Nanofilm, electronic device including the nanofilm, and method for manufacturing the nanofilm

Abstract

The present invention relates to a nanofilm, a method for manufacturing the nanofilm, and a nanofilm module comprising the nanofilm, the nanofilm comprising a polyimide fiber, the nanofilm comprising an oleophobic coating layer on the front surface or the back surface thereof, the nanofilm having a contact angle of 90 degrees or more with respect to a silicone oil having a surface tension of 20 dyne / cm when measured on the basis of ASTM D 5946, and a method for manufacturing the nanofilm, and a nanofilm module comprising the nanofilm. The dust collection efficiency of the nanofilm is greater than or equal to 95% based on the following measurement method. According to the determination method, determination is carried out based on AFT 8130 under the conditions that the dust particle size is 0.6 mu m, the air flow is 32 L / min and the determination area is 100 cm < 2 >.

Description

Technical Field

[0001] The present invention relates to a nano-membrane with excellent dust collection efficiency and waterproofness, an electronic device including the nano-membrane, and a method for manufacturing the nano-membrane. Background Art

[0002] In recent years, electronic devices such as smartphones and other communication devices are gradually becoming smaller, more integrated, and have low power consumption.

[0003] Communication devices such as smartphones have built-in microelectromechanical systems (MEMS), which contain various electronic components. In order to protect these electronic components from contamination by external pollutants, various research projects are underway on sealing materials.

[0004] However, commercialized sealing materials not only have insufficient dust collection efficiency but also lack oleophobicity. Therefore, during use, moisture such as saliva and rainwater, as well as foreign matter such as dust, enter the MEMS and cause electronic components to malfunction.

[0005] To address this issue, attempts were made to improve dust collection efficiency by reducing porosity, but this ultimately resulted in a significant increase in sound transmission loss. To prevent the introduction of moisture and dust, methods were proposed to reduce porosity or laminate a hydrophobic layer to the membrane surface, but this also resulted in problems such as increased sound transmission loss and decreased air permeability.

[0006] In addition, a method has been proposed in which oleophobic materials are mixed during the fiber manufacturing process. However, most MEMS manufacturing processes are performed at high temperatures above 280°C, and the traditionally used polymers have limitations as organic materials. As a result, problems such as membrane deformation due to thermal shrinkage or melting of the membrane at high temperatures and carbonization of the oleophobic material occur.

[0007] Therefore, there is still a need for a dust-proof and oleophobic nanofilm that can fully withstand MEMS manufacturing processes performed at high temperatures above 280°C and maintain the sound transmission loss rate while improving dust collection efficiency, water resistance, and oil resistance. Summary of the Invention

[0008] Technical issues

[0009] The present invention provides a nano-membrane having high heat resistance, dust collection efficiency and oleophobicity without reducing air permeability and sound transmittance.

[0010] Technical Solution

[0011] According to one aspect, a nanomembrane is provided, which is formed from polyimide fiber, and the nanomembrane includes an oleophobic coating on its surface or back side. When measured based on ASTM D 5946, the contact angle of the nanomembrane for silicone oil with a surface tension of 20 dyne / cm is greater than or equal to 90 degrees, and the dust collection efficiency of the nanomembrane based on the following measurement method is greater than or equal to 95%.

[0012] [Measurement method]

[0013] The dust particle size is 0.6 μm, the air flow rate is 32 L / min, and the measurement area is 100 cm 2 Measured based on AFT8130 under the conditions of .

[0014] According to one embodiment, the nanomembrane can be produced by electrospinning.

[0015] According to one embodiment, the oleophobic coating may include at least one of a fluorine compound, a silicon compound, and a hydrocarbon compound.

[0016] According to one embodiment, the fluorine compound may include a fluoroalkylacrylate copolymer, dimethylperfluorobutylethyl, methylperfluorobutylethyl, a fluoroalkylether copolymer, a perfluoro compound, or a combination thereof.

[0017] According to one embodiment, the silicon-based compound may include methylvinyl siloxane copolymer or a combination thereof.

[0018] According to one embodiment, the hydrocarbon compound may include C10-18 hydrocarbons or a combination thereof.

[0019] According to one embodiment, the polyimide fiber may include polyethyleneimide, polyamideimide, polyetherimide, or a combination thereof.

