阅读说明：本技术 雷达回射制品 (Radar retroreflective article ) 是由 金载源 穆赫辛·萨利希 迈克尔·A·麦科伊 苏姗娜·C·克利尔 于 2020-05-21 设计创作，主要内容包括：本公开整体涉及雷达回射制品,该雷达回射制品包括与反射层相邻的一个或多个介电层,其中该一个或多个介电层有助于增大该雷达回射制品的雷达横截面。(The present disclosure generally relates to radar retroreflective articles that include one or more dielectric layers adjacent to a reflective layer, where the one or more dielectric layers help increase the radar cross-section of the radar retroreflective article.)

1. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, and

an O metal layer coated on the cube corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 30,

wherein the dielectric layer is opaque and wherein the dielectric layer is,

wherein the dielectric layer has a thickness of 0.2mm to 15mm, and

wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article.

2. The retroreflective article of claim 1, wherein the dielectric layer has a thickness of 0.2mm to 10 mm.

3. The retroreflective article of claim 1, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article, wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 3 when the radar signal has an angle of incidence of 5 degrees relative to the plane of the retroreflective article.

4. The retroreflective article of claim 1, wherein the dielectric layer refracts radar signals having an entrance angle of 5 degrees relative to the plane of the retroreflective article by at least 60 degrees (30 degrees relative to a normal to the surface).

5. The retroreflective article of any of the preceding claims, wherein the radar signal is 76GHz to 81 GHz.

6. The retroreflective article of any of the preceding claims, wherein the radar signal is 21GHz to 27 GHz.

7. The retroreflective article of any of the preceding claims, wherein the radar signal is 105GHz to 115 GHz.

8. The retroreflective article of claim 1, wherein the reflective layer is immediately adjacent to the dielectric layer.

9. The retroreflective article of any of the preceding claims, wherein the retroreflective layer includes a metallic material.

10. The retroreflective article of any of the preceding claims, wherein the dielectric layer includes poly (methyl methacrylate), polyethylene terephthalate, polycarbonate, polyurethane, pvc, polyethylene, polypropylene, silicone, acrylates including trimethylolpropane and poly (ethylene glycol) acrylate, and combinations thereof.

11. The retroreflective article of any of the preceding claims, wherein the cube corner elements have a side dimension of 2mm to 20 mm.

12. The retroreflective article of any of the preceding claims, wherein the dielectric layer has a dielectric constant of 4 to 20.

13. The retroreflective article of any of the preceding claims, wherein the retroreflective article is a pavement marking.

14. The retroreflective article of any of the preceding claims, further comprising an adhesive layer adjacent to or in close proximity to the retroreflective layer.

15. The retroreflective article of any of the preceding claims, further comprising: an adhesive layer adjacent to or in close proximity to the retroreflective layer and a liner; the liner is adjacent or immediately adjacent to the adhesive layer.

Background

Radar-based systems are widely used in automotive and autonomous driving applications, such as adaptive cruise control, parking assist, lane change assist, and blind spot monitoring. Currently, there is a need for automotive radar systems that can distinguish between objects on the road or simply serve as a redundant data source with greater accuracy and under more challenging weather conditions than optical camera systems. The present inventors have also recognized a need to increase the detectability of workers who do not wear visible retroreflective personal protective clothing and equipment. The present disclosure provides an article that addresses the needs described in this paragraph by providing a radar-reflecting article having improved radar reflection performance.

Disclosure of Invention

In general, the present disclosure relates to reflective articles that include a dielectric layer and a reflective structure capable of reflecting radar signals. Examples of useful reflective articles include sign tapes, traffic cones or barrels, road signs, guard rails, automotive parts, and wearable articles, such as articles of clothing, helmets, badges, and other similar articles.

In one embodiment, the radar-reflecting structure includes a retroreflective layer capable of reflecting radar signals, which in turn may include cube corner elements (e.g., having side dimensions of 2mm to 65 mm) and a metal layer coated on the cube corner elements. In other embodiments, the radar-reflecting structure may include multiple antennas that create radar-reflecting surfaces, or may even be a reflector that includes one or more metal layers capable of reflecting radar signals.

In some embodiments, the dielectric layer may be a single layer that diffracts an incident radar signal such that the angle of incidence of the signal on the reflective layer increases relative to the angle of incidence on the surface of the dielectric layer. For radar signals having a low angle of incidence with respect to the plane of the reflective article, the radar signal refraction allows the radar signal to be reflected by the reflective article in the general direction of the signal source. In other embodiments, the dielectric layer may be a plurality of layers, each layer having a dielectric constant value that decreases from a high dielectric constant in a layer adjacent to the radar reflecting structure to a low dielectric constant in an outermost layer that is typically in contact with air. Alternatively, in other embodiments, the dielectric layer may have a dielectric constant gradient having a high dielectric constant in a portion of the layer adjacent to the radar reflecting structure and a low dielectric constant in an outermost portion that is typically in contact with air.

Unless defined otherwise, all scientific and technical terms used herein have the same meaning as commonly understood in the art. The definitions set forth herein are intended to facilitate an understanding of certain terms used frequently in this application and are not intended to exclude reasonable interpretation of those terms in the context of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical characteristics used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. a range of 1 to 5 includes, for example, 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

The words "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

The term "radar signal" refers to electromagnetic radiation having a frequency in the range of 1GHz to 120 GHz. Radar signals include, but are not limited to, electromagnetic radiation having a nominal frequency of 24GHz (which in this disclosure is considered to be in the range of 21GHz to 27 GHz), a signal nominally having a frequency of 77GHz (which in this disclosure is considered to be in the range of 76GHz to 81 GHz), and a signal nominally having a frequency of 110GHz (which in this disclosure is considered to be in the range of 105GHz to 115 GHz).

The term "opaque" refers to a property of an article, such as a layer in a film construction, that allows less than 80% visible light transmission of the article. Visible light in this disclosure refers to electromagnetic radiation having a wavelength in the range of 400nm to 740 nm.

The term "cube corner elements" refers to structures that are capable of retroreflecting electromagnetic radiation. Cube corner elements comprise truncated cube corner arrays in which the base edges of adjacent cube corner elements are generally coplanar. See, for example, fig. 3 a. Other cube corner element structures described as "full cubes" typically include at least two non-dihedral edges that are not coplanar. See, for example, fig. 3 b. Such structures typically exhibit higher total light return than truncated cube corner elements. Examples of cube corner elements are described in PCT patent application No. wo2004/081619, which is incorporated herein in its entirety.

As understood by the "adjacent" appearing in the context, the term "adjacent" refers to the relative position of two elements (such as, for example, two layers) that are in close proximity to each other, and may or may not need to be in contact with each other or may have one or more layers separating the two elements.

