Method for producing a mirror for a head-up display, optical imaging element, and head-up display

Abstract

An aspect of the invention relates to a method for producing an optical imaging element (5, 6) for a head-up display (1), comprising the following steps: - injection moulding a base body (8) from thermosetting plastic; - masking edge regions (12) of at least one front side (9) of the base body (8); - applying a reflective layer (11) to the front side (9) of the base body (8); and - after applying the reflective layer (11), applying at least one functional element (14) to the edge region (12), which functional element is separate from the base body (8) (said base body being already complete, at least in geometry, at this time).

Description

[0001] Method for manufacturing a mirror for a head-up display, optical imaging element, and head-up display

[0002] One aspect of the invention relates to a method for manufacturing an optical imaging element for a head-up display. Another aspect of the invention relates to an optical imaging element for a head-up display. A yet another aspect of the invention relates to a head-up display.

[0003] Head-up displays for vehicles typically have at least one optical imaging element, in particular a mirror, which reflects or deflects light from an image generation unit of the head-up display.

[0004] Such optical imaging elements must meet a wide variety of requirements. On the one hand, they should be designed to be as lightweight as possible. Furthermore, they must also be very rigid to ensure consistently high-precision reflection of the light beam. On the other hand, they must also withstand a wide range of environmental conditions, particularly varying temperatures, and remain dimensionally stable under these conditions.

[0005] Last but not least, such optical imaging elements in the head-up display are also arranged in a movable manner, so they must be designed to be functional in this respect as well.

[0006] German patent DE 10 2010 028 060 A1 discloses a method for manufacturing coatable optical imaging elements for a head-up display. This method specifies that the imaging element is made of a thermoset plastic. It further specifies that a coated central area of ​​this mirror is produced from the thermoset plastic during injection molding, and that retaining elements are simultaneously molded onto it. Thus, the manufacturing process of this mirror simultaneously forms this central part and the retaining elements directly molded onto and projecting from it.

[0007] Because of this approach, it is essential and necessary that these mounting elements are subsequently precisely shaped, requiring a separate stamping process. This method for manufacturing such an optical imaging element has several disadvantages. Firstly, it requires a relatively complex mold in which both the central body and the mounting elements can be cast simultaneously. This can also lead to imprecise contours in exposed areas, especially with thermosetting plastics. This is a key reason why a subsequent stamping process is necessary to achieve the required shape precision of the mounting elements.

[0008] However, this stamping process can also lead to stress on other parts of the mirror's central body and / or the coating due to the mechanical forces involved, for example, resulting in microcracking or similar issues. Because the stamping process occurs while the entire body is still inside the injection molding tool, access to all areas of the tool is also difficult. This can lead to suboptimal results and may even necessitate local re-grinding after the mirror has been removed from the mold.

[0009] The object of the present invention is to provide a method for manufacturing an optical imaging element in which the optical imaging element can be designed in a more efficient and variable manner. In particular, it is also an object to provide a corresponding optical imaging element and a head-up display incorporating such an optical imaging element.

[0010] These tasks are solved by the subject matter of the independent claims.

[0011] One aspect of the invention relates to a method for manufacturing an optical imaging element for a head-up display, in particular for a vehicle. The method preferably comprises the following steps:

[0012] Injection molding of a base body made of thermoset plastic;

[0013] Masking of edge areas of at least one front face of the base body;

[0014] Applying a reflective layer to the front of the base body; and subsequently, for the application of the reflective layer, attaching at least one functional element to the edge area that is separate from the base body, which at this point is already finished in terms of geometry.

[0015] In this process, the basic body, or central body, of the optical imaging element is therefore designed to be produced separately, namely by injection molding from thermoset plastic. This results in a simpler design for the injection mold itself. Specifically, this thermoset injection molding, which focuses solely on the basic body, avoids the disadvantages mentioned above.

