A container for a liquid comprising a thermochromic fill line

Abstract

The invention relates to a container for a liquid comprising a thermochromic fill line. At ambient temperature and when the container is empty, the fill line is preferably invisible. When the container is filled with a cold liquid such as a cold beverage, the thermochromic fill line preferably becomes visible thereby indicating that a sufficient volume of cold liquid has been filled into the container. Preferably, the thermochromic fill line does not become visible when the container is filled with in insufficient volume of a cold liquid at the bottom and an overhead froth.

Description

A container for a liquid comprising a thermochromic fill lineFIELD OF THE INVENTION

[0001] Priority is claimed of European patent application no. 23 217 921.8 that was filed on December 19, 2023.

[0002] The invention relates to a container for a liquid comprising a thermochromic fill line. At ambient temperature and when the container is empty, the fill line is preferably invisible. When the container is filled with a cold liquid such as a cold beverage, the thermochromic fill line preferably becomes visible thereby indicating that a sufficient volume of cold liquid has been filled into the container. Preferably, the thermochromic fill line does not become visible when the container is filled with an insufficient volume of a cold liquid at the bottom and an overhead froth.

[0003] A fill line is a marking on containers, such as cups, glasses and bowls, in particular drinking cups, indicating the volume of liquid held by the container. Many countries mandate fill lines on containers used commercially as a consumer protection measure. For example, in Austria, fill lines are governed by the Beverage Container Regulation, which provides error tolerances; glasses between 10 and 50 ml must be within 5% of the declared volume; larger containers must be accurate within 3%. In the United Kingdom, pint glasses typically hold one imperial pint (20 imp fl oz; 568 ml) when filled to the brim and commonly have a fill line for the volume of one-half of an imperial pint (284 ml).

[0004] Each of the European Union member states had a variety of weights and measures acts regarding legal metrology for all measuring devices used in commerce, including containers such as drinking cups. As part of the EU's 2004 Measuring Instruments Directive (2004 / 22 / EC), these were harmonized. The transitional period ended on 30 October 2016, meaning all containers such as drinking cups such produced or sold in the EU or Switzerland after this date must conform to the EU directive.

[0005] Containers, such as cups, glasses and bowls, in particular drinking cups, with fill lines have to include a bureau approved UK / CE mark. The CE mark on a product indicates that the manufacturer or importer of that product affirms its compliance with the relevant EU legislation and the product may be sold anywhere in the European Economic Area (EEA).

[0006] Previously, regulators accepted containers, such as drinking cups, particularly pints and half pints, with a fill line on the outside surface of a side wall as UK / CE labelled containers. This will no longer be the case from 2024 as it is too difficult to see where the fill line is on the inside of the container, in particular if the side wall of the container is opaque, such as a paper cup.

[0007] Currently used containers, in particular drinking cups such as paper cups, used to dispense beverages, e.g. a pint of beer, will therefore no longer be accepted for UK / CE marking in the UK (and EU).

[0008] Containers, in particular paper cups, comprising a plastic window on the top of the container have been provided. However, this adds unnecessary complexity and use of plastic.

[0009] WO 2018 / 026337 Al relates to a glass container having the characteristic of changing its color depending on the temperature of the material therein, thanks to the thermochromic coating applied thereon.

[0010] EP 3 257 908 Al relates to a smart container for food and fluids, which can take any shape, serving as a packaging for the commercialization of food and liquids, consisting for example in a vase or a bottle, which incorporates, on the outer surface thereof, an indivisible microencapsulation of printed plastic supports combined with thermochromic inks that react to temperature.

[0011] US 5,156,283 A relates to a beer stein made of wood and having an emblem or insert on the side which responds to environmental changes by changing its appearance. The insert may be thermochromic, motion-responsive, or the like. If thermochromic, it may respond to the temperature of the air, or that of the beer.

[0012] US 2002 0062691 Al relates to an infant drinking cup that has a first color when at room temperature. When the cup is filled with a cold beverage, the portion of the cup below the fill line changes to a second color. When handled by an infant, those areas below the fill line in contact with the infant's warm hands change color back to the first color. The process is fully reversible, such that the infant drinking cup can change from the cold color to the warm color, and vice versa, repeatedly.

[0013] US 2002 0097777 Al relates to a temperature indicating beverage cup comprising: a ceramic beverage holding cup, an integral, applied thermochromatic display fixedly printed on the outside wall of said ceramic cup, said thermochromatic display having a plurality of printed segments, each said segment correlating to a temperature range, and said segments revealing a written or numeric display as the temperature causes said thermochromatic to transition from opaque to transparent.

[0014] US 2004 0226363 Al relates to a level indicator and method which is intimately affixed to the outside surface of the outside wall of a container, for use in the determination of the level of the interface between a liquid and the void volume above it within a container. The level indicator includes a thermochromic leucodye ink layer which has at least one, and usually at least two, leucodye inks. Each of the leucodye inks responds chromatically within a different operating temperature range.

[0015] US 2007 0212501 Al relates to a beverage container holder comprising a tubular liner having an outside surface and a thermochromic ink composition on the outer surface forming at least a portion of a graphics pattern. The thermochromic ink composition has (1) a first state that matches or masks a portion of the graphics pattern at room temperature, (2) a second state that reacts to thermal change at a temperature above room temperature from a hot medium disposed in the container to reveal a first phase of the graphics pattern, and (3) a third state that reacts to a thermal change at a temperature below roomtemperature from a cold medium disposed in the container to reveal a second phase of the graphics pattern.

[0016] US 2012 0152781 Al relates to a beverage container having at least one surface visible to a user of the beverage container and a pattern formed of a thermochromic material that provides information to the user of the beverage container.

[0017] US 2013 0340885 Al relates to a thermochromic ink or print varnish that is formulated and printed to form a level indicator.

[0018] US 2018 0136052 Al relates to an activatable quality label operative to provide an indication of exceedance of a temperature threshold following activation thereof at a temperature less than or equal to an activation temperature.

[0019] GB 2 401 176 A relates to a container, e.g., for beverages comprises a first temperature sensitive area which produces a first visual signal at a first predetermined temperature; and a second temperature sensitive area which produces a second visual signal at a second predetermined temperature, the first and second signals being indicative of the suitability of the containers contents for consumption, during use.

[0020] DE 2020 10005171 U relates to a cardboard or plastic cup, which is provided with a special label or with a special imprint (heat indicator), for determining the ideal serving temperature of hot drinks by reversible color change. The heat-sensitive temperature range is printed with thermochromic inks containing microencapsulated liquids which discolor from their base color to another as the heat decreases or to a toned tone of their base.

[0021] E.S. Thamrin et al., IOP Conf. Series: Earth and Environmental Science, 1063 (2022) 012021, doi: 10. 1088 / 1755-1315 / 1063 / 1 / 012021 reviews thermochromic ink as a smart indicator on cold product packaging.

[0022] The containers, in particular drinking cups, of the prior art are not satisfactory in every respect and there is a demand for improved containers.

[0023] It is an object of the invention to provide appealing containers for a liquid, in particular drinking cups such as paper cups, which comprise a clearly visible fill line and comply with the regulatory requirements.SUMMARY OF THE INVENTION

[0024] This object has been achieved by the subject-matter of the patent claims.

