Emulsions, structures, and articles having structural color development properties

Abstract

Provided are: polymer fine particles having a number-basis average particle diameter of 50 to 450 nm and a number-basis particle diameter CV of 5% or less; or polymer fine particles that have structural coloration properties when in an ordered arrangement. The acid value of the polymer fine particles is 5 to 38 mgKOH / g. Also provided is an emulsion in which polymer fine particles are dispersed in a medium that is primarily water. Also provided is a structure in which polymer fine particles are in an ordered arrangement and generate a color.

Description

Technical Field

[0001] The present disclosure relates to polymer microparticles having structural colorability, an emulsion and a structure composed of the polymer microparticles, and an article on which the structure is formed.

Background Art

[0002] In recent years, there has been concern about the toxicity of azo pigments containing heavy metals. In addition, dyes have problems such as poor light resistance. Therefore, for the purpose of providing a colorant with low toxicity and good light resistance, arranging an object that exhibits structural color on the surface layer of a molded body has been considered. By arranging an object that exhibits structural color on the surface layer of a molded body, special effects such as providing a colorant with good light resistance without using heavy metals are expected. As objects that exhibit structural color, various materials have been studied. However, since polymer microparticles are easy to manufacture, they are often used as materials, and among them, it is desired to use a polystyrene-based polymer as a material.

[0003] As a method for producing a polystyrene-based polymer used as a material for an object that exhibits structural color, a method of producing by soap-free emulsion polymerization has been proposed (see Non-Patent Document 1). In addition, as a method for obtaining a structural color coating-forming paint composition, a method of producing core-shell type polymer microparticles by soap-free emulsion polymerization has been proposed (see Patent Document 1). In addition, a method of obtaining acrylic polymer microparticles as polymer powder by soap-free emulsion polymerization has been proposed (see Patent Document 2).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-249527 [Patent Document 2] International Publication No. 2013 / 062123 [Overview of the project]

[0006] The manufacturing method proposed in Non-Patent Document 1 had the problem of generating a large amount of cullet and deposits on the inner walls of the polymerization apparatus during polymerization, resulting in a low yield of polystyrene polymers. In addition, it had the problem of poor productivity due to the low solid content concentration (10% by mass) during polymerization.

[0007] The method proposed in Patent Document 1 had the problem of poor productivity due to the low solid content concentration (20% by mass) during polymerization. In addition, since the monomers used during the polymerization of the core layer were styrene, methyl methacrylate, and divinylbenzene, and the core layer was a polymer without acid value, a large amount of cullet and deposits on the inner wall of the polymerization apparatus were generated during polymerization, resulting in a low polymer yield. In the method proposed in Patent Document 2, the volume-average primary particle diameter of the obtained acrylic polymer fine particles is 600 nm or more, and the structure obtained when these polymer fine particles are arranged does not exhibit structural coloration in the visible light region. Furthermore, Patent Document 2 aims to obtain polymer fine particles in emulsion form by spray drying to produce a powder, and does not offer any suggestions regarding structural coloration.

[0008] The purpose of this disclosure is to solve the above-mentioned problems. Specifically, it is to provide polymer fine particles that can be used as a material for objects exhibiting structural color, and that generate little cullet during polymerization and deposits on the inner walls of polymerization apparatus, even at high solid content concentrations. [Means for solving the problem]

[0009] As a result of intensive studies to solve the above problems, the inventors of the present invention have found that when polymer microparticles have an acid value within a specific range, the generation of deposits on the kettle and the inner wall of the polymerization apparatus during polymerization is reduced even at a high solid content concentration, leading to the present disclosure.

[0010] That is, the gist of the present disclosure is as follows.

[0011] [1] Polymer microparticles having a number average particle diameter of 50 to 450 nm and a CV value of the particle diameter based on the number standard of 5% or less, where the acid value is 5 to 38 mgKOH / g the law of nature, The aforementioned polymeric fine particles are composed of a polystyrene polymer, The styrene unit content in the polystyrene polymer is 90.0% by mass or more. , polymer microparticles. [2] Preferably, the polymer microparticles are particles having a uniform resin composition, the polymer microparticles according to [1]. [3] Preferably, the Tg of the polymer microparticles is 50°C or higher, the polymer microparticles according to [1] or [2]. 4 Preferably, the polystyrene-based polymer contains acrylic acid units and / or methacrylic acid units, [1] to [3] the polymer microparticles according to. 5 [1] to 4 An emulsion in which the polymer microparticles according to any one of the above are dispersed in a water-based medium. 6 [1] to 5 A structure in which the polymer microparticles according to any one of the above are arranged and colored. 7 An article in which the structure according to 6 is formed on a substrate. 8 Preferably, the shape is film-like, 7 the article according to.

