Abstract:
A display apparatus for a vehicle and a method for producing the display apparatus are described. The display apparatus comprises a transparent plastic plate having a front side, a rear side, and an edge surface surrounding the plastic plate. The display apparatus has a switchable light source of visible light directed onto the edge surface of the plastic plate. The plastic plate has transparent display elements that are disposed as limited zones inside the plastic plate and have light-sensitive dopant particles. When the light source is switched on, the dopant particles scatter the light so that the display elements become visible from the front side.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. DE 10 2011 016 428.6, filed Apr. 8, 2011, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    A display apparatus for a vehicle and a method for producing the display apparatus are described. The display apparatus comprises at least one transparent plastic plate having a front side and a rear side as well as having an edge surface surrounding the plastic plate. The display apparatus has at least one switchable light source directed onto the edge surface of the plastic plate. 
       BACKGROUND 
       [0003]    Known from DE 10 2009 046 325 A1 is an instrument panel as a display apparatus which comprises a nanophosphor indicia which is not visible under normal lighting conditions and poor light conditions but emits visible light in response to UV light. To this end, the nanophosphor indicia is applied two-dimensionally as a coating to a substrate and is illuminated at an angle from the front or from behind by a switchable UV light source in order to make the nanophosphor indicia visible. This display apparatus has the disadvantage of a complex structure and uses a pollutive, ozone-generating UV light source, and the eyes of the observer must be protected from its radiation. 
         [0004]    It is at least one object to provide a display apparatus for a vehicle which is environmentally friendly and which can be used flexibly. A further object is to provide a method for producing such a display. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       SUMMARY 
       [0005]    A display apparatus for a vehicle and a method for producing the display apparatus are described. The display apparatus comprises a transparent plastic plate having a front side and a rear side as well as having an edge surface surrounding the plastic plate. The display apparatus has a switchable light source of visible light directed onto the edge surface of the plastic plate. The plastic plate has transparent display elements, which are disposed as limited zones inside the plastic plate and have light-sensitive dopant particles. When the light source is switched on, the dopant particles scatter the light so that the display elements become visible from the top. 
         [0006]    Such a display apparatus comprising a transparent plastic plate does not impede the view of the driver. Consequently, it can be disposed on the inner surface of a windshield and therefore can be disposed in the field of view of the driver. The driver can thus observe the road traffic unimpaired by the display apparatus and, if required, can have important operating data and driving parameters, such as speed, engine speed, cooling water temperature, or tank level, displayed without diverting his attention from the road traffic. 
         [0007]    The transparent display apparatus further can be inserted in a central instrument panel in front of a flat screen that provides additional information which is unfiltered and clearly identifiable as a result of the transparent display apparatus. Thus, navigation information and maps can be disposed either overlapping with, for example, a display apparatus in the form of a pointer instrument of the same transparent plastic disc or next to such an instrument area of the display apparatus. 
         [0008]    A large variety of instrumentation of a vehicle in, on, and behind the windshield as far as compact central instrument panels having integrated navigation displays and other helpful additional functions is thus obtained, which is arranged clearly behind the transparent plastic plate and can be made available to the driver of the vehicle. 
         [0009]    For the instrumentation, in a further embodiment the transparent display elements in the plastic plate are disposed in a ring shape to a central display instrument of the vehicle. At the same time, the different display elements can be disposed in different flat zones of the transparent plastic disc. For example, a ring of scaling elements can be provided in a first flat zone. In a second flat zone located deeper when viewed from the upper side, a ring of numerical values, for example, can be provided, these being excited to light up by an edge-side light source. In a lowest flat zone when viewed from the upper side, a homogeneous distribution of dopant particles can be provided so that this deeper region can serve as backlighting of the display apparatus when light is coupled in at the edge. 
         [0010]    At the same time, the individual zones can be excited to light up by differently colored light sources such as light-emitting diodes especially as the dopant particles provided do not transform the light wavelength, as in the case of UV radiation, but merely scatter the edge-side emission contained inside the plastic plate due to total reflection at the rear side and front side in a broad-band manner at the light-sensitive dopant particles and do not transform into different light wavelengths. 
