CN106442331B - Method for testing waterproof capability of sun-proof product - Google Patents
Method for testing waterproof capability of sun-proof product Download PDFInfo
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- CN106442331B CN106442331B CN201610872545.0A CN201610872545A CN106442331B CN 106442331 B CN106442331 B CN 106442331B CN 201610872545 A CN201610872545 A CN 201610872545A CN 106442331 B CN106442331 B CN 106442331B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N2021/1765—Method using an image detector and processing of image signal
Abstract
The invention provides a method for testing the water resistance of a cosmetic sunscreen product, which comprises the following steps: (i) the method comprises the steps of coating a sunscreen product on an area of human skin to be tested to form a coating area, then carrying out ultraviolet photography and reading luminance brightness data a of the area on the ultraviolet photography0(ii) a (ii) Washing the skin area with clear water for a prescribed time after a prescribed time interval to form a washing area, then performing UV photography on the area and reading the brightness data a of the area on the UV photography1(ii) a And (iv) calculating the brightness change rate delta of the photo before and after washing according to the following formula as an index of the skin residual quantity of the sunscreen product: Δ ═ a1‑a0)/a0。
Description
Technical Field
The invention relates to a method for testing the waterproof capability of a sunscreen product. The method can quickly determine the waterproof capability of the sunscreen product and simultaneously can prevent the skin of a tester from being damaged by ultraviolet rays.
Background
In addition to visible light, about 1% of sunlight can be irradiated with ultraviolet rays having a wavelength of 280 to 400 nm. The ultraviolet ray is divided into 3 bands, wherein UVA (320-400 nm) and UVB (280-320 nm) are mainly used for damaging skin. Prolonged exposure of the skin to ultraviolet light can lead to photoaging; short-term, high intensity uv irradiation can also cause acute damage to the skin, with UVB primarily causing erythema and UVA primarily causing skin darkening. In order to protect the skin from the damage of ultraviolet rays in sunlight, products with a sun-screening function are also becoming one of important products in the cosmetic industry, and common products comprise sun-screening products, day cream products, BB cream and CC cream with functions of concealing and repairing the face, and the like.
From the history of the development of sunscreen cosmetics, it is a classic attribute that sunscreen cosmetics have a water-resistant and sweat-resistant function. Since sunscreen cosmetics, particularly cosmetics having high sunscreen efficiency, are generally used in summer outdoor sports, the characteristics of seasons and use environments require sunscreen products having water-resistant and sweat-resistant properties, i.e., a certain sunscreen effect can be maintained even under the immersion of sweat or under the swimming condition. Therefore, the development of the waterproof performance of the sunscreen cosmetic is a new target continuously pursued by the cosmetic industry.
The national cosmetic hygiene code (2007 edition) specifies the use of the human evaluation method to test sunscreen products for sunscreen performance, which characterizes sunscreen products by SPF and PFA values. Wherein the SPF value is defined as: the ratio of the minimum erythema dose MED for protecting skin with sunscreen (the lowest dose or the shortest exposure time for erythema on skin) to the minimum erythema dose MED for skin without sunscreen obviously the greater the SPF value, the greater the ability of the product to protect skin from uv light. The PFA value is defined as: the ratio of the MPPD (minimum amount of persistent darkening) of the minimum erythema dose for protecting the skin by using the sunscreen cosmetic to the MPPD of the minimum erythema dose for protecting the skin without using the sunscreen cosmetic is obviously that the larger the PFA value is, the greater the damage capability of the product on the skin by ultraviolet rays is.
The human body evaluation method has certain advantages and defects. For example, SPF human test method is mentioned in cheng yan et al, "cosmetic sunscreen effect test method analysis and comparison" ("daily chemical science, 2008, 7 months, volume 31, 7 th period). Its advantages are high effect to prevent sunlight, and high effect to prevent sunlight. The main drawback of the SPF regimen is the difference in the responses of the european and american and yellow race to sunlight: the erythema reaction is universal and intuitive for European and American caucasians, and most of the skin of the European and American caucasians can generate acute erythema reaction and even burn after being irradiated by ultraviolet rays in sunlight. However, the main effect of sun exposure is not erythema for yellow and black people with relatively dark complexion, and erythema may not occur even after prolonged exposure to sunlight for black people.
