KR100973802B1 - Liquid crystal display - Google Patents

Abstract

A first insulating substrate having an inner surface and an outer surface, a common electrode formed on an inner surface of the first insulating substrate, having a first domain dividing means, a first alignment layer formed on the common electrode, having an inner surface and an outer surface, and having the first insulating substrate A second insulating substrate having an inner surface and an inner surface thereof facing each other, a pixel electrode formed on an inner surface of the second insulating substrate and having a second domain dividing means, and formed on an inner surface of the second insulating substrate and applied to the pixel electrode. A thin film transistor for turning on and off a signal voltage, a second alignment film formed on the pixel electrode, and a liquid crystal layer filled between the first alignment film and the second alignment film, wherein the first and second domain dividing means cooperate with each other. The pixel electrode is divided into a plurality of small domains, and at least one of the first alignment layer and the second alignment layer has a long side and a predetermined length. A pre-tilt formed by the forming direction also.

LCD, pretilt, rubbing, photo alignment, visibility

Description

Liquid crystal display

1 is a layout view of a thin film transistor substrate for a liquid crystal display according to a first exemplary embodiment of the present invention.

2 is a layout view of a color filter substrate for a liquid crystal display device according to a first embodiment of the present invention;

3 is a layout view of a liquid crystal display according to a first exemplary embodiment of the present invention;

4 is a cross-sectional view taken along line IV-IV 'of FIG. 3 of the present invention;

5 and 6 are views illustrating a rubbing direction of an alignment layer with respect to a director of liquid crystal molecules in a liquid crystal display according to a first exemplary embodiment of the present invention.

7 is a layout view of a thin film transistor substrate for a liquid crystal display according to a second exemplary embodiment of the present invention.

8 is a layout view of a color filter substrate for a liquid crystal display according to a second exemplary embodiment of the present invention.

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

10 is a cross-sectional view taken along line X-X 'of FIG. 9 of the present invention;

11 to 12 illustrate a pretilt direction of an alignment layer with respect to a director of liquid crystal molecules of a liquid crystal display according to a second exemplary embodiment of the present invention.

The present invention relates to a liquid crystal display device, and more particularly, to a vertical alignment mode 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.

However, it is an important disadvantage that the liquid crystal display device has a narrow viewing angle. To overcome these shortcomings, various methods for widening the viewing angle have been developed. Among them, the long axis of the liquid crystal molecules is oriented vertically with respect to the upper and lower substrates in the absence of an electric field, and a constant opening is formed in the pixel electrode and the common electrode opposite thereto. A method of forming a pattern or forming a projection is influential.

As a method of forming the opening pattern, an opening pattern is formed in each of the pixel electrode and the common electrode, and the viewing angle is widened by adjusting the direction in which the liquid crystal molecules lie down using a fringe field formed by the opening patterns. .

The protrusions are formed by forming protrusions on the pixel electrode and the common electrode formed on the upper and lower substrates, respectively, to adjust the lying direction of the liquid crystal molecules using an electric field distorted by the protrusions.

In another method, an opening pattern is formed on the pixel electrode formed on the lower substrate, and a protrusion is formed on the common electrode formed on the upper substrate, so that the liquid crystal lies down using the fringe field formed by the opening pattern and the protrusion. By adjusting the somatic domain.

However, in such a domain division type liquid crystal display, a texture is generated due to scattering of the arrangement of liquid crystal molecules near a short side of a domain. Textures reduce brightness and degrade picture quality. In addition, the opening ratio decreases due to a cutting pattern, protrusions, or the like formed by the domain dividing means. The decrease in the aperture ratio leads to a decrease in luminance. In addition, the side visibility is not sufficient because the liquid crystal molecules behave only vertically.

An object of the present invention is to improve side visibility of a vertical alignment mode liquid crystal display.

In order to solve this problem, in the present invention, in the vertical alignment mode liquid crystal display, an alignment layer in which the pretilt is formed in a direction forming a predetermined angle with the long side of the domain dividing unit is formed.

