A method for preparing and using a liquid crystal polymer film

Abstract

The application discloses a preparation method and application of a liquid crystal polymer film, relates to the technical field of LCP film used in high-frequency communication, and at least comprises the following heat treatment steps: S1, high-temperature compounding of liquid crystal polymer and a carrier at 200-350 DEG C to obtain a composite film of the liquid crystal polymer and the carrier; S2, multi-gradient temperature rising and falling treatment of the composite film at 200 DEG C-350 DEG C; S3, peeling of the carrier in the composite film to obtain a liquid crystal polymer film precursor; and heat treatment of the liquid crystal polymer film precursor, wherein the heat treatment temperature is lower than the glass transition temperature of the liquid crystal polymer, the heat treatment time is 1s-30min, and a finished liquid crystal polymer film is obtained. Through the heat treatment, the resin molecular weight of the liquid crystal polymer in the film is increased, the thermal expansion coefficient is increased, the thermal expansion coefficient of the liquid crystal polymer is close to that of copper foil, the resin melting point of the liquid crystal polymer is also increased, and the lead-free reflow soldering process of the FPC is met.

Description

Technical Field

[0001] This invention relates to the field of LCP thin film technology used in high-frequency communication, and more specifically, to a method for preparing and applying a liquid crystal polymer thin film. Background Technology

[0002] Liquid crystal polymers (LCPs) are an important type of polymer, typically consisting of fully aromatic molecules containing various heteroatom bonds, including ester and / or amide ester bonds. When heated to sufficiently high temperatures, LCPs melt to form a liquid crystal molten phase (often called the "anisotropic phase") rather than an isotropic molten phase. Due to their unique molecular chain rigidity, LCPs exhibit very little polymer-specific entanglement, unlike ordinary thermoplastic resins, and show significant orientation in the flow direction. The molecular chain orientation relaxation time is relatively long, allowing them to maintain orientation and solidify during injection molding and thermoforming. Therefore, LCPs exhibit significant anisotropy in terms of mechanical properties and other performance characteristics, and liquid crystal molecule orientation should be minimized during LCP film molding. Typically, LCPs consist of linear molecules ("rigid bars") that arrange themselves to form the desired liquid crystal sequence. LCPs possess excellent low moisture absorption, heat resistance, dimensional stability, and a low dielectric constant.

[0003] With the widespread adoption and vigorous promotion of 5G technology, the trend towards higher frequency communication is becoming increasingly apparent. Copper-clad laminates (CCLs), which form the substrate of 5G antennas, are mainly composed of copper foil and insulating films. Liquid crystal polymers are frequently used as the insulating film in CCLs. However, the CCL material constituting the antenna substrate requires good dimensional stability. To prepare CCL components with good dimensional stability, the coefficients of thermal expansion (CTE) of the copper foil and the liquid crystal polymer should be as close as possible. However, since one is composed of copper atoms and the other of molecular covalent bonds, their CTEs are difficult to make very similar. Furthermore, CCLs require soldering (at a temperature of 288°C), which requires the CCL to withstand high temperatures. This property is determined by the melting point of the liquid crystal polymer, but most liquid crystal polymers in the current technology do not reach 288°C. Therefore, to prepare liquid crystal polymers usable in the field of CCLs, the polymers must be treated to ensure that their CTE and melting point meet the required thermal properties.

[0004] When semiconductor components or impedance components are directly mounted on the surface of a circuit board, positional misalignment can easily occur if the coefficients of thermal expansion of the circuit board and the components differ. When thermoplastic liquid crystal polymers are extruded into thin films using methods such as blow molding, they generally become films with a negative coefficient of thermal expansion. When such thermoplastic liquid crystal polymer films are used as insulating layers on circuit boards, their coefficients of thermal expansion need to be increased during the circuit board manufacturing process to ensure they match those of the components. While the coefficient of thermal expansion of thermoplastic liquid crystal polymer films can be adjusted through heat treatment, increasing it, as documented by Kuraray in Japan, requires heat treatment at a temperature not lower than the film's melting point. However, high-temperature heat treatment can lead to resin degradation due to excessive heat load. Higher heat treatment temperatures make precise control of the film's coefficient of thermal expansion increasingly difficult, and can easily cause film deformation and other defects, hindering energy efficiency, increasing limitations on the device surface, raising costs, and posing various problems for industrial production.

