JP2013184830A - Surface-modified metal oxide nanoparticle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing surface-modified metal oxide nanoparticles by which synthesis of surface-modified metal oxide nanoparticle important for high refractive index resins can be performed in a short period of time and under mild conditions, and to provide surface-modified metal oxide nanoparticle obtained by the method.SOLUTION: This method for producing surface-modified metal oxide nanoparticles is characterized in that a mixture containing a metal oxide precursor and a surface modifier is irradiated with microwaves to generate a metal oxide and to form a portion modified by the surface modifier in at least part of the metal oxide surface. Surface-modified metal oxide nanoparticles are obtained by the method.

Description

  The present invention relates to surface-modified metal oxide nanoparticles useful as raw materials for organic-inorganic hybrid materials important for optical applications and the like, and a method for producing the same.

  With the rapid evolution of electronic devices in recent years, there is an increasing need for light-weight and easy-workable high refractive index resin-based optical members as compared to conventional inorganic optical materials such as glass. Yes.

  However, the refractive index of so-called general-purpose transparent resins such as polymethyl methacrylate, polystyrene, and polycarbonate is about 1.49 to 1.58, and it can be said that the fields that can be used as they are are limited. In addition, although it is said that a resin having a special structure such as polythiophene can have a refractive index of 2 or more, the resin is difficult to process due to coloring due to molecular structure, poor solubility in various solvents, high softening temperature, etc. It is said that designing a material with a refractive index exceeding 1.8 alone is difficult in practice.

  Therefore, attention has been focused on organic-inorganic hybrid materials of transparent resin as a base and inorganic high refractive index particles, and their development has been activated. In that case, an important point is a surface treatment technique that uses inorganic particles having a nano-order particle size and increases the affinity with the resin in order to avoid a decrease in light transmittance due to scattering.

  Various techniques have been studied for this purpose. In particular, there are the most reports on the method of simultaneously performing nanoparticle synthesis and hybrid structure formation by applying the sol-gel reaction, and the method of combining inorganic nanoparticles with a base resin after surface treatment with a silane coupling agent.

  Non-patent documents 1 to 3 are examples of reports of hybrid materials to which the former sol-gel reaction is applied. In this method, it is generally said that the process shrinkage of the curing reaction is large, alcohol and other by-products are likely to remain in the material, and the resulting inorganic nanoparticles are in an amorphous state with a low refractive index. .

  Patent Documents 1 to 3 are report examples of the surface treatment technique using the latter silane coupling agent. In general, when a silane coupling agent is used, it is said that it is not necessarily optimal for a high refractive hybrid material because it contains silicon with low atomic refraction. Moreover, the molecular structure of an available silane coupling agent is practically limited, and a reagent having a desired structure is not necessarily available.

  Furthermore, in recent years, a synthesis method has been developed in which supercritical water as shown in Patent Documents 4 to 7 is used as a reaction field to synthesize nanoparticles and simultaneously modify the surface of the nanoparticles, which is suitable for mass production. It is attracting attention because it is a technique. In this method, it is said that the modifier is excellent in stability because the modifier is bonded more firmly. However, it has been pointed out that since supercritical water is used, special equipment corresponding to high temperature and pressure is required, and side reactions such as decomposition of the modifier are likely to occur. Therefore, it cannot always be said that direct modification with a surface modifier having a desired structure is possible.

JP 2010-195646 A JP 2009-29931 A JP 2008-303299 A Japanese Patent No. 3663408 Japanese Patent No. 3925932 Japanese Patent No. 3925936 JP 2006-282503 A

Chem. Mater., 2010, 22, 3549 Chem. Lett., 2009, 38, 828 Eur. Polym. J., 2009, 45, 2749

  The problem to be solved by the present invention is that it is difficult to synthesize surface-modified metal oxide nanoparticles important for high refractive index resin applications in a short time and under mild conditions.

  Therefore, as a result of intensive studies to solve the above problems, the present inventors synthesized metal oxide nanoparticles from a metal oxide precursor using a microwave as a heating source in the presence of a surface modifier. At the same time, the inventors have found that the surface treatment of the nanoparticles can be performed, and have completed the present invention.

