A method for preparing a liquid crystal polymer composite film and a liquid crystal polymer composite film

Abstract

This application discloses a method for preparing a liquid crystal polymer composite film and the liquid crystal polymer composite film itself. The preparation method includes: dissolving soluble liquid crystal polymer particles in a first solvent and stirring to obtain a soluble liquid crystal polymer solution; mixing the soluble liquid crystal polymer solution, filler micropowder, and additives to obtain a first mixture; dispersing and degassing the first mixture to obtain a slurry; the filler micropowder includes at least one of titanium dioxide, barium titanate, barium zirconate, lead titanate, calcium zirconate, calcium titanate, carbon nanotubes, graphene oxide, and reduced graphene; coating the slurry onto a substrate to form a wet film on the substrate; drying and curing the wet film to obtain a first film; and peeling the first film off the substrate to obtain the liquid crystal polymer composite film. In this application, the filler micropowder and the liquid crystal polymer matrix work synergistically to achieve a high dielectric constant while maintaining low loss. It is also less prone to breakage or deformation under external forces.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and in particular to a method for preparing a liquid crystal polymer composite film and the liquid crystal polymer composite film. Background Technology

[0002] Liquid crystal polymers (LCPs) are polymeric materials that, due to their unique molecular structure, possess excellent mechanical properties, processability, high dimensional stability, resistance to high and low temperatures, chemical corrosion resistance, self-reinforcing properties, self-flame retardancy, and electrical insulation properties. Based on morphological differences, liquid crystal polymers can be classified into lyotropic liquid crystal polymers and thermotropic liquid crystal polymers.

[0003] Among them, soluble liquid crystal polymers, when prepared by coating methods, exhibit small anisotropic properties, are simple to process, and possess physicochemical properties such as low dielectric constant and low dielectric loss, making them potential high-performance thin film materials. However, the generally low dielectric constant of existing liquid crystal polymers limits their widespread application in the field of high dielectric constant materials. Summary of the Invention

[0004] This application aims to provide a method for preparing a liquid crystal polymer composite film and the liquid crystal polymer composite film, with the goal of improving the dielectric constant of the liquid crystal polymer composite film.

[0005] In a first aspect, this application provides a method for preparing a liquid crystal polymer composite film, comprising: providing soluble liquid crystal polymer particles; dissolving the soluble liquid crystal polymer particles in a first solvent and stirring to obtain a soluble liquid crystal polymer solution; providing filler powder and additives; mixing the soluble liquid crystal polymer solution, the filler powder, and the additives to obtain a first mixture; dispersing and degassing the first mixture to obtain a slurry; wherein the filler powder includes at least one of titanium dioxide, barium titanate, barium zirconate, lead titanate, calcium zirconate, calcium titanate, carbon nanotubes, graphene oxide, and reduced graphene; providing a substrate; coating the slurry onto the substrate and forming a wet film on the substrate; drying and curing the wet film to obtain a first film; and peeling the first film off the substrate to obtain a liquid crystal polymer composite film.

[0006] In some embodiments, before mixing the soluble liquid crystal polymer solution, the filler powder, and the additives, the preparation method further includes: placing the filler powder at 100°C to 120°C for drying pretreatment for 6 h to 8 h; the filler powder has a particle size of 50 nm to 5000 nm.

[0007] In some embodiments, the soluble liquid crystal polymer particles are polymerized from aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids; the molar percentage of the aromatic dicarboxylic acid is 35 mol% to 45 mol%; and / or, the molar percentage of the aromatic diol is 35 mol% to 45 mol%; and / or, the molar percentage of the aromatic hydroxycarboxylic acid is 10 mol% to 30 mol%.

[0008] In some embodiments, the additives include at least one of silane coupling agents, titanate coupling agents, surfactants, leveling agents, and defoamers.

[0009] In some embodiments, the solid content of the soluble liquid crystal polymer solution is 5% to 15% based on the total mass of the soluble liquid crystal polymer solution; and the viscosity of the soluble liquid crystal polymer solution is 1000 mPa·s to 5000 mPa·s.

[0010] In some embodiments, the dispersion treatment includes stirring and / or dispersing disc treatment; the stirring speed of the stirring treatment is 1100 rpm to 1300 rpm, and the speed of the dispersing disc treatment is 1400 rpm to 1600 rpm; the dispersion treatment duration is 20 min to 50 min; the degassing treatment pressure is -80 kPa to -90 kPa, and the degassing treatment duration is 30 min to 40 min.

[0011] In some embodiments, the drying and curing process of the wet film includes: placing the wet film in a first drying oven, wherein the first drying oven is heated to a first temperature at a heating rate of 0.25 °C / min to 0.5 °C / min, and maintained at the first temperature for a first duration; the first temperature is 130 °C to 150 °C, and the first duration is 1 h to 1.5 h; the first drying oven is heated to a second temperature at a heating rate of 1.8 °C / min to 2.5 °C / min, and maintained at the second temperature for a second duration; the second temperature is 250 °C to 320 °C, and the second duration is 1 h to 1.5 h; and the first drying oven is cooled to a third temperature at a cooling rate of 0.8 °C / min to 1.2 °C / min, wherein the third temperature is 50 °C to 60 °C.

[0012] In some embodiments, the thickness of the wet film is from 10 μm to 150 μm.

[0013] In some embodiments, the first solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and γ-butyrolactone.

[0014] Secondly, this application also provides a liquid crystal polymer composite film, which is prepared by the liquid crystal polymer composite film preparation method as described in any one of the first aspects.

