Polycycloolefin Monomer Composition for OLED Refractive Index Matching
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Solution Overview
Problem
Conventional OLEDs face challenges such as refractive index mismatch between organic layers and glass substrates, leading to photon loss, and require protective coatings that are sensitive to harsh conditions, with existing solutions being either unstable or requiring two-component systems.
Innovation Solution
A single-component mass polymerizable polycycloolefin monomer composition with a latent organo-transition metal catalyst and a compound capable of generating a Bronsted acid under photolytic conditions, which forms transparent optical layers with a refractive index matching the glass substrate, providing excellent optical transparency, insulation, and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLED structures are used with glass substrate, then device fabrication is simple, but refractive index mismatch causes photon loss and reduces light extraction efficiency
Solution Approach 1:
The patent introduces an intermediary layer comprising a polycycloolefin polymer (such as poly(norbornene) or poly(5-phenethyl-2-norbornene)) with refractive index of 1.7-1.9 as a mediator between the organic OLED layers and the glass substrate. This intermediary layer acts as a refractive index gradient transition zone that reduces the abrupt refractive index mismatch, thereby minimizing photon loss due to total internal reflection and improving light extraction efficiency without complicating the fabrication process.
2Reliability
If protective coatings are applied to protect OLED from harsh conditions, then OLED reliability improves, but the coatings require two-component systems that are complex and unstable
Solution Approach 1:
The patent merges the protective coating function with the existing OLED encapsulation layers by using a single-component polycycloolefin polymer composition that can be applied as a conformal coating. This eliminates the need for separate two-component protective coating systems, reducing fabrication complexity while maintaining protection against moisture and oxygen. The single-component nature also improves stability during storage and processing.
Solution Approach 2:
The polycycloolefin polymer composition serves multiple functions simultaneously: it provides protection against moisture and oxygen, acts as an optical layer with matched refractive index, and offers mechanical protection to the OLED structure. This multi-functional approach eliminates the need for separate protective coatings, simplifying the device structure while improving reliability.
3Ease of operation
If single-component mass polymerizable composition is used, then ease of dispensing and fabrication improves, but stability at room temperature must be maintained until activation
Solution Approach 1:
The patent employs a preliminary action approach by incorporating a photoinitiator system that remains dormant at room temperature but activates upon exposure to specific wavelengths of light (UV or visible). This allows the single-component polycycloolefin composition to be dispensed and processed at room temperature in its stable, unpolymerized state, then rapidly crosslinked in situ upon light exposure to form the final protective and optical layer. This preliminary stabilization enables ease of dispensing while maintaining composition stability.
Solution Approach 2:
The patent utilizes parameter changes by selecting photoinitiators with specific absorption spectra that allow the composition to remain stable at room temperature under ambient lighting conditions, then undergo rapid polymerization when exposed to activation wavelengths. The glass transition temperature (Tg) of the polycycloolefin polymer is also optimized to ensure stability during storage and processing, then rapid curing upon photoinitiation. This parameter optimization enables both ease of operation and compositional stability.
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 solution enables increased light extraction into the substrate, improved insulation, and stability at room temperature, with fast polymerization and adhesion to both OLED stacks and glass covers, forming a transparent film with high visible light transmission.
Implementation Method 1
a compound capable of generating a Bronsted acid under photolytic conditions
Implementation Method 2
mass polymerizable polycycloolefin monomer composition with a latent organo-transition metal catalyst and a compound capable of generating a Bronsted acid under photolytic conditions, which forms transparent optical layers
Data Source
AI summary
Embodiments in accordance with the present invention encompass compositions encompassing a latent catalyst and a compound capable of generating a Bronsted acid along with one or more monomers which undergo ring open metathesis polymerization (ROMP) when said composition is exposed to a suitable radiation to form a substantially transparent film. The monomers employed therein have a range of refractive index from 1.4 to 1.6 and thus these compositions can be tailored to form transparent films of varied refractive indices. The composition of this invention also features low dielectric constant (low k in the range of from about 2.2 to 3). Accordingly, compositions of this invention are useful in various opto-electronic applications, including as coatings, encapsulants, fillers, leveling agents, among others.