The term "immediately adjacent" refers to the relative position of two elements (such as, for example, two layers) immediately adjacent to and in contact with each other and without an intervening layer separating the two elements. However, the term "immediately adjacent" covers the following cases: one or both of the elements (e.g., layers) has been treated with a primer, or its surface has been modified to affect its properties such as by etching, embossing, or the like, or has been modified by a surface treatment that can improve adhesion or provide diffusion of incident electromagnetic radiation such as corona or plasma treatment, or the like.

The term "radar cross section" (RCS) is a measure of the ability of an object to reflect radar signals in the direction of a radar receiver. In the present disclosure, the RCS is calculated as shown in the examples section below.

The terms "retroreflection", "retroreflected", or "retroreflection" refer to the use of a retroreflective article (e.g., an article comprising a cube-corner layer) to reflect a signal back in the direction of the source. As used herein, the term "retroreflection" is a subset of the term "reflection".

The above summary is intended only to provide a rough overview of the subject matter of the present disclosure, and is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The following description more particularly exemplifies illustrative embodiments. In several places throughout this application, guidance is provided through lists of examples, which examples can be used in various combinations. In each case, the lists cited are intended as representative groups only and are not to be construed as exclusive lists.

Drawings

FIG. 1 is a schematic view of an optical metal retroreflector.

Fig. 2(a) is a schematic illustration of radar signals scattered by retroreflective articles, such as cube corner elements, having cube corner dimensions smaller than the wavelength of the incoming radar signals.

Fig. 2(B) is a schematic illustration of radar signals retroreflected by a retroreflective article (such as cube corner elements) having cube corner dimensions suitable for reflecting wavelengths of incoming radar signals.

Fig. 3(a) to 3(D) are graphical representations of the following retroreflective elements: (a) truncated cube corners, (b) full cube corners, (c) flat two-sided grooves, and (d) concave two-sided grooves.

Fig. 4 illustrates the retroreflection of radar signals by a configuration of dielectric layers having a relatively low dielectric constant.

Fig. 5 shows the retro-reflection of radar signals by a configuration of dielectric layers with a suitable (high) dielectric constant.

Fig. 6 shows a dielectric layer with a suitable (high) dielectric constant and clearly shows the retroreflection of the radar signal by the construction of the prismatic layer.

Fig. 7 shows the retroreflection of radar signals for a configuration with two dielectric layers.

Fig. 8A to 8F show different examples of the composite dielectric layer.

Fig. 9 shows the reflection of a radar signal by a construction having more than one dielectric layer, where the dielectric constant value of each layer decreases in the direction from the outermost layer (adjacent to air) to the layer adjacent to the reflective layer.

Fig. 10 shows the reflection of a radar signal by a configuration having a dielectric layer with a gradient in dielectric constant value that decreases in the direction from the outermost portion (adjacent to air) to the portion adjacent to the reflective layer.

FIG. 11 shows a cross-section of an optical retroreflector without a dielectric layer.

FIG. 12 shows a plan view of an optical retroreflector without a dielectric layer.

FIG. 13 shows a cross-section of an optical retroreflector with a dielectric layer having a dielectric constant of 4.8.

FIG. 14 shows a cross-section of an optical retroreflector with a dielectric layer having a dielectric constant of 8.

FIG. 15A shows a cross-section of an optical retroreflector with a dielectric layer having a dielectric constant of 4.8.

FIG. 15B shows a cross-section of an optical retroreflector having a dielectric layer with a dielectric constant of 4.8 and an additional layer stack with a dielectric constant of 1.98.

Fig. 16 shows an experimental setup for measuring the Radar Cross Section (RCS) of a material, as described in the examples.

Fig. 17 shows an example of a manufacturing process for embedding a reflector array in a matrix.

List of reference numerals

Detailed Description

Autonomous vehicles and Automated Driver Assistance Systems (ADAS) may use various sensors, including radar systems, to sense the environment, infrastructure, and other objects surrounding the vehicle. Radar systems typically comprise a radar signal emitting device (radar transmitter) and a radar radiation detecting device (radar detector) for detecting reflected radar signals redirected, for example, from other vehicles, obstacles or road infrastructure. Radar transmitters are typically mounted less than one meter above the ground and the reflected radar signals originate from elements at distances typically measured from a few feet to tens of feet to hundreds of feet. The detected reflected signals may then be processed to provide additional information about the location of the object that reflected the radar signal.

Due to the operational nature of radar systems, the radar system requires that the item to be detected have a surface that is not only capable of reflecting radar signals, but is also oriented in such a way that the reflected signals are directed towards the radar detector.

For typical vehicle radar systems that focus on scanning the environment in front of the vehicle, the radar signal has a relatively small angle of incidence with respect to road surface markings (such as centerline markings and lane dividers), making it difficult for the radar system to detect this type of item. The same problem exists with moving objects in which the angle of the reflective surface is changed, such as is the case with moving persons or moving/steering micro-mobile vehicles (such as scooters, motorcycles, bicycles, etc.).

In one aspect of the disclosure, the radar-reflecting article of the present disclosure is targeted to facilitate detection and identification of those objects in which the angle of incidence of the radar signal is relatively low relative to a plane containing the object to be detected. Those radar-reflecting articles may be part of pavement markings and wearable articles, such as vests or helmets that do not have typical vertical flat surfaces that are preferred for reflecting radar signals back to radar detectors. However, in other aspects, the reflective articles described herein can also be used to improve detection of other permanent or semi-permanent roadway infrastructure, such as guard rails, posts, signs (e.g., stop signs, yield signs, other informational signs, etc.), concrete barriers, temporary traffic signs (e.g., traffic cones or barrels), mile markers, license plates, labeling, or similar articles attached to a vehicle, and the like.

Generally, the radar-reflecting article of the present disclosure increases the radar signal reflected back to the radar detector by increasing the angle of incidence of the radar signal relative to the radar-reflecting surface. The angle of incidence of the radar signal is increased by refracting the radar signal through a dielectric layer of relatively high dielectric constant. For example, as shown in fig. 6, radar signal 603 has a relatively low angle of incidence (θ 1) with respect to the surface of dielectric layer 605, but a higher angle of incidence with respect to the plane of reflective layer 607. In other words, in essence, the reflective articles of the present disclosure can increase the radar cross-section of the radar reflecting structure by adding a suitable dielectric layer as described herein.

In some embodiments, the radar-reflecting article is a reflective article that includes a reflective layer capable of reflecting radar signals and a reflective layerAnd a dielectric layer adjacent to the emitter layer, wherein the dielectric layer has a dielectric constant of 4 to 100. The term "dielectric constant" in this disclosure means the relative dielectric constant (. epsilon.) unless otherwise specified_r) Which is the dielectric constant of the material divided by the dielectric constant of the vacuum (. epsilon.)₀). In other embodiments, the dielectric layer has a dielectric constant of 4 to 50, 4 to 30, 4 to 25, 2 to 20, 2 to 15, 4 to 10, and 4 to 8.

