A method of assessing photoprotection efficacy of a personal care composition

Abstract

The present invention relates to a method of assessing photoprotection efficacy of a personal care composition comprising a skin care active; and to a method of comparatively assessing photoprotection efficacy of two or more personal care compositions comprising a skin care active.

Description

[0001] A METHOD OF ASSESSING PHOTOPROTECTION EFFICACY OF A PERSONAL CARE COMPOSITION

[0002] Field of the Invention

[0003] The present invention relates to a method of assessing photoprotection efficacy of a personal care composition comprising a skin care active; and to a method of comparatively assessing photoprotection efficacy of two or more personal care compositions each comprising a skin care active.

[0004] Background of the Invention

[0005] Solar radiation includes about 5% ultraviolet (UV) radiation, wavelength of which is between 200 nm and 400 nm. It is further divided into three regions: from 320 to 400 nm (UV-A), 280 to 320 nm (UV-B) and from 200 to 280 nm (UV-C). Substantial portion of UV-C radiation is absorbed by ozone. Scientific studies have indicated that exposure to UV-A and UV-B radiation for short period causes pigmentation, reddening of the skin and localized irritation, whereas continued or prolonged exposure can lead to sunburn, melanoma, formation of wrinkles and age spots. UV radiation is also thought to cause significant damage to hair. Additionally, visible light (380 to 700 nm) e.g. blue light (380 to 500 nm), is also reported to contribute to providing unwanted effects e.g. aging, and pigmentation. Therefore, it is desirable to protect the skin and other keratinous substrates of the human body from the harmful effects of both UV-A and UV-B radiation as well as visible light e.g. blue light.

[0006] Various personal care compositions that comprise one or more skin care actives e.g. sunscreens, and pigments, are known in the art. Sunscreens are known for preventing and / or protecting the skin from harmful effects of UV radiations. Often, manufacturers of such compositions use terminologies e.g. ultraviolet A protection factor (UVAPF) and sun protection factor (SPF), which is typically followed by a number e.g. UVAPF 5 and SPF 35, that provides some indication of the photoprotection efficacy of such compositions, to the consumers.

[0007] While the photoprotection efficacy of such personal care compositions may well be perceived after using them for a certain period, consumer tend to prefer visualizing or appreciating the photoprotection efficacy of such compositions before purchasing the same. Inevitably for this, they also tend to compare the photoprotection efficacy of two or more personal care compositions comprising a skin care active e.g. a sunscreen. WO2007137936A1 discloses a product that can be used to demonstrate the efficacy of cosmetics against UV radiation, in a quick and simple manner, which would be of immense value to the consumers at the point of sale such as in shops and supermarkets and on the streets and educational institutions, to name a few. Another object of this invention is to provide a convenient product for the consumer to visualize the benefits of cosmetic material against UV radiation.

[0008] Consumers tend to look out for means using which they can assess, visualize or appreciate photoprotection efficacy of personal care compositions across a wider range e.g. a wider range of SPF e.g. 10 to 100.

[0009] A need therefore exists to provide a method of assessing photoprotection efficacy of a personal care composition comprising a skin care active where the method provides assessment across a wider range of photoprotection e.g. a wider range of SPF. A need also exists for providing a method of comparatively assessing photoprotection efficacy of two or more personal care compositions, each comprising a skin care active, where the method provides the assessment across a wider range of photoprotection e.g. a wider range of SPF.

[0010] The present invention has solved the problem and has provided a rapid method of assessing photoprotection efficacy of a personal care composition comprising a skin care active e.g. a sunscreen, over a wider range of SPF. The present invention also has provided a method of comparatively assessing photoprotection efficacy of two or more personal care compositions that each comprises a skin care active e.g. a sunscreen, over a wider range of SPF. The present invention has thus provided such rapid methods that are suitable for assessing or comparatively assessing photoprotection efficacy of one or more personal care compositions before consumers make a purchase. The present methods may be showcased at a point-of-sale (POS) and / or in laboratories as well.