[0005] To address this problem, another existing technique involves heat-treating a laminate (circuit board) composed of a thermoplastic liquid crystal polymer film and a metal foil before mounting surface-mount components onto it, so that the coefficient of thermal expansion of the film constituting the laminate is substantially the same as that of the mounting components (see Japanese Patent Application Laid-Open No. 10-157010). Various methods have also been proposed, such as heat-treating the laminate composed of a thermoplastic liquid crystal polymer film and a metal foil to modify the physical properties of the film (see USP 5,529,740). Summary of the Invention

[0006] To address the problems of insufficient cohesion leading to delamination, low coefficient of thermal expansion, low melting point, and large thermal shrinkage in existing liquid crystal polymer films, this invention provides a method for preparing and applying a liquid crystal polymer film. The liquid crystal polymer film provided by this invention, through a specific heat treatment method, increases the molecular weight of the liquid crystal polymer resin within the film, simultaneously improving its coefficient of thermal expansion to approach that of copper foil. This also raises the melting point of the liquid crystal polymer resin, making it suitable for lead-free reflow soldering processes in FPCs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a liquid crystal polymer film, the method comprising at least the following heat treatment steps:

[0009] S1: The liquid crystal polymer and the carrier are composited at a high temperature of 200~350℃ to obtain a composite film of liquid crystal polymer and carrier.

[0010] S2: The composite membrane is subjected to multi-gradient heating and cooling treatment at 200℃-350℃;

[0011] S3: Peel off the carrier in the composite film to obtain the liquid crystal polymer film precursor, and perform heat treatment on the liquid crystal polymer film precursor. The heat treatment temperature is lower than the glass transition temperature of the liquid crystal polymer, and the heat treatment time is 1s to 30min to obtain the finished liquid crystal polymer film.

[0012] Further, in step S1, the molecular weight of the liquid crystal polymer is 20,000 to 500,000, and the coefficient of thermal expansion is -100 to -1 ppm; the coefficient of thermal expansion of the carrier is 12 to 16 ppm; preferably, the absolute value of the difference between the coefficients of thermal expansion of the liquid crystal polymer and the carrier is 13 to 100 ppm.

[0013] Furthermore, the high-temperature compounding in step S1 uses a high-temperature roller press or a high-temperature pressing roller with a pressing temperature of 200~350℃.

[0014] Furthermore, the high-temperature roller press is selected from a five-axis high-temperature press or a three-axis high-temperature press; the temperature accuracy of the press rollers used is within ±5℃; and the unit pressure of the high-temperature pressing is 1KN-15KN.

[0015] Furthermore, the carrier in step S1 is selected from aluminum foil, copper foil, steel strip, polytetrafluoroethylene, titanium, chromium steel, or nickel.

[0016] Furthermore, the thickness of the carrier in step S1 is 5μm-500μm.

[0017] Furthermore, the multi-gradient heating and cooling process in step S2 is as follows: the first stage heats up to 220°C at a heating rate of 20°C / min; the second stage heats up to 240°C at a heating rate of 5°C / min; the third stage heats up to 260°C at a heating rate of 5°C / min; the fourth stage heats up to 300°C at a heating rate of 5°C / min; the heating time for each stage is 0.5h to 50h; and the fifth stage cools down to 25°C at a cooling rate of 30°C / min.

[0018] Furthermore, the heating equipment for the heat treatment in step S2 is selected from high-temperature furnaces and high-temperature ovens as heat sources, and at least one of hot air ovens, steam ovens, electric heaters, infrared heaters, ceramic heaters, hot rolling mills, hot presses, and electromagnetic wave irradiation machines is used.

[0019] Furthermore, the composite film in step S2 has a cohesive strength greater than 7 N / cm, an elongation of 2-6%, and a melting point of 260-300℃.

[0020] Furthermore, the shrinkage rate of the liquid crystal polymer film in step S3 at 150°C for 30 minutes is less than 0.08% in both the length and (or width) directions.

