WO2008144541A1

WO2008144541A1 - Compositions and devices for uv dosage indication

Info

Publication number: WO2008144541A1
Application number: PCT/US2008/063940
Authority: WO
Inventors: Keith Blakeley; Sang Beom Lee; Alan Rae; Lacramioara Trofin
Original assignee: Nanodynamics, Inc.
Priority date: 2007-05-17
Filing date: 2008-05-16
Publication date: 2008-11-27

Abstract

This invention relates to compositions and devices that may be used to provide information about exposure to ultraviolet radiation. The compositions comprise a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation; a dye that produces a characteristic change in response to the photocatalytic effect; and a binder, wherein the dye and the photocatalyst are dispersed in the binder, and wherein the composition is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation.

Description

COMPOSITIONS AND DEVICES FOR UV DOSAGE INDICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and any other benefit of US Provisional Application Serial No. 60/938,650, filed May 17, 2007, and US Provisional Application Serial No. 61/015,476, filed December 20, 2007, the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND

[0002] While many people like to enjoy uninhibited sunshine and to participate in outdoor activities, there are many hazards associated with exposure to the ultraviolet (UV) radiation in sunlight. The serious health consequences of overexposure to UV radiation include skin cancer (melanoma and non-melanoma), premature aging of the skin (including wrinkling and leathery skin), skin disorders (e.g. actinic keratoses), cataracts, and immune system suppression.

[0003] UV radiation is comprised of UV-A (320-400 nm), UV-B (290-320 nm), and UV- C (<290 nm). UV-C radiation is absorbed by the earth's atmosphere, but UV-B rays are only partially absorbed. UV-A radiation, which reaches the surface of the earth unimpeded, is needed by the human body for vitamin D synthesis, but excessive amounts cause aging, wrinkling, and loss of elasticity of the skin, as well as contributing to skin cancer and cataracts. The carcinogenicity of UV-B radiation is well established, and solar UV-B exposure is a significant risk factor for skin cancer. While UV-A is generally far less carcinogenic than UV-B radiation, it is more abundant in the sunlight that reaches the earth's surface than UV-B radiation and can, therefore, contribute to the carcinogenicity of sunlight. [0004] According to World Health Organization (WHO) estimates, worldwide 60,000 premature deaths in the year 2000 were caused by over-exposure to solar UV radiation. Furthermore, according to these estimates, excessive solar UV exposure caused the loss globally of about 1.5 million disability- adjusted life years (DALYs) in the year 2000, which represent 0.1% of the global burden of disease. In addition, according to WHO estimates, up to 20% of the 12 to 15 million annual cases of blindness due to cataracts are caused or enhanced by sun exposure, and the risk is independent of skin type. These numbers are expected to increase with ozone depletion. One WHO model predicts that a 10% decrease in stratospheric ozone will result globally in 300,000 more non-melanoma skin cancers, 4,500 melanoma skin cancers, and approximately 1.7 million more cases of cataracts each year. [0005] The lowest effective dose necessary to develop a sunburn depends distinctly on the skin sensitivity of the person (i.e. skin types). A common classification of skin types is the Fitzpatrick scale which rates skin types on a scale of I to VI (See Diffey, Phys. Med. Biol., 1991, Vol. 36. No. 3, 313-14). Fair-skinned Caucasians who never tan and who burn easily and severely have skin type I. Fair-skinned Caucasians who tan minimally and with difficulty and who burn easily and usually severely have skin type II. Medium-skinned Caucasians (average Caucasian) who burn moderately and tan about average have skin type III. Darker-skinned Caucasians who rarely burn and tan easily and substantially have skin type IV. Brown-skinned people who rarely burn and tan easily and substantially have skin type V. Black-skinned people who never burn and tan profusely have skin type VI. [0006] MED (Minimal Erythema Dose) is defined as the threshold dose that may produce sunburn. MED is a measurement of the amount of UV-B radiation received by the skin and corresponds to the UV dose required to produce a barely perceptible erythema. One MED is between 150 and 600 JYm² for skin types I through IV. The sensitivity of normal skin to ultraviolet radiation will vary with factors such as anatomical site, time of the day, size of irradiation field and season (Diffey, Phys. Med. Biol, 1982, Vol. 27. No. 5, 715-20). Goldsmith and Hellier (Recent Advances in Dermatology 2nd ed. New York: Blakiston, 1954) have reported that skin sensitivity is dependent upon the color of the skin, age, sex, thyroid function, pregnancy, blood flow, humidity, and temperature.

[0007] A metric for assessing the risk associated with the exposure to UV radiation from sunlight that is independent of skin type is the UV Index. The UV Index corresponds to the dose of harmful UV radiation that reaches the surface of the earth at a given time. A UV index of 1 represents 25 mW/m . A UV Index of 2 or less represents a low risk or danger from the sun's UV radiation, although people who burn easily should use sunscreen. A UV Index of 3 to 5 represents a moderate risk or danger from unprotected sun exposure. A UV Index of 6 or 7 means that there is a high risk associated with unprotected sun exposure, and protection against sunburn is needed. A UV Index of 8 to 10 represents a very high risk of harm from unprotected sun exposure, where unprotected skin will be damaged and burn quickly. A UV Index of 11 or higher represents an extreme risk of harm associated with unprotected sun exposure, and unprotected skin can burn in minutes.

