Patent Publication Number: US-2022236560-A1

Title: Head-up display

Description:
TECHNICAL FIELD 
     The present disclosure relates to a head-up display. 
     BACKGROUND ART 
     Head-up displays have been used which project display light emitted from a liquid crystal display onto a windshield of a vehicle and display a virtual image in front of the windshield. In this type of head-up display, external light, such as sunlight, enters through an exit port where display light is emitted, and therefore, suppression of damage of a liquid crystal display heated by the external light is required. 
     Therefore, Patent Document 1 discloses a head-up display employing a cold mirror, which reflects visible light and allows infrared light to pass, as a flat mirror to prevent a liquid crystal display from being heated by sunlight which penetrates into a housing and which is reflected by the flat mirror. However, the head-up display of Patent Document 1 may not prevent a visible light component of sunlight from reflecting off the cold mirror and heading toward the liquid crystal display. 
     Patent Document 2 discloses a head-up display including a hot mirror (which reflects visible light and absorbs infrared light), a retardation plate, and a polarizing plate which are installed in front of a liquid crystal display. According to such a head-up display, it is possible to prevent a liquid crystal display from being heated by a visible light component or infrared light of sunlight that may not be cut by a cold mirror. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent No. 4841815 
     Patent Document 2: Japanese Unexamined Patent Application Publication No. 2013-174855 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the head-up display of Patent Document 2 requires addition of a hot mirror, a retardation plate, and a polarizing plate in front of the liquid crystal display, and therefore, there arises a problem in that the number of components is increased. 
     Therefore, it is an object of the present disclosure to provide a head-up display having an enhanced heat-shielding property against external light without increasing the number of components. 
     Solution to Problem 
     According to an aspect of the present disclosure, a head-up display includes a lighting device ( 6 ), a display ( 3 ) which emits display light when being illuminated by the lighting device ( 6 ), and a reflector ( 4 ) which reflects the display light. The reflector ( 4 ) includes a reflective layer ( 41 ) including a plurality of layers of resin films having different refractive indices, an adhesive layer ( 42 ), and a base material ( 43 ) to which the reflective layer ( 41 ) is bonded via the adhesive layer ( 42 ). 
     Effect of the Invention 
     According to the present disclosure, a heat-shielding property against external light may be enhanced without increasing the number of components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top perspective view of an internal configuration of a head-up display according to an embodiment. 
         FIG. 1B  is a diagram schematically illustrating a head-up display mounted on a vehicle in a lateral view of the vehicle. 
         FIG. 2  is a cross-sectional view of a reflector according to a first embodiment. 
         FIG. 3  is a diagram illustrating an action of the reflector. 
         FIG. 4  is a cross-sectional view of a reflector according to a second embodiment. 
         FIG. 5  is a cross-sectional view of a reflector according to a third embodiment. 
         FIG. 6  is a cross-sectional view of a reflector according to a fourth embodiment. 
         FIG. 7  is a cross-sectional view of a reflector according to a fifth embodiment. 
         FIG. 8  is a cross-sectional view of a reflector according to a sixth embodiment. 
         FIG. 9  is an interior side view of a vertical fold type head-up display. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiments will be described in detail below with reference to the accompanying drawings. Note that, in  FIG. 1A  and other figures, for the sake of clarity, only some of a plurality of parts with the same attribute may be marked with a reference sign. 
     Configuration of Head-Up Display 
       FIG. 1A  is a top perspective view of an internal configuration of a head-up display  1  according to an embodiment.  FIG. 1B  is a diagram schematically illustrating the head-up display  1  mounted on a vehicle in a lateral view of the vehicle. Note that, in  FIG. 1A , illustrations of some components of the head-up display  1  are omitted. In  FIG. 1A , three mutually orthogonal directions, that is, X, Y, and Z directions, are defined in the right-handed system. In the following, the Z direction is formally referred to as a vertical direction, with a positive side being an upper side and a negative side being a lower side. 
     The head-up display  1  is mounted in an instrument panel  9  of the vehicle. The head-up display  1  may be mounted in such an orientation that the Y direction in  FIG. 1A  substantially corresponds to a vehicle width direction. 
     The head-up display  1  includes a case  2 , a TFT (Thin Film Transistor) panel unit  3  (an example of a display), a reflector  4 , a concave mirror  5 , and a backlight unit  6  (an example of a lighting device). 
