JP2000148028A - Planar display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the planar display device, equipped with a back light, which can prevent noise generated on its screen in case of a mechanical shock and also prevent the heat radiative property of a surface light source device from increasing. SOLUTION: A ground connection from a shield sheet 2 serving as a reflecting mirror of a tubular light source 24 to the shield case 31 of the planar display device 10 is made through a screw 15 for fixing the shield case 31 to the frame 21 of a back light unit 20 and a spring 1 which is pressed by the tip of the screw 15. Here, the shield sheet 2 serves as a reflecting sheet on the reverse surface of a light guide plate 22. The spring 1 is previously inserted into a screw hole 27 bored as a through hole of the frame 21 and pressed against the shield sheet 2 on the light guide plate 22 when the screw 15 is clamped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flat panel display having a backlight. In particular, the present invention relates to a liquid crystal display device provided with a sheet or plate for electromagnetic shielding around a backlight lamp.

[0002]

2. Description of the Related Art A flat display device such as a liquid crystal display device has been widely used as an image display device for various computers and the like by utilizing features such as thinness, light weight, and low power consumption. In particular, it has come to be widely used for portable televisions, small notebook personal computers and other various portable information terminals, and image display devices for car navigation systems for vehicles and the like.

Hereinafter, a light transmitting type liquid crystal display device for displaying a high definition image will be described.

A light transmission type liquid crystal display device has at least a liquid crystal panel having a liquid crystal layer held between a pair of transparent substrates, and a liquid crystal panel on a back side (a surface opposite to an image display surface) of the liquid crystal panel. A surface light source device (backlight) disposed to guide light source light to the liquid crystal panel, a driving circuit board for driving an image display of the liquid crystal panel, and a device for maintaining the mechanical strength of the liquid crystal display device and reducing electromagnetic noise. And a shield case.

Here, the lamp of the surface light source device usually comprises a fluorescent tube which operates at a high frequency and is a source of electromagnetic noise. Therefore, in order to prevent adverse effects on image display performance due to interference with the liquid crystal panel and the drive circuit board, a shield sheet is provided near the lamp, and the shield sheet is grounded to the shield case. .

[0006] Such a conventional liquid crystal display device will be described with reference to a schematic partial longitudinal sectional view of FIG. In the illustrated example, the surface light source device is of a sidelight type, and is a backlight unit 120 in which resin frames 121 and 125 are incorporated.

The shield sheet 102 is made of a resin frame 1
21 and 125 are arranged so as to cover the inner side surfaces. That is, the tubular light source (lamp) 124 is covered from three directions other than the light guide plate 122 side, and the back surface of the light guide plate 122 is covered. As the shield sheet 102, a sheet made of aluminum foil is usually used for cost reduction.

[0008] The ground connection from the shield sheet 102 to the shield case 103 is made via a number of members and parts as shown in the figure. That is, the tongue-like connecting piece (bello of the shield sheet) 106 and the drive circuit board (PCB)
05 and the tongue-shaped connection portion (bello of the shield case) 13 of the back side shield case 131
3, the conduction from the shield sheet 102 to the shield case 103 is performed.

The tongue-shaped connecting piece 106 on the shield sheet side is
A portion 106a in contact with the back surface of the shield sheet 102;
Thus, a portion 106b is drawn out of the backlight through a hole 126 provided in the cover-shaped frame 121 on the back side of the backlight. The drawn-out portion 106b is connected to the through-hole forming portion 151 from the display surface side by soldering. Further, on the back side of the through-hole forming portion 151, the back side shield case 1 is provided.
31 tongue-shaped connection part (bello of the shield case) 133
Connected by solder.

In the above description, since the shield sheet 102 is made of aluminum, soldering cannot be performed, and connection with the tongue-like connecting piece (bello of the shield sheet) 106 is made simply by contact. The tongue-shaped connection portion (bello of the shield case) 133 of the back side shield case 131 is a tongue-shaped portion obtained by cutting a part of the back side shield case 131 into a U-shape, and is directed to the display surface side. And soldered while being pressed against the through-hole forming portion 151 of the drive circuit board 105.

[0011]

According to the above prior art, there are the following problems.

