The present invention relates to a flexographic printing process comprising: applying an energy-curable primer to at least a portion of a surface of a substrate; curing said energy-curable primer to form a cured primer layer on the substrate; applying a metallic ink to at least a portion of the cured primer layer; and curing or drying the metallic ink; wherein the energy-curable primer is applied using a flexographic printing process; and wherein the metallic ink is applied using a flexographic printing process which uses an anilox roller having a transfer volume of from about 6 cm.sup.3/m.sup.2 to about 30 cm.sup.3/m.sup.2.

The present invention provides a UV-Vis radiation curable security ink for producing a security feature for securing value documents, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light. The UV-Vis radiation curable security ink comprises a cationically curable or a hybrid curable ink vehicle, and silver nanoplatelets bearing a surface stabilizing agent of general formula (I)

##STR00001## wherein the residue R.sup.A is a C.sub.2-C.sub.4alkyl group substituted with a hydroxy group; the residue R.sup.B is selected from a C.sub.1-C.sub.4 alkyl group, and a C.sub.2-C.sub.4alkyl group substituted with a hydroxy group; and Cat.sup.+ is a cation selected from the group consisting of Na.sup.+, K.sup.+, Cs.sup.+ and Rb.sup.+.

The present invention provides a UV-Vis radiation curable security ink for producing a security feature for securing value documents, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light. The UV-Vis radiation curable security ink comprises a cationically curable or a hybrid curable ink vehicle, and silver nanoplatelets bearing a surface stabilizing agent of general formula (I)

##STR00001## wherein the residue R.sup.A is a C.sub.2-C.sub.4alkyl group substituted with a hydroxy group; the residue R.sup.B is selected from a C.sub.1-C.sub.4 alkyl group, and a C.sub.2-C.sub.4alkyl group substituted with a hydroxy group; and Cat.sup.+ is a cation selected from the group consisting of Na.sup.+, K.sup.+, Cs.sup.+ and Rb.sup.+.

There is disclosed a method of printing onto the surface of a substrate, which method comprises i) coating a donor surface (12) with a monolayer of particles, ii) treating the substrate surface (80) to render at least selected regions tacky, and iii) contacting the substrate surface with the donor surface to cause particles to transfer from the donor surface only to the tacky regions of the substrate surface. After printing on a substrate (20), the donor surface (12) returns to the coating station (14) where the continuity of the monolayer is restored by recovering with fresh particles the regions of the donor surface exposed by the transfer of particles to the substrate.

There is disclosed a method of printing onto the surface of a substrate, which method comprises i) coating a donor surface (12) with a monolayer of particles, ii) treating the substrate surface (80) to render at least selected regions tacky, and iii) contacting the substrate surface with the donor surface to cause particles to transfer from the donor surface only to the tacky regions of the substrate surface. After printing on a substrate (20), the donor surface (12) returns to the coating station (14) where the continuity of the monolayer is restored by recovering with fresh particles the regions of the donor surface exposed by the transfer of particles to the substrate.

An apparatus for coating a donor surface that is movable relative to the apparatus with a layer of thermoplastic particles, the particles adhering more strongly to the surface than to one another. The apparatus comprises an application device to apply to the donor surface a fluid stream within which the particles are suspended, a housing surrounds the application device forming an interior plenum for confining the fluid stream, the housing prevents egress of particles from a sealing gap defined between the rim of the housing and the surface to be coated, and a suction source connected to the housing to extract from the plenum excess fluid and particles. In operation, the suction source extracts substantially all particles that are not in direct contact with the donor surface, leaving substantially a single particle layer adhering to the donor surface upon exiting the apparatus.

An apparatus for coating a donor surface that is movable relative to the apparatus with a layer of thermoplastic particles, the particles adhering more strongly to the surface than to one another. The apparatus comprises an application device to apply to the donor surface a fluid stream within which the particles are suspended, a housing surrounds the application device forming an interior plenum for confining the fluid stream, the housing prevents egress of particles from a sealing gap defined between the rim of the housing and the surface to be coated, and a suction source connected to the housing to extract from the plenum excess fluid and particles. In operation, the suction source extracts substantially all particles that are not in direct contact with the donor surface, leaving substantially a single particle layer adhering to the donor surface upon exiting the apparatus.

A flexographic printing plate includes at least one halftone printing area with a plurality of halftone dots. A halftone dot of said plurality of halftone dots is shaped as a relief area. Said relief area includes a central portion and a surrounding portion. Said central portion has a central dot floor with a first pattern of a plurality of pins protruding upwardly from the central dot floor. Said surrounding portion protrudes upwardly from the central dot floor and has a top side including a second pattern of a plurality of recesses. The first pattern and second pattern are such that the surrounding portion can be distinguished from the central portion.

A flexographic printing plate includes at least one halftone printing area with a plurality of halftone dots. A halftone dot of said plurality of halftone dots is shaped as a relief area. Said relief area includes a central portion and a surrounding portion. Said central portion has a central dot floor with a first pattern of a plurality of pins protruding upwardly from the central dot floor. Said surrounding portion protrudes upwardly from the central dot floor and has a top side including a second pattern of a plurality of recesses. The first pattern and second pattern are such that the surrounding portion can be distinguished from the central portion.

Energy curable compositions comprising polyols, and any blend of ethylenically unsaturated monomers and oligomers. The polyols of the invention are essentially free of any ethylenically unsaturated groups. It is preferred that the polyol substances according to the invention have greater than one hydroxy group and preferably have boiling points in excess of 170 C. The compositions of the invention are particularly useful for the printing or coating of food packaging and may be applied via any printing or coating method, although inkjet printing is a preferred method.