Multilayer Colorimetric Indicators

Abstract

The device 5 includes a first layer 20 including a colorimetric indicator, and a second layer 30 disposed over at least a portion 22 of the first layer 20, at least a portion of the second layer 30 configured to block and / or absorb radiation to which the indicator is sensitive or responsive, and configured to be substantially transparent to visible light.

Description

[Technical Field]

[0001] The present invention relates to colorimetric indicators, and in particular, but not exclusively, to devices for improving the visualization of color changes in colorimetric indicators. [Background technology]

[0002] Many products exist that visually indicate (via a color change) exposure to a specific amount of a particular compound or radiation. Such products typically include one or more colorimetric indicators. For example, colorimetric indicators utilize the optical properties of reactive dyes or inks. These dyes can exist in at least two distinct chemical states, with each dye form absorbing light within a specific wavelength range. When a reactive dye present in a first form is exposed to a substance, it reacts with the substance through a reversible chemical reaction, converting to a second form of the dye. The second form of the dye absorbs light at a different wavelength, resulting in a color change that is visible to an observer. Colorimetric indicators may be configured to display a reversible or irreversible color change, depending on their intended use and the chemical, radiation, or stimulus that causes the indicator's color change. Examples of colorimetric indicators that respond to ultraviolet (UVR) radiation are disclosed in WO 2010 / 070290 (Mills et al.), the contents of which are incorporated herein by reference in their entirety.

[0003] Surfaces may be exposed to certain types of radiation in some cases, either desirable or intentional, or undesirable or unintentional.

[0004] For example, while exposure to direct sunlight is desirable and may even be beneficial to some extent, excessive exposure to UV rays is recognized as harmful to health. Products exist, such as stickers and wristbands sold under the name Smartsun™, that contain colorimetric indicators that exhibit a color change after exposure to certain types or amounts of UV radiation, thereby providing visual confirmation to the user that they have been exposed to a predetermined amount of UV radiation.

[0005] Another example related to disinfection and sterilization is a product that includes a colorimetric indicator that displays a color change after exposure to a certain amount of UVC radiation, providing the user with a visual indication related to exposure to UVC radiation. UVC radiation is known as a technology for sterilizing and disinfecting surfaces in healthcare settings, the food industry, and elsewhere.

[0006] There are also products that use colorimetric indicators that change color when exposed to certain compounds or chemicals, such as carbon dioxide, oxygen, or ammonia. These are useful in the food industry, for example.

[0007] While products incorporating colorimetric indicators provide a useful indication of potential exposure to certain radiation, irritants, or chemicals, a challenge with these systems is that visually assessing a given color change can be difficult, that assessment may require interpretation, and subsequent decisions based on that assessment can be potentially counterproductive or even dangerous. Generally, a user will only notice a color change in the indicator when a significant color change occurs. For ultraviolet indicators, this can correspond to a relatively high exposure dose. Particularly when used in a hospital environment, relatively low exposure doses (e.g., 6 mJ / cm) can be tolerated. 2 It may be useful to visually detect the following areas on the indicator:

[0008] Some colorimetric indicators have one or more reference moieties that display a target color after exposure to a predetermined amount of radiation. Examples of such systems include U.S. Patent Application Publication No. 2017 / 0191866 (Balooch et al.), European Patent Application Publication No. 0487792 (Pugh et al.), and U.S. Patent Application No. 5,117,116 (Bannard et al.), which disclose colorimetric indicator systems having one or more reference moieties that correspond to the respective colors of the radiation-sensitive indicator when exposed to different predetermined amounts of radiation.

[0009] These systems suffer from a number of drawbacks. For example, the reference area is colored or printed with a non-reactive compound different from the indicator itself and therefore cannot perfectly match the color of the indicator, whether before or after exposure to a given amount of radiation. Furthermore, the color of the reference ink may vary from batch to batch and / or may fade or otherwise discolor over time or with exposure to the environment (e.g., light, temperature, humidity, etc.). As a result, these systems suffer from a lack of confidence that the reference area and the indicator will match the intended color under a given condition (e.g., unexposed or exposed).

