WO2009047390A1

WO2009047390A1 - Lcd display element, electronic information board and a method for cooling the lcd display element

Info

Publication number: WO2009047390A1
Application number: PCT/FI2008/050563
Authority: WO
Inventors: Niko Suomela; Pasi Karppanen; Jarmo MYLLYMÄKI
Original assignee: Symbicon Oy
Priority date: 2007-10-09
Filing date: 2008-10-08
Publication date: 2009-04-16
Also published as: FI20075714A0

Abstract

The object of the invention is an LCD display element comprising an LCD panel (10) and a backlight constructed of separate light sources (22). In the invention, the light sources have been placed in a separate backlight element (12) having its own cooling system for cooling the backlight element. The backlight element and the LCD panel have been fastened onto each other detachably using mechanical fastening means, such as screws. The backlight element comprises a casing (14) inside which the light sources have been placed. The casing has a back surface (16), sidewalls (18), and a translucent partition (20), which forms its front surface. The partition may be fastened either onto the walls of the casing or onto the frame structure of the LCD panel. The sidewalls of the casing have flow apertures (24) equipped with filters (26) used to lead cooling air in the casing and out of the casing. The flow of cooling air through the casing is created using a fan (28) arranged in connection with the casing. An object of the invention is also an electronic information board comprising a flat LCD display element according to the invention for displaying information. The information board has a display casing inside which the LGD display element has been placed, and a device casing inside which the electronic devices needed to control the operation of the information board have been placed. The information board also comprises devices for arranging a closed circulation of cooling air through the display casing and device casing. According to the invention, the display element in the display casing comprises a backlight element, which also has its own cooling system based on the flow through of cooling air.

Description

LCD display element, electronic information board and a method for cooling the LCD display element

The object of the invention is an LCD display element, comprising an LCD panel and at least one light source arranged on one surface of the panel. An object of the invention is also an electronic information board comprising an LCD display element according to the invention for displaying information. Also an object of the invention is a method for cooling such an LCD display element, which comprises an LCD panel and at least one light source arranged on one surface of the panel.

Electronic devices such as television sets, computers, and electronic information boards widely make use of LCD (Liquid Chrystal Display) elements. Such a display element comprises an LCD panel comprising two transparent panels with cells in between them which cells contain electrically guided light polarizing liquid. In order to increase the brightness and readability of the display element it is often fitted with a backlight, which is situated on the back side of the LCD panel viewed from the viewing side. LCD display elements with a backlight are used especially in display devices which call for great brightness, such as electronic information boards, placed outdoors. In known display elements the LCD panel and backlight have been built inside the same core structure forming one integrated structure. In order to maintain the functioning of the LCD panel the core structure has been constructed leak-proof and protected from dust.

Cooling is a problem with known LCD display elements with a backlight. Display modules, which need a great deal of brightness, such as the display modules of information boards placed outdoors, call for strong backlights which create much heat. Due to the leak-proof core structure, the heat can only exit the display element by conducting through the walls of the display element. The panel of the display element next to the backlight often contains layers, which conduct heat poorly, such as reflective surfaces and backboards, whereby a great portion of the heat is conducted out of the display element through the LCD panel, leading to a rise in the temperature of the panel. It is known that the highest permitted operating temperature of an LCD panel is ca. +70 ⁰C. To avoid exceeding this operating temperature, the power of the backlights of the display module must be restricted. However, in practice this often leads to the insufficient brightness of the display elements for the various locations of use, such as in the sunshine outdoors. There are also problems with the maintenance of the display elements. The backlight is the part of a display element most commonly damaged. Changing the backlight is difficult in known display elements as it always calls for dismantling the entire display element into its components. This operation calls for special tools and skills, and it can only be performed at the premises of an authorized maintenance company.

The aim of the invention is to provide a new LCD display element and a method for cooling the LCD display element, reducing the disadvantages and drawbacks of known display elements. Also an aim of the invention is to provide an electronic information board in which the readability of the display element and the quality of the picture are good in all circumstances, also in bright sunlight.

The aims according to the invention are reached using a display element, information board and method, which are characterized by what has been presented in the independent claims. Some preferred embodiments of the invention have been presented in the dependent claims.

