Back Light Unit Step Structure for Display Panel Flatness
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Solution Overview
Problem
The poor flatness of plastic frames in liquid crystal display units leads to deformation of the liquid crystal display panel and dark light leakage due to the tensile force of double-sided adhesives, exacerbated by the limited processing technology.
Innovation Solution
A back light unit design featuring a metal back plate with a step structure and integrated bosses to support the cover plate, providing a flatter surface and reducing deformation, along with a plastic frame adhered to the back plate using a first adhesive layer and buckles for secure fixation, which improves flatness and reduces light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plastic frame is used to support the cover plate, then the assembly structure is simple and easy to manufacture, but the flatness of the surface is poor (minimum flatness may be 0.35 mm) leading to panel deformation and dark light leakage
Solution Approach 1:
The support structure is segmented into multiple functional components: the back plate provides the base support, the step structure creates distinct height levels for different components, and multiple bosses are distributed around the circumference to provide localized support points. This segmentation allows each component to perform its specific function while achieving overall flatness and structural simplicity.
Solution Approach 2:
The step structure acts as an intermediary element between the back plate and the cover plate. It provides a transition zone that allows the plastic frame to be positioned at an optimal height while maintaining contact with the back plate, thereby ensuring both ease of assembly and sufficient flatness to prevent light leakage.
2Strength
If double-sided adhesive is used to fix the cover plate to the plastic frame, then the fixation is strong and simple, but the tensile force of the adhesive exacerbates the dark light leakage phenomenon
Solution Approach 1:
The support function is extracted from the plastic frame and transferred to the back plate through the step structure and bosses. This allows the plastic frame to focus on providing structural containment while the back plate provides the primary support and flatness, reducing the burden on the adhesive and minimizing light leakage.
Solution Approach 2:
The solution moves from a two-dimensional adhesive bonding problem to a three-dimensional structural support system. By creating the step structure with vertical height differences, the patent provides mechanical support in the vertical dimension, which reduces the tensile stress on the adhesive layer and prevents light leakage that would otherwise occur due to adhesive tension.
3Device complexity
If the plastic frame surface is used as the support for the cover plate, then no additional support structures are needed, but the poor flatness causes deformation of the liquid crystal display panel
Solution Approach 1:
Instead of requiring the entire plastic frame surface to have high flatness, the patent applies local quality by creating specific flat support zones at the boss locations where the cover plate makes contact. The step structure ensures these local areas provide sufficient flatness and stability, while the rest of the plastic frame can maintain its simpler, more easily manufactured form.
Data Source
AI summary
Provided is a back light unit, a display unit and a display apparatus. The back light unit is configured to be disposed on a side of a display panel away from a display side, and includes a back plate and a plastic frame. The back plate includes a bottom plate and a side plate connected to an edge of the bottom plate, and a step is formed on an inner side of the side plate. The step has a first side away from the bottom plate and a second side away from an outer side of the side plate. The plastic frame is supported on the first side surface of the step, and a supporting part is disposed on an end surface of the side plate away from the bottom plate.