[0010] Other publications, including US Patent Application Publication No. 2020 / 149960 (Foller et al.) and US Patent No. 9,658,101 (Levine et al.), disclose indicators having generally multi-layer structures that do not include any reference moieties. Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to address and / or alleviate one or more problems associated with the prior art. [Means for solving the problem]

[0012] According to a first aspect, there is provided an apparatus comprising a first layer comprising a colorimetric indicator and a second layer disposed over at least a portion of the first layer, at least a portion of the second layer configured to block and / or absorb radiation to which the indicator is sensitive or responsive, and configured to be substantially transparent to visible light.

[0013] One or more portions of the second layer are configured to block and / or absorb radiation to which the indicator is sensitive and are configured to be substantially transparent to visible light, and may be referred to as an active portion or portions.

[0014] The second layer may include at least one inactive portion. The one or more inactive portions may be configured to not block and / or absorb radiation to which the indicator is sensitive. The one or more inactive portions may be substantially transparent to visible light and / or radiation to which the indicator is sensitive. The one or more inactive portions may generally be substantially transparent to both visible light and radiation to which the indicator is sensitive.

[0015] One or more active portions of the second layer may be transparent to visible light. Preferably, one or more active portions of the second layer may prevent the indicator from changing color under visible light. Such a configuration may ensure that the presence of the second layer does not affect the color of the indicator as observed and / or perceived by a user viewing the indicator and / or the first layer through the second layer. In other words, the color of the indicator perceived by a user may be substantially the same whether viewing the first layer directly or indirectly through one or more active portions of the second layer.

[0016] The second layer, eg the active portion thereof, may be transparent to radiation in the range of about 400 to 800 nm, for example in the range of about 400 to 740 nm.

[0017] Preferably, the presence of an active portion configured to block and / or absorb radiation to which the indicator is sensitive and configured to be substantially transparent to visible light may enhance the reliability of the reference portion in the device. In particular, a region of the device that includes an active portion may correspond to or be defined as the reference portion. Because the active portion is configured to block and / or absorb radiation to which the indicator is sensitive, one or more regions covered by one or more active portions of the indicator will not change color when exposed to radiation that would normally cause a color change.

[0018] In this specification, the illumination to which the indicator is sensitive will be referred to as the "trigger illumination."

[0019] The indicator and / or first layer may include a first portion and a second portion. The first portion may be uncovered by the second layer or may be covered by the inactive portion of the second layer. The second portion may be covered by the active portion of the second layer.

[0020] Preferably, prior to exposure to the triggering radiation, the first and second portions of the indicator may display the same color. This allows the reference portion to perfectly match the color of adjacent portions of the device, e.g., portions of the indicator not covered by the active portion of the second layer, despite any potential variations between batches or small variations in the original (unexposed) color of the indicator. In contrast, prior art reference portions typically use non-reactive dyes, pigments, or inks that are different from the indicator itself, making a perfect match impossible.

[0021] Preferably, the colors of the first and second portions of the indicator in the first layer are perfectly matched before exposure to triggering radiation, such that the device allows a user to notice a visible color change after exposure to low levels or doses of triggering radiation, for example, after exposure to levels or doses of triggering radiation that are lower than the minimum dose at which a user would normally be able to detect a color change in the indicator.

[0022] Preferably, about 8 mJ / cm 2 , for example, about 6 mJ / cm 2 , for example, about 5 mJ / cm 2 After exposure to the trigger radiation of the dose, the user may be able to notice a color change of the indicator, for example a color change in the first portion thereof.

[0023] The active portion of the second layer may include a radiation absorbing component, e.g., a radiation absorber, configured to absorb trigger radiation. It will be understood that the radiation absorber selected for this active portion may vary depending on the particular colorimetric indicator used in the first layer. For example, the radiation absorber may be a UV radiation absorber, e.g., a UVC absorber. The radiation absorber may include one or more compounds selected from the group consisting of benzophenone, hydroxybenzophenone, hydroxyphenylbenzotriazole, phenolbenzotriazole, benzotriazole, hydroxyphenyltriazine, and oxanilide. The radiation absorber may include benzophenone and / or phenolbenzotriazole.

[0024] The second layer may include a coating or may be a coating. Generally, when the second layer includes a coating, the second layer may be disposed only on a portion of the first layer, e.g., only on the second portion. The second layer may be an active portion, may define an active portion, or may coincide with an active portion. Thus, the first portion of the first layer may not be covered by the coating, and the second portion of the first layer may be covered by the coating.

