Damming Wall Structure for Narrow Frame Organic EL Display
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Solution Overview
Problem
The film formation properties of organic layers in organic EL display devices using the ink-jet method are prone to surface state variations, making it difficult to precisely form the circumferential end parts of the sealing film, which results in a wider frame due to the need for oversized coverage.
Innovation Solution
A display device configuration with a base substrate, switching elements, a flattening film, light-emitting elements, and a sealing film comprising a stack of inorganic and organic layers, along with damming walls formed from specific materials to define the display and frame regions, allowing precise formation of the organic layer's circumferential end parts and narrowing the frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the organic layer is formed slightly oversized to completely cover the inorganic layer, then the sealing performance is improved, but the frame width increases
Solution Approach 1:
The patent applies preliminary action by forming damming walls (first and second damming walls) before forming the organic layer. These damming walls are positioned to define the exact boundary where the organic layer should end, preventing the organic layer from spreading beyond the desired position. This preliminary structural constraint allows the organic layer to be formed with precise dimensional control while maintaining complete coverage of the inorganic layer, thus achieving both good sealing performance and narrow frame width.
2Ease of manufacture
If the ink-jet method is used to form the organic layer, then the ease of manufacture is improved, but the manufacturing precision of the circumferential end parts deteriorates
Solution Approach 1:
The patent uses the damming walls as intermediary structures that mediate between the ink-jet deposition process and the final organic layer shape. The damming walls act as physical boundaries that constrain the organic material during and after deposition, ensuring that even though the ink-jet method is used (which tends to produce spread), the organic layer's circumferential end parts are precisely defined by the damming wall positions. This intermediary structure enables the combination of easy manufacture with high precision.
3Length of stationary object
If the frame width is reduced, then the display device size is minimized, but the organic layer coverage of the inorganic layer is compromised
Solution Approach 1:
The patent applies local quality by creating a differentiated structure where the damming walls are positioned at specific locations to provide localized constraint. The first damming wall is formed from a first organic material and the second damming wall from a second organic material, with the second damming wall including a top part and a bottom part at different heights. This localized structural differentiation allows precise control of the organic layer's circumferential end parts while maintaining complete coverage of the inorganic layer, enabling narrow frame width without compromising coverage.
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 damming walls, particularly the second damming wall with a bottom part formed from switching element material, enhance the precision of organic layer formation, suppressing organic resin spread and enabling a narrower frame while improving sealing performance with a silicon nitride second inorganic layer.
Implementation Method 1
the sealing film includes a stack of an inorganic layer and an organic layer... excellent barrier properties in the cured product
Implementation Method 2
an organic EL display element sealing agent which can be easily applied using an ink-jet method, and which has excellent curing properties
Data Source
AI summary
A first damming wall and a second damming wall are provided in a frame region. The first damming wall surrounds a display region formed from a first organic material and overlaps with a circumferential end part of an organic layer. The second damming wall includes a top part formed from a second organic material in the periphery of the first damming wall, and overlaps with an edge of the circumferential end part of the organic layer. The second damming wall includes a bottom part located closer to a base substrate, the bottom part being formed from a material constituting parts of switching elements.