[0016] Thermosets, correctly called thermosets, are primarily plastics that, once cured by heating or other means, can no longer be deformed. They mainly contain hard, amorphous, insoluble polymers.

[0017] This step alone is particularly advantageous for the subsequent process, namely the specific masking of individual zones of the base body, specifically the edge areas of a front face. If such very specific local zones of the base body are not to be subsequently coated with a reflective layer, this masking can then be carried out easily and in the appropriate chronological order, focusing solely on the base body. Existing additional elements or the like on the base body do not impede this masking, neither in terms of accessibility nor in terms of keeping such functional elements clear from the material of the reflective layer. This allows the base body to be divided with high precision into the zones that are to be coated with the reflective layer and those that are not.

[0018] Especially when, as provided for in the procedure, the edge areas of the front side are to be free of this reflective layer and therefore must be masked with high precision, the absence of additional functional elements to the base body at that time is very advantageous.

[0019] This approach is particularly advantageous when, following the creation of the base body with its locally applied reflective layer, one or more additional functional elements are subsequently added. In this case, the base body is already complete, and functional elements can then be precisely and individually provided, created, and attached, both locally and in terms of geometry and mounting position.

[0020] A particular advantage in this context is that at least one functional element, separate from the base body, is permanently attached to the edge area after masking and the application of a reflective layer. This allows functional elements to be attached very precisely, both in terms of shape and position, without requiring any subsequent rework. A further advantage is that the material composition of a functional element can differ from that of the thermoset base body. Moreover, different functional elements made of different materials can be individually molded, especially in comparison to each other and / or to the thermoset base body.This also allows for a high degree of variability for a wide variety of optical imaging elements without having to extensively change the processes individually, especially in the sequence.

[0021] In one embodiment, the functional element is injection-molded onto the base body in the edge region. Injection molding enables particularly precise positioning and shape accuracy, while simultaneously producing the functional element in its desired final form. Furthermore, injection molding creates a permanent and exceptionally strong bond. This effectively allows for the subsequent attachment of a separate functional element to the base body with exceptional mechanical stability. In particular, the functional element can then be precisely produced across virtually all edges of the base body. This means that the functional element extends both onto the front surface, specifically into the area of ​​the edge region, and across the edge formed between the front surface and the adjacent side wall, which determines the thickness of the base body.Thus, the functional element is at least partially attached directly to this side edge of the base body, in particular by injection molding. Such an edge-spanning, permanent attachment of the functional element allows for an even more stable fixation to the base body. Especially when the process is carried out according to the aspect mentioned above, this positioning of a functional element separate from the base body, which is only created in its final form during attachment, namely by injection molding, is very advantageous.

[0022] In one embodiment, the edge region on the front surface, which is not intended to be provided with the reflective layer, is produced as a continuous, closed surface. It is therefore preferably produced as a frame-like edge region. This also allows for the subsequent creation of one or more functional elements at numerous local points on the base body, or for the creation of a continuous, completely closed functional element on the base body. In particular, this also enables a particularly strong material bond, especially a form-fit and / or material-fit bond, between the functional element and the material of the base body, especially the thermoset. The reflective layer, which is applied to the other part of the front surface of the base body, is then arranged in a way that does not interfere with this bond or impair the material connection.

[0023] In one embodiment, the functional element is produced as a fully enclosed, frame-like element. Thus, the functional element is essentially a closed ring. The functional element is therefore produced without interruption in this direction of rotation. This allows it to serve, on the one hand, as a highly functional or multifunctional element. On the other hand, it can also serve as a fully enclosed impact protection for the base body.

[0024] In one embodiment, the functional element is produced projecting away from the front surface, particularly in a bead-like manner, compared to the reflective layer. This also means that the functional element is not flush with the front surface towards the base body, but rather raised in this respect, specifically projecting forward. Thus, the area of ​​the front surface that is provided with the reflective layer is essentially enclosed or framed by such a geometrically designed functional element.

