JP5446470B2 - Zinc oxide fine particle powder, sunscreen cosmetics - Google Patents

Description

  The present invention relates to a sunscreen cosmetic, and more particularly to a sunscreen cosmetic that has an excellent ultraviolet shielding function, in particular, a long wavelength ultraviolet (UVA) shielding function, excellent usability, and extremely high safety.

In recent years, since the ozone layer is being destroyed due to changes in the global environment, there is concern about the impact on the living body due to the arrival of ultraviolet rays in the low wavelength region to the surface of the earth.
Ultraviolet rays are generally classified into three types: long wavelength ultraviolet rays (UVA) having a wavelength of 320 to 400 nm, medium wavelength ultraviolet rays (UVB) having a wavelength of 290 to 320 nm, and short wavelength ultraviolet rays (UVC) having a wavelength of 290 nm or less.
Among these ultraviolet rays, short wavelength ultraviolet rays (UVC) are absorbed and scattered by the ozone layer above the atmosphere and do not reach the ground, so there is no risk of adverse effects on the human body, but long wavelength ultraviolet rays (UVA) and Wavelength ultraviolet rays (UVB) may cause damage when the human body is directly exposed to radiation, and thus requires attention.

Among these long-wavelength ultraviolet rays (UVA) and medium-wavelength ultraviolet rays (UVB), the medium-wavelength ultraviolet rays (UVB) have attracted attention from an early stage and are known to cause skin disorders such as sunburn and inflammation. In order to protect the skin from sunburn and inflammation, various sunscreen products have already been proposed and put into practical use. In this sunscreen product, an SPF (SUNPROTECT FACTOR) value is used as an index of ultraviolet protection ability.
On the other hand, long-wavelength ultraviolet (UVA) has a milder effect on the skin than medium-wavelength ultraviolet (UVB), but is contained in a large amount in sunlight and reaches the deep part of the skin. It attracts attention as it leads to aging. For this long wavelength ultraviolet ray (UVA), a PA display is used to show ultraviolet ray protection ability.

As an ultraviolet ray shielding agent that protects the human body from this long wavelength ultraviolet ray (UVA), dibenzoylmethane derivatives, bentorazole derivatives, benzophenone derivatives, anthranyl derivatives, etc. are used as organic ultraviolet ray shielding agents. In the agent, titanium oxide particles and zinc oxide particles are used.
By the way, the organic ultraviolet shielding agent has a limit in the amount and combination of blending due to problems in solubility, stability and the like. Therefore, in recent years, zinc oxide which is an inorganic ultraviolet shielding agent and has a high shielding ability against long wavelength ultraviolet rays (UVA) has been used. The ultraviolet shielding effect of zinc oxide is based on the absorption and scattering of ultraviolet rays.

(1) Ultraviolet absorption effect of zinc oxide Zinc oxide is an n-type metal oxide semiconductor, and the band gap energy Eg in its band structure is 3.2 eV. When this zinc oxide is irradiated with light having an energy equal to or higher than its band gap energy Eg, the electrons absorb the light energy and are excited from the valence band to the conduction band. Since the absorption edge of this zinc oxide is around 380 nm, it can absorb the wavelength region from long wavelength ultraviolet rays (UVA) to medium wavelength ultraviolet rays (UVB).
(2) Ultraviolet light scattering effect of zinc oxide When the particle size is close to the wavelength of light, zinc oxide light scattering occurs at Mie scattering, and is maximum at 1/2 of the wavelength. When the particle diameter is further reduced, Rayleigh scattering occurs, and the smaller the particle diameter, the smaller the longer wavelength side. Therefore, in order to shield the long wavelength side of ultraviolet rays (UV) by the scattering effect, it is advantageous to increase the particle diameter of zinc oxide.

  By the way, when using this zinc oxide for sunscreen cosmetics, it is necessary to make it natural color, maintaining the light transmittance of visible region. Therefore, by using zinc oxide fine particles having a primary particle diameter of 15 to 55 nm, the primary particle diameter of the zinc oxide fine particles is set to be less than the wavelength of visible light, whereby long wavelength ultraviolet light (UVA) and medium wavelength ultraviolet light (UVB). There has been proposed a cosmetic material that has a UV protection effect in both wavelength regions and has a transparent feeling (Patent Document 1).

