WO2019068381A1

WO2019068381A1 - Retroreflective microstructured plate, method for producing a retroreflective plate and use of a retroreflective plate as a traffic or motor vehicle licence plate

Info

Publication number: WO2019068381A1
Application number: PCT/EP2018/069318
Authority: WO
Inventors: Bernd Pfundstein
Original assignee: Erich Utsch Ag
Priority date: 2017-10-06
Filing date: 2018-07-16
Publication date: 2019-04-11
Also published as: DE102017123239A1

Abstract

The invention relates to a retroreflective plate (10) comprising a plate blank (14) made of a transparent plastic with a microstructured triple-mirror structure (22) formed and/or shaped on at least sections of a surface (18) of an inner side (20) of the plate blank (14), wherein the microstructured triple-mirror structure (22) has a plurality of triple mirrors (24) each with three mirror surfaces (26) arranged at right angles to one another for retroreflection, and the triple mirrors (24) are formed in the surface (18) of the inner side (20) and each have mirror surfaces (26) which are designed to be reflective from an outer side (12) of the plate blank (14) spaced apart from the inner side (20).

Description

Retroreflective microstructured shield, method of making a retroreflective shield and use of a retroreflective shield as a traffic or automotive

license plate

The invention relates generally to retroreflective, microstructured signs, in particular to traffic and / or license plates, which are preferably printable and / or embossable. More particularly, the present invention relates to retroreflective shields, a method of making retroreflective shields, and the use of retroreflective shields as traffic or license plate signs, wherein the shield plate of a retroreflective shield comprises a transparent plastic, and on the surface of an inner side of the shield plate microstructured corner mirror structure is formed.

Vehicle license plates with retroreflective properties are known in the art. Such license plates have, for example, a metal plate with a front side laminated, retroreflective sheeting. A legend is impressed in the metal plate, so that on the upper side a raised structure is formed. On the raised structure, a color layer is applied by means of a thermal transfer printing. Such license plates are thus made of a metal. In addition, they are designed in several parts and include different materials that can complicate the recycling of a license plate. In addition, the manufacture of a license plate is expensive because of the retroreflective sheeting.

Also known are license plates, which are made of a transparent plastic, wherein on a back of the license plate a retroreflective sheeting is adhered to provide the retroreflective properties of the license plate. Before the retroreflective sheeting is adhered to the transparent shield plate, a legend is previously printed on the retroreflective sheeting. Thus, in the legendary area, the retroreflective sheeting no longer has retroreflective properties. Such a known license plate is also constructed in several parts and can complicate the return process of a license plate. Due to the use the retroreflective sheeting is the known license plate in their manufacture expensive.

From DE 603 09 702 T2 a backlit license plate is known. The license plate has a transparent retroreflective sheeting which is adhered to a transparent polymeric carrier sheet by means of a transparent adhesive layer. The retroreflective sheeting is positioned to be rotated toward the light source and the transparent polymeric support sheet is oriented toward the viewer. The license plate includes a raised lettering that is colored on its raised surface to make it opaque or less transparent compared to the license plate background. The raised lettering is formed by embossing the laminate of the transparent polymeric backing sheet and the retroreflective sheeting. The license plate thus provides a multilayer structure of at least two films, wherein the retroreflective sheeting is adhered to a carrier film. The license plate is thus expensive to manufacture.

EP 1 477 368 describes a luminous license plate. The license plate comprises a light guide having on one side a light source for illuminating the light guide. On a front surface of the light guide, a label is arranged, on which a legend is glued. Between the light guide and the indicator a retroreflective sheeting is arranged. The disadvantage here is the multi-layered and complex structure of the license plate. It is also known that total internal reflection provides a largely lossless reflection, so that very high reflection values are achieved by this effect. By the appearance of the effect in the interior of a transparent body at the boundary layer to another, optically thinner medium no separately mirrored mirror surfaces need to be provided or manufactured. Furthermore, there is no problem that the reflectance of the mirror surfaces can be affected by external influences, for example by contamination.

There is a continuing need to further develop retroreflective tags to reduce their manufacturing costs and to provide traceability simplify as well as provide a method with which retroreflective signs are inexpensive to produce.

The present invention has the object to provide a retroreflective shield that is inexpensive to produce and easy to recycle. As well as to provide a corresponding method for producing the retroreflective shield according to the invention.

This object is achieved with a retroreflective shield with the features of claim 1 and with a method with the features of claim 21. Advantageous and / or preferred embodiments or developments of the invention are specified in the dependent claims. All combinations as well as isolated combinations between the features of the retroreflective shield, the method and the use can be used together. Furthermore, it is also provided and possible, as desired, to combine individual or several features of the retroreflective shield, the method and the use as desired.

According to the invention, a retroreflective shield is provided, comprising a shield plate of a transparent plastic with a microstructured triple mirror structure formed on at least one surface of an inner side of the shield plate, wherein the microstructured triple mirror structure comprises a plurality of triple mirrors each having three mirror surfaces arranged at right angles to each other for retroreflection comprises and the plurality of triple mirrors is formed in the surface of the inner side, wherein the respective mirror surfaces of the triple mirrors are formed from a mirror-shaped formed on the inside of the outer side of the shield plate. In principle, it is also possible, instead of retroreflective structures, which are each based on three mutually perpendicular mirror surfaces, to resort to alternative mirror geometries, which may for example be based on a larger number of mirror surfaces, which are not arranged at right angles to each other. It is thus provided that the retroreflective shield has a shield plate made of a transparent plastic. On a surface of an inner side of the shield plate, a microstructured triple structure is formed at least in sections.