[0008] Due to concern about the serious health consequences of UV exposure, there is interest in products that can protect users from the hazards of sun exposure. One method consumers use to protect themselves against these hazards is by using sunscreen products, such as lotions, creams, or sprays. As used herein, the term "sunscreen" means any product that absorbs and/or scatters UV radiation and prevents UV radiation from reaching the skin. [0009] Sun protection factor (SPF) is a measure of the effectiveness of a sunscreen product. The SPF value is determined as a ratio of the UV dose necessary to cause a minimum number of red spots (i.e., MED) on protected skin to that necessary to cause a minimum number of red spots on unprotected skin. One problem with sunscreen products is that users are unaware of when the sunscreen has worn off the skin and needs to be reapplied. [0010] While sunscreen preparations are, to varying degrees, reasonably effective in filtering out harmful radiation and limiting the skin's exposure to the sun, they are limited with respect to their duration of usefulness, and in many cases may also be worn away through physical activity, bathing, swimming, sweating, abrasion, absorption into the skin, migration on the skin, and photodegradation. As a result, sunscreens must typically be reapplied on a regular basis, the frequency of which may increase depending upon the physical activity of the user. However, users cannot tell when the sunscreen has stopped providing effective UV protection. La some situations, sunscreen users are engaged in activities that prevent them from reapplying sunscreen on a regular basis. In other cases, individuals merely forget to apply or reapply sunscreen. In yet other situations, an individual may inappropriately gauge the amount of sunscreen preparation necessary at any particular time of the day, or on any given day. Commercially available sunscreen preparations are rated on a sunscreen protection factor (SPF) scale. Generally, the higher the SPF factor the greater the sunscreen protection that is provided. However, often individuals are unaware of the intensity of the sun's rays during a particular time of day, or with changing weather conditions, and fail to apply sunscreen having an adequate SPF factor. The natural characteristics of the skin of different individuals, the rate at which different individuals perspire, and the activity of the individual (particularly if it involves swimming, surfing, or other water sports) will result in dramatic variation in the effectiveness of sunscreens for different people. Finally, it is often not appreciated by individuals that UV radiation can cause degradation of a sunscreen preparation, making further application of sunscreen necessary even in the absence of perspiration, swimming, or physical activity. [0011] These limitations of current sunscreen preparations are particularly important for children. Children are in a state of growth and development, hence they are more sensitive to environmental hazards than are adults. Children are more likely to spend days outdoors, more susceptible to sunburn, and more sensitive because their skin is thinner. Most skin damage occurs in the first 20 years of life; it has been estimated that up to 80% of a person's lifetime exposure is received by the age of 18. Children are also generally unaware of the harmful effects of UV exposure and sunlight.

[0012] There remains a need for a convenient and inexpensive UV dosimeter which provides a cumulative measure of the actual UV exposure of the skin, which can be calibrated so as to give a useful response over a wide range of total UV exposure.

SUMMARY

[0013] In accordance with various embodiments, photosensitive compositions are provided. The compositions can comprise a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation; a dye that produces a characteristic change in response to the photocatalytic effect; and a binder. The dye and the photocatalyst are dispersed in the binder. The composition is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation. [0014] In accordance with other embodiments, devices are provided. The devices can comprise an ultraviolet radiation detecting layer; a support layer adjacent to the ultraviolet detecting layer; and an attachment layer disposed to allow attachment of the device to a surface. The ultraviolet radiation detecting layer comprises a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation; a dye that produces a characteristic change in response to the photocatalytic effect; and a binder. The dye and the photocatalyst are dispersed in the binder. The ultraviolet radiation detecting layer is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation. [0015] Additional features and advantages of this disclosure will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the compositions and devices disclosed herein.

[0016] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the embodiments disclosed herein.

BMEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments disclosed herein, and together with the description, serve to explain principles of embodiments disclosed herein.

[0018] Figure 1 is a schematic representation of a UV device.

[0019] Figure 2 is a schematic representation of one embodiment of a composition that is sensitive to UV-A radiation only.

[0020] Figure 3 compares the degradation over time for a photosensitive composition at different temperatures (room temperature and 60⁰C) and in the presence and absence of a sunscreen with SPF 30.

