JP2008239462A - Metal oxide fine particle dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal oxide fine particle dispersion having a high refractive index in spite of a large half bandwidth of X-ray diffraction and also having reduced photocatalytic activity. <P>SOLUTION: The metal oxide fine particle dispersion has a half bandwidth of an X-ray diffraction peak of ≥3° and a refractive index of ≥2.0. A metal constituting the metal oxide fine particle may include one of titanium, zirconium, hafnium, barium and tin. The metal oxide fine particle may be one of a titanium oxide, zirconium oxide, a multiple oxide of titanium and zirconium and a multiple oxide of titanium and tin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal oxide fine particle dispersion having a high refractive index and a reduced photocatalytic activity in spite of a large half width of X-ray diffraction.

It is known that metal oxide fine particles having a particle size of 50 nm or less exhibit several characteristics different from particles having a larger particle size because the surface area per unit volume is very large. For example, it is known that the melting point decreases when the particle size is 50 nm or less, and the sintering temperature can be lowered. Further, when the particle size is 50 nm or less, the transparency to light is high, and in particular, in the single nano region, the dispersion is at a level that can be said to be almost transparent. Such a transparent dispersion can be widely used in optical filters, paints, fibers, cosmetics, plastic lenses, and the like, and can exhibit physical properties different from those of conventional ones without impairing transparency.
In particular, plastic lenses are lighter and harder to break than inorganic materials such as glass, and can be processed into various shapes. Therefore, plastic lenses have rapidly spread not only to spectacle lenses but also to optical materials such as portable camera lenses and pickup lenses in recent years. It's getting on.
Accordingly, it is required to increase the refractive index of the material itself for the purpose of reducing the thickness of the lens and the size of the imaging device. For example, a technique for introducing sulfur atoms into a polymer (Patent Document 1). 2 and 2), a technique for introducing a halogen atom or an aromatic ring into a polymer (see Patent Document 3), and the like have been actively studied.

  However, since it is difficult to increase the refractive index only with organic substances, a method for producing a high refractive index material by dispersing inorganic fine particles having a high refractive index in a resin matrix is disclosed (see Patent Document 4). . Thus, when the inorganic fine particles are reduced to a single nano-size, the surface area is relatively increased, so that the refractive index of the particles is lowered and it is difficult to obtain a desired refractive index. Conversely, in order to increase the refractive index, in order to increase crystallinity, firing at a high temperature or increasing the particle size is necessary, and particles with a small size and a high refractive index in a region close to a single nanosize are desired. It was.

  In addition, an organic-inorganic hybrid material having a high refractive index requires the introduction of an inorganic material mainly composed of titanium oxide having a high refractive index. However, titanium oxide is known for its high photocatalytic activity. Even when it is a composite oxide fine particle with other metal oxides, if it is dispersed in the base organic material, the surroundings of the particle are generated by holes generated by light irradiation. The organic matter is decomposed or modified, resulting in serious problems such as yellowing, increased haze, and brittle deterioration. In order to solve these problems, it is necessary to reduce the photocatalytic activity of titanium oxide or composite oxide fine particles containing titanium oxide.

JP 2002-131502 A Japanese Patent Laid-Open No. 10-298287 JP 2004-244444 A JP 2003-73599 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a metal oxide fine particle dispersion in which the photocatalytic activity is reduced because the metal oxide fine particles themselves are dispersed in a solvent without being modified with an organic substance.

Means for solving the problems are as follows. That is,
<1> A metal oxide fine particle dispersion having a half width of an X-ray diffraction peak of 3 ° or more and a refractive index of 2.0 or more.
<2> The metal oxide fine particle dispersion according to <1>, wherein the metal constituting the metal oxide fine particles contains any of titanium, zirconium, hafnium, barium, and tin.
<3> The metal oxide fine particles according to any one of <1> to <2>, wherein the metal oxide fine particles are any one of titanium oxide, zirconium oxide, a composite oxide of titanium and zirconium, and a composite oxide of titanium and tin. It is a metal oxide fine particle dispersion.
<4> The metal oxide fine particle dispersion according to any one of <1> to <3>, wherein a particle size determined by a TEM method is 0.5 nm to 20 nm.
<5> The metal oxide fine particle dispersion according to any one of <1> to <4>, wherein the particle size determined by a TEM method is 0.5 nm to 10 nm.

