Dispersion of fluoride particles, its manufacturing method, and optical film

Abstract

To provide a liquid dispersion of fluoride particles, which has a low viscosity and excellent dispersibility and is suitable for the production of an optical film such as an antireflective film; a method for producing the liquid dispersion; and an optical film using the liquid dispersion.SOLUTION: A liquid dispersion of fluoride, which is characterized in that particles of a fluoride represented by chemical formula: AxCFy (wherein A represents sodium or potassium; C represents silicon or boron; x represents 1 or 2; and y represents 4 or 6) are dispersed in an aprotic organic solvent having a relative dielectric constant of 5 to 40. And an optical film produced using the liquid dispersion of fluoride particles.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a dispersion of fluoride particles and an optical film, and more particularly to a dispersion of fluoride particles suitable for anti-reflection films for displays, lenses, etc., a production method thereof, and an optical film. [Background technology]

[0002] People today have many opportunities to come into contact with various displays, such as televisions, personal computers, smartphones, tablet devices, and car navigation systems. When light is irradiated onto a display, whether indoors or outdoors, light reflection can reduce visibility, which can cause eye fatigue and headaches. In recent years, coatings that can prevent light reflection have been developed to add a sense of luxury to decorative panels inside automobiles.

[0003] The anti-reflection coating is configured to include a high refractive index layer and a low refractive index layer, and prevents light reflection on the display surface and improves visibility by utilizing the phase difference of light reflected on the surface of each of the high refractive index layer and the low refractive index layer.

[0004] The method for forming the low refractive index layer is roughly divided into a gas phase method and a coating method. Of these, the coating method has good efficiency in using raw materials and is superior to the gas phase method in terms of mass production and equipment costs. Therefore, the coating method, which has good productivity, is currently used for forming the low refractive index layer.

[0005] Patent Document 1 describes that magnesium fluoride sol or magnesium fluoride fine powder, which are chemically stable and have a low refractive index, are effective as a filler for a coating agent for forming a low refractive index layer. However, the refractive index of magnesium fluoride is about 1.38, and the refractive index of the low refractive index layer cannot be made lower than that.

[0006] Patent Document 2 describes a dispersion of hollow spherical silica-based particles. Patent Document 3 describes a dispersion of hollow particles (core-shell particles) having a hollow core inside a shell made of magnesium fluoride. These patent documents also describe the use of silica-based particles or hollow particles as a filler for a coating agent to form an anti-reflective film with a lower refractive index. However, the silica-based particles of Patent Document 2 and the hollow particles of Patent Document 3 themselves have voids. Therefore, there is a problem that the mechanical strength and scratch resistance of an anti-reflective film using these as a filler is reduced.

[0007] Patent Document 4 describes the use of potassium silicofluoride (refractive index 1.34), which has a lower refractive index than magnesium fluoride, as a filler for anti-reflection coating. However, when potassium silicofluoride is dispersed in an organic solvent under atmospheric pressure, the viscosity of the dispersion increases significantly. In addition, there is a problem that the potassium silicofluoride particles aggregate, impairing light transmittance.

[0008] Patent Document 5 describes a fluoride microparticle dispersion in which magnesium fluoride microparticles are dispersed in a carboxylic acid. Patent Document 5 also describes that the moisture content in the fluoride microparticle dispersion is suppressed to 0.1% by weight or less. However, Patent Document 5 does not disclose any fluorides other than magnesium fluoride. In addition, about 3% by weight of carboxylic anhydride such as acetic anhydride used for removing moisture remains in the fluoride microparticle dispersion, and considering that the content of magnesium fluoride microparticles is about 4 to 8% by weight, a large amount of carboxylic anhydride remains in the fluoride microparticle dispersion. In addition, when the fluoride microparticle dispersion is used to form a low refractive index layer, there is no description or study regarding the light transmittance of the low refractive index layer. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 4655614 [Patent Document 2] Patent No. 4046921 [Patent Document 3] Patent No. 5943754 [Patent Document 4] Patent Publication No. 2011-195693 [Patent Document 5] JP2007-161509A Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a dispersion of fluoride particles which has low viscosity and excellent dispersibility and is suitable for producing optical films such as anti-reflection films, a method for producing the same, and an optical film using the same. [Means for solving the problem]

[0011] In order to solve the above problems, the dispersion liquid of the fluoride particles of the present invention is x CF y (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) is dispersed in an aprotic organic solvent having a relative dielectric constant of 5 to 40.

[0012] In the above-mentioned configuration, it is preferable that a water concentration [a] (mass %) in the dispersion of the fluoride particles relative to 100 mass % of the dispersion of the fluoride particles and a relative dielectric constant [b] of the aprotic organic solvent satisfy the relationship represented by the following formula (1). [a]≦0.06e 0.15[b] (1)

[0013] In the above-mentioned configuration, the aprotic organic solvent is preferably at least one selected from the group consisting of ketone solvents, amine solvents, ether solvents, and ester solvents.

[0014] Furthermore, the ketone solvent is preferably at least one selected from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, methyl butyl ketone, cyclohexanone, methylcyclohexanone, and acetylacetone.

[0015] The amine solvent is preferably at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea.

[0016] The ether solvent is preferably at least one selected from the group consisting of ethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, and tetrahydrofuran.

