Dispersion of fluoride particles, composition for forming optical films, and optical film

Abstract

To provide a liquid dispersion of fluoride particles, the dispersion having excellent dispersibility, being suitable for production of an optical film such as an anti-reflection film, and having a refractive index lower than that of magnesium fluoride, for example; a composition for forming an optical film; and an optical film.SOLUTION: A liquid dispersion of fluoride particles according to the present invention comprises fluoride particles, an anionic surfactant as a dispersing agent for the fluoride particles, and an organic solvent. The fluoride particles contain, in the compositional makeup thereof, at least aluminum and an alkali metal, and an alkaline-earth metal as an arbitrary element, and are dispersed in the organic solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersion of fluoride particles, a composition for forming optical films, and an optical film, and more particularly to a dispersion of fluoride particles, a composition for forming optical films, and an optical film suitable for anti-reflective coatings for displays, lenses, and the like. [Background technology]

[0002] Modern people have many opportunities to interact with various displays, such as televisions, personal computers, smartphones, tablet devices, and car navigation systems. However, when light shines on a display, whether indoors or outdoors, light reflection can reduce visibility and cause eye strain and headaches. Therefore, these displays are coated to prevent light reflection. In recent years, this coating has also been applied to decorative panels in automobiles to add a sense of luxury.

[0003] The anti-reflection coating consists of a high refractive index layer and a low refractive index layer. This coating prevents light reflection on the display surface and improves visibility by utilizing the phase difference of light reflected from the respective surface layers of the high and low refractive index layers.

[0004] Here, methods for forming low refractive index layers are broadly classified into vapor phase methods and coating methods. Of these, the coating method is more efficient in utilizing raw materials and is superior to the vapor phase method in terms of mass production and equipment costs. Therefore, currently, the coating method, which has good productivity, is used for forming low refractive index layers.

[0005] Patent Document 1 describes that a sol or fine powder of magnesium fluoride, which is chemically stable and has a low refractive index, is effective as a filler for a coating agent to form a low refractive index layer. However, the refractive index of magnesium fluoride is approximately 1.38, and it is not possible to lower the refractive index of the low refractive index layer below that.

[0006] Patent Document 2 describes a dispersion of hollow spherical silica-based fine 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 state that by using silica-based fine particles or hollow particles as fillers in coating agents, an anti-reflective film with an even lower refractive index can be formed. However, the silica-based fine particles in Patent Document 2 and the hollow particles in Patent Document 3 themselves have voids. Therefore, anti-reflective films using these as fillers have the problem of reduced mechanical strength and scratch resistance.

[0007] Patent Document 4 describes that hollow particles made of fluoroaluminate compounds, which have a lower refractive index than magnesium fluoride, are suitable as inorganic fillers for use in the low refractive index layer of anti-reflective coatings. However, as with Patent Documents 2 and 3, the hollow particles in Patent Document 4 have voids themselves, which leads to problems such as reduced mechanical strength and scratch resistance. Furthermore, while the examples in Patent Document 4 describe an anti-reflective coating using hollow particles made of fluoroaluminate compounds, there is no description of its optical performance, and it remains unclear.

[0008] Patent Document 5 describes forming a low-reflection film using ultrafine particles of sodium alumina hexafluoride (also known as cryolite (refractive index 1.33)), which has a lower refractive index than magnesium fluoride. In conventional low-reflection films, low-refractive-index particles are uniformly dispersed in a binder resin, thereby preventing the particles from aggregating and increasing haze, thus suppressing a decrease in visibility when applied to displays, etc. However, the low-reflection film disclosed in Patent Document 5 does not use a binder resin. Furthermore, Patent Document 5 does not mention haze, which is one of the important optical properties of a low-reflection film. [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 No. 6030893 [Patent Document 5] Japanese Patent Publication No. 2010-107583 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a dispersion of fluoride particles that has excellent dispersibility and is suitable for the manufacture of optical films such as anti-reflective films, for example, a composition for forming optical films, and an optical film using the same, which have a lower refractive index than magnesium fluoride. [Means for solving the problem]

[0011] The fluoride particle dispersion of the present invention, in order to solve the above-mentioned problems, comprises fluoride particles, an anionic surfactant as a dispersant for the fluoride particles, and an organic solvent, wherein the fluoride particles contain at least aluminum and alkali metals and an alkaline earth metal as an optional element in their composition, and are dispersed in the organic solvent.

[0012] In the above configuration, it is preferable that the counterion of the hydrophilic group in the anionic surfactant is a proton or an onium ion.

[0013] Furthermore, in the above configuration, it is preferable that the anionic surfactant is at least one of an anionic hydrocarbon surfactant represented by the following chemical formula (1) and an anionic fluorine carbide surfactant. RXM (1) (In the formula, R represents an alkyl group having 2 to 18 carbon atoms, an aryl group having 2 to 18 carbon atoms, a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms, an alkyl group having 2 to 18 carbon atoms and at least one hydrogen atom substituted with a fluorine atom, an aryl group having 2 to 18 carbon atoms and at least one hydrogen atom substituted with a fluorine atom, or a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms and at least one hydrogen atom substituted with a fluorine atom. X is -COO - , -PO4 - , -SO3 - or -SO4 - . M represents a proton or an onium ion.)

[0014] In the above configuration, the content of the anionic surfactant is preferably in the range of 0.2% to 8% by mass based on 100% by mass of the fluoride particles.

[0015] In the above configuration, the fluoride particles are preferably particles of at least one fluoride selected from the group consisting of Na3AlF6, Na5Al3F 14 , Na3Li3Al2F 12 , Na2MgAlF7, K2NaAlF6, LiCaAlF6 and LiSrAlF6.

[0016] In the above configuration, the water concentration in the dispersion of the fluoride particles is preferably 1.5% by mass or less based on 100% by mass of the dispersion of the fluoride particles.