         [0011]    In a further embodiment, it is provided that the display apparatus comprises at least one second plastic plate having homogeneously distributed light-sensitive dopant particles, which are illuminated by an optical beam and form an optical pointer, wherein the optical beam couples light into edge surfaces of a central opening or into outer edge surfaces of the second plastic plate. Such a pointer display can be achieved by a plurality of technical aids. Furthermore, it is also possible to equip the aforementioned screen, which is visible through the transparent plastic plate, with a pointer function so that such a pointer is visible through the transparent plastic plate. In this regard, an additional plastic plate with suitably homogeneously doped dopant particles can be dispensed with. 
         [0012]    Furthermore, it is also possible that a plurality of plastic plates having different transparent display elements such as scaling elements, numbers, or symbols can be joined to one another in different display planes to form a display instrument in order to separate the different light coupling-in planes from one another. A transparent adhesive is provided for joining the plurality of plastic plates, which additionally promotes the total reflection at the respective front and rear sides of the joined-together plastic plates through a suitably provided difference in the refractive index. 
         [0013]    In a further embodiment, the plastic plate is formed of poly (methyl methacrylate) (PMMA), such as Plexiglas available from Altuglas International of Bristol, Pa., which is partially and selectively doped with dopant particles in the regions of the display elements. The doping methods required for the selective introduction of dopant particles into such PMMA disks are presently being developed. In this case, the transparent display elements can comprise two- or three-dimensional scaling elements, numbers, or symbols made of a PMMA material provided with light-sensitive dopant particles. 
         [0014]    Such transparent display means can be manufactured or arranged separately two- or three-dimensionally as scaling elements, numbers, or symbols and then potted into a plate-shaped transparent plastic compound. In addition, it is also possible to provide three-dimensional recesses for the display elements in a transparent PMMA disk, which are then filled with plastic material enriched with dopant particles. Three-dimensional pre-fabricated display elements comprising a transparent plastic can be glued into these recesses of the PMMA plate. 
         [0015]    A possible method for producing a display apparatus for a vehicle comprises the following process steps. Firstly, dimensionally stable three-dimensional transparent display elements made of a plastic compound that can be excited to light up in color are produced. These display elements are then embedded in a transparent plastic plate made of a transparent plastic compound. Such embedding can be accomplished, as has already been mentioned above, by injection molding of a plate-shaped transparent plastic compound with inclusion of the three-dimensional display elements in the plastic compound. Embedding by incorporating the dimensionally stable three-dimensional transparent display elements in recesses of a plastic plate made of PMMA material is also possible. A switchable light source with a light bundle directed onto an edge surface of the transparent plastic plate is then applied. 
         [0016]    With the contemplated method, relatively flat transparent display apparatuses as far as the film thickness itself can be attached in the area of the windshield and thus provide a significant gain in driving safety since the vehicle driver is not diverted from the road traffic in order to check the operating parameters of the vehicle. 
         [0017]    To this end, the display elements can be disposed in a circular manner for a central display instrument. It is also possible to place a light-emitting diode strip around such an edge face of the plastic plate as the light source but this irradiation means can only be provided in a restricted manner, for example, in a lower edge if the display apparatus is to be provided in the area of the windshield. 
         [0018]    For a colored backlighting it is possible to dope a plastic plate homogeneously with dopant particles and illuminate from the outer edge sides. When the edge-side illumination source is switched on, a backlighting is therefore provided and when the light source is switched off, the plastic plate remains transparent. 
         [0019]    In a further modification of the method, for a pointer display it is provided to dope a plastic plate homogeneously. A movable optical beam from edge surfaces of a central opening or from outer edge surfaces of the plastic plate illuminates the homogeneously distributed dopants as a pointer or as a display region. 
         [0020]    It is further provided to glue a homogeneously doped plastic plate with an optical pointer and a selectively doped plastic plate with display elements onto one another with transparent plastic to form a display instrument. 
