A temperature control strong attachment water line for car film production and a composite process thereof

Abstract

The present application relates to the technical field of film processing, and particularly relates to a temperature control strong attachment flow line for car film production and a composite process thereof. The present application aims to provide a temperature control strong attachment flow line for car film production and a composite process thereof, which integrates electrostatic auxiliary lamination, gradient heat pressing and gradient cooling, effectively eliminates bubbles, reduces internal stress, and realizes high-quality composite between film layers. The temperature control strong attachment flow line for car film production comprises a feeding device for synchronously releasing at least two film substrates to be laminated; a pre-lamination device arranged downstream of the feeding device and used for preliminarily laminating the at least two film substrates; and the pre-lamination device comprises an electrostatic auxiliary lamination unit and a mechanical extrusion lamination unit. The present application achieves the effect of integrating electrostatic auxiliary lamination, gradient heat pressing and gradient cooling, effectively eliminating bubbles, reducing internal stress, and realizing high-quality composite between film layers.

Description

Technical Field

[0001] This invention relates to the field of membrane processing technology, and in particular to a temperature-controlled strong adhesion production line for automotive coating film production and its composite process. Background Technology

[0002] With the rapid development of the automotive window film industry, the demand for high-performance multilayer composite films is increasing. These films are typically made from multiple substrates with different functions through a hot-pressing composite process, requiring high light transmittance, low haze, excellent adhesion, good flatness, and long-term stability. In traditional film composite processes, direct hot pressing or adhesive bonding is usually used, but many technical challenges remain in actual production: First, air is easily trapped between layers in the initial bonding stage, forming bubbles or poor bonding, leading to optical defects and reduced adhesion. Second, improper temperature and pressure control during hot pressing can easily cause film deformation, shrinkage, or internal stress, affecting the dimensional stability and appearance flatness of the product. Third, uneven or excessively rapid cooling during the cooling stage can lead to stress concentration inside the film, causing wrinkles, warping, or even delamination, especially in wide-width, high-speed continuous production processes.

[0003] While existing technologies employ single-stage or multi-stage hot pressing and cooling devices, the coordination between different process stages is often insufficient, resulting in unsatisfactory pre-lamination effects. The hot pressing and cooling processes are also simplistic, making it difficult to simultaneously ensure interface fusion quality and stress control in efficient continuous production. This is especially true for products like automotive films, which have extremely high requirements for optical performance and appearance. Traditional processes struggle to achieve high-quality lamination with no bubbles, no wrinkles, and low stress under high-speed production. Therefore, there is an urgent need to develop a fully automated automotive film laminator and its hot pressing lamination process that integrates electrostatic assisted lamination, gradient hot pressing, and gradient cooling to effectively eliminate bubbles, reduce internal stress, and achieve high-quality interlayer lamination of the film. Summary of the Invention

[0004] In order to overcome the shortcomings of traditional processes that make it difficult to achieve high-quality lamination with no bubbles, no wrinkles, and low stress under high-speed production, the present invention aims to provide a temperature-controlled strong adhesion production line and its lamination process for automotive film production that integrates electrostatic assisted bonding, gradient hot pressing, and gradient cooling to effectively eliminate bubbles, reduce internal stress, and achieve high-quality interlayer lamination of film.

[0005] This invention is achieved through the following specific technical means:

[0006] A temperature-controlled adhesion production line for producing car wrap film, comprising, in sequence along the material conveying direction:

[0007] A feeding device is used to simultaneously release at least two layers of film substrate to be laminated;

[0008] A pre-lamination device, located downstream of the feeding device, is used to perform preliminary lamination of at least two layers of film substrates. The pre-lamination device includes: an electrostatic assisted lamination unit, used to apply a controllable electrostatic field to the at least two layers of film substrates, causing their surfaces to carry mutually attractive electrostatic charges; and a mechanical extrusion lamination unit, located downstream of the electrostatic assisted lamination unit, used to mechanically extrude the electrostatically charged film substrates, expel interlayer air, and achieve preliminary lamination. After processing by this unit, the layers of film substrates attract each other through the electrostatic attraction generated by the electrostatic charges on their surfaces, preventing delamination after lamination.

