Vehicle display device

Abstract

A vehicle display device (1) comprises a liquid crystal display element (20) that emits display light (L) that is to be reflected by a windshield (101) of a vehicle (100), sapphire glass (21) that is adhered to a back surface (20b) of the liquid crystal display element (20), and a temperature detection body (24) that is provided to the sapphire glass (21) and detects the temperature of the liquid crystal display element (20). Heat generated by the liquid crystal display element (20) is transmitted to the temperature detection body (24) via the sapphire glass (21).

Description

Vehicle display device

[0001] The present invention relates to a display device for a vehicle.

[0002] Some conventional vehicle display devices have a thermistor on a TFT (Thin Film Transistor) panel to detect the temperature of the TFT (see Patent Document 1). Other conventional vehicle display devices have a thermistor on a flexible printed circuit (FPC) on which a TFT drive circuit is formed (see Patent Document 2).

[0003] JP 2022-130236 A JP 2006-235252 A

[0004] However, in the above-described conventional vehicle display device, for example, the thermal conductivity of the TFT and FPC is low, so there is room for improvement in terms of accurately detecting the temperature of the TFT in response to temperature increases.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle display device that can accurately detect the temperature of a liquid crystal display element.

[0006] In order to achieve the above object, the vehicle display device of the present invention is characterized by comprising a liquid crystal display element that emits display light to be reflected by a transparent reflective member provided in the vehicle, a transparent plate-shaped heat conduction member that is adhered to either the display surface or the back surface of the liquid crystal display element, and a temperature detection body that is provided on the heat conduction member and detects the temperature of the liquid crystal display element.

[0007] The vehicle display device according to the present invention has the advantage that the temperature of the liquid crystal display element can be detected with high accuracy.

[0008] Fig. 1 is a schematic diagram showing an example of the configuration of a vehicle display device according to an embodiment. Fig. 2 is a perspective view showing the appearance of a display of the vehicle display device according to an embodiment. Fig. 3 is a cross-sectional view of the display shown in Fig. 2 taken along line AA. Fig. 4 is a partially enlarged view of Fig. 3. Fig. 5 is a cross-sectional view of the display shown in Fig. 2 taken along line BB. Fig. 6 is a plan view of the display shown in Fig. 2. Fig. 7 is a partial cross-sectional view of a display according to a modified example of the embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. That is, the components in the following embodiments include those that can be easily imagined by a person skilled in the art or those that are substantially the same, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0010] [Embodiment] The vehicle display device 1 shown in FIG. 1 is a head-up display device mounted on a vehicle 100 such as an automobile. The vehicle display device 1 projects a display image onto, for example, a windshield 101 of the vehicle 100. The vehicle display device 1 projects the display image onto the windshield 101 to display a virtual image in front of the driver's (not shown) eye point EP. The windshield 101 is an example of a reflective member and is semi-transparent, reflecting part of incident light and transmitting the other part. The windshield 101 transmits the view in front of the vehicle 100 while reflecting the display image projected from the vehicle display device 1 as display light L toward the driver's eye point EP. The vehicle display device 1 of this embodiment includes a case 2, two reflective mirrors 3 and 4, a display 5, and a display control unit 6.

[0011] In the following description, for convenience, of the illustrated X, Y, and Z directions, the X direction refers to the "width direction X," the Y direction refers to the "depth direction Y," and the Z direction refers to the "height direction Z." The width direction X, depth direction Y, and height direction Z are perpendicular to one another. The width direction X corresponds to, for example, the front-to-rear direction of the vehicle 100. The depth direction Y corresponds to, for example, the width direction of the vehicle 100. The height direction Z corresponds to, for example, the up-and-down direction of the vehicle 100. Unless otherwise specified, the directions used in the following description will be described as directions when each part of the vehicle display device 1 is assembled.