JP 2007-161648 A

By the way, in conventional cosmetics using zinc oxide fine particles, the primary particle diameter of zinc oxide fine particles is in the range of 15 to 55 nm in order to maintain transparency, but when the primary particle diameter is made fine as 15 to 55 nm. As compared with zinc oxide particles having a larger particle diameter, the ultraviolet scattering effect is lowered, and there is a problem that the long wavelength side, particularly the long wavelength ultraviolet ray (UVA) shielding ability is inferior.
Moreover, when the primary particle diameter of zinc oxide is very fine, it is generally excellent in transparency but inferior in concealment. In the case of sunscreen cosmetics, if there is no appropriate concealment, it is difficult to know how much sunscreen cosmetics were applied in which range when actually used, and it tends to cause problems of uneven coating. .
Furthermore, since such zinc oxide fine particles have a large specific surface area, they have a large amount of oil components to be retained. Therefore, the resulting cosmetic has a sticky feeling, a squeaky feeling, and a poor usability. there were.

In addition, when the particle diameter of zinc oxide is fine, the specific surface area increases and moisture absorption occurs. Since moisture absorption affects the subsequent dispersion process, problems such as increased viscosity and poor dispersion are likely to occur, and there is a problem in that variations are likely to occur when the product is made into a cosmetic.
Furthermore, when the primary particle diameter of the zinc oxide fine particles is reduced to 15 to 55 nm, the zinc oxide fine particles may be absorbed into the body from the sweat glands of the skin, and the safety to the human body and the production of this cosmetic. There is a risk of concern in terms of safety for workers involved in the process.

  The present invention has been made to solve the above problems, and provides a sunscreen cosmetic that has an excellent shielding function against ultraviolet rays, particularly long wavelength ultraviolet rays (UVA), has an excellent feeling of use, and has extremely high safety. The purpose is to do.

As a result of intensive studies to improve sunscreen cosmetics, the present inventors, as a component of sunscreen cosmetics, have fine particles of zinc oxide having an average primary particle size of 0.2 μm or more and 0.3 μm or less as a powder component. If the primary particle diameter of 90% or more of these zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less, ultraviolet rays, particularly long wavelength ultraviolet rays (UVA) can be effectively shielded. Furthermore, the zinc oxide fine particles having a primary particle size of 0.1 μm or more and 0.4 μm or less have a small specific surface area compared to the zinc oxide fine particles having a primary particle size of less than 100 nm, so that the amount of oil component retained is small. The present inventors have found that there is no stickiness, excellent usability, no danger of being absorbed into the body, and extremely high safety, and the present invention has been completed.

That is, the sunscreen cosmetic of the present invention is a sunscreen cosmetic containing zinc oxide fine particles, and the average primary particle diameter of the zinc oxide fine particle powder is 0.2 μm or more and 0.3 μm or less. The primary particle diameter of 90% or more of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less.

The average primary particle diameter of the zinc oxide fine particles is preferably 0.2 μm or more and 0.3 μm or less.
The primary particle diameter of the zinc oxide fine particles is preferably 0.2 μm or more and 0.4 μm or less.
The zinc oxide fine particles are preferably subjected to a hydrophobic treatment on the surface thereof.

According to the sunscreen cosmetic of the present invention, since the primary particle diameter of 90% or more of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less, ultraviolet rays, particularly long wavelength ultraviolet rays (UVA) are used. It can be effectively shielded.
Further, the zinc oxide fine particles having a primary particle diameter of 0.1 μm or more and 0.4 μm or less have a specific surface area smaller than that of the zinc oxide fine particles having a primary particle diameter of less than 100 nm, and thus there is no stickiness or roughness. The paste is good, so that the feeling of use can be improved while maintaining transparency.

Further, the zinc oxide fine particles having a primary particle diameter of 0.1 μm or more and 0.4 μm or less can suppress moisture absorption, and can suppress problems such as difficulty in dispersion in the subsequent dispersion process. Therefore, it is possible to provide cosmetics that do not vary as products.
Furthermore, the zinc oxide fine particles having a primary particle diameter of 0.1 μm or more and 0.4 μm or less have no danger of being absorbed into the body from the sweat glands of the skin and are excellent in safety to the human body. Moreover, there is no danger for the workers involved in the cosmetic manufacturing process, and the manufacturing process is excellent in safety.

