Dichroic Dye Orientation for OLED Contrast and Luminance
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Solution Overview
Problem
Display devices with OLED or QLED technology face issues with contrast ratio degradation due to external light reflection, leading to reduced luminance and color purity, especially when using polarizers with azo compounds that overlap with emission peak wavelengths.
Innovation Solution
A display device configuration featuring multiple light-emitting layers with distinct emission peak wavelengths and dichroic dyes with specific absorption peak wavelengths and molecular orientations to minimize light absorption and maximize contrast and luminance, including a reflective layer and light-absorbing members with dichroic dyes positioned between the light-emitting layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circular polarizer is provided on the surface of the display device to suppress external light reflection, then the contrast ratio is improved, but the luminance is reduced because the circular polarizer absorbs about half of the light emitted to the user side
Solution Approach 1:
The patent changes the optical parameters of the polarizing layer by using a specific molecular orientation angle (45 degrees or 135 degrees relative to the substrate plane) and selecting materials with appropriate refractive ratios. This parameter optimization allows the polarizing layer to suppress external light reflection while minimizing light absorption, thereby maintaining high luminance alongside improved contrast ratio.
2Object-affected harmful factors
If a polarizer formed of base material containing azo compounds is used to improve contrast ratio and color purity, then the bright place contrast ratio and color purity are improved, but the light usage efficiency is reduced because the emission peak wavelength from the light-emitting layer overlaps with the absorption wavelength range of the polarizer
Solution Approach 1:
The patent applies local quality by creating different optical characteristics in different wavelength regions. The polarizing layer is designed to have selective absorption properties where it strongly absorbs external light in the visible range while having minimal absorption at the specific emission wavelengths of the display device. This is achieved through careful selection of molecular orientation and material properties, allowing the same layer to simultaneously improve contrast ratio and maintain light usage efficiency.
3Productivity
If a reflective electrode is formed of material with relatively high reflectivity to efficiently emit light from the light-emitting layer, then the light emission efficiency is improved, but the contrast ratio is lowered under intense external light due to reflection of external light
Solution Approach 1:
The patent introduces a polarizing layer as an intermediary component between the reflective electrode and the external environment. This polarizing layer serves as a mediator that allows the reflective electrode to maintain its high reflectivity for light emission while simultaneously filtering out externally reflected light. The polarizing layer transmits the linearly polarized light from the display device while blocking externally reflected light, thus resolving the contradiction between light emission efficiency and contrast ratio under external light conditions.
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 achieves high bright place contrast ratio, high color purity, and high light usage efficiency by optimizing the absorption and reflection of external light, preventing luminance reduction and enhancing display quality.
Implementation Method 1
a first dichroic dye having an absorption peak wavelength between the first emission peak wavelength and the second emission peak wavelength, the second dichroic dye has an absorption peak wavelength between the second emission peak wavelength and the third emission peak wavelength
Implementation Method 2
a reflective layer configured to reflect light, the reflective layer being provided as a lower layer to the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer
Implementation Method 3
an angle of a molecule of the first dichroic dye in an absorption axis direction and an angle of a molecule of the second dichroic dye in an absorption axis direction with respect to a normal direction of the reflective layer are from 70 degrees to 90 degrees
Data Source
AI summary
A light absorbing member includes a first dichroic dye and a second dichroic dye. The first dichroic dye has an absorption peak wavelength between a first emission peak wavelength of the first light-emitting layer and a second emission peak wavelength of a second light-emitting layer. The second dichroic dye has an absorption peak wavelength between the second emission peak wavelength of the second light-emitting layer and a third emission peak wavelength of the third light-emitting layer. An angle of a molecule of the first dichroic dye in an absorption axis and an angle of a molecule of the second dichroic dye in an absorption axis with respect to a normal direction of the reflective layer are from 70 degrees to 90 degrees.