[0017] The ester solvent is preferably at least one selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate, and isobutyl acetate.

[0018] In the above-mentioned composition, it is preferable to contain a dispersant for dispersing the fluoride particles in the aprotic organic solvent.

[0019] In the above-mentioned composition, the average dispersed particle size of the fluoride particles is preferably within a range of 1 nm to 100 nm.

[0020] In the above-mentioned composition, the content of the fluoride particles is preferably within a range of 1% by mass to 30% by mass with respect to 100% by mass of the dispersion liquid of the fluoride particles.

[0021] In order to solve the above problems, the present invention provides a method for producing a dispersion of fluoride particles, comprising reacting an aqueous solution of a sodium salt or a potassium salt with a silicofluoride or a boron fluoride to produce a dispersion of fluoride particles A x CF y(wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6), a step of subjecting the slurry of the fluoride particles to solid-liquid separation, washing the obtained solid content of the fluoride particles, a step of drying the washed solid content of the fluoride particles, and a step of dispersing the dried fluoride particles in an aprotic organic solvent having a relative dielectric constant of 5 to 40 to prepare a dispersion liquid of the fluoride particles.

[0022] In the above-mentioned configuration, the step of preparing the dispersion of the fluoride particles is preferably performed by adjusting the water concentration [a] in the dispersion so that the water concentration [a] (mass %) in the dispersion of the fluoride particles relative to 100 mass % of the dispersion of the fluoride particles and the relative dielectric constant [b] of the aprotic organic solvent satisfy the relationship represented by the following formula (1). [a]≦0.06e 0.15[b] (1)

[0023] Furthermore, in the above-mentioned configuration, the water concentration [a] in the dispersion liquid is preferably adjusted by preparing the dispersion liquid of the fluoride particles in an inert gas atmosphere.

[0024] In order to solve the above problems, the optical film of the present invention is characterized in that it comprises a dried and cured film of a composition for forming an optical film, which contains a dispersion of the above fluoride particles. Effect of the Invention

[0025] The present invention can provide a dispersion liquid of fluoride particles having low viscosity and excellent dispersibility, and a refractive index smaller than that of, for example, magnesium fluoride, and a manufacturing method thereof. In addition, by using the fluoride dispersion liquid, an optical film such as an antireflection film having uniform and good optical properties such as light transmittance, haze, and light reflectance in a plane can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] (Fluoride particle dispersion) The dispersion of fluoride particles according to this embodiment (hereinafter, may be simply referred to as "dispersion") will be described below. The dispersion of the present embodiment includes at least fluoride particles and an aprotic organic solvent. In this specification, the term "dispersion" refers to a state in which a dispersoid is dispersed in a liquid dispersion medium. Therefore, the term "dispersion" does not include a dispersion such as a solid colloid (organogel) in which a dispersoid is dispersed in a solid dispersion medium and fluidity is lost.

[0027] The fluoride has the chemical formula A x CF y (wherein, A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6).

[0028] Specific examples of the fluorides represented by the above chemical formula include sodium silicofluoride (Na2SiF6, refractive index 1.31), potassium silicofluoride (K2SiF6, refractive index 1.34), sodium borofluoride (NaBF4, refractive index 1.31), and potassium borofluoride (KBF4, refractive index 1.33). The exemplified fluorides can be used alone or in combination of two or more. Among the exemplified fluorides, sodium silicofluoride and sodium borofluoride, which have a refractive index of less than 1.33 and low solubility in water, are particularly preferred.

[0029] The average dispersed particle diameter of the fluoride particles is preferably in the range of 1 nm to 100 nm, more preferably in the range of 10 nm to 50 nm. By making the average dispersed particle diameter 1 nm or more, it is possible to suppress the aggregation of the fluoride particles caused by intermolecular forces from becoming significant. On the other hand, by making the average dispersed particle diameter 100 nm or less, it is possible to reduce the detachment of the fluoride particles from the optical film and the loss of optical transparency when the fluoride particles are used as a filler for an optical film such as an anti-reflection film.

[0030] The content of the fluoride particles is preferably in the range of 1% by mass to 30% by mass, more preferably in the range of 2% by mass to 15% by mass, and further preferably in the range of 5% by mass to 10% by mass, based on 100% by mass of the dispersion of the fluoride particles. By making the content of the fluoride particles 1% by mass or more, it is possible to suppress the use of a large amount of dispersion liquid, for example, when mixing with a resin composition that is a constituent material of the optical film. This makes it possible to reduce the time required for removing the aprotic organic solvent when removing it during the film formation process of the optical film. On the other hand, by making the content of the fluoride particles 30% by mass or less, it is possible to suppress the dispersion time of the fluoride particles from becoming long, and to reduce the probability of the fluoride particles agglomerating with each other.

[0031] The aprotic organic solvent is an organic solvent that does not have proton-donating properties, and may be either polar or nonpolar.

[0032] The relative dielectric constant of the aprotic organic solvent is in the range of 5-40, and preferably in the range of 5-20.

[0033] The aprotic organic solvent may be, for example, at least one selected from the group consisting of ketone solvents, amine solvents, ether solvents, and ester solvents.

