KR20060079068A - Electroconductive paint composition and electroconductive film prepared therefrom - 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, the fine silver coating The present invention relates to an electroconductive shielding composition for electromagnetic wave shielding, in which durability of the conductive film is greatly improved by applying the copper powder.

The conductive paint composition for shielding electromagnetic waves of the present invention is a conductive paint composition comprising a water dispersion polyurethane dispersion, a metal powder, a solvent, and a rheology control agent, wherein the metal powder is silver having an average particle size (D50) of 2 to 20 μm. Coated copper powder or a mixture of the silver coated copper powder and a silver powder having an average particle size (D50) of 2 to 10 μm, wherein the water-dispersed polyurethane dispersion is a mixed disperse of at least two water-dispersed polyurethane dispersions. It is characterized by that.

Electromagnetic shielding, conductive paint, polyurethane dispersion, metal powder, solvent

Description

ELECTROCONDUCTIVE PAINT COMPOSITION AND ELECTROCONDUCTIVE FILM PREPARED THEREFROM

The present invention relates to a conductive paint composition for shielding electromagnetic waves, a conductive film for shielding electromagnetic waves applying the same, and a substrate for shielding electromagnetic waves including the conductive film. More specifically, the present invention includes a metal powder and a water-dispersed polyurethane dispersion as a conductive material. The present invention relates to a conductive paint composition excellent in conductive properties, viscosity properties, substrate adhesion, wear resistance and durability.

In general, electromagnetic waves generated from internal devices of various electronic devices such as mobile communication terminals, notebook PCs, office equipment, and medical devices are used for various diseases such as headache, visual acuity, leukemia, brain tumors, circulatory problems, reproductive function, and VDP syndrome. It has been reported that this may have an impact on the harmful debate on the human body of electromagnetic waves. In addition, due to the trend toward lighter weight of electronic products, as the degree of integration of devices increases, electromagnetic noise generated from each component may cause peripheral devices to malfunction, causing device failure.

Therefore, in recent years, in addition to strengthening shielding standards for electromagnetic waves generated from home, office, and industrial electronics 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 issues.

As a general shielding method for blocking electromagnetic waves, plating, vacuum deposition, spray coating methods and the like are known. 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. In particular, the conductive film coated inside the electronic device should not change its initial properties despite the various climate changes encountered during the distribution and use of the electronic device. If the conductive property of the coated conductive film is deteriorated due to climate change, or the adhesion of the substrate is poor, the durability of the conductive film is a required property because it may cause a malfunction of the electronic device.

The present invention is to meet the technical requirements of the technical field to which the present invention as described above, an object of the present invention is to form a more dense conductive film by atomizing the copper powder coated with silver and applied to the conductive paint having excellent durability It is to provide a conductive paint composition.

Another object of the present invention is to provide an electromagnetic shielding conductive film that maintains initial properties even after climate change that may occur during distribution and use after coating the electronic device with excellent electromagnetic shielding performance and excellent durability.

Still another object of the present invention is to provide a substrate for electromagnetic wave shielding which includes the conductive film and exhibits excellent electromagnetic wave blocking effect.

One aspect of the present invention for achieving the above object is a conductive paint composition comprising a water-dispersed polyurethane dispersion, a metal powder, a solvent, and a rheology control agent, wherein the metal powder has an average particle size (D50) of 2 to 20 A silver-coated copper powder or a mixture of the silver-coated copper powder and a silver powder having an average particle size (D50) of 2 to 10 μm, wherein the water-dispersed polyurethane disperse of the at least two water-disperse polyurethane It is related with the electrically conductive paint composition characterized by the mixed dispulsion.

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

Another aspect of the present invention for achieving the above object relates to a substrate for electromagnetic wave shield containing the conductive film of the present invention.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description of the invention and the preferred embodiments.

The conductive paint composition according to the present invention is characterized in that it comprises a water-dispersed polyurethane dispersion, a metal powder, a solvent, and a rheology control agent.

In the conductive paint composition of the present invention, the composition ratio of each component is preferably 1 to 60 wt% of water dispersion polyurethane dispersion, 10 to 60 wt% of metal powder, 10 to 60 wt% of solvent, and 5 to 20 wt% of rheology control agent.

Hereinafter, each component of this invention conductive paint composition is explained in full detail.

