Dispersion of fluoride particles

Abstract

Provided is a dispersion liquid of fluoride particles, which is suitable for an optical material of an optical film such as an antireflection film, an electrode material of a secondary battery, or the like, and which is capable of satisfactorily dispersing fluoride particles without using a conventional dispersant containing a surfactant. A dispersion liquid of fluoride particles according to the present invention is characterized by containing an organic solvent, fluoride particles dispersed in the organic solvent, and polyvinylidene fluoride as a dispersant for dispersing the fluoride particles.

Description

Technical Field

[0001] The present invention relates to a dispersion of fluoride particles which is suitable as an optical material in an optical film such as an antireflection film or as an electrode material for a secondary battery. Background Art

[0002] Fluoride (fluorine compound) is used as an optical material and electrode material in the fields of optical film, secondary battery, etc. Fluoride has a characteristic of having a lower refractive index than oxides, etc. Therefore, fluoride particles are used as a filler (filler) for anti-reflection films as disclosed in Patent Document 1. In addition, fluoride particles are also used as an electrode material in secondary batteries represented by lithium ion secondary batteries as described in Patent Documents 2 to 4.

[0003] Here, the film thickness of the anti-reflection film is generally about 100 nm, so the particle size of the fluoride particles used as the filler is required to be smaller than the film thickness. In addition, in the case of electrode materials for secondary batteries, the use of fine particles of fluoride sometimes helps to improve battery performance (Patent Documents 3 and 4).

[0004] However, it is not limited to the powder of the microparticles of the fluoride, and the primary particles thereof aggregate to form secondary aggregates. When the fluoride is used in the state of secondary aggregates, the particle size is too large, and therefore it is sometimes not suitable for the above-mentioned optical materials and electrode materials. Therefore, the particles of the fluoride are usually dispersed in a dispersion medium such as an organic solvent for use.

[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). In addition, as a dispersant, for example, a surfactant such as polyoxyalkylene alkyl ether phosphate (refractive index n = 1.46) can be used. However, such a surfactant has a high refractive index, so even if fluoride particles with a small refractive index are used, there is a problem of increasing the refractive index of the anti-reflection film itself. In addition, in a secondary battery, if a surfactant remains in the electrode, there is also a problem of reducing the battery characteristics.

[0006] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2011-195693 Patent Document 2: Japanese Patent Application Laid-Open No. 2014-191983 Patent Document 3: Japanese Patent Application No. 2008-536285 Patent Document 4: Japanese Patent Application Publication No. 2019-169438 Patent Document 5: Japanese Patent No. 4655614 Summary of the invention Technical problem to be solved by the invention The present invention has been completed in view of the above problems, and an object thereof is to provide a dispersion liquid of fluoride particles, which can disperse the fluoride particles well even without using a conventional dispersant containing a surfactant, and is suitable for optical materials such as antireflection films and electrode materials for secondary batteries.

[0007] Technical solution for solving technical problems In order to solve the above problems, the dispersion liquid of fluoride particles of the present invention is characterized by comprising an organic solvent, fluoride particles dispersed in the above organic solvent, and polyvinylidene fluoride as a dispersant for dispersing the above fluoride particles.

[0008] In the above constitution, the content of the polyvinylidene fluoride is preferably in the range of 0.01% by mass to 3% by mass with respect to the total mass of the dispersion liquid of the fluoride particles.

[0009] In the above constitution, the content of the fluoride particles is preferably in the range of 1% by mass to 20% by mass with respect to the total mass of the dispersion liquid of the fluoride particles.

[0010] In the above constitution, it is preferable that the fluoride particles contain at least one of the compounds represented by the following chemical formulas (1) to (3), and particles of any one of barium strontium lanthanum fluoride and barium strontium cerium fluoride.

[0011] 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 lanthanide element, 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 lanthanide element.) In the above constitution, the above M 1a M 2 b F （a+2b） Preferred are LiF, CaF2 or MgF2.

[0012] In the above-mentioned constitution, the above-mentioned M 1 c M 3 d F （c+3d） Preferably AlF3, Na3AlF6, Na5Al3F 14 , LaF3, CeF3, YF3, YbF3, NaYF4 or NaYbF4.

[0013] In the above-mentioned constitution, the above-mentioned M 2 M 3 F5 is preferably BaLaF5, BaCeF5, SrLaF5 or SrCeF5.