     The case  2  forms a housing of the head-up display  1 . The case  2  is a lower case which forms a lower portion of the housing of the head-up display  1 . The case  2  is coupled to an upper case not shown in  FIG. 1A . 
     The case  2  is formed of material with high heat conductivity, such as aluminum. The case  2  includes a heat dissipation portion  21  as shown in  FIG. 1A . The heat dissipation portion  21  is formed on an outer surface (a surface exposed to an outside) of the case  2 . The heat dissipation portion  21  has a function to dissipate heat generated in the backlight unit  6 . The heat dissipation portion  21  dissipates heat to the air flowing outside the case  2 . 
     The TFT panel unit  3  is a display which uses light emitted from the backlight unit  6  as backlight to emit display light for a display image. The TFT panel unit  3  in this embodiment includes a dot-matrix TFT (Thin Film Transistor) panel. The display image is an arbitrary image and may be an image representing, for example, navigation information or various vehicle information. 
     The TFT panel unit  3  is fixed to the case  2 . For example, the TFT panel unit  3  is fastened by screws  90  at two portions on both sides in the X direction as shown in  FIG. 1A . 
     The reflector  4  reflects the display light emitted from the TFT panel unit  3  toward the concave mirror  5 . 
     The concave mirror  5  reflects the display light reflected by the reflector  4  and causes the display light to be emitted from an exit port formed on an upper case (not shown) and directed to a windshield WS of a vehicle VC. The concave mirror  5  may be supported with respect to the case  2  in a rotation available manner so that a vertical position of an area where the display light hits in the windshield WS is adjustable. 
     As shown in  FIG. 1B , when the windshield WS is irradiated with the display light, a driver of the vehicle VC can see a display image (imaginary display) VI obtained by the irradiation in front of the windshield WS. Accordingly, the driver can see the display image VI superimposed on scenery in front of the driver, and can recognize vehicle information and the like in a manner that requires less eye movement, thereby improving convenience and safety. 
     The backlight unit  6  is disposed behind the TFT panel unit  3  (on a negative side in the Y direction). The backlight unit  6  generates display light in cooperation with the TFT panel unit  3 . 
     Configuration of Reflector 
     Next, a configuration of the reflector  4  will be described with reference to  FIGS. 2 and 3 . 
       FIG. 2  is a cross-sectional view of a reflector  4  according to a first embodiment.  FIG. 3  is a diagram illustrating an action of the reflector  4 . 
     As shown in  FIG. 2 , the reflector  4  of the first embodiment has a reflective layer  41 , an adhesive layer  42 , and a base material  43  to which the reflective layer  41  is bonded via the adhesive layer  42 . The reflective layer  41  faces the TFT panel unit  3  and the concave mirror  5 . The adhesive layer  42  and the base material  43  are formed behind the reflective layer  41 . 
     The reflective layer  41  is a reflective polarizing multilayer film. The reflective polarizing multilayer film includes hundreds of layers of polyester resin films having different refractive indices. 
     In the reflective layer  41 , refractive indices of the individual films are adjusted so as to reflect only a specific polarization component of visible light A. The reflective layer  41  has wavelength selectivity for reflected wavelengths and does not reflect infrared light B but allows the infrared light B to pass. The reflective layer  41  has a reflection axis and reflects a linearly polarized component of the visible light A which is parallel to a reflection axis direction C. The reflective layer  41  does not reflect the linearly polarized component of the visible light A which is perpendicular to the reflection axis direction C but allows the linearly polarized component of the visible light A which is perpendicular to the reflection axis direction C to pass. A detailed description will be made with reference to  FIG. 3 . When the reflection axis direction C of the reflective layer  41  is parallel to a direction orthogonal to an incident plane D (a plane formed by incident light E and reflection light F), the reflective layer  41  allows P-polarized light G (not shown) of the visible light A, which is a wave component parallel to the incident plane D, to pass. Furthermore, the reflective layer  41  reflects S-polarized light H of the visible light A, which is a wave component orthogonal to the incident plane D. 
     Accordingly, the reflector  4  having the reflective layer  41  allows the infrared light B to pass so as to prevent the infrared light B from reaching the TFT panel unit  3  in external light, such as sunlight, incident from the outside. Since the reflective layer  41  reflects only the S-polarized light H and allows the P-polarized light G to pass in the visible light A included in the external light, the visible light directed toward the TFT panel unit  3  may be reduced without arranging a glass plate with a polarizing film or the like in the vicinity of the TFT panel unit  3 . 
