JP2008203448A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance durability by surely preventing a charge-up phenomenon in an in-plane switching type liquid crystal display device. <P>SOLUTION: A conducting tape to ground a transparent conductive film to a circuit board is folded to form a structure of interposing the circuit board with the tape. By this structure, the conductive tape is prevented from peeling and a liquid crystal display device having high durability can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a horizontal electric field liquid crystal display device, and more particularly to a horizontal electric field display device that prevents display unevenness due to the influence of static electricity.

  A liquid crystal display device that controls liquid crystal using the horizontal electric field method applies changes in the light transmittance of the liquid crystal cell when an electric field is applied in a direction parallel to the liquid crystal panel surface and the liquid crystal molecules are rotated in the liquid crystal panel surface. Since the display is performed by using the display, it can be seen as a clear image even when observed from a large angle field of view, and has a feature that there is almost no dependency on the field of view (see, for example, Patent Document 1). ).

  However, although it has the characteristic of widening the viewing angle, there is a drawback that static electricity applied from the outside is easily accumulated in the liquid crystal cell and charge-up is likely to occur. Details are described below. In the case of the lateral electric field method, since the liquid crystal is controlled only by the electric field between the source electrode and the common electrode provided in a comb-teeth shape on the TFT substrate side, the cross section of the CF (color filter) substrate on the opposite side is made of ITO or the like. There are no electrodes.

Therefore, when the surface of the CF side polarizing plate is touched by hand, the static electricity reaches the CF glass substrate through the CF side polarizing plate, and a potential difference is generated between the TFT substrate and the CF substrate. In response to this potential difference, the liquid crystal molecules sealed in the liquid crystal cell malfunction and charge up occurs. A conventional configuration that has been adopted to solve the charge-up is shown in FIGS. FIG. 9 is a plan view schematically showing the configuration of a conventional liquid crystal display device. A liquid crystal layer is sealed between the substrate 2 on which the TFT is formed and the counter substrate 1, a transparent conductive film 4 is formed on the surface of the counter substrate 1, and a polarizing plate 3 is provided thereon. A liquid crystal driver IC 5 is mounted on a terminal portion of the substrate 2 and a mold resin 6 is provided. In addition, a circuit board 7 is connected to this terminal portion, and the transparent conductive film 4 on the counter substrate is grounded to the circuit board by a conductive tape 8 (see, for example, Patent Document 2). FIG. 10 shows a cross section taken along the dotted line cc ′ in FIG. As shown in the figure, the conductive tape 8 is bonded to the GND terminal electrode 11 on the circuit board 7. A chip component 10 is mounted on the back surface of the circuit board 7. Further, as shown in FIG. 11, a method of forming an ITO film 26 as a transparent conductive film on the surface of the polarizing plate 3 by a sputtering method (see, for example, Patent Document 3), or a transparent conductive film sheet as shown in FIG. A method of pasting 27 on the polarizing plate 3 (for example, see Patent Document 4) is known. In either method, the transparent conductive film 4 is connected (grounded) to the GND electrode terminal 11 of the circuit board 7 through a conductive member or a housing, and has a structure in which static electricity escapes.
JP-A-6-160878 Japanese Patent Laid-Open No. 2001-147441 JP-A-4-51220 Japanese Patent Laid-Open No. 11-185991

  In recent years, miniaturization of displays other than the effective display area has been required for miniaturization of display devices, and the area that can be provided for connection between the transparent conductive film on the liquid crystal panel and the conductive member has been reduced. In addition, in order to reduce the thickness, a flexible circuit board is used as a circuit board, and a display device without a housing is increasing. For this reason, the transparent conductive film on the liquid crystal panel uses a conductive tape obtained by applying a conductive adhesive to copper foil as a conductive material, and a method of connecting to the GND of the FPC via the conductive tape has come to be adopted. . However, the conductive tape affixed to the flexible circuit board is easy to peel off because it is flexible, and stable connection is difficult particularly when the flexible circuit board is bent and used. Furthermore, the method of COG mounting the liquid crystal driver IC on the liquid crystal panel has become the mainstream, and as shown in FIG. 10, the conductive tape 8 is disposed between the liquid crystal panel and the circuit board 7 on the mold resin 6 for COG mounting. Connected through. In general, since a silicone resin is used as the mold resin, the adhesive property of the conductive tape is poor and the connection stability is further reduced. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device that solves the above-mentioned drawbacks of the prior art and that completely prevents charge-up of a horizontal electric field type liquid crystal display device even in a small and thin display device.

