Method for efficiently stripping polyimide film by laser

Abstract

The invention relates to a method for efficiently stripping a polyimide film by laser, which comprises the following steps of: adding a layer of porous polyamide acid film as a sacrificial layer between a substrate and the polyimide film, and then performing laser cutting and stripping. The sacrificial layer is prepared by the following steps: dissolving a fluorine-containing diamine monomer, a fluorine-free diamine monomer and a fluorine-containing dianhydride monomer in an aprotic solvent to prepare a polyamide acid solution, coating the polyamide acid solution on the surface of the glass substrate, placing the glass substrate in a coagulating bath for 2-3 hours to obtain a porous polyamide acid film, forming a substrate / porous polyamide acid film structure, and then preparing a polyimide film. A porous polyamide acid film is used as a sacrificial layer, and a laser beam interacts with a material, so that laser stripping can form a stable and intelligent heat treatment production line, the cutting and stripping speed of a polyimide film is increased, the stripping time is shortened, the stripping efficiency is improved, and the polyimide film is effectively removed from the surface of a substrate; and the integrity of the polyimide film is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cutting, peeling and heat treatment production, and particularly relates to a method for efficiently laser peeling polyimide films. Background Art

[0002] The development of flexible display technology is rapid, and the market demand for it is growing continuously. It is widely used in many fields such as smart phones, wearable devices, tablet computers, and foldable screen devices. Users expect products to have characteristics such as high resolution, high brightness, fast response, wide viewing angle, low power consumption, light weight, portability, foldability and curliness, durability and reliability. These demands have promoted the development of all aspects of flexible display technology, including continuous innovation and progress in materials, device structures, manufacturing processes, etc.

[0003] Polyimide materials have excellent properties such as high temperature resistance, good mechanical properties, good chemical stability, radiation resistance, and low dielectric constant, and are often used in flexible displays. Polyimide materials penetrate the substrate, packaging and peeling processes of flexible display devices, and their performance directly affects the flexibility, reliability and manufacturing cost of the devices.

[0004] Laser lift-off technology (LLO) is a key process in flexible display manufacturing. Its core function is to accurately separate the flexible display panel from the rigid mother glass substrate, while protecting the fragile circuit and light-emitting layer, and realizing the transfer of the flexible display device to the target flexible substrate to manufacture products such as flexible display screens. However, this technology also faces challenges in application: on the one hand, during the laser peeling process of polyimide materials, due to their own performance limitations (such as light absorption characteristics, heat conduction performance, etc.), problems such as incomplete peeling, interface residue, and damage to the functional layer may occur, affecting the performance and yield of flexible display devices; on the other hand, the laser peeling process parameters (such as laser wavelength, energy density, pulse width, scanning speed, etc.) need to be accurately controlled. Otherwise, problems such as damage to the functional layer of the display device, material ablation, and thermal deformation may occur due to excessive energy, or the peeling effect may be poor and the efficiency may be low due to insufficient energy. In addition, polyimide materials with different structures and properties have different adaptabilities to the laser peeling process, and it is necessary to deeply study the relationship between the two, optimize the matching of materials and processes, and improve the manufacturing quality and efficiency of flexible displays. Summary of the Invention

[0005] Based on the technical problems existing in the laser cutting and peeling of polyimide films in the prior art, the object of the present invention is to provide a method for laser peeling polyimide films, specifically using a porous polyamic acid film as a sacrificial layer, and by the interaction of a high-energy density laser beam with the material, realizing the complete peeling and removal of the polyimide film from the substrate, thereby solving the technical problems of the complex peeling method of polyimide films in the prior art, low peeling efficiency or damage to polyimide films.

[0006] The object of the present invention is achieved by the following technical solutions: A method for efficiently laser stripping a polyimide film, characterized in that: a porous polyamic acid film is added as a sacrificial layer between the substrate and the polyimide film, and then laser cutting and stripping are carried out. The specific steps are as follows: (1) A fluorinated diamine monomer, a non-fluorinated diamine monomer, and a fluorinated dianhydride monomer are dissolved in an aprotic solvent to form a precursor solution. Under an inert atmosphere, the solution is stirred in a water bath to obtain a polyamic acid solution; (2) The polyamic acid solution is coated on the surface of a glass substrate and placed in a coagulation bath for 2 - 3 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure; (3) The precursor solution for preparing the polyimide film is coated on the surface of the porous polyamic acid film, and annealing treatment is carried out to thermally imidize to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure; (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser, and the polyimide film is cut and stripped from the substrate by laser stripping technology.

