Dispersion of fluoride particles

Abstract

Provided is a fluoride particle dispersion that is suitable for optical materials for an optical film such as an anti-reflection film, and suitable for secondary battery electrode materials, etc. In the dispersion, fluoride particles are well-dispersed without the use of any dispersing agent formed from a conventional surfactant. This fluoride particle dispersion is characterized by containing an organic solvent, fluoride particles dispersed in the organic solvent, and polyvinylidene fluoride as the dispersant that disperses the fluoride particles.

Description

Technical Field

[0001] The present invention relates to a dispersion liquid of fluoride particles suitable for optical materials in optical films such as antireflection films and electrode materials of secondary batteries.

Background Art

[0002] Fluorides (fluorine compounds) are used as optical materials and electrode materials in fields such as optical films and secondary batteries. Fluorides have the property of having a lower refractive index compared to oxides and the like. Therefore, fluoride particles are used as a filling material (filler) for antireflection films as disclosed in Patent Document 1. Further, fluoride particles are also used as electrode materials in secondary batteries typified by lithium-ion secondary batteries as described in Patent Documents 2 to 4.

[0003] Here, since the film thickness of the antireflection film is usually about 100 nm, fluoride particles used as the filling material are required to have a particle size smaller than the film thickness. Also, when used as an electrode material for secondary batteries, the use of fine fluoride particles may contribute to the improvement of battery performance (Patent Documents 3 and 4).

[0004] However, fine powder particles, not limited to fluorides, have their primary particles aggregated to form secondary aggregates. When fluorides are used in the state of secondary aggregates, the particle size may be too large, so they may not be suitable for the above-mentioned optical materials and electrode materials. Therefore, usually, fluoride particles are dispersed in a dispersion medium such as an organic solvent and used.

[0005] In such a dispersion of fluoride particles, a dispersant is added to improve the dispersibility of the fluoride particles or maintain a good dispersion state (Patent Document 5). As the dispersant, for example, a surfactant such as polyoxyalkylene alkyl ether phosphate ester (refractive index n = 1.46) is used. However, since such a surfactant has a high refractive index, there is a problem that even if fluoride particles with a small refractive index are used, the refractive index of the antireflection film itself increases. Also, in a secondary battery, there is a problem that the battery characteristics deteriorate if a surfactant remains in the electrode.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the above problems, and its object is to provide a dispersion of fluoride particles that can disperse fluoride particles well without using a dispersant composed of a conventional surfactant, and is suitable for optical materials such as antireflection films and electrode materials of secondary batteries.

Means for Solving the Problems

[0008] The dispersion of fluoride particles of the present invention is characterized by including an organic solvent, fluoride particles dispersed in the organic solvent, and polyvinylidene fluoride as a dispersant for dispersing the fluoride particles.

[0009] In the above configuration, it is preferable that the content of the polyvinylidene fluoride is in the range of 0.01% by mass to 3% by mass with respect to the total mass of the dispersion of the fluoride particles.

[0010] In the above configuration, it is preferable that the content of the fluoride particles is in the range of 1% by mass to 20% by mass with respect to the total mass of the dispersion of the fluoride particles.

[0011] In the above configuration, it is preferable that the fluoride particles contain at least one kind of particles of a compound represented by the following chemical formulas (1) to (3), barium strontium lanthanum fluoride, and barium strontium cerium fluoride. M 1 a M 2 b F (a+2b) (1) (In the formula, M 1 is an alkali metal, M 2 is an alkaline earth metal, and a and b are integers satisfying the conditions of 0 ≦ a ≦ 3 and 0 ≦ b ≦ 1.) M 1 c M 3 d F (c+3d) (2) (In the formula, M 1 is an alkali metal, M 3 is Al, Y or a lanthanoid, and c and d are integers satisfying the conditions of 0 ≦ c ≦ 5 and 0 < d ≦ 3.) M 2 M 3 F5(3) (In the formula, M 2 is an alkaline earth metal, M 3 is Al, Y or a lanthanoid.)

[0012] In the above configuration, the M 1 a M 2 b F (a+2b) is preferably LiF, CaF2 or MgF2.

[0013] In the above configuration, the M 1 c M 3 d F (c+3d) is preferably AlF3, Na3AlF6, Na5Al3F 14 , LaF3, CeF3, YF3, YbF3, NaYF4, or NaYbF4.

[0014] In the above configuration, the M 2 M 3 F5 is preferably BaLaF5, BaCeF5, SrLaF5, or SrCeF5.

[0015] In the above configuration, the organic solvent is preferably at least one selected from the group consisting of N-methyl-pyrrolidone, hexamethylphosphoramide, and dimethylacetamide.

