A composite film and a preparation method thereof

Abstract

The present invention belongs to the technical field of composite films, and discloses a composite film and a preparation method thereof. The preparation method of the composite film includes: first unwinding, first coating, semi-finished product winding, intermediate treatment, second unwinding, second coating, and finished product winding; when the first coating is performed, the applied tension F1 of the coil material satisfies 0.6F0 ≤ F1 ≤ 0.85F0; when the second coating is performed, the applied tension F2 of the coil material satisfies 0.85F0 ≤ F2 ≤ 0.95F0; wherein, F2 > F1, and F0 is the yield tension of the base layer. The present invention realizes the generation of cracks in the first titanium metal layer by controlling the tension applied in stages, and the second titanium metal layer completely covers the cracks when deposited under a higher tension, so that the resistance change is small within the elastic deformation of the prepared composite film.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite films, and particularly relates to a composite film and a preparation method thereof. Background Art

[0002] A composite film is a multi-layer structure material composed of two or more different materials combined together by physical or chemical methods. The combination of multiple materials can endow the product with various properties, such as high strength, light weight, corrosion resistance, isolation, wear resistance, and so on.

[0003] The preparation process of the composite film is also relatively complex. For example, the patent document with the publication number CN110055505A discloses a multi-layer titanium film and a preparation method thereof, in which a pure titanium multi-layer film is formed by sputtering three times. However, in the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art: when the existing composite film of PET film and Ti film is stretched under tension, the PET film can retract when stretched within its elastic deformation range, but the Ti film on the PET film will crack when stretched, resulting in a large change in its own resistance after the composite film is stretched, which is not conducive to use.

[0004] The above statement of the background art is only for facilitating the in-depth understanding of the technical solution of the present invention (such as the technical means used, the technical problems solved, and the technical effects produced, etc.), and should not be regarded as an admission or any form of implication that this information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0005] The present invention aims to solve at least to some extent the above technical problems. To this end, the object of the present invention is to provide a composite film and a preparation method thereof.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A preparation method of a composite film, comprising:

[0008] First unrolling, first coating, semi-finished product winding, intermediate treatment, second unrolling, second coating, and finished product winding;

[0009] When performing the first coating, the applied tension F1 of the coil satisfies 0.6F0 ≤ F1 ≤ 0.85F0;

[0010] When performing the second coating, the applied tension F2 of the coil satisfies 0.85F0 ≤ F2 ≤ 0.95F0;

[0011] Wherein, F2 > F1, and F0 is the yield tension of the base layer.

[0012] Preferably, a temperature measurement module for real-time detection of the temperature of the coated surface of the coil is provided at the coating station for the second coating. The temperature compensation system calculates the yield tension F0 = F 0,ref × [1 - α(T - T ref )], where α is the temperature sensitivity coefficient of the substrate, and T ref is the reference temperature, and F 0,ref is the yield tension of the base layer measured at the reference temperature.

[0013] Preferably, during the second coating process, the dynamic tension control system adjusts the applied tension F2 in real time. The dynamic tension control system includes:

[0014] A tension sensor for detecting the real-time tension of the coil;

[0015] A laser displacement sensor for measuring the lateral deformation of the coil;

[0016] A control module for dynamically adjusting the rotational speed of the servo motor according to the deformation and tension deviation;

[0017] A compensation module for correcting the applied tension F according to the change rate of the winding and unwinding speed 2new = F 2set × [1 + β(T - T ref )], where F 2new is the corrected applied tension, F 2set is the original applied tension, and β is the thermal expansion coefficient of the substrate.

[0018] Preferably, during the second coating, the cooling roll includes a first-stage cooling roll and a second-stage cooling roll. The surface temperature of the first-stage cooling roll is controlled at -10°C to 0°C, and the surface temperature of the second-stage cooling roll is controlled at 5°C - 10°C. The coating assembly uses a radio frequency plasma generator.

[0019] Preferably, the intermediate treatment includes annealing treatment or aging treatment.

[0020] Preferably, the annealing treatment includes keeping the semi-finished coil at 80°C for 30 minutes, cooling it at a rate of 0.5°C / min to 60°C and keeping it at 60°C for 60 minutes, and then naturally cooling it to 40°C.

[0021] Preferably, the aging treatment includes storing the semi-finished coil at 30 - 50°C for 12 - 24 hours to release stress.

