WO2009151143A1

WO2009151143A1 - Inorganic fine particle dispersion, organic-inorganic hybrid composition, shaped article and optical component

Info

Publication number: WO2009151143A1
Application number: PCT/JP2009/060973
Authority: WO
Inventors: Tetsuo Kawano; Masato Yoshioka; Osamu Sawanobori; Satoshi Yoneyama; Hiroaki Mochizuki; Ichiro Amimori
Original assignee: Fujifilm Corporation
Priority date: 2008-06-13
Filing date: 2009-06-10
Publication date: 2009-12-17
Also published as: JP5701474B2; TW201000202A; JP2009298658A

Abstract

An inorganic fine particle dispersion comprising inorganic fine particles having a particle size of from 1 to 15 nm in a concentration of from 1 to 70% by mass, a chlorine element in a concentration of at most 100 ppm, and at least one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles, is capable of keeping its high transparency even when mixed with a thermoplastic resin to give an organic-inorganic hybrid composition.

Description

DESCRIPTION

INORGANIC FINE PARTICLE DISPERSION, ORGANIC-INORGANIC HYBRID COMPOSITION, SHAPED ARTICLE AND OPTICAL COMPONENT

Technical Field

The present invention relates to an inorganic fine particle dispersion of the invention having a high transparency, an organic-inorganic hybrid composition having high refraction index and a high transparency, a method for producing the organic-inorganic hybrid composition, and a shaped article and optical component comprising the composition. In detail, present invention relates to an optical component such as optical materials (for example, eyeglass lens, lenses for optical appliances, lenses for opto-electronics, lenses for laser, pick-up lenses, lenses for in-vehicle camera, lenses for portable camera, lenses for digital camera, and lenses for OHP) .

Background Art

Active research works have been made recently on optical materials. In the field of lens materials, in particular, the development of materials with good refraction properties, transparency, ready moldability, lightweight properties, chemical resistance and solvent resistance has been desired strongly.

Compared with inorganic materials such as glass, plastic lens is of such a lightweight that it hardly cracks, so such lens can be processed in various shapes. Therefore, plastic lens is rapidly spreading into not only eyeglass lens but also optical materials such as lenses for portable camera and pick-up lenses .

Following the spread, it is needed now to prepare materials per se with large refractive indices for the purpose of preparing thin lenses. For example, the technique for introducing sulfur atom into polymers (see for example JP-A 2002-131502 and JP-A 10-298287) , the technique for introducing halogen atoms and aromatic rings into polymers (see for example JP-A 2004-244444) and the technique for utilizing a co-polymer of an indene derivative and a vinyl monomer (see for example JP-A 2001-89537) have been researched actively. However, not any plastic material with a sufficiently large refractive index and good transparency, which can be a glass alternative, has been developed yet.

It is difficult to increase the refractivity of a plastic material merely by adding a specific organic substance thereto, and therefore some trials have been made of producing a high-refractivity material by dispersing an inorganic oxide having a high refractive index to a resin matrix (see JP-A 61-291650 and JP-A 2003-73564) . In this case, for reducing the transmitted light attenuation through Rayleigh scattering, it is desirable to uniformly disperse inorganic oxide particles having a particle size of at most 15 nm in a resin matrix. However, the inorganic oxide particles are hydrophilic on their surfaces and are difficult to uniformly disperse in a resin matrix, therefore having a problem in that the transparency of the organic-inorganic hybrid composition to be obtained tends to lower. To solve the problem, proposed are a technique of using tetragonal zirconia particles (see JP 2007-99931) and a technique of modifying the surfaces of oxide particles with a surface modifier such as a silane coupling agent, a modified silicone or a surfactant (see JP-A 2007-217242, JP-A 2007-262252 and JP-A 2007-119617) .

However, limitation of the type of inorganic fine particles to tetragonal zirconia particles is problematic in that the use of the organic-inorganic hybrid composition is thereby limited. When the transparency of optical materials could be increased by some easier and simpler operation not according to the surface modification method of using a surface modifier such as a silane coupling agent, a modified silicone or a surfactant, it is favorable since the production process could be more simplified.

Disclosure of the Invention

The invention has been made in consideration of the above-mentioned situation, and its object is to provide an inorganic fine particle dispersion which, when mixed with a thermoplastic resin and dried, gives an organic-inorganic hybrid composition having a sufficient transparency. Another object of the invention is to provide a shaped article and an optical component having a high refractivity and transparency by use of the inorganic fine particle dispersion, which is free from the risk of mold corrosion in molding.

The present inventors have assiduously studied for the purpose of attaining the above-mentioned object and, as a result, have found that, when an inorganic fine particle dispersion comprising a chlorine element and an acid of which the content is controlled to fall within a specific range is used, then a shaped article having a high refractivity and transparency can be produced with little risk of mold corrosion, and have completed the invention. Specifically, as a means for solving the problems, the inventors have provided the invention described below.

[1] An inorganic fine particle dispersion comprising inorganic fine particles having a particle size of from 1 to 15 nm in a concentration of from 1 to 70% by mass, a chlorine element in a concentration of at most 100 ppm, and at least one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles. [2] The inorganic fine particle dispersion of [1] , wherein the organic acid is acetic acid.

[3] The inorganic fine particle dispersion of [1] or [2], wherein the concentration of the organic acid is at most 1% by mass.

[4] The inorganic fine particle dispersion of any one of [1] to [3] , wherein the inorganic fine particles are of zirconium oxide, titanium oxide or their mixture. [5] The inorganic fine particle dispersion of any one of [1] to [4] , wherein the dispersion comprises at least one dispersion medium selected from the group consisting of methanol, ethanol, 1-butanol, isopropanol, N,N-dimethylacetamide (DMAc), toluene, anisole, N-methyl-2-pyrrolidone, ethyl acetate and butyl acetate . [6] The inorganic fine particle dispersion of any one of [1] to [5] , wherein the inorganic fine particles are surface-modified with an aromatic carboxylic acid. [7] The inorganic fine particle dispersion of [6], wherein the aromatic carboxylic acid is at least one compound selected from the group consisting of 4-n-propylbenzoic acid, diphenylacetic acid and 4-phenylbenzoic acid. [8] A method for producing an organic-inorganic hybrid composition comprising mixing a thermoplastic rein and an inorganic fine particle dispersion of any one of [1] to [7] . [9] An organic-inorganic hybrid composition comprising a thermoplastic resin and inorganic fine particles having a particle size of from 1 to 15 nm, a chlorine element in a concentration of at most 100 ppm, and at least any one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles .

[10] The organic-inorganic hybrid composition of [9] , wherein the organic acid is acetic acid. [11] The organic-inorganic hybrid composition of [9] or [10], wherein the concentration of the organic acid is at most 1% by mass .

[12] The organic-inorganic hybrid composition of any one of [9] to [11] , wherein the inorganic fine particles are of zirconium oxide, titanium oxide or their mixture. [13] The organic-inorganic hybrid composition of any one of [9] to [12], which is produced by mixing an inorganic oxide transparent dispersion and a thermoplastic resin. The inorganic oxide transparent dispersion contains from 1 to 70% by mass of inorganic fine particles having a particle size of from 1 to 15 nm, containing a chlorine element in a concentration of at most 100 ppm, and containing at least any one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid mass of the inorganic fine particles. [14] A method for producing a shaped article comprising mixing a thermoplastic resin and an inorganic fine particle dispersion of any one of [1] to [7] to give an organic-inorganic hybrid composition, and shaping the resulting organic-inorganic hybrid composition by use of a mold.

[15] A shaped article produced by shaping an organic-inorganic hybrid composition of any one of [9] to [13] . [16] An optical component comprising an organic-inorganic hybrid composition of any one of [9] to [13] .

[17] The optical component of [15] , which is a lens substrate.

The inorganic fine particle dispersion of the invention has a high transparency, and is capable of keeping its high transparency even when mixed with a thermoplastic resin to give an organic-inorganic hybrid composition. According to the production method of the invention, a shaped article having a high refractivity and transparency can be produced with little risk of mold corrosion. The shaped article and the optical component produced according to the production method of the invention have a high refractivity and transparency.

Modes for Carrying out the Invention

The inorganic fine particle dispersion of the invention, the organic-inorganic hybrid composition, and shaped articles and optical components comprising the composition are described in detail below. The descriptions about the constitutive reguirements as described below are sometimes based on typical embodiments for carrying out the invention. However, the invention is never limited to such embodiments. Herein, the numerical range expressed with "to" means the range where the numerical figures before and after the word "to" are the lower limit and the upper limit, respectively.

[Inorganic Fine Particle Dispersion] (Characteristics)

The inorganic fine particle dispersion of the invention comprises from 1 to 70% by mass of inorganic fine particles having a particle size of from 1 to 15 nm, a chlorine element in a concentration of at most 100 ppm, and at least any one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles. The inorganic fine particle dispersion of the invention is transparent.

Having the characteristics as above, the inorganic fine particle dispersion has a high transparency and keeps its high transparency and can realize a high refractivity when mixed with a thermoplastic resin to give an organic-inorganic hybrid composition. The organic-inorganic hybrid composition produced by use of the inorganic fine particle dispersion having the characteristics is sufficiently resistant to mold corrosion, and therefore has an advantage in that, when shaped into a shaped article such as an optical component, it gives little damage to the mold used. (Inorganic Fine Particles)

The inorganic fine particles for use in the organic-inorganic hybrid composition of the invention are not specifically defined, for which, for example, usable are fine particles described in JP-A 2002-241612, 2005-298717,

2006-70069.

Concretely usable are oxide fine particles (e.g., aluminium oxide, titanium oxide, niobium oxide, zirconium oxide, magnesium oxide, tellurium oxide, yttrium oxide, indium oxide, tantalum oxide, hafnium oxide, bismuth oxide, tin oxide) , composite oxide fine particles (e.g., lithium niobate, potassium niobate, lithium tantalate, potassium tantalate, barium titanate, strontium titanate, lead titanate, barium zirconate, barium stannate, zircon) , IIB-VIb semiconductors (e.g., Zn or Cd chalcogenides (S, Se, Te) or oxides), etc. Above all, preferred are zirconium, zinc, tin or titanium compounds, concretely preferred is use of at least one selected from the group consisting of zirconium oxide, zinc oxide, tin oxide and titanium oxide.

Two or more different types of inorganic fine particles may be used herein, as combined.

The inorganic fine particles for use in the invention may be a composite of plural ingredients, from the viewpoint of the refractivity, the transparency and the stability thereof. For various purposes of photocatalyst activity reduction and water absorption reduction, the inorganic fine particles maybe doped with a different element, or their surface layer may be coated with a different metal oxide such as silica or alumina, or they may be surface-modified with a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, an organic acid (e.g., carboxylic acid, sulfonic acid, phosphoric acid, sulfonic acid) , a dispersion medium having an organic acid group or the like. Depending on the object, two or more of these may be combined for use in the invention. For example, preferred are fine particles of tin-containing rutile-type titanium oxide coated with zirconium oxide.

The refractivity of the inorganic fine particles for use in the invention is not specifically defined. In case where the organic-inorganic hybrid composition of the invention is used for optical components that are required to have a high refractivity, the inorganic fine particles preferably has a high refractivity. In this case, the refractive index of the inorganic fine particles is preferably from 1.90 to 3.00 at 22°C and at a wavelength of 589 nm, more preferably from 2.00 to 2.70, even more preferably from 2.10 to 2.50. When the refractive index of the fine particles is at most 3.00, then the refractivity difference between the particles and resin may be relatively small and therefore Rayleigh scattering thereof may tend to be reduced. When the refractive index is at least 1.9, the particles may be effective for refractivity increase.

The refractive index of the inorganic fine particles may be estimated, for example, according to a method comprising shaping a composite produced by compositing the particles with a thermoplastic resin for use in the invention into a transparent film, measuring the refractive index of the film with an Abbe's refractiometer (e.g., Atago's "DM-M4"), separately measuring the refractive index of the resin alone, and processing the data through computation, or a method comprising measuring separately the refractive index of fine particle dispersions having a different concentration and processing the data through computation to thereby determine the refractive index of the fine particles. Also employable is another method comprising forming a thin film of the inorganic fine particles on a substrate having known optical properties such as a silicon wafer or the like, through spin coating thereon, then fully drying it and determining the refractive index thereof through fitting to interference patterns with an ellipsometer.

