High-modulus low-thermal-expansion LCP (Liquid Crystal Polymer) coating film-forming process

Abstract

The invention relates to the technical field of high polymer material processing, and discloses a high-modulus low-thermal-expansion LCP (Liquid Crystal Polymer) coating film-forming process which comprises the following steps: dissolving LCP resin in an organic solvent, and adding a thermally reversible cross-linking agent and a liquid crystal additive to prepare an LCP composite solution; an automatic spin coater is adopted, the clean base material is evenly coated with the LCP composite solution, and an LCP wet film with the uniform thickness is formed; applying an external physical field during formation of an LCP wet film to guide highly-oriented self-assembly of LCP molecules and liquid crystal auxiliaries; after external field treatment, an LCP film is formed through in-situ chemical crosslinking; and coating or dropwise adding an LCP composite solution containing fluorinated acrylate in a layered manner to obtain an LCP film in gradient distribution. An external physical field is applied in the liquid crystal polymer LCP wet film forming process, LCP molecules and liquid crystal auxiliaries are effectively guided to be subjected to height directional self-assembly in the specific direction, and a stable three-dimensional network structure is constructed in the LCP film.

Description

Technical Field

[0001] The present application relates to the technical field of polymer material processing, and specifically to a high modulus and low thermal expansion LCP coating film forming process. Background Art

[0002] With the continuous advancement of science and technology, the demand for high-performance materials across various industries has reached unprecedented heights. In particular, the fields of electronics, information technology, communications, and aerospace have placed ever-more stringent demands on the comprehensive performance of materials. Against this backdrop, liquid crystal polymers (LCPs), as high-performance specialty engineering plastics, have garnered widespread attention due to their unique molecular structure and excellent inherent properties. LCP materials not only possess exceptional heat resistance, dimensional stability, and excellent dielectric properties, but also demonstrate superior mechanical strength and chemical resistance, making them an ideal choice for meeting the demands of modern high-end applications.

[0003] Currently, LCP materials have been widely used in a number of key areas. For example, in the electronics industry, LCP is used to manufacture high-frequency connectors, flexible circuit board (FPC) substrates, and chip packaging materials to meet the challenges of high-frequency signal transmission, miniaturization, and high integration. In the automotive industry, LCP is used to manufacture sensors, electronic control unit (ECU) housings, and connectors to adapt to the high temperature and complex environment in the engine compartment. In addition, LCP also plays an irreplaceable role in medical devices, precision instruments, and aerospace components due to its lightweight, high strength, and environmental adaptability.

[0004] In the preparation of high-performance LCP films in the prior art, traditional LCP film preparation processes often find it difficult to effectively control the precise orientation and arrangement of LCP molecules during the film formation process. The mechanical properties of the prepared LCP films, such as tensile modulus, are often difficult to reach the theoretical maximum value, and their thermal expansion coefficient is also difficult to further reduce. The surface functions of most traditional LCP films are relatively simple, and when facing complex or corrosive environments, their surface properties such as weather resistance and chemical stability are often insufficient. Therefore, the present invention provides a high-modulus and low-thermal expansion LCP coating film-forming process to address the shortcomings of the prior art. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the purpose of this application is to provide a high modulus and low thermal expansion LCP coating film forming process, which solves the problems in the existing technology that LCP films have poor dimensional stability under extreme temperature changes and it is difficult to achieve both high modulus and low thermal expansion coefficient.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A high modulus and low thermal expansion LCP coating film forming process comprises the following steps: S1. Dissolving a liquid crystal polymer (LCP) resin in an organic solvent to prepare a liquid crystal polymer (LCP) solution. Adding a thermoreversible crosslinker and a liquid crystal additive to the solution yields a liquid crystal polymer (LCP) composite solution. To ensure high uniformity, the liquid crystal polymer (LCP) solution undergoes ultrasonic dispersion treatment at a frequency of 20 kHz to 40 kHz for 30 to 60 minutes. The LCP composite solution includes functional nanoparticles, such as silver nanoparticles, to impart specific functionalities to the film.