  In the method for producing surface-modified metal oxide nanoparticles according to the present invention, a mixture containing a metal oxide precursor and a surface modifier is irradiated with microwaves to form a metal oxide, and the surface of the metal oxide A portion modified with a surface modifier is formed on at least a part of the surface.

  The method for producing surface-modified metal oxide nanoparticles according to the present invention is preferably characterized in that the modification amount of the surface modifier with respect to the metal oxide is 2 to 70% by weight.

Moreover, the method for producing surface-modified metal oxide nanoparticles according to the present invention is preferably characterized in that the surface modifier has the following formula (1) as a partial structure.
-Ar-R (1)
[In the formula, Ar represents an aromatic ring having 3 to 20 atoms constituting the ring skeleton or a structure in which a plurality of the aromatic rings are directly connected, R represents an aliphatic group having 1 to 20 carbon atoms, and an aromatic ring and an aliphatic group May be further substituted, and the aromatic ring may be a heterocyclic ring. ]

In the method for producing surface-modified metal oxide nanoparticles according to the present invention, preferably, the surface modifier is bonded to the metal oxide via a functional group represented by the following formula (2).
_{-NH 2, -OH, -CO 2 H} , -CONH 2, -SH, -SOH, -SO 2 H, -SO 3 H, -POH, -PO 2 H, -PO 3 H, -B (OH) ₂ (2)
[In the above formula, the heteroatom may be further substituted, and hydrogen may be dissociated as a proton. ]

  The method for producing surface-modified metal oxide nanoparticles according to the present invention is preferably characterized in that the refractive index of the metal oxide is 1.9 to 2.6.

  In addition, the present invention is characterized in that the surface-modified metal oxide nanoparticles are mixed with a resin and used as a refractive index adjusting material.

  Moreover, the present invention is an optical material characterized in that the surface-modified metal oxide nanoparticles are mixed with a resin so that the refractive index is 1.65 or more.

  According to the present invention, it is possible to synthesize surface-modified metal oxide nanoparticles at a lower temperature and lower pressure than in the conventional method. In addition, since it is possible to apply milder reaction conditions than before, it is possible to use reaction vessels made of glass, etc., and impurities are mixed into products due to metal corrosion as seen when using metal vessels. Can be reduced. In this way, since it is free from the problem of metal corrosion in the reactor, the selection range of the inorganic oxide raw material is widened, and it is possible to use a cheaper raw material. Furthermore, in comparison with a normal heating method that does not use microwave irradiation, the reaction time can be greatly shortened.

TEM image of Comparative Example 1 XRD data of Comparative Example 1 XRD data of Comparative Example 2 TEM image of Example 1 XRD data of Example 1 IR data of Example 1 TG-DTA data of Example 1 XRD data of Example 2 IR data of Example 2 TG-DTA data of Example 2 XRD data of Example 3 IR data of Example 3 TG-DTA data of Example 3 XRD data of Example 4 IR data of Example 4 TG-DTA data of Example 4 TEM image of Example 5 XRD data of Example 5 IR data of Example 5 TG-DTA data of Example 5 XRD data of Example 6 IR data of Example 6 TG-DTA data of Example 6 XRD data of Example 7 IR data of Example 7 TG-DTA data of Example 7 XRD data of Example 8 IR data of Example 8 TG-DTA data of Example 8 XRD data of Example 9 IR data of Example 9 TG-DTA data of Example 9 IR data of Example 10 TG-DTA data of Example 10 IR data of Example 11 TG-DTA data of Example 11 IR data of Example 12 TG-DTA data of Example 12 IR data of Example 13 TG-DTA data of Example 13

  Embodiments of the present invention will be described below. The configuration of the present invention is not limited to the contents of the following embodiment.

  In the method for producing surface-modified metal oxide nanoparticles according to the present invention, a mixture containing a metal oxide precursor and a surface modifier is irradiated with microwaves to form a metal oxide, and at the same time, a metal oxide A portion modified with a surface modifier is formed on at least a part of the surface.

In the present invention, the microwave to be used refers to an electromagnetic wave having a frequency of 300 MHz to 300 GHz, preferably 915 MHz to 2.45 GHz. The microwave irradiation density is energy required to reach the reaction temperature, and is preferably 0.1 to 100 W / cm ³ . If it is less than 0.1 W / cm ^3, it is difficult to heat to the reaction temperature. On the other hand, when it is higher than 100 W / cm ^3, it is easily heated to the reaction temperature or higher and it is difficult to keep the reaction temperature constant.

