CN111867406A

CN111867406A - Aerosol-generating article with thermal indicator

Info

Publication number: CN111867406A
Application number: CN201980019599.4A
Authority: CN
Inventors: T·李维尔
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2018-04-09
Filing date: 2019-04-09
Publication date: 2020-10-30
Also published as: EP3772250A1; EP3772250B1; US20210007403A1; KR20200139688A; JP2021520796A; WO2019197413A1; JP7408565B2; BR112020018722A2

Abstract

A heated aerosol-generating article (10) for use with an aerosol-generating device (510) having a heating element (520), the heated aerosol-generating article comprising a rod of aerosol-generating substrate (20); and an outer wrapper (60), wherein the outer wrapper wraps at least a portion of the aerosol generating substrate rod and at least a portion of an outer surface of the wrapper comprises a thermal indicator (100, 101, 102, 103). The thermal indicator comprises a thermochromic material, whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at said portion of the thermochromic material exceeds a threshold temperature, such that the outer wrapper material provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 175 ℃.

Description

Aerosol-generating article with thermal indicator

Technical Field

The present invention relates to a heated aerosol-generating article incorporating a thermal indicator comprising a thermochromic material, to the use of such a thermochromic material in such a heated aerosol-generating article, and to an aerosol-generating system comprising such a heated aerosol-generating article with a thermal indicator.

Background

Aerosol-generating articles in which an aerosol-generating substrate (such as a tobacco-containing substrate) is heated rather than combusted are known in the art. Typically, in such heated smoking articles, an aerosol is generated by transferring heat from a heat source to a physically separate aerosol generating substrate or material, which may be positioned in contact with the heat source, either internally, around or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in air drawn through the aerosol-generating article. As the released compound cools, the compound condenses to form an aerosol.

A number of prior art documents disclose aerosol-generating devices for consuming or drawing a heated aerosol-generating article. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by transferring heat from one or more electrical heating elements of the aerosol-generating device to an aerosol-generating substrate of a heated aerosol-generating article. One advantage of such electrically heated aerosol-generating devices is that they significantly reduce sidestream smoke.

In such aerosol-generating devices, the heating element is typically configured to heat the aerosol-generating substrate within a defined temperature range that has been selected by the manufacturer to provide an optimal aerosol release profile from the aerosol-generating article. Accordingly, the aerosol-generating article and the aerosol-generating device are particularly suitable for use in combination with each other.

However, in the event that the aerosol-generating article is used, either accidentally or intentionally, with an incompatible aerosol-generating device, it is unlikely that an optimal aerosol release profile will be provided to the consumer. The configuration of the heating element in a incompatible device is typically different from the configuration of a compatible device and so the heating profile of the aerosol-generating substrate may be different. Furthermore, the heater may not operate in the same manner over the same temperature range and therefore will not heat the aerosol-generating substrate under the same temperature profile as in a compatible device. Thus, the characteristics of the aerosol released from the substrate will not be as expected by the manufacturer. As a result, the consumer experience may be adversely affected by using the aerosol-generating article with an incompatible device.

Particular problems may arise when the aerosol-generating article is used in a device that heats an aerosol-generating substrate to a higher temperature than intended, such that at least a portion of the substrate is overheated. This may occur, for example, when an aerosol-generating article adapted to be heated by an internal heating element is instead used in an aerosol-generating device that externally heats the aerosol-generating article. Such devices that heat the substrate from the outside during use typically require a much higher operating temperature, and therefore at least the outer portion of the substrate may be heated to a much higher temperature than is provided using the internal heating element. In addition, overheating of the substrate may also occur by internal heating of the aerosol-generating article by a compatible or incompatible aerosol-generating device which internally heats the aerosol-generating article to a much higher operating temperature as well.

It is desirable to provide a novel arrangement of aerosol-generating articles that provides a visual indication or warning to a user that the aerosol-generating article is to be used with an incompatible aerosol-generating device, and in particular with any aerosol-generating device that heats an aerosol-generating substrate to a higher temperature than the substrate is intended for. It would also be desirable to provide such a novel arrangement of aerosol-generating articles which does not adversely affect the use of the aerosol-generating articles in compatible devices under normal heating conditions. It would be particularly desirable if such a novel arrangement of aerosol-generating articles could be readily provided without significantly affecting the construction of the aerosol-generating articles or the methods and apparatus for producing the aerosol-generating articles.

Disclosure of Invention

According to a first aspect of the present invention there is provided a heated aerosol-generating article for use with an aerosol-generating device having a heating element, the heated aerosol-generating article comprising: a rod of aerosol-generating substrate; and an outer wrapper, wherein the outer wrapper surrounds at least a portion of the rod of aerosol generating substrate and at least a portion of an outer surface of the wrapper comprises a thermal indicator. The thermal indicator comprises a thermochromic material, whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at said portion of the thermochromic material exceeds a threshold temperature, such that the outer wrapper material provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 175 ℃.

According to a second aspect of the present invention there is provided a heated aerosol-generating article for use with an aerosol-generating device having a heating element, the heated aerosol-generating article comprising: a rod of aerosol-generating substrate; and an outer wrapper, wherein at least a portion of an outer surface of the wrapper comprises a thermal indicator, wherein the thermal indicator is located downstream of the rod of aerosol generating substrate. The thermal indicator comprises a thermochromic material, whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at said portion of the thermochromic material exceeds a threshold temperature, such that the outer wrapper material provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 115 ℃.

According to a third aspect of the present invention there is provided the use of a thermochromic material in a thermal indicator located on a wrapper of an aerosol-generating substrate rod of a heated aerosol-generating article configured for use with an aerosol-generating device having a heating element, wherein the wrapper wraps at least a portion of the aerosol-generating substrate rod, and whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature, such that the wrapper provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 175 ℃.

According to a fourth aspect of the invention there is provided the use of a thermochromic material in a thermal indicator located on a wrapper of a heated aerosol-generating article configured for use with an aerosol-generating device having a heating element, and the heated aerosol-generating article comprising a rod of aerosol-generating substrate, whereby the thermal indicator is located downstream of the rod of aerosol-generating substrate, and at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature, such that the wrapper provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 115 ℃.