[0015] Unlike existing technologies, this application provides a method for preparing a liquid crystal polymer composite film. The method includes: providing soluble liquid crystal polymer particles; dissolving the soluble liquid crystal polymer particles in a first solvent and stirring to obtain a soluble liquid crystal polymer solution; providing filler powder and additives; mixing the soluble liquid crystal polymer solution, filler powder, and additives to obtain a first mixture; dispersing and degassing the first mixture to obtain a slurry; the filler powder includes at least one of titanium dioxide, barium titanate, barium zirconate, lead titanate, calcium zirconate, calcium titanate, carbon nanotubes, graphene oxide, and reduced graphene; providing a substrate; coating the slurry onto the substrate and forming a wet film on the substrate; drying and curing the wet film to obtain a first film; and peeling the first film off the substrate to obtain a liquid crystal polymer composite film. This application, by adding filler powder to the soluble liquid crystal polymer solution, achieves synergy between the filler powder and the liquid crystal polymer matrix, maintaining the original low loss of the liquid crystal polymer while possessing a high dielectric constant. Furthermore, after drying and curing, the liquid crystal polymer molecular chains can achieve orderly arrangement, which enhances the mechanical strength of the liquid crystal polymer composite film, making it less prone to breakage or deformation when subjected to external forces, and further improving the overall performance of the liquid crystal polymer composite film.

[0016] Additional aspects and advantages of the embodiments of this application will be described or shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0018] Figure 1 This is a flowchart illustrating a method for preparing a liquid crystal polymer composite film according to some embodiments of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0020] In this application, the term "embodiment" means that a particular feature, structure, or characteristic commonly described with respect to that embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0021] In the explanation of the embodiments of this application, technical terms such as "first" and "second" are used to distinguish different objects and should not be construed as indicating or implying relative importance, nor do they mean that the specified technical features have a specific meaning in terms of quantity, specific order, or primary and secondary relationship. In the explanation of the embodiments of this application, "multiple" refers to two or more, unless otherwise explicitly and specifically defined.

[0022] In the description of the embodiments of this application, the term "and / or" is used to describe the relationship between related objects, which can reflect three types of relationships. For example, A and / or B can present the following three situations: only A exists, A and B exist simultaneously, and only B exists. In addition, the character " / " in this document usually means that the related objects before and after are in an "or" relationship; " / " can also represent a proportional relationship; when " / " appears in a table, it can also indicate that the corresponding substance and parameter do not exist, and its specific meaning needs to be determined according to the actual scenario.

[0023] The technical features described in the different embodiments of this application below can be combined with each other as long as they do not conflict with each other.

[0024] Firstly, this application proposes a method for preparing a liquid crystal polymer composite film, please refer to... Figure 1 The preparation method includes the following steps: Step S1: Provide soluble liquid crystal polymer particles, dissolve the soluble liquid crystal polymer particles in a first solvent, stir and mix to obtain a soluble liquid crystal polymer solution.

[0025] Soluble liquid crystal polymer particles are a class of polymeric materials composed of rigid rod-shaped molecular chains. These chains can spontaneously align within specific solvent and concentration ranges to form a liquid crystal phase. Liquid crystal polymers possess characteristics such as heat resistance, thermal conductivity, high water resistance, and structural stability.

[0026] In some embodiments, the soluble liquid crystal polymer particles are polymerized from aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids. This results in the molecular chains of the soluble liquid crystal polymer particles containing both rigid aromatic ring segments and flexible segments. The rigid aromatic ring segments impart excellent high heat resistance and low dielectric loss to the material, while the flexible segments provide certain processability. The molar percentage of the aromatic dicarboxylic acid is 35 mol% to 45 mol%; and / or, the molar percentage of the aromatic diol is 35 mol% to 45 mol%; and / or, the molar percentage of the aromatic hydroxycarboxylic acid is 10 mol% to 30 mol%.

[0027] Aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalic acid. Aromatic diols include hydroquinone and bisphenol A. Aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Specifically, soluble liquid crystal polymer particles are polymerized from monomers comprising 40 mol% 2,6-naphthalic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid.

[0028] In some embodiments, the first solvent is a polar aprotic solvent. The first solvent includes at least one selected from N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and γ-butyrolactone. Preferably, the first solvent is N-methylpyrrolidone.

[0029] Soluble liquid crystal polymer particles are dissolved in a first solvent to form a soluble liquid crystal polymer solution with a solid content of 5% to 15%. The solid content of the soluble liquid crystal polymer solution can be any value from 5% to 15%, or any range between two values. For example, any value such as 5%, 7%, 9%, 11%, 13%, or 15%, or any range such as 5% to 10%, 6% to 9%, 6% to 13%, or 10% to 15%. When the solid content is controlled within the range of 5% to 15%, the soluble liquid crystal polymer solution has a suitable viscosity, which maintains good leveling properties, facilitating uniform coating, and reduces problems such as sagging and insufficient strength due to excessively thin film layers. Simultaneously, it can also improve defects such as coating bubbles and streaks caused by excessively high viscosity.

[0030] Preferably, the solid content of the soluble liquid crystal polymer solution is 8% to 10%. This makes the viscosity easier to control, which helps to reduce stress concentration caused by uneven film thickness during subsequent heat treatment, thereby improving the structural integrity and performance consistency of the liquid crystal polymer composite film.