Advantages of the Invention

[0016] According to the dispersion of fluoride particles of the present invention, by containing polyvinylidene fluoride, the fluoride particles can be well dispersed in an organic solvent. Thus, in the present invention, for example, the use of a dispersant composed of a conventional surfactant such as polyoxyalkylene alkyl ether phosphate (refractive index n = 1.46) can be omitted. Since the refractive index of polyvinylidene fluoride is 1.42, which is smaller than that of polyoxyalkylene alkyl ether phosphate, for example, when an optical film such as an antireflection film is formed using the dispersion of fluoride particles of the present invention, an increase in the refractive index of the optical film itself can be suppressed or reduced as compared with a conventional optical film using polyoxyalkylene alkyl ether phosphate. Further, polyvinylidene fluoride is a compound also used as a conductive auxiliary agent for the electrode active material of a secondary battery, and does not deteriorate the battery characteristics like a dispersant composed of a conventional surfactant. Therefore, the dispersion of fluoride particles of the present invention can be suitably used, for example, as an electrode material for a secondary battery.

Brief Description of the Drawings

[0017]

Figure 1

Embodiments for Carrying Out the Invention

[0018] (Dispersion of Fluoride Particles) The dispersion of fluoride particles according to the present embodiment (hereinafter sometimes referred to as "dispersion") will be described below.

[0019] The dispersion of the present embodiment contains at least fluoride particles, polyvinylidene fluoride, and an organic solvent. The fluoride particles are present in a dispersed state in the organic solvent. Further, the dispersion of the present embodiment may be in a form consisting only of fluoride particles, polyvinylidene fluoride, and an organic solvent.

[0020] As used herein, the term "dispersion" refers to a state in which a dispersed substance is dispersed in a liquid dispersion medium. Therefore, the "dispersion" does not include a dispersion such as a solid colloid (organogel) in which a dispersed substance is dispersed in a solid dispersion medium and the fluidity is lost.

[0021] The fluoride particles preferably contain at least one kind of particles of a compound represented by the following chemical formulas (1) to (3), barium strontium lanthanum fluoride (BaSrLaF7), or barium strontium cerium fluoride (BaSrCeF7). M 1 a M 2 b F (a+2b) (1) (In the formula, M 1 is an alkali metal, M 2 is an alkaline earth metal, and a and b are integers satisfying the conditions of 0 ≦ a ≦ 3 and 0 ≦ b ≦ 1.) M 1 c M 3 d F (c+3d) (2) (In the formula, M 1 is an alkali metal, M 3 is Al, Y, or a lanthanoid, and c and d are integers satisfying the conditions of 0 ≦ c ≦ 5 and 0 < d ≦ 3.) M 2 M 3 F5(3) (In the formula, M 2 is an alkaline earth metal, M 3 is Al, Y, or a lanthanoid.)

[0022] M 1 The alkali metal in M is not particularly limited, and examples thereof include lithium, sodium, potassium, and the like. Further, the alkaline earth metal in M is not particularly limited, and examples thereof include magnesium, calcium, barium, strontium, and the like. Furthermore, M 2 3 ​The lanthanoid is not particularly limited, and examples thereof include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0023] M 1 a M 2 b F (a+2b) Specifically, examples thereof include lithium fluoride (LiF), sodium fluoride (NaF), magnesium fluoride (MgF2), calcium fluoride (CaF2), barium fluoride (BaF2), lithium calcium fluoride (LiCaF3), lithium magnesium fluoride (LiMgF3), lithium barium fluoride (LiBaF3), sodium calcium fluoride (NaCaF3), sodium magnesium fluoride (NaMgF3), sodium barium fluoride (NaBaF3), potassium calcium fluoride (KCaF3), potassium magnesium fluoride (KMgF3), potassium barium fluoride (KBaF3), and the like. Among the particles of these fluorides, from the viewpoint of having a small refractive index value, lithium fluoride, calcium fluoride, magnesium fluoride, sodium magnesium fluoride, and potassium magnesium fluoride are preferable.

[0024] M 1 c M 3 d F (c+3d)Specifically, for example, aluminum fluoride (AlF3), yttrium fluoride (YF3), lanthanum fluoride (LaF3), cerium fluoride (CeF3), praseodymium fluoride (PrF3), neodymium fluoride (NdF3), promethium fluoride (PmF3), samarium fluoride (SmF3), europium fluoride (EuF3), gadolinium fluoride (GdF3), terbium fluoride (TbF3), dysprosium fluoride (DyF3), holmium fluoride (HoF3), erbium fluoride (ErF3), thulium fluoride (TmF3), ytterbium fluoride (YbF3), lutetium fluoride (LuF3), lithium hexafluoroaluminate (Li3AlF6), sodium hexafluoroaluminate (cryolite, Na3AlF6), potassium hexafluoroaluminate (K3AlF6), thiolite (Na5Al3F 14 ) and sodium yttrium fluoride (NaYF4), sodium ytterbium fluoride (NaYbF4), etc. can be mentioned. Among the particles of these fluorides, from the viewpoint of a small refractive index value, aluminum fluoride, cryolite, thiolite, lanthanum fluoride, cerium fluoride, yttrium fluoride, ytterbium fluoride, sodium yttrium fluoride, and sodium ytterbium fluoride are preferable.

