Stretchable polymer thick film compositions for thermoplastic substrates and wearables electronics
This invention is directed to stretchable polymer thick film compositions useful for wearable garments. More specifically, the polymer thick film may be used in applications where significant stretching is required, particularly on substrates that can be highly elongated. A particular type of substrate is a thermoplastic polyurethane substrate.
1. An article containing an electrical circuit comprising an element formed from a polymer thick film composition, said polymer thick film composition comprising a functional component and an organic medium, wherein said element is a conductor and wherein said functional component is silver powder in combination with silver chloride powder and said polymer thick film composition is a polymer thick film conductor composition comprising:
(a) silver powder in combination with silver chloride powder; and
(b) the organic medium comprising 5-50 wt % thermoplastic polyurethane resin dissolved in an organic solvent, said thermoplastic polyurethane resin having a percent elongation of at least 200% and a tensile stress necessary to achieve 100% elongation of less than 1000 psi, wherein the weight percent is based on the total weight of said organic medium; wherein
said composition is dried to remove said solvent and form said conductor.
2. The article of claim 1 , wherein said silver powder is in the form of silver flakes and wherein said thermoplastic polyurethane resin is selected from the group consisting of a polyester-based polymer, a urethane homopolymer and a predominantly linear hydroxyl polyurethane.
3. The article of claim 2 , said polymer thick film conductor composition comprising 20 to 92 wt % silver flakes in combination with silver chloride powder and 8 to 80 wt % organic medium, wherein the wt % are based on the total weight of said composition.
4. The article of claim 1 , wherein said conductor is covered by an overcoat layer formed from a polymer thick film carbon composition comprising:
(a) graphite, conductive carbon or a mixture thereof; and
(b) an organic medium comprising 5-50 wt % thermoplastic resin dissolved in an organic solvent, said thermoplastic polyurethane resin having a percent elongation of at least 200% and a tensile stress necessary to achieve 100% elongation of less than 1000 psi, wherein the weight percent is based on the total weight of said organic medium;
wherein said composition is dried to remove said solvent and form said overcoat layer.
5. The article of claim 1 , wherein said conductor is covered by an encapsulant layer formed from a polymer thick film encapsulant composition comprising:
(a) fumed silica; and
(b) an organic medium comprising 5-50 wt % thermoplastic polyurethane resin dissolved in an organic solvent, said thermoplastic polyurethane resin having a percent elongation of at least 200% and a tensile stress necessary to achieve 100% elongation of less than 1000 psi, wherein the weight percent is based on the total weight of said organic medium;
wherein said composition is dried to remove said solvent and form said encapsulant layer.
6. The article of claim 4 , wherein said overcoat layer is covered by an encapsulant layer formed from a polymer thick film encapsulant composition comprising:
(a) fumed silica; and
(b) an organic medium comprising 5-50 wt % thermoplastic polyurethane resin dissolved in an organic solvent, said thermoplastic polyurethane resin having a percent elongation of at least 200% and a tensile stress necessary to achieve 100% elongation of less than 1000 psi, wherein the weight percent is based on the total weight of said organic medium;
wherein said composition is dried to remove said solvent and form said encapsulant layer.
7. The article of claim 1 , wherein the article is a wearable garment.