JPH08269433A - Ultraviolet-shielding platy composite microparticle and its production - Google Patents

Abstract

PURPOSE: To obtain microparticles improved in transparency to visible light and ultraviolet shielding properties by forming a mixture containing a specified starting material for parent particles and a specified starting material for daughter particles into a liquid film, drying or firing this film and grinding the dried or fired film. CONSTITUTION: A mixture is obtained by mixing 10<-5> -20mol/L of a starting material for fluorine-compound-containing parent particles, comprising a sol containing particles constituting parent particles having a mean particle diameter of primary particles of 0.001-0.3μm and/or a solution which can form the particles when heat-decomposed and 10<-5> -10mol/L of at least one starting material for daughter particles, selected from a sol containing daughter particles comprising a metal oxide and having a mean particle diameter of 0.001-0.1μm, a powder of daughter particles and a solution which forms daughter particles when heat-decomposed. A substrate is immersed in a solution containing the above mixture to form a liquid film having an average liquid film thickness of 0.1-1000μm. This film is dried and /or fired at 100-1500 deg.C or dried at 100-1500 deg.C, heat-decomposed and fired to obtain a solid film. This film is ground to form platy microparticles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-like composite fine particle having high transparency in the visible light region and high shielding property in the ultraviolet light region, and a method for producing the same.

[0002]

2. Description of the Related Art Of the sunlight (infrared rays, visible rays, ultraviolet rays) reaching the earth, 5 to 6% is ultraviolet rays. Ultraviolet rays are electromagnetic waves with a short wavelength and therefore high energy,
It is known that it has degradability to many substances and widely damages the living body. Accordingly, ultraviolet shielding agents are used, for example, in cosmetics to protect the skin from inflammation or skin cancer caused by ultraviolet rays, or to be mixed with paints to prevent pigments from being decomposed by ultraviolet rays and discolored. I have. At this time, by increasing the transparency in the visible light range, it is possible to prevent whitening in the case of cosmetics and to prevent the color of the pigment from being impaired in the case of paints. It is desirable to protect against UV rays while maintaining the sex.

An ultraviolet ray shielding agent using an organic compound as an active ingredient prevents the composition from penetrating by absorbing characteristic ultraviolet rays, and is, for example, an ultraviolet ray composed of substituted N, N'-bis-aromatic formamidines. Absorbable compositions (JP-B-61-09993) and the like. However, the organic UV-screening agent has a drawback that it absorbs UV light and at the same time is decomposed by the action thereof, and thus has a drawback that its screening ability is attenuated over time. Further, in application to cosmetics, there are restrictions on the types and compounding amounts that can be compounded from the viewpoint of the effect on the human body, and it is difficult to exhibit high functions within the restrictions.

On the other hand, an ultraviolet shielding agent using an inorganic compound is a composition in which inorganic fine particles are blended as a composition, and the composition is prevented from penetrating by absorbing and scattering the ultraviolet rays. Such an inorganic ultraviolet shielding agent is superior to an organic shielding agent in that the composition does not deteriorate over time and has little effect on the human body. However, as compared to organic ultraviolet shielding agents, inorganic systems are in the form of particles, and it has been conventionally difficult to protect the ultraviolet system while maintaining high transparency in the visible light region. .

Visible light region (light wavelength 400 to 800 nm)
In order to effectively exhibit the shielding ability in the ultraviolet region while maintaining the high transparency, it is necessary to make the composition ultrafine particles to be in a highly dispersed state and enhance the ultraviolet scattering ability. But,
When ultrafine particles are used, the dispersion stability of the ultrafine particles due to their cohesiveness becomes a problem. There is also a method of coating the surface of the ultrafine particles with another substance to improve the dispersibility,
For example, a skin cosmetic in which hydrophobized titanium oxide powder is mixed with an oil-based cosmetic base (Japanese Patent Publication No. 59-15885).
However, it is necessary to select a solvent to disperse according to the properties of the surface coating layer, and the surface modification does not change the form of ultrafine particles, so there is a limit to reducing the cohesive force. .

In order to prevent the ultrafine inorganic particles from aggregating and losing their ability to scatter ultraviolet rays, there is an example in which they are compounded with other particles as a relatively large carrier. For example, a flaky shape containing fine metal compounds dispersed therein. Substance (JP-A-63-126818)
However, there is no disclosure about the specific constitution of the fine particles for improving both the ultraviolet shielding ability and the visible ray transparency.

Further, JP-A-1-143821 discloses a composite powder in which fine particle powder such as TiO ₂ is uniformly dispersed in plate-like particles of a metal oxide such as SiO ₂ and is disclosed in JP-A-6-116119. Contains 5 to 80% by weight of titania and 20 to 95% by weight of silica, respectively, and the total content of titania and silica is at least 80% by weight. A cosmetic material having a high absorption effect is disclosed. However, in the ultraviolet absorbers described in these publications, ultraviolet rays B (light wavelength of 280 to 320 nm), which penetrates to the epidermis and the upper layer of the dermis only to a relatively shallow portion and cause sunburn and skin cancer, are It is considered that there is an absorption effect due to the titania in the flaky particles, but ultraviolet rays A (light wavelength 32, which reaches the deep skin layer in the dermis layer and causes fiber degeneration within the dermis)
0 to 400 nm), a light wavelength of 35 close to visible light
There is no absorption effect from 0 to 400 nm. That is, the ultraviolet absorbers described in these publications mainly exhibit an effect of absorbing ultraviolet B by titania, and the anatase type has a light wavelength of about 300 nm, and the rutile type has a light wavelength of 32 nm.
It is limited to exhibiting an ultraviolet absorption effect of about 0 nm.

Of the ultraviolet rays reaching the surface of the earth, the ultraviolet ray A has an energy ratio of about 15 times that of the ultraviolet ray B. Therefore, considering the energy ratio of the ultraviolet ray, the ultraviolet ray A is not only the ultraviolet ray B or not only the ultraviolet ray B, but also the ultraviolet ray B. It is important to shield A. Moreover, blocking the ultraviolet rays B and A while maintaining high transparency in the visible light region is a major issue. Especially when blocking the ultraviolet rays A,
It is important to block ultraviolet rays having a light wavelength of 350 to 400 nm, which is close to visible light. Further, in order to improve the transparency in the visible light region, it is important to reduce the difference in refractive index between the ultraviolet absorber and the dispersion medium around it,
JP-A-1-143821 and JP-A-6-1161
In the composite powder containing titania described in Japanese Patent Publication No. 19, the refractive index of the composite powder is roughly determined by the composition ratio of the constituents, so that the refractive index of the composite powder is adjusted to the dispersion medium having a certain refractive index value. However, a limit naturally occurs, and it has been a major problem to control the refractive index of the composite powder so as to match the refractive index of the dispersion medium. There has been a demand for effective means for solving the above problems to be solved.

[0009]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems in the ultraviolet shielding agent, and has a plate-like composite fine particle having a high transparency of visible light and a high ultraviolet ray shielding property. And its manufacturing method.

[0010]

DISCLOSURE OF THE INVENTION The present inventors have dispersed fine particles (child particles) having a screening ability for ultraviolet rays B and / or A and child particles in order to make the performance of an inorganic ultraviolet screening agent high. Fine particle aggregate (mother particle) as a mother material to be contained
We have devised a plate-like composite fine particle that combines the former with the ultraviolet scattering and absorption ability of the former and the high dispersibility of the child particles with the latter. Then, it was found that the effect of the ultrafine particles can be maximized by focusing on the band gap energies of both and determining the combination based on the magnitude relationship.

