Backlight Unit Concave Light Guide for White Spot Elimination
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Solution Overview
Problem
Direct type backlight units experience a white-spot phenomenon due to the placement of the light source directly under the light irradiation area, leading to uneven illumination, and increasing the thickness of the light guide member with an air gap to mitigate this issue complicates the design of slim display devices.
Innovation Solution
A backlight unit design featuring a light source array with a first optical layer that includes a concave portion coupled to the light source, a second layer with optical patterns on its surface for guiding and emitting light, and a reflective layer to distribute light evenly, reducing the need for an air gap and maintaining a slim profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the light source is placed directly under the light irradiation area in a direct type backlight unit, then the structure is simple and compact, but a white-spot phenomenon occurs causing uneven illumination
Solution Approach 1:
The patent applies local quality by creating a concave portion at the light source position in the light guide member, which has different optical properties (light trapping) compared to the surrounding flat areas. This localized structural modification causes light to be redirected away from the direct light source position, eliminating the white-spot phenomenon while maintaining overall structural simplicity.
Solution Approach 2:
The patent utilizes curvature by forming a concave portion (curved surface) in the light guide member at the light source position. This curved structure redirects light rays that would otherwise travel directly toward the viewer, scattering them instead to achieve more uniform illumination across the display area.
2Illumination intensity
If the thickness of the light guide member is increased with an air gap to reduce the white-spot phenomenon, then illumination uniformity improves, but the backlight unit thickness increases making slim display devices difficult to implement
Solution Approach 1:
Instead of increasing thickness in the vertical dimension (adding air gaps and thicker light guide members), the patent solves the illumination uniformity problem by modifying the horizontal cross-sectional geometry of the light guide member through the concave portion. This dimensional approach to problem-solving eliminates the need for increased thickness while achieving the desired illumination uniformity.
Solution Approach 2:
The concave portion is nested within the light guide member structure itself, utilizing the existing material volume more effectively. By creating a recessed area that redirects light, the design achieves improved illumination uniformity without adding external layers or air gaps that would increase overall thickness.
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 effectively reduces the white-spot phenomenon by uniformly distributing light across the display area without increasing the thickness of the backlight unit, enabling the creation of slim display devices with improved illumination uniformity.
Implementation Method 1
a reflective layer disposed on the bottom of the first layer
Implementation Method 2
a second layer disposed on the first layer, the second layer guiding light incident from the first layer in one direction
Implementation Method 3
a plurality of optical patterns disposed on one surface of the second layer, the plurality of optical patterns selectively emitting light passing through the one surface
Implementation Method 4
The first layer may include at least one light diffusion particle that scatters light received from the light source
Data Source
AI summary
A backlight unit includes a light source array including at least one light source which emits light and a circuit board on which the light source is disposed, and a first optical layer disposed on the light source array. The first optical layer includes a first layer which defines at least one concave portion in a bottom of the first layer, where the at least one concave portion is coupled to the light source, a second layer disposed on the first layer, the second layer guiding light incident from the first layer in one direction, a plurality of optical patterns disposed on one surface of the second layer, the plurality of optical patterns selectively emitting light passing through the one surface, and a reflective layer disposed on the bottom of the first layer.