Oil-in-water emulsion and sunscreen composition

Abstract

The present invention addresses the problem of providing: an oil-in-water emulsion that, when used in a sunscreen composition, confers a good ultraviolet protection effect even at a low content of an organic ultraviolet absorber; and a sunscreen composition containing the same. The problem is solved by an oil-in-water emulsion containing an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant contains polyoxyethylene castor oil and / or a derivative thereof, and the weight ratio of the content of the surfactant to the content of the organic ultraviolet absorber (content of surfactant / content of organic ultraviolet absorber) is 0.6 or more.

Description

Oil-in-water emulsions and sunscreen compositions

[0001] The present invention relates to oil-in-water emulsions and sunscreen compositions.

[0002] Oil-in-water cosmetics containing organic ultraviolet absorbers used as sunscreen compositions generally contain 10% by weight or more of an organic ultraviolet absorber based on the total weight of the oil-in-water cosmetic (for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2020-158445

[0004] However, organic ultraviolet absorbers have skin irritation and degrade the feeling of use of sunscreen compositions, so it is desirable to reduce the amount of organic ultraviolet absorbers used in sunscreen compositions. On the other hand, when the content of the organic ultraviolet absorber is small, a favorable ultraviolet protection effect cannot be obtained.

[0005] An object of one aspect of the present invention is to provide an oil-in-water emulsion that can provide a favorable ultraviolet protection effect even when the content of an organic ultraviolet absorber is small when used in a sunscreen composition, and a sunscreen composition containing the same.

[0006] To solve the aforementioned problems, the present invention includes the following embodiments: [1] An oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or a derivative thereof, and the weight ratio of the surfactant content to the organic ultraviolet absorber content (surfactant content / organic ultraviolet absorber content) is 0.6 or more. [2] An oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or a derivative thereof, and the average particle size of the emulsion particles is 60 nm or less. [3] The oil-in-water emulsion according to [1] or [2], wherein the surfactant is polyoxyethylene hydrogenated castor oil and / or polyoxyethylene hydrogenated castor oil isostearate. [4] The oil-in-water emulsion according to any one of [1] to [3], wherein the oil comprises the organic ultraviolet absorber which is liquid at room temperature. [5] An oil-in-water emulsion according to any one of [1] to [4], further comprising a UV scattering agent. [6] A sunscreen composition comprising an oil-in-water emulsion according to any one of [1] to [5]. [7] A sunscreen composition according to [6], further comprising a UV scattering agent. [1A] An oil-in-water emulsion according to any one of [1] to [5], wherein the average particle size of the emulsion particles is 60 nm or less. [2A] An oil-in-water emulsion according to any one of [1] to [5], wherein the weight ratio of the surfactant content to the organic UV absorber content (surfactant content / organic UV absorber content) is 0.6 or more.

[0007] According to one aspect of the present invention, it is possible to provide an oil-in-water emulsion that, when used in a sunscreen composition, can provide a good UV protection effect even with a small amount of organic UV absorber, and a sunscreen composition containing the same.

[0008] Embodiments of the present invention will be described in detail below. However, the present invention is not limited thereto, and various modifications are possible within the scope described. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or greater, B or less".

[0009] [1. Oil-in-Water Emulsion] The inventors diligently studied to solve the above problems and prepared an oil-in-water emulsion by blending an organic UV absorber, a specific surfactant, an oil, and an aqueous medium, resulting in a nanoemulsion with emulsion particles of 60 nm or less. Surprisingly, they found that a sunscreen composition prepared using this nanoemulsion in which fine emulsion particles are dispersed provides good UV protection even with a small amount of organic UV absorber. Furthermore, the inventors found that if the ratio of the content of a specific surfactant to the content of the organic UV absorber in the oil-in-water emulsion is within a specific range, the average particle size of the emulsion particles tends to be 60 nm or less.

[0010] That is, an oil-in-water emulsion according to one embodiment of the present invention is an oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or its derivatives, and the weight ratio of the surfactant content to the organic ultraviolet absorber content (surfactant content / organic ultraviolet absorber content) is 0.6 or more.

[0011] Furthermore, another embodiment of the present invention is an oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or its derivatives, and the average particle size is 60 nm or less.

[0012] The oil-in-water emulsions according to these embodiments of the present invention exhibit good UV protection even when used in sunscreen compositions, despite containing only a small amount of organic UV absorber.

[0013] Furthermore, when these oil-in-water emulsions of the present invention are used in sunscreen compositions, they exhibit a synergistic UV protection effect when used in combination with an UV scattering agent, compared to when an organic UV absorber and a UV scattering agent are used individually.

[0014] In this disclosure, the term "ultraviolet protection effect" refers to the effect of preventing inflammation caused by ultraviolet rays. Generally, the SPF value, which is an indicator of the protection effect against UV-B with wavelengths of 290 nm to 320 nm, and the PA value, which is an indicator of the protection effect against UV-A with wavelengths of 320 nm to 400 nm, are known as indicators of the protection effect against inflammation caused by ultraviolet rays. In contrast, in the examples of this disclosure, the "SPF equivalent value" calculated from the measured value obtained by measuring the transmittance of ultraviolet rays in the 290 nm to 400 nm range is used as an indicator of the ultraviolet protection effect. Since ultraviolet rays in the 290 nm to 400 nm range cover the UV-B and UV-A regions, the "SPF equivalent value" in this disclosure can be said to be an indicator of the protection effect against inflammation caused by UV-B and UV-A.

