JP2002107696A - Noise reducing structure and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide noise reducing structure more effectively reducing electromagnetic disturbance and electromagnetic radiation of a circuit substrate by increasing contact pressure of a conductive sealing material and improving electric connectivity of the conductive sealing material. SOLUTION: The noise reducing structure is provided with a metal frame placed opposite to the circuit substrate holding a gap between a metal pattern region formed on the circuit substrate in a liquid crystal display device and itself. The metal frame is brought into contact with the conductive sealing material inserted into the gap and is electrically connected to the metal pattern region. At least a contact surface of the metal frame brought into contact with the conductive sealing material is treated so as to have 3-10 μm surface roughness Rmax value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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) having a liquid crystal display device. PC 1
00 signal line, ground line and power supply line
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.
Together with the case 102. Note that the image of the liquid crystal display device 103 is controlled by applying a video signal transmitted from the signal lines of the signal line group 101 to the liquid crystal display device 103.

If high-frequency noise leaks out of the device through the signal line group 101, it may cause a malfunction (EMI) of a personal computer. In addition, unless a proper shield is applied to the wiring or the substrate through which the video signal is transmitted, the wiring or the substrate itself functions as an antenna, and thereby, the E or E
It promotes MI and also loses the ability (immunity) of eliminating performance degradation due to external noise.

As a countermeasure against noise of the liquid crystal display device 103, the internal components (substrate or IC) are conventionally electrically connected to the metal frame 104 of the liquid crystal display device 103 which is a ground (potential reference point) to improve the immunity and EMI. I'm trying. For example, a plurality of ground patterns having a ground potential are provided on the surface of a circuit board to which a video signal is applied, and the ground pattern and the metal frame are electrically connected to each other via a flexible conductive seal (gasket). Let me. As a result, the ground potential of the circuit board is kept constant over the entire surface of the board, and a design for improving the immunity of the circuit board and a design for not providing the antenna function of radiating electromagnetic waves to the circuit board are implemented.

[0005]

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

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

The gasket 11 inserted between the circuit board (source circuit board) 114 and the 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. Thereby, the metal frame 1
Electrical conduction is provided between the ground pattern 115 and the ground pattern 115 through a gasket 111. If there is a problem in the reliability of the electrical connection, the contact resistance increases and electromagnetic noise cannot be sufficiently reduced. Here, it is known that increasing the contact pressure between the electric contacts can reduce the contact resistance of the electric contacts (see FIG. 5 of Japanese Patent Application Laid-Open No. 58-175220).

Similarly, in a liquid crystal display device, considering the deterioration of the elastic force of the gasket during a high temperature and high humidity test and the temporal change in the degree of adhesion between the gasket and the frame due to external vibration, etc. It is presumed that increasing the contact pressure at the interface is important for improving the reliability of the electrical connection. Furthermore, if the contact pressure is low,
It is known that the fluctuation of the contact resistance with respect to the change of the contact pressure is increased. Therefore, it is considered that even a slight pressure difference at the contact portion may cause a product variation of the contact resistance. However, Japanese Patent Application Laid-Open No.
Even with reference to Japanese Patent Publication No. 20, no specific method for increasing the contact pressure of the gasket can be found.

Accordingly, the present inventors have found that increasing the elastic reaction force of the gasket by using a harder gasket or using a large-sized gasket and thereby obtaining a high contact pressure can reduce electromagnetic wave noise. I thought it was effective. However, on the other hand, if the improvement of the contact pressure simply depends on the improvement of the hardness and shape of the gasket,
The following problems are also a concern.

(1) Disconnection between TCP (Tape Carrier Package) and the board The circuit board 114 is provided with a driver I as shown in FIGS.
It is connected to a liquid crystal display panel 118 via a film called TCP 116 on which C117 is mounted. Connection between circuit board 114 and TCP 116 and TCP
The connection between the liquid crystal display panel 118 and the liquid crystal display panel 118 is a high-density fine wiring. The circuit board 114 is a rigid base material having no flexibility.
14 is inadvertently pressed strongly, the stress of this pressing pressure is applied to the connection between the circuit board 114 and the TCP 116 and the T
Focusing on the connection between the CP 116 and the liquid crystal display panel 118,
The wiring may be broken at these connection portions.

