Patent ID: 7677702

Claim:
An inkjet printhead comprising: a plurality of nozzles; a bubble forming chamber corresponding to each of the nozzles respectively, the bubble forming chambers adapted to contain ejectable liquid; and, a generally planar heater element disposed in each of the bubble forming chambers respectively, the heater element being bonded on one side to the chamber so that the other side directly contacts the ejectable liquid, the heater element configured for receiving an energizing pulse to heat some of the ejectable liquid above its boiling point to form a gas bubble on the side facing into the chamber, whereby the gas bubble causes the ejection of a drop of the ejectable liquid from the nozzle; and, the chamber having a dielectric layer proximate the side of the heater element bonded to the chamber; wherein, the dielectric layer has a thermal product less than 1495 Jm −2 K −1 s −1/2 , the thermal product being (ρCk) 1/2 , where ρ is the density of the layer, C is specific heat of the layer and k is thermal conductivity of the layer.