[0017] In the above configuration, the organic solvent is preferably at least one of an alcohol solvent, a ketone solvent and an ether solvent.

[0018] In the above configuration, the average dispersed particle diameter of the fluoride particles is preferably in the range of 1 nm to 100 nm.

[0019] In the above configuration, it is preferable that the content of the fluoride particles is within the range of 1% to 30% by mass relative to 100% by mass of the dispersion of the fluoride particles.

[0020] In the above configuration, it is preferable that the Rsp value measured using pulsed NMR of the dispersion of fluoride particles is 5 or higher.

[0021] The optical film-forming composition of the present invention is characterized by containing a dispersion of the fluoride particles in order to solve the above-mentioned problems.

[0022] Furthermore, in order to solve the above-mentioned problems, the optical film of the present invention is characterized by comprising a cured film of the optical film forming composition. [Effects of the Invention]

[0023] According to the present invention, by using an anionic surfactant as a dispersant with fluoride particles containing at least aluminum and alkali metals in their composition, it is possible to provide a dispersion of fluoride particles with excellent dispersibility and a composition for forming optical films containing the same. Furthermore, since fluoride particles have a lower refractive index than, for example, magnesium fluoride, the dispersion of fluoride particles and the composition for forming optical films containing the same according to the present invention are suitable for producing optical films such as anti-reflective films. Moreover, by using the fluoride dispersion or the composition for forming optical films containing the same, it is possible to provide optical films such as anti-reflective films with uniform and good optical properties such as haze and light reflectance in the plane. [Modes for carrying out the invention]

[0024] (Dispersion of fluoride particles) The dispersion of fluoride particles according to this embodiment (hereinafter sometimes referred to as "dispersion") will be described below. The dispersion of this embodiment contains at least fluoride particles, an anionic surfactant as a dispersant, and an organic solvent. The fluoride particles are dispersed in the organic solvent.

[0025] In this specification, "dispersion" refers to a state in which a dispersed phase is dispersed in a liquid dispersion medium. Therefore, "dispersion" does not include dispersions such as solid colloids (organogels) in which a dispersed phase is dispersed in a solid dispersion medium and fluidity has been lost.

[0026] The fluoride in the aforementioned fluoride particles contains at least aluminum and alkali metals in its composition. The fluoride may also contain alkaline earth metals as an optional element.

[0027] Alkali metals are not particularly limited and include, for example, lithium, sodium, and potassium. Similarly, alkaline earth metals are not particularly limited and include, for example, magnesium, calcium, and strontium.

[0028] Specifically, examples of the aforementioned fluorides include Na3AlF6 (refractive index: 1.33) and Na5Al3F 14 (Refractive index: 1.33), Na3Li3Al2F 12 Examples include Na3AlF6 (refractive index: 1.34), Na2MgAlF7 (refractive index: 1.35), K2NaAlF6 (refractive index: 1.38), LiCaAlF6 (refractive index: 1.38), and LiSrAlF6 (refractive index: 1.38). These fluoride particles can be used individually or in mixtures of two or more types. Among the exemplified fluoride particles, Na3AlF6, which has a refractive index of less than 1.34 and low solubility in water, is particularly preferred.

[0029] The content of the fluoride particles is preferably in the range of 1% to 30% by mass, more preferably in the range of 2% to 15% by mass, and even more preferably in the range of 5% to 10% by mass, based on 100% by mass of the dispersion of fluoride particles. By setting the content of the fluoride particles to 1% by mass or more, the use of a large amount of dispersion can be suppressed when mixing with, for example, binder components (details will be described later) which are constituent materials of the optical film. This also reduces the time required to remove organic solvents during the optical film formation process. On the other hand, by setting the content of the fluoride particles to 30% by mass or less, the dispersion time of the fluoride particles is suppressed, and the probability of the fluoride particles agglomerating together is reduced.

[0030] The average dispersed particle diameter (d50) of the fluoride particles is preferably in the range of 1 nm to 100 nm, and more preferably in the range of 10 nm to 50 nm. By setting the average dispersed particle diameter to 1 nm or more, it is possible to suppress the aggregation of fluoride particles due to intermolecular forces. On the other hand, by setting the average dispersed particle diameter to 100 nm or less, for example, when using fluoride particles as a filler in an optical film such as an anti-reflective film, it is possible to reduce the detachment of fluoride particles from the optical film and the impairment of optical transparency. The method and apparatus for measuring the average dispersed particle diameter of the fluoride particles are not particularly limited and are, for example, as described in the examples below.

[0031] The anionic surfactant functions as a dispersant that imparts good dispersibility to fluoride particles. In this embodiment, examples of the anionic surfactant include anionic hydrocarbon surfactants and anionic fluorine carbide surfactants. Among these anionic surfactants, the refractive index of the anionic fluorine carbide surfactant is smaller than that of the anionic hydrocarbon surfactant, and therefore, when a dispersion containing the anionic fluorine carbide surfactant is used, it is suitable as a constituent material for an optical film. Furthermore, the anionic hydrocarbon surfactant and the anionic fluorine carbide surfactant may be used in combination.

[0032] Here, in this specification, the "anionic hydrocarbon surfactant" means a surfactant containing one or more hydrocarbon moieties and one or more anionic groups (hydrophilic moieties) in the molecule. Also, the "anionic fluorocarbon surfactant" means a surfactant containing one or more hydrocarbon moieties in which at least one hydrogen atom is substituted by a fluorine atom and one or more anionic groups in the molecule.

