Method for preparing polarized anti-counterfeiting base film through electrostatic attachment and polarized anti-counterfeiting base film

Abstract

The invention relates to the technical field of anti-counterfeiting film preparation, and discloses a method for preparing a polarized light anti-counterfeiting base film through electrostatic attachment and the polarized light anti-counterfeiting base film, and the method comprises the following steps: 1, melting a polymer material; 2, the melt flowing out of the die orifice is attached to a cold roller through an electrostatic attaching system, and the electrostatic attaching system is arranged at the position, close to the die orifice, of the cold roller and can make the melt vibrate according to a certain frequency; and 3, cooling the melt along with the rotation of the cold roller to form a casting film, namely the polarized anti-counterfeiting base film with characteristic patterns. According to the invention, the electrostatic belt capable of vibrating is arranged on the cold roller, so that the orientation degree of macromolecules in the melt is correspondingly changed, air can be eliminated, good heat transfer can be realized, the polarized light effect is more obvious, and the polarized anti-counterfeiting base film with characteristic patterns is formed.

Description

Technical Field

[0001] This invention relates to the technical field of anti-counterfeiting film preparation, and in particular to a method for preparing a polarized anti-counterfeiting base film by electrostatic adhesion and the polarized anti-counterfeiting base film. Background Technology

[0002] Polarized light is a type of light with polarization properties. Since the human eye cannot distinguish polarized light, other devices are needed to observe various phenomena of polarized light. Thin films with polarized light properties appear no different from ordinary films under normal conditions, but they exhibit distinct characteristics when observed through an array of polarizers. This makes the thin film suitable as a base film with anti-counterfeiting functions.

[0003] The film preparation process includes a casting system. Molten polymer is deposited onto a cooling roller and cooled to form a cast sheet. The cast sheet can then undergo subsequent treatments such as stretching, heat setting, edge trimming, dust removal, static electricity elimination, and corona treatment before being rolled into a large master roll. The casting system includes a die, a quenching roller, and an electrostatic attachment device. The die is crucial for the casting process, directly determining the shape and thickness uniformity of the cast sheet. The viscous polymer melt flowing from the die is rapidly cooled below its glass transition temperature on a uniformly rotating quenching roller to form a glassy, ​​uniformly thick cast sheet. The purpose of quenching is to create an amorphous structure and reduce crystallization, thus avoiding adverse effects on the subsequent stretching process. The electrostatic attachment device ensures close contact between the cast sheet and the quenching roller, preventing air entrapment during roller rotation and guaranteeing effective heat transfer and cooling.

[0004] Thin films with polarized light properties usually require multi-layer patterned structures or the addition of special polarizing materials. These processes all require relatively complex operating methods and preparation steps. Therefore, it is very necessary to develop a polarized anti-counterfeiting film preparation process that is suitable for conventional thin film production lines. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a polarized anti-counterfeiting base film via electrostatic bonding, and the polarized anti-counterfeiting base film itself. By setting an electrostatic bonding system on a cold roller, the melt can vibrate at a certain frequency, causing a change in the orientation of the polymer molecules within the polymer melt, thereby obtaining an anti-counterfeiting base film with a polarization effect.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a polarized anti-counterfeiting base film by electrostatic attachment, comprising the following steps: Step 1: Melt the polymer material; Step 2: The melt flowing out of the die is attached to the cold roller by an electrostatic attachment system. The electrostatic attachment system is set on the cold roller near the die and can make the melt vibrate at a certain frequency. Step 3: The melt is then cooled by the rotating cold rollers to form a cast film, which is a polarized anti-counterfeiting base film with characteristic patterns.