  According to the present invention, the conventional problems can be solved, and despite having a large half-value width of X-ray diffraction, it has a high refractive index, is optically transparent, has a high refractive index, and has a photocatalytic activity. A reduced metal oxide fine particle dispersion can be provided.

(Metal oxide fine particle dispersion)
The metal oxide fine particle dispersion of the present invention is optically transparent but has a high refractive index, the half-value width of the X-ray diffraction peak is 3 ° or more, and the refractive index is 2.0 or more. It is characterized by that.

The full width at half maximum of the X-ray diffraction peak is 3 ° or more, preferably 3.5 ° or more, and more preferably 4.0 ° or more. If the half width is less than 3 °, transparency may be impaired when dispersed in an organic material.
The refractive index is 2.0 or more, preferably 2.2 or more.

-Measurement of half-width of X-ray diffraction peak-
When the metal oxide fine particles are a dispersion, the X-ray diffraction measurement is performed by evaporating the solvent and taking out the solid content, and then grinding the powder with a mortar to prepare a powder. As the X-ray source, copper Kα ray, wavelength 1.5418１．５ is used. This measurement gives an X-ray profile of the powder. On the other hand, a specimen in which the crystallization of the metal oxide fine particles has been sufficiently progressed by firing is prepared, and this is separately measured, and the X-ray profile is similarly obtained. The full width at half maximum of the X-ray peak of the metal oxide fine particle of the present invention corresponding to the peak that can be confirmed to be a single peak in the X-ray diffraction profile of the sample is obtained. The value which shows the largest half value width in this is defined as the half value width of the X-ray diffraction peak of this invention. The half-width refers to the peak width at a position half the length of the X-ray diffraction profile obtained by subtracting the background and dropping the perpendicular from the peak top.

-Measurement of refractive index-
The refractive index of the particles in the metal oxide fine particle dispersion of the present invention is, for example, after mixing a thermoplastic resin whose refractive index is known and a metal oxide whose mass is measured, into a transparent pellet having an appropriate thickness. After molding, the refractive index of the pellet is measured to obtain the refractive index of the metal oxide fine particles. The refractive index measurement can be obtained by, for example, an Abbe refractometer, and for example, DR-M4 manufactured by Atago Co., Ltd. can be used. The wavelength for measuring the refractive index is 589 nm.

  The particle size determined by the TEM method of the metal oxide fine particle dispersion of the present invention is preferably from 0.5 nm to 20 nm, more preferably from 0.5 nm to 10 nm. When the particle size exceeds 20 nm, the Rayleigh scattering is large and the surface area / volume ratio is small, so that the characteristics of the fine particles may be difficult to be exhibited.

-Particle size measurement by transmission electron microscope (TEM) method-
The particle size by the TEM method is to measure the particle size by dropping the obtained metal oxide fine particles on a carbon-deposited copper mesh (microgrid) and observing the dried one with a transmission electron microscope. Can do. Specifically, after exposing an observation image obtained by a transmission electron microscope to a photographic negative or taking it in as a digital image, a print having a size capable of sufficiently observing the particle size is created. The particle size can be obtained from this print. Since the TEM image is a two-dimensional image, it is difficult to obtain an accurate particle diameter particularly in the case of an amorphous particle. However, in the present invention, the diameter of a circle equal to the projected area of the particle obtained as a two-dimensional image ( The equivalent circle diameter) is defined as the particle size. In the present invention, the equivalent circle diameter of 300 or more particles is thus measured, and the average value is defined as the particle size by the TEM method.

  The metal oxide fine particle dispersion of the present invention is not particularly limited as long as it satisfies the requirements for the half width of the X-ray diffraction peak and the refractive index, and includes all of the metal oxide fine particles, but at least the metal oxide fine particles And a strong acid are dispersed in an aqueous solution containing an alcohol, and contain a carboxylic acid compound and, if necessary, other components.