Further, in controlling the refractive index of the composite fine particles, the present inventors use a metal oxide or a fluorine compound having a low refractive index as the particles constituting the mother particles to control the composition of the child particles and the mother particles. The refractive index of the composite fine particles was controlled to be equal to the refractive index of the medium. As a result, the scattering of light at the interface between the composite fine particles and the medium is suppressed, and light penetrates well inside the composite fine particles regardless of the surface roughness of the composite fine particles, and the transparency in the visible light range is dramatically increased. It has been found that at the same time, the function of the ultrafine particles dispersed therein can be effectively exhibited and a high ultraviolet shielding property can be exhibited. When a substance having a low refractive index is used in the form of fine particles having a particle size of 0.3 μm or less, the visible light is not scattered even if a fine particle unit domain is formed in the composite fine particles, and the refractive index of the entire particle is lowered. Found that is possible.

Further, a mixture of a mother particle raw material and a child particle raw material which are constituent elements of the composite fine particles, that is, a sol containing particles constituting the mother particles having an average primary particle diameter of 0.001 to 0.3 μm, and And / or a mother particle raw material containing at least a fluorine compound formed of a solution capable of producing such particles by thermal decomposition, and having an average particle diameter of 0.001 to 0.
Mixing containing a mixture of a sol containing 1 μm child particles, a child particle powder, and one or more child particle raw materials selected from the group consisting of a solution capable of producing such child particles by thermal decomposition After the liquid is made into a liquid film, it is dried and / or
Alternatively, by firing or by pyrolyzing and / or firing after drying to obtain a solid film, and then crushing this solid film, the child particles are uniformly dispersed and immobilized inside, and high visible light transparency and It has been found that it is possible to continuously produce plate-like composite fine particles having an ultraviolet shielding property.

That is, the gist of the present invention is: (1) The average particle size of primary particles is 0.001 to 0.3 μm.
m is a composite fine particle composed of a mother particle formed by aggregating while maintaining its shape, and a child particle having an average particle size of 0.001 to 0.1 μm dispersed and fixed in the mother particle. The child particles have a smaller bandgap energy than the particles forming the mother particles and have an ultraviolet absorbing ability, and the particles forming the mother particles are a fluorine compound or a mixture of a fluorine compound and a metal oxide. The ultraviolet-shielding plate-like composite fine particles having transparency in the visible light region, wherein (2) the metal oxide is selected from SiO ₂ and / or Al ₂ O ₃ . ultraviolet shielding composite sheet particles, (3) the fluorine compound is MgF ₂ and / or polytetrafluoroethylene (1) or (2) ultraviolet shielding composite sheet microparticles described, (4) the mother particle Any of the above (1) to (3), wherein the particles formed are those obtained by adding perfluoropolyether to a fluorine compound, a metal oxide, or a mixture of the metal oxide and the fluorine compound, which is solid at room temperature. Or (5) the child particles are TiO ₂ , ZnO, CeO ₂ , or BaT.
(1) to (1), which is at least one selected from the group consisting of iO ₃ , CaTiO ₃ , SrTiO _3, and SiC.
(4) Ultraviolet-shielding plate-like composite fine particles according to any one of (6) Substantially the same as the refractive index of the plate-like composite fine particles (however, the difference in refractive index within ± 0.1 is considered to be similar). When it is suspended in a medium having a refractive index of 1, and the light transmittance is measured by an ultraviolet-visible spectrophotometer using an optical cell with an optical path length of 1 mm, the transmittance is 90% or more at a wavelength of 800 nm, and the transmittance is 40% at a wavelength of 400 nm. Above, and wavelength 3
The transmittance (5) or less at 50 nm, 320 nm, and / or 300 nm is 5% or less.
(5) An ultraviolet-shielding plate-like composite fine particle according to any one of the above, and (7) a method for producing an ultraviolet-shielding plate-like composite fine particle having transparency in the visible light region, which comprises the following steps:
(A) The average particle size of the primary particles is 0.001 to 0.3 μm.
And a mother particle raw material containing at least a fluorine compound consisting of a solution containing particles constituting the mother particles and / or a solution capable of producing such particles by thermal decomposition, and having an average particle diameter of 0.001 to 0.1 μm. A sol containing child particles, a child particle powder, and a mixed solution containing a mixture with one or more child particle raw materials selected from the group consisting of solutions capable of producing such child particles by thermal decomposition (B) The average liquid film thickness of the mixed liquid is 0.1 to
A step of forming a liquid film in the range of 1000 μm, (c) drying and / or baking the obtained liquid film in an atmosphere of 100 to 1500 ° C., or after drying at the atmospheric temperature, pyrolysis and / or baking To obtain a solid film by (d) pulverizing the solid film to form plate-like fine particles. Hereinafter, the present invention will be described in detail.

Fine particles having a relatively small particle size, which have a high shielding ability against ultraviolet rays, tend to agglomerate.
It is difficult to disperse it in a medium to express its function well. Therefore, by combining such fine particles with relatively large particles, that is, by immobilizing them as child particles in mother particles as a carrier, the dispersed state can be maintained and the ultraviolet shielding ability can be maintained. Further, in general, by encapsulating small particles having high surface activity in the mother particles, it is possible to suppress the influence of bad surface activity on the medium when the composite particles are suspended in the medium. In the present specification, the base particles of the composite fine particles refer to a base in which child particles are dispersed and contained, and the base particles are formed as aggregates in which the particles constituting the base particles are aggregated while maintaining their shapes. The child particles are particles having an ultraviolet shielding ability other than the mother particles. Further, the "plate shape" refers to a shape similar to a flat shape, a flake shape, etc., although its size and aspect ratio are not particularly limited.

Hereinafter, preferred embodiments of the plate-like composite fine particles of the present invention will be described in detail in terms of the band gap energy of the particles, the refractive index of the composite fine particles, and the grain boundaries of the particles.

(1) Band Gap Energy of Particles In the plate-like composite particles of the present invention, the particles used as child particles must have a shielding property in the ultraviolet region, which is divided into ultraviolet absorbing property and ultraviolet scattering property. To be The ultraviolet absorptivity is mainly due to exciton absorption of a semiconductor compound with respect to an inorganic compound, and a compound having a band gap energy of 3.0 to 4.0 eV effectively exhibits the property. The ultraviolet scattering property is strongly exhibited by Mie scattering, which becomes remarkable in the case of a high refractive index substance when the particle size is about ½ of the wavelength of ultraviolet light, that is, 0.2 μm or less.

In general, ceramics having semiconductivity are
Since the valence band and the conduction band are not continuous, it is known to absorb light having a wavelength corresponding to energy equal to or higher than the band gap energy which is the energy difference between the two levels.
For example, ZnO has a band gap energy of 3.2 eV.
And light having a wavelength of 390 nm or less, that is, ultraviolet ray A
Absorbs. The property of the inorganic ultraviolet shielding agent absorbing ultraviolet light is that its band gap energy is in the wavelength region of ultraviolet light.

Accordingly, in the plate-like composite fine particles of the present invention, in order to effectively exhibit the ultraviolet ray scattering and absorbing ability by the child particles, the band gap energy of the particles constituting the mother particles is larger than that of the child particles. is necessary. For example, when an aggregate of SiO ₂ particles is used as a mother particle, if ZnO fine particles having a smaller band gap energy than SiO ₂ is contained as a child particle, a wavelength of 20
Ultraviolet rays of 0 nm or less form particles (Si
O ₂ ), which is absorbed by exciton absorption corresponding to the bandgap energy of O ₂ ) and is transmitted without being absorbed by the mother particle, is based on the bandgap energy of the daughter particle while being multiply scattered by the child particle while being scattered in the vicinity of the wavelength of 200 to 390 nm. It is efficiently absorbed by exciton absorption. In this case, since SiO ₂ is highly transparent to visible light,
The composite fine particles have high visible light transparency and
It is possible to block ultraviolet rays in the wavelength region of 0 nm or less.