[0020] According to one embodiment, the thermal shrinkage rate of the nanofilm at 300° C. may be less than or equal to 1%.

[0021] According to one embodiment, the weight loss rate of the nanofilm at 300° C. may be less than or equal to 1 weight %.

[0022] According to one embodiment, at a 94 dB reference, the sound transmission loss of the nano-membrane may be less than 5 dB / Pa.

[0023] According to one aspect, a nanofilm assembly is provided, comprising: the nanofilm; and an adhesive layer interposed between the substrate and the nanofilm.

[0024] According to one aspect, an electronic device is provided, comprising the nanofilm.

[0025] According to one aspect, a method for manufacturing a nanomembrane is provided, which includes: an electrospinning step of electrospinning a polyamic acid solution to form a precursor; a processing step of adjusting the density and thickness of the precursor; a conversion step of determining the morphology of the precursor; obtaining a nanomembrane precursor by imidizing the converted precursor; and introducing functional groups on the surface by treating the nanomembrane precursor with an oleophobic processing agent, wherein the oleophobic processing agent is a solution including 1 wt % to 20 wt % of at least one of a fluorine compound, a silicon compound and a hydrocarbon compound, the imidization is performed at 200° C. to 500° C. for 10 to 30 minutes, and in the electrospinning step, air is blown in the direction in which the precursor is discharged, and the dust collection efficiency of the nanomembrane based on the following measurement method is greater than or equal to 95%.

[0026] [Measurement method]

[0027] The dust particle size is 0.6 μm, the air flow rate is 32 L / min, and the measurement area is 100 cm 2 Measured based on AFT8130 under the conditions of .

[0028] Beneficial effects

[0029] The nanomembrane according to the present invention is composed of polyimide fibers formed by electrospinning a polyimide precursor, and thus does not suffer quality degradation in a high-temperature process.

[0030] In addition, since the oleophobic coating formed on the surface or back has a contact angle of greater than or equal to 90 degrees for silicone oil with a surface tension of 20 dyne / cm when measured based on ASTM D 5946, it can effectively inhibit water permeation, and since the dust collection efficiency is greater than or equal to 95%, it can effectively prevent pollutants from passing through. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a nano-membrane assembly according to one embodiment of the present invention.

[0032] Figure 2 The above diagram shows a nano-membrane assembly manufactured according to an embodiment of the present invention.

[0033] Figure 3 It is a result graph of the oleophobicity test of the nanofilms prepared by Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0034] Hereinafter, terms such as "above" or "above" include not only cases where a component is directly in contact with the component but also cases where the component is not in contact with the component. Singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, when a component is described as "including" a certain component, it means that the component also includes the other components, not that the component is excluded, unless otherwise specified.

[0035] The term "said" and similar indicative terms can correspond to both the singular and the plural. The steps constituting the method can be performed in an appropriate order and are not necessarily limited to the order described unless otherwise explicitly stated.

[0036] As used herein, the terms "comprises," "includes," "formed," "having," "having," or any other modifications thereof encompass non-exclusive inclusion. For example, a process, method, article, or machine that comprises a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent to such process, method, article, or machine. Furthermore, unless expressly stated otherwise, "or" is intended to be an inclusive or, not an exclusive or.

[0037] All examples or exemplary terms used are used to describe the technical concept in detail, and these examples or exemplary terms do not limit the scope of the present invention unless otherwise defined in the claims.

[0038] Figure 1 is a schematic diagram of a nano-membrane assembly 10 including an oleophobic treated membrane 100, Figure 2 This is a picture showing a group of such nano-membrane modules 10 taken from above.

[0039] See also Figure 1 The nano-membrane assembly 10 includes: a nano-membrane 100, which is processed by oleophobic treatment; an adhesive layer 110, which is arranged on one side of the nano-membrane processed by oleophobic treatment along the edge of the nano-membrane; and a substrate 120, which is arranged on the adhesive layer.

[0040] The nano-membrane assembly 10 may be manufactured by disposing an adhesive film having an adhesive layer 110 disposed on a substrate 120 along an edge of the oleophobic-treated nano-membrane 100 on one side thereof.