[0033] The anionic surfactant of this embodiment can be represented by the following chemical formula (1). R-X-M (1)

[0034] R in the chemical formula (1) is a hydrocarbon moiety, an alkyl group having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 10 to 14 carbon atoms; an aryl group having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 10 to 14 carbon atoms; a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 8 to 12 carbon atoms; an alkyl group having 2 to 18 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 4 to 6 carbon atoms, in which at least one hydrogen atom is substituted by a fluorine atom; an aryl group having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 8 to 12 carbon atoms, in which at least one hydrogen atom is substituted by a fluorine atom; a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 8 to 12 carbon atoms, in which at least one hydrogen atom is substituted by a fluorine atom. Also, R may be either linear or branched. In this specification, when representing the range of the number of carbon atoms, the range means including all integer numbers of carbon atoms included in the range. Therefore, for example, an alkyl group of "1 to 3 carbon atoms" means all alkyl groups having 1, 2, and 3 carbon atoms.

[0035] X and M in the chemical formula (1) represent anionic groups (hydrophilic groups). Among these, X is -COO - , -PO4 - , -SO3- or -SO4 - This represents the counterion of the hydrophilic group, and in this embodiment, it represents a proton (H + ) or onium ions are preferred. These counterions can improve the solubility and dispersibility of fluoride particles in organic solvents.

[0036] Furthermore, the onium ion is preferably represented by the following chemical formula (2). H + ·[NR 1 R 2 R 3 (2) Here, R in chemical formula (2) 1 , R 2 and R 3 Each of these independently represents one of the following: hydrogen, an alkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms; an aryl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms; and a hydroxyalkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms. 1 , R 2 and R 3 The alkyl group, aryl group, and hydroxyalkyl group in this compound may be either linear or branched.

[0037] More specifically, examples of the onium ions include ammonium ions, methylammonium ions, trimethylammonium ions, ethylammonium ions, dimethylammonium ions, and triethanolammonium ions. Of these onium ions, ammonium ions are particularly preferred from the viewpoint of the solubility of fluoride particles in organic solvents.

[0038] Specific examples of the anionic hydrocarbon surfactants include, for example, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and their ammonium salts; heptanesulfonic acid, octanesulfonic acid, decanesulfonic acid, laurylsulfonic acid, and their ammonium salts; laurylbenzenesulfonic acid and its ammonium salt; heptyl sulfate, octyl sulfate, decyl sulfate, lauryl sulfate, and their ammonium salts; octyl phosphoric acid, decyl phosphoric acid, lauryl phosphoric acid, and their ammonium salts; polyoxyethylene lauryl ether sulfate and its ammonium salt; polyoxyethylene lauryl ether sulfonic acid and its ammonium salt; polyoxyethylene tridecyl ether phosphate ester, polyoxyethylene lauryl ether phosphate, and their ammonium salts. The exemplified anionic hydrocarbon surfactants can be used individually or in combination of two or more. Furthermore, among the exemplified anionic hydrocarbon surfactants, laurylbenzenesulfonic acid is preferred from the viewpoint of the dispersibility of fluoride particles in organic solvents. Furthermore, the anionic hydrocarbon surfactants exemplified can be used in any combination with the fluoride particles exemplified, in addition to the Na3AlF6 particles mentioned above.

[0039] Furthermore, commercially available surfactants can be used as the anionic hydrocarbon surfactant. Examples of commercially available surfactants include Neoperex® G-15, Neoperex G-25, Neoperex G-65, Neoperex GS (all are trade names, manufactured by Kao Corporation); Solspers® 3000, Solspers® 21000, Solspers® 26000, Solspers® 36600, Solspers® 41000 (all are trade names, manufactured by Nippon Lubrizol Co., Ltd.); DISPERBYK®-108, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-116, DISPERBYK-142, DISPERBYK-1 Examples include 45, DISPERBYK-180, DISPERBYK-2000, DISPERBYK-2001 (all trade names, manufactured by Big Chemie Co., Ltd.); Prysurf® A208N, Prysurf A208F, Prysurf A208B, Prysurf A219B, Prysurf AL, Prysurf A212C, Prysurf A215C (all trade names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Disparon® 3600N, Disparon 1850 (all trade names, manufactured by Kusumoto Kasei Co., Ltd.); PA111 (trade name, manufactured by Ajinomoto Fine Techno Co., Ltd.); EFKA4401, EFKA4550 (both trade names, manufactured by EFKA Additives Co., Ltd.). The commercially available surfactants exemplified can be used individually or in combination of two or more types. Furthermore, commercially available surfactants are not limited to those exemplified.

[0040] Furthermore, specific examples of anionic fluorinated carbide surfactants include, for example, 3H-tetrafluoropropionic acid, 5H-octafluoropentanoic acid, 7H-dodecafluoroheptanoic acid, and 9H-hexadecafluorononanoic acid. The exemplified anionic fluorinated carbide surfactants can be used individually or in combination of two or more. Among these anionic fluorinated carbide surfactants, 7H-dodecafluoroheptanoic acid is preferred from the viewpoint of the dispersibility of fluoride particles in organic solvents. In addition, the exemplified anionic fluorinated carbide surfactants can be used in any combination with the exemplified fluoride particles, as well as the Na3AlF6 particles mentioned above.

[0041] The content of the anionic surfactant is preferably in the range of 0.2% to 8% by mass, and more preferably in the range of 1% to 4% by mass, based on 100% by mass of fluoride particles. By increasing the content of the anionic surfactant to 0.2% by mass or more, the dispersibility of the fluoride particles can be improved. Furthermore, by decreasing the content of the anionic surfactant to 8% by mass or less, the compatibility between the fluoride particles and the binder component (details will be described later), such as acrylate resin, is improved during optical film formation, and the impairment of optical transparency can be reduced.

[0042] The organic solvent is not particularly limited, but alcohol solvents, ketone solvents, and ether solvents are preferred. These organic solvents can be used individually or in combination of two or more.

[0043] The alcohol solvent is not particularly limited and examples include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, cyclohexanol, methylcyclohexanol, 1-methoxy-2-propanol, 2-methoxy-1-propanol, and 3-methyl-1-butanol. These alcohol solvents can be used individually or in mixtures of two or more.