[0025] In one embodiment, the functional element is produced with a frame part that is directly injection-molded onto the base body. Furthermore, at least one freely cantilevered pin, particularly a mushroom-shaped pin, is produced, which is part of the functional element and projects from the frame part, specifically projecting freely. Such a design of the functional element significantly combines the aforementioned advantages. Mechanical stability, protective function, and simple mechanical coupling of this optical imaging element with other components, particularly in a head-up display, are all advantageously achieved and integrated within this functional element.

[0026] In one embodiment, the functional element is produced as a single piece, in particular in an injection molding process. It is therefore a one-piece element.

[0027] Another aspect of the invention relates to an optical imaging element, in particular a mirror, for a head-up display, obtainable by a method according to the above-mentioned aspect or an advantageous embodiment thereof.

[0028] Another aspect of the invention relates to an optical imaging element, in particular a mirror, for a head-up display, especially in a vehicle. The optical imaging element has a base body made of thermoset plastic, in particular injection-molded plastic. This base body has a front surface. This is, by design, the surface onto which light rays from an image generation unit of the head-up display strike in order to be deflected or reflected. A reflective layer is applied to this front surface, except for a peripheral area. The peripheral area is therefore formed without this reflective layer. Furthermore, the optical imaging element has at least one functional element separate from the base body, which is arranged at the peripheral area, in particular injection-molded onto it.The functional element is a functional element that is attached locally to the front side, particularly after the base body has been manufactured in its final form, and especially after the reflective layer has been applied.

[0029] Advantageous embodiments of the above-mentioned method are to be regarded as advantageous embodiments of the optical imaging element. The components of the optical imaging element specifically produced by each method step, whether local, material, and / or geometric, are also to be regarded as advantageous embodiments in this respect. A further aspect of the invention relates to a head-up display, particularly for a vehicle, with an optical imaging element according to one of the aspects mentioned above.

[0030] Exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings.

[0031] They show:

[0032] Fig. 1 shows a schematic representation of an embodiment of a head-up display according to the invention for a vehicle with an embodiment of an optical imaging element according to the invention;

[0033] Fig. 2 shows an intermediate manufacturing state during the production of an optical imaging element according to an embodiment of the invention; and

[0034] Fig. 3 shows a representation of a finished manufacturing state of an optical imaging element according to an embodiment of the invention.

[0035] In the figures, identical or functionally equivalent elements are given the same reference symbols.

[0036] Figure 1 shows a schematic representation of a head-up display 1. The head-up display 1 includes, in particular, a housing 2. An image generation unit 3 is arranged in the housing 2. Furthermore, in this embodiment, an optical system 4 is arranged. This optical system comprises a first optical imaging element 5 and a second, separate optical imaging element 6. Specifically, both optical imaging elements 5 and 6 are mirrors. Light L, which is generated and emitted by the image generation unit 3, is deflected or reflected by the first mirror 5 in the beam path to the second mirror 6 and is then directed or reflected outwards by this second mirror 6 through an exit opening 7 of the housing 2.

[0037] To manufacture an optical imaging element 5 or 6, an injection mold is first provided. This mold is designed to produce only a base body of the optical imaging element 5 or 6, in particular by injection molding. Figure 2 shows an intermediate manufacturing state in which a base body 8 of the optical imaging element 5 or 6 has already been produced. In particular, this base body 8 is plate-like and curved at least on its front side. It is made of thermoset plastic, in particular by injection molding.

[0038] This base body 8 has a front side 9 and a back side 10 opposite it. The front side 8 is the one onto which the light L is intended to strike.

[0039] A portion of the front surface 9 is left uncovered, in particular by masking, on which a reflective layer 1 1 is not to be applied. Specifically, this portion is an edge region 12 of the front surface 8. Once this masking has been completed, the reflective layer 1 1 is applied to the unmasked area of ​​the front surface 8, here the central area of ​​the front surface 8, in a subsequent manufacturing step. Specifically, the edge region 12 is created as a closed, frame-like edge region 12.

