Reflex reflector and lamp device including the reflex reflector

Abstract

To provide a reflex reflector having both excellent brilliance and radar wave transmissibility, and a lamp device including the reflex reflector.SOLUTION: A reflex reflector includes: a first resin layer 21 and a second resin layer 23 that are integrated together; a retroreflective interface 25R that is an interface between the first resin layer and the second resin layer, and a retroreflective uneven surface, wherein a refractive index of the first resin layer is greater than a refractive index of the second resin layer; and an islands-shaped metal layer 25M that is provided on the retroreflective interface and capable of transmitting radar wave from a radar unit, wherein a dielectric constant difference between the first resin layer and the second resin layer is within 5%.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a radar reflex reflector and a lamp device equipped with the reflex reflector, and more particularly to a radar reflex reflector and lamp device mounted in a vehicle lamp.

[0002] In recent years, various sensors such as cameras, LiDAR (Light Detection and Ranging), millimeter-wave sensors, in addition to acceleration sensors and GPS sensors, are widely used for driver assistance and autonomous driving.

[0003] In particular, millimeter-wave radar devices can maintain high environmental resistance, unaffected by nighttime and backlit environments, and bad weather such as dense fog, rain, and snow. They can also directly detect the distance and direction to an object, as well as its relative speed. Therefore, they are characterized by their ability to detect objects at close range with high speed and high accuracy.

[0004] For example, Patent Document 1 discloses a vehicle lamp having a reflex reflector attached to the inner surface and a shielding part provided on the front cover to cover a millimeter-wave radar from the front. Also, Patent Document 2 discloses a vapor-deposited retroreflective sheet that has excellent brightness and suppresses color unevenness in appearance.

[0005] Patent Document 3 discloses a metallic coating film that is an aggregate of fine islands and has metallic luster and is capable of transmitting electromagnetic waves. Patent Document 4 discloses an electromagnetic wave-transmitting metallic luster member that includes an indium oxide-containing layer that is continuously provided on the surface of a substrate, and a metal layer that includes a plurality of portions that are at least partially discontinuous from each other and that is laminated on the indium oxide-containing layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-135087 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-212144 [Patent Document 3] Patent No. 5465030 [Patent Document 4] Patent No. 6400062 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the shielding portion described in Patent Document 1, the dielectric constant of the front cover differs from that of the retroreflective sheet, resulting in a problem of large radar wave transmission loss. Furthermore, there is a demand for a component that combines both brilliance and electromagnetic wave transparency as a shielding member for a millimeter-wave radar mounted on the front part of an automobile, such as a front grille or emblem. There is also a demand for a lamp device that includes a radar unit and a shielding member for the radar unit that suppresses radar wave loss. [Means for solving the problem]

[0008] A reflex reflector according to one embodiment of the present invention comprises: 1. A reflex reflector for use with a radar unit, comprising: The first resin layer and the second resin layer are integrated together, the interface between the first resin layer and the second resin layer is a retroreflective interface that is a retroreflective uneven surface; the refractive index of the first resin layer is greater than the refractive index of the second resin layer; an island-shaped metal layer that is transmissive to radar waves from the radar unit is provided on the retroreflective interface; The difference in dielectric constant between the first resin layer and the second resin layer is within 5%.

[0009] A lamp device according to another embodiment of the present invention comprises: the reflex reflector; the radar unit disposed behind the rear surface of the second resin layer of the reflex reflector; A lamp unit; and a lamp case that houses the reflex reflector, the radar unit, and the lamp unit. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram schematically illustrating the inside of a lamp device having a radar reflex reflector according to a first embodiment of the present invention. FIG. [Figure 2] 1 is a cross-sectional view schematically showing a reflex reflector for radar according to a first embodiment. [Figure 3A] FIG. 10 is a diagram for explaining parameters used in calculating the combined dielectric constant of a reflex reflector. [Figure 3B] Formula (1) shows the composite relative permittivity of the reflex reflector. [Figure 4] FIG. 10 is a cross-sectional view schematically showing the configuration of a reflex reflector according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view schematically showing the configuration of a reflex reflector according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following, preferred embodiments of the present invention will be described, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

[0012] [First embodiment] 1 is a diagram schematically illustrating the inside of a lamp device 10 equipped with a radar reflex reflector 20 according to a first embodiment of the present invention. More specifically, the inside of the lamp device 10 is shown as viewed from the vertical direction.

