Skin external composition

Abstract

To provide a novel skin external composition with high photoprotective effect, particularly a skin external composition that reduces light transmittance around 1,900 nm, which is the wavelength at which the sun's scorching heat is felt.SOLUTION: A skin external composition of the present invention contains silver nanoparticles and carrier particles thereof. The skin external composition can use, for example, plate-shaped particles as silver nanoparticles and inorganic hydrate particles as carrier particles. The skin external composition can further contain a binder.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a composition for external application to the skin containing silver nanoparticles, and more specifically to a composition for external application to the skin having high infrared protection effect. [Background technology]

[0002] Silver nanoparticles are known to absorb strong light due to the plasmon resonance phenomenon, and the absorption wavelength range can be controlled by the crystal size. Patent Document 1 discloses a functional light-transmitting material obtained by forming an adsorption film containing hydrophobic organo-clay on the surface of a transparent substrate and adsorbing flat silver nanoparticles onto the surface of the adsorption film.

[0003] On the other hand, with regard to compositions for external use on the skin, compositions for protecting the skin from sunlight have been developed, but with the recent progress in global warming, compositions for external use on the skin for protecting against infrared rays have also been developed, which also have a function of protecting against infrared rays. For example, Patent Document 2 discloses a composition for external use on the skin for protecting against infrared rays, which contains a plate-like metal oxide having a thickness of 30 nm to 360 nm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-24214 A [Patent Document 2] Patent Publication No. 2021-070680 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a novel composition for external use on the skin that has a high photoprotective effect. [Means for solving the problem]

[0006] The present invention has the following aspects: Aspect 1 A composition for topical application to the skin comprising silver nanoparticles and carrier particles thereof. Aspect 2 The topical skin composition according to embodiment 1, further comprising a binder selected from the group consisting of cationic resins and clay minerals. Aspect 3 The topical skin composition according to aspect 2, wherein the binder comprises the clay mineral, and the clay mineral is an organically modified clay mineral. Aspect 4 A composition for external skin application according to aspect 3, comprising the organically modified clay mineral in an amount of 0.01% by mass or more and 5.0% by mass or less. Aspect 5 4. The composition for external skin application according to aspect 3, wherein the ratio of the long axis of the organically modified clay mineral to the long axis of the silver nanoparticles is within the range of 0.1 to 200. Aspect 6 3. The composition for external application to skin according to aspect 2, wherein the binder is the cationic resin and the cationic resin is contained in an amount of 0.01% by mass or more and 2.0% by mass or less. Aspect 7 The composition for external application to skin according to embodiment 1, further comprising an aqueous component and a water-retaining component. Aspect 8 The topical skin composition according to aspect 1, wherein the carrier particles comprise inorganic hydrate particles. Aspect 9: The topical skin composition according to aspect 8, wherein the inorganic hydrate particles comprise calcium carbonate and / or magnesium carbonate. Aspect 10 10. The topical skin composition according to aspect 9, wherein the silver nanoparticles and the inorganic hydrate particles form composite particles. Aspect 11 2. The topical skin composition according to claim 1, wherein at least a portion of the silver nanoparticles have a plate-like shape. Aspect 12 The topical skin composition according to embodiment 1, which is applied to a slide glass using a doctor blade film applicator with a gap of 500 μm to form a thin film, and allowed to stand for 5 minutes at 25° C. and a humidity of 50%, has a light transmittance of 70% or less at a wavelength of 850 nm when measured on the resulting thin film. Aspect 13 The topical skin composition according to embodiment 1, wherein the composition is applied to a slide glass using a doctor blade film applicator with a gap of 500 μm to form a thin film, and the thin film is allowed to stand for 5 minutes at 25° C. and a humidity of 50%, and the light transmittance at a wavelength of 1900 nm measured on the thin film is 60% or less. Aspect 14 The composition for external application to skin according to any one of aspects 1 to 13, wherein the spectroscopic properties change in response to moisture. Aspect 15 The composition for external application to the skin according to embodiment 1, which is for use as a sunscreen and / or antiperspirant. Effect of the Invention

