KR101095810B1 - Vertical aligned neomatic liquid crystal mode controlled by mixed-field - Google Patents

Abstract

The present invention relates to a mixed field vertical liquid crystal display device having improved performance by appropriately adjusting the direction of the vertical electric field and the horizontal magnetic field, the first substrate; A second substrate spaced apart from the first substrate; Gate wiring and data wiring formed on the first substrate by vertical crossing; A thin film transistor formed at an intersection of the gate wiring and the data wiring; A pixel electrode positioned inside the first substrate and connected to the thin film transistor; A first insulating layer formed inside the pixel electrode; A third common electrode which is a pattern electrode positioned inside the first insulating layer; A first vertical facing film positioned on an inner surface of the third common electrode; A first common electrode positioned inside the second substrate and formed in a plate shape; A second insulating layer formed on an inner surface of the first common electrode; A second common electrode serving as a pattern electrode on an inner surface of the second insulating layer; A second vertical facing film positioned on an inner surface of the second common electrode; A mixed field vertical liquid crystal display device including a liquid crystal layer positioned between the first vertically opposed film and the second vertically opposed film is provided.

Description

Vertical aligned neomatic liquid crystal mode controlled by mixed-field

The present invention relates to a mixed field vertical liquid crystal display device, and more particularly, to a mixed field vertical liquid crystal display device having improved performance by appropriately adjusting the directions of the vertical electric field and the horizontal magnetic field.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, notebook computers, the demand for light and thin flat panel device is gradually increasing. LCD (Liquid Crystal Display) and PDP (Plasma Display Panel) have been actively studied as such flat panel display devices. Among them, liquid crystal display (LCD), which can realize the ease of driving and high quality, has been in the spotlight. have.

One of the liquid crystal display devices may be a liquid crystal display device in a twisted neomatic (TN) mode.

In the TN mode liquid crystal display, since the light is not completely blocked in the off state, the contrast ratio is not good, and the contrast ratio changes with the angle, and it is difficult to obtain a stable image such that the brightness of the halftone is reversed as the angle changes.

In order to solve the above problems, various methods have been proposed. As a solution, a film compensation mode and a multi-domain mode for compensating a viewing angle by dividing pixels into multiple domains and varying the viewing angle of each domain are provided on the same substrate. There is a transverse electric field mode in which two electrodes are placed in a horizontal field so that a horizontal electric field occurs.

On the other hand, the vertical alignment (VA) liquid crystal display uses a negative liquid crystal having a negative dielectric anisotropy and a vertical alignment layer. In the state where no voltage is applied, the long axis of the liquid crystal molecules is vertically aligned with the plane of the alignment layer and attached to the substrate. The polarization axis of the polarizing plate is arranged perpendicular to the long axis of the liquid crystal molecules so as to display a black background mode. On the other hand, when a voltage is applied, the negative liquid crystal molecules are oriented obliquely with respect to the electric field so that the long axes of the liquid crystal molecules move toward the alignment layer plane in the vertical direction of the alignment layer plane and transmit light.

Such a vertical alignment mode liquid crystal display will be described with reference to the drawings.

FIG. 1 is a plan view of a PVA (PVA) patterned liquid crystal display device according to the prior art, and FIG. 2 is a cross-sectional view taken along line II of FIG.

The thin film transistor TFT may include a gate electrode branched from the gate line 112, a gate insulating layer stacked on the gate electrode, a semiconductor layer formed in an island shape on the gate electrode, and the data. It is composed of a source / drain electrode branched from the wiring 115 formed on the semiconductor layer.

On the other hand, the upper substrate 121 has a black matrix layer 122 for preventing light leakage generated in an area where it is difficult to control the alignment of the liquid crystal due to the unstable electric field, and the black matrix layer ( A color filter layer 123 of R, G, and B formed between the plurality of layers 122, a common electrode 124 stacked on one side of the color filter layer 123 to face the pixel electrode 117 of the lower substrate 111, Is formed on a predetermined portion of the common electrode 124 is formed on the front surface including a plurality of second slits 131 for controlling the liquid crystal director by the electric field distortion, and the common electrode 124 having the second slit 131 A second vertical alignment layer 130 for controlling the arrangement of liquid crystal molecules is provided.

In FIG. 2, reference numeral 160 denotes a retardation film, and 161 denotes a polarizing film. The retardation film and the polarizing film are attached to the outer surfaces of the upper and lower substrates 121 and 111, respectively.

The first slit 133 and the second slit 131 are alternately arranged in an oblique shape parallel to each other to form a multi-domain.

The inner surface of the pixel electrode 117 and the common electrode 124 is further provided with a first vertical alignment layer 129 for controlling the arrangement of the liquid crystal molecules.

