Method for efficiently laser stripping polyimide film

Abstract

The present application relates to a kind of high-efficiency laser stripping polyimide film method, increase a layer of porous polyamide acid film between substrate and polyimide film as sacrificial layer, then carry out laser cutting stripping, sacrificial layer is prepared polyamide acid solution by fluorine-containing diamine monomer, non-fluorine-containing diamine monomer and fluorine-containing dianhydride monomer are dissolved in aprotic solvent, polyamide acid solution is coated on the surface of glass substrate, placed in coagulation bath 2~3h obtain porous polyamide acid film, form substrate / porous polyamide acid film structure, then prepare polyimide film.Porous polyamide acid film is used as sacrificial layer, by laser beam and material interaction, so that laser stripping can form stable intelligent heat treatment production line, improve the cutting stripping speed of polyimide film, stripping time is shortened, stripping efficiency is improved, effectively remove polyimide film from the surface of substrate, and ensure the integrity of polyimide film.

Description

Technical Field

[0001] This invention relates to the field of laser cutting, peeling, and heat treatment production technology, and specifically to a method for efficient laser peeling of polyimide films. Background Technology

[0002] Flexible display technology is developing rapidly, and market demand for it is constantly growing. It is widely used in many fields such as smartphones, wearable devices, tablets, and foldable screen devices. Users expect products to have features such as high resolution, high brightness, fast response, wide viewing angle, low power consumption, thinness and portability, foldability, durability and reliability. These demands have driven the development of all aspects of flexible display technology, including continuous innovation and progress in materials, device structure, and manufacturing processes.

[0003] Polyimide materials possess excellent properties such as high temperature resistance, good mechanical properties, good chemical stability, radiation resistance, and low dielectric constant, and are commonly used in flexible displays. Polyimide materials are used throughout the substrate, encapsulation, and peeling processes of flexible display devices, and their performance directly affects the device's flexibility, reliability, and manufacturing cost.

[0004] Laser lift-off (LLO) is a key process in flexible display manufacturing. Its core function is to precisely separate the flexible display panel from the rigid mother glass substrate while protecting the fragile circuitry and light-emitting layer, enabling the transfer of flexible display devices onto a target flexible substrate to manufacture flexible displays and other products. However, this technology faces challenges in application: on the one hand, due to inherent limitations in its properties (such as light absorption characteristics and thermal conductivity), polyimide materials may experience incomplete lift-off, interface residues, and damage to functional layers during laser lift-off, affecting the performance and yield of flexible display devices. On the other hand, laser lift-off process parameters (such as laser wavelength, energy density, pulse width, and scanning speed) need precise control; otherwise, excessive energy may lead to damage to the functional layers of the display device, material ablation, and thermal deformation, while insufficient energy may result in poor lift-off effect and low efficiency. Furthermore, different polyimide materials with varying structures and properties exhibit different adaptability to the laser lift-off process, requiring in-depth research into the relationship between the two to optimize material and process matching and improve the quality and efficiency of flexible display manufacturing. Summary of the Invention

[0005] Based on the technical problems of laser cutting and peeling of polyimide films in the existing technology, the purpose of this invention is to provide a laser peeling method for polyimide films. Specifically, a porous polyamic acid film is used as a sacrificial layer, and the polyimide film is completely peeled off from the substrate by the interaction between a high-energy-density laser beam and the material. This solves the technical problems of existing polyimide film peeling methods being complex, having low peeling efficiency, or damaging the polyimide film.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for efficient laser peeling of polyimide films is characterized by: adding a porous polyamic acid film as a sacrificial layer between the substrate and the polyimide film before laser cutting and peeling; the specific steps are as follows:

[0008] (1) Fluorinated diamine monomer, non-fluorinated diamine monomer and fluorinated dianhydride monomer are dissolved in an aprotic solvent to form a precursor solution, and polyamic acid solution is obtained by stirring in a water bath under an inert atmosphere.

[0009] (2) Coating the surface of a glass substrate with a polyamic acid solution and placing it in a coagulation bath for 2-3 hours results in a porous polyamic acid film, forming a substrate / porous polyamic acid film structure.

