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(11) | EP 0 437 062 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and apparatus for printing with a drop-on-demand ink jet print head using an electric field |
| (57) A drop-on-demand ink jet has an ink chamber (12) coupled to a source of ink (14),
and an ink drop orifice (16) with an outlet (18). An acoustic driver (30) produces
a pressure wave in the ink and causes the ink to pass outwardly through the ink drop
orifice and outlet (18). A high voltage electric field is oriented to accelerate ink
drops along a path from the outlet to print medium (20). The electric field is time
invariant and is the only electric field present along the path during drop formation
and accelaration. The size of the ink drops may be varied, such as by driving the
acoustic driver with varying drive signals. One preferred form of acoustic drive signal
comprises of individual or combinations of plural bipolar drive pulses. The combination
of energy imparted by the acoustic driver (30) and the electric field accelerates
small and large drops such that the time for the drops to travel to the print medium
(20) is substantially the same. The ink jet printer of the present invention may be
used to print with a wide variety of inks, including phase change inks. |