Nano-Desiccant Encapsulation for OLED Light Transmittance
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Solution Overview
Problem
Organic light emitting devices are prone to deterioration due to water vapor and oxygen permeation, leading to instability and short lifetimes, and existing encapsulation methods are either bulky or opaque, limiting their use in front emission type displays.
Innovation Solution
A transparent encapsulation layer using nano-sized desiccant particles (100 nm or less) dispersed in a transparent sealant, such as epoxy silane or acrylate, with a low water vapor transmission rate, effectively preventing water vapor and oxygen ingress while maintaining high light transmittance, suitable for front emission type devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional airtight container with drying agent is used for encapsulation, then water vapor absorption capability is improved, but device transparency and light emission quality deteriorate
Solution Approach 1:
The patent changes the particle size parameter of the drying agent from conventional micrometer scale to nanometer scale (1-100 nm). This parameter change allows the drying agent particles to be sufficiently small to not scatter visible light, thereby maintaining high transparency while preserving water vapor absorption capability. The nanoscale dimension is the critical parameter that resolves the contradiction between absorption function and optical transparency.
Solution Approach 2:
The patent creates a composite material system by dispersing nanoscale drying agent particles within a transparent encapsulation resin matrix. This composite structure combines the water vapor absorption properties of the drying agent (such as alkali metal oxides, alkaline earth metal oxides, or their hydrates) with the optical transparency and structural integrity of the encapsulation resin, achieving both protection and visibility.
2Duration of action of stationary object
If encapsulation materials are used to prevent water vapor and oxygen permeation, then device lifetime is improved, but device thickness and bulkiness increase
Solution Approach 1:
The patent reduces the thickness of the encapsulation layer by utilizing nanoscale drying agent particles that provide high surface area to volume ratio. This allows effective water vapor absorption within a thinner layer, reducing the overall encapsulation thickness from conventional hundreds of micrometers to potentially tens of micrometers or less, while maintaining protective function and extending device lifetime.
3Reliability
If conventional drying agents are used in encapsulation, then water vapor absorption is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent simplifies the manufacturing process by specifying a narrow particle size range (1-100 nm) for the drying agent, which can be produced using standard nanotechnology techniques. This parameter specification enables consistent performance and simplifies quality control compared to conventional approaches that may use irregularly sized particles or require complex multi-layer structures.
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 provides a stable and long-lasting organic light emitting device with high transmittance, preventing water vapor and oxygen from reaching the organic light emitting unit, thus extending the device's lifetime and preventing dark spots, while allowing for thin and transparent encapsulation suitable for front emission displays.
Implementation Method 1
a desiccant, such as an alkali metal oxide, an alkaline earth metal oxide, a hydrate thereof, or a composite material including these materials
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
Disclosed is an organic light emitting device which includes a substrate (10); an encapsulation substrate (17), an organic light emitting unit (12) interposed between the substrate (10) and the encapsulation substrate (17). A water vapor absorption material-containing transparent sealant layer (16) covers the organic light emitting unit (12). The sealant layer includes a transparent sealant having a water vapor transmission rate (WVTR) of about 20 g/m2·day or less and a water vapor absorption material having an average particle size of about 100 nm or less.