Indicator device

Abstract

There is described an indicator device having indicator section that displays different visible properties in response to an activating agent, a barrier section that mitigates migration of the activating agent from the indicator section, and a contrast section that enhances the display of the different visible properties of the indicator section. The contrast section is at least semi-permeable to the activating agent so that the contrast section allows the movement of the activating agent to the indicator section. The activating agent may be carbon dioxide gas. Also described is a package or packaging comprising the indicator device, and a tape or film comprising the indicator device. There is also described a method of detecting the presence of an activating agent, and a method of detecting whether a sealed package has been compromised.

Description

[0001] INDICATOR DEVICE

[0002] Field of Invention

[0003] The present invention relates to an indicator device, a method for preparing an indicator device, and products derived therefrom. In particular, the present invention relates to a laminated indicator device comprising an indicator section that is sensitive to presence or absence of an activating agent. The products derived therefrom may include, for example, a multilayer adhesive tape or label, which (once activated) can be used to detect or report the presence of an activating agent. The indicator device can also be used to show that packaging has been compromised and / or that a device has been compromised. The indicator device can be used to detect oxidising agents, oxygen, water, reducing agents, UV light, carbon dioxide, amines, or ammonia.

[0004] A further example of the use of the indicator device is as a freshness indicator, for example, the freshness of food products. Perishable goods, and in particular drinks and foodstuffs, are often provided in some form of air-tight packaging. This packing can be applied in a modified atmosphere (known as modified atmosphere packaging (MAP)), which limits the presence of oxygen and which often involves purging the packaging with carbon dioxide. Alternatively, perishable goods may be packaged in normal atmospheric conditions.

[0005] Items that are packaged in air-tight packaging include: food, beverages, works of art, pharmaceuticals, medical diagnostic kits and sterilised packages. It is particularly desirable in the food industry to package goods such that their exposure to atmospheric conditions (and in particular, oxygen) after packaging is minimised. This can be used to effectively extend the shelf life of many perishable items. Background Art

[0006] The transport of gases in an industrial or commercial setting typically involves the flow of gases through pipes or tubes having valves, joins or other types of connections. For safety, gas detection frequently uses electronic monitoring devices to detect the presence of gases in undesirable concentrations. The device is normally placed within a room or other enclosed area, and a sensor detects the presence of a specific gas. The gases are usually hazardous to the health and safety of people working in the environment e.g. carbon monoxide or carbon dioxide. In operation, the sensor in the gas detection device will detect the presence of the gas above a set limit, and sound an alarm.

[0007] While electronic monitoring devices can detect the presence of a particular gas, they do not assist in locating the source of a leak from a pipe, tube, valve, join or connector.

[0008] Therefore, it is an object of the present invention to obviate or mitigate at least some of the disadvantages of the prior art.

[0009] It is a further object of the present invention to provide an indicator device that can be applied to pipes or hoses that transport gases, or valves, joins or connectors in such pipes or hoses. The indicator device can be used to detect and immediately locate the source of a leak of the gas being transported. The indicator device may be used, for example, in breweries, distilleries, pubs, restaurants, or laboratories. The indicator device may be also used with equipment, such as refrigeration units.

[0010] A further object of the invention is to provide an indicator device that can be applied to perishable goods such as food or drink and / or associated packaging, pharmaceuticals or chemical reagents and / or associated packaging, or any item where it is desirable to detect that the item has been opened.

[0011] Further objects of the invention are to provide a method for preparing an indicator device, and a method of detecting atmospheric conditions (such as oxygen, water, UV light, carbon dioxide, amines or ammonia) using an indicator device.

[0012] Definitions

[0013] The term “about” or “approximately” means an acceptable error for a particular value as determined by a person of ordinary skill in the art, which depends in part on how the value is measured or determined. The term “about” or “approximately” may mean within 1 , 2, 3 or 4 standard deviations. The term “about” or “approximately” may mean within 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.5% of a given value or range.

[0014] Unless otherwise specified, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description of the application and the appended claims, the singular forms “a,” “an,” and “the” are inclusive of their plural forms, unless contradicted by the context surrounding such.

[0015] The term “consisting” is closed and excludes additional, unrecited elements or method steps in the claimed invention.

[0016] The term “consisting essentially of” is semi-closed and occupies a middle ground between “consisting” and “comprising”. “Consisting essentially of” does not exclude additional, unrecited elements or method steps which do not materially affect the essential characteristic(s) of the claimed invention.

[0017] The term “comprising” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps in the claimed invention. The term is synonymous with “including but not limited to”. The term “comprising” encompasses three alternatives, namely (i) “comprising”, (ii) “consisting”, and (iii) “consisting essentially of”.

[0018] The terms “flexographic ink” or “flexographic dye” mean an ink or dye which is suitable for use in a flexographic printing process.

[0019] A flexographic printing process is a form of rotary printing in which an ink or dye is applied to various surfaces by means of flexible rubber (or other elastomeric) printing plates.

[0020] The term “thickness” means the distance through a section or layer. The term “thickness” may be referred to as “caliper”.

[0021] The thickness of a section or layer may be measured using an electronic micrometer. An example of a suitable electronic micrometer includes but is not limited to a Mitutoyo Digital Micrometer IP65, which measures thicknesses in the range of 0-1 inch, and has a digital step of 0.00005 inches (0.001 mm). In use, the anvil and spindle of the digital micrometer close on the section or layer being measured to apply a measuring force of 5-10 N i.e. the measuring force range / tolerance of the device has a reading Newton force / tolerance of between 5-1 ON.

[0022] The thickness of plastic films may be determined using ASTM standard D6988. Brief Description of the Figures

[0023] Certain aspects of the embodiments described herein may be more clearly understood by reference to the drawings, which is intended to illustrate but not limit, the invention, and wherein:

[0024] Figure 1 is a cross section of an indicator device according to the invention.

[0025] Figure 2 shows a representative laminated tape according to the invention applied to connectors in pipework. In the absence of an activating agent (e.g. carbon dioxide gas), the laminated tape has a first colour (e.g. purple).

[0026] Figure 3 shows a representative laminated tape according to the invention applied to connectors in pipework. In the presence of an activating agent (e.g. carbon dioxide gas), the laminated tape has a second colour (e.g. yellow) at the points at which the pipework is leaking.

[0027] Figure 4 is a cross section of an indicator device according to the invention.

[0028] Figure 5 is a cross section of an indicator device according to the invention.

[0029] Disclosure of the Invention

[0030] In one aspect, the present invention provides an indicator device comprising: an indicator section comprising an indicator material that displays different visible properties in response to the presence or absence of an activating agent; a barrier section comprising a barrier layer that mitigates migration of the activating agent from the indicator section; a contrast section comprising a contrast material; wherein the indicator section is located between the barrier section and the contrast section; wherein the contrast section enhances the display of the different visible properties of the indicator section; wherein the contrast section is configured to be at least semi- permeable to the activating agent such that the contrast section allows the movement of the activating agent to the indicator section; and wherein the activating agent effects a change in the visible properties of the indicator material.

[0031] The indicator device may be a laminate, or multi-layered, product.

[0032] The indicator material may be part of a composition. Depending on the nature of the indicator material, the indicator material, or indicator composition, may be activated by UV light, a reducing agent, an oxidising agent, carbon dioxide, a base, an alkali or an acid, such as carbon dioxide gas.

[0033] The indicator device may be configured to detect a change (increase or decrease) in the amount (i.e. , the concentration) of any of the activating agent in the device, or a change in pH.

[0034] The indicator material may display different visible properties in response to a predetermined minimum concentration of the activating agent. The predetermined minimum concentration of the activating agent may be established by assessing the visible detectable change of the indicator material against known amounts (e.g. concentrations), or against known pHs, of the activating agents.

[0035] Visible properties of the indicator material relate to the colour of the indicator material. The difference in the visible properties of the indicator material is a change of colour from a first colour to a second colour. The first colour is indicative of the absence of the activating agent, and the second colour is indicative of the presence of the activating agent. The enhancement of visible properties is the enhancement of at least one of the first colour and the second colour, typically the second colour (in the presence of activating agent).

[0036] The change in the visible properties of the indicator material is typically reversible. In this respect, the indicator device may change from a first colour (indicative of the absence of the activating agent) to a second colour (indicative of the presence of the activating agent), and then back to the first colour (indicative of the absence of the activating agent), and so on. In this way, the presence or absence of the activating agent may be monitored in real time by a user of the indicator device by assessing the colour of the indicator device.

[0037] The indicator section may comprise a substrate material.

[0038] The indicator material may be incorporated into a discrete indicator layer and the substrate material is incorporated into a discrete substrate layer, separate to the indicator layer. The substrate layer may have a thickness of between approximately 12 pm and approximately 100 pm.

[0039] The substrate material may be selected from one or more of the group consisting of: aluminium oxide foil, polypropylene, polyethylene terephthalate, and polyethylene.

[0040] The substrate material may be polyethylene.

[0041] The indicator layer may have a thickness of between approximately 1 pm and approximately 3 pm.

