DE102023201524A1 - Display device with heat sink - Google Patents

Abstract

The present invention relates to a display device (1) with a heat dissipator (5). The invention also relates to a means of transport with such a display device (1). The display device (1) has a housing (2), a display panel (3), a background lighting (4) for the display panel (3) and a heat dissipator (5). The background lighting (4) has a flat light guide (40) with two lateral coupling regions (400) arranged on opposite sides and two light source arrangements (41) arranged adjacent to the coupling regions (400). The heat dissipator (5) is designed to dissipate heat from the two light source arrangements (41) in a partial region (20) of the housing (2) out of the housing (2).

Description

The present invention relates to a display device with a heat dissipator. The invention also relates to a means of transport with such a display device.

The number and area of display devices in means of transport is constantly increasing. Display devices can be found on the market, for example, as instrument clusters for the driver, as central displays or as passenger displays. Non-self-luminous transmissive display devices require a background lighting to display images. The task of the background lighting is to illuminate the display panel used as evenly as possible over the entire active area in order to produce a display that is as homogeneous as possible right up to the edges. A maximum bright display is achieved by aligning a liquid crystal layer of the display panel in combination with the alignment of polarizing filters to allow maximum transmission.

A particular problem with TFT displays (TFT: Thin-Film Transistor) is the local heating caused by the LEDs of the backlight. This is particularly the case with so-called edge backlights, i.e. backlights in which the LEDs are arranged on the edge of the display panel adjacent to a flat light guide. With this type of design, the area of the polarizing filters near the LEDs is heated up. This can lead to the polarizing filters being destroyed, as the heating can impair the optical properties of the polarizing filters.

In the display devices currently used in automotive interiors, heat dissipation is achieved passively by design or actively through forced convection inside the device, often using fans. Components subject to high thermal loads are also connected to the housing or heat sink using thermally conductive pastes or pads.

High-performance lighting units can have very high power losses, which must be dissipated via the housing of the lighting unit. The housing parts must therefore have good thermal conductivity, which means that some materials are better suited for the housing, while others are not at all suitable. In addition, other electronic components that generate additional heat can be attached to the back of the housing. These can be glued directly or attached to offset screw domes and limit the effective convection area, making heat dissipation by means of convection even more difficult. In some cases, forced convection is not feasible, e.g. due to the ever smaller installation spaces, and thus conventional thermal management for a display device in the automotive interior is not possible.

To transport heat from a hot area to a cool heat sink, heat pipes can be used. The heat pipes and heat sinks are additional components within the case. The heat sink still requires air convection to be cooled.

Heat pipes use an evaporation and condensation cycle to transfer heat. If heat is supplied to one end of the heat pipe, the evaporator, a working medium evaporates. This flows along an adiabatic zone to a condenser. This flow is driven by the temperature or pressure gradient. The steam condenses at the condenser and releases its latent heat to an external heat sink. To maintain the cycle, the condensate must be fed back to the evaporator. An integrated capillary structure is usually used for this, often referred to as a wick structure. Groove structures, mesh structures or sintered structures can be used as capillary structures, for example.

In this context, US8,075,150 B2 a backlight unit for a display panel. The backlight unit includes a light source substrate, a base member, and a heat pipe. The light source substrate has a light source and faces the back of the display panel. The base member is made of metal sheet on which the light source substrate is mounted and is fixed to the back of a chassis of the backlight unit. The heat pipe is fixed to the base member and absorbs heat generated in the light source through the base member.

It is an object of the invention to provide improved solutions for thermal management for a display device.

This object is achieved by a display device having the features of claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

• - ein Gehäuse;
• - ein Anzeigepaneel;
• - eine Hintergrundbeleuchtung für das Anzeigepaneel, wobei die Hintergrundbeleuchtung einen flächigen Lichtleiter mit zwei an gegenüberliegenden Seiten angeordneten seitlichen Einkoppelbereichen und zwei angrenzend an die Einkoppelbereiche angeordnete Lichtquellenanordnungen aufweist; und
• - einen Wärmeableiter für die Lichtquellenanordnungen, wobei der Wärmeableiter eingerichtet ist, Wärme der beiden Lichtquellenanordnungen in einem Teilbereich des Gehäuses aus dem Gehäuse abzuleiten.

