JP2004149768A - Coating agent, method for producing structural body with hollow-containing layer and structural body with hollow-containing layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a coating agent for forming a hollow-containing layer, with which the inner structure of the layer can be controlled and, in addition, the layer is formed through easy processes, by solving problems concerning difficulty of controlling the shape of the hollow, complicated processes, necessity of a large-scale apparatus, or the like; to provide a method for producting a structural body with the hollow-containing layer using the coating agent; and the structural body with the hollow-containing layer. <P>SOLUTION: The coating agent for forming the hollow-containing layer is composed of at least three members of a photopolymerizable compound which is liquid at room temperature, a solvent which causes phase separation from the photopolymerizable compound and a photopolymerization initiator. The production of the structural body with the hollow-containing layer is characterized in that, after irradiating active energy rays onto a whole coated face containing the solvent in the state of phase separation, formed by applying the coating agent for forming the layer at least onto a substrate, the dispersed solvent alone is selectively volatilized to form the hollows. The structural body with the hollow-containing layer is obtained by using the coating agent and by the above-mentioned method. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for producing a structure having a coating agent and a cavity-containing layer having excellent internal structure controllability, and a structure having a cavity-containing layer.

  2. Description of the Related Art Conventionally, structures having a cavity therein have been used in various fields. For example, foams used for cushioning materials, heat insulating materials, etc., separation membranes used for production of ultrapure water, purification of chemicals, water treatment, etc., waterproof moisture-permeable films used for clothing, sanitary applications, batteries It is used in all industrial fields, such as a porous film used for a separator and the like, and a void-containing sheet used as a reflective substrate for a liquid crystal display and various lighting devices.

The methods for manufacturing these structures are classified into the following methods.
(1) A method of kneading a thermal foaming material into a raw resin to form a sheet, irradiating with an electron beam or the like, cross-linking and then foaming by heating (see Patent Document 1).
(2) A method in which a photo-decomposable compound is added to a raw material resin, coated on a base material, and then irradiated with active energy rays to decompose and foam the entire surface (see Patent Document 2).
(3) A raw material resin is dissolved in a good solvent, formed into an arbitrary shape such as a hollow fiber or a film, and the obtained molded body is immersed in a poor solvent, and a phase utilizing a two-phase separation phenomenon generated at that time. Method obtained by conversion method (see Non-Patent Document 1)
(4) After adding particles made of an inorganic filler such as silica, alumina and inorganic salts or an incompatible resin to the raw material resin and molding, the obtained molded body is stretched, and the resin and the inorganic filler and the like are stretched. (See Patent Document 3).
(5) A thermoplastic resin and a latent solvent which is a non-solvent near room temperature but becomes a solvent at a high temperature are mixed with the thermoplastic resin by heating and mixing once, and then cooled and solidified to form a resin phase. A method using a thermally induced phase separation method in which a porous body is obtained by phase separation with a solvent phase and then removing a high-temperature solvent by extraction or the like (see Non-Patent Document 2).
JP-A-3-221542 (page 2) JP-A-5-72727 (p. 3) JP-A-5-138844 (pages 3-4) Hiroyoshi Kawakami, Membrane, 26 (3), 110-115 (2001) Matsuyama Hideto, Membrane, 26 (3), 116-123 (2001)

  However, these methods have various problems.

  In the methods using foams (1) and (2), it is difficult to control the foam diameter. There is also a problem in the stability of the foamable compound. In (3), a step of immersion in a solvent or an extraction step is required, and much time is required. The method (4) requires a huge device for stretching the molded body. Also in (5), it is necessary to extract the separated high-temperature solvent.

  In addition, an operation such as melting at a high temperature is required as a whole when forming the raw material resin into a sheet.

  The present invention overcomes the problems of the prior art, such as the difficulty in controlling the cavity shape, the complexity of the process, and the need for a large-scale apparatus. An object of the present invention is to provide a coating agent for forming a void-containing layer, a method for producing a structure having a void-containing layer using the same, and a structure having a void-containing layer.

