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 sunscreen composition ” as used herein , is meant to include a composition for topical application to sun - exposed areas of the skin and / or hair of mammals , especially humans . such a composition may be generally classified as leave - on or rinse off , and includes any product applied to a human body for also improving appearance , cleansing , odor control or general aesthetics . it is more preferably a leave - on product . the composition of the present invention can be in the form of a liquid , lotion , cream , foam , scrub , gel , or toner , or applied with an implement or via a face mask , pad or patch . non - limiting examples of such sunscreen compositions include leave - on skin lotions , creams , antiperspirants , deodorants , lipsticks , foundations , mascara , sunless tanners and sunscreen lotions . “ skin ” as used herein is meant to include skin on the face and body ( e . g ., neck , chest , back , arms , underarms , hands , legs , buttocks and scalp ) and especially to the sun exposed parts thereof . the composition 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 providing photoprotection . an advantage of the present invention is that the sunscreen composition is capable of providing an spf of higher than 20 , more preferably at least 30 , further more preferably higher than 40 . it is preferred that the composition comprises at the most 10 % total organic sunscreens by weight of the composition . the composition of the invention comprises 0 . 05 to 15 % by weight compound of the formula a : compound of formula a is preferably present in 0 . 1 to 10 %, more preferably 0 . 1 to 7 % by weight of the composition . in the compound of formula a , r1 , r2 and r3 are each selected from any one of alkyl , branched alkyl , cycloalkyl , polycycloalkyl , heterocycloalkyl , alkaryl , alkoxy , aryl , aralkyl , alkenyl , alkynyl or fluorocarbon groups containing 1 to 50 carbon atom ( s ). preferred compound of formula a is 2 , 4 - bis -{[ 4 -( 2 - ethyl - hexyl - oxy )- 2 - hydroxy ]- phenyl }- 6 -( 4 - methoxy - phenyl )-( 1 , 3 , 5 )- triazine commercially sold under the brand names tinosorb s ( available from basf ) or escalol s ( available from ashland inc ). an important ingredient that contributes to the benefits of the present invention is a non - ionic surfactant . the non - ionic surfactant for use in the composition of the present invention has an hlb value of at least 9 . hlb is calculated using the griffin method wherein hlb = 20 × mh / m wherein mh is the molecular mass of the hydrophilic portion of the molecule and m is the molecular mass of the whole molecule , giving a result on an arbitrary scale of 0 to 20 . typical values for various surfactants are given below : a value from 7 to 11 indicates a w / o ( water in oil ) emulsifier a value from 12 to 16 indicates oil in water emulsifier a value of 16 to 20 indicates a solubiliser or hydrotrope the non - ionic surfactant is preferably selected from any one of the following groups : ( a ) fatty alcohol ethoxylates with saturated carbon chain and having hlb higher than 15 . 5 ; or ( b ) fatty alcohol ethoxylates with unsaturated carbon chain with hlb higher than 12 . ( c ) alkyl phenol ethoxylates having hlb higher than 15 ; ( d ) polyoxyethylene sorbitan alkyl esters with saturated c12 to c16 carbon chain and having hlb higher than 12 ; ( e ) polyoxyethylene sorbitan alkyl esters with unsaturated c18 carbon chain and having hlb higher than 9 ; suitable commercially available examples of ( a ) fatty alcohol ethoxylates with saturated carbon chain and having hlb higher than 15 . 5 or from ( b ) the class of fatty alcohol ethoxylates with unsaturated carbon chain with hlb higher than 12 are sold under the brand names brij 35 ( a c12eo23 compound ), brij 97 ( unsaturated c18eo12 ), brij 700 ( c18eo100 ) or brij 99 ( unsaturated c18eo20 ). suitable examples of ( c ) alkyl phenol ethoxylates with hlb higher than 15 for use in the composition of the invention are sold under the brand names triton x 165 , triton x 305 , triton 405 , or triton x 705 . suitable examples of ( d ) polyoxyethylene sorbitan alkyl esters with saturated c12 to c16 carbon chain and having hlb higher than 12 and ( e ) polyoxyethylene sorbitan alkyl esters with unsaturated c18 carbon chain and having hlb higher than 9 are sold under the brand names tween20 , tween21 , tween40 , tween80 , tween 81 or tween85 trioleate . the non - ionic surfactant is included in 0 . 1 to 5 %, preferably 0 . 2 to 4 %, more preferably 0 . 2 to 3 % by weight of the composition . the composition of the invention comprises a cosmetically acceptable base comprising 3 to 25 % fatty acid by weight of the composition . cosmetically acceptable bases are preferably in a cream , lotion , gel or emulsion format . a more preferred format is a cream , further more preferred a vanishing cream . preferred compositions of the invention comprise 3 to 20 % and more preferably 6 to 20 % fatty acid ( saturated or unsaturated fatty acids or their mixtures ) by weight of the composition . the composition preferably also comprises 0 . 1 to 10 %, more preferably 0 . 