     The adhesive layer  42  is made of acrylic resin and is a colorless transparent adhesive layer. The reflective layer  41  and the adhesive layer  42  are provided as a single component, a total thickness of which is approximately 60 μm. 
     The base material  43  is a member that holds the reflective layer  41  in excellent flatness and excellent planeness and has both vibration resistance and transparency. Examples of the base material  43  include transparent inorganic glass. Considering economy and rigidity, inorganic glass having a thickness in a range from 1.7 mm to 2.1 mm is employed as the reflector  4  of the head-up display  1 . 
     Arrangement of Reflector 
     The reflector  4  is arranged in such an orientation that the reflection axis direction C of the reflective layer  41  is substantially parallel to a polarization direction of the display light emitted from the TFT panel unit  3 . By arranging the reflector  4  in this manner, the display light emitted from the TFT panel unit  3  can be reflected in a direction of an occupant&#39;s viewpoint with less attenuation of the display light while the visible light A directed to the TFT panel unit  3  is reduced. 
     For example, the head-up display  1  of the present example shown in  FIG. 1A  is a so-called horizontal fold type in which the reflector  4  reflects the display light emitted from the TFT panel unit  3  in a horizontal direction (a direction closer to the horizontal direction than the vertical direction). Accordingly, the reflector  4  is arranged in such an orientation that the incident plane D of the display light emitted from the TFT panel unit  3  is closer to a horizontal plane than to a vertical plane and that the reflection axis direction C of the reflective layer  41  is substantially parallel to the direction orthogonal to the incident plane D. Specifically, the reflector  4  is arranged in such an orientation that the reflection axis direction C of the reflective layer  41  is a vertical direction (a direction closer to the vertical direction than the horizontal direction). 
     An angle of incidence of the display light emitted from the TFT panel unit  3  to the reflector  4  is preferably in a range from 30° to 40°. In this way, the concave mirror  5  and the TFT panel unit  3  can be arranged in close proximity so that the head-up display  1  can be miniaturized. 
     Other Embodiments of Reflector 
     Next, reflectors  4 B,  4 C,  4 D of second to fourth embodiments will be described with reference to  FIGS. 4 to 6 . However, for components common to the first embodiment, the description of the first embodiment is incorporated by using the same reference numerals as in the first embodiment. 
       FIG. 4  is a cross-sectional view of the reflector  4 B according to the second embodiment.  FIG. 5  is a cross-sectional view of the reflector  4 C according to the third embodiment.  FIG. 6  is a cross-sectional view of the reflector  4 D according to the fourth embodiment.  FIG. 7  is a cross-sectional view of a reflector  4 E according to a fifth embodiment.  FIG. 8  is a cross-sectional view of a reflector  4 F according to a sixth embodiment. In the following, a term “front side” of the reflector  4 F corresponds to an incident side of light (e.g., display light emitted from the TFT panel unit  3 ) to the reflector  4 F. 
     According to the reflector  4  of the first embodiment described above, the P-polarized light G of the infrared light B and the visible light A included in the external light, such as sunlight, is prevented from being directed toward the TFT panel unit  3 , thereby enhancing a heat-shielding property against the external light. However, in the reflector  4  of the first embodiment, as shown in  FIG. 2 , a portion of the light (the infrared light B and the P-polarized light G) transmitted through the reflective layer  41  may be reflected at a back surface of the base material  43  and transmitted through the reflective layer  41  again to the TFT panel unit  3 . Temperature rise of the TFT panel unit  3  due to such re-transmitted light may reach approximately 10° C. at sunlight of 1000 W/m2. When a retaining member of the reflector  4  is irradiated with the light transmitted through the reflective layer  41 , molding of the retaining member may be reflected in the display image. 
     As shown in  FIG. 4 , in the reflector  4 B of the second embodiment, a base material  43 B has a light-shielding property. The base material  43 B having the light-shielding property is not colorless or transparent but colored, and is composed of, for example, a black resin plate. According to the reflector  4 B described above, the light transmitted through the reflective layer  41  is absorbed by the base material  43 B so that a heat-shielding effect by the reflector  4 B may be enhanced. Furthermore, the base material  43 B having the light-shielding property can also prevent molding of the retaining member of the reflector  4 B from being reflected in the display image. 
