Zinc oxide powders, composition for oil-dispersible cosmetic, and cosmetic

Abstract

Provided are: zinc oxide powders from which a cosmetic capable of exhibiting excellent visible light transmittance and ultraviolet shielding ability when applied to the skin can be prepared; and a composition for an oil-dispersible cosmetic and a cosmetic in which the zinc oxide powders are blended.　Zinc oxide powders according to the present invention are characterized in that D50 in the number distribution obtained from a transmission electron microscope image is 100-200 nm, the aspect ratio is 1.1-1.4, and the crystallite diameter obtained from an X-ray diffraction spectrum is 70-200 nm. Moreover, a composition for an oil-dispersible cosmetic according to the present invention is characterized in that the zinc oxide powders according to the present invention are dispersed in oil. A water droplet-in-oil emulsion cosmetic according to the present invention and an oil droplet-in-water emulsion cosmetic according to the present invention are characterized in that the composition for an oil-dispersible cosmetic according to the present invention is blended or the zinc oxide powders according to the present invention are blended. A powder cosmetic according to the present invention is characterized in that the zinc oxide powders according to the present invention are blended.

Description

Zinc oxide powder, oil-dispersible cosmetic composition and cosmetic

[0001] The present invention relates to a zinc oxide powder that can be used to prepare cosmetics that exhibit excellent visible light transmittance and ultraviolet blocking ability when applied to the skin, and to an oil-dispersible cosmetic composition and cosmetic that use the zinc oxide powder.

[0002] Inorganic powders such as zinc oxide are sometimes blended into various cosmetic products, such as sunscreens, that are applied to the skin.

[0003] In recent years, there has been a trend toward the use of so-called non-nano zinc oxide with a particle size of 100 nm or more (e.g., Patent Document 1), due to concerns that fine zinc oxide powder may penetrate into the skin when cosmetics containing zinc oxide powder with a small particle size are applied, and methods for producing zinc oxide powder with a large particle size are also being investigated (e.g., Patent Document 2).

[0004] JP 2019-517514 A International Publication No. 2012 / 169611

[0005] However, in general, the smaller the particle size of zinc oxide powder, the better its UV-blocking ability, and when zinc oxide having a particle size of what is called non-nano zinc oxide is used, it is difficult to obtain a cosmetic product with good UV-blocking ability. For example, in the sunscreen composition described in Patent Document 1, bis-oxyhexyloxyphenol methoxyphenyl triazine, which has UV-blocking ability, is used in combination with non-nano zinc oxide to compensate for the UV-blocking ability that is insufficient with non-nano zinc oxide alone.

[0006] Furthermore, zinc oxide powder has the problem that, as the particle size increases, the transmittance of visible light when the cosmetic containing it is applied to the skin decreases, causing the skin to appear whitish, for example.

[0007] Therefore, there is a need to develop technology that will ensure that zinc oxide powder of a size known as non-nano zinc oxide has excellent visible light transmittance and ultraviolet blocking ability when it is incorporated into cosmetics and applied to the skin.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a zinc oxide powder that can be used to prepare a cosmetic that exhibits excellent visible light transmittance and ultraviolet blocking ability when applied to the skin, and an oil-dispersible cosmetic composition and cosmetic that contain the zinc oxide powder.

[0009] The zinc oxide powder of the present invention has a number distribution D determined from a transmission electron microscope image. ５０ The crystallite size is 100 to 200 nm, the aspect ratio is 1.1 to 1.4, and the crystallite size determined by X-ray diffraction spectroscopy is 70 to 200 nm.

[0010] The oil-dispersible cosmetic composition of the present invention is characterized in that the zinc oxide powder of the present invention is dispersed in oil.

[0011] Furthermore, the water-in-oil emulsion cosmetic of the present invention is characterized in that it contains the oil-dispersible cosmetic composition of the present invention or the zinc oxide powder of the present invention.

[0012] The oil-in-water emulsion cosmetic of the present invention is characterized in that it contains the oil-dispersible cosmetic composition of the present invention or the zinc oxide powder of the present invention.

[0013] Furthermore, the powder cosmetic of the present invention is characterized by containing the zinc oxide powder of the present invention.

[0014] According to the present invention, it is possible to provide a zinc oxide powder that can be used to prepare cosmetics that can exhibit excellent visible light transmittance and ultraviolet blocking ability when applied to the skin, as well as an oil-dispersible cosmetic composition and cosmetics (water-in-oil emulsion cosmetics, oil-in-water emulsion cosmetics, and powder cosmetics) that contain the zinc oxide powder.