On the other hand, if ZnO is used as the particles constituting the mother particles and SiO ₂ fine particles having a bandgap energy larger than that of ZnO are used as the child particles, a wavelength of 390 is obtained.
Ultraviolet rays having a wavelength of nm or less are absorbed by the mother particles by exciton absorption corresponding to the band gap energy of ZnO,
In this case, the ultraviolet rays do not reach the SiO ₂ as the child particles, and the child particles do not play the role of absorbing the ultraviolet rays.
The size at which the mother particles are recognized by visible light (particle diameter 0.2
If it is about μm or more), the visible light transparency is also deteriorated.

From these points, in the plate-like composite fine particles of the present invention, the band gap energy of the particles constituting the mother particles is preferably 3 to 9 eV, more preferably 5 to 9 eV. Further, in order to more reliably reach ultraviolet rays in the wavelength region expected to be absorbed and scattered by the child particles to the child particles, the bandgap energy of the child particles having the minimum bandgap energy constitutes the mother particle. 0.2e than the band gap energy of the particle
It is preferably smaller than V.

(2) Refractive index of composite fine particles When actually using the ultraviolet shielding fine particles, it is necessary to exhibit high transparency in the visible light region while maintaining high shielding property in the ultraviolet region. Here, (i) in order to maintain a high shielding property, a large difference in refractive index between the mother particles and the child particles improves the ultraviolet ray shielding ability in the child particles, and therefore the difference in the refractive index between the two particles is large. It is necessary and is preferably 0.1 or more in the present invention. Therefore, in the present invention, a metal oxide or a fluorine compound having a relatively low refractive index is used as a constituent material of the base particles for the child particles having a relatively high refractive index. Also, (ii) a substance (medium) around the composite fine particles in order to exhibit high transparency
It is necessary to minimize the difference in the refractive index between the composite fine particles and the medium in consideration of the difference in the refractive index between the composite fine particles and the medium. For this purpose, the refractive index of the composite fine particles must be controlled. The present invention has a feature of the present invention in that a fluorine compound, which is a low refractive index substance, is used for controlling the refractive index.

That is, in a suspension system of composite fine particles (that is, a state when used in cosmetics and the like), when the composite fine particles and the medium have different refractive indices, visible light is refracted or reflected at the interface between them to be transparent. Sex is impaired. Here, the refractive index is generally measured by a liquid immersion method (for example, Toshiharu Tayuki et al., "Optical Measurement Handbook" P.475, 1981,
Asakura Shoten), the refractive index of the medium having the highest transmittance of light having a wavelength of 589.3 nm is used as the refractive index of the sample. However, the liquid immersion method requires complicated operations and requires a long time, and therefore can be easily calculated from the refractive index and the volume ratio of the primary particles and the primary particles. Since the calculated refractive index may be very similar to the data obtained by the liquid immersion method, in such a case, the refractive index of the composite fine particles in the present invention uses such a simple method. Also referred to as the value obtained.

Generally used media have a refractive index n _D ²⁰ of 1.3 to 1.8, whereas most metal oxides such as TiO ₂ and ZnO having a high ultraviolet shielding property have a refractive index n _D. ^{Since 20} is 2.0 or more, it is necessary to make the refractive index of the composite fine particles close to the value of the medium by using a low-refractive index material as the mother particles when these are used as the child particles. That is, the refractive index of the composite fine particles is 1.3 to 1.8, preferably 1.3 to 1.8.
It is 1.7, and more preferably 1.4 to 1.5. Further, the difference in refractive index between the mother particles and the child particles in the plate-like composite fine particles of the present invention is preferably 0.1 or more. This is because the ultraviolet scattering ability at the mother-child particle interface is improved.

(3) Grain Boundary of Particles Regarding the primary particles of the mother particles, from the viewpoint of grain boundaries, the smaller the particle size, that is, the smaller the grain boundary inside the mother particles,
Visible light cannot recognize the fine grain boundaries, and the parent particles have transparency regardless of the crystallinity of the primary particles of the parent particles. Therefore, it can be explained that the composite fine particles also have transparency as a result.

Next, the method for producing the ultraviolet shielding plate-like composite fine particles of the present invention will be described for each step. The manufacturing process of the present invention is roughly divided into the following four processes. That is, (a) the average particle size of the primary particles is 0.001 to 0.3.
a mother particle raw material containing at least a fluorine compound consisting of a sol containing particles constituting the mother particles having a diameter of μm and / or a solution capable of producing such particles by thermal decomposition, and an average particle size of 0.001 to 0. Mixing containing a mixture of a sol containing 1 μm child particles, a child particle powder, and one or more child particle raw materials selected from the group consisting of a solution capable of producing such child particles by thermal decomposition A step of preparing a liquid, (b) the mixed liquid having an average liquid film thickness of 0.1
The step of forming a liquid film in the range of ˜1000 μm, (c) drying and / or firing the resulting liquid film in an atmosphere of 100 to 1500 ° C., or after drying at the ambient temperature, pyrolysis and / or firing And (d) a step of pulverizing the solid film to form plate-like fine particles.

Here, in the step of preparing the mixed solution which is the step (a), the average particle diameter of the child particles is 0.001.
When the ultrafine particle powder having a particle size of up to 0.1 μm is used, it is preferable to keep the dispersed state of the child particles in the mixed liquid by crushing or crushing the child particle powder by a treatment such as milling or high pressure dispersion.

Next, each raw material used in the production method of the present invention will be described. (1) The sub-particles constituting the composite fine particles have transparency in a visible light region and shielding properties in an ultraviolet region. That is, it is necessary that the child particles have a size which does not absorb visible light and scatter visible light.

As a substance constituting the child particles, there is no absorption in the visible light region, and it is necessary that the exciton absorption edge based on the bandgap energy exists in the ultraviolet wavelength region because of the requirement that it has an ultraviolet absorbing property. A substance, that is, a semiconductor compound having a band gap energy of 3.0 to 4.0 eV is preferable, and examples thereof include TiO ₂ , ZnO, and C.
eO ₂ , SiC, SnO ₂ , WO ₃ , SrTiO ₃ , B
aTiO ₃ , CaTiO _{3 and the} like strongly exhibit their properties, and among them, TiO ₂ , ZnO and CeO ₂ are generally often used as an ultraviolet shielding agent, and one or more selected from the group consisting of these Particularly preferred. In particular, ZnO, CeO _2, etc. are effective for shielding the ultraviolet A region (320 to 400 nm), and TiO ₂ is effective for shielding the ultraviolet B region (280 to 320 nm). In order to block the ultraviolet rays B and A, the child particles are ZnO, CeO ₂ , BaTiO ₃ , CaTiO ₃ , and S.
It is preferable to use TiO ₂ in combination with one or more selected from the group consisting of rTiO ₃ and SiC.

The shape of the child particles is not particularly limited and may be spherical, plate-shaped or needle-shaped. It is preferable that the particle diameter of the child particles is substantially the same as that of the primary particles of the base particles in order to improve the dispersion state of the child particles. On the other hand, the ultraviolet scattering property is strongly manifested by Mie scattering, which becomes remarkable when the particle diameter is about の of the wavelength of the ultraviolet light, that is, 0.2 μm or less. In order to satisfy the transparency and the shielding property in the ultraviolet region, the thickness is preferably 0.2 μm or less, more preferably 0.1 μm or less, particularly preferably 0.001 to 0.1 μm, and particularly preferably 0.1 to 0.1 μm.
It is more preferably at most 05 μm. In the present invention, the term “child particles” refers to particles in which the primary particles are dispersed and fixed independently and / or an aggregate formed by aggregating the primary particles. Therefore, the average particle diameter of the child particles also means the particle diameter of the aggregate.