[0044] The ketone solvent is not particularly limited and examples include methyl isobutyl ketone, methyl ethyl ketone, methyl butyl ketone, cyclohexanone, methylcyclohexanone, and acetylacetone. These ketone solvents can be used individually or in combination of two or more.

[0045] Examples of the ether solvent include ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and tetrahydrofuran. These ether solvents can be used individually or in combination of two or more.

[0046] The exemplified organic solvents can be used in any combination with the exemplified fluoride particles or the exemplified anionic hydrocarbon surfactants, in addition to the Na3AlF6 particles mentioned above. Among the exemplified organic solvents, 1-methyl-2-propanol, methyl ethyl ketone, methyl isobutyl ketone, and propylene glycol monomethyl ether are preferred in this embodiment. These organic solvents exhibit excellent solubility in acrylate-based solvents as binder components in optical film-forming compositions, for example, when a dispersion of fluoride particles in this embodiment is applied to the optical film-forming composition. sex These organic solvents also possess high volatility, making them suitable for the production of optical films such as anti-reflective coatings.

[0047] In this embodiment, the water concentration in the dispersion of fluoride particles is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.8% by mass or less, based on 100% by mass of the dispersion of fluoride particles. When the water concentration in the dispersion of fluoride particles is 1.5% by mass or less, the fluoride particles do not aggregate in the dispersion, and the stability of the dispersion can be ensured.

[0048] In the dispersion of fluoride particles, the Rsp value measured using pulsed NMR is preferably 5 or higher, and more preferably in the range of 10 to 25. When the Rsp value is 5 or higher, the solvent affinity of the dispersion of fluoride particles is high, suppressing aggregation of the fluoride particles and maintaining good dispersion stability of the fluoride particles. The Rsp value can be adjusted by controlling the content of the anionic surfactant and / or the water concentration in the dispersion. For example, the Rsp value can be increased by increasing the content of the anionic surfactant within the range not exceeding the aforementioned numerical range. The Rsp value can also be increased by decreasing the amount of water in the dispersion. The method for measuring the Rsp value will be described later in the examples.

[0049] From the viewpoint of ensuring good compatibility with the binder component to be contained in the optical film-forming composition, the viscosity of the dispersion is preferably in the range of 200 mPa·s or less.

[0050] (Method for producing fluoride particles) Next, the method for producing fluoride particles according to this embodiment will be described below, using Na3AlF6 particles as an example. Note that the production method described below is just one example, and the present invention is not limited to this method. Furthermore, the production method described below is also applicable to fluoride particles other than Na3AlF6 particles.

[0051] A method for producing Na3AlF6 particles includes the steps of: reacting an aqueous sodium salt solution and an aqueous aluminum salt solution with a fluoride precursor to obtain a slurry of Na3AlF6 particles; performing solid-liquid separation and washing of the obtained slurry; and removing water from the washed Na3AlF6 particle paste to obtain a dried solid of Na3AlF6 particles.

[0052] The sodium salt in the aqueous sodium salt solution is not particularly limited, and examples include sodium sulfate, sodium acetate, sodium nitrate, and sodium hydroxide. These sodium salts can be used individually or in combination of two or more.

[0053] The aluminum salt in the aforementioned aqueous solution of aluminum salt is not particularly limited, and examples include aluminum sulfate, aluminum acetate, aluminum nitrate, and aluminum hydroxide. These aluminum salts can be used individually or in combination of two or more.

[0054] The sodium salt aqueous solution and the aluminum salt aqueous solution are obtained by dissolving the sodium salt or aluminum salt in water, respectively. The dissolution temperature when dissolving the sodium salt or aluminum salt in water can be appropriately set according to the solubility of the sodium salt or aluminum salt in water. For example, when using a sodium salt and / or aluminum salt that shows sufficient solubility in water even at room temperature, the dissolution may be carried out at room temperature. Also, when using a sodium salt and / or aluminum salt that has low solubility in water at room temperature, the time required for dissolution may be shortened by heating the water to dissolve these salts.

[0055] The fluoride precursor is not particularly limited as long as it is a salt that is soluble in water. Examples of fluoride precursors include sodium fluoride, potassium fluoride, ammonium fluoride, quaternary ammonium fluoride, acidic ammonium fluoride, and hydrogen fluoride. These fluoride precursors can be used individually or in mixtures of two or more.

[0056] The reaction between the sodium salt aqueous solution and the aluminum salt aqueous solution and the fluoride precursor may be carried out after filtering the sodium salt aqueous solution and the aluminum salt aqueous solution in order to remove impurities from the aqueous solution.

[0057] The reaction between sodium salt aqueous solutions and aluminum salt aqueous solutions and fluoride precursors can be carried out by adding a solid fluoride precursor to a mixed solution containing the sodium salt aqueous solution and the aluminum salt aqueous solution. Alternatively, a solid fluoride precursor can be added to either the sodium salt aqueous solution or the aluminum salt aqueous solution, and then mixed with the sodium salt aqueous solution or the aluminum salt aqueous solution without the fluoride precursor to carry out the reaction. Furthermore, the sodium salt aqueous solution and the aluminum salt aqueous solution may be mixed with a fluoride precursor aqueous solution (in which the fluoride precursor is dissolved in water) in any order or simultaneously to carry out the reaction. In the case of mixing the sodium salt aqueous solution and the aluminum salt aqueous solution with the fluoride precursor aqueous solution to carry out the reaction, the manufacturing process can be simplified and the reaction can be facilitated. When using the above-mentioned fluoride precursor aqueous solution, filtration may be performed beforehand to remove foreign matter from the fluoride precursor aqueous solution.

