Retro-reflector and lamp device with same

Abstract

The invention provides a retro-reflector and a lamp device having the retro-reflector, the retro-reflector has both excellent brilliance and radar wave transmissivity, and the lamp device has the retro-reflector. The first resin layer and the second resin layer are integrated, the interface between the first resin layer and the second resin layer is a retro-reflective interface, the retro-reflective interface is a retro-reflective concave-convex surface, and the refractive index of the first resin layer is greater than that of the second resin layer. The retro-reflection interface is provided with an island-shaped metal layer capable of transmitting radar waves from the radar unit, and the dielectric constant difference between the first resin layer and the second resin layer is within 5%.

Description

Technical Field

[0001] The present invention relates to a radar retroreflector and a lamp device having the same, and more particularly to a radar retroreflector for a vehicle lamp and a lamp device. Background Art

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

[0003] In particular, millimeter-wave radar devices are not affected by environments such as night and backlight, and adverse weather such as fog, rain, and snow, and can maintain high environmental resistance. In addition, the distance and direction to an object and the relative speed with respect to the object can be directly detected. Therefore, it has the characteristics of being able to detect even a close object at high speed and with high precision.

[0004] For example, Patent Document 1 discloses a vehicle lamp in which a retroreflector is mounted on an inner surface, and a shielding portion that covers a millimeter-wave radar from the front is provided on a front cover. In addition, Patent Document 2 discloses a vapor deposition retroreflective sheet having excellent lightness and suppressing unevenness in appearance color.

[0005] In addition, Patent Document 3 discloses a metal film that is an aggregate of fine islands and can transmit electromagnetic waves having a metallic luster. In addition, Patent Document 4 discloses an electromagnetic wave-transmitting metallic luster member including: an indium oxide-containing layer provided in a continuous state on a substrate surface and a metal layer laminated on the indium oxide-containing layer and including at least a part in a discontinuous state with respect to each other in a plurality of parts.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-135087

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-212144

[0010] Patent Document 3: Japanese Patent No. 5465030

[0011] Patent Document 4: Japanese Patent No. 6400062 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, in the shielding portion described in Patent Document 1, since the dielectric constant of the front cover and the dielectric constant of the retroreflective sheet are different, there is a problem of large transmission loss of radar waves. In addition, as a shielding member for a millimeter-wave radar mounted on, for example, the front part of an automobile such as a front grille or a badge, a member having both brilliance and electromagnetic wave transmissivity is required. Further, a lamp device having a radar unit and a shielding member for the radar unit with reduced radar wave loss is required.

[0014] Means for Solving the Problem

[0015] A retroreflector according to an embodiment of the present invention is used together with a radar unit.

[0016] A first resin layer and a second resin layer are integrated.

[0017] An interface between the first resin layer and the second resin layer is a retroreflective interface, and the retroreflective interface is a concavo-convex surface having retroreflectivity.

[0018] The refractive index of the first resin layer is greater than the refractive index of the second resin layer.

[0019] An island-shaped metal layer capable of transmitting radar waves from the radar unit is provided on the retroreflective interface.

[0020] The difference in dielectric constant between the first resin layer and the second resin layer is within 5%.

[0021] A lamp device according to another embodiment of the present invention includes:

[0022] The retroreflector;

[0023] The radar unit, which is disposed behind the back side of the second resin layer of the retroreflector;

[0024] A lamp unit;

[0025] A lamp housing that houses the retroreflector, the radar unit, and the lamp unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. schematically shows the inside of a lamp device having a radar retroreflector according to a first embodiment of the present invention.

[0027] Figure 2 FIG. schematically shows a cross-sectional view of a radar retroreflector according to a first embodiment.

[0028] Figure 3A FIG. is a diagram for explaining parameters for calculating the composite dielectric constant of the retroreflector.

[0029] Figure 3B Expression (1) showing the composite relative dielectric constant representing the retroreflector is shown.

[0030] Figure 4 FIG. is a cross-sectional view schematically showing the structure of the retroreflector according to the second embodiment.

