JP4921749B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device using an OCB (Optically Compensated Bend) technique capable of realizing a wide viewing angle and a high-speed response.

  A typical liquid crystal display device as a flat display device includes a liquid crystal display panel configured by holding a liquid crystal layer between an array substrate and a counter substrate. This liquid crystal display panel includes an effective display unit configured by matrix display pixels.

In such a liquid crystal display panel, when a pixel defect occurs, various techniques for making the defect inconspicuous have been proposed. For example, according to Patent Document 1, the pixel electrode and the auxiliary capacitance electrode are short-circuited by laser irradiation, and the liquid crystal is driven by the voltage difference between the auxiliary capacitance electrode voltage and the counter electrode voltage, thereby making the defect inconspicuous. Further, in order to prevent light leakage at a short-circuit connection portion formed by laser irradiation, a light shielding film is disposed on the counter substrate side.
JP 08-313933 A

  In the OCB mode liquid crystal display device, when a pixel defect that becomes a bright spot occurs, by short-circuiting the auxiliary capacitance line of the black level potential and the pixel electrode by laser irradiation from the back side of the array substrate, Pixels can be darkened. When the darkening process is performed by a short circuit with a pixel electrode having optical transparency, high laser power is required. For this reason, the alignment film disposed on the surface of the array substrate may be damaged, causing alignment disorder of the liquid crystal molecules. Such alignment disturbance causes so-called light leakage in which the backlight light leaks from a part of the pixel that should originally be a dark spot, leading to deterioration in display quality.

  Such light leakage tends to appear in the rubbing direction from the laser irradiated point. For this reason, as a countermeasure against light leakage, it is necessary to dispose a light-shielding film over a wide range, resulting in a decrease in the aperture ratio of the pixel.

  The present invention has been made in view of the above-described problems. The object of the present invention is to increase the aperture ratio of a pixel and to apply to other layers in a darkening process for relieving a pixel defect. An object of the present invention is to provide a liquid crystal display device capable of reducing damage.

According to this embodiment,
An array substrate, a counter substrate facing the array substrate, a liquid crystal held between the array substrate and the counter substrate, and bend-aligned between the array substrate and the counter substrate with a predetermined bias applied A liquid crystal layer including molecules, a switch element including a semiconductor layer disposed in each pixel on the array substrate, a scan line to which a control signal for controlling driving of the switch element is supplied, and the scan line A storage capacitor line extending substantially in parallel and having a black level potential; a first insulating layer covering the scanning line and the storage capacitor line; and the scanning line and the storage capacitor line via the first insulating layer ; a signal line video signal to be written crossed to each pixel is supplied, and a source wiring connected to the signal line as well as contact with the semiconductor layer of the switching element in one corner portion of the pixel, Serial and drain wiring crossing the auxiliary capacitance line via the first insulating layer and the island-like semiconductor layer with contact to the semiconductor layer of the switching element at the corner portion, the signal line, the source wiring, and, the A second insulating film that covers the drain wiring, and the drain wiring is disposed on the second insulating film and is connected to the drain wiring through a contact hole formed in the second insulating film at the intersection of the drain wiring and the auxiliary capacitance line. A connected pixel electrode; an alignment film that covers the surface of the pixel electrode and is rubbed toward the corner portion; and a light-shielding film that is disposed on the counter substrate and faces the corner portion of the array substrate. An OCB mode liquid crystal display device is provided .

  According to the present invention, it is possible to provide a liquid crystal display device that can increase the aperture ratio of pixels and reduce damage to other layers in a darkening process for relieving pixel defects. Can do.

  Hereinafter, a display device, particularly a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a liquid crystal display device using an OCB (Optically Compensated Bend) mode method will be described as an example of the liquid crystal display device.

  As shown in FIGS. 1 and 2, the liquid crystal display device includes a liquid crystal display panel 100. That is, the liquid crystal display panel 100 includes a pair of substrates, that is, an array substrate (first substrate) 200 and a counter substrate (second substrate) 300, and a liquid crystal layer 400 held between the array substrate 200 and the counter substrate 300. It is configured. The array substrate 200 and the counter substrate 300 are bonded to each other by a sealing material 110, and a predetermined gap for holding the liquid crystal layer 400 is formed therebetween. The liquid crystal display panel 100 includes an effective display unit 120 that displays an image on the inner side surrounded by the sealing material 110. The effective display unit 120 includes a plurality of display pixels PX arranged in a matrix.