[0034] The ketone solvent is not particularly limited, and examples thereof include methyl isobutyl ketone (dielectric constant 13.1), methyl ethyl ketone (dielectric constant 18.5), methyl butyl ketone (dielectric constant 14.5), cyclohexanone (dielectric constant 16.1), methylcyclohexanone (dielectric constant 16.4), and acetylacetone (dielectric constant 27.2).

[0035] The amine solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (dielectric constant: 32.2), N,N-dimethylformamide (dielectric constant: 36.7), N,N-dimethylacetamide (dielectric constant: 37.8), and tetramethylurea (dielectric constant: 23.1).

[0036] The ether solvent is not particularly limited, and examples thereof include ethylene glycol dimethyl ether (relative dielectric constant: 7.2), propylene glycol monomethyl ether acetate (relative dielectric constant: 8.3), and tetrahydrofuran (relative dielectric constant: 7.6).

[0037] The ester solvent is not particularly limited, and examples thereof include methyl acetate (relative dielectric constant: 6.7), ethyl acetate (relative dielectric constant: 6.4), butyl acetate (relative dielectric constant: 5.0), and isobutyl acetate (relative dielectric constant: 5.3).

[0038] Among these aprotic organic solvents, methyl ethyl ketone and methyl isobutyl ketone have excellent solubility in acrylate solvents and are relatively volatile, and therefore are suitable for producing optical films such as anti-reflection films, etc. The aprotic organic solvents exemplified above can be used alone or in combination of two or more.

[0039] It is preferable that the water concentration [a] (the concentration (mass %) of the water contained in the dispersion relative to 100 mass % of the dispersion) and the relative dielectric constant [b] of the aprotic organic solvent satisfy the relationship represented by the following formula (1). [a]≦0.06e 0.15[b] (1)

[0040] By making the water concentration [a] of the dispersion and the relative dielectric constant [b] of the aprotic organic solvent satisfy the relationship represented by the above formula (1), the present invention makes it possible to specify the water concentration in the dispersion within an appropriate range according to the value of the relative dielectric constant of the aprotic organic solvent, i.e., according to the type of the aprotic organic solvent. In this way, the present invention does not uniformly specify the water concentration of the dispersion to a specific value or less, but specifies it according to the type of the aprotic organic solvent, thereby making it possible to obtain a dispersion with excellent dispersibility by suppressing the aggregation of fluoride particles for each aprotic organic solvent.

[0041] The water concentration [a] in the dispersion is set to 0.06e 0.15[b]By making the value of the dispersion liquid equal to or less than the value of the above, the viscosity of the dispersion liquid can be suppressed from increasing excessively, and the dispersibility of the fluoride particles can be maintained well. In addition, the compatibility with the resin composition, which is the constituent material of the optical film, can be prevented from decreasing, and the coarsening of the fluoride particles can be prevented. As a result, the optical transparency of the optical film can be maintained well.

[0042] In addition, since it is necessary to maintain the performance such as dispersibility of the dispersion for a long period of time from immediately after production, it is more preferable that the relationship between the water concentration [a] and the relative dielectric constant [b] of the aprotic organic solvent satisfies the relationship represented by the following formula (2), and it is even more preferable that the relationship represented by the following formula (3). [a]≦0.045e 0.15[b] (2) [a]≦0.03e 0.15[b] (3)

[0043] The dispersion liquid may contain a dispersant to disperse the fluoride particles well in the aprotic organic solvent. The addition of a dispersant is particularly effective when an organic solvent with low polarity is used as the aprotic organic solvent.

[0044] The dispersant is not particularly limited, and a general surfactant can be used. Examples of the surfactant include a nonionic hydrocarbon surfactant, a cationic hydrocarbon surfactant, an anionic hydrocarbon surfactant, and a nonionic fluorocarbon surfactant. 、 Examples of the surfactant include cationic fluorocarbon surfactants and anionic fluorocarbon surfactants.

[0045] Among the surfactants given above, those that impart good dispersibility to fluoride particles include anionic hydrocarbon surfactants and anionic fluorocarbon surfactants that have an acidic functional group. Examples of the acidic functional group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group.

[0046] Among the surfactants given as examples, surfactants having fluorine atoms, i.e., nonionic fluorocarbon surfactants, 、 Since cationic fluorocarbon surfactants and anionic fluorocarbon surfactants have low refractive indices, dispersions containing these surfactants are suitable as constituent materials for optical films.

[0047] The surfactant having a fluorine atom is not particularly limited, and examples thereof include acrylic resins obtained by copolymerizing fluoroalkyl(meth)acrylates having a fluoroalkyl group having 1 to 20 carbon atoms, an ethylenically unsaturated monomer having an acidic functional group, and, if necessary, other ethylenically unsaturated monomers. The (meth)acrylate includes both acrylate and methacrylate.

[0048] The fluoroalkyl (meth)acrylates having a fluoroalkyl group having 1 to 20 carbon atoms are not particularly limited, and examples thereof include 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 3-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorodecyl)ethyl (meth)acrylate, 2-(perfluoro-3-methylbutyl ... perfluoro-5-methylhexyl)ethyl (meth)acrylate, 2-(perfluoro-7-methyloctyl)ethyl (meth)acrylate, 1H,1H,3H-tetrafluoropropyl (meth)acrylate, 1H,1H,5H,octafluoropentyl (meth)acrylate, 1H,1H,7H-dodecafluoroheptyl (meth)acrylate, 1H,1H,9H-hexadecafluorononyl (meth)acrylate, 1H-1-(trifluoromethyl)trifluoroethyl (meth)acrylate, 1H,1H,3H-hexafluorobutyl (meth)acrylate, and the like.