[0014] In the above configuration, the organic solvent is preferably at least one selected from N-methyl-pyrrolidone, hexamethylphosphoramide and dimethylacetamide.

[0015] Effects of the Invention According to the dispersion of fluoride particles of the present invention, by containing polyvinylidene fluoride, fluoride particles can be well dispersed in an organic solvent. Therefore, in the present invention, for example, the use of a dispersant containing a conventional surfactant such as polyoxyalkylene alkyl ether phosphate (refractive index n = 1.46) can be omitted. The refractive index of polyvinylidene fluoride is 1.42, which is smaller than that of polyoxyalkylene alkyl ether phosphate. Therefore, for example, when an optical film such as an antireflection film is formed using the dispersion of fluoride particles of the present invention, the increase in the refractive index of the optical film itself can be suppressed or reduced compared to the conventional optical film using polyoxyalkylene alkyl ether phosphate. In addition, polyvinylidene fluoride is a compound that can also be used as a conductive auxiliary agent for an electrode active material of a secondary battery, and does not reduce the battery characteristics as in the conventional dispersant containing a surfactant. Therefore, the dispersion of fluoride particles of the present invention can also be suitable for use in, for example, an electrode material of a secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an electron microscope image showing the lithium fluoride particles of Example 1 of the present invention. DETAILED DESCRIPTION

[0017] (Dispersion of fluoride particles) Hereinafter, the dispersion liquid of fluoride particles according to the present embodiment (hereinafter, sometimes referred to as “dispersion liquid”) will be described.

[0018] The dispersion of the present embodiment contains at least fluoride particles, polyvinylidene fluoride, and an organic solvent. The fluoride particles exist in a state of being dispersed in the organic solvent. In addition, the dispersion of the present embodiment may also be a form that contains only fluoride particles, polyvinylidene fluoride, and an organic solvent.

[0019] Here, in the present specification, a "dispersion" refers to a liquid in a state where a disperse phase is dispersed in a liquid dispersion medium. Therefore, a "dispersion" does not include a dispersion such as a solid colloid (organic gel) in which the disperse phase is dispersed in a solid dispersion medium and loses fluidity.

[0020] The above-mentioned fluoride particles preferably contain at least one of the compounds represented by the following chemical formulas (1) to (3), and particles of any one of barium strontium lanthanum fluoride (BaSrLaF7) and barium strontium cerium fluoride (BaSrCeF7).

[0021] 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 lanthanide element, 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 lanthanide element.) As the alkali metal in M 1 , there is no particular limitation, and examples thereof include lithium, sodium, potassium, etc. In addition, as the alkaline earth metal in M 2 , there is no particular limitation, and examples thereof include magnesium, calcium, barium, strontium, etc. Furthermore, as the lanthanide element in M 3 , there is no particular limitation, and examples thereof include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0022] Specifically, M 1 a M2 b F （a+2b） For example, 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), etc. Among these fluoride particles, lithium fluoride, calcium fluoride, magnesium fluoride, sodium magnesium fluoride and potassium magnesium fluoride are preferred from the viewpoint of having a small refractive index value.

[0023] Specifically, M 1 c M 3 d F （c+3d） 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, cryolite) (Na3AlF6), potassium hexafluoroaluminate (K3AlF6), cryolite (Na5Al3F6), and ytterbium fluoride (YbF3). 14 ), sodium yttrium fluoride (NaYF4), sodium ytterbium fluoride (NaYbF4), etc. Among these fluoride particles, aluminum fluoride, cryolite, cone cryolite, lanthanum fluoride, cerium fluoride, yttrium fluoride, ytterbium fluoride, sodium yttrium fluoride and sodium ytterbium fluoride are preferred from the viewpoint of having a small refractive index value.

[0024] Specifically, M 2 M 3 Examples of F5 include barium lanthanum fluoride (BaLaF5), barium cerium fluoride (BaCeF5), strontium lanthanum fluoride (SrLaF5), and strontium cerium fluoride (SrCeF5). Among these fluoride particles, particles containing barium lanthanum fluoride or barium cerium fluoride are preferred from the viewpoint of further improving battery characteristics.

[0025] The particles containing the exemplified fluorides may be used alone or in combination of two or more thereof. Among the exemplified fluoride particles, particles containing Na3AlF6 having a refractive index of less than 1.34 and low solubility in water are particularly preferred.