[0007] Further, in the step (1), the molar ratio of the fluorinated diamine monomer, the non-fluorinated diamine monomer, and the fluorinated dianhydride monomer is 0.5 - 0.8 mol: 0.5 - 0.2 mol: 1 mol, and the solid content of the precursor solution is 12 - 18 wt%.

[0008] Further, in the step (1), the fluorinated diamine monomer is one or more of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 2,2'-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminooctafluorobiphenyl. Preferably, the fluorinated diamine monomer is TFMB. Further, in the step (1), the non-fluorinated aromatic diamine monomer is one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether (oda), 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane. Preferably, the non-fluorinated aromatic diamine monomer is ODA.

[0009] Further, in the step (1), the fluorinated dianhydride monomer is one or more of 4,4′-(hexafluoroisopropylidene) bisphthalic anhydride (6FDA), 2,2,3,3,4,4 - hexafluoroglutaric anhydride, 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride. Preferably, the fluorinated dianhydride monomer is 6FDA. Further, in the step (1), the aprotic solvent is one or more of DMF (N,N-dimethylformamide), DMAC (dimethylacetamide), NMP (N-methylpyrrolidone), DMSO (dimethyl sulfoxide), and THF (tetrahydrofuran). Preferably, the aprotic solvent is NMP. Further, in the step (1), the water bath stirring is to place the precursor solution in a water bath pot, heat it to 25~35°C, keep it warm and stir for 1~2 h, and then cool it to room temperature and stir for 10~18 h.

[0010] Further, in the step (2), the coating is spin coating, the spin coating speed is 900 - 1400 rpm, the spin coating time is 15~25 s, and the temperature of the glass substrate during spin coating is 40~45°C.

[0011] Further, in the step (2), the coagulation bath is formed by mixing an aprotic solvent, a surfactant, and water in a mass ratio of 35~45 g: 4~6 g: 55~65 g.

[0012] Further, in the step (2) coagulation bath, the surfactant is one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium stearate. Preferably, the surfactant used is sodium dodecyl sulfate.

[0013] Further, in the step (2) coagulation bath, the aprotic solvent is the same as the aprotic solvent in the step (1). Further, in the step (3), the annealing treatment is to cure at 50~60°C for 40~60 min, then heat up to 110~120°C for 40 min, heat up to 150~160°C for 40 min, heat up to 200~210°C for 40 min, heat up to 260~270°C for 40 min, and then cool to room temperature to complete the thermal imidization process.

[0014] Further, in the laser peeling, a laser beam with a wavelength of 450 nm and a laser energy density of 80 - 110 mJ / cm 2 is used for laser peeling.

[0015] Most specifically, a method for efficiently laser peeling a polyimide film, characterized by comprising the following steps: (1) Using fluorinated diamine monomer TFMB, non-fluorinated aromatic diamine monomer ODA, and fluorinated dianhydride monomer 6FDA dissolved in solvent NMP to form a precursor solution with a solid content of 12 - 18 wt%. Under an inert atmosphere, it is heated in a water bath to 25 - 35 °C and stirred at 200 - 250 rpm for 1 - 2 h, then cooled to room temperature and continuously stirred for 10 - 18 h to obtain a polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.5 - 0.8 mol: 0.2 - 0.5 mol: 1 mol; (2) Spin-coat the polyamic acid solution on the surface of a glass substrate and place it in a coagulation bath for 2 - 3 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1100 - 1900 rpm, and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 35 - 45 g: 4 - 6 g: 55 - 65 g; (3) Coating the precursor solution for preparing the polyimide film on the surface of the porous polyamic acid film, performing annealing treatment, and thermally imidizing to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 50 - 60 °C for 40 - 60 min, then raise the temperature to 110 - 120 °C and heat for 40 min, raise the temperature to 150 - 160 °C and heat for 40 min, raise the temperature to 200 - 210 °C and heat for 40 min, raise the temperature to 260 - 270 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process; (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser, and use a laser beam with a wavelength of 450 nm and a laser energy density of 80 - 110 mJ / cm 2 for laser cutting and peeling.