  The reaction temperature is preferably 100 ° C. or higher and lower than 250 ° C., more preferably 150 ° C. or higher and lower than 250 ° C. The reaction time depends on the type, concentration, solvent, and irradiation energy amount of the metal oxide precursor to be used, but is preferably 10 seconds to 60 minutes, and more preferably 1 minute to 10 minutes. In the present invention, a mixture containing a metal oxide precursor and a surface modifier may be put in a glass reaction vessel or the like, and the reaction may be carried out in a sealed state such as by covering with a metal. Surface-modified metal oxide nanoparticles can be obtained without requiring high-temperature and high-pressure conditions such as using an autoclave.

  In the present invention, usable metal oxide precursors can be used as long as they generate metal oxides by a hydrothermal reaction, but it is preferable to use metal oxides having high refraction. . Specifically, titanium oxide having a refractive index of 2.52 to 2.71, zirconium oxide having a refractive index of 2.40, cerium oxide having a refractive index of 2.20, and zinc oxide having a refractive index of 1.95. It is particularly preferred to use an oxide precursor.

  As titanium oxide synthesis applications, titanium hydroxide, titanium alkoxide, titanium halide, titanium oxysulfate, and the like can be used. The organic part of the titanium alkoxide preferably has 6 or less carbon atoms, specifically, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, t-butoxy, n-pentyloxy, isopentyloxy, cyclopentyloxy, n -Hexyloxy, isohexyloxy, cyclohexyloxy and the like are preferred. As the titanium halide, titanium tetrachloride, titanium bromide, titanium tetraiodide, or the like can be used.

  For zirconium oxide synthesis, zirconium hydroxide, zirconium alkoxide, zirconium halide, zirconium oxy salt, etc. can be used. As the organic part of the zirconium alkoxide, the same one as the above-mentioned titanium alkoxide can be used. As the zirconium halide, zirconium tetrachloride, zirconium bromide, zirconium tetraiodide and the like can be used. As the zirconium oxy salt, zirconyl chloride, zirconyl bromide, zirconyl iodide, zirconyl nitrate, zirconyl sulfate, zirconyl acetate, zirconium oxychloride and the like can be used.

For cerium oxide synthesis, cerium hydroxide, ammonium cerium nitrate, cerium sulfate, and the like can be used.
For zinc oxide synthesis, zinc hydroxide, zinc halide, zinc sulfate, zinc nitrate, etc. can be used.

In the present invention, usable surface modifiers can be used as long as they have a functional group (X) that binds to metal oxide nanoparticles. As the preferred functional _{group, -NH 2, -OH, -CO 2} H, -CONH 2, -SH, -SOH, -SO 2 H, -SO 3 H, -POH, -PO 2 H, -PO 3 H, —B (OH) ₂ [In the above formula, the heteroatom may be further substituted, and hydrogen may be dissociated as a proton. ] Etc. are mentioned.

As a partial structure of the surface modifier, a preferable partial structure for developing a high refractive index includes a structure represented by the following formula (1).
-Ar-R (1)

  In the formula (1), Ar represents an aromatic ring having 3 to 20 atoms constituting the ring skeleton or a structure in which a plurality of the aromatic rings are directly connected, R represents an aliphatic group having 1 to 20 carbon atoms, The group group may be further substituted, and the aromatic ring may be a heterocyclic ring.

  As a more preferable partial structure, in the formula (1), Ar is an aromatic ring having 5 to 12 atoms constituting the ring skeleton or a structure in which a plurality of the aromatic rings are directly connected, and R is an aliphatic group having 1 to 10 carbon atoms. The aromatic ring and the aliphatic group may be further substituted, and the aromatic ring may be a heterocyclic ring.

  As the most preferred partial structure, in formula (1), Ar represents an aromatic ring having 5 to 6 atoms constituting the ring skeleton, R represents an aliphatic group having 1 to 10 carbon atoms, and the aromatic ring and the aliphatic group are Furthermore, the structure which may be substituted and the aromatic ring may be a heterocyclic ring is mentioned.

