Laminate including colloidal crystal layer and method for manufacturing the same

Abstract

To provide a colloidal crystal film that satisfies a specific condition and that is extremely characteristic and excellent in design properties compared with a conventional colloidal crystal film.SOLUTION: A laminate has a base material and a colloidal crystal layer. When λ[10] is the maximum wavelength derived from Bragg reflection in a reflection spectrum in which an incident angle and a reflection angle relative to the colloidal crystal layer are both set to 10°, and λ[70] is the maximum wavelength derived from Bragg reflection in a reflection spectrum in which the incident angle and the reflection angle are both set to 70°, λ[10] and λ[70] indicate a predetermined relationship.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laminate that exhibits structural coloring. [Background technology]

[0002] Structural coloring refers to the coloring phenomenon caused by microscopic structures at or below the wavelength of light. Familiar examples of structural color include compact discs, soap bubbles, morpho butterflies, and jewel beetles. These objects themselves are not colored, but appear colored because light is reflected and interfered by their microscopic structures. In recent years, there has been progress in the development of artificially creating regular structures that exhibit structural color. For example, various methods have been proposed for producing structures in which the particles are regularly arranged in the planar direction on a substrate by using a dispersion of monodisperse particles dispersed in a medium, and then arranging, aligning, drying, and fixing the particles by pouring, spraying, coating, flowing, etc.

[0003] Colloidal crystals are known as such regularly arranged particles, and they are known to exhibit Bragg reflection and angular dependent structural colors. As a method for forming colloidal crystals to exhibit structural colors, Patent Document 1 proposes a method for inexpensively forming a laminate having a colloidal crystal layer by applying a coating composition containing solid particles such as silica particles or polymer microparticles to a substrate using a wire bar and drying the composition. Furthermore, Non-Patent Documents 1 and 2 discuss the color development behavior of a structure made of hollow particles, which are hollow inside, rather than solid particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-223915 [Non-patent literature]

[0005] [Non-Patent Document 1] ACS Appl.Mater.Interfaces 2023,15,38,45229-45238 [Non-patent document 2] JSR TECHNICAL REVIEW No.116 / 2009 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the method proposed in Patent Document 1 can produce angle-dependent structural colors, there has been a demand for a method that is more distinctive and has excellent design properties. Furthermore, in the method proposed in Non-Patent Document 1, the hollow particles forming the structure are not regularly arranged, resulting in a colloidal amorphous structure, and color development is insufficient. Furthermore, in the method proposed in Non-Patent Document 2, color development is not sufficiently discussed.

[0007] As a result of extensive research into solving the above problems, the present inventors discovered that a colloidal crystal film that satisfies certain conditions is a film that is extremely distinctive and has excellent design properties compared to conventional colloidal crystal films, and thus arrived at the present invention. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the present inventors discovered that the above-mentioned problems can be solved by using a laminate having a colloidal crystal layer in which colloidal crystals that exhibit structural color due to the interference of light are regularly arranged, and which has a maximum wavelength derived from a predetermined Bragg reflection, thereby completing the present invention.

[0009] That is, the present invention has the following features. [1] A laminate having a substrate and a colloidal crystal layer, wherein λ

[10] is the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle with respect to the colloidal crystal layer are both 10°, and λ

[70] is the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle are both 70°, and λ

[10] and λ

[70] satisfy the following relationship: λ

[10] ‐λ

[70] ≧200nm [2] The laminate according to [1], wherein the maximum wavelength resulting from backscattering appears in the wavelength range of 400 to 800 nm. [3] The laminate according to [1] or [2], characterized in that in the reflection spectrum when both the incident angle and the reflection angle are set to 70°, in addition to a reflection peak due to Bragg reflection, a peak due to thin film interference is observed in the wavelength range of 400 to 800 nm.

[0010] [4] The laminate according to [1] or [2], wherein λ

[10] is 400 nm or more and 1000 nm or less. [5] The laminate according to [1] or [2], wherein λ

[70] is 200 nm or more and 800 nm or less. [6] The laminate according to [1] or [2], wherein the colloidal crystal layer is made of hollow particles. [7] The laminate according to [6], wherein the hollow particles are hollow silica particles. [8] A method for producing a laminate including a colloidal crystal layer made of hollow particles, comprising the steps of: drying a dispersion of fine particles made of core-shell particles on a substrate to align the core-shell particles and form colloidal crystals; and removing the cores from the core-shell particles. [9] The method for producing a laminate according to [8], wherein the hollow particles are hollow silica particles. [Effects of the Invention]

[0011] The laminate of the present invention has a higher angle dependency of Bragg reflection than conventional laminates, and is therefore superior in design. Furthermore, the laminate of the present invention exhibits backscattering and thin-film interference in the visible light range, and is therefore superior in design. Specifically, when the ranges of the maximum wavelengths λ

[10] and λ

[70] resulting from Bragg reflection in the reflection spectrum at angles of incidence and reflection of 10° and 70°, respectively, and the relationship between the two satisfy predetermined conditions, the maximum wavelengths resulting from backscattering and peaks resulting from thin-film interference appear in the visible light range (400 to 800 nm), improving structural coloring and enabling the production of laminates with excellent design. In particular, when the colloidal crystal layer is made of hollow particles such as hollow silica particles, the structural coloring can be further enhanced, resulting in laminates with even better design. [Brief explanation of the drawings]

[0012] [Figure 1] 1. A cross-sectional SEM photograph of a core-shell particle portion of a laminate [1] made of core-shell particles in an example. [Figure 2] 1 is a cross-sectional SEM photograph of the hollow silica particle portion of the laminate described in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is one example (representative example) of an embodiment of the present invention, and the present invention is not limited to the following content as long as it does not exceed the gist of the present invention. Furthermore, when the expression "to" is used in this specification, it is intended to include the numerical values ​​or physical values ​​written before and after it. Furthermore, numerical values ​​or physical values ​​written as upper and lower limits are intended to include those values.

[0014] The present invention relates to a laminate having a substrate and a colloidal crystal layer. <Base material> The substrate is a material that serves as the base of the laminate, and is not particularly limited, and general materials such as metal, resin, wood, and paper can be used. For example, thermoplastic resin substrates such as polyvinyl chloride sheets, polyester films such as polyethylene terephthalate (PET), polypropylene films, polyethylene films, nylon films, polystyrene films, and polyvinyl alcohol films, metal substrates such as aluminum foil, glass substrates, and coated paper substrates can also be used.