[0007] In the melt casting section, high-temperature molten metal flows out from the slit of the die head. With the help of the electrostatic adhesion system, the molten film falls flat onto the rotating cooling roller, rapidly cooling to become a cast sheet. During the process of the molten metal adhering to the quenching roller, due to the continuous rotation of the quenching roller, the molten metal falling on it is subjected to traction and stretching, generally referred to as pre-stretching. The working principle of the electrostatic adhesion system is to use a DC voltage generated by a high-voltage generator to make the electrostatic belt and the cooling roller the positive and negative poles, respectively (the cooling roller is grounded). In this high-voltage electrostatic field, the cast sheet acquires an electrostatic charge of opposite polarity to that of the cooling roller due to electrostatic induction. Under the attraction of opposite charges, the cast sheet and the surface of the cooling roller are tightly adhered together, achieving the purpose of removing air and good heat transfer. At the same time, the electrostatic belt can vibrate. Appropriate vibration can not only improve the tight adhesion between the cast sheet and the cooling roller and the air removal effect, but also cause changes in the electrostatic adhesion effect, which in turn changes the stretching effect on the molten metal. The orientation degree of the polymer in the molten metal will also change accordingly, thus producing the desired polymer film with polarization effect.

[0008] The simultaneous action of pre-stretching and electrostatic bonding vibration of the cold roller can produce different polarization effects. By increasing the difference in orientation caused by the degree of pre-stretching and electrostatic bonding vibration, the filtering / torsion effect on light becomes more pronounced, resulting in a more significant polarization effect and forming a polarized anti-counterfeiting base film with characteristic patterns. The polymer film obtained from the above steps can be used directly or subjected to subsequent processing, such as uniaxial stretching, biaxial stretching, and / or coating and lamination processes, without losing the polarization properties obtained in the above steps.

[0009] Preferably, the polymer material is PET, PP or PA.

[0010] Preferably, when the polymer material is PET, the melting temperature is 270–300°C.

[0011] Preferably, when the polymer material is PP, the melting temperature is 250-270°C.

[0012] Preferably, when the polymer material is PA, the melting temperature is 230–250°C.

[0013] Preferably, the cast film comprises an upper surface layer, a core layer, and a lower surface layer in sequence.

[0014] Cast film is obtained through three-layer co-extrusion, which can make the pattern shape more visible while not significantly affecting the original structure and performance of the film.

[0015] Preferably, the raw material components of the upper and lower surface layers respectively include polymer materials and slip agents; the raw material components of the core layer include polymer materials.

[0016] Preferably, the thickness of a single surface layer (upper surface layer / lower surface layer) accounts for 5-10% of the total film thickness.

[0017] Preferably, the vibration frequency of the electrostatic strip is 20 to 100 Hz.

[0018] During operation, the vibration frequency of the electrostatic strip can operate at a fixed frequency or be changed as needed to obtain the desired polarized light pattern.

[0019] Preferably, the vibration amplitude of the electrostatic strip is 0.05 to 0.2 mm.

[0020] If the vibration amplitude is too small, the vibration effect will be too weak and will not have much impact on the degree of polymer orientation. If the vibration amplitude is too large, it will easily lead to malfunction of the electrostatic bonding system or even production interruption. During operation, the vibration amplitude of the electrostatic tape can be fixed or varied as needed to obtain the desired polarized light pattern.

[0021] Preferably, the electrostatic attachment system includes an electrostatic tape, a high-voltage generator, an electrode retraction torque motor, and a vibration generator; the electrostatic tape is positioned above the cold roller and is connected to the high-voltage generator to make the electrostatic tape positively charged, and the high-voltage generator is also connected to the electrode retraction torque motor; the electrostatic tape is also connected to the vibration generator to make the electrostatic tape vibrate; the cold roller is grounded and negatively charged, and the melt flows through the area between the electrostatic tape and the cold roller.

[0022] Preferably, the high-voltage generator outputs 5-15kV high-voltage direct current.

[0023] Preferably, the vertical distance between the lower end of the electrostatic strip and the upper surface of the melt is 1 to 10 mm.

[0024] Preferably, the vertical (shortest) distance between the die and the cold roller is 5 to 80 mm, more preferably 10 to 40 mm.

[0025] Preferably, the temperature of the cold roller is 10–40°C and the speed is 5–180 m / min; more preferably, the temperature of the cold roller is 15–30°C and the speed is 7–130 m / min.

