Pixel Defining Layer Processing for Residue and Outgas Control
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Solution Overview
Problem
Existing organic light emitting displays face issues with residues causing dark spots and pixel shrinkage due to incomplete removal during the developing step, and high outgas levels leading to reduced luminance and lifetime, necessitating improved methods for forming pixel defining layers.
Innovation Solution
A method involving a photosensitive composition with optimized developing and post-baking steps, including specific temperature and time ranges, to minimize residues and outgas, using a photosensitive composition with inorganic and organic pigments, and a binder resin with a cardo-based structure, to form a pixel defining layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If coloring patterns with large amounts of colorants are used to achieve vivid colors, then color saturation is improved, but outgas increases causing pixel shrinkage and dark spots
Solution Approach 1:
The patent changes the chemical composition parameters of the pixel defining layer by incorporating specific inorganic pigments (tungsten bronze, molybdenum bronze) with controlled particle sizes (0.1-10 μm) and ratios (1-50 wt% based on total pigment weight). These parameter changes enable achieving vivid colors while controlling outgas generation, as the inorganic pigments provide color saturation without the organic pigment outgas issues.
Solution Approach 2:
The patent uses composite materials by combining inorganic pigments (tungsten bronze, molybdenum bronze) with organic pigments or dyes in specific ratios. This composite approach allows the inorganic pigments to provide structural stability and reduced outgas while the organic components contribute to color vividness, achieving a balance between color saturation and outgas control.
2Manufacturing precision
If developing step is performed to remove residues, then pixel cleanliness is improved, but incomplete removal causes dark spots and pixel off
Solution Approach 1:
The patent optimizes developing parameters including temperature (20-30°C), time (30-120 seconds), and developer concentration (0.1-10 wt%). These parameter changes ensure complete residue removal while maintaining pixel pattern integrity, achieving both pixel cleanliness and functional reliability.
Solution Approach 2:
The patent replaces mechanical washing methods with chemical developing processes using controlled reagents. This substitution allows for more precise and complete residue removal through chemical reactions, improving both pixel cleanliness and reliability compared to mechanical cleaning approaches.
3Object-generated harmful factors
If post-baking is performed to reduce outgas, then outgas level is improved, but excessive baking causes pixel shrinkage
Solution Approach 1:
The patent optimizes post-baking parameters including temperature (100-200°C), time (30-120 minutes), and atmosphere (nitrogen or vacuum). These parameter changes enable effective outgas reduction while maintaining pixel dimensional stability, achieving both low outgas levels and proper pixel shape.
Solution Approach 2:
The use of inorganic pigment composites (tungsten bronze, molybdenum bronze) inherently generates less outgas during post-baking, allowing for effective outgas control at lower temperatures and shorter times, thereby preventing pixel shrinkage while achieving low outgas levels.
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 residue-free pixels and reduced outgas levels, enhancing display reliability and lifespan by minimizing dark spots and pixel shrinkage, while maintaining vivid colors.
Implementation Method 1
A method for preparing a pixel defining layer includes the steps of application and coating; pre-baking; exposure to light; developing; and post-baking of a photosensitive composition
Implementation Method 2
a binder resin with a cardo-based structure
Data Source
AI summary
An object of the present disclosure is to improve display reliability and lifetime as well as vivid colors. When there remain residues in the washing part due to incomplete removal during the developing step, it can cause dark spots or pixel off due to the residues, and thus residue-free pixels can be formed by optimizing the temperature and time for developing. Additionally, when the amount of outgas in the panel after post-baking is 15 ppm or more, it may cause a reduction in luminance and lifetime due to pixel shrinkage. Therefore, in order to minimize the amount of outgas after completion of the post-baking process, the generation of outgas in the panel state can be minimized by generating sufficient fume in the post-baking step, in addition to forming clean pixels in the developing step.