Lead-Free Piezoelectric Inkjet Head With Coercive Field Control
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Solution Overview
Problem
Lead-containing piezoelectric materials like PZT are harmful to the environment and have high material costs, making it difficult to implement lead-free piezoelectric materials in inkjet heads due to lower piezoelectric constants and material characteristics that are not comparable to conventional materials.
Innovation Solution
A liquid ejection head using a lead-free piezoelectric material, such as potassium sodium niobate, with a piezoelectric constant d33 of at least 200 pC/N, is designed with stacked layers that vibrate vertically and are driven by electric fields in both the polarization direction and an opposite direction, with the opposite electric field limited to half or less of the coercive electric field to prevent deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric material is used, then environmental harm is reduced, but piezoelectric constant and performance deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the electric field strength in the opposite polarization direction to be equal to or less than the coercive electric field. This parameter control prevents excessive reverse polarization while maintaining acceptable liquid ejection performance, thereby improving the piezoelectric constant of lead-free materials without compromising environmental benefits
Solution Approach 2:
The patent uses composite material approach by combining lead-free piezoelectric material with specific structural design (stacked layers) and controlled electric field application. This composite solution maintains environmental friendliness while achieving comparable displacement performance to lead-containing materials through optimized material structure and actuation method
2Ease of manufacture
If lead-free piezoelectric material is used, then material cost is reduced, but piezoelectric constant deteriorates
Solution Approach 1:
By changing the operating parameter (electric field strength in opposite direction) to be equal to or less than the coercive electric field, the patent achieves acceptable liquid ejection performance with lead-free materials, making their lower piezoelectric constant acceptable and thus enabling cost-effective manufacturing
3Productivity
If electric field in opposite polarization direction exceeds coercive electric field, then liquid ejection performance is improved, but piezoelectric member deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by pre-establishing the constraint that the electric field in the opposite polarization direction must be equal to or less than the coercive electric field. This preventive measure avoids excessive reverse polarization and piezoelectric member deterioration before they occur, ensuring long-term reliability while maintaining liquid ejection functionality
Solution Approach 2:
The patent optimizes the electric field parameter in the opposite polarization direction to be equal to or less than the coercive electric field, achieving a balance between liquid ejection performance and piezoelectric member durability through precise parameter control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution maintains liquid ejection performance, reduces material costs, and provides an environmentally friendly inkjet head and device by minimizing piezoelectric member deterioration while achieving comparable displacement to lead-containing materials.
Implementation Method 1
The piezoelectric element may comprise a plurality of stacked layers of the lead-free piezoelectric material. The layers may be stacked on the pressure chamber in a vertical direction. The piezoelectric element may vibrate back and forth along the vertical direction.
Data Source
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AI summary
According to one or more embodiments, a liquid ejection head includes an actuator and a driver. The actuator has a piezoelectric element made of a lead-free piezoelectric material. The driver applies a voltage to the actuator to vibrate the piezoelectric element in a first direction with a first electric field in a first polarization direction of the piezoelectric element and a second electric field in a direction opposite to the first polarization direction. The second electric field is controlled to be equal to or less than a coercive electric field of the piezoelectric element.