KR20100031963A - Viewing angle controllable liquid crystal display device using one panel - Google Patents

Abstract

PURPOSE: A liquid crystal display apparatus controlling view angle using a single panel is provided to control wide viewing angle and narrow viewing angle with same aperture ratio as a conventional display. CONSTITUTION: A liquid crystal display apparatus controlling view angle using a single panel comprises a upper substrate(2), upper second common electrode(3), vertical alignment layer, hydrid liquid crystal layer, horizontal alignment layer, pixel electrode(5), insulating layer(6), first common electrode(7), lower substrate(8), and lower polarizing plate(9). The upper substrate is placed at the lower portion of the upper polarizing plate. The second common electrode is placed at the lower portion of the upper substrate. The vertical alignment layer is placed at the lower portion of the second common electrode. The hybrid liquid layer is placed at the lower portion of the vertical alignment layer. The pixel electrode is placed at the lower portion of the horizontal alignment layer. The insulating layer is placed at the lower portion of the pixel electrode.

Description

Viewing Angle Controllable Liquid Crystal Display Device Using One Panel}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (Liquid Crystal Display: LCD), which is made of a single panel. It relates to a viewing angle control liquid crystal display device which is referred to as 'wide viewing angle') or invisible (this is called 'narrow viewing angle').

The liquid crystal display device is used as a light modulator by changing the polarization state of the liquid crystal due to the birefringence property of the liquid crystal itself, and acts as a light modulator. It has a problem of deterioration. In order to solve the viewing angle problem of the liquid crystal display, wide-viewing angle twisted nematic (WV-TN), film-compensated VA (vertical alignment) and FFS (Fringe-field Switching) modes are used. Wide viewing angle characteristics are being studied. This wide viewing angle characteristic has been a major issue for the liquid crystal display device to enter the mobile and TV market in the flat panel display market. However, recently, the wide viewing angle has caused a problem of privacy invasion due to the increase of information value and the increase of portable display. A narrow viewing angle display with a tendency opposite to that of a liquid crystal display with characteristics is also shown.

 In this regard, a viewing angle control liquid crystal display capable of actively adjusting a viewing angle according to a change of a user's preference and surrounding environment from a wide viewing angle to a wide viewing angle or a narrow viewing angle to a wide viewing angle has emerged. Looking at the characteristics of the conventional viewing angle control liquid crystal display device in terms of the structure of the liquid crystal cell, by additionally stacking the liquid crystal cell to the liquid crystal cell representing the image, the viewing angle adjustment method using the birefringent anisotropy of the liquid crystal layer itself and divided one pixel into two regions The method is divided into the pixel part that represents the main image and the pixel part that controls the viewing angle. In the case of the former (viewing angle adjusting method using birefringence anisotropy), since the liquid crystal cell is additionally stacked, the thickness is thicker than the existing display, and the power consumption is also increased, which is not suitable for the next generation display. In the latter case, the aperture ratio and brightness of the existing display tend to be reduced since the pixel portion, which serves as a viewing angle control, operates only by changing the viewing angle dependency of the dark state. In this case, the pixels are divided into two regions, which complicates the driving method and increases the production cost.

Accordingly, an object of the present invention is to develop a viewing angle control liquid crystal display device in which a wide viewing angle and a narrow viewing angle can be adjusted according to a user's use and environment without a reduction in aperture ratio using a single panel.

In order to achieve the above object, the present invention provides a first common electrode and a pixel electrode structure of a conventional FFS mode in which a second common electrode is additionally formed in a plane shape without a pattern, and a dielectric anisotropy is provided. Negative liquid crystal molecules are hybrid oriented from horizontal to vertical on the substrate. Switching between the wide viewing angle and the narrow viewing angle mode is controlled by the upper second common electrode, and implements the wide viewing angle mode when the upper second common electrode has a constant potential difference by the lower first common electrode, and when the potential difference does not occur. Implement narrow viewing angle mode.

Since the present invention does not use an additional liquid crystal panel and no additional pixels are used, the present invention has an aperture ratio and a thickness corresponding to that of an existing display, and the viewing angle adjustment can provide excellent characteristics in both directions without biasing either the wide viewing angle or the narrow viewing angle. .

In particular, the viewing angle control liquid crystal display according to the present invention makes the white appear dark and the dark appear white in the front outward direction, and secures the narrow viewing angle by reducing or reversing the luminance difference for each gray level, and the liquid crystals in the wide viewing angle mode. It can be rotated in the lying state to secure the transmittance and wide viewing angle characteristics.

Hereinafter, exemplary embodiments of the present invention and objects and advantages of the present invention will be described in detail with reference to the accompanying drawings.

