Thermal transfer assembly for ceramic imaging
A thermal transfer assembly that comprises a thermal transfer ribbon and a covercoated transfer sheet. The thermal transfer ribbon includes a support and a ceramic ink layer. The ceramic ink layer is present at a coating weight of from about 2 to about 15 grams per square meter, and it includes from about 15 to about 94.5 percent of a solid carbonaceous binder, and at least one of a film-forming glass frit, an opacifying agent and a colorant (at a combined level for the film forming glass frit, the opacifying agent and the colorant of at least 0.5 weight percent).
1. A thermal transfer assembly comprised of a thermal transfer ribbon, a covercoated transfer sheet, a film forming glass frit comprised of at least 5 weight percent of silica, and metal oxide containing ceramic colorant wherein:
(a) said thermal transfer ribbon is comprised of a support and, disposed above said support, a ceramic ink layer, wherein said ceramic ink layer is present at a coating weight of from about 2 to about 15 grams per square meter, and is comprised of from about 15 to about 94.5 weight percent of a solid, volatilizable carbonaceous binder;
(b) said covercoated transfer sheet is comprised of a support and, disposed above said support, a covercoat, wherein said covercoat is present at a coating weight of from about 1 to about 20 grams per square meter and is comprised of from about 15 to about 100 weight percent of a solid, volatilizable carbonaceous binder, and
(c) said film-forming glass frit is present in a said ceramic ink layer and/or said covercoat;
(d) said metal oxide containing ceramic colorant is selected from the group consisting of metal oxide containing pigment, metal oxide containing opacifying agent, and mixtures thereof;
(e) said metal oxide containing ceramic colorant is present in said ceramic ink layer and/or said covercoat; and
(f) said metal oxide containing ceramic colorant has a first refractive index, said film-forming glass frit has a second refractive index, and the difference between said first refractive index and said second refractive index is at least about 0.1.
2. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant is present in said ceramic ink layer.
3. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant present in said ceramic ink layer is a metal oxide containing pigment.
4. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant is present in said ceramic ink layer.
5. The thermal transfer assembly as recited in claim 4 , wherein said metal oxide containing ceramic colorant present in said ceramic ink layer is a metal oxide containing pigment.
6. The thermal transfer assembly as recited in claim 1 , wherein said solid, volatilizable carbonaceous binder, after it has been heated at a temperature greater than 500 degrees Celsius for at least 6 minutes in an atmosphere containing at least about 15 volume percent of oxygen, is substantially volatilized such that less than about 5 weight percent of said volatilizable carbonaceous binder remains as a solid phase.
7. The thermal transfer assembly as recited in claim 1 , wherein said film-forming frit has a melting temperature of greater than about 300 degrees Celsius.
8. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant has a particle size distribution such that substantially all of its particles are smaller than about 20 microns.
9. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant has a first melting point, said film-forming glass frit has a second melting point, and said first melting point exceeds said second melting point by at least about 50 degrees.
10. The thermal transfer assembly as recited in claim 1 , wherein said metal oxide containing ceramic colorant has a first concentration in said thermal transfer assembly, said film-forming glass flit has a second concentration in said thermal transfer assembly, and the ratio of said first concentration to said second concentration is no greater than about 1.25.
11. The thermal transfer assembly as recited in claim 1 , wherein said film-forming frit has a melting temperature of greater than 550 degrees Centigrade.
12. The thermal transfer assembly as recited in claim 1 , wherein said film-forming frit has a melting temperature of greater than 750 degrees Centigrade.
13. The thermal transfer assembly as recited in claim 1 , wherein said film-forming fit has a melting temperature of greater than 950 degrees Centigrade.
14. The thermal transfer assembly as recited in claim 1 , wherein said film-forming frit has a particle size distribution such that substantially all of its particles are smaller than about 10 microns.
15. The thermal transfer assembly as recited in claim 1 , wherein at least about 80 weight percent of said particles of said film-forming frit are smaller than about 5 microns.
16. The thermal transfer assembly as recited in claim 1 , wherein said carbonaceous binder has a softening point of from about 45 to about 150 degrees Centigrade.
17. The thermal transfer assembly as recited in claim 1 , wherein said carbonaceous binder is comprised of a mixture of a first synthetic resin and a second synthetic resin.
18. The thermal transfer assembly as recited in claim 1 , wherein said carbonaceous binder is comprised of polybutylmethacrylate and polymethylmethacrylate.