According to a fifth aspect of the present invention, there is provided an aerosol-generating system comprising: a heated aerosol-generating article according to the first or second aspects of the invention as hereinbefore described; and an aerosol-generating device adapted to receive the heated aerosol-generating article. The aerosol-generating device comprises a heater element configured to heat the strip of aerosol-generating material during use, wherein the heater element is controlled to operate below a maximum operating temperature during use. The thermal indicator of the heated aerosol-generating article is adapted such that a threshold temperature is not exceeded during use of the aerosol-generating system when the heater element is operating below a maximum operating temperature.

As used herein, the term "heated aerosol-generating article" refers to an aerosol-generating article for generating an aerosol, the aerosol-generating article comprising an aerosol-generating substrate which is intended to be heated rather than combusted in order to release volatile compounds that may form an aerosol. These articles are commonly referred to as "heated but not burned" products.

As used herein, the term "aerosol-generating substrate" refers to a substrate that is capable of releasing volatile compounds that can form an aerosol when heated. The aerosol generated by the aerosol-generating substrate of the aerosol-generating article described herein may be visible or invisible, and may comprise vapour (e.g. fine particles of a substance in the gaseous state, which is typically a liquid or solid at room temperature) as well as gas and liquid droplets of condensed vapour.

As used herein, the term "bar" refers to a generally cylindrical element having a generally polygonal cross-section and preferably having a circular, oval or elliptical cross-section. Unless otherwise indicated, the term "article" will refer to an aerosol-generating article.

As used herein, the term "longitudinal" refers to a direction corresponding to the major longitudinal axis of an aerosol-generating article, which direction extends between an upstream end and a downstream end of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term "transverse" refers to a direction perpendicular to the longitudinal axis.

As used herein, the terms "upstream" and "downstream" describe the relative position of an element or portion of an element of an aerosol-generating article with respect to the direction in which an aerosol is conveyed through the aerosol-generating article during use.

The aerosol-generating article according to the present invention is suitable for use in an aerosol-generating system comprising an electrically heated aerosol-generating device having an internal heating element for heating an aerosol-generating substrate. For example, aerosol-generating articles according to the invention have particular application in aerosol-generating systems comprising an electrically heated aerosol-generating device having an internal heater blade adapted to be inserted into a rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example in european patent application EP- ｃA-0822670.

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

As mentioned above, the aerosol-generating article according to the present invention incorporates an outer wrapper comprising a thermal indicator. The thermal indicator provides an effective means to warn of and prevent the use of aerosol-generating articles according to the invention in incompatible devices that heat aerosol-generating articles well above the desired operating temperature. When the aerosol-generating substrate rod is overheated, the thermal indicator will produce a visual change to alert the user to incorrect and/or potentially harmful use, which the user may see during or after use of the aerosol-generating article. In this way, users will be alerted that they have or are using the aerosol-generating article with an incompatible device or with a compatible device that is malfunctioning and that overheats the aerosol-generating article during use. The thermal indicator thus provides a means of preventing overheating of the aerosol-generating article.

As used herein with reference to the present invention, the term "thermochromic material" is used to describe any material that undergoes a visual change at a predetermined threshold temperature or temperature range.

Thermochromic materials may undergo a visual change when the temperature rises above or falls below a threshold temperature. As used herein with reference to the present invention, the term "threshold temperature" is used to describe the temperature at which the visual change of the thermochromic material is substantially complete thereafter.

Advantageously, the thermal indicator is adapted such that it will undergo a visual change at an excessively high operating temperature. Thus, when an aerosol-generating article according to the invention is heated normally in a compatible aerosol-generating device, the presence of the thermal indicator will not have a perceptible effect on the consumer's experience. In particular, the presence of the thermal indicator does not adversely affect the Resistance To Draw (RTD) of the aerosol-generating article.

An outer wrapper comprising a thermal indicator may conveniently be incorporated into an aerosol-generating article without significantly affecting the arrangement of other components of the article. Thus, the inclusion of the thermal indicator should not significantly affect the manufacture of the aerosol-generating article. Thus, aerosol-generating articles according to the invention can advantageously be manufactured using existing high-speed methods and apparatus (requiring only minor modifications).

The positioning of the thermal indicator on the outer wrapper, around the exterior of the aerosol-generating article, and the material selected for the thermal indicator determine the responsiveness of the thermal indicator to overheating due to use of the aerosol-generating article in an incompatible device having, for example, a peripheral heater which externally heats the aerosol-generating substrate.

In the event that the aerosol-generating article overheats such that the thermal indicator reaches its threshold temperature, for example in an incompatible device, the thermal indicator will be "activated" and undergo a visual change. Thus, activation of the thermal indicator will provide an effective means to warn and prevent the aerosol-generating article according to the present invention from being used in an incompatible device that heats the aerosol-generating article well above a set of desired operating temperatures and above a threshold temperature.

The "threshold temperature" of the thermal indicator corresponds to the temperature at which the thermal indicator will undergo a visual change, as described above. This typically corresponds to a threshold temperature of the material used to form the thermal indicator. As discussed in more detail below, the threshold temperature of the thermal indicator and the threshold temperature at the thermal indicator will be selected such that the threshold temperature is only reached or exceeded when the aerosol-generating article is overheated (i.e. heated above the expected operating temperature range). Thus, when the aerosol-generating substrate is heated above a maximum desired temperature (determined by the manufacturer), the threshold temperature will correspond to the temperature reached at the thermal indicator.

There are several possible ways to adjust the thermal indicator such that activation occurs at a desired threshold temperature and such that a visual change is produced at the thermal indicator to prevent further use of the aerosol-generating article.

Suitable materials should be selected for forming the thermal indicator, wherein the materials have an appropriate activation point or threshold temperature to ensure that the thermal indicator is not at risk of undergoing a visual change when the aerosol-generating article is heated to within the normal operating temperature range, but also such that the thermal indicator effectively undergoes a visual change when the aerosol-generating article is overheated to a temperature outside this range. This will avoid false indications of overheating when the aerosol-generating indicator is operating within the normal operating temperature range and provide a reliable indicator of overheating when the aerosol-generating indicator is operating outside or above the normal operating temperature range.

