Optical Sheet Extension for Uniform LED Backlight Brightness
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Solution Overview
Problem
In LED backlight units for LCD devices, gaps between the flexible PCB and the light guide plate cause light to be emitted in lines, leading to non-uniform brightness and deteriorated image quality due to the directional emission of red, green, and blue light.
Innovation Solution
The optical sheet is expanded with an extending portion that overlaps the flexible PCB, blocking light from passing through the gap between the PCB and the light guide plate, ensuring uniform brightness by preventing line emission of light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the flexible PCB is not attached to the light guide plate, then the assembly is simple and easy to manufacture, but a gap is generated between the flexible PCB and the light guide plate causing light to be emitted in lines and image quality to deteriorate
Solution Approach 1:
An extending portion made of optical sheet material is introduced as an intermediary element between the flexible PCB and the light guide plate. This extending portion fills the gap without requiring direct attachment of the PCB to the light guide plate, thus maintaining assembly simplicity while preventing line emission and improving brightness uniformity.
Solution Approach 2:
The optical sheet is divided into a main body portion and an extending portion. The extending portion is specifically designed to overlap the flexible PCB and fill the gap, separating the light-blocking function from the structural attachment function. This segmentation allows the PCB to remain unattached while still achieving uniform brightness.
2Manufacturing precision
If an extending portion is added to the optical sheet to overlap the flexible PCB, then brightness uniformity is improved by preventing line emission, but the device complexity increases
Solution Approach 1:
The extending portion is integrated into the optical sheet as a single continuous piece of optical material rather than being a separate component. This merging approach adds the light-blocking function to the existing optical sheet without increasing the number of discrete parts, thus improving brightness uniformity while minimizing the increase in device complexity.
Solution Approach 2:
The optical sheet serves multiple functions: it diffuses light from the LED, guides light distribution, and through its extending portion, blocks light from passing through the gap. This multi-functionality reduces the need for additional dedicated components, achieving brightness uniformity without proportionally increasing device complexity.
Data Source
AI summary
Provided is a backlight unit with an extending portion that extends from one of a plurality of sheets included in an optical sheet. The optical sheet is on a light guide plate, and a light emitting diode chip is disposed at a side of the light guide plate. A portion of a flexible printed circuit board, to which the light emitting diode chip is mounted, overlaps a portion of the light guide plate. The extending portion overlaps the portion of the flexible printed circuit board. Thus, the occurrence of lines of light due to light progressing between the light guide plate and the flexible printed circuit board can be prevented, thereby obtaining uniform brightness and improving image quality.