[0042] The indicator material may comprise a polymer binder selected from one or more of the group consisting of: polyvinyl butyral (PVB), nitrocellulose (NC), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), polyethylene glycol (PEG) and polyethylenimine (PEI).

[0043] The indicator material may comprise a polymer binder selected from one or more of the group consisting of: polyvinyl butyral (PVB), hydroxypropyl cellulose (HPC), polyethylene glycol (PEG) and polyethylenimine (PEI).

[0044] The indicator layer may comprise a plasticiser.

[0045] The plasticiser may be selected from one or more of the group consisting of: tributyl phosphate, diisodecyl adipate, tris-2-ethylhexyl phosphate, tributyl phosphate, glycerol and dimethyl phthalate.

[0046] The indicator material and the substrate material may be incorporated into the same layer so-forming a combined indicator and substrate layer, and wherein the indicator material is dispersed within the substrate material or vice versa.

[0047] The combined indicator and substrate layer may comprise a polymer composite, said polymer composite comprising at least one thermoplastic polymer, and at least one chemical indicator dispersed in the at least one thermoplastic polymer, the at least one chemical indicator comprising a particulate inorganic substrate, and at least one indicator material, reactive dye or ink coated on and / or impregnated within the particulate inorganic substrate.

[0048] The combined indicator and substrate layer may have a thickness of between approximately 30 pm and approximately 100 pm.

[0049] The indicator material may be selected from one or more of the group consisting of: a redox sensitive material, a carbon monoxide sensitive material, a carbon dioxide sensitive material, an oxygen sensitive material, an amine sensitive material, an ammonia sensitive material, a pH sensitive material, and an acid sensitive material.

[0050] The pH sensitive material may be selected from one or more of the group consisting of: m-Cresol Purple (MCP, Hydroxy triarylmethane), Thymolphthalein (3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2- benzofuran-1 -one), o-Cresolphthalein (3,3-Bis(4-hydroxy-3-methylphenyl)- 1 (3H)-isobenzofuranone), Acryloly florescein (AcF1 ), 13-methyl umbelliferon (BMLIB), Bromothymol blue (BTB, Hydroxy triarylmethane), 5' and 6-Carboxyseminaphtholfluorescein (c-SNAFL), 5' and 6'- Carboxyseminaphtholrhodamine (c-SNARF), Cresol Red (CR, o- Cresolsulfonephthalein), 2-(2,4-Dinitrophenylaxo)-1 -naphthol- 3,6- disulphonic acid (DNPA), tris(thenoyltrifluoroacetonato) europium (III) (Eu(tta)1 ), Fluorescein (Fl, resorcinolphthalein), 7-hydroxycoumarin-4- acetic acid (HCA), 1 , Hydroxypyrene-3,6,S-trisulphonic acid (HPTS), Neutral red (NR, toluylene red), Phenol Red (PR, phenolsulfonphthalein), Rhodamine 6G (R6G), Sulforhodamine 101 (SRh), Thymol blue (TB, thymolsulphonephthalein), Texas Red hydrazine (THR), Phenolphthalein (3,3-bis(4-hydroxyphenyl)isobenzofuran-1 (3H)-one), Thymol blue, Phenoltetraiodophthalein, Phenoltetrachlorophthalein, a-Naphtholbenzein and p-Xylenol blue.

[0051] The pH sensitive material may be selected from one or more of the group consisting of: Phenol Red (PR, phenolsulfonphthalein), m-Cresol Purple (MCP, Hydroxy triarylmethane) and Cresol Red (CR, o- Cresolsulfonephthalein).

[0052] The pH sensitive material may be selected from Cresol Red (CR, o- Cresolsulfonephthalein).

[0053] The pH sensitive material may have a pKa value equal to or greater than approximately 7.9.

[0054] The pH sensitive material may have a pKa equal to or greater than approximately 8.3, for example, equal to or greater than approximately 8.32.

[0055] The pH sensitive material may have a pKa value of between approximately 7.9 and approximately 8.3, for example, between approximately 7.9 and approximately 8.32.

[0056] The pH sensitive material may be an acid sensitive material. The activating agent may be at least one of an oxidising agent, water, carbon dioxide, amines, acids, carboxylic acids, ammonium hydroxide and ammonia.

[0057] The activating agent may be gaseous. The activating agent may be liquid.

[0058] The activating agent may be carbon dioxide gas.

[0059] When the indicator device is used as food freshness indicator, the activating agent may be a volatile organic acid. In this respect, volatile acids can be generated when food spoils.

[0060] The volatile organic acid may be selected from the group consisting of: formic acid, ethanoic acid, propanoic acid, n-butanoic acid, i-butanoic acid, valeric acid (n-pentanoic acid), 2-methylbutryric acid, isovaleric acid (3- methylbutrylic acid), pivalic acid (2,2-dimethylpropionic acid), and a combination thereof.

[0061] The indicator section may further comprise a first adhesive layer. The adhesive in the first adhesive layer is not particularly limited provided it does not adversely affect the contrast section, the indicator section, or the indicator device.

[0062] The first adhesive layer may be located between the contrast section and the indicator material, and wherein the first adhesive layer is at least semi-permeable to the activating agent such that the first adhesive layer allows the movement of the activating agent from the contrast layer to the indicator material, and wherein the activating agent effects a change in the visible properties of the indicator material. The first adhesive layer may be permeable to the activating agent such that the adhesive layer allows unrestricted movement of the activating from the contrast layer to the indicator section.

[0063] The first adhesive layer may be formed from an adhesive which is water- soluble. In this respect, the adhesive forming the first adhesive layer may not comprise an adhesive which is solvent-soluble. Without wishing to be bound by theory, it is believed that solvent-soluble adhesives are acidic.

[0064] The first adhesive layer may be formed from an adhesive which is pH neutral, or the first adhesive layer may be formed from an adhesive which has an alkaline pH. In this respect, the adhesive forming the first adhesive layer may not be an adhesive which is acidic. Without wishing to be bound by theory, it is believed that adhesives that are acidic adversely react with the indicator layer causing it to turn permanently one colour.

[0065] For example, when the indicator material is cresol red, an acidic adhesive adversely affects the cresol red indicator causing it to turn permanently yellow.

[0066] The first adhesive layer may be formed from an acrylic adhesive which is water-soluble and pH neutral. The first adhesive layer may be formed from an acrylic adhesive which is water-soluble and has an alkaline pH. The first adhesive layer may be formed from an acrylic adhesive which is water-soluble and has a pH in the range of approximately pH 7 to approximately pH 7.5.

[0067] The first adhesive layer may be selected from one or more (e.g. 1 , 2, 3, 4, or 5) of the group consisting of: an acrylic adhesive, a treated permanent acrylic, a coated permanent acrylic, a treated peelable acrylic, a coated peelable acrylic, a UV curing adhesive, a pressure sensitive adhesive, and UV curable pressure sensitive adhesive.

[0068] The first adhesive layer may be selected from one or more of the group consisting of an acrylic adhesive, and a coated permanent acrylic adhesive.

[0069] The first adhesive layer may have a thickness of between approximately 15 pm and approximately 50 pm, such as approximately 15 pm and approximately 30 pm. The thickness of the first adhesive layer affects the adhesiveness of the indicator device to a substrate surface. In this respect, a greater adhesive effect is seen when the thickness of the first adhesive layer increases, and vice versa. If desired, the first adhesive layer may be greater than approximately 50 pm. However, there does not appear to be a corresponding increase in adhesiveness when the thickness of the first adhesive layer is greater than approximately 50 pm.

[0070] A first adhesive layer having a thickness of less than approximately 15 pm may not exhibit sufficient adhesiveness to a substrate surface, particularly in combination with the contrast section as the contrast section also reduces the adhesiveness of the first adhesive layer.

[0071] The first adhesive layer may be located adjacent to the indicator section and arranged such that it covers at least the indicator section, thereby sealing the indicator section.

[0072] The indicator section may further comprise a second adhesive layer. The adhesive in the second adhesive layer is not particularly limited provided it does not adversely affect the contrast section, the indicator section, or the indicator device. When the indicator material is incorporated into a discrete indicator layer and the substrate material is incorporated into a discrete substrate layer, separate to the indicator layer, the second adhesive layer may be located between the discrete indicator layer and the discrete substrate layer, and wherein the second adhesive layer is at least semi-permeable to the activating agent such that the second adhesive layer allows the movement of the activating agent from the contrast layer to the discrete indicator layer, and wherein the activating agent effects a change in the visible properties of the indicator material.

[0073] Alternatively, when the indicator material is incorporated into a discrete indicator layer and the substrate material is incorporated into a discrete substrate layer, separate to the indicator layer, the discrete indicator layer may be located between the second adhesive layer and the discrete substrate layer. The second adhesive layer may be at least semi- permeable to the activating agent such that the second adhesive layer allows the movement of the activating agent from the contrast layer to the discrete indicator layer, and wherein the activating agent effects a change in the visible properties of the indicator material.

