Asymmetric Backlight Assembly for Thermal Management

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Solution Overview

Problem

Conventional backlight structures for transmissive displays, such as liquid crystal displays, suffer from inefficiencies due to large air gaps between light-emitting diodes and the light guide layer, leading to reduced power consumption and battery life in electronic devices.

Innovation Solution

A backlight assembly with a thermally conductive chassis that surrounds the light guide layer, featuring asymmetric light leakage promotion features and an asymmetric light source arrangement, where one side of the light guide layer receives light from a fixed light source and the other side from a movable light source, with the latter being a heat sink, and the light leakage features' peak density is closer to the movable side to compensate for brightness differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If large air gaps are used between light-emitting diodes and light guide layer to accommodate thermal expansion, then thermal expansion is accommodated, but backlight efficiency deteriorates

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidbacklight efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent extracts the light guide layer from direct contact with the chassis, allowing it to float freely within the chassis cavity. This separation enables the light guide layer to expand thermally without constraint while maintaining close proximity to light-emitting diodes through gravitational settling, thereby accommodating thermal expansion without sacrificing backlight efficiency

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a reflective layer as an intermediary between the light guide layer and the chassis. This reflective layer serves dual purposes: it reflects stray light back into the light guide layer to improve backlight efficiency, and it allows the light guide layer to maintain close proximity to light-emitting diodes while still accommodating thermal expansion

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If light-emitting diodes are placed close to light guide layer to improve backlight efficiency, then backlight efficiency is improved, but thermal expansion accommodation deteriorates

Engineering Contradiction:

Improvebacklight efficiencyVSAvoidthermal expansion accommodation

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent creates a dynamic system where the light guide layer can move freely within the chassis cavity in response to thermal expansion. The light guide layer settles close to light-emitting diodes at operating temperature to maximize light coupling efficiency, while having the freedom to expand without constraint, thereby dynamically adapting to thermal conditions

Inventive Principle:

Principle #15Dynamics

3Illumination intensity

If asymmetric light leakage promotion features are used to compensate for brightness differences, then backlight uniformity is improved, but device complexity increases

Engineering Contradiction:

Improvebacklight uniformityVSAvoidlight leakage feature asymmetry

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent applies local quality by varying the density of light leakage promotion features at different locations on the light guide layer. Areas with lower light intensity receive higher density features to scatter more light, while areas with higher intensity receive lower density features. This localized variation compensates for brightness differences and achieves uniform backlight without requiring complex asymmetric structures

Inventive Principle:

Principle #3Local quality

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 enhances backlight efficiency and uniformity, reducing overheating risks and improving power consumption while accommodating thermal expansion, thus extending battery life in electronic devices.

Implementation Method 1

a thermally conductive chassis that at least partially surrounds the light guide layer... The chassis may serve as a heat sink for the second light source

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

Light leakage promotion features may be provided on the surface of the light guide layer to allow light to escape from the light guide layer to the array of pixels

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentUS9897744B2Backlight assembly having assymetric light leakage promoting features

Publication Date: 2018.02.20 APPLE INC

AI summary

An electronic device may have a display including an array of display pixels and a backlight assembly that provides backlight for the array of pixels. The backlight assembly may include a light guide layer having first and second opposing sides. The first side of the light guide layer may receive light from a first light source and the second side of the light guide layer may receive light from a second light source. To avoid overheating the first light source, the light emitted by the first light source may be less bright than the light emitted by the second light source. To compensate for the reduced brightness of the first light source, light leakage promotion features on the light guide layer may have a peak density that is closer to the first side of the light guide layer than the second side of the light guide layer.