[0058] The reaction temperature between the sodium salt aqueous solution, the aluminum salt aqueous solution, and the fluoride precursor 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, vapor may be generated from the sodium salt aqueous solution, the aluminum salt aqueous solution, and / or the fluoride precursor aqueous solution, and the concentration of these mixtures (reaction solution) may change. From these viewpoints, the reaction temperature is preferably in the range of 20°C to 50°C, more preferably in the range of 23°C to 45°C, and particularly preferably in the range of 25°C to 40°C.

[0059] The method for separating the obtained Na3AlF6 particle slurry into solid and liquid is not particularly limited and includes, for example, suction filtration and centrifugal dehydration. However, if the Na3AlF6 particles are small and fine, solid-liquid separation may be difficult by suction filtration or centrifugal dehydration. In such cases, solid-liquid separation may be performed using a centrifuge, or the slurry itself may be evaporated to dryness.

[0060] The paste of Na3AlF6 particles obtained by solid-liquid separation can be washed, for example, by washing with water. This removes unreacted fluoride precursors and other anions. The washing temperature and washing time are not particularly limited and can be set as needed.

[0061] One method for removing moisture from the Na3AlF6 particle paste after washing is heat treatment. This allows for obtaining a dry powder of Na3AlF6 particles. The heat treatment method is not particularly limited; for example, the Na3AlF6 particle paste can be placed in an FRP tray and dried in a dryer.

[0062] The heating temperature (drying temperature) during the heat treatment is preferably in the range of 100°C to 300°C, and more preferably in the range of 100°C to 200°C. By heating to a temperature of 100°C or higher, the moisture contained in the Na3AlF6 particle paste can be sufficiently removed or reduced. On the other hand, by heating to a temperature of 300°C or lower, heat fusion between Na3AlF6 particles and particle growth of Na3AlF6 particles can be suppressed. Furthermore, the heating time (drying time) during the heat treatment is not particularly limited and can be set as appropriate and as needed.

[0063] The heat treatment may be carried out in the atmosphere or in an inert gas environment. The inert gas is not particularly limited and examples include nitrogen and argon. Furthermore, from the viewpoint of promoting the drying of the Na3AlF6 particle paste, the heat treatment may be carried out in a reduced pressure environment.

[0064] Furthermore, fluoride particles other than Na3AlF6 particles can be manufactured using known manufacturing methods. The raw materials and manufacturing conditions can also be set as appropriate.

[0065] (Method for producing a dispersion of fluoride particles) Next, the method for producing a dispersion of fluoride particles according to this embodiment will be described below. The dispersion of this embodiment can be obtained by mixing fluoride particles such as Na3AlF6 particles obtained by the manufacturing method described above, an anionic surfactant, and an organic solvent, thereby dispersing the fluoride particles in the organic solvent. The method for producing the dispersion of fluoride particles according to this embodiment may also include the method for producing the fluoride particles described above.

[0066] In the method for producing fluoride particles according to this embodiment, the mixing method and order of addition of the fluoride particles, anionic surfactant, and organic solvent are not particularly limited. For example, the fluoride particles may be added to the organic solvent, the mixture may be dispersed using a disperser, and then the anionic surfactant may be added to produce the dispersion of fluoride particles according to this embodiment. Alternatively, the fluoride particles, anionic surfactant, and organic solvent may be mixed all at once, and then dispersed using a disperser to produce the dispersion of fluoride particles according to this embodiment.

[0067] The method for dispersing fluoride particles in an organic solvent is not particularly limited and can be any of the following: wet bead mills, wet jet mills, ultrasonic methods, etc. The choice of dispersion method should be made considering the average dispersion particle size, purity, and other quality of the fluoride particles to be used, as well as the equipment used for grinding.

[0068] For example, if good dispersibility of fluoride particles is desired, a wet bead mill is preferable. Wet bead mills utilize media such as zirconia beads to refine the particles, thus improving the dispersion of fluoride particles. However, there is a possibility of contamination of the resulting dispersion by the media. Furthermore, if high purity of the dispersion is desired, a wet jet mill is preferable. A wet jet mill is a wet grinding method that does not use media, thus preventing contamination like that caused by a wet bead mill. However, because no media is used, the dispersion of fluoride particles may decrease. The dispersion time is not particularly limited and can be appropriately set depending on the type of fluoride particles, anionic surfactant, organic solvent, etc.

[0069] In the manufacturing process of the dispersion, it is preferable to control the water concentration in the dispersion. Methods for controlling the water concentration include, for example, wet grinding in a dew point controlled area such as a dry room, or carrying out the process in a sealed space under an inert gas environment so that the fluoride particles, organic solvents, and the dispersion containing them are not exposed to the outside air. The inert gas is not particularly limited and can be, for example, dry air, nitrogen, or argon.

[0070] Furthermore, before adding the fluoride particles to the organic solvent and dispersing them, surface-adsorbed water on the fluoride particles may be removed beforehand. Additionally, water may be removed from the organic solvent. For example, surface-adsorbed water can be removed by heat treatment. The drying temperature in the heat treatment is preferably in the range of 100°C to 200°C, and more preferably in the range of 110°C to 150°C. The drying time is preferably in the range of 2 hours to 34 hours, and more preferably in the range of 5 hours to 20 hours. Methods for removing water from the organic solvent include, for example, distillation, centrifugation, and the use of dehydrating agents (molecular sieves, zeolites, ion exchange resins, activated alumina, etc.). Alternatively, a method such as bubbling an inert gas such as nitrogen into an aprotic organic solvent may also be used.

[0071] (Composition for forming optical films and method for producing the same) Next, the optical film-forming composition and its manufacturing method according to this embodiment will be described below. The optical film-forming composition of this embodiment comprises at least a dispersion of fluoride particles and a binder component.

[0072] The content of the dispersion is preferably 15% by mass or more and 45% by mass or less, more preferably 18% by mass or more and 40% by mass or less, and particularly preferably 20% by mass or more and 35% by mass or less, based on the total mass of the optical film-forming composition. The content of the binder component is preferably 0.8% by mass or more and 5% by mass or less, more preferably 1% by mass or more and 4% by mass or less, and particularly preferably 2% by mass or more and 3% by mass or less, based on the total mass of the optical film-forming composition.