In the present invention, since it is preferable that the child particles are present in a state of being dispersed inside the composite fine particles, it is preferable to enhance the dispersibility and stability of the child particles in the sol.
For that purpose, the surface of the child particles may be coated with another substance, or a sol stabilizer may be mixed. For example, TiO
_{(2) When} ultrafine particles are used as child particles, the surface of
It is coated with iO ₂ , Al ₂ O ₃ or the like to improve dispersibility, or a basic stabilizer (for example, NH ₃ ) is mixed to form TiO 2.
_It is also good to stabilize the sol state of ₂ . When the ultrafine powder can be satisfactorily dispersed by surface modification, it can be used as a raw material for child particles. The sol used in the present invention is generally not recognized by an ordinary microscope, but is a substance in which a substance is dispersed in a liquid as particles larger than atoms or small molecules (Rikagaku Dictionary 3rd edition: Iwanami Shoten). To tell. Examples thereof include silica hydrosol and TiO ₂ ultrafine particle suspension.

Such child particles can also be obtained by a thermal decomposition reaction using a raw material (a raw material for thermal decomposition) in which particles are generated by thermal decomposition, and a solution of a salt containing the metal element is used as a raw material for the child particles ( It can also be used as a raw material for thermal decomposition). Types of metal salts include Ti (SO ₄ ) ₂ and TiC
l ₄ , ZnSO ₄ , Zn (NO ₃ ) ₂ , Ce (NO ₃ )
₃ etc., for example, when ZnO is used as a child particle, Zn
ZnO is produced by thermally decomposing an aqueous solution of (NO ₃ ) ₂ .

(2) The mother particles constituting the composite fine particles are required to satisfy the transparency in the visible light region in the same manner as the child particles in order to express the transparency of the composite fine particle suspension system. That is, it is desirable that the material be made of a material that does not absorb visible light, and that it have no primary particles exceeding 0.3 μm. For example, an aggregate of ultrafine particles having an average particle diameter of 0.01 μm is preferable.

The substance constituting the mother particles is a substance composed of a fluorine compound or a mixture of a fluorine compound and a ceramic having high transparency. Examples of such a ceramic include a metal oxide. As described above, since the agglomerates of fine particles usually form the mother particles, in order to satisfy the requirements of the mother particles, the average particle size of the fine particles (ie, primary particles) constituting the agglomerates is 0.3 μm or less. ,
That is, it is 0.001 to 0.3 μm, preferably 0.2 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less. Further, for the same reason as in the case of the child particles, the surfaces of the fine particles constituting the mother particles may be coated with another substance, or a sol stabilizer may be mixed. Examples of the coating substance and the stabilizing agent used here include those similar to the case of the child particles.

Many metal oxides are chemically stable solids,
It is suitable as a substance constituting the base particles. Examples of the metal oxide contained in the base particles include TiO ₂ , CuO,
ZnO, MgO, CeO ₂ , SnO ₂ , SiO ₂ , Fe
₂ O ₃ , Al ₂ O ₃ , NiO ₂ , MnO _{2 and the} like can be mentioned, and SiO ₂ is particularly preferable in view of the above-mentioned refractive index and transparency. Further, in terms of fine particles of ceramics having a large band gap energy, for example, Sn
Fine particles of O ₂ , In ₂ O ₃ , SiO ₂ , ZnO or the like are preferable.

Such a metal oxide can be contained in the mother particles by a thermal decomposition reaction using a raw material (a raw material for thermal decomposition) in which particles are generated by thermal decomposition. Salt is used. Examples of the metal element of the metal salt include an alkali metal, an alkaline earth metal, and a transition metal. Specifically, the alkali metal is Li, Na, K, Rb, Cs, Fr, the alkaline earth metal is Be, Mg, Ca, Sr, Ba, Ra, and the transition metal is the fourth period of the periodic table. Sc, Ti, V, C
r, Mn, Fe, Co, Ni, Cu, Zn, Ge, G
a, As, Y, Zr, Nb, Mo, Tc, R in the fifth cycle
u, Rh, Pd, Ag, Cd, In, Sn, Sb, 6th
Period La, Hf, Ta, W, Re, Os, Ir, P
In addition to t, Au, Hg, Tl, Pb, Bi, etc., Al, S
i and the like.

The type of the metal salt includes a hydrochloride, a nitrate, a phosphate, a carbonate, an acetate, a double salt composed of two or more kinds of salts, a complex salt containing a complex ion, and the like. Either salt or hydrous salt may be used.

As a specific example of the metal salt, Al (NO ₃ ) ₃
・ 9H ₂ O, Ti (SO ₄ ) ₂ , CuSO ₄・ 5H
₂ O, Zn (NO ₃ ) ₂ .6H ₂ O, Ca (NO ₃ ) ₂
・ 4H ₂ O, CaCl ₂ , MgCO ₃ , Fe ₃ (P
O ₄ ) ₂ , Cu (CH ₃ COO) ₂ , and KMgC for double salts
l ₃ , AlK (SO ₄ ) _{2 and the} like, in complex salts, K ₃ [Fe
(CN) ₆ ], [CoCl (NH ₃ ) ₅ ] Cl _{2 and the} like.

These metal salts are used alone or as a mixture. For example, when a mixture of a titanium salt and a zinc salt is used as the mixture, zinc titanate (Zn ₂
TiO ₄ ) is obtained and used as mother particles or child particles.

As the solvent of the metal salt solution, water or an organic solvent is used, but it is preferable that it does not interfere with the drying or thermal decomposition of the raw material droplets. Examples of the organic solvent include alcohols such as methanol and ethanol, and polar solvents such as N, N-dimethylformamide, dimethylsulfoxide, and hexamethylphosphoramide.

Many of the fluorine compounds contained in the mother particles are chemically stable and have a low refractive index, and are useful for controlling the refractive index of the resulting composite fine particles. Examples of the fluorine compound include a solid compound and a liquid compound at normal temperature. Examples of inorganic fluorine compounds that are solid at room temperature include M
gF ₂ , CaF ₂ , AlF ₃ , LiF, NiF ₂ , Ba
F _{2 and the} like, and examples of the organic fluorine compound include polytetrafluoroethylene (hereinafter abbreviated as PTFE), tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride And the like. Among them, when the fluorine compound is MgF ₂ and / or polytetrafluoroethylene, it is preferable in terms of the refractive index and transparency.

The average particle size of the fluorine compound which is solid at room temperature is preferably 0.3 μm or less, more preferably 0.2 μm or less. This means that the average particle size is 0.3 μm
If the size exceeds, the cohesive force between the particles becomes weak and the strength of the composite fine particles decreases.

Examples of the fluorine compound which is liquid at room temperature include perfluoropolyether (hereinafter abbreviated as PFPE). Examples of the PFPE include perfluoropolymethyl isopropyl ether (FOMBLIN HC manufactured by Nikko Chemicals Co., Ltd.). Such P
FPE not only reduces the refractive index of the composite fine particles,
It has the effect of imparting a moist touch to the skin and can be suitably used for fine particles for cosmetics and the like. When such a liquid fluorine compound is used, a solvent must be selected so that the child particle material and the base particle material do not phase-separate in the solvent. It is preferable to use an emulsion of a fluorine compound which is liquid at room temperature. For example, a perfluoropolyether emulsion (O / W type) may be used. The emulsion diameter is preferably 0.1 times or less the thickness of the liquid film. When the emulsion diameter exceeds 0.1 times the thickness of the liquid film, the emulsion becomes larger than the thickness of the plate-like particles produced, and it becomes difficult to produce plate-like particles.

