IPS-LCD Common Electrode Slit Orientation for Transmittance

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Solution Overview

Problem

IPS-Pro liquid crystal display devices face a reduction in transmittance due to the 'pixel end domain' effect, where liquid crystal molecules rotate in opposing directions at the edges of pixels, leading to a black line display and decreased brightness, especially in smaller pixel formats like 3.1-inch WVGA panels.

Innovation Solution

The implementation of a liquid crystal display panel with a common electrode having a stripe structure that includes slits stretching over multiple pixels, where the slits change direction between adjacent pixels, ensuring that the rotation direction of the liquid crystal molecules is consistent across the pixel edges, preventing the formation of the pixel end domain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a stripe-patterned common electrode is disposed close to the liquid crystal layer in IPS-Pro liquid crystal display devices, then transmittance is improved and brightness is enhanced, but pixel end domain forms at the edges of pixels causing black lines and reducing overall transmittance

Engineering Contradiction:

Improvedisplay brightnessVSAvoidpixel end domain

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The common electrode is segmented into multiple independent electrode regions corresponding to each pixel, with each region having stripe patterns that are independent of adjacent pixels. This segmentation prevents the formation of pixel end domain by eliminating the continuous stripe structure that causes opposing rotation directions at pixel edges.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the common electrode are designed with different stripe pattern configurations - each pixel region has stripes oriented to produce consistent rotation direction at pixel edges. This local customization of electrode structure ensures uniform liquid crystal rotation across the entire display area while maintaining high transmittance.

Inventive Principle:

Principle #3Local quality

2Productivity

If the number of pixels is increased and areal dimensions per pixel are decreased, then pixel count is improved, but the pixel end domain effect becomes more significant and reduces transmittance

Engineering Contradiction:

Improvepixel countVSAvoidtransmittance

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The common electrode is divided into independent electrode regions for each pixel, preventing the propagation of pixel end domain effects across adjacent pixels. This segmentation allows high pixel density to be achieved without the cumulative transmittance loss that would occur with continuous stripe patterns.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure parameters are optimized for small pixel dimensions by adjusting stripe width, spacing, and orientation in each pixel region. This parameter optimization ensures that the electrode structure remains effective at higher pixel densities while eliminating the pixel end domain effect that becomes more pronounced as pixel size decreases.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively inhibits the backward rotation of liquid crystal molecules at pixel edges, eliminating the pixel end domain and enhancing transmittance, thereby improving display brightness and reducing residual images when used with touch panels.

Implementation Method 1

drives a liquid crystal layer by applying an electric field whose major components are parallel to the substrate plane (so-called lateral electric field) to the liquid crystal layer

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

Applying a voltage causes a change in the liquid crystal layer that rotates the alignment substantially within the substrate plane

Methodology Applied

Scientific EffectLiquid crystal alignment rotation: Liquid Crystals

Data Source

PatentUS8294864B2Liquid crystal display device comprising a common electrode with a plurality of slits having first and second stretching directions that differ

Publication Date: 2012.10.23 MAGNOLIA PURPLE CORP

AI summary

To solve lowering of transmittance due to a pixel end domain, provided is a liquid crystal display device, including: a liquid crystal layer; and a substrate including pixel electrodes and, a common electrode disposed between the pixel electrodes and the liquid crystal layer and having a slit which stretches over adjacent pixel electrodes, in which: the slit has a first stretching direction at a center of one pixel electrode, and a second stretching direction in a gap between two adjacent pixel electrodes, different from the first stretching direction; in the slit, a portion where the first stretching direction is switched to the second stretching direction is located on one pixel electrode; and, with respect to an alignment direction, a first azimuth toward the first stretching direction and a second azimuth toward the second stretching direction have the same rotation direction, and the second azimuth is larger than the first azimuth.