United States Patent (19) 11 Patent Number: 4,793,668 Longstaff 45 Date of Patent: Dec. 27, 1988

54 SUNBATHING FILTER WITH INCOMPLETE the Photoprotective Efficiency of Against UV-B ABSORPTION DNA Damage by UVB', (1985). 76 Inventor: Eric Longstaff, 5 Cantey Pl., Atlanta, U.S. Dept. of H.E.W., NIOSH-"A Recommended Ga. 30327 Standard for Occupational Exposure to Ultra Violet Radiation', (1977). (21) Appl. No.: 930,602 Strickland, P. T., “Photocarcinogenesis by Near-Ul 22 Filed: Nov. 13, 1986 traviolet (UVA) Radiation in Sencar Mice", (1986). 51) Int. Cl* ...... G02B 5/22; G02B 7/00 Kugman & Kugman, "Review Article-The Nature of 52 U.S. C...... 350/1.1; 350/311; Photoaging: Its Prevention and Repair", (1986). 350/318 Primary Examiner-Bruce Y. Arnold 58 Field of Search ...... 350/1.1, 311, 318 Attorney, Agent, or Firm-Louis T. Isaf 56) References Cited U.S. PATENT DOCUMENTS 57) ABSTRACT 2,391,959 1/1946 Gallowhur...... 2/78 Apparatus for use in sunbathing comprises a screen 3,352,058 11/1967 Brant ...... 47/58 formed of a sheet of thermoplastic or fiber material 4,134,875 l/1979 Tapia ...... 260/42.66 which is transparent to the safe UV-A wavelengths of 4,179,547 12/1979 Allingham et al...... 525/2 solar radiation and the visible light range between 4,200,360 4/1980 Mutzhas ...... 350/36 400-450 nm but which contains uniformly distributed 4,529,269 7/1985 Mutzhas ...... 350/312 therethrough a first agent which absorbs at least 80% of FOREIGN PATENT DOCUMENTS the UV-B radiation in the 310-320 nm range and all 930621 8/1947 France . radiation below 310 nm, and a second agent and third 1540568 2/1979 United Kingdom . agent which prevent transmission therethrough of some 1586687 3/1981 United Kingdom . radiations above 450 nm wavelength, i.e. visible light 2097810 11/1982 United Kingdom . and infra-red. The second agent may be an absorbing dye or pigment. The third agent may be finely divided OTHER PUBLICATIONS carbon or ground glass. The screen may be mounted on Potten, C. S., "Radiation and Skin', (1985), p. 192. a frame or fabricated into clothing so as to shield the Hönigsmann, M.D., H. et al, "Immediate Pigment sunbather from the acutely and chronically harmful Darkening Phenomenon, A Reevaluation of its Mecha wavelengths of radiation, to prevent unpleasant over nisms', (1986). heating, and to provide subdued lighting. The relatively Black, G. et al, "Lack of Photoprotection against UV B-Induced Erythema by Immediate Pigmentation In small amount of UV-B transmitted through the material duced by 382 nm Radiation', (1985). stimulates the production of new in a sun Gange, R. W. et al., "Comparative Protection Effi bather, and this melanin will be later available for tan ciency of UVA- and UVB-Induced Tans... Sensitive ning by UV-A radiation. Sites in DNA by UVB in ', (1985). Arase & Jung, "How We Do It-In Vitro Evaluation of 11 Claims, 2 Drawing Sheets

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O 3OO 34O 38O 42O 46O 5OO 54O 58O 62O 66O WAVELENGTH IN MILLMCRONS 777 3 4,793,668 1. 2 ers such as acetophenone and pigments or dyes such as SUNBATHING FILTER WITHINCOMPLETEUV-B the soluble green dyestuff "Filter Blaugrun' as visible ABSORPTION light filters (British Pat. No. 1,060,780). Such materials are totally unsuitable for sunbathing because they en FIELD OF THE INVENTION tirely block the harmless UV-A light necessary for This invention relates in general to the definition of immediate pigment darkening as well as the small pro fabrics for use in the construction of filters suitable for portion of UV-B within the wavelength range 310-320 protecting human skin from the damaging effects of nm which is essential for melanogenesis. excessive exposure to solar radiation while permiting It can be seen therefore that the disadvantages of immediate pigment tanning and encouraging de novo 10 these earlier radiation screens are that they are either melanin synthesis. In addition, persons sunbathing in the prohobitively expensive to produce, overprotect the shadow cast by the embodiment of this invention will be sunbather from the UV-B sunburning and melanogenic protected from the damaging effects of excessive heat, rays, do not protect from the overheating infra-red rays eye-strain and , but will nevertheless enjoy the or they block out all the UV-light and prevent tanning benefit of a cosmetically appealing tan which will pro 15 altogether. None of the prior art inventions relating to gressively protect them from solarization-induced ery applied sunscreens are able to protect the sunbather thema, skin-aging, and possible malignant and other from dangerous intense visible or infra-red light which chronic disorders. is now thought to be potentially as