JP2007197278A - Inorganic oxide ultrafine particle and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inorganic oxide ultrafine particles e.g., useful to the materials for optical members, optical members such as antireflection agents and various applications, to provide a sol liquid, and to provide a method for producing the same. <P>SOLUTION: In the coated type inorganic oxide ultrafine particles, inorganic oxide ultrafine particles comprising titanium oxide with a rutile type crystal structure having a refractive index of 1.5 to 2.8 are used as nuclear fine particles, and each nuclear fine particle is provided with a coating layer composed of silicon oxide by a specified process. Each nuclear fine particle includes tin-modified rutile type titanium oxide ultrafine particles obtained by a specified process, and the coating layer composed of silicon oxide is a double layer coating type, and is obtained by coating an internal layer and an external layer by a specified process. Further, the coated type inorganic oxide ultrafine particles are composed of sol obtained by being dispersed into water or an organic solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical member material, an optical member such as an antireflective agent, inorganic oxide ultrafine particles useful for various applications, a sol solution, and a method for producing the same.

  More specifically, optical lenses (glass lenses, pickup lenses in information recording devices such as CDs and DVDs, lenses for photographing devices such as digital cameras), optical prisms, optical waveguides, optical fibers, thin film moldings, optical adhesives, Anti-reflective materials in plastic materials such as encapsulating materials for optical semiconductors, anti-plastic deterioration additives, cosmetic additives, automotive window glass, plasma displays, liquid crystal displays, EL displays, optical filters, etc. High transparency, dispersibility, storage stability, light resistance, weather resistance, etc. useful for applications such as optical materials such as dielectric materials and diffusion plates, metal materials, ceramic materials, glass materials, plastic materials, coating materials, etc. The present invention relates to a coated inorganic oxide ultrafine particle having a refractive index, a sol liquid, and a production method thereof.

  Inorganic glass is excellent in various physical properties such as excellent transparency, and is used in a wide field as an optical member. However, it is disadvantageous in that it is heavy and easily damaged, and the workability and productivity are poor. Thus, transparent optical resins have been actively developed as a material to replace inorganic glass. Non-represented by acrylic resin, styrene resin, polycarbonate resin, polyester resin, olefin resin, alicyclic acrylic resin, alicyclic olefin resin, polyurethane resin, polyether resin, polyamide resin, polyimide resin A curable resin such as a crystalline thermoplastic resin, or an epoxy resin, an unsaturated polyester resin, or a silicone resin has good transparency in the visible region wavelength, and is more moldable, mass-productive than an inorganic glass material, or It is a general-purpose transparent resin material having excellent characteristics such as flexibility, toughness and impact resistance. By giving a high refractive index to such a transparent resin material, a thin and light optical lens (plastic eyeglass lens, pickup lens in information recording equipment such as CD and DVD, lens for photographing equipment such as a digital camera), Development of materials such as optical prisms, optical waveguides, optical fibers, thin film moldings, optical adhesives, and optical semiconductor sealing materials is expected.

  For example, in the field of plastic eyeglass lenses, in order to meet the needs of fashionableness, it is necessary to lower the center thickness, edge thickness, and curvature of the lens, and to be thin overall. In this respect, a higher refractive index is required. In recent years, research into increasing the refractive index by using a monomer containing an element having a large atomic number such as sulfur or a halogen element has been actively conducted. Conventionally, diethylene glycol bisallyl carbonate resin (refractive index: 1.50) having a low refractive index has been used for spectacle lenses. Recently, a thiol compound and an isocyanate compound described in Patent Document 1 are thermally polymerized to obtain a thiol compound. Obtained by forming an epithiosulfide bond by ring-opening thermal polymerization of a resin lens (refractive index of 1.60 to 1.70) obtained by forming a urethane bond, and further a thioepoxy compound described in Patent Document 2. Resin-resin lenses (refractive index of 1.70 or more) have been developed. However, since it is a special high refractive index resin using a non-general special monomer, there is a problem that the industrial application field is extremely limited. Although it is increased by the introduction of such a halogen element or sulfur element, the refractive index of the organic resin is determined by the element used and the molecular structure, and is usually limited to a range of about 1.4 to 1.7. Therefore, amorphous resin represented by acrylic resin, styrene resin, polycarbonate resin, polyester resin, olefin resin, alicyclic acrylic resin, alicyclic olefin resin, polyurethane resin, polyether resin, polyamide resin, polyimide resin. High refractive index technology using a general-purpose transparent resin such as a curable thermoplastic resin, or a curable resin such as an epoxy resin or an unsaturated polyester resin, particularly a high refractive index resin having a refractive index of 1.7 or more is strongly demanded. ing.

  Also, for example, for a polymer optical fiber using an acrylic resin such as polymethyl methacrylate (PMMA), the refractive index of the core part (center part in the optical fiber cross section) is higher than that of the cladding part (same outer peripheral part). As the rate difference is larger, the numerical aperture corresponding to the maximum angle at which light can propagate can be increased.

  For example, in the light emitting diode, the light emitting element portion is sealed with epoxy resin, silicon resin, or the like. In general, the refractive index of a semiconductor constituting the semiconductor element portion is very high. If the refractive index of a substance in contact with the semiconductor element portion is low, the critical angle is small and total reflection tends to occur. Therefore, the angle at which the total reflection occurs can be increased by sandwiching the light emitting element with a material having a higher refractive index, and the light beam extraction efficiency is improved accordingly.

  Furthermore, there is a demand for the development of a material that uses a plurality of materials having different refractive indexes, such as an optical fiber, an optical waveguide, and some lenses, or has a distribution in the refractive index. In order to cope with these materials, it is indispensable to arbitrarily adjust the refractive index.

  In recent years, for the purpose of increasing the refractive index of resins, transparent inorganic oxide fine particles having a high refractive index having a crystal structure such as Zr, Sn, Sb, Mo, In, Zn, Ti, or composite oxides thereof have been dispersed. A technique for forming a colorless and transparent high refractive index resin by introducing it into the resin while maintaining the state has been proposed. Since high dispersibility and transparency are required for use in such applications, the inorganic oxide is preferably ultrafine particles having a particle size of 1 to 100 nm.

  However, in the above technique, it has not been sufficient to design a resin having a high refractive index while using a matrix amount that can maintain strength and the like. This is because if the content of fine particles is too large to increase the refractive index, the resin becomes brittle. In addition, it is difficult to obtain a transparent resin as it becomes more likely to be agglomerated as it becomes ultrafine particles.

