Patent Description:
Titanium oxide fine particles have a high refractive index and are suitably used as a material of a coating liquid for forming a coating film on an optical substrate such as a plastic lens. In particular, rutile crystalline titanium oxide fine particles show lower photocatalytic activity than the anatase type and thus give rise to a smaller reduction in the adhesion of the coating film with respect to a substrate stemming from the decomposition of organosilicon compounds or resin components forming the coating film.

Regarding the production of a dispersion of rutile crystalline titanium oxide fine particles, for example, Patent Literature <NUM> describes that a dispersion of rutile titanium oxide fine particles is obtained by adding hydrogen peroxide to a gel or sol of hydrous titanium oxide to dissolve the hydrous titanium oxide, and heating the solution in the presence of a tin compound in an amount of TiO<NUM>/SnO<NUM> = <NUM> to <NUM> (by weight). It is also described that the dispersion stability may be enhanced by obtaining the sol in such a manner that the aqueous solution resulting from the mixing of the aqueous titanic acid solution and the tin compound is further heated and hydrolyzed in the presence of a silicon compound.

Patent Literature <NUM> pertains to a coating liquid for forming a hard coating film having high refractive index, excellent transparency, excellent weather resistance and excellent adhesion with a substrate. It is disclosed therein that the coating liquid contains composite oxide fine particles including a titanium oxide component and an iron oxide component in Fe<NUM>O<NUM>/TiO<NUM> (by weight) of not less than <NUM> and less than <NUM>. Patent Literature <NUM> discloses a method for producing composite titanium oxide/iron oxide particles. Composite anatase titanium oxide/iron oxide fine particles obtained by the production method are less photocatalytically active, and a coating liquid containing such composite oxide fine particles can give coating films with outstanding weather resistance.

Patent Literature <NUM> discloses core-shell fine particles in which rutile titanium oxide fine particles as cores are coated with a composite oxide formed of silicon oxide and oxide of zirconium and/or aluminum. This configuration weakens the photocatalytic activity of the rutile titanium oxide fine particles, and a coating liquid containing such core-shell fine particles can give coating films with outstanding weather resistance.

The conventional titanium oxide fine particles are required to be enhanced in weather resistance and light resistance while maintaining their high refractive index.

It is therefore an object of the present invention to provide titanium oxide fine particles which are excellent in transparency and are less photocatalytically active while maintaining a high refractive index. Other objects of the present invention include to provide a dispersion of such fine particles, and to provide a method for producing such a dispersion.

The present inventors carried out extensive studies and have found that the above problem may be solved by allowing titanium oxide fine particles to contain a slight amount of iron and to have the rutile structure, thereby completing the present invention. A summary of the present invention is as described below.

According to the production method of the present invention, titanium oxide fine particles can be produced which have excellent transparency and are less photocatalytically active than the conventional titanium oxide fine particles while maintaining a high refractive index. The invention also provides core-shell fine particles each having the above fine particle as a core particle, dispersions of these fine particles, paint compositions including the fine particles, and methods for producing these products.

Further, coated substrates are also provided which have a hardcoat layer or a UV shield coat layer that is formed from the paint composition and has a high refractive index and suppressed photocatalytic activity.

The present invention will be described in detail hereinbelow.

A method of the present invention for producing a dispersion of iron-containing rutile titanium oxide fine particles includes the steps (<NUM>) to (<NUM>) discussed below.

The step (<NUM>) is a step of neutralizing an aqueous metal mineral acid salt solution containing Ti and Fe as metals to form an iron-containing hydrous titanic acid. In the aqueous solution, the masses of the metals in terms of oxide are such that mass of Fe<NUM>O<NUM>/(total mass of TiO<NUM> and Fe<NUM>O<NUM>) (hereinafter, also written as "Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>)") = <NUM> to <NUM>.

For example, the aqueous solution may be prepared by mixing a titanium mineral acid salt, an iron mineral acid salt and water together, or by mixing a titanium mineral acid salt and an iron mineral acid salt together (with the proviso that one or both of the mineral acid salts are in the form of an aqueous solution).

Examples of the titanium mineral acid salts include, although not limited to, titanium sulfate, titanium nitrate, titanium tetrachloride, titanyl sulfate and titanyl chloride.

Examples of the iron mineral acid salts include, although not limited to, ferric chloride, ferrous sulfate and ferric nitrate.

Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>) is <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%), and more preferably <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%). If the ratio (Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>)) is less than <NUM>, the photocatalytic activity of the iron-containing rutile titanium oxide fine particles cannot be reduced sufficiently. If the ratio (Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>)) is greater than <NUM>, the iron-containing rutile titanium oxide fine particles take on a yellow color and make yellow the color of a coating film containing the iron-containing rutile titanium oxide fine particles.

The reasons as to why iron lowers the photocatalytic activity of the titanium oxide fine particles are unclear, but are probably because iron adds an impurity level to the electron energy band of titanium oxide and this impurity level serves as a site of the recombination of excited electrons and holes, thus rendering the titanium oxide less photocatalytically active.

The aqueous metal mineral acid salt solution may be neutralized by being brought into contact with a basic material. Examples of the basic materials include ammonia. The basic material may be used in the form of an aqueous solution (for example, ammonia water).

The neutralization of the aqueous metal mineral acid salt solution gives an iron-containing hydrous titanic acid as a slurry. The iron-containing hydrous titanic acid may be separated from the slurry by, for example, filtering the slurry of the iron-containing hydrous titanic acid. The iron-containing hydrous titanic acid is a hydrous solid resulting from the neutralization of the aqueous metal mineral acid salt solution, and is based on hydrous titanic acid and contains a small amount of iron.

The iron-containing hydrous titanic acid is preferably washed by a medium such as pure water.

The step (<NUM>) is a step of adding an aqueous hydrogen peroxide solution to the iron-containing hydrous titanic acid obtained in the step (<NUM>) to form an aqueous solution of iron-containing peroxotitanic acid having an average particle size of <NUM> to <NUM>.

In the step (<NUM>), the mixture of the iron-containing hydrous titanic acid and the aqueous hydrogen peroxide solution is preferably stirred at a temperature of <NUM> to <NUM>. The stirring time is preferably <NUM> to <NUM> hours. Stirring under these conditions peptizes the iron-containing hydrous titanic acid, and therefore the average particle size of the iron-containing peroxotitanic acid in the aqueous solution can be controlled to the range of <NUM> to <NUM>. Although the liquid that is obtained is a dispersion of the iron-containing peroxotitanic acid particles, the liquid is written as an aqueous solution, not an aqueous dispersion. The iron-containing peroxotitanic acid is based on peroxotitanic acid and contains a small amount of iron which probably substitutes for part of titanium in the peroxotitanic acid.

The heating to <NUM> to <NUM> is desirably started immediately after the addition of the aqueous hydrogen peroxide solution to the iron-containing hydrous titanic acid, specifically, within <NUM> hours, and preferably within <NUM> hour after the addition. By such immediate heating to <NUM> to <NUM>, the iron-containing peroxotitanic acid attains small particle sizes.

The average particle size of the peptized iron-containing peroxotitanic acid is <NUM> to <NUM>, and preferably <NUM> to <NUM> as measured by the method described later in Examples or a method that is equivalent thereto. By controlling the average particle size of the peptized iron-containing peroxotitanic acid to the above range, the final iron-containing rutile titanium oxide fine particles attain an average particle size of <NUM> to <NUM>, and a highly transparent dispersion of the fine particles may be obtained stably.

