JP2008145941A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of taking a satisfactory EMI countermeasure by shielding an electromagnetic wave noise radiated from an image signal circuit. <P>SOLUTION: The liquid crystal display device comprises: a liquid crystal display panel; a driving circuit substrate which is mounted on a liquid crystal display panel and drives the liquid crystal display panel; a backlight disposed on the back surface of the liquid crystal display panel; a frame-like middle frame MFM which houses the liquid crystal display panel and the backlight; and an upper frame UFM which forms a frame of exposing an effective display region of the liquid crystal display panel, has a side wall extended to the middle frame MFM side and is fixed to the middle frame MFM, wherein an opening H2 is disposed on a part in vicinity to the driving circuit substrate of the upper frame UFM, a cap CAP having a screw hole CAH is inserted into the opening H2, a screw SCR is caused to pass through the screw hole CAH, thereby, the upper frame UFM is fixed to the middle frame MFM and, thereby, electric contact between the screw SCR and the upper frame UFM can be avoided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a countermeasure structure for EMI (Electro Magnetic Interference) in a liquid crystal display device.

  In a liquid crystal display device, basically, liquid crystal is sealed between two substrates, a first substrate and a second substrate, preferably a glass substrate, and applied to the liquid crystal from a pixel selection electrode provided on the substrate. This is an image display device utilizing the fact that the orientation direction of the liquid crystal changes according to the electric field. At present, the most widely used all-transmissive liquid crystal display device polarizes the light source light projected from the backlight installed on the back surface of the liquid crystal display element by about 90 degrees in the liquid crystal layer and transmits it through the polarizing plate. Thus, the electronic latent image can be visually recognized as a visible image.

  In an image display device using a liquid crystal display panel which is a non-light emitting type, an electronic latent image formed on the liquid crystal display panel is visualized by providing an external illumination means. Except for the structure using natural light, the external illumination means is provided with an illumination device on the back or front of the liquid crystal display panel. Especially for display devices that require high brightness, a structure in which an illuminating device is provided on the back of a liquid crystal display panel has become the mainstream. This is called a direct type backlight.

  The above-described liquid crystal display device using a direct backlight as an illumination light source has a frame-shaped metal frame made of a metal molded body in order to realize a narrow frame, light weight, and integration of the liquid crystal display panel. It is housed inside and held and fixed, and it is mechanically fixed to each side of the frame-shaped mold case from a resin molded body constituting a direct type backlight containing a linear light source, a reflector, and the like by appropriate screwing or the like. Structure is used.

  In general, in a liquid crystal display device, since a liquid crystal display panel is equipped with a video signal driving circuit for driving liquid crystal, it is known that electromagnetic waves are radiated from the video signal driving circuit.

  In this type of liquid crystal display device, in Patent Document 1 below, a transparent conductive film is provided on the surface of the liquid crystal display panel, the transparent conductive film is electrically connected to a metal shield case, and the metal shield case is connected to a drive circuit. A structure in which EMI countermeasures are taken by electrically connecting to a ground pattern of a substrate is disclosed.

  Patent Document 2 discloses a structure in which measures against EMI are taken by electrically connecting a liquid crystal display panel and a metal housing frame.

Japanese Patent Laid-Open No. 3-153212 JP 2003-98510 A

  However, in this type of liquid crystal display device, a liquid crystal display panel is provided with a plurality of types of drive signal circuits including a video signal circuit for driving a liquid crystal display element in the frame and arranged on the substrate in a high density. Because it is mounted, electromagnetic waves are generated from these drive signal circuits, and the electromagnetic waves propagate to the metal frame in the vicinity of the drive signal circuit and are electromagnetic waves to other electronic devices installed in the periphery. Since it has an influence as noise, further improvement of the EMI level has been demanded.

  Accordingly, the present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a liquid crystal with sufficient EMI countermeasures by shielding electromagnetic noise emitted from various drive signal circuits. It is to provide a display device.

