KR20080023904A - Liquid crystal display and fabricating method thereof - Google Patents

Abstract

An LCD and a method for manufacturing the same are provided to regulate cell gaps of a main pixel and a sub-pixel through a multi-layer structure of an insulating layer, thereby improving viewing angle, lateral visibility, and white brightness. An LCD comprises an upper substrate where color filters are arranged in a matrix type, and a lower substrate where thin film transistors are arranged in a matrix type. The lower substrate includes an insulating layer(162), a main pixel electrode(182), and a sub-pixel electrode(183). The insulating layer is formed on the thin film transistors. The insulating layer has a multi-layer structure, and the main pixel electrode and the sub-pixel electrode are formed on different layers of the insulating layer. The sub-pixel electrode is formed on a higher insulating film than the main pixel electrode.

Description

Liquid crystal display and its manufacturing method {LIQUID CRYSTAL DISPLAY AND FABRICATING METHOD THEREOF}

1 is a partial plan view of a lower substrate according to an embodiment of the present invention.

2 is a cross-sectional view of the lower substrate taken along the line II ′.

3 is a partial plan view of an upper substrate according to an embodiment of the present invention.

4 is a cross-sectional view of the upper substrate taken along the line II-II '.

5 is an equivalent circuit diagram of a unit pixel according to an exemplary embodiment of the present invention.

6 is a cross-sectional view illustrating a process of manufacturing a lower substrate of a liquid crystal display according to an exemplary embodiment of the present invention.

7 is a cross-sectional view illustrating a manufacturing process of an upper substrate of a liquid crystal display according to an exemplary embodiment of the present invention.

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

100: lower substrate 112: gate line

113: gate electrode 152: data line

153: source electrode 154: drain electrode

155: coupling electrode 182: main pixel electrode

183: sub pixel electrode 200: upper substrate

212: black matrix 222: color filter

242: common electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly, to a liquid crystal display device and a method for manufacturing the same, which easily control a cell gap of a main pixel and a sub pixel.

Liquid crystal display is a display device that realizes an image by controlling the amount of light incident from a light source using the optical anisotropy of liquid crystal molecules and the polarization characteristics of a polarizing plate. In addition, the power consumption is small, the application range is expanding rapidly in recent years.

Since the liquid crystal display device transmits light only through the light transmission axis of the liquid crystal molecules to realize an image, there is a problem that the viewing angle is relatively narrower than that of other display devices. Accordingly, various techniques for improving the viewing angle have been studied. Among them, the PVA (Patterned Vertically Aligned) method aligns liquid crystal molecules vertically with respect to the upper and lower substrates, and cuts them into the pixel electrode and the common electrode, which are opposite electrodes, respectively. A pattern or protrusion pattern is formed, thereby distorting an electric field formed between two electrodes, thereby forming a plurality of domains, thereby improving a viewing angle.

On the other hand, the recently developed super patterned vertically aligned (SPVA) method forms a main pixel and a sub pixel having different voltages in a unit pixel to form a light transmission axis of liquid crystal molecules for each region. By making this change, not only the viewing angle but also the side visibility is simultaneously improved.

However, since the sub pixel is driven by a voltage lower than that of the main pixel, the transmittance of light is lowered than that of the main pixel, resulting in a decrease in white luminance of the entire liquid crystal display panel. Accordingly, in order to increase the voltage of the subpixel, it is necessary to adjust a gap between the subpixel electrode and the common electrode, that is, a cell gap of the subpixel. Since the organic film pattern is formed, there is a problem in that a separate mask process for forming the organic film pattern as a cell gap control layer is added.

The present invention was derived to solve the above problems, and forms a multi-layer structure on a predetermined single layer using a single mask capable of differential exposure for each region, and adjusts the cell gap of the main pixel and the sub pixel through the multi-layer structure. Accordingly, an object of the present invention is to provide a new liquid crystal display device and a method of manufacturing the same, in which the viewing angle, side visibility, and white luminance can be simultaneously improved, and a separate mask process is not added.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes an upper substrate on which color filters are arranged in a matrix form, and a lower substrate on which thin film transistors are arranged in a matrix form, and the lower substrate is disposed on the thin film transistor. And a main pixel electrode and a sub pixel electrode formed on different layers of the insulating film.

