Single-Gap Transflective LCD Voltage Control

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Solution Overview

Problem

Single-gap transflective LCDs suffer from inversion issues where transmittance and reflectance do not peak in the same voltage range, while dual-gap designs have complex manufacturing processes and lower production yields.

Innovation Solution

A single-gap transflective LCD design that uses different applied voltages in transmission and reflection areas to alter the optical characteristics of the liquid crystal layer, allowing it to function as a half-wave plate in one state and a quarter-wave plate in another, without the need for additional wave plates, and potentially using a dielectric layer to reduce voltage across the reflection area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single-gap structure is used in transflective LCD, then the manufacturing process is simplified, but transmittance and reflectance do not reach peak values in the same voltage range causing inversion

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidoptical performance consistency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies different voltage potentials to different regions of the liquid crystal layer: a first voltage potential to the transmission area and a second voltage potential to the reflection area. This local differentiation allows each region to be optimized independently - the transmission area operates at higher voltage for maximum transmittance while the reflection area operates at lower voltage for maximum reflectance, eliminating the inversion problem without requiring different gap thicknesses

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the electrical parameter (voltage potential) applied to different regions of the liquid crystal layer. By applying a first voltage potential in the transmission area and a second voltage potential in the reflection area, the patent achieves different optical characteristics in each region using the same physical gap thickness, thereby simplifying manufacturing while maintaining optimal optical performance

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a dual-gap design is used in transflective LCD, then transmittance and reflectance are more consistent, but the manufacturing process becomes complex and production yield decreases

Engineering Contradiction:

Improveoptical performance consistencyVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of creating different physical gap thicknesses (dual-gap), the patent applies different voltage potentials to different regions. The transmission area receives a first voltage potential and the reflection area receives a second voltage potential, allowing each region to achieve its optimal optical state with the same uniform gap thickness, thereby simplifying manufacturing while maintaining optical consistency

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent replaces the mechanical approach of dual-gap design (different physical thicknesses) with an electrical approach (different voltage potentials). This substitution eliminates the need for complex gap control mechanisms while achieving the same optical performance benefits, significantly simplifying the manufacturing process

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Achieves matching transmittance and reflectance in both areas, simplifying manufacturing and improving optical performance comparable to dual-gap designs without the complexity of gap control.

Implementation Method 1

the liquid crystal layer 190 is used as a half-wave plate to change the linear polarization axis of the traversing light

Methodology Applied

Scientific EffectLiquid crystal polarization modulation: Liquid Crystals

Implementation Method 2

the liquid crystal layer 190 acts like a half-wave plate in both the transmission area and the reflection area

Methodology Applied

Scientific EffectWave plate effect: Birefringence

Implementation Method 3

light encountering the reflection area goes through the upper layer structure and the liquid crystal layer before it is reflected by a reflective electrode 160

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS7379138B2Transflective liquid crystal display having first and second voltage potentials selected to achieve predetermined polarization states for light encountering respectively the transmissive and reflective areas

Publication Date: 2008.05.27 OPTRONIC SCIENCES LLC

AI summary

In a transflective LCD, it is possible to cause the change in the optical characteristics of the liquid crystal layer in the transmission area between operating states to be different from the change in the optical characteristics of the liquid crystal layer in the reflection area by using different applied voltages in the transmission and reflection areas. In the first operating state, the liquid crystal layer in the transmission area and the liquid crystal layer in the reflection area are used as a half-wave plate to change the linear polarization axis of the traversing light. In the second operating state, the liquid crystal layer in the transmission area does not affect the polarization axis of the traversing light, but the liquid crystal layer in the reflection area is used as a quarter-wave plate. As such, no additional half-wave plates and quarter-wave plates are needed.