Dispersant for metal oxide particles, and dispersion

Abstract

To provide a dispersant for metal oxide particles capable of satisfactorily dispersing metal oxide particles.SOLUTION: A dispersant for metal oxide particles according to the present invention is used for dispersing metal oxide particles, and contains a compound represented by the general formula (1) in the figure (where R1 represents an alkylene group, m represents a number of 2-7, and n represents a number of 1-7). This dispersant for metal oxide particles can satisfactorily disperse metal oxide particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersant used to disperse metal oxide particles and a dispersion containing the dispersant. [Background technology]

[0002] Metal oxide particles have unique properties not found in organic polymer particles, making them extremely useful materials, for example, as various additives and fillers. Typical properties of metal oxide particles include a high refractive index, photocatalytic function, toughness, and transparency. By incorporating metal oxide particles with these properties into a target material, such as a resin, new properties can be imparted to the target material. Therefore, metal oxide particles are extremely valuable in creating new functional materials.

[0003] It is known that the various properties of metal oxide particles as described above depend strongly on their particle size, and in particular, when particle sizes reach the nanometer range, i.e., the so-called metal oxide nanoparticles range, new functions that are not possible with particles on the micrometer order can be realized. For this reason, the development of functional materials using nano-sized metal oxide particles has been actively pursued in recent years.

[0004] On the other hand, when the particle size of metal oxide particles reaches the nanoparticle size range, aggregation of particles due to an increase in specific surface area and other factors is likely to occur, and this aggregation becomes particularly pronounced in liquids such as solvents. From this perspective, it is also important to develop a technology that can more highly disperse metal oxide particles in solvents. For example, Patent Document 1 discloses a technology for dispersing zirconium oxide particles in a dispersion medium using a dispersant made of a compound having a specific structure. This technology is said to make it possible to disperse zirconium oxide particles even in nanometer sizes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-007144 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a demand for even higher dispersibility than before in order to more effectively utilize the excellent properties of metal oxide particles. By suppressing aggregation of metal oxide particles and further improving dispersibility, the inherent properties of metal oxide particles can be significantly exhibited. For example, materials incorporating highly dispersible metal oxide particles are expected to exhibit significantly improved functions such as a higher refractive index and transparency. From this perspective, there has been a strong demand for the development of dispersants that can highly disperse metal oxide particles.

[0007] The present invention has been made in view of the above, and aims to provide a dispersant for metal oxide particles that can disperse metal oxide particles well. Another aim of the present invention is to provide a dispersion that has excellent dispersibility of metal oxide particles and is suitable for forming a cured product that has both good transparency and a good refractive index. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above object, the present inventors have discovered that the above object can be achieved by applying a compound having a specific structure, and have thus completed the present invention.

[0009] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 A dispersant used to disperse metal oxide particles, The following general formula (1)

[0010] [ka]

[0011] (In formula (1), R 1 represents an alkylene group, m is a number from 2 to 7, and n is a number from 1 to 7. A dispersant for metal oxide particles, comprising a compound represented by the formula: Section 2 In the formula (1), R 1 Item 2. The dispersant for metal oxide particles according to Item 1, wherein is an alkylene group having 1 to 6 carbon atoms. Section 3 Item 3. A dispersion comprising the dispersant for metal oxide particles according to Item 1 or 2, metal oxide particles, and an acrylic compound. [Effects of the Invention]

[0012] The dispersant for metal oxide particles of the present invention can disperse metal oxide particles well.

[0013] The dispersion of the present invention has excellent dispersibility of metal oxide particles and can form a cured product that has both good transparency and a good refractive index. DETAILED DESCRIPTION OF THE INVENTION

[0014]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0015] 1. Dispersants for metal oxide particles The dispersant for metal oxide particles of the present invention contains a compound represented by the following general formula (1).

[0016] [ka]

[0017] Here, in formula (1), R 1 represents an alkylene group, m is a number from 2 to 7, and n is a number from 1 to 7.