         [0021]    A further modification of the method for producing a display apparatus for a vehicle provides the following process steps. Firstly a first PMMA plate is selectively doped with light-sensitive dopant particles in zones which are intended to make the display elements light up under edge-side illumination. In addition, a second PMMA plate is homogeneously doped with dopant particles and a central opening for arrangement of a movable laser beam pointer is incorporated in the PMMA plate. A pivotable deflecting mirror or a rotatable prism is then inserted in the opening of the homogeneously doped second PMMA plate, which rotatably deflects a stationary laser beam directed centrally onto the opening as a light pointer toward the edge surfaces of the opening. Finally, the first PMMA plate is seamlessly joined to the second PMMA plate to form a display instrument. 
         [0022]    Using this method, a plurality of transparent display apparatuses for vehicles that are inexpensive to manufacture can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0024]      FIG. 1  shows a schematic view of a vehicle with a display apparatus in the area of a windshield in accordance with an exemplary embodiment; 
           [0025]      FIG. 2  shows the display apparatus of  FIG. 1  in the area of the windshield in detail; 
           [0026]      FIG. 3  shows a schematic cross-section through a display apparatus with optical pointer; 
           [0027]      FIG. 4  shows a schematic plan view of a display apparatus with optical pointer of another embodiment; 
           [0028]      FIG. 5  shows a schematic perspective view of a display apparatus with flat display zones in accordance with a further embodiment; 
           [0029]      FIG. 6  shows a schematic side view of the display apparatus according to  FIG. 5 ; 
           [0030]      FIG. 7  shows a schematic plan view of a display apparatus comprising a plurality of display instruments of an instrument panel according to a further embodiment; 
           [0031]      FIG. 8  shows a schematic plan view of the display apparatus according to  FIG. 7  when the light source is switched off; 
           [0032]      FIG. 9  shows schematically a front view of an instrument panel according to a further embodiment, and 
           [0033]      FIG. 10  shows schematically a perspective view of the instrument panel according to  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0035]      FIG. 1  shows a schematic view of a vehicle  2  with a display apparatus  1  in the area of a windshield  20 . In this case, the display apparatus  1  is made of a transparent plastic with arcuately disposed transparent display elements  8 , which become visible when the display apparatus  1  is illuminated at the edge by a light source  7 . In this case, the light source  7  is located below a lower edge  19  of the windshield  20  so that it is not visible. The arcuate arrangement of display elements  8  becomes visible when light source  7  is switched on below the edge  19  of the windshield  20 . The border of the display apparatus  1  made of transparent plastic shown in  FIG. 1  is barely visible in practice even when the display elements  8  arranged in an arcuate manner in a transparent plastic plate  3  light up in color in the plastic plate  3  and, for example, clearly display the speed and/or engine speed on the windshield  20 . 
         [0036]      FIG. 2  shows the display apparatus  1  in the area of the windshield  20  in detail, where the position of a steering wheel  36  is indicated by dashed lines. The transparent plastic plate  3  or plastic film has a front side  4  directed toward the vehicle interior. In the center or along a lower edge face  6  of the plastic plate  3  or plastic film, the light source  7  is disposed in a first plastic plane adjoining the front side  4  and the arcuately disposed display elements  8  only become visible when the light source  7  is switched on. Since the display apparatus  1  consists of a transparent plastic plate  3  or plastic film, the driver&#39;s view of the road traffic is not restricted, especially as the arcuately disposed display elements  8  are transparent and only light up in color as a result of switching on the light source  7  located at the edge. 
         [0037]    Another plastic plate  3  or plastic film is glued with its front side onto the rear side of the plastic plate  3  or plastic film with a transparent plastic adhesive. The rear plastic plate or film differs from the front one in that display elements  8  are not introduced selectively into the rear plastic plate  3  or film but the rear plastic plate or film is doped homogeneously with light-sensitive dopant particles, which however are not visible. 