  In order to achieve such an object, a liquid crystal display device according to the present invention is installed on a liquid crystal display panel, a drive circuit board mounted on the liquid crystal display panel and driving the liquid crystal display panel, and a back surface of the liquid crystal display panel. A backlight, a frame-shaped mold case that houses the liquid crystal display panel and the backlight, a frame that exposes an effective display area of the liquid crystal display panel, and a side wall that extends toward the mold case and is fixed to the mold case. A metal frame that is provided with an opening in a portion close to the drive signal circuit of the metal frame, an insulating locking piece having a screw insertion hole is inserted into the opening, and the screw is passed through the screw insertion hole. By fixing the metal frame to the mold frame, electrical contact between the screw and the metal frame can be avoided. It is possible to solve the problem.

  Another liquid crystal display device according to the present invention is preferably characterized in that, in the above configuration, the screw is a metal screw.

  Another liquid crystal display device according to the present invention is preferably characterized in that, in the above configuration, the screw is a resin screw.

  In addition, this invention is not limited to the said structure, A various change is possible without deviating from the technical idea of this invention.

  According to the present invention, the electromagnetic wave radiated from the drive signal circuit mounted on the liquid crystal display panel is difficult to propagate to the metal frame, so that the electromagnetic wave noise is shielded and applied to other electronic devices installed in the periphery. On the other hand, it has an extremely excellent effect that a liquid crystal display device capable of taking sufficient EMI countermeasures can be obtained.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  1A and 1B are diagrams for explaining the configuration of an embodiment of a liquid crystal display device according to the present invention. FIG. 1A is a plan view of a main part viewed from above, and FIG. It is a side view. 2 is a schematic cross-sectional view of the main part of FIG. 1A, FIG. 2A is an enlarged cross-sectional view taken along the line AA 'of FIG. 1A, and FIG. It is an expanded sectional view which followed the BB 'line of 1 (a). FIG. 3 is a schematic exploded perspective view thereof.

  As shown in FIG. 3, a lower frame LFM made of a metal plate molded body is joined to the lower side of a frame-shaped middle frame MFM made of a resin molded body holding a liquid crystal display panel LCD. In the short side direction inside the lower frame LFM, a side mold SM made of a resin molded body that supports the optical compensation sheet laminate OCS and the diffusion plate DFP is joined by a screw SC (see FIG. 2B).

  A diffusion plate DFP and an optical compensation sheet laminate OCS for diffusing illumination light toward the back surface of the liquid crystal display panel LCD are installed above the side mold SM. In addition, a reflection sheet RS is laid on the inner bottom surface of the lower frame LFM, and a plurality of external electrode fluorescent discharge tubes EFL are held in parallel at predetermined intervals by the interval regulating plate SEP. And the backlight BL which reflects the radiated light from the some external electrode fluorescent discharge tube EFL to the back surface of the diffusion plate DFP by the reflective sheet RS is comprised.

  The lower frame LFM is formed of a metal plate molding, and the liquid crystal display panel LCD is integrated with the optical compensation sheet laminate OCS between the upper frame UFM and the metal frame molding. Yes. In FIG. 2, the optical compensation stacked body OCS is not shown.

  In the backlight BL having this configuration, as shown in FIG. 3, a spacer SPC for suppressing non-uniformity of illuminance distribution due to the deflection of the large-sized diffusion plate DFP is planted on the lower frame LFM, and the reflection sheet It is made to contact | abut to the back surface of the diffusion plate DFB through the hole provided in RS. The spacer SPC can be provided with a branch-like projection structure that suppresses the bending of the long fluorescent tube EFL. A liquid crystal display panel (not shown) is arranged on the middle frame MFM.

  In addition, an inverter circuit board INV for driving the plurality of fluorescent tubes EFL by inverting the phase is mounted on the surface of the lower frame LFM opposite to the surface on which the fluorescent tubes EFL are installed. The inverter circuit board INV has an inverter circuit composed of a toroidal coil type transformer and an electrolytic capacitor mounted on the board.

  Also, in the figure, the inverter circuit of the inverter circuit board INV has an external electrode provided on one end side of the plurality of external electrode fluorescent tubes EFL electrically connected to the power supply terminal TM of the side mold frame SML via power supply cables CBL1 and CBL2. It is connected to the.

