Organic EL Display Pixel Circuit with Broken Conductive Paths

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Solution Overview

Problem

Active matrix displays using organic electroluminescent (EL) technology suffer from image quality deterioration due to luminance unevenness caused by variations in drive current, leading to the formation of luminous or dark line-like tails in images, which are not effectively addressed by existing technologies.

Innovation Solution

The solution involves an organic EL display with pixels that include a drive control element, an organic EL element, and an output control switch, where specific conductive paths connecting the first electrode to the power supply and the video signal line are intentionally broken using a laser beam to prevent the formation of luminous or dark line-like tails by ensuring consistent drive current and reducing the influence of short circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a current signal is written as a video signal in a pixel circuit, then the drive current can be controlled to eliminate threshold value and mobility variations, but luminous or dark line-like tails appear in the image due to disconnections or short circuits

Engineering Contradiction:

Improvedrive current consistencyVSAvoidluminous or dark line-like tails

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by intentionally breaking conductive paths during the manufacturing process before the display is put into service. Specifically, conductive paths connecting video signal lines to pixels in non-display regions are broken to prevent short circuits that would cause luminous or dark line-like tails, while maintaining proper connections in display regions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the conductive paths into different regions: display regions where connections are maintained for proper pixel operation, and non-display regions where connections are broken to prevent harmful effects. This spatial segmentation allows the system to achieve both drive current consistency and eliminate line-like defects

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If conductive paths are broken in non-display regions, then the formation of luminous or dark line-like tails is prevented, but manufacturing complexity increases due to additional laser processing steps

Engineering Contradiction:

Improveluminous or dark line-like tailsVSAvoidmanufacturing process

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical or manual methods of preventing short circuits with a laser-based approach. The laser beam precisely breaks conductive paths in non-display regions, providing a clean and controllable method that is more efficient than manual intervention while achieving the desired isolation effect

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the potential harm of incomplete manufacturing or unintended short circuits into a benefit by intentionally creating controlled breaks in non-display regions. This deliberate action prevents the formation of luminous or dark line-like tails, turning a potential defect source into a protective measure

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 approach effectively prevents the appearance of luminous or dark line-like tails in images by ensuring consistent luminance across pixels, thereby improving image quality by breaking conductive paths in specific pixels to eliminate the impact of short circuits and variations in drive current.

Implementation Method 1

specific conductive paths connecting the first electrode to the power supply and the video signal line are intentionally broken using a laser beam

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS7944413B2Organic EL display

Publication Date: 2011.05.17 MAGNOLIA WHITE CORP

AI summary

An organic EL display includes plural pixels, each including a drive control element, an organic EL element and an output control switch. The drive control element includes a control terminal, a first terminal connected to a first power supply terminal, and a second terminal outputting a current with a magnitude corresponding to a voltage between the control terminal and the first terminal. The organic EL element includes a first electrode, a second electrode connected to a second power supply terminal, and an active layer interposed between the first and second electrodes. The output control switch is connected between the second terminal and the first electrode. In a part of the pixels, a conductive path electrically connecting the first electrode to the first power supply terminal is broken at a portion which connects the output control switch to the first electrode.