[0012] 9 In polymer microparticles having structural colorability when arranged, the acid value is 5 to 38 mgKOH / g the law of nature, ​​​​​​ The aforementioned polymeric fine particles are composed of a polystyrene polymer, The styrene unit content in the polystyrene polymer is 90.0% by mass or more. , polymer microparticles.

[10] Preferably, the polymer microparticles are the polymer microparticles according to

[10] , which are particles having a uniform resin composition. 11 Preferably, the polymer microparticles according to

[10] or

[11] , wherein the Tg of the polymer microparticles is 50 °C or higher. 12 Preferably, the polystyrene-based polymer contains acrylic acid units and / or methacrylic acid units, [9] to

[11] the polymer microparticles described above. 13 9 ~ 12 An emulsion in which the polymer microparticles according to any one of ~ are dispersed in a water-based medium. 14 9 ~ 13 A structure in which the polymer microparticles according to any one of ~ are arranged and colored. 15 On a substrate 15 An article in which the structure of ~ is formed. 16 Preferably, the shape is film-like, 15 the article described above.

Advantages of the Invention

[0013] The polymer microparticles of the present disclosure have a high solid content concentration and little adhesion to the kettle during polymerization and the inner wall of the polymerization apparatus, etc., so they can be produced in a high yield. Further, since they have excellent structural color development properties, they are suitable as a material for an object exhibiting a structural color. The object exhibiting the structural color of the present disclosure exhibits excellent structural color development, so it is suitable for improving the design property of an article.

Modes for Carrying Out the Invention

[0014] ​​​​​​​​The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is just one example (representative example) of an embodiment of the present invention, and the present invention is not limited to the following unless it exceeds the gist of the invention. Furthermore, when the expression "~" is used in this specification, it shall be used to include the numerical or physical values ​​described before and after it. Also, numerical or physical values ​​described as upper and lower limits shall be used to include those values.

[0015] The polymer microparticles have a number-average particle diameter of 50-450 nm, a CV value of the particle diameter based on the number of particles of 5% or less, and an acid value of 5-38 mgKOH / g.

[0016] [Number-average particle size] The number-average particle size of polymer microparticles is 50-450 nm. If the average particle size is within the above range, the structural coloration will be good. The method for measuring the number-average particle size is as described in the examples. The number-average particle size of polymer microparticles can be set to the above range during manufacturing by adjusting, for example, the types and proportions of monomer components other than styrene and acidic monomers.

[0017] [CV value of particle size based on number of particles] The coefficient of variation (CV) of particle size based on the number of polymer microparticles is 5% or less. The CV value is also called the "coefficient of variation" or "relative standard deviation," and in this disclosure, it is calculated as (standard deviation / average particle diameter) × 100. If the CV value of the particle size based on the number of particles falls within the above range, the structural color development will be good. The method for measuring the CV value of particle size based on the number of particles is as described in the examples. The coefficient of variation (CV) of particle size based on the number of polymer microparticles can be adjusted during manufacturing by, for example, selecting a polymerization method as described later, or by performing operations such as sieving on the pulverized material after polymerization, and can be set to 5% or less.

[0018] [Acid value] The acid value of polymer microparticles is 5-38 mgKOH / g. If the acid value is 5 mg KOH / g or higher, cullet formation during polymerization is reduced. Furthermore, if the acid value is 38 mg KOH / g or lower, the stability during polymerization is improved. The acid value of polymer microparticles can be set to the above range by, for example, adjusting the blending ratio of acidic monomers constituting the polymer microparticles during the manufacturing process.

