Liquid crystal display device

The present invention relates to a liquid crystal display device capable of controlling a viewing angle, and more particularly to a liquid crystal display device using an FFS (Fringe Field Switching) method.

Liquid crystal display devices, especially liquid crystal display devices using TFTs (Thin Film Transistors), are widely used in mobile phones and large televisions. Under such circumstances, when considering the visual recognition by a plurality of people, a liquid crystal display device having a wide viewing angle that allows the display contents to be visually recognized from a visual field other than the front is desired.

FIG. 6 is an explanatory diagram of a conventional liquid crystal display device having a concealment mode. Against this background, as an example, a display having a concealment mode as shown in FIG. 6 has been proposed (see, for example, Patent Document 1). In FIG. 6, as the backlight that illuminates the liquid crystal panel from the back side, a backlight having strong directivity is used. Then, for example, a polymer-dispersed liquid crystal panel (scattering non-scattering switch layer) that can switch between a scattered state and a non-scattering state is provided between a normal liquid crystal panel and the directional backlight.

When the scattering layer is in the non-scattering state, the light from the backlight is radiated only to the front, so that the display cannot be seen from an angle. On the other hand, when the scattering layer is in a scattered state, the light from the backlight is also emitted in an oblique direction, so that the display can be viewed diagonally and the display can be shared by a plurality of people. In this case, since it is necessary to provide a special liquid crystal panel in addition to the normal liquid crystal panel, there is a problem that the price becomes high.

Next, a conventional FFS type liquid crystal display device in which the viewing angle is improved by making the common electrode into a dogleg shape will be described. FIG. 7 is a plan view of each RGB pixel of the conventional FFS type liquid crystal display device. Further, FIG. 8 is an explanatory diagram of the operation of the liquid crystal molecules by applying a voltage to the conventional FFS type liquid crystal display device.

As shown in FIG. 7, in this liquid crystal display device, a dogleg-shaped common electrode is formed in order to define the direction in which the liquid crystal falls. Then, the liquid crystal molecules are oriented in the vertical direction as shown in FIG. 8A in the state where no voltage is applied. On the other hand, when the voltage is applied, the liquid crystal molecules collapse in the direction determined by the influence of the oblique electric field by the common electrode, that is, in the direction perpendicular to the extending direction of the common electrode. As a result, the liquid crystal can be tilted in two directions corresponding to the dogleg, and a liquid crystal display device having a good viewing angle is realized.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 5-72529 (Page 1, Fig. 1)</text></patcit>

<p> However, the conventional liquid crystal display device has the following problems. Although the visibility in a specific direction was improved by forming the common electrode into a dogleg shape, it was not possible to switch the common electrode so as to have concealment as necessary.</p><p> The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a liquid crystal display device capable of adjusting the viewing angle in the vertical and horizontal directions without the need to provide a special liquid crystal panel. ..</p>

<p> The liquid crystal display device according to the present invention includes a pixel electrode and a common electrode having a dogleg shape, and displays a display screen composed of a set of RGB pixels whose orientation is controlled so that the liquid crystal molecules are tilted by the FFS method. The liquid crystal display device has a liquid crystal molecule that tilts from the horizontal state to the vertical or horizontal direction by applying a control voltage via a viewing angle control line formed by a transparent electrode separate from the RGB pixel. Orientation controlled<u style="single">, Give confidentiality to the display information by the RGB pixels</u>It is equipped with a viewing angle control pixel, and the viewing angle control pixel is inside.<u style="single">To give confidentiality to the displayed information in the left-right direction</u>Left-right common electrode, or<u style="single">To keep the information displayed in the vertical direction confidential</u>One of the common electrodes in the vertical direction is present.</p>

<p> According to the present invention, together with each RGB pixel whose orientation is controlled so that the liquid crystal molecules are tilted by the FFS method, a viewing angle control pixel whose orientation is controlled so that the liquid crystal molecules are tilted in the vertical or horizontal direction is further formed. Therefore, it is not necessary to provide a special liquid crystal panel, and it is possible to obtain a liquid crystal display device capable of adjusting the viewing angle in the vertical and horizontal directions.</p>

Hereinafter, preferred embodiments of the liquid crystal display device of the present invention will be described with reference to the drawings.

Embodiment 1. FIG. 1 is a plan view of each RGB pixel and a viewing angle control pixel of the liquid crystal display device according to the first embodiment of the present invention. Each RGB pixel in FIG. 1 includes a pixel electrode and a common electrode 11. The common electrode 11 provided on each pixel has a dogleg shape.

