Electro-optical Device Substrate Storage Capacitor Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrophoretic display devices face challenges in achieving high precision pixels with sufficient storage capacitance, leading to display unevenness and increased energy consumption due to the difficulty in designing storage capacitors that do not interfere with scanning lines and gate insulation films, which affects the performance of thin-film transistors (TFTs).
Innovation Solution
The design of an electro-optical device substrate with a storage capacitor configuration where the storage capacitor electrode is formed in the same layer as the source and drain electrodes of the pixel switching element, allowing independent setting of film thickness and inductive capacity, and the use of overlapping storage capacitors to increase capacitance without occupying more space, thereby reducing leakage current and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the storage capacitor is formed with the capacitor lower electrode in the same layer as the scanning line, then the storage capacitance can be increased, but the risk of short circuit between the scanning line and capacitor lower electrode increases
Solution Approach 1:
The patent transitions from planar capacitor configuration to three-dimensional overlapping structure. The capacitor lower electrode and upper electrode are positioned in different layers with vertical separation, allowing sufficient capacitance without lateral expansion that would cause short circuits with scanning lines.
Solution Approach 2:
The capacitor is divided into two separate electrodes (lower and upper) positioned in different layers, with the gate insulation film forming the capacitor insulation. This segmentation allows independent positioning of each electrode to avoid short circuits while maintaining capacitance.
2Reliability
If the pixel size is increased to prevent short circuit between scanning line and capacitor lower electrode, then short circuit prevention is improved, but the manufacturing precision of high precision pixels deteriorates
Solution Approach 1:
By moving the capacitor structure to three-dimensional overlapping configuration in vertical layers, the patent eliminates the need for lateral spacing between capacitor electrodes and scanning lines, thereby maintaining pixel precision without compromising short circuit prevention.
3Quantity of substance
If the capacitor insulation film is made thin or high specific inductive capacity material is used to increase storage capacitance, then the storage capacitance is improved, but the leakage current of TFT increases
Solution Approach 1:
The patent extracts the capacitor insulation function from the gate insulation film by using the gate insulation film itself as the capacitor insulation. This allows the gate insulation film to be optimized for TFT performance (thicker, lower leakage) while the capacitor achieves sufficient capacitance through the overlapping electrode structure.
4Reliability
If the storage capacitance is insufficient, then the feed-through voltage increases and display unevenness occurs, but increasing the capacitance requires more space that compromises pixel precision
Solution Approach 1:
The overlapping electrode configuration in vertical layers provides sufficient storage capacitance to reduce feed-through voltage and eliminate display unevenness, while the compact three-dimensional structure maintains pixel precision by avoiding lateral expansion.
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 enables reliable suppression of display unevenness and reduced energy consumption by maintaining pixel potential effectively, allowing for high precision pixels with sufficient capacitance without compromising TFT characteristics.
Implementation Method 1
a first storage insulation film formed of a second insulation film so as to cover at least the first storage capacitor electrode, and a second storage insulation film formed of a third insulation film so as to cover at least the second storage capacitor electrode
Implementation Method 2
using a material with a high specific inductive capacity in a capacitor insulation film
Implementation Method 3
the pixel electrode formed so as to overlap with the first storage capacitor electrode at least partially with the first storage insulation film interposed therebetween
Data Source
AI summary
In an electro-optical device substrate, first and second pixel switching elements each include a gate electrode formed of a first conductive film, a gate insulation film formed of a first insulation film, a semiconductor layer, a source electrode formed of a second conductive film, and a drain electrode formed of the second conductive film. A first storage capacitor includes a first storage capacitor electrode formed of the second conductive film, a protective film formed of a second insulation film so as to over at least the first storage capacitor electrode, and a pixel electrode formed so as to overlap with the first storage capacitor electrode at least partially with the protective film interposed therebetween.