Photosensitive Resin Composition for OLED Black Pixel Defining Layer
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Solution Overview
Problem
Conventional black photosensitive resin compositions used in display devices, such as OLEDs, face issues with external light reflection, leading to reduced contrast ratio and visibility due to insufficient light blocking and unbalanced curing, which affects sensitivity and taper characteristics.
Innovation Solution
A photosensitive resin composition is developed, incorporating a binder resin, photopolymerizable monomers, and a combination of first and second photopolymerization initiators with different maximum absorption wavelengths in a specific weight ratio, along with organic and inorganic black colorants, to enhance light absorption and curing uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photopolymerization initiator is used in the black photosensitive resin composition, then the formulation is simple, but the curing is unbalanced leading to poor sensitivity and taper characteristics
Solution Approach 1:
The photopolymerization initiator is segmented into two distinct types: a first photopolymerization initiator with maximum absorbance in the blue region (400-480nm) and a second photopolymerization initiator with maximum absorbance in the green region (500-560nm). This segmentation allows each initiator to be optimized for specific wavelength regions, enabling balanced and uniform curing across the entire spectrum while maintaining good sensitivity and taper characteristics.
2Object-affected harmful factors
If black colorant is added to increase light blocking, then external light reflection is reduced improving contrast ratio, but the photopolymerization efficiency decreases leading to unbalanced curing
Solution Approach 1:
The patent changes the key parameter of photopolymerization initiator absorption wavelengths to overcome the light blocking effect of black colorant. By selecting initiators with maximum absorbance in the blue (400-480nm) and green (500-560nm) regions, the system achieves effective photopolymerization even in the presence of black colorant, which primarily absorbs in the red region. This parameter change enables both high light blocking performance and reliable curing efficiency.
3Productivity
If the photosensitive resin composition is optimized for high sensitivity, then the curing speed improves, but the taper characteristics deteriorate
Solution Approach 1:
The photopolymerization process is segmented into two complementary actions: the first initiator (blue region absorption) provides high sensitivity and fast curing speed, while the second initiator (green region absorption) ensures uniform curing and good taper characteristics. This segmentation of functional roles between two initiators allows the system to simultaneously achieve both high productivity and manufacturing precision.
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 composition effectively blocks external light reflection, improving contrast ratio and visibility, ensuring uniform curing and maintaining high sensitivity and pattern characteristics, thereby preventing short circuits and enhancing the reliability of display devices.
Implementation Method 1
a photopolymerization initiator including a first photopolymerization initiator and a second photopolymerization initiator; the first photopolymerization initiator having maximum absorbance in a wavelength region of about 270 nm to about 300 nm or about 390 nm to about 450 nm
Implementation Method 2
the first photopolymerization initiator and the second photopolymerization initiator having different maximum absorption wavelengths
Implementation Method 3
a black colorant; effectively blocks external light reflection, improving contrast ratio and visibility
Data Source
AI summary
A photosensitive resin composition, a pixel defining layer, and a display device, the composition including a binder resin; a photopolymerizable monomer; a photopolymerization initiator including a first photopolymerization initiator and a second photopolymerization initiator; a black colorant; and a solvent, wherein the first photopolymerization initiator is represented by Chemical Formula 1, the second photopolymerization initiator has a different maximum absorption wavelength from the first photopolymerization initiator, and the first photopolymerization initiator and the second photopolymerization initiator are included in a weight ratio of about 3:7 to about 7:3,