[0049] The dispersant may be a commercially available surfactant. For example, examples of dispersants having an acidic functional group include Solsperse (registered trademark) 3000, Solsperse 21000, Solsperse 26000, Solsperse 36600, and Solsperse 41000 (all trade names, manufactured by Lubrizol Japan Co., Ltd.); Disperbyk 108, Disperbyk 110, Disperbyk 111, Disperbyk 112, Disperbyk 116, Disperbyk 142, Disperbyk 180, Disperbyk 2000, and Disperbyk 2001 (all trade names). Product names, manufactured by BYK-Chemie Co., Ltd.); Plysurf (registered trademark) A208N, Plysurf A208F, Plysurf A208B, Plysurf A219B, Plysurf AL, Plysurf A212C, Plysurf A215C (all trade names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Disparlon (registered trademark) 3600N, Disparlon 1850 (all trade names, manufactured by Kusumoto Chemical Industries Co., Ltd.); PA111 (trade name, manufactured by Ajinomoto Fine-Techno Co., Ltd.); EFKA4401, EFKA4550 (all trade names, manufactured by EFKA Additives Co., Ltd.), etc. However, commercially available surfactants are not limited to those exemplified.

[0050] The concentration of the dispersant is preferably in the range of 0.05% by mass to 5% by mass, more preferably in the range of 0.5% by mass to 1% by mass, based on 100% by mass of the dispersion liquid. When the concentration of the dispersant is 0.05% by mass or more, the dispersibility of the fluoride particles can be further improved. On the other hand, when the concentration of the dispersant is 5% by mass or less, the dispersant itself forms micelles, and thus the dispersibility of the fluoride particles can be prevented from decreasing.

[0051] The viscosity of the dispersion is preferably in the range of 200 mPa·s or less from the viewpoint of improving compatibility with a binder component (described in detail below) contained in the optical film-forming composition.

[0052] (Method of manufacturing fluoride particles) Next, a method for producing fluoride particles according to the present embodiment will be described below. Note that the method for producing the fluoride particles described below is an example, and the present invention is not limited to this method.

[0053] The method for producing the fluoride particles includes the steps of: etc.” ) is reacted with a silicofluoride or a boron fluoride (hereinafter referred to as "silicofluoride, etc.") to obtain the above-mentioned A x CF y The method includes a step of obtaining a slurry of fluoride particles represented by the formula (I), a step of performing solid-liquid separation of the obtained slurry and washing the solid content of the slurry, and a step of drying the solid content (paste) of the washed fluoride particles to remove moisture.

[0054] The sodium salt in the aqueous sodium salt solution is not particularly limited, and examples thereof include sodium chloride, sodium sulfate, sodium acetate, sodium nitrate, sodium hydroxide, etc. These sodium salts may be used alone or in combination of two or more.

[0055] The potassium salt in the potassium salt aqueous solution is not particularly limited, and examples thereof include potassium chloride, potassium sulfate, potassium acetate, potassium nitrate, potassium hydroxide, etc. These potassium salts can be used alone or in combination of two or more.

[0056] The sodium salt aqueous solution and potassium salt aqueous solution are obtained by dissolving a sodium salt or a potassium salt (hereinafter referred to as "sodium salt, etc."), respectively, in water. The dissolution temperature when dissolving the sodium salt, etc. in water can be appropriately set depending on the solubility of the sodium salt, etc. in water. For example, when using a sodium salt, etc. that shows sufficient solubility in water even at room temperature, the dissolution may be carried out at room temperature. In addition, when using a sodium salt, etc. that has low solubility in water at room temperature, the sodium salt, etc. may be dissolved in water by heating, thereby shortening the time required for dissolution.

[0057] The silicofluoride is not particularly limited as long as it is a salt that is soluble in water. Examples of the silicofluoride include sodium silicofluoride, potassium silicofluoride, ammonium silicofluoride, and hydrosilicofluoric acid. These silicofluorides can be used alone or in combination of two or more.

[0058] The boron fluoride is not particularly limited as long as it is a salt that is soluble in water. Examples of the boron fluoride include sodium boron fluoride, potassium boron fluoride, ammonium boron fluoride, and hydrofluoric acid. These boron fluorides can be used alone or in combination of two or more.

[0059] The reaction of the sodium salt aqueous solution or the like with the silicofluoride or the like may be carried out after filtering the sodium salt aqueous solution or the like for the purpose of removing foreign matter contained in the sodium salt aqueous solution or the like.

[0060] In addition, the reaction between the aqueous solution of sodium salt or the like and the silicofluoride or the like may be carried out by adding a solid silicofluoride or the like to the aqueous solution of sodium salt or the like, or by mixing the aqueous solution of sodium salt or the like with an aqueous solution of silicofluoride or the like obtained by dissolving the silicofluoride or the like in water. In the latter case, the manufacturing process can be simplified and the reaction can be facilitated. In addition, when the aqueous solution of silicofluoride or the like is used, filtration may be carried out in advance to remove foreign matter in the aqueous solution of silicofluoride or the like.

