OLED Pixel Circuit Redundancy for Dark Dot Defect Mitigation
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Solution Overview
Problem
Display devices using OLEDs are susceptible to dark dot defects caused by dust during the manufacturing process, which affects display quality and increases production costs, particularly due to the adherence of organic thin films to deposition devices and potential short circuits between electrodes.
Innovation Solution
A pixel circuit configuration is implemented where the specific color pixel, susceptible to dark dots or with the highest relative luminosity factor, has more sets of pixel circuit elements, including drive transistors, holding capacitors, and light-emitting elements, and a multi-layered film structure with a thinner organic thin film stack to minimize the impact of defects, while maintaining pixel area efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLEDs are manufactured with multi-layered organic thin films, then light emission characteristics are improved, but dust adherence during deposition increases causing dark dot defects
Solution Approach 1:
The pixel circuit is divided into multiple independent sets, each capable of functioning autonomously. When dust causes a dark dot defect in one set, other sets remain operational, segmenting the impact of defects and maintaining overall display reliability.
Solution Approach 2:
The patent implements redundant pixel circuit sets as a preventive measure against dust-induced defects. This cushioning approach ensures that even if some sets fail during or after manufacturing, the display maintains acceptable quality without requiring rework or scrapping the entire panel.
2Reliability
If the number of pixel circuit elements is increased to suppress dark dot defects, then display quality is improved, but pixel area increases
Solution Approach 1:
Multiple pixel circuit sets are merged into a single logical pixel unit, sharing common structure elements such as the lower electrode, organic thin films, and upper electrode. This combining approach achieves defect suppression through redundancy while avoiding proportional increases in pixel area.
Solution Approach 2:
The common structure elements serve multiple functions: they provide electrical connections for all sets, act as structural support, and reduce the overall pixel area by eliminating redundant components. The lower electrode and upper electrode, for example, serve all pixel circuit sets within the unit.
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 effectively suppresses the impact of dark dot defects on screen display without increasing pixel area, ensuring improved display quality and reduced production costs by distributing the risk of defects across multiple light-emitting elements.
Implementation Method 1
An OLED is an electro-optical element that takes advantage of light emission as a result of application of an electric field to the organic thin films
Data Source
AI summary
A display device according to the present invention includes pixel units. Each of the pixel units is made up of N consecutive pixels. One of N (N≧3) colors including R (red), G (green) and B (blue) is assigned to each of the N pixels. Each of the N pixels includes a sampling transistor Ms, drive transistor Md, holding capacitor Cs and light-emitting element (organic light-emitting diode OLED). Of the N pixels, a specific color pixel that is susceptible to a dark dot (e.g., B) or that has the highest relative luminosity factor (e.g., G) has more sets of pixel circuit elements including the drive transistor Md, holding capacitor Cs and organic light-emitting diode OLED than other color pixels and has two or more sets thereof.