Polyimide film having improved breakdown characteristics and method for manufacturing same

Abstract

The present invention provides a polyimide film comprising: a polyimide containing a dianhydride monomer and a diamine monomer as repeating units; and nanoparticles having an average particle diameter of 100 nm to 500 nm, in which a breakdown voltage (BDV) of the polyimide film is equal to or greater than 350 kV / mm, and a value of roughness (Ra) of the polyimide film is equal to or greater than 0.01 nm.

Description

Technical Field

[0001] This disclosure relates to a polyimide film with improved breakdown properties and a method for manufacturing the same. More specifically, this disclosure relates to a polyimide film with improved breakdown properties by comprising nanoparticles with an average particle size of 100 nm to 500 nm and a method for manufacturing the same. Background Technology

[0002] Typically, polyimide (PI) films are formed by molding polyimide resin. Polyimide resin refers to a high-heat-resistant resin, which is prepared by solution polymerization of aromatic dianhydrides and aromatic diamines or aromatic diisocyanates to prepare polyamic acid derivatives, followed by ring-closure and dehydration of the polyamic acid derivatives at high temperature to achieve imidization.

[0003] Polyimide resin is an insoluble and infusible ultra-high heat-resistant resin. With its high glass transition temperature, excellent thermal oxidation stability, heat resistance, radiation resistance, low-temperature properties, chemical resistance, and electrical properties, this resin is widely used in the electrical, electronic, automotive, and aerospace industries in various forms, including films, resins, molded parts, adhesives, and insulating components. In particular, as a material in the electronics industry, this resin possesses excellent insulating properties, thermal stability, and chemical stability; therefore, its application as an interlayer insulating film in semiconductor chips is continuously expanding.

[0004] In various applications, polyimide films used in secondary batteries require breakdown voltage (BDV) as a primary physical property. Furthermore, breakdown voltage is directly proportional to film thickness; films with high breakdown voltage per unit thickness can meet the required breakdown voltage at thinner thicknesses, thus achieving miniaturization and weight reduction. Simultaneously, in the roll-to-roll process of polyimide films, fillers must be used to obtain the required roughness to ensure the film's rollability.

[0005] Therefore, there is an urgent need to develop a polyimide film that can meet the required roughness and improve the breakdown voltage. Summary of the Invention

[0006] Technical issues One object of this disclosure is to provide a polyimide film with improved breakdown characteristics and a roughness that meets the requirements for ensuring the rollability of the sample, and a method thereof for manufacturing the same.

[0007] Furthermore, another object of the present invention is to provide a secondary battery comprising the polyimide film.

[0008] Technical solution Because this disclosure can have many variations and implementations, detailed illustrations and descriptions of specific implementations are provided below. However, this is not intended to limit this disclosure to the specific implementations, but should be understood to include all modifications, equivalents, and alternatives within the spirit and technical scope of this disclosure.

[0009] The terminology used in this application is for describing particular embodiments only and is not intended to limit this disclosure. Unless the context clearly specifies otherwise, singular expressions include plural expressions. In this application, terms such as "comprising" or "having" are intended to indicate the presence of features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0010] In this specification, when quantities, concentrations or other numerical values ​​or parameters are given in the form of ranges, preferred ranges, or a series of preferred upper and lower limits, it should be understood that all ranges formed by any pairing of any upper or preferred value with any lower or preferred value are specifically disclosed, regardless of whether such ranges are disclosed individually.

[0011] In this specification, unless otherwise stated, when referring to a range of values, the range includes its endpoints, and the range disclosed in the parent specification is not intended to be limited to the specific values ​​mentioned when the range is defined.

[0012] In this specification, "dianhydride" is intended to include its precursors or derivatives, and may also be referred to as "dianhydride acid," "dianhydride," or "acid dianhydride." These substances may not be dianhydrides in the strict sense, but can still react with diamines to form polyamic acid, which is then converted into polyimide.