[0021] In a second aspect, the present invention also provides a laminate having the liquid crystal polymer film described in the first aspect.

[0022] Compared with the prior art, the present invention has the following advantages when applying the technical solution of the present invention:

[0023] The liquid crystal polymer film provided by this invention effectively solves a series of problems caused by insufficient cohesion in the original liquid crystal polymer film, such as delamination, small coefficient of thermal expansion, and large thermal shrinkage, through a specific heat treatment method. It increases the molecular weight of the liquid crystal polymer resin in the film, thereby increasing the coefficient of thermal expansion to be close to that of copper foil. It also increases the melting point of the liquid crystal polymer resin, so that the heat resistance is no longer limited by the melting point of the resin raw material, thus meeting the requirements of lead-free reflow soldering process of FPC. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 A schematic cross-sectional view of a liquid crystal polymer film provided according to an embodiment of the present invention is shown;

[0026] The above figures include the following reference numerals: 1 is the liquid crystal polymer film; 2 is the carrier. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] Liquid crystal polymers (LCPs) possess high strength, high modulus, high temperature resistance, chemical corrosion resistance, and high dimensional stability, making them widely used in aerospace, defense, and specialized industries. However, LCP films suffer from a series of problems, including insufficient cohesion leading to delamination, low coefficient of thermal expansion, and large thermal shrinkage.

[0031] To address this problem, this application provides a method for preparing a liquid crystal polymer film and its application.

[0032] In a typical embodiment of this application, in a first aspect, the present invention provides a method for preparing a liquid crystal polymer film, the method comprising at least the following heat treatment steps: S1, performing high-temperature composite treatment of a liquid crystal polymer and a carrier at 200~350℃ to obtain a composite film of liquid crystal polymer and carrier; S2, subjecting the composite film to multi-gradient heating and cooling treatment at 200℃-350℃; S3, peeling the carrier from the composite film to obtain a liquid crystal polymer film precursor, and performing heat treatment on the liquid crystal polymer film precursor, wherein the heat treatment temperature is lower than the glass transition temperature of the liquid crystal polymer, and the heat treatment time is 1s~30min, to obtain the finished liquid crystal polymer film.

[0033] In step S2, the composite film is subjected to multi-gradient heating and cooling treatment at 200℃-350℃, which can control the molecular weight growth process to stably improve the film strength and prevent excessively drastic local high or low temperatures.

[0034] In step S3, the heat treatment temperature is lower than the glass transition temperature of the liquid crystal polymer because when the temperature is below the Tg point, the molecular chain ends cannot move, and the heat treatment has no effect.

[0035] In a typical embodiment of this application, the molecular weight of the liquid crystal polymer in step S1 is 20,000 to 500,000, and its coefficient of thermal expansion is -100 to -1 ppm; the coefficient of thermal expansion of the carrier is 12 to 16 ppm; preferably, the absolute value of the difference between the coefficients of thermal expansion of the liquid crystal polymer and the carrier is 13 to 100 ppm. The coefficient of thermal expansion of the carrier used in the heat treatment process of step S1 is preferably greater than the coefficient of thermal expansion of the liquid crystal polymer supplied before heat treatment.

[0036] In a typical embodiment of this application, considering the heat resistance and processability of the film, the high-temperature lamination in step S1 uses a high-temperature roller press or a pressure roller with a high-temperature pressing temperature of 200~350℃. Further, the high-temperature roller press is selected from a five-axis or three-axis high-temperature press; the temperature accuracy of the pressure roller is within ±5℃; and the unit pressure of the high-temperature pressing is 1KN-15KN. If the unit pressure of the high-temperature pressing is lower than 1KN, the LCP film cannot adhere to the carrier; if the unit pressure of the high-temperature pressing is higher than 15KN, after heat treatment, the tight bond with the support prevents the LCP film from separating well from the support.

[0037] In a typical embodiment of this application, the carrier in step S1 is selected from aluminum foil, copper foil, steel strip, polytetrafluoroethylene, titanium, chromium steel, or nickel.