DETAILED DESCRIPTION

[0021] Compositions and devices disclosed herein will now be described by reference to more detailed embodiments, with occasional reference to the accompanying drawings. Embodiments disclosed herein may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the compositions and devices to those skilled in the art. [0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting. As used in the description, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. [0023] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

[0024] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein. [0025] hi some embodiments, photosensitive compositions are contemplated. These compositions may also be integrated into a device that alerts users when a certain amount of UV radiation has been received by the device. By device it is meant any device and/or system comprising at least one layer of photosensitive composition. [0026] In some embodiments, a photosensitive composition comprises at least a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation, a dye that produces a characteristic change in response to the photocatalytic effect, and a binder. In some embodiments, the dye and the photocatalyst are dispersed in the binder. The composition is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation. In some embodiments, the composition also may contain a curing agent for the binder. The binder may be a film-forming polymer, or a mixture of polymers, which may act as a dispersion matrix for other components. [0027] A photocatalyst may be used that produces a photocatalytic effect. For purposes of defining and describing the present invention, the term "photocatalytic effect" shall be understood as referring to any reaction or other change that produces a characteristic change to a dye. For example, one suitable photocatalytic effect is the production of at least one electron that may degrade a dye to produce a characteristic color change or transition. For example, in some embodiments, the color transition of a dye occurs by a photocatalyst catalyzing the degradation of the dye, for example from colored to colorless. Suitable photocatalysts include but are not limited to TiO₂, ZnO, and Fe₂O₃.

[0028] In some embodiments, the photocatalysts may be in the form of nanoparticles. In some embodiments, the nanoparticle photocatalysts may have an average particle diameter chosen from about 1.0 to 1000, 2.0 to 1000, 3.0 to 1000, 4.0 to 1000, 5.0 to 1000, 6.0 to 1000, 7.0 to 1000, 8.0 to 1000, 9.0 to 1000, 10 to 1000, 25 to 1000, 50 to 1000, 75 to 1000, 100 to 1000, 250 to 1000, 500 to 1000, 750 to 1000, 1.0 to 750, 1.0 to 500, 1.0 to 250, 1.0 to 100, 1.0 to 75, 1.0 to 50, 1.0 to 25, 1.0 to 10, 1.0 to 9.0, 1.0 to 8.0, 1.0 to 7.0, 1.0 to 6.0, 1.0 to 5.0, 1.0 to 4.0, 1.0 to 3.0, 1.0 to 2.0, less than 1.0, less than 2.0, less than 3.0, less than 4.0, less than 5.0, less than 6.0, less than 7.0, less than 8.0, less than 9.0, less than 10, less than 25, less than 50, less than 75, less than 100, less than 250, less than 500, less than 750, less than 1000, greater than 1.0, greater than 2.0, greater than 3.0, greater than 4.0, greater than 5.0, greater than 6.0, greater than 7.0, greater than 8.0, greater than 9.0, greater than 10, greater than 25, greater than 50, greater than 75, greater than 100, greater than 250, greater than 500, greater than 750, and greater than 1000 nanometers.

[0029] In some embodiments, the photocatalyst may be TiO₂, which has the characteristic of absorbing UV light in such a way that the energy absorbed causes an electronic transition from the valence band to the conduction band (Ken Onda, Bin Li, Jin Zhao, Kenneth D. Jordan, Jinlong Yang, Hrvoje Petek, "Wet Electrons at the H₂O/TiO₂(110) Surface", Science 2005, 308, 1154-1158). In some embodiments, the TiO₂ may be a nanopowder. For example, titanium dioxide P25 manufactured by Degussa, which has an average primary particle size of about 21 nm and a specific surface of about 50 m²/g may be used.

[0030] In other embodiments, the photocatalyst may be modified by doping or deposition of species that may enhance the photocatalytic activity of the photocatalyst. Suitable species include but are not limited to nitrogen, Ag, JErj, Pt, Pd, and photosensitizing dyes. Nitrogen- doped TiO₂ (TiO_2-χNχ) is yet another example of a modified photocatalyst. [0031] While not being limited to any particular mechanism, it may be noted that electrons promoted to the conduction band in TiO₂ can interact with water and/or molecular oxygen, generating hydroxyl and/or superoxide radicals. Dye molecules in proximity to the photocatalyst surface may be oxidized by electron transfer to the holes in the valence band, before or after reaction with reactive oxygen species. Alternatively, dye molecules may be reduced directly by accepting electrons promoted to the TiO₂ conduction band. [0032] The dye may be able to undergo a characteristic change, for example, a color change from colored to colorless or from colorless to colored, when exposed to UV light in the presence of a photocatalyst. For purposes of defining and describing the present invention, the term "characteristic change" refers to visible change of the dye. In some embodiments, suitable dyes include, but are not limited to, ethyl violet, reactive yellow 17, reactive yellow 14, methyl violet 1OB, reactive blue 4, sulforhodamine B, eosine yellowish, methyl orange, acid orange 7, amido black 1OB, reactive black 5, C.I. direct red 23 and procion red MX-5B. In other embodiments, suitable dyes are those that may be soluble in organic solvents, including but not limited to Millijet Blue 45, Millijet Blue 28, Millijet Yellow 26, Millijet Red 17, Millijet Black JlO, Millijet Orange 31 and Millijet Violet 82 (trade names for dyes made by Milliken & Company, Spartanburg, SC); as well as, Sudan™ black, Sudan™ deep black, Sudan™ black B, Sudan I, Sudan II, Sudan™ red BB, Sudan™ red 7B, Sudan™ yellow 146, Sudan™ yellow 150, Sudan™ orange 220; Neozapon™ red 335A, Neozapon™ blue 807, Neozapon™ black X51A, Fluorol™ Green Gold 084 and Fluorol™ Yellow 084, Oracet™ yellow 3GN, Oracet™ violet TR, Oracet™ blue G, Oracet™ red GN, oil yellow, ceres red 3R, ceres black BN, solvent yellows 14, 21, 28 and 56; solvent reds 1, 4, 23, 24, 41, 49 and 125; solvent oranges 2, 62 and 63, solvent greens 3 and 5, solvent blues 4, 14, 35, 36 and 59; and solvent blacks 3, 5, 7, 13, 29 and 70. Dyes suitable for solubility in polymers, such as the Oracet™ dyes, may also be used. [0033] In some embodiments, the composition may also contain crosslinking agents, which may crosslink the binder and/or the dye molecules. The embodiments that are made with crosslinking agents may be adjusted to have different degrees of resistance to water, hi some embodiments, the crossHnking agent may be chosen from diisocyanates. In some embodiments, the crosslinking agent may be diisocyanate. hi still some embodiments, the diisocyanate may be Bayhydur® 302.

