Display Device Scan Line Routing to Reduce Parasitic Capacitance
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Solution Overview
Problem
In organic EL display devices, parasitic capacitance interferes with the bootstrapping action, leading to reduced light emission brightness and deteriorated image quality due to uneven brightness across pixels.
Innovation Solution
The display device is designed with a pixel array section that includes write and correction scan lines, where the write scan line and light emission control scan line do not intersect with the wiring pattern connected to the gate electrode of the drive transistor, minimizing parasitic capacitance and ensuring a bootstrap gain close to unity, thereby securing appropriate drive current for the organic EL element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If scan lines are routed through the pixel array to provide write and light emission control signals, then the display device can be driven with active matrix control, but parasitic capacitance is introduced at the gate electrode of the drive transistor, reducing bootstrap gain and light emission brightness
Solution Approach 1:
The scan line routing is segmented into separate paths: one path goes above the pixel array and another path goes below the pixel array. This segmentation prevents the scan lines from passing through the pixel array, thereby eliminating parasitic capacitance at the drive transistor gate electrode while still enabling active matrix control functionality.
Solution Approach 2:
Insulating films are introduced as intermediary layers between the scan lines and the drive transistor gate electrode. These insulating films act as mediators that prevent direct electrical interaction, thereby reducing parasitic capacitance while allowing the scan lines to maintain their control functions.
2Manufacturing precision
If more scan lines are added to increase display resolution, then image quality improves, but parasitic capacitance increases, reducing bootstrap gain and causing uneven brightness
Solution Approach 1:
By segmenting the scan line routing to go above and below the pixel array rather than through it, the design allows for increased display resolution with more scan lines without introducing additional parasitic capacitance at the drive transistor gate electrode, thereby maintaining brightness uniformity across the display.
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 suppresses the reduction of light emission brightness caused by parasitic capacitance, resulting in improved image quality with uniform brightness across the display.
Implementation Method 1
An organic EL element is a type of current-driven electro-optical element whose light emission brightness changes according to the current flowing through the element. This type of element relies on the phenomenon that an organic thin film emits light when applied with an electric field.
Data Source
AI summary
A display device includes a pixel array section, the pixel array section having pixels arranged in a matrix form, at least one of the pixels including an electro-optical element, a write transistor, a capacitor, a drive transistor, and a switching transistor. A write scan line is disposed for each pixel row of the pixel array section and adapted to convey a write signal to be applied to a gate electrode of the write transistor. The wiring structure of the write scan line does not cross a wiring pattern connected to a gate electrode of the drive transistor.