UV indicator with protective layer

Abstract

An apparatus (5) comprising a first layer (20) comprising a colourimetric indicator; and a second layer (30) provided on at least a portion of the first layer (20), the second layer (30) comprising or consisting of a protective material, wherein the protective material is transparent or substantially transparent to UV radiation, and wherein the protective material comprises or consists of a glass material or a polymeric material.

Description

[0001] UV Indicator with Protective Layer

[0002] Field of the Invention

[0003] The present invention relates to an ultraviolet (UV) colourimetric indicator. In particular, but not exclusively, the invention relates to a UV colourimetric indicator exhibiting improved properties, such as reduced variability of reactivity and / or reduced propensity to temperature variability.

[0004] Background

[0005] Many products exist, that provide a visual indication (through a colour change) of exposure to a certain amount of a particular compound or radiation. Such products typically include one or more colourimetric indicators. For example, colourimetric indicators rely on the optical properties of reactive dyes or inks. These dyes can exist in at least two different chemical states, with each form of the dye absorbing light in a particular range of wavelength. When such a reactive dye existing in a first form is exposed to a given substance, it reacts with the substance via a reversible chemical reaction, thereby turning into a second form of the dye. As the second form of the dye absorbs light at a different wavelength, the chemical reaction provides a colour change which is visible by an observer. Colourimetric indicators may be configured to display reversible colour changes or irreversible colour changes, depending on their intended use, and the chemical substance, radiation or stimulus causing the colour change in the indicator. An example of a colourimetric indicator reactive to irradiation by ultraviolet radiation (UVR) is disclosed in WO 2010 / 070290 (Mills et al), the content of which is incorporated herein by reference in its entirety.

[0006] Exposing a surface to a given type of radiation may be either desired or deliberate, or may be undesirable or unintentional.

[0007] For example, whilst exposure of one’s skin to direct sunlight may be desired and to some extent beneficial, overexposure to ultraviolet radiation is a recognised health hazard. Certain products exist, such as stickers or wristbands marketed under the name Smartsun™, which include a colourimetric indicator that displays a colour change after exposure to a certain type and / or quantity of UV radiation. This provides a user with a visual indication associated with exposure to a predetermined amount of UV radiation.

[0008] In another example related to sterilization and disinfection, products include a colorimetric indicator that displays a colour change after exposure to a certain amount of UVC radiation. This provides a user with a visual indication associated with exposure to UVC radiation. UVC irradiation is a known technique for and disinfecting and sterilizing surfaces, for example in a medical environment or in the foodstuff industry.

[0009] Other products rely on colourimetric indicators that exhibit a colour change when exposed to a particular compound or chemical substance, such as carbon dioxide, oxygen, ammonia, or the like. These can be useful, for example, in the food industry.

[0010] A problem with existing indicators, and in particular with UV indicators, is that the reactivity (speed of reaction) of the colourimetric indicators, typically in the form of a photochromic ink printed on a substrate, is dependent on temperature. Typically, the higher the temperature, the quicker the colour change. As such, although the intensity of the colour change will ultimately depend on the exposure dose, the speed of reaction may vary depending on temperature.

[0011] Various types of indicators may include covering layers or other forms of protection against UV light.

[0012] For example, CN1317536A discloses a photochromic layer sandwiched between two glass layers. However, this document does not relate to a UV indicator, and the purpose of the glass layer is to provide anti-ultraviolet function and a glare-shielding function.

[0013] JPS60205429A, which does not relate to a UV indicator, has a glass layer to prevent damage to the reactive material.

[0014] JPS59136669A relates to a photoluminescent (fluorescent) glass material, and the reactive glass is protected from pre-dose reaction by a coating of MgF2 on the glass.

[0015] US2017023681 A1 (Patel) relates to radiation-sensitive devices a surface of which is protected from UV light by UV reflective layers.

[0016] US3290499A discloses a radiation indicator protected against visible and ultraviolet light by the incorporation of ultraviolet absorbers.

[0017] GB1210047A discloses a threshold dosimeter shielded from environmental influences by embedding it in a transparent base of water-soluble polyvinyl alcohol.

[0018] US5028792A discloses a film for monitoring dosage of ionizing radiation, and protection against UV light is afforded by incorporation of UV absorbers.