[0074] The second adhesive layer may be permeable to the activating agent such that the adhesive layer allows unrestricted movement of the activating from the contrast layer to the indicator section.

[0075] The second adhesive layer may be formed from an adhesive which is water-soluble. In this respect, the adhesive forming the second adhesive layer may not comprise an adhesive which is solvent-soluble. Without wishing to be bound by theory, it is believed that solvent-soluble adhesives are acidic.

[0076] The second adhesive layer may be formed from an adhesive which is pH neutral, or the second adhesive layer may be formed from an adhesive which has an alkaline pH. In this respect, the adhesive forming the second adhesive layer may not be an adhesive which is acidic. Without wishing to be bound by theory, it is believed that adhesives that are acidic adversely react with the indicator layer causing it to turn permanently one colour. For example, when the indicator material is cresol red, an acidic adhesive adversely affects the cresol red causing it to turn permanently yellow.

[0077] The second adhesive layer may be formed from an acrylic adhesive which is water-soluble and pH neutral. The second adhesive layer may be formed from an acrylic adhesive which is water-soluble and has an alkaline pH. The second adhesive layer may be formed from an acrylic adhesive which is water-soluble and has a pH in the range of approximately pH7 to approximately pH 7.5.

[0078] The second adhesive layer may be selected from one or more (e.g. 1 , 2, 3, 4, or 5) of the group consisting of: an acrylic adhesive, a treated permanent acrylic, a coated permanent acrylic, a treated peelable acrylic, a coated peelable acrylic, a UV curing adhesive, a pressure sensitive adhesive, and UV curable pressure sensitive adhesive.

[0079] The second adhesive layer may be selected from one or more of the group consisting of an acrylic adhesive, and a coated permanent acrylic adhesive. The second adhesive layer may have a thickness of between approximately 15 pm and 50 pm, such as approximately 15 pm and approximately 30 pm.

[0080] The barrier section comprises a barrier layer that mitigates migration of the activating agent from the indicator section. The barrier section therefore may be impermeable or substantially impermeable to the activating agent. In this instance, the barrier section may trap the activating agent under its surface such that the activating agent effects a more effective visible change in the properties of the indicator material. The activating agent therefore is in contact with the indicator material for a longer period of time than if the barrier section were permeable and the activating agent permitted to disperse into the atmosphere.

[0081] The barrier section also mitigates or prevents substances external to the indicator device adversely affecting the indicator section. For example, the barrier section may prevent oils from the hands of a person handling the indicator device contacting the indicator section and adversely affecting its activity. Likewise, the barrier section may prevent other environmental chemicals contacting the indicator section and adversely affecting its activity. Environmental chemicals may include atmospheric gases, such as atmospheric oxygen or atmospheric carbon dioxide, which may interact with the indicator device and give a false-positive result.

[0082] The barrier section may be transparent or substantially transparent. Typically, the barrier section is transparent as this permits the visible properties of the indicator material, together with the enhanced display of the contrast section, to be more effectively viewed by an observer. The thickness of the barrier section is not particularly limiting but will depend on the final format of the indicator device. When the indicator device is a tape, the tape may be wound around a cylindrical core or upon itself into a roll. In this instance, the thickness of the barrier section may be selected such that the tape unwinds smoothly from the roll by the user but does not lift or unwind by itself.

[0083] When the indicator device is a label, it may be desirable for the label to have greater rigidity than a tape. As such, the thickness of the barrier section may be thicker than for a tape. Alternatively, it may be desirable for the label to be more flexible than a tape. In this instance, the thickness of the barrier section may be thinner than that of a tape.

[0084] The barrier section may have a thickness of between approximately 5 pm and approximately 100 pm.

[0085] The barrier section may have a thickness of between approximately 10 pm and approximately 50 pm, such as between approximately 15 pm and approximately 35 pm.

[0086] The barrier section may have a thickness of approximately 23 pm.

[0087] The barrier section may be larger in width than the indicator section in at least one axis.

[0088] The barrier section may be the same width as the indicator section in at least one axis. Alternatively, the barrier section may be substantially the same width as the indicator section in at least one axis. The barrier layer may be selected from one or more of the group consisting of: polyethylene terephthalate, ethylene vinyl alcohol, polyvinylidene chloride, polyvinyl acetate, polypropylene, polyester and aluminium oxide coated polyethylene terephthalate.

[0089] The barrier layer may be polyethylene terephthalate.

[0090] The barrier layer may comprise a release layer. When the indicator device is a tape, the tape may be wound around a cylindrical core or upon itself into a roll. Alternatively, the indicator device may be a label, and two or more labels applied one on top of another. In these instances, a release layer may prevent adhesives tacking to the barrier section of the tape or stickers. The release layer therefore assists both with the deployment of the tape or sticker, as well as the removal of them after use.

[0091] The barrier layer may comprise a first major surface and a second major surface opposite the first major surface; the indicator layer comprises a first major surface and a second major surface opposite the first major surface; the first major surface of the barrier layer is oriented such that it faces the first major surface of the indicator section; the second major surface of the barrier layer comprises a release layer; and the release layer is adhered or substantially adhered to the second major surface of the barrier layer.

[0092] The release layer may be adhered or substantially adhered to the second major surface of the barrier layer during normal use of the indicator device.

[0093] The release layer may comprise silicone. The barrier layer may be polyethylene terephthalate and the release layer may comprise silicone.

[0094] The basis weight of the barrier layer is not particularly limiting but will depend on the final format of the indicator device. When the indicator device is a tape, the tape may be wound around a cylindrical core or upon itself into a roll. In this instance, the basis weight of the barrier layer may be selected such that the tape unwinds smoothly from the roll by the user but does not lift or unwind by itself.

[0095] When the indicator device is a label, it may be desirable for the label to have greater rigidity than a tape. As such, the basis weight of the barrier layer may be greater than for a tape. Alternatively, it may be desirable for the label to be more flexible than a tape. In this instance, the basis weight of the barrier layer may be less than for a tape.

[0096] The barrier layer may have a basis weight of in the range of approximately 10 to approximately 100 gsm (grams per square meter). The basis weight of the barrier layer may be in the range of approximately 20 to approximately 50 gsm. The basis weight of the barrier layer may be > approximately 10 gsm. The basis weight of the barrier layer may be > approximately 15 gsm. The basis weight of the barrier layer may be > approximately 20 gsm. The basis weight of the barrier layer may be > approximately 25 gsm. The basis weight of the barrier layer may be > approximately 30 gsm.

[0097] The basis weight of the barrier layer may be < approximately 100 gsm.

[0098] The basis weight of the barrier layer may be < approximately 90 gsm. The basis weight of the barrier layer may be < approximately 80 gsm. The basis weight of the barrier layer may be < approximately 70 gsm. The basis weight of the barrier layer may be < approximately 60 gsm. The basis weight of the barrier layer may be < approximately 50 gsm.

[0099] The basis weight of the barrier layer may be in the range of approximately 30 to approximately 35 gsm, such as approximately 32 gsm.

[0100] The barrier layer may be polyethylene terephthalate and have a basis weight in the ranges described above, and the release layer may comprise silicone. In particular, the barrier layer may be polyethylene terephthalate and have a basis weight of approximately 30 to approximately 35 gsm (such as approximately 32 gsm), and the release layer may comprise silicone.

[0101] The barrier section may further comprise a third adhesive layer. The adhesive in the third adhesive layer is not particularly limited provided it does not adversely affect the barrier section, the indicator section, or the indicator device.

[0102] The third adhesive layer may be located between the barrier layer and the indicator section.

[0103] The third adhesive layer may be at least semi-permeable to the activating agent such that the adhesive layer allows the movement of the activating agent to the indicator section, and wherein the activating agent effects a change in the visible properties of the indicator material. The third adhesive layer may be permeable to the activating agent such that the adhesive layer allows unrestricted movement of the activating in the indicator section.

[0104] The third adhesive layer may be formed from an adhesive which is water- soluble. In this respect, the adhesive forming the third adhesive layer may not comprise an adhesive which is solvent-soluble. Without wishing to be bound by theory, it is believed that solvent-soluble adhesives are acidic.

[0105] The third adhesive layer may be formed from an adhesive which is pH neutral, or the third adhesive layer may be formed from an adhesive which has an alkaline pH. In this respect, the adhesive forming the third adhesive layer may not be an adhesive which is acidic. Without wishing to be bound by theory, it is believed that adhesives that are acidic adversely react with the indicator layer causing it to turn permanently one colour. For example, when the indicator material is cresol red, an acidic adhesive adversely affects the cresol red causing it to turn permanently yellow.

[0106] The third adhesive layer may be formed from an acrylic adhesive which is water-soluble and pH neutral. The third adhesive layer may be formed from an acrylic adhesive which is water-soluble and has an alkaline pH. The third adhesive layer may be formed from an acrylic adhesive which is water-soluble and has a pH in the range of approximately pH7 to approximately pH 7.5.

