Pixel Define Layer Patterning for OLED Moisture Control
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Solution Overview
Problem
Organic light emitting displays face issues with moisture content in the panel, leading to pixel shrinkage, dark spots, and reduced lifespan due to insufficient crosslinking and high moisture absorption, which affects luminance and reliability.
Innovation Solution
A method involving a photosensitive resin composition with a specific process including prebaking, exposure, development, post-exposure, and post-heat treatment is used to minimize moisture content, utilizing a photomask with varying transmittance sections and a cardo-based binder resin to achieve low moisture absorption and efficient curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If colored patterns are formed using conventional photolithography process, then vivid colors can be achieved, but moisture content increases leading to pixel shrinkage and reduced lifespan
Solution Approach 1:
The patent changes the chemical parameters of the resin composition by incorporating specific crosslinking agents and adjusting the ratio of photoinitiators to monomers. This enables sufficient crosslinking during the development process itself, rather than relying solely on post-heat treatment, thereby reducing moisture content to 50 ppm or less while maintaining vivid colors
Solution Approach 2:
The patent performs preliminary crosslinking action during the development process by optimizing the photosensitive resin composition with crosslinking agents. This preliminary crosslinking prevents moisture absorption before the post-heat treatment step, addressing the moisture problem at an earlier stage in the process
2Reliability
If post-heat treatment is performed at high temperature for long duration, then moisture is removed effectively, but panel damage increases and process time extends
Solution Approach 1:
The patent changes the thermal parameters by optimizing the post-heat treatment conditions to 80-150°C for 1-30 minutes, rather than using conventional high-temperature long-duration treatment. This parameter optimization achieves sufficient moisture removal while minimizing panel damage and reducing process time
Solution Approach 2:
The patent performs preliminary moisture removal and crosslinking during the development process through optimized resin composition. This preliminary action reduces the moisture burden before post-heat treatment, allowing shorter and lower-temperature post-heat treatment steps
3Ease of manufacture
If conventional photomask with uniform transmittance is used, then simple process is maintained, but two-layer patterning requires separate processes increasing complexity
Solution Approach 1:
The patent applies local quality by using a photomask with different transmittance regions: a first region with 40-70% transmittance for the pixel defining layer and a second region with 10-30% transmittance for the color filter layer. This allows selective exposure and formation of two layers in one process
Solution Approach 2:
The patent makes the photomask multi-functional by designing it to perform two patterning functions simultaneously. The same photomask with differentiated transmittance regions enables patterning of both the pixel defining layer and color filter layer in a single exposure step, eliminating the need for separate photomasks and processes
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 method effectively reduces moisture content to 50 ppm or less, enhancing display reliability and lifespan by integrating two patterning processes into one, minimizing damage and maintaining vivid colors.
Implementation Method 1
a photosensitive resin composition... performing exposure; performing development; performing post-exposure
Implementation Method 2
performing post-heat treatment, wherein the post-heat treatment step is performed at an oven temperature of 210° C. to 300° C. for 30 to 120 minutes
Data Source
AI summary
Provided is a method not only to ensure vivid colors, but also to increase display reliability and lifespan by integrating two patterning processes into one to form a step height and implementing a colored pattern with low moisture content on an electrode substrate, which in other words is to shorten the process time and minimize damage to the panel due to the additional development process and post-heat treatment process by forming the pixel separation layer and metal mask support layer at once after the exposure and development process, and to minimize a decrease in the luminance and a decrease in the lifespan by preventing pixel shrinkage.