[0026] Preferably, the cast film is stretched longitudinally or first stretched longitudinally and then stretched laterally to form a polarized anti-counterfeiting base film with characteristic patterns.

[0027] Preferably, the longitudinal stretching ratio is 2 to 15, and the stretching temperature is higher than the glass transition temperature of the polymer material.

[0028] Preferably, the stretching ratio of the transverse stretching is 2 to 10, and the stretching temperature is higher than the glass transition temperature of the polymer material.

[0029] Preferably, the cast film is stretched longitudinally or stretched longitudinally and then laterally, and then heat-set and post-treated to form a polarized anti-counterfeiting base film with characteristic patterns.

[0030] Preferably, the heat setting temperature is 220–250°C, and more preferably 230–245°C.

[0031] Preferably, the post-processing includes edge trimming, dust removal, static electricity elimination, and corona treatment.

[0032] Secondly, the present invention also provides a polarizing anti-counterfeiting base film prepared by the above-mentioned preparation method.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) By setting an electrostatic bonding system on the cold roller, the electrostatic bonding effect will change, which will cause the stretching effect on the melt to change accordingly. The orientation degree of the polymer in the melt will also change accordingly, so that the desired polymer film with polarization effect can be obtained. (2) The electrostatic bonding system also makes the casting sheet and the surface of the cold roller adhere tightly together, so as to remove air and achieve good heat transfer; (3) By making the difference between the degree of pre-stretching and the degree of orientation caused by electrostatic bonding vibration greater, the effect of filtering / torsuring light is more obvious, making the polarized light effect more significant, forming a polarized anti-counterfeiting base film with characteristic patterns. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the apparatus for forming the cast film in this invention.

[0035] Figure 2 This is a schematic diagram of the polarization array setup during polarization verification.

[0036] Figure 3 This is an optical pattern photograph used for polarization verification in Embodiment 1 of the present invention.

[0037] The attached figures are labeled as follows: 1. Die head; 2. Electrostatic attachment system; 2-1. Electrostatic belt; 3. Cold roller; 4. Peeling roller; 5. Cast film. Detailed Implementation

[0038] The technical solution of the present invention will be illustrated below with specific embodiments, taking polyester film as an example, but the scope of protection of the present invention is not limited thereto.

[0039] Example 1 The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0040] Step Two: The melt from the main and auxiliary extruders, after being filtered, converges at the die head and flows out from the die orifice, such as... Figure 1 As shown, the melt flowing out through the die head 1 is attached to the cold roller 3 (the core layer is sandwiched between two surface layers, so one surface layer faces the electrostatic tape and the other surface layer is attached to the cold roller). At the same time, an electrostatic attachment system 2 is provided on the cold roller 3 near the die head 1. The die head 1 is located above the cold roller 3. The vertical distance between the die opening and the cold roller 3 is 25mm, and the shortest vertical distance between the die opening and the electrostatic attachment system 2 is 15mm.

[0041] The electrostatic attachment system 2 includes an electrostatic tape 2-1, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic tape 2-1 is arranged parallel above the cold roller 3 and extends along the length of the cold roller 3. The electrostatic tape 2-1 is connected to the high-voltage generator to make the electrostatic tape 2-1 positively charged. The high-voltage generator is connected to the electrode retraction torque motor. The electrostatic tape 2-1 is also connected to the vibration generator to make the electrostatic tape 2-1 vibrate. The cold roller 3 is grounded and negatively charged. The melt flows through the area between the electrostatic tape 2-1 and the cold roller 3.

[0042] The electrostatic belt 2-1 has a width of 3 mm, and the vertical distance between the lower end of the electrostatic belt 2-1 and the upper surface of the melt is 3 mm. The electrostatic belt 2-1 vibrates at a fixed frequency of 50 Hz with a fixed vibration amplitude of 0.1 mm. The temperature of the cooling roller 3 is 22 ℃, and the speed is 65 m / min. Afterward, the melt is cooled by rotating with the cooling roller 3, and after passing through the peeling roller 4, a cast film 5 (three-layer structure) with characteristic patterns is formed.