[0026] 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 further preferably in the range of 5% to 10% by mass, relative to the total mass of the dispersion of the fluoride particles. By making the content of the fluoride particles above 1% by mass, for example, even when the dispersion of the fluoride particles of this embodiment is used as a material for an optical film, and the fluoride particles are applied to fillers of optical films such as anti-reflection films, it is possible to maintain good low refractive index properties. On the other hand, by making the content of the fluoride particles below 20% by mass, it is possible to suppress the dispersion time of the fluoride particles from becoming longer, and reduce the probability of the fluoride particles agglomerating with each other.

[0027] The average dispersed particle size (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 further preferably in the range of 1 nm to 50 nm. By making the average dispersed particle size greater than 1 nm, it is possible to suppress the situation where the aggregation of fluoride particles caused by intermolecular forces becomes significant. On the other hand, by making the average dispersed particle size less than 500 nm, for example, when using fluoride particles as fillers for optical films such as anti-reflection films, it is possible to reduce the situation where fluoride particles are detached from the optical film or the light transmittance is impaired. It should be noted that the method and device for measuring the average dispersed particle size of the fluoride particles are not particularly limited, for example, as described in the embodiments described later.

[0028] The shape of the fluoride particles is not particularly limited, and may be, for example, substantially spherical, cubic, chain, needle, plate, scale, rod, fiber, or irregular.

[0029] Polyvinylidene fluoride functions as a dispersant for fluoride particles. Thus, the dispersibility of fluoride particles in organic solvents can be improved. In addition, the refractive index of polyvinylidene fluoride is 1.42, which is smaller than that of conventional surfactants used as dispersants.

[0030] For example, in the case of forming an optical film using a polyoxyalkylene alkyl ether phosphate having a refractive index of 1.46 as a surfactant and magnesium fluoride having a refractive index of 1.38 as fluoride particles, if polyoxyalkylene alkyl ether phosphate remains in the optical film, the refractive index of the optical film itself will also increase because the refractive index of the polyoxyalkylene alkyl ether phosphate is greater than that of magnesium fluoride. However, in the case of using polyvinylidene fluoride, as described above, the refractive index value is smaller than that of the polyoxyalkylene alkyl ether phosphate, so the refractive index of the optical film itself can be suppressed from increasing. As a result, compared with the conventional optical film formed using a surfactant as a dispersant, an optical film having excellent low refractive index can be formed.

[0031] In the present embodiment, polyvinylidene fluoride can use polyvinylidene fluoride having any one of the crystal structures of type I, type II and type III without limitation. Type I refers to the case where the crystal structure is a planar serrated structure, type II refers to the case where the crystal structure is a twisted structure, and type III refers to 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 one of the crystal structures of type I to type III can be used alone, or any two or more of them can be used in combination. In addition, polyvinylidene fluoride having any of the crystal structures of type I to type III can be used in any combination with the fluoride particles exemplified above.

[0032] The content of polyvinylidene fluoride is preferably in the range of 0.01 mass % to 3 mass %, more preferably in the range of 0.05 mass % to 2 mass %, and further preferably in the range of 0.1 mass % to 1 mass % relative to the total mass of the dispersion of fluoride particles. By making the content of polyvinylidene fluoride 0.01 mass % or more, the dispersibility of the fluoride particles can be improved. In addition, by making the content of polyvinylidene fluoride 3 mass % or less, the light transmittance of the optical film can be reduced from being excessively impaired.

[0033] The mass average molecular weight of polyvinylidene fluoride is not particularly limited, but is usually 1.0×10 5 ~1.7×10 6 , preferably 1.5×10 5 ~1.5×10 6 , more preferably 2.5×10 5 ~1.2×10 6 By making the mass average molecular weight of polyvinylidene fluoride 1.0×10 5 The above can suppress the aggregation of fluoride particles and improve the dispersibility. On the other hand, by making the weight average molecular weight of polyvinylidene fluoride 1.7×10 6 The following can improve the solubility in an organic solvent.

[0034] As the organic solvent, there is no particular limitation, and an organic solvent that dissolves polyvinylidene fluoride is preferred. As such an organic solvent, for example, N-methyl-pyrrolidone, hexamethylphosphoramide and dimethylacetamide can be cited. These organic solvents can be used alone or in combination with two or more. In addition, the exemplified organic solvent can be used in any combination with the fluoride particles exemplified above, or polyvinylidene fluoride having a crystal structure of type I to type III.