[0010] (3) The precursor liquid used to prepare the polyimide film is coated on the surface of the porous polyamic acid film, annealed, and thermally imidized to obtain the polyimide film, forming a substrate / porous polyamic acid film / polyimide film structure.

[0011] (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser and cut and peel the polyimide film off the substrate using laser ablation technology.

[0012] Furthermore, in step (1), the molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer and 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%.

[0013] Further, in 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, and 4,4'-diaminooctafluorobiphenyl. Preferably, the fluorinated diamine monomer is TFMB.

[0014] Further, in step (1), the unfluorinated 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, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane. Preferably, the unfluorinated aromatic diamine monomer is ODA.

[0015] Further, in step (1), the fluorinated diamine monomer is one or more of 4,4′-(hexafluoroisopropylidene) bisphthalic anhydride (6FDA), 2,2,3,3,4,4-hexafluoroglutaric anhydride, and 9,9-bis(trifluoromethyl)oxanthracene-2,3,6,7-tetracarboxylic dianhydride. Preferably, the fluorinated dianhydride monomer is 6FDA.

[0016] Furthermore, in 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 NMP.

[0017] Furthermore, in step (1), the water bath stirring involves placing the precursor liquid in a water bath and heating it to 25-35°C, stirring it for 1-2 hours, and then cooling it to room temperature and stirring it for 10-18 hours.

[0018] Furthermore, in 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 is 40-45℃ during spin coating.

[0019] Furthermore, the coagulation bath in step (2) is formed by mixing aprotic solvent, surfactant and water in a mass ratio of 35~45g:4~6g:55~65g.

[0020] Furthermore, in the coagulation bath of step (2), the surfactant is one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, or sodium stearate. Preferably, the surfactant used is sodium dodecyl sulfate.

[0021] Furthermore, in the coagulation bath of step (2), the aprotic solvent is the same as that in step (1).

[0022] Furthermore, in step (3), the annealing process is to cure at 50~60℃ for 40~60min, then heat to 110~120℃ for 40min, heat to 150~160℃ for 40min, heat to 200~210℃ for 40min, heat to 260~270℃ for 40min, and then cool to room temperature to complete the thermal imidization process.

[0023] Furthermore, the laser ablation process uses a wavelength of 450 nm and a laser energy density of 80-110 mJ / cm². 2 Laser beams are used for laser stripping.

[0024] Most specifically, a method for efficient laser exfoliation of polyimide films is characterized by comprising the following steps:

[0025] (1) A precursor solution with a solid content of 12-18 wt% was prepared by dissolving TFMB (a fluorinated diamine monomer), ODA (a non-fluorinated aromatic diamine monomer), and 6FDA (a fluorinated dianhydride monomer) in NMP solvent. The solution was heated to 25-35°C in a water bath under an inert atmosphere and stirred at 200-250 rpm for 1-2 h. The solution was then cooled to room temperature and stirred for another 10-18 h to obtain a polyamic acid solution. The molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer was 0.5-0.8 mol: 0.2-0.5 mol: 1 mol.

[0026] (2) Spin-coating a polyamic acid solution onto the surface of a glass substrate and placing it in a coagulation bath for 2-3 hours to form a porous polyamic acid film, thereby 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.

[0027] (3) The precursor liquid for preparing the polyimide film is coated on the surface of the porous polyamic acid film and annealed. The polyimide film is obtained by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing process is to cure at 50~60℃ for 40~60min, then heat to 110~120℃ for 40min, heat to 150~160℃ for 40min, heat to 200~210℃ for 40min, heat to 260~270℃ for 40min, and then cool to room temperature to complete the thermal imidization process.

[0028] (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser with a wavelength of 450 nm and a laser energy density of 80-110 mJ / cm². 2 The laser beam is used for laser cutting and peeling.

[0029] During the preparation of the sacrificial layer, since the raw materials for both the sacrificial layer and the polyimide are the same, improper control can lead to a strong bond between the sacrificial layer and the polyimide film. This can cause more severe damage to the polyimide film during laser separation. Furthermore, poor flatness of the sacrificial layer during preparation can result in poor flatness and thickness uniformity of the polyimide film on its surface, thus reducing the performance of the polyimide film. In addition, the heat-affected zone in the green light band is typically large, making it prone to damage to the polyimide film.

