Nanomembrane, electronic device including same, and method for manufacturing said nanomembrane

Abstract

The present invention relates to a nanomembrane made of polyimide fiber, which includes an oil-repellent coating layer on the front or back surface of the nanomembrane, and which has a contact angle of 90 degrees or more with silicone oil having a surface tension of 20 dyne / cm as measured according to ASTM D5946, and which has a dust collection efficiency of 95% or more as measured by the following method: [Measurement method] Dust size: 0.6 μm; Air flow: 32 L / min; Measurement area: 100 cm; Manufacturing method thereof; and Nanomembrane assembly including the same. 2 Measure according to AFT8130.

Description

[Technical Field]

[0001] The present invention relates to a nanomembrane having excellent dust collection efficiency and waterproofing, an electronic device including the same, and a method for manufacturing the nanomembrane. [Background technology]

[0002] Recently, electronic devices, such as communication devices such as smartphones, have become smaller, more integrated, and consume less power.

[0003] Communication devices such as smartphones contain built-in microelectromechanical systems (MEMS), which contain a variety of electronic components. To prevent these electronic components from being contaminated by external contaminants, extensive research has been conducted on sealing materials.

[0004] However, the encapsulation materials that have been successfully commercialized to date still lack dust collection efficiency and oil repellency, which means that moisture such as saliva and rainwater, as well as foreign substances such as dust, can get inside the MEMS during use, causing malfunctions of electronic components.

[0005] To solve these problems, attempts have been made to reduce porosity to improve dust collection efficiency, but this has reached a limit where sound transmission loss increases significantly. Methods have also been proposed to reduce porosity or to layer a water-repellent layer on the membrane surface to prevent the intrusion of moisture and dust, but these also have reached a limit where sound transmission loss increases and air permeability decreases.

[0006] Another method has been devised in which oil-repellent materials are mixed into the fibers during production, but the MEMS manufacturing process is often carried out at high temperatures of over 280°C, and the polymers that have been used so far have limitations on organic materials, causing the membrane to shrink or melt at high temperatures, and the oil-repellent material to carbonize, resulting in a limit to the deformation of the membrane.

[0007] As a result, there is still a demand for dust-proof and oil-repellent nanomembranes that can withstand the high temperatures of over 280°C during the manufacturing process of microelectromechanical systems (MEMS), and that have improved dust collection efficiency, water resistance, and oil resistance while maintaining sound transmission loss. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides nanomembranes that have high heat resistance, dust collection efficiency, and oil repellency without exhibiting a decrease in air / sound transmission. [Means for solving the problem]

[0009] According to one aspect, there is provided a nanomembrane formed of polyimide fibers, the nanomembrane comprising an oil-repellent coating layer on the front or back surface thereof, the nanomembrane having a contact angle of 90 degrees or more measured according to ASTM D5946 using silicone oil having a surface tension of 20 dyne / cm, and the nanomembrane having a dust collection efficiency of 95% or more measured by the following measurement method.

[0010] [Measurement method] Dust size: 0.6 μm; Air flow: 32 l / min; Measurement area: 100 cm 2 Measured by AFT8130 at

[0011] According to one embodiment, the membrane may be manufactured by electrospinning.

[0012] According to an embodiment, the oil-repellent coating layer may include at least one of a fluorine-based compound, a silicone-based compound, and a hydrocarbon-based compound.

[0013] According to an embodiment, the fluorine-based compound may include a fluoroalkyl acrylate copolymer, dimethyl perfluorobutylethyl, methyl perfluorobutylethyl, a fluoroalkylether copolymer, a perfluoro compound, or a combination thereof.

[0014] According to an embodiment, the silicone-based compound may include a methyl vinyl siloxane copolymer or a combination thereof.

[0015] According to an embodiment, the hydrocarbon-based compound may include a C10-18 hydrocarbon compound or a combination thereof.

[0016] According to an embodiment, the polyimide fibers may include polyethyleneimine, polyamideimide, polyetherimide, or a combination thereof.

[0017] According to one embodiment, the nanomembrane may have a thermal shrinkage rate of 1% or less at 300°C.