[0007] According to the present invention, a novel composition for external application to the skin having a high photoprotective effect can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows the transmission spectra of the external skin compositions of Example 4 and Comparative Example 7. [Diagram 2] FIG. 2 shows the transmission spectrum when mist-like water is sprayed onto the measurement sample of Example 1 from a distance of 60 cm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] One embodiment of the invention in this disclosure is a skin topical composition containing silver nanoparticles and their carrier particles. The inventors have found that the composition containing silver nanoparticles and their carrier particles has an unexpectedly high photoprotection effect compared to the dispersion of silver nanoparticles alone and the dispersion of carrier particles alone. Although not bound by theory, it is believed that this is because the silver nanoparticles and the carrier particles are close to each other at a moderate distance, and together with the water attached to the surface of the carrier particles, they affect the plasmon resonance phenomenon, greatly increasing the absorption in the infrared region.

[0010] In addition, the composition for external use on the skin of this embodiment can also have the effect of enhancing the photoprotective effect in response to moisture. This effect is due to the change in the spectral characteristics of the composition for external use on the skin in response to moisture. In addition, due to the change in the spectral characteristics, the composition for external use on the skin can also have the effect of improving the design of the coating film formed by applying the composition for external use on the skin.

[0011] This form of topical skin composition can be applied to a glass slide using a doctor blade film applicator with a gap of 500 μm to form a thin film, and the thin film obtained by leaving it to stand for 5 minutes at 25°C and a humidity of 50% can have a light transmittance at a wavelength of 850 nm of 70% or less, 65% or less, 60% or less, 55% or less, or 50% or less.

[0012] The skin topical composition of this embodiment can have an average light transmittance of 75% or less, 70% or less, 65% or less, 60% or less, or 55% or less at wavelengths of 850 nm to 1200 nm as measured by the above method. Also, the skin topical composition of this embodiment can have an average light transmittance of 75% or less, 70% or less, 65% or less, or 60% or less at wavelengths of 850 nm to 1900 nm as measured by the above method.

[0013] The skin topical composition of this embodiment can have a light transmittance at a wavelength of 1900 nm measured by the above method of 65% or less, 60% or less, 55% or less, or 50% or less. Near-infrared rays around 1900 nm give the skin a hot feeling like the sun, so reducing the light transmittance around this wavelength is very advantageous for a skin topical composition.

[0014] <Silver nanoparticles> Silver nanoparticles are not limited to a specific size, but may have a major axis of 100 nm or less, and can selectively absorb light such as near-infrared light by the plasmon resonance phenomenon. The particle size of silver nanoparticles can be calculated from the number-average major axis based on a large number of photographs taken at arbitrary positions using a scanning electron microscope.

[0015] The shape of the silver nanoparticles is not particularly limited, and may be plate-like (plate-like), spherical, columnar, or amorphous. From the viewpoint of absorbing near-infrared light, it is preferable that the shape of the silver nanoparticles is plate-like. When the silver nanoparticles are plate-like, the thickness may be 1 nm or more and 50 nm or less. When the silver nanoparticles are plate-like, the major axis of the major axis may be 10 nm or more and 5000 nm or less, assuming that the surface with the largest area is the major axis. The aspect ratio (the ratio of the major axis to the thickness) may be 3 or more. These measurements can be performed in the same manner as the method for measuring the particle size of silver nanoparticles as described above.

[0016] The content of silver nanoparticles in the composition for external use on the skin may be 0.00001% by mass or more, 0.001% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, and may be 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less. The content of silver nanoparticles in the composition for external use on the skin may be 0.00001% by mass or more and 10% by mass or less, or 0.05% by mass or more and 1% by mass or less.

[0017] Silver nanoparticles can be prepared, for example, according to the method described in Japanese Patent No. 5970638.

[0018] <Carrier particles> The carrier particles are not particularly limited as long as they can enhance the light protection effect when used together with the silver nanoparticles, and for example, inorganic particles can be used.

[0019] The carrier particles can form a complex with silver nanoparticles. The form of the complex is not particularly limited as long as it can enhance the light protection effect, but may be a form in which silver nanoparticles are chemically or physically adsorbed on the surface of the carrier particles. For example, the complex may be a state in which nanoparticles are attached to the surface of the carrier particles.