[0018] The dispersant for metal oxide particles of the present invention (hereinafter sometimes simply referred to as "the dispersant of the present invention") contains the above-mentioned compound, and thus has the property of being able to disperse metal oxide particles well. Therefore, the dispersant of the present invention can be suitably used as a raw material for forming a dispersion described below, and is particularly ideal as a dispersant used to disperse metal oxide particles. Such a dispersion contains the dispersant for metal oxide particles of the present invention and metal oxide particles, and therefore has excellent dispersibility of the metal oxide particles, is less likely to cause sedimentation, and is highly transparent.

[0019] In particular, the dispersion of the present invention has excellent dispersibility and is less likely to cause an increase in viscosity even when the solid content of the metal oxide particles is increased, and therefore has excellent handleability. Furthermore, since the solid content of the metal oxide particles can be increased, the functionality of the metal oxide particles can be more effectively exhibited.

[0020] In the formula (1), R 1 may be a linear alkylene group or a branched alkylene group, and is preferably a linear alkylene group.

[0021] In the formula (1), R 1 The number of carbon atoms in the alkylene group is not particularly limited. In terms of easily increasing the dispersibility of metal oxide particles, for example, 1 is preferably an alkylene group having 1 to 6 carbon atoms (1 or more and 6 or less). 1 is more preferably an alkylene group having 2 or more carbon atoms, more preferably an alkylene group having 5 or less carbon atoms, even more preferably an alkylene group having 4 or less carbon atoms, and particularly preferably an alkylene group having 3 or less carbon atoms.

[0022] R 1 Specific examples include -CH2-, -(CH2)2-, -(CH2)3-, and -(CH2)4-.

[0023] In the formula (1), m is a number from 2 to 7, i.e., a number from 2 to 7. If m is less than 2, the dispersibility of the metal oxide particles may decrease, and if m exceeds 7, the dispersibility of the metal oxide particles may decrease. m is preferably 3 or more and 6 or less. m may be an integer or a decimal point.

[0024] In the formula (1), the method for adjusting the value of m is not particularly limited, and for example, the value can be adjusted by appropriately selecting the type of raw material (cyclic ester compound, etc.) used when producing the compound represented by formula (1).

[0025] In the formula (1), n ​​is "-(CH2) m "n" means the repeating unit of the "-COO-" moiety, more specifically the number average repeating unit, in other words, n means the number average degree of polymerization of the compound represented by formula (1).

[0026] n is a number from 1 to 7, i.e., a number from 1 to 7. If n is less than 1, the dispersibility of the metal oxide particles may decrease, and if n exceeds 7, the dispersibility of the metal oxide particles may decrease. n is preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, and particularly preferably 3 or less. n may be an integer or a decimal point. The value of n can be estimated from the 1H-NMR spectrum of the compound represented by formula (1).

[0027] In the formula (1), the method for adjusting the value of n is not particularly limited, and for example, it can be adjusted by appropriately selecting the proportions of the raw materials (cyclic ester compound and fatty acid) used when producing the compound represented by formula (1).

[0028] The method for producing the compound represented by formula (1) is not particularly limited. For example, the compound represented by formula (1) can be produced by reacting a cyclic ester compound with a fatty acid.

[0029] The cyclic ester compound can be exemplified by a compound represented by the following general formula (2).

[0030] [ka]

[0031] In formula (2), m has the same meaning as in formula (1). The compound represented by formula (2) is -(CH2) m - is a cyclic compound in which the ester bonded to the ring.

[0032] Examples of the compound represented by the formula (2) include ε-caprolactone and γ-butyrolactone.

[0033] The fatty acid may be, for example, a saturated fatty acid having a phenyl group at the terminal. 1 Examples of fatty acids are those represented by -COOH. 1 In -COOH, "ph" means a phenyl group (-C6H5-), and R 1 is R in the formula (1). 1 Examples of the fatty acid include 3-phenylpropanoic acid.

[0034] When the compound represented by formula (1) is produced by reacting the cyclic ester compound with the fatty acid, the reaction conditions are not particularly limited, and a wide variety of reaction conditions, such as those for known ring-opening polymerization and known dehydration reactions, can be used. In the reaction, a catalyst, water, etc. can be used as needed, and p-toluenesulfonic acid can be used as the catalyst. The amounts of catalyst and water used are not particularly limited, and can be, for example, catalytic amounts. For purification after the reaction, an alkali such as sodium hydroxide can be used. The reaction temperature and reaction time for the ring-opening polymerization and dehydration reaction are also not particularly limited, and can be the same as those for known reactions.