     As shown in  FIG. 5 , in the reflector  4 C of the third embodiment, an adhesive layer  42 C has a light-shielding property. The adhesive layer  42 C having the light-shielding property is not colorless or transparent but colored, and is composed of, for example, a black adhesive. According to the reflector  4 C described above, the same effect as that of the reflector  4 B of the second embodiment may be obtained. 
     As shown in  FIG. 6 , the reflector  4 D of the fourth embodiment includes a light-shielding layer  44  having a light-shielding property on a back surface of a base material  43  (a surface opposite to a reflective layer  41 ). The light-shielding layer  44  includes a printing layer which is not colorless or transparent but is printed with colored ink, and a colored adhesive film. According to the reflector  4 D described above, the same effect as that of the reflector  4 B of the second embodiment may be obtained. When the light-shielding layer  44  is composed of the printing layer, black oil-based ink or UV-curable ink having a refractive index close to that of the base material  43  is preferably used. When the light-shielding layer  44  is composed of an adhesive film, a black adhesive film is preferably used that is attached via an adhesive having a refractive index close to that of the base material  43 . This configuration reduces a reflectance at a boundary surface between the base material  43  and the light-shielding layer  44  so that the light transmitted through the reflective layer  41  may be reliably absorbed by the light-shielding layer  44 . 
     As shown in  FIG. 7 , the reflector  4 E of the fifth embodiment is different from the reflector  4  of the first embodiment in that the base material  43  is replaced by a base material  43 E. The base material  43 E has a different cross-sectional shape and is formed of the same material with respect to the base material  43  of the reflector  4  of the first embodiment. Specifically, in the base material  43 E, a first surface  431  (i.e., a surface on an incident side of the display light) in contact with an adhesive layer  42  and a second surface  432  on an opposite side of the first surface  431  are non-parallel. In other words, the base material  43 E has a wedge-shaped cross section. Furthermore, the base material  43 E does not have a constant thickness in the cross-sectional view (i.e., the view shown in  FIG. 7 ) cut by an incident plane D of the display light (a plane formed by incident light E and reflection light F). 
     In the example shown in  FIG. 7 , the first surface  431  and the second surface  432  are both planar and form an angle of α. The formed angle α is arbitrarily determined as long as the angle is significantly greater than 0 and significantly less than 90 degrees. The formed angle α may be set such that a traveling direction of reflection light R 1 , which will be described below, is a desired direction (a desired direction within a range that is not toward the TFT panel unit  3 ). 
     According to the reflector  4 E of the fifth embodiment, as in the first to fourth embodiments described above, a reflective layer  41  including a plurality of resin films having different refractive indices may allow infrared light B in external light, such as sunlight, incident from the outside to pass so as to prevent the infrared light B from reaching the TFT panel unit  3 . Since the reflective layer  41  reflects only S-polarized light H and allows P-polarized light G to pass in visible light A included in the external light, the visible light directed toward the TFT panel unit  3  may be reduced without arranging a glass plate with a polarizing film or the like in the vicinity of the TFT panel unit  3 . In this way, the reflector  4 E of the fifth embodiment can also enhance the heat-shielding property against the external light without increasing the number of components, as in the first to fourth embodiments described above. 
     According to the reflector  4 E of the fifth embodiment, even when a part of the light (infrared light B and P-polarized light G) transmitted through the reflective layer  41  is reflected on the second surface  432  of the base material  43 , the reflection light R 1  is not parallel to S-polarized light H, as schematically shown in  FIG. 7 . Since the reflection light R 1  is not parallel to the S-polarized light H, even when the reflection light R 1  is transmitted through the reflective layer  41  again, the possibility that the reflection light R 1  is directed to the TFT panel unit  3  as retransmitted light as described above is low. Accordingly, according to the reflector  4 E of the fifth embodiment, the above-described disadvantage (e.g., temperature rise of the TFT panel unit  3 ) caused by the reflection light R 1  reflected at the second surface  432  may be reduced. 
     Note that the fifth embodiment can be combined with the differences of the second to fourth embodiments described above relative to the first embodiment described above. For example, the base material  43 E may have a light-shielding property, as in the base material  43 B of the reflector  4 B of the second embodiment, the adhesive layer  42  may have a light-shielding property, as in the reflector  4 C of the third embodiment, or the second surface  432  (back surface) of the base material  43 E may include a light-shielding layer  44 , as in the reflector  4 D of the fourth embodiment. 