[0020] The inorganic particles can be, but are not limited to, particles of a material selected from the group consisting of metals, metalloids, and combinations thereof, as well as their oxides, hydroxides, carbonates, phosphates, ammonium salts, sulfates, nitrates, nitrides, carbides, and borides, or composite materials thereof. For example, the inorganic particles can be particles containing or consisting of a material selected from the group consisting of silicon, aluminum, titanium, zirconium, zinc, iron, copper, nickel, lead, tungsten, and alloys containing them, as well as compounds thereof (particularly oxides, hydroxides, carbonates, phosphates, ammonium salts, sulfates, nitrates, nitrides, carbides, and borides), or composite materials thereof.

[0021] Among these, inorganic particles capable of forming hydrates are preferred, and calcium carbonate can be mentioned in particular. By using these, the light absorption due to the above-mentioned plasmon resonance phenomenon can be further increased. For example, calcium carbonate is known to have a spatial cooling effect due to its absorption and scattering effect on mid- to far-infrared rays (Cell Reports Physical Science Volume 1, Issue 10, 21 October 2020, 100221), and can be an optimal carrier particle for achieving the object of the present invention. In addition, without being bound by theory, inorganic particles capable of forming hydrates such as calcium carbonate and magnesium carbonate can have structural water on the surface, which is thought to greatly increase absorption in the infrared region.

[0022] In addition, alkaline earth metal salts can also be used as the carrier particles. The alkaline earth metal salts are sulfates, carbonates, nitrates, etc. of alkaline earth metals Be, Mg, Ca, Sr, Ba, and Ra. Among these, calcium carbonate is preferred from the viewpoints of availability and infrared light absorption function.

[0023] The particle size of the carrier particles, particularly when the carrier particles are calcium carbonate, can usually be 0.01 μm or more, 0.1 μm or more, 1.0 μm or more, or 3.0 μm or more, and can be 100 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The particle size of the carrier particles may be 0.01 μm or more and 100 μm or less, or 1.0 μm or more and 30 μm or less. The particle size of the carrier particles refers to the volume average particle size measured by a laser diffraction scattering method.

[0024] The content of the carrier particles in the composition for external use on the skin may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 5.0% by mass or more, or 10% by mass or more, and may be 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content of the carrier particles in the composition for external use on the skin may be 0.1% by mass or more and 40% by mass or less, or 1.0% by mass or more and 20% by mass or less.

[0025] <Binder> The skin topical composition of this embodiment may contain a binder. Examples of the binder include clay minerals, cationic resins, etc. In particular, examples of the binder include substances containing ionic moieties, particularly substances containing cationic moieties.

[0026] By including a binder, the silver nanoparticles and the carrier particles can be maintained in close proximity to each other, which is believed to enhance the light protection effect of the silver nanoparticles and the carrier particles.

[0027] As the clay mineral, in particular, a clay-based intercalation compound can be used. For example, as the clay-based intercalation compound, smectite clay minerals such as montmorillonite, saponite, hectorite, beidellite, stevensite, nontronite, vermiculite, halloysite, mica, etc. can be mentioned. Among these, in particular, a lipophilic clay-based intercalation compound can be mentioned, for example, synthetic smectite. Interlayer water arranged in the layered structure of clay, etc. has a greater effect on absorption in the infrared region than the structural water of hydrate-based carrier particles, and it is considered that the electric field between the layers creates a state close to protons from neutral water, causing a plasmon resonance phenomenon (which greatly affects the collective vibration of electrons) in the vicinity.

[0028] In addition, examples of the clay mineral include organically modified clay minerals. Examples of the organically modified clay minerals include clay-based intercalation compounds that have been lipophilically treated. The lipophilic treatment is not particularly limited as long as the clay mineral can hold the silver nanoparticles and the carrier particles in close proximity to each other, but examples of the lipophilic treatment include a treatment in which an organic cation is added to the surface or between the layers of the clay mineral by adding and mixing a quaternary ammonium salt to the clay mineral. As such a quaternary ammonium salt, a cationic surfactant well known in the art, such as benzyl trimethyl ammonium chloride, can be used. In addition, examples of the organically modified clay minerals include commercially available organically treated clay minerals, such as disteardimonium hectorite, stearalkonium hectorite, and dimethyl distearyl ammonium bentonite.