Further, the liquid crystal layer 100 is further formed between the upper and lower substrates 111 and 121. In the liquid crystal display of the VA mode, a negative liquid crystal having a negative dielectric anisotropy is used, and the long axis of the liquid crystal molecules is initially perpendicular to the substrate plane. To be arranged.

The liquid crystal display device formed as described above includes a multi-domain divided into a plurality of regions by the first slit 133 of the lower substrate 111 and the second slit 131 of the upper substrate 121 with respect to one unit pixel. multi-domain).

When a constant voltage is applied to the PVA mode liquid crystal display device, an equipotential surface 110 as shown in FIG. 2 is formed, and the liquid crystal molecules of the liquid crystal layer 100 are in a predetermined direction along the equipotential surface 110. You lie down and light passes through it.

However, referring to FIGS. 3A and 3B, when a voltage is applied to the liquid crystal display, a vertical electric field is almost applied to the central portion A between the first slit 133 and the second slit 131. The liquid crystal element in the center portion A has a weak response line due to a decrease in response speed due to the vertical electric field, and due to this problem, the gap between slits cannot be widened beyond a certain value. Has a limit. Moreover, even when a low voltage (1V) is applied as in FIG. 3A, the same problem occurs that the response speed is lowered. For this reason, the liquid crystal display has a problem in that transmittance has a limit of improvement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device further improving transmittance by appropriately adjusting a horizontal magnetic field and a vertical magnetic field using a plurality of common electrodes.

The present invention to achieve the above object, the first substrate; A second substrate spaced apart from the first substrate; Gate wiring and data wiring formed on the first substrate by vertical crossing; A thin film transistor formed at an intersection of the gate wiring and the data wiring; A pixel electrode positioned inside the first substrate and connected to the thin film transistor; A first insulating layer formed inside the pixel electrode; A third common electrode which is a pattern electrode positioned inside the first insulating layer; A first vertical alignment layer disposed on an inner surface of the third common electrode; A first common electrode positioned inside the second substrate and formed in a plate shape; A second insulating layer formed on an inner surface of the first common electrode; A second common electrode serving as a pattern electrode on an inner surface of the second insulating layer; A second vertical alignment layer disposed on an inner side surface of the second common electrode; A mixed field vertical liquid crystal display device including a liquid crystal layer positioned between the first vertical alignment layer and the second vertical alignment layer is provided.

Preferably, a color filter is disposed between the second substrate and the first common electrode, and the pattern of the second common electrode is alternately arranged with the pattern of the third common electrode.

In addition, when a current of varying polarity is applied to the pixel electrode, it is preferable to further include a voltage conversion supply unit for switching the polarity of the second and third common electrodes according to the polarity of the current applied to the pixel electrode.

According to the present invention described above, the negative electric liquid may be quickly responded without a disclination line phenomenon by using a plurality of common electrodes to cause a vertical electric field slightly inclined in all the pixels.

In addition, according to the present invention, it is possible to further improve the transmittance by forming a wide interval between the pattern of the common electrode.

1 is a plan view of a conventional liquid crystal display device.
FIG. 2 is a cross-sectional view of II of FIG. 1.
FIG. 3A is a diagram illustrating electrical characteristics of a liquid crystal when 1V is applied to the liquid crystal display of FIG. 1.
3B is a diagram illustrating electrical characteristics of the liquid crystal when 3V is applied to the liquid crystal display of FIG. 1.
4 is a plan view of a liquid crystal display device according to a first embodiment of the present invention.
5 is a cross-sectional view of the II-II part of FIG.
6 a and b illustrate electrical characteristics of the liquid crystal display device according to the first embodiment of the present invention.
7 a and b illustrate electrical characteristics of the liquid crystal display device according to the second embodiment of the present invention.
8 is a cross-sectional view of a liquid crystal display device according to a third embodiment of the present invention.
<Brief description of symbols for the main parts of the drawings>
10: first substrate 15: second substrate
20: pixel electrode 40: third common electrode
50: first common electrode 60: second common electrode
70: liquid crystal layer

Hereinafter, a liquid crystal display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a plan view of a liquid crystal display device according to a first exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view of the II-II part of FIG. 4.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It should be understood that various equivalents and modifications may be present.

4 and 5, the liquid crystal display device according to the first embodiment of the present invention, the first and second substrates 10 and 15, the gate wiring 11, the data wiring 12, the thin film transistor 13 ), Pixel electrodes 20, first and second insulating layers 35 and 55, first to third common electrodes 50 and 60 and 40, and first and second vertical alignment layers 45 and 65, It consists of the color filter 16, the polarizing plate 80, and the liquid crystal layer 70.