  The array substrate 200 includes a plurality of scanning lines Y (1, 2, 3,..., M) extending in the row direction of the display pixels PX and the column direction of the display pixels PX in the effective display unit 120. A plurality of signal lines X (1, 2, 3,..., N) extending and a plurality of storage capacitor lines 250 extending substantially in parallel with the scanning line Y are provided. It is formed in a region surrounded by the scanning line Y and the signal line X. Each scanning line Y is supplied with a control signal for controlling driving of the switch element 220 (switch element on / off). A video signal to be written to each display pixel PX is supplied to each signal line X. Each auxiliary capacitance line 250 is set to a black level potential necessary for displaying a black image among the potentials applied to the liquid crystal layer 400.

  In addition, the array substrate 200 includes a switch element 220 disposed at one corner portion PXC where the signal line X and the scanning line Y intersect each other in each display pixel PX, and a pixel connected to the switch element 220 of each display pixel PX. The electrode 230 is provided.

  The counter substrate 300 includes a counter electrode 330 common to the plurality of display pixels PX in the effective display unit 120.

  In addition, the liquid crystal display panel 100 includes a connection part 131 disposed on the outer peripheral part 130 located outside the effective display part 120. The connection portion 131 can be connected to a driving IC chip or a flexible wiring board that functions as a signal supply source. In the example shown in FIG. 1, the connection portion 131 is disposed on the extending portion 200 </ b> A of the array substrate 200 that extends outward from the end portion 300 </ b> A of the counter substrate 300.

  Each of the scanning lines Y (1, 2, 3,..., M) arranged in the effective display unit 120 is connected to the connection unit 131 via the outer peripheral unit 130. Similarly, each of the signal lines X (1, 2, 3,..., N) is connected to the connection portion 131 via the outer peripheral portion 130.

  Next, the structures of the array substrate 200 and the counter substrate 300 will be described in more detail.

  As shown in FIGS. 3 and 4, the array substrate 200 is formed using an insulating substrate 210 having optical transparency such as glass. The switch element 220 is configured by a thin film transistor (TFT) including a semiconductor layer 221 such as an amorphous silicon film or a polycrystalline silicon film.

That is, the gate electrode 222 of the switch element 220 is connected to the scanning line Y on one main surface (front surface) of the insulating substrate 210 (here, the gate electrode 222 is formed integrally with the scanning line Y). And are arranged at the corner portion PXC of the display pixel PX. The auxiliary capacitance line 250 is also disposed on the insulating substrate 210. The gate electrode 222, the scanning line Y, and the auxiliary capacitance line 250 correspond to the first metal layer M1 formed of a light-shielding metal material such as molybdenum-tungsten (MoW), for example. 223. The gate insulating film 223 is formed of, for example, a silicon oxide film (SiO ₂ ) and a silicon nitride film (SiN).

  The semiconductor layer 221 of the switch element 220 is disposed on the gate electrode 222 through the gate insulating film 223, and the channel region is covered with the protective film 224.

  The source line 225 is connected to the signal line X at the corner portion PXC of the display pixel PX (here, the source 225 is formed integrally with the signal line X). The source wiring 225 is in contact with the semiconductor layer 221 of the switch element 220 and constitutes a source electrode.

  The drain wiring 227 is in contact with the semiconductor layer 221 of the switch element 220 in the corner portion PXC of the display pixel PX, and constitutes a drain electrode. The source wiring 225, the signal line X, and the drain wiring 227 are a laminated body formed of a metal material having light shielding properties such as molybdenum (Mo) / aluminum (Al) / molybdenum (Mo), for example. It corresponds to the second metal layer M2 and is covered with an interlayer insulating film 229. The interlayer insulating film 229 is made of, for example, a silicon nitride film (SiN).