[0029] Since clay minerals can also retain water as a water-holding component, when applied to the skin, the infrared protection effect due to moisture such as sweat becomes significant. In addition, by including clay minerals, when the clay minerals adjacent to the silver nanoparticles react with moisture to form hydrates, Raman scattering occurs on the surface of the silver nanoparticles, which can change the hue of the skin topical composition.

[0030] The particle diameter (major axis) of the clay mineral is not particularly limited, but when dispersed in water and swollen, it can be 0.01 μm or more, 0.02 μm or more, 0.05 μm or more, 0.1 μm or more, or 0.3 μm or more, and can be 10 μm or less, 5.0 μm or less, 3.0 μm or less, 1.0 μm or less, or 0.5 μm or less. The particle diameter of the carrier particle may be 0.01 μm or more and 10 μm or less, or 0.1 μm or more and 1.0 μm or less. The particle diameter (major axis) of the clay mineral refers to the volume average particle diameter measured by a laser diffraction scattering method.

[0031] On the other hand, from the viewpoint of the change in hue due to the Raman scattering phenomenon, the ratio of the major axis of the clay mineral to the major axis of the silver nanoparticles is preferably in the range of 0.1 to 200, more preferably in the range of 0.5 to 100, and even more preferably in the range of 1 to 100. The major axis of the silver nanoparticles and the major axis of the organically modified clay mineral can be calculated from the number-average major axis based on a large number of photographs taken at arbitrary positions using a scanning electron microscope.

[0032] A composite of silver nanoparticles and a clay mineral can be prepared, for example, according to the methods described in Japanese Patent No. 6080233 and International Publication No. 2014 / 84026.

[0033] Examples of cationic resins that can be used as binders include salts of polyallylamine such as polydiallyldimethylammonium chloride and polyallylamine hydrochloride, and also include aliphatic and aromatic polylimonenes.

[0034] The content of the binder in the composition for external use on the skin may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, or 3.0% by mass or more, and may be 10% by mass or less, 5.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or 0.5% by mass or less. The content ratio of the binder in the composition for external use on the skin may be 0.001% by mass or more and 10% by mass or less, or 0.01% by mass or more and 5.0% by mass or less.

[0035] In the composition for external use on the skin, the cationic resin usable as a binder may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, and 5.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or 0.5% by mass or less. The content of the cationic resin as a binder in the composition for external use on the skin may be 0.001% by mass or more and 5.0% by mass or less, or 0.01% by mass or more and 2.0% by mass or less. In such a range, the feel after application is good and the stability of the preparation can be increased.

[0036] In the skin topical composition, the clay mineral or organic modified clay mineral usable as a binder is preferably blended in an amount of 0.001% by mass or more and 6.0% by mass or less. More preferably, it is 0.01% by mass or more and 5.0% by mass. It may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, or 10.0% by mass or less, 8.0% 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. The content ratio of the clay mineral or organic modified clay mineral as a binder in the skin topical composition may be 0.001% by mass or more and 10.0% by mass or less, or 0.01% by mass or more and 5.0% by mass or less. In such a range, the feel after application is good and the stability of the preparation can be increased.

[0037] <Water-based components and water-holding components> The composition for external use on the skin in this embodiment preferably contains an aqueous component and a water-retentive component. By containing an aqueous component and a water-retentive component, the coating film formed by applying the composition for external use on the skin can retain water, so that the effect of the moisture response described above can be easily obtained.

[0038] The aqueous component is not particularly limited as long as it can dissolve the water-soluble polymer and can be incorporated into the composition for external use on skin, and examples of the aqueous component include water, alcohol, polyol, and the like.

[0039] Examples of the water-holding component include polyhydric alcohols, natural water-soluble polymers such as plant-based polymers (e.g., gum arabic, tragacanth gum, galactan, guar gum, carob gum, karaya gum, carrageenan, pectin, agar, quince seed, algae colloids (kasso extract), starch (rice, corn, potato, wheat), and glycyrrhizic acid); microbial polymers (e.g., xanthan gum, dextran, succinoglucan, pullulan, etc.); animal polymers (e.g., collagen, casein, albumin, gelatin, etc.); starch-based polymers (e.g., carboxymethyl starch, methylhydroxypropyl starch, etc.); cellulose-based polymers (methylcellulose, ethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, ... Examples of synthetic water-soluble polymers include semi-synthetic water-soluble polymers such as cellulose acetate, sodium cellulose sulfate, hydroxypropyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, crystalline cellulose, cellulose powder, etc.; alginic acid polymers (e.g., sodium alginate, propylene glycol alginate, etc.), vinyl polymers (e.g., polyvinyl alcohol, polyvinyl methyl ether, polyvinylpyrrolidone, carboxyvinyl polymer, etc.); polyoxyethylene polymers (e.g., polyethylene glycol 20,000, 40,000, 60,000, etc.); acrylic polymers (e.g., sodium polyacrylate, polyethyl acrylate, polyacrylamide, etc.); polyethyleneimine; and cationic polymers.

