Surface-modified polyimide film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of surface modification, and particularly relates to a surface-modified polyimide film as well as a preparation method and application thereof. The surface modification method of polyimide provided by the invention comprises the following steps: mixing a polyimide film with an alkali solution, carrying out modification treatment, and then carrying out acid pickling to obtain a surface-modified polyimide film, the molar concentration of the aqueous alkali is 0.01 mol / L to 0.2 mol / L. The alkali solution with specific molar concentration is selected for surface modification of polyimide, a passivation layer can be removed to form a polar functional group-COO <->, the-COO <-> in the surface-modified polyimide can react with hydroxyl in the adhesive to generate chemical bonding, the interface bonding condition of the adhesive and a polyimide film is improved, and the adhesion property of the adhesive and the polyimide film is improved. The adhesion performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification, and particularly relates to a surface-modified polyimide film, a preparation method thereof, and an application thereof. Background Art

[0002] Polyimide (PI for short) films are widely used in the microelectronics industry as dielectric spacer layers, protective cover layers for metal films, and substrates due to their excellent mechanical properties, high-temperature resistance, radiation resistance, low dielectric constant, and high resistivity. However, due to the poor surface hydrophilicity of PI films, their adhesion to metals through adhesives is poor. In order to improve the adhesion of PI films, it is necessary to modify the surface of PI films. Currently, the main methods for surface modification of PI films are plasma treatment, ion implantation, and surface grafting. Among them, the bonding effect of modified polyimide after plasma treatment will weaken with the extension of time; although the adhesion of modified polyimide after ion implantation or surface grafting treatment is significantly improved and durable, its process is complex and the treatment cost is high. Summary of the Invention

[0003] In view of this, the present invention provides a surface-modified polyimide film, a preparation method thereof, and an application thereof. After modifying the surface of polyimide according to the method provided by the present invention, the adhesion between polyimide and adhesive can be improved, thereby increasing the service life of the corresponding product.

[0004] In order to solve the above technical problems, the present invention provides a method for surface modification of polyimide, which includes the following steps:

[0005] Mix the polyimide film and an alkali solution for modification treatment, and then perform pickling to obtain a surface-modified polyimide film;

[0006] The molar concentration of the alkali solution is 0.01 - 0.2 mol / L.

[0007] Preferably, the alkali solution includes sodium hydroxide solution, potassium hydroxide solution, or ammonia water.

[0008] Preferably, the modification treatment method includes a first modification treatment or a second modification treatment;

[0009] The first modification treatment is to immerse the polyimide in the alkali solution;

[0010] The second modification treatment is to perform hydrothermal treatment on the mixed system of polyimide and the alkali solution.

[0011] Preferably, the temperature of the immersion is 40 - 80 °C, and the time of the immersion is 30 - 90 min.

[0012] Preferably, the temperature of the hydrothermal treatment is 40 to 80 °C, and the time of the hydrothermal treatment is 30 to 90 min.

[0013] Preferably, the acid solution for pickling includes hydrochloric acid solution, phosphoric acid solution or oxalic acid solution.

[0014] Preferably, the molar concentration of the acid solution is 0.08 to 0.12 mol / L.

[0015] Preferably, after pickling, it further includes: washing the pickled product with water and then drying.

[0016] The present invention also provides a surface-modified polyimide film obtained by the surface modification method of the polyimide according to the above technical solution.

[0017] The present invention also provides an application of the surface-modified polyimide film according to the above technical solution in a flexible copper clad laminate.

[0018] The present invention provides a surface modification method of polyimide, including the following steps: mixing a polyimide film and an alkali solution for modification treatment and then performing pickling to obtain a surface-modified polyimide film; the molar concentration of the alkali solution is 0.01 to 0.2 mol / L. The present invention selects an alkali solution with a specific molar concentration to perform surface modification on polyimide, which can remove the passivation layer to form polar functional groups -COO-, and the -COO- in the surface-modified polyimide will react with the hydroxyl groups in the adhesive to produce chemical bonding, improving the interfacial bonding condition between the adhesive and the polyimide film and enhancing the adhesion performance. Description of the Drawings

[0019] Figure 1 It is an optical microscope image of the surface of the polyimide film in Example 1;

[0020] Figure 2 It is an optical microscope image of the surface of the surface-modified polyimide film obtained in Example 1;

[0021] Figure 3 It is an optical microscope image of the surface of the surface-modified polyimide film obtained in Example 2;

[0022] Figure 4 It is an optical microscope image of the surface of the surface-modified polyimide film obtained in Example 3. Detailed Description of the Invention

[0023] The present invention provides a surface modification method of polyimide, including the following steps:

[0024] Mixing a polyimide film and an alkali solution for modification treatment and then performing pickling to obtain a surface-modified polyimide film;

[0025] The molar concentration of the alkali solution is 0.01 - 0.2 mol / L.

