Sunscreen cosmetics

Abstract

The purpose of the present invention is to provide a sunscreen cosmetic in which an eco-friendly and highly waterproof powdery component is used as a substitute for microplastic beads or silica so that high ultraviolet protective performance can be achieved even by using a small amount of an ultraviolet protecting agent, further, which has characteristics of showing an improved ultraviolet protective effect upon contact with water, sweat, etc., compared to the effect immediately after application and which has excellent usability.　The sunscreen cosmetic according to the present invention is characterized by comprising (A) an oily phase thickener, (B) an ultraviolet protective agent, and (C) a wax powder having a volume average particle size of 1-30 μm.

Description

[Technical Field]

[0001] The present invention relates to a sunscreen cosmetic, and more specifically, to a sunscreen cosmetic that can achieve high UV protection by incorporating an oil phase thickener and a specific wax powder without incorporating a large amount of UV protection agent, and that has the property that the UV protection effect improves upon contact with water, sweat, etc. compared to immediately after application, and that is also easy to use. [Background technology]

[0002] Protecting skin from the harmful effects of ultraviolet rays is one of the important issues in skin care and body care, and various UV care cosmetics have been developed to minimize the adverse effects of ultraviolet rays on the skin. Sunscreen cosmetics, one type of UV care cosmetic, are cosmetics that are intended to protect the skin from the harmful effects of ultraviolet rays by covering the skin with a coating film containing ultraviolet protection agents such as ultraviolet absorbers and ultraviolet scattering agents, thereby absorbing or scattering UVA and UVB rays and reducing the amount of ultraviolet rays that reach the skin (Non-Patent Document 1).

[0003] UV absorbers are incorporated into many sunscreen cosmetics because they provide high UV protection, are compatible with the skin, and are resistant to sweat and water. However, some UV absorbers generate heat or undergo chemical reactions when absorbing UV rays, causing redness, itching, and even allergies on the skin. For example, ethylhexyl methoxycinnamate (octyl methoxycinnamate) has traditionally been widely used in sunscreen cosmetics as a representative UV absorber that absorbs UVB, but it can be a burden for users with sensitive skin. Patent Document 1 proposes incorporating dimethyl ether into topical skin preparations to mitigate the irritation caused by ethylhexyl methoxycinnamate.

[0004] Furthermore, many UV absorbers are solid at room temperature, and a certain amount of oil is required to stably dissolve them in cosmetics without precipitating. Therefore, incorporating a high amount of UV absorber necessitates an increase in the amount of oil, which can cause stickiness and impair the feel of use. Therefore, instead of incorporating a high amount of oil-soluble UV absorber, a water-soluble UV absorber may be incorporated. However, water-soluble UV absorbers generally tend to have inferior UV protection power compared to oil-soluble ones, and it is difficult to achieve sufficient UV protection power even when incorporating a high amount of water-soluble UV absorber. Furthermore, when a water-soluble UV absorber is incorporated, the stability of the cosmetic may be reduced due to the influence of the salt (neutralizing salt) incorporated therewith.

[0005] In light of these circumstances, it has been proposed to use UV scattering agents that are relatively gentle on the skin instead of UV absorbers, and cosmetics that claim to be "UV absorber-free" or "chemical-free" have been marketed. For example, Patent Document 2 discloses a sunscreen cosmetic that contains hydrophobized zinc oxide and / or hydrophobized titanium oxide as a UV scattering agent, does not contain any organic UV absorbers, and has excellent UV protection effect, emulsion stability, and usability. Furthermore, Patent Document 3 proposes blending multiple powder components with UV scattering properties without containing UV absorbers such as ethylhexyl methoxycinnamate, which can cause irritation if it gets into the eyes.

[0006] However, in order to obtain a high UV protection effect using only UV scattering agents, it is necessary to incorporate a large amount of UV scattering agents, which may result in an unnatural white appearance (white cast) when applied to the skin, or may result in poor usability in terms of spreadability and compatibility with the skin.

[0007] Therefore, there is a need to achieve a higher UV protection effect while keeping the blending amount of these UV protection agents low. As a result of investigations by the present inventors, it has been found that the UV protection effect can be improved by blending particles made of silica, silicone polymer, polymethyl methacrylate, etc.

