CN111093614A

CN111093614A - Skin cosmetic and method for evaluating elasticity of cosmetic

Info

Publication number: CN111093614A
Application number: CN201880054792.7A
Authority: CN
Inventors: 相见牧子; 吉田那绪子; 河野贵胤
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2017-08-30
Filing date: 2018-08-30
Publication date: 2020-05-01
Also published as: JPWO2019045020A1; WO2019045020A1; JP7026691B2; JP2021181502A

Abstract

The present invention provides a skin cosmetic comprising a water-soluble polymer having a cyclic structure in a main chain or a side chain, a water-soluble polymer having a dimethyl or trimethyl amino group, and a water-soluble polymer forming a coating film at room temperature, and a method for evaluating the elasticity of the cosmetic, comprising: the ratio of the second area to the first area is calculated by measuring the first area, which is the area of the non-dried film, and the second area, which is the area of the dried film, which are formed from a cosmetic containing a substance to be measured for its elastic feel, a water-soluble polymer that forms a film at room temperature, and a coloring substance, and calculating the ratio of the second area to the first area.

Description

Skin cosmetic and method for evaluating elasticity of cosmetic

Technical Field

The present invention relates to a skin cosmetic and a method for evaluating the elasticity of a cosmetic.

Background

It is known that the uneven structure (texture) on the skin surface is smoothed with age, the size is also uneven, and the elastic force is reduced (the elastic feeling disappears). Further, although the skin with regular texture reflects a large amount of light and reflects the light uniformly as a whole, the aged skin reflects a small amount of light and has a biased direction, and the elasticity of the appearance is lost.

Cosmetics comprising water-soluble polymers having a film-forming ability, water-dispersible polymers having a hydrophobic film-forming ability, and the like have been proposed. For example, japanese patent No. 3905457 discloses a cosmetic composition that can provide an appropriate elastic force when dry.

In addition, as for the elastic force, there has been proposed an elastic feeling evaluation method in which a luminance grayscale image is obtained for a cheek region of a face image of a subject, and an area ratio of a high luminance region to a medium luminance region or the like is used as an evaluation index of the elastic feeling. For example, japanese patent No. 5250956 discloses that in a medium-to-high brightness region, the width and shape thereof correspond to the evaluation of the feeling of elasticity.

Disclosure of Invention

Technical problem to be solved by the invention

The cosmetic disclosed in japanese patent No. 3905457 is a cosmetic that is spread thinly on the skin and is removed by water or warm water after a coating film is formed on the skin, and it is not intended to make the coating film itself exhibit elasticity.

The evaluation method described in japanese patent No. 5250956 is a method of acquiring a face image and requiring image analysis, and is not easy to use, and is difficult to use for screening or designing components contained in cosmetics.

An object of one embodiment of the present invention is to provide a skin cosmetic capable of improving elasticity by forming a film structure having stretchability on a skin surface.

An object of another embodiment of the present invention is to provide a method for evaluating the elasticity of a cosmetic that can objectively evaluate the stretchability of a coating film formed of a substance to be measured.

Means for solving the technical problem

Means for solving the above problems include the following embodiments.

[ 1] A cosmetic for skin, which contains at least one selected from a water-soluble polymer having a cyclic structure in the main chain or side chain and a water-soluble polymer having a dimethyl or trimethyl amino group, and at least one selected from water-soluble polymers that form a coating film at room temperature.

<2> the cosmetic for skin according to <1> above, wherein the water-soluble polymer having a cyclic structure in a main chain or a side chain is at least one selected from the group consisting of polyimide-1 and polyvinylpyrrolidone.

<3> the cosmetic for skin according to <1> or <2>, wherein the water-soluble polymer having a dimethyl group or a trimethyl amino group is at least one selected from the group consisting of a polyacrylic copolymer having a dimethyl group or a trimethyl amino group and a polymethacrylic copolymer having a dimethyl group or a trimethyl amino group.

<4> the cosmetic for skin according to any one of <1> to <3>, wherein the water-soluble polymer forming the coating film at room temperature is at least one selected from water-soluble polymers of polysaccharides.

<5> the cosmetic for skin according to any one of <1> to <4>, wherein the water-soluble polymer of polysaccharide is at least one selected from the group consisting of xanthan gum, carrageenan, gellan gum, pullulan, gum arabic, guar gum, locust bean gum, agar, alginic acid, pectin, cellulose, corn starch, and derivatives thereof.