     Furthermore, although the second surface  432  is planar in the fifth embodiment, the second surface  432  may include curved portions. Moreover, the second surface  432  may be realized by a combination of a plurality of planes. In this case, the plurality of planes may all be non-parallel to the first surface  431 , or only one of the plurality of planes may be parallel to the first surface  431 . 
     As shown in  FIG. 8 , the reflector  4 F of the sixth embodiment is different from the reflector  4  of the first embodiment in that a reflective layer  41  is disposed on the back side. That is, in the reflector  4  of the first embodiment (the same applies to the second to fifth embodiments), the reflective layer  41  is disposed on the incident side of the display light relative to the base material  43 , whereas in the reflector  4 F of the sixth embodiment, the base material  43 F is disposed on the incident side of the display light relative to the reflective layer  41 . 
     Specifically, the reflector  4 F of the sixth embodiment includes, from the front side, a surface layer  40 F, a base material  43 F, an adhesive layer  42 F, and a reflective layer  41 . The layers on the front side relative to the reflective layer  41  have translucency. That is, the surface layer  40 F, the base material  43 F, and the adhesive layer  42 F have translucency. As a result, even when the reflective layer  41  is disposed on the back side, the same function as the reflective layer  41  of the first to fifth embodiments described above may be realized. 
     The surface layer  40 F is a coating layer formed by coating, such as an overcoat, for example. The surface layer  40 F may be formed by applying various translucent resins, such as polyimide, acrylic, and epoxy, in a form of a film. The adhesive layer  42 F is a translucent adhesive layer which is colorless and transparent and may be the same as the adhesive layer  42  of the reflector  4  of the first embodiment. The base material  43 F may be formed, for example, by transparent inorganic glass. In this case, the base material  43 F may have the same configuration as the base material  43  of the reflector  4  of the first embodiment. 
     According to the reflector  4 F of the sixth embodiment, as in the first to fifth embodiments described above, the reflective layer  41  including a plurality of resin films having different refractive indices may allow infrared light B in external light, such as sunlight, incident from the outside to pass so as to prevent the infrared light B from reaching the TFT panel unit  3 . Since the reflective layer  41  reflects only the S-polarized light H and allows the P-polarized light G to pass in the visible light A included in the external light, the visible light directed toward the TFT panel unit  3  may be reduced without arranging a glass plate with a polarizing film or the like in the vicinity of the TFT panel unit  3 . In this way, the reflector  4 F of the sixth embodiment can also enhance the heat-shielding property against external light without increasing the number of components, as in the first to fourth embodiments described above. 
     According to the reflector  4 F of the sixth embodiment, since the reflective layer  41  is not located on the most front side of the reflector  4 F, the possibility of damage to the reflective layer  41  (e.g., damage that may occur when an object hits the reflector  4 F during assembly) may be reduced. That is, according to the reflector  4 F of the sixth embodiment, the base material  43 F and the surface layer  40 F may function as a protective layer for protecting the reflective layer  41 . 
     Note that, although the surface layer  40 F is disposed on the front side of the base material  43 F in the sixth embodiment so as to protect the base material  43 F, the present disclosure is not limited to this. Specifically, the surface layer  40 F may be omitted. 
     Application to Vertical Fold Type Head-Up Display 
     Next, a case where the reflector  4  (including the reflectors  4 B,  4 C, and  4 D) of the above-described embodiments is applied to the reflector  4 G of a so-called vertical fold type head-up display  1 G will be described with reference to  FIGS. 3 and 9 . 
       FIG. 9  is an interior side view of the vertical fold type head-up display  1 G. 
     In the vertical fold type head-up display  1 G shown in  FIG. 9 , the reflector  4 G reflects display light emitted from a TFT panel unit  3 G in a vertical direction (closer to the vertical direction than the horizontal direction). Accordingly, the reflector  4 G is arranged in such an orientation that an incident plane D of the display light emitted from the TFT panel unit  3 G is closer to a vertical plane than to a horizontal plane and that the reflection axis direction C of the reflective layer  41  is substantially parallel to a direction orthogonal to the incident plane D. Specifically, the reflector  4 G is disposed in such an orientation that the reflection axis direction C of the reflective layer  41  is a horizontal direction (a direction closer to the horizontal direction than the vertical direction). According to such an arrangement of the reflector  4 G, the same effect as that of the above-described horizontal fold type head-up display  1  may be obtained. 