[0026] As a specific embodiment of the present invention, the polyimide film may be Kapton of DuPont.

[0027] As a specific embodiment of the present invention, the alkali solution may include sodium hydroxide solution, potassium hydroxide solution or ammonia water; the molar concentration of the alkali solution is 0.01 - 0.02 mol / L, and may specifically be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L or 0.2 mol / L. The present invention has no special limitation on the dosage of the alkali solution, as long as the polyimide film can be immersed.

[0028] As a specific embodiment of the present invention, the manner of the modification treatment may include the first modification treatment or the second modification treatment. As a specific embodiment of the present invention, the first modification treatment is to immerse the polyimide in the alkali solution; the immersion temperature may be 40 - 80 °C, and may specifically be 40 °C, 50 °C, 60 °C, 70 °C or 80 °C; the immersion time may be 30 - 90 min, and may specifically be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min. As a specific embodiment of the present invention, the second modification treatment is to perform hydrothermal treatment on the mixed system of polyimide and the alkali solution; the hydrothermal treatment temperature may be 40 - 80 °C, and may specifically be 40 °C, 50 °C, 60 °C, 70 °C or 80 °C; the hydrothermal treatment time may be 30 - 90 min, and may specifically be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min. As a specific embodiment of the present invention, the hydrothermal treatment may be carried out in a reaction kettle.

[0029] As a specific embodiment of the present invention, the acid solution for pickling may include hydrochloric acid solution, oxalic acid solution or phosphoric acid solution; the molar concentration of the acid solution may be 0.08 - 0.12 mol / L, and may specifically be 1 mol / L.

[0030] The present invention uses an alkali solution to modify the surface of the polyimide film, remove the passivation layer, form polar functional groups -COO-, react with the silanol groups in the silicone rubber adhesive to generate chemical bonding, and improve the interfacial bonding condition between the silicone rubber adhesive and the polyimide film. Taking sodium hydroxide solution as the alkaline solution and hydrochloric acid as the acid solution as an example, the reaction equations occurring during the surface modification and pickling of polyimide are as follows:

[0031]

[0032] As a specific embodiment of the present invention, after pickling, it may further include: washing the pickled product with water and then drying it; the water used for washing may be deionized water, and the number of washing times may be 1 to 3 times; through washing in the present invention, the residual acid solution can be removed. As a specific embodiment of the present invention, the drying may be air drying, and the present invention has no special requirements for the air drying, as long as the solvent can be removed.

[0033] The method for modifying the polyimide film with an alkali solution of a specific concentration in the present invention is simple and effective, and does not damage the surface of the substrate. The present invention uses NaOH aqueous solution, KOH aqueous solution and NH3·H2O aqueous solution to treat the surface of the PI film, and improves its adhesion performance on the premise of not affecting the apparent quality and internal mechanical properties of the PI film.

[0034] The present invention also provides a polyimide film with surface modification obtained by the surface modification method of the polyimide according to the above technical solution. The modified polyimide film obtained by the modification method provided by the present invention has good adhesion performance with the adhesive.

[0035] The present invention also provides the application of the polyimide film with surface modification described in the above technical solution in a flexible copper clad laminate.

[0036] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0037] Example 1

[0038] The polyimide film (Kapton purchased from DuPont) was immersed in a sodium hydroxide solution with a molar concentration of 0.05 mol / L, soaked at a temperature of 80°C for 90 min, then taken out and rinsed with a hydrochloric acid solution with a molar concentration of 0.1 mol / L, and the rinsed product was washed with deionized water 3 times and then air dried to obtain a polyimide film with surface modification.

[0039] Example 2

[0040] The polyimide film was surface modified according to the method of Example 1, except that the sodium hydroxide solution with a molar concentration of 0.05 mol / L was replaced with ammonia water with a molar concentration of 0.05 mol / L.

[0041] Example 3

[0042] The polyimide film was surface-modified according to the method of Example 1, except that the sodium hydroxide solution with a molar concentration of 0.05 mol / L was replaced with a potassium hydroxide solution with a molar concentration of 0.05 mol / L.

[0043] Optical microscopic observations were made on the polyimide film in Example 1 and the surface-modified polyimide films obtained in Examples 1 to 3, and Figures 1 to 4 wherein, Figure 1 is the optical micrograph of the surface of the polyimide film in Example 1, Figure 2 is the optical micrograph of the surface of the surface-modified polyimide film obtained in Example 1, Figure 3 is the optical micrograph of the surface of the surface-modified polyimide film obtained in Example 2, Figure 4 is the optical micrograph of the surface of the surface-modified polyimide film obtained in Example 3.