[0030] This invention utilizes a specifically formulated polyamic acid solution for spin coating, combined with a step-by-step annealing process with progressively increasing temperatures. This effectively regulates the porous distribution and component structure of the polyamic acid film while maintaining a functional pre-film on its surface. The porous structure of the sacrificial layer in the porous polyamic acid film provides a large specific surface area, optimizing its absorption and scattering characteristics for a specific green wavelength laser during irradiation. This better matches the laser source wavelength used in practical applications, enabling more efficient absorption of laser energy. The relatively low energy density laser energy is absorbed by the pore walls and the material within the pores, undergoing multiple reflections and scatterings between the pore walls. This increases the energy residence time and range of action within the sacrificial layer, promoting energy transfer to the surrounding area and improving energy utilization efficiency. This allows the sacrificial layer to reach the required energy threshold for peeling more quickly under laser irradiation, achieving efficient peeling while simultaneously reducing laser damage to the polyimide film.

[0031] Furthermore, due to the differences in physicochemical properties between the prepared porous polyamic acid film and the polyimide film, the physical changes of the sacrificial layer during laser irradiation, such as thermal expansion and phase transition due to energy absorption, are asynchronous with those of the adjacent polyimide film layer. This difference leads to stress concentration at the interface. When the stress exceeds the interfacial bonding force, the sacrificial layer separates from the polyimide film, achieving selective peeling and avoiding unnecessary damage to other functional layers, thus ensuring the integrity of the flexible display device's performance. Moreover, 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 forces weaken, and the material strength decreases, making it easier to peel off from the multilayer structure. The thermal decomposition products may have low adhesion or volatility, which helps the sacrificial layer detach from the substrate or other layers, further promoting the peeling process and improving the peeling effect and efficiency.

[0032] The present invention has the following technical effects:

[0033] Using a porous polyamic acid film as a sacrificial layer, a high-energy-density laser beam interacts with the material to form a stable and intelligent heat treatment production line for laser ablation. This improves the ablation speed of the polyimide film, shortens the glass removal time, and achieves a stable ablation effect with high ablation efficiency. It effectively removes the polyimide film from the substrate surface and ensures the integrity and property stability of the removed polyimide film. Attached Figure Description

[0034] Figure 1 : A schematic diagram of the cross-section of the substrate / porous polyamic acid film / polyimide film stack in this invention, where 1 is the substrate, 2 is the sacrificial layer, and 3 is the polyimide film.

[0035] Figure 2(a) Scanning electron microscope (SEM) image of the cross-section of the unannealed sacrificial layer film prepared in Example 1; (b) Scanning electron microscope (SEM) image of the cross-section of the sacrificial layer film after annealing; (c) Scanning electron microscope (SEM) image of the cross-section of the porous polyamic acid film after laser exfoliation; (d) Scanning electron microscope (SEM) image of the cross-section of the polyimide film after annealing and laser exfoliation.

[0036] Figure 3 Example 1: A physical image of the porous polyamic acid film prepared by coagulation bath.

[0037] Figure 4 Physical images of the porous polyamic acid film / polyimide film stacked structures 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.

[0038] Figure 5 Comparison chart showing the time it takes for Example 1, Comparative Example 1, and Comparative Example 2 to achieve complete peeling from the glass substrate using laser at different laser densities. Detailed Implementation

[0039] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection 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 description.

[0040] Example 1

[0041] A method for efficient laser exfoliation of polyimide films includes the following steps:

[0042] (1) A precursor solution with a solid content of 12% was prepared by dissolving TFMB (fluorinated diamine monomer), ODA (non-fluorinated aromatic diamine monomer), and 6FDA (fluorinated dianhydride monomer) in NMP solvent. The solution was heated to 30°C in a water bath under an inert atmosphere and stirred at 200 rpm for 1.5 h. Then it was cooled to room temperature and stirred for another 12 h to obtain a pale yellow polyamic acid solution. The molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer was 0.7 mol: 0.3 mol: 1 mol.

