JP3650044B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a direct-type backlight in which a plurality of linear lamps such as fluorescent lamps are arranged directly under a back surface of a liquid crystal panel.
[0002]
[Prior art]
Until now, CRTs have been mainly used for color televisions. Recently, however, liquid crystal televisions have been put into practical use by taking advantage of thin liquid crystal display devices and low power consumption. In a liquid crystal display device for a television or a large monitor, a TFT type LCD using a TFT as a switching element for driving each pixel has become mainstream. In the case of this TFT type, the scanning lines and signal lines connected to the TFTs are formed in a matrix on one glass substrate constituting the liquid crystal panel, and the input terminals for these scanning lines and signal lines are arranged on the peripheral edge of the glass substrate. doing. Since there are generally more signal lines than scanning lines, the input terminals of the signal lines are concentrated on the long side edge of the glass substrate, and the input terminals of the scanning lines are concentrated on the short edge of the glass substrate. . A source driving circuit board is connected to the input terminal of the signal line via TAB, and a gate driving circuit board is connected to the input terminal of the scanning line via TAB, and a signal is supplied from each driving circuit board to each line. . A control circuit board is provided separately from the source drive circuit board and the gate drive circuit board, and the control circuit board and each drive circuit board are electrically connected by a flexible board.
[0003]
Backlights arranged on the back side of the liquid crystal panel include a side edge type in which a linear lamp is arranged on the side surface of the light guide plate and a direct type in which a light source is arranged directly under the back side of the liquid crystal panel. Side-edge type backlights are mainly used for liquid crystal display devices such as notebook computers and small portable terminals because they are particularly thin. However, liquid crystal display devices for liquid crystal televisions and large monitors require particularly high brightness. Mainly direct type backlight is adopted. In the case of the direct type, a plurality of light sources such as fluorescent lamps are arranged on the back side of the liquid crystal panel so as to face the liquid crystal panel, and a diffusion plate, a light control plate, and the like are arranged between the light source and the liquid crystal panel. Fluorescent lamps are housed in a back case made of, for example, Al. However, in the case of the direct type, fluorescent light is supplied in order to prevent uneven brightness by supplying light of uniform intensity to the entire display portion of the liquid crystal panel. It is necessary to adjust the distance between the lamp and the liquid crystal panel, and if the number of fluorescent lamps decreases, the distance between the lamp and the liquid crystal panel will be increased accordingly. It has a shape that protrudes greatly on the back side of the liquid crystal panel. The light from the fluorescent lamp is efficiently supplied to the liquid crystal panel by causing the inner surface of the rear case to act as a reflector, or by disposing a reflector between the rear case and the fluorescent lamp.
[0004]
FIG. 7 is a rear perspective view of the liquid crystal display device. Reference numeral 50 denotes a frame for housing and supporting the liquid crystal panel, 51 is a metal back case, and 52 is a front cover having an open display portion. The frame 50 containing the liquid crystal panel is sandwiched between the back case 51 and the front cover 52, and the fixing portion 53 at the periphery of the front cover 52 is bent toward the back case 51 to be integrated. A control circuit board is attached to the back surface of the back case 51 and covered with a protective case 54. 55 is a flexible board that electrically connects the source drive circuit board attached to the liquid crystal panel and the control circuit board attached to the back case 51, and 56 is an electrical connection between the gate drive circuit board and the control circuit board. It is a flexible board and supplies each signal from the control circuit board.
[0005]
[Problems to be solved by the invention]
Conventionally, the flexible substrates 55 and 56 are left free without being fixed. However, in the case of a liquid crystal display device for a TV or a large monitor, the number of pixels increases with the increase in size and definition, so that the number of signal lines increases, and in particular, the flexible substrate 55 connected to the source drive circuit substrate becomes larger. End up. Therefore, the flexible substrate 55 is easily caught when the liquid crystal display device is handled, and there is a problem that the connection failure or breakage of the flexible substrate 55 occurs.
[0006]
There is also a method of fixing the back case to the flexible substrate with double-sided tape etc. In this case, it is necessary to remove or replace the double-sided tape every time the maintenance of the liquid crystal display device is performed, and there is a disadvantage that the maintainability is poor. It was.