The mirror surfaces of the individual triple mirrors of the triple mirror structure are reflective of visible light due to total internal internal reflection at the plastic-air interface over a wide range of angles of incidence. The inside is preferably the back of the sign, which usually faces the motor vehicle when the sign is arranged as a license plate on a motor vehicle. The microstructured triple structure is formed on the surface of the inside of the shield plate. This means that the microstructured triple structure is formed directly in the shield plate, that is, the layer imparting the rigidity of the shield. Preferably, the shield plate is integrally formed. In principle, however, it is also possible that the shield can be of multilayer construction, the individual layers being connected to one another in a captive manner. However, it is essential to the invention that the microstructured cusp mirror structure is formed directly in the shield plate, that is to say the layer which gives the plate the mechanical stiffness, and not z. B. realized via a separate layer wist such. B. on a film which is adhered to the shield plate.

The microstructured triple mirror structure has a plurality of triple mirrors each having three mirror surfaces arranged at right angles to each other for retroreflection, wherein the triple mirrors are formed in the surface of the inner side and each have three mirror surfaces. Microstructured means that the characteristic dimensions of the triple mirrors of the triple mirror structure are in the range of a few microns to a maximum of a few hundred microns. In the context of the present invention, microstructured means that a depth of the individual triple mirrors of the triple mirror structure preferably has a value of between 100 μm and 400 μm, preferably between 100 μm and 300 μm, and particularly preferably 150 μm. The depth of the tri-mirror structure preferably indicates a distance from the surface of the inner side to the lowest point of the individual triple mirrors of the triple mirror structure. The mirror surfaces of the triple mirrors can, for example, be triangular, here in particular equilateral, or quadrangular, here in particular square. Corner mirrors with square mirror surfaces are also referred to as "fill cube corner" retro-reflectors, which are particularly preferably used in connection with the present invention because they have a particularly high retroreflectivity over a wide range of angles of incidence.

Microstructured triple mirror structures in a transparent plastic can be advantageously produced by molding from a master, for example in an injection molding process or by an embossing process by means of a microstructured embossing punch, which may be flat or cylindrical, for example.

The master may for example consist of a metallic material such as steel.

A master for a triple mirror structure with triple mirrors with triangular mirror surfaces can be produced for example by a machining mechanical machining of a metallic surface, for. B. by three regular grid of adjacent V-shaped grooves are introduced into the surface by milling, which are oriented at 60 ° relative to each other.

A master for a triple mirror structure with triple mirrors with square mirror surfaces can be produced, for example, by a removing micromechanical laser machining of a metallic surface.

The use of a microstructured cusp mirror structure to realize retroreflective properties of the shield plate offers the significant advantage that such microstructures can be printed in the simplest manner by means of common printing methods, even if the surfaces to be printed are inclined relative to the print head. By means of such printing z. As security features such as watermarks, bar or QR codes or sovereignty symbols or alphanumeric characters z. B. a license plate legend are printed on the shield plate. For example, common industrial inkjet printers can be used. But also thermal transfer printing method, which will be discussed in more detail below, can be used. In principle, all printing methods known from the prior art are suitable, which allow printing of plastic surfaces which are inclined against the printhead and which allow a working distance of the surface to be printed from the printhead in the range of several tens to several hundred microns. The printing of the mirror surfaces destroys the total internal reflection at such mirror surfaces and thus locally suppresses the retroreflectivity of the license plate. Thus, symbols imprinted on the mirror surfaces or the like are. not only under diffuse illumination, but also to recognize under retroflecting conditions, which is advantageous, for example, in such a design of a license plate legend or even in the application of macroscopic security features as extending over substantially the entire board height or width wavy lines.

Particular advantages arise when the printed characters or symbols are printed in a color that corresponds substantially to the background color of the finished license plate or even the color of a laminated on the back of the shield plate protective film, which will be discussed in more detail below. In this case, the printed sign or symbol is practically invisible under diffuse illumination, but clearly recognizable under retroreflective conditions.

The mirror surfaces are mirror-formed over a wide range of angles of incidence, due to total internal internal reflection at the interface between the shield plate material and the adjacent half-space (i.e., air) from an outside of the shield plate spaced from the inside. The outside is thus the side visible to the outside, which faces the viewer in a arranged on a motor vehicle sign. In this way, a light beam which impinges on the mirror surfaces of a triple mirror of the microstructured triple structure formed on the inside from the outside via the outside of the shield plate can be multiply reflected by a total internal reflection. The geometry of the corner mirror structure provides retroreflection of the shield in this manner.

Thus, a retroreflective shield is provided which has retroreflective properties, and is preferably made of a material, whereby the recycling process of the shield can be simplified. By the Forming the microstructured triple structure directly in the shield plate may provide a retroreflective shield that does not have a laminated retroreflective sheeting, thereby reducing the cost of manufacturing the retroreflective shield.

A transparent plastic is preferably to be understood as a plastic which is translucent without significant parts of it being absorbed. Preferably, the plastic is optically clear and / or has a transmission of 80% to nearly 100%. Non-translucent plastics are excluded for the shield board. The plastics PMMA (polymethyl methacrylate), PET, polyamide, polystyrene and polycarbonate (in particular Macrolon®) have proved to be particularly suitable.

In an advantageous development of the invention it is provided that the transparent plastic of the shield plate is injection-moldable and / or die-castable. In an injection molding process, the transparent plastic is injected into a mold and cures in this. In a die casting process, two negative molds are preferably combined under pressure to mold a plastic introduced between the molds. In this way, a plastic is specified with the shield plates are inexpensive to produce. In addition, methods are called, with which Schildplatinen inexpensive and can be produced in a consistent quality.