[0015] (Organic UV Absorber) In one embodiment of the present invention, the "organic UV absorber" is not particularly limited as long as it is an organic substance that absorbs ultraviolet light, and is an absorber that absorbs at least one of UV-A and UV-B. The organic UV absorber preferably absorbs both UV-A and UV-B. Commercially available organic UV absorbers can be suitably used as the organic UV absorber. Typically, organic UV absorbers are solids or liquids and are oil-soluble organic substances that are poorly soluble in water. Preferred examples of organic UV absorbers include organic UV absorbers that mainly absorb UV-A, such as diethylaminohydroxybenzoyl hexyl benzoate and avobenzone; organic UV absorbers that mainly absorb UV-B, such as ethylhexyl methoxycinnamate (OMC), octocrylene, and homosalate; and organic UV absorbers that absorb both UV-A and UV-B, such as bisethylhexyloxyphenol methoxyphenyl triazine (BEMT). The organic UV absorber may be used alone or in combination of two or more types. It is preferable to use two or more types of organic ultraviolet absorbers in combination.

[0016] If an organic UV absorber is liquid at room temperature (e.g., 25°C), it can also function as an oil, as described later. That is, an organic UV absorber that is liquid at room temperature can also function as an oil. It is preferable that at least one of the organic UV absorbers contained in the oil-in-water emulsion is a liquid oil at room temperature.

[0017] The upper limit of the content of the organic ultraviolet absorber in the oil-in-water emulsion according to one embodiment of the present invention is preferably 21% by weight or less, 17% by weight or less, 13% by weight or less, or 11% by weight or less, relative to the total weight of the oil-in-water emulsion. The lower limit of the content of the organic ultraviolet absorber in the oil-in-water emulsion according to one embodiment of the present invention is preferably 2% by weight or more, relative to the total weight of the oil-in-water emulsion. If the content of the organic ultraviolet absorber is within the above range, an excellent ultraviolet protection effect can be obtained when a sunscreen composition is prepared using the oil-in-water emulsion. Furthermore, if the content of the organic ultraviolet absorber is within the above range, a very excellent ultraviolet protection effect can be obtained when an ultraviolet scattering agent is used in combination with the oil-in-water emulsion when a sunscreen composition is prepared using the oil-in-water emulsion.

[0018] (Surfactants) In one embodiment of the present invention, the "surfactant" is not particularly limited as long as it contains polyoxyethylene castor oil and / or its derivatives.

[0019] The surfactant is more preferably a nonionic surfactant. Furthermore, the surfactant is more preferably an HLB of 9 to 16. In one embodiment, the surfactant, which is polyoxyethylene castor oil and / or a derivative thereof, satisfies one or more of the above preferred conditions. In one embodiment, the surfactant includes other surfactants other than polyoxyethylene castor oil and / or a derivative thereof, and the other surfactant satisfies one or more of the above preferred conditions. In one embodiment, all surfactants contained in the oil-in-water emulsion satisfy one or more of the above preferred conditions.

[0020] Examples of polyoxyethylene castor oil and its derivatives include polyoxyethylene castor oil, polyoxyethylene castor oil isostearate, polyoxyethylene castor oil stearate, polyoxyethylene castor oil laurate, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil isostearate, polyoxyethylene hydrogenated castor oil stearate, and polyoxyethylene hydrogenated castor oil laurate. For example, polyoxyethylene hydrogenated castor oil is a mixture of ethers and esters obtained by addition polymerization of ethylene oxide to hydrogenated castor oil.

[0021] The average number of moles of ethylene oxide added to polyoxyethylene castor oil and / or its derivatives is not particularly limited, but is preferably 2 moles to 100 moles, and more preferably 10 moles to 50 moles.

[0022] Examples of commercially available polyoxyethylene castor oils include Kolliphor EL (BASF), NIKKOL CO-3, CO-10, and CO-35 (Nikko Chemicals). Examples of commercially available hydrogenated polyoxyethylene castor oils include NIKKOL HCO-10, HCO-20, HCO-30, HCO-40, and HCO-50 (Nikko Chemicals); EMALEX HC-10, HC-20, HC-30, HC-40, and HC-50 (Nippon Emulsion Co., Ltd.). Examples of commercially available hydrogenated polyoxyethylene castor oils with isostearate include EMALEX RWIS-140EX, 150EX, 110, 120, 130, 140, and 150 (Nippon Emulsion Co., Ltd.). One type of surfactant may be used alone, or two or more types may be used in combination.

[0023] From the viewpoint of transdermal absorption, polyoxyethylene castor oil and / or polyoxyethylene hydrogenated castor oil isostearate are more preferable than polyoxyethylene hydrogenated castor oil and / or isostearate.

[0024] The surfactant may contain, in addition to polyoxyethylene castor oil and / or its derivatives, surfactants other than polyoxyethylene castor oil and / or its derivatives. The content of polyoxyethylene castor oil and / or its derivatives relative to the total weight of the surfactant is preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 100% by weight.

[0025] The surfactant content in the oil-in-water emulsion according to one embodiment of the present invention is preferably 30% by weight or less, more preferably 25% by weight or less, and even more preferably 24% by weight or less, 23% by weight or less, or 22% by weight or less, relative to the total weight of the oil-in-water emulsion, from the viewpoint of emulsion stability and homogeneity of emulsion particles. Furthermore, since it is easy to obtain an oil-in-water emulsion with an average particle diameter of 60 nm or less, the lower limit of the surfactant content in the oil-in-water emulsion is preferably 6% by weight or more, more preferably 13% by weight or more, and even more preferably 16% by weight or more, relative to the total weight of the oil-in-water emulsion.

