WO2024056613A1

WO2024056613A1 - Humidity absorbing wrapper for aerosol-generating article

Info

Publication number: WO2024056613A1
Application number: PCT/EP2023/074920
Authority: WO
Inventors: Matteo Bologna
Original assignee: Philip Morris Products S.A.
Priority date: 2022-09-12
Filing date: 2023-09-11
Publication date: 2024-03-21

Abstract

The invention relates to an aerosol-generating article (10) comprising a plurality of elements, and a stick wrap, wherein the stick wrap is configured to connect the elements to form the aerosol-generating article, and wherein the aerosol-generating article is further configured to reveal a visually perceivable marking (60) upon contact of the stick wrap with humidity. The invention also relates to an aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article. The invention also relates to a method of manufacturing an aerosol-generating article, comprising providing a plurality of elements, providing a stick wrap connecting the elements by wrapping the stick wrap around the rod-shaped elements to form the aerosol-generating article, and wherein the aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.

Description

HUMIDITY ABSORBING WRAPPER FOR AEROSOL-GENERATING ARTICLE

The present invention relates to an aerosol-generating article comprising a humidity absorbing wrapper. The present invention also relates to an aerosol-generating system comprising the aerosol-generating article and a method of manufacturing the aerosolgenerating article.

One type of aerosol-generating system is an electrically operated aerosol-generating system. Known handheld electrically operated aerosol-generating systems typically comprise an aerosol-generating device comprising a battery, control electronics and an electric heater for heating an aerosol-generating article designed specifically for use with the aerosolgenerating device. The aerosol-generating article comprises an aerosol-forming substrate. In some examples, the aerosol-forming substrate is in the form of a plug, such as a tobacco plug, and the electric heater contained within the aerosol-generating device is inserted into the aerosol-forming substrate when the smoking article is inserted into the aerosol-generating device.

Typically, such aerosol-generating articles are made of a combination of multiple rodshaped elements, which may also be referred to as plugs. Each plug may be wrapped by a plug wrap. A stick wrap may be used to connect the individual rod-shaped elements and to form an elongated aerosol-generating article. A proximal end of the aerosol-generating article is intended to come into contact with the user’s lips. A distal end of the aerosol-generating article is intended to be inserted inside an aerosol-generating device and is intended to be heated for generating an inhalable aerosol. An aerosol-generating article may include at a distal end a substrate plug holding aerosol-forming substrate and a mouthpiece filter (MPF) at the proximal end. Other plugs may be provided between the substrate plug and the mouthpiece filter. Such plugs could be for instance a cardboard tube, cooling element made from polylactic acid (PLA) or a hollow acetate tube (HAT).

Electrically heated aerosol-generating articles are heated but not burned during consumption and are therefore also referred to as heat-not burn articles (HnB articles). HnB articles may not necessarily change their appearance during consumption such that a user may have a hard time distinguishing between used and unused HnB articles. This can be a problem when a consumer puts back a used aerosol-generating article in its original packaging together with other new (unused) aerosol-generating articles, as it could be the case when there is no bin nearby to dispose of the used/consumed aerosol-generating article.

It would be desirable to provide an aerosol-generating article that allows to easily distinguish a used from an unused aerosol-generating article. It would be particularly desirable to provide an aerosol-generating article having a front plug and a coated stick wrap, wherein a used aerosol-generating article can nevertheless be easily distinguished form an unused aerosol-generating article.

It would further be desirable to provide an aerosol-generating article that allows to permanently distinguish a used from an unused aerosol-generating article, and at least over a time period of several days.

According to an embodiment of the present invention an aerosol-generating article comprises a plurality of elements and a stick wrap. The stick wrap is configured to connect the rod-shaped elements to form the aerosol-generating article. The aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.

As used herein, the term “heated aerosol-generating article” refers to an aerosolgenerating article for producing an aerosol comprising an aerosol-generating substrate that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol. Such articles are commonly referred to as “heat-not-burn” products.

As used herein, the term “aerosol-generating substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol. The aerosol generated from aerosol-generating substrates of aerosol-generating articles described herein may be visible or invisible and may include vapours (for example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or solid at room temperature) as well as gases and liquid droplets of condensed vapours.

As used herein, the terms “rod” or “rod-shaped element” refer to a generally cylindrical element of substantially polygonal cross-section and preferably of circular, oval or elliptical cross-section. The term “article” will refer to an aerosol-generating article, unless otherwise stated.

As used herein, the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term “transverse” refers to the direction that is perpendicular to the longitudinal axis.

As used herein, the terms “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use.

Aerosol-generating articles according to the present invention are suitable for use in an aerosol-generating system comprising an electrically heated aerosol-generating device having an internal heating element for heating the aerosol-generating substrate. For example, aerosol-generating articles according to the invention find particular application in aerosol- generating systems comprising an electrically heated aerosol-generating device having an internal heater blade which is adapted to be inserted into the rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example, in European patent application EP-A-0 822 670.

As used herein, the term “aerosol-generating device” refers to a device comprising a heating element that interacts with the aerosol-generating substrate of the aerosol-generating article to generate an aerosol.

As used herein, the term “hydrochromic portion” refers to a portion of one of the wrappers used in the aerosol-generating system which shows a visibly perceivable reaction upon contact with humidity. The visibly perceivable reaction of the hydrochromic portion may comprise one or more of a change of color and a change of opacity of the hydrochromic portion.

As described above, the aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity. As will be discussed in more detail below, the article may be configured in various ways such as to be capable to reveal the visually perceivable marking. The aerosol-generating article may be configured to comprise a permanent marking, which is not visually perceivable in an unused aerosol-generating article, but which becomes visually perceivable upon use of the aerosol-generating article. Alternatively, the aerosol-generating article in the unused state may not comprise a marking, but the marking may be generated upon use of the aerosol-generating article. In the latter case, the marking may also be described as to appear upon use of the aerosol-generating article.

By configuring the aerosol-generating article such that a visually perceivable marking is revealed or appears upon use, a user can readily distinguish between used and unused aerosol-generating articles.

This may be particularly advantageous when a consumer puts back a used aerosolgenerating article in its original packaging where also unused aerosol-generating articles are kept. This situation might occur when there is no thrash bin available to dispose the used aerosol-generating article. With the aerosol-generating articles as described herein, a user can readily tell the difference between used and unused aerosol-generating articles and may thereby avoid unpleasant and potentially harmful user experiences.

Further since users can differentiate between a used and an unused article, they might be more inclined to keep the unused aerosol-generating articles, rather than being tempted to think about littering and improper disposing of the used aerosol-generating articles.

According to embodiments of the invention at least a part of a wrapper of the aerosolgenerating article may be configured as a hydrochromic portion. According to embodiments of the invention at least a part of the stick wrap of the aerosol-generating article may be configured as a hydrochromic portion. A hydrochromic portion is a portion that changes its visual appearance upon contact with humidity. The hydrochromic portion may change its color or opacity upon contact with humidity.