<Metal oxide fine particles>
There is no restriction | limiting in particular as a metal which comprises the said metal oxide microparticles | fine-particles, According to the objective, it can select suitably, A metal may be individual and 2 or more types of metals may be compounded. In addition, the core portion and the shell portion may constitute a layered structure in which constituent metals are different. The layered structure may be three or more layers.
The phrase “mainly composed of metal oxide fine particles” means that 30% or more of metal atoms in the metal oxide fine particles are occupied.

Examples of the metal oxide constituting the metal oxide fine particles include titanium oxide, zirconium oxide, composite oxide of titanium and zirconium, composite oxide of titanium, zirconia and hafnium, composite oxide of titanium and barium, titanium and aluminum. Composite oxide of titanium, composite oxide of titanium, silicon, composite oxide of titanium, silicon, and aluminum, composite oxide of titanium, zirconium, and aluminum, composite oxide of titanium, zirconium, and silicon, titanium, zirconium, aluminum, and silicon A composite oxide of titanium, tin, a composite oxide of titanium, zirconia, and tin. Among these, titanium oxide, zirconium oxide, composite oxide of titanium and zirconium, and composite oxide of titanium and tin are particularly preferable.
The metal oxide may contain other metal elements as dopants. The kind of metal element to be added and the amount added can be appropriately selected depending on the purpose. For example, at least one metal element selected from Fe, Co, Ni, Cu, Zn, Nb, Y, Rh, Pb, Ag, Ta, Pt, and Au can be doped. The content of these metal elements is preferably 0.1 atomic percent to 20 atomic percent, more preferably 0.1 atomic percent to 10 atomic percent, and still more preferably 0.1 atomic percent to 5 atomic percent.

  The metal oxide fine particles preferably have crystallinity. Here, having crystallinity means that when the solvent is evaporated from the metal oxide fine particle dispersion and the solid content is taken out, a powder is prepared, and when X-ray diffraction measurement is performed on this powder, the crystal peak is Say what is observed. As the X-ray source, copper Kα ray, wavelength 1.5418４ is used. The observation of a crystal peak means that a peak within a half width of 10 ° is obtained, and in this case, it is defined as having crystallinity. In the case of a broad peak exceeding a half-value width of 10 °, it is defined as having no crystallinity.

  The metal oxide fine particle dispersion is preferably a dilute solution having a content of metal oxide fine particles of less than 0.1% by mass from the viewpoint of suppressing the aggregation. From the point of dispersing the solution, a too dilute solution imposes a load on the subsequent thickening step. Therefore, the content of the metal oxide fine particles contained in the dispersion is more preferably 0.1% by mass or more and 20% by mass or less.

<Dispersion solvent>
As the dispersion solvent, alcohol and water are used. The alcohol is particularly important at the start of hydrolysis of the metal alkoxide as the metal oxide precursor. The water serves as a reaction after the start of hydrolysis and as a dispersion medium for the metal oxide.
The content of the alcohol dispersion is preferably 6% by volume to 60% by volume, and more preferably 10% by volume to 50% by volume. Outside this range, depending on the preparation conditions of the dispersion, the dispersion may be in the form of a gel, or the particles may aggregate to fail to form a dispersion.

The alcohol is preferably a lower alcohol compatible with water, such as methanol, ethanol, propanol, isopropanol, ethylene glycol, methoxyethanol, ethoxyethanol, methoxypropanol, and ethoxypropanol. Butanol can be used depending on the application. is there. The alcohol preferably coexists when the metal alkoxide is hydrolyzed, and preferably coexists after the hydrolysis starts and before being dispersed in water.
The water is preferably deionized water containing no inorganic ions. The content in the final dispersion varies depending on the type and size of the metal oxide fine particles to be produced, and cannot be defined unconditionally, but it is preferable that the water occupies 40% or more of the final dispersion volume.