  The drain wiring 227 described above extends so as to intersect the auxiliary capacitance line 250 through the gate insulating film 223. At the intersection CP between the drain wiring 227 and the auxiliary capacitance line 250, an island-shaped semiconductor layer 221C is interposed between the drain wiring 227 and the auxiliary capacitance line 250. That is, the semiconductor layer 221 </ b> C is interposed in addition to the gate insulating film 223 between the auxiliary capacitance line 250 formed in the first metal layer M <b> 1 and the drain wiring 227 formed in the second metal layer M <b> 2. . Thereby, an interlayer short circuit between the first metal layer M1 and the second metal layer M2 at the intersection CP can be suppressed.

  Similarly, the scanning line Y and the auxiliary capacitance line 250 formed in the first metal layer M1 and the signal line X formed in the second metal layer M2 intersect via the gate insulating film 223. In order to suppress an interlayer short-circuit at the intersection, it is desirable to interpose a semiconductor layer 221A in addition to the gate insulating film 223 as shown in FIG.

  The pixel electrode 230 is disposed on the interlayer insulating film 229. The pixel electrode 230 is electrically connected to the drain wiring 227 through a contact hole 231 formed at the intersection CP of the drain wiring 227 and the auxiliary capacitance line 250 in the corner portion PXC of the display pixel PX. As described above, by arranging the contact hole for connecting the drain wiring 227 and the pixel electrode 230 on the auxiliary capacitance line 250, the drain wiring 227 is drawn into the display pixel PX and connected to the pixel electrode 230. Compared to a simple configuration, a high aperture ratio can be achieved.

  In a transmissive liquid crystal display panel that selectively transmits backlight and displays an image, the pixel electrode 230 transmits light such as indium tin oxide (ITO) or indium zinc oxide (IZO). It is formed of a metallic material having properties.

  The surface of the pixel electrode 230 is covered with an alignment film 240 for controlling the alignment of the liquid crystal molecules 410 included in the liquid crystal layer 400. The alignment film 240 is rubbed toward the corner portion PXC of the display pixel PX (arrow A in FIGS. 2 and 3).

  The counter substrate 300 is formed using a light-transmitting insulating substrate 310 such as glass. The counter electrode 330 is disposed corresponding to the effective display unit 120. The counter electrode 330 is formed of a light-transmissive metal material such as ITO or IZO. The surface of the counter electrode 330 is covered with an alignment film 350 for controlling the alignment of the liquid crystal molecules 410 included in the liquid crystal layer 400. Similar to the alignment film 240, the alignment film 350 is also rubbed toward the corner portion PXC of the display pixel PX (arrow A in FIGS. 2 and 3). That is, the alignment films 240 and 350 are subjected to parallel alignment processing. Thereby, the optical axis of the liquid crystal molecules 410 is parallel to the arrow A in the figure. In a state where an image can be displayed, that is, in a state where a predetermined bias is applied, the liquid crystal molecules 410 are arranged in the cross section of the liquid crystal layer 400 defined by the arrow A as shown in FIG. Bend with 300.

  The counter substrate 300 includes at least a light shielding film 340 facing the corner portion PXC in each display pixel PX of the array substrate 200.

  In the color display type liquid crystal display device, the liquid crystal display panel 100 includes a plurality of colors of display pixels, for example, red (R), green (G), and blue (B) pixels. That is, the red pixel includes a red color filter that transmits red wavelength light, the green pixel includes a green color filter that transmits green wavelength light, and the blue pixel includes a blue color filter that transmits blue wavelength light. Yes. These color filters are arranged on the main surface of the array substrate 200 or the counter substrate 300.

  Such an OCB mode liquid crystal display device has a retardation (phase difference) of the liquid crystal layer 400 including the liquid crystal molecules 410 bend-aligned as shown in FIG. 4 in a predetermined display state where a voltage is applied to the liquid crystal layer 400. An optical compensation element for optically compensating is provided. That is, the first compensation element 510 is arranged on one main surface of the liquid crystal display panel 100, that is, the outer surface on the array substrate 200 side. The second compensation element 520 is disposed on the other main surface of the liquid crystal display panel 100, that is, the outer surface on the counter substrate 300 side.

