JP2011027879A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of surely eliminating electrostatic charge in a conductive polarizing plate without using a bezel and canceling display unevenness occurring by charge accumulated in the polarizing plate. <P>SOLUTION: The liquid crystal display device is constructed of a liquid crystal display panel 1 and a backlight unit 10 arranged on the back face side of the liquid crystal display panel 1. The liquid crystal display panel 1 includes: an array substrate 2 having a common electrode 5 and a pixel electrode 6 formed on the common electrode 5 via a transparent insulating film 7; and a counter substrate 3 arranged at a predetermined distance with the first substrate. A liquid crystal layer 4 is clamped between the array substrate 2 and the counter substrate 3, and the orientation direction of the liquid crystal layer 4 is controlled by a lateral electric field occurring between the common electrode 5 and the pixel electrode 6. On the surface of the counter substrate 3 of the liquid crystal display panel 1, the conductive polarizing plate 9 is installed. The liquid crystal display panel 1 is fixed to backlight unit 10 by a conductive tape 11, and the conductive tape 11 is electrically connected to the conductive polarizing plate 9. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a so-called lateral electric field drive type liquid crystal display device such as an IPS (In Plane Swiching) method and an FFS (Fringe Field Swiching) method, and more particularly to improvement of a fixing structure and a conduction structure of a liquid crystal display panel.

  As a method for controlling the alignment of the liquid crystal layer in the liquid crystal display device, VA (white) and non-transmissive (black) are expressed by aligning liquid crystal molecules vertically in an initial state and tilting the liquid crystal molecules by applying a voltage. Typical examples include a vertical alignment (IPS) method, an IPS method in which light is switched by applying an electric field (lateral electric field) in the plane direction of the substrate, and rotating liquid crystal molecules in a plane parallel to the substrate. Among these, horizontal electric field drive type liquid crystal display devices such as the IPS method and the FFS method have advantages such as a wide viewing angle, and improvements are being made in various fields.

  However, in a horizontal electric field drive type liquid crystal display device, static elimination is required to prevent the liquid crystal display panel from being charged. For example, when charge is accumulated in a liquid crystal display panel (such as a substrate surface on the color filter side) and an electric field (vertical electric field) is generated in a direction perpendicular to the main surface of the liquid crystal display panel, the alignment control of liquid crystal molecules is disturbed. This causes display unevenness. Therefore, in the horizontal electric field drive type liquid crystal display device, it is necessary to quickly release the accumulated electric charge and to suppress the generation of the vertical electric field.

  2. Description of the Related Art Conventionally, as a structure for eliminating static electricity, generally, a polarizing plate or a cell (liquid crystal display panel) is made conductive and is electrically connected to a metal bezel. For example, the liquid crystal display device described in Patent Document 1 also employs such a structure.

  That is, in the liquid crystal display device described in Patent Document 1, a liquid crystal panel having a conductive polarizing plate is mounted on the main surface of a resin case containing an optical member including a backlight so that the conductive polarizing plate is the uppermost layer. The resin case is housed in a bottomed and uncovered metal rear case so that the main surface is exposed. And the conductive sheet with an adhesive is affixed on at least one corner of the four corners of the liquid crystal panel from the conductive polarizing plate to the main surface of the resin case and the side surface of the rear case. In the liquid crystal display device described in Patent Document 1, by adopting the above configuration, the surface charge of the conductive polarizing plate is discharged to the rear case through the conductive sheet with the adhesive, and the charge is discharged on the surface of the conductive polarizing plate. Prevents accumulation.

JP 2006-330230 A

  However, in a configuration using a metal rear case (so-called bezel), there is a problem that the weight of the liquid crystal module becomes heavy. In recent years, in the field of electronic devices in which liquid crystal modules are incorporated, it has been required to reduce the thickness and weight as much as possible, and the increase in weight is a major drawback.

  Moreover, it is difficult to obtain sufficient electrical conduction between the polarizing plate and the metal rear case only by attaching the conductive sheet with the adhesive to the corners, and there is a possibility that the charge removal becomes insufficient. In order to avoid this, if the area of the conductive sheet to be attached to the corner is increased and sufficient electrical connection is to be realized, it is necessary to increase the frame width, and the liquid crystal module has a larger display area than the effective display area. The problem arises that the size must be increased.