[0043] Step 3: The cast film 5 is fed into the longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0044] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0045] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0046] Example 2 The difference from Example 1 is that the electrostatic strip vibrates at a fixed frequency of 100Hz with a fixed vibration amplitude of 0.15mm.

[0047] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0048] Step 2: The melt from the main and auxiliary extruders is filtered and then converges at the die head and flows out from the die orifice. The melt flowing out through the die head adheres to the cold roller. At the same time, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is located above the cold roller, and the vertical distance between the die orifice and the cold roller is 25mm. The shortest vertical distance between the die orifice and the electrostatic adhesion system is 15mm.

[0049] The electrostatic bonding system includes an electrostatic belt, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic belt is positioned parallel above the cooling roller, extending along the length of the roller. The molten material flows through the area between the electrostatic belt and the cooling roller. The electrostatic belt is 3 mm wide, and the vertical distance between the lower end of the belt and the upper surface of the molten material is 3 mm. The belt vibrates at a fixed frequency of 100 Hz with a fixed amplitude of 0.15 mm. The cooling roller is at a temperature of 22°C and a speed of 65 m / min. The molten material then rotates and cools with the cooling roller. After passing through a peeling roller, it forms a cast film (three-layer structure) with a characteristic pattern.

[0050] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0051] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0052] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0053] Example 3 The difference from Example 1 is that the electrostatic strip vibrates at a fixed frequency of 100Hz with a fixed vibration amplitude of 0.2mm.

[0054] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0055] Step 2: The melt from the main and auxiliary extruders, after filtration, converges at the die head and flows out from the die orifice. The melt flowing out through the die head adheres to the cold roller. Simultaneously, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is positioned above the cold roller, with a vertical distance of 25mm between the die orifice and the cold roller, and a minimum vertical distance of 15mm between the die orifice and the electrostatic adhesion system.

[0056] The electrostatic bonding system includes an electrostatic belt, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic belt is positioned parallel above the cooling roller, extending along the length of the roller. The molten material flows through the area between the electrostatic belt and the cooling roller. The electrostatic belt is 3 mm wide, and the vertical distance between the lower end of the belt and the upper surface of the molten material is 3 mm. The belt vibrates at a fixed frequency of 100 Hz with a fixed vibration amplitude of 0.2 mm. The cooling roller is at a temperature of 22°C and a speed of 65 m / min. The molten material then rotates and cools with the cooling roller. After passing through the peeling roller, it forms a cast film (three-layer structure) with a characteristic pattern.

[0057] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0058] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0059] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0060] Example 4 The difference from Example 1 is that the vertical distance between the die and the cold roller is 40mm, and the shortest vertical distance between the die and the electrostatic bonding system is 30mm.

[0061] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0062] Step Two: The melts from the main and auxiliary extruders, after filtration, converge at the die head and flow out through the die orifice. The melt flowing out through the die head adheres to the cold roller. Simultaneously, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is positioned above the cold roller, with a vertical distance of 40mm between the die orifice and the cold roller, and a minimum vertical distance of 30mm between the die orifice and the electrostatic adhesion system.

[0063] The electrostatic bonding system includes an electrostatic tape, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic tape is positioned parallel above the cooling roller, extending along the length of the cooling roller. The molten material flows through the area between the electrostatic tape and the cooling roller. The electrostatic tape is 3 mm wide, and the vertical distance between the lower end of the electrostatic tape and the upper surface of the molten material is 3 mm. The electrostatic tape vibrates at a fixed frequency of 50 Hz with a fixed vibration amplitude of 0.1 mm. The temperature of the cooling roller is 22°C, and its speed is 65 m / min. The molten material then rotates and cools with the cooling roller. After passing through the peeling roller, it forms a cast film (three-layer structure) with a characteristic pattern.

[0064] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0065] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0066] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0067] Example 5 The difference from Example 1 is that the vertical distance between the die and the cold roller is 60mm, and the shortest vertical distance between the die and the electrostatic bonding system is 15mm.