[0018] According to one embodiment, the weight loss rate of the nanomembrane at 300°C may be 1 wt% or less.

[0019] According to one embodiment, the sound transmission loss of the nanomembrane may be less than 5 dB / pa at 94 dB.

[0020] According to one aspect, there is provided a nanomembrane assembly including the nanomembrane; and an adhesive layer interposed between the substrate and the nanomembrane.

[0021] According to one aspect, there is provided an electronic device comprising the nanomembrane.

[0022] According to one aspect, a method for manufacturing a nanomembrane includes: an electrospinning step of electrospinning a polyamic acid solution to produce a precursor; a processing step of adjusting the density and thickness of the precursor; a converting step of determining the morphology of the precursor; and a step of imidizing the converted precursor to obtain a nanomembrane precursor; and a step of treating the nanomembrane precursor with an oil-repellent agent to introduce functional groups onto the surface. The oil-repellent agent is a solution containing 1 to 20 wt % of at least one of a fluorine-based compound, a silicone-based compound, and a hydrocarbon-based compound. The imidization is performed at 200 to 500°C for 10 to 30 minutes. During the electrospinning step, air is blown in the direction of the precursor being discharged. The nanomembrane has a dust collection efficiency of 95% or more, as measured by the following method.

[0023] [Measurement method] Dust size: 0.6 μm; Air flow: 32 l / min; Measurement area: 100 cm 2 Measured by AFT8130. [Effects of the Invention]

[0024] The nanomembrane of the present invention is made of polyimide fibers formed by electrospinning a polyimide precursor, so there is no deterioration in quality even during high-temperature processes.

[0025] In addition, the oil-repellent coating layer formed on the front or back surface effectively prevents moisture from passing through by achieving a contact angle of 90 degrees or more when measured in accordance with ASTM D5946 with silicone oil having a surface tension of 20 dyne / cm, and a dust collection efficiency of 95% or more, effectively preventing the passage of pollutants. [Brief explanation of the drawings]

[0026] [Figure 1]1 is a schematic diagram of a nanomembrane assembly according to an embodiment of the present invention. [Figure 2] 1 is a photograph taken from above of a nanomembrane assembly manufactured according to an embodiment of the present invention. [Figure 3] 1 is a photograph showing the results of an oil repellency experiment on the nanomembranes produced in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, the terms "top" and "above" may refer not only to something directly on top in contact with the object, but also to something on top without contact. The singular expression includes the plural expression unless the context clearly indicates otherwise. Furthermore, when a part is described as "comprising" a certain element, this does not mean that other elements are excluded, but that other elements may also be included, unless otherwise specified.

[0028] The use of the term "said" and similar directives can refer to both the singular and the plural. Unless a clear order is stated for method steps or a statement to the contrary, these steps can be performed in any suitable order and are not necessarily limited to the order stated.

[0029] As used herein, the terms "comprise," "comprising," "formed," "has," "having," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements, but may include other elements that are not expressly listed or that are inherent in such process, method, article, or apparatus. Furthermore, unless clearly stated to the contrary, "or" refers to an inclusive or and not an exclusive or.

[0030] The use of any examples or exemplary terms is merely to illustrate the technical concepts in detail, and such examples or exemplary terms are not intended to limit the scope unless otherwise limited by the claims.

[0031] FIG. 1 is a schematic diagram of a nanomembrane assembly (10) including an oil-repellent treated membrane (100), and FIG. 2 is a photograph of a group of such nanomembrane assemblies (10) taken from above.

[0032] Referring to Figure 1, the nanomembrane assembly (10) includes an oil-repellent nanomembrane (100), an adhesive layer (110) disposed on one side of the oil-repellent nanomembrane along the periphery of the nanomembrane, and a substrate (120) disposed on the adhesive layer.

[0033] The nanomembrane assembly (10) can be manufactured by placing an adhesive film having an adhesive layer (110) on a substrate (120) over the entire surface along the periphery of the oil-repellent treated nanomembrane (100).

