JP2009116177A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of performing an excellent display by suppressing a light leakage affected by the alignment state of a pixel peripheral portion. <P>SOLUTION: Disclosed is the OCB (Optically Compensated Bend) type liquid crystal display device having a first substrate 1 and a second substrate 2 disposed opposite each other, a liquid crystal layer 3 sandwiched between the first substrate 1 and second substrate 2, and a display unit comprising a plurality of display pixels PX disposed in a matrix form, where the first substrate 1 has pixel electrodes PE disposed for respective display pixels PX, the second substrate 2 has a counter electrode CE opposed to the pixel electrode PE and a light shield layer BMI disposed in a peripheral pixel region SA enclosing the display pixels PX, and a light shield layer BM has an extension portion where ends of the pixel electrodes PX area disposed extending to inside the display pixels PX beyond ends defined by geometrical optics. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to an OCB type liquid crystal display device.

  An OCB (Optically Compensated Bend) type liquid crystal display device has characteristics of a high-speed response and a wide viewing angle as compared with a liquid crystal display device such as a TN mode. The OCB type liquid crystal display device can obtain a good display state by initially performing a transition from the splay alignment to the bend alignment and maintaining the bend alignment.

  Therefore, in the OCB type liquid crystal display device, the alignment state is changed from the splay alignment, which is the alignment state of the liquid crystal molecules when the power is off, to the bend alignment, which is the alignment state of the liquid crystal molecules when the power is on (hereinafter referred to as transition). And, conversely, a driving method for preventing a change in the alignment state from the bend alignment to the splay alignment (hereinafter referred to as reverse transition) is required.

Conventionally, in an OCB type liquid crystal display device, in order to prevent a reverse transition phenomenon, a proposal has been made to perform black insertion driving by periodically applying a high voltage corresponding to black display to a liquid crystal layer (see Patent Document 1). .
JP 2002-202491 A

  However, the alignment state of the pixel peripheral portion to which the drive application voltage is not applied has not been clarified so far, and it has been found that light leakage may occur due to the influence of the alignment state of the pixel peripheral portion. In addition, it has been found that such light leakage at the periphery of the pixel is likely to occur particularly in a high-definition display device.

  The present invention has been made in view of the above-described problems, and is a liquid crystal display capable of suppressing the occurrence of light leakage due to the influence of the orientation state of the peripheral portion of a pixel in an OCB type liquid crystal display device and capable of good display. An object is to provide an apparatus.

  A liquid crystal display device according to a first aspect of the present invention includes a first substrate and a second substrate that are arranged to face each other, a liquid crystal layer that is sandwiched between the first substrate and the second substrate, and a matrix shape. An OCB type liquid crystal display device comprising a plurality of display pixels disposed on the display substrate, wherein the first substrate includes pixel electrodes disposed on the display pixels, and the second substrate. Includes a counter electrode facing the pixel electrode, and a light shielding layer disposed in a peripheral pixel region surrounding the display pixel, and the light shielding layer has an end portion of the pixel electrode geometrically optically And an extending portion that is arranged so as to extend from the end defined by the above to the inside of the display pixel.

  A liquid crystal display device according to a second aspect of the present invention includes a first substrate and a second substrate which are arranged to face each other, a liquid crystal layer sandwiched between the first substrate and the second substrate, and a matrix shape. An OCB-type liquid crystal display device comprising: a display unit including a plurality of display pixels disposed on the display substrate, wherein the first substrate includes a pixel electrode disposed on each of the display pixels and the plurality of display pixels. And the second substrate has a counter electrode opposite to the pixel electrode, and the potential difference between the auxiliary capacitor line and the counter electrode is determined by the display. It is set to be approximately one half or more of the difference between the maximum value and the minimum value of the voltage applied to the pixel.

  According to the present invention, it is possible to provide a liquid crystal display device capable of suppressing the occurrence of light leakage due to the influence of the alignment state of the peripheral portion of the pixel and capable of good display.

  Hereinafter, a liquid crystal display device according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the liquid crystal display device according to the present embodiment controls an OCB mode liquid crystal display panel DP, a backlight BL that illuminates the liquid crystal display panel DP, and the liquid crystal display panel DP and the backlight BL. A controller CNT is provided.

