Temperature-sensitive product bearing a representation.
The present invention relates to a product comprising a temperature sensitive element and which changes appearance depending upon temperature.
There are various dyes available which will change colour with a change in temperature. This attribute has been used, for example, in the manufacture of HYPERCOLOUR™ T-shirts, which change colour due to the wearer's body heat. Temperature sensitive inks have also been used which are effectively invisible at room temperature and become visible upon cooling. These inks have been used by soft drinks manufacturers to indicate when the contents of a soft drinks can or bottle are desirably cold.
According to the present invention there is provided a product bearing a representation, the product comprising a substrate carrying a temperature sensitive first element and a second element, at a first temperature the first and second elements combining to obscure the representation, and at a selected second temperature the appearance of at least the first element changing to reveal the representation.
Typically the product is a printed product, for example, paper, a greetings card, an item of stationery, a label and the like.
The second element is preferably a conventional temperature stable ink. Most preferably, the temperature stable ink defines the representation with the first element creating an obscuring or confusing pattern adjacent to or overlapping the representation. The representation may be in the form of words and/or symbols. The temperature sensitive first element is preferably a temperature sensitive ink which changes its appearance depending on temperature. Thus, the representation to be revealed may be printed in a conventional ink, in a shade and texture that matches that of the temperature sensitive ink at ambient temperature. This change in appearance experienced by the temperature sensitive ink may be a
colour change, or most preferably a visual change such that the first element is visible in the visible spectrum at the first temperature but invisible in the visible spectrum at the second temperature. Preferably, the change in appearance of the temperature sensitive first element occurs in a reversible manner. The temperature sensitive element may change appearance at one of a variety of temperatures. Preferably the temperature sensitive element has one appearance at ambient temperatures, between about 10° - 30°C, and changes appearance at either lower temperatures (for example, refrigeration temperatures of about 4°C) or higher temperatures (for example, body temperature of about 37°C) .
In one embodiment the temperature sensitive element changes appearance at temperatures higher than normal ambient temperatures, for example >30°C. In such a case the representation is obscured at or below ambient temperatures and is revealed at temperatures above 30°C, typically at or around body temperature. This would permit the representation to be revealed by, for example, breathing on the product or pressing a hand on the product.
In a further embodiment the temperature sensitive element changes appearance at temperatures lower than normal ambient temperatures, for example >10°C. In this case the representation is obscured at or above ambient temperature and is revealed at temperatures below 10°C.
This would permit the representation to be revealed by, for example, placing the product in a refrigerator or freezer.
In a second aspect, the present invention provides a printed paper or card product bearing a representation and carrying a temperature sensitive first ink and a second ink, at ambient temperatures the first and second inks combining to obscure the representation and at or near body temperature the appearance of the first ink changing to reveal the representation.
In one embodiment, the product may be in the form of a greetings card, for example a birthday card or
valentine's card. A representation in the form of a personal message may be printed on the card using a temperature stable ink, but the message is normally obscured by a temperature sensitive ink. The receiver of the card warms the print, which results in the temperature sensitive ink becoming effectively invisible against a background, thus revealing the personal message. In another embodiment, the product may form part of a book, wherein the product is designed to have an educational function. For instance, the book may be a children's book in which a series of questions are put to the child. The child may be then offered a number of answers, of which only one is correct. Beside each answer is a patch or area of obscured print. The child then places his or her hand over the patch corresponding to the answer which he or she believes to be correct. The heat from the child's hand results in the temperature sensitive ink becoming invisible and revealing the temperature stable ink message which shows the answer to be "correct" or "incorrect". In a similar educational application the product may be used to help with the learning of a foreign language. A student would be shown an object, such as a ball, and beside this object is a patch or area of obscured print. The student would then decide what the object is, in the foreign language, before placing his or her hand over the patch, to reveal the word or words (in the same manner as described above) in the foreign language, thereby revealing whether or not they were correct. It would also be possible to print the object in temperature sensitive ink, such that heating the object causes the object to effectively disappear and reveal the words in the object's place. In another application, the product may be in the form of a competition card. In order for a competitor to determine whether they are a winner or loser, they apply heat, for example by breathing, onto a patch of heat stable print which has been obscured by a temperature sensitive print. The heat so applied results in the temperature sensitive
print becoming effectively invisible and revealing a temperature stable message such as "You Win" or "You Lose".
These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows a competition card in accordance with a preferred embodiment of the present invention at a first temperature; and
Figure 2 shows the competition card of Figure 1, at a second temperature.
Figure 3 shows a competition card in accordance with a further embodiment of the present invention at a first temperature; and
Figure 4 shows the competition card of Figure 3, at a second temperature.
Figure 1 illustrates a competition card, in accordance with a preferred embodiment of the present invention. The card 10 has been printed with a space cartoon which shows a space alien apparently talking to an astronaut in an alien language. The alien words 12 are shown in a "speech bubble" 13 coming from the alien's mouth. The alien words 12 have been printed using temperature sensitive characters 14 and temperature stable characters 16. The temperature stable characters 16 represent a message in English. However, at an ambient temperature of around 10°-30°C, the heat sensitive characters 14 and heat stable characters 16 have a similar appearance and so the English message is obscured.
To reveal the message, the competitor heats the "speech bubble" by placing his or her hand over it, or by breathing on it. The temperature sensitive characters then become effectively invisible, by blending into the background, because of the rise in temperature. The message depicted by the heat stable characters then appears, as shown in Figure 2. In this particular instance the competitor is a winner.
Figure 3 illustrates a competition card, in accordance
with a further embodiment of the present invention. The card 20 has been split into two halves 22, 24. One half 22 is printed with instructions 23 for the competitor. In this case the competitor has to chill the card to reveal whether or not they have won. The other half 24 has been printed using two inks. One of the inks is temperature stable and conveys a winning or losing message 26 and the other ink is temperature (cold) sensitive and provides an obscuring background to the message 26. For ease of visualisation and understanding of the Figure, the background 28 and message 26 are shown as different shades. However, in actual use, at the first temperature of around 20 - 30°C, the shades of the message 26 and the background 28 will be substantially identical, so that the message 26 cannot be seen and is obscured by the background 28.
In order to reveal the message 26, the competitor cools the card 22 to below 10°C, for example, by placing the card 20 in a refrigerator. The temperature sensitive background 28 then changes colour allowing the temperature stable "win" (or "lose") message to appear, as shown in Figure 4.
It will be clear to those of skill in the art that the above described embodiments are merely exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the invention. In one example, the present invention may be embodied in a humorous greetings card including instructions that, for the message to be revealed the card must be placed next to the recipient's heart. The resulting exposure of the card to the recipient's body heat (or any other heat source) warms the card sufficiently to reveal the previously hidden or obscured message. In still further embodiments more than one message may be carried by a card, the different messages being revealed as the card is exposed to higher temperatures.