Stable infrared films

1. An infrared film comprising a substrate and at least one layer, wherein said at least one layer comprises an aminium radical cation dye in a crystalline state and an organic polymer selected from the group consisting of a divinyl ether polymer, a fluoropolymer, and a silicone polymer, wherein said aminium radical cation dye has formed crystals in said at least one layer.

2. The infrared film of claim 1 , wherein said aminium radical cation dye is a salt of an aminium radical cation, wherein the anion of said salt is selected from the group consisting of hexafluoroantimonate and hexafluorophosphate.

3. The infrared film of claim 1 , wherein said aminium radical cation compound is a salt of a tetrakis(phenyl)-1,4-benzenediamine radical cation.

4. The infrared film of claim 1 , wherein said aminium radical cation dye is a salt of a tris(phenyl)-aminium radical cation.

5. The infrared film of claim 1 , wherein said at least one layer of said infrared film has an absorption peak in the range of 800 to 900 nm.

6. The infrared film of claim 5 , wherein the absorption of said at least one layer of said infrared film in the range of 420 to 680 nm is less than 20% of the absorption at said absorption peak in the range of 800 to 900 nm.

7. The infrared film of claim 5 , wherein the absorption of said at least one layer of said infrared film in the range of 420 to 680 nm is less than 10% of the absorption at said absorption peak in the range of 830 to 860 nm.

8. The infrared film of claim 1 , wherein said divinyl ether polymer is selected from the group of polymers of the divinyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol.

9. The infrared film of claim 8 , wherein said at least one layer comprising said aminium radical cation dye and said divinyl ether polymer further comprises an aliphatic urethane polymer.

10. The infrared film of claim 1 , wherein said fluoropolymer is a polyvinylidene fluoride.

11. The infrared film of claim 10 , wherein said at least one layer comprising said aminium radical cation dye and said polyvinylidene fluoride further comprises an aliphatic urethane polymer.

12. The infrared film of claim 1 , wherein said silicone polymer is a dimethylpolysiloxane polymer.

13. The infrared film of claim 12 , wherein said at least one layer comprising said aminium radical cation dye and said dimethylpolysiloxane polymer further comprises an aliphatic urethane polymer.

14. The infrared film of claim 1 , wherein said at least one layer comprising said aminium radical cation dye comprises a divinyl ether polymer and a fluoropolymer.

15. The infrared film of claim 14 , wherein said at least one layer comprising said aminium radical cation dye further comprises an aliphatic urethane polymer.

16. The infrared film of claim 1 , wherein said at least one layer comprising said aminium radical cation dye comprises a divinyl ether polymer and a silicone polymer.

17. The infrared film of claim 16 , wherein said at least one layer comprising said aminium radical cation dye further comprises an aliphatic urethane polymer.

18. The infrared film of claim 1 , wherein said substrate comprises a reflective opaque substrate.

19. The infrared film of claim 1 , wherein said substrate is a white polyester film.

20. The infrared film of claim 1 , wherein said infrared film comprises a water repellent layer overlying said at least one layer comprising said aminium radical cation dye, wherein a water drop on said water repellent layer has at least a contact angle of 90°.

21. The infrared film of claim 20 , wherein said water repellent layer comprises a fluoropolymer.

22. The infrared film of claim 20 , wherein said water repellent layer comprises a silicone polymer.

23. The infrared film of claim 22 , wherein said silicone polymer of said water repellent layer is a crosslinked silicone polymer.

24. A test strip for analysis of fluids, wherein said test strip comprises said infrared film of claim 1 .

25. A test strip for analysis of fluids, wherein said test strip comprises an infrared film comprising:

a. a white polyester film;

b. a first layer comprising an aminium radical cation dye in a crystalline state, an aliphatic urethane polymer, and a divinyl ether polymer;

c. a second layer overlying said first layer, wherein said second layer comprises a silicone polymer,

wherein said aminium radical cation dye has formed crystals in said first layer, and wherein a water drop on said second layer has at least a contact angle of 90°.

26. A security marking, wherein said security marking comprises said infrared film of claim 1 .

27. An optical article, wherein said optical article comprises said infrared film of claim 1 .

28. The optical article of claim 27 , wherein said infrared film comprises a laser imaged pattern on at least one of said at least one layer comprising said aminium radical cation dye, wherein the infrared absorption of said aminium radical cation dye has been changed by exposure to a laser and said laser imaged pattern is readable in the infrared region.

29. The optical article of claim 28 , wherein said laser imaged pattern is readable in the eye-safe region above 1400 nm.

30. A method of making an infrared film, wherein said method comprises the steps of providing:

a. a substrate,

b. a first layer overlying said substrate, wherein said first layer comprises an aminium radical cation dye in a crystalline state and an organic polymer selected from the group consisting of a divinyl ether polymer, a fluoropolymer, and a silicone polymer;

c. a water repellent second layer overlying said first layer

wherein said aminium radical cation dye has formed crystals in said first layer, and wherein a water drop on said second layer has at least a contact angle of 90°.

31. The method of claim 30 , wherein said second layer comprises a fluoropolymer.

32. The method of claim 30 , wherein said second layer comprises a silicone polymer.

33. The method of claim 30 , wherein said substrate is a reflective opaque substrate.

34. The method of claim 33 , wherein said reflective opaque substrate is a white polyester film.