Primer coating for enhancing adhesion of liquid toner to polymeric substrates
A primer coating is provided for use on polymeric substrates to enhance adhesion of liquid toner to the substrates for printing in an electrophotographic printing device. The primer coating is water-based and includes a dispersion of a copolymer of ethylene and acrylic or methacrylic acid, and a compatible adhesion enhancer selected from an aliphatic polyurethane dispersion, a hydrogenated hydrocarbon rosin or rosin ester dispersion, and an amorphous acrylic polymer dispersion. The coating may also include additives such as wetting agents, antiblocking agents, matting agents, and waxes. The primer coating may be applied to a variety of polymeric substrates including polypropylene, biaxially oriented polpypropylene, polyethylene terephthalate, and polyvinyl chloride.
1. A primer coating for enhancing adhesion of liquid toner to a polymeric substrate, said coating comprising a mixture of
a) from about 60 to about 95 wt % of a dispersion of a copolymer of ethylene and acrylic or methacrylic acid;
b) from about 5 to about 40 wt % of a compatible adhesion enhancer selected from the group consisting of an aliphatic polyurethane dispersion, a hydrogenated hydrocarbon rosin or rosin ester dispersion, and an amorphous acrylic polymer dispersion; and
c) from about 0.05 to about 1.0% by weight of a metal hydroxide.
2. The primer coating of claim 1 further including a wetting agent.
3. The primer coating of claim 2 wherein said wetting agent is selected from the group consisting of alcohols and surfactants.
4. The primer coating of claim 1 further including a matting agent.
5. The primer coating of claim 4 wherein said matting agent comprises amorphous silica.
6. The primer coating of claim 1 further including an antiblocking agent selected from the group consisting of crosslinking agents, waxes, silica, and mixtures thereof.
7. The primer coating of claim 6 comprising from about 0.5 to 5% by weight of a crosslinking agent.
8. The primer coating of claim 6 comprising from about 4 to 15% by weight of a wax.
9. The primer coating of claim 1 wherein said copolymer dispersion contains 35% total solids.
10. The primer coating of claim 1 wherein said adhesion enhancer comprises an aliphatic polyurethane dispersion containing 33% total solids.
11. The primer coating of claim 1 wherein said adhesion enhancer comprises a hydrogenated hydrocarbon rosin or rosin ester dispersion containing 55% total solids.
12. The primer coating of claim 1 wherein said adhesion enhancer comprises an amorphous acrylic polymer dispersion containing 35% total solids.