WO2008012964A1 - Illumination device for display device - Google Patents

Abstract

An illumination device placed on the rear side of a display section. Fans (30 (30A-30D)) are arranged in a region between the outer edge of a screen display section (X) and a case outer peripheral frame, and the fans are located at positions at which the fans generate convection in the direction along the entire periphery of the screen display section.

Description

 Specification

 Lighting device for display device

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a lighting device for a display device, and is particularly suitably used for a large-sized television or the like.

Thus, the quality of the display screen is improved by suppressing variations in the internal temperature.

 Background art

 [0002] Normally, in a display device such as a television, a direct-type knock light unit is disposed on the back side of the display unit, and the backlight unit also has a large number of cold-cathode tubes on the reflector. The lamps are arranged side by side, and the inverter connected to these lamps is arranged at the lower end or the left and right ends.

[0003] When the multiple lamps are turned on, heat is generated. In particular, the inverter is the most heat generating source, and the electrode discharge surfaces of the multiple cold cathode tubes generate heat, and the air temperature in the vicinity of these heat generating sources. The temperature rises locally and the heated air rises, so the upper side of the display device becomes hot and the air temperature inside the display device becomes uneven.

 The brightness of the lamp varies depending on the ambient temperature, and as shown in Fig. 6, the cold cathode tube has the highest brightness at around 40 ° C, and the brightness decreases at temperatures higher than 40 ° C. The brightness tends to decrease even at lower temperatures. In this way, uneven brightness occurs when the temperature distribution is non-uniform, and this uneven brightness becomes visible when a temperature difference of 10 ° C occurs. Therefore, even if the heat generating portion is simply cooled, if the internal temperature is lowered as a whole, the luminance is lowered as a whole and an unclear image tends to be obtained.

 Therefore, when using a cold-cathode tube, the temperature inside the display device should be kept as low as possible in order to avoid uneven brightness, which is most desirable when the air temperature inside the display device is made uniform around 40 ° C. It is preferable to make it uniform without variation.

Furthermore, in the display unit, the glass substrate and the polarizing film disposed on the surface thereof have different thermal expansion coefficients. Therefore, if there is a temperature difference in the display screen, display unevenness due to the difference in thermal expansion occurs. It becomes easy. Therefore, inside the display device, the heated air stays on the upper side and the upper side is prevented from being heated to a high temperature, and the temperature from the lower side is reduced. It is necessary to prevent variation in the degree distribution.

 Conventionally, Japanese Patent Laid-Open No. 2001-283624 (Patent Document 1) has been provided as a means for preventing the temperature inside the knocklight from partially rising. In the knocklight of Patent Document 1, as shown in FIGS. 7A and 7B, the knocklight reflector 1 is provided with an air outlet 2 and an air outlet 3, and a fan is provided on the outer surface facing the air outlet 2. The 5 fans installed on the outer surface of the 5 are also forced to blow outside air into the reflector 1, and the inside air is expelled from the exhaust port 3.

 Patent Document 1: Japanese Patent Application Laid-Open No. 2001-283624

 Disclosure of the invention

 Problems to be solved by the invention

[0006] In the backlight of Patent Document 1, the force forcing external air into the reflector by a fan attached to the outer surface of the reflector is configured as described above. There is a risk of air containing dust or other foreign matter being sent into the display. If air containing foreign matter enters the display device, it may cause malfunction or foreign matter may appear on the display screen.

 In addition, if outside air is sent locally to a part of the reflector that generates a lot of heat, such as both ends of the light source, this part will be overcooled and cause temperature variations.

 As shown in FIG. 6, since the luminance varies depending on the ambient temperature, it is possible to eliminate the occurrence of luminance unevenness even if the high temperature portion is locally cooled by introducing the outside air shown in Patent Document 1. Absent.

 Furthermore, an inverter of a power supply circuit is connected to a light source composed of a cold cathode tube, and this inverter is the largest heat generation source. However, Patent Document 1 does not consider the heat generation in the inverter. Therefore, the fluctuation in temperature distribution in the display device to which the knocklight of Patent Document 1 is attached cannot be eliminated.

[0007] The present invention intends to solve the above problem, and makes the air temperature inside the display device uniform throughout, particularly in an illumination device comprising a backlight as a heat source incorporated in the display device. The air temperature is made uniform to prevent the uneven brightness of the lamp in the lighting device, and the internal temperature of the lighting device is made uniform, so that the display device The task is to make the temperature uniform inside.