(1) Shield sheet 102 and tongue-shaped connecting piece 1
Since 06 is electrically connected simply by contact, the contact is temporarily disconnected due to mechanical shock or the like, and noise (image display disturbance) occurs on the screen. The same is true even if the contact is made by screwing.

(2) Hole 1 is formed in the frame 121 of the backlight.
Since the holes 26 are opened, the heat dissipation is increased by the holes 126. Therefore, when the flat display device is used in a low-temperature environment, the rise of the luminance of the display surface tends to be poor.

(3) A large number of steps and members are required for the ground connection of the shield sheet 102, leading to an increase in assembly costs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to prevent a screen noise generated when a mechanical shock is applied, and to prevent an increase in heat radiation of a surface light source device. Another object of the present invention is to provide a flat display device capable of reducing the cost of assembly.

[0016]

According to a first aspect of the present invention, there is provided a flat panel display device comprising a transmissive display panel, a circuit board for driving the display panel, a light guide plate, and a side end face of the light guide plate. Surface light source device including a tubular light source, and a flat conductor member disposed close to the tubular light source for reducing electromagnetic noise, an electromagnetic shield case for reducing electromagnetic noise, and a flat conductor In a flat panel display device having at least an outer member, a ground connection from the flat conductor member to the outer member made of a conductor is made via a conductive elastic member.

With this configuration, it is possible to prevent noise on the screen caused by receiving a mechanical shock, to prevent an increase in heat radiation of the surface light source device, and to reduce the cost of members and assembly. be able to.

According to a third aspect of the present invention, in the flat panel display device, the conductive elastic member is pressed by a screw for joining the conductor outer member to the surface light source device.

With such a configuration, the assembly cost can be further reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS.
2 will be described.

FIG. 1 is a schematic partial longitudinal sectional view of the liquid crystal display device 10. FIG. 2 is a schematic external perspective view of the liquid crystal display device 10 from the back side. In these figures,
The upper side of the paper is the back side of the liquid crystal display device 10, and the lower side of the paper is the display side.

On the display surface side of the liquid crystal display device 10, the liquid crystal panel 4 is overlaid on the backlight unit 20, and a frame-shaped bezel cover 32 covering the periphery of the liquid crystal panel 4 is covered.

In the backlight unit 20, a rectangular light guide plate 22 is sandwiched between a tray-like resin frame 21 on the back surface side and a frame-like resin frame 25 on the display surface side. A tubular light source (for example, a cold cathode tube) 24 is disposed in an elongated gap between the frames 21 and 25. The entire display surface side of the light guide plate 22 is covered with the lens sheet 23.

As shown in the drawing, one shield sheet 2 is disposed in the backlight unit 20 so as to cover substantially the entire inner surfaces of the resin frames 21 and 25.

The shield sheet 2 also serves as a reflection mirror of the tubular light source 24, a reflection sheet on the back surface of the light guide plate 22, and an electromagnetic shield for suppressing electromagnetic noise from the tubular light source 24. That is, the portion of the shield sheet 2 that covers the tubular light source 24 from the back side, the outer peripheral side, and the display surface side serves as a reflection mirror for directing the light of the tubular light source 24 to the light guide plate 22, and the light guide plate 22. Of the light guide plate 22 serves as a reflection sheet from the inside to the back side (see Japanese Patent Application No. 10-240506). In addition, since an aluminum layer is laminated as a conductive layer on the side in contact with the resin frames 21 and 25, the whole functions as an electromagnetic shielding sheet. By providing the members integrally in this way, the number of parts is reduced,
We are trying to save costs.

On the back side of the liquid crystal display device 10, a drive circuit board (PCB) 5 is arranged so as to cover a part of the back surface of the backlight unit 20, and the arrangement area is almost covered by a back side shield case 31. The back side shield case 31 is fixed to the back side resin frame 21 of the backlight unit 20 by screws 15.

The screw hole 27 of the resin frame 21 is a through hole for exposing the shield sheet 2, and the metal helical spring 1 is inserted into the screw hole 27 in advance. Therefore, the screw 15 is attached to the back side shield case 3
1 through the screw opening 33 and the resin frame 21
When the screw is screwed into the screw hole 27, the back side shield case 31 and the shield sheet 2 are electrically conducted through the screw 15 and the spring 1. Here, the back side shield case 31 is mechanically and electrically connected to the bezel cover 32, and these constitute one shield case 3.