Specific examples of these partial structures are as follows.
In the formula (1), Ar is an aromatic ring having 3 atoms constituting a cyclic skeleton such as a cyclopropenyl cation ring, a cyclopentadienyl anion ring, a thiophene ring, a furan ring, a 2H-pyrrole ring, an imidazole ring, or a pyrazole. 6 ring atoms constituting a ring skeleton such as an aromatic ring having 5 atoms constituting a ring skeleton such as a ring, isothiazole ring, isoxazole ring, and furazane ring, a benzene ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, and a pyridazine ring. Aromatic ring, aromatic ring having 7 atoms constituting a ring skeleton such as cycloheptatrienyl cation ring, pentalene ring, thienofuran ring, pyrazolooxazole ring, imidazothiazole ring, oxathiolopyrrole ring, dioxoloimidazole ring, etc. Aromatic ring having 8 atoms constituting the ring skeleton, indene ring, benzothiophene ring, benzofuran ring, Ring skeletons such as benzofuran ring, indolizine ring, isoindole ring, indole ring, 3H-indole ring, 1H-indazole ring, purine ring, indoline ring, isoindoline ring, 2,3-dithia-1,5-diazaindane Aromatic ring having 9 atoms, naphthalene ring, chromene ring, 4H-quinolidine ring, isoquinoline ring, quinoline ring, phthalazine ring, naphthyridine ring, quinoxaline ring, quinazoline ring, cinnoline ring, pteridine ring, isochroman ring, chroman ring, Pyridooxazine ring, pyrazinopyridazine ring, monothiaphthalene ring, dithianaphthalene ring, trithiaphthalene ring, tetrathiaphthalene ring, monoazanaphthalene ring, diazanaphthalene ring, triazanaphthalene ring, tetraazanaphthalene ring, Monooxanaphthalene ring, dioxa Aromatic ring with 10 atoms that constitutes the ring skeleton such as phthalene ring, trioxanaphthalene ring, tetraoxanaphthalene ring, monophosphanaphthalene ring, diphosphanaphthalene ring, triphosphanaphthalene ring, tetraphosphanaphthalene ring, azulene ring , Aromatic ring having 11 atoms constituting a ring skeleton such as benzoxepin ring, aromatic ring having 12 atoms constituting a ring skeleton such as heptalene ring, biphenylene ring, indacene ring, acenaphthene ring, fluorene ring, naphthothiophene ring, naphthofuran Ring, carbazole ring, perimidine ring, furocinoline ring, and other aromatic rings, phenanthrene rings, anthracene rings, thianthrene rings, xanthene rings, phenoxaline rings, phenanthridine rings, acridine rings, phenance rings Lorin ring, phenazine ring, phenothia Ring skeletons such as aromatic ring having 14 atoms constituting ring skeleton such as gin ring and phenoxazine ring, acephenanthrylene ring, oxaacephenanthrylene ring, thiaacephenanthrylene ring, azaacephenanthrylene ring An aromatic ring having 15 atoms, fluoranthene ring, aceanthrylene ring, pyrene ring, oxafluoranthene ring, oxaaceanthrylene ring, oxaspirene ring, thiafluoranthene ring, thiaaceanthrylene ring, thiapyrene ring, Atoms constituting a ring skeleton such as an aromatic ring having 16 atoms constituting a ring skeleton such as an azafluoranthene ring, an azaacethrylene ring, an azapyrene ring, a benzofluorene ring, a pyridocarbazole ring, a pyridoimidazoquinoxaline ring Number 17 aromatic ring, triphenylene ring, chrysene ring, naphthacene ring, pradacene ring, terphenyl , Oxatriphenylene ring, oxacrysene ring, oxananaphthacene ring, oxapredacene ring, oxaterphenyl ring, thiatriphenylene ring, thiachrysene ring, thianaphthacene ring, thiapredacene ring, thiaterphenyl ring, azatriphenylene ring, azachrysene ring, An aromatic ring having 18 atoms constituting a ring skeleton such as azanaphthacene ring, azapredacene ring, azaterphenyl ring, naphthylindene ring, naphthylindole ring, naphthylindazole ring, naphthylpurine ring, naphthylbenzofuran ring, naphthylbenzofuran ring, Naphtyl benzofuran ring, naphthyl benzofuran ring, naphthyl benzothiophene ring, naphthyl benzoofen ring, naphthyl benzoofen ring, naphthyl benzoofen ring, quinolyl indene ring, quinolyl indole ring Quinolyl indazole ring, quinolyl purine ring, quinolyl benzofuran ring, quinolyl benzofuran ring, quinolyl benzofuran ring, quinolyl benzofuran ring, quinolyl benzothiophene ring, quinolyl benzoofen ring, quinolyl benzoofen ring, quinolyl benzoofen ring 19-membered aromatic ring, perylene ring, binaphthalene ring, naphthylazulene ring, oxoperylene ring, oxobinaphthalene ring, oxonaphthylazulene ring, thiaperylene ring, thiabinaphthalene ring, thianaphthylazulene ring constituting a ring skeleton such as a ring , An aromatic ring having 20 atoms constituting a ring skeleton such as an azaperylene ring, an azabinaphthalene ring and an azanaphthylazulene ring.

