JP4841880B2 - Inorganic oxide particles - Google Patents

Description

  The present invention relates to inorganic oxide particles. In more detail, it is preferable to have a core part composed mainly of silica and a coating layer of a silica-based composite oxide composed mainly of an oxide of a group 4 or group 14 metal other than silica and silicon. The present invention relates to a novel inorganic oxide particle having a sphere formation and suitable for blending into a light scatterer.

  2. Description of the Related Art In recent years, liquid crystal display devices have been used in various fields, and in particular, many are used in the electronic industry such as mobile terminals such as mobile phones, personal computers, and liquid crystal display televisions. Conventionally, liquid crystal display devices have been required to improve the display quality of the liquid crystal display surface. For this reason, the backlight used in the liquid crystal display device is required to supply as much light as possible to the liquid crystal unit and to supply uniform light.

  On the other hand, the liquid crystal display device is characterized by power saving, and the backlight used to take advantage of this feature is also required to be a power saving type.

  In order to send light from the backlight in a large amount and uniformly and to reduce the power used, particles with high light scattering efficiency and high light scattering properties (hereinafter referred to as “light scattering particles”). And a light scatterer (sheet) using them. The light scatterer has a function of diffusing light emitted from the backlight in an arbitrary direction by refraction or reflection.

  For example, JP-A-6-59107 discloses a light diffusing sheet containing a transparent resin, synthetic resin particles and particles having a refractive index higher than that of the transparent resin as a light diffusing layer. However, zirconium oxide is used as particles having a refractive index higher than that of the transparent resin (see Patent Document 1). JP-A-11-302330 discloses copolymer particles containing a divinylbiphenyl monomer having an average particle diameter of 1 to 80 μm and a refractive index of 1.60 to 1.67 ( Patent Document 2).

  However, an inorganic substance such as zirconium oxide has been pointed out as having a problem that light is not diffused uniformly because of its high refractive index and high light scattering efficiency but poor transparency. Various types of resin beads as described above are also known, but the average particle diameter cannot be freely controlled, or sufficient light scattering efficiency cannot be obtained due to the relatively small refractive index. There was a problem.

  On the other hand, the light scattering particles as described above are also used in the antireflection layer (film) of the liquid crystal display device and the flat television and the cosmetic field.

  For example, Japanese Patent Application Laid-Open No. 2003-121617 discloses a technique such as a light diffusion film for the purpose of antiglare using resin beads as light scattering particles (see Patent Document 3).

Japanese Patent Application Laid-Open No. 8-225316 discloses a spherical inorganic oxide powder having high light diffusibility while maintaining transparency in order to prevent whitening and make wrinkles less noticeable. The _{composition, BaSO 4, Al 2 O 3} · nH 2 O ( where, n = 0~3), and _{aAl 2 O 3 · bSiO 2 ·} nH 2 O ( where, a / b = 0.1~100, n / (a + b) = 0-10) is exemplified (see Patent Document 4).

  Incidentally, Japanese Patent Application Laid-Open No. 2003-252616 discloses silica-based composite oxide particles having high optical transparency and high refractive index. This particle is prepared by hydrolyzing silicon alkoxide with a specific amount of water and then mixing with metal alkoxide other than silicon to hydrolyze and condense the raw material in a hydrous organic solvent containing a catalyst. However, in such a method, it takes time to produce a large one having an average particle diameter exceeding 1 μm, and the monodispersibility also decreases, and the particles actually produced in the examples average at most A particle size of 0.45 μm was at most (see Patent Document 5).

  JP 2002-284515 A discloses a spherical inorganic oxide particle comprising a core part mainly composed of silica and a coating layer of a composite oxide mainly composed of silica and titania. Is disclosed. In this inorganic oxide particle, the coating layer is prepared by dropping a mixture raw material of a hydrolyzable organic titanium compound and a hydrolyzable organosilicon compound into an alkaline hydrous alcohol solvent containing silica particles as a core, and Manufactured by hydrolyzing raw materials. However, in such a method for producing a coating layer, if the titania content increases, stable particle growth becomes difficult. If the titania content exceeds 20 mol%, the resulting inorganic oxide particle spheres There was a problem that the shape suddenly collapsed (see Patent Document 6).

JP-A-6-59107 JP-A-11-302330 JP 2003-121617 A JP-A-8-225316 JP 2003-252616 A JP 2002-284515 A

  Conventional light scattering particles made of resin beads have a problem that light scattering efficiency is low due to the low refractive index of resin beads although the total light transmittance is high (no specific absorption in the visible region). It was.

  In the case of using inorganic particles, an amorphous material such as silica has no absorption and high total light transmittance, but has a problem that the light scattering efficiency is low because the refractive index of the particles is low. On the other hand, high-refractive-index materials such as alumina, zirconia, and titania are also known. However, since these materials are generally crystalline, there is a problem that although the light scattering efficiency is high, the total light transmittance is low.

  In addition, the inorganic oxide particles described in Patent Document 5 and Patent Document 6 can be manufactured with considerably high both in light scattering efficiency and total light transmittance. It was not sufficient and was not satisfactory for use in the light scatterer of the liquid crystal display device described above.

  The present invention has been made to solve the above-described problems, and both the light scattering efficiency and the total light transmittance are high, has a spherical shape or a substantially spherical shape, and has a sufficiently large particle diameter. Therefore, it is an object to provide inorganic particles useful for blending into a light scatterer (sheet).

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, even if the inorganic oxide particles having a specific structure and composition are amorphous, they have a high total light transmittance because they are amorphous, and have a high refractive index that cannot be achieved with conventional resin beads. Furthermore, it has been found that this product can obtain a good sphericity and particle size, and the present invention has been completed.

That is, the present invention comprises a core portion mainly composed of silica, and a coating layer of a silica-based composite oxide mainly composed of an oxide of a group 4 or 14 metal other than silica and silicon. An inorganic oxide particle having an average particle diameter of 1.1 to 10 μm, a circularity determined from an image taken by an electron microscope of 0.8 or more, and the covering layer being 0.03 μm has a thickness of at least, an oxide of group 4 of the periodic table or 14 metal other than silicon-free machine oxide particles contained in the range of 22 to 70 mol%, of the coating layer of inorganic oxide particles It is a resin composition for light scatterers, which is blended with a transparent resin having a refractive index smaller by 0.1 or more than the refractive index .

  The inorganic oxide particles of the present invention are high-concentrations composed of a silica-based composite oxide mainly composed of a core part mainly composed of silica and an oxide of a group 4 or group 14 metal other than silica and silicon. It is composed of a refractive index coating layer. Light scattering with high light scattering efficiency and high total light transmittance by using a silica-based composite oxide with a specific composition for the coating layer and controlling the average particle diameter and the thickness of the coating layer to a specific range Particles can be provided.

