Organic EL Device Optical Path Length Adjusting Layer Refractive Index

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Solution Overview

Problem

Existing organic EL devices face luminosity reduction and increased level differences between pixels due to refractive index interfaces and excessive current flow, particularly when using silicon oxide for optical path length adjustment, leading to decreased color stability and reliability.

Innovation Solution

An organic EL device with a refractive index mismatch reduction between the optical path length adjusting layer and the protective layer, using materials like silicon nitride, titanium oxide, or tantalum oxide to form an insulating layer with a higher refractive index than the protective layer, and optimizing layer thickness to minimize refractive index interfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If silicon oxide (SiO2) is used for optical path length adjustment, then the refractive index difference between layers is reduced, but the film thickness must be increased which causes increased level difference between pixels

Engineering Contradiction:

Improverefractive index matchingVSAvoidfilm thickness

Core Design Contradiction:

Stability of the object's compositionVSLength of stationary object

Solution Approach 1:

The patent changes the material parameter (refractive index) of the optical path length adjusting layer from low refractive index materials like silicon oxide to high refractive index materials like silicon nitride, titanium oxide, or tantalum oxide. This parameter change allows achieving the desired optical path length adjustment with a thinner film, thereby reducing the level difference between pixels while maintaining refractive index matching benefits

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If silicon oxide (SiO2) is used for optical path length adjustment, then the refractive index difference between layers is reduced, but the level difference between pixels increases causing potential sealing film damage

Engineering Contradiction:

Improverefractive index matchingVSAvoidsealing film integrity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent changes the refractive index parameter of the optical path length adjusting layer to use high refractive index materials (silicon nitride, titanium oxide, or tantalum oxide with refractive index of 2.0 or more). This allows achieving the required optical path length adjustment with a thinner film thickness, thereby reducing the level difference between pixels and preventing sealing film damage while maintaining the refractive index matching advantage

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If silicon oxide (SiO2) is used for optical path length adjustment, then the refractive index interface is reduced, but excessive current flows to thin portions causing decreased color stability

Engineering Contradiction:

Improverefractive index interface reductionVSAvoidcurrent distribution uniformity

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The patent changes the material parameter (refractive index) of the optical path length adjusting layer to high refractive index materials. This enables achieving the desired optical path length adjustment with a thinner film, which prevents the formation of excessive thin portions in the OLED layer. Consequently, current distribution remains uniform and color stability is maintained while still benefiting from reduced refractive index interfaces

Inventive Principle:

Principle #35Parameter changes

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 prevents luminosity reduction, reduces level differences between pixels, enhances color stability, and improves reliability by minimizing refractive index interfaces and optimizing layer thickness, thereby improving the overall performance of the organic EL device.

Implementation Method 1

the optical path length adjustment is performed by silicon oxide (SiO2) on the protective layer... The optical distance is obtained by the product of the refractive index and the film thickness

Methodology Applied

Scientific EffectOptical path length adjustment: Refraction

Data Source

PatentUS10431775B2Organic EL device, method for manufacturing organic EL device, and electronic instrument

Publication Date: 2019.10.01 SEIKO EPSON CORP

AI summary

An organic EL device has at least a first pixel and a second pixel different in the optical path length, in which the first pixel and the second pixel have a reflective layer, a protective layer, an optical path length adjusting layer, a first electrode, a light emitting function layer, and a second electrode, and the optical path length adjusting layer is an insulating layer and has a refractive index higher than a refractive index of the protective layer.