[0011] Summary of the Invention

[0012] Accordingly, in the first aspect, the present invention relates to a method of assessing photoprotection efficacy of a personal care composition comprising a skin care active, comprising the steps:

[0013] a. providing a film that is coated with a photoresponsive coating,

[0014] b. applying the personal care composition either on

[0015] i. the film; or

[0016] ii. on to a suitable in-vitro substrate that may be placed on top of the film, c. exposing the film or the suitable in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; and

[0017] d. measuring change in color intensity after the light exposure,

[0018] wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns.

[0019] Further, in a second aspect, the present invention relates to a method of comparatively assessing a comparison of photoprotection efficacy of two or more personal care compositions comprising a skin care active, comprising the steps:

[0020] a. providing a film that is coated with a photoresponsive coating,

[0021] b. applying the two or more personal care compositions side-by-side without any overlaps either on,

[0022] i. one surface of the film; or

[0023] ii. on one surface of a suitable in-vitro substrate that may be placed on top of the film,

[0024] c. exposing the film or the suitable in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; and

[0025] d. measuring change in color intensity after the light exposure,

[0026] wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns.

[0027] Detailed Description of the Invention

[0028] These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight / weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description and claims indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated. By a “personal care composition” as used herein, is meant to include a composition for topical application to sun-exposed areas of the skin and / or hair of humans. Such a composition may be classified as leave-on or rinse off, and includes any product applied to a human body for improving appearance, cleansing, odour control or general aesthetics. The composition of the present invention can be in the form of a liquid, a lotion, a cream, a foam, a stick, a spray or a gel. A personal care composition may also be referred to as a cosmetic composition.

[0029] "Skin" as used herein is meant to include skin on the face and body (e.g., neck, chest, back, arms, underarms, hands, legs and scalp) and especially to the sun exposed parts thereof. Compositions of the invention is also of relevance to applications on any other keratinous substrates of the human body other than skin e.g. hair, where products may be formulated with specific aim of improving photoprotection.

[0030] Preferably, by “Photoprotection”, it is meant as protection from any or all of IIV-A, IIV-B, visible light e.g. blue light, contained in the sunlight. Alternatively, photoprotection may be referred to as “sun-care” or “sun-protection”; and it means the same as photoprotection.

[0031] Accordingly, the term ‘photoprotection efficacy’ preferably means, efficacy of a personal care composition in protecting the skin from any or all of IIV-A, IIV-B, visible light e.g. blue light. Similarly, the terms ‘sun-care efficacy’ or ‘sun-protection efficacy’ means the same as photoprotection efficacy. Thus, the terms ‘photoprotection efficacy’, ‘sun-care efficacy’ and ‘sunprotection’ efficacy may be used interchangeably; and they mean the same.

[0032] In the first aspect, the present invention relates to a method of assessing photoprotection efficacy of a personal care composition comprising a skin care active, comprising the steps:

[0033] a. providing a film that is coated with photoresponsive coating,

[0034] b. applying the personal care composition either on

[0035] i. the film; or

[0036] ii. on to a suitable in-vitro substrate that may be placed on top of the film, c. exposing the film or the in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; and

[0037] d. measuring change in color intensity after the light exposure,

[0038] wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns. When the method of the first aspect of the present invention is carried out, photoprotection efficacy of a personal care composition is assessed in a rapid and consumer perceivable way. Such method is suitable for assessing such photoprotection efficacy at the point of sale.

[0039] Step a.:

[0040] In step a, a film that is coated with a photoresponsive coating is provided. The film has roughness in the range 0.1 to 6 microns. If the film is a glossy finish film, then preferably, the roughness is in the range 0.1 to 1 micron, preferably 0.1 to 0.5 microns. On the other hand, if the film is a matt finish film, then the roughness is preferably in the range 1 to 6 microns, preferably 2 to 4 microns. A matt finish film is preferred.

