KR20200036649A - Electromagnetic wave transmitting cover - Google Patents

Abstract

The present invention relates to an electromagnetic wave transmission cover comprising a transparent resin layer and a metal layer, wherein the metal layer is a dried product of a composition comprising aluminum powder and a binder resin, and 0.005 to 0.05 part by weight of the aluminum powder is contained with respect to 100 parts by weight of the binder resin.

Description

Electromagnetic wave transmission cover {ELECTROMAGNETIC WAVE TRANSMITTING COVER}

It relates to an electromagnetic wave transmission cover.

The auto cruise control system is a technology that measures the inter-vehicle distance or relative speed between the front vehicle and the host vehicle by a sensor mounted in front of the vehicle, controls the brakes based on this information, and controls the inter-vehicle distance while accelerating / decelerating the host vehicle. As a sensor used in an auto cruise control system, a radar device, which is an electromagnetic wave transmitting and receiving device such as a millimeter wave radar, is generally used.

Radar devices mounted on the front of the vehicle body are generally placed behind the front grille, which is typically equipped with vehicle manufacturer emblems or ornaments. The millimeter wave irradiated from the radar device is radiated to the front through the front grill or the emblem, reflected from an object such as a vehicle in front or an obstacle, and the reflected light is returned to the radar device through the front grill or the like. Therefore, there is a need for a material or paint that has a low electromagnetic wave transmission loss and is capable of imparting a desired aesthetic to a portion disposed in a beam path of a radar device such as a front grill or emblem.

An embodiment of the present invention provides an electromagnetic wave transmission cover that can economically implement excellent metal luster, adhesion, and excellent electromagnetic wave transmittance.

In one embodiment of the present invention, a transparent resin layer and a metal layer, the metal layer is a dried product of a composition comprising aluminum powder and a binder resin, and the aluminum powder is 0.005 parts by weight to 0.05 parts by weight compared to 100 parts by weight of the binder resin It provides an electromagnetic wave transmission cover containing as a content of wealth.

The electromagnetic wave transmission cover can economically implement excellent metallic luster, adhesion, and excellent electromagnetic wave transmittance.

1 is a schematic cross-sectional view showing a positional relationship between an electromagnetic wave transmission cover and a radar device mounted in front of a vehicle body and a front grill according to an embodiment of the present invention.
Figure 2 schematically shows the form of the aluminum powder contained in the metal layer according to another embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to embodiments described below. However, the present invention will not be limited to the embodiments disclosed below, but will be implemented in various different forms, Only the present embodiments are provided to make the disclosure of the present invention complete, and to provide those who have ordinary knowledge in the art to which the present invention pertains, to fully disclose the scope of the invention, and the present invention is defined by the scope of the claims. It just works.

In the drawings, thicknesses are enlarged to clearly represent various layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for convenience of description. The same reference numerals refer to the same components throughout the specification.

Also, in the present specification, when a part such as a layer, film, region, plate, etc. is said to be "above" or "above" another part, this is not only when the other part is "directly above" but also when there is another part in the middle Also includes. Conversely, when one part is "just above" another part, it means that there is no other part in the middle. In addition, when a part of a layer, film, region, plate, etc. is said to be "below" or "below" another part, this is not only when the other part is "just below" but also when there is another part in the middle. Includes. Conversely, when one part is "just below" another part, it means that there is no other part in the middle.

In one embodiment of the present invention, a transparent resin layer and a metal layer, the metal layer is a dried product of a composition comprising aluminum powder and a binder resin, the aluminum powder is 0.005 parts by weight to 0.05 parts by weight compared to 100 parts by weight of the binder resin It provides an electromagnetic wave transmission cover containing as a content of wealth.

The radar device is a device that measures the distance between the vehicle in front of the host vehicle and the relative speed by irradiating the millimeter wave, controls the brakes based on this information, and controls the distance between the vehicle and acceleration and deceleration. The electromagnetic wave transmission cover is located between the radar device mounted on the front of the vehicle body and the front grill, and it is required to exhibit excellent aesthetics by providing continuity to the metallic luster indicated by the front grill with low electromagnetic wave transmission loss and excellent metallic luster. . Typically, the electromagnetic wave transmission cover includes a metal layer to impart continuity to the metallic luster indicated by the front grill. At this time, it is common to use indium having good electromagnetic wave transmittance as the metal of the metal layer. However, indium has an uneconomical problem as an expensive raw material.

