Display Panel Sub-Pixel TFT Width-to-Length Ratio Adjustment

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Solution Overview

Problem

In OLED display panels, the uneven current distribution caused by load and storage capacitors in sub-pixel circuits leads to varying brightness across the panel, especially noticeable in larger displays and at low grayscale levels, affecting overall display quality.

Innovation Solution

The display panel is designed with sub-pixel regions arranged along a scan line, where each driving TFT's channel region has a progressively smaller width-to-length ratio from the signal input to the output end, ensuring uniform current distribution and brightness across the panel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If load capacitor and storage capacitor are used in sub-pixel circuit, then current magnitude increases from left to right, but brightness uniformity deteriorates

Engineering Contradiction:

Improvecurrent magnitudeVSAvoidbrightness uniformity

Core Design Contradiction:

PowerVSIllumination intensity

Solution Approach 1:

The patent applies local quality by dividing the display panel into multiple sub-pixel regions and assigning different width-to-length ratios to driving TFTs in different regions. Specifically, TFTs closer to the signal input end have larger width-to-length ratios while those farther away have smaller ratios, creating localized adjustments that compensate for the cumulative RC effect and achieve uniform brightness across the entire panel.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If display panel size increases, then resolution and area improve, but brightness uniformity deteriorates

Engineering Contradiction:

Improvedisplay panel areaVSAvoidbrightness uniformity

Core Design Contradiction:

Area of stationary objectVSIllumination intensity

Solution Approach 1:

The patent segments the display panel into multiple sub-pixel regions along the scan line direction. Each region contains sub-pixels with driving TFTs having specific width-to-length ratios. This segmentation allows independent optimization of TFT parameters in different regions, enabling the panel to maintain brightness uniformity even as the overall panel size increases.

Inventive Principle:

Principle #1Segmentation

3Use of energy by moving object

If grayscale level decreases, then power consumption reduces, but current magnitude difference deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidcurrent magnitude uniformity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent changes the physical parameters of the driving TFTs by adjusting their width-to-length ratios across different sub-pixel regions. This parameter modification compensates for the increased RC effect that occurs at low grayscale levels, maintaining current magnitude uniformity even when power consumption is reduced.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11296168B2Display panel comprising at least three sub-pixel regions for each sub-pixel and display device having the same

Publication Date: 2022.04.05 SHENZHEN CHINA STAR OPTOELECTRONICS SEMICON DISPLAY TECH CO LTD

AI summary

The present invention provides a display panel. The display panel includes at least three sub-pixel regions. The sub-pixel regions are arranged along a direction of a scan line. A channel region of each driving TFT in the same sub-pixel region has a same width-to-length ratio. Along a direction from a signal input end to a signal output end of the scan line, the width-to-length ratio of the channel region of each driving TFT of any of the sub-pixel regions is smaller than that of a previous one of the sub-pixel regions.