Thermal imaging system
View Patent ↗A multicolor imaging system is described wherein at least two, and preferably three, different image-forming layers of a thermal imaging member are addressed at least partially independently by a thermal printhead or printheads from the same surface of the imaging member by controlling the temperature of the thermal printhead(s) and the time thermal energy is applied to the image-forming layers. Each color of the thermal imaging member can be printed alone or in selectable proportion to the other color(s). Novel thermal imaging members are also described.
1. A thermal imaging member comprising
(a) a substrate having first and second opposed surfaces;
(b) first and second image-forming layers carried by said first surface of said substrate, said first image-forming layer being closer to said first surface of said substrate than said second image-forming layer, said first image-forming layer having a lower activation temperature than said second image-forming layer;
(c) a first interlayer positioned between said first and second image-forming layers;
(d) a third image-forming layer carried by said first surface of said substrate, said third image-forming layer being farther from said first surface of said substrate than said second image-forming layer and having a higher activation temperature than said second image-forming layer; and
(e) a second interlayer positioned between said second and third image-forming layers.
2. The thermal imaging member as defined in claim 1 wherein at least one of said first and second interlayers comprises an inert material.
3. The thermal imaging member as defined in claim 1 wherein at least one of said first and second interlayers includes a material which undergoes a phase change upon the application of heat thereto.
4. The thermal imaging member as defined in claim 1 wherein said first second and third image-forming layers each has a thickness of from about 0.5 to about 4.0 μm.
5. The thermal imaging member as defined in claim 1 wherein at least one of said first second and third image-forming layers has a thickness of about 2 μm.
6. The thermal imaging member as defined in claim 1 wherein said first interlayer has a thickness of from about 1 to about 40 μm.
7. The thermal imaging member as defined in claim 1 wherein said first interlayer has a thickness of from about 14 to about 25 μm.
8. The thermal imaging member as defined in claim 1 wherein said second interlayer is thinner than said first interlayer.
9. The thermal imaging member as defined in claim 1 wherein said first image-forming layer has a thickness of from about 0.5 to about 4 μm and comprises a leuco dye and a developer material, each having a melting point of from about 90° C. to about 140° C., said second image-forming layer has a thickness of from about 0.5 to about 4 μm and comprises a leuco dye and a developer, each having a melting point of from about 150° C. to about 250° C., said third image-forming layer having a thickness of from about 0.5 to about 4 μm and comprising a leuco dye having a melting point of at least 150° C. and a developer having a melting point of at least 250° C.
10. The thermal imaging member as defined in claim 1 wherein said first image-forming layer has a thickness of from about 0.5 to about 4 μm and comprises a leuco dye and a developer material, each having a melting point of from about 90° C. to about 140° C., said second image-forming layer has a thickness of from about 0.5 to about 4 μm and comprises a leuco dye and a developer, each having a melting point of from about 150° C. to about 250° C., said third image-forming layer having a thickness of from about 0.5 to about 4 μm and comprising a compound which forms color intramolecularly at a temperature of at least 300° C. in from about 0.1 to about 2 milliseconds.
11. The thermal imaging member as defined in claim 1 and further including a topcoat layer and a backcoat layer.
12. The thermal imaging member as defined in claim 1 wherein the thickness of said substrate is less than about 20 μm.
13. The thermal imaging member as defined in claim 1 wherein said substrate has a thickness of about 5 μm.
14. The thermal imaging member as defined in claim 1 wherein at least one of said first second and third image-forming layers comprises a compound which forms color intramolecularly.
15. A thermal imaging member comprising
(a) a substrate having first and second opposed surfaces;
(b) first and second image-forming layers carried by said first surface of said substrate, said first image-forming layer being closer to said first surface of said substrate than said second image-forming layer, said first image-forming layer having a lower activation temperature than said second image-forming layer; and
(c) an interlayer positioned between said first and second image-forming layers, wherein said interlayer includes a material which undergoes a phase change upon the application of heat thereto.
16. The thermal imaging member as defined in claim 15 wherein said interlayer has a thickness of from about 1 to about 40 μm.
17. The thermal imaging member as defined in claim 15 wherein said first interlayer has a thickness of from about 14 to about 25 μm.
18. The thermal imaging member as defined in claim 15 wherein at least one of said first and second layers comprises a compound which forms color intramolecularly.