The form for implementing the sunscreen cosmetics of this invention is demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

The sunscreen cosmetic of the present embodiment is a sunscreen cosmetic containing zinc oxide fine particles, and the primary particle diameter of the zinc oxide fine particles is preferably 0.1 μm or more and 0.4 μm or less, more Preferably they are 0.2 micrometer or more and 0.4 micrometer or less, More preferably, they are 0.2 micrometer or more and 0.3 micrometer or less.
The reason why the primary particle diameter of the zinc oxide fine particles is limited to 0.1 μm or more and 0.4 μm or less is that the above range can effectively shield ultraviolet rays, particularly long wavelength ultraviolet rays (UVA), and has a transparent feeling. This is because it is possible to improve the feeling of use while maintaining it and to ensure sufficient safety related to the fine particles.

  Here, when the primary particle diameter of the zinc oxide fine particles is less than 0.1 μm, ultraviolet rays, particularly long wavelength ultraviolet rays (UVA) cannot be shielded, and the shielding ability against long wavelength ultraviolet rays (UVA) is insufficient. On the other hand, when the primary particle diameter exceeds 0.4 μm, the zinc oxide fine particles may be devitrified or the transparency may be reduced, so that makeup may be promoted. This is because when used as a material, it becomes impossible to maintain the same degree of transparency as that of normal zinc oxide fine particles.

Conventionally, some zinc oxide particles used for applications other than cosmetics have primary particle diameters exceeding 0.5 μm, but the zinc oxide particles have a particle size distribution even though the average particle diameter is not so large. Since it contains a wide range of, for example, very large particles exceeding 1 μm, the degree of whiteness becomes too strong, and the transparency required for cosmetics cannot be obtained sufficiently. Therefore, as a sunscreen cosmetic, Not suitable for use.
On the other hand, the zinc oxide fine particles used in the present embodiment are necessary as cosmetics because the primary particle diameter of 90% or more of the total number of fine particles is within the range of 0.1 μm to 0.4 μm. Sufficient transparency can be secured.

The average primary particle diameter of the zinc oxide fine particles is preferably 0.2 μm or more and 0.3 μm or less, more preferably 0.2 μm or more and 0.25 μm or less.
In this zinc oxide fine particle, the balance between transparency and concealability (good skin covering property) can be improved by narrowing the particle size distribution as much as possible.
Here, the reason why the average primary particle diameter of the zinc oxide fine particles is 0.2 μm or more and 0.3 μm or less is that when the average primary particle diameter is less than 0.2 μm, as the particle diameter decreases, ultraviolet rays, particularly long This is because problems such as a decrease in shielding effect in the wavelength ultraviolet (UVA) region, a decrease in covering power such as skin spots, and a decrease in feeling of use due to a squeaky sensation occur, while the average primary particle diameter is 0. If it exceeds 3 μm, the white color is emphasized when used, and as a result, the transparency is lost.

  As described above, the primary particle size of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less, and the average primary particle size is 0.2 μm or more and 0.3 μm or less. The effect of securing, maintaining the same transparency as ordinary zinc oxide fine particles, dispersing and transparency of zinc oxide fine particles in cosmetics, improving the feeling of use, and ensuring the homogeneity of cosmetics as products Can be increased.

When the particle size distribution of the zinc oxide fine particles is expressed as a percentage of the number of particles with respect to the primary particle size, the number of zinc oxide fine particles having a primary particle size of 0.1 μm to 0.4 μm The total particle number is preferably 90% or more, more preferably 95% or more, and still more preferably 97% or more.
Here, the content ratio of the zinc oxide fine particles having a primary particle diameter in the above-mentioned range was set to 90% or more because the content range is an ultraviolet ray, particularly a long wavelength ultraviolet ray (UVA) shielding effect, sticky feeling and squeaky feeling. It is possible to express the improvement of the skin, the goodness of the glue, etc., and further, by having an appropriate shielding property, it becomes possible to cover the skin spots, wrinkles, etc., and thus the feeling of use while maintaining transparency. This is because it is within a range where the effect of improving the image quality can be obtained. In addition, when the content rate of this zinc oxide fine particle will be less than 90%, these effects cannot be anticipated, Therefore, the effect of improving a feeling of use and skin covering property, maintaining transparency, is not acquired.