[0041] A dustproof portion B is configured in the portion of the nanomembrane assembly 10 where the adhesive film is not arranged. The dustproof portion B is breathable, but actually prevents dust of several microns from passing through, and has oleophobicity that substantially blocks water permeability. Therefore, when this nanomembrane assembly is suitable for a microelectromechanical system (MEMS), it can prevent the performance of the MEMS from being degraded due to the introduction of foreign matter such as saliva and dust.

[0042] The adhesive layer 110 may use a known adhesive that can firmly maintain adhesion between the oleophobically treated nanofilm 100 and a subsequently applied MEMS. Examples of such adhesives include epoxy adhesives, polyurethane adhesives, acrylic adhesives, thermosetting adhesives, and petroleum resin adhesives.

[0043] For example, the adhesive layer 110 may include a thermosetting adhesive.

[0044] The substrate 120 may be a release film that serves as a carrier for placing an adhesive film on the oleophobically treated nanomembrane 100 to prevent contamination of the adhesive layer before the nanomembrane assembly 10 is subsequently used in an acoustic element such as MEMS.

[0045] The substrate 120 may be selected from known films that can be easily peeled from the adhesive layer 110 .

[0046] The oleophobically treated nanomembrane 100 may be a nanomembrane formed of polyimide fibers having an average diameter of 0.1 μm to 15 μm.

[0047] The polyimide fiber refers to a polymer containing imide bonds in the main chain, which may include polyethylene imide, polyamide imide, polyether imide, or a combination thereof.

[0048] According to one embodiment, the polyimide fiber may be produced by heating a solution containing a polyimide precursor to imidize the solution.

[0049] Polyamic acid may be used as the polyimide precursor.

[0050] The polyamic acid solution may be prepared by dissolving a diamine monomer and a dianhydride monomer in a solvent.

[0051] The diamine monomer may be one or more selected from the group consisting of 4,4′-diaminodiphenyl ether (4,4′-oxydianiline, ODA), 1,3-bis(4-aminophenoxy)benzene (1,3-bis(4-aminophenoxy)benzene, RODA), p-phenylenediamine (p-PDA) and o-phenylene diamine (o-PDA), preferably 4,4′-diaminodiphenyl ether, p-phenylenediamine, o-phenylene diamine or a mixture thereof.

[0052] The dianhydride monomer may be one or more selected from pyromellyrtic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-diphenyl ether dianhydride (ODPA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and bis(3,4-dicarboxyphenyl)dimethylsilanedianhydride (SiDA).

[0053] The solvent may be one or more selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate, tetrahydrofuran (THF), chloroform and γ-butyrolactone.

[0054] The polyamic acid solution may have a solid content of 5% to 30% by weight, and a solution viscosity of 100 to 500 poise. For example, the polyamic acid solution may have a solid content of 10% to 20% by weight, and a solution viscosity of 200 to 300 poise. The solution viscosity can be measured at 23°C using the KS MISO 2555 method. The solid content and solution viscosity may affect the quality and thickness of the resulting fiber. When these solid content and solution viscosity are met, polyimide fibers with a thickness of 0.1 μm to 15 μm can be obtained.

[0055] The electrospinning step forms a precursor by electrospinning a polyamic acid solution. To disperse the precursor during the electrospinning step, air may be blown in the direction in which the precursor is discharged. The direction of the air may be adjusted to various angles based on the direction in which the precursor is dispersed to disperse the precursor.

[0056] During the electrospinning process, a polyamic acid solution is spun from a nozzle to form a precursor. The precursor is dispersed by the electrostatic force generated between the spun precursors. At this point, air can be blown toward the precursors at a predetermined angle to disperse the precursors over a wider area. The air pressure causes the precursors to disperse and aggregate over a wider area. During this process, the solvent contained in the precursors is removed.

[0057] In the present invention, the precursor can be dispersed over a wider range by blowing air toward the precursor, so that the nanofilm 100 manufactured thereby has pores with large diameters and high air permeability.

[0058] In addition, high-temperature air can be injected horizontally during the electrospinning step to fully remove the solvent, and the pore size, porosity, and physical properties of the nanomembrane 100 can be finely controlled by adjusting the air and precursors used to disperse the horizontal injection.