<6> the cosmetic for skin according to any one of <1> to <5>, wherein the water-soluble polymer forming a coating film at room temperature is contained in an amount of 0.01 to 5% by mass based on the total mass of the cosmetic for skin.

<7> a method for evaluating the elasticity of a cosmetic, which comprises a step of applying a cosmetic containing a substance to be measured for elasticity, a water-soluble polymer forming a coating film at room temperature, and a coloring substance onto a transparent solid, the method comprising: the area of the undried film formed by applying the cosmetic to the transparent solid was measured as a first area, and the area of the dried film formed by drying the undried film was measured as a second area, and the ratio of the second area to the first area was calculated.

<8> the evaluation method according to <7>, wherein the substance to be measured whose ratio of the second area to the first area is 5% or more is selected.

Effects of the invention

According to one embodiment of the present invention, a skin cosmetic capable of improving elasticity by forming a film structure having stretchability on a skin surface can be provided.

According to another embodiment of the present invention, it is possible to provide a method for evaluating the elasticity of a cosmetic that can objectively evaluate the elasticity of a coating film formed of a substance whose elasticity is to be measured.

Drawings

Fig. 1 is an image obtained in the evaluation of the coating film of the example.

FIG. 2 is a graph showing the results of the coating evaluation of the examples.

Fig. 3 is a photograph taken of the texture of the skin surface in the evaluation of the texture of the embodiment.

Detailed Description

Hereinafter, an example of an embodiment of the skin cosmetic and the method for evaluating the elasticity of the cosmetic according to the present invention will be described. However, the present invention is not limited to the following embodiments, and can be implemented by being appropriately modified within the scope of the present invention.

In the present specification, a numerical range represented by "to" means a range in which numerical values before and after "to" are included as a minimum value and a maximum value, respectively.

In the numerical ranges recited in the present specification, the upper limit or the lower limit recited in one numerical range may be replaced with the upper limit or the lower limit recited in another numerical range recited in a stepwise manner. In addition, in the numerical ranges described in the present specification, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples.

In the present specification, the amount of each component in the composition means the total amount of a plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition.

In the present invention, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present invention, the room temperature is 25 ℃.

< cosmetics for skin >

The skin cosmetic of the present invention (hereinafter, may be simply referred to as "skin cosmetic") is a skin cosmetic containing at least one of a water-soluble polymer having a cyclic structure in a main chain or a side chain and a water-soluble polymer having a dimethyl or trimethyl amino group, and at least one of water-soluble polymers forming a coating film at room temperature.

According to the cosmetic of the present invention, the elasticity can be improved by forming the film structure having elasticity on the skin surface.

In the present invention, the water-soluble polymer means that no precipitation and/or precipitation of the polymer is observed in water when the polymer is dissolved in water at a predetermined concentration (5g/L) by heating and then cooled to 25 ℃.

In the present invention, at least one of a water-soluble polymer having a cyclic structure in a main chain or a side chain and a water-soluble polymer having a dimethyl or trimethyl amino group (hereinafter, may be referred to as "first polymer") preferably has a property of giving elasticity to the skin.

The water-soluble polymer having a cyclic structure in the main chain or side chain is not particularly limited, but the cyclic structure is preferably a 5-membered ring structure containing a nitrogen atom, more preferably pyrrolidone or maleimide, and still more preferably a structure in which the nitrogen atom of pyrrolidone is bonded to the side chain of the water-soluble polymer or a structure in which the carbon-carbon bond of maleimide is contained in the main chain of the water-soluble polymer. Specific examples of the water-soluble polymer having a cyclic structure in the main chain or side chain include polyimide-1, polyvinylpyrrolidone, and copolymers thereof.

Polyimide-1, also known as AQUAFLEX (registered trademark) XL-30(AQUAFLEX XL-30), is an isobutylene/dimethylaminopropylmaleimide/ethoxylated maleimide/maleic acid copolymer (isobutelene/dimethyllaproppyl maleimide/ethoxylated maleimide/maleic acid copolymer). The polyvinylpyrrolidone is not particularly limited, but polyvinylpyrrolidone K30, polyvinylpyrrolidone K90 and the like are preferable.