In order to overcome the defects of the existing human body evaluation method, the field provides an in-vitro method for testing the sun-screening performance of the sun-screening product. For example, "physical method test of sunscreen properties of sunscreen articles", Yankeeson et al (proceedings of the university of inner Mongolia (Han. Nature science), 2006, 3.2006, volume 35, No. 1) discloses a method for testing the sunscreen properties of a sunscreen product by coating the sunscreen product on the surface of a quartz plate and then testing the ultraviolet transmittance of the product in a dual-beam ultraviolet-visible spectrophotometer.
Compared with the human body evaluation method, the in vitro method is rapid, labor-saving, low in cost and good in repeatability, but is also influenced by various factors such as: the smearing method of the product, the film forming property, the dosage form of the product, the particle size of the powder contained in the product and other factors. In addition, the in vitro method has a better linear relation for the sunscreen cream which is prepared by adding the same ultraviolet absorbers in the same formula but with different addition amounts and is easy to form a film after being smeared. But it has the greatest disadvantage that the actual sunscreen effect and possible side effects cannot be accurately evaluated neglecting the skin reaction after the sunscreen cosmetic is used.
The prior art attempts to correlate in vitro methods with human evaluators, thereby characterizing the results of human evaluators with the data of the in vitro methods by a calibration factor. For example, sunin et al, "in vitro tests of UVA protective efficacy of sunscreen cosmetics are compared with results of human tests" ("fragrance and fragrance cosmetics", 2016, 4/month, 2.) evaluation of UVA protective performance of cosmetics was conducted by in vitro methods and human tests, and the correlation of the results of the two methods was examined. The result shows that the in vitro test result has good correlation with the human body method test result. However, the correlation is only limited to the UVA band, and it is not mentioned whether the in vitro test result can still have good correlation with the human method test result for the ultraviolet ray of the UVB band.
Ultraviolet reflectance photography is commonly used in criminal investigation for, for example, sweat fingerprinting of the surface of an extract. Ba xi et al in "digital camera-Long wave ultraviolet reflectance photography technical research" ("criminal police techniques", see the netbook) text defines ultraviolet reflectance photography as: ultraviolet reflection photography is a photographic technique in which an object to be inspected is irradiated with ultraviolet rays, and the difference in the reflection and absorption of the ultraviolet rays by a substance is utilized to increase the difference in brightness between a trace and a carrier, thereby recording the distribution of the ultraviolet rays reflected by the object on a photosensitive material.
Chinese patent application CN105427306A to buddlei et al discloses an image analysis method and apparatus for skin glossiness, which includes collecting digital images of a subject's skin under the same light source conditions, calculating the frequency distribution of pixels, setting the extraction conditions of highlight portions, and calculating the pixel proportion of highlight portions extracted according to the extraction conditions as an index of skin glossiness. However, it does not relate to the determination of the sunscreen properties of sunscreen products.
In addition, the national cosmetic hygiene code (2007 edition) also stipulates that the water resistance of sunscreen products is tested by human assessment. The method provides that if the product is declared to have water resistance or to have superior water resistance, the identified SPF value should be the SPF value determined after the product has been subjected to a water resistance test for 40min or 80 min. And identifying the measured value after bathing, referring to the SPF value identified before the product waterproof test or the predicted SPF value, and if the measured value after bathing is reduced by more than 50%, the product cannot be marked to have the waterproof function. The use of the national standard method requires a certain number of human trials, the time required for each subject to complete the trial is long (each subject needs at least 60min in water and waiting time), and the skin of the subject is sunburned during the trial, thereby providing the subject with a high cost.
Obviously, the existing evaluation method for the water resistance of the sunscreen product has two main defects:
(i) the evaluation of the sunscreen performance itself requires an intuitive erythemal response, which for asians, for example, requires higher irradiation doses, resulting in greater damage to human skin;
(ii) the test of waterproof performance is time-consuming, laborious, and the cost is higher.
Thus, there is a need for a faster, simpler, less expensive test method to determine the relative water resistance of a sunscreen product.
Disclosure of Invention
The object of the present invention is to provide a quick, simple and inexpensive test method to determine the relative water resistance of a sunscreen product.