[0035] The content of the organic solvent is preferably in the range of 80 to 99 mass %, more preferably 85 to 97 mass %, and further preferably 90 to 95 mass %, based on the total mass of the dispersion of the fluoride particles.

[0036] In order to further improve the dispersibility of fluoride particles, the dispersion of fluoride particles of the present embodiment can contain a fluorinated surfactant. In this case, the dispersion of the present embodiment can be a mode that only comprises fluoride particles, polyvinylidene fluoride, an organic solvent and a fluorinated surfactant. The refractive index of the fluorinated surfactant is, for example, smaller than that of a hydrocarbon-based surfactant. Therefore, even if a fluorinated surfactant is added to the dispersion of fluoride particles, compared with the situation of using a hydrocarbon-based surfactant, the refractive index becomes larger, and the excessive reduction in the reflectivity of the anti-reflection film can be suppressed.

[0037] The fluorine-containing surfactant is not particularly limited, and examples thereof include anionic fluorocarbon surfactants, etc. Here, in this specification, "anionic fluorocarbon surfactant" refers to a surfactant including one or more hydrocarbon moieties and one or more anionic groups in the molecule, wherein the hydrocarbon moiety is a hydrocarbon moiety in which at least one hydrogen atom is substituted by a fluorine atom.

[0038] The anionic fluorocarbon surfactant can be represented by the following chemical formula (4).

[0039] RXM (4) In the above chemical formula (4), R is a hydrocarbon part, and represents an alkyl group having 2 to 18 carbon atoms, preferably 2 to 10 carbon atoms, and 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, and 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, and more preferably 8 to 12 carbon atoms, in which at least one hydrogen atom is substituted by a fluorine atom. In addition, R may be either a straight chain or a branched chain. It should be noted that in the present specification, when a range of carbon atoms is represented, the range refers to the carbon number of all integers contained in the range. Therefore, for example, an alkyl group "having 1 to 3 carbon atoms" refers to all alkyl groups having 1, 2, and 3 carbon atoms.

[0040] In the above chemical formula (4), X and M represent anionic groups (hydrophilic groups). - ,-PO4 - 、-SO3 - or -SO4 - In addition, the above-mentioned M represents a counter ion of a hydrophilic group, and in the present embodiment, a proton (H + If it is the above counter ion, the solubility and dispersibility of the fluoride particles in the organic solvent can be improved.

[0041] Furthermore, the onium ion is preferably an onium ion represented by the following chemical formula (5).

[0042] H + ·[NR 1 R 2 R 3 ] (5) Here, R in the chemical formula (5) 1 , R 2 and R 3 Each independently represents hydrogen; an alkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms; an aryl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms; and a hydroxyalkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms. In addition, R 1 , R 2 and R 3 The alkyl, aryl and hydroxyalkyl groups may be straight chain or branched.

[0043] More specifically, the onium ion includes, for example, ammonium ion, methylammonium ion, trimethylammonium ion, ethylammonium ion, dimethylammonium ion, triethanolammonium ion, etc. Among these onium ions, ammonium ion is particularly preferred from the viewpoint of solubility of fluoride particles in an organic solvent.

[0044] In addition, as specific examples of anionic fluorocarbon surfactants, for example, 3H-tetrafluoropropionic acid, 5H-octafluoropentanoic acid, 7H-dodecafluoroheptanoic acid, 9H-hexafluorononanoic acid, etc. can be cited. The exemplified anionic fluorocarbon surfactants can be used alone or in combination of two or more. In addition, among these anionic fluorocarbon surfactants, 7H-dodecafluoroheptanoic acid is preferred from the viewpoint of the dispersibility of fluoride particles in organic solvents. Furthermore, the exemplified anionic fluorocarbon surfactants can be used in any combination with any of the exemplified fluoride particles, polyvinylidene fluoride, and organic solvents.