[0016] During the preparation of the sacrificial layer, since the raw material types of the sacrificial layer and polyimide are the same, if not well controlled, it will lead to a good bonding force between the sacrificial layer and the polyimide film, and more serious damage will be caused to the polyimide film during laser separation. And during the preparation process, due to the low flatness of the sacrificial layer, the flatness and thickness uniformity of the polyimide film on its surface are poor, thus reducing the performance of the polyimide film. In addition, usually, the thermal influence area in the green light band is large, which is likely to cause damage to the polyimide film.

[0017] The present invention performs spin coating with a specifically formulated polyamic acid solution, combined with an annealing treatment step with gradually increasing temperature. In the case of having a functional original film on its surface, the porous distribution and component structure distribution of the polyamic acid film are effectively adjusted. The porous structure of the porous polyamic acid film sacrificial layer has a large specific surface area. When irradiated by a laser beam, its absorption and scattering characteristics for a specific green light wavelength laser reach the optimum, better matching the laser source wavelength in actual applications, and being able to absorb laser energy more effectively. After the lower energy density laser energy is absorbed by the pore walls in the porous structure and the substances in the pores, it is reflected and scattered multiple times between the pore walls, increasing the residence time and action range of the energy inside the sacrificial layer, promoting the transfer of energy to the surrounding area, improving the energy utilization efficiency, enabling the sacrificial layer to reach the energy threshold required for peeling faster under the action of the laser, achieving efficient peeling, and at the same time reducing the damage of the laser to the polyimide film.

[0018] In addition, due to the differences in physical and chemical properties between the prepared porous polyamic acid film and the polyimide film. During laser irradiation, the physical changes such as thermal expansion and phase change of the sacrificial layer due to energy absorption are not synchronized with the adjacent polyimide film layer. This difference generates stress concentration at the interface. When the stress exceeds the interfacial bonding force, the sacrificial layer separates from the polyimide film, achieving selective peeling, avoiding unnecessary damage to other functional layers, and ensuring the performance integrity of the flexible display device. And under the action of laser energy, the polyamic acid film can undergo a thermal decomposition reaction. During the decomposition process, the chemical structure changes, the intermolecular force weakens, the material strength decreases, and it is more easily peeled off from the multilayer structure. The thermal decomposition products may have low adhesion or volatility, which helps the sacrificial layer to detach from the substrate or other layers, further promoting the peeling process and improving the peeling effect and efficiency.

[0019] The present invention has the following technical effects: Using the porous polyamic acid film as the sacrificial layer, through the interaction between a high energy density laser beam and the material, a stable and intelligent heat treatment production line for laser peeling is formed, improving the peeling speed of the polyimide film. While shortening the glass time, it has a stable peeling effect, high peeling efficiency, effectively removes the polyimide film from the substrate surface, and ensures the integrity and property stability of the removed polyimide film. Description of the Drawings

[0020] Figure 1 : Schematic cross-sectional view of the substrate / porous polyamic acid film / polyimide film stack in the present invention, 1 is the substrate, 2 is the sacrificial layer, and 3 is the polyimide film.

[0021] Figure 2: (a) Cross-sectional scanning electron microscope image of the unannealed sacrificial layer film prepared in Example 1 without the annealing process; (b) Cross-sectional scanning electron microscope image of the sacrificial layer film after the annealing process; (c) Cross-sectional scanning electron microscope image of the porous polyamic acid film after laser lift-off; (d) Cross-sectional scanning electron microscope image of the polyimide film after laser lift-off following annealing.

[0022] Figure 3 : Physical image of the porous polyamic acid film prepared in Example 1 through the coagulation bath.

[0023] Figure 4 : Physical images of the laminated structures of the pure polyimide film, the porous polyamic acid film / polyimide film prepared in Example 1, Comparative Example 1, and Comparative Example 2, (a) pure polyimide film; (b) Example 1; (c) Comparative Example 1; (d) Comparative Example 2.