[0026] (Oil) In one embodiment of the present invention, "oil" is not particularly limited as long as it is an oil-soluble substance that is liquid at room temperature (e.g., 25°C) and can be used in food, pharmaceuticals, and cosmetics.

[0027] Examples of oils include avocado oil, olive oil, sesame oil, almond oil, bergamot oil, camellia oil, evening primrose oil, macadamia nut oil, corn oil, rapeseed oil, peach kernel oil, wheat germ oil, sasanqua oil, castor oil, linseed oil, safflower oil, cottonseed oil, elm oil, soybean oil, peanut oil, tea seed oil, kaya oil, rice bran oil, tili oil, canola oil, safflower oil, kukui nut oil, grapeseed oil, hazelnut oil, and castor oil. Examples of suitable oils include vegetable oils such as squalane oil, rosehip oil, pistachio nut oil, coconut oil, and vegetable squalane; and synthetic oils such as diisopropyl adipate (DIA), ethylhexyl methoxycinnamate (OMC), medium-chain triglyceride, triethylhexanoin, isopropyl myristate, octyldodecyl myristate, hexyldecanol, octyldodecanol, and liquid paraffin. Only one oil may be used, or two or more may be used in combination. More preferably, the oils are diisopropyl adipate (DIA) and ethylhexyl methoxycinnamate (OMC). Using oils is preferable because it allows for the acquisition of a stable oil-in-water emulsion.

[0028] In one embodiment of the present invention, the oil may also be an organic ultraviolet absorber. More specifically, if the organic ultraviolet absorber is a liquid at room temperature (e.g., 25°C), then since the organic ultraviolet absorber is oil-soluble, it can also be said that such an organic ultraviolet absorber is an oil. That is, oil includes organic ultraviolet absorbers that are liquid at room temperature. An example of such an oil is ethylhexyl methoxycinnamate (OMC). For example, if OMC is contained in an emulsion, OMC functions as both an organic ultraviolet absorber and an oil. In this way, when the oil also functions as an organic ultraviolet absorber, that substance is included in both the content of the organic ultraviolet absorber and the content of the oil.

[0029] The oil content in the oil-in-water emulsion according to one embodiment of the present invention is preferably 10% by weight or less, more preferably 7% by weight or less, and even more preferably 5% by weight or less, relative to the total weight of the oil-in-water emulsion, from the viewpoint of the stability of the emulsion particles. Furthermore, the oil content in the oil-in-water emulsion is preferably 1% by weight or more, and more preferably 2% by weight or more, relative to the total weight of the oil-in-water emulsion, from the viewpoint of the stability of the emulsion particles.

[0030] (Aqueous medium) In one embodiment of the present invention, the "aqueous medium" is not particularly limited as long as it is a medium containing water, and is usually water. Examples of water include ultrapure water, distilled water, and deionized water.

[0031] Furthermore, the aqueous medium may be various buffer solutions such as phosphate buffer solution, physiological saline, etc. Alternatively, the aqueous medium may contain an organic solvent. The organic solvent may include alcohols such as ethanol, glycerin, butanediol, dipropylene glycol, and propylene glycol. Only one type of aqueous medium may be used, or two or more types may be used in combination.

[0032] The content of the aqueous medium in the oil-in-water emulsion is not particularly limited as long as an oil-in-water emulsion can be formed. The lower limit of the content of the aqueous medium in the oil-in-water emulsion according to one embodiment of the present invention is preferably 50% by weight or more, 60% by weight or more, or 70% by weight or more, based on the total weight of the oil-in-water emulsion. The upper limit of the content of the aqueous medium in the oil-in-water emulsion according to one embodiment of the present invention is preferably 98% by weight or less, 95% by weight or less, or 90% by weight or less, based on the total weight of the oil-in-water emulsion. Within this range, it is preferable because an oil-in-water emulsion with a small average particle size of emulsion particles can be suitably formed, and it is also preferable because the concentration of the organic ultraviolet absorber does not become too low.

[0033] (Other components) The oil-in-water emulsion according to one embodiment of the present invention may contain preservatives, antioxidants, pH adjusters, dyes, fragrances, chelating agents, thickeners, etc., as long as at least one of the effects of the present invention is not impaired. The total content of other components is preferably 5% by weight or less of the total weight of the oil-in-water emulsion.

[0034] (Content ratio of each component) The lower limit of the weight ratio of the surfactant content to the organic ultraviolet absorber content in the oil-in-water emulsion according to one embodiment of the present invention, i.e., (surfactant content / organic ultraviolet absorber content), is preferably 0.6 or more, 1 or more, 1.5 or more, or 2 or more. The upper limit of the weight ratio of the surfactant content to the organic ultraviolet absorber content in the oil-in-water emulsion according to one embodiment of the present invention, i.e., (surfactant content / organic ultraviolet absorber content), is preferably 50 or less, 30 or less, 20 or less, 12 or less, or 5 or less. It is preferable that (surfactant content / organic ultraviolet absorber content) is within the above range because the average particle size of the emulsified particles of the oil-in-water emulsion tends to be 60 nm or less. Furthermore, when such an oil-in-water emulsion is used in a sunscreen composition, a good ultraviolet protection effect can be obtained even with a small amount of organic ultraviolet absorber. It is more preferable that the surfactant content is greater than the organic ultraviolet absorber content.