[0034] A dustproof section (B) is formed in the part of the nanomembrane assembly (10) where the adhesive film is not placed, and the dustproof section (B) allows air to pass through but not substantially allows dust particles of a few microns to pass through, and has oil-repellent properties that substantially prevent the passage of moisture. Therefore, when such a nanomembrane assembly is applied to a microelectromechanical system (MEMS), it can prevent the performance of the MEMS from being degraded by the inflow of foreign substances such as saliva and dust.

[0035] The adhesive layer (110) can be made of a known adhesive that can firmly maintain adhesion between the oil-repellent nanomembrane (100) and the MEMS that will be applied subsequently, and examples of such adhesives include epoxy adhesives, urethane adhesives, acrylic adhesives, thermosetting adhesives, and petroleum resin adhesives.

[0036] For example, the adhesive layer (110) may include a thermosetting adhesive.

[0037] The substrate 120 can be a release film, which acts as a carrier for placing an adhesive film on the oil-repellent nanomembrane 100 and prevents contamination of the adhesive layer before applying the nanomembrane assembly 10 to an acoustic device such as a MEMS.

[0038] The substrate (120) can be selected from known films that are easily peeled from the adhesive layer (110).

[0039] The oil-repellent nanomembrane (100) may be a nanomembrane formed of polyimide fibers having an average diameter of 0.1 to 15 μm.

[0040] The polyimide fiber refers to a polymer containing an imide bond in the main chain, and may include polyethyleneimine, polyamideimide, polyetherimide, or a combination thereof.

[0041] According to an embodiment, the polyimide fiber may be prepared by heating a solution containing a polyimide precursor to imidize it.

[0042] The polyimide precursor may be a polyamic acid.

[0043] The polyamic acid solution can be prepared by dissolving a diamine monomer and a dianhydride monomer in a solvent.

[0044] The diamine monomer may be at least one selected from the group consisting of 4,4'-oxydianiline (ODA), 1,3-bis(4-aminophenoxy)benzene (RODA), p-phenylene diamine (p-PDA), and o-phenylene diamine (o-PDA), and preferably 4,4'-oxydianiline (ODA), p-phenylene diamine (p-PDA), o-phenylene diamine (o-PDA), or a mixture thereof.

[0045] The dianhydride monomer may be at least one selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,4,3',4'-biphenyltetracarboxylic dianhydride (BPDA), and bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SiDA).

[0046] The solvent may be one or more selected from the group consisting of m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), acetone, diethyl acetate, tetrahydrofuran (THF), chloroform, and γ-butyrolactone.

[0047] The polyamic acid solution may have a solids content of 5 to 30 wt % and a solution viscosity of 100 to 500 poise. For example, the polyamic acid solution may have a solids content of 10 to 20 wt % and a solution viscosity of 200 to 300 poise. The solution viscosity can be measured at 23°C according to the method of KS M ISO 2555. The solids content and solution viscosity can affect the quality and thickness of the resulting fiber, but if the solids content and solution viscosity are satisfied, polyimide fibers of 0.1 to 15 μm can be obtained.

[0048] The electrospinning step is a step of electrospinning a polyamic acid solution to produce a precursor. To disperse the precursor during the electrospinning step, air can be blown in the direction of the precursor being extruded. The direction of the air can be adjusted at various angles based on the direction of the precursor being extruded to disperse the precursor.

[0049] During electrospinning, a polyamic acid solution is spun from a nozzle to produce a precursor, which is dispersed by electrostatic forces generated between the spun precursors. To disperse the precursor over a wider area, air can be blown toward the precursor at a predetermined angle. The pressure of the air allows the precursor to be dispersed and collected over a wider area. During this process, the solvent contained in the precursor is removed.

[0050] In the present invention, by blowing air toward the precursor, the precursor can be dispersed over a wider area, and the nanomembrane (100) thus produced has pores with large diameters and high air permeability.

[0051] In addition, in order to thoroughly remove the solvent during the electrospinning step, high-temperature air can be injected horizontally, and the temperature and amount of the horizontally injected air and the air for dispersing the precursor can be adjusted to finely adjust the pore size, porosity, and physical properties of the nanomembrane (100).