[0015] The water-in-oil emulsion cosmetic of the present invention and the oil-in-water emulsion cosmetic of the present invention can have increased transparency, can suppress white cast when applied to the skin, and exhibit excellent UV-shielding ability.Furthermore, the powder cosmetic of the present invention can suppress white cast when applied to the skin and exhibit excellent UV-shielding ability.

[0016] <Zinc oxide powder> The zinc oxide powder of the present invention has a D of number distribution determined from a transmission electron microscope (TEM) image. ５０ (Particle size at a cumulative frequency of 50% based on the number of particles. Hereinafter, simply referred to as "D ５０ The crystallite diameter (hereinafter sometimes simply referred to as "crystallite diameter") determined from an X-ray diffraction spectrum is 70 nm or more and 200 nm or less, the aspect ratio is 1.1 or more and 1.4 or less, and the crystallite diameter (hereinafter sometimes simply referred to as "crystallite diameter") determined from an X-ray diffraction spectrum is 70 nm or more and 200 nm or less.

[0017] The zinc oxide powder of the present invention corresponds to the so-called non-nano zinc oxide, and D ５０ That is, the "non-nano zinc oxide" in this specification is a powder having a diameter of 100 nm or more. ５０ As described above, zinc oxide of this size has inferior ultraviolet shielding ability compared to zinc oxide of a smaller size, and also reduces the transmittance of visible light when used in a cosmetic, and is likely to cause a whitish appearance when the cosmetic is applied to the skin, for example.

[0018] In the zinc oxide powder of the present invention, D ５０ The upper limit of the above is limited, and the aspect ratio and crystallite size are set to fall within specific ranges, so that when the composition is blended in a cosmetic product, for example, the cosmetic product can have improved visible light transmittance and ultraviolet light shielding ability when the cosmetic product is applied to the skin.

[0019] As described above, the zinc oxide powder is D ５０ is 100 nm or more, but D ５０ If the D of the zinc oxide powder is too large, the visible light transmittance and ultraviolet shielding ability of the cosmetic composition containing the zinc oxide powder will decrease when the cosmetic composition is applied to the skin. ５０ is preferably 200 nm or less, more preferably 195 nm or less, and even more preferably 190 nm or less.

[0020] Furthermore, in zinc oxide powder, the D of the number distribution obtained from the TEM image １０(Particle size at a cumulative frequency of 10% based on the number of particles. Hereinafter, simply referred to as "D １０ ") is preferably 100 nm or more and 200 nm or less, more preferably 100 nm or more and 160 nm or less, and even more preferably 100 nm or more and 135 nm or less.

[0021] Furthermore, in terms of ensuring excellent ultraviolet shielding ability and achieving a good balance between this ultraviolet shielding ability and the visible light transmittance when the blended cosmetic is applied to the skin, the zinc oxide powder preferably has an aspect ratio of 1.4 or less and 1.1 or more, and more preferably 1.2 or more.

[0022] Furthermore, if the crystallite diameter of zinc oxide powder is too small, the visible light transmittance will decrease when, for example, a cosmetic containing the zinc oxide powder is applied to the skin. Therefore, from the viewpoint of increasing the visible light transmittance when the cosmetic containing the zinc oxide powder is applied to the skin and achieving a good balance between this visible light transmittance and ultraviolet shielding ability, the crystallite diameter of the zinc oxide powder is 70 nm or more. However, if the crystallite diameter of zinc oxide powder is too large, the ultraviolet shielding ability will decrease. Therefore, from the viewpoint of ensuring excellent ultraviolet shielding ability and achieving a good balance between this ultraviolet shielding ability and visible light transmittance when the cosmetic containing the zinc oxide powder is applied to the skin, the crystallite diameter of the zinc oxide powder is preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 160 nm.

[0023] D of zinc oxide powder referred to in this specification ５０ , D １０ The diameter and aspect ratio are values ​​determined by the following method. From an image obtained by photographing zinc oxide powder with a TEM [number of particles (primary particles): 100], the particle diameter (particle diameter of primary particles), major axis (major axis of primary particles), minor axis (minor axis of primary particles), and aspect ratio of each powder are calculated using image analysis particle size distribution measurement software. The Heywood diameter (diameter equivalent to projected area) is used as the method for calculating particle diameter. The major axis refers to the length of the long side of a rectangle when the area of ​​the rectangle circumscribing the selected particle is minimum, and the minor axis refers to the length of the short side of a rectangle when the area of ​​the rectangle circumscribing the selected particle is minimum. D５０ and D １０ is calculated by the software based on the particle diameter of each particle obtained. The aspect ratio is the average value of all particles (100 particles) of the aspect ratios (major axis / minor axis) calculated by the software for each particle.