[0012] The case 2 is formed, for example, from a synthetic resin material into a box shape. The case 2 accommodates and supports the reflecting mirrors 3 and 4, the display 5, and the display control unit 6. The case 2 has an opening 2a that communicates between the inside and outside of the vehicle display device 1. The opening 2a is provided in a position on the case 2 facing the windshield 101. The vehicle display device 1 emits display light L from the case 2 through the opening 2a toward the windshield 101. The display light L is light that is emitted from the display 5 and reflected by the reflecting mirrors 3 and 4.

[0013] The reflecting mirrors 3 and 4 are arranged on the optical path of the display light L from the display 5 to the windshield 101 and are an optical system that reflects the display light L emitted from the display 5 toward the windshield 101. The reflecting mirror 3 has a flat reflecting surface and is arranged in a position facing the display 5. The reflecting mirror 3 totally reflects the display light L emitted from the display 5 toward the reflecting mirror 4. The reflecting mirror 4 has a concavely curved reflecting surface and is arranged in a position facing the reflecting mirror 3. The reflecting mirror 4 totally reflects the display light L reflected by the reflecting mirror 3 toward the windshield 101 through the opening 2a. The reflecting mirror 4 functions as a magnifying mirror. That is, the reflecting mirror 4 magnifies and reflects the display image represented by the display light L after reflection by the reflecting mirror 4 so that the display image represented by the display light L after reflection by the reflecting mirror 4 is relatively larger than the display image represented by the display light L before reflection by the reflecting mirror 4.

[0014] The display 5 emits a display image to be projected onto the windshield 101 as display light L. As shown in FIG. 2 , the display 5 includes a housing 10, a backlight unit 11, and a liquid crystal display unit 14.

[0015] The housing 10 is composed of an upper cover 12 and a lower case 13, and has an internal storage space 10a. The housing 10 accommodates a backlight unit 11 including a light source LS, and a liquid crystal display unit 14 in the storage space 10a.

[0016] The upper cover 12 is attached to the lower case 13 from above in the height direction Z. The upper cover 12 has a rectangular opening 12a when viewed from the height direction Z. The opening 12a is a portion through which display light L emitted from the liquid crystal display unit 14 passes toward the reflective mirror 3 when the upper cover 12 is attached to the lower case 13.

[0017] The lower case 13 is made of a thermally conductive metal material and is a box-shaped member that opens upward in the height direction Z. The lower case 13 houses the liquid crystal display unit 14 on its upper side, which is one side in the height direction Z, and houses and supports the backlight unit 11 on its lower side, which is the other side in the height direction Z. As shown in Figures 3 to 5 , the lower case 13 has an outer peripheral wall 40 made of a thermally conductive metal material, and supports the liquid crystal display unit 14 by means of support portions 41 provided on the outer peripheral wall 40.

[0018] The backlight unit 11 illuminates the liquid crystal display unit 14 from the back side. The backlight unit 11 is driven by, for example, power obtained from a battery (not shown) in the vehicle 100. The light source LS emits light toward the liquid crystal display unit 14 and is, for example, an LED (Light Emitting Diode) as a light-emitting element. The light source LS is mounted on, for example, a light source board (not shown). The light source board is connected to a heat dissipation section 11a exposed to the outside of the housing 10.

[0019] The liquid crystal display unit 14 includes a liquid crystal display element 20, a sapphire glass 21, an adhesive portion 22, and a temperature detector 24.

[0020] The liquid crystal display element 20 is disposed on the optical path of the display light L from the light source LS to the reflecting mirror 3, and transmits or reflects the display light L incident from a back surface 20b facing the backlight unit 11, thereby displaying an image on a display surface 20a facing the reflecting mirror 3. The liquid crystal display element 20 is, for example, a TFT-LCD (Thin Film Transistor-Liquid Crystal Display). The liquid crystal display element 20 is a film-like member including a liquid crystal layer, glass electrodes, polarizing plates, and the like. One end of the liquid crystal display element 20 in the width direction X is physically and electrically connected to the display control unit 6 via wiring 15. The wiring 15 is formed, for example, of a flexible printed circuit (FPC) or the like.