1 to 3 % soap . c 12 to c 20 fatty acids are especially preferred in vanishing cream bases , further more preferred being c 14 to c 18 fatty acids . in creams , the fatty acid is preferably substantially a mixture of stearic acid and palmitic acid . soaps in the vanishing cream base include alkali metal salt of fatty acids , like sodium or potassium salts . the soap is preferably the potassium salt of the fatty acid mixture . the fatty acid in vanishing cream base is often prepared using hystric acid which is substantially ( generally about 90 to 95 %) a mixture of stearic acid and palmitic acid . thus , inclusion of hystric acid and its soap to prepare the vanishing cream base is within the scope of the present invention . the cosmetically acceptable base is usually from 10 to 99 . 9 %, preferably from 50 to 99 % by weight of the composition . the composition of the invention is preferably an oil - in - water emulsion composition . the cosmetically acceptable base preferably includes water . water is preferably included in 35 to 90 %, more preferably 50 to 85 %, further more preferably 50 to 80 % by weight of the composition . the composition of the invention preferably comprises an additional uv - a or uv - b sunscreen , other than the compound of formula a . these sunscreens are preferably chosen from compounds of the following seven major groups : ( 1 ) benzophenones , ( 2 ) anthranilates , ( 3 ) dibenzoylmethanes ( 4 ) salicylates , ( 5 ) cinnamates , ( 6 ) camphores and ( 7 ) p - amino benzoic acids ( paba ) or mixtures . the preferred uva sunscreen for use in the composition of the invention is a compound of the dibenzoylmethane class . preferred dibenzoylmethane derivative are selected from 4 - tert - butyl - 4 ′- methoxydibenzoylmethane , 2 - methyldibenzoylmethane , 4 - methyl - dibenzoyl - methane , 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 or 2 , 6 - dimethyl - 4 - tert - butyl - 4 ′- methoxy - dibenzoylmethane . the most preferred dibenzoylmethane derivative is 4 - tert .- butyl - 4 ′- methoxydibenzoylmethane . the composition of the invention preferably comprises 0 . 1 to 5 %, more preferably 0 . 2 to 5 %, further more preferably 0 . 4 to 3 %, compound of the dibenzoylmethane class by weight of the composition . the additional uv - b organic sunscreen which may be included in the composition of the invention is preferably oil soluble . it is preferably selected from the class of cinnamic acid , salicylic acid , diphenyl acrylic acid compounds . a few of the preferred oil soluble uv - b sunscreens which are commercially available and useful for inclusion in the composition of the invention are octisalate ™, homosalate ™, neohelipan ™, octocrylene ™, oxybenzone ™ or parsol mcx ™. the composition of the invention preferably comprises 0 . 1 to 7 %, more preferably 0 . 2 to 5 %, further more preferably 0 . 4 to 3 % uv b sunscreen , by weight of the composition . a useful aspect of the present invention is that high spf values can be obtained even when the total amount of organic sunscreens ( excluding the compound of formula a ) are present in small amounts which may be in the range of 0 . 1 to 7 %, preferably from 0 . 5 to 6 %, more preferably 1 to 5 %, by weight of the composition . other useful photostabilizers may be preferably used in the present invention . this include derivatives of diphenylacrylate , benzylidene camphor , napthalate , fluorene and diarylbutadiene etc . the composition of the invention preferably includes solubilisers to enhance the solubility of compound of formula a , thereby increasing its sun — protection efficacy . solubilisers are preferably of the class of esters of aryl alcohol , akyl or cycloalkyl carboxylic acid or carbonic acid . of these , the class of esters of aryl alcohol is preferred for use as a solubliser . preferred solubilisers are phenethyl , benzyl or substitued benzyl alcohols . most preferred solubilisers may be selected from the compounds given below : solublisers are preferably included in 0 . 1 to 15 %, more preferably in 0 . 5 to 10 %, further more preferably 0 . 5 to 5 % by weight of the composition . other useful sun - protective agents e . g . inorganic sun - blocks may be preferably used in the present invention . these include , for example , zinc oxide , iron oxide , silica , such as fumed silica , or titanium dioxide . the total amount of sun block that is preferably incorporated in the composition according to the invention is from 0 . 1 to 5 % by weight of the composition . the composition of the invention may additionally comprise a skin lightening agent . the skin lightening agent is preferably chosen from a vitamin b3 compound or its derivative e . g . niacin , nicotinic acid , niacinamide or other well known skin lightening agents e . g . aloe extract , ammonium lactate , azelaic acid , kojic acid , citrate esters , ellagic acid , glycolic acid , green tea extract , hydroquinone , lemon extract , linoleic acid , magnesium ascorbyl phosphate , vitamins like vitamin b6 , vitamin b12 , vitamin c , vitamin a , a dicarboxylic acid , resorcinol derivatives , hydroxycarboxylic acid like lactic acid and their salts e . g . sodium lactate , and mixtures thereof . vitamin b3 compound or its derivative e . g . niacin , nicotinic acid , niacinamide are the more preferred skin lightening agent as per the invention , most preferred being niacinamide . niacinamide , when used , is preferably present in an amount in the range of 0 . 1 to 10 %, more preferably 0 . 