PMOLED Touch Sensors Using Segmented Anodes to Reduce Parasitic Capacitance

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Solution Overview

Problem

In-cell touch sensor arrangements for PMOLED display panels face challenges due to high parasitic capacitance between anode and cathode layers, which obstructs finger touch detection and is exacerbated by sunlight-induced photocurrent noise, leading to poor dynamic range and interference in touch sensing.

Innovation Solution

The anode layer is used for both display-driving and touch-sensing, with cathodes and anodes configured into isolated areas to reduce parasitic capacitance, and operated in a time-multiplexed mode, with cathodes connected to high impedance during touch-sensing to mitigate photocurrent noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the anode layer and cathode layer are placed in close proximity to achieve a compact OLED structure, then the device compactness is improved, but the parasitic capacitance between the layers increases, degrading touch sensing performance

Engineering Contradiction:

ImproveOLED stack thicknessVSAvoidparasitic capacitance

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The anode layer is divided into multiple isolated anode regions that are separated by insulating barriers. This segmentation reduces the overlapping area between anodes and cathodes, thereby reducing parasitic capacitance while maintaining the compact OLED structure. Each anode region is electrically isolated from adjacent regions through insulating material layers.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If the anode layer is used for both display-driving and touch-sensing functions, then the device complexity is reduced, but the dynamic range for touch sensing deteriorates due to high parasitic capacitance

Engineering Contradiction:

Improvenumber of layersVSAvoidtouch sensing dynamic range

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The anode layer is segmented into multiple isolated regions with insulating barriers between them. This segmentation reduces the parasitic capacitance of each individual anode region, thereby improving the dynamic range for touch sensing while maintaining the dual-functionality of the anode layer for both display driving and touch sensing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Insulating barrier structures are strategically placed at specific locations where anodes and cathodes overlap. This local modification reduces parasitic capacitance at critical overlapping regions while preserving the overall compact structure and dual functionality of the anode layer.

Inventive Principle:

Principle #3Local quality

3Productivity

If the cathodes and anodes are configured in overlapping patterns for efficient display driving, then the display efficiency is improved, but the photocurrent noise from sunlight increases, interfering with touch sensing

Engineering Contradiction:

Improvedisplay driving efficiencyVSAvoidphotocurrent noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The overlapping regions between cathodes and anodes are segmented by insulating barriers, which reduce the area susceptible to photocurrent generation. This segmentation maintains efficient display driving in non-overlapping regions while minimizing photocurrent noise in overlapping regions that are used for touch sensing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The insulating barriers that reduce parasitic capacitance also serve to block photocurrent paths in overlapping regions. By converting the harmful photocurrent effect into a blocked path, the same structural modification addresses both parasitic capacitance and photocurrent noise issues simultaneously.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

This configuration enhances the dynamic range of touch sensing by reducing parasitic capacitance and minimizes sunlight-induced noise, allowing robust detection of finger touches while maintaining display functionality.

Implementation Method 1

The capacitive coupling between the anodes and the touch sensors is relatively low. This is good for the touch sensors to sense approaching fingers as this allows a relatively large dynamic range in sensing the changes of capacitance caused by finger touches.

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

Passive matrix organic light emitting display panels

Methodology Applied

Scientific EffectOrganic light-emitting diode: Organic Light-emitting Diode

Implementation Method 3

sunlight-induced photocurrent noise

Methodology Applied

Scientific EffectPhotocurrent: Photoelectric Effect

Data Source

PatentUS10318085B2Passive matrix organic light emitting display panels having touch sensors using anode and cathode electrodes

Publication Date: 2019.06.11 SOLOMON SYSTECH SHENZHEN LTD

AI summary

A PMOLED touch-sensing display panel using anodes as in-cell touch sensors is provided. The anodes and the cathodes are respectively and correspondingly configured into two or more electrically isolated areas of cathodes and anodes such that the heavy parasitic capacitance due to close proximity of the anode layer and the cathode layer is eliminated, hence providing a full dynamic range in sensing the changes in capacitance due to finger touches.