Low Structure Carbon Black for Black Matrix Optical Density
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Solution Overview
Problem
Existing carbon blacks used in black matrices for liquid crystal displays face challenges in achieving a balance between optical density, electrical resistivity, and viscosity, with high loading levels often compromising these properties due to increased conductivity and hydrophilicity from alkali metal additions, and higher surface area leading to higher viscosity and reduced optical density.
Innovation Solution
Development of low structure carbon blacks with specific DBP values, iodine numbers, and M-ratios, characterized by low alkali metal content and high hydrophobicity, allowing for higher loadings while maintaining resistivity and optical density, and reducing viscosity, which enables the production of coatings and black matrices with improved electrical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If carbon black loading level is increased to achieve desired optical density, then optical density improves, but viscosity increases and resistivity decreases
Solution Approach 1:
The patent changes the structural parameters of carbon black by controlling the DBP absorption value to be within 20-45 cc/100g and M-ratio to be less than 1.25. This parameter optimization allows the carbon black to achieve low structure while maintaining high surface area, enabling higher loading levels without excessive viscosity increase and while preserving electrical resistivity.
2Device complexity
If alkali or alkaline metal elements are added to control carbon black structure, then structure decreases and viscosity reduces, but conductivity increases and optical density decreases
Solution Approach 1:
The patent precisely controls the concentration of alkali and alkaline earth metal elements to be within the range of 0.01-10 μg/g, and specifically limits Group IA and IIA elements to at most y + (15×I2 number) where y=250. This controlled parameter approach achieves low structure (DBP 20-45 cc/100g) while minimizing the harmful effects of increased conductivity and optical density loss.
3Illumination intensity
If surface area is increased to improve optical density, then optical density improves, but viscosity increases and manufacturability decreases
Solution Approach 1:
The patent optimizes the balance between surface area and structure by controlling DBP absorption (20-45 cc/100g) and M-ratio (<1.25). This allows achieving high surface area for improved optical density while maintaining low structure that prevents excessive viscosity increase, thereby preserving manufacturability.
4Illumination intensity
If carbon black loading is increased to achieve high optical density, then optical density improves, but resistivity decreases
Solution Approach 1:
The patent controls the structural parameters (DBP 20-45 cc/100g, M-ratio <1.25) and metal content (alkali and alkaline earth metals: 0.01-10 μg/g) to enable higher carbon black loading while maintaining electrical resistivity. The low structure prevents excessive particle interaction that would otherwise reduce resistivity at high loadings.
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 use of low structure carbon blacks with controlled properties enables higher carbon black loadings, resulting in coatings and black matrices with enhanced optical density and resistivity, improved manufacturability, and compatibility with a wider range of polymers, while maintaining Newtonian flow characteristics and reducing defects in the final coating.
Implementation Method 1
Black pigments such as carbon black have been used in polymer compositions to make resistive black matrices... the film might have only a modest resistivity, limiting its ability to inhibit photo-induced currents
Implementation Method 2
The black matrix also prevents the formation of photo-induced currents due to reflected light in the TFT... a highly resistive film were produced, the OD might be too low to be commercially viable
Data Source
AI summary
A black matrix or coating includes carbon black including a first carbon black having an h number from 30 mg/g to 200 mg/g and a DBP from 20 cc/100g to 45 cc/100g.