[0025] It has been surprisingly found that a thermochromic fill line can be applied to a container, preferably a drinking cup such as a paper cup. The thermochromic fill line preferably is invisible at ambient temperature (23 °C) and when the container is empty. When the container is filled with a cold liquid or a hot liquid, the thermochromic fill line preferably becomes visible, thereby indicating that a sufficientvolume of liquid has been filled into the container. Thus, the thermochromic fill line is easily visible, also when applied on the outside of the container and when the sidewall of the container is opaque.

[0026] Further, it has been found that thermochromic ink, preferably made from microcapsules, is particularly useful for a thermochromic fill line, especially on opaque containers such as paper cups. Preferably, the microcapsules encapsulate a pigment or dye at ambient temperature (23 °C), and are disrupted thereby releasing pigment or dye upon cooling to a cold-activation temperature or heating to a hot- activation temperature.

[0027] Still further, it has been surprisingly found that the thermochromic fill line does not become visible when the container is filled with an insufficient volume of a cold liquid, e.g. beer, at the bottom and an overhead froth.

[0028] Furthermore, the container for liquids comprising the thermochromic fill line complies with the regulatory requirements. Thus, windowless containers, particularly paper cups, with a UK / CE mark can be provided.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 shows the heat conductivity of different baseboards.

[0030] Figure 2 to 5 schematically illustrate a perspective view of a preferred container according to the invention.DETAILED DESCRIPTION OF THE INVENTION

[0031] A first aspect of the invention relates to a container for a liquid comprising a thermochromic fill line.

[0032] When the container is empty, it has a maximal fill volume (=100%), i.e. a maximal capacity for liquid without overflow when the container is placed in an upright position. The fill line is typically located at a position indicating a predetermined fill volume that is less than the maximal fill volume (e.g. 90% of the maximal fill volume). The container and the thermochromic fill line are preferably customized such that the thermochromic fill line changes visual appearance when the container is filled with a volume of liquid at least corresponding to the predetermined fill volume as indicated by the fill line, wherein the liquid has a temperature that differs from ambient temperature.

[0033] For the purpose of the specification, a "fill line" is a marking on a container indicating the volume of liquid held by the container.

[0034] For the purpose of the specification, "thermochromism" is the property of a substance to change its visual appearance, more preferably its color, due to a change in temperature. Thus, a thermochromic fill line preferably changes its visual appearance, more preferably its color, depending on temperature: At ambient temperature (23 °C), the thermochromic fill line preferably is invisible. Upon (i) cooling toa cold-activation temperature or (ii) heating to a hot-activation temperature, the thermochromic fill line preferably changes its visual appearance, more preferably its color.

[0035] For the purpose of the specification, "ambient temperature" is the actual temperature, preferably as measured by a thermometer, of the air (or other medium and surroundings) in any particular place. In particular, "ambient temperature" means 23°C.

[0036] Preferably, at ambient temperature (23 °C) the thermochromic fill line is invisible.

[0037] Preferably, at ambient temperature (23 °C) the thermochromic fill line is white, colorless, transparent or translucent.

[0038] For the purpose of the specification, "invisible" means that the thermochromic fill line on the container is impossible to be seen, preferably from a distance of 2 m, at daylight and with the naked eye. Visibility of the thermochromic fill line at ambient temperature (23°C) may depend on the properties of the container such as material and color of the container. For example, if both the container and the thermochromic fill line are white at ambient temperature (23°C), the thermochromic fill line may be invisible. If the thermochromic fill line then changes its color and becomes e.g. blue, the thermochromic fill line may become visible on the white container.

[0039] Preferred embodiments regarding cold activation

[0040] In preferred embodiments, the thermochromic fill line is visible at a temperature of 4°C.

[0041] Preferably, the thermochromic fill line is colored or black; preferably blue; at a temperature of 4°C.

[0042] Preferably, the thermochromic fill line comprises or essentially consists of a cold-activatable thermochromic ink.

[0043] For the purpose of the specification, a "thermochromic ink" is a temperature sensitive compound that changes its visual appearance, preferably its color, with exposure to cold or heat. Thermochromic inks are preferably based on liquid crystals or leuco dyes. Liquid crystals preferably have a low-temperature crystallic phase, an anisotropic chiral or twisted nematic phase, and a high-temperature isotropic liquid phase. Liquid crystals may be capable of displaying different colors at different temperatures. The color change is typically dependent on selective reflection of certain wavelengths by the crystallic structure of the material, as it changes between the different phases. Preferably, the high temperature phase will reflect blue-violet, while the low-temperature phase will reflect red-orange. Leuco dyes preferably have a colorless leuco form and a colored form. Leuco dyes are preferably applied in the form of microcapsules with a mixture of one or more other suitable chemicals sealed inside, such as an acid. Suitable leuco dyes are spirolactones, fluorans, spiropyrans, and fulgides. Suitable acids include bisphenol A, parabens, 1,2,3-triazole derivates, and 4-hydroxycoumarin. The acid acts as proton donor, preferably changing the dye molecule between its leuco form and its protonated colored form; stronger acids canmake the change irreversible. Leuco dyes typically have less accurate temperature response than liquid crystals.

[0044] Preferably, the thermochromic ink is made from microcapsules, which preferably undergo color transformation in response to changes in temperature. The thermochromic ink is particularly useful for high-speed commercial printing environments and various brand applications. The applications encompass various industries, including CPG food and beverage thermochromic ink packaging, medical and pharmaceutical supply chain indicators, product security, authentication, and anti-counterfeiting features.

[0045] Preferably, the ink becomes visible when it is cooled to a temperature equal to or below a coldactivation temperature, preferably on the outside of the container, thereby denoting the position of the volume of the liquid with regards to the fill line. In preferred embodiments, the thermochromic fill line is applied by means of a label. Preferably, pigment formulation and density level are formulated to give the most amount of contrast from the background color as soon as the cold-activation temperature is reached. Preferably, the thermochromic ink changes color and becomes blue at a temperature equal to or below a cold-activation temperature. Preferably, the contrast can be improved by screen printing, preferably litho printing.

[0046] Cold-activatable thermochromic inks are known to the skilled person and commercially available, e.g. (i) Chromatic Technologies Inc., Colorado Springs, CO; (ii) Thermometer Site, division of LCRHallcrest, Glenview, IL 60026; (iii) COLORS Printing Inks, Navi Mumbai: 400705, Maharashtra, India; (iv) SpotSee, Dalls, TX.

[0047] Preferably, the thermochromic fill line at ambient temperature (23 °C) is present in an activatable state and can be activated by cooling to a cold-activation temperature.

[0048] Preferably, the thermochromic fill line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23°C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon cooling to a cold-activation temperature.

[0049] Preferably, the thermochromic fill line is configured to change its visual appearance upon cooling to a cold-activation temperature.

[0050] The container according to the invention is preferably configured to change the visual appearance of the fill line upon filling the container with water having a temperature equal to or below a coldactivation temperature; preferably 4°C.

[0051] Preferably, after filling the container with the water, the change of visual appearance of the fill line occurs within at most 15 seconds; preferably at most 14 seconds; more preferably at most 13 seconds; still more preferably at most 12 seconds; yet more preferably at most 11 seconds; even more preferably at most 10 seconds; most preferably at most 9 seconds; and in particular at most 8 seconds.

[0052] The container according to the invention is preferably configured not to change the visual appearance of the fill line upon filling the container with froth having a temperature equal to or below a cold-activation temperature; preferably 4°C.