If the average particle size of the iron-containing peroxotitanic acid is less than <NUM>, the iron-containing peroxotitanic acid exhibits so low dispersion stability in the aqueous solution that the final iron-containing rutile titanium oxide fine particles contain coarse particles which can deteriorate the transparency of the dispersion. If the average particle size is greater than <NUM>, the iron-containing rutile titanium oxide fine particles become so large in diameter that the transparency of the dispersion may be lowered.

The aqueous hydrogen peroxide solution is preferably added in such an amount that the mass ratio of hydrogen peroxide to titanium (in terms of oxide) in the iron-containing hydrous titanic acid satisfies mass of H<NUM>O<NUM>/mass of TiO<NUM> = <NUM> to <NUM>. When the amount of the aqueous hydrogen peroxide solution is in this range, the iron-containing peroxotitanic acid will not be excessively small in particle size and will exhibit excellent dispersion stability in the aqueous solution.

The aqueous solution of iron-containing peroxotitanic acid is preferably adjusted to a titanium concentration in terms of TiO<NUM> of not more than <NUM> mass%, and more preferably not more than <NUM> mass%. When the titanium concentration (in terms of TiO<NUM>) is in this range, the iron-containing peroxotitanic acid particles are less likely to aggregate and consequently the average particle size of the iron-containing rutile titanium oxide fine particles can be rendered small.

The step (<NUM>) is a step of adding a tin compound to the aqueous solution of iron-containing peroxotitanic acid obtained in the step (<NUM>) in such an amount that the masses of Sn and Ti in the aqueous solution in terms of oxide satisfy mass of TiO<NUM>/mass of SnO<NUM> (hereinafter, also written as "TiO<NUM>/SnO<NUM>") = <NUM> to <NUM>.

Examples of the tin compounds include, although not limited to, potassium stannate, tin nitrate and tin chloride.

If TiO<NUM>/SnO<NUM> is less than <NUM>, the weather resistance of the iron-containing rutile titanium oxide fine particles is lowered. If TiO<NUM>/SnO<NUM> is more than <NUM>, anatase crystals are formed in the iron-containing rutile titanium oxide fine particles.

If foreign ions are present in the aqueous solution obtained in the step (<NUM>), the next step (<NUM>) may fail to give the desired particles. It is therefore preferable that such foreign ions be removed in the step (<NUM>). For example, the foreign ions may be removed by, although not limited to, using an ion exchange resin or an ultrafiltration membrane.

The step (<NUM>) is a step of adding a sol of silica-based fine particles to the solution obtained in the step (<NUM>). The silica-based fine particles contain Si and at least one metal element (M) selected from the group consisting of Al, Zr, Sb, Zn, Ni, Ba, Mg and V in such amounts that the masses thereof in terms of oxide satisfy mass of SiO<NUM>/mass of MOx/<NUM> (x is the valence of M) (hereinafter, also written as "SiO<NUM>/MOx/<NUM>") = <NUM>/<NUM> to <NUM>/<NUM>. The addition is made so that the masses in terms of oxide of the metal elements in the solution obtained in the step (<NUM>) and the masses in terms of oxide of the silicon and the metal element or elements in the sol satisfy mass of SiO<NUM>/(total mass of TiO<NUM>, SnO<NUM>, Fe<NUM>O<NUM>, SiO<NUM> and MOx/<NUM>) (hereinafter, also written as "SiO<NUM>/(TiO<NUM> + SnO<NUM> + Fe<NUM>O<NUM> + SiO<NUM> + MOx/<NUM>)") = <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%).

The sol of the silica-based fine particles may be produced by a known method, for example, the method described in <CIT> or the method described in <CIT>.

Although the reasons are unclear, the addition of the sol of the silica-based fine particles allows the final iron-containing rutile titanium oxide fine particles to be stably dispersed in the dispersion without being sedimented or precipitated, prevents the fine particles from being aggregated or coarsened, and makes it possible to control the particle size and grain size distribution of the fine particles in the dispersion.

If the sol of the silica-based fine particles is not added, the final iron-containing rutile titanium oxide fine particles in the dispersion are not controlled in particle size and exhibit poor dispersion stability. If the sol of the silica-based fine particles is replaced by a sol of silica fine particles containing no metal elements M, the dispersion of the final iron-containing rutile titanium oxide fine particles may contain coarse particles or particle aggregates.

SiO<NUM>/MOx/<NUM> is <NUM>/<NUM> to <NUM>/<NUM>, and preferably <NUM>/<NUM> to <NUM>/<NUM>. If SiO<NUM>/MOx/<NUM> in the silica-based fine particles is larger than <NUM>/<NUM>, the fine particles tend to show poor dispersion stability in the aqueous solution of the iron-containing peroxotitanic acid particles. If SiO<NUM>/MOx/<NUM> is less than <NUM>/<NUM>, the silica-based fine particles tend to show low solubility into the aqueous solution of the iron-containing peroxotitanic acid particles during hydrothermal treatment.

The letter x indicates the valence of the metal element M. The present invention assumes that the valences of Al, Zr, Sb, Zn, Ni, Ba, Mg and V are III, IV, III, II, II, II, II and V, respectively.

The sol of the silica-based fine particles is added so that SiO<NUM>/(TiO<NUM> + SnO<NUM> + Fe<NUM>O<NUM> + SiO<NUM> + MOx/<NUM>) = <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%), and preferably <NUM> to <NUM>. If SiO<NUM>/(TiO<NUM> + SnO<NUM> + Fe<NUM>O<NUM> + SiO<NUM> + MOx/<NUM>) is less than <NUM> mass%, the iron-containing rutile titanium oxide fine particles tend to fail to attain sufficiently low photocatalytic activity. If SiO<NUM>/(TiO<NUM> + SnO<NUM> + Fe<NUM>O<NUM> + SiO<NUM> + MOx/<NUM>) is above <NUM> mass%, the silica-based fine particles are hardly dissolved during hydrothermal treatment and the sol of the silica-based fine particles tends to fail to produce sufficient effects.

The specific surface area of the silica-based fine particles is preferably <NUM> to <NUM><NUM>/g, more preferably <NUM> to <NUM><NUM>/g, and still more preferably <NUM> to <NUM><NUM>/g. This specific surface area of the silica-based fine particles ensures that the addition of the sol of the silica-based fine particles will produce sufficient effects.

The step (<NUM>) is a step of hydrothermally treating the solution obtained in the step (<NUM>) to produce a dispersion of iron-containing rutile titanium oxide fine particles.

The hydrothermal treatment conditions may be appropriately adopted from the conventional conditions under which a titanium oxide fine particle dispersion is produced by hydrothermal treatment. The temperature is preferably <NUM> to <NUM>, and the amount of time is preferably <NUM> to <NUM> hours. The hydrothermal treatment under these conditions gives a dispersion of iron-containing rutile titanium oxide fine particles with excellent dispersibility. In the step (<NUM>), the dispersion is obtained as an aqueous dispersion.

A dispersion of iron-containing rutile titanium oxide fine particles obtained by the production method of the present invention may be concentrated appropriately by a known technique such as distillation under reduced pressure, or ultrafiltration, depending on use application.

The dispersion of iron-containing rutile titanium oxide fine particles may be an aqueous dispersion, a dispersion in water and an organic solvent, or a dispersion in an organic solvent. A dispersion including an organic solvent as the dispersion medium may be produced by, for example, substituting part or the whole of water in an aqueous dispersion with an organic solvent by a known technique such as a rotary evaporator or an ultrafiltration membrane.

Examples of the organic solvents will be described later.

Iron-containing rutile titanium oxide fine particles according to the present invention satisfy the requirements (a) to (f) below:.