[0031] In some embodiments, the viscosity of the soluble liquid crystal polymer solution is from 1000 mPa·s to 5000 mPa·s. The viscosity of the soluble liquid crystal polymer solution can be selected from any value within the range of 1000 mPa·s to 5000 mPa·s, or a range between any two values. For example, any value such as 1000 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 4000 mPa·s, or 5000 mPa·s can be selected, or any range such as 1000 mPa·s to 2000 mPa·s, 2000 mPa·s to 4000 mPa·s, or 3000 mPa·s to 5000 mPa·s can be selected. Controlling the viscosity within this range helps ensure the operability and uniformity of the soluble liquid crystal polymer solution during subsequent mixing with filler powders, additives, and coating processes.

[0032] Preferably, the viscosity of the soluble liquid crystal polymer solution is between 2000 mPa·s and 3000 mPa·s. This viscosity range is more conducive to achieving uniform dispersion of the slurry and stable coating of the subsequent wet film, thus laying a good foundation for the preparation of high-performance liquid crystal polymer composite films. The mixing process can be carried out using stirring equipment such as magnetic stirrers or mechanical stirrers. The stirring time and speed can be adjusted according to the actual situation to ensure that the soluble liquid crystal polymer particles are fully dissolved to form a uniform and stable solution. For example, stirring can be carried out at a stirring speed of 300 rpm to 500 rpm at room temperature for 4 to 6 hours until there are no obvious particles in the soluble liquid crystal polymer solution, and it is uniformly transparent or translucent.

[0033] Step S2: Provide filler powder and additives, mix the soluble liquid crystal polymer solution, filler powder and additives to obtain a first mixture; perform dispersion treatment and degassing treatment on the first mixture to obtain a slurry; the filler powder includes at least one of titanium dioxide (TiO2), barium titanate (BaTiO3), barium zirconate (BaZrO3), lead titanate (PbTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), carbon nanotubes (CNT), graphene oxide (GO), and reduced graphene (rGO).

[0034] Filler powders can leverage their excellent dielectric properties to synergistically enhance the overall dielectric constant of liquid crystal polymer (LCD) composite films by interacting with the soluble LCD matrix. For example, barium titanate and barium zirconate possess high dielectric constants; introducing them into the LCD matrix can effectively improve the overall dielectric constant of the LCD composite film, thus addressing the low dielectric constant of existing LCDs. Carbon-based fillers such as carbon nanotubes, graphene oxide, and reduced graphene can not only improve the dielectric constant to a certain extent but may also impart other superior properties to the LCD composite film, such as enhanced mechanical properties and improved thermal conductivity. In practical applications, single filler powders or combinations of multiple filler powders can be selected based on the specific requirements for the dielectric and other comprehensive properties of the LCD composite film. For instance, barium titanate is preferred as the main filler for preparing LCD composite films with high dielectric constants. If improvements in mechanical properties are also required, a combination of carbon nanotubes and barium titanate can be considered.

[0035] In some embodiments, before mixing the soluble liquid crystal polymer solution, filler powder, and additives, the preparation method further includes: subjecting the filler powder to a drying pretreatment at 100°C to 120°C for 6 to 8 hours. This drying pretreatment helps remove adsorbed moisture and other volatile impurities from the surface of the filler powder, reducing bubbles or pores generated during subsequent mixing and film formation, thereby ensuring the uniformity of the slurry and the density of the liquid crystal polymer composite film.

[0036] In some embodiments, the particle size of the filler microparticles is from 50 nm to 5000 nm. The particle size of the filler microparticles can be selected from any value within the range of 50 nm to 5000 nm, or a range between any two values. For example, any value such as 50 nm, 100 nm, 500 nm, 1000 nm, 2000 nm, 3000 nm, 4000 nm, or 5000 nm can be selected, or any range such as 50 nm to 500 nm, 100 nm to 1000 nm, 500 nm to 2000 nm, 1000 nm to 3000 nm, or 2000 nm to 5000 nm can be selected. A particle size of 50 nm to 5000 nm helps the filler microparticles to disperse more uniformly in the matrix, increasing the interfacial area and thus better exerting their role in enhancing dielectric properties.

[0037] It should be noted that for non-spherical particles such as graphene and carbon nanotubes, it is sufficient that their sheet diameter or length is between 50nm and 5000nm.

[0038] In some embodiments, the additives include at least one of silane coupling agents, titanate coupling agents, surfactants, leveling agents, and defoamers.

[0039] Silane coupling agents are a class of commonly used additives. Their molecular structure contains groups that can chemically react with the surface of inorganic materials (such as filler powder) and groups that are compatible with organic polymers (such as soluble liquid crystal polymers). By adding silane coupling agents, the interfacial bonding force between filler powder and the liquid crystal polymer matrix can be effectively improved, interfacial defects can be reduced, thereby improving the mechanical and dielectric stability of the liquid crystal polymer composite film. Silane coupling agents include γ-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), and γ-methacryloyloxypropyltrimethoxysilane (KH570), etc.

[0040] Titanate coupling agents improve interfacial compatibility by reacting the alkoxy groups in the molecule with the hydroxyl groups on the surface of the filler powder, while the long-chain alkyl groups or other functional groups at the other end can entangle or react with the polymer molecular chains. For example, a monoalkoxy type titanate coupling agent (KR-TTS) can be used.

[0041] Surfactants are substances that can significantly reduce the surface tension of liquids or the interfacial tension between two phases. Their molecular structure is amphiphilic, meaning they simultaneously contain hydrophilic (polar) and hydrophobic (non-polar) groups. In the preparation method of this application, adding a surfactant helps to further improve the dispersibility of the filler micropowder in the soluble liquid crystal polymer solution, reduces the surface tension of the slurry, and facilitates the spreading and leveling of the slurry on the substrate. For example, surfactants include 1,3-N,N-dimethyldodecyl ammonium bromide, sodium dodecyl sulfate (SDS), Tween 80, or Span 60.