  The present invention has been proposed in view of such a conventional situation, and it is possible to reliably remove static electricity from a conductive polarizing plate without using a bezel, and charges are accumulated on the surface of the polarizing plate. It is an object of the present invention to provide a liquid crystal display device that can eliminate display unevenness caused by this, and can realize a reduction in weight, a narrow frame, and the like.

  In order to achieve the above object, a liquid crystal display device according to the present invention includes a first substrate having a common electrode and a pixel electrode formed on the common electrode through a transparent insulating film, and the first substrate. And a second substrate disposed at a predetermined interval, a liquid crystal layer is sandwiched between the first substrate and the second substrate, and a lateral generated between the common electrode and the pixel electrode. A liquid crystal display panel in which the orientation direction of the liquid crystal layer is controlled by an electric field, and a backlight unit installed on the back side of the liquid crystal display panel. In the liquid crystal display panel, the liquid crystal layer of the second substrate And a liquid crystal display panel is fixed to the backlight unit with a conductive tape, and the conductive tape is electrically connected to the conductive polarizing plate. Being And features.

  In the liquid crystal display device of the present invention, a structure in which the liquid crystal display panel and the backlight unit are fixed by a conductive tape without using a metal bezel and the electric charge accumulated in the conductive polarizing plate is released to the backlight unit side. It is said. Since no metal bezel is used, weight reduction is not caused and weight reduction is realized. In addition, it is easy to establish electrical conduction between the conductive polarizing plate and the conductive tape, the neutralization of the conductive polarizing plate is surely performed, the occurrence of display unevenness is suppressed, and the overlapping of the conductive polarizing plate and the conductive tape is also necessary. Narrow frame is also realized because it is minimal.

  In the liquid crystal display device of the present invention, it is possible to reliably remove static electricity from the conductive polarizing plate while omitting the bezel. Therefore, it is possible to provide a light-weight liquid crystal display device free from display unevenness due to charge accumulation. . In addition, a narrow frame can be realized.

It is a figure which shows typically the mode of the drive of the liquid crystal molecule in the liquid crystal display device of a FFS system. It is a schematic sectional drawing which shows an example of the liquid crystal display device to which this invention is applied. The example which made the form which a conductive tape runs on a polarizing plate is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic sectional drawing. It is a schematic plan view which shows an example of the electroconductive tape which made the edge part serrated. The example which made the edge part of an electroconductive tape sawtooth-shaped is shown, (a) is a principal part schematic plan view, (b) is the side view seen from the arrow direction of (a). The other example which made the edge part of an electroconductive tape sawtooth-shaped is shown, (a) is a principal part schematic plan view, (b) is the side view seen from the arrow direction of (a). 1A and 1B show an example of a conductive tape in which each piece at the end of the conductive tape has an arc shape, where FIG. 1A is a schematic plan view, and FIG. 2B is a conductive tape in which arc-shaped pieces are intermittently formed. (C) is a schematic plan view showing an example of a conductive tape in which the inclination angle of a triangular segment is changed, and (d) is a schematic diagram showing an example of a conductive tape in which a trapezoidal segment is formed. It is a top view. It is a schematic plan view which shows the example of installation of the electroconductive tape in a corner part. It is a schematic plan view which shows an example of the electroconductive tape which integrally formed the part corresponding to a corner part and each side. It is a figure which shows typically the mode of the drive of the liquid crystal molecule in the IPS type liquid crystal display device.

  Hereinafter, embodiments of a liquid crystal display device to which the present invention is applied will be described in detail with reference to the drawings.

  The liquid crystal display device of this embodiment is a lateral electric field drive type liquid crystal display device. First, a basic configuration of an FFS mode liquid crystal display device, which is a kind of lateral electric field drive type liquid crystal display device, will be described. FIG. 1 schematically shows how liquid crystal molecules are driven in an FFS liquid crystal display device.

  A liquid crystal display panel 1 used in an FFS liquid crystal display device basically has a liquid crystal layer 4 between a pair of substrates (an array substrate 2 as a first substrate and a counter substrate 3 as a second substrate). Switching is performed by changing the direction of the liquid crystal molecules LC constituting the liquid crystal layer 4 by the sandwiching and fringe electric field F.