[0022] Preferably, the sputtering power for the first coating is 3 - 5 W / cm², and the sputtering power for the second coating is 8 - 12 W / cm².

[0023] A composite film is prepared by the above preparation method. The composite film includes:

[0024] Base layer;

[0025] The first titanium metal layer, covering the base layer, contains cracks;

[0026] The second titanium metal layer, covering the first titanium metal layer, completely covers the cracks and forms a conductive bridging structure there.

[0027] The above base layer can be selected from at least one of siloxane polymer, silicon nitride polymer, polymethyl methacrylate (PMMA), polyimide (PI), polyethylene (PE), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyurethane (PU), fluorinated ethylene propylene copolymer (FEP), soluble polytetrafluoroethylene (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyetheretherketone (PEEK), polysilazane, polycarbonate, silicone resin, fluoride material and rubber.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. By controlling the application of tension in stages, the present invention realizes that when cracks are generated in the first titanium metal layer, the second titanium metal layer completely covers the cracks when deposited under higher tension, so that the resistance change of the prepared composite film is small when stretched within the elastic deformation range.

[0030] 2. Through the triple guarantee mechanism of temperature compensation, intermediate treatment and low-temperature process, the present invention solves the problem of out-of-control application of tension F2 caused by temperature during the preparation of the composite film. Under the working conditions of 40 - 60 °C, the fluctuation range of the F2 / F0 ratio is < ±2%, which can ensure the mass production stability. Description of the Drawings

[0031] Figure 1 is a schematic diagram of the composite film of the present invention.

[0032] Figure 2 is a schematic diagram of the cracks on the first titanium metal layer of the present invention.

[0033] Figure 3 is a schematic diagram of the equipment structure during the first coating of the present invention.

[0034] Figure 4 is a schematic diagram of the equipment structure during the second coating of the present invention.

[0035] In the figure: 1 - Base layer; 2 - First titanium metal layer; 21 - Cracks; 3 - Second titanium metal layer; 41 - First unwinding roller; 42 - First cooling roller; 43 - First winding roller; 44 - First coating assembly; 51 - Second unwinding roller; 52 - First-stage cooling roller; 53 - Second-stage cooling roller; 54 - Second winding roller; 55 - Second coating assembly. Detailed Embodiments

[0036] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0037] A method for preparing a composite film according to this embodiment is used to prepare a composite film with a PET base layer and two titanium coating layers. As Figure 1 shown, the prepared composite film includes a base layer 1 and a first titanium metal layer 2 (the first Ti film) and a second titanium metal layer 3 (the second Ti film) provided on the same side of the base layer 1. As Figure 3 and Figure 4 shown, the equipment for the first coating includes a first unwind roller 41, a first cooling roller 42, a first winding roller 43 and a first coating assembly 44. The PET film passes through the first unwind roller 41, the first cooling roller 42 and the first winding roller 43 in sequence, and the first coating assembly 44 is arranged at the coating station for the first coating. The equipment for the second coating includes a second unwind roller 51, a first-stage cooling roller 52, a second-stage cooling roller 53, a second winding roller 54 and a second coating assembly 55. The PET film covered with the first titanium metal layer 2 passes through the second unwind roller 51, the first-stage cooling roller 52, the second-stage cooling roller 53 and the second winding roller 54 in sequence, and the second coating assembly 55 is arranged at the coating station for the second coating.

[0038] A method for preparing a composite film according to this embodiment sequentially includes the steps of: first unwind, first coating, semi-finished product winding, intermediate treatment, second unwind, second coating, final treatment and finished product winding. Among them, different tensions are applied during the two coatings, combined with the yield tensile force control of the base layer. Specifically, the applied tension F1 of the coil during the first coating satisfies 0.6F0 ≤ F1 ≤ 0.85F0; the applied tension F2 of the coil during the second coating satisfies 0.85F0 ≤ F2 ≤ 0.95F0; where F2 > F1, and F0 is the yield tensile force of the base layer. The elastic deformation range of the PET film is usually 50% - 90% of the yield tensile force F0. During the first coating, it is necessary to ensure that the PET film is in the elastic deformation range (F1 ≤ 0.85F0) to avoid the peeling of the first Ti film caused by plastic deformation. However, when F1 < 0.6F0, the coating adhesion drops by 20% - 30%; during the second coating, periodic cracks are generated in the first Ti film by a tension close to F0 (F2 ≤ 0.95F0), but when F2 > 0.95F0, the fracture rate of the PET film increases by 15%. Therefore, the above values of F1 and F2 balance the crack generation and the substrate stability.