The water-soluble polymer having a dimethyl group or a trimethyl amino group is not particularly limited, but is preferably at least one of polyacrylic acid having a dimethyl group or a trimethyl amino group and polymethacrylic acid copolymer having a dimethyl group or a trimethyl amino group. In the present invention, a phosphorylcholine group is included as a trimethylamino group.

Specific examples of the water-soluble polymer having a dimethyl or trimethyl amino group include an amine oxide-based polymer (acrylate/lauryl acrylate/stearyl acrylate/ethyl amine methacrylate) copolymer, a (methacryloyloxyethylcarboxybetaine/alkyl methacrylate) copolymer, polymethacryloxyethylphosphocholine, polyquaternium-51, polyquaternium-64, polyquaternium-72, and the like.

Specific examples of the water-soluble polymer having a dimethyl or trimethyl amino group include Diafomer Z-651, Yukaforder 301, Lipidure HM, Lipidure PMB, and Lipidure C.

The cosmetic for skin of the present invention preferably contains 0.01 to 5% by mass of the total amount of at least one (first polymer) of the water-soluble polymer having a cyclic structure in the main chain or side chain and the water-soluble polymer having a dimethyl or trimethyl amino group in the cosmetic for skin, more preferably 0.1 to 3% by mass, and still more preferably 1 to 3% by mass. When the amount is within this range, the skin cosmetic composition is applied to the skin and dried at room temperature, and a film is formed and shrinks, thereby easily giving elasticity to the skin.

In the present invention, it is preferable that at least one of the water-soluble polymers forming a coating at room temperature (hereinafter, sometimes referred to as "second polymer") has a property of being capable of forming a coating when dissolved in a cosmetic together with the first polymer and applied to skin or the like at room temperature and dried.

The water-soluble polymer forming a film at room temperature is not particularly limited as long as it is a water-soluble polymer forming a film at room temperature, and is preferably a polysaccharide. In the present invention, the polysaccharide is preferably at least one selected from the group consisting of xanthan gum, carrageenan, gellan gum, pullulan, gum arabic, guar gum, locust bean gum, agar, alginic acid, pectin, cellulose, corn starch, and derivatives thereof. The polysaccharide is more preferably at least one selected from the group consisting of xanthan gum, carrageenan, gellan gum, pullulan, guar gum, pectin, cellulose, corn starch and derivatives thereof, and even more preferably at least one selected from the group consisting of xanthan gum, pullulan, gellan gum, guar gum, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carrageenan, pectin and modified corn starch.

Further, as commercially available water-soluble polymers capable of forming a coating film at room temperature, there may be mentioned, specifically, NOMCORT (registered trademark) Z, SAN ACE (registered trademark) C, Echo Gum (registered trademark), KELCOGEL (registered trademark) HM, CG-LA, GLYLOID (registered trademark) 6C, KELTROL (registered trademark) CG series, GENUVISCO (registered trademark) type PJ-JPE, SUNALGIN200/80, SUPERGEL CSA200/50, GEGUNUM (registered trademark) type RL-200-J, JAGUAR (registered trademark) HP-105, NEOVISCO MC, SANHEC, GENUGENUGEL (registered trademark) WG-108, GEERGEL CSA J, GENU (registered trademark) LN-5CD-J, MIR USTYLE CP, Sangolose (registered trademark) 90L, 60M, AMAZE and the like.

In the cosmetic for skin of the present invention, the content of the water-soluble polymer forming a coating film at room temperature can be appropriately selected depending on the type and purpose of the application mode. The total amount of the water-soluble polymer (second polymer) forming a film at room temperature is preferably 0.01 to 5% by mass, more preferably 0.1 to 1% by mass, based on the total mass of the cosmetic for skin. When the amount is within this range, a film is easily formed when the skin cosmetic is applied to the skin and dried.

The skin cosmetic of the present invention may contain an additive component as appropriate depending on the form of the skin cosmetic, within a range not impairing the effect of the present invention.

The skin cosmetic of the present invention is not particularly limited as long as it is a skin cosmetic. Examples of the cosmetic composition include, but are not limited to, skin care cosmetic compositions (lotions, milky lotions, creams, whitening cosmetics, etc.), sunscreen cosmetic compositions, makeup precursors (primers), foundation compositions (foundation), and makeup cosmetics (makeup cosmetics) such as lipstick.