  In addition, since these particles have a large particle size, they have good dispersibility in solvents and resins, and when used for blending into a light scatterer, the properties are stable and the light scattering efficiency is high. . In addition, the sphericity is also good, since the circularity required from the image taken by the electron microscope is 0.8 or more and excellent in the uniformity of the shape, when used in the above applications, the reproducibility of the light scattering performance is good, It is also excellent in that the resin can be highly filled.

  Furthermore, in the inorganic oxide particles of the present invention, those using titania as the oxide of the group 4 or group 14 metal constituting the silica-based composite oxide are promising as cosmetics having a high ultraviolet shielding effect, for example. In addition, those using zirconia are also promising as fillers for dental composite resins having a high X-ray contrast effect.

  The inorganic oxide particles of the present invention have a core part mainly composed of silica. That is, silica is useful because of its characteristics such as low water absorption and low thermal expansion coefficient. However, as other characteristics, it is spherical or substantially spherical, and in particular, the degree of circularity obtained from a captured image of an electron microscope described later is 0. There is a point that it is easy to obtain particles close to true spheres of 8 or more.

  Here, as the light scattering particles used for the light scattering body, those having a uniform shape and high reproducibility of the average particle diameter and particle size distribution are desirable, more spherical, and excellent in monodispersity. Those are preferred. Since the shape of the obtained inorganic oxide particles is greatly influenced by the shape of the core part, the state inorganic oxide particles in the present invention are obtained by using the above-mentioned particles containing silica as a main component as the core part. The properties required for the light scattering particles used in the light scattering body are satisfactorily satisfied.

  It is difficult to obtain such spherical particles with other oxides. In particular, when obtaining spherical particles with a large particle diameter, the effect of using particles containing silica as a main component as a core is remarkably exhibited. The Specifically, the particle diameter of the core is preferably 0.1 μm or more, preferably 0.2 to 8 μm, and more preferably 0.5 to 5 μm. Further, the degree of circularity obtained from a photographed image of an electron microscope is 0.8 or more, preferably 0.85 or more, more preferably 0.90 or more, and most preferably 0.92 or more.

  In addition, the silica which forms a nucleus part may contain other metal oxides other than a silica in the range which does not impair the property which is easy to obtain spherical shape. In general, the content of silica in the core is 80 mol% or more, preferably 85 mol% or more, more preferably 90 mol% or more. In particular, in order to form the core portion having a high degree of circularity, the silica content is preferably 99 mol% or more. Other metal oxides other than silica include metal oxides of the periodic table 1 group that can be combined with silica such as sodium oxide and potassium oxide, and periodic table 2 that can be combined with silica such as magnesium oxide and calcium oxide. Periodic Table Group 13 metal oxides that can be bonded to silica such as boron oxide and aluminum oxide, and Periodic Tables 4 or 14 that can be bonded to silica such as titanium oxide and germanium oxide And metal oxides.

  As a typical method for producing the core, the sol-gel method is applied as described in JP-A-6-254383, JP-A-8-048505, JP-A-62-72516, and the like. Method.

  According to the above method, a particle having a coefficient of variation of 10% or less, which is an index of monodispersity, can be easily obtained, which is effective for improving the monodispersity of the resulting inorganic oxide particles.

  The inorganic oxide particle of the present invention is a silica-based composite oxide in which the core part mainly composed of silica is composed mainly of an oxide of a Group 4 or Group 14 metal other than silica and silicon. It has a two-layer structure coated with a coating layer made of a product.

Examples of the oxide of the Group 4 or Group 14 metal other than silicon include GeO ₂ , SnO ₂ , PbO ₂ , TiO ₂ , ZrO ₂ , and HfO ₂ . Among these, TiO ₂ (titania) and ZrO ₂ (zirconia) are inexpensive and easily available, and have a high refractive index, so that a coating layer having a high refractive index can be easily formed by adding a small amount. Therefore, it can employ | adopt very suitably. In addition to the two-component system of silica-titania and silica-zirconia, a three-component system of silica-titania-zirconia is also suitable.

  The silica-based composite oxide used for the coating layer of the present invention is, for example, a composite of silica and titania uniformly in molecular order when the oxide of the Group 4 or 14 metal other than silicon is titania. However, it is simply different from a mixture of silica and titania. Therefore, in the silica-based composite oxide, the constituent components of the group 4 or group 14 metal oxides other than silica and silicon are generally chemically bonded, and these constituent components are physically separated. It is usually not possible to separate them automatically. The fact that both components are chemically bonded can be confirmed by measuring the infrared spectrum and refractive index (particle optical transparency).

  Note that the inorganic oxide particles of the present invention are amorphous unless otherwise fired at a high temperature, and thus are highly optically isotropic and good. However, the refractive index of the silica-based composite oxide layer as the coating layer In order to improve the temperature, it may be fired at a temperature of about 1000 ° C. When fired at a high temperature of around 1000 ° C., some of the oxides of metals of Group 4 or 14 of the periodic table other than silicon (for example, titania and zirconia) may crystallize, but optical transparency is improved. If it can be maintained, it can be used without any problem. That is, the particles can be used without any problem as long as they are within a range in which the particles do not sinter or the crystals become too large and become opaque in the visible light region (the total light transmittance is not significantly reduced). For this purpose, the firing temperature of the particles is preferably 300 to 1100 ° C, more preferably 500 to 1050 ° C. The degree of crystallinity can be analyzed by means such as X-ray diffraction.

  In the inorganic oxide particles of the present invention, the oxides of metals of Group 4 or 14 of the periodic table other than silicon contained in the coating layer are generally high refractive index materials, and the higher the content thereof, the higher the refractive index. When the coating layer is used for compounding into a light scatterer, that is, the refractive index difference between the light scatterer and the matrix resin can be increased, and particles capable of increasing the light scattering efficiency can be obtained.

  In general, particles having a refractive index exceeding 1.6 are regions that could not be achieved with commercially available resin beads, and are extremely useful as particles for blending into light scatterers. For this reason, also in the composite oxide particles of the present invention, the coating layer has a refractive index in the range of 1.6 to 2.0, preferably in the range of 1.65 to 1.95, more preferably 1.70 to 1. A range of 90 is preferred.

  In the present invention, the refractive index is a value measured by an immersion method using light having a wavelength of 589 nm at 25 ° C.