As described above, in the present invention, a fluorine compound which is liquid at room temperature can be used as the substance having a low refractive index contained in the mother particles. In this case, in order to increase the degree of freedom in controlling the refractive index, It is used in combination with the above metal oxide and / or the fluorine compound which is solid at room temperature.

As a combination of the child particles and the mother particles in the present invention as described above, the child particles are TiO ₂ and / or ZnO, and the mother particles are composed of MgF ₂ and / or perfluoropolyether and SiO _2. If
It is preferable in terms of safety and stability as an ultraviolet shielding agent.

In the present invention, the child particles and the mother particles may contain the above-mentioned substances other than the metal oxide and the fluorine compound. For example, when the composite fine particles are produced by drying and / or firing the sol liquid film, a stabilizer for the raw material sol, a coating agent for the sol particles, etc. may be mixed in the mother particles. If they do not interfere with the expression, they may be mixed.

Next, the preparation of the raw material liquid using the above raw materials and the method for producing the plate-like composite fine particles will be specifically described. When preparing the raw material liquid, the mixed liquid containing the above-mentioned child particle raw material and mother particle raw material, so that the child particles can exist in a state in which the child particles are dispersed on the surface and / or inside of the produced composite fine particles, the child particle raw material and the mother particle It is important to mix the mixed solution uniformly so that the raw materials are well mixed and the child particles are easily dispersed in the mother particles.

Water or an organic solvent is used as the solvent for the above-mentioned raw material for the child particles and the raw material for the mother particles, but it is preferable that it does not interfere with the drying or firing of the raw material liquid film or the thermal decomposition of the metal salt. Examples of the organic solvent include alcohols such as methanol and ethanol, and polar solvents such as N, N-dimethylformamide, dimethylsulfoxide, and hexamethylphosphoramide, which adversely affect the production of the ultraviolet shielding plate-like composite fine particles. If not, the solvent may be the same as or different from the solvent of the metal salt solution described above.

The concentration of the child particle raw material in the mixed liquid containing the child particle raw material and the mother particle raw material as the raw material liquid is 10 ^{−5 to} 10 mo.
It is preferably in the range of 1 / L, preferably 10 ^{−4 to 1} mol
The range of / L is good. The reason is that the concentration is 10 ^-5 mol /
When it is lower than L, the amount of child particles in the plate-like composite fine particles is extremely small and it is difficult to express the optical characteristics of the child particles.
When it is higher than 0 mol / L, it is difficult to disperse the raw materials in the liquid, and it is difficult to form a liquid film having a uniform composition when forming a liquid film.

The concentration of the mother particle raw material in the mixed liquid containing the child particle raw material and the mother particle raw material as the raw material liquid is 10 ^{−5 to} 20 mo.
It is preferably in the range of 1 / L, preferably 10 ⁻⁴ to 10 mo
A range of 1 / L is good. The reason is that the concentration is 10 ^-5 mol
When it is lower than / L, the production amount of metal oxide fine particles or fluorine compound fine particles becomes extremely small, and the amount is 20 mol / L.
This is because when it is higher than L, the solubility limit of the above-mentioned fluorine compound, metal salt or the like has been reached.

The average liquid film thickness of the liquid film obtained from these raw material liquids (mixed liquid) is 0.1 to 1000 μm, preferably 0.1 to 500 μm, and particularly preferably 0.1 to 100 μm.
It is preferable that the liquid film thickness distribution is as narrow as possible in the range of m. When the average liquid film thickness is smaller than 0.1 μm, it is difficult to form such a liquid film, and when it is larger than 1000 μm, the thickness of the particles obtained by drying and firing such a liquid film is small. Because it becomes too big.
Incidentally, the liquid film thickness, the liquid film weight is measured, from the liquid film weight value and its particle mixture concentration, to calculate the particle mixture weight in the liquid film,
The particle mixture volume can be determined from the calculated value and the density (weighted average) value of the particle mixture, and the ratio of the volume value to the substrate area can be determined as the average liquid film thickness.

The method of forming the liquid film is not particularly limited, but for example, 1) spin coating, 2) pouring a certain amount of the raw material liquid into a frame-shaped substrate, and 3) dipping the substrate in the raw material liquid. , A method of pulling up (dip method), 4) a spray coating method, and the like. Of these, it is desirable to use 1) or 3) to stably obtain a relatively thin film.

The material of the substrate is not particularly limited, but metals such as copper, stainless steel, and Hastelloy are preferable, and those having high heat resistance, corrosion resistance, surface smoothness, etc. are desirable.

The temperature at which the obtained liquid film is dried, calcined or pyrolyzed may be appropriately set depending on the type of raw material and the type of solvent, and is not particularly limited,
The range of 00 to 1500 ° C. is preferable and 100 to 1000
The range of ° C is more preferable. Drying speed below this range,
It tends to be difficult to form a homogeneous solid film because the firing rate or the thermal decomposition reaction rate becomes extremely low.If it exceeds this range, it is difficult to control the solid film thickness due to rapid evaporation of the solvent. Is not preferable because it tends to occur. In the drying and / or firing, those temperatures may be arbitrarily set within the above range and may be divided into multiple stages as necessary. The average film thickness of the solid film obtained here is about 0.001 to
It is about 100 μm. The solid film thickness after drying and baking can be measured by, for example, a light scattering film thickness measuring device, an electron microscope, or the like.

The heat treatment atmosphere for the liquid film is not particularly limited, but may be air, nitrogen or the like for drying and / or firing the liquid film.
Alternatively, a gas that does not hinder the thermal decomposition reaction may be used.

The method for pulverizing the solid film obtained by the above-mentioned method is not particularly limited, but for example, a dry pulverizing method such as a mill is preferable, and a method capable of efficiently making the particle diameter after pulverization uniform is preferable. . The obtained plate-like fine particles may be used after being pulverized and classified to have uniform particle diameters. An electron microscope can be used to grasp the particle size and shape of the generated particles.

The ultraviolet-shielding plate-like composite fine particles of the present invention are
Although obtained by the above-described manufacturing method, the structure is a mother particle, which is an aggregate formed by closely coagulating primary particles while maintaining their shape, and a child particle is a mother particle surface and It is present dispersed within the mother particles. If the dispersibility of the child particles is poor, the optical characteristics of the child particles will not be exhibited. Ultraviolet rays that hit the child particles present on the surface of the base particles are partially absorbed and the rest are scattered outside the composite fine particles. Ultraviolet rays are absorbed and scattered by the child particles present therein, and the ultraviolet rays are effectively shielded.

The size of the plate-like composite fine particles of the present invention is not particularly limited. Various sizes are used depending on the usage scene. For example, as powders for cosmetics, plate-like particles having an average particle size of sub μm to 100 μm adhere to the skin,
It is preferable in terms of good elongation on the skin and handling. The average thickness of the particles is 0.001 to 100 μm,
It is preferably 0.01 to 10 μm. Further, in the present invention, by making the composite fine particles into a plate shape, it is possible to improve the condition of attachment to the skin, good elongation on the skin, handling and the like.

The proportion of the child particles in the plate-like composite fine particles may be such that the child particles are dispersed in the composite fine particles without causing significant aggregation, and is usually 0.1 to 50% by volume, preferably 0.1. To 30% by volume, more preferably 0.5 to 2
It is 0% by volume. Further, the proportion of the fluorine compound in the plate-like composite fine particles is at least 1% by weight or more.