The "iron-containing rutile titanium oxide fine particles" are fine particles which are identified to have a rutile titanium oxide crystal structure by XRD measurement or the like, and which contain silicon and metal elements other than titanium (iron, tin, metal elements M described hereinabove). Part of the titanium sites in the rutile titanium oxide are probably replaced by all or part of silicon and the metal elements other than titanium.

The iron-containing rutile titanium oxide fine particles are less photocatalytically active than the conventional titanium oxide fine particles, and still maintain a high refractive index.

The iron-containing rutile titanium oxide fine particles have high shape uniformity. The fine particles may be confirmed to be of high shape uniformity by observing the fine particles with a scanning electron microscope (SEM). Thus, the iron-containing rutile titanium oxide fine particles are also excellent in transparency.

Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>) is <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%), and preferably <NUM> to <NUM> (i.e., <NUM> to <NUM> mass%). If Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>) is less than <NUM>, the photocatalytic activity of the iron-containing rutile titanium oxide fine particles is not sufficiently low. If Fe<NUM>O<NUM>/(TiO<NUM> + Fe<NUM>O<NUM>) is more than <NUM>, the iron-containing rutile titanium oxide fine particles take on a yellow color and make yellow the color of a coating film containing the iron-containing rutile titanium oxide fine particles.

Core-shell iron-containing rutile titanium oxide fine particles according to the present invention each include the iron-containing rutile titanium oxide fine particle of the invention, and a layer covering the fine particle (hereinafter, the layer will be also written as the "coating layer"), the layer comprising an oxide and/or a composite oxide containing Si and at least one metal element selected from the group consisting of Al, Zr and Sb.

The coating layer weakens the photoactivity of the iron-containing rutile titanium oxide fine particles as core particles to a still lower level. For example, the coating layer may be formed by the method described in <CIT>.

Specifically, an aqueous solution of a hydroxide, peroxide, alkoxide and/or inorganic salt which each contain Si and at least one metal element selected from the group consisting of Al, Zr and Sb may be gradually added at a temperature of <NUM> to <NUM> to an aqueous dispersion of the iron-containing rutile titanium oxide fine particles of the invention, and, after the completion of the addition, the mixture may be aged for <NUM> to <NUM> hours and the resultant dispersion may be hydrothermally treated to give an aqueous dispersion of core-shell iron-containing rutile titanium oxide fine particles coated with the coating layer described above.

The amount of the coating layer in the core-shell iron-containing rutile titanium oxide fine particles is preferably <NUM> to <NUM> parts by mass per <NUM> parts by mass of the iron-containing rutile titanium oxide fine particles which are the core particles. This amount may be controlled by manipulating the amounts in which the iron-containing rutile titanium oxide fine particles and the raw materials of the coating layer are fed.

The dispersion of the core-shell iron-containing rutile titanium oxide fine particles may be an aqueous dispersion, a dispersion in water and an organic solvent, or a dispersion in an organic solvent. A dispersion including an organic solvent as the dispersion medium may be produced by, for example, substituting part or the whole of water in a dispersion with an organic solvent by a known technique such as a rotary evaporator or an ultrafiltration membrane.

Examples of the organic solvents which may be used in the dispersion of the iron-containing rutile titanium oxide fine particles and in the dispersion of the core-shell iron-containing rutile titanium oxide fine particles include:.

To ensure that the core-shell iron-containing rutile titanium oxide fine particles will be dispersed in an organic solvent or a resin-dispersed solution without being aggregated in the dispersion, the surface of the core-shell iron-containing rutile titanium oxide fine particles may be hydrophobized with a surface treating agent.

This hydrophobization step is a step in which a surface treating agent is added into the dispersion and the mixture is further heated or hydrothermally treated as required. This step may be performed before water in the aqueous dispersion described hereinabove is replaced by a solvent (hereinafter, this operation will be also written as the "solvent replacement"), or may be performed concurrently with or after the solvent replacement. A catalyst such as ammonia may be used in this step as required.

Known surface treating agents may be used, with examples including alkoxide compounds such as tetraethoxysilane and triisopropoxyaluminum, coupling agents such as silane coupling agents and titanium coupling agents, low-molecular or high-molecular surfactants such as nonionic, cationic or anionic surfactants, and metal soap salts such as fatty acid metal salts and naphthenic acid metal salts.

The dispersion of the core-shell iron-containing rutile titanium oxide fine particles in water and/or an organic solvent may be used as a coating liquid for forming coating films, or may be added to a resin composition in accordance with conventionally known methods appropriately.

A paint composition according to the present invention includes the core-shell iron-containing rutile titanium oxide fine particles of the invention, and a matrix component. The paint composition may further include a curing catalyst or an additive.

The paint composition may be a thermally curable paint composition or a photocurable paint composition.

The thermally curable paint composition includes the core-shell iron-containing rutile titanium oxide fine particles, the matrix component, and optionally a thermal curing catalyst or an additive as required, and may be produced by mixing these components, for example, based on the description in <CIT>.

The photocurable paint composition includes the core-shell iron-containing rutile titanium oxide fine particles, the matrix component, and optionally a photocuring catalyst or an additive as required, and may be produced by mixing these components, for example, based on the description in <CIT>.

Examples of the matrix components include methyltrimethoxysilane, ethyltriethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, phenylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(<NUM>,<NUM>-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β(aminoethyl)y-aminopropyltrimethoxysilane, N-β(aminoethyl)y-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane. These may be used singly, or two or more may be used in combination.

Examples of the thermal curing catalysts include amines such as n-butylamine, triethylamine, guanidine and biguanidide, amino acids such as glycine, metal acetylacetonates such as aluminum acetylacetonate, chromium acetylacetonate, titanyl acetylacetonate and cobalt acetylacetonate, organic acid metal salts such as sodium acetate, zinc naphthenate, cobalt naphthenate, zinc octylate and tin octylate, perchloric acid and salts thereof such as perchloric acid, ammonium perchlorate and magnesium perchlorate, acids such as hydrochloric acid, phosphoric acid, nitric acid and p-toluenesulfonic acid, and metal chlorides which are Lewis acids such as SnCl<NUM>, AlCl<NUM>, FeCl<NUM>, TiCl<NUM>, ZnCl<NUM> and SbCl<NUM>. These may be used singly, or two or more may be used in combination.

Examples of the photocuring catalysts include bis(<NUM>,<NUM>,<NUM>-trimethylbenzoyl)phenylphosphine oxide, bis(<NUM>,<NUM>-dimethoxybenzoyl)-<NUM>,<NUM>,<NUM>-trimethyl-pentylphosphine oxide, <NUM>-hydroxy-methyl-<NUM>-methyl-phenyl-propane-<NUM>-ketone, <NUM>,<NUM>-dimethoxy-<NUM>,<NUM>-diphenylethan-<NUM>-one, <NUM>-hydroxy-cyclohexylphenyl-ketone and <NUM>-methyl-<NUM>-[<NUM>-(methylthio)phenyl]-<NUM>-morpholinopropan-<NUM>-one. These may be used singly, or two or more may be used in combination.

Examples of the additives include surfactants, leveling agents, UV absorbers, light stabilizers, diluting solvents, preservatives, antifouling agents, antimicrobial agents, antifoaming agents, UV degradation inhibitors and dyes. These may be used singly, or two or more may be used in combination.

A coated substrate according to the present invention includes a substrate and a coating film disposed on a surface of the substrate, the coating film being formed from the paint composition of the present invention.

Examples of the substrates include various glass or plastic substrates. Specific examples include plastic substrates used as optical lenses or the like.