(2) Light Leakage of Backlight Light The metal frame 112 has a function of holding the liquid crystal display panel 118 and a function of preventing light leakage of the backlight light. Around 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 leakage of backlight light to the outside. Gasket 11
1 strongly presses the metal frame 112, the metal frame 1
The clearance L2 between the liquid crystal display panel 118 and the liquid crystal display panel 118 is increased, which causes a light leakage defect.

The present invention has been made to solve the above problems, and 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. Another object of the present invention is to provide a noise reduction structure that more effectively reduces electromagnetic interference and 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 radiation of the circuit board. At the same time, an object of the present invention is to provide a liquid crystal display device capable of preventing disconnection of connection wiring between a film member and a liquid crystal display panel and light leakage of backlight light.

[0014]

According to the present invention, there is provided a noise reduction structure having a metal frame disposed opposite to a circuit board with a gap from a metal pattern area formed on the circuit board in a liquid crystal display device. The metal frame contacts the conductive seal inserted into the gap to be electrically conductive with the metal pattern region, and at least the contact surface of the metal frame in contact with the conductive seal has a surface roughness Rmax value. It is characterized by being processed to 3 to 10 μm.

Here, the surface roughness Rmax value is determined according to JIS B
No. 0601 is used.

It is preferable that the conductive seal is compressed and deformed and inserted into the gap.

Preferably, the metal pattern region is connected to a ground wiring of the circuit board.

Preferably, a plurality of the metal pattern regions are formed with an insulating region of the circuit board interposed therebetween.

Further, the conductive seal is preferably a gasket having a mesh metal, a conductive rubber or a metal spring.

Also, the liquid crystal display device of the present invention comprises a circuit board, a metal pattern region formed on the circuit board, a liquid crystal display panel electrically connected to the circuit board via a film member, and 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 contacts a conductive seal inserted into the gap. At least a contact surface of the metal frame, which is electrically connected to the metal pattern region and is in contact with the conductive seal, is processed to have a surface roughness Rmax of 3 to 10 μm.

Here, the surface roughness Rmax value is determined according to JIS B
No. 0601 is used.

Preferably, the conductive seal is compressed and deformed and inserted into the gap.

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.

It is preferable that the metal pattern region is connected to a ground wiring of the circuit board.

Preferably, a plurality of the metal pattern regions are formed with an insulating region of the circuit board interposed therebetween.

Further, the conductive seal is preferably a gasket having a mesh metal, a conductive rubber or a metal spring.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a noise reduction structure and a liquid crystal display device using the same will be described 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 a 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: about 100 μm or less) via the TCP 6 on which the driver IC 7 is mounted.

The liquid crystal display panel 8 is held by a stainless steel upper metal frame 2 (hereinafter referred to as a metal frame) and a lower metal frame 3. Here, a light diffusion plate 9, a lens sheet 10, a light guide plate 11 and a 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. Is provided with a backlight light source 13 and a resin holder 17. An opening 14 is provided at the center of the metal frame 2 so that the display section of the liquid crystal display panel 8 can be visually recognized. In addition to preventing light leakage, the backlight light source 13
The periphery of the upper glass substrate 15 of the liquid crystal display panel 8 has
Covered with. Upper glass substrate 15 and metal frame 2
, The width L1 of the overlapping portion is about 2 mm.
The clearance 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 in a planar manner, and then enters the liquid crystal display panel 8. The 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. .