[0007] S2, using an automatic spin coater to evenly coat the obtained liquid crystal polymer LCP composite solution on a clean substrate to form a liquid crystal polymer LCP wet film with uniform thickness. The spin coating process includes dropping the LCP composite solution onto the center of the clean substrate, and the centrifugal force generated by the high-speed rotation of the automatic spin coater causes the LCP composite solution to be evenly spread around the surface of the clean substrate, and the automatic spin coater drives the clean substrate to rotate at a set spin coating speed of 1000rpm-3000rpm for a continuous spin coating time of 30 seconds-90 seconds. The clean substrate may include a silicon wafer, a glass sheet, or a polyimide film.

[0008] S3. During the formation of the liquid crystal polymer (LCP) wet film, applying an external physical field to the liquid crystal polymer (LCP) wet film to guide the liquid crystal polymer (LCP) molecules and the liquid crystal additive to highly directional self-assemble along a specific direction. Applying the external physical field includes placing the liquid crystal polymer (LCP) wet film in an area of ​​action of the external physical field and applying the external physical field. The external physical field is applied for a duration of 1 minute to 10 minutes. The external physical field may be a shear field, an electric field, or a magnetic field.

[0009] When the external physical field is a shear field, a controllable shear force is applied by placing the LCP wet film in a specific shear mold, and the maintenance time is 1 minute to 5 minutes. When the external physical field is an electric field, a DC or AC electric field is applied by placing parallel electrodes above and below the LCP wet film, and the electric field strength is 100V / cm-1000V / cm. When the external physical field is a magnetic field, a magnetic field is applied around the LCP wet film, and the magnetic field strength is 0.1 Tesla to 1 Tesla. Through the interaction of the external physical field with the LCP molecules and the liquid crystal additive, the LCP molecules and the liquid crystal additive are highly ordered along a specific direction, completing the directed self-assembly.

[0010] S4. Heat-curing the coated substrate after external field treatment to form a liquid crystal polymer LCP film, wherein the heat curing comprises placing the coated substrate treated by the external field and having the liquid crystal polymer LCP molecules and the liquid crystal additive highly self-assembled in a specific direction in an oven or a heating platform. The temperature of the oven or the heating platform is set in the range of 180°C-220°C, and the curing time is maintained at 30 minutes-60 minutes. Through the heating process with set temperature and time, on the basis of the highly self-assembly of the liquid crystal polymer LCP molecules and the liquid crystal additive in a specific direction, in-situ chemical cross-linking occurs between the thermoreversible cross-linking agent and the liquid crystal polymer LCP molecular chain and the specific functional groups of the liquid crystal additive to construct a stable three-dimensional network structure, thereby forming a liquid crystal polymer LCP film with high modulus and low thermal expansion.

[0011] S5. Based on the formed liquid crystal polymer (LCP) film, a surface modification treatment is performed by introducing fluorine-containing functional groups to obtain a liquid crystal polymer (LCP) film with a gradient distribution. The method of obtaining the liquid crystal polymer (LCP) film with a gradient distribution includes using a multilayer co-coating technique or a method of dynamically controlling the components of a coating solution. During the formation of the liquid crystal polymer (LCP) wet film, liquid crystal polymer (LCP) composite solutions of different components are added to different thickness positions of the liquid crystal polymer (LCP) wet film. Through the multilayer coating or dynamic control process, a gradient distribution of fluorine-containing functional groups along the thickness direction of the liquid crystal polymer (LCP) film is achieved during the formation of the liquid crystal polymer (LCP) film.

[0012] In summary, this application includes at least one of the following beneficial technical effects: 1. By applying an external physical field during the formation of a liquid crystal polymer (LCP) wet film, the present invention effectively guides the highly directional self-assembly of LCP molecules and liquid crystal additives along a specific direction. This ordered molecular arrangement, combined with subsequent in-situ chemical crosslinking with a thermoreversible crosslinker, creates a stable three-dimensional network structure within the LCP film. This structure significantly limits the film's anisotropic expansion during temperature fluctuations, thereby improving the LCP film's dimensional stability under extremely short temperature changes. This achieves both a high modulus and a low thermal expansion coefficient, resolving the issue of existing LCP films being susceptible to temperature-dependent dimensional changes.