[0019] [Particles with a uniform resin composition] The polymer fine particles are preferably particles with a uniform resin composition. Particles with a uniform resin composition mean that, when polymer microparticles are copolymers, the resin composition is substantially the same throughout the polymer microparticles. In other words, it means that the resin composition is substantially uniform throughout the entire particle, and there is no bias in the resin composition, except for, for example, compositional biases that are unavoidable during manufacturing. Particles with a uniform resin composition can be produced, for example, by keeping the composition of the supplied monomers the same from the initial stage of polymerization to the final stage. If the resin composition of the particles is uniform, the difference in refractive index between the inside and outside of the particles becomes larger, which is preferable because it improves structural color development.

[0020] [Tg is 50℃ or higher] Polymeric fine particles preferably have a Tg of 50°C or higher. To achieve a Tg of 50°C or higher for polymeric fine particles, a polymer with a Tg of 50°C or higher should be used, and these particles should be formed into fine particles. Examples of polymers with a Tg of 50°C or higher include polyamides, polyimides, low-density polyethylene, high-density polyethylene, poly(meth)acrylic acid esters, polystyrene and its derivatives, polystyrene-based polymers, polyvinyl chloride, phenolic resins, and polycarbonates. Among these, poly(meth)acrylic acid esters and polystyrene polymers are preferred because the raw materials are readily available and it is easy to produce fine particles with uniform particle size, and polystyrene polymers are more preferred because they yield polymers with a high refractive index. High refractive index polymers are preferable because they increase the refractive index difference between the inside and outside of the particles, improving structural color development. In this specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0021] The Tg of the polymer fine particles is more preferably 60°C or higher, and even more preferably 70°C or higher. If the Tg of polymer fine particles is 50°C or higher, the structure will be maintained even under high-temperature operating environments; therefore, a Tg of 50°C or higher is preferable.

[0022] The polymer fine particles preferably have a Tg of 50°C or higher, as described above. In this case, the polymer fine particles may be composed of a non-crosslinked polymer or a crosslinked polymer. Note that Tg is a value calculated from Fox's formula.

[0023] [Poly(meth)acrylic acid esters] Poly(meth)acrylic acid esters are polymers whose main component is (meth)acrylic acid ester units. Here, "main component" means that the content of (meth)acrylic acid ester units is 50% by mass or more, and more specifically, 60% by mass or more, of the total polymer.

[0024] Examples of (meth)acrylic acid esters that can be used as raw materials for (meth)acrylic acid ester units include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. Among these, methyl (meth)acrylate is preferred, and methyl methacrylate is more preferred, because the resulting polymer has a Tg of 50°C or higher.

[0025] Poly(meth)acrylic acid esters may be either random copolymers or block copolymers, but are generally random copolymers. In addition to the (meth)acrylic acid esters described above, poly(meth)acrylic acid esters may also be copolymerized with any monomer.

[0026] [Polystyrene polymer] Polystyrene polymers are polymers whose main component is styrene units. Here, "main component" means that the content of styrene units in the total polymer is 50% by mass or more, and more specifically, 60% by mass or more. Polystyrene polymers can be either random copolymers or block copolymers, but they are generally random copolymers.

[0027] To achieve the effects of this disclosure, the polystyrene polymer has the shape of fine particles with uniform particle size (specifically, fine particles with a number-average particle size of 50 to 450 nm and a CV value of 5% or less). To obtain fine particles with uniform particle size, one method is to obtain polymers of appropriate size using methods such as bulk polymerization, suspension polymerization, emulsion polymerization, or solution polymerization, then pulverize them into fine powders, and standardize the particle size through operations such as sieving. Alternatively, fine particles with uniform particle size can be directly obtained by soap-free emulsion polymerization. Among these methods, the soap-free emulsion polymerization method is preferred due to its superior productivity.

[0028] [Monomer units of polystyrene polymers] The polystyrene polymer preferably contains styrene units and acidic monomer units. In other words, the polystyrene polymer is a copolymer of styrene and an acidic monomer, and is preferably composed of constituent units derived from styrene and constituent units derived from the acidic monomer. The styrene used as the raw material for styrene units is not particularly limited; any general-purpose styrene can be used.

[0029] Examples of acidic monomers that serve as raw materials for acidic monomer units include monomers having carboxyl groups such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and cinnamic acid; monomers having sulfonic acid groups such as sulfonated styrene; and monomers having sulfonamide groups such as vinylbenzenesulfonamide. Among these, acrylic acid and methacrylic acid are preferred, with acrylic acid being more preferred, because they are water-soluble and have a significant effect on reducing cullet during polymerization. Acidic monomers may be used individually or in combination of two or more.

