Backlight Joining Layer Refractive Index Gradient
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Solution Overview
Problem
Conventional backlight units for liquid crystal display devices face issues with reduced surface luminance due to light scattering from air gaps between optical sheets and LED lamps, and inadequate heat management leading to decreased light emission efficiency.
Innovation Solution
A backlight unit design featuring a plurality of light emitting devices with semiconductor elements, an optical sheet, and a joining layer with refractive indices satisfying n1≦n2≦n3, where n1 is the optical sheet, n2 is the joining layer, and n3 is the light emitting device, along with a reflective part and a thermally stable silicone resin joining layer to enhance light transmission and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If air gaps are left between optical sheet and LED lamp, then assembly is easier, but light transmission is reduced due to scattering
Solution Approach 1:
A joining layer with intermediate refractive index (n2) is introduced between the optical sheet (n1) and LED lamp (n3) to serve as a mediator. This gradient refractive index structure (n1≦n2≦n3) reduces total internal reflection at interfaces and minimizes light scattering, thereby improving light transmission and surface luminance while still allowing for practical assembly procedures
Solution Approach 2:
The refractive index parameter of the joining layer is specifically optimized to satisfy n1≦n2≦n3, creating a gradient that matches the optical properties between the optical sheet and LED lamp. This parameter optimization reduces optical impedance mismatch and improves light transmission efficiency without requiring complete contact between components
2Illumination intensity
If distance between optical sheet and base substrate is shortened to eliminate air gaps, then light transmission improves, but heat dissipation becomes inadequate
Solution Approach 1:
The joining layer is applied locally only at the interface between the optical sheet and LED lamp where light transmission is critical, rather than throughout the entire structure. This localized application optimizes optical performance at the light path interface while maintaining adequate thermal pathways through the base substrate and housing for heat dissipation
Solution Approach 2:
The joining layer acts as an optical intermediary that improves light transmission without becoming a thermal barrier. By selecting materials with appropriate optical and thermal properties, the layer transmits light effectively while allowing heat to conduct through to the cooling structures
3Ease of manufacture
If optical material is placed between LED lamp and light guide plate, then assembly is simplified, but light transmission may be insufficient due to refractive index mismatch
Solution Approach 1:
The refractive index of the joining layer is specifically engineered to satisfy n1≦n2≦n3, creating a gradient that optimizes optical matching between the optical sheet and LED lamp. This parameter optimization ensures high light transmission efficiency while maintaining assembly simplicity
Solution Approach 2:
The joining layer is formulated as a composite material that simultaneously provides optical matching (refractive index n2 between n1 and n3) and mechanical bonding properties. This composite structure achieves both light transmission efficiency and assembly simplicity without requiring separate optical and structural components
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 effectively transmits light from LED lamps to the optical sheet, improving surface luminance and maintaining light emission efficiency even under continuous use by restricting total reflection and managing heat effectively.
Implementation Method 1
light radiated from the light emission part based on a refractive index or the like of respective parts cannot be sufficiently transmitted to an optical sheet
Implementation Method 2
a condition of n1≦n2≦n3 is satisfied, where n1 is a refractive index of the optical sheet, n2 is a refractive index of the joining layer, and n3 is a refractive index of the light emitting device
Implementation Method 3
a sufficient heat release structure has not been adopted so far
Data Source
AI summary
A backlight unit 1 includes a plurality of light emitting devices 2 constituted with, for example, LED lamps, and an optical sheet 4 disposed on light emission surface 2b sides of the light emitting devices 2. The light emission surface sides of the plural light emitting devices are joined to the optical sheet 4 via joining layers 5. The backlight unit 1 satisfies a condition of n1≦n2≦n3, where n1 is a refractive index of the optical sheet 4, n2 is a refractive index of the joining layer 5, and n3 is a refractive index of the light emitting device 2.