[0024] The values ​​described in the examples below were determined using a TEM "JEM-1230" manufactured by JEOL Ltd. and image analysis type particle size distribution measurement software "Mac-View" manufactured by Mountec Co., Ltd. The D of the number distribution of zinc oxide powder described in the examples below ９０ (Particle size at a cumulative frequency of 90% based on the number of particles. Hereinafter, simply referred to as "D ９０ ") also ５０ This value was calculated in the same way as

[0025] The crystallite diameter of zinc oxide powder referred to in this specification is a value determined by the following method: An X-ray diffraction spectrum of zinc oxide powder is determined using an X-ray diffractometer with Cu-Kα radiation at an X-ray output of 45 kV and 40 mA. The half-width of the peak near 36° (peak at 36.0±0.5°) in the obtained X-ray diffraction spectrum is measured, and the crystallite diameter of zinc oxide is calculated from this half-width using Scherrer's equation.

[0026] The values ​​described in the examples below were determined using an X-ray diffraction device "Xpert-PRO" manufactured by PANalytical.

[0027] In the zinc oxide powder of the present invention, the ratio (Tt550 / Tt370) of the transmittance of light having a wavelength of 550 nm (Tt550) to the transmittance of light having a wavelength of 370 nm (Tt370), determined using a spectral transmittance curve obtained from a film formed with nitrocellulose (a film formed from zinc oxide powder and nitrocellulose), can be 3.5 or more. Light having a wavelength of 370 nm corresponds to ultraviolet light, while light having a wavelength of 550 nm is in the visible light region. Therefore, Tt550 / Tt370 is an index of the balance between ultraviolet blocking ability and visible light transmittance in cosmetics containing zinc oxide powder. When this value is 3.5 or more, for example, cosmetics containing zinc oxide powder have a better balance between ultraviolet blocking ability and visible light transmittance. There is no particular upper limit for the Tt550 / Tt370 value in zinc oxide powder, but it is typically 8.0. If Tt550 / Tt370 exceeds 8.0, there is a high possibility that the product will no longer be classified as non-nano zinc oxide.

[0028] Furthermore, the transmittance (Tt370) of light having a wavelength of 370 nm, determined using the spectral transmittance curve obtained from a film formed from zinc oxide powder and nitrocellulose, can be 24 or less, preferably 23 or less, and more preferably 22 or less, thereby ensuring better ultraviolet shielding ability in, for example, cosmetics formulated with zinc oxide powder. There is no particular restriction on the lower limit of the Tt370, but it is usually 10. If the Tt370 is 10, it is possible to achieve an SPF (Sun Protection Factor) of 50 when the amount blended in a sunscreen is 25% by mass, which is the international upper limit.

[0029] Furthermore, the transmittance (Tt550) of light having a wavelength of 550 nm, determined using the spectral transmittance curve obtained from a film formed from zinc oxide powder and nitrocellulose, can be 80 or more, preferably 82 or more, which makes it possible to improve the transparency of, for example, cosmetics containing zinc oxide powder by increasing the visible light transmittance, and further suppress the appearance of a whitish cast when the cosmetics are applied to the skin. There is no particular upper limit for the Tt550, but it is usually 92. If the Tt550 exceeds 92, there is a high possibility that the product will no longer be classified as non-nano zinc oxide.

[0030] Tt370 and Tt550 in this specification are values ​​determined by the following method.

[0031] The membrane used for the measurement was prepared as follows: 100.0 g of nitrocellulose, 140.0 g of ethyl acetate, 210.0 g of n-butyl acetate, 70.0 g of ethylene glycol mono-n-butyl ether, and 180.0 g of toluene were placed in a 1000 mL sealed container and mixed for 12 hours at 100 rpm using a shaker to prepare a nitrocellulose solution. 40.0 g of this nitrocellulose solution, 1.0 g of zinc oxide powder, and 50.0 g of φ1.5 mm glass beads were placed in a 100 mL sealed container and shaken and dispersed for 1 hour using a test disperser at 1725 rpm to prepare a zinc oxide powder dispersion.

[0032] The dispersion of zinc oxide powder is applied to a polypropylene film and dried to obtain a film formed from zinc oxide and nitrocellulose. The total light transmittance of this film is measured using a spectrophotometer to obtain a spectral transmittance curve. From this spectral transmittance curve, the transmittance at a wavelength of 370 nm and the transmittance at a wavelength of 550 nm are read to determine Tt370 and Tt550.