[0019] US 2020 / 0149960 A1 (Foller) discloses a wearable indicator which is covered with a protective layer in the form of a superstrate film. The superstrate film may be treated with an oleophobic coating.

[0020] Thus, none of these documents addresses the problem of mitigating the dependence of a UV indicators’ reactivity on temperature. It is an object of the invention to address and / or mitigate one or more problems associated with the prior art.

[0021] The present invention is based on the findings that the above-mentioned problem may be mitigated (whilst maintaining the full functionality of the dosimeter) by covering the indicator with a glass layer or a polymeric layer. This is surprising because, typically, glass is considered to absorb at least some types of UV radiation, and is not generally considered to be compatible with a UV indicator. Similarly, many types of polymers are considered to absorb at least some types of UV radiation, and are not generally considered to be compatible with a UV indicator.

[0022] According to a first aspect there is provided an apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, the second layer comprising or consisting of a protective material, wherein the protective material is transparent or substantially transparent to UV radiation, and wherein the protective material comprises or consists of a glass material or a polymeric material.

[0023] Preferably, the second layer, e.g. protective layer, may cover the first layer.

[0024] Preferably, the second layer, e.g. protective layer, may cover the colourimetric indicator.

[0025] The second layer, e.g. protective layer, may block less than about 50%, e.g. less than about 40%, e.g. less than about 30%, e.g. less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1 %, of UV radiation, e.g. UV-A, UV- B, and / or UV-C radiation.

[0026] Glass embodiment

[0027] The protective material may comprise or may consist of a glass material.

[0028] The glass material may comprise or may consist of glass having a silica content of at least 80 wt%, e.g. at least 85 wt%, e.g. at least 90 wt%, e.g. at least 95 wt%, e.g. at least 99 wt%, silica. Advantageously, using a glass material having a high silica content may confer advantageous optical properties to the glass material, including transparency to UV radiation. Advantageously, the glass material may be transparent or substantially transparent to UV radiation, e.g. to UV-A, UV-B, and / or UV-C radiation. The glass material may block less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1%, of UV radiation, e.g. IIV-A, IIV-B, and / or IIV-C radiation.

[0029] The glass material may comprise or may consist of high silica glass.

[0030] The glass material may comprise or may consist of quartz glass (also called fused quartz or fused silica).

[0031] Thus, in an embodiment, there is provided an apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a glass material that is transparent or substantially transparent to UV radiation.

[0032] The glass material may block less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1 %, of UV radiation, e.g. UV-A, UV-B, and / or UV-C radiation.

[0033] In another embodiment, there is provided an apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a glass material, wherein the glass material comprises or consists of high silica glass.

[0034] The glass material may comprise or may consist of quartz glass (also called fused quartz or fused silica).

[0035] The glass material may comprise or may consist of glass having a silica content of at least 80 wt%, e.g. at least 85 wt%, e.g. at least 90 wt%, e.g. at least 95 wt%, e.g. at least 99 wt%, silica.

[0036] It was surprisingly found that the provision of a UV-transparent glass layer on the indicator reduces or prevents temperature-induced fluctuations of colourimetric change in the indicator upon exposure. Without wishing to be bound by theory, it is believed that the provision of a glass layer may block or may reflect at least some of the heat associated with the UV radiation, e.g. heat generated by the UV source, thereby minimising temperature fluctuations on or within the indicator upon exposure.

[0037] At least a portion of the second layer, e.g. the glass material, may be substantially transparent to visible light. By such provision, the provision of the second layer may not adversely affect observation of the first layer, e.g. of the indicator, by a user or observer.

[0038] The second layer, e.g. the glass material, may have a thickness of about 0.1 - 1 mm, e.g. about 0.1 to 0.5 mm, e.g. about 0.2 to 0.5 mm, e.g. about 0.3 mm. Polymer embodiment

[0039] The protective material may comprise or may consist of a polymeric material.

[0040] The polymeric material may comprise or may consist of a polyolefin and / or of a fluorinated polymer.

[0041] The polymeric material may comprise or may consist of a fluorinated polymer.

[0042] The polymeric material may comprise or may consist of a fluorinated addition homo or copolymer.