The thickness of the coating film may vary depending on the use application of the coated substrate, but is preferably <NUM> to <NUM>.

When the thermally curable paint composition is used, the coated substrate of the invention may be produced based on the description of, for example, <CIT>. When the photocurable paint composition is used, the coated substrate may be produced based on the description of, for example, <CIT>. The thermally curable paint composition or the photocurable paint composition may be applied onto the substrate by a known technique such as dipping, spraying, spinner coating process, roll coating process or bar coating process, followed by drying, and the coating film may be cured by treatment such as heating or UV irradiation.

During the production of the coated substrate of the present invention, the surface of the substrate may be pretreated, for example, treated with an alkali, an acid or a surfactant, polished with inorganic or organic fine particles, or treated with a primer or plasma, for the purpose of enhancing the adhesion between the substrate, for example, a plastic substrate, and the coating film.

The present invention will be described in greater detail based on Examples hereinbelow. However, it should be construed that the scope of the present invention is not limited to such Examples.

The measurement methods and the evaluation methods used in the following discussion such as Examples will be described below.

Particles were diluted with a dispersion medium so that the solid concentration would be <NUM> wt%, and the particle size distribution was measured with a fine particle grain size analyzer (ELS-Z manufactured by OTSUKA ELECTRONICS Co. ) based on a dynamic light scattering method. The refractive index and viscosity of the dispersion medium were used as the refractive index and viscosity of the solution. The average particle size was determined by cumulant analysis.

<NUM> of a sol of silica fine particles or silica-based fine particles was adjusted to pH <NUM> with HNO<NUM>, and <NUM> of <NUM>-propanol was added. The sol was dried at <NUM> for <NUM> hours. The residue was ground with a mortar and calcined in a muffle furnace at <NUM> for <NUM> hour to give a specimen.

The specimen was analyzed on a specific surface area measurement device (model: MULTISORB <NUM>, manufactured by Yuasa Ionics) by a nitrogen adsorption method (a BET method) to determine the amount of nitrogen adsorbed. Based on the adsorption amount, the specific surface area was calculated by a single point BET method. Specifically, <NUM> of the specimen was placed on a measurement cell and was degassed at <NUM> for <NUM> minutes in a stream of a gas mixture containing <NUM> vol% nitrogen and <NUM> vol% helium. The specimen was then held at a liquid nitrogen temperature in a stream of the gas mixture to equilibrate the nitrogen adsorption on the specimen. Next, under a stream of the gas mixture, the specimen temperature was gradually increased to room temperature and the amount of nitrogen desorbed during this process was determined. The specific surface area (m<NUM>/g) of the silica fine particles or the silica-based fine particles was calculated based on a preliminarily constructed calibration curve.

The solvent of a sample was removed by treatment including infrared irradiation, and the residue was calcined at <NUM> for <NUM> hour to give an ignition residue (a solid). The weight ratio of the ignition residue to the sample was calculated as the solid concentration.

To <NUM>, in terms of solid, of a dispersion of inorganic oxide fine particles in water or methanol, a solvent was appropriately added so that the water/methanol ratio (by weight) would be <NUM>/<NUM> and the solid concentration would be <NUM> wt%. Next, the dispersion was mixed together with glycerol so that the weight ratio (weight of dispersion/weight of glycerol) would be <NUM>/<NUM>. The mixture was added to a quartz cell <NUM> in depth, <NUM> in width and <NUM> in height. The YI value was measured with a colorimeter/turbidity meter (COH-<NUM> manufactured by NIPPON DENSHOKU INDUSTRIES CO.

An aqueous dispersion of inorganic oxide fine particles was placed into a zirconia bowl, and water was removed by infrared irradiation. Na<NUM>O<NUM> and NaOH were added to the resultant dry residue, and the mixture was heated to give a melt. Further, hydrochloric acid was added to the melt, and pure water as a diluent was added.

The amounts of titanium, tin and silicon in terms of oxide (TiO<NUM>, SnO<NUM> and SiO<NUM>) in the solution obtained above were measured with use of an ICP apparatus (ICPS-<NUM> manufactured by Shimadzu Corporation).

The aqueous dispersion of inorganic oxide fine particles was placed onto a platinum dish. Hydrofluoric acid and sulfuric acid were added thereto, the mixture was heated, and hydrochloric acid was added thereto, to dissolve the oxide particles. The solution was diluted with pure water and was analyzed on an ICP apparatus (ICPS-<NUM> manufactured by Shimadzu Corporation) to determine the amounts of zirconium and aluminum in terms of oxide (ZrO<NUM> and Al<NUM>O<NUM>).

The aqueous dispersion of inorganic oxide fine particles was placed onto a platinum dish. Hydrofluoric acid and sulfuric acid were added thereto, the mixture was heated, and hydrochloric acid was added thereto, to dissolve the oxide particles. The solution was diluted with pure water and was analyzed on an atomic absorption apparatus (Z-<NUM> manufactured by Hitachi, Ltd. ) to determine the amounts of potassium and sodium in terms of oxide (K<NUM>O and Na<NUM>O).

Based on the measurement results, the contents of the components in the inorganic oxide fine particles were calculated.

Approximately <NUM> of an aqueous dispersion of inorganic oxide fine particles (core particles) was placed into a magnetic crucible (model: B-<NUM>) and was dried at <NUM> for <NUM> hours. The residue was added to a desiccator and was cooled to room temperature. Next, the residue was crushed in a mortar for <NUM> minutes and was analyzed on an X-ray diffractometer (RINT <NUM> manufactured by Rigaku Corporation) to identify the crystalline form.

The shape of inorganic oxide fine particles was observed with a scanning electron microscope (SEM) (S-<NUM> manufactured by Hitachi High-Technologies Corporation) at an accelerating voltage of <NUM> kV. The sample for observation was prepared as follows.

An aqueous dispersion sol of inorganic oxide fine particles was diluted with water to a solid concentration of <NUM>%. The diluted dispersion was applied to a collodion-coated metal grid (Okenshoji Co. ) and was irradiated with a <NUM> W lamp for <NUM> minutes to evaporate the solvent. A sample for observation was thus fabricated.

To <NUM>, in terms of solid, of a dispersion of inorganic oxide fine particles in water or methanol, a solvent was appropriately added so that the water/methanol ratio (by weight) would be <NUM>/<NUM> and the solid concentration would be <NUM> wt%. Next, the dispersion was mixed together with a glycerol solution of sunset yellow dye having a solid concentration of <NUM> wt% so that the weight ratio (weight of dispersion/weight of glycerol solution) would be <NUM>/<NUM>. The sample thus prepared was added to a quartz cell <NUM> in depth, <NUM> in width and <NUM> in height. Next, a UV lamp (SLUV-<NUM> manufactured by AS ONE) preset to emit a range of wavelengths including i-line wavelength (<NUM>) was arranged <NUM> away from a <NUM> in width × <NUM> in height face of the quartz cell, and the sample was UV irradiated on that face at an intensity of <NUM> mW/cm<NUM> (in terms of <NUM> wavelength) for <NUM> hours.

