Display unit

Abstract

To provide a display unit that can prevent a trouble in display.SOLUTION: A display unit comprises: a display 10 that has a front face emitting display light LD and a back face being an opposite face of the front face; and an optical member 20 that is arranged on at least one of a front face side and a back face side. The optical member 20 has a thermal diffusion layer 21 that is arranged facing the display 10 and diffuses heat of the display 10, and an optical element layer 25 that is laminated on the thermal diffusion layer 21 and reflects external light incident on the display 10 in a predetermined direction. The thermal diffusion layer 21 has a higher thermal conductivity than the optical element layer 25.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a display device for a vehicle or the like. [Background technology]

[0002] Conventionally, a liquid crystal display device having a triangular prism on the display surface is known in order to suppress the deterioration of display characteristics caused by external light and suppress the decrease in contrast. When this display device is mounted on a head-up display, it suppresses the projection of unnecessary images that should not be displayed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-118271 A Summary of the Invention [Problem to be solved by the invention]

[0004] Nowadays, head-up displays have become larger in size and the display distance is set farther away, resulting in a larger optical magnification. This means that external light such as sunlight is concentrated in an extremely small area on the display device, which may cause a local increase in the temperature of the display device. This may cause a malfunction of the display device, resulting in a failure to display the desired image.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a display device that can suppress display defects. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the display device of the present invention comprises a display having a front side from which display light is emitted and a back side opposite the front side, and an optical member arranged on at least one of the front side and the back side, the optical member having a thermal diffusion layer arranged facing the display and diffusing heat from the display, and an optical element layer laminated on the thermal diffusion layer and reflecting external light incident on the display in a predetermined direction. Effect of the Invention

[0007] In the display device of the present disclosure, display defects can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a display device according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a cross-sectional view showing a display device as a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the display device of the present disclosure will be described with reference to the attached drawings. The display device of the present disclosure can be applied to a display device mounted on a vehicle such as an automobile or motorcycle, a ship, an agricultural machine, or a construction machine. The display device of the present disclosure can be applied to a display device mounted on a head-up display (HUD) that projects an image onto a projection member such as a windshield to allow a viewer to view a virtual image, or an aerial projection display that projects a real image into the air.

[0010] FIG. 1 is a cross-sectional view showing a display device 1 according to the present embodiment.

[0011] In the following description, "front", "rear", "right" and "left" follow the definitions of "Fr.", "Re.", "R" and "L" in FIGS.

[0012] When the display device 1 is mounted in a HUD, for example, it is disposed in an instrument panel of a vehicle. The HUD reflects display light LD showing an image displayed by the display device 1 using a relay optical system such as a plane mirror and a concave mirror, and irradiates the image on the windshield or the like of the vehicle. The driver (viewer) of the vehicle visually recognizes the reflected light as a virtual image in front of the windshield.

[0013] The display device 1 includes a display unit 10 and an optical member 20.

[0014] The display 10 is, for example, a liquid crystal display panel of a TFT (Thin Film Transistor) type. The display 10 has a front surface (display surface) from which display light LD is emitted forward, and a rear surface, which is the surface opposite to the front surface and to which light from a backlight unit 11 is incident backward. The display 10 has a pair of glass substrates that encapsulate a liquid crystal layer. Transparent electrodes are formed on the pair of glass substrates using ITO (Indium Tin Oxide) or the like. The display 10 also has a pair of polarizing plates (polarizing filters) arranged to sandwich the pair of glass substrates.

[0015] A backlight unit 11 is disposed behind (on the back side of) the display 10. The backlight unit 11 has a plurality of LEDs (Light Emitting Diodes). Light emitted from the LEDs illuminates the display 10, and the display unit 30 emits display light LD related to an image to be viewed by a viewer.