[0052] For example, the temperature of the air injected in the electrospinning step may be 40° C. to 80° C. When the temperature of the injected air is within this range, a porous structure can be formed that can improve dust collection efficiency without sound transmission loss even after oil repellent treatment.

[0053] The discharge rate in the electrospinning step is 0.5 to 8 ml / min, e.g., 2 to 7 ml / min, or 3 to 5 ml / min. By controlling the discharge rate in the electrospinning step within this range, a sufficient amount of fibers can be discharged and collected from the collector, and the solvent can be sufficiently evaporated to form a membrane, thereby increasing the dust collection efficiency.

[0054] A certain electric field can be applied between the nozzle and the collector to produce a nanomembrane with nanofibers of a certain thickness. The strength of the electric field can be 3 to 80 kV. When the electric field strength is within this range, a certain amount of spinning solution can be continuously discharged, making it possible to produce a nanofiber web of uniform thickness. On the other hand, if the electric field strength is too low, for example, less than 3 kV, the spinning solution cannot be discharged smoothly, which can lead to nozzle clogging. If the electric field strength is too high, for example, more than 80 kV, the solvent in the scattered fibers reaches the collector without being completely removed, making it difficult to obtain nano-sized fibers.

[0055] The nanofiber web may be formed by bonding fibers arranged in a specific direction or randomly arranged in a collector. For example, the nanofiber web may have a structure formed by bonding fibers in the form of a nonwoven fabric.

[0056] The processing step is a step of adjusting the density and thickness of the precursor accumulated in the electrospinning step, and can be carried out through a two-stage continuous calender. The processing step is carried out at a temperature of 20 to 100°C and a pressure of 20 to 200 kgf / cm. 2For example, the processing step can be carried out at a temperature of 30 to 80°C and a pressure of 30 to 150 kgf / cm. 2 By carrying out the processing step within the above temperature and pressure ranges, there is no sound transmission loss due to void destruction caused by excessive density increase, and excellent durability can be achieved.

[0057] The converting step determines the shape of the processed precursor and can include cross-cutting, such as slitting to obtain a product of the desired width and guillotining to obtain a product of the desired length, and can include, for example, flat or rotary die cutting to obtain a product of the desired shape.

[0058] The converted precursor can then be imidized to form a strong bond between the fibers.

[0059] The imidization can be carried out by thermal imidization, chemical imidization, or a combination thereof.

[0060] For example, the thermal imidization process can be carried out by heating the converted precursor at a temperature of 200°C to 500°C for 10 to 30 minutes, or at a temperature of 350 to 450°C for 15 to 25 minutes.

[0061] When the thermal imidization process is carried out within the above range, a polyimide nanomembrane with desired physical properties can be obtained without destruction or thermal shrinkage of the polyimide nanomembrane.

[0062] For example, the chemical imidization step can be carried out by contacting the converted precursor with a solvent such as an acid anhydride, such as acetic anhydride, or a tertiary amine, such as pyridine.

[0063] The polyimide nanomembrane that has undergone the imidization process can have an imidization rate of 90% or more, which allows it to have excellent heat resistance and durability, even at temperatures above 280°C.

[0064] Furthermore, the polyimide nanomembrane obtained through the imidization process may have a porosity of 50 to 90%. For example, the porosity of the polyimide nanomembrane may be 60 to 90%, 70 to 90%, or 60 to 80%.

[0065] The polyimide nanomembrane that has undergone the imidization process may have a dust collection efficiency of 95% or more, as measured by the following method. For example, the dust collection efficiency of the polyimide nanomembrane may be 96% or more, 97% or more, 98% or more, or 99% or more.

[0066] [Measurement method] Dust size: 0.6 μm; Air flow: 32 l / min; Measurement area: 100 cm 2 Measured by AFT8130 at

[0067] The polyimide nanomembranes prepared as described above are described in further detail below.