[0024] Figure 5 : Time comparison diagram for complete laser lift-off from the glass substrate by Example 1, Comparative Example 1, and Comparative Example 2 at different laser densities. Detailed implementation mode

[0025] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0026] Example 1 A method for highly efficient laser lift-off of polyimide film, comprising the following steps: (1) Using a fluorinated diamine monomer as TFMB, a non-fluorinated aromatic diamine monomer as ODA, and a fluorinated dianhydride monomer as 6FDA, dissolved in the solvent NMP to form a precursor solution with a solid content of 12%. Under an inert atmosphere, water bath heat to 30 °C, stir at 200 rpm for 1.5 h, then cool to room temperature and continue stirring for 12 h to obtain a light yellow polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.7 mol: 0.3 mol: 1 mol; (2) Spin-coat the polyamic acid solution on the surface of a glass substrate at a temperature of 40 °C, and place it in a coagulation bath for 2.5 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1500 rpm, and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 40 g: 5 g: 60 g; (3) Coat a colorless precursor solution for preparing polyimide film (1.4332 g of 6FDA, 0.969 g of ODA, 1.5497 g of TFMB, and 50 g of NMP, stirred vigorously in an ice-water bath for 18 h under a nitrogen atmosphere) on the surface of the porous polyamic acid film, followed by annealing treatment. Through thermal imidization, a polyimide film is obtained, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 55 °C for 50 min, then raise the temperature to 115 °C and heat for 40 min, raise the temperature to 155 °C and heat for 40 min, raise the temperature to 205 °C and heat for 40 min, raise the temperature to 265 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process, obtaining a substrate / porous polyamic acid film / polyimide film structure; (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser, and use a laser beam with a wavelength of 450 nm and a laser energy density of 90 mJ / cm 2 for laser cutting and peeling, with a laser moving speed of 0.5 mm / s.

[0027] In Example 1, the thickness of the sacrificial layer of the porous polyamic acid film is 160 μm, the total peeling time is 71 min, and there is no residual polyimide film on the surface of the substrate after peeling, and the integrity of the polyimide film is excellent. Figure 2 In (a) is the scanning electron microscope image of the unannealed porous polyamic acid film prepared on the substrate in Example 1. It can be seen that obvious pore structures with different pore sizes are formed in the film. (b) is the cross-sectional scanning electron microscope image after annealing. It can be seen that after annealing, the pore size structure has changed significantly. (c) is the electron microscope image of the porous polyamic acid film after laser peeling. It can be seen that the laser treatment causes the sacrificial layer to absorb laser energy, resulting in an increase in air holes and the peeling of the air holes due to rupture. (d) After laser peeling, the polyimide film has excellent integrity and no obvious damage.

[0028] Experiment (1) By adjusting the spin-coating time of the sacrificial layer, sacrificial layers with equal area and different thicknesses are obtained, and then polyimide films with equal area and equal thickness are prepared to detect the influence of the sacrificial layer thickness on the laser peeling of the polyimide film. The peeling efficiency refers to the proportion of the intact and undamaged films in each group of polyimide films obtained by laser peeling (100 parts in each group). Here, intact and undamaged means that the residual rate (thickness residue) of the polyimide film on the substrate after peeling is less than 10 nm, and the thermal damage (edge heat-affected zone) of the film is <100 nm. The results are shown in Table 1.

[0029] Table 1:

[0030] Under the same laser treatment, with the change of the sacrificial layer thickness, there are obvious differences in the peeling time of the polyimide film. When the spin coating rate is 1100 - 1900 rpm, the obtained sacrificial layer thickness is 135 - 195 μm. The film peeling time significantly shortens with the increase of the sacrificial layer thickness, and a high peeling efficiency is maintained. When the spin coating thickness is relatively thick, due to the unsatisfactory effect of the annealing process on the pore and component distribution of the sacrificial layer, the utilization rate of laser energy during laser treatment decreases, resulting in a significant increase in the peeling time and a decrease in the peeling efficiency. When the sacrificial layer thickness is small, although the peeling time decreases, the relatively thin sacrificial layer is also completely imidized under the annealing process, and the bonding force with the polyimide film is significantly improved, which cannot reduce the peeling damage but will instead have a counter - effect, leading to a decrease in the peeling efficiency.

[0031] Experiment (2) By adjusting the components of the polyamic acid solution for preparing the sacrificial layer (in the table, the fluorinated diamine monomer TFMB is denoted as 'T', the non - fluorinated aromatic diamine monomer ODA is denoted as 'O', the fluorinated dianhydride monomer 6FDA is denoted as 'F', and the solid content of the solution is maintained at 12 wt%), a sacrificial layer with the same thickness as that in Example 1 is obtained, and the influence of the sacrificial layer components on the laser peeling of the same polyimide film is detected. The results are shown in Table 2.