  In order to achieve the above-described object, the present invention basically employs a technical configuration as described below. That is, in the first aspect of the liquid crystal display device according to the present invention, a transparent conductive film is formed on the opposite side of the transparent substrate of the liquid crystal panel, and the transparent conductive film is grounded to the circuit board via a conductive tape. The electric field type liquid crystal display device is characterized in that the conductive tape has a structure sandwiching the circuit board, and the second mode is on the opposite side of the liquid crystal of the transparent substrate of the liquid crystal panel. In a horizontal electric field type liquid crystal display device in which a transparent conductive film is formed and this transparent conductive film is grounded to a circuit board via a conductive tape, the width of the conductive tape is wider on the circuit board side than on the liquid crystal panel side. The circuit board is sandwiched by folding on the circuit board, and the third aspect has a transparent conductive film formed on the opposite side of the liquid crystal of the transparent substrate of the liquid crystal panel, This transparent In a horizontal electric field type liquid crystal display device in which a conductive film is grounded to a circuit board via a conductive tape, the conductive tape is grounded to the circuit board on a back surface side folded on the circuit board. Is.

  In the liquid crystal display device of the present invention, since the conductive tape sandwiches the circuit board, the conductive tape does not peel off from the circuit board, and the transparent conductive film on the liquid crystal panel can be reliably grounded via the conductive tape. . As a result, the static electricity generated on the surface of the liquid crystal panel quickly escapes to GND, so that it is possible to prevent display defects due to charge-up in the horizontal electric field liquid crystal display device, and to provide a liquid crystal display device with good display quality. Become.

  The display device of the present invention includes a substrate on which a thin film transistor is formed, a counter substrate that holds the liquid crystal opposite to the substrate, and an electrode formed on the substrate for driving the liquid crystal with an electric field in a direction parallel to the substrate. And a circuit board disposed adjacent to the horizontal electric field liquid crystal panel, the transparent conductive film and the transparent conductive film formed on the opposite surface of the counter substrate to the liquid crystal The conductive tape has a conductive tape for grounding the film to the circuit board, and the conductive tape is bent so as to sandwich the circuit board, and the conductive tape is bonded to the transparent conductive film and the front and back surfaces of the circuit board.

  Further, the conductive tape has a structure that is not bent at a portion that is bonded to the surface of the transparent conductive film and the circuit board, and is bent at a portion that is bonded to the front surface of the circuit board and the back surface of the circuit board. Further, the width of the conductive tape is wider on the circuit board side than on the liquid crystal panel side, and the circuit board is sandwiched by folding back on the circuit board. Alternatively, the conductive tape is formed in a substantially L-shaped outer shape.

  In any of the above-described configurations, the conductive tape is grounded to the circuit board on the folded back side. The circuit board was a flexible circuit board. Further, the liquid crystal driver IC was configured to be COG-mounted on the terminal portion on the substrate and provided with a mold resin on the terminal portion. Further, the mold resin was a silicon resin.

  Embodiments of the present invention will be described below with reference to the drawings.

  The configuration of the liquid crystal display device of this embodiment is schematically shown in FIGS. 1 to 3, 7 and 8. FIG. 1 is a plan view of the liquid crystal display device of the present invention, FIG. 2 is a cross-sectional view of the panel section when the liquid crystal display device of FIG. 1 is cut at the position aa ′, and FIG. 3 is the liquid crystal display device of FIG. 7 is a cross-sectional view of the circuit board portion of the liquid crystal display device when cut at the position bb ′, FIG. 7 is a schematic cross-sectional view of the liquid crystal display panel used in the present invention, and FIG. FIG. 13 is a detailed view showing the cross-sectional structure of the polarizing plate of the liquid crystal display device of the present invention. First, the substrate 2 on which TFTs as switching elements are formed will be described with reference to FIGS. A drain bus line 22 and a gate bus line 21 are formed vertically and horizontally on the transparent glass substrate 2, and the drain bus line 22 is connected to the source electrode 25 through the switching element 15. The common electrode 24 and the source electrode 23 have a comb-like shape opposed to each other, and the alignment state of the liquid crystal is controlled by an electric field applied between these two electrodes. A protective insulating film 16 is formed so as to cover these electrodes, and an alignment film 17 is formed thereon.