[0013] The figure shows a three-axis coordinate system in which the traveling direction of the vehicle VH to which the lamp device 10 is attached is the y direction, the left direction is the x direction, and the downward direction (direction of gravity) is the z direction. In other words, when the vehicle VH is placed horizontally, the horizontal plane is the xy plane, and the direction of gravity is the z direction.

[0014] The lamp device 10 according to this embodiment is a vehicle lamp and is used as a headlamp disposed on the left and right sides of the front of the vehicle VH. Since the left and right headlamps have the same basic configuration, only one of the lamp devices 10 (left headlamp) disposed on the front left of the vehicle VH will be illustrated and described below.

[0015] Although the lamp device 10 will be described as a headlamp for main driving, it may also be a lamp device having the purpose and function of emitting light to the outside, such as a tail lamp or backlight.

[0016] In this specification, the vehicle VH will be described as an automobile, but the present invention is not limited to this. That is, in this specification, the term "vehicle" refers to vehicles such as ships and aircraft, as well as manned and unmanned transportation or mobility means.

[0017] As shown in FIG. 1, the lamp device 10 is attached to a vehicle VH, and the lamp devices 10 as left and right headlights are configured to be symmetrical to each other.

[0018] The lamp device 10 has a lamp case 13 consisting of a housing 11, which is the base of the lamp device 10, and a transparent cover 12 (also called an outer lens or outer cover) attached to the housing 11 and covering the front opening of the housing 11.

[0019] The lamp device 10 has a lamp unit 15 and a radar unit 17 housed in a lamp chamber (lamp body space) 13K defined by a lamp case 13.

[0020] The lamp unit 15 has a light source such as an LED and optical components such as a lens, and radiates light from the light source forward of the vehicle VH (radiated light LE).

[0021] The radar unit 17 is disposed to the side of the lamp unit 15 within the lamp device 10. The radar unit 17 has an antenna 17A, which is a radar transmitter / receiver that transmits electromagnetic waves (radar waves) and receives waves reflected by obstacles. The radar unit 17 is disposed so as to radiate millimeter-wave band radar waves RW toward the side of the lamp device 10.

[0022] Furthermore, a reflex reflector 20 is disposed in front of the radar wave RW emitted from the radar unit 17. However, the arrangement of the radar unit 17 and the reflex reflector 20 is not limited to this, and they can be disposed in any suitable position and at any suitable angle within the lamp device 10.

[0023] (1) Structure of the reflex reflector FIG. 2 is a cross-sectional view schematically showing the configuration of a reflex reflector 20 according to the first embodiment of the present invention. The reflex reflector 20 is disposed in front of the antenna 17A of the radar unit 17, and is positioned so that the radar waves RW from the radar unit 17 are incident on the rear side of the reflex reflector 20. The reflex reflector 20 covers and conceals the radar unit 17 behind it, making it difficult to see from the outside.

[0024] The reflex reflector 20 has a plate shape, and the front surface 20A of the first resin layer 21 is the surface (light incident surface) onto which the incident light LW (external light) is incident, and the back surface 20B of the second resin layer 23 is the surface (radar wave incident surface) onto which the radar wave RW of the radar unit 17 is incident. Both of these surfaces are smooth and have no irregularities, and the distance between the two surfaces, which corresponds to the plate thickness, is almost the same at any point, making them smooth surfaces.

[0025] The retro-reflector 20 is formed by integrating a first resin layer 21 and a second resin layer 23, for example, by multi-color molding. The first resin layer 21 is, for example, polycarbonate, and the second resin layer 23 is, for example, acrylic. Note that the first resin layer 21 and the second resin layer 23 can be selected from various thermoplastic resins such as polycarbonate-based resins, acrylic-based resins, epoxy-based resins, polyamide-based resins, and polyethylene-based resins.

[0026] The interface between the first resin layer 21 and the second resin layer 23 of the retro-reflector 20 is formed as a retro-reflective uneven surface (hereinafter also referred to as the resin interface 25R). For example, an interface with a cube corner type uneven structure can be used for the resin interface 25R.