  The present invention employs the following means in order to solve such a problem. That is, the coating agent for forming a void-containing layer of the present invention comprises a photopolymerizable compound which is liquid at normal temperature, a solvent having a property of phase-separating from the photopolymerizable compound, and a photopolymerization initiator. It is characterized by the following.

  Further, the method for producing a structure having a cavity-containing layer according to the present invention comprises applying a coating agent for forming a cavity-containing layer on at least a substrate, and irradiating the entire surface with active energy rays in a state where the solvent is phase-separated. Then, only the dispersed solvent is volatilized to form a cavity.

  Further, the structure having the cavity-containing layer of the present invention is characterized by being produced by the above method using the coating agent of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the coating film which has the space | gap whose internal structure was controlled by an easy process.

  The present invention intensively studies the above-mentioned problem, that is, a coating agent that can be manufactured by an easy process in addition to controlling the internal structure, and a specific photopolymerizable compound, a solvent and a light having a specific property. When a composition composed of at least three polymerization initiators was used as a coating agent, it was found that the above problems were solved at once, and that a coating film excellent in forming a cavity-containing layer was formed. is there.

  That is, the coating agent of the present invention is characterized by comprising at least three components of a photopolymerizable compound which is liquid at normal temperature, a solvent which is phase-separated from the photopolymerizable compound, and a photopolymerization initiator. .

  The core of the concept of the present invention is to cure only the matrix portion made of the photopolymerizable compound while the solvent is dispersed and contained, and finally volatilize the dispersed solvent without curing, and create a cavity inside. Is produced. The points are control of the dispersion state of the solvent, photo-curing, and a drying-less process after application.

  As the photopolymerizable compound used in the present invention, a photopolymerizable compound which is liquid at room temperature at a solid content of 100% is used. In other words, when used as a coating agent, even without using a diluent, it refers to a material having good applicability without significant appearance of application streaks. For example, when the viscosity is measured at 25 ° C., 30,000 mPa · s or less. Such a photopolymerizable compound means a monomer, oligomer, or polymer that is polymerized by light irradiation, and among such photopolymerizable compounds, an ethylenically unsaturated polymerizable compound is preferable, and among them, two or more ethylenically unsaturated polymers are preferable. Compounds having a saturated group are more preferred, and compounds having three or more ethylenically unsaturated groups are particularly preferred.

  Examples of such photopolymerizable compounds include hexanediol triacrylate, tripropylene glycol triacrylate, trimethylolpropane triacrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, lauryl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, and isooctyl. Acrylate, tridecyl acrylate, caprolactone acrylate, ethoxylated nonylphenol acrylate, N, N-dimethylacrylamide, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropylacrylamide, acryloylmorpholine, N-isopropylacrylamide, N, N-diethylacrylamide, 1,3-butanediol diacrylate, 1,4-butane Diol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, propoxylated neopentyl glycol diacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, ethoxylated Trimethylolpropane triacrylate, pentaerythritol triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hydroxypentaacrylate, ethoxylated pentaerythritol tetraacrylate, Te Lahydrofurfuryl methacrylate, cyclohexyl methacrylate, isodecyl methacrylate, lauryl methacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, diethylene glycol dimethacrylate, 1,9- Nonanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, ethoxylated bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid diacrylate, ethoxy Paracumylphenol acrylate, ethylhexyl carbitol Acrylate, N-vinyl-2-pyrrolidone, isobornyl acrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyester (meth) acrylate, polyurethane (meth) acrylate, epoxy (Meth) acrylate and the like are preferably used.

  These photopolymerizable compounds may be used alone or in combination of two or more. When a compound having at least three ethylenically unsaturated groups is contained in order to enhance shape retention and coating strength, three-dimensional crosslinking is possible, and as a result, the rigidity of the cured product is improved, This is preferable because the change can be suppressed. Further, as such a photopolymerizable compound, from the viewpoint of dispersing a solvent stably or imparting shape retention, it has an appropriate viscosity, that is, preferably 300 to 100,000 mPa · s, more preferably 5000 to 20,000 mPa. It is preferable to use one having a viscosity of s.