[0015] The substrate may have a smooth or uneven surface, and may be transparent, translucent, or opaque. It is also possible to use a substrate that has been pre-colored, such as black. Two or more of the above substrates may be laminated together. The substrate may be subjected to a corona treatment or plasma treatment in advance to improve the coatability of the dispersion of the present invention. A primer layer may be provided on the substrate. From the viewpoint of thin film interference, the refractive index of the substrate is preferably 1.49 or more. For the purpose of surface protection, an overcoat layer may be provided on the surface of the colloidal crystal layer, if necessary.

[0016] [Overcoat layer] The overcoat layer is a layer for protecting the surface of the colloidal crystal layer, and is not particularly limited as long as it is made of a material that forms a film on the surface of the colloidal crystal layer. The overcoat layer preferably covers the surfaces of the fine particles and also fills spaces between the fine particles. Examples of the resin that constitutes the overcoat layer include acrylic resin, acrylic urethane resin, silicone resin, and epoxy resin. The resin is generally in the form of a resin precursor that can be cured by heat or light, a resin solution diluted with a solvent, or an emulsion dispersed in water.

[0017] The thickness of the overcoat layer is not particularly limited, as long as it is thick enough to cover the colloidal crystal layer or thicker. The overcoat layer can be formed on the surface of the colloidal crystal layer by applying a thin film of a resin precursor, resin solution, or emulsion that can be cured by heat or light onto the colloidal crystal layer, and then subjecting it to light irradiation, heat treatment, or the like as necessary.

[0018] <Fine particles> The colloidal crystal layer is a layer having a structure in which fine particles are periodically arranged three-dimensionally. The fine particles used in the present invention preferably have a volume average particle size of 180 to 800 nm and a CV value of particle size based on number of 15% or less.

[0019] [Volume average particle size] The volume average particle diameter of the microparticles is preferably 180 nm or more, preferably 190 nm or more, more preferably 200 nm or more, and even more preferably 210 nm or more. It is also preferably 800 nm or less, preferably 780 nm or less, more preferably 750 nm or less, and even more preferably 700 nm or less. If the volume average particle diameter is within the above range, the structural color of the resulting laminate appears in the visible light region, which is preferable because it provides good design properties. Furthermore, if the volume average particle diameter is within the above range, it can be said to be a colloid. The method for measuring the volume average particle diameter in the present invention is as described in the Examples.

[0020] [CV value of particle size based on number] The CV value of the particle size based on the number of particles of the present invention is preferably 15% or less, preferably 10% or less, and more preferably 5% or less. There is no particular restriction on the lower limit of the CV value of the particle size based on the number, but it is usually 1% or more. If the CV value of the particle size based on the number is within the above range, it is preferable because the design properties are good. The CV value is also called the "coefficient of variation" or "relative standard deviation," and in the present invention means the relationship between the standard deviation in the particle size distribution based on the number and the number average particle size, (standard deviation / number average particle size) x 100 It is calculated as follows. The microparticles have the CV value of the particle diameter based on the number as described above, and therefore, when a colloidal crystal layer is formed using the raw material microparticles by the method described below, the colloidal crystals are arranged in a regular pattern, which can produce structural coloring and contribute to improved design.

[0021] [Type and structure of particles] The fine particles have a number average particle size and a CV value of the particle size based on number within the above range. The fine particles are not particularly limited and may be organic fine particles, inorganic fine particles, or organic-inorganic hybrid particles. Furthermore, the fine particles may be hollow particles or core-shell particles in which the surface layer (shell layer) and the inner layer (core layer) are made of different materials. Among these, from the viewpoint of improving and further enhancing the structural coloring properties, particles in which the refractive index of the particle surface is much higher than the refractive index of the particle interior are preferred, and for example, hollow particles and core-shell particles in which the refractive index of the core layer is much lower than the refractive index of the shell layer are preferably used.

[0022] [Fine particle materials] Materials constituting the inorganic fine particles include metals, metal oxides, and silicon oxides such as silica. Materials constituting the organic fine particles include organic materials such as polymeric materials. Furthermore, the core and shell of the core-shell particles may both be made of inorganic or organic materials, or may be hybrid particles of inorganic and organic materials. The core and shell may be made of both inorganic materials or both organic materials, but different materials are used. As a material for forming the inorganic fine particles, silica fine particles are preferred because they are easily available and have excellent transparency.

[0023] Examples of the polymeric material include polyolefins, polystyrenes, poly(meth)acrylic acid esters, polyamides, polyimides, polyvinyl chloride, phenolic resins, and polycarbonates. Among these polymer materials, polymers with a high refractive index are preferred because they increase the difference in refractive index between the inside and outside of the particle and improve structural coloring. These polymer materials may be non-crosslinked or crosslinked polymers.

[0024] (Polyolefins) Examples of the polyolefins include polyethylenes such as low-density polyethylene and high-density polyethylene, polypropylene, and ethylene-propylene copolymers.

[0025] (Polystyrenes) The polystyrenes are polymers whose main component is a styrene unit, where the main component means that the content of the styrene unit relative to the entire polymer is 50% by mass or more, and further 60% by mass or more. The polystyrenes may be either random copolymers or block copolymers, but are generally random copolymers. The polystyrenes may be copolymerized with any monomer in addition to styrene.

[0026] Examples of the optional monomer include styrenes other than styrene, such as methylstyrene and chlorostyrene; metal salts such as sodium salt of styrenesulfonic acid; acidic monomers such as acrylic acid and methacrylic acid; (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate; and acrylamides such as acrylamide and N-propylacrylamide. Among these, metal salts such as sodium salt of styrenesulfonic acid are preferred because they allow good control of the particle size. When a crosslinked structure is to be introduced into polystyrenes, a known polyfunctional monomer may be copolymerized.

[0027] The polystyrene preferably contains 80.0 to 99.75% by mass of styrene units. If the content of styrene units is within the above range, the refractive index of the particles is increased, and structural coloring is improved, which is preferable. The content of styrene units is more preferably 90.0% by mass or more, and more preferably 99.4% by mass or less.

[0028] The polystyrene preferably contains 0.25 to 20.0% by mass of a monomer unit having a substituent reactive with the compound forming the shell layer. If the content of the monomer having a substituent reactive with the compound forming the shell layer is within the above range, side reactions during shell layer formation can be suppressed, which is preferable. The content of the monomer having a substituent reactive with the compound forming the shell layer is more preferably 0.5% by mass or more, and more preferably 10% by mass or less.

