Wedge-Shaped Light Guide Plate for Uniform Backlight Brightness
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Solution Overview
Problem
Liquid crystal display devices with side-view type LEDs and divided light guiding plates face issues with uneven brightness due to positional variations between the LEDs and the light-incident face of the divided light guiding plates, leading to reduced brightness and uneven color distribution across the screen.
Innovation Solution
A configuration where the side-view type LEDs are mounted on a wiring substrate with divided light guiding plates, featuring a wedge-shaped design and a reflection sheet supported between the plates, with the LEDs inserted into holes at a step formed on the plates, ensuring the light-emitting face is always positioned higher than the light-incident face to maintain consistent brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If side-view type LEDs are used with divided light guiding plates, then the backlight can be made thinner and the device can be lighter, but uneven brightness is generated due to positional variations between LEDs and light-incident face
Solution Approach 1:
The light guiding plate is designed with a wedge shape where the thickness varies locally. The light-incident face is positioned at a higher location than the light-emitting face, creating a local thickness variation that compensates for positional deviations of LEDs, thereby maintaining uniform light extraction and brightness across the display surface.
Solution Approach 2:
The wedge shape configuration is pre-designed into the light guiding plate before LED mounting. This preliminary structural design ensures that even if LEDs are positioned with variations during assembly, the light path and extraction efficiency are already optimized to produce uniform brightness without requiring precise LED positioning.
2Device complexity
If the light-incident face is positioned at the same level as the light-emitting face, then the structure is simpler, but brightness becomes uneven when LED position varies
Solution Approach 1:
Instead of maintaining uniform thickness throughout, the light guiding plate employs local quality variation through its wedge shape. The thickness is deliberately increased at the light-incident face region compared to the light-emitting face region, creating a localized structural feature that ensures uniform light extraction despite LED positional variations.
3Ease of manufacture
If conventional mounting methods are used, then assembly is easier, but assembly accuracy must be very high to prevent uneven brightness
Solution Approach 1:
The wedge shape configuration is pre-designed into the light guiding plate before LED mounting. This preliminary structural design ensures that even if LEDs are positioned with variations during assembly, the light path and extraction efficiency are already optimized to produce uniform brightness without requiring precise LED positioning.
Solution Approach 2:
The invention changes the geometric parameters of the light guiding plate by introducing a wedge shape with varying thickness. This parameter change transforms the rigid requirement for precise LED positioning into a more tolerant design where a range of LED positions can achieve acceptable brightness uniformity, thereby easing manufacturing precision requirements.
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 configuration effectively suppresses uneven brightness and color distribution across the screen, maintaining brightness without requiring precise assembly accuracy or improved LED package dimensions, while allowing for a degree of freedom in assembly.
Implementation Method 1
a light source unit including a side-view type LED 30
Implementation Method 2
a reflection sheet 60 arranged on the back face of the divided light guiding plates 51
Data Source
AI summary
A cross section of each divided light guiding plate is formed in a wedge shape, a step is formed at a portion of each divided light guiding plate where LEDs are arranged, and holes used for accommodating the LEDs are formed at the step. A plated face is formed on a lower face of each LED, and is coupled to a wiring substrate through solder. Each LED includes a light-emitting face, a lower frame, and an upper frame. The height of the lower frame of each LED is larger than the height of the upper frame, so that a lower end of the light-emitting face of each LED can be always located higher than a lower end of the divided light guiding plate.