[0041] Preferably, the film is made up of paper or plastic or is a laminated film. More preferably, the film is a laminated film.

[0042] The film is coated with a photoresponsive coating preferably selected from spiropyrans, spirooxazines, diarylethenes, azobenzenes photochromic quinones and inorganic photochromies and mixtures thereof. More preferably, the film is coated with spiropyrans, spirooxazines and mixtues thereof.

[0043] Such films coated with photoresponsive coating are commercially available from Zhejiang Beibo Crafts, China.

[0044] Preferably, the photoresponsive coating is of thickness in the range 0.01 to 2 microns, preferably 0.01 to 0.5 micron.

[0045] Preferably, the film is printed with appropriate indicia that helps visualize the change in color intensity and thereby photoprotection efficacy. Such indicia may be a photograph, a drawing or a geometric shape e.g. a circle and a rectangle.

[0046] Step b.:

[0047] In step b., a personal care composition is applied either on the film described in step a. above; or it is applied on to a suitable in-vitro substrate that may be placed on top of the film described in step a. above. Such in-vitro substrate is preferably selected from a polymethyl methacrylate (PMMA) plate, vitro-skin, helioscreen, helioplates, polymethyl siloxane (PDMS) elastomer, polyethylene, polypropylene, transpore tape, more preferably a PMMA plate. The roughness of such in-vitro substrate is in the range from 0.1 to 6 microns, preferably 1 to 6 microns, preferably 2 to 4 microns.

[0048] More preferably, a PMMA plate that may be used in step b., has roughness in the range 1 to 6 microns, preferably 6 microns.

[0049] An advantage of applying a personal care composition on to a suitable in-vitro substrate and placing it on top of the film is such that the film may be re-used in the methods as per the present invention.

[0050] Alternatively, such in-vitro substrate may first be coated with a photoresponsive coating described above; and the same may be used instead of a film coated with a photoresponsive coating; with the rest of the method carried out as described.

[0051] In any case, the roughness, either of the film or that of the suitable in-vitro substrate on to which a personal care composition may be applied and spread, is found to contribute to the robustness of the method in terms of its ability to differentiate across a wider range of photoprotection e.g. a wider range of SPF. Such ability is further found to be enhanced when used in combination with a source of light having its critical emission spectrum in the range of wavelength from 360 to 370 nm e.g. 365 nm.

[0052] Preferably, the term ‘wider range’ as used in the context of the phrase ‘wider range of SPF’ preferably means SPF in the range from 10 to 100, preferably 15 to 60, preferably 30 to 50.

[0053] Spreading of a personal care composition on a surface where the roughness of the surface is less than 0.1 microns, e.g. a glass slide with roughness 0.05 microns, was found to lead to uneven spreading as the composition tended to aggregate upon spreading on such surface. This uneven spreading left pockets through which UV radiation could still pass through.

[0054] In any case, a personal care composition may preferably be applied in quantity in the range 2 mg to 6 mg / cm2, preferably 2 to 4 mg / cm2.

[0055] A suitable personal care composition comprising a skin care active is described hereinbelow. Step c.:

[0056] In step c., the film, either as such or along with the in-vitro substrate that may be placed over it as described in step b. above, is exposed to a source of light for a duration of 5 seconds to 30 minutes.

[0057] Preferably, the exposure is carried out for a duration of 10 seconds to 25 minutes, preferably 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes, preferably 45 seconds to 10 minutes, preferably 1 minute to 5 minutes.

[0058] Preferably, exposure to light is carried out using a source of ultraviolet light having wavelength from 280 to 400 nm, preferably 300 to 380 nm, preferably 320 to 370 nm, preferably 340 to 370, e.g. 365 nm, for a duration as described above. When exposure to light is carried out using a source of ultraviolet light as described, the skin care active comprised in a personal care composition is a sunscreen. A sunscreen is preferably selected from an organic sunscreen, an inorganic sunscreen and mixtures thereof. Examples of such sunscreens are described hereinbelow. The method is suitable for assessing photoprotection efficacy of personal care compositions over a wider range of SPF.

