Water-in-oil emulsion cosmetic

Abstract

To provide a water-in-oil type emulsion cosmetic containing zinc oxide-based particles in which crystallization is reduced or suppressed by an approach different from a conventional one in a system with a small amount of water, and a drug such as tranexamic acid.SOLUTION: The water-in-oil emulsion cosmetic of the present disclosure contains (a) zinc oxide-based particles, (b) a drug, (c) an oil component, and (d) water in an amount of 14.0% by mass or more and less than 30.0% by mass, wherein (a) the zinc oxide-based particles have an average particle diameter of 1.0 μm or more, and (b) the drug is at least one selected from the group consisting of tranexamic acid, a tranexamate, a tranexamic acid derivative, ascorbic acid, an ascorbate, and an ascorbic acid derivative.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a water-in-oil emulsion cosmetic. [Background technology]

[0002] In recent years, water-in-oil emulsion cosmetics containing various ingredients such as tranexamic acid and zinc oxide have been developed.

[0003] Patent Document 1 discloses a water-in-oil emulsion composition containing (A) tranexamic acid or a derivative thereof or a salt thereof, (B) D-pantothenyl alcohol, and (C) a poly(oxyethylene-oxypropylene) methylpolysiloxane copolymer, wherein the pH of the aqueous phase is 4 to 7.

[0004] Patent Document 2 discloses a water-in-oil emulsion cosmetic that contains (A) an organically modified clay mineral, (B) fine particle metal oxide such as zinc oxide, (C) polyether-modified silicone, (D) polyglycerin-modified silicone, (E) a hydroxy fatty acid having 12 to 22 carbon atoms, and (F) a cyclic silicone, and contains 0.2% by mass or more and 0.8% by mass or less of (A) based on the total amount.

[0005] Patent Document 3 discloses a water-in-oil emulsion cosmetic containing (a) 1.0 to 5.0 mass % of tranexamic acid or a salt thereof, (b) 3.0 to 30.0 mass % of silica-coated zinc oxide, and (c) 10.0 to 40.0 mass % of water.

[0006] Patent Document 4 discloses that when zinc oxide is contained as an ultraviolet scattering agent in a water-in-oil emulsion cosmetic, and tranexamic acid or ascorbic acid is used in combination as a whitening agent, crystals derived from zinc oxide may form in the cosmetic. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-152525 [Patent Document 2] Japanese Patent Publication No. 2022-177621 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-201660 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-129276 Summary of the Invention [Problem to be solved by the invention]

[0008] As described in Patent Documents 3 and 4, when zinc oxide is used in combination with a drug such as tranexamic acid or ascorbic acid in a system with a relatively small amount of water, such as a water-in-oil emulsion cosmetic, it is known that the elution of zinc ions from the zinc oxide and / or the surface activity of the zinc oxide can result in the formation of crystals derived from the drug and zinc oxide (e.g., zinc tranexamate).This crystallization poses the problem of not being able to fully exhibit the functions (e.g., whitening function) of the zinc oxide, tranexamic acid, or ascorbic acid.

[0009] To solve these problems, Patent Document 3 uses silica-coated zinc oxide, in which the surface of zinc oxide is coated with silica, and Patent Document 4 uses rhododendrol or a derivative thereof as a whitening agent, in combination with a specific emulsifier and oil.

[0010] Therefore, a subject of the present disclosure is to provide a water-in-oil emulsion cosmetic containing zinc oxide-based particles and a drug such as tranexamic acid, in which crystallization is reduced or inhibited using an approach different from conventional approaches in a system with a small amount of water. [Means for solving the problem]

[0011] <Aspect 1> (a) zinc oxide-based particles; (b) drugs, (c) oil, and (d) 14.0% by mass or more but less than 30.0% by mass of water; Including, The (a) zinc oxide-based particles have an average particle size of 1.0 μm or more, and the drug (b) is at least one selected from the group consisting of tranexamic acid, tranexamic acid salts, tranexamic acid derivatives, ascorbic acid, ascorbic acid salts, and ascorbic acid derivatives; Water-in-oil emulsion cosmetics. <Aspect 2> A cosmetic preparation according to aspect 1, wherein the content of the (a) zinc oxide-based particles is 1.0% by mass or more. <Aspect 3> A cosmetic preparation according to aspect 1 or 2, wherein the (a) zinc oxide-based particles are hydrophobic particles. <Aspect 4> A cosmetic preparation according to aspect 3, wherein the (a) zinc oxide-based particles have a moiety derived from a fatty acid. <Aspect 5> A cosmetic preparation according to any one of Aspects 1 to 4, wherein the amount of silica coated on the (a) zinc oxide-based particles is less than 7.0% by mass. <Aspect 6> A cosmetic preparation according to any one of Aspects 1 to 5, wherein the (a) zinc oxide-based particles comprise at least one selected from the group consisting of zinc oxide particles and zinc oxide phosphor particles. <Aspect 7> 7. The cosmetic preparation according to any one of aspects 1 to 6, wherein the content of the agent (b) is 1.0% by mass or more. <Aspect 8> (e) The cosmetic preparation according to any one of aspects 1 to 7, further comprising a dispersant. <Aspect 9> A cosmetic preparation according to Aspect 8, wherein the (e) dispersant comprises isostearic acid. <Aspect 10> A cosmetic preparation according to Aspect 8, wherein the (e) dispersant comprises isostearic acid and sorbitan sesquiisostearate. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a water-in-oil emulsion cosmetic containing zinc oxide-based particles and a drug such as tranexamic acid, in which crystallization is reduced or inhibited using an approach different from conventional approaches in a system with a small amount of water. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

[0014] The water-in-oil emulsion cosmetic of the present disclosure comprises (a) zinc oxide-based particles, (b) a medicinal agent, (c) an oil component, and (d) 14.0% by mass or more and less than 30.0% by mass of water, wherein the (a) zinc oxide-based particles have an average particle size of 1.0 μm or more, and the (b) medicinal agent is at least one selected from the group consisting of tranexamic acid, tranexamic acid salts, tranexamic acid derivatives, ascorbic acid, ascorbate salts, and ascorbic acid derivatives.