[0013] In this specification, "diamine" is intended to include its precursors or derivatives, although these substances may not be diamines in the strict sense, but they can still react with dianhydrides to produce polyamic acids, which in turn are converted into polyimides.

[0014] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the meaning commonly understood by one of ordinary skill in the art. Terms such as those defined in general dictionaries shall be interpreted as having a meaning consistent with that in the relevant technical field, and shall not be interpreted in an idealized or overly formal manner unless expressly defined otherwise in this application. Specific details of implementing this disclosure will be described below.

[0015] This invention relates to a polyimide film with improved breakdown properties and a method for manufacturing the same.

[0016] polyimide film This disclosure provides a polyimide film. The polyimide film comprises: a polyimide containing a dianhydride monomer and a diamine monomer as polymerization units; and nanoparticles having an average particle size of 100 nm to 500 nm, wherein the breakdown voltage (BDV) of the polyimide film is equal to or greater than 350 kV / mm, and the roughness (Ra) of the polyimide film is equal to or greater than 0.01 nm.

[0017] The average particle size of the nanoparticles can be from 100 nm to 500 nm, preferably equal to or greater than 100 nm and less than 500 nm, more preferably 110 nm to 400 nm, 120 nm to 350 nm, 130 nm to 300 nm, 135 nm to 290 nm, 140 nm to 280 nm, 145 nm to 270 nm, 148 nm to 260 nm, and even more preferably 150 nm to 250 nm. If the average particle size of the nanoparticles is less than 100 nm, the roughness (Ra) value is low, which is undesirable; if the average particle size of the nanoparticles is greater than 500 nm, it may lead to dispersion problems of the nanoparticles in the film, which is also undesirable.

[0018] According to one implementation, the average particle size of the nanoparticles can be measured using a laser diffraction particle size analyzer (SHIMADZU, model SALD-2201).

[0019] The breakdown voltage (BDV) of the polyimide film can be equal to or greater than 350 kV / mm. For example, the lower limit of the breakdown voltage can be 353 kV / mm, 355 kV / mm, 358 kV / mm, 360 kV / mm or higher. There is no particular limit to the upper limit of the breakdown voltage; it can be less than or equal to 500 kV / mm, less than or equal to 400 kV / mm, less than or equal to 350 kV / mm, less than or equal to 330 kV / mm, or less than or equal to 320 kV / mm.

[0020] Breakdown voltage (BDV) can be measured using methods known in the art. In one example, breakdown voltage can be measured according to the ASTM D149 standard specification. Specifically, the polyimide film is pretreated in an oven at 100°C to remove moisture, fixed in a measuring apparatus (PHENIX TECHNOLOGIES 6CCE50-5) set to room temperature, and the breakdown voltage is measured by applying an AC voltage of 10 kV to the upper and lower electrodes and increasing the AC voltage from 0 at a constant rate.

[0021] The roughness (Ra) value of the polyimide film can be equal to or greater than 0.01 nm. For example, the lower limit of the roughness (Ra) value can be 0.0105 nm, 0.0108 nm, 0.0110 nm, 0.0115 nm, 0.0118 nm, 0.012 nm or higher. There is no particular limit to the upper limit of the roughness (Ra) value, which can be less than or equal to 0.05 nm, less than or equal to 0.04 nm, less than or equal to 0.035 nm, or less than or equal to 0.03 nm.

[0022] Roughness (Ra) refers to the arithmetic mean roughness, which can be measured by methods known in the art. In one example, roughness (Ra) can be measured using a film roughness analyzer manufactured by Kosaka Laboratory Ltd.

[0023] Nanoparticles may include nano-silica.

[0024] The polyimide film may include nanoparticles of 1,000 ppm to 5,000 ppm, preferably 1,500 ppm to 4,500 ppm, 1,800 ppm to 4,200 ppm, 2,000 ppm to 4,000 ppm, 2,300 ppm to 3,700 ppm, 2,500 ppm to 3,500 ppm, and more preferably 2,800 ppm to 3,200 ppm.