[0013] 2. The present invention performs ultrasonic dispersion treatment on the LCP solution to ensure the high uniformity of the solution, and uses an automatic spin coater to precisely control the spin coating speed and duration, thereby obtaining an LCP wet film with uniform thickness and few defects. This ensures the structural and performance consistency of each region of the film during the preparation process, effectively improving the dimensional accuracy and reliability of the LCP film, and by controlling the heating and curing temperature and time, promoting sufficient cross-linking between molecular chains, ensuring the performance of the film under extreme conditions.

[0014] 3. The present invention introduces fluorine-containing functional groups for surface modification and makes it present a gradient distribution in the thickness direction of the LCP film, thereby effectively enhancing the weather resistance and chemical stability of the film. By introducing functional nanoparticles into the LCP composite solution, the LCP film is endowed with electrical conductivity and provides good antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the process flow chart of this application. DETAILED DESCRIPTION

[0016] The following is combined with Figure 1 , further details of this application are given.

[0017] Please see the attached Figure 1 : LCP resin optional SIVERAS TM LCP resin, manufactured by Toray Industries, Ltd.

[0018] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0019] Example 1: Raw material components (by mass fraction): LCP resin (SIVERAS TM LCP resin): 10 parts by mass; Organic solvent (N-methylpyrrolidone): 90 parts by mass; Thermally reversible crosslinker (bismaleimide crosslinker): 0.2 parts by mass; Liquid crystal additive (4-cyano-4 ’ -pentylbiphenyl): 0.5 parts by mass; Fluorine-containing acrylate (trifluoroethyl methacrylate): 3 parts by mass.

[0020] Process steps: S1. Prepare a high-modulus, low-thermal-expansion LCP composite solution: Dissolve LCP resin in an organic solvent to prepare an LCP solution. Then, add a thermoreversible crosslinker and a liquid crystal additive to obtain an LCP composite solution. Ultrasonic dispersion of the LCP solution is performed at a frequency of 30 kHz for 45 minutes to ensure uniform dispersion.

[0021] S2. Coating a wet film and applying an external physical field for orientation: Using an automatic spin coater, evenly drip the obtained LCP composite solution onto a clean silicon wafer substrate. The automatic spin coater is driven to spin at a high speed of 2000 rpm for 60 seconds to form an LCP wet film of uniform thickness. During the formation of the LCP wet film, the wet film is placed in the area of ​​action of an external physical field. An electric field is applied as the external physical field with an electric field strength of 550 V / cm for 5 minutes to guide the LCP molecules and liquid crystal additives to highly oriented self-assembly along a specific direction.

[0022] S3. Heat-curing to form a thin film: The coated silicon wafer substrate, after external field treatment, is placed in an oven for heat curing. The oven temperature is set at 200°C and the curing time is maintained for 45 minutes. During this process, the thermoreversible crosslinker undergoes in-situ chemical crosslinking with the highly oriented LCP molecular chains and liquid crystal additives, forming a stable LCP film.

[0023] S4. Surface modification: Based on the formed LCP film, LCP composite solutions containing fluorinated acrylate (trifluoroethyl methacrylate) at different concentrations are prepared. Using multi-layer co-coating technology, during the wet film formation process, an LCP composite solution without fluorinated components is first applied to form a base layer by multi-layer coating or layer-by-layer addition. At different time points or at specific thickness locations, an LCP composite solution containing a higher concentration of fluorinated acrylate is layered or added dropwise. By controlling the coating thickness of each layer and the concentration of the fluorine-containing component, the gradient distribution of the fluorine-containing acrylate (trifluoroethyl methacrylate) along the thickness direction of the film is achieved, and an LCP film with a gradient distribution is obtained.

[0024] Example 2: Raw material components (by mass fraction): LCP resin (SIVERAS TM LCP resin): 15 parts by mass; Organic solvent (N-methylpyrrolidone): 85 parts by mass; Thermally reversible crosslinker (bismaleimide crosslinker): 0.4 parts by mass; Liquid crystal additive (4-cyano-4 ’ -pentylbiphenyl): 1.0 parts by mass; Fluorine-containing acrylate (trifluoroethyl methacrylate): 5 parts by mass.