  In the formula (1), R is methyl group, ethyl group, propyl group, cyclopropyl group, butyl group, cyclobutyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, cycloheptyl group, octyl group. , Cyclooctyl group, nonyl group, cyclononyl group, decyl group, cyclodecyl group, undecyl group, cycloundecyl group, dodecyl group, cyclododecyl group, tridecyl group, cyclotridecyl group, tetradecyl group, cyclotetradecyl group, pentadecyl group , Cyclopentadecyl group, hexadecyl group, cyclohexadecyl group, heptadecyl group, cycloheptadecyl group, octadecyl group, cyclooctadecyl group, nonadecyl group, cyclononadecyl group, eicosanyl group, cycloeicosanyl group, etc. Dehydrogenation Aliphatic group such like. These are further methyl, ethyl, propyl, cyclopropyl, butyl, cyclobutyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl Group, cyclononyl group, decyl group, cyclodecyl group, undecyl group, cycloundecyl group, dodecyl group, cyclododecyl group, tridecyl group, cyclotridecyl group, tetradecyl group, cyclotetradecyl group, pentadecyl group, cyclopentadecyl group, A hexadecyl group, a cyclohexadecyl group, a heptadecyl group, a cycloheptadecyl group, an octadecyl group, a cyclooctadecyl group, a nonadecyl group, a cyclononadecyl group and the like, and a partially dehydrogenated aliphatic group, fluorine, chlorine, bromine, Halogens such as iodine Atom, hydroxyl group, alkoxy group, alkenyloxy group, alkynyloxy group, aryloxy group, thiol group, alkenylthio group, alkynylthio group, arylthio group, amino group, alkylamino group, alkenylamino group, alkynylamino group, arylamino It may be substituted with a group or the like.

  From the above description, the surface modifier in the present invention can be expressed as X-Ar-R, and at least a part of the surface of the metal oxide is bonded via the functional group X as shown in the above formula (2). Qualify. Although the modification principle of this surface modifier has not been fully elucidated, it can be modified in a state in which the hydrogen of the functional group X dissociates as a proton and coordinates to the Lewis acid point on the surface of the metal oxide, or as a proton. It is considered that the modification is performed in such a state that a hydrogen bond is formed with the hydroxyl group on the surface of the metal oxide without separation.

  In this invention, it is preferable that the modification amount of the surface modifier with respect to a metal oxide nanoparticle is 2-70 weight%. Further, as long as the metal oxide nanoparticles are not partially exposed and cause a harmful effect, the entire surface of the metal oxide nanoparticles may not be completely covered. The modification amount of the surface modifier can be determined by thermogravimetric analysis.

  The surface-modified metal oxide nanoparticles according to the present invention are highly compatible with various resins and are useful for producing good organic-inorganic nanohybrid materials. The resin that can be used depends on the surface modification group of the surface-modified metal oxide nanoparticles, but in general, the following resins can be used.

  That is, polyethylene, polypropylene, polystyrene, polyamide, polyester, polyimide, polyethylene terephthalate, polyphenylene sulfide, polycyclohexylene dimethylene terephthalate, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyarylate, liquid crystal polymer, polyamide Examples thereof include imide, polyether imide, polyphenylene ether, polybenzoxazole, polybenzimidazole, epoxy resin, silicone resin, and fluorine resin.