Accordingly, in one aspect of the present invention, there is provided a method for testing the water resistance of a cosmetic sunscreen product comprising the steps of:
(i) carrying out ultraviolet photography on the skin area of a human body to be tested and reading the brightness data a of the area on the ultraviolet photography0,
(ii) Applying a sunscreen product to the area of human skin and recording the amount of sunscreen product applied per unit area of skin;
(iii) washing the skin area with clear water for a prescribed time after a prescribed time interval, then performing UV photography on the area and reading the brightness data a of the area on the UV photography1；
(iv) Calculating the light intensity change rate delta of the pictures before smearing and after washing according to the following formula as an index for calculating the skin residual quantity of the sunscreen product:
△＝(a0-a1)/a0；
(v) coating a series of sunscreen products with unit area coating amount in a test area, photographing before and after coating, calculating light intensity and change rate before and after coating, correspondingly obtaining a series of light intensity change rates, and drawing the light intensity change rates by the unit area coating amount to obtain a standard curve;
(vi) the rate of change Δ of the light intensity measured above was converted into the amount of coating per unit area, i.e., the amount of residual after cleaning, based on the calibration curve.
In one embodiment of the present invention, the method further comprises the steps of:
(vii) the residual ratio r is calculated according to the following formula:
r-residual amount/initial application amount.
In addition, the invention also provides application of the ultraviolet image analysis method in evaluating the waterproof effect of the sunscreen product.
Drawings
The invention is further described below with reference to the accompanying drawings. In the drawings:
fig. 1 is a uv photograph of a human arm before and after application of a sunscreen product and after washing, wherein,
FIGS. 1a, 1c and 1e are UV photographs taken before (FIG. 1a) and after (FIG. 1c) and after (FIG. 1e) rinsing with clear water, respectively, a herborist sunscreen purchased from Shanghai nationality;
FIGS. 1b, 1d and 1f are UV photographs taken before (FIG. 1b) and after (FIG. 1d) and after rinsing (FIG. 1f), respectively, with a suitable herbal sunscreen available from Shanghai-compatible herbal cosmetics, Inc.;
FIG. 2 is a standard curve of the coating weight per unit area versus the rate of change of light intensity for a corresponding sunscreen product in an embodiment of the present invention, with the vertical axis representing the rate of change of light intensity and the horizontal axis representing the amount of sunscreen product applied (mg/cm)2)。
Detailed Description
The inventor finds that the light intensity of the sun protection product irradiated by ultraviolet rays is obviously reduced after the sun protection product is smeared on the skin, and the light intensity of the sun protection product irradiated by ultraviolet rays is obviously increased if the sun protection product does not have the waterproof capability and can be removed after the sun protection product is washed by clear water. On the contrary, if the sunscreen product has a good water-proofing ability, the light intensity does not increase so much after the sunscreen product is washed with water and irradiated with ultraviolet rays. Based on the findings, the inventor provides a sunscreen product waterproof performance test method which is simple, convenient and easy to implement and does not cause damage to skin and can not cause ultraviolet irradiation to a sunscreen product area at two time points before and after application, obtains a light intensity change rate, converts the residual quantity of a sunscreen product by combining the light intensity change rate and a sunscreen product unit skin area coating quantity standard curve, and further calculates the residual rate of the sunscreen product, namely the waterproof capacity of the sunscreen product.
FIG. 1 is a UV photograph of a human arm before and after two groups of different sunscreen products were applied and after rinsing with clear water. As shown in fig. 1, the uv photographs of the same area of the arm produced significant intensity variations before and after application of the sunscreen product. The invention calculates the residual quantity of the sun-proof product by measuring the light intensity change rate and combining the standard curve of the light intensity change rate of the sun-proof product to the coating quantity of unit skin area, further calculates the residual rate of the sun-proof product, namely the waterproof capability of the sun-proof product, and can easily evaluate the waterproof effect of the sun-proof product.
The invention provides a human body test method for the waterproof capacity of a cosmetic sunscreen product. Suitable sunscreen products for use in the method of the present invention may be any cosmetic skin care product containing sunscreen agents or having sunscreen and anti-uv functions, such as, by way of non-limiting example, sunscreens, sunblocks, sun creams and the like.