[0068] The polyimide nanomembrane may have a thickness of 0.5 to 20 μm. The thickness of the nanomembrane may vary depending on the method of coating the nanomembrane and the components contained in the coating solution. However, when measuring the physical properties of the nanomembrane, a difference in thickness of 1 to 3 μm does not significantly affect the physical properties of the nanomembrane.

[0069] The air permeability of the nanomembrane is 0.5 to 200 cm 3 / cm 2 For example, the air permeability of the nanomembrane may be 1 to 200 cm / sec. 3 / cm 2 / sec, 5 to 190cm 3 / cm2 / sec, 10 to 180cm 3 / cm 2 / sec, 15 to 170 cm 3 / cm 2 / sec, 20 to 160 cm 3 / cm 2 / sec, 25 to 150cm 3 / cm 2 / sec, or 30 to 140 cm 3 / cm 2 / sec may be possible.

[0070] The nanomembrane has a unit weight of 0.1 to 10 g / m 2 For example, the nanomembrane may have a unit weight of 1 to 5 g / m 2 , or 1 to 3 g / m 2 It is possible.

[0071] The thermal shrinkage of the nanomembrane can be 1% or less at 300°C.

[0072] The weight loss rate of the nanomembrane at 300°C may be 1% by weight or less.

[0073] The nanomembrane may have a sound transmission loss of less than 5 dB / pa at a 94 dB standard.

[0074] The polyimide nanomembrane may have an oil-repellent functional group on its surface by treating the surface with an oil-repellent agent. The oil-repellent agent may be a solution of a fluorine-based compound, a silicone-based compound, or a hydrocarbon-based compound dissolved in a solvent. In this case, the compound may be contained in the solvent at 1 to 20 wt %. For example, the compound may be contained in the solvent at 3 to 15 wt %.

[0075] For example, the fluorine-based compound may include a fluoroalkyl acrylate copolymer, dimethyl perfluorobutylethyl, methyl perfluorobutylethyl, a fluoroalkylether copolymer, a fluoropolyether compound, a perfluoro compound, or a combination thereof.

[0076] For example, the fluorine-based compound may be a fluoroalkyl acrylate copolymer.

[0077] The perfluoro compound can be perfluorotri-N-butylamine.

[0078] For example, the silicone-based compound may include, but is not limited to, a methylvinyl siloxane copolymer, or a combination thereof.

[0079] For example, the hydrocarbon-based compound may include, but is not necessarily limited to, a C10-18 hydrocarbon compound or a combination thereof.

[0080] The oil repellent agent can be applied to the surface of the polyimide nanomembrane by spray coating, dip coating, pad dry coating, gravure coating, plasma treatment, or a combination thereof, preferably by spray coating. By applying the oil repellent agent to the nanomembrane by spray coating, the oil repellent agent can be evenly dispersed and applied to the front and back surfaces of the polyimide nanomembrane without blocking the pores of the polyimide nanomembrane, thereby providing oil repellency throughout the polyimide nanomembrane.

[0081] Figure 3 shows the photographs used to measure the contact angle on the surface of a nanomembrane that was not treated with an oil repellent agent (left) and a nanomembrane that was treated with an oil repellent agent (right).

[0082] The nanomembrane treated with the oil repellent agent has a uniform surface treatment on both the front and back sides, and can have a contact angle of 90 degrees or more when measured according to ASTM D5946 against silicone oil with a surface tension of 20 dyne / cm.

[0083] The nanomembrane treated with the oil repellent agent has a uniform surface treatment on both the front and back sides, and can have a contact angle of 90 degrees or more when measured according to ASTM D5946 using ultrapure water with an electrical conductivity of 1 μs / cm or less and a surface tension of 72 dyne / cm.

[0084] The nanomembrane treated with the oil repellent agent may have a difference of 50 or less or 45 or less between the contact angle of silicone oil measured in accordance with ASTM D5946 and the contact angle measured in accordance with ASTM D5946 using ultrapure water with an electrical conductivity of 1 μs / cm or less and a surface tension of 72 dyne / cm.

[0085] The nanomembrane treated with the oil repellent agent can improve the contact angle with water such as pure water and at the same time improve the contact angle with oil such as silicone oil by being treated with the oil repellent agent.