The change of color or opacity of the hydrochromic portion of the stick wrap may be irreversible. The change of color or opacity of the hydrochromic portion of the stick wrap may be irreversible at least at when considering a time scale at which a user can be reasonably expected to carry with himself an used aerosol-generating article. In order to qualify as an irreversible change of color, the change shall be lasting for at least 10 days, for at least 5 days or for at least 3 days. The change of color or opacity of the hydrochromic portion of the stick wrap may last at least 24 hours.

Due to the change of color or opacity of the hydrochromic portion of the stick wrap the marking of the aerosol-generating article is revealed. The change of color or opacity of the hydrochromic portion of the stick wrap may increase the contrast ration of the marking with respect to surrounding portion of the aerosol-generating article. The change of contrast ratio may be at least between 0.5 and 30. The change of contrast ratio may be between 1 and 20. The change of contrast ratio may be between 2 and 15. The change of contrast ratio may be between 3 and 10.

The aerosol-generating article may be configured to be heated during use. By heating the aerosol-generating article an aerosol may be formed by evaporation of volatile components of an aerosol-forming substrate comprised in the aerosol-generating article.

The aerosol-generating article may have a proximal end and a distal end. The elements wrapped by the stick wrap may define an internal air flow path from the distal end to the proximal end of the aerosol-generating article. The elements wrapped by the stick wrap may be rod-shaped. The elements wrapped by the stick wrap may be cylindrical and may have a generally circular cross section.

The elements of the aerosol-generating article may include a substrate plug comprising aerosol-forming substrate. The elements of the aerosol-generating article may additionally include one or more of a frontend filter, a mouthpiece filter, a PLA filter, a hollow acetate tube and a cardboard tube.

One or more of the individual elements from which the aerosol-generating article is formed, may comprise a plug wrap. The plug wrap may be a paper wrapper as is commonly used in the manufacture of aerosol-generating articles.

The humidity with which the hydrochromic portion comes into contact, may be humidity that is generated upon heating of the aerosol-generating article and subsequent condensation of air and the generated aerosol during a user experience. As described above the aerosol generated from aerosol-generating substrates of aerosol-generating articles described herein may include vapours as well as gases and liquid droplets of condensed vapours. Accordingly, an increase in humidity is indicative of the occurrence of a user experience. In turn this increase in humidity is used in the mechanisms described herein in order to distinguish used from unused aerosol-generating articles. Using a stick wrap comprising a hydrochromic portion is a suitable and inexpensive way of introducing a differentiating feature that allows a user to recognize a used aerosol-generating article.

There are plural ways as how to configure an aerosol-generating article such that a marking is revealed upon contact of the aerosol-generating article with humidity. In the following suitable ways to provide such marking are disclosed.

According to embodiments the stick wrap may comprise a hydrochromic portion, which covers a portion of the outer surface of a rod-shaped element of the aerosol-generating article. The portion of the outer surface of a rod-shaped element that is covered by the hydrochromic portion of the stick wrap may carry a permanent marking. The hydrochromic portion of the stick wrap may be configured to be opaque as long as the aerosol-generating article is unused and is not in contact with increased level of humidity. The hydrochromic portion of the stick wrap may be further configured to become less opaque upon contact with humidity.

The stick wrap of such aerosol-generating article, covers the marking before use. Due to the opacity of the hydrochromic portion of the stick wrap the permanent marking underneath the hydrochromic portion of the stick wrap is not visually perceivable by the user. Thus, such aerosol-generating article can be readily identified as an unused aerosol-generating article. During a user experience the aerosol-generating article is heated and the user draws air through the aerosol-generating article. Thereby an aerosol is formed that is cooled down within the aerosol-generating article before inhalation. Cooling down of the heated aerosol leads to condensation and a general increase of the humidity level in the air flow path through the aerosol-generating article. The hydrochromic portion of the stick wrap comes into contact with the humidity generated within the aerosol-generating article. Upon contact with this humidity the hydrochromic portion of the stick wrap becomes less opaque and the permanent marking underneath the hydrochromic portion of the stick wrap becomes visually perceivable by the user from the outside.

The hydrochromic portion of the stick wrap may be formed from conventional paper used in manufacture of aerosol-generating articles. When such paper is contacted with humidity it may become more transparent than in the dry state. This may be caused by the similarity of the index of refraction of water and the cellulose fibers of the paper. The increased humidity leads to wetting of the stick wrap, and the water droplets occupying the cavities between the cellulose fibers lead to a higher homogeneity of the overall index of refraction of the wet humid stick wrap. Accordingly, the light going through the wet stick wrap undergoes less internal total reflection increasing transparency of the stick wrap. The stick wrap becomes less opaque and the marking underneath such hydrochromic portion of the stick wrap becomes apparent. It was discovered that this effect does not disappear completely upon drying-up of the stick wrap. Thus, even after the humidity level in the stick wrap has returned to ambient conditions, the marking may still be visible as compared with an unused aerosol-generating article.

The hydrochromic portion of the stick wrap may be formed from a paper sheet material having a thickness of less than 100 micrometers. The hydrochromic portion of the stick wrap may be formed from a paper sheet material having a thickness of less than 65 micrometers, of less than 60 micrometers, of less than 55 micrometers, of less than 50 micrometers, of less than 45 micrometers, of less than 40 micrometers or of less than 35 micrometers. The thinner the paper material the more enhanced may be the effect on change of opacity upon wetting of the paper material.

The grammage of the paper sheet material from which the hydrochromic portion of the stick wrap is formed may amount to less than 65 grams per squaremeter, to less than 60 grams per squaremeter, to less than 55 grams per squaremeter, to less than 50 grams per squaremeter, to less than 45 grams per squaremeter, to less than 40 grams per squaremeter, to less than 35 grams per squaremeter, to less than 30 grams per squaremeter, to less than 25 grams per squaremeter or to less than 20 grams per squaremeter.

The hydrochromic portion of the stick wrap may be formed from a paper sheet material having a higher porosity as compared with cigarette papers typically used for HnB products. The hydrochromic portion of the stick wrap may be formed from a paper sheet material having a porosity that leads to an increased air permeability. The air permeability of the paper sheet material used for the hydrochromic portion of the stick wrap may be above 30 corresta units (CU) at an applied pressure difference of 1 kilopascal (kPa).

The hydrochromic portion of the stick wrap may be formed from a paper sheet material that has any color in the dry state. Preferably, the hydrochromic portion of the stick wrap may be formed from a paper sheet material that is white colored in the dry state.

Without wishing to be bound by theory, conventional paper material is generally opaque because the cellulose fiber material forms a porous structure that includes hollow air filled cavities in addition, paper material typically also comprises mineral fillers located in between the cellulose fibers. The mineral fillers are provided in a crystalline form. In a dray paper sheet, in which the mineral fillers are surrounded by air, light is scattered at these filler materials due to the high difference in the index of refraction between the air and the mineral fillers. Hence, the paper material appears opaque.

When such paper material comes into contact with humidity the porous structure becomes filled with water. Water has a different index of refraction, which is closer to the index of refraction of the paper material and the mineral filler materials comprised in the paper. Due to this lower difference in the index of refraction between water and the paper material or mineral filler less scattering occurs and the paper material becomes more translucent. Hydrocarbons like glycerin may contribute in at least two ways in increasing translucence of paper material. On the one hand fatty materials also do have an increased index of refraction. Accordingly for the same reason as discussed above, also contact of the paper material with glycerin increases translucence of the paper material. In addition, the presence of glycerin helps to maintain the moisture level of the aerosol-forming substrate at an increased level. This increased moisture level in turn enhances aerosol formation and the generation of humidity during use of the aerosol-generating system. Thus, hydrocarbon materials such as glycerin directly and indirectly increase the effect of the present invention.

