Electrical devices comprising conductive polymers

Claim 2

An electrical device which comprises (1) a laminar resistive element which is composed of a conductive polymer composition which (a) exhibits PTC behavior, (b) comprises an organic polymer and, dispersed in the polymer, a particulate conductive filer, and (c) has a melting temperature, T m ; and (2) two electrodes which can be connected to a source of electrical power and which comprise a material which (a) has a resistivity of 1.0×10 -6 to 1.0×10 -2 ohm-cm, and (b) exhibits ZTC behavior at temperature less than T m , said electrodes (i) each having a length 1, of 0.1 to 1,000,000 inches and a width, w, of 0.005 to 10 inches such that the length to width ratio is at least 1000:1, (ii) each having a thickness of 0.0001 to 0.01 inch, (iii) each having a resistance, R e , of 0.1 to 10,000 ohms, (iv) each attached to a flat laminar surface of the resistive element, and said resistive element having a resistance, R cp , which is less than R e and is from 0.1 to 10,000 ohms when connected to a source of electrical power and the electrical device having a resistance, R h , the resistances R e , R cp and R h being measured when the electrodes are first connected to a source of electrical power with the whole device being at a uniform temperature of 23° C.

Claim 3

A device according to claim 1 wherein both electrodes are on the same surface of the resistive element.

Claim 4

A device according to claim 1 wherein the electrodes are on opposite surfaces of the resistive element.

Claim 5

A device according to claim 1 wherein the resistive element comprises conductive polymer that has been melt-extruded.

Claim 6

A device according to claim 1 wherein the conductive polymer is a polymer thick film ink.

Claim 7

A device according to claim 1 wherein R e is at least 50% of R h .

Claim 8

A device according to claim 6 wherein R e is at least 60% of R h .

Claim 9

A device according to claim 7 wherein R e is at least 70% of R h .

Claim 10

A device according to claim 1 wherein the ratio of R e to R cp is at least 10:1.

Claim 11

A device according to claim 9 wherein the ratio of R e to R cp is at least 100:1.

Claim 12

A device according to claim 1 wherein the electrodes comprise copper.

Claim 13

A device according to claim 11 wherein the copper electrodes have been formed by etching a continuous layer of copper to produce a serpentined pattern.

Claim 14

A device according to claim 1 wherein the electrical device is a heater for mirrors.

Claim 15

A device according to claim 13 wherein the electrodes (a) comprise a material with a resistivity of 1×10 -6 to 1×10 -5 ohm-cm, (b) have a length of at least 100 inches, (c) have a length to width ratio of at least 1500:1, and (d) have a resistance of 0.5 to 200 ohms.

Claim 16

A device according to claim 1 wherein the resistance per unit length of at least one electrode varies.

Claim 17

A device according to claim 15 wherein the resistance per unit length varies by at least 5%.

Claim 18

A device according to claim 16 wherein the resistance per unit length varies by at least 10%.

Claim 19

A device according to claim 17 wherein the resistance per unit length varies by at least 20%.

Claim 20

A device according to claim 18 wherein the resistance per unit length varies by at least 25%.

Claim 21

A heated mirror for use on vehicles, which comprises (1) a mirror comprising a front mirrored surface and a back surface; and (2) attached to the back surface of the mirror, a heater which comprises (a) a laminar resistive element which is composed of a conductive polymer composition which exhibits PTC behavior; (b) two electrodes which can be connected to a source of electrical power and which comprise a material which has a resistivity of 1×10 -6 to 1×10 -4 ohm-cm exhibits ZTC behavior, said electrodes (i) each having a length of 10 to 1000 inches and a width of 0.005 to 1 inch such that the length to width ratio is at least 1000:1, (ii) each having a thickness of 0.0005 to 0.005 inch, (iii) each having a resistance, R e , of 0.1 to 1000 ohms, (iv) each attached to a flat laminar surface of the resistive element, and (v) together covering 10 to 90% of the surface area of the resistive element, said resistive element having a resistance R cp which is less than R e and is from 0.1 to 1000 ohms when connected to a source of electrical power and the heater having a resistance R h , the resistances R e , R cp , and R h being measured when the electrodes are first connected to a source of electrical power with the whole device being at a uniform temperature of 23° C.

Claim 22

A heated mirror for use on vehicles, which comprises (1) a mirror comprising a front mirrored surface and a back surface; and (2) attached to the back surface of the mirror, a heater which comprises (a) a laminar resistive element which is composed of a conductive polymer composition which exhibits PTC behavior; (b) two electrodes which can be connected to a source of electrical power and which comprise a material which has a resistivity of 1×10 -6 to 1×10 -4 ohm-cm exhibits ZTC behavior, said electrodes (i) each having a length of 10 to 1000 inches and a width of 0.005 to 1 inch such that the length to width ratio is at least 1000:1, (ii) each having a thickness of 0.0005 to 0.005 inch, (iii) each having a resistance, R e , of 0.1 to 1000 ohms, (iv) each attached to a flat laminar surface of the resistive element, and (v) together covering 10 to 90% of the surface area of the resistive element, said resistive element having a resistance R cp which is less than R e and is from 0.1 to 1000 ohms when connected to a source of electrical power and the heater having a resistance R h , the resistances R e , R cp , and R h being measured when the electrodes are first connected to a source of electrical power with the whole device being at a uniform temperature of 23° C.