[0044] It can be seen from Figures 1 to 4 that the surface of the original polyimide film is relatively uniform and flat with fewer bumps. Compared with the original polyimide film, the surface of the polyimide film after alkali modification treatment has some mechanically scratched pits caused by stress during the treatment process and some corroded pits, and the surface roughness has increased significantly. This is because the surface of the polyimide film is corroded under the combined action of an alkaline solution and high temperature (the five-membered ring in the polyimide molecular chain is opened to generate carboxyl groups), and the corrosion appearance is pitting corrosion. Comparing the polyimide films treated with NaOH, NH3·H2O, and KOH, it can be observed that the surface roughness of the film treated with KOH increases most significantly.

[0045] Example 4

[0046] The polyimide film (Kapton from DuPont) was immersed in a potassium hydroxide solution with a molar concentration of 0.05 mol / L and then transferred to a reaction kettle for hydrothermal treatment at 80 °C for 90 min. The hydrothermally treated polyimide film was taken out and rinsed with a hydrochloric acid solution with a molar concentration of 0.1 mol / L, and then washed with deionized water three times and dried to obtain a surface-modified polyimide film.

[0047] Examples 5 to 12

[0048] The polyimide film was surface-modified according to the method of Example 4, except that the molar concentration of the potassium hydroxide solution, the temperature of the hydrothermal treatment, and the time of the hydrothermal treatment were specifically referred to in Table 1.

[0049] The contact angles (the contact angles between water droplets and the film were measured by dropping water on the film) of the surface-modified polyimide films obtained in Examples 4 to 12 were tested, and the results are listed in Table 1.

[0050] Table 1 Condition parameters of surface modification treatment for Examples 4 - 12 and contact angles after modification

[0051]

[0052] According to Table 1, the average contact angles of Examples 4 - 6 (molar concentration of potassium hydroxide is 0.05 mol / L) are 60°, the average contact angles of Examples 7 - 9 (molar concentration of potassium hydroxide is 0.1 mol / L) are 77.3°, and the average contact angles of Examples 10 - 12 (molar concentration of potassium hydroxide is 0.2 mol / L) are 70°; the range of the potassium hydroxide molar concentration factor is 17.3°; where, range = maximum value of average contact angle - minimum value of average contact angle.

[0053] According to Table 1, the average contact angles of Examples 5, 7, 10 (hydrothermal treatment time is 30 min) are 71.7°, the average contact angles of Examples 6, 8, 11 (hydrothermal treatment time is 60 min) are 68.3°, and the average contact angles of Examples 4, 9, 12 (hydrothermal treatment time is 90 min) are 67.3°; the range of the hydrothermal treatment time factor is 4.4°; where, range = maximum value of average contact angle - minimum value of average contact angle.

[0054] According to Table 1, the average contact angles of Examples 5, 7, 10 (hydrothermal treatment temperature is 40 °C) are 71.7°, the average contact angles of Examples 6, 8, 11 (hydrothermal treatment temperature is 60 °C) are 68.3°, and the average contact angles of Examples 4, 9, 12 (hydrothermal treatment temperature is 80 °C) are 67.3°; the range of the hydrothermal treatment time factor is 4.4°; where, range = maximum value of average contact angle - minimum value of average contact angle.

[0055] Based on the above range results (the larger the range, the greater the influence of the level change of this factor on the test results), it can be seen that the factor with the greatest influence on the contact angle of the surface - modified polyimide film is the alkali concentration (Factor A), followed by the hydrothermal treatment time (Factor B) and the hydrothermal treatment temperature (Factor C). That is, the optimal conditions for hydrothermal treatment are an alkali concentration of 0.05 mol / L, a hydrothermal treatment time of 90 min, and a hydrothermal treatment temperature of 80 °C.

[0056] Using an alkali solution for surface modification treatment of polyimide films can remove the surface passivation layer, improve the surface wettability of polyimide films, and thus improve the adhesion effect at the interface with the coating.

[0057] Examples 13 - 20

[0058] The polyimide film was surface-modified according to the method of Example 4, except that the type of the alkali solution and the molar concentration of the alkali solution were specifically referred to Table 2.

[0059] Comparative Example 1

[0060] The polyimide film was surface-modified according to the method of Example 1, except that the sodium hydroxide solution was replaced with deionized water as a blank control; the specific steps were as follows:

[0061] The polyimide film (Kapton purchased from DuPont) was immersed in deionized water, soaked at 80 °C for 90 min, taken out, washed 3 times with deionized water, and then dried to obtain a comparative polyimide film.

