Crosslinked Polyimide Film for OLED Encapsulation
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Solution Overview
Problem
Conventional polyimide materials in OLED devices face issues such as signal delay and power loss due to high dielectric constant, low transmittance, and encapsulation difficulties, which are not adequately addressed by existing technologies.
Innovation Solution
A crosslinked polyimide film is developed using a diamine monomer with long chain pendant groups and a crosslinked agent like p-xylylenediamine, which reduces the dielectric constant and increases transmittance by disrupting polymer crystallization and widening molecular chain spacing, facilitating the formation of a polyimide film with a low dielectric constant and high transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimide is used in OLED devices, then the material provides structural support and basic dielectric properties, but it causes signal delay and power loss due to high dielectric constant
Solution Approach 1:
The patent changes the chemical structure parameters of polyimide by introducing long chain pendant groups (such as carbazole and triphenylamine groups) and crosslinking structures, which fundamentally alter the dielectric constant from conventional high values to below 2.0, thereby reducing signal delay and power loss in OLED devices
Solution Approach 2:
The patent creates a composite polyimide structure combining rigid aromatic rings with flexible long chain pendant groups and crosslinking agents, forming a multi-component molecular architecture that achieves both low dielectric constant and high transmittance properties
2Reliability
If conventional polyimide is used in OLED devices, then the material provides structural support, but it exhibits low light transmittance
Solution Approach 1:
The patent modifies the optical parameters of polyimide by changing the molecular structure to include long chain pendant groups that reduce molecular packing density and crystallinity, thereby increasing light transmittance to above 80% while maintaining structural integrity
Solution Approach 2:
The patent uses small molecule crosslinking agents (such as p-xylylenediamine) that form permanent crosslinked structures within the polyimide matrix, effectively creating a durable low-dielectric constant material that maintains its properties throughout the device lifetime
3Reliability
If conventional polyimide is used in OLED devices, then the material provides basic encapsulation, but it presents high encapsulation difficulty
Solution Approach 1:
The patent changes the thermal and chemical parameters of polyimide through crosslinking, improving thermal stability and chemical resistance to enable effective encapsulation of OLED devices against moisture and oxygen, while the solution processing capability maintains ease of manufacture
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 crosslinked polyimide film achieves a dielectric constant of 1.5 to 2 and light transmittance of 80% to 99%, addressing signal delay, power loss, and encapsulation challenges in OLED devices.
Implementation Method 1
reduces the dielectric constant and increases transmittance by disrupting polymer crystallization and widening molecular chain spacing
Implementation Method 2
the crosslinked polyimide solution is crosslinked and cured by a flexible film post-drying machine to form a polyimide film
Implementation Method 3
removing 70% of a solvent in the crosslinked polyimide solution by high temperature vacuum drying
Data Source
AI summary
A crosslinked polyimide, a polyimide film and a method for preparing thereof, an organic light emitting diode (OLED) device. 4,40-diamino-400-N-carbazolyltriphenylamine and 1,2,4,5-cyclohexanetetracarboxylic dianhydride and a p-xylylenediamine crosslinker are introduced in the present invention. The introduction of a diamine monomer with a large volume of pendant groups increases an asymmetry of the polyimide, destroys a close structure of the polymer, and reduces crystallization properties of the polypolymer, thereby effectively increasing its transmissibility. At the same time, a cross-linked agent, p-xylylenediamine, is introduced, and the cross-linked agent widens a molecular chain spacing, so that the polyimide molecule has a larger free volume. At the same time, the formation of cross-linked is beneficial to reduce a polarizability of the molecule, thereby reducing a dielectric constant of the material. An OLED device with a novel low dielectric constant and high transmittance is prepared in this way.