The specific surface area of the zinc oxide fine particles is preferably 3 m ² / g or more and 10 m ² / g or less, more preferably 3 m ² / g or more and 5 m ² / g or less, more preferably 3.5 m ² / g or more and 4 or less. 0.5 m ² / g or less.
When the specific surface area is in the above range, the effects of dispersion and transparency of zinc oxide fine particles in the cosmetic, improvement in the feeling of use, and ensuring uniformity of the cosmetic as a product can be further enhanced.

  The shape of the zinc oxide fine particles is not particularly limited, such as a spherical shape, a lump shape, a spindle shape, or a flake shape, but a spindle shape or a flake shape is preferable. The spindle shape has a high effect of suppressing secondary aggregation, and even in an actual cosmetic, it can be blended in a state close to primary particles. In addition, the flake shape is more likely to be packed more densely than the spherical shape, has a high shielding power against ultraviolet rays (UV), suppresses secondary aggregation, suppresses a squeaky feeling, and improves a feeling of use (expansion).

The zinc oxide fine particles are preferably subjected to a hydrophobic treatment on the surface thereof.
Although it does not specifically limit as this hydrophobic processing agent, 1 type (s) or 2 or more types selected from the group of a silicone compound, a fatty acid, fatty acid soap, fatty acid ester, and an organic titanate compound are used suitably.

  Examples of the silicone compound include silicone oils such as methylhydrogenpolysiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane; alkylsilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, and octyltrimethoxysilane; Examples thereof include fluoroalkylsilanes such as trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane.

  Examples of the fatty acid include palmitic acid, isostearic acid, stearic acid, lauric acid, myristic acid, behenic acid, oleic acid, rosin acid, 12-hydroxystearic acid, and the like. Examples of the fatty acid soap include aluminum stearate, calcium stearate, and aluminum 12-hydroxystearate. Examples of the fatty acid ester include dextrin fatty acid ester, cholesterol fatty acid ester, sucrose fatty acid ester, starch fatty acid ester and the like.

  Examples of the organic titanate compound include isopropyl triisostearoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tri (dodecyl) benzenesulfonyl titanate, neopentyl (diallyl) oxytri (dioctyl) phosphate titanate, neopentyl (diallyl) oxytritriate. And neododecanoyl titanate.

Examples of a method for subjecting the surface of the zinc oxide fine particles to a hydrophobic treatment using the hydrophobic treatment agent include a wet method and a dry method.
The wet method is a method in which a hydrophobic treatment agent and zinc oxide fine particles are put into a solvent and mixed with stirring, then the solvent is removed, the hydrophobic treatment agent is baked on the zinc oxide fine particles, and then pulverized, thereby the surface of the zinc oxide fine particles. Is a method of hydrophobic treatment.
In the dry method, the hydrophobic treatment agent and the dried zinc oxide fine particles are put into a dry mixer such as a mixer, mixed with stirring, and then the hydrophobic treatment agent is baked into the zinc oxide fine particles and then pulverized, thereby obtaining the zinc oxide fine particles. This is a method of hydrophobizing the surface.

  The content of the zinc oxide fine particles in the sunscreen cosmetic is preferably 1% by mass or more and 30% by mass or less in order to effectively shield ultraviolet rays, particularly long wavelength ultraviolet rays (UVA). Is 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less.

In addition to the zinc oxide fine particles, the sunscreen cosmetics include a hydrophobic dispersion medium, inorganic fine particles, inorganic pigment, dispersion medium, fats and oils, surfactant, moisturizer, thickener, pH adjuster, as necessary. You may contain a nutrient, antioxidant, a fragrance | flavor, etc.
Hydrophobic dispersion media include liquid paraffin, squalane, isoparaffin, branched light paraffin, petroleum oils such as petrolatum and ceresin, ester oils such as isopropyl myristate, cetyl isooctanoate and glyceryl trioctanoate, Silicone oils such as methylcyclopentasiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, higher fatty acids such as uric acid, myristic acid, palmitic acid, stearic acid, lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, isostearyl alcohol And higher alcohols.

  Examples of inorganic fine particles and inorganic pigments include calcium carbonate, calcium phosphate (apatite), magnesium carbonate, calcium silicate, magnesium silicate, aluminum silicate, kaolin, talc, titanium oxide, aluminum oxide, yellow iron oxide, and γ-oxidation. Examples include iron, cobalt titanate, cobalt violet, and silicon oxide.