[0053] Preferably, the thermochromic fill line does not change the visual appearance when the container is filled with an insufficient volume of a cold liquid at the bottom and an overhead froth. Preferably, froth and liquid have essentially the same temperature, but the specific latent heat capacity of the liquid is 3.9 J / g-K whilst the specific latent heat capacity of the froth is 0. 17 J / g-K. Therefore, the rate of heat transfer for the thermochromic fill line, which preferably is on the side wall, is 22 times faster for the liquid than the froth. If within a certain time frame the froth starts to change the visual appearance, preferably color, of the thermochromic fill line, indication of the fill line would be void. The half life of beer froth typically is 41 seconds. The rate of heat transfer will therefore decrease by 50% every 41 seconds. All these factors have to be taken into consideration when determining the cold-activation temperature.

[0054] Preferably, after filling the container with the froth, the change of visual appearance of the fill line does not occur for at least 1 minute; preferably at least 2 minutes; more preferably at least 3 minutes; still more preferably at least 4 minutes; yet more preferably at least 5 minutes; even more preferably at least 10 minutes; most preferably at least 15 minutes; and in particular at least 30 minutes.

[0055] Preferably, the change of visual appearance includes a change of at least one optical property; preferably selected from color, contrast, brightness, saturation, opacity and any combination thereof; more preferably at least color.

[0056] Preferably, the change of visual appearance is irreversible.

[0057] Preferably, the relative difference of ambient temperature (23°C) to the cold-activation temperature; is at least 2.5°C; preferably at least 5.0°C; more preferably at least 7.5°C; still more preferably at least 10°C; yet more preferably at least 12.5°C; even more preferably at least 15°C; most preferably at least 17.5°C; and in particular at least 20°C.

[0058] Preferably, the thermochromic fill line is visible at the cold-activation temperature.

[0059] Preferably, the thermochromic fill line is colored or black; preferably blue; at the cold-activation temperature.

[0060] In preferred embodiments, the thermochromic fill line is invisible at ambient temperature (23°C) and visible at a temperature of 4°C. Preferably, at ambient temperature (23°C) the thermochromic fill line is present in an activatable state and can be activated by cooling to a cold-activation temperature. Upon cooling to the cold-activation temperature, the thermochromic fill line preferably changes its visual appearance, more preferably its color, and becomes visible. The thermochromic fill line is therefore preferably visible at a temperature equal to or below the cold-activation temperature.

[0061] For the purpose of the specification, the "cold-activation temperature" is the temperature below ambient temperature (23°C), at which the thermochromic fill line, preferably the thermochromic ink, can be activated. Preferably, the activated thermochromic fill line changes its visual appearance, more preferably its color, and becomes visible when activated. Preferably, the thermochromic fill line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23 °C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon cooling to the cold-activation temperature.

[0062] Preferably, the cold-activation temperature is set to a specific temperature for the thermochromic fill line to become visible as soon as the temperature of the liquid is sufficiently low to cause a change. The thermochromic ink preferably remains invisible at ambient temperature (23 °C) indoors as well as outside during outdoor events. The more the cold-activation temperature differs from the temperature of the liquid, the more contrast can preferably be generated from the background color and the faster is the rate of change of the color of the fill line. The temperature of the working environment should therefore be taken into account, when determining the cold-activation temperature.

[0063] In a preferred embodiment, the thermochromic fill line, preferably the thermochromic ink, can be activated and thus changes color at a cold-activation temperature of 15°C. It preferably forms a blue fill line within seconds on the outside of the container, when filled with a cold beverage, preferably beer, having a temperature of 4-6°C. Preferably, the cold beverage cools the container wall at the position of the fill line.

[0064] Preferred embodiments regarding hot activation

[0065] In preferred embodiments, the thermochromic fill line is visible at a temperature of 55°C.

[0066] Preferably, the thermochromic fill line is colored or black; preferably blue at a temperature of 55°C.

[0067] Preferably, the thermochromic fill line comprises or essentially consists of a hot-activatable thermochromic ink.

[0068] Preferably, the ink becomes visible when it is heated to a temperature equal to or above a hot- activation temperature, preferably on the outside of the container, thereby denoting the position of the volume of the liquid with regards to the fill line. In preferred embodiments, the thermochromic fill line is applied by means of a label. Preferably, pigment formulation and density level are formulated to give the most amount of contrast from the background color as soon as the hot-activation temperature is reached. Preferably, the thermochromic ink changes color and becomes blue at a temperature equal to or above a hot-activation temperature.

[0069] Hot-activatable thermochromic inks are known to the skilled person and commercially available, e.g. (i) Chromatic Technologies Inc., Colorado Springs, CO; (ii) Thermometer Site, division ofLCRHallcrest, Glenview, IL 60026; (iii) COLORS Printing Inks, Navi Mumbai: 400705, Maharashtra, India; (iv) SpotSee, Dalls, TX.

[0070] Preferably, the thermochromic fill line at ambient temperature (23 °C) is present in an activatable state and can be activated by heating to a hot-activation temperature.

[0071] Preferably, the thermochromic fill line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23 °C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon heating to a hot-activation temperature.

[0072] Preferably, the thermochromic fill line is configured to change its visual appearance upon heating to a hot-activation temperature.

[0073] The container according to the invention is preferably configured to change the visual appearance of the fill line upon filling the container with water having a temperature equal to or above a hot- activation temperature; preferably 55 °C.

[0074] Preferably, after filling the container with the water, the change of visual appearance of the fill line occurs within at most 15 seconds; preferably at most 14 seconds; more preferably at most 13 seconds; still more preferably at most 12 seconds; yet more preferably at most 11 seconds; even more preferably at most 10 seconds; most preferably at most 9 seconds; and in particular at most 8 seconds.

[0075] The container according to the invention is preferably configured not to change the visual appearance of the fill line upon filling the container with froth having a temperature equal to or above a hot-activation temperature; preferably 55°C.

[0076] Preferably, after filling the container with the froth, the change of visual appearance of the fill line does not occur for at least 1 minute; preferably at least 2 minutes; more preferably at least 3 minutes; still more preferably at least 4 minutes; yet more preferably at least 5 minutes; even more preferably at least 10 minutes; most preferably at least 15 minutes; and in particular at least 30 minutes.

[0077] Preferably, the change of visual appearance includes a change of at least one optical property; preferably selected from color, contrast, brightness, saturation, opacity and any combination thereof; more preferably at least color.

[0078] Preferably, the change of visual appearance is irreversible.

[0079] Preferably, the relative difference of ambient temperature (23°C) to the hot-activation temperature is at least 2.5°C; preferably at least 5.0°C; more preferably at least 7.5°C; still more preferably at least 10°C; yet more preferably at least 12.5°C; even more preferably at least 15°C; most preferably at least 17.5°C; and in particular at least 20°C.

[0080] Preferably, the thermochromic fill line is visible at the hot-activation temperature.

[0081] Preferably, the thermochromic fill line is colored or black; preferably blue; at the hot-activation temperature.

[0082] In preferred embodiments, the thermochromic fdl line is invisible at ambient temperature (23°C) and visible at a temperature of 55 °C. Preferably, at ambient temperature (23 °C) the thermochromic fdl line is present in an activatable state and can be activated by heating to a hot-activation temperature. Upon heating to the heat-activation temperature, the thermochromic fdl line preferably changes its visual appearance, more preferably its color, and becomes visible. The thermochromic fdl line is therefore preferably visible at a temperature equal to or above the hot-activation temperature.