     Although the embodiments have been described in detail above, the present disclosure is not limited to the specific embodiments, and various modifications and changes may be made within the scope of the claims. Furthermore, all or a number of the components of the foregoing embodiments described above may be combined. 
     For example, although the concave mirror  5  is disposed in the foregoing embodiments, the concave mirror  5  may be omitted. 
     The following appendices are disclosed in connection with the embodiments described above. 
     Appendix 1 
     A head-up display ( 1 ) includes a lighting device ( 6 ), a display ( 3 ) which emits display light when being illuminated by the lighting device ( 6 ), and a reflector ( 4 ) which reflects the display light. The reflector ( 4 ) includes a reflective layer ( 41 ) including a plurality of layers of resin films having different refractive indices, an adhesive layer ( 42 ), and a base material ( 43 ) to which the reflective layer ( 41 ) is bonded via the adhesive layer ( 42 ). 
     Appendix 2 
     In the head-up display according to Appendix 1, at least one of the base material ( 43 ) and the adhesive layer ( 42 ) has a light-shielding property. 
     Appendix 3 
     In the head-up display according to Appendix 1, the base material ( 43 ) includes a light-shielding layer ( 44 ) having a light-shielding property on a surface opposite to the reflective layer ( 41 ). 
     Appendix 4 
     In the head-up display according to appendix 3, the light-shielding layer ( 44 ) is formed by UV-cured ink or black oil-based ink. 
     Appendix 5 
     In the head-up display according to any one of Appendices 1 to 4, the reflector ( 4 ) is disposed in such an orientation that a reflection axis direction (C) of the reflective layer ( 41 ) is substantially parallel to a polarization direction of the display light emitted from the display ( 3 ). 
     Appendix 6 
     In the head-up display according to Appendix 1, the base material ( 43 ) is disposed on an incident side of the display light relative to the reflective layer ( 41 ). 
     Appendix 7 
     In the head-up display according to any one of Appendices 1 to 6, the reflector ( 4 ) is disposed in such an orientation that the reflection axis direction (C) of the reflective layer ( 41 ) is substantially parallel to the polarization direction of the display light emitted from the display ( 3 ). 
     Appendix 8 
     In the head-up display according to Appendix 7, the reflector ( 4 ) is disposed in such an orientation that an incident plane (D) of the display light emitted from the display ( 3 ) is closer to a horizontal plane than to a vertical plane and that the reflection axis direction (C) of the reflective layer ( 41 ) is substantially parallel to a direction orthogonal to the incident plane (D). 
     In this case, the display may emit S-polarized display light, and the reflector may have an S-polarized reflectance higher than a P-polarized reflectance. 
     Appendix 9 
     In the head-up display according to Appendix 7, the reflector ( 4 ) is disposed in such an orientation that an incident plane (D) of the display light emitted from the display ( 3 ) is closer to a vertical plane than to a horizontal plane and that the reflection axis direction (C) of the reflective layer ( 41 ) is substantially parallel to a direction orthogonal to the incident plane (D). 
     In this case, the display may emit S-polarized display light, and the reflector may have an S-polarized reflectance higher than a P-polarized reflectance. 
     Appendix 10 
     In the head-up display according to any one of Appendices 1 to 5 and 7 to 9, the base material ( 43 ) has a first surface ( 431 ) in contact with the adhesive layer ( 42 ) and a second surface ( 432 ) on a back side of the first surface ( 431 ), the first surface ( 431 ) being non-parallel to the second surface ( 432 ). 
     DESCRIPTION OF REFERENCE NUMERALS 
       1 ,  1 G Head-up display 
       2  Case 
       3 ,  3 G TFT panel unit 
       4 ,  4 B,  4 C,  4 D,  4 E,  4 F,  4 G Reflector 
       5  Concave mirror 
       6  Backlight Unit 
       9  Instrument panel 
       21  Heat dissipation portion 
       41  Reflective layer 
       42 ,  42 C,  42 F Adhesive layer 
       43 ,  43 B,  43 E,  43 F Base material 
       44  Light-shielding layer 
       90  Screw 
     A Visible light 
     B Infrared light 
     C Reflection axis direction 
     D Incident plane 
     E Incident light 
     F Reflection light 
     G P-Polarized light 
     H S-Polarized light