Scattering Film for Organic EL Light Utilization Efficiency

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Solution Overview

Problem

Conventional organic EL light emitting devices suffer from low light utilization efficiency, viewing angle dependency, and reflection issues when turned off, due to total reflection and wavelength separation at interfaces between light-emitting layers.

Innovation Solution

A scattering film with a specific scattering layer is applied to the light-emitting surface, comprising a binder resin and particles with different refractive indices, which scatters and mixes light to improve efficiency and reduce reflection, while maintaining durability and optical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a light outcoupling layer of low refractive index material is provided, then light utilization efficiency is improved, but wavelength separation problem remains unresolved

Engineering Contradiction:

Improvelight utilization efficiencyVSAvoidwavelength separation countermeasure

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent uses a composite scattering layer comprising a binder resin and inorganic particles with different refractive indices. This composite structure enables both light outcoupling enhancement and wavelength mixing, resolving the limitation of single-material low refractive index layers that cannot address wavelength separation.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The scattering layer is positioned specifically on the light-emitting surface where light outcoupling is needed, while the inorganic particles provide localized refractive index variation throughout the layer. This localized quality distribution enables efficient light extraction without causing wavelength separation issues.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If a scattering member is placed on the light outcoupling surface, then light utilization efficiency is improved, but viewing angle dependency is not effectively addressed

Engineering Contradiction:

Improvelight utilization efficiencyVSAvoidviewing angle dependency

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent changes the refractive index parameter distribution by incorporating inorganic particles with refractive indices different from the binder resin. This parameter variation creates effective scattering that mixes wavelengths and reduces viewing angle dependency while maintaining high light utilization efficiency.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by stationary object

If the organic EL light emitting device is turned off, then power consumption is reduced, but reflection of outside scenery adversely affects appearance

Engineering Contradiction:

Improvepower consumptionVSAvoidreflection of outside scenery

Core Design Contradiction:

Use of energy by stationary objectVSObject-affected harmful factors

Solution Approach 1:

The scattering layer acts as an intermediary between the organic EL element and the external environment. When the device is off, this layer scatters and diffuses reflected light from outside scenery, reducing the adverse reflection effect on appearance while not affecting power consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Illumination intensity

If multiple light-emitting layers with different refractive indexes are combined, then color emission is achieved, but optical path length difference causes hue change depending on viewing angle

Engineering Contradiction:

Improvecolor emissionVSAvoidhue change with viewing angle

Core Design Contradiction:

Illumination intensityVSEase of operation

Solution Approach 1:

The patent introduces a new dimension of light interaction by adding the scattering layer with inorganic particles. This creates additional light paths and scattering events that randomize the optical path length differences between different light-emitting layers, thereby mixing wavelengths and eliminating hue changes with viewing angle while preserving color emission.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 scattering film enhances light utilization efficiency, reduces viewing angle dependency, and prevents reflection when the device is turned off, thereby improving overall performance.

Implementation Method 1

a scattering film including a scattering layer on a light-emitting surface side of the organic EL light emitting device

Methodology Applied

Scientific EffectLight scattering: Scattering

Implementation Method 2

the particles have a refractive index different from the refractive index of the binder resin

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentEP2744301B1Scattering film for organic el light emitting device and organic el light emitting device using same

Publication Date: 2019.02.20 KIMOTO CO LTD

Figure 1

AI summary

There is provided a scattering film that can be used in organic EL light emitting devices and that not only improves efficiency for light utilization and improves viewing angle dependency, which have conventionally been problems, but also can solve the problem of reflection when lights-off. This scattering film for organic EL is used in organic EL light emitting devices. The scattering film comprises a scattering layer that includes a binder resin and particles having a refractive index different from the binder resin. The average particle size of the particles is 10 µm or less, and the coefficient of variation of the average particle size for the particles is 30% or greater.