Optical Films from Styrenic Fluoropolymer Solutions
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Solution Overview
Problem
Existing optical films made from styrenic fluoropolymers face challenges in achieving a balance between clarity, adhesion to the substrate, and retardation values, as solvents that enhance one property often compromise others, necessitating a method for selecting solvents or solvent blends that optimize these properties simultaneously.
Innovation Solution
The method involves selecting a solvent or solvent blend based on Hansen solubility parameters (HSPs) that satisfy specific relations between the fluoropolymer, substrate, and solvent blend, ensuring optimal clarity, adhesion, and retardation by calculating and matching the total and partial HSPs to achieve the desired film properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a solvent is selected to enhance clarity of the optical film, then the film clarity is improved, but adhesion to the substrate deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying the Hansen solubility parameters (HSPs) of the solvent blend to optimize the balance between clarity and adhesion. Specifically, the invention adjusts the ratios of solvents with different HSP characteristics (e.g., combining a first solvent with higher clarity but lower adhesion and a second solvent with lower clarity but higher adhesion) to achieve an optimal overall HSP match that simultaneously improves both clarity and adhesion properties of the optical film.
2Strength
If a solvent is selected to enhance adhesion to the substrate, then the adhesion is improved, but clarity of the optical film deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the solvent blend parameters to include a combination of solvents with complementary HSP characteristics. The method calculates the overall HSP of the solvent blend and adjusts the solvent composition to ensure the blend's HSP is optimally matched to both the fluoropolymer and the substrate, thereby achieving simultaneous improvement in adhesion and clarity rather than sacrificing one for the other.
3Reliability
If a solvent is selected to optimize retardation values, then the retardation is improved, but clarity and adhesion compromise
Solution Approach 1:
The patent applies parameter changes by optimizing the solvent blend's Hansen solubility parameters to achieve the desired retardation characteristics. The method involves calculating and adjusting the HSP of the solvent blend to match the fluoropolymer and substrate properties, thereby controlling the film's optical retardation while maintaining good clarity and adhesion through balanced solvent selection.
4Device complexity
If a single solvent is used to simplify the formulation, then the manufacturing complexity is reduced, but the ability to balance multiple properties deteriorates
Solution Approach 1:
The patent applies the merging principle by combining multiple solvents into a blended formulation that integrates the advantageous properties of each component. Instead of using a single solvent that cannot simultaneously provide clarity, adhesion, and retardation control, the invention merges a first solvent (providing clarity) with a second solvent (providing adhesion and retardation control) to create a composite solvent blend that achieves all desired properties synergistically.
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 improved clarity, adhesion, and retardation values, as demonstrated by the use of specific solvent blends like PGMEA/ethyl acetate and MEK/toluene, which provide a good balance of properties essential for optical devices such as LCDs.
Implementation Method 1
The polymer solution comprises a styrenic fluoropolymer and a solvent or solvent blend that is selected based on Hansen solubility parameters (HSPs) of the fluoropolymer, the substrate, and the solvent/solvent blend
Data Source
AI summary
A method for casting a styrenic fluoropolymer film on a substrate includes preparing a polymer solution by dissolving the fluoropolymer in a solvent or solvent blend whose Hansen solubility parameters (HSPs. MPa1/2) satisfy the following relations: |SPb−SPp|<5, |SPb−SPs|<4, |SPb(H)−SPp(H)|<7, and 2<|SPb(H)−SPs(H)|<10 wherein SPb, SPp, SPs, are the total Hansen solubility parameters of solvent/solvent blend, fluoropolymer, and substrate, respectively; SPb(H), SPp(H), and, SPs(H) are the hydrogen-bond Hansen solubility parameters of solvent/solvent blend, fluoropolymer, and substrate, respectively; wherein the fluoropolymer comprises a moiety of:wherein R1, R2, and R3 are each independently hydrogen atoms, alkyl groups, substituted alkyl groups, or halogens, wherein at least one of R1, R2, and R3 is a fluorine atom, and wherein R is each independently a substituent on the styrenic ring, n is an integer from 0 to 5 representing the number of the substituents on the styrenic ring.