Electrically conductive one component (1K) epoxy formulation

1 . An electrically conductive composition comprising:

a) a resin component comprising

1) A first epoxy resin selected from the group consisting of aliphatic epoxy resin, cycloaliphatic epoxy resin, epoxy novolac resin, bisphenol-A-epoxy resin, bisphenol-F-epoxy resin, hydrogenated bisphenol-A-epoxy resin, hydrogenated bisphenol-F-epoxy resin, bisphenol-A epichlorohydrin based epoxy resin, polyepoxies, propylene glycol epoxy resin, reaction products of polyether-polyol with epichlorohydrin, epoxy silicone co-polymers and mixtures thereof, said first epoxy resin being present in amounts of from 4 to 17% by weight of the total composition; and

2) a second epoxy resin selected from the group consisting of epichlorohydrin formaldehyde phenol resin, epichlorohydrin phenol novolac resin, epichlorohydrin o-cresol novolac resin, epichlorohydrin m-xylenediamine resin, epichlorohydrin diamino diphenyl methane resin, epichlorohydrin trimethylol propane resin and mixtures thereof, said second epoxy resin being present in amounts of 0.3 to 3% by weight of the total weight of the composition; and/or a functionalised polybutadiene resin present in amounts of 0.1 to 15% by weight of the total weight of the composition, and/or a functionalised butadiene-acrylonitrile copolymer resin present in amounts of 0.1 to 5% by weight of the total weight of the composition and mixtures thereof any of the above;

b) an electrically conductive filler;

c) a curative for epoxy resin;

d) a core shell rubber toughener present in amounts of 0.3 to 4.0% by weight of the total composition; and

e) a reactive diluent component comprising

1) A monofunctional epoxy reactive diluent and/or

2) a polyfunctional epoxy reactive diluent;

wherein said composition further comprises a curing agent if said functionalized polybutadiene resin is present in said resin component; wherein said composition is in the absence of a cyanate ester; and

wherein the glass transition temperature (Tg) is 96-98° C. and the ΔCTE Tg is 16-29 ppm/° C. as measured by thermochemical analysis in accordance with ASTM E831 after thermal cycling between −40 C and 85 C for at least 200 cycles according to IEC 61315 10.11.

2 . An electrically conductive composition according to claim 1 , wherein said functionalised polybutadiene resin is present in amounts of 0.1 to 15% by weight of the total weight of the composition and is selected from the group consisting of maleic anhydride functionalised polybutadiene, vinyl functionalised polybutadiene, maleic anhydride grafted vinyl functionalised polybutadiene, epoxidized polybutadiene and mixtures thereof, and wherein said functionalised butadiene-acrylonitrile copolymer, when present, is selected from the group consisting of epoxy-modified butadiene-acrylonitrile copolymer, carboxyl-modified butadiene-acrylonitrile copolymer, amine-modified butadiene-acrylonitrile copolymer, alcohol-modified butadiene-acrylonitrile copolymer and mixtures thereof.

3 . An electrically conductive composition according to claim 1 , wherein said curative is an amine-based curative or a nitrogen containing epoxy adduct.

4 . An electrically conductive composition according to claim 1 , wherein said electrically conductive filler is selected from the group consisting of: silver; nickel; carbon; carbon black; graphite; graphene; copper; gold; platinum; aluminium; iron; zinc; cobalt; lead; tin alloys; silver coated nickel; silver coated copper; silver coated graphite; silver coated polymers; silver coated aluminium; silver coated glass; silver coated carbon; silver coated boron nitride; silver coated aluminium oxide; silver coated aluminium hydroxide; nickel coated graphite; and mixtures thereof; and wherein said electrically conductive filler is present in amounts from 55 to 80% by weight of the total weight of the composition.

5 . An electrically conductive composition according to claim 1 , wherein said core shell rubber toughener is selected from the group consisting of rubber-modified bisphenol-A-epoxy resin, rubber-modified bisphenol-F-epoxy resin, rubber-modified butadiene-acrylonitrile copolymer, rubber modified acrylonitrile and mixtures thereof.

6 . An electrically conductive composition according to claim 1 , wherein said monofunctional epoxy reactive diluent is selected from the group consisting of an aliphatic monoglycidyl ether containing C4-14 alkyl chains, aromatic monoglycidyl ether containing a benzene ring, epoxidized alpha olefin having C8-C16 linear alkyl chain, epoxidized alpha olefin having C8-C16 branched alkyl chain and mixtures thereof.

7 . An electrically conductive composition according to claim 1 , wherein said polyfunctional epoxy reactive diluent is selected from the group consisting of 1,4-bis(2,3-epoxypropyloxy) butane, epoxypropoxypropyl terminated dimer acid, epoxypropoxypropyl terminated polydimethylsiloxane, polyglycol chain diepoxy and mixtures thereof; and wherein said polyfunctional epoxy reactive diluent is present from 2 to 8% by weight of the total weight of the composition.

8 . An electrically conductive composition according to claim 1 , wherein said curing agent is an organic peroxide selected from the group consisting of dicumyl peroxide, tert-amyl peroxypivalate, tert-amyl peroxy-2-ethylhexanoate, tertiary-butylperoxy 2-ethylhexanoate, 1,1-di-(tert-amylperoxy) cyclohexane, 1,1-di-(tert-butylperoxy) cyclohexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, ethyl-3,3-di-(tert-amylperoxy) butyrate, di-tert butyl peroxide, di-tert amyl peroxide, tert-butyl hydroperoxide and mixtures thereof; and is present in amounts from 0.05 to 2% by weight of the total weight of the composition.