Regarding the number-average primary particle size of the inorganic fine particles for use in the invention, when the fine particles are too small, then their characteristics intrinsic to the substance constituting them may change; but on the contrary, when the number-average primary particle size is too large, then the Rayleigh scattering of the particles may be remarkable and the transparency of the organic-inorganic hybrid composition may greatly lower. Accordingly, the lowermost limit of the number-average primary particle size of the inorganic fine particles for use in the invention is preferably at least 1 nm, more preferably at least 2 nm, even more preferably at least 3 nm/ and the uppermost limit thereof is preferably at most 15 nm, more preferably at most 10 nm, even more preferably at most 7 nm. Specifically, the number-average primary particle size of the inorganic fine particles in the invention is preferably from 1 nm to 15 nm, more preferably from 2 nm to 10 nm, even more preferably from 3 nm to 7 nm.

Preferably, the inorganic fine particles for use in the invention satisfy the above-mentioned mean particle size and have a narrower particle size distribution. The monodispersed particles of the type may be defined variously, and for example, the numerical definition range described in JP-A 2006-160992 may apply to the particle size distribution range preferred for the fine particles for use in the invention.

The number-average primary particle size as referred to herein can be determined, for example, using an X-ray diffractiometry (XRD) apparatus or a transmission electronic microscope (TEM) . The production method for the inorganic fine particles for use in the invention is not specifically defined, and the particles may be produced in any known method.

For example, a starting material of metal salts or metal alkoxides may be hydrolyzed in a water-containing reaction system to give the desired oxide fine particles. The details of the method are described, for example, in "Journal of Applied Physics", Vol. 37, pp. 4603-4608 (1998) or "Langmuir", Vol. 16, No. 1, pp. 241-246 (2000) . In use of those inorganic fine particles produced in the water-containing reaction system, water may have some negative influence on the dispersion. In such a case, therefore, water in the inorganic fine particles produced may be substituted with any other suitable organic solvent. If desired, a suitable dispersion medium may be used in uniformly dispersing the particles of the type, not detracting from the dispersibility of the particles.

Apart from the method of hydrolysis in water, employable is a method of producing inorganic fine particles in an organic solvent or in an organic solvent containing a thermoplastic resin for use in the invention dissolved therein. In this case, if desired, various surface-treating agents (e.g., silane coupling agents, aluminate coupling agents, titanate coupling agents, organic acids (e.g., carboxylic acids, sulfones, phosphonic acids) ) may exist in the reaction system.

Examples of the solvent for use in these methods include acetone, 2-butanone, dichloromethane, chloroform, toluene, ethyl acetate, cyclohexanone, anisole. One or more of these may be used either singly or as combined. In case where the inorganic particles are produced in a solution, the characteristics, the particle size and the coagulation condition of the inorganic particles to be produced differ depending on the temperature at which the particles are produced, and therefore, it is important to determine suitable conditions for the production. However, under normal pressure, it is impossible to produce the particles at a temperature not lower than the boiling point of the solution. In case where the particles must be produced at a high temperature owing to their characteristics, for example, the particles may be produced under high pressure, using a pressure container such as an autoclave, thereby making them have the necessary characteristics .

Apart from the production method in a liquid phase alone of the inorganic fine particles as in the above, the production method of the particles may additionally include a firing step of high-temperature treatment. The firing step may be for increasing the degree of crystallinity of the fine particles produced in a liquid phase; or the starting material may be directly reacted to produce the fine particles in the firing step; or a precursor of the fine particles may be produced in a liquid phase, and this may be further processed in a firing step to produce the intended fine particles. An example of the firing process is described in JP-A 2003-19427, which comprises dissolving starting ingredients for inorganic fine particles along with other inorganic compounds, spraying the resulting solution for thermal decomposition to give particles, then washing them to remove the inorganic compounds from the inorganic fine particles; and the method is for producing particles of high crystallinity.

JP-A 2006-16236 discloses a method comprising forming a precursor of particles in a liquid phase and then crystallizing it through firing with preventing the aggregation of the formed particles in the presence of an inorganic salt. Further mentioned are vapor-phase production methods according to a vacuum process such as a molecular beam epitaxial process or a CVD process, for example, various ordinary production methods for fine particles as in JP-A 2006-70069.

The degree of crystallinity of inorganic fine particles varies depending on the production conditions; and inorganic particles of any crystallinity can be used in the invention in accordance with the situation. The particles for use herein maybe crystalline particles showing definite peaks in analysis through XRD, or amorphous particles showing broad halos in such analysis. In general, inorganic fine particles having a high degree of crystallinity have a higher refractive index than those having a low degree of crystallinity, and are therefore advantageous for application to high-refractivity materials. However, for example, in case of a material having a high photocatalytic activity such as titanium oxide, it is known that the photocatalytic activity of the material can be reduced by lowering the degree of crystallinity thereof. The photocatalytic activity of inorganic fine particles may cause a serious problem in that, when the organic-inorganic hybrid composition comprising the particles is irradiated with light, then the rein is decomposed. In such a case, inorganic nanoparticles having a low degree of crystallinity may be used to lower the photocatalytic activity of the composite. In case where the inorganic fine particles have a core/shell structure, the degree of crystallinity of the core part may be the same as or different from the degree of crystallinity of the shell part. The combination of the core part and the shell part may be physically determined depending on the crystal structure, the lattice constant and other parameters of the particles; however, the core/shell combination may be artificially designed by varying the production condition. The core and the shell must be so combined that they may effectively exhibit their characteristics in the combined structure.

Of the above-mentioned production methods for inorganic fine particles, preferably employed in the invention is a method of using a chloride in producing the inorganic fine particles. More preferred is a method of starting from a metal chloride to produce the inorganic fine particles. The metal chloride includes zirconium oxychloride, zirconium sulfate, zirconium nitrate and their hydrates. Preferred are zirconium oxychloride and its hydrate. In case where zirconium oxychloride or its hydrate is used as the starting material, an aqueous solution of zirconium oxychloride is neutralized to give a zirconium hydrate cake, and this is processed for hydrothermal treatment at high temperature and high pressure to give zirconium oxide fine particles; and the method may be employed in the invention.