[0009] A multi-stage gradient hot-pressing laminating device is located downstream of the pre-lamination device and is used to heat and pressurize the pre-laminated and adsorbed film to complete the interface fusion. The multi-stage gradient hot-pressing laminating device includes at least two sets of hot-pressing rollers arranged in series along the conveying direction. The temperature and / or pressure of each set of hot-pressing rollers are independently controllable and arranged in a gradient.

[0010] A multi-stage gradient cooling and shaping device is located downstream of the multi-stage gradient hot-pressing laminating device and is used to cool and shape the film after hot-pressing lamination. The multi-stage gradient cooling and shaping device includes at least two independently temperature-controlled cooling rollers arranged in series along the conveying direction, and the surface temperature of each cooling roller is set in a gradient. The multi-stage gradient cooling and shaping device also includes a negative pressure adsorption unit, which is located on the film inlet side of at least one of the cooling rollers and is used to generate local negative pressure to make the film adhere tightly to the surface of the cooling roller.

[0011] A winding device, located downstream of the multi-stage gradient cooling and shaping device, is used to wind up the laminated film product.

[0012] Furthermore, the electrostatic-assisted bonding unit includes an electrostatic generator and an electrode assembly connected to the high-voltage electrostatic generator. The electrode assembly is disposed on both sides or one side of the film transport path and is used to apply charges of different polarities to different layers of film substrates.

[0013] Furthermore, the mechanical extrusion bonding unit includes a fixed extrusion roller and a floating extrusion roller that cooperates with the fixed extrusion roller. Both the fixed extrusion roller and the floating extrusion roller are arc-shaped rollers with a central protrusion facing the side where the film is input. The cooperation of the two extrusion rollers forms an arc-shaped pressing line. This pressing line starts from the highest point in the middle of the film width direction and extends symmetrically to both sides as the film advances until it covers the entire width of the film.

[0014] Furthermore, the multi-stage gradient hot pressing composite device includes a first hot pressing roller group, a second hot pressing roller group, and a third hot pressing roller group arranged in series along the conveying direction; the first hot pressing roller group has a first operating temperature T1 and is configured to apply a first pressure P1 to the film; the second hot pressing roller group has a second operating temperature T2 and is configured to apply a second pressure P2 to the film, and T2 > T1, P2 > P1; the third hot pressing roller group has a third operating temperature T3 and is configured to apply a third pressure P3 to the film, and T3 ≤ T2, P3 ≤ P2.

[0015] Furthermore, the multi-stage gradient cooling and shaping device includes a first cooling roller, a second cooling roller, and a third cooling roller arranged in series along the conveying direction; the surface temperature of the first cooling roller is a first cooling temperature C1; the surface temperature of the second cooling roller is a second cooling temperature C2, and C2 > C1; the surface temperature of the third cooling roller is a third cooling temperature C3, and C3 is higher than C2 and close to the ambient temperature; wherein, the temperature gradient from C1 to C2 is less than the temperature gradient from the film temperature output by the multi-stage gradient hot pressing composite device to C1.

[0016] Furthermore, the negative pressure adsorption unit includes a suction hood disposed on one side of the cooling roller and a negative pressure generator connected to the suction hood.

[0017] A car wrap film lamination process includes the following steps:

[0018] S1: At least two layers of film substrate are simultaneously unwound by the unwinding device;

[0019] S2: The thin film substrate is passed through the electrostatic assisted bonding unit in the pre-lamination device, and a controllable electrostatic field is applied to make the surface of each layer of thin film substrate carry mutually attractive electrostatic charges.

[0020] S3: The electrostatically charged thin film substrate is introduced into the mechanical extrusion bonding unit in the pre-lamination device, where mechanical extrusion is performed to expel interlayer air and complete the initial bonding; in this step and thereafter, the thin films are attracted to each other by the electrostatic attraction generated by the electrostatic charge to prevent delamination.

[0021] S4: The pre-bonded film adsorbed by electrostatics enters the multi-level gradient hot-pressing composite device and passes through the hot-pressing roller group with temperature and pressure gradients in sequence to complete the interface molecule activation, diffusion fusion and stress pre-release.

[0022] S5: The hot-pressed composite film is fed into the multi-stage gradient cooling and shaping device. With the assistance of the negative pressure adsorption unit, the film is tightly bonded to the surface of multiple cooling rollers with temperature gradients, and is subjected to rapid cooling and shaping, slow cooling and stress relief, and room temperature stabilization in sequence.