  That is, even if the viscosity of the photopolymerizable compound is too low or too high, the intended cavity-containing layer can be produced, but if it is too low, the solvent floats up after a while, or the coating is performed. If the film thickness is too high, there is a tendency that streaks and the like are formed at the time of application, making it difficult to form a smooth coating film, and easy to catch bubbles.

  The viscosity of the photopolymerizable compound may be selected and used in consideration of the viscosity of the coating composition as a whole.For example, when a plurality of compounds are mixed, the viscosity increases due to the interaction between molecules. Therefore, instead of the viscosity alone, the viscosity in the case where a plurality of photopolymerizable compounds are mixed, and the viscosity in the state further containing a solvent, 1000 mPas or more, adjusted to 2000 to 20000 mPas Is preferred. Further, phase separation means that the compound has low compatibility, that is, it is a poor solvent. Therefore, it is preferable to select a compound that does not aggregate during mixing.

  It is preferable to use a photosensitive oligomer such as polyester acrylate, urethane acrylate, or epoxy acrylate in consideration of the properties of the coating film after curing and the stable dispersibility of the solvent.

  The solvent used in the present invention is a solvent that phase-separates from the photopolymerizable compound. The phase separation phenomenon may occur at room temperature or may occur at the time of heating. Phase separation at room temperature refers to a state in which, for example, when mixed at 25 ° C., they do not dissolve. The phrase “phase separation in a heated state” refers to, for example, a method in which a composition that is compatible and transparent at normal temperature is heated to reduce the compatibility and cause phase separation. This includes, for example, a case where two components that are compatible at room temperature due to the action of hydrogen bonding break the hydrogen bonds by heating, and the respective components aggregate to form a phase separation state. Can be However, when heating, it is naturally necessary to perform the treatment in a temperature range sufficiently lower than the boiling point of the solvent. Here, it is preferable to perform phase separation at room temperature because the process is simplified and energy is saved.

  As examples of such a solvent, a wide variety of solvents can be used in accordance with the photopolymerizable compound. For example, alcohols such as methanol, ethanol, isopropanol, butanol and octanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethyl acetate, butyl acetate, ethyl lactate, γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene Esters such as glycol monoethyl ether acetate, ethers such as ethylene glycol monomethyl ether and diethylene glycol monobutyl ether, aromatic hydrocarbons such as benzene, toluene, xylene, and amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone , Water and the like can be used, but not all such solvents can be used.

  That is, such a solvent must be a solvent having a property of phase-separating from the photopolymerizable compound, and must be selected from the above-mentioned solvents. For example, when the photopolymerizable compound is a polyester acrylate, it is preferable to select and use a compound such as water, methanol, and ethanol that separates with the polyester acrylate. Among the above-mentioned solvents, it is preferable to use water from the viewpoint of safety and health, handling problems due to flammability, and effects on the natural environment.

  The amount of the solvent is preferably 1 to 30 wt%, more preferably 1 to 20 wt% in the coating agent. That is, if the amount of the solvent is too large, the curing of the coated film may be inhibited even by irradiation with actinic rays, and if too small, the original content is small, and the influence of volatilization and the like. , Sufficient cavities may not be formed.

  Further, in the step of producing the cavity-containing layer, if the boiling point of the solvent is too high, it is difficult to evaporate the solvent to form cavities, and if the boiling point of the solvent is too low, volatilization during the process is difficult. And it becomes difficult to maintain the amount of the solvent in the coating film, so that stable production tends to be difficult.

  When water is used as the solvent, it is also a preferable embodiment to further add a water-soluble compound as a composition of the coating agent. In this case, since the water-soluble compound dissolves in water, the phase separation state of the coating agent has a structure in which a phase in which water and the water-soluble compound are dissolved in the photopolymerizable compound is dispersed. In this case, since the water-soluble compound remains in the dispersed phase even after water as a solvent is volatilized, the obtained structure has a nested structure in which a resin lump is further contained in the cavity.

  By using a nested structure, it is possible to reduce the amount of solvent to be added, as compared with a case where the inside is completely hollow, so that drying shrinkage of the structure can be reduced. It has the feature that the number of solid interfaces can be increased.

