KR100527084B1 - Ffs liquid crystal display device - Google Patents

Abstract

The present invention is a wide viewing angle product with a wide process margin as a method of improving the black line-type mura when rubbing occurs due to process margins in FFS (Fringe Field Switching) mode which overcomes the narrowness of the viewing angle which is a disadvantage of the existing mode. The present invention relates to a FSF LCD liquid crystal display device without a black line mura generated during rubbing, wherein the counter electrode, the gate bus line, the counter electrode bus line, and the insulating layer are formed in a box shape formed of a first ITO. The lower substrate is composed of a data bus line, a TFT (Thin Film Transistor), and a second ITO, and a pixel electrode formed with different patterning for each region to form an electric field in different directions. The upper substrate, anti-parallel or parallel to the rubbing direction of the rubbing direction, and positive or negative The polarization axis of the liquid crystal injected with a rate characteristic and the polarizing plate attached to the outside of the lower substrate coincides with the rubbing direction of the lower substrate, and the polarization axis of the upper substrate attached to the outside of the upper substrate crosses the polarization axis of the lower substrate. The pixel electrode is patterned so that the angle (β) formed between the initial rubbing direction and the electric field direction is different in a unit pixel of a black line-shaped mura generated during rubbing. By understanding the exact characteristics of mura, it is a useful invention that contributes to the improvement of yield and screen quality by designing wider process margin by changing pixel structure in subpixel.

Description

FPS liquid crystal display device {FFS LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a FSF (Fringe Field Switching) liquid crystal display device, and more particularly to the black line-shaped mura when rubbing occurs due to the process margin in the FSF mode overcoming the narrowness of the viewing angle which is a disadvantage of the existing mode. The present invention relates to a fs liquid crystal display device without black line mura generated during rubbing, which can realize a wide viewing angle product having a wide process margin.

TN (Twisted Nematic) mode is most commonly used as a conventional liquid crystal display device, which is a disadvantage of the narrow viewing angle. On the other hand, in order to improve the viewing angle, the technology related to the F mode has been disclosed in Korean Patent Application No. 98-9243. FIG. 1 is a plan view showing unit pixels in a conventional FPS structure. In order to obtain a maximum transmittance in the conventional structure, a negative electrode is adjacent to a gate bus line 2 and a gate electrode line 2 in the case of a negative liquid crystal. Rubbing at ± 12 ° with respect to gate busline 3 overlapping with 6), turn table at 12 ° for rubbing at ± 12 ° with respect to gate bus line 2 for negative liquid crystal, Roll head angle can be set to 0 ° after the straight motion, or the table can be set to 0 ° and the roll head angle should be set to 12.1˝ considering the correction angle. However, when rubbing in this manner, black lines 10 are generated in the horizontal direction as shown in FIG. 2. Reference numeral 8 denotes a pixel electrode and A denotes a rubbing direction. Reference numeral 4 also denotes a data busline.

Although black lines look very thin even when no voltage is applied, they are generally visible in eye-sensitive areas of more than Vth (threshold voltage) when voltage is applied, that is, in gray areas where the boundary is clearly distinguished even with slight luminance cotton. As a result, the luminance unevenness (black line) generated in a horizontal band shape in a specific gray pattern serves as a problem of degrading the image quality.

An object of the present invention has been made to improve the problems in the conventional liquid crystal display device as described above, in the form of black lines during rubbing caused by the lack of process margin in the fs mode overcome the narrowness of the viewing angle which is a disadvantage of the TN mode In order to improve mura, there is provided a fs liquid crystal display device without black line mura generated during rubbing.

According to a preferred embodiment of the present invention for achieving the above object, a data bus formed with a counter electrode, a gate bus line and a counter electrode bus line formed in a box shape made of a first ITO, and an insulating layer interposed therebetween. It consists of a pixel electrode consisting of a line, a thin film transistor (TFT), a second ITO, and differently patterned for each region to form a different electric field direction. The lower substrate rubbed at a specific angle, and the rubbing of the lower substrate. The polarization axis of the upper substrate which is anti-parallel or parallel to the direction, the injected liquid crystal having positive or negative permittivity characteristics, and the polarizing plate attached to the outer side of the lower substrate is the lower substrate. The polarization axis of the upper substrate coinciding with the rubbing direction of the upper substrate is attached to cross the polarization axis of the lower substrate. The pixel electrode is patterned so that the angle? Between the initial rubbing direction and the electric field direction is different from each other in the unit pixel of the black line-shaped mura generated during rubbing. A liquid crystal display device is provided.