The content of the inorganic fine particles in the inorganic fine particle dispersion of the invention is from 1 to 70% by mass, preferably from 1 to 50% by mass, more preferably from 1 to 45% by mass, even more preferably from 1 to 40% by mass, still more preferably from 1 to 35% by mass. When the content is less than 1% by mass, then it is unfavorable since the amount of the solvent in introducing the necessary particle mass may be extremely large; but on the contrary, when the content is more than 70% by mass, then it is also unfavorable since the transmittance of the dispersion may greatly lower. (Chlorine Element)

The inorganic fine particle dispersion of the invention comprises a chlorine element in a concentration of at most 100 ppm. The concentration of the chlorine element is preferably from 0.1 to 100 ppm, more preferably from 0.1 to 80 ppm, even more preferably from 0.1 to 70 ppm, still more preferably from 0.1 to 60 ppm. When the chlorine element concentration is more than 100 ppm, then it is unfavorable since the inorganic fine particle dispersion may cause mold corrosion when it is mixed with a thermoplastic resin and when the mixture is molded. The lowermost limit of the chlorine element concentration may be, for example, at least 0.5 ppm, or at least 1 ppm, or at least 3 ppm, or at least 10 ppm. The chlorine element concentration may be determined according to the method described in Examples given below.

The chlorine element to be in the inorganic fine particle dispersion of the invention may be in the form of a chloride ion, or may be in the form of a chlorine atom-containing compound (chloride) . The chlorine element may exist in the surface or in the inside of the inorganic fine particles, or may exist in the dispersion medium. Preferably, many chlorine elements exist in the surface or in the inside of the inorganic fine particles . The method of controlling the chlorine element concentration in the inorganic fine particle dispersion of the invention to be at most 100 ppm is not specifically defined. In case where the chlorine element concentration is desired to be larger within the range of at most 100 ppm of the chlorine element concentration, a chloride may be added to the dispersion. The additive includes hydrochloric acid. The timing of the addition is not specifically defined. On the contrary, when the chloride element concentration is desired to be lower, employable is a method of electrodialysis or ultrafiltration. (Acid)

The inorganic fine particle dispersion of the invention comprises at least any one of an organic acid and an inorganic acid.

The type of the organic acid that may be in the inorganic fine particle dispersion of the invention is not specifically defined. For example, acetic acid, propionic acid or the like is usable.

The type of the inorganic acid that may be in the inorganic fine particle dispersion of the invention is not specifically defined. For example, hydrochloric acid, nitric acid, sulfuric or the like is usable.

A mixture of different types of organic acids or inorganic acids may be used herein; or an organic acid and an inorganic acid may be combined for use herein. Preferably, at least an organic acid is in the dispersion; and more preferably at least acetic acid or propionic acid is therein.

In producing the inorganic fine particle dispersion of the invention, the timing of adding an organic acid and/or an inorganic acid is not specifically defined. In general, the acid may be added to the system before or during the particles are dispersed in the final solvent.

In the inorganic fine particle dispersion of the invention, the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles, preferably from 0.01 to 0.14 times, more preferably from 0.01 to 0.13 times, even more preferably from 0.01 to 0.12 times. When the total concentration of the organic acid and the inorganic acid is not less than 0.15 times the solid concentration of the inorganic fine particles, then it is unfavorable since, when the inorganic fine particle dispersion is mixed with a thermoplastic resin to prepare an organic-inorganic hybrid composition, the resulting composition may be cloudy and the transmittance thereof may lower. In case where an organic acid and an inorganic acid is added to the dispersion, it may be considered that the acid amount is preferably larger; however, unexpectedly, the present inventors have found that it is rather desirable to limit the acid amount within the above-mentioned predetermined range. The total concentration of organic acid and inorganic acid, and the ratio thereof to the solid concentration of the inorganic fine particles may be determined according to the method described in Examples given below.

In the inorganic fine particle dispersion of the invention, the total concentration of the organic acid and the inorganic acid is preferably at most 1.2% by mass of the dispersion, more preferably at most 1.0% by mass . For example, it is desirable that the concentration of the inorganic fine particles is from 8 to 12% by mass and the total concentration of the organic acid and the inorganic acid is from 0.2 to 1.2% by mass, more preferably from 0.2 to 0.8% by mass.

Preferably, in the inorganic fine particle dispersion of the invention, the ratio of the total concentration A of the organic acid and the inorganic acid to the chlorine element concentration B (A/B) is from 3 to 30, more preferably from 4 to 25, even more preferably from 5 to 20. (Dispersion Medium)

As the dispersion medium in the inorganic fine particle dispersion of the invention, usable is an alcohol dispersion medium, an ester dispersion medium, an ether dispersion medium, a ketone dispersion medium, an aryl dispersion medium, an amide dispersion medium or the like. In addition, a surface modifier for the inorganic fine particles may also be used as the dispersion medium. Preferably, the dispersion medium is at least one selected from the group consisting of methanol, ethanol, 1-butanol, isopropanol, N,N-dimethylacetamide (DMAc), toluene, anisole, N-methyl-2-pyrrolidone, ethyl acetate and butyl acetate. Of those, more preferred is at least one dispersion medium selected from the group consisting of methanol, N,N-dimethylacetamide (DMAc), ethyl acetate and butyl acetate. Most preferred is butyl acetate. Also preferred is adding to the dispersion of an aromatic carboxylic acid that functions as a surface modifier for the inorganic fine particles.

(Other Ingredients)

The inorganic fine particle dispersion of the invention may comprise any other ingredients than the above in accordance with the object thereof. Preferably, the concentration of sodium element and potassium element that may be in the inorganic fine particle dispersion of the invention is suppressed to be not higher than a predetermined level. Concretely, the concentration of those elements is preferably at most 70 ppm, more preferably at most 50 ppm, even more preferably at most 30 ppm. In case where the impurity concentration of sodium element and potassium element is too high, the transparency of the shaped article of the dispersion as combined with a thermoplastic resin may be low, or impurities may tend to precipitate in the shaped article. [Organic-inorganic hybrid composition] (Production Method)

The inorganic fine particle dispersion of the invention may be mixed with a thermoplastic resin to produce an organic-inorganic hybrid composition.