Specifically, the first insulating substrate having an inner surface and an outer surface, a common electrode formed on the inner surface of the first insulating substrate and having a first domain dividing means, a first alignment layer formed on the common electrode, and having an inner surface and an outer surface. A second insulating substrate having an inner surface and an inner surface of the first insulating substrate facing each other, a pixel electrode formed on an inner surface of the second insulating substrate and having a second domain dividing means, and formed on an inner surface of the second insulating substrate A thin film transistor for turning on and off a signal voltage applied to the pixel electrode, a second alignment film formed on the pixel electrode, and a liquid crystal layer filled between the first alignment film and the second alignment film, wherein the first and second domain divisions are performed. Means cooperate to divide the pixel electrode into a plurality of small domains, wherein at least one of the first alignment layer and the second alignment layer is formed of the small domain; To provide a liquid crystal display device with a pre-tilt direction is formed by forming the sides with a predetermined angle.

At this time, the predetermined angle preferably has a range between 40 ° ~ 50 °.

Further, both the first and second alignment layers are pretilt formed in a direction forming the predetermined angle with respect to the long side of the small domain, and the pretilt direction of the first alignment layer and the pretilt direction of the second alignment layer are They may be formed in the same direction as each other, or may be formed in different directions.

The liquid crystal display may further include first and second polarizing plates, and the polarization axis may be formed in a direction parallel to the pretilt direction of the first and second alignment layers.

In addition, the pretilt is preferably formed using rubbing or photoalignment.                     

In addition, when using the optical alignment, it is preferable to change the pretilt formation direction with respect to at least one small domain using a mask.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Next, a liquid crystal display according to a first exemplary embodiment of the present invention will be described with reference to the drawings.

1 is a layout view of a thin film transistor substrate for a liquid crystal display according to a first embodiment of the present invention, FIG. 2 is a layout view of a color filter substrate for a liquid crystal display according to a first embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along line IV-IV 'of FIG. 3 of the present invention, and FIGS. 5 and 6 are liquid crystal display according to the first embodiment of the present invention. It is a figure which shows the rubbing direction of the oriented film with respect to the director of the liquid crystal molecule of a display device.                     

The liquid crystal display includes an upper insulation in which the lower compensation film 13, the lower polarizing plate 12, and the inner surface of the liquid crystal display 110 which are sequentially disposed on the outer surface of the lower insulating substrate 110 face the inner surface of the lower insulating substrate 110. Injection between the substrate 210, the upper compensation film 23 and the upper polarizing plate 22 sequentially disposed on the outer surface of the upper insulating substrate 210, and between the lower insulating substrate 110 and the upper insulating substrate 210. And a liquid crystal layer 3 containing liquid crystal molecules oriented perpendicular to the substrates 110 and 210.

On the lower substrate 110 made of a transparent insulating material such as glass, a pixel electrode 190 made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) and having a first domain dividing means is formed. Each pixel electrode 190 is connected to a thin film transistor to receive an image signal voltage. In this case, the thin film transistor is connected to the gate line 121 for transmitting the scan signal and the data line 171 for transmitting the image signal, respectively, to turn on and off the pixel electrode 190 according to the scan signal. . In addition, a lower alignment layer 11 made of a polymer material such as polyimide and polyamide is formed on the pixel electrode 190. At this time, the lower alignment layer 11 is formed with a pretilt in a direction forming a predetermined angle with the long side of the first domain dividing means. In addition, the lower compensation film 13 and the lower polarizing plate 12 are sequentially attached to the lower surface of the lower substrate 110. In the case of the reflective liquid crystal display device, the pixel electrode 190 may not be made of a transparent material, and in this case, the lower polarizer 12 is also unnecessary.