[0007]
Further, in the case of conventional flexible substrates, EMI (Electromagnetic Interference) measures have not been sufficient. Since the liquid crystal display device for TV is large and requires high image quality, EMI countermeasures for the flexible substrate 55, which has become larger with the increase in the number of pixels, have become more important than ever, and there is a need for such countermeasures.
[0008]
Accordingly, an object of the present invention is to propose a liquid crystal display device in which a flexible substrate can be fixed easily and detachably and sufficient EMI countermeasures are taken.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a liquid crystal panel in which liquid crystal is sealed between a pair of substrates and scanning lines and signal lines are arranged in a matrix on one substrate, and a plurality of liquid crystal panels arranged directly below the liquid crystal panel. A liquid crystal display device comprising a light source, a back case that houses the light source and covers the back side of the liquid crystal panel, and a front cover that is disposed on the front surface of the liquid crystal panel and is fixed to the back case is mounted on the liquid crystal panel. The first control circuit board for supplying image signals to the signal lines, the second control circuit board disposed on the back surface of the back case, the first control circuit board, and the second control circuit board. And a fixing means for detachably fixing the flexible board to the back case.
[0010]
Further, the fixing means of the present invention includes a holding portion formed on the back case and a protective plate that is detachably supported by the holding portion, and the flexible substrate is attached to the back surface by the protective plate when the protective plate is attached to the holding portion. It is characterized by being held in a state of being pressed against the case.
[0011]
With the above configuration, the flexible substrate can be easily attached to the rear case, the flexible substrate can be prevented from being damaged during the manufacturing and maintenance of the liquid crystal display device, the assembling workability is improved, and the storage space for the flexible substrate is reduced. . In addition, the flexible substrate can be easily removed during maintenance, and the maintainability is improved.
[0012]
Further, the present invention is characterized in that the holding portion is formed by cutting and raising a part of the back case, and the protective plate is made of resin and bendable. With the above configuration, an inexpensive fixing means can be realized.
[0013]
The present invention also includes a rear case in which at least a portion to which the flexible substrate is pressed is made of metal, and a flexible substrate having a metal film for EMI countermeasures, and the flexible substrate is fixed to the rear case by fixing means. The metal film is electrically connected to the metal portion of the back case.
[0014]
With the above configuration, the metal film for EMI countermeasure of the flexible substrate is grounded via the back case, and the EMI countermeasure of the flexible substrate is taken.
[0015]
In addition, the present invention is characterized in that a metal foil bonded over most of the flexible substrate is used as the metal film for the EMI countermeasure of the flexible substrate. With the above configuration, EMI countermeasures can be taken at low cost.
[0016]
Further, the present invention is characterized in that a metal mesh that covers most of the flexible substrate is used as a metal film for EMI countermeasures of the flexible substrate.
[0017]
In addition, the present invention is characterized in that as a metal film for EMI countermeasures of a flexible substrate, a flexible substrate is made into a multilayer and a GND pattern formed over the single layer is used.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a rear perspective view of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a front view of the liquid crystal display device, FIG. 3 is a front view when a front cover of the liquid crystal display device is removed, and FIG. FIG. 5 is an enlarged schematic view of region A in FIG. 1, and FIG. 6 is an enlarged schematic view of region B in FIG.
[0019]
In the liquid crystal panel 1, a pair of glass substrates 5 and 6 are bonded together in a hollow shape, and liquid crystal is sealed between the glass substrates 5 and 6. A plurality of signal lines and a plurality of scanning lines are formed in a matrix on one glass substrate 5, TFTs are provided at intersections between the signal lines and the scanning lines, and pixel electrodes are provided in regions surrounded by the signal lines and the scanning lines, respectively. Provide. The TFT has a gate electrode connected to the scanning line, a source electrode connected to the signal line, a drain electrode connected to the pixel electrode, and the TFT is turned on / off by a scanning signal supplied to the scanning line and supplied to the signal line. A voltage based on the image signal is supplied to the pixel electrode. On the other glass substrate 6, a light-shielding film is formed at a portion facing the scanning line or the signal line, and a color filter of a predetermined color is formed according to each pixel. A common electrode is formed on the light shielding film and the color filter so as to face the pixel electrode, and the arrangement state of the liquid crystal molecules is controlled by an electric field between the common electrode and the pixel electrode.