[0031] Figure 5 FIG. is a cross-sectional view schematically showing the structure of the retroreflector according to the third embodiment.

[0032] (Reference Signs)

[0033] 10: Lamp device

[0034] 15: Lamp unit

[0035] 17: Radar unit

[0036] 17A: Antenna

[0037] 20: Retroreflector

[0038] 21: First resin layer

[0039] 23: Second resin layer

[0040] 25, 45, 55: Retroreflective structure

[0041] 25M, 45M, 55M: Island-shaped metal layer

[0042] 25R: Resin interface (retroreflective interface)

[0043] 55A: Base layer

[0044] LW: Incident light (external light)

[0045] RW: Radar wave Detailed Embodiments

[0046] Hereinafter, preferred embodiments of the present invention will be described, but these embodiments can be appropriately modified and combined. In addition, in the following description and drawings, substantially the same or equivalent parts will be denoted by the same reference numerals.

[0047] [First Embodiment]

[0048] Figure 1 FIG. is a view schematically showing the inside of the lamp device 10 having the radar retroreflector 20 according to the first embodiment of the present invention. More specifically, the inside of the lamp device 10 when viewed from the vertical direction is shown.

[0049] In addition, in the figure, a three-axis coordinate system is shown with the traveling direction of the vehicle VH equipped with the lamp device 10 as the y-direction, the left direction as the x-direction, and the downward direction (gravity direction) as the z-direction. That is, when the vehicle VH is placed horizontally, the horizontal plane is the xy-plane, and the gravity direction is the z-direction.

[0050] The lamp device 10 according to the present embodiment is a vehicle lamp and is used as a headlamp disposed on the left and right sides of the front portion of the vehicle VH. Since the basic structures of the left and right headlamps are the same, hereinafter, one lamp device 10 (left headlamp) disposed on the left front portion of the vehicle VH will be shown and described.

[0051] In addition, although the case where the lamp device 10 is a headlamp for main traveling is described as an example, the lamp device 10 can be a taillight and a backlight lamp device having the purpose and function of emitting light to the outside.

[0052] In addition, in this specification, an automobile is illustrated as the vehicle VH, but the present invention is not limited thereto. That is, in this specification, a vehicle refers to, for example, a transportation means such as a ship or an airplane, and a manned and unmanned transportation or moving tool.

[0053] As Figure 1 shown, although the lamp device 10 is mounted on the vehicle VH, the lamp devices 10 as the left and right headlamps are configured to be bilaterally symmetric with each other.

[0054] The lamp device 10 has a lamp housing 13, which is composed of a housing 11 serving as a base of the lamp device 10 and a transparent cover 12 (also referred to as an outer lens or an outer cover) mounted on the housing 11 and covering the front opening of the housing 11.

[0055] The lamp device 10 includes a lamp unit 15 and a radar unit 17 accommodated in a lamp chamber (lamp body space) 13K defined by the lamp housing 13.

[0056] The lamp unit 15 has a light source such as an LED and optical components such as a lens, and emits light from the light source to the front of the vehicle VH (emitted light LE).

[0057] The radar unit 17 is disposed on the side of the lamp unit 15 in the lamp device 10. The radar unit 17 has an antenna 17A, which is a radar transceiver unit for transmitting electromagnetic waves (radar waves) and receiving reflected waves reflected by an obstacle. The radar unit 17 is configured to emit radar waves RW in the millimeter wave band to the side of the lamp device 10.

[0058] In addition, a retroreflector 20 is disposed in front of the emission of the radar wave RW of the radar unit 17. However, the configurations of the radar unit 17 and the retroreflector 20 are not limited thereto, and they can be disposed at appropriate positions in the lamp device 10 at appropriate angles.

[0059] (1) Structure of retroreflector

[0060] Figure 2 is a cross-sectional view schematically showing the structure of a retroreflector 20 according to a first embodiment of the present invention.

