KR20060078790A - Electrically conductive paint compositions - Google Patents

Abstract

The present invention relates to a conductive paint composition for shielding electromagnetic waves that can effectively solve the electromagnetic interference (EMI) and RFI (Radio Frequency Interference) caused by the electromagnetic waves generated from the internal devices of various electronic devices, more specifically Containing a water-soluble polyurethane dispersion and two different rheology control agents to reduce the change in viscosity of the paint over time, to maintain a constant working viscosity when using the paint, and to improve the electromagnetic wave shielding conductive paint composition It is about.

Electromagnetic shielding, conductive paint, rheology control agent, polyurethane dispersion, metal powder, solvent

Description

 Conductive paint composition {ELECTRICALLY CONDUCTIVE PAINT COMPOSITIONS}

The present invention relates to an electrically conductive paint composition for shielding electromagnetic waves, and more particularly, to a water-soluble polyurethane dispersion and two different rheology control agents, which are excellent in conductive properties, viscosity properties, substrate adhesion, wear resistance, and durability. It relates to a conductive paint composition.

Electromagnetic waves generated from internal devices of various electronic devices such as mobile communication terminals, notebook PCs, office equipment, and medical devices may affect various diseases such as headache, visual acuity, leukemia, brain tumors, circulatory disorders, reproductive function, and VDP syndrome. It has been reported that it can be crazy, and controversy over the harmful effects of electromagnetic waves on the human body. In addition, as the integration of devices increases due to the trend toward lighter weight of electronic products, electromagnetic noise generated from each component may cause peripheral devices to malfunction, causing device failure. Therefore, in recent years, in addition to strengthening the shielding standards for electromagnetic waves generated from home, office, and industrial electronic products such as computers, wireless telephones, automobiles, medical devices, and multimedia players, EMI and Radio Frequency Interference (RFI) emissions have been strengthened. As regulations on Korea have been tightened, electromagnetic wave shielding measures for various electronic devices and components have emerged as important tasks.

Common shielding methods for blocking electromagnetic waves include plating, vacuum deposition, and spray coating. Electromagnetic shielding method by plating has been used for a long time, but the manufacturing cost is high, the production process is complicated, and there is a problem that causes environmental pollution, it is required to compensate for this. On the other hand, the electromagnetic shielding method by vacuum deposition is used only when the cost is very high and the long-term reliability is a problem is extremely limited. On the other hand, electromagnetic shielding technology by spray coating using metal powder is widely used because it is easy to apply and can solve environmental problems.

The spray coating method is spray coating a coating liquid containing a mixture of an adhesive resin and a conductive metal on a substrate, and the conductive coating film obtained by spray coating has excellent conductive properties, substrate adhesion, abrasion resistance, and changes in initial physical properties due to environmental changes. There should be no.

The most important point for obtaining such a conductive coating film is the viscosity of the paint during the spraying process. Higher viscosities of the paint make it difficult to spray, and too low viscosities make it difficult to control the amount of spray, resulting in uneven coating surfaces.

The present invention is to overcome the above-mentioned problems of the prior art, one object of the present invention is to introduce a water-soluble polyurethane disulsion and two different rheology control agents to reduce the change in paint viscosity over time, always the same It is to provide a conductive paint composition capable of obtaining a uniform conductive film under working conditions.                         

Another object of the present invention is to provide an electromagnetic wave shielding conductive film having excellent electromagnetic wave shielding performance and excellent viscosity characteristics.

One aspect of the present invention for achieving the above object relates to a conductive paint composition comprising a water-soluble polyurethane dispersion, a metal powder, a solvent and two different rheology control agents.

Another aspect of the present invention relates to an electromagnetic wave shielding conductive film produced by the conductive paint composition of the present invention.

Hereinafter, the present invention will be described in more detail.

The conductive paint composition according to the present invention comprises two different types of rheology control agents together with a water-soluble polyurethane disulsion, a metal powder and a mixed solvent.

The water-soluble polyurethane dispersion used in the present invention has a structure represented by the following formula (1), and is a water-soluble polyurethane dispersion synthesized by mixing aromatic polyhydric acid and aliphatic polyhydric acid.