The concrete method for the mixing is not specifically defined. As one typical example, there may be mentioned a method comprising dissolving a thermoplastic resin in an organic solvent and adding the inorganic fine particle dispersion of the invention to the solution. Preferably, the dispersion is gradually and dropwise added to the solution with stirring. After all have been mixed, the organic solvent may be removed to give the organic-inorganic hybrid composition of the invention. The blend ratio of the inorganic fine particle dispersion and the thermoplastic resin may be suitably determined depending on the use and the function of the organic-inorganic hybrid composition to be produced. The content of the thermoplastic resin in the organic-inorganic hybrid composition is preferably from 5 to 80% by mass, more preferably from 30 to 75% by mass, even more preferably from 40 to 70% by mass . (Thermoplastic Resin)

The structure of the thermoplastic resin for use in the organic-inorganic hybrid composition of the invention is not specifically defined. For example, the resin may have any known structure of poly (meth) acrylate, polystyrene, polyamide, polyvinyl ether, polyvinyl ester, polyvinylcarbazole, polyolefin, polyester, polycarbonate, polyurethane, polythiourethane, polyimide, polyether, polythioether, polyether ketone, polysulfone, polyether sulfone, etc. From the viewpoint of the production method thereof, the resin may be selected from any known polymers of vinyl polymer produced through polymerization of vinyl monomer, polyether produced through polymerization of epoxy monomer, ring-opening metastasis polymerization polymer and condensation polymer

(e.g., polycarbonate, polyester, polyamide, polyether ketone, polyether sulfone) and others; and preferred are vinyl polymer, ring-opening metastasis polymerization polymer, polycarbonate and polyester; and from the viewpoint of producibility, more preferred is vinyl polymer. In the invention, preferred is a thermoplastic resin having at least a functional group capable of forming a chemical bond to inorganic fine particles at the polymer chain terminal or in the side branches thereof. <Unit Structure of Formula (1)>

Preferably, the thermoplastic resin for use in the invention has at least one unit structure of a formula (1) . Also preferably, the thermoplastic resin for use in the invention is a random copolymer having a carboxyl group in the side branches thereof. Formula (1)

In the formula (1) , R¹ to R³ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted acyloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted amino group, or a cyano group.

The thermoplastic resin for use in the invention may have only one type of a unit structure of the formula (1) in one molecule or may have different types of unit structures. The specific unit structure of the formula (1) may exist as continuous blocks or at random in the molecule. The unit structure of the formula (1) may be formed through polymerization of a monomer of the following formula (2):

Formula (2)

R² ^C≡≡N

In the formula (2) , R¹ to R³ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted acyloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted amino group, or a cyano group.

Specific examples of the monomer of the formula (2) are shown below as A-I to A-30; however, the monomer employable in the invention should not be limited to these examples.

A-15 A-16 A-17 A-18

The thermoplastic resin for use in the invention preferably comprises from 1 to 70% by mass of the unit structure of the formula (1) , more preferably from 3 to 70% by mass, even more preferably from 5 to 50% by mass, still more preferably from 7 to 30% by mass. The thermoplastic resin comprising from 1 to 70% by mass of the structural unit of the formula (1) as referred to herein is meant to indicate a thermoplastic resin produced through polymerization of a monomer mixture that comprises a monomer capable of giving the structure of the formula (1) through polymerization (monomer of the formula (2)) in an amount of from 1 to 70% by mass of the total monomer amount. <Copolymerizable Monomer>

The thermoplastic resin for use in the invention can be produced through copolymerization of the monomer capable of forming the unit structure of the formula (1) through polymerization, with any other monomer. As the other monomer, for example, usable are those described in Polymer Handbook 2nd ed., J. Brandrup, Wiley Interscience (1975), Chapter 2, pp. 1-483.

Specifically, compounds , having one addition-polymerizable unsaturated bond selected from styrene derivatives, 1-vinylnapphthalene, 2-vinylnaphthalene, vinylcarbazole, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, allyl compounds, vinyl ethers, vinyl esters, dialkyl itaconates, dialkyl esters or monoalkyl esters of fumaric acid, and the like can be exemplified. Preferably, the thermoplastic resin for use in the invention comprises the structure unit derived from the above-mentioned copolymer!zable monomer in an amount of from 30 to 99% by mass, more preferably from 30 to 97% by mass, even more preferably from 50 to 95% by mass, still more preferably from 70 to 93% by mass. Preferably, thermoplastic resin for use in the invention comprises a unit structure derived from an aromatic group-having vinyl monomer in an amount of from 20 to 99% by mass, more preferably from 30 to 97% by mass, even more preferably from 40 to 93% by mass. Preferably in the invention, a monomer having a functional group capable of forming a chemical bond with inorganic fine particles is used as the copolymerizable monomer. The functional group capable of forming a chemical bond with inorganic fine particles includes, for example, those having the following structure.

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵ and R¹⁶ independently represent hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or an atom or group forming a salt; -SO3H or a salt thereof; -OSO₃H or a salt thereof; -CO₂H or a salt thereof; -OH or a salt thereof; and -Si (OR¹⁷) _nR¹⁸3-n wherein R¹⁷ and R¹⁸ independently represent hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or an atom or group forming a salt; and n represents an integer of 1 to 3.

For introducing the functional group capable of forming a chemical bond with inorganic particles into the thermoplastic resin, employable is a method of polymerization of a polymerizing monomer having the functional group or its precursor; or a method of reacting the resin with a reactant to thereby introduce the functional group or its precursor into the resin. From the easiness in controlling the amount of the functional group to be introduced, preferred is the method of polymerization of a polymerizing monomer having the functional group or its precursor to give the resin.

In case where the resin is produced through polymerization, a diol compound, a dithiol compound, a dicarboxylic acid compound or the like capable of copolymerizable with the other monomer to be used in the invention can be used as the monomer having a functional group capable of forming a chemical bond with inorganic particles.

Preferably, the thermoplastic resin for use in the invention comprises the structure unit derived from the above-mentioned functional group-having vinyl monomer in an amount of from 0.1 to 5% by mass, more preferably from 0.3 to 3% by mass, even more preferably from 0.4 to 2.5% by mass . Also preferably, the thermoplastic resin for use in the invention comprises the above-mentioned functional group in an amount of from 0.1 to 20 groups/polymer chain on average, more preferably from 0.5 to 10 groups, still more preferably from 1 to 5 groups. The monomer copolymerizable with the monomer that forms the unit structure of the formula (1) through polymerization includes, for example, the following; however, the monomer employable in the invention should not be limited to these examples . In the following, n indicates an integer of 1 or more .

{^NA)-H'πO^~H^0H

Preferably, the number-average molecular weight of the thermoplastic resin for use in the invention is from 10000 to 200000, more preferably from 20000 to 200000, even more preferably from 50000 to 200000.

Also preferably, the glass transition temperature (Tg) of the thermoplastic resin for use in the invention is from 8O⁰C to 400°C from the viewpoint of the heat resistance and the moldability thereof, more preferably from 100 to 380°C, even more preferably from 100 to 300⁰C.

