JP2007178900A - Liquid crystal display device and method for manufacturing liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device whose viewing angle can vertically and horizontally be adjusted without the need to provide white pixels. <P>SOLUTION: The liquid crystal display device has a display screen composed of a set of pixels and each of the pixels has a display control region 10 brought under alignment control so that liquid crystal molecules of (n) type liquid crystal tilt and a viewing angle control region 20 which is brought under alignment control so that liquid crystal molecules of (n) type liquid crystal tilt vertically and horizontally and is applied with a control voltage through a viewing angle control line 30 independent of a common line of the display control region 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device capable of controlling a viewing angle and a method for manufacturing the same, and more particularly to an n-type liquid crystal display device.

  2. Description of the Related Art Liquid crystal display devices, particularly liquid crystal display devices using TFTs (Thin Film Transistors), are widely used in mobile phones and large-sized televisions. Under such circumstances, a display device that can be used personally is required to be a display device that can be seen by the person who is using it but cannot be seen even when looking from the side. In particular, a display screen that is shared by a large number of people at a certain time and can be used only by an individual at a certain time is desired.

  FIG. 7 is an explanatory diagram of a conventional liquid crystal display device having a secret mode. Under such background, as an example, a display having a secret mode as shown in FIG. 7 has been proposed (see, for example, Patent Document 1). In FIG. 7, a backlight having a high directivity is used as a backlight for illuminating the liquid crystal panel from the back side. For example, a polymer-dispersed liquid crystal panel (scattering non-scattering switch layer) that can switch between a scattering state and a non-scattering state is provided between the normal liquid crystal panel and the directional backlight.

  When the scattering layer is in a non-scattering state, the light from the backlight is irradiated only on the front side, so that the display cannot be seen from an oblique direction. On the other hand, when the scattering layer is in a scattering state, the light from the backlight is also irradiated in an oblique direction, so that the display can be seen from an oblique direction, 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 has been a problem that it becomes expensive.

  As a measure for solving this problem, a method using a vertical alignment type liquid crystal display device has been proposed. The basic principle will be described below with reference to FIGS. FIG. 8 is a diagram showing a state of liquid crystal molecules when the vertical alignment type liquid crystal display device is viewed from the front. In the state where no voltage is applied in FIG. 8A, the liquid crystal molecules are vertically aligned, and when a voltage is applied as shown in FIG. 8B, the liquid crystal molecules are tilted upward. The polarizer and the analyzer have their absorption axes directed in the vertical and horizontal directions, respectively.

  FIG. 8A shows a case where a vertically aligned liquid crystal panel with no voltage applied is viewed from the front. The birefringence of the liquid crystal molecules does not appear and no light leaks. On the other hand, FIG. 8B shows a case where a liquid crystal panel to which a voltage is applied is viewed from the front. The optical axis of the liquid crystal molecules is parallel to the absorption axis of the polarizer, and as a result, birefringence does not appear and no light leaks.

  On the other hand, FIG. 9 is a diagram showing a state of liquid crystal molecules when the vertical alignment type liquid crystal display device is viewed from an oblique direction. As shown in FIG. 9A, when no voltage is applied, the liquid crystal molecule axis appears parallel to the absorption axis of the analyzer, so light does not leak. On the other hand, as shown in FIG. 9B, in the case of voltage application, the axis of the liquid crystal molecules is deviated from the axis of the polarizer or analyzer, birefringence is developed, and light leaks.

  If this light leakage is used, the display contrast will be extremely lowered in the left-right direction, and it will not be understood what is written even if the display is viewed from the horizontal direction. Therefore, the confidentiality of the display can be controlled using this phenomenon.

  FIG. 10 is a diagram showing a specific configuration for controlling the confidentiality of display. In FIG. 10, in one pixel, in addition to the RGB subpixels, a white (W) subpixel is provided. FIG. 11 is a diagram showing an arrangement state of liquid crystal molecules of each sub-pixel in FIG. As shown in FIG. 11, the alignment state of the liquid crystal molecules in the white pixel portion is different from the other RGB in the vertical direction.