In principle, it is conceivable that, after the manufacture of a shield plate, the microstructured triple mirror structure is subsequently formed in the surface of the inner side. For this purpose, it may be provided that a negative mold of the microstructured triple mirror structure is formed on a roller, which is rolled or rolled over the surface of the inner side of the shield plate after the manufacturing process of the shield plate to form the microstructured triple reflector structure accordingly. In addition, it is possible to provide a stamp designed as a negative mold of the microstructured triple mirror structure, by way of which the microstructured triple mirror structure can be stamped and / or stamped into the surface. For the stamping process and / or the rolling process it can be provided that the roller, the stamp and / or the shield plate are previously heated. A preferred embodiment of the invention is in that the microstructured triple mirror structure can be embossed and / or stamped and / or rolled into the surface of the shield plate.

It is particularly preferably provided that the microstructured triple mirror structure is embossed and / or stamped into the surface of the shield plate during the injection molding process and / or the pressure casting process. For this purpose, the corresponding forms of the injection molding method or die casting method preferably have a negative mold with the microstructured cusp mirror structure, so that the microstructured cusp mirror structure is simultaneously formed during the manufacture and formation of the shield plate. In this way, the manufacturing process of a retroreflective shield can be accelerated and / or the manufacturing costs of the shield can be reduced.

It is conceivable that a transparent plastic is used, which is suitable for injection molding and / or die casting and also at least partially deformable by embossing.

A preferred embodiment of the invention is that the transparent plastic is a thermoplastic material. A thermoplastic material may preferably be heated for the manufacturing process of the shield plate and thus be easily brought into the corresponding shape of the shield during the injection molding and / or Diegießvorgangs. A thermoplastic material has the advantage that this is easily deformed by supplying heat, and the shield plate is inexpensive to produce.

A preferred development of the invention is that the transparent plastic is a polymeric plastic. Preferably the plastic comprises a polycarbonate such as e.g. Macrolon® on. Macrolon® has proven to be a particularly advantageous thermoplastic transparent plastic which can be embossed in a simple manner.

In an advantageous development of the invention, the mirror surfaces have a substantially triangular or substantially quadrangular configuration. In a quadrangular configuration of the mirror surfaces, it is preferably provided that the mirror surfaces are square. According to the invention, the microstructured triple mirror structure has, at least in regions, a plurality of triple mirrors. The cusp mirrors are preferably spaced and most preferably substantially contiguous. In this way, the microstructured triple mirror structure has a plurality of preferably juxtaposed triple mirrors. The larger the proportion of the surface of the shield plate, which is covered by triple mirrors, the more incident light can be reflected by the respective triple mirrors. In a preferred embodiment of the present invention, the triple mirror structure does not extend over the entire surface of the shield, but saves certain areas. Thus, it has proved to be advantageous if certain areas of the surface in which certain information, such as nationality markings, sovereign symbols or insurance or registration information of a vehicle are arranged in the case of an individualized sign, are not designed to be retroreflective. Such a shield thus has at least microscopic, preferably macroscopic coherent surface areas in which no triple mirrors are arranged. Accordingly, in the injection molding tool provided for making such a shield, there are surface areas covered with negative patterns of the triple mirrors to be incorporated in the shield, and adjacent surface areas associated with the same surface of the shield to be made, which are free of negative structures. In principle, it can be provided that the shield has a legend. A legend preferably comprises one or more characters and / or numbers. It can be provided that on the outside of the shield plate a preferably one and / or multi-colored formed legend can be glued and / or laminated and / or printed. The legend is particularly preferably formed opaque. In this way, in the areas with the legend, the retroreflection of the shield can be inhibited so that the legend becomes visible.

A preferred embodiment of the invention is that the shield plate is embossed and / or has an embossable plastic. Embossed means that the shield plate is designed such that in the shield plate preferably via a stamping tool is a legend einprägbar, as is known, for example, metal shield plates. By imprinting the legend can be formed on the inside of a depression and / or on the outside of the shield a raised structure. Preferably, the shield plate and / or embossing tool for the embossing process are heated to reduce material stresses in the shield during the embossing process. The legend is particularly preferably embossed in the section having the microstructured cusp mirror structure. The shield plate is thus embossable by means of a stamping tool and locally deformable. In this way, a legend can be impressed into the shield by known means and at low cost.

A preferred embodiment of the invention provides that the shield plate is heat embossed. This means that the shield plate and / or the embossing tool are heated to a corresponding temperature for deforming the shield plate in order to form the legend in the shield plate by an embossing process, which is preferably carried out in an embossing device. The term heat-embossable means that the shield plate and / or the embossing tool to a temperature between 100 ° C and 150 ° C, preferably between 120 ° C and 130 ° C are heated. The hot embossing process can be gentle on the legend to reduce the risk of breaks in the shield plate during the embossing process. Likewise, the microstructured triple mirror structure can be formed by the hot embossing process. For this purpose, the stamp and / or the roller and / or the shield plate is heated accordingly.

In a preferred embodiment of the invention it is provided that the legend is embossed in the section of the shield plate having the microstructured cusp mirror structure. Preferably, a stamping tool is placed on the inside of the shield plate and stamped in the shield plate. By the embossing process, a depression is formed on the inside of the shield plate. In this case, the microstructured triple mirror structure in the region of the legend can be locally damaged. Damage to the microstructured cusp mirror structure in the region of the legend is irrelevant, since in the area of the legend a retroreflection should be reduced and / or even prevented in order to make the legend visible. In principle, it may be sufficient for the embossing process to damage the microstructured triple mirror structure in the area of the embossing and to form a depression on the inside, in order to reduce retroreflection of the sign in the area of the embossing in this way. An advantageous development of the invention provides that the legend is impressed into the shield plate such that a recess is formed by the embossing process on the inside and on the outside of a survey is formed. In this way, an elevation is formed by the embossing process on the outside, wherein the elevation preferably has a height of 0.1 mm to 1.5 mm, advantageously between 0.2 mm to 1 mm and particularly preferably of 0.5 mm. The height describes the distance from the original outside to the farthest point of the projection formed by the embossment.