The invention adopts an ultraviolet photography method to evaluate the waterproof performance of the sunscreen product. The UV photography process is known per se. For example, Ba xi et al, in "digital camera-long wave ultraviolet reflection photography technique research" ("criminal police technique", see the web) mention ultraviolet reflection photography. The inventors of the present invention have found that the water resistance of sunscreen products can be evaluated by uv reflectance photography, which is safe, fast and inexpensive.
The method of the invention comprises applying a sunscreen product to an area of human skin to be tested. The requirements for the selected tested human skin are the same as the requirements for the human skin area by a human evaluation method in 'cosmetic hygiene code' (2007), namely, the selected tested human skin area is required to be a healthy male or female volunteer subject of 18-60 years old, the subject has no history of photosensitive diseases and does not use drugs influencing the photosensitivity in the near future, the skin of the tested part has no pigmentation, inflammation, scar, pigmented nevus, hairy and the like, and the subject is excluded from anti-inflammatory drugs such as corticosteroid hormone for pregnancy, lactation, oral administration or external use, or similar subjects received in the near month.
The ultraviolet photography method used is a known ultraviolet photography method, and for example, the ultraviolet reflection photography method is mentioned in "digital camera-long wave ultraviolet reflection photography technical research" by baxi et al (criminal police technology, see gay). Ultraviolet photography equipment is commercially available, for example, from the American Canfield company VISIA-CR ultraviolet photography equipment.
To avoid the effect of ambient uv light on the accuracy of the photography, in one embodiment of the invention, the uv photography is performed in a dark room.
The uv wavelengths used to illuminate the skin area of the subject in uv photography are conventional in the art. In one embodiment of the invention, the ultraviolet light irradiating the skin area to be tested is at a wavelength of 200-400nm (i.e., covering all wavelengths from short wavelength Ultraviolet (UVC) to long wavelength Ultraviolet (UVA)). In another embodiment of the present invention, the ultraviolet light that irradiates the skin area to be tested has a wavelength of 290nm to 320nm, i.e., medium Ultraviolet (UVB). In yet another embodiment of the present invention, the ultraviolet light that irradiates the area of skin under test has a wavelength of 320nm to 400nm, i.e., long-wave ultraviolet light (UVA).
After obtaining the ultraviolet photo of the tested area, reading the light intensity value a of the tested area from the photo0. Reading photo light intensity value a0The method of (3) is not particularly limited and may be a known method. In one embodiment of the invention, the photo light intensity value a is read using the analytical measurement image software Imagepro-Plus (IPP software)0。
The method of the present invention comprises applying a sunscreen product to the human skin to form an application zone. The area of the coating region and the amount of application are not particularly limited and may be conventional coating areas and amounts known in the art. In one example of the invention, the application area and the amount of application meet the requirements of the cosmetic hygiene code (2007). In one embodiment of the invention, the coating area is 3-20cm2Preferably 6-12cm2More preferably 8-10cm2. In another embodiment of the present invention, the coating amount is 1 to 3mg/cm2Preferably 1.5 to 2.5mg/cm2Preferably 2mg/cm2。
In one embodiment of the invention, the sample is applied uniformly to the area of skin being tested using a latex finger cuff to form an application area, followed by waiting a defined time, e.g., 10-50 minutes, preferably 15-40 minutes, and more preferably 20-30 minutes, and rinsing with clear water for a defined time, e.g., 0.5-4 minutes, preferably 1-3.5 minutes, and more preferably 2-3 minutes, to form a rinsing area.
The terms "rinsing with clear water" and "cleaning with water", "contacting with water" and "washing with water" are used interchangeably herein and are used to simulate the scenario in which a sunscreen product is in contact with water during daily use, and thus include, but are not limited to, water soaking, water rinsing, water washing, and the like.
Therefore, the method using the water rinsing is not particularly limited, and may be a conventional cleaning method known in the art, for example, water soaking, water rinsing, water washing, and the like.
The method also comprises the steps of carrying out ultraviolet photography on the washing area and reading the light intensity data a of the area on the ultraviolet photography1. The conditions and equipment for uv-photography of the washing zone are exactly the same as those described above for uv-photography of the coated (test) area of human skin to be tested. Reading the light intensity value a of the UV picture by using an analysis image software, such as an IPP software1。
In the present invention, the terms "photograph" and "image" are used interchangeably to refer to a photograph or image obtained by ultraviolet photography.