[0025] M 2 M 3 Specifically, for example, F5 includes barium lanthanum fluoride (BaLaF5), barium cerium fluoride (BaCeF5), strontium lanthanum fluoride (SrLaF5), strontium cerium fluoride (SrCeF5), etc. Among the particles of these fluorides, from the viewpoint of further improving battery characteristics, particles composed of barium lanthanum fluoride or barium cerium fluoride are preferable.

[0026] The particles composed of the exemplified fluorides can be used alone or in combination of two or more. Among the particles of the exemplified fluorides, particles composed of Na3AlF6 with a refractive index of less than 1.34 and a low solubility in water are particularly preferable.

[0027] The content of the fluoride particles is preferably in the range of 1% to 20% by mass, more preferably in the range of 3% to 15% by mass, and even more preferably in the range of 5% to 10% by mass with respect to the total mass of the dispersion liquid of the fluoride particles. By setting the content of the fluoride particles to 1% by mass or more, for example, even when the dispersion liquid of the fluoride particles of the present embodiment is used as a material for an optical film and the fluoride particles are applied as a filler for an optical film such as an antireflection film, good low refractive index properties can be maintained. On the other hand, by setting the content of the fluoride particles to 20% by mass or less, it is possible to suppress the lengthening of the dispersion time of the fluoride particles and reduce the probability of aggregation of the fluoride particles with each other.

[0028] The average dispersed particle diameter (d50) of the fluoride particles is preferably in the range of 1 nm to 500 nm, more preferably in the range of 1 nm to 100 nm, and even more preferably 1 nm to 50 nm. By setting the average dispersed particle diameter to 1 nm or more, it is possible to suppress the aggregation of the fluoride particles due to intermolecular forces from becoming significant. On the other hand, by setting the average dispersed particle diameter to 500 nm or less, for example, when the fluoride particles are used as a filler for an optical film such as an antireflection film, it is possible to reduce the detachment of the fluoride particles from the optical film and the impairment of light 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.

[0029] The shape of the fluoride particles is not particularly limited, and may be, for example, substantially spherical, cubic, chain-like, needle-like, plate-like, scaly, rod-like, fibrous, or irregular.

[0030] Polyvinylidene fluoride functions as a dispersant for the fluoride particles. Thereby, the dispersibility of the fluoride particles in an organic solvent can be improved. Further, the refractive index of polyvinylidene fluoride is 1.42, and the refractive index value is small compared to conventional surfactants used as dispersants.

[0031] For example, when an optical film is formed using a polyoxyalkylene alkyl ether phosphate ester with a refractive index of 1.46 as a surfactant and magnesium fluoride with a refractive index of 1.38 as fluoride particles, if the polyoxyalkylene alkyl ether phosphate ester remains in the optical film, since the refractive index of the polyoxyalkylene alkyl ether phosphate ester is larger than that of magnesium fluoride, there is a problem that the refractive index of the optical film itself increases. However, when using polyvinylidene fluoride, as described above, since the refractive index value is smaller than that of the polyoxyalkylene alkyl ether phosphate ester, it is possible to suppress the increase in the refractive index of the optical film itself. As a result, an optical film excellent in low refractive index properties can be formed as compared with a conventional optical film formed using a surfactant as a dispersant.

[0032] In the present embodiment, polyvinylidene fluoride of any of the crystal structures of type I, type II, and type III can be used without limitation. Type I means the case where the crystal structure is a planar zigzag structure, type II means the case where the crystal structure is a twisted structure, and type III means the case where the crystal structure is in an intermediate state between type I and type II. In the present invention, polyvinylidene fluoride having any of the crystal structures of type I to type III may be used alone, or any two or more of these may be used in combination. Further, any of the polyvinylidene fluorides having the crystal structures of type I to type III can be used in arbitrary combination with the above-described exemplified fluoride particles.

[0033] The content of polyvinylidene fluoride is preferably in the range of 0.01% by mass to 3% by mass, more preferably in the range of 0.05% by mass to 2% by mass, and still more preferably in the range of 0.1% by mass to 1% by mass with respect to the total mass of the dispersion of fluoride particles. By setting the content of polyvinylidene fluoride to 0.01% by mass or more, the dispersibility of the fluoride particles can be improved. Further, by setting the content of polyvinylidene fluoride to 3% by mass or less, it is possible to reduce the excessive impairment of the light transparency of the optical film.

[0034] The mass average molecular weight of polyvinylidene fluoride is not particularly limited, but is usually 1.0×10 5 ~1.7×10 6 and preferably 1.5×10 5 ~1.5×10 6 , more preferably 2.5×10 5 ~1.2×10 6 Polyfluoride Bi The mass average molecular weight of 1.0×10 5 By setting the above, it is possible to suppress the aggregation of fluoride particles and improve the dispersibility. Bi The mass average molecular weight of 1.7×10 6 By setting the following, it is possible to improve the solubility in the organic solvent.