  The liquid crystal display panel DP has a 9-inch diagonal display area and has [(800 × 3) × 480] display pixels PX. That is, the pitch of the display pixels PX is 246 μm. The liquid crystal display panel DP has a pair of substrates, that is, an array substrate 1 and a counter substrate 2, and a liquid crystal layer 3 sandwiched between the array substrate 1 and the counter substrate 2, and is normally white. The display operation is realized. The liquid crystal layer 3 includes, for example, OCB mode liquid crystal that is previously transitioned from splay alignment to bend alignment as a liquid crystal material. In the present embodiment, the reverse transition from the bend alignment of the liquid crystal to the splay alignment is prevented by periodically applying a driving voltage corresponding to black display to the liquid crystal layer 3.

  In addition, the liquid crystal display panel DP has a display unit composed of display pixels PX arranged in a substantially matrix shape. The array substrate 1 has a transparent insulating substrate such as glass. On the transparent insulating substrate, a plurality of pixel electrodes PE are arranged for each display pixel PX.

  The counter substrate 2 is, for example, a color filter (not shown) composed of red, green, and blue colored layers disposed on a transparent insulating substrate such as glass, and a color filter facing a plurality of pixel electrodes PE. The counter electrode CE and the like are disposed.

  Each pixel electrode PE and counter electrode CE are made of a transparent electrode material such as ITO, for example, and covered with an alignment film (not shown) that is rubbed in a direction D parallel to each other. Each pixel electrode PE and counter electrode CE constitute a display pixel PX together with a pixel region which is a part of the liquid crystal layer 3 controlled by the liquid crystal molecular arrangement corresponding to the electric field from the pixel electrode PE and counter electrode CE.

  Each of the plurality of display pixels PX has a liquid crystal capacitance Clc configured by sandwiching the liquid crystal layer 3 between the pixel electrode PE and the counter electrode CE. The liquid crystal capacitance Clc is determined by the relative dielectric constant of the liquid crystal material, the pixel electrode area, and the liquid crystal cell gap. Further, the storage capacitor Cs is configured by superimposing the pixel electrode PE and the storage capacitor line C disposed so as to extend substantially parallel to the scanning line G via an insulating film.

  Furthermore, the array substrate 1 includes a plurality of scanning lines G (G1 to Gm) and a plurality of pixel electrodes PE arranged along a row in which a plurality of pixel electrodes PE are arranged in a peripheral region SA surrounding the display pixel PX. A plurality of signal lines S (S1 to Sn) arranged along a column in which are arranged, and a plurality of pixel switches W arranged in the vicinity of the intersection positions of the scanning lines G and the signal lines S. In the liquid crystal display device according to the present embodiment, the peripheral area SA refers to an area outside the area where the pixel electrode PE is disposed.

  Each pixel switch W is electrically connected between the corresponding signal line S and the corresponding pixel electrode PE when driven through the corresponding scanning line G. Each pixel switch W is made of, for example, a thin film transistor. The gate of the pixel switch W is connected to the scanning line G, and the source-drain path is connected between the signal line S and the pixel electrode PE.

  Further, the counter substrate 2 has a light shielding layer BM made of a metal material arranged in a lattice shape corresponding to the peripheral area SA. The light shielding layer BM is disposed so as to extend inside the display pixel PX from the position where the end of the pixel electrode PE is disposed. In other words, the light shielding layer BM has an auxiliary capacitance line C so that light emitted from between the signal line S and the auxiliary capacitance line C is not visually recognized in the viewing angle direction even if the optical path is changed due to the influence of refraction or the like. 1 μm from the end of the display to the inside of the display pixel PX. Further, the light shielding layer BM is arranged to extend 1.5 μm further inside the display pixel PX from the end defined by geometrical optics.

  A pixel voltage generated between the pixel electrode PE and the counter electrode CE is not applied to the liquid crystal layer 3 in the peripheral area SA. Therefore, the liquid crystal molecules in the peripheral region SA are not in a controlled alignment state, and the domain DM is generated. Moreover, the domain DM extends on the pixel electrode PE as the voltage applied to the display pixel PX decreases. The light incident on the domain DM may be irregularly reflected by liquid crystal molecules aligned in various directions. The light irregularly reflected in this manner is emitted from the opening without being blocked by the light blocking layer BM, and may be visually recognized as light leakage particularly when viewed from an oblique direction of the display screen.

