JPH08268707A - Ultraviolet-ray shielding platy composite fine particles and their production - Google Patents

Abstract

PURPOSE: To obtain platy composite fine particles having high transparency to visible light and high UV shielding property by combining fine particles (child particles) having UV B and/or A shielding ability with aggregates of fine particles (mother particles) as a matrix in which the child particles are dispersed and contained. CONSTITUTION: The objective composite fine particles consist of mother particles formed by aggregating fine particles having 0.001-0.3μm average particle diameter of primary particles while retaining the shape and child particles having 0.001-0.1μm average particle diameter dispersed and fixed in the mother particles. The child particles have lower band gap energy than the constituent particles of the mother particles and have UV absorbing ability. The constituent part.icles of the mother particles are made of a metal oxide such as SiO2 or Al2 O3 and the child particles are made of ZnO, CeO2 , BaTiO3 , CaTiO3 , SrTiO3 , SiC, TiO2 , etc.

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 metal oxide such as SiO ₂ and further, JP-A-6-116119. Titania is 5-80 in the publication
Disclosed is a cosmetic composition having a high UV absorption effect, which contains 20% to 95% by weight of silica and 20 to 95% by weight of silica, respectively, and the total content of titania and silica is at least 80% by weight. Has been done. However, the ultraviolet absorbers described in these publications penetrate only to a relatively shallow portion of the epidermis and the upper layer of the dermis, and the ultraviolet ray B (light wavelength 280 to 320 nm) that causes sunburn and skin cancer It is considered that titania in the flaky particles has an absorption effect, but ultraviolet rays A (light wavelength 320, which is considered to be the cause of sun turn and fiber degeneration in the dermis reach the deep skin layer of the dermal layer.
-400 nm), a light wavelength of 350 close to visible light
There is no absorption effect at 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 320 nm.
It is limited to exhibiting an ultraviolet absorption effect of about nm.

Of the ultraviolet rays reaching the surface of the earth, ultraviolet rays A are about 15 times as much as ultraviolet rays B in energy ratio. Therefore, when considering the energy ratio of ultraviolet rays, it is important to shield not only the ultraviolet rays B but also the ultraviolet rays B as well as the ultraviolet rays 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. There has been a demand for effective means for solving such 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, a raw material for the child particles and the mother particles which are constituents of the composite fine particles, that is, a sol and / or a sol containing particles constituting the mother particles having an average primary particle diameter of 0.001 to 0.3 μm. A mother particle raw material consisting of a solution capable of producing such particles by thermal decomposition, a sol containing child particles having an average particle size of 0.001 to 0.1 μm, child particle powder, and heat such child particles. After forming a liquid film of a mixed solution containing a mixture with one or more child particle raw materials selected from the group consisting of solutions that can be generated by decomposition, drying and / or firing, or thermal decomposition after drying And / or firing to obtain a solid film, and then the solid film is crushed to continuously disperse the plate-like composite fine particles having high visible light transparency and ultraviolet shielding property in which the child particles are uniformly dispersed and fixed. To generate I found that I can do it.