[0023] S6: The cooled and shaped composite film product is wound up using the winding device.

[0024] Furthermore, in step S3, the alignment pre-bonding device first pre-presses the middle of the film, and then performs gradient expansion pressing towards the two edges of the film, so that air is discharged from the middle to both sides.

[0025] Furthermore, in step S2, the intensity of the electrostatic field is 10~80kV, and the polarity of the electrostatic charge carried by the two adjacent thin film substrates is opposite.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention achieves the effect of integrating electrostatic assisted bonding, gradient hot pressing and gradient cooling, effectively eliminating bubbles, reducing internal stress and realizing high-quality interlayer composite of thin films.

[0028] By using a pre-bonding method of "electrostatic adsorption pilot + arc-shaped extrusion venting", electrostatic attraction makes the film flat and close together and prevents delamination after bonding, while the unique arc-shaped pressing line enables air to be smoothly discharged from the center to both sides, eliminating the generation of air bubbles from the source.

[0029] The multi-level gradient hot pressing process, through the scientific path of "low-temperature activation - high-temperature main composite - cooling and shaping pressure release", not only ensures the full fusion of polymer interfaces to achieve high composite strength, but also effectively controls the generation of thermal history and internal stress, resulting in more stable product performance.

[0030] By combining a multi-stage gradient cooling process with negative pressure adsorption, the forced film bonding cooling roller ensures uniform and efficient heat exchange; rapid cooling quickly shapes and locks in the form, while slow cooling promotes stress relaxation, ultimately giving the finished film excellent optical flatness, low shrinkage, and long-term dimensional stability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the temperature-controlled strong adhesion production line for producing car wrap film according to the present invention.

[0032] Figure 2 This is a schematic diagram of the mechanical extrusion bonding unit structure of the present invention.

[0033] The labels in the attached diagram are as follows: 1- Feeding device, 2- Pre-lamination device, 3- Multi-stage gradient hot-pressing composite device, 4- Multi-stage gradient cooling and shaping device, 5- Winding device, 21- Electrostatic assisted lamination unit, 211- Electrostatic generator, 212- Electrode assembly, 22- Mechanical extrusion lamination unit, 221- Fixed extrusion roller, 222- Floating extrusion roller, 31- First hot-pressing roller group, 32- Second hot-pressing roller group, 33- Third hot-pressing roller group, 41- First cooling roller, 42- Second cooling roller, 43- Third cooling roller, 44- Negative pressure adsorption unit, 441- Suction hood, 442- Negative pressure generator. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings: Example

[0035] A temperature-controlled strong adhesion production line for car wrap film production, such as Figures 1-2 As shown, it includes:

[0036] The feeding device 1 is used to simultaneously release at least two layers of film substrate to be laminated;

[0037] A pre-lamination device 2, located downstream of the feeding device 1, is used to perform preliminary lamination of at least two layers of film substrates. The pre-lamination device 2 includes: an electrostatic assisted lamination unit 21, used to apply a controllable electrostatic field to the at least two layers of film substrates, causing their surfaces to carry mutually attractive static charges; and a mechanical extrusion lamination unit 22, located downstream of the electrostatic assisted lamination unit 21, used to mechanically extrude the statically charged film substrates, expel interlayer air, and perform preliminary lamination. After processing by this unit, the layers of film substrates are attracted to each other by the electrostatic attraction generated by the static charges on their surfaces, preventing delamination after lamination.

[0038] A multi-level gradient hot-pressing composite device 3 is located downstream of the pre-lamination device 2 and is used to heat and pressurize the pre-lamination and adsorption film to complete the interface fusion. The multi-level gradient hot-pressing composite device 3 includes at least two sets of hot-pressing rollers arranged in series along the conveying direction. The temperature and / or pressure of each set of hot-pressing rollers are independently controllable and are arranged in a gradient.