[0029] For example, when a shell layer is formed using a silane-based compound such as tetraalkoxysilane, examples of a monomer having a substituent that exhibits reactivity with the compound that forms the shell layer include 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 3-methacryloxymethyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and p-styryltrimethoxysilane.

[0030] When the polystyrenes contain the optional monomer unit and / or polyfunctional monomer unit, the content thereof is preferably 3% by mass or less, more preferably 2% by mass or less. If the content is 3% by mass or less, the particle size can be well controlled.

[0031] (Poly(meth)acrylic acid esters) Poly(meth)acrylic esters are polymers whose main component is a (meth)acrylic ester unit. Here, the term "main component" means that the content of the (meth)acrylic ester unit relative to the entire polymer is 50% by mass or more, and more preferably 60% by mass or more.

[0032] Examples of the (meth)acrylic acid ester that serves as a raw material for the (meth)acrylic acid ester unit include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate.

[0033] The poly(meth)acrylic acid esters may be either random copolymers or block copolymers, but are generally random copolymers. The poly(meth)acrylic acid esters may be copolymerized with any monomer in addition to the above-mentioned (meth)acrylic acid esters. Examples of this optional monomer include styrenes such as styrene and methylstyrene; metal salts such as sodium salt of styrenesulfonic acid; acidic monomers such as acrylic acid and methacrylic acid; and acrylamides such as acrylamide and N-propylacrylamide.

[0034] Among these, metal salts such as sodium salt of styrenesulfonic acid are preferred because they allow good control of the particle size. When a crosslinked structure is to be introduced into the poly(meth)acrylic acid ester, a known polyfunctional monomer may be copolymerized.

[0035] (Preferred particulate material) The core layer of the core-shell particle is preferably an organic fine particle, and among the above, preferred materials for use therein are poly(meth)acrylic acid esters and polystyrenes, since raw materials are easily available and fine particles with a uniform particle size can be easily produced, and polystyrenes are more preferred, since polymers with a high refractive index can be obtained. Furthermore, among the above, preferred materials for use in the shell layer of the core-shell particles include silica from the viewpoints of strength and ease of formation, and poly(meth)acrylic acid esters and polystyrenes are preferred because raw materials are easily available, with polystyrenes being more preferred because polymers with high refractive indexes can be obtained. Furthermore, from the viewpoint of strength, inorganic fine particles (hollow inorganic particles) are preferred as the hollow particles, and among the above, silica is preferred as a material used for these particles from the viewpoint of ease of forming a shell layer. Among these, hollow inorganic particles, particularly hollow silica particles, are preferred, as they are more likely to exhibit the characteristic of the present invention, which is that the structural coloring can be improved and made more prominent.

[0036] [Production of fine particles] The colloidal crystal layer of the present invention exhibits structural color when regularly arranged, and therefore it is important that the colloidal crystals forming the colloidal crystal layer are fine particles that satisfy the above-mentioned number-average particle size and number-based particle size CV value and have a uniform particle size.

[0037] (Production of organic fine particles as particles (core particles) forming the core layer) To obtain organic fine particles having a number-average particle size and a CV value of particle size based on the number, for example, a method of obtaining a polymer of an appropriate size by bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, etc., pulverizing the polymer into a fine powder, and then sieving the powder to obtain a uniform particle size can be used. Another method is to directly obtain organic fine particles having a uniform particle size by soap-free emulsion polymerization. Among these, the method using soap-free emulsion polymerization is preferred because of its excellent productivity. This soap-free emulsion polymerization is a known polymerization method, for example, as follows. Deionized water is charged into a reaction vessel, and while heating and stirring as necessary, a polymerization aid is added to thoroughly disperse the polymerization aid in the deionized water. Next, a polymerization initiator is added while continuing to stir. Then, while continuing to stir, the monomers are gradually added dropwise to initiate the polymerization reaction. As the polymerization proceeds, particles are formed.

[0038] The solid concentration during polymerization, that is, the concentration of fine particles relative to the entire system during polymerization, is preferably 20 to 40% by mass. If the solid content concentration during polymerization is equal to or higher than the lower limit, productivity of organic fine particles is improved, and if it is equal to or lower than the upper limit, no cullet is generated during polymerization and no deposits are formed on the inner walls of the polymerization apparatus. When a polymerization initiator is used, the polymerization temperature is generally set to 60 to 90° C. After the reaction is completed, organic fine particles are taken out as an emulsion. In this manner, organic fine particles as particles (core particles) that form the core layer can be produced.

[0039] The pH of the emulsion is preferably 3.0 to 11.0 If the pH of the emulsion is outside the above range, productivity will be poor from the viewpoint of metal corrosion. Therefore, if the pH of the emulsion is outside the above-mentioned preferred range, it is preferable to adjust the pH by adding an alkali or acid as appropriate. Since the pH of the emulsion obtained by the production of the organic fine particles is usually about 2.0 to 7.0, the pH is generally adjusted by adding an alkali. The alkali used for pH adjustment is preferably ammonia water, because it can be easily removed from the structure by heating or the like.

[0040] 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-based polymerization initiators formed by combining an oxidizing agent and a reducing agent. These may be used alone or in combination of two or more. Among these, water-soluble polymerization initiators are preferred because they are easy to handle.

[0041] (Production of inorganic fine particles as core particles) The inorganic fine particles used as core particles in the present invention can be obtained by granulating metal or metal oxide to a predetermined size and then sieving the particles to make the particle diameter uniform.

[0042] (Production of core-shell particles) The core-shell particles can be produced by producing fine particles such as organic fine particles or inorganic fine particles as a core layer by the above-mentioned method, and then forming a shell layer on the surface thereof. When the shell layer is made of silica, it can be produced by adding a mixed solution of a silane compound such as tetraalkoxysilane to a water-containing dispersion of the fine particles.

[0043] (Production of hollow silica particles) Hollow silica particles can be produced by producing core-shell particles, in which the core layer is made of a polymeric material and the shell layer is made of silica, using the method described above, and then removing the core layer by decomposition, such as by photolysis. Hollow silica particles also include those in which the core layer is not completely removed. For example, when the entire volume of the inner region of the shell layer (the volume of the core layer) is taken as 100%, the volume of the removed region should be 50% or more, preferably 60% or more, and more preferably 70% or more. If the volume of the removed region is 50% or more, a sufficient spatial region is obtained, which results in improved and more pronounced structural color development of the resulting laminate.