[0043] The polymeric material may comprise or may consist of a tetrafluoroethylene (TFE) homo- or co-polymer.

[0044] The polymeric material may comprise or may consist of a fluorinated polyolefin.

[0045] The polymeric material comprises or may consist of ETFE (ethylene tetrafluoroethylene copolymer) or FEP (fluorinated ethylene propylene).

[0046] The polymeric material may comprise or may consist of a perfluoroether homo- or co- polymer.

[0047] The polymeric material may comprise or may consist of a perfluoroalkoxy alkane (PFA) polymer.

[0048] Advantageously, the polymeric material may be transparent or substantially transparent to UV radiation, e.g. to IIV-A, IIV-B, and / or IIV-C radiation. The polymeric material may block less than about 50%, e.g. less than about 40%, e.g. less than about 30%, e.g. less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1 %, of UV radiation, e.g. UV-A, UV-B, and / or UV-C radiation.

[0049] Thus, in an embodiment, there is provided an apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a polymeric material that is transparent or substantially transparent to UV radiation.

[0050] The polymeric material may block less than about 50%, e.g. less than about 40%, e.g. less than about 30%, e.g. less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1%, of UV radiation, e.g. UV-A, UV-B, and / or UV-C radiation.

[0051] In another embodiment, there is provided an apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a polymeric material, wherein the polymeric material comprises or consists of a fluorinated addition homo or copolymer.

[0052] It was surprisingly found that the provision of a UV-transparent polymeric layer on the indicator reduces or prevents temperature-induced fluctuations of colourimetric change in the indicator upon exposure. Without wishing to be bound by theory, it is believed that the provision of a polymeric layer, e.g. ETFE, FEP or PFA, may block or may reflect at least some of the heat associated with the UV radiation, e.g. heat generated by the UV source, thereby minimising temperature fluctuations on or within the indicator upon exposure.

[0053] At least a portion of the second layer, e.g. the polymeric material, may be substantially transparent to visible light. By such provision, the provision of the second layer may not adversely affect observation of the first layer, e.g. of the indicator, by a user or observer.

[0054] The second layer, e.g. the polymeric material, may have a thickness of about 0.1 - 0.5 mm, e.g. about 0.1 to 0.4 mm or about 0.2 to 0.5 mm, e.g. about 0.2 to 0.4 mm, e.g. about 0.2 to 0.3 mm.

[0055] The following may apply to either embodiment above.

[0056] Preferably, the second layer, e.g. the protective layer, may be provided adjacent and / or in contact with the first layer.

[0057] The second layer may be adhered to the first layer and / or to a substrate of the apparatus, e.g. with an adhesive.

[0058] The first layer, e.g. the indicator layer, may be provided on a substrate.

[0059] The substrate may comprise a self-supporting layer. The substrate may comprise a film, sheet, or the like.

[0060] The first layer may be provided on the substrate. The substrate may be provided on a bottom side of the apparatus, in use.

[0061] The second layer may be provided on the first layer or portion thereof. The second layer may be provided on an upper side of the apparatus, in use.

[0062] The first layer may be provided between the substrate and the second layer.

[0063] The apparatus may be or may be provided as an article, e.g. a wearable article such as a band, e.g. a wristband, a patch, a sticker, or a non-wearable article such as a dosimeter article in any suitable form, e.g. a dosimeter card. The first layer and / or the substrate may have a thickness above a predetermined level. Typically, the substrate, optionally the substrate with the first layer, may have a thickness of at least 0.1mm.

[0064] The second layer may be adhered to the substrate and / or to the first layer, e.g. with an adhesive.

[0065] The colourimetric indicator may be capable of exhibiting a colour change in response to exposure to UV radiation, e.g. to UVA, UVB and / or UVC radiation. The trigger radiation may be selected from the group consisting of UVA, UVB, UVC, or combinations thereof.

[0066] The colourimetric indicator may be or may comprise a UV indicator.

[0067] The colourimetric indicator may be substantially as described in WO 2010 / 070290 (Mills et al), the content of which is incorporated herein by reference.

[0068] In an embodiment, the colourimetric indicator may be a UVA and / or UVB indicator. The trigger radiation may be UVA and / or UVB. The trigger radiation may be in the region of 280-400 nm. In such instance, the apparatus may be a sunburn indicator, which may be provided in the form of a wearable item such as a band, patch, sticker, tape, or the like.