[0027] Also, an island-shaped metal layer 25M is formed on the first resin layer 21 side (that is, within the first resin layer 21) on the retro-reflective resin interface 25R. More specifically, the island-shaped metal layer 25M is an aggregate of fine islands IS, and is an electromagnetic wave transmissive film having a metallic luster and capable of transmitting electromagnetic waves. More specifically, in the island-shaped metal layer 25M, the metal islands IS are arranged separately and independently from each other, or are partially adjacent or in contact with each other within the layer. As shown in FIG. 2, the incident light LW to the first resin layer 21 is retro-reflected by the island-shaped metal layer 25M (retro-reflected light LW1).

[0028] Also, in the retro-reflector 20, the refractive index n1 of the first resin layer 21 is larger than the refractive index n2 of the second resin layer 23 (n2 < n1). As shown in FIG. 2, the incident light LW to the first resin layer 21 is also retro-reflected by the retro-reflective resin interface 25R (retro-reflected light LW2).

[0029] That is, although some light passes through the island-shaped metal layer 25M (half-mirror transmission), the light that passes through the island-shaped metal layer 25M is totally reflected due to the difference in refractive index between the first resin layer 21 and the second resin layer 23, and is therefore also retroreflected by the resin interface 25R (retroreflected light LW2). Therefore, a high reflectance can be obtained for the incident light LW from the front of the reflex reflector 20.

[0030] As described above, the resin interface 25R and the island-shaped metal layer 25M provide the retroreflective structure 25 with high reflectivity.

[0031] On the other hand, the island-shaped metal layer 25M is a metal coating in which minute metal islands IS are arranged within the layer, and which has a metallic luster and is capable of transmitting radar waves. Therefore, as shown in Figure 2, radar waves RW from the radar unit 17 are transmitted through the second resin layer 23, the retroreflective structure 25, and the first resin layer 21, and are radiated forward of the reflex reflector 20.

[0032] The metal of the island-shaped metal layer 25M may be, but is not limited to, indium, palladium, aluminum, nickel, nickel alloy, copper, copper alloy, silver, silver alloy, tin, tin alloy, etc. The island-shaped metal layer 25M may be formed by electroless plating of these metals.

[0033] Here, the island-shaped metal layer 25M has a structure in which countless minute island-shaped metals (fine islands IS) are formed. By adjusting the size and density of the fine islands IS, it is possible to form an island-shaped metal layer that transmits electromagnetic waves of a desired wavelength. The size and density of the fine islands IS can be adjusted by adjusting the formation conditions (plating conditions). That is, when the size of the minute islands IS (island-shaped metal) is sufficiently small compared to the wavelength of the radar wave RW, the radar wave RW is not affected by the minute islands IS and passes through the island-shaped metal layer 25M. For example, although this is just one example, a minute island IS having a size of about several tens of nanometers (e.g., 20 nm) is sufficiently small compared to the wavelength of 3.9 mm at 76.5 GHz.

[0034] Therefore, even if the radar unit 17 is disposed behind the reflex reflector 20 and the radar wave RW is incident on the rear surface 20B of the reflex reflector 20, the obstacle detection function of the radar unit 21 is fully exhibited.

[0035] That is, the reflex reflector 20 has sufficient retroreflection performance and can suppress attenuation and reflection of the radar wave RW and the reflected radar wave (i.e., the radar wave received by the radar unit 17), without changing the electromagnetic wave radiation pattern.

[0036] This also increases the degree of freedom in arranging the radar unit 17, making it possible to apply it to obstacle detection for various purposes. Furthermore, since the radar unit 17 is arranged behind the reflex reflector 20, it is difficult to see from the outside, and the radar unit 17 can be hidden, which is advantageous in terms of design.

[0037] (2) Dielectric constant and thickness of the reflex reflector The difference in dielectric constant between the first resin layer 21 and the second resin layer 23 of the reflex reflector 20 causes reflection of the transmitted radar waves RW, resulting in electromagnetic wave loss. Therefore, it is preferable that the difference in dielectric constant between the first resin layer 21 and the second resin layer 23 is small. Specifically, when the relative dielectric constant of the first resin layer 21 is εr1 and the relative dielectric constant of the second resin layer 23 is εr2, it is preferable that the difference in relative dielectric constant Δεr is within 5%.

