OLED Pixel Defining Layer Thickness Control via Segmented Inkjet Printing
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Solution Overview
Problem
OLED displays face issues with dark spots due to insufficient thickness of the pixel defining layer, which can cause pixel pressing and unwanted capacitance between electrodes, affecting display quality.
Innovation Solution
The pixel defining layer is formed with a sufficiently large thickness by using a medium layer with distinct regions of varying wettability, allowing for precise application of layers like the light emission layer and second pixel defining layer, thereby preventing pixel pressing and reducing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel defining layer is made thicker to prevent pixel pressing and reduce capacitance, then pixel protection and capacitance reduction are improved, but the manufacturing complexity and process difficulty increase
Solution Approach 1:
The pixel defining layer is divided into two separate layers: a first pixel defining layer formed by photolithography with thickness of 1 μm or less, and a second pixel defining layer formed by inkjet printing with thickness greater than 1 μm. This segmentation allows each layer to serve specific functions - the first layer provides precise patterning while the second layer provides adequate thickness for pixel protection and capacitance reduction, resolving the contradiction between thickness requirements and manufacturing complexity
Solution Approach 2:
The second pixel defining layer is selectively formed only in regions where additional thickness is needed for pixel protection, while the first pixel defining layer maintains precise boundaries. This local quality approach ensures that the pixel defining layer has sufficient thickness in critical areas without unnecessarily increasing complexity across the entire structure
2Reliability
If the pixel defining layer is made thicker to reduce capacitance between electrodes, then capacitance reduction is improved, but the manufacturing precision and process control difficulty increase
Solution Approach 1:
The pixel defining layer is segmented into two layers with different thickness characteristics. The first pixel defining layer (≤1 μm) is formed by photolithography which provides excellent thickness control and precision. The second pixel defining layer (>1 μm) is formed by inkjet printing which allows precise deposition of thicker material. This segmentation resolves the contradiction by using appropriate manufacturing techniques for different thickness requirements
Solution Approach 2:
The invention changes the manufacturing parameter (thickness) of the pixel defining layer by using two different formation processes. The first layer uses photolithography for thin, precise layers while the second layer uses inkjet printing for thicker layers. This parameter change approach allows achieving the required thickness for capacitance reduction while maintaining manufacturing precision through appropriate process selection
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 approach effectively suppresses dark spots and reduces unwanted capacitance, maintaining film uniformity and enhancing overall display quality by ensuring the pixel defining layer's thickness is adequate without compromising the uniformity of the medium layer.
Implementation Method 1
The medium layer may include a first region and a second region... The second region may have lower wettability than the first region
Data Source
AI summary
An organic light emitting diode (OLED) display is provided. The OLED display includes: a substrate; a first electrode on the substrate; a first pixel defining layer exposing at least a portion of the first electrode; a medium layer on the first pixel defining layer and the first electrode, the medium layer including a first region and a second region; a second pixel defining layer overlapping the first pixel defining layer with the first region therebetween; a light emission layer overlapping the first electrode with the first region therebetween; and a second electrode covering the second pixel defining layer and the light emission layer.