KR100656901B1 - a liquid crystal display - Google Patents

Abstract

In the present invention, a horizontal gate line and a gate electrode connected to the gate line are formed on the substrate. The gate line and the gate electrode are covered with a gate insulating film, on which a semiconductor layer and an ohmic contact layer are formed. A data line in the vertical direction, a source electrode connected to the data line and a drain electrode opposite the source electrode, and an electric field enhancement electrode connected to the drain electrode are formed, and a protective insulating layer is formed thereon. The protective insulating film is formed with a contact hole and a valley exposing the drain electrode, which is located above the field enhancement electrode. A pixel electrode having an opening is formed on the protective insulating film. The opening is located at the top of the bone and has the same shape as the bone and the full length enhancement electrode. In such a liquid crystal display, an opening is formed in the pixel electrode and a valley or a field enhancement electrode is formed below the pixel electrode to stably arrange the liquid crystal molecules.

Bone, full-length enhancement electrode, PVA, fringe field

Description

Liquid crystal display {a liquid crystal display}

1 is a view illustrating a state where upper and lower substrates of a liquid crystal display are arranged;

2 is a layout view of a lower substrate of a liquid crystal display according to a first exemplary embodiment of the present invention.

3A and 3B are cross-sectional views of a liquid crystal display according to a first exemplary embodiment of the present invention and correspond to planes cut along lines IIIa-IIIa ′ and IIIb-IIIb ′ in FIG. 2, respectively. Shows a cross section of a thin film transistor,

4 is a layout view of a lower substrate of a liquid crystal display according to a second exemplary embodiment of the present invention.

5A and 5B correspond to planes cut along lines Va-Va ′ and Vb-Vb ′ in FIG. 4, respectively, illustrating an arrangement of liquid crystal molecules and a cross section of a thin film transistor,

6 to 9 illustrate an arrangement state of equipotential lines and liquid crystal molecules generated according to an embodiment of the present invention.

10 to 14 illustrate an arrangement state of equipotential lines and liquid crystal molecules generated when the applied voltage is changed in the embodiment of the present invention.

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a wide viewing angle.

In general, a liquid crystal display device injects a liquid crystal material between an upper substrate on which a common electrode, a color filter, and the like are formed, and a lower substrate on which a thin film transistor and a pixel electrode are formed. By applying a different potential to form an electric field to change the arrangement of the liquid crystal molecules, and through this to control the light transmittance is a device that represents the image.

The liquid crystal display device has a disadvantage of having a narrow viewing angle. In order to overcome this disadvantage, various methods for widening the viewing angle have been proposed. For example, a patterned vertical alignment (PVA) method in which the liquid crystal molecules are vertically aligned with respect to the upper and lower substrates and an opening pattern is formed in the pixel electrode and the common electrode is one example.

However, in the case of the PVA method, the liquid crystal molecules are divided and aligned by a fringe field, which is a curved electric field that appears in an opening pattern when voltage is applied to the pixel electrode and the common electrode. This can happen.

SUMMARY OF THE INVENTION An object of the present invention is to manufacture a liquid crystal display device that widens a viewing angle by stably dividing pixels without generating a foreground.

In order to solve this problem, in the present invention, a valley is formed under the opening of the pixel electrode to stably divide the pixel.

In the liquid crystal display according to the present invention, a first insulating film is formed on a substrate, and a field generating electrode having an opening is formed thereon, and a valley is formed in the first insulating film under the opening.

The apparatus may further include a field enhancement electrode formed under the valley and electrically connected to the field generating electrode.

In the liquid crystal display according to the present invention, a plurality of gate lines are formed between the substrate and the first insulating film, and a second insulating film is formed thereon. A plurality of data lines, a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode separated from the source electrode are formed on the second insulating layer, and are covered with the first insulating film, and a portion of the gate line and the source electrode and the drain are formed. An electrode forms a thin film transistor which receives a scanning signal from a gate line and switches an image signal from a data line.

The lower portion of the valley may form a field enhancement electrode made of the same material as the drain electrode, and the field enhancement electrode is connected to the drain electrode.

In the liquid crystal display according to the present invention, the valley may be extended to the second insulating layer under the first insulating layer, and in this case, the electric field enhancement electrode connected to the drain electrode may be further formed under the valley with the same material as the gate line.

It is preferable that the width of the full length enhancement electrode is equal to or greater than the width of the bone.

The angle formed by the surface perpendicular to the substrate and the valley is preferably greater than 0 degrees and 80 degrees or less, and the width of the valley is preferably 10 μm or less.

In the liquid crystal display according to the present invention, it is preferable to form a pair of the valley formed in the insulating film on the substrate and the opening formed in the field generating electrode on the insulating film.