According to a first aspect of the invention, a display device comprises:

• - a housing;
• - a display panel;
• - a backlight for the display panel, the backlight having a flat light guide with two lateral coupling regions arranged on opposite sides and two light source arrangements arranged adjacent to the coupling regions; and
• - a heat dissipator for the light source arrangements, wherein the heat dissipator is designed to dissipate heat from the two light source arrangements in a partial region of the housing out of the housing.

The solution according to the invention uses a cooling concept that accesses the heat sources directly and thus ensures good heat management, especially for critical areas in the housing. In this way, heat transfer to other parts of the housing or optical films of the backlight is reduced. In addition, the electronic components, the installed plastic elements and the mechanical connections are also protected, which has a positive effect on the life expectancy of the display device. The heat dissipation from the housing also reduces the heating of a cover glass of the display device. This avoids possible injuries to a user if the display device is designed as a touch display. Especially with devices that have very limited installation space or rely on lightweight construction, heat dissipation is increasingly a limitation of performance. The solution according to the invention makes it possible to prevent overheating and potential self-destruction without requiring a reduction in performance. Because the heat is only dissipated from the housing in a partial area of the housing, no major changes to the geometry or an increase in the thickness of the housing are required for cooling. It is also possible to design the display device to be largely free-standing and to only provide a fastening in the heat dissipation area. The two light source arrangements arranged adjacent to the coupling areas can be switched on simultaneously during operation. Alternatively, it is also possible that, depending on the operating situation, only one of the light source arrangements is active.

According to one aspect of the invention, the heat sink has two or more heat pipes. Heat pipes as passive, closed systems are very well suited for use in display devices for motor vehicles due to their robustness, freedom from maintenance and design options. The heat pipes can mainly be used in two applications, firstly as heat distributors and secondly as linear heat exchangers. In the present solution, the heat pipes essentially serve as heat exchangers. Due to their low thermal resistance, which is typically less than 1 K/W, heat pipes can be used particularly well for cooling the light source arrangements. Their maximum cooling capacity depends on numerous factors, such as the effective length, any bend, the integrated capillary structure used, the position relative to the direction of gravity, the ambient temperature, etc. The heat pipes can be suitably dimensioned using appropriate simulations. The heat pipes can be coated with an insulating material in the area of the adiabatic zone, i.e. a material with low thermal conductivity. This improves heat transfer and prevents any heat transfer from the heat pipes into the housing.

According to one aspect of the invention, a group of heat pipes is assigned to each of the light source arrangements. Due to the position of the heat sources, two groups of heat pipes can be formed in the present application in order to dissipate the heat generated from the housing. A first group of heat pipes serves to cool the first light source arrangement, a second group of heat pipes to cool the second light source arrangement. The heat pipes within a group preferably run parallel. The heat pipes of the two groups can be nested like a comb. In this way, the heat pipes only add a small amount of bulk. Alternatively, it is also possible to stack the heat pipes of the two groups, which means that a larger number of heat pipes can be installed. Both approaches make it possible to ensure surface heat dissipation without the possibility of surface convection.

According to one aspect of the invention, the heat pipes of at least one of the groups of heat pipes are curved. Due to the curvature, the heat pipes can initially run parallel to the flat light guide to save space and then be guided out of the housing away from the flat light guide. In particular, the heat pipes can be curved so that the heat pipes of the various groups lie in one plane outside the housing. Those areas of the heat pipes that can come into contact with the housing can be provided with a protective coating. This can both offer protection against damage and prevent any heat transfer from the heat pipes into the housing.

According to one aspect of the invention, the heat pipes have a substantially rectangular cross-section. Preferably, the cross-section is The dimensions are chosen so that the heat pipes are flat, ie the width is significantly greater than the height. For example, the width can be 12.1 mm while the height is only 1.0 mm. This allows the heat pipes to be bent easily along the wide side, while bending along the short side is practically impossible. Heat pipes with an essentially rectangular cross-section can be produced, for example, by flattening heat pipes that were originally cylindrical.