Example

1 is a view schematically showing a viewing angle control liquid crystal display using a single panel according to the present invention. As illustrated, the lower first common electrode 7 is disposed in an unpatterned plane shape on the lower substrate 8, and the insulating layer 6 is interposed on the first common electrode 7. The pixel electrodes 5 are patterned at regular intervals, and the upper substrate 2 is positioned on the plane of the second common electrode 3 having a plane with a negative liquid crystal 4 layer therebetween. In this case, the upper polarizing plate 1 and the lower polarizing plate 9 have a transmission axis of 90 ° to each other, and are positioned outside the upper substrate 2 and the lower substrate 8, respectively. The liquid crystal 4 layer is hybridly oriented from the horizontal orientation to the vertical orientation from the lower substrate 9 to the upper substrate 2.

When the driving method is described in detail, the wide viewing angle and the narrow viewing angle can be adjusted by the potential difference between the upper second common electrode 3 with respect to the lower first common electrode 7, and the image representation of each mode is lower first common. This is enabled by the electrode 7 and the pixel electrode 5. In the case of the wide viewing angle mode, this occurs when the second common electrode 3 of the upper substrate 2 generates a vertical electric field between the common electrodes of the lower substrate, and a negative liquid crystal lies in parallel to the substrate by the vertical electric field. The liquid crystals are twisted by the lower fringe field in order to express transmittance. When the liquid crystals lie parallel to the substrate by the vertical electric field, the initial liquid crystal director coincides with the absorption axis of the polarizer to express the dark state, and the wide viewing angle is exhibited by the small viewing angle dependence of the horizontally arranged liquid crystal layers. In the narrow viewing angle mode, when there is no potential difference between the first common electrode 7 and the second common electrode 3, the driving is performed in the same manner as the conventional HAN-FFS (Hybrid Aligned Nematic-Fringe-Field Switching) mode. The liquid crystal molecules standing vertically on the top give a narrow viewing angle.

In more detail, the viewing angle characteristics of the display may be confirmed by observing the director of the liquid crystal 4 as shown in FIG. 2 because the image quality and viewing angle characteristics of the display depend on the dark state of the panel.

The left figure of FIG. 2 is a liquid crystal array showing the dark state of the narrow viewing angle mode, and the upper second common electrode 3 is present before the voltage is applied to the lower first common electrode 7, and the pixel electrode 5 is also present. It exists in the state before voltage application. Since the liquid crystal 4 is not affected by any electric field, it maintains the hybrid alignment which is an initial alignment condition. Due to the hybrid orientation of the liquid crystal 4, half of the liquid crystal 4 layer is erected, causing light leakage in the viewing angle direction, thereby realizing a narrow viewing angle in the dark state. In the wide viewing angle mode, both the lower first common electrode 7 and the upper second common electrode 3 are used as shown in the right figure of FIG. 2, and in particular, the upper second common electrode 3 and the lower first common electrode ( 7) A vertical electric field is generated by having a constant potential difference between them, and by this vertical electric field, negative liquid crystals (4) lie parallel to the substrate to express a dark state with wide viewing angle characteristics.

Such a structure can be applied to a multi-domain FFS in which the direction of the electric field is different by changing the pattern of the pixel electrode as shown in FIGS. 3A and 3B. Hereinafter, a description will be given of the structure and operation of the FFS adopting multi-domain. 3A is a plan view illustrating a lower substrate of a viewing angle control liquid crystal display using a multi-domain FFS electrode structure according to an exemplary embodiment of the present invention.

As shown, a gate bus line 10 and a data bus line 11 are arranged and intersected on the lower substrate 8, and a switching element is provided at the intersection point of the gate bus line 10 and the data bus line 11. A thin film transistor TFT is disposed. The pixel electrode 5, the lower first common electrode 7, and the upper second common electrode (not shown) are disposed by the gate bus line 10 and the data bus line 11 that cross each other, and the pixel electrode 5 is disposed. ) Is formed such that the upper slit S2 and the lower slit S3 have a symmetrical slope of + θ or -θ based on the center slit S1 to form a multi-domain. When negative liquid crystal is used, the directions 12a and 13b of the initial liquid crystal molecules are rubbed parallel to the data bus line 11. At this time, the inclination of the upper slit (S2) and the lower slit (S3) are all available up to 0 ~ 90 ° but less than ± 45 ° by the transmittance generation principle, it is preferable to limit to 2 to 20 ° for high transmittance Do. Under these conditions, the widths of the slits S1, S2, and S3 are about 1 to 10 µm, and the spacing between the slits is also limited to 1 to 10 µm. 3B is a cross-sectional view of the present invention taken along line AA ′ of FIG. 3A. The upper second common electrode 3 is positioned to face the lower first common electrode 7 in an unpatterned plane shape.

In this structure, in the implementation of the mid-gradation and the white state, the mid-gradation and the white state of the wide viewing angle and the narrow viewing angle are expressed by applying a voltage to the pixel electrode 5 with respect to the lower first common electrode 7.

