Organic Light-Emitting Element Ink Solvent Mixture
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Solution Overview
Problem
The challenge in forming organic light-emitting elements is achieving uniform film thickness and planarity of functional layers, especially at microscopic scales, as existing methods struggle to maintain evenness when forming layers with thicknesses in the tens to hundreds of nanometers, leading to uneven edges and centers during the wet process.
Innovation Solution
The use of an ink comprising a first solvent and a second solvent with equal or similar boiling points, where the first solvent forms a functional layer thicker at edges and the second solvent forms a layer thicker at the center, neutralizing these characteristics to achieve intermediate planarity and controlled evaporation for uniform layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a functional layer is formed by a wet process where ink is filled between banks and then dried, then the functional layer can be formed relatively easily even in a large panel, but the film thickness becomes greater at edges than at the center, making it difficult to secure uniformity in film thickness
Solution Approach 1:
The patent changes the physical parameters of the solvent by using a mixed solvent system with specific boiling point ranges (first solvent: 150-250°C, second solvent: 200-300°C) and controlled ratios (95:5 to 50:50 by volume). This parameter optimization allows the ink to maintain appropriate viscosity during filling while enabling uniform evaporation that prevents edge-thickening, thus achieving both ease of manufacture and uniform film thickness.
Solution Approach 2:
The patent uses a composite solvent system combining two different solvents with complementary properties. The first solvent (lower boiling point) and second solvent (higher boiling point) work together in specific proportions to create a mixed solvent that balances filling performance and evaporation characteristics, resolving the contradiction between ease of formation and thickness uniformity.
2Productivity
If the solvent evaporates from an ink puddle filled between banks, then drying progresses and the functional layer is formed, but the ink flows from the center toward the edges because the solvent evaporates more easily at the edges than the center, causing uneven film thickness
Solution Approach 1:
The patent optimizes the evaporation parameters by selecting solvents with specific boiling points (first solvent: 150-250°C, second solvent: 200-300°C). This parameter control ensures that evaporation proceeds at a moderate, uniform rate that prevents rapid edge-drying and subsequent ink flow, thereby maintaining both productivity and planarity.
Solution Approach 2:
The mixed solvent system acts as an intermediary that mediates between the conflicting requirements of efficient drying and uniform evaporation. The combination of two solvents with different boiling points creates a buffer effect that prevents the ink from flowing to the edges during drying, thus maintaining planarity while preserving drying efficiency.
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 functional layer with a higher degree of planarity and uniformity, reducing the likelihood of unevenness and extending the lifespan of organic light-emitting elements by maintaining film thickness uniformity within a narrow range.
Implementation Method 1
the boiling point of the first solvent is equal or similar to the boiling point of the second solvent
Implementation Method 2
the ink flows from the center toward the edges of the ink puddle because the solvent evaporates more easily at the edges than the center
Data Source
AI summary
An ink for an organic light-emitting element includes a first solvent, a second solvent, and a functional material. The first and second solvents have equal or similar boiling points. The first solvent is such that an imitatively formed functional layer formed by replacing the second solvent with the first solvent, in a light-emitting region of an organic light-emitting element, is thicker at both end portions than at a central portion and the top surfaces of the end portions are positioned higher than the top surface of the central portion. The second solvent is such that an imitatively formed functional layer formed by replacing the first solvent with the second solvent, in a light-emitting region of an organic light-emitting element, is thicker at a central portion than at both end portions and the top surface of the central portion is positioned higher than the top surfaces of the end portions.