  The inorganic oxide particles of the present invention are particles having a two-layer structure in which a core part mainly composed of silica is coated with the silica-based composite oxide having a high refractive index. It is difficult to measure directly. For reference, FIG. 1 shows the relationship between the titania content of the silica-titania composite oxide particles fired at 1050 ° C. for 12 hours and the refractive index of the particles. As is apparent from FIG. 1, the refractive index of the silica-based composite oxide particles is substantially proportional to the titania content, and thus it can be seen that the refractive index of the particles can be freely adjusted by controlling the titania content. In the present invention, the refractive index of the coating layer is a metal of Group 4 or Group 14 other than silicon in the silica-based composite oxide particles obtained under the same drying or firing conditions as shown in FIG. This is a value obtained by conversion from the composition of the coating layer based on the relationship between the oxide content and the refractive index of the particles.

  Here, in order to set the refractive index of the coating layer in the above range, the content of the oxide of a metal of Group 4 or Group 14 of the periodic table such as titania or zirconia is in the range of 22 to 70 mol%, preferably It is necessary to set it as the range of 25-65 mol%, More preferably, 30-60 mol%. Here, the content of the metal oxide of the Group 4 or 14 metal in the periodic table means that the number of moles of silicon constituting the silica-based composite oxide is Si, and the metal of the Group 4 or Group 14 other than silicon. When the number of moles of the metal element constituting the oxide is M, it is represented by M / (Si + M) × 100. When the content is less than 22 mol%, the light scattering effect may be small, and when it exceeds 70 mol%, the oxide of a metal of Group 4 or Group 14 other than silicon, such as titania, is easily crystallized. There is a concern that the total light transmittance is reduced.

  As described above, the particles of the present invention are not formed of a single composition of a metal oxide such as titania or zirconia but a metal oxide by forming a composite oxide with silica. Is characterized in that particles having a high total light transmittance can be obtained.

  The average particle size of the inorganic oxide particles of the present invention is 1.1 to 10 μm, preferably 1.20 to 5 μm. When the particle diameter is less than 1.1 μm, the dispersibility in a solvent or a resin is lowered due to the small particle diameter, which makes it difficult to use. Moreover, considering that the wavelength range of visible light is about 0.4 to 0.8 μm, if the average particle diameter is so small, there is a concern that the light scattering efficiency is lowered. On the other hand, when the particle diameter exceeds 10 μm, when the particles of the present invention are applied to a coating agent, the sedimentation speed of the particles is increased, so that the handling property is deteriorated, or the surface unevenness is severe when manufacturing a light scattering sheet or the like. There is also a concern that the light scattering characteristics may be adversely affected.

  In the present invention, it is important that the thickness of the coating layer is 0.03 μm or more. When the thickness of the coating layer is thin, light easily passes through the particles via the coating layer, so that the light scattering efficiency may be reduced. Therefore, the thickness of the coating layer is 0.03 μm or more, preferably 0.05 to 2 μm, and more preferably 0.1 to 1 μm, from the viewpoint of improving the light scattering efficiency.

  Furthermore, the inorganic oxide particles of the present invention have a circularity determined from an image taken by an electron microscope of 0.8 or more, preferably 0.85 or more, more preferably 0.90 or more, and most preferably 0.92. That's it. The reason why the particles of the present invention are excellent in sphericity as described above is because silica particles having high sphericity are used in the core portion as described above, and are formed outside the core portion. This is because the coating layer to be formed becomes spherical following this. Here, when the circularity is 0.8 or more, when used for a light scatterer, the light scattering is isotropic, and the reproducibility of the light scattering performance is also improved. When the degree of circularity is less than 0.8, it is difficult to fill the resin with a high degree, and when applied to a coating agent, the viscosity becomes high, or when the coating film is formed, the surface becomes rough and easily damaged. There is also concern about becoming.

Information such as the circularity, particle shape, average particle diameter, coefficient of variation of particle diameter, and the like can be examined by image analysis of an electron microscope image. In addition, circularity is a value calculated | required by image-processing the picked-up image of an electron microscope here. If the area of the particle obtained by image processing is S and the circumference of the particle is L,
Circularity = (4 · π · S) / (L ² )
It is. By calculating the average value for 200 or more samples, a substantially constant value with reproducibility can be obtained.

  In the inorganic oxide particles of the present invention, the surface of the coating layer may be further coated with silica as the outermost layer. For example, in the case of a silica-based composite oxide in which the core is silica and the coating layer is made of silica and titania, a part of the titania component may be exposed on the surface. Although titania is known to have a so-called photocatalytic ability that decomposes organic substances by absorbing ultraviolet rays, there is a concern that the resin binder and the like deteriorate when used under sunlight for a long period of time. In such a case, the outermost layer of the inorganic oxide particles of the present invention is further coated with silica to reduce or eliminate the problem of photodegradation. The outermost silica coating layer has a thickness of 1 nm or more, preferably 2 to 1000 nm, more preferably 3 to 100 nm.

  Since the inorganic oxide particles of the present invention are spherical and have a certain particle diameter, they can be used without limitation for various applications that require such properties. Examples of such applications include gap materials for liquid crystal displays, various optical fillers (for example, light scattering particles, light reflecting particles, light diffusing particles for antireflection films, matte particles for matting paper and films, etc.) , Photocatalysts, cosmetics having a function of preventing ultraviolet rays, fillers of various resins (for example, adhesives and sealants for dental composite resins, various optical elements and optical semiconductor devices), and the like.

  In addition to these properties, the inorganic oxide particles have the characteristics that both the light scattering efficiency and the total light transmittance are high as described above. Therefore, the inorganic oxide particles are best used for blending into a light scatterer. is there. As a light scatterer, it has the property to transmit and scatter light efficiently, and the member used using these properties is targeted without limitation. Specific examples include molding members used for various illuminations, light emitters, line markers, etc. In the present invention, in particular, a light diffusion sheet for a backlight for liquid crystal, and an antireflection sheet having an antiglare effect. And screens for projectors and projection televisions. In the present invention, the sheet includes a thin film generally called a film.

  When the inorganic oxide particles of the present invention are used for blending into the light scatterer, the refractive index of the coating layer of the inorganic oxide particles using the inorganic oxide particles is 0.1 or more, preferably 0.15 to It is blended with a transparent resin having a small refractive index of 0.7 to obtain a resin composition for a light scatterer, which is molded into a desired shape and used. By using such a transparent resin, a light scatterer with higher light scattering efficiency can be obtained. In this case, a plurality of particles having different average particle diameters can be mixed and used as particles having a distribution.

  The transparent resin generally has a refractive index in the range of 1.40 to 1.60, preferably 1.47 to 1.55. By blending with a transparent resin having a refractive index, the above-described excellent light scattering efficiency is remarkably exhibited.