In certain preferred embodiments, the dielectric layer is not transparent to visible light, but is opaque. The thickness of the dielectric layer may vary depending on its dielectric constant value. For example, for higher dielectric constants, the thickness of the dielectric layer may be lower than the thickness of a dielectric layer having a lower dielectric constant. In some embodiments, the dielectric layer has a thickness of 0.2mm to 25mm, 0.2mm to 20mm, 0.2mm to 15mm, 0.2mm to 10mm, 0.2mm to 5mm, 0.2mm to 3mm, 0.2mm to 1 mm.

In certain embodiments, the reflective layer is a retroreflective layer comprising a layer of cube-corner elements and a metal layer coated on the cube-corner elements. In some cases, a cube corner element layer may include a body portion that generally has a substantially planar front surface and a structured rear surface that includes a plurality of cube corner elements. The cube corner elements may be truncated cube corner arrays (e.g., fig. 3(a)) or full cube corner elements (e.g., fig. 3 (b)). Regardless of type, each cube corner element includes three generally mutually perpendicular optical faces to retroreflect incident radiation.

In some embodiments, the cube corner elements have lateral dimensions of 2mm to 65mm, 2mm to 50mm, 2mm to 40mm, 2mm to 30mm, 2mm to 20mm, 2mm to 10mm, and 2mm to 5 mm. In other embodiments, the cube corner elements have lateral dimensions of 5mm to 65mm, 5mm to 50mm, 5mm to 40mm, 5mm to 30mm, 5mm to 20mm, and 5mm to 10 mm.

In other embodiments, the reflective layer includes radar reflective structures, such as suitable antennas that cause reflected radar radiation to transmit energy back to the radar transceiver. For example, the radar reflecting structure may comprise a plurality of antennas spaced apart on a planar surface to receive incident radar waves and reflect the radar waves in a direction from which they are received. The spacing of the antennas may be determined based on the angle of incidence and the expected frequency of the radar. In this embodiment, the antenna may be a linear slot antenna, a U-shaped antenna, or other shaped antenna.

In other embodiments, the reflective layer comprises a continuous metal layer. Suitable metals for the metal layer include copper, aluminum, silver, gold, iron, or combinations or alloys thereof. Continuous metal layers may be beneficial because these are easy to apply and may provide reliable reflection of radar signals.

Similarly, in some embodiments, the reflective layer may include elements that are or make the layer conductive, such as at least one discrete metallic element. Likewise, suitable metals for the metal elements may include copper, aluminum, silver, iron, gold, or combinations or alloys thereof. The discrete metal elements may be formed of metal. Alternatively, the discrete metallic elements may be formed from a non-metallic material (e.g., a non-metallic carrier comprising ceramic, carbon fiber, glass fiber, epoxy, and combinations thereof) having a metallic coating thereon. Such discrete metal elements may be beneficial because they may help to save material compared to a continuous metal layer.

However, in other embodiments, the reflective layer includes a conductive layer comprising a conductive material, such as a bulk metal layer, a foil, and a conductive coating. In such examples, the reflective layer may be formed by etching or otherwise removing portions of the conductive layer. In other words, the reflective layer may comprise a conductive layer, wherein parts of the conductive layer have been removed in the shape of the radar-reflecting structure, such that the radar-reflecting structure forms open or empty areas in the conductive material.

In other embodiments, the reflective layer may comprise a conductive material disposed on or embedded in a non-conductive dielectric layer or sheet. The conductive material may be copper or other metallic material etched on a non-conductive substrate. In another example, the conductive material may include any metal or conductive material deposited onto the non-conductive substrate via masked vapor deposition, micro-contact printing, conductive ink, or other suitable process. In other words, the reflective layer may be formed by depositing a conductive material on another layer rather than removing the conductive material from the conductive layer.

In general, the reflective layer may be configured to reflect radar radiation of a particular wavelength, such as radiation having a nominal frequency of 24GHz in the range of 21GHz to 27GHz, a signal having a nominal frequency of 77GHz in the range of 76GHz to 81GHz, and a signal having a nominal frequency of 110GHz in the range of 105GHz to 115 GHz. It should be understood that the wavelengths are merely exemplary wavelengths and that other ranges of wavelengths are possible.

To simplify the disclosure and description of the following figures, the description may refer to pavement markings. However, the radar-reflecting article of the present disclosure may be equally applicable to examples in which the reflecting article is part of: wearable articles, such as vests and helmets; as well as other planar structures attached to vehicles (e.g., license plates, labels, or similar articles) or to other roadway substrates (such as guard rails, traffic lights, temporary traffic control articles), and all other articles previously described.

Fig. 1 refers to a typical retroreflective sheeting for retroreflecting visible light (105 and 107), which generally includes a retroreflective layer (101) and a metal layer (103). The figure shows two types of visible light rays, namely a ray 105 with a relatively high angle of incidence and a ray 107 with a lower angle of incidence. In both cases, the refraction of visible light is small compared to the refraction by the relatively high dielectric constant dielectric layer of the reflective article of the present invention.

Fig. 2 shows retroreflective sheeting for retroreflecting visible light (fig. 2(a)) and for retroreflecting radar signals (fig. 2 (b)). The retroreflective sheeting includes a retroreflective layer (201) and a metal layer (203). Fig. 2(a) shows two types of radar signals: (1) radar signal 205 having a relatively high angle of incidence, and (2) radar signal 207 having a relatively low angle of incidence. Since the cube corner elements are not sized for the wavelength of the radar signal, none of the radar signal is retroreflected. Fig. 2(b) shows two types of radar signals: (1) radar signal 209 having a relatively high angle of incidence, and (2) radar signal 211 having a relatively low angle of incidence. In this case, only radar signals having a relatively high angle of incidence are retroreflected, while signals having a relatively low angle of incidence are reflected only in a direction different from the direction of the radar signal source. In this case, in contrast to the reflective articles of the present disclosure, the retroreflective sheeting of fig. 2(b) does not contain a dielectric layer having a suitable dielectric constant.

Fig. 3 shows different examples of retroreflective elements: fig. 3(a) shows a truncated cube corner, fig. 3(b) shows a full cube corner, fig. 3(c) shows a flat two-sided groove, and fig. 3(d) shows a concave two-sided groove.

Fig. 4 illustrates a retroreflective sheeting suitable for retroreflecting radar signals. However, the sheet is either completely free of dielectric layers or comprises dielectric layers having a relatively low dielectric constant. The results are similar to those of FIG. 2 (b). The retroreflective sheeting is only capable of retroreflecting radar signals (401) having relatively high entrance angles. Radar signals (403) having relatively low angles of incidence are reflected, but not in the direction of the signal source (i.e., do not retroreflect).

Fig. 5 illustrates retroreflective sheeting having relatively high dielectric constant values according to the present disclosure. In this case, the two radar signals (501 and 503) are retroreflected, including radar signals with relatively low angles of incidence.

Fig. 6 illustrates retroreflective sheeting in more detail according to the present disclosure. The retroreflective sheeting of fig. 6 is similar to the retroreflective sheeting of fig. 5 except that it shows a prismatic layer 609 and an optional adhesive layer 611. In this case, both radar signals 601 and 603 are properly retroreflected back to the signal source.

