JP3498263B2 - Noise reduction structure and liquid crystal display device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reduction structure and a liquid crystal display device using the same. More specifically, the present invention relates to a noise reduction structure that improves contact characteristics of a ground connection in order to reduce the problem of EMI (Electro Magnetic Interference), and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view of a personal computer (personal computer) equipped with a liquid crystal display device. PC 1
00 signal line, ground line and power line (hereinafter,
The signal line group 101) is connected to the liquid crystal display device 103, and the liquid crystal display device 103 is connected to the signal line group 101.
It is also stored in the case 102. The image of the liquid crystal display device 103 is controlled by applying the video signal transmitted from the signal lines of the signal line group 101 to the liquid crystal display device 103.

If high frequency noise is transmitted through the signal line group 101 and leaks to the outside of the device, it may cause malfunction of the personal computer (EMI). In addition, if the wiring or the board on which the video signal is transmitted is not appropriately shielded, these wiring and the board itself function as an antenna, so that E
MI is promoted and the ability to eliminate performance deterioration due to external noise (immunity) is lost.

As a countermeasure against noise of the liquid crystal display device 103, conventionally, an internal part (a substrate or an IC) is electrically connected to a metal frame 104 of the liquid crystal display device 103 which is a ground (potential reference point) to improve the internity and the EMI. I am trying. For example, multiple ground patterns with ground potential are provided on the surface of a circuit board to which a video signal is applied, and the ground patterns and the metal frame are electrically connected via a flexible conductive seal (gasket). I am letting you. As a result, the ground potential of the circuit board is kept constant over the entire surface of the board, and the circuit board is designed to enhance the immunity of the circuit board and to prevent the circuit board from having an antenna function of radiating electromagnetic waves.

[0005]

However, in the conductive seal (gasket) insertion method for making an electrical connection between the circuit board and the metal frame, it has been found that the following problems must be solved.

FIG. 6 is a plan view of an essential part showing a liquid crystal display device (however, a metal frame is not shown). FIG. 7 is a sectional view taken along line II-II of the liquid crystal display device shown in FIG.

A gasket 11 inserted between a circuit board (source circuit board) 114 and a metal frame 112.
1 is a flexible member. The gasket 111 is compressed and deformed in the height direction, and the gasket 111 presses both the metal frame 112 and the ground pattern 115 by the elastic pressure of the gasket 111. This allows the metal frame 1
The gasket 12 and the ground pattern 115 are electrically connected to each other. If there is a problem with the reliability of the electrical connection, the contact resistance increases and electromagnetic noise cannot be sufficiently reduced. Here, it is known that the contact resistance of the electric contacts can be reduced by increasing the contact pressure between the electric contacts (see FIG. 5 of JP-A-58-175220).

Similarly, in a liquid crystal display device, when deterioration of the elastic force of the gasket at the time of high temperature and high humidity test and a temporal change of the degree of adhesion between the gasket and the frame due to external vibration are taken into consideration, the difference between the two is considered. It is presumed that increasing the contact pressure at the interface is important for improving the reliability of electrical connection. Furthermore, if the contact pressure is low,
It is known that the variation of the contact resistance with respect to the change of the contact pressure is increased, and this may cause the product variation of the contact resistance even with a slight pressure difference at the contact portion. However, the above-mentioned JP-A-58-1752
Even taking the publication No. 20 into consideration, it is not possible to find out a concrete measure for increasing the contact pressure of the gasket.

Therefore, the inventors of the present invention increase the elastic reaction force of the gasket, for example, by using a harder gasket or a large-sized gasket, thereby obtaining a high contact pressure, thereby reducing electromagnetic noise. I thought it was effective. However, on the other hand, if the improvement of the contact pressure and contact pressure is simply dependent on the improvement of the hardness and shape of the gasket,
There are also concerns about the following problems.

