Phosphorescent Composition Solvent Segmentation for Film Flatness
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Solution Overview
Problem
There is a need for a composition comprising a phosphorescent compound and a solvent that is useful for producing a film with excellent flatness when used in a discharge type application method, particularly for light emitting devices that exhibit higher light emission efficiency compared to those using fluorescent compounds.
Innovation Solution
A composition comprising a phosphorescent compound, solvent (A) with a boiling point under 1 atm of 200°C or higher, and solvent (B) with a boiling point below 200°C, where the boiling point difference between the two solvents is between 70°C and 120°C, and the content of solvent (B) is less than or equal to solvent (A), along with specific aromatic hydrocarbon or ether solvents, is used to form a light emitting layer in a light emitting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a phosphorescent compound is used in a light emitting device, then light emission efficiency is improved, but film flatness deteriorates when using conventional single-solvent compositions
Solution Approach 1:
The invention divides the solvent system into two distinct components: a high-boiling-point solvent (200°C or higher) and a low-boiling-point solvent (below 200°C). This segmentation allows each solvent to perform its specific function - the high-boiling-point solvent ensures film flatness while the low-boiling-point solvent aids in inkjet printing characteristics, resolving the contradiction between achieving good film formation and maintaining printing performance with phosphorescent compounds
Solution Approach 2:
The invention changes the physical parameters of the solvent system by carefully selecting solvents with specific boiling point differences (70-120°C) and controlling their weight ratios (where the high-boiling-point solvent constitutes 50% or more). This parameter optimization enables the composition to simultaneously achieve excellent film flatness and suitable inkjet printing characteristics when using phosphorescent compounds
2Manufacturing precision
If a single high-boiling-point solvent is used, then film flatness is improved, but inkjet printing characteristics worsen
Solution Approach 1:
The solvent system is segmented into two functional components with distinct boiling points. The high-boiling-point solvent (≥200°C) provides the necessary film flatness, while the low-boiling-point solvent (<200°C) contributes to better inkjet printing characteristics by facilitating proper ink flow and drying. This segmentation resolves the contradiction between film quality and printing performance
Solution Approach 2:
By optimizing the boiling point difference between the two solvents (70-120°C) and controlling their weight ratios (high-boiling-point solvent ≥50%), the invention achieves a balance where the composition maintains excellent film flatness while exhibiting suitable inkjet printing characteristics
3Ease of operation
If a single low-boiling-point solvent is used, then inkjet printing characteristics are improved, but film flatness deteriorates
Solution Approach 1:
The invention segments the solvent system into two components where the low-boiling-point solvent (<200°C) enhances inkjet printing characteristics by improving ink flow and drying behavior, while the high-boiling-point solvent (≥200°C) compensates for film flatness issues by providing the necessary viscosity control and film formation quality. This segmentation allows both requirements to be met simultaneously
4Stability of the object's composition
If two solvents with small boiling point difference are used, then composition stability is improved, but film flatness deteriorates
Solution Approach 1:
The invention optimizes the boiling point difference parameter between the two solvents to be within 70-120°C. This specific parameter range ensures that the solvents have sufficiently different evaporation rates and physical properties to achieve good film flatness, while still maintaining composition stability. The weight ratio control (high-boiling-point solvent ≥50%) further stabilizes the system while ensuring film quality
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
The composition enables the production of a light emitting device with a film that is excellent in flatness, enhancing light emission efficiency and luminance life, while maintaining the advantages of discharge type application methods.
Implementation Method 1
A light emitting device using a phosphorescent compound showing light emission from triplet excited state (phosphorescence emission) in a light emitting layer shows higher light emission efficiency
Implementation Method 2
the boiling point under 1 atm of the solvent (A): bpA (° C.) and the boiling point under 1 atm of the solvent (B) (bpB (° C.)) satisfy the formula (11) and the formula (12)
Data Source
AI summary
A composition containing a phosphorescent compound and solvents, which is useful for producing a film having excellent flatness when used in a discharge type application method, is provided. The composition contains a phosphorescent compound, a solvent (A) and a solvent (B), in which the boiling point under 1 atm of the solvent (A) (bpA (° C.)) and the boiling point under 1 atm of the solvent (B) (bpB (° C.)) satisfy formulas (11) and (12), and the content of the solvent (A) (wtA (by weight)) and the content of solvent (B) (wtB (by weight)) satisfy formula (13):bpB<200° C.≤bpA (11)70° C.≤bpA−bpB≤120° C. (12)wtB≤wtA (13).