[0008] However, as the problem of environmental pollution caused by plastics becomes more serious every year, the movement to eliminate plastic microbeads is accelerating in the cosmetics industry as well, and it is preferable to avoid using silicone polymers, polymethyl methacrylate, etc., which may fall under the category of plastic microbeads. There is no established definition of microplastic beads, and they may refer only to the scrub beads used in rinse-off products. However, in this specification, the term refers to solid plastic particles with a diameter of 5 mm or less, such as polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, acrylate copolymers, and silicone polymers.

[0009] On the other hand, although silica does not fall under the category of microplastic beads, it has poor water resistance, and when it comes into contact with water, sweat, etc., its UV protection effect tends to decrease compared to immediately after application. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 3683533 [Patent Document 2] Patent No. 5554308 [Patent Document 3] Patent No. 5813745 [Non-patent literature]

[0011] [Non-Patent Document 1] "New Cosmetics Science", 2nd edition, edited by Takeo Mitsui, 2001, Nanzando Publishing, pp. 497-504 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a sunscreen cosmetic that is easy to use and that can achieve high UV protection even with the use of a small amount of UV protection agent by incorporating an environmentally friendly, highly water-resistant powder component that can replace microplastic beads or silica, and that has the property that the UV protection effect improves upon contact with water, sweat, etc. compared to immediately after application. [Means for solving the problem]

[0013] As a result of intensive research conducted by the present inventors to solve the above problems, they discovered that by blending an oil phase thickener and a specified wax powder into a sunscreen cosmetic containing an ultraviolet protection agent, a uniform coating film with excellent water resistance is formed on the skin, thereby improving the ultraviolet protection ability and, moreover, achieving excellent usability, which led to the completion of the present invention.

[0014] That is, the present invention provides the following components (A) to (C): (A) an oil phase thickener, (B) UV protection agents, and (C) Wax powder having a volume average diameter of 1 to 30 μm The gist of the present invention is a sunscreen cosmetic containing the above. [Effects of the Invention]

[0015] By adopting the above-mentioned configuration, the present invention can improve the ultraviolet protection power of the coating film and also realize a sunscreen cosmetic that is easy to use. Wax powder is also more environmentally friendly than microplastic beads, which do not decompose naturally and remain semi-permanently. Furthermore, wax powder is highly water-resistant, meaning its UV protection effect does not decrease when it comes into contact with water or sweat, as does silica.

[0016] Furthermore, the amount of UV absorbers, which can be harmful to the skin, can be kept to a minimum, making it possible to provide a highly safe sunscreen cosmetic.Furthermore, since a high level of UV protection is achieved without the need for a high amount of UV scattering agents, the white cast and poor skin compatibility that are typical of UV scattering agents are unlikely to occur. DETAILED DESCRIPTION OF THE INVENTION

[0017] The sunscreen cosmetic of the present invention is characterized by containing (A) an oil phase thickener, (B) an ultraviolet protection agent, and (C) a wax powder. Each component constituting the cosmetic of the present invention will be described in detail below.

[0018] <(A) Oil phase thickener> The oil phase thickener (A) of the present invention can be appropriately selected from substances used as components that thicken the oil phase by dissolving in oil or swelling with oil in ordinary cosmetics, etc. For example, it is preferable to blend one or more selected from dextrin fatty acid esters, sucrose fatty acid esters, glyceryl fatty acid esters, amino acid-based thickeners, acrylic polymers, solid or semi-solid hydrocarbon oils, fatty acids or their salts, etc.

[0019] The dextrin fatty acid ester is an ester of dextrin or reduced dextrin with a higher fatty acid, and any dextrin commonly used in cosmetics can be used without any particular limitation. It is preferable to use dextrin or reduced dextrin with an average degree of glycopolymerization of 3 to 100. Furthermore, it is preferable to use saturated fatty acids having 8 to 22 carbon atoms as the constituent fatty acids of the dextrin fatty acid ester. Specific examples include dextrin palmitate, dextrin oleate, dextrin stearate, dextrin myristate, and dextrin (palmitate / 2-ethylhexanoate).

[0020] The sucrose fatty acid ester can preferably be one in which the fatty acid is linear or branched, saturated or unsaturated, and has a carbon number of 12 to 22. Specific examples include sucrose caprylate, sucrose caprate, sucrose laurate, sucrose myristate, sucrose palmitate, sucrose stearate, sucrose oleate, and sucrose erucate.

