Rear Pad Connection Layout for Narrow-Bezel Display Panels
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Solution Overview
Problem
Existing display devices face challenges in maximizing the display area by minimizing the non-display area, particularly due to limitations in reducing the width of the bezel or non-display area without increasing the risk of defects in the bending regions.
Innovation Solution
The display device incorporates a substrate structure with a pad area connected to a driving substrate through the rear side of the display panel, utilizing conductive inks to establish electrical connections, and includes flexible substrates and driver chips to reduce the non-display area without bending, thereby enhancing connectivity and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the width of the bezel or non-display area is reduced to maximize display area, then the display area is expanded, but the risk of defects in the bending regions increases
Solution Approach 1:
The substrate is divided into a rigid first substrate and a flexible second substrate. The first substrate provides structural support and houses the display area, while the flexible second substrate accommodates the non-display area and bending regions. This segmentation allows the display area to be maximized on the rigid substrate while the flexible substrate handles the bending requirements, thereby expanding display area without compromising reliability.
Solution Approach 2:
The patent transitions from a single-plane substrate structure to a multi-layer stacked structure with the first substrate and second substrate arranged in different dimensions. The pad area is positioned on the rear side of the first substrate, utilizing the third dimension (thickness direction) to route connections. This dimensional change allows the non-display area to be minimized while maintaining reliable electrical connections through the stacked configuration.
2Area of moving object
If the non-display area is minimized to expand display area, then the display area increases, but the complexity of electrical connections and routing increases
Solution Approach 1:
The electrical connection structure utilizes the thickness direction (third dimension) by forming pad contact holes through the second substrate and barrier film to reach the pad electrode on the first substrate. This vertical routing approach simplifies the electrical connections compared to lateral routing within the plane, thereby minimizing the non-display area while managing connection complexity through dimensional transition.
Solution Approach 2:
The pad contact holes are formed by etching through the second substrate and barrier film layers to access the pad electrode on the first substrate. The conductive structures are nested within the stacked layers, with the pad electrode on the first substrate, barrier film, and second substrate all aligned vertically. This nested configuration simplifies routing by utilizing the vertical stack rather than requiring complex lateral pathways.
3Area of moving object
If pads are connected to the rear side of the display panel, then the non-display area is reduced, but the manufacturing precision required for alignment increases
Solution Approach 1:
The pad electrode is formed on the first substrate before the second substrate and barrier film are stacked. The pad contact holes are then formed by etching through the second substrate and barrier film to expose the pad electrode. This preliminary formation of the pad electrode establishes a reference structure that guides subsequent alignment and etching processes, thereby reducing the non-display area while managing manufacturing precision through sequential fabrication steps.
Solution Approach 2:
The barrier film serves as an intermediary layer between the first substrate (containing the pad electrode) and the second substrate. This intermediate layer facilitates controlled etching and alignment during the formation of pad contact holes, as the barrier film provides a defined etching boundary and protective function. The intermediary barrier film structure simplifies the alignment process compared to direct contact between the first and second substrates.
Data Source
AI summary
A display device includes: a first substrate, a barrier film, and a second substrate; a thin-film transistor layer, an emission material layer, an encapsulation layer and a touch detecting unit stacked on the second substrate; and a pad area in a non-display area and comprising pads connected to a driving substrate and facing the first substrate, the pads comprising: a pad contact hole formed by etching the second substrate and the barrier film; a first inorganic film and a pad electrode stacked on an inner circumferential surface of the pad contact hole; and a rear contact hole etched through a portion of the first substrate, and a pad bonded to the rear contact hole, with a middle hole connecting the pad contact hole with the rear contact hole, and the pad of the driving substrate is electrically connected to the pad electrode through a lower conductive ink.