The skin cosmetic of the present invention can be produced by a usual method using the above-mentioned ingredients. Specifically, the skin cosmetic of the present invention can be obtained by stirring and mixing the first and second polymers or a mixture obtained by adding a solvent such as water to the first and second polymers as necessary. The skin cosmetic of the present invention can be obtained by mixing components that can be added as needed by a conventional method.

As an example of a method of using the skin cosmetic of the present invention, it can be applied to the skin as a skin cosmetic by spreading it thinly on the skin. When applied to the skin, the skin cosmetic is dried to form a coating film, thereby imparting elasticity to the skin.

< method for evaluating elasticity of cosmetic >

The method for evaluating the elasticity of a cosmetic according to the present invention (hereinafter, may be simply referred to as "evaluation method") includes a step of applying a cosmetic containing a substance to be measured for elasticity, a water-soluble polymer forming a coating film at room temperature, and a coloring substance onto a transparent solid, and includes: the area of the undried film formed by applying the cosmetic to the transparent solid was measured as a first area, and the area of the dried film formed by drying the undried film was measured as a second area, and the ratio of the second area to the first area was calculated.

By the evaluation method of the present invention, the stretchability (i.e., the feeling of elasticity) of a coating film formed of a substance to be measured for the feeling of elasticity contained in a cosmetic can be objectively evaluated without directly applying the cosmetic to the skin. The evaluation method of the present invention can be preferably used for selecting components contained in a skin cosmetic from the viewpoint of imparting an elastic feeling to the skin.

In the method for evaluating the elasticity of a cosmetic of the present invention, the cosmetic for measurement used for evaluating the elasticity contains a substance to be measured for elasticity, a water-soluble polymer forming a coating film at room temperature, and a coloring substance. The cosmetic for measurement may contain other components as necessary.

The substance to be measured for elasticity is not particularly limited, but is preferably a polymer having a property of imparting elasticity to the skin. The content of the cosmetic of the substance to be measured for the feeling of elasticity is not particularly limited. From the viewpoint of searching for a practical range of use in cosmetics, the content of the substance to be measured for elasticity is preferably the same as the content of the first polymer described above in the description of skin cosmetics. The substance to be measured for the sense of elasticity may contain one or two or more kinds in the cosmetic for measurement.

The water-soluble polymer forming a film at room temperature is the same as the water-soluble polymer forming a film at room temperature in the cosmetic for skin. The content of the water-soluble polymer forming the coating at room temperature is not particularly limited. From the viewpoint of searching for a practical range of use in cosmetics, the content of the water-soluble polymer forming a coating at room temperature is preferably the same as the content of the second polymer described above in the description of skin cosmetics. The water-soluble polymer forming a coating film at room temperature may contain one or more than two kinds in the cosmetic for measurement.

In the evaluation method, it is preferable to select a substance to be measured for which the ratio of a second area (area of the dried film) obtained by drying the cosmetic to a first area (area of the undried film) formed by applying the cosmetic for measurement containing the substance to be measured for the feeling of elasticity is 5% or more. That is, the ratio of the second area to the first area can be understood as the shrinkage rate of the coating film when the coating film is dried. This shrinkage is considered to be related to the elastic feeling of the skin to which the cosmetic is applied. In the evaluation method, the ratio of the second area to the first area is preferably 5% or more, and more preferably 30% or more, from the viewpoint of imparting elasticity to the skin. The upper limit is preferably 60% or less, and more preferably 50% or less.

The coloring matter is preferably astaxanthin, lycopene, β carotene, Gardenia (Gardenia jasminoides), safflower (Carthamus tinctorius), Monascus purpureus (Monascus purpureus), cochineal (cochineal), shellac, Beet Red (Beet Red), anthocyanins, capsicum, annatto (annatto), marigold (marigold), natural pigments such as caramel chlorophyll, or legal pigments such as Red No. 2, Red No. 3, Red No. 102, Red No. 104, (1) of Red No. 105, Red No. 106, Red No. 201, Red No. 213, Red No. 214, Red No. 227, Red No. 401, orange No. 205, yellow No. 203, Green No. 202, blue No. 1, blue No. 2, blue No. 205, iron oxide, or the like.