[0038] For example, in the case of the reflex reflector 20 described above, the relative dielectric constant εr1 of the first resin layer 21 (polycarbonate) is 2.6, the relative dielectric constant εr2 of the second resin layer 23 (acrylic) is 2.7, and the relative dielectric constant difference Δεr is 3.8%.

[0039] Furthermore, the transmission characteristics of radar waves can be optimized by adjusting the plate thickness T of the reflex reflector 20. Fig. 3A is a diagram for explaining parameters used in calculating the combined dielectric constant of the reflex reflector 20.

[0040] When the maximum and minimum distances between the surface 20A of the first resin layer 21 and the resin interface 25R are d1MAX and d1MIN, respectively, the maximum and minimum distances between the back surface 20B of the second resin layer 23 and the resin interface 25R are d2MAX and d2MIN, respectively, the average layer thickness of the first resin layer 21 is d1ave (= (d1MAX + d1MIN) / 2), and the average layer thickness of the second resin layer 23 is d2ave (= (d2MAX + d2MIN) / 2), the composite relative dielectric constant εr of the reflex reflector 20 is expressed by equation (1) shown in Figure 3B.

[0041] In this case, if the speed of light is C and the frequency of the radar wave in the synthetic resin is f, the wavelength of the radar wave in the synthetic resin is λ = (C / f) × εr -1 / 2 is.

[0042] Therefore, the plate thickness Top of the reflex reflector 20 that is optimal for transmitting radar waves is given by, where n is an integer equal to or greater than 1: Top=(λ / 2)×εr -1 / 2 ×n Formula (2) It is expressed as:

[0043] Therefore, it is preferable that the thickness T of the reflex reflector 20 satisfies the above formula (2) (T=Top).

[0044] Multi-color molding allows the thickness T of the reflex reflector 20 to be formed with high precision. Also, the back surface 20B of the second resin layer 23, which is the incident surface of the radar waves RW, can be made smooth.

[0045] As described above, the reflex reflector of this embodiment provides a shielding member that has both excellent brightness and radar wave transmittance. Additionally, the radar unit 17 and the reflex reflector 20 can be positioned in a suitable position within the lamp device 10 at a suitable angle.

[0046] [Second embodiment] FIG. 4 is a cross-sectional view schematically showing the configuration of a reflex reflector 40 according to a second embodiment of the present invention.

[0047] Similar to the reflex reflector 20 of the first embodiment, the reflex reflector 40 of the present embodiment has a plate shape. The reflex reflector 40 is formed by integrating the first resin layer 21 and the second resin layer 23 by multi-color molding.

[0048] In the reflex reflector 40, the interface between the first resin layer 21 and the second resin layer 23 is a resin interface 25R which is a retroreflective uneven surface. For example, an interface with a cube corner type uneven structure can be used for the resin interface 25R.

[0049] On the retroreflective resin interface 25R, island-shaped metal layers 45M are formed on the second resin layer 23 side (that is, inside the second resin layer 23). The island-shaped metal layer 45M is an electromagnetic wave transmissive coating having a metallic luster and capable of transmitting radar waves RW.

[0050] As shown in FIG. 4, the incident light LW to the first resin layer 21 is retroreflected (retroreflected light LW1) at the interface between the first resin layer 21 and the island-shaped metal of the island-shaped metal layer 45M.

[0051] Also, in the reflex reflector 40, the refractive index n1 of the first resin layer 21 is larger than the refractive index n2 of the second resin layer 23 (n2 < n1), and the incident light LW to the first resin layer 21 is totally reflected by the refractive index difference, so it is also retroreflected by the resin interface 25R (retroreflected light LW2).

[0052] That is, a retroreflective structure 45 having a high reflectivity is obtained by the resin interface 25R and the island-shaped metal layer 45M.

[0053] Also, in the present embodiment as well, it is preferable that the plate thickness T of the reflex reflector 40 satisfies the above formula (2) (T = Top).

[0054] As described above, the reflex reflector of this embodiment provides a shielding member that combines excellent brilliance and radar wave transparency. Furthermore, the radar unit 17 and the reflex reflector 20 can be disposed in a suitable position and at a suitable angle within the lamp device 10.