[0025] Process steps: S1. Prepare an LCP composite solution: Dissolve an LCP resin in an organic solvent to prepare an LCP solution. Add a thermoreversible crosslinker and a liquid crystal additive to obtain an LCP composite solution. Ultrasonic dispersion of the LCP solution is performed at a frequency of 20 kHz for 30 minutes to ensure uniform dispersion.

[0026] S2. Coating a wet film and applying an external physical field for orientation: Use an automatic spin coater to evenly drip the obtained LCP composite solution onto a clean glass substrate, drive the automatic spin coater, and spin at a high speed of 1000 rpm for 30 seconds to form an LCP wet film with uniform thickness. During the formation of the LCP wet film, the wet film is placed in the action area of ​​an external physical field. A shear field is applied as an external physical field. By placing the LCP wet film in a specific shear mold, a controllable shear force is applied for 1 minute to guide the LCP molecules and liquid crystal additives to highly oriented self-assembly along a specific direction.

[0027] S3. Heat-curing to form a thin film: Place the coated glass substrate, after external field treatment, on a heating platform for heat curing. Set the heating platform temperature to 180°C and maintain the curing time for 30 minutes. During this process, the thermoreversible crosslinker undergoes in-situ chemical crosslinking with the highly oriented LCP molecular chains and liquid crystal additives, forming a stable LCP film.

[0028] S4. Surface modification: Based on the formed LCP film, LCP composite solutions containing different concentrations of fluorinated acrylate (trifluoroethyl methacrylate) are prepared. A multi-layer co-coating technique is used. During the wet film formation process, an LCP composite solution without fluorinated components is first coated to form a bottom layer by multi-layer coating or layer-by-layer addition. At different time points or at specific thickness positions, an LCP composite solution containing a higher concentration of fluorinated acrylate is layered or added dropwise. By controlling the coating thickness of each layer and the concentration of the fluorine-containing component, the gradient distribution of the fluorine-containing acrylate (trifluoroethyl methacrylate) along the thickness direction of the film is achieved, and an LCP film with a gradient distribution is obtained.

[0029] Example 3: Raw material components (by mass fraction): LCP resin (SIVERAS TM LCP resin): 5 parts by mass; Organic solvent (N-methylpyrrolidone): 95 parts by mass; Thermally reversible crosslinker (bismaleimide crosslinker): 0.1 parts by mass; Liquid crystal additive (4-cyano-4 ’ -pentylbiphenyl): 0.2 parts by mass; Fluorine-containing acrylate (trifluoroethyl methacrylate): 1 part by mass.

[0030] Process steps: S1. Preparing an LCP composite solution: Dissolve LCP resin in an organic solvent to prepare an LCP solution. Add a thermoreversible crosslinker and a liquid crystal additive to obtain an LCP composite solution. Ultrasonic dispersion of the LCP solution is performed at a frequency of 40 kHz for 60 minutes to ensure uniform dispersion.

[0031] S2. Coating a wet film and applying an external physical field for orientation: Using an automatic spin coater, evenly drip the obtained LCP composite solution onto a clean polyimide film substrate. Drive the automatic spin coater to spin at a high speed of 3000 rpm for 90 seconds to form an LCP wet film of uniform thickness. During the formation of the LCP wet film, the wet film is placed in the area of ​​action of an external physical field. A magnetic field is applied as the external physical field with a magnetic field intensity set to 1 Tesla for 10 minutes to guide the LCP molecules and liquid crystal additives to highly oriented self-assembly along a specific direction.

[0032] S3. Heat-curing to form a thin film: The coated polyimide film substrate, after external field treatment, is placed in an oven for heat curing. The oven temperature is set at 220°C and the curing time is maintained for 60 minutes. During this process, the thermoreversible crosslinker undergoes in-situ chemical crosslinking with the highly oriented LCP molecular chains and liquid crystal additives, forming a stable LCP film.

[0033] S4. Surface modification: preparing LCP composite solutions containing different concentrations of fluorinated acrylate (trifluoroethyl methacrylate), and using multi-layer co-coating technology. During the wet film formation process, first apply the LCP composite solution without fluorinated components to form a bottom layer by multi-layer coating or layer-by-layer addition. At different time points or at specific thickness positions, layer-by-layer coating or drop-addition of the LCP composite solution containing a higher concentration of fluorinated acrylate is performed; By controlling the coating thickness of each layer and the concentration of the fluorine-containing component, the gradient distribution of the fluorine-containing acrylate (trifluoroethyl methacrylate) along the thickness direction of the film is achieved, and an LCP film with a gradient distribution is obtained.

