KR100850737B1 - multi domain Liquid Crystal Display Device - Google Patents

Abstract

In the present invention, the first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; By providing a multi-domain liquid crystal display device disposed on the inner surface of each of the common electrode and the pixel electrode and including the first and second alignment layers formed on the slit, it is possible to improve the wide viewing angle characteristics and to stabilize the multi-domain structure. It can effectively block the light leakage from the foreground line, thereby increasing the reliability of the product.

Description

Multi domain Liquid Crystal Display Device             

1 is a schematic cross-sectional view of one pixel portion of a conventional two domain liquid crystal display using an orientation split method.

Figures 2a to 2b is a cross-sectional view showing a manufacturing step of the orientation split process according to FIG.

3 is a schematic cross-sectional view of one pixel portion of a conventional two domain liquid crystal display using electric field distortion.

4 is a schematic cross-sectional view of one pixel portion of a two domain liquid crystal display according to the present invention;

FIG. 5 is a plan view illustrating a plane corresponding to region “V” of FIG. 4.

6a to 6d respectively correspond to another modification of FIG. 5;

<Description of the symbols for the main parts of the drawings>

100: transparent substrate 102: upper substrate

104: lower substrate 106: liquid crystal layer

107: liquid crystal molecule 108: pixel electrode                 

110: lower alignment layer 112: common electrode

113: black matrix 114: upper alignment layer

116: electric field 120: slit

III: First Domain IV: Second Domain

θ ₁ , θ ₂ : pretilt angle

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a multi domain liquid crystal display device.

Recently, liquid crystal displays have been spotlighted as next generation advanced display devices having low power consumption, good portability, technology-intensive, and high added value.

The liquid crystal display device injects a liquid crystal between an array substrate including a thin film transistor (TFT) and a color filter substrate to obtain an image effect by using a difference in refractive index of light according to the anisotropy of the liquid crystal. It is a non-light emitting image display device.

On the inner surface of the array and the color filter substrate, an alignment layer is formed to guide the arrangement of liquid crystal molecules in a predetermined direction.                         

In general liquid crystal display devices, a mono domain structure, which maintains an array of liquid crystals uniformly over the entire surface of a substrate, is mainly used. In such a structure, gray scale inversion is changed according to a change in viewing angle due to optical and refractive anisotropy of the liquid crystal. It becomes large and there exists a problem that contrast ratio becomes nonuniform.

In order to solve this problem, recently, a single pixel area is divided by using electrical or liquid crystal properties, and a multi-domain liquid crystal display device which improves a viewing angle by using different liquid crystal alignment characteristics between divided areas, that is, domains. Research is being actively conducted.

Hereinafter, a conventional multidomain structure will be described with reference to the drawings.

1 is a schematic cross-sectional view of a pixel portion of a conventional two-domain liquid crystal display device by an orientation division method. In the domain division by the orientation division method, a region in which liquid crystal alignment is different at the same pixel voltage without division of pixel electrodes is performed. How to form.

As shown, the upper and lower substrates 2 and 4 are spaced at regular intervals, and the liquid crystal layer 6 composed of liquid crystal molecules 16 is interposed between the upper and lower substrates 2 and 4. On the contact surfaces of the upper and lower substrates 2 and 4 with the liquid crystal layer 6, upper portions having different pretilt angles θ ₁ and θ ₂ ; however, θ ₁ > θ ₂ with respect to the center. And lower alignment layers 8 and 12 are formed.

The liquid crystal molecules 16 are arranged symmetrically with respect to the central part by the pretilt angles having different sizes, and one pixel part is arranged in the first and second domains I by the alignment method of the liquid crystal molecules 16. , II).

The first and second domain regions I and II have respective visual characteristics, but the visual characteristics that the viewer actually feels are made by the average characteristic of the first and second domain regions I and II.

That is, the average characteristic of the two regions is close to that seen from the front, and the luminance inversion in the halftone is also reduced, and the viewing angle characteristic is improved.