The object of the invention is an LCD display element comprising a flat LCD panel and at least one light source arranged on one surface of the panel for illuminating the LCD panel. The LCD panel is a component of known technology comprising two translucent panels with cells in between them which cells contain electrically guided light polarizing liquid. The panel also comprises a frame structure and the control circuits needed for controlling the panel operations. Advantageously the frame structure has been formed of aluminium profile. In the invention, the light sources used for illuminating the LCD panel have been placed in a separate backlight element, which has been constructed as a structural component of its own, having its own cooling system for cooling the backlight element. The purpose of the cooling system is to transfer the heat created by the light sources in the backlight element out of the display element efficiently. Advantageously the backlight element and the LCD panel have been fastened together side by side, and there is a translucent partition between them. The partition may be a rigid sheet-like part, or a flexible film-like part, or a curtain-like part.

In another advantageous embodiment of the LCD panel according to the invention the backlight element comprises a casing with a back surface and sidewalls. The light sources have been placed inside said casing. Advantageously, the surfaces on the backside of the casing and the surfaces of the sidewalls coming towards the inside of the casing both reflect light. The translucent partition may be fastened at its edges to the sidewalls of the casing or onto the frame structure of the LCD panel.

In a third preferred embodiment of the LCD panel according to the invention, said cooling system of the backlight element comprises flow apertures arranged into the walls of the casing to conduct a medium, such as cooling air, inside the casing and out of the casing, as well as at least one actuator, such as a fan, arranged in connection with the casing to generate a flow of medium through the casing. Advantageously the flow apertures have been made into the sidewalls of the casing and they have been covered with filters, which let the medium through.

An object of the invention is also an electronic information board comprising a flat LCD display element according to the invention for displaying information. The display element comprises an LCD panel and at least one light source arranged on one side of the panel. The light sources forming the backlight have been placed in a separate backlight element. The display element has its own cooling system for cooling the backlight element. Advantageously the backlight element and the LCD panel have been fastened together side by side using mechanical fastening devices such as screws.

An advantageous embodiment of the electronic information board according to the invention also comprises a display casing inside which said LCD display element has been placed. Said cooling system of the backlight element comprises flow apertures arranged into the walls of the backlight element casing, into which apertures flow channels have been joined, the flow channels leading through the wall of the display casing and outside of the casing, and at least one actuator, such as a fan, arranged in connection with the flow channels, to force a medium, such as cooling air, along the flow channel into the casing. Advantageously filters have been arranged into the flow channels.

Another advantageous embodiment of the electronic information board according to the invention also comprises a device casing inside which the electronic devices needed to control the operation of the information board have been placed and means for arranging a closed circulation of cooling air through the display casing and device casing.

In a third advantageous embodiment of the electronic information board according to the invention, said means for arranging a closed circulation of cooling air comprises at least one circulation fan used to create a flow of air through the display casing and the device casing. Advantageously the information board also comprises a fan casing, into which said circulation fan has been placed.

In a fourth advantageous embodiment of the electronic information board according to the invention, said means for arranging the circulation of cooling air also comprise a cooling device used to cool the air flowing through the display casing and the device casing. Advantageously said cooling device is a cross flow cell comprising first flow channels running to the first flow direction and second flow channels running to the second flow direction.

In the method according to the invention, cooling of the LCD display element com- prising an LCD panel and at least one light source arranged on one surface of the panel, is arranged in such a way, that the light sources are placed into a separate backlight element detached from the display element, and the backlight element is cooled using its own cooling system. Advantageously a translucent partition is arranged between the backlight element and the LCD panel.

In a preferred embodiment of the method according to the invention, the backlight element comprises a casing, and the light sources are placed inside the casing. Advantageously the backlight element is cooled by creating a flow of a medium, such as cooling air, through the casing.

The advantage of the invention is that it enables the use of backlights in display elements which backlights have a clearly greater light output than earlier, in which case the clarity of the display also improves remarkably. The increase of brightness improves the readability of the display element and the picture quality, for instance in sunshine. Thus the invention makes it possible to build LCD display elements suitable for outdoor spaces subject to sunshine.

Additionally, an advantage of the invention is that the maintenance costs of the display element are reduced, because a broken backlight can be changed on site without special skills and tools. This means that for example outdoor advertisement companies can use the same maintenance organisation and personnel for maintaining both electronic display boards and traditional poster advertisements.

A further advantage of the invention is that it makes it possible to efficiently conduct the heat generated by the greatest heat source of the LCD display element, namely the backlight, out of the element itself, whereby the heat load of the LCD panel is reduced. The improved heat management of the element increases the durability and reliability of the LCD panel. Yet another advantage of the invention is that it makes it easier to modify the LCD display element. Different types of light sources can be flexibly utilised in a display element according to the invention. As light sources are further developed, the display element may be "updated" to suit new technology without renewing the entire device, leading to savings in costs.