[0034] Comparative Example 1: Compared with Example 1, the difference is that the step of applying an external physical field to the liquid crystal polymer LCP wet film is omitted, and the remaining steps are the same.

[0035] Comparative Example 2: Compared with Example 1, the difference is that no thermally reversible crosslinking agent is added when preparing the LCP composite solution, and the other steps are the same.

[0036] Comparative Example 3: Compared with Example 1, the difference is that the liquid crystal polymer LCP solution is not subjected to ultrasonic dispersion treatment, and the other steps are the same.

[0037] Comparative Example 4: Compared with Example 1, the difference is that the surface modification treatment of introducing fluorine-containing functional groups into the formed liquid crystal polymer LCP film is omitted, and the remaining steps are the same.

[0038] Experiment 1: Experimental purpose: To evaluate the effect of applying an external physical field on the modulus and thermal expansion coefficient of liquid crystal polymer (LCP) films during the LCP wet film formation process.

[0039] Experimental steps: Sample preparation: When preparing the samples of Example 1 (including the control groups: Example 2 and Example 3), ensure that an electric field is applied to the LCP wet film, the electric field strength is set to 550 V / cm, and the action time is 5 minutes; When preparing the sample of Comparative Example 1, ensure that the step of applying an external physical field to the LCP wet film is skipped; All samples should be prepared under the same environmental conditions to minimize the influence of other variables.

[0040] Modulus test: The prepared Example 1 (including the control groups: Example 2 and Example 3) and Comparative Example 1 were cut into test strips of standard size; Perform tensile modulus testing on each test bar using a dynamic mechanical analyzer (DMA) or a tensile testing machine; At the set temperature and strain rate, the stress-strain curve of the sample is recorded and its Young's modulus is calculated. Multiple groups of parallel tests are performed on each sample type to ensure the reliability and statistical significance of the data.

[0041] Thermal expansion coefficient test: The prepared Example 1 (including the control group: Example 2 and Example 3) and Comparative Example 1 were cut into samples of sizes that met the requirements of a thermomechanical analyzer (TMA), and a thermal expansion test was performed on each sample using a thermomechanical analyzer (TMA); The sample is placed in a TMA instrument and heated at a preset heating rate. The dimensional change of the sample at different temperatures is recorded. The coefficient of thermal expansion (CTE) of the sample is calculated based on the dimensional change and temperature range. Multiple groups of parallel tests are performed on each sample type to obtain representative data.

[0042] The experimental results are shown in Table 1.

[0043] Table 1: LCP film modulus and thermal expansion coefficient test data Sample type Young's modulus (GPa) Thermal expansion coefficient (ppm / ℃) Example 1 12.7 5.8 Example 1 12.1 6.1 Example 2 13.8 4.9 Example 2 14.2 4.7 Example 3 10.8 8.2 Example 3 11.1 7.9 Comparative Example 1 8.9 25.3 Comparative Example 1 9.4 28.1 As can be seen from Table 1, Example 1 (including the control group: Example 2 and Example 3) treated with an external physical field shows an improvement in modulus, while Example 2 and Example 3, as the upper and lower limits of Example 1, show a significant decrease in thermal expansion coefficient. Applying an external physical field, such as an electric field, before the LCP wet film solidifies can provide an additional driving force for the liquid crystal polymer LCP molecules and liquid crystal additives, guiding them to overcome their tendency to random orientation and self-assemble in a highly oriented manner along a specific direction. This ordered arrangement at the molecular level provides an ideal structural foundation for the subsequent in-situ chemical crosslinking of the thermoreversible crosslinker, allowing the crosslinking reaction to proceed between highly oriented molecular chains, thereby constructing a more regular, dense, and stable three-dimensional network structure.