[0021] 6, the liquid crystal display element 20 has an image display area 30 and an image non-display area 31. The image display area 30 is a portion that displays an image and is formed in a rectangular shape when viewed from a height direction Z that is perpendicular to the planar direction of the liquid crystal display element 20. The image non-display area 31 is provided on the opposite side of the image display area 30 along the planar direction, sandwiching a first display edge 30a, which is one of the four sides that make up the image display area 30, and is a portion that does not display an image.

[0022] The sapphire glass 21 is a transparent glass member formed in a rectangular, flat plate shape, and transmits display light L. The sapphire glass 21 of this embodiment is an example of a thermally conductive member, and is formed by artificially growing high-purity alumina (aluminum oxide) into large crystals, and has a thermal conductivity at least higher than that of air. As shown in FIGS. 3 to 5 , the sapphire glass 21 is adhered to the rear surface 20b of the liquid crystal display element 20 by an adhesive 22. The sapphire glass 21 is adhered to the liquid crystal display element 20 by optical bonding, such as OCA (Optical Clear Adhesive) or OCR (Optical Clear Resin).

[0023] By bringing the sapphire glass 21 into contact with the liquid crystal display element 20, heat from the liquid crystal display element 20 is more easily conducted to the sapphire glass 21. It is desirable that the contact area of ​​the sapphire glass 21 with the liquid crystal display element 20 be large. For example, the sapphire glass 21 is in contact with the entire back surface 20b of the liquid crystal display element 20. It is preferable that the sapphire glass 21 covers the entire image display area 30 of the liquid crystal display element 20. This prevents stress from being applied to localized areas of the liquid crystal display element 20, thereby suppressing whitening. The thickness of the sapphire glass 21 may be greater than the thickness of the liquid crystal display element 20. The sapphire glass 21 in contact with the liquid crystal display element 20 increases the thermal capacity of the liquid crystal display element 20, absorbing heat generated by the liquid crystal display element 20.

[0024] 6, the sapphire glass 21 is larger than the size of the liquid crystal display element 20 in the depth direction Y, and is disposed so that the image display area 30 is located inside the outer periphery. Specifically, the sapphire glass 21 is formed so that at least one end in the width direction X (the wiring 15 side) extends opposite in the height direction Z to an image non-display area 31 adjacent to the image display area 30, with the first display edge 30a in between. The sapphire glass 21 of this embodiment has an image display area-facing area 21a and a non-image non-display area-facing area 21b.

[0025] The image display area facing region 21a is located opposite the image display area 30 in the height direction Z when the sapphire glass 21 is bonded to the liquid crystal display element 20. On the other hand, the image non-display area facing region 21b is located opposite the image non-display area 31 in the height direction Z when the sapphire glass 21 is bonded to the liquid crystal display element 20. The sapphire glass 21 of this embodiment has a temperature detector 24 provided below (on the light source LS side) the image non-display area facing region 21b in the height direction Z.

[0026] The temperature detector 24 is provided on the sapphire glass 21 and detects the temperature of the liquid crystal display element 20. The temperature detector 24 includes a temperature detector 25 and a printed circuit board 26.

[0027] The temperature detection element 25 is provided in the image non-display area facing area 21b of the sapphire glass 21 via the printed circuit board 26 and a thermally conductive sheet member 28 (e.g., a thermal sheet). The temperature detection element 25 is, for example, a thermistor. As shown in Fig. 5, the temperature detection element 25 is arranged on the printed circuit board 26 at a position corresponding to a center P in the extension direction (width direction X) of the image non-display area facing area 21b. This center P is the position in the image non-display area facing area 21b that is closest to the heat source in the liquid crystal display unit 14.