[0042] Leveling agents are substances that promote the formation of a smooth, uniform surface during the drying and film-forming process of coating slurries. They effectively reduce the surface tension of the slurry, minimizing defects such as pinholes caused by differences in surface tension, ensuring uniform spreading of the slurry after coating, thereby obtaining a wet film of uniform thickness and a smooth surface. For example, leveling agents can be polyether-modified polydimethylsiloxane, acrylate copolymers, etc.

[0043] Defoamers are substances that can inhibit or eliminate the generation of bubbles in slurry during preparation and subsequent processing. For example, defoamers can include BYK-322.

[0044] In practical applications, the appropriate type and amount of additives can be selected based on the type of filler powder, the characteristics of the liquid crystal polymer, and the requirements for the performance of the slurry and the final film. For example, when barium titanate is used as the filler powder, an appropriate amount of KH550 silane coupling agent can be added to modify its surface, thereby improving its dispersibility and compatibility in N-methylpyrrolidone solvent and liquid crystal polymer matrix.

[0045] In some embodiments, based on the total mass of the slurry, the slurry comprises the following components in parts by mass: 100 to 120 parts of a soluble liquid crystal polymer solution, 10 to 80 parts of filler powder, and 2 to 5 parts of additives.

[0046] In some embodiments, the dispersion process includes a stirring process. The stirring speed during the stirring process is from 1100 rpm to 1300 rpm.

[0047] In some embodiments, the dispersion process includes dispersion disc processing. The dispersion disc processing rotates at a speed of 1400 rpm to 1600 rpm.

[0048] In some embodiments, the dispersion processing time is 20 min to 50 min.

[0049] In some embodiments, the dispersion process is a combination of stirring and dispersion disc treatment. For example, stirring is first performed at 1100 rpm to 1300 rpm for 20 minutes to initially disperse the filler powder and additives in the soluble liquid crystal polymer solution. Then, dispersion disc treatment is performed at 1400 rpm to 1600 rpm for 30 minutes to further break down any small agglomerates that may exist in the first mixture through high shear force, thereby ensuring that the filler powder and additives are uniformly dispersed in the soluble liquid crystal polymer solution.

[0050] Degassing treatment refers to removing air bubbles introduced into the first mixture during stirring and dispersion. This reduces the likelihood of defects such as pinholes and voids in the film layer during subsequent film formation and heat treatment, thus improving the structural integrity and performance stability of the liquid crystal polymer composite film.

[0051] In some embodiments, the degassing process employs a vacuum degassing method. Specifically, the first mixture after dispersion treatment is placed in a vacuum environment with a pressure of -80 kPa to -90 kPa for 30 to 40 minutes for degassing. Degassing reduces the bubble content in the first mixture, resulting in a smoother surface of the subsequently prepared liquid crystal polymer composite film, free from pinholes or depressions caused by obvious bubbles.

[0052] In some embodiments, the slurry that has undergone dispersion and degassing treatment can be homogenized to form a finer and more stable system. Homogenization can be performed using a high-pressure homogenizer, which cycles the slurry 1 to 3 times under a pressure of 50 MPa to 100 MPa. This utilizes strong shearing, impact, and cavitation effects to further refine the particle agglomerates in the slurry and improve dispersion uniformity.

[0053] Step S3: Provide a substrate, apply the slurry to the substrate, and form a wet film on the substrate.

[0054] The substrate is a support used to carry the slurry and give the wet film its initial shape. In this application, the substrate needs to have good chemical stability, heat resistance, and appropriate surface energy so that the slurry can be uniformly coated and separated from the cured first film.

[0055] In some embodiments, the substrate includes a glass substrate, a polytetrafluoroethylene sheet, a stainless steel foil, an aluminum foil, a copper foil, or a polyimide film, etc.

[0056] In some embodiments, the coating method includes blade coating, slot coating, dip coating, spray coating, or cast coating. For example, blade coating. The thickness of the wet film can be controlled by the gap height between the blade and the substrate.

[0057] In some embodiments, the thickness of the wet film is from 10 μm to 150 μm. The thickness of the wet film can be selected within the range of 10 μm to 150 μm according to actual needs. For example, any value such as 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, or any range such as 10 μm to 50 μm, 30 μm to 80 μm, 50 μm to 120 μm, 80 μm to 150 μm can be selected. By controlling the thickness of the wet film within this range, it is possible to reduce the risk of film damage after drying due to an excessively thin wet film, and also to reduce problems such as slow solvent evaporation, uneven drying, or stress cracking inside the film layer due to an excessively thick wet film.

[0058] Preferably, the wet film thickness is 50 μm to 60 μm. During the subsequent drying and curing process, the solvent evaporates more uniformly, resulting in a more uniform surface condition and a denser structure in the formed liquid crystal polymer composite film.

[0059] Step S4: Dry and cure the wet film to obtain the first film.

[0060] The purpose of drying and curing the wet film is to remove the primary solvent and other volatile components that may remain in the wet film, and to promote the further orientation and solidification of the soluble liquid crystal polymer molecular chains, thereby forming a film with certain mechanical properties and structural stability.