[0044] <Dispersion> In the present invention, a particle dispersion is obtained by incorporating the above-described particles and a dispersion medium. Here, the dispersion means that the particles are dispersed in the dispersion medium.

[0045] Any medium can be used as the dispersion medium, including, for example, water, aqueous media such as media mainly composed of water, and organic solvents. A medium mainly composed of water means that the water ratio is 50% by mass or more, and even 60% by mass or more. As a component other than water, any organic solvent soluble in water can be selected.

[0046] Examples of organic solvents include alcohols such as methanol, ethanol, isopropyl alcohol, and 1-methoxy-2-propanol alcohol, ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, ester-based solvents such as ethyl acetate and butyl acetate, alkanes such as hexane, cyclohexane, heptane, decane, and hexadecane, halogen-based solvents such as methyl chloride, methylene chloride, chloroform, and carbon tetrachloride, and ether-based solvents such as tetrahydroxyfuran, dioxane, ethylene glycol diethyl ether, and ethylene glycol monobutyl ether. These may be used alone or in combination of two or more. Among the above, aqueous media such as water and media mainly containing water are preferred as the dispersion medium, as they are likely to give a colloidal crystal layer with high structural color development.

[0047] The content of the fine particles in the dispersion of the present invention is preferably 1% by mass to 70% by mass relative to the total mass of the dispersion. The content of the fine particles is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, based on the total mass of the dispersion, and more preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 35% by mass or less. If the content of the fine particles is within the above range, the structural color development of the resulting colloidal crystal layer will be good. The dispersion can be maintained in a dispersed state by adding a dispersant such as sodium dodecyl sulfate or sodium dodecylbenzenesulfonate to the fine particles. The content of the dispersant is sufficient if it is added in an amount of about 0.001% by mass to 5% by mass relative to the mass of the fine particles contained in the dispersion. If it is less than this, the dispersibility of the dispersion tends to become unstable. On the other hand, although it may be more than this, the effect relative to the amount used will not be sufficient, so a content of 5% by mass is sufficient.

[0048] [Dispersion concentration] The solid content of the dispersion of the present invention is preferably 10% by mass or more. The solid content of the dispersion is preferably 20% by mass or more, more preferably 25% by mass or more, and the upper limit of the solid content of the dispersion is preferably 60% by mass or less, more preferably 50% by mass or less. When the solid content concentration of the dispersion is within the above range, film-forming properties are good, and the structural color development of the resulting colloidal crystal film is good. Here, the solid content of the dispersion refers to the components other than the dispersion medium in the dispersion, and is usually the total of the fine particles and other components that may be contained as needed. The solids concentration of the dispersion can be measured in the same manner as the solids concentration of the emulsion described in the Examples section below, but it can also be calculated from the solids concentration and component amounts of each component used in producing the dispersion.

[0049] [Viscosity of dispersion] The viscosity of the dispersion of the present invention is 11.0 cP or less, which results in good structural color development of the resulting colloidal crystal layer. The viscosity of the dispersion of the present invention is preferably 10 cP or less, more preferably 8.0 cP or less, and even more preferably 5.0 cP or less, while the viscosity of the dispersion of the present invention is preferably 1.0 cP or more, more preferably 1.5 cP or more, and even more preferably 2.0 cP or more. Here, the viscosity of the dispersion is the viscosity at 25° C. The viscosity of the dispersion can be measured using, for example, a Brookfield viscometer.

[0050] [Other ingredients] The dispersion of the present invention may contain other components such as a plasticizer, a film-forming aid, a pH adjuster, etc., in addition to the fine particles and the dispersion medium, as needed, within the scope of the present invention.

[0051] [Method for preparing dispersion] The dispersion of the present invention can be prepared by mixing the fine particles, the dispersion medium, and other components used as needed. For example, it can be prepared by mixing the emulsion containing fine particles produced by the above-mentioned method, a dispersion medium, and other components used as needed.

[0052] The resulting colloidal crystal layer can be covered with the overcoat layer, if necessary. For example, the overcoat layer can be formed by applying a precursor of the material constituting the overcoat layer, a heated fluid, a resin solution diluted with a solvent, or an emulsion of a resin dispersed in water to the surface of the colloidal crystal layer, followed by curing, cooling, or the like.

[0053] <Manufacturing of laminated bodies and colloidal crystal layers> Examples of the method for producing the laminate of the present invention and the method for forming the colloidal crystals include the following methods. The dispersion containing the fine particles is applied onto the substrate, and then dried at an appropriate temperature, thereby aligning the fine particles.

[0054] The method for applying the dispersion to the substrate can be any of printing methods that do not use a plate, such as inkjet, spray, dipping, or spin coating, and printing methods that use a plate, such as an offset gravure coater, gravure coater, doctor coater, bar coater, blade coater, flexo coater, or roll coater.

[0055] The coating thickness of the dispersion of the present invention varies depending on the solid content concentration of the dispersion, but is preferably 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 30 μm. When the coating thickness is 1 μm or more, the structural coloring of the resulting structure is improved. When the coating thickness is 100 μm or less, the ordered arrangement of the resulting structure is improved, and the structural coloring is improved.

[0056] There are no particular limitations on the drying method used after coating the dispersion of the present invention on a substrate, and any conventionally known method can be used, such as heat drying, hot air drying, infrared drying, microwave drying, drum drying, etc. The above drying methods may be used alone or in combination. If the drying temperature is too high, the dispersion medium will volatilize rapidly, disrupting the alignment of the microparticles and adversely affecting color development. On the other hand, if the drying temperature is too low, uneven drying may occur, making it impossible to obtain a uniform colloidal crystal film. From the viewpoint of the alignment of the microparticles, the drying temperature is preferably in the range of 10 to 120°C, particularly 90 to 110°C. The drying time varies depending on the drying temperature, but from the viewpoint of the alignment of the fine particles, it is preferably 0.5 to 30 minutes, more preferably 1 to 10 minutes. The laminate according to the present invention can be obtained by the above method, and the aligned fine particles can be dried by the above method to form a colloidal crystal layer.