In order to demonstrate the effect of the present invention, the phenomenon of light leakage in the viewing angle direction of the dark state is illustrated in FIGS. 3A and 3B. Referring to FIG. 4, light is not leaked from the front even when switching from the wide viewing angle mode to the narrow viewing angle mode, whereas light is leaked approximately 10 times in the left and right viewing angle directions. As the left and right viewing angles leak light only in the viewing angle direction, it can be confirmed that the front viewing angle and the contrast ratio can be implemented in the narrow viewing angle mode without large loss.

FIG. 5 is a curve illustrating brightness, contrast, and contrast ratio of light, dark states according to the viewing angle in the wide viewing angle mode and the narrow viewing angle mode. Referring to the bright state of the wide viewing angle mode of Figure 4 it can be seen that the brightness is the highest in the front, and evenly distributed luminance according to the viewing angle. On the other hand, in the bright state of the narrow viewing angle mode, the brightness at the front side decreases rapidly toward the viewing angle direction, which means that the white at the front side becomes dark in the viewing angle direction. Compared to the dark state, the light leakage of 0.014778, which is 70% of the maximum light leakage in the wide viewing angle mode, appeared in the viewing angle of 60 ° or more, whereas the corresponding light leakage appeared in the viewing angle of 10 ° or more in the narrow viewing angle mode. Suddenly the light can see the fountain. As a result, the viewing angle is limited to within 20 ° in the narrow viewing angle mode and the viewing angle is above 70 ° in the wide viewing angle mode.

As described above, the viewing angle control liquid crystal display using the single panel according to the present invention uses a single panel capable of switching between wide viewing angle mode and narrow viewing angle mode by using a negatively arranged liquid crystal and introducing a common electrode on the upper side. The viewing angle control liquid crystal display device can be manufactured.

The upper second common electrode introduced for the viewing angle control may be applied to the viewing angle control liquid crystal display in the form of a patterned common electrode instead of an unpatterned plane shape. However, when the patterned common electrode is used, since the generated gradient electric field causes dark light leakage, it is necessary to use film compensation or to have a small gap between the patterned electrodes.

In addition, the effective phase delay value of this panel should be manufactured within the phase delay range that can bring the dark state of the narrow viewing angle, and the width and electrode spacing of the fringe field electrode are important for the wide viewing angle and the narrow viewing angle. Adjustable according to

1 is a cross-sectional view schematically showing a viewing angle control liquid crystal display device using a single panel according to an embodiment of the present invention.

2 is a view illustrating a liquid crystal arrangement in a dark state of the viewing angle control liquid crystal display device of the narrow viewing angle and the wide viewing angle according to the present invention.

3A is a plan view of a viewing angle adjusting liquid crystal display for explaining an embodiment according to the present invention.

3B is a cross-sectional view of the present invention taken along line AA ′ of FIG. 3A.

4 is a view illustrating a phenomenon in which light leaks in the narrow viewing angle mode compared to the wide viewing angle of the viewing angle control liquid crystal display device according to the present invention.

5 is a view showing a brightness characteristic and contrast curve according to the viewing angle of the viewing angle control liquid crystal display device according to the present invention;

* Description of the main parts of the drawing

1. Upper polarizer

2. Upper substrate

3. Upper second common electrode

4. LCD

5. Pixel electrode

6. Insulation layer

7. Lower first common electrode

8. Lower substrate

9. Lower polarizer

10. Gate line

11. Data Bus Line

12a. Before applying liquid crystal molecular voltage

After 12a 'upper liquid crystal molecular voltage

13b Before applying the liquid crystal molecular voltage

After 13b 'liquid crystal molecular voltage is applied

14. Alignment film

15. Insulation film

Claims (3)

An upper polarizer; An upper substrate positioned below the upper polarizer; An upper second common electrode in an unpatterned plane shape positioned below the upper substrate; A vertical alignment layer disposed below the second common electrode; A hybrid liquid crystal layer positioned below the vertical alignment layer and vertically aligned at an upper portion adjacent to the vertical alignment layer, and horizontally aligned as it proceeds downward; A horizontal alignment layer disposed under the hybrid liquid crystal layer; A patterned pixel electrode under the horizontal alignment layer; An insulating layer under the pixel electrode; A first common electrode having a planar shape under the insulating layer; A lower substrate positioned below the common electrode; And a lower polarizer disposed under the lower substrate. The method of claim 1, In the patterned pixel electrode under the horizontal alignment layer A viewing angle control liquid crystal display using a single panel, characterized in that the unit pixel is formed of a multi-domain or more than the dual domain with a different direction of the electric field by changing the pattern of the pixel electrode. In claim 1 or 2, A pixel electrode divided into first and second subpixel electrodes on the passivation layer The divided pixel electrode is formed in a different size and shape to improve the transmittance and visibility.

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