OLED Touch Electrode Groove Design Reduces Parasitic Capacitance

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Solution Overview

Problem

The touch report rate of flexible active-matrix organic light-emitting diode (AMOLED) on-cell display screens is low due to a short distance between touch electrodes and the cathode, resulting in significant parasitic capacitance and a decreased scanning frequency.

Innovation Solution

The OLED display panel incorporates a design with grooves in the pixel definition layer, increasing the distance between the common electrodes and touch electrodes, which reduces parasitic capacitance by varying the thickness of the encapsulation layer within these grooves, thereby enhancing touch report rate and sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If touch electrodes are fabricated directly on the film encapsulation layer, then the device structure is simple, but the parasitic capacitance between touch electrodes and cathode becomes large

Engineering Contradiction:

Improvedevice structureVSAvoidparasitic capacitance

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces grooves in the pixel definition layer to create vertical depth dimension, transforming the flat two-dimensional structure into a three-dimensional structure. This increases the distance between touch electrodes and common electrode by utilizing the vertical dimension, thereby reducing parasitic capacitance without complicating the overall device structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The pixel definition layer with grooves acts as an intermediary structure between the touch electrodes and the common electrode. This intermediate layer with varying thickness (thinner at groove bottoms, thicker elsewhere) serves as a spacer that increases the distance between the touch electrodes and common electrode, reducing parasitic capacitance while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Length of stationary object

If the film encapsulation layer is made thin, then the device thickness is reduced, but the distance between touch electrodes and cathode becomes short

Engineering Contradiction:

Improvedevice thicknessVSAvoiddistance between touch electrodes and cathode

Core Design Contradiction:

Length of stationary objectVSLength of moving object

Solution Approach 1:

Instead of increasing the horizontal distance between electrodes, the patent utilizes the vertical dimension by creating grooves in the pixel definition layer. The varying thickness of the encapsulation layer over the grooves (thinner at groove bottoms, thicker elsewhere) creates vertical spacing that increases the effective distance between touch electrodes and common electrode while maintaining thin overall device thickness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The encapsulation layer is designed with non-uniform thickness: thinner portions over the groove bottoms and thicker portions elsewhere. This local variation in thickness allows the device to maintain thin overall profile while creating specific regions with increased distance between electrodes to reduce parasitic capacitance.

Inventive Principle:

Principle #3Local quality

3Productivity

If parasitic capacitance is reduced by increasing distance between electrodes, then touch report rate improves, but the current-limiting resistor delay increases

Engineering Contradiction:

Improvetouch report rateVSAvoidresistor delay

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent changes the geometric parameters of the pixel definition layer by introducing grooves with specific depths and widths. This modifies the capacitance parameters of the system, reducing parasitic capacitance between touch electrodes and common electrode. By adjusting the groove dimensions, the patent optimizes the balance between reducing parasitic capacitance (improving touch report rate) and maintaining acceptable signal transmission characteristics.

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

This design effectively increases the touch report rate and sensitivity by reducing parasitic capacitance between the common electrodes and touch electrodes, improving the overall performance of the OLED display panel.

Implementation Method 1

a distance between the touch electrodes and a cathode is short and a parasitic capacitance between the touch electrodes and the cathode is large

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS11532677B2OLED display panel reducing parasitic capacitance between common electrodes and touch electrodes and display device

Publication Date: 2022.12.20 WUHAN CHINA STAR OPTOELECTRONICS SEMICONDUCTOR DISPLAY TECHNOLOGY CO LTD

AI summary

The present disclosure provides an organic light emitting diode (OLED) display panel and a display device. The OLED display panel includes a substrate, a driving circuit layer, a planarization layer, a luminescent functional layer, an encapsulation layer, and a touch layer including touch electrodes. The luminescent functional layer includes a pixel electrode layer, a pixel definition layer, a luminescent material layer, and a common electrode layer. The pixel definition layer is patterned to form pixel definition regions and grooves. Projections of the touch electrodes on the substrate and projections of the grooves on the substrate are at least partially overlapped, thereby improving a touch report rate of the OLED display panel.