[0069] In another embodiment, the colourimetric indicator may be a UVC indicator or a UVC dosimeter. The trigger radiation may be UVC. The trigger radiation may be in the region of 100-280 nm. In such instance, the apparatus may be a disinfection indicator and / or a sterilisation indicator. The apparatus may be a UVC indicator, e.g. a UVC curing indicator.

[0070] The colourimetric indicator may have a first state associated with a first colour. The first state and / or first colour may be associated with an absence of colour change. For example, the first state and / or first colour may be associated with the absence of exposure of the indicator to the trigger radiation or to the exposure of the indicator to the trigger radiation below a predetermined and / or threshold activation level, e.g. below 0.1 mJ / cm2, e.g. below 0.5 mJ / cm2, e.g. below 1 mJ / cm2.

[0071] The colourimetric indicator may have a second state associated with a second colour. The second state and / or second colour may be associated with a full or final colour change. For example, the second state and / or second colour may be associated with full exposure of the indicator to the trigger radiation or to the exposure of the indicator to the trigger radiation above a predetermined and / or upper activation level, e.g. above 0.1 mJ / cm2, e.g. below 0.5 mJ / cm2, e.g. below 1 mJ / cm2. The colourimetric indicator may have one or more intermediate states each associated with a corresponding intermediate colour. The one or more intermediate states and / or one or more intermediate colours may be or may comprise one or more states and / or colours between the first state and / or first colour and the second state and / or second colour. Each intermediate state and / or intermediate colour may be associated with a predetermined level or dose of exposure to the trigger radiation.

[0072] Each of the first state and / or first colour, intermediate state(s) and / or intermediate colour(s), and second state and / or second colour, may each correspond to or may each be associated with a predetermined level or dose of exposure to the trigger radiation.

[0073] The apparatus may further comprise at least one additional reference colour region. The at least one additional reference colour region may correspond to the first colour, the second colour, and any of the intermediate colours. By such provision, in use, a user or observer may be able to obtain further visual assessment by comparing the colour of the indicator or first layer (e.g. first region thereof) to the colour of the at least one additional reference colour region. In an embodiment, at least one additional reference colour region may be configured to substantially match the colour of the indicator in second (active) portion. By such provision, the additional reference colour region may provide a further reference region in addition to the reference region defined by the second portion of the apparatus and / or the active portion of the second layer.

[0074] According to a second aspect there is provided a method for preparing an indicator apparatus, the method comprising: providing a device having a first layer, wherein the first layer comprises a colourimetric indicator; and applying a second layer on at least a portion of the first layer, the second layer comprising or consisting of a protective material, wherein the protective material is transparent or substantially transparent to UV radiation, and wherein the protective material comprises or consists of a glass material or a polymeric material.

[0075] The method may comprise laminating the second layer on the first layer.

[0076] The method may comprise bonding, e.g. using an adhesive, the second layer on the first layer.

[0077] The features described in relation to the apparatus according to the first aspect may apply to the method according to the second aspect, and, merely for brevity, are not repeated here. Brief Description of Drawings

[0078] Embodiments of the present disclosure will now be given by way of example only, and with reference to the accompanying drawings, which are:

[0079] Figure 1 a schematic view of an apparatus according to a first embodiment;

[0080] Figure 2 a schematic view of an apparatus according to a second embodiment;

[0081] Figure 3 a schematic view of an apparatus according to a third embodiment;

[0082] Figure 4 images of an apparatus of Figure 1 , when exposed to different a UVC radiation dose of ~90 mJ / cm2, with (bottom half) or without (top half) a protective varnish; Figure 5 a comparison of an indicator apparatus when covered and not covered with a quartz glass layer using a Natgraph UV device;

[0083] Figure 6 a comparison of an indicator apparatus when covered and not covered with a quartz glass layer using an “AUV” UV device;

[0084] Figure 7 a comparison of an indicator apparatus, having either no glass cover (7(a)), or having a peripheral portion not covered with glass and a central circular portion covered with a quartz glass layer (7(b)), using an “1ST” irradiation device, using a dose of ~30 mJ / cm2

[0085] Figure 8 a comparison of an indicator apparatus, having either no glass cover (8(a)), or having a peripheral portion not covered with glass and a central circular portion covered with a quartz glass layer (8(b)), using an “AUV” irradiation device, using a dose of ~30 mJ / cm2.