Preferably, the sub pixel electrode is formed on an insulating layer of a higher layer than the main pixel electrode.

The insulating film includes a first layer having a first thickness T ₁ , a second layer having a second thickness T ₂ , and a third layer having a third thickness T ₃ , wherein each layer has a thickness T ₁ <T ₂ It is preferable to have a relationship of <T ₃ .

Preferably, the main pixel electrode is formed on the second layer of the insulating film, and the sub pixel electrode is formed on the third layer of the insulating film.

The insulating layer further includes a through region, and the main pixel electrode is electrically connected to a lower thin film transistor through the through region.

Preferably, an incision pattern is formed on at least one of the main pixel electrode and the sub pixel electrode.

According to an aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, the method including: (a) forming an insulating film and a photosensitive film on a substrate having a predetermined structure; and (b) differentially exposing the photosensitive film for each region. Post-development to form the photoresist film in a multilayer structure; (c) etching the entire photoresist film and the insulation film to form a multilayer structure, and (d) forming a multilayer structure on the different layers of the insulation film in a multilayer structure. Forming a main pixel electrode and a sub pixel electrode.

In the step (b), the photosensitive film is exposed using a halftone mask in which light transmittance is controlled for each region. In this case, the halftone mask includes a first region having a first transmittance P ₁ , a second region having a second transmittance P ₂ , a third region having a third transmittance P ₃ , and a fourth transmittance ( And a fourth region having P ₄ ), wherein the transmittance of each region has a relationship of P ₁ > P ₂ > P ₃ > P ₄ .

The multi-layered insulating film of step (c) may include a first layer having a first thickness T ₁ , a second layer having a second thickness T ₂ , and a third layer having a third thickness T ₃ . Each layer has a thickness of T ₁ <T ₂ <Is preferably formed to have a relationship of T _3.

In the step (d), the transmissive conductive film is formed on the multilayer insulating film, and the patterned pattern is formed to form the main pixel electrode and the sub pixel electrode, wherein the sub pixel electrode is larger than the main pixel electrode. It is formed on an insulating film of a high layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like reference numerals in the drawings refer to like elements.

1 is a partial plan view of a lower substrate according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view of the lower substrate taken along the line II ′.

1 and 2, the lower substrate 100 formed of a transparent insulating substrate such as glass or the like has a plurality of gate lines 112 extending in one direction and a plurality of data lines 152 extending in the other direction. Etc. are formed. A pixel region is defined by an intersection of the gate line 112 and the data line 152, and each pixel region includes a switching element Q, pixel electrodes 182 and 183, a coupling electrode 155, and a sustain electrode. The electrode 115 is formed.

 The switching element Q includes amorphous silicon, polycrystalline silicon, or the like as a channel layer, and includes a gate electrode 113, a source electrode 153, and a drain electrode 154. It is effective to use a thin film transistor (TFT). In this case, the gate electrode 113 is connected to the gate line 112, and the source electrode 153 is connected to the data line 152.

The pixel electrodes 182 and 183 are connected to the drain electrode 154 through the contact hole 163 and the sub pixel electrode 183 electrically separated from the drain electrode 154. ). The main pixel electrode 182 and the sub pixel electrode 183 constitute the first liquid crystal capacitor Clc1 and the second liquid crystal capacitor Clc2 together with the common electrode 242 of the upper substrate 200 which will be described later. The domain regulation means for adjusting the alignment direction of the liquid crystal molecules is provided with a plurality of incision patterns.

Here, the main pixel electrode 182 and the sub pixel electrode 183 are formed on different layers of the second insulating layer 162 having a multilayer structure, whereby the cell gap is adjusted differently. For example, in the present exemplary embodiment, the second insulating layer 162 is formed in a three-layer structure, the main pixel electrode 182 is formed in a part of the second layer, and the sub pixel electrode ( 183 is formed. As such, since the sub pixel electrode 183 is formed on the multilayer structure of the second insulating layer 162 thicker than the main pixel electrode 182, the cell gap becomes relatively small.