[0035] The dispersant of the present invention may contain other components in addition to the compound represented by formula (1), or may consist solely of the compound represented by formula (1). The dispersant of the present invention preferably contains 90% by mass or more of the compound represented by formula (1), more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0036] The dispersant of the present invention can disperse metal oxide particles well. Examples of the types of metal oxide particles include a wide range of metal oxide particles contained in the dispersion described below, and is particularly suitable for dispersing zirconium oxide (zirconia), titanium oxide (titania), etc.

[0037] The dispersant of the present invention can disperse metal oxide particles well in various solvents, among which the acrylic compounds described below can be preferably used as the solvent.

[0038] When dispersing metal oxide particles using the dispersant of the present invention, for example, the amount of dispersant used per 100 parts by mass of metal oxide particles can be 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 3 to 18 parts by mass, even more preferably 5 to 16 parts by mass, and particularly preferably 6 to 12 parts by mass.

[0039] 2. Dispersion and cured product of the dispersion The dispersion of the present invention contains the above-mentioned dispersant for metal oxide particles, metal oxide particles, and an acrylic compound. Because the dispersion contains the dispersant of the present invention, it has excellent dispersibility of the metal oxide particles.

[0040] (metal oxide particles) In the metal oxide particles, the type of metal can be, for example, one metal selected from the group consisting of metal elements belonging to Periods 4, 5, and 6 of the Periodic Table (IUPAC 1991), and among these, metal elements of Groups 2 to 14 are preferred.

[0041] More specifically, the metal element constituting the metal oxide particles is preferably a metal that can impart a high refractive index when a metal oxide is formed, such as zirconium, titanium, tin, antimony, zinc, cerium, indium, or yttrium.

[0042] Specific examples of metal oxide particles include zirconium oxide, titanium oxide, tin oxide, antimony pentoxide, zinc oxide, cerium oxide, tin-doped indium oxide, antimony-doped tin oxide, and yttrium oxide. Of these, zirconium oxide, titanium oxide, and tin oxide are preferred, zirconium oxide and titanium oxide are more preferred, and zirconium oxide is particularly preferred.

[0043] In the dispersion of the present invention, the size of the metal oxide particles is not particularly limited as long as it does not reduce dispersibility. For example, the D50 volume average particle diameter of the metal oxide particles is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 3 nm or more, and particularly preferably 5 nm or more, and is preferably 1000 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less. The D50 volume average particle diameter of the metal oxide particles refers to the particle diameter at the point where the volume cumulative distribution is 50% on the particle size distribution curve. The D50 volume average particle diameter of the metal oxide particles refers to a value measured using a dynamic light scattering (DLS) particle size distribution analyzer (Nanotrac Wave II (manufactured by Microtrack Bell)).

[0044] The shape of the metal oxide particles is not particularly limited, and may be, for example, the same as that of known metal oxide particles.

[0045] The metal oxide particles can be obtained, for example, in the form of a powder or a dispersion liquid from a commercial product, etc. Alternatively, the metal oxide particles can be produced, for example, by a known production method.

[0046] (acrylic compounds) The acrylic compound contained in the dispersion of the present invention serves as a dispersion medium for the metal oxide particles in the dispersion, and since the acrylic compound is polymerizable, it is also a component that can become a polymer by curing the dispersion.

[0047] Examples of acrylic compounds include (meth)acrylate compounds. In this specification, "(meth)acrylic" means "acrylic" or "methacrylic", and "(meth)acrylate" means "acrylate" or "methacrylate". The (meth)acrylate compound is preferably one or more compounds selected from the group consisting of monofunctional (meth)acrylate compounds and polyfunctional (meth)acrylate compounds.