In the conductive paint composition of the present invention, the metal powder is characterized in that the copper powder having a predetermined particle size coated with the atomized silver is used alone or the copper powder coated with the silver is mixed with the silver powder.

Although silver powder is mainly applied to the conductive paint for shielding electromagnetic waves of an electronic device, which is small in size and integrated with circuits, such as a conventional mobile phone, the silver powder has excellent conductivity and is expensive compared to other materials. There was a problem of increasing the process cost, in the case of the copper powder has the advantage of low price, while lowering the durability of the conductive film had a problem that is difficult to actually apply.

Therefore, the conventional silver-coated copper powder was used as a metal powder to solve this problem, but by using a flake powder having an average particle size (D50) of 30 ~ 50㎛ coating when manufacturing a conductive film using the conductive pate composition using the same The surface of the conductive film was roughened and the durability was poor.

Therefore, in the present invention, in order to solve the above problems at once, the silver powder of the copper coating of 2 ~ 20㎛ size which is the optimum average particle size (D50) range alone or as an average particle size of 1 ~ 10㎛ Phosphorus silver powder is used in combination with. More preferably, the silver-coated copper powder having an average particle size range of 8 to 20 µm may be used alone or mixed with the silver powder having an average particle size of 4 to 10 µm.

At this time, if the silver-coated copper powder having an average particle size of less than 2㎛ is used, it is impossible to obtain an economic effect that can be obtained by using the copper powder due to a sharp increase in the price of the metal powder, When using the above, the surface of the coated conductive film may be roughened and durability may be degraded as described above.

Specific examples of the silver-coated copper powder usable in the present invention include Ferrosa AgCu-400, AgCu-450, AgCu-550 and the like. Specific examples of the silver powder usable in the present invention include Ferrosa SF-70A. , SF-9ED, SF-9 and HRP, SF-162 and the like, but is not particularly limited thereto.

When the metal powder of the present invention is mixed with the silver powder coated copper powder and silver powder, the mixing ratio is silver coated copper powder: silver powder = 99: 1 to 30:70 (w / w) It is preferable that it is a range. If the proportion of the silver-coated copper powder in the total metal powder is less than 30% by weight, the economic effect to be obtained by mixing the silver-coated copper powder cannot be achieved.

In addition, in the conductive paint composition of the present invention, the metal powder may be a surface treated with a fatty acid of C ₄ ~ C ₂₂ . Using the metal powder surface-treated with fatty acids as described above has the advantage of preventing oxidation of the metal powder and increasing affinity with the binder resin. At this time, the fatty acid may be oleic acid (Oleic acid), stearic acid (Stearic acid) and the like, but is not limited thereto.

It is preferable that the usage-amount of the said metal powder is 10 to 60 wt% with respect to the whole conductive paint composition of this invention. If the amount of the metal powder is less than 10wt%, there may be a problem of poor conductivity, and if the amount of the metal powder exceeds 60wt%, manufacturing cost may increase.

At least two or more kinds of polyurethane dispersion mixtures may be used as the water-dispersed polyurethane dispersion which is another component used in the conductive paint composition of the present invention.

Preferably, the polyurethane dispulsion (A) polymerized by reacting a polyester-based polyol having an aromatic structure and an isocyanate and the polyurethane disperse polymerized by reacting a polyester-based polyol having an aliphatic structure with an isocyanate (B) ) Can be used by mixing at least one or more.

At this time, the mixing ratio of the (A) and (B) is preferably in the range of 70:30 ~ 20:80 (w / w), the solid content of the polyurethane dispersion is preferably from 1 to 50wt%. Do. When two or more kinds of polyurethane dispersions having different structures are mixed as described above, an improvement in adhesion and salt water resistance may be achieved in comparison with one polyurethane dispersion alone.

Products commercially available as the polyurethane dispersion of (A) include PS-3, PS-6 (Ortec) and SANCURE1591 (Noveon), and the like, and are commercially available as the polyurethane dispersion of (B). Products include SANCURE 12954, SANCURE2715 (Noveon) and Neorez-R-9679 (Avecia), but are not particularly limited thereto.

The amount of the polyurethane dispulsion is preferably in the range of 1 to 60wt% with respect to the entire conductive paint composition of the present invention, which may be poor in adhesion and wear resistance of the device when the content is less than 1wt%. It is because there exists a possibility that resistance may rise when exceeding%.

