KR101935052B1 - Manufacturing method for electro-magnetic interfernce shielding film and electro-magnetic interference shielding film using the same - Google Patents

Abstract

The present invention provides a manufacturing method of an electro-magnetic interference shielding film, which includes the steps of: a) preparing a polymer solution by dissolving a cellulose-based polymer in water; b) preparing a first composition for an electromagnetic wave interference shielding film by adding carbon nanotubes, copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm, and a surfactant into the polymer solution, and irradiating an ultrasonic wave to the polymer solution by using an ultrasonic wave horn; c) preparing a second composition by mixing carbon black with the composition and agitating the mixture by using a paste mixer; and d) applying the second composition onto a substrate and drying the substrate applied with the second composition, wherein in the step b), the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles are added at a weight ratio of 1 : 2-2.5.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an electromagnetic wave shielding film, and an electromagnetic wave shielding film using the same. BACKGROUND ART [0002]

The present invention relates to a method for producing an electromagnetic wave shielding film and an electromagnetic wave shielding film produced using the same.

Techniques for adding an electromagnetic shielding property to a polymer material include adding an inorganic material or a carbon-based material capable of shielding electromagnetic waves to the polymer resin. However, recently, a small amount of carbon nanotubes are added to a polymer resin, Studies are underway to satisfy both shielding performance and moldability

Carbon nanotubes have high electrical conductivity, thermal stability, tensile strength and resilience, so they are used as additives for various composites. When carbon nanotubes are used as an additive for a composite material, how uniformly the bundles of carbon nanotubes are dispersed is a very important factor.

On the other hand, the carbon nanotubes have a relatively long length as compared with the diameter, and a strong attraction force between the carbon nanotubes has a problem that the dispersion has a very low dispersion degree to the polymer. One of the conventional techniques for solving this problem is a technique for increasing the degree of dispersion of carbon nanotubes by impregnating carbon nanotubes in nitric acid, sulfuric acid, or a mixed solution thereof to oxidize the surface.

However, this technique has various problems such as safety problems or environmental problems because the acid solution is used in the production process, and it is difficult to ensure process stability in mass production.

The present invention relates to a carbon nanotube composite material which can uniformly disperse carbon black, carbon nanotubes, and two or more specific conductive nanomaterial composites in a polymer solution to sufficiently exhibit high conductivity characteristics, exhibit excellent adhesion to a substrate, And to provide an electromagnetic wave shielding film produced by the method.

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The present invention provides a method for preparing a polymer solution, comprising the steps of: a) dissolving a cellulose-based polymer in water to prepare a polymer solution; b) adding carbon nanotubes, copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm and a surfactant to the polymer solution, To produce a first composition for an electromagnetic wave shielding film; c) mixing the composition with carbon black, and stirring the mixture with a paste mixer to prepare a second composition; And d) applying and drying the second composition on a substrate, wherein in step b), the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles have a weight ratio of 1: 2 to 2.5 To the electromagnetic wave shielding film.

Hereinafter, a method of manufacturing an electromagnetic wave shielding film according to a specific embodiment of the present invention will be described in detail.

As described above, according to one embodiment of the present invention, there is provided a method of preparing a polymer solution, comprising: a) dissolving a cellulose-based polymer in water to prepare a polymer solution; b) adding carbon nanotubes, copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm and a surfactant to the polymer solution, Irradiating ultrasound to produce a composition for an electromagnetic wave shielding film; c) mixing the composition with carbon black and stirring with a paste mixer; And d) applying the composition on a substrate and drying the composition.

The inventors of the present invention concluded that the above-mentioned series of steps comprises simultaneously the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles having a specific average particle diameter as a conductive metal, And copper-silver core shell nanoparticles are contained in the polymer solution at a specific weight ratio, and when the carbon black and the carbon nanotubes are dispersed together in the polymer solution, the conductive nanometal composite and the carbon nanotubes are uniformly dispersed in the polymer solution The present inventors have confirmed through experiments that the electromagnetic wave shielding film to be manufactured exhibits high conductivity characteristics sufficiently, has excellent adhesion to a substrate, and has an excellent electromagnetic wave shielding effect, and completed the invention.

First, a polymer solution is prepared by dissolving a cellulose-based polymer in water (step a).