[0043] (2) A polyamic acid solution is spin-coated onto the surface of a glass substrate at a temperature of 40°C and placed in a coagulation bath for 2.5 h to form a porous polyamic acid film, thereby 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.

[0044] (3) A colorless precursor solution (6FDA 1.4332g, ODA 0.969g, TFMB 1.5497g, NMP 50g, stirred vigorously in an ice-water bath for 18h under a nitrogen atmosphere) was coated on the surface of a porous polyamic acid film and subjected to annealing treatment. The polyimide film was obtained by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing treatment was performed by curing at 55°C for 50min, then heating at 115°C for 40min, heating at 155°C for 40min, heating at 205°C for 40min, heating at 265°C for 40min, and then cooling to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0045] (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser with a wavelength of 450 nm and a laser energy density of 90 mJ / cm². 2 The laser beam is used for laser cutting and peeling, and the laser moving speed is 0.5 mm / s.

[0046] The porous polyamic acid film prepared in Example 1 has a sacrificial layer thickness of 160 μm and a total peeling time of 71 min. No polyimide film residue was found on the substrate surface after peeling, indicating excellent polyimide film integrity. Figure 2 (a) is a scanning electron microscope (SEM) image of the unannealed porous polyamic acid film prepared on the substrate in Example 1. It can be seen that a pore structure with different pore sizes is formed in the film. (b) is a cross-sectional SEM image after annealing. It can be seen that the pore structure has changed significantly after annealing. (c) is an SEM 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 pores, which then break and peel off. (d) After laser peeling, the polyimide film is thin and has excellent film integrity with no obvious damage.

[0047] Experiment (1)

[0048] By adjusting the spin-coating time of the sacrificial layer, sacrificial layers of equal area but different thicknesses were obtained. Then, polyimide films of equal area and thickness were prepared. The effect of the sacrificial layer thickness on the laser ablation of the polyimide films was investigated. The ablation efficiency refers to the percentage of intact films obtained from each group of 100 laser-ablated polyimide films. Here, "intact and undamaged" means that the residual polyimide film on the substrate after ablation has a thickness of less than 10 nm and thermal damage (edge ​​heat-affected zone) of less than 100 nm. The results are shown in Table 1.

[0049] Table 1:

[0050]

[0051] Under the same laser treatment, the peel time of the polyimide film showed significant differences with varying sacrificial layer thickness. When the spin coating rate was 1100–1900 rpm and the obtained sacrificial layer thickness was 135–195 μm, the peel time decreased significantly with increasing sacrificial layer thickness while maintaining high peel efficiency. However, when the spin coating thickness was thicker, the annealing process had an ineffective effect on the porosity and component distribution of the sacrificial layer, leading to a decrease in the utilization rate of laser energy during laser treatment, resulting in a significant increase in peel time and a decrease in peel efficiency. Conversely, when the sacrificial layer thickness was smaller, although the peel time decreased, the thinner sacrificial layer was completely imidized under annealing, significantly increasing its adhesion to the polyimide film. This failed to reduce peel damage and instead had a counterproductive effect, leading to a decrease in peel efficiency.

[0052] Experiment (II)

[0053] By adjusting the composition of the polyamic acid solution used to prepare the sacrificial layer (TFMB, a fluorinated diamine monomer, is designated as "T" in the table; ODA, an unfluorinated aromatic diamine monomer, is designated as "O" in the table; and 6FDA, a fluorinated dianhydride monomer, is designated as "F" in the table; and the solid content of the solution is kept at 12 wt%), a sacrificial layer of the same thickness as in Example 1 was obtained. The effect of the sacrificial layer composition on the laser exfoliation of the same polyimide film was then investigated, and the results are shown in Table 2.

[0054] Table 2:

[0055]

[0056] It can be seen that as the proportion of TFMB in the polyamic acid solution used to prepare the sacrificial layer gradually decreases, the laser exfoliation time of the polyimide film first shortens and then lengthens. The exfoliation efficiency of the same polyimide film generally shows a gradually decreasing trend. Furthermore, when the ratio of TFMB to ODA is less than 1:1, the exfoliation efficiency of the polyimide film decreases significantly, resulting in more severe damage. When there is no ODA in the polyamic acid solution, although the exfoliation time is the shortest, the exfoliation efficiency is not ideal. When there is no TFMB in the polyamic acid solution, the exfoliation time is longer, and the damage to the polyimide film is also more pronounced.