A conductive seal typified by a gasket 1 (a shield form manufactured by Nippon Zipper Tubing Co., Ltd.) is inserted between the ground pattern 5 of the circuit board 4 and the metal frame 2. This gasket 1
Is a rectangular sponge material of 3 mm × 5 mm × 3.5 mm wound with a mesh metal (two-layered copper and nickel plated on the surface of a polyester cloth).
In addition, as the gasket 1, besides a sponge wound with mesh metal, for example, conductive rubber (rubber mixed with metal powder) or a metal spring may be used.

The gap between the metal frame 2 and the circuit board 4 is about 1.5 mm in design, 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 gasket 1 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 metal frame 2
The connection characteristics between the gasket 1 and the metal frame 2 are improved by treating the connection surface (close contact surface) of the gasket 1 with a rough surface, and the reliability of the electrical connection between the gasket 1 and the metal frame 2 is also improved. The following experiment verified that it can be improved.

First, the connection surface of the metal frame made of stainless steel which is in close contact with the gasket is formed with a surface roughness Rmax value of 3 μm.
Treated metal frame and surface roughness Rmax value = 10 µm
Along with a liquid crystal display device using a metal frame treated to
A liquid crystal display device using a metal frame having no roughened surface (surface roughness Rmax value = 1 μm) was prepared. As a rough surface treatment method, a method of roughening the contact surface of a stainless steel metal frame which comes into contact with the conductive seal with a polishing grindstone having a roughness of # 150 to # 180 was adopted. In addition, the said surface roughness evaluated the maximum value Rmax value of the surface roughness measurement result based on JISB0601.

With respect to the 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). In order to evaluate data variation for each product of the liquid crystal display device, a surface roughness Rmax value = 1
Sampling measurement was performed on three liquid crystal display devices each having a μm, a surface roughness Rmax value of 3 μm, and a surface roughness Rmax value of 10 μm.

FIG. 3 shows the measurement results. In FIG. 3, the horizontal axis represents the surface roughness Rmax (μm). The vertical axis represents the electromagnetic wave intensity of noise, and this unit is expressed as electric field intensity (dBμV).
/ M). In FIG. 3, the average value (marked by ●) 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.

According to the above experimental results, the surface roughness was 3 μm,
For μm, when the surface is not roughened (roughness 1 μm)
It has been found that the average value of the electromagnetic wave intensity can be reduced and the variation between products can be improved as compared with the case of the above.

For example, as shown in FIG. 4A, if the surface of the metal frame 2 is smooth, the contact pressure between the gasket 1 and the metal frame 2 over the entire contact area A is equal. That value is substantially 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 rough, in the contact area B between the gasket 1 and the metal frame 2, the convex portion of the uneven surface of the metal frame 2 is formed. As a result, the contact pressure between the gasket 1 and the metal frame 2 locally increases. This allows
It is considered that the ground pattern potential of the circuit board 4 can be stably maintained at a constant potential (frame potential) via the gasket 1 and 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 connection between the products is reduced with less variation between products. Can be improved in reliability.

The surface roughness Rmax may be 3 μm or more.
The effect of reducing the electromagnetic wave intensity is the same even at μm, and it can be seen that the electromagnetic wave noise can be stably eliminated if the Rmax value is between 3 and 10 μm. If the surface roughness is too large, the mechanical strength of the metal frame tends to be impaired. Therefore, it can be said that it is preferable to set the surface roughness Rmax to 10 μm or less from the viewpoint of the experimental results and the maintenance of the strength of the metal frame.

In the present embodiment, the contact surface of the metal frame in contact with the conductive seal has a surface roughness Rmax of 3 to 10
Although it is treated to a thickness of μm, it is considered that it is desirable to set the surface roughness Rmax value on the ground pattern surface side to 3 to 10 μm for the same reason.

As described above, the surface of the metal frame of the circuit board in contact with the gasket is subjected to the roughening treatment (Rmax
When the liquid crystal display device is mounted on a personal computer, EMI countermeasures of the personal computer can be more effectively performed.