In order to prevent external air humidity to trigger the transparency of the stick wrap, the stick wrap may have an outer layer or coating that extends at least over the hydrochromic portion of the stick wrap. The coating may be hydrophobic and transparent. The coating may prevent the coated areas of the stick wrap of coming into contact with ambient humidity.

According to embodiments the stick wrap may be configured to be generally transparent. The stick wrap may be further configured to have a hydrochromic portion. The hydrochromic portion may be configured to be opaque in a dry state and to become less opaque upon contact with humidity. Again, upon contact with humidity, the hydrochromic portion becomes less opaque and the marking at an outer surface of an element located beneath the hydrochromic portion becomes visible.

The hydrochromic portion of the stick wrap may also be configured to change color upon contact with humidity. This color change may be perceived by the user and can be used as indication or marking of the aerosol-generating device having been used.

For example, the stick wrap may be provided with a hydrochromic portion that is formed by applying a stripe of hydrochromic ink on the outer surface of the stick wrap. Such hydrochromic ink may have a yellowish color in a dry state. Upon contact with humidity the hydrochromic ink may change its colour for example to blue. In order to make the hydrochromic portion invisible when the stick has not yet been used, the color of the remaining portions of the stick wrap might be configured to be about the same color than the hydrochromic ink in the dry state. Thus, before use the complete stick wrap has a homogeneous yellowish appearance and no marking is visible. Upon contact with humidity the hydrochromic portion changes its colour to blue being indicative of having been contacted by humidity, and in turn of having been consumed in a user experience.

The stick wrap may be generally transparent and may have a hydrochromic portion which is configured to be opaque in the unused or dry state. The hydrochromic portion may be further configured to change its transparency upon being contacted with humidity. Again, the aerosolgenerating article is configured to exhibit a permanent marking at the outer surface of the elements covered by the hydrochromic portion of the stick wrap. When the hydrochromic portion of the stick wrap is contacted with humidity, the hydrochromic portion becomes transparent unveiling the marking underneath. Again, the marking becomes visible after use and allows the user to distinguish between used and unused aerosol-generating articles.

In further embodiments the aerosol-generating article comprises a color pigment which is transported by humidity and the capillarity of the stick wrap to the outer surface of the stick wrap. Upon contact of the humidity carrying the color pigment with the stick wrap, a marking appears at the stick wrap, which is indicative of the aerosol-generating article having been used. The color pigment is preferably provided within the elements of the aerosol-generating article. The color pigment may be provided in a plug wrap used for wrapping an element of the aerosol-generating article. Humidity created in the inner volume of the aerosol-generating article and traveling radially outward through the plug wrap and further on into the stick wrap may carry the color pigment to the stick wrap and generate a marking at the stick wrap, which is visually perceivable by the user.

The stick wrap may be configured to have a capillarity that is higher than the capillarity of the plug wraps used for the elements of the aerosol-generating article. Using a stick wrap having a higher capillarity helps to cope with effects caused by ambient humidity. Because of its higher capillarity, any ambient humidity entering the stick wrap from the outside, will remain within the stick wrap and will not come into contact with the color pigment. Only humidity that is created internally in the aerosol-generating article will travel through the plug wrap and will be able to carry the color pigment towards the outer surface of the stick wrap. Thus, by using a stick wrap with a high capillarity an outer coating protecting the stick wrap from ambient humidity may be dispensed with. The protective effect of the higher capillarity of the stick wrap depends on the difference of the capillarities used in the wrapper materials. The higher this difference, the better is the protective effect. Using a stick wrap with high capillarity may thus help to reduce spontaneous migration of color pigment provided in the aerosol-generating article.

The marking of the aerosol-generating element may have any suitable form that can be easily perceived and understood by a user. The marking may comprise a word, a graphical element or a symbol, which may be useful to convey information to the user. The marking may be a printed marking. The marking may include the terms “used”, “empty”, “dispose” or similar. A symbol may include an “X” (capital X), a “I” (exclamation mark), an attention sign or any other symbol suitable for warning or alerting a user.

The marking may further be configured to indicate the quantity of humidity received in a marking zone. The quantity of humidity, which relates to the level of consumption of the aerosol-generating article, may be converted into a size of the area of marking. The quantity of humidity may be converted into a quantity of the appearing marking. For example, the marking may be provided in the form of a progressive marking. The larger the marking or the larger the fraction of the part of the marking that has been subjected to humidity, the higher the level of exposure to humidity, and the higher the level of consumption. Thus, the progress of the colour change may be used to give to the user an indication of how much the aerosolgenerating article has been used. The area reached by the humidity may be controlled according to the quantity of humidity by using paper treatments, which allow to have a gradation of the humidity. While such treatments may be available for hydrochromic inks, such achievement are not easily achievable by using thermochromic ink. Thermochromic ink is typically sensitive on the value of the maximally achieved temperature and not on the amount of heat involved. Thus, as the maximum temperature is already reached during the first user experience, an aerosol-generating article with a thermochromic ink indicator would show the same indication for a fully consumed aerosol-generating article than for an aerosol-generating article heated just for one-puff.

The area where the marking appears may be any specific part of the aerosol-generating article. It may be provided such that it is readily recognizable by the user upon taken the aerosol-generating article out of the package, or upon introducing the aerosol-generating article into the aerosol-generating device. Preferably the marking is at a position at which it is still visible when the aerosol-generating article is already inserted into the aerosol-generating device. In this way the user may still have the chance to detect that he is about to re-use a depleted aerosol-generating article.

The marking may be provided in a longitudinal position downstream from the substrate plug comprising the aerosol-forming substrate. Since the main heating takes place at the substrate plug, condensation occurs mainly in the elements of the aerosol-generating article located downstream from the substrate plug.

In order to promote migration of humidity in radial direction towards the stick wrap, one or more of the elements of the aerosol-generating article may comprise small openings or perforations that extend in a general radial direction. For example, a cardboard tube placed downstream from the substrate plug may comprise small openings in the cardboard tube under the plug wrap so that a small part of the heated air and aerosol generated within the cardboard tube may reach the stick wrap.

The areas of the aerosol-generating article that could be reached by humidity could be different and may depend on the kind of heating system of the aerosol-generating device with which the aerosol-generating article is to be used.

In case of an internal heater, such as an inductively heated susceptor provided longitudinally in the center of a plug of aerosol-forming substrate, the main heat is generated in the center of the plug. Humidity, which is caused by condensation of heated air and aerosol, will mainly develop in cooler parts at the peripheral regions of the substrate and in the plug wrap. From there, humidity will spread according to the capillarity of the plug wrap and will migrate toward the stick wrap. In case of an external heater, heat is mainly generated at the peripheral regions of the substrate plug. The temperature around and near the substrate plug would be probably too high to allow humidity to reach the substrate plug wrap. However, humidity caused by the condensation of the heated air and aerosol may occur at elements located downstream from the substrate plug. In such embodiments, dedicated small air paths going from the inside core of one of the downstream elements to their plug wrap may be used. Humidity may then travel along these channels in a radial direction so as to reach the stick wrap.