In the following, the invention is described in detail. In the description, a reference is made to the enclosed drawings, in which

Fig. 1 a illustrates by way of example a display element according to the invention as a cross-section,

Fig. 1 b illustrates by way of example a preferred embodiment of a display element according to the invention as a cross-section,

Fig. 2 illustrates by way of example an electronic information board according to the invention as a cross-section.

Fig. 1a illustrates an example of an LCD display element according to the inven- tion as a cross-section. The display element comprises a flat LCD panel 10 and a backlight element 12 of essentially the same area as the panel, arranged on one surface of the panel. The backlight element and the LCD panel are structurally separate components, which have been fastened together detachably with fastening means, such as screws. The LCD panel has two translucent panels with cells in between them which cells contain electrically guided light polarizing liquid. The panel also has a frame structure 13 formed of aluminium profile and control circuits needed for controlling the operation of the panel (the control circuits are not shown in the figures). The structure of the LCD panels is of commonly known technology and therefore it is not described in detail here.

The backlight element 12 comprises a casing 14 with a rectangular shaped sheet- like back surface 16, a partition 20 essentially parallel with the back surface, and sidewalls 18, which join together the partition and the back surface. The distance between the partition of the casing and the back surface is clearly smaller than the side measurements of the casing meaning that the casing is of a flat shape. Ad- vantageously the distance between the partition and the back surface is 30-40 mm. The areas of the partition of the casing and of the back surface are substantially the same as the area of the LCD panel fastened onto the backlight element. The back surface 16 and the sidewalls 18 do not let light through and their surfaces against the inside of the casing reflect light. The back surface and sidewalls have been made of a suitable material, such as a material based on plastic, or advantageously of metal, such as aluminium. The light reflecting surface of the back surface and the sidewalls can be formed in various ways, for instance using a suitable coating, or advantageously using a reflecting film fastened onto the sur- face. The partition of the casing 20 is a translucent plane-shaped part parallel with the LCD panel, fastened detachably to the sidewalls and/or the back surface of the casing with mechanical fastening means, such as screws (the screws are not shown in the figures). The partition may be either entirely or for its essential parts translucent, or it may contain parts, which are translucent in different ways. Advan- tageously the partition is made of translucent material, such as acryl or glass. The partition can be a clear or dim milky-white plate, a so-called opal plate. The partition may be a rigid sheet-like part, or a flexible film-like part, or a curtain-like part.

One or more light sources 22 have been fastened inside the casing together with the power sources required by the light sources (the power sources are not shown in the figures). The power sources may also be placed outside the casing. Advantageously there are several light sources, and they have been placed substantially at even spaces throughout the entire area of the casing. The light sources may be any suitable light sources, such as cold cathode ray fluorescence tubes, regular fluorescence tubes, or LED lights. The partition 20 of the backlight element 12 cas- ing 14 is removable so that, if necessary, the light sources 22 inside the casing can be changed or serviced easily without special tools. Also the back surface 16 of the casing may be constructed as removable, in which case the light sources can be changed through there. When in operation, the light sources create heat causing the air inside the casing to warm up. The partition 20 acts as an insulating structure preventing the heat created by the light sources from being transferred by convection to the LCD panel. The partition also reduces heat transfer by radiation from the light source to the LCD panel.

The sidewall protruding downward 18 and the sidewall protruding upward have flow apertures 24, via which cooling air is made to flow through the backlight ele- ment. The flow apertures have been covered with filters 26, which let air through and prevent dirt from entering the backlight element. Cooling air (arrow A) is blown into the casing from the surrounding space through the flow aperture at the lower edge of the casing, using a fan 28. While travelling through the casing, the cooling air flushes the surfaces of the light sources 22, and heat is transferred from the light source into the cooling air. The warmed cooling air (arrow B) leaves the casing back into the surrounding space through the flow aperture at the upper edge of the casing. The fan may be arranged in connection with the LCD display element, or it can be a part of a more extensive cooling system, which belongs to a device containing an LCD display element. A first thermometer 30 has been placed inside a casing 14 for measuring the inside temperature of the casing, and a second thermometer 32 outside the casing for measuring the temperature of the cooling air outside the casing. The cooling of the backlight element is guided with a control unit 34 connected to the fan which control unit regulates the blowing power of the fan 28 according to the temperature values measured with the thermometers. Cooling power is increased by increasing the blowing power of the fan, and cool- ing power is reduced by reducing the blowing power of the fan. A heat exchanger or a cooling apparatus can be arranged along the flow route of the cooling air (the heat exchanger and cooling apparatus are not shown in the figure) with which the temperature of the cooling air blown into the casing can be reduced.

