Tapered Pixel Electrodes and Sacrificial Layers for Display Manufacturing
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Solution Overview
Problem
Current display devices face challenges in achieving high reliability, low cost, high resolution, and high aperture ratio due to limitations in manufacturing methods, particularly with the use of metal masks which lead to deviations in shape and position of organic films, dust generation, and short circuits.
Innovation Solution
The display device employs a metal maskless structure with tapered pixel electrodes and EL layers of varying thicknesses, using sacrificial films and layers to form EL layers without shadow masks, ensuring precise coverage and reducing defects, and includes a common electrode shared by light-emitting elements for efficient manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal masks are used in manufacturing, then manufacturing precision can be maintained, but dust is generated and shape/position deviations occur in organic films
Solution Approach 1:
The patent removes the metal mask from the manufacturing process entirely. Instead of using a metal mask to define the organic film pattern, the invention uses a sacrificial layer that is deposited and patterned separately, then removed to leave the desired organic film structure without generating dust from metal mask handling.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary substance. This sacrificial layer is deposited over the organic film, patterned to define the desired structure, and then removed. This intermediary approach allows precise pattern definition without requiring metal masks that generate dust.
2Manufacturing precision
If metal masks are used in manufacturing, then manufacturing precision can be maintained, but short circuits occur
Solution Approach 1:
The patent removes the metal mask from the manufacturing process entirely. By eliminating the metal mask and using a sacrificial layer instead, the invention prevents the short circuits that occur when metal masks contact or proximity to organic films during handling.
Solution Approach 2:
The sacrificial layer serves as a non-conductive intermediary that defines the organic film pattern without creating electrical pathways. This eliminates the short circuit risk associated with metal masks while maintaining manufacturing precision.
3Area of stationary object
If EL layer thickness is reduced to ≤150 nm, then aperture ratio increases, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent performs preliminary patterning of the sacrificial layer before depositing the EL layer. By pre-defining the pattern and thickness requirements in the sacrificial layer, the subsequent EL layer deposition can achieve precise thickness control (≤150 nm) without compromising manufacturing precision.
Solution Approach 2:
The sacrificial layer acts as a template and thickness reference for the EL layer. By depositing the EL layer over the sacrificial layer and then removing the sacrificial layer, the invention maintains precise thickness control for the EL layer at ≤150 nm while achieving high aperture ratio.
4Reliability
If pixel electrode end portions are made tapered, then EL layer coverage is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary patterning of the pixel electrode end portions into tapered shapes before subsequent processing steps. This preliminary formation of the tapered geometry ensures proper EL layer coverage while the patterning process itself integrates into existing manufacturing flows, minimizing overall complexity.
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 results in a highly reliable, cost-effective display device with high resolution and aperture ratio, minimizing defects and improving manufacturing yield by eliminating the need for shadow masks and reducing dust-related issues.
Implementation Method 1
Light-emitting elements (also referred to as EL elements) utilizing an electroluminescence (hereinafter referred to as EL) phenomenon
Data Source
AI summary
A highly reliable display device is provided. The display device includes a first light-emitting element and a second light-emitting element adjacent to the first light-emitting element. The first light-emitting element includes a first pixel electrode, a first EL layer over the first pixel electrode, and a common electrode over the first EL layer, and the second light-emitting element includes a second pixel electrode, a second EL layer over the second pixel electrode, and the common electrode over the second EL layer. An end portion of the first pixel electrode and an end portion of the second pixel electrode each have a tapered shape. The first EL layer covers the end portion of the first pixel electrode, and the second EL layer covers the end portion of the second pixel electrode. The first EL layer includes a region with a thickness less than or equal to 150 nm.