[0033] The values ​​described in the examples below were determined using the following materials and under the following conditions.・Nitrocellulose: "Nitrocellulose (H1 / 2)" manufactured by Kishida Chemical Co., Ltd. ・Ethyl acetate, n-butyl acetate, ethylene glycol mono-n-butyl ether, toluene: manufactured by Sigma-Aldrich ・Airtight container: "J Bottle, round, wide mouth, 1000 mL" manufactured by Nikko Hansen ・J Bottle, round, wide mouth, 100 mL" manufactured by Nikko Hansen ・Shaker: "Thermo Shaker Z-1" manufactured by Thermonix ・Test disperser: "Paint Conditioner 1400" manufactured by RedDevil ・Polypropylene film: "Plain OPP sheet #40" manufactured by Mitsui Chemicals Tohcello Co., Ltd. ・Spectrophotometer: "U-4100" manufactured by Hitachi High-Technologies Corporation (using an integrating sphere) ・Measurement conditions using the spectrophotometer Scan speed: 300 nm / min Sampling time: 2 nm Measurement wavelength: 250 to 700 nm

[0034] In the examples described later, the transmittance of light having a wavelength of 320 nm, Tt320, will also be described, but this is a value determined in the same manner as Tt370 and the like.

[0035] In the case of the zinc oxide powders described above, Tt370, Tt550 and Tt550 / Tt370 can be set to the above values.

[0036] Zinc oxide powder can be produced, for example, by mixing an aqueous zinc chloride solution with an aqueous sodium carbonate solution to prepare a slurry containing basic zinc carbonate, and then extracting the basic zinc carbonate from the slurry and calcining it.

[0037] It is preferable that the aqueous zinc chloride solution and the aqueous sodium carbonate solution used to prepare the slurry containing basic zinc carbonate have a small content of impurities (components other than zinc chloride and water in the aqueous zinc chloride solution, and components other than sodium carbonate and water in the aqueous sodium carbonate solution). This reduces the D of the zinc oxide powder finally obtained. ５０ and D １０ Furthermore, it becomes easy to adjust the aspect ratio and crystallite size to the above-mentioned values.

[0038] The zinc chloride concentration in the aqueous zinc chloride solution used to prepare the slurry containing basic zinc carbonate is, for example, 1 to 30 mass %, and the sodium carbonate concentration in the aqueous sodium carbonate solution used to prepare the slurry containing basic zinc carbonate is, for example, 1 to 20 mass %.

[0039] The basic zinc carbonate extracted from the slurry may be calcined under the conditions of, for example, a calcination temperature of 500 to 650° C. and a calcination time of 2 to 12 hours.

[0040] The zinc oxide powder may be surface-treated. Examples of surface treatment agents for the surface treatment of zinc oxide powder include at least one material (hydrophobic treatment agent) selected from the group consisting of silicone oil, fatty acid, and alkylsilane. Zinc oxide powder is hydrophilic, but by performing surface treatment with the above-mentioned surface treatment agent that functions as a hydrophobic treatment agent, the hydrophobicity of the surface of the zinc oxide powder can be increased, thereby improving the dispersibility in oil (oily components) used in cosmetics, and preventing the zinc oxide powder from falling off the skin due to moisture such as sweat when cosmetics are applied to the skin.

[0041] Examples of silicone oils include so-called straight silicone oils such as dimethicone (dimethylpolysiloxane), phenyldimethicone (methylphenylpolysiloxane), and hydrogendimethicone (methylhydrogenpolysiloxane); and so-called branched silicone oils such as trimethylsiloxysilicate and triethoxysilylethylpolydimethylsiloxyethylhexyldimethicone.

[0042] Examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and behenic acid.

[0043] Examples of alkylsilanes include alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, and decyltrimethoxysilane; and silazanes such as hexamethyldisilazane.

[0044] From the viewpoint of ensuring the water resistance improving effect and hydrophobicity improving effect (the effect of improving dispersibility in oil) resulting from its use, the content of the surface treatment agent in the zinc oxide powder is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, when the amount of the zinc oxide component in the powder is 100 parts by mass. Moreover, if the amount of the surface treatment agent in the zinc oxide powder is too large, for example, the amount of the zinc oxide component itself in the powder may become too small, and the effect of its use may be reduced. Therefore, the content of the surface treatment agent in the zinc oxide powder is preferably 30 parts by mass or less, and more preferably 25 parts by mass or less, when the amount of the zinc oxide component in the powder is 100 parts by mass.

[0045] The surface treatment using the surface treatment agent can be carried out by directly contacting the zinc oxide powder with the surface treatment agent, for example by mixing them together, or by contacting the zinc oxide powder with the surface treatment agent, for example by mixing the zinc oxide powder with a solution in which the surface treatment agent is dissolved in an organic solvent (e.g., toluene).