The first substrate 10 is disposed spaced apart from the second substrate 15 by a predetermined interval, and the first and second substrates 10 and 15 are made of glass material.

A scan signal is applied to the gate wiring 11 from an external driving circuit, an image signal is applied to the data wiring 12, and the gate wiring 11 and the data wiring 12 are formed to cross each other.

The thin film transistor 13 is formed at an intersection of the data line 12 and the gate line 11.

Meanwhile, a pixel electrode 20 connected to the thin film transistor 13 is installed inside the first substrate 10 (upper side in FIG. 5). The pixel electrode 20 has a plate shape and is connected to the thin film transistor 13 to operate a liquid crystal.

A first insulating layer 35 is formed inside the pixel electrode 20, and the first insulating layer 35 is made of silicon dioxide (SiO ₂ ) or silicon nitride (SiNx). The first insulating layer 35 insulates the pixel electrode 20 from the third common electrode 40 to prevent a short circuit between both electrodes.

A third common electrode 40 is formed inside the first insulating layer 35. The third common electrode 40 is formed as a patterned electrode, and the pattern is in the form of a Severon. Although described in the present embodiment in the shape of a Severon, other shapes such as a straight shape are also possible, of course.

A first vertical alignment layer 45 is formed on an inner surface of the third common electrode 40 and the first insulating layer 35, and the first vertical alignment layer 45 has a function of orienting liquid crystal molecules. .

On the other hand, a first common electrode 50 having a plate shape is formed on the inner side (lower side of FIG. 5) of the second substrate 15. The voltage applied to the first common electrode 50 may vary depending on the width and spacing of the patterned electrode.

A color filter layer 16 is formed between the second substrate 15 and the first common electrode 50, and a second insulating layer 55 and a second common layer below the first common electrode 50. The electrodes 60 are positioned sequentially. The second common electrode 60 is a patterned electrode, and has a different polarity from that of the third common electrode 40. The voltage applied depends on the type of liquid crystal.

The first to third common electrodes 50, 60, and 40 may be made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The first to third common electrodes 50 and 60 and 40 are fixed at a constant voltage, and the pixel electrode represents various brightnesses of the pixel by changing the voltage according to a signal. In this embodiment, the first common electrode is set to 0V, the second common electrode is set to 1.5V, the third common electrode is set to -1.5V, and the pixel electrode is set to 1V.

Meanwhile, in the present exemplary embodiment, a direct current is applied to the pixel electrode 20 and the voltages of the first to third common electrodes 50, 60, and 40 are fixed. However, polarity is applied to the pixel electrode 20. When the periodically changing current is applied, the voltage conversion supply unit switches the polarity of the voltage applied to the second and third common electrodes 60 and 40 according to the polarity of the current applied to the pixel electrode. And a converted voltage is applied to the second and third common electrodes 60 and 40 according to the voltage applied to the pixel electrode.

The voltage conversion supply unit 90 applies + voltage to the second common electrode and-voltage to the third common electrode when + voltage is applied to the pixel electrode, and applies-voltage to the pixel electrode. The negative voltage is applied to the second common electrode and the voltage converted to the positive voltage is applied to the third common electrode.

The voltage conversion supply unit 90 applies + voltage to the second common electrode, + voltage to the third common electrode when + voltage is applied to the pixel electrode, and + voltage to the pixel electrode. The second common electrode may be supplied with a voltage, and the third common electrode may be converted with a voltage.

In the voltage conversion supply unit 90, the polarity of the second common electrode is changed to be the same as that of the pixel electrode. However, if the polarity of the second common electrode and the third common electrode is different from each other, the second common electrode is connected to the pixel electrode. It is also possible to convert them differently.

The pattern of the second common electrode 60 is alternately formed with the pattern of the third common electrode 40. The second insulating layer 55 is made of silicon dioxide (SiO ₂ ) or silicon nitride (SiNx), which is an insulating material, and is formed between the first common electrode 50 and the second common electrode 60. A short circuit is prevented between the first common electrode 50 and the second common electrode 60.

A second vertical alignment layer 65 is formed inside the second common electrode 60 and the second insulating layer 55 to align the liquid crystal molecules.

Further, a liquid crystal layer 70 made of negative liquid crystals having negative dielectric anisotropy is formed between the first and second vertical alignment layers 45 and 65, and outside the first and second substrates 10 and 15. The polarizing plate 80 is provided.

Hereinafter, the liquid crystal display device according to the first embodiment of the present invention configured as described above operates as follows.