The absorbances (A<NUM>) and (A<NUM>) at <NUM> wavelength of the sample were measured before the UV irradiation or after the UV irradiation, respectively, with an ultraviolet visible light spectrophotometer (V-<NUM> manufactured by JASCO). The color fading rate of the dye was calculated using the following equation.

he surface of a thermally cured coating film on a substrate was cut with a knife at intervals of <NUM> so as to leave eleven parallel scratches in each of the vertical and horizontal directions. One hundred squares were thus drawn. Next, the coated substrate was subjected to an accelerated exposure test using a xenon weather meter (SX-<NUM> manufactured by Suga Test Instruments Co. , UV intensity: <NUM> W/m<NUM>, testing conditions in accordance with JIS-K7350-<NUM>), and an adhesive cellophane tape was attached to the squares. Next, the adhesive cellophane tape was peeled, and the presence or absence of squares that had been stripped was confirmed. When all the squares remained laminated, the coated substrate was subjected again to the accelerated exposure test, and an adhesive cellophane tape was attached to the squares and peeled therefrom. This cycle was repeated, and the total UV irradiation time to the stripping of one or more squares was determined.

The surface of a photocured coating film on a film was cut with a knife at intervals of <NUM> so as to leave eleven parallel scratches in each of the vertical and horizontal directions. One hundred squares were thus drawn. Next, the coated film was subjected to an accelerated exposure test using a xenon weather meter (SX-<NUM> manufactured by Suga Test Instruments Co. , UV intensity: <NUM> W/m<NUM>), and an adhesive cellophane tape was attached to the squares. Next, the adhesive cellophane tape was peeled, and the count of the squares that remained laminated on the film was determined.

Another film coated with a photocured coating film was provided and was visually inspected for the degree of cracks on the coating film.

The symbols in Table <NUM> have the following meanings.

An aqueous dispersion sol having a solid concentration of <NUM>% was placed into a cell having an optical length of <NUM>. The total light transmittance and the haze were measured with a colorimeter/turbidity meter (COH-<NUM> manufactured by NIPPON DENSHOKU INDUSTRIES CO.

<NUM> of an aqueous titanium tetrachloride solution (manufactured by OSAKA Titanium technologies Co. ) containing <NUM> wt% titanium tetrachloride in terms of TiO<NUM> was mixed together with <NUM> of an aqueous ferric chloride solution containing <NUM> wt% ferric chloride (manufactured by Hayashi Pure Chemical Ind. ) in terms of Fe<NUM>O<NUM>. The resultant mixture was mixed together with <NUM> of ammonia water (manufactured by UBE INDUSTRIES, LTD. ) containing <NUM> wt% ammonia to give a light yellow brown slurry having a pH of <NUM>. Next, the slurry was filtered, and the residue was washed with pure water. Thus, <NUM> of an iron-containing hydrous titanic acid cake with a solid concentration of <NUM> wt% was obtained.

Next, <NUM> of an aqueous hydrogen peroxide solution (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC. ) containing <NUM> wt% hydrogen peroxide and <NUM> of pure water were added to the cake. The mixture was stirred at a temperature of <NUM> for <NUM> hour, and further <NUM> of pure water was added. Thus, <NUM> of an aqueous iron-containing peroxotitanic acid solution was obtained which contained an iron-containing peroxotitanic acid in an amount of <NUM> wt% in terms of titanium and iron as TiO<NUM> and Fe<NUM>O<NUM>, respectively. The aqueous iron-containing peroxotitanic acid solution was transparent yellow brown, had a pH of <NUM>, and had a particle size of the particles in the aqueous solution (in Table <NUM>-<NUM>, written as the "peroxotitanic acid particle size") of <NUM>.

Next, <NUM> of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation) was admixed to <NUM> of the aqueous iron-containing peroxotitanic acid solution. While performing stirring, <NUM> of an aqueous potassium stannate solution containing <NUM> wt% potassium stannate (manufactured by Showa Kako Corporation) in terms of SnO<NUM> was gradually added thereto.

Next, the cation exchange resin which had trapped ions such as potassium ions was separated from the aqueous solution. Thereafter, to the aqueous solution were admixed <NUM> of pure water and <NUM> of a sol (hereinafter also written as the "silica-based sol <NUM>", pH: <NUM>, solid concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% aluminum in terms of Al<NUM>O<NUM>. The resultant mixture was heated in an autoclave (manufactured by TAIATSU TECHNO CORPORATION, <NUM>) at a temperature of <NUM> for <NUM> hours.

Next, the sol obtained above was cooled to room temperature and was concentrated with an ultrafiltration membrane apparatus (ACV-<NUM> manufactured by Asahi Kasei Corporation). Thus, <NUM> of an aqueous dispersion sol having a solid concentration of <NUM> wt% was obtained.

The fine particles contained in the aqueous dispersion sol were iron-containing titanium oxide fine particles which had a rutile crystal structure and contained tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 1A"). The contents of metal components (including silicon, the same applies hereinafter) in the inorganic oxide fine particles 1A were, in terms of oxide, <NUM> wt% TiO<NUM>, <NUM> wt% SnO<NUM>, <NUM> wt% SiO<NUM>, <NUM> wt% K<NUM>O, <NUM> wt% Fe<NUM>O<NUM>, and <NUM> wt% Al<NUM>O<NUM>.

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous titanium tetrachloride solution and the aqueous ferric chloride solution were changed to <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing rutile titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 2A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous titanium tetrachloride solution and the aqueous ferric chloride solution were changed to <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 3A").

The procedures in Example <NUM> were repeated, except that the amount of the aqueous titanium tetrachloride solution was changed to <NUM> and the aqueous ferric chloride solution was not added. An aqueous dispersion sol was thus obtained which contained titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 4A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous titanium tetrachloride solution and the aqueous ferric chloride solution were changed to <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 5A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous titanium tetrachloride solution and the aqueous ferric chloride solution were changed to <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 6A").

<NUM> of an aqueous titanium tetrachloride solution (manufactured by OSAKA Titanium technologies Co. ) containing <NUM> wt% titanium tetrachloride in terms of TiO<NUM> was mixed together with ammonia water (manufactured by UBE INDUSTRIES, LTD. ) containing <NUM> wt% ammonia to give a white slurry having a pH of <NUM>. Next, the slurry was filtered, and the residue was washed with pure water. Thus, <NUM> of a hydrous titanic acid cake having a solid concentration of <NUM> wt% was obtained.

Next, <NUM> of an aqueous hydrogen peroxide solution (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC. ) containing <NUM> wt% hydrogen peroxide and <NUM> of pure water were added to <NUM> of the cake. The mixture was stirred at a temperature of <NUM> for <NUM> hour. Thus, <NUM> of an aqueous peroxotitanic acid solution was obtained which contained a peroxotitanic acid in an amount of <NUM> wt% in terms of TiO<NUM>. The aqueous peroxotitanic acid solution was transparent yellow brown and had a pH of <NUM>.

Next, <NUM> of pure water and <NUM> of a sol (concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM>% aluminum in terms of Al<NUM>O<NUM> were admixed to <NUM> of the aqueous peroxotitanic acid solution. The resultant mixture was heated in an autoclave (manufactured by TAIATSU TECHNO CORPORATION, <NUM>) at a temperature of <NUM> for <NUM> hours.

The fine particles contained in the aqueous dispersion sol were titanium oxide fine particles which had an anatase crystal structure and contained silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 7A").

The procedures in Comparative Example <NUM> were repeated, except that the amount of the aqueous titanium tetrachloride solution was changed to <NUM>, and <NUM> of an aqueous ferric chloride solution having a concentration of <NUM>% in terms of Fe<NUM>O<NUM> was added thereto. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having an anatase crystal structure and containing silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 8A").