  Next, the counter substrate 1 on which the color filter is formed will be described. On the counter substrate 1 made of transparent glass, a black matrix 13 is formed in a matrix shape, and colored layers 12 of R (red), G (green), and B (blue) are formed in stripes so as to cover them. Is formed. In order to protect these colored layers 12, a transparent protective film 14 is formed, and an alignment gap 17 is formed thereon. A liquid crystal 19 having a positive dielectric anisotropy is held between the substrate 2 and the counter substrate 1, and the liquid crystal 19 is substantially parallel to the two substrates 1 and 2 via the alignment film 17. Oriented. Further, in order to control the cell thickness, a post spacer 18 is formed on the counter substrate 1, and a bar spacer is added to the peripheral sealing agent 20 outside the display portion. A transparent conductive film 4 is formed on the side of the counter substrate 1 opposite to the side in contact with the liquid crystal 19, and a pair of polarizing plates 3 are attached to the outermost sides of the substrate 2 and the counter substrate 1. The pair of polarizing plates 3 are so-called crossed Nicols arranged so that the transmission axes are orthogonal to each other. The transmission axis of one polarizing plate is arranged so as to coincide with the alignment direction of the liquid crystal molecules 19, and the transmission axis of the other polarizing plate is arranged so as to be orthogonal to the transmission axis of one polarizing plate.

  Next, the structure of the conductive tape portion for preventing charge-up, which is a feature of the liquid crystal display device of the present invention, will be described with reference to FIGS. A liquid crystal driver IC 5 is COG mounted on the terminal portion of the substrate 2, and a molding agent 6 is applied to the periphery of the liquid crystal driver IC 5 in order to improve durability. The flexible circuit board 7 is provided with a wiring pattern 9 and a chip component 10 necessary for driving a liquid crystal panel such as a resistor and a capacitor on one surface, and a GND terminal electrode 11 is provided on the other surface. The transparent conductive film 4 on the counter substrate 1 is grounded to the GND terminal electrode 11 on the flexible circuit board 7 via the conductive tape 8 so as to prevent charge-up. As shown in FIGS. 2 and 3, the conductive tape 8 is bent and pasted so as to sandwich the liquid crystal display panel and the flexible circuit board 7. As the conductive tape, a metal foil coated with a conductive adhesive can be used. For example, an Al foil conductive tape 1170 manufactured by Sumitomo 3M Limited or a product name 1181 obtained by applying a conductive adhesive to a Cu foil. Etc. can be used.

  With the structure of this example, the conductive tape was not peeled off from the circuit board, and the transparent conductive film 4 on the liquid crystal panel could be reliably grounded through the conductive tape. As a result, the static electricity generated on the surface of the liquid crystal panel quickly escapes to GND, so that it is possible to prevent display defects due to charge-up in the horizontal electric field liquid crystal display device, and to provide a liquid crystal display device with good display quality. became.

  The structure of the liquid crystal display device of this example is schematically shown in FIGS. 4 is a plan view of the liquid crystal display device of the present invention, and FIG. 5 is a cross-sectional view of the circuit board portion of the liquid crystal display device when the liquid crystal display device of FIG. 4 is cut at the position b-b ′. In this embodiment, the conductive tape 8 has a shape in which the width of the conductive tape is wider on the circuit board side than the liquid crystal panel side as shown in FIG. 4, and the conductive tape 8 is folded back only at the flexible circuit board 7 as shown in FIG. I made it.

