Polyimide paste, method of manufacturing polyimide film, and method of improving interfacial adhesion between polyimide film and inorganic layer

Abstract

This invention proposes a polyimide slurry, a method for preparing a polyimide film, and a method for improving the interlayer adhesion between the polyimide film and inorganic layers. The slurry includes two aromatic polyamic acid slurries, A and B, an organic solvent, and a coupling agent. Polyamic acid A is the main component of the slurry, while polyamic acid B is used as an additive. This invention uses a specific polyamic acid component as an interface modifier. During the subsequent baking process, the structural characteristics of the additive polyamic acid B cause it to tend to aggregate at the material interface. The polyimide corresponding to polyamic acid B exhibits excellent interlayer adhesion with inorganic interfaces such as glass. This results in a polyimide film with high adhesion to inorganic layers such as SiNx or SiOx. Furthermore, compared to general small-molecule additives, the aromatic polyimide after baking with polyamic acid B exhibits extremely high thermal stability, improving the interlayer adhesion without compromising the thermal stability of the substrate polyimide film.

Description

Technical Field

[0001] This invention relates to the field of polyimide slurry synthesis technology, specifically, it demonstrates polyimide slurry, methods for preparing polyimide films, and methods for improving the interlayer bonding strength between polyimide films and inorganic layers. Background Technology

[0002] Polyimide films are widely used in the electronics industry due to their excellent high-temperature stability and good electrical insulation properties. They are often used as key materials in the manufacture of semiconductor devices that require high durability and stability, such as integrated circuits, capacitors, inductors, and ultrasonic detectors.

[0003] In the field of flexible OLED displays, polyimide is widely used as a flexible substrate material due to its excellent heat resistance. However, polyimide itself has weak water vapor and oxygen barrier capabilities. Therefore, in the actual screen panel manufacturing process, it is necessary to prepare inorganic thin film layers such as silicon oxide (SiOx) or silicon nitride (SiNx) on it to provide effective water and oxygen barrier functions.

[0004] In this multilayer device structure, the interfacial bonding strength between the layers is crucial. Insufficient bonding between the polyimide layer and the inorganic barrier layer will directly lead to a decrease in production yield and pose a potential risk of interlayer delamination during subsequent use. Therefore, effectively enhancing the interfacial bonding between the polyimide film and the inorganic layer has become a key technical issue for ensuring device reliability and improving process yield. Summary of the Invention

[0005] The purpose of this invention is to design a polyimide slurry that can bond strongly with SiNx or SiOx, thereby improving the reliability of multilayer structures.

[0006] The technical solution is as follows: In a first aspect, the present invention provides a polyimide slurry, comprising: The matrix is ​​polyamic acid, which is polymerized from aromatic dianhydrides and aromatic diamines; Organic solvents; The interface-modified polyamic acid is miscible with the matrix polyamic acid in solution, and the polyimide formed by imidization has a higher interlayer bonding force with the silicon oxide or silicon nitride inorganic substrate than the polyimide formed by imidization of the matrix polyamic acid. The amount of the interface-modifying polyamic acid added is 0.1% to 10% of the total mass of the slurry.

[0007] In addition, the above embodiments of the present invention may also have the following additional technical features: According to one embodiment of the present invention, the amount of the interface-modifying polyamic acid added is 0.5% to 5% of the total mass of the slurry.

[0008] According to another embodiment of the present invention, the amount of the interface-modifying polyamic acid added is 1% to 3% of the total mass of the slurry.

[0009] Preferably, the matrix polyamic acid is polymerized from biphenyl tetracarboxylic dianhydride and aromatic diamine.

[0010] More preferably, the interface-modified polyamic acid is polymerized from pyromellitic anhydride and 4,4'-diaminodiphenyl ether.

[0011] Secondly, the present invention provides a method for preparing a polyimide film, comprising the following steps: Provide the polyimide slurry as described in the first aspect above; The slurry is coated onto the surface of the inorganic layer; The coated slurry is heated to imidize it and form a polyimide film.

[0012] Preferably, the temperature of the heat treatment is between 50 °C and 470 °C.

[0013] More preferably, the 180° peel strength between the polyimide film and the silicon oxide substrate is greater than 0.5 N / cm.