[0073] The binder component is not particularly limited and examples include resins, polymerizable monomers, and the like.

[0074] The aforementioned resin is not particularly limited, and known thermosetting resins, thermoplastic resins, etc., can be used. More specifically, examples include acrylic resins, polyester resins, polycarbonate resins, polyamide resins, urethane resins, vinyl chloride resins, fluororesins, silicone resins, epoxy resins, melamine resins, phenolic resins, butyral resins, vinyl acetate resins, etc. These resins can be used individually or in mixtures of two or more. They may also be used as copolymers or modified products composed of two or more resins. Among the exemplified resins, resins containing fluorine atoms, such as fluororesins, are preferred because they can reduce the refractive index of the optical film.

[0075] 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, examples include 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-styrene sulfonates, and their salts, etc.), cationic monomers (N-(3-acrylamidopropyl)ammonium methacrylate, N-(2-methacryloyloxyethyl)-N,1,2-dimethyl-5-vinylpyridinium methosulfate, and their salts, etc.), and crosslinked monomers (divinylbenzene, ethylene diacrylate, N,N'-methylenebisacrylamide, etc.). These polymerizable monomers can be used individually or in combination of two or more. Among the exemplified polymerizable monomers, polymerizable monomers containing a fluorine atom are preferred because they can reduce the refractive index of the optical film.

[0076] The optical film-forming composition may contain other additives, to the extent that they do not impair the objectives and effects 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, and the like. The amounts of these additives can be appropriately set as needed.

[0077] Furthermore, a photopolymerization initiator refers to an additive that generates radical species upon irradiation with active energy rays such as ultraviolet light, and examples include 1-hydroxycyclohexylphenyl ketone.

[0078] The method for producing the optical film-forming composition is not particularly limited, and it can be produced by mixing predetermined amounts of a dispersion of fluoride particles and a binder component. Furthermore, if an additive is to be included, it can be produced by adding a predetermined amount to the mixture of the dispersion of fluoride particles and the binder component.

[0079] (Optical film and method for manufacturing the same) Next, the optical film according to this embodiment and its manufacturing method will be described below. The optical film of this embodiment consists of a dried and cured film of the optical film-forming composition described above. This optical film uniformly contains fluoride particles as fillers and has a lower refractive index compared to, for example, an optical film using magnesium fluoride particles. Furthermore, it has high light transmittance and reduced haze and light reflectance, resulting in uniform and excellent optical properties within the plane.

[0080] The optical film of this embodiment can be used, for example, as an anti-reflective coating.

[0081] The fluoride particle content in the optical film is preferably in the range of 40% to 90% by volume relative to 100% by volume of the optical film. If the fluoride particle content is within this range, it is practical because it can 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.

[0082] Furthermore, the thickness of the optical film is not particularly limited and can be set as appropriate and as needed.

[0083] The optical film can be formed, for example, by the following method: An optical film-forming composition is applied to a substrate or the like, and the coated film of the optical film-forming composition is dried. Subsequently, the dried coated film is photocured by irradiating it with ultraviolet light of a predetermined intensity. This yields the optical film of this embodiment.

[0084] The method of applying the optical film-forming composition is not particularly limited and includes, for example, the dip method, spray method, spinner (spin coating) method, roll coating method, reverse coating method, gravure coating method, rod coating method, bar coating method, die coating method, and spray coating method. When forming a low refractive index layer, the reverse coating method, particularly the reverse coating method using a small-diameter gravure roll, is preferred from the viewpoint of coating accuracy.

[0085] The substrate is not particularly limited and includes, for example, plastic sheets, plastic films, plastic panels, and glass. Furthermore, the materials constituting the plastic sheets, plastic films, and plastic panels are not particularly limited and include, for example, polycarbonate, acrylic resin, polyethylene terephthalate (PET), and triacetylcellulose (TAC).

[0086] Furthermore, the optical film-forming composition may be applied to the substrate after being further added to a solvent. The solvent is added for the purpose of improving the workability of the 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, for example, propylene glycol monomethyl ether can be used.

[0087] The amount of solvent used is not particularly limited as long as it is within a range suitable for optical film formation, but is usually in the range of 10% to 95% by mass relative to 100% by mass of the optical film-forming composition.

[0088] The drying method for the optical film-forming composition applied to the substrate (including when it is further added to the aforementioned solvent) is not particularly limited and can be carried out by natural drying or by blowing hot air. The drying time and drying temperature are not particularly limited and can be set appropriately according to the thickness of the coating film, the constituent materials, etc.

[0089] Furthermore, the method and conditions for irradiating the coated film with ultraviolet light after drying are not particularly limited. The irradiation conditions can be appropriately set according to the type and amount of components of the optical film-forming composition.

[0090] As described above, the optical film of this embodiment can be formed on a substrate. In this embodiment, the dispersion of fluoride particles has low viscosity and good dispersibility of fluoride particles. Therefore, the optical film formed using the optical film-forming composition containing this dispersion has a low refractive index and uniform optical properties such as haze and light reflectance in the plane. As a result, the optical film of this embodiment is suitable for anti-reflective films and the like. [Examples]

[0091] Preferred embodiments of this invention will be described in detail below. However, unless otherwise specified, the materials and proportions described in these embodiments do not limit the scope of this invention to those described.

