JP2012062242A - Composite oxide fine particle and optical material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite oxide which has greatly improved light fastness while maintaining a high refractive index and is applied for an optical material or the like, and to provide an optical material (optical lens or the like) using the same.SOLUTION: Composite oxide fine particles comprising titanium and niobium and/or tantalum have a BET equivalent particle diameter of ≤100 nm.

Description

The present invention relates to composite oxide fine particles, an optical material using the same, and an optical lens.

Resins such as epoxy resin, unsaturated polyester resin, silicone resin, acrylic resin, polycarbonate resin, polyester resin, olefin resin, polyurethane resin, polyether resin, polyamide resin, polyimide resin are excellent in the visible light region. And has excellent performance such as impact resistance and flexibility.

Therefore, development of a transparent optical resin that imparts a high refractive index to such a transparent resin material has been carried out, such as optical lenses, optical prisms, optical waveguides, optical fibers, thin film moldings, optical adhesives, diffraction gratings, Application to highly refractive optical materials such as a light guide plate, a liquid crystal substrate, a light reflector, and an antireflection material is expected.

For the purpose of increasing the refractive index of such a resin, a method of adjusting the refractive index of the resin by dispersing a high refractive index metal oxide such as titanium oxide in the resin has been studied. Since titanium oxide has a particularly high refractive index and high transparency, it is possible to increase the refractive index of the resin in a smaller amount than other inorganic oxide fine particles.

However, a material in which titanium oxide fine particles are dispersed in a resin has a disadvantage that the organic material is decomposed by electron-holes generated by light absorption due to the photocatalytic action of titanium oxide, and the light resistance of the material is lowered.

Regarding a material in which titanium oxide particles are dispersed, Patent Document 1 discloses that titanium oxide sol particles include (a) a hydrated oxide of silicon, (b) a hydrated oxide of silicon and tin, or (c A titanium oxide sol having high transparency and light resistance, which is coated with a hydrated oxide of silicon, a hydrated oxide of tin or the like, and a hydrated oxide of antimony has been proposed. However, there is a concern that the high refractive index peculiar to titanium oxide is not maintained by the surface coating, and the light resistance is not sufficient.

International Publication No. 2008/129693

The present invention solves the above-described problems, and provides a composite oxide that can be applied to an optical material and the like, and an optical material (such as an optical lens) using the same, which significantly improves light resistance while maintaining a high refractive index. The purpose is to provide.

The present invention relates to composite oxide fine particles of titanium and niobium and / or tantalum having a BET equivalent particle size of 100 nm or less.

In the composite oxide fine particles, the content ratio of the titanium and the niobium and / or the tantalum is preferably 99.9 / 0.1 to 0.1 / 99.9, and 99.9 / 0.1 More preferably, it is -70/30, and it is still more preferable that it is 99.9 / 0.1-90 / 10.
Further, the composite oxide fine particles are preferably manufactured by a combustion method.

The present invention provides the composite oxidation comprising a step A in which an organic titanium compound solution, an organic niobium compound solution and / or an organic tantalum compound solution are sprayed in the presence of an oxidizing substance and burned in a gas phase, and a cooling step B. The present invention relates to a method for producing fine particles.

In the manufacturing method, it is preferable that the organic titanium compound solution, the organic niobium compound solution, and / or the organic tantalum compound solution installed in a nitrogen atmosphere are sent to the combustion field of the step A.

The present invention relates to an optical material containing the composite oxide fine particles and a curable resin. Here, the curable resin is an epoxy resin, silicone resin, acrylic resin, urethane resin, ester resin, urethane acrylate resin, silicone acrylate resin, epoxy acrylate resin, ester acrylate resin, polyamide resin. It is preferably at least one selected from the group consisting of a resin, a polyimide resin, a polycarbonate resin, and a phenol resin.
The present invention also relates to an optical lens having a high refractive index layer formed by coating the optical material.

According to the present invention, since it is a composite oxide fine particle of titanium and niobium and / or tantalum having a BET equivalent particle size of 100 nm or less, light resistance is greatly improved while maintaining a high refractive index in an optical material or the like, Also, excellent transparency can be obtained.

4 is an X-ray diffraction _{pattern of} Ti _0.90 Nb _0.10 O ₂ nanoparticles prepared in Example 3. FIG.