[0061] The retroreflector 20 is disposed in front of the antenna 17A of the radar unit 17 and is arranged such that the radar wave RW of the radar unit 17 is incident from the back side of the retroreflector 20. The retroreflector 20 covers the rear radar unit 17, making it difficult to visually recognize from the outside.

[0062] The retroreflector 20 has a plate shape. The surface 20A of the first resin layer 21 is the surface (light incident surface) on which 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) on which the radar wave RW of the radar unit 17 is incident. Both of these surfaces are surfaces without irregularities, the interval between the two surfaces corresponding to the plate thickness is almost the same at any point, and they are smooth surfaces.

[0063] The retroreflector 20 is integrally formed with the first resin layer 21 and the 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.

[0064] In addition, the first resin layer 21 and the second resin layer 23 can be selected from various thermoplastic resins such as polycarbonate resin, acrylic resin, epoxy resin, polyamide resin, and polyethylene resin.

[0065] The interface between the first resin layer 21 and the second resin layer 23 of the retroreflector 20 is formed into a retroreflective uneven surface (hereinafter also referred to as the resin interface 25R). As the resin interface 25R, for example, an interface having a cube-corner type uneven structure can be used.

[0066] In addition, an island-shaped metal layer 25M is formed on the first resin layer 21 side (i.e., within the first resin layer 21) on the retroreflective resin interface 25R.

[0067] 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 fine islands IS are separated from each other and arranged independently, or are partially adjacent or in contact within the layer.

[0068] As Figure 2 shown, the incident light LW on the first resin layer 21 is retroreflected (retroreflected light LW1) by the island-shaped metal layer 25M.

[0069] In addition, in the retroreflector 20, the refractive index n1 of the first resin layer 21 is greater than the refractive index n2 of the second resin layer 23 (n2 < n1). As Figure 2 shown, the incident light LW on the first resin layer 21 is also retroreflected by the retroreflective resin interface 25R (retroreflected light LW2).

[0070] That is, although there is also light that passes through the island-shaped metal layer 25M (semi-mirror-like transmission), the light that passes through the island-shaped metal layer 25M is totally reflected due to the refractive index difference between the first resin layer 21 and the second resin layer 23, and thus is also retroreflected by the resin interface 25R (retroreflected light LW2). Therefore, a high reflectance for the incident light LW from in front of the retroreflector 20 can be obtained.

[0071] As described above, the retroreflective structure 25 with a high reflectance is obtained by the resin interface 25R and the island-shaped metal layer 25M.

[0072] On the other hand, the island-shaped metal layer 25M is a metal film with a metallic luster and capable of transmitting radar waves, in which fine islands IS (metal islands) are arranged in the layer. Therefore, as Figure 2 shown, the radar wave RW from the radar unit 17 passes through the second resin layer 23, the retroreflective structure 25, and the first resin layer 21, and is emitted forward of the retroreflector 20.

[0073] The metal of the island-shaped metal layer 25M can be, for example, indium, palladium, aluminum, nickel, nickel alloy, copper, copper alloy, silver, silver alloy, tin, tin alloy, etc., but is not limited thereto. The island-shaped metal layer 25M can be formed by electroless plating of these metals.

[0074] Here, the island-shaped metal layer 25M has a structure in which countless fine island-shaped metals (fine islands IS) are formed. By adjusting the size and density of the fine islands IS, an island-shaped metal layer that transmits electromagnetic waves of a desired wavelength can be formed. The size and density of the fine islands IS can be adjusted by adjusting the formation conditions (plating conditions).

[0075] That is, when the size of the fine 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 fine islands IS and passes through the island-shaped metal layer 25M. For example, only as an example, micro-islands IS with a size of about several tens of nm (for example, 20 nm) are sufficiently small compared to the wavelength of 3.9 mm at 76.5 GHz.

[0076] Therefore, even when the radar unit 17 is arranged behind the retroreflector 20 and the radar wave RW is incident from the back surface 20B of the retroreflector 20, the obstacle detection function of the radar unit 17 is fully exerted.