The refractive index of the thermoplastic resin for use in the invention is not specifically defined. In case where the organic-inorganic hybrid composition of the invention is used for optical members that are required to have a high refractivity, then the thermoplastic resin preferably has high refractivity characteristics. In this case, the refractive index of the thermoplastic resin is preferably at least 1.55 at 22°C and at a wavelength of 589 nm, more preferably at least 1.57, even more preferably at least 1.58. (Additives)

In the invention, various additives may be suitably added to the composition in addition to the indispensable ingredients in the invention, that is, the above-mentioned thermoplastic resin and inorganic fine particles, from the viewpoint of the uniform dispersibility, the flowability and the releasability in molding, the weather resistance, etc. For example, the additives may include surface-treating agent, plasticizer, antistatic agent, dispersant, release agent, etc. In addition, any other resin than those specifically mentioned in the above as the thermoplastic resin may be added to the composition . The type of the additional resin is not specifically defined. Preferably, however, the additional resin also has similar optical properties, thermophysical properties and molecular weight to those of the above-mentioned thermoplastic resin.

The amount of the additives to be in the composition varies depending on the object thereof. Preferably, the amount is from 0 to 50% by mass relative to the sum total of the inorganic fine particles and the thermoplastic resin, more preferably from 0 to 30% by mass, even more preferably from 0 to 20% by mass . <Plasticizer>

In case where the glass transition temperature of the thermoplastic resin in the invention is high, the organic-inorganic hybrid composition is not always easy to mold. For this, a plasticizer may be added to the organic-inorganic hybrid composition of the invention for the purpose of lowering the molding temperature of the composition. The amount of the plasticizer to be added, if any, may be preferably from 1 to 50% by mass of the total amount of the organic-inorganic hybrid composition, more preferably from 2 to 30% by mass, even more preferably from 3 to 20% by mass.

The plasticizer for use in the invention must be selected totally in consideration of the compatibility thereof with resin, the weather resistance and the plasticization effect thereof. The most suitable plasticizer could not be mentioned indiscriminately as depending on the other materials; however, from the viewpoint of the refractivity of the composition, those having an aromatic ring is preferred. Typical examples of the preferred compounds are those represented by the following formula (11) :

Formula (11)

In the formula (11) , R¹ and R² each independently represent a substituent. L represents an oxy group or a methylene group, a indicates 0 or 1. ml and rα2 each independently indicate an integer of from 0 to 5.

Compounds of the following formulae (12) to (14) are also preferred as the plasticizer.

Formula (12)

Formula (13)

Formula (14)

In the formulae (12) to (14), R³, R⁴, R⁵, R⁶ and R⁷ each independently represent a substituent. Z¹, Z², Z³ and Z⁴ each independently represent a hydrogen atom or a substituent. m3, m4 and m^β each independently indicate an integer of from 0 to 4. m5 and m7 each independently indicate an integer of from 0 to 5. bl, b2 and b3 each independently indicate an integer of 2 or more.

Further, compounds of the following formula (15) are also preferred as the plasticizer. Formula (15)

In the formula (15) , Ra, Rb and Rc each independently represent a substituent. A¹ represents an oxy group or a methylene group. A² represents an oxy group, a substituted or unsubstituted alkylene group, a carbonyl group, a substituted or unsubstituted imino group, or a group comprising at least two of these groups, nl and n2 each independently indicate an integer of from 0 to 5. n3 indicates an integer of from 0 to 4. p, q and r each independently indicate 0 or 1. When q is 0, then r is 0.

(Properties of Organic-inorganic hybrid composition)

The organic-inorganic hybrid composition of the invention has a high transparency and is characterized in that, when shaped into an article having a specific thickness, it has a high refractivity. In addition, in molding, the composition is highly resistant to corrosion of molds of stainless steel or the like, and therefore can effectively retard the damage to molds. Accordingly, in repeated molding in the same mold, the organic-inorganic hybrid composition is useful. When the organic-inorganic hybrid composition is shaped into an article having a thickness of 1 mm, its transmittance is preferably at least 70%, more preferably at least 75%, even more preferably at least 80%.

[Method for Producing Shaped Article]

When the inorganic fine particle dispersion of the invention is mixed with a thermoplastic resin solution to prepare an organic-inorganic hybrid composition, the composition can be, directly as it is in a state of solution, cast into a transparent shaped article . According to the method, a shaped article can be produced extremely simply, rapidly and inexpensively. In addition, the shaped article thus produced has an extremely high transparency. When a conventional organic-inorganic hybrid composition is shaped, it may often be cloudy, and therefore, the drying speed for it must be lowered and the shaped article must be dried, taking a lot of time. Contrary to this, when the organic-inorganic hybrid composition of the invention is shaped, it is free from the risk of cloudiness, and therefore it can be dried rapidly. Since the composition of the invention can give a transparent shaped article, not taking a lot of time, the invention has realized increased production efficiency and reduced production cost.

The shaped article can be produced in any other method than the above-mentioned casting method. For example, according to a method of concentration or freeze drying of a solution or according to a method of reprecipitation from a suitable poor solvent, the solvent is removed from the organic-inorganic hybrid composition of the invention, and then according to a known method of injection molding, compression molding or the like, the powdered solid may be molded. In this case, the powdery organic-inorganic hybrid composition may be shaped into articles such as lenses or the like through direct melting or compression under heat. Apart from this, the composition may be formed into a preform (precursor) having a predetermined weight and a predetermined shape according to a method of extrusion, and thereafter the preform may be further worked through compression molding into optical components such as lenses, etc. In this case, for efficiently forming the intended shape, the preform may be made to have a suitable curvature.

Formed as a master batch, the organic-inorganic hybrid composition may be mixed with any other resin.

[Optical Component]

By shaping the organic-inorganic hybrid composition of the invention, the optical component of the invention can be produced.

The optical component of the invention has the refractive index and the optical properties as described in the column about the organic-inorganic hybrid composition.

Among the optical components of the invention, those having a high refractive index with a thickness of 0.1 mm or more are particularly useful. Preferable are those having a thickness of 0.1 to 5 mm and particularly preferable are those having a thickness of 1 to 3 mm.

Molded articles of such thickness are generally produced, with much difficulty, by solution cast methods, because the solvent therein can hardly be drawn out. When the organic-inorganic hybrid composition of the invention is used, however, molding is readily done to readily prepare complicated shapes such as non-spherical shapes. As described above, in accordance with the invention, optical components with good transparency can be obtained, using the high refractive index properties of the fine particles.