The present invention is a composite oxide fine particle of titanium and niobium and / or tantalum having a BET equivalent particle size of 100 nm or less. For example, in the case of composite particles in which the surface of titanium oxide is coated with a silicon compound or the like, the photocatalytic action is suppressed and the light resistance is improved by the coating, but it is difficult to maintain the high refractive index peculiar to titanium oxide. In contrast, in the present invention it intrudes is Nb and / or Ta in the composite oxide nanoparticles (of TiO ₂ crystal structure of Ti and Nb and / or Ta to Nb is dissolved in the TiO ₂ crystal The composite oxide nanoparticles in a solid state that maintain the original crystal structure shape) can greatly improve light resistance, and are solid oxide composite oxide particles. Therefore, the high refractive index peculiar to titanium oxide can also be maintained. Furthermore, by maintaining the nanoparticle state in the composite material dispersed in a resin or the like, a high refractive index can be imparted to the material while maintaining transparency and light resistance. Therefore, for example, in an optical material in which the composite oxide fine particles of the present invention are dispersed in a curable resin, a high refractive index, light resistance, and transparency can be simultaneously obtained.

The composite oxide fine particles of the present invention have a BET equivalent particle size of 100 nm or less, preferably 5 to 90 nm, more preferably 5 to 50 nm. By setting it to 100 nm or less, high transparency can be obtained, and high refractive index and light resistance can also be obtained. In the present invention, the BET equivalent particle size of the composite oxide fine particles is measured by a specific surface area measuring device BELSORP mini II manufactured by Nippon Bell.

In the composite oxide fine particles, the content ratio of titanium and niobium and / or tantalum (Ti amount / total amount of Nb and Ta (molar ratio)) is preferably 99.9 / 0.1 to 0.1 / 99. 9, more preferably 99.9 / 0.1 to 70/30, still more preferably 99.9 / 0.1 to 90/10. By adjusting the ratio within the above range, light resistance can be greatly improved while maintaining a high refractive index peculiar to titanium oxide.

The method for producing the composite oxide fine particles of the present invention is not particularly limited as long as the composite oxide having the BET equivalent particle diameter can be prepared. For example, the composite oxide fine particles can be suitably produced by one kind of combustion method of the gas phase method. . Use of the combustion method makes it easy to produce multi-element oxides, enables powder sampling, has few impurities on the particle surface, is suitable for precision material applications, is easy to produce dope products, and is produced It is possible to use inexpensive raw materials because the hydrolysis is suppressed when the organic metal solution used as the raw material is set in a dry nitrogen atmosphere and particles are produced in an environment that is not exposed to the air. There are advantages.

In addition, when applying nanoparticles to optical material applications, it is required that the transparency and other optical properties of the nanoparticle-resin composite material are not impaired. When the particle size is large or the dispersibility is poor, the transparency is lowered. On the other hand, the composite oxide fine particles of the present invention obtained by the combustion method are nanoparticles, and since the state of the nanoparticles can be maintained even in the composite material, high transparency can be obtained even when applied to the composite material.

As a manufacturing method by a combustion method, for example, an organic titanium compound solution and an organic niobium compound solution and / or an organic tantalum compound solution are sprayed in the presence of an oxidizing substance and burned in a gas phase, and a cooling step The method containing B is mentioned. By sequentially performing steps A and B, composite oxide nanoparticles of Ti and Nb and / or Ta can be suitably produced.
In the above production method, the organic titanium compound solution, the organic niobium compound solution and / or the organic tantalum compound solution installed in a nitrogen atmosphere are preferably sent to the combustion field (oxidation reaction field) in step A. . Thereby, since hydrolysis is suppressed, an inexpensive raw material can be used.

(Process A)
In the organic titanium compound solution, organic niobium compound solution, and organic tantalum compound solution used in step A, at least each metal (Ti, Nb, Ta) is used as the organic metal compound (organic titanium compound, organic niobium compound, organic tantalum compound). ), Compounds containing carbon and hydrogen atoms can be used, for example, each metal alkoxide (metal methoxide, ethoxide, n-propoxide, i-propoxide, n-butoxide, sec-butoxide, tert-butoxide, t-amyloxide Etc.). Specifically, titanium alkoxides such as titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, and titanium tetrabutoxide; niobium alkoxides such as niobium pentamethoxide, niobium pentaethoxide, niobium pentapropoxide, and niobium pentaboxide Tantalum alkoxides such as tantalum pentamethoxide, tantalum pentaethoxide, tantalum pentapropoxide, and tantalum pentaboxide. In addition, when using each metal alkoxide, since a metal alkoxide may hydrolyze easily, it is preferable to use metal alkoxide stabilized as a solution of an organic solvent.