That is, the gist of the present invention is as follows: (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. And the child particles have a band gap energy smaller than that of the particles constituting the mother particles and have an ultraviolet absorbing ability, and the ultraviolet ray shielding plate having transparency in the visible light region. Composite fine particles, (2) UV-shielding plate-like composite fine particles according to (1), wherein the particles constituting the mother particles are metal oxides, (3) The metal oxide is selected from SiO ₂ and / or Al ₂ O _3. The ultraviolet-shielding plate-like composite fine particles according to (2) above, (4) the child particles being ZnO, CeO ₂ , BaTiO ₃ , or C.
The ultraviolet-shielding plate-like composite fine particles according to any one of (1) to (3) above, which is one or more selected from the group consisting of aTiO ₃ , SrTiO ₃ and SiC, (5) ZnO and CeO _{2 as} child particles , BaTiO ₃ , C
The ultraviolet-shielding plate-like composite fine particles according to any one of (1) to (3) above, which is combined with TiO ₂ and one or more kinds selected from the group consisting of aTiO ₃ , SrTiO ₃ and SiC, (6) plate-like Using an optical cell with an optical path length of 1 mm, suspended in a medium having a refractive index that is substantially the same as the refractive index of the composite fine particles (however, the difference in refractive index within ± 0.1 is considered to be the same). When the light transmittance was measured with an ultraviolet-visible spectrophotometer, the transmittance was 90% or more at a wavelength of 800 nm, the transmittance was 40% or more at a wavelength of 400 nm, and the wavelength was 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.
A mother particle raw material comprising a sol containing particles constituting the mother particles and / or a solution capable of producing such particles by thermal decomposition, and child particles having an average particle diameter of 0.001 to 0.1 μm. Sol, a child particle powder, and a step of preparing a mixed solution containing a mixture with one or more child particle raw materials selected from the group consisting of a solution capable of producing such child particles by thermal decomposition, ( b) a step of forming a liquid film in the range of an average liquid film thickness of 0.1 to 1000 μm, (c) drying and / or baking the obtained liquid film in an atmosphere of 100 to 1500 ° C., or A step of obtaining a solid film by thermal decomposition and / or firing after drying in the ambient temperature, (d) a step of crushing the solid film to form plate-like fine particles,
Regarding 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 band gap energy of particles and grain boundaries of particles.

(1) Band Gap Energy of Particles In the plate-like composite fine particles of the present invention, the fine particles used as child particles are required to have a shielding property in the ultraviolet region, which is divided into an ultraviolet absorbing property and an 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.

Therefore, 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 must be 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, ZnO is used as the particles constituting the mother particles.
And using SiO ₂ fine particles having a bandgap energy larger than this as a child particle, ultraviolet rays having a wavelength of 390 nm or less are absorbed by the mother particle by exciton absorption corresponding to the bandgap energy of ZnO. 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. In addition, if the mother particles have a size that can be recognized by visible light (particle diameter is about 0.2 μm or more), the transparency to visible light also deteriorates.

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) Grain Boundary of Particle Regarding the primary particle of the mother particle, from the viewpoint of the grain boundary, the smaller the particle diameter, that is, the smaller the grain boundary inside the mother particle,
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 comprising a sol containing particles constituting the mother particles having a size of μm and / or a solution capable of producing such particles by thermal decomposition, and an average particle size 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) a step of forming the mixed solution into a liquid film having an average liquid film thickness in the range of 0.1 to 1000 μm, (c) drying the resulting liquid film in an atmosphere of 100 to 1500 ° C., and / or Or a step of firing or drying in the ambient temperature, followed by thermal decomposition and / or firing to obtain a solid film, and (d) a step of crushing 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, the exciton absorption edge based on the bandgap energy is present in the ultraviolet wavelength region because of the requirement that it has no absorption in the visible light region and has an ultraviolet absorption 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-like or needle-like. 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 the child particles are preferably 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 produced 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 made of highly transparent ceramics, for example, a metal oxide or the like is used. As described above, the agglomerates of the fine particles usually form the mother particles, and therefore the fine particles (ie, primary particles) constituting the agglomerates are required to satisfy the requirements of the mother particles.
Has an average particle diameter of 0.3 μm or less, that is, 0.001 to
It is 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 mother particles can also be obtained by a thermal decomposition reaction using a raw material (a raw material for thermal decomposition) whose particles are generated by thermal decomposition. In that case, a metal salt is used as a raw material. . Examples of the metal element of the metal salt include an alkali metal, an alkaline earth metal, and a transition metal. Specifically, as the alkali metal, Li, Na,
K, Rb, Cs, Fr, B as an alkaline earth metal
e, Mg, Ca, Sr, Ba, Ra, and as transition metals, Sc, Ti, V, Cr, Mn, Fe of the 4th period of the periodic table,
Co, Ni, Cu, Zn, Ge, Ga, As, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, A of the fifth period
g, Cd, In, Sn, Sb, La, Hf in the sixth period,
Ta, W, Re, Os, Ir, Pt, Au, Hg, T
In addition to 1, Pb, Bi, etc., Al, Si, etc. may be mentioned.