[0045] Regarding the content of the fluorine-containing surfactant, for example, when the dispersion of the present embodiment is used as a material for an optical film, it is preferably contained within a range in which the refractive index of the optical film itself does not increase excessively. In addition, in the case of an electrode material for a secondary battery, it is preferably contained within a range in which the battery characteristics do not decrease excessively. Specifically, relative to 100 mass % of the fluoride particles, the content of the fluorine-containing surfactant is preferably in the range of 1 mass % to 10 mass %, and more preferably in the range of 2 mass % to 5 mass %. By making the content of the fluorine-containing surfactant greater than 1 mass %, the dispersibility of the fluoride particles can be improved. In addition, by making the content of the fluorine-containing surfactant less than 10 mass %, for example, when used for the formation of an optical film, it is possible to reduce the situation in which the refractive index of the optical film is excessively suppressed and the light transmittance is impaired.

[0046] The dispersion of fluoride particles of the present embodiment may contain at least any one of 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 thereof 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% by mass to 250% by mass, more preferably in the range of 100% by mass to 200% by mass, relative to 100% by mass of the fluoride particles.

[0049] The FSI salt is not particularly limited, and specific examples thereof include trimethylhexylammonium bis(trifluoromethanesulfonyl)imide (TMHA-TFSI), trimethylhexylammonium bis(fluorosulfonyl)imide (TMHA-FSI), tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide (TBMA-TFSI), triethylmethylphosphonium bis(trifluoromethanesulfonyl)imide (TEMP-TFSI), and tri-n-butylmethylphosphonium bis(trifluoromethanesulfonyl)imide (TBMP-TFSI).

[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, relative to 100% by mass of the fluoride particles.

[0051] The fluorine-containing sodium salt is not particularly limited, and specific examples thereof include Na2FePO4F, Na2VPO4F, Na2MnPO4F, Na2CoPO4F, Na2NiPO4F, NaFeSO4F, NaMnSO4F, NaCoSO4F, Na3FeF6, Na2MnF6, NaPF6, NaAsF6, NaSbF6, NaBF4, NaCF3SO3, and NaN(SO2CF3)2.

[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, relative to 100% by mass of the fluoride particles.

[0053] The fluorine-containing potassium salt is not particularly limited, and specific examples thereof include K2FePO4F, K2MnPO4F, K2CoPO4F, KFeSO4F, KCoSO4F, KMnSO4F, KNiSO4F, K3FeF6, K2MnF6, KPF6, KAsF6, KSbF6, KBF4, KCF3SO3, and KN(SO2CF3)2.

[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 thereof include Rb3FeF6, Rb2MnF6, RbPF6, RbAsF6, RbSbF6, RbBF4, RbCF3SO3, and RbN(SO2CF3)2.

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

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

[0058] The content of the fluorine-containing cesium salt is preferably in the range of 100 mass % to 250 mass %, more preferably in the range of 100 mass % to 200 mass %, relative to 100 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 further preferably 0.8% by mass or less relative to 100% by mass of the dispersion of the fluoride particles. If the water concentration in the dispersion of the fluoride particles is 1.5% by mass or less, the fluoride particles are suppressed from agglomerating in the dispersion, and the stability of the dispersion is further achieved.

[0060] The dispersion of the fluoride particles of the present embodiment may further contain other components within the range that does not hinder the dispersibility of the fluoride particles and other effects of the present invention. Such other components include, for example, acrylic resins, polyester resins, polycarbonate resins, polyamide resins, polyurethane resins, vinyl chloride resins, fluororesins, silicone resins, epoxy resins, melamine resins, phenolic resins, butyral resins, vinyl acetate resins, etc.

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

[0062] The dispersion liquid of the fluoride particles according to the present embodiment can be obtained by mixing fluoride particles, polyvinylidene fluoride, and an organic solvent to disperse the fluoride particles in the organic solvent.

[0063] In the manufacturing method of the dispersion liquid of the present embodiment, the mixing method and the order of addition of fluoride particles, polyvinylidene fluoride and organic solvent are not particularly limited. For example, fluoride particles can be added to an organic solvent, and after the mixed solution is subjected to dispersion treatment using a disperser, polyvinylidene fluoride is added to manufacture the dispersion liquid of the present embodiment. In addition, fluoride particles, polyvinylidene fluoride and organic solvent can be mixed at one time, and then dispersed using a disperser to manufacture the dispersion liquid of the present embodiment.

[0064] The method for dispersing the fluoride particles in the organic solvent is not particularly limited, and examples thereof include a wet bead mill, a wet jet mill, a method using ultrasonic waves, etc. The selection of the dispersion method may be carried out in consideration of the target fluoride particles' average dispersed particle size, purity, and other qualities, and the device used for pulverization.