[0035] In the oil-in-water emulsion according to one embodiment of the present invention, the lower limit of the weight ratio of the surfactant content to the total content of the organic ultraviolet absorber and oil, i.e., (surfactant content / (organic ultraviolet absorber content + oil content)), is preferably 0.75 or higher. In the oil-in-water emulsion according to one embodiment of the present invention, the upper limit of the weight ratio of the surfactant content to the total content of the organic ultraviolet absorber and oil, i.e., (surfactant content / (organic ultraviolet absorber content + oil content)), is preferably 18 or lower. If (surfactant content / (organic ultraviolet absorber content + oil content)) is within the above range, the particle size of the emulsion particles tends to be small, and monodisperse nanoemulsions are easily obtained.

[0036] In the oil-in-water emulsion according to one embodiment of the present invention, the lower limit of the weight ratio of the oil content to the organic ultraviolet absorber content, i.e., (oil content / organic ultraviolet absorber content), is preferably 0.1 or more, 0.2 or more, or 0.4 or more. In the oil-in-water emulsion according to one embodiment of the present invention, the upper limit of the weight ratio of the oil content to the organic ultraviolet absorber content, i.e., (oil content / organic ultraviolet absorber content), is preferably 10 or less. Note that if the organic ultraviolet absorber is liquid at room temperature, the weight of its components is included in both the oil and the organic ultraviolet absorber. If (oil content / organic ultraviolet absorber content) is 10 or less, the amount of organic ultraviolet absorber added will not be too small, and the sunscreen composition containing the oil-in-water emulsion will have excellent ultraviolet protection effects. Furthermore, if the weight ratio is 0.1 or more, precipitation of the organic ultraviolet absorber will not occur, which is preferable.

[0037] In the oil-in-water emulsion according to one embodiment of the present invention, the lower limit of the weight ratio of the surfactant content to the oil content, i.e., (surfactant content / oil content), is preferably 1.5 or higher. In the oil-in-water emulsion according to one embodiment of the present invention, the upper limit of the weight ratio of the surfactant content to the oil content, i.e., (surfactant content / oil content), is preferably 20 or lower. When the weight ratio of the surfactant content to the oil content is within this range, the particle size of the emulsified particles in the oil-in-water emulsion becomes smaller, and the sunscreen composition has excellent ultraviolet protection effect.

[0038] (Form of oil-in-water emulsion) The emulsion of the present invention is an oil-in-water emulsion. In the present invention, "oil-in-water" means that oil droplets are dispersed in a continuous phase of water.

[0039] The upper limit of the average particle diameter of the emulsion particles in the oil-in-water emulsion according to one embodiment of the present invention is preferably 60 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less. The lower limit of the average particle diameter of the emulsion particles in the oil-in-water emulsion according to one embodiment of the present invention may be 5 nm or more, 10 nm or more, or 15 nm or more. If the average particle diameter of the emulsion particles is 60 nm or less, a good UV protection effect can be obtained even with a small amount of organic UV absorber when used in a sunscreen composition. Furthermore, when used in a sunscreen composition, a synergistic UV protection effect can be obtained by using an UV scattering agent in combination, compared to when the organic UV absorber and the UV scattering agent are used individually. In this specification, the average particle diameter of the emulsion particles refers to the Z-average value measured using a Zetasizer Nano ZS (manufactured by Malvern Panalytical).

[0040] In one embodiment of the present invention, the PDI (polydispersion index) of the emulsion particles is preferably 0.12 or less. If the PDI is within this range, an emulsion with excellent stability is easily obtained. Here, the PDI (polydispersion index) of the emulsion particles refers to the value measured using a Zetasizer Nano ZS (manufactured by Malvern Panalytical).

[0041] The oil-in-water emulsion according to one embodiment of the present invention preferably does not contain emulsion particles larger than 100 nm. The oil-in-water emulsion according to one embodiment of the present invention preferably is a single dispersion. A single dispersion means a dispersion having only one peak in its particle size distribution. A single dispersion of the oil-in-water emulsion is preferable because it has excellent stability.

[0042] In one embodiment, the oil-in-water emulsion remains stable for 180 days or more at 25°C.

[0043] [2. Method for producing an oil-in-water emulsion] The method for producing an oil-in-water emulsion according to an embodiment of the present invention is not particularly limited, and includes a mixing step of mixing a surfactant, an oil, and an organic ultraviolet absorber. The respective components and their blending ratios are as described in [1. Oil-in-water emulsion].

[0044] The order of mixing the surfactant, the oil, and the organic ultraviolet absorber is not particularly limited. All components may be mixed simultaneously; the organic ultraviolet absorber may be mixed after mixing the surfactant and the oil; the oil may be mixed after mixing the surfactant and the organic ultraviolet absorber; or the surfactant may be mixed after mixing the oil and the organic ultraviolet absorber.

[0045] The method for mixing the respective components is not particularly limited as long as it can uniformly dissolve the surfactant, the oil, and the organic ultraviolet absorber. For example, a method of mixing and stirring the respective components may be mentioned. In this step, each component can be uniformly dissolved without applying a strong shearing force. For example, each component can be uniformly dissolved by stirring using a magnetic stirrer.