[0030] In other words, the styrene-based polymer preferably contains acrylic acid units and / or methacrylic acid units in addition to the main component styrene units, and more preferably contains acrylic acid units. In this case, it becomes easier to adjust the Tg of the polymer fine particles.

[0031] When introducing a crosslinked structure into a polystyrene polymer, known polyfunctional monomers can be copolymerized. Examples of polyfunctional monomers include divinylbenzene, hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, hexaethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and diallyl phthalate. Among these, divinylbenzene and hexanediol diacrylate are preferred. Polyfunctional monomers may be used individually or in combination of two or more. In this specification, (meth)acrylate means acrylate and / or methacrylate.

[0032] Polystyrene polymers may further contain other monomer units. Other monomer units refer to monomer units other than styrene units, acrylic acid units, and methacrylic acid units. Other monomers that can be used as raw materials for other monomer units include, for example, styrenes other than styrene such as methylstyrene, chlorostyrene, dichlorostyrene, pt-butylstyrene, pn-butylstyrene, and pn-nonylstyrene; metal salts such as sodium salt of styrene sulfonic acid; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hydroxyethyl (meth)acrylate, and ethylhexyl (meth)acrylate; and acrylamides such as acrylamide, N-propylacrylamide, N,N-dimethylacrylamide, N,N-dipropylacrylamide, and N,N-dibutylacrylamide. Among these, metal salts such as sodium salts of styrene sulfonic acid are preferred because they allow for good control of particle size.

[0033] [Composition of polystyrene polymers] The polystyrene polymer preferably contains 80.0 to 99.75% by mass of styrene units. A styrene unit content within this range is preferable because it increases the refractive index of the particles and improves structural color development. A styrene unit content of 90.0% by mass or more is more preferable. Furthermore, 99.4% by mass or less is even more preferable.

[0034] The polystyrene polymer preferably contains 0.25 to 20.0% by mass of acidic monomer units. A content of acidic monomer units within this range is preferable because it reduces cullet formation during polymerization. The content of acidic monomer units is more preferably 0.6% by mass or more. Furthermore, it is more preferably 10.0% by mass or less.

[0035] When a polystyrene polymer contains polyfunctional monomer units and / or other monomer units, the content of these units is preferably 3% by mass or less. A content of 3% by mass or less of polyfunctional monomer units and / or other monomer units is preferable because it allows for good control of particle size. The content of polyfunctional monomer units and / or other monomer units is more preferably 2% by mass or less.

[0036] [Method for producing polymer microparticles] Polymeric fine particles are preferably obtained by soap-free emulsion polymerization. Soap-free emulsion polymerization is a known polymerization method, for example, as follows. Deionized water is placed in the reaction vessel, and polymerization aids are added while heating and stirring as needed, ensuring that the polymerization aids are thoroughly dispersed in the deionized water. Next, the polymerization initiator is added while continuing to stir. Then, monomers are added dropwise while continuing to stir to initiate the polymerization reaction. As polymerization progresses, particles are formed. It is preferable that the composition of the monomers added dropwise remains the same from the beginning to the end of the dropping process.

[0037] The solid content concentration during polymerization, i.e., the concentration of polymer fine particles relative to the entire system during polymerization, is preferably 20 to 40% by mass. If the solid content concentration during polymerization is above the lower limit, the productivity of polymer fine particles will improve. Furthermore, if it is below the upper limit, there will be no generation of cullet or deposits on the inner walls of the polymerization apparatus during polymerization. The polymerization temperature is generally set to 60-90°C when a polymerization initiator is used. After the reaction is complete, the polymer microparticles are removed as an emulsion. In this specification, high solids concentration means that the concentration of solids (specifically polymer microparticles) during polymerization is, for example, 20% by mass or more.

[0038] Examples of polymerization initiators used in soap-free emulsion polymerization 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; and redox polymerization initiators consisting of a combination of an oxidizing agent and a reducing agent. These may be used individually or in combination of two or more types. Among these, water-soluble polymerization initiators are preferred due to their ease of handling.

