Capacitor Line Structure for Liquid Crystal Device Aperture Ratio
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Solution Overview
Problem
In liquid crystal devices, forming a storage capacitor with sufficient capacitance often degrades the quality of the display image due to the need for a wide capacitor line, which reduces the aperture ratio and affects display light transmission, particularly in VA and IPS modes.
Innovation Solution
The solution involves a capacitor line structure with a first portion extending parallel to the scanning line and a second portion overlapping cutouts or bent portions between sub-pixel electrodes, allowing for sufficient capacitance without decreasing display light emission, and optionally a third portion connecting these, to maintain high image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitor line width is increased to provide sufficient capacitance for the storage capacitor, then the capacitance value is improved, but the aperture ratio decreases and display light transmission is reduced
Solution Approach 1:
The capacitor line is extended in the vertical direction (along the scanning line) to increase capacitance, rather than expanding horizontally which would reduce aperture ratio. The first capacitor line portion extends parallel to the scanning line, utilizing the vertical dimension to accumulate sufficient capacitance while preserving horizontal aperture space for light transmission.
Solution Approach 2:
The capacitor line is divided into multiple portions: a first capacitor line portion extending parallel to the scanning line, and a second capacitor line portion overlapping the cutout region. This segmentation allows the capacitor line to occupy non-display areas while maintaining sufficient total capacitance without compromising the aperture ratio in the display region.
2Reliability
If the capacitor line width is increased to reduce resistance, then the resistance is reduced, but the aperture ratio and display quality are degraded
Solution Approach 1:
The capacitor line length is increased in the vertical dimension (parallel to scanning line direction) to reduce resistance, rather than increasing width horizontally. The extended first capacitor line portion provides a longer conductive path that compensates for resistance while maintaining a narrow profile that preserves aperture ratio.
Solution Approach 2:
The capacitor line is segmented into multiple portions that collectively provide sufficient conductive path length for low resistance. The first and second capacitor line portions work together to achieve adequate current flow capacity without requiring a wide single continuous line that would reduce aperture ratio.
3Manufacturing precision
If the pixel electrode is divided into sub-pixel electrodes to control liquid crystal alignment, then the alignment control is improved, but domain regions are created where display light is reduced
Solution Approach 1:
The cutout regions between sub-pixel electrodes, which create domain regions that reduce display light, are utilized as locations for the second capacitor line portion. This converts the harmful effect of domain regions into a beneficial use of otherwise wasted space for capacitance, without further reducing display light since these regions already do not contribute to display.
Data Source
AI summary
A liquid crystal device have an element substrate including a scanning line, a data line and a pixel electrode, a cutout is formed on the pixel electrode. A capacitor line for providing a storage capacitor is formed on the element substrate. The capacitor line has a first and second portions. The first portion extends along with the scanning line, and a second line portion overlaps the cutout of the pixel electrode.