[0083] For the purpose of the specification, the "hot-activation temperature" is the temperature above ambient temperature (23°C), at which the thermochromic fdl line, preferably the thermochromic ink, can be activated. Preferably, the activated thermochromic fdl line changes its visual appearance, more preferably its color, and becomes visible when activated. Preferably, the thermochromic fdl line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23 °C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon heating to the hot-activation temperature.

[0084] Further preferred embodiments

[0085] The following embodiments are preferred regarding cold activation as well as hot activation.

[0086] Preferably, a label comprising the thermochromic fdl line is attached to the container according to the invention.

[0087] Preferably, the thermochromic fdl line is configured to indicate a volume of liquid to fdl the container.

[0088] Preferably, the volume of liquid to fdl the container is selected from(a) 50 mb, 100 mb, 150 mb, 200, mb, 250 mb, 300 mb, 330 mb, 400 mb, 500 mb, 750 mb and 1000 mb; or(b) 12 oz, 16 oz, 22 oz and 32 oz.

[0089] The container according to the invention preferably comprises a side wall having an inside surface and an outside surface, wherein the thermochromic fdl line is applied to a location of the outside surface; optionally by means of a label.

[0090] Preferably, the label is designed to ensure maximum visibility of change of visual appearance, preferably color, and minimum amount of thermochromic fdl line, preferably thermochromic ink, used. Thermochromic inks typically cost more than 10 times the cost of regular ink and need 15 times the volume per cm2to achieve the desired contrast, as well as to detect the fdl level in a way that is satisfactory to the user and to the regulator. This thermochromic ink is 150 times more expensive than regular ink, which has a huge impact on the overall cost of the container. To economize the amount of ink used is therefore preferred for the cost viability of the container.

[0091] The container according to the invention preferably additionally comprises a circular bottom and a circular top rim, wherein the side wall is circumferential and extends from the bottom to the top rim.

[0092] The container according to the invention preferably is a drinking cup.

[0093] The container according to the invention preferably is for single use.

[0094] The container according to the invention preferably is made from an opaque material.

[0095] The container according to the invention preferably is made from a material comprising cardboard.

[0096] Preferably, thickness and grammage (area weight) of the cardboard are selected to indicate optimal activation (e.g. color change) of the thermochromic fill line upon filling the container with a liquid having a temperature that differs from ambient temperature. Optimal activation (e.g. color change) of the thermochromic fill line is typically achieved when there is sufficient heat transfer between the liquid inside the container and the thermochromic fill line through the container wall within a reasonable serving time, preferably within a few seconds, without compromising other properties of the container such as mechanical strength. The direction of heat transfer depends upon the temperature of the liquid. On the one hand, when the liquid is colder than ambient temperature, heat flows from the thermochromic fill line at the outside of the container to the liquid inside the container thereby cooling the thermochromic fill line. When the liquid is warmer than ambient temperature, heat flow is in opposite direction thereby heating the thermochromic fill line.

[0097] Heat transfer depends inter alia upon the nature (e.g. specific heat capacity) and thickness of the material from which the container is made, and the relative temperature difference AT of the liquid inside the container to ambient temperature. When the container is made from a multilayer material, heat transfer depends upon the nature and thickness of each individual layer and possibly also on the mode of bonding adjacent layers to one another.

[0098] The time that is required to activate the thermochromic fill line by changing its temperature (e.g. to induce the color change) is a function of heat transfer and activation temperature of the thermochromic fill line. As a general rule, the thinner the container material, the faster the activation will occur.

[0099] Preferably, the area weight and / or thickness of the cardboard are selected to allow for sufficient heat transfer such that the fill line changes its visual appearance upon filling the container with water having a temperature of 4°C, wherein after filling the container with the water, the change of visual appearance of the fill line occurs within at most 15 seconds.

[0100] In preferred embodiments, the cardboard has an area weight, determined according to ISO 536, within the range of 280±225 g / m2; preferably 280±200 g / m2; more preferably 280±175 g / m2; still more preferably 280±150 g / m2; yet more preferably 280±125 g / m2; even more preferably 280±100 g / m2; most preferably 280±75 g / m2; and in particular 280±50 g / m2.

[0101] Preferably, the cardboard is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE).

[0102] Preferably, the layer has a thickness, determined according to the mill method, within the range of 15±12.5 pm; preferably 15±10 pm; more preferably 15±7.5 pm; still more preferably 15±5.0 pm; yet more preferably 15±2.5 pm.

[0103] Preferably, the cardboard has athickness, determined according to ISO 534, within the range of 400±225 pm; preferably 400±200 pm; more preferably 400±175 pm; still more preferably 400±150 pm; yet more preferably 400±125 pm; even more preferably 400±100 pm; most preferably 400±75 pm; and in particular 400±50 pm.

[0104] In preferred embodiments, the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 247±50 g / m2; preferably 247±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 340±50 pm; preferably 340±25 pm.

[0105] Preferably, the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 232±50 g / m2; preferably 232±25 g / m2;- a thickness, determined according to ISO 534, within the range of 330±50 pm; preferably 330±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 215±50 mN; preferably 215±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 95±50 mN; preferably 95±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±l .0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

[0106] In other preferred embodiments, the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 275±50 g / m2; preferably 275±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 380±50 pm; preferably 380±25 pm.

[0107] Preferably, the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 260±50 g / m2; preferably 260±25 g / m2;- a thickness, determined according to ISO 534, within the range of 370±50 pm; preferably 370±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 290±50 mN; preferably 290±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 130±50 mN; preferably 130±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±l .0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

[0108] In still other preferred embodiments, the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 310±50 g / m2; preferably 310±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 420±50 pm; preferably 420±25 pm.

[0109] Preferably, the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 295±50 g / m2; preferably 295±25 g / m2;- a thickness, determined according to ISO 534, within the range of 410±50 pm; preferably 410±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 380±50 mN; preferably 380±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 170±50 mN; preferably 170±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±l .0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

[0110] In still other preferred embodiments, the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 345±50 g / m2; preferably 345±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 460±50 pm; preferably 460±25 pm.

[0111] Preferably, the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 330±50 g / m2; preferably 330±25 g / m2;- a thickness, determined according to ISO 534, within the range of 450±50 pm; preferably 450±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 500±50 mN; preferably 500±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 230±50 mN; preferably 230±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

[0112] Preferably, the cardboard is designed to accelerate the change of the visual appearance of the thermochromic fill line, preferably of the thermochromic ink. Preferably, paper grammage per square meter (gsm) and thermal conductivity (U-value) are especially formulated to ensure maximum contrast and to increase the rate of change of visual appearance. Lower paper gsm and itp values lowers the u- value, which means that the less insulative properties between liquid and thermochromic fill line, preferably of the thermochromic ink, ensure a faster rate change of visual appearance, preferably color.

[0113] Preferably, the base board is based on a three layer fiber construction with chemical thermo mechanical pulp (CTMP) in the middle layer.