Fig. 7 shows a retroreflective sheeting that includes at least two different dielectric layers (705 and 707) in contact with each other, where layer (705) has a lower dielectric constant than layer (707). As can be seen, each dielectric layer refracts the radar signal to such an extent that specular reflection of the signal is reduced, even for low angle-of-incidence signals. A base layer (not shown) is typically adjacent to both the reflective layer and the first dielectric layer 707. That is, the base layer is between the reflective layer and the first dielectric layer.

These types of step-gradient permittivity configurations provide a smooth or step-wise change in permittivity from the first layer to the second layer, such that the permittivity of an individual layer does not have to be as high as the permittivity of other individual layers necessary to achieve the same level of total refraction.

In this embodiment, the reflective article includes a first dielectric layer (707) comprising a first continuous matrix of a first material having a first relative permittivity (ε 1) and a second dielectric layer (705) adjacent to the first dielectric layer, the second dielectric layer having a second relative permittivity (ε 2). In this case, the first dielectric layer has a first thickness (T1); and the second dielectric layer has a second thickness (T2). In this case, the first dielectric constant ε 1 is larger than the second dielectric constant ε 2.

Fig. 8 shows different embodiments of dielectric layers in which elements made of a material with a high dielectric constant are embedded in a resin matrix (801, 813, 805, 817, and 823) with a low dielectric constant. Referring to fig. 8(a), the pure resin layer 801 is optional and the composite layer 803 contains particles of a high dielectric constant material in a resin matrix.

Fig. 8(b) shows a similar construction to fig. 8(a), except that the high dielectric constant material is in the form of a plate or rod to form a composite layer 807. Fig. 8(c) shows two separate composite layers (809 and 811), each having a different type (different composition or different shape or both) of high dielectric constant material. In this embodiment, layer 811 includes two types of high dielectric constant materials.

Fig. 8(d) shows a similar configuration to that of fig. 8(a), except that the composite layer 815 comprises two different types (different compositions or different shapes or both) of high dielectric constant material.

Fig. 8(e) shows three separate layers (817, 819, and 821). Layer 817 is composed of a resin without high dielectric constant elements, while compound layers 819 and 821 each have a different type (different composition or different shape or both) of high dielectric constant material.

Fig. 8(f) shows a similar construction to that of fig. 8(c), except that the composite layer 825 includes only one type of high dielectric constant material, unlike the two-component composite layer 815 of fig. 8 (c).

Fig. 9 shows a step gradient dielectric constant configuration similar to that of fig. 7, except that fig. 9 shows three separate dielectric layers, each having a different dielectric constant. In this embodiment, the dielectric constant increases from the lowest dielectric constant value at the outermost layer (in contact with air) to the highest dielectric constant value in the layer adjacent to the reflective layer. The premix layer shown on this figure is identical to the base layer described above with respect to figure 7. In some embodiments, the pre-mix layer (base layer) refers to a pavement marking composition or layer (or a set of layers corresponding to a pavement marking).

Fig. 10 shows a similar configuration to that of fig. 9, except that the configuration in fig. 9 shows a single dielectric layer having a relatively continuous gradient of dielectric constant, rather than a dielectric layer having a step gradient.

Generally, the dielectric constant of the dielectric layer varies from the dielectric constant closest to the first medium to the dielectric constant closest to the second medium. For example, the dielectric layer may have a varying dielectric constant that starts close to that of air (low dielectric constant) on one side and transitions toward a portion having a high dielectric constant at a portion adjacent to the reflective layer. Such smooth or stepped transitions may significantly reduce dielectric boundary reflections that would otherwise occur at these boundary transitions.

With respect to potential uses of the reflective articles of the present disclosure, as noted above, including reflective articles made in the form of pavement marking tapes, can be used to mark lanes, centerlines, edges or other features of a vehicle lane. In such examples, the dimensions of the band may conform to a suitable standard. For example, for pavement markings used to mark roadways, the material may be between about 7.5 centimeters and 30 centimeters (between 3 inches and 12 inches) wide and 30 centimeters (12 inches) long or longer. In the united states, pavement marking tapes are about 4 inches, about 6 inches, or about 8 inches wide (about 10cm to about 20 cm). In europe, pavement marking tapes are typically about 15 centimeters or about 30 centimeters wide.

In other embodiments, the reflective article can include an adhesive layer adjacent or immediately adjacent to the reflective layer and a liner adjacent or immediately adjacent to the adhesive layer. For example, in some embodiments, and independent of other features described herein, the radar-reflecting article can be manufactured in the form of a tape or a self-adhesive tape. The adhesive tape comprises an adhesive layer, such as, for example, a hot melt adhesive layer, a pressure sensitive adhesive layer, a UV curable adhesive layer, a silicone based adhesive layer, a polyurethane based adhesive layer, or any other suitable adhesive layer or combination of adhesives, by which the tape may be permanently or temporarily attached to a road, a surface of a wearable item, or to another surface. The tape for temporary attachment to the road surface may be removable from the road surface. Self-adhesive tape may comprise a layer of pressure sensitive adhesive for attachment to a road surface or to another surface, and a suitable backing.

The reflective article may also include a backing or liner layer. The backing/liner layer may comprise any suitable film or layer to protect the adhesive properties of the adhesive layer and also to prevent the article from accidentally adhering to an undesired surface. Suitable materials for the backing layer include plastic films, coated or uncoated paper, and the like. Generally, the backing/liner layer may be selected such that it does not have strong adhesion to the adhesive layer itself, and thus may be easily removed by hand or with limited tools.

In some embodiments, the backing layer may include a compliant layer that may enable the radar-reflecting article to remain substantially planar when attached to a rough surface, for example, by conforming to uneven surfaces in a vehicle aisle or other materials to which the aisle article may be applied. In other words, the conformable layer may allow the reflective article to be applied to a rough surface to conform to and adhere to the surface while ensuring that the rough surface does not substantially deform the radar reflecting layer.

In some embodiments, the reflective article can include a thin, high abrasion resistance and/or dust resistant coating applied to the top surface of the reflective article to protect the reflective article from traffic wear and dirt accumulation. In some preferred embodiments, the protective layer may be radar and light transmissive.

In other embodiments, the slip control particles may be partially embedded in the protective layer or in a layer on top of the protective layer. Anti-skid control particles may be referred to as anti-skid particles and may be included in the upper surface of the pavement marking tape to improve traction of the vehicle.

The protective layer may be a single layer or multiple layers, for example, further comprising a top film covering the underlying layers. In some examples, aliphatic polyurethanes may be used for the top film, as aliphatic polyurethane properties may include clarity, resistance to soil buildup, sufficient flexibility to conform to the road surface, adhesion to inorganic skid particles, and resistance to discoloration from exposure to ultraviolet radiation.