[0040] In addition, as the water-holding component, a higher fatty acid and a higher alcohol may form an α-gel in the external aqueous phase together with a hydrophilic surfactant. Here, α-gel refers to an association consisting of a lamellar bilayer formed by a higher alcohol, a higher fatty acid, and a hydrophilic surfactant (Fukushima Shoji, "Physical Chemistry of Cetyl Alcohol," Fragrance Journal Publishing, pp. 79-83, 1992). Since the packing of the alkyl chain is higher than that of lamellar liquid crystals, it has high occlusion properties and excellent water retention, so it can be widely used to stabilize oil-in-water formulations.

[0041] Furthermore, depending on the formulation, organically modified clay minerals can be contained as the water-holding component. Examples of organically modified clay minerals include dimethyl distearyl ammonium modified hectorite, benzyl dimethyl stearyl ammonium modified hectorite, and trioctyl methyl ammonium hectorite. These are preferably used in, for example, W / O formulations. Even if the organically modified clay mineral is the same substance as the binder, it can exert different effects on the skin topical composition depending on the formulation, the timing of addition during the manufacturing process, and the like. When the organically modified clay mineral is added to the skin topical composition as a water-holding component, for example, it can be made to function as a water-holding component by adding it during the emulsification process of the skin topical composition. In this case, the contribution of the water-holding component can be confirmed by whether or not the film holds a certain amount of water when the coating film of the skin topical composition is prepared and dried. On the other hand, when the organically modified clay mineral is added to the skin topical composition as a binder, for example, the organically modified clay mineral can be added during the process of forming a complex.

[0042] <Other ingredients> In addition to the above-mentioned components, the composition for external use on the skin of this embodiment may contain other components that can be blended into the composition for external use on the skin. Examples of other components include powders, ultraviolet absorbents, moisturizers, surfactants, active ingredients, preservatives, etc., and one or more of these may be contained within a range that does not impair the effects of the present invention.

[0043] Examples of the powder include inorganic powder, organic powder, inorganic pigment, and organic pigment.

[0044] <<Method for producing a composition for external use on skin>> The method for producing the skin topical composition of the present invention is not particularly limited, and a known method can be appropriately used according to the formulation of the skin topical composition.For example, the silver nanoparticle composite can be uniformly dispersed in water and an aqueous medium using a disperser or the like, and then components other than water and the aqueous medium are mixed and further stirred and mixed using a homogenizer or the like.When the skin topical composition is a water-in-oil type emulsion composition or an oil-in-water type emulsion composition, a method can be used in which the water phase and the oil phase are prepared separately and then mixed.

[0045] <How to protect your skin from infrared rays> The present invention also provides a method for protecting the skin from infrared rays, comprising the step of applying the composition for external use on the skin of the present invention to the skin. The method for protecting the skin from infrared rays of the present invention is not particularly limited as long as it comprises the step of applying the composition for external use on the skin of the present invention to the skin. The method for applying the composition for external use on the skin to the skin includes coating, spraying, etc.