The coupling electrode 155 is formed by extending a portion of the drain electrode 154. At least a portion of the coupling electrode 155 overlaps the sub pixel electrode 183 to form a coupling capacitor Ccp.

The sustain electrode 115 is formed together in the same step when forming the gate line 112 or the data line 152. The storage electrode 115 is formed such that at least a portion thereof overlaps the upper pixel electrodes 182 and 183 to form the storage capacitor Cst. The sustain capacitor Cst maintains an image signal transmitted to a specific pixel for a predetermined frame (usually one frame). Of course, the sustain capacitor Cst, which plays an auxiliary role of the first and second liquid crystal capacitors Clc1 and Clc2, may be omitted.

3 is a partial plan view of an upper substrate according to an exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view of the upper substrate taken along a line II-II '.

3 and 4, the upper substrate 200 formed of a light-transmissive insulating substrate such as glass or the like has a black matrix 212 for preventing optical interference between adjacent pixel regions, and red for coloring incident light ( A common electrode 242 for forming an electric field in the liquid crystal layer is formed together with the color filters 222 of R, green G, and blue B, and the pixel electrodes 182 and 183 facing each other.

An overcoat layer 232 may be formed between the color filter 222 and the common electrode 242 to improve adhesion and flatness of the interface.

Column spacers having a predetermined height in each layer of the upper substrate 200, for example, at least one of the black matrix 212, the color filter 222, the overcoat layer 232, and the common electrode 242. Can be formed. Of course, the column spacer may be formed anywhere on the upper substrate 200 or the lower substrate 100, and may be replaced by a spherical spacer having a predetermined particle diameter.

Although not shown, the common electrode 242 may be provided with a plurality of cutting patterns as domain regulating means for adjusting the alignment direction of the liquid crystal molecules like the pixel electrodes 182 and 183 described above. Of course, the incision pattern may be replaced with a plurality of protrusion patterns protruding at a predetermined height.

The liquid crystal display according to the present exemplary embodiment includes an upper substrate 200 and a lower substrate 100 disposed up and down at a predetermined distance, and a liquid crystal layer (not shown) formed between the two substrates 200 and 100. It includes.

Opposing surfaces of the two substrates 200 and 100 include an alignment film (not shown) that is rubbed in a predetermined direction, and liquid crystal molecules are aligned in a predetermined direction by rubbing characteristics of the alignment film. At this time, the alignment direction of the liquid crystal molecules is preferably a vertical alignment so as to be perpendicular to each of the substrates 200 and 100, but may not be a vertical alignment. In addition, the liquid crystal molecules are divided and aligned into a plurality of domains by the cutting patterns of the pixel electrodes 182 and 183 and the common electrode 242, which are domain regulating means. For example, this embodiment is segmentally oriented into eight domains by eight incision patterns.

5 is an equivalent circuit diagram of a unit pixel according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the unit pixel includes a first liquid crystal capacitor Clc1 serving as a main pixel, a second liquid crystal capacitor Clc2 serving as a sub pixel, a sustain capacitor Cst, and a coupling capacitor Ccp.

Here, the first liquid crystal capacitor Clc1 is directly connected to the drain electrode 154, and the second liquid crystal capacitor Clc2 is indirectly connected to the drain electrode 154 through the coupling capacitor Ccp. Accordingly, the data signal transmitted through the drain electrode 154 is applied to the first and second liquid crystal capacitors Clc1 and Clc2 connected thereto. The second liquid crystal capacitor Clc2 is charged with the coupling capacitor Ccp. Since the remaining data signal is applied, it has a lower voltage than the first liquid crystal capacitor Clc1. As such, the light transmission axis of the liquid crystal molecules is aligned to have a multi-directionality as the voltages of the main pixel and the sub-pixel are different in the same data signal. Is improved.

In addition, the cell gap of the sub pixel electrode 183 and the main pixel electrode 182 is controlled by the second insulating layer 162 having a multilayer structure, and the sub pixel electrode 183 has a thicker layer than the main pixel electrode 182. Since it is formed on, the cell gap of the sub pixel becomes relatively small. Since the cell gap and the electric field are inversely related, when the cell gap is reduced, a larger electric field is generated to drive the liquid crystal molecules. As a result, the low voltage of the servo pixel is compensated and the white luminance is improved.