[0057] When producing a laminate having colloidal crystals composed of the hollow particles, core-shell particles having a core layer made of the polymeric material and a shell layer made of silica are used, and a colloidal crystal layer is formed by the method described above. After that, the core layer made of the polymeric material constituting the particles is decomposed and removed by photolysis or the like, thereby obtaining a colloidal crystal layer composed of hollow particles. The decomposition of the core layer may be carried out over the entire colloidal crystal layer or only partially. Partial core decomposition can produce a laminate that exhibits different color development between the decomposed and undecomposed core regions. Such a laminate exhibits different color development in adjacent regions, allowing for displays with good visibility and the expression of distinctive color tones.

[0058] <Structural coloring> The fine particles of the present invention have structural coloring properties when they are formed into a regularly arranged colloidal crystal layer. Structural coloring means that structural color is exhibited when fine particles of uniform particle diameter are regularly arranged. Structural coloring is a phenomenon in which a material has a crystalline structure in which fine particles are regularly arranged, and optical physical phenomena such as interference and scattering occur depending on the wavelength of light, causing the material to appear colored.

[0059] Since structural coloring is due to the properties of light, it appears not only in the visible light region but also in the ultraviolet and infrared regions. To produce structural color in the ultraviolet region, for example, in the case of particles made of polystyrene, fine particles with a small volume average particle diameter, for example, fine particles with a volume average particle diameter of 180 to 150 nm, can be used, and to produce structural color in the infrared region, fine particles with a large volume average particle diameter, for example, fine particles with a volume average particle diameter of 360 to 800 nm can be used. In the present invention, structural coloring is used to improve the design of articles, and it is therefore preferable to exhibit structural colors in the visible light region. For example, in the case of particles made of polystyrene, when the volume average particle diameter of the fine particles is around 180 to 230 nm, blue or indigo structural colors are exhibited, when it is around 230 to 260 nm, blue or green structural colors are exhibited, and when it is around 260 to 300 nm, green or red structural colors are exhibited.

[0060] 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.

[0061] [Colloidal crystal layer] The colloidal crystal layer of the present invention refers to a substance that exhibits structural color, in which the fine particles contained in the dispersion are regularly arranged, specifically a substance containing colloidal aggregates that exhibit structural color. Here, the colloidal aggregate refers to a colloidal crystal or a colloidal amorphous aggregate, and at least a part of the colloidal crystal is contained. By arranging the fine particles, the fine particles form a colloidal crystal or a colloidal amorphous aggregate, i.e., a colloidal aggregate. Furthermore, a material that exhibits structural color is one in which fine particles of uniform diameter are regularly arranged, causing diffraction and interference of light, resulting in an angle-dependent color that appears to change depending on the viewing angle.

[0062] Examples of the colloidal crystal layer include a substrate on which fine particles are arranged, and a substrate on which fine particles are arranged, from which colloidal crystals have been peeled off without damaging the regular arrangement of the fine particles.

[0063] In one embodiment, the colloidal crystal layer of the present invention is characterized by containing fine particles having a number-average particle diameter of 180 to 800 nm and a CV value of the particle diameter on a number basis of 15% or less. In this case, the fine particles contained in the colloidal crystal layer preferably have the same properties as the fine particles in the dispersion of the present invention described above, and more preferable ranges can also be considered similar.

[0064] [Reflectance of colloidal crystal layer] The colloidal crystal layer of the present invention preferably has a reflectance derived from structural coloring of 5% or more in the wavelength range of 180 to 800 nm. The reflectance of the colloidal crystal layer can be increased to 5% or more by using, for example, the dispersion of the present invention. The reflectance is more preferably 10% or more, and even more preferably 20% or more. If the reflectance is 5% or more, it is preferable because the structural coloring property is excellent. There is no particular upper limit to the reflectance resulting from the structural coloring of the colloidal crystal layer of the present invention, but it is usually 90% or less. The reflectance due to structural coloring can be measured by the method described in the Examples below.

[0065] [Gloss change rate] The colloidal crystal layer of the present invention preferably exhibits a change in gloss of 0.3 or more before and after the physical durability test described below.

[0066] (Physical durability test) The colloidal crystal layer is fixed, and a JK wiper with a 50 g weight placed on it is slid once over the colloidal crystal layer. (Glossiness change rate) = (glossiness after physical durability test) / (glossiness before physical durability test) To achieve a gloss change rate of 0.3 or more, for example, the dispersion of the present invention may be used. The gloss change rate is more preferably 0.5 or more, and even more preferably 0.7 or more. A gloss change rate of 0.3 or more is preferable because it provides excellent physical strength.

[0067] The glossiness can be measured by the following method. Using a wire bar (OSG, OSP-25), the dispersion of fine particles is applied at 15 mm / sec onto a plasma-treated polyester film (Toray Films, Lumirror (black), 100 μm thick). After leaving the film at 25°C for 30 minutes, a 5 cm square sample is cut out from the formed colloidal crystal layer and the gloss is measured at a 45° angle using the JIS Z8741 parallel light method using a gloss meter VG7000 (manufactured by Nippon Denshoku Industries Co., Ltd.) to obtain the gloss.

[0068] [Maximum wavelength] In the laminate of this invention, when the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle are both 10° is defined as λ

[10] , and the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle are both 70° is defined as λ

[70] , the difference between λ

[10] and λ

[70] (λ

[10] - λ

[70] ) satisfies the following relationship: The difference between λ

[10] and λ

[70] should be 200 nm or more, preferably 250 nm or more. If the difference is greater than 200 nm, the color develops with higher angle dependency, and the characteristic of excellent design can be exhibited. On the other hand, there is no particular upper limit, but considering the upper and lower limits of λ

[10] and λ

[70] described below, a value of 600 nm or less is sufficient.

[0069] Incidentally, λ

[10] is preferably 200 nm or more, and more preferably 400 nm or more. On the other hand, it is preferably 1000 nm or less, more preferably 800 nm or less, and more preferably 750 nm or less. When the λ

[10] value is within the above range, a laminate with excellent design properties is obtained.

[0070] Furthermore, λ

[70] is preferably 200 nm or more, and more preferably 250 nm or more. On the other hand, it is preferably 800 nm or less, and more preferably 750 nm or less. When the λ

[70] value is within the above range, a laminate with excellent design properties can be obtained.