[0065] For example, when the dispersibility of fluoride particles is to be good, it is preferred to use a wet bead mill. In a wet bead mill, particles are miniaturized using media such as zirconium oxide beads, so that the dispersibility of fluoride particles can be good. However, the obtained dispersion may be contaminated by the media. In addition, when the purity of the dispersion is to be good, it is preferred to use a wet jet mill. A wet jet mill is a wet pulverizing method that does not use a medium, and can prevent contamination caused by a medium such as in a wet bead mill. However, since no medium is used, the dispersibility of fluoride particles is sometimes reduced. It should be noted that 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 manufacturing process of the dispersion, it is preferred to control the water concentration in the dispersion. As a method for controlling the water concentration, for example, wet grinding is performed in a place such as a drying room where dew point management is performed, and the method is performed in a closed space and under an inert gas or dry air environment in a manner that does not expose the fluoride particles, polyvinylidene fluoride, organic solvent, and the dispersion containing them to the external air. As the inert gas, there is no particular limitation, and for example, nitrogen, argon, etc. can be mentioned.

[0067] In addition, the surface adsorbed water of the fluoride particles can be removed in advance before adding the fluoride particles to the organic solvent to disperse them. Furthermore, water can also be removed from the organic solvent. As a method for removing surface adsorbed water, for example, it can be carried out by heat treatment. As the drying temperature in the heat treatment, it is preferably in the range of 100°C to 200°C, and more preferably in the range of 110°C to 150°C. In addition, as a drying time, it is preferably in the range of 2 hours to 34 hours, and more preferably in the range of 5 hours to 20 hours. In addition, as a method for removing water from an organic solvent, for example, distillation, centrifugal separation, use of a dehydrating material (molecular sieve, zeolite, ion exchange resin, activated alumina, etc.) and the like can be cited. In addition, it can also be a method of bubbling an inactive gas such as nitrogen in a non-protonic organic solvent.

[0068] When adding any component (i.e., the above-mentioned 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) and the above-mentioned other components to the dispersion of fluoride particles, the mixing method and the order of addition of these components are not particularly limited. For example, any component can be added to the dispersion treatment of the mixed solution containing fluoride particles, polyvinylidene fluoride and an organic solvent to prepare the dispersion of fluoride particles. In addition, any component can also be added after the dispersion treatment of the mixed solution containing fluoride particles, polyvinylidene fluoride and an organic solvent is completed, and ultrasonic treatment is further performed to prepare the dispersion of fluoride particles.

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

[0070] In the optical film made using the dispersion of fluoride particles of the present embodiment, the fluoride particles as fillers can be uniformly contained in the film. Here, polyvinylidene fluoride is, for example, a dispersant having a smaller refractive index than the conventional dispersant containing surfactants such as polyoxyalkylene alkyl ether phosphate. Therefore, even if polyvinylidene fluoride remains in the film of the optical film, the increase in the refractive index of the optical film itself can be suppressed. As a result, the optical film made using the dispersant of fluoride particles of the present embodiment has a lower refractive index than the optical film formed using the conventional dispersant, and has uniform and good optical properties in the plane. It should be noted that the optical film is not particularly limited, and for example, an anti-reflection film can be cited.

[0071] In addition, polyvinylidene fluoride is a compound that can also be used as a conductive auxiliary agent for electrode active materials of secondary batteries, and does not reduce battery characteristics like conventional dispersants containing surfactants. Therefore, in the electrode of a secondary battery made using the dispersion of fluoride particles of the present embodiment, the reduction in battery characteristics can be reduced or suppressed compared to the electrode formed using conventional dispersants.

[0072] Example Hereinafter, preferred embodiments of the present invention will be described in detail by way of example, but the materials, blending amounts, etc. described in the embodiments do not limit the scope of the present invention to these unless otherwise specified.

[0073] (Example 1) 190 g of N-methylpyrrolidone (NMP, manufactured by Hayashi Pure Chemical Industries, Ltd., Chemical Pure CP) and 0.2 g of polyvinylidene fluoride (PVDF, manufactured by Kureha Co., Ltd., product number: #1100) were mixed and stirred until PVDF was dissolved. It should be noted that the crystal structure of polyvinylidene fluoride is type II, and the mass average molecular weight is 2.8×10 5 .