  On the other hand, plastic eyeglass lenses have the disadvantage of being scratch resistant and easily scratched. Therefore, a coating composition using silica sol and an organosilicon compound or a photo-curable coating composition is prepared, and the hard coating film is coated on the surface. The method of providing in is performed. In addition, plastic spectacle lenses have the disadvantage of low impact resistance. Therefore, a method of applying a primer film between the base material and the hard coating film to absorb impact is used. However, since the substrate has a high refractive index and a low refractive index, interference fringes due to a difference in refractive index from the substrate can be seen in the coating film, resulting in a problem of poor appearance. Therefore, the refractive index of the hard coating film, primer film, or photocurable hard coating film needs to be close to the refractive index equivalent level of the substrate.

  So far, antimony oxide has been recommended as the inorganic oxide ultrafine particles and sol solution to be added to the coating composition for increasing the refractive index of the coating film, but the refractive index of the plastic substrate of the lens is 1.6 as recently. In these cases, this antimony oxide can no longer be used. This is because antimony oxide itself has a refractive index of 1.7, but is used by being filled in an organosilicon compound having a low refractive index, so that the refractive index as a coating film is lower than that of the substrate.

  Similarly, ultra-fine particles with a high refractive index and sol solution that are excellent in transparency, dispersibility, storage stability, light resistance, weather resistance, etc. are optical lenses (optical pickup lenses in information recording devices such as eyeglass lenses, CDs, DVDs, digital Lenses for photographic equipment such as cameras), optical prisms, optical waveguides, optical fibers, thin film moldings, optical adhesives, materials for high refractive optical members such as optical semiconductor sealing materials, etc., as well as plastic deterioration prevention additives , Cosmetic additives, automotive window glass, plasma displays, liquid crystal displays, EL displays, optical materials such as anti-reflective materials in dielectric filters, diffusers, metal materials, ceramic materials, glass materials, plastic materials, coatings It is also required in product fields such as materials.

  Therefore, a method using titanium oxide ultrafine particles has been proposed. Since titanium oxide has a particularly high refractive index and high transparency, it is possible to increase the refractive index of the resin composition and the coating film in a smaller amount than other fine particles. Titanium oxide includes a rutile type and an anatase type as typical crystal types. So far, materials mainly composed of anatase-type titanium oxide ultrafine particles having a refractive index no = 2.56 and ne = 2.49 have been mainly used as the inorganic oxide ultrafine particle sol solution for high refractive index. Yes. On the other hand, the refractive index of rutile-type titanium oxide has a refractive index no = 2.61, ne = 2.9 (no: refractive index for ordinary light, ne: refractive index for extraordinary light) (Chemical Society of Japan, Experimental Science) It is known that the optical properties such as high refractive index and ultraviolet absorption are superior to those of anatase type, and attempts to synthesize the rutile titanium oxide ultrafine particles and sol liquid are positive. It was done. However, the rutile type titanium oxide ultrafine particles and sol liquid that can be used industrially have not been obtained yet. For example, Jpn. J. et al. Appl. Phys. , 37, 4603 (1998), aggregates having an aggregate particle diameter of 200 to 400 nm formed by gathering long fibrous rutile type titanium oxide are produced, but cannot be used industrially as they are. there were.

  On the other hand, when these titanium oxide ultrafine particles are used in optical materials, coating materials, resin compositions, etc., particularly when used in combination with an organic medium such as a resin, it is generated by light absorption due to the photocatalytic action of titanium oxide. Organic matter decomposition due to electron-holes occurs, and scratch resistance, surface hardness, abrasion resistance, transparency, heat resistance, light resistance, weather resistance, ultraviolet shielding performance and the like are problems.

  At present, for the purpose of improving the light resistance of such anatase-type titanium oxide ultrafine particles, for example, as disclosed in Patent Document 3, ultrafine particles combining anatase-type titanium oxide and an inorganic oxide, or anatase-type titanium oxide is inorganic. Ultrafine particles coated with oxide have been applied.

  All of these are aimed at inactivating the anatase-type titanium oxide ultrafine particles by coating with an inorganic oxide. Thus, light resistance is improved by coat | covering a titanium oxide ultrafine particle with an inorganic oxide. However, since titanium oxide used is anatase type, the refractive index is about 2.5, and when coated with an inorganic oxide to improve light resistance, the refractive index is greatly reduced. The refractive index is lower than that of the original anatase-type titanium oxide, and the effect of improving the refractive index is low. Even if the amount of the inorganic oxide to be coated is reduced and the refractive index is increased, the light resistance is insufficient, and no material satisfying both the refractive index and the light resistance has been obtained.

  Furthermore, it is necessary to disperse the titanium oxide ultrafine particles and the sol solution thereof in the organic medium as described above. However, since the titanium oxide ultrafine particle sol solution is usually stable in an acidic region and gelation and precipitation occur in a neutral to basic region, the usable pH region is limited. Or when it tries to disperse | distribute to an organic solvent etc., the problem on utilization that stability is easy to be impaired has arisen.

On the other hand, the rutile type titanium oxide having a higher refractive index than the conventional anatase type titanium oxide, as described above, has no ultrafine particles and sol liquid that can be used.
Japanese Patent Laid-Open No. 9-110956 JP 2002-140883 A JP 2001-123115 A

  The object of the present invention has been achieved in view of the above circumstances, and is excellent in transparency, dispersibility, storage stability, light resistance, weather resistance and the like useful for applications such as optical materials, coating materials, and resin compositions. It is another object of the present invention to provide coated inorganic oxide ultrafine particles having a high refractive index and an average particle diameter of 1 to 100 nm, a sol solution, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that tin compounds used as a sintering agent prevent long fiber formation and aggregation, and tin-modified rutile titanium oxide ultrafine particles. Sol liquid with excellent dispersibility can be obtained, and this is used as a core ultrafine particle to provide transparency, dispersibility, storage stability, light resistance, weather resistance by providing a coating layer containing silicon oxide by a specific method. It was found that coated inorganic oxide ultrafine particles having a high refractive index and an average particle diameter of 1 to 100 nm, which are excellent in properties and the like, can be obtained.