Specifically, the cellulose-based polymer may be eco-friendly, water-soluble, and has excellent chemical stability and durability. Examples of the cellulose polymer include Methyl Cellulose, Hydroxy Ethyl Cellulose, Hydroxypropylmethylcellulose Propyl methyl cellulose, hydroxy ethyl methyl cellulose, methyl ethyl cellulose, carboxy methyl cellulose and hydroxy propyl cellulose), polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, And may include two or more kinds of cellulose-based polymers. On the other hand, the cellulose may have a fiber width of 20 to 35, more specifically 25 to 30 占 퐉. On the other hand, the cellulose-based polymer may be dissolved in 10 to 15 parts by weight based on 100 parts by weight of water, specifically 5 parts by weight of methylethylcellulose and 5 parts by weight of hydroxypropylcellulose.

When the cellulose polymer is contained in an amount exceeding the above range, the electromagnetic wave shielding performance may be deteriorated. If the cellulose polymer is included in the range above, the uniform dispersion of the carbon nanotubes and the metal conductive nanoparticles may be inhibited.

Next, carbon nanotubes, copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm, and a surfactant were charged into the polymer solution, The first composition for an electromagnetic wave shielding film is prepared by irradiating ultrasonic waves with a horn (step b).

Carbon nanotubes are widely used in electronic materials, composite materials, conductive resin materials, and printed electronic device materials because of their excellent mechanical and electrical properties. They are used in various fields. Structure, and can be classified into single wall, double wall, and multi-wall carbon nanotubes.

Carbon nanotubes are made of carbon and have high thermal conductivity, mechanical strength is 100 times stronger than steel, 10 times more than strength of existing bulletproof vests, and elasticity is better. It is chemically very stable due to a structure similar to graphite, which has strong covalent bonds, and has excellent electrical conductivity. Also, it is small in size and can exist in powder state, so that when mixed with other kinds of powders, the physical / chemical properties of the powder can be modified. For example, when carbon nanotubes are mixed with a polymer, properties such as electrical conductivity and mechanical strength can be greatly improved.

Meanwhile, the carbon nanotubes used in an embodiment of the present invention may be a combination of single-walled carbon nanotubes and multi-walled carbon nanotubes. In the present invention, the carbon nanotubes can remarkably improve electrical conductivity But they are easily agglomerated and are difficult to be uniformly dispersed in a solution. However, in the present invention, uniform dispersion can be achieved by ultrasonic treatment and paste mixer stirring, which will be described later, to give excellent electrical conductivity to the composition of the present invention.

Specifically, the carbon nanotube may be included in an amount of 7 to 12 parts by weight based on 100 parts by weight of the polymer solution. Particularly, when the carbon nanotubes are contained in an amount exceeding the above-mentioned weight range, uniform dispersion is difficult and coagulation phenomenon may occur severely. On the other hand, when the carbon nanotubes are contained in the weight part or less, it may be difficult to effectively maintain the electromagnetic wave shielding performance. Particularly, in the present invention, although carbon nanotubes are included in the above-described range, the carbon nanotubes do not easily aggregate and are effectively dispersed because the carbon nanotubes are separated from the surface of the copper- Particles and copper-silver core-shell nanoparticles are physically and chemically bonded to each other to improve dispersibility and further agitated in a paste mixer for 20 to 40 minutes and ultrasonic wave irradiation is performed at a frequency of 50 kHz to 55 kHz, This is due to the above-mentioned steps several times for dispersion.

On the other hand, the copper-nickel core-shell nanoparticles are obtained by coating nano-sized nickel particles on the surface of a core made of copper. The copper is a metal having good electrical conductivity next to silver and has excellent electrical conductivity. It is economical because it can be easily supplied and received. On the other hand, the copper-silver core-shell nanoparticles are also coated with nano-sized silver particles on the surface of copper core.

The average particle diameter of the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles according to an embodiment of the present invention is 30 to 70 nm, more specifically, the copper-nickel core-shell nanoparticles have a diameter of 60 to 70 nm, The copper-silver core-shell nanoparticles may be particles having an average particle diameter of 30 to 40 nm and having a different average particle diameter.

Specifically, according to an embodiment of the present invention, in the mixed solution for preparing the first composition in step b, the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles have a weight ratio of 1: 2 to 2.5 And the metal nanoparticles of the two core shell structures are packed tightly in the weight ratio range and the average particle diameter range so that the metal nanoparticles can be uniformly dispersed in the substrate without drying when applied to the substrate. The shape of the copper-nickel core shell or the copper-silver core shell nanoparticle is not particularly limited, but may be an angled polygonal shape, a columnar shape, a spherical shape, or a mixed shape thereof, for example, a spherical shape.