As a solvent (dilution solvent) of the organometallic compound solution, mineral spirit, mineral thinner, petroleum spirit, white spirit, mineral turpentine, kerosene, n-hexane, hexanoic acid, 2-ethylhexanoic acid, cyclohexane, Isoheptane, ethanol, methanol, 1-propanol, acetic acid, 1-pentanol, valeric acid, toluene, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzene, xylene, tetrahydrofuran, dimethyl sulfoxide, dimethyl Formamide, methylcyclohexane, dioxane, acetone, ethyl acetate, butyl acetate, methyl isobutyryl ketone, diethyl ether, t-butyl methyl ether, acetylacetone, di Sobuchirirumetan, dipivaloylmethane, octyl acid, and propylene glycol monomethyl ether. These solvents may be used alone or in combination of two or more. Further, the concentration of the solution is not particularly limited.

The oxidizing substance used in step A is not particularly limited as long as it has the property of burning (oxidizing) an organometallic compound, and oxygen, oxygen and other gases (for example, inert gas such as nitrogen and argon) Mixed gas in which oxygen is mixed in an arbitrary ratio), air, water, nitrous oxide, and the like. These oxidizing substances may be used alone or in combination of two or more.

In the process A, as a spraying method (spraying method), conventionally known methods such as a two-fluid nozzle, an ultrasonic nozzle, a piezo nozzle, a thermal head nozzle, and an electrostatic spray nozzle can be used. The spraying conditions are not particularly limited, and the spraying amount, the size of the sprayed mist particles, the spraying time, etc. can be appropriately selected according to the purpose, and the nozzle type (caliber d, number of holes, pattern), input pressure (liquid / liquid) Air) and the like can be selected as appropriate.

In the combustion reaction (oxidation reaction) in the gas phase in the process A, the organometallic compound solution is ejected and vaporized into the reaction space of the high-temperature atmosphere, and the organometallic compound is combusted by the oxidizing substance ejected into the reaction space. (Oxidized). The reaction conditions are not particularly limited as long as the oxidation (combustion) of the organometallic oxide proceeds. The organometallic compound solution and the oxidizing substance may be mixed before combustion, or the organometallic compound solution is heated to a temperature higher than the decomposition temperature of the compound and then released into the oxidizing substance to be mixed with the oxidizing substance. You may burn while.

It is desirable to mix the organometallic compound and the oxidizing substance under conditions such that the mixed state is complete. If the mixing is insufficient, the composition of the obtained composite oxide fine particles may be non-uniform. In addition, when mixing is insufficient and the organometallic compound does not completely burn (oxidize), the quality and particle size are not stabilized due to the remaining of unreacted substances and the fusion of fine particles due to the longer reaction time. The particle size may also increase.

The amount of the oxidizing substance used is preferably 0.5 to 40 times mol, more preferably 1 to 30 times mol, and still more preferably 1 to 20 times mol of the amount of oxygen for complete combustion (complete oxidation) of the organometallic compound. If it is less than 0.5 times mol, fine particles may aggregate. If it exceeds 40 moles, the combustion (oxidation) reaction may become unstable. Further, this is not the case when the oxidizing substance plays the role of a cooling gas or when the apparatus is large.

The combustion temperature (oxidation reaction temperature) in step A is preferably 400 ° C. or higher, particularly preferably in the range of 500 to 10,000 ° C. If it is lower than 400 ° C, unreacted raw materials may remain. Further, if the combustion temperature is too high, problems such as enlarging the generated particle diameter, deterioration of the material of the apparatus, and mixing of impurities may occur. The reaction time may be appropriately adjusted within a range in which combustion (oxidation) proceeds and desired fine particles are generated.