In the present invention, the terms "lightness" and "light intensity" are used interchangeably to refer to the lightness or light intensity of a particular area obtained from an ultraviolet image with photographic software, such as IPP software.
And finally, calculating the light intensity change rate delta of the washing area by using the following formula as an index for calculating the skin residual quantity of the sunscreen product:
△＝(a0-a1)/a0。
in a preferred embodiment of the present invention, the method for testing the skin retention of a sunscreen product of the present invention comprises the steps of: spotting the test site, and photographing the subject in a darkroom using a VISIA-CR photography system (Canfield, USA) to acquire an ultraviolet skin image of the spotted site; and applying a product containing a sunscreen agent to the dotted area. Subsequently, after a predetermined time interval, the spotted area is rinsed with clear water, and a skin ultraviolet image of the rinsed area is acquired according to the method in the above step. Respectively cutting out rectangular areas in the range of the points, calculating average light intensity by adopting IPP software, and calculating the light intensity change rate delta according to the average light intensity before coating and after washing of the coating area.
In one embodiment of the present invention, the method comprises the steps of: the method comprises the following steps of pointing an arm part, acquiring a skin image of the pointed part of the arm, and photographing a subject by using a VISIA-CR photographing system (Canfield company, USA), wherein the image photographing conditions are as follows: the light source mode is UV-NF, the optical filter is standard, ISO is 250, the aperture is F9, white balance is sunlight, and shooting is carried out in a darkroom, so that external light interference is avoided. The sunscreen product to be tested is then applied.
After a certain time, the tracing part is cleaned by water, and then an ultraviolet skin image of the tracing part of the cleaned arm is acquired according to the steps.
And setting a region to be analyzed, and respectively intercepting rectangular regions in the range of the points. And then calculating the average light intensity by using IPP software to obtain the light intensity change rate delta.
Since the light intensity change rate delta and the coating amount of the sunscreen product or the coating amount of the sunscreen product per unit skin surface area are in a nonlinear relationship, in order to convert the light intensity change rate delta into the sunscreen product retention amount of the cleaned coating area, a standard curve of the light intensity change rate delta and the coating amount of the sunscreen product per unit skin surface area of the sunscreen product needs to be drawn.
In the present invention, the term "applied amount of sunscreen product" is used interchangeably with "applied amount of sunscreen product per unit skin surface area" and refers to the applied amount of sunscreen product tested per unit skin area.
In one embodiment of the present invention, the method for plotting the calibration curve comprises setting a series of coating amounts of the sunscreen product, measuring a corresponding series of light intensity change rates Δ by the method of the present invention, and plotting the light intensity change rates Δ against the coating amounts of the sunscreen product to obtain the desired calibration curve.
FIG. 2 is a graph showing the light intensity change rate Δ/coating amount standard curve of a commercial herborist sunscreen product and a corresponding herbal sunscreen product, with which the light intensity change rate Δ can be easily converted into the corresponding coating amount or the retention amount of the sunscreen product after cleaning.
In another embodiment of the present invention, the method of the present invention comprises the steps of:
(1) acquiring skin images of a subject under specific and consistent ultraviolet light source conditions;
(2) applying a sunscreen-containing product to the area to be tested;
(3) after the sun-proof product is coated, the sun-proof product is washed by clean water for 3 minutes at an interval of 15 minutes;
(4) cleaning, drying and then collecting the skin image again by using the ultraviolet light source in the step (1);
(5) selecting a region to be analyzed on the obtained skin image;
(6) calculating the average light intensity of the area to be analyzed;
(7) calculating the light intensity change rate according to the light intensity values before smearing and after cleaning;
(8) smearing a series of sunscreen products with different amounts on arms, measuring corresponding light intensities before and after smearing, calculating a light intensity change rate, and drawing a standard curve by taking the light intensity change rate as a vertical coordinate and the sunscreen product amount as a horizontal coordinate;
(9) converting and cleaning the residual quantity of the sun-proof product through the standard curve of the sun-proof product according to the light intensity change rate;
(10) and calculating the residual rate of the sunscreen product according to the residual quantity.