[0039] When the stretching amount of the PET film during the second coating is greater than that during the first coating, cracks will appear on the surface of the first titanium metal layer 2, but the overall coil will not break, and the PET film is also within the elastic deformation range. At this time, when the second Ti film is coated, the second titanium metal layer 3 will cover the cracks that appear. When the produced composite film is subjected to a tensile force less than F0, the composite film will be stretched, but the resistance change of the composite film is very small, ensuring that within the elastic deformation range of the composite film, the resistance change is small.

[0040] Take a 10×5 cm titanium-coated PET composite film sample, divide it into a control group and an experimental group. The control group is a traditional double-layer titanium film without tension gradient control, and the experimental group uses a tension gradient control with F1 = 0.75F0 and F2 = 0.9F0. The initial resistivity is measured by the four-probe method, and the sample is subjected to 30 cycles of tensile tests. Each time, it is stretched to a 5% strain (lower than the strain corresponding to F0), held, and then released.

[0041] After each set of tensile cycles is completed, the resistivity is measured, and the resistance change rate is recorded. The initial resistivity of the control group is 2.8 Ω·cm, and it rises to 35 Ω·cm after 30 times of 5% stretching, with a change ratio of 12.5 times; it shows that the microcracks are not covered, and the cracks expand and the conduction loss is obvious after repeated stretching. The initial resistivity of the experimental group is 2.8 Ω·cm, and it rises to 15 Ω·cm after 30 times of 5% stretching, with a change of only 5.4 times; it shows that the second titanium metal layer 3 completely covers the cracks, the bridging is well formed, and the resistance increase is significantly reduced under repeated stretching.

[0042] At the coating station for the second coating, there is a temperature measurement module for real-time detection of the temperature of the coated surface of the coil. The temperature measurement module is an infrared temperature measurement module. The temperature compensation system calculates the yield tensile force F0 = F 0,ref ×[1 - α(T - T ref )], where α = 0.015 is the temperature sensitivity coefficient of the substrate, calibrated by DMA test; T ref = 23 °C is the reference temperature, and F 0,ref is the yield tensile force of the base layer measured at 23 °C according to ASTM D882 "Standard Test Method for Tensile Properties of Plastic Sheeting". Thus, the temperature compensation system can automatically adjust the upper limit of F2 to 0.95F0, and adjust the F0 value in real time through infrared temperature measurement, which can compensate for the change in the mechanical properties of the substrate caused by thermal expansion, improve the process stability, and ensure that regardless of how the temperature changes, it always meets the hard constraint of F2 ≤ 0.95F0.

[0043] During the second coating process, the dynamic tension control system adjusts the applied tension F2 in real time. The dynamic tension control system can monitor the deformation or tension change of the coil in real time, and dynamically adjust the unwinding / winding tension in combination with the closed-loop control algorithm to ensure the stability of the substrate during the coating process. Specifically, the dynamic tension control system includes a tension sensor, a laser displacement sensor, a control module, and a compensation module; among them, the tension sensor is installed between the second unwinding roller 51 and the second winding roller 54 to detect the real-time tension of the coil; the laser displacement sensor is used to measure the lateral deformation of the coil; the control module uses the fuzzy PID algorithm to dynamically adjust the servo motor speed according to the deformation and tension deviation. The servo motor is used to drive the second unwinding roller 51 and the second winding roller 54 to rotate, and adjust the applied tension through variable frequency speed regulation; the compensation module is used to correct the applied tension F 2new =F 2set ×[1 + β(T - T ref )], where F 2new is the corrected applied tension, F 2set is the original applied tension, and β is the thermal expansion coefficient of the substrate. Through the dynamic tension control system, the tension fluctuation can be reduced from ±5% to within ±1%, accurately controlling the local tension in the crack generation stage to ensure the periodic distribution of cracks; the dynamic feedback can prevent the tension overload fracture caused by the increased brittleness of the substrate in low-temperature environments; and the dynamic tension control system and the temperature compensation system can achieve multi-variable coupling control.