[0014] Thirdly, the present invention provides a method for improving the interlayer bonding strength between a polyimide film and an inorganic layer, characterized in that it comprises: An interface-modifying polyamic acid is added to a matrix polyamic acid solution to form a mixed solution. The interface-modifying polyamic acid, after imidization, has a higher bonding strength with the inorganic layer than the matrix polyamic acid after imidization. The amount of interface-modifying polyamic acid added is 0.01% to 10% of the total mass of the mixed solution. The mixed solution is coated onto the surface of the inorganic layer and then subjected to imidization treatment.

[0015] The inorganic layer is a silicon oxide layer or a silicon nitride layer.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the matrix polyamic acid, namely aromatic copolyamic acid, is polymerized from aromatic dianhydride and aromatic diamine, while the interface-modifying polyamic acid is a different polyamic acid structure with a different monomer composition than the matrix material. Compared with the polyamic acid substrate, the interface-modifying polyamic acid, as an interface modifier, has better bonding force with the inorganic interface. During the baking process, due to the difference in surface energy, the interface-modifying polyamic acid tends to aggregate at the interface between the matrix polyimide material and the inorganic material, playing a transitional role. This curing characteristic allows the obtained polyimide film to have excellent heat resistance and dimensional stability at the same time. The interface modifier of the present invention is also a highly heat-resistant polyimide material, and there is no thermal stability problem that is common in small molecule interface modifiers.

[0017] This invention introduces a polyamic acid with a specific structure as a second component into a base polyamic acid slurry. A modified polyamic acid slurry is obtained through simple mixing, with a controlled addition ratio. This process produces a polyimide film with high adhesion to inorganic layers such as SiNx or SiOx, which can be used as an organic light-emitting diode (OLED) substrate material, helping to improve product yield and stability. Attached Figure Description

[0018] Figure 1 A simplified schematic diagram illustrating the miscibility of PAA-1 and PAA-2 in solution. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a polyimide slurry comprising a matrix aromatic copolymer polyamic acid, an organic solvent, and a polyamic acid interface modifier. The matrix aromatic copolymer polyamic acid is polymerized from biphenyl dianhydride and an aromatic diamine. Polyimide films obtained by baking this type of polyamic acid exhibit weak interfacial adhesion with inorganic materials such as silica. In contrast, the interface modifier polyamic acid is polymerized from pyromellitic dianhydride and the aromatic diamine 4,4'-diaminodiphenyl ether. This type of polyamic acid slurry exhibits strong interfacial adhesion with polyamic acid slurries such as silica after baking.

[0021] Polyamic acid, an interface modifier, is added at a rate of 0.1% to 10% of the total amount, preferably 0.5% to 5%, and more preferably 1% to 3%.

[0022] The organic solvent can be N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

[0023] Comparative Example 1: This comparative example is used to demonstrate the performance of a matrix polyimide film without added interface modifiers.

[0024] To a dry 150 mL three-necked flask equipped with a mechanical stirrer and a condenser, add 32 g of N-methylpyrrolidone (NMP) solvent. While stirring, add 2.5 g of p-phenylenediamine monomer and dissolve it completely. Then, while stirring, add 6.0 g of 4,4'-biphenyltetracarboxylic dianhydride (BPDA) monomer in three portions. Continue stirring the reaction at room temperature for 2 hours to obtain a polyamic acid (PAA-1) slurry with a solid content of approximately 20%. After the reaction is complete, filter the slurry using a 0.45 μm filter membrane for later use.

[0025] The filtered PAA-1 slurry was applied to a glass substrate with a silicon oxide (SiOx) layer on its surface using a blade coating method, with the wet film thickness controlled at 60 mm. μm; The coated substrate was placed in a programmed temperature oven and heat-treated under a nitrogen protective atmosphere according to the following procedure: slowly increasing the temperature from 50°C to 300°C for about 1 hour, then increasing it to 450°C and holding it for 0.5 hours to complete imidization. After naturally cooling to room temperature, it was peeled off from the substrate to obtain the polyimide film PI-1.

[0026] The test results showed that the 180° peel strength between the PI-1 film and the SiOx substrate was 0.05 N / cm, indicating that the interfacial adhesion was weak.

[0027] Comparative Example 2: This comparative example is used to demonstrate the performance of films formed by polyamic acid as an interface modifier alone.