[0040] As can also be seen in Fig. 2, the base body 8 has a side edge 13. This essentially determines the thickness of the base body 8. It terminates at the front 9 and the back 10. In particular, edges or transition edges are thus formed between the front 9 and the side edge 13, as well as between the back 10 and the side wall 13.

[0041] Following the local application of a reflective layer 11 to the front surface 9, a functional element separate from the base body 8 is arranged on the base body 8, in particular permanently attached, especially by injection molding. Such a functional element 14 is shown in Fig. 3. Fig. 3 shows a finished or manufactured end state of an optical imaging element 5, 6 in this respect. The functional element 14 is preferably designed as a fully enclosed element, in particular as a frame-like functional element 14. The functional element 14 is permanently attached to the base body 8 with respect to the front surface 9, or only to the edge region 12, in particular by injection molding.

[0042] In one embodiment, the functional element 14 is also arranged or attached to the side edge 13, in particular directly, and in particular permanently. It is also injection-molded there. This creates a functional element 14 that spans the entire edge and is thus subsequently attached to the base body 8.

[0043] It is intended that, viewed perpendicularly to the surface of the front side 9, the functional element 14 is raised, in particular forming a bulge towards the front side 9 in comparison to this front side 9.

[0044] As shown in Fig. 3, in one embodiment the functional element 14 can be produced with the frame part 14a and, by way of example, two pins 14b molded directly onto it. These pins project freely from the side of the frame part 14a. In particular, the functional element 14 is produced as a single piece by injection molding. The optical imaging element 5 or 6 can also be rotatably mounted in the housing 2 using these pins 14b.

[0045] Preferably, the material of the functional element 14 differs from that of the base body 8. This can be the case both with regard to the material components and with regard to the proportions of any identical materials that may be present. In the exemplary embodiment, the functional element 14 also has a further bearing part 14c, which is integrally molded onto the frame part 14a, in particular by injection molding.

Claims

Patent claims 1. Method for manufacturing an optical imaging element (5, 6) for a head-up display (1), comprising the following steps: Injection molding of a base body (8) from thermoset plastic; Masking of edge areas (12) of at least one front face (9) of the base body (8); Applying a reflective layer (11) to the front face (9) of the base body (8); and subsequently, for the application of the reflective layer (11), attaching at least one functional element (14) separate from the base body (8) to the edge area (12).

2. Method according to claim 1, wherein the functional element (14) is attached to the base body (8) is injected in the edge area (12).

3. Method according to claim 1 or 2, wherein the edge region (12) is produced as a frame-like edge region (12) in a circumferentially closed manner.

4. Method according to one of the preceding claims, wherein the functional element (14) is produced as a frame-like functional element (14) in a circumferentially closed form.

5. Method according to one of the preceding claims, wherein the functional element (14) is located on the front side in comparison to the reflective layer (11). (9) is produced away, especially in a bulge-like, protruding manner.

6. Method according to one of the preceding claims, wherein the functional element (14) is produced with a frame part (14a) which is directly injection-molded onto the base body (8) and with at least one freely a projecting cone (14b), in particular a mushroom-like cone, is produced which protrudes from the frame part (14a).

7. Method according to claim 6, wherein the functional element (14) is produced as one piece by injection molding.

8. Optical imaging element (5, 6), in particular mirror, for a head-up display (1), obtainable by a method according to one of the preceding claims.

9. Optical imaging element (5, 6), in particular mirror, for a head-up display (1), comprising a base body (8) injection-molded from thermoset plastic, which has a front side (9) on which, except for an edge area (12), a reflective, in particular mirrored, layer (11) is applied, and comprising at least one functional element (14) separate from the base body (8), which is injection-molded onto the edge area (12).

10. Head-up display (1) with an optical imaging element (5, 6) according to claim 8 or 9.

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