The electromagnetic wave transmission cover includes a transparent resin layer and a metal layer, the metal layer is a dried product of a composition comprising aluminum powder and a binder resin, and the aluminum powder has an amount of 0.005 parts to 0.05 parts by weight compared to 100 parts by weight of the binder resin. Is included. The electromagnetic wave transmission cover includes aluminum, not indium, and can exhibit economical, excellent metallic luster, adhesion, and excellent electromagnetic wave transmittance at the same time.

The metal layer may include the aluminum powder in the above range, and simultaneously exhibit excellent metal gloss and excellent electromagnetic transmittance. Specifically, when the content of the aluminum powder is less than the above range, there is a problem such as deterioration of the metallic luster, and the luminance is less than the metallic texture, and when it exceeds the above range, the electromagnetic wave transmittance is lowered and good propagation sensitivity can be obtained. There is no, there is a problem that the interlayer peeling occurs due to insufficient adhesion, the metal is corroded.

The metal layer may not include glass particles or mica. Glass particles, mica, etc. may have a good electromagnetic transmittance. However, when a metal layer is formed by mixing glass particles or mica, the gloss is remarkably deteriorated, so that the metal feeling is reduced. On the other hand, the metal layer does not include glass particles or mica, and may exhibit excellent electromagnetic transmittance equal to or greater than excellent adhesion with a significantly improved metallic luster including the aluminum powder.

The transparent resin layer is polymethyl methacrylate (Poly (methyl methacrylate), PMMA), polycarbonate (polycarbonate, PC), polyethylene terephthalate (polyethyleneterephthalate, PET), polypropylene (Polypropylene, PP), polyethylene, (Polyethylene, PE), polyvinylchloride (PVC), and combinations thereof.

The transparent resin layer is located adjacent to the front grill. The transparent resin layer includes the resin, and may serve as a support in the electromagnetic wave transmission cover. In addition, the metallic luster of the metal layer can be well recognized outside the vehicle, and it can exhibit excellent transmittance to electromagnetic waves emitted from the radar device and reflected from the object.

The electromagnetic wave transmission cover is Acrylonitrile Butadiene Styrene (ABS), Acrylonitrile Styrene Acrylate (ASA), Acrylonitrile Ethylene Styrene (AES), Acrylonitrile Ethylene Propylene Diene styrene (Acrylonitrile- (Ethylene-Propylene-Diene) -Stylene, AEPDS) and may further include a base layer comprising one resin selected from the group consisting of a combination thereof.

The base layer is positioned adjacent to the radar device, and the base layer may include the resin to improve the strength of the electromagnetic wave transmission cover. In addition, the substrate layer is opaque to prevent the radar device from being recognized in front of the vehicle to prevent spoiling, and can exhibit excellent transmittance to electromagnetic waves emitted from the radar device and reflected from the object.

The thickness (z) of the aluminum powder may be about 0.02 μm to about 0.04 μm. For example, it may be about 0.025 μm to about 0.035 μm or about 0.025 μm to about 0.03 μm. The aluminum powder may be formed using a milling process. For example, the aluminum powder may be formed by adding an aluminum thin film or an aluminum deposited film to a solvent or the like and pulverizing it in a ball mill. At this time, the milling process may be selected from ion beam milling, ball milling, satellite milling, jet milling, slit milling, 2-roll milling, 3-roll milling, basket milling, grab milling, attrition milling, screw mixing milling and sand milling. It may include one or more milling processes. Specifically, the aluminum powder may form a uniform composition by using 3-roll milling, and may form a dense metal layer.