In this case the marking has to be provided in a portion of the stick wrap that is remote from the substrate plug. Providing the marking remote from the substrate plug may anyway be desirable, since such positioning limits the chance that the material constituting the marking or the material constituting the hydrophobic coating may form harmful and potentially harmful constituents during heating.

As discussed above, the aerosol-generating article may comprise a plurality of elements. Each of these elements may be circumscribed by a plug wrap. The elements themselves or the material of the plug wraps may have been subjected to a specific treatment before being combined into an aerosol-generating article. Such treatment may aim at controlling various humidity related properties of the elements. Such treatment may be a treatment that adjusting water repellent property, water absorption or water tension level of the elements such as to drive and/or control the humidity in the aerosol-generating article.

In particular, the individual plug wraps or the elements may be configured to have a rather low porosity or may be configured to be highly hydrophobic. In this way it may be ensured that as much as possible of the humidity created upon condensation of the aerosol during the user experience is available for migration to the stick wrap comprising the hydrochromic portion.

In addition an advantageous stick construction may also assist in enhancing migration of the humidity towards the stick wrap. For example, during construction of the aerosolgenerating article, a tiny air gap may be formed between the outer surface of the plug wraps of the wrapped elements and the inner surface of the stick wrap. In the dry state, the plug wraps and the stick wrap are not in direct contact. This aspect contributes to increase the opacity of the stick wrap such that any underneath marking becomes even less visible. During the user experience when humidity is created, this humidity also may fill the air gap between the wrappers. This layer of humidity creates a kind of “bridge” by replacing the air gap formerly existing in between the two wrappers and may establish a direct contact between the wrappers. This effect also increases visibility of the underneath marking during and after use of the aerosol-generating system.

As discussed above it may be advantageous to form the stick wrap from paper material having a rather low thickness and a reduced grammage. However, using such material may lead to a reduced strength of the wrapped structure. In order to compensate for the reduced thickness and low grammage of the stick wrap, one or more of the plug wraps, in particular the aerosol-forming material plug wrap, may be formed from thicker and higher grammage material.

In order to further control humidity transport and distribution within the aerosol-generating article, the aerosol-generating article may comprise an element having increased capillarity. With this element humidity may be transported to dedicated portions of the aerosol-generating article. The element having increased capillarity may be used for transporting humidity towards the portion of the aerosol-generating article comprising the marking. The element having increased capillarity may be a longitudinal element. The element having increased capillarity may be a strip, a thread, a yarn, a wick or any other suitable capillary element.

The capillary element may extend in parallel to the longitudinal axis of the aerosolgenerating article and may assist in homogenously distributing humidity along the full length of the aerosol-generating article.

The capillary element may be coated with hydrophobic material. By coating the capillary element with hydrophobic material, the capillary element effectively forms an element that acts like a tube. Humidity can enter at one end of the capillary element and is transported through the capillarity of the element towards its other end. Since the length of the capillary material is coated with hydrophobic material, humidity may not or only to a reduced amount enter into the capillary element through the hydrophobic coating. Such element may be particularly useful to be used in combination with a capsule holding color pigment. Humidity entrailing the color pigment may be guided along the capillary element toward a pre-determined portion of the stick wrap. At the output end of the capillary element humidity carrying the colour pigment is released onto the stick wrap thereby forming a visually perceivable marking at the outer surface of the stick wrap.

An aerosol-generating article may comprise a plurality of elements, including the rod of aerosol-generating substrate.

Aerosol-generating articles commonly may comprise a hollow acetate tube directly adjacent to the aerosol-generating substrate. The rod of aerosol-generating substrate may be formed of an aerosol-forming material, which may comprise homogenised tobacco material.

As used herein, the term “homogenised tobacco material” encompasses any tobacco material formed by the agglomeration of particles of tobacco material. Sheets or webs of homogenised tobacco material are formed by agglomerating particulate tobacco obtained by grinding or otherwise powdering of one or both of tobacco leaf lamina and tobacco leaf stems. In addition, homogenised tobacco material may comprise a minor quantity of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco. The sheets of homogenised tobacco material may be produced by casting, extrusion, paper making processes orany other suitable processes known in the art.

In preferred embodiments, the rod comprises one or more sheets of a homogenised tobacco material that have been gathered to form a plug and circumscribed by an outer wrapper. As used herein with reference to the invention, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof. As used herein with reference to the invention, the term “gathered” describes a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosol-generating article.

Sheets of homogenised tobacco material for use in the invention may have a tobacco content of at least about 40 percent by weight on a dry weight basis, more preferably of at least about 50 percent by weight on a dry weight basis more preferably at least about 70 percent by weight on a dry weight basis and most preferably at least about 90 percent by weight on a dry weight basis.

Preferably, the sheets of homogenised tobacco material comprise an aerosol former. The sheets of homogenised tobacco material may comprise a single aerosol former. Alternatively, the sheets of homogenised tobacco material may comprise a combination of two or more aerosol formers.

Suitable aerosol-formers are known in the art and include, but are not limited to: monohydric alcohols like menthol, polyhydric alcohols, such as triethylene glycol, 1 ,3- butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate, dimethyl tetradecanedioate, erythritol, 1 ,3-butylene glycol, tetraethylene glycol, triethyl citrate, propylene carbonate, Ethyl laurate, triacetin, meso-erythritol, a diacetin mixture, a diethyl suberate, triethyl citrate, benzyl benzoate, benzyl phenyl acetate, ethyl vacillate, tributyrin, lauryl acetate, lauric acid, myristic acid, and propylene glycol.

Preferably, the sheets of homogenised tobacco material have an aerosol former content of greater than 5 percent on a dry weight basis. The sheets of homogenised tobacco material may have an aerosol former content of between approximately 5 percent and approximately 30 percent on a dry weight basis. In a preferred embodiment, the sheets of homogenised tobacco material have an aerosol former content of approximately 20 percent on a dry weight basis.

Sheets of homogenised tobacco material for use in the invention may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco. Alternatively, or in addition, sheets of homogenised tobacco material for use in the aerosolgenerating substrate may comprise other additives including, but not limited to, tobacco and nontobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and nonaqueous solvents and combinations thereof.

Suitable extrinsic binders for inclusion in sheets of homogenised tobacco material for use in the invention are known in the art and include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins, and combinations thereof.

Suitable non-tobacco fibres for inclusion in sheets of homogenised tobacco material for use in the aerosol-generating substrate are known in the art and include, but are not limited to: cellulose fibers, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof. Prior to inclusion in sheets of homogenised tobacco material for use in the aerosol-generating substrate, non-tobacco fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping, refining, chemical pulping, bleaching, sulfate pulping, and combinations thereof.

Sheets of homogenised tobacco for use in the invention preferably have a width of between about 70 mm and about 250 mm, for example between about 120 mm and about 160 mm. Preferably, the thickness of the sheets of homogenised tobacco material is between about 50 micrometres and about 300 micrometres, more preferably between about 150 micrometres and about 250 micrometres.

