Flexible Substrate Barrier Film Lamination 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 formation of air bubbles when folded, compromising water vapor barrier properties 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 improve folding resistance.

Engineering Contradictions & Design Principles

VSEngineering 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

Engineering Contradiction:

Improvewater vapor barrier propertyVSAvoidwarping

Core Design Contradiction:

ReliabilityVSShape

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.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure consisting of the plastic substrate, the isobutene-based adhesive layer, and the barrier layer. This multi-layer composite structure combines materials with different properties to achieve both water vapor barrier functionality and dimensional stability by reducing thermal expansion mismatch through the specific adhesive layer composition.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a barrier layer is provided on the plastic substrate to improve water vapor barrier property, then water vapor protection is improved, but the barrier layer is damaged during production steps

Engineering Contradiction:

Improvewater vapor barrier propertyVSAvoidbarrier layer integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The adhesive layer comprising a polymer with constitutional units derived from isobutene is applied to the plastic substrate before the barrier layer is formed. This preliminary application of the adhesive layer creates a protective and bonding interface that prevents direct contact between the barrier layer and the plastic substrate during subsequent production steps, thereby preventing damage to the barrier layer while maintaining its water vapor barrier function.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If a plastic substrate is used to achieve flexibility, then foldability is improved, but air bubbles form in the adhesive layer when repeatedly folded

Engineering Contradiction:

ImprovefoldabilityVSAvoidfolding resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the adhesive layer by using a polymer with constitutional units derived from isobutene. This specific polymer composition provides appropriate adhesion strength and flexibility, allowing the adhesive layer to accommodate repeated folding without generating air bubbles, thereby maintaining folding resistance while preserving the foldability of the flexible substrate.

Inventive Principle:

Principle #35Parameter changes

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, maintaining superior folding resistance and barrier properties despite using a flexible substrate.

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

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the aforementioned adhesive layer comprises a crosslinked polymer having an isobutene-isoprene copolymer chain

Methodology Applied

Scientific EffectCrosslinking: Chemical Bonding

Implementation Method 3

since the plastic substrate is inferior in water vapor barrier property to glass substrates, a barrier layer may be provided on the plastic substrate

Methodology Applied

Scientific EffectWater vapor barrier: Permeation

Data Source

PatentUS20250374754A1Electronic device

Publication Date: 2025.12.04 AJINOMOTO CO INC

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.