Calvin F. Quate

Acoustic ink printing

An acoustic beam focused on a free liquid surface is used to eject discrete ink droplets of controlled diameter. The liquid surface, adjusted to be at the focal plane of a suitable focusing element, is excited with a burst of acoustic energy. Spherical lead zirconate titanate (PZT) shells, acoustic microscope lenses, spherical lenses etched in silicon, and Fresnel acoustic lenses are used successfully to eject droplets. Droplet diameter scales directly with the focal spot size, and inversely with the acoustic frequency. Droplet formation is experimentally demonstrated over the frequency range of 5 to 300 MHz, with corresponding droplet diameters from 300 to 5 mu m. This droplet ejection process is successfully utilized for a printing application by using ink as the liquid medium. Acoustic ink printing with a single lens and with an array of lenses is described.<<ETX>>

Hot melt ink acoustic printing

To facilitate the use of hot melt inks in acoustic ink printers of the type having a printhead including one or more acoustic droplet ejectors for supplying focused acoustic beams, such a printer comprises a carrier for transporting a generally uniformly thick film of hot melt ink across its printhead, together with a heating means for liquefying the ink as it nears the printhead. The droplet ejector or ejectors are acoustically coupled to the ink via the carrier, and their output focal plane is essentially coplanar with the free surface of the liquefied ink, thereby enabling them to eject individual droplets of ink therefrom on command. The ink, on the other hand, is moved across the printhead at a sufficiently high rate to maintain the free surface which it presents to the printhead at a substantially constant level. A variety of carriers may be employed, including thin plastic and metallic belts and webs, and the free surface of the ink may be completely exposed or it may be partially covered by a mesh or perforated layer. A separate heating element may be provided for liquefying the ink, or the lower surface of the carrier may be coated with a thin layer of electrically resistive material for liquefying the ink by localized resistive heating.