[0032] Table 2:

[0033] It can be seen that as the proportion of TFMB in the components of the polyamic acid solution for preparing the sacrificial layer gradually decreases, the laser peeling time of the polyimide film first shortens and then prolongs, and the peeling efficiency of the same polyimide film basically shows a gradually decreasing trend. And when the ratio of TFMB to ODA is lower than 1:1, the peeling efficiency of the polyimide film significantly decreases, and at this time, the damage to the polyimide film is relatively serious. When there is no ODA in the polyamic acid solution, although its peeling time is the shortest, the peeling efficiency is not ideal. When there is no TFMB in the polyamic acid solution, the peeling time is longer, and the damage to the polyimide film is also relatively obvious.

[0034] Comparative Example 1 Compared with Example 1, the annealing process is as follows: Cure at 55 °C for 50 min, then heat to 115 °C for 30 min, heat to 145 °C for 30 min, heat to 175 °C for 30 min, heat to 205 °C for 30 min, heat to 235 °C for 30 min, heat to 265 °C for 30 min, and then cool to room temperature to complete the thermal imidization process, obtaining the substrate / porous polyamic acid film / polyimide film structure.

[0035] Compared with Example 1, in Comparative Example 1, the temperature rising section was increased, changing from the original 4-stage temperature rising to 6-stage temperature rising. The temperature interval for each stage of temperature rising was 30 °C, and the heating time for each stage of temperature was shortened.

[0036] Comparative Example 2 Compared with Example 1, the annealing process is as follows: Cure at 55 °C for 50 min each, then heat up to 115 °C and heat for 40 min, heat up to 165 °C and heat for 40 min, heat up to 215 °C and heat for 40 min, heat up to 265 °C and heat for 40 min, and then cool down to room temperature to complete the thermal imidization process, obtaining a substrate / porous polyamic acid film / polyimide film structure.

[0037] Compared with Example 1, in Comparative Example 1, the temperature rising section was increased, maintaining the original 4-stage temperature rising, but the temperature interval for each stage of temperature rising was 50 °C.

[0038] Figure 3 This is the porous polyamic acid film prepared on the surface of the substrate in the present invention. Figure 4 It is the polyimide film prepared on the surface of the pure substrate, as well as the substrate / porous polyamic acid film / polyimide film structures prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0039] Experiment (3) Through the different annealing procedures of Example 1 and Comparative Example 1, a substrate / porous polyamic acid film / polyimide film structure was prepared, and the effect of annealing on the sacrificial layer was detected, and finally the influence on the laser lift-off of the polyimide film. The results are shown in Table 3.

[0040] Table 3:

[0041] It can be seen that after more segmented temperature rising annealing treatment in Comparative Example 1, it has an obvious effect on the sacrificial layer structure, resulting in a longer lift-off time in laser lift-off and a significant decrease in the lift-off efficiency of the polyimide film. In Comparative Example 2, the temperature interval for temperature rising is constant at 50 °C, and the lift-off time is longer in laser lift-off, and the lift-off efficiency of the polyimide film further decreases. In the present invention, through 4-stage segmented temperature rising, and the temperature interval for each stage of temperature rising increases step by step.

[0042] The substrate / porous polyamic acid film / polyimide film structures prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to laser lift-off at different laser densities, and the comparison of lift-off times is as Figure 5As shown, as the laser density increases, the peeling time of the polyimide film becomes shorter. However, in Example 1 compared with Comparative Example 1 and Comparative Example 2, as the laser density increases, the peeling time decreases more significantly. This is because different annealing processes have different effects on the sacrificial layer structure, resulting in differences in the final utilization rate of laser energy.