However, in the method of dividing the domain only by the orientation dividing method, in the state where no voltage is applied, the liquid crystal can be controlled in a two domain structure by the alignment dividing treated alignment film, but if it is maintained for a long time in the voltage applied state, The liquid crystal array of the two-domain structure is rearranged in a certain direction along the electric field generating direction to change into a mono domain structure.

In addition, a disclination line is generated at the boundary between the first and second domain regions I and II according to the application of a voltage. In this case, the black line is driven in a normally black mode. In the liquid crystal display, when the voltage is applied, the foreground line becomes a bright line in the bright state, and no separate shading is necessary. When the voltage is not applied, since the liquid crystal molecules are almost parallel to the substrate, the problem related to the image quality characteristics is not so large. In a normally white mode liquid crystal display, a pattern for blocking the foreground line is required.

In the present specification, the viewing angle and image quality characteristics of the liquid crystal display device driving in the normally white mode are improved. The liquid crystal display device in the following description refers to a liquid crystal display device driving in the normally white mode.

The stabilization of the domain structure is to fix the position of the foreground line, it is possible to effectively block the foreground line, the two-domain structure becomes unstable when the voltage application time is prolonged by the orientation split method, The multi-domain structure has a problem that it is difficult to effectively improve the viewing angle and image quality.

2A to 2B are cross-sectional views illustrating a manufacturing process of the orientation splitting process according to FIG. 1. The upper substrate of FIG. 1 will be described as an example.

In FIG. 2A, after the alignment film 8 is applied onto the substrate 2, a rubbing treatment is performed on the surface of the alignment film 8 to form a high pretilt angle θ ₁ .

The high pretilt angle θ ₁ may be formed by adjusting the number of times of rubbing, the depth of rubbing, the moving speed of the rubbing cloth, and the like during the rubbing treatment.

In FIG. 2B, ultraviolet rays are irradiated to a portion of the alignment film 8 subjected to the rubbing process to change the pretilt angle on the region to which the ultraviolet rays are irradiated.

The size of the pretilt angle can be adjusted by the irradiation amount and irradiation distance of ultraviolet rays.

In more detail, after placing the mask 20 which has the ultraviolet-ray blocking part 20a and the ultraviolet-ray transmitting part 20b on the said board | substrate 2, it irradiates an ultraviolet-ray and respond | corresponds to this ultraviolet-ray transmitting part 20b. The high pretilt angle θ ₁ on the alignment film 8 is changed to the low pretilt angle θ ₂ .

FIG. 3 is a schematic cross-sectional view of one pixel portion of a conventional multi-domain liquid crystal display using electric field distortion, and the illustration of the alignment layer is omitted for convenience of description.

As shown, the upper and lower substrates 22 and 24 are arranged at regular intervals, and the liquid crystal layer 26 is interposed between the upper and lower substrates 22 and 24, and the upper and lower substrates are disposed. On the inner surfaces of the 22 and 24, the common electrode 28 and the pixel electrode 30 which are electrodes which apply a voltage to this liquid crystal layer 26 are formed, respectively.

At this time, a slit (s) for dividing the pixel region is formed in the central portion of the pixel electrode 30, so that electric field distortion occurs when the voltage is applied as the boundary of the slit (s).

In addition, since the long axis of the liquid crystal molecules 27 is arranged in a direction parallel to the electric field 32 indicated by the dotted lines in the liquid crystal layer 26, the electric field distortion curve formed in the slit portion s is reduced. Thus, the arrangement of the liquid crystal molecules 27 is divided to form two domains.

However, the method of dividing the domain by using the electric field distortion phenomenon has an effect only when voltage is applied, and thus the domain dividing ability is reduced when no voltage is applied.

On the other hand, as part of the method for improving the problem, a method of dividing the domain by a polymer stabilization method by introducing a lattice-shaped polymer to the liquid crystal, keeping the arrangement of the liquid crystal constant regardless of voltage application Although this has been proposed, such a domain division method has a disadvantage in that the manufacturing cost and process are complicated, and device reliability and product yield are inferior.

