Blue Color Filter Chromaticity for EBU Standard Compliance

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Solution Overview

Problem

Organic EL devices struggle to meet the color reproduction range specified in the EBU Standard, particularly in bright conditions where display contrast is lowered due to reflection of extraneous light, and existing solutions like circular polarizers and color filters have limitations in efficiency and effectiveness.

Innovation Solution

An organic EL device comprising a blue light emitter and a blue color filter with specific chromaticity coordinates (0.150, 0.060), (0.143, 0.031), and (0.130, 0.049) on the CIE chromaticity diagram, combined with suitable green and red light emitters, using triarylmethane dyes, lake pigments, or copper-phthalocyanine pigments to enhance heat and light resistance, ensuring comprehensive color reproduction within the EBU Standard.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a circular polarizer is attached to the organic EL device to prevent reflection of extraneous light, then reflection prevention is improved, but luminous efficiency deteriorates due to absorption of more than half of the emitted light

Engineering Contradiction:

Improvereflection of extraneous lightVSAvoidluminous efficiency

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent applies color filters with specific chromaticity coordinates to modify the color characteristics of emitted light. By selecting color filters with optimized chromaticity values, the device achieves both extraneous light reflection prevention and maintained luminous efficiency, avoiding the energy loss associated with circular polarizers.

Inventive Principle:

Principle #32Color changes

Solution Approach 2:

The patent changes the parameters of the color filter system by specifying precise chromaticity coordinates (x, y values) for blue, green, and red color filters. This parameter optimization allows the system to achieve EBU Standard compliance while maintaining high luminous efficiency, resolving the contradiction between reflection prevention and energy loss.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If a color filter is used to control the hue of emitted light, then hue control is improved, but effectiveness in preventing reflection of extraneous light deteriorates compared to circular polarizer

Engineering Contradiction:

Improvehue control capabilityVSAvoidreflection of extraneous light

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent employs a composite color filter system combining multiple color filters (blue, green, red) with specifically optimized chromaticity coordinates. This composite approach achieves both effective hue control and sufficient extraneous light reflection prevention, balancing the two requirements that cannot be simultaneously optimized by a single filter type.

Inventive Principle:

Principle #40Composite materials

3Loss of energy

If the three-color-films-coating method is used to achieve color display, then luminous efficiency is improved, but color reproduction range deteriorates compared to methods using white-light-emitting layer with color filters

Engineering Contradiction:

Improveluminous efficiencyVSAvoidcolor reproduction range

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent optimizes the chromaticity parameters of the three color filters used in conjunction with the three-color-films-coating method. By carefully selecting color filters with specific chromaticity coordinates that comply with EBU Standard, the system achieves both high luminous efficiency (inherent advantage of three-color method) and expanded color reproduction range, resolving the contradiction between these two parameters.

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 enables organic EL displays to achieve excellent color reproduction range, effectively covering the entire EBU Standard, while maintaining high luminous efficiency and resistance to heat and light, thus addressing the limitations of previous technologies.

Implementation Method 1

An organic EL device comprises an organic EL emitter that emits blue light

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

a blue color filter through which the light emitted from the organic EL emitter passes, wherein the chromaticity of the light, the light that has passed through the blue color filter

Methodology Applied

Scientific EffectSelective light transmission and absorption: Absorption (EM radiation)

Data Source

PatentUS8962156B2Organic EL device, color filter, and organic EL display

Publication Date: 2015.02.24 DAI NIPPON PRINTING CO LTD

AI summary

An organic EL device includes an organic EL emitter that emits blue light and a blue color filter through which the light emitted from the organic EL emitter passes. The blue color filter contains a coloring material selected from the group consisting of a triarylmethane dye, a lake pigment, a copper-phthalocyanine pigment, and a mixture of a copper-phthalocyanine pigment and a dioxazine pigment. The chromaticity of the light that has passed through the blue color filter after being emitted from the organic EL emitter, is in the range defined by lines connecting three chromaticity coordinates (0.150, 0.060), (0.143, 0.031), and (0.130, 0.049) on the CIE chromaticity diagram.