  Here, as the water-soluble compound, the molecule has a hydrophilic group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, an amino group or a salt thereof, an amide group, a hydroxyl group, and a polyoxyethylene group. Compounds and the like are preferable, and among them, a compound which is solid at normal temperature or a photopolymerizable compound which is solidified by irradiation with active energy rays is preferable.

  Examples of the compound which is solid at normal temperature include the above-mentioned water-soluble polyester resin containing a hydrophilic group, polyurethane resin, acrylic resin and the like. The glass transition temperature (Tg) of these resins is preferably 40 ° C. or higher, more preferably 50 ° C. or higher. Examples of the water-soluble photopolymerizable compound which is solidified by irradiation with an active energy ray are not particularly limited as long as they have an ethylenically unsaturated bond in the molecule. In this case, the Tg of the solidified product is also preferably 40 ° C. or higher, more preferably 50 ° C. or higher. Here, the reason for using a compound that is solid at room temperature or solidified by active energy rays is to prevent the nested structure from relaxing after the formation of the structure.

  Examples of the photopolymerization initiator include, for example, 2,2-dimethoxy-1,2-diphenylethan-1-one, p-tert-butyltrichloroacetophenone, 2,2′-diethoxyacetophenone, and 2-hydroxy-2. Acetophenones such as -methyl-1-phenylpropan-1-one, benzophenone, ketones such as 4,4'-bisdimethylaminobenzophenone, 2-chlorothioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone and 2-isopropylthioxanthone And benzoin ethers such as benzoin, benzoin methyl ether, benzoin isopropyl ether and benzoin isobutyl ether, and benzyl ketals such as benzyl dimethyl ketal and hydroxycyclohexyl phenyl ketone. These photopolymerization initiators are selected in consideration of the respective photosensitive wavelengths, wavelengths of active energy rays, thickness of the coating film, and the like. Therefore, these photopolymerization initiators may be used alone or in combination. The addition amount of the photopolymerization initiator is preferably 0.1 to 10% by weight based on the photosensitive component.

  A surfactant is preferably added to the coating agent for forming a cavity-containing layer of the present invention. By adding such a surfactant, stable dispersion of the solvent is realized, and the dispersion state is maintained over time, and the internal structure can be easily controlled.

  As examples of such a surfactant, a nonionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant and the like are preferably used.

  Examples of such nonionic surfactants include polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenyl ether type, polyoxyethylene sterol ether type, polyoxyethylene lanolin derivative type, polyoxyethylene glycerin fatty acid ester type, and polyoxyethylene sorbitan. Fatty acid ester type, polyoxyethylene sorbitol fatty acid ester type, polyethylene glycol fatty acid ester type, fatty acid glyceride type, polyglycerin fatty acid ester type, sorbitan fatty acid ester type, propylene glycol fatty acid ester type, fatty acid alkanolamide type, polyoxyethylene fatty acid amide Type, polyoxyethylene alkylamine type, alkylamine oxide type and the like.

  Examples of the cationic surfactant include aliphatic primary amine salts, secondary amine salts, tertiary amine salts, quaternary ammonium salts, benzalkonium salts, benzenetonium chloride, pyridinium salts, An imidazolinium salt or the like is used.

  Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids and salts thereof, alkyl ether carboxylates, carboxylates such as acylated peptides, sulfated oils, higher alcohol sulfates, and alkyl ether sulfates. , Polyoxyethylene alkyl phenyl ether sulfate, sulfate such as fatty acid alkylol amide sulfate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfo acetate, α-olefin sulfone For example, sulfonates such as acid salts, phosphate salts such as alkyl ether phosphate salts, and alkyl phosphate ester salts are used.

  As the amphoteric surfactant, carboxybetaine type, aminocarboxylic acid type, imidazolinium betaine type, lecithin type and the like are used.

  As a numerical value representing the characteristics of a surfactant, there is an HLB value. When the HLB value is low, a water-in-oil dispersion state tends to be obtained, and when the HLB value is high, an oil-in-water dispersion state tends to be obtained.