<Strong acid>
The strong acid means an acid that is almost completely ionized in an aqueous solution such as HCl, and does not include an acid that is slightly ionized in an aqueous solution such as acetic acid.
The strong acid is preferably used as one that promotes the hydrolysis reaction of the metal alkoxide as the metal oxide precursor. For example, nitric acid, perchloric acid, hydrochloric acid, HBr water, HI water, HPF ₆ , HClO ₃ , HIO _{4 and the} like.
As the strong acid, it is preferable that the anion when dissociated is structurally bulky because the effect of increasing the transparency of the final sol is large.

-Strong acid containing bulky anions-
It is considered that the bulky anion has few hydrated water molecules, and can reduce the viscosity of the metal oxide fine particle dispersion and suppress aggregation of the metal oxide fine particles. Mechanically, the effect of suppressing aggregation by a strong acid having a bulky structure decreases as the alcohol content in the solvent increases.
The acid compound containing a bulky anion includes an anion having a B value of −0.01 or less in the following formula (1) by Jones and Dole et al.
η = η ⁰ (1 + A√c + Bc) (1)
However, in said Formula (1), (eta) represents the viscosity of a solution, (eta) ⁰ represents the viscosity of a solvent, A and B represent an acid-specific constant, and c represents the concentration of the solution.
Here, the B value relates to the steric bulk of the anion, and the larger the negative B value, the more sterically bulky the anion is (G. Jones and M. Dole J. Am. Chem. Soc., 51 2950 (1929)). Moreover, according to HSAB theory, it means that it becomes soft by becoming three-dimensionally bulky.

Examples of the bulky anion having a B value of −0.01 or less include, for example, Br ⁻ (−0.042), I ⁻ (−0.068), PF ₆ ⁻ (−0.021), ClO ₃ ^−. (−0.024), NO ₃ ⁻ (−0.046), ClO ₄ ⁻ (−0.056), IO ₄ ⁻ (−0.065), and the like. In contrast, Cl ⁻ (−0.007) and F ⁻ (+0.096) having a B value exceeding −0.01 are not included in the bulky anion.
Examples of the acid compound containing a bulky anion include HBr, HI, HPF ₆ , HClO ₄ , HClO ₃ , HNO ₃ , HIO ₄ , or salts thereof. Examples of the salt include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH) _{3, and the} like.

  The content of the strong acid in the metal oxide fine particle dispersion varies depending on the type and size of the metal oxide fine particles to be produced and cannot be specified unconditionally, but is preferably 0.1 mol to 1 mol, preferably 0.2 mol to 0 mol per mol of metal. .9 mol is more preferable.

<Carboxylic acid compound>
The metal oxide fine particle dispersion of the present invention preferably contains a carboxylic acid compound for the purpose of enhancing the dispersibility of the particles. As the carboxylic acid compound, at least one selected from carboxylic acids, salts of carboxylic acids, and carboxylic anhydrides is used.

-Carboxylic acid-
The carboxylic acid is not particularly limited and may be appropriately selected depending on the intended purpose. For example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, capryl Saturated aliphatic carboxylic acids such as acid, capric acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid; acrylic acid, propiolic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid And unsaturated aliphatic carboxylic acids such as lactic acid, tartaric acid, malic acid, citric acid and the like. These may be used individually by 1 type and may use 2 or more types together.
The content of the carboxylic acid in the metal oxide fine particle dispersion varies depending on the type and size of the metal oxide fine particles to be produced, and cannot be specified unconditionally, but is preferably 0.15 mol to 3 mol per mol of metal.

-Salt of carboxylic acid-
By dissociating the carboxylic acid salt, substantially the same effect as when the corresponding carboxylic acid is used is recognized.
Examples of the carboxylic acid in the carboxylic acid salt include the same carboxylic acids as those described above.
Examples of the salt of the carboxylic acid salt include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH) _{3, and the} like. Is mentioned.
The content of the carboxylic acid salt in the metal oxide fine particle dispersion varies depending on the type and size of the metal oxide fine particles to be produced, and cannot be specified unconditionally, but is preferably 0.15 mol to 3 mol per mol of metal.