[0025] The coating may be configured or provided in the form of a varnish.

[0026] Generally, the first layer, eg, the indicator layer, may be a solvent-based composition.

[0027] The second layer, e.g., a coating or varnish, may be a solvent-based coating composition, which may improve the compatibility of the coating with the first layer, e.g., the indicator layer.

[0028] The coating may include a polymer binder and a solvent.

[0029] The radiation absorbing component may be a component of the coating, for example forming part of the binder.

[0030] The radiation absorbing component may be a radiation absorber additive. Thus, the coating may include a polymer binder, a solvent, and a radiation absorber. The radiation absorber may include one or more compounds selected from the group consisting of benzophenone, hydroxybenzophenone, hydroxyphenylbenzotriazole, phenolbenzotriazole, benzotriazole, hydroxyphenyltriazine, and oxanilide. The radiation absorber may include benzophenone and / or phenolbenzotriazole.

[0031] The coating may include a radiation absorber configured to absorb the triggering radiation. It will be appreciated that the radiation absorber selected in the coating may vary depending on the particular colorimetric indicator used in the first layer.

[0032] In some embodiments, the coating may include or be a composition such as those sold by Fujifilm as APR VA401 or Fujifilm Sericol PY433 EL Overprint, or by Mara® Mold MPC 910. The second layer may have a relatively high viscosity. Advantageously, the inventors have unexpectedly discovered that a higher viscosity enhances the second layer's ability to block and / or absorb radiation, e.g., UV radiation. This may allow the second layer to block and / or absorb this and other radiation even without the inclusion of a radiation absorber additive.

[0033] The second layer may include or be a laminate layer. The second layer may be laminated onto the first layer, for example, onto the indicator layer. The second layer may be a self-supporting layer, for example, a film.

[0034] The adhesive may be disposed between the second layer and the first layer, and the second layer may include an adhesive layer or other adhesive layer and may be configured to adhere to the first layer.

[0035] The second layer may be devoid of adhesive and may be configured to be laminated onto the first layer, for example, by heat lamination or pressure lamination.

[0036] Generally, when the second layer includes a self-supporting layer and / or a laminate layer, the second layer may be provided only on a portion of the first layer, for example only on the second portion, or may be provided on both at least a portion of the first portion and the second portion of the first layer.

[0037] If the second (self-supporting) layer is provided only on a portion of the first layer, e.g., only on the second portion, the second layer may define or correspond to the active portion, and thus the first portion of the first layer may not be covered by the second (self-supporting) layer.

[0038] When the second (self-supporting) layer is disposed over both at least a portion of the first portion and the second portion of the first layer, the second layer may include the first portion and the second portion.

[0039] The first portion of the second (self-supporting) layer may include or define the inactive portion of the second layer, and the first or inactive portion may be substantially transparent to visible light and to radiation to which the indicator is responsive, such as trigger radiation.

[0040] The second portion of the second (self-supporting) layer may include or define the active portion of the second layer. The second or active portion may be substantially transparent to visible light but may be configured to block and / or absorb radiation to which the indicator responds, such as trigger radiation.

[0041] The second (self-supporting) layer may comprise a polymer. In general, the coating may be comprised of a polymer binder and the radiation absorber or other radiation absorbers.

[0042] The active portion of the second (self-supporting) layer may include a radiation absorber configured to absorb the triggering radiation. It will be appreciated that the radiation absorber selected for the active portion may vary depending on the particular colorimetric indicator used in the first layer.

[0043] A first layer, for example an indicator layer, may be provided on a substrate.

[0044] The substrate may include a self-supporting layer. The substrate may include a film, a sheet, or the like.

[0045] The first layer may be provided on a substrate, which may be provided on the underside of the device in use.

[0046] The second layer may be provided on top of the first layer or a portion thereof. The second layer may be provided on the top side of the device when in use.

[0047] The device may be or be provided as an article, for example a wearable article such as a band, eg a wristband, a patch, a sticker, or the like.

[0048] The first layer may have a thickness exceeding a predetermined level. The first layer may have a thickness of at least 0.1 mm. The inventors have unexpectedly found that when the first layer has a thickness exceeding about 0.1 mm, the presence of the second layer may be difficult to visually detect before exposure to trigger radiation.