Fig. 1 b illustrates an example of an advantageous embodiment of the LCD display element according to the invention in which the partition 20 has been fastened at its edges to the frame structure 13 of the LCD panel 10. In this embodiment the partition is not a part belonging to the casing; instead it is an integral part of the LCD panel. The casing 14 has been placed against the partition in such a way that the edges of its sidewalls 18 come against the surface of the partition plate. There is an edge sealing 19 between the edges of the sidewalls and the surface of the partition plate, which ensures the tightness of the casing. Otherwise, as regards its structure, the embodiment illustrated in Fig. 1 b corresponds to the invention shown in Fig. 1a. In the event the partition is a rigid sheet-like part, it also acts as a structural part, which braces the LCD panel. In such a case the frame structure of the LCD panel may be of a light-weight construction. If the partition is a film-like or curtain-like part, it does not have a great bracing effect. In such a case the frame structure of the LCD panel must alone be rigid enough to keep the LCD panel together.

The partition 20 may also be a completely separate part, which is not an integral part of the casing 14 or the LCD panel. In such a case the partition is placed, in connection with the assembling of the LCD display element, between the casing and the LCD panel as illustrated in Figs. 1a and 1 b, and the casing is fastened at its sidewall directly onto the frame structure 13 of the LCD panel using screws, for instance. In such a case the partition plate is left clamped between the casing and the frame structure and it stays well in its place. Advantageously, an edge sealing is used at the joining points between the sidewalls, partition and frame structure, making sure that the joining points are leak-proof against air and dust.

Fig. 2 illustrates by way of example an information board according to the invention, shown as a cross section into which information board an LCD display ele- ment according to the invention has been placed. The information board comprises a frame 40 into which display casing 50 has been formed. Into said display casing a LCD display element, constructed of the backlight element 12 and the LCD panel 10 has been placed. The display casing comprises a back wall 52 and a transparent front plate 54 forming the front surface of the information board. The LCD display element has been supported at its edges with flexible support structures to the edge part of the display casing in such a way that a slot enabling the circulation of air is left between the walls of the display casing and the outer surface of the display element (the support structures are not shown in the figure). On another side of the back wall 52 of the display casing, to the upper part of the in- formation board a device casing 60 has been fixed, inside which casing substantially all of the electronic devices needed for guiding the operation of the LCD display element and the entire information board, such as a computer, the display control unit and the power sources of the control unit and the display backlight have been placed. A fan casing 70 has been fastened to the lower part of the other half of the back wall 52 of the display casing inside which circulation fans 72 have been placed to circulate cooling air. Between the device casing 60 and the fan casing 70 there is a cross-flow cell 80, the purpose of which is to cool the air flowing through the device and display casings. The walls of the device casing and the fan casing facing against the cross-flow cell have flow apertures 74, which en- able the flow of air from the fan casing via the cross-flow cell to the device casing. Additionally, there is a flow aperture 74 at the upper part of the back wall of the display casing, opening towards the device casing, through which air can flow from the device casing to the display casing, and there is a flow aperture 74 at the lower part of the back wall of the display casing through which air can flow from the dis- play casing to the fan casing 70.

The cross-flow cell is a heat transferring device known as such in air-conditioners, for instance, in which there are several first flow channels running in the first direction and several second flow channels running in the second direction. In the information board shown in Fig. 2, the first flow channels of the cross-flow cell run in the direction of the vertical axle of the information board, whereby air is able to flow along the flow channels through the cross-flow cell from the fan casing to the device casing. The second flow channels of the cross-flow cell run in a horizontal direction, and forced air flow is formed into them using cooling fans (the cooling fans are not shown in the figure). The first and second flow channels are situated alternately in the cross-flow cell, and they have a common partition made of a ma- terial with good thermal conductivity, such as aluminium. The cooling activity of the cross-flow cell is based on the fact that the heat of the air flowing in the first flow channels is transferred via the common partitions into the second flow channels and further into the air flowing in the second flow channels. As a result of the heat transfer, the air in the first flow channels cools down as it passes through the cross-flow cell.