  On the other hand, in the liquid crystal display device according to the present embodiment, the light shielding layer BM is arranged to extend from the peripheral region SA to the display pixel PX by 1.5 μm further from the geometrically defined end. Even when the voltage applied to the pixel PX is small, the light irregularly reflected by the domain DM is reliably shielded by the light shielding layer BM, and light leakage can be suppressed. In this embodiment, the light-shielding layer BM is further extended to the display pixel PX side by 1.5 μm from the end defined by geometrical optics. However, if it is 1 μm or more, there is no problem in display. In order to ensure a sufficient aperture ratio, it is desirable not to extend 1% or more of the pixel pitch from the end defined by geometrical optics, and it is more preferable not to extend more than 0.5% of the pixel pitch. .

  The control / drive circuit unit CNT includes a gate driver GD that sequentially drives the plurality of scanning lines G1 to Gm so that the plurality of pixel switches W are turned on in units of rows, and the pixel switches W in each row are turned on by driving the corresponding scanning lines G. The source driver SD that outputs the pixel voltage Vd to the plurality of signal lines S1 to Sn, the backlight driver LD that drives the backlight BL, the gate driver GD, the source driver SD, and the backlight driver (inverter) A controller 5 for controlling the LD is provided.

  The controller 5 is configured to perform an initialization process for changing the liquid crystal molecules from the splay alignment to the bend alignment by changing the counter voltage Vcom and applying a relatively large driving voltage to the liquid crystal layer 3 when the power is turned on.

  The controller 5 outputs a control signal CTG generated based on the synchronization signal input from the external signal source SS to the gate driver GD, and a control signal CTS generated based on the synchronization signal input from the external signal source SS. , And the video signal or black insertion signal input from the external signal source SS is output to the source driver SD. Further, the controller 5 outputs a counter voltage Vcom to the counter electrode CE.

  In the controller 5, based on the synchronization signal input from the external signal source SS, as shown in FIG. 3, the first period and the second period are set within one frame period (1Fr). The first period is used to perform reverse transition prevention voltage writing for writing the reverse transition prevention voltage Vb to the plurality of display pixels PX. The second period is used to perform video signal writing for writing the video signal Vs to the plurality of display pixels PX. The total time length of the first period and the second period is equal to one frame period.

  The gate driver GD sequentially drives the plurality of scanning lines G1 to Gm so as to sequentially select the rows of the plurality of display pixels PX as reverse transition prevention voltage writing in the first period under the control of the control signal CTG.

  In the second period following the first period, the gate driver GD sequentially drives the plurality of scanning lines G1 to Gm so as to sequentially select the rows of the plurality of display pixels PX as video signal writing scans.

  The source driver SD outputs the reverse transition prevention voltages Vb (+) and Vb (−) for one row as signal line voltages (source voltages) while each of the scanning lines G1 to Gm is driven in the first period. To do. The source driver SD outputs the video signal Vs for one row as a video level signal line input voltage (source voltage) while each of the scanning lines G1 to Gm is driven in the second period. As described above, the source driver SD drives the plurality of signal lines S1 to Sn in parallel. Vb (+) and Vb (−) are source voltages when a reverse transition prevention voltage is applied when each pixel potential is positive or negative with respect to the counter voltage Vcom.

  The source voltage is applied to the pixel electrode PE of the display pixel PX in the selected row via the corresponding pixel switch W. The potential difference between the source voltage applied to the pixel electrode PE and the counter voltage Vcom applied to the counter electrode CE is held in the liquid crystal capacitor Clc. Note that the source voltage for all the display pixels PX is set to a reverse polarity for each column of the display pixels PX in the case of column inversion driving, and is set to a reverse polarity for each frame in the case of frame inversion driving.

  The auxiliary capacitance voltage Vcs is a voltage signal applied to the auxiliary capacitance line C (C1 to Cm). In the case of the liquid crystal display device according to the present embodiment, the voltage applied to the storage capacitor line C is, for example, a DC voltage that is substantially the same as the counter voltage Vcom applied to the counter electrode CE.