[0021] Glyceryl fatty acid esters are esterification reaction products obtained by reacting glycerin, a dibasic acid having 18 to 28 carbon atoms, and a fatty acid having 8 to 28 carbon atoms (excluding dibasic acids), and any glyceryl fatty acid commonly used in cosmetics can be used without particular limitation. Specific examples include glyceryl (behenate / isostearate / eicosanedioate), glyceryl (behenate / eicosanedioate), and polyglyceryl-10 (behenate / eicosanedioate).

[0022] Examples of amino acid thickeners include dibutyl lauroyl glutamide, dibutyl ethyl hexanoyl glutamide, polyamide-8, and polyamide-3.

[0023] Examples of the acrylic polymer include ester polymers of acrylic acid and aliphatic alcohol, and for example, polyalkyl acrylate (C10-30) can be suitably used.

[0024] The solid or semi-solid hydrocarbon oil is a hydrocarbon that is solid or semi-solid at room temperature (25°C), and specific examples include petrolatum, hydrogenated palm oil, hydrogenated castor oil (castor wax), hydrogenated palm kernel oil, hydrogenated castor oil, hydrogenated peanut oil, hydrogenated rapeseed seed oil, hydrogenated camellia oil, hydrogenated soybean oil, hydrogenated olive oil, hydrogenated macadamia nut oil, hydrogenated sunflower oil, hydrogenated wheat germ oil, hydrogenated rice germ oil, hydrogenated rice bran oil, hydrogenated cottonseed oil, hydrogenated avocado oil, and waxes.

[0025] The fatty acid is not particularly limited as long as it can be used in cosmetics and the like, and can be selected from fatty acids having a linear or branched, saturated or unsaturated hydrocarbon group. Particularly preferred are higher fatty acids that are solid at room temperature and have 8 to 22 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid (behenic acid), oleic acid, isomyristic acid, and isopalmitic acid. Among these, it is particularly preferred to use one or more fatty acids selected from stearic acid, palmitic acid, and behenic acid. Examples of fatty acid salts include metal salts such as sodium salts, calcium salts, magnesium salts, and aluminum salts. Furthermore, amide derivatives and ester derivatives of fatty acids can also be used.

[0026] The amount of oil phase thickener (A) in the sunscreen cosmetic of the present invention is adjusted so that the moisture content of the coating film when it comes into contact with water is sufficient for the oil phase thickener to migrate within the coating film. Specifically, the amount of oil phase thickener (A) can be 0.3 to 4 mass%, preferably 0.5 to 4 mass%, and more preferably 0.5 to 3 mass% of the total amount of the sunscreen cosmetic. In particular, a blending amount of oil phase thickener (A) of 4 mass% or less is preferred, as it provides a smooth and pleasant feel to the touch.

[0027] <(B) UV Protection Agent (UV Absorber and / or UV Scatterer)> The ultraviolet protection agent (B) in the present invention means an ultraviolet absorbing agent and / or an ultraviolet scattering agent, and those that are usually incorporated into cosmetics can be used.

[0028] Examples of ultraviolet absorbers include benzoic acid derivatives, salicylic acid derivatives, cinnamic acid derivatives, dibenzoylmethane derivatives, β,β-diphenylacrylate derivatives, benzophenone derivatives, benzylidene camphor derivatives, phenylbenzimidazole derivatives, triazine derivatives, phenylbenzotriazole derivatives, anthranil derivatives, imidazoline derivatives, benzalmalonate derivatives, 4,4-diarylbutadiene derivatives, etc. Specific examples and trade names are listed below, but the present invention is not limited to these.

[0029] Examples of benzoic acid derivatives include ethyl para-aminobenzoate (PABA), ethyl-dihydroxypropyl PABA, ethylhexyl-dimethyl PABA (e.g., Escarol 507; ISP), glyceryl PABA, PEG-25-PABA (e.g., Uvinal P25; BASF), and diethylaminohydroxybenzoylhexyl benzoate (e.g., Uvinal A Plus).

[0030] Examples of salicylic acid derivatives include homosalate (Eusolex HMS; Rona / EM Industries), ethylhexyl salicylate or octyl salicylate (e.g., NeoHeliopan OS; Herman & Reimer), dipropylene glycol salicylate (e.g., Dipsal; Skell), and TEA salicylate (e.g., NeoHeliopan TS; Herman & Reimer).