dangerous as exces sive short wave band (290-310 nm) UV-B with respect BACKGROUND OF THE INVENTION 20 to cancer induction and skin aging, nor do they provide Many varied attempts have been made previously to for a mechanism whereby de novo melanin synthesis formulate and construct a safe sun-screen which would can be encouraged. encourage protective suntanning but these have been generally ineffective because they are specifically de SUMMARY OF THE INVENTION signed to remove all, or substantially all of the entire 25 The basic object of the current invention is therefore short wave UV-B (290–320 nm) either by employing a non-applied radiation-protective filter which makes it chemical absorbers (e.g. Gallowhur U.S. Pat. No. 2,391,959; Solvay et Cie, French Pat. No. 2,236,195, possible in the case of natural solar or artificially gener Sear U.K. Pat. No. 2,097,810, Mutzhas U.S. Pat. No. ated solar radiation to simultaneously tan quickly by 4,529,269), by mechanical processing of thermoplastic 30 inducing the immediate pigmend darkening of pre-exist resins or yarns so as to impart UV-B filtering character ing cutaneous melanin and to also initiate new pigment istics (e.g. Solvay et Cie, French Pat. No. 7,324,647; synthesis at a greater rate in a pleasant and safe manner. Stotzer, French Pat. No. 8,020,161; Mariac, French Pat. This object is accomplished according to the inven No. 930,621; Glaser, West German Pat. No. 3,101,390) tion by interposing a filter made of solid material be or by including ground glass particles in the support 35 tween the sun and the body which blocks out radiation resin and providing multiple spatially arranged lami energy intensities in those wavelength ranges which are nates each with unique but additive absorption charac physiologically harmful but not to completely inhibit a teristics (e.g. Mutzhas, British Pat. Nos. 1,586,687 and mild painless erythema which is the stimulus for de 1,567,979 and U.S. Pat. No. 4,200,360). novo pigment synthesis. However, no previous attempts have been made to In order to understand full the significance of these preferentially reduce only certain wavelengths in all improvements in the design and construction of sun three categories of dangerous light, which it now seems selecting filters and fabrics, it is first necessary to reveiv can interact synergistically to represent a very serious in detail the natural process of suntanning. Terrestrial cosmetic and health threatening environment to man, has been considered to consist of, with very while at the same time providing sufficient transmission 45 slight variations of definintions, short-wave ultra-violet of certain wavelengths of UV-B energy within the nar light (UV-B, 290-320 nm), long-wave light row band 310-320 nm now known to stimulate melano (UV-A, 320-400 nm), visible light (400-700 nm) and genesis. infra-red light (wavelengths ranging from 700 nm to 15 Recognition of the health hazard of UV-radiation has microns). On a clear day at sea level, the distribution of already prompted the U.S. Department of Health Edu 50 solar radiation is about 1-2% UV, 42-53% visible light cation and Welfare (via NIOSH) to recommend occu and 57-63% infra-red. At higher altitudes at any given pational exposure limits to UV radiation including that latitude, the amount of solar radiation avaiable, espe of natural sunlight (HSM Pub. Nr. 73-11009) and there cially UV, is increased so much that at the highest alti have also been calls by general medical practitioners for tudes at sub-zero temperatures a climber needs very stricter controls on UV-parlors. Also, a recent U.S. 55 effective sunburn protection. Bureau of Food and Drug Administration advisory Generally, it is now recognized that all UV-B is dan panel recommended after reviewing available topical gerous to health and excessive natural exposure can lead sunscreens, that all sun protection products should be to Sun-burn (erythema), skin aging and cancer. How placarded with the advisory phrase "Over-exposure to ever, not all wavelengths of UV-B are equally danger the sun may lead to premature aging of the skin and skin ous, the range 310-320 nm being at least so. UV-A is cancer. The liberal and regular use of this product may apparently harmless at natural intensities and induces reduce the chance of premature aging of the skin and immediate pigment darkening or skin tanning. Visible '. or white-light has also been considered safe although In addition, safety plastic or glass filters have been there are now reports that there are some disorders of formulated and used for eye protection against the very 65 the skin, particularly those involving photosensitivity short wavelengths ultra-violet rays (UV-C) artificially reactions, skin aging and cancers, which can occur in produced by electric carbon arc welding equipment. those individuals exposed to intense light. The most These glasses employ very broad spectrum UV block serious commonly occurring hazards of excessive expo 4,793,668 3 4. sure to visible and infra-red light involve dehydration UV-B radition while permitting some UV-A transmis due to over-heating, ultimately leading to unconscious sion for immediate pigment darkening effects. It is now ness, sunstroke and even death. known that UV-A at natural intensities will not initiate Current literature surveys confirm that the deleteri melanogenesis to any significant degree and that the tan ous rays of the sun are in the UV region and the sun- 5 effect induced by UV-A will not protect from sunburn burning rays (UV-B) are carcinogenic. UV-A on the ing by UV-B. Thus, while such physical instruments are other hand requires vastly higher exposure doses that not dangerous in themselves they do not promote the UV-B to produce papillomas and carcinomas. essential de novo synthesis of new pigment which is Sunlight extend from the UV-region into the regions required if the sunbather intends to pursue the habit of of visible light, infra-red and ultimately radio waves. 10 suntanning over several days or weeks and gain not The latter can probably be disregarded with respect to only an immediate light tan but a self-protecting deep dermal effects, but visible radiation cannot. Harmful suntan derived from the darkening of greater quantities effects such as phototoxic reactions through DNA of recently synthesized melanin pigment. cross-linking to tumor enhancement have been re To get a good lasting and protective tan according to corded. Visible light also causes in some 15 the present invention, a small daily dose of UV-B radia people. tion is needed to stimulate the malanocytes to produce The precancers and cancers resulting from excessive greater quantities of new melanin which will be later and prolonged UV radiation are now well recognized, available for tanning by the UV-A. This essential fur but the fact that acute heat exposure can also cause ther synthesis of melanin starts between 2 and 19 days squanmous cell carcinomas or that chronic heat expo 20 after the first exposure, especially to those wavebands sure in the physiological range can result in which acutely damage the (i.e., 290-320 nm), induction is insufficiently well appreciated. Evidence but sufficient stimulation has been shown to be achieved for these effects is derived from China (Kang cancers), with the present invention within the restricted wave India (Kangri cancers of Kashmir), Japan (Kairo can band 310-320 nm without a painful erythemic response cer), Ireland (Turf or Peat Fire Cancer), and Australia 25 resulting. (epithelioma due to spectacles focusing IR radiation on The objective of the current invention is therefore the cheeks. The similarities between IR and UV in realized by careful formulation so as to provide an appa duced skin cancers are strikingly obvious. In addition, it ratus for the transmission of experimentally predeter seems that skin aging (Elastosis and the like), erythema mined maximum energy levels characterized in terms of ab igne, and cancers, can be produced by either route 30 milliwatts per square centimeter of exposed skin at and indeed there is a distinct probability that enhance given wavelengths or ranges. Also, because the appara ment of chronic actinic damage by IR radiation is of tus may need to be used for protracted periods for sun great importance in the etology of human cancers. bathing in areas of high solarization, the effective and Clearly, whenever insulation is high, heat is a concomi useful life of the material needs to be carefully extended tant factor and sunbathing in the midday sun entails 35 and defined by the incorporation of free-radical scaven being irradiated by the far from innocuous UV-B and gers and other substances known to be suitable by those IR rays. skilled in the art of extending the weatherability of It is advocated in the prior art that to protect the skin exposed synthetic fabrics. of the human body against sunburn which is generated Embodiments of the invention will now be further by excessive exposure to wavelengths of sunlight described with references to the accompanying draw shorter than 320 nm (UV-B), it is helpful to either coat ings. the body with suntan oil, cream or lotion, or to protect the skin by remaining in the shade of an absolute UV-B BRIEF DESCRIPTION OF DRAWINGS filter. The suntan cosmetics function by including in FIG. 1 is an absorption diagram illustrating ideal their formulation a histocompatible