[0039] A multi-stage gradient cooling and shaping device 4, located downstream of the multi-stage gradient hot-pressing laminating device 3, is used to cool and shape the film after hot-pressing lamination. The multi-stage gradient cooling and shaping device 4 includes at least two independently temperature-controlled cooling rollers arranged in series along the conveying direction, with the surface temperature of each cooling roller set in a gradient. The multi-stage gradient cooling and shaping device 4 also includes a negative pressure adsorption unit 44, which is located on the film inlet side of at least one of the cooling rollers and is used to generate local negative pressure to make the film adhere tightly to the surface of the cooling roller. A winding device 5, located downstream of the multi-stage gradient cooling and shaping device 4, is used to wind up the laminated film product.

[0040] The electrostatic assisted bonding unit 21 includes an electrostatic generator 211 and an electrode assembly 212 connected to the high-voltage electrostatic generator. The electrode assembly 212 is disposed on both sides or one side of the film transport path and is used to apply charges of different polarities to different layers of film substrates.

[0041] The mechanical extrusion bonding unit 22 includes a fixed extrusion roller 221 and a floating extrusion roller 222 that cooperates with the fixed extrusion roller 221. Both the fixed extrusion roller 221 and the floating extrusion roller 222 are arc-shaped rollers with a central protrusion facing the side where the film is input. The cooperation of the two extrusion rollers forms an arc-shaped pressing line. This pressing line starts from the highest point in the middle of the film width direction and extends symmetrically to both sides as the film advances until it covers the entire width of the film.

[0042] The multi-stage gradient hot-pressing composite device 3 includes a first hot-pressing roller group 31, a second hot-pressing roller group 32, and a third hot-pressing roller group 33 arranged in series along the conveying direction; the first hot-pressing roller group 31 has a first operating temperature T1 and is configured to apply a first pressure P1 to the film; the second hot-pressing roller group 32 has a second operating temperature T2 and is configured to apply a second pressure P2 to the film, and T2 > T1, P2 > P1; the third hot-pressing roller group 33 has a third operating temperature T3 and is configured to apply a third pressure P3 to the film, and T3 ≤ T2, P3 ≤ P2;

[0043] The multi-stage gradient cooling and shaping device 4 includes a first cooling roller 41, a second cooling roller 42, and a third cooling roller 43 arranged in series along the conveying direction; the surface temperature of the first cooling roller 41 is a first cooling temperature C1; the surface temperature of the second cooling roller 42 is a second cooling temperature C2, and C2 > C1; the surface temperature of the third cooling roller 43 is a third cooling temperature C3, and C3 is higher than C2 and close to the ambient temperature; wherein, the temperature gradient from C1 to C2 is less than the temperature gradient from the film temperature output by the multi-stage gradient hot pressing composite device 3 to C1.

[0044] Working principle:

[0045] This invention achieves high-quality, defect-free film lamination through multi-stage synergistic effects. The system includes five functional modules along the material conveying direction: feeding, pre-lamination, hot-pressing lamination, cooling and shaping, and winding. Its core lies in the organic combination of electrostatic assisted adsorption, gradient hot pressing, and gradient cooling technologies to form a continuous, stable, and controllable lamination process.

[0046] Specifically, the feeding device 1 first releases at least two layers of film substrate to be laminated simultaneously. After entering the pre-lamination stage, the electrostatic generator 211 applies electrostatic charges of opposite polarity to the surfaces of different layers of film substrate through the electrode assembly 212, causing the surfaces to carry electrostatic charges of opposite polarity, thereby generating electrostatic attraction between them. Subsequently, the film enters the mechanical extrusion lamination unit 22, which uses a combination of arc-shaped extrusion rollers with a raised center to form an arc-shaped pressing line that extends symmetrically from the middle of the film to both sides. Under the action of mechanical extrusion, the interlayer air is effectively discharged, completing the preliminary lamination. The arc-shaped pressing line starts from the highest point in the middle of the film, and as the film moves forward, the pressing area extends symmetrically to both sides. This pressing method can effectively discharge the air between the two layers of film smoothly from the middle to both sides, minimizing the generation of air bubbles. After the preliminary lamination by extrusion, the film layers maintain an adsorption state by means of electrostatic attraction. This force field effectively prevents re-delamination caused by film tension fluctuations or slight vibrations before entering the hot-press lamination stage, ensuring the temporary stability of the structure before lamination.

