Backlight Diffusion Layer Transmittance for LCD Uniformity
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Solution Overview
Problem
Current illumination devices for large-screen liquid crystal display devices face challenges in achieving both thinness and luminance uniformity, as increasing the number of light sources to reduce thickness leads to higher costs and potential light source deterioration, while conventional solutions that enhance luminance uniformity often compromise on light efficiency and thickness.
Innovation Solution
The illumination device features a light-emitting layer with scattered light sources and a diffusion layer where transmittance varies by distance from the sources, with directivity in light emission to reduce light intensity directly above sources, and different emission directions for multiple sources to ensure uniform illumination without increasing source count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of light sources is increased to reduce thickness and improve luminance uniformity, then luminance uniformity is improved, but cost increases
Solution Approach 1:
The patent applies local quality by making the diffusion layer's transmittance position-dependent. The diffusion layer has higher transmittance in regions farther from light sources and lower transmittance in regions closer to light sources, creating non-uniform local properties that compensate for the non-uniform light distribution from scattered light sources, achieving uniform luminance without increasing light source count
Solution Approach 2:
The patent changes the transmittance parameter of the diffusion layer as a function of position. By varying the transmittance parameter spatially (higher away from sources, lower near sources), the system compensates for the inverse-square law attenuation of light, achieving uniform illumination output without adding more light sources
2Length of stationary object
If the distance between light sources and liquid crystal panel is shortened to reduce thickness, then thickness is reduced, but luminance uniformity deteriorates
Solution Approach 1:
The diffusion layer is designed with spatially varying transmittance properties where regions closer to light sources have lower transmittance and regions farther away have higher transmittance. This local quality variation compensates for the non-uniform light intensity distribution that occurs when light sources are placed close to the panel, enabling uniform luminance despite reduced thickness
Solution Approach 2:
The diffusion layer acts as an intermediary element between the scattered light sources and the liquid crystal panel. It mediates the non-uniform light distribution by selectively transmitting or diffusing light based on position, converting the scattered light pattern into uniform illumination on the panel surface
3Illumination intensity
If a light-shielding layer with large density is provided directly above fluorescent light to achieve uniform illumination, then luminance uniformity is improved, but light utilization efficiency decreases
Solution Approach 1:
The diffusion layer serves as an intermediary that optically couples the scattered light sources to the display panel. Instead of using dense light-shielding layers that block and waste light, the diffusion layer mediates light distribution through controlled diffusion and position-dependent transmittance, achieving uniform illumination while preserving light utilization efficiency
Solution Approach 2:
The patent replaces the mechanical/optical approach of using light-shielding layers (which block and waste light) with a diffusion-based approach. The diffusion layer uses optical diffusion and position-dependent transmittance to achieve uniform illumination, substituting the light-blocking mechanism with a light-redistributing mechanism that maintains efficiency
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 configuration achieves excellent luminance uniformity and reduced thickness by optimizing light distribution and reducing light loss, making it suitable for large-screen displays without increasing the number of light sources, thus maintaining efficiency and extending light source lifespan.
Implementation Method 1
a diffusion layer which diffuses light from the light-emitting layer
Implementation Method 2
the light sources each having directivity in a light emission direction, the directivity being such that a light component in a direction parallel to a boundary surface between the light-emitting layer and the diffusion layer is larger than a light component in a direction perpendicular to the boundary surface
Data Source
AI summary
A liquid crystal display device (1) of the present invention includes a display panel (3) and a backlight (2) (an illumination device). The backlight (2) includes a light-emitting layer (20) in which a plurality of light sources (5) are scattered and a diffuser (7) (a diffusion layer) that is formed on the light-emitting layer and diffuses light from the light-emitting layer. The light sources (5) that are present within the light-emitting layer (20) emit light in a direction (a direction of an arrow) substantially parallel to a boundary surface between the light-emitting layer (20) and the diffuser (7). In the diffuser (7), a transmittance of light in an area (7c) close to each of the light sources is smaller than a transmittance of light in an area that is far from each of the light sources.