[0071] The above maximum wavelength and its relationship can be satisfied by having the above-mentioned laminate structure and by using hollow particles, particularly hollow silica particles, in the colloidal crystal layer. Furthermore, by having the above-mentioned maximum wavelength and its relationship, the structural coloring property is improved, and the resulting laminate has excellent design properties.

[0072] [Backscatter] In the laminate according to the present invention, the maximum wavelength of backscattering, where incident light is reflected toward the incident side, i.e., the maximum wavelength resulting from backscattering in the backscattering spectrum, preferably appears in the wavelength range of 380 to 1000 nm, more preferably in the wavelength range of 400 to 800 nm, thereby allowing backscattering to occur in the visible light range, thereby improving the design properties of the resulting laminate.

[0073] [Thin film interference] The laminate of this invention exhibits thin-film interference, i.e., the reflection spectrum at the upper surface of the colloidal crystal layer and the reflection spectrum at the lower surface of the colloidal crystal layer interfere with each other to produce a wave (interference wave). This interference wave also appears in the wavelength range of 400 to 800 nm, and thin-film interference is considered to have occurred if the difference between the maximum and minimum peak values ​​of the interference wave appearing in this wavelength range is 3% or more. When this thin-film interference occurs, structural colors due to this thin-film interference appear, contributing to improved structural coloring and enabling the resulting laminate to have excellent design properties.

[0074] [Application] The laminate of the present invention has good structural coloring properties due to the regularly arranged colloidal layers, and is therefore suitable for use in decorative films such as color sheets and decorative films, as well as optical materials such as reflective displays, discoloration sensors, anti-counterfeiting agents, electrodeposited color plates, color filters, and polarizing films. The laminate of the present invention can also be suitably used, either alone or as a secondary processed material, for decorative films such as color sheets and decorative films; and optical materials such as reflective displays, discoloration sensors, anti-counterfeiting agents, electrodeposited color plates, color filters, and polarizing films. [Example]

[0075] 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 as long as the gist of the invention is not exceeded. In the following description, "parts" and "%" indicate "parts by mass" and "% by mass", respectively.

[0076] [Evaluation method] In the following examples and comparative examples, various physical properties were measured by the following methods.

[0077] (1) Volume average particle size of fine particles In the present invention, the volume median diameter is used as the volume average particle diameter. Measurements were performed using NanotracWave II manufactured by Microtrac Bell Co., Ltd. and the company's analysis software, Date Management System for Microtrac. Specifically, a sample dispersion was prepared by mixing 0.2 g of the particle dispersion with 30 mL of a diluted solution of Newcol 220-L(20)D (concentration: 0.02%), and this sample dispersion was placed in a sample cell and measured under the following conditions: solvent refractive index: 1.333, measurement time: 180 seconds, number of measurements: 1. Other conditions were: particle refractive index: 1.59, transparency: transparent, shape: spherical, density: 1.00.

[0078] (2) CV value of particle size based on the number of fine particles After applying the microparticle dispersion to a substrate and drying, an image of the microparticles was observed using an electron microscope with a magnification of 10,000 times or more. The diameters of at least 400 microparticles in the image were measured. Using the measured diameters, the CV value of the particle diameter based on the number was calculated by multiplying the standard deviation by the average particle diameter by 100.

[0079] (3) Solids concentration of dispersion The solid content of the dispersion was determined by heating 3 g of the dispersion at 190°C for 60 minutes to evaporate the water using a heat-drying moisture meter MX-50 manufactured by A&D Corporation.

[0080] (4) Maximum wavelength (λ

[10] , λ

[70] ) The reflectance spectrum of the fabricated laminate was measured in the wavelength range of 180 to 800 nm using a UV-visible-near-infrared spectrophotometer (JASCO V-770) and an absolute reflectance measurement unit (JASCO ARSN-917). The mirror in the absolute reflectance measurement unit (JASCO ARSN-917) was used as the reference in the measurements. The maximum value of reflectance in the obtained reflectance spectrum was defined as the reflectance derived from Bragg reflection, and the wavelength at that point was defined as the maximum wavelength. Taking the direction perpendicular to the laminate as the reference (0°), the maximum wavelength when the incident angle and reflection angle were both 10° was defined as λ

[10] , and the maximum wavelength when the incident angle and reflection angle were both 70° was defined as λ

[70] . The maximum wavelength λ

[10] - λ

[70] was evaluated.

[0081] (5) Maximum wavelength due to backscattering The maximum wavelength resulting from backscattering of the fabricated laminate was confirmed by measuring the reflectance in the wavelength range of 250 to 800 nm using an ultraviolet-visible-near-infrared spectrophotometer (JASCO Corporation: V-670) and an absolute reflectance measurement unit (JASCO Corporation: ARMN-735). The normal direction to the laminate was set as the reference (0°), and the incident angle was set at 70° and the detection angle was set at 60°. The mirror in the absolute reflectance measurement unit was used as the reference in the measurements. The maximum value of reflectance in the obtained reflection spectrum was taken as the reflectance resulting from backscattering, and the wavelength at that time was taken as the maximum wavelength resulting from backscattering.

[0082] (6) Thin film interference The presence or absence of thin film interference in the fabricated laminate was confirmed by measuring the reflectance in the wavelength range of 200 to 800 nm using an ultraviolet-visible-near-infrared spectrophotometer (JASCO Corporation: V-670) and an absolute reflectance measurement unit (JASCO Corporation: ARMN-735). S-polarized light was used as the light source, and the incident angle and reflection angle were both set at 70°, with the perpendicular direction to the laminate as the reference (0°). The mirror in the absolute reflectance measurement unit was used as the reference for the measurements. The maximum value of reflectance in the obtained reflection spectrum was taken as the reflectance derived from Bragg reflection, and the wavelength at that point was taken as the maximum wavelength. If an interference wave with a difference between the maximum and minimum values ​​exceeding 3% was observed in the wavelength range of 400 to 800 nm, longer than the maximum wavelength, it was determined that thin film interference was present.