[0061] The reaction temperature between the sodium salt aqueous solution and the silicofluoride is not particularly limited, but if the reaction temperature is too low, the reaction may proceed slowly. On the other hand, if the reaction temperature is too high, steam may be generated from the sodium salt aqueous solution and / or the silicofluoride aqueous solution, and the concentration of the mixture (reaction solution) may change. From these viewpoints, the reaction temperature is preferably within the range of 20°C to 50°C.

[0062] The method for solid-liquid separation of the obtained slurry of fluoride particles is not particularly limited, and examples thereof include suction filtration, centrifugal dehydration, etc. In addition, when the particle size of the fluoride particles is small and fine, solid-liquid separation may be difficult by suction filtration or centrifugal dehydration. In such a case, solid-liquid separation may be performed using a centrifuge, or the slurry itself may be evaporated to dryness.

[0063] The paste of fluoride particles obtained by solid-liquid separation can be washed, for example, by washing with water. This makes it possible to remove unreacted silicofluorides and other anions. The washing temperature and washing time are not particularly limited and can be set appropriately as needed.

[0064] A method for removing moisture from the paste of fluoride particles after washing includes, for example, heat treatment. This allows dry powder of fluoride particles to be obtained. The heat treatment method is not particularly limited, and includes, for example, a method in which the paste of fluoride particles is placed in an FRP tray and dried in a dryer.

[0065] The heating temperature (drying temperature) during the heat treatment is preferably within the range of 100°C to 300°C, more preferably within the range of 100°C to 200°C. By setting the heating temperature at 100°C or higher, the moisture contained in the paste of fluoride particles can be sufficiently removed or reduced. On the other hand, by setting the heating temperature at 300°C or lower, thermal fusion between fluoride particles and thermal decomposition of fluoride particles can be prevented. In addition, the heating time (drying time) during the heat treatment is not particularly limited and can be set appropriately as needed.

[0066] The heat treatment may be performed in air or in an inert gas environment. The inert gas is not particularly limited, and examples thereof include nitrogen, argon, etc. From the viewpoint of promoting drying of the paste of fluoride particles, the heat treatment may be performed in a reduced pressure environment.

[0067] (Method for producing a dispersion of fluoride particles) Next, a method for producing a dispersion liquid of fluoride particles according to the present embodiment will be described below. The dispersion liquid of the present embodiment can be obtained by adding the fluoride particles obtained by the above-mentioned production method to an aprotic organic solvent and dispersing the fluoride particles in the aprotic organic solvent. The production method of the dispersion liquid of fluoride particles according to the present embodiment may also include the above-mentioned production method of fluoride particles.

[0068] The method for dispersing the fluoride particles in the aprotic organic solvent is not particularly limited, and examples thereof include a method using a wet bead mill, a wet jet mill, ultrasonic waves, etc. As for the dispersion method, a grinding device may be selected in consideration of the average dispersed particle size of the target fluoride particles, the quality such as purity, etc.

[0069] For example, if one wishes to improve the dispersibility of fluoride particles, a method using a wet bead mill is preferred. In a wet bead mill, media such as zirconia beads are used to refine particles, so that the dispersing power of fluoride particles can be improved. However, there is a possibility of contamination of the obtained dispersion liquid by the media. Also, if one wishes to improve the purity of the dispersion liquid, a method using a wet jet mill is preferred. A wet jet mill is a wet grinding method that does not use media, and it is possible to prevent contamination by media, as in a wet bead mill. However, since no media is used, the dispersing power of fluoride particles may be reduced.

[0070] In the process of producing the dispersion, it is preferable to control the water concentration [a] in the dispersion. Specifically, it is preferable to perform the process so that the water concentration [a] in the dispersion satisfies the relationship represented by the above-mentioned formula (1). As a method for controlling the water concentration [a], for example, a method of performing wet grinding in a place where the dew point is controlled, such as a dry room, or a method of performing wet grinding in an inert gas atmosphere in a sealed space so that the fluoride particles, the aprotic organic solvent, and the dispersion containing them are not exposed to the outside air. Or dry air The inert gas is not particularly limited, and examples thereof include 、 Examples of the gas include nitrogen and argon.

[0071] Before adding and dispersing the fluoride particles in an aprotic organic solvent, the surface adsorbed water of the fluoride particles may be removed in advance. Examples of a method for removing the surface adsorbed water include a method of drying at a drying temperature of 100°C to 200°C for a drying time of 2 hours to 34 hours, preferably 5 hours to 20 hours. Examples of a method for removing water from an aprotic organic solvent include distillation, centrifugation, and the use of a dehydrating agent (molecular sieves, zeolite, ion exchange resin, activated alumina, etc.). A method of bubbling an inert gas such as nitrogen into an aprotic organic solvent may also be used.

[0072] (Composition for optical film formation) Next, the composition for forming an optical film according to the present embodiment will be described below. The composition for forming an optical film of the present embodiment contains at least a dispersion of fluoride particles and a binder component.

[0073] The contents of the dispersion liquid and the binder component are not particularly limited, and can be set appropriately as necessary.

