acrylic monomers, (poly)ethylene glycol mono(meth)acrylate, (poly)propylene glycol mono(meth)acrylate and other (poly)alkylene glycol (meth)acrylic monomers, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether And the like, and hydroxyl group-containing allyl monomers such as allyl alcohol and 2-hydroxyethyl allyl ether. In addition, these compounds can be used individually by 1 type or in combination of 2 or more types.

(Method for producing polymer particles, first methacrylic polymer, second layer (meth)acrylic polymer)
The method for producing the polymer particles of the present embodiment is not particularly limited, and known methods such as emulsion polymerization method, soap-free emulsion polymerization method, microsuspension polymerization method, miniemulsion polymerization method and dispersion polymerization method can be used. Of these, precipitation polymerization and emulsion polymerization are preferable because the particle size is easy to control and they are suitable for industrial production.

The content of the polymerizable monomer in the reaction solution in such a polymerization method is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, further preferably 3 to 20% by mass in the total reaction solution. %. In such a polymerization method, even if the amount of the monomer in the reaction system is increased, the aggregate of the particles does not extremely increase, but when the content of the raw material monomer exceeds 50% by mass, the particles are monodispersed. It becomes difficult to obtain a high yield in a condensed state. On the other hand, if it is less than 1% by mass, it takes a long time to complete the reaction, and it is not practical from an industrial viewpoint.

The reaction temperature at the time of polymerization varies depending on the type of solvent used and cannot be specified unconditionally, but is usually about 10 to 200°C, preferably 30 to 130°C, more preferably 40 to 90°C. Is. Further, the reaction time is not particularly limited as long as it is a time required for the desired reaction to be almost completed, and the monomer species and their blending amounts, the types of functional groups, the viscosity of the solution, the concentration and the objective Although it largely depends on the particle size and the like, for example, in the case of 40 to 90° C., it is 1 to 72 hours, preferably 2 to 24 hours.

The following initiators can be used for polymerizing the monomers, for example. 2'-azobis{2-[N-(2-carboxyethyl)amidinopropane, 2,2'-azobis[2-(phenylamidino)propane]dihydrochloride (VA-545, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) , 2,2'-Azobis{2-[N-(4-chlorophenyl)amidino]propane}dihydrochloride (VA-546, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2'-azobis{2-[N -(4-Droxyphenyl)amidino]propane}dihydrochloride (VA-548, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2'-azobis[2-(N-benzylamidino)propane]dihydrochloride (VA) -552, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 2,2'-azobis[2-(N-allylamidino)propane]dihydrochloride (VA-553, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2 ′-Azobis(2-amidinopropane)dihydrochloride (V-50, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2′-azobis{2-[N-(4-hydroxyethyl)amidino]propane}dihydrochloride (VA-558, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride (VA-041, Fujifilm Wako Pure Chemical Industries, Ltd.) Ltd.), 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044, Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2-azobis[2-( 4,5,6,7-Tetrahydro-1H-1,3-diazepin-2-yl)propane]dihydrochloride (VA-054, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2-azobis[2-( 3,4,5,6-Tetrahydropyrimidin-2-yl)propane]dihydrochloride (VA-058, FUJIFILM Wako Pure Chemical Industries, Ltd.), 2,2-azobis[2-(5-hydroxy-3,4) ,5,6-Tetrahydropyrimidin-2-yl)propane]dihydrochloride (VA-059, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2-azobis{2-[1-(2-hydroxyethyl)-2. -Imidazolin-2-yl]propane} dihydrochloride (VA-060, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2,2-azobis[2-(2-imidazolin-2-yl)propane] (VA-061, FUJIFILM Wako Pure Chemical Industries, Ltd.), 2,2'-azobis[N- (2-carboxyethyl)-2-methylpropionamidine] (VA-057, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), potassium peroxodisulfate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and ammonium peroxodisulfate (FUJIFILM Chemicals) Koujunyaku Co., Ltd.).
These may be used alone or in combination of two or more. The content of the radical polymerization initiator is usually 0.1 to 10 mol%, preferably 0.1 to 5 mol%, and more preferably 0.1 to 2 mol% with respect to 100 mol% of the polymerizable monomer. . The functional group may be added with a polymer dispersant or a surfactant.