UV-B filter, the 45 absorption characteristics within the wavelength range concentration and specificity of which defines the sun 290-540 nm for a apparatus according to a protection factor (SPF) afforded by the product. preferred embodiment of the present invention. In a similar manner, physical sunscreens such as poly FIG. 2 illustrates the relative erythemic effects of UV vinyl chloride resins in the form of films have been energy produced by various wavelengths that is, the described which contain UV-B blocking agents which 50 relative effectiveness of ultraviolet energy of various remove substantially all the available energy in the wavelengths in producing erythema. Taken from M. wavelengths shorter than 320 nm, and thus have an A. Pathak, F. C. Riley and T. B. Fitzpatrick, Journal of infinite sun protection factro which totally inhibits ery Investigative Dermatology 39, p. 435 (1962). thema. Both these types of products have inherent FIG. 3 illustrates the action spectrum for immediate weaknesses in their design. In the former case of suntan 55 pigment darkening. Taken from M. Luckiesh and A. H. lotions and related cosmetic preparations, one cannot Taylor, General Electric Review 42, p. 274 (1939). assume with certainty that every part of the exposed part of the body is adequately covered and protected, DESCRIPTION OF PREFERRED and indeed the protective liquid film may be inadver EMBODIMENTS tently removed by rubbing against a towel or during 60 The plastics material, which preferable is a thermo swimming. Further, no protection against eyestrain or plastic material or acrylic resin in the form of either a overheating is provided even by the most carefully thin film or woven or knitted material, must exhibit the applied cosmetic system and it has even been suggested property of being transparent to long wave UV-A radi that some of the chemical ingredients in suntan lotion ation of wavelengths between 320 and 400 nm and to preparations may be in themselves chemical carcino- 65 visible light in the range between 400 and 450 nm which gens, or photoallegens. In the latter case of are those particularly associated with immediate pig physical barriers to UV-B, those which have been de ment tanning. In addition, the intense light associated scribed to date are constructed so as to remove all with eye damage within the range 450-700 nm and a 4,793,668 5 6 major portion of the IR wavelengths greater than 700 (Hoescht) at a concentration of 0.1% w/w provide nm are absorbed to exclude the heating element of the ideal visible light absorption as well as imparting attrac sun's radiation, prevent carcinogenesis, and teh syner tive coloration, and a heat sink comprising thermal gistic effects which cause skin aging or tumor promo black (finely divided carbon black) at a concentration of tion. for example, 0.5% w/w to absorb IR radiation. Film Suitable materials for the screen support material, compounded from plasticized PVC and containing the when in film form, are resins of vinyl chloride, polyole above ingredients serves to transmit 20% UV-B in the fins such as polyethylene and polypropylene, or acrylic wavelength range 310-320 nm, but excludes substan resins such as polymethyl-methacrylate. The vinyl chlo tially all UV-B in the range 290-310 nm. This transmit ride resins referred to are homopolymers or copolymers 10 ted quantity of UV-B energy represents a maximum skin of vinyl chloride and such resins may, in addition, con surface UV-B radiance of about 1 mW/cm2. tain plasticizer preferably of phathallate esters. Copoly Similar levels of UV-B irradiance in the range mers such as polyethylene/vinyl acetate and butadie 310-320 nm would be achieved by deployment of the ne/styrene would also suffice. previously described fiber fabrics, suitably surface A preferred material for the screen is a plasticized 15 printed or dyed with disperse dyes such as Dispersol polyvinyl chloride film of thickness between 100 and Red B2-B at 2.25% w/w concentration. Infra-red may 300 microns, for example, 175 microns, and this may be be absorbed by carbon black as previously described or a single film or a laminate formed with a reinforcing reflected by . The selection of suitable nylon or polyesternet to give greater physical strength. pigments and dyestuffs is of course important in the Whichever of the aforementioned resins is used, it 20 invention from two standpoints. Firstly, the colors must should not have a significant absorption, i.e., greater not absorb UV light between 320 and 400 nm or be than 30%, of radiation of wavelengths between 310 and tween 400 and 450 nm; otherwise the efficiency of the 450 nm. The resin should also be light-stable and non sunscreen will