[0046] The present invention will be described in more detail below by showing examples, but the scope of the present invention is not limited to the following examples. EXAMPLES

[0047] Example of production <Production of Plate-shaped Silver Nanoparticle Aqueous Dispersion> An aqueous dispersion of plate-shaped silver nanoparticles was prepared by the following procedure. All reagents used were of the highest grade manufactured by Wako Pure Chemical Industries, Ltd. (i) 1000 μL of a 150 mM aqueous trisodium citrate solution, 200 μL of a 50 mM aqueous silver nitrate solution, and 240 μL of a 30% aqueous hydrogen peroxide solution were added successively to 50 mL of ultrapure water with stirring. (ii) With further vigorous stirring, 500 μL of a 100 mM aqueous solution of sodium tetrahydroborate prepared at ice temperature was added. (iii) After the sodium tetrahydroborate aqueous solution was added, the mixture was stirred vigorously for at least 30 minutes, and then allowed to stand for 5 days or more to obtain an aqueous dispersion of silver nanoplate cores A. (iv) 1250 μL of the aqueous dispersion of the silver nanoplate cores A and 65 μL of a 20 mM aqueous ascorbic acid solution were added successively to 20 ml of ultrapure water with stirring. (v) With further vigorous stirring, 4750 μL of 0.5 mM aqueous silver nitrate solution was added at a flow rate of 1000 μL / min. (vi) Immediately after the addition of the silver nitrate aqueous solution was completed, 1000 μL of a 150 mM trisodium citrate aqueous solution was added, and the stirring speed was reduced. After stirring for 4 hours, an aqueous dispersion of silver nanoplate cores B was obtained. (vii) 1250 μL of the aqueous dispersion of the silver nanoplate cores B and 78 μL of a 20 mM aqueous ascorbic acid solution were added successively to 18 ml of ultrapure water with stirring. (viii) With further vigorous stirring, 5700 μL of 0.5 mM aqueous silver nitrate solution was added at a flow rate of 1000 μL / min. (ix) After the addition of the silver nitrate aqueous solution was completed, the stirring speed was reduced and stirring was continued for 4 hours, after which an aqueous dispersion of the target plate-like silver nanoparticles was obtained.

[0048] Preparation of Silver Nanoparticle Composite Dispersion 1 A dispersion of a silver nanoparticle composite of silver nanoparticles and calcium carbonate carrier particles was prepared as follows.

[0049] When 50cc of the plate-shaped silver nanoparticle aqueous dispersion (0.004wt%) was dropped into 10cc of water containing 2.4g of calcium carbonate (manufactured by Fujii Pharmaceutical Co., Ltd.) while stirring, a blue precipitate immediately formed and the supernatant liquid became colorless. The blue precipitate was collected to obtain silver nanoparticle composite 1 of silver nanoparticles and carrier particles. This silver nanoparticle composite 1 was dispersed in water to a concentration of 40 mass%, and silver nanoparticle composite dispersion 1 was obtained.

[0050] Preparation of Silver Nanoparticle Composite Dispersion 2 A dispersion of a silver nanoparticle composite of silver nanoparticles, calcium carbonate as a carrier particle, and synthetic smectite as a clay mineral as a binder was prepared as follows.

[0051] After dropping and mixing 1 cc of a 0.3 wt% aqueous dispersion of synthetic smectite prepared in advance into 10 cc of a plate-shaped silver nanoparticle aqueous dispersion (0.004 wt%), 20 μL of a 0.1 wt% aqueous solution of benzyltrimethylammonium chloride as a quaternary ammonium salt was added and left for 3 days. The resulting indigo precipitate was collected in its entirety and dropped into 10 cc of an aqueous calcium carbonate solution (18 wt%) while stirring, at which point a blue precipitate immediately formed and the supernatant liquid became colorless. As the resulting blue precipitate, a silver nanoparticle composite 2 consisting of silver nanoparticles, carrier particles, and binder was obtained. This silver nanoparticle composite 2 was dispersed in water to a concentration of 50 mass%, and a silver nanoparticle composite dispersion 2 was obtained.

[0052] Preparation of Silver Nanoparticle Composite Dispersion 3 A dispersion of a silver nanoparticle composite of silver nanoparticles, calcium carbonate as a carrier particle, and cationic resin as a binder was prepared as follows.

[0053] 20μL of 0.1wt% aqueous solution of polydiallyldimethylammonium chloride (Sigma-Aldrich) prepared in advance was added to 10cc of the plate-shaped silver nanoparticle aqueous dispersion (0.004wt%) and left for 3 days. The resulting indigo precipitate was collected in its entirety and dropped into 10cc of an aqueous calcium carbonate solution (18wt%) while stirring. A blue precipitate was immediately formed and the supernatant liquid became colorless. The resulting blue precipitate was silver nanoparticle composite 3, which is made of silver nanoparticles, carrier particles, and binder. This silver nanoparticle composite 3 was dispersed in water to a concentration of 50% by mass, to obtain silver nanoparticle composite dispersion 3.