[0086] In addition, the oil-repellent treatment effectively blocks the intrusion of hydrophilic and lipophilic substances from the outside, thereby improving the dust collection efficiency.

[0087] In conclusion, in the past, sound transmission loss could not be prevented by adjusting the porosity to improve dust collection efficiency, but the nanomembrane according to one embodiment of the present invention has the effect of improving dust collection efficiency while maintaining sound transmission loss at a similar level to before the oil repellent treatment by the oil repellent treatment.

[0088] The nanomembrane assembly according to an embodiment of the present invention can be used in various electronic devices including MEMS, such as mobile phones, electronic pads, microphones, and speakers. [Example]

[0089] The present invention will be described in more detail below through specific examples, but the present invention is not limited to the following examples.

[0090] Example 1 5 L of polyamic acid solution was prepared with a solids content of 11 wt % and a solution viscosity of 250 poise (KSMISO2555, 23° C.).

[0091] The prepared polyamic acid solution was transferred to a solution tank and then supplied to a spinning chamber equipped with 20 nozzles and a high voltage of 60 kV via a metering gear pump. The precursor was electrospun. The discharge rate was 4 ml / min, the ratio of the distance between the nozzle and the accumulating plate to the distance at the nozzle tip was 1.2, and air at 70°C was blown in the direction of the precursor discharge to disperse the precursor. The precursor was then transferred in a roll-to-roll fashion and processed using a two-stage continuous calender maintained at 65°C, applying a linear pressure of 100 kgf / cm. After the converting process, the precursor was processed to a thickness of 5 μm and a unit weight of 3 g / m. 2 The converted precursor was then transferred in a roll-to-roll manner and imidized for 20 minutes in a continuous heat treatment furnace maintained at a temperature of 400°C, resulting in a final thickness of 4 μm and a unit weight of 2 g / m. 2 A polyimide nanomembrane was fabricated.

[0092] An oil-repellent nanomembrane was produced by spraying a mixture of an oil-repellent agent made of a fluoropolymer dissolved in isopropyl alcohol at a concentration of 5% by weight onto the surface of the polyimide nanomembrane at a rate of 5 cc per minute.

[0093] <Examples 2 to 14> The reaction conditions were modified as shown in Table 1 below, and an oil-repellent nanomembrane was prepared in the same manner as in Example 1. In Table 1 below, the perfluoro compound is perfluorotri-N-butylamine.

[0094] <Comparative Example 1> 5 L of polyamic acid solution was prepared with a solids content of 11 wt % and a solution viscosity of 250 poise (KSMISO2555, 23° C.).

[0095] The prepared polyamic acid solution was transferred to a solution tank and then supplied to a spinning chamber equipped with 20 nozzles and a high voltage of 60 kV via a metering gear pump. The precursor was electrospun. The discharge rate was 4 ml / min, the ratio of the distance between the nozzle and the accumulating plate to the distance at the nozzle tip was 1.2, and air at 70°C was blown in the direction of the precursor discharge to disperse the precursor. The precursor was then transferred in a roll-to-roll fashion and processed using a two-stage continuous calender maintained at 65°C, applying a linear pressure of 100 kgf / cm. After the converting process, the precursor was processed to a thickness of 5 μm and a unit weight of 3 g / m. 2 The converted precursor was then transferred in a roll-to-roll manner and imidized for 20 minutes in a continuous heat treatment furnace maintained at a temperature of 300°C, resulting in a final thickness of 4 μm and a unit weight of 2 g / m. 2 A polyimide nanomembrane was fabricated.

[0096] <Comparative Examples 2 to 7> The reaction conditions were modified as shown in Table 2 below, and an oil-repellent nanomembrane was produced in the same manner as in Example 1. In Table 2 below, the perfluoro compound is perfluorotri-N-butylamine.

[0097] <Comparative Example 8> Polyvinylidene difluoride (PVDF) was dissolved in dimethylformamide (DMF) solvent to prepare 5 L of electrospinning solution with a solid content of 15 wt % and a solution viscosity of 250 poise (KS MISO 2555, 23°C).