Further, the liquid crystal display device of the present invention further has a viewing angle control pixel 20 for controlling the viewing angle in addition to the RGB pixels. The viewing angle control pixel 20 is oriented so that the liquid crystal molecules are tilted in the vertical or horizontal direction, and a control voltage is applied via a viewing angle control line (not shown) separate from the RGB pixels. In the viewing angle control pixel 20, either the left-right common electrode 21a or the vertical common electrode 21b exists.

In FIG. 1, the common electrode 21a in the left-right direction is shown. By applying a control voltage to the viewing angle control pixel 20 via the viewing angle control line, the liquid crystal molecules can be tilted in the front-rear direction or the left-right direction, and the viewing angle can be controlled.

The viewing angle control pixel 20 is supplied with an applied voltage via a viewing angle control line separate from the RGB pixel. Then, by forming the viewing angle control line, which is an independent common line for the viewing angle control pixel 20, with the transparent electrode, a merit that a large aperture ratio can be obtained can be obtained. Further, since the common lines are independent, the applied voltage of the viewing angle control pixel 20 can be input as an arbitrary waveform.

Further, the viewing angle control pixel 20 does not directly contribute to the display, but contributes to make the display information difficult to see. Therefore, there is an advantage that it is not necessary to provide a colored layer on the color filter substrate side facing the viewing angle control pixel 20.

Next, the operation of the liquid crystal molecules in the viewing angle control pixel 20 with / without voltage applied will be described. FIG. 2 is an explanatory diagram of the operation of the liquid crystal molecules in the viewing angle control pixel 20 having the common electrodes 21a in the left-right orientation according to the first embodiment of the present invention.

In the viewing angle control pixel 20 having the common electrodes 21a in the left-right orientation, when no voltage is applied, the liquid crystal is in a horizontal state as shown in FIG. 2A. Therefore, the display of the viewing angle control pixel 20 remains black and does not affect the overall display. This also applies to the front, up / down / left / right, and oblique viewing angles, and the display itself using RGB pixels can be used quite naturally.

On the other hand, when a voltage is applied to the viewing angle control pixel 20 having the common electrodes 21a in the left-right direction, the liquid crystal molecules are formed between the central portion of the common electrodes and the common electrodes as shown in FIG. 2 (b). It stands vertically in the center. Therefore, when viewed from the left-right direction, the portion containing the common electrode 21a in the left-right direction allows light to escape brightly. On the contrary, when viewed from the vertical direction, light does not leak to the portion where the common electrode 21a in the left-right direction is inserted.

On the other hand, in the viewing angle control pixel 20 having the common electrode 21b in the vertical direction, when a voltage is applied, the liquid crystal molecules are located at the center of the common electrode in a direction 90 degrees different from that in FIG. 2 (b). It stands vertically at the center between the part and the common electrode. Therefore, when viewed from the left-right direction, light does not leak from the portion where the common electrode 21b in the vertical direction is inserted. On the contrary, when viewed from the vertical direction, the portion containing the common electrode 21b in the vertical direction allows light to escape brightly.

As a result, when a voltage is applied to the viewing angle control pixel 20, the viewing angle control region having the left and right common electrodes 21a is white, and the viewing angle having the vertical common electrodes 21b is viewed from the left and right directions. The angle control area will be recognized as black. On the contrary, with respect to the field of view from the vertical direction, the viewing angle control area having the common electrode 21a in the left-right direction is recognized as black, and the viewing angle control area having the common electrode 21b in the vertical direction is recognized as white.

Then, these patterns overlap with the normal display pattern by RGB pixels, and when the patterns are viewed from the left-right direction and the up-down direction in each pixel, it is possible to make it difficult to understand what is written. The displayed information can be kept confidential.

As described above, the viewing angle control pixel 20 corresponding to each RGB pixel has either a pixel having a common electrode 21a in the left-right direction or a pixel having a common electrode 21b in the vertical direction. By applying a voltage to the viewing angle control pixel 20, it is possible to whiten the display for both the left-right direction and the up-down direction. As a result, it is possible to display with confidentiality with respect to the field of view other than the front.

FIG. 3 is a diagram showing a viewing angle-dependent brightness distribution of the viewing angle control pixel 20 by applying a voltage according to the first embodiment of the present invention, in the case where the viewing angle control pixel has a common electrode 21a in the left-right direction. Is shown. When no voltage is applied to the viewing angle control pixel 20, the brightness is equivalent to that of a black screen in both the front and the diagonal directions from the top, bottom, left, and right. On the other hand, when a voltage is applied to the viewing angle control pixel 20, the front surface is black, but light comes out and becomes brighter in the diagonal direction from the left and right.