[0039] In this disclosure, for example, by using acidic monomers such as acrylic acid and methacrylic acid from the initial stages of polymerization, in addition to the main monomer, as monomers supplied into the polymerization system, the generation of cullet and deposits on the inner walls of the polymerization apparatus during polymerization can be further reduced. This allows for further improvement of the yield during polymerization, thereby increasing the productivity of polymer microparticles.

[0040] Furthermore, in conventional techniques, polymerization has been carried out by lowering the solid content concentration to avoid the generation of cullet and deposits on the inner walls of the polymerization apparatus. However, in this disclosure, the generation of cullet and deposits can be reduced, making it possible to increase the solid content concentration during polymerization. This further improves the productivity of polymer microparticles.

[0041] [Emulsion] Since polymer microparticles are obtained by soap-free emulsion polymerization, they are obtained in emulsion form. Here, emulsion means that polymer microparticles are dispersed in a water-based medium. A water-based medium means that the water content is 50% by mass or more, and more specifically, 60% by mass or more. In addition to water, any organic solvent soluble in water can be selected as a component.

[0042] The emulsion may be in the state obtained by soap-free emulsion polymerization, or it may be an emulsion obtained by soap-free emulsion polymerization that has been appropriately diluted, or it may be a polymer fine particle obtained as a powder dispersed in a medium.

[0043] [Structural color development] Polymer microparticles exhibit structural coloration. Structural coloration means that when particles of uniform size are arranged regularly, they exhibit structural color. Structural coloration is a phenomenon in which a material appears to emit color due to optical and physical phenomena such as interference and scattering caused by the regular arrangement of particles in a crystalline structure, depending on the wavelength of light.

[0044] Since structural coloration is due to the properties of light, it manifests similarly not only in the visible light region but also in the ultraviolet and infrared regions. To exhibit structural coloration in the ultraviolet region, polymer nanoparticles with a small number-average particle size should be used, while to exhibit structural coloration in the infrared region, polymer nanoparticles with a large number-average particle size should be used. In this disclosure, structural coloration is used to improve the design of the article, so it is preferable that the article has structural coloration in the visible light region.

[0045] Here, the visible light region refers to wavelengths of 360 to 830 nm, the ultraviolet region refers to wavelengths of 200 to 359 nm, and the infrared region refers to wavelengths of 831 to 2500 nm.

[0046] [Structure and its manufacturing method] The structure is a material in which the polymer microparticles are arranged periodically and exhibit structural color, that is, a state in which color is produced. Here, "arrangement" refers to the formation of colloidal crystals or colloidal amorphous crystals by polymer microparticles. Structural color refers to a type of material in which polymer microparticles of uniform size, when arranged in a regular pattern, exhibit angle-dependent coloration where the color changes depending on the viewing angle due to the diffraction and interference of light caused by the arrangement of the particles.

[0047] The manufacturing method for the structure is as follows, for example: An emulsion of polymer microparticles obtained by soap-free emulsion polymerization is appropriately diluted, and a dispersion of carbon black is added to it. This is referred to as the "mixed sample." After thoroughly dispersing the carbon black, the mixed sample is applied to a smooth substrate. Next, the mixed sample is dried at an appropriate temperature to obtain the desired product.

[0048] Because polymer microparticles have a uniform particle size, they exhibit structural color through colloidal crystallization by arranging periodically.

[0049] [Articles and their manufacturing methods] The article is an object on which the aforementioned structure is formed on a base material. There are no particular restrictions on the base material; common materials such as metal, resin, wood, and paper can be used. By applying the above mixed sample onto a substrate, an article exhibiting structural color can be obtained. For surface protection purposes, a surface protective layer may be provided on the surface of the article exhibiting structural color, if necessary.

[0050] [film] The film is the aforementioned article in the form of a film. To form the aforementioned article into a film, a film-like material can be used as the base material. For the purpose of surface protection, a surface protection layer may be provided on the surface of the film as needed. [Examples]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the essence of the invention. In the following description, "parts" and "%" refer to "parts by mass" and "% by mass," respectively. In the following examples and comparative examples, various physical properties were measured by the methods described below.

[0052] [Evaluation Method] (1) Number-average particle size An emulsion of polymer microparticles was applied to a substrate and dried. Images of the polymer microparticles were then observed using an electron microscope at a magnification of 20,000x or higher. The diameters of at least 400 particles in the images were measured, and the number-average particle diameter was calculated by taking an arithmetic mean of these measurements.