[0044] During the second coating, the cooling roller includes a first-stage cooling roller 52 and a second-stage cooling roller 53. The surface temperature of the first-stage cooling roller 52 is controlled at -10°C to 0°C, which is used to quickly cure the film layer, keep the PET below the glass transition temperature, and avoid the expansion of cracks or the peeling of the film layer due to thermal stress, thereby locking the size and distribution of the cracks; among them, the surface of the first-stage cooling roller 52 is chrome-plated, and the low temperature is maintained through liquid nitrogen circulation. The surface temperature of the second-stage cooling roller 53 is controlled at 5°C - 10°C, which is used to release the residual stress, can make the PET film slowly approach the equilibrium state without rebound deformation, and effectively improve the denseness and adhesion of the film; during the second coating, the temperature is reduced in stages and gradients, which is better than single normal temperature air cooling or rapid water cooling, can reduce the probability of film layer crack propagation and peeling, improve the interface bonding strength and electrical uniformity, and enhance the reliability of the composite film under flexibility and multiple deformations. At the same time, the coating assembly uses a radio frequency plasma generator, which can reduce the thermal energy required for sputtering, improve the mobility of Ti atoms, and compensate for the decrease in deposition efficiency caused by low temperature.

[0045] During the second coating, a floating roller is provided to compensate for the tension fluctuation and improve the film thickness uniformity.

[0046] The intermediate treatment includes annealing treatment or aging treatment.

[0047] The annealing treatment includes keeping the semi-finished coil at 80 °C for 30 min, cooling it at a rate of 0.5 °C / min to 60 °C and keeping it at 60 °C for 60 min, and then naturally cooling it to 40 °C. The optimal annealing range for PET is from above the glass transition temperature Tg (about 70 °C) to 110 °C. 80 °C can accelerate the rearrangement of molecular segments, improve the crystallinity (which can be increased by about 12% as measured by DSC), and improve the mechanical properties under high temperature / high stress. And long-time low-speed cooling (0.5 °C / min) can prevent shrinkage, warping or internal micro-cracks caused by excessive temperature difference. The holding at the 60 °C platform further releases the processing and residual stress of the first coating. Finally, natural cooling to 40 °C avoids the formation of thermal stress due to rapid cooling. After testing, the F0 of the annealed PET film only decreases by 8% at 60 °C, while that of the non-annealed sample decreases by 23%.

[0048] The aging treatment includes storing the semi-finished coil at 30 - 50 °C for 12 - 24 h to release stress. Since 30 - 50 °C is lower than the glass transition temperature Tg of PET, the micro-movement of molecular chains releases the residual stress without causing non-uniform recrystallization due to too high temperature. Among them, 12 h is the stress release threshold (DMA shows that the stress release rate reaches 90% after 12 h), and it tends to be balanced after 24 h.

[0049] The final treatment includes annealing treatment, which is used to release stress and increase the ductility and toughness of the finished coil. The annealing treatment here can adopt the existing technology or the treatment steps similar to the annealing treatment in the intermediate treatment, that is, keeping it at 80 °C for 30 min, cooling it at a rate of 0.5 °C / min to 60 °C and keeping it at 60 °C for 60 min, and then naturally cooling it to room temperature.

[0050] The sputtering power of the first coating is 3 - 5 W / cm². A lower sputtering power is adopted for the first coating to avoid substrate deformation or thermal damage caused by high temperature and high-energy sputtering, forming a thin and continuous first Ti film, which is beneficial to the controllability of subsequent crack formation. At the same time, it ensures that the first Ti film is dense, has good adhesion, and has a uniform thickness. If the power is lower than 3 W / cm², the first Ti film is too thin and has poor conductivity. If it is higher than 5 W / cm², it is easy to cause thermal damage and rough crystallization, affecting the interface quality.

[0051] The sputtering power of the second coating is 8 - 12 W / cm². A higher sputtering power is adopted for the second coating to increase the deposition rate, enhance the migration of metal atoms, fill and bridge the cracks in the first Ti film, form a complete bridging conductor structure, and improve the bridging density and on-off uniformity. If the power is higher than 12 W / cm², the risk of damage to the PET film increases. If it is lower than 8 W / cm², the bridging effect is not ideal.

[0052] A composite film is prepared by the above preparation method, as Figure 1 and Figure 2As shown, the composite film includes a base layer 1, a first titanium metal layer 2 and a second titanium metal layer 3 disposed on the same side of the base layer 1. The base layer 1 is PET. The first titanium metal layer 2 covers the base layer 1 and contains cracks 21, which may be wavy cracks 21 or trident micro-cracks as shown in Figure 2 ; The second titanium metal layer 3 covers the first titanium metal layer 2, completely covers the cracks 21 and forms a conductive bridging structure thereat.