Specifically, the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles may be included in an amount of 55 to 60 parts by weight based on 100 parts by weight of the polymer solution. When used within the above-mentioned range, the amount of metal conductive particles to be used is reduced compared to the prior art, and the electromagnetic wave shielding effect higher than that of the prior art can be achieved.

Specific examples of the surfactant include nonionic surfactants such as stearylmethylammonium chloride and bromotrimethylammonium, anionic surfactants such as sodium dodecylbenzenesulfonate, polyethylene glycol paranonylphenylether and the like Can be used.

According to one embodiment of the present invention, the surfactant may be included as a nonionic surfactant in an amount of 3 to 7 parts by weight based on 100 parts by weight of the polymer solution.

In the meantime, after the step of injecting, a process of effectively dispersing the metal nanoparticles in the polymer solution is performed by irradiating ultrasonic waves with an ultrasonic horn.

Specifically, the ultrasonic horn is provided in a horn type ultrasonic wave irradiator. The horn type ultrasonic wave irradiator generates ultrasonic waves by a piezoelectric ceramics and an ultrasonic vibrator that convert electric energy into mechanical vibration energy by using an inverse piezoelectric effect, A booster and a horn are provided in the vibrator to increase the amplitude of the vibrator.

The horn type ultrasonic wave irradiator has a very high internal temperature and pressure of the cavitation bubble generated when the ultrasonic wave is irradiated in the aqueous solution, and when the bubbles grow and rupture, a shock wave of high temperature and high pressure is generated, It is commonly used to mix or disperse heterogeneous liquids that are difficult to mix.

According to one embodiment of the present invention, the ultrasonic irradiation may be performed by irradiating at a frequency of, for example, 40 kHz to 60 kHz, specifically, 50 kHz to 55 kHz. It is possible to more effectively disperse the carbon nanotubes and the core shell metal nanoparticles within the frequency range as described above. Accordingly, the metal nanoparticles and the carbon nanotubes of the two core shell structures are uniformly dispersed in the polymer solution, When the electromagnetic wave shielding film is produced as described below, the electromagnetic wave shielding film exhibits a uniform electrical conductivity improving effect throughout the film, and thus exhibits a uniform electromagnetic wave shielding effect on the film, Further, the mechanical strength of the film can be improved by using carbon nanotubes. If irradiated below the above-mentioned frequency range, uniform dispersion is difficult to be effectively performed, and when irradiated beyond the above-mentioned frequency range, damage to the metal nanoparticles of the core shell structure or damage of the carbon nanotubes may occur, There is a problem that uniform dispersion may be difficult and electrical conductivity may be deteriorated. On the other hand, the ultrasound irradiation time may be 5 to 10 minutes, more specifically about 7 minutes.

According to an embodiment of the present invention, in the step b), oxidation, thiocyanation, silver cyanation, cyanation silver, carbonic acid silver, silver nitrate, nitrite silver, silver sulfate, silver phosphate, perchlorination , At least one silver nanoparticle precursor selected from the group consisting of fluoroborate, acetylacetonate, acetic acid, lactic acid, and oxalic acid can be further added. The injected silver nanoparticle precursor is grown as silver nanoparticles of several nanometers to several tens of nanometers through the ultrasonic treatment in step b. The silver nanoparticles are uniformly dispersed in the polymer solution, and the electrical conductivity of the finally produced electromagnetic wave shielding film It can also serve as an additional enhancement.

Next, the first composition is mixed with carbon black and stirred with a paste mixer to prepare a second composition (step c).

Carbon black, which is used as a conductive filler, may have an average primary particle diameter of 60 to 70 nm. Specifically, carbon black, Ketjen black, Super-P, Denka black, and acetylene black And the like.

On the other hand, the carbon black may have a BET specific surface area of 1500 to 3000 m ² / g. If the BET specific surface area of the carbon black is less than 1500 m ² / g, the volume fraction of the particles may be relatively low, and thus the formation of an electrical conduction network between the particles may deteriorate and the electrical conductivity may be deteriorated. If the surface area is larger than 3000 m ² / g, the viscosity of the composition may increase, which may cause problems in workability. On the other hand, the carbon black may be surface-modified under an oxidizing agent condition.

