Conductive thermal transfer ribbon
A thermal transfer ribbon comprised of a support and an ink layer disposed above the support. The ink layer has a thickness of from about 0.1 to about 10 microns; it contains at least 75 weight percent of particulate conductive metal material and from about 1 to about 25 weight percent of binder; and it has a surface resistivity of less than about 1,000,000 ohms per square. When the ink layer is transferred to a substrate, the surface resistivity of the transferred ink is less than 100 ohms per square when printed onto a flexible substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules per square centimeter. The particulate conductive metal preferably contains a noble metal and has a melting point of at least 800 degrees Celsius and a particle size such that least about 95 weight percent of its particles are smaller than 50 microns.
1 . A thermal transfer ribbon comprised of a support and a conductive ink layer disposed above the support, wherein:
(a) said conductive ink layer is comprised of at least 75 weight percent of particulate conductive metal material and from about 1 to about 25 weight percent of binder, and it has a surface resistivity of less than about 1,000,000 ohms per square;
(b) said conductive ink layer has a thickness of from about 0.1 to about 10 microns;
(c) said particulate conductive metal has a particle size such that least about 95 weight percent of its particles have a maximum dimension smaller than 50 microns; and
(d) when said conductive ink layer is thermally printed onto a flexible polyester substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules per square centimeter, its surface resistivity is less than about 100 ohms/square;
2 . The thermal transfer ribbon as recited in claim 1 , wherein said particulate metal material is comprised of a noble metal.
3 . The thermal transfer ribbon as recited in claim 2 , wherein said noble metal is selected from the group consisting of silver, gold, platinum, palladium, iridium, rhenium, mercury, ruthenium, osmium, and mixtures thereof.
4 . The thermal transfer ribbon as recited in claim 3 , wherein said particulate conductive metal has a melting point of at least 800 degrees Celsius.
5 . The thermal transfer ribbon as recited in claim 4 , wherein said noble metal is selected from the group consisting of silver, gold, and mixtures thereof.
6 . The thermal transfer ribbon as recited in claim 5 , wherein, when said conductive ink layer is thermally printed onto a flexible polyester substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules per square centimeter and thereafter polished; said printed and polished conductive ink layer has a surface resistivity is less than about 50 ohm/square;
7 . The thermal transfer ribbon as recited in claim 5 , wherein said conductive metal particles are comprised of an element that has a reduction potential of at least about 0.5 volts at 25 degrees Celsius and 1 atmosphere pressure; and wherein said conductive ink layer has a thickness of less than about 8 microns.
8 . The thermal transfer ribbon as recited in claim 5 , wherein when said conductive ink layer is thermally printed onto a flexible substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules per square centimeter, it has a volume resistivity that is less than about 100 microohm-cm;
9 . A thermal transfer ribbon comprised of a support and a conductive ink layer disposed above the support, wherein:
(a) said conductive ink layer is comprised of at least 75 weight percent of particulate conductive metal material and from about 1 to about 25 weight percent of binder, and it has a surface resistivity of less than about 100 ohms per square;
(b) said conductive ink layer has a thickness of from about 0.1 to about 10 microns;
(c) said particulate conductive metal has a particle size such that least about 95 weight percent of its particles have a maximum dimension smaller than 50 microns; and
(d) said particulate metal material is comprised of a noble metal.
10 . The thermal transfer ribbon as recited in claim 9 , wherein said particulate conductive metal material is in the form of a flake.
11 . The thermal transfer ribbon as recited in claim 10 , wherein said noble metal is selected from the group consisting of silver, gold, and mixtures thereof.
12 . The thermal transfer ribbon as recited in claim 11 , wherein, when said conductive ink layer is thermally printed onto a flexible polyester substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules per square centimeter, said printed conductive ink layer has a surface resistivity of less than about 10 ohms/square;
13 . The thermal transfer ribbon as recited in claim 1 , wherein said binder is a thermoplastic binder.
14 . The thermal transfer ribbon as recited in claim 13 , wherein said conductive ink layer is comprised of from about 1 to about 15 weight percent of said thermoplastic binder.
15 . The thermal transfer ribbon as recited in claim 14 , wherein said conductive ink layer is comprised of at least about 90 weight percent of said particulate conductive metal material.
16 . The thermal transfer ribbon as recited in claim 15 , wherein said thermoplastic binder has a softening point of from about 45 to about 150 degrees Celsius.
17 . The thermal transfer ribbon as recited in claim 16 , wherein said particulate conductive metal material has a particle size such that least about 95 weight percent of its particles have a maximum dimension smaller than 15 microns.
18 . The thermal transfer ribbon as recited in claim 10 , wherein said particulate conductive material comprises a mixture of a noble metal and a non-noble metal.
19 . The thermal transfer ribbon as recited in claim 18 , wherein said non-noble metal is copper.
20 . The thermal transfer ribbon as recited in claim 19 , wherein said noble metal is silver.
21 . The thermal transfer ribbon as recited in claim 20 , wherein said particulate conductive material is comprised of from about 5 to about 40 weight percent of silver, by total weight of silver and copper.
22 . The thermal transfer ribbon as recited in claim 21 , wherein said particulate conductive material is comprised of from about 10 to about 20 weight percent of silver, by total weight of silver and copper.
23 . The thermal transfer ribbon as recited in claim 22 , wherein said silver is coated onto said copper at a coating thickness of from about 0.3 to about 0.7 microns.
24 . The thermal transfer ribbon as recited in claim 5 , wherein said particulate metal material is in the form of a flake.
25 . The thermal transfer ribbon as recited in claim 24 , wherein, when said conductive ink layer is thermally printed onto a flexible substrate at a printing speed of 2 centimeters per second and a printing energy of 7.6 joules/square centimeter and has a volume resistivity is less than about 100 micro ohm-cm;
26 . The thermal transfer ribbon as recited in claim 25 , wherein at least about 90 weight percent of said particulate conductive material is present in said conductive ink layer;
27 . The thermal transfer ribbon as recited in claim 26 , wherein said binder is a thermoplastic binder with a softening point of from about 45 to about 150 degrees Celsius;
28 . The thermal transfer ribbon as recited in claim 5 , wherein said particulate conductive metal material has a particle size such that least about 95 weight percent of its particles have a maximum dimension smaller than 100 nanometers.