That is, the present invention
[1] An inorganic oxide ultrafine particle containing titanium oxide having a rutile crystal structure with a refractive index of 1.5 to 2.8 is used as a nucleus (A), and is composed of a coating layer (B) containing silicon oxide. Coated inorganic oxide ultrafine particles having an inorganic oxide coating layer,
The rutile type titanium oxide ultrafine particles in the inorganic oxide ultrafine particles containing titanium oxide having the rutile type crystal structure of the nucleus (A),
In the presence of a tin compound having a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2, a titanium compound aqueous solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of −1 to 3. Obtained tin-modified rutile titanium oxide ultrafine particles having a Sn / Ti composition molar ratio of 0.001 to 0.5,
The coating layer containing silicon oxide (B) is of a two-layer coating type, the inner layer has a coating layer obtained by the step (1), and the outer layer is obtained by the step (2), Coated inorganic oxide ultrafine particles, wherein the weight ratio of the oxide coating layer is 0.001 to 20 in terms of SiO ₂ .
(1) Step of reacting silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ with the nucleus (A) under the condition of pH <7 (2) with respect to the nucleus (A) The step of reacting the silicon oxide having a weight ratio of 0.001 to 10 in terms of SiO ₂ with the coated ultrafine particles obtained in (1) under the condition of pH ≧ 7 [2] The coated inorganic oxide 2. The coated inorganic oxide ultrafine particles according to 1 above, wherein the ultrafine particles have a minor axis and a major axis of 2 to 20 nm.
[3] Coated inorganic oxide ultrafine particles having an average aggregate particle diameter of 10 to 100 nm of the ultrafine particle aggregate composed of the coated inorganic oxide ultrafine particles as described in 1 or 2 above.
[4] A sol in which the coated inorganic oxide ultrafine particles according to any one of 1 to 3 are dispersed in water or an organic solvent.
It is about.

  The tin-modified rutile type titanium oxide ultrafine particles of the present invention can be provided as ultrafine particles and sol liquid having a high refractive index that cannot be obtained by the conventional production method and that cannot be obtained by the anatase type. The coated inorganic oxide ultrafine particles of the present invention have high refractive index and ultraviolet shielding properties as rutile titanium oxide by coating tin-modified rutile titanium oxide ultrafine particles with silicon oxide by a specific method. However, the photocatalytic property is effectively suppressed. By using the resulting coated inorganic oxide ultrafine particles and sol solution with excellent transparency, dispersibility, storage stability, light resistance, weather resistance, etc., scratch resistance, surface hardness, abrasion resistance , Optical lenses with excellent transparency, heat resistance, weather resistance, UV shielding, etc. (glass lenses, pick-up lenses for information recording equipment such as CDs and DVDs, lenses for photography equipment such as digital cameras), optical prisms, light Not only materials for high refractive optical members such as waveguides, optical fibers, thin film moldings, optical adhesives, and optical semiconductor sealing materials, but also plastic deterioration prevention additives, cosmetic additives, automotive window glass, plasma displays, liquid crystals Optical members such as anti-reflective materials, dielectric materials, and diffusion plates for displays, EL displays, optical filters, etc., metal materials, ceramic materials, glass materials Plastic materials, can be suitably used in product areas such as coating materials.

  Hereinafter, the present invention will be described in more detail.

  The present invention provides a coating composed of a coating layer containing silicon oxide, wherein the inorganic oxide ultrafine particles containing titanium oxide having a rutile crystal structure with a refractive index of 1.5 to 2.8 are used as the core fine particles. Type inorganic oxide ultrafine particles and a sol solution thereof.

That is, an inorganic oxide ultrafine particle containing titanium oxide having a rutile crystal structure with a refractive index of 1.5 to 2.8 is used as a nucleus (A), and it is composed of a coating layer (B) containing silicon oxide. A coated inorganic oxide ultrafine particle having an inorganic oxide coating layer,
The rutile type titanium oxide ultrafine particles in the inorganic oxide ultrafine particles containing titanium oxide having the rutile type crystal structure of the nucleus (A),
In the presence of a tin compound having a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2, a titanium compound aqueous solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of −1 to 3. Obtained tin-modified rutile titanium oxide ultrafine particles having a Sn / Ti composition molar ratio of 0.001 to 0.5,
The coating layer containing silicon oxide (B) is of a two-layer coating type, the inner layer has a coating layer obtained by the step (1), and the outer layer is obtained by the step (2), A coated inorganic oxide ultrafine particle, wherein the weight ratio of the oxide coating layer is 0.001 to 20 in terms of SiO ₂ .
(1) Step of reacting silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ with the nucleus (A) under the condition of pH <7 (2) with respect to the nucleus (A) The step of reacting the silicon oxide having a weight ratio of 0.001 to 10 in terms of SiO ₂ with the coated ultrafine particles obtained in (1) under the condition of pH ≧ 7

  As described above, since the rutile type has a higher refractive index than the anatase type, it is possible to achieve a higher refractive index by using ultrafine particles of rutile type titanium oxide. Furthermore, in order not to impair the transparency of the resin, the rutile titanium oxide needs to be ultrafine particles.

  In the present invention, the inorganic oxide ultrafine particles containing titanium oxide having a rutile-type crystal structure, as long as it contains rutile-type titanium oxide formed into ultrafine particles as described above, the rutile-type crystal structure Even if it is a complex with a titanium oxide having a rutile crystal structure, it may be a shape that covers a titanium oxide having a rutile type crystal structure, and is not particularly limited. The ratio of rutile type titanium oxide is 5 to 100% (weight ratio), preferably 50 to 100%, and more preferably 70 to 100%.

  Further, the components other than the ultrafine particles of rutile titanium oxide are not particularly limited as long as they do not impair the dispersion stability of the ultrafine particles of the present invention. Among them, inorganic oxides are desirable. Specific examples include oxides such as Al, Si, V, Fe, Zn, Zr, Nb, Mo, Sn, Sb, and W, and preferably oxidation of Al, Si, Zr, Sn, and Sb. It is a thing.

  In the present invention, a preferable rutile-type titanium oxide ultrafine particle has a Ti concentration of 0.07 to 5 mol / l in the presence of a tin compound having a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2. Tin-modified rutile-type titanium oxide ultrafine particles obtained by reacting an aqueous titanium compound solution in a pH range of −1 to 3, and the Sn / Ti composition molar ratio of the ultrafine particles is 0.001 to 0.5. A tin-modified rutile-type titanium oxide ultrafine particle characterized by the above, and a tin-modified rutile-type titanium oxide ultrafine particle characterized by having a minor axis and a major axis of 2-20 nm of the crystal diameter of the ultrafine particle. .

  The crystal diameter referred to here is a so-called primary particle diameter, and is expressed by the lengths in the a and c axis directions as described in Chemical Handbook Revision 3 (Basic Edition Maruzen Co., Ltd.). In this specification, they are called a short axis and a long axis, respectively. Moreover, the average aggregated particle diameter represents a particle diameter obtained by aggregating primary particles.

  First, a method for producing tin-modified rutile titanium oxide ultrafine particles will be described.