The method calculates the residual quantity of the sunscreen product according to the light intensity change rate obtained by ultraviolet irradiation before and after the sunscreen product is smeared and after the sunscreen product is washed by water, and further calculates the residual rate of the sunscreen product for representing the waterproof capability of the sunscreen product.
The invention provides the waterproof effect of the sunscreen product by measuring the skin remaining amount of the sunscreen product after being washed by clear water, thereby providing a basis for evaluating the waterproof effect of the sunscreen product.
The image analysis method is established based on the change of the light intensity of the product containing the sun-screening agent by ultraviolet irradiation before and after the product containing the sun-screening agent is used on human skin, in the process, the contact time of the ultraviolet and the skin is short, the skin damage cannot be caused, and a subject can be recycled, so that the evaluation efficiency of the waterproof performance of the sun-screening agent can be greatly improved from four aspects of time, cost, subject selection and damage degree.
The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.
Example 1
This example compares the difference in the rate of change of light intensity caused by two different products.
1) The method comprises the following steps of (1) carrying out point tracing on an arm part, and acquiring an arm part skin image: subjects were photographed using VISIA-CR (Canfield, usa) under the following image photographing conditions: the light source mode is UV-NF, the optical filter is standard, ISO is 250, the aperture is F9, white balance is sunlight, shooting is carried out in a dark room, and interference of external light is avoided, and the images of the arm obtained under the light source condition are shown in the figures 1a and 1 b.
2) Applying sunscreen product on the spot, wherein the left arm is herborist fresh clear repairing sunscreen liquid (SPF30+, PA + +, available from Shanghai Co., Ltd.), and the right arm is proper herbal water clear sunscreen lotion (SPF30, PA + + +, available from Shanghai Co., Ltd.) with an area of 2 × 4cm2(ii) a The coating amount is 2mg/cm2. Wherein herborist is declared to have waterproof capability, while the corresponding herbs are not declared to have waterproof capability.
After the product is applied for 15 minutes, the same arm skin image is collected again according to the image collection method in the step 1), and the image is shown in fig. 1c and 1 d.
3) After image acquisition, the sun-proof product is washed by clear water, the washing time is 3 minutes, and the distance between a water source and the skin is 5 cm.
After washing, the skin is naturally dried, and the skin image of the arm part is collected again according to the image collection method in the step 1), wherein the image is shown in fig. 1e and fig. 1 f.
4) Setting a region to be analyzed, and respectively cutting off a little smaller than 2 multiplied by 4cm from each image in the range of the point2And (3) in order to intercept the region to be analyzed, calculating the average light intensity by adopting IPP software.
The UV photo light intensity before the sunscreen product was applied was recorded as a0The intensity of the UV photo after rinsing the coating area with clear water is recorded as a1The intensity change rate Δ was calculated from the average intensity after washing with clear water using the sunscreen product:
△＝(a0-a1)/a0
the results are shown in table 1 below:
table 1: light intensity and light intensity change rate corresponding to herborist and suitable herbal products before smearing and after washing with clear water
| Sample name | Before smearing | After washing | △ |
| Herborist new clear and thorough repair sunscreen liquid | 100.33 | 44.08 | 56.1％ |
| Water-rich clear sun-screening lotion suitable for herbal medicine | 91.75 | 55.51 | 39.5％ |
As can be seen from the above test results, the Bai-cao-ji sunscreen lotion alleged to have the water-repellent property has a significantly higher rate of change in light intensity than the corresponding herbal sunscreen lotion which is not alleged to have the water-repellent property. Therefore, the test method provided by the invention can reflect the waterproof performance of the sunscreen product through light intensity change.
Example 2
This example compares the wash retention or water resistance of two different products.
A. Drawing a standard curve
1) To the arm partThe dots are drawn in rows, and the area of each group of dots is 2 multiplied by 4cm2An image of the skin of the arm was taken and the subject was photographed using VISIA-CR (Canfield, usa) under the following image photographing conditions: the light source mode is UV-NF, the optical filter is standard, ISO is 250, the aperture is F9, white balance is sunlight, and shooting is carried out in a darkroom, so that external light interference is avoided.
