Temperature-sensitive indicator

1. A temperature indicator product comprising a visual indicator comprising a first thermochromic colour-change composition which comprises an electron-donating colouring organic compound (A), an electron-accepting colouring organic compound (B) and reaction medium compound (C) and a second composition selected from:

i. an irreversible colour change ink;

ii. a second thermochromic colour-change composition in its higher temperature state and wherein the first thermochromic colour-change composition is in its lower temperature state; and

iii. a mixture of i) and ii).

2. A temperature indicator product according to claim 1 in which the lower temperature state of the first thermochromic composition is coloured and the higher temperature state of the second thermochromic composition is colourless.

3. A temperature indicator product according to claim 1 in which the first thermochromic composition and the second thermochromic composition are different compositions.

4. A temperature indicator product according to claim 1 comprising the said ink and in which the said ink has a colour change temperature below the colour change temperature of the first thermochromic composition.

5. A temperature indicator product according to claim 1 adapted for use as a tamper-evident indicator.

6. A temperature indicator product according to claim 1 adapted for use as a temperature indicator to indicate exposure below the higher of the T2 temperature, minimum discoloured state retaining temperature of the first composition and the second composition or a freeze indicator.

7. A temperature indicator product according to claim 1 wherein the first composition and second composition are intimately mixed.

8. A temperature indicator product according to claim 1 wherein the visual indicator comprises a first portion comprising the first composition and a, separate, second portion comprising the second composition.

9. A temperature indicator product according to claim 1 wherein the first thermochromic composition and second composition are, respectively, in a state such that:

i. an increase in the temperature of the indicator to the T3 temperature, maximum colour-retaining temperature of the first composition will change the state of the first composition and a decrease in the temperature of the indicator to the T2 temperature, minimum discoloured state retaining temperature of the first composition will change the state of the second composition; or

ii. an increase in the temperature of the indicator to the T3 temperature, maximum colour-retaining temperature of the first composition will change the state of the second composition and a decrease in the temperature of the indicator to the T2 temperature, minimum discoloured state retaining temperature of the first composition will change the state of the first composition.

10. A temperature indicator product according to claim 9 in which the first thermochromic composition is in a coloured state at a temperature between its T2 temperature and its T3 temperature and the second composition is in a colourless state between its T2 temperature and T3 temperature.

11. A medical product comprising the label of claim 9 or a temperature indicator product comprising a visual indicator comprising a first thermochromic colour-change composition which comprises an electron-donating colouring organic compound (A), an electron-accepting colouring organic compound (B) and a reaction medium compound (C), and a second composition selected from:

i. an irreversible colour change ink;

ii. a second thermochromic colour-change composition in its higher temperature state and wherein the first thermochromic colour-change composition is in its lower temperature state; and

iii. a mixture of i) and ii).

12. A temperature indicator product according to claim 1 in which the first thermochromic colour-change composition is non-polymeric.

13. A label comprising a temperature indicator product according to claim 1 .

14. A temperature indicator product comprising a visual indicator comprising a first thermochromic colour-change composition which comprises an electron-donating colouring organic compound (A), an electron-accepting colouring organic compound (B) and a reaction medium compound (C), and a second composition which is of the same composition as the first thermochromic colour-change composition and wherein the second thermochromic colour-change composition is in its higher temperature state and wherein the first thermochromic colour-change composition is in its lower temperature state.

15. A temperature indicator product according to claim 14 in which the first thermochromic composition has been subjected to a temperature not above its T2 temperature, minimum discoloured state retaining temperature prior to application to the product and the second composition has been subjected to a temperature not below its T3 temperature, maximum colour-retaining temperature prior to application to the product.

16. A temperature indicator product comprising a visual indicator comprising a first thermochromic colour-change composition which comprises an electron-donating colouring organic compound (A), an electron-accepting colouring organic compound (B) and a reaction medium compound (C), and a second composition selected from:

i. an irreversible colour change ink;

ii. a second thermochromic colour-change composition in its higher temperature state and wherein the first thermochromic colour-change composition is in its lower temperature state and

iii. a mixture of i) and ii);

wherein the component C) comprises a compound of formula (I):

wherein:

R 1 , and R 2 are independently selected from an aryl group having not more than 14 carbon atoms, a linear or branched alkyl group, a substituted linear or branched alkyl group, alkenyl group, alkoxy group, and an alkylene aryl group; having from 5 to 22 carbon atoms;

X 1 and X 2 are independently selected from —OC(O)—, —CO 2 — and O;

R 3 , R 4 and R 5 are independently selected from hydrogen and a linear or branched hydrocarbyl group or a substituted linear or branched hydrocarbyl group;

R 6 is selected from hydrogen, halogen R 3 , —X 1 R 1 , aryl and substituted aryl;

Y 1 , Y 2 , Y 3 and Y 4 are independently selected from hydrogen, R 3 , —OR 3 and halogen;

a is 0 to 4; b is 0 or 1; x and y are independently 0 or 1.

17. A process for producing a temperature indicator product comprising a first thermochromic colour-change composition which comprises an electron-donating colouring organic compound (A), an electron-accepting colouring organic compound (B) and a reaction medium compound (C) and a second composition selected from:

i. an irreversible colour change ink;

ii. a second thermochromic colour-change composition in its higher temperature state and wherein the first thermochromic colour-change composition is in its lower temperature state; and

iii. a mixture of i) and ii);

the process comprising providing a support with the first thermochromic colour-change composition, having colour change temperatures T1, complete colouring temperature T2, minimum discoloured state retaining temperature T3, maximum colour-retaining temperature T4, complete discolouring temperature, heating the first composition to a temperature exceeding T4, cooling the second composition, to a temperature below T1, applying the second composition to the support and drying the first and second compositions at temperature not exceeding temperature T3 and not below temperature T2.