Inkjet Deposition of 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 nozzle diameter and speed.
Innovation Solution
A method involving ink with a weight-average molecular weight between 340,000 and 400,000, where the Ohnesorge number reciprocal (Z) and ejection speed (V) are within specific ranges, allowing for easier estimation of preferred flight characteristics by controlling two variables, Z and V, to ensure accurate ink drop placement and prevent breakup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the application method is used to manufacture organic light-emitting elements, then the need for vacuum chambers and masks is eliminated, but the flight characteristics of ink drops become difficult to control
Solution Approach 1:
The patent applies parameter changes by establishing specific ranges for ink properties (molecular weight 340,000-400,000, density 0.95-1.05 g/cm³, surface tension 25-35 mN/m, viscosity 1-10 cP) and ejection parameters (frequency 1-100 kHz, voltage 10-100 V, temperature 20-80°C) to control ink drop flight characteristics and achieve uniform film formation
2Manufacturing precision
If multiple ink properties and ejection parameters are adjusted to control flight characteristics, then ink drop placement accuracy improves, but the time and complexity to determine optimal conditions increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing the optimal parameter ranges through prior research and experimentation, allowing manufacturers to directly apply these proven parameters without needing to conduct extensive trial-and-error evaluations each time ink or equipment is replaced
Solution Approach 2:
The patent defines specific parameter ranges for ink properties and ejection settings that have been optimized to provide preferred flight characteristics, enabling straightforward selection of operating conditions without extensive experimentation
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 accurately estimating and controlling ink drop flight characteristics, reducing the time and complexity in determining optimal conditions for inkjet deposition.
Implementation Method 1
causing the inkjet device to eject a drop of the ink onto the base layer of the substrate
Implementation Method 2
forming the functional layer by drying the ink ejected onto the base layer of the substrate
Data Source
AI summary
A method of efficiently manufacturing an organic light-emitting element with excellent light-emitting characteristics is provided. The method includes: preparing ink and filling an inkjet device having an ink ejection nozzle with the ink; preparing a substrate having a base layer including a first electrode; positioning the inkjet device above the substrate; and causing the inkjet device to eject a drop of the ink onto the base layer. 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.