[0057] Comparative Example 1

[0058] Compared with Example 1, the annealing process is as follows:

[0059] The substrate was cured at 55°C for 50 min, then heated to 115°C for 30 min, then to 145°C for 30 min, then to 175°C for 30 min, then to 205°C for 30 min, then to 235°C for 30 min, then to 265°C for 30 min, and finally cooled to room temperature to complete the thermal imidization process, thus obtaining the substrate / porous polyamic acid film / polyimide film structure.

[0060] Compared with Example 1, Comparative Example 1 increased the number of temperature stages for heating, changing from 4 stages to 6 stages, with each stage having a temperature interval of 30°C, and shortening the heating time for each stage.

[0061] Comparative Example 2

[0062] Compared with Example 1, the annealing process is as follows:

[0063] Each film was cured at 55°C for 50 min, then heated to 115°C for 40 min, then to 165°C for 40 min, then to 215°C for 40 min, then to 265°C for 40 min, and finally cooled to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0064] Compared with Example 1, Comparative Example 1 increased the temperature range of the heating, while maintaining the original 4 heating ranges, but the temperature interval between each heating range was 50°C.

[0065] Figure 3 This refers to the porous polyamic acid film prepared on the substrate surface in this invention. Figure 4 Polyimide films prepared on pure substrate surfaces, and substrate / porous polyamic acid film / polyimide film structures prepared in Examples 1, 1, and 2.

[0066] Experiment (3)

[0067] Using different annealing procedures in Example 1 and Comparative Example 1, substrate / porous polyamic acid film / polyimide film structures were prepared. The effect of annealing on the sacrificial layer and its final influence on the laser lift-off of the polyimide film were investigated. The results are shown in Table 3.

[0068] Table 3:

[0069]

[0070] It can be seen that in Comparative Example 1, the more segmented heating and annealing treatments significantly affected the sacrificial layer structure, resulting in longer peeling times during laser exfoliation and a marked decrease in the peeling efficiency of the polyimide film. In Comparative Example 2, the heating interval was kept constant at 50°C, leading to even longer peeling times during laser exfoliation and a further decrease in the peeling efficiency of the polyimide film. In contrast, this invention employs four segmented heating stages, with the temperature interval between each stage increasing progressively.

[0071] The substrate / porous polyamic acid film / polyimide film structures prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to laser ablation at different laser densities, with the ablation time being compared to... Figure 5 As shown, the peeling time of the polyimide film decreases with increasing laser density. However, compared with Comparative Examples 1 and 2, the peeling time of Example 1 decreases more with increasing laser density. 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.

[0072] Example 2

[0073] A method for efficient laser exfoliation of polyimide films includes the following steps:

[0074] (1) A precursor solution with a solid content of 18wt% was prepared by dissolving TFMB (fluorinated diamine monomer), ODA (non-fluorinated aromatic diamine monomer), and 6FDA (fluorinated dianhydride monomer) in NMP solvent. The solution was heated to 25°C in a water bath under an inert atmosphere and stirred at 240 rpm for 1 h. Then it was cooled to room temperature and stirred for another 18 h to obtain a polyamic acid solution. The molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer was 0.8 mol: 0.5 mol: 1 mol.

[0075] (2) A polyamic acid solution is spin-coated onto the surface of a glass substrate at a temperature of 45°C and placed in a coagulation bath for 3 hours to form a porous polyamic acid film, thereby 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.

[0076] (3) The precursor solution used to prepare the polyimide film (6FDA 1.4332g, ODA 0.969g, TFMB 1.5497g, NMP 50g, stirred vigorously in an ice-water bath for 18h under nitrogen atmosphere) was coated on the surface of the porous polyamic acid film and annealed. The polyimide film was obtained by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing process was to cure at 50°C for 60min, then heat to 120°C for 40min, heat to 160°C for 40min, heat to 210°C for 40min, heat to 270°C for 40min, and then cool to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0077] (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser with a wavelength of 450 nm and a laser energy density of 110 mJ / cm². 2 The laser beam is used for laser cutting and peeling, and the laser moving speed is 0.5 mm / s.