The tin compound used in the present invention is not particularly limited, but specifically, for example, a tin salt compound such as tin chloride, tin nitrate, tin sulfate, stannate, or an oxide, hydroxide, metal Preferred examples include tin compounds selected from tin and the like.
The titanium compound used in the present invention is not particularly limited. Specifically, for example, titanium chloride oxide, titanium sulfate, titanium nitrate, titanium alkoxide, hydrated titanium oxide (a titanium compound in advance under alkaline conditions). Preferred examples include titanium compounds selected from such as hydrolyzed ones).

  First, a tin compound is added to an aqueous solution, and a titanium compound is added thereto. The tin compound and the titanium compound may be added at the same time, or either one may be first. Moreover, the form of a mixed compound may be sufficient. The reaction medium is preferably water, but may be an organic solvent such as alcohol or a mixed medium of water and an organic solvent.

  The amount of tin compound used in the reaction as a modifier for controlling crystal growth of rutile titanium oxide is such that the molar ratio of tin to titanium (Sn / Ti) is 0.001 to 2, preferably 0.01 to 1. It is desirable. If the tin amount is less than the above range, rutile-type titanium oxide ultrafine particles are produced, but the crystal diameter and aggregated particle diameter are increased, and therefore the dispersibility may be deteriorated. Further, when dispersed in an organic medium or the like, the transparency of the medium may be lowered. Further, even if the amount is larger than the above range, it is possible to synthesize the titanium oxide ultrafine particles having the rutile type, but the time required for the reaction becomes long. In this case, a large amount of tin compound is contained in the rutile type titanium oxide ultrafine particles. There is a possibility that a product with attached will be obtained. On the other hand, if it is larger than this, the amount of the residual tin compound increases, and the particle refractive index may decrease.

  The Ti concentration in the reaction solution is 0.07 to 5 mol / l, preferably 0.1 to 1 mol / l. When the Ti concentration is lower than the above range, there is a possibility that anatase-type and rutile-type mixed titanium oxide ultrafine particles may be produced even if a tin compound is added in the range of 0.01 to 0.03 as Sn / Ti (molar ratio). is there. Similarly, at a Ti concentration lower than the above range, if a tin compound is added in a range larger than 0.03 as Sn / Ti (molar ratio), there is a possibility that titanium oxide-tin oxide mixed ultrafine particles having rutile tin oxide are generated. is there.

  The pH of the reaction solution is desirably −1 to 3. Adjust with hydrochloric acid or nitric acid as necessary. When the reaction is carried out under a condition where the pH is greater than 3, anatase-type titanium oxide is obtained in the case where no tin compound is added, and in order to avoid this, a tin compound is added to obtain a rutile structure. There is a possibility that foreign substances other than rutile-type titanium oxide are produced.

  Regarding the reaction temperature, the Ti concentration and pH may be in the above ranges, and there is no particular limitation, but preferably −10 to 100 ° C., more preferably 20 to 60 ° C. is recommended. Although the reaction completion time is determined depending on the reaction temperature, it is usually carried out in 0.5 to 10 hours.

  The amount of tin compound contained in the tin-modified rutile-type titanium oxide ultrafine particles produced by the above reaction is preferably Sn / Ti molar ratio = 0.001 to 0.5. If the amount of tin is made smaller than the above range, the particle diameter of the rutile titanium oxide ultrafine particles becomes large and the dispersibility may be deteriorated. Also, if the amount is larger than the above range, crystal growth and aggregation can be controlled more efficiently, and ultrafine particles with a small particle diameter can be obtained, but a rutin-type titanium oxide ultrafine particle with a large amount of tin compound attached can be obtained. As a result, ultrafine particles having a low refractive index may be obtained.

  The minor axis and major axis of the tin-modified rutile-type titanium oxide ultrafine particles obtained by this method have a minor axis and a major axis of 2 to 20 nm, and an average aggregated particle diameter of 10 to 100 nm.

  Although the reaction mechanism (reaction mechanism) by which the tin-modified rutile-type titanium oxide ultrafine particles of the present invention are obtained is not sufficiently clear at present, this is characterized in that the surface is modified with a tin compound. It is presumed that the tin compound used as the raw material, the tin ion dissociated in the solution, or the tin compound generated in the solution by hydrolysis or the like adhered to the titanium oxide surface by coordination, adsorption, chemical bonding, or the like. In addition, it is presumed that the tin compound was originally added as a modifier under the conditions for producing rutile type titanium oxide instead of the anatase type, and this was caused as a result of the inhibition of crystal growth in the major axis direction. This indicates that the amount of the modified tin compound necessary for obtaining tin-modified titanium oxide ultrafine particles having a crystal diameter of 2 to 20 nm is far from the amount of titanium oxide coated without a gap, and the molar ratio to titanium is 0. It can be seen from the small amount of 001-0.5.

  The reaction product obtained as described above may be used as tin-modified rutile-type titanium oxide ultrafine particles or sol liquid as it is, or may be subjected to a desired post-treatment. That is, it can be purified by a known method such as vacuum concentration using an evaporator or ultrafiltration, and concentrated to an appropriate concentration. Centrifugation can yield a white precipitate that can be redispersed in water or other desired media. The sol liquid in which tin-modified rutile-type titanium oxide ultrafine particles are dispersed in water is substituted with an organic solvent such as alcohols such as methanol and cellosolves such as 2-methoxyethanol, and organic solvent-dispersed tin-modified rutile-type titanium oxide It can also be used as an ultrafine particle sol solution.

  It is preferable that the minor axis and the major axis of the tin-modified rutile-type titanium oxide ultrafine particles obtained by the present invention are 2 to 20 nm and the average aggregate particle diameter is 10 to 100 nm. When the crystal diameter is smaller than 2 nm, the scratch resistance and hardness are insufficient when a coating film is prepared using a coating solution containing these, and the originally obtained refractive index may not be obtained. If it is larger than 20 nm, light scattering may occur. When the average aggregate particle diameter is larger than 100 nm, the obtained medium may become cloudy and opaque.

  Next, a method for preparing the coating layer (B) containing silicon oxide will be described.