[0086] Figure 9 a comparison of an indicator apparatus, having either no glass cover (9(a)), or having a peripheral portion not covered with glass and a central circular portion covered with a quartz glass layer (9(b)), using an “1ST” irradiation device, using a dose of -150-160 mJ / cm2.

[0087] Figure 10 a comparison of an indicator apparatus, having either no glass cover (10(a)), or having a peripheral portion not covered with glass and a central circular portion covered with a quartz glass layer (10(b)), using an “AUV” irradiation device, using a dose of -150-160 mJ / cm2;

[0088] Figure 11 Images illustrating temperature shielding of a quartz glass layer and of ETFE layers on a temperature indicator when exposed to high heat UV radiation;

[0089] Figure 12 Images illustrating temperature shielding of a quartz glass layer and of ETFE layers on a temperature indicator. Detailed Description

[0090] Referring to Figure 1 there is shown an indicator apparatus, generally designated 5, according to a first embodiment.

[0091] The apparatus 5 includes a substrate 10. In this embodiment, the substrate 10 is in the form of a film.

[0092] The apparatus has a first layer 20 comprising a colourimetric indicator. The first layer 20 is provided on an upper side of the substrate 10, i.e., on a side of the substrate configured to face a source of radiation 40, in use.

[0093] The apparatus has a second layer 30 provided on an upper side of the first layer 20 and covering the first layer 20. Thus, the second layer 30 covers the indicator. The second layer 30 is provided adjacent and is in contact with the first layer 20.

[0094] As such, any radiation 40 directed towards the indicator within the first layer 30 will interact with the second layer 30 before interacting with the first layer 20.

[0095] The second layer is made of a glass material or a polymeric material.

[0096] In one embodiment, the second layer is made of quartz glass. Advantageously, quartz glass has a very high purity (silica content), typically at least 99 wt% silica, and as such quartz glass is highly transparent to UV radiation. In another embodiment, the second layer may be made of a fluorinated polyolefin such as ETFE, FEP or PFA.

[0097] It was surprisingly found that the provision of a UV-transparent quartz glass layer 30 on the indicator 20 reduces or prevents temperature-induced fluctuations of colourimetric change in the indicator upon exposure to UV radiation 40. Without wishing to be bound by theory, it is believed that the provision of a glass layer 30 may block or may reflect at least some of the heat associated with the UV radiation 40, e.g. heat generated by the UV source, thereby minimising temperature fluctuations on or within the indicator 20 upon exposure.

[0098] Advantageously, the provision of a quartz glass layer also means the second layer 30 is substantially transparent to visible light, which allows does not adversely affect observation of the first layer 20 by a user or observer.

[0099] In this embodiment, the second layer 20 has a thickness of 0.3 mm.

[0100] In the embodiment of Figure 1 , the first layer 20 covers substantially the entire upper surface of the substrate 10, and the second (glass) layer 30 covers substantially the entire upper surface of the first layer 20. In the embodiment of Figure 2, the first layer 120 covers part of the upper surface of the substrate 110, and the second (glass) layer 130 covers substantially the entire upper surface of the first layer 120.

[0101] In the embodiment of Figure 3, the first layer 220 covers part of the upper surface of the substrate 10, and the second (glass) layer 230 covers substantially the entire upper surface of the first layer 220 and also overlaps with the upper surface of the substrate 210.

[0102] The second (glass) layer 230 may be secured by use of an adhesive. The adhesive is shown in Figure 3, which in this embodiment is provided between the second (glass) layer 230 and the substrate 210. An adhesive 250 is provided to bond the second (glass) layer 230 to the substrate 210.

[0103] Referring to Figure 4, there is shown an image of an apparatus 305 as generally described in Figure 1 , when exposed to a UVC radiation dose of ~90 mJ / cm2, with (bottomhalf) or without (tophalf) a protective varnish.

