Research and Development

The system used generally in an inkjet printer includes a “thermal system” to print by emitting ink with a pressure of a bubble generated from boiling of ink by heat generation and a “piezo-system” to print by emitting ink with a pressure of a piezo-element that changes its form when voltage is applied. Konica Minolta has developed an inkjet head using a share mode type piezoelectric element that is one of piezo-elements.

The shear mode piezo inkjet head emits ink with deformation of piezoelectric element, not by its expansion and shrinkage but by its shearing. It has the advantage that multiple channels are possible and various types of ink having respective characteristics can be used, because it can be driven under a low electrical power. The trend for smaller droplets, higher speed and higher driving efficiency has been realized in this head by optimizing the shape of the ink channels (pressure chamber) and the form of the nozzles.

Highly accurate design and development are carried out based on the results of analyses using computer simulation about characteristics of the head, which are difficult to measure because of microscopic structure. We have developed a head structure which offers greater displacement under low voltage, on the basis of structural analyses and electrical field analyses about characteristics of an actuator (pressure chamber partition). In addition, the form and size are optimized based on data about hydrokinematic analyses and bubble exclusivity analyses for the flow channel including an ink channel (pressure chamber) and nozzles.

Ink is ejected from a nozzle as droplets, when voltage is applied to the actuator (pressure chamber partition) made of a piezoelectric material and the form of the actuator is changed in the direction to increase internal pressure within the channel. Ink is supplied from an ink chamber to the nozzle by capillary attraction to make up for the used ink, so that the nozzle is continually ready for the next ink ejection.

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“Red” shows the state of pressurization and “blue” shows the state of decompression.

Shearing means that two forces which are the same in strength, but opposite each other, are applied respectively on both sides of the plane in an object, and slippage is caused in the object.