Liquid Crystal Display Gray-Scale Inversion via Dual Pixel Electrodes

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Solution Overview

Problem

Conventional TN mode liquid crystal displays suffer from gray-scale inversion issues, particularly in the downward direction, which deteriorate viewing angle characteristics.

Innovation Solution

The implementation of a liquid crystal display design featuring a first and second pixel electrode with different voltages, achieved through thin film transistors with distinct ON currents, which are connected to a common electrode, allowing for different liquid crystal orientation directions and widening the angle of gray-scale inversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional TN mode liquid crystal display is used, then manufacturing is simple and device complexity is low, but gray-scale inversion occurs in downward direction at about 20° viewing angle, deteriorating viewing angle characteristics

Engineering Contradiction:

Improveviewing angle characteristicsVSAvoidpixel electrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pixel electrode is divided into first and second pixel electrodes with different areas and voltages. The first pixel electrode has a first area and the second pixel electrode has a second area, creating multiple regions with different electric field strengths to control liquid crystal orientation in different viewing directions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel electrode are given different properties through varying areas and voltages. The first pixel electrode with first voltage and second pixel electrode with second voltage create local differences in electric field distribution to prevent gray-scale inversion in specific viewing angles.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If single pixel electrode with uniform voltage is used, then device structure is simple, but display quality deteriorates at downward viewing angles due to gray-scale inversion

Engineering Contradiction:

Improvedisplay qualityVSAvoidpixel electrode voltage control

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The pixel driving device dynamically controls different voltages for first and second pixel electrodes based on viewing angle requirements. The voltage drop between first and second pixel electrodes is controlled to be within a specific range to maintain display quality across different viewing angles.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The voltage parameters of pixel electrodes are changed to optimize display performance. By controlling the voltage drop between first and second pixel electrodes within a specific range and adjusting their respective voltages, gray-scale inversion is prevented in downward viewing directions.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If different ON currents are used for first and second pixel driving devices, then viewing angle characteristics are improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvegray-scale representationVSAvoidtransistor ON current control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Different ON currents are assigned to first and second pixel driving devices to create localized control over voltage distribution. This allows optimization of liquid crystal orientation in different regions to prevent gray-scale inversion while maintaining overall display quality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses partial control over transistor ON currents rather than requiring precise matching. By controlling the voltage drop to be within a specific range and using different (but not precisely matched) ON currents, the system achieves gray-scale inversion prevention without demanding extreme manufacturing precision.

Inventive Principle:

Principle #16Partial or excessive action

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 improves viewing angle characteristics by maintaining display quality beyond 20° in the downward direction, enhancing gray-scale representation and overall display performance.

Implementation Method 1

The first and second pixel electrodes having mutually different voltages cause the liquid crystal layer to have two liquid crystal orientation areas with mutually different orientation directions

Methodology Applied

Scientific EffectLiquid crystal orientation: Liquid Crystals

Data Source

PatentUS7358945B2Liquid crystal displays with improved gray-scale

Publication Date: 2008.04.15 AU OPTRONICS CORP

AI summary

A liquid crystal display with improved gray-scale display. The liquid crystal display includes a plurality of pixel areas, each including first and second substrates disposed opposite each other and a liquid crystal layer interposed therebetween. A first pixel electrode and a first pixel driving device electrically connected thereto are formed on part of the first substrate. A second pixel electrode and a second pixel driving device electrically connected thereto are formed on part of the first substrate. A common electrode is formed on the interior of the second substrate. The first and second pixel driving devices have mutually different ON currents, resulting in the first and second pixel electrodes having mutually different voltages.