  The transparent resin preferably does not have specific absorption in the visible light range and has high transparency. Usually, when a film having a thickness of 100 μm is used, the parallel light transmittance (measured according to JIS K 7105 and obtained at a wavelength of 600 nm) is 80% or more, preferably 85% or more, and more preferably 90%. It is preferable to use the above. Specific examples of such a transparent resin include acrylic resin, polycarbonate resin, cycloolefin polymer (COP), polystyrene resin, polyester resin, acrylic styrene (AS) resin, methacryl styrene (MS) resin, hard vinyl chloride resin, polyvinyl chloride. Examples include alcohol (PVA) resin, polypropylene (PP) resin, polyethylene terephthalate (PET) resin, triacetyl cellulose (TAC) resin, and epoxy resin.

  Moreover, as a light-scattering body, the thing which formed the coat layer containing the inorganic oxide particle of this invention in the base material sheet may be used. In this embodiment, a substrate sheet such as a PET film, a TAC film, or a COP film is preferably used as the substrate sheet. Furthermore, a plastic substrate made of acrylic resin, polycarbonate resin, COP resin, or the like, or a glass substrate can also be suitably used.

  The coating layer containing the inorganic oxide particles is manufactured by manufacturing a resin composition in which the particles are dispersed and mixed in a solvent together with the binder resin selected from the above-described transparent resin, and coating the resultant on a base sheet. It is common to provide it. Among the binder resins exemplified above, non-crosslinkable (linear) polymers are preferable because they are easily dissolved in a solvent.

  Furthermore, a monomer that is polymerized and cured by light or heat can also be used as a binder resin by coating and curing the substrate sheet. Specifically, it is preferable to use a monomer having two or more ethylenically unsaturated groups. In the case of having two or more ethylenically unsaturated groups, a crosslinked structure can be introduced into the film, so that a coat layer having excellent heat resistance and scratch resistance can be formed.

  Examples of monomers having two or more ethylenically unsaturated groups include esters of polyhydric alcohols and (meth) acrylic acid (eg, ethylene glycol di (meth) acrylate, 1,4-dichlorohexane diacrylate, penta Erythritol tetra (meth) acrylate), pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, 1,3,5-cyclohexanetriol trimethacrylate, polyurethane polyacrylate, polyester polyacrylate), vinylbenzene (Eg, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (eg, divinyl sulfone), acrylamide (eg, methylenebisacrylamide) and methacryl Amides are included. Among these, an acrylate or methacrylate monomer having at least three functional groups, and further an acrylate monomer having at least five functional groups are preferable in terms of film hardness, that is, scratch resistance.

  These monomers having an ethylenically unsaturated group can be cured by a polymerization reaction by ionizing radiation or heat after being dissolved in a solvent, coated and dried together with various polymerization initiators and other additives.

  Instead of or in addition to the monomer having two or more ethylenically unsaturated groups, a crosslinked structure may be introduced into the binder by the reaction of a crosslinkable group. Examples of the crosslinkable functional group include isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group. Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. That is, in the present invention, the crosslinkable functional group may not react immediately but may exhibit reactivity as a result of decomposition. The binder having these crosslinkable functional groups can form a crosslinked structure by heating after coating.

  The inorganic oxide particles of the present invention are essentially hydrophilic. When the binder resin is hydrophilic, a good dispersion state between the particles and the resin or solvent can be obtained. However, when the resin or solvent is hydrophobic, the particles may not be uniformly dispersed. Therefore, when the binder resin is hydrophobic, the particles are preferably surface-treated with a silane coupling agent or the like, or a dispersant is added.

Examples of the silane coupling agent include vinyl silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-N-phenyl-γ- Amino silane coupling agents such as aminopropyltrimethoxysilane; epoxy silane coupling agents such as γ-glycidoxypropyltrimethoxysilane; acryloxy silane coupling agents such as acryloxypropyltrimethoxysilane; Methacryloxy silane coupling agents such as loxypropyltrimethoxysilane; mercapto silane coupling agents such as 3-mercaptopropyltrimethoxysilane; methyltrimethoxysilane, trimethylmethoxysilane, decyltriethoxysilane, An alkyl-based silane coupling agent such as hydroxyethyltrimethoxysilane; a silicon compound having a fluorine-containing organic group such as (tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane can be used.
In addition to the above, various aluminum such as diisopropoxy aluminum ethyl acetoacetate, diisopropoxy aluminum alkyl acetoacetate, diisopropoxy aluminum monomethacrylate, aluminum stearate oxide trimer, isopropoxy aluminum alkyl acetoacetate mono (dioctyl phosphate) Coupling agents, zirconium di-n-butoxide (bis-2,4-pentanedionate), zirconium tri-n-butoxide pentadionate, various zirconium compounds such as zirconium dimethacrylate dibutoxide, isopropyl triisostearoyl titanate, isopropyl Trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl Li decyl benzenesulfonyl titanate, titanate coupling agents such as isopropyl tricumylphenyl titanate.

  In the present invention, the blending ratio of the inorganic oxide particles and the transparent resin depends on the usage, the light scatterer, the thickness of the coat layer, etc. A range of 0.01 to 300 parts by weight, preferably 0.1 to 100 parts by weight of the inorganic oxide particles is suitable.

  The production method of the inorganic oxide particles of the present invention is not limited as long as particles having the above-described requirements are obtained. The following method is mentioned as a suitable manufacturing method.

  That is, first, spherical silica particles serving as a core are produced by hydrolyzing and condensing a silicon alkoxide in a hydrous organic solvent (1) containing a catalyst, and then a silicon alkoxide and a periodic table other than silicon are produced. By hydrolyzing and condensing a raw material mixed with a group 4 or group 14 metal alkoxide in a water-containing organic solvent (2) containing a catalyst in which the silica particles are dispersed, the surface of the silica particles other than silica and silicon is used. The method of forming the coating layer which consists of an oxide of a periodic table group 4 or group 14 metal is mentioned.

  Here, as the organic solvent in the hydrous organic solvents (1) and (2) used, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert- Alcohols such as butyl alcohol, pentyl alcohol and hexyl alcohol, polyhydric alcohols such as ethylene glycol and glycerin, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane and diethyl ether, esters such as ethyl acetate, and other water Are used alone or in combination.

  In the water-containing organic solvent (1), since lower alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol have high compatibility with metal alkoxides and water and have low viscosity, the particles that are the core part are particularly preferred. It is suitably used when manufacturing.