[0025] If the content of nanoparticles in the polyimide film is less than 1000 ppm, the breakdown voltage value is low and undesirable; if the content of nanoparticles in the polyimide film exceeds 5000 ppm, the improvement in breakdown voltage relative to the nanoparticles used is not significant, the efficiency is low, and it is also undesirable.

[0026] The dianhydride monomer may include at least one selected from the group consisting of: pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), diphenyl sulfone-3,4,3',4'-tetracarboxylic dianhydride (DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylenebis(triphenylene) The anhydride composition may include: bis(triphenylene ...

[0027] The diamine monomer may include at least one selected from the group consisting of: 1,4-diaminobenzene (PPD), 4,4'-diaminodiphenyl ether (ODA), 2,2-diaminophenoxyphenylpropane (BAPP), m-phenylenediamine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzoic acid (DABA), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-toluidine), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'- Diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 4,4'-diaminobenzoylaniline, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodibenzophenone, 4,4'-diaminodibenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-di... Aminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1 4-Bis(3-aminophenoxy)benzene (TPE-Q), 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-(4-phenylphenoxy)benzophenone, 3,3'-diamino-4,4'-bis(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylthio)benzene, 1,3-bis(4-aminophenylthio)benzene, 1,4-bis(4-aminophenylthio)benzene, 1,3-bis(3-aminophenylsulfonyl)benzene, 1,3-bis(4-aminophenylsulfonyl)benzene, 1,4-bis(4-aminophenylsulfonyl)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-Bis[2-(4-aminophenyl)isopropyl]benzene, 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl] Ketones, bis[3-(4-aminophenoxy)phenyl]ketones, bis[4-(3-aminophenoxy)phenyl]ketones, bis[4-(4-aminophenoxy)phenyl]ketones, bis[3-(3-aminophenoxy)phenyl]sulfides, bis[3-(4-aminophenoxy)phenyl]sulfides, bis[4-(3-aminophenoxy)phenyl]sulfides, bis[4-(4-aminophenoxy)phenyl]sulfides, bis[3-(3-aminophenoxy)phenyl]sulfones, bis[3-(4-aminophenoxy)phenyl]sulfones, bis[4-(3-aminophenoxy)phenyl]sulfones [Phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane The mixture comprises 1,4-diaminobenzene (PPD) and 4,4'-diaminodiphenyl ether (ODA).

[0028] According to one embodiment, the content of 1,4-diaminobenzene (PPD) in the total diamine monomers can be greater than 0 mol% and less than or equal to 50 mol%. For example, the upper limit can be less than or equal to 48 mol%, less than or equal to 45 mol%, less than or equal to 43 mol%, less than or equal to 40 mol%, less than or equal to 38 mol%, less than or equal to 35 mol%, less than or equal to 32 mol%, or less than or equal to 30 mol%, and the lower limit can be greater than or equal to 1 mol%, greater than or equal to 2 mol%, greater than or equal to 3 mol%, greater than or equal to 4 mol%, greater than or equal to 5 mol%, greater than or equal to 6 mol%, greater than or equal to 7 mol%, greater than or equal to 8 mol%, greater than or equal to 9 mol%, greater than or equal to 10 mol%, greater than or equal to 12 mol%, greater than or equal to 14 mol%, greater than or equal to 16 mol%, greater than or equal to 18 mol%, or greater than or equal to 20 mol%. Preferably, the content of 1,4-diaminobenzene (PPD) in the total diamine monomers can be from 20 mol% to 30 mol%.

[0029] If the content of 1,4-diaminobenzene (PPD) exceeds 50 mol%, the heat resistance will improve, but the resulting film will be brittle, which is not ideal. Similarly, if the content of 1,4-diaminobenzene (PPD) is 0 mol%, the heat resistance will be low, which is also undesirable.