In order to solve the above problems, the present invention provides a liquid crystal display device capable of maintaining a wide viewing angle characteristic by forming a stable multi-domain structure irrespective of whether voltage is applied by appropriately using an orientation split method and an electric field distortion phenomenon. For the purpose of

In the present invention according to the first aspect to achieve the above object, the first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; The first and second alignment layers may be disposed on inner surfaces of the common electrode and the pixel electrode, respectively, and may have different pretilt angles. It provides a multi-domain liquid crystal display device between the substrate and the common electrode further comprises a black matrix at a position corresponding to the region where the slit is formed.

The slit is formed in the center of the pixel electrode, characterized in that divided into at least two domains.

delete

The slits may be any one of a straight line, an oblique line, a zigzag shape, or a plurality of slits repeatedly spaced apart from each other in the same longitudinal direction.

The slanted and zigzag slits have an inclination of 45 ° or less based on the position at which the straight slits are formed, and the width of the slits is preferably 4 μm to 5 μm.

The liquid crystal layer is formed of either liquid crystal mode of twisted nematic (TN), electrically controlled birefringence (ECB), or low twisted nematic (LTN).
The different pretilt angles are formed by rubbing the first and second alignment layers in a predetermined direction to form a high pretilt angle, and irradiating ultraviolet rays onto the substrate on which the high pretilt angle is formed. Characterized in that it is formed through the step of forming a tilt angle.
In addition, the present invention according to the second aspect, the first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; Located on the inner surface of each of the common electrode and the pixel electrode, and formed on the slit, and includes a first and a second alignment layer having a horizontal alignment characteristic, and the region where the slit is formed between the second substrate and the common electrode; Provided is a multi-domain liquid crystal display characterized in that a black matrix is further formed at a corresponding position.
In addition, the present invention according to the third aspect, the first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; The first and second alignment layers may be disposed on inner surfaces of the common electrode and the pixel electrode, respectively, and may have different pretilt angles. Provided is a multi-domain liquid crystal display device further comprising a black matrix at a position corresponding to a region where the slit is formed on a substrate.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

delete

delete

delete

4 is a schematic cross-sectional view of one pixel portion of a two-domain liquid crystal display according to the present invention. In particular, TN (Twisted) in which the upper alignment layer and the lower alignment layer are rubbed in the 0 ° and 90 ° directions perpendicular to each other in a horizontal alignment method A nematic mode liquid crystal display device will be described as an example.

As shown, the upper and lower substrates 102 and 104 are spaced apart from each other by a predetermined distance, and the liquid crystal layer 106 is interposed between the upper and lower substrates 102 and 104.

On the transparent substrate 100 of the lower substrate 104, a pixel electrode 108 having a slit 120 is formed in a central portion thereof, and the pixel electrode 108 is formed on the pixel electrode 108 with the slit 120 as a boundary. The lower alignment layer 110 formed of the first and second lower alignment layers 110a and 110b having different pretilt angles θ ₁ and θ ₂ ; however, θ ₁ > θ ₂ is formed.

The common electrode 112 is formed under the transparent substrate 100 of the upper substrate 102, and is disposed below the common electrode 112, and corresponds to the first and second lower alignment layers 110a and 110b, respectively. An upper alignment layer 114 including first and second upper alignment layers 114a and 114b having different pretilt angles θ ₂ and θ ₁ in different regions is formed.

In this case, the center portion of the slit 120 is characterized by coinciding with the boundary line between the regions having different sizes of the pretilt angle, and the regions divided based on the slit 120 are respectively the first and second domains ( III, IV).

In the method of configuring the size of the pretilt angle differently for each domain, an orientation split method according to FIGS. 2A and 2B may be applied.