[0034] hi some embodiments, the binder may be an insoluble polymer matrix that binds all or some of the components together. Suitable polymers include, but are not limited to, polyurethanes, gelatin, chitosan, polybutadienes, natural rubber, polyvinylalcohols, cellulose and its derivates, polyethylenes, polyethylene oxides, polycarbonates, polyacrylates, polyvinyl pyrrolidones, polyvinyl acetates, polysaccharides, polystyrene derivatives, polyacryl amides, and crosslinkable silicone polymers. Copolymers and mixtures of these polymers are also suitable for use as binders in the present disclosure. In some embodiments, the binder may be an elastomer that may flex when attached to the skin of the user. [0035] hi some embodiments, the composition may further comprise an additive. The additive may be a plasticizer and/or softener, hi some embodiments, the additive may be included to increase the water resistance and/or waterproof nature of a photosensitive composition, hi some embodiments, the additive may be polyethyleneglycol- methylmethacrylate. In some embodiments, the additive chosen may be one suitable to allow free radical polymerization of the binder, hi other embodiments, the additive chosen may be one suitable to allow a polycondensation reaction to polymerize the binder, hi still other embodiments, additives may be chosen to increase the stability of a photosensitive composition to water, salt water, sea water, heat, cold, wind, sand, dirt, mud, or any other environmental factor, including factors introduced by the user, such as, poking, scratching, cutting, dripping food, drink, blood, and/or any other bodily or non-bodily fluid onto. In still other embodiments, the additives can be dispersing and wetting agents; these agents may be chosen to improve the dispersability of the photocatalyst particles into the binder matrix. Examples of the wetting agents include, but are not limited to, nonionic and ionic surfactants, salts of alkyl naphthalene sulfonic acids and alkyl aryl sulfonic acids in polyglicols or mineral oils, polyethylene glycols and polypropylene glycols.

[0036] The photosensitive compositions may be calibrated to exhibit the characteristic change of the dye, such as turning from colored to colorless after exposure to a predetermined total amount of UV-A and UV-B. The calibration is discussed further herein. Alternatively, the compositions may be calibrated to change from colored to colorless after a specified amount of only UV-A has been received, or they may be calibrated to change color after a specified amount of only UV-B has been received. The composition may be optimized or calibrated in such a way so as to indicate exposure to a dose of UV appropriate to a certain skin type. For example, for a user having skin type I (fair skin), it is may be necessary that the color of the composition change sooner than it does for user having skin type III. The calibrations may be done for each different skin type. A suitable color change time would be the exposure time necessary to yield a minimum erythema dose (MED) of 1.0, using a UV meter. An MED of 1.0 (equal to 21 ± 3 mJ/cm at 297 nm for type II skin) will produce a minimum erythema (reddening) on skin areas not ordinarily subjected to UV radiation.

[0037] In some embodiments, compositions are provided that produce a color change only under exposure to UV-A radiation. The compositions comprise at least one photocatalyst coated with at least one UV-B absorber. In addition, the compositions comprise at least one photosensitive dye. The photocatalyst may be as discussed herein. In some examples, the photocatalyst comprises zinc oxide particles. In other examples, the photocatalyst comprises titanium oxide particles. The photosensitive dye may also be as discussed herein, and a suitable binder may also be used as discussed herein, hi some examples, the dye may be Millijet blue 45. In yet other examples, the binder may be polyurethane in dioxane.

[0038] Any suitable UV-B absorber may be used. The UV-B absorber is chosen to absorb UV radiation in the UV-B range only, hi some examples, the UV-B absorber may be an organic absorber. For example, ethylhexl methoxycinnamate may be used as the UV-B abosorber. It will be understood that the compositions may be prepared in any suitable manner, and the compositions may be chosen to provide an indication of UV-A exposure at any desired amount of exposure. Other examples of UV-B absorbers include, but are not limited to, octyl-N-dimethyl-p-aminobenzoate, octyl triazone, and 2-ethylhexyl alpha-cyano- beta-phenylcinnamate (octocrylene) .