In some embodiments, reflective articles of the present disclosure may include other human or machine detectable features in addition to radar reflection. For example, the reflective article can include a colored (e.g., yellow, white, etc.) surface that can be detected by a human or machine vision system. That is, at least a portion of the reflective article can be colored in the human visible spectrum such that the reflective article is perceptible to a human. In other embodiments, a combination of opaque and light transmissive colorants may be used. In this way, the reflective article will have an effective daytime and nighttime color. The colored elements may be selected to avoid interfering with the function of the radar reflecting layer.

As another example, at least a portion of the reflective article may include text, images, or other visual information. Similarly, the reflective article may comprise a machine-perceptible surface. For example, at least a portion of the reflective article can be detected via an infrared camera.

Reflective articles of the present disclosure having radar reflective properties in combination with other sensible elements may provide additional advantages over other types of marker bands or wearable articles. For example, these items may be detected by other sensor systems (such as magnetic detectors) mounted on the vehicle to provide additional redundancy. This redundancy may enable the use of sensors to provide greater confidence in the detection of pavement markings or wearable items under a wider range of conditions, and enable discrimination between the items of the present disclosure and other radar-reflecting objects in the field of view.

Comprising a reflective layer and a plurality of dielectric layers or having a gradient in dielectric constantExemplary embodiment of a single dielectric layer

1. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε₂，

Wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

2. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε of 2 to 5₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε of 1 to 2.5₂And is and

wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

3. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε of 1.5 to 5_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε of 2 to 5₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε of 1 to 2.5₂And is and

wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂。

4. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε of 1.5 to 5_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε of 2.5 to 5₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε of 1.5 to 3₂And an

A third dielectric layer adjacent to the second dielectric layer, the third dielectric layer having a third dielectric constant ε of 1 to 2.5₃And is and

wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a second dielectric constant ε₂Greater than the third dielectric constant ε₃And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

5. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε of 1.5 to 5_s，

A first dielectric layer adjacent to the reflective layer, the first dielectric layer having a first dielectric constant ε of 2 to 5₁And a first thickness of 0.4mm to 0.8mm, an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε of 1 to 2.5₂And a second thickness of 0.5mm to 0.9mm, and

wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

6. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε of 2 to 5₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε of 1 to 2.5₂，

Wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁And is and

wherein at least one of the first dielectric layer or the second dielectric layer is opaque.

7. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A first dielectric layer adjacent to the base layer, the first dielectric layer having a first dielectric constant ε₁And an

A second dielectric layer adjacent to the first dielectric layer, the second dielectric layer having a second dielectric constant ε₂，

Wherein the first dielectric constant ε₁Greater than the second dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁And is and

wherein the reflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the reflective article,

wherein the combined effect of the first dielectric layer and the second dielectric layer refracts a radar signal having an angle of incidence of 5 degrees relative to the plane of the reflective article by at least 60 degrees (30 degrees relative to the normal to the surface).

8. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂A gradient of dielectric constant of, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

9. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂The gradient of the dielectric constant of (a) is,

wherein the dielectric constant₁Is 2 to 5 and has a dielectric constant ε₂Is 1 to 2.5, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

10. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε of 1.5 to 5_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂The gradient of the dielectric constant of (a) is,

wherein the dielectric constant₁Is 2 to 5 and has a dielectric constant ε₂Is 1 to 2.5, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

11. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε of 1.5 to 5_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂The gradient of the dielectric constant of (a) is,

wherein the dielectric constant₁Is 2 to 5 and has a dielectric constant ε₂Is 1 to 2.5, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁，

Wherein the dielectric layer has a thickness of 0.4mm to 2 mm.

12. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂The gradient of the dielectric constant of (a) is,

wherein the dielectric constant₁Is 2 to 5 and has a dielectric constant ε₂Is 1 to 2.5, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁。

Wherein the reflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the reflective article,

wherein the dielectric layer refracts a radar signal having an angle of incidence of 5 degrees relative to the plane of the reflective article by at least 60 degrees (30 degrees relative to the normal to the surface).

13. A reflective article, comprising:

a reflective layer, which is capable of reflecting radar signals,

a base layer adjacent to the reflective layer, the base layer having a dielectric constant ε_s，

A dielectric layer adjacent the base layer and having a first major surface and an opposing second major surface,

wherein the first major surface of the dielectric layer is adjacent to the substrate layer,

wherein the dielectric layer has a dielectric constant epsilon from the first main surface₁To its second main surface₂The gradient of the dielectric constant of (a) is,

wherein the dielectric constant₁Is 2 to 5 and has a dielectric constant ε₂Is 1 to 2.5, and

wherein the dielectric constant ε₁Greater than the dielectric constant ∈₂And a dielectric constant ε_sGreater than the first dielectric constant ε₁，

Wherein the dielectric layer is opaque.

14. The reflective article of any of the preceding embodiments, wherein the substrate layer has a dielectric constant ε of 1.5 to 5_s。

15. The reflective article of any of the preceding embodiments, wherein the substrate layer has a dielectric constant ε of 2 to 5_s。

16. The reflective article of any of the preceding embodiments, wherein the substrate layer has a dielectric constant ε of 2.5 to 5_s。

17. The reflective article of any of the preceding embodiments, wherein the first dielectric constant, ε₁In the range of 2 to 5, and a second dielectric constant ∈ of₂In the range of 1 to 2.5.

18. The reflective article of any of the preceding embodiments, wherein the gradient dielectric layer has a thickness in a range from 0.4mm to 2 mm.

19. The reflective article of any of the preceding embodiments, wherein the first thickness is in a range from 0.4mm to 0.8mm (or from 0.45mm to 0.75mm or from 0.5mm to 0.7mm) and the second thickness is in a range from 0.5mm to 0.9mm (or from 0.6mm to 0.85mm or from 0.65mm to 0.8 mm).

20. The reflective article of any of the preceding embodiments, wherein the first dielectric constant, ε₁In the range of 2 to 5, and a second dielectric constant ∈ of₂In the range of 1 to 2.5, and wherein the first thickness is in the range of 0.4mm to 0.8mm (or 0.45mm to 0.75mm or 0.5mm to 0.7mm) and the second thickness is in the range of 0.5mm to 0.9mm (or 0.6 to 0.85mm or 0.65 to 0.8 mm).

21. The reflective article of any of the preceding embodiments, wherein at least one of the first dielectric layer or the second dielectric layer is opaque.

22. According to the foregoingThe reflective article of any of the embodiments, further comprising a third dielectric layer adjacent to the second dielectric layer, the third dielectric layer having a third dielectric constant ε₃Wherein the second dielectric constant ε₂Greater than the third dielectric constant ε₃。

23. The reflective article of any of the preceding embodiments, further comprising a third dielectric layer adjacent to the second dielectric layer, the third dielectric layer having a third dielectric constant ε in a range of 1.5 to 3₃Wherein the second dielectric constant ε₂Greater than the third dielectric constant ε₃。

24. The reflective article of any of the preceding embodiments, further comprising a third dielectric layer adjacent to the second dielectric layer and having a third dielectric constant, ε₃Wherein the first dielectric constant ε_1is2.5 to 5, a second dielectric constant ε₂Is 1.5 to 3, and a third dielectric constant ε₃Is 1 to 2.5.