9 . A cured product of the electrically conductive composition according to claim 1 .

10 . A photovoltaic module comprising a series-connected string of two or more solar cells in a shingle pattern having an electrically conductive bonding between said two or more solar cells, wherein said electrically conductive bonding is formed with an electrically conductive composition according to claim 1 .

11 . A photovoltaic module according to claim 10 , wherein said electrically conductive composition is applied by dispensing, jetting or printing.

12 . An electrically conductive composition comprising:

a) a resin component consisting of

1) A first epoxy resin selected from the group consisting of aliphatic epoxy resin, cycloaliphatic epoxy resin, epoxy novolac resin, bisphenol-A-epoxy resin, bisphenol-F-epoxy resin, hydrogenated bisphenol-A-epoxy resin, hydrogenated bisphenol-F-epoxy resin, bisphenol-A epichlorohydrin based epoxy resin, polyepoxies, propylene glycol epoxy resin, reaction products of polyether-polyol with epichlorohydrin, epoxy silicone co-polymers and mixtures thereof, said first epoxy resin being present in amounts of from 4 to 17% by weight of the total composition; and

2) a second epoxy resin selected from the group consisting of epichlorohydrin formaldehyde phenol resin, epichlorohydrin phenol novolac resin, epichlorohydrin o-cresol novolac resin, epichlorohydrin m-xylenediamine resin, epichlorohydrin diamino diphenyl methane resin, epichlorohydrin trimethylol propane resin and mixtures thereof, said second epoxy resin being present in amounts of 0.3 to 3% by weight of the total weight of the composition; and/or a functionalised polybutadiene resin present in amounts of 0.1 to 15% by weight of the total weight of the composition, and/or a functionalised butadiene-acrylonitrile copolymer resin present in amounts of 0.1 to 5% by weight of the total weight of the composition and mixtures thereof any of the above;

b) an electrically conductive filler;

c) a curative for epoxy resin;

d) a core shell rubber toughener present in amounts of 0.3 to 4.0% by weight of the total composition; and

e) a reactive diluent component consisting of

1) A monofunctional epoxy reactive diluent and/or

2) a polyfunctional epoxy reactive diluent;

wherein said composition may optionally include a curing agent if said functionalized polybutadiene resin is present in said resin component,

wherein said composition may optionally include plasticizers; stabilizers; UV stabilizers; non-epoxy cyclic co-monomers; non-epoxy functional flexibilizers; tougheners other than core-shell rubber particles; adhesion promoters; conductivity promoters; anti-corrosion agents; anti-bleed agents; rheological adjuvants; particulate silica; modified silica; alumina; modified alumina; wetting agents; surfactants; antioxidants; radical scavengers; drying agents; fungicides; flame retardants; colour pigments; colour pastes; non-reactive solvents; or combinations thereof, and

wherein the glass transition temperature (Tg) is 96-98° C. and the ΔCTE Tg is 16-29 ppm/° C. as measured by thermochemical analysis in accordance with ASTM E831 after thermal cycling between −40 C and 85 C for at least 200 cycles according to IEC 61315 10.11.

13 . An electrically conductive composition according to claim 1 , wherein said second epoxy resin is epichlorohydrin phenol novolac resin.

14 . An electrically conductive composition according to claim 12 , wherein said second epoxy resin is epichlorohydrin phenol novolac resin.

15 . An electrically conductive composition comprising:

a) a resin component comprising

1) A first epoxy resin selected from the group consisting of aliphatic epoxy resin, cycloaliphatic epoxy resin, epoxy novolac resin, bisphenol-A-epoxy resin, bisphenol-F-epoxy resin, hydrogenated bisphenol-A-epoxy resin, hydrogenated bisphenol-F-epoxy resin, bisphenol-A epichlorohydrin based epoxy resin, polyepoxies, propylene glycol epoxy resin, reaction products of polyether-polyol with epichlorohydrin, epoxy silicone co-polymers and mixtures thereof, said first epoxy resin being present in amounts of from 4 to 17% by weight of the total composition; and

2) a second epoxy resin selected from the group consisting of epichlorohydrin formaldehyde phenol resin, epichlorohydrin phenol novolac resin, epichlorohydrin o-cresol novolac resin, epichlorohydrin m-xylenediamine resin, epichlorohydrin diamino diphenyl methane resin, epichlorohydrin trimethylol propane resin and mixtures thereof, said second epoxy resin being present in amounts of 0.3 to 3% by weight of the total weight of the composition; and a functionalised polybutadiene resin present in amounts of 0.1 to 15% by weight of the total weight of the composition, and optionally a functionalised butadiene-acrylonitrile copolymer resin present in amounts of 0.1 to 5% by weight of the total weight of the composition and mixtures thereof any of the above;

b) an electrically conductive filler;

c) a curative for epoxy resin;

d) a core shell rubber toughener present in amounts of 0.3 to 4.0% by weight of the total composition; and

e) a reactive diluent component comprising

1) A monofunctional epoxy reactive diluent and/or

2) a polyfunctional epoxy reactive diluent;

wherein said composition further comprises a curing agent; wherein said composition is in the absence of a cyanate ester; and wherein the glass transition temperature (Tg) is 96-98° C. and the ΔCTE Tg is 16-29 ppm/° C. as measured by thermochemical analysis in accordance with ASTM E831 after thermal cycling between −40 C and 85 C for at least 200 cycles according to IEC 61315 10.11.