[0020]
The glass substrate 5 on which the scanning lines and the signal lines are formed is slightly larger than the glass substrate 6 on which the color filter is formed, and one long side portion of the glass substrate 5 when the glass substrate 5 and the glass substrate 6 are bonded together. And the short side is exposed. A signal line input terminal is disposed on the exposed long side portion, and a scanning line input terminal is disposed on the exposed short side portion. The input terminal of the signal line is connected to the source drive circuit board (hereinafter referred to as source PWB) 8 which is the first control circuit board via the TAB 7, and an image signal is supplied from the source PWB 8 to the signal line. The input terminal is connected to a gate drive circuit board (hereinafter referred to as gate PWB) 10 via TAB 9, and a gate signal is supplied from the gate PWB10 to the scanning line. Both the source PWB 8 and the gate PWB 10 are formed of an elongated rectangular printed board, and each control circuit is arranged on the printed board.
[0021]
Reference numeral 3 denotes a resin frame, which has an opening in the central portion, and is provided with locking portions that are in contact with the side portions of the glass substrate 5 and are positioned at several places. When the liquid crystal panel 1 is placed on the frame body 3, the glass substrate 5 can be brought into contact with the locking portion 11 so that the liquid crystal panel 1 can be held in the frame body 3. The front cover 2 is disposed on the front side of the liquid crystal panel 1 held by the frame 3 and the rear case 4 is disposed on the rear side. The liquid crystal panel 1 and the frame 3 are sandwiched between the front cover 2 and the rear case 4. A liquid crystal display device is configured by fixing.
[0022]
The front cover 2 is formed of a metal such as Al, and a portion corresponding to the display unit of the liquid crystal panel 1 is opened. The peripheral portion of the front cover 2 is bent so as to cover the side surface of the frame body 3, and a fixing portion 12 formed by cutting out a part of the peripheral portion is provided. The front cover 2 can be fixed to the back case 4 by bending the fixing portion 12 to the back case 4 side.
[0023]
In this embodiment, a direct-type backlight is used, and a plurality of light sources such as fluorescent lamps are housed in the back case 4, and the fluorescent lamps are arranged along the longitudinal direction of the liquid crystal panel 1. Reference numeral 13 denotes a lead wire of a fluorescent lamp led to the outside of the back case 4. The back case 4 is made of a metal such as Al, and the inner surface thereof efficiently reflects the light from the fluorescent lamp. A reflector may be disposed between the fluorescent lamp and the back case 4. The shape of the back case 4 protrudes greatly on the back side so that a fluorescent lamp can be stored.
[0024]
A control circuit board (hereinafter referred to as control PWB) 14 as a second control circuit board is disposed on a part of the back surface of the back case 4, and the control PWB 14 is covered with a protective cover 15. The control PWB 14 is provided with a control circuit that supplies each signal to the source PWB 8 and the gate PWB 10. Reference numeral 16 denotes an FPC (flexible substrate) that connects the source PWB 8 and the control PWB 14, and 17 denotes an FPC (flexible substrate) that connects the gate PWB 10 and the control PWB 14. The FPC 17 is not illustrated in FIG. 1 because it is covered with the protective cover 15.
[0025]
The FPC 16 is bifurcated on the control PWB 14 side, and is provided with a wiring pattern for electrically connecting the source PWB 8 and the control PWB 14, such as Al or Cu, which is a metal film for EMI countermeasure that insulates the wiring pattern. The metal foil 18 is affixed to the FPC 16. The hatched portion of the FPC 16 in FIG. The metal foil 18 is formed on most of the surface of the FPC 16 that faces the back case 4 and the surface that does not face the back case 4, and the metal foils 18 on both sides are electrically connected. As for the method of connecting the metal foils 18 on both sides, a method of providing the metal foils 18 on both sides at the end of the FPC 16 or forming a contact hole at an appropriate position of the FPC 16 and electrically connecting the metal foils 18 on both sides at the contact hole part. You may perform the process connected to. In this embodiment, since the metal foil 18 is affixed to the FPC 16, an EMI countermeasure can be achieved with a simple configuration and at a low cost.
