Patent ID: 7276136

Claim:
A laser in combination with a plastic part having a dye for absorbing radiation at a welding wavelength for through-transmission laser welding of plastics comprising: an absorber dye with (i) an absorption band above about 350 nm that includes the welding wavelength, (ii) an absorption trough in the visible spectrum, and (iii) strong transmission of light in the visible spectrum, and said dye efficiently absorbing the laser radiation and via vibronic relaxation transmitting heat to weld the plastics, a plastic part combined with said dye at a concentration to form a dyed substrate, and prior to welding said dye concentration providing a ratio comprising a substrate independent optical density (OD) value within the (ii) absorption trough that is a fraction of the substrate independent optical density (OD) value within the (i) absorption band; a top part being highly transmissive of the welding wavelength; and a laser emitting radiation at said top part adjacent said dyed substrate to produce a weld where the irradiated dye remains disposed only within the weld and the matching of the absorption band to the welding wavelength is independent of plastic part contribution and interference.