[0114] Preferably, heat resistance of the cardboard increases with the area weight and the bulkiness of the base board. Preferably, the higher the heat resistance of the cardboard is, the slower is the change of visual appearance, preferably color, of the thermochromic fill line, preferably the thermochromic ink. Preferably, the lower the area weight of the cardboard is, the faster is the change of visual appearance, preferably color, of the thermochromic fill line, preferably the thermochromic ink. Preferably, the lower the area weight of the cardboard is, the lower is the bending resistance (stiffness), which means that the container may become unstable at lower grammages, for example when holding 568.25ml (pint). Selecting the preferred area weight of the cardboard is therefore preferably a compromise between a fast change of visual appearance, preferably color, of the thermochromic fill line, preferably the thermochromic ink and the stability of the container, for example when holding 568.26ml.

[0115] In preferred embodiments, the thermochromic fill line has a thickness of at most 5.0 mm; preferably at most 4.0 mm; more preferably at most 3.0 mm; still more preferably at most 2.0 mm; yet more preferably at most 1.0 mm.

[0116] In preferred embodiments, the thermochromic fdl line has a length of at most 5.0 cm; preferably at most 4.0 cm; more preferably at most 3.0 cm; still more preferably at most 2.0 cm; yet more preferably at most 1.0 cm.

[0117] In preferred embodiments, the thermochromic fill line has a length of at least 1.0 cm; preferably at least 2.0 cm; more preferably at least 3.0 cm; still more preferably at least 4.0 cm; yet more preferably at least 5.0 cm, even more preferably at least 6.0 pm, most preferably at least 7.0 pm, and in particular at least 8.0 pm.

[0118] Preferably, the thermochromic fill line is present in essentially horizontal arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially parallel to the thermochromic fill line.

[0119] Preferably, the thermochromic fill line is present in essentially vertical arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially orthogonal to the thermochromic fill line.

[0120] Preferably, the thermochromic fill line is a straight line.

[0121] Another aspect of the invention relates to a use of a thermochromic ink for printing a thermochromic fill line of a container according to the invention as described above.

[0122] Another aspect of the invention relates to a use of a label comprising a thermochromic fill line according to the invention as described above for indicating a volume of liquid to fill a container.

[0123] Another aspect of the invention relates to a process for the preparation of a container according to the invention as described above comprising the steps of(a) providing a label with a thermochromic fill line; and(b) adhering the label- to the container or- to a material and subsequently forming the container from said material; wherein the label is adhered at a location such that the fill line indicates a volume of liquid to fill the container.

[0124] Preferably, step (a) of the process according to the invention involves printing the thermochromic fill line onto the label.

[0125] Another aspect of the invention relates to a process for the preparation of a container according to the invention as described above comprising the step of printing a thermochromic fill line onto- a container or- a material and subsequently forming the container from said material;wherein the thermochromic fill line is printed at a location such that the fill line indicates a volume of liquid to fill the container.

[0126] Preferably, printing comprises flexo printing and / or gravure printing.

[0127] Preferably, the thermochromic fill line is printed with a water based thermochromic ink.

[0128] Preferably, printing does not involve treatment with UV irradiation.

[0129] Preferably, flexo printing and / or gravure printing includes the maximum amount of microcapsules per cm2without the use of UV irradiation drying technology. UV irradiation drying technologies are typically difficult to use for food safety regulations (FDA, Reach) and also are inclined to leave an odor which is unsuitable for the consumption of beverages.

[0130] The following table shows the density of water as a function of temperature from 15 to 35°C and in compliance with the regulation EN4787:

[0131] The following table shows the density of water as a function of temperature from 0 to 30.9°C by 0.1°C increments and in compliance with the regulation EN4787:

[0132] Particularly preferred embodiments of the invention are summarized as clauses 1 to 52 hereinafter:Clause 1 : A container for a liquid comprising a thermochromic fill line.Clause 2: The container according to clause 1, wherein at ambient temperature (23 °C) the thermo- chromic fill line is invisible.Clause 3: The container according to clause 1 or 2, wherein at ambient temperature (23°C) the thermo- chromic fill line is white, colorless, transparent or translucent.Clause 4: The container according to any of the preceding clauses, wherein the thermochromic fill line is visible (i) at a temperature of 4°C; or (ii) at a temperature of 55°C.Clause 5 : The container according to any of the preceding clauses, wherein the thermochromic fill line is colored or black; preferably blue; (i) at a temperature of 4°C; or (ii) at a temperature of 55°C.Clause 6: The container according to any of the preceding clauses, wherein the thermochromic fill line comprises or essentially consists of (i) a cold-activatable thermochromic ink; or (ii) a hot-activatable thermochromic ink.Clause 7 : The container according to any of the preceding clauses, wherein the thermochromic fill line at ambient temperature (23°C) is present in an activatable state and can be activated (i) by cooling to a cold-activation temperature; or (ii) by heating to a hot-activation temperature.Clause 8: The container according to any of the preceding clauses, wherein the thermochromic fill line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23°C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon (i) cooling to a cold-activation temperature; or (ii) heating to a hot-activation temperature.Clause 9: The container according to any of the preceding clauses, wherein the thermochromic fill line is configured to change its visual appearance upon (i) cooling to a cold-activation temperature; or (ii) heating to a hot-activation temperature.Clause 10: The container according to any of the preceding clauses, which is configured to change the visual appearance of the fill line upon filling the container with water having a temperature (i) equal to or below a cold-activation temperature; preferably 4°C; or (ii) equal to or above a hot-activation temperature; preferably 55°C.Clause 11: The container according to clause 10, wherein after filling the container with the water, the change of visual appearance of the fill line occurs within at most 15 seconds; preferably at most 14 seconds; more preferably at most 13 seconds; still more preferably at most 12 seconds; yet more preferably at most 11 seconds; even more preferably at most 10 seconds; most preferably at most 9 seconds; and in particular at most 8 seconds.Clause 12: The container according to any of the preceding clauses, which is configured not to change the visual appearance of the fill line upon filling the container with froth having a temperature (i) equal to or below a cold-activation temperature; preferably 4°C; or (ii) equal to or above a hot-activation temperature; preferably 55 °C.Clause 13: The container according to clause 12, wherein after filling the container with the froth, the change of visual appearance of the fill line does not occur for at least 1 minute; preferably at least 2minutes; more preferably at least 3 minutes; still more preferably at least 4 minutes; yet more preferably at least 5 minutes; even more preferably at least 10 minutes; most preferably at least 15 minutes; and in particular at least 30 minutes.Clause 14: The container according to any of clauses 9 to 13, wherein the change of visual appearance includes a change of at least one optical property; preferably selected from color, contrast, brightness, saturation, opacity and any combination thereof; more preferably at least color.Clause 15: The container according to any of clauses 9 to 14, wherein the change of visual appearance is irreversible.Clause 16: The container according to any of clauses 7 to 15, wherein the relative difference of ambient temperature (23°C) to (i) the cold-activation temperature; or (ii) the hot-activation temperature is at least 2.5°C; preferably at least 5.0°C; more preferably at least 7.5°C; still more preferably at least 10°C; yet more preferably at least 12.5°C; even more preferably at least 15°C; most preferably at least 17.5°C; and in particular at least 20°C.Clause 17: The container according to any of clauses 7 to 16, wherein the thermochromic fdl line is visible (i) at the cold-activation temperature; or (ii) at the hot-activation temperature.Clause 18: The container according to any of clauses 7 to 17, wherein the thermochromic fdl line is colored or black; preferably blue; (i) at the cold-activation temperature; or (ii) at the hot-activation temperature.Clause 19: The container according to any of the preceding clauses, wherein a label comprising the thermochromic fdl line is attached to the container.Clause 20: The container according to any of the preceding clauses, wherein the thermochromic fdl line is configured to indicate a volume of liquid to fdl the container.Clause 21: The container according to clause 20, wherein the volume is selected from (a) 50 mb, 100 mb, 150 mb, 200, mb, 250 mb, 300 mb, 330 mb, 400 mb, 500 mb, 750 mb and 1000 mL; or (b) 12 oz, 16 oz, 22 oz and 32 oz.Clause 22: The container according to any of the preceding clauses, which comprises a side wall having an inside surface and an outside surface, wherein the thermochromic fdl line is applied to a location of the outside surface; optionally by means of a label.Clause 23: The container according to clause 22, which additionally comprises a circular bottom and a circular top rim, wherein the side wall is circumferential and extends from the bottom to the top rim.Clause 24: The container according to any of the preceding clauses, which is a drinking cup.Clause 25: The container according to any of the preceding clauses, which is for single use.Clause 26: The container according to any of the preceding clauses, which is made from an opaque material.Clause 27: The container according to any of the preceding clauses, which is made from a material comprising cardboard.Clause 28: The container according to clause 27, wherein the cardboard has an area weight, determined according to ISO 536, within the range of 280±225 g / m2; preferably 280±200 g / m2; more preferably 280±175 g / m2; still more preferably 280±150 g / m2; yet more preferably 280±125 g / m2; even more preferably 280±100 g / m2; most preferably 280±75 g / m2; and in particular 280±50 g / m2.Clause 29: The container according to clause 27 or 28, wherein the cardboard is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE).Clause 30: The container according to clause 29, wherein the layer has a thickness, determined according to the mill method, within the range of 15±12.5 pm; preferably 15±10 pm; more preferably 15±7.5 pm; still more preferably 15±5.0 pm; yet more preferably 15±2.5 pm.Clause 31: The container according to any of clauses 27 to 30, wherein the cardboard has a thickness, determined according to ISO 534, within the range of 400±225 pm; preferably 400±200 pm; more preferably 400±175 pm; still more preferably 400±150 pm; yet more preferably 400±125 pm; even more preferably 400±100 pm; most preferably 400±75 pm; and in particular 400±50 pm.Clause 32: The container according to any of the preceding clauses, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein - the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 247±50 g / m2; preferably 247±25 g / m2; - the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and - the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 340±50 pm; preferably 340±25 pm.Clause 33 : The container according to clause 32, wherein the baseboard has one or more of the following properties: - an area weight, determined according to ISO 536, within the range of 232±50 g / m2; preferably 232±25 g / m2; - a thickness, determined according to ISO 534, within the range of 330±50 pm; preferably 330±25 pm; - a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 215±50 mN; preferably 215±25 mN; - a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 95±50 mN; preferably 95±25 mN; - a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%; - a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%; - a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min: and / or - a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.Clause 34: The container according to any of clauses 1 to 31, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein - the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 275±50 g / m2; preferably 275±25 g / m2; - the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and - the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 380±50 pm; preferably 380±25 pm.Clause 35 : The container according to clause 34, wherein the baseboard has one or more of the following properties: - an area weight, determined according to ISO 536, within the range of 260±50 g / m2; preferably 260±25 g / m2; - a thickness, determined according to ISO 534, within the range of 370±50 pm; preferably 370±25 pm; - a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 290±50 mN; preferably 290±25 mN; - a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 130±50 mN; preferably 130±25 mN; - a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%; - a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%; - a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or - a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.Clause 36: The container according to any of clauses 1 to 31, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein - the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 310±50 g / m2; preferably 310±25 g / m2; - the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and - the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 420±50 pm; preferably 420±25 pm.Clause 37: The container according to clause 36, wherein the baseboard has one or more of the following properties: - an area weight, determined according to ISO 536, within the range of 295±50 g / m2; preferably 295±25 g / m2; - a thickness, determined according to ISO 534, within the range of 410±50 pm; preferably 410±25 pm; - a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 380±50 mN; preferably 380±25 mN; - a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 170±50 mN; preferably 170±25 mN; - a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%; - a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%; - a surface smoothness Bendtsen, determined according to ISO 8791-2, within therange of 300±50 ml / min; preferably 300±25 ml / min; and / or - a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.Clause 38: The container according to any of clauses 1 to 31, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein - the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 345±50 g / m2; preferably 345±25 g / m2; - the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and - the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 460±50 pm; preferably 460±25 pm.Clause 39: The container according to clause 38, wherein the baseboard has one or more of the following properties: - an area weight, determined according to ISO 536, within the range of 330±50 g / m2; preferably 330±25 g / m2; - a thickness, determined according to ISO 534, within the range of 450±50 pm; preferably 450±25 pm; - a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 500±50 mN; preferably 500±25 mN; - a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 230±50 mN; preferably 230±25 mN; - a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%; - a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%; - a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or - a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.Clause 40: The container according to any of the preceding clauses, wherein the thermochromic fill line has a thickness of at most 5.0 mm; preferably at most 4.0 mm; more preferably at most 3.0 mm; still more preferably at most 2.0 mm; yet more preferably at most 1.0 mm.Clause 41 : The container according to any of the preceding clauses, wherein the thermochromic fill line has a length of at most 5.0 cm; preferably at most 4.0 cm; more preferably at most 3.0 cm; still more preferably at most 2.0 cm; yet more preferably at most 1.0 cm.Clause 42: The container according to any of the preceding clauses, wherein the thermochromic fill line has a length of at least 1.0 cm; preferably at least 2.0 cm; more preferably at least 3.0 cm; still more preferably at least 4.0 cm; yet more preferably at least 5.0 cm, even more preferably at least 6.0 pm, most preferably at least 7.0 pm, and in particular at least 8.0 pm.Clause 43 : The container according to any of the preceding clauses, wherein the thermochromic fill line is present in essentially horizontal arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially parallel to the thermochromic fill line.Clause 44: The container according to any of the preceding clauses, wherein the thermochromic fdl line is present in essentially vertical arrangement, such that when the container is fdled with a liquid, the surface of the liquid is essentially orthogonal to the thermochromic fdl line.Clause 45 : Use of a thermochromic ink for printing a thermochromic fdl line of a container according to any of the preceding clauses.Clause 46: Use of a label comprising a thermochromic fdl line as defined in any of the preceding clauses for indicating a volume of liquid to fdl a container.Clause 47: A process for the preparation of a container according to any of clauses 1 to 44 comprising the steps of (a) providing a label with a thermochromic fdl line; and (b) adhering the label - to the container or - to a material and subsequently forming the container from said material; wherein the label is adhered at a location such that the fdl line indicates a volume of liquid to fdl the container.Clause 48: The process according to clause 47, wherein step (a) involves printing the thermochromic fdl line onto the label.Clause 49: A process for the preparation of a container according to any of clauses 1 to 44 comprising the step of printing a thermochromic fdl line onto - a container or - a material and subsequently forming the container from said material; wherein the thermochromic fdl line is printed at a location such that the fdl line indicates a volume of liquid to fdl the container.Clause 50: The process according to clause 48 or 49, wherein printing comprises flexo printing and / or gravure printing.Clause 51: The process according to any of clauses 48 to 50, wherein the thermochromic fdl line is printed with a water based thermochromic ink.Clause 52: The process according to any of clauses 48 to 51, wherein printing does not involve treatment with UV irradiation.