In addition to the TN mode, the liquid crystal display may also apply an electrically controlled irefringence (ECB) in which upper and lower alignment layers are rubbed at the same angle, or a low twisted nematic (LTN) mode in which a rubbing process is performed to have an angle difference smaller than 90 °. .

In addition, the common electrode and the pixel electrodes 112 and 108 are made of a transparent conductive material, and particularly, indium tin oxide (ITO).

In addition, a black matrix 113 is formed on the common electrode 112 at a position corresponding to the slit 120.

Hereinafter, operation characteristics of the two domain liquid crystal display according to the present invention will be described according to whether voltage is applied.

When a voltage is applied, an electric field 116 represented by a dotted line is formed inside the liquid crystal layer 106 between the common electrode 112 and the pixel electrode 108 in a direction parallel to the direction in which the electric field 116 is formed. Liquid crystal molecules 107 are arranged. In the present invention, the slit 120 is formed on the pixel electrode 108, and the electric field 116 distortion is generated through the slit 120.

The electric field 116 distortion forms an electric field 116 curve which is symmetrical with each other between the first and second domains III and IV around the slit 120, thereby dividing the first and second domains III and IV. Serves to further strengthen.

In the voltage-free state, the alignment direction of the liquid crystal by the electric field 116 of the slit 120 and the alignment direction of the liquid crystal due to the high pretilt angle θ ₁ formed on different substrates for each domain coincide with each other. Thus, the two-domain structure according to the present invention can be formed stably regardless of whether a voltage is applied.

Although not shown in the drawings, the black matrix 113 may be formed in a gate wiring forming process on a position corresponding to the slit 120 of the lower substrate 104.

That is, in the present invention, the foreground line generated between the first and second domain regions III and IV has a clear position of the foreground line, so that light leakage can be effectively shielded through the black matrix 113 having a corresponding area.

FIG. 5 is a plan view illustrating a plane corresponding to area “V” of FIG. 4.

As shown, in the present invention, the alignment direction A of the liquid crystal by the electric field in the slit 120 and the alignment direction B of the liquid crystal by the alignment film (110 in FIG. 4) coincide with each other to apply voltage. Regardless of whether or not the position of the boundary M between the first and second domains III and IV is kept stable.

The width w of the slit 120 is preferably formed as narrow as possible, and more preferably 4 μm to 5 μm.

In addition, even when the pixel electrode 108 is divided into the first and second domains III and IV, since the mutual voltage must be applied, the slit 120 is formed to be located inside the pixel electrode 108. It is preferable that the length of this slit 120 is a value close to the domain boundary M length.

Meanwhile, in the liquid crystal display according to the present invention, the alignment direction A of the liquid crystal due to the electric field in the region corresponding to the slit 120 is not limited to the positions of the first and second domain boundaries. The domain division method can be variously performed by variously changing the alignment direction B of the liquid crystal by the alignment layer.                     

Hereinafter, other modifications will be described with reference to the drawings.

6A through 6D are views corresponding to still another modified example of FIG. 5, and are illustrated based on one pixel electrode.

In the above modified examples, the angle formed between the position at which the slit is formed and the alignment direction (hereinafter, abbreviated to the alignment direction) of the liquid crystal by the alignment layer is formed to be inclined or divided into a plurality of pieces other than the vertical condition as shown in FIG. 5. As to the case, in the above modifications, it is a common feature that the alignment directions of the liquid crystals by the slit and the alignment layer correspond to each other.

In FIG. 6A, as illustrated, the slits 120 are formed in a straight line parallel to the width direction of the pixel electrode 108, and the alignment direction C is a predetermined slope in a direction orthogonal to the slits 120. In an oblique direction with, the first and second domains (III, IV) are formed with symmetry.

That is, based on the alignment direction of FIG. 5, in the first domain (III), the alignment direction is inclined at about 45 °, and in the second domain (IV) at a position facing the first domain (III), An orientation direction inclined at about 135 ° is formed.