 Means for solving the problem

 [0008] In order to solve the above problem, a holding frame for holding both ends of a plurality of lamps or a region between the outer edge of the screen display unit of the reflector arranged on the back of the lamp and the case outer peripheral frame, Provided is a lighting device for a display device, characterized in that a plurality of fans are arranged at intervals at positions where convection is generated in the entire circumferential direction.

 [0009] The lighting device of the present invention is most preferably used for a liquid crystal display device such as a large-sized television, and is therefore preferably a direct type backlight, but a sidelight type backlight in which lamps are arranged on both sides. It can also be applied to lights.

 [0010] The mounting portion of the fan may be, for example, a holding frame that holds a plurality of lamps at both ends, a reflector disposed on the back of the lamp, or the like, and may be fixed to the surface of these mounting portions. An opening for mounting the fan may be provided in the mounting portion, and the fan may be fitted and fixed in the opening. In any case, as described above, a fan is disposed in the region between the outer edge of the screen display unit and the case outer peripheral frame at a position where convection is generated in the entire circumferential direction of the screen display unit.

 [0011] Specifically, the fan has a total of four force points at the four corners of the top, bottom, left and right, four force points at the center of each of the top, bottom, left and right edges, or one at the center of the left and right corners of the upper edge and the bottom edge It is preferable to install it at three locations.

 When the fan is arranged at the above position, the internal air is forced to generate convection over the entire outer periphery of the screen display area, and variations in the internal air temperature can be suppressed.

 As described above, when a difference of 10 ° C or more occurs in the ambient temperature, the brightness unevenness becomes visible, while at a temperature difference of 5 ° C or less, the brightness unevenness decreases and becomes invisible. Therefore, in the present invention, the internal temperature difference is suppressed to 5 ° C. or less by convection of the internal air.

 In addition, because the internal air is forced to convection, even if the inverter is placed along the left and right side edges, the heated air in the vicinity of the inverter is convected and the lamp in the vicinity of the inverter is particularly heated. Can be prevented.

[0012] The fan is located on the outer peripheral side of the screen display area and in a narrow area on the inner side of the lighting device A small fan is used for placement. The structure of the fan is not limited, but a fan whose blades are rotated by an electric motor is preferably used.

 It is preferable that the motors of a plurality of fans are connected to a drive control device to control the drive timing. For example, all the fans may be driven at the same time, or a temperature sensor may be attached to each fan, and the fans may be driven when the set temperature is exceeded.

 As described above, in the present invention, the temperature distribution of the internal air is caused by convection of the heated air that is not introduced into the outside air presented in Patent Document 1 and discharged from the heated air to cool the heated portion. Therefore, it is possible to prevent intrusion of foreign substances that are likely to occur when outside air is introduced.

 In addition, even if the surrounding air is heated by the heat generated by the electrode discharge surfaces arranged at both ends of the lamp composed of a cold cathode tube, the heated air is also forced to flow as convection, and each cold cathode tube itself The temperature distribution can be equalized, and uneven brightness in each lamp can be prevented. Furthermore, the heated air can be prevented from rising and staying at the top, and display unevenness due to the difference in the thermal expansion coefficient between the glass substrate and the polarizing film on the upper side can also be prevented.

[0014] Usually, in the display device, the ambient temperature of the lamp on the upper side becomes high. For example, the brightness is highest at around 40 ° C. On the other hand, if the ambient temperature of the lower lamp is low and close to 30 ° C, the luminance on the lower side decreases and uneven brightness occurs at the top and bottom of the entire display screen. If the upper side reaches 50 ° C and the lower side is around 40 ° C, the luminance on the upper side decreases and the luminance on the lower side increases, and in this case, luminance unevenness also occurs. In either case, the temperature distribution in the screen display area is non-uniform throughout, resulting in uneven brightness. In addition, a liquid crystal television equipped with a color liquid crystal display unit is provided with a TFT array substrate and a color filter substrate facing each other, each of which is a glass substrate to which a polarizing film is attached. Have different thermal expansion coefficients. Therefore, if hot air stays in the upper part, a difference in expansion occurs due to a difference in thermal expansion coefficient between the two glass substrates and the polarizing film, and display unevenness tends to occur on the upper side of the screen display area. . As described above, since the problem is likely to occur when the temperature distribution of the internal air of the display device is non-uniform, the internal space of the display device can be reduced by incorporating the lighting device of the present invention inside the display device. This is effective in making the air temperature uniform.