-Carboxylic anhydride-
In the carboxylic acid anhydride, the same effect as that of the corresponding carboxylic acid can be obtained in an aqueous solution of the carboxylic acid anhydride in which two carboxylic acid molecules are condensed by losing one water molecule.
The carboxylic acid anhydride is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, and phthalic anhydride. These may be used individually by 1 type and may use 2 or more types together.
The content of the carboxylic acid anhydride in the metal oxide fine particle dispersion varies depending on the type and size of the metal oxide fine particles to be produced and cannot be defined unconditionally, but is preferably 0.075 mol to 1.5 mol per mol of metal.

<Method for producing metal oxide fine particle dispersion>
The method for producing the metal oxide fine particle dispersion includes a metal oxide fine particle forming step, and further includes other steps as necessary.

-Metal oxide fine particle formation process-
The metal oxide fine particle forming step is a step of forming metal oxide fine particles by mixing at least a metal oxide precursor, a strong acid, and, if necessary, a carboxylic acid compound in an aqueous solution containing an alcohol.

The hydrolysis reaction is initiated by the action of a metal alkoxide as the metal oxide precursor and a strong acid, but the alcohol may be mixed with the metal alkoxide in advance or with a strong acid, and the hydrolysis starts. They may be mixed immediately after being formed, and are preferably present in a system for hydrolyzing the metal alkoxide. The strong acid is preferably such that the anion when dissociated is bulky in structure.
The alcohol, the strong acid, and the carboxylic acid compound can be appropriately selected from those described above.

The metal oxide precursor preferably contains, for example, any one of an organometallic compound, a metal salt, and a metal hydroxide.
The state of the metal oxide precursor may be solid or liquid, but is preferably dissolved in water and can be handled as an aqueous solution.
The metal component of the metal salt corresponds to the metal component of the corresponding metal oxide.
Examples of the metal salts include chlorides, bromides, iodides, nitrates, sulfates, and organic acid salts of desired metals. Examples of the organic acid salt include acetate, propionate naphthenate, octylate, stearate, and oleate.
As the metal hydroxide, for example, amorphous titanium hydroxide obtained by neutralizing an aqueous titanium tetrachloride solution with an alkali solution, zirconium hydroxide, a composite hydroxide of titanium and zirconium, or the like can be used.

Examples of the organometallic compound include metal alkoxide compounds and metal acetylacetonate compounds.
Examples of the metal alkoxide compound include tetraalkoxy titanium and alkoxy zirconium.
Examples of the tetraalkoxytitanium include tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, tetraisobutoxytitanium, tetrakis (2-methylpropoxy) titanium, tetrakispentoxytitanium, tetrakis ( 2-ethylbutoxy) titanium, tetrakis (octoxy) titanium, tetrakis (2-ethylhexoxy) titanium and the like. If the alkoxyl group contained in the tetraalkoxytitanium has too many carbon atoms, hydrolysis may be insufficient. If the alkoxyl group has too few carbon atoms, the reactivity may increase and the reaction control may be difficult. For this reason, tetrapropoxytitanium and tetraisopropoxytitanium are particularly preferred.
Examples of the alkoxyzirconium include methoxyzirconium, ethoxyzirconium, propoxyzirconium, butoxyzirconium, isobutoxyzirconium, kiss (2-methylpropoxy) zirconium and the like. Of these, butoxyzirconium is particularly preferred.
As metal alkoxide compounds other than titanium and zirconium, the metal is hafnium, aluminum, silicon, barium, tin, magnesium, calcium, iron, bismuth, gallium, germanium, indium, molybdenum, niobium, lead, antimony, strontium, tungsten, Yttria and the like are preferable. If necessary, these metal alkoxides can be produced by reacting a metal alkoxide such as potassium alkoxide or sodium alkoxide with a desired metal.

Examples of the metal salts include chlorides, bromides, iodides, nitrates, sulfates, and organic acid salts of desired metals. Examples of the organic acid salt include acetate, propionate naphthenate, octylate, stearate, oleate and the like.
As the metal hydroxide, for example, amorphous titanium hydroxide obtained by neutralizing an aqueous titanium tetrachloride solution with an alkali solution, zirconium hydroxide, a composite hydroxide of titanium and zirconium, or the like can be used.