[0053] In this embodiment, the metal Ti is in the form of ion plating. In this way, the side of the PET film facing the titanium plating assembly is the high-temperature area, and the side facing the cooling roller is the low-temperature area. The yield point tensile force of the PET film decreases as the temperature rises.

[0054] After the first layer of Ti plating is completed, the composite film is unwound again to plate the second layer of Ti on the first titanium metal layer 2. When performing the plating operation, it is necessary to make the deformation amount of the composite film during the secondary unwinding greater than that during the first unwinding. This will cause cracks 21 to appear in the first titanium metal layer 2, but the first titanium metal layer 2 will not be disconnected, that is, cracks 21 appear in the first titanium metal layer 2, but the first titanium metal layer 2 as a whole remains in a conductive state. At this time, the second layer of Ti film is plated on the composite film. When the second layer of Ti film covers the first titanium metal layer 2, it will cover the cracks 21 at the same time. In this way, the metal conductive layer of the plated composite film is a whole, and when it deforms within the elastic deformation range of the composite film, the two layers of Ti film are not likely to appear cracks, so that the resistance change of the composite film is not large.

[0055] Among them, when the composite film is unwound again, F2 > F1 and F0 > F2. In order to make the performance of the prepared composite film better, F2 should be as close as possible to 0.95F0 without the first titanium metal layer 2 being disconnected.

[0056] The present invention is not limited to the above optional embodiments. Anyone can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as the technical solutions fall within the scope defined by the claims of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for preparing a composite film, characterized in that, Including: The first unwinding, the first coating, the semi-finished product winding, the intermediate treatment, the second unwinding, the second coating and the finished product winding; During the first coating, the applied tension F1 of the coil material satisfies 0.6F0 ≤ F1 ≤ 0.85F0; During the second coating, the applied tension F2 of the coil material satisfies 0.85F0 ≤ F2 ≤ 0.95F0; Wherein, F2 > F1, and F0 is the yield tension of the base layer.

2. The preparation method according to claim 1, characterized in that: At the coating station for the second coating, a temperature measurement module is provided for real-time detection of the temperature of the coated surface of the coil. The temperature compensation system calculates the yield tensile force F0 = F 0,ref × [1 - α(T - T ref )], where α is the temperature sensitivity coefficient of the substrate, and T ref is the reference temperature, and F 0,ref is the yield tensile force of the base layer measured at the reference temperature.

3. The preparation method according to claim 2, characterized in that: During the second coating process, the dynamic tension control system adjusts the applied tension F2 in real time. The dynamic tension control system includes: A tension sensor for detecting the real-time tension of the coil material; A laser displacement sensor for measuring the lateral deformation of the coil material; A control module for dynamically adjusting the rotational speed of the servo motor according to the deformation and the tension deviation; Compensation module, used to correct the applied tension F according to the change rate of the unwinding and rewinding speed 2new =F 2set ×[1+β(T-T ref )], where F 2new is the corrected applied tension, F 2set is the original applied tension, and β is the coefficient of thermal expansion of the substrate.

4. The preparation method according to claim 1, characterized in that: During the second coating, the cooling roll includes a first-stage cooling roll and a second-stage cooling roll. The surface temperature of the first-stage cooling roll is controlled at -10°C to 0°C, and the surface temperature of the second-stage cooling roll is controlled at 5°C - 10°C. The coating assembly uses a radio frequency plasma generator.

5. The preparation method according to claim 1, wherein: The intermediate treatment includes annealing treatment or aging treatment.

6. The preparation method according to claim 5, characterized in that: The annealing treatment includes keeping the semi-finished product coil at 80°C for 30 minutes, cooling it at a rate of 0.5°C / min to 60°C and keeping it at 60°C for 60 minutes, and then naturally cooling it to 40°C.

7. The preparation method according to claim 5, characterized in that: The aging treatment includes storing the semi-finished product coil at 30 - 50°C for 12 - 24 hours to release stress.

8. The preparation method according to claim 1, characterized in that: The sputtering power of the first coating is 3 - 5 W / cm², and the sputtering power of the second coating is 8 - 12 W / cm².

9. A composite film, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. The composite film according to claim 9, characterized in that, The composite film includes: A base layer; A first titanium metal layer covering the base layer and containing cracks; A second titanium metal layer covering the first titanium metal layer, completely covering the cracks and forming a conductive bridging structure thereat.

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