As described above, the liquid crystal display according to the present exemplary embodiment may be driven by different voltages of the main pixel and the sub pixel, thereby improving viewing angle and side visibility, and at the same time, through the second insulating layer 162 having the multilayer structure, White brightness is improved by adjusting the cell gap to compensate for the low voltage of the sub-pixel.

The manufacturing method of the liquid crystal display device which has such a structure is as follows.

6 is a cross-sectional view illustrating a manufacturing process of a lower substrate of a liquid crystal display according to an exemplary embodiment of the present invention.

First, as shown in FIG. 6A, a first conductive film is formed on one side of the substrate 100 by CVD, PVD, sputtering, or the like, and then a patterning process using the first mask is performed to form the gate electrode 113. The gate wirings including the gate lines 112 and the like are formed, and at the same time, the sustain electrodes 115 and the sustain lines 114 are formed in other regions not shown. In this case, it is preferable to use a single layer or multiple layers formed of at least one material selected from Mo, Al, Cr, and Ti as the first conductive film.

6B, the first insulating layer 122, the active layer 132, and the ohmic contact layer 142 may be formed on the substrate 100 on which the gate wiring is formed by, for example, plasma enhanced chemical vapor deposition (PECVD). After stacking sequentially to form a semiconductor layer, a patterning process using a second mask is performed to form an isolated island-shaped semiconductor layer on the gate electrode 113. In this case, the first insulating layer 122 uses one or more insulating materials selected from inorganic insulating materials including silicon nitride (SiN _x ) or silicon oxide (SiO ₂ ) having excellent adhesion and insulation properties. An amorphous silicon layer (a-Si) is used as 132 and an amorphous silicon layer ((n + a-Si) doped with n-type impurities is used as the ohmic contact layer 142. Do.

Subsequently, as shown in FIG. 6C, a second conductive layer is formed on the substrate 100 on which the semiconductor layer is formed by CVD, PVD, sputtering, or the like, and then a patterning process using a third mask is performed. A data wiring including the 153, the drain electrode 154, the data line 152, and the like is formed, and at the same time, the coupling electrode 155 is formed in another region not shown. In addition, when the ohmic contact layer 142 is separated between the source electrode 153 and the drain electrode 154 as a barrier, the substrate 100 is arranged in a lattice form corresponding to each unit pixel. The thin film transistor TFT is formed. In this case, it is preferable to use a single layer or multiple layers formed of at least one material selected from Mo, Al, Cr, and Ti as the second conductive film.

Subsequently, as illustrated in FIG. 6D, the second insulating film 161 and the photosensitive film 171 are sequentially formed on the substrate 100 on which the data line is formed, and then the photosensitive film 171 is formed using the fourth mask 300. Is subjected to differential exposure for each region and then developed to form a photosensitive film 172 having a multilayer structure.

The fourth mask 300 preferably uses a half-tone mask (HTM) that is capable of differential exposure by adjusting light transmittance for each region. For example, the halftone mask 300 according to the present embodiment has a first region M ₁ having a transmittance of P ₁ , a second region M ₂ having a transmittance of P ₂ , and a transmittance of P ₃ . the third region is composed of a fourth area (M ₄₎ having a transmittance of (M ₃₎ and P _4, and provides a differential of the exposure area during exposure step 4. Here, the transmittance of each region has a relationship of P ₁ > P ₂ > P ₃ > P ₄ , and P ₁ is 100%, P ₂ is 50%, P ₃ is 30%, and P ₄ is 0%. . Therefore, when the photosensitive film 171 is differentially exposed using the halftone mask 300 and then developed, the photosensitive film 172 having a multi-layered structure having a different thickness is formed.

Subsequently, as shown in FIG. 6E, the photoresist film 172 and the second insulating film 161 formed in the multilayer structure are etched in the entire surface to form the second insulating film 162 having the multilayer structure.

For example, FIG. 6E (b) shows an enlarged cross-sectional structure of the second insulating film 162 corresponding to the exposure areas A ₁ to A ₄ of the fourth mask 300. 162) comprises a first layer (162a), the second the third layer has a thickness (T ₂₎ the second layer (162b) and the third thickness having (T ₃₎ (162c) having a first thickness (T ₁₎ It includes, and further comprises a through area (162d).