[0053] (2) CV value of particle size Using the diameter measurements of at least 400 particles as described above, the coefficient of variation (CV) of particle diameter was calculated using the formula (standard deviation / average particle diameter) × 100.

[0054] (3) Volume-average particle diameter In this disclosure, the median volume diameter is used as the volume-average particle diameter. Volume median diameter (Dv) of polymer microparticles 50 The measurements were taken using the Nanotrac WaveII manufactured by Microtrac-Bell Corporation, and the Data Management System for Microtrac analysis software manufactured by the same company. Specifically, 0.02 g of emulsion was mixed with 20 ml of diluted sodium dodecylbenzenesulfonate solution (0.02% concentration) to prepare a sample dispersion. This dispersion was then placed into a sample cell, and measurements were taken under the following conditions: solvent refractive index: 1.333, measurement time: 180 seconds, number of measurements: 1. Other setting conditions were: particle refractive index: 1.59, transmittance: transparent, shape: spherical, density: 1.00.

[0055] (4) Acid value The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 gram of resin. The acid value was determined according to the method of JIS K0070, except that THF was used as the solvent.

[0056] (5) Solid content concentration The emulsion solid content concentration was determined using an A&D Company, Limited (A&D) MX-50 heating and drying moisture meter, by heating 10 g of emulsion at 190°C for 60 minutes to evaporate the water.

[0057] (6) Yield The yield was calculated as follows: The emulsion after the polymerization reaction was filtered through a double layer of nonwoven gauze (Treat) (F3), and its total weight was measured (A) g. Subsequently, the solid content concentration was measured (B)% by the method described in (5). The weight of the solids after the polymerization reaction was calculated from the weight and solids concentration of the emulsion obtained after the polymerization reaction, and then divided by the theoretical solids weight (C) g to determine the amount of solids after the polymerization reaction. In other words, the yield was calculated as (A × B / 100) / C [%].

[0058] (7) Structural color development The predetermined structural coloration according to Bragg's formula was visually confirmed. (7-1) Wavelength and color assumed from Bragg's equation Bragg’s formula is given by the following equation: λ max =(8 / 3) 1 / 2 ·D·(n ave 2 -sin 2 θ) 1 / 2 Here, D: Diameter of colloidal particles n ave =n1φ1+n2φ2 n: refractive index φ: Volume fraction Subscript 1: Colloidal particles Subscript 2: This represents an air gap. in particular, n1=1.592 φ1=0.74 n²=1.0 and φ²=0.26 were used. Here, the number-average particle diameter of the polymer microparticles was used for the diameter of the colloidal particles. Regarding color development, the wavelength obtained from Bragg's formula was compared with the wavelength of visible light to determine the result.

[0059] (7-2) Presence or absence of structural coloration I visually checked whether the colors predicted by Bragg's formula were being produced.

[0060] [Raw materials, etc.] Styrene (manufactured by Denka Co., Ltd.) Acrylic acid (manufactured by Mitsubishi Chemical Corporation) Sodium styrene sulfonate (manufactured by Tosoh Finechem Co., Ltd.) Sodium bicarbonate (manufactured by Fujifilm Wako Co., Ltd.) Ammonium persulfate (manufactured by Kanto Chemical Co., Ltd.) Carbon black (manufactured by Mitsubishi Chemical Corporation)

[0061] [Example 1] A monomer mixture was prepared by mixing 98.4 parts of styrene with 1.5 parts of acrylic acid. Meanwhile, an auxiliary solution [A] was prepared by dissolving 0.1 parts sodium styrenesulfonate and 0.15 parts sodium bicarbonate in 16.4 parts deionized water. In a reaction vessel equipped with a stirring device, a heating and cooling device, a nitrogen introduction device, and a raw material / auxiliary agent charging device, 177.5 parts of deionized water were charged, and then auxiliary agent solution [A] was charged while rotating at 150 rpm, and the internal temperature was raised to 80°C. Next, an initiator solution, in which 0.42 parts of ammonium persulfate was dissolved in 33.7 parts of deionized water, was added to the reaction vessel, and after 5 minutes, the monomer mixture was added dropwise over 3 hours. After the monomer mixture was added dropwise, polymerization was carried out over 5 hours. During the polymerization reaction after the addition of the monomer mixture, deionized water was added as needed to maintain the liquid level. Subsequently, the polymerization reaction product was filtered through nonwoven gauze (Treat) to obtain an emulsion of high-molecular-weight microparticles.