[0035] The organic solvent is not particularly limited, but is preferably one in which polyvinylidene fluoride dissolves. Examples of such organic solvents include N-methyl-pyrrolidone, hexamethylphosphoramide, and dimethylacetamide. These organic solvents can be used alone or in combination of two or more. In addition, the exemplified organic solvents can be used in any combination with the fluoride particles and polyvinylidene fluoride having crystal structures of I to III types as exemplified above.

[0036] The content of the organic solvent is preferably within the range of 80% by mass to 99% by mass, more preferably within the range of 85% by mass to 97% by mass, and even more preferably within the range of 90% by mass to 95% by mass, based on the total mass of the dispersion of fluoride particles.

[0037] The dispersion of fluoride particles in this embodiment may contain a fluorine-containing surfactant for the purpose of further improving the dispersibility of the fluoride particles. In this case, the dispersion of this embodiment may be in a form consisting only of fluoride particles, polyvinylidene fluoride, an organic solvent, and a fluorine-containing surfactant. The refractive index of the fluorine-containing surfactant is, for example, smaller than that of a hydrocarbon-based surfactant. Therefore, even if a fluorine-containing surfactant is added to the dispersion of fluoride particles, it is possible to suppress an excessive decrease in the light reflectance of the antireflection film due to an increase in the refractive index compared with the case of using a hydrocarbon-based surfactant.

[0038] The fluorine-containing surfactant is not particularly limited, and examples thereof include anionic fluorocarbon surfactants. Here, in this specification, the "anionic fluorocarbon surfactant" means a surfactant containing in the molecule one or more hydrocarbon moieties in which at least one hydrogen atom is replaced by a fluorine atom, and one or more anionic groups.

[0039] The anionic fluorocarbon surfactant can be represented by the following chemical formula (4). R-X-M (4)

[0040] R in the chemical formula (4) is a hydrocarbon moiety, having 2 to 18 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 4 to 6 carbon atoms, and is an alkyl group in which at least one hydrogen atom is substituted by a fluorine atom; having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 8 to 12 carbon atoms, and is an aryl group in which at least one hydrogen atom is substituted by a fluorine atom; having 2 to 18 carbon atoms, preferably 5 to 15 carbon atoms, more preferably 8 to 12 carbon atoms, and is a polyoxyalkylene alkyl ether group in which at least one hydrogen atom is substituted by a fluorine atom. Also, R may be either linear or branched. In the present 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 having "1 to 3 carbon atoms" means all alkyl groups having 1, 2, and 3 carbon atoms.

[0041] X and M in the chemical formula (4) represent anionic groups (hydrophilic groups). Among these, X is -COO - , -PO4 - , -SO3 - or -SO4 - . Also, M represents a counter ion of the hydrophilic group, and in the present embodiment, a proton (H + ) or an onium ion is preferred. When these are counter ions, the solubility and dispersibility of the fluoride particles in the organic solvent can be improved.

[0042] Furthermore, the onium ion is preferably represented by the following chemical formula (5). H + ·[NR 1 R 2 R 3 (5) Here, R 1 , R 2 and R 3Each independently represents 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; or a hydroxyalkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms. Also, R 1 、R 2 and R 3 The alkyl groups, aryl groups and hydroxyalkyl groups in may be either straight-chain or branched-chain.

[0043] More specifically, examples of the onium ion include ammonium ion, methylammonium ion, trimethylammonium ion, ethylammonium ion, dimethylammonium ion, triethanolammonium ion and the like. Among these onium ions, ammonium ion is particularly preferable from the viewpoint of the solubility of the fluoride particles in the organic solvent.

[0044] Specific examples of the anionic fluorocarbon surfactant include, for example, 3H-tetrafluoropropionic acid, 5H-octafluoropentanoic acid, 7H-dodecafluoroheptanoic acid, 9H-hexadecafluorononanoic acid and the like. The exemplified anionic fluorocarbon surfactants can be used alone or in combination of two or more. Among these anionic fluorocarbon surfactants, 7H-dodecafluoroheptanoic acid is preferable from the viewpoint of the dispersibility of the fluoride particles in the organic solvent. Further, the exemplified anionic fluorocarbon surfactants can be arbitrarily combined with any of the exemplified fluoride particles, polyvinylidene fluoride, and the organic solvent and used.

[0045] When using the dispersion of this embodiment as a material for an optical film, for example, the content of the fluorine-containing surfactant is preferably included within a range where the refractive index of the optical film itself does not increase excessively. Also, when used as an electrode material for a secondary battery, it is preferably included within a range where the battery characteristics do not decrease excessively. Specifically, the content of the fluorine-containing surfactant is preferably in the range of 1% to 10% by mass, more preferably in the range of 2% to 5% by mass, based on 100% by mass of the fluoride particles. By setting the content of the fluorine-containing surfactant to 1% by mass or more, the dispersibility of the fluoride particles can be improved. Also, by setting the content of the fluorine-containing surfactant to 10% by mass or less, for example, when used for forming an optical film, it is possible to reduce the excessive suppression of the refractive index of the optical film and the impairment of light transmittance.