[0046] The temperature at which the respective components are mixed and stirred is also not particularly limited. For example, the liquid temperature is preferably 20°C or higher or 30°C or higher, and is also preferably 90°C or lower or 75°C or lower.

[0047] The method for producing an oil-in-water emulsion according to an embodiment of the present invention further includes an aqueous medium adding step of mixing the composition obtained in the mixing step with an aqueous medium. The aqueous medium and its blending ratio are as described in [1. Oil-in-water emulsion]. In the aqueous medium adding step, the entire amount of the aqueous medium may be added at once, or may be added in several portions while stirring.

[0048] There is no particular limitation on the method for mixing the composition obtained by the mixing step and an aqueous medium, as long as the method can disperse the composition as emulsified particles in the aqueous medium. For example, a method of mixing and stirring the composition and an aqueous medium can be mentioned. In this step, the composition can be dispersed as emulsified particles in the aqueous medium without applying a strong shearing force. For example, the composition and the aqueous medium can be stirred using a magnetic stirrer.

[0049] There is also no particular limitation on the temperature when mixing and stirring the composition and the aqueous medium. For example, the liquid temperature is preferably 20°C or higher, or 30°C or higher, and is also preferably 90°C or lower, or 85°C or lower.

[0050] [3. Use of Oil-in-Water Emulsions] The sunscreen composition using the oil-in-water emulsion according to one embodiment of the present invention can obtain a favorable ultraviolet protection effect even when the content of the organic ultraviolet absorber is small. Therefore, the oil-in-water emulsion according to one embodiment of the present invention can be suitably used for a sunscreen composition with reduced skin irritation derived from organic ultraviolet absorbers. Accordingly, one embodiment of the present invention also includes a sunscreen composition comprising the oil-in-water emulsion.

[0051] (Sunscreen Composition) In one embodiment, examples of the sunscreen composition include cosmetics such as ultraviolet sunscreen creams, sunscreen lotions, sunscreen gels, sunscreen sprays, sunscreen milks, foundations, concealers, makeup bases, and makeup cosmetics.

[0052] The sunscreen composition may contain an oil-in-water emulsion. Typically, the sunscreen composition is produced by adding water and other components (moisturizing components, bases, etc.) to the oil-in-water emulsion. In other words, the sunscreen composition is prepared by diluting the oil-in-water emulsion and adding other components as needed. In one embodiment, the lower limit of the content of components other than the oil-in-water emulsion in the sunscreen composition is preferably 0.5% by weight or more, 1% by weight or more, or 5% by weight or more, based on the total weight of the sunscreen composition. In one embodiment, the upper limit of the content of components other than the oil-in-water emulsion in the sunscreen composition is preferably 95% by weight or less, 90% by weight or less, 75% by weight or less, 50% by weight or less, or 25% by weight or less, based on the total weight of the sunscreen composition.

[0053] In one embodiment, the lower limit of the content of the organic ultraviolet absorber in the sunscreen composition is preferably 0.05% by weight or more, 0.1% by weight or more, or 0.2% by weight or more, based on the total weight of the sunscreen composition. In one embodiment, the upper limit of the content of the organic ultraviolet absorber in the sunscreen composition is preferably 10% by weight or less, 8% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the sunscreen composition. If the content of the organic ultraviolet absorber is within the above range, skin irritation derived from the organic ultraviolet absorber can be reduced.

[0054] In one embodiment, components other than the oil-in-water emulsion in the sunscreen composition may include an aqueous medium. Here, the aqueous medium included as a component other than the oil-in-water emulsion is the same as the aqueous medium described in [1. Oil-in-Water Emulsion]. The aqueous medium may also be used as the base of the sunscreen composition. The lower limit of the aqueous medium content in the sunscreen composition is preferably 40% by weight or more, or 45% by weight or more, based on the total weight of the sunscreen composition. The upper limit of the aqueous medium content in the sunscreen composition is preferably 90% by weight or less, or 80% by weight or less, based on the total weight of the sunscreen composition. Here, the aqueous medium content in the sunscreen composition is the total content of the aqueous medium contained in the oil-in-water emulsion and the aqueous medium included as a component other than the oil-in-water emulsion. If the aqueous medium content is within the above range, the content of the organic ultraviolet absorber will be low, and thus the skin irritation derived from the organic ultraviolet absorber can be reduced.

[0055] In one embodiment, the sunscreen composition may further contain an ultraviolet scattering agent. When the oil-in-water emulsion according to one embodiment of the present invention is used in a sunscreen composition, the combined use of an ultraviolet scattering agent results in a synergistic ultraviolet protection effect compared to the use of an organic ultraviolet absorber and an ultraviolet scattering agent individually. Therefore, when the sunscreen composition further contains an ultraviolet scattering agent, the ultraviolet protection effect of the sunscreen composition is significantly improved.

[0056] The ultraviolet scattering agent is not particularly limited as long as it is an ultraviolet scattering agent used in the field of sunscreen compositions. The ultraviolet scattering agent is usually an inorganic substance, such as titanium dioxide or zinc oxide. The particle size, surface treatment, and shape of the ultraviolet scattering agent are not particularly limited. One type of ultraviolet scattering agent may be used, or two or more types may be used in combination. The ultraviolet scattering agent may be dispersed in an aqueous medium and added to an oil-in-water emulsion.