[0077] That is, the retroreflector 20 has sufficient retroreflective performance, can suppress the attenuation and reflection of the radar wave RW and the reflected radar wave (i.e., the received radar wave of the radar unit 17), and does not change the electromagnetic wave emission mode.

[0078] In addition, the degree of freedom in the configuration of the radar unit 17 is increased, and it can be applied to obstacle detection for various purposes. In addition, since the radar unit 17 is arranged behind the retroreflector 20, it is difficult to visually recognize the radar unit 17 from the outside, and the radar unit 17 can be hidden, which is also advantageous in terms of design.

[0079] (2) Dielectric constant and plate thickness of the retroreflector

[0080] Reflection of the transmitted radar wave RW is caused by the difference in dielectric constant between the first resin layer 21 and the second resin layer 23 of the retroreflector 20, 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, the relative dielectric constant difference Δηr is preferably within 5%.

[0081] For example, in the case of the above-mentioned retroreflector 20, 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 Δηr is 3.8%.

[0082] In addition, by adjusting the plate thickness T of the retroreflector 20, the transmission characteristics of the radar wave can be optimized. Figure 3A It is a diagram for explaining the parameters for calculating the composite dielectric constant of the retroreflector 20.

[0083] When the maximum distance and the minimum distance between the surface 20A of the first resin layer 21 and the resin interface 25R are d1MAX and d1MIN respectively, the maximum distance and the minimum distance between the back surface 20B of the second resin layer 23 and the resin interface 25R are d2MAX and d2MIN respectively, and 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 retroreflector 20 is represented by Figure 3B the formula (1) shown.

[0084] At this time, when the speed of light is C and the frequency of the radar wave in the composite resin is f, the wavelength of the radar wave in the composite resin is λ = (C / f) × εr -1 / 2 .

[0085] Therefore, when n is an integer greater than 1, the plate thickness Top of the retroreflector 20 that is most suitable for the transmission of radar waves

[0086] Top = (λ / 2) × ε r -1 / 2 × n Equation (2)

[0087] is represented by.

[0088] Therefore, the plate thickness T of the retroreflector 20 preferably satisfies the above Equation (2) (T = Top).

[0089] In addition, the plate thickness T of the retroreflector 20 can be formed with high precision by multi-color molding. Furthermore, the back surface 20B of the second resin layer 23, which is the incident surface of the radar wave RW, can be a smooth surface.

[0090] As described above, according to the retroreflector of the present embodiment, a shielding member having both excellent brilliance and radar wave transmissivity can be obtained.

[0091] In addition, the radar unit 17 and the retroreflector 20 can be arranged at appropriate positions in the lamp device 10 at appropriate angles.

[0092] [Second Embodiment]

[0093] Figure 4 is a cross-sectional view schematically showing the structure of a retroreflector 40 according to a second embodiment of the present invention.

[0094] Similar to the retroreflector 20 of the first embodiment, the retroreflector 40 of the present embodiment has a plate shape. The retroreflector 40 is integrally formed with a first resin layer 21 and a second resin layer 23 by multi-color molding.

[0095] In the retroreflector 40, the interface between the first resin layer 21 and the second resin layer 23 is a resin interface 25R, and the resin interface 25R is a concavo-convex surface for retroreflection. As the resin interface 25R, for example, an interface having a cubic corner type concavo-convex structure can be used.

[0096] An island-shaped metal layer 45M is formed on the second resin layer 23 side (i.e., within the second resin layer 23) of the retroreflective resin interface 25R. The island-shaped metal layer 45M is an electromagnetic wave transmissive film having a metallic luster and capable of transmitting the radar wave RW.

[0097] As Figure 4 shown, the incident light LW on 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.

[0098] In addition, in the retroreflector 40, the refractive index n1 of the first resin layer 21 is greater than the refractive index n2 of the second resin layer 23 (n2 < n1). The incident light LW on the first resin layer 21 is totally reflected due to this refractive index difference, and thus is also retroreflected by the resin interface 25R (retroreflected light LW2).