[0046] Further, the dispersion of the fluoride particles of this embodiment may contain at least one of a fluorine-containing lithium salt, FSI salt, fluorine-containing sodium salt, fluorine-containing potassium salt, fluorine-containing rubidium salt, and fluorine-containing cesium salt, within a range that does not inhibit the dispersibility of the fluoride particles.

[0047] The fluorine-containing lithium salt is not particularly limited, and examples include LiPF6, LiBF4, Li2SiF6, LiPO2F2, Li2PO3F, LiCF3SO3, LiN(FSO2)2, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C4F9SO2), LiC(C2F5SO2)3, LiAsF6, Li[B(C2O4)F2], Li[P(C2O4)F4], Li[P(C2O4)2F2], and the like.

[0048] The content of the fluorine-containing lithium salt is preferably in the range of 100% to 250% by mass, more preferably in the range of 100% to 200% by mass, based on 100% by mass of the fluoride particles.

[0049] The FSI salt is not particularly limited. Specifically, for example, trimethylhexylammonium bis(trifluoromethanesulfonyl)imide (TMHA-TFSI), trimethylhexylammonium bis(fluorosulfonyl)imide (TMHA-FSI), tri-n-butylmethylammonium bis(trifluoromethylsulfonyl)imide (TBMA-TFSI), triethylmethylphosphonium bis(trifluoromethylsulfonyl)imide (TEMP-TFSI), tri-n-butylmethylphosphonium bis(trifluoromethylsulfonyl)imide (TBMP-TFSI), etc. can be mentioned.

[0050] The content of the FSI salt is preferably in the range of 100% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, based on 100% by mass of the fluoride particles.

[0051] The fluorine-containing sodium salt is not particularly limited. Specifically, for example, Na2FePO4F, Na2VPO4F, Na2MnPO4F, Na2CoPO4F, Na2NiPO4F, NaFeSO4F, NaMnSO4F, NaCoSO4F, Na3FeF6, Na2MnF6, NaPF6, NaAsF6, NaSbF6, NaBF4, NaCF3SO3, NaN(SO2CF3)2, etc. can be mentioned.

[0052] The content of the fluorine-containing sodium salt is preferably in the range of 100% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, based on 100% by mass of the fluoride particles.

[0053] The fluorine-containing potassium salt is not particularly limited. Specifically, for example, K2FePO4F, K2MnPO4F, K2CoPO4F, KFeSO4F, KCoSO4F, KMnSO4F, KNiSO4F, K3FeF6, K2MnF6, KPF6, KAsF6, KSbF6, KBF4, KCF3SO3, KN(SO2CF3)2, etc. can be mentioned.

[0054] The content of the fluorine-containing potassium salt is preferably in the range of 100% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, based on 100% by mass of the fluoride particles.

[0055] The fluorine-containing rubidium salt is not particularly limited, and specific examples include Rb3FeF6, Rb2MnF6, RbPF6, RbAsF6, RbSbF6, RbBF4, RbCF3SO3, RbN(SO2CF3)2, and the like.

[0056] The content of the fluorine-containing rubidium salt is preferably in the range of 100% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, based on 100% by mass of the fluoride particles.

[0057] The fluorine-containing cesium salt is not particularly limited, and specific examples include Cs3FeF6, Cs2MnF6, CsPF6, CsAsF6, CsSbF6, CsBF4, CsCF3SO3, CsN(SO2CF3)2, and the like.

[0058] The content of the fluorine-containing cesium salt is preferably in the range of 100% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, based on 100% by mass of the fluoride particles.

[0059] In the present embodiment, the water concentration in the dispersion of the 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 the fluoride particles. When the water concentration in the dispersion of the fluoride particles is 1.5% by mass or less, aggregation of the fluoride particles in the dispersion is suppressed, and the stability of the dispersion can be further improved.

[0060] The dispersion of fluoride particles in this embodiment may further contain other components as long as the effects of the present invention such as the dispersibility of the fluoride particles are not inhibited. Examples of such other components include 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, and the like.

[0061] (Method for producing a dispersion of fluoride particles) Next, the method for producing the dispersion of fluoride particles according to this embodiment will be described below.

[0062] The dispersion of fluoride particles in this embodiment can be obtained by mixing fluoride particles, polyvinylidene fluoride, and an organic solvent, and dispersing the fluoride particles in the organic solvent.

[0063] In the method for producing the dispersion of this embodiment, the mixing method and the addition order of the fluoride particles, polyvinylidene fluoride, and the organic solvent are not particularly limited. For example, the fluoride particles may be added to the organic solvent, and after performing a dispersion treatment on this mixed solution using a disperser, polyvinylidene fluoride may be added to produce the dispersion of this embodiment. Also, the fluoride particles, polyvinylidene fluoride, and the organic solvent may be mixed at once, and then a dispersion treatment may be performed using a disperser to produce the dispersion of this embodiment.