  On the other hand, in the water-containing organic solvent (2), n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and long chain alcohols such as pentyl alcohol and hexyl alcohol. Are suitable for controlling the reactivity of the metal alkoxide, and may be particularly suitable for forming a coating layer. That is, the reactivity of hydrolysis / condensation of the raw material in which the alkoxide of silicon and the alkoxide of group 4 or 14 of the periodic table other than silicon are mixed is much higher than that of silicon alkoxide, so tert-butyl alcohol The use of such a long-chain alcohol can suppress the generation of fine particles and is suitable for forming a coating layer.

  The ratio of the organic solvent in the hydrous organic solvents (1) and (2) containing the catalyst is preferably about 3 to 95%, preferably 60 to 90%.

Further, a metal alkoxide as a catalyst to hydrolysis, N _{(CH 3)} amine _{3 etc., N (CH 3) 4 OH} , ammonia, LiOH, NaOH, bases such as KOH are preferably used. In particular, in the case of ammonia or amine, if the produced inorganic oxide particles are baked, no base remains in the particles, which is extremely suitable as a catalyst for hydrolysis. The amount of catalyst added varies depending on the type of catalyst used and the type and content of water and organic solvent in the water-containing organic solvent, but it cannot be generally stated, but added so that the pH is 10 or more, preferably 11 or more. It is preferable to do this. In the case of ammonia most suitable as a catalyst, the range of 2 to 10%, preferably 3 to 7% by weight as NH ₃ is suitable.

  The proportion of water in the water-containing organic solvents (1) and (2) containing the catalyst varies depending on the type of metal alkoxide used, but cannot be generally stated, but is 3 to 95%, preferably 5 to 40%, more preferably Is preferably in the range of 5 to 20%.

  As the metal alkoxide, a known compound can be used without any limitation as long as it is hydrolyzed in a water-containing organic solvent containing the catalyst to become a metal oxide.

As a typical example of a silicon alkoxide used as a raw material for silica, for example, a silicon alkoxide represented by the general formula Si (OR) ₄ or SiR ′ _n (OR) _4-n , or a silicon alkoxide partially A low condensate obtained by hydrolysis is easily industrially available, and one or a mixture of two or more thereof is preferably used. In the general formula of the silicon alkoxide, R and R ′ are alkyl groups, for example, lower alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl groups are preferred. n is an integer of 1 to 3.

In addition, as the metal alkoxide used as the raw material of the oxide of the Group 4 or 14 metal other than silicon, the alkoxide of the Group 4 or 14 metal other than silicon is not particularly limited and used. For example, a metal alkoxide represented by the general formula M (OR) ₄ (where R is an alkyl group) or one or two alkoxide groups (OR) in the above general formula are substituted with a carboxyl group or a β-dicarbonyl group. The compounds obtained are preferred. Here, M is a group 4 or 14 of the periodic table other than silicon. Specifically, for example, Ge, Sn, Pb, Ti, Zr, Hf and the like are preferably used. More specifically, the above-mentioned compounds that are generally preferably used in the present invention are exemplified by Ti (O-isoC ₃ H ₇ ) ₄ , Ti (O-nC ₄ H ₉ ) _{4 and the} like, and Ti, Examples thereof include compounds of metals of Group 4 or Group 14 of the periodic table substituted with Ge, Sn, Pb, Zr, Hf, and the like.

  In order to obtain inorganic oxide particles with higher sphericity, Ti and / or Zr alkoxides can be most preferably used among the above compounds.

  As described above, a known technique can be adopted when manufacturing a core part mainly composed of silica. Specific methods are described in, for example, JP-A-06-254383, JP-A-08-048505, JP-A-62-72516, and the like. If the method as described above is employed, particles having silica having a higher sphericity as a main component can be obtained.

  When manufacturing a coating layer of a silica-based composite oxide mainly composed of silica and an oxide of a group 4 or 14 metal other than silicon, known particles of such a silica-based composite oxide are known. Manufacturing methods can be applied.

  That is, in order to produce a coating layer, the above-described silicon alkoxide as a metal alkoxide and a group 4 or 14 metal alkoxide other than silicon are used in combination of one or more, What was mixed beforehand can be used as a raw material. In particular, in order to obtain the inorganic oxide particles of the present invention, it is effective to partially hydrolyze a part or all of the silicon alkoxide in advance (hereinafter also referred to as partial hydrolysis) before mixing the two. Furthermore, as described below, it is extremely effective to control the amount of water used for partial hydrolysis.

  A silicon alkoxide is partially hydrolyzed with water under the following conditions, and then mixed with an alkoxide of a Group 4 or 14 metal other than silicon to prepare a composite alkoxide, thereby comprising a silica-based composite oxide. A coating layer can be manufactured efficiently. As in the particles of the present invention, in the silica-based composite oxide forming the coating layer, those having a high content of 22 mol% or more of the periodic table group 4 or group 14 oxide other than silicon are particularly It is desirable to perform partial hydrolysis under the conditions shown below.

That is, X is the content (mol%) of the oxide of the group 4 or group 14 metal other than silicon in the silica-based composite oxide, and Y is the group 4 or group 14 metal other than silicon. When the equivalent of water to alkoxide is
i) When 22 ≦ X <30,
Y = 2-4
ii) When 30 ≦ X ≦ 50,
−0.06X + 3.5 <Y <−0.06X + 4.5
Preferably,
-0.06X + 3.7 <Y <-0.06X + 4.3
iii) 50 <X ≦ 70
(100 / X-1) -0.5 <Y <(100 / X-1) +0.5
Preferably,
(100 / X-1) -0.3 <Y <(100 / X-1) +0.3
The range of is good.

  If the amount of water in partially hydrolyzing the silicon alkoxide is less or greater than the above range, it becomes difficult to control the reaction when forming the coating layer, and the resulting inorganic oxide particles are spherical. Sex is reduced. In addition, fine particles are likely to be generated, many fused particles are generated, and in extreme cases, particles may be aggregated during particle synthesis.

  The purpose of the partial hydrolysis is to generate a silanol group (SiOH) in the molecule by hydrolyzing a part of the silicon alkoxide, and then to a metal of Group 4 or 14 of the periodic table other than the silanol group and silicon. The present inventors consider that a compound alkoxide of a group 4 or 14 metal other than silicon and silicon other than silicon is reacted to produce a composite alkoxide of silicon. Therefore, it is considered necessary to precisely control the molar ratio of the alkoxide of silicon, the alkoxide of a metal other than silicon, and the water used for the prehydrolysis.

