Color-forming compounds and use thereof in imaging members and methods
View Patent ↗There are described novel rhodamine color-forming 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. Thermal imaging members containing these color-formers are also described.
1. A compound represented by the formula (I):
wherein:
R 1 -R 10 are alkyl or hydrogen;
at least one of R 11 , R 15 , R 16 and R 20 is alkyl or halogen;
at least one of R 11 , R 13 , R 15 , R 16 , R 18 and R 20 is fluorine;
and R 11 -R 20 are chosen from the group consisting of hydrogen, alkyl, substituted alkyl, halogen, alkoxy, and substituted carbonyl.
2. The compound of claim 1 in which:
R 1 -R 10 are hydrogen;
at least one of R 11 , R 15 , R 16 and R 20 is alkyl or halogen;
at least one of R 11 , R 13 , R 15 , R 16 , R 18 and R 20 is fluorine;
and R 11 -R 20 are chosen from the group consisting of hydrogen, alkyl, substituted alkyl, halogen, alkoxy, and substituted carbonyl.
3. The compound of claim 1 in which:
R 1 -R 10 are hydrogen;
at least one of R 11 , R 15 , R 16 and R 20 is alkyl or fluorine;
at least one of R 11 , R 12 , R 13 , R 14 , and R 15 is fluorine;
at least one of R 16 , R 17 , R 18 , R 19 , and R 20 is fluorine;
and R 11 -R 20 are chosen from the group consisting of hydrogen, alkyl, substituted alkyl, halogen, alkoxy, and substituted carbonyl.
4. The compound of claim 1 in which:
R 1 -R 10 , R 12 , R 14 , R 15 and R 17 -R 20 are hydrogen;
R 11 is methyl; and
R 13 and R 16 are fluorine.
5. A thermal imaging composition comprising a compound represented by the formula (I):
wherein:
R 1 -R 10 are alkyl or hydrogen;
at least one of R 11 , R 15 , R 16 and R 20 is alkyl or halogen;
at least one of R 11 , R 13 , R 15 , R 16 , R 18 and R 20 is fluorine;
and R 11 -R 20 are chosen from the group consisting of hydrogen, alkyl, substituted alkyl, halogen, alkoxy, and substituted carbonyl;
wherein said compound is in the crystalline form.
6. The thermal imaging composition as defined in claim 5 wherein said compound represented by formula (I) has a glass transition temperature of at least 50° C.
7. The thermal imaging composition as defined in claim 5 wherein said image-forming layer further comprises at least one thermal solvent.
8. The thermal imaging composition as defined in claim 7 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.
9. The thermal imaging composition as defined in claim 5 further comprising at least one compound comprising a phenolic grouping.
10. The thermal imaging composition as defined in claim 9 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.
11. A thermal imaging member comprising a substrate having first and second opposed surfaces, said first surface bearing a color-forming layer comprising a thermal imaging composition as defined in claim 5 .
12. A thermal imaging method comprising
(a) providing an imaging member as defined in claim 11 ; and
(b) converting at least a portion of said compound to an amorphous form in an image-wise pattern
whereby an image is formed.
13. The thermal imaging method as defined in claim 12 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.