[0049] The colorimetric indicator may be capable of exhibiting a color change in response to exposure to UV radiation, for example UVA, UVB, and / or UVC radiation. The trigger radiation may be selected from the group consisting of UVA, UVB, UVC, or combinations thereof. The colorimetric indicator may be or may include a UV indicator. The colorimetric indicator may be substantially as described in WO 2010 / 070290 (Mills et al.), the contents of which are incorporated herein by reference.

[0050] In embodiments, the colorimetric indicator may be a UVA and / or UVB indicator. The triggering radiation may be UVA and / or UVB. The triggering radiation may be in the 280-400 nm range. In such an example, the device may be a sunburn indicator and may be provided in the form of a wearable item such as a band, patch, sticker, tape, or the like.

[0051] In another embodiment, the colorimetric indicator may be a UVC indicator. The triggering radiation may be UVC. The triggering radiation may be in the 100-280 nm range. In such an example, the device may be a sterilization indicator and / or a germicidal indicator.

[0052] The colorimetric indicator may have a first state associated with a first color. The first state and / or first color may be associated with the absence of a color change. For example, the first state and / or first color may be associated with the absence of exposure of the indicator to trigger radiation or below a predetermined activation level and / or threshold activation level, e.g., 0.1 mJ / cm. 2 Less than, for example, 0.5 mJ / cm 2 Less than, for example, 1 mJ / cm 2 The indicator may be associated with exposure to a triggering radiation of less than 1000 .mu.m.

[0053] The colorimetric indicator may have a second state associated with a second color. The second state and / or second color may be associated with a full or final color change. For example, the second state and / or second color may occur upon full exposure of the indicator to trigger radiation or upon exceeding a predetermined activation level and / or upper activation level, e.g., 0.1 mJ / cm. 2 exceeding, for example, 0.5 mJ / cm 2 Less than, for example, 1 mJ / cm 2 The indicator may be associated with exposure to a triggering radiation of less than 1000 .mu.m.

[0054] The colorimetric indicator may have one or more intermediate states, each associated with a corresponding intermediate color. The one or more intermediate states and / or one or more intermediate colors may be or include one or more states and / or colors between a first state and / or color and a second state and / or color. Each intermediate state and / or color may be associated with exposure to a predetermined level or amount of triggering radiation.

[0055] Each of the first state and / or first color, one or more intermediate states and / or one or more intermediate colors, and the second state and / or second color may correspond to or be associated with exposure to a predetermined level or amount of trigger radiation.

[0056] The device may further include at least one additional reference color region. This at least one additional reference color region may correspond to any of the first color, the second color, and the neutral color. Such an embodiment may allow a user or observer, in use, to obtain an additional visual assessment by comparing the color of the indicator or the first layer (e.g., the first region thereof) with the color of the at least one additional reference color region. In embodiments, the at least one additional reference color region may be configured to substantially match the color of the indicator of the second (active) portion. Such an embodiment may provide a further reference region in addition to the reference region defined by the second portion of the device and / or the active portion of the second layer.

[0057] Embodiments of the present disclosure will now be given, by way of example only, and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0058] [Figure 1] 1 is a schematic diagram of a device according to a first embodiment. [Figure 2] FIG. 10 is a schematic view of a device according to a second embodiment. [Figure 3]FIG. 10 is a schematic view of a device according to a third embodiment. [Figure 4] 2A-2C are diagrams of the device of FIG. 1 when exposed to different doses of radiation. DETAILED DESCRIPTION OF THE INVENTION

[0059] With reference to Figure 1, an indicator device, generally designated 5, according to a first embodiment is shown.

[0060] The device 5 includes a substrate 10. In this embodiment, the substrate 10 is in the form of a film.

[0061] The device has a first layer 20 that includes a colorimetric indicator. The first layer 20 is provided on the top side of the substrate 10, i.e., the side of the substrate that is configured to face the illumination source, in use.

[0062] A first portion 21 of the first layer 20, in this embodiment the peripheral portion 21, is exposed to the environment on its top side, i.e., opposite the substrate 10. Thus, when the indicator in the first layer 20 is exposed to triggering radiation, this causes a color change in the indicator in the first layer.

