Touch Sensor Curved Boundary Design for Flexible Displays

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Solution Overview

Problem

Conventional touch screen panels lack flexibility and are prone to cracking when bent, which limits their application on flexible flat panel display devices, and they also have visibility issues due to the sensing patterns.

Innovation Solution

A touch sensor design featuring sensing patterns with convex and concave curved boundaries and bridge electrodes, which reduces stress concentration and visibility by using dummy patterns and specific curvature radii to enhance flexibility and sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional sensing patterns are used in touch screen panels, then touch sensing function is achieved, but the patterns become visible and reduce display quality

Engineering Contradiction:

Improvetouch sensing functionVSAvoidvisibility of sensing patterns

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The sensing patterns are designed with curved boundaries instead of straight lines, creating convex and concave portions that reduce light reflection and visibility while maintaining the electrical connectivity and touch sensing functionality of the pattern network

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Manufacturing precision

If rigid sensing patterns are used, then manufacturing precision is achieved, but flexibility and bendability are lost

Engineering Contradiction:

Improvepattern formation precisionVSAvoidflexibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

Curved boundaries with specific radius of curvature are introduced to the sensing patterns, allowing the rigid pattern structure to flex and bend without cracking while maintaining manufacturing precision through controlled curvature parameters

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The sensing patterns are divided into unit patterns connected by connection parts, with curved boundaries between them that allow relative movement and flexing, enabling the overall pattern to maintain structural integrity during bending

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If sensing patterns with sharp boundaries are used, then manufacturing precision is achieved, but stress concentration occurs during bending causing cracks

Engineering Contradiction:

Improveboundary definition precisionVSAvoidcrack resistance during bending

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

Sharp boundaries are replaced with curved boundaries having a specific radius of curvature, which distributes mechanical stress uniformly during bending operations, preventing stress concentration and crack formation while maintaining clear pattern definition

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

Curved boundary portions are designed in advance to act as stress-absorbing elements that prevent crack propagation, cushioning the impact of bending forces before they can reach critical stress points in the pattern structure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10133406B2Touch sensor

Publication Date: 2018.11.20 DONGWOO FINE CHEM CO LTD

AI summary

A touch sensor includes a sensing pattern including a first pattern and has unit patterns connected with each other through connection parts thereof, and a second pattern having separated unit patterns, and bridge electrodes connecting the separated unit patterns, wherein at least a portion of a boundary between the first pattern and the second pattern includes convex parts of a curved line and concave parts of a curved line between the convex parts, and the convex part of the first pattern and the concave part of the second pattern face each other, and the concave part of the first pattern and the convex part of the second pattern face each other. The touch sensor has excellent touch sensitivity while suppressing an occurrence of cracks in the sensing pattern due to a stress concentration during bending, and preventing the sensing pattern from being viewed by a user.