  When the silicon alkoxide is partially hydrolyzed, it is preferable to use an organic solvent such as a lower alcohol such as methanol or ethanol that is compatible with both the alkoxide and water. When an organic solvent such as alcohol is not used, the silicon alkoxide and water tend to phase-separate, and partial hydrolysis may not proceed or the reaction may be very slow. Moreover, in order to advance partial hydrolysis rapidly, it is also preferable to add a catalyst to the water. An acid is suitable as the catalyst, and specific examples include hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, and the like, but there is no particular limitation. The acid concentration is preferably added so that the pH of water is in the range of 1 to 4.

  As described above, after preparing a raw material comprising a composite alkoxide by partially hydrolyzing a silicon alkoxide with water and then mixing with a alkoxide of a group 4 or 14 metal other than silicon, silica is the main component. The raw material is hydrolyzed and condensed in a water-containing organic solvent (2) containing a basic catalyst in which the core particles are dispersed (hereinafter also referred to as a reaction solution) to form a coating layer made of a silica-based composite oxide.

  The raw material is preferably dropped in the liquid. Dropping in the liquid means that the tip of the dropping port is immersed in the reaction liquid when the raw material is dropped in the reaction liquid. The position of the tip of the dropping port is not particularly limited as long as it is in the liquid, but a position where stirring is sufficiently performed such as the vicinity of a stirring blade is desirable. For example, when the liquid is dropped from above the reaction liquid without dropping in the liquid, it is not preferable because the particles easily aggregate.

  Moreover, you may add simultaneously the alkaline solution prepared separately with the said raw material to the water-containing organic solvent containing a catalyst. As this alkaline aqueous solution, 10-30 mass% ammonia water etc. are suitable. The supply ratio is such that the number of moles of water in the alkaline aqueous solution is 1 to 6 times, preferably 2 to 5 times, the total number of moles of silicon and metals other than silicon in the raw material. It is preferable to add an alkaline aqueous solution dropwise. Although it is not necessary to drop the alkaline aqueous solution in the liquid, it is preferable that the alkaline aqueous solution is dropped in the liquid near the stirring blade because stirring in the reaction liquid is sufficiently performed. By simultaneously dropping the alkaline aqueous solution as described above, particles can be synthesized with a high solid content concentration, so that a synthesis with a high yield is possible.

  Further, the dropping rate is also an important factor for increasing the monodispersity of the particles. The monodispersibility tends to increase as the dropping rate is made as slow as possible. However, when the dropping speed is slow, it takes a long time to complete the synthesis, and is not practical. For this reason, it is also a preferable aspect in practicing the present invention to lower the dropping speed at the initial stage of synthesis and increase the dropping speed after the latter half.

  It is preferable that the raw material composed of the composite alkoxide and the alkaline aqueous solution are continuously dropped from the start of dropping until the end thereof. The term “continuous” as used herein means that an interval of preferably 10 minutes or longer, more preferably 3 minutes or longer is not provided. The dropping speed is not necessarily constant, but it is desirable to change continuously when changing the dropping speed. In JP-A-4-77309, it is described that water is added in several times. However, in such a method, the atmosphere in the reaction solution is disturbed by the rapid addition of water, and the particles are dispersed. Agglomeration, generation of new core particles, and the like occur.

  The temperature of the reaction vessel when performing the hydrolysis may be in the range of 0 to 50 ° C., and is appropriately selected depending on the type of alkoxide used.

  In addition, a well-known thing is employ | adopted as a reaction container used for a hydrolysis, reaction conditions other than the above, without any limitation.

  By adopting the synthesis method as described above, it is possible to efficiently form a coating layer made of a silica-based composite oxide that satisfies the requirements specified in the present invention, around the core portion mainly composed of silica. .

  The particles after the synthesis are obtained as a colloidal particle dispersion dispersed in the reaction solution. Depending on the application, it may be used as it is, or after replacing the solvent of the reaction solution with an organic solvent such as water or alcohol.

  Further, after the particles are synthesized, they may be separated into solid and liquid by a method such as centrifugation, filtration, distillation, spray drying, etc., and taken out in the form of powder. The extracted powder can be dried. The drying temperature is preferably in the range of 50 to 300 ° C., and the drying time is preferably from several hours to several days. The dried powder can be fired at higher temperatures.

  The firing temperature is preferably in the range of 300 to 1100 ° C., and the firing time is preferably in the range of 1 to 24 hours. The dried or fired particles can be crushed into individual particles using a ball mill or a jet mill. Moreover, when using it disperse | distributing to resin, a solvent, etc., particle | grains can be disintegrated simultaneously with dispersion | distribution to resin or a solvent by using a high shear disperser. Further, in order to improve the dispersibility in a resin or a solvent, the particles may be treated with a surface treatment agent such as a silane coupling agent, or the dispersibility can be improved by using a surfactant in combination. .

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
(Average particle diameter, variation coefficient of particle diameter, circularity)
The shape of the particles was confirmed from a photographed image of a scanning electron microscope (hereinafter referred to as SEM). The average particle diameter, the coefficient of variation of the particle diameter, and the circularity were obtained by processing the SEM photographed image with an image analyzer. The number of samples for image processing was 200 or more. Note that the circularity defined here is obtained by image processing of a SEM image. That is, when the area of the particle obtained by image processing is S and the peripheral length of the particle is L, the circularity = (4 · π · S) / (L ² ). As the particle diameter, the equivalent circle diameter = (4 · S / π) ^1/2 was used.
(Refractive index of particles)
The refractive index of the particles was measured by an immersion method. That is, a solvent having a different refractive index (for example, toluene, 1-bromonaphthalene, 1-chloronaphthalene, diiodomethane, sulfur-containing diiodomethane, etc.) is appropriately mixed to form a mixed solvent having an arbitrary refractive index, and particles therein The refractive index of the most transparent particle dispersion solution at 25 ° C. was taken as the refractive index of the particles. The refractive index of the solvent was measured using light having a wavelength of 589 nm at 25 ° C. using an Abbe refractometer.

  In the inorganic oxide particles of the present invention, since the refractive index of the coating layer is difficult to actually measure, the titania in the silica-based composite oxide particles having no core part, which was previously produced under the same firing conditions. A correlation diagram showing the relationship between the content rate and the refractive index was created (FIG. 1), and based on this, it was determined as a value converted from the titania content rate of the coating layer.

  The method for creating the correlation diagram of FIG. 1 is as follows.

Several raw material solutions composed of composite alkoxides with various ratios of methyl silicate and tetraisopropoxy titanium were prepared, and silica particles were prepared in the same manner as in the production example of nuclear particles in the inorganic oxide particles of the present invention described later (Example 13). Several kinds of silica-based composite oxide particles having a uniform composition composed of and titania were synthesized. Each synthesized particle was dried and then calcined in air at 1050 ° C. for 12 hours. The refractive index of several kinds of silica-based composite oxide particles having different cores and thus having no core is measured by the above immersion method, and the correlation between the titania content and the refractive index is obtained. It was shown in FIG.
(Production and evaluation of light scatterers)
Using the inorganic oxide particles of the present invention, a light scatterer composed of the following coating film was made as a prototype, and the characteristics as light scattering particles were evaluated.