According to one aspect of the invention, the housing has openings for the heat pipes. The openings allow the heat pipes to be led out of the housing without contact with the housing. The openings also facilitate both the assembly of the display device and the disassembly, e.g. for repair purposes.

According to one aspect of the invention, the heat dissipator has liquid channels arranged in the housing. As an alternative or in addition to the heat pipes, liquid cooling can be implemented. A liquid circulates through the channels arranged in the housing, transporting the heat generated to a part of the housing in which the heat can be easily dissipated.

According to one aspect of the invention, the heat dissipator is connected to a heat sink. By connecting to a suitable heat sink arranged outside the housing, a high heat dissipation performance is ensured, since such a heat sink enables good heat transfer to the environment.

According to one aspect of the invention, the heat sink has cooling fins or at least one fan. The cooling fins increase the surface area of the heat sink, which further improves heat transfer to the environment and thus cooling. Alternatively or additionally, fans can be used if natural convection is not sufficient to dissipate the heat. Such fans can be mounted on the heat sink or adjacent to the heat sink. The fans or cooling fins can be arranged in a convection channel for targeted heat transport.

Preferably, a display device according to the invention is used in a means of transport. The means of transport can be, for example, a motor vehicle, but alternatively also an aircraft, a rail vehicle or a watercraft.

Further features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the figures.

Figure overview

• 1 shows schematically the structure of a display device with an edge backlight;
• 2 shows schematically the principle of a display device according to the invention;
• 3 shows a first embodiment of a display device according to the invention;
• 4 shows an enlarged detail of the display device from 3 ;
• 5 shows a rear view of the housing of the display device 3 ;
• 6 shows a first group of heat pipes;
• 7 shows a second group of heat pipes;
• 8 shows a heat sink for connecting the heat pipes;
• 9 shows a second embodiment of a display device according to the invention;
• 10 shows a first section through the display device from 9 ;
• 11 shows a second section through the display device from 9 ;
• 12 shows a detailed view of fluid channels of the display device from 9 ; and
• 13 shows schematically a means of transport that uses a display device according to the invention.

Character description

In order to better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. The same reference numerals are used in the figures for the same or equivalent elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the embodiments shown and that the described features can also be combined or modified without departing from the scope of the invention as defined in the appended claims.

1 the structure of a display device 1 with an edge backlight. A section through the display device 1 is shown. The display device device 1 has a housing 2 in which a display panel 3 and a background lighting 4 for backlighting the display panel 3 are located. The background lighting 4 has a flat light guide 40 with two lateral coupling areas 400 arranged on opposite sides. Light source arrangements 41 are arranged adjacent to the coupling areas 400. The light source arrangements 41 each have a number of light-emitting diodes 42 which are arranged on a circuit board 43 and whose light is coupled into the flat light guide 40. The underside of the flat light guide 40 is provided with a reflector 401 in order to reduce light losses through the underside. A film stack 402 is arranged on the top side of the flat light guide 40, which can comprise, for example, a polarizing filter and other optically effective films. The housing 2 is closed off by a cover glass 7 which is connected to the housing 2 by means of adhesive 8. The light source arrangements 41 cause a considerable heat input, which must be counteracted by cooling the housing 2.

2 shows schematically the principle of a display device 1 according to the invention. The display device 1 largely corresponds to the display device 1 from 1 , however, has a heat dissipator 5 for the light source arrangements 41. The heat dissipator 5 is designed to dissipate heat from the two light source arrangements 41 from the housing 2. The dissipation of the heat by the heat dissipator 5 only takes place over a partial area 20 of the housing 2.