Wherein R ¹ is an aliphatic hydrocarbon having 4 to 12 carbon atoms, a cyclic aliphatic hydrocarbon having 6 to 15 carbon atoms, or a mixture thereof; R ² is an aliphatic hydrocarbon having 2 to 12 carbon atoms; R ³ is an aliphatic hydrocarbon having 2 to 20 carbon atoms and an aromatic hydrocarbon having 6 to 20 carbon atoms; R ⁴ and R ⁵ are hydrogen or a methyl group; R ⁶ is an aliphatic hydrocarbon having 3 or 4 carbon atoms; R ⁷ is hydrogen or an aliphatic hydrocarbon having 1 to 9 carbon atoms; R ⁸ is an aliphatic hydrocarbon having 1 to 10 carbon atoms, a cyclic aliphatic hydrocarbon having 3 to 10 carbon atoms, or a mixture thereof; the ratio of n1: (n2 + n4 + n6): n3: n4 is 0.2-1.5: 1.0-3.0: 0.01-0.3: 0.1-1.0; n5 is 0.1 to 1.0, x is 1 to 20, the sum of y and z is 5 to 200, and the polyurethane resin includes a repeating unit in which R ³ is an aromatic hydrocarbon and a repeating unit in which R ³ is aliphatic hydrocarbon. .

The water-soluble polyurethane dispersion is easy to mix when mixed with the metal powder, and gives sufficient wettability to the metal surface to impart adhesion to the substrate. Representative examples of the water-soluble polyurethane dispersion usable in the present invention include AMPUD-6 manufactured by Ortec.

The content of the water-soluble polyurethane dispersion in the conductive paint composition of the present invention is 5 to 40 wt%, preferably 10 to 25 wt% (based on product weight). If the content is less than 5wt%, the adhesion and wear resistance of the device is poor, if the content exceeds 40wt% there is a fear that the resistance increases. In addition, the water-soluble polyurethane dispersion is a solid content of 10 to 50%, preferably 20 to 40%.

The metal powder used for the conductive paint composition of the present invention uses a flake-like copper powder coated with flakes having an average particle size (D50) of 30 to 40 µm. Silver-coated copper powder is cheaper than silver powder and is widely used as an electromagnetic shielding material of relatively large electronic devices such as notebooks. Compared to the electromagnetic shielding material using silver powder, the metal powder and the water-soluble polyurethane dispersion content are low, so the viscosity of the paint is low, and when the paint is used, no diluent is used or the content is less than the paint using the silver powder. The low viscosity of the paint does not prevent the settling of the relatively high specific silver coated copper powder, which eventually separates into a mixed layer of a water-soluble polyurethane disperse and a solvent and a metal powder layer. If this layer separation is prolonged for a long time, the agitation does not return to a uniform dispersion state as in the initial state of paint production. This shortens the service life of the product. In order to prevent sedimentation of the metal powder having a high specific gravity, it is possible to increase the viscosity of the paint.

The content of the metal powder in the conductive paint composition of the present invention is 10 to 60wt%, preferably 15 to 50wt%. If the content is less than 10wt%, the conductivity is poor, if it exceeds 60wt% there is a disadvantage that the manufacturing cost rises.

Examples of the solvent used in the conductive paint composition of the present invention include methanol, ethanol, isopropanol, normal butanol and isobutanol. In the present invention, since a mild alcohol solvent is used instead of a strong corrosive solvent such as methyl ethyl ketone (MEK), it has little effect on the plastic surface and is good in terms of environmental safety of workers. In addition, by selecting a solvent having a low boiling point, it is possible to mass-produce under low temperature drying conditions after spray coating, thereby reducing cost.

The preferred content of the solvent in the conductive paint composition of the present invention is in the range of 20 wt% to 40 wt%. If the content is less than 20wt%, the coating itself is difficult, while if it exceeds 60wt%, the conductivity decreases and the coating quality is degraded.

In the conductive paint composition of the present invention, the rheology control agent includes 1) an copolymer formed of an acrylic acid polymer and an alkyl acrylate having 10 to 30 carbon atoms, and 2) an homopolymer of acrylic acid. Arcylic acid homopolymer) is mixed and used. The rheology control agent of 1) is soluble in solvents of alcohols and is effective in preventing sedimentation and spray workability of metals without affecting conductivity, and representative examples are manufactured by Novon. Carbo-pol EZ-2 is mentioned. In addition, the rheology control agent of 2) has the effect of preventing the sedimentation of the metal by increasing the initial viscosity through physical bonding with the water-soluble polyurethane disulsion and EZ-2, a representative example of the cabo manufactured by Novon Paul EP-1 can be mentioned.