[0028] The printed circuit board 26 is provided with a temperature detection element 25 and is made of a thermally conductive metal material. The printed circuit board 26 is, for example, an aluminum board. The printed circuit board 26 forms a temperature detection circuit 27 that is electrically connected to the temperature detection element 25. As shown in FIG. 6 , the printed circuit board 26 is disposed in a position facing the non-image area facing region 21b and extends along the first display edge 30a. The printed circuit board 26 has a rectangular shape when viewed from the height direction Z. The printed circuit board 26 has a connector 29 disposed at one end in the depth direction Y that protrudes toward the outside of the printed circuit board 26. The connector 29 electrically connects the temperature detection circuit 27 of the printed circuit board 26 to an external device or the like.

[0029] Here, we will explain the support structure for the liquid crystal display unit 14 in the lower case 13 of the housing 10. The support portion 41 is formed on the outer peripheral wall 40 of the lower case 13, protruding from the inner wall surface 40a toward the housing space 10a, and is a portion that supports the sapphire glass 21 that is arranged and adhered to the back surface 20b of the liquid crystal display element 20. As shown in Figure 4, this support portion 41 has a first support surface 42 and a second support surface 43.

[0030] The first support surface 42 is a portion that supports the sapphire crystal 21 when the liquid crystal display unit 14 is housed in the lower case 13. The first support surface 42 is in direct contact with the sapphire crystal 21 when the liquid crystal display unit 14 is housed in the lower case 13, and heat transferred to the sapphire crystal 21 is easily conducted to the support portion 41 via the first support surface 42.

[0031] The second support surface 43 is formed continuously with the first support surface 42, and is a portion that supports the sapphire glass 21 via the printed circuit board 26 and the sheet member 28. The second support surface 43 is in direct contact with the printed circuit board 26 when the liquid crystal display unit 14 is housed in the lower case 13, and heat transferred to the support part 41 via the first support surface 42 is easily conducted to the printed circuit board 26 via the second support surface 43.

[0032] The display control unit 6 is electrically connected to the liquid crystal display element 20 and the printed circuit board 26 and controls their operation. The display control unit 6 is configured, for example, with an IC chip or the like, and is driven by power obtained from a battery in the vehicle 100. For example, when the temperature detected by the temperature detector 24 is higher than a threshold value, the display control unit 6 executes a temperature reduction operation to reduce the temperature of the display unit 5. Here, the temperature reduction operation includes, for example, dimming or turning off the display unit 5. Specifically, when the temperature detected by the temperature detector 24 is higher than the threshold value, the display control unit 6 transmits a dimming signal or a turning off signal to the display unit 5 in accordance with the detection signal received from the temperature detector 24, thereby dimming or turning off the display unit 5.

[0033] Next, the heat transfer paths for the temperature detector 24 of the liquid crystal display unit 14 of the vehicle display device 1 will be described with reference to FIG. 4 . As described above, the heat source in the liquid crystal display unit 14 is, for example, the image display area 30 of the liquid crystal display element 20. Heat transferred from the image display area 30 to the sapphire glass 21 via the adhesive portion 22 is conducted from the image non-display area facing area 21b through the sheet member 28 to the printed circuit board 26, and then from the printed circuit board 26 to the temperature detector 25 (heat transfer path R1). Furthermore, heat transferred to the image non-display area facing area 21b is conducted to the support portion 41 via the first support surface 42 and then to the printed circuit board 26 via the second support surface 43 (heat transfer path R2). Thus, in the vehicle display device 1 of this embodiment, heat transferred from the liquid crystal display element 20 to the sapphire glass 21 is transferred to the temperature detector 25 via multiple heat transfer paths R1 and R2.

[0034] As described above, the vehicle display device 1 of this embodiment comprises a liquid crystal display element 20 that emits display light L to be reflected by the windshield 101 provided on the vehicle 100, a sapphire glass 21 that is adhered to the back surface 20b of the liquid crystal display element 20, and a temperature detector 24 that is provided on the sapphire glass 21 and detects the temperature of the liquid crystal display element 20.