(1) The disconnection circuit board 114 between the TCP (Tape Carrier Package) and the board is, as shown in FIGS.
It is connected to a liquid crystal display panel 118 via a film called TCP 116 equipped with C117. Connection between circuit board 114 and TCP 116 and TCP
Both the connection between 116 and the liquid crystal display panel 118 is high-density fine wiring. The circuit board 114 is a hard base material having no flexibility, and the gasket 111 is used for the circuit board 1.
If 14 is inadvertently and strongly pressed, the stress of this pressing pressure will cause a stress at the connecting portion between the circuit board 114 and the TCP 116 or at T.
Focus on the connection between the CP 116 and the liquid crystal display panel 118,
The wiring may be broken at these connecting portions.

(2) Light Leakage of Backlight Light The metal frame 112 has a role of holding the liquid crystal display panel 118 and a role of preventing light leak of the backlight light. In the vicinity of the liquid crystal display panel 118, the specifications of the clearance between the metal frame 112 and the liquid crystal display panel 118 are strictly limited in order to prevent light leakage of the backlight to the outside. Gasket 11
If you press the metal frame 112 strongly with 1, the metal frame 1
The clearance amount L2 between the liquid crystal display panel 118 and the liquid crystal display panel 118 is increased to cause a light leakage defect.

The present invention has been made to solve the above problems. A first object of the present invention is to increase the contact pressure of a conductive seal to improve the electrical connectivity of the conductive seal. , To obtain a noise reduction structure that more effectively reduces electromagnetic interference and electromagnetic radiation of a circuit board.

A second object is to increase the contact pressure of the conductive seal to improve the electrical connectivity of the conductive seal, thereby more effectively reducing electromagnetic interference and electromagnetic radiation of the circuit board. At the same time, it is to obtain a liquid crystal display device capable of preventing disconnection of connection wiring between the film member and the liquid crystal display panel and leakage of backlight light.

[0014]

Noise reduction structure of the problem-solving means for the present invention is formed on the circuit board in the liquid crystal display device, the circuit
There is a metal frame arranged facing the circuit board with a gap from a metal pattern region connected to the ground wiring of the board, and the metal frame is compressed and deformed into the gap.
In contact with the conductive seal to be inserted turned to the metal pattern region electrically Te, 3 at the contact surface is a surface roughness Rmax of the metal frame in contact with at least said conductive seal
It is characterized in that it is processed to 10 μm.

Here, the surface roughness Rmax value is determined according to JIS B
What was measured by the method according to 0601 is used.

[0016]

[0017]

Further, it is preferable that a plurality of the metal pattern regions are formed so as to sandwich the insulating region of the circuit board.

Further, it is preferable that the conductive seal is a gasket having mesh metal, conductive rubber or metal spring.

Further, the liquid crystal display device of the present invention includes a circuit board, and a ground wiring formed on the circuit board.
A metal pattern region connected to the line, a liquid crystal display panel electrically connected to the circuit board via a film member,
A backlight light source and a metal frame that covers the periphery of the liquid crystal display panel and is disposed to face the circuit board with a gap therebetween, and the metal frame is inserted into the gap by being deformed by compression. It is characterized in that the contact surface of the metal frame, which is in contact with the conductive seal and is electrically connected to the metal pattern region and which is in contact with the conductive seal, is processed to have a surface roughness Rmax value of 3 to 10 μm. To do.

Here, the surface roughness Rmax value is determined according to JIS B
What was measured by the method according to 0601 is used.

[0022]

Further, it is preferable that the film member is connected to the liquid crystal display panel by wiring having a pitch of 100 μm or less.

Further, it is preferable that the metal frame shields light emitted from the backlight light source.

[0025]

Further, it is preferable that a plurality of the metal pattern regions are formed so as to sandwich the insulating region of the circuit board.

Further, it is preferable that the conductive seal is a gasket having mesh metal, conductive rubber or metal spring.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A noise reduction structure and a liquid crystal display device using the same will be described below with reference to the accompanying drawings.