be impaired; and secondly, they must be volatile at the relatively high temperatures used in ex light fast. The integrity of the finished sunscreen ac trusion or callendering (i.e. about 150-200 C). Be 25 cording to the invention maintained after 400 hours cause these resins are transparent to substantially all of QUV when exposed to artifical accelerated weathering the available energy into the UV-A and UV-B wave according to ASTM G53-77. (QUV, as used herein, lengths and most of the visible and IR spectrum, addi refers to "Quartz UV Light', which defines a known tional agents described below need to be added to the process of accelerated weathering using artificial light.) formulations to selectively filter the wave bands of light 30 The apparatus may comprise a framework adapted to previously mentioned in order to achieve the desired support said sheet or fabric material. Such framework photobiological effects. may comprise a central support member and a plurality As an alternative to rigid or plasticized thermoplastic of support rods extending radially from one end of said film, a woven or knitted fabric perferably of nylon or central support member. Preferably, the support rods polyester filaments may be employed as the support 35 are hingedly attached to the central support member material. The advantage of this form of the invention is whereby the apparatus may be folded for storage and that such fabrics may readily be made up into wearing /or transportation purposes. apparel. A suitable support material is the polyester Alternatively, the support rods may be detachably polyethylene terephthalate. Care must be taken to en securable to the central support member for such pur sure that the particular cross-section of fiber, the num poses. ber of fibers per element and the orientation of the fiber Alternatively, the framework may comprise a plural in the woven or knitted fabric does not cause excessive ity of support rods over which said sheet material may light reflection or defraction. Suitable examples include extend so as to define a screened space therebelow. In first, ICI polyester 15 50 desitecs weight, 20 filament this case, the support rods may be hingedly or detach round cross-section T1001 Terinda (R) yarn made up by ably secured to each other. Tricot warp knitting as a fabric having a locknit within As a further alternative the sheet material may be the range 21-40 kneedles per inch, for example 28 gauge adapted to be worn by a person so as to shield a part of knitting. The fabric weight should be less than 100 that person's body, for example in the form of a hat. gm/meter, for example 86 gm at 16 wales/cmx21 Referring now to FIG. 1, there is shown a spectro courses/cm. 50 graph idealizing the absorption characteristics of the A second fabric alternative to rigid film would be present invention. Very little of the shorter range UV-B Tietex (R) 18 gauge warp-knitted polyester. This partic (in the wavelength range 290-310 nm) is transmitted ular fabric has highly organized linear orientated fibers while about 20% of the available longer-range UV-B in which minimizes light defraction and encourages high the wavelength range 310-320 nm is transmitted, which general light transmission. 55 represents a maximum possibly achievable global en Because these polyesters have a high UV-B absorbing ergy level of about 1 mW/cm2 at the exposed skin sur capacity in their own right, i.e. without additional UV face. absorbing agents, only those agents imparting visible Referring now to FIG. 2, it can be seen that from and IR absorption need be added to create an ideal recent estimates of the erythema action spectrum which sunscreen according to the invention. have shown that the effectiveness of UVR at wave The agent used typically in the rigid or plasticized lengths greater than 300 nm drops off very rapidly, film to achieve UV-B leakage in the range 310-320 mm falling at 320 nm to about 1% of that at 300 nm (Farr & is ethylhexyl-p-methoxycinnamate at a concentration of Diffey 1985), the present invention permits minimal 0.05% w/w, when the film thickness is between erythema within those wavelengths ranges now known 100-300 microns. (As used throughout this specifica 65 to initiate new melanin synthesis. tion, “w/w' refers to “weight for weight'.) For the Referring now to FIG, 3, it can be seen that immedi same film, pigments such as Microlith Violet B-K, Cro ate pigment darkening (darkening of already existing moptal Blue A3R (Ciba-Geigy) and PV Carmine HF4C melanin, probably as a result of an oxidation reaction) is 4,793,668 7 8 caused by a broadband of radiation extending from 300 which said substrate containing at least one first agent nm to 660 