In the evaluation method, the temperature at which the coating film (non-dried coating film) having the first area to be measured is dried is not limited as long as the temperature is a temperature at which the coating film can be dried, and may be a temperature of a room in which measurement is performed, and may be 0 to 40 ℃.

In the evaluation method, the cosmetic for measurement was applied on a transparent solid.

Transparent means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more. The transparent solid is not limited as long as it is a transparent solid, and examples thereof include a transparent glass plate, a transparent resin molded body, and the like.

Examples of the transparent resin include polycarbonate polymers, polyester polymers such AS polyethylene terephthalate and polyethylene naphthalate, a (meth) acrylic polymer such AS polymethyl methacrylate, and a styrene polymer such AS polystyrene and an acrylonitrile-styrene copolymer (AS resin). Further, examples thereof include polyolefins such as polyethylene and polypropylene, olefin polymers such as ethylene-propylene copolymers, and epoxy polymers. Further, a film obtained by laminating two or more layers of transparent resins may be used.

The shape of the transparent solid is not limited, and may be, for example, a rectangular shape, a polygonal shape, a circular shape, an elliptical shape, or the like, and may be appropriately selected according to the shape of the coating film (coating film) to be measured.

The thickness of the transparent solid is not particularly limited, and is, for example, preferably 0.5mm to 1.5mm, more preferably 0.8mm to 1.2 mm.

The method for applying the cosmetic to the transparent solid is not particularly limited, and any method may be used as long as the method can apply the cosmetic in an amount sufficient to form a thin film in order to suppress the consumption of the material. Specifically, the amount of the cosmetic to be applied for forming the first area (the area of the non-dried film) may be appropriately set within the range of 10. mu.L to 1000. mu.L, preferably within the range of 10. mu.L to 500. mu.L, and more preferably within the range of 10. mu.L to 100. mu.L. In the evaluation method of the present invention, for example, a circular patch formed by spreading 50. mu.L of a cosmetic on a transparent solid was used as an undried film.

In the evaluation method, a first area and a second area are measured, and a ratio of the second area to the first area is calculated. The first area can be obtained by previously describing a predetermined region to be coated (for example, a circular spot) to which the cosmetic is to be applied on the transparent solid and calculating the area of the region to be coated, thereby omitting measurement. The first area can be measured using an image pickup device (e.g., a digital camera, a CCD camera, etc.). The second area (area of the dry coating) can be obtained by a known method of performing image processing using an image pickup device.

The ratio of the second area to the first area is calculated as the percentage (%) of the second area to the first area.

The first area, the second area, and the ratio of the second area to the first area can be obtained by a method used in the embodiment described later.

Examples

Hereinafter, a skin cosmetic and a method for evaluating the elasticity of the cosmetic will be described in more detail with reference to examples. The following examples are illustrative of the embodiments and the present invention is not limited to the examples.

In addition, "%" is based on mass unless otherwise specified.

[ examples 1 to 33, comparative examples 1 to 4]

The ingredients described in tables 1 to 6 were heated to 80 ℃ and stirred for 1 hour while maintaining the temperature of 80 ℃, thereby obtaining a skin cosmetic.

The following components were used for the components shown in tables 1 to 4.

Polyimide-1: aquaflex (registered trade Mark) XL-30 (30% aq), Ashland.

Polyvinylpyrrolidone 1: polyvinylpyrrolidone K-30 (100% powder), NIPPON shokubali co.

Polyvinylpyrrolidone 2: polyvinylpyrrolidone K-90 (100% powder), NIPPON shokubali co., LTD.

(vinylpyrrolidone/VA) copolymer 1: PVP/VAW-735 (vinyl acetate-vinyl pyrrolidone copolymer), Ashland.

(vinylpyrrolidone/VA) copolymer 2: PVP/VAS-630 (vinyl acetate-vinyl pyrrolidone copolymer), ashland.

(acrylate/lauryl acrylate/stearyl acrylate/ethyl amine methacrylate oxide) copolymer: diafomer (registered trademark) Z651 (30% aq), Mitsubishi Chemical Corporation.

(methacryloyloxyethylcarboxybetaine/alkyl methacrylate) copolymer: yukaforder (registered trademark) 301 (30% aq), Mitsubishi Chemical Corporation.

Polymethacryloxyethylphosphorylcholine: lipidure (registered trademark) HM (40% aq), nofcorroposition.