[0062] Comparative Example 2

[0063] The polyimide film was surface-modified according to the method of Example 1, except that the sodium hydroxide solution was replaced with hydrochloric acid solution for comparison; the specific steps were as follows:

[0064] The polyimide film (Kapton purchased from DuPont) was immersed in a hydrochloric acid solution with a molar concentration of 0.05 mol / L, soaked at 80 °C for 90 min, taken out, rinsed with a sodium hydroxide solution with a molar concentration of 0.1 mol / L, washed 3 times with deionized water for the rinsed product, and then dried to obtain a surface-modified polyimide film.

[0065] Table 2 Types and molar concentrations of alkali solutions in Comparative Examples 1 and 2, and Examples 4, 13 - 20

[0066]

[0067]

[0068] The adhesion properties of the surface-modified polyimide films obtained in Examples 4 and 13 - 20 with different adhesives were tested. Specifically, the surface-modified polyimide film and the filter membrane were bonded with the adhesive, and the test results are listed in Table 3. The width of the test specimen was 30 mm.

[0069] Table 3 Adhesion properties of the films in Comparative Examples 1 and 2, and Examples 4, 13 - 19 with different adhesives

[0070]

[0071] Table 3 shows the peel strength of polyimide films treated with alkali solutions of different concentrations when bonded to aluminum films using silicone rubber adhesives. The peel strength of the untreated polyimide film bonded to the aluminum film using silicone rubber adhesive is only 0.49 N / mm. After hydrothermal treatment with low-concentration (≤0.05 mol / L) hydrochloric acid solution, the peel strength of the film bonded to the aluminum film decreases, indicating that hydrochloric acid treatment significantly reduces the friction coefficient of polyimide and is suitable for scenarios where lubrication performance needs to be improved. After hydrothermal treatment with low-concentration (≤0.05 mol / L) alkali solution, the peel strength of the film bonded to the aluminum film increases significantly, up to 2.04 N / mm at most, indicating that the polyimide film treated with alkali solution has good bonding strength with the aluminum film.

[0072] Table 3 shows the peel strength of polyimide films treated with alkali solutions of different concentrations when bonded to aluminum films using polyurethane adhesives. The peel strength of the untreated polyimide film bonded to the aluminum film using the adhesive is only 0.12 N / mm. After hydrothermal treatment with low-concentration (≤0.05 mol / L) alkali solution, the peel strength of the film bonded to the aluminum film increases, up to 0.32 N / mm at most, indicating that the polyimide film treated with alkali solution has good bonding strength with the aluminum film.

[0073] Table 3 shows the peel strength of epoxy adhesive films treated with alkali solutions of different concentrations when bonded to aluminum films using silicone rubber adhesives. The peel strength of the untreated polyimide film bonded to the aluminum film using the adhesive is only 0.32 N / mm. After hydrothermal treatment with low-concentration (≤0.05 mol / L) alkali solution, the peel strength of the film bonded to the aluminum film increases somewhat, up to 0.76 N / mm at most, indicating that the polyimide film treated with alkali solution has good bonding strength with the aluminum film.

[0074] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for surface modification of polyimide, characterized in that, It includes the following steps: Mix the polyimide film and the alkali solution for modification treatment and then perform pickling to obtain the surface-modified polyimide film; The molar concentration of the alkali solution is 0.01 - 0.2 mol / L.

2. The surface modification method of the polyimide according to claim 1, wherein The alkali solution includes sodium hydroxide solution, potassium hydroxide solution or ammonia water.

3. The surface modification method of the polyimide according to claim 1 or 2, characterized in that, The modification treatment method includes the first modification treatment or the second modification treatment; The first modification treatment is to immerse the polyimide in the alkali solution; The second modification treatment is to perform hydrothermal treatment on the mixed system of polyimide and the alkali solution.

4. The surface modification method of the polyimide according to claim 3, characterized in that, The temperature of the immersion is 40 - 80 °C, and the time of the immersion is 30 - 90 min.

5. The surface modification method of the polyimide according to claim 3, characterized in that, The temperature of the hydrothermal treatment is 40 - 80 °C, and the time of the hydrothermal treatment is 30 - 90 min.

6. The surface modification method of the polyimide according to claim 1, characterized in that, The acid solution used for pickling includes hydrochloric acid solution, phosphoric acid solution or oxalic acid solution.

7. The surface modification method of the polyimide according to claim 6, wherein The molar concentration of the acid solution is 0.08 - 0.12 mol / L.

8. The surface modification method of the polyimide according to claim 1, 6 or 7, characterized in that After pickling, it further includes: washing the pickled product with water and then drying.

9. The surface-modified polyimide film obtained by the surface modification method of the polyimide according to any one of claims 1 - 8.

10. The application of the surface-modified polyimide film according to claim 9 in a flexible copper clad laminate.

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