Also, in the present invention, when using a liquid crystal having a negative dielectric constant characteristic, the specific angle β is formed to be ± 45 degrees or less on the basis of the rubbing angle in a portion of the pixel electrode, and in the other region, the specific angle β The angle of + α is formed to be less than ± 45 degrees relative to the rubbing direction, and the liquid crystal molecules in a region having a specific angle (β) + α are more easily rotated to generate transmittance when an electric field is applied.

       In addition, in the present invention, when a liquid crystal having positive dielectric constant characteristics is used, a specific angle β is formed to be ± 45 degrees or more based on the rubbing direction in a portion of the pixel electrode, and in another region, the specific angle ( [beta]) + [alpha] is formed over ± 45 ° based on the rubbing direction, and liquid crystal molecules in a region having a specific angle ([beta] + [alpha]) rotate more easily when electric fields are applied to generate transmittance.

In addition, in the present invention, the specific angle β is ± 12 degrees based on the rubbing direction in the partial region of the pixel electrode, and the specific angle β + α angle is ± 24 in the rubbing direction in the other partial region. , The liquid crystal molecules in the region of ± 24 degrees rotates more easily when the electric field is applied to generate a transmittance.

In addition, in the present invention, the specific angle β is ± 78 degrees with respect to the rubbing direction in the partial region of the pixel electrode, and the specific angle β-α angle is ± 64 with respect to the rubbing direction in the other partial region. , Characterized in that the liquid crystal molecules in the region of ± 64 degrees rotates more easily when an electric field is applied to generate transmittance.

Further, in the present invention, it is characterized in that at least one region in one sub-pixel has a different angle angle β 'with respect to a specific angle β.

Further, in the present invention, in the case of a negative liquid crystal, a specific angle (β) + α angle region and in the case of a positive liquid crystal, the specific angle (β)-α angle region are 1/2 or 1 / on a subpixel basis. It is characterized by three.

In addition, in the present invention, when a region having a specific angle (β) + α or a specific angle (β) -α is 1/2 in one subpixel, the specific angle (β) + α or specified in one subpixel. It is characterized by at least one region having an angle (?)-Α.

Moreover, in this invention, the characteristic of (DELTA) nd of a liquid crystal cell is 0.20-0.50 micrometer, It is characterized by the above-mentioned.

The present invention is a technique for preventing black mura occurring in a structure having a normally black electro-optical characteristic such as FSF mode or IPS mode, and generally has an electric field effect in an eye-sensitive gray region to which a voltage above Vth is applied. In the area where the rubbing effect acts more than the effect), the area that is sensitive to the change in brightness is designed with the maximum transmittance and the existing transmittance designed to alleviate the extent of the black line-type mura caused by the non-uniformity of the rubbing cloth. The liquid crystal molecules were easily rotated with respect to the electric field by dividing one pixel from rubbing a pixel that was 12 ° with respect to the electric field, and as a result, it became insensitive to rubbing unevenness and prevented black line-shaped mura.