[0031] Examples of cinnamic acid derivatives include octyl methoxycinnamate or ethylhexyl methoxycinnamate (e.g., Parsol MCX; Hoffmann-La Roche), isopropyl methoxycinnamate, isoamyl methoxycinnamate (e.g., Neo Heliopan E1000; Herman & Reimer), cinnoxate, DEA methoxycinnamate, diisopropyl methylcinnamate, glyceryl ethylhexanoate dimethoxycinnamate, and di-(2-ethylhexyl)-4'-methoxybenzalmalonate.

[0032] Examples of dibenzoylmethane derivatives include 4-tert-butyl-4'-methoxydibenzoylmethane (for example, Parsol 1789).

[0033] Examples of β,β-diphenylacrylate derivatives include octocrylene (for example, "Uvinal N539T"; BASF).

[0034] Examples of benzophenone derivatives include benzophenone-1 (e.g., "Uvinal 400"; BASF), benzophenone-2 (e.g., "Uvinal D50"; BASF), benzophenone-3 or oxybenzone (e.g., "Uvinal M40"; BASF), benzophenone-4 (e.g., "Uvinal MS40"; BASF), benzophenone-5, benzophenone-6 (e.g., "Helisorb 11"; Norquay), benzophenone-8 (e.g., "Spectra-Sorb UV-24"; American Cyanamid), benzophenone-9 (e.g., "Uvinal DS-49"; BASF), and benzophenone-12.

[0035] Examples of benzylidene camphor derivatives include 3-benzylidene camphor (e.g., "Mexoryl SD"; Cimex), 4-methylbenzylidene camphor, benzylidene camphorsulfonic acid (e.g., "Mexoryl SL"; Cimex), benzalkonium camphor methosulfate (e.g., "Mexoryl SO"; Cimex), terephthalidene discamphorsulfonic acid (e.g., "Mexoryl SX"; Cimex), and polyacrylamidomethyl benzylidene camphor (e.g., "Mexoryl SW"; Cimex).

[0036] Examples of phenylbenzimidazole derivatives include phenylbenzimidazole sulfonic acid (e.g., "Eusolex 232"; Merck) and disodium phenyldibenzimidazole tetrasulfonate (e.g., "Neo Heliopan AP"; Herman & Reimer).

[0037] Examples of triazine derivatives include bisethylhexyloxyphenol methoxyphenyl triazine (e.g., "Tinosorb S"; Ciba Specialty Chemicals), ethylhexyl triazone (e.g., "Uvinal T150"; BASF), diethylhexylbutamido triazone (e.g., "Uvasorb HEB"; Sigma-3V), 2,4,6-tris(diisobutyl-4'-aminobenzalmalonate)-s-triazine, and 2,4,6-tris[4-(2-ethylhexyloxycarbonyl)anilino]-1,3,5-triazine.

[0038] Examples of phenylbenzotriazole derivatives include drometrizole trisiloxane (e.g., "Silatrizole"; Rhodia-Chemie), methylenebis(benzotriazolyltetramethylbutylphenol) (e.g., "Tinosorb M"; Ciba Specialty Chemicals).

[0039] Examples of anthranil derivatives include menthyl anthranilate (for example, "Neo Heliopan MA"; Herman & Reimer).

[0040] Examples of imidazoline derivatives include ethylhexyldimethoxybenzylidene dioxoimidazoline propionate.

[0041] Examples of benzalmalonate derivatives include polyorganosiloxanes having benzalmalonate functional groups (for example, polysilicone-15; "Parsol SLX"; DSM Nutrition Japan).

[0042] Examples of 4,4-diarylbutadiene derivatives include 1,1-dicarboxy(2,2'-dimethylpropyl)-4,4-diphenylbutadiene.

[0043] Particularly preferred examples of the ultraviolet absorber include octocrylene, octyl salicylate, and homosalate, and it is preferable to include at least one of these.

[0044] The ultraviolet scattering agent is not particularly limited, but examples thereof include fine particle metal oxides such as zinc oxide, titanium oxide, iron oxide, cerium oxide, and tungsten oxide.

[0045] The ultraviolet scattering agent may be untreated or may be subjected to various hydrophobic surface treatments, but those subjected to hydrophobic surface treatments are preferably used. Surface treatment agents that can be used include those commonly used in the field of cosmetics, such as silicones such as dimethicone and alkyl-modified silicone, alkoxysilanes such as octyltriethoxysilane, dextrin fatty acid esters such as dextrin palmitate, and fatty acids such as stearic acid.