[0026]
Reference numeral 19 denotes a holding piece which is a holding portion formed on the back case 4, and 20 denotes a protective plate held by the holding piece 19. The holding piece 19 is formed by cutting and raising a part of the back case 4, and is positioned between both sides of the FPC 16 in the lateral width direction and the two crotch portions of the FPC 16. The protection plate 20 is formed in a horizontally long plate shape made of a resin such as plastic, can be bent with respect to the force applied from the longitudinal direction, and has a restoring force to return to the original shape when the applied force is removed. doing. The protective plate 20 may be formed of metal. However, when using a protective plate made of metal that is inferior in resilience after being bent compared to the protective plate 20 made of resin, the shape of the holding piece 19 or The arrangement needs to be suitable for a metal protective plate. When the protection plate 20 is attached to the holding piece 19, one end of the protection plate 20 is hooked on one holding piece 19 located on the side of the FPC 16, and protection is performed with the FPC 16 interposed between the protection plate 20 and the back case 4. The plate 20 is bent, the other end of the protective plate 20 is inserted into the other holding piece 19 positioned on the side of the FPC 16, and is fitted into the holding piece 19 by the restoring force of the protective plate 20. At this time, the protection plate 20 is supported and fixed by the holding piece 19, and the FPC 16 is attached to the back case 4 by the protection plate 20.
[0027]
In this embodiment, the side surface portion (portion where the FPC is located) of the back case 4 that protrudes largely on the back surface is an inclined surface, and the holding piece 19 is formed on the inclined surface to fix the FPC 16. Therefore, when the FPC 16 is fixed to the rear case 4, the FPC 16 is not deformed into an unreasonable shape, and an extra load is not applied to the protective plate 20 and the holding piece 19 that are pressing the FPC 16. Further, by making the side surface portion for fixing the FPC 16 of the back case 4 into an inclined surface, a space for forming the holding piece 19 and the like can be widened, and the manufacturing of the holding piece 19 and the attaching / detaching work of the protection plate 20 are easy. Can be done.
[0028]
When the FPC 16 is pressed against the back case 4, the metal foil 18 of the FPC 16 comes into contact with the metal back case 4, so that the metal foil 18 is grounded via the back case 4. Become. There are various ways of grounding the back case 4. For example, the back case 4 may be connected to a ground line on each circuit board, and grounded when the liquid crystal display device is attached to a housing such as a large monitor. It may be configured.
[0029]
In this embodiment, since the FPC 16 that has been free without being fixed is fixed to the back case 4, the FPC 16 is prevented from being caught and damaged during assembly or the like. Further, since the protection plate 20 can be attached to and detached from the holding piece 19, the FPC 16 can be easily detached during maintenance, and the maintainability is improved. Further, the storage space for the FPC 16 is reduced. In this embodiment, since the holding piece 19 obtained by cutting and raising a part of the back case 4 and the protective plate 20 made of resin such as plastic are used as fixing means, it can be easily manufactured at low cost, and the protective plate 20 can be attached and detached. Easy to do.
[0030]
In this embodiment, the metal foil 18 is pasted as an EMI countermeasure for the FPC 16, but the present invention is not limited to this embodiment. For example, the entire FPC 16 may be covered with a metal mesh, and the metal mesh may be brought into contact with the metal back case 4. Further, a multilayer FPC is used for the FPC 16, and a GND (ground) pattern is formed on at least an arbitrary layer, for example, on the outer layer over most of the FPC 16. Also, a method of making the back case 4 electrically conductive, such as exposing a part of the GND pattern, and electrically connecting the GND pattern of the multi-layer FPC and the back case 4 when holding the FPC 16 to the back case 4 with the protective plate 20 is also possible. Good.
[0031]
In addition, forms other than the above-described embodiment are possible as long as they do not depart from the gist of the present invention. For example, the protection plate may be screwed to the back case, or the holding piece provided separately from the back case may be fixed to the back case. In this embodiment, the TFT is used as the switching element connected to the pixel electrode. However, the present invention is not particularly limited to the TFT, and an MIM or the like may be used as the switching element.