[0057] The lower limit of the UV scattering agent content in the sunscreen composition is preferably 0.1% by weight or more, or 0.25% by weight or more, relative to the total weight of the sunscreen composition. The upper limit of the UV scattering agent content in the sunscreen composition is preferably 10% by weight or less, or 7% by weight or less, relative to the total weight of the sunscreen composition. If the UV scattering agent is a UV scattering agent that has undergone surface treatment such as aluminum hydroxide treatment or silica treatment, the weight of the UV scattering agent refers to the weight after surface treatment. If the UV scattering agent is a UV scattering agent that has undergone surface treatment such as aluminum hydroxide treatment or silica treatment, the lower limit of the UV scattering agent content (titanium dioxide, zinc oxide, etc.) before surface treatment in the sunscreen composition is preferably 0.08% by weight or more, or 0.20% by weight or more, relative to the total weight of the sunscreen composition. The upper limit of the UV scattering agent content (titanium dioxide, zinc oxide, etc.) before surface treatment in the sunscreen composition is preferably 9% by weight or less, or 6% by weight or less, relative to the total weight of the sunscreen composition.

[0058] In one embodiment, the sunscreen composition may contain other components to add functionality, to the extent that it does not impair the effects of the invention. Examples of other components include colorants, fragrances, thickeners, defoamers, humectants, surfactants, preservatives, chelating agents, and pH adjusters. The other components are preferably present in an amount of 30% by weight or less of the total weight of the sunscreen composition.

[0059] (Method for producing a sunscreen composition) The method for producing a sunscreen composition according to one embodiment of the present invention is not particularly limited, and (i) after preparing an oil-in-water emulsion, components other than the oil-in-water emulsion may be added, or (ii) after mixing the components constituting the oil-in-water emulsion with at least a portion of the components other than the oil-in-water emulsion to prepare an oil-in-water emulsion, the remaining components may be added.

[0060] In particular, from the viewpoint of ease of quality control, (i) a method of adding components other than the oil-in-water emulsion after preparing the oil-in-water emulsion is more preferred. If the oil-in-water emulsion contains an ultraviolet scattering agent, it becomes difficult to measure the average particle size of the emulsion particles, so it is preferable to add the ultraviolet scattering agent after preparing the oil-in-water emulsion.

[0061] (ii) In a method in which an oil-in-water emulsion is prepared by mixing the components constituting the oil-in-water emulsion with at least a portion of components other than the oil-in-water emulsion, and then the remaining components are added, for example, a method can be adopted in which an oil-in-water emulsion is prepared by mixing the components constituting the oil-in-water emulsion with an ultraviolet scattering agent, and then the remaining components are added. In such a case, the oil-in-water emulsion prepared by mixing with an ultraviolet scattering agent can also be said to be an oil-in-water emulsion further containing an ultraviolet scattering agent in [1. Oil-in-water emulsion].

[0062] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0063] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0064] [Evaluation Method] The oil-in-water emulsions obtained in the examples and comparative examples were evaluated by the following method.

[0065] <Average particle size and PDI (polydispersion index) of emulsified particles in oil-in-water emulsions> Samples for measurement were prepared by diluting the oil-in-water emulsions obtained in the examples and comparative examples 20 times with deionized water. PDI was measured using a Zetasizer Nano ZS (Malvern Panalytical). The particle size of the emulsified particles was measured based on the Z-average value. Three measurements were performed using the same sample, and the average value was taken as the average particle size of the emulsified particles.

[0066] <Average SPF equivalent value of sunscreen composition containing oil-in-water emulsion> (Preparation of sunscreen composition) The oil-in-water emulsions obtained in the examples and comparative examples, the ultraviolet scattering agents listed in the table, and water were weighed into a 10 mL beaker in the weight ratios listed in the table. The mixture in the weighed beaker was stirred using a magnetic stirrer for about 1 hour at room temperature until the contents were uniformly dispersed to obtain the sunscreen composition.

[0067] (SPF equivalent value of sunscreen composition) The obtained sunscreen composition was applied to an SPF cell (manufactured by JASCO Corporation), and a sample for measurement was prepared by covering it with a quartz glass slide. The transmittance of ultraviolet light from 290 nm to 400 nm was measured using SolidSpec-3700 (manufactured by Shimadzu Corporation). The value calculated using the total light transmittance obtained from the measurement and the following formula (1) was taken as the SPF equivalent value. A sample for measurement was prepared for each measurement, and after 7 measurements were taken, the average value of the 5 measurement values ​​excluding the maximum and minimum values ​​was taken as the average SPF equivalent value. In equation (1), E(λ) is the radiant intensity of sunlight (using the reference solar spectrum as defined in ASTM G173-03 and IEC 60904-3), R(λ) is the erythematizing spectrum (CIE-98), and T(λ) is the total light transmittance (%).