A box-shaped counter electrode, a gate bus line and a counter electrode bus line basically formed of first ITO are formed, and a data bus line and a thin film transistor (TFT) are formed with an insulating layer interposed therebetween. The pixel electrode made of the second ITO is formed by patterning the pixel electrode such that the viewing angle β formed between the initial rubbing direction and the electric field direction is different in one sub-pixel. As a result, when a negative angle liquid crystal (beta) is used in the same rubbing direction with respect to the same rubbing direction in one sub-pixel, a partial angle (here, β = 12 degrees) is formed in some regions, and in another region, the angle angle (here β = 24 degrees). Of course, a region having an angle β of 24 degrees may be formed to be 1/2 or 1/3 in one pixel, and a specific angle (β = 24 degrees) in a case of 1/2 region in one unit pixel. It is also possible to form one or more regions. Similarly, the same angle between the reference rubbing direction (β) in one unit pixel is formed at a specific angle (β = 78 degrees) in some areas when the positive liquid crystal is used, and the angle (β = 64 degrees in other areas) To form). Of course, an area having a specific angle (β = 64 degrees) may be formed to be 1/2 or 1/3 in one pixel, and in the case of 1/2 area in one sub-pixel, within the 1/2 area One or more specific angle (β = 64 degrees) regions may be formed. In the above structure, the rubbing of the lower plate rubs at a specific angle in consideration of the transmittance, and the rubbing of the upper substrate is anti-parallel or parallel to the rubbing direction of the lower substrate. In general, when using liquid crystals having negative permittivity characteristics, rubbing is rubbing ideally to ± 12 degrees or less relative to the gate bus line, and when using liquid crystals having positive permittivity characteristics, rubbing is the gate bus line. Rubbing over ± 45 degrees, ideally ± 78 degrees, and the polarization axis of the polarizing plate attached to the outer side of the lower substrate coincides with the rubbing direction of the lower substrate, the polarization axis of the upper substrate attached to the outer side of the upper substrate It is attached to the polarization axis of cross (crossed) to create a normal black mode (Normally Black Mode) that becomes dark when no voltage is applied.

In the structure as described above, the area sensitive to the eye above Vth (threshold voltage) when applied to the electric field. In the gray area where the rubbing effect acts rather than the electric field effect, the patterned area is specified at a specific angle (β = 12 degrees in this case). Liquid crystal molecules more easily react to electric fields and transmit light. When the liquid crystal molecules are more easily reacted to the electric field and transmit the light when the electric field is applied, the effect is that the electric field effect is enhanced rather than the rubbing effect. Therefore, it is possible to prevent the black line-shaped mura caused by the uneven rubbing force due to the unevenness.

3 is a view showing an embodiment of the present invention, which is a detailed view in the case where a region where the angle β between the rubbing direction A and the electric field is a specific angle (β = 24 degrees) is 1/3. As shown in Fig. 3, the region 2 is a region where? = 24 degrees, and occupies one third of one unit pixel. In FIG. 3, reference numerals 16 and 18 denote counter electrodes and pixel electrodes, respectively.

FIG. 4A illustrates the relationship between the rubbing direction A and the field direction E1 and the arrangement of the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are arranged and turned off in the regions 1 and 3 of FIG. 3. FIG. 4B shows the relationship between the rubbing direction A and the field direction E1 in the region 2 and the arrangement relationship between the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are arranged and turned off.

With the above structure, the liquid crystal molecules react more easily with respect to the electric field applied in the region having the angle β of 24 degrees than the region having the angle β of 12 degrees when manufacturing the panel. As a result, rather than having only 12 degrees of interstitial angles (β) in one unit pixel, one-third area is a unit with 24 degrees of interstitial angle (β), and the remaining 2/3 regions is a unit with 12 degrees of interstitial angle (β). When the voltage is applied to the pixel, the liquid crystal molecules are easily twisted, so that the electric field effect is relatively larger than the rubbing effect in the gray region sensitive to the eye above Vth, thereby reducing the black line-shaped mura caused by the nonuniformity of the rubbing intensity.

FIG. 5 shows another embodiment of the present invention, in which a region where the angle β between the rubbing direction and the electric field is a specific angle (β = 24 degrees) is 1/2. As shown in Fig. 5, the area 2 and the area 3 are areas where? = 24 degrees, and occupy 1/2 of one unit pixel. FIG. 6A illustrates the relationship between the rubbing direction A and the field direction E1 in the regions 1 and 4 of FIG. 5 and the arrangement relationship between the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are disposed and turned off. 6B illustrates the relationship between the rubbing direction A and the field direction E1 and the arrangement of the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are arranged and turned off in the regions 2 and 3 of FIG. 5. .