3 shows a first embodiment of a display device 1 according to the invention. Shown is an oblique view of the back of the display device 1. An enlarged detail is shown in 4 shown. At the upper edge and at the lower edge of the display device 1 there is a light source arrangement 41, the heat of which must be dissipated. For this purpose, the display device 1 has a heat dissipator 5, which in this embodiment comprises two groups 500, 501 of heat pipes 50. The first group 500 of heat pipes 50 serves to dissipate heat from the light source arrangement 41 at the lower edge. The second group 501 of heat pipes 50 serves to dissipate heat from the light source arrangement 41 at the upper edge, which in 3 is covered by the housing 2 and is therefore not visible. The heat pipes 50 have a substantially rectangular cross-section and run parallel within the respective group 500, 501. The cross-section is selected so that the heat pipes 50 are flat, i.e. that the width is significantly greater than the height. The heat pipes 50 of the first group 500 are led away from the flat light guide 40 essentially perpendicularly. The heat pipes 50 of the second group 501 are curved and initially run downwards parallel to the flat light guide 40 to save space. The curvature then leads the heat pipes 50 away from the flat light guide 40 out of the housing 2. The housing 2 has corresponding openings 21 for leading the heat pipes 50 through the housing 2. A rear view of the housing 2 of the display device 1, in which these openings 21 can be clearly seen, is shown in 5 shown. The openings 21 are located in a partial area 20 of the housing 2, i.e. the heat dissipation from the housing essentially takes place in this partial area 20. Outside the housing 2, the heat pipes 50 of the two groups 500, 501 lie in one plane and are nested like a comb. Alternatively, it is also possible to stack the heat pipes 50 of the two groups 500, 501, whereby a larger number of heat pipes 50 can be installed. In the embodiment shown, the partial area 20 for heat dissipation is in a lower area of the housing 2. However, it can just as well be in an upper area of the housing 2. In this case, the heat pipes 50 of the first group 50 are curved. Alternatively, it can also be arranged in the middle. In this case, all heat pipes 50 can be curved.

6 shows the first group 500 of heat pipes 50, which serves to dissipate heat from the light source arrangement at the lower edge of the display device. In this example, the group 500 consists of eight heat pipes 50, each of which has an evaporator 51, an adiabatic zone 53 and a condenser 52. In this example, the heat pipes 50 each have a length of 100 mm ± 0.5 mm, a height of 1.0 mm ± 0.05 mm and a width of 12.1 mm ± 0.1 mm. The rectangular cross-section can be achieved by flattening heat pipes 50 with an originally cylindrical shape and a diameter of approximately 8 mm. The wall thickness can be in the range of 0.2 mm to 0.3 mm, for example. The heat pipes 50 can be made of copper and have a nickel-plated surface. Water is a suitable working medium, and a mesh structure is preferably used as the capillary structure. A mesh structure is characterized by good performance and also works well against gravity. As a cheaper alternative, the capillary structure can be implemented in the form of grooves in the wall. However, this type of capillary structure is less efficient and only works to a limited extent against gravity. It is therefore more suitable for horizontally installed heat pipes. As a particularly efficient alternative, the capillary structure can be implemented using a sintered structure. This type of capillary structure is more complex to manufacture, but works particularly well against gravity.

7 shows the second group 501 of heat pipes 50, which serves to dissipate heat from the light source arrangement at the upper edge of the display device. In this example, the group 501 consists of seven heat pipes 50, each of which has an evaporator 51, an adiabatic zone 53 and a condenser 52. In this example, the heat pipes 50 each have a length of 200 mm ± 0.5 mm, a height of 1.0 mm ± 0.05 mm and a width of 12.1 mm ± 0.1 mm. The heat pipes 50 are curved with a bending radius of 40 mm. Apart from the length and curvature, the heat pipes 50 of the second group 501 are identical to those of the first group. In the example shown, those areas of the adiabatic zone 53 of the heat pipes 50 that can come into contact with the housing are covered with an insulating material 54, ie a material with low thermal conductivity. This improves heat transfer and prevents any heat transfer from the heat pipes 50 into the housing. A material suitable for this purpose is, for example, Poron.

