Surface-Emission Light Unit Recess Structure for Thin Uniform Backlights
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Solution Overview
Problem
Direct-lit backlights for display devices, such as liquid crystal display devices, face challenges in achieving improved light extraction efficiency and reduced thickness while maintaining uniform luminance and size reduction.
Innovation Solution
A light-emitting unit configuration that includes a wiring board with light-emitting elements, a light reflecting member covering lateral surfaces, wavelength conversion layers, light reflecting layers, and a protecting layer with recesses to enhance light extraction and uniformity, along with a manufacturing method that involves forming these layers to optimize light distribution and reduce thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a plurality of light-emitting elements are two-dimensionally arrayed to improve light extraction efficiency, then light extraction efficiency is improved, but the thickness and size cannot be reduced
Solution Approach 1:
The patent introduces a vertical dimension solution by forming a light guiding layer with a specific refractive index between the light-emitting elements and the wavelength conversion layer. This optical layer creates total internal reflection at interfaces, guiding light vertically through the thickness direction rather than allowing lateral leakage, thus improving extraction efficiency without increasing horizontal dimensions or overall thickness
Solution Approach 2:
The patent changes the refractive index parameter by introducing a light guiding layer with refractive index n3 that is higher than the wavelength conversion layer (n4) and the encapsulation resin (n2). This parameter change enables total internal reflection at the interfaces, controlling light propagation direction and improving extraction efficiency while maintaining compact thickness
2Length of moving object
If the thickness is reduced to meet display device requirements, then the device becomes more compact, but uniform luminance becomes difficult to maintain
Solution Approach 1:
The patent applies local quality by providing a light guiding layer specifically at the interfaces between light-emitting elements and wavelength conversion material, where light extraction is most critical. This localized optical structure ensures uniform light distribution across the thin profile by controlling light propagation at the precise locations where extraction occurs
Solution Approach 2:
The light guiding layer acts as an intermediary optical element between the light-emitting elements and the wavelength conversion layer. It mediates light propagation by creating total internal reflection at its interfaces, ensuring uniform luminance distribution while enabling the overall structure to maintain reduced thickness
3Illumination intensity
If lateral surfaces of light-emitting elements are covered with light reflecting member, then luminance is improved, but device complexity increases
Solution Approach 1:
The patent merges the light guiding function and the protective encapsulation function into a single integrated structure. The light guiding layer is formed as part of the encapsulation process, combining optical guidance with physical protection, thus improving luminance through total internal reflection while avoiding the need for separate complex reflecting member structures
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 configuration effectively suppresses uneven luminance and reduces the thickness and size of the light-emitting unit, improving light extraction efficiency and maintaining uniform light distribution.
Implementation Method 1
a light reflecting member provided on the wiring board, the light reflecting member covering a lateral surface of each of the plurality of light-emitting elements
Implementation Method 2
a plurality of wavelength conversion layers each provided on or above an emission surface of a corresponding one of the plurality of light-emitting elements
Implementation Method 3
a plurality of light reflecting layers provided on the plurality of wavelength conversion layers, respectively
Implementation Method 4
a protecting layer configured to transmit light and provided on the light reflecting member, the protecting layer covering at least a lateral surface of the plurality of wavelength conversion layers and at least a lateral surface of the plurality of light reflecting layers
Data Source
AI summary
A light-emitting unit includes: a wiring board; light-emitting elements on the wiring board; a light reflecting member on the wiring board, the light reflecting member covering a lateral surface of each of the light-emitting elements; wavelength conversion layers each provided on or above an emission surface of a corresponding one of the plurality of light-emitting elements; light reflecting layers on the wavelength conversion layers, respectively; and a protecting layer configured to transmit light and provided on the light reflecting member. The light-transmitting protecting layer covers at least a lateral surface of the wavelength conversion layers and at least a lateral surfaces of the light reflecting layers. An upper surface of the protecting layer has a first recess in a region where the plurality of light reflecting layers are not present in a top view. The first recess includes at least one concave surface.