LED Array Edge Redish Problem in LCD Backlight Units
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Solution Overview
Problem
In liquid crystal display devices with LED backlights, the 'redish' problem occurs where the red light from the last arrayed LED is overly bright at the edge of the panel due to inadequate mixing with other lights, leading to uneven color brightness distribution, which existing solutions attempt to address by reducing the brightness of the last LED but introduce complexity and cost issues.
Innovation Solution
The solution involves rearranging the LED array so that only half of the outermost LED is included within the area covered by the liquid crystal display panel and optical sheet, with the other half excluded, and altering the shape or position of the last red LED to ensure proper mixing with adjacent LEDs, thereby reducing the redish effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the last red LED is positioned at the edge of the LCD panel to provide backlight, then the backlight coverage is improved, but the red light from the end red LED is radiated without proper mixing causing the redish problem at the edge portion
Solution Approach 1:
The harmful red light radiation from the outermost red LED is extracted and blocked by positioning a light blocking structure (black matrix or reflective layer) at the edge portion of the LCD panel, preventing the redish problem while maintaining backlight coverage
Solution Approach 2:
Different regions of the LCD panel are treated differently: the edge portion receives light blocking to prevent redish problem, while the central region maintains normal backlight transmission for display purposes
2Illumination intensity
If the brightness of the lastly positioned LED is lowered to solve the redish problem, then the color brightness distribution is improved, but the circuit implementation complexity and manufacturing cost increase
Solution Approach 1:
A light blocking structure (intermediary element) is introduced between the outermost red LED and the LCD panel to control light distribution, replacing the need for complex brightness adjustment circuits while achieving even color brightness distribution
3Stability of the object's composition
If the outermost LED is positioned completely within the LCD panel area, then the light mixing is improved, but the light amount from the outermost LED is insufficient and the redish problem persists
Solution Approach 1:
The LED array is segmented such that the outermost red LED is positioned partially outside the LCD panel area, allowing it to contribute to backlight coverage while a light blocking structure prevents excessive red light radiation at the edge
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 approach effectively reduces the redish problem by adjusting the effective light amount of the outermost LED, ensuring even color brightness distribution across the LCD panel without increasing manufacturing complexity or costs.
Implementation Method 1
Recently, the light emitting diode (or LED) is being applied to the back light unit as the light source
Implementation Method 2
an optical sheet disposed under the liquid crystal display panel
Data Source
AI summary
The present disclosure relates to a back light unit having an LED array structure for reducing light leakage problem at edge portion. A liquid crystal display device comprises a liquid crystal display panel; an optical sheet disposed under the liquid crystal display panel; and an LED array having red LED, green LED and blue LED are sequentially arrayed under the optical sheet, wherein one portion of an outermost LED of the LED array is included within an area covered by the liquid crystal display panel, and other portion of the outermost LED of the LED array is excluded from the area covered by the liquid crystal display panel.