[0133] Preferred embodiments of the invention are in the following described with reference to the drawings which, however, should not be construed as limiting the scope of the invention.

[0134] Figure 1 shows the heat conductivity of different baseboards.

[0135] Figure 2 schematically illustrates a perspective view of a preferred container (1) according to the invention for a liquid comprising a thermochromic fdl line (6). The container (1) comprises an interior (2) for receiving the liquid, which is formed by a side wall (3) having rim (4) and bottom (5). The thermochromic fdl line (6) is applied to a location of an outside surface of the sidewall (3) and may be invisible (6A), preferably at ambient temperature (23°C), or visible (6B), preferably at a temperature of 4°C or 55°C. Preferably, the thermochromic fdl line (6) at ambient temperature (23°C) is present in an activatable state and can be activated by (i) cooling to a cold-activation temperature or (ii) heating to a hot-activation temperature. Further, the thermochromic fdl line (6) is preferably configured to change its visual appearance, preferably color, upon (i) cooling to a cold-activation temperature or (ii) heatingto a hot-activation temperature. Preferably, the thermochromic fill line (6) is present in essentially horizontal arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially parallel to the thermochromic fill line.

[0136] Figure 3 schematically illustrates a perspective view of a preferred embodiment of the container (1) shown in Figure 2, wherein the container (1) is filled with a cold beverage (7). Figure 3A schematically illustrates a container (1), wherein the surface of the cold beverage (7) is below the thermochromic fill line (6), which is invisible (6A). Figure 3B schematically illustrates a container (1), wherein the surface of the cold beverage (7) is above the thermochromic fill line (6), which is visible (6B). Preferably, when the cold beverage (7) is below the thermochromic fill line (6), the thermochromic fill line (6) at ambient temperature (23°C) is present in an activatable state and is invisible. When the surface of the cold beverage (7) reaches the thermochromic fill line (6), the fill line (6) preferably is cooled to the coldactivation temperature and changes its visual appearance, thereby becoming visible (6B).

[0137] Figure 4 schematically illustrates a perspective view of a preferred embodiment of the container (1) shown in Figure 2, wherein the container (1) is filled with beer (7) at the bottom and an overhead beer froth (8). The surface of the beer (7) is below the thermochromic fill line (6), which is invisible (6A). The beer froth (8) is above the thermochromic fill line (6). Preferably, upon filling the container (1) with froth having a temperature equal to or below the cold-activation temperature, the fill line (6) is not cooled to the cold-activation temperature and does not change its visual appearance.

[0138] Figure 5 schematically illustrates a perspective view of a preferred embodiment of the container (1) shown in Figure 2, wherein the thermochromic fill line comprises a first part, which is present in essentially horizontal arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially parallel to the first part of the thermochromic fill line and a second part, which is present in essentially vertical arrangement, such that when the container is filled with a liquid, the surface of the liquid is essentially orthogonal to the second part of the thermochromic fill line. The container (1) is filled with a cold beverage (7). The surface of the cold beverage (7) is above the thermochromic fill line (6), which is visible (6B). Preferably, when the surface of the cold beverage (7) is below the first part and the second part of the thermochromic fill line (6), the thermochromic fill line (6) at ambient temperature (23°C) is present in an activatable state and is invisible. When the surface of the cold beverage (7) reaches the first part or the second part of the thermochromic fill line (6), the respective part of the fill line (6) preferably is cooled to a cold-activation temperature and changes its visual appearance, thus becoming visible (6B). Preferably, the second part of the thermochromic fill line (6) becomes visible piece by piece while filling the container (1) with the cold beverage (7).Reference numerals:1 - container;2 - interior;3 - sidewall;- rim; - botom; A - fill line invisible;B - fill line visible; - cold beverage; - beer froth; - vertical indicator;

Claims

Patent claims:

1. A container for a liquid, wherein the container is made from a material comprising cardboard, wherein the container comprises a thermochromic fdl line configured to change its visual appearance upon cooling to a cold-activation temperature below ambient temperature (23 °C).

2. The container according to claim 1, wherein the cardboard has an area weight, determined according to ISO 536, within the range of 280±225 g / m2; preferably 280±200 g / m2; more preferably 280±175 g / m2; still more preferably 280±150 g / m2; yet more preferably 280±125 g / m2; even more preferably 280±100 g / m2; most preferably 280±75 g / m2; and in particular 280±50 g / m2.

3. The container according to claim 1 or 2, wherein at ambient temperature (23 °C) the thermochromic fill line is invisible.

4. The container according to any of the preceding claims, wherein at ambient temperature (23°C) the thermochromic fill line is white, colorless, transparent or translucent.

5. The container according to any of the preceding claims, wherein at a temperature of 4°C the thermochromic fill line is visible.

6. The container according to any of the preceding claims, wherein at a temperature of 4°C the thermochromic fill line is colored or black; preferably blue.

7. The container according to any of the preceding claims, wherein the thermochromic fill line comprises or essentially consists of a cold-activatable thermochromic ink.

8. The container according to any of the preceding claims, wherein the thermochromic fill line at ambient temperature (23°C) is present in an activatable state and can be activated by cooling to a cold-activation temperature.

9. The container according to any of the preceding claims, wherein the thermochromic fill line comprises microcapsules that encapsulate a pigment or dye at ambient temperature (23°C), and wherein the microcapsules are disrupted thereby releasing pigment or dye upon cooling to a coldactivation temperature.

10. The container according to any of the preceding claims, which is configured to change the visual appearance of the fill line upon filling the container with water having a temperature equal to or below a cold-activation temperature; preferably 4°C.

11. The container according to claim 10, wherein after filling the container with the water, the change of visual appearance of the fill line occurs within at most 15 seconds; preferably at most 14 seconds; more preferably at most 13 seconds; still more preferably at most 12 seconds; yet morepreferably at most 11 seconds; even more preferably at most 10 seconds; most preferably at most 9 seconds; and in particular at most 8 seconds.

12. The container according to any of the preceding claims, which is configured not to change the visual appearance of the fill line upon filling the container with froth having a temperature equal to or below a cold-activation temperature; preferably 4°C.

13. The container according to claim 12, wherein after filling the container with the froth, the change of visual appearance of the fill line does not occur for at least 1 minute; preferably at least 2 minutes; more preferably at least 3 minutes; still more preferably at least 4 minutes; yet more preferably at least 5 minutes; even more preferably at least 10 minutes; most preferably at least 15 minutes; and in particular at least 30 minutes.

14. The container according to any of the preceding claims, wherein the change of visual appearance includes a change of at least one optical property; preferably selected from color, contrast, brightness, saturation, opacity and any combination thereof; more preferably at least color.

15. The container according to any of the preceding claims, wherein the change of visual appearance is irreversible.

16. The container according to any of the preceding claims, wherein the relative difference of ambient temperature (23°C) to the cold-activation temperature is at least 2.5°C; preferably at least 5.0°C; more preferably at least 7.5°C; still more preferably at least 10°C; yet more preferably at least 12.5°C; even more preferably at least 15°C; most preferably at least 17.5°C; and in particular at least 20°C.