[0047] The initially bonded film then enters the multi-stage gradient hot-pressing laminating device 3. The film first enters the first hot-pressing roller group 31 with relatively low temperature and pressure. The main purpose is to gently heat and activate the functional layer or adhesive layer on the film surface, giving it a certain degree of adhesion, while avoiding film deformation or stress caused by sudden high temperature and pressure. The film then enters the second hot-pressing roller group 32 with higher temperature and pressure. Under this condition, the molecular chain segment mobility of the film interface layer is greatly enhanced. Driven by pressure, sufficient mutual diffusion and entanglement occur between molecules, thereby achieving a firm interface fusion and completing the main lamination process. Finally, the film enters the third hot-pressing roller group 33 with moderately reduced temperature and pressure, allowing the fused interface to moderately cool and solidify while maintaining pressure, stabilizing the composite structure. At the same time, by adjusting the temperature and pressure, some of the internal stress accumulated in the previous stage is released, reducing shrinkage and deformation during subsequent winding and use.

[0048] After hot pressing, the film immediately enters the multi-stage gradient cooling and shaping device 4. When the film enters the cooling rollers of the cooling and shaping device, the negative pressure adsorption unit 44 generates local negative pressure on the film inlet side of the cooling roller, tightly "adsorbing" or "adhering" the film, which is still in a high-temperature softened state, to the surface of the cooling roller. This ensures high heat conduction efficiency between the film and the cooling roller and prevents the film from wrinkling or deforming during the cooling process. The film is rapidly cooled on the first cooling roller 41 at a lower temperature, allowing the film surface and composite interface to quickly pass through the glass transition zone, fixing the formed composite structure and obtaining preliminary dimensional stability. Subsequently, the film is slowly cooled on the second cooling roller 42 at a higher temperature. The smaller cooling gradient allows sufficient time for the residual stress inside the film to relax and release, avoiding the generation of new internal stress due to excessively rapid cooling, thereby improving the flatness and long-term stability of the film. Then, the film is cooled on the third cooling roller 43, which is close to the ambient temperature, so that the overall temperature of the film is uniformly reduced to room temperature, completing the final shaping process. Finally, the high-quality composite film after cooling and shaping is neatly wound up by the winding device 5, completing the entire automated production process.

[0049] In summary, this invention achieves bubble-free initial lamination through electrostatic assisted bonding, and then combines multi-level gradient hot pressing and cooling processes to achieve high-quality fusion and stress optimization control of the film interface under precisely controlled temperature, pressure and cooling rate, thereby producing a composite car wrap film product with firm adhesion, smooth surface, excellent optical performance and no internal defects.

[0050] The control method of this invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, since this invention is mainly used to protect mechanical devices, the control method and circuit connection will not be explained in detail here.

[0051] Although this disclosure has been described in detail with reference to exemplary embodiments, it is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the scope of this disclosure.