Sheets of homogenised tobacco for use in the aerosol-generating article of the present invention may be made by methods known in the art, for example the methods disclosed in International patent application WO-A-2012/164009 A2.

In a preferred embodiment, sheets of homogenised tobacco material for use in the aerosol-generating article are formed from a slurry comprising particulate tobacco, guar gum, cellulose fibres and glycerine by a casting process.

As an alternative to the use of a gathered sheet of homogenised tobacco material, as described above, the aerosol-generating substrate may be formed of a plurality of strips or shreds of a sheet of homogenised tobacco material. For example, the aerosol-generating substrate may be formed of a plurality of shreds of homogenised tobacco material that are aligned in the longitudinal direction and have been brought together and wrapped to form a rod of aerosol-forming substrate.

The shreds of homogenised tobacco material preferably have a length of between about 10 millimetres and about 20 millimetres, more preferably between about 12 millimetres and about 18 millimetres, more preferably between about 14 millimetres and about 16 millimetres, more preferably about 15 millimetres. Alternatively, or in addition, the shreds of homogenised tobacco material preferably have a width of between about 0.4 millimetres and about 0.8 millimetres.

Preferably, the density of the sheet of homogenised tobacco material from which the shreds are formed is between about 500 and about 1500 milligrams per cubic centimetre, more preferably between about 800 and about 1200 milligrams per cubic centimetre, more preferably between about 900 and about 1 100 milligrams per cubic centimetre, and most preferably between about 900 and about 970 milligrams per cubic centimetre.

Preferably, the bulk density of the shreds of homogenised tobacco material within the aerosol-generating substrate is between about 0.4 grams per cubic centimetre and about 0.8 grams per cubic centimetre, preferably between about 0.5 grams per cubic centimetre and about 0.7 grams per cubic centimetre and most preferably between about 0.65 grams per cubic centimetre and about 0.67 grams per cubic centimetre.

As described above, the homogenised tobacco material may be formed by the casting of a slurry. Alternatively, the homogenised tobacco material may be formed by another suitable method, such as for example, an extrusion method.

Preferably, the aerosol-generating substrate comprises a rod of the homogenised tobacco material circumscribed by a wrapper, wherein the wrapper is provided around and in contact with the homogenised tobacco material. The wrapper may be formed from any suitable sheet material that is capable of being wrapped around homogenised tobacco material to form an aerosol-forming substrate. The wrapper may be porous or non-porous. Preferably, the wrapper is a paper wrapper but the wrapper may alternatively be non-paper.

The rod of aerosol-forming substrate preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

Preferably, the rod of aerosol-generating substrate has an external diameter of at least 5 millimetres. The rod of aerosol-generating substrate may have an external diameter of between about 5 millimetres and about 12 millimetres, for example of between about 5 millimetres and about 10 millimetres or of between about 6 millimetres and about 8 millimetres. In a preferred embodiment, the rod of aerosol-generating substrate has an external diameter of 7.2 millimetres, to within 10 percent.

The rod of aerosol-generating substrate may have a length of between about 7 millimetres and about 15 mm. In one embodiment, the rod of aerosol-generating substrate may have a length of about 10 millimetres. In a preferred embodiment, the rod of aerosol- forming substrate has a length of about 12 millimetres.

Preferably, the rod of aerosol-generating substrate has a substantially uniform crosssection along the length of the rod. Particularly preferably, the rod of aerosol-generating substrate has a substantially circular cross-section. The aerosol-generating articles according to the invention preferably comprise one or more elements in addition to the rod of aerosol-forming substrate. For example, aerosolgenerating articles may further comprise at least one of: a mouthpiece, an aerosol-cooling element and a support element such as a hollow acetate tube. For example, in one preferred embodiment, an aerosol-generating article comprises, in linear sequential arrangement, a rod of aerosol-generating substrate as described above, a support element located immediately downstream of the aerosol-generating substrate, an aerosol-cooling element located downstream of the support element, and a stick wrap circumscribing the rod, the support element and the aerosol-cooling element.

Aerosol-generating systems according to the present invention comprise an aerosolgenerating article as described in detail above in combination with an aerosol-generating device which is adapted to receive the upstream end of the aerosol-generating article during a user experience. The aerosol-generating device comprises a heating element which is configured to heat the aerosol-generating substrate in order to generate an aerosol during use. Preferably, the heating element is adapted to penetrate the aerosol-generating substrate when the aerosol-generating article is inserted into the aerosol-generating device. For example, the heating element is preferably in the form of a heater blade.

The heater element may also be an external heating element that surrounds the aerosolgenerating article during use.

The heating element may be a resistive heating element or an inductive heating element.

The heating element is controlled during use to operate with a defined operating temperature range, below a maximum operating temperature. The thermal indicator of the aerosol-generating article is adapted such that the threshold temperature will not be reached during normal use of the aerosol-generating article in the aerosol-generating device with the heating element operating below the maximum operating temperature. This ensures that when the aerosol-generating article and aerosol-generating device are used together, the thermal indicator will not be activated during normal use.

Preferably, the aerosol-generating device additionally comprises a housing, an electrical power supply connected to the heating element and a control element configured to control the supply of power from the power supply to the heating element.

Suitable aerosol-generating devices for use in the aerosol-generating system of the present invention are described in WO-A-2013/098405.

The present invention also relates to a method of manufacturing an aerosol-generating article, comprising providing a plurality of elements, and providing a stick wrap. The method further comprises connecting the elements by wrapping the stick wrap around the elements to form the aerosol-generating article. The aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity. Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example 1 : An aerosol-generating article comprising: a plurality of elements, and a stick wrap, wherein the stick wrap is configured to connect the elements to form the aerosol-generating article, wherein the aerosol-generating article is further configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.

Example 2: An aerosol-generating article according to example 1 , wherein the aerosol-generating article is configured to be heated such that an aerosol is formed by evaporation of volatile components of the aerosol forming substrate.

Example 3: An aerosol-generating article according to any one of the preceding examples, wherein the aerosol-generating article has a proximal end and a distal end, and the rod-shaped elements define an internal air flow path from the distal end to the proximal end of the aerosol-generating article.

Example 4: An aerosol-generating article according to any one of the preceding examples, wherein the elements include a substrate plug comprising aerosol-forming substrate.

Example 5: An aerosol-generating article according to the preceding examples, wherein the substrate plug comprises glycerin.

Example 6: An aerosol-generating article according to any one of the preceding examples, wherein the rod-shaped elements include one or more of a frontend filter, a mouthpiece filter, a hollow acetate tubes and a cardboard tube.

Example 7: An aerosol-generating article according to any one of the preceding examples, wherein one or more of the elements comprise a plug wrap.

Example 8: An aerosol-generating article according to any one of the preceding examples, wherein at least a part of the stick wrap is configured as a hydrochromic portion, that changes color or opacity upon contact with humidity.

Example 9: An aerosol-generating article according to any one of the preceding examples, wherein the hydrochromic portion of the stick wrap covers a portion of the outer surface of an element, wherein the portion of the outer surface of an element carries a marking and wherein the hydrochromic portion of the stick wrap is configured to become less opaque upon contact with humidity.