It is also made of a black matrix 220 to prevent light leakage on the lower surface of the upper substrate 210 made of a transparent insulating material such as glass, a color filter 230 of red, green, and blue and a transparent conductive material such as ITO or IZO. The common electrode 270 is formed. Here, the second domain dividing means is formed in the common electrode 270. The black matrix 220 may be formed not only in the peripheral portion of the pixel region but also in the portion overlapping the second domain dividing means 271, 272, and 273 of the common electrode 270. This is to prevent light leakage caused by the cutting patterns 271, 272, and 273 when the second domain dividing means is the cutting pattern. In addition, an upper alignment layer 21 made of a polymer material such as polyimide or polyamide is formed on the common electrode 270. At this time, the upper alignment layer 21 is pretilt formed in a direction forming a predetermined angle with the long side of the second domain dividing means. In addition, an upper compensation film 23 and an upper polarizer 22 are sequentially attached to the lower surface of the upper substrate 210.

Next, the liquid crystal display according to the first exemplary embodiment of the present invention will be described in more detail.

The gate line 121 is formed on the lower insulating substrate 110. The gate line 121 is elongated in the horizontal direction and includes a gate electrode 124 that is a part of the gate line 121. At this time, one end portion 129 of the gate line 121 is extended in width for connection with an external circuit.

The gate line 121 may be formed of a single layer, but may be formed of a double layer or a triple layer. In the case of forming a single layer, it may be made of aluminum (Al) or aluminum (Al) -neodymium (Nd) alloy, and in the case of forming a double layer, physicochemical such as chromium (Cr), molybdenum (Mo), or molybdenum alloy film A lower layer made of a material having excellent properties may be formed, and an upper layer made of a material having low specific resistance such as aluminum (Al) or an aluminum alloy may be formed.

A gate insulating layer 140 made of silicon nitride (SiNX) is formed on the entire surface of the substrate including the gate line 121.

A semiconductor layer 150 made of amorphous silicon or the like is formed on the gate insulating layer 140. The semiconductor layer 150 includes a linear semiconductor 151 that is elongated in the longitudinal direction, and an island-type semiconductor 154 that protrudes from the linear semiconductor 151 and is formed at a portion corresponding to the gate electrode 124.

An ohmic contact layer 160 formed by doping a high concentration of n-type impurities to a semiconductor material such as amorphous silicon is formed on the semiconductor layer 150. The ohmic contact layer 160 is formed on the linear semiconductor 151 in such a pattern and has two island-type ohmic contact members facing each other with respect to the gate electrode 124 and the linear ohmic contact member 161. 163, 165).

The data line 171 is formed on the ohmic contact layer 160 and the gate insulating layer 140.

The data line 171 vertically intersects the gate line 121 to define a pixel region, is a branch of the data line 171, and is connected to the ohmic contact layer 163 and the source electrode 173 and the source electrode 173. And a drain electrode 175 formed on the island-like ohmic contact layer 165 opposite to the source electrode 173 with respect to the gate electrode 123. At this time, one end portion 179 of the data line 171 is extended in width for connection with an external circuit.

The data line 171 may be formed of a single layer like the gate line 121, but may also be formed of a double layer or a triple layer. In the case of forming a single layer, it may be made of aluminum (Al) or aluminum (Al) -neodymium (Nd) alloy, and in the case of forming a double layer, physical and chemical such as chromium (Cr), molybdenum (Mo), or molybdenum alloy film A lower layer made of a material having excellent properties may be formed, and an upper layer made of a material having low specific resistance such as aluminum (Al) or an aluminum alloy may be formed.

A passivation layer 180 made of a nitride material is formed on the data line 171 and the gate insulating layer 140. In this case, the passivation layer 180 has a first contact hole 181 exposing one end portion 129 of the gate line 121 and a second contact hole 182 exposing one end portion 179 of the data line 171. The contact portion 188 exposing the third contact hole 185 exposing the drain electrode 175 is formed. On the passivation layer 180, one end portion 129 of the pixel line 190 connected to the drain electrode 175 through the third contact hole 185 and the gate line 121 through the first contact hole 181. And a data contact assistant member 82 connected to one end portion 179 of the data line 171 through a gate contact assistant member 81 and a second contact hole 182 connected to each other. The pixel electrode 190 and the contact auxiliary members 81 and 82 are made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrode 190 is divided into a plurality of small domains by the first domain dividing means. At this time, the first domain dividing means formed on the pixel electrode extends from the diagonal cutouts 91, 92, 95, 96 and the horizontally cutouts formed in the diagonal directions in the upper and lower portions of the pixel region, respectively. There is a diagonal incision (91, 92, 95, 96) and the central incision (93, 94) having a branch incision parallel to each. At this time, the diagonal cutouts 91 and 92 and the diagonal cutouts 95 and 96 are perpendicular to each other. This is to evenly distribute the direction of the fringe field in four directions. In FIG. 1, six first domain dividing means are shown, but the number of these domain dividing means can be changed as necessary.