[0059] For example, the temperature of the air injected during the electrospinning step may be 40° C. to 80° C. When the temperature of the injected air satisfies the above range, a porous structure may be provided, which can improve dust collection efficiency during oleophobic treatment without causing sound transmission loss.

[0060] In the electrospinning step, the discharge rate may be 0.5 mL / min to 8 mL / min, for example, 2 mL / min to 7 mL / min, or 3 mL / min to 5 mL / min. By adjusting the discharge rate to the above range in the electrospinning step, the solvent is fully volatilized and stacked until a sufficient amount of fibers are discharged and collected in the collector, thereby forming a film, and ultimately the dust collection efficiency can be improved.

[0061] A constant electric field is applied between the nozzle and the collector to produce a nanofilm with nanofibers of constant thickness. The intensity of the electric field can be 3kV to 80kV. When the intensity of the electric field meets the range, a certain amount of spinning solution can be continuously discharged, and a nanofiber web with uniform thickness can be made. In addition, when the intensity of the electric field is too low, for example, less than 3kV, nozzle clogging may occur because the spinning solution cannot be discharged smoothly. When the intensity of the electric field is too high, for example, greater than 80kV, the solvent of the scattered fibers reaches the collector in an incompletely removed state, making it difficult to obtain nanometer-sized fibers.

[0062] The nanofiber web may be formed by combining fibers aligned in a constant direction or randomly arranged on a collector. For example, the nanofiber web may have a structure formed by combining fibers in a non-woven fabric form.

[0063] The processing step is a step of adjusting the density and thickness of the precursor gathered in the electrospinning step, which can be performed by a two-stage continuous calender. The processing step can be performed by applying 20 kgf / cm2 at a temperature of 20°C to 100°C. 2 Up to 200kgf / cm 2 For example, the processing step may be performed by applying 30 kgf / cm2 at a temperature of 30°C to 80°C. 2 Up to 150kgf / cm 2 Since the processing step is performed within the above temperature and pressure ranges, excellent durability can be achieved without causing sound transmission loss due to destruction of voids due to excessive density increase.

[0064] The conversion step is a step for determining the shape of the processed precursor. The conversion may include slitting to obtain a product of desired width and guillotining to obtain a product of desired length, and may include flat press or rotary die cutting to obtain a product of desired shape.

[0065] The converted precursor can then be imidized to form strong bonds between the fibers.

[0066] The imidization may be performed by thermal imidization, chemical imidization, or a combination thereof.

[0067] For example, the thermal imidization process may be performed by heating the converted precursor at 200° C. to 500° C. for 10 to 30 minutes, or at 350° C. to 450° C. for 15 to 25 minutes.

[0068] When the thermal imidization process is performed within the above range, a polyimide nanofilm having desired physical properties can be obtained without the polyimide nanofilm being damaged or thermally shrunk.

[0069] For example, the chemical imidization process may be performed by contacting the converted precursor with an acid anhydride such as acetic anhydride or a tertiary amine solvent such as pyridine.

[0070] The polyimide nanofilm subjected to the imidization process can have an imidization rate greater than or equal to 90%. Since the imidization rate reaches 90% or higher, the polyimide nanofilm can have excellent heat resistance and durability capable of withstanding high temperatures above 280°C.

[0071] Furthermore, the polyimide nanofilm subjected to the imidization process may have a porosity of 50% or 90%. For example, the porosity of the polyimide nanofilm may be 60% to 90%, 70% to 90%, or 60% to 80%.

[0072] The dust collection efficiency of the polyimide nanofilm after the imidization process can be greater than or equal to 95% as measured by the following measurement method. For example, the dust collection efficiency of the polyimide nanofilm can be greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, or greater than or equal to 99%.

[0073] [Measurement method]

[0074] The dust particle size is 0.6 μm, the air flow rate is 32 L / min, and the measurement area is 100 cm 2 The measurement was performed based on AFT 8130.

[0075] The polyimide nanofilm prepared as above is described in further detail below.

[0076] The polyimide nanofilm may have a thickness of 0.5 μm to 20 μm. The thickness of the nanofilm may vary depending on the method of coating the nanofilm and the components contained in the coating solution. However, when measuring the physical properties of the nanofilm, a thickness difference of 1 μm to 3 μm does not affect the physical properties of the nanofilm.