Claims

1. A temperature-controlled strong adhesion production line for producing car wrap film, characterized in that, Along the material conveying direction, the following are included in sequence: The feeding device (1) is used to simultaneously release at least two layers of film substrate to be laminated; A pre-lamination device (2) is located downstream of the feeding device (1) and is used to perform preliminary lamination of at least two layers of film substrates. The pre-lamination device (2) includes: an electrostatic assisted lamination unit (21) for applying a controllable electrostatic field to the at least two layers of film substrates, so that their surfaces are respectively covered with mutually attractive static charges; and a mechanical extrusion lamination unit (22) located downstream of the electrostatic assisted lamination unit (21) for mechanically extruding the film substrates covered with static charges, expelling interlayer air and performing preliminary lamination. A multi-level gradient hot-pressing composite device (3) is located downstream of the pre-lamination device (2) and is used to heat and pressurize the pre-lamination and adsorption film to complete the interface fusion. The multi-level gradient hot-pressing composite device (3) includes at least two sets of hot-pressing rollers arranged in series along the conveying direction. The temperature and / or pressure of each set of hot-pressing rollers are independently controllable and are arranged in a gradient. A multi-level gradient cooling and shaping device (4) is disposed downstream of the multi-level gradient hot-pressing composite device (3) and is used to cool and shape the film after hot-pressing composite. The multi-level gradient cooling and shaping device (4) includes at least two independently temperature-controlled cooling rollers arranged in series along the conveying direction, and the surface temperature of each cooling roller is set in a gradient. The multi-level gradient cooling and shaping device (4) also includes a negative pressure adsorption unit (44), which is disposed on the film inlet side of at least one of the cooling rollers. A winding device (5) is located downstream of the multi-stage gradient cooling and shaping device (4) and is used to wind up the composite film product. The mechanical extrusion bonding unit (22) includes a fixed extrusion roller (221) and a floating extrusion roller (222) that cooperates with the fixed extrusion roller (221). Both the fixed extrusion roller (221) and the floating extrusion roller (222) are arc-shaped rollers with a central protrusion facing the side where the film is input. The cooperation of the two extrusion rollers forms an arc-shaped pressing line. The pressing line starts from the highest point in the middle of the film width direction and extends symmetrically to both sides as the film advances until it covers the entire width of the film. The multi-stage gradient hot pressing composite device (3) includes a first hot pressing roller group (31), a second hot pressing roller group (32), and a third hot pressing roller group (33) arranged in series along the conveying direction; the first hot pressing roller group (31) has a first operating temperature T1 and is configured to apply a first pressure P1 to the film; the second hot pressing roller group (32) has a second operating temperature T2 and is configured to apply a second pressure P2 to the film, and T2 > T1, P2 > P1; the third hot pressing roller group (33) has a third operating temperature T3 and is configured to apply a third pressure P3 to the film, and T3 ≤ T2, P3 ≤ P2; The multi-stage gradient cooling and shaping device (4) includes a first cooling roller (41), a second cooling roller (42), and a third cooling roller (43) arranged in series along the conveying direction; the surface temperature of the first cooling roller (41) is a first cooling temperature C1; the surface temperature of the second cooling roller (42) is a second cooling temperature C2, and C2 > C1; the surface temperature of the third cooling roller (43) is a third cooling temperature C3, and C3 is higher than C2 and close to the ambient temperature; wherein, the temperature gradient from C1 to C2 is less than the temperature gradient from the film temperature output by the multi-stage gradient hot pressing composite device (3) to C1; The electrostatic assisted bonding unit (21) includes an electrostatic generator (211) and an electrode assembly (212) connected to the electrostatic generator (211). The electrode assembly (212) is disposed on both sides or one side of the film transport path and is used to apply charges of different polarities to different layers of film substrates.

2. The temperature-controlled strong adhesion production line for producing car wrap film according to claim 1, characterized in that, The negative pressure adsorption unit (44) includes a suction hood (441) disposed on one side of the cooling roller and a negative pressure generator (442) connected to the suction hood (441).

3. A car wrap film lamination process, employing a temperature-controlled strong adhesion production line for car wrap film production as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1: At least two layers of film substrate are simultaneously unwound by the unwinding device (1); S2: The thin film substrate is passed through the electrostatic assisted bonding unit (21) in the pre-bonding device (2), and a controllable electrostatic field is applied to make the surface of each layer of thin film substrate carry mutually attractive static charges; S3: The electrostatically charged thin film substrate is brought into the mechanical extrusion bonding unit (22) in the pre-bonding device (2) and mechanically extruded to expel interlayer air and complete the initial bonding; in this step and thereafter, the thin films are attracted to each other by the electrostatic attraction generated by the electrostatic charge to prevent delamination. S4: The pre-bonded film adsorbed by electrostatics enters the multi-level gradient hot-pressing composite device (3) and passes through the hot-pressing roller group with temperature and pressure gradients in sequence to complete the interface molecular activation, diffusion fusion and stress pre-release. S5: The hot-pressed composite film is brought into the multi-level gradient cooling and shaping device (4). With the assistance of the negative pressure adsorption unit (44), the film is tightly bonded to the surface of multiple cooling rollers with temperature gradients, and is subjected to rapid cooling and shaping, slow cooling and stress relief and room temperature stabilization in sequence. S6: The cooled and shaped composite film product is wound up by the winding device (5).

4. The car wrap film lamination process according to claim 3, characterized in that, In step S3, the mechanical extrusion bonding unit (22) first pre-presses the middle of the film, and then performs gradient expansion pressing on both sides of the film, so that air is discharged from the middle to both sides.

5. The car wrap film lamination process according to claim 3, characterized in that, In step S2, the polarities of the electrostatic charges carried by two adjacent thin film substrates are opposite.

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