[0030] According to one embodiment, the content of 4,4'-diaminodiphenyl ether (ODA) in the total diamine monomers can be greater than or equal to 50 mol% and less than 100 mol%. For example, the upper limit can be less than or equal to 99 mol%, less than or equal to 98 mol%, less than or equal to 97 mol%, less than or equal to 96 mol%, less than or equal to 95 mol%, less than or equal to 94 mol%, less than or equal to 93 mol%, less than or equal to 92 mol%, less than or equal to 91 mol%, less than or equal to 90 mol%, less than or equal to 88 mol%, less than or equal to 86 mol%, less than or equal to 84 mol%, less than or equal to 82 mol%, or less than or equal to 80 mol%, and the lower limit can be greater than or equal to 52 mol%, greater than or equal to 55 mol%, greater than or equal to 57 mol%, greater than or equal to 60 mol%, greater than or equal to 62 mol%, greater than or equal to 65 mol%, greater than or equal to 68 mol%, or greater than or equal to 70 mol%. Preferably, the content of 4,4'-diaminodiphenyl ether (ODA) in the total diamine monomers can be from 70 mol% to 80 mol%.

[0031] If the content of 4,4'-diaminodiphenyl ether (ODA) is less than 50 mol%, the heat resistance will be improved, but the resulting membrane will be brittle, which is not ideal. At the same time, if the content of 4,4'-diaminodiphenyl ether (ODA) is 100 mol%, the flexibility (elongation) of the membrane will be improved, but the heat resistance (Tg) will be reduced, which is also not ideal.

[0032] The molar ratio of dianhydride monomer to diamine monomer can be from 1:2 to 2:1, preferably 1:1.

[0033] The polyimide may contain 90 mol% to 110 mol% of diamine monomer, preferably 95 mol% to 105 mol%, more preferably 98 mol% to 102 mol%, and even more preferably 99 mol% to 101 mol%.

[0034] The polyimide may contain 90 mol% to 110 mol% dianhydride monomer, preferably 95 mol% to 105 mol%, more preferably 98 mol% to 102 mol%, and even more preferably 100 mol%.

[0035] Based on a diamine monomer content of 100 mol% in polyimide, the dianhydride monomer content can range from 95 mol% to 105 mol%. For example, the lower limit can be greater than or equal to 95.5 mol%, greater than or equal to 96 mol%, greater than or equal to 96.5 mol%, greater than or equal to 97 mol%, greater than or equal to 97.5 mol%, greater than or equal to 98 mol%, greater than or equal to 98.5 mol%, greater than or equal to 99 mol%, or greater than or equal to 99.5 mol%, and the upper limit can be less than or equal to 105 mol%, less than or equal to 104 mol%, less than or equal to 103 mol%, less than or equal to 102 mol%, less than or equal to 101 mol%, or less than or equal to 100 mol%.

[0036] The thickness of the polyimide film can be appropriately selected based on factors such as its application, operating environment, and physical properties. For example, the thickness of the polyimide film can be 1μm to 100μm, 15μm to 70μm, 25μm to 50μm, or 30μm to 45μm, but is not limited to these.

[0037] Another embodiment of this disclosure provides a secondary battery including the polyimide film.

[0038] Methods for manufacturing polyimide films The method for manufacturing a polyimide film will be described below. In describing the method for manufacturing a polyimide film according to this disclosure, content overlapping with the polyimide film described above is omitted; however, the content described in the polyimide film description also applies to the method for manufacturing a polyimide film described below.

[0039] This disclosure provides a method for manufacturing a polyimide film. The method includes the following steps: (a) adding a dianhydride monomer and a diamine monomer to a solvent and performing an imidization reaction to prepare a polyamic acid solution; (b) adding nanoparticles with an average particle size of 100 nm to 500 nm to the polyamic acid solution and stirring to prepare a mixed solution; and (c) coating and drying the mixed solution to manufacture a polyimide film, wherein the breakdown voltage (BDV) of the polyimide film is equal to or greater than 350 kV / mm, and the roughness (Ra) of the polyimide film is equal to or greater than 0.01 nm.