[0046] The ultraviolet protection agent (B) in the present invention includes an embodiment consisting of only an ultraviolet absorber, an embodiment consisting of only an ultraviolet scattering agent, and an embodiment containing both an ultraviolet absorber and an ultraviolet scattering agent.

[0047] The blending amount of (B) UV protection agent is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 10 to 20% by mass, based on the total amount of the sunscreen cosmetic. If the blending amount of (B) UV protection agent is less than 5% by mass, it is difficult to obtain a sufficient UV protection effect, and even if it is blended in more than 40% by mass, it is not possible to expect an increase in UV protection effect commensurate with the blending amount, and it is not preferable in that it actually deteriorates stability and usability.

[0048] <(C) Wax Powder> The wax powder (C) in the present invention is a powder obtained by pulverizing wax having a melting point of 35°C or higher, more preferably 80°C or higher, and is not particularly limited as long as it can be blended into cosmetics. The wax constituting the wax powder is not limited to a specific wax, but wax powder of natural origin is preferred because it has a low environmental impact. Examples of such waxes include carnauba wax, rice bran wax, beeswax, biodegradable wax, microcrystalline wax, and paraffin wax. Among these, carnauba wax and rice bran wax are particularly preferred.

[0049] The method for powdering the wax is not particularly limited, and any known pulverization method can be used. Specific examples include a method of mechanically pulverizing the wax using a jetmizer or the like, and a method of dissolving the wax in a volatile solvent and spray-drying the resulting solution. The volume average diameter of the wax powder is in the range of 1 to 30 μm, more preferably in the range of 1 to 20 μm, and even more preferably in the range of 5 to 15 μm. The volume average diameter can be measured in accordance with the standard test method for particle size distribution by laser light scattering (ASTM D4464).

[0050] The blending amount of (C) wax powder is preferably 0.5 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass, of the total amount of the sunscreen cosmetic. If the blending amount of (C) wax powder is less than 0.5% by mass, it becomes difficult to obtain a sufficient improvement in UV protection power, and if it is blended in more than 20% by mass, usability tends to deteriorate.

[0051] <Optional ingredients> In addition to the above components (A) to (C), the sunscreen cosmetic of the present invention may contain other components commonly used in cosmetics, provided that the effects of the present invention are not impaired. For example, gelling agents, surfactants, oils, aqueous components, powder components, pH adjusters, chelating agents, preservatives, antioxidants, drugs, alcohols, coloring agents, pigments, etc. may be appropriately blended as needed.

[0052] In particular, it is preferable to incorporate (D) an organically modified clay mineral as a gelling agent in an amount of about 0.1 to 2% by mass based on the total amount of the sunscreen cosmetic, as this can further improve stability and usability. (D) Organically modified clay minerals are a type of colloidal hydrous aluminum silicate with a three-layer structure, and are typically clay minerals represented by the following general formula (1) modified with a quaternary ammonium salt-type cationic surfactant. (X,Y) 2―3 (Si,Al)O 10 (OH)2Z 1 / 3 nH2O (1) (However, X=Al, Fe(III), Mn(III), Cr(III), Y=Mg, Fe(II), Ni, Zn, Li, Z=K, Na, Ca)

[0053] Specific examples include dimethyl distearammonium hectorite (disteardimonium hectorite), dimethyl alkyl ammonium hectorite, benzyl dimethyl stearyl ammonium hectorite, distearyl dimethyl ammonium chloride-treated magnesium aluminum silicate, etc. Commercially available products that can be used include Bentone 27 (benzyl dimethyl stearyl ammonium chloride-treated hectorite: manufactured by Elementis Japan Co., Ltd.) and Bentone 38 (distearyl dimethyl ammonium chloride-treated hectorite: manufactured by Elementis Japan Co., Ltd.). The blending amount of (D) organically modified clay mineral is preferably about 0.1 to 2 mass %, more preferably 0.2 to 2 mass %, and even more preferably 0.3 to 2 mass %, based on the total amount of the sunscreen cosmetic.

[0054] Furthermore, blending (E) usability-improving powder as a powder component in an amount of about 0.5 to 15 mass % relative to the total amount of the sunscreen cosmetic is preferable in terms of usability, as it spreads more easily on the skin. (E) The usability-improving powder is preferably a spherical powder, and examples thereof include cellulose powder, spherical silica, talc, mica, sericite, starch powder, and biodegradable resins. Among these, starch powder is preferred because it is naturally derived and has excellent water resistance.