The type of metal salt may be 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 and 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.

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 Zn.
O or ZnO and mother particles of SiO ₂ are preferable from the viewpoint of safety and stability as an ultraviolet shielding agent. Further, as the raw material of the child particles and the mother particle, at least one of sol, ultrafine particle powder, and metal salt raw material in which particles are generated by thermal decomposition reaction can be used.

In the present invention, the child particles and the mother particles may contain a substance which does not correspond to the above metal oxide. For example, when a sol is used, a stabilizer for the raw material sol, a coating agent for the sol particles, etc. may be mixed in the mother particles, but if they do not prevent the expression of the optical characteristics of the plate-shaped composite fine particles, they are mixed. It doesn't matter.

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 a solvent for the above-mentioned child particle raw material and mother particle raw material, but it is preferable to use one which does not interfere with the drying, firing, or thermal decomposition of the metal salt of the raw material liquid film. 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 mother particle raw material and the child particle raw material, which is 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
This is because when it is lower than / L, the production amount of the metal oxide fine particles becomes extremely small, and when it is higher than 20 mol / L, the solubility limit of the metal salt and the like is 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, and a commonly used known method can be used. For example, 1) a spin coating method, 2) a method of pouring a certain amount of a raw material liquid into a frame-shaped substrate, 3) a method of dipping or lifting the substrate in the raw material liquid (dip method), 4) a spray coating method, etc. Can be given. 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 kind of the raw material and the kind of the 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 as long as it is a gas that does not interfere with the drying, firing or thermal decomposition reaction of the liquid film.

The method for pulverizing the solid film obtained by the above 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 pulverizing 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.

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.

Here, the refractive index is generally measured by the liquid immersion method (for example, Toshiharu Tayuki et al., "Optical Measurement Handbook").
P. 475, 1981, published by Asakura Shoten), wavelength 589.
The refractive index of the sample is the refractive index of the medium that maximizes the transmittance of 3 nm light. 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.

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.

[0053]

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 of a concentration of 20.5% by weight), 0.814 g of zinc oxide ultrafine particles (FINEX75 manufactured by Sakai Chemical Industry Co., Ltd.), and water were mixed to make 1 L, which was used as a raw material liquid (that is, SiO 2).
The concentrations of ₂ and ZnO are 0.25 mol / L and 0.01 mol / L, respectively, and the raw material liquid contains the particle mixture at 1.58 wt%. ).

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.

A surface-polished stainless steel substrate (SUS316: thickness 2 mm) was dipped in this mill-dispersed raw material liquid, and then pulled up (pulling speed: 50 cm / mi).
n) to prepare 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, and from the liquid film weight value and the particle mixture concentration, the particle mixture weight in the liquid film is calculated, and the calculated value is obtained. The volume of the particle mixture was determined 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 600 ° C. (1 hour).

The release film obtained after firing was pulverized by a pulverizer (A10 type manufactured by IKA Co., Ltd.) (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 phase of the composite fine particles is identified by an X-ray diffraction method, wurtzite ZnO (child particles) is obtained.
And Cristobalite type SiO close to amorphous
₂ (mother particles), and the fine particles are ZnO.
It was found to be / 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. Further, transmission result of observing the cross section by ultramicrotomy using an electron microscope, ZnO ultrafine particles (average particle size about in the aggregates of SiO ₂ ultrafine particles (average particle size about 0.01 [mu] m) 0. 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 aggregates of 6) were mother particles, and ZnO (bandgap energy was about 3.2 eV and refractive index was about 1.99) were ZnO / SiO ₂ plate-like composite fine particles having child particles.
The ratio of the child particles in the composite fine particles is SiO ₂ and Z.
The particle density of nO was 2.27 g / cm ³ and 5.7, respectively.
8 g / cm ³ and calculated from the composition ratio of the raw material liquid, it is estimated to be about 2.1% by volume.