This sunscreen cosmetic may further contain one or more organic ultraviolet absorbers.
Specific examples of the organic ultraviolet absorber include the following various organic ultraviolet absorbers.
Examples of the benzotriazole ultraviolet absorber include 2,2′-hydroxy-5-methylphenylbenzotriazole, 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole, and 2- (2′-). Examples include hydroxy-5′-methylphenylbenzotriazole.
Examples of the benzoylmethane ultraviolet absorber include dibenzalazine, dianisoylmethane, 4-tert-butyl-4′-methoxydibenzoylmethane, 1- (4′-isopropylphenyl) -3-phenylpropane-1,3- Examples include dione and 5- (3,3′-dimethyl-2-norbornylidene) -3-pentan-2-one.

Benzoic acid-based ultraviolet absorbers include paraaminobenzoic acid (PABA), PABA monoglycerin ester, N, N-dipropoxy PABA ethyl ester, N, N-diethoxy PABA ethyl ester, N, N-dimethyl PABA ethyl ester, N, Examples thereof include N-dimethyl PABA butyl ester and N, N-dimethyl PABA methyl ester.
As the anthranilic acid ultraviolet absorber, homomenthyl-N-acetylanthranilate and the like can be mentioned.
Examples of the salicylic acid ultraviolet absorber include amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-2-propanol phenyl salicylate and the like.

  Cinnamic acid-based UV absorbers include octylmethoxycinnamate, di-paramethoxycinnamic acid-glyceryl mono-2-ethylhexanoate, octylcinnamate, ethyl-4-isopropylcinnamate, methyl-2,5- Diisopropylcinnamate, ethyl-2,4-diisopropylcinnamate, methyl-2,4-diisopropylcinnamate, propyl-p-methoxycinnamate, isopropyl-p-methoxycinnamate, isoamyl-p-methoxycinnamate, octyl- p-methoxycinnamate (2-ethylhexyl-p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2- Ethylhexyl -Α-cyano-β-phenylcinnamate, glyceryl mono-2-ethylhexanoyl-diparamethoxycinnamate and the like.

  Silicone cinnamate UV absorbers include [3-bis (trimethylsiloxy) methylsilyl-1-methylpropyl] -3,4,5-trimethoxycinnamate, [3-bis (trimethylsiloxy) methylsilyl-3- Methylpropyl] -3,4,5-trimethoxycinnamate, [3-bis (trimethylsiloxy) methylsilylpropyl] -3,4,5-trimethoxycinnamate, [3-bis (trimethylsiloxy) methylsilylbutyl ] -3,4,5-trimethoxycinnamate, [3-tris (trimethylsiloxy) silylbutyl] -3,4,5-trimethoxycinnamate, [3-tris (trimethylsiloxy) silyl-1-methylpropyl] -3,4-dimethoxycinnamate and the like.

  Other organic ultraviolet absorbers include 3- (4′-methylbenzylidene) -d, l-camphor, 3-benzylidene-d, l-camphor, urocanic acid, urocanic acid ethyl ester, 2-phenyl-5 Examples include methylbenzoxazole, 5- (3,3′-dimethyl-2-norbornylidene) -3-pentan-2-one, silicone-modified UV absorber, and fluorine-modified UV absorber.

According to the sunscreen cosmetic of the present embodiment, the primary particle diameter of the zinc oxide fine particles is distributed in a narrow range of 0.1 μm or more and 0.4 μm or less, so that even if the primary particle diameter is 0.1 μm or more, suntan Transparency sufficient as a stop cosmetic can be obtained, and on the contrary, skin spots and the like can be satisfactorily covered without whitening the skin.
Further, since the primary particle diameter of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less, the cohesive force between the particles is not strong, and therefore, the secondary aggregation of the zinc oxide fine particles can be suppressed. Thereby, zinc oxide microparticles | fine-particles can be disperse | distributed in the state close | similar to a primary particle in cosmetics, and transparency can be maintained.

Moreover, since the amount of oil absorption of the zinc oxide fine particles can be suppressed, a cosmetic with no stickiness and good usability can be obtained.
Furthermore, there is almost no moisture absorption of the zinc oxide fine particles, and there is no problem of viscosity increase or poor dispersion even in the cosmetic dispersion process, so there is almost no variation in the cosmetics as a product, ensuring homogeneity. it can.