[0048] Specific examples of the monofunctional (meth)acrylate compound include alkyl (meth)acrylates in which the alkyl group has 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate. Acrylates; (meth)acrylate compounds having an aromatic ring such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3-phenoxybenzyl acrylate, and EO-modified orthophenylphenol acrylate; alkoxyalkyl (meth)acrylates such as butoxyethyl (meth)acrylate; aminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate; diethylene glycol monoethyl ether (meth)acrylate, triethylene glycol monobutyl ether (meth)acrylate Polyalkylene glycol monoalkyl ether (meth)acrylates such as tetraethylene glycol monomethyl ether (meth)acrylate, hexaethylene glycol monomethyl ether (meth)acrylate, octaethylene glycol monomethyl ether (meth)acrylate, nonaethylene glycol monomethyl ether (meth)acrylate, dipropylene glycol monomethyl ether (meth)acrylate, heptapropylene glycol monomethyl ether (meth)acrylate, and tetraethylene glycol monoethyl ether (meth)acrylate; polyalkylene glycol monoaryl ether (meth)acrylates such as hexaethylene glycol monophenyl ether (meth)acrylate; (meth)acrylate compounds having an alicyclic structure such as cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, and methylene oxide-added cyclodecatriene (meth)acrylate; (meth)acrylate compounds having a heterocyclic ring such as (meth)acryloylmorpholine and tetrahydrofurfuryl (meth)acrylate;Fluorinated alkyl (meth)acrylates such as heptadecafluorodecyl (meth)acrylate; (meth)acrylate compounds having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, triethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, hexaethylene glycol mono(meth)acrylate, and octapropylene glycol mono(meth)acrylate; glycidyl ( (Meth)acrylate compounds having a glycidyl group such as 2-(2-(meth)acryloyloxyethyloxy)ethyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, and other (meth)acrylate compounds having an isocyanate group; polyalkylene glycol mono(meth)acrylates such as tetraethylene glycol mono(meth)acrylate, hexaethylene glycol mono(meth)acrylate, and octapropylene glycol mono(meth)acrylate; and the like.

[0049] Specific examples of polyfunctional (meth)acrylate compounds include alkylene glycol di(meth)acrylates such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate; tri(meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate, ethylene oxide-added trimethylolpropane tri(meth)acrylate, and tris(2-acryloyloxyethyl)isocyanurate; ethylene oxide-added pentaerythritol tetra(meth)acrylate, and trimethylolpropane tetra(meth)acrylate; tetra(meth)acrylate compounds such as tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; (meth)acrylate compounds having an alicyclic structure such as tricyclodecane dimethanol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, 1,3-adamantane dimethanol di(meth)acrylate, hydrogenated bisphenol A (poly)ethoxy di(meth)acrylate, hydrogenated bisphenol A (poly)propoxy di(meth)acrylate, hydrogenated bisphenol F (poly)ethoxy di(meth)acrylate, hydrogenated bisphenol F (poly)propoxy di(meth)acrylate, hydrogenated bisphenol S (poly)ethoxy di(meth)acrylate, and hydrogenated bisphenol S (poly)propoxy di(meth)acrylate.

[0050] The acrylic compound is preferably a monofunctional (meth)acrylate compound, and more preferably a (meth)acrylate compound having an aromatic ring as described above. In this case, not only is the dispersibility of the metal oxide particles likely to be improved, but the refractive index of the cured product is also likely to be increased.

[0051] (Dispersion and cured product of dispersion) In the dispersion of the present invention, the content ratios of the dispersant, metal oxide particles, and acrylic compound can be various as long as the effects of the present invention are not impaired.

[0052] In the dispersion of the present invention, the content of metal oxide particles can be 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more, based on the total mass of the dispersant, metal oxide particles, and acrylic compound. It is particularly noteworthy that the dispersion of the present invention is resistant to a decrease in dispersibility or an increase in viscosity even when the solid content of the metal oxide particles is increased, and from this perspective, the content of metal oxide particles can be 45% by mass or more, based on the total mass of the dispersant, metal oxide particles, and acrylic compound, and a high solid content concentration of 50% by mass or more can be achieved, and even 55% by mass or more is possible.