  The external electrode fluorescent tubes EFL are supplied with drive voltages that are phase-inverted with each other in synchronization with the external electrodes provided at both ends thereof. As for this drive voltage, the high frequency output of the inverter circuit is supplied to one external electrode, and the high frequency output whose phase is inverted is supplied to the other external electrode.

  As shown in these drawings, in the liquid crystal display panel LCD, a liquid crystal layer is sealed between translucent glass substrates having electrodes (not shown) for forming pixels. As shown in FIGS. 2 and 3, two sides of one glass substrate (usually also referred to as an active matrix substrate) protrude from the other substrate (usually also referred to as a color filter substrate). As shown in FIG. 3, a flexible printed circuit board FPC1 mounted with a scanning signal line driving circuit chip and a flexible printed circuit board FPC2 mounted with a data signal line driving circuit chip are connected to the protruding portion.

  As shown in FIG. 2A, the liquid crystal display panel LCD configured as described above has a frame-like upper frame UFM formed of a metal plate molded body and a frame-shaped medium formed of a resin material molded body. Spacers SP1 and SP2 are interposed between the frame MFM and held and fixed at predetermined positions. As shown in FIG. 1 (a), the upper frame UFM is formed into a frame shape by supporting and fixing two kinds of frame pieces having different lengths to each other by a locking member ST such as a rivet by combining the ends thereof. Yes.

  The flexible printed circuit boards FPC1 and FPC2 are arranged in the vertical direction with the liquid crystal display panel LCD and along the side wall of the upper frame UFM, for example, as shown in FIG.

  In FIG. 1, H1 is an alignment hole between the upper frame UFM and the middle frame MFM, ULC is a connection portion between the upper frame UFM and the middle frame MFM, and H2 is a drive signal circuit mounted on the liquid crystal display panel LCD. A rectangular opening formed in a portion close to the board, INV is an inverter circuit board holding part, and TC is a control board holding part.

  When joining the metal upper frame UFM and the resin middle frame MFM, conventionally, a metal screw is inserted from the upper surface of the upper frame UFM (the surface on which the liquid crystal display panel LCD is exposed) into the apparatus. It comes to fix by.

  However, as shown in FIG. 2A, the flexible printed circuit boards FPC1 and FPC2 are arranged in the upper frame UFM, and the screws for fixing the upper frame UFM are flexible printed circuit boards FPC1 and FPC2. It will be arranged in the vicinity. As described above, the configuration in which the metal screw is in contact with the metal upper frame UFM and is placed in the vicinity of the circuit such as the flexible printed circuit boards FPC1 and FPC2 is a factor that causes electromagnetic noise. The inventors have found that there is.

  A configuration for eliminating the electromagnetic noise caused by the fixing of the upper frame UFM will be described below.

  FIG. 4 is a diagram illustrating a structure in which the metal upper frame UFM and the resin middle frame MFM are joined and fixed. FIG. 4A is a side view of the main part of the inner wall surface viewed from the inside of the upper frame UFM, and FIG. 4B is an enlarged cross-sectional view of part A of FIG. 4A which is a characteristic configuration of the present invention. The same parts as those in the above-mentioned figure are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the upper frame UFM has a rectangular opening H2. Further, as shown in FIG. 1A, the openings H2 are provided at two locations on the long frame side of the upper frame UFM. The middle frame MFM for fixing the upper frame UFM is provided with a screw hole MFH through which a screw is passed through a portion corresponding to the opening H2.

  5A and 5B are views for explaining the structure of the cap CAP to be fitted into the opening H2 of the upper frame UFM. FIG. 5A is a plan view, and FIG. 5B is an AA view of FIG. FIG. 5C is a cross-sectional view taken along the line AA ′ in FIG. 5A, and FIG. 5D is a cross-sectional view taken along the line BB in FIG. 5A. It is sectional drawing cut | disconnected along 'line.

  The cap CAP is formed of, for example, an ABS resin molded body as a resin material. The cap CAP has a concave central portion of the cap body, and a screw hole CAH into which a screw is inserted is formed in the central portion. In addition, a pair of locking claws HAG that extend outward in the concave direction is integrally formed at the end of the cap body in the length direction.