  The dispersion state also changes depending on the mixing ratio of each compound in the composition. For this reason, it is possible to easily change the internal dispersion form by the type and mixing ratio of the surfactant added to the coating agent of the present invention, and the internal structure of the cavity-containing layer produced using this coating agent can be changed. You will be able to control it. Further, the addition of such a surfactant is preferable because the temporal stability of the dispersed state of the entire coating composition is improved. In order to advantageously provide such effects, the amount of the surfactant added is preferably set to 1 to 20% by weight.

  The coating agent of the present invention preferably contains a photopolymerizable emulsifier. As such an emulsifier, those having a polymerizable carbon-carbon unsaturated double bond in the molecule in the skeleton of the surfactant described above can be preferably used. By using such a polymerizable emulsifier having surface activity, it is possible to suppress bleeding after curing. The addition amount of the photopolymerizable emulsifier is preferably 1 to 20% by weight from the viewpoint of exhibiting the above effects.

  The structure in which the resin particles are dispersed in the cavity is an oil-in-water type. In the case of the coating agent of the present invention, since the solid content ratio is large, a part of the coating agent tends to be an oil-in-water type. For example, there is a structure in which a resin layer is provided on the front surface and the bottom surface, and resin particles are contained in a space interposed therebetween.

  The structure in which the cavities are dispersed in the resin is a water-in-oil type. Further, the co-continuous structure of the resin and the cavity is intermediate between them.

  Of these, which structure can be arbitrarily changed depending on the composition to be used, particularly the combination of a surfactant or a photopolymerizable emulsifier.

  Various additives may be used in the coating agent of the present invention. As such additives, fillers such as inorganic particles, film forming aids, ultraviolet absorbers, light stabilizers, heat stabilizers, pigments, dyes, plasticizers, viscosity modifiers, antioxidants and the like are used. .

  The method for producing a structure having a void-containing layer according to the present invention includes a step of applying a coating agent on a substrate, irradiating the entire surface of the coating film in a phase-separated state with active energy rays, and finally evaporating the solvent.

  The coating method can be performed by a method such as multi-roll coating, blade coating, wire bar coating, slit die coating, gravure coating, knife coating, reverse roll coating, spray coating, offset gravure coating, or spin coating.

  In the forming method of the present invention, a drying step after application is not required. In the case of a thick film, since this step may be rate-determining, high productivity can be realized by omitting it.

  Further, the coating film is preferably in a phase-separated state at room temperature, but the phase-separated state may be induced by slightly heating, and in this case, a heating step is performed after the application.

  Here, it is preferable to avoid evaporation of the solvent during the process. For example, in order to avoid evaporation of water from a coating film in which water, which is a preferred solvent, is dispersed, it is preferable to thoroughly control humidity during the coating process. Further, a treatment such as attaching a cover film to the coating film surface may be performed.

  After application, by irradiating the entire surface with an active energy ray, the solvent is cured while maintaining the dispersed shape in the coating film. As the active energy ray here, ultraviolet ray, visible light, electron beam, X-ray and the like are used, and among them, ultraviolet ray or electron beam is preferably used. Further, when the coating film is heated by the active energy rays applied during the irradiation, the solvent evaporates. Therefore, it is preferable that a heat ray cut filter or the like is installed in the irradiation apparatus.

  After curing, it is preferable to heat or dry under reduced pressure in order to volatilize the dispersed solvent.

  Also, here, the phase-separated state is cured with active energy rays, but depending on the combination of the compositions, the void-containing layer may be formed even when the solvent is volatilized after the compatible coating film is cured. is there. In this case, since the solvent is compatible with the coating film, the dispersion diameter tends to be smaller than that of the phase separation system.

  The cavity-containing structure of the coating film formed by the coating agent of the present invention has a nested structure in which resin particles are dispersed in cavities, a structure in which cavities are dispersed in resin, a structure in which resin particles are dispersed in cavities, and a resin and cavity. Is a structure selected from the bicontinuous structures of

  The thickness of the coating film formed by such a coating agent is not particularly limited, but is preferably in the range of 5 to 200 μm, from the viewpoint of easy production. Such a cavity-containing layer of the present invention can be used as a single layer, or can be used as a laminated structure together with a substrate.

