Multicolor thermal imaging method and thermal printer
View Patent ↗A multicolor direct thermal imaging method wherein a multicolor image is formed in a thermal imaging member comprising at least first and second different image-forming compositions and a thermal printer for use in practicing the method. Heat is applied to at least the second image-forming composition while the first image-forming composition is at a first baseline temperature (T 1 ) to form an image in at least the second image-forming composition, and heat is applied to at least the first image-forming composition while it is at a second baseline temperature (T 2 ) to form an image in at least the first image-forming composition, wherein T 1 is different from T 2 .
1. A thermal imaging member comprising:
(a) a substrate comprising first and second opposed surfaces;
(b) a first oxygen barrier layer carried by one of said first and second surfaces;
(c) a first color-forming layer having an activating temperature of at least about 70° C. overlying said oxygen barrier layer;
(d) a first spacer layer or layers overlying said first color-forming layer;
(e) a second color-forming layer overlying said first spacer layer or layers, having an activating temperature at least about 30° C. above the activating temperature of said first color-forming layer;
(f) a second spacer layer or layers overlying said second color-forming layer;
(g) a third color-forming layer overlying said second spacer layer or layers, said third color-forming layer having an activating temperature at least about 30° C. above the activating temperature of said second color-forming layer;
(h) a second oxygen barrier layer overlying said third color-forming layer; and
(i) an overcoat layer overlying said second oxygen barrier layer.
2. The thermal imaging member described in claim 1 , further comprising a fluorescent brightener underlying said first spacer layer or layers.
3. The thermal imaging member described in claim 1 , further comprising an ultraviolet-absorbing material overlying said third image-forming layer.
4. The thermal imaging member described in claim 1 , wherein said third image-forming layer has an activating temperature of at least 200° C.
5. The thermal imaging member described in claim 1 , wherein said first spacer layer or layers has at least three times the thickness of said second spacer layer or layers.
6. The thermal imaging member described in claim 1 , wherein said first image-forming layer comprises a crystalline material that melts below 130° C., said second image-forming layer comprises a crystalline material that melts between 130° C. and 170° C., and said third image-forming layer comprises a crystalline material that melts above 170° C.
7. The thermal imaging member described in claim 1 , wherein a fourth image-forming layer is carried by the surface of said substrate that does not carry said first, second and third image-forming layers.
8. The thermal imaging member described in claim 7 wherein said first and second oxygen barrier layers are absent.