Nonlinear Reflection Sheet Boundary for Backlight Brightness Uniformity
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Solution Overview
Problem
Backlight units in liquid crystal display devices experience uneven brightness due to the design of the reflection sheet, where the boundary between the bottom and slanted portions tends to be darker than other areas, resulting in reduced light emission and increased brightness variations.
Innovation Solution
A lighting device with a reflection sheet featuring a nonlinear boundary shape between the bottom and slanted portions, specifically a square-wave shape, to minimize the visibility of dark areas and reduce brightness unevenness, while using LEDs with diffuser lenses to enhance light distribution and reduce the number of light sources required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a light source with high directivity (such as an LED) is arranged with its light axis aligned with the direction from the bottom plate to the liquid crystal panel, then the light emission efficiency is improved, but the area around the boundary between the bottom portion and the slanted portion of the reflection sheet becomes darker, causing uneven brightness
Solution Approach 1:
The boundary between the bottom portion and slanted portion is designed with an asymmetric nonlinear shape rather than a straight line. This asymmetric configuration redistributes the reflected light paths, ensuring that light from the high-directivity LED source is more evenly distributed across the reflection sheet surface, including the boundary area that previously appeared dark.
Solution Approach 2:
The boundary is designed with a curved nonlinear shape instead of a linear configuration. This curvature modifies the reflection geometry, allowing light rays to be redirected at varied angles that cover the previously dark boundary region, thereby achieving more uniform brightness distribution while maintaining the efficiency benefits of the high-directivity LED source.
2Speed
If the slanted portion extends from the periphery of the bottom portion to direct reflected light toward the liquid crystal panel side, then the light directionality is improved, but the area around the boundary becomes darker due to increased distance from the light source and greater angle to the light axis
Solution Approach 1:
The nonlinear asymmetric boundary shape creates varied reflection angles along the boundary, allowing some regions to reflect light more effectively toward the liquid crystal panel while others compensate for the increased distance and angle effects, thereby maintaining both directionality and brightness uniformity.
Solution Approach 2:
Different segments of the nonlinear boundary are designed with locally optimized characteristics. Certain portions of the boundary have specific curvature radii and angles tailored to compensate for the increased distance from the light source and greater angle to the light axis in those specific regions, ensuring uniform light distribution across the entire boundary area.
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 nonlinear boundary design reduces the perception of dark areas, achieving more uniform brightness and lowering the number of parts needed, thus simplifying handling and manufacturing, while using LEDs with diffuser lenses ensures efficient light distribution and lower power consumption.
Implementation Method 1
a reflection sheet provided on an inner surface of the chassis and configured to reflect light from the at least one light source
Implementation Method 2
using LEDs with diffuser lenses to enhance light distribution
Data Source
AI summary
A lighting device, uneven brightness of which is suppressed, is provided. A lighting device of the present invention includes LEDs 17, a chassis 14 that houses the LEDs 17 therein, and a chassis reflection sheet 22 that is provided on an inner surface of the chassis 14 and configured to reflect light from the LEDs 17. The LEDs 17 are provided on a bottom plate 14a of the chassis 14. The chassis reflection sheet 22 has a bottom portion 31 that extends along the bottom plate 14a and slanted portions 32 that extend from a periphery of the bottom portion 31. The slanted portions 32 slant to a direction in which the LED emits light with respect to the bottom portion. A boundary L between the bottom portion 31 and the slanted portions 32 is formed in a nonlinear shape in a plan view.