When no voltage is applied to the liquid crystal display, the liquid crystal elements of the liquid crystal layer are positioned in the vertical direction by the first and second vertical alignment layers 45 and 65.

Referring to FIG. 6A, in order to operate the liquid crystal device, a voltage of 1 V is applied to the pixel electrode of the liquid crystal display device, 1.5 V is applied to the second common electrode 60, and the first common electrode 50 is applied. 0V, which is lower than the pixel electrode 20 and the second common electrode 60, is applied to the third electrode 40, and the voltage is lower than that of the first common electrode 50 and the pixel electrode 20. And -1.5V is applied to the opposite polarity of the second common electrode.

When the above voltages are applied to the respective electrodes, a vertical electric field is formed between the pixel electrode 20 and the first common electrode 50, and between the pixel electrode 20 and the third common electrode 40. Horizontal electric field occurs. At the same time, a horizontal electric field is generated between the first common electrode 50 and the second common electrode 60, and a compliant electric field is generated between the second common electrode 60 and the third common electrode 40. There is a slightly inclined vertical electric field everywhere in the pixel. In particular, when looking at the equipotential surface 95 of the slit and the "B" portion of the slit, it can be seen that the inclined electric field is formed in that it is not formed horizontally but is inclined in one direction.

Accordingly, when a voltage is applied to the pixel electrode 20, the negative liquid crystal responds quickly as a whole to improve responsiveness, thereby increasing transmittance by increasing the width of the slit.

This phenomenon can be seen clearly when the vertical electric field is higher.

FIG. 6B is a diagram illustrating electrical characteristics of the liquid crystal display when the vertical electric field is increased by applying 3 V to the pixel electrode. Referring to FIG. 6B, even when the voltage of the pixel electrode 20 is increased to 3V to increase the vertical electric field, the equipotential surface of the “B” portion is still formed to be inclined to form an inclined vertical electric field.

7 a and b illustrate electrical characteristics of the liquid crystal display device according to the second embodiment of the present invention.

In the liquid crystal display device according to the second embodiment of the present invention, the width of the pattern of the third common electrode is formed to 5 μm, and the pattern interval is increased to 20 μm by increasing the pattern interval from the first embodiment of the present invention (15 μm). If set. Referring to FIGS. 7A and 7B, it can be seen that even when the pattern spacing is increased to 20 μm, the inclined vertical electric field is applied everywhere in the pixel. The equipotential surface 295 of the “C” portion is also inclined to one side. Able to know.

8 is a cross-sectional view of a liquid crystal display device according to a third embodiment of the present invention.

8, the liquid crystal display according to the third embodiment of the present invention is to place the third common electrode of the first embodiment in the lateral direction of the second common electrode, the rest of the configuration is the first embodiment Is the same as

Therefore, the description of the same configuration as in the first embodiment will be omitted, and the description will be mainly given on the difference configuration.

In the liquid crystal display according to the third exemplary embodiment of the present invention, the second common electrode 360 and the third common electrode alternately disposed inside the insulating layer 355 formed on the inner surface of the first common electrode 350. 340 is provided.

The second and third common electrodes 360 and 340 are patterned electrodes, and different polarities are applied to both common electrodes. A second vertical alignment layer 365 is formed on the inner surfaces of the second and third common electrodes 360 and 340.

Referring to the operation of the liquid crystal display device according to the third embodiment of the present invention, when a direct current is applied to the pixel electrode 320, a constant voltage or 0 V is applied to the first common electrode 350 as a reference electrode. In addition, predetermined voltages having opposite polarities are applied to the second and third common electrodes 360 and 340.

In this way, when a voltage is applied to each electrode, a vertical electric field is generated between the pixel electrode 320 and the first to third common electrodes 350, 360, and 340, respectively, and the first common electrode 350 A horizontal electric field is generated between the second and third common electrodes 360 and 340 and between the second common electrode 360 and the third common electrode 340.

Therefore, the liquid crystal display device according to the third embodiment of the present invention also generates a vertical electric field and a horizontal electric field simultaneously.

On the other hand, when a current whose polarity is periodically changed is applied to the pixel electrode 320, the second and third common electrodes 360 and 340 are applied to the pixel electrode 320 according to the polarity of the current applied to the pixel electrode 320. A voltage conversion supply unit 390 for applying a voltage by changing polarity is further provided. The voltage applied to the second and third common electrodes 360 and 340 is changed according to the voltage applied to the pixel electrode.

The voltage conversion supply unit 390 applies a + voltage to the second common electrode 360 and a-voltage to the third common electrode 340 when a + voltage is applied to the pixel electrode 320. When a negative voltage is applied to 320, a negative voltage is applied to the second common electrode 360, and a positive voltage is applied to the third common electrode 340.