[0062] The obtained polymer microparticles had a number-average particle size of 238 nm, a CV value of 3.8%, an acid value of 14.1 mg KOH / g, a solid content concentration of 29.1%, and a yield of 95%. Furthermore, since only one type of monomer mixture was used, the polymer microparticles had a uniform resin composition, and the Tg was calculated to be 100°C using Fox's formula.

[0063] This emulsion was diluted with deionized water to a solid content concentration of 10%, and a 20% carbon black dispersion was added so that the carbon black content was 0.5 parts per 100 parts of solid content in the emulsion, and a mixed sample was prepared. After thoroughly dispersing the mixed sample, it was applied to a smooth substrate using a dropper, and the structure was obtained by drying it together with the substrate at 55°C.

[0064] [Example 2] A monomer mixture was prepared by mixing 98.43 parts of styrene with 1.5 parts of acrylic acid. Meanwhile, an auxiliary solution [B] was prepared by dissolving 0.07 parts of sodium styrenesulfonate and 0.15 parts of sodium bicarbonate in 16.4 parts of deionized water. In a reaction vessel equipped with a stirring device, a heating and cooling device, a nitrogen introduction device, and a raw material / auxiliary agent charging device, 177.5 parts of deionized water were charged, and then auxiliary agent solution [B] was charged while rotating at 150 rpm, and the internal temperature was raised to 80°C. From this point onward, an emulsion of polymer microparticles was obtained in the same manner as in Example 1. Similar to Example 1, deionized water was added as needed during the polymerization reaction after the monomer mixture was added dropwise to maintain the liquid level, although the amount added was slightly excessive. As a result, the solid content concentration was slightly lower than expected.

[0065] The obtained polymer microparticles had an acid value of 13.0 mg KOH / g, a solid content concentration of 27.7%, and a yield of 95%. In Example 2, the number-average particle diameter was not measured, but it was calculated to be 308 nm by converting it using the formula: number-average particle diameter = volume-average particle diameter × 0.9775. In Example 2, the CV value of the particle size was not measured, but it was calculated as 2.7% by multiplying the CV value obtained from the measurement of the volume-average particle size by 0.1131. Furthermore, since only one type of monomer mixture was used, the polymer microparticles had a uniform resin composition, and the Tg was calculated to be 100°C using Fox's formula.

[0066] Using the obtained emulsion, a structure was obtained by performing the same procedure as in Example 1.

[0067] [Comparative Example 1] 99.9 parts of styrene were prepared as a monomer. On the other hand, an auxiliary solution [C] was prepared by dissolving 0.1 parts sodium styrenesulfonate and 0.16 parts sodium bicarbonate in 16.6 parts deionized water. In a reaction vessel equipped with a stirring device, a heating and cooling device, a nitrogen introduction device, and a raw material / auxiliary agent charging device, 181.6 parts of deionized water were charged, and then auxiliary agent solution [C] was charged while rotating at 150 rpm, and the internal temperature was raised to 80°C. Next, an initiator solution prepared by dissolving 0.42 parts of ammonium persulfate in 34.2 parts of deionized water was added to the reaction vessel, and after 5 minutes, the monomers were added dropwise over 3 hours. After the monomers were added dropwise, polymerization was carried out over 5 hours. During the polymerization reaction after the monomer addition, deionized water was added as needed to maintain a constant liquid level. Subsequently, the polymerization reaction product was filtered through nonwoven gauze to obtain an emulsion of polymer microparticles.

[0068] The obtained polymer microparticles had a number-average particle size of 273 nm, a CV value of 1.8%, an acid value of 3.2 mg KOH / g, a solid content concentration of 30.4%, and a yield of 86%. Furthermore, since only one type of monomer was used, the polymer microparticles had a uniform resin composition, and the Tg was calculated to be 100°C using Fox's formula.

[0069] Using the obtained emulsion, a structure was obtained by performing the same procedure as in Example 1.