The optical component using the organic-inorganic hybrid composition of the invention is not specifically limited so long as it utilizes the excellent optical properties of the organic-inorganic hybrid composition of the invention. The organic-inorganic hybrid composition can also be used to lens substrate and optical components that transmit light (so-called passive optical components) . Examples of an optically functional device provided with such an optical component include various display devices (liquid crystal display, plasma display and the like), various projector devices (OHP, liquid crystal projector and the like) , optical fiber communication devices (optical waveguide, optical amplifier and the like) , and photographic devices such as cameras and video. Examples of the passive optical component used in an optically functional device include lenses, prisms, prism sheets, panels, films, optical waveguides, optical discs, and encapsulants of LED.

[Lens] The optical component using the organic-inorganic hybrid composition of the invention is particularly suitable to a lens substrate. The lens substrate produced using the organic-inorganic hybrid composition of the invention has light transmission properties and lightweight properties in combination, and thus is excellent in optical properties. Further, it is possible to optionally adjust a refractive index of a lens substrate by appropriately adjusting the kind of monomers constituting the organic-inorganic hybrid composition and the amount of the inorganic fine particles dispersed.

The "lens substrate" used herein means a simple member that can exhibit lens function. A film or a member can be provided on the surface of or around the lens substrate according to use environment or the purpose of use of the lens. For example, a protective layer, an antireflective film, a hard coat layer or the like can be formed on the surface of the lens substrate. Further, the circumference of the lens substrate can be fitted in a substrate-holding frame or the like to fix. However, those films and frames are a member to be added to the lens substrate intended in the invention, and are distinguished from the lens substrate itself intended in the invention.

There are mentioned the following three typical methods of shaping the organic-inorganic hybrid composition into a lens substrate. However, the shaping method for the lens substrate of the invention should not be limited to these.

(1) A dispersion of the organic-inorganic hybrid composition is dried and solidified into a dry powder having, for example, a specific surface area (surface area/volume) of at least 15 mm^"1, and the resulting powder is heated under compression to give a lens substrate having a predetermined shape.

(2) A dispersion of the organic-inorganic hybrid composition is dropwise added to a liquid in which the organic-inorganic hybrid composition is insoluble, thereby forming a lens-shaped float of the organic-inorganic hybrid composition dispersion floating on the surface of the liquid and having a size equivalent to or slightly larger than the size of the intended lens substrate. In this case, the composition of the dispersion and the type of the liquid are so selected that both the interface between the dispersion and the liquid and the interface between the dispersion and air could have a convex-curved surface owing to the surface tension thereof. The dispersion medium is removed from the thus-formed, lens-shaped dispersion thereby giving a lens substrate having a predetermined shape. If desired, this may be further worked in at least one step of pressing, heating and compression.

(3) Using an extruder or the like, the organic-inorganic hybrid composition is extruded under heat, and the extruded material is cut into a massive intermediate, and thereafter the intermediate is pressed and heated under compression to give a lens substrate.

When the lens substrate of the invention is utilized as a lens, the lens substrate itself of the invention may be used as a lens, or a film or a frame is added to the lens substrate, and the assembly may be used as a lens. Kind and shape of a lens using the lens substrate of the invention is not particularly limited. The lens substrate of the invention is used in, for example, eyeglasses, lenses for optical instruments, lenses for optoelectronics, lenses for lasers, lenses for pickups, taking lenses (including various kinds of known taking lenses such as lenses for in-vehicle cameras, lenses for portable cameras, lenses for digital cameras, zoom lenses, progressive/regressive power lenses) , lenses for OHP and microlens arrays .

EXAMPLES

The characteristics of the invention are described more specifically by referring to the following Examples. In the following Examples, the material used, its amount and ratio, the details of the treatment and the treatment process may be suitably modified or changed not overstepping the spirit and the scope of the invention. Accordingly, the invention should not be limited to the Examples mentioned below.

[Example 1]

(1) Production of Zirconium Oxide Fine Particles:

A zirconium oxychloride solution having a concentration of 50 g/liter was neutralized in an aqueous 48% sodium hydroxide solution to prepare a zirconium hydrate dispersion. The dispersion was filtered and then washed with ion-exchanged water to prepare a zirconium hydrate cake. The cake was mixed with ion-exchanged water serving as a solvent to prepare a mixture having a zirconium oxide concentration of 15% by mass. This was put into an autoclave and processed for hydrothermal treatment at 15O⁰C under a pressure of 150 atmospheres for 24 hours to give a dispersion of zirconium oxide fine particles. In TEM, formation of zirconium oxide fine particles having a number-average particle size of from 3.2 nm with a standard deviation of 0.5 nm was confirmed. The dispersion of zirconium oxide fine particles was filtered, and mixed in methanol serving as a solvent to give a dispersion of zirconium oxide fine particles having a zirconium oxide concentration of 10% by mass .

(2) Production of zirconium oxide fine particle dispersion in butyl acetate :

4-N-propylbenzoic acid (9.00 g) was dissolved in butyl acetate (500.00 g) . This was added to a zirconium oxide fine particle dispersion (450.00 g) previously prepared, and well stirred. Next, this was evaporated to remove methanol, thereby having a solid content of 8.5% by mass, and a zirconium oxide fine particle dispersion in butyl acetate was thus produced.

(3) Analysis and evaluation of inorganic particle dispersion: Thus obtained, the inorganic particle dispersion was analyzed and evaluated in the manner mentioned below. The results are shown in Table 1. (3-1) Chlorine concentration:

The chlorine concentration in the inorganic particle dispersion was determined through ion chromatography. Concretely, a predetermined amount of the inorganic particle dispersion was put on a quartz board, and then analyzed with a combustion-type halogen analyzer (AQF-100 by Dia Instruments) . (3-2) Acid/inorganic fine particle concentration ratio:

The acid concentration in the inorganic particle dispersion was determined through gas chromatography with GC-2010 (by Shimadzu) , and was expressed as a ratio thereof to the solid concentration (10% by mass) of the inorganic fine particles in the dispersion.

(3-3) Transparency evaluation:

The inorganic particle dispersion was visually checked for the transparency thereof. It was confirmed that all the inorganic particle dispersions of Examples 1 to 4 had a high transparency . (4) Production of organic-inorganic hybrid composition:

The polymer having the following structure (100 parts by mass) and m-terphenyl (9 parts by mass) were dissolved in butyl acetate, then the zirconium oxide fine particle dispersion dispersed in butyl acetate in (2) was dropwise added to the resulting solution, taking 5 minutes, and this was stirred for 1 hour, and then the solvent was removed to give an organic-inorganic hybrid composition. The organic-inorganic hybrid composition comprised 45.83% by mass of the polymer having the following structure, 41.67% by mass of zirconium oxide fine particles, 8.33% by mass of 4-n-propylbenzoic acid and 4.17% by mass of m-terphenyl.