[0054] Examples 1 to 3 and Comparative Examples 1 to 3: Preparation of oil-in-water emulsions Oil-in-water emulsions were prepared according to the formulations shown in Table 1 below. Specifically, the infrared protection component was added to water and an aqueous medium, and uniformly dispersed with a stirrer to obtain a dispersion. Next, components other than water and the aqueous medium were added to the dispersion, and the mixture was further stirred with a stirrer to obtain the oil-in-water emulsions of Examples 1 to 3 and Comparative Examples 1 to 3. In Comparative Example 2, the plate-shaped silver nanoparticle aqueous dispersion (0.004 wt%) used to produce the silver nanoparticle composite dispersions 1 and 2 was used as is.

[0055] Examples 4 to 5 and Comparative Examples 4 to 6: Preparation of oil-in-water creams Oil-in-water creams were prepared according to the formulations shown in Table 2 below. Specifically, the infrared protection component was added to water and an aqueous medium, and uniformly dispersed with a stirrer to obtain a dispersion. Next, ingredients other than water and the aqueous medium were added to the dispersion, and further stirred with a stirrer to obtain the oil-in-water creams of Examples 4 to 5 and Comparative Examples 4 to 6.

[0056] Examples 6 to 8 and Comparative Examples 7 to 9: Preparation of water-in-oil creams Water-in-oil creams were prepared according to the formulations shown in Table 3 below. Specifically, the infrared protection component was added to water and an aqueous medium, and uniformly dispersed with a stirrer to obtain a dispersion. Next, ingredients other than water and the aqueous medium were added to the dispersion, and further stirred with a stirrer to obtain the water-in-oil creams of Examples 6 to 8 and Comparative Examples 7 to 9.

[0057] "evaluation" The prepared skin topical compositions of the Examples and Comparative Examples were evaluated by the following methods.

[0058] Infrared protection rate Using a doctor blade film applicator (gap: 500 μm), the skin topical composition of each Example and Comparative Example was applied to a slide glass to form a thin film, and the sample was left to stand at 25° C. and 50% humidity for 5 minutes to prepare a measurement sample. Similarly, an uncoated glass substrate was used as a background sample.

[0059] The transmittance of the measurement sample at wavelengths of 300 to 2500 nm was measured using a spectrophotometer. The "average value of the transmittance at wavelengths of 850 nm and 1900 nm" of the measurement sample was taken as the transmittance X (%), and 100-X (%) was taken as the near-infrared protection rate. The larger this value, the higher the near-infrared protection effect of the skin topical composition itself.

[0060] The transmission spectra of the skin topical compositions according to Example 4 and Comparative Example 7 are shown in Fig. 1. The change in the transmission spectrum when mist-like water was sprayed onto the measurement sample according to Example 1 from a distance of 60 cm is shown in Fig. 2.

[0061] The near infrared protection rate was measured to one decimal place.

[0062] (Suppresses rise in skin temperature) Approximately 100 mg of the skin topical composition of the Examples and Comparative Examples was evenly applied to an area of ​​approximately 5 cm x 5 cm on the inside of the forearm of three expert panelists, and dried for 10 minutes under an environment of 25°C and 50% RH.Then, using a solar simulator ("HAL-320W" manufactured by Asahi Spectroscopy Co., Ltd.), the applied area was irradiated with light from a distance of 50 cm for 6 minutes.

[0063] The skin temperature change during irradiation was measured using an infrared thermograph (FLIR Systems' "E6-XT"). Using the same method, the skin temperature change when the skin topical composition was not applied was also measured, and each table shows (temperature rise (°C) when the skin topical composition was not applied) - (temperature rise (°C) when the skin topical composition was applied). The larger this value, the higher the effect of suppressing the rise in skin temperature.

[0064] The effect of suppressing an increase in skin temperature was measured to one decimal place.