[0068] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0069] Step 2: The melt from the main and auxiliary extruders, after filtration, converges at the die head and flows out from the die orifice. The melt flowing out through the die head adheres to the cold roller. At the same time, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is located above the cold roller, with a vertical distance of 60mm between the die orifice and the cold roller, and a minimum vertical distance of 15mm between the die orifice and the electrostatic adhesion system.

[0070] The electrostatic bonding system includes an electrostatic tape, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic tape is positioned parallel above the cooling roller, extending along the length of the cooling roller. The molten material flows through the area between the electrostatic tape and the cooling roller. The electrostatic tape is 3 mm wide, and the vertical distance between the lower end of the electrostatic tape and the upper surface of the molten material is 3 mm. The electrostatic tape vibrates at a fixed frequency of 50 Hz with a fixed vibration amplitude of 0.1 mm. The temperature of the cooling roller is 22°C, and its speed is 65 m / min. The molten material then rotates and cools with the cooling roller. After passing through the peeling roller, it forms a cast film (three-layer structure) with a characteristic pattern.

[0071] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0072] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0073] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0074] Example 6 The difference from Example 1 is that the temperature of the cold roller is 15°C and the speed is 50 m / min.

[0075] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0076] Step 2: The melt from the main and auxiliary extruders, after filtration, converges at the die head and flows out from the die orifice. The melt flowing out through the die head adheres to the cold roller. Simultaneously, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is positioned above the cold roller, with a vertical distance of 25mm between the die orifice and the cold roller, and a minimum vertical distance of 15mm between the die orifice and the electrostatic adhesion system.

[0077] The electrostatic bonding system includes an electrostatic tape, a high-voltage generator, an electrode retraction torque motor, and a vibration generator. The electrostatic tape is positioned parallel above the cooling roller, extending along the length of the roller. The molten material flows through the area between the electrostatic tape and the cooling roller. The electrostatic tape is 3 mm wide, and the vertical distance between the lower end of the tape and the upper surface of the molten material is 3 mm. The tape vibrates at a fixed frequency of 50 Hz with a fixed vibration amplitude of 0.1 mm. The cooling roller is at a temperature of 15°C and a speed of 50 m / min. The molten material then rotates and cools with the cooling roller. After passing through a peeling roller, it forms a cast film (three-layer structure) with a characteristic pattern.

[0078] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0079] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0080] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0081] Comparative Example 1 The difference from Example 1 is that the electrostatic strip vibrates at a fixed frequency of 50Hz with a fixed vibration amplitude of 0.3mm.

[0082] The preparation of the polarized anti-counterfeiting base film includes the following steps: Step 1: Dry the pure polyester chips at 150℃ for 4 hours, ensuring the moisture content is below 50 ppm. The dried chips are then fed into the main extruder for plasticizing and melting. Next, the pure polyester chips are mixed with silicone-containing polyester chips, ensuring the total silica content is controlled at 1500 ppm to obtain a blend. The molten pure polyester and the blend are then separately fed into three twin-screw vented extruders for plasticizing and melting, with the pure polyester serving as the core layer and the blend as the surface layer.

[0083] Step 2: The melt from the main and auxiliary extruders, after filtration, converges at the die head and flows out from the die orifice. The melt flowing out through the die head adheres to the cold roller. Simultaneously, an electrostatic adhesion system is installed on the cold roller near the die head. The die head is positioned above the cold roller, with a vertical distance of 25mm between the die orifice and the cold roller, and a minimum vertical distance of 15mm between the die orifice and the electrostatic adhesion system.

[0084] The electrostatic bonding system includes an electrostatic belt, a high-voltage generator, an electrode tension motor, and a vibration generator. The electrostatic belt is positioned parallel above the cooling roller, extending along the length of the cooling roller. The molten material flows through the area between the electrostatic belt and the cooling roller. The electrostatic belt is 3 mm wide, and the vertical distance between the lower end of the electrostatic belt and the upper surface of the molten material is 3 mm. The electrostatic belt vibrates at a fixed frequency of 50 Hz with a fixed vibration amplitude of 0.3 mm. The temperature of the cooling roller is 22°C, and its speed is 65 m / min. The molten material then rotates and cools with the cooling roller. After passing through the peeling roller, it forms a cast film (three-layer structure) with characteristic patterns.

