Organic EL Display Wavelength Selective Absorption Filter
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Solution Overview
Problem
Existing organic EL display devices face challenges in reducing external light reflection while maintaining brightness, as circularly polarizing plates and neutral density filters either reduce brightness significantly or increase reflection brightness, thereby decreasing contrast ratios.
Innovation Solution
The implementation of an organic EL display device with a wavelength selective absorption filter that absorbs light in a spectrum with negative correlation to the outgoing light spectrum, combined with an anti-reflective film and a silicon nitride sealing film, which absorbs shorter wavelengths, to minimize external light reflection and enhance contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circularly polarizing plate is arranged on the display surface to reduce external light reflection, then the reflection brightness is reduced, but the white brightness is reduced by half
Solution Approach 1:
The patent applies different optical properties to different wavelength ranges by using a wavelength selective absorption filter that selectively absorbs specific wavelength bands (complementary to the OLED emission spectrum) while allowing other wavelengths to pass through. This local quality approach reduces external light reflection in critical wavelength ranges without uniformly reducing all light transmission, thereby maintaining higher white brightness compared to broadband solutions like circularly polarizing plates.
Solution Approach 2:
The patent changes the spectral parameters of the absorption filter to match the complementary spectrum of the OLED emission. By adjusting the absorption spectrum to have negative correlation with the outgoing spectrum, the filter selectively targets external light wavelengths while preserving OLED emission wavelengths, resolving the contradiction between reflection reduction and brightness maintenance.
2Illumination intensity
If a neutral density filter with higher transmittance is used to maintain brightness, then the white brightness is increased, but the reflection brightness increases more significantly
Solution Approach 1:
The wavelength selective absorption filter applies selective absorption properties to different wavelength ranges, allowing high transmittance for OLED emission wavelengths while providing strong absorption for external light wavelengths. This local quality differentiation enables the filter to maintain high white brightness without proportionally increasing reflection brightness, unlike uniform transmittance ND filters.
Solution Approach 2:
The patent utilizes spectral selectivity where the absorption filter's transmission characteristics change across different wavelengths. The filter appears transparent to OLED emission wavelengths while being absorptive to external light wavelengths, effectively using color/spectral differentiation to resolve the contradiction between brightness and reflection control.
3Illumination intensity
If electric power supplied to OLED is increased to compensate for brightness loss, then the white brightness is increased, but the deterioration of light emitting layer is accelerated
Solution Approach 1:
The patent converts the potential harm of external light reflection (which degrades image quality) into a benefit by using the absorption filter to selectively remove harmful reflected wavelengths while preserving useful OLED emission wavelengths. This approach maintains brightness without requiring increased power, thereby avoiding accelerated deterioration of the light emitting layer.
Solution Approach 2:
By changing the spectral parameters of the absorption filter to match the complementary spectrum of OLED emission, the system optimizes the transmission of useful light while blocking harmful reflected light. This parameter optimization maintains adequate brightness levels without requiring increased drive current, thus preserving light emitting layer durability.
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
This configuration reduces external light reflection by 25% while limiting brightness reduction to 30%, thereby improving the contrast ratio and maintaining relatively low brightness loss compared to conventional filters.
Implementation Method 1
an absorption filter that absorbs a light in a given absorption spectrum uniform in the display region, in which the absorption spectrum has a negative correlation with an outgoing spectrum
Implementation Method 2
an anti-reflective film and a silicon nitride sealing film, which absorbs shorter wavelengths, to minimize external light reflection
Implementation Method 3
a silicon nitride sealing film, which absorbs shorter wavelengths
Data Source
AI summary
An organic EL display device ensures brightness and improves a contrast ratio by a reduction in external light reflection. The organic EL display device includes a wavelength selective absorption filter that absorbs a light in a given absorption spectrum uniform in a display region. An absorption spectrum has a negative correlation with an outgoing spectrum in which respective spectrums of R pixels, G pixels, and B pixels are synthesized together.