[0104] In this embodiment, the 0.3 mm-thick quartz glass layer 330 was positioned over only part of the indicator layer 320 in order to demonstrate the effect the presence of the quartz glass layer 330. The glass layer was present in the semi-circle region composed of regions 302 and 304. Regions 301 and 303 were not covered by a quartz glass layer 330.

[0105] In this embodiment, the UVC indicator layer 320 contained Thymol Blue as pH indicator, NaOH, diphenyliodonium chloride (DPIC) as photo-acid generator, and Poly(vinyl butyral) as a binder.

[0106] Irradiation of the apparatus 305 was performed using a UVC mercury lamp (~254nm). The radiation dose was ~90 mJ / cm2. In the lower half 322 of the apparatus 305 (consisting of non-covered portion 303 and glass-covered portion 304), a varnish was applied, absorbing some of the radiation. In the upper half 321 of the apparatus 305 (consisting of non-covered portion 301 and glass-covered portion 302), no varnish was applied, thereby creating overexposure of the upper half 321 relative to the lower half 322.

[0107] It can be seen from the lower half that the portion 304 covered with glass did not reach the final colour change (as per non-covered portion 303) as quickly. Further, it can be observed from the upper half that the portion 302 covered with glass layer 330 showed an intense colour change due to the higher exposure level, but did not reach the colour change associated with overexposure shown in the non-covered portion 301 . Referring now to Figures 5 and 6, there is shown a comparison of an indicator apparatus, generally similar to the apparatus 305 of Figure 4, having a top portion not covered with glass, and a bottom portion covered with a quartz glass layer.

[0108] The results of Figure 5 were obtained using a Natgraph as the source of UV irradiation, and the results of Figure 6 were obtained using an AUV device as the source of UV irradiation. The two machines both produce UV, but generate different amounts of heat during operation (‘AUV’ is hotter than ‘Natgraph’).

[0109] For each of figures 5 and 6, the irradiation dose was (a) 50mJ / cm2, (b) 100mJ / cm2, and (c) 200m J / cm2.

[0110] Referring to Figure 5, it can be seen that the portion 402 covered with glass did not reach the final colour change as quickly as the non-covered portion 401 , for the higher exposure doses of 100 m J / cm2and 200 m J / cm2exposure doses (Figs 5(b) and 5(c)). However, the difference was barely noticeable at the lower exposure dose of 50 mJ / cm2.

[0111] Referring to Figure 6, it can be seen that the portion 502 covered with glass did not reach the final colour change as quickly as the non-covered portion 501 , for the higher exposure doses of 100 mJ / cm2and 200 mJ / cm2exposure doses (Figs 6(b) and 6(c)). However, the difference was barely noticeable at the lower exposure dose of 50 mJ / cm2(Figure 6(a)).

[0112] Figures 7 to 10 show a comparison of an indicator apparatus, generally similar to the apparatus 305 of Figure 4, having a peripheral portion not covered with glass, and a central circular portion (including the “+” marks) covered with a quartz glass layer.

[0113] For each of Figures 7 to 10, there is shown an indicator (a) without cover, and (b) with a quartz glass cover.

[0114] Figure 7 shows the results using an “1ST” irradiation device, using a dose of ~30 mJ / cm2. Figure 8 shows the results using an “AUV” irradiation device, using a dose of ~30 mJ / cm2. Figure 9 shows the results using an “1ST” irradiation device, using a dose of -150-160 mJ / cm2. Figure 10 shows the results using an “AUV” irradiation device, using a dose of -150-160 mJ / cm2.

[0115] 1ST & AUV are two different machines. AUV produces more heat during operation than 1ST.

[0116] As can be seen from Figures 7 and 8, at lower exposure doses, there is little or no visible difference between the glass-covered portion 602b, 702b and the respective non-covered portion 601 b, 701b. However, as can be seen from Figures 9 and 10, at higher exposure doses, there is a visible difference between the glass-covered portion 802b, 902b and the respective non-covered portion 801b, 901 b.

[0117] Without wishing to be bound by theory, this is likely because both machines produce much more heat at 150 mJ / cm2than at 30 mJ / cm2. Therefore, there is no visible difference between glass-covered and non-covered portions at low temperatures (Figures 7 and 8) but a clear difference at higher temperature (Figures 9 and 10). This confirms that the quartz glass cover exhibits an ability to block or repel heat, but not UV radiation.

