Silver-containing aqueous formulation and its use to produce electrically conductive or reflective coatings
View Patent ↗A silver-containing, disperse, water-containing formulation and its use to produce electrically conductive and/or optically reflective coatings is described. The formulation contains at least a) 0.5 to 30 parts by wt. of silver metal particles with an effective diameter of at most 150 nm, preferably at most 100 nm, particularly preferably 40 to 80 nm, with a bimodal size distribution, b) 50 to 99.5 parts by wt. of water and optionally up to 30 parts by wt. of solvent, c) 0.01 to 10 parts by wt. of at least one, in particular polymeric, dispersant, d) 0 to 5 parts by wt. of film-producer, e) 0 to 5 parts by wt. of additives, f) 0 to 5 parts by wt. of conductive polymers, and has a viscosity of at most 150 mPa.s.
1. A silver-containing, disperse, water-containing formulation containing at least
a) 0.5 to 30 parts by wt. of silver metal particles with an effective diameter of at most 150 nm, with a bimodal size distribution of the silver metal particles, determined using laser correlation spectroscopy,
b) 50 to 99.5 parts by wt. of water and optionally up to 30 parts by wt. of solvent,
c) 0.01 to 10 parts by wt. of at least one polymeric dispersant,
d) 0 to 5 parts by wt. of film-producer,
e) 0 to 5 parts by wt. of additives,
f) conductive polymers, in an amount of up to 5 parts by wt.,
said formulation having a viscosity of at most 150 mPa.s.
2. A formulation according to claim 1 , wherein the dispersant is at least one agent selected from the group consisting of:
alkoxylates, alkylolamides, esters, amine oxides, alkyl polyglucosides, alkylphenols, arylalkylphenols, water-soluble homopolymers, water-soluble random copolymers, water-soluble block copolymers, and water-soluble graft polymers.
3. The formulation of claim 2 , wherein said dispersant is at least one agent selected from the group consisting of polyvinyl alcohols, copolymers of polyvinyl alcohols and polyvinyl acetates, polyvinylpyrrolidones, cellulose, starch, gelatine, gelatine derivatives, polymers of amino acids, polylysine, polyaspartic acid, polyacrylates, polyethylene sulfonates, polystyrene sulfonates, polymethacrylates, condensation products of aromatic sulfonic acids and formaldehyde, naphthalene sulfonates, lignin sulfonates, copolymers of acrylic monomers, polyethylenimines, polyvinylamines, polyallylamines, poly(2-vinylpyridines), block copolyethers, block copolyethers with polystyrene blocks, polydiallyldimethylammonium chloride and combinations thereof.
4. A formulation according to claim 3 , wherein the dispersant is selected from the group consisting of: block copolyethers and block copolyethers with polystyrene blocks.
5. A formulation according to claim 1 , wherein the solvent b) is selected from the group consisting of: C 1 - to C 5 -alcohols, ethers, and ketones.
6. A formulation according to claim 5 , wherein said C 1 - to C 5 -alcohols are C 1 - to C 3 -alcohols, said ethers are dioxalan and said ketones are acetone.
7. A formulation according to claim 1 , wherein the film-producer d) is selected from the group consisting of: polydimethylsiloxane, polyacrylate, ammonium salts of polyacrylates, siloxanes, wax combinations, copolymers with pigment-active groups, low molecular weight polymers, hydroxyethyl cellulose and polyvinylalcohol.
8. A formulation according to claim 1 , wherein the additive e) is selected from the group consisting of: pigments, antifoam agents, light stabilisers, optical brighteners, corrosion inhibitors, antioxidants, algicides, plasticisers, thickeners and surface-active substances.
9. A formulation according to claim 1 , wherein the conductive polymer f) is selected from the group consisting of: polypyrrole, polyaniline, polythiophene, polyphenylenevinylene, polyparaphenylene, polyethylene-dioxythiophene, polyfluorene and polyacetylene.
10. The formulation of claim 9 , wherein said conductive polymer f) is polyethylene-dioxythiophene/polystyrene sulfonic acid.
11. A formulation according to claim 1 , wherein the silver particles a) have an effective particle diameter of 10 to 150 nm, determined by laser correlation spectroscopy.
12. The formulation of claim 11 , wherein said effective particle diameter is 40 to 80 nm.
13. A formulation according to claim 1 , wherein the silver particles a) are present in a proportion of 1 to 20 parts by wt.
14. A formulation according to claim 1 , wherein the concentration of dispersant c) is 0.02 to 5 parts by wt.
15. A formulation according to claim 1 , wherein the dispersed silver particles are subjected to membrane filtration with a filter fineness of at most 100,000 Da.
16. Conductor strips having a line width of less than 100 μm formed of the formulation of claim 1 .
17. A process for producing conductor strips with a line width of less than 100 μm, which comprises printing a line of the formulation of claim 1 at a width of less than 100 μm onto a substrate surface using inkjet technology and thermally thermally treating said line at a temperature of at most 140° C., to remove water and optionally solvent.
18. A process for producing conductor strips with a line width of less than 20 μm, which comprises applying the formulation of claim 1 into a predetermined structuring of a substrate, in which the structuring has a line width of <20 μm, and the applied formulation at a temperature of at most 140° C. to remove water and optionally solvent.
19. A transparent plastics substrate, with an electrically conductive and/or optically reflective coating formed of the formulation according to claim 1 .
20. A substrate according to claim 19 , wherein the coating comprises conductor strips having a line width of less than 100 μm and the conductivity in the conductor strips is at least 7·10 6 S/m.