Piezoelectric Laminate Moist Heat Stability via Acid Value Control
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Solution Overview
Problem
Polymeric piezoelectric bodies with aliphatic polyester layers having acid values experience reduced stability and adhesive force when exposed to moist heat environments, leading to operational failures in sensors and actuators.
Innovation Solution
A layered body comprising a polymeric piezoelectric body with an optically active aliphatic polyester and a layer with an acid value of 10 mgKOH/g or less, containing a stabilizer with functional groups like carbodiimide, epoxy, or isocyanate, and a nitrogen content of 0.05% to 10% by mass, enhancing both stability and adhesive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a layer with an acid value is used to protect or bond the polymeric piezoelectric body, then adhesive force is improved, but stability (moist heat resistance) deteriorates due to acid component decomposition
Solution Approach 1:
The patent applies parameter changes by precisely controlling the acid value of the layer to be 10 mgKOH/g or less. This quantitative parameter control resolves the contradiction by finding the optimal threshold where sufficient adhesive force is maintained while acid-induced decomposition is suppressed, improving moist heat resistance without sacrificing bonding performance.
2Reliability
If an extremely small amount or no acid component is included in the layer to suppress decomposition, then stability is improved, but adhesive force between the polymeric piezoelectric body and the layer is reduced
Solution Approach 1:
The patent resolves this contradiction by establishing the optimal parameter range for acid value (0.01-10 mgKOH/g). This quantitative control ensures sufficient adhesive force is maintained while preventing excessive acid-induced decomposition, achieving both good bonding and moist heat resistance simultaneously.
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 provides excellent moist heat resistance and adhesive force between the polymeric piezoelectric body and the layer, maintaining high piezoelectric constant and mechanical strength even under challenging environmental conditions.
Implementation Method 1
the polymeric piezoelectric body includes from 0.01 parts by mass to 10 parts by mass of a stabilizer (B), which has at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group
Implementation Method 2
a polymeric piezoelectric body which contains an optically active aliphatic polyester (A) having a weight average molecular weight of from 50,000 to 1,000,000 and has crystallinity obtained by a DSC method, of from 20% to 80%
Data Source
Figure 1
AI summary
A layered body including a polymeric piezoelectric body which includes an optically active aliphatic polyester (A) having a weight average molecular weight of from 50,000 to 1,000,000 and has crystallinity obtained by a DSC method, of from 20% to 80%, and a layer (X) which is in contact with the polymeric piezoelectric body and has an acid value of 10 mg KOH/g or less.