[0107] The third adhesive layer may be selected from one or more (e.g. 1 , 2, 3, 4, or 5) of the group consisting of: an acrylic adhesive, a treated permanent acrylic, a coated permanent acrylic, a treated peelable acrylic, a coated peelable acrylic, a UV curing adhesive, a pressure sensitive adhesive, and UV curable pressure sensitive adhesive. The third adhesive layer may be selected from one or more of the group consisting of an acrylic adhesive, and a coated permanent acrylic adhesive.

[0108] Alternatively, the third adhesive layer may be impermeable or substantially impermeable to the activating agent such that the adhesive layer mitigates migration of the activating from the indicator section.

[0109] The third adhesive layer may have a thickness of between approximately 15 pm and 50 pm, such as approximately 15 pm and approximately 30 pm.

[0110] The third adhesive layer may be located adjacent to the barrier section and arranged such that it covers at least the indicator section, thereby sealing the indicator section.

[0111] The barrier layer and third adhesive layer (if present) may be substantially transparent. The barrier layer and third adhesive layer (if present) may be transparent. Typically, the barrier layer and third adhesive layer (if present) are transparent as this permits the visible properties of the indicator material, together with the enhanced display of the contrast section, to be viewed by an observer.

[0112] The contrast section comprises a contrast material. The contrast section enhances the display of the different visible properties of the indicator section. The contrast section therefore highlights the colour change of the indicator section and allows the colour change to be more easily noticeable when the indicator device is against or adjacent to a range of surfaces, the latter of which may have a colour in their own right, such as brass, copper and steel surfaces or pipes, or painted surfaces.

[0113] In the absence of a contrast section, the colour change may be more difficult to detect by eye after the indicator device has been deployed in use.

[0114] The colour of the contrast section or contrast material in not particularly limiting provided the change in the visible properties of the indicator section are capable of being viewed by eye. Typically, the colour of the contrast section or contrast material is white or substantially white.

[0115] The contrast section is configured to be at least semi-permeable to the activating agent such that the contrast section allows the movement of the activating agent to the indicator section.

[0116] The contrast section may comprise a contrast layer.

[0117] The contrast layer may be formed from a flexographic ink, flexographic dye, or combination thereof. The contrast layer may be formed from a flexographic ink. The contrast layer may be formed from a flexographic dye. The contrast layer may be formed from a combination of a flexographic ink and a flexographic dye.

[0118] The contrast layer may be formed from a flexographic ink comprising an insoluble, inorganic pigment, such as titanium dioxide (TiC ). In this instance, the colour of the contrast layer will be white or substantially white. The contrast layer may be formed from a flexographic ink, and the flexographic ink further comprises a transparent flexographic diluent i.e. a flexographic diluent which is unpigmented.

[0119] The transparent flexographic diluent may be UV curable.

[0120] The transparent flexographic diluent may be surfactant-free.

[0121] The transparent flexographic diluent may be free of the surfactants selected from one or more of the group consisting of benzophenone, isopropylthioxanthone (ITX), and benzildimethylketal (BDK).

[0122] The w / w % ratio of the flexographic ink to transparent flexographic diluent may be from approximately 100 w / w % : approximately 0 w / w % to approximately 25 w / w % : approximately 75 w / w%.

[0123] The w / w % ratio of the flexographic ink to transparent flexographic diluent may be from approximately 70 w / w % : approximately 30 w / w % to approximately 25 w / w % : approximately 75 w / w%.

[0124] The w / w % ratio of the flexographic ink to transparent flexographic diluent may be from approximately 50 w / w % : approximately 50 w / w % to approximately 25 w / w % : approximately 75 w / w%.

[0125] The w / w % ratio of the flexographic ink to flexographic diluent may be approximately 25 w / w % : approximately 75 w / w %.

[0126] The indicator device may comprise a template design. The template may be printed (e.g. by flexographic printing), stamped or the like with any suitable flexographic ink, flexographic dye, or flexographic diluent described herein.

[0127] The contrast section and contrast material are generally inert or substantially inert to the activating agent during normal use of the indicator device. The activating agent therefore does not adversely affect or degrade the contrast section or contrast material, or adversely affect the outcome of using the indicator device under normal conditions.

[0128] When the indicator device is for use with consumable items, such as foods, beverages, pharmaceuticals and the like, it is desirable that the contrast section and contrast material are not toxic to humans or animals in the quantities utilised in the indicator device i.e. the contrast section and contrast material are “food-safe”.

[0129] The contrast layer is also of benefit when the first adhesive layer is present in the indicator device. In this instance, the contrast layer may reduce the tack of the first adhesive layer such that the first adhesive layer is modified from a permanent adhesive to one which is removable, and which eliminates or mitigates the risk of adhesive residue being left on a surface (e.g. a pipe) after prolonged application of the indicator tape.

[0130] Without wishing to be bound by theory, it is believed that the microscopic topography of the first adhesive is not perfect, and comprises peaks and troughs. It is believed that the contrast layer settles into the troughs, for example, when composition comprising a flexographic ink is printed in a flexographic printing process onto the first adhesive layer. The adhesiveness of the first adhesive layer is reduced by virtue of the contrast layer residing in the troughs. The first adhesive layer, however, retains some adhesiveness due to the peaks which remain uncoated or substantially uncoated by the contrast layer.

[0131] When the indicator device is a tape, the tape may be wound around a cylindrical core or upon itself into a roll. In this instance, the modified (reduced) tack of the first adhesive layer can be configured such that the first adhesive layer removably adheres to the barrier section without leaving residue on the barrier section when the tape is deployed in use.

[0132] The indicator device may further comprise a release section adjacent to the contrast section, wherein the release section is detachable from the contrast section, and wherein the contrast section is located between the indicator section and the release section.

[0133] The release section may comprise a release layer.

[0134] The release layer may have a thickness of between approximately 50 pm and approximately 100 pm.

[0135] The release layer may have a thickness of between approximately 60 pm and approximately 70 pm.

[0136] The release layer may be selected from one or more of the group consisting of: glassine, siliconised glassine paper, and a silicon treated polymer.

[0137] The indicator device may comprise: an indicator section comprising an indicator material that displays different visible properties in response to the presence or absence of an activating agent, a barrier section comprising a barrier layer that mitigates migration of the activating agent from the indicator section; a contrast section comprising a contrast material; wherein the indicator section is located between the barrier section and the contrast section; wherein the contrast section enhances the display of the different visible properties of the indicator section; wherein the contrast section is configured to be at least semi- permeable to the activating agent such that the contrast section allows the movement of the activating agent to the indicator section; wherein the activating agent effects a change in the visible properties of the indicator material; and wherein:

[0138] • the activating agent is carbon dioxide gas;

[0139] • the barrier layer comprises a first major surface and a second major surface opposite the first major surface; the indicator layer comprises a first major surface and a second major surface opposite the first major surface; the first major surface of the barrier layer is oriented such that it faces the first major surface of the indicator section; the second major surface of the barrier layer comprises a release layer; and the release layer is adhered or substantially adhered to the second major surface of the barrier layer;

[0140] • the barrier layer is polyethylene terephthalate;

[0141] • the release layer comprises silicone;

[0142] • the contrast section comprises a contrast layer;

[0143] • the contrast layer is formed from a flexographic ink, flexographic dye, or combination thereof;

[0144] • the indicator device further comprises a first adhesive layer; • wherein the first adhesive layer is located between the contrast section and the indicator material, and wherein the first adhesive layer is at least semi-permeable to the activating agent such that the adhesive layer allows the movement of the activating agent from the contrast layer to the indicator material;

[0145] • the indicator device further comprises a third adhesive layer, and wherein the third adhesive layer is located between the barrier layer and the indicator section; and

[0146] • wherein the first and third adhesives are independently formed an acrylic adhesive which is water-soluble and has a pH in the range of approximately pH 7 to approximately pH 7.5.

[0147] In another aspect, the present invention provides a package or packaging comprising the indicator device as described herein.

[0148] In another aspect, the present invention provides a tape or film comprising the indicator device as described herein.

[0149] In another aspect, the present invention provides a method of detecting the presence of an activating agent, comprising the steps of: a) providing an indicator device as described herein; b) activating the indicator device with an activating agent; and c) subsequently detecting a visible change in the indicator material whereby the presence of the activating agent is revealed.

[0150] In another aspect, the present invention provides a method of detecting whether a sealed package has been compromised, comprising the steps of: a) providing an indicator device as described herein; b) activating the indicator device with an activating agent; and c) subsequently detecting a visible change in the indicator material whereby the compromise of the package is revealed.

[0151] The indicator device of the present invention may be used, for example, in breweries, distilleries, pubs, restaurants, or laboratories. The indicator device of the present invention may also be used with equipment, such as refrigeration units.

[0152] The indicator device, particularly when the indicator device is an adhesive tape, can be applied around hoses or pipes that carry an activating agent, e.g. carbon dioxide gas or oxygen gas. The indicator device may be wound around the hose or pipe to provide a visual confirmation as to whether the hose or pipe is gas tight. If the hose or pipe is not gas tight, the activating agent which escapes the hose or pipe effects a change in the visible properties of the indicator material, thus establishing that repair, rectification or replacement of the hose or pipe is required.

