White Color Filter for Display Device External Light Reflection

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Solution Overview

Problem

Organic electroluminescence (EL) panels face significant external light reflection issues due to the structure of their light-emitting elements and color filters, leading to decreased display quality, increased power consumption, and unwanted color changes in reflected light.

Innovation Solution

Incorporating a white color filter with neutral density (ND) transmittance uniform across the visible light spectrum and adjusting its transmittance in specific wavelength bands using coloring agents, while varying the aperture ratio of white pixels relative to colored pixels, to minimize external light reflection and control the hue of reflected light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a circularly polarizing plate is provided on the surface of the organic EL panel to reduce external light reflection, then external light reflection is reduced, but the brightness of organic-EL intrinsic light is decreased to half, causing power consumption to increase

Engineering Contradiction:

Improveexternal light reflectionVSAvoidpower consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent applies different transmittance characteristics to different wavelength bands by using a color filter that selectively absorbs specific wavelengths. The color filter has high transmittance in the wavelength band where organic EL emits light, maintaining brightness, while having low transmittance in wavelength bands where external light reflection occurs, thereby reducing reflection without significantly affecting power consumption

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the transmittance parameter of the color filter across different wavelength bands. By designing the color filter to have wavelength-dependent transmittance characteristics, it achieves selective reduction of external light reflection in specific wavelength bands while maintaining high transmittance in the organic EL emission band, thus avoiding the 50% brightness loss associated with circularly polarizing plates

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the aperture ratio of white pixels is decreased or neutral density (ND) filter is provided to reduce external light reflection, then external light reflection is reduced, but the color of reflected light cannot be controlled, resulting in hue change

Engineering Contradiction:

Improveexternal light reflectionVSAvoidcolor uniformity of reflected light

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent uses a color filter that selectively transmits and absorbs different wavelengths of light. The color filter is designed to have low transmittance in wavelength bands where external light reflection is problematic, thereby controlling the color/hue of reflected light. This approach actively manages the spectral composition of reflected light rather than simply reducing overall intensity

Inventive Principle:

Principle #32Color changes

Solution Approach 2:

The color filter applies different optical properties to different wavelength bands, creating local quality variations in the transmittance spectrum. This allows selective suppression of reflection in specific wavelength ranges while maintaining transmission in others, enabling control over the color characteristics of reflected light

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If high transmittance color filters are used in organic EL panels, then light absorption is insufficient, but this causes light to go out of the panel, resulting in large amount of reflection components

Engineering Contradiction:

Improvelight transmittanceVSAvoidreflection component

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the transmittance parameter of the color filter to be wavelength-dependent. The color filter is designed with high transmittance in the wavelength band where organic EL emits light to maintain illumination intensity, while having low transmittance in wavelength bands where external light reflection occurs, thereby reducing reflection components without compromising display brightness

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

Effectively reduces external light reflection without significantly decreasing the brightness of intrinsic light, allowing for precise control of the color of reflected light, thus enhancing display quality and reducing power consumption.

Implementation Method 1

transmittance in a particular wavelength band in the entire wavelength band of the visible light is decreased to be lower than the ND transmittance

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS9368557B2Display device and electronic device

Publication Date: 2016.06.14 SONY GROUP CORP

AI summary

There is provided a display device including a light-emitting element corresponding to a pixel for a color, and a white color filter corresponding to a white pixel. Transmittance of the white color filter is based on neutral density (ND) transmittance that is uniform throughout an entire wavelength band of visible light, and transmittance in a particular wavelength band in the entire wavelength band of the visible light is decreased to be lower than the ND transmittance.