The coating layer (B), that is, the coating layer containing silicon oxide, is a two-layer coating type, in which the inner layer is obtained by the step (1) and the outer layer is obtained by the step (2). The weight ratio of the material coating layer is 0.001 to 20 in terms of SiO ₂ .
(1) Step of reacting silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ with the nucleus (A) under the condition of pH <7 (2) with respect to the nucleus (A) The step of reacting the silicon oxide having a weight ratio of 0.001 to 10 in terms of SiO ₂ with the coated ultrafine particles obtained in (1) under the condition of pH ≧ 7

  In the present invention, when the tin-modified rutile-type titanium oxide ultrafine particles synthesized above or a sol solution thereof is used for an optical material, a coating material, a resin composition, etc., in order to prevent deterioration of surrounding organic substances due to the photocatalytic property of titanium oxide, It is necessary to impart light resistance. For this purpose, a rutile titanium oxide ultrafine particle is provided with a coating layer containing silicon oxide. In addition, a coating means both the form which covered the ultrafine particle surface completely, or the form with which the clearance gap was vacant.

  Examples of the silicon oxide used for the coating include silicates such as colloidal silica, silicate sol, sodium silicate, or potassium silicate. The silicon oxide here may be an amorphous oxide, a crystalline oxide, or a hydrated state. Further, it may be silicic acid, silicic acid oligomer, or a salt thereof, and may be in a state in which they are adsorbed and bound to the surface of the nuclear fine particles.

  As a method for forming the coating layer, first, a sol solution of tin-modified rutile-type titanium oxide ultrafine particles is prepared. It is desirable to dilute or concentrate the sol solution prepared above so that the solid content is 0.01 to 20% by weight, preferably 0.1 to 5% by weight. When the solid content concentration of the dispersion is less than 0.01% by weight, the productivity is low and not industrially effective, and when the solid content concentration of the dispersion exceeds 20% by weight, the resulting ultrafine particles may become aggregates. There is sex.

  A solution in which silicon oxide is dissolved in water and / or an organic solvent is continuously or intermittently added to a reaction liquid containing nuclear fine particles (in this case, tin-modified rutile-type titanium oxide ultrafine particles which are nuclei (A)). Add to react on the surface of the core particle. It is desirable to drop over 0.1 to 100 hours (to the extent that the core fine particle sol solution does not gel). The concentration after the completion of dropping of the silicon oxide in the reaction solution is preferably 0.01 to 5 wt% in terms of silicon oxide. If it is smaller than this, the productivity is low and it is not industrially effective, and if it is larger than this, polymerization may proceed too much and an insoluble substance of silicon oxide may be formed.

[Step (1): A step of reacting a silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ with the nucleus (A) under the condition of pH <7.

First, the core fine particles, that is, the core (A) and the silicon oxide having a weight ratio with respect to the core (A) of 0.001 to 10 in terms of SiO ₂ are reacted under the condition of pH <7.

Although there is no restriction | limiting in particular as a silicon oxide used here, Colloidal silica and silicate sol are preferable. The amount to be used, the weight ratio of the nucleus (A) is 0.001 to 10 is preferable in terms of SiO ₂ is preferably 0.01 to 0.5. If it is in this range, that is, greater than 10, a sufficient refractive index may not be obtained. If it is less than this range, that is, 0.001, dispersion stability may be lowered.

  The pH of the reaction solution is preferably less than 7, and more preferably 2-4. If the pH is 7 or more, tin-modified rutile titanium oxide ultrafine particles, which are core fine particles, may cause aggregation and gelation. You may adjust pH by adding an acidic compound or a basic compound as needed. Examples of acidic compounds include hydrochloric acid, sulfuric acid, and nitric acid, and basic compounds include sodium hydroxide and potassium hydroxide.

  In this step, a solution in which silicon oxide is dissolved in water and / or an organic solvent is continuously or intermittently added to the reaction liquid containing the nuclear fine particles to react on the surface of the fine nuclear particles. It is desirable to drop the sol solution so that the core fine particle sol solution does not gel over 0.1 to 100 hours. Longer than this is not economically efficient. If it is shorter than this, the reaction may be insufficient.

  Although reaction temperature does not have a restriction | limiting in particular, 0-200 degreeC is preferable and 30-100 degreeC is more preferable. If it is in this range, that is, higher than 200 ° C., ultrafine particles may be aggregated. If it is less than this range, that is, 0 ° C., the reaction may not proceed sufficiently.

[Step (2): The silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ is reacted with the coated ultrafine particles obtained in (1) under the condition of pH ≧ 7. Process]

The coated ultrafine particles or sol solution obtained in the step (1) is dissolved as necessary. Subsequently, the weight ratio of the coated ultrafine particles obtained in (1) to the nucleus (A) is calculated in terms of SiO ₂ . The silicon oxide which becomes 0.001 to 10 is reacted under the condition of pH ≧ 7.

Although there is no restriction | limiting in particular as a silicon oxide used here, Colloidal silica and silicate sol are preferable. The amount to be used, the weight ratio of the nucleus (A) is 0.001 to 10 is preferable in terms of SiO ₂ is preferably 0.1 to 1. If it is in this range, that is, greater than 10, a sufficient refractive index may not be obtained. If this range is smaller than 0.001, sufficient light resistance may not be obtained.

  The pH of the reaction solution is preferably 7 or more, more preferably 8-11. What is necessary is just to adjust pH to this range suitably. If the pH is less than 7, a dense coating layer may not be formed. The pH may be adjusted appropriately by adding a basic compound. Examples of the basic compound include sodium hydroxide and potassium hydroxide.

  In this step, a solution in which silicon oxide is dissolved in water and / or an organic solvent is continuously or intermittently added to the reaction liquid containing the nuclear fine particles to react on the surface of the fine nuclear particles. It is desirable to add over 0.1 to 100 hours. Longer than this is not economically efficient. If it is shorter than this, the reaction may be insufficient.

  Although reaction temperature does not have a restriction | limiting in particular, 0-200 degreeC is preferable and 80-200 degreeC is more preferable. If it is in this range, that is, higher than 200 ° C., fine particles may aggregate. If it is less than this range, that is, 0 ° C., the reaction may not proceed sufficiently.

  Other inorganic oxides contained in the coating layer (B), that is, the coating layer containing silicon oxide, are not particularly limited as long as they do not impair the light resistance, dispersibility, and storage stability of the resulting fine particles. However, specific examples include oxides such as Al, Si, V, Fe, Zn, Zr, Nb, Mo, Sn, Sb, and W, and preferably Al, Si, Zr, Sn, and Sb. The oxide of this is mentioned.

  Moreover, as the coating layer, only the coating layer made of the two-layered silicon oxide described above is desirable, but another inorganic oxide coating layer may be provided. In this case, it is desirable to provide inside the coating layer made of the two-layered silicon oxide described above.

  The minor axis and major axis of the double-layered silicon oxide-coated tin-modified rutile-type titanium oxide ultrafine particles obtained according to the present invention are preferably 2 to 20 nm and the average aggregated particle diameter is 10 to 100 nm. If the crystal diameter is smaller than 2 nm, the originally obtained refractive index may not be obtained. If it is larger than 20 nm, light scattering may occur. If the average aggregate particle diameter is larger than 100 nm, the organic medium may become cloudy and opaque.