In addition, a lower alignment layer 11 made of a polymer material such as polyimide and polyamide is formed on the pixel electrode 190. At this time, the lower alignment layer 11 is pretilted in a direction forming a predetermined angle with the long side of the small domain divided by the first domain dividing unit. At this time, the pretilt direction is preferably formed in a direction forming an angle of 40 to 50 ° with the long side of the small domain, and most preferably is formed in a 45 ° direction with the long side of the small domain. Accordingly, when the electric field is applied, the liquid crystal directors move vertically and horizontally, thereby improving side visibility. In addition, it is preferable to form pretilt using rubbing or photo-alignment.

Further, on the passivation layer 180, a storage wiring connecting leg 84 is formed to connect the storage electrode 133a and the storage electrode line 131 across the gate line 121. The storage wiring connecting bridge 84 is in contact with the storage electrode 133a and the storage electrode line 131 through the contact holes 183 and 184 formed over the passivation layer 180 and the gate insulating layer 140. The sustain wiring connection leg 84 overlaps the leg metal piece 172. The sustain wiring connection bridge 84 serves to electrically connect the entire sustain wiring on the lower substrate 110. This holding wiring can be used to repair the defect of the gate line 121 or the data line 171, if necessary, and the leg metal piece 172 is held with the gate line 121 when irradiating a laser for such repair. It is formed to assist the electrical connection of the wiring connection bridge (84).

In addition, the lower compensation film 13 and the lower polarizing plate 12 are sequentially attached to the lower surface of the lower substrate 110. Meanwhile, the pixel electrode 190 may not be made of a transparent material in the case of a reflective liquid crystal display, and in this case, the lower polarizer 12 may also be unnecessary.

The pretilt direction of the lower alignment layer 11 is formed in a direction parallel to the polarization axis of the lower polarizing plate 12. Accordingly, it is possible to minimize the light leakage phenomenon to prevent the contrast ratio from being lowered.

On the upper insulating substrate 210, a black matrix 220 made of a single layer of chromium for preventing light leakage, a double layer of chromium and chromium oxide, or an organic material to which black pigment is added is formed on the lower surface of the insulating substrate 210.

The red, green, and blue color filters 230 are formed on the black matrix 220. At this time, one red, green, and blue color filter 230 is formed for each pixel area partitioned by the black matrix 220.

An overcoat layer 250 is formed on the color filter 230. The overcoat layer 250 is to prevent the color filter 230 from being exposed through the cutouts 271, 272, 273, 274, 275 and 276 of the common electrode 240 formed thereon.

The common electrode 240 made of a transparent conductive material and having a second domain division means is formed on the overcoat layer 250. The second domain dividing means is a cutout 271, 272, 273, 274, 275, 276 of the common electrode 240.

Here, the second domain dividing means of the common electrode 270 is formed in parallel with the first domain dividing means with the first domain dividing means of the pixel electrode 190 in the center. That is, the second domain dividing means also includes diagonal cutouts 271, 272, 275, and 276 formed in diagonal directions on the upper and lower portions of the common electrode 270, and cutouts extending in the horizontal direction and diagonal cuts. And a central incision 273, 274 having branch incisions parallel to the portions 271, 272, 275, 276, respectively. At this time, the diagonal cutouts 271 and 272 and the diagonal cutouts 275 and 276 are perpendicular to each other. This is to evenly distribute the direction of the fringe field in four directions. In FIG. 2, six second domain dividing means are shown, but the number of these domain dividing means may be changed as necessary.