[0061] In some embodiments, drying and curing the wet film includes: placing the wet film in a first drying oven, wherein the first drying oven is heated to a first temperature at a heating rate of 0.25 °C / min to 0.5 °C / min, and held at the first temperature for a first duration; the first temperature is 130 °C to 150 °C, and the first duration is 1 h to 1.5 h. The first drying oven is heated to a second temperature at a heating rate of 1.8 °C / min to 2.5 °C / min, and held at the second temperature for a second duration; the second temperature is 250 °C to 320 °C, and the second duration is 1 h to 1.5 h. The first drying oven is cooled to a third temperature at a cooling rate of 0.8 °C / min to 1.2 °C / min, and the third temperature is 50 °C to 60 °C.

[0062] In the above process, the first drying oven is heated to 130°C to 150°C at a heating rate of 0.25°C / min to 0.5°C / min and held for 1 hour to 1.5 hours. The main purpose of this stage is to slowly remove most of the initial solvent from the wet film. Using a lower heating rate reduces the formation of bubbles or cracking of the film due to rapid solvent evaporation, and also facilitates the initial orientation and alignment of the soluble liquid crystal polymer molecular chains during solvent evaporation. Holding at the initial temperature ensures sufficient and uniform solvent evaporation, allowing the wet film to gradually solidify and form a preliminary film structure with a certain strength. Subsequently, the first drying oven is heated to 250°C to 320°C at a relatively faster heating rate of 1.8°C / min to 2.5°C / min and held for 1 hour to 1.5 hours. This high-temperature treatment aims to further promote the ordered alignment of the soluble liquid crystal polymer molecules, thereby endowing the first film with good mechanical and dielectric properties. Finally, the first drying oven cools the film to 50°C to 60°C at a rate of 0.8°C / min to 1.2°C / min. Slow cooling helps reduce thermal stress within the film caused by rapid temperature changes, minimizing defects such as warping and cracking, and ensuring the dimensional stability and structural integrity of the first film. Once the temperature drops to the third temperature, the substrate carrying the first film can be removed from the first drying oven.

[0063] Step S5: Peel the first film from the substrate to obtain the liquid crystal polymer composite film.

[0064] In some embodiments, the first film can be peeled off from the substrate by mechanical peeling or solvent-assisted peeling, and then wound up and slit to obtain a liquid crystal polymer composite film.

[0065] The liquid crystal polymer composite film prepared in this application, through blending with high-dielectric filler micropowder, significantly improves its dielectric constant to 6.62 to 20.68, representing a maximum improvement of 477% compared to pure liquid crystal polymer films. Further dispersion with additives and degassing treatment maintains the dielectric loss of the liquid crystal polymer composite film at 0.0042 to 0.042. Therefore, the liquid crystal polymer composite film prepared in this application possesses characteristics of high dielectric constant, low dielectric loss, and low linear expansion, while also maintaining a certain degree of flexibility and bendability, making it easy to process and meeting the application requirements of high-dielectric flexible films in the electronic circuit field.

[0066] Furthermore, the preparation method of this application is highly compatible with existing coating production lines, making it easy to achieve high-efficiency, low-cost roll-to-roll continuous manufacturing, with a clear prospect for industrialization.

[0067] This application provides a method for preparing a liquid crystal polymer composite film. The method includes: providing soluble liquid crystal polymer particles; dissolving the soluble liquid crystal polymer particles in a first solvent and stirring to obtain a soluble liquid crystal polymer solution; providing filler powder and additives; mixing the soluble liquid crystal polymer solution, filler powder, and additives to obtain a first mixture; dispersing and degassing the first mixture to obtain a slurry; the filler powder includes at least one of titanium dioxide, barium titanate, barium zirconate, lead titanate, calcium zirconate, calcium titanate, carbon nanotubes, graphene oxide, and reduced graphene; providing a substrate; coating the slurry onto the substrate and forming a wet film on the substrate; drying and curing the wet film to obtain a first film; and peeling the first film off the substrate to obtain a liquid crystal polymer composite film. This application, by adding filler powder to the soluble liquid crystal polymer solution, achieves synergy between the filler powder and the liquid crystal polymer matrix, maintaining the original low loss of the liquid crystal polymer while possessing a high dielectric constant. Furthermore, after drying and curing, the liquid crystal polymer molecular chains can achieve orderly arrangement, which enhances the mechanical strength of the liquid crystal polymer composite film, making it less prone to breakage or deformation when subjected to external forces, and further improving the overall performance of the liquid crystal polymer composite film.

[0068] Secondly, embodiments of this application also provide a liquid crystal polymer composite film, which is prepared using the liquid crystal polymer composite film preparation method of any one of the first aspects.

[0069] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0070] Example 1 (1) The soluble liquid crystal polymer solution was prepared by fully dissolving 100 g of liquid crystal polymer particles (polymerized from 40 mol% 2,6-naphthalenedicarboxylic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid) in 900 g of NMP solvent to form a solution with a solid content of 10 wt% and a viscosity of 3000 mPa·s; the TiO2 powder was of analytical grade and had a particle size of 2000 nm.

[0071] (2) 1000 g of soluble liquid crystal polymer solution, 500 g of TiO2 powder, and 10 g of silane coupling agent (KH-560) were sequentially poured into a reactor equipped with a stirring paddle and a dispersion disc. The stirring speed was set to 1200 rpm, the dispersion disc speed to 1500 rpm, and the stirring time to 30 min. After stirring, the bubbles in the mixed solution were removed by degassing under reduced pressure (-85 kPa) for 30 min to obtain a slurry.