[0040] The mixed solution may include 1,000 ppm to 5,000 ppm of the nanoparticles, preferably 1,500 ppm to 4,500 ppm, 1,800 ppm to 4,200 ppm, 2,000 ppm to 4,000 ppm, 2,300 ppm to 3,700 ppm, 2,500 ppm to 3,500 ppm, and more preferably 2,800 ppm to 3,200 ppm.

[0041] If the content of nanoparticles in the mixed solution is less than 1000 ppm, the breakdown voltage of the resulting polyimide film will be low, which is not ideal. If the content of nanoparticles in the mixed solution exceeds 5000 ppm, the improvement in breakdown voltage relative to the nanoparticles used will not be significant, resulting in low efficiency, which is also not ideal.

[0042] The solvent may include at least one selected from the group consisting of: N,N'-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), diethylacetamide (DEAc), N-ethyl-2-pyrrolidone (NEP), N,N'-diethylformamide (DEF), dimethylpropionamide (DMPA), and γ-butyrolactone (GBL).

[0043] In this disclosure, based on 100 parts by weight of a polyamic acid solution, the solid content of the polyamic acid solution can be from 15 wt% to 50 wt%. The lower limit of the solid content can be 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt% or higher, and the upper limit of the solid content can be 45 wt%, 40 wt%, 35 wt%, 30 wt%, 27 wt%, 25 wt% or lower. By adjusting the solid content of the polyamic acid solution, the increase in viscosity during the curing process can be controlled and the processing time can be shortened.

[0044] Another embodiment of this disclosure provides a secondary battery comprising a polyimide film prepared by a method for manufacturing a polyimide film.

[0045] Beneficial effects According to the polyimide membrane and its preparation method disclosed herein, by including nanoparticles with an average particle size of 100 nm to 500 nm, the breakdown strength is improved, thereby increasing the breakdown voltage and improving the electrical properties of the membrane, thus enhancing the practicality of the membrane in secondary batteries.

[0046] Furthermore, the polyimide film and its preparation method according to this disclosure have the effect of satisfying the roughness required to ensure the winding properties of samples in roll-to-roll processes.

[0047] Furthermore, the polyimide film according to this disclosure has the effect of being suitable for secondary batteries. Detailed Implementation

[0048] Best mode Examples are provided to aid in understanding this disclosure. The following examples are provided merely for the purpose of understanding this disclosure, and the content of this disclosure is not limited to these examples.

[0049] <Example: Manufacturing of Polyimide Film> Example 1 A polyamic acid solution was prepared by mixing 100 mol% of a diamine monomer and 100 mol% of a dianhydride monomer in a 100 mol% dimethylformamide (DMF) solvent. In this solution, the diamine monomer comprised 25 mol% of 1,4-diaminobenzene (PPD) and 75 mol% of 4,4'-diaminodiphenyl ether (ODA), and the dianhydride monomer comprised 100 mol% of pyromellitic dianhydride (PMDA).

[0050] A mixed solution was prepared by adding 3000 ppm of nano-silica with an average particle size of 100 nm and a catalyst to a polyamic acid solution and stirring.

[0051] The defoamed mixture was coated onto a glass plate. The solvent-to-solid ratio was then calculated, and a coater was used to spread the mixture evenly on the surface. Curing was then performed under the following conditions: 130°C (3 minutes) → 280°C (4 minutes) → 420°C (4 minutes) to obtain a polyimide film. The film thickness was 12.5 μm.

[0052] Examples 2 to 5 The polyimide film was manufactured in the same way as in Example 1, except that nano-silica with different average particle sizes as shown in Table 1 below was used.