[0028] 32 g of NMP solvent was added to a dry 150 mL three-necked flask equipped with a mechanical stirrer and a condenser. 5.0 g of 4,4'-diaminodiphenyl ether (ODA) monomer was added under stirring and allowed to dissolve completely. Subsequently, 6.0 g of pyromellitic dianhydride (PMDA) monomer was added in three portions under stirring. The reaction was continued at room temperature for 2 hours to obtain a polyamic acid (PAA-2) slurry with a solid content of approximately 20%. After the reaction was completed, the slurry was filtered using a 0.45 μm filter membrane.

[0029] Using the same coating and heat treatment process as Comparative Example 1, PAA-2 slurry was deposited on a SiOx substrate to obtain a polyimide film PI-2.

[0030] Tests showed that the PI-2 film exhibited a peel strength of up to 4.2 N / cm at 180° to the SiOx substrate, indicating that the polyimide obtained by imidization of PI-2 has excellent inherent bonding strength with the inorganic substrate.

[0031] Example 1: Preparation of polyimide film PI-3 containing 0.1% interface modifier.

[0032] Accurately weigh 99.9 g of the PAA-1 slurry prepared in Comparative Example 1 into a clean beaker, then weigh 0.1 g of the PAA-2 slurry prepared in Comparative Example 2 and add it to the PAA-1 slurry. At room temperature, use a mechanical stirrer to stir and mix at 300 rpm for 30 minutes to ensure uniform mixing, and obtain composite polyamic acid slurry PAA-3; wherein, the amount of PAA-2 added is 0.1% of the total mass of the slurry.

[0033] Using the same process as Comparative Example 1, PAA-3 slurry was coated onto a SiOx / glass substrate by a blade coating method, with a wet film thickness of 60 μm. Subsequently, a programmed temperature rise heat treatment was performed under nitrogen protection: from 50°C to 300°C in 1 hour, then to 450°C in 0.5 hours and held for 0.5 hours to complete imidization. After cooling, a polyimide film PI-3 was obtained.

[0034] Example 2: Preparation of polyimide film PI-4 containing 0.5% interface modifier Accurately weigh 99.5 g of the PAA-1 slurry prepared in Comparative Example 1 into a clean beaker, then weigh 0.5 g of the PAA-2 slurry prepared in Comparative Example 2 and add it to the PAA-1 slurry. At room temperature, use a mechanical stirrer to stir and mix at 300 rpm for 30 minutes to ensure uniform mixing, and obtain composite polyamic acid slurry PAA-4. The amount of PAA-2 added is 0.5% of the total mass of the slurry.

[0035] Using the same coating and heat treatment process as in Example 1, PAA-4 slurry was made into polyimide film PI-4.

[0036] Example 3: Preparation of polyimide film PI-5 containing 1.0% interface modifier Accurately weigh 99.0 g of the PAA-1 slurry prepared in Comparative Example 1 into a clean beaker, then weigh 1.0 g of the PAA-2 slurry prepared in Comparative Example 2 and add it to the PAA-1 slurry. At room temperature, use a mechanical stirrer to stir and mix at 300 rpm for 30 minutes to ensure uniform mixing, and obtain composite polyamic acid slurry PAA-5. The amount of PAA-2 added is 1.0% of the total mass of the slurry.

[0037] Using the same coating and heat treatment process as in Example 1, PAA-5 slurry was made into polyimide film PI-5.

[0038] Example 4: Preparation of polyimide film PI-6 containing 2.0% interface modifier Accurately weigh 98.0 g of the PAA-1 slurry prepared in Comparative Example 1 into a clean beaker, then weigh 2.0 g of the PAA-2 slurry prepared in Comparative Example 2 and add it to the PAA-1 slurry. At room temperature, use a mechanical stirrer to stir and mix at 300 rpm for 30 minutes to ensure uniform mixing, and obtain composite polyamic acid slurry PAA-6. The amount of PAA-2 added is 2.0% of the total mass of the slurry.

[0039] Using the same coating and heat treatment process as in Example 1, PAA-6 slurry was made into polyimide film PI-6.

[0040] Example 5: Preparation of polyimide film PI-7 containing 3.0% interface modifier Accurately weigh 97.0 g of the PAA-1 slurry prepared in Comparative Example 1 into a clean beaker, then weigh 3.0 g of the PAA-2 slurry prepared in Comparative Example 2 and add it to the PAA-1 slurry. At room temperature, use a mechanical stirrer to stir and mix at 300 rpm for 30 minutes to ensure uniform mixing, and obtain composite polyamic acid slurry PAA-7. The amount of PAA-2 added is 3.0% of the total mass of the slurry.

