Backlight Module with Circular Polarization for Double-Sided Display

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Solution Overview

Problem

Existing double-sided liquid crystal display devices suffer from poor light utilization due to absorption of linearly polarized light by polarizers, leading to reduced efficiency in the backlight module.

Innovation Solution

A backlight module design featuring a light emitting component with opposing light exit surfaces, each equipped with liquid crystal brightness enhancement films and quarter-wave plates, where the rotation structures of these films are symmetrical and grooves with triangular cross-sections are used to redirect light, minimizing reflection loss and enhancing light utilization efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a common backlight module structure with polarizers is used in double-sided liquid crystal display devices, then the device can achieve double-sided display function, but the light utilization efficiency is poor due to absorption of linearly polarized light by polarizers

Engineering Contradiction:

Improvedouble-sided display functionVSAvoidlight utilization efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent changes the polarization state parameter from linear to circular by introducing quarter-wave plates. The circularly polarized light can pass through the liquid crystal panel without being absorbed by polarizers, thereby improving light utilization efficiency while maintaining double-sided display function

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful reflection loss at the air-liquid crystal interface into a beneficial effect by using circularly polarized light. The circularly polarized light maintains its polarization state after reflection, allowing it to be effectively utilized by the opposite liquid crystal panel, thus turning the reflection that was previously a loss into a useful light source

Inventive Principle:

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

2Illumination intensity

If light is emitted from a light guide plate in a common backlight module, then the light can reach the liquid crystal panel, but significant light loss occurs due to reflection within the light guide plate

Engineering Contradiction:

Improvelight output to liquid crystal panelVSAvoidreflection loss in light guide plate

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent converts the harmful reflection loss within the light guide plate into a beneficial effect. By using circularly polarized light, the reflected light maintains its polarization state and can be effectively utilized by the opposite liquid crystal panel, transforming what was previously a loss into a useful light source

Inventive Principle:

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

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 solution significantly improves light utilization efficiency by ensuring that circularly polarized light is effectively reflected and converted to linearly polarized light, reducing reflection loss and enhancing the display effect in double-sided liquid crystal display devices.

Implementation Method 1

A first liquid crystal brightness enhancement film and a first quarter-wave plate are sequentially disposed along a light emitting direction of the first light exit surface. A second liquid crystal brightness enhancement film and a second quarter-wave plate are sequentially disposed along a light emitting direction of the second light exit surface.

Methodology Applied

Scientific EffectCircular polarization: Polarisation

Implementation Method 2

A first liquid crystal brightness enhancement film and a first quarter-wave plate are sequentially disposed along a light emitting direction of the first light exit surface.

Methodology Applied

Scientific EffectWave plate polarization conversion: Polarisation

Implementation Method 3

a plurality of grooves with a longitudinal section of triangular shape are disposed on each light exit surface, and the plurality of grooves on the first light exit surface are interlaced with the plurality of grooves on the second light exit surface; the plurality of grooves on the first light exit surface are arranged to redirect light emitted by the light source to the second light exit surface

Methodology Applied

Scientific EffectLight redirection through geometric structure: Reflection

Data Source

PatentUS10642101B2Backlight module and double-sided liquid crystal display device

Publication Date: 2020.05.05 BOE TECHNOLOGY GROUP CO LTD

AI summary

The present disclosure provides a backlight module and a double-sided liquid crystal display device. The light utilization efficiency of the backlight module is improved. The backlight module includes a light emitting component, the light emitting component includes a first light exit surface and a second light exit surface disposed opposite to each other. A first liquid crystal brightness enhancement film and a first quarter-wave plate are sequentially disposed along a light emitting direction of the first light exit surface. A second liquid crystal brightness enhancement film and a second quarter-wave plate are sequentially disposed along a light emitting direction of the second light exit surface. A rotation structure of the first liquid crystal brightness enhancement film is opposite to a rotation structure of the second liquid crystal brightness enhancement film.