[0118] Figure 11 shows images of temperature indicators following exposure of the temperature indicator to a UV source (H bulb) using an “AUV” UV device that characteristically emits high heat levels, for a duration of less than 2s, e.g. about 1-2s, for (a) an uncovered control 1005a, (b) an indicator 1005b covered with a 0.3mm-thick quartz glass layer, (c) an indicator 1005c covered with a 100pm-thick ETFE layer, (d) an indicator 1005d covered with a 300pm-thick ETFE layer, and (e) an indicator 1005e covered with a 400pm-thick ETFE layer.

[0119] Figure 12 shows another iteration of the same experiment described above in relation to Figure 11.

[0120] As shown in Figure 11(a) and Fig 12(a), it can be seen that, when without the presence of a protective layer, the indicator 1005a, 1105a shows a temperature increase to about 62.5°C.

[0121] As shown in Figure 11(b) and Fig 12(b), it can be seen that, in the presence of a quartz glass protective layer, the indicator 1005b, 1105b only reached about 50°C.

[0122] As shown in Figures 11 (c)-11(e) and Fig 12(c)-12(e), it can be seen that, in the presence of an ETFE layer of between 100 and 400 pm in thickness, the indicator 1005c- 1005e,1105c-1105e only reached about 50°C with the 100 pm-thick layer, remained below 50°C with the 300 and 400 pm-thick layers.

[0123] This demonstrates the advantageous effects of both quartz glass layers and ETFE layers to at least partially block heat from a UV source.

[0124] Investigation of UV transmission of various materials

[0125] Various covers were applied to a radiometer, and the percentage of radiation that was transmitted through each cover material, was measured.

[0126] The following examples were investigated:

[0127] - no cover (“control”); - a 0.3mm-thick quartz glass layer (“glass”);

[0128] - a lOOpm-thick ETFE layer (“F1OO);

[0129] - a 300pm-thick ETFE layer (“F300”);

[0130] - a 400pm-thick ETFE layer (“F400”);

[0131] - a 50-pm-thick PVC layer (“PC50”);

[0132] - a 70-pm-thick PVC layer (“v750”).

[0133] The “PC50” layer was a 50-|jm-thick PVC layer coated with a pressure-sensitive acrylic adhesive, marketed as PC50MICP2 by Helix®.

[0134] The “V750” layer was a 70-pm-thick PVC layer coated with a pressure-sensitive acrylic adhesive, marketed as PC50MICP2 by Helix®.

[0135] In each case, the measurement was expressed as a percentage of the detected radiation relative to the radiation detected by the control (uncovered radiometer). All measurements were obtained using the same machine settings.

[0136] These experiments were conducted both at “high” and “low” UVC exposures (approximately 140 & 80 mJ / cm2, respectively).

[0137] Table 1 below shows the results of the measurements.

[0138] Table 1 :

[0139] The following conclusions can be drawn from the results presented in Table 1 :

[0140] The 0.3mm-thick quartz glass layer provided excellent UV transmission for all types of UV radiation;

[0141] Each of the ETFE layers (F100, F300, and F400) provided a useful level of UV transmission. Unsurprisingly, increasing the layer thickness reduced UV transmission;

[0142] Other polymeric materials including PC50 and V750 blocked most of the UV radiation, despite being thinner than F100, F300 and F400. This demonstrates that not all polymeric materials can be expected to allow suitable transmission of UV radiation to allow their use in a UV indicator;

[0143] The radiation dose did not impact the relative UV transmission by each of the materials.

[0144] Alternative fluoropolymer types were tested as a protective layer, namely: alternative fluoropolymer types including FEP and PFA; and other types of polymer, namely polyurethane (PU) from Buitink, and polyethylene terephthalate (PET) from Folienwerk Wolfen . UV transmission and temperature resistance were measured for each film, and the results are shown in Tables 2 and 3 below. Table 2 shows the results of experiments conducted at “low” UVC exposure, and Table 3 shows the results of experiments conducted at “high” UVC exposures (approximately 80 & 140 mJ / cm2, respectively). Table 2

[0145] The following conclusions can be drawn from the results presented in Table 2: ETFE provided good UV transmission and good temperature regulation for all thicknesses. Unsurprisingly, increasing the layer thickness reduced UV transmission;

[0146] - Alternative fluoropolymer types including FEP and PFA also provided good UV transmission and good temperature regulation for all thicknesses.