[0059] Preferably, the term ‘wider range’ as used in the context of the phrase ‘wider range of SPF’ preferably means SPF in the range from 10 to 100, preferably 15 to 60, preferably 30 to 50.

[0060] Alternatively, exposure to light may be carried out using a source of visible light having wavelength from 380 to 750 nm, preferably to a source of blue light having wavelength from 380 to 500 nm, e.g. 420 nm, for a duration as described above. When exposure to light is carried out using a source of visible light e.g. a source of blue light, a skin care active comprised in a personal care composition is preferably selected from a pigment and a skin benefit agent. Such pigments and skin benefit agents are described hereinbelow.

[0061] Step d.:

[0062] In step d., change in color intensity after the exposure to light as described in step c. above, is measured. Such measurement of change in intensity may be carried out using an appropriate instrument e.g. a chromameter; or the change in color intensity may be assessed based on the visual analysis.

[0063] Such change in color intensity after the exposure to the light either using a source of ultraviolet light or a source of visible light, for select duration, shows consumer perceivable assessment of photoprotection efficacy of the personal care composition applied in step b. This is based on the ability of the personal care composition to either absorb, or reflect or block the light shown upon it in step c. The photoprotection efficacy of a personal care composition is directly proportional to its ability of either absorbing or reflecting or blocking the light to which it is exposed, thereby allowing less and lesser amount of light to be passed through on to the film that is coated with a photoresponsive coating as described in step a. As the film contains appropriate indicia and the photoresponsive coating, upon exposure to the light in step c., a color gets developed, and the intensity of which may be measured suitably as described in step d. above, thereby assessing the photoprotection efficacy.

[0064] Further, in a second aspect, the present invention relates to a method of comparatively assessing photoprotection efficacy of two or more personal care compositions each comprising a skin care active, comprising the steps:

[0065] a. providing a film that is coated with a photoresponsive coating,

[0066] b. applying the two or more personal care compositions side-by-side without any overlaps either on,

[0067] i. one surface of the film; or

[0068] ii. on one surface of a suitable in-vitro substrate that may be placed on top of the film,

[0069] c. exposing the film or the suitable in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; and

[0070] d. measuring change in color intensity after the light exposure,

[0071] wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns.

[0072] Whilst all of the features described in the first aspect hereinabove are equally applicable to the second aspect herein, the method of the second aspect differs from that in the first aspect such that, in step b., two or more personal care compositions are applied side-by-side, without any overlaps, on to the film or on to a suitable in-vitro substrate that may be placed on top of the film. The rest of the steps are carried out in the same manner as described in the first aspect hereinabove.

[0073] When carried out, the method of the second aspect provides comparative assessment of photoprotection efficacy of two or more personal care compositions, each comprising a skin care active, applied side-by-side without any overlaps. The change in color intensity after the exposure to the light in step d. of the second aspect, provides a comparison of photoprotection efficacy of the two or more personal care compositions each comprising a skin care active. A skin care active that may be comprised in the two or more personal care compositions may differ from each other, for example, they may contain different sunscreens, differing amounts of the same or different types of sunscreens. This may include sunscreen mixtures of organic and inorganic sunscreens described hereinbelow.

[0074] At least two different personal care compositions are applied on the film or on to the in-vitro substrate for the comparison. However, in an aspect, more than two e.g. three, different personal care compositions may also be applied without any overlaps. In other words, based on the size of the film used in step a., suitable number of different personal care compositions may be applied side-by-side, as long as there is no overlap.

[0075] A personal care composition suitable for to be used in the method of the first or the second aspect, is described below.

