MULTILAYER COLOURIMETRIC INDICATOR

Abstract

An apparatus 5 comprises a first layer 20 comprising a colourimetric indicator; and a second layer 30 provided on at least a portion 22 of the first layer 20, at least a portion of the second layer 30 being configured to block and/or absorb a radiation to which the indicator is sensitive or reactive and being configured to be substantially transparent to visible light.

Claims

1. An apparatus comprising: a first layer comprising a colourimetric indicator; and a second layer provided on at least a portion of the first layer, at least a portion of the second layer being configured to block and/or absorb a radiation to which the indicator is sensitive or reactive and being configured to be substantially transparent to visible light.

2. An apparatus according to claim 1, wherein the portion(s) of the second layer being configured to block and/or absorb a radiation to which the indicator is sensitive and being configured to be substantially transparent to visible light, define(s) an active portion or active portions.

3. An apparatus according to claim 1, wherein the second layer comprises at least one passive portion, wherein the at least one passive portion is substantially transparent both to visible light and to a radiation to which the indicator is sensitive.

4. An apparatus according to claim 1, wherein the active portion(s) of the second layer is transparent to radiations in the region of about 400-800 nm.

5. An apparatus according to claim 1, wherein the first layer comprises a first portion and a second portion.

6. An apparatus according to claim 5, wherein the first portion is not covered by the second layer, or is covered by a/the passive portion of the second layer.

7. An apparatus according to claim 5, wherein the second portion is covered by an/the active portion of the second layer.

8. An apparatus according to claim 1, wherein an/the active portion of the second layer comprises a radiation absorber configured to absorb the trigger radiation.

9. An apparatus according to claim 1, wherein the second layer comprises a coating.

10. An apparatus according to claim 9, wherein the second layer is provided only on the second portion of the first layer.

11. An apparatus according to claim 9, wherein the coating is provided in the form of a varnish.

12. An apparatus according to claim 1, wherein the first layer or the second layer comprises a solvent-based composition.

13. (canceled)

14. An apparatus according to claim 1, wherein the second layer comprises a self-supporting layer, optionally a film.

15. An apparatus according to claim 14, wherein the second layer is laminated on the first layer, or wherein an adhesive is provided between the second layer and the first layer.

16. (canceled)

17. An apparatus according to claim 14, wherein the second layer is provided only on the second portion of the first layer, and the second layer defines or coincides with the active portion.

18. An apparatus according to claim 14, wherein the second layer is provided both on at least part of the first portion and on the second portion of the first layer, and the second layer comprises a corresponding first portion and second portion, and wherein the first portion of the second layer defines the passive portion, and wherein the second portion of the second layer defines the active portion.

19. (canceled)

20. An apparatus according to claim 1, wherein the first layer has a thickness of at least 0.1 mm.

21. An apparatus according to claim 1, wherein the apparatus is provided as a wearable article.

22. An apparatus according to claim 1, wherein the colourimetric indicator is a UVA and/or a UVB indicator, or wherein the colourimetric indicator is a UVC indicator.

23. (canceled)

24. An apparatus according to claim 1, wherein the apparatus further comprises at least one additional reference colour region.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0059] Embodiments of the present disclosure will now be given by way of example only, and with reference to the accompanying drawings, which are:

[0060] FIG. 1 a schematic view of an apparatus according to a first embodiment;

[0061] FIG. 2 a schematic view of an apparatus according to a second embodiment;

[0062] FIG. 3 a schematic view of an apparatus according to a third embodiment;

[0063] FIG. 4 images of an apparatus of FIG. 1, when exposed to different doses of irradiation.

DETAILED DESCRIPTION

[0064] Referring to FIG. 1 there is shown an indicator apparatus, generally designated 5, according to a first embodiment.

[0065] The apparatus 5 includes a substrate 10. In this embodiment, the substrate 10 is in the form of a film.

[0066] 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, in use.

[0067] A first portion 21, in this embodiment a peripheral portion 21, of the first layer 20, is exposed to the environment on its upper side, that is, on a side opposite the substrate 10. Thus, when the indicator in the first layer 20 is exposed to a trigger radiation, this will cause a colour change in the indicator of the first layer.

[0068] A second portion 22, in this embodiment a central portion 22, of the first layer is covered, by a second layer 30. In this embodiment the second layer 30 is a coating or varnish.

[0069] The coating 30 includes a radiation absorber which blocks or absorbs the trigger radiation to which the indicator is reactive. In this embodiment, the radiation absorber was a phenolic benzotriazole.

[0070] 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.

[0071] In use, before exposure of the apparatus 5 to a source of irradiation 40, the colour of the first portion 21 in the first layer 20 which is free of coating 30 and of the second portion 22 covered by the coating 30 are a perfect match to an observer, since the entire first layer 20 includes the same indicator.