[0015] Without being limited by the theory, the mechanism by which the water-in-oil emulsion cosmetic of the present disclosure is able to reduce or inhibit crystallization using an approach different from conventional approaches, despite the small amount of water, is believed to be as follows.

[0016] As described in Patent Documents 3 and 4, zinc oxide used in water-in-oil emulsion cosmetics generally has an average particle size of less than 1.0 μm. The present inventors have unexpectedly discovered that when zinc oxide-based particles, such as zinc oxide having an average particle size of 1.0 μm or more, are used, crystallization can be reduced or inhibited, even when used in combination with a drug such as tranexamic acid in a system with a small amount of water.

[0017] Although the principle behind the effect of reducing or inhibiting crystallization obtained by employing zinc oxide-based particles having an average particle size of 1.0 μm or more is unclear, one reason is believed to be that zinc oxide-based particles such as zinc oxide require a certain absolute amount depending on the use of the cosmetic, and by using zinc oxide-based particles with a large particle size, it is possible to maintain this certain absolute amount while keeping the surface area of ​​the entire zinc oxide-based particles small.

[0018] Furthermore, water-in-oil emulsion cosmetics contain less water than oil-in-water emulsion cosmetics, and the water in the cosmetics is dispersed in the oil phase in the form of tiny droplets. These droplets contain drugs such as tranexamic acid or ascorbic acid. Zinc oxide-based particles with an average particle size of 1.0 μm or more are less likely to be encapsulated in such tiny droplets than particles with an average particle size of less than 1.0 μm. As a result, contact with drugs such as tranexamic acid is reduced or inhibited, which is thought to reduce or inhibit crystallization.

[0019] <Water-in-oil emulsion cosmetics> The water-in-oil emulsion cosmetic of the present disclosure comprises (a) zinc oxide-based particles, (b) a drug, (c) an oil component, and (d) water.

[0020] (a) Zinc oxide particles In the present disclosure, the term "zinc oxide-based particles" is not limited to zinc oxide particles but also encompasses particles based on zinc oxide, such as phosphors derived from zinc oxide (sometimes referred to as "zinc oxide phosphors"). Zinc oxide phosphors can be obtained, for example, by calcining zinc oxide in a reducing atmosphere such as H or CO. Zinc oxide particles are sometimes used in the field of cosmetics as UV scattering agents or white pigments. Meanwhile, zinc oxide phosphors have the ability to convert UV rays, which are harmful to the skin, into light beneficial to the skin, such as light that exhibits cell activation. Here, "cell activation" in the present disclosure refers to the promotion of metabolism or turnover, improvement of function, promotion of proliferation, inhibition of oxidation, improvement of resistance to fatigue or external stimuli, and inhibition of decline in function or activity in animal cells, including human cells, such as skin fibroblasts and / or keratinocytes. Skin cell activation can contribute to the prevention or improvement of, for example, wrinkles, age spots, skin aging, and photoaging.

[0021] Zinc oxide phosphor can be called an ultraviolet wavelength conversion material, and can convert the wavelength of ultraviolet rays contained in incident light and emit outgoing light with a wavelength longer than that of the ultraviolet rays.

[0022] The ultraviolet light may include UVA, UVB, UVC, etc. In one embodiment, the ultraviolet light is light having a peak wavelength of 200 nm to 400 nm. The ultraviolet light contained in the incident light may be, for example, the ultraviolet light contained in sunlight, or may be artificially generated ultraviolet light contained in fluorescent lamps, etc.

[0023] The emitted light from the zinc oxide phosphor has a wavelength longer than that of ultraviolet light. From the viewpoint of cell activation, it is preferable that the emitted light has a peak wavelength of, for example, 500 nm to 700 nm. The emitted light may have one or more peaks at 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm, or within any range of these values. The emitted light may be red light, orange light, green light, blue light, or the like. In one embodiment, the zinc oxide phosphor emits light having a dominant wavelength of 500 nm to 700 nm when excited with excitation light of 200 nm to 400 nm.

[0024] The zinc oxide-based particles may be used alone or in combination of two or more kinds. Among them, from the viewpoint of whitening effect, cell activation effect, etc., it is preferable to include at least one kind selected from the group consisting of zinc oxide particles and zinc oxide phosphor particles, and it is more preferable to include zinc oxide phosphor particles, or zinc oxide and zinc oxide phosphor particles.

[0025] The zinc oxide-based particles used in the present disclosure have an average particle diameter of 1.0 μm or more. The use of zinc oxide-based particles of this size can reduce or inhibit crystallization associated with co-administration with drugs such as tranexamic acid, as described below. From the perspective of reducing or inhibiting crystallization, the average particle diameter is preferably, for example, greater than 1.0 μm, 1.2 μm or more, 1.5 μm or more, 1.7 μm or more, or 2.0 μm or more. The upper limit of the average particle diameter is not particularly limited, and can be, for example, 5.0 μm or less, 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, or 3.0 μm or less. Here, the average particle diameter of the zinc oxide-based particles refers to the particle diameter (area-equivalent circle particle diameter) when converted into a circular particle having the same area as the projected area of ​​the particle observed with a transmission electron microscope. The area-equivalent circle particle size can be defined as the average value of 10 or more, 50 or more, or 100 or more (for example, 10, 50, or 100) particles.