[0045]

According to the invention according to claims 1 to 5,
In the connection between the conductive seal and the metal frame, the contact surface of the metal frame has a surface roughness Rmax of 3 to 10 μm.
By treating to m, the contact pressure of the conductive seal can be increased, and the electrical connectivity has been improved, so that it is possible to obtain a noise reduction structure that more effectively reduces electromagnetic interference and electromagnetic radiation of the circuit board.

Further, according to the invention of claims 5 to 12, in the connection between the conductive seal and the metal frame, the contact surface of the metal frame has a surface roughness Rmax of 3 to 10%.
By processing to 10 μm, the contact pressure of the conductive seal can be increased, and this electrical connectivity has been improved, so that the electromagnetic interference and radiation of the circuit board can be reduced more effectively, and the 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 the drawings]

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

FIG. 2 is a cross-sectional view of the liquid crystal display device as viewed from a cross section taken along line II of FIG.

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

FIG. 4 (a) is a view for explaining a contact pressure between a gasket and a metal frame having a rough surface, and FIG.
(B) is a figure explaining the contact pressure between a gasket and a metal frame with a rough surface.

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 a main part showing a conventional liquid crystal display device.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasket 2 Upper metal frame (metal frame) 3 Lower metal frame 4 Circuit board 5 Ground pattern 6 TCP 7 Driver IC 8 Liquid crystal display panel 9 Light diffusing plate 10 Lens sheet 11 Light guide plate 12 Reflective layer 13 Back light source 14 Opening 15 Upper glass substrate 16 Lower glass substrate 17 Resin holding material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 HA40 JA10 LA41 MA06Y PA17 QA10 TA07 TA13 TA18 2H092 GA47 GA50 GA56 NA25 PA04 PA09

Claims (12)

[Claims] 1. A liquid crystal display device, comprising: a metal frame disposed on a circuit board in a liquid crystal display device so as to face the circuit board with a gap therebetween, and the metal frame is inserted into the gap. It is electrically conductive with the metal pattern region in contact with the conductive seal, and at least the contact surface of the metal frame in contact with the conductive seal is processed to have a surface roughness Rmax of 3 to 10 μm. Noise reduction structure. 2. The noise reduction structure according to claim 1, wherein the conductive seal is inserted after being compressed and deformed. 3. The noise reduction structure according to claim 1, wherein the metal pattern region is connected to a ground wiring of the circuit board. 4. The noise reduction structure according to claim 1, wherein a plurality of said metal pattern regions are formed with an insulating region of said circuit board interposed therebetween. 5. The noise reduction structure according to claim 1, wherein the conductive seal is a gasket having mesh metal, conductive rubber, or a metal spring. 6. A circuit board, a metal pattern region formed on the circuit board, a liquid crystal display panel electrically connected to the circuit board via a film member, a backlight light source, and a periphery of the liquid crystal display panel. And a metal frame disposed opposite the circuit board with a gap therebetween, the metal frame being in contact with a conductive seal inserted into the gap to electrically connect to the metal pattern region. A liquid crystal display device wherein a contact surface of a metal frame that is conductive and contacts at least the conductive seal is processed to have a surface roughness Rmax of 3 to 10 μm. 7. The liquid crystal display device according to claim 6, wherein the conductive seal is inserted after being compressed and deformed. 8. The liquid crystal display device according to claim 6, wherein the film member is connected to the liquid crystal display panel with a wiring having a pitch of 100 μm or less. 9. The liquid crystal display device according to claim 6, wherein the metal frame blocks light emitted from the backlight light source. 10. The liquid crystal display device according to claim 6, wherein the metal pattern region is connected to a ground line of the circuit board. 11. The liquid crystal display device according to claim 6, wherein a plurality of the metal pattern regions are formed with an insulating region of the circuit board interposed therebetween. 12. The liquid crystal display device according to claim 6, wherein the conductive seal is a gasket having mesh metal, conductive rubber, or a metal spring.