[0046] <Oil-dispersible cosmetic composition> The oil-dispersible cosmetic composition of the present invention is a composition used in cosmetics, and contains the zinc oxide powder of the present invention and oil (oil component), with the zinc oxide powder being dispersed in the oil.

[0047] As oils that can be used in the oil-dispersible cosmetic composition, those that have been conventionally used in cosmetics that are applied to the skin, such as sunscreens, are preferred, and examples thereof include ester oils (liquid at 25°C), hydrocarbons (liquid at 25°C), and silicone oils (liquid at 25°C).

[0048] Examples of ester oils that are liquid at 25°C include isononyl isononanoate, caprylic / capric triglyceride, ethylhexyl palmitate, ethylhexyl methoxycinnamate, triethylhexanoin, cetyl ethylhexanoate, methylheptyl laurate, methylheptyl myristate, and alkyl (C12-15) benzoate.

[0049] Examples of hydrocarbons that are liquid at 25° C. include hydrogenated polyisobutene, isododecane, mineral oil, and squalane.

[0050] Examples of silicone oils that are liquid at 25°C include dimethicone, cyclopentasiloxane, cyclomethicone, and diphenylsiloxyphenyl trimethicone.

[0051] The amount of zinc oxide powder to be blended in the oil-dispersible cosmetic composition is not particularly limited, but is usually 20 to 70% by mass.

[0052] <Water-in-oil emulsion cosmetic and oil-in-water emulsion cosmetic> The water-in-oil emulsion cosmetic of the present invention and the oil-in-water emulsion cosmetic of the present invention are emulsion cosmetics that contain the oil-dispersible cosmetic composition of the present invention or the zinc oxide powder of the present invention. That is, to obtain the water-in-oil emulsion cosmetic and the oil-in-water emulsion cosmetic, the zinc oxide powder of the present invention may be dispersed in oil to prepare the oil-dispersible cosmetic composition of the present invention, and this may be used to prepare the water-in-oil emulsion cosmetic or the oil-in-water emulsion cosmetic, or the water-in-oil emulsion cosmetic or the oil-in-water emulsion cosmetic may be prepared without going through the step of dispersing the zinc oxide powder in oil.

[0053] When zinc oxide powder that has been surface-treated with the above-mentioned surface treatment agent (hydrophobic treatment agent) is used, the zinc oxide powder has a high surface hydrophobicity, and therefore, a high proportion of the zinc oxide powder is present in the oil phase of a water-in-oil emulsion cosmetic or an oil-in-water emulsion cosmetic. On the other hand, when zinc oxide powder that has not been surface-treated is used, the zinc oxide powder has a high surface hydrophilicity, and therefore, when this zinc oxide powder is used, a high proportion of the zinc oxide powder is present in the aqueous phase of a water-in-oil emulsion cosmetic or an oil-in-water emulsion cosmetic. To make the zinc oxide powder present in the oil phase, a surfactant with a low HLB (Hydrophile-Lipophile Balance) can be used in combination.

[0054] The amount of zinc oxide powder blended in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics may be determined as required depending on the intended use, but is usually 0.1 to 40% by mass.

[0055] Furthermore, because water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics are emulsions, they contain water. The amount of water blended in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics may be determined to be the amount required depending on the form (whether it is a water-in-oil emulsion or an oil-in-water emulsion cosmetic, etc.) and the intended use, but is typically 10 to 80% by mass.

[0056] Furthermore, because water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics are emulsions, they contain oil. Examples of oils that can be used in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics include those previously exemplified as oils that can be incorporated into oil-dispersible cosmetic compositions. The amount of oil incorporated in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics may be determined according to the type (whether it is a water-in-oil emulsion or an oil-in-water emulsion cosmetic, etc.) and intended use, but is typically 10 to 80% by mass.

[0057] Furthermore, water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics are typically formulated with a surfactant to emulsify the water and oil. The surfactant can be any of the various surfactants (cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants) that are typically formulated in cosmetics.

[0058] The amount of surfactant blended in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics may be any amount that can maintain a good emulsified state, and is usually 1 to 10% by mass.

[0059] Furthermore, water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics can be blended with components required depending on the intended use, etc., from among the various components blended in ordinary cosmetics. Examples of such components include fats and oils, higher alcohols, waxes, silicones, lower alcohols, ultraviolet absorbers, feel-improving agents, extender pigments, clay minerals, film-forming agents, thickeners, moisturizers (such as polyhydric alcohols), preservatives, pH adjusters, fragrances, etc.

[0060] <Powder Cosmetic> The powder cosmetic of the present invention is one that contains the zinc oxide powder of the present invention. The amount of zinc oxide powder in the powder cosmetic may be an amount required depending on the intended use, etc., but is usually 0.1 to 40% by mass.

