Liquid Ejecting Head With Lead-Gradient Electrodes for Crack Prevention
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Solution Overview
Problem
Existing liquid ejection heads, such as those described in JP-A-2002-319714, suffer from stress concentration in the lower electrode due to high lead content, leading to potential damage like cracking.
Innovation Solution
A liquid ejection head design with a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode, where the first electrode includes a lead-containing layer with varying lead content percentages in different regions to mitigate stress concentration, specifically with a higher lead content percentage in regions farther from the center, reducing stress and preventing peeling or cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower electrode contains high lead content to improve electrical conductivity, then electrical conductivity is improved, but stress concentration occurs leading to cracking
Solution Approach 1:
The patent applies local quality by creating a lead-containing layer with non-uniform lead distribution. The lead content is higher in regions farther from the center of the first electrode and lower near the center, allowing different regions to serve different functions: outer regions provide better electrical conductivity while inner regions reduce stress concentration, thereby resolving the contradiction between conductivity and stress resistance
Solution Approach 2:
The patent changes the parameter of lead content distribution within the electrode layer. By controlling the lead content percentage to vary across different regions (higher at outer regions, lower at center), the patent optimizes both electrical conductivity and stress distribution, preventing cracking while maintaining conductive performance
2Ease of manufacture
If uniform lead content is used throughout the electrode layer, then manufacturing is simplified, but stress concentration causes damage
Solution Approach 1:
The patent introduces local quality variation in the lead-containing layer, where lead content differs by region. This allows the electrode to have optimized properties in different areas without requiring complex multi-layer structures, maintaining manufacturing feasibility while preventing stress concentration-related damage
3Strength
If lead content is reduced to prevent stress concentration, then cracking is prevented, but electrical conductivity deteriorates
Solution Approach 1:
The patent resolves this contradiction by implementing local quality differentiation: outer regions maintain higher lead content for electrical conductivity, while inner regions have lower lead content to reduce stress concentration. This spatial variation allows both requirements to be satisfied simultaneously within the same electrode layer
Solution Approach 2:
The patent creates a composite structure within the electrode layer by combining regions with different lead content percentages. This internal composite approach allows the electrode to exhibit both good electrical conductivity (from lead-rich outer regions) and stress resistance (from lead-poor inner regions)
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 design effectively reduces stress concentration and prevents damage by ensuring adequate functioning of the active piezoelectric element regions, enhancing durability and performance.
Implementation Method 1
a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode... the piezoelectric layer is formed of a piezoelectric material containing lead as a constituent element
Data Source
AI summary
A liquid ejection head includes: a vibration plate, and a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode, which are laminated in a lamination direction, wherein the piezoelectric layer is formed of a piezoelectric material containing lead as a constituent element, the first electrode has an electrode layer and a lead-containing layer disposed between the electrode layer and the vibration plate and containing lead, and when, of two regions arranged in a crossing direction, which is a direction crossing the lamination direction, when seen in the lamination direction, a region farther away from a center of the first electrode is a first region and a region closer to the center of the first electrode is a second region, a lead content percentage in the lead-containing layer in the first region is higher than a lead content percentage in the lead-containing layer in the second region.