[0153] Similarly, the indicator device of the present invention, particularly when the indicator device is an adhesive tape, may be wound around the connections in hoses or pipes that carry an activating agent as described above.

[0154] The indicator device of the present invention can be applied to foodstuffs and the like by end users in the home. Alternatively, it can be used in a commercial setting such as the catering and retail industries. Therefore, the indicator device can be used to indicate when a foodstuff is no longer fit for consumption, or it can be used to show when a sealed package has been opened. This helps to prevent both consumption of unfit foodstuffs and the unnecessary disposal of consumable foodstuffs. Examples of Preparation of Ink for Indicator Layer

[0155] Preparation of a (pH) acid sensitive ink

[0156] A pH (acid) sensitive ink was prepared as follows.

[0157] To prepare a sample of ink, 5g of 15% (w / w) hydroxypropyl cellulose in ethanol was weighed and to it was added 0.5g of glycerol. The solution was gently stirred. To the solution was then added 3mL of 40% (w / w) tetrabutylammonium hydroxide in water, and the solution was again gently stirred. Finally, 0.5g of Phenol Red (PR, phenolsulfonphthalein), 5mL of 40% (w / w) tetrabutylammonium hydroxide in water and 2mL of ethanol was added and the solution was stirred.

[0158] The Phenol Red ink changes colour depending on pH. In particular, the ink is pink above pH 8.2 and transitions through red and orange to yellow below pH 6.8.

[0159] Alternative indicator compounds are m-Cresol Purple (MCP, Hydroxy triarylmethane), Thymolphthalein (3,3-bis(4-hydroxy-2-methyl-5-propan-2- ylphenyl)-2-benzofuran-1 -one), o-Cresolphthalein (3,3-Bis(4-hydroxy-3- methylphenyl)-1 (3H)-isobenzofuranone), Acryloly florescein (AcF1 ), 13- methyl umbelliferon (BMLIB), Bromothymol blue (BTB, Hydroxy triarylmethane), 5' and 6-Carboxyseminaphtholfluorescein (c-SNAFL), 5' and 6'-Carboxyseminaphtholrhodamine (c-SNARF), Cresol Red (CR, o- Cresolsulfonephthalein), 2-(2,4-Dinitrophenylaxo)-1 -naphthol- 3,6- disulphonic acid (DNPA), tris(thenoyltrifluoroacetonato) europium (III) (Eu(tta)1 ), Fluorescein (Fl, resorcinolphthalein), 7-hydroxycoumarin-4- acetic acid (HCA), 1 , Hydroxypyrene-3,6,S-trisulphonic acid (HPTS), Neutral red (NR, toluylene red), Rhodamine 6G (R6G), Sulforhodamine 101 (SRh), Thymol blue (TB, thymolsulphonephthalein), Texas Red hydrazine (THR), Phenolphthalein (3,3-bis(4- hydroxyphenyl)isobenzofuran-1 (3H)-one), Thymol blue, Phenoltetraiodophthalein, Phenoltetrachlorophthalein, a-Naphtholbenzein and p-Xylenol blue.

[0160] In particular, indicator compounds are chosen from Phenol Red (PR, phenolsulfonphthalein, pKa = 7.9), m-Cresol Purple (MCP, Hydroxy triarylmethane, pKa = 8.3) and Cresol Red (CR, o-Cresolsulfonephthalein, pKa = 8.32).

[0161] Alternative polymers are polyvinyl butyral (PVB), nitrocellulose (NC), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC), polyethylene glycol (PEG) and polyethylenimine (PEI).

[0162] The polymer and / or the indicator materials used are soluble in ethanol or the solvent being used.

[0163] Alternative bases / agents for deprotonating the indicator compound are potassium hydroxide, calcium hydroxide, caesium hydroxide, magnesium hydroxide, tetrabutylammonium hydroxide, tetraoctylammonium hydroxide.

[0164] The pH (acid) sensitive ink described above comprises a polymer binder (hydroxypropyl cellulose), a colour changing dye (Phenol Red), a base or agent for deprotonating the dye (tetrabutylammonium hydroxide) and a solvent (ethanol).

[0165] Other inks that can be used with the device of the present invention can be prepared by combining a binder material (often a polymer), a dye and a plasticiser. A solvent is typically added to make a printable ink solution. Typical formulations are as illustrated below.

[0166] Base Sensitive Example Ink Formulation 1

[0167] 50 g of 15% w / v polyvinyl butyral and 5 mL of 40 mg / mL bromophenol blue in ethanol were combined to make a first base sensitive ink. 4g of this first solution were combined with 0.2 mL of tributyl phosphate to create a base version of the ink.

[0168] Base Sensitive Example Ink Formulation 2

[0169] 50 g of 15% w / v polyvinyl butyral and 5 mL of 20 mg / mL Bromophenol blue in ethanol were combined to make a first base sensitive ink. 4g of this first base sensitive ink were combined with 0.3 mL of tributyl phosphate to create a base version of the ink.

[0170] Base Sensitive Example Ink Formulation 3

[0171] 50 g of hydraCOAT HV 1105 S F and 5 mL of 160 mg / mL bromophenol blue in ethanol were combined to make a first base sensitive ink. 4 g of this base sensitive ink solution were combined with 0.1 mL of tributyl phosphate to create a base version of the ink.

[0172] Plasticiser

[0173] Higher quantities of plasticiser typically shortens the time the indicators take to change colour, whereas decreasing the plasticiser content lengthens the time.

[0174] Plasticisers that can be used include diisodecyl adipate, tris-2-ethylhexyl phosphate, tributyl phosphate and dimethyl phthalate. Without wishing to be bound by theory, it is thought that in one embodiment glycerol acts as a plasticiser. Binder

[0175] Different polymers have different permeabilities to activating agents, hence changing the polymer can alter the times. Since the timers are based on diffusion, the timers take longer to change colour at lower temperatures than higher temperatures (i.e. a timer stored in the fridge will take longer to change colour than when stored at room temperature).

[0176] Polymer binders that can be used include polyvinyl butyral (PVB), nitrocellulose (NC), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC) and hydroxypropyl cellulose (HPC), polyethylene glycol (PEG) and polyethylenimine (PEI).

[0177] Preparation of Combined Indicator and Substrate Layer

[0178] The combined indicator and substrate layers were prepared in accordance with the procedure and materials outlined in GB 2474571 , the contents of which are incorporated herein by reference.

[0179] Silica (silicon dioxide) and alumina (aluminium oxide) were chosen as inorganic substrates for preparation of the indicators. Silica pigment was found to be a particularly suitable inorganic substrate because of its wide utilisation as a polymer filler, low cost, ready availability, ease of handling, safety, and lack of colour (white). Indicators were prepared using both hydrophobic pigments (silica or alumina), and hydrophilic pigments (silica or alumina).

[0180] Titania was also used in connection with the preparation of oxygensensitive indicators. Titania was chosen because it is a semiconducting material which can act as a photocatalyst in the reduction and thus the activation of certain oxygen-sensitive dyes. The compounds that were used in the preparation of pH (acid) sensitive indicators were: cresol red, meta-cresol purple and phenol red. Alternative compounds as listed herein can, of course, be used.

[0181] Hydrophobic Silica or Alumina for CO2 indicators

[0182] Approximately 0.04 g of pH (acid) sensitive indicator (indicator material) was added to a beaker containing 2.0 g of hydrophobic silica (Degussa / Evonik Aerosil R812; S.S.A. = 260 + / - 30 m2 / g; average particle size = 7 nm) and approximately 100 mL of methanol. 1 mL of 1 M tetrabutylammonium hydroxide in methanol was added. The mixture was well stirred / sonicated, the resulting solution was transferred to a round- bottomed flask and the methanol removed with the aid of a rotary evaporator at 30°C under vacuum. The resultant powder was removed and ground into a fine powder using a pestle and mortar.

[0183] Pigments based on hydrophobic alumina (Degussa / Evonik Aeroxide Alu C805), rather than silica were also prepared as above and proved equally effective.

[0184] Alternative bases to tetrabutylammonium hydroxide can also be used, including sodium hydroxide and sodium bicarbonate.

[0185] Alternative solvents to methanol can also be used, including ethanol, ethyl acetate and / or water.

[0186] Hydrophilic Silica or Alumina for CO2 indicators

[0187] Typically, a lower ratio of dye to inorganic pigment was used with hydrophilic silica (Degussa / Evonik Aerosil 300) and hydrophilic alumina (Degussa / Evonik Aeroxide Alu C). To 15.0 g of hydrophilic silica (Degussa / Evonik Aerosil 300), 0.12 g of indicator material was added. Approximately 100 mL water and 12 mL of 1.5 M tetrabutylammonium hydroxide in water was added. After stirring, the solvent (water) was evaporated under reduced pressure to produce a fine powder.

[0188] Pigments based on hydrophilic alumina (Degussa / Evonik Aeroxide Alu C), rather than silica were also prepared as above and proved equally effective.