  Each of the first compensation elements 510 and 520 includes a plurality of optical elements having functions as a polarizing plate and a retardation plate. Examples of the optical element include a retardation plate mainly having retardation in its thickness direction, and a retardation plate mainly having retardation in its in-plane direction. The respective polarizing plates are arranged so that their transmission axes are orthogonal to each other and form an angle of 45 ° with respect to the liquid crystal alignment direction A.

  Thus, if the retardation amount of the object between the pair of polarizing plates is effectively 0 or an integral multiple of the wavelength, no light is transmitted and a black image is displayed. On the other hand, if the retardation amount of the object between the pair of polarizing plates is effectively λ / 2 with respect to the incident light having the wavelength λ, the light is transmitted and a white image (or color image) is displayed.

  By the way, in the liquid crystal display device having the above-described configuration, when a pixel defect that becomes a bright spot occurs, a laser beam is emitted from the back surface side of the array substrate 200 (that is, the surface side on which the first optical compensation element 510 is disposed). , And a darkening process for darkening the display pixels is performed. In the OCB mode liquid crystal display device, even if the pixel electrode 230 and the scanning line Y are short-circuited, the scanning line Y is not at a black level potential, so that it cannot be darkened. For this reason, the auxiliary capacitance line 250 having the black level potential and the pixel electrode 230 are short-circuited to achieve a dark spot.

  In the configuration described above, the drain wiring 227 and the auxiliary capacitance line 250 can be short-circuited at the intersection CP between the drain wiring 227 and the auxiliary capacitance line 250, as shown in FIGS. Since the drain wiring 227 is electrically connected to the pixel electrode 230 and is substantially at the same potential as the pixel electrode 230, short-circuiting the drain wiring 227 and the auxiliary capacitance line 250 can be connected to the pixel electrode 230. This is the same as short-circuiting the capacitor line 250.

  Therefore, in the darkening process according to this embodiment, a laser beam is irradiated from the back side of the array substrate 200 at the intersection CP. As a result, as shown in FIG. 5, the drain wiring 227 and the auxiliary capacitance line 250 are short-circuited. In FIG. 5, only the array substrate 200 is shown. Here, the drain wiring 227 and the auxiliary capacitance line 250 are both formed of a metal material having a light shielding property. For this reason, the laser power necessary for short-circuiting the drain wiring 227 and the auxiliary capacitance line 250 compared to the case where the auxiliary capacitance line 250 and the pixel electrode 230 formed of a light-transmissive metal material are short-circuited. Can be reduced.

  In this darkening process, as shown in FIGS. 3 and 4, the first metal layer such as the scanning line Y and the auxiliary capacitance line 250 and the third metal layer M3 such as the pixel electrode 230 are overlapped. In the region that does not become necessary, the source wiring 225 and the drain wiring 227 formed in the second metal layer M2 are irradiated with a laser beam. Thereby, as shown in FIG. 5, the source wiring 225 is disconnected from the signal line X, and the drain wiring 227 is disconnected from the pixel electrode 230.

  That is, the drain wiring 227 and the auxiliary capacitance line 250 can be short-circuited with a small laser power, and the pixel electrode 230 can be separated from the signal line X, and the pixel defect that has become a bright spot is darkened (that is, the pixel It is possible to relieve defects).

  Further, in such a darkening process, the laser power necessary for the process can be reduced, so that damage to other layers, particularly the alignment film 240 on the array substrate 200 side, can be reduced. For this reason, it is possible to suppress the occurrence of alignment disorder of the liquid crystal molecules 410 due to the damage of the alignment film 240.

  On the other hand, since the light shielding film 340 is disposed on the counter substrate 300 side to face the corner portion PXC where the darkening process as described above is performed on the array substrate 200 side, the alignment film 240 is damaged. Even if the alignment disorder of the liquid crystal molecules 410 occurs, light leakage due to the alignment disorder can be prevented. For this reason, it is possible to suppress a decrease in display quality.

