Transflective Display Contrast via Reflection Preventing Means

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Solution Overview

Problem

Transflective liquid crystal displays with twisted nematic polymer layers suffer from poor contrast in the dark state due to light reflections from the rear side of the transflector, which degrades the black state and reduces display contrast in transmissive mode.

Innovation Solution

Incorporating a reflection preventing means, such as a light absorbing layer or anti-reflection coating, between the transflector and the twisted nematic polymer layer to prevent light with reversed polarization from being transmitted back to the polymer layer, thereby enhancing contrast in the dark state without affecting the reflective mode performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a twisted nematic polymer layer is used to provide circular polarization and improve light transmission, then transmission ratio is improved, but contrast in the dark state deteriorates due to light reflections from the rear side of the transflector

Engineering Contradiction:

Improvelight transmission ratioVSAvoidcontrast in dark state

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful light reflections that degrade the dark state into a beneficial configuration by adding a reflection preventing means. This means the reflected light is redirected or absorbed constructively, transforming the harmful reflection into a controlled optical path that no longer degrades image quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces a reflection preventing means as an intermediary element between the transflector and the twisted nematic polymer layer. This intermediary component manages the reflected light by redirecting it through the liquid crystal layer, preventing it from directly degrading the dark state while maintaining the polarization benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a linear polarizer and quarter-wave retarder are used to transform light to circular polarization, then polarization accuracy is improved, but transmission ratio deteriorates due to absorption of wrong polarization light

Engineering Contradiction:

Improvepolarization accuracyVSAvoidlight transmission ratio

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent changes the polarization mechanism from using a linear polarizer with quarter-wave retarder to using a twisted nematic polymer layer. This parameter change in the optical system achieves circular polarization through the twisted structure of the polymer layer, which allows 50% of the light to pass through while maintaining accurate polarization, thereby improving transmission ratio.

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

The reflection preventing means effectively eliminates light reflections that degrade the black state, resulting in improved contrast in the transmissive mode by ensuring that only correctly polarized light is transmitted through the transflector, thus enhancing display performance.

Implementation Method 1

a rear stack polarizing means (302) which is transmissive for light having a desired polarization and reflective for light having an opposite, undesired polarization

Methodology Applied

Scientific EffectOptical rotation: Polarisation

Implementation Method 2

a transflector (301) arranged between the backlight and the rear stack polarizing means, and being transmissive for a first part of light emitted by the backlight and non-transmissive for a second part of light emitted by the backlight

Methodology Applied

Scientific EffectPolarization-dependent reflection: Reflection

Implementation Method 3

reflection preventing means (306) arranged between the transflector and the twisted nematic polymer layer and being operative to prevent the second part of light from propagating back towards the twisted nematic polymer layer

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS7760296B2Transflective display having improved contrast

Publication Date: 2010.07.20 INNOLUX CORP

AI summary

The present invention provides for improved contrast in the transmissive mode of a transflective liquid crystal display having a rear stack polarizing means (302) which is transmissive for light having a desired polarization and reflective for light having an opposite, undesired polarization. The contrast is improved due to enhancements of the black state provided by the inclusion of a reflection preventing means (306). The reflection preventing means is arranged between the transflector (301) and the rear stack polarizer (302), and serves to stop light transmitted through the rear stack polarizer (302) towards the transflector (301) from being reflected by the transflector (301) back to the rear polarizer (302). Thereby undesired reflections having wrong polarization are stopped from being transmitted through the transflector (301) and thus from affecting the transmissive mode black state of the display.