It is also desirable to select a suitable location for the thermal indicator on the aerosol-generating article. The appropriate location of the thermal indicator will depend to some extent on the material selected so that the threshold temperature can be appropriately defined. This will avoid accidental activation of the thermal indicator during normal use of the aerosol-generating article.

Typically, during use, the aerosol-generating article will be inserted into an aerosol-generating device such that the aerosol-generating substrate is heated, directly or indirectly, by a heating element within the device. The temperature within the aerosol-generating article is highest in the vicinity of the heating element and decreases longitudinally along the aerosol-generating article with increasing distance from the heating element. Thus, the appropriate threshold temperature of the thermal indicator will vary depending on how far downstream the thermal indicator is placed in the aerosol-generating substrate. In particular, the further downstream the thermal indicator is placed on the aerosol-generating substrate, the lower the threshold temperature will be required in order to activate the thermal indicator.

The temperature profile in and around the aerosol-generating article may be readily measured using a thermocouple, so that an appropriate threshold temperature may be determined to ensure that the thermal indicator is activated only when the substrate is deemed to be overheated (i.e. above a defined maximum temperature).

The thermal indicator may suitably be located anywhere on the outer surface of the outer wrapper. The thermal indicator may be at least near and/or around the aerosol-generating substrate rod.

As mentioned above, the threshold temperature of a thermal indicator according to the present invention is selected depending on its location along the aerosol-generating article having a preferred operating temperature range.

Advantageously, the threshold temperature may be below about 300 ℃.

Advantageously, the threshold temperature may be between about 115 ℃ and about 300 ℃. For example, the threshold temperature may be between about 120 ℃ and about 300 ℃. For example, the threshold temperature may be between about 155 ℃ and about 300 ℃. For example, the threshold temperature may be between about 160 ℃ and about 300 ℃. For example, the threshold temperature may be between about 170 ℃ and about 300 ℃. For example, the threshold temperature may be between about 175 ℃ and about 300 ℃.

Advantageously, the threshold temperature may be below about 275 ℃.

Advantageously, the threshold temperature may be between about 115 ℃ and about 275 ℃. For example, the threshold temperature may be between about 120 ℃ and about 275 ℃. For example, the threshold temperature may be between about 155 ℃ and about 275 ℃. For example, the threshold temperature may be between about 160 ℃ and about 275 ℃. For example, the threshold temperature may be between about 170 ℃ and about 275 ℃. For example, the threshold temperature may be between about 175 ℃ and about 275 ℃.

Advantageously, the threshold temperature may be below about 250 ℃.

Advantageously, the threshold temperature may be between about 115 ℃ and about 250 ℃. For example, the threshold temperature may be between about 120 ℃ and about 250 ℃. For example, the threshold temperature may be between about 155 ℃ and about 250 ℃. For example, the threshold temperature may be between about 160 ℃ and about 250 ℃. For example, the threshold temperature may be between about 170 ℃ and about 250 ℃. For example, the threshold temperature may be between about 175 ℃ and about 250 ℃.

According to a first aspect of the invention, the thermal indicator may be located around at least a portion of the rod of aerosol-generating substrate. The thermal indicator may define and cover the entire surface area of the aerosol-generating substrate strip. Alternatively or additionally, the thermal indicator may define at least a portion of the aerosol-generating substrate rod and at least a further downstream portion of the aerosol-generating article. Alternatively, the thermal indicator may define only a portion of the entire circumference or perimeter of the aerosol-generating article, preferably around a portion of the rod of aerosol-generating substrate.

According to a first aspect of the invention, the thermal indicator is disposed above the aerosol-generating substrate rod and the threshold temperature is preferably at least about 175 ℃, more preferably about 180 ℃ and most preferably about 185 ℃. Preferably, the threshold temperature is at least about 220 ℃. The threshold temperature may not exceed about 300 deg.c. This ensures that the thermal indicator is sufficiently sensitive to heating of the aerosol-generating substrate above a maximum desired temperature. In such embodiments, the threshold temperature of the thermal indicator will need to be relatively high, since it may be close to the heating element of the aerosol-generating device during use.

According to a second aspect of the invention, the thermal indicator may be located downstream of the aerosol-generating substrate rod, or "substrate/distal end" of the aerosol-generating article. As used herein with reference to the present invention, the term "substrate/distal end" refers to the upstream end of an aerosol-generating article, which is also the end of an aerosol-generating substrate that is configured to be heated. The "mouth end" of the aerosol-generating article is the downstream end of the aerosol-generating article, which is opposite the "substrate/distal end".

According to a second aspect of the invention, the thermal indicator, or a portion thereof, is disposed downstream of the aerosol-generating substrate rod, the threshold temperature preferably being at least about 115 ℃, more preferably about 120 ℃ and most preferably about 125 ℃. The threshold temperature may not exceed about 200 ℃. This ensures that the thermal indicator is sufficiently sensitive to heat the aerosol-generating substrate above a maximum desired temperature. In such embodiments, the threshold temperature of the thermal indicator needs to be lower as it may be further away from the heating element of the aerosol-generating device during use.

According to all aspects of the invention, the thermal indicator extends longitudinally along at least a portion of the length of the aerosol-generating article. For example, the length of the thermal indicator may be between about 1 millimeter and 20 millimeters. Further, the length of the thermal indicator may be between about 1 millimeter and 15 millimeters.

The thermal indicator may extend longitudinally along at least 20% of the length of the aerosol-generating article, more preferably along at least 25% of the length of the aerosol-generating article. Preferably, the thermal indicator may extend longitudinally along at least 50% of the length of the aerosol-generating article.

The length of the thermal indicator may be the same as the length of the aerosol-generating article, or may be the same as the length of the rod of aerosol-generating substrate. Preferably, the length of the thermal indicator may be at least 75% of the length of the aerosol-generating substrate rod, and more preferably at least 50% of the length of the aerosol-generating substrate rod.

The thermal indicator may extend at least partially circumferentially around the aerosol-generating article. Preferably, the thermal indicator extends around the entire circumference of the aerosol-generating article.

