Inspection Pixels for Detecting Misregistration in Laser-Transferred OLED Layers
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Solution Overview
Problem
The laser transfer method for forming organic light-emitting display devices faces challenges with misregistration and width variation of light-emission layers, leading to issues like color mixture and nonuniform film thickness distribution, which are difficult to detect early and correct, resulting in significant yield loss.
Innovation Solution
Incorporating an inspection region with inspection pixels or patterns outside the effective region, where the distance or width of inspection elements is adjusted relative to display pixels, allowing for early detection of misregistration or width variations by measuring chromaticity or spectrum shape changes, enabling timely correction of laser head or beam positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scanning speed of the laser or substrate is increased to improve productivity, then productivity increases, but misregistration and width variation of light-emission layers worsen
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual position and width of transferred light-emission layers using inspection pixels and photodetectors, then using this measurement information to correct misregistration and width variation in real-time, allowing high scanning speeds to be maintained while preserving manufacturing precision
Solution Approach 2:
The patent replaces mechanical measurement methods with optical measurement using photodetectors and light emission patterns, enabling non-contact, high-speed detection of layer position and width that can keep pace with increased scanning speeds
2Productivity
If multi-laser heads or multi-beams are used to reduce processing time per substrate, then productivity increases, but misregistration and width variation worsen due to variations in distance, beam intensity, and space between beams
Solution Approach 1:
The patent uses inspection pixels and photodetectors to measure the actual transfer characteristics of each laser head and beam, then applies correction based on these measurements to compensate for variations in distance, beam intensity, and spacing, enabling multi-head/multi-beam systems to maintain precision while improving productivity
Solution Approach 2:
The patent adjusts laser beam parameters (intensity, position, timing) based on measurement feedback from inspection pixels, dynamically correcting for variations between multiple laser heads and beams to maintain consistent transfer quality across all channels
3Reliability
If the film thickness of the light-emission layer is reduced to some 10 nm to some 100 nm to improve device performance, then device performance improves, but detection precision worsens because the layer becomes hard to recognize
Solution Approach 1:
The patent introduces inspection pixels as intermediary elements that provide optical contrast for detecting the position and width of thin light-emission layers. These inspection pixels emit light that interacts with the light-emission layer, creating measurable signals that enable detection of layers too thin to be directly observed
Solution Approach 2:
The patent utilizes chromaticity and spectrum shape changes of light emitted by inspection pixels as indicators of light-emission layer characteristics. By measuring color changes in the emitted light, the system can detect the presence, position, and width of ultra-thin layers that would otherwise be invisible
4Adaptability or versatility
If the size of the metal mask is increased to accommodate larger substrates, then adaptability improves, but manufacturing precision worsens due to deformation from weight and thermal expansion
Solution Approach 1:
The patent removes the metal mask from the system entirely, replacing the mask-based patterning approach with a maskless laser transfer method. This eliminates the problems of mask deformation and thermal expansion while maintaining the ability to pattern large substrates with high precision
Solution Approach 2:
The patent replaces the mechanical metal mask system with an optical laser-based system, using light to define patterns without physical contact. This substitution eliminates mechanical deformation issues while enabling precise patterning of large-area substrates
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 enables early detection and correction of misregistration and width variations, preventing color mixture and nonuniformity issues, thus improving yield and reducing start-up time in mass production by ensuring accurate layer formation.
Implementation Method 1
transferring the transfer layer to the transferred substrate by irradiating with a laser beam in a reduced pressure environment
Implementation Method 2
an organic light-emitting element (organic EL (Electroluminescence) element) in which a first electrode, plural organic layers including a light emission layer, and a second electrode are sequentially laminated
Data Source
AI summary
A display device capable of early finding a sign such as misregistration or width variation of an emission layer formed by a layer transfer method, and a manufacturing method of the same are provided. In an inspection region 150 outside of an effective region 110, inspection pixels Px2 made up of organic light-emitting elements 10R, 10G and 10B are provided, and a distance W2 between the inspection pixels Px2 on both sides of a color targeted for inspection is shorter than a distance W1 between display pixels Px1 on both sides of the color targeted for inspection. Based on a change in a chromaticity or a spectrum shape of EL or PL light emission of the inspection pixel Px2, a sign such as misregistration of a red-light emission layer 15CR, a green-light emission layer 15CG, is found at an early stage.