[0074] The binder component is not particularly limited, and examples thereof include resins and polymerizable monomers.

[0075] The resin is not particularly limited, and known thermosetting resins, thermoplastic resins, etc. can be used. More specifically, for example, acrylic resin, polyester resin, polycarbonate resin, polyamide resin, urethane resin, vinyl chloride resin, fluororesin, silicone resin, epoxy resin, melamine resin, phenol resin, butyral resin, vinyl acetate resin, etc. can be mentioned. These resins can be used alone or in combination of two or more. They may also be used as copolymers or modified bodies made of two or more resins. Among the resins exemplified above, resins containing fluorine atoms such as fluororesins are preferable because they can reduce the refractive index of the optical film.

[0076] The polymerizable monomer is not particularly limited, and known monomers that can be polymerized by radical polymerization, anionic polymerization, cationic polymerization, etc. can be used. More specifically, for example, nonionic monomers (styrene, methyl methacrylate, 2-hydroxyethyl acrylate, etc.), anionic monomers (methacrylic acid, maleic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, o- and p-styrenesulfonate, and salts thereof, etc.), cationic monomers (N-(3-acrylamidopropyl)ammonium methacrylate, N-(2-methacryloyloxyethyl)-N, 1,2-dimethyl-5-vinylpyridinium methosulfate, and salts thereof, etc.), crosslinking monomers (divinylbenzene, ethylene diacrylate, N,N-methylenebisacrylamide, etc.), etc. can be used alone or in combination of two or more of these polymerizable monomers. Among the polymerizable monomers exemplified above, polymerizable monomers containing fluorine atoms are preferable because they can reduce the refractive index of the optical film.

[0077] The optical film forming composition may contain other additives within a range that does not impair the purpose or effect of the present invention. Examples of other additives include photopolymerization initiators, photocurable compounds, polymerization inhibitors, photosensitizers, leveling agents, surfactants, antibacterial agents, antiblocking agents, plasticizers, ultraviolet absorbers, infrared absorbers, antioxidants, silane coupling agents, conductive polymers, conductive surfactants, inorganic fillers, pigments, dyes, etc. The amount of these additives added can be appropriately set as needed.

[0078] (Optical film and its manufacturing method) Next, an optical film and a manufacturing method thereof according to the present embodiment will be described below. The optical film of the present embodiment is made of the dried and cured film of the optical film-forming composition described above. The optical film contains fluoride particles as a filler uniformly, and has a lower refractive index than an optical film using magnesium fluoride, for example. In addition, the optical film has high light transmittance, reduced haze and light reflectance, and other uniform and good optical properties in the plane.

[0079] The optical film of the present embodiment can be used, for example, as an anti-reflection film.

[0080] The content of the fluoride particles in the optical film is preferably within a range of 20% by mass to 90% by mass with respect to 100% by mass of the optical film. If the content of the fluoride particles is within the above range, it is practical because it is possible to maintain the effect of lowering the refractive index of the optical film while suppressing a decrease in the physical and chemical strength of the optical film.

[0081] The thickness of the optical film is not particularly limited and can be set appropriately as required.

[0082] The optical film can be formed, for example, by the following method. That is, after applying the composition for forming an optical film to a substrate or the like, the coating film of the composition for forming an optical film is dried. Next, ultraviolet light of a predetermined light intensity is irradiated to photo-cure the coating film after drying. In this way, the optical film of the present embodiment is obtained.

[0083] The method for applying the composition for forming an optical film is not particularly limited, and examples thereof include a dip method, a spray method, a spinner (spin coating) method, a roll coating method, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, a spray coating method, etc. When a low refractive index layer is formed, the reverse coating method, particularly the reverse coating method using a small diameter gravure roll, is preferred from the viewpoint of coating accuracy.

[0084] The substrate is not particularly limited, and examples thereof include a plastic sheet, a plastic film, a plastic panel, glass, etc. The material constituting the plastic sheet, the plastic film, and the plastic panel is not particularly limited, and examples thereof include polycarbonate, an acrylic resin, polyethylene terephthalate (PET), and triacetyl cellulose (TAC).

[0085] The optical film-forming composition may be applied to a substrate in a state where it is further added to a solvent. The solvent is blended for the purpose of improving the workability of application (including printing). The solvent is not particularly limited as long as it dissolves the optical film-forming composition or is compatible with the optical film-forming composition, and any known solvent may be used.

[0086] The amount of the solvent used is not particularly limited as long as it is within a range suitable for forming an optical film, but is usually within the range of 10% by mass to 95% by mass relative to 100% by mass of the composition for forming an optical film.

[0087] The method for drying the coating film of the composition for forming an optical film applied to the substrate is not particularly limited, and can be performed by natural drying or by blowing hot air, etc. The drying time and drying temperature are not particularly limited, and can be appropriately set depending on the thickness of the coating film, the constituent materials, etc.

[0088] The method and conditions for irradiating the dried coating film with ultraviolet light are not particularly limited. The irradiation conditions can be appropriately set depending on the types and amounts of the components of the optical film-forming composition.