[0043] Example 2 A method for efficiently laser-peeling a polyimide film, comprising the following steps: (1) Using a fluorinated diamine monomer as TFMB, a non-fluorinated aromatic diamine monomer as ODA, and a fluorinated dianhydride monomer as 6FDA, dissolve them in a solvent NMP to form a precursor solution with a solid content of 18 wt%. Under an inert atmosphere, heat it in a water bath to 25°C and stir at 240 rpm for 1 h. Then cool it to room temperature and continue stirring for 18 h to obtain a polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.8 mol: 0.5 mol: 1 mol; (2) Spin-coat the polyamic acid solution on the surface of a glass substrate at a temperature of 45°C and place it in a coagulation bath for 3 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1100 - 1900 rpm, and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 45 g: 6 g: 55 g; (3) Coat the precursor solution for preparing the polyimide film (under a nitrogen atmosphere, 1.4332 g of 6FDA, 0.969 g of ODA, 1.5497 g of TFMB, 50 g of NMP, and stir vigorously in an ice-water bath for 18 h) on the surface of the porous polyamic acid film, carry out annealing treatment, and thermally imidize to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 50°C for 60 min, then raise the temperature to 120°C and heat for 40 min, raise the temperature to 160°C and heat for 40 min, raise the temperature to 210°C and heat for 40 min, raise the temperature to 270°C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process and obtain a substrate / porous polyamic acid film / polyimide film structure; (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser, and use a laser beam with a wavelength of 450 nm and a laser energy density of 110 mJ / cm 2 to perform laser cutting and peeling, and the laser moving speed is 0.5 mm / s.

[0044] Example 3 A method for efficiently laser-peeling a polyimide film, comprising the following steps: (1) A precursor solution with a solid content of 15 wt% is prepared by dissolving a fluorinated diamine monomer TFMB, a non-fluorinated aromatic diamine monomer ODA, and a fluorinated dianhydride monomer 6FDA in a solvent NMP. Under an inert atmosphere, it is heated in a water bath to 20 °C and stirred at 250 rpm for 2 h, then cooled to room temperature and stirred for another 10 h to obtain a polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.5 mol: 0.2 mol: 1 mol; (2) The polyamic acid solution is spin-coated on the surface of a glass substrate at a temperature of 40 °C and placed in a coagulation bath for 2 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1100 - 1900 rpm, and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 35 g: 4 g: 65 g; (3) The precursor solution for preparing the polyimide film (1.4332 g of 6FDA, 0.969 g of ODA, 1.5497 g of TFMB, 50 g of NMP, and stirred vigorously in an ice-water bath for 18 h under a nitrogen atmosphere) is coated on the surface of the porous polyamic acid film, followed by annealing treatment and thermal imidization to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 60 °C for 40 min, then raise the temperature to 110 °C and heat for 40 min, raise the temperature to 150 °C and heat for 40 min, raise the temperature to 200 °C and heat for 40 min, raise the temperature to 260 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure; (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser, and a laser beam with a wavelength of 450 nm and a laser energy density of 80 mJ / cm 2 is used for laser cutting and peeling, and the laser moving speed is 0.5 mm / s.

[0045] The above examples belong to the small-scale test stage. Therefore, the laser used is a picosecond laser, and the laser moving rate is 0.5 mm / s. In order to study whether the sacrificial layer in the present invention can also play a corresponding role when facing a faster laser moving rate in actual industrial production, we tried to use an industrial excimer laser for laser peeling (the laser moving rate is 200 mm / s).

[0046] Example 4 A method for highly efficient laser peeling of polyimide films, comprising the following steps: (1) Using a fluorinated diamine monomer as TFMB, a non-fluorinated aromatic diamine monomer as ODA, and a fluorinated dianhydride monomer as 6FDA, dissolve them in a solvent NMP to form a precursor solution with a solid content of 12%. Under an inert atmosphere, heat it in a water bath to 30 °C, stir at 200 rpm for 1.5 h, then cool to room temperature and continue stirring for 12 h to obtain a pale yellow polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.7 mol: 0.3 mol: 1 mol; (2) Spin-coat the polyamic acid solution on the surface of a glass substrate at a temperature of 40 °C and place it in a coagulation bath for 2.5 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1500 rpm and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 40 g: 5 g: 60 g; (3) Coat a colorless precursor solution for preparing a polyimide film (under a nitrogen atmosphere, 1.4332 g of 6FDA, 0.969 g of ODA, 1.5497 g of TFMB, 50 g of NMP, and stir vigorously in an ice-water bath for 18 h) on the surface of the porous polyamic acid film, carry out annealing treatment, and thermally imidize to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 55 °C for 50 min each, then raise the temperature to 115 °C and heat for 40 min, raise the temperature to 155 °C and heat for 40 min, raise the temperature to 205 °C and heat for 40 min, raise the temperature to 265 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process and obtain a substrate / porous polyamic acid film / polyimide film structure; (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser, and use a laser beam with a wavelength of 450 nm and a laser energy density of 90 mJ / cm 2 for laser cutting and peeling, and the laser moving speed is 200 mm / s.