The procedures in Example <NUM> were repeated, except that the amount of the silica-based sol <NUM> (manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) was changed to <NUM>, and the amount of pure water to be mixed with the silica-based sol <NUM> was changed to <NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 9A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous iron-containing peroxotitanic acid solution, the cation exchange resin and the aqueous potassium stannate solution were changed to <NUM>, <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 10A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous iron-containing peroxotitanic acid solution, the cation exchange resin and the aqueous potassium stannate solution were changed to <NUM>, <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 11A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous iron-containing peroxotitanic acid solution, the cation exchange resin and the aqueous potassium stannate solution were changed to <NUM>, <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 12A").

The procedures in Example <NUM> were repeated, except that the amounts of the aqueous iron-containing peroxotitanic acid solution, the cation exchange resin and the aqueous potassium stannate solution were changed to <NUM>, <NUM> and <NUM>, respectively. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 13A"). The crystalline form of the inorganic oxide fine particles 13A was a rutile anatase mixed crystal.

The procedures in Example <NUM> were repeated, except that the amount of the silica-based sol <NUM> was changed to <NUM>, and the amount of pure water to be mixed with the silica-based sol <NUM> was changed to <NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing rutile titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 14A").

The procedures in Example <NUM> were repeated, except that the amount of the silica-based sol <NUM> was changed to <NUM>, and the amount of pure water to be mixed with the silica-based sol <NUM> was changed to <NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 15A").

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (i.e. silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% aluminum in terms of Al<NUM>O<NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 16A").

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (i.e. silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% aluminum in terms of Al<NUM>O<NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 17A").

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM>%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (i.e. silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% aluminum in terms of Al<NUM>O<NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 18A").

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (hereinafter also written as the "silica-based sol <NUM>", pH: <NUM>) of silica fine particles (i.e. silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% zirconium in terms of ZrO<NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles having a rutile crystal structure and containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 19A").

The procedures in Example <NUM> for obtaining an aqueous iron-containing peroxotitanic acid solution were changed so that <NUM> of the aqueous hydrogen peroxide solution containing <NUM>% hydrogen peroxide and <NUM> of pure water were added to <NUM> of the iron-containing hydrous titanic acid cake, the mixture was stirred at <NUM> for <NUM> hour, and further <NUM> of pure water was added. Thus, <NUM> of an aqueous iron-containing peroxotitanic acid solution was obtained which contained an iron-containing peroxotitanic acid in an amount of <NUM> wt% in terms of TiO<NUM> + Fe<NUM>O<NUM>. The aqueous iron-containing peroxotitanic acid solution was transparent and a little yellow brown, had a pH of <NUM>, and had a particle size of the particles in the aqueous solution of <NUM>.

Except that the aqueous iron-containing peroxotitanic acid solution was obtained using the iron-containing hydrous titanic acid cake as described above, the procedures in Example <NUM> were repeated and <NUM> of an aqueous dispersion sol having a solid concentration of <NUM> wt% was obtained.

The fine particles contained in the aqueous dispersion sol were iron-containing titanium oxide fine particles which had a rutile crystal structure and contained tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 20A").

The procedures in Example <NUM> for obtaining an aqueous iron-containing peroxotitanic acid solution were changed so that <NUM> of the aqueous hydrogen peroxide solution containing <NUM>% hydrogen peroxide and <NUM> of pure water were added to <NUM> of the iron-containing hydrous titanic acid cake, the mixture was stirred at room temperature for <NUM> hours so as to slowly peptize the iron-containing hydrous titanic acid, thereafter the mixture was stirred at <NUM> for <NUM> hour, and further <NUM> of pure water was added. Thus, <NUM> of an aqueous iron-containing peroxotitanic acid solution was obtained which contained an iron-containing peroxotitanic acid in an amount of <NUM> wt% in terms of TiO<NUM> + Fe<NUM>O<NUM>. The aqueous iron-containing peroxotitanic acid solution was a little whitened yellow brown, had a pH of <NUM>, and had a particle size of the particles in the aqueous solution of <NUM>.

The fine particles contained in the aqueous dispersion sol were iron-containing titanium oxide fine particles which had a rutile crystal structure and contained tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 21A").

The procedures in Example <NUM> for obtaining an aqueous iron-containing peroxotitanic acid solution were changed so that <NUM> of the aqueous hydrogen peroxide solution containing <NUM>% hydrogen peroxide and <NUM> of pure water were added to <NUM> of the iron-containing hydrous titanic acid cake, the mixture was stirred at room temperature for <NUM> hours and was further stirred at <NUM> for <NUM> hour, and further <NUM> of pure water was added. Thus, <NUM> of an aqueous iron-containing peroxotitanic acid solution was obtained which contained an iron-containing peroxotitanic acid in an amount of <NUM> wt% in terms of TiO<NUM> + Fe<NUM>O<NUM>. The aqueous iron-containing peroxotitanic acid solution was slightly whitened yellow brown, had a pH of <NUM>, and had a particle size of the particles in the aqueous solution of <NUM>.

The fine particles contained in the aqueous dispersion sol were iron-containing titanium oxide fine particles which had a rutile crystal structure and contained tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 22A").

The procedures were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles which had a specific surface area of <NUM><NUM>/g and contained no aluminum. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 23A"). The crystalline form of the inorganic oxide particles 23A was a rutile anatase mixed crystal.

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM> wt%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles which had a specific surface area of <NUM><NUM>/g and contained no aluminum. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 24A"). The crystalline form of the inorganic oxide particles 24A was a rutile anatase mixed crystal.

The procedures in Example <NUM> were repeated, except that the silica-based sol <NUM> was replaced by a sol (pH: <NUM>, concentration: <NUM>%, manufactured by JGC CATALYSTS AND CHEMICALS LTD. ) of silica fine particles (i.e. silica-based fine particles) which had a specific surface area of <NUM><NUM>/g and contained <NUM> wt% aluminum in terms of Al<NUM>O<NUM>. An aqueous dispersion sol was thus obtained which contained iron-containing titanium oxide fine particles containing tin and silicon (hereinafter, the fine particles will be written as the "inorganic oxide fine particles 25A"). The crystalline form of the inorganic oxide fine particles 25A was a rutile anatase mixed crystal.

Tables <NUM>-<NUM> to <NUM>-<NUM> describe the raw materials, the characteristics of the inorganic oxide fine particles and of the dispersions, and the evaluation results in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>.

While performing stirring, ammonia water containing <NUM> wt% ammonia was gradually added to <NUM> of an aqueous zirconium oxychloride solution containing <NUM> wt% zirconium oxychloride (manufactured by TAIYO KOKO CO. ) in terms of ZrO<NUM>. A slurry with a pH of <NUM> was thus obtained. Next, the slurry was filtered, and the residue was washed with pure water to give <NUM> of a cake containing <NUM> wt% zirconium component in terms of ZrO<NUM>.

Next, <NUM> of pure water was added to <NUM> of the cake, and the system was rendered alkaline by the addition of <NUM> of an aqueous potassium hydroxide solution containing <NUM> wt% potassium hydroxide (manufactured by KANTO CHEMICAL CO. Thereafter, <NUM> of an aqueous hydrogen peroxide solution containing <NUM> wt% hydrogen peroxide was added, and the mixture was heated to a temperature of <NUM> to dissolve the cake. Further, <NUM> of pure water was added. Thus, <NUM> of an aqueous peroxozirconic acid solution containing <NUM> wt% peroxozirconic acid in terms of ZrO<NUM> was obtained. The pH of the aqueous peroxozirconic acid solution was <NUM>.

Separately, commercial water glass (manufactured by AGC Si-Tech Co. ) was diluted with pure water and was dealkalized using a cation exchange resin (manufactured by Mitsubishi Chemical Corporation). Thus, an aqueous silicic acid solution containing <NUM> wt% silicon component in terms of SiO<NUM> was obtained. The pH of the aqueous silicic acid solution was <NUM>.

