1. Field of the Invention
The present invention relates to a molded article for the protection of radar equipment. In particular, the invention relates to a molded article that is located in the beam path of radar equipment mounted behind the front grill of an automobile.
2. Background Art
A radar device 100 equipped on an automobile, as shown in
The front grill and the emblem, particularly the portions thereof that are located in the beam path of the radar device, are manufactured using a material and paint that have only a small amount of radio transmission losses and which provide certain esthetic exterior. The emblem, in particular, is painted with a metallic color paint.
(Patent Document 1) JP Patent Publication (Kokai) No. 2000-159039 A
(Patent Document 2) JP Patent Publication (Kokai) No. 2000-49522 A
(Patent Document 3) JP Patent Publication (Kokai) No. 2000-344032 A
JP Patent Publication (Kokai) Nos. 2000-159039 and 2000-344032 disclose that an indium film is deposited on the front grill. JP Patent Publication (Kokai) No. 2000-49522 discloses that a ceramic film of silicon dioxide is provided on the emblem or radome.
While the indium film, which provides a metallic color, is suitable for the coating of the emblem or the like, it has a large radio transmission loss. Therefore, if it is mounted in front of the radar device, the beam from the radar device is attenuated. An indium film easily peels off and lacks in durability. Moreover, indium is a metal and is therefore subject to potential corrosion.
The ceramic film made of silicon dioxide has excellent durability and is used for the protection of a film or paint. However, it is colorless and cannot provide esthetic exterior, such as that of a metallic color.
It is an object of the invention to provide a molded article located in the beam path of a radar device that has only a small amount of radio transmission loss.
It is another object of the invention to provide a molded article located in the beam path of the radar device that has a luminous color.
In accordance with the invention, a layer of a ceramic material is provided on the external surface of a substrate. The ceramic material includes nitride ceramics, oxide ceramics, carbide ceramics, and mixtures thereof. The ceramic material includes titanium nitride and/or aluminum nitride.
In accordance with the invention, a molded article with only a small amount of radio transmission loss is provided that is located in the beam path of the radar device.
In accordance with the invention, a molded article with a luminous color is provided that is located in the beam path of the radar device.
In the present example, the ceramic material layer 12 is preferably made from titanium nitride TiN or aluminum nitride AlN.
b) shows a second example of the invention. In this example, the molded article comprises a substrate 10, a layer 12 of a first ceramic material, and a layer 13 of a second ceramic material, the two layers being disposed on the substrate. The two ceramic material layers 12 and 13 are made from two different ceramic materials selected from a group of ceramic materials consisting of the aforementioned nitride ceramics, oxide ceramics, and carbide ceramics. Preferably, however, titanium nitride TiN and aluminum nitride AlN are used.
More preferably, the lower layer 12 of the first ceramic material is a titanium nitride TiN layer, and the upper layer 13 of the second ceramic material is an aluminum nitride AlN layer. By thus forming the aluminum nitride AlN layer, which has transparent and iridescent interference colors, on the titanium TiN layer, which exhibits a metallic color, an aesthetic exterior of metallic and iridescent interference colors can be obtained.
c) shows a third example of the invention. In this example, the molded article comprises a substrate 10 and a mixed-ceramics material layer 14 disposed on the substrate 10. The mixed-ceramics material layer 14 is made from a mixture of two or more ceramic materials. The ceramic materials for forming the mixture may be selected from the examples mentioned above, of which titanium nitride TiN and aluminum nitride AlN are preferable.
d) shows a fourth example of the invention. In this example, the molded article comprises a substrate 10, a first mixed-ceramic material layer 14 on the substrate 10, and a second mixed-ceramic material layer 15. The two mixed-ceramic material layers 14 and 15 have different ceramic material compositions. Each mixture may be made of the examples of the ceramic materials mentioned above. Preferably, however, titanium nitride TiN and aluminum nitride AlN are used. In this case, the respective contents of titanium nitride TiN and aluminum nitride AlN are different in the two mixture layers 14 and 15.
The ceramic material layers 12 and 13 and the mixed-ceramic material layers 14 and 15 may be formed by sputtering. Each layer in the ceramic material layers 12 and 13 and in the mixed-ceramic material layers 14 and 15 preferably has a thickness from 0.1 nm to 1000 nm, or more preferably, from 10 nm to 500 nm.
By suitably selecting the type of ceramic materials used in the ceramic material layers 12 and 13 and the mixed-ceramic material layers 14 and 15 and the thickness of each layer, a desired color can be exhibited.
The substrate 10 is made of a material that has only a small amount of radio transmission loss and excellent dielectric properties. The dielectric properties include the dielectric constant ∈′ and the dielectric loss tan δ. The substrate 10 is made of a transparent resin, preferably polycarbonate.
With reference to
b) shows a sixth example of the invention. In this example, the molded article comprises a substrate 10, an undercoat layer 11 disposed on the substrate 10, a first ceramic material layer 12 disposed on the undercoat layer 11, and a second ceramic material layer 13. The molded article of this example differs from the example of
c) shows a seventh example of the invention. In this example, the molded article comprises a substrate 10, an undercoat layer 11 disposed on the substrate 10, and a mixed-ceramic material layer 14 disposed on the undercoat layer 11. This molded article differs from the example of
In the following, the results of experiments conducted to compare the examples of the invention with the examples of the prior art will be described.
With reference to
The result shows that in the examples of the invention, a desired color can be obtained with luminance from transparent to silver by adjusting the thickness of the titanium nitride film.
Now, the dielectric loss tan δ will be considered. Curves c0, c1, c2, and c3 indicate the measurement results of the dielectric loss tan δ for Samples 0, 1, 2, and 3. For Sample 4, the dielectric loss tan δ could not be measured. The dielectric loss tan δ decreases in the order of Samples 0, 1, 2, and 3 (curves c0, c1, c2, and c3). Namely, the dielectric loss tan δ of Sample 0 (curve c0), which is the substrate, is the smallest, the dielectric losses tan δ of Samples 1 and 2 (curves c1 and c2) of the invention are larger, and the dielectric loss tan δ of Sample 3 (curve c3) of the prior art is the largest.
It will be seen that the transmission losses shown in
With reference to
The abrasive element 803 had a stroke of 100 mm and it was moved at a rate of 50 reciprocations per minute. The number of reciprocations the abrasive element had executed when the coating on the surface of the sample started to peel off was measured. The peeling of the film was identified visually. Sample 1 of the invention and Sample 4 of the prior art were prepared and then an abrasion test was conducted.
The results are shown in Table 3.
As will be seen from Table 3, Sample 1 of the invention has higher abrasion resistance than Sample 4 of the prior art.
With reference to
The measurement results are shown in Table 4.
As will be seen from Table 4, Sample 1 of the invention had higher hardness than Sample 4 of the prior art.
The molded article according to the invention that is located in the beam path of the radar device thus has high abrasion resistance and hardness. Therefore, the advantage can be obtained that there is no need to coat the surface of the molded article with a protective film of silicon dioxide, as required in the prior art. Optionally, however, a transparent protective film may be further provided on the surface of the molded article shown in
While the invention has been particularly shown and described with reference to preferred examples thereof, it will be understood by those skilled in the art that various changes can be made therein without departing from the scope of the appended claims.
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