Organic EL Display Pixel Electrode Insulation via Liquid Droplet Ejection
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Solution Overview
Problem
Conventional organic EL display devices require a bank structure to prevent shortcircuits and increase numerical aperture, which complicates the manufacturing process and limits display definition due to the need for photolithography and tapered bank sides.
Innovation Solution
The use of a liquid droplet ejection method to form a sufficient thickness of the EL common layer covering the pixel electrode's surface and end, eliminating the need for a bank and thereby preventing shortcircuits and improving surface flatness without the need for photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bank structure is used to prevent shortcircuits and increase numerical aperture, then reliability and display quality are improved, but device complexity and manufacturing difficulty increase due to photolithography requirements
Solution Approach 1:
The patent extracts and eliminates the bank structure from the device architecture. Instead of using a separate insulating bank to prevent shortcircuits, the invention integrates the pixel electrode design with the EL common layer to achieve the same protective function, thereby removing the complex photolithography-based bank structure entirely
Solution Approach 2:
The EL common layer is given multiple functions: it serves as both the common electrode for the EL element and as the insulating structure that prevents shortcircuits between pixel electrodes. This multi-functional design eliminates the need for separate bank structures while maintaining reliability
2Manufacturing precision
If a bank structure is used to increase numerical aperture, then display definition is improved, but manufacturing precision requirements increase due to tapered bank sides
Solution Approach 1:
The patent removes the bank structure that required tapered sides formed through photolithography. By eliminating this structure, the manufacturing process no longer requires the complex alignment and patterning steps needed to create precise tapered banks, thereby improving ease of manufacture while maintaining display definition through the liquid droplet ejection method
3Manufacturing precision
If photolithography is used to form banks, then manufacturing precision is improved, but productivity decreases due to additional manufacturing steps
Solution Approach 1:
The patent replaces the photolithography-based mechanical patterning system with a liquid droplet ejection system. This substitution eliminates the need for photoresist coating, exposure, and development steps, directly forming the pixel electrodes and EL common layer structures through precise liquid deposition, thereby significantly improving productivity while maintaining manufacturing precision
Solution Approach 2:
The liquid droplet ejection method enables continuous formation of pixel electrodes and EL common layers without the intermittent steps required by photolithography (coating, drying, exposing, developing). This continuous manufacturing process improves production speed and productivity while maintaining the necessary manufacturing precision for display definition
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 simplifies the manufacturing process, enhances display definition by eliminating the bank structure, and prevents shortcircuits between pixel and common electrodes, leading to improved image quality and reduced production steps.
Implementation Method 1
The use of a liquid droplet ejection method to form a sufficient thickness of the EL common layer covering the pixel electrode's surface and end
Data Source
AI summary
A display device preventing light leak to an adjacent pixel and thus to prevent color mixing to improve image quality is provided. An organic EL display device includes a plurality of pixels. The plurality of pixels each include a light emitting element; the light emitting element includes a pixel electrode, a common electrode, an EL common layer, and a light emitting layer; the EL common layer and the light emitting layer are provided between the pixel electrode and the common electrode; the EL common layer covers a main surface and an end of the pixel electrode; the pixel electrode is provided on an insulating layer; and the common electrode is in contact with the insulating layer between the plurality of pixels.