  As a result, when no voltage is applied to the white pixel portion, this portion does not contribute to the display at all, so that normal display is realized. On the other hand, when a voltage is applied to the white pixel portion, white display is performed in the left-right direction on the front surface. As a result, the contrast of the display is lowered in the left-right viewing angle direction, and the possibility that the display can be seen by others is reduced.

  Next, a conventional FFS (Fringe Field Switching) type liquid crystal display device that improves the viewing angle by changing the shape of the common electrode to a square shape will be described. FIG. 12 is a plan view of the vicinity of a pixel of a conventional FFS mode liquid crystal display device. Further, FIG. 13 is an explanatory diagram of the operation of liquid crystal molecules by voltage application in a conventional FFS type liquid crystal display device.

  As shown in FIG. 12, in this liquid crystal display device, a common electrode on a cross is formed in order to define the direction in which the liquid crystal falls. The liquid crystal molecules are oriented in the vertical direction as shown in FIG. 13A when no voltage is applied. On the other hand, the liquid crystal molecules fall in a direction determined by the influence of an oblique electric field by the common electrode, that is, a direction perpendicular to the direction in which the common electrode extends, as shown in FIG. As a result, the liquid crystal can be tilted in two directions corresponding to the character shape, and a liquid crystal display device having a good viewing angle is realized.

JP-A-5-72529 (first page, FIG. 1)

  However, the conventional liquid crystal display device has the following problems. The first problem is that white pixels are provided. However, white resin needs to be newly provided, and driving is different from the conventional one. In addition, as a second problem, it is possible to improve the visibility in a specific direction by making the common electrode a U-shape, but it is not possible to provide a display with confidentiality depending on the situation.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a liquid crystal display device capable of adjusting the viewing angle in the vertical and horizontal directions without having to provide white pixels and a method for manufacturing the same. And

  The liquid crystal display device according to the present invention is a liquid crystal display device having a display screen made up of a set of pixels, each of which has a display control region in which liquid crystal molecules of n-type liquid crystal are controlled to tilt, A viewing angle control region in which liquid crystal molecules of n-type liquid crystal are tilted in the vertical direction and the horizontal direction, and a control voltage is applied via a viewing angle control line independent of the common line of the display control region. Is.

  The method for manufacturing a liquid crystal display device according to the present invention includes a first step of forming a gate electrode, a gate pad, and a data pad on a substrate, a gate insulating film, and a source electrode and a drain electrode on the gate electrode. A second step of forming a contact hole, a third step of forming a contact hole after sequentially forming a first passivation layer and a photoacrylic layer on the entire surface of the substrate, and a display whose orientation is controlled so that liquid crystal molecules of n-type liquid crystal are tilted A fourth step of separately forming a common electrode for the control region and a common electrode for controlling the viewing angle so that liquid crystal molecules of n-type liquid crystal are tilted in the vertical and horizontal directions; A fifth step of forming a contact hole after forming a passivation layer on the entire surface of the substrate, and forming a pixel electrode in the display control region, It is obtained by a sixth step of the viewing angle control region corresponding to the display control area for forming the vertical and horizontal directions in the viewing angle control electrode so that the liquid crystal molecules are inclined by an n-type liquid crystal.

  According to the present invention, the liquid crystal molecules controlled by the n-type liquid crystal are controlled so that the liquid crystal molecules formed by the n-type liquid crystal are tilted in the vertical and horizontal directions together with the display control region controlled so that the liquid crystal molecules by the n-type liquid crystal are tilted. By further forming a viewing angle control region to which a control voltage is applied via a viewing angle control line that is independent of the one in one pixel, it is not necessary to provide a white pixel, and the viewing angle is adjusted in the vertical and horizontal directions. A liquid crystal display device and a method for manufacturing the same can be obtained.