Here, the electric field improving electrode that is electrically connected to the field generating electrode may be further formed under the bone.

In such a liquid crystal display, valleys may be formed in the insulating layer under the opening of the pixel electrode to stably arrange the liquid crystal molecules. In addition, since the effect of the fringe field may be reduced by forming the electric field enhancement electrode under the valley, the arrangement of the liquid crystal molecules may be easily performed at the boundary of the divided region, thereby widening the viewing angle of the liquid crystal display without generating the foreground.

Next, a liquid crystal display according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a view illustrating a state where upper and lower substrates are disposed in a liquid crystal display according to an exemplary embodiment of the present invention. The two substrates 1 and 5 face each other at a predetermined distance, and the two substrates 1 and 5 are disposed on the substrate. The pixel electrode 2 and the common electrode 6 which are electric field generating electrodes are formed in the inner surface of the inside, but the opening part is formed in the pixel electrode 2 of the lower board | substrate 1, respectively. Vertical alignment films 3 and 7 are formed on the electrodes 2 and 6, respectively, and a liquid crystal layer 9 having negative dielectric anisotropy is positioned between the two alignment films 3 and 7. On the outer surface of each of the substrates 1 and 5, polarizers 4 and 8 are attached to the lower substrate 1 to polarize the light entering the liquid crystal layer 9 and the light passing through the liquid crystal layer 9. The polarization axis of the attached polarizing plate 4 forms an angle of 90 degrees with respect to the polarization axis of the polarizing plate 8 attached to the upper substrate 5.

FIG. 2 is a layout view of a lower substrate of the liquid crystal display according to the first exemplary embodiment of the present invention, and FIGS. 3A and 3B are cross-sectional views of the liquid crystal display according to the first exemplary embodiment of the present invention, respectively. Corresponding to the plane cut along the line and IIIb-IIIb 'line, the arrangement of the liquid crystal molecules and the cross section of the thin film transistor are shown.

First, as shown in FIGS. 2 to 3B, a gate line 21 extending in the horizontal direction and a gate electrode 22 extending from the gate line 21 are formed on the substrate 10.

The gate insulating layer 30 covers the gate line 21 and the gate electrode 22, and a semiconductor layer 31 made of a material such as amorphous silicon is formed thereon and positioned on the gate electrode 22.

On the semiconductor layer 31, ohmic contacts 32 and 33 made of amorphous silicon doped at high concentration with n-type impurities such as phosphorus (P) are formed.

On the gate insulating film 30, data line 41, source and drain electrodes 42 and 43, and field enhancement electrodes 401, 402 and 403 connected to the drain electrode 43 are formed. The data line 41 extends in the vertical direction, and the source electrode 42 and the drain electrode 43 separated from the data line 41 face each other with respect to the gate electrode 22. The electric field enhancement electrodes 401, 402, and 403 may be omitted.

A protective insulating film 50 is formed on the data line 41, the source and drain electrodes 42 and 43, and the field enhancement electrodes 401, 402, and 403, and the drain electrode 43 is formed on the protective insulating film 50. Troughs 501, 502, and 503 are formed on the contact holes 501 exposing the electrodes and the field enhancement electrodes 401, 402, and 403.

The pixel electrode 60 is formed in the pixel region, which is a region defined by the gate line 21 and the data line 41 crossing each other. The rectangular pixel electrode 60 is formed with a first opening portion 601 slanted from the right side to the left side in the middle portion thereof, and both entrance portions of the first opening portion 601 are bent at a gentle angle with their corners cut off. When the pixel electrode 60 is divided into an upper part and a lower part with the first opening part 601 as the center, second and third opening parts 602 and 603 are formed in the upper part and the lower part, respectively. The second and third openings 602 and 603 are dug in the diagonal direction toward the upper right and the lower right from the left near the center of the pixel electrode 60, respectively. The first to third openings 601, 602, and 603 overlap the valleys 501, 502, and 503 and the field enhancement electrodes 401, 402, and 403 thereunder.

In addition to such a shape, the pixel electrode 60 may be formed to have various types of openings having a rectangular, sawtooth, or cross shape.

The valleys 401, 402, and 403 may be formed to have the same shape as the openings 601, 602, and 603. The widths may be smaller than the openings 601, 602, and 603 within 10 μm.

The electric field enhancement electrodes 401, 402, and 403 are formed in the same shape as the valleys 501, 502, and 503 and the openings 601, 602, and 603, and the width thereof is the same as or larger than the openings 601, 602, and 603. You may.

In FIG. 3A, a vertical alignment layer is formed on the pixel electrode 60 and the protective insulating layer 50, but is not shown here.