According to a first aspect of the invention, the thermal indicator may overlie at least 1mm of the outer surface area of the rod of aerosol-generating substrate². Preferably, the thermal indicator may overlie at least 5mm of the outer surface area of the rod of aerosol-generating substrate²。

According to the first aspect of the invention, the thermal indicator may overlie at least 20% of the outer surface area of the rod of aerosol-generating substrate. Preferably, the thermal indicator may overlie at least 25% of the outer surface area of the rod of aerosol-generating substrate. Preferably, the thermal indicator may overlie at least 50% of the outer surface area of the rod of aerosol-generating substrate.

In certain embodiments according to the first aspect of the present invention, the thermochromic material may be arranged such that the visual change occurs only within a circumferential portion of the outer wrapper, wherein the circumferential portion may extend only partially around the circumference of the aerosol-generating article. In such embodiments, the thermal indicator may be adapted to provide a local visual change at a specific circumferential position around the aerosol-generating article, preferably around the rod of aerosol-generating substrate. For example, a circumferential portion of the outer surface of the wrapper may include a thermal indicator, or a circumferential portion of the thermal indicator may be configured to undergo a visual change, or both. The circumferential portion may extend for at least 5% of the circumference of the article, more preferably for at least 10% of the circumference of the article and most preferably for at least 20% of the circumference of the article. In such embodiments, the threshold temperature is preferably at least about 175 ℃, more preferably about 180 ℃ and most preferably about 185 ℃. Preferably, the threshold temperature is at least about 220 ℃. The threshold temperature may not exceed about 300 deg.c. This ensures that the thermal indicator is sufficiently sensitive to overheating of the aerosol-generating substrate above a maximum desired temperature. When heated, the temperature distribution along and/or through the rod of substrate may not be uniform, and thus local portions of the outer surface of the aerosol-generating substrate rod may be overheated and other portions may not be overheated. In such embodiments, the threshold temperature of the thermal indicator also needs to be relatively high, since the thermal indicator may be close to the heating element of the aerosol-generating device during use. In addition to local overheating of the substrate, the local visual change may also provide for alignment of the heating element of the aerosol-generating device relative to the outer wrapper and the rod of the aerosol-generating substrate. If the heating element is configured to internally heat the substrate, the threshold temperature may be such that the local visual change may indicate that the region of the outer wrapper where the local visual change has occurred is likely to be closest to the heating element.

As described above, for all aspects of the invention, the thermal indicator configuration undergoes a visual change upon exceeding a threshold temperature. As described above, the visual change may occur over a portion or all of the thermal indicator, depending on which portions of the thermal indicator have exceeded their respective threshold temperatures. The visual change may involve changing from a first color to a second color, or from substantially colorless to a first color, or from a first color to substantially colorless. The visual change may involve changing from a first color to a second color and then to a third color. The visual change may involve a transition from substantially colorless through a plurality of different colors to a final color. The visual change may involve transitioning from an initial color through a plurality of different colors to a final color. Each color may provide a specific indication of the degree of superheat in the matrix. The visual change may include the thermal indicator not displaying any warning indicia or message to displaying a warning indicia or message. The warning indicia or message may include a logo or any form of graphical representation.

The visual change may be immediate or gradual over a wide range of color transitions.

Advantageously, the visual change may be irreversible or reversible, more preferably irreversible. The visual change of the thermal indicator is irreversible or substantially permanent, allowing the thermal indicator to properly communicate a misuse message of the aerosol-generating article to the user upon the visual change. The temperature at the thermal indicator may exceed the threshold temperature before the user or consumer runs out of the product. Therefore, an irreversible visual change is advantageous for ensuring that the user is informed about misuse after the article has been used up.

The visual change may encompass any combination of the above characteristics.

The thermal indicator may comprise a single thermochromic material having a particular threshold temperature and a visual change. Alternatively, the thermal indicator may comprise a plurality of different thermochromic materials, wherein each of the different thermochromic materials may comprise a different threshold temperature and/or visual change from one another.

The thermal indicator may comprise a single thermochromic material, wherein the threshold temperature is uniform across and along the thermal indicator. Alternatively, the thermal indicator may comprise a single thermochromic material, wherein the threshold temperature varies longitudinally and/or along the thermal indicator. For example, the threshold temperature may decrease or increase in a downstream direction or an upstream direction along the thermal indicator.

In all embodiments of the invention, the thermal indicator is formed from a thermochromic material. The thermochromic material may be applied or adhered to a surface of the outer wrapper in the form of a paint, ink, dye or another layer of material having thermochromic material applied thereto. Alternatively, the outer wrapper may comprise a temperature indicating sensor paper, whereby the thermochromic material is an integral part of the temperature indicating sensor paper. The thermochromic material may also be integrated with at least any other component, layer or portion of the outer wrapper.

From Sensor Products

(http:// www.sensorprod.com/thermex. php) is an example of an irreversible thermochromic material suitable for use in providing the thermal indicators of the present invention.

Is a tactile surface temperature indicating material provided in a sheet and configured to be placed between two contact surfaces, and after exposure to a particular threshold temperature or range of threshold temperatures,

the sheet instantaneously and permanently changes color. The color change is permanent or irreversible and the operating threshold temperature range is 90 to 149 ℃. Other suitable irreversible thermochromic materials generally known to the skilled person may be used.

The thermal indicator may comprise a combination of reversible and irreversible thermochromic materials. In this case, the thermal indicator may undergo both reversible and irreversible visual changes. Suitable reversible thermochromic materials generally known to the skilled person may be used.

As described above, the thermal indicator can be easily provided without significantly affecting the construction of the aerosol-generating article or the method and apparatus for producing the aerosol-generating article. The thermal indicator may thus be easily provided or applied or adhered to the inner and/or outer surface of the outer package material, preferably to the outer surface of the outer package material. The thermal indicator may be disposed between two layers of wrapper material which may form an outer wrapper material. The thermal indicator may be incorporated into the outer package material in a separate process so that the process of assembling the outer package material around the article is not affected.

Aerosol-generating articles according to the invention may comprise a plurality of elements, including a rod of aerosol-generating substrate and a thermal indicator located on the outer wrapper of the article. The overwrap material may comprise cigarette paper.