  Here, the primary particle diameter range of the zinc oxide fine particles is narrowed to 0.2 μm or more and 0.4 μm or less, and further 0.2 μm or more and 0.3 μm or less, thereby ensuring the safety and ensuring transparency. The above-described various effects can be further enhanced.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

Example 1
After putting 35.0 parts by mass of decamethylcyclopentasiloxane, 3.0 parts by mass of polyoxyethylene / polyalkylsiloxane, and 1.0 parts by mass of the modified clay mineral into a heating type container, the mixture was heated to 60 degrees and homomixer The mixture was stirred and dispersed to obtain a dispersion A.
Subsequently, surface treatment is performed on the zinc oxide fine particles A having a primary particle size of 0.10 μm or more and 0.40 μm or less (average primary particle size: 0.23 μm) by a wet method using methylhydrogenpolysiloxane, and then subjected to a hydrophobic treatment. Zinc oxide fine particles A were obtained.
The primary particle diameter and average primary particle diameter of the hydrophobic treated zinc oxide fine particles A were the same as before the treatment.

Next, 12.0 parts by mass of hydrophobically treated zinc oxide fine particles A and 2.0 parts by mass of hydrophobically treated talc were added to the dispersion A, and the mixture was sufficiently stirred and mixed with a homomixer to obtain a mixture A1.
On the other hand, 5.0 parts by mass of 1,3 butylene glycol, 0.1 parts by mass of EDTA / 2NA (ethylenediamine-tetraaceticacid / 2naphtylamine), paraben (appropriate amount), perfume (appropriate amount), and purified water (remaining amount) are mixed. A mixture A2 having a total amount of 47.0 parts by mass was obtained.
Next, the mixture A2 was gradually added to the mixture A1, and then this was sufficiently mixed with a homomixer to prepare the sunscreen cream of Example 1.

(Example 2)
Example according to Example 1 except that zinc oxide fine particles B having a primary particle size of 0.1 μm or more and 0.4 μm or less (average primary particle size: 0.22 μm) were used in place of the zinc oxide fine particles A 2 sunscreens were made.

(Example 3)
Example according to Example 1 except that instead of the zinc oxide fine particles A, zinc oxide fine particles C having a primary particle size of 0.2 μm or more and 0.4 μm or less (average primary particle size: 0.3 μm) were used. 3 sunscreen creams were made.

Example 4
Example according to Example 1 except that instead of the zinc oxide fine particles A, zinc oxide fine particles D having a primary particle size of 0.2 μm or more and 0.3 μm or less (average primary particle size: 0.25 μm) were used. 4 sunscreen creams were made.

(Comparative Example 1)
A comparative example according to Example 1 except that zinc oxide fine particles E having a primary particle size of 0.02 μm or more and 0.05 μm or less (average primary particle size: 0.035 μm) were used instead of the zinc oxide fine particles A. 1 sunscreen cream was made.

(Comparative Example 2)
Comparative Example according to Example 1 except that zinc oxide fine particles F having a primary particle size of 0.3 μm or more and 0.6 μm or less (average primary particle size: 0.5 μm) were used instead of the zinc oxide fine particles A 2 sunscreens were made.

(Evaluation)
A. Primary particle diameter of zinc oxide fine particles The primary particle diameter of each of the zinc oxide fine particles A to F in Examples 1 to 4 and Comparative Examples 1 and 2 was evaluated by the following method.
A scanning electron microscope (SEM) was used to arbitrarily select 120 zinc oxide fine particles in the field of view, and the maximum diameter among a plurality of diameters passing through the center point of these fine particles was defined as the primary particle size.
As a result, the zinc oxide fine particles A used in Example 1 were in the range of the primary particle diameter of 91% of the fine particles in Table 1 and the zinc oxide fine particles B used in Example 2 were 95%. The primary particle diameter of the fine particles was within the range of the primary particle diameter in Table 1, and the zinc oxide fine particles C used in Example 3 were subjected to the primary particle diameter of 91% of the fine particles within the range of the primary particle diameter in Table 1. In the zinc oxide fine particles D used in Example 4, the primary particle size of 90% of the fine particles was in the range of the primary particle size in Table 1.

B. Average primary particle diameter of zinc oxide fine particles The average primary particle diameters of the zinc oxide fine particles AF of Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated by the following methods.
Using a scanning electron microscope (SEM), arbitrarily select 120 zinc oxide fine particles in the field of view, and set the maximum diameter among a plurality of diameters passing through the center point of these fine particles as the primary particle diameter, and the number average of the primary particle diameters Was the average primary particle size.
Each average primary particle diameter is shown in Table 1.