[0076] A personal care composition comprises a skin care active. Preferably, the skin care active is selected from a sunscreen, when the exposure to light is carried out using a source of ultraviolet light as described above; and it may be selected from a pigment, a skin benefit agent and mixtures when the exposure to light is carried out using a source of visible light as described above. It is possible that a personal care composition comprises a mixture of one or more sunscreens; and at the same time also contains a pigment and / or a benefit agent described below. In such case, it would be understood that the assessment would depend on the source of light e.g. ultraviolet or visible, that may be used in step c.

[0077] Sunscreens

[0078] Preferably, if the skin care active selected is a sunscreen, the same may be selected from one or more of organic sunscreens, inorganic sunscreens and mixtures thereof, described below.

[0079] Preferably, organic sunscreens may be selected from oil-soluble organic sunscreens, water-soluble organic sunscreens and mixtures thereof described below.

[0080] Oil-soluble organic sunscreens

[0081] By ‘oil-soluble’, it is preferably meant those organic sunscreens which have a solubility in water of less than 10 g / l, preferably less than 5 g / l, more preferably less than 2 g / l, at 25°C. Oil-soluble sunscreens could be of the IIV-B type or of the IIV-A type. When an oil soluble IIV-B organic sunscreen is selected, it is preferably one or more of octyl salicylate, 3,3,5-trimethylclohexyl 2-hydroxybenzoate, ethylhexyl salicylate, 2-ethylhexyl 2-cyano-3,3-diphenyl-2-propenoate which is also known as octocrylene, 2-ethylhexyl-4-methoxycinnamate or octylmethoxycinnamate, ethylhexyl triazone, 3-benzylidene camphor, cinoxate, diethylhexyl butamido triazone, para amino benzoic acid (PABA), ethyl dihydroxypropyl PABA, ethylhexyl dimethoxy benzylidene dioxoimidazoline propionate, isoamyl p-methoxycinnamate, isopentyl trimethoxycinnamate trisiloxane, isopropyl benzyl salicylate, isopropyl methoxycinnamate, 4-methylbenzylidene camphor, PEG-25 PABA, and pentyl dimethyl PABA. More preferred oil-soluble UVB sunscreens are selected from one or more of octyl salicylate, 3,3,5-trimethylclohexyl 2-hydroxybenzoate, ethylhexyl salicylate, 2-ethylhexyl 2-cyano-3,3-diphenyl-2-propenoate, and 2-ethylhexyl-4-methoxycinnamate and further more preferred are selected from one or more of 2-ethylhexyl-4-methoxycinnamate, ethylhexyl salicylate and 2-ethylhexyl 2-cyano-3,3-diphenyl-2-propenoate. Some of the well known brands under which the above sunscreens are sold are Octisalate®, Homosalate®, Neo Heliopan®, Neo Heliopan® AV, Neo Heliopan® OS, Octocrylene® and Parsol® MCX. The oil-soluble IIV-B sunscreen has Amax from 280 to 320 nm.

[0082] When an oil-soluble IIV-A organic sunscreen is selected, it is preferably selected from one or more of a dibenzoylmethane compound, diethylamino hydroxy benzoyl hexyl benzoate and menthyl anthranilate. A dibenzoyl methane compound is most preferred for an oil-soluble UVA-sunscreen. Suitable dibenzoyl methane compounds are selected from one of more of t-butylmethoxy dibenzoylmethane, 2-methyldibenzoylmethane, 4-methyl-dibenzoyl-ethane, 4-isopropyldibenzoyl-methane, 4-tert-butyldibenzoylmethane, 2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane, 4,4'-diisopropyl-dibenzoylmethane, 2-methyl-5-isopropyl-4'-methoxydibenzoylmethane, 2-methyl-5-tert-butyl-4'-methoxy-dibenzoyl methane, 2,4-dimethyl-4'-methoxy dibenzoylmethane and 2,6-dimethyl-4-tert-butyl-4'-methoxy-dibenzoylmethane. The most preferred dibenzoyl methane compound is t-butyl methoxy dibenzoylmethane. Commercially available as Parsol 1789.