[0089] In this way, the optical film of the present embodiment can be formed on a substrate. Here, the dispersion of fluoride particles of the present embodiment has low viscosity and good dispersibility of the fluoride particles. Therefore, the optical film formed using the optical film forming composition containing the dispersion has a low refractive index and optical properties such as light transmittance, haze, and light reflectance are uniform within the surface. Therefore, the optical film of the present embodiment is suitable for anti-reflection films and the like. EXAMPLES

[0090] Preferred examples of the present invention are described in detail below. However, the materials and amounts of ingredients described in the examples are not intended to limit the scope of the present invention unless otherwise specified.

[0091] (Method for measuring average particle size) The average dispersed particle diameter of the fluoride particles in the dispersion was measured using a particle size distribution analyzer (Microtrac, NanotracUPA, UPA-UZ152, manufactured by Microtrac-Bell Co., Ltd.). The average dispersed particle diameter (d50) is a particle diameter defined as 50 volume percent of the total sample particles being composed of particles with an average dispersed particle diameter or less. Measurement principle: Dynamic light scattering method Frequency analysis (FFT-heterodyne method) Light source: 3mW semiconductor laser 780nm (2 units) Setting range: 10℃~80℃ Measurement particle size distribution range: 0.8nm~6.5406μm Measurement target: Colloid particles

[0092] Unless otherwise specified, the average dispersed particle size in the examples and comparative examples refers to the average particle size converted into volume as measured by the dynamic light scattering method described above.

[0093] (Moisture measurement method) The moisture concentration in the dispersion of fluoride particles was measured by the Karl Fischer method. The moisture measuring device used was TQV-2200S (product name) manufactured by Hiranuma Sangyo Co., Ltd. The measurement method was volumetric titration based on JIS K 0068 (2001).

[0094] (Viscosity measurement method) The viscosity of the dispersion of the fluoride particles was measured using a Brookfield viscometer, DV-I PRIME (trade name) manufactured by Brookfield Corporation, USA. The measurement was carried out based on JIS K 5600-2-2 (2004).

[0095] Example 1 190g of methyl ethyl ketone (reagent), 10g of sodium silicofluoride (manufactured by Stella Chemifa Co., Ltd.), and 2g of Plysurf A212C (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant were mixed in a 500cc fluororesin container to prepare a slurry in which sodium silicofluoride was aggregated. Next, the slurry was put into a bead mill (manufactured by Shinmaru Enterprises Co., Ltd.) in a nitrogen environment with a dew point of -40°C or less, and a dispersion process was performed. Zirconia beads (manufactured by Nikkato Co., Ltd.) were used as the beads. During the dispersion process, the dispersion was sampled at regular intervals to measure the particle size distribution. The dispersion process was performed until the average dispersed particle diameter (volume conversion, d50) of the sodium silicofluoride particles stopped decreasing, and 180g of a dispersion of sodium silicofluoride particles (particle concentration: 5% by mass relative to the total mass of the dispersion) was obtained. Table 1 shows the physical properties of the dispersion according to this Example 1.

[0096] Example 2 In this example, except that N-methyl-2-pyrrolidone (NMP) was used instead of methyl ethyl ketone, a dispersion according to this example was obtained in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0097] Comparative Example 1 In this comparative example, the dispersion treatment in a nitrogen environment was changed to a dispersion treatment in an air environment (room temperature 25°C, relative humidity 60%). A gel-like dispersion according to this comparative example was obtained in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0098] Comparative Example 2 In this comparative example, isopropanol (IPA, a protic organic solvent) was used instead of methyl ethyl ketone. What happened Other than that, the dispersion according to this comparative example was obtained in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0099] Comparative Example 3 In this comparative example, 1-methoxy-2-propanol (PGME, a protic organic solvent) was used instead of methyl ethyl ketone, and no dispersant was used. Other than that, a dispersion according to this comparative example was obtained in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0100] [Table 1]

[0101] Example 3 7.3g of the dispersion liquid prepared in Example 1 was mixed with 2.9g of a commercially available acrylate paint. Furthermore, 0.37g of 1-hydroxycyclohexyl phenyl ketone was dissolved in the mixed solution to prepare an optical film-forming composition. Next, 0.1g of this optical film-forming composition was diluted with 99.9g of propylene glycol monomethyl ether to prepare a low refractive index paint.

[0102] 500 μl of the diluted low refractive index paint was applied by spin coating to one side of a PET film (Toray Industries, Inc., Lumirror (registered trademark) U34: thickness 100 μm). The applied coating film was dried at 130° C. and then exposed to ultraviolet light of 400 mJ / cm 2 . 2 The resin was then photocured by irradiation with light, and an anti-reflection film (low refractive index layer, optical film) was laminated thereon.

[0103] Example 4 0.01g of 1-hydroxycyclohexyl phenyl ketone was dissolved in 0.18g of commercially available acrylate paint. Furthermore, 3.10g of the dispersion liquid prepared in Example 1 was mixed into the mixed solution to prepare an optical film-forming composition. Next, 3.3g of this optical film-forming composition was diluted with 6.72g of propylene glycol monomethyl ether to prepare a low refractive index paint.

[0104] 300 μl of the diluted low refractive index paint was applied by spin coating to one side of a PET film (Toray Industries, Inc., Lumirror (registered trademark) T60: 100 μm). The applied coating film was dried at 130 °C and then exposed to ultraviolet light of 400 mJ / cm. 2The resin was then photocured by irradiation with light, and an anti-reflection film (low refractive index layer, optical film) was laminated thereon.

