Flexible Substrate Barrier Film Bonding to Suppress Warping
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Solution Overview
Problem
Plastic substrates used in flexible electronic devices suffer from warping due to thermal expansion coefficient differences with barrier layers, damage to barrier layers during production, and the generation of air bubbles when folded, compromising water vapor protection and folding resistance.
Innovation Solution
An electronic device with a flexible substrate and a sealing layer that includes a barrier film via an adhesive layer containing a polymer derived from isobutene, which is crosslinked and may include a hygroscopic filler, to prevent warping and bubble formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic substrate with a barrier layer is used to improve water vapor barrier property, then water vapor protection is improved, but warping occurs due to thermal expansion coefficient difference between the plastic substrate and barrier layer
Solution Approach 1:
An adhesive layer comprising a polymer with constitutional units derived from isobutene is introduced as an intermediary between the plastic substrate and the barrier layer. This adhesive layer has a thermal expansion coefficient that intermediates between the plastic substrate and the barrier layer, reducing the thermal expansion coefficient difference and suppressing warping while maintaining the water vapor barrier function of the barrier layer.
2Reliability
If a barrier layer is provided on the plastic substrate to improve water vapor protection, then water vapor barrier property is improved, but the barrier layer is damaged during the production step
Solution Approach 1:
The adhesive layer is applied to the plastic substrate before the barrier layer is formed or attached. This preliminary action of the adhesive layer provides a cushioning effect that protects the barrier layer from damage during subsequent production steps, while still allowing the barrier layer to fulfill its water vapor protection function.
3Adaptability or versatility
If a plastic substrate is used to achieve flexibility, then folding resistance is improved, but air bubbles are generated in the adhesive layer when repeatedly folded
Solution Approach 1:
The adhesive layer is designed with specific material parameters - comprising a polymer with constitutional units derived from isobutene - that provide both flexibility and resistance to air bubble generation during repeated folding. The unique molecular structure of the isobutene-derived polymer allows the adhesive layer to flex without trapping air bubbles, maintaining both flexibility and folding resistance.
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 device effectively suppresses warping and protects against water vapor, while maintaining superior folding resistance by using a polymer derived from isobutene in the adhesive layer.
Implementation Method 1
the substrate is prone to warping based on the difference in thermal expansion coefficient between the plastic substrate and the barrier layer due to the thermal history at that time
Implementation Method 2
since the plastic substrate is inferior in water vapor barrier property to glass substrates, a barrier layer may be provided on the plastic substrate
Implementation Method 3
a foldable electronic device is required to be less likely to generate air bubbles, etc. in the adhesive layer and the like, even when repeatedly folded
Data Source
AI summary
The present invention aims to provide an electronic device that suppresses warping, can sufficiently protect electronic elements from water vapor, and is superior in folding resistance, even though it includes a flexible substrate. The present invention relates to an electronic device having a flexible substrate, an electronic element formed on the flexible substrate, and a sealing layer that seals the electronic element, the electronic device further including a barrier film provided via an adhesive layer on a surface of the flexible substrate opposite to the surface on which the electronic element is formed, and the adhesive layer containing a polymer containing constitutional units derived from isobutene.