Optical Film Coating Defect Control via Solvent and Substrate Engineering
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Solution Overview
Problem
The challenge is to produce high-quality optical films with minimal coating defects such as streaks and uneven drying when using a coating solution with an organic solvent on cellulose acylate films, while ensuring environmental safety and stability, particularly for larger image display devices.
Innovation Solution
The solution involves controlling the physical properties of the transparent support, such as thickness uniformity and surface plasticizer distribution, and using specific materials like hollow particulate silica and fluorine-containing polymers in the functional layers, along with a coating process that ensures even solvent penetration and drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a coating solution comprising an organic solvent is spread over a cellulose acylate film, then the optical functional layer can be formed, but coating defects such as coating streak and drying unevenness occur
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating solution, specifically using a mixed solvent system with controlled ratios of good solvents (e.g., esters, ketones) and poor solvents (e.g., alcohols, hydrocarbons). The solvent composition is optimized to achieve balanced penetration and evaporation rates, preventing coating defects while maintaining film formation quality.
Solution Approach 2:
The patent employs a composite coating solution comprising multiple solvent components with different solubility parameters and evaporation characteristics. This composite solvent system works synergistically to control the coating process, ensuring uniform penetration into the cellulose acylate substrate and uniform drying without streaking or other defects.
2Area of stationary object
If the screen size of image display device is increased, then the display area is enlarged, but coating defects become more easily recognized
Solution Approach 1:
The patent optimizes coating solution parameters including viscosity, solvent composition ratios, and concentration to ensure uniform coating across large areas. The mixed solvent system provides controlled penetration depth and evaporation rate that maintains consistency over extended substrate areas, preventing visible defects on large screens.
3Stability of the object's composition
If a solvent with good dissolving power is used, then the coating solution stability is improved, but the environmental burden and toxicity increase
Solution Approach 1:
The patent formulates a composite solvent system combining environmentally favorable solvents (such as esters, ketones, and alcohols with high flash points) in optimized ratios. This composite approach maintains adequate dissolution power and coating solution stability while reducing reliance on highly toxic or environmentally harmful solvents like chlorinated hydrocarbons.
Solution Approach 2:
The patent adjusts solvent composition parameters to achieve the minimum necessary dissolving power while prioritizing environmental safety. By carefully balancing solvent strength and environmental impact, the formulation maintains coating solution stability without requiring excessive amounts of harmful solvents.
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
This approach results in optical films with excellent scratch resistance and anti-reflection properties, reducing reflection and enhancing viewability in image display devices, while minimizing environmental impact and coating defects.
Implementation Method 1
the power of penetration of the coating solution into the transparent support are affected
Implementation Method 2
drying unevenness
Data Source
AI summary
An optical film comprises: a transparent support; and at least one functional layer provided the transparent support, wherein an unevenness in thickness of the transparent support is not greater than ±5% from an average thickness, and an unevenness in an amount of surface plasticizer on the transparent support on the functional layer side thereof is not greater than ±20% from an average residual amount of surface plasticizer.