[0078] Example 3

[0079] A method for efficient laser exfoliation of polyimide films includes the following steps:

[0080] (1) A precursor solution with a solid content of 15wt% was prepared by dissolving TFMB (fluorinated diamine monomer), ODA (non-fluorinated aromatic diamine monomer), and 6FDA (fluorinated dianhydride monomer) in NMP solvent. The solution was heated to 20°C in a water bath under an inert atmosphere and stirred at 250 rpm for 2 h. Then it was cooled to room temperature and stirred for another 10 h to obtain a polyamic acid solution. The molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer was 0.5 mol: 0.2 mol: 1 mol.

[0081] (2) A polyamic acid solution is spin-coated onto the surface of a glass substrate at a temperature of 40°C and placed in a coagulation bath for 2 hours to form a porous polyamic acid film, thereby 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.

[0082] (3) The precursor solution used to prepare the polyimide film (6FDA 1.4332g, ODA 0.969g, TFMB 1.5497g, NMP 50g, stirred vigorously in an ice-water bath for 18h under nitrogen atmosphere) was coated on the surface of the porous polyamic acid film and annealed. The polyimide film was obtained by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing process was performed by curing at 60°C for 40min, then heating at 110°C for 40min, heating at 150°C for 40min, heating at 200°C for 40min, heating at 260°C for 40min, and then cooling to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0083] (4) Place the substrate / porous polyamic acid film / polyimide film structure under a laser with a wavelength of 450 nm and a laser energy density of 80 mJ / cm². 2 The laser beam is used for laser cutting and peeling, and the laser moving speed is 0.5 mm / s.

[0084] The above embodiments are in the pilot stage, so the laser used is a picosecond laser with a laser movement rate of 0.5 mm / s. In order to study whether the sacrificial layer in this invention can also play a corresponding role in actual industrial production when faced with a faster laser movement rate, we tried to use an industrial excimer laser for laser ablation (laser movement rate of 200 mm / s).

[0085] Example 4

[0086] A method for efficient laser exfoliation of polyimide films includes the following steps:

[0087] (1) A precursor solution with a solid content of 12% was prepared by dissolving TFMB (fluorinated diamine monomer), ODA (non-fluorinated aromatic diamine monomer), and 6FDA (fluorinated dianhydride monomer) in NMP solvent. The solution was heated to 30°C in a water bath under an inert atmosphere and stirred at 200 rpm for 1.5 h. Then it was cooled to room temperature and stirred for another 12 h to obtain a pale yellow polyamic acid solution. The molar ratio of fluorinated diamine monomer, non-fluorinated diamine monomer, and fluorinated dianhydride monomer was 0.7 mol: 0.3 mol: 1 mol.

[0088] (2) A polyamic acid solution is spin-coated onto the surface of a glass substrate at a temperature of 40°C and placed in a coagulation bath for 2.5 h to form a porous polyamic acid film, thereby 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.

[0089] (3) The colorless precursor solution used to prepare the polyimide film (6FDA 1.4332g, ODA 0.969g, TFMB 1.5497g, NMP 50g, stirred vigorously in an ice-water bath for 18h under nitrogen atmosphere) was coated on the surface of the porous polyamic acid film and annealed. The polyimide film was obtained by thermal imidization, forming a substrate / porous polyamic acid film / polyimide film structure. The annealing process was to cure at 55°C for 50min, then heat to 115°C for 40min, heat to 155°C for 40min, heat to 205°C for 40min, heat to 265°C for 40min, and then cool to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0090] (4) The substrate / porous polyamic acid film / polyimide film structure is placed under a laser with a wavelength of 450 nm and a laser energy density of 90 mJ / cm². 2 The laser beam is used for laser cutting and peeling, and the laser moving speed is 200 mm / s.