[0016] The optical member 20 is disposed to prevent external light LO, such as sunlight, incident from the outside from being reflected at the forefront of the display 10 in a direction different from the direction in which the display light LD is emitted, from reaching the viewer's eyes. The optical member 20 faces the display 10 and is disposed on the front side of the display 10. The optical member 20 has a thermal diffusion layer 21 and an optical element layer 25.

[0017] The thermal diffusion layer 21 is disposed on the front side of the display 10, facing the display 10. The thermal diffusion layer 21 has a function of uniformly diffusing the heat of external light LO mainly focused on the display 10, thereby suppressing local temperature increases. The thermal diffusion layer 21 is a transparent plate-like member having a pair of surfaces parallel to the front surface of the display 10.

[0018] The thermal diffusion layer 21 is made of a material having a higher thermal conductivity than the optical element layer 25, for example, glass (a material with a thermal conductivity of approximately 1 W / m K). Specifically, the thermal diffusion layer 21 is made of transparent ceramics such as sapphire, quartz crystal, or YAG (Yttrium Aluminum Garnet), and is particularly preferably made of sapphire from the viewpoint of thermal conductivity.

[0019] The optical element layer 25 is arranged by being laminated on the thermal diffusion layer 21. The optical element layer 25 reflects unnecessary external light LO incident on the front surface of the display device 10 in a direction different from the optical path of the display light LD. The optical element layer 25 has a surface that is non-parallel to the front surface of the display device 10 on the front surface opposite to the surface facing the thermal diffusion layer 21. That is, the optical element layer 25 is a transparent resin having a so-called sawtooth shape, which has a plurality of prisms arranged on the left and right sides of the base in a cross-sectional view in the thickness direction, which is the front-rear direction. From the viewpoint of miniaturization of the display device 1 and suppression of display deterioration due to the provision of a discontinuous exit surface on the exit surface of the display light LD, it is preferable that the thickness of the optical element layer 25 is thin. Specifically, it is preferable that the dimensions and pitch of the prism shape of the optical element layer 25 are set so that the thickness of the optical element layer 25 is thinner than the thickness of the thermal diffusion layer 21.

[0020] The optical element layer 25 is, for example, a UV curable resin molded by UV curing on the thermal diffusion layer 21. The optical element layer 25 may also be a prism sheet molded by a role-to-role method. In this case, the optical element layer 25 is attached to the thermal diffusion layer 21 with a transparent adhesive or pressure sensitive adhesive.

[0021] Such an optical member 20 is adhered to the front surface of the display 10 with a transparent adhesive 28 so that the thermal diffusion layer 21 faces the front surface of the display 10. Alternatively, the optical member 20 may simply be disposed on the display 10 so as to be in contact with the display 10, without using an adhesive such as the transparent adhesive 28. Also, a thin film for preventing reflection may be formed on the adhesive surface of the optical member 20.

[0022] Here, if the optical member 20 does not have the thermal diffusion layer 21 and is, for example, only the optical element layer 25 made of optical glass, the optical glass has a thermal conductivity substantially equal to that of the display 10, and its heat capacity is proportional to its volume, so the optical member 20 itself can have a heat dissipation effect to a certain extent. However, if a heat dissipation path by convection or radiation cannot be obtained due to its relationship with the surrounding members, the optical member 20 will have a heat insulating effect. If the optical member 20 is made of a transparent resin with a lower thermal conductivity, such a heat insulating effect may lead to an even more serious situation.

[0023] In contrast, the display device 1 of the present embodiment can effectively diffuse heat by providing a thermal diffusion layer 21 on a part of the optical member 20, even if a local temperature rise occurs in the display 10 due to external light LO. As a result, the display device 1 can suppress display defects caused by a local temperature rise.

[0024] Moreover, the optical member 20 is not entirely made of a material such as sapphire, which has excellent thermal diffusion properties but is expensive, but is made of a composite material by providing a thermal diffusion layer 21 made of such a material in part. This allows the display device 1 to have a thermal diffusion function while suppressing an increase in cost.