The solvent which is another component used in the conductive paint composition of the present invention includes methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, methylpyrrolidone, acetone, methyl cellulsolve, ethyl cellulsolve and butyl cellulsolve One or more selected from the group can be used.

It is preferable that the usage-amount of the said solvent is 10-60 wt% with respect to the whole conductive paint composition of this invention.

The rheology control agent which is another component used in the conductive paint composition of the present invention is not particularly limited, but an acrylic polymer may be used. Examples of commercially available products as the rheology control agent include, but are not limited to, Carbopol's EZ-2, C676 and Rhenox's Rheolate 5000.

The rheology control agent may preferably be a paste, and the use of the pasted rheology control agent may prevent aggregation of the rheology control agent powder that may occur upon direct administration. As a method of pasting the rheology control agent, a method commonly used in the art may be used.

The rheology control agent is 5 to 20wt%, preferably 8 to 15wt% with respect to the whole conductive paint composition of the present invention. If the content is less than 5wt%, metal particles are precipitated, and if the content is more than 20wt%, there is a problem in that the resistance is increased.

On the other hand, the conductive paint composition of the present invention may optionally further contain 0.1 to 10wt% of other additives, such as leveling agent, dispersant, if necessary within the range of not impairing its physical properties.

The conductive paint composition prepared according to the present invention is coated on a plastic housing (polycarbonate or polycarbonate alloy, acrylobutadiene styrene, etc.) such as a mobile phone, PDA, laptop PC vehicle navigation, GPS equipment for the purpose of electromagnetic shielding Can be used as

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.

Rheology Of control agent (Cabopol EZ-2)  Paste Production Example

The production method of the rheology control agent used in the present invention is as follows.

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

Example  One

Using a Dispermat D-51580 model (VMA GETZMANN GMBH), add 70 g of a water-dispersed polyurethane dispulsion (NOC's SANCURE 12954 and Oltec's Reactizol PS-3 in a 2: 1 weight ratio) 125 g of a commercially available silver coated copper powder (AgCu-550, D50: 8-15 μm, manufactured by Ferro, USA) was added thereto, and the mixture was stirred at 2000 rpm for 30 minutes. 245 g of ethanol was added thereto, mixed at 500 rpm for 10 minutes, and then 60 g of the carbopol paste prepared above was added thereto, followed by stirring at 1000 rpm for 30 minutes, followed by viscosity adjustment.

The prepared sample was diluted with 100 vol% 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, and the coated specimen was dried in a 60 ° C. drying furnace for 15 minutes. It was. Evaluation of the physical properties of the obtained coating specimens are shown in Table 1 below.

Example  2

Using a Dispermat D-51580 model (VMA GETZMANN GMBH), add 85 g of a water-dispersed polyurethane dispulsion (NOC's SANCURE 12954 and Oltec's Reactizol PS-3 in a 2: 1 weight ratio) 100 g of commercially available silver powder (SF-70A, Ferro, USA) and 100 g of silver-coated copper powder (AgCu-550, D50: 8-15 μm, Ferro, USA) were added thereto, and the mixture was stirred at 2000 rpm for 30 minutes. 140 g of ethanol was added thereto, mixed at 500 rpm for 10 minutes, and then 75 g of carbopol paste was added, followed by stirring at 1000 rpm for 30 minutes to finish the viscosity adjustment.

The prepared sample was diluted with 100 vol% 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, and the coated specimen was dried in a 60 ° C. drying furnace for 15 minutes. It was. Evaluation of the physical properties of the obtained coating specimens are shown in Table 1 below.

Comparative example  One

A commercially available silver-coated copper powder (AgCu-250, D50: 35 µm) manufactured by Metal Powders was used in the same manner as in Example 1.

Comparative example  2

The same method as in Example 2 except that 100 g of silver powder (SF-70A, Ferro, USA) and 100 g of silver coated copper powder (AgCu-200, D50, 45 μm, Ferro, USA) were used as metal powders. Was performed.

Comparative example  3

The same procedure as in Example 1 was conducted except that SANCURE 12954 from Noven, USA was added alone as a water-dispersed polyurethane dispersion.

Comparative example  4

The same procedure as in Example 1 was carried out except that Riteczol PS-3, which was manufactured by Alltec, was added as a water-dispersible polyurethane dispersion.