[0026] The amount of zinc oxide-based particles to be blended is not particularly limited and can be appropriately set depending on the intended use of the cosmetic (e.g., sunscreen cosmetic). The amount can be, for example, 1.0% by mass or more, 1.5% by mass or more, 2.0% by mass or more, 2.5% by mass or more, 3.0% by mass or more, 3.5% by mass or more, 4.0% by mass or more, 4.5% by mass or more, or 5.0% by mass or more, and can be 40.0% by mass or less, 30.0% by mass or less, 20.0% by mass or less, 15.0% by mass or less, 10.0% by mass or less, 8.0% by mass or less, or 6.0% by mass or less, relative to the total amount of the cosmetic.

[0027] In some embodiments, the zinc oxide-based particles are hydrophobic particles, which makes them less likely to be encapsulated by water droplets and, as a result, less likely to come into contact with drugs such as tranexamic acid, thereby further reducing or inhibiting crystallization.

[0028] When hydrophobic zinc oxide-based particles having an average particle size of 1.0 μm or more are used, such particles are typically contained in a dispersion medium containing oil (oil phase), and water droplets (aqueous phase) dispersed in this dispersion medium may contain a drug such as tranexamic acid, which will be described later.

[0029] Hydrophobic zinc oxide-based particles can be obtained, for example, by subjecting untreated zinc oxide-based particles to a hydrophobic treatment. Examples of hydrophobic treatments include silicone treatments (treatments with silicone oils such as methylhydrogenpolysiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane; alkylsilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, and octyltrimethoxysilane; fluoroalkylsilanes such as trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane; and silicone ethers such as triethoxycaprylylsilane), fatty acid treatments (treatments with palmitic acid, isostearic acid, stearic acid, lauric acid, myristic acid, behenic acid, oleic acid, rosin acid, and 12-hydroxystearic acid), fatty acid soap treatments (treatments with aluminum stearate, calcium stearate, and 12-hydroxystearic acid), and fatty acid ester treatments (treatments with dextrin fatty acid esters, cholesterol fatty acid esters, sucrose fatty acid esters, and starch fatty acid esters). Other examples include lecithin treatment, amino acid treatment (treatment with N-acyl glutamic acid, etc.), titanate treatment (treatment with alkyl titanate, etc.), fluorine-based treatment (treatment with perfluoroalkyl phosphate ester, perfluoroalcohol, etc.), and alkyl phosphate ester treatment. The hydrophobic treatment can be carried out according to a conventional method, and can be used alone or in combination. Among them, fatty acid treatment and silicone treatment are preferred from the viewpoints of reducing or inhibiting crystallization, emulsion stability, redispersibility of zinc oxide-based particles, etc., and stearic acid treatment and silicone ether treatment (especially triethoxycaprylylsilane treatment) are more preferred. For example, zinc oxide-based particles treated with a fatty acid (e.g., stearic acid treatment) or a silicone ether (e.g., triethoxycaprylylsilane treatment) have a moiety derived from a fatty acid (e.g., stearic acid) or a silicone ether (e.g., triethoxycaprylylsilane).

[0030] The water-in-oil emulsion cosmetic of the present disclosure uses zinc oxide-based particles with an average particle size of 1.0 μm or more, thereby reducing or inhibiting crystallization associated with co-use with drugs such as tranexamic acid, as described below. Therefore, the surfaces of the zinc oxide-based particles may be coated with silica, but they do not have to be. The amount of silica coated on the surfaces of the zinc oxide-based particles can be less than 7.0% by mass, 6.5% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 3.0% by mass or less, 1.0% by mass or less, or 0.5% by mass or less, relative to the zinc oxide-based particles, and can be 0% by mass or more or greater than 0% by mass. Methods for measuring the proportion of silica in the zinc oxide-based particles, i.e., the amount of silica coated, include, for example, quantitative analysis of silicon element by inductively coupled plasma (ICP) atomic emission spectrometry. In this case, assuming that all atoms coated on the surface are in the form of oxide, the obtained silicon value can be calculated by converting it to the oxide, i.e., silica.

[0031] In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure also contains zinc oxide-based particles with an average particle size of less than 1.0 μm. Because the water-in-oil emulsion cosmetic of the present disclosure contains zinc oxide-based particles with an average particle size of 1.0 μm or more, crystallization associated with co-use with drugs such as tranexamic acid, as described below, can be reduced or inhibited compared to a cosmetic containing only zinc oxide-based particles with an average particle size of less than 1.0 μm. In this configuration, the zinc oxide-based particles with an average particle size of 1.0 μm or more can be referred to as "first zinc oxide-based particles," and the zinc oxide-based particles with an average particle size of less than 1.0 μm can be referred to as "second zinc oxide-based particles." The average particle size of these second zinc oxide-based particles can be 0.8 μm or less, 0.5 μm or less, 0.3 μm or less, 0.1 μm or less, or 0.05 μm or less, and can be 0.01 μm or more, 0.015 μm or more, or 0.02 μm or more.

[0032] When using second zinc oxide-based particles, the surfaces of the second zinc oxide-based particles are preferably coated with silica from the viewpoint of reducing or suppressing crystallization. The amount of silica coated on the surfaces of the second zinc oxide-based particles can be 7.0% by mass or more, 8.0% by mass or more, 10.0% by mass or more, 13.0% by mass or more, or 15.0% by mass or more, 25.0% by mass or less, 20.0% by mass or less, or 18.0% by mass or less, based on the second zinc oxide-based particles. The second zinc oxide-based particles can be made hydrophobic by similarly applying the above-mentioned hydrophobization treatment.