[0099] That is, a retroreflective structure 45 with a high reflectivity is obtained through the resin interface 25R and the island-shaped metal layer 45M.

[0100] In addition, in the present embodiment, the plate thickness T of the retroreflector 40 preferably also satisfies the above formula (2) (T = Top).

[0101] As described above, according to the retroreflector of the present embodiment, a shielding member having both excellent brilliance and radar wave transmissivity can be obtained. In addition, the radar unit 17 and the retroreflector 20 can be arranged at appropriate positions in the lamp device 10 at appropriate angles.

[0102] [Third Embodiment]

[0103] Figure 5 FIG. is a cross-sectional view schematically showing the structure of a retroreflector 50 according to the third embodiment of the present invention.

[0104] The retroreflector 50 of the present embodiment has a resin interface 25R as a concavo-convex surface for retroreflection, and a base layer 55A as an amorphous indium tin oxide (ITO) layer is disposed on the first resin layer 21 side of the resin interface 25R. Then, an island-shaped metal layer 55M is formed on the base layer 55A. The island-shaped metal layer 55M is an electromagnetic wave transmissive film having a metallic luster and capable of transmitting the radar wave RW.

[0105] As Figure 5 shown, the incident light LW on the first resin layer 21 is retroreflected by the island-shaped metal layer 55M (retroreflected light LW1). In addition, the incident light LW on the first resin layer 21 transmits through the base layer 55A and is totally reflected due to the refractive index difference between the base layer 55A and the second resin layer 23 and is retroreflected (retroreflected light LW2).

[0106] That is, a retroreflective structure 55 with a high reflectivity is obtained through the resin interface 25R, the base layer 55A, and the island-shaped metal layer 55M.

[0107] In the retroreflector 50, since an ITO layer is provided as the base layer 55A, metals such as aluminum (Al) attached in the form of the base layer 55A can be made into a discontinuous island-shaped structure, and the electromagnetic wave transmissivity can be improved. That is, a retroreflector capable of more easily adjusting the electromagnetic wave transmissivity of the island-shaped metal layer of various metals can be provided.

[0108] As the base layer 55A, not limited to indium tin oxide (ITO), a light-transmissive metal oxide such as indium oxide or indium zinc oxide (IZO), or a layer including them may be used.

[0109] Therefore, according to the retroreflector of the present embodiment, a shielding member having both excellent brilliance and radar wave transmittance can be obtained. In addition, a retroreflector capable of more easily adjusting the electromagnetic wave transmittance of the island-shaped metal layer of various metals can be provided.

[0110] As described above, according to the present invention, a retroreflector having both excellent brilliance and radar wave transmittance can be provided, and it can be mounted on a moving object of an automobile such as a front grille and a badge. In addition, a lamp device can be provided in which a radar unit and a shielding member for suppressing radar wave loss are provided at appropriate positions and angles in the lamp device.

Claims

1. A retroreflector for use with a radar unit, wherein the retroreflector includes an integrated first resin layer and second resin layer, the interface between the first resin layer and the second resin layer is a retroreflective interface, and the retroreflective interface is a concavo-convex surface with retroreflectivity, the refractive index of the first resin layer is greater than that of the second resin layer, an island-shaped metal layer capable of transmitting 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%.

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

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

4. The retroreflector according to claim 1, wherein the retroreflector has a base layer provided between the retroreflective interface and the island-shaped metal layer and containing a metal oxide.

5. The retroreflector according to claim 4, wherein the base layer contains indium tin oxide.

6. The retroreflector according to claim 1, wherein when the composite relative dielectric constant of the retroreflector is εr and n is an integer of 1 or more, the plate thickness Top of the retroreflector satisfies the following formula: Top = (λ / 2) × εr -1 / 2 × n。 7. A lamp device having: the retroreflector according to any one of claims 1 to 6; the radar unit disposed rearward on the back side of the second resin layer of the retroreflector; a lamp unit; a lamp housing that internally houses the retroreflector, the radar unit, and the lamp unit.

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