[0047] By adjusting the composition of the polyamic acid solution for preparing the sacrificial layer to when there is no TFMB and when there is no ODA (the solid content of the solution remains 12 wt%), a sacrificial layer with the same thickness as that in Example 4 is obtained, and the influence of the sacrificial layer composition on the laser peeling of the polyimide film with the same thickness and the same area on the surface of the sacrificial layer is detected. The results are shown in Table 4.

[0048] Table 4:

[0049] It can be seen that when the components of the polyamic acid solution for preparing the sacrificial layer are without TFMB and without ODA, compared with Example 4, the influence trends on the stripping time and the stripping efficiency of the polyimide film are consistent with those in the small-scale test, indicating that the sacrificial layer prepared by the specific components in the present invention can effectively reduce the stripping time, improve the stripping efficiency of the film, and reduce the damage to the film during the stripping process when laser-stripping the polyimide film.

[0050] Comparative Example 3 Compared with Example 4, the annealing process is as follows: Cure at 55°C for 50 min each, then raise the temperature to 115°C and heat for 30 min, raise the temperature to 145°C and heat for 30 min, raise the temperature to 175°C and heat for 30 min, raise the temperature to 205°C and heat for 30 min, raise the temperature to 235°C and heat for 30 min, raise the temperature to 265°C and heat for 30 min, and then cool to room temperature to complete the thermal imidization process, obtaining a substrate / porous polyamic acid film / polyimide film structure.

[0051] Compared with Example 4, Comparative Example 3 increases the temperature rising segments, changing from the original 4 segments of temperature rising to 6 segments of temperature rising, with each segment of temperature rising by 30°C, and shortening the heating time of each segment of temperature.

[0052] Comparative Example 4 Compared with Example 4, the annealing process is as follows: Cure at 55°C for 50 min each, then raise the temperature to 115°C and heat for 40 min, raise the temperature to 165°C and heat for 40 min, raise the temperature to 215°C and heat for 40 min, raise the temperature to 265°C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process, obtaining a substrate / porous polyamic acid film / polyimide film structure.

[0053] Compared with Example 4, Comparative Example 1 increases the temperature rising segments, maintaining the original 4 segments of temperature rising, but the temperature interval for each segment of temperature rising is 50°C.

[0054] Through the different annealing procedures of Example 1 and Comparative Example 1, a substrate / porous polyamic acid film / polyimide film structure is prepared, and the effect of annealing on the sacrificial layer and finally the influence on the laser stripping of the polyimide film are detected. The results are shown in Table 5.

[0055] Table 5:

[0056] It can be seen that at a relatively high laser moving speed, the trends of the peeling time and peeling efficiency of the polyimide film in Example 4, Comparative Example 3, and Comparative Example 4 are consistent with those of Example 1, Comparative Example 1, and Comparative Example 2 in the small-scale test. This shows that at a high industrial laser moving rate, the specific sacrificial layer prepared in the present invention can also effectively reduce the peeling time during the laser peeling process, while improving the peeling efficiency and reducing the damage to the polyimide film during the peeling process.

Claims

1. A method for efficiently laser-stripping a polyimide film, characterized in that: A porous polyamic acid film is added as a sacrificial layer between the substrate and the polyimide film, and then laser cutting and peeling are carried out. The specific steps are as follows: (1) A fluorinated diamine monomer, a non-fluorinated diamine monomer, and a fluorinated dianhydride monomer are dissolved in an aprotic solvent to form a precursor solution. Under an inert atmosphere, the solution is stirred in a water bath to obtain a polyamic acid solution; (2) The polyamic acid solution is coated on the surface of a glass substrate and placed in a coagulation bath for 2 - 3 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure; (3) The precursor solution for preparing the polyimide film is coated on the surface of the porous polyamic acid film, and annealing treatment is carried out to obtain a polyimide film by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure; (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser, and the polyimide film is cut and peeled off from the substrate by laser peeling technology.