[0077] The air permeability of the nanofilm can be 0.5cm 3 / cm2 / sec to 200cm 3 / cm 2 / sec. For example, the air permeability of the nanofilm can be 1cm 3 / cm2 / sec to 200cm 3 / cm2 / sec、5cm 3 / cm 2 / sec to 190cm 3 / cm 2 / sec、10cm 3 / cm2 / sec to 180cm 3 / cm 2 / sec、15cm 3 / cm2 / sec to 170cm 3 / cm 2 / sec、20cm 3 / cm2 / sec to 160cm 3 / cm 2 / sec、25cm 3 / cm2 / sec to 150cm 3 / cm2 / sec, or 30cm 3 / cm2 / sec to 140cm 3 / cm2 / sec.

[0078] The unit weight of the nanofilm can be 0.1 g / m 2 Up to 10g / m 2 For example, the unit weight of the nanofilm can be 1 g / m 2 Up to 5g / m 2 , or 1g / m 2 Up to 3g / m 2 .

[0079] The thermal shrinkage rate of the nanofilm at 300° C. may be less than or equal to 1%.

[0080] The weight loss rate of the nanofilm at 300° C. may be less than or equal to 1 weight %.

[0081] At a 94 dB reference, the sound transmission loss of the nanomembrane can be less than 5 dB / Pa.

[0082] The polyimide nanofilm may have oleophobic functional groups on its surface by treating the surface with an oleophobic finishing agent. The oleophobic finishing agent may be a solution of a fluorine compound, a silicon compound, and a hydrocarbon compound dissolved in a solvent. In this case, the compound may be included in an amount of 1% to 20% by weight in the solvent. For example, the compound may be included in an amount of 3% to 15% by weight in the solvent.

[0083] For example, the fluorine compound may include fluoroalkyl acrylate copolymer, dimethyl perfluorobutylethyl, methyl perfluorobutylethyl, fluoroalkyl ether copolymer, fluoropolyether compound, perfluoro compound, or a combination thereof.

[0084] For example, the fluorine compound may be a fluoroalkyl acrylate copolymer.

[0085] The perfluorinated compound may be perfluorotri-N-butylamine.

[0086] For example, the silicon-based compound may include methyl vinylsiloxane copolymer or a combination thereof, but is not necessarily limited thereto.

[0087] For example, the hydrocarbon compound may include C10-18 hydrocarbons or a combination thereof, but is not necessarily limited thereto.

[0088] The oleophobic processing agent can be treated on the surface of the polyimide nanofilm by spraying, dipping, pad-dry coating, gravure coating, plasma treatment or a combination thereof, preferably by spraying. The oleophobic processing agent is treated by spraying on the nanofilm, thereby not blocking the gaps in the polyimide nanofilm, and is evenly dispersed and coated on the surface and back of the polyimide nanofilm, and can provide oleophobicity to the entire polyimide nanofilm.

[0089] Figure 3 This is a graph showing the measurement of the surface contact angles of a nanofilm that has not been treated with an oleophobic treatment agent (left side) and a nanofilm that has been treated with an oleophobic treatment agent (right side).

[0090] In the nanofilm treated with the oleophobic treatment agent, the surface and the back surface are uniformly treated, so that the contact angle of the nanofilm to silicone oil with a surface tension of 20 dyne / cm is greater than or equal to 90 degrees when measured according to ASTM D5946.

[0091] The nanofilm treated with the oleophobic treatment agent has its front and back surfaces uniformly treated so that the contact angle is greater than or equal to 90 degrees when measured based on ASTM D 5946 using ultrapure water having a conductivity of less than or equal to 1 μs / cm and a surface tension of 72 dyne / cm.

[0092] In the nanomembrane treated with the oleophobic processing agent, the difference between the contact angle with silicone oil when measured based on ASTM D 5946 and the contact angle when measured based on ASTM D 5946 using ultrapure water having a conductivity of less than or equal to 1 μs / cm and a surface tension of 72 dyne / cm is less than or equal to 50 degrees or less than or equal to 45 degrees.

[0093] The nanofilm treated with the oleophobic treatment agent can simultaneously increase the contact angle with respect to water such as pure water and the contact angle with respect to oil such as silicone oil due to the treatment with the oleophobic treatment agent.