         [0038]    These particles light up under edge-side irradiation. For this purpose, light beams are provided for two display instruments  34  and  35  shown here, which are projected into the rear plastic plate or film at coupling-in points  21  and  22  and can be pivoted in the directions of the arrows A, B so that with these pivotable optical pointers, it is possible to display values, for example, for speed and engine speed to the driver by means of this optical pointer without the view of the traffic situation outside the vehicle being impaired. It is also possible to show the display elements in color by the optical pointer through different color projections from the edge face  6 . 
         [0039]    Consequently, in this embodiment two display instruments  34  and  35  are provided to display the speed of the vehicle through the display instrument  34  and to display the engine speed through the display instrument  35  on the windshield  20 . To this end, in addition to the arcuately disposed display elements  8 , respectively one of a number of optical pointers  12  is provided, which can be pivoted in the directions of the arrows A and B. The optical pointers  12  are merely pivotable light beams, which are coupled in via coupling-in points  21  and  22  for each display instrument  34  and  35  from an edge face  6 . In this case, each light beam is scattered at light-sensitive dopant particles distributed homogeneously in one plane of the plastic plate  3  or plastic film and is visible at the front side  4  as optical pointer  12 . 
         [0040]      FIG. 3  shows a schematic cross-section through a display apparatus  1  with an optical pointer  12 , with which the values of the display elements  8  are indicated. The display elements  8  are disposed in three layers or transparent plastic plates  3 ,  30 , and  33 . In the uppermost plastic plate  3 , for example, transparent three-dimensional numbers  14  are embedded as display elements  8 . Scaling elements  13  or symbols  15  are arranged in a ring shape in the plastic plates  30  or  33  or plastic layers located thereunder. 
         [0041]    The optical pointer  12  is pivoted by a rotatable deflecting mirror  31  or a rotatable prism whereby, for example, a stationary laser beam  18  is deflected via a stationary deflecting mirror  29  toward the rear side  5  in the directions E and F of pivotable deflecting mirrors  31  and couples in the laser beam in the direction of the edge face  6  of a central opening  32  of a disk-shaped display apparatus  1 . 
         [0042]    In this case, the deflecting mirror  31  or the prism is pivoted according to the measured values by a corresponding angle from a zero position in the direction of the arrow F or E so that the optical pointer scatters the light in the region of the deflected laser beam  18  of a laser beam device  40  such that from the upper side  4  of the transparent first uppermost plastic plate  3 , a luminous pointer  12  is visible in the homogeneously doped lowest plastic plate  10 . To this end, the drive of the deflecting mirror or the prism is electrically connected via a controller to the respective measuring transducer such as a speed sensor, an engine speed sensor, or a temperature sensor. 
         [0043]      FIG. 4  shows a schematic plan view of a display apparatus with optical pointer  12 ′ of another embodiment. The pointer  12 ′ differs from the pointer  12  shown in  FIG. 3  in that a single laser beam is not coupled into the central coupling-in points  21  or  22  but the disk-shaped display apparatus  1  is surrounded in its outer edge face  6  by an optically opaque ring  23 , which covers the edge face  6  of the disk-shaped homogeneously doped plastic plate  10  apart from a tubular opening  39 . Through the tubular opening light can shine onto the homogeneously doped plastic plate  10  so that the optical pointer flag is visible toward the center as an optical pointer  12 ′. In this case, an optically opaque region  38  can be provided at the center, which delimits the length of the optical pointer  12 ′. 
         [0044]    In this view according to  FIG. 4 , it should be noted that a lower disk-shaped plastic plate  10  homogeneously doped with dopant particles is provided to show the pointer and a first disk-shaped plastic plate  3  is located thereover, the edge faces  6  whereof are not shielded by an optically opaque ring  23  so that the scaling elements  13  disposed in the first plastic plate  3  light up. 
         [0045]    The two plastic plates are seamlessly joined by means of a transparent plastic adhesive having a refractive index that promotes total reflection of light projected from the edge so that under edge-side exposure to light, only the light-sensitive dopant particles at which the light is scattered light up. 
