Laser curing of coatings and inks - where coating comprises polymer and/or oligomer and/or monomer and photoinitiator(s) which pref. absorbs laser light

摘要

In curing a coating by irradiating it with u.v. laser light, the coating comprises a liq. or solid polymer and/or oligomer and/or monomer and at least one photoinitiator (I). The wavelength of the laser is so chosen that its light energy is pref. absorbed by (I) rather than the other components. Pref. the laser light is applied to the coating in pulses where at least 25 (partic. at least 50) pulses are required to effect a cure. Pref. the single pulse fluence is less than 3 (partic. less than 0.5) mJ/cm2. Pref. the pulse repetition rate is low, partic. 250 Hz or less. Pref. the process is carried out under a N2 atmos. Opt. the coating can be clear or can contain a pigment which minimally absorbs the laser light at the selected wavelength. Opt. the coating can contain two (I), pref. absorbing at different wavelengths, where one is selected for effecting a cure through the coating and the other for effecting a cure at the surface. The clear coating pref. comprises 56.4 wt.% epoxy acrylate oligomer, 37.6 wt.% hexane diol diacrylate, 3 wt.% phenyl benzophenone and 3 wt.% methyl diethanolamine.