[0055] [Third embodiment] FIG. 5 is a cross-sectional view schematically showing the configuration of a reflex reflector 50 according to a third embodiment of the present invention.

[0056] The reflex reflector 50 of this embodiment has a resin interface 25R that is a retroreflective uneven surface, and an underlayer 55A that is an amorphous indium tin oxide (ITO) layer is provided on the resin interface 25R on the side facing the first resin layer 21. An island-shaped metal layer 55M is formed on the underlayer 55A. The island-shaped metal layer 55M is an electromagnetic wave transparent coating that has a metallic luster and is capable of transmitting radar waves RW.

[0057] 5, the incident light LW to the first resin layer 21 is retroreflected by the island-shaped metal layer 55M (retroreflected light LW1). The incident light LW to the first resin layer 21 also passes through the base layer 55A, and is totally reflected and retroreflected due to the difference in refractive index between the base layer 55A and the second resin layer 23 (retroreflected light LW2).

[0058] That is, the resin interface 25R, the underlayer 55A, and the island-shaped metal layer 55M provide a retroreflective structure 55 with high reflectivity.

[0059] In the reflex reflector 50, an ITO layer is provided as the base layer 55A, so that metal such as aluminum (Al) attached to the base layer 55A can be made into an island-shaped discontinuous structure, thereby improving the electromagnetic wave transmittance. In other words, it is possible to provide a reflex reflector in which the electromagnetic wave transmittance can be more easily adjusted for island-shaped metal layers of various metals. The base layer 55A is not limited to indium tin oxide (ITO), but may be a light-transmitting metal oxide such as indium oxide or indium zinc oxide (IZO), or a layer containing these.

[0060] Therefore, the reflex reflector of this embodiment can provide a shielding member that combines excellent brilliance and radar wave transmittance. Also, it can provide a reflex reflector in which the electromagnetic wave transmittance can be more easily adjusted for island metal layers made of various metals.

[0061] As described above in detail, the present invention can provide a reflex reflector that combines excellent brilliance and radar wave transmittance and is mounted on a moving body such as an automobile, for example, in a front grille or emblem. It can also provide a lamp device in which a radar unit and a radar unit shielding member that suppresses radar wave loss are disposed at a suitable position and angle within the lamp device. [Explanation of symbols]

[0062] 10: Lamp unit 15: Lamp unit 17: Radar unit 17A: Antenna 20: Reflex Reflector 21: First resin layer 23: Second resin layer 25, 45, 55: Retroreflective structure 25M, 45M, 55M: Island metal layer 25R: Resin interface (retroreflective interface) 55A: Base layer LW: Incident light (external light) RW: Radar wave

Claims

1. 1. A reflex reflector for use with a radar unit, comprising: the first resin layer and the second resin layer are integrated together, an interface between the first resin layer and the second resin layer is a retroreflective interface that is a retroreflective uneven surface; the refractive index of the first resin layer is greater than the refractive index of the second resin layer; an island-shaped metal layer that is transmissive to radar waves from the radar unit is provided on the retroreflective interface; A reflex reflector, wherein the difference in dielectric constant between the first resin layer and the second resin layer is within 5%.

2. The reflex reflector according to claim 1 , wherein the island-shaped metal layer is provided on the first resin layer side of the retroreflective interface.

3. The reflex reflector according to claim 1 , wherein the island-shaped metal layer is provided on the second resin layer side of the retroreflective interface.

4. 2. The reflex reflector according to claim 1, further comprising an underlayer containing a metal oxide, the underlayer being provided between the retroreflective interface and the island-shaped metal layer.

5. 5. The reflex reflector of claim 4, wherein the underlayer comprises indium tin oxide (ITO).

6. The thickness Top of the reflex reflector is expressed as follows, where εr is the composite relative dielectric constant of the reflex reflector and n is an integer equal to or greater than 1: Top = (λ / 2) × εr －１／２ ×n Formula (2) 2. The reflex reflector according to claim 1, which satisfies the following:

7. A reflex reflector according to any one of claims 1 to 6; the radar unit disposed behind the rear surface of the second resin layer of the reflex reflector; A lamp unit; a lamp case that accommodates the reflex reflector, the radar unit, and the lamp unit therein;

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