[0091] By adjusting the composition of the polyamic acid solution used to prepare the sacrificial layer to be without TFMB and without ODA (the solid content of the solution was kept at 12wt%), a sacrificial layer of the same thickness as in Example 4 was obtained. The effect of the sacrificial layer composition on the laser ablation of polyimide films of the same thickness and area on the surface of the sacrificial layer was detected, and the results are shown in Table 4.

[0092] Table 4:

[0093]

[0094] It can be seen that when the components of the polyamic acid solution used to prepare the sacrificial layer are without TFMB and without ODA, the trend of its influence on peeling time and peeling efficiency of polyimide film is consistent with that in the small-scale test, compared with Example 4. This indicates that the sacrificial layer prepared by the present invention with specific components can effectively reduce peeling time and improve peeling efficiency of film when laser peeling of polyimide film, while reducing damage to film during peeling.

[0095] Comparative Example 3

[0096] Compared with Example 4, the annealing process is as follows:

[0097] Each film was cured at 55°C for 50 min, then heated to 115°C for 30 min, then to 145°C for 30 min, then to 175°C for 30 min, then to 205°C for 30 min, then to 235°C for 30 min, then to 265°C for 30 min, and finally cooled to room temperature to complete the thermal imidization process, thus obtaining the substrate / porous polyamic acid film / polyimide film structure.

[0098] Compared with Example 4, Comparative Example 3 increased the number of temperature stages for heating, changing from 4 stages to 6 stages, with each stage heating at 30°C, and shortened the heating time for each stage.

[0099] Comparative Example 4

[0100] Compared with Example 4, the annealing process is as follows:

[0101] Each film was cured at 55°C for 50 min, then heated to 115°C for 40 min, then to 165°C for 40 min, then to 215°C for 40 min, then to 265°C for 40 min, and finally cooled to room temperature to complete the thermal imidization process and obtain the substrate / porous polyamic acid film / polyimide film structure.

[0102] Compared with Example 4, Comparative Example 1 increased the temperature range of the heating, while maintaining the original 4 heating ranges, but the interval between each heating range was 50°C.

[0103] Using different annealing procedures in Example 1 and Comparative Example 1, substrate / porous polyamic acid film / polyimide film structures were prepared. The effect of annealing on the sacrificial layer and its final influence on the laser lift-off of the polyimide film were investigated. The results are shown in Table 5.

[0104] Table 5:

[0105]

[0106] It can be seen that at higher laser moving speeds, the peeling time and peeling efficiency of the polyimide film in Examples 4, 3, and 4 are consistent with the trends observed in Examples 1, 1, and 2 in the small-scale test. This indicates that at industrial-scale high laser moving speeds, the specific sacrificial layer prepared in this invention can effectively reduce the peeling time during laser peeling, while simultaneously improving peeling efficiency and reducing damage to the polyimide film during peeling.

Claims

1. A method for efficiently laser ablation of a polyimide film, characterized by: Add a layer of porous polyamide acid film between the substrate and the polyimide film as a sacrificial layer, and then perform laser cutting and peeling, the specific steps are as follows: (1) The fluorine-containing diamine monomer, non-fluorine-containing diamine monomer and fluorine-containing dianhydride monomer are dissolved in an aprotic solvent to form a precursor solution, and the polyamide acid solution is obtained by stirring in an inert atmosphere, the molar ratio of the fluorine-containing diamine monomer, non-fluorine-containing diamine monomer and fluorine-containing dianhydride monomer is 0.5-0.8mol:0.5-0.2mol:1mol, and the solid content of the precursor solution is 12-18wt%; (2) The polyamide acid solution is coated on the surface of the glass substrate, and is placed in a coagulation bath for 2-3h to obtain a porous polyamide acid film, forming a substrate / porous polyamide acid film structure, the coagulation bath is formed by mixing an aprotic solvent, a surfactant and water in a mass ratio of 35-45g:4-6g:55-65g; (3) The precursor solution for preparing the polyimide film is coated on the surface of the porous polyamide acid film, and annealing treatment is performed to heat imidize to obtain a polyimide film, forming a substrate / porous polyamide acid film / polyimide film structure, the annealing treatment is solidified at 50-60℃ for 40-60min, then heated to 110-120℃ for 40min, heated to 150-160℃ for 40min, heated to 200-210℃ for 40min, heated to 260-270℃ for 40min, and then cooled to room temperature, completing the heat imidization process, thereby obtaining a polyimide film; (4) The substrate / porous polyamide acid film / polyimide film structure is placed under a laser, and the polyimide film is cut and peeled from the substrate by laser peeling technology.

