Surface-Modifying Layer for OLED Bubble-Free Bonding
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Solution Overview
Problem
Organic electroluminescent devices face issues with water and oxygen degradation, leading to short lifetimes and light leakage due to air bubbles trapped between substrates during the bonding process, which also necessitate an overcoat layer that increases the distance between light-emitting elements and color layers, reducing light extraction efficiency.
Innovation Solution
A surface-modifying layer with higher surface energy than the materials involved is applied to the color and light-shielding layers, allowing the filling layer to easily fill the space without trapping air bubbles, eliminating the need for an overcoat layer and reducing the distance between light-emitting elements and color layers, thereby enhancing light extraction and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an overcoat layer is provided to planarize the surfaces of color layers and light-shielding layer, then air bubbles are prevented from being trapped, but the distance between light-emitting elements and color layers increases, reducing light extraction efficiency
Solution Approach 1:
The patent changes the surface energy parameter of the color layers and light-shielding layer by applying a surface-modifying layer. This allows the filling layer to wet the surfaces properly without requiring an overcoat layer, thus maintaining short distance for efficient light extraction while achieving adequate surface planarity for bubble-free bonding
Solution Approach 2:
The surface-modifying layer acts as an intermediary between the color layers/light-shielding layer and the filling layer. It modifies the surface properties to improve wetting and adhesion, enabling the filling layer to fill the space without trapping air bubbles, eliminating the need for an overcoat layer
2Reliability
If a non-water absorbable overcoat layer is used to prevent water degradation, then color layers and light-shielding layer are protected, but the overcoat layer is not wettable to the liquid adhesive layer, causing filling difficulties and extended filling time
Solution Approach 1:
The patent applies local quality modification by adding a surface-modifying layer specifically on the color layers and light-shielding layer. This layer provides local wetting improvement where the adhesive layer contacts, while the underlying non-water absorbable overcoat layer maintains water resistance. The surface-modifying layer has different properties (high surface energy) than the overcoat layer to enable proper adhesive wetting
3Object-generated harmful factors
If the area of light-shielding layer is increased to prevent light leakage, then light leakage to adjacent pixels is reduced, but the aperture area of color layers is reduced, degrading light extraction efficiency
Solution Approach 1:
The patent changes the surface energy parameter of the sealing substrate surfaces through the surface-modifying layer. This improvement in wetting and adhesion allows for better filling layer distribution and reduced voids, enabling more efficient light extraction from the color layers without requiring increased light-shielding layer area
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 solution ensures efficient light extraction with a fine pixel pitch and wide viewing angle, while also improving the adhesion and curing performance of the sealing layers, resulting in a longer-lasting and more reliable organic electroluminescent device with reduced water absorption and mechanical stress.
Implementation Method 1
A surface-modifying layer made of a material having a higher surface energy to the material of the filling layer than the surface energy to the surfaces of the color layers and light-shielding layer
Implementation Method 2
The element substrate and the sealing substrate are bonded to each other with an adhesive layer therebetween
Data Source
AI summary
An organic electroluminescent device includes an element substrate including a plurality of light-emitting elements, each including a pair of electrodes with an organic luminescent layer therebetween, and a coating layer covering the light-emitting elements. A sealing substrate is opposed to the element substrate. The sealing substrate includes a plurality of color layers and a light-shielding layer separating the color layers from each other. An outer region sealing layer bonds the outer region of the sealing substrate to the outer region of the element substrate. A filling layer is surrounded by the outer region sealing layer, and bonds the sealing substrate and the element substrate together in the region in which the light-emitting elements and the color layers are arranged. The color layers and the light-shielding layer of the sealing substrate are covered with a surface-modifying layer made of a material having a higher surface energy to the material of the filling layer than the surface energy to the surfaces of the color layers and light-shielding layer.