It would be desirable, for advertising or promotional purposes, to be able to print a logo or message on to a drinking straw. However, this would be a difficult task given that conventionally straws are manufactured from plastics material by extrusion at high speed and have a thin wall, the surface of which is curved and shiny. Even if printing were possible, it would be a costly exercise to perform in relation to the extremely low cost of the item itself, and registering more than one color of print would be difficult.

SUMMARY OF THE INVENTION It is an aim of the invention to provide a practical drinking straw bearing a printed message or design, and to provide opportunities for playing promotional games in connection with the message or design.

Accordingly, the present invention provides a drinking straw comprising a plastics tubular layer and a sleeve in contact with the layer and bearing at least one printed indicium, logo, message, design or the like.

Said plastics tubular layer may, for example, be of polypropylene and may comprise color-changing thermochromic resin to give an additional eye-catching feature.

The sleeve, which is usually of a plastics film material such as extruded polyvinyl chloride, and may have a thickness between 1-and 100 pm, preferably 50 Rm, is preferably heat shrunk into place.

In a most preferred embodiment of the invention, the sleeve is printed with color-changing ink, and optionally one or more standard non-color-changing inks."Color- changing ink"means ink that changes from colorless to colored or opaque, from one color to another, or from opaque to clear under predetermined conditions. For example, thermochromic ink, which changes color on inserting the straw into a hot or cold drink, may be used.

Preferably, the thermochromic ink would change its appearance on insertion into a cold drink at between-5 and 20 oc and more preferably between 0 and 10 oc. It could, however, change by being rubbed or on insertion into a hot drink and thus being heated to between 27 and 65 °C, more preferably between 35 and 55 oc. Alternatively the color- changing ink may comprise photochromic ink, which responds to light of a specific wavelength, hydrochromic ink, which responds to the presence of moisture, or other color- changing ink.

One or more inks may be printed on the outside of the sleeve or the inside, if the sleeve is transparent. The indicium or the like may be printed in a color-changing ink, or it may be printed in a non-color-changing ink with color-changing ink arranged to reveal and/or change the appearance of the indicium or the like under the predetermined conditions. For example, one or more additional words, patterns, shapes, letters, numbers or combinations thereof may be revealed. This may convey an advertising message or design or information required to win a prize.

In a particular example the sleeve is printed with a permanent ink on its outside and a color-changing ink on its inside.

Preferably, when the straw is to be used with cold liquids, the color changing ink is used to print the design

or message to be revealed, which is substantially or totally invisible at ambient temperature, and becomes visible when cooled.

In another embodiment, the straw is to be used in conjunction with a liquid hotter than ambient temperature and the color changing ink is dark (e. g. black) at ambient temperature and masks the design or information to be revealed. On warming, the dark masking layer changes color or loses color and the design beneath (which can be printed in non-color-changing ink) is revealed.

It will be appreciated that the invention provides a mechanism for revealing a winning or losing message on a straw when the straw is used to imbibe a liquid. When a straw is used it is usually in front of the user for a period of time, and therefore constitutes an ambient medium for communicating to the user of the straw. The invention has achieved its aim of advertising or performing a promotional game on a drinking straw, and provides an advertising medium which can be displayed to a largely "captive audience".

The present invention also provides a method of manufacturing a drinking straw comprising forming a plastics tubular layer and applying a sleeve to the layer, the sleeve bearing at least one printed indicium, logo, message, design or the like.

Preferably, the plastics tubular layer is formed by extruding a material such as polypropylene, optionally containing a color-changing resin. The tubular layer is preferably extruded in a length longer than one straw and cut into appropriate lengths for straws.

Advantageously, the sleeve is formed by extruding a plastics film material such as polyvinyl chloride of for

example about 50 Am thickness, either in a tube or preferably as a web. The tube or web may then be printed with the indicium or the like in a high-speed continuous reel to reel printing process, thus saving manufacturing costs. Preferably, the printing comprises the use of a color-changing ink and it may also include the use of a non-color-changing ink.

The step of applying the sleeve to the tubular layer may comprise wrapping the sleeve around the tubular layer and heating the sleeve to an elevated temperature (say 150 oC) to cause it to shrink into place around the tubular layer.

Alternative steps for applying the sleeve to the tubular layer include sonic or heat welding or gluing processes.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example only with reference to the accompanying drawings, in which: Figures la and lb show a drinking straw according to an embodiment of the invention; Figures 2a and 2b show a drinking straw according to a second embodiment ; and Figures 3a and 3b show a drinking straw according to a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS -Figures la, 2a and 3a show how three different extruded polypropylene drinking straws appear at ambient temperature. In each case a transparent extruded polyvinyl chloride web has had a message printed with color changing

ink, which is invisible at ambient temperature, on one side. In the embodiments of Figures 2a and 3a, a permanently visible message 1 has additionally been printed with non-color-changing ink on the other side of the web.

The web has been heat shrunk into place around the straw as a sleeve, so that the optional permanently visible message 1 is on the outside and the invisible message on the inside.

As shown in Figures lb, 2b and 3b, on insertion of the straw into a cool drink, the previously invisible message 2 becomes visible. In Figures lb and 2b, this message 2 is used in conjunction with a promotional game and informs the consumer that he or she has won a prize.

In Figure 3b, the previously invisible message 2 provides additional advertising information.

Additionally or alternatively, the indicium or the like can comprise a digrammatical or numerical design or a pattern of different colors.