Specifically as a manufacturing method of the said metal oxide fine particle dispersion, the following aspects are mentioned.
(1) At room temperature, a metal alkoxide compound was mixed with alcohol and stirred for 10 minutes. Then, after adding a strong acid and stirring for 10 minutes, a metal oxide fine particle dispersion can be produced by making a large amount of water act and heat-treating suitably.
In addition, in the above (1), the following production method (1 ′) in which the addition time of the strong acid is changed is also suitable.
(1 ′) A strong acid was added to the alcohol at room temperature, and the mixture was stirred for 10 minutes. Furthermore, after adding a metal alkoxide compound and stirring for 10 minutes, a large amount of water is allowed to act, and a heat treatment is appropriately performed to produce a metal oxide fine particle dispersion.
In addition, in the above (1), the following production method (1 ″) in which alcohol is not allowed to coexist is also preferable.
(1 ″) At room temperature, a strong acid was added to the metal alkoxide compound and stirred for 10 minutes. After that, the alcohol was added and stirred for 10 minutes, and then a large amount of water was allowed to act and the metal oxide was appropriately heated. A fine particle dispersion can be prepared.

In the above (1), (1 ′), and (1 ″), as the metal alkoxide, for example, titanium oxide includes, for example, titanium tetraisopropoxide, titanium tetrabutoxide, titanium tetraproxide, etc. Zirconium oxide Examples thereof include zirconium tetrabutoxide, zirconium tetratertbutoxide, zirconium diethoxide, zirconium tetraisopropoxide and the like.
The alcohol and strong acid can be appropriately selected from those described above, and examples of the alcohol include methanol, ethanol, propanol, isopropanol, ethoxymethanol, ethoxyethanol, and ethoxypropanol. Examples of the strong acid include nitric acid, perchloric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the like, and nitric acid and perchloric acid, in which the anion when dissociated is structurally bulky, are particularly preferable.

  The washing method is not particularly limited as long as excess ions can be removed, and a conventionally known method can be adopted, for example, an ultrafiltration membrane method, a filtration separation method, a centrifugal filtration method, an ion exchange resin. Law.

<Application>
The metal oxide fine particle dispersion of the present invention can be used as a dispersion as it is or after being concentrated, and a binder component (resin component) is added to form a film-forming composition (coating composition). This can be applied to a substrate to form a fine particle dispersion film, or can be similarly incorporated into a binder component (resin component) to form a molding resin composition. Moreover, after removing a solvent by concentration to dryness or centrifugation, it can also be heated and dried and handled as fine particle powder.

  The binder component is not particularly limited and may be appropriately selected depending on the purpose. For example, silicone alkoxide binder, acrylic resin, polyester resin, fluororesin, etc., thermoplastic or thermosetting (thermosetting, Examples include various binder resins such as ultraviolet curable, electron beam curable, moisture curable, and combinations thereof, and organic binders such as natural resins. Examples of the synthetic resin include alkyd resin, amino resin, vinyl resin, acrylic resin, epoxy resin, polyamide resin, polyurethane resin, thermosetting unsaturated polyester resin, phenol resin, chlorinated polyolefin resin, silicone resin, and acrylic silicone. Examples thereof include resins, fluororesins, xylene resins, petroleum resins, ketone resins, rosin-modified maleic acid resins, liquid polybutadiene, and coumarone resins. Examples of the natural resin include shellac, rosin (pine resin), ester gum, cured rosin, decolorized shellac, and white shellac. These may be used individually by 1 type and may use 2 or more types together.

  When the metal oxide fine particles are dispersed in the resin composition, for example, a dispersant, an oil component, a surfactant, a pigment, a preservative, alcohol, water, a thickener, and a humectant are blended as necessary. It can be used in various forms such as dilute solution, tablet, lotion, cream, paste, and stick. The dispersant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a compound having a phosphate group, a polymer having a phosphate group, a silane coupling agent, and a titanium coupling agent. It is done.