[0038] In a typical embodiment of this application, the thickness of the carrier in step S1 is 5μm-500μm. If the thickness of the carrier is less than 5μm, there is insufficient support, resulting in wrinkles during LCP peeling; if the thickness of the carrier is greater than 500μm, the carrier is too thick to be peeled and rolled up, and the cost is high.

[0039] In a typical embodiment of this application, the multi-gradient heating and cooling process of step S2 is as follows: the first stage heats up to 220°C at a heating rate of 20°C / min; the second stage heats up to 240°C at a heating rate of 5°C / min; the third stage heats up to 260°C at a heating rate of 5°C / min; the fourth stage heats up to 300°C at a heating rate of 5°C / min; the heating time for each stage is 0.5h to 50h; and the fifth stage cools down to 25°C at a cooling rate of 30°C / min.

[0040] In a typical embodiment of this application, the heating device for the heat treatment in step S2 is selected from at least one of a high-temperature furnace, a high-temperature oven, a hot air oven, a steam oven, an electric heater, an infrared heater, a ceramic heater, a hot rolling mill, a hot press, and an electromagnetic wave irradiation machine.

[0041] In a typical embodiment of this application, the composite film in step S2 has a cohesive strength greater than 7 N / cm, an elongation of 2-6%, and a melting point of 260-320°C. Only through this method can a cohesive strength greater than 7 N / cm be obtained, resulting in increased elongation and a higher melting point.

[0042] In a typical embodiment of this application, the shrinkage rate of the liquid crystal polymer film in step S3 at 150°C for 30 min is less than 0.08% in the length direction and (or width direction).

[0043] In a second aspect, the present invention also provides a laminate having the liquid crystal polymer film described in the first aspect.

[0044] In a preferred embodiment of this application, when the metal is copper foil, a laminate consisting of a liquid crystal polymer film and copper foil is formed, which can be used as a circuit substrate. Through the aforementioned multiple heat treatments, the coefficient of thermal expansion of the liquid crystal polymer film can be improved, resulting in a good film with a coefficient of thermal expansion adjusted to the desired level. The coefficient of thermal expansion of the obtained liquid crystal polymer film is close to that of the copper foil.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] Example 1: A 50μm thick film (coefficient of thermal expansion of -30ppm) was blown using Polyplastics A950RX resin. The film was then laminated onto a 40μm thick aluminum foil (coefficient of thermal expansion of 14ppm) using a roller press at 265℃ and 12KN. The resulting composite was then heat-treated in a tunnel oven, with the temperature raised from room temperature to 240℃ and held for 2 hours, then raised to 260℃ and held for 6 hours, and then raised to 270℃ and held for 6 hours. After holding, the temperature was lowered to room temperature. The aluminum foil was then peeled off from the heat-treated composite film. The LCP film was then placed in the tunnel oven and heat-treated at 230℃ for 3 minutes before being removed to obtain the finished liquid crystal polymer film.

[0047] Example 2: A 50μm thick film (coefficient of thermal expansion of -1ppm) was blown using Polyplastics A950RX resin. The film was then laminated onto a 40μm thick aluminum foil (coefficient of thermal expansion of 14ppm) using a roller press at 265℃ and 12KN. The resulting composite was then heat-treated in a tunnel oven, with the temperature raised from room temperature to 240℃ and held for 2 hours, then raised to 260℃ and held for 6 hours, and then raised to 270℃ and held for 6 hours. After holding, the temperature was lowered to room temperature. The aluminum foil was then peeled off from the heat-treated composite film. The LCP film was then placed in the tunnel oven and heat-treated at 230℃ for 3 minutes before being removed to obtain the finished liquid crystal polymer film.

[0048] Example 3: A 50 μm thick film (coefficient of thermal expansion of -100 ppm) was blown using Polyplastics A950RX resin. The film was then laminated onto a 40 μm thick aluminum foil (coefficient of thermal expansion of 14 ppm) using a roller press at 265°C and 12 KN. The resulting composite was then heat-treated in a tunnel oven, with the temperature raised from room temperature to 240°C and held for 2 hours, then raised to 260°C and held for 6 hours, and then raised to 270°C and held for 6 hours. After holding, the temperature was lowered to room temperature. The aluminum foil was then peeled off from the heat-treated composite film. The LCP film was then placed in the tunnel oven and heat-treated at 230°C for 3 minutes before being removed to obtain the finished liquid crystal polymer film.