[0083] [Raw materials, etc.] In the following examples and comparative examples, the raw materials used to produce the dispersions are as follows: Styrene (Fujifilm Wako Pure Chemical Industries, Ltd.) Sodium p-styrenesulfonate (Fujifilm Wako Pure Chemical Industries, Ltd.) Sodium bicarbonate (Fujifilm Wako Pure Chemical Industries, Ltd.) Ammonium persulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) 3-Methacryloxypropyltriethoxysilane (Shin-Etsu Chemical Co., Ltd.: KBE-503) 10% by weight ammonia water (Fujifilm Wako Pure Chemical Industries, Ltd.) Ethanol (Kanto Chemical Co., Ltd.) Tetraethoxysilane (Tokyo Chemical Industry Co., Ltd.) Aqueous solution of sodium linear alkylbenzene sulfonate (Nippon Nyukazai Co., Ltd.: Newcol 220-L(20)D) Polyester film (plasma-treated, Toray Films: Lumirror, black, 100 μm thick) Silica particle aqueous dispersion 1 (Fuji Chemical Co., Ltd.: Houtform Silbol-EX220, solid silica particles, silica particle diameter: 220 nm) Silica particle aqueous dispersion 2 (Fuji Chemical Co., Ltd.: Houtform Silbol-EX250, solid silica particles, silica particle diameter: 220 nm)

[0084] [Preparation of core particle dispersion] (Preparation of core particle dispersion [1]) An auxiliary solution was prepared by dissolving 1.20 parts of sodium p-styrenesulfonate and 1.5 parts of sodium hydrogencarbonate in 2081 parts of ion-exchanged water. The auxiliary agent solution was charged into a reaction vessel equipped with a stirrer, a heating / cooling device, a nitrogen introducing device, and a raw material / auxiliary agent charging device, and the internal temperature was raised to 77°C. Next, a polymerization initiator solution prepared by dissolving 4.4 parts of ammonium persulfate in 10 parts of ion-exchanged water was added to the reaction vessel, and 5 minutes later, 857 parts of styrene was successively added dropwise over 170 minutes. After the dropwise addition of styrene was completed, a mixed liquid of 19 parts of styrene and 26 parts of 3-methacryloxypropyltriethoxysilane was successively added dropwise over 10 minutes. Thereafter, stirring was continued at 77° C. for 90 minutes, and then the internal temperature was raised to 90° C. Thereafter, stirring at 90° C. was maintained for 3 hours. After cooling the internal temperature to 20°C, the polymerization reaction mixture was filtered through nonwoven gauze (product name "Cross Gauze No. 2", manufactured by Osaki Medical Co., Ltd.) to obtain an emulsion of fine particles. The pH of the emulsion was adjusted to 7.0 by adding 10 wt% ammonia water. Furthermore, ion-exchanged water was added appropriately to adjust the solid content to 29.0%, thereby obtaining a core particle dispersion liquid [1]. The resulting microparticles had a volume average particle diameter of 243 nm.

[0085] (Preparation of core particle dispersion [2]) A core particle dispersion liquid [2] was obtained by carrying out the same operation as in (Preparation of core particle dispersion liquid [1]) except that the amount of sodium p-styrenesulfonate added was 0.90 parts. The resulting microparticles had a volume average particle size of 300 nm.

[0086] (Preparation of core particle dispersion [3]) Core particle dispersion liquid [3] was obtained by carrying out the same operation as in (Preparation of core particle dispersion liquid [1]) except that the amount of sodium p-styrenesulfonate added was 0.80 parts. The resulting microparticles had a volume average particle diameter of 335 nm.

[0087] (Preparation of core particle dispersion [4]) A core particle dispersion [4] was obtained by carrying out the same procedure as in (Preparation of core particle dispersion [1]) except that the amount of sodium p-styrenesulfonate added was 0.75 parts. The resulting microparticles had a volume average particle diameter of 352 nm.

[0088] [Preparation of core-shell particle dispersion] (Preparation of core-shell particle dispersion [1]) A reactor was charged with 60 parts of core particle dispersion [1], 8.8 parts of 10 wt% aqueous ammonia, 107 parts of ethanol, and 24 parts of water, and the mixture was stirred with a stirrer. A mixture of 35 parts of tetraethoxysilane and 117 parts of ethanol was divided into six portions and added to the reactor once per hour, a total of six times. Stirring was then continued for 24 hours to allow the silica shell formation reaction to occur. The resulting dispersion was repeatedly centrifuged and redispersed in water to prepare an aqueous dispersion with a solids concentration of 25%. Next, 0.03 parts of Newcol 220-L(20)D was added to 100 parts of the dispersion to obtain core-shell particle dispersion [1]. The obtained particles had a volume average particle diameter of 284 nm and a CV value of 8%.

[0089] (Preparation of core-shell particle dispersion [2]) Core-shell particle dispersion liquid [2] was obtained by carrying out the same operation as in (Preparation of core-shell particle dispersion liquid [1]), except that 60 parts of core particle dispersion liquid [2] was used instead of 60 parts of core particle dispersion liquid [1]. The obtained particles had a volume average particle diameter of 347 nm and a CV value of 12%.

[0090] (Preparation of core-shell particle dispersion [3]) Core-shell particle dispersion liquid [3] was obtained by carrying out the same operation as in (Preparation of core-shell particle dispersion liquid [1]), except that 60 parts of core particle dispersion liquid [3] was used instead of 60 parts of core particle dispersion liquid [1]. The obtained particles had a volume average particle diameter of 398 nm and a CV value of 14%.

[0091] (Preparation of core-shell particle dispersion [4]) Core-shell particle dispersion liquid [4] was obtained by carrying out the same operation as in (Preparation of core-shell particle dispersion liquid [1]), except that 60 parts of core particle dispersion liquid [4] was used instead of 60 parts of core particle dispersion liquid [1]. The obtained particles had a volume average particle diameter of 412 nm and a CV value of 13%.

[0092] [Preparation of laminates made of core-shell particles] (Preparation of laminate [1] consisting of core-shell particles) The core-shell particle dispersion [1] was applied to a plasma-treated polyester film using a wire bar (OSG, OSP-10) at a rate of 15 mm / sec, and then dried at 25°C for 10 minutes to form a colloidal crystal layer and obtain a laminate [1] in which the core-shell particles were layered on the substrate. The λ

[10] of the obtained laminate was 566 nm, λ

[70] was 442 nm, and λ

[10] -λ

[70] was 124 nm. A cross-sectional SEM photograph (magnification: 30,000 times) of the core-shell particle portion of the obtained laminate is shown in Figure 1. This SEM photograph was taken using a scanning electron microscope (SEM, manufactured by JEOL Ltd.: JSM-IT800HL).