  On the array substrate 2, the common electrode 5 is formed as a planar electrode, and the pixel electrode 6 is formed on the common electrode 5 via the transparent insulating film 7 corresponding to each pixel. On the other hand, a color filter layer and a black matrix layer are formed on the counter substrate 3, but an electrode for controlling the liquid crystal molecules LC of the liquid crystal layer 4 is not formed. Further, polarizing plates 8 and 9 are installed on the surfaces of the array substrate 2 and the counter substrate 3 opposite to the liquid crystal layer 4 so that the polarization axes are orthogonal to each other.

  In the FFS mode liquid crystal display device having the above-described configuration, as shown on the left side of FIG. 1, when the pixel electrode 6 is in the OFF state, the fringe electric field F is not generated, and the liquid crystal molecules LC are in a certain direction (here, perpendicular to the paper surface). The light irradiated from the back side of the array substrate 2 is blocked by the polarizing plate 9 on the counter substrate 3 side without changing the polarization direction. That is, in the off state, light is not transmitted (black).

  On the other hand, as shown on the right side of FIG. 1, when the pixel electrode 6 is in the on state, a substantially fringe electric field F is generated in the horizontal direction, and the liquid crystal molecules LC of the liquid crystal layer 4 are aligned accordingly. Thereby, the light irradiated from the back side of the array substrate 2 is transmitted through the polarizing plate 9 on the counter substrate 3 side. That is, in the on state, light is transmitted (white).

  In the liquid crystal display panel 1 described above, no electrode is formed on the counter substrate 3 side. Therefore, when the counter substrate 3 itself is charged or when the polarizing plate 9 is charged, the liquid crystal layer 4 is inadvertent due to the accumulated charge. An electric field is applied to the image quality, which may affect the image quality. Therefore, in the liquid crystal display device of the present embodiment, a conductive polarizing plate is used as the polarizing plate 9, and the polarizing plate 9 is made conductive with a conductive tape and fixed to the backlight unit. 9 is prevented from being charged. Hereinafter, the configuration of the liquid crystal display device of the present embodiment will be described.

  FIG. 2 shows a schematic configuration of the liquid crystal display device of the present embodiment. As described above, the liquid crystal display device of the present embodiment is a liquid crystal display device including the FFS-type liquid crystal display panel 1, and the liquid crystal display panel 1 includes an array substrate 2 and a counter substrate 3. The liquid crystal layer is sandwiched, and the alignment of liquid crystal molecules in the liquid crystal layer is controlled by a fringe electric field F generated between the common electrode and the pixel electrode formed on the array substrate 2.

  A so-called backlight unit 10 is installed on the back surface of the liquid crystal display panel 1, and an image of the liquid crystal display panel 1 is displayed by irradiating the planar light. Here, it is necessary to fix the liquid crystal display panel 1 and the backlight unit 10, but in the liquid crystal display device of this embodiment, a liquid crystal display panel is used by using a conductive tape 11 without using a metal bezel. 1 and the backlight unit 10 are fixed, and the charge accumulated in the conductive polarizing plate 9 is released to the backlight unit 10 side.

  That is, in the liquid crystal display device according to the present embodiment, the conductive tape 11 is routed from the outer peripheral portion of the upper surface of the liquid crystal display panel 1 to the backlight unit 10, for example, to the side surface and further to the bottom surface of the metal frame. 1 is fixed to the backlight unit 10. The leading edge of the conductive tape 11 is abutted against the conductive polarizing plate 9 attached to the surface side of the liquid crystal display panel 1 so as to achieve electrical conduction. Thereby, the electric charge accumulated in the polarizing plate 9 is guided to the backlight unit 10 via the conductive tape 11, and is quickly discharged by, for example, grounding the backlight unit 10.

  However, when a structure in which the leading edge of the conductive tape 11 is abutted against the outer peripheral end surface of the polarizing plate 9 is employed, there is a problem that it is difficult to obtain sufficient conduction. If the conduction between the conductive tape 11 and the polarizing plate 9 is insufficient, it may be difficult to reliably remove charges accumulated in the polarizing plate 9.