Aerosol-generating articles typically comprise a hollow acetic acid tube directly adjacent to an aerosol-generating substrate.

The aerosol-generating substrate rod is formed from an aerosol-forming material, which is particularly preferably a homogenized tobacco material.

As used herein, the term "homogenized tobacco material" encompasses any tobacco material formed by agglomeration of particles of tobacco material. A sheet or web of homogenized tobacco material is formed by agglomerating particulate tobacco obtained by grinding or otherwise powdering one or both of a tobacco lamina and a tobacco stem. In addition, the homogenized tobacco material may include small amounts of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during processing, handling, and transport of the tobacco. The sheet of homogenized tobacco material may be produced by casting, extrusion, a papermaking process, or any other suitable process known in the art.

In a preferred embodiment, the rod comprises one or more sheets of homogenized tobacco material that have been gathered to form a plug and defined by an outer packaging material. As used herein with reference to the present invention, the term "sheet" describes a layered element having a width and length substantially greater than its thickness. As used herein with reference to the present invention, the term "gathered" describes a sheet material that spirals, folds, or otherwise compresses or contracts substantially transverse to the longitudinal axis of the aerosol-generating article.

Advantageously, the aerosol-generating substrate comprises a gathered textured sheet of homogenised tobacco material. As used herein with reference to the present invention, the term "textured sheet" describes a sheet that has been curled, embossed, debossed, perforated or otherwise deformed.

The use of a textured sheet of homogenised tobacco material may advantageously facilitate aggregation of the sheet of homogenised tobacco material to form the aerosol-generating substrate.

The aerosol-generating substrate may comprise a gathered textured sheet of homogenised tobacco material comprising a plurality of spaced apart recesses, protrusions, perforations or any combination thereof.

In certain preferred embodiments, the aerosol-generating substrate comprises a gathered crimped sheet of homogenised tobacco material. As used herein with reference to the present invention, the term "crimped sheet" describes a sheet having a plurality of generally parallel ridges or corrugations. Advantageously, when the aerosol-generating article is assembled, the substantially parallel ridges or corrugations extend along, or parallel to, a longitudinal axis of the aerosol-generating article. This promotes aggregation of the crimped sheet of homogenised tobacco material to form the aerosol-generating substrate.

However, it will be appreciated that the crimped sheet of homogenized tobacco material for inclusion in the aerosol-generating substrate of an aerosol-generating article according to the invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations which are disposed at an acute or obtuse angle to the longitudinal axis of the aerosol-generating article when the aerosol-generating article has been assembled.

The sheet of homogenized tobacco material for use in the present invention may have a tobacco content of at least about 40 weight percent on a dry weight basis, more preferably at least about 50 weight percent on a dry weight basis, more preferably at least about 70 weight percent on a dry weight basis, most preferably at least about 90 weight percent on a dry weight basis.

Preferably, the sheet of homogenized tobacco material comprises an aerosol former. The sheet of homogenized tobacco material may comprise a single aerosol former. Alternatively, the sheet of homogenized tobacco material may comprise a combination of two or more aerosol-formers.

Suitable aerosol-forming agents are known in the art and include, but are not limited to: monohydric alcohols such as menthol, polyhydric alcohols such as triethylene glycol, 1, 3-butanediol and glycerol; esters of polyhydric alcohols, such as glycerol monoacetate, glycerol diacetate, or glycerol triacetate; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate, dimethyl tetradecanedioate, erythritol, 1, 3-butanediol, tetraethylene glycol, triethyl citrate, propylene carbonate, ethyl laurate, triacetin, meso-erythritol, diacetin mixtures, diethyl suberate, triethyl citrate, benzyl benzoate, benzyl phenylacetate, ethyl vanillate, glyceryl tributyrate, lauryl acetate, lauric acid, myristic acid and propylene glycol.

Preferably, the sheet of homogenized tobacco material has an aerosol former content of greater than 5% by dry weight.

The sheet of homogenized tobacco material may have an aerosol former content of about 5% to about 30% on a dry weight basis.

In a preferred embodiment, the sheet of homogenized tobacco material has an aerosol former content of about 20% by dry weight.

The sheet of homogenized tobacco material used in the present invention may comprise one or more intrinsic binders (i.e., tobacco endogenous binders), one or more extrinsic binders (i.e., tobacco exogenous binders), or a combination thereof, to aid in agglomerating the particulate tobacco. Alternatively or additionally, the sheet of homogenized tobacco material for use in an aerosol-generating substrate may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof.

Suitable external binders for inclusion in the sheet of homogenized tobacco material for use in the present invention are known in the art and include, but are not limited to: gums such as guar gum, xanthan gum, gum arabic and locust bean gum; cellulose binders such as hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides, such as starch; organic acids such as alginic acid; conjugate base salts of organic acids, such as sodium alginate, agar, and pectin; and combinations thereof.

Suitable non-tobacco fibres for inclusion in a sheet of homogenized tobacco material for use in an aerosol-generating substrate are known in the art and include, but are not limited to: cellulose fibers; softwood fibers; hardwood fibers; jute fibers and combinations thereof. The non-tobacco fibres may be treated by suitable processes known in the art, including but not limited to: mechanically pulping; refining; chemical pulping; bleaching; sulfate pulping; and combinations thereof.

The sheet of homogenized tobacco used in the present invention preferably has a width of between about 70mm to about 250mm, for example between about 120mm to about 160 mm. Preferably, the thickness of the sheet of homogenized tobacco material is between about 50 microns and about 300 microns, more preferably between about 150 microns and about 250 microns.

Sheets of homogenized tobacco for use in the aerosol-generating articles of the invention may be manufactured by methods known in the art, for example the method disclosed in international patent application WO-A-2012/164009A 2.

In a preferred embodiment, a sheet of homogenized tobacco material for use in an aerosol-generating article is formed from a slurry comprising particulate tobacco, guar gum, cellulose fibres and glycerol by a casting process.

As mentioned above, instead of using a gathered sheet of homogenized tobacco material, the aerosol-generating substrate may be formed from a plurality of strips or pieces of homogenized tobacco material sheet. For example, the aerosol-generating substrate may be formed from a plurality of fragments of homogenized tobacco material aligned in the longitudinal direction and gathered together and packaged to form a rod of aerosol-generating substrate.