On the other hand, the carbon black may be contained in an amount of 8 to 12 parts by weight based on 100 parts by weight of the polymer solution. When the carbon black is contained in an amount exceeding the above range, the viscosity of the composition may be increased. When the carbon black is contained in the above range, the effect of increasing the electrical conductivity may be insignificant.

In step c, the mixture is stirred for 20 to 40 minutes with a paste mixer. Specifically, when the mixture is stirred at 1000 to 1500 rpm using the paste mixer, the copper- One or more particles selected from the copper-silver core-shell nanoparticles among the nickel core shells can be present in a combined form.

In addition to the step b, the carbon black is mixed in the step c in the case of a hollow structure / porous structure such as Ketjen black, and there is a possibility that structural collapse is caused by the ultrasonic treatment in the step b, This is because there is a problem of the sudden drop in the number. Therefore, the mixing of the carbon black is performed after the ultrasonic treatment in the step b, and stirring is performed by the paste mixer for uniform dispersion of the carbon black.

After step c), the second composition is finally applied on the substrate and dried (step d).

The composition for an electromagnetic wave shielding film according to one embodiment of the present invention may be applied on a substrate, for example, a polymer substrate to be formed into a film.

The substrate may be quartz, glass, or a plastic substrate such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polypropylene, polyvinyl chloride, and the like.

On the other hand, the substrate may be washed with an alcohol and then subjected to a surface modification process. On the other hand, when applying the composition for electromagnetic wave shielding film, the coating method is not particularly limited, but dip coating, spray coating, spin coating, screen printing, spray coating, roll coating, blade coating, gravure coating, doctor blading have.

Meanwhile, step d according to an embodiment of the present invention includes pre-curing in a hot air drying condition; Evaporating the solvent; And a curing step for curing the polymer, may be sequentially performed.

Specifically, in the present invention, the drying process is performed in three stages, and when dried through a single step according to the prior art, bubbles and cracks are generated, thereby damaging the surface of the coating layer formed of the composition during drying, The shielding function may be deteriorated.

On the other hand, according to the present invention, the drying process is divided into three steps, and pre-curing is performed in a hot air drying condition; Evaporating the solvent; And a curing step for polymer curing, it is possible to prevent bubbles and cracks unlike the prior art, to prevent the surface of the coating layer formed of the composition during drying from being damaged, and thus to lower the electromagnetic wave shielding function Can also be prevented. Specifically, the pre-curing by hot air drying may be performed by using hot air at a temperature of about 70 to 80 for 30 minutes to 1 hour, and the solvent evaporation process may be performed within a temperature range of 50 to 55 for 4 to 6 hours The solvent may be evaporated, and the curing process may be curing at a temperature of 170 to 180 for 1 to 2 hours.

Specifically, the thickness of the electromagnetic wave shielding film obtained through the above-described process may be about 5 to 15 탆, more specifically, 7 to 13 탆.

According to the present invention, carbon black, carbon nanotubes and two or more conductive nanometal composites are uniformly dispersed in a polymer solution to sufficiently exhibit high conductivity characteristics, excellent adhesion to a substrate, and excellent electromagnetic wave shielding effect A shielding film can be manufactured.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

The terms used in the present invention are intended to illustrate specific embodiments and are not intended to limit the present invention. The singular presentation should be understood to include plural meanings, unless the context clearly indicates otherwise. The word " comprises " or " having " means that there is a feature, a number, a step, an operation, an element, or a combination thereof described in the specification. The present invention is not limited to the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

Example 1

50 g of hydroxyethylcellulose and 50 g of methylethylcellulose were mixed with 1 kg of purified water to prepare a mixed polymer solution. Single-walled carbon nanotubes and multi-walled carbon nanotubes (average diameter: 5 to 20 m, length: 1 to 10 m) 220 g of copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, 440 g of copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm, and 55 g of sodium dodecylbenzenesulfonate as a nonionic surfactant And then irradiated for 7 minutes while maintaining the frequency range of 50 kHz to 55 kHz by ultrasonic horn to prepare a composition (first composition) for an electromagnetic wave shielding film.

Next, 100 g of Super-P as carbon black was mixed with the first composition, and the mixture was stirred for 30 minutes with a paste mixer maintained at 1000 to 1500 rpm to prepare a second composition.