17. The container according to any of the preceding claims, wherein at the cold-activation temperature the thermochromic fill line is visible.

18. The container according to any of the preceding claims, wherein at the cold-activation temperature the thermochromic fill line is colored or black; preferably blue.

19. The container according to any of the preceding claims, wherein a label comprising the thermochromic fill line is attached to the container.

20. The container according to any of the preceding claims, wherein the thermochromic fill line is configured to indicate a volume of liquid to fill the container.

21. The container according to claim 20, wherein the volume is selected from (a) 50 mb, 100 mb, 150 mL, 200, mL, 250 mb, 300 mb, 330 mb, 400 mb, 500 mb, 750 mb and 1000 mb; or (b) 12 oz, 16 oz, 22 oz and 32 oz.

22. The container according to any of the preceding claims, which comprises a side wall having an inside surface and an outside surface, wherein the thermochromic fdl line is applied to a location of the outside surface; optionally by means of a label.

23. The container according to claim 22, which additionally comprises a circular bottom and a circular top rim, wherein the side wall is circumferential and extends from the bottom to the top rim.

24. The container according to any of the preceding claims, which is a drinking cup.

25. The container according to any of the preceding claims, which is for single use.

26. The container according to any of the preceding claims, which is made from an opaque material.

27. The container according to any of the preceding claims, wherein the cardboard is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE).

28. The container according to claim 27, wherein the layer has a thickness, determined according to the mill method, within the range of 15±12.5 pm; preferably 15±10 pm; more preferably 15±7.5 pm; still more preferably 15±5.0 pm; yet more preferably 15±2.5 pm.

29. The container according to any of the preceding claims, wherein the cardboard has a thickness, determined according to ISO 534, within the range of 400±225 pm; preferably 400±200 pm; more preferably 400±175 pm; still more preferably 400±150 pm; yet more preferably 400±125 pm; even more preferably 400±100 pm; most preferably 400±75 pm; and in particular 400±50 pm.

30. The container according to any of the preceding claims, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 247±50 g / m2; preferably 247±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 340±50 pm; preferably 340±25 pm.

31. The container according to claim 30, wherein the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 232±50 g / m2; preferably 232±25 g / m2;- a thickness, determined according to ISO 534, within the range of 330±50 pm; preferably 330±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 215±50 mN; preferably 215±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 95±50 mN; preferably 95±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

32. The container according to any of claims 1 to 29, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 275±50 g / m2; preferably 275±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 380±50 pm; preferably 380±25 pm.

33. The container according to claim 32, wherein the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 260±50 g / m2; preferably 260±25 g / m2;- a thickness, determined according to ISO 534, within the range of 370±50 pm; preferably 370±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 290±50 mN; preferably 290±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 130±50 mN; preferably 130±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

34. The container according to any of claims 1 to 29, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferably a polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 310±50 g / m2; preferably 310±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 420±50 pm; preferably 420±25 pm.

35. The container according to claim 34, wherein the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 295±50 g / m2; preferably 295±25 g / m2;- a thickness, determined according to ISO 534, within the range of 410±50 pm; preferably 410±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 380±50 mN; preferably 380±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 170±50 mN; preferably 170±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

36. The container according to any of claims 1 to 29, wherein the cardboard is composed of a baseboard which is coated with a layer comprising or essentially consisting of a polymer; preferablya polyolefin; more preferably polyethylene; still more preferably low density polyethylene (LDPE); and wherein- the polymer coated cardboard has an area weight, determined according to ISO 536, within the range of 345±50 g / m2; preferably 345±25 g / m2;- the layer has a thickness, determined according to the mill method, within the range of 15±5.0 pm; preferably 15±2.5 pm; and- the polymer coated cardboard has a thickness, determined according to ISO 534, within the range of 460±50 pm; preferably 460±25 pm.

37. The container according to claim 36, wherein the baseboard has one or more of the following properties:- an area weight, determined according to ISO 536, within the range of 330±50 g / m2; preferably 330±25 g / m2;- a thickness, determined according to ISO 534, within the range of 450±50 pm; preferably 450±25 pm;- a bending resistance L&W 15° in machine direction, determined according to ISO 2493-1, within the range of 500±50 mN; preferably 500±25 mN;- a bending resistance L&W 15° in cross direction, determined according to ISO 2493-1, within the range of 230±50 mN; preferably 230±25 mN;- a moisture, determined according to ISO 287, within the range of 8.0±2.0%; preferably 8.0±1.0%;- a brightness D65 / 10, top, determined according to ISO 2470-2, within the range of 84±10%; preferably 84±5%;- a surface smoothness Bendtsen, determined according to ISO 8791-2, within the range of 300±50 ml / min; preferably 300±25 ml / min; and / or- a stretch in cross direction, determined according to ISO 1924-3, within the range of 6.0±2.0%; preferably 6.0±1.0%.

38. The container according to any of the preceding claims, wherein the thermochromic fill line is a straight line.

39. The container according to any of the preceding claims, wherein the thermochromic fill line has a thickness of at most 5.0 mm; preferably at most 4.0 mm; more preferably at most 3.0 mm; still more preferably at most 2.0 mm; yet more preferably at most 1.0 mm.

40. The container according to any of the preceding claims, wherein the thermochromic fill line has a length of at most 5.0 cm; preferably at most 4.0 cm; more preferably at most 3.0 cm; still more preferably at most 2.0 cm; yet more preferably at most 1.0 cm.

41. The container according to any of the preceding claims, wherein the thermochromic fdl line has a length of at least 1.0 cm; preferably at least 2.0 cm; more preferably at least 3.0 cm; still more preferably at least 4.0 cm; yet more preferably at least 5.0 cm, even more preferably at least 6.0 pm, most preferably at least 7.0 pm, and in particular at least 8.0 pm.

42. The container according to any of the preceding claims, wherein the thermochromic fdl line is present in essentially horizontal arrangement, such that when the container is fdled with a liquid, the surface of the liquid is essentially parallel to the thermochromic fdl line.

43. The container according to any of the preceding claims, wherein the thermochromic fdl line is present in essentially vertical arrangement, such that when the container is fdled with a liquid, the surface of the liquid is essentially orthogonal to the thermochromic fdl line.

44. Use of a thermochromic ink for printing a thermochromic fdl line of a container according to any of the preceding claims.

45. Use of a label comprising a thermochromic fdl line as defined in any of the preceding claims for indicating a volume of liquid to fdl a container.

46. A process for the preparation of a container according to any of claims 1 to 43 comprising the steps of (a) providing a label with a thermochromic fdl line; and (b) adhering the label- to the container or- to a material and subsequently forming the container from said material; wherein the label is adhered at a location such that the fdl line indicates a volume of liquid to fdl the container.

47. The process according to claim 46, wherein step (a) involves printing the thermochromic fdl line onto the label.

48. A process for the preparation of a container according to any of claims 1 to 43 comprising the step of printing a thermochromic fdl line onto- a container or- a material and subsequently forming the container from said material; wherein the thermochromic fdl line is printed at a location such that the fdl line indicates a volume of liquid to fdl the container.

49. The process according to claim 47 or 48, wherein printing comprises flexo printing and / or gravure printing.

50. The process according to any of claims 47 to 49, wherein the thermochromic fdl line is printed with a water based thermochromic ink.

51. The process according to any of claims 47 to 50, wherein printing does not involve treatment with UV irradiation.

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