In addition, an upper alignment layer 21 made of a polymer material such as polyimide or polyamide is formed on the common electrode 270. At this time, the upper alignment layer 21 is pretilt formed in a direction forming a predetermined angle with the long side of the second domain dividing means. At this time, the pretilt forming direction is preferably formed in a direction forming an angle 40-40 ° with the long side of the small domain, and most preferably is formed in a 45 ° direction with the long side of the small domain. Accordingly, when the electric field is applied, the liquid crystal directors move vertically and horizontally, thereby improving side visibility. In addition, it is preferable to form pretilt using rubbing or photo-alignment.

In addition, the upper compensation film 23 and the upper polarizing plate 22 are sequentially attached to the upper surface of the upper substrate 210. The pretilt forming direction of the upper alignment film 21 is formed in a direction parallel to the polarization axis of the upper polarizing plate 22. Accordingly, it is possible to minimize the light leakage phenomenon to prevent the contrast ratio from being lowered.

When the thin film transistor substrate and the color filter substrate having the above structure are aligned and combined, and a liquid crystal material is injected and vertically aligned therebetween, the basic structure of the liquid crystal display according to the present invention is provided. When the thin film transistor substrate and the color filter substrate are aligned, the first domain dividing means of the pixel electrode 190 and the second domain dividing means of the common electrode 270 divide the pixel region into a plurality of small domains. These small domains are classified into four types according to the average major axis direction of the liquid crystal molecules located therein.

In this case, when a driving voltage is generally applied between the common electrode 270 and the pixel electrode 190, the fringe field is formed by the first domain dividing means of the pixel electrode 190 and the second domain dividing means of the common electrode 270. Is formed so that the liquid crystal molecules are inclined in a direction perpendicular to the long side of the small domain. The direction of the inclined liquid crystal molecules is evenly distributed in four directions, thus improving the side viewing angle. However, only by dispersing the inclination direction of the liquid crystal molecules in four directions by using the first and second domain division means, there is a limit in improving side visibility.                     

However, when the pretilt is formed in the direction in which the upper and lower alignment layers 21 and 11 form 45 ° with respect to the long side of the small domain, as in the present invention, the liquid crystal molecules try to be perpendicular to the long side of the small domain. You are affected by both the force and the force you want to lie along the pretilt direction. Therefore, the liquid crystal molecules are inclined at an angle of 45 ° with respect to the long side of the small domain on the surface of the alignment layer, and the further away from the alignment layer, the direction in which the liquid crystal molecules are inclined is perpendicular to the long side of the small domain. In other words, the liquid crystal molecules have a vertical behavior and a horizontal behavior, thereby greatly improving side visibility. Here, the pretilt formed in the direction of 45 ° with respect to the long side of the small domain may be performed only in either of the upper and lower alignment films, or both. When both the upper and lower alignment layers are pretilted, the upper and lower alignment layers may be pretilt in the same direction, or pretilts may be formed in the opposite directions.

Next, a liquid crystal display according to a second exemplary embodiment of the present invention will be described with reference to the drawings.

7 is a layout view of a thin film transistor substrate for a liquid crystal display according to a second embodiment of the present invention, FIG. 8 is a layout view of a color filter substrate for a liquid crystal display according to a second embodiment of the present invention, and FIG. FIG. 10 is a layout view of a liquid crystal display according to a second exemplary embodiment of the present invention, FIG. 10 is a cross-sectional view taken along line IV-IV ′ of FIG. 3, and FIGS. 11 and 12 are liquid crystal according to the second exemplary embodiment of the present invention. It is a figure which shows the pretilt direction of the oriented film with respect to the director of the liquid crystal molecule of a display device.                     

The liquid crystal display according to the second exemplary embodiment differs from the shape and arrangement of the first domain dividing unit and the second domain dividing unit in the liquid crystal display according to the first exemplary embodiment. Therefore, hereinafter, the description of other structures will be omitted, and only the form and arrangement of the first domain dividing means and the second domain dividing means will be described.

