Segmented Pixel-Defining Layers for Inkjet Display Thickness Control
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Solution Overview
Problem
Conventional display apparatuses with inkjet-formed emission layers experience a reduction in repellent characteristic of pixel-defining layers when these layers cross hydrophilic layers, leading to thickness inconsistencies and reduced reliability.
Innovation Solution
The display apparatus incorporates a design with first and second pixel-defining layers of different characteristics, where the first pixel-defining layers have a repellent characteristic and the second pixel-defining layers are hydrophilic, with specific thickness and positioning configurations to maintain the repellent characteristic, including grooves in the via insulating layer to support the pixel-defining layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a repellent pixel-defining layer is formed to cross a hydrophilic pixel-defining layer, then the pixel-defining layer structure is completed, but the thickness of the repellent pixel-defining layer is reduced and its repellent characteristic is weakened
Solution Approach 1:
The pixel-defining layer is divided into multiple segments: a repellent pixel-defining layer and a hydrophilic pixel-defining layer. These segments are arranged in an overlapping configuration where the repellent layer is positioned at specific regions and the hydrophilic layer is positioned at other regions, allowing each layer to maintain its thickness and functional characteristics without being compromised by crossing another layer.
Solution Approach 2:
Different regions of the pixel-defining layer are assigned different properties: the repellent pixel-defining layer has a repellent characteristic in specific regions while the hydrophilic pixel-defining layer has a hydrophilic characteristic in other regions. This local differentiation allows each region to maintain its optimal thickness and functional properties, preventing the thickness reduction that would occur if a single layer crossed another layer.
2Ease of manufacture
If the thickness of the repellent pixel-defining layer is reduced at crossing portions, then the layer can be formed continuously, but the repellent characteristic is reduced
Solution Approach 1:
The pixel-defining layer is segmented into distinct repellent and hydrophilic regions that are formed separately and then combined. This segmentation allows each layer to be formed continuously at its optimal thickness without the need to cross or overlap with the other layer, thereby maintaining both manufacturing continuity and the required repellent characteristic consistency.
Solution Approach 2:
The solution moves from a two-dimensional overlapping configuration to a three-dimensional stacked configuration. The repellent pixel-defining layer and hydrophilic pixel-defining layer are positioned at different vertical levels, allowing both layers to maintain their full thickness and functional characteristics while still achieving the necessary structural integration.
3Device complexity
If a single pixel-defining layer is used, then the structure is simple, but the spreadability of ink during inkjet process is compromised
Solution Approach 1:
The pixel-defining layer is designed with different local properties: a repellent pixel-defining layer in specific regions and a hydrophilic pixel-defining layer in other regions. This local quality differentiation enables the inkjet process to deposit emission layer material with controlled spreadability - the hydrophilic regions promote ink spreadability while the repellent regions provide defined boundaries, achieving both simple structure and controlled ink behavior.
Solution Approach 2:
The pixel-defining layer is constructed as a composite structure combining a repellent pixel-defining layer and a hydrophilic pixel-defining layer. This composite material approach allows the structure to simultaneously provide inkjet process control (through the hydrophilic regions) and maintain structural integrity (through the repellent regions), achieving both simplicity and functional performance.
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 configuration enhances the reliability of the display apparatus by maintaining the repellent characteristic of the pixel-defining layers, improving the spreadability of ink during the inkjet process and preventing a loss in thickness, thus ensuring consistent performance.
Implementation Method 1
the first pixel-defining layers have a repellent characteristic
Implementation Method 2
the second pixel-defining layers may have a hydrophilic characteristic
Data Source
AI summary
A display apparatus includes: a substrate; a pixel-circuit layer including a pixel circuit; a via insulating layer on the pixel-circuit layer; a first electrode on the via insulating layer; a pixel-defining layer on the first electrode and exposing a portion of the first electrode; and a second electrode on the first electrode. The pixel-defining layer includes: first pixel-defining layers extending in a first direction and adjacent to each other in a second direction crossing the first direction; and second pixel-defining layers respectively between adjacent ones of the first pixel-defining layers. The second pixel-defining layers are spaced apart from each other, and the via insulating layer has a groove in at least a portion of a region at where the first pixel-defining layers overlaps the via insulating layer.