[0061] Powder cosmetics can contain ingredients other than zinc oxide powder, such as inorganic powders other than zinc oxide powder, organic powders such as polymer powders, surfactant metal salt powders (metal soaps), pigments, fragrances, preservatives, binders, etc.

[0062] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0063] <Preparation of Zinc Oxide Powder> Example 1: 132 g of a 47% by mass zinc chloride aqueous solution was diluted with 519 g of ion-exchanged water, and 430 g of a 10% by mass sodium carbonate aqueous solution prepared by dissolving 43 g of sodium carbonate in 387 g of ion-exchanged water was added to obtain a white slurry. The resulting slurry was filtered to recover a precipitate, which was then repeatedly washed with ion-exchanged water until the electrical conductivity of the filtered water was 150 μS / cm or less. The cake obtained by this operation was then dried at 130°C for 12 hours and then calcined at 500°C for 4 hours. The powder obtained by this calcination was pulverized using a pin mill to obtain a zinc oxide powder.

[0064] Example 2 A zinc oxide powder was obtained in the same manner as in Example 1, except that the baking conditions after drying the cake were changed to 500°C for 6 hours.

[0065] Example 3 A zinc oxide powder was obtained in the same manner as in Example 1, except that the baking conditions after drying the cake were changed to 550°C for 6 hours.

[0066] Example 4 A zinc oxide powder was obtained in the same manner as in Example 1, except that the baking conditions after drying the cake were changed to 600°C for 2 hours.

[0067] Comparative Example 1 A zinc oxide powder was obtained in the same manner as in Example 1, except that the baking conditions after drying the cake were changed to 600° C. for 6 hours.

[0068] Comparative Example 2: 132 g of a 47% by mass zinc chloride aqueous solution was diluted with 396 g of ion-exchanged water, and 207 g of a 10% by mass ammonia aqueous solution was added thereto to generate zinc oxide nuclei. Subsequently, 352 g of a 10% by mass sodium hydroxide aqueous solution was added to the resulting slurry to obtain a white slurry. The slurry was then heated to 90°C over 60 minutes with stirring, and further heated and aged at 90°C for 30 minutes with stirring. After heat aging, the resulting slurry was filtered to recover a precipitate. The precipitate was then washed with ion-exchanged water repeatedly until the electrical conductivity of the filtered water was 150 μS / cm or less. The cake obtained by this operation was then dried at 130°C for 12 hours and then calcined at 600°C for 2 hours. The powder obtained by this calcination was pulverized using a pin mill to obtain zinc oxide powder.

[0069] Comparative Example 3 Zinc oxide slurry was obtained by dispersing 16.28 g of fine zinc oxide particles "MZ-150" (primary particle diameter: 80 nm) manufactured by Teica Corporation in 500 g of ion-exchanged water. Furthermore, 20.77 g of hydrogen peroxide water (manufactured by Wako Pure Chemical Industries, Ltd.) was diluted with 500 g of ion-exchanged water to prepare an aqueous hydrogen peroxide solution. Subsequently, the aqueous hydrogen peroxide solution was added to the stirred slurry, and the mixture was stirred at 25°C for 6 hours. The resulting liquid was then filtered, and the precipitate in the liquid was collected and washed with water. The cake obtained by this operation was dried at 110°C for 12 hours and then calcined at 600°C for 2 hours. The powder obtained by this calcination was pulverized using a pin mill to obtain zinc oxide powder.

[0070] The physical properties of the zinc oxide powders of the Examples and Comparative Examples are shown in Table 1.

[0071] Furthermore, for the zinc oxide powders of the Examples and Comparative Examples, Tt320, Tt370 and Tt550 were determined by the above-mentioned method, and Tt550 / Tt370 was calculated. These results are shown in Table 2.

[0072] Furthermore, the specific surface areas of the zinc oxide powders of the examples and comparative examples were measured by the BET method using a fully automatic specific surface area measuring device ("Macsorb HM model-1208" manufactured by Mountech Co., Ltd.). The degassing step during the measurement was carried out at 150°C for 20 minutes. The results are also shown in Table 1.

[0073]

[0074]

[0075] As shown in Tables 1 and 2, D ５０ The zinc oxide powders of Examples 1 to 4, which had appropriate values ​​for all of the aspect ratio and crystallite size, had low Tt370 values, high Tt550 values, and also high Tt550 / Tt370 values, and thus had a high level of well-balanced ultraviolet shielding ability and visible light transmittance (ultraviolet shielding ability and visible light transmittance when blended in cosmetics, etc.; the same applies hereinafter to the ultraviolet shielding ability and visible light transmittance of zinc oxide powder). ５０ The zinc oxide powder of Example 4, which had a relatively large crystallite size, had a higher Tt370 value and slightly inferior ultraviolet shielding ability compared to the zinc oxide powders of Examples 1 to 3, but still maintained properties at a practical level.