[0098] The electrospinning solution was transferred to a solution tank and then supplied to a spinning chamber consisting of 20 nozzles and a high voltage of 60 kV via a metering gear pump to produce PVDF nanomembranes by electrospinning. The discharge rate was 4 ml / min, and the ratio of the distance between the nozzle and the integrating plate to the distance at the tip of the nozzle was 1.2.

[0099] [Table 1]

[0100] [Table 2]

[0101] <Nanomembrane evaluation> The unit weight, thickness, porosity, air permeability, pore size, contact angle (oil), sound transmission loss, dust collection efficiency (dustproofness), and heat shrinkage rate of the nanomembranes of Examples 1 to 12 and Comparative Examples 1 to 8 were measured using the following methods, and the results are shown in Table 3.

[0102] (1) Unit weight: KSK0514 or ASTM D3776 (2) Thickness: KSK0506 or KSK ISO 9073-2, ISO 4593

[0103] (3) Porosity: Calculated as the ratio of air volume to the total volume of the nanofiber membrane according to the following formula 1 (total volume was calculated by manufacturing a rectangular or circular sample and measuring its width, length, and thickness, and air volume was calculated by measuring the mass of the sample and subtracting the polymer volume, calculated from the density, from the total volume).

[0104] [Formula 1] Porosity (%) = [1-(A / B)] x 100 = {1-[(C / D) / B]} x 100

[0105] In Equation 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.

[0106] (4) Air permeability: ASTM D737, area 38 cm 2 , measured under a constant pressure of 125 Pa (cm 3 / cm 2 / sec) can be converted to CFM (Cubic Feet per Minute), the conversion factor is 0.508016, and the unit is ft 3 / ft 2 / min (CFM).

[0107] (5) Average pore diameter: Using a capillary flow porometer (CFP) specified in ASTM F316, the average pore size and pore size distribution were measured from the diameter of the limiting pore, which is the pore size at the narrowest section.

[0108] (6) Contact angle (oil): This was measured using an SEO Phoenix 300 Touch (equipment name) in accordance with the method specified in ASTM D 5946. After dropping a certain amount of silicone oil (surface tension of 20 dyne / cm@20℃) onto the nanomembrane, the angle formed between the stationary droplet and the surface was measured. The larger the contact angle of the silicone oil, the greater the oil repellency.

[0109] (7) Sound transmission loss: The change in microphone sensitivity was confirmed in the speaker frequency range (100 to 20,000 Hz), and the degree of sound loss was evaluated by measuring the sensitivity when the nanomembrane assembly was attached to the MEMS that detects the microphone sensitivity and when it was not attached.

[0110] (8) Dust collection efficiency (dustproof): Dust size 0.6 μm, air flow rate 32 l / min, and measurement area 100 cm 2 Measured using AFT8130.

[0111] (9) Heat shrinkage rate (%): After heat treatment in an oven at 300°C±2°C for 30±2 minutes, the sample was left at 23°C±2°C and 50%±5% humidity (relative humidity) for 24 hours, and then the change in length was measured.

[0112] (10) Weight loss rate: 0.5 g of each sample was prepared, and the samples were heated under nitrogen conditions at a rate of 20°C / min from room temperature to 800°C using a TGA analyzer (Thermoplus EVOII TG8120, Rigaku Co., Ltd.), and the resulting weight change was measured.

[0113] [Table 3]

[0114] As shown in Table 3, the oil-repellent treated nanomembrane of Example 1 had similar levels of air permeability, porosity, and sound transmission loss to the untreated nanomembranes (Comparative Examples 1 and 3), but the oil contact angle was significantly increased, resulting in a dust collection efficiency of over 98%. Furthermore, due to its excellent heat resistance, there was virtually no membrane loss during high-temperature operation. Furthermore, Example 1, which had an oil repellent component concentration of 5 wt%, had significantly less sound transmission loss and significantly better air permeability than Comparative Example 2, which had an oil repellent component concentration of 25 wt%, and Comparative Example 6, which had an oil repellent component concentration of 40 wt%.