  As described above, in the liquid crystal display device according to the present embodiment, the light emitted from the light shielding layer BM between the signal line S and the auxiliary capacitance line C is not viewed from the viewing angle direction on geometric optics. Furthermore, it extends to the pixel PX side so as not to be viewed from the viewing angle direction due to the influence of an undesired domain DM, and thereby light leakage from the peripheral pixel region SA to the display pixel PX can be suppressed. Therefore, for example, the light transmittance in the case of black display can be minimized, and as a result, the contrast can be improved.

  That is, according to the liquid crystal display device according to the present embodiment, it is possible to provide a liquid crystal display device capable of suppressing the occurrence of light leakage due to the influence of the alignment state of the peripheral portion of the pixel and performing good display.

  Next, a liquid crystal display device according to a second embodiment of the present invention will be described below with reference to the drawings. In the following description, the same components as those of the liquid crystal display device according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  The liquid crystal display device according to the present embodiment includes an OCB mode liquid crystal display panel, similarly to the liquid crystal display device according to the first embodiment described above. On the transparent insulating substrate of the array substrate 1, a plurality of pixel electrodes PE are arranged for each display pixel PX. The counter substrate 2 has a counter electrode CE disposed on the transparent insulating substrate so as to face the plurality of pixel electrodes PE.

  Each pixel electrode PE and counter electrode CE are covered with an alignment film (not shown) that is rubbed in a direction D parallel to each other. Each pixel electrode PE and counter electrode CE constitute a display pixel PX together with a pixel region which is a part of the liquid crystal layer 3 controlled by the liquid crystal molecular arrangement corresponding to the electric field from the pixel electrode PE and counter electrode CE.

  The counter substrate 2 has a light shielding layer BM arranged in a lattice shape corresponding to the peripheral area SA. In the liquid crystal display device according to the present embodiment, as shown in FIG. 4, the light shielding layer BM in the peripheral pixel region SA extends to the end that is geometrically defined on the display pixel PX side. Only the end side in the rubbing direction D of the alignment film of the light shielding layer BM is arranged to extend from the peripheral region SA to the display pixel PX by 1.5 μm from the geometrically defined end.

  Here, the end side in the rubbing direction D is the end side of the vector component DA substantially parallel to the scanning line G in the rubbing direction D and the vector component DB substantially parallel to the signal line S in the rubbing direction D. For example, when rubbing in the direction D as shown in FIG. 1, the terminal side of the vector component DA of the light shielding layer BM is the left side of the light shielding layer BM shown in FIG.

  The liquid crystal display device according to the present embodiment is the same as the liquid crystal display device according to the first embodiment described above, except for the configuration of the light shielding layer BM. Due to differences in rubbing and rubbing during the rubbing treatment of the alignment film, a domain DM that is an area in which the alignment state of liquid crystal molecules is not controlled tends to occur on the end side in the rubbing direction D in the peripheral pixel area SA. .

  Therefore, as shown in FIG. 4, the end side in the rubbing direction D of the light shielding layer BM is effectively extended by being arranged to extend inside the display pixel PX by 1.5 μm from the geometrically defined end. A high aperture ratio can be ensured while suppressing light leakage from between the signal line S and the auxiliary capacitance line C.

  Next, a liquid crystal display device according to a third embodiment of the present invention will be described below with reference to the drawings. The liquid crystal display device according to the present embodiment includes an OCB mode liquid crystal display panel, similarly to the liquid crystal display device according to the first embodiment described above.

  In the liquid crystal display device according to the present embodiment, the generation region of the domain DM is reduced by appropriately setting the voltage of the electrode forming the auxiliary capacitor Cs. For example, in a normally white type OCB liquid crystal display device, one of the voltages Vb (+) and Vb (−) in the vicinity of the voltage Vb (+) corresponding to black display is used as the auxiliary capacitor line C. It may be selected as the voltage Vcs to be applied to.

  In the liquid crystal display device according to the present embodiment, as the voltage Vcs applied to the storage capacitor line C for reducing the domain DM, a voltage capable of ensuring a desired potential difference with respect to the counter voltage Vcom, for example, a voltage corresponding to black display Vb (+) or voltage Vb (−) is used.

