Thermal imaging

1. A thermosensitive recording medium comprising:

a. a base sheet;

b. a thermosensitive composition on at least one surface of the base sheet comprising a binder and a thermosensitive material comprising:

i. one or more oxidizing agents; and

ii. a dye precursor having the formula;

wherein R 1 and R 2 can be the same or different and are: H, alkyl of 1-4 C, NH 2 , OH, COOR′ wherein R′ is alkyl of 1-4C or H, CONH 2 , halogen, OR″ wherein R″ is alkyl of 1-4C, CH 2 OH, CH 2 NH 2 , CONR′R″ wherein R′ and R″ can be the same or different; R 3 is H or alkyl of 1-4C or COR″; R 4 , R 5 can be the same or different and are: H, alkyl of 1-4C, NH 2 , OH, COOH, CONH 2 , halogen, OR″, NO 2 , SO 3 , HNR″, or NR″R″ or any pharmaceutically acceptable salts thereof or mixtures thereof, and wherein R 6 and R 7 can be the same or different and can be hydrogen, a carboxylate group, a borate group or a silicate group.

2. The thermosensitive recording medium of claim 1 , wherein the binder comprises a resin chosen from polystyrene, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyethylene glycol, proteinaceous binders, gelatin, modified gelatins, phthaloyl gelatine, polysaccharides, starch, gum arabic and dextran, water-soluble cellulose, resin having an ether bond, resin having a carbamoyl group, resin having a carboxyl group, derivatives or combinations thereof.

3. The thermosensitive recording medium of claim 1 , further comprising sodium bicarbonate, potassium bicarbonate, microencapsulated sodium bicarbonate or microencapsulated potassium bicarbonate.

4. The thermosensitive recording medium of claim 1 , wherein the dye precursor is chosen from L-DOPA, R-DOPA or pharmaceutically acceptable salts thereof or mixtures thereof.

5. The thermosensitive recording medium of claim 1 , wherein R 1 and R 2 are non hydrogen substituents and the dye precursor comprises two or more diastereomers.

6. The thermosensitive recording medium of claim 1 , wherein the oxidizing agent is a pharmaceutically acceptable salt whose anion is chosen from peroxide, periodate, persulfate, perborate, iodate peroxydisulfate, monopersulfate, or hypochlorite.

7. The thermosensitive recording medium of claim 1 , wherein the oxidizing agent is chosen from sodium periodate, potassium periodate, ammonium periodate or mixtures thereof.

8. The thermosensitive recording medium of claim 1 , further comprising one or more pharmaceutically acceptable carbonate salts.

9. The thermosensitive recording medium of claim 1 , wherein the oxidizing agent is a metal salt.

10. The thermosensitive recording medium of claim 1 , wherein the oxidizing agent is a transition metal salt.

11. The thermosensitive recording medium of claim 1 , wherein the oxidizing agent is a metal salt chosen from copper, titanium, zinc, iron, nickel, cobalt, lead, silver and manganese.

12. The thermosensitive recording medium of claim 1 , wherein the thermosensitive recording medium is substantially free of organic base.

13. The thermosensitive recording medium of claim 1 , wherein the mole ratio of the oxidizing agent to the dye precursor is greater than about 0.05 and less than about 2.0.

14. The thermosensitive recording medium of claim 1 , further comprising an ester capable of retarding the oxidation of the dye precursor.

15. The thermosensitive recording medium of claim 14 , wherein the ester is a borate or a silicate.

16. The thermosensitive recording medium of claim 1 , wherein at least some of the one or more oxidizing agents are microencapsulated.

17. The thermosensitive recording medium of claim 1 , wherein the dye precursor is microencapsulated.