  In the configuration of this example, the conductive tape 8 did not protrude beyond the liquid crystal panel, and a more compact liquid crystal display device could be obtained.

  The configuration of the liquid crystal display device of this example is shown in FIG. In the present embodiment, in the configuration of the second embodiment, as shown in FIG. 6, the GND terminal electrode 11 on the flexible circuit board 7 is formed on the same surface as the wiring pattern 9 and grounded on the back surface side where the conductive tape 8 is folded. Made the configuration. In the configuration of this example, the wiring pattern 9 and the GND terminal electrode 11 of the flexible circuit board can be formed on the same surface, and the manufacturing cost of the flexible circuit board can be reduced.

  Since it is possible to provide a liquid crystal display device that is securely grounded via a conductive tape, it can be applied to a display device of a portable information device that requires high durability.

It is a top view which shows typically the liquid crystal display device of this invention. It is sectional drawing in the liquid crystal panel part of the liquid crystal display device of FIG. It is sectional drawing in the circuit board part of the liquid crystal display device of FIG. It is a top view which shows typically the structure of the liquid crystal display device of this invention. It is sectional drawing in the circuit board part of the liquid crystal display device of FIG. It is sectional drawing in the circuit board part of the liquid crystal display device of another structure. It is sectional drawing which shows typically the structure of the liquid crystal display panel used for this invention. It is a schematic diagram explaining the active element part of the liquid crystal display panel used for this invention. It is a top view which shows typically the structure of the conventional liquid crystal display device. It is sectional drawing which shows the structure of the conventional liquid crystal display device typically. It is sectional drawing which shows the structure of the conventional liquid crystal display device typically. It is sectional drawing which shows the structure of the conventional liquid crystal display device typically.

Explanation of symbols

1 counter substrate 2 substrate 3 polarizing plate 4 transparent conductive film 5 liquid crystal driver IC
6 Molding Agent 7 Flexible Circuit Board 8 Conductive Member 9 Wiring Pattern 10 Chip Component 11 GND Terminal Electrode 12 Color Filter 13 Black Matrix 14 Protective Film 15 Switching Element 16 Protective Insulating Film 17 Alignment Film 18 Post Spacer 19 Liquid Crystal 20 Sealing Agent 21 Gate Bus Line 22 Drain bus line 23 Source electrode 24 Common electrode 25 Source electrode 26 Transparent conductive film 27 Transparent conductive film sheet

Claims (8)

A substrate on which a thin film transistor is formed; a counter substrate that faces the substrate and sandwiches liquid crystal between the substrate; and the liquid crystal is formed on the substrate to drive the liquid crystal with an electric field in a direction parallel to the substrate. A lateral electric field liquid crystal panel comprising electrodes;
A circuit board disposed adjacent to the lateral electric field liquid crystal panel;
A transparent conductive film formed on a surface of the counter substrate opposite to the liquid crystal;
While having a conductive tape for grounding the transparent conductive film to the circuit board,
The liquid crystal display device, wherein the conductive tape is bent so as to sandwich the circuit board, and the conductive tape is bonded to the transparent conductive film and the front and back surfaces of the circuit board.   The conductive tape has a structure that is not bent at a portion that is bonded to the surface of the transparent conductive film and the circuit board, and is bent at a portion that is bonded to the surface of the circuit board and the back surface of the circuit board. The liquid crystal display device according to claim 1.   3. The liquid crystal display device according to claim 2, wherein the width of the conductive tape is wider on the circuit board side than the liquid crystal panel side, and the circuit board is sandwiched by folding back on the circuit board.   The liquid crystal display device according to claim 2, wherein the conductive tape has a substantially L-shaped outer shape.   The liquid crystal display device according to claim 1, wherein the conductive tape is grounded to the circuit board on a folded back surface side.   The liquid crystal display device according to claim 1, wherein the circuit board is a flexible circuit board.   The liquid crystal display device according to claim 1, wherein a liquid crystal driver IC is COG mounted on a terminal portion on the substrate, and a mold resin is provided on the terminal portion.   The liquid crystal display device according to claim 7, wherein the mold resin is a silicon resin.

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