Polyquaternium-51: lipidure (registered trademark) PMB (5% aq), nof corport.

Polyquaternium-64: lipidure (registered trademark) C (5% aq), NOF CORPORATION.

The following components were used for the components shown in tables 5 and 6, respectively.

Polyimide-1: aquaflex (registered trade Mark) XL-30 (30% aq), Ashland.

Pullulan: the cosmetic comprises pullulan polysaccharide, Hayashibara Co, Ltd.

Alginic acid: SUNALGIN200/80, SANSHO co.

Locust bean gum: genungau (registered trademark) RL-200J, SANSHO co.

Gellan gum: kellogel (registered trademark) CG-LA, SANSHO co.

Guar gum: SUPERGEL CSA200/50, SANSHO Co., Ltd.

Hydroxypropyl guar: JAGUAR (registered trademark) HP-105, SANSHO co.

Hydroxypropyl methylcellulose: neovsco MC, SANSHO co.

Hydroxyethyl cellulose: sanhe c, SANSHO co.

Kappa carrageenan 1: GENUGEL (registered trademark) type WR-78-J, SANSHO Co., Ltd.

Kappa carrageenan 2: GENUGEL (registered trademark) type WG-108, SANSHO co.

Pectin: GENU (registered trademark) PECTIN LN-5CD-J, SANSHO Co., Ltd.

Polyquaternium-72: MIRUSTYLE CP (HEC modified); further, as an ingredient, phenoxyethanol and water, IPROS CORPORATION, are contained in the form of a mixture

Hydrophobized hydroxypropylmethylcellulose 1: Saint-Gerose (registered trademark) 90L, Daido chemical corporation

Hydrophobized hydroxypropylmethylcellulose 2: Saint-Gerose (registered trademark) 60M, Daido chemical corporation

The obtained skin cosmetic was evaluated according to the following method.

1. Evaluation based on the elastic feeling of panelists (sensory evaluation)

After 100. mu.L of each of the skin cosmetics of examples 1 to 33 and comparative examples 1 to 4 was uniformly applied to the forearms of 5 panelists, the feeling of elasticity was evaluated according to the following evaluation criteria. Next, the results of panelists were arithmetically averaged, and the average was obtained for the elasticity of each skin cosmetic, and sensory evaluation was performed according to the following evaluation criteria. The results are shown in tables 1 to 6.

(1) Evaluation criteria for sense of elasticity

5: the feeling that the coating film is formed on the portion to which the skin cosmetic is applied can be felt, and the feeling of being strained is strongly felt.

4: the feeling of the film formed on the part coated with the skin cosmetic and the feeling of being strained can be simultaneously sensed.

3: although the feeling of the film formed on the portion to which the skin cosmetic is applied can be felt, the feeling of being strained is only slightly felt.

2: the feeling of the film formed on the part to which the skin cosmetic is applied and the feeling of being strained are both slightly felt.

1: the feeling of the film formed on the part coated with the skin cosmetic and the feeling of being strained were hardly felt.

(2) Evaluation criteria for sensory evaluation

A is an average value of 3.5 to 5.0 of the feeling of elasticity

B, the average value of the elastic feeling is more than 3.1 and less than 3.5

C, the average value of the elastic feeling is less than 3.1

2. Evaluation of elasticity feeling by coating film (coating film evaluation)

The skin cosmetics of examples 1 to 33 and comparative examples 1 to 4 were evaluated for the elasticity of the coating film by calculating the area and the shrinkage rate (ratio of the area) according to the following procedure.

(1) Measurement of formation of a first area of an undried coating

A glass slide was placed on a piece of paper printed with a perfect circle (diameter 2 cm). After collecting 50 μ L of the prepared skin cosmetic product with a syringe, each skin cosmetic product was spread on a slide glass to have the above perfect circle size to prepare a sample.

(2) Measuring formation of a second area of the dried coating

The sample prepared in (1) was allowed to stand at room temperature for 20 hours or more to form a coating on the slide glass.

(3) Calculation of first and second areas and shrinkage

The coated side on the slide glass was set to the upper side, and each sample was imaged under the imaging conditions shown below.

The above perfect circle is extracted from the captured image by using image analysis software, and after the size of the perfect circle is calculated, the size of the perfect circle is normalized to 800 × 800 pixels as an RGB image.