The optical characteristics of the ultraviolet-shielding plate-like composite fine particles of the present invention can be quantified by measuring the light transmittance by ultraviolet-visible light spectroscopic analysis. The preferable ultraviolet shielding ability of the plate-like composite fine particles of the present invention is to suspend them in a medium having a refractive index similar to that of the composite fine particles, and to transmit light by UV-visible spectroscopic analysis using an optical cell having an optical path length of 1 mm. When measured, the transmittance is 90% or more at a wavelength of 800 nm, and the transmittance is 4 at a wavelength of 400 nm.
The transmittance is 0% or more and the transmittance is 5% or less at at least one of the wavelengths of 350 nm, 320 nm, and 300 nm. With this performance, it is possible to satisfy the high transparency particularly in the visible light region and the high shielding property in the ultraviolet region. Incidentally, the same degree as the refractive index of the composite fine particles means that the difference in the refractive index between the composite fine particles and the medium is within ± 0.1,
It preferably means within ± 0.05.

The evaluation by such ultraviolet / visible light spectroscopic analysis is specifically carried out as follows. The composite fine particles are added to and suspended in a medium having a refractive index similar to that of the plate-like composite fine particles of the present invention to prepare a composite fine particle suspension having an arbitrary concentration. The composite fine particles are well dispersed using an ultrasonic disperser or the like so that the suspension becomes uniform. An optical cell having an optical path length of 1 mm is prepared, and the suspension is filled therein. The optical cell does not absorb or scatter in the ultraviolet and visible light range, and for example, a quartz cell or the like is used. A UV-Visible spectrophotometer is used to measure the transmittance of light passing through this optical cell. At this time, an equivalent optical cell filled with only the medium before the suspension of the composite fine particles is used as a control to remove the background.

[0061]

EXAMPLES The present invention will be described in more detail below by showing Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples and the like.

Example 1 Silica sol (manufactured by Nissan Chemical Industries, Ltd. ST-C, SiO ₂
73.3 g, titanium oxide sol (titania sol manufactured by Taki Kagaku Kogyo KK, anatase type, Ti
O ₂ concentration 4% by weight) 50 g, PFPE (perfluoropolyether) O / W emulsion (FOMBLIN HC / 04 water-soluble base manufactured by Nikko Chemicals Co., Ltd., average emulsion diameter about 0.26 μm, emulsion concentration 6
5% by weight) (2.31 g) and water were mixed to make 1 L to prepare a raw material liquid. (That is, the concentrations of SiO ₂ , TiO ₂ and PFPE are 0.25 mol / L and 0.025 mol, respectively.
/ L and 0.001 mol / L, and the raw material liquid contains the particle mixture at 1.85% by weight. )

In order to improve the dispersibility and uniform mixing of the fine particles in the above raw material liquid, the raw material liquid was appropriately stirred and then subjected to ultrasonic dispersion treatment (about 30 minutes).

A surface-polished stainless steel substrate (SUS316: thickness 2 m) was added to the ultrasonically dispersed raw material liquid.
m) and then pulling up (pulling speed: 50 cm
/ Min) to form a liquid film (thickness: about 30 μm). In this example and the following examples, the thickness of the liquid film is measured by measuring the liquid film weight, the liquid film weight value and its particle mixture concentration, to calculate the particle mixture weight in the liquid film, the calculated value and The volume of the particle mixture was calculated from the density (weighted average) value of the particle mixture, and the ratio of the volume value to the substrate area was defined as the average liquid film thickness. This liquid film was first dried at 50 ° C. in an air atmosphere furnace (5 minutes), then transferred to another air atmosphere furnace and subjected to secondary drying (5 minutes) at a furnace temperature of 100 ° C. After the obtained solid film was scraped off from the stainless steel substrate, the peeled film was put into an alumina crucible and baked at a furnace temperature of 250 ° C. (1 hour).

The release film obtained after firing was pulverized by a pulverizer (A10 type manufactured by IKA Co.) (rotation speed of the cutter: 20,000).
rpm), and then the pulverized powder was classified by a dry airflow classifier (SPEDIC CLASSIFIER manufactured by Seishin Enterprise Co., Ltd.) to obtain fine particles.

The obtained particles were white and exhibited a smooth touch on the skin. When the crystal phases of the composite fine particles are identified by an X-ray diffraction method, they are found to be anatase-type TiO ₂ (child particles) close to amorphous and cristobalite-type SiO ₂ (mother particles) close to amorphous,
Therefore, the fine particles are TiO ₂ / (SiO ₂ , PFP
E) It was found to be composite fine particles. As a result of observation with a scanning electron microscope, it was found to be plate-like fine particles having an average particle size of 1.7 μm and an average thickness of 0.46 μm. In addition, as a result of observing the cross section by an ultra-thin section method using a transmission electron microscope, it was found that TiO ₂ ultra-fine particles were contained in mother particles made of a mixture of SiO ₂ ultra-fine particles (average particle diameter of about 0.01 μm) and PFPE. (Average particle size about 0.01 μm)
Was found to be dispersed and fixed.

That is, the particles have SiO ₂ (bandgap energy of about 6.2 eV and refractive index of about 1.4 eV).
6) and PFPE (refractive index of about 1.29) are mother particles, and TiO ₂ (bandgap energy of about 3.4 eV, refractive index of about 2.52 (anatase type)) is a child particle. It was a certain TiO ₂ / (SiO ₂ , PFPE) plate-like composite fine particles. The amount of the daughter particles in the composite fine particles _is, SiO _2, TiO 2 and PFPE particle densities respectively ^{2.27g / cm 3, 3.84g / cm} 3, 1.8
The amount is set to 7 g / cm ^3, and is calculated to be about 6.6% by volume from the composition ratio of the raw material liquid.

Since the refractive index of the composite fine particles calculated from the volume ratio of the mother / child particles is about 1.51, glycerin (refractive index = 1.47) was used as the dispersion medium for the composite fine particles, and 60 mg of particles were suspended to prepare 2 g of a glycerin suspension in which 3% by weight of particles were suspended. About this UV-visible spectrophotometer (UV-160 manufactured by Shimadzu Corporation)
The light transmittance was measured according to A). The results of measuring the light transmittance in the wavelength range of 200 to 800 nm using a quartz cell having an optical path length of 1 mm are shown in FIG.

In this figure, the light transmittance is almost 0% in the ultraviolet B and C regions having a wavelength of 300 nm or less, and at the same time, it is 80% at 400 nm and 97 at 800 nm.
%, The light transmittance is extremely high in the entire visible light range of 400 to 800 nm, and it is found that the produced composite particles have high transparency in the visible light region and high shielding property in the ultraviolet B region. It was

Comparative Example 1 Silica sol (manufactured by Nissan Chemical Industries, Ltd. ST-C, SiO ₂
73.3 g, titanium oxide sol (titania sol manufactured by Taki Kagaku Kogyo KK, anatase type, Ti
O ₂ concentration 4% by weight) 50 g and water are mixed to make 1 L,
The raw material liquid was used (namely, the concentrations of SiO ₂ and TiO ₂ were 0.25 mol / L and 0.025 mol / L, respectively, and the raw material liquid contained 1.7% by weight of the particle mixture).

This raw material liquid was subjected to dispersion treatment in the same manner as in Example 1. The raw material liquid subjected to the ultrasonic dispersion treatment was subjected to a liquid film formation (thickness of about 30 μm), drying and baking treatment in the same manner as in Example 1. The release film obtained after firing was pulverized and classified in the same manner as in Example 1 to obtain fine particles.