First, the module configuration of the liquid crystal display device will be described. As shown in FIGS. 1 and 2, the surface of the circuit board (source circuit board) 4 is plated with a metal film (Au film) having an area of about 3 mm × 10 mm. It is preferable that a plurality of such metal film pattern regions (hereinafter referred to as ground patterns 5) are formed with the insulating region of the circuit board 4 interposed therebetween. The ground pattern 5 is connected to the ground wiring (not shown) in the circuit board 4.

On the other hand, the circuit board 4 is connected to the lower glass substrate 16 of the liquid crystal display panel 8 by fine wiring (pitch of about 100 μm or less) via the TCP 6 mounted with the driver IC 7.

The liquid crystal display panel 8 is held by an upper metal frame 2 (hereinafter referred to as a metal frame) made of stainless steel and a lower metal frame 3. Here, the light diffusion plate 9, the lens sheet 10, the light guide plate 11 and the reflection layer 12 are arranged between the liquid crystal display panel 8 and the lower metal frame 3, and between the circuit board 4 and the lower metal frame 3. A backlight light source 13 and a resin holding material 17 are arranged. Further, an opening 14 is provided in the center of the metal frame 2 so that the display portion of the liquid crystal display panel 8 can be visually recognized. Further, while preventing light leakage, the backlight source 13
In order to block the extraordinary light emitted from the liquid crystal display panel 8, the upper glass substrate 15 of the liquid crystal display panel 8 has a ring-shaped metallic frame 2 around
Is covered with. Upper glass substrate 15 and metal frame 2
In the overlapping portion, the width L1 of the overlapping portion is about 2 mm.
The clearance amount L2 between the upper glass substrate 15 and the metal frame 2 is an important design specification in terms of preventing light leakage. The light from the backlight light source 13 is made uniform by the light guide plate 11 into a planar shape, and then enters the liquid crystal display panel 8. This incident light is emitted or shut out to the outside by a liquid crystal (not shown) between the upper and lower glass substrates 15 and 16 and an optical shutter function of a polarizing plate (not shown) attached to the upper and lower glass substrates 15 and 16. .

Between the ground pattern 5 of the circuit board 4 and the metal frame 2, a conductive seal typified by the gasket 1 (shield foam made by Japan Zipper Tubing Co., Ltd.) is inserted. This gasket 1
Is a 3 mm × 5 mm × 3.5 mm rectangular sponge material wrapped with mesh metal (polyester cloth having two layers of copper and nickel plated on its surface).
As the gasket 1, in addition to a sponge wound with a mesh metal, for example, conductive rubber (rubber mixed with metal powder) or a metal spring may be used.

By design, the gap between the metal frame 2 and the circuit board 4 is about 1.5 mm, and the gasket 1
Has a height of about 3.5 mm. Therefore, the metal frame 2
When the gasket 1 is inserted between the ground pattern 5 and the ground pattern 5, the gasket 1 is compressed by about 2 mm.
By doing so, the gasket 1 is in close contact with the ground pattern 5 and also in close contact with the metal frame 2, and the ground pattern 5 and the metal frame 2 are electrically connected via the gasket 1.

Next, a verification experiment for improving the electrical connection characteristics between the gasket 1 and the metal frame 2 will be described.

Gasket 1 for the metal frame 2
By roughening the connection surface (adhesion surface) with and to improve the connection characteristics between the gasket 1 and the metal frame 2, the reliability of the electrical connection between the gasket 1 and the metal frame 2 is also improved. It was verified by the experiments shown below that it can be improved.

First, the surface roughness Rmax of the connection surface of the metal frame made of stainless steel, which closely adheres to the gasket, is Rmax = 3 μm.
Treated metal frame and surface roughness Rmax value = 10 μm
With a liquid crystal display device using a metal frame treated to
A liquid crystal display device using a metal frame without rough surface treatment (surface roughness Rmax value = 1 μm) was prepared. As a method of roughening the surface, a method of roughening the contact surface of a stainless steel metal frame which comes into contact with the conductive seal with a grinding wheel having a roughness of # 150 to 180 was adopted. The surface roughness was evaluated by the maximum value Rmax of the surface roughness measurement results according to JIS B0601.