In this context, a preferred embodiment of the invention provides that the collection of the legend, a color layer, in particular an opaque color layer, preferably by means of a thermal transfer method, is applied. In a thermal transfer process, a color layer applied to a carrier film is locally heated and partially transferred to a substrate. For this purpose, the color layer is brought into mechanical contact with the substrate. The color layer preferably has a black color. However, it is not limited thereto and may be any other opaque color. In this manner, retroreflection can be reduced, inhibited, and / or inhibited by the color layer applied to the protrusions of the legend, thus making the legend visible to the retroreflective portion of the shield plate.

Alternatively and / or in addition thereto, a preferred development of the invention resides in the fact that the indentation formed by impressing the legend is colored on the inside. Preferably, the recess is colored with a water-resistant ink, which is particularly preferably introduced into the depression with an inkjet printing device. The formation of the recess in the course of the stamping operation of the legend can damage the retroreflective corner mirror structure, which can reduce retroreflection in these areas. The color introduced into the recess makes it possible, in particular in the areas damaged by the embossing process, to make a color contrast to the retroreflective area. In a preferred development of the invention, it is provided that the microstructured triple mirror structure has a hydrophobizing coating and / or is hydrophobicized. A hydrophobizing coating is a water-repellent coating. The hydrophobizing coating can be, for example, a polymer-based coating. But even a coating with silanes has hydrophobic properties. The hydrophobization of the microstructured cusp mirror structure may prevent and / or reduce moisture adhesion in the microstructured cusp mirror structure, such that an air interface may be secured to the cusp mirror structure for total internal reflection. In this way, the retroreflective properties of the sign can be maintained even in humid environments.

A preferred embodiment of the invention is that a protective film is arranged on the microstructured triple mirror structure. In this way, the microstructured triple mirror structure can be covered by the protective film. Between the microstructured triple mirror structure and the protective film, an air cushion is at least partially formed, so that the retroreflective properties of the shield in the region of the air cushion are not impaired. The protective film can protect the retroreflective corner mirror structure from moisture and / or external influences.

In principle, the protective film can be arranged at a distance from the triple mirror structure. A preferred development of the invention provides that the protective film is arranged directly on the microstructured cusp mirror structure, so that a mechanical contact between the raised tips of the cusp mirror structure and the protective film can result. Nevertheless, at least partially and / or partially an air cushion can form between the individual triple mirrors and the protective film. In this way, the structure of the shield can be simplified. In addition, in this way the height of the sign can be reduced.

In a preferred embodiment of the invention it is provided that the shield plate on the inside has a peripheral, preferably flat edge, on which the protective film is arranged, preferably glued or welded. Preference is given to a weather-resistant connection between the Edge and the protective film made. Particularly preferably, a sealed connection between shield plate and protective film is produced along the circumferential edge, so that the inner space enclosed by shield plate and protective film, to which the above-mentioned air poster belongs, is hermetically sealed. Such a sealed connection can be produced in a particularly simple manner if the peripheral edge is planar, in particular if it has no structure.

Preferably, the protective film comprises a polymeric material, in particular a thermoplastic material, or consists of such. Preferably, a polymeric material with high mechanical resistance is used, which in particular has a high tensile strength and a high ductility.

It is also conceivable to use a multilayer film with at least one layer of a thermoplastic material for thermal weldability of the film with the shield plate and a further layer of a polymeric material which provides the required mechanical properties of the protective film.

The protective film may in principle be transparent. A preferred development of the invention is that the protective film is formed one or more colors. The protective film determines the color impression of the sign viewed from the front.

The thickness of the protective film is typically between 30 and 300 micrometers, preferably between 50 and 150 micrometers.

In principle, the protective film can be flat and / or structureless. A preferred development of the invention is that the protective film has a structure, preferably a polygonal structure, in particular a honeycomb structure. In this way, the stability, in particular the tear strength, of the protective film can be increased.

A preferred embodiment of the invention provides that on a side facing the microstructured triple mirror structure side of the protective film applied a legend and / or a security feature, in particular imprinted or is lasered or lasered. But also the application of separately trained security features we z. As holograms, etc., which are transmitted from a separate carrier film on the protective film and with this z. B. are thermally welded, may be advantageous. However, the legend and / or the security feature may possibly only be of limited visibility, since the microstructured triple mirror structure is arranged in front of the printed legend or the security feature and thus incident light is reflected. Under diffuse light, the legend and / or security feature is visible, but disappears under retroreflective observation conditions because it is outshone by the back-reflected light.

In an alternative embodiment, the legend or the security feature is printed onto the surface of the shield plate which carries the triple mirror structures or is lasered into it. In this embodiment, the legend or security feature can be recognized both under diffuse incidence of light and under retroreflective conditions.

A further advantageous embodiment of the invention is that the shield plate has a shield thickness between 0.5 mm and 3 mm, preferably between 1 mm and 2.5 mm, and particularly preferably between 1.5 mm and 2 mm. In this way, a shield plate is provided, which has a shield thickness which is easily stampable by means of a stamping tool. In addition, the shield thickness is comparable to the thickness of known shield thicknesses, so that the shield plate can be arranged in a simple manner in the usual shield holders. Compared to the metal tag, the plastic retroreflective shield may be lighter in weight.