The obtained particles were white and exhibited a smooth touch on the skin. When the crystal phases of the composite fine particles are identified by an X-ray diffraction method, they are found to be anatase-type TiO ₂ (child particles) close to amorphous and cristobalite-type SiO ₂ (mother particles) close to amorphous,
Therefore, it was found that the fine particles were TiO ₂ / SiO ₂ composite fine particles. As a result of observation with a scanning electron microscope, it was found to be plate-like fine particles having an average particle size of 1.7 μm and an average thickness of 0.45 μm. Moreover, as a result of observing the cross section by an ultrathin section method using a transmission electron microscope, S
TiO ₂ ultrafine particles (average particle size of about 0. 0) in mother particles which are aggregates of iO ₂ ultrafine particles (average particle size of about 0.01 µm).
It was found that (01 μm) existed as dispersed and fixed.

That is, this particle has SiO ₂ (bandgap energy of about 6.2 eV and refractive index of about 1.4 eV).
The aggregate of 6) is a mother particle, and TiO ₂ (band gap energy of about 3.4 eV, refractive index of about 2.52 (anatase type)) is a child particle of TiO ₂ / SiO ₂ plate-like composite fine particles. there were. The ratio of the child particles in the above composite fine particles is such that the particle densities of SiO ₂ and TiO ₂ are 2.2.
7 g / cm ³ , 3.84 g / cm ³ and calculated from the composition ratio of the raw material liquid, it is estimated to be about 7.3% by volume.

Since the refractive index of the composite fine particles calculated from the volume ratio of the mother / child particles is about 1.53, glycerin (refractive index = 1.47) was used as the dispersion medium for the composite fine particles, and 60 mg of particles were suspended to prepare 2 g of a glycerin suspension in which 3% by weight of particles were suspended. The light transmittance of this was measured in the same manner as in Example 1. Wavelength range 200-8 using a quartz cell with an optical path length of 1 mm
The result of measuring the light transmittance at 00 nm is shown in FIG.

In this figure, the light transmittance is approximately 0% and 400 nm in the ultraviolet rays B and C regions having a wavelength of 300 nm or less.
However, when compared with Example 1, since the composite fine particles do not contain PFPE which is a low refractive index substance, the difference in refractive index between the composite fine particles and the dispersion medium is 53%. Is large, visible light range (especially light wavelength 800n
It can be seen that the transparency in m) is poor.

Example 2 Magnesium fluoride sol (MFS manufactured by Nissan Chemical Industries, Ltd.)
-10, MgF ₂ concentration 10.5% by weight) 148 g, ultrafine zinc oxide particles (FINEX75 manufactured by Sakai Chemical Industry Co., Ltd.)
0.814 g, titanium oxide sol (titania sol manufactured by Taki Chemical Industry Co., anatase type TiO ₂ concentration 4% by weight) 2
5.0 g and water were mixed to make 1 L and used as a raw material liquid (that is, the concentrations of MgF ₂ , ZnO and TiO ₂ were 0.25 mol / L, 0.01 mol / L and 0.01, respectively).
25 mol / L, and the raw material liquid was 1.
It contains 74% by weight. ).

A solution prepared by mixing this raw material liquid and glass beads (average particle diameter 0.1 mm) in a weight ratio of 325: 175 was used in a bead mill (IGARASHIKIKA).
I TSG-6H), and the blade rotation speed was 2000 r.
p. m. For 6 hours. Using the mill-dispersed raw material liquid, in the same manner as in Example 1,
A liquid film was formed (thickness: about 30 μm) and dried. After the obtained solid film was scraped off from the stainless steel substrate, the peeled film was put into an alumina crucible and baked at a furnace temperature of 800 ° C. (1 hour). Then, pulverization and classification were performed in the same manner as in Example 1 to obtain fine particles.

The obtained particles were white and exhibited a smooth touch on the skin. When the crystal phase of the composite fine particles is identified by an X-ray diffraction method, wurtzite type ZnO (child particles), anatase type TiO ₂ (child particles) close to amorphous and anatase type MgF ₂ (mother particle) close to amorphous are obtained. It was found that there are (ZnO, T
It was found to be iO ₂ ) / MgF ₂ composite fine particles.
As a result of observation with a scanning electron microscope, the average particle size was 1.9.
It was found that the particles were plate-like fine particles with a thickness of 0.5 μm and an average thickness of 0.52 μm. In addition, as a result of observing the cross section by an ultrathin section method using a transmission electron microscope, it was found that ZnO ultrafine particles (average particle size of about 0.02 μm) were found in aggregates of MgF ₂ ultrafine particles (average particle size of about 0.02 μm). It was found that (01 μm) and TiO ₂ ultrafine particles (average particle size of about 0.01 μm) were dispersed and immobilized.

That is, in this particle, an aggregate of MgF ₂ (bandgap energy is about 6 eV, refractive index is about 1.38) is a mother particle, and ZnO (bandgap energy is about 3.2 eV, refractive index is about. 1.99) and TiO
₂ (bandgap energy is about 3.4 eV, refractive index is about 2.52) is a child particle (ZnO, TiO ₂ ) /
It was MgF ₂ plate-like composite fine particles. The ratio of the child particles in the composite fine particles is such that the particle densities of MgF ₂ , ZnO and TiO ₂ are 3.15 g / cm ³ and 5.78 g / c, respectively.
m ^3, and 3.84 g / cm ^3, calculated from the composition ratio of the raw material liquid, is estimated to be about 7.52% by volume.

The refractive index of the composite fine particles calculated from the volume ratio of the mother / child particles is about 1.45. Therefore, glycerin (refractive index = 1.47) was used as the dispersion medium for the composite fine particles, and 120 mg of particles are suspended and 6 particles are suspended.
2 g of a glycerin suspension having a weight% suspension was prepared. The light transmittance of this was measured by the same method as in Example 1, and the results are shown in FIG.

In this figure, the light transmittance is almost 0% in the ultraviolet rays A, B, and C regions having a wavelength of 325 nm or less, and at the same time, it is 90% at 400 nm and about 98% at 800 nm, and the visible wavelength of 400 to 800 nm. It was found that the light transmittance was extremely high in the entire light range, and the produced composite particles had high transparency in the visible light region and high shielding properties in the ultraviolet B and A regions.

Example 3 Aqueous aluminum nitrate solution (Al manufactured by Wako Pure Chemical Industries, Ltd.)
_{(NO 3) 3 · 9H 2} O ( special grade reagent) what the solution concentration dissolved in water to make 1.0 mol / L) 500 g, manufactured by magnesium fluoride sol (Nissan Chemical Industries (Ltd.) MFS-
10, MgF ₂ concentration 10.5% by weight) 5.92 g, cerium oxide sol (manufactured by Taki Chemical Co., Ltd., Nedral W-1)
5, 10.5 g of CeO ₂ concentration 15% by weight) and water were mixed to make 1 L, and used as a raw material liquid (that is, Al ₂ O ₃ , Mg).
The concentration of F ₂ and CeO ₂ are each 0.25 mol /
L, 0.01 mol / L, and 0.01 mol / L, and the raw material liquid contains 2.78% by weight of the particle mixture. ).

In order to improve the dispersibility and uniform mixing of the fine particles in the raw material liquid, the raw material liquid was appropriately stirred and then subjected to ultrasonic dispersion treatment (about 30 minutes). Using the ultrasonically dispersed raw material liquid, a liquid film was formed (thickness of about 30 μm) and dried in the same manner as in Example 1. After scraping off the obtained solid film from the stainless steel substrate, the peeled film was put into an alumina crucible, and the thermal decomposition of aluminum nitrate (1 hour) and firing (1
Time) went. By the thermal decomposition of this aluminum nitrate, Al ₂ O ₃ is obtained as mother particles. The release film obtained after the thermal decomposition and firing was pulverized and classified in the same manner as in Example 1 to obtain fine particles.