[0053] There is no particular upper limit to the content of the metal oxide particles, and in terms of being able to easily suppress an increase in viscosity, the content of the metal oxide particles is preferably 80 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less, and particularly preferably 65 mass% or less, based on the total mass of the dispersant, the metal oxide particles, and the acrylic compound.

[0054] In the dispersion of the present invention, the content of the dispersant can be 0.5 parts by mass or more, preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, and particularly preferably 5 parts by mass or more, per 100 parts by mass of the metal oxide particles. The content of the dispersant can be 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 18 parts by mass or less, even more preferably 16 parts by mass or less, and particularly preferably 12 parts by mass or less, per 100 parts by mass of the metal oxide particles.

[0055] In the dispersion of the present invention, the content of the acrylic compound can be 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, and particularly preferably 90 parts by mass or more, per 100 parts by mass of the metal oxide particles. The content of the acrylic compound can be 300 parts by mass or less, preferably 250 parts by mass or less, more preferably 200 parts by mass or less, even more preferably 150 parts by mass or less, and particularly preferably 130 parts by mass or less, per 100 parts by mass of the metal oxide particles.

[0056] The dispersion of the present invention may contain other components in addition to the dispersant, metal oxide particles, and acrylic compound, as long as the effects of the present invention are not impaired. Examples of other components include the photopolymerization initiator described below, as well as additives such as light stabilizers, antioxidants, preservatives, flame retardants, pigments, colorants, mildew inhibitors, and lubricants. When the photopolymerization initiator is contained in the coating agent described below, it does not need to be contained in the dispersion. The additives contained in the dispersion may be one or more types.

[0057] The method for preparing the dispersion of the present invention is not particularly limited, and for example, the dispersion can be prepared by blending a dispersant, metal oxide particles, an acrylic compound, and other components added as needed in a predetermined ratio. The metal oxide particles used to prepare the dispersion may be in a powder state, may be dispersed in a solvent, or may be in other forms. For example, a commercially available mixer or the like can be used to prepare the dispersion, and a disperser or the like can also be used as needed to disperse the metal oxide particles.

[0058] The dispersion of the present invention is obtained by dispersing metal oxide particles in an acrylic compound. The dispersion of the present invention contains a dispersant for metal oxide particles, and therefore has excellent dispersibility of metal oxide particles, and is resistant to increases in viscosity and sedimentation even when the solids concentration (i.e., the concentration of metal oxide particles) is high, and also has high transparency. In particular, the dispersion of the present invention has excellent dispersibility and is resistant to increases in viscosity even when the solids concentration of metal oxide particles is high, and therefore has excellent handleability.

[0059] As described above, the dispersion of the present invention can have a high solids concentration, which allows the metal oxide particles to exhibit their functions (e.g., high refractive index) more effectively. Furthermore, the dispersion can be cured to form a cured product that maintains a good dispersion state, and the cured product can have good transparency and a good refractive index.

[0060] The dispersion of the present invention contains a polymerizable (curable) acrylic compound, and therefore can be cured to form a cured product. For example, the dispersion of the present invention is applied to a substrate to form a coating film, and the coating film is cured to form a cured product (which can also be called a cured film) of the dispersion.

[0061] To promote curing of the dispersion, the dispersion may contain a photopolymerization initiator. The type of photopolymerization initiator is not particularly limited, and for example, a wide range of known photopolymerization initiators can be used. Examples of photopolymerization initiators include polymerization initiators that are activated by active energy rays such as ultraviolet rays.

[0062] Examples of the photopolymerization initiator include aromatic ketones such as benzophenone, aromatic compounds such as anthracene and α-chloromethylnaphthalene, and sulfur compounds such as diphenyl sulfide and thiocarbamate.

[0063] Examples of polymerization initiators using active energy rays other than visible light, such as ultraviolet rays, include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, benzoin propyl ether, benzoin ethyl ether, benzil dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl- Examples of such an alkyl ester include 1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone).