2) Grouping: the hand front arm parts were divided into groups (areas) by coating amount per unit skin area, and 5 groups were assigned: blank group (no sunscreen product applied); 0.25mg/cm2Group (d); 0.5mg/cm2Group (d); 1mg/cm2Group (d); 2mg/cm2And (4) grouping. The test samples were respectively herborist fresh clear and clear sun protection lotion (SPF30+, PA + +, available from shanghai combined chemicals gmbh) and suitable herbal clear and clear sun protection lotion (SPF30, PA + +, available from shanghai suitable herbal cosmetics gmbh), wherein herborist was declared to have water-proofing ability, and suitable herbal was not declared to have water-proofing ability.
And (3) coating sunscreen products on the dotted parts according to the coating amount, and collecting the skin image of the arm part again according to the image collecting method in the step 1) after the sun screening products are coated for 15 minutes.
3) Setting the region to be analyzed, and respectively cutting slightly less than 2 × 4cm within the range of the point2And (3) in order to intercept the region to be analyzed, calculating the average light intensity of each region by using IPP software. The rate of change of light intensity for each region is calculated using the following equation:
light intensity change rate (intensity before application-intensity after application)/intensity before application
4) Drawing a standard curve: the light intensity change rate is used as the ordinate, the sunscreen product amount is used as the abscissa, and a standard curve is drawn, and the result is shown in fig. 2.
The residual amount of the sunscreen product after being washed with clean water was converted according to the standard curve in combination with the rate of change of light intensity obtained in example 1.
Calculating the residual rate according to the residual quantity: residual rate as residual amount/initial coating amount
The initial application amount in this example was 2mg/cm2。
The results describe: FIG. 2 is a standard curve of a herborist and a suitable herbal sunscreen product. It can be seen from the figure that the greater the amount of sunscreen product applied to the skin, the greater the rate of change of light intensity. According to the standard curve, the light intensity change rate after washing with clear water relative to that before application can be converted into the residual quantity of the sunscreen product on the skin after washing, and then the residual rate can be calculated.
Table 2: the residual quantity and the residual rate are calculated according to the standard curve
| Sample name | Rate of change of light intensity | Residual amount (mg/cm)2) | Residual rate |
| Herborist new clear and thorough repair sunscreen liquid | 56.1％ | 1.257 | 62.85％ |
| Water-rich clear sun-screening lotion suitable for herbal medicine | 39.5％ | 0.5 | 25％ |
As can be seen from the test results, compared with the corresponding herbal sunscreen lotion which is not declared to have the waterproof performance, the herborist waterproof liquid with the waterproof performance is declared to have obviously high residual rate (or washing retention), and the reliability and the practicability of the method are proved.
Example 3
In the method, after a group of subjects use two different sunscreen products (the difference is whether waterproof capability is declared) and wash with clean water, the residual rates of the two sunscreen products are compared to represent the waterproof capability, and the feasibility of the method is demonstrated. The two products are respectively: the herborist and herborist new clear and thorough repair sunscreen lotion (alleged to have waterproof capability) and the proper herborist clear and thorough sunscreen lotion (not alleged to have waterproof capability).
Volunteer selection: 12 healthy female subjects of 25-55 years old are selected, and the front side arm parts of hands have no obvious scars or pigmentation and are required to have white skin color.
Dotting and grouping: the front arm part of the hand is subjected to point drawing and grouping, and the area of each group of point drawing is 2 multiplied by 4cm2The experiments were divided into 2 groups, with herborist and appropriate herbs randomly distributed on both arms.
Image acquisition, interception and analysis: image acquisition is performed on each group of regions according to the method in the embodiment 1, corresponding samples are smeared, the regions to be analyzed are intercepted, and the average light intensity is calculated.
Calculating the light intensity change rate: the rate of change of light intensity was calculated according to the formula in example 1.
Drawing a standard curve: standard curves for herborist and appropriate herbal sunscreen products were drawn according to the procedure in example 2
And (3) calculating the residual quantity of the sunscreen product after being washed by clear water, namely calculating the residual quantity of the sunscreen product on the skin after being washed by the clear water according to the light intensity change rate and a standard curve.