[0074] Next, 10 g of LiF particles (manufactured by Stella Chemifa Co., Ltd.) were added to N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in which the LiF particles were agglomerated. The slurry was put into a wet bead mill (manufactured by NIPPON COKE & ENGINEERING CO., LTD.), and zirconium oxide beads (manufactured by NIKKATO Co., Ltd.) were added for dispersion treatment. After the slurry was put into the slurry, the part of the slurry exposed to the external gas was set to a nitrogen atmosphere. A dispersion of the LiF particles of this embodiment was obtained. The obtained dispersion was confirmed by electron microscopy to be LiF particles of less than 100 nm. Figure 1 An electron microscope image of LiF particles obtained by electron microscopy is shown. Table 1 also shows the physical property values ​​of the obtained dispersion.

[0075] (Example 2) 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 Kureha Corporation, product number: #1100) were mixed and stirred until PVDF was dissolved.

[0076] Next, 3 g of LiF particles (manufactured by Stella Chemifa Co., Ltd.) were added to N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in which the LiF particles were agglomerated. The slurry was put into a wet bead mill (manufactured by NIPPON COKE & ENGINEERING CO., LTD.), and zirconium oxide beads (manufactured by NIKKATO Co., Ltd.) were added for dispersion treatment. After the slurry was put into the slurry, the part of the slurry exposed to the external gas was set to a nitrogen atmosphere. A dispersion of the LiF particles of this embodiment was obtained. The obtained dispersion was confirmed by an electron microscope to be particles of less than 100 nm. The physical properties of the obtained dispersion are shown in Table 1.

[0077] (Example 3) In this example, CaF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Example 1 was performed to obtain a dispersion of CaF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0078] (Example 4) In this example, CaF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Example 2 was performed to obtain a dispersion of CaF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0079] (Example 5) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Example 1 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0080] (Example 6) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Example 2 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties 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 Kureha Corporation, product number: #1100) were mixed and stirred until PVDF was dissolved.

[0082] Next, 3 g of LiF particles (manufactured by Stella Chemifa Co., Ltd.) and 23 g of LiPO2F were added to N-methylpyrrolidone in which PVDF was dissolved to prepare a slurry in which the LiF particles were agglomerated. The slurry was put into a wet bead mill (manufactured by NIPPONCOKE & ENGINEERING CO., LTD.), and zirconium oxide beads (manufactured by NIKKATO Co., Ltd.) were added for dispersion treatment. After the slurry was put into the slurry, the part of the slurry exposed to the external gas was set to a nitrogen atmosphere. The obtained dispersion was confirmed by an electron microscope to be particles below 100 nm. A dispersion of LiF particles of this embodiment was obtained. The physical properties of the obtained dispersion are shown in Table 1.

[0083] (Example 8) In this example, LiPF6 was used instead of LiPO2F2. The same operation as in Example 7 was performed to obtain a dispersion of LiF particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0084] (Example 9) In this example, tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide (TBMA-TFSI) was used instead of LiPO2F2. The same operation as in Example 7 was performed to obtain a dispersion of LiF particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0085] (Example 10) In this example, N,N-dimethylacetamide (DMAc, manufactured by Hayashi Jun Chemical Industry Co., Ltd.) was used as an organic solvent instead of N-methylpyrrolidone. The same operation as in Example 1 was performed to obtain a dispersion of LiF particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0086] (Example 11) In this example, Na3AlF6 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Example 1 was performed to obtain a dispersion of Na3AlF6 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0087] (Example 12) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. In addition, the amount of polyvinylidene fluoride added was changed from 0.2 g to 0.02 g. Other than this, the same operation as in Example 1 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0088] (Example 13) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. In addition, the amount of MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) added was changed from 10 g to 20 g. Other than this, the same operation as in Example 1 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0089] (Example 14) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. In addition, the amount of MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) added was changed from 10 g to 30 g. Other than this, the same operation as in Example 1 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0090] (Example 15) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. In addition, KPF6 was used instead of LiPO2F2. Except for this, the same operation as in Example 7 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0091] (Example 16) In this example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. In addition, 7H-dodecafluoroheptanoic acid was used instead of LiPO2F2. Except for this, the same operation as in Example 7 was performed to obtain a dispersion of MgF2 particles of this example. The physical properties of the obtained dispersion are shown in Table 1.