[0032]
【The invention's effect】
According to the present invention, the flexible substrate that connects the first control circuit board mounted on the liquid crystal panel and the second control circuit board disposed on the back surface of the back case can be attached to and detached from the back case by the fixing means. As the fixing means, a holding part formed on the back case and a protective plate removably supported by the holding part are provided, and when the protective plate is attached to the holding part, the flexible board is attached by the protective plate. It is held in a pressed state on the back case. Therefore, the flexible substrate can be easily attached to the back case in a removable manner, and the flexible substrate can be prevented from being damaged during the manufacturing and maintenance of the liquid crystal display device, the assembling workability is improved, and the storage space for the flexible substrate is reduced. . In addition, the flexible substrate can be easily removed during maintenance, and the maintainability is improved.
[0033]
In addition, the holding part is formed by cutting and raising a part of the back case, and the protective plate is made of resin so that it can be bent, so it is possible to realize an inexpensive fixing means with a simple configuration, and easy attachment and detachment of the protective plate Can be done.
[0034]
In addition, when the flexible substrate is fixed to the back case, the metal film of the flexible substrate is electrically connected to the metal part of the back case, so that the metal film for EMI countermeasure of the flexible substrate is grounded through the back case, Measures against flexible substrate EMI can be achieved. Further, since the metal foil bonded over the most part of the flexible substrate is used as the metal film for EMI countermeasure, the EMI countermeasure can be achieved at a low cost with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a rear perspective view of a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a front view of the liquid crystal display device with a front cover attached.
FIG. 3 is a front view of the liquid crystal display device with a front cover removed.
FIG. 4 is a side view of a liquid crystal display device.
FIG. 5 is an enlarged schematic view of a region A in FIG.
6 is an enlarged schematic view of a region B in FIG.
FIG. 7 is a rear perspective view of a conventional liquid crystal display device.
[Explanation of symbols]
1 Liquid Crystal Panel 2 Front Cover 3 Frame 4 Back Case 8 Source PWB
14 Control PWB
16 FPC
19 Holding piece 20 Protection plate

Claims (7)

Liquid crystal is sealed between a pair of substrates, and a liquid crystal panel in which scanning lines and signal lines are arranged in a matrix on one substrate, a plurality of light sources arranged immediately below the liquid crystal panel, and the light sources are stored and A liquid crystal display device comprising a back case that covers the back side of a liquid crystal panel, and a front cover that is disposed on the front surface of the liquid crystal panel and is fixed to the back case. Electrically connecting a first control circuit board for supplying image signals to the second control circuit board, a second control circuit board disposed on the back surface of the back case, and the first control circuit board and the second control circuit board. A liquid crystal display device, comprising: a flexible substrate connected to the substrate; and fixing means for detachably fixing the flexible substrate to the back case. The fixing means includes a holding portion formed on the back case and a protective plate that is detachably supported by the holding portion, and the flexible plate allows the flexible plate when the protective plate is attached to the holding portion. The liquid crystal display device according to claim 1, wherein the substrate is held while being pressed against the back case. 3. The liquid crystal display device according to claim 2, wherein the holding portion is formed by cutting and raising a part of the back case, and the protective plate is made of resin and bendable. The rear case in which at least a portion to which the flexible substrate is pressed is made of metal, and the flexible substrate having a metal film for EMI countermeasures, and when the flexible substrate is fixed to the rear case by the fixing means, 4. The liquid crystal display device according to claim 1, wherein the metal film of the flexible substrate is electrically connected to the metal portion of the back case. 5. The liquid crystal display device according to claim 4, wherein the metal film for EMI countermeasures of the flexible substrate is a metal foil bonded over most of the flexible substrate. 5. The liquid crystal display device according to claim 4, wherein the metal film for EMI countermeasures of the flexible substrate is a metal mesh that covers most of the flexible substrate. 5. The liquid crystal display device according to claim 4, wherein the metal film for EMI countermeasures on the flexible substrate is a GND pattern formed on the flexible substrate in multiple layers.

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