[0064] The method for dispersing the fluoride particles in the organic solvent is not particularly limited, and examples include a wet bead mill, a wet jet mill, a method using ultrasonic waves, and the like. The selection of the dispersion method may be made in consideration of the average dispersed particle diameter of the target fluoride particles, the quality such as purity, and the apparatus used for grinding.

[0065] For example, when it is desired to improve the dispersibility of fluoride particles, a method using a wet bead mill is preferred. In a wet bead mill, since media such as zirconia beads are used to refine the particles, the dispersing power of the fluoride particles can be improved. However, there is a possibility of contamination by the media in the resulting dispersion. Also, when it is desired to improve the purity of the dispersion, a method using a wet jet mill is preferred. A wet jet mill is a wet grinding method that does not use media, and contamination by media as in the case of a wet bead mill can be prevented. However, since no media is used, the dispersing power of the fluoride particles may decrease. Incidentally, the dispersion time is not particularly limited and can be appropriately set according to the types of fluoride particles, organic solvents, etc.

[0066] In the process of manufacturing the dispersion, it is preferable to control the moisture concentration in the dispersion. As a method for controlling the moisture concentration, for example, a method of performing wet grinding in a dew point-controlled place such as a dry room, or a method of performing it in an environment of an inert gas or dry air in a sealed space so that the fluoride particles, polyvinylidene fluoride, organic solvent, and the dispersion containing these are not exposed to the outside air can be mentioned. The inert gas is not particularly limited, and examples include nitrogen, argon, etc.

[0067] Also, before adding the fluoride particles to the organic solvent and dispersing them, the surface adsorbed water of the fluoride particles may be removed in advance. Further, moisture may be removed from the organic solvent. As a method for removing the surface adsorbed water, for example, it can be performed 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. Also, 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. As a method for removing moisture from the organic solvent, for example, distillation, centrifugation, use of a dehydrating material (molecular sieves, zeolite, ion exchange resin, activated alumina, etc.), etc. can be mentioned. Also, a method of bubbling an inert gas such as nitrogen into an aprotic organic solvent may be used.

[0068] When adding optional components (i.e., the aforementioned fluorine-containing surfactant, fluorine-containing lithium salt, FSI salt, fluorine-containing sodium salt, fluorine-containing potassium salt, fluorine-containing rubidium salt, and fluorine-containing cesium salt) or the other aforementioned components to the dispersion of fluoride particles, the mixing method and addition order of these components are not particularly limited. For example, during the dispersion treatment of a mixed solution composed of fluoride particles, polyvinylidene fluoride, and an organic solvent, optional components may be added to prepare a dispersion of fluoride particles. Alternatively, after the dispersion treatment of the mixed solution composed of fluoride particles, polyvinylidene fluoride, and an organic solvent is completed, optional components may be added, and further ultrasonic treatment may be performed to prepare a dispersion of fluoride particles.

[0069] (Other matters) The dispersion of fluoride particles of the present embodiment can be used as an optical material for an optical film such as an antireflection film by mixing with a known binder component, for example. Further, the dispersion of fluoride particles of the present embodiment can also be suitably used as an electrode material for a secondary battery.

[0070] In the optical film produced using the dispersion of fluoride particles of the present embodiment, fluoride particles as fillers can be uniformly contained in the film. Here, polyvinylidene fluoride is a dispersant having a small refractive index compared with conventional dispersants composed of surfactants such as polyoxyalkylene alkyl ether phosphate esters, for example. Therefore, even if polyvinylidene fluoride remains in the film of the optical film, an increase in the refractive index of the optical film itself can be suppressed. As a result, the optical film produced using the dispersion liquid of fluoride particles of the present embodiment has a lower refractive index and has uniform and good optical properties in the plane compared with an optical film formed using a conventional dispersion liquid . Note that the optical film is not particularly limited, and examples thereof include an antireflection film.

[0071] In addition, polyvinylidene fluoride is a compound also used as a conductive aid for the electrode active material of a secondary battery, and does not deteriorate the battery characteristics like a dispersant composed of a conventional surfactant. Therefore, in the electrode of a secondary battery produced using the dispersion liquid of fluoride particles of the present embodiment, it is possible to reduce or suppress the deterioration of battery characteristics as compared with an electrode formed using a conventional dispersion. liquid The deterioration of battery characteristics can be reduced or suppressed compared to an electrode formed using a conventional dispersion.

Examples

[0072] Preferred embodiments of the present invention will be exemplarily described in detail below. However, the materials, compounding amounts, etc. described in this embodiment do not limit the scope of the present invention only to those, unless otherwise specifically limited.