The invention additionally relates to a method for producing a retroreflective shield, comprising a shield plate made of a transparent plastic with a microstructured triple mirror structure formed at least in sections on one surface of an inner side of the shield plate, wherein the microstructured triple mirror structure comprises a plurality of triple mirrors each having three mutually perpendicular mirror surfaces for retroreflection comprises, and the triple mirrors are formed in the surface of the inside and each having mirror surfaces, which due to total internal reflection of an inner side spaced outside of the Schildplatine from under a plurality of angles of incidence are formed mirror-like, comprising at least the following steps:

Producing a shield plate made of a transparent plastic;

- Introducing a microstructured cusp mirror structure on and / or in a surface of an inner side of the shield plate by embossing and / or hot stamping and / or rolling and / or pressing.

It is thus provided that the shield plate is made of a transparent plastic, wherein on the surface of the inside of the shield plate at least partially a microstructured triple mirror structure is formed and / or molded. The microstructured cusp mirror structure is thus formed directly in the shield plate, so that an integrally formed shield plate with microstructured cusp mirror structure is provided. Integral means that the microstructured cusp mirror structure is directly formed in the sign plate providing strength to the shield and is not adhered to the shield plate via a foil.

In principle, further layers can be arranged on the shield plate, which are connected captive to the shield plate. Preferably, another layer may be a legend printed on the outside of the sign.

The microstructured triple mirror structure is embossed in and / or on the surface of the inside of the shield plate at ambient temperature, embossed by means of hot stamping, rolled in and / or pressed. In this way, a method is provided with which a shield plate, which has retroreflective properties, can be produced inexpensively.

Basically, it is provided in the context of the present invention that the microstructured corner mirror structure is formed after the manufacture of the shield plate by embossing at ambient temperature and / or hot stamping and / or rolling and / or pressing. In an alternative embodiment of the invention, however, it is provided that the shield plate is produced by injection molding and / or die casting. In this way, methods are provided with which a shield plate made of plastic can be produced in a simple manner. A preferred development is that the microstructured triple mirror structure is formed during the injection molding and / or die casting process. It is particularly advantageously provided that the microstructured triple mirror structure is introduced by means of a negative mold into the surface on the inner side of the shield plate. For this purpose, the forms of the injection molding process and / or the pressure casting process have corresponding negative forms of the microstructured triple mirror structure. Thus, the manufacturing process of the microstructured trile mirror structure having shield plate can be accelerated.

An advantageous development of the invention lies in the fact that a legend is embossed into the section of the shield plate having the microstructured cusp mirror structure with an embossing tool. For this purpose, the shield plate is preferably formed from an embossable plastic, most preferably from a thermoplastic material. The embossing process can damage and / or deform the microstructured triple mirror structure such that a total reflection in the region of the embossing is reduced and / or prevented. This is intentional and / or insignificant, since in the area of the embossing a retractive reflection should be reduced.

According to a preferred embodiment of the invention, it is provided that the legend is impressed into the shield plate by means of hot stamping. This means that the embossing tool for embossing the legend and / or the shield plate, preferably to a temperature between 100 ° C and 150 ° C, and most preferably to a temperature between 120 ° C to 130 ° C, are heated.

When choosing a suitable plastic, embossing at ambient temperature may also be possible. Exemplary of such a plastic is called Makroion®.

An advantageous development of the invention is that the legend is stamped into the shield plate in such a way that a recess is formed on the inside by the stamping process and an elevation is formed on the outside. In this context, an advantageous development of the invention lies in the fact that a color layer is applied to the elevation produced by embossing. The ink layer is preferably opaque, so that in the region of the survey a retroreflection can be reduced and / or prevented. The ink layer is preferably applied to the survey by means of a thermal transfer process.

Alternatively and / or in addition thereto, a preferred development of the invention provides that the recess formed by the stamping in of the legend is colored on the inside. This is preferably done with an inkjet printer. In this way, a color contrast can be made to the unembossed portion of the shield plate, whereby the legend can be made visible. A further preferred embodiment of the invention is that by means of a printing process, a security feature, a nationality identifier, a QR or a barcode, an alphanumeric identifier or a license plate legend can be printed on the surface of the license plate, on which the triple mirror structures are arranged. It is also possible to print the mirror surfaces. In the preferred development of the method, this therefore comprises the step of printing the surface of the license plate, on or in which the triple mirror structures are arranged, to form a visually perceptible marking. A preferred development of the invention is that a hydrophobizing coating is applied to the microstructured triple mirror structure. A hydrophobizing coating is a water-repellent coating. The hydrophobizing coating may preferably be a polymer based coating. The hydrophobization of the microstructured triple mirror structure may prevent and / or reduce moisture adhesion in the microstructured cusp mirror structure such that an air interface may be formed on the cusp mirror structure for total internal reflection. In this way, the retroreflective properties of the sign can be maintained even in humid environments. In a preferred embodiment of the invention, it is provided that a protective film is arranged on the microstructured triple mirror structure. In this way, the microstructured triple mirror structure can be covered by the protective film. Between the microstructured triple mirror structure and the protective film, an air cushion is at least partially formed, so that the retroreflective properties of the shield are not impaired. The protective film may preferably protect the retroreflective corner mirror structure from external influences, in particular from moisture. The arrangement of the protective film on the retroreflective corner mirror structure is preferably carried out by gluing and / or lamination and / or welding.

If the method also includes printing on the surface of the license plate, on or in which the triple mirror structures are arranged, to form a visually perceptible marking, then this method step is advantageously carried out before covering this surface of the license plate with the protective foil.