[0092] (Comparative Example 1) Add 190g of N-methylpyrrolidone (NMP, manufactured by Hayashi Pure Chemical Industries, Ltd., Chemical Pure CP (Chemical Pure)) and 10g of LiF particles (manufactured by Stella Chemifa Co., Ltd.) to prepare a slurry in which the LiF particles are agglomerated. The slurry is put into a wet bead mill (manufactured by NIPPON COKE & ENGINEERING CO., LTD.), and zirconium oxide beads (manufactured by NIKKATO Co., Ltd.) are added for dispersion treatment. After the slurry is put into the slurry, the part of the slurry exposed to the external gas is set to a nitrogen atmosphere. A dispersion of LiF particles of this comparative example is obtained. The physical properties of the obtained dispersion are shown in Table 1.

[0093] (Comparative Example 2) In this comparative example, CaF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Comparative Example 1 was performed to obtain a dispersion of CaF2 particles of this comparative example. The physical properties of the obtained dispersion are shown in Table 1.

[0094] (Comparative Example 3) In this comparative example, MgF2 particles (manufactured by Stella Chemifa Co., Ltd.) were used as fluoride particles instead of LiF particles. The same operation as in Comparative Example 1 was performed to obtain a dispersion of MgF2 particles of this comparative example. The physical properties of the obtained dispersion are shown in Table 1.

[0095] [Table 1] (Evaluation of dispersion) The dispersibility of the fluoride particles in the dispersion of the fluoride particles obtained in each of the Examples and Comparative Examples was evaluated as follows.

[0096] That is, first, visually observe the dispersion of fluoride particles obtained in each embodiment and comparative example to confirm whether the fluoride particles are precipitated, agglomerated and separated into two layers. Next, irradiate the dispersion of each fluoride particle with a green laser pointer to confirm whether the Tyndall phenomenon occurs. For the dispersion in which the Tyndall phenomenon is confirmed, the dispersibility is set to ○. In addition, for the state of agglomeration or sedimentation of fluoride particles in the dispersion, or the dispersion in which the Tyndall phenomenon is not confirmed, the dispersibility is set to ×. The results are shown in Table 1.

[0097] As shown in Table 1, it was confirmed that the dispersions of Examples 1 to 16 to which PVDF was added as a dispersant for fluoride particles had better dispersibility than the dispersions of Comparative Examples 1 to 3 to which PVDF was not added.

Claims

1. A dispersion of fluoride particles, characterized in that: Include: Organic solvents, Fluoride particles dispersed in the organic solvent, and Polyvinylidene fluoride is used as a dispersant for dispersing the fluoride particles.

2. The dispersion of fluoride particles according to claim 1, wherein The content of the polyvinylidene fluoride is in the range of 0.01% by mass to 3% by mass relative to the total mass of the dispersion of the fluoride particles.

3. The dispersion of fluoride particles according to claim 1, wherein The content of the fluoride particles is in the range of 1 mass % to 20 mass % relative to the total mass of the dispersion of the fluoride particles.

4. The dispersion of fluoride particles according to claim 1, wherein The fluoride particles include at least one compound represented by the following chemical formulas (1) to (3), and particles of any one of barium strontium lanthanum fluoride and barium strontium cerium fluoride. M 1 a M 2 b F （a+2b） (1) In formula (1), M 1 Alkali metal, M 2 is an alkaline earth metal, a and b are integers satisfying the conditions of 0≤a≤3, 0≤b≤1, M 1 c M 3 d F （c+3d） (2) In formula (2), M 1 is an alkali metal, M 3 is Al, Y or a lanthanide element, and c and d are integers satisfying the conditions 0 ≤ c ≤ 5, 0 < d ≤ 3. M 2 M 3 F5 (3) In formula (3), M 2 Alkaline earth metal, M 3 It is Al, Y or a lanthanide element.

5. The dispersion of fluoride particles according to claim 4, wherein The M 1 a M 2 b F （a+2b） It is LiF, CaF2 or MgF2.

6. The dispersion of fluoride particles according to claim 4, wherein The M 1 c M 3 d F （c+3d） AlF3, Na3AlF6, Na5Al3F 14 , LaF3, CeF3, YF3, YbF3, NaYF4 or NaYbF4.

7. The dispersion of fluoride particles according to claim 4, wherein The M 2 M 3 F5 is BaLaF5, BaCeF5, SrLaF5 or SrCeF5.

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

Images