As a heat source (heating means) for creating a reaction space in a high temperature atmosphere, a plasma generator can be suitably used. For example, a discharge gas (argon gas and a mixed gas of helium gas, hydrogen gas, nitrogen gas, etc.) is used. You can use the equipment supplied. The plasma temperature can be controlled by changing the composition of the supplied gas. In addition, a combustion burner, a high-frequency heating device, an infrared heating device, an electric heater, a heating medium heating device, or the like can also be used as a heating means, and the combustion reaction can proceed.

(Process B)
Subsequently, a cooling process is performed on the fine particles generated in the process A. The cooling step can be performed by a cooling means such as a known indirect cooling means or direct cooling means. As the indirect cooling means, a refrigerant cooling device for disposing a jacket for refrigerant (water, etc.) and cooling from the outside of the reaction vessel, and as the direct cooling means, cooling gas (oxygen gas, etc.) is provided inside the reaction vessel. And a cooling gas spraying device for spraying a liquid (such as water) into the reaction vessel.

A specific example of the method for producing the composite oxide fine particles is a method using a flash vapor deposition method (FCM). In FCM, a raw material (organic metal compound solution) vaporized with high energy such as plasma and a reaction gas containing a cooling gas are allowed to flow into a reaction space in a high temperature atmosphere, and a combustion reaction (oxidation reaction) proceeds by heat treatment. In this method, particles are produced and the produced particles are instantaneously cooled to produce fine particles (nanoparticles).

The production of composite oxide fine particles by the instantaneous gas phase generation method can be performed using, for example, an FCM apparatus (FCM-MINI or the like) manufactured by Hosokawa Micron. Specifically, an FCM apparatus is used to quantitatively supply a mixture of an organometallic compound solution and an oxidizing substance to a combustion apparatus such as a tubular electric furnace (spray method or the like), and the mixture is contained in the combustion apparatus. The composite oxide fine particles are generated by being heated to become gaseous, and the gaseous mixture burns. The produced complex oxide fine particles are collected by a collector or the like. Examples of the FCM device include those described in JP-A-2005-218937 and JP-A-2008-208195.

The composite oxide fine particles of the present invention can be expected to be applied to various applications, and among them, can be suitably used for optical materials. Examples of the optical material include those containing the composite oxide fine particles and a curable resin (a resin having a curable functional group). The compounding amount of the composite oxide fine particles is preferably 10 to 900 parts by weight, and more preferably 40 to 250 parts by weight with respect to 100 parts by weight of the curable resin. If it exceeds 900 parts by mass, it becomes a poorly cured film, and if it is less than 10 parts by mass, the refractive index tends to decrease.

The refractive index of the material when applied to an optical material is not particularly limited, but is preferably 1.60 or more, and more preferably 1.65 or more.

Examples of the curable resin include a thermosetting resin and a photo-curable resin. Specifically, epoxy-based, silicone-based, acrylic-based, urethane-based, ester-based, urethane acrylate-based, silicone acrylate-based, epoxy acrylate-based resins. , Ester acrylate-based, polyamide-based, polyimide-based, polycarbonate-based and phenol-based resins.

Examples of the epoxy resins include bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, glycidyl ether type epoxy resins, glycidyl amine type epoxy resins, Use naphthalene type epoxy resin, biphenyl type epoxy resin, stilbene type epoxy resin, triphenolmethane type epoxy resin, phenol aralkyl type epoxy resin, naphthol type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, etc. Can do.

Examples of the silicone resin include those of condensation reaction system, addition reaction system, radical reaction system, ultraviolet ray or electron beam curing system. Examples of the silicone resin of the above condensation reaction system include those in which a polydimethylsiloxane having a terminal OH group and a polydimethylsiloxane having a -H group at the terminal are subjected to a condensation reaction using an organotin catalyst to form a three-dimensional crosslinked structure. . Examples of the addition reaction type silicone resin include those in which a polydimethylsiloxane having a vinyl group introduced at its terminal and hydroxypolydimethylsiloxane are subjected to an addition reaction using a platinum catalyst to form a three-dimensional crosslinked structure. Examples of the ultraviolet curable silicone resin include those that use the same radical reaction as that of silicone rubber crosslinking, and those that are photocured by introducing an acrylic group.