The voltage conversion supply unit 390 changes the polarity of the second common electrode 360 to be the same as that of the pixel electrode 320, but the polarity of the second common electrode 360 and the third common electrode 340. In this case, the second common electrode 360 may be different from the pixel electrode 320.

In order to further improve the response speed by applying the horizontal voltage more efficiently, the voltage conversion supply unit 390 may be formed of a thin film transistor.

As described above, although the present invention has been described with reference to a limited embodiment of the PVA type using a pattern electrode and the drawings, the present invention is not limited thereto, and MVA (Multi- is formed to form a lip on the common electrode instead of the pattern electrode). Various modifications and variations can be made by those skilled in the art to which the present invention pertains, such as a domain Vertical Alignment type, within the scope of the technical spirit of the present invention and the appended claims.

Claims (11)

A first substrate 10; A second substrate 15 spaced apart from the first substrate 10;
A gate wiring 11 and a data wiring 12 formed on the first substrate 10 by vertical crossing;
A thin film transistor (13) formed at an intersection of the gate line (11) and the data line (12);
A pixel electrode 20 positioned inside the first substrate 10 and connected to the thin film transistor 13;
A first insulating layer 35 formed inside the pixel electrode 20;
A third common electrode 40 which is a pattern electrode positioned inside the first insulating layer 35;
A first vertical alignment layer 45 positioned on an inner surface of the third common electrode 40;
A first common electrode 50 positioned inside the second substrate 15 and formed in a plate shape;
A second insulating layer 55 formed on an inner surface of the first common electrode 50;
A second common electrode 60 which is a pattern electrode positioned on an inner surface of the second insulating layer 55;
A second vertical alignment layer 65 positioned on an inner surface of the second common electrode 60;
Mixed field vertical liquid crystal display device including a liquid crystal layer 70 positioned between the first vertical alignment layer 45 and the second vertical alignment layer 65. The mixed field vertical liquid crystal display device of claim 1, further comprising a color filter (16) positioned between the second substrate (15) and the first common electrode (50). The method according to claim 1,
The pattern of the second common electrode is mixed with the pattern of the third common electrode are arranged vertically liquid crystal display device. The method according to claim 1,
The first common electrode (50) is 0V, the second common electrode (60) and the third common electrode (40) is a mixed field vertical liquid crystal display device of opposite polarity. The method according to claim 1,
A mixed field vertical liquid crystal display device further comprising first and second polarizing plates (80, 81) positioned outside the first and second substrates (10, 15), respectively. The method according to claim 1,
The first to third common electrodes (50, 60, 40) is a mixed field vertical liquid crystal display device made of a transparent conductive material. The method according to claim 1,
A voltage converting supply unit 90 is applied to the pixel electrode to switch the polarity of the second and third common electrodes 60 and 40 according to the polarity of the current applied to the pixel electrode. Mixed field vertical liquid crystal display device further comprising. The method according to claim 7,
The polarity of the second common electrode 60 and the third common electrode 40 are opposite to each other when the polarity of the second and third common electrodes 60 and 40 is changed. A first substrate 10; A second substrate 215 spaced apart from the first substrate 10;
A gate wiring 11 and a data wiring 12 formed on the first substrate 10 by vertical crossing;
A thin film transistor (13) formed at an intersection of the gate line (11) and the data line (12);
A pixel electrode 220 positioned inside the first substrate 10 and connected to the thin film transistor 13;
A first vertical alignment layer 245 positioned on an inner surface of the pixel electrode 220;
A first common electrode 250 positioned inside the second substrate 215 and having a plate shape;
An insulating layer 255 formed on an inner surface of the first common electrode 250;
A second common electrode 260 which is a pattern electrode positioned on an inner surface of the insulating layer 255;
A third common electrode 240 disposed on an inner surface of the insulating layer 255 and a pattern electrode to which a polarity voltage different from that of the second common electrode 260 is applied;
A second vertical alignment layer 265 positioned on inner surfaces of the second common electrode 260 and the third common electrode 240;
Mixed field vertical liquid crystal display device including a liquid crystal layer 270 positioned between the first vertical alignment layer 245 and the second vertical alignment layer 265. The method according to claim 9,
A current having a different polarity is applied to the pixel electrode, and a voltage conversion supply unit 390 for switching the polarity of the second and third common electrodes 260 and 240 according to the polarity of the current applied to the pixel electrode. Mixed field vertical liquid crystal display device comprising. The method according to claim 10,
The voltage conversion supply unit 390 is a mixed field vertical liquid crystal display device consisting of a thin film transistor.

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