[0094] In addition, the oleophobic processing effectively blocks the external hydrophilic and oleophilic substances from entering the interior and improves the dust collection efficiency.

[0095] Ultimately, the prior art cannot prevent sound transmission loss by adjusting the porosity to improve dust collection efficiency, but the nanomembrane according to one embodiment of the present invention maintains a similar sound transmission loss as before the oleophobic treatment due to the oleophobic treatment, while the dust collection efficiency is improved.

[0096] The nano-membrane assembly according to one embodiment of the present invention can be used in various electronic devices including MEMS, such as mobile phones, tablet computers, microphones, and speakers.

[0097] Implementation Method

[0098] Hereinafter, the present invention will be further described in detail through specific examples, but the present invention is not limited thereto.

[0099] Example 1

[0100] 5 L of a polyamic acid solution was prepared, wherein the solid content was 11 wt % and the solution viscosity was 250 poise (KS MISO 2555, 23° C.).

[0101] The prepared polyamic acid solution is transferred to a solution tank and supplied to a spinning chamber with 20 nozzles and a high voltage of 60kV through a quantitative gear pump, and the precursor is made by electrospinning. At this time, the discharge rate is 4mL / min, the ratio of the distance between the nozzle and the collecting plate to the distance at the end of the nozzle is 1.2, and air at 70°C is blown in the direction of the precursor discharge to disperse the precursor. Afterwards, while the precursor is transferred by a roll-to-roll method, a two-stage continuous calender with a temperature maintained at 65°C is used to apply a linear pressure of 100kgf / cm for processing, and a film with a thickness of 5μm and a unit weight of 3g / m is produced through a conversion process. 2 The converted precursor was then transferred in a roll-to-roll manner and imidized in a continuous heat treatment furnace maintained at 400°C for 20 minutes, ultimately producing a 4μm thick, 2g / m2 2 polyimide nanofilm.

[0102] An oleophobic processing agent composed of a fluorine-containing polymer was dissolved in isopropyl alcohol at a rate of 5 wt % to prepare a mixed solution, and the mixed solution was used to process the surface of the polyimide nanofilm at a rate of 5 cc per minute, thereby preparing an oleophobic nanofilm.

[0103] Example 2 to Example 14

[0104] The reaction conditions were modified to those shown in Table 1 below, and an oleophobic nanofilm was prepared by the same method as in Example 1. The perfluorinated compound in Table 1 below is perfluorotri-n-butylamine.

[0105] Comparative Example 1

[0106] 5 L of a polyamic acid solution was prepared, wherein the solid content was 11 wt % and the solution viscosity was 250 poise (KS MISO 2555, 23° C.).

[0107] The prepared polyamic acid solution was transferred to a solution tank and supplied to a spinning chamber with 20 nozzles and a high voltage of 60kV through a quantitative gear pump, and the precursor was made by electrospinning. At this time, the discharge rate was 4mL / min, the ratio of the distance between the nozzle and the collecting plate to the distance at the end of the nozzle was 1.2, and air at 70°C was blown in the direction of the precursor discharge to disperse the precursor. Afterwards, while the precursor was transferred by a roll-to-roll method, a two-stage continuous calender with a temperature maintained at 65°C was used to apply a linear pressure of 100kgf / cm for processing, and a film with a thickness of 5μm and a unit weight of 3g / m was produced through a conversion process. 2 The converted precursor was then transferred in a roll-to-roll manner and imidized in a continuous heat treatment furnace maintained at 300°C for 20 minutes, ultimately producing a 4μm thick, 2g / m2 2 polyimide nanofilm.

[0108] Comparative Examples 2 to 7

[0109] The reaction conditions were modified to those shown in Table 2 below, and an oleophobic nanofilm was prepared by the same method as in Example 1. The perfluorinated compound in Table 2 below is perfluorotri-n-butylamine.

[0110] Comparative Example 8

[0111] 5 L of electrospinning solution was prepared by dissolving polyvinylidene difluoride (PVDF) in dimethylformamide (DMF). The solid content of the solution was 15 wt % and the solution viscosity was 250 poise (KS MISO 2555, 23° C.).