C. Evaluation of Sunscreen Cream For each of the sunscreen creams of Examples 1 to 4 and Comparative Examples 1 and 2, the feeling of use, the covering property of the skin, the long wavelength ultraviolet ray (UVA) shielding effect, and the transparency were examined by the following evaluation methods. . The evaluation results are shown in Table 1.
(1) Feeling of use The sunscreen cream was actually used by 30 monitors, and the feelings obtained for each of the items "Goodness of spread", "No stickiness" and "No feeling of squeaking" were obtained. We had you evaluate by. The evaluation criteria are as follows.
(Double-circle): It is a very favorable feeling of use.
○: Good feeling in use.
Δ: Normal use feeling.
X: Use feeling is inferior.

(2) Skin coverage The sunscreen cream was actually used by 30 monitors and evaluated for "skin coverage". The evaluation criteria are as follows.
A: The skin coverage is very good.
○: The skin covering property is good.
(Triangle | delta): The cover property of skin is the same as a normal thing.
X: The skin covering property is inferior.

(3) UVA shielding effect An sunscreen cream was applied onto a non-woven nursing tape at a coating amount of ² mg / cm ² to prepare an evaluation sample. Subsequently, the UVA shielding effect of the coating film of this evaluation sample was measured using an ultraviolet shielding ability evaluation apparatus UV-1000S (manufactured by Labsphere). The evaluation criteria are as follows.
A: UVA-Ratio is 0.8 or more. UVA shielding ability is very high.
○: UVA-Ratio is 0.6 or more and less than 0.8. UVA shielding ability is high.
Δ: UVA-Ratio is 0.4 or more and less than 0.6.
X: UVA-Ratio is less than 0.4 UVA shielding ability is low.

(4) Transparency When the sunscreen cream was applied onto a non-woven nursing tape at a coating amount of ² mg / cm ² , the transparency of the coating film was visually examined. The evaluation criteria are as follows.
A: The transparency is very high.
○: High transparency.
Δ: Normal transparency.
X: Low transparency.

According to Table 1, the sunscreens of Examples 1 to 4 were excellent in use feeling, UVA shielding effect and transparency, and were particularly excellent in “UVA shielding effect” and “good skin coverage”. .
On the other hand, the sunscreen cream of Comparative Example 1 uses extremely fine zinc oxide fine particles having a primary particle size of 0.02 μm or more and 0.05 μm or less, so that the transparency is excellent but the hiding power is weak, Almost no cover property was obtained. In addition, the feeling of use was not different from that of a normal sunscreen cream.
Moreover, since the sunscreen cream of Comparative Example 2 used zinc oxide particles having a primary particle size of 0.30 μm or more and 0.60 μm or less, which is too large, the coating film becomes clouded and the transparency is unacceptable. Worsened. Moreover, the denseness of the coating film was lowered, and the UVA shielding effect was also lowered as compared with Examples 1-3.

  The sunscreen cosmetic of the present invention is effective for ultraviolet rays, particularly long wavelength ultraviolet rays (UVA), by setting the primary particle diameter of 90% or more of the zinc oxide fine particles to 0.1 μm or more and 0.4 μm or less. Since it can be shielded, has no sticky feeling or squeaky feeling, has a good paste, and thus can improve the feeling of use while maintaining transparency, not to mention the sunscreen cream described above, It can be widely used as a cosmetic requiring an ultraviolet shielding effect, and its industrial value is extremely high.

Claims (4)

A powder of zinc oxide fine particles used for sunscreen cosmetics,
The zinc oxide fine particles have an average primary particle size of 0.2 μm or more and 0.3 μm or less,
A zinc oxide fine particle powder, wherein a primary particle diameter of 90% or more of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less. A sunscreen cosmetic containing zinc oxide fine particles,
The average primary particle diameter of the zinc oxide fine particle powder is 0.2 μm or more and 0.3 μm or less,
A sunscreen cosmetic, wherein a primary particle diameter of 90% or more of the zinc oxide fine particles is 0.1 μm or more and 0.4 μm or less. Sunscreen cosmetic of claim 2 Symbol mounting, wherein the primary particle size of the zinc oxide particles is 0.2μm or more and 0.4μm or less. The sunscreen cosmetic according to any one of claims 2 and 3 , wherein the surface of the zinc oxide fine particles is subjected to a hydrophobic treatment.