  10 parts by weight of a water slurry containing 4% by mass of inorganic oxide particles of the present invention (in the comparative example, light scattering particles) and 100 parts by weight of a 10% polyvinyl alcohol (transparent resin) aqueous solution were mixed and dispersed. An appropriate amount of ethyl alcohol was added as a diluent solvent, applied onto a slide glass using a bar coater, and dried at room temperature for 24 hours to produce a light scatterer. The thickness of the coating film was adjusted to 50 ± 5 μm.

The light scatterer was measured for total light transmittance and diffuse transmittance according to JIS K 7105 using a spectrophotometer with an integrating sphere, and a haze value was obtained. The total light transmittance, diffuse transmittance, and haze value showed values at a wavelength of 600 nm.
The physical properties of the coating film made of only polyvinyl alcohol were a refractive index of 1.50, a total light transmittance of 92%, a diffuse transmittance of 1.0%, and a haze of 1.1%.
Example 1
First, a raw material made of an alkoxide of silicon and titanium was prepared as a raw material for forming a coating layer made of a silica-based composite oxide.

Into a 3 liter Erlenmeyer flask, 203.1 g of methyl silicate (Si (OMe) ₄ , Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 101.5 g of methyl alcohol and 0.035 mass 24 g of hydrochloric acid was added, and methyl silicate was partially hydrolyzed by stirring at room temperature for about 10 minutes.

Subsequently, a solution obtained by diluting 189.3 g of tetraisopropoxytitanium (Ti (OiPr) ₄ , Nippon Soda Co., Ltd., product name; A-1 (TPT)) with 378.6 g of isopropyl alcohol was added, and the solution was added to the transparent homogeneous solution. Thus, 896.5 g of a raw material for forming a coating layer (a composite alkoxide of Si and Ti) was obtained. From the charged composition, the Ti content at this time was 33.3 mol%.

  In addition, the equivalent (Y value) of water with respect to the alkoxide of the group 4 or group 14 metal other than silicon at the time of the partial hydrolysis was 2.0.

  Next, a core part mainly composed of silica was produced.

640 g and 160 g of tert-butyl alcohol and ammonia water (25% by mass) are charged in a glass reaction vessel (internal volume 5 liters) with a stirrer, respectively, and mixed well to prepare a reaction solution. Held at 0C. A reaction solution of a raw material obtained by diluting 65.5 g of methyl silicate (Si (OMe) ₄ , Tama Chemical Co., Ltd., trade name: normal methyl silicate) with 32.7 g of methyl alcohol and 38.0 g of aqueous ammonia (25% by mass) Each was independently dropped into the liquid simultaneously. About 10 minutes after the start of dropping, the reaction solution started to become cloudy, and it was found that silica particles were generated. All the raw materials and aqueous ammonia were added dropwise over about 2 hours to produce silica particles serving as the core. In addition, a part of solution after completion | finish of dripping was sampled and used for the later analysis.

  Subsequently, 896.5 g of the raw material for forming the coating layer and 189.2 g of aqueous ammonia (25% by mass) were dropped independently into the reaction vessel to form a coating layer on the surface of the core particles. In addition, the dropping ratio of the raw material and ammonia water was made substantially constant, the dropping speed was first slowed, and in the latter half, all the raw materials were dropped over about 6 hours to produce inorganic oxide particles.

  After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5-liter beaker, and allowed to stand. The product was washed by repeating decantation several times using pure water as a solvent. The precipitate was dried and then calcined in air at 1050 ° C. for 12 hours to prepare inorganic oxide particles.

  The sampled core (silica particles) was also fired under the same conditions as the coated particles (inorganic oxide particles), followed by SEM observation to evaluate particle physical properties. As a result, it was found that the core part is a highly monodisperse spherical particle having an average particle diameter of 0.78 μm, a coefficient of variation of 6.5%, and a circularity of 0.97 determined from an image taken by an electron microscope. It was.

  On the other hand, the coated particles were found to be highly monodisperse spherical particles having an average particle diameter of 1.10 μm, a coefficient of variation of 7.8%, and a circularity of 0.96 determined from an image taken by an electron microscope. . The thickness of the coating layer was estimated to be 0.16 μm from the average particle diameter of the core and the coated particles.

Moreover, when the surface analysis of the said particle | grains was performed using Auger electron spectroscopy (AES) for confirmation, Si and Ti were detected from the surface layer of particle | grains, and also while sputtering the surface by argon ion, Ti's When the distribution in the depth direction was examined, it was found that the thickness of the surface layer containing Ti was about 0.15 μm. It was also found that the ratio of Si and Ti in the surface layer was Ti: Si = 1: 2.
As described above, it was confirmed that the inorganic oxide particles had a two-layer structure in which silica particles were coated with a silica-based composite oxide composed of silica and titania.
Next, a light scatterer was prototyped using the inorganic oxide particles, and the physical properties of the light scattering particles were evaluated.

The results are shown in Table 1, and as such, the total light transmittance was high and the haze value was also high, which proved useful as light scattering particles.
Examples 2-6
Except for changing the particle size of the core and the thickness of the coating layer by adjusting the composition and amount of the reaction solution, the amount of methyl silicate dropped when the core is manufactured, and the amount of the coating layer raw material dropped Basically, various inorganic oxide particles were produced in the same manner as in Example 1.

Tables 1 and 2 show the measurement results of the physical properties of the particles and the evaluation results of the light scatterers.
Examples 7-9
Various inorganic oxide particles were synthesized basically in the same manner as in Example 1 except that the blending ratio of titanium as the coating layer raw material was variously changed.
The physical property measurement results of the particles and the evaluation results of the light scatterer are shown in Table 1.
In addition, the usage-amount of hydrochloric acid used for the partial hydrolysis at the time of preparing the raw material for coating layers was changed in proportion to the content rate of the metal (titanium) of the periodic table group 4 or 14 other than silicon. Table 2 also shows the equivalent (Y value) of water to titanium alkoxide.
Example 10
After forming the core portion and the coating layer in the same manner as in Example 8, methyl silicate and aqueous ammonia (25% by mass) were added dropwise simultaneously to further add only silica onto the surface of the silica-based composite oxide coating layer. The outermost layer consisting of was formed.

  The physical property measurement results of the particles and the evaluation results of the light scatterer are shown in Table 2.