[0065] (Suppression of skin temperature rise when water is applied) Approximately 100 mg of the skin topical composition of the Examples and Comparative Examples was evenly applied to an area of ​​approximately 5 cm x 5 cm on the inside of the forearm of three expert panelists, and dried for 10 minutes in an environment of 25°C and 50% RH. Then, mist water was sprayed from a location 60 cm away from the application site, and light was irradiated to the application site from a distance of 50 cm for 6 minutes using a solar simulator ("HAL-320W" manufactured by Asahi Spectroscopy Co., Ltd.).

[0066] The skin temperature change during irradiation was measured using an infrared thermograph (FLIR Systems' "E6-XT"). Using the same method, the skin temperature change when the skin topical composition was not applied was also measured, and the table shows (temperature rise (°C) when the skin topical composition was not applied) - (temperature rise (°C) when the skin topical composition was applied). The larger this value, the higher the effect of suppressing the rise in skin temperature.

[0067] The effect of suppressing an increase in skin temperature was measured to one decimal place.

[0068] <No squeaking sensation when applied to the skin> 100 mg of each topical skin composition was evenly applied to the back of the hand to obtain a cosmetic film, which was then rated on a 5-point scale by five experienced evaluators according to the following criteria, with the average score being the evaluation result. (Evaluation Criteria) 5: Natural and squeaky-free 4: There is little creaking, but it feels a bit strange. 3: Neither 2: Slightly creaking 1: I feel a lot of creaking

[0069] "result" The composition and evaluation results of each composition are shown in Tables 1 to 3 below.

[0070] [Table 1]

[0071] [Table 2]

[0072] [Table 3]

[0073] An emulsion was produced in the same manner as in Example 1, except that 2.4 g of magnesium carbonate (Fujifilm, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 2.4 g of calcium carbonate when producing silver nanoparticle composite dispersion liquid 1. The silver nanoparticle composite obtained here was obtained as a blue precipitate, similar to the production of silver nanoparticle composite dispersion liquid 1.

[0074] When mist-like water was sprayed onto the emulsion thus produced from a distance of 60 cm in the same manner as in obtaining the transmission spectrum of FIG. 2, a color change similar to that in Example 1 occurred.

Claims

1. A composition for topical application to the skin comprising silver nanoparticles and carrier particles thereof.

2. The composition for topical application to skin according to claim 1 , further comprising a binder selected from the group consisting of cationic resins and clay minerals.

3. The composition for external application to skin according to claim 2 , wherein the binder comprises the clay mineral, and the clay mineral is an organically modified clay mineral.

4. The composition for external application to skin according to claim 3 , comprising the organically modified clay mineral in an amount of 0.01% by mass or more and 5.0% by mass or less.

5. The composition for external application to skin according to claim 3, wherein the ratio of the long axis of the organically modified clay mineral to the long axis of the silver nanoparticles is within the range of 0.1 to 200.

6. The composition for external application to skin according to claim 2 , wherein the binder is the cationic resin, and the cationic resin is contained in an amount of 0.01% by mass or more and 2.0% by mass or less.

7. The composition for external application to skin according to claim 1 , further comprising an aqueous component and a water-retaining component.

8. The topical skin composition according to claim 1 , wherein the carrier particles comprise inorganic hydrate particles.

9. The composition for external application to skin according to claim 8 , wherein the inorganic hydrate particles contain calcium carbonate and / or magnesium carbonate.

10. The composition for external application to skin according to claim 9 , wherein the silver nanoparticles and the inorganic hydrate particles form composite particles.

11. The topical skin composition according to claim 1 , wherein at least a portion of the silver nanoparticles have a plate-like shape.

12. The topical skin composition according to claim 1, which is applied to a slide glass using a doctor blade film applicator with a gap of 500 μm to form a thin film, and the thin film obtained by leaving it to stand for 5 minutes at 25° C. and a humidity of 50% has a light transmittance of 70% or less at a wavelength of 850 nm.

13. The topical skin composition according to claim 1, which is applied to a slide glass using a doctor blade film applicator with a gap of 500 μm to form a thin film, and the thin film obtained by leaving it to stand for 5 minutes at 25° C. and a humidity of 50% has a light transmittance of 60% or less at a wavelength of 1900 nm.

14. The composition for external application to skin according to any one of claims 1 to 13, wherein the spectroscopic characteristics change in response to moisture.

15. The composition for external application to the skin according to claim 1 , which is for sunscreen and / or antiperspirant use.

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