A conventionally well-known thing can be used as acrylic resin, For example, a polyol acrylate resin etc. can be used conveniently. Examples of polyol acrylate resins include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and alkyl-modified dipentaerythritol pentaacrylate. And resins such as ethylene glycol (meth) acrylate, polyethylene glycol di (meth) acrylate, and glycerin tri (meth) acrylate. Conventionally known photoreaction initiators and / or photosensitizers can be added to these resins.

Urethane resins include various urethane resins (ester urethane resins, ether urethane resins, carbonate urethanes) obtained by reacting diisocyanate compounds with diol compounds such as polyether diols, polyester diols, and polycarbonate diols. Resin, etc.).

Specific examples of ester resins include polyethylene terephthalate, polybutylene terephthalate, and other homopolyesters, polyethylene terephthalate / isophthalate, polyethylene terephthalate / sebacate, polyethylene terephthalate / adipate, polytetramethylene terephthalate / isophthalate, and others. Examples include copolyester.

Examples of urethane acrylate resins include polyol resins such as polyester polyol, polyether polyol, acrylic polyol, epoxy polyol, polybutadiene polyol, polycaprolactone polyol, and urethane polyol, and hexamethylene diisocyanate, xylylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate. It is obtained by reacting a product obtained by reacting an isocyanate monomer or prepolymer such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate and the like with an acrylate monomer having a hydroxyl group. Can be mentioned.

Examples of the silicone acrylate resin include a reaction product of an acrylate compound and an alkoxy group-containing silane compound. Here, as the acrylate compound, there is a monomer or polymer containing two or more functional groups selected from acryloxy group and methacryloxy group. Specifically, 1,6-hexanediol diacrylate, 1,4-butanedioldi Acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, 1,4-butanediol dimethacrylate, poly (butanediol) diacrylate, tetraethylene glycol diacrylate Examples include methacrylate, 1,3-butylene glycol diacrylate, and triethylene glycol diacrylate. Examples of alkoxy group-containing silane compounds include monomethoxytrimethylsilane, dimethoxydimethylsilane, trimethoxymethylsilane, monoethoxytriethylsilane, diethoxydiethylsilane, triethoxyethylsilane, monopropoxytripropoxysilane, and dipropoxydipropylsilane. Etc.

Examples of the epoxy acrylate resins include those obtained by reacting an epoxy resin with (meth) acrylic acid. Specifically, a bisphenol A type epoxy (meth) acrylate obtained by reacting a bisphenol A type epoxy resin with (meth) acrylic acid, and a cresol novolac type epoxy obtained by reacting a cresol novolac type epoxy resin with (meth) acrylic acid (meth ) Acrylate resin, and glycerol type epoxy (meth) acrylate resin obtained by reacting glycerol polyglycidyl ether with (meth) acrylic acid.

Examples of ester acrylate resins include those obtained by reacting polyester polyols with acrylate monomers having a hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and the like.

Examples of the polyamide resin include polyamide 6, polyamide 66, polyamide 46, polyamide 11, polyamide 12, polyamide MXD6, polyamide 6T copolymer, polyamide 9T, polyamide 612, and copolymers thereof.

Examples of the polyimide resin include polymers having an imide group in the structure such as polyimide, polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, polysiloxaneimide, and the like.

Examples of the polycarbonate-based resin include aromatic polycarbonates based on bisphenols such as bisphenol A-type polycarbonate resins, and aliphatic polycarbonates such as diethylene glycol bisallyl carbonate.

Examples of phenolic resins include novolac type phenolic resins, resol type phenolic resins, and resol type xylene resins. Specifically, alkylated (methyl, ethyl, propyl, isopropyl, butyl) phenol, p-tert-amylphenol, 4,4′-sec-butylidenephenol, p-tert-butylphenol, o-, m- or Formaldehyde condensation such as p-cresol, p-cyclohexylphenol, 4,4'-isopropylidenephenol, p-nonylphenol, p-octylphenol, 3-pentadecylphenol, phenol, phenyl-o-cresol, p-phenylphenol, xylenol Things.

