Method for preparing liquid crystal polymer film, liquid crystal polymer film and application thereof
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Solution Overview
Problem
Existing methods for preparing liquid crystal polymer films, such as tape casting and polyimide coating, face challenges including high production costs, energy consumption, poor mechanical strength, and unfavorable dielectric properties.
Innovation Solution
A method involving spinning liquid crystal polymer into fibers, maintaining them under controlled temperature and vacuum conditions, weaving the fibers into cloth, and then pressing and stretching the cloth to form a film with enhanced mechanical and dielectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If tape casting, film blowing, or calendering methods are used to prepare wholly aromatic polyester films, then the films can be produced using standard industry processes, but the preparation conditions are harsh, production cost is high, defective rate is high, and mechanical strength is low
Solution Approach 1:
The invention changes the fundamental preparation parameters by using melt spinning instead of conventional film forming methods. The liquid crystal polyester is melted and extruded through a spinneret to form fibers, which are then heat-treated and woven into cloth, and finally pressed into film. This parameter change from direct film forming to fiber-based film formation resolves the contradiction by enabling high mechanical strength while using a standardized manufacturing process.
Solution Approach 2:
The invention creates a composite structure by weaving heat-treated liquid crystal polyester fibers into cloth before pressing into film. The fiber reinforcement and woven structure provide high mechanical strength, while the final pressing process integrates the fibers into a cohesive film. This composite approach resolves the contradiction between ease of manufacture and mechanical strength.
2Adaptability or versatility
If amide groups are introduced into liquid crystal polyester to increase polarity and solubility, then the material can be dissolved in common solvents, but water absorption increases and high-frequency dielectric properties decrease
Solution Approach 1:
The invention extracts and removes the problematic amide groups from the liquid crystal polyester structure. By using wholly aromatic polyester without amide modifications, the material maintains low polarity and insolubility in common solvents, but crucially maintains low water absorption and excellent high-frequency dielectric properties. This extraction of the harmful functional group resolves the contradiction.
Solution Approach 2:
The invention maintains the local quality of the polymer chains by using unmodified wholly aromatic polyester structures. The rigid aromatic rings and ester linkages are preserved without introducing polar amide groups, ensuring that the local molecular structure maintains low polarity and excellent dielectric properties while being suitable for high-frequency applications.
3Ease of manufacture
If liquid crystal polyester with special structure is used for coating method, then the material can be processed by coating, but a large amount of organic solvents is needed causing pollution and energy consumption is high
Solution Approach 1:
The invention replaces the chemical-based coating process (which requires organic solvents) with a mechanical melt processing approach. Liquid crystal polyester is melted, extruded into fibers, and processed into film through mechanical operations like spinning, weaving, and pressing. This substitution eliminates the need for organic solvents, reducing pollution and energy consumption associated with solvent evaporation and handling.
Solution Approach 2:
The invention creates an inert processing environment by using melt processing instead of solvent-based coating. The high-temperature melt spinning and pressing operations occur in controlled atmospheres without requiring volatile organic solvents, thereby eliminating pollution and reducing energy consumption associated with solvent management while maintaining ease of manufacture.
4Reliability
If liquid crystal polyester is used for circuit substrates, then excellent dielectric properties are achieved, but standard film preparation methods result in high dielectric loss tangent angle
Solution Approach 1:
The invention changes the processing parameters by using melt spinning and high-temperature heat treatment instead of conventional film forming methods. The fibers are heat-treated at temperatures of 200-400°C for extended periods, which optimizes the molecular orientation and crystalline structure. This parameter change reduces dielectric loss tangent angle while maintaining excellent dielectric properties, resolving the contradiction for high-frequency circuit substrate applications.
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 resulting liquid crystal polymer film exhibits a tensile strength exceeding 170 MPa, a dielectric constant less than 3, and a small dielectric loss tangent angle, making it suitable for applications in flexible printed circuit boards.
Implementation Method 1
When these polymers are melt, they can orient to form a liquid crystal phase
Implementation Method 2
maintaining the fibers for 0.1 hour to 36 hours at a temperature of 200° C. to 400° C. under a vacuum degree less than 500 Pa
Implementation Method 3
When these polymers are melt, they can orient to form a liquid crystal phase
Data Source
AI summary
A method for preparing a liquid crystal polymer film, comprising: (1) spinning a liquid crystal polymer into fibers, and maintaining the fibers for 0.1 hour to 36 hours at a temperature of 200° C. to 400° C. under a vacuum degree less than 500 Pa for later use; (2) weaving the fibers prepared in step (1) into cloth for later use; and (3) pressing the cloth prepared in step (2) into a film at a temperature of 200° C. to 400° C., and then stretching the film to obtain the liquid crystal polymer film. The liquid crystal polymer film prepared by the preparation method is good in mechanical property, and has a tensile strength that can exceed 170 MPa. The prepared liquid crystal polymer film is applied to a FPC, which makes the FPC have a dielectric constant less than 3, and a small dielectric loss tangent angle.