 The invention's effect

 [0015] As described above, in the illumination device for a display device according to the present invention, the fan for attaching the convection of the internal air as a whole is attached to make the temperature distribution uniform to the internal air. The ambient temperature can be made uniform, and the occurrence of luminance unevenness caused by the difference in the ambient temperature can be suppressed or prevented, so that a high-quality screen display function can be achieved. Brief Description of Drawings

 FIG. 1 (A) is a schematic perspective view of the entire display device of the first embodiment, and (B) is an exploded perspective view.

FIG. 2 is a schematic perspective view showing the front side force of the lighting device in FIG.

 FIG. 3 is an exploded perspective view of the lighting device.

 FIG. 4 is a perspective view of a fan mounting portion.

 [FIG. 5] (A) and (B) are schematic front views showing modifications of the fan position.

 FIG. 6 is a diagram showing the relationship between lamp brightness and ambient temperature.

 [FIG. 7] (A) and (B) are drawings showing a conventional example.

 Explanation of symbols

[0017] 10 knock lights

 11 Reflector

 12 Cold cathode tube

 13A, 13B Holding frame

 18 Inverter

 20 LCD unit

 30 (30A ~ 30D) Fan

 100 display devices

 101 outer frame

 X screen display area

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

 1 to 4 show a first embodiment, and a fan is attached to a direct type backlight in the display device 100 having a large color liquid crystal television as shown in FIGS. 1 (A) and 1 (B).

A direct backlight 10 shown in FIGS. 2 and 3 has a large number of cold-cathode tubes 12 arranged in a horizontal direction on the surface side of a reflector 11 having a rectangular outer shape and arranged in parallel in the vertical direction. The left and right ends of the cold cathode tubes 12 are held by a pair of left and right holding frames 13A and 13B.

 As shown in FIG. 1B, an optical sheet group 15 in which a light guide plate 14, a diffusion sheet 15a, a prism sheet 15b, and a diffusion sheet 15c are stacked is arranged on the surface side of the arrangement portion of the cold cathode tube 12. is doing. A back case 17 is disposed on the back side of the reflecting plate 11, and a frame-like front case 19 is attached to the front side of the optical sheet group 15 to constitute a unit.

The inverter 18 connected to the cold cathode tube 12 of the backlight 10 is connected to the wiring portions of the left and right holding frames 13A and 13B and is arranged on both the left and right sides in the display device 100.

 A liquid crystal display unit 20 is disposed on the surface side of the optical sheet group 15 of the backlight 10. The liquid crystal display unit 20 is provided with a force filter substrate 23 arranged to face the TFT substrate 21 via the liquid crystal layer 22, and a polarizing film 21b is attached to the bottom side of the glass substrate 21a of the TFT substrate 21, A polarizing film 23b is attached to the surface side of the glass substrate 23a of the color filter substrate 23! /.

 The components including the backlight 10, the left and right inverters 18, the liquid crystal display unit 20, and the like are accommodated in the outer frame 101 of the display device 100 and assembled by joining the outer peripheral frame 102.

A pair of left and right holding frames 13 A and 13 B for holding the left and right ends of a large number of cold cathode fluorescent lamps 12 of the backlight 10 are arranged in the vertical direction along the left and right side edges in the display device 100. Fans 30 (30A, 30B, 30C, 30D) are attached to the outer surfaces of both end faces of the left and right holding frames 13A, 13B, respectively, and these fans 30 are arranged at substantially the same height as the cold cathode tubes 12. . In this attached state, in FIG. 2, the fans 30 are respectively arranged at the four corners of the upper, lower, left and right positions outside the outer edge Xa of the screen display area X and inside the outer frame 101 of the entire display device. . Each fan 30 has a general shape in which an impeller 32 is attached to a main shaft 31a of a micro electric motor 31 as shown in FIG. The motors 31 of the fans 30A and 30B are connected to the power supply line 33 wired in the holding frame 13A, and the motors 31 of the fans 30C and 30D are connected to the power supply line 33 wired in the holding frame 13B. These feeders 33 and 33 are connected to the left and right inverters 18 and 18, respectively. Power is supplied to the cold cathode tube 12 from the inverters 18 and 18 so as to light up, and at the same time, the fans 30A to 30D are driven to rotate the impeller 32.

 [0023] As shown in Fig. 2, the impellers 32 of the four fans 30A to 30D are set to rotate clockwise in the same direction, and are convected clockwise along the entire outer periphery of the screen display region X. Is set to generate convection in the same direction within the screen display area X.

