Flexible Display Device with Neutral Plane Transistor

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Solution Overview

Problem

Flexible display devices suffer from reduced lifespan and reliability due to damage from external stress when bent, as the oxide thin film transistor array is subjected to stress, leading to cracks and deterioration of electrical properties.

Innovation Solution

A flexible display device is manufactured with an oxide thin film transistor array positioned between two polyimide-based layers, forming a neutral plane where compressive and tensile stresses are balanced, preventing deformation and damage from bending.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the oxide thin film transistor array is formed on a flexible substrate to enable bending, then flexibility is achieved, but the transistor array suffers from stress damage and cracks when bent

Engineering Contradiction:

ImproveflexibilityVSAvoidtransistor array integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces a neutral plane dimension within the flexible display device structure. By positioning the oxide thin film transistor array on this neutral plane (between the first and second polyimide-based layers), the transistors are located at a position that experiences minimal stress during bending, thus resolving the contradiction between flexibility and reliability

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent uses the neutral plane as an intermediary position between the flexible substrate and the transistor array. This neutral plane acts as a stress-buffering zone that protects the transistor array from direct mechanical stress while maintaining the overall flexibility of the device

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the flexible display device is greatly bent to demonstrate flexibility, then adaptability is improved, but stress is transmitted to the electric device causing cracks and property deterioration

Engineering Contradiction:

Improvebending capabilityVSAvoidstress damage to electric device

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

By creating a neutral plane dimension within the device structure, the patent provides a stress-free zone where the transistor array can be positioned. This allows the device to be bent to various degrees without transmitting harmful stress to the electronic components

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent employs multiple flexible polyimide-based layers that can bend without transmitting stress to the transistor array. These flexible films encapsulate the transistor array on the neutral plane, allowing external bending while protecting the internal components

Inventive Principle:

Principle #30Flexible shells and thin films

3Adaptability or versatility

If the flexible display device is repeatedly bent or the area is enlarged, then flexibility and coverage are improved, but lifespan and reliability decrease due to accumulated stress damage

Engineering Contradiction:

Improverepeated bending capabilityVSAvoiddevice lifespan

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The neutral plane provides a permanent stress-free dimension within the device structure. This allows the device to undergo repeated bending cycles without accumulating stress damage in the transistor array, thereby extending device lifespan while maintaining flexibility

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent pre-positions the transistor array on the neutral plane before any bending occurs. This beforehand positioning ensures that the transistors are always in a stress-free zone, providing prior protection against accumulated stress damage from repeated bending

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10305051B2Flexible display device and method of manufacturing the same

Publication Date: 2019.05.28 UNIVERSITY INDUSTRY COOPERATION GROUP OF KYUNG HEE UNIVERSITY

AI summary

Provided are a flexible display device and a method of manufacturing the same. More particularly, the method of manufacturing the flexible display device according to the present invention includes a step of forming a first polyimide-based layer by coating a polyimide-based solution on a carrier substrate; a step of forming an oxide thin film transistor array on the first polyimide-based layer; a step of forming a second polyimide-based layer by coating a polyimide-based solution on the oxide thin film transistor array; a step of forming an organic light emitting diode on the second polyimide-based layer; and a step of removing the carrier substrate, wherein, in the step of forming the oxide thin film transistor array, the oxide thin film transistor array is disposed between the first polyimide-based layer and the second polyimide-based layer.