[0063] A second portion 22 of the first layer 20, in this embodiment the central portion 22, is covered by a second layer 30. In this embodiment, the second layer 30 is a coating or varnish.

[0064] The coating 30 includes a radiation absorber that blocks or absorbs the trigger radiation to which the indicator responds. In this embodiment, the radiation absorber was phenol benzotriazole.

[0065] The second layer 30 is substantially transparent to visible light, allowing a user to observe the second portion 22 of the first layer through the second layer.

[0066] In use, before the device 5 is exposed to the radiation source 40, the color of the first portion 21 of the first layer 20 that does not include the coating 30 and the color of the second portion 22 that is covered by the coating 30 will match perfectly to an observer because the entire first layer 20 contains the same indicator.

[0067] After the device is exposed to radiation 40, the indicator not covered by coating 30 reacts in first portion 21 of first layer 20, resulting in a color change. Second portion 22 therefore acts as a reference portion, allowing a user to detect a color change in first portion 21 after exposure to a low level or dose of trigger radiation 40, for example, after exposure to a level or dose of trigger radiation 40 that is lower than the minimum dose at which a color change in the indicator would normally be detected.

[0068] Referring to Figure 2, there is shown an indicator device according to a second embodiment, generally designated by the numeral 105. Indicator device 105 is generally similar to indicator device 5 of Figure 1, with like components being designated by like numerals, but with the addition of 100.

[0069] In this embodiment, the second layer 130 is a self-supporting layer that is laminated onto the first layer 120. The second layer has a first portion 131 on the outside and a second portion 132 on the inside.

[0070] First portion 131 of second layer 130 defines an inactive portion of second layer 130 and is substantially transparent to visible light and to triggering radiation 140 to which the indicator in first layer 120 is sensitive. Thus, the first portion does not affect how first layer 120 responds to triggering radiation 140.

[0071] A second portion 132 of the second layer 130 defines an active portion of the second layer 130. The active portion 132 is substantially transparent to visible light but includes a radiation absorber that absorbs or blocks trigger radiation 140 to which the indicator is sensitive.

[0072] In use, before the device 105 is exposed to the irradiation source 140, the color of the first portion 121 of the first layer 120 that is covered by the inactive portion 131 of the second layer 130 and the color of the second portion 122 that is covered by the active portion 132 or the second layer 130 will match perfectly to an observer because the entire first layer 120 contains the same indicator.

[0073] After the device 105 is exposed to radiation 140, the indicator covered by the inactive portion 131 of the second layer 130 reacts in the first portion 121 of the first layer 120, resulting in a color change. The second portion 122 therefore acts as a reference portion, allowing a color change in the first portion 121 to be detected after exposure to a low level or dose of trigger radiation 140, for example, after exposure to a level or dose of trigger radiation 140 that is lower than the minimum dose that would normally allow a user to detect a color change in the indicator.

[0074] Figure 3 shows a third embodiment of an indicator device generally designated by the numeral 205. Indicator device 205 is generally similar to indicator device 105 of Figure 2, with like components designated by like numerals, but with the increment 100.

[0075] In this embodiment, the second layer 230 is also a self-supporting layer laminated onto the first layer 220. However, in this embodiment, the second layer 230 has an outer first portion 231 that covers only a portion of the first layer 220.

[0076] Thus, first portion 221 of first layer 220 has a coated area 221a that is covered by inactive portion 231 of the second layer, and an uncoated area 221b. Because inactive portion 231 of second layer 230 is substantially transparent to visible light and to triggering radiation 240 to which the indicator of first layer 220 is sensitive, first portion 221 of first layer 220 responds to radiation 240 in the same manner in its coated and uncoated areas 221a and 221b.

[0077] Referring to Figure 4, a diagram of an apparatus 305 as generally described in Figure 1 is shown when exposed to different doses of radiation. In this embodiment, the apparatus 305 includes a UVC indicator in a first layer 320, with a central portion of the first layer covered by a coating 330 including a UVC radiation absorber. In this embodiment, the UVC indicator included thymol blue as a pH indicator, sodium hydroxide and diphenyliodonium chloride (DPIC) as photoacid generators, and poly(vinyl butyral) as a binder.

[0078] The coating was Fujifilm APR VA401.