[0039] Without wishing to be bound and referring to Figure 2 showing an exemplary embodiment using zinc oxide particles, it is believed that a UV-B absorber forms a coating on the photocatalyst and absorbs any UV-B radiation that may be present. The UV-A radiation may pass through the coating and cause the photocatalyst to emit electrons responsible for UV-A. The emission of electrons may cause the photosensitive dye to degrade, causing a color change.

[0040] In yet another embodiment, devices are provided. The devices comprise an ultraviolet radiation detecting layer, a support layer adjacent to the ultraviolet detecting layer, and an attachment layer disposed to allow attachment of the device to a surface. The ultraviolet radiation detecting layer may comprise the photosensitive compositions discussed herein. One example of a device 10 is shown in Figure IA. As can be seen in Figure IA, an ultraviolet radiation detecting layer 12 may be disposed on a support layer 14, and an attachment layer 16 maybe disposed adjacent to the support layer 14.

[0041] In some embodiments and referring to Figure IB, the support layer 14 may further comprise an image 18. The image is disposed between the ultraviolet radiation detecting layer 12 and the support layer 14. The image 18 may become visible upon exposure of the device 10 to a predetermined amount of ultraviolet radiation due to the characteristic change of the dye. hi some examples, the image 18 is printed and/or otherwise created on the support layer 14. hi other examples, the image 18 is disposed on the support layer 14 but not printed and/or otherwise created on the support layer. hi some embodiments, the support layer 14 and the attachment layer 16 comprise a single layer. [0042] In some examples, the image 18 may be of a color that matches the initial color of the ultraviolet radiation sensitive layer 12 and, therefore, not readily perceived until the device 10 is exposed to a predetermined amount of ultraviolet radiation. Upon exposure to a predetermined level of radiation, the photosensitive composition may become colorless, or alternatively it may transform to a different color through which the image 18 may be perceptible.

[0043] The image 18 may comprise any suitable image. For example, the image may be composed of a graphic image, text, or a combination thereof, hi other examples, the image 18 may depict an object or may be a design, including an abstract design. In some embodiments, the image 18 may be visually appealing to users of the patch, including children. In embodiments where the image 18 is disposed on the support layer, the image 18 may be made from any material which is compatible with the support layer 14 and which may be capable of maintaining its color, hi some embodiments, the image 18 is visually dramatic and may be monitored from a distance, as might be required if a parent or guardian wishes to monitor a child's exposure during play or other outdoor activities. In yet other embodiments, all the aforementioned graphic patterns may be applied directly to the adhesive layer, therefore no substrate layer would be needed.

[0044] In some examples, the device 10 may be made water resistant in any suitable manner. For example, the device 10 may be made water resistant by lamination and/or by applying a layer of UV transparent film, for example. The device 10 may be rated/calibrated for different SPF values and/or skin types, so that a user may choose a particular device for their particular needs.

[0045] hi other embodiments, the ultraviolet radiation detecting layer 12 may be calibrated such that at least a first region (not shown) in which the characteristic change of the dye occurs in response to a first predetermined amount of ultraviolet radiation and a second region (not shown) in which the characteristic change of the dye occurs in response to a second predetermined amount of ultraviolet radiation. It will be understood that more than two regions may be provided. For example, three, four, five, six, seven, or more regions may be provided, and each region may be calibrated to provide a characteristic change in response to one or more different levels of ultraviolet radiation. In some examples, this configuration may be used to show when the protection provided by different SPF levels has expired. For example, a device 10 may indicate that a user, if wearing a sunscreen having an SPF 10 level of protection, has received the maximum allowable exposure, but that he or she is still protected if wearing SPF 30 sunscreen.

[0046] Similarly, in another embodiment, a the region or regions of the ultraviolet radiation sensitive layer 12 of the device 10 may be calibrated to indicate that a user has received a maximum allowable exposure to UV if he or she has skin type I or II, but is still safe if he or she has skin type III or TV. In some embodiments, the device 10 may contain a reference (not shown) which may be an image that is visible prior to exposure of the device to ultraviolet radiation that a user may compare the image 18 to.

[0047] Any suitable attachment layer 16 may be used. For example, the attachment layer may comprise an adhesive layer that may also be removable from a surface. hi some embodiments, the adhesive layer may be a pressure sensitive adhesive layer, hi other embodiments, the adhesive layer may comprise any adhesive not toxic to skin. In some embodiments, the adhesive layer may comprise Velcro®. hi yet some embodiments, the photosensitive composition may be applied directly to the Velcro®, which may or may not comprise a graphic pattern for detection.

[0048] hi some embodiments, a backing layer (not shown) may be used to cover the attachment layer 16 prior to its application to a surface, in order to protect the attachment layer 16 and/or to assist in the packaging and/or application of the device 10. The backing layer may be any suitable backing layer. For example, the backing layer may be comprised of a layer of cellulose and/or plastic that may be peeled away from the attachment layer 16 prior to use.