[0053] Comparative Examples 1 to 4 The method for manufacturing the polyimide film is the same as in Example 1, except that calcium phosphate is used instead of nano-silica, and different average particle sizes and contents of calcium phosphate are used as shown in Table 1 below.

[0054] Comparative examples 5 to 7 The polyimide film was manufactured in the same way as in Example 1, except that nano-silica with different average particle sizes as shown in Table 1 below was used.

[0055] Table 1 below lists the types of nanoparticles (nano silica, calcium phosphate), average particle size, and content used in the preparation of polyimide films in Examples 1 to 5 and Comparative Examples 1 to 7.

[0056] Table 1

[0057] <Experimental Example: Evaluation of the Physical Properties of Polyimide Films> Experimental Example 1: Evaluation of Breakdown Voltage (BDV) For the polyimide films manufactured in the examples and comparative examples, the breakdown voltage (BDV) of the films was measured according to the ASTM D149 standard specification. Specifically, the polyimide films were pretreated in an oven at 100°C to remove moisture, and then fixed in a measuring device (PHENIX TECHNOLOGIES 6CCE50-5) set to room temperature. The breakdown voltage was measured by applying an AC voltage of 10 kV to the upper and lower electrodes and increasing the AC voltage from 0 at a constant rate. The measurement results are shown in Table 2 below.

[0058] Experimental Example 2: Measurement of Roughness (Ra) Value For the polyimide films manufactured in the examples and comparative examples, the roughness (Ra) of the films was measured using a film roughness analyzer manufactured by Kosaka Laboratories Co., Ltd. The measurement results are shown in Table 2 below.

[0059] Table 2

[0060] As shown in Table 2, Examples 1 to 5, which use nano-silica with an average particle size of 100 nm to 500 nm, all have excellent BDV values ​​(≥350 kV / mm) and roughness (Ra) values ​​(≥0.010 nm).

[0061] It is also known that comparative examples 1 to 4, which use calcium phosphate with average particle sizes of 1 μm and 2 μm, have excellent roughness (Ra) values, but low BDV values.

[0062] Furthermore, comparative examples 5 to 7, which use nano-silica with an average particle size of less than 100 nm, exhibit low roughness values.

[0063] On the other hand, Example 5, which uses nano-silica with an average particle size of 500 nm, has excellent BDV value (≥350 kV / mm) and roughness (Ra) value (≥0.010 nm), but is not ideal due to the possibility of filler dispersion problems.

[0064] Based on these results, the polyimide film and its manufacturing method disclosed herein can enhance the breakdown strength by including nanoparticles with an average particle size of 100 nm to 500 nm, thereby increasing the breakdown voltage and improving the electrical properties, thus enhancing the practicality of the film in secondary batteries.

[0065] Furthermore, the polyimide film and its manufacturing method disclosed herein can achieve the effect of meeting the roughness required to ensure sample winding in roll-to-roll processes by including nanoparticles with an average particle size of 100 nm to 500 nm.

[0066] Furthermore, the polyimide film disclosed herein has the effect of being suitable for secondary batteries.

[0067] In this specification, detailed descriptions of content that can be fully understood and derived by one of skill in the art to which this disclosure pertains are omitted, and various modifications may be made without departing from the technical spirit or basic structure of this disclosure, except for the specific examples described herein. Therefore, this disclosure may be implemented in ways different from the specific descriptions and illustrations herein, as will be understood by one of skill in the art.

Claims

1. A polyimide film, comprising: A polyimide comprising a dianhydride monomer and a diamine monomer as polymerization units; as well as Nanoparticles, wherein the average particle size of the nanoparticles is 100 nm to 500 nm. The breakdown voltage (BDV) of the polyimide film is equal to or greater than 350 kV / mm, and the roughness (Ra) of the polyimide film is equal to or greater than 0.01 nm.

2. The polyimide film according to claim 1, wherein, The nanoparticles include nano-silica.

3. The polyimide film according to claim 1, wherein, The polyimide film comprises 1000 ppm to 5000 ppm of the nanoparticles.