The invention also relates to the use of the retroreflective shield according to the invention as a license plate for mounting on a motor vehicle. Furthermore, it relates to the use as a retroreflective traffic or information sign.

Further features and advantages of the present invention will become apparent from the dependent claims and the following embodiments. The exemplary embodiments are not limiting, but rather to be understood as exemplary, rather they should enable the person skilled in the art to carry out the invention. The Applicant reserves the right to make individual or several of the features disclosed in the exemplary embodiments the subject matter of patent claims or to include such features in existing claims. The embodiments are explained in more detail with reference to figures. In these show:

Fig. 1: a retroreflective shield in a plan view according to a preferred embodiment of the invention, FIG. 2 is a side sectional view of the retroreflective shield of FIG. 1 taken along the line in FIG. 3 shows a view of a triple mirror of a microstructured triple mirror structure according to the preferred exemplary embodiment of the invention, FIG.

4 shows a side sectional view of the retroreflective shield along the section line B-B shown in FIG. 1, according to a first embodiment of the stamping of a legend, FIG.

5 is a side sectional view of the retroreflective shield along the in FIG. 1 shows a sectional view B-B according to a second embodiment of the stamping of a legend,

6 is a side sectional view of the retroreflective shield along the section line BB shown in FIG. 1, according to a third embodiment of the embossment of a legend; FIG. 7 is a side sectional view of the retroreflective shield along the section line BB shown in FIG the second embodiment, wherein a protective film is disposed on the microstructured cusp mirror structure, and Fig. 8: a process flow for producing the retroreflective shield according to an embodiment of the invention.

FIG. 1 shows a retro-reflective shield 10 in a plan view. Shown is an outer side 12 of the retroreflective shield 10, which has a shield plate 14 made of a transparent plastic. A legend 16 is embossed sublime in the shield plate 14, wherein the raised surfaces of the legend are dyed black by means of ink transfer of a transfer film. The outer side 12 of the retroreflective shield 10 faces a viewer, so that it can visually perceive the legend 16. FIG. 1 shows the section lines A: A and B: B, to which reference will now be made. FIG. 2 shows a side sectional view of the retroreflective shield 10 along the section line AA shown in FIG. The section AA is guided in a region of the retroreflective shield 10 in which no legend 16 is embossed. Shield plate 14 is formed from a transparent plastic and has microstructured triple mirror structures 22 formed at least in sections on a surface 18 of an inner side 20 arranged at a distance from outer side 12. The inside 20 is the back of the retroreflective shield 10, which is usually facing the motor vehicle when the retroreflective shield 10 is disposed on a motor vehicle as a license plate.

The shield plate 14 is made of Macrolon® and has a thickness of 1.2 millimeters. The microstructured triple structure 22 is formed on the surface 18 of the inner side 20 of the shield plate 14 and covers substantially the entire surface. The microstructured triple mirror structure 22 has a multiplicity of side by side arranged triple mirrors 24, which adjoin one another directly, wherein in each case a triple mirror 24 has three mutually perpendicular arranged mirror surfaces 26 for retroreflection. In the present embodiment, microstructured means that a depth of the triple mirror structure 22, which indicates a distance from the surface 18 of the inner side 22 to the lowest point of the triple mirror 24, has a value between 150 pm and 250 pm. The microstructured triple structure 22 is formed directly in the shield plate 14 and thus integrally therewith. The shield plate 14 gives the shield 10 the rigidity.

The mirror surfaces 26 are mirror-formed from the outside 12 of the shield plate 14 at a plurality of angles of incidence due to total internal reflection in the shield plate 14 material at the interface to the adjacent gas / air filled half space. In this way, a light beam 28 which strikes the mirror surfaces 26 of the triple mirror 24 of the microstructured triple structure 22 formed on the inner side 20 from the outside via the outer side 12 of the shield plate 14, by multiple total internal reflection at the multiple mirror surfaces 26 of a corner mirror structure 22nd be reflected back in its direction of incidence, ie. be retroreflected. FIG. 3 shows in detail a triple mirror 24 of the microstructured triple mirror structure 22 shown in FIG. The triple mirror 24 has three mirror surfaces 26 arranged at right angles to one another. The light beam 28 striking the shield plate 14 from the outside is guided via the outer side 12 to the mirror surfaces 26. The light beam 28 strikes the first mirror surface 26a of the triple mirror 24. The first mirror surface 26a reflects the light beam 28 to the second mirror surface 26b arranged at right angles to the first mirror surface 26a. From the second mirror surface 26b, the light beam 28 is reflected onto the third mirror surface 26c, which is arranged at right angles to the second mirror surface 26b. The third mirror surface 26 c reflects the light beam 28, so that it emerges from the shield plate 14 via the outer side 12.

FIG. 4 shows a side sectional view of the retroreflective shield 10 along the section line BB shown in FIG. 1 according to a first embodiment of the embossing of the legend 16. The shield plate 14 is made of a thermoplastic embossable plastic for embossing the at least one legend 16 into the microstructured cusp mirror structure 22 having formed section. For this purpose, an embossing tool is placed on the microstructured triple mirror structure 22 having portion and by means of the embossing tool a z. B. embossed alphanumeric character. This can preferably take place via an embossing device, wherein the embossing tool and / or the shield plate 14 are advantageously heated before the embossing process. The embossing process locally damages the microstructured triple mirror structure 22 in the area of the embossing, so that the retroreflective properties in this area are reduced or completely suppressed.