[0092] (Method for measuring average particle size) The average dispersed particle size (d50) of fluoride particles in a dispersion was measured using a particle size analyzer (Microtrac, NanotracUPA, UPA-UZ152, manufactured by Microtrac-Bell Co., Ltd.). The average dispersed particle size (d50) is defined as the particle size at which 50% by volume of the total sample particles are equal to or less than the average dispersed particle size. Measurement principle: Dynamic light scattering frequency analysis (FFT-heterodyne method) Light source: 3mW semiconductor laser 780nm (2 lasers) Setting range: 10℃~80℃ Measurement particle size distribution range: 0.8 nm to 6.5406 μm Measurement target: colloidal particles

[0093] Unless otherwise specified, the average dispersed particle diameter in the examples and comparative examples refers to the average particle diameter on a volume basis measured by the dynamic light scattering method described above.

[0094] (Moisture measurement method) The water concentration in the dispersion of fluoride particles was measured using the Karl Fischer method. The water concentration measuring device used was the TQV-2200S (product name) manufactured by Hiranuma Sangyo Co., Ltd. The measurement method was performed by volumetric titration in accordance with JIS K 0068 (2001).

[0095] (Viscosity measurement method) The viscosity of a dispersion of fluoride particles was measured using a B-type viscometer. The B-type viscometer used was the DV-I PRIME (product name) manufactured by Brookfield, Inc., USA. The measurements were performed in accordance with JIS K 5600-2-2 (2004).

[0096] (Method for measuring solvent affinity) The solvent affinity index (Rsp value) of a dispersion of fluoride particles was calculated by pulsed NMR measurement. A Magritek Spinsolve 60 ULTRA Phosphorus was used as the measurement instrument, and measurements were performed using 1H NMR and the CPMG (Carr-Purcell-Meiboom-Gill sequence) method. The Rsp value was calculated using the following formula (1).

[0097] Rsp = (Rav - Rb) / (Rb) (1) (In equation (1), Rsp is an index of solvent affinity, Rav is the reciprocal of the relaxation time of the dispersion of fluoride particles, and Rb is the reciprocal of the relaxation time of the blank solvent excluding the fluoride particles in the dispersion of fluoride particles.)

[0098] (Example 1) 1600g of propylene glycol monomethyl ether (PGME, reagent) and 80g of Na3AlF6 particles (manufactured by Stella Chemifa Co., Ltd.) were mixed in a fluororesin container to prepare a slurry in which the Na3AlF6 particles were aggregated. This slurry was put into a bead mill (manufactured by Nippon Coke Industries Co., Ltd.) and dispersed. After the slurry was put in, the part of the slurry exposed to the outside air was subjected to a nitrogen atmosphere. Zirconia beads (manufactured by Nikkatoh Co., Ltd.) were used. During the dispersion process, the dispersion was sampled at regular intervals and the particle size distribution was measured. Dispersion was continued until the average particle size (volume equivalent, d50) of the Na3AlF6 particles stabilized, and 1000g of a mixture containing Na3AlF6 particles was obtained. Subsequently, 1g of Prisurf A212C (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant was added to this mixture and sonication was performed for 1 minute. This resulted in a dispersion of Na3AlF6 particles in which the Na3AlF6 particle content was 5% by mass relative to the total mass of the dispersion, and the dispersant, Prysurf A212C, was 2% by mass relative to 100% by mass of Na3AlF6 particles. The physical properties of the obtained dispersion are shown in Table 1.

[0099] (Example 2) In this example, the amount of Prysurf A212C added as a dispersant was changed to 2 g (4% by mass relative to 100% by mass of Na3AlF6 particles). Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0100] (Example 3) In this example, Neoperex GS (trade name, manufactured by Kao Corporation) was used as the dispersant instead of Prysurf A212C. Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0101] (Example 4) In this example, 7H-dodecafluoroheptanoic acid was used as a dispersant instead of Prysurf A212C. The amount of 7H-dodecafluoroheptanoic acid added was also changed to 0.1 g per 1000 g of dispersion (0.2% by mass relative to 100% by mass of Na3AlF6 particles). Except for these changes, the dispersion according to this example was prepared using the same method as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0102] (Example 5) In this example, heptanoic acid was used as a dispersant instead of Prisurf A212C. The amount of heptanoic acid added was also changed to 0.1 g per 1000 g of dispersion (0.2% by mass relative to 100% by mass of Na3AlF6 particles). Aside from these changes, the dispersion according to this example was prepared using the same method as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0103] (Example 6) In this example, the slurry preparation conditions were modified so that the Na3AlF6 particle content was 1% by mass relative to the total mass of the dispersion. Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0104] (Example 7) In this example, the slurry preparation conditions were modified so that the Na3AlF6 particle content was 30% by mass relative to the total mass of the dispersion. Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0105] (Example 8) In this embodiment, Na5Al3F is used instead of Na3AlF6 particles. 14 The dispersion according to this example was prepared using the same method as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0106] (Example 9) In this example, LiCaAlF6 particles (manufactured by Stella Chemifa Co., Ltd.) were used instead of Na3AlF6 particles as fluoride particles. Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0107] (Example 10) In this example, 2-propanol (IPA, reagent) was used as the dispersion solvent instead of PGME. Otherwise, the dispersion according to this example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0108] (Example 11) In this example, methyl ethyl ketone (MEK, reagent) was used as the dispersion solvent instead of PGME. Also, 7H-dodecafluoroheptanoic acid was used as the dispersant instead of Prysurf A212C. Except for these differences, the dispersion according to this example was prepared using the same method as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0109] (Comparative Example 1) In this comparative example, Neugen (registered trademark, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), a nonionic surfactant, was used as a dispersant. Otherwise, the dispersion for this comparative example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0110] (Comparative Example 2) In this comparative example, a cationic surfactant, Futergent® 310 (trade name, manufactured by Neos Co., Ltd.), was used as a dispersant. Otherwise, the dispersion for this comparative example was prepared in the same manner as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0111] (Comparative Example 3) In this comparative example, the dispersion was prepared in the same manner as in Example 1, except that a dispersant was not used. The physical properties of the obtained dispersion are shown in Table 1.

