Thermoformable polymer thick film silver conductor and its use in capacitive switch circuits

Patent metadata

Field	Value
Publication number	US-9245666-B2
Application number	US-201414175085-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Sep 20, 2011
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

This invention is directed to a polymer thick film conductive composition that may be used in applications where thermoforming of the base substrate occurs, e.g., as in capacitive switches. Polycarbonate substrates are often used as the substrate and the polymer thick film conductive composition may be used without any barrier layer. Thermoformable electric circuits benefit from the presence of an encapsulant layer over the dried polymer thick film conductive composition. The electrical circuit is subsequently subjected to an injection molding process.

First claim

What is claimed is:

1. A capacitive switch circuit comprising a dried encapsulant layer covering a dried polymer thick film conductive composition, said polymer thick film conductive composition comprising:
(a) 30-70 wt % silver;
(b) 10-40 wt % first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in a first organic solvent, wherein the weight percent of the thermoplastic urethane resin is based on the total weight of the first organic medium; and
(c) 10-40 wt % second organic medium comprising 10-50 wt % thermoplastic polyhydroxyether resin dissolved in a second organic solvent wherein the weight percent of the thermoplastic polyhydroxyether resin is based on the total weight of the second organic medium;

wherein the weight percent of said silver, said first organic medium and said second organic medium are based on the total weight of said polymer thick film conductive composition and wherein said polymer thick film conductive composition is dried before said encapsulant layer comprising the same polymers but in different ratios than present in said polymer thick film conductive composition is deposited and dried.

2. The capacitive switch circuit of claim 1 , said polymer thick film conductive composition further comprising:
(d) 1-20 wt % of a third organic solvent, wherein the third organic solvent is diacetone alcohol and wherein the weight percent is based on the total weight of said polymer thick film conductive composition.

3. The capacitive switch circuit of claim 2 , wherein said capacitive switch circuit is thermoformed.

4. The capacitive switch circuit of claim 3 , wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

5. The capacitive switch circuit of claim 1 , wherein said silver is in the form of silver flakes and said thermoplastic urethane resin is a urethane homopolymer or a polyester-based copolymer.

6. The capacitive switch circuit of claim 3 , wherein said capacitive switch circuit is thermoformed.

7. The capacitive switch circuit of claim 6 , wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

8. An electrical circuit comprising a conductor formed from a dried polymer thick film conductive composition with a dried encapsulant layer over said dried polymer thick film conductive composition, said polymer thick film conductive composition comprising:
(a) 30-70 wt % silver;
(b) 10-40 wt % first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in a first organic solvent, wherein the weight percent of the thermoplastic urethane resin is based on the total weight of the first organic medium; and
(c) 10-40 wt % second organic medium comprising 10-50 wt % thermoplastic polyhydroxyether resin dissolved in an organic solvent wherein the weight percent of the thermoplastic polyhydroxyether resin is based on the total weight of the second organic medium;

wherein the weight percent of said silver, said first organic medium and said second organic medium are based on the total weight of said polymer thick film conductive composition, wherein said polymer thick film conductive composition is dried before said encapsulant layer comprising the same polymers but in different ratios than present in said polymer thick film conductive composition is deposited and dried, and wherein said electrical circuit is thermoformed.

9. The electrical circuit of claim 8 , said polymer thick film conductive composition further comprising:
(d) 1-20 wt % of a third organic solvent, wherein the third organic solvent is diacetone alcohol and wherein the weight percent is based on the total weight of said polymer thick film conductive composition.

10. The electrical circuit of claim 9 , wherein said electrical circuit has been subsequently subjected to an injection molding process.

11. The electrical circuit of claim 8 , wherein said silver is in the form of silver flakes and said thermoplastic urethane resin is a urethane homopolymer or a polyester-based copolymer.

12. The electrical circuit of claim 11 , wherein said electrical circuit has been subsequently subjected to an injection molding process.

13. The electrical circuit of claim 8 , wherein said electrical circuit has been subsequently subjected to an injection molding process.

14. A capacitive switch circuit comprising a UV-cured encapsulant layer covering a dried polymer thick film conductive composition, said polymer thick film conductive composition comprising:
(a) 30-70 wt % silver;
(b) 10-40 wt % first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in a first organic solvent, wherein the weight percent of the thermoplastic urethane resin is based on the total weight of the first organic medium; and
(c) 10-40 wt % second organic medium comprising 10-50 wt % thermoplastic polyhydroxyether resin dissolved in a second organic solvent wherein the weight percent of the thermoplastic polyhydroxyether resin is based on the total weight of the second organic medium;

wherein the weight percent of said silver, said first organic medium and said second organic medium are based on the total weight of said polymer thick film conductive composition and wherein said polymer thick film conductive composition is dried before said encapsulant layer comprising one or more UV-curable polymers is deposited and UV-cured.

15. The capacitive switch circuit of claim 14 , said polymer thick film conductive composition further comprising:
(d) 1-20 wt % of a third organic solvent, wherein the third organic solvent is diacetone alcohol and wherein the weight percent is based on the total weight of said polymer thick film conductive composition.

16. The capacitive switch circuit of claim 15 , wherein said capacitive switch circuit is thermoformed.

17. The capacitive switch circuit of claim 16 , wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

18. The capacitive switch circuit of claim 14 , wherein said silver is in the form of silver flakes and said thermoplastic urethane resin is a urethane homopolymer or a polyester-based copolymer.

19. The capacitive switch circuit of claim 14 , wherein said capacitive switch circuit is thermoformed.

20. The capacitive switch circuit of claim 19 , wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

21. An electrical circuit comprising a conductor formed from a dried polymer thick film conductive composition with a UV-cured encapsulant layer over said dried polymer thick film conductive composition, said polymer thick film conductive composition comprising:
(a) 30-70 wt % silver;
(b) 10-40 wt % first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in a first organic solvent, wherein the weight percent of the thermoplastic urethane resin is based on the total weight of the first organic medium; and
(c) 10-40 wt % second organic medium comprising 10-50 wt % thermoplastic polyhydroxyether resin dissolved in an organic solvent wherein the weight percent of the thermoplastic polyhydroxyether resin is based on the total weight of the second organic medium;

wherein the weight percent of said silver, said first organic medium and said second organic medium are based on the total weight of said polymer thick film conductive composition, wherein said polymer thick film conductive composition is dried b

Assignees

• Du Pont

Inventors

• Dorfman Jay Robert
• Arancio Vincenzo

Classifications

• C08K3/08

  Metals · CPC title

• H05K1/095

  for polymer thick films, i.e. having a permanent organic polymeric binder · CPC title

• H01B3/18

  mainly consisting of organic substances {(organic macromolecular compounds or compositions C08)} · CPC title

• H05K1/16

  incorporating printed electric components, e.g. printed resistors, capacitors or inductors · CPC title

• H03K2017/9602

  characterised by the type or shape of the sensing electrodes · CPC title