[0055] The sunscreen cosmetic of the present invention can be provided in any form, but oil-based cosmetic and water-in-oil emulsion cosmetic are particularly preferred. Specific product forms include gel, emulsion, cream, lotion, etc., and can be produced using conventional methods suitable for each formulation.

[0056] In the sunscreen cosmetic of the present invention, the UV protection effect of the coating film is improved by contact with moisture. "The UV protection effect is improved by contact with moisture" can be roughly defined as follows. First, a predetermined amount of a cosmetic sample is dropped onto a measurement plate, applied to a predetermined area, and dried to form a coating film. The absorbance of the coating film is measured over a range of 400 to 280 nm using a spectrophotometer or the like, and the integrated absorbance value of the coating film before the water bath is determined using the absorbance of an uncoated measurement plate as a reference. Next, the measurement plate on which the coating film has been formed is immersed in water with a hardness of 50 to 500 at room temperature for about 20 minutes to 1 hour, and after drying for about 10 to 30 minutes, the absorbance of the coating film is measured and the integrated absorbance value after the water bath is calculated in the same manner.

[0057] The rate of change in the integrated absorbance value after the water bath treatment is calculated according to the following formula. [Change in absorbance after water bath (%)] = ([integrated absorbance value after water bath] / [integrated absorbance value before water bath]) x 100 When the rate of change in the integrated absorbance value exceeds 100%, it is defined that the UV protection effect is improved. In the cosmetic of the present invention, the rate of change in the integrated absorbance value exceeds at least 100%, preferably 103% or more, more preferably 105% or more, even more preferably 110% or more, and particularly preferably 115% or more. [Example]

[0058] The present invention will be described in further 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 % relative to the total amount of the sunscreen cosmetic. Before describing each example in detail, the evaluation methods used will be explained.

[0059] <Improvement rate of UV protection (SPF boost effect)> Each sample was applied at 2 mg / cm to an S-plate (5 x 5 cm V-groove PMMA plate, SPFMASTER-PA01). 2 The solution was dropped onto the plate in an amount of 100 ml, applied with a finger for 60 seconds, and then allowed to dry for 15 minutes to form a coating film. Using an uncoated plate as a control, the absorbance of the coating film (400-280 nm) was measured using a Hitachi U-3500 self-recording spectrophotometer, and the integrated absorbance value was calculated from the obtained measurement data. Abs=-log(T / To) T: transmittance of sample, To: transmittance of uncoated sample Using Comparative Example 1, which did not contain wax powder, as a standard, the SPF boost effect was calculated using the following formula and evaluated based on the following evaluation criteria. [SPF Boost Effect (%)] = ([Sample Abs] / [Comparative Example 1 Abs]) x 100 "Evaluation Criteria" A: SPF boost effect of 110% or more B: SPF boost effect is 100% or more but less than 110% C: SPF boost effect is less than 100%

[0060] <Change rate of integrated absorbance value after water bath (Abs change rate after water bath)> Each sample was applied at 2 mg / cm to an S-plate (5 x 5 cm V-groove PMMA plate, SPFMASTER-PA01). 2 The plate was then applied with a finger for 60 seconds and allowed to dry for 15 minutes to form a coating film. Using an uncoated plate as a control, the absorbance of the coating film (400-280 nm) was measured using a Hitachi U-3500 self-recording spectrophotometer, and the integrated absorbance value before the water bath was calculated from the obtained measurement data. Next, the plate was thoroughly immersed in water with a hardness of 50 to 500 and stirred in the water for 30 minutes (300 rpm with a 3-1 motor). After that, it was dried for 15 to 30 minutes until all water droplets on the surface disappeared, and the absorbance was measured again. The integrated absorbance value after the water bath was calculated from the obtained measurement data. The rate of change (%) in the integrated absorbance value after the water bath was calculated using the following formula and evaluated based on the following evaluation criteria. [Change in absorbance after water bath (%)] = ([integrated absorbance value after water bath] / [integrated absorbance value before water bath]) x 100 "Evaluation Criteria" A: The rate of change in the integrated absorbance value after water bath is 110% or more B: The rate of change in the integrated absorbance value after the water bath is 100% or more but less than 110% C: The change in the integrated absorbance value after the water bath is less than 100%.