[0093] (Preparation of laminate [2] consisting of core-shell particles) A laminate [2] made of core-shell particles was obtained by the same procedure as in (Preparation of laminate [1] made of core-shell particles), except that core-shell particle dispersion [2] was used instead of core-shell particle dispersion [1]. The λ

[10] of the obtained laminate was 708 nm, λ

[70] was 544 nm, and λ

[10] - λ

[70] was 164 nm.

[0094] (Preparation of a laminate [3] consisting of core-shell particles) A laminate [3] consisting of core-shell particles was obtained by the same procedure as in (Preparation of laminate [1] consisting of core-shell particles), except that core-shell particle dispersion [3] was used instead of core-shell particle dispersion [1]. The λ

[10] of the obtained laminate was 768 nm, λ

[70] was 588 nm, and λ

[10] - λ

[70] was 180 nm.

[0095] (Preparation of laminates [4] consisting of core-shell particles) A laminate [4] consisting of core-shell particles was obtained by the same procedure as in (Preparation of laminate [1] consisting of core-shell particles), except that core-shell particle dispersion [4] was used instead of core-shell particle dispersion [1]. The λ

[10] of the obtained laminate was 796 nm, λ

[70] was 608 nm, and λ

[10] - λ

[70] was 188 nm.

[0096] [Example 1] A laminate [1] consisting of core-shell particles was irradiated with light (temperature 63°C, humidity 50%, illuminance 0.4 kW / m², 24 hours) using a metaling vertical weather meter (MV3000, Suga Test Instruments Co., Ltd.). As a result, the cores of the core-shell particles that make up the colloidal crystal layer in the laminate disappeared, and a laminate consisting of hollow silica particles was formed. The λ

[10] of the resulting laminate was 454 nm, λ

[70] was 230 nm, λ

[10] - λ

[70] was 224 nm, and the maximum wavelength due to backscattering was 417 nm, confirming thin film interference. A cross-sectional SEM photograph (magnification: 30,000 times) of the obtained hollow silica particles is shown in Figure 2. This SEM photograph was taken using the above-mentioned scanning electron microscope.

[0097] [Example 2] A laminate composed of hollow silica particles was formed by performing the same operation as in Example 1 on the laminate [2] composed of core-shell particles. The λ

[10] of the obtained laminate was 574 nm, λ

[70] was 286 nm, λ

[10] -λ

[70] was 288 nm, and the maximum wavelength due to backscattering was 519 nm, confirming thin film interference.

[0098] [Example 3] A laminate composed of hollow silica particles was formed by performing the same operation as in Example 1 on the laminate [3] composed of core-shell particles. The λ

[10] of the obtained laminate was 636 nm, λ

[70] was 314 nm, λ

[10] -λ

[70] was 322 nm, and the maximum wavelength due to backscattering was 581 nm, confirming thin film interference.

[0099] [Example 4] A laminate consisting of hollow silica particles was formed by performing the same operation as in Example 1 on the laminate [4] consisting of core-shell particles. The λ

[10] of the obtained laminate was 656 nm, λ

[70] was 326 nm, λ

[10] -λ

[70] was 330 nm, and the maximum wavelength due to backscattering was 612 nm, confirming thin film interference.

[0100] [Comparative Example 1] Silica particle aqueous dispersion 1 was applied to a plasma-treated polyester film using a wire bar at 15 mm / sec and then dried at 25°C for 10 minutes to obtain a laminate containing a colloidal crystal layer composed of silica particles. The λ

[10] of the resulting laminate was 458 nm, λ

[70] was 338 nm, λ

[10] -λ

[70] was 120 nm, and the maximum wavelength due to backscattering was 339 nm, with no evidence of thin film interference.

[0101] Comparative Example 2 Silica particle aqueous dispersion 2 was applied to a plasma-treated polyester film using a wire bar at 15 mm / sec and then dried at 25°C for 10 minutes to obtain a laminate containing a colloidal crystal layer composed of silica particles. The λ

[10] of the resulting laminate was 516 nm, λ

[70] was 380 nm, λ

[10] -λ

[70] was 136 nm, and the maximum wavelength due to backscattering was 382 nm, with no evidence of thin film interference.

[0102] [Table 1]

[0103] [result] The laminates of Examples 1 to 4 had larger λ

[10] -λ

[70] values ​​than the laminates of Comparative Examples 1 and 2, indicating that the Bragg reflection had a stronger angular dependency and exhibited a more specific color tone. Furthermore, the laminates of Examples 1 to 5 exhibited backscattering in the visible light region, indicating that they exhibited a more specific color tone than the laminates of Comparative Examples 1 and 2. Additionally, the laminates of Examples 1 to 4 exhibited peaks due to thin-film interference in the visible light region, indicating that they exhibited a more specific color tone than the laminates of Comparative Examples 1 and 2. 1 and 2, it was confirmed that hollow silica particles were obtained in Example 1. It was also confirmed that the layers of hollow silica particles in the laminate obtained in Example 1 were regularly arranged.

Claims

1. A laminate having a substrate and a colloidal crystal layer, A laminate characterized in that, when the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle with respect to the colloidal crystal layer are both 10° is defined as λ[10], and the maximum wavelength resulting from Bragg reflection in the reflection spectrum when the incident angle and reflection angle are both 70° is defined as λ[70], the following relationship exists between λ[10] and λ[70]. λ[10]-λ[70]≧200nm

2. 2. The laminate according to claim 1, wherein the maximum wavelength resulting from backscattering appears in the wavelength range of 400 to 800 nm.

3. 3. The laminate according to claim 1, wherein in the reflection spectrum when both the incident angle and the reflection angle are set to 70°, in addition to a reflection peak due to Bragg reflection, a peak due to thin film interference is observed in a wavelength range of 400 to 800 nm.

4. 3. The laminate according to claim 1, wherein the λ[10] is 400 nm or more and 1000 nm or less.

5. The laminate according to claim 1 or 2, wherein the λ[70] is 200 nm or more and 800 nm or less.

6. 3. The laminate according to claim 1, wherein the colloidal crystal layer is made of hollow particles.

7. The laminate according to claim 6 , wherein the hollow particles are hollow silica particles.

8. A method for producing a laminate including a colloidal crystal layer made of hollow particles, comprising: a step of drying a dispersion of fine particles made of core-shell particles on a substrate to align the core-shell particles and form colloidal crystals; and a step of removing the cores from the core-shell particles.

9. The method for producing a laminate according to claim 8 , wherein the hollow particles are hollow silica particles.

Images