  Further, if the resin is a transparent resin as exemplified below, the surface-modified metal oxide nanoparticles according to the present invention are used as a refractive index adjusting material, so that the refractive index usable for optical applications is 1.65 or more. An optical material having an optical characteristic with a high refractive index can be obtained. Since the refractive index of this optical material depends on the refractive index of the surface-modified metal oxide nanoparticles used and the blending ratio thereof, the upper limit is theoretically the refractive index of the metal oxide nanoparticles themselves.

  That is, polycarbonate, polymethyl methacrylate, MS resin, polystyrene, ABS resin, AS resin, polyvinyl chloride, cyclic polyolefin, alicyclic acrylic resin, alicyclic epoxy resin, cardo type epoxy resin, cardo type epoxy acrylate resin, poly -4-methylpentene, cyclohexadiene resin, amorphous polyester resin, transparent polyimide, transparent polyamide, transparent polyurethane, transparent fluororesin, thermoplastic elastomer, polylactic acid and the like.

  As a method for producing optical materials having optical characteristics having a high refractive index, a method in which the surface-modified metal oxide nanoparticles according to the present invention are directly mixed with a resin using a kneader or the like, or the present invention in a solvent. It is possible to use both the method of removing the solvent after dissolving and dispersing the surface-modified metal oxide nanoparticles and the resin. In using these techniques, a polymerization reaction may be performed after uniformly dispersing the surface-modified metal oxide nanoparticles according to the present invention using a resin monomer or precursor instead of the resin itself. Moreover, what is necessary is just to adjust suitably the addition amount of the surface modification metal oxide nanoparticle with respect to resin according to the refractive index at the time of mixing with resin completely.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

(Comparative Example 1)
A Teflon (registered trademark) inner cylinder is set in a stainless steel 200 mL autoclave manufactured by Pressure Glass Co., Ltd., and 40.54 g of 0.1 M ZrOCl ₂ aqueous solution and 2.36 g of stearic acid are placed therein, and the inner temperature is 190. The mixture was stirred at 60 ° C. for 60 minutes. After cooling, the contents were taken out, and unmodified modifiers and the like were removed using a poor solvent such as acetone as a washing solvent.

  The obtained crude particles were redispersed in a good solvent such as toluene, and after removing the coarse particles with a centrifugal separator, drying was performed under reduced pressure to obtain 1.04 g of surface-modified nanoparticles. A TEM image of the particles is shown in FIG. 1, and XRD data is shown in FIG. From the XRD results, zirconia crystals were not confirmed.

(Comparative Example 2)
A Teflon (registered trademark) inner cylinder is set in a stainless steel 200 mL autoclave manufactured by Pressure Glass Co., Ltd., and 40.09 g of a 0.1 M ZrO (OH) ₂ aqueous solution and 2.32 g of stearic acid are placed therein. The mixture was heated and stirred at an internal temperature of 190 ° C. for 60 minutes. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.24 g of surface-modified nanoparticles. The XRD data of the particles is shown in FIG. From the XRD results, zirconia crystals were not confirmed.

Example 1
Put 19.93 g of 0.1M ZrOCl ₂ aqueous solution and 1.15 g of stearic acid in a 20 mL glass reaction vessel, and irradiate microwaves with a frequency of 2.45 GHz using Biotage's microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 1 hour in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.20 g of surface-modified metal oxide nanoparticles. FIG. 4 shows a TEM image of the particles, FIG. 5 shows XRD data, FIG. 6 shows IR data, and FIG. 7 shows TG-DTA data. From the TEM image, the particle size was about 10 nm. In addition, the isolated nanoparticles are in a white powder state and can be easily redispersed in a good solvent such as toluene. When redispersed, the nanoparticles are dispersed in a primary particle state of about 10 nm. Was.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, the modification amount of the surface modifier in the obtained surface modification metal oxide nanoparticle was 31 mass% from TG-DTA data.

(Example 2)
A 0.1 mL ZrOCl ₂ aqueous solution (5.10 g) and stearic acid (0.30 g) were placed in a 5 mL glass reaction vessel, and microwaves with a frequency of 2.45 GHz were irradiated using the Biotage microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 30 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.24 g of surface-modified metal oxide nanoparticles. FIG. 8 shows XRD data, FIG. 9 shows IR data, and FIG. 10 shows TG-DTA data.

  XRD results confirmed the presence of cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 63% by mass.