As a result, since the light leaks only in the diagonal direction of the left-right direction, it becomes difficult to recognize the displayed screen when viewed from the diagonal direction of the left-right direction, and it becomes possible to give the information confidentiality.

FIG. 4 is another plan view of each RGB pixel and the viewing angle control pixel of the liquid crystal display device according to the first embodiment of the present invention. The configuration of each RGB pixel and the viewing angle control pixel 20 in FIG. 4A shown in the upper part is the same as that in FIG. 1 above. Each RGB pixel in FIG. 4A is provided with a dogleg-shaped common electrode 11a for improving visibility in the left-right direction. Further, by applying a voltage to the common electrode 21a in the left-right direction provided in the viewing angle control pixel 20, the display information in the left-right direction can be made confidential.

On the other hand, the configurations of the RGB pixels and the viewing angle control pixel 20 in FIG. 4 (b) shown in the lower part are configurations having visibility and concealment 90 degrees different from those in FIG. 4 (a). Each RGB pixel in FIG. 4B is provided with a dogleg-shaped common electrode 11b in order to improve visibility in the vertical direction. Further, by applying a voltage to the vertical common electrode 21b provided on the viewing angle control pixel 20, the vertical display information can be made confidential.

FIG. 5 is another diagram showing a viewing angle-dependent brightness distribution due to voltage application of the viewing angle control pixel 20 according to the first embodiment of the present invention. FIG. 5 shows a case where the viewing angle control pixels have a common electrode 21a in the left-right direction and a common electrode 21b in the vertical direction are mixed in the display screen. When no voltage is applied to the viewing angle control pixel 20, the brightness is equivalent to that of a black screen in both the front and the diagonal directions from the top, bottom, left, and right.

On the other hand, when a voltage is applied to the viewing angle control pixel 20, the front surface is black, but light is emitted from the top and bottom and the diagonal direction from the left and right to become bright. As a result, light leaks in the diagonal directions of the left-right direction and the up-down direction, so that it becomes difficult to recognize the displayed screen when viewed from the diagonal directions of the left-right direction and the up-down direction, and the information can be kept confidential. It will be possible.

A liquid crystal display device having desired concealment by appropriately arranging the viewing angle control pixel having the common electrode 21a in the left-right direction and the viewing angle control pixel having the common electrode 21b in the vertical direction in the display screen. Can be obtained.

As described above, according to the first embodiment, by providing the viewing angle control pixels independent of the RGB pixels, it is possible to obtain a liquid crystal display device capable of adjusting the viewing angle in the vertical and horizontal directions.

Further, by appropriately arranging the viewing angle control pixel having the common electrode in the left-right direction and the viewing angle control pixel having the common electrode in the up-down direction in the display screen, the liquid crystal having concealment in the up-down-left-right direction. The display device can be easily realized. Further, it is not necessary to provide a colored layer on the color filter substrate facing the viewing angle control pixel, and it is possible to reduce the cost.

<figref num="1">It is a top view of each RGB pixel and the viewing angle control pixel of the liquid crystal display device in Embodiment 1 of this invention.</figref><figref num="2">It is explanatory drawing of the operation of the liquid crystal molecule in the viewing angle control pixel which has the common electrode of the right-right direction in Embodiment 1 of this invention.</figref><figref num="3">It is a figure which shows the brightness distribution which depends on the viewing angle by applying the voltage of the viewing angle control pixel in Embodiment 1 of this invention.</figref><figref num="4">It is another plan view of each RGB pixel and the viewing angle control pixel of the liquid crystal display device in Embodiment 1 of this invention.</figref><figref num="5">It is another figure which shows the viewing angle-dependent luminance distribution by the voltage application of the viewing angle control pixel in Embodiment 1 of this invention.</figref><figref num="6">It is explanatory drawing of the conventional liquid crystal display device which has a concealment mode.</figref><figref num="7">It is a top view of each RGB pixel of the conventional FFS type liquid crystal display device.</figref><figref num="8">It is explanatory drawing of the operation of the liquid crystal molecule by the voltage application of the conventional FFS type liquid crystal display device.</figref>

Code description

11, 11a, 11b common electrodes, 20 viewing angle control pixels, 21a, 21b common electrodes.