2. The method for highly efficient laser stripping of polyimide film as described in claim 1, characterized in that: In the step (1), the molar ratio of the fluorinated diamine monomer, the non-fluorinated diamine monomer, and the fluorinated dianhydride monomer is 0.5 - 0.8 mol: 0.5 - 0.2 mol: 1 mol, and the solid content of the precursor solution is 12 - 18 wt%.

3. A method for laser lift-off of a polyimide film using a porous polyamic acid film as a sacrificial layer according to claim 1 or 2, characterized in that: In the step (1), the fluorinated diamine monomer is at least one of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 2,2'-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminooctafluorobiphenyl; the non-fluorinated aromatic diamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether (oda), 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane; the fluorinated dianhydride monomer is at least one of 4,4′-(hexafluoroisopropylidene) bisphthalic anhydride (6FDA), 2,2,3,3,4,4-hexafluoroglutaric anhydride, 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride, and the aprotic solvent is at least one of DMF (N,N-dimethylformamide), DMAC (dimethylacetamide), NMP (N-methylpyrrolidone), DMSO (dimethyl sulfoxide), and THF (tetrahydrofuran).

4. A method for efficiently laser stripping a polyimide film according to any one of claims 1-3, characterized in that: In the step (1), the water bath stirring is to heat the precursor solution in a water bath to 25 - 35 °C, keep it warm and stir for 1 - 2 h, and then cool it to room temperature and stir for 10 - 18 h.

5. The method for efficiently laser stripping a polyimide film according to claim 4, characterized in that: In the step (2), the coating is spin coating, the spin coating speed is 900 - 1400 rpm, and the spin coating time is 15 - 25 s.

6. The method for efficiently laser-stripping a polyimide film according to claim 4 or 5, characterized in that: In the step (2), the coagulation bath is formed by mixing an aprotic solvent, a surfactant, and water in a mass ratio of 35 - 45 g: 4 - 6 g: 55 - 65 g.

7. A method for efficiently laser stripping a polyimide film according to any one of claims 4-6, characterized in that: In the coagulation bath of the step (2), the surfactant is one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium stearate. Preferably, the surfactant used is sodium dodecyl sulfate.

8. The method for efficiently laser-stripping a polyimide film according to claim 7, wherein: In step (3), the annealing treatment is to cure at 50-60 °C for 40-60 min, then heat to 110-120 °C and heat for 40 min, heat to 150-160 °C and heat for 40 min, heat to 200-210 °C and heat for 40 min, heat to 260-270 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process, thereby obtaining a polyimide film.

9. The method for efficiently laser stripping a polyimide film according to claim 8, characterized in that: In the laser lift-off process, a laser beam with a wavelength of 450 nm and a laser energy density of 80 - 110 mJ / cm 2 is used for laser lift-off.

10. A method for efficiently laser-stripping a polyimide film, characterized in that, It includes the following steps: (1) Using a fluorinated diamine monomer as TFMB, a non-fluorinated aromatic diamine monomer as ODA, and a fluorinated dianhydride monomer as 6FDA, dissolve them in a solvent NMP to form a precursor solution with a solid content of 12-18 wt%. Under an inert atmosphere, heat in a water bath to 25-35 °C, stir at 200-250 rpm for 1-2 h, then cool to room temperature and continue to stir for 10-18 h to obtain a polyamic acid solution. The molar ratio of the fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer is 0.5-0.8 mol: 0.2-0.5 mol: 1 mol; (2) Spin-coat the polyamic acid solution on the surface of a glass substrate and place it in a coagulation bath for 2-3 h to obtain a porous polyamic acid film, forming a substrate / porous polyamic acid film structure. The spin-coating speed is 1100-1900 rpm, and the spin-coating time is 60 s. The coagulation bath is formed by mixing NMP, sodium dodecyl sulfate, and water in a mass ratio of 35-45 g: 4-6 g: 55-65 g; (3) Coat the precursor solution for preparing the polyimide film on the surface of the porous polyamic acid film, perform annealing treatment, and thermally imidize to obtain a polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment is to cure at 50-60 °C for 40-60 min, then heat to 110-120 °C and heat for 40 min, heat to 150-160 °C and heat for 40 min, heat to 200-210 °C and heat for 40 min, heat to 260-270 °C and heat for 40 min, and then cool to room temperature to complete the thermal imidization process; (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser, and use a laser beam with a wavelength of 450 nm and a laser energy density of 80 - 110 mJ / cm 2 for laser cutting and peeling.

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