  Since the metal oxide fine particle dispersion of the present invention has excellent dispersion stability and a low photocatalyst, it can be suitably used for optical filters, paints, fibers, cosmetics, and lenses.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
140 mL of isopropyl alcohol was added to 88 mL of titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred for 10 minutes while maintaining at 15 ° C. Here, 15 ml of HNO ₃ (60% by mass) was added over 10 minutes with stirring. At this time, the temperature of the solution was controlled to be 15 ° C. After stirring this mixed liquid for 30 minutes, it heated up at 60 degreeC and aged for 30 minutes, and the dispersion of the titanium oxide of Example 1 was obtained.
The obtained titanium oxide fine particle dispersion was mixed with a toluene solution in which “KAYAMER PM-21” manufactured by Nippon Kayaku Co., Ltd. was dissolved in toluene, stirred for 8 hours at 30 ° C., and then the toluene solution was extracted to adjust the concentration. Thus, a toluene dispersion of the titanium oxide fine particles of Example 1 was produced.

<Particle size by transmission electron microscope (TEM) method>
The obtained dispersion of titanium oxide fine particles of Example 1 was dropped onto a carbon-deposited copper mesh (microgrid), dried, observed with a transmission electron microscope, and the image was baked on a photographic negative. A total of 300 particle photographs were obtained by changing the field of view. The images of these photographic negatives were captured using a Carl Zeiss KS300 system, and the equivalent circle diameter of each particle was determined by image processing. The average size of these equivalent circle diameters was 3.1 nm. The results are shown in Table 1.

<Measurement of X-ray diffraction spectrum>
The obtained dispersion of titanium oxide fine particles of Example 1 was measured for an X-ray diffraction spectrum using RINT 1500 (X-ray source: copper Kα ray, wavelength 1.5418 mm) manufactured by Rigaku Corporation. A peak with a full width at half maximum of 3.7 ° was observed around 2θ = 47.5 °. The results are shown in Table 1.

<Measurement of refractive index>
-Synthesis of thermoplastic resin-
Unichemical Co., Ltd. Phosmer PE (trade name) 0.05 g, methyl methacrylate 4.95 g, and azobisisobutyronitrile 0.25 g were added to toluene and polymerized at 70 ° C. in a nitrogen atmosphere. And a thermoplastic resin was synthesized. The refractive index of the resin measured with an Abbe refractometer (manufactured by Atago Co., Ltd., using DR-M4, wavelength 589 nm) was 1.58.
To the prepared thermoplastic resin, the toluene dispersion of titanium oxide fine particles of Example 1 was added so that the solid content of titanium oxide was 7.5% by volume, and the solvent was concentrated and distilled off. Then, compression molding was performed with a pressure of 12 MPa and a time of 2 minutes to obtain a transparent molded body having a thickness of 1 mm. It was 1.64 when the refractive index of the transparent molded object was measured. Therefore, since the sum of (volume fraction of titanium oxide) × (refractive index of titanium oxide) and (volume fraction of resin) × (refractive index of resin) is 1.64, the refractive index of titanium oxide is 2 .4. The results are shown in Table 1.

(Comparative Example 1)
20 ml of HCl (37% by mass) was added to 88 mL of titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) over 10 minutes while stirring. After stirring this mixed liquid for 30 minutes, it heated up at 95 degreeC and ripened for 240 minutes, and the dispersion of the titanium oxide of the comparative example 1 was obtained.
A toluene solution in which the obtained titanium oxide fine particle dispersion and “KAYAMER PM-21” manufactured by Nippon Kayaku Co., Ltd. were dissolved in toluene were mixed and stirred at 30 ° C. for 8 hours, and then the toluene solution was extracted. The titanium oxide fine particle toluene dispersion of Comparative Example 1 was prepared by adjusting the concentration.

<Measurement of X-ray diffraction>
The obtained dispersion of titanium oxide fine particles of Comparative Example 1 was subjected to X-ray diffraction spectrum measurement using RINT 1500 (X-ray source: copper Kα ray, wavelength 1.5418 mm) manufactured by Rigaku Corporation. A peak with a full width at half maximum of 2.1 ° was observed around 2θ = 47.5 °. The results are shown in Table 1.