The refractive index of the composite fine particles calculated from the volume ratio of the mother / child particles is about 1.47. 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. About this UV-visible spectrophotometer (UV-16 manufactured by Shimadzu Corporation)
The light transmittance was measured according to 0A). 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 rays A, B, and C regions having a wavelength of 350 nm or less, and at the same time, it is 89% at 400 nm and 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 2 Silica sol (manufactured by Nissan Chemical Industries, Ltd. ST-C, SiO ₂
(Concentration 20.5% by weight) 73.3 g, zinc oxide ultrafine particles (Finex 75 manufactured by Sakai Chemical Industry Co., Ltd.) 0.814 g,
Titanium oxide sol (titania sol manufactured by Taki Chemical Industry Co., Ltd.,
Anatase type, 25.0 g of TiO ₂ concentration 4% by weight) and water were mixed to make 1 L to prepare a raw material liquid (ie Si
The concentrations of O ₂ , ZnO and TiO ₂ are each 0.25 m
ol / L, 0.01 mol / L and 0.0125 mol
/ L, and the raw material liquid is 1.68% by weight of the particle mixture.
It is contained. ).

The dispersion treatment of this raw material liquid was carried out in the same manner as in Example 1. Using this raw material liquid that has been subjected to the mill dispersion treatment, a liquid film was formed (thickness: about 30 by the same method as in Example 1).
μm) and its drying and firing, followed by pulverization and classification,
Fine particles were obtained.

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 cristobalite type SiO close to amorphous.
₂ (mother particles), the fine particles (Zn
It was found to be O, 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 0.44 μm. Moreover, as a result of observing the cross section by an ultrathin section method using a transmission electron microscope, it was found that ZnO was contained in an aggregate of SiO ₂ ultrafine particles (average particle diameter of about 0.01 μm).
It was found that ultrafine particles (average particle diameter of about 0.01 μm) and TiO ₂ ultrafine particles (average particle diameter of about 0.01 μm) were dispersed and immobilized.

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 ZnO (bandgap energy is about 3.2 eV, refractive index is about 1.99) and TiO ₂ (bandgap energy is about 3.4 eV,
The refractive index of about 2.52 is a child particle (ZnO, TiO 2).
₂ ) / SiO ₂ plate-like composite fine particles. The ratio of the child particles in the above composite fine particles is SiO ₂ , ZnO and TiO ₂ .
The particle densities of ₂ were 2.27 g / cm ³ and 5.78, respectively.
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 5.7% by volume.

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 120 mg of particles are suspended and 6 particles are suspended.
2 g of a glycerin suspension having a weight% suspension was prepared. For this, the light transmittance was measured by ultraviolet-visible spectroscopic analysis in the same manner 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 350 nm or less, and at the same time, the visible light having a wavelength of 400 to 800 nm is 81% at 400 nm and 98% at 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 Aluminum nitrate aqueous solution (Al manufactured by Wako Pure Chemical Industries, Ltd.)
500 g of (NO ₃ ) ₃ 9H ₂ O (special grade reagent dissolved in water to a solution concentration of 1.0 mol / L), cerium oxide sol (Neidral W-, manufactured by Taki Kagaku Co., Ltd.)
15, 10.5 g of CeO ₂ concentration of 15% by weight) and water were mixed to make 1 L and used as a raw material liquid (that is, the concentrations of Al ₂ O ₃ and CeO ₂ were 0.25 mol / L and 0.
01 mol / L, and the raw material liquid was a mixture of particles of 2.
It contains 72% by weight. ).