[0044] This highly oriented and chemically cross-linked microstructure is the key to achieving high modulus and low thermal expansion coefficient. Orderly arranged LCP molecular chains can transfer stress more effectively when subjected to force, thereby improving the overall stiffness and Young's modulus of the material. At the same time, because the molecular chains are tightly stacked along a specific direction and fixed by chemical bonds, the molecular spacing and segment movement of the film are more strongly restricted when the temperature changes, thereby significantly suppressing the volume expansion of the material, ultimately manifesting as an extremely low thermal expansion coefficient. Therefore, this experiment fully proves that introducing an external physical field to guide the directional self-assembly of molecules during the LCP coating and film formation process is the best way to prepare high-performance LCP films and solve their dimensional stability problems at extreme temperatures.

[0045] Experiment 2: Experimental purpose: To evaluate the effects of the introduction of a thermoreversible crosslinker and the homogeneity of the LCP solution on the structural stability of the final LCP film.

[0046] Experimental steps: Sample preparation: Prepare the samples of Example 1 (including control groups: Example 2 and Example 3), ensure that the LCP composite solution contains a thermoreversible crosslinker, and is ultrasonically dispersed; The sample of Comparative Example 2 was prepared without adding a thermoreversible crosslinking agent during the preparation of the LCP composite solution; The sample of Comparative Example 3 was prepared by skipping the ultrasonic dispersion step during the LCP solution pretreatment; All samples should be prepared under the same environmental conditions to minimize the influence of other variables.

[0047] Stress relaxation test: The prepared Example 1 (including the control groups: Example 2 and Example 3), Comparative Example 2, and Comparative Example 3 were cut into strip samples of standard test size, and a stress relaxation test was performed on each test strip using a dynamic mechanical analyzer (DMA); Clamp the sample onto a DMA instrument and quickly apply a constant initial strain. This strain is then maintained constant, and the stress changes over time at a set temperature (25°C or higher) are recorded. The stress decay curve over time is observed and recorded. Slower stress decay indicates a more stable material structure and a lower creep tendency. Multiple parallel tests are performed on each sample type to ensure data reliability.

[0048] Creep test: The prepared Example 1 (including the control group: Example 2 and Example 3), Comparative Example 2 and Comparative Example 3 were cut into strip samples of standard test size, and a creep test was performed on each test strip using a dynamic mechanical analyzer (DMA) or a creep tester; Clamp the sample on the test equipment, apply a constant load (constant stress), and record the change in sample length (strain) over time. Observe and record the strain growth curve over time. Slower strain growth indicates greater creep resistance and structural stability. Perform multiple parallel tests on each sample type to obtain representative data.

[0049] The experimental results are shown in Table 2.

[0050] Table 2: LCP film stress relaxation and creep test data As can be seen from Table 2, Example 1 (including the control group: Example 2 and Example 3) Example 2 and Example 3 are used as the upper and lower limits of Example 1. Compared with Comparative Example 2 without adding a thermoreversible crosslinker and Comparative Example 3 without ultrasonic dispersion treatment, the sample of Example 1 showed better structural stability in both stress relaxation and creep tests. This directly verifies the core role of the thermoreversible crosslinker in the formation process of the LCP film: it can undergo in-situ chemical crosslinking with the LCP molecular chains and liquid crystal additives that have been highly oriented by an external physical field. This chemical crosslinking reaction solidifies the molecular chains that may have been only physically entangled into a stable three-dimensional network structure at the molecular level, greatly enhancing the film's ability to resist external stress deformation, reducing the material's creep tendency and delaying stress relaxation, thereby giving the film excellent long-term structural stability.

[0051] In addition, this experiment also highlights the importance of uniformity of LCP composite solution. In Comparative Example 3, which has not been subjected to ultrasonic dispersion treatment, the LCP molecules and additives may be agglomerated or unevenly distributed in the solution. Even if an external physical field is subsequently applied, this initial unevenness will affect the efficiency of molecular orientation and the degree of perfection of the final cross-linked network. In Example 1, which has been subjected to ultrasonic dispersion treatment, the LCP molecules and additives in the solution can be highly evenly dispersed, providing an ideal homogeneous basis for subsequent external physical field-induced orientation and in-situ chemical cross-linking, ensuring the consistency of the internal structure of the final film and excellent overall structural stability.

[0052] Experiment 3: Experimental purpose: To evaluate the effect of key process parameters such as spin coating speed and curing temperature outside the set range on the macroscopic properties of LCP films.