Optical material applications using the composite oxide fine particles include optical lenses (glass lenses, Fresnel lenses, pick-up lenses for information recording equipment such as CDs and DVDs, lenses for photographing equipment such as digital cameras), optical prisms, and light guides. Examples thereof include a high refractive index optical member such as a waveguide, an optical fiber, a thin film molding, an optical adhesive, a diffraction grating, a light guide plate, a liquid crystal substrate, a light reflection plate, and an antireflection material. Specifically, it can be suitably used as an optical lens having a high refractive index layer formed by coating the optical material. It can also be used for various display materials, image sensors, and optical semiconductor elements such as light emitting diodes.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following examples, composite oxide fine particles were produced using FCM-MINI manufactured by Hosokawa Micron. Further, the BET equivalent particle diameter is a value calculated from a BET specific surface area measured using a Nippon Bell specific surface area measuring device BELSORP mini II.

Example 1
A mixed solution of 9.9 g of titanium tetra-2-ethylhexoxide and 5.6 g of niobium ethoxide was diluted with 24.5 g of mineral spirits, and a raw material solution having a metal concentration of 6.2% was placed in a nitrogen atmosphere. The solution was fed into a 2,000 ° C. burner flame at a rate of 2.4 g / min, and sprayed with 9.0 L / min of oxygen. A combustion reaction (oxidation reaction) was performed for 700 seconds, and the reaction mixture was instantaneously cooled to obtain a titanium-niobium composite oxide (Ti _0.50 Nb _0.50 O ₂ ) with a yield of 98% by mass. The BET equivalent particle size (primary particle size) measured by the BET method was 12 nm.

(Examples 2 to 5)
Except for adjusting the titanium solution and the niobium solution so that the content ratios of Ti and Nb were 70/30, 90/10, 94/6, and 98/2, the titanium-niobium composite oxide (Ti _0.70 Nb _0.30 O ₂ , Ti _0.90 Nb _0.10 O ₂ , Ti _0.94 Nb _0.06 O ₂ , and Ti _0.98 Nb _0.02 O ₂ ). The BET equivalent particle diameter (primary particle diameter) measured by the BET method was 12 nm, 16 nm, 16 nm, and 20 nm, respectively.

(Example 6)
A raw material solution in which a mixed solution of 48.1 g of titanium tetra-2-ethylhexoxide and 4.1 g of tantalum butoxide was diluted with 27.8 g of mineral spirit to a metal concentration of 6.9% was placed in a nitrogen atmosphere, The solution was fed into a 2,000 ° C. burner flame at a rate of 2.8 g / min and sprayed with 9.0 L / min of oxygen. A combustion reaction (oxidation reaction) was performed for 1,320 seconds, and the reaction mixture was instantaneously cooled to obtain a titanium tantalum composite oxide (Ti _0.92 Ta _0.08 O ₂ ) with a yield of 78% by mass. The BET equivalent particle size (primary particle size) measured by the BET method was 19 nm.

X-ray diffraction of the composite oxide fine particles prepared in each example was measured, and it was confirmed that Nb or Ta was dissolved in the TiO ₂ crystal. Incidentally, the X-ray diffraction pattern of _Ti 0.90 _{Nb 0.10} O ₂ nanoparticles prepared in Example 3 in Figure 1.

[Evaluation]
The following evaluation was performed about each composite oxide fine particle obtained in the Example. In addition, the evaluation using the commercially available titanium oxide microparticles | fine-particles (BET conversion particle size 25nm) obtained by the combustion method as the comparative example 1 was also performed, and the result was shown to Tables 1-3.

(Light resistance test (particles))
5 mg of each fine particle was added to 50.0 g of 20 ppm methylene blue aqueous solution and stirred for 5 minutes, and then the liquid was transferred to a petri dish and covered. While stirring the liquid, UV light having an intensity of 40 mW / cm ² was irradiated with “UVL-1500M2-N1” manufactured by Ushio Electric Co., Ltd., sampled after irradiation for 10 minutes, and absorbance at a wavelength of 667 nm was measured with a spectrophotometer. It was measured. Absorbance remaining rate (methylene blue dye remaining rate) was calculated when the pre-irradiation was 100%, and it was determined that the smaller the decrease, the lower the photoactivity (better light resistance).
○: Dye remaining ratio is 50% or more Δ: Dye remaining ratio is 30% or more and less than 50% x: Dye remaining ratio is less than 30%