[0147] Unsurprisingly, increasing the layer thickness reduced UV transmission;

[0148] Other polymeric materials including PU and PET blocked unacceptably high levels of the UV radiation. For example, even the very thin (77pm) PU film blocked almost as much UV as the 400-pm thick ETFE film. As such, these polymer types do not provide the combination of properties provided by the fluoropolymers tested above.

[0149] Table 3 The following conclusions can be drawn from the results presented in Table 3:

[0150] ETFE provided good UV transmission and good temperature regulation for all thicknesses. Unsurprisingly, increasing the layer thickness reduced UV transmission; - Alternative fluoropolymer types including FEP and PFA also provided good UV transmission. Temperature regulation was also achieved for the larger thicknesses, particularly from around 200 pm for FEP and from around 150 pm for PFA. This is believed to be because higher UV exposures cause a greater temperature increase than lower UV exposures such as those tested in Table 2;

[0151] Other polymeric materials including PU and PET blocked unacceptably high levels of the UV radiation. As such, these polymer types do not provide the combination of properties provided by the fluoropolymers tested above.

Claims

CLAIMS:

1. An apparatus comprising: a first layer comprising a colourimetric UV indicator; and a second layer provided on at least a portion of the first layer, the second layer comprising or consisting of a protective material, wherein the protective material is transparent or substantially transparent to UV radiation, and wherein the protective material comprises or consists of a glass material or a polymeric material.

2. An apparatus according to claim 1 , wherein the second layer blocks less than about 40%, e.g. less than about 30%, e.g. less than about 20%, e.g. less about 10%, e.g. less than about 5%, e.g. less than about 1%, of UV radiation, e.g. UV-A, UV-B, and / or UV-C radiation.

3. An apparatus according to claim 1 or claim 2, wherein the protective material comprises or consists of a polymeric material.

4. An apparatus according to claim 3, wherein the polymeric material comprises or consists of a fluorinated addition homo or copolymer.

5. An apparatus according to claim 3 or claim 4, wherein the polymeric material comprises or consists of a fluorinated polyolefin.

6. An apparatus according to any one of claims 3 to 5, wherein the polymeric material comprises or consists of a tetrafluoroethylene (TFE) homo- or co-polymer.

7. An apparatus according to any one of claims 3 to 5, wherein the polymeric material comprises or consists of ETFE (ethylene tetrafluoroethylene copolymer) or FEP (fluorinated ethylene propylene.

8. An apparatus according to any one of claims 3 to 5, wherein the polymeric material comprises or consists of a perfluoroether homo- or co- polymer.

9. An apparatus according to claim 8, wherein the polymeric material comprises or consists of a perfluoroalkoxy alkane (PFA) polymer.

10. An apparatus according to any preceding claim, wherein the polymeric material has a thickness of about 0.1 to 0.5 mm.

11. An apparatus according to claim 1 or claim 2, wherein the protective material comprises or consists of a glass material.

12. An apparatus according to claim 11 , wherein the glass material comprises or consists of glass having a silica content of at least 80 wt% silica.

13. An apparatus according to claim 11 , wherein the glass material comprises or consists of quartz glass.

14. An apparatus according to claim 11 , wherein the glass material has a thickness of about 0.1 - 1 mm.

15. An apparatus comprising: a first layer comprising a colourimetric UV indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a glass material, wherein the glass material comprises or consists of high silica glass.

16. An apparatus comprising: a first layer comprising a colourimetric UV indicator; and a second layer provided on at least a portion of the first layer, wherein the second layer covers the colourimetric indicator, and wherein the second layer is made of a polymeric material, wherein the polymeric material comprises or consists of a fluorinated addition homo or copolymer.

17. A method for preparing an indicator apparatus, the method comprising: providing a device having a first layer, wherein the first layer comprises a colourimetric UV indicator; and applying a second layer on at least a portion of the first layer, the second layer comprising or consisting of a protective material, wherein the protective material istransparent or substantially transparent to UV radiation, and wherein the protective material comprises or consists of a glass material or a polymeric material.

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