The weight ratio of the silicon oxide coating layer to the core particles obtained by the above method is 0.001 to 20 in terms of SiO _2. The refractive index and light resistance of the ultrafine particles themselves can be adjusted by the amount of the coating layer. Thereby, the desired light resistance can be imparted and the refractive index can be adjusted to 1.5 to 2.8.

  The reaction product obtained as described above may be used as it is as a two-layer silicon oxide-coated tin-modified rutile-type titanium oxide ultrafine particle sol solution, or may be subjected to a desired post-treatment. That is, it can be purified by a known method such as vacuum concentration using an evaporator or ultrafiltration, and concentrated to an appropriate concentration. Centrifugation can yield a white precipitate that can be redispersed in water or other desired media. In particular, by performing ultrafiltration, it is possible to remove the ion component that causes the aggregation of the fine particles by shielding the electric double layer around the fine particles, so that the dispersion stability is improved. The aqueous sol solution in which the two-layer silicon oxide coated tin-modified rutile titanium oxide ultrafine particles are dispersed is replaced with an organic solvent such as alcohols such as methanol and cellosolves such as 2-methoxyethanol, and dispersed in the organic solvent. It is also possible to use it as a sol solution.

  Titanium oxide ultrafine particles usually have an equipotential point in the neutral region and are stable sols in the acidic region in the conventional production method. For this reason, the titanium oxide ultrafine particle sol solution produced by the conventional method has a problem that the neutral to basic flocculation causes aggregation and gelation, and the range of use is limited. Moreover, when it tried to substitute to an organic solvent, there existed a problem of causing aggregation and gelatinization and impairing stability. Furthermore, even when the dispersion medium is water, if it is concentrated to 10% by weight or more, gelation is caused, and it is difficult to obtain a sol solution dispersed at a high concentration, resulting in low productivity. By reacting the silicon oxide according to the present invention in the range of pH <7, there is no aggregation or gelation in a wide range of pH, particularly 14> pH> 3, and it is a thin film excellent in dispersibility and storage stability. A titanium oxide ultrafine particle sol solution coated with a silicon oxide layer can be obtained, and a dense and thick silicon oxide coating layer can be provided by reacting in a range of pH ≧ 7.

In general, the surface of a titanium oxide ultrafine particle sol that is stable in an acidic region is positively charged. By reacting there under the above conditions, by selecting ultrafine particles having the opposite sign charge and smaller in size than the nuclear fine particles, heteroaggregation is caused on the surface of the nuclear fine particles, and the thin layer is more effectively and uniformly formed. It is considered that a silicon oxide film is formed, thereby imparting SiO ₂ characteristics to the surface of the core fine particle, and the titanium oxide ultrafine particle sol according to the present invention is stable in a wide pH range of pH = 3-14. By growing a dense and thick silicon oxide layer under basic conditions of pH ≧ 7, ultrafine particles having light resistance and weather resistance can be obtained while maintaining high dispersibility. That is, ultrafine titanium oxide particles having a two-layer structure of a coating inner layer formed at pH <7 and a coating outer layer formed at pH ≧ 7 and excellent in transparency, dispersibility, storage stability, light resistance, weather resistance, etc. A sol solution.

  With the silicon oxide coating, the concentration of the sol solution is stable over a wide range of pH even when the concentration is as high as 20% by weight or more, further 35% by weight or more in terms of solid content, and even when replaced with an organic medium. Stable in concentration.

  By modifying the coated inorganic oxide ultrafine particles obtained by the present invention, that is, the bilayer silicon oxide-coated tin-modified rutile titanium oxide ultrafine particles with carboxylic acid, amine, organic silicon oxide, or organic polymer, It can also be used as a surface-modified double-layer silicon oxide-coated tin-modified rutile-type titanium oxide ultrafine particle sol solution. Thereby, the dispersibility and compatibility with an organic medium etc. improve.

  As the carboxylic acid used for the surface treatment, acetic acid, propionic acid, acrylic acid, methacrylic acid, tartaric acid, glycolic acid and the like are preferably used.

  Further, as the amine used for the surface treatment, propylamine, diisopropylamine, butylamine and the like are preferably used. In order to perform surface treatment with these, for example, ultrafine particles or a sol solution is mixed in a solution such as water or alcohol, and after adding a catalyst as necessary, it is left at room temperature for a predetermined time or is subjected to heat treatment. Good.

  For the organosilicon oxide surface treatment, tetramethoxysilane, methyltrimethoxysilane, (3-glycidoxypropyl) trimethoxysilane, or the like is preferably used. As a treatment method, a sol solution is mixed with a solvent containing an organosilicon oxide, a catalyst is added if necessary, and the mixture is heated for a predetermined time in a range of room temperature to 60 ° C. and then subjected to ultrafiltration, centrifugation, or the like. It is performed by a method such as removing unreacted components in the mixed solution.

  The organic polymer is preferably a polymer having a functional group capable of interacting with the surface of the fine particles such as amino group and carboxylic acid group, such as reaction and adsorption. Polystyrene aminated, chloromethylated, sulfonated, and their derivatives, styrene resins, polymethyl methacrylate, polyethyl acrylate, polyacrylic acid, polyacrylamide and other acrylic resins, vinyl alcohol resins, epoxy Based resins and the like. The surface treatment method may be performed by the method described above. The amount of the surface treatment agent to be used is appropriately set in consideration of dispersibility in the organic solvent, organic medium and the like to be used.

  By this method, silicon oxide-coated tin-modified rutile titanium oxide ultrafine particles having a minor axis and a major axis of 2 to 20 nm and an average aggregated particle diameter of 10 to 100 nm are obtained. When the crystal diameter is smaller than 2 nm, there is a possibility that the refractive index originally obtained when used for a medium containing these may not be obtained. If it is larger than 20 nm, light scattering may occur. If the average aggregate particle diameter is larger than 100 nm, the organic medium may become cloudy and opaque.

  The coated inorganic oxide ultrafine particles of the present invention are usually in the form of a sol dispersed in water depending on the production process, but by solvent substitution, alcohols such as methanol and ethanol, methyl cellosolve, ethyl Organic solvents such as cellosolves such as cellosolve, esters such as ethyl acetate, ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone and methyl isobutyl ketone, halogen hydrocarbons such as chloroform, hydrocarbons such as toluene and heptane, etc. It is also possible to make a sol solution dispersed in the sol.