[0068] [Materials Used] The following materials were used for the preparation and evaluation of the oil-in-water emulsion. (Surfactants) ・Polyoxyethylene hydrogenated castor oil isostearate (PEG-50 hydrogenated castor oil isostearate) (manufactured by Nippon Emulsion Co., Ltd., EMALEX RWIS-150EX) ・Polyoxyethylene castor oil (PEG-35 castor oil) (manufactured by Nikko Chemicals Co., Ltd., NIKKOL CO-35) ・Polysorbate 80 (Polyoxyethylene sorbitan monooleate (20 E.O.), manufactured by Kao Corporation, Leodol TW-O120V) (Oils) ・Diisopropyl adipate (DIA) ・Ethylhexyl methoxycinnamate (OMC) (Organic UV absorbers) ・Bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) ・Diethylamino hydroxybenzoyl hexyl benzoate (manufactured by BASF, Uvinul A Plus) Granular (hereinafter sometimes referred to as "Uvinul A") ・Ethylhexyl methoxycinnamate (OMC) ・Avobenzone octocrylene homosalate *Of these, OMC, octocrylene, and homosalate are liquids at room temperature and are also classified as oils. (Ultraviolet scattering agent) ・Aluminum hydroxide surface-treated titanium oxide (manufactured by Titanium Industry Co., Ltd., ST461WD, titanium oxide content: 89.6% by weight) ・Silica surface-treated titanium oxide (manufactured by Titanium Industry Co., Ltd., ST455WS, titanium oxide content: 86.2% by weight) ・Zinc oxide dispersion (manufactured by Sakai Chemical Industry Co., Ltd., DIF-AB-33W, zinc oxide content: 54%)

[0069] [Preparation of Oil-in-Water Emulsion] For each example and comparative example, the organic ultraviolet absorber, oil, and surfactant listed in Tables 1 to 6 were weighed into a 10 mL beaker in the weight ratios listed in Tables 1 to 6. The mixture in the beaker was stirred using a magnetic stirrer at 60°C until the contents were uniform, obtaining a viscous liquid composition for preparing an oil-in-water emulsion. Deionized water was added to this oil-in-water emulsion composition in the weight ratios listed in Tables 1 to 6, and the mixture was stirred further at 80°C for 20 to 30 minutes. After visually confirming that there were no unevenly dissolved undissolved substances or lumps, the mixture was cooled to room temperature in an ice bath to obtain an oil-in-water emulsion.

[0070] In this specification, blank spaces in the tables indicate that the corresponding component was not added. Therefore, in the preparation of the oil-in-water emulsion in Comparative Example 1, the same procedure as described above was performed, except that an organic ultraviolet absorber was not added. The average particle size of the emulsified particles, the PDI, and the average SPF equivalent value of the sunscreen composition were evaluated for the obtained oil-in-water emulsion using the evaluation method described above. The PDI evaluation results are not shown in Tables 1 to 6, but the PDI of the oil-in-water emulsions in all examples was 0.12 or less.

[0071] [Examples 1-1, 1-2, 2-5, Comparative Examples 1 and 2]

[0072]

[0073] In Table 1, Comparative Example 1 and Example 1-2 differ in whether or not the oil-in-water emulsion contains an organic ultraviolet absorber. Example 1-1 and Example 1-2 differ in whether or not the sunscreen composition contains an ultraviolet scattering agent. The average SPF equivalent value (49.3) of the sunscreen composition of Example 1-2, which contains both 5 parts by weight of an ultraviolet scattering agent and 0.45 parts by weight of an organic ultraviolet absorber, was much higher than the sum of the average SPF equivalent values ​​(11.4) of the sunscreen compositions of Comparative Example 1 and Example 1-1, which contain each individually. According to these results, when the oil-in-water emulsion according to one embodiment of the present invention is used in combination with an ultraviolet scattering agent, the organic ultraviolet absorber in the oil-in-water emulsion exhibits a synergistic ultraviolet protection effect with the ultraviolet scattering agent. Note that the average SPF equivalent value of the sunscreen composition according to Example 1-1 is 3.2, which is lower than that of the sunscreen composition according to Comparative Example 1. However, the sunscreen composition according to Example 1-1 has the same UV protection effect as the sunscreen composition (average SPF equivalent value of 3.2) obtained by adding a UV scattering agent to a commercially available oil-in-water emulsion containing a UV absorber (Comparative Example 7), which will be described later. Furthermore, the sunscreen composition according to Example 1-1 has a superior feel due to the absence of a UV scattering agent. In addition, it is easier to control quality by creating an oil-in-water emulsion without a UV scattering agent, measuring the particle size of the emulsion particles, and then adding the UV scattering agent. Thus, from the viewpoint of manufacturing process, quality control, and product characteristics, oil-in-water emulsions or sunscreen compositions without UV scattering agents, such as those in Example 1-1, also have industrial advantages.

[0074]

[0075] The oil-in-water emulsions listed in Table 2 contain an organic UV absorber, oil, an aqueous medium, and polyoxyethylene hydrogenated castor oil isostearate as a surfactant. The sunscreen compositions of Examples 1-2, 2-5, which included an oil-in-water emulsion with a (surfactant content / organic UV absorber content) of 0.6 or higher, demonstrated that a good average SPF equivalent value could be obtained even with a small amount of organic UV absorber (0.45% by weight). Furthermore, the average particle size of the emulsion particles in the oil-in-water emulsions of Examples 1-2, 2-5 was 60 nm or less. In contrast, the sunscreen composition of Comparative Example 2, which included an oil-in-water emulsion with a (surfactant content / organic UV absorber content) of 0.4, contained the same amount of organic UV absorber as Examples 1-2, 2-5, but showed a lower average SPF equivalent value. The average particle size of the emulsion particles in the oil-in-water emulsion of Comparative Example 2 was a large 169 nm, indicating that the average particle size of the emulsion particles affects the UV protection effect.