With respect to the above-mentioned three types of liquid crystal display devices, the intensity of electromagnetic wave noise at a frequency of 46.5 MHz was measured in an anechoic chamber for measuring radiation noise (the distance between the measurement antenna and the liquid crystal display device was 3 m). Surface roughness Rmax value = 1 in order to evaluate the data variation of each liquid crystal display device product.
Three liquid crystal display devices each having a surface roughness Rmax value of 3 μm and a surface roughness Rmax value of 10 μm were sampled and measured.

The measurement results are shown in FIG. In FIG. 3, the horizontal axis represents the surface roughness Rmax (μm). The vertical axis is the electromagnetic wave intensity of noise, and this unit is expressed in electric field intensity (dBμV
/ M). In FIG. 3, the average value (● mark) of the electromagnetic wave intensity data is plotted, and the width of the maximum value and the minimum value of the intensity data is indicated by a vertical bar.

From the above experimental results, the surface roughness was 3 μm, 10
For μm, when roughening is not applied (roughness 1 μm)
It was found that the average value of the electromagnetic wave intensity can be reduced and the variation between the products can be improved as compared with.

For example, as shown in FIG. 4A, when the surface of the metal frame 2 is smooth, the contact pressure between the gasket 1 and the metal frame 2 is equal on the entire contact area A between the two. The value is almost equal to the value obtained by dividing the compression reaction force of the gasket 1 by the cross-sectional area of the gasket 1. On the other hand, as shown in FIG. 4B, if the surface of the metal frame 2 is a rough surface, in the contact area B between the gasket 1 and the metal frame 2, a convex portion of the uneven surface of the metal frame 2 is formed. Therefore, the contact pressure between the gasket 1 and the metal frame 2 is locally increased. By this,
It is considered that the ground pattern potential of the circuit board 4 can be stably maintained at a constant potential (frame potential) through the gasket 1 and the generation of electromagnetic noise can be prevented.

Therefore, when the surface of the metal frame is roughened, the connection characteristics between the gasket and the metal frame are improved, the electromagnetic wave intensity can be reduced, and the variation between products can be reduced. The reliability of can be improved.

The surface roughness Rmax value should be 3 μm or more, and even if the surface is further roughened, for example, Rmax10.
Even with μm, the effect of reducing the electromagnetic wave intensity is the same, and it can be seen that electromagnetic wave noise can be stably eliminated if the Rmax value is within the range of 3 to 10 μm. If the surface roughness is too large, the mechanical strength of the metal frame is likely to be impaired. Therefore, it can be said that the surface roughness Rmax value is preferably set to 10 μm or less from the viewpoint of maintaining the strength of the metal frame and the experimental results.

In this embodiment, the contact surface of the metal frame which comes into contact with the conductive seal has a surface roughness Rmax value of 3 to 10.
Although it is processed to have a surface roughness Rmax of 3 μm to 10 μm, the surface roughness Rmax on the ground pattern surface side is desired to be 3 to 10 μm for the same reason.

As described above, the surface of the metal frame of the circuit board that contacts the gasket is roughened (Rmax
When the liquid crystal display device is mounted on a personal computer, the EMI countermeasure for the personal computer can be more effectively performed.

[0045]

According to the inventions according to claims 1 to 3 ,
In the connection between the conductive seal and the metal frame, the contact surface of the metal frame has a surface roughness Rmax value of 3 to 10 μm.
By treating m, the contact pressure of the conductive seal can be increased and the electrical connectivity has been improved. Therefore, it is possible to obtain a noise reduction structure that more effectively reduces electromagnetic interference and electromagnetic radiation of the circuit board.

