Organic EL Display Panel Sub-Pixel Optical Length Optimization
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Solution Overview
Problem
The challenge in organic electroluminescence (EL) display panels is the short lifespan of blue organic EL elements and the need for precise shadow masks, which increases manufacturing costs and reduces productivity, especially when forming charge generating layers in blue sub-pixels, and the inefficiency of red and green organic EL elements due to increased drive voltage.
Innovation Solution
An organic EL display panel design featuring a substrate with defined sub-pixel regions, light-reflective electrodes, and a charge generating layer present in all sub-pixel regions, allowing for the elimination of precise shadow masks and optimizing optical lengths to enhance light extraction efficiency and color purity, particularly in blue sub-pixels, while suppressing unwanted blue light extraction in red and green sub-pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a precision shadow mask is used to form charge generating layers only in blue sub-pixels, then blue organic EL element longevity is improved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent divides the display panel into multiple sub-pixel regions (red, green, blue, and white) with distinct charge generating layer configurations. By segmenting the charge generating layer formation to specific sub-pixel regions rather than using a universal shadow mask approach, the patent eliminates the need for precision shadow masks while maintaining selective charge generation where needed, thereby improving productivity without sacrificing blue element longevity.
Solution Approach 2:
The patent applies different layer structures and materials to different sub-pixel regions. Specifically, charge generating layers are formed only in blue and white sub-pixel regions while being absent in red and green regions. This local differentiation allows the patent to optimize blue element longevity through targeted charge generation without requiring precision shadow masks for uniform layer formation across all sub-pixels.
2Duration of action of stationary object
If a precision shadow mask is used to form charge generating layers, then blue organic EL element longevity is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the charge generating layer formation process from the universal layer deposition process. Instead of using precision shadow masks to selectively form charge generating layers during vacuum deposition, the patent forms charge generating layers only in specific sub-pixel regions (blue and white) through a separate, simplified process that does not require precision shadow masks, thereby reducing manufacturing cost while maintaining blue element longevity.
Solution Approach 2:
The patent replaces expensive precision shadow masks with a simpler, more cost-effective layer formation approach. By using a general deposition process combined with selective region treatment rather than expensive precision shadow masks, the patent achieves the same functional result at lower manufacturing cost.
3Use of energy by moving object
If optical length is reduced to 20-50nm in red and green sub-pixels, then light extraction efficiency is improved, but blue light extraction is suppressed
Solution Approach 1:
The patent applies different optical length configurations to different sub-pixel regions. In blue and white sub-pixel regions, the optical length is optimized for blue light extraction (20-50nm), while in red and green sub-pixel regions, the optical length is adjusted to suppress blue light extraction while maintaining efficiency for the respective color wavelengths. This local optimization allows each region to extract light efficiently at its intended wavelength while suppressing unwanted wavelengths.
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 design improves the longevity of blue organic EL elements, reduces manufacturing costs, and increases productivity by eliminating the need for precise shadow masks, while enhancing light extraction efficiency and maintaining color purity across different sub-pixels.
Implementation Method 1
light-reflective electrodes, disposed above the substrate in the red sub-pixel region, the green sub-pixel region, the blue sub-pixel region, and the white sub-pixel region, each of the light-reflective electrodes having a light-reflective surface
Implementation Method 2
organic electroluminescence (EL) display panels that use electroluminescence of organic materials
Data Source
AI summary
An organic EL display panel includes light-reflective electrodes, a first red light-emitting layer, a green light-emitting layer, a first blue light-emitting layer, a second red light-emitting layer, a charge generating layer, a second blue light-emitting layer, and a light-transmissive electrode. In a red and a white sub-pixel region, a first optical length is from 20 nm to 50 nm, and a second optical length is from 210 nm to 230 nm. In a green sub-pixel region, the first optical length is from 20 nm to 50 nm, and the second optical length is from 240 nm to 295 nm. In a blue sub-pixel region, the first optical length is from 20 nm to 60 nm, and the second optical length is from 195 nm to 205 nm.