[0072] (3) The homogenized slurry is precisely coated on the polyimide film by casting to obtain a wet film. The thickness of the wet film is adjusted by adjusting the height of the slit between the coating blade and the polyimide film. The thickness of the wet film is 50 μm.

[0073] (4) Place the wet film in an oven to dry and cure. Increase the temperature to 150 ℃ at a heating rate of 0.25 ℃ / min and hold for 1 h. Then increase the temperature to 280 ℃ at a heating rate of 2 ℃ / min and hold for 1 h. Then decrease the temperature to 60 ℃ at a cooling rate of 1 ℃ / min to obtain the first film.

[0074] (5) The polyimide film is peeled off by an automatic film peeling machine, so that the first film body is separated from the polyimide film and a liquid crystal polymer composite film is obtained.

[0075] Example 2 (1) The soluble liquid crystal polymer solution was prepared by fully dissolving 100 g of liquid crystal polymer particles (polymerized from 40 mol% 2,6-naphthalenedic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid) in 900 g of NMP solvent to form a solution with a solid content of 10 wt% and a viscosity of 2000 mPa·s; the CaTiO3 powder was of analytical grade and had a particle size of 2000 nm.

[0076] (2) Dry the CaTiO3 powder at 100℃ for 7h.

[0077] (3) 1000 g of soluble liquid crystal polymer solution, 500 g of dried CaTiO3 powder, and 20 g of titanate coupling agent (KR-TTS) were sequentially poured into a reactor equipped with a stirring paddle and a dispersion plate. The stirring speed was set to 1200 rpm, the dispersion plate speed to 1500 rpm, and the stirring time to 30 min. After stirring, the bubbles in the mixed solution were removed by degassing under reduced pressure (-85 kPa) for 30 min to obtain a slurry.

[0078] (4) The slurry is homogenized by a homogenizer and then precisely coated on the polyimide film by casting to obtain a wet film. The thickness of the wet film is adjusted by adjusting the height of the slit between the coating blade and the polyimide film. The thickness of the wet film is 50 μm.

[0079] (5) Place the wet film in an oven to dry and cure. Increase the temperature to 150 ℃ at a heating rate of 0.25 ℃ / min and hold for 1 h. Then increase the temperature to 280 ℃ at a heating rate of 2 ℃ / min and hold for 1 h. Then decrease the temperature to 60 ℃ at a cooling rate of 1 ℃ / min to obtain the first film.

[0080] (6) The polyimide film is peeled off by an automatic film peeling machine, so that the first film body is separated from the polyimide film and a liquid crystal polymer composite film is obtained.

[0081] Example 3 (1) The soluble liquid crystal polymer solution is formed by fully dissolving 100 g of liquid crystal polymer particles (polymerized from 40 mol% 2,6-naphthalenedic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid) in 900 g of NMP solvent to form a solution with a solid content of 10 wt% and a viscosity of 3000 mPa·s; the CNT powder is of analytical grade, with a diameter of 5 nm to 20 nm and a length of 2000 nm.

[0082] (2) Dry the CNT powder at 100°C for 7 hours.

[0083] (3) 1000 g of soluble liquid crystal polymer solution, 20 g of dried CNT powder, 5 g of silane coupling agent (KH-540), and 5 g of surfactant (1,3-N,N-dimethyldodecylammonium bromide) were sequentially poured into a reactor equipped with a stirrer and a dispersion plate. The stirring speed was set to 1200 rpm, the dispersion plate speed to 1500 rpm, and the stirring time to 30 min. After stirring, the bubbles in the mixed solution were removed by degassing under reduced pressure (-85 kPa) for 30 min to obtain a slurry.

[0084] (4) The slurry is homogenized by a homogenizer and then precisely coated on the polyimide film by casting to obtain a wet film. The thickness of the wet film is adjusted by adjusting the height of the slit between the coating blade and the polyimide film. The thickness of the wet film is 50 μm.

[0085] (5) Place the wet film in an oven to dry and cure. Increase the temperature to 150 ℃ at a heating rate of 0.25 ℃ / min and hold for 1 h. Then increase the temperature to 280 ℃ at a heating rate of 2 ℃ / min and hold for 1 h. Then decrease the temperature to 60 ℃ at a cooling rate of 1 ℃ / min to obtain the first film.

[0086] (6) The polyimide film is peeled off by an automatic film peeling machine, so that the first film body is separated from the polyimide film and a liquid crystal polymer composite film is obtained.

[0087] Example 4 (1) The soluble liquid crystal polymer solution was prepared by dissolving 100 g of liquid crystal polymer particles (polymerized from 40 mol% 2,6-naphthalenedic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid) in 900 g of NMP solvent to form a solution with a solid content of 10 wt% and a viscosity of 3000 mPa·s; the GO powder was of analytical grade and had a length of 5000 nm.

[0088] (2) Dry the GO powder at 100℃ for 7h.

[0089] (3) 1000 g of soluble liquid crystal polymer solution, 20 g of dried GO powder, 5 g of silane coupling agent (KH-540), 2.5 g of surfactant (1,3-N,N-dimethyldodecylammonium bromide), and 2.5 g of defoamer (BYK-322) were sequentially poured into a reactor equipped with a stirring paddle and a dispersion disc. The stirring speed was set to 1200 rpm, the dispersion disc speed to 1500 rpm, and the stirring time to 30 min. After stirring, the bubbles in the mixed solution were removed by degassing under reduced pressure (-85 kPa) for 30 min to obtain a slurry.