(Example 3)
Put 19.79 g of 0.1M ZrOCl ₂ aqueous solution and 1.13 g of stearic acid in a 20 mL glass reaction vessel, and irradiate microwaves with a frequency of 2.45 GHz using Biotage's microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.27 g of surface-modified metal oxide nanoparticles. FIG. 11 shows XRD data of the particles, FIG. 12 shows IR data, and FIG. 13 shows TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, the modification amount of the surface modifier in the obtained surface modification metal oxide nanoparticle was 41 mass% from TG-DTA data.

Example 4
Put 20.00 g of 0.1M ZrOCl ₂ aqueous solution and 1.16 g of stearic acid in a 20 mL glass reaction vessel, and irradiate microwaves with a frequency of 2.45 GHz using Biotage's microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 5 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.26 g of surface-modified nanoparticles. FIG. 14 shows XRD data of the particles, FIG. 15 shows IR data, and FIG. 16 shows TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, the modification amount of the surface modifier in the obtained surface modification metal oxide nanoparticle was 41 mass% from TG-DTA data.

(Example 5)
Put 20.98 g of 0.02M ZrOCl ₂ aqueous solution and 0.27 g of stearic acid in a 20 mL glass reaction vessel, and irradiate microwaves with a frequency of 2.45 GHz using Biotage's microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 60 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.10 g of surface-modified nanoparticles. FIG. 17 shows a TEM image of the particles, FIG. 18 shows XRD data, FIG. 19 shows IR data, and FIG. 20 shows TG-DTA data.

  From the TEM image, the particle diameter was about 5 nm. XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 58% by mass.

(Example 6)
Put 20.07 g of 0.02M ZrOCl ₂ aqueous solution and 0.23 g of stearic acid in a 20 mL glass reaction vessel, and irradiate microwaves with a frequency of 2.45 GHz using Biotage's microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 30 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.10 g of surface-modified nanoparticles. FIG. 21 shows XRD data of the particles, FIG. 22 shows IR data, and FIG. 23 shows TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 58% by mass.

(Example 7)
A 20 mL glass reaction vessel was charged with 20.22 g of a 0.02 M ZrO (OH) ₂ aqueous solution and 1.23 g of stearic acid, and a microwave with a frequency of 2.45 GHz was used using a microwave heating synthesizer Initiator 60 manufactured by Biotage. The mixture was heated and stirred at 190 ° C. for 30 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.26 g of surface-modified nanoparticles. FIG. 24 shows XRD data of the particles, FIG. 25 shows IR data, and FIG. 26 shows TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 75% by mass.

(Example 8)
A 20 mL glass reaction vessel was charged with 20.25 g of a 0.1 M ZrO (OH) ₂ aqueous solution and 1.26 g of oleic acid, and a microwave with a frequency of 2.45 GHz was used using the Biotage microwave heating synthesizer Initiator 60. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.48 g of surface-modified nanoparticles. FIG. 27 shows the XRD data of the particles, FIG. 28 shows the IR data, and FIG. 29 shows the TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 60% by mass.

Example 9
A 20 mL glass reaction vessel is charged with 20.21 g of a 0.1 M ZrO (OH) ₂ aqueous solution and 0.95 g of 4-octylbenzoic acid, and a frequency of 2.45 GHz using a microwave heating synthesizer Initiator 60 manufactured by Biotage. Were heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.50 g of surface-modified nanoparticles. FIG. 30 shows XRD data of the particles, FIG. 31 shows IR data, and FIG. 32 shows TG-DTA data.

  XRD results confirmed the presence of monoclinic zirconia and cubic or tetragonal zirconia. From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 63% by mass.

(Example 10)
A 20 mL glass reaction vessel was charged with 20.34 g of a 0.1 M ZrOCl ₂ aqueous solution and 0.83 g of 4-bromobenzoic acid, and a microwave with a frequency of 2.45 GHz using a microwave heating synthesizer Initiator 60 manufactured by Biotage. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain surface-modified nanoparticles. FIG. 33 shows IR data of the particles and FIG. 34 shows TG-DTA data.

  From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. From the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 48% by mass.

(Example 11)
A 20 mL glass reaction vessel was charged with 20.33 g of a 0.1 M ZrOCl ₂ aqueous solution and 1.01 g of 4-iodobenzoic acid, and a microwave having a frequency of 2.45 GHz using a microwave heating synthesizer Initiator 60 manufactured by Biotage. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain surface-modified nanoparticles. FIG. 35 shows IR data of the particles, and FIG. 36 shows TG-DTA data.