According to the inventions according to claims 4 to 8 , in the connection between the conductive seal and the metal frame, the contact surface of the metal frame has a surface roughness Rmax value of 3 to 3.
By treating to 10 μm, the contact pressure of the conductive seal can be increased, and the electrical connectivity has been improved, so that electromagnetic interference and electromagnetic radiation of the circuit board can be more effectively reduced, and fine wiring (pitch About 100μ
(m or less), it is possible to obtain a liquid crystal display device capable of preventing disconnection of connection wiring between the film member and the liquid crystal display panel and preventing light leakage of backlight light.

[Brief description of drawings]

FIG. 1 is a main part plan view showing an embodiment of a liquid crystal display device of the present invention.

2 is a cross-sectional view of the liquid crystal display device seen from a cross section taken along line I-I shown in FIG.

FIG. 3 is a diagram showing the relationship between the surface roughness of the metal frame that contacts the gasket and the electromagnetic wave intensity of noise emitted from the liquid crystal display device.

FIG. 4 (a) is a diagram for explaining contact pressure between a gasket and a metal frame whose surface is not rough, FIG.
(B) is a figure explaining contact pressure between a gasket and a metal frame whose surface is rough.

FIG. 5 is a schematic diagram of a personal computer (personal computer) including a liquid crystal display device.

FIG. 6 is a plan view of an essential part showing a conventional liquid crystal display device.

7 is a cross-sectional view taken along the line II-II of the liquid crystal display device shown in FIG.

[Explanation of symbols]

1 gasket 2 Upper metal frame (metal frame) 3 Lower metal frame 4 circuit board 5 ground patterns 6 TCP 7 Driver IC 8 Liquid crystal display panel 9 Light diffuser 10 lens sheet 11 Light guide plate 12 Reflective layer 13 Backlight light source 14 openings 15 Upper glass substrate 16 Lower glass substrate 17 Resin holding material

Continuation of front page (56) Reference JP-A-11-352506 (JP, A) JP-A-6-265922 (JP, A) JP-A-8-201781 (JP, A) JP-A-58-175220 (JP , A) Actual Kaihei 6-50035 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/1333 G02F 1/1345 G09F 9/00 348

Claims (8)

(57) [Claims] 1. A metal frame, which is formed on a circuit board in a liquid crystal display device and has a metal pattern region connected to a ground wiring of the circuit board and is arranged to face the circuit board with a gap therebetween. The metal frame is in the gap
The contact surface of the metal frame, which comes into contact with the conductive seal inserted by being compressed and deformed to be electrically connected to the metal pattern region, and which is in contact with at least the conductive seal, has surface roughness R
A noise reduction structure characterized by being processed to a maximum value of 3 to 10 μm. 2. A noise reducing structure of claim 1 Symbol mounting the metal pattern areas across the insulating region of the circuit board is characterized in that it is formed in plural. 3. The noise reduction structure of claim 1 or 2, wherein said conductive seal is a gasket having a mesh metal, conductive rubber or metal spring. 4. A circuit board, formed on the circuit board ,
A metal pattern region connected to the ground wiring of the circuit board, a liquid crystal display panel electrically connected to the circuit board via a film member, a backlight light source, and covering the periphery of the liquid crystal display panel and separating a gap. And a metal frame arranged to face the circuit board, the metal frame comes into electrical contact with the metal pattern region by coming into contact with a conductive seal inserted by being compressed and deformed in the gap, A liquid crystal display device, wherein at least a contact surface of a metal frame in contact with the conductive seal is treated to have a surface roughness Rmax value of 3 to 10 μm. 5. The liquid crystal display device according to claim 4 , wherein the film member is connected to the liquid crystal display panel by wiring having a pitch of 100 μm or less. Wherein said metal frame, according to claim 4 or 5 a liquid crystal display device according to, characterized in that shields light emitted from the backlight source. Wherein said circuit liquid crystal display device according to claim 4, 5 or 6, wherein the metal pattern regions sandwiching the insulating region of the substrate is characterized in that it is formed in plural. 8. The liquid crystal display device according to claim 4 , 5 , 6 or 7 , wherein the conductive seal is a gasket having mesh metal, conductive rubber or a metal spring.