[0076] In contrast, D ５０ The zinc oxide powder of Comparative Example 1, whose aspect ratio and crystallite size are too large, has a high Tt370 value, a low Tt550 value, and also a low Tt550 / Tt370 value, so that it is inferior in both ultraviolet shielding ability and visible light transmittance.In addition, the zinc oxide powder of Comparative Example 2, whose aspect ratio and crystallite size are too large, has a high Tt370 value, and a low Tt550 / Tt370 value, so that it is inferior in ultraviolet shielding ability, and the balance between ultraviolet shielding ability and visible light transmittance is also poor.Furthermore, the zinc oxide powder of Comparative Example 3, whose crystallite size is too small, has a low Tt550 value, so that it is inferior in visible light transmittance.

[0077] From the above results, it can be seen that the zinc oxide powders of Examples 1 to 4 can be used to form water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics that have excellent UV-shielding ability, are relatively transparent, and are capable of suppressing white cast when applied to the skin, and can also be used to form powder cosmetics that have excellent UV-shielding ability and are capable of suppressing white cast when applied to the skin.

[0078] <Preparation of Cosmetics> (Preparation of Surface-Treated Zinc Oxide Powder) Example 5 The zinc oxide powder of Example 1 was surface-treated by contacting it with octyltriethoxysilane to prepare the surface-treated zinc oxide powder of Example 5.

[0079] Comparative Example 4 A surface-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the zinc oxide powder of Comparative Example 1 was used.

[0080] Comparative Example 5 A surface-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the zinc oxide powder of Comparative Example 2 was used.

[0081] Comparative Example 6 A surface-treated zinc oxide powder was prepared in the same manner as in Example 5, except that the zinc oxide powder of Comparative Example 3 was used.

[0082] (Preparation of water-in-oil emulsion cosmetics) Examples 6 to 8 and Comparative Examples 7 to 9 The water-in-oil emulsion cosmetics of Examples 6 to 8 and Comparative Examples 7 to 9 were prepared by blending the components shown in Table 3 in the proportions shown in Table 3 (all of these cosmetics after preparation were water-in-oil emulsions).

[0083] The UV-shielding ability (UV protection effect) of the water-in-oil emulsion cosmetics of Examples 6 to 8 and Comparative Examples 7 to 9 was evaluated (in vitro test). The evaluation was based on the SPF measurement method (ISO 24443), and each of the water-in-oil emulsion cosmetics of the Examples and Comparative Examples was applied to an evaluation plate ("HELIOPLATE (registered trademark) HD6" manufactured by Helioscreen) at a concentration of 1.3 mg / cm. ２and dried at room temperature for 30 minutes to prepare a measurement sample, after which the SPF and UVAPF (Ultraviolet A Protection Factor) were measured using an SPF analyzer ("UV-2000S" manufactured by Labsphere). In addition, the transmittance at a wavelength of 450 nm was determined from the spectral transmittance curve obtained during this SPF measurement, and the transparency of each water-in-oil emulsion cosmetic was also evaluated.

[0084] These results are also shown in Table 3. In Table 3, the blending amount of each component is shown in % so that the total cosmetic amount is 100%, but all of these % are mass %. Furthermore, in these tables, the % indication is omitted and only the numerical value indicating the blending amount is shown (the same applies to Tables 4 to 7 described below). Furthermore, the "titanium oxide powder (A)" shown in Table 3 is "MT-N1" manufactured by Teika Corporation, and the "spherical silica powder" is "TMS-T05DCB" manufactured by Teika Corporation (the same applies to Tables 5 to 7 described below).

[0085]

[0086] As shown in Table 3, the water-in-oil emulsion cosmetics of Examples 6 to 8 had higher SPF and UVAPF values ​​and excellent UV blocking ability than the cosmetics of Comparative Examples 7 to 9. Furthermore, all of the water-in-oil emulsion cosmetics of Examples 6 to 8 had relatively high transmittance at a wavelength of 450 nm and excellent transparency.

[0087] (Preparation of oil-in-water emulsion cosmetics) Examples 9 to 11 and Comparative Examples 10 to 18 The oil-in-water emulsion cosmetics of Examples 9 to 11 and Comparative Examples 10 to 18 were prepared by blending the components shown in Tables 4 to 6 in the proportions shown in Tables 4 to 6 (all of these cosmetics after preparation were oil-in-water emulsions).