The rheology control agent of the present invention as described above is a copolymer formed of an acrylic acid polymer (Arcylic acid polymer) and alkyl acrylate (Alkyl acrylate) having 10 to 30 carbon atoms, and an acrylic acid homopolymer (Arcylic acid homopolymer) is 1 Mixed materials may be used in a weight ratio of: 99 to 99: 1.

The content of the rheology control agent in the conductive paste composition of the present invention is 5 to 20%, preferably 8 to 15wt%. If the content is less than 5wt%, metal particles are precipitated, and if the content is more than 20wt%, the resistance is increased.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples are merely to explain preferred embodiments of the present invention, and should not be construed as limiting the protection scope of the present invention.

Production Example of Paste of Rheology Control Agent (Cabopol EZ-2)

The rheology control agent EZ-2 used in the present invention was applied by processing it into a paste form before preparing paint. The reason why it is applied after processing into paste form is to reduce the time required for manufacturing the paint and to increase the thickening effect.

First, 950 g of ethanol was added to a predetermined vessel, and 20 g of Carbopol EZ-2 was added while stirring at 700 rpm with a high speed stirrer. After stirring at 800 rpm for 30 minutes, the product was neutralized with 30 g of product name Ethomeen C-25 from Akzo. After the amine addition, the mixture was stirred for 1 hour at 1000 rpm.

Example 1

Using a Dispermat D-51580 model (VMA GETZMANN GMBH), 60 g of a water-soluble polyurethane dispulsion (AMPUD-6, Oltec, Inc.) was added, and then 100 g of commercially available silver coated copper powder (AgCu-250, Ferro, USA) was added. It was prepared by stirring for 30 minutes at 2000rpm. 275 g of ethanol was added thereto, mixed at 500 rpm for 10 minutes, and 50 g of Carbopol paste EZ-2 was added thereto, followed by stirring at 1000 rpm for 10 minutes. 15 g of Carbopol EP-1 was added thereto, followed by stirring for 20 minutes at 1500 rpm.

The prepared sample was diluted with 20 wt% of ethanol again, spray-coated to a polycarbonate sheet having a width of 15 cm, a length of 6 cm, and a thickness of 2 mm so as to have a dry coating thickness of 12.5 μm, and the coated specimen was dried in a 60 ° C. drying furnace for 15 minutes. . Evaluation of the physical properties of the obtained coating specimens are shown in Table 1 below.

Comparative Example 1

Using a Dispermat D-51580 model (VMA GETZMANN GMBH), 60 g of water-soluble polyurethane dispulsion (PS-3, Oltec) was added and 100 g of commercially available silver-coated copper powder (AgCu-250 from Ferro, USA) was used. It was prepared by stirring for 30 minutes at 2000rpm. 275 g of ethanol was added thereto, mixed for 10 minutes at 500 rpm, and 50 g of Carbopol paste EZ-2 was added thereto, followed by stirring at 1000 rpm for 10 minutes. 15 g of Carbopol EP-1 was added thereto, followed by stirring for 20 minutes at 1500 rpm.

The prepared sample was diluted with 20 wt% of ethanol again, spray-coated to a polycarbonate sheet having a width of 15 cm, a length of 6 cm, and a thickness of 2 mm so as to have a dry coating thickness of 12.5 μm, and the coated specimen was dried in a 60 ° C. drying furnace for 15 minutes. . Evaluation of the physical properties of the obtained coating specimens are shown in Table 1 below.

Comparative Example 2

Add 100 g of commercially available silver coated copper powder (AgCu-250 from Ferro, USA) after adding 60 g of water-soluble polyurethane dispulsion (AMPTECH-6 from Oltec) using Dispermat D-51580 model (VMA GETZMANN GMBH). It was prepared by stirring for 30 minutes at 2000rpm. 275 g of ethanol was added thereto, mixed for 10 minutes at 500 rpm, and 65 g of Carbopol paste EZ-2 was added, followed by stirring at 1000 rpm for 30 minutes.

The prepared sample was diluted with 20wt% of ethanol and spray-coated to a polycarbonate sheet having a width of 15 cm, a length of 6 cm, and a thickness of 2 mm so that the dry film thickness was 12.5 μm. It was. Evaluation of the physical properties of the obtained coating specimens are shown in Table 1 below.