  Then, the cap CAP shown in FIG. 5 is inserted into the opening H2 of the upper frame UFM shown in FIG. 4 in the direction of arrow B as shown in FIG. As a result, the cap CAP is fitted into the opening H2 because it spreads outward along the back direction of the upper frame UFM.

  Then, as shown in FIG. 7, the upper frame UFM is firmly fixed to the middle frame MFM by screwing the metal screw SCR into the screw hole CAH formed in the central recess of the cap CAP.

  In such a configuration, since electrical contact between the screw SCR and the metal upper frame UFM can be avoided, electromagnetic wave noise radiated from the video signal circuit is shielded and propagated to the metal upper frame UFM. Since it becomes difficult, the EMI level of electromagnetic noise can be improved. The screw SCR may be an insulating type.

  In the above-described embodiment, the case where the upper and lower frames of the metal upper frame UFM are provided with openings and the caps are fitted into the openings and screwed is described. However, the present invention is limited to this installation location. However, it is possible to obtain a sufficient effect even if the screw fastening at a position close to the drive signal circuit where electromagnetic waves are likely to be generated is made the configuration shown in FIG.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of one Example of the liquid crystal display device by this invention, Fig.1 (a) is the principal part top view seen from upper direction, FIG.1 (b) is the side view seen from the arrow A direction. 2A is a schematic cross-sectional view of a main part of FIG. 1A, FIG. 2A is an enlarged cross-sectional view taken along the line AA ′ of FIG. 1A, and FIG. 2B is a cross-sectional view of FIG. It is an expanded sectional view along a BB 'line. It is a model expansion perspective view of the liquid crystal display device by this invention. It is a figure which shows the structure which joins and fixes the metal upper frame and resin middle frames, FIG.4 (a) is the principal part side view of the inner wall surface seen from the inner side of the upper frame, FIG.4 (b) ) Is an enlarged cross-sectional view of a portion A in FIG. It is a figure which shows the structure of the cap inserted in opening of an upper flame | frame, FIG. 5 (a) is a top view, FIG.5 (b) is the perspective view cut | disconnected along the AA 'line of Fig.5 (a). 5C is a cross-sectional view taken along the line AA ′ in FIG. 5A, and FIG. 5D is a cross-sectional view taken along the line BB ′ in FIG. 5A. It is. It is sectional drawing which shows the structure which fitted the cap in opening of an upper flame | frame. It is sectional drawing which shows the structure which screwed the metal screw in the screw hole formed in the center recessed part of a cap.

Explanation of symbols

  LCD: liquid crystal display panel, FPC1: flexible printed circuit board on which scanning signal line driving circuit chip is mounted, FPC2: flexible printed circuit board on which data signal line driving circuit chip is mounted, UFM: upper frame , MFM ... middle frame, ST ... locking member, H1 ... positioning hole, ULC ... connection part, H2 ... opening, LFM ... lower frame, OCS ... optical Compensation sheet laminate, DFP ... diffusion plate, SM ... side mold, SC ... screw, RS ... reflection sheet, EFL ... external electrode fluorescent discharge tube, BL ... backlight, MFH ... Screw holes, CAP ... Caps, CAH ... Screw holes, HAG ... Locking claws, SCR ... Screws.

Claims (3)

A liquid crystal display panel;
A drive circuit board that is mounted on the liquid crystal display panel and drives the liquid crystal display panel;
A backlight installed on the back of the liquid crystal display panel;
A frame-shaped mold case that houses the liquid crystal display panel and the backlight; and
A metal frame that forms a frame that exposes an effective display area of the liquid crystal display panel and that has a side wall extending toward the mold case and is fixed to the mold case;
With
An opening is provided in a portion of the metal frame adjacent to the drive circuit board, an insulating locking piece having a screw hole is fitted into the opening, and the screw is passed through the screw hole, whereby the metal frame is inserted into the mold frame. A liquid crystal display device characterized by being fixed to a liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the screw is a metal screw.   The liquid crystal display device according to claim 1, wherein the screw is a resin screw.

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