4. The polyimide film according to claim 1, wherein, The dianhydride monomer comprises at least one selected from the group consisting of: pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), diphenyl sulfone-3,4,3',4'-tetracarboxylic dianhydride (DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride. Anhydrides, p-phenylenebis(triphenylenetriol monoester anhydride), p-biphenylenebis(triphenylenetriol monoester anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic anhydride, p-terphenyl-3,4,3',4'-tetracarboxylic anhydride, 1,3-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic anhydride.

5. The polyimide film according to claim 4, wherein, The dianhydride monomer includes pyromellitic dianhydride (PMDA).

6. The polyimide film according to claim 1, wherein, The diamine monomer comprises at least one selected from the group consisting of: 1,4-diaminobenzene (PPD), 4,4'-diaminodiphenyl ether (ODA), 2,2-diaminophenoxyphenylpropane (BAPP), m-phenylenediamine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzoic acid (DABA), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-toluidine), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diphenylbenzene. Aminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 4,4'-diaminobenzoylaniline, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodibenzophenone, 4,4'-diaminodibenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzphenone, 3,3'-diaminodiphenyl ether 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1 4-Bis(3-aminophenoxy)benzene (TPE-Q), 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-(4-phenylphenoxy)benzophenone, 3,3'-diamino-4,4'-bis(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylthio)benzene, 1,3-bis(4-aminophenylthio)benzene, 1,4-bis(4-aminophenylthio)benzene, 1,3-bis(3-aminophenylsulfonyl)benzene, 1,3-bis(4-aminophenylsulfonyl)benzene, 1,4-bis(4-aminophenylsulfonyl)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-Bis[2-(4-aminophenyl)isopropyl]benzene, 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ether [-aminophenoxy)phenyl]one, bis[3-(4-aminophenoxy)phenyl]one, bis[4-(3-aminophenoxy)phenyl]one, bis[4-(4-aminophenoxy)phenyl]one, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[3-(4 ... [3-(3-aminophenoxy)phenyl] sulfone, bis[4-(3-aminophenoxy)phenyl] sulfone, bis[4-(4-aminophenoxy)phenyl] sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3 ... [4-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane.

7. The polyimide film according to claim 6, wherein, The diamine monomers include 1,4-diaminobenzene (PPD) and 4,4'-diaminodiphenyl ether (ODA).

8. The polyimide film according to claim 7, wherein, The content of 1,4-diaminobenzene (PPD) in the total diamine monomers is greater than 0 mol% and less than or equal to 50 mol%, and the content of 4,4'-diaminodiphenyl ether (ODA) in the total diamine monomers is greater than or equal to 50 mol% and less than 100 mol%.

9. The polyimide film according to claim 1, wherein, The thickness of the polyimide film is from 1 μm to 100 μm.

10. A secondary battery comprising the polyimide film according to claim 1.

11. A method for manufacturing a polyimide film, comprising the following steps: (a) Adding dianhydride monomers and diamine monomers to a solvent and polymerizing them to prepare a polyamic acid solution; (b) Adding nanoparticles with an average particle size of 100 nm to 500 nm to the polyamic acid solution and stirring to prepare a mixed solution; and (c) Coating and drying the mixed solution to produce a polyimide film. The breakdown voltage (BDV) of the polyimide film is equal to or greater than 350 kV / mm, and the roughness (Ra) of the polyimide film is equal to or greater than 0.01 nm.

12. The polyimide film according to claim 11, wherein, The mixed solution comprises 1000 ppm to 5000 ppm of the nanoparticles.

13. The polyimide film according to claim 11, wherein, The solvent comprises at least one selected from the group consisting of: N,N'-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), diethylacetamide (DEAc), N-ethyl-2-pyrrolidone (NEP), N,N'-diethylformamide (DEF), dimethylpropionamide (DMPA), and γ-butyrolactone (GBL).

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