[0076] [Examples 6-8 and Comparative Examples 3-5] Examples 6-8 and Comparative Examples 3-5 are examples in which OMC, BEMT, and Uvinul A were used as organic ultraviolet absorbers. Of these, OMC is liquid at room temperature and therefore also functions as an oil. Note that Comparative Example 3 in Table 3 did not emulsify, and therefore an oil-in-water emulsion was not obtained. In Table 3, the "-" indicates that evaluation was not performed.

[0077]

[0078]

[0079] Table 3 shows that Example 6, which contains OMC, BEMT, and Uvinul A as organic ultraviolet absorbers, exhibits excellent ultraviolet protection when used in combination with an ultraviolet scattering agent.

[0080] Table 3, Example 7, shows that the sunscreen composition of Example 7, which contains an oil-in-water emulsion with polyoxyethylene castor oil as a surfactant, also yielded a good average SPF equivalent value even with a small amount of organic UV absorber (0.75% by weight). Furthermore, the average particle size of the emulsion particles in the oil-in-water emulsion of Example 7 was 60 nm or less. On the other hand, Comparative Example 3, which contained polysorbate 80 as a surfactant, did not yield an oil-in-water emulsion.

[0081] The oil-in-water emulsions listed in Table 4 contain an organic UV absorber, oil, an aqueous medium, and polyoxyethylene hydrogenated castor oil isostearate as a surfactant. The sunscreen compositions of Examples 6 and 8, which included oil-in-water emulsions with a (surfactant content / organic UV absorber content) of 0.6 or higher, demonstrated that a good average SPF equivalent value could be obtained even with a small amount of organic UV absorber (0.75% by weight). Furthermore, the average particle size of the emulsion particles in the oil-in-water emulsions of Examples 6 and 8 was 60 nm or less. In contrast, the sunscreen compositions of Comparative Examples 4 and 5, which included oil-in-water emulsions with a (surfactant content / organic UV absorber content) of less than 0.6, showed lower average SPF equivalent values. Additionally, the average particle size of the emulsion particles in the oil-in-water emulsions of Comparative Examples 4 and 5 was large, exceeding 119 nm, demonstrating that the average particle size of the emulsion particles affects the UV protection effect.

[0082] [Examples 9-14 and Comparative Example 6] Examples 9-13 are examples in which various organic ultraviolet absorbers were incorporated. Of these, OMC, octocrylene, and homosalate are liquid at room temperature and therefore also function as oils. Examples 14 and Comparative Example 6 are examples in which zinc oxide was used instead of titanium dioxide as an ultraviolet scattering agent.

[0083]

[0084] As shown in Table 5, the sunscreen compositions of Examples 9 and 10 demonstrated that good average SPF values ​​could be obtained even with small amounts of organic UV absorbers, at 0.35% and 0.65% by weight, respectively. Furthermore, the average particle size of the emulsified particles in the oil-in-water emulsions of Examples 9 and 10 was 60 nm or less. When using the same amount of oil-in-water emulsion, the sunscreen composition of Example 10, which used OMC functioning as both a UV absorber and an oil, had a higher average SPF value than Example 9, which used an oil that was not a UV absorber. The sunscreen compositions of Examples 11-13, which used octocrylene, homosalate, or avobenzone as organic UV absorbers, also demonstrated that good average SPF values ​​could be obtained even with small amounts of organic UV absorbers, at 0.65% and 0.4% by weight, respectively. Additionally, the sunscreen composition of Example 14, which used zinc oxide as a UV scattering agent, had a higher average SPF value than Comparative Example 6, which did not contain an oil-in-water emulsion containing an organic UV absorber.

[0085] [Comparison with commercially available organic UV absorber-containing oil-in-water emulsion] Table 6 shows the evaluation results when a sunscreen composition containing 5.0 parts by weight of a UV scattering agent was prepared using a commercially available organic UV absorber-containing oil-in-water emulsion (BASF Tinosorb S lite aqua, containing 20% ​​by weight of BEMT as an organic UV absorber, average particle size: 300 nm) as Comparative Example 7, along with the evaluation results when using the oil-in-water emulsion of Example 9. In Table 6, values ​​indicated by "-" indicate that the value is unknown.

[0086]

[0087] As shown in Table 6, the sunscreen composition of Example 9 had a significantly higher SPF equivalent value than the average SPF equivalent value of the sunscreen composition prepared using the commercially available product in Comparative Example 7.

[0088] This invention can be used in sunscreen compositions that reduce skin irritation derived from organic ultraviolet absorbers.

Claims

1. An oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or a derivative thereof, and the weight ratio of the surfactant content to the organic ultraviolet absorber content (surfactant content / organic ultraviolet absorber content) is 0.6 or more.

2. An oil-in-water emulsion comprising an organic ultraviolet absorber, a surfactant, an oil, and an aqueous medium, wherein the surfactant comprises polyoxyethylene castor oil and / or a derivative thereof, and the average particle size of the emulsion particles is 60 nm or less.

3. The oil-in-water emulsion according to claim 1 or 2, wherein the surfactant is polyoxyethylene hydrogenated castor oil and / or polyoxyethylene hydrogenated castor oil isostearate.

4. The oil-in-water emulsion according to claim 1 or 2, wherein the oil comprises the organic ultraviolet absorber which is liquid at room temperature.

5. The oil-in-water emulsion according to claim 1 or 2, further comprising an ultraviolet scattering agent.

6. A sunscreen composition comprising the oil-in-water emulsion according to claim 1 or 2.

7. The sunscreen composition according to claim 6, further comprising an ultraviolet scattering agent.

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