Thermal imaging members and methods
View Patent ↗There are described thermal imaging members and thermal imaging methods utilizing unsymmetrical rhodamine compounds. The rhodamine color-forming compounds exhibit a first color when in a crystalline form and a second color, different from the first color, when in an amorphous form.
1. A compound represented by formula (I):
wherein:
R 1 and R 4 -R 12 are hydrogen, alkyl, alkoxy or halo, and at least one of R 1 or R 4 -R 8 is alkyl;
R 2 is hydrogen or alkyl;
R 3 is aryl or substituted aryl;
R 13 is hydrogen or alkyl;
R 14 -R 18 are hydrogen, alkyl, alkoxy, or halo, wherein at least one of R 14 -R 18 is halo; and
X 1 is carbon;
with the provision that either (a) R 3 is 4-halophenyl, (b) R 16 is halo, or (c) R 3 is 4-halophenyl and R 16 is halo;
with the provision that either (a) R 3 is 4-halophenyl, (b) R 16 is halo, or (c) R 3 is 4-halophenyl and R 16 is halo.
2. The compound of claim 1 , wherein at least two of R 1 or R 4 -R 8 are alkyl.
3. The compound of claim 1 , wherein at least two of R 1 or R 4 -R 8 are propyl.
4. The compound of claim 1 , wherein R 3 is substituted phenyl.
5. The compound of claim 1 , wherein R 2 and R 13 are hydrogen.
6. The compound of claim 1 , wherein R 16 is fluoro.
7. The compound of claim 1 , wherein:
R 1 , R 2 , R 5 , R 6 , R 8 -R 15 , R 17 , and R 18 are hydrogen;
R 3 is substituted phenyl;
R 4 and R 7 are alkyl; and
R 16 is halo.
8. The compound of claim 7 , wherein:
R 3 is 4-fluorophenyl;
R 4 and R 7 are propyl; and
R 16 is fluoro.
9. A thermal imaging member comprising a compound represented by the formula (I):
wherein:
R 1 and R 4 -R 12 are hydrogen, alkyl, alkoxy or halo, and at least one of R 1 or R 4 -R 8 is alkyl;
R 2 is hydrogen or alkyl;
R 3 is aryl or substituted aryl;
R 13 is hydrogen or alkyl;
R 14 -R 18 are hydrogen, alkyl, alkoxy, or halo, wherein at least one of R 14 -R 18 is halo; and
X i is carbon;
with the provision that either (a) R 3 is 4-halophenyl, (b) R 16 is halo, or (c) R 3 is 4-halophenyl and R 16 is halo; and
wherein said compound is in the crystalline form;
with the provision that either (a) R 3 is 4-halophenyl, (b) R 16 is halo, or(c) R 3 is 4-halophenyl and R 16 is halo.
10. The thermal imaging member as defined in claim 9 , wherein
R 1 , R 2 , R 5 , R 6 , R 8 -R 15 , R 17 , and R 18 are hydrogen;
R 3 is substituted phenyl;
R 4 and R 7 are alkyl; and
R 16 is halo.
11. The thermal imaging member as defined in claim 9 , wherein said compound represented by formula (I) has a glass transition temperature of at least 50° C.
12. The thermal imaging member as defined in claim 9 , further comprising at least one thermal solvent.
13. The thermal imaging member as defined in claim 12 , wherein said thermal solvent is selected from the group consisting of 1,2-bis(2,4-dimethylphenoxy)ethane, 1,4-bis(4-methylphenoxymethyl)benzene, bis(4-phenoxyphenoxymethyl)benzene and 1,4-bis(benzyloxy)benzene, and mixtures thereof.
14. The thermal imaging member as defined in claim 9 , further comprising at least one compound comprising a phenolic grouping.
15. The thermal imaging member as defined in claim 14 , wherein said compound comprising a phenolic grouping is selected from the group consisting of 4,4′-butylidenebis[2-(1,1-dimethylethyl)-5-methyl-phenol], 2,2′-methylenebis(6-tert-butyl-4-methylphenol), 2,2′-methylenebis(6-tert-butyl-4-ethyl-phenol), 2,2′-ethylidenebis(4,6-di-tert-butylphenol), bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]-methane, 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, 2,6-bis[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl]-4-methyl-phenol, 2,2′-butylidenebis[6-(1,1-dimethylethyl)-4-methyl-phenol, 2,2′-(3,5,5-trimethylhexylidene)bis[4,6-dimethyl-phenol], 2,2′-methylenebis[4,6-bis(1,1-dimethylethyl)-phenol, 2,2′-(2-methylpropylidene)bis[4,6-dimethyl-phenol], 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 2,2′-thiobis (4-tert-octylphenol), and 3-tert-butyl-4-hydroxy-5-methylphenyl sulfide.
16. The thermal imaging member as defined in claim 3 , further comprising a stabilizer comprising 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate.
17. A thermal imaging method comprising (a) providing an imaging member as defined in claim 3 ; and (b) converting at least a portion of said compound to an amorphous form in an image-wise pattern whereby an image is formed.
18. The thermal imaging method as defined in claim 17 wherein step (b) comprises applying an image-wise pattern of thermal energy to said imaging member, said thermal energy being sufficient to convert at least some of said compound of formula (I) to an amorphous form.