[0085] Step 3: The cast film is fed into a longitudinal stretching machine for longitudinal stretching. It is heated by several hot rollers at a temperature of 115°C, and then quickly cooled by cold rollers at a temperature of 28°C. After passing through several cold rollers, the stretching ratio is 3.4 times.

[0086] Step 4: The longitudinally stretched film is then fed into a transverse stretching machine for transverse stretching. The stretching temperature is 130℃ and the transverse stretching ratio is set to 4 times.

[0087] Step 5: After the transverse stretching is completed, the film is heat-set at 240℃. After edge trimming, dust removal, static electricity elimination, corona treatment, etc., it is rolled into a large master roll to produce a polarized anti-counterfeiting base film.

[0088] Polarization verification: like Figure 2As shown, the prepared anti-counterfeiting film was placed in a polarizer array for inspection. The polarizer array consists of two polarizers and a light source. The two polarizers are arranged in a parallel orientation, with the observer and the light source positioned on the upper and lower sides of the polarizers, respectively. The film sample to be inspected is placed between the two polarizers. The light emitted from the light source passes sequentially through the lower polarizer, the film, and the upper polarizer before reaching the observer, thus allowing the inspection of the characteristic optical patterns hidden on the film. Ten observers were selected to observe the polarization effect, selecting patterns at three different locations on the film for observation. The patterns were scored based on their completeness, clarity, and the degree of distinction between bright and dark areas, with a maximum score of 5 points, and the average score was taken.

[0089] Table 1 As shown in Table 1, the polarized anti-counterfeiting base film in this invention can clearly exhibit periodic bright and dark characteristic patterns in the polarization array, such as... Figure 3 As shown, through observation and measurement, the average widths of the characteristic bright and dark areas of the polarized anti-counterfeiting base film obtained in Example 1 are 10 mm and 25 mm, respectively. Furthermore, according to the polarization evaluation results conducted by the observer, it is evident that the polarization effect of the polarized anti-counterfeiting base film in this invention is excellent.

[0090] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a polarized anti-counterfeiting base film by electrostatic bonding, characterized in that, Includes the following steps: Step 1: Melt the polymer material; Step 2: The melt flowing out of the die is attached to the cold roller by an electrostatic attachment system. The electrostatic attachment system is set on the cold roller near the die and can make the melt vibrate at a certain frequency. Step 3: The melt is then cooled by the rotating cold rollers to form a cast film, which is a polarized anti-counterfeiting base film with characteristic patterns.

2. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 1, characterized in that, The polymer material is PET, PP, or PA.

3. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 1, characterized in that, The electrostatic attachment system includes an electrostatic tape and a vibration generator connected to the electrostatic tape; the electrostatic tape is positioned above the cold roller, and the melt flows through the area between the electrostatic tape and the cold roller.

4. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 3, characterized in that, The vibration frequency of the electrostatic strip is 20~100Hz; the vibration amplitude of the electrostatic strip is 0.05~0.2mm.

5. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 1, characterized in that, The vertical distance between the die opening and the cold roller is 5~80mm.

6. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to any one of claims 1-5, characterized in that, The temperature of the cooling roller is 10~40℃, and the speed is 5~180m / min.

7. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 1, characterized in that, The cast film is stretched longitudinally or first longitudinally and then laterally to form a polarized anti-counterfeiting base film with characteristic patterns.

8. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 7, characterized in that, The longitudinal stretching temperature is higher than the glass transition temperature of the polymer material, and the stretching ratio is controlled to be 2~15.

9. The method for preparing a polarized anti-counterfeiting base film by electrostatic bonding according to claim 7 or 8, characterized in that, The stretching temperature of the transverse stretching is higher than the glass transition temperature of the polymer material, and the stretching ratio is controlled to be 2~10.

10. A polarizing anti-counterfeiting base film prepared by the preparation method according to any one of claims 1-9.

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