Then, from the RGB image via L^*a^*b^*Calculating chroma C from the image according to the following formula (1)^*。

Chroma C^*＝{(a^*)²+(b^*)²}^1/2… … type (1)

Extraction of C^*The area of > 21.2 is the area,the total area of the extraction regions is set as a second area.

In addition, the first area was calculated as the area of a perfect circle (diameter 2 cm).

The shrinkage was determined from the following formula (2), and the elastic feeling of the film was evaluated from the following evaluation criteria.

Shrinkage factor (second area)/(first area) × 100 (%) … … formula (2)

The results are shown in tables 1 to 6, and fig. 1 and 2.

Fig. 1 is an image captured in the above-described coating evaluation. Fig. 2 is a graph showing the relationship between the sense of elasticity and the shrinkage rate of the cosmetics of examples and comparative examples, and in this graph, the results of examples 3, 4, 5, 6, 9, 10 and 12 and comparative example 1 are shown.

Evaluation criteria for shrinkage

The shrinkage is more than 30 percent: a. the

A shrinkage ratio of 5% or more and less than 30%: b is

Shrinkage rate is less than 5%: c

No film formation: d

3. Evaluation of texture

Each skin cosmetic of example 3 and comparative example 1 was uniformly applied to the forearm of a test subject (1) in an amount of 100 μ L, and the texture of the skin surface was photographed by a shape analysis laser microscope (VK-X1000, KEYENCE corporation). The results are shown in FIG. 3.

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

[ Table 6]

As is clear from tables 1 to 6 and fig. 2, the results of the film evaluation as the evaluation method of the present invention showed the same tendency as the results of the sensory evaluation of skin. This means that the evaluation method of the present invention is a method capable of evaluating the sense of elasticity without directly applying the cosmetic to the skin, and is useful.

As is clear from fig. 3 (the left photograph in fig. 3 shows comparative example 1, and the right photograph in fig. 3 shows example 3), the skin cosmetic of the present invention has a sense of elasticity of the skin due to the fine texture in sensory evaluation. This indicates that the skin cosmetic of the present invention is a cosmetic that can adjust the texture of the skin and has an elastic feeling, and is useful.

Claims

1. A cosmetic for skin contains at least one selected from a water-soluble polymer having a cyclic structure in a main chain or a side chain and a water-soluble polymer having a dimethyl or trimethyl amino group, and at least one selected from water-soluble polymers forming a coating film at room temperature.

2. The cosmetic for skin according to claim 1,

the water-soluble polymer having a cyclic structure in the main chain or side chain is at least one selected from the group consisting of polyimide-1, polyvinylpyrrolidone and a copolymer thereof.

3. The cosmetic for skin according to claim 1 or 2, wherein,

the water-soluble polymer having a dimethyl or trimethyl amino group is at least one selected from a polyacrylic copolymer having a dimethyl or trimethyl amino group and a polymethacrylic copolymer having a dimethyl or trimethyl amino group.

4. The cosmetic for skin according to any one of claims 1 to 3, wherein,

the water-soluble polymer forming the coating at room temperature is at least one selected from water-soluble polymers of polysaccharides.

5. The cosmetic for skin according to any one of claims 1 to 4, wherein,

the water-soluble polymer of polysaccharide is at least one selected from xanthan gum, carrageenan, gellan gum, pullulan, acacia, guar gum, locust bean gum, agar, alginic acid, pectin, cellulose, corn starch and their derivatives.

6. The cosmetic preparation for skin according to any one of claims 1 to 5, wherein the water-soluble polymer forming a coating film at room temperature is contained in an amount of 0.01 to 5% by mass based on the total mass of the cosmetic preparation for skin.

7. A method for evaluating the elasticity of a cosmetic, which comprises a step of applying a cosmetic containing a substance to be measured for elasticity, a water-soluble polymer forming a coating film at room temperature, and a coloring substance onto a transparent solid, the method comprising:

the area of the undried film formed by applying the cosmetic to the transparent solid was measured as a first area, and the area of the dried film formed by drying the undried film was measured as a second area, and the ratio of the second area to the first area was calculated.

8. The evaluation method according to claim 7, wherein a substance whose elasticity feeling is to be measured is selected such that a ratio of the second area to the first area is 5% or more.