Comparative example  5

Except for using SANCURE 12954 from Noven, USA, as a water-dispersed polyurethane dispersion, and using silver-coated copper powder (AgCu-250, D50: 35 μm, USA), which is commercially available as a metal powder. It was carried out in the same manner as 1.

TABLE 1

[Property evaluation method]

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

Adhesion: evaluated by ASTM D3359.

Durability evaluation was performed on the conductive film obtained in the above example as shown in Table 2 below.

* Evaluation of high temperature and high humidity performance: evaluation of physical properties after standing at 85 ℃, 85% RH for 72 hours

* Thermal shock performance evaluation: Physical property evaluation after repeated 20 times for 1 hour at -20 ℃ and 1 hour at 80 ℃

* Salt water resistance evaluation: After leaving for 72 hours in 25 ℃, 5% brine after drying for 20 minutes at 60 ℃ to evaluate the physical properties

TABLE 2

As confirmed through the results of Table 2, the conductive film of the conductive paint using a copper powder coated with silver having a conventional average particle size of 30 ~ 50㎛ after the durability evaluation, the resistance increases and the adhesive force deteriorates while the average particle size The conductive paint conductive film of the present invention prepared using the copper powder coated with atomized silver of 2 to 20 μm obtained the same results as the initial physical properties even after the durability evaluation. In addition, the use of a mixture of polyurethane dispersion polymerized with a polyester series having an aromatic structure and a polyurethane dispersion polymerized using an aliphatic polyester-based polyol is more effective than adhesive and salt water resistance. It was confirmed that it was excellent.

As described in detail above, the conductive paint composition according to the present invention is excellent in the electrical properties and the carrying property of the conductive film, and the initial physical properties do not change even in the durability evaluation, the electromagnetic wave of several MHz to several GHz band when manufactured as a conductive film for electromagnetic wave shielding Can effectively solve the problems of electromagnetic interference (EMI) and radio frequency interference (RFI) caused by electromagnetic waves generated from internal devices such as mobile communication terminals, notebook PCs, car navigation, weapons, medical devices, etc. Provides a significant effect.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Thus, the claims include any such modifications or variations that fall within the spirit of the invention.

Claims (13)

In a conductive paint composition comprising a water-dispersed polyurethane disulsion, a metal powder, a solvent and a rheology control agent, The metal powder is a copper powder coated with silver having an average particle size (D50) of 2 to 20 µm or a mixture of the silver coated copper powder and a silver powder having an average particle size (D50) of 2 to 10 µm, wherein the aqueous polyurethane dispersion A conductive paint composition, which is a mixed disperse of at least two or more water-dispersed polyurethane dispersions. The conductive paint composition according to claim 1, wherein an average particle size of the silver coated copper powder is 8 to 20 µm, and an average particle size (D50) of the silver powder is 4 to 10 µm. The conductive paint composition of claim 1, wherein the mixing ratio of the metal powder is silver coated copper powder: silver powder = 99: 1 to 30:70 (w / w). The conductive paint composition of claim 1, wherein the metal powder is surface treated with a C ₄ to C ₂₂ fatty acid. The method of claim 1, wherein the water-dispersed polyurethane disperse is a reaction between a polyester polyol having an aromatic structure and an isocyanate to polymerize the polyurethane disperse (A) and the aliphatic polyester-based polyol and isocyanate A conductive paint composition characterized by mixing at least one or more polymerized polyurethane dispersions (B), respectively. The conductive paint composition according to claim 5, wherein the mixing ratio of the polyurethane dispulsion of the above-mentioned (A) and the polyurethane dispersion of the above-mentioned (B) is 70:30 to 20:80 (w / w). The conductive paint composition of claim 1, wherein the solids content of the polyurethane dispulsion is 1 to 50 wt%. 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 A conductive paint composition characterized by being at least one species. The conductive paint composition of claim 1, wherein the rheology control agent is an acrylic polymer. 10. The conductive paint composition according to claim 9, wherein the rheology control agent is paste. The method of claim 1, wherein the conductive paint composition is 1 to 60wt% water dispersion polyurethane dispersion; Metal powder 10-60 wt%; Solvent 10-60 wt%; And 5 to 20 wt% of a rheology control agent. A conductive film for shielding electromagnetic waves, which is produced by the conductive paint composition according to any one of claims 1 to 11. An electromagnetic shielding substrate comprising the conductive film for shielding electromagnetic waves of claim 12.