[0064] Commercially available active energy ray polymerization initiators include, for example, Omnirad 184, 369, 651, 500, 819, 907, 784, 2959, 1000, 1300, 1700, 1800, and 1850 manufactured by IGM Resins BV, Lucirin TPO manufactured by BASF, Ubecryl P36 manufactured by UCB, Esacure KIP150, KIP100F, KT37, KT55, KTO46, TZT, and KIP75LT manufactured by Fratelli Lamberti, and Kayacure DETX manufactured by Nippon Kayaku Co., Ltd.

[0065] When the dispersion contains a photopolymerization initiator, the content of the photopolymerization initiator is not particularly limited and is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass per 100 parts by mass of the acrylic compound.

[0066] Examples of the substrate for forming a cured product of the dispersion of the present invention include a resin film, a resin sheet, and a resin plate, and may also be a substrate formed of glass, metal, inorganic material, etc.

[0067] The method for applying the dispersion to the substrate is not particularly limited, and for example, the dispersion can be applied to the substrate using a known coating machine such as a bar coater, thereby forming a coating film of the dispersion on the substrate. The method for curing the coating is also not particularly limited, and examples thereof include a method of irradiating the coating film with active energy rays and a method of heating the coating film. Examples of active energy rays include high-pressure mercury lamps, electron beams, gamma rays, carbon arc lamps, xenon lamps, and metal halide lamps. When curing by heating, the composition can be cured by heating to a temperature range of 60 to 250°C.

[0068] Since the cured product is formed from the dispersion of the present invention, the metal oxide particles can maintain a good dispersion state even in the cured product, and therefore the metal oxide particles are less likely to aggregate in the cured product, which can result in the cured product having excellent transparency.

[0069] Furthermore, since the dispersibility of the metal oxide particles in the cured product is excellent, the properties of the metal oxide particles themselves are likely to be effectively exhibited. For example, if the metal oxide particles are capable of imparting a high refractive index, the high refractive index of the metal oxide particles is likely to be reflected in the cured product (film), resulting in a cured product with a high refractive index.

[0070] Furthermore, the cured product formed from the dispersion of the present invention has excellent transparency because it contains a specific dispersant, metal oxide particles, and a polymer of an acrylic compound.

[0071] The shape of the cured product formed from the dispersion of the present invention is not particularly limited, and examples thereof include various shapes such as a film, a plate, a lump (block), and a particle.

[0072] As described above, the dispersion of the present invention can form a cured product having the above-mentioned various properties, and therefore can be applied to various applications, and is suitable for use as, for example, a coating agent for forming a cured product. Such a coating agent contains the dispersion of the present invention and can contain other components as necessary. For example, when the dispersion does not contain the above-mentioned photopolymerization initiator, the coating agent can contain the same photopolymerization initiator as above, and the content thereof is as described above.

[0073] By using the coating agent, a cured product of the dispersion can be formed, and therefore it can be used for coating a substrate, etc., and can impart, for example, high transparency and refractive index.

[0074] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification. [Example]

[0075] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] Example 1 To 1.0 mol of 3-phenylpropanoic acid, 1.0 mol of ε-caprolactone, 0.03 mol of p-toluenesulfonic acid monohydrate, and 0.28 mol of pure water were added, and the mixture was stirred at 80°C for approximately 8 hours. After that, the mixture was dehydrated under reduced pressure (30 kPa) and stirred for another 2 hours. Finally, the 3-phenylpropanoic acid remaining in the reaction system was distilled off, and the mixture was purified (washed with water three times) and dried to give Dispersant 1 (R in Formula (1)). 1The compound (where m is ethylene, m is 5, and n is 2) was obtained.

[0077] (Comparative Example 1a) Instead of the dispersant 1 obtained in Example 1, dispersant C1 (R 1 A compound in which m is ethylene, m is 5, and n is 10 was prepared. Dispersant C1 was obtained in the following manner. 1.0 mol of 3-phenylpropanoic acid was added to 1.0 mol of ε-caprolactone, 0.03 mol of p-toluenesulfonic acid monohydrate, and 0.3 mol of pure water, and the mixture was stirred at 80°C for approximately 8 hours. After that, the mixture was dehydrated under reduced pressure (30 kPa) and stirred for another 2 hours. Finally, the 3-phenylpropanoic acid remaining in the reaction system was distilled off, and the mixture was subjected to a purification process (washed with water three times) and a drying process, yielding Dispersant C1.