[0061] <Usability> Each sample of the Examples and Comparative Examples was actually used by a panel of 10 experts, who evaluated its usability (e.g., spreadability upon application, non-stickiness). Each panelist was asked to perform a sensory evaluation on a 5-point scale according to the following evaluation criteria, and the total score was used to make a judgment based on the following evaluation criteria. "Evaluation criteria" 5: Excellent 4: Excellent 3: Normal 2: Inferior 1: Very poor "Evaluation Criteria" A: Total score is 40 or more B: Total score is 30-39 points C: Total score is 20-29 points D: Total score is 19 points or less

[0062] <Examples 1 to 6 and Comparative Examples 1 to 4> Water-in-oil sunscreen cosmetics were prepared having the compositions shown in Tables 1 and 2. According to the evaluation methods described above, the improvement rate of UV protection power (SPF boost effect), the rate of change in integrated absorbance value after bathing in water (rate of change in Abs after bathing in water), and usability were evaluated.

[0063] [Table 1] Wax powder A: Carnauba wax with a volume average particle size of 6 to 8 μm Wax powder B: A mixed wax of carnauba and rice bran wax with a volume average particle size of 4 to 14 μm Wax powder C: Carnauba wax with a volume average particle size of 100 μm Spherical silica: volume average particle size 5 μm

[0064] [Table 2] Wax powder A: Carnauba wax with a volume average particle size of 6 to 8 μm

[0065] As shown in Table 1 above, when an oil phase thickener and an ultraviolet protection agent were included, a relatively high ultraviolet protection effect was obtained even without adding wax powder, but the usability was significantly poor (Comparative Example 1). In contrast, when wax powder with a volume average diameter of 1 to 30 μm was blended in addition to the oil phase thickener and UV protection agent, the SPF boost effect and ease of use were clearly improved (Examples 1 to 3).Furthermore, it was found that the SPF boost effect and ease of use were improved by further blending an organically modified clay mineral as a gelling agent (Example 2). On the other hand, the incorporation of wax powder with a volume average diameter of 100 μm did not improve usability at all, and in fact resulted in a loss of UV protection effect (Comparative Example 2). Furthermore, when spherical silica was incorporated instead of wax powder, although usability was excellent, it was confirmed that the UV protection effect was significantly reduced by water bathing (Comparative Example 3). Since Comparative Example 2 exhibited significantly poorer SPF boosting effect and usability, measurement of the Abs change rate after water bathing was omitted.

[0066] As shown in Table 2 above, even when the type of oil phase thickener was changed, excellent results in SPF boost effect and ease of use were obtained (Examples 4 to 6). On the other hand, when no oil phase thickener was added, it was confirmed that the UV protection effect after bathing was significantly impaired (Comparative Example 4).

Claims

1. For the total amount of cosmetics, (A) oil phase thickener 0.3 to 4 mass%, (B) 5 to 40% by mass of an ultraviolet protection agent, and (C) Wax powder having a volume average diameter of 1 to 30 μm: 0.5 to 20% by mass containing Water-in-oil emulsion sunscreen cosmetic.

2. 2. The water-in-oil emulsion sunscreen cosmetic according to claim 1, wherein the wax constituting the wax powder (C) is one or more waxes selected from the group consisting of carnauba wax, rice bran wax, beeswax, biodegradable wax, microcrystalline wax, and paraffin wax.

3. 3. The water-in-oil emulsion sunscreen cosmetic according to claim 1 or 2, wherein the oil phase thickener (A) is one or more selected from the group consisting of dextrin fatty acid esters, sucrose fatty acid esters, glyceryl fatty acid esters, amino acid-based thickeners, acrylic polymers, solid or semi-solid hydrocarbon oils, and fatty acids or salts thereof.

4. The water-in-oil emulsion sunscreen cosmetic according to any one of claims 1 to 3, further comprising (D) a gelling agent selected from organically modified clay minerals.

5. 5. The water-in-oil emulsion sunscreen cosmetic according to claim 4, wherein the blending amount of the gelling agent (D) selected from organically modified clay minerals is 0.1 to 2% by mass based on the total amount of the cosmetic.

6. 6. The water-in-oil emulsion sunscreen cosmetic according to any one of claims 1 to 5, further comprising (E) a usability-improving powder, wherein (E) the usability-improving powder is a spherical powder selected from the group consisting of cellulose powder, spherical silica, talc, mica, sericite, starch powder, and biodegradable resins.

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