(Refractive index measurement)
Fine particles, acrylic resin (TMPTA (trimethylolpropane triacrylate): “M-309” manufactured by Toa Gosei Co., Ltd.) or urethane acrylate resin (“NK Oligo U-15HA” manufactured by Shin-Nakamura Chemical Co., Ltd.) Are mixed at the compounding ratios shown in Tables 2 and 3, and 5% by mass of “Irgacure 907” manufactured by Ciba Specialty Chemicals Co., Ltd. is added as an initiator with respect to the amount of acrylic resin or urethane acrylate resin. The solution was spin-coated on a Si wafer substrate at a speed of 1,000 rpm, and after prebaking at 90 ° C. for 2 minutes, a cured film having a thickness of about 0.1 μm was produced by UV irradiation at about 1,000 mJ. Using the cured film, the refractive index was measured by irradiating light having a wavelength of 633 nm with an automatic ellipsometer “DHA-XA2 / S6” manufactured by Mizoji Optical Co., Ltd.

(Light resistance test (thin film))
A cured film (thin film) produced by the same method as the refractive index measurement was submerged in 25.0 g of a 20 ppm methylene blue aqueous solution, and while stirring the solution, 40 mW / w was applied by “UVL-1500M2-N1” manufactured by Ushio Electric Co., Ltd. The sample was irradiated with UV light having an intensity of cm ² , sampled after 30 minutes, and the absorbance at a wavelength of 667 nm was measured with a spectrophotometer. Absorbance remaining rate (methylene blue dye remaining rate) was calculated when the pre-irradiation was 100%, and it was determined that the smaller the decrease, the lower the photoactivity (better light resistance).
○: Dye remaining rate is 80% or more Δ: Dye remaining rate is 70% or more and less than 80% x: Dye remaining rate is less than 70%

From the light resistance evaluation of the fine particles in Table 1, it was revealed that the nanoparticles in which Nb or Ta was dissolved in the TiO2 crystal can significantly improve the light resistance as compared with the titanium oxide nanoparticles. In addition, excellent light resistance was obtained even with a composite material in which nanoparticles were dispersed in a resin, and at the same time, a high refractive index unique to titanium oxide could be sufficiently maintained. Furthermore, the results of the light resistance test of Table 2 showed that photoactivity can be suppressed while maintaining the crystal form of TiO ₂ (maintaining a high refractive index) by using a complex oxide of Nb and Ta. . This is considered to be due to the fact that Nb and Ta are not pure TiO ₂ crystals but have Nb or Ta in the crystal structure, suggesting that Nb or Ta is dissolved in the TiO ₂ crystals. ing.

In addition, since the composite materials produced in the examples also have high transparency, application to optical materials can be sufficiently expected.

Claims (10)

Composite oxide fine particles of titanium and niobium and / or tantalum having a BET equivalent particle size of 100 nm or less. 2. The composite oxide fine particle according to claim 1, wherein a content ratio of the titanium to the niobium and / or the tantalum is 99.9 / 0.1 to 0.1 / 99.9. 2. The composite oxide fine particle according to claim 1, wherein a content ratio of the titanium to the niobium and / or the tantalum is 99.9 / 0.1 to 70/30. 2. The composite oxide fine particle according to claim 1, wherein a content ratio of the titanium to the niobium and / or the tantalum is 99.9 / 0.1 to 90/10. The composite oxide fine particles according to any one of claims 1 to 4, produced by a combustion method. 5. The method according to claim 1, comprising a step A in which an organic titanium compound solution, an organic niobium compound solution and / or an organic tantalum compound solution are sprayed in the presence of an oxidizing substance and burned in a gas phase, and a cooling step B. A method for producing the composite oxide fine particles according to claim 1. The composite oxide fine particle production according to claim 6, wherein the organic titanium compound solution, the organic niobium compound solution and / or the organic tantalum compound solution placed in a nitrogen atmosphere are sent to the combustion field of the step A. Method. An optical material comprising the composite oxide fine particles according to claim 1 and a curable resin. The curable resin is epoxy resin, silicone resin, acrylic resin, urethane resin, ester resin, urethane acrylate resin, silicone acrylate resin, epoxy acrylate resin, ester acrylate resin, polyamide resin, polyimide 9. The optical material according to claim 8, wherein the optical material is at least one selected from the group consisting of a series resin, a polycarbonate series resin, and a phenol series resin. An optical lens having a high refractive index layer formed by coating the optical material according to claim 8 or 9.

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