[0083] The personal care composition suitable for use in the method of the invention may comprise both; an organic oil-soluble UVB and an organic oil-soluble UVA sunscreen, selected from those described above. Alternately, certain oil soluble sunscreens which have both a UVA and UVB screening efficacy may also be selected e.g. bis-ethylhexyloxyphenol methoxyphenyl triazine, drometrizole trisiloxane, benzophenone and its derivatives. Oil-soluble organic sunscreens may be present in the range 0.1 to 25 wt% in the composition. Water-soluble organic sunscreen

[0084] By ‘water soluble’ sunscreen, whether of the UVA type, or of the UVB type, is meant that the solubility in water of the sunscreen is higher than 10 g / l preferably higher than 50 g / l at 25°C.

[0085] Preferably, a water-soluble organic sunscreen is selected from a IIV-A and / or a IIV-B water-soluble organic sunscreens described below.

[0086] Examples of such sunscreens include phenyl benzimidazole sulphonic acid (PBSA), benzophenone-4 or benzylidene camphor sulfonic acid. PBSA also known as Ensulizole is commercially available as Eusolex 232 (from Merck KGaA). PBSA is also available under the brand names Neo Heliopan Hydro (from Symrise), Parsol HS (from DSM) and Sunsafe ES (from Uniproma). There are certain water-soluble sunscreens which have both a UVA screening efficacy as well as a UVB screening efficacy. Such sunscreens provide both UVA and UVB protection e.g. benzophenone-4 (sold as Sulisobenzone).

[0087] Examples of such water-soluble UVA organic sunscreen include disodium phenyl dibenzimidazole tetrasulfonate (Neoheliopan AP) or terephthalylidene dicamphor sulfonic acid (TDSA). Di sodium phenyl dibenzimidazole tetra sulfonate is also known as bisdisulizole disodium. This is commercially available as Neo heliopan AP (from Symrise Shanghai Ltd) or as Sunsafe DPDT (from Uniproma). Terephthalylidene dicamphor sulfonic acid (TDSA) is also known as Ecamsule. Water soluble organic sunscreens, whether of UV-A or UV-B type, may be used in the range 0.1 to 5 wt% in the personal care composition.

[0088] Inorganic sunscreens

[0089] Alternatively, a sunscreen may be selected from inorganic sunscreens e.g. titanium dioxide, zinc oxide and mixture thereof.

[0090] Pigments

[0091] Preferably, a skin care active may be selected from pigments. Examples of such pigments include various grades of iron oxides, tin oxides, mica and mixtures thereof. Preferably, these pigments are other than the inorganic sunscreens e.g. titanium dioxide and zinc oxide described above. Skin benefit agent

[0092] Preferably, skin benefit agent is selected from xanthochrome, high molecular weight polyphenols and mixtures thereof. These ingredients are known to provide protection from blue light.

[0093] Thus, a skin care active comprised in a personal care composition is preferably selected from a sunscreen, a pigment, a skin benefit agent and mixtures thereof; of which it is a sunscreen if the exposure is carried out to ultraviolet light; and it is either a pigment or the benefit agent as described above, if exposure is carried out to visible light.

[0094] A personal care composition comprising a sunscreen as the skin care active used in the method of the invention may have:

[0095] • sun protection factor (SPF) in the range from 10 to 100, preferably 15 to 85, preferably 20 to 75, preferably 25 to 65, preferably 30 to 55, preferably 40 to 50; or

[0096] • UV-A protection factor (LIVAPF) in the range from 5 to 20, preferably 7 to 15, preferably 9 to 12; or

[0097] • if known PA scale is used then PA+, PA++, PA+++, PA++++.

[0098] Such SPF, LIVAPF and PA+++ may be measured using well known methods in the art.