  Hereinafter, preferred embodiments of a liquid crystal display device and a manufacturing method thereof according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a plan view of the vicinity of a pixel of the liquid crystal display device according to Embodiment 1 of the present invention. One pixel in FIG. 1 includes a display control region 10 and a viewing angle control region 20. The display control area 10 is an area that is controlled so that liquid crystal molecules by the n-type liquid crystal are tilted. In the display control region 10, pixel electrodes 11 that are hollowed out in a circular shape are formed.

  Next, the operation of the liquid crystal molecules in the voltage application / non-application state of the display control region 10 will be described. FIG. 2 is an explanatory diagram of the operation of the liquid crystal molecules in the display control region 10 having the pixel electrode 11 hollowed out in a circular shape in the first embodiment of the present invention.

  When no voltage is applied, the liquid crystal stands vertically as shown in FIG. Therefore, the display of the pixel remains black. In such a black screen, the front and the oblique viewing angles other than the front are similarly recognized as the black screen.

  On the other hand, when a voltage is applied, as shown in FIG. 2B, the liquid crystal molecules are aligned in the direction determined by the influence of the electric field by the pixel electrode 11 that is hollowed out, that is, the pixel electrode 11. In the vicinity of the outer circumference, the body falls in a direction perpendicular to the outer circumference. Therefore, the white screen display can be visually recognized over 360 degrees even at the front and oblique viewing angles other than the front.

  In the display control area 10 of each RGB pixel, the pixel electrode 11 that is hollowed out in the circular shape as described above is formed, and furthermore, by applying a voltage to the pixel to be displayed, the display for the omnidirectional visual field can be performed. Can be white. As a result, the display control region 10 can perform color display with 360-degree visibility even at the front and oblique viewing angles other than the front.

  On the other hand, the viewing angle control region 20 is controlled such that liquid crystal molecules of n-type liquid crystal are tilted in the vertical and horizontal directions, and a control voltage is applied via a viewing angle control line 30 separate from the display control region 10. It is an area. In the viewing angle control region 20, both a region in which the left and right common electrodes 21a are provided and a region in which the vertical common electrodes 21b are provided coexist.

  In the present invention, an n-type liquid crystal is employed. In the case of this n-type liquid crystal, both the common electrodes 21a and 21b as shown in FIG. 1 are present in one pixel without mask rubbing. Can be made. As a result, by applying a control voltage via the viewing angle control line 30, the liquid crystal molecules can be tilted forward and backward and left and right within the viewing angle control region 20, thereby enabling viewing angle control.

  As shown in FIG. 1, an applied voltage is supplied to the viewing angle control region 20 via a viewing angle control line 30 that is separate from the display control region 10. Then, by forming the viewing angle control line 30 that is an independent common line for the viewing angle control region 20 with a transparent electrode, a merit that a large aperture ratio can be obtained is obtained. Further, since the common lines are independent, it is possible to input the voltage applied to the viewing angle control region 20 as an arbitrary waveform.

  Next, the operation of the liquid crystal molecules in the viewing angle control pixel 20 in the voltage application / non-application state will be described. FIG. 3 is an explanatory diagram of the operation of liquid crystal molecules in the viewing angle control pixel 20 having the left and right common electrodes 21a in the first embodiment of the present invention.

  In the viewing angle control pixel 20 having the left and right common electrodes 21a, when no voltage is applied, the liquid crystal is in a horizontal state as shown in FIG. Therefore, the display of the viewing angle control pixel 20 remains black and does not affect the entire display. The same applies to the front, top / bottom / 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 electrode 21a in the horizontal direction, as shown in FIG. 3B, the liquid crystal molecules are located between the central portion of the common electrode and the common electrode. In the center, it stands upright. Accordingly, when viewed from the left-right direction, the portion where the common electrode 21a in the left-right direction is inserted brightly emits light. On the contrary, when viewed from above and below, light does not leak from the portion where the common electrode 21a in the horizontal direction is inserted.

  On the other hand, in the viewing angle control pixel 20 having the vertical common electrode 21b, when a voltage is applied, the liquid crystal molecules are aligned at the center of the common electrode in a direction different by 90 degrees from FIG. In a central portion between the electrode and the common electrode, it stands vertically. Therefore, when viewed from the left-right direction, light does not leak from the portion where the vertical common electrode 21b is inserted. On the other hand, when viewed from above and below, light enters the portion where the common electrode 21b in the up-and-down direction enters and brightly passes through.