Table 1

[Property evaluation method]

 * Resistance: The surface resistance per unit area was evaluated using a multimeter.

 Adhesion: evaluated by ASTM D3359.

 * Viscosity was measured using a BROOKFILED viscometer.

 * Separation rate is to pour the paint into the 100ml measuring cylinder and plug the inlet. After standing at room temperature, the height of the metal powder layer generated due to the sedimentation of the metal powder was expressed as a percentage of the total height.

The conductive paint composition according to the present invention is excellent in electrical properties and carrying property of the conductive film, has little change in viscosity even after a long time after the manufacture and can prevent the sedimentation of the metal powder for electromagnetic wave shielding having the same physical properties under the same spray conditions within the period of use A conductive film can be obtained, and electromagnetic waves of several MHz to several GHz bands can be cut off, and electromagnetic interference (EMI) caused by electromagnetic waves generated from internal devices such as mobile communication terminals, notebook PCs, car navigation systems, office equipment, medical devices, etc. And a remarkable effect of effectively solving the radio frequency interference (RFI) problem.

Claims (9)

In a conductive paint composition comprising a water-soluble polyurethane dispersion, a metal powder, a solvent, and a rheology control agent, the rheology control agent is composed of an acrylic acid polymer and an alkyl acrylate having 10 to 30 carbon atoms. A conductive paint composition, characterized in that the mixture formed of a copolymer (Copolymer), and acrylic acid homopolymer (Arcylic acid homopolymer). The composition of claim 1, wherein said composition is a) water soluble polyurethane dispersion 5-40 wt%; b) 10-60 wt% metal powder; c) 20-40 wt% of solvent; And d) 5-20 wt% rheology control agent Conductive paint composition comprising a. The conductive paint composition according to claim 1, wherein the water-soluble polyurethane dispersion has a structure represented by the following formula (1), and is a water-soluble polyurethane disulsion synthesized by mixing aromatic polyhydric acid and aliphatic polyhydric acid. [Formula 1]

Wherein R ¹ is an aliphatic hydrocarbon having 4 to 12 carbon atoms, a cyclic aliphatic hydrocarbon having 6 to 15 carbon atoms, or a mixture thereof; R ² is an aliphatic hydrocarbon having 2 to 12 carbon atoms; R ³ is an aliphatic hydrocarbon having 2 to 20 carbon atoms and an aromatic hydrocarbon having 6 to 20 carbon atoms; R ⁴ and R ⁵ are hydrogen or a methyl group; R ⁶ is an aliphatic hydrocarbon having 3 or 4 carbon atoms; R ⁷ is hydrogen or an aliphatic hydrocarbon having 1 to 9 carbon atoms; R ⁸ is an aliphatic hydrocarbon having 1 to 10 carbon atoms, a cyclic aliphatic hydrocarbon having 3 to 10 carbon atoms, or a mixture thereof; the ratio of n1: (n2 + n4 + n6): n3: n4 is 0.2-1.5: 1.0-3.0: 0.01-0.3: 0.1-1.0; n5 is 0.1 to 1.0, x is 1 to 20, the sum of y and z is 5 to 200, and the polyurethane resin includes a repeating unit in which R ³ is an aromatic hydrocarbon and a repeating unit in which R ³ is aliphatic hydrocarbon. . The conductive paint composition according to claim 1, wherein the solid content of the water-soluble polyurethane dispersion is 10 to 50%. The method of claim 1, wherein the rheology control agent is a copolymer formed of acrylic acid polymer (Arcylic acid polymer) and alkyl acrylate (Alkyl acrylate) having 10 to 30 carbon atoms, and the acrylic acid homopolymer (Arcylic acid homopolymer) is 1 A conductive paint composition, characterized in that mixed in a weight ratio of: 99 to 99: 1. The conductive paint composition of claim 1, wherein the metal powder is flake-coated copper powder having an average particle size (D50) of 30 to 40 µm. The method of claim 1, wherein the solvent is selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, methyl pyrrolidone, acetone, methyl cell solution, ethyl cell solution, butyl cell solution Conductive paint composition. The conductive paint composition of claim 1, wherein the rheology control agent is paste. Electromagnetic shielding conductive film prepared by the conductive paint composition of claim 1.