The length of the pieces of homogenized tobacco material is preferably between about 10 and about 20 mm, more preferably between about 12 and about 18 mm, more preferably between about 14 and about 16 mm, more preferably about 15 mm. Alternatively or additionally, the width of the pieces of homogenized tobacco material is preferably between about 0.4 mm and about 0.8 mm.

Preferably, the sheet of homogenized tobacco material used to form the pieces has a density of between about 500 mg/cc and about 1500 mg/cc, more preferably between about 800 mg/cc and about 1200 mg/cc, more preferably between about 900 mg/cc and about 1100 mg/cc, and most preferably between about 900 mg/cc and about 970 mg/cc.

Preferably, the bulk density of the pieces of homogenized tobacco material within the aerosol-generating substrate is between about 0.4 g/cc and about 0.8 g/cc, preferably between about 0.5 g/cc and about 0.7 g/cc, and most preferably between about 0.65 g/cc and about 0.67 g/cc.

As mentioned above, the homogenized tobacco material may be formed by casting of a slurry. Alternatively, the homogenized tobacco material may be formed by another suitable method, such as an extrusion method.

Preferably, the aerosol-generating substrate comprises a strip of homogenized tobacco material defined by a wrapper, wherein the wrapper is disposed around and in contact with the homogenized tobacco material. The wrapper may be formed from any suitable sheet material that can be wrapped around the homogenized tobacco material to form an aerosol-generating substrate. The packaging material may be porous or non-porous. Preferably, the wrapper is a paper wrapper, but alternatively the wrapper may be non-paper.

The outer diameter of the rod of aerosol-generating substrate is preferably approximately equal to the outer diameter of the aerosol-generating article.

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

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

Preferably, the rod of aerosol-generating substrate has a substantially uniform cross-section along the length of the rod. Particularly preferably, the aerosol-generating substrate rod has a substantially circular cross-section.

The aerosol-generating article according to the present invention preferably comprises one or more elements in addition to the aerosol-generating substrate rod and the thermal indicator. For example, aerosol-generating articles according to the present invention may further comprise at least one of: a mouthpiece, an aerosol-cooling element and a support element, such as a hollow cellulose acetate tube. For example, in one preferred embodiment, an aerosol-generating article comprises 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 an outer wrapper defining the rod, the support element and the aerosol-cooling element, arranged in linear order. As mentioned above, the thermal indicator may be provided at a defined location around the aerosol-generating substrate rod and/or at any other location around the article.

The aerosol-generating system according to the invention comprises an aerosol-generating article as described in detail above in connection with an aerosol-generating device adapted to receive an upstream end of the aerosol-generating article during smoking. The aerosol-generating device comprises a heating element configured to heat the aerosol-generating substrate so as 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.

During use, the heating element is controlled to operate at a defined operating temperature range (i.e. below a maximum operating temperature). The thermal indicator of the aerosol-generating article is adapted such that when the heater element is operated below a maximum operating temperature, the threshold temperature is not reached during normal use of the aerosol-generating article in the aerosol-generating device. This ensures that the thermal indicator is not activated during normal use when the aerosol-generating article and aerosol-generating device are used together.

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

Drawings

The invention will now be further described with reference to the accompanying drawings, in which:

figure 1 shows a perspective view of an aerosol-generating article according to the present invention;

figure 2 shows a perspective view of an aerosol-generating article having an "activated" thermal indicator according to a first embodiment of the present invention;

figure 3 shows a perspective view of an aerosol-generating article having an "activated" thermal indicator according to a second embodiment of the present invention;

figure 4 shows a perspective view of an aerosol-generating article having an "activated" thermal indicator according to a third embodiment of the present invention;

fig. 5a and 5b show schematic cross-sectional views of an aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article according to the invention.

Detailed Description

The aerosol-generating article 10 shown in the drawings comprises four elements arranged in coaxial alignment: a rod of aerosol-generating substrate 20, a support element 30, an aerosol-cooling element 40 and a mouthpiece 50 (shown in figures 5a and 5 b). Each of the four elements is defined by a corresponding plug wrap (not shown). These four elements are arranged in sequence and defined by an outer wrapper 60 to form the aerosol-generating article 10. The aerosol-generating article 10 has a proximal or mouth end 70 into which a user inserts during use into his or her mouth, and a distal end 80 located at the end of the aerosol-generating article 10 opposite the mouth end 70.

In use, air is drawn through the aerosol-generating article from the distal end 80 to the mouth end 70 by a user. The distal end 80 of the aerosol-generating article may also be described as the upstream end of the aerosol-generating article 10, and the mouth end 70 of the aerosol-generating article 10 may also be described as the downstream end of the aerosol-generating article 10. The elements of the aerosol-generating article 10 positioned between the mouth end 70 and the distal end 80 may be described as being upstream of the mouth end 70, or alternatively downstream of the distal end 80.

When a heating element of an aerosol-generating device is inserted into the aerosol-generating substrate 20, the support element 30 is in position to prevent the aerosol-generating substrate 20 from being pushed downstream within the aerosol-generating article 10 towards the aerosol-cooling element 40. The support element 30 also acts as a spacer to separate the aerosol-cooling element 40 of the aerosol-generating article 10 from the aerosol-generating substrate 20.

The aerosol-cooling element 40 is positioned immediately downstream of the support element 30. In use, volatile materials released from the aerosol-generating substrate 20 pass along the aerosol-cooling element 40 towards the mouth end 70 of the aerosol-generating article 10. The volatile material can be cooled within the aerosol-cooling element 40 to form an aerosol for inhalation by a user. The aerosol-cooling element comprises a crimped and gathered polylactic acid sheet defined by a wrapper 60. The crimped and gathered polylactic acid sheet defines a plurality of longitudinal channels extending along the length of the aerosol-cooling element 40.

The mouthpiece 50 is positioned immediately downstream of the aerosol-cooling element 40 and abuts the aerosol-cooling element 40. The mouthpiece 50 comprises a conventional cellulose acetate tow filter of low filtration efficiency.