  As a result, in a state where 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 common electrodes 21b in the vertical direction with respect to the viewing direction from the left and right directions. The corner control area is recognized as black. On the other hand, for the visual field from the vertical direction, the viewing angle control area having the left and right common electrodes 21a is recognized as black, and the viewing angle control area having the vertical common electrodes 21b is recognized as white.

  And these patterns will overlap with the normal display pattern by RGB pixels, and in each pixel, when looking at the pattern from the left and right direction and the up and down direction, it is not possible to understand what is written, The display information can be kept confidential.

  As described above, the viewing angle control region 20 corresponding to each display control region 10 includes the pixels having the left and right common electrodes 21a and the pixels having the vertical common electrodes 21b. By applying a voltage to the corner control region 20, the display for both the left and right visual fields can be whitened. Thereby, the display which has desired confidentiality is attained.

Next, a process for manufacturing such a viewing angle control region 20 will be described.
FIG. 4 is a process explanatory diagram of the manufacturing method of the liquid crystal display device according to Embodiment 1 of the present invention. First, the gate electrode 41, the gate pad 42, and the data pad 43 are formed on the substrate 40 by the first step.

  Next, in the second step, a gate insulating film 44 is formed, an a-Si layer and an N + a-Si layer are sequentially formed, a metal layer is formed on the N + a-Si layer, and holes are formed by etching. Then, the source electrode 45 and the drain electrode 46 are formed on the gate electrode 41.

  Next, after a passivation layer 47a and a photoacryl layer 50 (or an insulating layer) are sequentially formed on the entire surface of the substrate 40 in the third step, contact holes are formed. Next, individual common electrodes 51 a and 51 b are formed on the channel and display control region 10 by the fourth step.

  Next, in the fifth step, the second passivation layer 47b is formed on the entire surface of the substrate 40, and then contact holes are formed. Then, in the final sixth step, the pixel electrode 48 is formed in the display control region 10 whose orientation is controlled so that the liquid crystal molecules of n-type liquid crystal are tilted, and the orientation control is performed so that the liquid crystal molecules are tilted in the vertical and horizontal directions. A viewing angle control electrode 49 is further formed in the viewing angle control region 20 to which a control voltage is applied via the independent viewing angle control line 30.

  FIG. 5 is a plan view of the vicinity of a pixel formed by the manufacturing process of FIG. 4 of the liquid crystal display device according to Embodiment 1 of the present invention, and shows an example of a plan view of an R pixel. As a result of such a process, the structure of FIG. 5 is finally formed. As shown in FIG. 5, the viewing angle control region 20 has a merit that it is not necessary to provide a colored layer by a color filter because it plays the role of providing confidentiality in the display in the horizontal direction and the vertical direction.

  By going through the 6-mask process as described above, the independent viewing angle control line 30 can be formed with a transparent electrode, and by devising the mask in the sixth step, the field of view corresponding to the horizontal and vertical directions The corner control area 20 can be embedded.

  FIG. 6 is a diagram showing a viewing angle dependent luminance distribution by voltage application in the viewing angle control region 20 according to the first embodiment of the present invention. When no voltage is applied to the viewing angle control region 20, the luminance is the luminance corresponding to the 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 region 20, the front is black, but light is extracted and brightened in an oblique direction from the top, bottom, left, and right.

  As a result, since light leaks only in the oblique direction, it is difficult to recognize the displayed screen when viewed from the oblique direction, and the information can be kept confidential. In the n-type liquid crystal, the visibility in all directions can be improved by using the pixel electrode 11 that is cut out in a circular shape in the display control region 10. Furthermore, by having the viewing angle control region 20 according to the present invention, it is possible to provide information confidentiality in the vertical and horizontal directions.

