IPS LCD Common Electrode Shielding for Higher Aperture
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Solution Overview
Problem
In IPS liquid crystal display devices, the high electrode area ratio and lateral electric field drive lead to low aperture factor and longitudinal crosstalk due to the comb-teeth arrangement of pixel and common electrodes, with existing solutions either increasing cost or compromising aperture factor improvement.
Innovation Solution
A liquid crystal display device with a bank-like insulating film on the video signal line covered by the common electrode and a light shield electrode underneath, which is not electrically connected to other electrodes, to reduce the extension of the common electrode and minimize aperture factor reduction while effectively shielding electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the video signal line is perfectly covered by the common electrode via insulating films, then the aperture factor is improved and longitudinal crosstalk is reduced, but the extension of the common electrode increases causing load capacity problems
Solution Approach 1:
The insulating film structure is segmented into two parts: a first insulating film covering the video signal line and a second insulating film covering the pixel electrode, source electrode, and drain electrode. This segmentation allows the common electrode to extend only over the first insulating film rather than covering the entire display area, improving aperture factor while reducing load capacity.
Solution Approach 2:
The second insulating film is selectively formed only in regions where pixel electrodes and control electrodes are located, not across the entire display area. This local quality approach allows the common electrode to be present only where needed for shielding, reducing unnecessary extension and load capacity while maintaining shielding effectiveness in critical areas.
2Object-affected harmful factors
If the common electrode is extended to cover the video signal line for shielding, then longitudinal crosstalk is reduced, but the electrode area ratio increases reducing aperture factor
Solution Approach 1:
The insulating film system is divided into a first insulating film that extends across the video signal line region and a second insulating film that is localized to pixel electrode regions. This segmentation enables the common electrode to provide shielding where needed while minimizing its presence in display areas, thus reducing longitudinal crosstalk without significantly compromising aperture factor.
Solution Approach 2:
The first insulating film acts as an intermediary structure that allows the common electrode to shield the video signal line from longitudinal crosstalk while preventing direct contact between the common electrode and the video signal line. This intermediary approach enables effective shielding with minimal impact on aperture factor.
3Ease of manufacture
If transparent insulating film is coated on the entire surface, then manufacturing is simplified, but aperture factor is reduced due to non-transparent regions
Solution Approach 1:
The insulating film coating process is segmented into two distinct steps: first forming a first insulating film across the entire surface including the video signal line region, then forming a second insulating film selectively in pixel electrode regions. This segmented approach maintains manufacturing simplicity while avoiding the need for a continuous transparent insulating film across the entire display area, thereby preserving aperture factor.
Solution Approach 2:
Instead of coating the insulating film across the entire surface, the second insulating film is applied partially only where pixel electrodes and control electrodes are located. This partial action approach maintains ease of manufacture through simple coating processes while maximizing aperture factor by leaving display areas uncovered.
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 enhances the aperture factor and reduces longitudinal crosstalk while maintaining low drive voltage and cost-effectiveness, and minimizes light leakage and contrast reduction during black display.
Implementation Method 1
a light shield electrode which is not electrically connected to any other signal electrode
Implementation Method 2
a substantially bank-like insulating film is formed on the video signal line and covered by the common electrode
Implementation Method 3
a liquid crystal layer sandwiched between the first and second substrates
Implementation Method 4
pixels each being formed in each of the areas defined on the first substrate by the scanning signal lines and the video signal lines, pixel electrodes each being connected to the thin film transistor corresponding to each pixel, a common electrode being provided to provide a reference potential
Data Source
AI summary
An active matrix type liquid crystal display device in the lateral electric field system is disclosed, in which a high aperture factor is ensured even in a narrow pitch case, while also ensuring high contract and reduced vertical stroke is disclosed. In a liquid crystal display device, in which substantially bank-like third insulating film 208 is formed a video signal line 204 and covered by a common electrode 210, a light shield electrode 213 is formed underneath an extension of a common electrode 210 from an edge of a video signal line 204. With this arrangement, a liquid crystal display device is realized, which shields light from the sides of a step part as well as ensuring high aperture factor and high contrast.