[0070] [Table 1]

[0071] As shown in Table 1, in Example 1, the wavelength from an angle of 0 degrees calculated from Bragg's formula was 559 nm, but it appeared yellowish-green to the naked eye, confirming that it possessed the expected structural coloration. Similarly, the wavelength from an angle of 45 degrees was 451 nm, but it appeared blue to the naked eye, confirming that it also possessed the expected structural coloration. In Example 2, the color observed visually from an angle of 0 degrees was red. The color observed visually from an angle of 45 degrees was green. Comparative Example 1, with a wavelength of 641 nm at an angle of 0 degrees, appeared red to the naked eye, confirming that it possessed the expected structural coloration. Similarly, with a wavelength of 516 nm at an angle of 45 degrees, it appeared green to the naked eye, confirming that it also possessed the expected structural coloration.

[0072] From this, it was confirmed that Examples 1 and 2 exhibit structural coloration, similar to Comparative Example 1, which does not use acrylic acid, an acidic monomer. Furthermore, it was confirmed that there was no effect on structural color development in both the region with smaller particle size (Example 1) and the region with larger particle size (Example 2) compared to Comparative Example 1. This confirmed that structural color development does not depend on particle size.

[0073] The polymeric fine particles of Example 1 exhibited low adhesion to cullet and the inner walls of the polymerization apparatus during polymerization, even when polymerized at a high solids content concentration of approximately 29%, resulting in a high yield of 95%. The polymeric fine particles of Example 2 exhibited low adhesion to cullet and the inner walls of the polymerization apparatus during polymerization, even when polymerized at a high solids content concentration of approximately 28%, resulting in a high yield of 95%. In Comparative Example 1, the polymer fine particles exhibited significant adhesion to cullet and the inner walls of the polymerization apparatus during polymerization, resulting in a yield of 86%, which was inferior to that of Examples 1 and 2.

[0074] Furthermore, it was confirmed that the examples using acrylic acid, an acidic monomer, showed good yields in both the region with smaller particle sizes (Example 1) and the region with larger particle sizes (Example 2) compared to Comparative Example 1. This confirmed that the yield does not depend on particle size.

Claims

1. An emulsion in which polymer microparticles having a number-average particle size of 50 to 450 nm and a CV value of 5% or less based on particle size are dispersed in a water-based medium, The acid value of the aforementioned polymer fine particles is 5 to 38 mg KOH / g. The aforementioned polymeric fine particles are composed of a polystyrene polymer, The styrene unit content in the polystyrene polymer is 90.0% by mass or more. An emulsion in which the polystyrene polymer contains monomer units derived from a metal salt of styrenesulfonic acid.

2. The emulsion according to claim 1, wherein the polymer fine particles are particles with a uniform resin composition.

3. The emulsion according to claim 1 or 2, wherein the Tg of the polymer fine particles is 50°C or higher.

4. The emulsion according to any one of claims 1 to 3, wherein the polystyrene polymer contains acrylic acid units and / or methacrylic acid units.

5. A structure in which the polymer fine particles contained in the emulsion according to any one of claims 1 to 4 are arranged and develop color.

6. An article having the structure of claim 5 formed on a base material.

7. The article according to claim 6, wherein the shape is film-like.

8. An emulsion in which polymer microparticles that exhibit structural coloration when arranged are dispersed in a water-based medium, The acid value of the aforementioned polymer microparticles is 5 to 38 mg KOH / g. The aforementioned polymeric fine particles are composed of a polystyrene polymer, The styrene unit content in the polystyrene polymer is 90.0% by mass or more. An emulsion in which the polystyrene polymer contains monomer units derived from a metal salt of styrenesulfonic acid.

9. The emulsion according to claim 8, wherein the polymer fine particles are particles with a uniform resin composition.

10. The emulsion according to claim 8 or 9, wherein the Tg of the polymer fine particles is 50°C or higher.

11. The emulsion according to any one of claims 8 to 10, wherein the polystyrene polymer contains acrylic acid units and / or methacrylic acid units.

12. A structure in which the polymer fine particles contained in the emulsion according to any one of claims 8 to 11 are arranged and develop color.

13. An article having the structure of claim 12 formed on a base material.

14. The article according to claim 13, wherein the shape is film-like.

Images