  Further, instead of the organic solvent as described above, it may be directly dispersed in an organic medium such as a resin monomer. As a result, the fine particle-dispersed organic medium can be directly cured, and the manufacturing method can be simplified. Examples thereof include monomers such as epoxy resin, acrylic resin, and silicon resin.

  The refractive index of the bilayer silicon oxide-coated tin-modified rutile-type titanium oxide ultrafine particles obtained by the above method is 1.5 to 2.8, particularly 2.0 to 2.8. It is set as appropriate.

  Therefore, the coated inorganic oxide ultrafine particles according to the present invention, that is, the double-layered silicon oxide-coated tin-modified rutile titanium oxide ultrafine particles have a high refractive index, transparency, dispersibility, storage stability, light resistance, and weather resistance. The organic medium formed using the ultrafine particles has high refractive index, transparency, light resistance, weather resistance, heat resistance, molding processability, etc., and can adjust the refractive index arbitrarily. It is suitable for an optical member. Specifically, for example, optical lenses (glass lenses, pickup lenses in information recording devices such as CDs and DVDs, lenses for photographing devices such as digital cameras, etc.), optical prisms, optical waveguides, optical fibers, thin film molded products, optical adhesives Anti-reflection in plastics, anti-degradation additive, cosmetic additive, automotive window glass, plasma display, liquid crystal display, EL display, optical filter, etc. Product fields such as optical members such as materials, dielectric materials and diffusion plates, metal materials, ceramic materials, glass materials, plastic materials, coating materials, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

(Preparation of tin-modified rutile titanium oxide ultrafine particles and sol solution)
[Production Example 1]
Tin tetrachloride pentahydrate 0.27 g was charged into a 100 ml eggplant type flask, dissolved in 50 ml of ion-exchanged water, and 5 ml of a hydrochloric acid aqueous solution of titanium oxide chloride (containing 15 wt% Ti) was added. The pH of the solution was -0.1. (Feed Ti concentration = 0.45, Sn / Ti = 0.03) When stirred with a magnetic stirrer and heated at 50 ° C. for 1 hour, a white precipitate was obtained. Centrifugation was performed, and the white precipitate was collected and redispersed in ion-exchanged water. Ultrafiltration was performed to obtain a sol solution having a solid content of 2% by weight. This solid was subjected to powder X-ray diffraction measurement and electron microscope observation. When powder X-ray diffraction measurement was performed after hot-air drying at 120 ° C. for 2 hours, it was a titanium oxide rutile type. The crystal diameter was calculated from the half-value width of the diffraction peak using the Debye-Scherrer equation. As a result, the average crystal diameter was 5 nm for the minor axis and 8 nm for the major axis, respectively. The observation with an electron microscope was performed using a transmission electron microscope, and a solution obtained by dropping a diluted sol solution onto a mesh was observed at a magnification of 200,000 times and 2 million times. As a result, it was a rutile type titanium oxide having an average aggregated particle size of 23 nm. The elemental molar ratio of Sn / Ti by inductively coupled plasma analysis was 0.02.

[Production Example 2]
The same operation as in Example 1 was carried out except that 0.9 g of tin tetrachloride pentahydrate was used in Production Example 1. (Feed Ti concentration = 0.45, Sn / Ti = 0.1) When the solid content of the obtained sol solution was analyzed in the same manner as in Production Example 1, the average crystal diameter was 5 nm for the minor axis and 8 nm for the major axis, respectively. It was a rutile type titanium oxide having an average aggregated particle size of 20 nm. The element molar ratio of Sn / Ti was 0.06.

(Preparation of bilayer silicon oxide-coated tin-modified rutile-type titanium oxide ultrafine particle sol solution)

  After 2500 g of this tin-modified rutile type titanium oxide ultrafine particle sol solution was adjusted to pH <7, it was heated to 80 ° C. 125 g of a 2% by weight aqueous silicon oxide solution was added dropwise over 1 hour, and the mixture was further heated for 30 minutes. After cooling to room temperature, a 1 mol / l sodium hydroxide aqueous solution was added to form a basic sol solution. The temperature was raised to 80 ° C., and 625 g of a 2 wt% aqueous silicon oxide solution was added dropwise over 2 hours, and further heated for 4 hours. The mixture was purified by ultrafiltration to obtain a 2 wt% sol solution. When elemental analysis was performed by inductively coupled plasma method after hot-air drying at 120 ° C. for 2 hours, the weight ratio of silicon oxide / tin-modified titanium oxide was 0.11 / 1 in terms of oxide. The solvent was replaced with methanol by a rotary evaporator and concentrated to obtain a 30 wt% methanol-dispersed sol.

  A 2 wt% sol solution and a solvent-dispersed and concentrated solution were prepared in the same manner as in Example 1 except that the tin-modified rutile-type titanium oxide ultrafine particle sol solution prepared in Production Example 2 was used to prepare a 30 wt% methanol-dispersed sol solution. did.

[Comparative Example 1]
To 2 L of ion-exchanged water, 20 ml of a hydrochloric acid aqueous solution of titanium oxide chloride (Ti content: 15% by weight) was added and heated at 60 ° C. for 6 hours. After cooling to room temperature, it was concentrated and deionized by ultrafiltration to obtain a sol solution having a solid content of 2% by weight. When the solid content of the obtained sol solution was analyzed in the same manner as in Production Example 1, it was anatase-type titanium oxide having an average of 5 nm on both the minor axis and the major axis.

(Preparation of zirconium oxide-coated anatase-type titanium oxide ultrafine particle sol solution)
[Comparative Example 2]
To 2 L of ion-exchanged water, 20 ml of a hydrochloric acid aqueous solution of titanium oxide chloride (Ti content: 15% by weight) was added and heated at 60 ° C. for 6 hours. 50 g of an aqueous solution in which 32 g of zirconium oxide chloride octahydrate was dissolved was dropped, heated to 90 ° C., and heated for 1 hour. After cooling to room temperature, ultrafiltration was performed. After cooling to room temperature, it was concentrated and deionized by ultrafiltration to give a 2 wt% sol solution. When the solid content of the obtained sol solution was analyzed in the same manner as in Example 1, it was anatase-type titanium oxide having an average of 5 nm on both the minor axis and the major axis. The composition of the zirconium oxide-coated anatase-type titanium oxide ultrafine particles was zirconium oxide / titanium oxide weight ratio = 0.85 / 1 in terms of oxide.

  The sol solution prepared by the above method was evaluated for light resistance, refractive index, dispersion stability, and storage stability as shown below. The results are shown in Table 1.