The second composition prepared through the above process was sprayed onto a UV-treated PVC substrate having a size of 15 mm X 15 mm to form a coating layer, followed by applying hot air of 70 to 80 for 30 minutes, Temperature for 6 hours to evaporate the solvent. The solution was cured at a temperature of 170 to 180 for 1 hour, and then peeled off from the substrate to produce an electromagnetic wave shielding film having a thickness of about 12 mu m.

Comparative Example 1

Except that 220 g of copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm and 440 g of copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm were used in the same manner as in Example 1 However,

Comparative Example 2

An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that 660 g of copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm and copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm Respectively.

Comparative Example 3

Except that copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm were not used and only 660 g of copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm were used I used it differently.

Comparative Example 4

An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that the ultrasonic wave irradiation was performed at a frequency of 30 kHz.

Comparative Example 5

An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that the ultrasonic wave irradiation was performed at a frequency of 70 kHz.

Comparative Example 6

An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that the drying process was not performed in three stages but dried in a vacuum oven at 50 ° C. for 7 hours.

[Experiment 1: Evaluation of electromagnetic wave shielding property]

Typically, the "surface resistance" was measured using a 4-point probe (SR1000N) by using the electromagnetic wave shielding film produced according to Examples 1 to 5. After contacting the film with 4 probes, the test unit was fixed at Ω / sq and measured 10 times.

The electromagnetic wave shielding efficiency (EMI) was measured in the frequency region of 1.0 GHz.

Film Properties Sheet resistance (Ω / sq) Shielding Efficiency (Db) Example 1 4.92 61.31 Comparative Example 1 10.6 44.12 Comparative Example 2 11.8 46.54 Comparative Example 3 10.1 35.13 Comparative Example 4 12.3 49.64 Comparative Example 5 10.7 45.27 Comparative Example 6 12.1 39.51

[Experiment 2: Evaluation of dispersion degree]

The dispersions of the metal nanoparticles and the carbon nanotubes in the electromagnetic wave shielding compositions of Examples 1 to 6 were visually evaluated and the results are shown in the following Table 2 (in the case of homogeneously dispersed O, uniform X if not dispersed, and Δ when moderately dispersed).

Evaluation of dispersion degree Example 1 O Comparative Example 1 X Comparative Example 2 Δ Comparative Example 3 X Comparative Example 4 Δ Comparative Example 5 X Comparative Example 6 Δ

Referring to Tables 1 and 2 and the results of Experiments 1 and 2, it can be seen that the conductive ink composition according to an embodiment of the present invention exhibits excellent characteristics in terms of sheet resistance and shielding ratio compared to the comparative examples, Carbon black, and carbon nanotubes and two or more conductive nanomaterial composites are uniformly dispersed in a polymer solution to sufficiently exhibit high-conductivity characteristics, excellent adhesion to a substrate, and excellent electromagnetic shielding effect I can confirm that I can.

Claims (5)

a) dissolving the cellulose-based polymer in water to prepare a polymer solution;
b) adding carbon nanotubes, copper-nickel core-shell nanoparticles having an average particle diameter of 60 to 70 nm, copper-silver core-shell nanoparticles having an average particle diameter of 30 to 40 nm and a surfactant to the polymer solution, To produce a first composition for an electromagnetic wave shielding film;
c) mixing the composition with carbon black, and stirring the mixture with a paste mixer to prepare a second composition; And
d) applying and drying the second composition on a substrate,
Wherein the copper-nickel core-shell nanoparticles and the copper-silver core-shell nanoparticles are charged at a weight ratio of 1: 2 to 2.5 in step (b). The method according to claim 1,
In the step b), oxidation, thiocyanation, cyanation silver, cyanation silver, carbonic acid silver, silver nitrate silver, nitrite silver, sulfuric acid silver, phosphoric silver silver, perchloric acid silver, tetrafluoroborate silver, Wherein at least one silver nanoparticle precursor selected from the group consisting of silver nitrate, acetic acid, lactic acid, and oxalic acid is further added. The method according to claim 1,
D) pre-curing in a hot air drying condition; Evaporating the solvent; And a curing step for curing the polymer, wherein the three steps are sequentially performed. delete The method according to claim 1,
Wherein the ultrasonic irradiation in the step (b) is carried out by irradiation with a frequency of 50 kHz to 55 kHz.