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 were identified by an X-ray diffraction method, it was found that they were fluorite-type CeO ₂ (child particles) close to amorphous and α-type Al ₂ O ₃ (mother particles) close to amorphous, It was found that the fine particles were CeO ₂ / Al ₂ O ₃ 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 1.8 μm and an average thickness of 0.50 μm. In addition, as a result of observing the cross section by an ultrathin section method using a transmission electron microscope,
In the aggregate of Al ₂ O ₃ ultrafine particles (average particle size of about 0.01 μm), CeO ₂ ultrafine particles (average particle size of about 0.01 μm).
m) was found to be dispersed and fixed.

That is, this particle has an Al ₂ O ₃ content (bandgap energy of about 8.3 eV and a refractive index of about 1.7).
The agglomerates of 3) were mother particles, and CeO ₂ (bandgap energy was about 3 eV, refractive index was about 2) were CeO ₂ / Al ₂ O ₃ plate-like composite fine particles that were child particles. The ratio of the child particles in the above composite fine particles is Al ₂ O ₃ and Ce.
The particle densities of O ₂ are 3.99 g / cm ³ and 7.1, respectively.
It is set to 3 g / cm ³ and calculated from the composition ratio of the raw material liquid, and is estimated to be about 3.6% by volume.

Since the refractive index of the composite fine particles calculated from the volume ratio of mother / child particles is about 1.74, 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. For this, the light transmittance was measured by ultraviolet-visible spectroscopic analysis in the same manner 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 335 nm or less, and at the same time, the light transmittance is 85% at 400 nm 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.

[0074]

INDUSTRIAL APPLICABILITY The ultraviolet-shielding plate-like composite fine particles of the present invention exhibit high light transmittance in the visible light region when dispersed in a liquid or solid medium having an appropriate refractive index,
In the ultraviolet region, the scattering and absorbing ability of the child particles appears, and a high shielding property is exhibited. 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. Also, 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, are not uneven, and are excellent in transparency and have no unnatural whitening and a high ultraviolet shielding effect. In addition, when the plate-like composite fine particles of the present invention are used in a coating composition, since they have excellent transparency, they do not impair the color of the coating composition and have a high degree of freedom in the amount blended into the coating composition.

[Brief description of drawings]

FIG. 1 is a chart showing the measurement results of the light transmittance of the ultraviolet shielding plate-like composite fine particles obtained in 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 front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C01G 23/04 C01G 23/04 Z C09K 3/00 104 C09K 3/00 104Z // 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 and ultraviolet absorptivity than the particles constituting the mother particles, and have an ultraviolet shielding property having transparency in the visible light region. Plate-shaped composite fine particles. 2. The ultraviolet-shielding plate-like composite fine particles according to claim 1, wherein the particles constituting the mother particles are metal oxides. 3. The metal oxide is SiO ₂ and / or Al ₂
The ultraviolet-shielding plate-like composite fine particles according to claim 2, which are selected from O ₃ . 4. The child particles are ZnO, CeO ₂ , and BaTiO 3.
The ultraviolet shielding plate-like composite fine particles according to any one of claims 1 to 3, which is one or more selected from the group consisting of ₃ , CaTiO ₃ , SrTiO _3, and SiC. 5. The child particles are ZnO, CeO ₂ , and BaTiO 3.
The ultraviolet-shielding plate-like composite fine particles according to any one of claims 1 to 3, wherein one or more kinds selected from the group consisting of ₃ , CaTiO ₃ , SrTiO ₃ and SiC is combined with TiO ₂ . 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.
A mother particle raw material comprising a sol containing particles constituting the mother particles and / or a solution capable of producing such particles by thermal decomposition, and child particles having an average particle diameter of 0.001 to 0.1 μm. Sol, a child particle powder, and a step of preparing a mixed solution containing a mixture with one or more child particle raw materials selected from the group consisting of a solution capable of producing such child particles by thermal decomposition, ( b) a step of forming a liquid film in the range of an average liquid film thickness of 0.1 to 1000 μm, (c) drying and / or baking the obtained liquid film in an atmosphere of 100 to 1500 ° C., or A step of obtaining a solid film by thermal decomposition and / or firing after drying in the ambient temperature, (d) a step of crushing the solid film to form plate-like fine particles,