2. The method of claim 1, wherein the polyimide film is a high-reflectivity laser lift-off polyimide film. The fluorine-containing diamine monomer in step (1) 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, and 4,4'-diamino octafluorobiphenyl; the non-fluorine-containing aromatic diamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl methane, 4,4'-diamino diphenyl ether ODA, 1,4-bis(4-aminophenoxy) benzene, and 2,2-bis[4-(4-aminophenoxy) phenyl] propane; the fluorine-containing dianhydride monomer is at least one of 4,4′-(hexafluoroisopropylidene) bisphthalic anhydride 6FDA, 2,2,3,3,4,4-hexafluoroglutaric anhydride, and 9,9-bis(trifluoromethyl) xanthene-2,3,6,7-tetraoic dianhydride; and the aprotic solvent is at least one of N,N-dimethylformamide DMF, dimethylacetamide DMAC, N-methyl pyrrolidone NMP, dimethyl sulfoxide DMSO, and tetrahydrofuran THF.

3. The method of claim 1 or 2, wherein the polyimide film is a high- efficiency laser release polyimide film. In step (1), the water bath stirring is to heat the precursor solution in a water bath kettle to 25-35℃, and then stir for 1-2h, and then cool to room temperature and stir for 10-18h.

4. The method of claim 3, wherein the polyimide film is a high-reflectivity laser lift-off polyimide film. In step (2), the coating is spin coating, the spin coating speed is 900-1400rpm, and the spin coating time is 15-25s.

5. The method of claim 4, wherein the polyimide film is a high-reflectivity laser lift-off polyimide film. The surface active agent in the coagulation bath is one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and sodium stearate.

6. The method of claim 5, wherein the polyimide film is a high-reflectivity laser lift-off polyimide film. The laser beam used in the laser stripping has a wavelength of 450 nm and a laser energy density of 80-110 mJ / cm2.

7. A method for efficiently laser ablation of a polyimide film, characterized by, The method comprises the following steps: (1) a precursor solution with a solid content of 12-18 wt% is prepared by dissolving fluorine-containing diamine monomers as TFMB, non-fluorine-containing aromatic diamine monomers as ODA and fluorine-containing dianhydride monomers as 6FDA in a solvent NMP, and then the precursor solution is heated to 25-35 DEG C in an inert atmosphere, stirred at 200-250 rpm for 1-2 h, and then cooled to room temperature and continuously stirred for 10-18 h, wherein the molar ratio of the fluorine-containing diamine monomers, the non-fluorine-containing diamine monomers and the fluorine-containing dianhydride monomers is 0.5-0.8:0.2-0.5:1; (2) the polyamic acid solution is spin-coated on the surface of a glass substrate, and then placed in a coagulation bath for 2-3 h to obtain a porous polyamic acid film, thereby forming a substrate / porous polyamic acid film structure, wherein the spin-coating speed is 1100-1900 rpm, and the spin-coating time is 60 s, and the coagulation bath is formed by mixing NMP, sodium dodecyl sulfate and water according to a mass ratio of 35-45 g:4-6 g:55-65 g; (3) a precursor solution for preparing a polyimide film is coated on the surface of the porous polyamic acid film, and then annealing treatment and thermal imidization are performed to obtain a polyimide film, thereby forming a substrate / porous polyamic acid film / polyimide film structure, wherein the annealing treatment comprises solidifying at 50-60 DEG C for 40-60 min, heating at 110-120 DEG C for 40 min, heating at 150-160 DEG C for 40 min, heating at 200-210 DEG C for 40 min, heating at 260-270 DEG C for 40 min, and then cooling to room temperature to complete the thermal imidization process; and (4) the substrate / porous polyamic acid film / polyimide film structure is placed under a laser, and laser cutting stripping is performed by using a laser beam with a wavelength of 450 nm and a laser energy density of 80-110 mJ / cm2.

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