[0053] Experimental steps: Sample preparation: Prepare samples of Example 1 (including control groups: Example 2 and Example 3), ensuring that the spin coating speed, curing temperature and surface modification treatment all meet the intermediate parameters; The sample of Comparative Example 4 was prepared by omitting the surface modification treatment of the fluorine-containing functional group; All samples should be prepared under the same environmental conditions to minimize the influence of other variables.

[0054] Water contact angle test: The prepared Example 1 (including the control group: Example 2 and Example 3) and Comparative Example 4 (with and without surface modification) were placed on a clean test bench respectively, and a drop of a standard volume of deionized water was dropped on the sample surface using a contact angle meter.

[0055] The contact angle between a water droplet and the sample surface is calculated. A larger contact angle indicates a more hydrophobic surface, which is generally associated with better weather resistance and certain chemical stability. Multiple measurements are performed for each sample type and the average is calculated.

[0056] Chemical corrosion resistance test: The prepared samples of Example 1 (including controls: Example 2 and Example 3) and Comparative Example 4 were immersed in a specific corrosive solution (e.g., a dilute acid, a dilute base, or an organic solvent) for a fixed immersion time and temperature. After immersion, the samples were removed, rinsed with deionized water, and dried.

[0057] Visually observe whether there is obvious damage on the surface of the sample (such as discoloration, swelling, cracks, etc.), and perform the tensile strength test again to evaluate its performance retention rate. Perform multiple groups of parallel tests for each sample type.

[0058] The experimental results are shown in Table 3.

[0059] Table 3: Test data of tensile strength, water contact angle and chemical corrosion resistance of LCP films As can be seen from Table 3, Example 1 is the best embodiment of the intermediate parameters, and its various performance indicators are excellent. Example 2 represents the upper limit of the performance of the LCP film under specific parameter conditions, showing higher tensile strength, elongation at break, water contact angle and chemical corrosion resistance. Example 3 represents the lower limit of the performance of the LCP film under relatively mild parameter conditions. Compared with Example 4, which has not undergone surface modification, Example 1 modified with a gradient distribution of fluorine-containing functional groups shows significant advantages in water contact angle and chemical corrosion resistance. This is attributed to the fact that in the present invention, a gradient distribution of fluorine-containing functional groups along the thickness direction of the film is achieved through multi-layer co-coating technology or dynamic regulation of the coating liquid components. This unique surface structure gives the LCP film excellent hydrophobicity, thereby improving its weather resistance. At the same time, the introduction of fluorine-containing functional groups also significantly enhances the film's ability to resist erosion by specific chemical media.

[0060] The examples of this specific embodiment are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.

Claims

1. A high modulus and low thermal expansion LCP coating film forming process, characterized in that: The following steps are involved: S1, dissolving a liquid crystal polymer (LCP) resin in an organic solvent to prepare a liquid crystal polymer (LCP) solution, and adding a thermoreversible crosslinking agent and a liquid crystal auxiliary agent to obtain a liquid crystal polymer (LCP) composite solution; S2. Using an automatic spin coater, the obtained liquid crystal polymer (LCP) composite solution is evenly coated on a clean substrate to form a liquid crystal polymer (LCP) wet film with uniform thickness; S3, during the formation of the liquid crystal polymer (LCP) wet film, applying an external physical field to the liquid crystal polymer (LCP) wet film to guide the liquid crystal polymer (LCP) molecules and the liquid crystal additive to highly directional self-assemble along a specific direction; S4, heating and curing the coated substrate after the external field treatment, and forming a liquid crystal polymer (LCP) film by in-situ chemical crosslinking between the liquid crystal polymer (LCP) molecular chains and the specific functional groups of the liquid crystal additive via a thermoreversible crosslinking agent based on the highly directional self-assembly of the liquid crystal polymer (LCP) molecules and the liquid crystal additive along a specific direction; S5. Based on the formed liquid crystal polymer LCP film, prepare an LCP composite solution containing fluorinated acrylate at different concentrations, and layer-coat or drop-add the fluorinated acrylate LCP composite solution to obtain a liquid crystal polymer LCP film with a gradient distribution.