To assemble the aerosol-generating article 10, the four elements are aligned and tightly wrapped within the outer wrapper 60. In the embodiment shown in the figures, the outer wrapper 60 is a conventional cigarette paper. A distal portion of the outer wrapper 60 of the aerosol-generating article 10 is defined by a band of tipping paper (not shown).

The aerosol-generating substrate 20 is located at the very distal or upstream end of the aerosol-generating article 10. In the embodiment shown in fig. 5a and 5b, the aerosol-generating substrate 20 comprises a gathered sheet of crimped homogenized tobacco material defined by a wrapper. The crimped sheet of homogenized tobacco material comprises glycerides as aerosol former.

The thermal indicator 100 is disposed at a location on the outer surface of the outer wrapper 60. The thermal indicator 100 includes a thermochromic material configured to undergo a visual change when a temperature at the thermal indicator 100 is above a threshold temperature.

Fig. 1 shows the outer wrapper 60 of the aerosol-generating article prior to activation of the thermal indicator 100. In the following embodiments described herein, the thermal indicator 100 is not visible until the thermal indicator "activates" or begins to undergo a visual change when the temperature is above the threshold temperature.

Fig. 2 shows the article 10 after activation of the thermal indicator 101 according to the first embodiment when the temperature at the thermal indicator 101 is above the threshold temperature of the thermochromic material. In this first embodiment, the thermal indicator is located around the rod of aerosol-generating substrate 20 and the threshold temperature is at least about 175 ℃. In the first embodiment of the article 10, the thermal indicator 101 extends longitudinally along the entire length of the rod of aerosol-generating substrate 20. However, in other arrangements according to the first embodiment, the thermal indicator 101 may extend partially longitudinally along the aerosol-generating substrate rod. For example, the thermal indicator 101 may extend at least 50% of the total length of the rod of aerosol-generating substrate 20.

FIG. 3 shows the article 10 after activation of the thermal indicator 102 according to the second embodiment when the temperature at the thermal indicator 102 is above the threshold temperature. In a second embodiment, the thermal indicator is located partially around the rod of aerosol-generating substrate 20, or the thermal indicator 102 does not completely define the outer surface of the aerosol-generating article. The threshold temperature of the thermal indicator 102 is at least about 175 deg.c. However, the threshold temperature of the thermal indicator 102 according to the second embodiment may be higher than the threshold temperature of the thermal indicator 101 according to the first embodiment.

Fig. 4 shows the article 10 after activation of the thermal indicator 103 according to the third embodiment when the temperature at the thermal indicator 103 is above the threshold temperature. In a third embodiment, the thermal indicator 103 is located around the article 10 at a position downstream of the aerosol-generating substrate rod, away from the distal end 80 of the article 10. The thermal indicator 103 may partially define an outer surface of the aerosol-generating article, and may also define a portion of the aerosol-generating substrate rod. The threshold temperature of the thermal indicator 103 is at least about 115 ℃. Due to the relative distance of the thermal indicator 103 from the aerosol-generating substrate 20, the threshold temperature of the third embodiment may be lower than the threshold temperatures of the first and second embodiments.

As described in detail above, the visual change in the thermal indicator is configured to inform a user of the article 10 that the aerosol-generating substrate 20 of the article 10 has been overheated, either because the article 10 has been misused with an incompatible aerosol-generating device or because the article has been used with an aerosol-generating device that may fail in a manner that overheats the aerosol-generating substrate 20. Thus, to convey such information of misuse of the article 10, the visual change of the

thermal indicator

101, 102, 103 is preferably irreversible, such that upon removal of the article 10 from the aerosol-generating device, the visual change does not "disappear" and remains visible to the user as the substrate 20 cools. As shown in fig. 2, 3 and 4, the irreversible visual change includes a color change from colorless to red and the appearance of a warning message or graphical representation.

The aerosol-generating article shown in the figures described above is designed to engage with an aerosol-generating device comprising a heating element for consumption by a user. In use, the heating element of the aerosol-generating device heats the aerosol-generating substrate of the aerosol-generating article to a sufficient temperature to form an aerosol, which is drawn downstream through the aerosol-generating article and inhaled by a user.

Fig. 5a and 5b illustrate an aerosol-generating system 500 comprising an aerosol-generating device 510 and an aerosol-generating article 10 according to any of the embodiments described above and illustrated in the above figures. It will be appreciated that the aerosol-generating device 510 may be used in combination with alternative aerosol-generating articles according to the present invention.

The aerosol-generating device 510 comprises a heating element 520. As shown in fig. 5a and 5b, the heating element 520 is mounted within the aerosol-generating article-receiving chamber 515 of the aerosol-generating device 510. In use, a user inserts the aerosol-generating article 10 into the aerosol-generating article-receiving chamber 515 of the aerosol-generating device 510 such that the heating element 520 is inserted directly into the aerosol-generating substrate 20 of the aerosol-generating article 10, as shown in figure 5 b. In the embodiment shown in fig. 5a and 5b, the heating element 520 of the aerosol-generating device 510 is a heater blade.

The aerosol-generating device 510 comprises a power source and electronics (not shown) that allow the heating element 520 to be actuated. Such actuation may be manually operated, or may occur automatically in response to a user drawing on an aerosol-generating article 10 inserted into an aerosol-generating article receiving chamber of the aerosol-generating device 510. A plurality of openings (not shown) may be provided in the aerosol-generating device 510 to allow air to flow to the aerosol-generating article 10.

Once the internal heating element 520 is inserted into the aerosol-generating substrate 20 of the aerosol-generating article 10 and the heating element 520 is actuated, the aerosol-generating substrate 20 of the aerosol-generating article 10 is heated by the heating element 520 of the aerosol-generating device 510 to a temperature of approximately 350 ℃. At this temperature, volatile compounds are emitted from the aerosol-generating substrate 20 of the aerosol-generating article 10. As a user draws on the mouth end 70 of the aerosol-generating article 10, volatile compounds emitted from the aerosol-generating substrate 20 are drawn downstream through the aerosol-generating article 10 and condense to form an aerosol which is drawn into the user's mouth through the mouthpiece 50 of the aerosol-generating article 10.

