Backlight Unit Light Guide Plate Prism Patterns Moire Reduction
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Solution Overview
Problem
Modern liquid crystal display devices face challenges in controlling output light and reducing moire due to low light concentration effects caused by patterned light guide plates, which are exacerbated by the reduction in optical sheets and the generation of moire from patterns on the light guide plate, optical sheets, and the liquid crystal display device's black matrix.
Innovation Solution
A backlight unit is designed with a light guide plate featuring lower patterns of a prism shape on its surface, comprising inclined and sub-inclined surfaces, which are configured to improve light concentration and reduce moire by varying pattern pitch, width, length, and depth, and tilting columns or rows of patterns relative to the vertical or horizontal axis, along with a fabrication method that forms these patterns on the light guide plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If patterns are formed on the light guide plate to compensate for reduction in optical sheets, then the number of optical sheets is reduced and thickness is decreased, but light concentration effect is lowered and control of output light becomes difficult
Solution Approach 1:
The patent applies local quality by creating patterns with different characteristics in different regions of the light guide plate. Specifically, the pattern pitch, width, length, and depth are varied depending on the position relative to the light source, allowing each region to optimize light extraction and concentration locally while maintaining overall thinness
Solution Approach 2:
The patent implements parameter changes by systematically varying multiple geometric parameters of the patterns including pitch, width, length, and depth. These parameter variations are designed to control light extraction efficiency and concentration at different positions, resolving the contradiction between thinness and light concentration capability
2Productivity
If patterns are formed on the light guide plate, then light guidance is improved, but moire is generated due to interaction with optical sheet patterns and black matrix
Solution Approach 1:
The patent applies asymmetry by designing patterns that are tilted relative to the vertical or horizontal axis rather than being aligned symmetrically. This asymmetric orientation disrupts the periodic interaction between patterns from the light guide plate, optical sheets, and black matrix, thereby preventing moire while maintaining effective light guidance
Solution Approach 2:
The patent introduces a new dimensional parameter by tilting the patterns at specific angles relative to the vertical or horizontal axis. This adds an angular dimension to the pattern design, allowing light guidance functionality to be maintained while avoiding the periodic alignment that causes moire artifacts
3Volume of moving object
If the number of optical sheets is reduced, then device thickness is decreased, but light distribution control becomes insufficient
Solution Approach 1:
The patent implements multi-functionality by designing the light guide plate patterns to simultaneously perform multiple functions: light extraction, light concentration, light distribution control, and moire prevention. This eliminates the need for separate optical sheets while maintaining comprehensive light control capability through the patterned light guide plate alone
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 enhances light utilization efficiency, increases brightness, and prevents moire generation by optimizing light distribution and alignment with the liquid crystal panel's black matrix, thereby improving image quality.
Implementation Method 1
lower patterns of a prism shape formed on a lower surface of the light guide plate by inclined surfaces and sub-inclined surfaces
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Disclosed are a backlight unit (100) and a liquid crystal display device (20) having the same which may facilitate control of output light through a light guide plate (140), improve light concentration effect, and reduce moire. The backlight unit includes light sources (120) generating light, a light guide plate (140) guiding light through an incidence surface (149) opposite the light sources (120), emitting the light through an emission surface, and having lower patterns of a prism shape formed on the lower surface (144) of the light guide plate opposite the emission surface by inclined surfaces (147a) and sub-inclined surfaces (147b), and at least one optical sheet (110) stacked on the emission surface.