<Measurement of refractive index>
-Synthesis of thermoplastic resin-
Unichemical Co., Ltd. Phosmer PE (trade name) 0.05 g, methyl methacrylate 4.95 g and azobisisobutyronitrile 0.25 g were added to toluene, and polymerization was performed at 70 ° C. in a nitrogen atmosphere. A thermoplastic resin was synthesized. The refractive index of the resin measured with an Abbe refractometer (manufactured by Atago Co., Ltd., using DR-M4, wavelength 589 nm) was 1.58.
Next, the toluene dispersion of the titanium oxide fine particles of Comparative Example 1 was added to the prepared thermoplastic resin so that the solid content of titanium oxide was 7.5% by volume, and the solvent was concentrated and distilled off. The residue was heat compression molded at 150 ° C., a pressure of 12 MPa, and a time of 2 minutes to produce a transparent molded body having a thickness of 1 mm. It was 1.64 when the refractive index of the transparent molded object was measured. Therefore, since the sum of (volume fraction of titanium oxide) × (refractive index of titanium oxide) and (volume fraction of resin) × (refractive index of resin) is 1.64, the refractive index of titanium oxide is Calculated as 2.4. The results are shown in Table 1.

<Particle size by transmission electron microscope (TEM) method>
The obtained dispersion of titanium oxide fine particles of Comparative Example 1 was dropped onto a carbon-deposited copper mesh (microgrid), dried, observed with a transmission electron microscope, and the image was baked on a photographic negative. A total of 300 particle photographs were obtained by changing the field of view. The images of these photographic negatives were captured using a Carl Zeiss KS300 system, and the equivalent circle diameter of each particle was determined by image processing. The average size of these equivalent circle diameters was 8.3 nm. The results are shown in Table 1.

<Evaluation of photocatalytic properties by methylene blue>
The dispersion of titanium oxide prepared in Example 1 and Comparative Example 1 was diluted to 1% by mass with a dilute nitric acid solution (concentrated nitric acid diluted with 1/100 water). %) Was added. From this, 4 cc was taken out and filled into a Bayer bottle. Using UVLMS-38 manufactured by UVP, 365 nm light was irradiated at a distance of 5 cm for 8 hours. The change in transmittance before and after UV light irradiation of 670 nm absorption of methylene blue was measured. The light absorption of methylene blue was measured by pouring the solution into a quartz cell having an optical path length of 1 cm and using a U-3310 spectrophotometer manufactured by Hitachi, Ltd. The transmittance was expressed as a relative value with the transmittance of methylene blue before irradiation as 100. The results are shown in Table 1.

表１の結果から、実施例１の酸化チタン粒子は、比較例１に比べてＵＶ光照射によるメチレンブルー色素の分解が少なく（透過率が小さく）、光触媒活性が低いことが分かった。

From the results in Table 1, it was found that the titanium oxide particles of Example 1 had less decomposition of methylene blue dye by UV light irradiation (small transmittance) and lower photocatalytic activity than Comparative Example 1.

  Since the metal oxide fine particle dispersion of the present invention has high transparency in the visible range and low photocatalytic activity, it can be widely used for optical filters, paints, fibers, cosmetics, lenses, and the like. In addition, it has little aggregation, has reduced photocatalytic activity, and has a high surface area per volume, so it is also useful as a catalyst material. Furthermore, single particles with low aggregation are very useful as fine particles for drug delivery systems.

Claims (5)

  A metal oxide fine particle dispersion, wherein the half width of the X-ray diffraction peak is 3 ° or more and the refractive index is 2.0 or more.   The metal oxide fine particle dispersion according to claim 1, wherein the metal constituting the metal oxide fine particles contains any one of titanium, zirconium, hafnium, barium and tin.   3. The metal oxide fine particle dispersion according to claim 1, wherein the metal oxide fine particles are any of titanium oxide, zirconium oxide, a composite oxide of titanium and zirconium, and a composite oxide of titanium and tin. .   The metal oxide fine particle dispersion according to any one of claims 1 to 3, wherein a particle size determined by a TEM method is 0.5 nm or more and 20 nm or less.   The metal oxide fine particle dispersion according to any one of claims 1 to 4, wherein a particle size determined by a TEM method is 0.5 nm or more and 10 nm or less.