Example 10: An aerosol-generating article according to any one of examples 8 or 9, wherein the stick wrap is generally transparent, wherein the stick wrap is provided with an hydrochromic portion which is opaque in a dry state, and wherein the hydrochromic portion becomes less opaque upon contact with humidity.

Example 11 : An aerosol-generating article according to any one of examples 1 to 8, wherein the hydrochromic portion of the stick wrap is configured to change color upon contact with humidity.

Example 12: An aerosol-generating article according to example 1 1 , wherein the hydrochromic portion of the stick wrap is configured to have the same or a similar color as the stick wrap before coming in contact with humidity, and wherein the hydrochromic portion of the stick wrap is further configured to change its color upon contact with humidity.

Example 13: An aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises color pigment which is transported by humidity and the capillarity of the stick wrap to the outer surface of the stick wrap.

Example 14: An aerosol-generating article according to any preceding example, wherein the humidity created by condensation of heated air or aerosol makes contact with the hydrochromic portion of the stick wrap.

Example 15: An aerosol-generating article according to any preceding example, wherein the plug wraps and the stick wrap are made from paper material having different thickness or different grammage.

Example 16: An aerosol-generating article according to any preceding example, wherein the marking comprises a word, a graphical element or a symbol, which are useful to convey information to the user.

Example 17: An aerosol-generating article according to the preceding example, wherein the marking is configured to indicate the quantity of humidity received in a marking zone.

Example 18: An aerosol-generating article according to any preceding example, wherein the marking is provided in a longitudinal position downstream from the substrate plug comprising the aerosol-forming substrate.

Example 19: An aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises an element having increased capillarity for transporting the humidity to dedicated portions of the aerosol-generating article.

Example 20: An aerosol-generating article according to the preceding example, wherein the aerosol-generating article comprises an element having increased capillarity for transporting the humidity towards the portion of the aerosol-generating article comprising the marking.

Example 21 : An aerosol-generating article according to the preceding example, wherein the element having increased capillarity is a thread. Example 22: An aerosol-generating article according to the preceding example, wherein the thread is coated with hydrophobic material, such that humidity from one end of the thread is carried to the other end of the thread which is advantageously in contact with the stick wrap.

Example 23: An aerosol-generating article according to any preceding example, wherein one or more of the rod-shaped elements may comprise perforations or openings to enhance radial transfer of humidity from the air flow channel towards the stick wrap.

Example 24: An aerosol-generating article according to any preceding example, wherein the stick wrap is covered by a hydrophobic layer.

Example 25: An aerosol-generating article according to any one of the preceding examples, wherein the change of color or opacity of the hydrochromic portion is irreversible.

Example 26: An aerosol-generating system comprising: an aerosol-generating device; and an aerosol-generating article according to any preceding example.

Example 27: A method of manufacturing an aerosol-generating article, comprising: providing a plurality of rod-shaped elements, and providing a stick wrap, connecting the rod-shaped elements by wrapping the stick wrap around the rod-shaped elements to form the aerosol-generating article, wherein the aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows a schematic view of an aerosol-generating article;

Fig. 2 shows a schematic view of the construction of an aerosol-generating article;

Fig. 3 shows details of an inductively heated aerosol-generating article comprising stick wrap with a hydrochromic portion;

Fig. 4 shows an aerosol-generating article with covered and revealed marking;

Fig. 5 shows a further mechanism for revealing a marking on an aerosol-generating article;

Fig. 6 shows an embodiment of an aerosol-generating article comprising a transparent stick wrap;

Fig. 7 shows an aerosol-generating article comprising a colour pigment; Fig. 8 shows various features of a marking provided on an aerosol-generating article; and

Fig. 9 shows an aerosol-generating article comprising a capillary thread.

Fig. 1 shows a schematic view of a conventional aerosol-generating article 10. The aerosol-generating article 10 is a rod-shaped article comprising a plurality of rod-shaped elements 12, 14, 16, 18 that are connected to each other by a stick wrap 30. The stick wrap 30 is made from conventional cigarette paper. The aerosol-generating article 10 comprises four elements, a front plug 12, a sensorial media plug 14, comprising aerosol-forming substrate 15, a hollow acetate tube 16, and a mouthpiece filter 18.

Each of the elements is separately wrapped in a wrapping material (not shown), the so-called plug wrap to hold the material of each element together. These wrapped elements are in turn wrapped together by the stick wrap 30 to form the stick structure of the aerosolgenerating article 10 as depicted in Fig. 1 .

Outside air 22, drawn into the aerosol-generating article 10 by the user, enters mainly through the front plug 12 at the distal or upstream end 24 of the aerosol-generating article 10. The outside air 22 is guided through the aerosol-forming substrate 15 and mixes with vapours and other volatiles created upon heating of the aerosol-forming substrate 15 to form an aerosol 26. Heated air and aerosol 26 is then guided onwards through the further elements of the aerosol-generating article 10 and exits the aerosol-generating article 10 at the proximal or downstream end 28 through the mouthpiece filter 18. All elements form an internal airflow path 29 through the aerosol-generating article 10.

Fig. 2 illustrates an aerosol-generating article 10 comprising three elements 12, 14, 16, each being wrapped by a plug wrap 32, 34, 36. Upon manufacture of the aerosol-generating article 10, the individual elements 12, 14, 16 are being aligned and abuted to each other, as indicated by the two arrows at either end of the aerosol-generating article 10. Subsequently the elements 12, 14, 16 are wrapped in an outer wrapping material, the stick wrap 32. In general, there could be several stick wraps that may overlap each other. For instance, the tipping paper usually denotes a stick wrap covering the mouthpiece filter and connecting the mouthpiece filter to the rest of the aerosol-generating article 10. This connection can be done by overlapping part of another stick wrap, the so-called cigarette wrapper, which connects the other components of the aerosol-generating article 10. The aerosol-generating articles of the present invention are in principle comprising corresponding elements and are manufactured as explained with the illustrations of Figs. 1 and 2.

Fig. 3 shows a schematic of an aerosol-generating article 10 according to the present invention. The aerosol-generating article 10 again comprises four rod-shaped elements, a front plug 12, a sensorial media plug 14, comprising aerosol-forming substrate 15, a hollow acetate tube 16, and a mouthpiece filter 18. Each of these elements is wrapped individually in a plug wrap 32, 34, 36, 38.

Front plug 12, sensorial media plug 14, and hollow acetate tube 16 are wrapped together using a first stick wrap 30 to form a front part of the aerosol-generating article 10. Mouthpiece filter 18 is attached to this front part with a second stick wrap that is usually referred to as a tipping paper 52.

The sensorial media plug 14 comprises a susceptor element 40 which is used to inductively heat the aerosol-forming substrate 15. Outside air 22 enters the aerosol-generating article 10 through the front plug 12 at the upstream end 24 of the aerosol-generating article 10. The outside air 22 is heated and entrails volatilized flavours as it is guided through the sensorial media plug 14.