The obtained particles were white with a slight yellowish tint, and showed a smooth touch on the skin. When the crystal phases of the composite fine particles are identified by an X-ray diffraction method, fluorite-type CeO ₂ (child particles) close to amorphous, α-type Al ₂ O ₃ (mother particles) close to amorphous, and rutile-type close to amorphous are obtained. It was found to be MgF ₂ (mother particles), and these fine particles are CeO ₂ / (Al ₂ O ₃ , MgF ₂ )
It was found to be composite fine particles. As a result of observation with a scanning electron microscope, the average particle size was 1.8 μm and the average thickness was 0.1 μm.
It was found to be plate-like fine particles of 51 μm. In addition, as a result of observing the cross section by the ultrathin section method using a transmission electron microscope, Al ₂ O ₃ ultrafine particles (average particle diameter of about 0.0
1 μm) and MgF ₂ ultrafine particles (average particle size of about 0.02)
It was found that CeO ₂ ultrafine particles (average particle diameter of about 0.01 μm) were dispersed and immobilized in the aggregate of (μm).

That is, this particle has Al ₂ O ₃ (bandgap energy of about 8.3 eV and a refractive index of about 1.7).
3) and MgF ₂ (bandgap energy of about 6e
V, an agglomerate having a refractive index of about 1.38) is the mother particle, and C
eO ₂ (band gap energy of about 3 eV, refractive index of about 2) is a child particle of CeO ₂ / (Al ₂ O ₃ , Mg
F ₂ ) Plate-shaped composite fine particles. The ratio of the child particles in the composite fine particles is such that the particle densities of Al ₂ O ₃ , MgF ₂ and CeO ₂ are 3.99 g / cm ³ and 3.15 g / cm ³ , respectively.
cm ³ , 7.13 g / cm ³ and calculated from the composition ratio of the raw material liquid, it is estimated to be about 3.5% by volume.

Since the refractive index of the composite fine particles calculated from the volume ratio of the mother / child particles is about 1.73, diiodomethane (refractive index = 1.74) was used as the dispersion medium for the composite fine particles, and 2 g of diiodomethane suspension in which 120 mg of particles are suspended and 6% by weight of particles are suspended.
Was prepared. The light transmittance of this was measured by the same method as in Example 1, and the results are shown in FIG.

In this figure, the light transmittance is almost 0% in the ultraviolet rays A, B and C regions having a wavelength of 325 nm or less, and at the same time, the light transmittance is 400% at 87% and 99% at 800 nm. It was found that the produced composite particles had a high transparency in the visible light region and a high shielding property in the ultraviolet B and A regions, although they had a slight yellow tint.

[0088]

INDUSTRIAL APPLICABILITY When the ultraviolet shielding plate-like composite fine particles of the present invention are dispersed in a liquid or solid medium having an appropriate refractive index, the refractive index of the composite fine particles is controlled so as to match the refractive index. As a result, a high light transmittance is exhibited in the visible light region, and scattering and absorption ability by the child particles appears in the ultraviolet light region to exhibit a high shielding property. In addition, since most of the child particles having high catalytic activity are enclosed inside the mother particles, the catalytic activity of the child particles rarely affects the surrounding medium and the like. That is, the plate-like composite fine particles of the present invention are optical particles of ultrafine particles which are highly transparent in the visible light region and have high light shielding properties in the ultraviolet light region by converting the ultrafine particles having the ultraviolet light shielding ability into composite fine particles. It has a characteristic that stable properties are stably expressed with a fine particle size that is easy to handle. Further, for example, when the plate-like composite fine particles of the present invention are used in cosmetics, they have good slipperiness, excellent extensibility on the skin, no unevenness, excellent transparency, no unnatural whitening, and high. It becomes a cosmetic having an ultraviolet shielding effect, and also
When the plate-like composite fine particles of the present invention are used in a paint, the transparency is excellent, so that the color of the paint is not impaired and the degree of freedom in the amount of the compound added to the paint is high.

[Brief description of drawings]

FIG. 1 is a chart showing the measurement results of light transmittance of an ultraviolet-shielding plate-like composite fine particle obtained in Example 1 and Comparative Example 1 by an ultraviolet-visible spectrophotometer.

FIG. 2 is a chart showing the measurement results of the light transmittance of the ultraviolet-shielding plate-like composite fine particles obtained in Example 2 by an ultraviolet-visible spectrophotometer.

FIG. 3 is a chart showing the results of measuring the light transmittance of the ultraviolet shielding plate-like composite fine particles obtained in Example 3 with an ultraviolet-visible spectrophotometer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C01G 23/04 C01G 23/04 B // A61K 7/42 A61K 7/42

Claims (7)

[Claims] An average particle diameter of primary particles is 0.001 to 1.
Composite fine particles consisting of mother particles formed by aggregating particles having a size of 0.3 μm while maintaining their shape, and child particles having an average particle size of 0.001 to 0.1 μm dispersed and fixed in the mother particles. Wherein the child particles have a smaller bandgap energy than the particles forming the mother particles and have an ultraviolet absorbing ability, and the particles forming the mother particles are a fluorine compound or a fluorine compound and a metal oxide. UV-shielding plate-like composite fine particles having transparency in the visible light region, which is a mixture of 2. The metal oxide is SiO ₂ and / or Al ₂
The ultraviolet-shielding plate-like composite fine particles according to claim 1, which are selected from O ₃ . 3. The ultraviolet-shielding plate-like composite fine particles according to claim 1, wherein the fluorine compound is MgF ₂ and / or polytetrafluoroethylene. 4. The particles constituting the mother particles are a fluorine compound, a metal oxide, or a mixture of the metal oxide and the fluorine compound, which is solid at room temperature, to which perfluoropolyether is further added. Item 3. The ultraviolet-shielding plate-like composite fine particles according to any one of Items 1 to 3. 5. The child particles are TiO ₂ , ZnO, CeO ₂ ,
BaTiO ₃ , CaTiO ₃ , SrTiO ₃ and SiC
1 or more types selected from the group consisting of:
4. The ultraviolet-shielding plate-like composite fine particles according to any one of 4 above. 6. The optical path length is suspended in a medium having a refractive index substantially the same as the refractive index of the plate-like composite fine particles (however, the difference in refractive index within ± 0.1 is regarded as the same). When the light transmittance is measured with an ultraviolet-visible spectrophotometer using an optical cell of 1 mm, the transmittance is 90% or more at a wavelength of 800 nm, the transmittance is 40% or more at a wavelength of 400 nm, and at least 350 nm, 320 nm, and 300 nm. The transmittance of either one is 5% or less.
5. The ultraviolet-shielding plate-like composite fine particles according to any one of 5 above. 7. A method for producing ultraviolet-shielding plate-like composite fine particles having transparency in the visible light region, which comprises the following steps. (A) The average particle size of the primary particles is 0.001 to 0.3 μm.
And a mother particle raw material containing at least a fluorine compound consisting of a solution containing particles constituting the mother particles and / or a solution capable of producing such particles by thermal decomposition, and having an average particle diameter of 0.001 to 0.1 μm. A sol containing child particles, a child particle powder, and a mixed solution containing a mixture with one or more child particle raw materials selected from the group consisting of solutions capable of producing such child particles by thermal decomposition (B) The average liquid film thickness of the mixed liquid is 0.1 to
A step of forming a liquid film in the range of 1000 μm, (c) drying and / or baking the obtained liquid film in an atmosphere of 100 to 1500 ° C., or after drying at the atmospheric temperature, pyrolysis and / or baking To obtain a solid film by (d) crushing the solid film to form fine particles in plate form,