The aluminum powder has a thickness in the above range, and although it contains a small amount of aluminum powder in the metal layer, it can simultaneously exhibit excellent metal gloss and excellent electromagnetic transmittance equal to or higher than a metal layer formed by indium deposition. Specifically, when the thickness of the aluminum powder is less than the above range, the metallic luster is lowered and the metallic texture is lowered, which may cause problems in appearance. And, when it exceeds the above range, the electromagnetic wave transmittance is lowered, it is not possible to obtain a good electromagnetic wave sensitivity, and accordingly, there may be a problem that the auto cruise control system cannot operate properly.

The aluminum powder may have a plate-like structure. The plate-shaped means a structure having a thin film shape with a smaller Z-axis length (thickness) than a cross-sectional area represented by the lengths of the X- and Y-axes. The cross-sectional shape represented by the lengths of the X-axis and the Y-axis may be a polygonal shape including circular, elliptical, triangular, square, and rectangular shapes. The aluminum powder has a plate-like structure, thereby increasing gloss in the composition, thereby exhibiting excellent metallic texture.

The average particle diameter (D50) of the aluminum powder may be 1 μm to 20 μm. The average particle diameter (D50) is defined as the particle diameter of a point that becomes 50% of the cumulative curve when the cumulative curve of particle size distribution is obtained by setting the total weight of the aluminum powder to 100%. For example, the average particle diameter (D50) of the aluminum powder may be about 5 μm to about 15 μm. The particle diameter can be measured through a particle size analyzer and SEM image.

The particle diameter, that is, the diameter of the particles, is defined as the longest length in each of the X-axis and the Y-axis in a cross section represented by the lengths of the plate-like X and Y axes. For example, FIG. 2 schematically shows a form of aluminum powder included in a metal layer according to another embodiment of the present invention. As shown in Figure 2, the diameter of the aluminum powder means the length of the longest X-axis or the longest Y-axis, among the lengths of the X-axis and Y-axis perpendicular to each other. When the average particle diameter (D50) of the aluminum powder is less than the above range, there may be a problem that the gloss is lowered and the metal texture is lowered, and if it exceeds the above range, there may be a problem that the radio wave transmittance is lowered.

The metal layer may include an acrylic resin as a binder. The metal layer may exhibit improved adhesion to the transparent resin layer by including the acrylic resin. And, it is possible to impart excellent heat resistance and impact resistance to the metal layer. Accordingly, it is possible to prevent the metal layer from being oxidized and discolored by heat generated inside the vehicle, and to provide an environment in which the metal texture can be maintained for a long time under severe conditions due to heat, moisture, and ultraviolet rays. Specifically, the acrylic resin may have a weight average molecular weight of about 50,000 to about 500,000. The acrylic resin may be milled with aluminum to form a metal layer. Accordingly, the aluminum powder may be uniformly dispersed in the metal layer to exhibit excellent metal gloss, adhesion, and electromagnetic wave transmittance.

For example, the acrylic resin may be a polymer of a monomer mixture containing a (meth) acrylic acid ester-based monomer and a crosslinkable monomer. It is preferable that the said acrylic resin does not contain a carboxyl group as a crosslinkable functional group. For example, as a monomer constituting the acrylic resin, a monomer containing a carboxyl group such as acrylic acid may cause yellowing or clouding.

Specifically, the (meth) acrylic acid ester-based monomer may be an alkyl (meth) acrylate. In this case, if the alkyl group included in the monomer becomes too long, it may be difficult to control the viscosity of the composition, and thus may be an alkyl (meth) acrylate having an alkyl group having 1 to 14 carbon atoms, specifically 1 to 8 carbon atoms. . Such monomers are methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) Acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (Meth) acrylate, isobornyl (meth) acrylate, isononyl (meth) acrylate, and combinations thereof.

The crosslinkable monomer may be a monomer containing a polymerizable functional group (ex. Carbon-carbon double bond) and a crosslinkable functional group simultaneously in the molecular structure. The crosslinkable functional group may be a hydroxyl group-containing monomer including a hydroxyl group. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8- It may be one selected from the group consisting of hydroxyoctyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, and combinations thereof.

