Green Color Filter Pigment Selection for OLED Chromaticity
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Solution Overview
Problem
Existing color filters for broadband OLED displays fail to provide improved color rendition, particularly in achieving the desired 1931 CIE x,y chromaticity coordinates and spectral curve shape, leading to compromised color gamut and efficiency.
Innovation Solution
A green color filter comprising a bridged aluminum phthalocyanine pigment and a second pigment with maximum absorption between 400 to 500 nm, where at least 90% of particles are less than 300 nm in size, offering high transmittance in the green region and minimal transmittance in the red and blue regions, thereby enhancing color gamut and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional color filters are used in broadband OLED displays, then the display can be manufactured with standard filters, but the color rendition and chromaticity coordinates do not meet the desired standards
Solution Approach 1:
The patent changes the spectral parameters of the color filter by selecting a pigment with maximum absorption specifically in the 400-500 nm range and controlling particle size distribution (at least 90% of particles less than 300 nm). This parameter optimization achieves the desired chromaticity coordinates (x≤0.24, y≥0.68) and spectral curve shape that conventional filters fail to provide.
Solution Approach 2:
The patent uses a composite approach by combining bridged aluminum phthalocyanine pigment with a second pigment having maximum absorption at 400-500 nm. This composite pigment system creates the necessary spectral characteristics for pure green color reproduction while maintaining compatibility with broadband OLED emission profiles.
2Manufacturing precision
If color filters with narrow transmission bands are used to achieve pure color, then color gamut is improved, but transmittance efficiency in the green region decreases
Solution Approach 1:
The patent applies local quality by creating a filter with highly selective absorption characteristics - the second pigment absorbs strongly only in the 400-500 nm blue region while the bridged aluminum phthalocyanine provides the green transmission window. This localized absorption approach achieves pure green color (blocking blue and red) while maintaining high transmittance (≥60%) in the desired green region at 520 nm.
3Device complexity
If existing green filters are used, then the display structure remains simple, but the spectral curve shape does not match the desired profile for pure green emission
Solution Approach 1:
The patent achieves the desired spectral curve shape by optimizing specific parameters: maximum absorption wavelength (400-500 nm), particle size distribution (90% < 300 nm), and absorption intensity. These parameter changes create a spectral profile with a sharp cutoff in the blue region and maintained transmission in the green region, producing the characteristic pure green emission profile without complicating the filter structure.
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 provides improved color rendition with better chromaticity coordinates and spectral curve shape, resulting in a more efficient and purer green color representation, surpassing the limitations of existing filters.
Implementation Method 1
a bridged aluminum phthalocyanine pigment
Implementation Method 2
a second pigment having its maximum absorption at a wavelength from 400 to 500 nm
Data Source
AI summary
A green color filter having a green filter layer comprising a bridged aluminum phthalocyanine pigment and a second pigment having its maximum absorption at a wavelength from 400 to 500 nm.