  As described above, according to the first embodiment, when the visibility in all directions is improved using the pixel electrode that is hollowed out in the n-type liquid crystal, the influence of the signal delay depends on the thickness of the acrylic layer. Since the transparent electrode can be used as the viewing angle control line, a liquid crystal display device capable of adjusting the viewing angle in the vertical and horizontal directions while improving the aperture ratio can be obtained.

  Further, the viewing angle control regions of the horizontal direction and the vertical direction can coexist in the same pixel, and a liquid crystal display device having information confidentiality in the vertical and horizontal directions can be realized. Furthermore, it is not necessary to provide a color filter in the viewing angle control region, and it is possible to reduce costs.

FIG. 3 is a plan view of the vicinity of a pixel of the liquid crystal display device according to Embodiment 1 of the present invention. It is explanatory drawing of operation | movement of the liquid crystal molecule in the display control area | region which has the pixel electrode hollowed in the circular shape in Embodiment 1 of this invention. It is explanatory drawing of operation | movement of the liquid crystal molecule in the viewing angle control area | region which has a common electrode of the left-right direction in Embodiment 1 of this invention. It is process explanatory drawing of the manufacturing method of the liquid crystal display device in Embodiment 1 of this invention. FIG. 5 is a plan view of the vicinity of a pixel formed by the manufacturing process of FIG. 4 of the liquid crystal display device according to Embodiment 1 of the present invention. It is a figure which shows the viewing angle dependent luminance distribution by the voltage application of the viewing angle control area | region in Embodiment 1 of this invention. It is explanatory drawing of the conventional liquid crystal display device which has a secrecy mode. It is the figure which showed the mode of the liquid crystal molecule when a vertical alignment type liquid crystal display device was seen from the front. It is the figure which showed the mode of the liquid crystal molecule when a vertical alignment type liquid crystal display device was seen from diagonally. It is the figure which showed the specific structure for controlling the confidentiality of a display. It is the figure which showed the alignment state of the liquid crystal molecule of each subpixel in FIG. It is a top view of the pixel vicinity of the conventional liquid crystal display device of a FFS system. It is explanatory drawing of operation | movement of the liquid crystal molecule by the voltage application of the conventional FFS system liquid crystal display device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Display control area, 11 Pixel electrode, 20 Viewing angle control area, 21a, 21b Common electrode, 30 Viewing angle control line, 40 Substrate, 41 Gate electrode, 42 Gate pad, 43 Data pad, 44 Gate insulating film, 45 Source electrode 46 drain electrode, 47a passivation layer, 47b second passivation layer, 48 pixel electrode, 49 viewing angle control electrode, 50 photoacrylic layer, 51a, 51b common electrode.

Claims (3)

A liquid crystal display device having a display screen composed of a set of pixels,
Each pixel is
a display control region controlled so that liquid crystal molecules by the n-type liquid crystal are tilted;
A viewing angle control region that is controlled such that liquid crystal molecules of n-type liquid crystal are tilted in the vertical direction and the horizontal direction, and a control voltage is applied via a viewing angle control line that is independent of the common line of the display control region. A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1.
A liquid crystal display device characterized in that a colored layer made of a color filter is not provided on a substrate facing the viewing angle control region. A first step of forming a gate electrode, a gate pad, and a data pad on the substrate;
Forming a gate insulating film and forming a source electrode and a drain electrode on the gate electrode;
A third step of forming contact holes after sequentially forming a first passivation layer and a photoacrylic layer on the entire surface of the substrate;
Common electrode for display control region whose orientation is controlled so that liquid crystal molecules by n-type liquid crystal tilt, and common electrode for viewing angle control whose orientation is controlled so that liquid crystal molecules by n-type liquid crystal tilt in the vertical and horizontal directions A fourth step of separately forming
A fifth step of forming a contact hole after forming a second passivation layer on the entire surface of the substrate;
A pixel electrode is formed in the display control region, and a viewing angle control electrode is formed in the viewing angle control region corresponding to the display control region of each pixel so that liquid crystal molecules of n-type liquid crystal are inclined in the vertical direction and the horizontal direction. A method for manufacturing a liquid crystal display device, comprising: a sixth step.

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