With the structure as described above, the liquid crystal molecules react more easily with respect to the electric field applied in the region (region 2 and region 3) having the angle β of 24 degrees than the region having the angle β of 12 degrees. As a result, the liquid crystal molecules are easily twisted when voltage is applied to the unit pixel having the angle β of 24 degrees in one unit pixel and the remaining half region of the angle β of 12 degrees, and the eye above Vth (threshold voltage) In the gray area, which is sensitive to the electric field, the effect of the electric field is relatively greater than the rubbing effect, thereby reducing the black line-mura due to the nonuniformity of the rubbing intensity. This embodiment is more effective in terms of Mura reduction in the form of black lines than the embodiment in which the region β is 24 degrees, but is disadvantageous in terms of maximum and transmittance. Reference numerals 26 and 28 denote pixel electrodes and counter electrodes, respectively.

FIG. 7 is a detailed view of the modified structure of FIG. 5 in a case where a region where the angle β between the rubbing direction and the electric field is a specific angle (β = 24 degrees) is 1/2 in another embodiment of the present invention. to be. As shown in Fig. 7, the area 2, the area 4, and the area 6 are areas where? = 24 degrees and occupy 1/2 of one unit pixel. Herein, reference numerals 36 and 38 which are not described refer to the counter electrode and the pixel electrode, respectively. FIG. 8A shows the relationship between the rubbing direction A and the field direction E1 in the region 1, the region 3, and the region 5 of FIG. The relationship and arrangement of the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are arranged and off are shown. FIG. 8B illustrates the relationship between the rubbing direction A and the field direction E1 and the arrangement of the liquid crystal molecules 20 when the upper and lower polarizers 22 and 24 are arranged and turned off in the regions 2, 4, and 6 of FIG. 7. It is shown.

In the same structure as described above, the liquid crystal molecules react more easily with respect to the electric field applied in the region having the angle β of 24 degrees than the region having the angle β of 12 degrees during panel fabrication. As a result, rather than having only 12 degrees of interstitial angle β within one unit pixel, the half area (regions 2, 4, 6) has a 24 degree angle between them, and the other half region (region 1). (3,5) is easily shifted when the liquid crystal molecules are applied to the unit pixel having a β angle of 12 degrees, and the electric field effect is relatively larger than the rubbing effect in the eye-sensitive gray region above the Vth (threshold voltage), resulting in a non-uniformity. It is possible to reduce the mura in the form of black lines due to the uneven rubbing strength generated. The present embodiment is more effective in terms of reducing Mura in the form of black lines than the embodiment in which the region β is 24 degrees, but is disadvantageous in terms of maximum and transmittance.

FIG. 9 is a simulation result of the present invention, which shows a Δn = 0.077 of liquid crystal and a cell gap d showing transmittance characteristics of voltages according to an angle β in a unit pixel under 4 μm. As shown in the drawing, the result of VT characteristics according to the angle angle β in one unit pixel can be seen, where the angle angle β is 12 degrees and 24 degrees in one unit pixel, and β Transmittance characteristics for each voltage for the case of 1/2 and 1/3 in the region of = 24 degrees. As can be seen from this result, it can be seen that the transmittance near Vth occurs more easily when voltage is applied as the region having the angle angle β of 24 degrees becomes larger. FIG. 10 is an enlarged graph near the Vth (threshold voltage) in FIG. 9.

Accordingly, according to the above-described FPS liquid crystal display device without black line mura generated during rubbing according to the present invention, the present invention is a process of changing the pixel structure in a unit pixel by understanding the exact characteristics of the black line mura during rubbing. It is a useful invention that contributes to improved yield and screen quality with a wider margin design.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the scope of the claims You will have to look.

1 is a plan view showing a unit pixel of a conventional fs-mode liquid crystal display device.

2 is a screen showing a state where black lines occur in a conventional liquid crystal display device.

3 is a plan view illustrating a unit pixel of an FSF mode liquid crystal display device according to an exemplary embodiment of the present invention.

4A and 4B are diagrams showing the relationship between the rubbing direction and the field direction in each region in FIG. 3 and the arrangement of liquid crystal molecules when the upper and lower polarizers are arranged and turned off;

3 is a plan view illustrating a unit pixel of an FSF mode liquid crystal display device according to an exemplary embodiment of the present invention.