The common electrode 80 is formed on the inner surface of the upper substrate 70 disposed above the pixel electrode 60 at a predetermined distance, and a vertical alignment layer is formed on the common electrode 80. Not shown.

In the liquid crystal display, when no voltage is applied, the liquid crystal molecules 90 between the two electrodes 60 and 80 are arranged perpendicular to the two electrodes 60 and 80 and the valleys 501, 502, and 503. have.

However, as shown in FIG. 3A, when a voltage equal to or greater than a threshold voltage is applied between the two electrodes 60 and 80, the liquid crystal molecules 90 are inclined by an electric field generated between the two electrodes 60 and 80. You lose. At this time, the liquid crystal molecules 90 have a symmetrical arrangement in the left part and the right part of the valley 503 of FIG. 3A.

First, at the left edge of the pixel electrode 60, the liquid crystal molecules 90 standing vertically are rotated clockwise by a fringe field and tilted to the right with respect to the directions perpendicular to the two substrates 10 and 70. You are in a lost state.

On the other hand, the liquid crystal molecules 90 on the left side of the valleys 503 are also rotated in a clockwise direction so that the liquid crystal molecules 90 are inclined to the right with respect to the direction perpendicular to the two substrates 10 and 70. This is because the initial major axis direction is located to the right with respect to the direction of the fringe field.

In contrast, the liquid crystal molecules 90 positioned on the right side of the valley 503 and the liquid crystal molecules 90 on the right edge of the pixel electrode 60 rotate in a counterclockwise direction so that the two substrates 10 and 70 are perpendicular to each other. It is inclined to the left of the direction.

Thus, the boundary between two regions in which the liquid crystal molecules 90 are inclined is different from the opening 603 or the valley 503. If no valley 503 is formed, the liquid crystal molecules 90 on the left side of the valley 503 rotate counterclockwise and the liquid crystal molecules 90 on the right side of the valley rotate clockwise. Due to the elastic force of 90, the boundary between the two regions may not be constant and may appear up to the entire opening 603 and even the pixel electrode 60.

In addition, when the same potential as that of the pixel electrode 60 is applied to the electric field enhancement electrode 403 formed under the valley 503, the fringe formed by the opening 603 of the pixel electrode 60 is formed in the portion where the valley 503 is formed. There are two electric fields in the vertical direction by the field and the field enhancement electrode 403. Therefore, the electric field Et acting on this portion is a vector sum of the two electric fields and has a direction closer to the vertical direction of the substrates 10 and 70 than the fringe field as shown in FIG. 3A. Therefore, the liquid crystal molecules 90 rotate in the clockwise direction more easily than in the absence of the electric field enhancement electrode 403.

In this case, the liquid crystal molecules 90 near the pixel electrode 60 and the common electrode 80 maintain the vertical alignment state because the force of the alignment layer is greater than that of the electric field.

Here, the electric field enhancement electrode 403 may be formed in two ways. First, when forming the drain electrode 43 as in the previous embodiment can be formed so as to be connected to the drain electrode 43, the other is formed when forming the gate line 21 and the gate electrode 22 You may. However, at this time, the portion 301 connected to the drain electrode 43 should be formed. Figures for this are shown in Figures 4 and 5b. FIG. 4 is a layout view of a lower substrate of a liquid crystal display according to a second exemplary embodiment of the present invention, and FIGS. 5A and 5B are cross-sectional views of a liquid crystal display according to a second exemplary embodiment of the present invention, respectively. Corresponding to the plane cut along the line and Vb-Vb 'line, the arrangement of the liquid crystal molecules and the cross section of the thin film transistor are shown.

As such, the method of easily dividing and arranging the liquid crystal molecules 90 by forming the valleys 501, 502, and 503 under the openings 601, 602, and 603 may be performed by other types of LCDs such as a super twisted nematic (STN) method. It can also be applied to liquid crystal displays.

6 to 9 illustrate equipotential lines and liquid crystal molecules generated when a voltage is applied according to a slope of a valley, that is, an angle α between the portion perpendicular to the substrates 10 and 70 in FIG. 3A and the valley 503. A graph showing the state of an array. Here, the lower part of the horizontal axis shows the pixel electrode 60 and the valley 503 corresponding to the left part of FIG. The vertical axis shows the distance between the two electrodes.

6 and 7 illustrate a case in which the slope α of the valley is 45 degrees, and FIG. 6 illustrates a case where an applied voltage is 1 V and FIG. 7 illustrates a case where an applied voltage is 4 V. FIG.