The heated air and aerosol 26 go mainly along the longitudinal axis of the aerosolgenerating article 10, but a part 44 thereof flows in a radial direction to the outer periphery of the sensorial media plug 14 as indicated by arrow 44. At the periphery of the sensorial media plug 14 the heated air and aerosol 26 gets colder and condensates thereby turning into humidity 46. This humidity 46 travels through the sensorial media plug wrap 34 by capillary action and reaches the inner surface of the stick wrap 30.

In the embodiment depicted in Fig. 3, the stick wrap 30 has a hydrochromic portion 50. The hydrochromic portion 50 is a portion of the stick wrap 30, which is printed with a hydrochromic ink. In a dry state the hydrochromic ink has a color that corresponds to the color of the remaining portions of the stick wrap 30. Thus, in a dry state the hydrochromic portion 50 is not optically perceivable by the user.

Upon contact with humidity 46 generated during a user experience, the hydrochromic ink of the hydrochromic portion 50 irreversibly changes its color from the initial paper-like color to a blue color, which represents a strong contrast with the initial paper color. Thus, a user can readily perceive the hydrochromic portion 50 after use. Accordingly, the hydrochromic portion 50 forms a visually perceivable marking, which allows the user to easily distinguish a used aerosol-generating article 10 from unused aerosol-generating articles 10.

On the outside of the stick wrap 30 there is provided a transparent hydrophobic coating 54 that extends over the full surface of the stick wrap 30. The transparent hydrophobic coating 54 protects the stick wrap 30 from ambient humidity.

Fig. 4 shows a further embodiment of an aerosol-generating article comprising a stick wrap with a hydrochromic portion 50. In Fig. 4 only the area of the aerosol-generating article 10 is shown that comprises the hydrochromic portion 50 and a marking 60. The left-hand view in Fig. 4 shows an unused aerosol-generating article 10, and the right-hand view in Fig. 4 shows the same aerosol-generating article 10 after having been used. The aerosol-generating article 10 comprises an element 16 which in this case is a PLA filter element. The filter element 16 is wrapped by a plug wrap 36. At the outer surface of the plug wrap 36 a marking 60 is provided. Marking 60 is provided in the form of a colored stripe. The plug wrap is further wrapped with a stick wrap 30 that is used to connect the element 16 to adjacent elements of the aerosol-generating article 10. In Fig. 4 the inner surface 30a and the outer surface 30b of the stick wrap 30 is depicted.

In Fig. 4 at least the depicted portion of the stick wrap 30 of the aerosol-generating article 10 is made from normal cigarette paper. This cigarette paper is opaque in a dry state but becomes less opaque when being subjected to humidity 46. Accordingly, the depicted portion of the stick wrap forms a hydrochromic portion 50 in the sense of the present invention. Before use the depicted portion of the stick wrap 30 is opaque and a user cannot recognize the permanent marking 60 provided at the plug wrap 36 underneath the stick wrap 30. Upon use of the aerosol-generating article 10 humidity 46 is created in the interior volume of the aerosol-generating article 10. A part of this humidity 46 travels towards the stick wrap 30, thereby increasing the humidity level in the stick wrap 30. After use of the aerosol-generating article 10, the depicted portion of the stick wrap 30 covering the marking 60 has been exposed to humidity 46 and becomes less opaque. Therefore, a user can visually perceive the marking 60 below the stick wrap 30 after use of the aerosol-generating article 10, as indicated in the right-hand view of Fig. 4.

Fig. 5 shows a further embodiment of an aerosol-generating article comprising a stick wrap with a hydrochromic portion 50. Similarly as in Fig. 4, Fig. 5 shows only the area of the aerosol-generating article 10 that comprises the hydrochromic portion 50 and the marking 60. The left-hand view in Fig. 5 shows an unused aerosol-generating article 10, and the right-hand view in Fig. 5 shows the same aerosol-generating article 10 after having been used. The construction of the aerosol-generating article 10 is largely identical to the construction of the aerosol-generating article 10 depicted in Fig. 4. However, in Fig. 5 the stick wrap is now provided with a stripe of hydrochromic ink that forms a hydrochromic portion 50.

The color of the stripe-shaped hydrochromic portion 50 is chosen to be more or less identical to the color of the stick wrap. Thus, in the unused aerosol-generating article 10 the hydrochromic portion 50 on the stick wrap 30 is not visually perceivable by a user. Instead, the outer surface of the aerosol-generating article appears to have a homogeneous color.

Upon use of the aerosol-generating article 10 humidity 46 is created in the interior volume of the aerosol-generating article 10. A part of this humidity travels towards the stick wrap 30, thereby increasing the humidity level in the stick wrap 30 and also in the hydrochromic portion 50 printed thereon. Upon interaction with this humidity 46, the hydrochromic ink changes its colour to form a strong contrast over the color of the remaining portion of the stick wrap. In the example of Fig. 5 the hydrochromic portion turns blue upon contact with humidity 46. A user can now again visually perceive the marking 60 on the stick wrap 30 after use of the aerosol-generating article 10. In order to protect external air humidity to trigger the change of color of the hydrochromic portion 50, the stick wrap 30 might be provided with a hydrophobic and transparent outer coating.

Fig. 6 shows a further embodiment of an aerosol-generating article comprising a stick wrap with a hydrochromic portion 50. Again, the left-hand view in Fig. 6 shows an unused aerosol-generating article 10, and the right-hand view in Fig. 6 shows the same aerosolgenerating article 10 after having been used. The construction of the aerosol-generating article 10 is largely identical to the construction of the aerosol-generating article 10 depicted in Fig. 4. Again, the outer surface of the plug wrap 36 is provided with a marking 60 in the form of a colored stripe. The plug wrap is further wrapped with a stick wrap 30 that is used to connect the element 16 to adjacent elements of the aerosol-generating article 10. In Fig. 6 the stick wrap 30 is generally transparent.

Stick wrap 30 comprises a hydrochromic portion 50 which is opaque as long as it is not on contact with humidity. The hydrochromic portion 50 is provided at the inner surface of the stick wrap 30 and completely covers the marking 60 of the plug wrap 36. Accordingly, as indicated in the left-hand view of Fig. 6, in the dry state the opaque hydrochromic portion 50 covers the marking 60, such that the marking 60 is not visually perceivable by the user.

Upon use of the aerosol-generating article 10 humidity 46 is created in the interior volume of the aerosol-generating article 10. A part of this humidity travels towards the stick wrap 30, thereby increasing the humidity level in the stick wrap 30 and also in the hydrochromic portion 50 printed on the inner surface thereof. Upon interaction with this humidity 46, the hydrochromic ink changes its opacity and becomes transparent. Due to the change of opacity of the hydrochromic portion 50, the marking underneath the hydrochromic portion 50 is revealed. Thus, a user can again visually perceive the marking 60 through the stick wrap 30 after use of the aerosol-generating article 10. In order to protect external air humidity to trigger the change of color of the hydrochromic portion 50, the stick wrap 30 might be provided with a hydrophobic and transparent outer coating.