Inside the fan casing there are circulation fans 72 using which a closed circulation of cooling air is created through the fan casing 70, cross-flow cell 80, device casing 60, and display casing 50. When the circulation fans are in action, air flows from the fan casing into the cross flow cell, from the cross flow cell into device cas- ing 60, from the device casing to the upper part of display casing 50, and through the flow aperture at the lower part of the display casing back into the fan casing after which a new cycle begins. The operation of the circulation fans is guided with a control unit 34 situated in the device casing.

When the information board is in operation, the LCD display element and the elec- tronic devices in the device casing heat up, causing the temperature of the device casing 60 and the display casing 50 to rise. In the information board according to the invention, a flow of air circulating through the device and display casings is formed to keep the temperature of the casings within the desired limits. The circulating flow of air flushes the surfaces of parts which warm up, such as the surface of the LCD display element, causing the temperature from the warming components to transfer effectively straight into the flow of air. Sensors for measuring the temperature (not shown in the figures) have been placed in the device and display casings, and they have been connected to the control unit 34 in the device casing of the information board. The control unit controls the operation of the circulation fans 72 based on the measured temperatures according to a predetermined control logic. With the help of the internal cooling air circulation produced by the circulation fans, the temperatures of the inner parts of the display casing and device casing can be regularized, and the heat can be effectively transferred out of the casings.

In the electronic information board according to the invention, a separate flow of cooling air has additionally been arranged for cooling the backlight element 12 be- longing to the LCD display element. The sidewall protruding downward and the sidewall protruding upward in the backlight casing 14 are equipped with flow apertures 24, which are connected to flow channels 90 leading through the walls of the display casing 50, outside the display casing and outside the entire information board. Filters 26, which let air through, have been arranged into the flow channels, preventing dirt from getting inside the backlight element. Cooling air from the space surrounding the information board is blown with fans 28 into the casing 14 along the flow channel via the flow aperture at the lower edge of the casing. The warmed cooling air leaves the casing and goes back into the space surrounding the information board through the flow aperture at the upper edge of the casing and through the connected flow channel. The fan 28 may be arranged at any suitable point along the flow channel. Advantageously, cooling air is led into the casing 14 along a flow channel running inside the base part 76 of the information board, and the fan 28 has been arranged in connection with the flow channel in- side the base part. The fan 28 can be connected to the control unit 34 of the information board in which case all the electric devices of the information board can be controlled using the same control unit.

In an advantageous embodiment of the information board according to the invention, a separate flow of cooling air is not formed through the backlight element; instead a flow of air created by the circulation fans 72 is used to cool the backlight element. In this solution, part of the flow of air entering the display casing is led to run through the casing 14 of the backlight element 12. Air deflectors may be arranged in connection with the opening of the casing flow aperture to divert part of the cooling air flow into the casing.

Some advantageous embodiments of the LCD display element and electronic information board according to the invention have been described above. The present invention is not limited to the solutions described above, but rather the idea of the invention can be applied in numerous ways within the scope of the claims.

Claims

1. An LCD display element comprising an LCD panel (10) and at least one light source (22) arranged on one side of a panel, characterized in that said light sources have been placed into a separate backlight element (12) and the display element has its own cooling system for cooling the backlight element.

2. A display element according to claim 1 , characterized in that the backlight element (12) and the LCD panel (10) have been fastened to each other detachably with mechanical fastening means, such as screws.

3. A display element according to claim 1 or 2, characterized in that the back- light element (12) and LCD panel have been fastened to each other side by side and there is a translucent partition (20) between them.

4. A display element according to claim 3, characterized in that the partition (20) is a rigid sheet-like part or a flexible film-like or curtain-like part.

5. A display element according to claim 3 or 4, characterized in that the LCD panel (10) has a frame structure (13) and the partition has been fastened at its edges onto the frame structure.

6. A display element according to any one of claims 1-5, characterized in that the backlight element (12) comprises a casing (14) with a back surface (16) and sidewalls (18) and light sources (22) have been placed inside the casing.

7. A display element according to claim 6, characterized in that the surfaces of the back surface (16) and sidewalls (18) facing against the inside of the casing (14) is light reflecting.

8. A display element according to claim 6 or 7, characterized in that the partition (20) has been fastened at its edges onto the sidewalls (18) of the casing (14).

