Process of forming transparent conductive coatings with sintering additives
A process is disclosed for the delayed sintering of metal nanoparticles in a self-assembled transparent conductive coating by incorporating a sintering additive into the water phase of the emulsion used to form the coating. The sintering additive reduces the standard reduction potential of the metal ion of the metal forming the nanoparticles by an amount greater than 0.1V but less than the full reduction potential of the metal ion. Emulsion compositions used in the process are also disclosed.
1. A liquid coating composition in the form of an emulsion for forming a transparent conductive coating on a substrate comprising: (a) an oil phase comprising a solvent that is non-miscible with water having dispersed therein metal nanoparticles, and (b) a water phase comprising water or a water-miscible solvent and an additive for delayed sintering of the nanoparticles,
wherein the additive is selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, and halide salts.
2. The composition of claim 1 wherein the additive is a halide salt.
3. The composition of claim 2 wherein the halide salt is a quaternary ammonium salt.
4. The composition of claim 2 wherein the halide salt is selected from the group consisting of sodium chloride, ammonium chloride, potassium chloride, and combinations thereof.
5. The composition of claim 1 wherein the additive is present in the water phase at a concentration of 0.001M to 0.1M.