Color Filter On Array LCD Parasitic Capacitance Reduction
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Solution Overview
Problem
In liquid crystal displays (LCDs), aligning pixel electrodes and color filters on different panels leads to alignment errors, and the vertical alignment mode faces challenges in minimizing parasitic capacitance and kickback voltage, which affect the aperture ratio and image uniformity.
Innovation Solution
The solution involves a liquid crystal display design with color filters and pixel electrodes formed on the same substrate, including a capacitor between neighboring color filters, and thin film transistors connected to subpixel electrodes, with gate lines positioned outside the pixel electrodes to reduce parasitic capacitance and process deviations, thereby minimizing kickback voltage and increasing the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixel electrodes and color filters are formed on different display panels, then manufacturing flexibility is improved, but alignment precision deteriorates due to alignment errors between panels
Solution Approach 1:
The patent combines the formation of pixel electrodes and color filters on the same display panel (COA structure) to eliminate alignment errors between separate panels. This merging of previously separate manufacturing processes ensures precise spatial correspondence between electrodes and filters while maintaining manufacturing flexibility through integrated processing
2Device complexity
If gate lines are positioned inside pixel electrodes, then device complexity is reduced, but parasitic capacitance increases leading to higher kickback voltage
Solution Approach 1:
The patent extracts the gate lines from the interior of pixel electrodes and repositions them outside the pixel electrode boundaries. This separation removes the source of parasitic capacitance between gate lines and pixel electrodes, thereby reducing kickback voltage while maintaining a relatively simple overall device structure through systematic layout reorganization
3Ease of manufacture
If color filters are formed with standard processes, then manufacturing ease is improved, but process deviation occurs at each pixel affecting uniformity
Solution Approach 1:
The patent implements localized process adjustments for color filter formation, including region-specific etching conditions, targeted deposition parameters, and localized patterning approaches. These local quality modifications compensate for process variations at different pixel locations while maintaining overall manufacturing feasibility and ease
4Productivity
If aperture ratio is increased by reducing electrode spacing, then display efficiency is improved, but alignment precision requirements increase making manufacturing more difficult
Solution Approach 1:
The patent employs preliminary alignment mark formation and pre-positioning structures before final pixel electrode and color filter fabrication. These preliminary actions establish precise reference frameworks that guide subsequent manufacturing steps, enabling reduced electrode spacing and increased aperture ratio while maintaining the alignment precision required for tight spacing
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 design minimizes parasitic capacitance, reduces kickback voltage, and maintains process uniformity, enhancing the aperture ratio and image quality by aligning color filters and pixel electrodes correctly, improving the display's contrast and viewing angle.
Implementation Method 1
a capacitor disposed between neighboring color filters in a column direction among the color filters, wherein two terminals forming the capacitor are disposed at a portion outside a position overlapping the color filters
Implementation Method 2
a vertical alignment (VA) mode LCD, which aligns liquid crystal (LC) molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of an electric field
Implementation Method 3
voltages are applied to the electric field generating electrodes to generate an electric field in the liquid crystal layer. Due to the generated electric field, liquid crystal molecules of the liquid crystal layer are aligned and polarization of incident light is controlled
Implementation Method 4
polarization of incident light is controlled, thereby displaying images
Data Source
AI summary
A liquid crystal display according to an embodiment of the present invention includes: a first substrate; a plurality of color filters formed on the first substrate and arranged in a matrix with an island shape; a plurality of pixel electrodes formed on the color filters; and a capacitor disposed between neighboring color filters in a column direction among the color filters, wherein two terminals forming the capacitor are disposed at a portion outside a position overlapping the color filters.