4A and 4B are diagrams showing the relationship between the rubbing direction and the field direction in each region in FIG. 3 and the arrangement of liquid crystal molecules when the upper and lower polarizers are arranged and turned off;

5 is a plan view illustrating a unit pixel of an FSF mode liquid crystal display device according to another exemplary embodiment of the present invention.

6A and 6B are views showing the relationship between the rubbing direction and the field direction in each region in FIG. 5 and the arrangement of liquid crystal molecules when the upper and lower polarizers are arranged and turned off;

7 is a plan view illustrating a unit pixel of an FSF mode liquid crystal display device according to still another exemplary embodiment of the present invention.

8A and 8B are diagrams showing the relationship between the rubbing direction and the field direction in each region in FIG. 7 and the arrangement relationship between liquid crystal molecules when the upper and lower polarizers are arranged and turned off;

9 is a graph illustrating V-T characteristic results according to angles between unit pixels.

10 is an enlarged graph near the threshold voltage.

<Description of Symbols for Main Parts of Drawings>

2: gate bus line 3: counter electrode gate bus line

4: data bus line 6: counter electrode

8: pixel electrode

Claims (9)

The lower substrate rubbed at a specific angle, A gate electrode line arranged on the lower substrate, a counter electrode formed in the form of a box made of a first ITO partially overlapping the gate bus line adjacent to the gate bus line, a pixel electrode made of a second ITO, A data bus line having an insulating layer interposed between the gate bus line, An upper substrate rubbed with one of anti-parallel and parallel to the rubbing direction of the lower substrate, A liquid crystal injected with a dielectric constant of either positive or negative, A lower polarizer attached to an outer side of the lower substrate and having a polarization axis coinciding with a rubbing direction of the lower substrate; In the FSF liquid crystal display device attached to the outside of the upper substrate, the polarizing axis crosses the polarization axis of the lower polarizing plate (cross), The pixel electrode has two or more regions in which one specific pixel has a specific angle β different from an initial rubbing direction and an electric field direction within a range in which the direction in which the liquid crystal is rotated is the same direction. Fs liquid crystal display device, characterized in that patterned to. delete delete The liquid crystal display device according to claim 1, wherein when a liquid crystal having a negative dielectric constant is used as the liquid crystal, a specific angle is +12 degrees based on a rubbing direction in a partial region of the pixel electrode, and a specific angle in another partial region of the pixel electrode. +24 degrees with respect to the rubbing direction, or -12 degrees with respect to the rubbing direction in the partial region of the pixel electrode, and -24 degrees with respect to the rubbing direction in the other partial region of the pixel electrode. And the liquid crystal molecules in the region of +24 degrees or -24 degrees rotate more easily when the electric field is applied to generate the transmittance. The liquid crystal display device according to claim 1, wherein when a liquid crystal having positive dielectric constant is used as the liquid crystal, a specific angle is +78 degrees based on a rubbing direction in a partial region of the pixel electrode, and a specific angle in another partial region of the pixel electrode. +64 degrees with respect to the rubbing direction, or -78 degrees with respect to the rubbing direction in the partial region of the pixel electrode, and -64 degrees with respect to the rubbing direction in the other partial region of the pixel electrode. And a liquid crystal molecule having a degree of +64 degrees or -64 degrees, which is more easily rotated to generate transmittance when an electric field is applied. delete 5. The pixel electrode of claim 4, wherein the pixel electrode has a specific angle of any one of +24 degrees and -24 degrees within one unit pixel, and any one of +12 degrees and -12 degrees different from the specific angle. A region having an angle between the regions occupies any one of 1/2 and 1/3, respectively. 8. The pixel electrode of claim 7, wherein the pixel electrode has a region of any one of +24 degrees and -24 degrees within one unit pixel having a specific angle of 1/2. And a region having a specific angle of any one of -24 degrees is divided into at least one or more. The fs liquid crystal display device according to claim 1, wherein Δnd, which is a product of the refractive index anisotropy value Δn of the liquid crystal and the distance d between the lower substrate and the upper substrate, is 0.20 to 0.50 μm.