[0049] It will be understood that the device may be attached to any suitable surface. For example, the surface may be chosen from skin, synthetic skin, plexiglass, fabric, articles of clothing, other objects, and anything a user may have on their person. In other examples, the surface may be an object such as a chair, towel, bag, or structure that may be exposed to ultraviolet radiation.

[0050] The calibration of the device 10 may be done in any suitable manner. In some embodiments, the calibration may be done, for example, by varying the amount of the photocatalyst in the ultraviolet radiation detecting layer 12 of the device 10, an amount or concentration of thedye, and/or the UV transparency of the ultraviolet radiation detecting layer 12 and/or of any additional layers over the ultraviolet radiation detecting layer 12. In some embodiments, the thickness of the ultraviolet radiation detecting layer 12 may be varied to vary the sensitivity to UV light. In some embodiments, the thickness of the ultraviolet radiation detecting layer may be chosen to be from about 10 microns to about 500 microns, less than 10 microns, less than 15 microns, less than 20 microns, less than 30 microns, less than 40 microns, less than 50 microns, less than 75 microns, less than 100 microns, less than 250 microns, less than 500 microns, greater than 10 microns, greater than 15 microns, greater than 20 microns, greater than 30 microns, greater than 40 microns, greater than 50 microns, greater than 75 microns, greater than 100 microns, greater than 250 microns, greater than 500 microns, from 10 to 250, from 10 to 100, from 10 to 75, from 10 to 50, from 10 to 40, from 10 to 30, from 10 to 20, from 10 to 15, from 15 to 500, from 20 to 500, from 30 to 500, from 40 to 500, from 50 to 500, from 75 to 500, from 100 to 500, and from 250 to 500 microns. [0051] It will be understood that a series of factors may influence the calibration of the device 10. These factors may include, but are not limited to: the type and concentration of a binder, the type and concentration of a dye, the concentration and type of the photocatalyst, the type and concentration of a crosslinking agent, the type and concentration of any extra additive, the curing time and/or temperature for a photosensitive composition, the mode of application, the thickness of a formed film, and type of support layer that a photocomposition is applied on. EXAMPLES

[0052] All percentages expressed in this disclosure are by weight, unless otherwise indicated.

Example 1: Preparation of Photosensitive Compositions

[0053] Photosensitive compositions were prepared by dissolving one gram of polyurethane granules in 20 ml of dioxane under stirring for 24 hrs. After the polyurethane completely dissolved, 1% of Millijet™ Blue 45 (Milliken & Co₅, Spartanburg, SC) was added and the mixture was stirred for 2 hrs using a magnetic bar. Then 1% TiO₂ (Aeroxide™ P25, Degussa, Darmstadt, Germany) was added and stirred for one more hour. For water- resistant compositions, 1% of a crosslinking agent (Bayhydur® 302 brand of diisocyanate, Bayer, Leverkusen, Germany) was added and the mixture was mixed for 20 minutes more. The composition was applied to a glass slide or piece of paper using an applicator to control the thickness of the film formed. Finally, the compositions were cured at room temperature, 5O⁰C, or 6O⁰C.

[0054] The compositions were then exposed to a UV light source (either from a 365 nm UV lamp or sunlight). The addition of Bayhydur® impeded the degradation of the patches, which did not degrade completely even after 7 hrs. The patches cured at 6O⁰C for 15 hrs were waterproof. The compositions cured at room temperature started to dissolve immediately in water, while the ones cured at 5O⁰C started to dissolve after 2 hours.

Example 2: Effect of TiO? Concentration on the Compositions

[0055] Three photocompositions were prepared, each with the same binder (polyurethane in dioxane at lg/20 ml) as in Example 1. The following substances were added, respectively, to each composition:

Composition 1 l% Millijet™ Blue 45

Composition 2 l% Millijet™ Blue 45 l% TiO₂

Composition 3

1% Millijet™ Blue 45

2% TiO₂.

[0056] Each composition was applied in a very thin film (thickness of the film was 20 microns) on pieces of photopaper containing cartoons. Then they were exposed to a UV light source (either from a long wavelength 365 nm UV lamp, or sunlight). The degradation (i.e., the change from colored to colorless) time of the dye decreased as the amount of TiO₂ increased. As expected, the composition without TiO₂ did not degrade.

Example 3 : Effect of Dye Concentration on the Compositions

[0057] To study the influence of dye concentration, three compositions were prepared as in example 1 as follows: Composition 1 l% Millijet™ Blue 45 l% TiO₂

Composition 2

2% Millijet™ Blue 45 l% TiO₂

Composition 3

0.5 % Millijet™ Blue 45

1% TiO₂.

[0058] They were then applied in a very thin film (the film thickness was 20 microns) on pieces of photopaper containing cartoons. Then they were exposed to a UV light source (either from a long wavelength 365 nm UV lamp, or sunlight). The degradation time of the sun patch increased as the amount of dye in final composition increased.