[0189] Titania

[0190] Titania was used in connection with the preparation of certain oxygensensitive indicators. Titania was chosen because, in particular grades, it is a semiconducting material which can act as a photocatalyst in the reduction and thus the activation of certain oxygen-sensitive indicators. Because titania must be able to act as more than a support and drive the photoreduction of the dye to a form that is oxygen sensitive, the titania inorganic substrate was chosen in an untreated form so as to preserve its photocatalytic properties.

[0191] Incorporation in Polymer a) Hydrophobic polymers Polyethylene was chosen as a particularly suitable hydrophobic polymer due to its low cost, ease of manufacture and processability, and wide range of applications, including food packaging and medical applications.

[0192] In order to be compatible with polyethylene, the indicators used for incorporation into such polymer films were indicators based on hydrophobic silica, hydrophobic alumina, or untreated titania. Typically 0.4 g of the hydrophobic indicator was added to 2.0 - 4.0 g of powdered polyethylene. The two powders were further ground until the colour was uniform. A small sample of the resulting powder was heat pressed at 115°C for 5 minutes under 5 tonnes pressure using a Specac Atlas™ Series Heated Platens, before being allowed to cool. A 0.1 mm- thick plastic film was obtained.

[0193] This procedure is similar to that used in making extruded polymer films in which the pigment is dispersed, thus producing very thin polymer films.

[0194] Alternatively, the polymer film comprising the indicator may be prepared using an extruder. b) Hydrophilic polymers

[0195] Polyethylene oxide was chosen as a suitable hydrophilic polymer.

[0196] In order to be compatible with polyethylene oxide, the indicators used for incorporation into such polymer films were indicators based on hydrophilic silica, hydrophilic alumina, or untreated titania.

[0197] Typically 0.4 g of the hydrophilic indicator was added to 2.0 - 4.0 g of powdered polyethylene oxide. The two powders were further ground until the colour was uniform. A small sample of the resulting powder was heat pressed at 65°C for 5 minutes under 5 tonnes pressure using a Specac Atlas™ Series Heated Platens, before being allowed to cool. A 0.1 mm- thick plastic film was obtained.

[0198] Example Combined Indicator and Substrate Layer A meta-cresol purple aqueous hydrophilic silica (Aerosil 150) dispersion was prepared. This was then spray-dried to produce a dry free-flowing ‘intelligent pigment’.

[0199] A masterbatch formulation was prepared according to the following formula:

[0200] 59.5% by weight low density polyethylene (LDPE)

[0201] 20% by weight linear low density polyethylene (LLDPE) 20% by weight intelligent pigment (from above) 0.5% by weight zinc stearate.

[0202] The masterbatch was used to make an indicator film having a combined indicator and substrate.

[0203] The prepared indicator film has a three layer co-extruded structure, in which the core layer contains intelligent pigment at 5% to 20% by weight. The outer layers generally consist of LDPE or medium density polyethylene (MDPE), however these can be varied to give varying film properties.

[0204] The combined indicator and substrate layer can be prepared as a film by spray-drying, master-batching and film extrusion, using standard industrial techniques.

[0205] Detailed Description

[0206] Referring now to Figure 1 , there is shown at 110 an indicator device in accordance with one embodiment of the invention. The indicator device 110 has a barrier section 200, an indicator section 300, and a contrast section 400. In this embodiment, the indicator device has a first and third adhesive layers 120, 116 (but no second adhesive layer).

[0207] The barrier section 200 consists of a barrier layer 114, a release layer 112, and an adhesive layer 116. The barrier layer 114 is a polyethylene terephthalate substrate comprising a silicone release layer 112. The release layer 112 is adhered or substantially adhered to the barrier layer 114. The release layer 112 is one of two outermost layers of the indicator device 110.

[0208] The adhesive layer 116 is described herein as the third adhesive layer. The barrier layer 114 is in contact with the third adhesive layer 116. The third adhesive layer 116 is on the opposite side of the barrier layer 114 to the release layer 112. The third adhesive layer 116 is an acrylic adhesive layer. The adhesive is an acrylic adhesive which is water-soluble and pH neutral. Alternatively, the adhesive may be an acrylic adhesive which is water-soluble and which has an alkaline pH.

[0209] The indicator section 300 consists of a combined indicator and substrate layer 118, and an adhesive layer 120 (described herein as the first adhesive layer 120). The combined indicator and substrate layer 118 is pH / acid sensitive (and hence the indicator section 300 is also pH / acid sensitive).

[0210] The combined indicator and substrate layer 118 is located between and in contact with the first adhesive layer 120 and the third adhesive layer 116.

[0211] The combined indicator and substrate layer 118 may be a polymer film. The substrate in the combined indicator and substrate layer 118 may be polyethylene. The indicator in the combined indicator and substrate layer 118 may be selected from one or more of the group consisting of: Phenol Red (PR, phenolsulfonphthalein), m-Cresol Purple (MCP, Hydroxy triarylmethane) and Cresol Red (CR, o-Cresolsulfonephthalein), such as Cresol Red (CR, o-Cresolsulfonephthalein).

[0212] The first adhesive layer 120 is located between and is in contact with the combined indicator and substrate layer 118 and the contrast section 400. The first adhesive layer 120 is an acrylic adhesive layer. The adhesive is formed from an acrylic adhesive which is water-soluble and pH neutral. Alternatively, the adhesive may be formed from an acrylic adhesive which is water-soluble and which has an alkaline pH.

[0213] The contrast section 400 is a contrast layer 122. The contrast layer is in contact with the first adhesive layer 120. The contrast layer 122 is the other of the two outermost layers of the indicator device 110.

[0214] The contrast layer 122 is a composition consisting of a white opaque flexographic ink and a transparent flexographic diluent. The w / w% of the white opaque flexographic ink : a transparent flexographic diluent is 25:75 wt%. The transparent flexographic diluent is surfactant-free.

[0215] For storage and transport, the indicator device 110 may be formed into a roll such that the first adhesive layer 120 and contrast layer 122 removably adheres to the release layer 112.

[0216] Alternatively, the indicator device 110 may comprise a release section (not shown) which is removably detachable from the contrast layer 122. The release section may comprise a glassine release layer or release liner (not shown).

[0217] In use, the indicator device 110 can be applied to pipework or the connections in pipework. In this embodiment, the pipework conducts the activating agent (e.g. carbon dioxide gas) and the indicator device 110 is used to monitor leaks from the pipework or connections thereof.

[0218] The indicator device 110 as illustrated in Figure 1 can also be applied to foodstuffs or packaging either before or after they are sealed and / or opened, depending on the anticipated colour change of the indicator layer, and the longevity of the product to which it is attached. The first adhesive layer 120 and contrast layer 122 may be selected such that they are “food safe” i.e. they are made from materials approved for use next to foodstuffs.

[0219] Irrespective of whether the indicator device is applied to foodstuffs, packaging, pipework or the connections in pipework, the indicator device 110 is applied by detachably removing the indicator device 110 from a roll or removing the release liner (not shown and which is typically discarded). The tack of the first adhesive layer 120 is reduced by the contrast layer 122. The first adhesive layer 120 is used to apply the indicator device to the item to be monitored, thus allowing the combined indicator and substrate layer 118 to be exposed to the activating agent.

[0220] For example, the indicator material may be chosen to detect carbon dioxide being supplied through pipework to a piece of equipment (see Figure 2). The indicator device 110 is attached around connectors in the pipework (see the box in Figure 2). The combined indicator and substrate layer 118 is visible to a user through the barrier section 200 i.e. the barrier section 200 is sufficiently transparent to permit a user to see the combined indicator and substrate layer 118. The indicator device is constructed and located in such a way that carbon dioxide gas leaking from the connectors can reach the indicator layer 118 via the contrast section 400 and first adhesive layer 120.

[0221] In the absence of carbon dioxide gas, the indicator layer is a first colour, such as purple when the indicator material is cresol red (see Figure 2). In the presence of carbon dioxide gas, the colour of the combined indicator and substrate layer 118 changes from the first colour to a second colour, for example, from purple to yellow, at the point or points where the leak occurs (see the box in Figure 3).

[0222] The barrier layer 114 is impermeable or substantially impermeable to the carbon dioxide gas. As such, the gas is retained in contact with the combined indicator and substrate layer 118 for longer.

[0223] In this example, the contrast layer 122 is white. The contrast layer 122 allows the colour of the combined indicator and substrate layer 118 in the indicator section 300 to be clearly visible to the user. The contrast layer 122 greatly enhances the colours and visibility of the indicator in the combined indicator and substrate layer 118 in the indicator section 300.

[0224] The indicator device as illustrated in Figure 1 is prepared as follows.

[0225] A barrier section 200 is prepared by transfer laminating an adhesive to a commercially available polyethylene terephthalate barrier layer 114 having a precoated silicone layer 112. The silicone layer 112 is coated to the barrier layer 114 and cured. The silicone layer 112 is not removable during normal use of the indicator device 110. The adhesive forms the third adhesive layer 116.