As shown in FIG. 6, the liquid crystal molecules on the pixel electrode A remain vertically aligned, and the liquid crystal molecules in the portion corresponding to the valley B are inclined at a 45 degree angle near the lower substrate. As it goes to the top, it gets closer to the substrate, making a vertical arrangement near the upper substrate. It can be seen that the equipotential lines of the portions where the pixel electrode A and the valley B meet are convex, which is an arrangement D of liquid crystal molecules inclined by the valley B above the pixel electrode A. It appears to be continuously connected to the liquid crystal molecules to help the liquid crystal molecules rotate in the clockwise direction.

Subsequently, as shown in FIG. 7, when the applied voltage reaches 4 V, the liquid crystal molecules are all rotated clockwise to be inclined to the right of the vertical direction of the substrate as described above with reference to FIG. 3A.

8 and 9 illustrate a case in which the inclination α of the valley is 80 degrees, and FIG. 8 illustrates a case where an applied voltage is 1 V and FIG. 9 illustrates a case where an applied voltage is 4 V. FIG.

As shown in FIG. 8, the liquid crystal molecules stand vertically with respect to the substrate on the pixel electrode A and are inclined slightly to the right even inside the valley B. FIG. However, as shown in FIG. 9, when the applied voltage becomes 4V, the liquid crystal molecules are all rotated in the clockwise direction but inclined to the right side of the vertical direction of the substrate.

As shown in the experimental results of FIGS. 8 and 9, when the valley B is formed and the liquid crystal molecules are inclined more than 10 degrees with respect to the vertical direction of the substrate, even if a fringe field is generated, the liquid crystal molecules are formed on the right side of the vertical direction of the substrate. Inclined to Therefore, the inclination α of the bone can be formed at 80 degrees or less.

As described above, the smaller the inclination α of the valley is, the greater the force of rotation of the liquid crystal molecules increases, and the inclination α of the valley can be formed within a range of 0 degrees to 80 degrees.

Meanwhile, FIGS. 10 to 14 illustrate arrangement states of equipotential lines and liquid crystal molecules generated when the inclination α of the bone is formed at 45 degrees and the applied voltage is changed in FIG. 3A. Here, the lower portion of the horizontal axis shows the pixel electrode 60, the valley 5030, and the electric field enhancement electrode 403 of FIG. 3A. The valley 5030 has a flat center portion unlike the V-shape of FIG. 3A. Reference numeral 61 denotes an alignment film. The vertical axis shows the distance between the two electrodes.

FIG. 10 shows an initial state, FIG. 11 is an applied voltage of 2V, FIG. 12 is 2.5V, FIG. 13 is 3V, and FIG. 14 is 4V. As shown in FIGS. 11 and 12, since the liquid crystal molecules hardly move when the applied voltage is 2V and the liquid crystal molecules move when the applied voltage is 2.5V, the threshold voltage has a value between 2V and 2.5V.

As shown in FIGS. 10 to 14, as the applied voltage increases above the threshold voltage, the degree of warp of the equipotential lines in the valley 5030 increases, and the liquid crystal molecules 90 also lay down on the substrate much. The pixel electrode 60 It can be seen that the liquid crystal molecules 90 are stably arranged around the valley 5030 without generation of the foreground.

In the present invention, by forming a valley in a portion corresponding to the opening of the pixel electrode, it is possible to stably divide the pixel in the pixel electrode without generating the foreground to widen the viewing angle of the liquid crystal display.

Claims (11)

Board, A field generating electrode formed on the substrate and having an opening; A first insulating film formed between the substrate and the field generating electrode and having a valley located below the opening; and A field enhancement electrode formed under the valley and electrically connected to the field generating electrode Liquid crystal display comprising a. delete In claim 1, A plurality of gate lines formed between the substrate and the first insulating film, A second insulating film formed on the gate line; A plurality of data lines formed on the second insulating film and covered with the first insulating film, A thin film transistor comprising a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode separated from the source electrode, and receiving a scan signal from the gate line to switch an image signal from the data line Liquid crystal display further comprising. In claim 3, The electric field enhancement electrode includes the same material as the drain electrode and is connected to the drain electrode. In claim 3, And the valley extends to the second insulating film under the first insulating film. In claim 5, The field enhancement electrode includes the same material as the gate line and is connected to the drain electrode. The method according to any one of claims 1, 4 and 6, The width of the electric field enhancement electrode is greater than or equal to the width of the valley. In claim 1, And an angle formed between the surface perpendicular to the substrate and the valley is greater than 0 degrees and less than 80 degrees. In claim 1, The width of the valley is 10μm or less liquid crystal display device. Board, An insulating film formed on the substrate and having a valley, A field generating electrode formed over said insulating film and having an opening, and A field enhancement electrode formed under the valley and electrically connected to the field generating electrode Including; And the valley and the opening are paired. delete

Images