Preferably, a recess 30 is formed by the embossing process on the inner side 20 in the region of the embossing. The formed by the imprinting of the legend 16 recess 30 is colored on the inside 20 with a color 32. Preferably, the color 32 is formed as a waterproof color. For example, the ink 32 may be introduced into the recess 30 with an ink jet printing apparatus. In this way, the legend 16 can be color-coded from the section surrounding the legend 16 and comprising the microstructured cusp mirror structure 22, whereby the legend 16 is determined via the outside 12 for a section Viewer is perceived both in diffuse lighting and under retroreflective conditions.

In an alternative embodiment of the shield according to FIG. 4, which is not shown, the ink 32 has such a small layer thickness that the ink layer formed substantially follows the contour of the surface to which it is applied.

FIG. 5 shows a side sectional view of the retroreflective shield 10 along the section line B - B shown in FIG. 1 according to a second embodiment of the stamping of the legend 16. In contrast to the retroreflective shield 10 shown in FIG. 4, the legend 16 is embossed in such a way that the indentation 30 on the inside 20 and also a protrusion 34 on the outside 12 are formed by the embossing process. The elevation 34 has a height of 0.5 mm, wherein the height indicates the distance from the original outer side 12 to the farthest point of the projection 34 formed by the embossment. On the elevation 34 of the legend 16, an opaque color layer 36, preferably by means of a thermal transfer method applied. The color layer 36 preferably has a black color. In this way, the color layer 36 applied to the bumps 34 of the legend 16 can reduce and / or eliminate the retroreflection in the region of the legend 16, thus rendering the legend 16 in both diffuse illumination and retroreflective conditions over the retroreflective portion the shield plate 14 to make visible.

FIG. 6 shows a side sectional view of the retroreflective shield 10 along the section line BB shown in FIG. 1 according to a third embodiment of the stamping of the legend 16. In the third embodiment, the legend 16 is analogous to the embodiment shown in Figure 5, so that by the embossing process on the inside 20, a recess 30 and on the outside 12, a survey 34 is formed. Likewise, an opaque ink layer 36 is applied by means of a thermal transfer printing on the survey 34. In addition, the recess 30 is colored by means of a color 32. In this way, the retroreflective properties in the region of legend 16 can be further reduced. FIG. 7 shows a further development of the retroreflective shield 10 known from FIG. 5 in section along the section line BB shown in FIG. The further development consists in that a protective film 38 is arranged on the microstructured triple mirror structure 22. In this way, the microstructured triple mirror structure 22 can be covered by the protective film 38. Between the microstructured corner mirror structure 22 and the protective film 38, an air cushion 40 is formed in sections, so that the retroreflective properties of the shield 10 are not impaired. The protective film 38 may protect the retroreflective cusp mirror structure 22 from moisture and / or external influences. The protective film 38 is arranged directly on the microstructured triple mirror structure 22, so that an air cushion 40 can form between the individual triple mirrors 24 and the protective film. In this way, the overall height of a shield 10 can be reduced with a weather-resistant, microstructured corner mirror structure 22.

The shield plate 10 has on the inside 20 a circumferential flat edge 42 on which the protective film 38 is arranged. Particularly preferably, the protective film 38 is glued peripherally and without interruption on the edge 42, laminated and / or welded. The peripheral edge 42 has no structure, so that a weather-resistant, hermetically sealed connection between the edge 42 and the protective film 38 can be produced.

In the exemplary embodiment shown in FIG. 7, the protective film 38 is a coextruded film and, as such, has a two-layered construction. It has an approximately 75 micron thick adhesive layer of thermoplastic PET and a layer of a mechanically heavy-duty PET-G (glycol-modified PET) about 125 microns thick, with the protective film 38 oriented toward the shield plate 38 with the PET-A layer and with this along the peripheral edge 42 high-frequency or ultrasonic welded.

In the embodiment shown in Figure 7, the protective film 38 is not only along the peripheral edge 42 connected to the shield plate 14, but also in the area of the embossed alphanumeric character 16 at a plurality of positions selectively welded to the shield plate 14 thermally. The protective film 38 may in principle be transparent. In the present exemplary embodiment, the protective film 38 is monochrome, in particular in the color white. Common colors in the license plate area include, for example, yellow with a black colored legend and blue with a white colored legend.

FIG. 8 shows a method sequence for producing the retroreflective shield 10 according to the invention. In a first step 100, the shield plate 14 is made of a transparent plastic. The transparent plastic is a thermoplastic. In particular, the thermoplastic is a polymeric plastic, preferably Macrolon®. The shield plate 14 is produced by the injection molding method and / or by the die casting method. In a second step 110, a microstructured corner mirror structure 22 is introduced onto and / or into the surface 18 of the inner side 20 of the shield plate 14 by embossing and / or hot stamping and / or rolling and / or pressing. In this way, a method is provided with which a retroreflective properties shield plate 14 can be produced inexpensively.

In an alternative process control, the surface of the mold used for the injection molding or die casting method has negative forms of the retroreflective microstructures according to the invention to be introduced into the shield plate in one of its surfaces. These are molded directly into the shield plate 14 during injection molding or pressure casting.

reference numeral

10 Retroreflective shield

12 outside

14 shield plate

16 legend

18 surface

20 inside

22 Microstructured triple mirror structure 24 Triple mirror

26 mirror surface

26a First mirror surface

26b Second mirror surface

26c Third mirror surface

28 light beam

30 deepening

32 color

34 survey

36 color layer

38 protective film

40 air posters

42 edge

100 step 1

110 step 2

Claims

claims

A retroreflective shield (10), comprising a shield plate (14) made of a transparent plastic with a on a surface (28) of an inner side (20) of the shield plate (14) at least partially formed and / or integrally formed microstructured triple mirror structure (22), wherein

the microstructured triple mirror structure (22) comprises a plurality of triple mirrors (24) each having three mirror faces (26) arranged at right angles to each other for retroreflection, and

the triple mirrors (24) are formed in the surface (28) of the inner side (20) and each have mirror surfaces (26) spaced from the inside (20) of an outer side (12) of the shield plate (14) against an optically thinner one Medium like air are formed mirroring.