As the aerosol passes downstream through the aerosol-cooling element 40, the temperature of the aerosol is reduced due to the transfer of thermal energy from the aerosol to the aerosol-cooling element 40. When the aerosol enters the aerosol-cooling element 40, its temperature is approximately 60 ℃. Due to the cooling within the aerosol-cooling element 40, the temperature of the aerosol is approximately 40 ℃ when the aerosol leaves the aerosol-cooling element.

In fig. 5a and 5b, the heating element 520 of the aerosol-generating device 510 is shown in a simplified manner. In particular, the heating element 520 of the aerosol-generating device 510 is not drawn to scale in fig. 5a and 5 b. Parts not relevant for understanding of the embodiments have been omitted to simplify fig. 5a and 5 b.

As shown in fig. 5a and 5b, the aerosol-generating device 510 comprises a housing 530. The heating element 520 is mounted within an aerosol-generating article receiving chamber within a housing 530. The aerosol-generating article 10 is inserted into the aerosol-generating article-receiving chamber 515 within the housing 530 of the aerosol-generating device 510 such that the heating element 520 is directly inserted into the aerosol-generating substrate 20 of the aerosol-generating article 10.

Within the housing 530 is a power source (not shown), such as a rechargeable lithium ion battery. A controller (not shown) is connected to the heating element 520, the power source, and a user interface (not shown), such as a button or display. The controller of the aerosol-generating device controls the power supplied to the heating element 520 in order to regulate its temperature.

During such normal use of the aerosol-generating article according to the present invention with a compatible aerosol-generating device 510 shown in fig. 5a and 5b, the thermal indicator of the aerosol-generating article remains "deactivated" as the article is used with a compatible aerosol-generating device, and therefore no overheating occurs in the aerosol-generating substrate.

In the event that an aerosol-generating article according to the invention is used with an incompatible device and is overheated above a preferred maximum operating temperature, the thermal indicator will "activate", i.e. undergo a visual change, upon reaching a predetermined threshold temperature of the thermal indicator. When the user sees the article's "activated" thermal indicator, she will be notified of the article's misuse when removing the article from the aerosol-generating device.

Thus, the incorporation of a thermal indicator into the aerosol-generating article of the present invention provides an effective means to protect consumers from using the aerosol-generating article in an unintended manner in an incompatible device and/or from using the article in a defective or malfunctioning compatible device.

Claims

1. A heated aerosol-generating article for use with an aerosol-generating device having a heating element, the heated aerosol-generating article comprising:

a rod of aerosol-generating substrate; and

an outer wrapper, wherein the outer wrapper wraps at least a portion of the aerosol-generating substrate rod and at least a portion of an outer surface of the wrapper comprises a thermal indicator comprising:

a thermochromic material, whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature, such that the outer wrapper material provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 175 ℃.

2. A heated aerosol-generating article according to claim 1 in which the threshold temperature is at least about 220 ℃.

3. A heated aerosol-generating article according to any preceding claim in which the thermal indicator extends longitudinally along at least 50% of the total length of the aerosol-generating substrate rod.

4. A heated aerosol-generating article according to any preceding claim in which the thermochromic material is arranged such that the visual change occurs only within a circumferential portion of the outer wrapper, wherein the circumferential portion extends only partially around the circumference of the aerosol-generating article.

5. A heated aerosol-generating article for use with an aerosol-generating device having a heating element, the heated aerosol-generating article comprising:

a rod of aerosol-generating substrate; and

an outer wrapper, wherein at least a portion of an outer surface of the wrapper comprises a thermal indicator, wherein the thermal indicator is located downstream of the aerosol-generating substrate rod, the thermal indicator comprising:

a thermochromic material, whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature, such that the outer wrapper material provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 115 ℃.

6. A heated aerosol-generating article according to any preceding claim in which the visual change is irreversible.

7. A heated aerosol-generating article according to any preceding claim in which the thermal indicator extends longitudinally along at least 20% of the total length of the heated aerosol-generating article.

8. A heated aerosol-generating article according to any preceding claim in which the visual change comprises a colour change.

9. A heated aerosol-generating article according to any preceding claim in which the visual change comprises displaying a graphical representation and/or a warning sign or message.

10. A heated aerosol-generating article according to any preceding claim in which the outer wrapper comprises a temperature indicating sensor paper, whereby the thermochromic material is integral with the temperature indicating sensor paper.

11. A heated aerosol-generating article according to any of claims 1 to 9 in which the thermochromic material comprises a thermochromic paint, ink or dye applied to at least a portion of an outer surface of the packaging material.

12. A heated aerosol-generating article according to any preceding claim further comprising:

A mouthpiece located downstream of the aerosol-generating substrate rod;

a support element located immediately downstream of the aerosol-generating substrate rod; and

an aerosol-cooling element located between the support element and the mouthpiece.

13. Use of a thermochromic material in a thermal indicator on an outer wrapper of a rod of aerosol-generating substrate of a heated aerosol-generating article configured for use with an aerosol-generating device having a heating element, wherein the outer wrapper is wrapped around at least a portion of the rod of aerosol-generating substrate and whereby at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature such that the outer wrapper provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 175 ℃.

14. Use of a thermochromic material in a thermal indicator located on a wrapper of a heated aerosol-generating article configured for use with an aerosol-generating device having a heating element, and the heated aerosol-generating article comprising a rod of aerosol-generating substrate, whereby the thermal indicator is located downstream of the rod of aerosol-generating substrate, and at least a portion of the thermochromic material is adapted to undergo a visual change when the temperature at the portion of the thermochromic material exceeds a threshold temperature, such that the wrapper provides a visual indication that the temperature at the thermal indicator has exceeded the threshold temperature, wherein the threshold temperature is at least about 115 ℃.

15. An aerosol-generating system comprising:

a heated aerosol-generating article according to any preceding claim; and

an aerosol-generating device adapted to receive the heated aerosol-generating article, the aerosol-generating device comprising a heater element configured to heat a strip of aerosol-generating material during use, wherein the heater element is controlled to operate below a maximum operating temperature during use,

wherein the thermal indicator of the heated aerosol-generating article is adapted such that the threshold temperature is not exceeded during use of the aerosol-generating system when the heater element is operating below the maximum operating temperature.