 The second domain dividing means of the common electrode 270 is a cutout 271 extending in the vertical direction, and the first domain dividing means of the pixel electrode 190 also sandwiches the second domain dividing means. Side by side are incisions 91, 92 extending in the longitudinal direction. The pixel region is divided into a plurality of small domains by the first and second domain dividing means. These small domains are classified into two types according to the average major axis direction of the liquid crystal molecules located therein.

In this case, in general, when a driving voltage is applied between the common electrode 270 and the pixel electrode 190, a fringe field is formed by the first domain dividing means and the second domain dividing means of the pixel electrode 190. It is inclined in a direction perpendicular to the long side of the small domain. Thus, the side viewing angle is improved. However, there is a limit in improving side visibility only by dispersing the inclination direction of the liquid crystal molecules in two directions using the first and second domain dividing means.

However, when the upper and lower alignment layers 21 and 11 are rubbed in the direction of 45 ° with respect to the long side of the small domain as in the present invention, the force and rubbing of the liquid crystal molecules to be perpendicular to the long side of the small domain are rubbing. You are all affected by the power to lie along the direction. Therefore, the liquid crystal molecules are inclined at an angle of 45 ° with respect to the long side of the small domain on the surface of the alignment layer, and the further the liquid crystal molecules are inclined toward the long side of the small domain as the further away from the alignment layer. In other words, the liquid crystal molecules have a vertical behavior and a horizontal behavior, thereby greatly improving side visibility. Here, rubbing which consists of 45 degrees with respect to the long side of small domain may be performed only in any one of an upper and a lower oriented film, and may be performed in both. In addition, when rubbing both the upper and lower alignment layers, the upper and lower alignment layers may be rubbed in the same direction, or may be rubbed in opposite directions.

Although the above has been described with reference to a preferred embodiment of the present invention, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. It belongs to the scope of rights. In particular, the arrangement of the openings formed in the pixel electrode and the common electrode may be variously modified, and modifications such as placing protrusions instead of forming the opening may be possible.

Through the above configuration, the side visibility of the vertical alignment mode liquid crystal display device can be improved.

Claims (8)

A first insulating substrate having an inner surface and an outer surface, A common electrode formed on an inner surface of the first insulating substrate and having a plurality of first domain dividing means, A first alignment layer formed on the common electrode, A second insulating substrate having an inner surface and an outer surface and disposed to face the inner surface and the inner surface of the first insulating substrate, A pixel electrode formed on an inner surface of the second insulating substrate and having a second domain dividing means, A thin film transistor formed on an inner surface of the second insulating substrate and turning on and off a signal voltage applied to the pixel electrode; A gate line and a data line connected to the thin film transistor and crossing each other; A second alignment layer formed on the pixel electrode, Liquid crystal layer filled between the first alignment layer and the second alignment layer Including, The first and second domain dividing means are inclined with respect to the gate line or data line, and the first and second domain dividing means cooperate to divide the pixel electrode into a plurality of small domains, and the first alignment layer And at least one of the second alignment layers is pretilt formed in a direction forming a predetermined angle with a long side of the small domain. In claim 1, The predetermined angle is a liquid crystal display device having a range between 40 ° ~ 50 °. In claim 1, Pretilt is formed in both the first and second alignment layers in a direction forming the predetermined angle with respect to the long side of the small domain, and the pretilt formation direction of the first alignment layer and the pretilt formation direction of the second alignment layer are A liquid crystal display device having at least one of the same direction or opposite directions to each other. In claim 1, The liquid crystal display further comprises first and second polarizing plates, wherein the polarization axis is formed in a direction parallel to the pretilt forming direction of the first and second alignment layers. In claim 1, The pretilt is formed using rubbing or photo alignment. In claim 5, The optical alignment device uses a mask to change a pretilt forming direction with respect to at least one small domain. In claim 1, And a corner of the pixel electrode is chamfered. In claim 7, At least one of the chamfered sides is parallel to the boundary line of the first domain dividing means or the second domain dividing means.

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