Next, <NUM> of pure water was added to <NUM> of the aqueous dispersion sol obtained in Example <NUM> which contained the inorganic oxide fine particles 1A, and the mixture was stirred to give an aqueous dispersion sol having a solid concentration of <NUM> wt%. Next, the aqueous dispersion sol was heated to a temperature of <NUM>, and <NUM> of the aqueous peroxozirconic acid solution and <NUM> of the aqueous silicic acid solution were gradually added thereto. After the completion of the addition, the liquid mixture obtained was aged at a constant temperature of <NUM> for <NUM> hour while performing stirring.

Next, the aged liquid mixture was placed into an autoclave (manufactured by TAIATSU TECHNO CORPORATION, <NUM>) and was heat treated at a temperature of <NUM> for <NUM> hours.

Next, the liquid mixture was cooled to room temperature and was concentrated using an ultrafiltration membrane apparatus (SIP-<NUM> manufactured by Asahi Kasei Corporation). Thus, an aqueous dispersion sol 1B having a solid concentration of <NUM> wt% was obtained.

The fine particles contained in the aqueous dispersion sol 1B were core-shell iron-containing rutile titanium oxide fine particles which were each composed of an iron-containing titanium oxide fine particle (a core particle) having a rutile crystal structure and containing tin and silicon, and a composite oxide containing zirconium and silicon which covered the surface of the fine particle (hereinafter, the core-shell fine particles will be written as the "inorganic oxide fine particles 1B"). The aqueous dispersion sol 1B was transparent and slightly yellow brown.

While performing stirring, the aqueous dispersion sol 1B obtained in the step (<NUM>) was added to a methanol solution of tetraethoxysilane (manufactured by Tama Chemicals Co. ) as a surface treating agent.

Next, the liquid mixture was heated at a temperature of <NUM> for <NUM> hours, cooled to room temperature, and passed through an ultrafiltration membrane apparatus to replace water as the dispersion medium by methanol (manufactured by CHUSEI OIL CO.

Further, the methanol dispersion obtained was concentrated with an ultrafiltration membrane apparatus (SIP-<NUM> manufactured by Asahi Kasei Corporation). Thus, a methanol dispersion sol 1Bm was prepared which had a solid concentration of <NUM> wt% and contained the inorganic oxide fine particles 1B.

The methanol dispersion sol 1Bm was transparent and slightly yellow brown.

The procedures in Example <NUM> were repeated, except that the aqueous dispersion sol obtained in Example <NUM> was replaced by the aqueous dispersion sol obtained in Example <NUM> which contained the inorganic oxide fine particles 3A. Thus, an aqueous dispersion sol 3B was obtained which contained core-shell iron-containing rutile titanium oxide fine particles that were each composed of an iron-containing titanium oxide fine particle (a core particle) having a rutile crystal structure and containing tin and silicon, and a composite oxide containing zirconium and silicon which covered the surface of the fine particle (hereinafter, the core-shell fine particles will be written as the "inorganic oxide fine particles 3B"). The aqueous dispersion sol 3B was transparent yellow brown.

The procedures in the step (<NUM>) in Example <NUM> were repeated, except that the aqueous dispersion sol 1B was replaced by the aqueous dispersion sol 3B. Thus, a methanol dispersion sol 3Bm was prepared which had a solid concentration of <NUM> wt% and contained the inorganic oxide fine particles 3B.

The methanol dispersion sol 3Bm was transparent and slightly yellow brown.

<NUM> of a <NUM>% aqueous solution of NaOH (manufactured by AGC Inc. ) in pure water was added to <NUM> of the aqueous dispersion sol obtained in Example <NUM> which contained the inorganic oxide fine particles 10A, thereby adjusting the pH to approximately <NUM>. Thereafter, <NUM> of pure water was added, and the mixture was heated to <NUM>. To the heated aqueous dispersion sol, <NUM> of a <NUM> wt% aqueous silicic acid solution prepared in the same manner as in Example <NUM> and <NUM> of an aqueous sodium aluminate solution prepared by diluting sodium aluminate (manufactured by Asahi Chemical Co. ) with pure water to <NUM>% in terms of Al<NUM>O<NUM> were added concurrently over a period of <NUM> hours. Thereafter, the liquid mixture was aged at <NUM> for <NUM> hour, cooled, and concentrated with an ultrafiltration membrane apparatus (SIP-<NUM> manufactured by Asahi Kasei Corporation). Thus, an aqueous dispersion sol 10B having a solid concentration of <NUM> wt% was obtained.

The fine particles contained in the aqueous dispersion sol 10B were core-shell iron-containing rutile titanium oxide fine particles which were each composed of an iron-containing titanium oxide fine particle (a core particle) having a rutile crystal structure and containing tin and silicon, and a composite oxide containing silicon and aluminum which covered the surface of the fine particle (hereinafter, the core-shell fine particles will be written as the "inorganic oxide fine particles 10B"). The aqueous dispersion sol 10B was slightly yellow brown.

A cation exchange resin (manufactured by Mitsubishi Chemical Corporation) was added to the aqueous dispersion sol 10B until the pH became <NUM>. Thereafter, methanol was added in the same amount as the aqueous dispersion sol, and the mixture was passed through an ultrafiltration membrane apparatus to replace water as the dispersion medium by methanol and to concentrate the sol. Thus, a methanol dispersion sol 10Bm was prepared which had a solid concentration of <NUM> wt% and contained the inorganic oxide fine particles 10B.

The procedures in the step (<NUM>) in Example <NUM> were repeated, except that the aqueous dispersion sol obtained in Example <NUM> was replaced by the aqueous dispersion sol obtained in Comparative Example <NUM> which contained the inorganic oxide fine particles 4A. Thus, an aqueous dispersion sol 4B was obtained which contained core-shell rutile titanium oxide fine particles that were each composed of a titanium oxide fine particle (a core particle) having a rutile crystal structure and containing tin and silicon, and a composite oxide containing zirconium and silicon which covered the surface of the fine particle (hereinafter, the core-shell fine particles will be written as the "inorganic oxide fine particles 4B"). The aqueous dispersion sol 4B was transparent and slightly milky white.

Further, the procedures in the step (<NUM>) in Example <NUM> were repeated, except that the aqueous dispersion sol 1B was replaced by the aqueous dispersion sol 4B. Thus, a methanol dispersion sol 4Bm was prepared which had a solid concentration of <NUM> wt% and contained the inorganic oxide fine particles 4B.

The methanol dispersion sol 4Bm was transparent and slightly blue.

The procedures in the step (<NUM>) in Example <NUM> were repeated, except that the aqueous dispersion sol obtained in Example <NUM> was replaced by the aqueous dispersion sol obtained in Comparative Example <NUM> which contained the inorganic oxide fine particles 8A. Thus, an aqueous dispersion sol 8B was obtained which contained core-shell iron-containing anatase titanium oxide fine particles that were each composed of an iron-containing titanium oxide fine particle (a core particle) having an anatase crystal structure and containing silicon, and a composite oxide containing zirconium and silicon which covered the surface of the fine particle (hereinafter, the core-shell fine particles will be written as the "inorganic oxide fine particles 8B"). The aqueous dispersion sol 8B was transparent and slightly milky white.

Further, the procedures in the step (<NUM>) in Example <NUM> were repeated, except that the aqueous dispersion sol 1B was replaced by the aqueous dispersion sol 8B. Thus, a methanol dispersion sol 8Bm was prepared which had a solid concentration of <NUM> wt% and contained the inorganic oxide fine particles 8B.