[0079] In this embodiment, five fixtures 305a, 305b, 305c, 305d, 305e each emit a respective dose of UVC radiation, namely 2, 4, 6, 8, 10 mJ / cm 2 was exposed to.

[0080] Samples 305a and 305b show 2 and 4 mJ / cm 2 It can be seen that none of the doses of radiation were sufficient to cause any visible change in the first (indicator) layers 320a and 320b.

[0081] However, sample 305c had a luminance of 6 mJ / cm 2 1 shows that a visible color change can be visually detected in a first portion of the first layer 320c when exposed to a UVC irradiance of 6 mJ / cm. The central portion of the first layer 320c is coated with a second layer 330c containing a UVC absorber, and therefore serves as a reference portion that maintains the color of the indicator in an unexposed state. As a result, the color change of the first layer 320c in the portion adjacent to the second (central) layer 330c is smaller than that which would otherwise occur at 6 mJ / cm. 2 This makes the color change much more easily detectable by an observer who may not have been able to reliably and confidently detect that a color change had occurred after exposure to light.

[0082] 8 mJ / cm from samples 305d and 305e, respectively. 2 , and 10 mJ / cm 2 After exposure at 100° C., it is confirmed that the color change of the indicators of the first layers 320d and 320e is more pronounced.

[0083] It should be understood that the described embodiments are not intended to limit the scope of the invention, and that the invention may be practiced otherwise than as described.

Claims

1. A first layer including a colorimetric indicator including a UV indicator; a second layer disposed on at least a portion of the first layer; the first layer includes a first portion and a second portion adjacent to the first portion; at least a portion of the second layer defines an active portion and is configured to block and / or absorb radiation when exposed to radiation to which the indicator is sensitive or responsive so as to prevent a color change in the second portion of the first layer, and the active portion is configured to be substantially transparent to visible light; the second portion of the first layer is covered by the active portion of the second layer; wherein the first portion of the first layer is either uncovered by the second layer or covered by an inactive portion of the second layer, the inactive portion being substantially transparent to both visible light and to radiation to which the indicator is sensitive.

2. the second layer includes at least one inactive portion, the at least one inactive portion being substantially transparent to both visible light and radiation to which the indicator is sensitive; 10. The device of claim 1.

3. one or more active portions of the second layer are transparent to radiation in the range of about 400 to 800 nm; 3. The device of claim 1 or 2.

4. the active portion of the second layer comprises a radiation absorber configured to absorb the radiation; 4. An apparatus according to any one of claims 1 to 3.

5. the second layer comprises a coating; 5. An apparatus according to any one of claims 1 to 4.

6. the second layer is disposed only on the second portion of the first layer; 6. The device of claim 5.

7. The coating is provided in the form of a varnish.

7. The device according to claim 5 or 6.

8. the first layer comprises a solvent-based composition; 8. An apparatus according to any one of claims 1 to 7.

9. the second layer comprises a solvent-based composition; 9. An apparatus according to any one of claims 1 to 8.

10. the second layer includes a self-supporting layer, and the self-supporting layer may be a film; 5. An apparatus according to any one of claims 1 to 4.

11. The second layer is laminated onto the first layer.

11. The device of claim 10.

12. an adhesive is provided between the second layer and the first layer; 11. The device of claim 10.

13. the second layer is disposed only on a second portion of the first layer, the second layer defining or corresponding to an active portion; 13. An apparatus according to any one of claims 10 to 12.

14. the second layer is provided on both at least a part of the first portion and the second portion of the first layer, and the second layer includes corresponding first and second portions; 13. An apparatus according to any one of claims 10 to 12.

15. a first portion of the second layer defining an inactive portion and a second portion of the second layer defining an active portion; 15. The device of claim 14.

16. the first layer has a thickness of at least 0.1 mm; 16. An apparatus according to any one of claims 1 to 15.

17. The device is provided as a wearable article.

17. An apparatus according to any one of claims 1 to 16.

18. the colorimetric indicator is a UVA and / or UVB indicator; 18. An apparatus according to any one of claims 1 to 17.

19. the colorimetric indicator is a UVC indicator; 18. An apparatus according to any one of claims 1 to 17.

20. the device further comprising at least one additional reference color region; 20. An apparatus according to any preceding claim.

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