  In this embodiment, the voltage Vb (+) or the voltage Vb (−) corresponding to the black display that has the least influence on the display and can ensure a sufficient potential difference is applied to the auxiliary capacitance line C. It is possible to reduce the domain DM even with a voltage corresponding to an intermediate gradation. In this embodiment, since a normally white mode liquid crystal is described as an example, the voltage Vb (+) or the voltage Vb (−) corresponding to black display is used as a voltage capable of securing a sufficient potential difference. In a normally black mode liquid crystal, a voltage corresponding to white display can be used. In any case, it is important to apply a voltage that is set to be equal to or higher than the potential difference at which the domain DM does not occur to the storage capacitor line. For this reason, the voltage applied to the storage capacitor line is set to be approximately one half or more of the maximum potential difference during the display operation applied to the display pixel.

  As a result, as shown in FIG. 5, the vertical electric field between the counter electrode CE and the auxiliary capacitance line C can be strengthened, and the size of the domain DM under the light shielding layer BM can be reduced. When the size of the domain DM is reduced, the light emitted to the liquid crystal layer 3 from between the signal line S and the auxiliary capacitance line C is suppressed from being affected by the domain DM. Therefore, by applying the voltage Vb (+) or Vb (−) to the auxiliary capacitance line C as described above, light leakage of light emitted to the liquid crystal layer 3 from between the signal line S and the auxiliary capacitance line C. Can be suppressed.

  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 scope of the invention in the implementation stage. In the first and second embodiments described above, it is desirable to adopt one that is suitable for the design of the applied liquid crystal display device in consideration of the quality of the displayed image, the aperture ratio, and the like.

  Further, various inventions can be formed by appropriately combining a plurality of constituent elements 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.

1 is a diagram schematically showing a configuration example of a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a diagram schematically showing an example of a cross section of a display pixel and a peripheral pixel region of the liquid crystal display device shown in FIG. 1. FIG. 3 is a diagram for explaining an example of a driving method of the liquid crystal display device illustrated in FIG. 1. The figure which shows roughly an example of the cross section of the display pixel and peripheral pixel area | region of the liquid crystal display device which concerns on 2nd Embodiment of this invention. The figure which shows schematically an example of the cross section of the display pixel and peripheral pixel area | region of the liquid crystal display device which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  PX ... display pixel, PE ... pixel electrode, CE ... counter electrode, SA ... peripheral pixel region, BM ... light shielding layer, Vcom ... counter voltage, 1 ... array substrate, 2 ... counter substrate, 3 ... liquid crystal layer

Claims (4)

A display unit comprising a first substrate and a second substrate arranged to face each other, a liquid crystal layer sandwiched between the first substrate and the second substrate, and a plurality of display pixels arranged in a matrix An OCB type liquid crystal display device comprising:
The first substrate has a pixel electrode disposed on each of the display pixels,
The second substrate includes a counter electrode facing the pixel electrode, and a light shielding layer disposed in a peripheral pixel region surrounding the display pixel,
The OCB-type liquid crystal display device, wherein the light-shielding layer includes an extending portion in which an end portion of the pixel electrode extends from the end defined by geometrical optics to the inside of the display pixel. The first substrate and the second substrate have a pair of alignment films rubbed in directions substantially parallel to each other,
The OCB type liquid crystal display device according to claim 1, wherein the extending portion of the light shielding layer is located on a terminal side in the rubbing direction. A display unit comprising a first substrate and a second substrate arranged to face each other, a liquid crystal layer sandwiched between the first substrate and the second substrate, and a plurality of display pixels arranged in a matrix An OCB type liquid crystal display device comprising:
The first substrate includes a pixel electrode disposed in each of the display pixels, and an auxiliary capacitance line disposed in a peripheral pixel region surrounding the plurality of display pixels,
The second substrate has a counter electrode facing the pixel electrode,
An OCB type liquid crystal display device in which a potential difference between the auxiliary capacitance line and the counter electrode is set to be approximately one half or more of a difference between a maximum value and a minimum value of a voltage applied to the display pixel.   4. The OCB type liquid crystal display device according to claim 3, wherein the voltage applied to the auxiliary capacitance electrode is a voltage in the vicinity of a potential of a negative electrode or a positive electrode used for black display.

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