Calculating the residual rate: residual rate as residual amount/initial coating amount
The results describe: table 3 shows the corresponding light intensity values, light intensity change rates and the calculated residual rates for different sunscreen products (herborist and appropriate herbs) after washing with clear water and before applying the sunscreen products. From table 3, it can be seen that the residue rate of the herborist sunscreen product (alleged to have a waterproof function) after being washed with clean water is higher than that of the corresponding herbal material (not alleged to have a waterproof function), which indicates that the herborist sunscreen product has a higher waterproof capability than that of the corresponding herbal material, which is consistent with the results obtained by the conventional method. The method can distinguish the difference of the waterproof capability of different sunscreen products.
Table 3: washing different sun-proof products with clear water, corresponding light intensity, light intensity change rate and residue rate (X + -SD; n is 12)
| Sunscreen product | I (before painting) | I (after washing) | Rate of change of light intensity | Residual rate |
| Herborist | 81.31±12.84 | 39.53±5.66 | 50.89±6.76％ | 51.06±26.11％# |
| Corresponding herbal medicine | 80.07±11.52 | 47.06±6.13 | 40.92±4.43％ | 31.92±10.38％ |
# represents a significant difference relative to the corresponding herb, P < 0.1.
Claims (18)
1. The application of an ultraviolet image analysis method in evaluating the waterproof effect of a sunscreen product comprises the following steps:
(i) carrying out ultraviolet photography on the skin area of a human body to be tested and reading the brightness data a of the area on the ultraviolet photography0,
(ii) Applying a sunscreen product to the area of human skin and recording the amount of sunscreen product applied per unit area of skin;
(iii) washing the skin area with clear water for a prescribed time after a prescribed time interval, then performing UV photography on the area and reading the brightness data a of the area on the UV photography1；
(iv) Calculating the light intensity change rate delta of the pictures before smearing and after washing according to the following formula as an index for calculating the skin residual quantity of the sunscreen product:
Δ＝(a0-a1)/a0。
2. the use according to claim 1, further comprising the steps of:
(v) coating a series of sunscreen products with unit area coating amount in a test area, photographing before and after coating, calculating light intensity and change rate before and after coating, correspondingly obtaining a series of light intensity change rates, and plotting the unit area coating amount to the light intensity change rate to obtain a standard curve;
(vi) the light intensity change rate Δ measured above was converted into the coating amount per unit area, i.e., the residual amount after cleaning, based on the calibration curve.
3. The use according to claim 2, further comprising the steps of:
(vii) the residual ratio r is calculated according to the following formula:
r-residual amount/initial application amount.
4. Use according to any one of claims 1 to 3, characterized in that the wavelength of the UV light used for UV photography is 200-400 nm.
5. Use according to any one of claims 1 to 3, characterized in that the wavelength of the ultraviolet light used for ultraviolet photography is between 290nm and 320 nm.
6. Use according to any one of claims 1 to 3, characterized in that the wavelength of the ultraviolet light used for ultraviolet photography is from 320nm to 400 nm.
7. Use according to any one of claims 1 to 3, characterized in that the coating area of the coating zone is from 3 to 20cm2。
8. Use according to any one of claims 1 to 3, characterized in that the coating area of the coating zone is between 6 and 12cm2。
9. Use according to any one of claims 1 to 3, characterized in that the coating area of the coating zone is 8 to 10cm2。
10. Use according to any one of claims 1 to 3, characterized in that the application area is applied in an amount of 1 to 3mg/cm2。
11. Use according to any one of claims 1 to 3, characterized in that the application area is applied in an amount of 1.5 to 2.5mg/cm2。
12. Use according to any one of claims 1 to 3, characterized in that the application area is applied in an amount of 2mg/cm2。
13. Use according to any one of claims 1 to 3, characterised in that the interval in step (iii) is between 10 and 20 minutes.
14. Use according to any one of claims 1 to 3, characterised in that the interval in step (iii) is from 12 to 18 minutes.
15. Use according to any one of claims 1 to 3, characterised in that the interval of time in step (iii) is 15 minutes.
16. Use according to any one of claims 1 to 3, characterised in that step (iii) is rinsed with clean water for 0.5 to 4 minutes.
17. Use according to any one of claims 1 to 3, characterised in that step (iii) is rinsed with clean water for 1 to 3.5 minutes.
18. Use according to any one of claims 1 to 3, characterised in that step (iii) is rinsed with clean water for 2 to 3 minutes.
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