[0025] Furthermore, in the display device 1, the thickness of the optical element layer 25 is made thinner than the thickness of the thermal diffusion layer 21. As a result, even if the optical element layer 25 has a lower thermal conductivity than the thermal diffusion layer 21, it can have a certain degree of thermal diffusion due to its thinness, and the optical element layer 25 itself can obtain a heat dissipation effect by radiant heat transfer from the surface.

[0026] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0027] For example, in the display device 1, an example has been described in which the optical element layer 25 has a plurality of prisms and has a sawtooth shape in cross section, but the shape of the optical element layer 25 is not limited to this. Fig. 2 is a cross-sectional view showing a display device 101 as a modified example.

[0028] Display device 101 differs from display device 1 in that optical element layer 125 is composed of a single prism. In display device 101, configurations and parts corresponding to those of display device 1 are given the same reference numerals, and duplicated explanations will be omitted.

[0029] The optical element layer 125 is made of optical glass or transparent resin. The optical element layer 125 has a surface that is non-parallel to the front surface of the display device 10 on the front surface opposite to the surface facing the thermal diffusion layer 21. That is, the optical element layer 125 is a triangular prism having a triangular shape in a cross section in the thickness direction. The optical element layer 125 has a similar shape to each prism of the optical element layer 25. The optical element layer 125 has a thickness that is thicker than the thickness of the thermal diffusion layer 21. As a result, the optical element layer 125 also has a heat capacity, and by storing and dissipating the heat of the display device 10 in combination with the thermal diffusion layer 21, the temperature rise of the display device 10 can be suppressed. At this time, the thickness of the thermal diffusion layer 21 only needs to have a thickness that can obtain a required thermal diffusion effect, and it is preferable that the thickness is thinner than the optical element layer 125 from the viewpoint of cost.

[0030] In the display devices 1, 101, examples have been described in which the front surface of the optical members 20, 120 formed on the front surface of the optical element layers 25, 125 has a prism shape that is linearly inclined with respect to the front surface of the display 10, but the front surface may also have a curved shape such as a wave shape (a cross section viewed in the thickness direction that has a curved shape).

[0031] The optical members 20 and 120 may be disposed on the rear side of the display 10. In this case, the shape of the rear surface of the optical members 20 and 120 (the rear surface of the optical element layer 25 and 125) may be appropriately set in relation to the optical path of the backlight unit 11 incident on the rear surface of the display 10.

[0032] The display 10 may be a transmissive or reflective liquid crystal display such as a TFT, or may be a self-luminous display such as an organic EL (Electroluminescence) display. [Explanation of symbols]

[0033] 1, 101 display device 10 Display 11 Backlight unit 20, 120 Optical components 21 Thermal diffusion layer 25, 125 Optical element layer 28 Transparent adhesive 30 Display Unit LD display light LO External Light

Claims

1. A display device having a front surface from which display light is emitted and a back surface opposite to the front surface; an optical member disposed on at least one of the front side and the rear side, The optical member is a heat diffusion layer disposed facing the display and diffusing heat from the display; an optical element layer laminated on the thermal diffusion layer and configured to reflect external light incident on the display in a predetermined direction.

2. The display device according to claim 1 , wherein the thermal diffusion layer has a higher thermal conductivity than the optical element layer.

3. the thermal diffusion layer is a plate-like member having a pair of surfaces parallel to the front surface, The display device according to claim 1 , wherein the optical element layer has a surface opposite to the surface facing the thermal diffusion layer that is non-parallel to the front surface.

4. The display device according to claim 3 , wherein the optical element layer has a sawtooth shape in a cross section in a thickness direction.

5. The display device according to claim 4 , wherein the optical element layer has a thickness smaller than a thickness of the thermal diffusion layer.

6. The display device according to claim 3 , wherein the optical element layer has a triangular shape in a cross section in a thickness direction.

7. The display device according to claim 6 , wherein the optical element layer has a thickness greater than a thickness of the thermal diffusion layer.

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