As a result of analysis, it was confirmed that the particles of Example 8 had a three-layer structure in which the surface of the particles was coated with a 0.03 μm silica layer. Further, the characteristics as light scattering particles were not inferior to those of Example 8 at all.
Example 11
After forming the core and the coating layer, inorganic oxide particles were synthesized in the same manner as in Example 10 except that the amounts of methyl silicate and aqueous ammonia that were dropped simultaneously were changed.

  The physical property measurement results of the particles and the evaluation results of the light scatterer are shown in Table 2.

As a result of analysis, it was confirmed that the particles of Example 8 had a three-layer structure in which a silica layer of 0.005 μm was coated. Further, the characteristics as light scattering particles were not inferior to those of Example 8 at all.
Example 12
Inorganic oxide particles having a coating layer made of silica-zirconia were prepared in the same manner as in Example 1 except that tetrabutoxyzirconium was used instead of tetraisopropoxytitanium. In addition, the thickness of the coating layer was controlled by adjusting the dripping amount of the coating layer raw material.

Table 2 shows the physical properties of the particles and the evaluation results as light scattering particles.
Example 13
Inorganic oxide particles were produced in the same manner as in Example 1 except that the particles constituting the core were produced by the following procedure.

Into a 3 liter Erlenmeyer flask, 794.5 g of methyl silicate (Si (OMe) ₄ , Tama Chemical Co., Ltd., trade name: normal methyl silicate) was charged, and 300 g of methyl alcohol and 0.035% by mass hydrochloric acid were stirred. 42 g was added and the methyl silicate was partially hydrolyzed by stirring for about 10 minutes at room temperature.

Subsequently, a solution obtained by diluting 221.7 g of tetraisopropoxytitanium (Ti (OiPr) ₄ , Nippon Soda Co., Ltd., product name: A-1 (TPT)) with 469 g of isopropyl alcohol is added, and a raw material comprising a transparent uniform solution 1827 g of (Si and Ti composite alkoxide) was obtained. From the charged composition, the Ti content at this time was 13.0 mol%. In addition, the equivalent (Y value) of water to the alkoxide of the Group 4 or Group 14 metal other than silicon at the time of the partial hydrolysis was 3.0.

  Next, 390 g and 110 g of isopropyl alcohol and ammonia water (25% by mass) are charged in a glass reaction vessel (internal volume 5 liters) with a stirrer, respectively, and mixed well to prepare a reaction solution. Maintained at 40 ° C. The above composite alkoxide solution as a raw material and 350 g of aqueous ammonia (25% by mass) were simultaneously dropped into the reaction solution simultaneously. Several minutes after the start of dropping, the reaction solution started to become cloudy, and it was found that composite oxide particles composed of silica and titania were produced. All the raw materials and aqueous ammonia were dropped over about 7 hours to produce composite oxide particles that became the core.

  After removing half of the slurry in the reaction vessel, a coating layer was subsequently formed in the same manner as in Example 1 to produce inorganic oxide particles.

  In addition, when the composite oxide particle used as the nucleus extracted above was analyzed, it was a 0.5 micrometer spherical particle.

Comparative Example 1
Using the core particles (silica) produced in the same manner as in Example 3, the properties as light scattering particles were evaluated.

The physical properties of the particles and the evaluation results as light scattering particles are shown in Table 3.
Comparative Example 2
Inorganic oxide particles were prepared in the same manner as in Example 3 except that the thickness of the coating layer was 0.01 μm.

  The physical properties of the particles and the evaluation results as light scattering particles are shown in Table 3.

As described above, it was found that when the thickness of the particles or the coating layer made only of silica was as small as 0.01 μm, the haze value was small and the light scattering performance was insufficient.
Comparative Example 3
A commercially available polymer bead (made of acrylic resin, refractive index 1.49, average particle diameter 1.52 μm) was used as light scattering particles, and a light scattering body was produced in the same manner as in Example 1.

The evaluation results are shown in Table 3, and the light scattering efficiency was very low.
Comparative Example 4
A commercially available crystalline alumina particle (refractive index: 1.76, average particle size: 2.05 μm) was used as the light scattering particle, and a light scattering material was produced in the same manner as in Example 1.

  The evaluation results are shown in Table 3. Although the haze value was high, it was found that the total light transmittance was low. That is, it was predicted that the crystalline light scattering particles might be used to shield light transmission. In addition, since the shape of the filler was indefinite and contained coarse particles, it was difficult to produce a smooth coat film (coating streaks were likely to occur and the surface of the coat film was rough).

Example 14
The light resistance of the coating film using the inorganic oxide particles of the present invention was examined. 1 g of each of the inorganic oxide particles obtained in Examples 8, 10, and 11 and 4 g of acrylic resin were sufficiently mixed using a high shear blender using methyl ethyl ketone as a solvent to prepare a coating solution. This coating solution was applied on a glass substrate so that the film thickness after drying was about 100 μm. In the light resistance test, a sunshine weather meter (xenon lamp 40 W / m ² ) was used to observe the deterioration of the film every 24 hours.

  As a result, the three-layer structure particles (Examples 10 and 11) in which the outermost layer of the particle was coated with a silica layer were compared with the two-layer structure particles (Example 8) in which the silica layer was not coated. It was found that the deterioration was suppressed to about 1/3 or less.

FIG. 1 shows the relationship between the titania content and the refractive index of silica-based composite oxide particles having no core, which were used to convert the refractive index of the coating layer in the inorganic oxide particles of the present invention. It is a correlation diagram.

Claims (3)

An inorganic oxide particle comprising a core part mainly composed of silica and a coating layer of a silica-based composite oxide mainly composed of an oxide of a Group 4 or Group 14 metal other than silica and silicon. The average particle diameter of the particles is 1.1 to 10 μm, the circularity obtained from an electron microscope image is 0.8 or more, and the coating layer has a thickness of 0.03 μm or more. , no machine oxide particles of the oxide of group 4 of the periodic table or 14 metal other than silicon contained in the range of 22 to 70 mol%, 0 than the refractive index of the coating layer of inorganic oxide particles. A resin composition for light scatterers, which is blended with a transparent resin having a refractive index smaller by 1 or more . The inorganic oxide particles are inorganic oxide particles in which the oxide of the Group 4 or 14 metal other than silicon in the coating layer of the inorganic oxide particles is titania and / or zirconia. The resin composition for a light scatterer according to claim 1. 3. The resin composition for a light scatterer according to claim 1 , wherein the inorganic oxide particles are inorganic oxide particles in which a silica layer is coated on the surface of the coating layer as an outermost layer.

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