8 shows a heat sink 6 for connecting the heat pipes of the display device made of 3 . In this example, the heat sink 6 is a metal component. Cooling fins 60 are arranged on the heat sink 6. The cooling fins 60 increase the surface area of the heat sink 6, which further improves heat transfer to the environment and thus cooling. In addition, two fans 61 are mounted on the heat sink 6 to increase convection. The cooling fins 60 and the fans 61 are arranged in convection channels 62 for targeted heat transport.

9 shows a second embodiment of a display device 1 according to the invention. 10 shows a section through the cover glass 7, the light guide 40 and the housing 2 along the line A-A'. 11 shows a section along the line B-B'. In this embodiment, the housing has 2 liquid channels 22 through which a cooling liquid circulates. 12 shows a detailed view of the liquid channels 22. The cooling liquid transports the heat generated into a partial area 20 of the housing 2, in which the heat can be easily dissipated. To dissipate the heat, the liquid channels 22 can be connected, for example, to a cooling circuit located outside the housing 2. For this purpose, the housing 2 can have an inlet 23 and an outlet 24. It is also possible to dissipate the heat transported by the cooling liquid from the partial area 20 through heat pipes.

13 shows a schematic of a means of transport 70 that uses a display device 1 according to the invention. In this example, the means of transport 70 is a motor vehicle. In this example, the display device 1 is arranged in a dashboard. Data on the vehicle's surroundings can be recorded using a sensor system 71. The sensor system 71 can in particular comprise sensors for detecting the environment, e.g. ultrasonic sensors, laser scanners, radar sensors, lidar sensors or cameras. The information recorded by the sensor system 71 can be used to generate content to be displayed for the display device 1. Other components of the motor vehicle in this example are a navigation system 72, through which position information can be provided, and a data transmission unit 73. Using the data transmission unit 73, a connection to a backend can be established, for example in order to obtain updated software for components of the motor vehicle. A memory 74 is provided for storing data. The data exchange between the various components of the motor vehicle takes place via a network 75.

List of reference symbols

1

Display device

2

Housing

20

Sub-area

21

opening

22

Fluid channel

23

Inflow

24

Sequence

3

Display panel

4

Backlight

40

Light guide

400

Coupling area

401

reflector

402

Slide stack

41

Light source arrangement

42

LED

43

Circuit board

5

Heat sink

50

Heat pipe

500

Group of heat pipes

501

Group of heat pipes

51

Evaporator

52

capacitor

53

Adiabatic zone

54

Insulating material

6

Heatsink

60

Cooling fin

61

fan

62

Convection channel

7

Cover glass

8

Glue

70

Means of transport

71

Sensor technology

72

Navigation system

73

Data transmission unit

74

memory

75

network

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 8075150 B2 [0008]

Claims (10)

Display device (1) with: - a housing (2); - a display panel (3); - a background lighting (4) for the display panel (3), wherein the background lighting (4) has a flat light guide (40) with two lateral coupling regions (400) arranged on opposite sides and two light source arrangements (41) arranged adjacent to the coupling regions (400); and - a heat dissipator (5) for the light source arrangements (41), wherein the heat dissipator (5) is designed to dissipate heat from the two light source arrangements (41) in a partial region (20) of the housing (2) out of the housing (2). Display device (1) according to Claim 1 , wherein the heat sink (5) has two or more heat pipes (50). Display device (1) according to Claim 2 , wherein the light source arrangements (41) are each assigned a group (500, 501) of heat pipes (50). Display device (1) according to Claim 3 , wherein the heat pipes (50) of at least one of the groups (500, 501) of heat pipes (50) are curved. Display device (1) according to one of the Claims 2 until 4 , wherein the heat pipes (50) have a substantially rectangular cross-section. Display device (1) according to one of the Claims 2 until 5 , wherein the housing (2) has openings (21) for the heat pipes (50). Display device (1) according to one of the preceding claims, wherein the heat dissipator (5) has liquid channels (22) arranged in the housing (2). Display device (1) according to one of the preceding claims, wherein the heat dissipator (5) is connected to a heat sink (6). Display device (1) according to Claim 8 , wherein the heat sink (6) has cooling fins (60) or at least one fan (61). Means of transport (70) with a display device (1) according to one of the preceding claims.

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