2. A high modulus, low thermal expansion LCP coating film forming process according to claim 1, characterized in that: In step S1, the liquid crystal polymer LCP solution is subjected to ultrasonic dispersion treatment, the ultrasonic frequency is 20 kHz to 40 kHz, and the treatment time is 30 minutes to 60 minutes.

3. A high modulus, low thermal expansion LCP coating film forming process according to claim 1, characterized in that: The LCP composite solution includes functional nanoparticles, and the functional nanoparticles are nanosilver particles.

4. A high modulus, low thermal expansion LCP coating film forming process according to claim 1, characterized in that: In step S2, the process of uniformly coating the obtained liquid crystal polymer (LCP) composite solution on a clean substrate using an automatic spin coater comprises the following steps: The obtained liquid crystal polymer LCP composite solution is dropped onto the center position of the clean substrate; The liquid crystal polymer LCP composite solution is evenly spread around the surface of the clean substrate by the centrifugal force generated by the high-speed rotation of the automatic spin coater, thereby forming the liquid crystal polymer LCP wet film with uniform thickness.

5. A high modulus, low thermal expansion LCP coating film forming process according to claim 4, characterized in that: The automatic spin coater drives the cleaning substrate to rotate at a set spin coating speed of 1000 rpm-3000 rpm, and the continuous spin coating time is 30 seconds-90 seconds. The cleaning substrate includes a silicon wafer, a glass sheet or a polyimide film.

6. A high modulus low thermal expansion LCP coating film forming process according to claim 1, characterized in that: In step S3, applying an external physical field to the liquid crystal polymer LCP wet film comprises the following steps: During the preparation of the formed liquid crystal polymer LCP wet film, the liquid crystal polymer LCP wet film is placed in an action area of ​​an external physical field; An external physical field is applied, and the action time of the external physical field is 1 minute to 10 minutes. Through the interaction between the external physical field and the liquid crystal polymer LCP molecules and the liquid crystal additive, the liquid crystal polymer LCP molecules and the liquid crystal additive are guided to be highly ordered along a specific direction, thereby completing the directional self-assembly.

7. A high modulus, low thermal expansion LCP coating film forming process according to claim 6, characterized in that: The external physical field is a shear field, an electric field or a magnetic field, specifically: When the external physical field is a shear field, a controllable shear force is applied by placing the liquid crystal polymer LCP wet film in a specific shear mold, and the maintenance time is 1 minute to 5 minutes; When the external physical field is an electric field, a DC or AC electric field is applied by placing parallel electrodes above and below the liquid crystal polymer LCP wet film, and the electric field strength is 100 V / cm-1000 V / cm; When the external physical field is a magnetic field, a magnetic field is applied around the liquid crystal polymer LCP wet film, and the intensity of the magnetic field is 0.1 Tesla-1 Tesla.

8. A high modulus, low thermal expansion LCP coating film forming process according to claim 1, characterized in that: In step S4, the step of heating and curing the coated substrate after the external field treatment comprises the following steps: Placing the coated substrate treated by an external field and having the liquid crystal polymer LCP molecules and the liquid crystal additive highly self-assembled in a specific direction in an oven or a heating platform; Set the temperature of the oven or heating platform to 180-220°C and maintain the curing time to 30-60 minutes; Through a heating process with set temperature and time, an in-situ chemical cross-linking reaction occurs between the thermoreversible cross-linking agent and the highly oriented liquid crystal polymer LCP molecular chains and the specific functional groups of the liquid crystal additive, thereby constructing a stable three-dimensional network structure based on molecular orientation to form a liquid crystal polymer LCP film.

9. A high modulus, low thermal expansion LCP coating film forming process according to claim 1, characterized in that: In step S5, the step of obtaining a liquid crystal polymer (LCP) film having a gradient distribution comprises the following steps: Using a multi-layer co-coating technology or a method of dynamically controlling the components of the coating liquid, during the formation of the liquid crystal polymer (LCP) wet film, liquid crystal polymer (LCP) composite solutions of different components are added to different thickness positions of the liquid crystal polymer (LCP) wet film; Through multi-layer coating or dynamic regulation process, when forming liquid crystal polymer LCP film, LCP composite solution containing higher concentration of fluorinated acrylate is layered coated or added dropwise to obtain liquid crystal polymer LCP film with gradient distribution.

Images