[0033] The presence of the first zinc oxide-based particles and the second zinc oxide-based particles in a water-in-oil emulsion cosmetic can be confirmed, for example, using a transmission electron microscope and a scanning electron microscope (especially, energy dispersive X-ray fluorescence spectroscopy (SEM-EDX analysis)) to confirm the presence of two types of zinc oxide-based particles in the cosmetic. The particle size distribution of the water-in-oil emulsion cosmetic can then be measured using, for example, laser diffraction / scattering with a Beckman Coulter particle size distribution analyzer (LS I3 320). The presence of two types of zinc oxide-based particles with different average particle sizes can be confirmed from the number of peaks in the particle size distribution graph. Alternatively, the presence of the first zinc oxide-based particles and the second zinc oxide-based particles can be confirmed from the difference in the silica coating amount, for example, using inductively coupled plasma (ICP) optical emission spectroscopy or a scanning electron microscope (especially, energy dispersive X-ray fluorescence spectroscopy (SEM-EDX analysis)) to evaluate the silica coating amount of the zinc oxide-based particles.

[0034] When the zinc oxide-based particles contain other zinc oxide-based particles (for example, second zinc oxide-based particles) in addition to the first zinc oxide-based particles, the proportion of the first zinc oxide-based particles relative to the total zinc oxide-based particles is preferably 20.0 mass% or more, 30.0 mass% or more, 40.0 mass% or more, 50.0 mass% or more, or more than 50.0 mass%, from the viewpoint of reducing or suppressing crystallization. The upper limit of this proportion is not particularly limited, and can be less than 100 mass%, 90.0 mass% or less, 80.0 mass% or less, 70.0 mass% or less, or 60.0 mass% or less.

[0035] As the zinc oxide-based particles, second zinc oxide-based particles having a silica coating amount of less than 7.0 mass% or second zinc oxide-based particles that are not silica-coated may be used, as long as this does not adversely affect the reduction or inhibition of crystallization. However, from the viewpoint of reducing or inhibiting crystallization, the proportion of such second zinc oxide-based particles relative to the total zinc oxide-based particles is preferably 20.0 mass% or less, 15.0 mass% or less, 10.0 mass% or less, 5.0 mass% or less, or 1.0 mass% or less, and it is more preferable that such second zinc oxide-based particles are not included in the cosmetic.

[0036] (b) Drugs The water-in-oil emulsion cosmetic of the present disclosure contains at least one drug selected from the group consisting of tranexamic acid, tranexamic acid salts, tranexamic acid derivatives, ascorbic acid, ascorbic acid salts, and ascorbic acid derivatives. Such drugs are generally used as whitening agents in the cosmetic field, and are prone to crystallization when used in combination with zinc oxide-based particles.

[0037] The amount of the drug to be added is not particularly limited and can be set appropriately depending on the intended use of the cosmetic (e.g., whitening cosmetic). The amount can be, for example, 1.0% by mass or more, 1.3% by mass or more, 1.5% by mass or more, 1.8% by mass or more, 2.0% by mass or more, 2.5% by mass or more, 3.0% by mass or more, 3.5% by mass or more, or 4.0% by mass or more relative to the total amount of the cosmetic, and can be 10.0% by mass or less, 7.0% by mass or less, 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, 3.5% by mass or less, or 3.0% by mass or less.

[0038] The salt form of tranexamic acid salt and ascorbate is not particularly limited, and examples thereof include alkali metal salts (e.g., sodium salt, potassium salt, lithium salt), alkaline earth metal salts (e.g., magnesium salt, calcium salt), ammonium salt, amino acid salt, sulfate, hydrochloride, etc.

[0039] Tranexamic acid derivatives and ascorbic acid derivatives typically refer to compounds obtained by chemically modifying tranexamic acid or ascorbic acid, and examples include compounds in which the hydroxyl groups of tranexamic acid or ascorbic acid have been chemically modified.

[0040] Examples of tranexamic acid derivatives include tranexamic acid dimers (e.g., trans-4-(trans-aminomethylcyclohexanecarbonyl)aminomethylcyclohexanecarboxylic acid hydrochloride), esters of tranexamic acid and hydroquinone (e.g., trans-4-aminomethylcyclohexanecarboxylic acid 4'-hydroxyphenyl ester), esters of tranexamic acid and gentisic acid (e.g., 2-(trans-4-aminomethylcyclohexylcarbonyloxy)-5-hydroxybenzoic acid and its salts), and amides of tranexamic acid (e.g., trans-4-aminomethylcyclohexanecarboxylic acid methylamide and its salts, trans-4-(p-methoxybenzoyl)aminomethylcyclohexanecarboxylic acid and its salts, trans-4-guanidinomethylcyclohexanecarboxylic acid and its salts). Other derivatives include, for example, methylaminomethylcyclohexanecarboxamide HCl. Salt forms similar to those described above for tranexamic acid salts can also be used.

[0041] Examples of ascorbic acid derivatives include L-ascorbic acid monoesters such as L-ascorbic acid monophosphate and L-ascorbic acid 2-sulfate, L-ascorbic acid glucosides such as L-ascorbic acid 2-glucoside, and salts thereof. The salt forms can be similar to those described above for tranexamate and the like.

[0042] <(c) Oil> The oils that can be used in the water-in-oil emulsion cosmetics of the present disclosure are not particularly limited, and volatile and / or non-volatile oils can be used. Specific examples include non-polar oils (e.g., non-polar hydrocarbon oils) and polar oils. Oils can be used alone or in combination. Here, "non-volatile" refers to an oil that exhibits a volatile content of 5.0% by mass or less when left at 105°C under atmospheric pressure for 3 hours. In contrast, "volatile" refers to an oil that exhibits a volatile content of more than 5.0% by mass when left at 105°C under atmospheric pressure for 3 hours.