[0035] The vehicle display device 1 according to this embodiment has the above-described configuration, which enables the temperature detector 24 to detect the temperature of the liquid crystal display element 20 via the sapphire glass 21. The thermal conductivity of this sapphire glass 21 is at least 40 times that of the liquid crystal display element 20, allowing the temperature detector 24 to accurately detect the temperature of the liquid crystal display element 20. Furthermore, by bonding the sapphire glass 21 to the liquid crystal display element 20, the vehicle display device 1 can suppress temperature increases in the liquid crystal display element 20 through the heat dissipation effect of the sapphire glass 21.

[0036] Furthermore, in the vehicle display device 1 according to this embodiment, the temperature detector 24 includes a temperature detection element 25 and a printed circuit board 26 on which the temperature detection element 25 is provided and which is made of a thermally conductive metal material. The temperature detection element 25 is provided on the sapphire glass 21 via the printed circuit board 26 and a thermally conductive sheet member 28. Thus, by interposing the thermally conductive sheet member 28 between the sapphire glass 21 and the printed circuit board 26, the vehicle display device 1 can improve thermal conductivity from the sapphire glass 21 to the printed circuit board 26. Furthermore, if the printed circuit board 26 is made of aluminum, for example, its thermal conductivity is four to five times greater than that of sapphire glass. This improves heat transfer from the printed circuit board 26 to the temperature detection element 25, and also provides a heat dissipation effect via the printed circuit board 26.

[0037] Furthermore, in the vehicle display device 1 according to this embodiment, the printed circuit board 26 is positioned opposite the non-image area facing region 21b of the sapphire crystal 21 and extends along the first display edge 30a. This allows the vehicle display device 1 to expand the heat transfer area from the non-image area facing region 21b to the printed circuit board 26. As a result, the temperature detector 24 can detect temperatures with improved accuracy compared to conventional printed circuit boards. Furthermore, in the vehicle display device 1, the temperature detector 25 is positioned on the printed circuit board 26 at a position corresponding to the center P of the non-image area facing region 21b in the extension direction. In conventional liquid crystal display units, when a temperature detector is provided for a liquid crystal display element, it is difficult to provide it near the image display area, which is a heat source, due to the layout of the wiring connected to the liquid crystal display element (see, for example, Figure 2 of Patent Document 2). In the vehicle display device 1 according to this embodiment, the sapphire crystal 21 is provided on the back surface 20b of the liquid crystal display element 20, and the temperature detector 24 is provided on the back surface of the sapphire crystal 21. As a result, the vehicle display device 1 allows the temperature detection element 25 to be positioned closer to the image display area 30, which is the heat source, compared to conventional vehicle display devices, thereby improving the accuracy of temperature detection of the liquid crystal display element 20 by the temperature detection element 25.

[0038] Furthermore, in the vehicle display device 1 according to this embodiment, the housing 10 has an outer peripheral wall 40 formed of a thermally conductive metal material, and the outer peripheral wall 40 has a support portion 41 that supports the sapphire glass 21 and the printed circuit board 26. This allows the vehicle display device 1 to transmit heat from the liquid crystal display element 20 to the temperature detection element 25 not only via the sapphire glass 21 but also via the support portion 41, thereby improving the accuracy of temperature detection.

[0039] In the above embodiment, the sapphire glass 21 is bonded to the rear surface 20b of the liquid crystal display element 20, but this is not limiting and the sapphire glass 21 may be bonded to the display surface 20a of the liquid crystal display element 20. In addition, the sapphire glass 21 is used as a transparent member having thermal conductivity, but this is not limiting.

[0040] Furthermore, in the above embodiment, the temperature detector 24 includes the temperature detector element 25 and the printed circuit board 26, but is not limited to this. Fig. 7 is a partial cross-sectional view of a display according to a modified embodiment. The temperature detector 25A shown in Fig. 7 is, for example, a thermocouple or a thermistor. The temperature detector 25A is connected to an external temperature detection circuit (not shown) via wiring W. The temperature detector 25A is provided between the non-image area facing region 21b of the sapphire glass 21 and the support portion 41 of the housing 10, and is placed in contact with the sapphire glass 21 while being housed in a recess of the support portion 41. In this manner, the temperature detector 24 may be a temperature detector element.