25. The reflective article of any of the preceding embodiments, further comprising a third dielectric layer adjacent to the second dielectric layer and having a third dielectric constant, ε₃Wherein the first dielectric constant ε₁2.5 to 5, a second dielectric constant ε₂Is 1.5 to 3, and a third dielectric constant ε₃Is 1 to 2.5, wherein the second dielectric constant ε₂Greater than the third dielectric constant ε₃And wherein the third dielectric layer has a thickness in a range of 0.4mm to 0.8 mm.

26. The reflective article of any of the preceding embodiments, wherein the reflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the reflective article, wherein the combined effect of the first dielectric layer and the second dielectric layer refracts a radar signal having an angle of incidence of 5 degrees relative to the plane of the reflective article by at least 60 degrees (30 degrees relative to a normal to the surface).

27. The reflective article of any of the preceding embodiments, wherein the reflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the reflective article, wherein the dielectric layer refracts radar signals having an angle of incidence of 5 degrees relative to the plane of the reflective article by at least 65 degrees (25 degrees relative to a normal to the surface).

28. The reflective article of any of the preceding embodiments, wherein the reflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the reflective article, wherein the dielectric layer refracts radar signals having an angle of incidence of 5 degrees relative to the plane of the reflective article by at least 70 degrees (20 degrees relative to a normal to the surface).

29. The reflective article of any of the preceding embodiments, further comprising a fourth dielectric layer adjacent to the third dielectric layer, the fourth dielectric layer having a fourth dielectric constant, ε₄Wherein the third dielectric constant ε₃Greater than a fourth dielectric constant ε₄。

30. The reflective article of any of the preceding embodiments, wherein the radar signal is from 76GHz to 81 GHz.

31. The reflective article of any of the preceding embodiments, wherein the radar signal is 21GHz to 27 GHz.

32. The reflective article of any of the preceding embodiments, wherein the radar signal is from 105GHz to 115 GHz.

33. The reflective article of any of the preceding embodiments, wherein the reflective layer is immediately adjacent to the dielectric layer.

34. The reflective article of any of the preceding embodiments, wherein the reflective layer comprises:

a. a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising cube corner elements having a side dimension of 2mm to 65mm, and

b. a metal layer coated on the cube-corner elements.

35. The reflective article of any of the preceding embodiments, wherein the reflective layer comprises a metal layer.

36. The reflective article of any of the preceding embodiments, wherein the reflective layer comprises a plurality of antennas.

37. The reflective article of any of the preceding embodiments, wherein the reflective layer comprises a plurality of antennas including a first antenna, a second antenna partially surrounding the first antenna, and a third antenna partially surrounding the first antenna and the second antenna.

38. The reflective article of any of the preceding embodiments, wherein any one of the dielectric layers, independently of each other, comprises poly (methyl methacrylate), polyethylene terephthalate, polycarbonate, polyurethane, pvc, polyethylene, polypropylene, silicone, acrylates including trimethylolpropane and poly (ethylene glycol) acrylate, and combinations thereof.

39. The reflective article of any of the preceding embodiments, wherein any one of the dielectric layers comprises two or more phases independently of each other.

40. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers, independently of each other, is a composite material comprising at least one material having a low dielectric constant of 1.5 to 3.5 and at least one material having a dielectric constant of 20 to 50.

41. The reflective article of any of the preceding embodiments, wherein any one of the dielectric layers, independently of each other, comprises particles selected from barium titanate, glass, ABO3 type oxides, AB (Ox, N1-x)3 type oxynitrides, and combinations thereof, wherein a is selected from ionic Ba, Sr, Pb, Ca, Ln, lanthanide groups, and B is selected from ionic Ti, Nb, Cr, Bi, Nd, Zr, Cu.

42. The reflective article according to any of the preceding embodiments, wherein any one of the dielectric layers independently of each other comprises particles having a shape selected from the group consisting of spherical, elongated, plate-shaped, rod-shaped, and wherein the particles comprise a material selected from the group consisting of barium titanate, glass, ABO3 type oxides, AB (Ox, N1-x)3 type oxynitrides, and combinations thereof, wherein a is selected from the group consisting of ions Ba, Sr, Pb, Ca, Ln, lanthanide groups, and B is selected from the group consisting of ions Ti, Nb, Cr, Bi, Nd, Zr, Cu.

43. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other have a dielectric constant of 4 to 100.

44. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other has a dielectric constant of 4 to 50.

45. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other has a dielectric constant of 4 to 30.

46. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other have a dielectric constant of 4 to 20.

47. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other has a dielectric constant of 4 to 15.

48. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other have a dielectric constant of 4 to 10.

49. The reflective article of any of the preceding embodiments, wherein any of the dielectric layers independently of each other have a dielectric constant of 4 to 8.

50. The reflective article of any of the preceding embodiments, wherein the reflective article is a pavement marking.

51. The reflective article of any of the preceding embodiments, wherein the reflective article is a transportation bucket.

52. The reflective article of any of the preceding embodiments, wherein the reflective article is a pavement marking.

53. The reflective article of any of the preceding embodiments, wherein the reflective article is a traffic cone.

54. The reflective article of any of the preceding embodiments, wherein the reflective article is a guard rail.

55. The reflective article of any of the preceding embodiments, wherein the reflective article is an automotive part.

56. A wearable article comprising the reflective article of any of the preceding embodiments.

57. An article of clothing comprising the reflective article according to any of the preceding embodiments.

58. A helmet comprising the reflective article of any of the preceding embodiments.

59. An emblem comprising the reflective article of any of the preceding embodiments.

60. The reflective article of any of the preceding embodiments, further comprising a protective layer adjacent or immediately adjacent to the dielectric layer.

61. The reflective article of any of the preceding embodiments, further comprising an anti-corrosion layer adjacent or immediately adjacent to the reflective layer.

62. The reflective article of any of the preceding embodiments, further comprising a substrate adjacent or immediately adjacent to the reflective layer.

63. The reflective article of any of the preceding embodiments, further comprising a substrate adjacent or in close proximity to the dielectric layer.

64. The reflective article of any of the preceding embodiments, further comprising an adhesive layer adjacent or immediately adjacent to the reflective layer.

65. The reflective article of any of the preceding embodiments, further comprising: an adhesive layer adjacent or in close proximity to the reflective layer and a liner; the liner is adjacent or in close proximity to the adhesive layer.

66. The reflective article of any of the preceding embodiments, further comprising an adhesive layer adjacent to or in close proximity to the reflective layer, wherein the adhesive is selected from the group consisting of thermoplastic adhesives and pressure sensitive adhesives.

Exemplary embodiments including a retroreflective layer and a dielectric layer to diffract radar signals

1. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 100.

2. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 50, and

wherein the dielectric layer is opaque.

3. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 50, wherein the dielectric layer is opaque, and

wherein the thickness of the dielectric layer is 0.2mm to 25 mm.

4. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 30,

wherein the dielectric layer is not transparent to light,

wherein the thickness of the dielectric layer is 0.2mm to 15 mm.

Wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article, an

Wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 3 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

5. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 30,

wherein the dielectric layer is not transparent to light,

wherein the thickness of the dielectric layer is 0.2mm to 15 mm.

Wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 3 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article, and

wherein the dielectric layer refracts a radar signal having an angle of incidence of 5 degrees relative to the plane of the retroreflective article by at least 60 degrees (30 degrees relative to the normal to the surface).

6. A retroreflective article comprising:

a retroreflective layer capable of reflecting radar signals, the retroreflective layer comprising:

o cube corner elements having side dimensions of 2mm to 65mm, an

O-metal layer coated on the cube-corner elements,

a dielectric layer adjacent to the retroreflective layer and having a dielectric constant of 4 to 30,

wherein the dielectric layer is not transparent to light,

wherein the thickness of the dielectric layer is 0.2mm to 15 mm.

Wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 3 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article, and

wherein the radar signal is 76GHz to 81 GHz.

7. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer is opaque.

8. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 25 mm.

9. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 20 mm.

10. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 15 mm.

11. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 10 mm.

12. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 5 mm.

13. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 3 mm.

14. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.2mm to 1 mm.

15. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 25 mm.

16. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 20 mm.

17. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 15 mm.

18. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 10 mm.

19. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 5 mm.

20. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 3 mm.

21. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.3mm to 1 mm.

22. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 25 mm.

23. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 20 mm.

24. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 15 mm.

25. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 10 mm.

26. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 5 mm.

27. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 3 mm.

28. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 0.5mm to 1 mm.

29. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 25 mm.

30. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 20 mm.

31. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 15 mm.

32. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 10 mm.

33. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 5 mm.

34. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1mm to 3 mm.

35. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 25 mm.

36. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 20 mm.

37. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 15 mm.

38. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 10 mm.

39. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 5 mm.

40. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a thickness of 1.5mm to 3 mm.

41. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 3 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

42. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 5 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

43. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is greater than 10 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

44. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is 3 to 100 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

45. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is 3 to 50 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

46. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer has a first major surface and an opposing second major surface, and the first major surface defines a plane of the retroreflective article,

wherein a ratio of a radar cross-section with the dielectric layer to a radar cross-section without the dielectric layer is 3 to 20 when the radar signal has an angle of incidence of 5 degrees with respect to a plane of the retroreflective article.

47. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer refracts radar signals having an entrance angle of 5 degrees relative to a plane of the retroreflective article by at least 60 degrees (30 degrees relative to a normal to the surface).

48. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer refracts radar signals having an entrance angle of 5 degrees relative to a plane of the retroreflective article by at least 65 degrees (25 degrees relative to a normal to the surface).

49. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer refracts radar signals having an entrance angle of 5 degrees relative to a plane of the retroreflective article by at least 70 degrees (20 degrees relative to a normal to the surface).

50. The retroreflective article of any of the preceding embodiments, wherein the radar signal is 76GHz to 81 GHz.

51. The retroreflective article of any of the preceding embodiments, wherein the radar signal is 21GHz to 27 GHz.

52. The retroreflective article of any of the preceding embodiments, wherein the radar signal is 105GHz to 115 GHz.

53. The retroreflective article of any of the preceding embodiments, wherein the reflective layer is immediately adjacent to the dielectric layer.

54. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer includes a metallic material.

55. The retroreflective article of any of the preceding embodiments, wherein the retroreflective layer includes a metal selected from silver, gold, copper, or a combination thereof.

56. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer includes poly (methyl methacrylate), polyethylene terephthalate, polycarbonate, polyurethane, pvc, polyethylene, polypropylene, silicone, acrylates including trimethylolpropane and poly (ethylene glycol) acrylate, and combinations thereof.

57. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer and the cube corner elements are made of the same material.

58. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer includes two or more phases.

59. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer is a composite material including at least one material having a dielectric constant of 1.5 to 3.5 and at least one material having a dielectric constant of 10 to 50.

60. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer is a composite material including at least one material having a dielectric constant of 1.5 to 3.5 and at least one material having a dielectric constant of 20 to 50.

61. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer comprises a material selected from the group consisting of barium titanate, glass, ABO₃Type oxide, AB (O)_x,N_1-x)₃Oxynitride-type and combinations thereof, wherein A is selected from ions Ba, Sr, Pb, Ca, Ln, lanthanide groups, and B is selected from ions Ti, Nb, Cr, Bi, Nd, Zr, Cu.

62. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer includes particles having a shape selected from the group consisting of spherical, elongated, platy, rod-shaped, and wherein the particles comprise particles selected from the group consisting of barium titanate, glass, ABO₃Type oxide, AB (O)_x,N_1-x)₃Oxynitride-type and combinations thereof, wherein A is selected from ions Ba, Sr, Pb, Ca, Ln, lanthanide groups, and B is selected from ions Ti, Nb, Cr, Bi, Nd, Zr, Cu.

63. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer includes particles of a material having a dielectric constant of 10 to 50.

64. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a structure and/or composition as shown in fig. 8.

65. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of from 2mm to 50 mm.

66. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 40 mm.

67. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 30 mm.

68. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 20 mm.

69. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 10 mm.

70. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 15 mm.

71. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 5 mm.

72. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 2mm to 4 mm.

73. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 3mm to 15 mm.

74. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 3mm to 10 mm.

75. The retroreflective article of any of the preceding embodiments, wherein the cube corner elements have a side dimension of 3mm to 5 mm.

76. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 100.

77. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 50.

78. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 30.

79. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 20.

80. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 15.

81. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 10.

82. The retroreflective article of any of the preceding embodiments, wherein the dielectric layer has a dielectric constant of 4 to 8.

83. The retroreflective article of any of the preceding embodiments, wherein a surface of the dielectric layer that is not adjacent to the retroreflective layer has an increased surface roughness relative to an untreated dielectric layer surface.

84. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is a pavement marking.

85. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is a traffic bucket.

86. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is a traffic cone.

87. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is a pavement marking.

88. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is a guard rail.

89. The retroreflective article of any of the preceding embodiments, wherein the retroreflective article is an automotive part.

90. A wearable article comprising the retroreflective article of any of the preceding embodiments.

91. An article of clothing comprising the retroreflective article of any of the preceding embodiments.

92. A helmet comprising the retroreflective article of any of the preceding embodiments.

93. An emblem comprising the retroreflective article of any of the preceding embodiments.

94. The retroreflective article of any of the preceding embodiments, further comprising a protective layer adjacent or immediately adjacent to the dielectric layer.

95. The retroreflective article of any of the preceding embodiments, further comprising a corrosion protection layer adjacent or immediately adjacent to the metal layer.