2 to 5 % by weight of the composition . the composition according to the invention may also comprise other diluents . the diluents act as a dispersant or carrier for other materials present in the composition , so as to facilitate their distribution when the composition is applied to the skin . diluents other than water can include liquid or solid emollients , solvents , humectants , thickeners and powders . the composition of the invention may comprise a conventional deodourant base as the cosmetically acceptable carrier . by a deodorant is meant a product in the stick , roll - on , or propellant medium which is used for personal deodorant benefit e . g . application in the under - arm or any other area which may or may not contain anti - perspirant actives . deodorant compositions can generally be in the form of firm solids , soft solids , gels , creams , and liquids and are dispensed using applicators appropriate to the physical characteristics of the composition . the compositions of the present invention can comprise a wide range of other optional components . the ctfa cosmetic ingredient handbook , second edition , 1992 , which is incorporated by reference herein in its entirety , describes a wide variety of non - limiting cosmetic and pharmaceutical ingredients commonly used in the skin care industry , which are suitable for use in the compositions of the present invention . examples include : antioxidants , binders , biological additives , buffering agents , colorants , thickeners , polymers , astringents , fragrance , humectants , opacifying agents , conditioners , exfoliating agents , ph adjusters , preservatives , natural extracts , essential oils , skin sensates , skin soothing agents , and skin healing agents . the invention is now further described by way of the following non - limiting examples . examples a to c and 1 to 4 : spf obtained with compositions outside the invention ( a to c ) and those within the invention ( 1 to 4 ) photoprotective personal care vanishing cream compositions as shown in table 1 were prepared . in vitro - spf was measured for all the samples using a optometrics 290s instrument model . the substrate used was a 8 cm transpore tape procured from 3m company . the sample was applied at 2 mg / cm 2 . the spf as measured is shown in table 1 . in the table 1 above the following compounds are referred to brij l23 : with n = 12 and m = 23 has the following general structure and was sourced from croda . it is also sold under the brand name of brij - 35 . it has hlb value of 16 . 9 . tinosorb s : has the following structure and was sourced from basf parsol mcx : has the following structure and was sourced from chem spec . the data in table - 1 indicates that compositions as per the invention ( examples 1 to 4 ) provide for vastly superior spf values as compared to compositions outside the invention ( examples a to c ). examples d and 5 , 6 : photostability of compositions of the invention ( 5 & amp ; 6 ) as compared to control ( example d ) photoprotective personal care vanishing cream compositions as shown in table — 2 were prepared . the compositions were measured for photostability using the following procedure : the compositions were applied (˜ 2 mg / cm2 ) on two clean glass plates to generate thin films of uniform thickness . out of these , one plate was exposed to atlas solar simulated radiations ( uva flux , 5 . 5 mw / cm 2 for 60 minutes of uv exposure . the other plate was kept un - exposed which served as control . subsequent to completion of the above protocol , all the films of the cream were separately extracted in hplc grade methanol . the quantification of the active was done using perkin elmer uv / visible spectrometer or high performance liquid chromatography ( hplc ). the absorbance at a scanning range of 200 - 800 nm was measured for each solution , using quartz cuvette and respective blank solutions on a spectrometer . relative absorbance values were recorded at a wavelength of 355 nm ( for uva ). % photostability of the uv - a sunscreen was determined and plotted against time of exposure . uvr for exposure was generated using a solar simulator ( atlas kw system ) with a irradiance of 5 . 5 mj cm − 2 , at a distance of ˜ 20 cm . the irradiance was measured using a radiometer ( solar light co . pma2200uv ). relative absorbance values were recorded at a wavelength of 310 nm ( for uvb ). % photostability of the uv - b sunscreen was determined and plotted against time of exposure . the photostability of the uva and uvb sunscreen is shown in table 2 . the data in table 2 indicates that compositions as per the invention ( examples 5 and 6 ) provide for vastly superior uva and uvb stability as compared to a control sample example d ( outside the invention ). examples e and 7 to 9 : effect of fatty acid concentration photoprotective personal care cream compositions as shown in table 3 were prepared and the in vitro - spf was measured similar to the examples 1 to 4 . the spf values as measured are shown in table 3 . compositions as shown in table 4 below were prepared . the in - vitro spf was measured using the procedure already mentioned earlier . the spf values of the various compositions are given in table 4 . the data in table 4 indicates that inclusion of a solubiliser ( example 10 ) provides for enhanced spf while inclusion of a preferred solubliser as per the invention ( example 11 ) provides further enhanced spf .
the invention relates to a photostable sunscreen composition that not only provides enhanced sun protection by way of high spf , but does that over sustained period of time after applying the composition on the skin . the present inventors have found that when a compound of the triazine group is used without additional uva or uvb sunscreen , and a non - ionic surfactant is included in a cosmetic base comprising fatty acids , it is possible to achieve high spf .