 [0024] Note that a temperature sensor may be attached to the fan, and the fan may be driven to rotate when the detected temperature reaches a predetermined temperature or higher. In that case, a temperature sensor is attached to each of the fans 30A to 30D, or to the fans 30A and 30C arranged on the upper side, or to one fan, and according to the detection signal of the temperature sensor force. A control unit for driving and controlling the motors of the fans 30A to 30D may be provided, and the fans 30A to 30D may be simultaneously driven to rotate when the detected temperature becomes equal to or higher than a set value of 45 ° C, for example. Furthermore, only the upper fan may be driven to rotate, or a temperature sensor may be additionally provided, and only the fan that has detected a set temperature or higher may be driven to rotate.

 [0025] In the display device 100, which is a color liquid crystal television that incorporates the knock light 10 having the above-mentioned configuration power, when the cold cathode tube 12 is turned on, the inverters 18, 18 on both the left and right sides generate heat, and the inverter 18, The electrode discharge surfaces near both ends of the cold cathode tube 12 close to 18 generate heat. That is, in the display device 100, the air on the left and right side edges is heated to the highest temperature. At that time, for example, if the temperature of the air rises to near 50 ° C, the brightness on both the left and right sides will be lower than the center, resulting in uneven brightness at the center of the screen display area X and both the left and right sides. It becomes.

As the fans 30A to 30D are driven, the heated air on the left and right sides is forced to convection downward and upward as one large vortex as shown by arrows in the figure. Can be made. Accordingly, the temperature decreases on both the left and right sides, and the temperature on both the upper and lower sides and the screen display area X increases, and the air temperature in the entire display device 100 is equalized. As a result, the ambient temperatures of many cold cathode fluorescent lamps 12 are also equalized, so that uneven brightness can be suppressed and prevented from occurring throughout the entire screen display area X.

 In this way, the occurrence of uneven brightness due to differences in ambient temperature can be prevented, and if the overall air temperature can be maintained at the highest brightness around 40 ° C, the entire display screen can be clearly displayed. Can be displayed.

 Further, the heated air rises and stays in the upper portion. The upper air is forcibly sent downward by the fan 30C, and the upper portion is prevented from being heated. As a result, in the liquid crystal display unit 20, the difference in elongation due to the temperature difference does not occur between the glass substrate 21a and the polarizing film 21b of the TFT substrate 21 and the glass substrate 23a and the polarizing film 23b of the color filter substrate 23. As a result, it is possible to prevent display unevenness due to the difference in expansion coefficient between the glass substrate and the polarizing film.

FIGS. 5A and 5B show a modified example in which the arrangement positions of the fans 30 are different.

 In Fig. 5 (A), fans 30A to 30D are arranged in the center of the top, bottom, left, and right side edges that are not at the four corners. These fans 30A to 30D are attached to the back case 17 shown in FIG. 1, and the fans 30A to 30D are arranged at substantially the same height as the cold cathode tubes.

 Even if the fans 30A to 30D are arranged as described above, the internal air temperature can be made uniform by convection of the internal air as one large vortex along the outer periphery.

[0027] FIG. 5 (B) uses three fans 30A to 30C, which are arranged at three force points on the left and right sides of the upper edge and the central part of the lower edge. In this case, three fans 30A to 30C are attached to the back case 17.

 When the fans 30A to 30C are arranged as described above, as shown in the drawing, two vortex flows can be generated to make the internal air temperature uniform. Also, fan drive power can be reduced by changing the number of fans from four to three.

Claims

The scope of the claims  [1] Convection in the entire periphery direction of the screen display section in the area between the outer edge of the screen display section of the holding frame for holding both ends of the plurality of lamps or the reflector on the back of the lamp and the case outer peripheral frame. A lighting device for a display device, wherein a plurality of fans are arranged at intervals at a position where they are generated.  [2] The illumination device for a display device according to [1], wherein the illumination device comprises a direct type backlight.  [3] The fan has 3 locations in total, 4 locations at the top, bottom, left and right corners, 4 locations at the center of the top, bottom, left and right edges, or 1 location at the top left and right corners and the center of the bottom edge. The illumination device for a display device according to claim 1 or 2, wherein the illumination device is attached to the display device. [4] The fan according to any one of claims 1 to 3, wherein the fan also has a fan force for rotating blades by an electric motor, and the motors of the plurality of fans are connected to a drive control device and the drive timing is controlled. A lighting device for a display device according to item.