Example 4: Effect of Sunscreen Coating on the Degradation Time of the Sunpatch [0059] Three identical compositions ( 97% polyurethane in dioxane, 1% Millijet™ Blue 45, 1% TiO₂ P25 and 1% polyethyleneglycol-methylmethacrylate as a curing agent) were each applied as a thin film on a glass slide and cured at 6O⁰C for 15 hours. One glass slide was left untreated without any sunscreen as a control, on the second one a sunscreen with SPF 4 was applied, and on the third one a sunscreen with SPF 30 was applied. The slides were then exposed to a UV lamp The degradation time increased as the SPF of the sunscreen increased. Example 5: Effect of Sunscreen Coating and Curing Temperature on the Degradation Time of Compositions

[0060] Ig polyurethane per 20 ml dioxane, 1% Millijet™ Blue 45, 2% TiO₂ P25 and 0.5% Bayhydur® 302 as a curing agent compositions were prepared as in Example 1 and were applied to pieces of paper containing writing. Two patches were cured at room temperature, and two were cured at 6O⁰C. One patch cured at each temperature was left untreated without any sunscreen, and on one patch cured at each temperature a sunscreen with SPF 30 was applied. The patches were then exposed to a UV lamp. The patches cured at room temperature exhibited degradation a rate that was greater as compared with those cured at 6OC; at each point of time, 30min, 1 hr and 1.5 hrs, the room temperature cured-patches were less intense in color. When treated with SPF 30 sunscreen, both patches cured at room temperature and 6OC did not show any color degradation after 1,5 hrs exposure. ) Figure 3 shows the patches initially, after 30 minutes of UV exposure, after 1 hr of UV exposure, and after 1.5 hrs of UV exposure, respectively.

Example 6: Preparation of Photosensitive Compositions that Degrade Under UV-A [0061] Preparation of photosensitive compositions that degrade under UV-A exposure are provided, a) Polyurethane preparation: One gram of polyurethane granules was dissolved in 20 ml of dioxane under stirring for 24 hrs. b) Preparation of the ZnO particles coated with ethylhexyl methoxycinnamate (Eusolex 2292 from EMD Chemicals): ZnO nanoparticles (20nm in diameter) were mixed with the Eusolex 2290 in different ratio and sonicated for 30 min. After that they were saved in in the dark, c) Preparation of the final composition: After the polyurethane completely dissolved, 2% of ZnO/Eusolex 2292 (ratio 1:1) was added, mixed for 10 min and sonicated for 30 minutes. 1% of Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC) was added and the mixture was stirred for 2 hrs using a magnetic bar. Finally, the compositions were cured at 6O⁰C for 12 hours.

Example 7: Effect of adding Eusolex 2292 and ZnO/Eusolex 2292 on the photosensitive composition degradation

[0062] Four photocompositions were prepared, each with the same binder (polyurethane in dioxane at lg/20 ml) and 1% Millijet Blue 45, as in Example 1. The following substances were added, respectively, to each composition:

Formulation SP-23: 1% ZnO (Alfa-Aesar, 20-30 nm APS powder)

Formulation SP-26: 1.5% Eusolex 2292

Formulation SP-27: 2% ZnO: Eusolex 2292 (1:1)

Formulation SP-28: 4% ZnO: Eusolex 2292 (1:1)

[0063] Each composition was applied in a very thin film (thickness of the film was 20 microns) on glass slides. Then they were exposed to a UV-B light source and UV-B light source, separately, in order to asses degradation at different wavelengths. The degradation (i.e., the change from blue colored to colorless) time was registered and the UV-B and UV-A dosages were calculated.

[0064] Table 1 shows the UV-A and UV-B dosages at which the compositions turned from colored to colorless.

[0065] The UV-A bulb emits 80 J/m² x s and the UV-B bulb emits 0.5 J/ m². One

minimal erythema dosage is ~ 150 J/ m² UV-B. There is no UV-A dosage threshold, however the UV-A protection factors will be shown as a function of KJ/ m² received by the skin. As

seen in Table 1, composition that contains only ZnO particles degrades fast under both UV-A and UV-B. On the other hand, adding only Eusolex 2292 to the composition doesn't affect the dye under both UV-A and UV-B. Compositions with 2 and 4% ZnO:Eusolex 2292 (ratio 1 : 1) degrade under UV-A but not even after 25 MED (UV-B mainly).

Example 8: Photosensitive Compositions

[0066] The formulations were prepared with the same binder polyurethane in dioxane at lg/20 ml and 1% 1% polyethyleneglycol-methylmethacrylate in accordance with example 1. The following substances were added, respectively, to each composition:

Formulation SP-03

1% TiO₂

1% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

Formulation SP-06

2% TiO₂

1% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

Formulation SP-15

1% TiO₂

0.5% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

Formulation SP- 16

2% TiO₂

0.5% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

Formulation SP-17 3% TiO2 0.5% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

Formulation SP- 19

3% TiO2

1% Millijet™ Blue 45 (Milliken & Co, Spartanburg, SC)

[0067] Each composition was applied in a very thin film (thickness of the film was 20 microns) on glass slides. Then they were exposed to a UVB light source and UVA light source, separately, in order to asses degradation at different wavelengths. The degradation (i.e., the change from blue colored to colorless) time was registered and the UVB and UVA dosages were calculated.

