Pixel Defining Layer Post-Baking for Low-Moisture OLED Patterning
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Solution Overview
Problem
Existing organic light emitting displays face issues with high moisture content in the pixel defining layer, leading to pixel shrinkage, dark spots, and reduced lifetime due to moisture absorption, which affects luminance and display reliability.
Innovation Solution
A method is developed to prepare a pixel defining layer using a photosensitive composition that includes a colorant with low moisture content, involving application, pre-baking, exposure to light, developing, and post-baking at controlled temperatures to minimize moisture to 50 ppm or less, using a photosensitive composition with specific resin and pigment formulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a coloring pattern is formed using pigment dispersion without sufficient crosslinking, then the coloring pattern can be formed with vivid colors, but the moisture content becomes high causing pixel shrinkage, dark spots, and electrode oxidation
Solution Approach 1:
The patent applies parameter changes by implementing a post-baking process at elevated temperatures (100-200°C) to alter the physical and chemical state of the pigment dispersion. This thermal treatment promotes crosslinking reactions and evaporates residual solvents, reducing moisture content from high levels (causing pixel shrinkage) to acceptable levels (50 ppm or less), thereby improving display reliability while maintaining vivid colors
Solution Approach 2:
The patent employs preliminary action by incorporating a post-baking step immediately after the developing process. This preliminary thermal treatment prevents moisture absorption from the environment and eliminates residual solvents before the device is sealed, avoiding pixel shrinkage, dark spots, and electrode oxidation that would occur if moisture were allowed to remain
2Reliability
If post-baking is performed at lower temperatures for longer periods, then moisture removal is more thorough, but production time and energy consumption increase
Solution Approach 1:
The patent optimizes the post-baking process by changing temperature parameters to achieve the desired moisture removal effect. By conducting post-baking at elevated temperatures (100-200°C) for controlled durations (30-120 minutes), the process achieves thorough moisture removal (reducing moisture content to 50 ppm or less) while balancing production efficiency, avoiding excessive time consumption
3Ease of manufacture
If external light is blocked using polarizing film, then reflected light is blocked improving display quality, but the device cannot be applied to flexible devices due to lack of bending properties
Solution Approach 1:
The patent substitutes the mechanical/light-based light blocking mechanism (polarizing film) with a chemical/structural approach using a pixel-defining layer containing light-absorbing pigment dispersion. This substitution eliminates the need for rigid polarizing films, enabling the display device to be applied to flexible substrates while maintaining the ability to block reflected light and improve display quality
Solution Approach 2:
The patent employs composite materials by combining a photosensitive composition with pigment dispersion (containing organic or inorganic colorants) to form the pixel-defining layer. This composite structure provides both light blocking functionality and flexibility, replacing rigid polarizing films with a adaptable pigment-based system suitable for flexible devices
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 results in a pixel defining layer with low moisture content, enhancing display reliability and lifetime by minimizing moisture absorption, thereby maintaining vivid colors and reducing pixel shrinkage and dark spots.
Implementation Method 1
exposure to light
Implementation Method 2
post-baking at controlled temperatures to minimize moisture
Data Source
AI summary
Provided is an implementation of a coloring pattern with a low moisture content on an electrode substrate to thereby improve display reliability and lifetime as well as vivid colors. That is, since when the moisture content is 50 ppm or more, it may cause a reduction in luminance and lifetime due to pixel shrinkage, in order to minimize the moisture content after completion of the post-baking process, the generation of moisture in the panel state is minimized by generating sufficient heat and time in the post-baking step, by including the colorant of the presently claimed subject matter.