[0043] The non-polar hydrocarbon oil is not particularly limited, and examples thereof include petrolatum, liquid paraffin, tetraisobutane, hydrogenated polydecene, microcrystalline wax, olefin oligomer, isododecane, isohexadecane, squalane, polybutene, hydrogenated polybutene, polyisobutene, and hydrogenated polyisobutene. The non-polar hydrocarbon oils can be used alone or in combination.

[0044] The oil component other than the non-polar hydrocarbon oil may include, but is not limited to, liquid oils, semi-solid oils, solid oils, waxes, silicone oils, and synthetic ester oils, which may be used alone or in combination.

[0045] Examples of liquid oils include avocado oil, camellia oil, turtle oil, macadamia nut oil, corn oil, mink oil, olive oil, rapeseed oil, egg yolk oil, sesame oil, persic oil, wheat germ oil, camellia oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, soybean oil, peanut oil, tea seed oil, Japanese kaya oil, rice bran oil, Chinese tung oil, Japanese tung oil, jojoba oil, germ oil, and triglycerin. Here, liquid oils refer to oils that are liquid at room temperature (e.g., 25°C).

[0046] Examples of semi-solid fats and oils include dipentaerythrityl hexa(hydroxystearate / stearic acid / rosin acid), dipentaerythrityl hexa(hydroxystearate / stearic acid / rosin acid), dipentaerythrityl (hydroxystearate / isostearate), dipentaerythrityl hexahydroxystearate, phytosteryl macadamiate, phytosteryl / isostearyl / cetyl / stearyl / behenyl dimer dilinoleate, and phytosteryl / isostearyl / cetyl / stearyl / behenyl dimer dilinoleate. Examples of semi-solid oils and fats include phytosteryl / isostearyl / cetyl / stearyl / behenyl dimer dilinoleate, bis(behenyl / isostearyl / phytosteryl) dimer dilinoleate, C10-18 triglyceride, pentaerythrityl tetra(behenate / benzoate / ethylhexanoate), phytosteryl / behenyl dimer dilinoleate, and macadamia nut oil polyglyceryl-6 esters behenate. In the present disclosure, the term "semi-solid oil" refers to an oil having a hardness of 0.1 to 10 N at room temperature (e.g., 25°C). This hardness is measured using a rheometer manufactured by Rheotech Corporation with a pressure-sensitive shaft of 5φ, a penetration speed of 2 cm / min, and a penetration depth of 3 mm.

[0047] Examples of solid fats include cocoa butter, coconut oil, hardened coconut oil, palm oil, palm kernel oil, Japan wax kernel oil, hardened oil, Japan wax, and hardened castor oil. Here, the term "solid fats" refers to fats that are solid at room temperature (e.g., 25°C).

[0048] Examples of waxes include beeswax, candelilla wax, cotton wax, carnauba wax, bayberry wax, Ibota wax, montan wax, rice bran wax, lanolin, kapok wax, lanolin acetate, liquid lanolin, sugarcane wax, lanolin fatty acid isopropyl, hexyl laurate, reduced lanolin, jojoba wax, hard lanolin, shellac wax, POE lanolin alcohol ether, POE lanolin alcohol acetate, POE cholesterol ether, lanolin fatty acid polyethylene glycol, and POE hydrogenated lanolin alcohol ether.

[0049] Examples of silicone oils include linear silicones such as trisiloxane, dimethylpolysiloxane (dimethicone), methylphenylpolysiloxane (diphenylsiloxyphenyltrimethicone), and methylhydrogenpolysiloxane; and cyclic silicones such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. Examples of dimethylpolysiloxanes include low-molecular-weight, volatile linear dimethylpolysiloxanes such as those with a viscosity of 0.65 cs, 1 cs, 1.5 cs, and 2 cs. Other examples include high-molecular-weight, non-volatile linear dimethylpolysiloxanes with a viscosity of 6 cs or more, 10 cs or more, 15 cs or more, or 20 cs or more. These viscosities refer to kinematic viscosities at 25°C.

[0050] Examples of synthetic ester oils include isopropyl myristate, cetyl octanoate, octyldodecyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, hexyldecyl dimethyloctanoate, cetyl lactate, myristyl lactate, lanolin acetate, isocetyl stearate, isocetyl isostearate, cholesteryl 12-hydroxystearate, ethylene glycol di-2-ethylhexanoate, dipentaerythritol fatty acid esters, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glycerin di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexanoate, triisostearin, trimethylolpropane triisostearate, pentaerythritol tetra-2-ethylhexanoate, Glyceryl tri-2-ethylhexanoate, glyceryl trioctanoate, glyceryl triisopalmitate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glyceryl trimyristate, tri-2-heptylundecanoic acid glyceride, castor oil fatty acid methyl ester, oleyl oleate, acetoglyceride, 2-heptylundecyl palmitate, adipyl diisobutyl phosphate, N-lauroyl-L-glutamic acid 2-octyldodecyl ester, di-2-heptylundecyl adipate, ethyl laurate, di-2-ethylhexyl sebacate, 2-hexyldecyl myristate, 2-hexyldecyl palmitate, 2-hexyldecyl adipate, diisopropyl sebacate, 2-ethylhexyl succinate, alkyl (C12-15) benzoate, and triethyl citrate.

[0051] Such synthetic ester oils fall under the category of polar oils. Polar oils and non-polar oils can be distinguished by their IOB value. The IOB value of polar oils can be, for example, 0.10 or more, 0.11 or more, 0.12 or more, or 0.13 or more, and can be 0.50 or less, 0.45 or less, or 0.40 or less. Here, the IOB value is an abbreviation for Inorganic / Organic Balance, which represents the ratio of inorganic value to organic value and is an index of the degree of polarity of an organic compound. Specifically, the IOB value is expressed as IOB value = inorganic value / organic value. The "inorganic value" and "organic value" are set according to the type of atom or functional group, such as 20 for one carbon atom in a molecule and 100 for one hydroxyl group. The IOB value of an organic compound can be calculated by adding up the "inorganic value" and "organic value" of all atoms and functional groups in the organic compound (see, for example, "Organic Conceptual Diagram - Fundamentals and Applications" by Yoshio Koda, pp. 11-17, Sankyo Publishing, 1984).

