Bubble jet print head having improved multiplex actuation construction

Claim 1

In a drop-on-demand ink jet printer of the kind having a plurality of orifices, a thin film drop ejection device including a corresponding plurality of drop ejection heater elements and manifold means of supplying ink to said heater elements, the improvement wherein said drop ejection device comprises: (a) a support substrate; (b) a first circuit portion comprising a plurality of circuit branches that each include a resistive heater element and a diode device formed in spaced relation on said substrate and coupled in series by first circuit branch electrode lines to terminal regions; (c) a dielectric passivation layer overlying said first circuit portion except at the discrete terminal regions of said first circuit portion branches; (d) a second circuit portion comprising a plurality of multiplex electrode lines overlying said dielectric passivation layer including connection sections extending through said dielective passivation layer into contact with terminal regions of said first circuit portion; and (e) a second passivation layer overlying said second circuit portion, but not overlying said resistive heater elements.