Polycycloolefin Encapsulant for OLED Light Extraction
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Solution Overview
Problem
Conventional OLEDs face challenges such as photon loss due to refractive index mismatch between organic layers and glass substrates, sensitivity to harsh conditions, and the need for stable, single-component mass polymerizable compositions that can polymerize under specific conditions like 3D printing without premature polymerization.
Innovation Solution
A single-component composition comprising norbornene-based olefinic monomers, a latent organo-ruthenium compound, a photosensitizer, and a UV blocker, which remains stable at temperatures up to 80°C and undergoes mass polymerization only under actinic radiation, forming transparent optical layers with tailored refractive index and optical transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional OLED structures are used, then device functionality is achieved, but photon extraction efficiency is limited to about 50% due to refractive index mismatch
Solution Approach 1:
The patent modifies the refractive index parameter of the encapsulant material to match that of the organic light emitting layer (n=1.7-1.9). By selecting polycycloolefin compositions with specific refractive index values within this range, the invention optimizes optical coupling between layers, enabling 80-90% light extraction efficiency compared to conventional 50% extraction
Solution Approach 2:
The invention uses composite polycycloolefin-based encapsulant materials that combine optical transparency, refractive index matching, and thermal stability properties. These composite materials integrate multiple functions: optical coupling, moisture barrier, and thermal management, thereby improving photon extraction without proportionally increasing device complexity
2Reliability
If OLEDs are exposed to harsh atmospheric conditions, then device testing and operation proceed, but OLED performance degrades due to sensitivity to moisture and oxygen
Solution Approach 1:
The patent employs polycycloolefin-based encapsulant materials that create an inert protective barrier around the OLED active layers. This encapsulation isolates the sensitive organic materials from harmful atmospheric factors including moisture and oxygen, thereby enhancing device reliability and operational stability in harsh environments
Solution Approach 2:
The invention uses thin film encapsulation layers made from polycycloolefin compositions that provide protective functionality while maintaining device flexibility and optical transparency. These thin films serve as barriers against moisture and oxygen penetration, protecting the OLED structure without adding significant bulk or compromising optical performance
3Stability of the object's composition
If two-component mass polymerizable compositions are used, then refractive index can be tailored, but storage stability deteriorates due to premature polymerization
Solution Approach 1:
The patent separates the polymerization catalyst from the monomer composition, storing them in distinct components that are mixed only prior to application. This segmentation prevents premature polymerization during storage while allowing refractive index tailoring through monomer selection. The catalyst is activated only when needed, maintaining composition stability during storage
Solution Approach 2:
The invention performs preliminary selection and combination of monomers with specific refractive index properties before catalyst activation. The monomer mixture is prepared in advance with desired optical properties, and the catalyst is added just before application to initiate polymerization. This preliminary preparation allows refractive index tailoring while maintaining storage stability
4Productivity
If liquid compositions are stored in 3D printer vats, then fabrication process proceeds, but premature polymerization occurs due to air exposure and light
Solution Approach 1:
The patent formulates the liquid composition with components that are stable in inert atmospheres and protects the composition during 3D printing by minimizing exposure to air and light until the moment of application. The latent catalyst system remains inactive during storage and handling, preventing premature polymerization while maintaining fabrication efficiency
Solution Approach 2:
The invention uses an inert atmosphere (such as nitrogen or argon) as an intermediary barrier between the liquid composition and harmful environmental factors (oxygen and light). This intermediary protection allows the composition to be stored and handled during 3D printing operations without premature polymerization, maintaining both productivity and composition 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 composition achieves high optical transparency, compatibility with OLED stacks, low shrinkage, and extended shelf life, enabling the fabrication of 3D objects and OLED devices with improved light extraction and thermal properties.
Implementation Method 1
undergoes mass polymerization only when subjected to suitable actinic radiation to form transparent optical layers
Implementation Method 2
a compound capable of blocking the ultraviolet light
Implementation Method 3
a photosensitizer
Data Source
AI summary
Embodiments in accordance with the present invention encompass compositions encompassing a latent organo-ruthenium compound, a pyridine compound, a photosensitizer and an ultra violet light blocking compound along with one or more monomers which undergo ring open metathesis polymerization (ROMP) when said composition is exposed to suitable actinic radiation to form a substantially transparent film or a three dimensional object. Surprisingly, the compositions are very stable at ambient conditions to temperatures up to 80° C. for several days and undergo mass polymerization only when subjected to actinic radiation under inert atmosphere such as for example a blanket of nitrogen. Accordingly, compositions of this invention are useful in various opto-electronic applications, including as 3D printing materials, coatings, encapsulants, fillers, leveling agents, among others.