[0226] A polymer film 118 comprising an indicator material (such as cresol red) is prepared as described above.

[0227] An adhesive is transfer laminated to the polymer film 118 to form the first adhesive layer 120. The adhesive may be an acrylic adhesive which is water-soluble and pH neutral. Alternatively, the adhesive may be an acrylic adhesive which is water-soluble and which has an alkaline pH.

[0228] A contrast section 400 consisting of a contrast layer 122 is printed onto the adhesive layer 120 of the indicator section 300. The printing process is a flexographic printing process.

[0229] The barrier section 200 is laminated to the polymer film of the indicator section 300. The barrier section 200 is joined to the indicator section 300 through the adhesive layer 116 adhering to the polymer film 118 of the indicator section 300.

[0230] The indicator device 110 is self-winding and may be stored as a reel of tape.

[0231] Referring now to Figure 4, there is shown at 110 an indicator device in accordance with another embodiment of the invention. The indicator device 110 has a barrier section 200, an indicator section 300, and a contrast section 400.

[0232] In this embodiment, the indicator device has a first and second adhesive layers 120, 132 (but no third adhesive layer). The release layer 112, the barrier layer 114, the first adhesive layer 120 and contrast ink 122 are as described above in the first embodiment of the invention.

[0233] The indicator section 300 consists of an indicator ink layer 130, an adhesive layer 132 (described herein as the second adhesive layer) and a polyethylene substrate layer 134.

[0234] The indicator ink may be prepared as described above.

[0235] The second adhesive layer 132 is located between and is in contact with the indicator ink layer 130 and the polyethylene substrate layer 134. The second adhesive layer 132 is an acrylic adhesive layer. The adhesive is formed from an acrylic adhesive which is water-soluble and pH neutral. Alternatively, the adhesive may be formed from an acrylic adhesive which is water-soluble and which has an alkaline pH.

[0236] The barrier layer 114 is in contact with the indicator ink layer 130.

[0237] The polyethylene substrate layer 134 is between and is in contact with the first and second adhesive layers 120, 132.

[0238] The contrast section 400 is a contrast layer 122. The contrast layer is in contact with the first adhesive layer 120. The contrast layer 122 is the other of the two outermost layers of the indicator device 110.

[0239] For storage and transport, the indicator device 110 may be formed into a roll such that the first adhesive layer 120 and contrast layer 122 removably adheres to the release layer 112. Alternatively, the indicator device 110 may comprise a release section (not shown) which is removably detachable from the contrast layer 122. The release section may comprise a glassine release layer or release liner (not shown).

[0240] The indicator device of this embodiment may be used as described above for the first embodiment. The polyethylene substrate 134 is sufficiently porous to the activating agent (e.g. carbon dioxide gas) such that the indicator ink 130 is exposed to the activating agent in use.

[0241] The indicator device 110 as illustrated in Figure 4 is prepared as follows.

[0242] An indicator section 300 is prepared by transfer laminating an adhesive to a commercially available polyethylene substrate layer 134. The adhesive forms the second adhesive layer 132.

[0243] The indicator ink is then printed onto the second adhesive layer 132 to form the indicator ink layer 130. The printing process is a flexographic printing process.

[0244] A barrier section 200 is a commercially available polyethylene terephthalate barrier layer 114 having a silicone layer 112 as described above. The barrier section 200 is transfer laminated to the indicator section such that the second adhesive layer 132 adheres to the barrier layer 114 through the indicator ink layer 130.

[0245] An adhesive is transfer laminated to the polyethylene substrate layer 134 to form the first adhesive layer 120. A contrast section 400 consisting of a contrast layer 124 is printed onto the adhesive layer 120 of the indicator section 300. The printing process is a flexographic printing process.

[0246] The indicator device 110 is self-winding and may be stored as a reel of tape.

[0247] Referring now to Figure 5, there is shown at 110 an indicator device in accordance with another embodiment of the invention. The indicator device 110 is as described in Figure 4 and the second embodiment above. Figure 5 shows an alternative arrangement of the adhesive layer 132 and indicator layer 130 within the indicator section.

[0248] The indicator device 110 has a barrier section 200, an indicator section 300, and a contrast section 400.

[0249] In this embodiment, the indicator device has a first and second adhesive layers 120, 132 (but no third adhesive layer).

[0250] The release layer 112, the barrier layer 114, the first adhesive layer 120 and contrast ink 122 are as described above in the first embodiment of the invention.

[0251] The indicator section 300 consists of an adhesive layer 132 (described herein as the second adhesive layer), an indicator ink layer 130, and a polyethylene substrate layer 134.

[0252] The indicator ink may be prepared as described above. The second adhesive layer 132 is located between and is in contact with the barrier layer 114 and the indicator ink layer 130. The second adhesive layer 132 is an acrylic adhesive layer. The adhesive is an acrylic adhesive which is water-soluble and pH neutral. Alternatively, the adhesive may be an acrylic adhesive which is water-soluble and which has an alkaline pH.

[0253] The barrier layer 114 is between and is in contact with release layer 112 and the third adhesive layer 132.

[0254] The polyethylene substrate layer 134 is between and is in contact with the indicator ink layer 130 and the first adhesive layer 120.

[0255] The contrast section 400 is a contrast layer 122. The contrast layer is in contact with the first adhesive layer 120. The contrast layer 122 is the other of the two outermost layers of the indicator device 110.

[0256] For storage and transport, the indicator device 110 may be formed into a roll such that the first adhesive layer 120 and contrast layer 122 removably adheres to the release layer 112.

[0257] Alternatively, the indicator device 110 may comprise a release section (not shown) which is removably detachable from the contrast layer 122. The release section may comprise a glassine release layer or release liner (not shown).

[0258] The indicator device of this embodiment may be used as described above for the first embodiment. The polyethylene substrate 134 is sufficiently porous to the activating agent (e.g. carbon dioxide gas) such that the indicator ink 130 is exposed to the activating agent in use. The indicator device 110 as illustrated in Figure 5 is prepared as follows.

[0259] An indicator section 300 is prepared by printing the indicator ink onto the polyethylene substrate layer 134 to form the indicator layer 130. The printing process is a flexographic printing process.

[0260] An adhesive is than transfer laminated to the indicator layer 130. The adhesive forms the second adhesive layer 132.

[0261] A barrier section 200 is a commercially available polyethylene terephthalate barrier layer 114 having a silicone layer 112. The barrier section 200 is transfer laminated to the indicator section such that the second adhesive layer 132 adheres to the barrier layer 114.

[0262] An adhesive is transfer laminated to the polyethylene substrate layer 134 to form the first adhesive layer 120.

[0263] A contrast section 400 consisting of a contrast layer 124 is printed onto the adhesive layer 120 of the indicator section 300. The printing process is a flexographic printing process.

[0264] The indicator device 110 is self-winding and may be stored as a reel of tape.

[0265] Embodiments and / or optional features of the invention have been described above. Any aspect of the invention may be combined with any other aspect of the invention, unless the context demands otherwise. Any of the embodiments or optional features of any aspect may be combined, singly or in combination, with any aspect of the invention, unless the context demands otherwise. The invention will now be described further by reference to the following examples, which are intended to illustrate but not limit, the scope of the invention.

[0266] Examples

[0267] Example 1

[0268] An indicator device 110 in the form of a removably adhesive tape is made having the laminated structure as set out in Figure 1 and as described in the first embodiment above.

[0269] The adhesive used to form the first and third adhesive layers 116, 120 is an acrylic adhesive which is water-soluble and pH neutral.

[0270] A polymer film 118 comprising cresol red as an indicator is prepared as described above. The polymer film therefore is a combined indicator and substrate layer, wherein the indicator material is dispersed within the substrate material.

[0271] Cresol red is an indicator which is purple in the absence of carbon dioxide. In the presence of carbon dioxide, however, the colour of cresol red changes to orange and then to yellow depending on the increasing concentration of carbon dioxide present.

[0272] The contrast layer is formed from composition comprising a flexographic ink and a transparent flexographic diluent. The w / w % ratio of the flexographic ink to flexographic diluent may be approximately 25 w / w % : approximately 75 w / w %. The flexographic ink is commercially available from Flint Ink (UK) Ltd as Flexocure Force Opaque White (UF090091408N).

[0273] The transparent flexographic diluent is commercially available from Paragon Inks as UV Dry Flexo Special Tinting Medium (L546 Tint medium).

[0274] Application of the Indicator Device 110

[0275] Figure 2 illustrates the application of the indicator device 110 to connectors in a pipe transporting carbon dioxide gas. The indicator device 110 is in the form of a self-adhering tape is wound around and removably adhered both to metal surface of the connectors and to itself.

[0276] When carbon dioxide gas flows through the pipe and a suitable seal is maintained by the connector such that no carbon dioxide leaks out into the surrounding environment, the cresol red indicator remains purple as the indicator device 110 does not come into contact with the carbon dioxide gas (see Figure 2).