[0049] Example 4: A 50 μm thick film (coefficient of thermal expansion of -80 ppm) was blown using Polyplastics A950RX resin. The film was then laminated onto a 5 μm thick aluminum foil (coefficient of thermal expansion of 14 ppm) using a roller press at 265°C and 12 KN. The resulting composite was then heat-treated in a tunnel oven. The temperature was raised from room temperature to 240°C and held for 2 hours, then raised to 260°C and held for 6 hours, then raised to 270°C and held for 6 hours. After holding, the temperature was lowered to room temperature. The aluminum foil was then peeled off from the heat-treated composite film. The LCP film was then placed in the tunnel oven and heat-treated at 230°C for 3 minutes before being removed to obtain the finished liquid crystal polymer film.

[0050] Example 5: A 50 μm thick film (coefficient of thermal expansion of -80 ppm) was blown using Polyplastics A950RX resin. The film was then laminated onto a 500 μm thick aluminum foil (coefficient of thermal expansion of 14 ppm) using a roller press at 265°C and 12 KN. The resulting composite was then heat-treated in a tunnel oven, with the temperature raised from room temperature to 240°C and held for 2 hours, then raised to 260°C and held for 6 hours, then raised to 270°C and held for 6 hours, and finally cooled to room temperature. The aluminum foil was then peeled off from the heat-treated composite film. After peeling, the LCP film was placed in the tunnel oven and heat-treated at 230°C for 3 minutes to obtain the finished liquid crystal polymer film.

[0051] Example 6: A 50 μm thick film (coefficient of thermal expansion of -80 ppm) was blown using Polyplastics A950RX resin. This film was then laminated onto a 40 μm thick aluminum foil (coefficient of thermal expansion of 14 ppm) using a roller press at 265°C and 12 KN. The resulting composite was then heat-treated in a tunnel oven. The first stage involved heating to 220°C at a rate of 20°C / min; the second stage involved heating to 240°C at a rate of 5°C / min; the third stage involved heating to 260°C at a rate of 5°C / min; the fourth stage involved heating to 300°C at a rate of 5°C / min; the heating time for each stage ranged from 0.5 h to 50 h; and the fifth stage involved cooling to 25°C at a rate of 30°C / min. The aluminum foil was then peeled off from the heat-treated composite film. After peeling, the LCP film was placed back into the tunnel oven and heat-treated at 230°C for 3 min to obtain the finished liquid crystal polymer film.

[0052] Comparative Example 1: A 50 μm thick film (coefficient of thermal expansion of -100 ppm) was blown into film using Polyplastics A950RX resin and tested directly without heat treatment.

[0053] Performance testing:

[0054] (1) Melting point: The film was heated to a rate of 20°C / min using a differential scanning calorimeter until it was completely melted. Then the melt was rapidly cooled to 50°C at a rate of 50°C / min. The temperature was then increased again at a rate of 20°C / min. The position of the endothermic peak that appeared at this time was recorded as the melting point Tm of the film.

[0055] (2) Coefficient of thermal expansion: Using a thermomechanical analysis apparatus (TMA), a tensile load of 1g was applied to both ends of a film with a width of 5mm and a length of 20mm. The film was heated from room temperature to 200℃ at a rate of 5℃ / min, cooled to 30℃ at a rate of 20℃ / min, and then heated again at a rate of 5℃ / min. The coefficient of thermal expansion was calculated from the change in length between 30℃ and 150℃.

[0056] (3) Shrinkage rate: Take a 150mm*150mm square sample, make a 100mm×100mm sample using a template, draw a "+" on the corresponding position with a blade, measure the length of the TD / MD direction at room temperature (using a two-dimensional or vernier caliper), then put it in a 150℃ oven, bake for 30 minutes, take it out, let it stand for 15 minutes, measure the TD / MD length again, and calculate the shrinkage size.