[0112] The prepared electrospinning solution was transferred to a solution tank and supplied via a metering gear pump to a spinning chamber equipped with 20 nozzles and applying a high voltage of 60 kV. PVDF nanomembranes were electrospun at a discharge rate of 4 mL / min, and the ratio of the distance between the nozzle and the collecting plate to the distance at the nozzle tip was 1.2.

[0113] [Table 1]

[0114]

[0115]

[0116] [Table 2]

[0117]

[0118] Evaluation of nanofilms

[0119] The unit weight, thickness, porosity, air permeability, pore size, contact angle (oil), sound transmission loss, dust collection efficiency (dustproofness), and thermal shrinkage of the nanofilms in Examples 1 to 12 and Comparative Examples 1 to 8 were measured according to the following methods. The results are shown in Table 3.

[0120] (1) Unit weight: KS K 0514 or ASTM D 3776

[0121] (2) Thickness: KS K 0506 or KS K ISO 9073-2, ISO 4593

[0122] (3) Porosity: The ratio of the air volume to the overall volume of the nanofiber membrane is calculated according to the following mathematical formula 1 (the overall volume is calculated by measuring the width, length and thickness of a rectangular or circular sample, and the air volume is calculated by subtracting the polymer volume from the overall volume, and the polymer volume is calculated by inverse calculation from the density after measuring the mass of the sample).

[0123] [Mathematical formula 1]

[0124] Porosity (%) = [1-(A / B)] × 100 = {1-[(C / D) / B]} × 100

[0125] In Mathematical Formula 1, A is the density of the nanomembrane, B is the density of the nanomembrane polymer, C is the weight of the nanomembrane, and D is the volume of the nanomembrane.

[0126] (4) Air permeability: ASTM D 737, area 38cm 2 , static pressure 125Pa. 3 / cm 2 / sec) to CFM, the conversion factor is 0.508016, the unit is ft 3 / ft 2 / min(CFM).

[0127] (5) Average pore size: The average pore size and pore size distribution are determined by the diameter of the limiting pores (i.e., the pore size in the narrowest area) using a capillary flow porometer (CFP) specified in ASTM F316.

[0128] (6) Contact angle (oil): Measured using a SEO Phoenix 300Touch (equipment name) according to ASTM D 5946. A certain amount of silicone oil (surface tension 20 dyne / cm @ 20°C) was dropped onto the nanofilm, and the angle between the stationary droplet and the surface was measured. A larger angle indicates higher oleophobicity.

[0129] (7) Sound transmission loss: The sensitivity change of the microphone is confirmed within the frequency range of the speaker (100 Hz to 20,000 Hz). The sensitivity is measured when the nanofilm component is attached to the MEMS for identifying the microphone sensitivity and when it is not attached, thereby evaluating the degree of sound transmission loss.

[0130] (8) Dust collection efficiency (dust resistance): Dust size 0.6 μm, air flow rate 32 L / min, measurement area 100 cm 2 The measurement was performed using AFT 8130.

[0131] (9) Thermal shrinkage (%): After heat treatment in an oven at 300°C ± 2°C for 30 ± 2 minutes, the length change was measured after placing at 23°C ± 2°C and 50% ± 5% (relative humidity) for 24 hours.

[0132] (10) Weight loss rate: 0.5 g of each sample was prepared and heated from room temperature to 800°C at a rate of 20°C / min under nitrogen conditions using a Thermoplus EVO II TG8120 (Rigaku Corporation, Japan), and the corresponding weight change was measured.

[0133] [Table 3]

[0134]

[0135]

[0136] As shown in Table 3 above, Example 1, an oleophobic-treated nanomembrane, exhibited similar air permeability, porosity, and sound transmission loss levels to those of the untreated nanomembranes (Comparative Examples 1 and 3). However, its oil contact angle was significantly increased, resulting in a dust collection efficiency exceeding 98%. Furthermore, due to its excellent heat resistance, virtually no membrane loss was observed during high-temperature operation. Furthermore, compared to Comparative Example 2, which had an oleophobic agent concentration of 25 wt %, and Comparative Example 6, which had an oleophobic agent concentration of 40 wt %, Example 1 (at a 5 wt % concentration) exhibited no sound transmission loss and exhibited significantly superior air permeability.