[0068] Table 2 shows the UVA and UVB dosages at which the compositions turned from colored to colorless.

[0069] It will be obvious to those skilled in the art that various changes may be made

without departing from the scope of the invention, which is not to be considered limited to what is described in the specification.

Claims

What is claimed is:

1. A photosensitive composition comprising: a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation; a dye that produces a characteristic change in response to the photocatalytic effect; and a binder, wherein the dye and the photocatalyst are dispersed in the binder, and wherein the composition is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation.

2. The photosensitive composition of claim 1, wherein the binder is selected from polyurethanes, gelatin, chitosan, polybutadienes, natural rubber, polyvinylalcohols, polyvinyl chloride, polyethylenes, polyethylene oxides, polycarbonates, polyesters, polyamides, polyacrylates, polyvinyl pyrrolidone, polyvinyl acetate, cellulose, polystyrene derivatives, cellulose derivatives, polysaccharides, polyacrylamides, silicone polymers, and copolymers and combinations thereof.

3. The photosensitive composition of claim 2, wherein the binder is an elastomer.

4. The photosensitive composition of claim 3, wherein the binder is a polyurethane.

5. The photosensitive composition of claim 1, wherein the photocatalyst is selected from TiO₂, ZnO, and Fe₂O₃.

6. The photosensitive composition of claim 5 wherein the photocatalyst has an average primary particle size from 0.001 micrometers to 1.0 micrometers.

7. The photosensitive composition of claim 1 , wherein the photocatalyst is TiO₂.

8. The photosensitive composition of claim 9, wherein the binder is present in an amount of from about 50% to 99.8% by weight; the photocatalyst is present in an amount from about 0.1% to 10% by weight; and the dye is present in an amount from about 0.1% to 10% by weight.

9. The composition of claim 1, wherein the photocatalyst is selected to produce a photocatalytic effect in the presence of only UV-A radiation.

10. The composition of claim 9, wherein the photocatalyst comprises a photocatalyst at least partially coated with a UV-B absorber such that the photocatalyst produces a photocatalytic effect in response to UV-A radiation.

11. The composition of claim 10, wherein the UV-B absorber comprises ethylhexyl methoxycinnamate, octyl-N-dimethyl-p-aminobenzoate, octyl triazone, or 2-ethylhexyl alpha-cyano-beta-phenylcinnamate (octocrylene).

12. The composition of claim 10, wherein the photocatalyst is selected from TiO₂, ZnO, and Fe₂O₃.

13. The composition of claim 1, wherein the photocatalyst is selected to produce a photocatalytic effect in the presence of both UV-A and UV-B radiation.

14. The composition of claim 1, wherein the characteristic change of the dye comprises a change from colored to colorless.

15. The composition of claim 1, wherein the characteristic change of the dye comprises a change from colorless to colored.

16. The composition of claim 1, wherein the photocatalyst comprises a modified photocatalyst.

17. The composition of claim 16, wherein the modified photocatalyst comprises a photocatalyst modified with at least one of N, Ag, |Er), Pt, Pd, and photosensitizing dyes.

18. The composition of claim 16, wherein the modified photocatalyst comprises TiO_2-χNχ.

19. A device comprising: an ultraviolet radiation detecting layer comprising: a photocatalyst that produces a photocatalytic effect in the presence of ultraviolet radiation; a dye that produces a characteristic change in response to the photocatalytic effect; and a binder, wherein the dye and the photocatalyst are dispersed in the binder, and wherein the ultraviolet radiation detecting layer is calibrated such that the characteristic change of the dye occurs in response to a predetermined amount of ultraviolet radiation; a support layer adjacent to the ultraviolet detecting layer; and an attachment layer disposed to allow attachment of the device to a surface.

20. The device of claim 19, wherein the attachment layer comprises a pressure sensitive adhesive.

21. The device of claim 19, wherein the support layer further comprises an image disposed between the ultraviolet radiation detecting layer and the support layer.

22. The device of claim 21, wherein the image is disposed such that the image will become visible upon exposure of the device to the predetermined amount of ultraviolet radiation.

23. The device of claim 21, wherein the image is printed on the support layer.

24. The device of claim 21, wherein the image is disposed on the support layer.

25. The device of claim 19, wherein the image comprises a graphical image.

26. The device of claim 19, wherein the support layer and the attachment layer comprise a single layer.

27. The device of claim 19, wherein the ultraviolet radiation detecting layer is calibrated such at least a first region of the ultraviolet radiation detecting layer has the characteristic change of the dye in response to a first predetermined amount of ultraviolet radiation and a second region of the ultraviolet radiation detecting layer has the characteristic change of the dye in response to a second predetermined amount of ultraviolet radiation.