Foldable Touch Sensor Electrode Segmentation for Reduced Curvature

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Solution Overview

Problem

Foldable mobile terminals with OLED displays face reliability issues due to the thinning of the window and supporting structure, leading to weak OLEDs, which can be damaged when folded, and existing touch sensors are vulnerable to damage when the curvature radius becomes too small.

Innovation Solution

A mobile terminal design featuring a flexible display unit with a touch sensor comprising multiple transparent electrodes and a drive IC that can sense touch inputs across different areas, allowing the display to bend with a smaller curvature radius while preventing damage to the touch sensor by maintaining horizontal electrodes in the folded state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the window and supporting structure are thinned to enable folding, then the foldable mobile terminal can be achieved, but the OLED becomes weak and vulnerable to damage when folded

Engineering Contradiction:

Improvefoldable capabilityVSAvoidOLED durability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The touch sensor is divided into multiple independent transparent electrode layers (first, second, and third transparent electrodes) arranged in different orientations. This segmentation allows each layer to independently handle touch detection in different directions, preventing stress concentration on a single electrode structure during folding, thereby protecting the OLED from damage while maintaining foldable capability.

Inventive Principle:

Principle #1Segmentation

2Volume of moving object

If the display is folded with a small curvature radius, then the terminal thickness is reduced, but the touch sensor becomes vulnerable to damage

Engineering Contradiction:

Improveterminal thicknessVSAvoidtouch sensor durability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

Different transparent electrode layers are strategically positioned and oriented in different regions of the display. The first transparent electrodes extend in a first direction, the second in a second direction, and the third in a third direction, creating locally optimized electrode configurations that can withstand small curvature radius folding without damage, enabling thin folded terminal design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The touch sensor employs a composite structure of multiple transparent electrode layers with different orientations and materials properties. This composite electrode architecture distributes mechanical stress during folding across multiple layers, preventing any single layer from failing under small curvature radius conditions, thus maintaining touch sensor durability in thin folded states.

Inventive Principle:

Principle #40Composite materials

3Reliability

If multiple transparent electrodes are added to protect the touch sensor during folding, then the electrode structure becomes more complex

Engineering Contradiction:

Improvetouch sensor protectionVSAvoidelectrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Each transparent electrode layer serves multiple functions: the first, second, and third transparent electrodes collectively provide touch detection capability in multiple directions, offer mechanical protection during folding, and maintain display transparency. This multi-functionality reduces the need for separate protective structures, simplifying the overall design despite the multiple electrode layers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhanced touch sensor structure enables the flexible display to maintain reliability and durability by allowing it to bend with a smaller curvature radius without damaging the horizontal electrodes, thus reducing the terminal's thickness in the folded state and preventing touch sensor damage.

Implementation Method 1

a touch sensor comprising a first transparent electrode extended in a y-axis direction and a horizontal transparent electrode extended in an x-axis direction

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11023086B2Foldable mobile terminal extracting a touch input coordinate from horizontal electrodes overlapped by the touch input

Publication Date: 2021.06.01 LG ELECTRONICS INC

AI summary

A mobile terminal including a first body; a second body arranged side by side with the first body in a first direction; a hinge unit connecting the first body and the second body and configured to vary an angle defined by the first body and the second body; a flexible display unit including a first area provided in one surface of the first body, a second area provided in one surface of the second body, and a third area provided in an area corresponding to the hinge unit; and a touch sensor in the flexible display unit. In addition, the touch sensor includes a plurality of first transparent electrodes extended in a second direction perpendicular to the first direction and arranged side by side in the first direction; a plurality of second transparent electrodes provided in the first area, and extended in the first direction and arranged side by side in the second direction; a plurality of third transparent electrodes provided in the second area, and extended in the first direction and arranged side by side in the second direction; and a drive IC configured to determine a touch point based on a touch signal sensed in the first transparent electrodes, the second transparent electrodes and the third transparent electrodes.