(5) Molding:

The obtained, organic-inorganic hybrid composition was introduced into a mold (circular mold having a diameter of 5.08 cm) of which the surface to be in contact with the composition was made of Stavax steel, and compression-molded therein into a molded article having a thickness of 1.0 mm. (6) Analysis and evaluation of molded article:

Thus obtained, the molded article was analyzed and evaluated in the manner mentioned below. (6-1) Transmittance measurement: Using a UV/visible light spectrometer, "UV-3100" (by Shimadzu) , the transmittance of the molded article at a wavelength of 589 nm was measured. In Comparative Example 1 and Comparative Example 3, the molded articles were obviously cloudy, and therefore, their transmittance was not measured. The results are shown in Table 1. (6-2) Refractive index measurement:

Using an Abbe's refractiometer (Atago's "DR-M4") at a wavelength of 589 nm, the refractive index of the molded article was measured. In Comparative Example 1 and Comparative Example

3, the molded articles were cloudy, and therefore, their refractivity was not measured. The molded articles of Examples

1 to 4 and Comparative Example 2 all had a high refractivity.

( 6-3) Evaluation of corrosion resistance in continuous molding: Using the same mold, the sample was molded repeatedly 10 times, and thereafter the surface of the mold was visually checked. The corrosion resistance was evaluated according to the following standards. In Comparative Example 1 and

Comparative Example 3, the molded articles were cloudy in the first-pass molding, and therefore these were not tested for the corrosion resistance, as valueless for evaluation.

O: Excellent appearance with no corrosion at all.

Δ: No corrosion in 1-pass molding, but some corrosion was found in 2-pass molding and later. X : Corrosion was found in 1-pass molding, and in 10-pass molding, remarkable corrosion was found.

[Examples 2 to 4, Comparative Examples 1 to 3]

In the same manner as in Example 1 but changing the chlorine concentration, the type of the acid and the acid concentration as in Table 1, inorganic particle dispersions and organic-inorganic hybrid compositions were produced.

The chlorine concentration was controlled through ultrafiltration. The acid concentration was controlled by adding the acid to the solvent.

The inorganic particle dispersions and the organic-inorganic hybrid compositions obtained in Examples and Comparative Examples were analyzed and evaluated in the same manner as in Example 1. The results are shown in Table 1. Table 1

CT)

As obvious from the results in Table 1, the inorganic fine particle dispersions of Examples 1 to 4 satisfying the requirements in the invention had a sufficient transparency; and the molded articles of the organic-inorganic hybrid composition produced by mixing the dispersion with a thermoplastic resin also had a sufficient transparency and a high refractivity. In addition, when the same mold was repeatedly used in producing the molded articles, the mold was not corroded. As opposed to these, in Comparative Example 1 and Comparative Example 3 where the concentration ratio of acid/inorganic fine particles is outside the scope of the invention, the samples were cloudy; and in Comparative Example 2 where the chlorine element concentration is outside the scope of the invention, the mold was corroded and the results were not good. These support the superiority of the invention.

Claims

1. An inorganic fine particle dispersion comprising: inorganic fine particles having a particle size of from 1 to 15 nm in a concentration of from 1 to 70% by mass, a chlorine element in a concentration of at most 100 ppm, and at least one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles.

2. The inorganic fine particle dispersion according to Claim 1, wherein the organic acid is acetic acid.

3. The inorganic fine particle dispersion according to Claim 1 or 2, wherein the concentration of the organic acid is at most 1% by mass.

4. The inorganic fine particle dispersion according to any one of Claims 1 to 3, wherein the inorganic fine particles are of zirconium oxide, titanium oxide or their mixture. 5. The inorganic fine particle dispersion according to any one of Claims 1 to 4, wherein the dispersion comprises at least one dispersion medium selected from the group consisting of methanol, ethanol, 1-butanol, isopropanol, N,N-dimethylacetamide, toluene, anisole, N-methyl-2-pyrrolidone, ethyl acetate and butyl acetate. β. The inorganic fine particle dispersion according to any one of Claims 1 to 5, wherein the inorganic fine particles are surface-modified with an aromatic carboxylic acid.

7. The inorganic fine particle dispersion according to Claim 6, wherein the aromatic carboxylic acid is at least one compound selected from the group consisting of 4-n-propylbenzoic acid, diphenylacetic acid and 4-phenylbenzoic acid.

8. A method for producing an organic-inorganic hybrid composition comprising mixing a thermoplastic rein and an inorganic fine particle dispersion of any one of Claims 1 to 7.

9. An organic-inorganic hybrid composition comprising: a thermoplastic resin, inorganic fine particles having a particle size of from 1 to 15 run, a chlorine element in a concentration of at most 100 ppm, and at least any one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid concentration of the inorganic fine particles.

10. The organic-inorganic hybrid composition according to Claim 9, wherein the organic acid is acetic acid.

11. The organic-inorganic hybrid composition according to Claim 9 or 10, wherein the concentration of the organic acid is at most 1% by mass.

12. The organic-inorganic hybrid composition according to any one of Claims 9 to 11, wherein the inorganic fine particles are of zirconium oxide, titanium oxide or their mixture.

13. The organic-inorganic hybrid composition according to any one of Claims 9 to 12, which is produced by mixing an inorganic oxide transparent dispersion and a thermoplastic resin, the inorganic oxide transparent dispersion comprising from 1 to 70% by mass of inorganic fine particles having a particle size of from 1 to 15 nm, a chlorine element in a concentration of at most 100 ppm, and at least any one of an organic acid and an inorganic acid, wherein the total concentration of the organic acid and the inorganic acid is less than 0.15 times the solid mass of the inorganic fine particles.

14. A method for producing a shaped article comprising mixing a thermoplastic resin and an inorganic fine particle dispersion of any one of Claims 1 to 7 to give an organic-inorganic hybrid composition, and shaping the resulting organic-inorganic hybrid composition by use of a mold. 15. A shaped article produced by shaping the organic-inorganic hybrid composition of any one of Claims 9 to 13.

16. An optical component comprising the organic-inorganic hybrid composition of any one of Claims 9 to 13.

17. The optical component according to Claim 15, which is a lens substrate.