The aluminum powder may be included in an amount of about 0.0005 parts by weight to about 0.005 parts by weight based on 100 parts by weight of the composition. The metal layer may include the aluminum powder in the above range, and simultaneously exhibit excellent metal gloss and excellent electromagnetic transmittance. Specifically, when the content of the aluminum powder is included in the composition below the above range, there may be problems such as deterioration in metallic luster and inability to reach the metallic texture. And, when it exceeds the above range, the electromagnetic wave transmittance is lowered, and thus good radio wave sensitivity cannot be obtained, and accordingly, the auto cruise control system cannot operate properly. In addition, there may be a problem that the adhesion between the metal layer containing the aluminum powder and the transparent resin layer is lowered.

The metal layer is a dried product of the composition comprising the aluminum powder and the binder resin, and the composition may have a viscosity of about 1 cps to about 100 cps at 25 ° C. The composition has a viscosity in the above range, the aluminum powder may exhibit excellent dispersibility with respect to the binder. Accordingly, excellent electromagnetic transmittance can be exhibited. Specifically, when the viscosity of the composition is less than the above range, there is a problem that the metal texture cannot be achieved with a low coating film thickness, and when it exceeds the above range, the metal layer is not uniformly formed with an appropriate thickness, and the electromagnetic wave transmittance is poor and good propagation There may be a problem that sensitivity cannot be obtained.

The thickness of the metal layer may be about 0.5㎛ to about 1.0㎛. The metal layer has a thickness in the above range, and although the aluminum powder is contained in a small amount, it may exhibit a metallic luster equal to or higher than that of the indium-deposited metal layer. At the same time, it is possible to exhibit excellent electromagnetic transmittance to the electromagnetic wave transmission cover.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or describing the present invention, and the present invention is not limited thereto.

< Example  And Comparative example >

Example  One:

A mixture of 0.005 parts by weight of aluminum powder compared to 100 parts by weight of poly (methyl methacrylate) (PMMA) having a weight average molecular weight of 400,000 is formed to form a mixture, 5 to 10 times in a three roll mill The aluminum powder was mixed and processed to have an average particle size (D ₅₀ ) of 10 μm to 15 μm and a thickness of 0.02 μm to 0.04 μm by passing.

PGME (Propylene glycol methyl ether) was added to the mixture to dilute the total solid content to 10% by weight to prepare a composition. Thereafter, a metal layer was formed by coating the composition with a thickness of 0.5 µm to 1.0 µm on a polycarbonate (PC) that is a transparent resin layer using a spray coater. That is, an electromagnetic wave transmission cover including a sheet of a transparent resin layer and a metal layer was manufactured.

Example  2:

An electromagnetic wave transmission cover was prepared in the same manner as in Example 1, except that 0.05 parts by weight of aluminum powder was mixed with 100 parts by weight of PMMA resin having a weight average molecular weight of 400,000.

Comparative example  One:

An electromagnetic wave transmission cover was prepared in the same manner as in Example 1, except that 0.0005 parts by weight of aluminum powder was mixed with 100 parts by weight of PMMA resin having a weight average molecular weight of 400,000.

Comparative example  2:

An electromagnetic wave transmission cover was prepared in the same manner as in Example 1, except that 0.1 part by weight of aluminum powder was mixed with 100 parts by weight of PMMA resin having a weight average molecular weight of 400,000.

<Evaluation>

Experimental example  1: electromagnetic wave Loss rate

In the 77 GHz region, which is a frequency used for autonomous vehicle radar systems, 1-Way electromagnetic transmittance was measured using the SM5899 System, a KEYCOM electromagnetic transmittance measuring device.

Specifically, samples of the transparent resin layer and the metal layer of Examples and Comparative Examples were cut to 200 mm (W, width) x 200 mm (L, length) x 3 mm (T, thickness) to prepare samples. Then, the electromagnetic wave measured from the electromagnetic wave transmittance measuring apparatus was converted into an electromagnetic wave loss rate (dB) using the following Equation 1, and the results are shown in Table 1 below.

(Equation 1)

Electromagnetic loss rate = 20 log _{10 │} S _21│ (dB)

The S21 = means millimeter waves measured by the transparent resin layer and the metal layer sheets of Examples and Comparative Examples, and then irradiated by the radar device.