[0057] (4) Cohesion: The prepared LCP is double-sided bonded to copper foil. After bonding, the peel force is tested according to IPC TM650. At this time, the peel force is greater than 7N / CM, and the destructive interface is no longer the LCP layer delamination.

[0058] (5) Elongation: Take an A4-sized sample, make a jig with a size of 15mm×15mm using a template, cut 5 strips of TD / MD each with a knife, fix the sample in the tensile tester, set the preload / stress to 5N, set the preload / stress speed to 20mm / min, set the elongation rate in the test speed column to 100mm / min, wait for the instrument to stretch until the diaphragm breaks, and read the value.

[0059] Table 1: Test results of Examples 1-6 and Comparative Example 1

[0060]

[0061] From the above description, it can be seen that the embodiments of the present invention achieve the following technical effects: the tensile strength of the embodiments of the present invention is significantly higher than that of Comparative Example 1, the melting point is lower than that of Comparative Example 1, and the shrinkage rate is significantly lower than that of Comparative Example 1. Because the composite film described in this application undergoes multi-gradient heating and cooling treatment at 200℃-350℃, the molecular weight growth process can be controlled to stably improve the film strength. If the thickness of the carrier is less than 5μm, the lack of support will cause wrinkles during LCP peeling; if the thickness of the carrier is greater than 500μm, the carrier is too thick to be peeled and rolled up, and the cost is high.

[0062] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a liquid crystal polymer film, characterized in that: The preparation method includes at least the following heat treatment steps: S1: The liquid crystal polymer and the carrier are composited at a high temperature of 200~350℃ to obtain a composite film of liquid crystal polymer and carrier. S2: The composite membrane is subjected to multi-gradient heating and cooling treatment at 200~350℃; The multi-gradient heating and cooling process is as follows: the first stage heats up to 220℃ at a heating rate of 20℃ / min; the second stage heats up to 240℃ at a heating rate of 5℃ / min; the third stage heats up to 260℃ at a heating rate of 5℃ / min; the fourth stage heats up to 300℃ at a heating rate of 5℃ / min; the heating time for each stage is 0.5h~50h; and the fifth stage cools down to 25℃ at a cooling rate of 30℃ / min. S3: Peel off the carrier in the composite film to obtain the liquid crystal polymer film precursor, and perform heat treatment on the liquid crystal polymer film precursor at a temperature of 230°C for 3 minutes to obtain the finished liquid crystal polymer film; the shrinkage rate of the liquid crystal polymer film at 150°C for 30 minutes is less than 0.08% in the length and / or width directions.

2. The method for preparing a liquid crystal polymer film according to claim 1, characterized in that: The liquid crystal polymer in step S1 has a molecular weight of 20,000 to 500,000 and a coefficient of thermal expansion of -100 to -1 ppm; the thermal expansion coefficient of the carrier has a coefficient of thermal expansion of 12 to 16 ppm; and the absolute value of the difference between the coefficients of thermal expansion of the liquid crystal polymer and the carrier is 13 to 100 ppm.

3. The method for preparing a liquid crystal polymer film according to claim 1, characterized in that: The high-temperature composite process in step S1 uses a high-temperature roller press or a high-temperature pressing roller with a pressing temperature of 200~350℃.

4. The method for preparing the liquid crystal polymer film according to claim 3, characterized in that: The high-temperature roller press is selected from a five-axis high-temperature press or a three-axis high-temperature press; the temperature accuracy of the press rollers used is within ±5℃; the unit pressure of the high-temperature pressing is 1kN-15kN.

5. The method for preparing a liquid crystal polymer film according to claim 1, characterized in that: The carrier in step S1 is selected from aluminum foil, copper foil, steel strip, polytetrafluoroethylene, titanium, chromium steel or nickel.

6. The method for preparing a liquid crystal polymer film according to claim 1, characterized in that: The thickness of the carrier in step S1 is 5μm-500μm.

7. The method for preparing a liquid crystal polymer film according to claim 1, characterized in that: The composite film in step S2 has a cohesive strength greater than 7 N / cm, an elongation of 2-6%, and a melting point of 260-320℃.

8. A laminate comprising at least one liquid crystal polymer film prepared by the method of any one of claims 1 to 7.

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