THERMOFORMABLE POLYMER THICK FILM SILVER CONDUCTOR AND ITS USE IN CAPACITIVE SWITCH CIRCUITS

• US 20140154501A1
• Filed: 02/07/2014
• Published: 06/05/2014
• Est. Priority Date: 09/20/2011
• Status: Active Grant

• Current Assignee: Du Pont China Limited (DuPont de Nemours, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: DORFMAN, JAY ROBERT, Arancio, Vincenzo
• Granted Patent: US 9,245,666 B2
• Time in Patent Office: Days
• US Class Current: 428/328
• CPC Class Codes: C08G 2650/56 Polyhydroxyethers, e.g. phenoxy resins
• CPC Class Codes: C08K 3/08 Metals
• CPC Class Codes: C08L 71/00 Compositions of polyethers obtained by reactions forming an ether link in the main chain of polyacetals C08L59/00; of epoxy resins C08L63/00; of polythioether-ethers C08L81/02; of polyether-sulfones C08L81/06; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 71/02 Polyalkylene oxides
• CPC Class Codes: C08L 75/04 Polyurethanes
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01B 3/18 mainly consisting of organic substances organic macromolecular compounds or compositions C08
• CPC Class Codes: H01G 4/008 Selection of materials
• CPC Class Codes: H01H 1/029 comprising conducting material dispersed in an elastic support or binding material
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches
• CPC Class Codes: H05K 1/0326 containing O
• CPC Class Codes: H05K 1/095 for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: H05K 1/16 incorporating printed electric components, e.g. printed resistor, capacitor, inductor
• CPC Class Codes: H05K 2201/0129 Thermoplastic polymer, e.g. auto-adhesive layer; Shaping of thermoplastic polymer
• CPC Class Codes: H05K 2201/10053 Switch
• CPC Class Codes: H05K 2203/1327 Moulding over PCB locally or completely applying non-metallic protective coatings for encapsulating mounted components H05K3/284
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/31554 Next to second layer of polyamidoester
• CPC Class Codes: Y10T 428/31609 : Particulate metal or metal compound-containing

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.

Claims

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 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.

4. The capacitive switch circuit of claim 1, wherein said capacitive switch circuit is thermoformed.

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

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

10. The capacitive switch circuit of claim 5, wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

6. 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.

7. The electrical circuit of claim 6, 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.

8. The electrical circuit of claim 6, wherein said silver is in the form of silver flakes and said thermoplastic urethane resin is a urethane homopolymer or a polyester-based copolymer.

11. The electrical circuit of claim 6, wherein said electrical circuit has been subsequently subjected to an injection molding process.

12. The electrical circuit of claim 7, 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 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.

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

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

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

23. The capacitive switch circuit of claim 18, wherein said capacitive switch circuit has been subsequently subjected to an injection molding process.

19. 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 before said encapsulant layer comprising one or more UV-curable polymers is deposited and UV-cured, and wherein said electrical circuit is thermoformed.

20. The electrical circuit of claim 19, 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.

21. The electrical circuit of claim 19, wherein said silver is in the form of silver flakes and said thermoplastic urethane resin is a urethane homopolymer or a polyester-based copolymer.

24. The electrical circuit of claim 19, wherein said electrical circuit has been subsequently subjected to an injection molding process.

25. The electrical circuit of claim 20, wherein said electrical circuit has been subsequently subjected to an injection molding process.

26. The electrical circuit of claim 21, wherein said electrical circuit has been subsequently subjected to an injection molding process.