96. The retroreflective article of any of the preceding embodiments, further comprising a substrate adjacent to or in close proximity to the retroreflective layer.

97. The retroreflective article of any of the preceding embodiments, further comprising a substrate adjacent or in close proximity to the metal layer.

98. The retroreflective article of any of the preceding embodiments, further comprising an adhesive layer adjacent to or in close proximity to the retroreflective layer.

99. The retroreflective article of any of the preceding embodiments, further comprising: an adhesive layer adjacent or in close proximity to the retroreflective layer; the liner is adjacent or in close proximity to the adhesive layer.

100. The retroreflective article of any of the preceding embodiments, further comprising an adhesive layer adjacent to or in close proximity to the retroreflective layer, wherein the adhesive is selected from the group consisting of thermoplastic adhesives and pressure sensitive adhesives.

101. The retroreflective article of any of the preceding embodiments, further comprising a set of dielectric layers (or a single dielectric layer having a gradient in dielectric constant) as in any of the embodiments preceding this embodiment section.

Examples

All parts, percentages, ratios, and the like in the examples and the remainder of the specification are by weight unless otherwise indicated or clearly evident from the context.

A computational modeling of a prismatic retroreflector with a metal coating was performed and baseline samples in which air was adjacent to the radar source side of the prismatic layer were compared to inventive samples in which different dielectric layers were adjacent to the prismatic layer. The model simulates radar signals incident on the sample at various angles when calculating the RCS of the sample. The sample parameters varied included: dielectric constant of the dielectric layer, thickness of the dielectric layer, and size of the element of the retroreflector. Some models include a weathering layer adjacent to a dielectric layer, where the weathering layer has a dielectric constant value similar to a dust or dirt layer, to determine the effect on RCS performance.

Computational modeling section

Test method for computational modeling

Modeling is performed through an electromagnetic modeling tool CST Microwave studio. The RSC (radar cross section) of the samples with and without dielectric layers was calculated.

a. First sample without dielectric layer

The size of the sample was 25mm by 25mm, and the dimensions of the retroreflector are in fig. 12, and the incident radar signal came from an angle of 85 ° relative to an axis perpendicular to the plane of the retroreflector (fig. 11).

b. Second sample with dielectric layer (dielectric constant 4.8)

See fig. 13.

c. Third sample with dielectric layer (dielectric constant ═ 8)

See fig. 14.

Here are the calculated RCS results for 3 samples with an incident radar signal of 85 °.

At 78GHz	RCS[mm2]
		Air (a)	1,724
Dielectric constant 4.8	16,560
		Dielectric constant of 8	28,010

d. Weather and dust induced additional layer stacks

For practical use, deterioration of the retroreflection performance should be considered in consideration of rain, snow, dust, and the like. If no dielectric layer is present on top of the retroreflector, this additional layer stack will directly cause EM wave refraction, which will critically alter the retroreflection performance. However, with a dielectric layer on top, the angle of incidence at the retroreflector surface will not change due to rain, snow, dust, etc., regardless of any additional layer stack on the dielectric layer, as shown in fig. 15.

e. Different thicknesses of the dielectric layer (dielectric constant 8): 500 μm/1mm/2mm

Thickness of dielectric layer	RCS (mm) at 78GHz2)
		500μm	16,300
1mm	18,000
		2mm	28,010

Description of the preferred embodiment

Test method for hypothetical experiments

For RCS measurements, a set of standard antennas at 77GHz was used. One as a transmitter antenna (Tx) and the other as a receiver antenna (Rx). See fig. 16. The antennas are located near each other, facing the sample, and thus present the same angle to the sample. The transmitter antenna is connected to a radio frequency signal generator and the receiver antenna is connected to a spectrum analyzer. The sample is placed on a flat surface that is non-retro-reflective to radar signals.

The RCS is calculated by measuring the transmit power and the receive power by subtracting the transmit power and the receive power at the terminals to calculate the power loss. This power reduction is due in part to losses in the connecting cable and free space, depending on the cable properties and the distance between the sample and the antenna. If the transmit antenna and cable are the same as those on the receive side, the ratio of the receive power and the transmit power gives the RCS.

Preparative prophetic examples

One sample consisted of a silicone prism substrate with a vapor-coated silver metal layer on top of the prism layer. This sample has no dielectric layer and is used as a comparative sample. Another sample had a silicone prism substrate and a vapor coated silver metal layer, but also included a dielectric layer on top of the silver layer.

The silicon prism substrate was replicated by 3D printing the mold. A silver conductive layer is then coated on top of the silicon substrate. After the silver is applied, a dielectric layer is applied.

Fig. 17 is an example of a manufacturing process for embedding a reflector array in a substrate. Depending on the application, the substrate may be flexible.

The preparation of the various dielectric layers is described below.

1: continuous phase, discontinuous high dielectric constantElectrically constant dielectric material

A first particulate high dielectric low loss material having a maximum particle size of about 100 microns to 200 microns is dispersed into a continuous phase of relatively low viscosity (10,000cP or less) until uniformly mixed. The continuous phase may be a mixture of low loss carbon-based or silicon-based monomers/oligomers, or a solution of a polymer, or a combination thereof, and has a lower dielectric constant than the discontinuous phase. The high dielectric material has a higher density than the continuous phase. The mixture is applied to the metallized layer by a suitable method (e.g., slot die, gravure coating, flood coating). Sufficient residence time is provided before the coating solution becomes solid such that the dense high dielectric phase settles towards the cavities in the metallization layer, thereby creating a gradient in dielectric constant from a lower value at the air interface to a higher value at the metallization interface. Curing of the coating can be achieved by drying in an oven, curing the reactive material in an oven, exposure to actinic radiation, or some combination of all three. The composition may also include leveling agents, dispersants, and drying agents.

Another example of a continuous phase having a discontinuous high dielectric constant dielectric material includes discontinuous phases wherein at least one shape of the discontinuous phase has a width to thickness aspect ratio greater than 10. The phase may exhibit (i) rod-like or (ii) plate-like morphology. The high aspect ratio discontinuous phase has a higher density than the continuous phase. Both the continuous and discontinuous phases can be deposited in the same process (see examples above) and, after coating, give the discontinuous sheet sufficient residence time to settle and form aligned structures with long directions approximately parallel to the air-dielectric surface.

2. Continuous phase, two discontinuous dielectrics

The same procedure described immediately above in 1 was followed, but the composition also contained particles in the same size range, which were less dense and had a lower dielectric coefficient than the continuous phase (e.g., glass bubbles)

3. A continuous phase, an added discontinuous dielectric and a via-process additionAdded discontinuous dielectric

Following the same procedure described above in 1, except that the composition may also contain a surfactant, and the composition is slightly foamed prior to application, causing bubbles to rise and create air gaps in the cured coating, while denser particles settle out

4. A continuous phase, an added discontinuous dielectric and a discontinuous dielectric added via a process

Two-layer coextrusion in which 1) is coated as a base layer and 2) or the blister layer is not added with a dielectric as the layer closest to the air interface.