  Even in the case of using a single layer, in the production, it is applied to a substrate once to adjust the form, and then used after peeling off from the substrate.

  In the case of a laminated structure, examples of the base material used include organic film base materials such as polyester resin, polyolefin resin and acrylic resin, metal base materials such as stainless steel, aluminum, aluminum alloy, iron, steel, and titanium, and slate. It can be applied to inorganic substrates such as concrete and the like. In addition, such a base material may be one that has been subjected to a treatment such as a base adjustment material and an undercoat material. These substrates are preferably laminated to any material, such as transparent, colored, and cloudy, without any particular limitation. That is, a configuration as a composite with a substrate having another function is also preferable.

  The thickness of the substrate is not particularly limited, and varies depending on the type of the substrate. For example, when a film substrate such as polyethylene terephthalate is used, the thickness is 20 to 500 μm, more preferably 30 to 300 μm, and still more preferably 50 to 200 μm from the viewpoint of mechanical strength and the like.

  Various effects can be expected by the void-containing coating film of the present invention.

  Light diffusivity and light reflectivity can be obtained by utilizing a high refractive index difference between the matrix resin and air. In addition, a sheet having a low specific gravity, a low dielectric constant, a heat insulating property, and an insulating property can be obtained from the feature of containing a cavity. Further, a coating having a low refractive index in which the apparent refractive index of the system is reduced by miniaturizing the cavity is obtained, and can be used as an antireflection film or the like.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not necessarily limited thereto.

(Example 1)
The following composition 1 was applied to a PET film (“Lumirror” (R) QT40, 100 μm thick, manufactured by Toray Industries, Inc.) with a thickness of 100 μm using a blade coater.

(Composition 1)
Polyester acrylate 10 parts by weight Aronix 8060 (Toa Gosei Co., Ltd.)
Water 0.5 parts by weight Photopolymerization initiator 0.05 parts by weight Irgacure 907 (manufactured by Ciba Specialty Chemicals)
That is, the above composition was mixed with a spatula, allowed to stand for 15 minutes, and then applied. The composition after standing was phase-separated and was in a cloudy state. When the coating was observed after standing for 5 hours, the coating was in a two-layer separated state in which water floated on the surface.

The entire surface of the obtained coating film was exposed to 200 mJ / cm ² using an ultra-high pressure mercury lamp. Next, the desired void-containing layer was formed by vacuum drying at room temperature for 20 minutes.

  The haze of the obtained film was 73%. Observation of the cross section showed a structure in which microcavities having distribution were dispersed in the resin.

(Examples 2 and 3)
A cavity-containing layer was formed in the same manner as in Example 1, except that the amount of water was changed to 1.25 parts by weight (Example 2) and 2.5 parts by weight (Example 3).

  After standing for 15 minutes, both coatings were phase-separated and clouded. After standing for 5 hours, two layers were similarly separated.

  The haze of the obtained film was 91% (Example 2) and 92% (Example 3). Further, when the cross section was observed, it was found that the microcavities were dispersed in the resin as in Example 1.

(Example 4)
The following composition 2 was applied on a PET film ("Lumirror" QT40, 100 μm thick, manufactured by Toray Industries, Inc.) with a thickness of 100 μm using a blade coater.

(Composition 2)
Polyester acrylate 10 parts by weight Aronix 8060 (Toa Gosei Co., Ltd.)
Surfactant 1.5 parts by weight Neugen ET-143 (HLB: 12.1 by Daiichi Kogyo Seiyaku Co., Ltd.)
Water 1.5 parts by weight Photopolymerization initiator 0.05 parts by weight Irgacure 907 (manufactured by Ciba Specialty Chemicals)
That is, the above composition was mixed with a spatula, allowed to stand for 15 minutes, and then applied. After standing, the composition was phase-separated and in a cloudy state, and was foamed by mixing and mixing bubbles. Further, it was confirmed that the coating agent was stably dispersed even after standing for 5 hours and after standing for 1 day.

The entire surface of the obtained coating film was exposed to 200 mJ / cm ² using an ultra-high pressure mercury lamp. Next, the desired void-containing layer was formed by vacuum drying at room temperature for 20 minutes.