[0072] Following exposure of the apparatus to radiation 40, the indicator which is not covered by the coating 30 reacts in the first portion 21 of the first layer 20 and changes colour as a result. The second portion 22 thus acts as a reference portion, and allows detection of a colour change in the first portion 21 after exposure to a low level or dose of trigger radiation 40, e.g. after exposure to a level or dose of trigger radiation 40 which is lower than the minimum dose at which a user would normally be able to detect a colour change in the indicator.

[0073] Referring to FIG. 2 there is shown an indicator apparatus, generally designated 105, according to a second embodiment. The indicator apparatus 105 is generally similar to the indicator apparatus 5 of FIG. 1, like parts denoted by like numerals, incremented by ‘100’.

[0074] In this embodiment, the second layer 130 is a self-supported layer which is laminated on top of the first layer 120. The second layer has a first, outer, portion 131 and a second, inner, portion 132.

[0075] The first portion 131 of the second layer 130 defines a passive portion of the second layer 130, and is substantially transparent to visible light and to the trigger radiation 140 to which the indicator in the first layer 120 is sensitive. The, thus first portion does not affect how the first layer 120 reacts to a trigger radiation 140.

[0076] The 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 which absorbs or blocks the trigger radiation 140 to which the indicator is sensitive.

[0077] In use, before exposure of the apparatus 105 to a source of irradiation 140, the colour of the first portion 121 in the first layer 120 which is covered by the passive portion 131 of second layer 130 and of the second portion 122 which is covered by the active portion 132 or the second layer 130 are a perfect match to an observer, since the entire first layer 120 includes the same indicator.

[0078] Following exposure of the apparatus 105 to radiation 140, the indicator which is covered by the passive portion 131 of the second layer 130 reacts in the first portion 121 of the first layer 120 and changes colour as a result. The second portion 122 thus acts as a reference portion, and allows detection of a colour change in the first portion 121 after exposure to a low level or dose of trigger radiation 140, e.g. after exposure to a level or dose of trigger radiation 140 which is lower than the minimum dose at which a user would normally be able to detect a colour change in the indicator.

[0079] FIG. 3 shows a third embodiment of an indicator apparatus, generally designated 205. The indicator apparatus 205 is generally similar to the indicator apparatus 105 of FIG. 2, like parts denoted by like numerals, incremented by ‘100’.

[0080] In this embodiment, the second layer 230 is also a self-supported layer which is laminated on top of the first layer 220. However, in this embodiment, the second layer 230 has a first, outer, portion 231 which only covers part of the first layer 220.

[0081] As such the first portion 221 of the first layer 220 has a covered region 221a which is covered by the passive portion 231 of the second layer, and an uncovered region 221b. Because the passive portion 231 of the second layer 230 is substantially transparent to visible light and to the trigger radiation 240 to which the indicator in the first layer 220 is sensitive, the first portion 221 of the first layer 220 will react to irradiation 240 in the same manner in its covered region 221a and in its uncovered region 221b.

[0082] Referring to FIG. 4, there is shown an image of an apparatus 305 as generally described in FIG. 1, when exposed to different doses of irradiation. In this embodiment, the apparatus 305 includes a UVC indicator in its first layer 320, and a central portion of the first layer is covered by a coating 330 which includes a UVC radiation absorber. In this embodiment, the UVC indicator contained Thymol Blue as pH indicator, NaOH, diphenyliodonium chloride (DPIC) as photo-acid generator, and Poly(vinyl butyral) as a binder.

[0083] The coating was Fujifilm APR VA401.

[0084] In this embodiment each of the five apparatuses 305a, 305b, 305c, 305d, 305e was exposure to a respective dose of UVC radiation, namely 2, 4, 6, 8, and 10 mJ/cm.sup.2, respectively.

[0085] It can be seen from samples 305a and 305b that an irradiation dose of 2 or 4 mJ/cm.sup.2 was not sufficient to trigger a visible change in the first (indicator) layer 320a and 320b, respectively.

[0086] However, sample 305c shows that a visible change in colour can be detected visually in the first portion of the first layer 320c when exposure to a UVC dose of 6 mJ/cm.sup.2. The central portion of the first layer 320c is coated with second layer 330c which contains a UVC absorber, and therefore acts as a reference portion which maintains the colour of the indicator in a non-exposed state. As a result, the change of colour in the first layer 320c in the portion adjacent the second (central) layer 330c is much more easily detectable by an observer, which might not otherwise be able to detect reliably and confidently that a change of colour had taken place after exposure at 6 mJ/cm.sup.2.

[0087] Samples 305d and 305e confirm a sharper change of colour in the indicator of the first layer 320d 320e, after exposure to 8 mJ/cm.sup.2 and 10 mJ/cm.sup.2, respectively.

[0088] It will be appreciated that the described embodiments are not meant to limit the scope of the present invention, and the present invention may be implemented using variations of the described examples.