[0052] There are no particular limitations on the oil content in the water-in-oil emulsion cosmetic of the present disclosure, and it can be, for example, 15.0% by mass or more, 20.0% by mass or more, 25.0% by mass or more, 30.0% by mass or more, 35.0% by mass or more, 40.0% by mass or more, or 45.0% by mass or more relative to the total amount of the cosmetic, and can also be 70.0% by mass or less, 65.0% by mass or less, 60.0% by mass or less, 55.0% by mass or less, 50.0% by mass or less, or 45.0% by mass or less.

[0053] 〈(d)Water〉 There are no particular limitations on the water that can be used in the water-in-oil emulsion cosmetic of the present disclosure, and water that is used in cosmetics, quasi-drugs, etc. Specifically, for example, ion-exchanged water, distilled water, ultrapure water, and tap water can be used.

[0054] It has been known that in systems with relatively low amounts of water, such as water-in-oil emulsion cosmetics, when zinc oxide-based particles are used in combination with a drug such as tranexamic acid, crystals derived from the drug and zinc oxide-based particles (e.g., zinc tranexamate) are formed. Although the water-in-oil emulsion cosmetic of the present disclosure contains a low amount of water, at 14.0% by mass or more and less than 30.0% by mass, by employing zinc oxide-based particles of a specific size, it is possible to reduce or inhibit crystallization that occurs when used in combination with a drug such as tranexamic acid.

[0055] The amount of water can be, for example, 14.0% by mass or more, 14.5% by mass or more, 15.0% by mass or more, 15.5% by mass or more, or 16.0% by mass or more relative to the total amount of the cosmetic, and can also be less than 30.0% by mass, 29.0% by mass or less, 28.0% by mass or less, 27.0% by mass or less, 26.0% by mass or less, 25.5% by mass or less, or 25.0% by mass or less.

[0056] <Optional ingredients> In addition to the various components described above, the water-in-oil emulsion cosmetic of the present disclosure may contain optional components (for example, various additive components that can be typically added to cosmetics) within a range that does not adversely affect the effects of the present invention. Examples of such optional ingredients include surfactants, moisturizers (e.g., 1,3-butylene glycol, propylene glycol, dynamite glycerin), water-soluble polymers, oil-soluble polymers, film-forming agents, sequestering agents, neutralizing agents, lower alcohols (e.g., ethanol), polyhydric alcohols (e.g., PEG 6000 and dipropylene glycol), higher alcohols (e.g., batyl alcohol), various extracts, sugars, amino acids, organic amines, polymer emulsions, chelating agents, UV absorbers, UV scattering agents (e.g., titanium oxide), pH adjusters, skin nutrients, vitamins, water-soluble drugs applicable to pharmaceuticals, quasi-drugs, cosmetics, etc., transdermal absorption inhibitors, antioxidants, buffers, preservatives, antioxidant aids, thickeners (e.g., disteardimonium hectorite, sodium polyacrylate), dispersants, propellants, usable powders (e.g., silica), colorants (e.g., pigments, pearlescent agents, dyes, colorants), fragrances, acidic components, and alkaline components. These optional ingredients can be used alone or in combination of two or more, and can be appropriately blended into the oil phase or the aqueous phase. Some of the optional ingredients will now be described in detail.

[0057] (surfactant) Surfactants (emulsifiers) are generally present near the interface between the aqueous phase and the oil phase, i.e., near the periphery of the water droplets, with some dispersed in the oil. The surfactants that can be used in the water-in-oil emulsion cosmetic of the present disclosure are not particularly limited, and known surfactants (e.g., anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants) can be used alone or in combination of two or more. Among these, silicone-based surfactants and hydrocarbon-based surfactants are preferred, with silicone-based surfactants being more preferred, from the standpoints of crystallization reduction or inhibition effect, emulsion stability, redispersibility, etc.

[0058] Examples of hydrocarbon surfactants that can be used include glyceryl diisostearate, PEG-4 sorbitan triisostearate, POE (2) stearyl ether, self-emulsifying propylene glycol monostearate, glyceryl myristate, glyceryl monostearate, self-emulsifying glyceryl monostearate, glyceryl monoisostearate, glyceryl monooleate, hexaglyceryl tristearate, decaglyceryl pentastearate, decaglyceryl pentaisostearate, decaglyceryl pentaoleate, sorbitan monostearate, sorbitan tristearate, POE (6) sorbitan hexastearate, POE (3) castor oil, PEG (2) monostearate, and ethylene glycol monostearate.

[0059] As the silicone surfactant, for example, a silicone surfactant modified with a polyether group or a polyglycerin group can be used.

[0060] Examples of silicone surfactants modified with a polyether group include PEG-11 methyl ether dimethicone, PEG-10 dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone, and cetyl PEG / PPG-10 / 1 dimethicone. Of these, PEG-10 dimethicone and PEG-9 polydimethylsiloxyethyl dimethicone are preferred from the standpoints of reducing or inhibiting crystallization, emulsion stability, redispersibility, etc.

[0061] Examples of silicone surfactants modified with a polyglycerin group include polyglyceryl-3 disiloxane dimethicone, polyglyceryl-3 polydimethylsiloxyethyl dimethicone, and lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone.