         [0046]      FIG. 5  shows a schematic perspective view of a display apparatus  1  with different display zones  25 ,  26 ,  27 , and  28 . These display zones  25  to  28  can be achieved by disk-shaped plastic plates  3 ,  10 ,  30 , and  33  glued onto one another. Whereas numbers  14  are introduced in the uppermost first disk-shaped plastic plate  3  as display elements, scaling elements  13  are provided in the second disk-shaped plastic plate  30  below the first disk-shaped plastic plate  3 , and finally symbols  15  are disposed in another disk-shaped plastic plate  33 . The lowest disk-shaped plastic plate  10  is homogeneously doped with dopants and can thus be used either as a disk-shaped plastic plate  10  for an optical pointer or for a backlight. 
         [0047]    For a backlight the annular edge face  6  of the lower disk-shaped plastic plate  10  is uniformly irradiated. For an optical pointer display, as already discussed above, a central opening can be provided, in which the edge face  6  can be used, for example, for coupling in a pivotable laser beam, as shown in  FIG. 3 . 
         [0048]      FIG. 6  shows a schematic side view of the display apparatus according to  FIG. 5 . The four display zones  25 ,  26 ,  27 , and  28  layered onto one another are achieved by the corresponding disk-shaped plastic plates  3 ,  10 ,  30 , and  33 . The plastic plates  3 ,  10 ,  30 , and  33 , are joined onto one another with a transparent adhesive. This adhesive promotes the total reflection of the light projected via the edge faces  6  into the plastic plates  3 ,  10 ,  30 , and  33  as a result of a suitably large difference in the refractive index of the transparent plastic layer compared with the refractive index of the plastic plates  3 ,  10 ,  30 , and  33 . 
         [0049]    As already mentioned, three-dimensional number elements are disposed in the uppermost plastic plate  3 , scaling elements  13  on the one hand and symbols  15  on the other hand are suitably disposed in the central plastic plate  30  or  33 , and in this form the lower homogeneously doped disk-shaped plastic plate  10  is used to represent a backlight. This backlight only becomes visible when light is coupled into the edge face  6  of the lowest plastic plate so that the homogeneously distributed dopant particles light up. 
         [0050]      FIG. 7  shows a schematic plan view of a display apparatus  1  comprising a plurality of display instruments  34 ,  35 ,  37 , and  41  of an instrument panel  24  according to a further embodiment. In this case, the optical pointers provided individually for each display instrument are omitted and only annular scalings for the individual display instruments are shown when light is incident from the edge faces on the individual display zones of a display instrument. 
         [0051]    In this instrument panel  24 , a scaling for the vehicle speed becomes visible with the display instrument  34 , a scaling for the engine speed becomes visible with the display instrument  35 , a scaling for the cooling water temperature becomes visible with the display instrument  37 , and a scaling for the tank filling becomes visible with the display instrument  41  when light is coupled in at the edge. 
         [0052]      FIG. 8  shows a schematic plan view of the instrument panel  24  according to  FIG. 7  when the light sources are switched off so that only the edge faces  6  stand out and possibly cover caps  42  for deflecting mirrors of optical pointers can be seen at the center of the display instruments  34 ,  35 ,  37 , and  41 . 
         [0053]      FIG. 9  shows schematically a front view of another instrument panel  24 ′ according to a further embodiment. The instrument panel  24 ′ of this embodiment comprises a single plastic plate  3  in which four display instruments  34 ,  35 ,  37 , and  41  with annular or arcuately disposed display elements  8  are provided, which however have a pointer function without light being coupled in at the edge. On the contrary, this pointer function uses the transparency of the plastic plate  3 , in which a flat screen is disposed behind the plastic plate  3  on which the pointer functions are imaged as pivotable optical pointers  12 ″. 
         [0054]      FIG. 10  shows schematically a perspective view of the instrument panel  24 ′ according to  FIG. 9  with the plastic plate  3  and the flat screen  43  disposed on the rear side of the plastic plate  3  as well as a display of the optical pointer  12 . Furthermore, additional information can be displayed with the aid of the flat screen  43 . 
         [0055]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.