  From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 60% by mass.

(Example 12)
A 20 mL glass reaction vessel was charged with 20.29 g of a 0.1 M ZrOCl ₂ aqueous solution and 0.61 g of 4-vinylbenzoic acid, and a microwave with a frequency of 2.45 GHz was used using a microwave heating synthesizer Initiator 60 manufactured by Biotage. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain surface-modified nanoparticles. FIG. 37 shows IR data of the particles, and FIG. 38 shows TG-DTA data.

  From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 58% by mass.

(Example 13)
A 20 mL glass reaction vessel was charged with 20.48 g of a 0.1 M ZrOCl ₂ aqueous solution and 0.56 g of 4-hydroxybenzoic acid, and a microwave with a frequency of 2.45 GHz was used using a microwave heating synthesizer Initiator 60 manufactured by Biotage. The mixture was heated and stirred at 190 ° C. for 10 minutes in a sealed state with a lid. Post-treatment was performed in the same manner as in Comparative Example 1 to obtain 0.42 g of surface-modified nanoparticles. FIG. 39 shows IR data of the particles, and FIG. 40 shows TG-DTA data.

  From the IR data, CH stretching vibration and carboxy anion absorption derived from the surface modifier were observed, and it was confirmed that the organic modifying group was bonded to the zirconia particles. Moreover, from the TG-DTA data, the modification amount of the surface modifier in the obtained surface-modified metal oxide nanoparticles was 43% by mass.

(Example 14)
0.75 g of 4-octylbenzoic acid-modified ZrO2 particles obtained in Example 9 and 0.25 g of MS resin were dissolved and dispersed in 10 g of toluene, and a thin film was applied onto a silicon wafer with a spin coater, followed by drying at 120 ° C. A nanohybrid film having a thickness of about 1 μm was formed. The refractive index at 594 nm evaluated using a prism coupler Model 2010 / M manufactured by Metricon was 1.66.

  Since the surface-modified metal oxide nanoparticles obtained by the present invention are highly compatible with various resins, they can be used for producing a good organic-inorganic nanohybrid material, for example, a lens that requires a high refractive index, It can be effectively used for optical members such as LED sealing materials and antireflection films.

Claims (8)

  The mixture containing the metal oxide precursor and the surface modifier is irradiated with microwaves to form a metal oxide, and at least a part of the surface of the metal oxide is modified with the surface modifier. A method for producing surface-modified metal oxide nanoparticles, wherein:   The method for producing surface-modified metal oxide nanoparticles according to claim 1, wherein the modification amount of the surface modifier with respect to the metal oxide is 2 to 70% by weight. The method for producing surface-modified metal oxide nanoparticles according to claim 1 or 2, wherein the surface modifier has the following formula (1) as a partial structure.
-Ar-R (1)
[In the formula, Ar represents an aromatic ring having 3 to 20 atoms constituting the ring skeleton or a structure in which a plurality of the aromatic rings are directly connected, R represents an aliphatic group having 1 to 20 carbon atoms, and an aromatic ring and an aliphatic group May be further substituted, and the aromatic ring may be a heterocyclic ring. ] The method for producing surface-modified metal oxide nanoparticles according to any one of claims 1 to 3, wherein the surface modifier is bonded to the metal oxide via a functional group represented by the following formula (2).
_{-NH 2, -OH, -CO 2 H} , -CONH 2, -SH, -SOH, -SO 2 H, -SO 3 H, -POH, -PO 2 H, -PO 3 H, -B (OH) ₂ (2)
[In the above formula, the heteroatom may be further substituted, and hydrogen may be dissociated as a proton. ]   The method for producing surface-modified metal oxide nanoparticles according to any one of claims 1 to 4, wherein the metal oxide has a refractive index of 1.9 to 2.6.   Surface-modified metal oxide nanoparticles obtained by the method according to claim 1.   The surface-modified metal oxide nanoparticles according to claim 6, which are mixed with a resin and used as a refractive index adjusting material.   8. An optical material, wherein the surface-modified metal oxide nanoparticles according to claim 7 are mixed with a resin so that the refractive index is 1.65 or more.