The haze of the obtained film was 93%. Observation of the cross section showed a structure in which a 5 μm layer was formed on the substrate side and on the surface, and resin spherical particles having a distribution of about several to 20 μm were dispersed inside the layer.
(Example 5)
The following composition 3 was applied to a PET film ("Lumirror" QT40 manufactured by Toray Industries, Inc., thickness: 100 μm) with a blade coater to a thickness of 100 μm.

(Composition 3)
Polyester acrylate 10 parts by weight Aronix 8060 (Toa Gosei Co., Ltd.)
Surfactant 2.5 parts by weight Neugen ET-135 (HLB manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: 13.3)
Water 2.5 parts by weight Photopolymerization initiator 0.05 parts by weight Irgacure 907 (manufactured by Ciba Specialty Chemicals)
That is, the above composition was mixed with a spatula, allowed to stand for 15 minutes, and then applied. After standing, the composition was phase-separated and was cloudy. Further, it was confirmed that the coating agent was stably dispersed even after standing for 5 hours and after standing for 1 day.

The entire surface of the obtained coating film was exposed to 200 mJ / cm ² using an ultra-high pressure mercury lamp. Next, the desired void-containing layer was formed by vacuum drying at room temperature for 20 minutes.

  The haze of the obtained film was 83%. Observation of the cross section revealed that the microcavities were dispersed in the resin.

(Example 6)
The following composition 4 was applied on a PET film (“Lumirror” (R) QT40, 100 μm thick, manufactured by Toray Industries, Inc.) with a thickness of 100 μm using a blade coater.

(Composition 4)
Polyurethane acrylate 10 parts by weight Unidick RS23-179 (Dainippon Ink Co., Ltd.)
3 parts by weight of water-soluble polyester resin aqueous solution (solid content: 25%)
Photopolymerization initiator 0.05 parts by weight Irgacure 907 (manufactured by Ciba Specialty Chemicals)
The entire surface of the obtained coating film was exposed to 300 mJ / cm ² using an ultra-high pressure mercury lamp. Next, the desired void-containing layer was formed by vacuum drying at room temperature for 20 minutes.

  The haze of the obtained film was 75%. Observation of the cross section confirmed a nested structure in which the resin was contained in cavities having a distribution of 5 to 20 μm.

(Comparative Example 1)
An experiment was performed in the same manner as in Example 1 except that the water of the composition 1 was replaced with methyl ethyl ketone in which a polyester acrylate as a photopolymerizable compound was dissolved. The composition remained transparent after mixing.

  The coating film after the entire surface exposure and vacuum drying was also transparent, and no cavities were found inside when the cross section was observed.

Claims (10)

A coating agent for forming a void-containing layer, comprising a photopolymerizable compound which is liquid at ordinary temperature, a solvent having a property of phase-separating from the photopolymerizable compound, and a photopolymerization initiator. The coating agent for forming a void-containing layer according to claim 1, wherein the coating agent for forming a void-containing layer contains a surfactant. The coating agent for forming a void-containing layer according to claim 1 or 2, wherein the photopolymerizable compound is a photopolymerizable emulsifier. The coating agent for forming a void-containing layer according to any one of claims 1 to 3, wherein the solvent is water. The coating agent for forming a cavity-containing layer according to claim 4, wherein the coating agent contains a water-soluble compound which is solid at normal temperature. The coating agent for forming a cavity-containing phase according to claim 4, wherein the coating agent contains a water-soluble photopolymerizable compound which solidifies upon irradiation with an active energy ray. The coating agent for forming a void-containing layer according to claim 4, wherein the coating agent for forming a void-containing layer does not contain an organic solvent. Applying the coating agent for forming a cavity-containing layer according to any one of claims 1 to 7 on at least a substrate, and irradiating the entire surface with an active energy ray in a state where the solvent is phase-separated, and then dispersing. A method for producing a structure having a cavity-containing layer, wherein a cavity is formed by volatilizing only a solvent that is present. A structure having a void-containing layer, which is manufactured by the method according to claim 8. 10. A structure having a cavity-containing layer according to claim 9, wherein the cavity has a nested structure.