[0115] It can also be seen that Example 1, in which the concentration of the oil repellent component is 5% by weight, exhibits a higher contact angle (oil) than Comparative Example 7, in which the concentration is 0.5% by weight.

[0116] Furthermore, Comparative Example 5, in which the imidization temperature was 600°C, was carbonized and the physical properties could not be measured, and Comparative Example 4, in which the imidization temperature was 180°C, was confirmed to have a sound transmission loss four times or more that of Example 1, in which the imidization temperature was 400°C.

[0117] On the other hand, it can be seen that Example 1 using polyamic acid is far superior to Comparative Example 8 using PVDF in air permeability and dust collection efficiency.

[0118] As such, the nanomembrane according to the present invention can be used without quality degradation in the MEMS manufacturing process, which involves high-temperature operations, and is also recognized as having overcome the existing technical challenge of adjusting the porosity and pore size of conventional polyimide nanomembranes to improve their dust collection efficiency, which required an increase in sound transmission loss. [Industrial Applicability]

[0119] The present invention can provide a nanomembrane that is made of polyimide fibers formed by electrospinning a polyimide precursor, and therefore does not suffer from quality degradation even during high-temperature processes.

Claims

1. A nanomembrane formed of polyimide fibers, The nanomembrane includes an oil-repellent coating layer on the front or back surface thereof; The nanomembrane has a contact angle of 90 degrees or more when measured with a silicone oil having a surface tension of 20 dyne / cm according to ASTM D5946; The nanomembrane has a dust collection efficiency of 95% or more as measured by the following method: [Measurement method] Dust size: 0.6 μm; Air flow: 32 l / min; Measurement area: 100 cm ２ Measured by AFT8130 at .

2. The nanomembrane of claim 1 , wherein the membrane is fabricated by electrospinning.

3. The nanomembrane of claim 1 , wherein the oil-repellent coating layer comprises at least one of a fluorine-based compound, a silicone-based compound, and a hydrocarbon-based compound.

4. 4. The nanomembrane of claim 3, wherein the fluorine-based compound comprises a fluoroalkyl acrylate copolymer, a dimethyl perfluorobutylethyl, a methyl perfluorobutylethyl, a fluoroalkylether copolymer, a perfluoro compound, or a combination thereof.

5. 4. The nanomembrane of claim 3, wherein the silicone-based compound comprises a methyl vinyl siloxane copolymer, or a combination thereof.

6. The nanomembrane of claim 3 , wherein the hydrocarbon-based compound comprises a C10-18 hydrocarbon compound or a combination thereof.

7. 10. The nanomembrane of claim 1, wherein the polyimide fibers comprise polyethyleneimine, polyamideimide, polyetherimide, or a combination thereof.

8. The nanomembrane according to claim 1, wherein the nanomembrane has a thermal shrinkage rate of 1% or less at 300°C.

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

10. 10. The nanomembrane of claim 1, wherein the nanomembrane has a sound transmission loss of less than 5 dB / pa at a 94 dB standard.

11. Base material; The nanomembrane of any one of claims 1 to 10; and an adhesive layer interposed between the substrate and the nanomembrane; A nanomembrane assembly comprising:

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

13. an electrospinning step of electrospinning a polyamic acid solution to prepare a precursor; a processing step for adjusting the density and thickness of the precursor; a converting step to determine the form of the precursor; and imidizing the converted precursor to obtain a nanomembrane precursor; and The nanomembrane precursor is treated with an oil repellent agent to introduce functional groups onto the surface, The oil repellent agent is a solution containing at least one of a fluorine-based compound, a silicone-based compound, and a hydrocarbon-based compound in an amount of 1 to 20% by weight, The imidization is carried out at 200 to 500° C. for 10 to 30 minutes. A method for manufacturing a nanomembrane, characterized in that air is blown in the direction in which the precursor is discharged during the electrospinning step, and the nanomembrane has a dust collection efficiency of 95% or more as measured by the following method: [Measurement method] Dust size: 0.6 μm; Air flow: 32 l / min; Measurement area: 100 cm ２ Measured by AFT8130 at .

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