The methanol dispersion sol 8Bm was light yellow brown.

Table <NUM> describes the characteristics of the inorganic oxide fine particles and of the dispersions, and the evaluation results in Examples <NUM> to <NUM> and Comparative Examples <NUM> and <NUM>.

<NUM> of methanol (manufactured by CHUSEI OIL CO. ) was added to <NUM> of γ-glycidoxypropyltrimethoxysilane (manufactured by Momentive Performance Materials Japan Limited Liability Company). While performing stirring, <NUM> of <NUM> N hydrochloric acid was added dropwise. The mixture was further stirred at room temperature for a whole day and night to hydrolyze the γ-glycidoxypropyltrimethoxysilane.

Next, <NUM> of the methanol dispersion sol 1Bm, <NUM> of propylene glycol monomethyl ether (manufactured by Dow Chemical Japan Ltd. ), <NUM> of itaconic acid (manufactured by Kishida Chemical Co. ), <NUM> of dicyandiamide (manufactured by Kishida Chemical Co. ) and <NUM> of a silicone surfactant (L-<NUM> manufactured by Dow Corning Toray Co. ) as a leveling agent were added to the above liquid mixture. The resultant mixture was stirred at room temperature for a whole day and night. Thus, a thermally curable paint composition (hereinafter, written as the "hardcoat paint 1BmH") was prepared.

As many commercial plastic lens substrates (name of monomer: "MR-<NUM>" manufactured by Mitsui Chemicals, Inc. ) with <NUM> refractive index as required were provided and were etched by being soaked in a <NUM> wt% aqueous KOH solution kept at <NUM> for <NUM> minutes. The substrates were collected, water washed and sufficiently dried.

The hardcoat paint 1BmH obtained above was applied to the surface of the plastic lens substrates to form coating films. This application of the paint composition was performed by dipping (lift-up rate: <NUM>/min). The coating films were cured by heat treatment at <NUM> for <NUM> minutes and then at <NUM> for <NUM> hours. Thus, coated substrates 1BmHF having a thermally cured coating film were obtained.

A thermally curable paint composition (hereinafter, written as the "hardcoat paint 3BmH") was prepared and coated substrates 3BmHF having a thermally cured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 3Bm.

A thermally curable paint composition (hereinafter, written as the "hardcoat paint 10BmH") was prepared and coated substrates 10BmHF having a thermally cured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 10Bm.

A thermally curable paint composition (hereinafter, written as the "hardcoat paint 4BmH") was prepared and coated substrates 4BmHF having a thermally cured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 4Bm.

A thermally curable paint composition (hereinafter, written as the "hardcoat paint 8BmH") was prepared and coated substrates 8BmHF having a thermally cured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 8Bm.

Table <NUM> describes the results of evaluations of the coated substrates obtained in Examples <NUM> to <NUM> and Comparative Examples <NUM> and <NUM>.

<NUM>% Aqueous ammonia solution was added to <NUM> of the methanol dispersion sol 1Bm having a solid concentration of <NUM> wt% so that the ammonia concentration would be <NUM> ppm. Next, <NUM> of <NUM>-methacryloxypropyltrimethoxysilane (KBM-<NUM> manufactured by Shin-Etsu Chemical Co. ) was added, and the mixture was stirred at <NUM> for <NUM> hours. Next, <NUM> of propylene glycol monomethyl ether (hereinafter, written as "PGME", manufactured by SANKYO KASEI CO. ) was added. The mixture was treated in a rotary evaporator at an elevated temperature under reduced pressure to remove the solvent, the weight reaching <NUM>. Thereafter, PGME was further added. Thus, a PGME dispersion sol 1Bp having a solid concentration of <NUM> wt% was obtained. The viscosity of the PGME dispersion sol 1Bp was <NUM> mPa·s.

While performing stirring, <NUM> of PGME (SANKYO KASEI CO. ), <NUM> of acetone (Kishida Chemical Co. ), <NUM> of DPHA (KAYARAD DPHA manufactured by Nippon Kayaku Co. ), <NUM> of <NUM>,<NUM>-hexanediol diacrylate (SR-238F manufactured by TOMOE Engineering Co. ) and <NUM> of a photocuring catalyst (IRGACURE <NUM> manufactured by BASF) were admixed to <NUM> of the PGME dispersion sol 1Bp. Thus, a photocurable paint composition 1BpU was obtained.

The photocurable paint composition 1BpU was applied to a <NUM> primer-coated PET film (A4300 manufactured by TOYOBO CO. ) with use of a bar coater (#<NUM>). The solvent was removed by heat treatment at <NUM> for <NUM> minutes. The film was placed into a container, which was then tightly closed and filled with nitrogen. The film was UV irradiated at <NUM> mJ/cm<NUM> using Heraeus UV-H valve. A coated film 1BpUF having a photocured coating film was thus obtained.

A PGME dispersion sol 4Bp having a solid concentration of <NUM> wt% (viscosity: <NUM> mPa·s), a photocurable paint composition 4BpU, and a coated film 4BpUF having a photocured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 4Bm.

A PGME dispersion sol 8Bp having a solid concentration of <NUM> wt% (viscosity: <NUM> mPa·s), a photocurable paint composition 8BpU, and a coated film 8BpUF having a photocured coating film were obtained in the same manner as in Example <NUM>, except that the methanol dispersion sol 1Bm was replaced by the methanol dispersion sol 8Bm.

Table <NUM> describes the results of evaluations of the coated films with a photocured coating film obtained in Example <NUM> and Comparative Examples <NUM> and <NUM>.

Claim 1:
A method for producing a dispersion of iron-containing rutile titanium oxide fine particles, comprising:
a step (<NUM>) of neutralizing an aqueous metal mineral acid salt solution containing Ti and Fe as metals to form an iron-containing hydrous titanic acid, the masses of the metals in the aqueous solution in terms of oxide being such that mass of Fe<NUM>O<NUM>/(total mass of TiO<NUM> and Fe<NUM>O<NUM>) = <NUM> to <NUM>;
a step (<NUM>) of adding an aqueous hydrogen peroxide solution to the iron-containing hydrous titanic acid obtained in the step (<NUM>) to form an aqueous solution of iron-containing peroxotitanic acid having an average particle size of <NUM> to <NUM>;
a step (<NUM>) of adding a tin compound to the aqueous solution of iron-containing peroxotitanic acid obtained in the step (<NUM>) in such an amount that the masses of Sn and Ti in the aqueous solution in terms of oxide satisfy mass of TiO<NUM>/mass of SnO<NUM> = <NUM> to <NUM>;
a step (<NUM>) of adding a sol of silica-based fine particles to the solution obtained in the step (<NUM>), the silica-based fine particles containing Si and at least one metal element (M) selected from the group consisting of Al, Zr, Sb, Zn, Ni, Ba, Mg and V in such amounts that the masses thereof in terms of oxide satisfy mass of SiO<NUM>/mass of MOx/<NUM> (x is the valence of M) = <NUM>/<NUM> to <NUM>/<NUM>, the addition being made so that the masses in terms of oxide of the metal elements in the solution obtained in the step (<NUM>) and the masses in terms of oxide of the silicon and the metal element or elements in the sol satisfy mass of SiO<NUM>/(total mass of TiO<NUM>, SnO<NUM>, Fe<NUM>O<NUM>, SiO<NUM> and MOx/<NUM>) = <NUM> to <NUM>; and
a step (<NUM>) of hydrothermally treating the solution obtained in the step (<NUM>) to produce a dispersion of iron-containing rutile titanium oxide fine particles.