[0105] Example 5 In this example, the dispersion liquid prepared in Example 2 was used instead of the dispersion liquid prepared in Example 1. Except for that, the antireflection film according to this example was laminated in the same manner as in Example 4.

[0106] Comparative Example 4 In this comparative example, the dispersion prepared in Comparative Example 1 was used instead of the dispersion prepared in Example 1. Except for that, the anti-reflection film according to this comparative example was laminated in the same manner as in Example 3.

[0107] Comparative Example 5 In this comparative example, the dispersion liquid prepared in Comparative Example 1 was used instead of the dispersion liquid prepared in Example 1. body Other than that, the antireflection film according to this comparative example was laminated in the same manner as in Example 4.

[0108] (Haze measurement, total light transmittance measurement and minimum light reflectance measurement) The haze value of the antireflective film (low refractive index layer), the total light transmittance of the low refractive index layer, and the minimum light reflectance of the antireflective film (low refractive index layer) were measured using an ultraviolet-visible-near infrared spectrophotometer (product name: V670, manufactured by JASCO Corporation) in accordance with JIS K 7136.

[0109] The physical properties of the antireflection films according to Examples 3 to 5 and Comparative Examples 4 and 5 are shown in Table 2. The numerical values ​​of Examples 3 to 5 and Comparative Example 5 in Table 2 are relative values ​​to the optical property of the antireflection film of Comparative Example 4, which is set as 100 (reference value). For the total light transmittance in Table 2, a higher numerical value indicates a more excellent optical property of the antireflection film. For the haze and minimum light reflectance, a lower numerical value indicates a more excellent optical property of the antireflection film.

[0110] [Table 2]

Claims

1. Chemical formula A ｘ CF ｙ (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) is dispersed in an aprotic organic solvent having a relative dielectric constant of 5 to 40 (excluding N,N-dimethylformamide), The average dispersed particle size of the fluoride particles is within a range of 1 nm to 100 nm; a water concentration [a] (mass%) in the dispersion of the fluoride particles relative to 100 mass% of the dispersion of the fluoride particles and a relative dielectric constant [b] of the aprotic organic solvent satisfy the relationship represented by the following formula (1), A dispersion of fluoride particles for forming an optical film, the dispersion of fluoride particles having a viscosity of 200 mPa·s or less. [a]≦0.06e 0.15[b] (1)

2. 2. The dispersion of fluoride particles for forming an optical film according to claim 1, wherein the aprotic organic solvent is at least one selected from the group consisting of ketone solvents, amine solvents, ether solvents and ester solvents.

3. 3. The dispersion of fluoride particles for forming an optical film according to claim 2, wherein the ketone solvent is at least one selected from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, methyl butyl ketone, cyclohexanone, methylcyclohexanone and acetylacetone.

4. 3. The dispersion of fluoride particles for forming an optical film according to claim 2, wherein the amine solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and tetramethylurea.

5. 3. The dispersion of fluoride particles for forming an optical film according to claim 2, wherein the ether solvent is at least one selected from the group consisting of ethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, and tetrahydrofuran.

6. 3. The dispersion of fluoride particles for forming an optical film according to claim 2, wherein the ester solvent is at least one selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate and isobutyl acetate.

7. 7. The dispersion of fluoride particles for forming an optical film according to claim 1, further comprising a dispersant for dispersing the fluoride particles in the aprotic organic solvent.

8. The dispersion liquid of fluoride particles for forming an optical film according to any one of claims 1 to 7, wherein the content of the fluoride particles is within a range of 1 mass% to 30 mass% relative to 100 mass% of the dispersion liquid of fluoride particles.

9. A sodium salt aqueous solution or a potassium salt aqueous solution is reacted with a silicofluoride or a boron fluoride to obtain A ｘ CF ｙ (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6), A step of subjecting the slurry of the fluoride particles to solid-liquid separation and washing the solid content of the obtained fluoride particles; drying the solid content of the fluoride particles after washing; and dispersing the dried fluoride particles in an aprotic organic solvent (excluding N,N-dimethylformamide) having a relative dielectric constant of 5 to 40 to prepare a dispersion of fluoride particles having an average dispersed particle diameter in the range of 1 nm to 100 nm; The viscosity of the dispersion of the fluoride particles is 200 mPa s or less, The step of preparing a dispersion liquid of fluoride particles includes: The method for producing a dispersion of fluoride particles for forming an optical film includes adjusting a water concentration [a] in the dispersion so that a water concentration [a] (mass %) in the dispersion of fluoride particles relative to 100 mass % of the dispersion of fluoride particles and a relative dielectric constant [b] of the aprotic organic solvent satisfy a relationship represented by the following formula (1): [a]≦0.06e 0.15[b] (1)

10. 10. The method for producing a dispersion liquid of fluoride particles for forming an optical film according to claim 9, wherein the water concentration [a] in the dispersion liquid is adjusted by producing the dispersion liquid of fluoride particles in an inert gas atmosphere.

11. 9. An optical film obtained by drying a composition for forming an optical film, the composition comprising a dispersion of fluoride particles for forming an optical film according to claim 1, and then photocuring the composition.

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