[0073] (Example 1) 190 g of N-methylpyrrolidone (NMP, manufactured by Hayashi Pure Chemical Industries, Ltd., CP (Chemical Pure) for chemical use) and 0.2 g of polyvinylidene fluoride (PVDF, manufactured by Kuraray Co., Ltd., product number: #1100) were mixed and stirred until the PVDF was dissolved. Note that the crystal structure of polyvinylidene fluoride was type II, and the mass average molecular weight was 2.8×10 Bi This was the case. 5

[0074] Next, 10 g of LiF particles (manufactured by Stella Chemifa Corporation) were added to the N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in a state where the LiF particles were aggregated. This slurry was put into a wet bead mill (manufactured by Nippon Coke & Engineering Co., Ltd.), zirconia beads (manufactured by Nikkato Corporation) were added, and a dispersion treatment was performed. After the slurry was put in, the portion where the slurry was exposed to the outside air was set to a nitrogen atmosphere. A dispersion liquid of LiF particles according to this example was obtained. The obtained dispersion liquid was confirmed with an electron microscope, and it was confirmed that the LiF particles were 100 nm or less. Fig. 1 shows an electron microscope image of the LiF particles obtained with an electron microscope. In addition, the physical property values of the obtained dispersion liquid are shown in Table 1.

[0075] (Example 2) ​192 g of N-methylpyrrolidone (NMP, manufactured by Hayashi Junyaku Kogyo Co., Ltd., Chemical Pure for chemical use) and 5 g of polyvinylidene fluoride (PVDF, manufactured by Kureha Corporation, product number: #1100) were mixed, and stirring was carried out until PVDF was dissolved.

[0076] Next, 3 g of LiF particles (manufactured by Stella Chemifa Corporation) were added to the N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in a state where the LiF particles were aggregated. This slurry was put into a wet bead mill (manufactured by Nippon Coke Industry Co., Ltd.), zirconia beads (manufactured by Nikkato Corporation) were added, and dispersion treatment was performed. After the slurry was charged, the portion where the slurry was exposed to the outside air was set to a nitrogen atmosphere. A dispersion of LiF particles according to this example was obtained. The obtained dispersion was confirmed by an electron microscope and confirmed to be particles of 100 nm or less. The physical property values of the obtained dispersion are shown in Table 1.

[0077] (Example 3) In this example, CaF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Example 1, a dispersion of CaF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0078] (Example 4) In this example, CaF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Example 2, a dispersion of CaF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0079] (Example 5) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Example 1, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0080] (Example 6) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Example 2, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0081] (Example 7) 192 g of N-methylpyrrolidone (NMP, manufactured by Hayashi Pure Chemical Industries, Ltd., Chemical Pure (CP)) and 5 g of polyvinylidene fluoride (PVDF, manufactured by Kuraray Co., Ltd., product number: #1100) were mixed and stirred until PVDF was dissolved.

[0082] Next, 3 g of LiF particles (manufactured by Stella Chemifa Corporation) and 3 g of LiPO2F2 were added to the N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in a state where the LiF particles were aggregated. This slurry was put into a wet bead mill (manufactured by Nippon Coke & Engineering Co., Ltd.), zirconia beads (manufactured by Nikkato Corporation) were added, and a dispersion treatment was performed. After the slurry was put in, the part where the slurry was exposed to the outside air was made into a nitrogen atmosphere. The obtained dispersion was confirmed with an electron microscope and confirmed to be particles of 100 nm or less. A dispersion of LiF particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0083] (Example 8) In this example, LiPF6 was used instead of LiPO2F2. Otherwise, in the same manner as in Example 7, a dispersion of LiF particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0084] (Example 9) In this example, tri-n-butylmethylammonium bis(trifluoromethylsulfonyl)imide (TBMA-TFSI) was used instead of LiPO2F2. Otherwise, in the same manner as in Example 7, a dispersion of LiF particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0085] (Example 10) In this example, N,N-dimethylacetamide (DMAc, manufactured by Hayashi Junyaku Co., Ltd.) was used as the organic solvent instead of N-methylpyrrolidone. Otherwise, in the same manner as in Example 1, a dispersion of LiF particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0086] (Example 11) In this example, Na3AlF6 particles (manufactured by Stella Chemifa Corporation) were used as the fluoride particles instead of LiF particles. Otherwise, in the same manner as in Example 1, a dispersion of Na3AlF6 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0087] (Example 12) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used as the fluoride particles instead of LiF particles. Also, the addition amount of polyvinylidene fluoride was changed from 0.2 g to 0.02 g. Otherwise, in the same manner as in Example 1, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0088] (Example 13) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used as the fluoride particles instead of LiF particles. Also, the addition amount of MgF2 particles (manufactured by Stella Chemifa Corporation) was changed from 10 g to 20 g. Otherwise, in the same manner as in Example 1, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0089] (Example 14) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used as the fluoride particles instead of LiF particles. Also, the addition amount of MgF2 particles (manufactured by Stella Chemifa Corporation) was changed from 10 g to 30 g. Otherwise, in the same manner as in Example 1, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0090] (Example 15) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Also, KPF6 was used instead of LiPO2F2. Otherwise, in the same manner as in Example 7, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0091] (Example 16) In this example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Also, 7H-dodecafluoroheptanoic acid was used instead of LiPO2F2. Otherwise, in the same manner as in Example 7, a dispersion of MgF2 particles according to this example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0092] (Comparative Example 1) 190 g of N-methylpyrrolidone (NMP, manufactured by Hayashi Pure Chemical Industries, Ltd., Chemical Pure (CP)) and 10 g of LiF particles (manufactured by Stella Chemifa Corporation) were added to prepare a slurry in which the LiF particles were aggregated. This slurry was put into a wet bead mill (manufactured by Nippon Coke & Engineering Co., Ltd.), zirconia beads (manufactured by Nikkato Corporation) were added, and a dispersion treatment was performed. After the slurry was charged, the portion where the slurry was exposed to the outside air was set to a nitrogen atmosphere. A dispersion of LiF particles according to this comparative example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0093] (Comparative Example 2) In this comparative example, CaF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Comparative Example 1, a dispersion of CaF2 particles according to this comparative example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0094] (Comparative Example 3) In this comparative example, MgF2 particles (manufactured by Stella Chemifa Corporation) were used instead of LiF particles as the fluoride particles. Otherwise, in the same manner as in Comparative Example 1, a dispersion of MgF2 particles according to this comparative example was obtained. The physical property values of the obtained dispersion are shown in Table 1.