nm, with a maximum effect occurring be which absorbs at least 80% of the UV-B radiation tween 360 and 440 nm. By comparison of these data in the range 310-320 nm but substantially all UV-B with the spectral characteristic of the present invention in the range 290-310 nm, said substrate containing described in FIG. 1, it can be realized that adequate 5 at least one second agent which prevents transmit transmission of these wavelengths needed for melanin tal of a biologically significant proportion, being darkening are transmitted by the present sunscreen 50% or more, of the visible and IR radiation of material. wavelengths in the range 450-700 nm and It should now be seen how the prior art is extended 700-15,000 nm respectively through said substrate, by the current invention to accommodate new concepts 10 said agents being substantially uniformly dispersed of the mechanism of suntanning and the knowledge that throughout said substrate; and the protective value of a suntan gained after several at least one third agent which is a heat absorbing days exposure to wavelengths in the UV-B range about material, 310 nm is more protective against further UV-B insult wherein the relatively small portion of UV-B not than that generated by only UV-A. 15 absorbed by the apparatus stimulates the produc In the many possible embodiments of the apparatus of tion of new melanin in a sunbather, which will be the invention the sheet material is transparent to the later available for tanning by UV-A radiation. tanning UV-A radiation, but includes substances which 2. Apparatus according to claim 1 wherein said sub absorb all of the UV-B radiation in the 290 to 310 nm. strate comprises a sheet. 20 3. Apparatus according to claim 2, wherein said sub wavelength range, all but 20% in the range 310-320 nm, strate comprises thermoplastic material. as little as possible in the range 320-450 nm, and at least 4. Apparatus according to claim 3 wherein the ther 50% of the visible light and IR wavelengths above 450 moplastic material is a homopolymer of resin selected nm. By means of the invention a person can be shielded from the group consisting of styrene, butadiene, vinyl from the deleterious effects of the sun and will develop 25 chloride, polyolefin, and an acrylic resin. a tissue protective suntan while relaxing or being active 5. Apparatus according to claim 1 wherein said sub outdoors without the necessity of either the frequent strate is a synthetic fiber selected from the group con application of creams, lotions or the like or the wearing sisting of nylon and polyester. of restricting or undesirable clothing. 6. Apparatus according to claim 1 wherein said sub Alternative embodiments of apparatus will be readily 30 strate comprises a thermoplastic material and the con apparent to persons skilled in the art. For example the centration ratio of the weight of said first agent to the screen material may be laminated with nylon or polyes weight of said thermoplastic material absent said first, ternet to provide sufficient strength for it to be used for second and third agents is between 0.01/100 and example, as a roof for an enclosure such as a swimming 0.5/100. pool or tennis court. Also many other configurations of 35 7. Apparatus according to claim 1, wherein the con framework may be used, for example, a simple upright centration ratio of the weight of said second agent to support screen. Alternatively the screen material may the weight of said substrate absent said first, second and be formed in the shape of, for example, a wide brimmed third agents is less than 2.5/100. hat such as may be worn by a person exposed to the sun. 8. Apparatus according to claim 1 wherein the second It should be understood that the foregoing relates 40 agent comprises a light and heat stable pigment. only to preferred embodiments of the present invention, 9. Apparatus of claim 1, wherein the concentration and that many changes and modifications can be made ratio of the weight of said third agent to the weight of therein without departing from the spirit and scope of said substrate absent said first, second and third agents is the invention as defined in the following claims. less than 0.5/100. I claim: 45 10. Apparatus according to claim 1 wherein said 1. Apparatus for use in sunbathing, comprising: substrate is supported by a framework. a substrate screen material which is substantially 11. Apparatus according to claim 1 wherein said transparent to the safe UV-A wavelengths of solar substrate comprises a flexible plastic fiber fabricated radiation in the range 320-400 nm and light in the into wearing apparel. range 400-450 nm; SO k is is :

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