[0137] Furthermore, Example 1 (concentration of 5 wt %) exhibited a higher contact angle (oil) than Comparative Example 7 in which the concentration of the oleophobic agent component was 0.5 wt %.

[0138] Furthermore, carbonization was confirmed in Comparative Example 5 with an imidization temperature of 600°C, and its physical properties could not be measured. The sound transmission loss of Comparative Example 1 with an imidization temperature of 180°C was four times that of Example 1 with an imidization temperature of 400°C.

[0139] Furthermore, compared to Comparative Example 8 using PVDF, Example 1 using polyamic acid was superior in air permeability, dust collection efficiency, and the like.

[0140] As described above, the nanomembrane according to the present invention can be used in a MEMS manufacturing process operating at high temperature without quality degradation, and solves the problem in the prior art of accepting increased sound transmission loss when adjusting the porosity and pore size to improve the dust collection efficiency of the polyimide nanomembrane.

[0141] Industrial Applicability

[0142] The invention forms polyimide fibers by electrospinning a polyimide precursor, thereby providing a nano-membrane with no quality degradation under a high-temperature process.

Claims

1. A nanofilm formed from polyimide fibers, comprising: an oleophobic coating located on the surface or back of the nanofilm, Wherein, when measured based on ASTM D 5946, the contact angle of the nanofilm to silicone oil with a surface tension of 20 dyne / cm is greater than or equal to 90 degrees, The dust collection efficiency of the nanofilm is greater than or equal to 95% based on the following measurement method, Determination method: The dust particle size is 0.6μm, the air flow rate is 32L / min, and the measurement area is 100cm. 2 The measurement was performed based on AFT 8130 under the conditions of .

2. The nanofilm according to claim 1, wherein The nanofilm is produced by electrospinning.

3. The nanofilm according to claim 1, wherein The oleophobic coating includes at least one of a fluorine compound, a silicon compound, and a hydrocarbon compound.

4. The nanofilm according to claim 3, wherein The fluorine compound includes fluoroalkyl acrylate copolymer, dimethyl perfluorobutyl ethyl, methyl perfluorobutyl ethyl, fluoroalkyl ether copolymer, perfluoro compound, or a combination thereof.

5. The nanofilm according to claim 3, wherein The silicon compound includes methyl vinyl siloxane copolymer or a combination thereof.

6. The nanofilm according to claim 3, wherein The hydrocarbon compound includes C10-18 hydrocarbons or a combination thereof.

7. The nanofilm according to claim 1, wherein The polyimide fiber includes polyethyleneimide, polyamideimide, polyetherimide, or a combination thereof.

8. The nanofilm according to claim 1, wherein The thermal shrinkage rate of the nanofilm at 300° C. is less than or equal to 1%.

9. The nanofilm according to claim 1, wherein The weight loss rate of the nanofilm at 300° C. is less than or equal to 1 weight %.

10. The nanofilm according to claim 1, wherein At a reference of 94 dB, the sound transmission loss of the nano-membrane is less than 5 dB / Pa.

11. A nano-membrane assembly comprising: substrate; The nanofilm according to any one of claims 1 to 10; as well as An adhesive layer is sandwiched between the substrate and the nanofilm.

12. An electronic device comprising the nanofilm according to any one of claims 1 to 10.

13. A method for manufacturing a nanofilm, comprising: an electrospinning step of electrospinning a polyamic acid solution to form a precursor; a processing step to adjust the density and thickness of the precursor; a conversion step, determining the morphology of the precursor; Obtaining a nanomembrane precursor by imidizing the converted precursor; as well as The nanofilm precursor is treated with an oleophobic agent to introduce functional groups on the surface. The oleophobic treatment agent is a solution comprising 1 wt% to 20 wt% of at least one of a fluorine compound, a silicon compound, and a hydrocarbon compound. The imidization is performed at 200° C. to 500° C. for 10 to 30 minutes. In the electrospinning step, air is blown in the direction in which the precursor is discharged, and the dust collection efficiency of the nanofilm based on the following measurement method is greater than or equal to 95%, Determination method: The dust particle size is 0.6 μm, the air flow rate is 32 L / min, and the measurement area is 100 cm 2 The measurement was performed based on AFT 8130 under the conditions of .

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