Compounds for reducing background color in color change compositions
Aspects of the invention include color change compositions having a color former and color developer composition that transitions from a first color state to a second color state upon application of an applied stimulus and an amount of a copolymer sufficient to eliminate background color of the color former and color developer composition during transition from the first color state to the second color state. Methods for preparing and devices employing the color change compositions of the invention are also described.
1. A color change composition comprising:
a composition comprising a color former and a color developer that transitions from a first color state to a second color state upon application of an applied stimulus, wherein the color former changes color in response to a phase transition of the color developer; and
an amount of a copolymer sufficient to eliminate background color of the composition during transition from a first color state to a second color state.
2. The color change composition according to claim 1 , wherein the copolymer comprises the formula:
where n is an integer from 10 to 1000, m is an integer from 10 to 1000 and R is an alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, acyl, substituted acyl, acyloxy, substituted acyloxy, alkoxycarbonyl, substituted alkoxycarbonyl, carboxyl or substituted carboxyl.
3. The color change composition according to claim 2 , wherein the copolymer comprises the formula:
wherein:
n is an integer from 10 to 1000;
m is an integer from 10 to 1000; and
R a is hydrogen, alkyl or substituted alkyl.
4. The color change composition according to claim 2 , wherein the copolymer comprises the formula:
wherein:
n is an integer from 10 to 1000;
m is an integer from 10 to 1000; and
R b is hydrogen, alkyl or substituted alkyl.
5. The color change composition according to claim 1 , wherein copolymer is present in the color change composition in an amount of 1% to 10% w/w.
6. The color change composition according to claim 1 , wherein the phase transition is from solid to liquid.
7. The color change composition according to claim 1 , wherein the applied stimulus is a change in temperature.
8. The color change composition according to claim 7 , wherein the composition transitions from a colorless state to a colored state upon exposure to a change in temperature.
9. The color change composition according to claim 8 , wherein the composition transitions from a colored state to a colorless state upon exposure to a change in temperature.
10. The color change composition according to claim 1 , wherein the applied stimulus is solvation.
11. The color change composition according to claim 10 , wherein the composition transitions from a colorless state to a colored state upon exposure to increasing solvation.
12. The color change composition according to claim 1 , wherein the color former is a thermochromic dye.
13. The color change composition according to claim 12 , wherein the thermochromic dye is a leuco dye.
14. The color change composition according to claim 1 , wherein the color developer is a glycerol monostearate derivative.
15. The color change composition according to claim 1 , wherein the color former comprises two or more distinct leuco dyes.
16. The color change composition according to claim 15 , wherein the two or more distinct leuco dyes exhibit opposing transition characteristics in response to the same applied stimulus.
17. The color change composition according to claim 16 , wherein the color change composition transitions from a red color state to a green color state upon application of the applied stimulus.
18. The color change composition according to claim 1 , wherein the color developer consists of a glycerol monostearate derivative.
19. A method of making a color change composition, the method comprising:
combining a composition comprising a color former and a color developer with an amount of a copolymer to produce a color change composition which changes from a first color state to a second color state upon application of an applied stimulus, wherein the color former changes color in response to a phase transition of the color developer.
20. The color change composition according to claim 1 , wherein the color former, color developer and copolymer are microencapsulated.
21. The color change composition according to claim 20 , wherein the color former, color developer and copolymer are microencapsulated together within the same microcapsules.