Fig. 7 shows a further embodiment of an aerosol-generating article comprising a stick wrap with a hydrochromic portion 50. The left-hand view in Fig. 7 shows an unused aerosolgenerating article 10, and the right-hand view in Fig. 7 shows the same aerosol-generating article 10 after having been used. The construction of the aerosol-generating article 10 is largely identical to the construction of the aerosol-generating article 10 depicted in Fig. 4. In addition, in Fig. 5 there is color pigment 62 provided between element 16 and the stick wrap 30. The color pigment is not mobile in the unused aerosol-generating article 10. The color pigment 62 is covered by the opaque stick wrap 30 such that the color pigment 62 is not visible in the unused article. At least the hydrochromic portion 50 of the stick wrap 30 has an increased capillarity. The term “increased capillarity” means that the capillarity is larger than the capillarity of the plug wrap 36.

Upon use of the aerosol-generating article 10 humidity 46 is created in the interior volume of the aerosol-generating article 10. A part of this humidity travels radially through the plug wrap 36 towards the stick wrap 30. The color pigment 62 is carried by the internal humidity 46 and the increased capillarity of the stick wrap 30 toward the outer surface of the stick wrap 30. On the outer surface of the stick wrap the color pigment becomes visible. Thus, the color pigment forms a visually perceivable marking 60 showing that the aerosol-generating article 10 has been used. This embodiment is less susceptible to ambient humidity, since the increased capillarity keeps ambient humidity within the stick wrap 30 and thereby prevents that the ambeint humidity comes into contact with the color pigment 62. Nevertheless, it would still be possible to provide the stick wrap with a hydrophobic and transparent outer coating to further reduce influence of ambient humidity.

In Fig. 8 various configurations for the marking are depicted. The marking could for example consist in the word “used” being revealed at the outer surface of the aerosolgenerating article 10. In addition, in the embodiment of Fig. 8, the marking comprises a progressive portion, which is indicative of the level of depletion of the aerosol-generating article 10. The progressive marking is an arrow symbol comprising four segments. The first and the second segment is already visible. The further segments are not yet visible and are only indicated by the dotted lines. Thus, the user can derive from this progressive marking that the aerosol-generating article 10 is already depleted by 50 percent. The amount of the appearing segments of the marking depends on the quantity of humidity created, which in turn is indicative of how intense the aerosol-generating article 10 was used. Such progressive markings cannot easily be obtained with thermochromic ink, since thermochromic ink is sensitive on the absolute temperature only, and is not able to give an indication of how long an aerosolgenerating article has been subjected to such temperature.

Fig. 9 depicts an aerosol-generating article 10 comprising a plurality of rod-shaped elements 12, 14, 16, 18 that are connected to each other by a stick wrap 30. The stick wrap 30 is made from conventional cigarette paper. The aerosol-generating article 10 comprises four elements, a front plug 12, a sensorial media plug 14, comprising aerosol-forming substrate 15, a hollow acetate tube 16, and a mouthpiece filter 18.

The sensorial media plug and the hollow acetate tube are separately wrapped in a plug wrap 34, 36. The plug wrap 36 of the hollow acetate tube 16 carries a marking 60 in the form of a printed graphic icon. The icon shows a red triangle with an exclamation mark. The aerosolgenerating article 10 further comprises a capillary element in the form of a capillary thread 64. The capillary thread 64 essentially extends over the full length of the aerosol-generating article 10. In the center view of Fig. 9 the aerosol-generating article 10 is depicted in fully assembled form. The stick wrap 30, which is a conventional cigarette paper, extends over the complete aerosol-generating article 10 and joins together the individual elements, including the capillary thread 64. As long as the aerosol-generating article 10 is not used, the stick wrap 30 is dry and opaque. In this state, the stick wrap 30 covers also the marking 60, which is therefore not or only hardly visible to the user.

In the bottom view of Fig. 9 the aerosol-generating article 10 is depicted after use. The humidity created during use has been spread via the capillary thread 64 over the full length of the aerosol-generating article 10. A portion of the stick wrap 30 has reacted with this humidity and has become less opaque during use. This portion, which includes the area of the hollow acetate tube 16 carrying the marking 60, is the hydrochromic portion 50 of the stick wrap 30. Since this portion has become less opaque the marking 60 underneath this portion is revealed. The change in contrast ratio of the marking 60 between the unused and the used aerosolgenerating article 10 is about 4. Accordingly, the user can now clearly and easily distinguish between used and unused aerosol-generating articles 10.

Claims

1 . An electrically heated aerosol-generating article comprising: a plurality of elements, and a stick wrap, wherein the stick wrap is configured to connect the elements to form the aerosol-generating article, wherein the aerosol-generating article is further configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.

2. An electrically heated aerosol-generating article according to any one of the preceding claims, wherein at least a part of the stick wrap is configured as a hydrochromic portion, that changes color or opacity upon contact with humidity.

3. An electrically heated aerosol-generating article according to any one of the preceding claims, wherein the hydrochromic portion of the stick wrap covers a portion of the outer surface of an element, wherein the portion of the outer surface of an element carries a marking and wherein the hydrochromic portion of the stick wrap is configured to become less opaque upon contact with humidity.

4. An electrically heated aerosol-generating article according to any one of claims 2 or 3, wherein the stick wrap is generally transparent, wherein the stick wrap is provided with an hydrochromic portion which is opaque in a dry state, and wherein the hydrochromic portion becomes less opaque upon contact with humidity.

5. An electrically heated aerosol-generating article according to any one of claims 1 or 2, wherein the hydrochromic portion of the stick wrap is configured to change color upon contact with humidity.

6. An electrically heated aerosol-generating article according to claim 5, wherein the hydrochromic portion of the stick wrap is configured to have the same or a similar color as the stick wrap before coming in contact with humidity, and wherein the hydrochromic portion of the stick wrap is further configured to change its color upon contact with humidity.

7. An electrically heated aerosol-generating article according to any preceding claim, wherein the aerosol-generating article comprises color pigment which is transported by humidity and the capillarity of the stick wrap to the outer surface of the stick wrap.

8. An electrically heated aerosol-generating article according to any preceding claim, wherein the humidity created by condensation of heated air or aerosol makes contact with the hydrochromic portion of the stick wrap.

9. An electrically heated aerosol-generating article according to the preceding claim, wherein the marking is configured to indicate the quantity of humidity received in a marking zone.

10. An electrically heated aerosol-generating article according to any preceding claim, wherein the aerosol-generating article comprises an element having increased capillarity for transporting the humidity to dedicated portions of the aerosol-generating article.

11. An electrically heated aerosol-generating article according to any preceding claim, wherein one or more of the rod-shaped elements may comprise perforations or openings to enhance radial transfer of humidity from the air flow channel towards the stick wrap.

12. An electrically heated aerosol-generating article according to any preceding claim, wherein the stick wrap is covered by a hydrophobic layer.

13. An electrically heated aerosol-generating article according to any one of the preceding claims, wherein the change of color or opacity of the hydrochromic portion is irreversible.

14. An aerosol-generating system comprising: an aerosol-generating device; and an electrically heated aerosol-generating article according to any preceding claim.

15. A method of manufacturing an electrically heated aerosol-generating article, comprising: providing a plurality of rod-shaped elements, and providing a stick wrap, connecting the rod-shaped elements by wrapping the stick wrap around the rod-shaped elements to form the electrically heated aerosol-generating article, wherein the electrically heated aerosol-generating article is configured to reveal a visually perceivable marking upon contact of the stick wrap with humidity.