2. Shield according to claim 1, characterized in that a depth of the triple mirrors (24) of the triple mirror structure (22) has a value between 100 pm to 400 pm, preferably between 100 pm and 300 pm and particularly preferably 150 pm.

3. Shield according to claim 1 or 2, characterized in that the transparent plastic of the shield plate (14) is injection-moldable and / or die-cast bar.

4. Shield according to one of claims 1 to 3, characterized in that the microstructured triple mirror structure (22) in the surface (18) einprägbar and / or stampable and / or einwalzbar.

5. Shield according to one of claims 1 to 4, characterized in that the transparent plastic is a thermoplastic material.

6. Shield according to one of claims 1 to 5, characterized in that the transparent plastic is a polymeric plastic.

7. Shield according to one of claims 1 to 6, characterized in that the mirror surfaces (26) are formed substantially triangular or substantially quadrangular.

8. Shield according to one of claims 1 to 7, characterized in that the microstructured triple mirror structure (22) at least partially a plurality of triple mirrors (24), which are preferably formed substantially adjacent to each other.

9. Shield according to one of claims 1 to 8, characterized in that the shield plate (14) is embossed and / or has an embossable plastic.

10. Shield according to claim 9, characterized in that a legend (16) in which the microstructured triple mirror structure (22) having portion of the shield plate (14) embossed or impressed impressed.

11. Shield according to one of claims 9 or 10, characterized in that the shield plate (14) for forming raised or recessed structures mechanically embossed, in particular Heißprägbar is.

12. Shield according to one of claims 10 to 11, characterized in that the legend (16) is stamped into the shield plate (14) such that by the embossing process on the inside (20) has a recess (30) is formed and on the Outside (12) has an elevation (34) is formed.

13. Shield according to claim 12, characterized in that on the survey (34) of the legend (16) a color layer, in particular an opaque color layer, preferably by means of a thermal transfer method, is applied.

14. Shield according to one of claims 10 to 13, characterized in that by the impressing of the legend (16) formed recess (30) on the inside (20) is colored.

15. Shield according to one of claims 1 to 14, characterized in that the microstructured triple mirror structure (22) has a hydrophobizing coating and / or is hydrophobicized.

16. Shield according to one of claims 1 to 15, characterized in that on the microstructured triple mirror structure (22) a protective film (38) is arranged.

17. A shield according to claim 16, characterized in that the protective film (38) is arranged directly on the microstructured cusp mirror structure (22) such that a. the highest elevations of the triple mirror structure (22) are in mechanical contact with the protective film (38) and

b. between the individual triple mirrors (24) and the protective film (38) at least partially and / or partially an air cushion (40) is formed.

18. Shield according to claim 16 or 17, characterized in that the

Schildplatine (14) on the inside (20) has a circumferential, preferably flat edge (42) on which the protective film (38) arranged, preferably glued and / or laminated and / or welded.

19. Shield according to one of claims 16 to 18, characterized in that a legend and / or a security feature is printed on one of the microstructured triple mirror structure (22) facing side of the protective film (38).

20. Shield according to one of claims 1 to 19, characterized in that the shield plate (14) has a shield thickness between 0.5 mm and 3 mm, preferably between 1 mm and 2.5 mm, and particularly preferably between 1.5 mm and 2 mm.

21. A method for producing a retroreflective shield according to any one of claims 1 to 20, comprising at least the following steps:

- Preparing a shield plate (14) made of a transparent plastic (100); - Introducing a microstructured triple mirror structure (22) on and / or in a surface (18) of an inner side (20) of the shield plate (14) by embossing and / or hot stamping and / or rolling and / or pressing (110).

22. The method according to claim 21, characterized in that the shield plate (14) is produced by injection molding and / or die casting.

23. Method according to claim 22, characterized in that the microstructured triple mirror structure (22) is formed during the injection molding process and / or the pressure casting process.

24. The method according to any one of claims 21 to 23, characterized in that the microstructured triple mirror structure (22) by means of a negative mold in the surface (18) on the inside (20) of the shield plate (14) is introduced.

25. The method according to any one of claims 21 to 24, characterized in that a legend (16) in which the microstructured corner mirror structure (22) having portion of the shield plate (14) is impressed with an embossing tool.

26. The method according to claim 25, characterized in that the legend (16) in the shield plate (14) by means of mechanical embossing, in particular by means of hot stamping, is impressed.

27. The method according to claim 25 or 26, characterized in that the legend (16) is embossed in the shield plate (14) such that by the embossing process on the inside (20) a recess (30) is formed and on the outside ( 12) is formed a survey (34).

28. Method according to claim 27, characterized in that a color layer (36), preferably by means of a thermal transfer printing, is applied to the elevation (34).

29. The method according to claim 27 or 28, characterized in that by the impressing of the legend (16) formed recess (30) on the inside (20) is colored.

30. The method according to any one of claims 21 to 29, characterized in that on the microstructured triple mirror structure (22) a hydrophobizing coating is applied.

31. The method according to any one of claims 21 to 30, characterized in that on the microstructured triple mirror structure (22) a protective film (38) is arranged.

32. Use of a retroreflective shield (10) according to any one of claims 1 to 20 as a license plate for mounting on a motor vehicle.