[0090] (4) The slurry is homogenized by a homogenizer and then precisely coated on the polyimide film by casting to obtain a wet film. The thickness of the wet film is adjusted by adjusting the height of the slit between the coating blade and the polyimide film. The thickness of the wet film is 50 μm.

[0091] (5) Place the wet film in an oven to dry and cure. Increase the temperature to 150 ℃ at a heating rate of 0.25 ℃ / min and hold for 1 h. Then increase the temperature to 280 ℃ at a heating rate of 2 ℃ / min and hold for 1 h. Then decrease the temperature to 60 ℃ at a cooling rate of 1 ℃ / min to obtain the first film.

[0092] (6) The polyimide film is peeled off by an automatic film peeling machine, so that the first film body is separated from the polyimide film and a liquid crystal polymer composite film is obtained.

[0093] Comparative Example 1 (1) The soluble liquid crystal polymer solution is formed by fully dissolving 100 g of liquid crystal polymer particles (polymerized from 40 mol% 2,6-naphthalenedic acid, 40 mol% hydroquinone, and 20 mol% p-hydroxybenzoic acid) in 900 g of NMP solvent to form a solution with a solid content of 10 wt% and a viscosity of 3000 mPa·s.

[0094] (2) A soluble liquid crystal polymer solution is precisely coated on a polyimide film by casting to obtain a wet film. The thickness of the wet film is adjusted by adjusting the height of the slit between the coating blade and the polyimide film. The thickness of the wet film is 50 μm.

[0095] (3) The wet film was placed in an oven to dry and cure. The temperature was increased to 150 ℃ at a heating rate of 0.25 ℃ / min and held for 1 h. The temperature was then increased to 280 ℃ at a heating rate of 2 ℃ / min and held for 1 h. The temperature was then decreased to 60 ℃ at a cooling rate of 1 ℃ / min to obtain the first film.

[0096] (4) The polyimide film is peeled off by an automatic film peeling machine, so that the first film body is separated from the polyimide film and a liquid crystal polymer film is obtained.

[0097] The films prepared in Examples 1 to 4, and Comparative Example 1, were tested as follows.

[0098] Dielectric property testing: The dielectric constant and dielectric loss of the thin film samples were determined using the resonant cavity method according to the IPC-TM-650 standard. Samples were cut into 80 mm × 80 mm squares, dried in an oven at 60 °C for 2 hours, and then equilibrated at 25 °C and 50% RH for 24 hours. The testing equipment consisted of a Keysight E5071 network analyzer and a discrete dielectric resonator SPDR fixture. The test frequency was 10 GHz, the test temperature was 25 °C, and the ambient humidity was 50% RH.

[0099] Linear expansion coefficient test: According to ISO-11359-2 standard, the sample was cut into strips of 4.5 mm × 24 mm using a cutter, and the linear expansion coefficient of the sample was determined using the tensile mode. The testing equipment was a TMA450 thermomechanical analyzer manufactured by TA Instruments, with a load of 0.05 N and a heating rate of 10 ℃ / min. The linear expansion coefficient of the sample in the temperature range of 50 ℃ to 100 ℃ was determined.

[0100] Dimensional stability test: According to IPC-TM-650 standard, the sample was cut into a 10.5-inch × 11.5-inch rectangle with a punch, and holes with a diameter of 0.005 inches were punched at specified locations. After the sample was left to stand at 25 ℃ and 50%RH for 3 hours, the distance between the holes was measured. After baking the sample at 150 ℃ for 30 minutes, the distance between the holes was measured again after equilibration at 25 ℃ and 50%RH for 24 hours. Dimensional stability was calculated based on the two measurement results.

[0101] Folding endurance test: According to JIS C 5016 standard, the sample is cut into a strip of 15 mm × 100 mm. The sample is vertically clamped in the MIT folding endurance tester, and a tension of 4.9 N is applied. Under the conditions of temperature 23 ℃±2 ℃ and humidity 50 % RH±5 % RH, the sample is folded back and forth at a speed of 175 times / minute and an angle of 135° until the sample breaks. The number of double folds at this point is recorded as the folding endurance.

[0102] The test results of Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

[0103] Table 1

[0104] As shown in Table 1, compared with Comparative Example 1, the liquid crystal polymer composite films prepared in Examples 1 to 4 all exhibited significantly improved dielectric constants. Among them, Example 4 showed the highest dielectric constant, reaching 20.68, representing an improvement of approximately 477% compared to the pure liquid crystal polymer film of Comparative Example 1. This indicates that adding the filler powder described in this application to the soluble liquid crystal polymer solution can effectively improve the dielectric constant of the liquid crystal polymer composite film, demonstrating that the filler powder and the liquid crystal polymer matrix in this application can synergistically enhance dielectric properties.

[0105] The dielectric losses of Examples 1 to 4 were 0.0042, 0.0044, 0.042, and 0.027, respectively, all at a low level. The dielectric losses of Examples 1 and 2 were closer to those of Comparative Example 1 (0.0037), indicating that the composite film maintained good dielectric loss characteristics even with the addition of CaTiO3 and TiO2 powders. The dielectric losses of Examples 3 and 4 were slightly higher than those of Comparative Example 1, which may be related to the conductivity of the CNT and GO powders themselves and their dispersion state in the matrix, but overall remained within an acceptable range, and no significant degradation in dielectric loss was observed.