[0041] In the above embodiment, the printed circuit board 26 is preferably made of aluminum, but is not limited to this. It may be an FR4 PCB with many vias, or an FPC with good thermal conductivity.

[0042] In the above embodiment, sapphire glass 21 has been described as an example of a heat-conducting member, but the present invention is not limited to this. For example, blue plate glass or white plate glass may be used as the heat-conducting member instead of sapphire glass 21, although these have lower thermal conductivity than sapphire glass.

[0043] Furthermore, in the above embodiment, the sapphire glass 21 contacts the printed circuit board 26 via the sheet member 28, but this is not limited to this, and the structure may be such that the sapphire glass 21 contacts the printed circuit board 26 directly without the sheet member 28 being interposed therebetween.

[0044] In addition, in the above embodiment, the windshield 101 is used as the reflective member of the vehicle 100, but this is not limited thereto, and a combiner, for example, may also be used.

[0045] In the above embodiment, the vehicle display device 1 includes two reflecting mirrors 3 and 4, but is not limited to this and may include only one reflecting mirror. The vehicle display device 1 may also directly emit the display light L onto the windshield 101.

[0046] REFERENCE SIGNS LIST 1 Vehicle display device 5 Display 10 Housing 20 Liquid crystal display element 20a Display surface 20b Back surface 21 Sapphire glass 24 Temperature detector 100 Vehicle 101 Windshield L Display light

Claims

1. A display device for a vehicle comprising: a liquid crystal display element that emits display light to be reflected by a transparent reflective member provided in a vehicle; a transparent, plate-shaped heat conductive member that is adhered to either the display surface or the back surface of the liquid crystal display element; and a temperature detector that is provided on the heat conductive member and detects the temperature of the liquid crystal display element.

2. The vehicle display device according to claim 1, wherein the temperature detection body includes a temperature detection element and a printed circuit board on which the temperature detection element is mounted and which is formed of a thermally conductive metal material, the printed circuit board forms a temperature detection circuit which is conductively connected to the temperature detection element, and the temperature detection element is mounted on the thermal conduction member via the printed circuit board and a thermally conductive sheet member.

3. The vehicle display device according to claim 2, wherein the liquid crystal display element has an image display area formed in a rectangular shape when viewed from a direction perpendicular to the planar direction of the liquid crystal display element and displaying an image, and a non-image display area provided on the opposite side of the image display area along the planar direction across a first display edge, which is one of four sides constituting the image display area; the heat conduction member has an image non-display area facing area in a position facing the image non-display area when the heat conduction member is adhered to the back surface of the liquid crystal display element; the printed circuit board is arranged in a position facing the image non-display area facing area and is formed extending along the first display edge; and the temperature detection element is arranged on the printed circuit board at a position corresponding to a center in the extension direction of the image non-display area facing area.

4. A vehicle display device as claimed in claim 2 or 3, further comprising a housing having an accommodation space for accommodating the liquid crystal display element, the heat conductive member, and the temperature detector, the housing having an outer peripheral wall formed of a metal material having thermal conductivity, the outer peripheral wall being formed so as to protrude from an inner wall surface towards the accommodation space and having a support portion for supporting the heat conductive member arranged by adhering to the back surface of the liquid crystal display element, the support portion having a first support surface for supporting the heat conductive member, and a second support surface formed continuously with the first support surface and for supporting the heat conductive member via the printed circuit board and the sheet member.

5. The vehicle display device according to claim 1, wherein the temperature detector is composed of a temperature detection element that is conductively connected to a temperature detection circuit, and the temperature detection element is in direct contact with the heat conductive member.

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