[0062] The surfactant can be appropriately blended to obtain the desired performance (e.g., emulsion stability and redispersibility). Specifically, the blending amount can be, for example, 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, and 8.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, or 3.0% by mass or less, relative to the total amount of the cosmetic.

[0063] (ultraviolet absorber) The UV absorber is not particularly limited, and known inorganic or organic UV absorbers can be used alone or in combination. Examples of organic UV absorbers include octyl methoxycinnamate (ethylhexyl methoxycinnamate), octocrylene, polysilicone-15, t-butyl methoxydibenzoylmethane, ethylhexyl triazone, bisethylhexyloxyphenol methoxyphenyl triazine, diethylaminohydroxybenzoyl hexyl benzoate, oxybenzone-3, methylenebisbenzotriazolyltetramethylbutylphenol, homosalate, drometrizole trisiloxane, and ethylhexyl salicylate. Such organic UV absorbers can also be considered polar oils with an IOB of 0.10 or more.

[0064] The ultraviolet absorber can be appropriately blended to obtain the desired performance (e.g., sunscreen performance). Specifically, the blending amount can be, for example, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 8.0% by mass or more, and 20.0% by mass or less, 15.0% by mass or less, 13.0% by mass or less, 10.0% by mass or less, or 9.0% by mass or less, relative to the total amount of the cosmetic.

[0065] (dispersant) In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure contains a dispersant. A water-in-oil emulsion cosmetic containing a dispersant can improve emulsion stability and redispersibility of zinc oxide-based particles, etc. The dispersants can be used alone or in combination.

[0066] Examples of dispersants include polyglycerin-modified silicones (e.g., polyglyceryl-3 polydimethylsiloxyethyl dimethicone, polyglyceryl-3 disiloxane dimethicone, bisbutyl dimethicone polyglyceryl-3, and lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone), glycerin fatty acid esters (e.g., polyglyceryl-6 polyricinoleate), liquid higher fatty acids (e.g., isostearic acid, oleic acid, linoleic acid, and linolenic acid), and sorbitan fatty acid esters (e.g., sorbitan isostearate, sorbitan sesquioleate, sorbitan sesquiisostearate, and sorbitan trioleate). Here, liquid higher fatty acids refer to higher fatty acids that are liquid at room temperature (e.g., 25°C). Of these, isostearic acid is preferred from the viewpoint of emulsion stability and redispersibility, and it is more preferred to use isostearic acid in combination with sorbitan sesquiisostearate.

[0067] The dispersant can be appropriately blended to obtain the desired performance (e.g., emulsion stability and redispersibility). Specifically, the blending amount can be, for example, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, and can be 8.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less, relative to the total amount of the cosmetic.

[0068] <Performance of water-in-oil emulsion cosmetics> The water-in-oil emulsion cosmetic of the present disclosure exhibits at least the effect of reducing or inhibiting crystallization, and in some embodiments, may also exhibit other concomitant effects.

[0069] (Crystallization reduction or suppression performance) In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure can exhibit an "A" rating, i.e., a rating of "no crystal precipitation," in the crystallization test described below.

[0070] (Emulsification stability) In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure can exhibit an "A" rating, i.e., a rating of "no gelation," in the emulsion stability test described below.

[0071] (Redispersibility) In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure can exhibit an "A" rating, i.e., a rating of "no sediment and redispersed," in the redispersibility test described below.

[0072] (viscosity) In some embodiments, the water-in-oil emulsion cosmetic of the present disclosure can be a low-viscosity cosmetic, which can result in good spreadability and usability. The viscosity of the cosmetic can be evaluated using the viscosity test described below. For example, the viscosity immediately after preparation of the cosmetic and / or after leaving it in a 25°C atmosphere for 4 weeks can be 10,000 mPa·s or less, 8,000 mPa·s or less, 6,000 mPa·s or less, 5,000 mPa·s or less, or 4,500 mPa·s or less. There is no particular restriction on the lower limit of the viscosity, and the viscosity can be, for example, 500 mPa·s or more, 1,000 mPa·s or more, 2,000 mPa·s or more, 3,000 mPa·s or more, or 4,000 mPa·s or more.

[0073] <<Uses of water-in-oil emulsion cosmetics>> The product form of the water-in-oil emulsion cosmetic of the present disclosure is not particularly limited, and examples include skin care cosmetics such as emulsions, creams, face oils, body oils, and serums; makeup cosmetics such as foundations, makeup bases, lipsticks, blushers, eye shadows, mascara, and mascara bases; skin cleansers such as makeup removers; hair cleansers; hair cosmetics such as hair treatments and hair oils; sunscreen cosmetics; hair dyes, etc. In particular, the water-in-oil emulsion cosmetic of the present disclosure can be suitably used as a sunscreen cosmetic because the zinc oxide-based particles can suitably block ultraviolet rays or convert ultraviolet rays into light suitable for the skin.

[0074] <<Method for producing water-in-oil emulsion cosmetics>> The water-in-oil emulsion cosmetic of the present disclosure can be produced by a conventional method. For example, zinc oxide particles and a surfactant are added to an oil component and stirred to prepare a base, and an aqueous solution containing a drug such as tranexamic acid is added to the base and stirred to obtain a water-in-oil emulsion cosmetic. If necessary, the above-mentioned optional ingredients may be appropriately blended with the water or oil component, and heating means may also be applied.

[0075] The water-in-oil emulsion cosmetic of the present disclosure can be prepared by using known methods such as a dispersion method and an aggregation method.

[0076] The dispersion method is a method of mechanically breaking down clumps of the dispersed phase into smaller particles. Specifically, it is a method of emulsifying by utilizing the crushing force of an emulsifier, and examples of such methods include high-pressure emulsification, in which high shear force is applied using a high-pressure homogenizer.

