Organic EL Pixel Electrode Stepped Portion Cut Prevention
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Solution Overview
Problem
In organic electroluminescence (EL) devices, particularly the top emission type, a cut portion often occurs at the periphery of pixel electrodes, especially the thinnest ones like the blue member, leading to display failures and black points, which degrade full color display quality due to incomplete light emission.
Innovation Solution
The implementation of a connective conduction portion with multiple light-transmitting conductive films that cover the stepped portions of the reflective film, ensuring better connection to the switching element and organic light emission layer, preventing cut portions and enhancing light emission by using thicker films closer to the reflective film and thinner films closer to the transflective film, with the thickest film laminated to repair any cut portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the pixel electrode is formed by a thin conductive film to adjust the resonant wavelength for blue light emission, then the optical distance between the cathode and reflective film can be optimized for blue wavelength, but the conductive film is more prone to cut portions occurring at the stepped portion of the reflective film
Solution Approach 1:
The patent applies local quality by varying the thickness of the conductive film across different regions. The film is thickest at the stepped portion of the reflective film (where cut portions occur) and thinnest at the center (for optical resonance). This gradient thickness distribution prevents cut portions at the stepped portion while maintaining the resonant wavelength for blue light emission at the center region.
2Reliability
If the conductive film is made thicker to prevent cut portions, then the reliability of the pixel electrode is improved, but the resonant wavelength cannot be optimized for blue light emission
Solution Approach 1:
The patent segments the conductive film thickness into different zones: a thick region at the stepped portion for reliability and cut portion prevention, and a thin region at the center for optical resonance optimization. This segmentation allows each zone to fulfill its specific function without compromising the other.
3Illumination intensity
If the pixel electrode thickness is reduced to achieve full color display with optimized resonant wavelengths, then the display quality is improved, but the cut portion occurs more frequently at the periphery of the pixel electrode
Solution Approach 1:
The patent implements preliminary action by pre-forming a thick conductive film base layer at the stepped portion before forming the thinner upper layer. This preliminary thick base prevents cut portions from occurring during subsequent processing steps, ensuring manufacturing precision while allowing the final thin structure to achieve optimized resonant wavelengths for full color display.
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 effectively prevents cut portions, ensures reliable light emission, and maintains high display quality by covering a wider area of the stepped portions, thereby avoiding black points and ensuring a satisfactory full color display.
Implementation Method 1
an organic luminescence element (hereinafter, referred to as an organic EL element) is known. The organic EL element includes an organic functional layer having an organic light emission layer formed of an organic EL material between anodes supplying electron holes and cathodes supplying electrons, and emits light when the supplied electron holes and the supplied electrons are recombined.
Implementation Method 2
The top emission type organic EL device includes a reflective film which reflects the light emitted from the anode toward the cathode.
Implementation Method 3
a configuration in which the cathode is configured as a transflective film and the anode and the reflective film form a resonator may be taken into consideration... it is possible to adjust an optical distance between the cathodes and the reflective film, that is, a resonant wavelength.
Data Source
AI summary
An organic EL device includes: a first electrode which have a light-transmitting property; a transflective film; an organic light emission layer which is disposed between the first electrodes and the transflective film; a reflective film which is disposed on opposite side of the first electrode than the transflective film; and a first light emission pixel which includes a connective conduction portion formed to cover a stepped portion of the end of the reflective film. The connective conduction portion includes conductive films having a light-transmitting property and is electrically connected to a switching element of the first light emission pixel. In addition, the first electrode is formed by selecting and patterning at least one layer of the conductive films included in the connective conduction portion.