[0095]

Table 1

[0096] (Evaluation of dispersibility) Regarding the dispersibility of fluoride particles in the dispersion liquids of fluoride particles obtained in each of the examples and comparative examples, it was evaluated as follows. That is, first, the dispersion liquids of fluoride particles obtained in each of the examples and comparative examples were visually observed to confirm whether the fluoride particles had settled, aggregated, and separated into two layers. Subsequently, a green laser pointer was irradiated onto each dispersion liquid of fluoride particles to confirm the presence or absence of the Tyndall phenomenon. For the dispersion liquid in which the Tyndall phenomenon was confirmed, the dispersibility was rated as ○. Also, for the dispersion liquid in which the fluoride particles in the dispersion liquid had aggregated or settled, or for the dispersion liquid in which the Tyndall phenomenon could not be confirmed, the dispersibility was rated as ×. The results are shown in Table 1.

[0097] As shown in Table 1, regarding the dispersion liquids of Examples 1 to 16 in which PVDF was added as a dispersant for fluoride particles, it was confirmed that the dispersibility was good compared to the dispersion liquids of Comparative Examples 1 to 3 in which PVDF was not added.

Claims

1. an organic solvent, fluoride particles dispersed in the organic solvent, and polyvinylidene fluoride as a dispersant for dispersing the fluoride particles, wherein the content of the fluoride particles is in the range of 1% by mass to 20% by mass based on the total mass of the dispersion of the fluoride particles, the content of the polyvinylidene fluoride is in the range of 0.01% by mass to 3% by mass based on the total mass of the dispersion of the fluoride particles, the fluoride particles contain at least one kind of particles of a compound represented by the following chemical formulas (1) to (3), barium strontium lanthanum fluoride, and barium strontium cerium fluoride: a dispersion of fluoride particles. M1aM2bF(a + 2b) (1) (In the formula, M1 is an alkali metal, M2 is an alkaline earth metal, and a and b are integers satisfying the conditions of 0 ≦ a ≦ 3 and 0 ≦ b ≦ 1.) M1cM3dF(c + 3d) (2) (In the formula, M1 is an alkali metal, M3 is Al, Y or a lanthanoid, and c and d are integers satisfying the conditions of 0 ≦ c ≦ 5 and 0 < d ≦ 3.) M2M3F5 (3) (In the formula, M2 is an alkaline earth metal, and M3 is Al, Y or a lanthanoid.)

2. The aforementioned M １ ａ M ２ ｂ F （ａ＋２ｂ） is LiF, CaF ２ or MgF ２ The dispersion of fluoride particles according to claim 1, wherein the dispersion is such.

3. Said M １ ｃ M ３ ｄ F （ｃ＋３ｄ） wherein, is AlF ３ , Na ３ AlF ６ , Na ５ Al ３ F １４ , LaF ３ , CeF ３ , YF ３ , YbF ３ , NaYF ４ , or NaYbF ４ The dispersion liquid of fluoride particles according to claim 1, which is

4. Said M ２ M ３ F ５ is BaLaF ５ , BaCeF ５ , SrLaF ５ or SrCeF ５ The dispersion of fluoride particles according to claim 1, wherein the dispersion is such that

5. The dispersion of fluoride particles according to claim 1, wherein the organic solvent is at least one selected from the group consisting of N-methyl-pyrrolidone, hexamethylphosphoramide, and dimethylacetamide.

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