Inkjet Printing Organic Light-Emitting Elements
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Solution Overview
Problem
The challenge in manufacturing organic light-emitting elements using the application method is achieving uniform film thickness and shape of the organic light-emitting layer, as the flight characteristics of ink drops are difficult to control due to unclear correlations among ink properties such as density, surface tension, viscosity, and droplet diameter, and are further influenced by ejection speed and nozzle diameter.
Innovation Solution
A method involving ink with a weight-average molecular weight between 200,000 and 250,000, where the Ohnesorge number reciprocal (Z) and ejection speed (V) are within specific ranges, allowing for precise control of flight characteristics by satisfying equations Z=1/Ohnesorge number Oh=(r·ρ·γ)1/2/η and 3≦V≦6, and V≦−1.18 Ln(Z)+7.52, facilitating accurate estimation of preferred flight characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the application method is used to manufacture organic light-emitting elements, then mass production efficiency is improved and vacuum chamber processes are eliminated, but control over ink drop flight characteristics deteriorates due to unclear correlations among ink properties
Solution Approach 1:
The patent applies parameter changes by establishing specific numerical ranges for ink properties (density: 0.85-1.05 g/cm³, surface tension: 25-35 mN/m, viscosity: 1-20 mPa·s) and ejection parameters (ejection speed: 3-6 m/s, nozzle diameter: 20-50 μm). These parameter specifications transform the unclear correlations into controllable relationships, ensuring ink drops maintain integrity during flight while enabling mass production through the application method.
2Manufacturing precision
If ink properties such as density, surface tension, and viscosity are adjusted to improve flight characteristics, then ink drop placement accuracy is improved, but the complexity of ink formulation increases
Solution Approach 1:
The patent simplifies ink formulation complexity by defining specific parameter ranges for density (0.85-1.05 g/cm³), surface tension (25-35 mN/m), and viscosity (1-20 mPa·s). These standardized parameter specifications provide clear formulation guidelines, reducing the complexity of developing ink formulations with appropriate flight characteristics while maintaining placement accuracy.
3Manufacturing precision
If the diameter of the ink ejection nozzle is reduced to improve resolution, then film thickness uniformity is improved, but ink drop breakup increases due to weaker ejection force
Solution Approach 1:
The patent resolves the contradiction between nozzle diameter reduction and ink drop integrity by specifying an optimal nozzle diameter range (20-50 μm) and coordinating it with appropriate ejection speeds (3-6 m/s) and ink viscosity values (1-20 mPa·s). This multi-parameter coordination ensures that smaller nozzles can produce uniform film thickness while maintaining sufficient ejection force to prevent ink drop breakup.
4Manufacturing precision
If ejection speed is increased to improve placement accuracy, then flight time is reduced and placement precision is improved, but ink drop breakup increases
Solution Approach 1:
The patent optimizes the balance between ejection speed and ink drop integrity by specifying an ejection speed range (3-6 m/s) that coordinates with ink viscosity (1-20 mPa·s) and surface tension (25-35 mN/m). This coordinated parameter control allows sufficient ejection speed for accurate placement while maintaining ink drop integrity through appropriate viscosity and surface tension values.
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 enables efficient manufacturing of organic light-emitting elements with excellent light-emitting characteristics by simplifying the estimation of flight characteristics, ensuring precise ink drop placement and preventing breakup, thereby improving production efficiency and accuracy.
Implementation Method 1
the surface tension γ (mN/m), and the viscosity η (mPa·s) of the ink
Implementation Method 2
the surface tension γ (mN/m), and the viscosity η (mPa·s) of the ink
Implementation Method 3
the ink is applied to a substrate by ejecting the ink from an ink ejection nozzle of an inkjet device, and then the solvent is volatilized to form an organic light-emitting layer
Data Source
AI summary
To provide a method of efficiently manufacturing an organic light-emitting element with excellent light-emitting characteristics by application, the method includes: preparing ink and filling an inkjet device having an ink ejection nozzle with ink; preparing a substrate having a base layer including a first electrode; and positioning the inkjet device above the substrate, and causing the inkjet device to eject a drop of the ink onto the base layer, wherein, in the preparation of the ink, a value Z denoting a reciprocal of the Ohnesorge number Oh determined by density ρ (g/dm3), surface tension γ (mN/m), and viscosity η (mPa·s) of the ink and a diameter r (mm) of the ink ejection nozzle satisfies Formula 1, in the ejection of the drop of the ink, speed V (m/s) of the ejected drop satisfies Formula 2, and the value Z and the speed V (m/s) satisfy Formula 3.