[0099] It would be understood that the method claimed through the present invention is a method that shows a visually perceivable assessment of photoprotection efficacy of a single personal care composition; or that of a comparison photoprotection efficacy of two or more personal care compositions.

[0100] In other words, the method of the present invention is not a method of measuring or estimating SPF, LIVAPF or PA factors. Rather, the method of the present invention shows a visual assessment of effectiveness of one or more personal care compositions. For such method, personal care compositions of known LIVAPF, SPF or PA factors may be employed, and their effectiveness may be visualized in a rapid and consumer perceivable way

[0101] For example, personal care compositions of e.g. SPF 15 and SPF 30 may be applied side-by-side, without any overlaps, on a PMMA plate 6 microns roughness placed on a laminated film coated with sporioxazine coating and exposed to UV light for 1 minute; and change in color intensity may be measured. A skin care active e.g. a sunscreen, contained in such personal care compositions absorbs the UV light shown, and as a result allows proportionately low amount of UV light to pass through, leading to development of color of varying intensity turning the indicia colored variably. The personal care composition may be in the form of a gel, a cream, a spray, a stick, a lotion or a serum.

[0102] The invention is now further described with the help of the following non-limiting examples.

[0103] Examples

[0104] A known personal care composition that may be in the form of a gel, a cream, a spray, a stick, a lotion or a serum may be used in the method.

[0105] In the example 1 below, a marketed product, SPF 50 gel was used that contained 18 wt% sunscreens. As a control (example A), a gel without any sunscreen was used.

[0106] In step a., a laminated film of roughness 1 micron coated with spirooxazine as the photoresponsive coating was used.

[0107] In step b., gel compositions as mentioned above were applied on to separate PMMA plates having roughness of 6 microns and the PMMA plates were placed on top of the film. In either case, the personal care composition was used in amounts 2 mg / cm2.

[0108] In step c., and the exposure to the light was carried out using a wood lamp having wavelength 365 nm for 1 minute.

[0109] In step d., the change in color intensity was assessed.

[0110] Such assessment was carried out based on visual appearance and was graded on a scale with a score of 1 to 5 as follows:

[0111] 1: No purple color at all,

[0112] 2: Faint purple,

[0113] 3: Purple,

[0114] 4: Very purple; and

[0115] 5: Dark purple. The results obtained were as follows:

[0116] Table 1

[0117] Example 1 (SPF 50) Example A

[0118] (As per the present invention) (Control; no sunscreens) Color intensity score 1 5

[0119]

[0120] Further, marketed compositions that provide SPF 30 (example 2) and SPF 15 (example 3) were taken in addition to the composition of example 1 (SPF 50).

[0121] In step a., a laminated film of roughness 1 micron coated with spirooxazine as the photoresponsive coating was used.

[0122] In step b., the three compositions were then applied (2 mg / cm2) on to separate glass slides (roughness 0.05 microns; control); and on to separate PMMA plates (an example of the suitable in-vitro substrate; roughness 6 microns).

[0123] In step c., exposure to UV radiation was carried out using the wood lamp having wavelength 365 nm for 1 minute.

[0124] In step d., change in color intensity was measured on the scale provided above; and the same was found to be as in table 3 below.

[0125] In addition, spreading of was assessed visually which was found to be as shown in table 2 below.

[0126] Table 2

[0127] Roughness Example 1 Example 2 Example 3

[0128] (microns) (SPF 50) (SPF 30) (SPF 15)

[0129] 0.05 (glass slide) Uneven Uneven Uneven

[0130] 6 (PMMA plate) Even Even Even

[0131]

[0132] The data in table 2 above showed that when roughness was in the range as per the present invention, even spreading of compositions was obtained. Further, color intensity for these compositions, when applied on a glass slide; and when applied on a PMMA plate, separately, was assessed on the scale described above. The same was found to be as follows:

[0133] Table 3:

[0134] Color intensity scores

[0135] 1 2 3

[0136] Example

[0137] (SPF 50) (SPF 30) (SPF 15)

[0138] Glass slide

[0139] 3 3 3

[0140] (roughness: 0.05 microns)

[0141] PMMA plate

[0142] 1 2 3

[0143] (roughness: 6 microns)

[0144]

[0145] The data in table 3 above showed that when the method as per the present invention is used where roughness of a suitable in-vitro substrate was in the range as per the present invention, the method provided differentiation amongst compositions that otherwise have different SPF values (these values are often supplied by manufacturers; and may be assessed using known methods of assessing SPF as described in ISO 24444).

[0146] Thus, the present invention not only provides a method of assessing photoprotection efficacy of a personal care composition; or provides a method of comparative assessment of photoprotection efficacy; but it also provides such assessment across a wider range of photoprotection e.g. a wider range of SPF.

Claims

Claims1. A method of assessing photoprotection efficacy of a personal care composition comprising a skin care active, comprising the steps:a. providing a film that is coated with a photoresponsive coating,b. applying the personal care composition either oni. the film; orii. on to a suitable in-vitro substrate that may be placed on top of the film, c. exposing the film or the suitable in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; andd. measuring change in color intensity after the light exposure,wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns.

2. A method of comparatively assessing photoprotection efficacy of two or more personal care compositions each comprising a skin care active, comprising the steps:a. providing a film that is coated with a photoresponsive coating,b. applying the two or more personal care compositions side-by-side without any overlaps either on,i. one surface of the film; orii. on one surface of a suitable in-vitro substrate that may be placed on top of the film,c. exposing the film or the suitable in-vitro substrate that may be placed on top of the film, to a source of light for 5 seconds to 30 minutes; andd. measuring change in color intensity after the light exposure,wherein the film or the suitable in-vitro substrate has roughness in the range 0.1 to 6 microns.

3. The method as claimed in claims 1 or 2 wherein the film used in step a., is a glossy film that has roughness in the range 0.1 to 1 microns; or is a matte film that has roughness in the range 1 to 6 microns.

4. The method as claimed in any one of claims 1 to 3 wherein the film is made up of paper or plastic or is a laminated film.

5. The method as claimed in any one of claims 1 to 4 wherein the film is coated with photoresponsive coating selected from spiropyrans, spirooxazines, diarylethenes, azobenzenes photochromic quinones, inorganic photochromies and mixtures thereof.

6. The method as claimed in any one of claims 1 to 5 wherein the suitable in-vitro substrate used in step b. is selected from a polymethyl methacrylate (PMMA) plate, vitro-skin, helioscreen, helioplates, polymethyl siloxane (PDMS) elastomer, polyethylene, polypropylene, transpore tape.

7. The method as claimed in claim 6 wherein the roughness of the suitable in-vitro substrate is in the range 1 to 6 microns.

8. The method as claimed in any one of claims 1 to 7 wherein the exposure to a source of light is carried out for 10 seconds to 25 minutes, preferably 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes, preferably 45 seconds to 10 minutes, preferably 1 minute to 5 minutes.

9. The method as claimed in any one of claims 1 to 8 wherein the exposure to light is carried out using a source of ultraviolet light having wavelength from 280 to 400 nm; and wherein the skin care active is a sunscreen.

10. The method as claimed in claim 9 wherein the sunscreen is selected from an organic sunscreen, an inorganic sunscreen and mixtures thereof.

11. The method as claimed in claim 9 or 10 wherein the personal care composition has sun protection factor (SPF) in the range from 10 to 100.

12. The method as claimed in any one of claims 1 to 8 wherein the exposure to light is carried out using a source of visible light having wavelength from 380 to 500 nm; and the skin care active is selected from a pigment and a skin benefit agent.

13. The method as claimed in any one of claims 1 to 14 wherein the personal care composition is in the form of a cream, a gel, a lotion, a stick or a serum.

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