In FIG. 6B, slits 122 are formed in an oblique shape at a central portion of the pixel electrode 208, are symmetrical to each other with the longitudinal direction of the slits 122 as the central axis, and have a predetermined inclination direction ( D) is formed.

In this example, the domain boundary M 'is formed in an oblique direction corresponding to the formation direction of the slit 122.                     

In FIG. 6C, a zigzag-shaped slit 124 is formed at the center of the pixel electrode 308, and the alignment direction E is the center axis of the slit 124 and is based on the boundary M ′ between domains. It is symmetrical and has a predetermined slope.

In FIG. 6D, a plurality of slits 126 repeatedly formed at a predetermined interval in the same longitudinal direction are formed to have a structure in which the potential difference in the pixel electrode 408 is reduced.

That is, the middle of the slit 126 may be connected.

The above example can also be applied to the modification according to FIGS. 6B to 6C.

In the above modification, the inclination angle of the diagonal and zig-zag slits with the central portion of the pixel electrode is preferably 45 ° or less in order to facilitate the formation of the alignment direction.

Since the inverse relationship is established between the slit area and the aperture ratio, the longitudinal direction of the slit is preferably formed in a direction parallel to or close to the width direction of the pixel electrode.

However, the present invention is not limited to the above embodiments and can be carried out in various ways without departing from the spirit of the present invention.

For example, in the present invention, the present invention is not limited to a two-domain structure, and can be similarly applied to a multi-domain structure within a range in which the relationship between the slit and the orientation direction is applied.

As described above, in the present invention, by using the orientation division method and the electric field distortion phenomenon properly, by providing a stable multi-domain structure regardless of whether the voltage is applied, it is possible to improve the wide viewing angle characteristics, the stabilization of the multi-domain structure in the foreground It can effectively block light leakage, which can increase the reliability of the product.

Claims (13)

A first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; First and second alignment layers positioned on inner surfaces of each of the common electrode and the pixel electrode, and the alignment directions formed in regions corresponding to each other have different pretilt angles. And a black matrix between the second substrate and the common electrode, the black matrix being positioned at a position corresponding to the region where the slit is formed. The method of claim 1, The slit is formed in the central portion of the pixel electrode, and divided into at least two domains. delete A first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; First and second alignment layers disposed on the inner surfaces of the common electrode and the pixel electrode, respectively, and formed on the slits and having horizontal alignment characteristics; And a black matrix further formed between the second substrate and the common electrode at a position corresponding to a region where the slit is formed. The method of claim 1, The slit is a multi-domain liquid crystal display device of any one of a straight, oblique, zigzag. The method of claim 1, And the slits are a plurality of slits which are repeatedly spaced apart from each other in the same longitudinal direction by a plurality of slits. The method of claim 5, wherein And wherein the diagonal and zig-zag slits have an inclination of 45 ° or less with respect to the position at which the straight slits are formed. The method of claim 1, The width of the slit is a 4 to 5 ㎛ multi-domain liquid crystal display device. The method of claim 1, The liquid crystal layer is a multi-domain liquid crystal display of any one of a liquid crystal mode of twisted nematic (TN), electrically controlled irefringence (ECB) or low twist nematic (LTN). delete delete The method of claim 1, The different pretilt angles are formed by rubbing the first and second alignment layers in a predetermined direction to form a high pretilt angle, and irradiating ultraviolet rays onto the substrate on which the high pretilt angle is formed. A multi-domain liquid crystal display device formed by forming a tilt angle. A first substrate; A second substrate spaced apart from the first substrate by a predetermined distance; A liquid crystal layer interposed between the first and second substrates; A pixel electrode disposed on an inner surface of the first substrate and having at least one slit therein and composed of at least two domains having different alignment directions of the liquid crystals by the slit; A common electrode formed on an inner surface of the second substrate; First and second alignment layers positioned on inner surfaces of each of the common electrode and the pixel electrode, and the alignment directions formed in regions corresponding to each other have different pretilt angles. And a black matrix at a position corresponding to a region where the slit is formed on the first substrate.

Images