An emulsifier can be used together to improve the dispersibility of the polymer particles. Examples of emulsifiers that can be used in this embodiment include anionic emulsifiers and nonionic emulsifiers.
Specific examples of the anionic emulsifier include sodium alkylbenzene sulfonate, sodium lauryl sulfonate, potassium oleate and the like, and sodium dodecylbenzene sulfonate is particularly preferably used.
Specific examples of the nonionic emulsifier include polyoxyethylene nonylphenyl ether and polyoxyethylene lauryl ether.

(Structural color variable sheet)
The structural color variable sheet is a film obtained by kneading the main polymer particles in which the first methacrylic polymer layer and the second (meth)acrylic polymer layer are provided on the surface of the polymer particles. In addition, black particles are preferably dispersed from the viewpoint of clarifying the color of the structural color. Any black particles can be used, but among them, it is preferable to use carbon particles because the color can be made clear with a small amount. The blending amount of carbon particles is preferably 1% by mass or less based on the mass of the present polymer particles. Further, in order not to make the black color too strong, it is more preferably 0.5% by mass or less.

From the viewpoint of improving the deformation recovery property, the film is preferably crosslinked with a crosslinking agent. As a method for crosslinking, any method can be used as long as it can react with the reactive functional group in the second layer of the polymer particles.
As an example of the cross-linking agent, a polyfunctional epoxy compound, an isocyanate compound, a thiol compound, an amine compound or the like can be used. As an example of producing a structural color variable sheet, when the second layer has a hydroxyl group, it can be crosslinked by kneading with a blocked isocyanate compound, molding and then heating. The amount of the cross-linking agent based on the polymer particles is preferably 5% by mass to 20% by mass. In particular, if it is a blocked isocyanate, it is preferable to use a blocked isocyanate because it is easy to mold without causing crosslinking during heating and kneading of particles.

Hereinafter, embodiments of the present invention will be described in detail with reference to examples. However, these examples are merely specific examples for explaining the present invention, and the present invention is not limited thereto.
(Example 1)
(Synthesis of cross-linked polystyrene particles (polymer particles))
After adding 63 g of styrene, 7 g of butanediol diacrylate (BDDA), and 200 g of sodium dodecyl sulfate aqueous solution (0.3 mass %) to a 1 L flask, the temperature was raised to 75°C. Thereafter, 0.35 g of potassium peroxodisulfate was added, and the polymerization was continued for 4 hours.

(Formation of first methacrylic polymer layer)
To the above dispersion obtained after the polymerization, 3 g of allyl methacrylate, 27 g of methyl methacrylate, and 40 g of a 0.3 mass% sodium dodecyl sulfate aqueous solution were added, and the polymerization was continued at 75° C. for 4 hours to obtain the first methacrylic acid. A polymer layer was formed.

(Formation of second (meth)acrylic polymer layer)
To the particle dispersion liquid on which the first methacrylic polymer layer (first shell) was formed, 130 g of ethyl acrylate, 2.6 g of hydroxyethyl methacrylate, and 140 g of 0.3% by mass aqueous sodium dodecyl sulfate solution were added, Polymerization was continued at 75° C. for 4 hours to form a second (meth)acrylic polymer layer.

(Production of structural color variable sheet)
Methanol was added to the particle dispersion liquid on which the second (meth)acrylic polymer layer had been formed as described above to cause aggregation, and then the polymer particles were filtered and dried at 80° C. for 12 hours. To 100 g of the obtained polymer particles, 3 g of blocked isocyanate and 0.1 g of carbon black were kneaded at 120° C. with a heat kneader and formed into a film with a press. The obtained film was heated at 180° C. for 10 minutes to crosslink the film.

(Reflection spectrum measurement)
The reflection spectrum of the film was measured with a spectrophotometer. Further, after the film was stretched and stretched by 25%, the reflection spectrum was measured again, and then the film was further unloaded, and the reflection spectrum was measured again.

