Conformal coating systems

Claim 1

A two-part coating composition, especially useful for conformal coating, comprising: (1) a first part comprising at least one urethane-acrylate or urethane-methacrylate compound, a mono or polyfunctional acrylate or methacrylate reactive diluent and a polymerization initiator of the photoinitiator type; and (2) a second part comprising a polyisocyanate containing adduct, at least one component of said first part containing unreacted hydroxyl groups, said composition having an equivalent weight excess of isocyanate groups in said second part to the hydroxyl groups in said first part of at least 2:1.

Claim 14

A method of forming a UV curing polymerizable conformal coating on a substrate wherein said substrate has one or more shadow areas, comprising the steps in sequence of: (1) providing a two-part coating composition, the first part of which comprises at least one urethane-acrylate or urethane-methacrylate compound, a mono or polyfunctional acrylate or methacrylate reactive diluent and a polymerization initiator of the photo-initiator part, and a second part which comprises a polyisocyanate containing adduct at least one component of said first part containing unreacted hydroxyl groups, said composition having an equivalent weight excess of isocyanate groups in said second part to the hydroxyl groups in said first part of at least 2:1; (2) blending said first and second parts to form a coating composition; (3) applying said coating composition to said substrate; (4) exposing the coated substrate to UV light wave length and intensity to effect UV cure of exposed areas of said coating; and (5) storing said coated substrate under conditions of temperature and humidity such as to promote curing of unexposed (shadow) areas of said coating through a built-in secondary moisture cure mechanism.

Claim 15

A method of forming a UV curing polymerizable conformal coating on a substrate wherein said substrate has one or more shadow areas, comprising the steps in sequence of: (1) providing a two-part coating composition, the first part of which comprises at least one urethane-acrylate or urethane-methacrylate compound, a mono or polyfunctional acrylate or methacrylate reactive diluent and a polymerization initiator of the photo-initiator part, and a second part which comprises a polyisocyanate containing adduct at least one component of said first part containing unreacted hydroxyl groups, said composition having an equivalent weight excess of isocyanate groups in said second part to the hydroxyl groups in said first part of at least 2:1; (2) blending said first and second parts to form a coating composition; (3) applying said coating composition to said substrate; (4) exposing the coated substrate to UV light wave length and intensity to effect UV cure of exposed areas of said coating; and (5) storing said coated substrate under conditions of temperature and humidity such as to promote curing of unexposed (shadow) areas of said coating through a built-in secondary moisture cure mechanism.