[0112] (Comparative Example 4) In this comparative example, magnesium fluoride particles (manufactured by Stella Chemifa Co., Ltd.) were used instead of Na3AlF6 particles as fluoride particles. Furthermore, no dispersant was used. Aside from these differences, the dispersion for this comparative example was prepared using the same method as in Example 1. The physical properties of the obtained dispersion are shown in Table 1.

[0113] [Table 1]

[0114] (Example 12) 27.5 g of the dispersion prepared in Example 1 was mixed with 1.2 g of commercially available acrylate paint (acrylic resin). Furthermore, 0.6 g of 1-hydroxycyclohexyl phenyl ketone (photopolymerization initiator) was dissolved in the mixed solution to prepare an optical film-forming composition. Next, 10 g of this optical film-forming composition was diluted with 10.9 g of propylene glycol monomethyl ether to prepare a low refractive index paint.

[0115] A PET film (Toray Industries, Inc., Lumirror® U34: 100 μm thick) was coated on one side with 300 μl of diluted low refractive index paint by spin coating. After drying the coated film at 130°C, it was exposed to ultraviolet light at 400 mJ / cm². 2 The material was irradiated with light to cure it, and an anti-reflective coating (low refractive index layer, optical film) was laminated onto it.

[0116] (Example 13) In this embodiment, the dispersion prepared in Example 2 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0117] (Example 14) In this embodiment, the dispersion prepared in Example 3 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0118] (Example 15) In this embodiment, the dispersion prepared in Example 4 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0119] (Example 16) In this embodiment, the dispersion prepared in Example 5 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0120] (Example 17) In this embodiment, the dispersion prepared in Example 6 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0121] (Example 18) In this embodiment, the dispersion prepared in Example 7 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0122] (Example 19) In this embodiment, the dispersion prepared in Example 8 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0123] (Example 20) In this embodiment, the dispersion prepared in Example 9 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0124] (Example 21) In this embodiment, the dispersion prepared in Example 10 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0125] (Example 22) In this embodiment, the dispersion prepared in Example 11 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this embodiment was laminated in the same manner as in Example 12.

[0126] (Comparative Example 5) In this comparative example, the dispersion prepared in Comparative Example 1 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this comparative example was laminated in the same manner as in Example 12.

[0127] (Comparative Example 6) In this comparative example, the dispersion prepared in Comparative Example 2 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this comparative example was laminated in the same manner as in Example 12.

[0128] (Comparative Example 7) In this comparative example, the dispersion prepared in Comparative Example 3 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this comparative example was laminated in the same manner as in Example 12.

[0129] (Comparative Example 8) In this comparative example, the dispersion prepared in Comparative Example 4 was used instead of the dispersion prepared in Example 1. Otherwise, the anti-reflective film according to this comparative example was laminated in the same manner as in Example 12.

[0130] (Haze measurement and minimum light reflectance measurement) The haze value and minimum light reflectance of the anti-reflective coating (low refractive index layer) were measured in accordance with JIS K 7136 using an ultraviolet-visible-near-infrared spectrophotometer (product name: V670, manufactured by JASCO Corporation).

[0131] Table 2 shows the physical properties of the anti-reflective coatings for Examples 12-22 and Comparative Examples 5-8. Note that the anti-reflective coating of Comparative Example 8 had high light transmittance, and its haze value was equivalent to that of the PET film alone. Therefore, the values ​​for Examples 12-22 and Comparative Examples 5-7 in Table 2 are relative values ​​to the optical properties of the anti-reflective coating of Comparative Example 8, which is set to 100 (reference value). In Table 2, smaller values ​​for haze and minimum light reflectance indicate superior optical properties of the anti-reflective coating.

[0132] [Table 2]

Claims

1. A dispersion of fluoride particles comprising fluoride particles, an anionic surfactant as a dispersant for the fluoride particles, and an organic solvent, The fluoride particles are Na ３ AlF ６ , Na ５ Al ３ F １４ , K ２ NaAlF ６ , LiCaAlF ６ or LiSrAlF ６ and are dispersed in the organic solvent, The aforementioned anionic surfactant is either an anionic hydrocarbon surfactant or an anionic fluorine carbide surfactant represented by the following chemical formula (1): Furthermore, the anionic hydrocarbon surfactant is heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, alkylbenzenesulfonic acid, ammonium salt of laurylbenzenesulfonic acid, polyoxyethylene tridecyl ether phosphate, or polyoxyethylene lauryl ether phosphate. The aforementioned anionic fluorocarbon surfactant is 3H-tetrafluoropropionic acid, 5H-octafluoropentanoic acid, 7H-dodecafluoroheptanoic acid, or 9H-hexadecafluorononanoic acid. The organic solvent is 1-methyl-2-propanol, 2-propanol, methyl ethyl ketone, methyl isobutyl ketone, or propylene glycol monomethyl ether. The content of the anionic surfactant is in the range of 0.2% to 8% by mass relative to 100% by mass of the fluoride particles. The content of the fluoride particles is in the range of 1% to 30% by mass relative to 100% by mass of the dispersion of the fluoride particles. A dispersion of fluoride particles, wherein the average dispersed particle size of the fluoride particles is in the range of 1 nm to 100 nm. R-X-M (1) (In the formula, R represents an alkyl group having 2 to 18 carbon atoms, an aryl group having 2 to 18 carbon atoms, a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms, an alkyl group having 2 to 18 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, an aryl group having 2 to 18 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, or a polyoxyalkylene alkyl ether group having 2 to 18 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. X is -COO) － , -PO ４ － , -SO ３ － or -SO ４ － (This represents a proton or onium ion.)

2. The dispersion of fluoride particles according to claim 1, wherein the Rsp value measured using pulsed NMR of the dispersion of fluoride particles is 5 or greater.

3. A composition for forming an optical film, comprising a dispersion of fluoride particles according to claim 1 or 2.

4. An optical film comprising a cured film of the optical film forming composition described in claim 3.

Images