Experimental example  2: Adhesion with transparent resin layer

The adhesion of the sheet of the transparent resin layer and the metal layer of the examples and comparative examples was measured through a cross-cut adhesion test according to ASTM D3359. Specifically, the transparent resin layer surface of the electromagnetic wave transmission cover was drawn horizontally and vertically with a razor blade at intervals of 1 mm to create a total of 100 square checkered eyes. Then, after attaching the adhesive tape on the transparent resin layer, when the tape was peeled off again, the number of peeled cross cuts was counted to evaluate the degree of adhesion. Specifically, the adhesion was evaluated by the following evaluation criteria, and the results are shown in Table 1 below. The smaller the number of peeled cross cuts, the better the adhesion.

(Evaluation standard)

5B: The number of peeled cross cuts is 0 to 4

4B: The number of peeled cross cuts is 5 to 14

3B: The number of peeled cross cuts is 15 to 34

2B: 35 to 64 number of peeled crosscuts

1B: When the number of peeled crosscuts is 65 or more

Experimental example  3: Metal texture

The metal textures of the sheets of the transparent resin layer and the metal layer of the examples and comparative examples were confirmed by a micro gloss meter (BYK Gardner) measurement. The value measured at 60 ° was used as the gloss value. At 60 °, it can be considered that the metal texture is excellent when the minimum gloss is 300 or more, and when it is 300 or less, the metal texture is poor.

Radar transmittance Adhesion Metal texture Example 1 -0.17 5B 310 Example 2 -0.32 5B 360 Comparative Example 1 -0.01 5B 230 Comparative Example 2 -20.3 3B 450

As shown in Table 1, while the Examples show excellent adhesion and metal texture with excellent radar transmittance, Comparative Example 1 significantly reduces the metal texture, Comparative Example 2 decreases the adhesion, and the radar transmittance falls significantly. Can confirm that.

D: Radar device
M: Electromagnetic wave transmission cover
F: Front grill
L1: Irradiated millimeter wave
L2: Reflected millimeter wave

Claims (10)

It includes a transparent resin layer and a metal layer,
The metal layer is a dried product of a composition comprising aluminum powder and a binder resin,
The aluminum powder contains 0.005 parts by weight to 0.05 parts by weight relative to 100 parts by weight of the binder resin
Electromagnetic wave transmission cover.
According to claim 1,
The transparent resin layer is polymethyl methacrylate (Poly (methyl methacrylate), PMMA), polycarbonate (polycarbonate, PC), polyethylene terephthalate (polyethyleneterephthalate, PET), polypropylene (Polypropylene, PP), polyethylene, (Polyethylene, PE), polyvinyl chloride (Polyvinylchloride, PVC) and a resin selected from the group consisting of a combination thereof
Electromagnetic wave transmission cover.
According to claim 1,
Acrylonitrile Butadiene Styrene (ABS), Acrylonitrile Styrene Acrylate (ASA), Acrylonitrile Ethylene Styrene (AES), Acrylonitrile Ethylene Styrene (Acesonitrile), Acrylonitrile -(Ethylene-Propylene-Diene) -Stylene, AEPDS) and further comprising a base layer comprising one resin selected from the group consisting of
Electromagnetic wave transmission cover.
According to claim 1,
The thickness of the aluminum powder is 0.02㎛ to 0.04㎛
Electromagnetic wave transmission cover.
According to claim 1,
The average particle diameter (D50) of the aluminum powder is 1㎛ to 20㎛
Electromagnetic wave transmission cover.
According to claim 1,
The aluminum powder is plate-shaped
Electromagnetic wave transmission cover.
According to claim 1,
The binder is an acrylic resin
Electromagnetic wave transmission cover.
According to claim 1,
The aluminum powder is contained in an amount of 0.0005 parts by weight to 0.005 parts by weight relative to 100 parts by weight of the composition
Electromagnetic wave transmission cover.
According to claim 1,
The viscosity of the composition is 1cps to 100cps at 25 ℃
Electromagnetic wave transmission cover.
According to claim 1,
The thickness of the metal layer is 0.5㎛ to 1.0㎛
Electromagnetic wave transmission cover.

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