[0277] When the connection in the pipe leaks, carbon dioxide gas escapes and activates the indicator material in the indicator device. Figure 3 illustrates that the tape changes colour from purple to yellow at the source of the leak. If further carbon dioxide escapes, the tape will continue to change colour to yellow at the source of the leak.

[0278] Example 2

[0279] A series of compositions comprising a flexographic ink and a transparent flexographic diluent are prepared. Indicator devices 110 in the form of tapes are individually prepared generally as described in Example 1 using the compositions.

[0280] Each indicator device 110 is then assessed for its (a) relative level of remaining adhesion, and (b) relative level of contrast.

[0281] The results are shown in the table below:

[0282] As can be seen, indicator devices 110 can be prepared having good levels of contrast when using compositions comprising white opaque ink from 25 w / w% to 100 w / w%.

[0283] The ability of the resulting indicator device to adhere to a surface can be modified according to the surface in question. When stronger adhesion is required (for example, with textured surfaces), compositions can be prepared having greater w / w% quantities of the transparent flexographic diluent.

[0284] When gentler (weaker) adhesion is required, compositions can be prepared having reduced w / w% quantities of the transparent flexographic diluent. Compositions can also be prepared having no transparent flexographic diluent when the indicator device is for use with delicate surfaces. Example 3

[0285] Approximately 4 weeks after preparation, the composition of Example 2 having 50:50 flexographic ink:transparent flexographic diluent was shown to have a good level of tack and retained good contrast. Therefore, the level of tack increased over this time period.

Claims

CLAIMS1 . An indicator device comprising: an indicator section comprising an indicator material that displays different visible properties in response to the presence or absence of an activating agent; a barrier section comprising a barrier layer that mitigates migration of the activating agent from the indicator section; a contrast section comprising a contrast material; wherein the indicator section is located between the barrier section and the contrast section; wherein the contrast section enhances the display of the different visible properties of the indicator section; wherein the contrast section is configured to be at least semi-permeable to the activating agent such that the contrast section allows the movement of the activating agent to the indicator section; and wherein the activating agent effects a change in the visible properties of the indicator material.

2. An indicator device as claimed in claim 1 , wherein the indicator material displays different visible properties in response to a predetermined minimum concentration of the activating agent.

3. An indicator device as claimed in claim 1 or claim 2, wherein the indicator section comprises a substrate material.

4. An indicator device as claimed in claim 3, wherein the indicator material is incorporated into a discrete indicator layer and thesubstrate material is incorporated into a discrete substrate layer, separate to the indicator layer.

5. An indicator device as claimed in claim 3 or claim 4, wherein the substrate material is selected from one or more of the group consisting of: aluminium oxide foil, polypropylene, polyethylene terephthalate, and polyethylene.

6. An indicator device as claimed in claim 3, wherein the indicator material and the substrate material are incorporated into the same layer so-forming a combined indicator and substrate layer, and wherein the indicator material is dispersed within the substrate material or vice versa.

7. An indicator device as claimed in claim 6, wherein the combined indicator and substrate layer comprises a polymer composite, said polymer composite comprising at least one thermoplastic polymer, and at least one chemical indicator dispersed in the at least one thermoplastic polymer, the at least one chemical indicator comprising a particulate inorganic substrate, and at least one indicator material, reactive dye or ink coated on and / or impregnated within the particulate inorganic substrate.

8. An indicator device as claimed in any preceding claim, wherein the indicator material is selected from one or more of the group consisting of: a redox sensitive material, a carbon monoxide sensitive material, a carbon dioxide sensitive material, an oxygen sensitive material, an amine sensitive material, an ammonia sensitive material, a pH sensitive material, and an acid sensitive material.

9. An indicator device as claimed in claim 8, wherein the pH sensitive material is selected from one or more of the group consisting of: m- Cresol Purple (MCP, Hydroxy triarylmethane), Thymolphthalein (3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1- one), o-Cresolphthalein (3,3-Bis(4-hydroxy-3-methylphenyl)-1 (3H)- isobenzofuranone), Acryloly florescein (AcF1 ), 13-methyl umbelliferon (BMLIB), Bromothymol blue (BTB, Hydroxy triarylmethane), 5' and 6-Carboxyseminaphtholfluorescein (c- SNAFL), 5' and 6'-Carboxyseminaphtholrhodamine (c-SNARF), Cresol Red (CR, o-Cresolsulfonephthalein), 2-(2,4- Dinitrophenylaxo)-1 -naphthol- 3,6-disulphonic acid (DNPA), tris(thenoyltrifluoroacetonato) europium (III) (Eu(tta)1 ), Fluorescein (Fl, resorcinolphthalein), 7-hydroxycoumarin-4-acetic acid (HCA), 1 , Hydroxypyrene-3,6,S-trisulphonic acid (HPTS), Neutral red (NR, toluylene red), Phenol Red (PR, phenolsulfonphthalein), Rhodamine 6G (R6G), Sulforhodamine 101 (SRh), Thymol blue (TB, thymolsulphonephthalein), Texas Red hydrazine (THR), Phenolphthalein (3,3-bis(4-hydroxyphenyl)isobenzofuran-1 (3H)- one), Thymol blue, Phenoltetraiodophthalein, Phenoltetrachlorophthalein, a-Naphtholbenzein and p-Xylenol blue.

10. An indicator device as claimed in any preceding claim, wherein the activating agent is at least one of an oxidising agent, water, carbon dioxide, amines, acids, carboxylic acids, ammonium hydroxide and ammonia.

11. An indicator device as claimed in claim 10, wherein the activating agent is gaseous.

12. An indicator device as claimed in claims 10 or claim 11 , wherein the activating agent is carbon dioxide gas.

13. An indicator device as claimed in any preceding claim, wherein the barrier layer is selected from one or more of the group consisting of: polyethylene terephthalate, ethylene vinyl alcohol, polyvinylidene chloride, polyvinyl acetate, polypropylene, polyester and aluminium oxide coated polyethylene terephthalate.

14. An indicator device as claimed in claim 13, wherein the barrier layer comprises a first major surface and a second major surface opposite the first major surface; the indicator layer comprises a first major surface and a second major surface opposite the first major surface; the first major surface of the barrier layer is oriented such that it faces the first major surface of the indicator section; the second major surface of the barrier layer comprises a release layer; and the release layer is adhered or substantially adhered to the second major surface of the barrier layer.

15. An indicator device as claimed in claim 14, wherein the release layer comprises silicone.

16. An indicator device as claimed in any one of the preceding claims, wherein the contrast section comprises a contrast layer.

17. An indicator device as claimed in claim 16, wherein the contrast layer is formed from a composition comprising a flexographic ink, flexographic dye, or combination thereof.

18. An indicator device as claimed in claim 17, wherein the flexographic ink comprises an insoluble inorganic pigment, such as titanium dioxide.

19. An indicator device as claimed in claim 17 or claim 18, wherein the composition further comprises a transparent flexographic diluent.

20. An indicator device as claimed in claim 19, wherein the w / w % ratio of the flexographic ink to flexographic diluent is from approximately 100 w / w % : approximately 0 w / w % to approximately 25 w / w % : approximately 75 w / w%.21 . An indictor device as claimed in claim 19 or claim 20, wherein the w / w % ratio of the flexographic ink to flexographic diluent is from approximately 50 w / w % : approximately 50 w / w % to approximately 25 w / w % : approximately 75 w / w%.

22. An indicator device as claimed in any one of the preceding claims, wherein the indicator device further comprises a first adhesive layer, wherein the first adhesive layer is located between the contrast section and the indicator material, and wherein the first adhesive layer is at least semi-permeable to the activating agent such that the adhesive layer allows the movement of the activating agent from the contrast layer to the indicator section.

23. An indicator device as claimed in any one of the preceding claims, wherein the indicator device further comprises a second adhesive layer in the indicator section.

24. An indicator device as claimed in any one of the preceding claims, wherein the barrier section further comprises a third adhesive layer, and wherein the third adhesive layer is located between the barrier layer and the indicator section.

25. An indicator device as claimed in any one of claims 22 to 24, wherein the first, second and third adhesive layers are independently selected from one or more of the group consisting of: an acrylic adhesive, a treated permanent acrylic, a coated permanent acrylic, a treated peelable acrylic, a coated peelable acrylic, a UV curing adhesive, a pressure sensitive adhesive, and UV curable pressure sensitive adhesive.

26. A package or packaging comprising the indicator device as claimed in any one of claims 1 to 25.

27. A tape or film comprising the indicator device as claimed in any one of claims 1 to 25.

28. A method of detecting the presence of an activating agent, comprising the steps of: a) providing an indicator device as claimed in any one of claims 1 to 25; b) activating the indicator device with an activating agent; andc) subsequently detecting a visible change in the indicator material whereby the presence of the activating agent is revealed.

29. A method of detecting whether a sealed package has been compromised, comprising the steps of: a) providing an indicator device as claimed in any one of claims 1 to 25; b) activating the indicator device with an activating agent; and c) subsequently detecting a visible change in the indicator material whereby the compromise of the package is revealed.

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