  Further, light leakage tends to appear toward the downstream side in the rubbing direction A from the point irradiated with the laser. In this embodiment, the light leakage corresponds to the downstream side in the rubbing direction A as shown in FIG. Since the darkening process is performed at the corner portion PXC of the display pixel PX, it is not necessary to dispose a light shielding film over a wide range. In addition, a contact hole 231 for contacting the pixel electrode 230 and the switch element 220 (strictly speaking, contacting the drain wiring 227) is disposed at this corner portion. As described above, the location where the darkening process is performed and the contact location with the pixel electrode 230 are shared at the intersection CP (that is, the location where the darkening process is performed and the contact location with the pixel electrode 230 overlap). As a result, the aperture ratio of the display pixel PX can be increased.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

  In the above-described embodiment, the OCB mode liquid crystal display device has been described as an example, but it goes without saying that the present invention may be applied to other display mode liquid crystal display devices.

FIG. 1 schematically shows a configuration of a liquid crystal display panel of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing the configuration of display pixels on the array substrate of the liquid crystal display panel shown in FIG. FIG. 3 is an enlarged plan view of a corner portion of the display pixel in the array substrate shown in FIG. 4 is a cross-sectional view showing a structure in which the corner portion shown in FIG. 3 is cut along line AB. FIG. 5 is a cross-sectional view schematically showing the structure of the array substrate after the darkening process.

Explanation of symbols

  PX ... display pixel, PXC ... corner portion, CP ... intersection, Y ... scanning line, X ... signal line, 100 ... liquid crystal display panel, 110 ... sealing material, 120 ... effective display portion, 200 ... array substrate, 210 ... insulation Substrate, 220 ... switch element, 221 ... semiconductor layer, 221C ... island semiconductor layer, 222 ... gate electrode, 223 ... gate insulating film, 224 ... protective film, 225 ... source wiring, 227 ... drain wiring, 229 ... interlayer insulating film , 230 ... pixel electrode, 240 ... alignment film, 250 ... storage capacitor line, 300 ... counter substrate, 310 ... insulating substrate, 330 ... counter electrode, 340 ... light shielding film, 350 ... alignment film, 400 ... liquid crystal layer, 410 ... liquid crystal Molecules 510 ... compensation element 520 ... compensation element M1 ... first metal layer M2 ... second metal layer M3 ... third metal layer A ... rubbing direction (orientation direction)

Claims (3)

An array substrate;
A counter substrate facing the array substrate;
A liquid crystal layer including liquid crystal molecules held between the array substrate and the counter substrate and bend-aligned between the array substrate and the counter substrate in a state where a predetermined bias is applied ;
A switch element including a semiconductor layer disposed in each pixel on the array substrate;
A scanning line to which a control signal for controlling the driving of the switch element is supplied;
An auxiliary capacitance line extending substantially parallel to the scanning line and having a black level potential;
A first insulating layer covering the scanning line and the auxiliary capacitance line;
A signal line for supplying a video signal to be written to each pixel across the scanning line and the auxiliary capacitance line through the first insulating layer;
And a source wiring connected to the signal line as well as contact with the semiconductor layer of the switching element in one corner portion of the pixel,
A drain wiring that contacts the semiconductor layer of the switch element at the corner and intersects the storage capacitor line via the first insulating layer and the island-shaped semiconductor layer;
A second insulating film covering the signal line, the source wiring, and the drain wiring;
Said second disposed on the insulating film, the drain wiring and the storage capacitor line and a pixel electrode connected to the drain wiring through a contact hole formed in the second insulating film at the intersection of,
An alignment film that covers the surface of the pixel electrode and is rubbed toward the corner portion;
A light-shielding film disposed on the counter substrate and facing a corner portion of the array substrate;
An OCB mode liquid crystal display device comprising:   2. The liquid crystal display device according to claim 1, wherein at least one of the source wiring and the drain wiring is cut and the drain wiring and the auxiliary capacitance line are electrically connected at the intersection.   The liquid crystal display device according to claim 1, wherein the drain wiring and the auxiliary capacitance line are formed of a metal material having a light shielding property.

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