[0106] The linear expansion coefficients of Examples 3 and 4 were 17 ppm / K and 18 ppm / K, respectively, lower than the 20 ppm / K of Comparative Example 1. Examples 1 and 2 were the same as Comparative Example 1, both at 22 ppm / K. This indicates that adding CNT and GO fillers helps reduce the linear expansion coefficient of the composite membrane and improves its dimensional stability. Dimensional stability test results showed that the dimensional stability of Examples 3 and 4 was 0.3 × 10⁻⁶. -4 This is superior to the 0.4 × 10⁻⁶ of Comparative Example 1. -4 This indicates that carbon-based fillers such as CNT and GO are more effective in improving the thermal stability of materials. Although Examples 1 and 2 are lower than Comparative Example 1, they are not significantly degraded, indicating that the modified film still has good structural stability.

[0107] Comparative Example 1 showed the highest folding endurance at 223,000 cycles. The folding endurance of Examples 1 to 4 all decreased, with Example 4 at 202,000 cycles, Example 3 at 193,000 cycles, Example 1 at 124,000 cycles, and Example 2 at 115,000 cycles. This indicates that the addition of filler powder affected the flexibility of the composite film to some extent. However, Examples 1 to 4 still maintained a high number of folding cycles (all above 100,000 cycles), and the overall film still exhibited excellent bending resistance, meeting the requirements of conventional molding and processing.

[0108] In summary, the method for preparing the liquid crystal polymer composite film proposed in this application, by adding specific filler micropowders to a soluble liquid crystal polymer solution and combining it with coupling agents, surfactants, and other additives for dispersion and composite formation, can significantly improve the dielectric constant of the composite film while ensuring low dielectric loss. Simultaneously, improvements are also achieved in dimensional stability and linear expansion coefficient. In Example 4, by adding GO powder and combining it with a silane coupling agent (KH-540), a surfactant (1,3-N,N-dimethyldodecylammonium bromide), and an antifoaming agent (BYK-322), the prepared composite film exhibited well-balanced and excellent comprehensive performance in terms of dielectric constant (20.68), dielectric loss (0.0027), linear expansion coefficient (18 ppm / K), dimensional stability (0.3×10⁻⁴), and folding endurance (202,000 cycles), demonstrating the effectiveness and superiority of this preparation method.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a liquid crystal polymer composite film, characterized in that, include: A soluble liquid crystal polymer particle is provided, and the soluble liquid crystal polymer particle is dissolved in a first solvent and stirred to obtain a soluble liquid crystal polymer solution. A filler powder and an additive are provided. The soluble liquid crystal polymer solution, the filler powder, and the additive are mixed to obtain a first mixture. The first mixture is then dispersed and degassed to obtain a slurry. The filler powder includes at least one of titanium dioxide, barium titanate, barium zirconate, lead titanate, calcium zirconate, calcium titanate, carbon nanotubes, graphene oxide, and reduced graphene. Provide a substrate, apply the slurry to the substrate, and form a wet film on the substrate; The wet film is dried and cured to obtain a first film. The first film is peeled off from the substrate to obtain a liquid crystal polymer composite film.

2. The preparation method according to claim 1, characterized in that, Before mixing the soluble liquid crystal polymer solution, the filler powder, and the additives, the preparation method further includes: The filler powder is subjected to a drying pretreatment at 100°C to 120°C for 6 to 8 hours; the particle size of the filler powder is 50 nm to 5000 nm.

3. The preparation method according to claim 1, characterized in that, The soluble liquid crystal polymer particles are polymerized from aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids. The aromatic dicarboxylic acid has a molar percentage of 35 mol% to 45 mol%; and / or, the aromatic diol has a molar percentage of 35 mol% to 45 mol%; and / or, the aromatic hydroxycarboxylic acid has a molar percentage of 10 mol% to 30 mol%.

4. The preparation method according to claim 1, characterized in that, The additives include at least one of silane coupling agents, titanate coupling agents, surfactants, leveling agents, and defoamers.

5. The preparation method according to claim 1, characterized in that, Based on the total mass of the soluble liquid crystal polymer solution, the solid content of the soluble liquid crystal polymer solution is 5% to 15%; The viscosity of the soluble liquid crystal polymer solution is from 1000 mPa·s to 5000 mPa·s.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The dispersion process includes stirring and / or dispersing disc treatment; the stirring speed for the stirring process is 1100 rpm to 1300 rpm, and the speed for the dispersing disc treatment is 1400 rpm to 1600 rpm; the dispersion process lasts for 20 min to 50 min. The degassing treatment is performed at a pressure of -80 kPa to -90 kPa and for a duration of 30 min to 40 min.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The drying and curing process of the wet film includes: The wet film is placed in a first drying oven, which is heated to a first temperature at a rate of 0.25 ℃ / min to 0.5 ℃ / min and maintained at the first temperature for a first duration; the first temperature is 130 ℃ to 150 ℃ and the first duration is 1 h to 1.5 h. The first drying oven is heated to a second temperature at a heating rate of 1.8 ℃ / min to 2.5 ℃ / min, and held at the second temperature for a second duration; the second temperature is 250 ℃ to 320 ℃, and the second duration is 1 h to 1.5 h; The first drying oven cools down to a third temperature at a rate of 0.8 ℃ / min to 1.2 ℃ / min, wherein the third temperature is 50 ℃ to 60 ℃.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The thickness of the wet film is from 10 μm to 150 μm.

9. The preparation method according to claim 1, characterized in that, The first solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and γ-butyrolactone.

10. A liquid crystal polymer composite film, characterized in that, It is prepared by the method for preparing liquid crystal polymer composite film as described in any one of claims 1 to 9.

Images