[0077] The aggregation method is a colloid preparation method that utilizes surface chemistry characteristics, in which a uniformly dissolved state is made supersaturated by some means to produce a dispersed phase. Specific methods include HLB temperature emulsification, phase inversion emulsification, non-aqueous emulsification, D-phase emulsification, and liquid crystal emulsification. [Example]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the blending amounts are expressed in mass %. Furthermore, the various evaluation methods described in the examples are not limited to the cosmetic preparations described in the examples, but can also be applied to cosmetic preparations containing the above-mentioned components.

[0079] Examples 1 to 11 and Comparative Examples 1 to 6 Test samples of water-in-oil emulsion cosmetics were prepared by conventional methods using the formulations shown in Table 1. The following tests were carried out on these samples. The results are shown in Table 1.

[0080] Evaluation Method (Crystallization test) The test sample was left in a thermostatic chamber at 70°C for one week, and then evaluated for the presence or absence of crystal precipitation as follows, where a rating of A is considered to be a pass, and ratings of B and C are considered to be a fail: A: No crystal precipitation. B: Crystal precipitation is observed. C: Compared to the B grade, there is significant crystal precipitation.

[0081] (Emulsion stability test) The test sample was left to stand in an atmosphere at 25°C for 4 weeks, and then evaluated for the presence or absence of gelation as follows: A: No gelation. B: Gelling occurred. C: Compared to the B grade, gelation was significant.

[0082] (Redispersibility test) A 100 mL test sample was placed in a lidded container with a diameter of approximately 2 cm and a height of approximately 25 cm. The container containing the test sample was inverted 10 times to mix and completely disperse the particles in the test sample. The test sample was then placed on a horizontal surface to allow the particles in the test sample to settle. After being placed, the test sample was vigorously shaken by hand 10 times, and the sediment that had accumulated at the bottom of the container was evaluated as follows: A: No sediment was found and the product was redispersed. B: Some of the sediment remained without being redispersed. C: The precipitate did not redisperse.

[0083] (Viscosity evaluation test) The viscosity of the test sample immediately after preparation was measured using a VDA type viscometer (Shibaura Systems Co., Ltd., DIGITAL VISMETRON VDA) with rotor No. 3 or No. 4 at a rotation speed of 12 rpm for 1 minute. The measured viscosity was evaluated as follows: A: Viscosity was 5,000 mPa·s or less. B: Viscosity was greater than 5,000 mPa·s and less than 10,000 mPa·s. C: Viscosity was over 10,000 mPa·s.

[0084] [Table 1]

[0085] <result> As can be seen from the results of Examples 1 to 3 and Comparative Examples 1 to 4, it was confirmed that crystallization can be suppressed when the average particle size of the zinc oxide based particles is increased.

[0086] As can be seen from the results of Examples 2 and 3, the hydrophobic treatment of zinc oxide-based particles does not have an adverse effect on the suppression of crystallization, and on the other hand, it has been found to improve emulsion stability and redispersibility.

[0087] As can be seen from the results of Examples 4 to 7, it was confirmed that when zinc oxide-based particles with a large average particle size are used, crystallization can be suppressed even if the amount of water is as small as less than 30 mass %. On the other hand, the result of Comparative Example 5 revealed that more than 13 mass % of water is required to suppress crystallization.

[0088] As can be seen from the results of Examples 1, 8, and 9, the use of a dispersant does not have an adverse effect on the suppression of crystallization, while the use of isostearic acid, more preferably isostearic acid and sorbitan sesquiisostearate, as a dispersant can contribute to improving emulsion stability and redispersibility.

[0089] As can be seen from the results of Example 10, it was confirmed that the use of zinc oxide-based particles with a large average particle size can also have an effect of inhibiting crystallization of ascorbic acid-based drugs. Furthermore, the results of Comparative Example 6 showed that more than 13 mass % of water is required to inhibit crystallization even in ascorbic acid-based drugs.

[0090] As can be seen from the results of Example 11, it was confirmed that the effect of suppressing crystallization can be achieved by using zinc oxide-based particles with a large average particle size, even without using silica-coated zinc oxide-based particles.

Claims

1. (a) zinc oxide-based particles, (b) a drug, (c) oils, and (d) 14.0% by mass or more and less than 30.0% by mass of water; Including, The (a) zinc oxide-based particles have an average particle size of 1.0 μm or more, and the drug (b) is at least one selected from the group consisting of tranexamic acid, tranexamic acid salts, tranexamic acid derivatives, ascorbic acid, ascorbic acid salts, and ascorbic acid derivatives; Water-in-oil emulsion cosmetics.

2. 2. The cosmetic according to claim 1, wherein the content of the zinc oxide-based particles (a) is 1.0% by mass or more.

3. The cosmetic preparation according to claim 1 or 2, wherein the zinc oxide-based particles (a) are hydrophobic particles.

4. The cosmetic according to claim 3 , wherein the zinc oxide-based particles (a) have a moiety derived from a fatty acid.

5. 3. The cosmetic according to claim 1, wherein the amount of silica coated on the zinc oxide-based particles (a) is less than 7.0% by mass.

6. 3. The cosmetic according to claim 1, wherein the (a) zinc oxide-based particles comprise at least one selected from the group consisting of zinc oxide particles and zinc oxide phosphor particles.

7. The cosmetic preparation according to claim 1 or 2, wherein the content of the agent (b) is 1.0% by mass or more.

8. The cosmetic preparation according to claim 1 or 2, further comprising (e) a dispersing agent.

9. The cosmetic preparation according to claim 8, wherein the dispersant (e) comprises isostearic acid.

10. The cosmetic preparation according to claim 8, wherein the dispersant (e) comprises isostearic acid and sorbitan sesquiisostearate.

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