Floating Gate TFT for LCD Aperture Ratio and Side Visibility

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Solution Overview

Problem

Vertically aligned mode liquid crystal display devices face challenges in maintaining high contrast ratios and wide viewing angles while experiencing deterioration in side visibility compared to front visibility.

Innovation Solution

The implementation of a liquid crystal display device with a single pixel divided into subpixels, where each subpixel receives a different voltage, utilizing a unique transistor configuration and capacitor design to control liquid crystal molecule tilt angles, thereby improving aperture ratio and side visibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a vertically aligned mode liquid crystal display device uses multiple domains with different alignment directions to widen the reference viewing angle, then the viewing angle is improved, but the side visibility deteriorates compared to front visibility

Engineering Contradiction:

Improveviewing angleVSAvoidside visibility deterioration

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The pixel electrode is divided into multiple subpixel electrodes (first subpixel electrode and second subpixel electrode) with different alignment directions. Each subpixel electrode controls a specific domain of liquid crystal molecules to tilt in different directions, enabling wide viewing angle coverage while maintaining good side visibility through coordinated voltage control of the segmented subpixels

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions (subpixels) of the pixel electrode are given different alignment characteristics and voltage control. The first subpixel electrode has liquid crystal molecules tilted in a first direction while the second subpixel electrode has molecules tilted in a second direction, allowing each local region to optimize for specific viewing angles while collectively achieving both wide viewing angle and good side visibility

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the pixel electrode is divided into multiple subpixel electrodes with different alignment directions, then side visibility is improved, but the aperture ratio may be reduced due to increased electrode structure complexity

Engineering Contradiction:

Improveside visibilityVSAvoidaperture ratio

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

Multiple subpixel electrodes with different alignment directions are merged within a single pixel structure, sharing common elements such as the liquid crystal layer and common electrode. This integration allows achieving improved side visibility through multiple domains while minimizing the increase in overall electrode structure area, thereby maintaining a reasonable aperture ratio

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of expanding the electrode structures in the planar dimension which would reduce aperture ratio, the solution utilizes the vertical dimension and molecular orientation space by tilting liquid crystal molecules in different directions (first direction and second direction) within the same pixel area. This dimensional approach allows multiple domains to coexist without proportionally increasing electrode area

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 ratio and side visibility of the liquid crystal display device by varying the voltages applied to subpixels, ensuring better image quality from both front and side perspectives.

Implementation Method 1

The liquid crystal display device generates an electric field in the liquid crystal layer by applying voltage to the field generating electrodes

Methodology Applied

Scientific EffectElectric field generation: Electric Field

Implementation Method 2

determines the direction of liquid crystal molecules of the liquid crystal layer by the generated electric field, thus controlling polarization of incident light

Methodology Applied

Scientific EffectPolarization control: Polarisation

Implementation Method 3

The electrically floating gate electrode and the drain electrode defined by the extended portion of the divided reference voltage line may form a first capacitor, and the electrically floating gate electrode and the source electrode defined by the extended portion of the terminal of the second thin film transistor may form a second capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9632376B2Liquid crystal display device including switching element with floating terminal

Publication Date: 2017.04.25 SAMSUNG DISPLAY CO LTD

AI summary

A liquid crystal display device includes: a first substrate for which a single pixel includes: first, second and third thin film transistors on the first substrate; a pixel electrode including a first subpixel electrode and a second subpixel electrode which are connected to the first thin film transistor and the second thin film transistor, respectively; and a divided reference voltage line connected to the third thin film transistor; a second substrate facing the first substrate; a common electrode on the second substrate; and a liquid crystal layer between the pixel electrode and the common electrode and including liquid crystal molecules. The third thin film transistor includes an electrically floating gate electrode, a source electrode defined by an extended portion of a terminal of the second thin film transistor, and a drain electrode defined by an extended portion of the divided reference voltage line.