[0041] Using the same coating and heat treatment process as in Example 1, PAA-7 slurry was made into polyimide film PI-7.

[0042] The polyimide films obtained in the comparative examples and embodiments above were subjected to 180° peel strength tests, and the results are summarized in Table 1 below.

[0043] Table 1: Comparison of peel strength between polyimide film and SiOx substrate Results analysis: As shown in Table 2, the following can be seen: 1. The bonding force between the substrate polyimide film PI-1 (pure PAA-1 system) and the SiOx substrate is extremely weak, with a peel strength of only 0.05 N / cm.

[0044] 2. Interface-modulated polyamic acid film PI-2 (pure PAA-2 system) exhibits extremely strong adhesion to SiOx substrate, with a peel strength of 4.2 N / cm, which proves the effectiveness of the PAA-2 system as an interface reinforcement material.

[0045] 3. When a small amount of PAA-2 is added to PAA-1, although both PAA-1 and PAA-2 are completely miscible in solution due to the large number of carboxyl functional groups in their chemical structures, they are not completely miscible. Figure 1 As shown, during the film formation process, due to the large differences in the PI structure formed, the affinity of the substrate material such as silicon oxide varies greatly during the imidization process. PI-2 has a strong affinity for silicon oxide, and PI-2 tends to aggregate at the interface with the substrate during the film formation process. Although the amount of PAA-2 added is small, it has a certain improvement on the interfacial adhesion between the substrate material PI-1 and silicon oxide.

[0046] 4. As a fully aromatic polyimide structure, PI-2 has a significant advantage in thermal stability compared to ordinary small molecule coupling agents. This approach not only improves the interfacial bonding strength of PI-1, but also maintains the material's high-temperature resistance. Furthermore, because the amount of PAA-2 added is relatively small, the basic parameters of the resulting polyimide film, such as mechanical and optical properties, are close to those of PI-1.

[0047] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A polyimide slurry, characterized in that, include: The matrix is ​​polyamic acid, which is polymerized from aromatic dianhydrides and aromatic diamines; Organic solvents; The interface-modified polyamic acid is miscible with the matrix polyamic acid in solution, and the polyimide formed by imidization has a higher interlayer bonding force with the silicon oxide or silicon nitride inorganic substrate than the polyimide formed by imidization of the matrix polyamic acid. The amount of the interface-modifying polyamic acid added is 0.1% to 10% of the total mass of the slurry.

2. The polyimide slurry according to claim 1, characterized in that, The amount of the interface-modifying polyamic acid added is 0.5% to 5% of the total mass of the slurry.

3. The polyimide slurry according to claim 1, characterized in that, The amount of the interface-modifying polyamic acid added is 1% to 3% of the total mass of the slurry.

4. The polyimide slurry according to claim 1, characterized in that, The matrix polyamic acid is polymerized from biphenyltetracarboxylic dianhydride and aromatic diamine.

5. A polyimide slurry according to claim 1 or 4, characterized in that, The interface-modified polyamic acid is polymerized from pyromellitic anhydride and 4,4'-diaminodiphenyl ether.

6. A method for preparing a polyimide film, characterized in that, Includes the following steps: Provide a polyimide slurry as described in any one of claims 1 to 5; The slurry is coated onto the surface of the inorganic layer; The coated slurry is heated to imidize it and form a polyimide film.

7. The method for preparing a polyimide film according to claim 6, characterized in that, The temperature of the heat treatment is from 50 °C to 470 °C.

8. The method for preparing a polyimide film according to claim 6, characterized in that, The 180° peel strength between the polyimide film and the silicon oxide substrate is greater than 0.5 N / cm.

9. A method for improving the interlayer bonding strength between polyimide films and inorganic layers, characterized in that, include: An interface-modifying polyamic acid is added to a matrix polyamic acid solution to form a mixed solution. The interface-modifying polyamic acid, after imidization, has a higher bonding strength with the inorganic layer than the matrix polyamic acid after imidization. The amount of interface-modifying polyamic acid added is 0.01% to 10% of the total mass of the mixed solution. The mixed solution is coated onto the surface of the inorganic layer and then subjected to imidization treatment.

10. The method for improving the interlayer bonding strength between polyimide film and inorganic layers according to claim 9, characterized in that, The inorganic layer is a silicon oxide layer or a silicon nitride layer.

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