(A) Light resistance Sodium alizarin red sulfonate (hereinafter referred to as AR) was used as a dye. A sol solution ultrafiltered in a quartz cell was taken out in an amount equivalent to 6 mg of solid content, and 3 g of an AR aqueous solution of 2 × 10 ⁻⁴ mol / l was added and stirred. After mixing, the mixture was stirred in the dark and irradiated with a xenon lamp, assuming that the adsorption equilibrium was reached when the absorption peak ceased to change. Infrared light was cut using an H ₂ O filter at the irradiation light exit. A cell was placed at a position 10 cm from the outlet and stirred. The illuminance at this position was 120 to 130 mW / cm ² and about 2.5 times that of normal sunlight. Absorption spectrum is measured every 10 minutes, the horizontal axis is time, the vertical axis is the dye residual ratio (A / A ₀ ) (the ratio of the absorption intensity (A) at each time to the maximum absorption intensity (A ₀ ) before irradiation) As a result, a graph was prepared and compared with each sol solution. The absorption spectrum was measured using a spectrophotometer UV-2200 (manufactured by Shimadzu Corporation). The result is shown in FIG.

(B) Refractive index To 15 g of (3-glycidoxypropyl) trimethoxysilane, 3.5 g of 0.001 N hydrochloric acid was added dropwise over 2 hours and stirred for 3 hours. 30 g of ethyl cellosolve was added to prepare a solution of a partial hydrolyzate of (3-glycidoxypropyl) trimethoxysilane. Next, 9.3 g of each methanol sol solution (Examples 1 and 2 and Comparative Example 2) subjected to silicon oxide coating treatment (adjusted to a total solid concentration of 20% by weight) was added to the aforementioned (3-glycidoxy Propyl) Trimethoxysilane partial hydrolyzate solution 5.3 g was added, and further 50 mg of aluminum acetylacetonate and 10 mg of surfactant (manufactured by Nihon Unicar Co., Ltd .: L7604) were added as a curing agent and stirred to create a coating solution did. Next, the coating solution was applied on a quartz substrate by spin coating to a film thickness of about 700 mm, and dried with hot air at 120 ° C. for 2 hours to produce an automatic wavelength scanning ellipsometer M-150 (JASCO Corporation) Was used to measure the refractive index.

  Further, polyvinyl pyrrolidone in the same amount as the solid content contained in the sol solution is added to each sol solution (Examples 1 and 2 and Comparative Example 2) subjected to the silicon oxide coating treatment, and spin coating is performed on the quartz substrate. The refractive index of the coating film applied to a film thickness of about 700 mm and dried at 120 ° C. (hot air for 2 hours) was measured immediately using the ellipsometer. The refractive index of the solid content was evaluated from the volume fraction of the contained solid content. The results are shown in Table 1.

＊微粒子ナシでの塗膜屈折率：１．４７

* Coating film refractive index with fine particle pear: 1.47

(C) Dispersibility, storage stability The aqueous solution of sol dispersed in water is added with an aqueous hydrochloric acid solution or an aqueous sodium hydroxide solution to adjust the pH to the values shown in Table 2 below. evaluated.
○… No change ×… Gelation, aggregation and precipitation

Moreover, the change when the 30 wt% methanol sol solution obtained by adjusting the solvent and solid content concentration of each sol solution was stored at room temperature for half a year was evaluated by the following indices. The results are shown in Table 2.
○… No change △… Thickened ×… Gelled (or gelled during solvent replacement or concentration)

  As can be seen from the above results, the use of the bilayer silicon oxide-coated tin-modified rutile type titanium oxide ultrafine particles has a high refractive index that cannot be obtained when anatase type titanium oxide is used as the core fine particles, and the fine particles It can be seen that the photocatalytic property is effectively suppressed and ultrafine inorganic oxide particles having excellent dispersion stability and storage stability in a wide pH range are obtained.

  The coated inorganic oxide ultrafine particles obtained by the present invention, that is, the double-layered silicon oxide-coated tin-modified rutile titanium oxide ultrafine particles, or the sol solution thereof is an optical lens (glass lens, CD, DVD or other information recording device) In addition to materials for high refractive optical members such as optical lenses, optical waveguides, thin film moldings, optical adhesives, and sealing materials for optical semiconductors, etc. Plastic deterioration prevention additive, cosmetic additive, automotive window glass, plasma display, liquid crystal display, EL display, optical member such as anti-reflective material in dielectric filter, diffusion plate, metal material, ceramic material, glass material , Transparency useful for applications such as plastic materials, coating materials, Dispersibility, light resistance, have utility that can provide a member having a high refractive index which is excellent in weather resistance.

It is the figure which showed the time change of the pigment | dye residual ratio (A / _A0 ) in an Example etc.

Claims (4)

Inorganic oxidation composed of a coating layer (B) containing silicon oxide with an inorganic oxide ultrafine particle containing titanium oxide having a rutile crystal structure having a refractive index of 1.5 to 2.8 as a nucleus (A) A coated inorganic oxide ultrafine particle having a material coating layer,
The rutile type titanium oxide ultrafine particles in the inorganic oxide ultrafine particles containing titanium oxide having the rutile type crystal structure of the nucleus (A),
In the presence of a tin compound having a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2, a titanium compound aqueous solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of −1 to 3. Obtained tin-modified rutile titanium oxide ultrafine particles having a Sn / Ti composition molar ratio of 0.001 to 0.5,
The coating layer containing silicon oxide (B) is of a two-layer coating type, the inner layer has a coating layer obtained by the step (1), and the outer layer is obtained by the step (2), Coated inorganic oxide ultrafine particles, wherein the weight ratio of the oxide coating layer is 0.001 to 20 in terms of SiO ₂ .
(1) Step of reacting silicon oxide having a weight ratio with respect to the nucleus (A) of 0.001 to 10 in terms of SiO ₂ with the nucleus (A) under the condition of pH <7 (2) with respect to the nucleus (A) The step of reacting the silicon oxide having a weight ratio of 0.001 to 10 in terms of SiO ₂ with the coated ultrafine particles obtained in (1) under the condition of pH ≧ 7   The coated inorganic oxide ultrafine particles according to claim 1, wherein the minor axis and the major axis of the coated inorganic oxide ultrafine particles are 2 to 20 nm.   Coated inorganic oxide ultrafine particles having an average aggregate particle diameter of 10 to 100 nm of the ultrafine particle aggregate comprising the coated inorganic oxide ultrafine particles according to claim 1 or 2.   A sol obtained by dispersing the coated inorganic oxide ultrafine particles according to claim 1 in water or an organic solvent.

Images