Inkjet printhead chip with trace orientation to enhance performance characteristics

1. An ink jet print head chip, which comprises

a substrate that defines a plurality of ink inlet channels;

a plurality of nozzle chamber structures positioned on the substrate to define nozzle chambers in fluid communication with the ink inlet channels and an ink ejection nozzle in fluid communication with each nozzle chamber;

drive transistor circuitry positioned on the substrate and connectable to data and power supplies;

a plurality of elongate actuators that are each fast with the substrate at one end to receive actuating signals from the drive transistor circuitry to be displaceable towards and away from the substrate; and

a plurality of ink ejection members that are fast with respective actuators at opposite ends, each ink ejection member being positioned in a respective nozzle chamber such that displacement of the respective actuators results in the ejection of a drop of ink from the ink ejection nozzle, wherein

the transistor circuitry includes traces that are interposed between each actuator and the substrate and oriented substantially orthogonally to a longitudinal axis of each respective actuator.

2. An ink jet print head chip as claimed in claim 1 , in which the transistor circuitry defines a plurality of transistors that are interposed between the substrate and corresponding actuators so that each actuator receives an electrical signal from one corresponding transistor.

3. An ink jet print head chip as claimed in claim 2 , in which each transistor comprises a poly layer having a plurality of the traces.

4. An ink jet print head chip as claimed in claim 1 , in which each elongate actuator includes an actuator arm of a laminated structure comprising a resiliently flexible inner layer, a conductive layer and a compensation layer, the inner layer being interposed between the conductive and compensation layers, the conductive layer being positioned between the inner layer and the substrate and defining an electrical heating circuit such that, when heated by an electrical current received from the associated transistor, the conductive layer expands and causes the actuator arm to bend away from the substrate, with subsequent cooling and contraction resulting in the actuator arm bending back towards the substrate.

5. An ink jet print head chip as claimed in claim 4 , in which the conductive layer defines a series of corrugations which are generally aligned with the traces.

6. An ink jet print head chip as claimed in claim 4 , in which each ink ejection member is a paddle that is connected to the conductive layer of the respective actuator, the conductive layer defining a discontinuity between the paddle and the heating circuit to insulate the paddle from the heating circuit.

7. An ink jet print head chip as claimed in claim 4 , in which the conductive layer and the compensation layer are of substantially the same material to compensate for stresses that are generated in the actuator arm as a result of reciprocal bending of the actuator arm.