[0078] (Comparative example 1b) Instead of dispersant 1 obtained in Example 1, 3-phenylpropanoic acid (i.e., the compound in which n is 0 in (1)) was prepared as dispersant C2.

[0079] (Comparative example 1c) Instead of the dispersant 1 obtained in Example 1, a compound represented by the following formula (a)

[0080] [ka]

[0081] (in formula (a), n = 17) was prepared as dispersant C3. This compound was obtained by modifying the nonionic surfactant "Noigen EA-157" (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. with a carboxylic acid.

[0082] (Comparative Example 1d) Instead of dispersant 1 obtained in Example 1, a phosphate ester-based anionic surfactant "Plysurf AL" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was prepared as dispersant C4.

[0083] (raw materials) Predetermined raw materials were selected from the raw materials shown below (metal oxide particles, dispersant for metal oxide particles, acrylic compound) to prepare dispersions of Examples 2-1 to 2-9 and Comparative Examples 2 to 4 described below.

[0084] <Metal oxide particles> Metal oxide particles 1: Zirconium oxide methanol dispersion (D50 = approx. 10 nm) manufactured by Sakai Chemical Industry Co., Ltd. Metal oxide particles 2: Zirconium oxide methanol dispersion (D50 = approx. 50 nm) manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd. Metal oxide particles 3: Zirconium oxide methanol dispersion (D50 = approx. 3 nm) manufactured by Sakai Chemical Industry Co., Ltd.

[0085] <Dispersant for metal oxide particles> Dispersant 1: the compound obtained in Example 1 Dispersant C1 (for comparison): the compound prepared in Comparative Example 1a Dispersant C2 (for comparison): the compound prepared in Comparative Example 1b Dispersant C3 (for comparison): the compound prepared in Comparative Example 1c Dispersant C4 (for comparison): the compound prepared in Comparative Example 1d

[0086] <Acrylic compounds> Acrylic compound 1:3-phenoxybenzyl acrylate ("Light Acrylate POB-A" manufactured by Kyoeisha Chemical Co., Ltd.) Acrylic compound 2: EO-modified orthophenylphenol acrylate (Dai-ichi Kogyo Seiyaku Co., Ltd. "New Frontier OPPE (registered trademark)") Acrylic compound 3: Benzyl acrylate

[0087] Example 2-1 A dispersion was obtained by mixing predetermined raw materials according to the formulation conditions shown in Table 1. Specifically, 55 parts by mass of Metal Oxide Particles 1 as metal oxide particles, 5.5 parts by mass of Dispersant 1 as a dispersant, and 39.5 parts by mass of Acrylic Compound 1 as an acrylic compound were blended and mixed to obtain a dispersion. Note that the blending amounts of the metal oxide particles and dispersant shown above and in Table 1 are amounts converted to solid content, and do not include the amount of volatile matter such as the solvent.

[0088] (Example 2-2) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that metal oxide particles 2 were used instead of metal oxide particles 1.

[0089] (Example 2-3) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that metal oxide particles 3 were used instead of metal oxide particles 1.

[0090] (Examples 2-4) A dispersion was obtained in the same manner as in Example 2-1, except that the amount of metal oxide particles 1 was changed to 60 parts by mass, the amount of dispersant 1 was changed to 6 parts by mass, and the amount of acrylic compound 1 was changed to 34 parts by mass, as shown in Table 1.

[0091] (Examples 2-5) A dispersion was obtained in the same manner as in Example 2-1, except that the amount of metal oxide particles 1 was changed to 50 parts by mass, the amount of dispersant 1 was changed to 5 parts by mass, and the amount of acrylic compound 1 was changed to 45 parts by mass, as shown in Table 1.

[0092] (Examples 2-6) A dispersion was obtained in the same manner as in Example 2-1, except that the amount of dispersant 1 was changed to 1 part by mass and the amount of acrylic compound 1 was changed to 44 parts by mass, as shown in Table 1.