(Example 2)
Synthesis and evaluation were performed in the same manner as in Example 1 except that hexanediol diacrylate was used instead of butanediol diacrylate in the synthesis of the crosslinked polystyrene particles.

(Example 3)
Synthesis and evaluation were performed in the same manner as in Example 1 except that divinylbenzene was used instead of butanediol diacrylate in the synthesis of crosslinked polystyrene.

(Example 4)
Synthesis and evaluation were performed in the same manner as in Example 1 except that methacrylic acid was used instead of hydroxyethyl methacrylate in the formation of the second methacrylic polymer layer.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the first methacrylic polymer layer was not formed.

(Comparative example 2)
When the second methacrylic polymer layer of Example 1 was formed, it was performed in the same manner except that hydroxyethyl methacrylate (PHEMA) was not used.

(Comparative example 3)
The evaluation was performed in the same manner as in Example 1 except that the cross-linking agent was not used when the structural color variable sheet was formed.

Crosslinked polystyrene particles (polymer particles) used in the above Examples 1 to 4 and Comparative Examples 1 to 3, the average particle size thereof, the formation of the first methacrylic polymer layer (shell 1), the second (meth) The formation of the acrylic polymer layer (shell 2) and its reactive functional groups are summarized in Table 1.

The symbols in Table 1 are as follows.
BDDA: Butanediol diacrylate ST: Styrene PAM: Allyl methacrylate MMA: Methyl methacrylate PHEMA: Hydroxyethyl methacrylate PEA: Ethyl acrylate HDDA: Hexanediol diacrylate EGDA: Divinylbenzene PMA: Methacrylic acid

In Table 2, the addition amount of the crosslinking agent (block isocyanate) used in Examples 1 to 4 and Comparative Examples 1 to 3, the addition amount of carbon black (carbon particles), the absorption wavelength before deformation, and the absorption after 25% elongation The wavelength and the absorption wavelength after the deformation recovery are shown together.

In Examples 1 to 4 according to the present invention, the absorption wavelength before deformation was different from the absorption wavelength at 25% elongation, and the structural color was changed. As in Comparative Examples 1 to 3, the absorption wavelength after deformation recovery was equal to the absorption wavelength before deformation in Examples 1 to 4 of the present invention, but in Comparative Examples 1 to 3, before deformation. The absorption wavelength was different from that of.

Claims (11)

At least a part of the surface of the polymer particles has a layer containing a first methacrylic polymer and a layer containing a second (meth)acrylic polymer different from the first methacrylic polymer, The (meth)acrylic polymer is a structural color variable sheet having a structural unit having a reactive functional group and further crosslinked with a crosslinking agent. The structural color variable sheet according to claim 1, wherein the polymer particles are crosslinked polystyrene particles. The structural color variable sheet according to claim 2, wherein the crosslinked polystyrene particles are crosslinked polystyrene containing alkylenediol di(meth)acrylate or divinylbenzene. The structural color variable sheet according to any one of claims 1 to 3, wherein a glass transition point (Tg) of the second (meth)acrylic polymer layer is lower than that of the polymer particles. The structural color variable sheet according to any one of claims 1 to 4, wherein the first methacrylic polymer layer contains a methacrylate having an allyl group in a structural unit. The structural color variable sheet according to any one of claims 1 to 5, wherein the average particle size of the polymer particles is 150 to 750 nm. The structural color variable sheet according to claim 1, wherein the crosslinking agent is a blocked isocyanate. The structural color variable sheet according to any one of claims 1 to 7, further comprising carbon particles. The structural color variable sheet according to any one of claims 1 to 8, which has an adhesive layer on a part or all of at least one main surface. The polymer particles used for the structural color variable sheet according to any one of claims 1 to 9, wherein the polymer particles have a layer containing a first methacrylic polymer on at least a part of the surface of the polymer particles, At least a part of the layer containing the first methacrylic polymer has a layer containing the second (meth)acrylic polymer, and the second (meth)acrylic polymer has a structural unit containing a reactive functional group. Polymer particles used in the structural color variable sheet. A method for manufacturing a structural color variable sheet, comprising the steps of kneading and molding the polymer particles used in the structural color variable sheet according to claim 10 and a crosslinking agent.