[0088] The oil-in-water emulsion cosmetics of Examples 9 to 11 and Comparative Examples 10 to 18 were evaluated for UV-shielding ability (UV protection effect) and transparency in the same manner as the water-in-oil emulsion cosmetic of Example 6. The results are shown in Tables 4 to 6.

[0089]

[0090]

[0091]

[0092] As shown in Table 4, the oil-in-water emulsion cosmetic of Example 9 had a higher SPF value and excellent UV-shielding ability, as well as a high transmittance at a wavelength of 450 nm and excellent transparency, compared to the cosmetics of Comparative Examples 10 to 12, which had the same component composition except for the surface-treated zinc oxide powder.

[0093] Furthermore, as shown in Table 5, the oil-in-water emulsion cosmetic of Example 10 had a higher SPF value and excellent UV-shielding ability than the cosmetics of Comparative Examples 13 to 15, which had the same component composition except for the surface-treated zinc oxide powder, and also had a high transmittance at a wavelength of 450 nm and excellent transparency.

[0094] Furthermore, as shown in Table 6, the oil-in-water emulsion cosmetic of Example 11 had a higher SPF value and excellent UV-shielding ability than the cosmetics of Comparative Examples 16 to 18, which had the same component composition except for the surface-treated zinc oxide powder, and also had a high transmittance at a wavelength of 450 nm and excellent transparency.

[0095] (Preparation of Powder Cosmetics) The components shown in Table 7 were blended in the proportions shown in Table 7 to prepare the powder cosmetics of Example 12 and Comparative Examples 19 to 21.

[0096] The powder cosmetics of Example 12 and Comparative Examples 19 to 21 were evaluated for UV blocking ability (UV protection effect) in the same manner as the water-in-oil emulsion cosmetic of Example 6. The results are also shown in Table 7. The "titanium oxide powder (B)" shown in Table 7 is "MPY-1133M" manufactured by Teika Corporation, and the "titanium oxide powder (C)" is "MT-100TV" manufactured by Teika Corporation.

[0097]

[0098] As shown in Table 7, the powder cosmetic of Example 12 had higher SPF and UVAPF values ​​than the cosmetics of Comparative Examples 19 to 21, and had excellent ultraviolet screening ability.

[0099] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0100] The water-in-oil emulsion cosmetic, oil-in-water emulsion cosmetic, and powder cosmetic of the present invention can be applied to various cosmetics blended with zinc oxide powder (sunscreen, foundation, emulsion, skin cream, etc.). The zinc oxide powder of the present invention can constitute the oil-dispersible cosmetic composition, water-in-oil emulsion cosmetic, oil-in-water emulsion cosmetic, and powder cosmetic of the present invention, and the oil-dispersible cosmetic composition of the present invention can constitute the water-in-oil emulsion cosmetic and oil-in-water emulsion cosmetic of the present invention.

Claims

1. D of the number distribution obtained from transmission electron microscope images ５０ A zinc oxide powder characterized by having a wavelength of 100 to 200 nm, an aspect ratio of 1.1 to 1.4, and a crystallite size determined from the X-ray diffraction spectrum of 70 to 200 nm.

2. D of the number distribution obtained from transmission electron microscopy images １０ The zinc oxide powder according to claim 1, wherein the wavelength is 100 to 200 nm.

3. The zinc oxide powder according to claim 1, wherein the ratio of the transmittance of light at a wavelength of 550 nm (Tt550) to the transmittance of light at a wavelength of 370 nm (Tt370), determined using a spectral transmittance curve obtained from a film formed with nitrocellulose, is 3.5 or more (Tt550 / Tt370).

4. The zinc oxide powder according to claim 3, wherein Tt370 is 24 or less.

5. The zinc oxide powder according to claim 3, wherein Tt550 is 80 or more.

6. The zinc oxide powder according to claim 1, which is surface-treated.

7. The zinc oxide powder according to claim 6, which is surface-treated with at least one surface treatment agent selected from the group consisting of silicone oil, fatty acids, and alkylsilanes.

8. An oil-dispersible cosmetic composition characterized in that the zinc oxide powder described in any one of claims 1 to 7 is dispersed in oil.

9. An oil-in-water droplet type emulsified cosmetic characterized by containing the oil-dispersible cosmetic composition described in claim 8.

10. An oil-in-water emulsion cosmetic characterized by containing the oil-dispersible cosmetic composition described in claim 8.

11. An oil-in-water droplet type emulsified cosmetic characterized by containing zinc oxide powder according to any one of claims 1 to 7.

12. An oil-in-water emulsion cosmetic characterized by containing zinc oxide powder according to any one of claims 1 to 7.

13. A powder cosmetic characterized by containing zinc oxide powder according to any one of claims 1 to 7.