  In order to solve this problem, for example, as shown in FIGS. 3A and 3B, a part of the conductive tape 11 may be placed on the polarizing plate 9. The conductive tape 11 rides on the polarizing plate 9 and the overlapping portion k where the conductive tape 11 and the polarizing plate 9 overlap is formed, so that the conductive tape 11 and the polarizing plate 9 can be reliably connected. It is.

  In addition, when the conductive tape 11 is bonded so as to overlap the polarizing plate 9 as described above, if the edge of the conductive tape 11 is linear, conduction with the polarizing plate 9 can be secured, but the overlapping There is a possibility that air easily remains in the portion k and the workability is poor. In such a case, as shown in FIG. 4, it is preferable that the shape of the portion of the conductive tape 11 that overlaps the polarizing plate 9 is a sawtooth shape in which triangular segments 11a are continuous.

  FIG. 5A and FIG. 5B show an example of the state of bonding of the conductive tape 11 whose edge shown in FIG. 4 has a sawtooth shape. FIG.5 (b) is the side view which looked at Fig.5 (a) from the arrow direction. In the case of this example, the conductive tape 11 is bonded so that the entire triangular piece 11 a overlaps the conductive polarizing plate 9. By providing the serrated irregularities on the end portion of the conductive tape 11, air can easily escape at the concave end portion between the triangular sections 11a, thereby improving workability.

  FIG. 6A and FIG. 6B show another example of the state of bonding of the conductive tape 11 whose edge shown in FIG. 4 has a sawtooth shape. FIG.6 (b) is the side view which looked at Fig.6 (a) from the arrow direction. In the case of this example, the position of the bonding is changed, and the conductive tape 11 is bonded so that only the tip portion of the triangular section 11 a overlaps the conductive polarizing plate 9. In this way, when only the tip portion of the triangular section 11a is overlapped on the conductive polarizing plate 9, air can be easily removed, workability can be improved, and the width of the overlapping portion can be improved. Therefore, the transmission region of the polarizing plate 9 can be enlarged.

  In each of the above-described examples, the end surface of the conductive tape 11 has a sawtooth shape with continuous triangular segments 11a. For example, as shown in FIG. It is also possible, and it becomes possible to expand the adhesion area as compared with the sawtooth shape while suppressing the generation of bubbles on the adhesion surface. In this case, as shown in FIG. 7B, the arc-shaped piece 11b may be formed intermittently. Alternatively, as shown in FIG. 7C, the triangular section 11a can be formed intermittently by changing the inclination angle, or as shown in FIG. 7D, a trapezoidal section 11c can be formed. is there.

  FIG. 8 shows an installation example of the conductive tape 11 at the corner. For example, when the conductive tape 11 is installed so that the end face of the conductive tape 11 abuts against the end face of the polarizing plate 9, as shown in FIG. In such a case, as shown in FIG. 8, it is preferable that the strip-shaped conductive tape 12 is diagonally attached to the corner portion to establish conduction with the polarizing plate 9. In this case, since the conductive tape 12 is pasted so as to cross the corner portion, the conductive tape 12 can be more securely fixed and both ends of the conductive tape 12 can be extended to the backlight unit. For example, since the two-point connection form is used, there is an effect that the discharge is more reliably performed.

  Alternatively, as shown in FIG. 9, an integrated conductive tape 13 in which a corner portion 13a and portions 13b and 13c corresponding to each side are integrated may be attached. In this case, the line x can be folded in a mountain and the line y can be folded in a valley, so that it can be bonded to the polarizing plate 9 so as to partially overlap the corner 9 and is compared with the configuration shown in FIG. Thus, a conductive connection in a large area can be taken. Even in this case, each of the side portions 13b and 13c corresponding to the polarizing plate 9 of the conductive tape 13 needs to be extended so as to reach the backlight unit, but either one of the side portions 13b or Even in a configuration in which only 13c is extended to the backlight unit, the same effect can be exhibited.

