Liquid Crystal Display Capacitor Structure for High Aperture Ratio
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Solution Overview
Problem
In active matrix liquid crystal display devices using a vertical electric field mode, the presence of light-shield electrodes and wiring lines for capacitors reduces the aperture ratio and luminance due to their light-shield properties, necessitating an improvement in display quality while maintaining necessary capacitance.
Innovation Solution
The design eliminates the need for light-shield wiring lines by forming a capacitor between the pixel electrode and the common electrode via an insulation film, allowing the common electrode to extend beyond the source and gate lines, thereby increasing capacitance and reducing the thickness of the insulation film to enhance transmittance and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light-shield wiring lines and storage capacitance electrodes are provided to maintain necessary capacitance, then capacitance is secured, but aperture ratio and luminance decrease due to light-shield properties
Solution Approach 1:
The patent extracts the light-shield function from the capacitor structure by eliminating the need for light-shield wiring lines. The capacitor is formed using only transparent electrodes (pixel electrode and common electrode) separated by an insulation film, removing the harmful light-shield elements while maintaining capacitance functionality.
Solution Approach 2:
The insulation film serves multiple functions: it acts as both the dielectric layer for capacitance and the light-shield barrier. The transparent electrodes serve dual purposes as both capacitive elements and light-transmitting components, eliminating the need for separate light-shield wiring lines.
2Reliability
If light-shield wiring lines are used for capacitors, then capacitance is maintained, but aperture ratio decreases
Solution Approach 1:
The patent removes the light-shield wiring lines that occupied pixel area, extracting the light-shield function from the capacitor structure. The capacitor is formed using only transparent components, allowing the entire pixel area to contribute to light transmission while maintaining capacitance.
Solution Approach 2:
The patent changes the material property of the capacitor components from light-shield materials to transparent materials. By using transparent electrodes and insulation films, the optical properties are improved while maintaining the electrical capacitance function.
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 improves the aperture ratio, transmittance, and luminance per pixel, while maintaining the necessary capacitance for image display, and reduces fabrication costs and the risk of electrostatic breakdown.
Implementation Method 1
liquid crystal molecules are switched by an electric field which is produced between a pixel electrode formed on an array substrate, and a common electrode formed on a counter-substrate
Implementation Method 2
liquid crystal molecules are switched by an electric field
Implementation Method 3
A capacitor functions to retain a voltage, which is applied to a liquid crystal layer, for a predetermined time period
Data Source
AI summary
According to one embodiment, a liquid crystal display device includes a first interlayer insulation film located above a first gate line and a second gate line, a first common electrode extending over the first interlayer insulation film, a second interlayer insulation film covering the first common electrode, and a first pixel electrode disposed on the second interlayer insulation film. The first common electrode extends, from a position opposed to the first pixel electrode, beyond the source line in the first direction and beyond the gate line in the second direction.