Pixel Circuit Laser Repair for Organic EL Displays
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Solution Overview
Problem
It is challenging to effectively divide pixel circuits in organic EL display devices into regions, provide individual organic EL elements, and fuse only non-functional elements without affecting operational ones, as existing methods require high laser output and risk adhesion of the fused wiring layer, leading to potential failures.
Innovation Solution
The display device incorporates a configuration with data lines, scanning lines, pixel circuits, scanning line and data line drive circuits, and initialization transistors, where the first conductive terminal of the second initialization transistor is electrically connected to the initialization line using a laser beam to ensure the organic EL element is in a constantly lighting-off state, and a connection wire is used to connect the initialization line to the semiconductor layer, allowing for precise repair without fusing the initialization line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laser beam with large output is used to fuse the metal wiring layer, then the non-functional organic EL element can be cut off from the pixel circuit, but the fused wiring layer may adhere to another spot causing repair failure
Solution Approach 1:
The patent segments the pixel circuit into multiple regions with individual organic EL elements, allowing selective repair of defective elements without affecting others. This segmentation enables precise laser irradiation targeting only the defective region's wiring, preventing unwanted adhesion to adjacent areas.
Solution Approach 2:
The patent applies local quality by making different parts of the pixel circuit have different functions - specifically, providing multiple organic EL elements in different regions within the same pixel circuit. This allows the laser beam to be applied locally to only the defective region's wiring, ensuring that the high output laser does not cause harmful adhesion to other spots while still achieving reliable repair.
2Ease of repair
If each pixel circuit is divided into multiple regions with individual organic EL elements, then selective repair becomes possible, but it becomes difficult to surely fuse only the non-functional element without affecting functional ones
Solution Approach 1:
The patent divides each pixel circuit into multiple regions, each containing its own organic EL element. This segmentation provides clear spatial separation between functional and non-functional elements, making it easier to target the laser beam precisely at the defective element's wiring without accidentally fusing or affecting the wiring of functional elements.
Solution Approach 2:
The patent introduces an intermediary structure - the segmented regional configuration with separate organic EL elements - that acts as a spatial buffer between the laser beam and functional components. This intermediary arrangement allows the laser to fuse the wiring of the non-functional element while the physical separation prevents harmful effects on functional elements, thus improving both ease of repair and manufacturing precision.
3Productivity
If the pixel circuit is turned to constantly lighting-off state for repair, then manufacturing yield can be improved, but the display may show black dots which affect image quality
Solution Approach 1:
The patent segments the pixel circuit into multiple regions with individual organic EL elements, allowing the defective element to be turned off (creating a black dot) while other elements in the same pixel circuit remain functional. This segmentation minimizes the visual impact by isolating the defect to a smaller area, thereby maintaining acceptable display quality while improving manufacturing yield through repair capability.
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 approach ensures that even if a pixel circuit fails, the organic EL element can be kept in a constantly lighting-off state, maintaining the display as a black dot, improving manufacturing yield and reducing manufacturing costs by preventing line defects and power consumption issues.
Implementation Method 1
a laser beam irradiating a semiconductor layer to evaporate an insulating film and melt the semiconductor layer
Implementation Method 2
a laser beam irradiating a semiconductor layer to evaporate an insulating film and melt the semiconductor layer
Data Source
AI summary
From a back side of an insulating substrate 90, a laser beam is applied to a spot where an initialization line Vini is superimposed on the semiconductor layer SI that serves as a first conductive terminal of a second initialization transistor T7 while sandwiching an insulating film therebetween. Thus, a gate insulating film 91 and a first interlayer insulating film 92, which are sandwiched between the semiconductor layer SI and the initialization line Vini, disappear by evaporation, and a laser irradiation area LA of the semiconductor layer SI is connected to the initialization line Vini, by which a connection portion CP is formed. As a result, a voltage to be applied to the organic EL element OLED becomes equal to or less than a threshold voltage. Therefore, the organic EL element OLED is constantly in a lighting-off state, and the pixel circuit 11 is constantly kept black.