[0093] (Examples 2-7) A dispersion was obtained in the same manner as in Example 2-1, except that the amount of dispersant 1 was changed to 10 parts by mass and the amount of acrylic compound 1 was changed to 35 parts by mass, as shown in Table 1.

[0094] (Examples 2-8) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that acrylic compound 2 was used instead of acrylic compound 1.

[0095] (Examples 2-9) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that acrylic compound 3 was used instead of acrylic compound 1.

[0096] (Comparative Example 2) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that Dispersant C1 was used instead of Dispersant 1.

[0097] (Comparative Example 3) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that Dispersant C2 was used instead of Dispersant 1.

[0098] Comparative Example 4 As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that Dispersant C3 was used instead of Dispersant 1.

[0099] (Comparative Example 5) As shown in the formulation conditions in Table 1, a dispersion was obtained in the same manner as in Example 2-1, except that Dispersant C4 was used instead of Dispersant 1.

[0100] (Evaluation method) The dispersibility, resistance to sedimentation, and refractive index of the dispersions obtained in each of the Examples and Comparative Examples were evaluated by the following procedures.

[0101] <Dispersibility of Dispersed Materials> The dispersibility of the dispersion was evaluated based on the viscosity measured with an E-type viscometer and the total light transmittance of the dispersion. The viscosity of the dispersion was measured at 25°C using a commercially available E-type viscometer (Tokyo Keiki Co., Ltd.), and the total light transmittance of the dispersion was measured using a Haze Meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd. Based on these values, the dispersion was evaluated according to the following criteria. <Evaluation Criteria> A: The viscosity of the dispersion is less than 1000 mPa·s, and the total light transmittance is 80% or more, so the transparency is extremely high and the dispersibility is particularly excellent. B: The viscosity of the dispersion is 1000 mPa·s or more and less than 10000 mPa·s, and the total light transmittance is 75% or less and less than 80%, so that the dispersion has high transparency and excellent dispersibility. C: The viscosity of the dispersion is 10,000 mPa·s or more, and the total light transmittance is less than 75%, resulting in extremely poor fluidity and transparency, and poor dispersibility.

[0102] <Resistance to settling of dispersion> The dispersion was placed in a screw tube and shaken together with the screw tube to disperse uniformly. After that, the screw tube was left to stand, and the time until the particles began to settle was measured, and the resistance to settling of the dispersion was evaluated according to the following criteria. <Evaluation Criteria> A: It took more than 24 hours for the particles to settle, and settling was extremely difficult to occur. B: Although the time until particle settling occurred was within 24 hours, settling did not occur for a while immediately after leaving the sample to stand, and settling was unlikely to occur. C: Sedimentation occurred immediately after standing, and sedimentation was extremely likely to occur.

[0103] <Refractive index of dispersion> The refractive index of the dispersion was measured at 25°C using an Abbe refractometer (trade name: NAR-IT, manufactured by Atago Co., Ltd.). <Evaluation Criteria> A: The dispersion has a high refractive index of 1.65 or more. B: The refractive index of the dispersion is less than 1.65, which is a low refractive index.

[0104] Table 1 shows the blending conditions for the dispersions obtained in each example and comparative example, as well as the above-mentioned evaluation results. Note that in the blending conditions in Table 1, blank cells indicate that the raw material was not used.

[0105] As can be seen from Table 1, the dispersions obtained in each Example contained a dispersant for metal oxide particles containing a predetermined compound, and thus had excellent dispersibility of metal oxide particles. Furthermore, the dispersions obtained in the Examples were less susceptible to sedimentation and aggregation, and had high transparency and a high refractive index.

[0106] [Table 1]

Claims

1. A dispersant used to disperse metal oxide particles, The following general formula (1) 【Chemical 1】 (In formula (1), R １ represents an alkylene group, m is a number from 2 to 7, and n is a number from 1 to 7. A dispersant for metal oxide particles, comprising a compound represented by the formula:

2. In the formula (1), R １ 2. The dispersant for metal oxide particles according to claim 1, wherein is an alkylene group having 1 to 6 carbon atoms.

3. A dispersion comprising the dispersant for metal oxide particles according to claim 1 or 2, metal oxide particles, and an acrylic compound.

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