As described above, the shield sheet 2 is
5 and to the shield case 3 via the spring 1. In order to reduce the contact resistance between the spring 1 and the shield sheet 2, a pad may be provided integrally at the end of the spring 1 on the shield sheet 2 side.

According to the present embodiment, since the ground connection from the shield sheet 2 disposed close to the tubular light source 24 to the shield case 31 is made via the spring 1, it is possible to maintain the contact state even when receiving vibration. Can be. For this reason, it is possible to almost completely prevent the occurrence of screen noise due to the temporary disconnection of the contact for grounding.

Further, only a screw hole 27 is formed in the frame 21 of the backlight unit 20, and when the liquid crystal display device is assembled, the screw 15 is closed. Emissions rarely occur. That is, even when the flat display device is used in a low temperature environment, there is no adverse effect on the rise in luminance.

Further, since only the spring 1 is added to the above-mentioned ground connection, the cost of the members can be reduced as compared with the prior art shown in FIG. 4, and in particular, the cost for assembly is reduced. be able to.

Next, a modified example is shown in FIG. In the present modification, a spring-loaded screw 11 in which a part of a helical spring is wound around the peripheral surface of the distal end portion 16 of the screw shaft is used. here,
The distal end portion 16 of the screw shaft has a diameter slightly smaller than that of the threaded screw shaft, and includes a locking projection 18 for preventing the spring 17 from falling off. The outer diameter of the wound spring 12 is set smaller than the inner diameter of the screw hole 27, and the spring 17 does not prevent the spring-loaded screw 11 from passing through the screw hole 27 and screwing.

According to this modification, the same effect as in the above embodiment can be obtained. Moreover, the labor can be reduced somewhat as compared with the case where the spring 1 and the screw 15 are separately inserted into the screw holes 27.

Although a helical spring is used in the above-described embodiment and modified examples, a metal spring having another shape such as a clip shape may be used. Further, instead of a metal spring, a rubber wound copper wire or metal foil can be used.

In the above embodiments and modifications, the shield sheet 2 has been described as covering the tubular light source 24 from three sides. For example, the shield sheet 2 including a metal layer is the only part on the back side that covers the tubular light source 24. Thus, the display surface side and the side portions may be simply reflection sheets.

[0036]

According to the present invention, it is possible to prevent the screen noise generated when receiving a mechanical shock, to prevent an increase in the heat radiation of the surface light source device, and to reduce the cost of members and assembly. A flat display device capable of performing the above can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic partial longitudinal sectional view of a liquid crystal display device of an embodiment.

FIG. 2 is a schematic external perspective view of the liquid crystal display device according to the example, as viewed from the back.

FIG. 3 is a partial longitudinal sectional view illustrating a main part of a liquid crystal display device according to a modification.

FIG. 4 is a schematic partial longitudinal sectional view of a conventional flat display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spring 15 Screw 2 Shield sheet 20 Backlight unit 21 Resin frame on the back side of backlight unit 22 Light guide plate 23 Lens system sheet 24 Tubular light source 25 Resin frame on display side of backlight unit 3 Shield case 31 Shield case on back side 32 Bezel cover 4 LCD panel 5 Drive circuit board (PCB)

Claims (5)

[Claims] 1. A transmission type display panel, a circuit board for driving the display panel, a light guide plate, a tubular light source arranged along a side end face of the light guide plate, and a tubular light source for reducing electromagnetic noise. A flat display device comprising at least a surface light source device including a flat conductor member arranged in proximity, an electromagnetic shield case for reducing electromagnetic noise, and a flat shell member made of a conductor, wherein the flat conductor member Wherein the ground connection to the outer member made of a conductor is made via a conductive elastic member. 2. The flat display device according to claim 1, wherein the elastic member having conductivity is a metal spring. 3. The flat display device according to claim 1, wherein the conductive elastic member is pressed by a screw for joining the conductor outer member to the surface light source device. 4. The flat conductive member covers at least a part of the rear surface of the light guide plate, and the conductive elastic member is pressed by the tip of the screw through the flat conductive member. 4. The flat display device according to claim 3, wherein the flat display device is pressed against the conductor plate. 5. The flat panel display according to claim 1, wherein said flat conductor member is made of aluminum foil.