9. A display element according to any one of claims 6-8, characterized in that said cooling system of the backlight element (12) comprises flow apertures (24) arranged onto the walls of the casing (14) to conduct a medium, such as cooling air, into the casing and out of the casing, and at least one actuator, such as a fan (28), arranged in connection with the casing for generating a flow of the medium through the casing.

10. A display element according to claim 9, characterized in that the flow apertures (24) have been covered with filters (26), which let the medium through.

11. A display element according to claim 9 or 10, characterized in that the flow apertures (24) have been formed onto the sidewalls (18) of the casing (14).

12. An electronic information board comprising an LCD display element for displaying information in which display element there is an LCD panel (10) and at least one light source (22) arranged on one side of the panel, characterized in that said light sources have been placed into a separate backlight element (12) and the display element has its own cooling system for cooling the backlight ele- ment.

13. An information board according to claim 12, characterized in that the backlight element (12) and LCD panel (10) have been fastened side by side and there is a translucent partition (20) between them.

14. An information board according to claim 12 or 13, characterized in that the LCD panel (10) has a frame structure (13) and the partition has been fastened at its edges onto the frame structure.

15. An information board according to any one of claims 12-14, characterized in that the backlight element (12) comprises a casing (14) with a back surface (16) and sidewalls (18) and light sources (22) have been placed inside the casing.

16. An information board according to claim 15, characterized in that the partition (20) has been fastened at its edges onto the sidewalls (18) of the casing (14).

17. An information board according to claim 15 or 16, characterized in that it also comprises a display casing (50) inside which said LCD display element has been placed, and said cooling system of the backlight element (12) comprises flow apertures (24) arranged onto the walls of the casing (14), the flow apertures being connected to flow channels (90), which extend through the wall of the display casing (50) outside the display casing, and at least one actuator arranged in connection with the flow channels, such as a fan (28), for generating a flow of the medium through the casing.

18. An information board according to claim 17, characterized in that filters (26) have been arranged into the flow channels (90).

19. An information board according to claim 17 or 18, characterized in that it comprises a base part (76) and at least one of said fans (28) has been placed inside the base part.

20. An information board according to any one of claims 17-19, characterized in 5 that the display casing (50) comprises a back wall (52) and transparent front panel

(54), in which case the LCD display element has been supported into the display casing in such a way that there is a gap allowing the circulation of air between the LCD panel (10) of the display element and the front panel of the display casing and between the backlight element (12) of the display panel and back wall of the 10 display casing.

21. An information board according to any one of claims 17-20, characterized in that it also comprises a device casing (60) inside which the electronic devices needed to control the operation of the information board have been placed and means for arranging a closed circulation of cooling air through the display casing

15. (50) and device casing.

22. An information board according to claim 21 , characterized in that said means for arranging a closed circulation of cooling air comprise at least one circulating fan (72) for generating a flow of air through the display casing (50) and device casing (60).

20 23. An information board according to claim 22, characterized in that it also comprises a fan casing (70) into which at least one said circulation fan (72) has been placed.

24. An information board according to any one of claims 21-23, characterized in that said devices for arranging a closed circulation of cooling air also comprise a

25 cooling device used to cool the air flowing through the display casing (50) and device casing (60).

25. An information board according to claim 24, characterized in that said cooling device is a cross-flow cell (80) comprising first flow channels running in the first flow direction and second flow channels running in the second flow direction.

30 26. An information board according to claim 25, characterized in that the device casing (60) and fan casing (70) have been fastened onto the back wall (52) of the display casing (50), the cross-flow cell (80) has been placed between the device casing and the fan casing, and there are flow apertures (74) in the walls of the dis- play casing, device casing and fan casings to form a closed route of air circulation leading from the fan casing through the cross-flow cell into the device casing, from the device casing into the display casing and from the display casing into the fan casing.

27. A method for cooling a LCD display element, which display element comprises an LCD panel (10) and at least one light source (22) arranged on one side of the panel, characterized in that the light sources are placed into a separate backlight element (12) separate from the display element and the backlight element is cooled with its own cooling system.

28. A method according to claim 27, characterized in that a translucent partition (20) is arranged between the backlight element (12) and the LCD panel.

29. A method according to claim 27 or 28, characterized in that the backlight element (12) comprises a casing (14) and the light sources (22) are placed inside the casing.

30. A method according to claim 29, characterized in that the backlight element (12) is cooled by creating a flow of a medium, such as cooling air, through the casing.