  In the liquid crystal display device of the present embodiment having the above-described configuration, the liquid crystal display panel 1 and the backlight unit 10 are fixed by the conductive tape 11, and the conductive tape 11 is electrically connected to the polarizing plate 9 of the liquid crystal display panel 1. Therefore, it is possible to quickly release the charge accumulated in the polarizing plate 9. In addition, since it is not necessary to use a metal bezel for fixing the liquid crystal display panel 1 and the backlight unit 10 and for removing static electricity from the polarizing plate 9, it is possible to reduce the weight of the liquid crystal display device and further reduce the frame. Can also be realized.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the previous embodiment, the FFS liquid crystal display device has been described as an example, but the present invention can also be applied to a liquid crystal display device including an IPS liquid crystal display panel.

  FIG. 10 schematically shows how liquid crystal molecules are driven in an IPS liquid crystal display panel.

  In the IPS liquid crystal display panel, a liquid crystal layer 23 is sandwiched between a pair of substrates (an array substrate 21 as a first substrate and a counter substrate 22 as a second substrate), and the liquid crystal layer 23 is formed by a lateral electric field S. The liquid crystal molecules LC to be rotated are rotated in a plane parallel to the substrate 21 to perform switching.

  In the IPS liquid crystal display panel, a common electrode 24 and a pixel electrode 25 are formed on the array substrate 21 with a predetermined interval through a transparent insulating film 26. An electrode for controlling the liquid crystal molecules LC of the liquid crystal layer 23 is not formed on the counter substrate 22. Further, polarizing plates 27 and 28 are provided on the surfaces of the array substrate 21 and the counter substrate 22 opposite to the liquid crystal layer 23 so that the polarization axes are orthogonal to each other.

  In the IPS liquid crystal display panel having the above-described configuration, as shown on the left side of FIG. 10, when the pixel electrode 25 is in the off state, no lateral electric field S is generated, and the liquid crystal molecules LC are in a certain direction (here, perpendicular to the paper surface). The light irradiated from the back side of the array substrate 21 is blocked by the polarizing plate 28 on the counter substrate 22 side without changing the polarization direction. That is, in the off state, light is not transmitted (black).

  On the other hand, as shown on the right side of FIG. 10, when the pixel electrode 25 is in the ON state, a lateral electric field S parallel to the substrate surface is generated between the spaced apart common electrode 24 and the pixel electrode 25, and the liquid crystal molecules LC of the liquid crystal layer 23. Rotates in a plane parallel to the substrate surface. Thereby, the light irradiated from the back side of the array substrate 21 is transmitted through the polarizing plate 28 on the counter substrate 22 side. That is, in the on state, light is transmitted (white).

  Also in the liquid crystal display device including the IPS liquid crystal display panel having the above configuration, the liquid crystal display panel and the backlight unit are fixed with a conductive tape, and the conductive tape is brought into contact with the conductive polarizing plate 28. Thus, the charge accumulated in the polarizing plate 28 can be quickly eliminated. In addition, since a metal bezel is unnecessary, the liquid crystal display device can be reduced in weight.

2, 21 array substrate (first substrate), 3, 22 counter substrate, 4, 23 liquid crystal layer, 8, 9, 27, 28 polarizing plate, 10 backlight unit, 11 conductive tape, 12 strip-shaped conductive tape, 13 Integrated conductive tape

Claims (5)

A first substrate having a common electrode and a pixel electrode formed on the common electrode through a transparent insulating film; and a second substrate disposed at a predetermined interval with respect to the first substrate. A liquid crystal display panel in which a liquid crystal layer is sandwiched between the first substrate and the second substrate, and an orientation direction of the liquid crystal layer is controlled by a lateral electric field generated between the common electrode and the pixel electrode;
A backlight unit installed on the back side of the liquid crystal display panel;
In the liquid crystal display panel, a conductive polarizing plate is installed on the surface opposite to the liquid crystal layer of the second substrate,
A liquid crystal display device, wherein the liquid crystal display panel is fixed to a backlight unit by a conductive tape, and the conductive tape is electrically connected to the conductive polarizing plate.   2. The liquid crystal display device according to claim 1, wherein the conductive tape is disposed so that a part thereof overlaps the conductive polarizing plate.   The liquid crystal display device according to claim 2, wherein an edge of the conductive tape has an uneven shape.   4. The liquid crystal display device according to claim 3, wherein the uneven shape is a sawtooth shape in which triangular segments are continuous.   2. The liquid crystal display device according to claim 1, wherein at least a part of the conductive tape is obliquely installed at a corner portion of the liquid crystal display panel.

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