COF Expansion Bonding for Flexible Display Resolution
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Solution Overview
Problem
Current flexible OLED displays face limitations in increasing the number of connection pins without expanding the bonding region width, which restricts the resolution improvement of the display device.
Innovation Solution
The flexible display device features a COF with expansion bonding portions at both ends of the main body portion, equipped with multiple connection pins along three edges, allowing for bonding to the flexible display panel without increasing the bonding region width, thereby enhancing the resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of connection pins is increased to improve resolution, then the display resolution is improved, but the bonding region width must be increased which reduces the screen ratio
Solution Approach 1:
The COF structure transitions from a simple rectangular shape to an L-shaped configuration with expansion portions extending in multiple directions. This dimensional change allows connection pins to be distributed across multiple edges and regions, increasing the total number of connection pins without requiring a proportional increase in the overall bonding region width, thereby resolving the contradiction between resolution improvement and bonding region area constraints
2Quantity of substance
If the bonding region width is increased to accommodate more connection pins, then the number of connection pins is increased, but the screen ratio is reduced
Solution Approach 1:
The COF is segmented into distinct functional portions: a main body portion and multiple expansion bonding portions extending from different edges. This segmentation allows connection pins to be distributed across multiple separated regions rather than concentrated in a single large bonding area, enabling increased pin quantity while maintaining a compact overall bonding region footprint that preserves screen ratio
3Quantity of substance
If the COF structure is modified to include expansion portions, then the number of connection pins is increased without increasing bonding region width, but the COF structure becomes more complex
Solution Approach 1:
The COF utilizes a flexible thin film structure that can be formed through standard flexible PCB manufacturing processes. The expansion portions are created using the same lamination and routing techniques as conventional COF designs, maintaining manufacturing simplicity despite the increased structural complexity. This allows the COF to achieve enhanced pin distribution capabilities without introducing prohibitively complex fabrication steps
Data Source
AI summary
A flexible display device includes a flexible display panel and a chip on film (COF) bonded to the flexible display panel; wherein the flexible display panel is divided into a display region, a bonding region on a side of the display region, and a bending region between the display region and the bonding region; wherein the COF comprises a main body portion and two expansion bonding portions respectively disposed at two ends of one side of the main body portion; wherein an edge of the main body portion adjacent to the two expansion bonding portions are disposed with a plurality of connection pins; wherein the COF is bonded to the bonding region of the flexible display panel through the plurality of connection pins.