Here, the thickness of each layer is T ₁ <T ₂ Has a relationship of <T ₃ , and the first layer 162a is used as a protective layer for protecting the lower layer, the second layer 162b is used to adjust the cell gap of the main pixel electrode 182, and the third layer The layer 162c is used to adjust the cell gap of the sub pixel electrode 183. In addition, the through region 162d is used as a contact layer for electrical connection with the underlying layer.

As described above, in the fourth mask process, the second insulating layer 162 having the multilayer structure may be formed, and the cell gap control layer of the contact layer, the protective layer, the main pixel, and the sub pixel may be formed using one half-tone mask. The thickness of each layer may be easily changed by adjusting the transmittance of each region of the halftone mask 300.

Subsequently, as illustrated in FIG. 6F, a transmissive conductive film is formed on a substrate on which the second insulating film 162 having a multilayer structure is formed, and then a patterning process using a fifth mask is performed to expose the drain electrode through the contact hole 163. The main pixel electrode 182 connected to the 154 and the sub pixel electrode 183 separated from the drain electrode 154 are formed. In this case, indium tin oxide (ITO) or indium zinc oxide (IZO) may be used as the light transmissive conductive film. In addition, the main pixel electrode 182 and the sub pixel electrode 183 may be formed with a plurality of cutting patterns together as domain regulating means for adjusting the alignment direction of the liquid crystal molecules.

As described above, the lower substrate 100 is formed by performing a five-step mask process. However, the lower substrate 100 is not limited thereto and may be formed by performing a five-step mask process or a five-step mask process.

7 is a cross-sectional view illustrating a manufacturing process of an upper substrate of a liquid crystal display according to an exemplary embodiment of the present invention.

First, as shown in FIG. 7A, a black matrix light blocking film is coated on another substrate 200, and then patterned to form a black matrix 212 arranged in a lattice form.

Subsequently, as shown in FIG. 7B, an organic film for color filters is coated on the black matrix 212 and then patterned to form R, G, and B color filters 222 overlapping the black matrix 212. do.

Next, as shown in FIG. 7C, the overcoat layer 232 is formed on the entire structure including the black matrix 212 and the color filter 222. The overcoat layer 232 is formed to improve adhesion and flatness, but may be omitted as necessary.

Subsequently, as illustrated in FIG. 7D, a transparent conductive film is formed on the overcoat layer 232 and patterned to form a common electrode 242. In this case, indium tin oxide (ITO) or indium zinc oxide (IZO) may be used as the light transmissive conductive film. In addition, it is preferable to form a plurality of cutting patterns (not shown) together on the common electrode 242 as domain regulating means for adjusting the alignment direction of the liquid crystal molecules.

Of course, in manufacturing the upper substrate 200, a light-transmitting organic film is coated on the overcoat layer 232 and then patterned to form a column space for maintaining a cell gap, and an ITO thin film or an IZO thin film thereon. Deposition may be performed to form the common electrode 242. In addition, the column spacers may be replaced by dispersing spherical spacers having a predetermined particle diameter on one substrate without forming the column spacers.

Subsequently, although not shown, rubbing treatment is performed by applying an alignment film (not shown) to the two substrates 100 and 200 to align the liquid crystal molecules, respectively, and a thermosetting resin or an ultraviolet curable resin along the edge of one substrate. A seal material such as a resin is applied to form a frame-shaped seal pattern, and then heated and compressed to bond the two substrates 100 and 200, and then the liquid crystal is injected through the opening of the seal pattern and then encapsulated. A cell process is performed to manufacture a liquid crystal display device. Of course, the liquid crystal layer may also be formed through a liquid crystal dropping method other than the liquid crystal injection method described above.

In the liquid crystal display manufactured by the above method, the cell gap can be easily adjusted by using each layer of the second insulating layer 162 having a multilayer structure as a cell gap adjusting layer of the main pixel and the sub pixel, so that the voltage is lower than that of the main pixel. It is possible to compensate for the low luminance of the sub-pixel driven. In addition, the multilayer structure of the second insulating layer 162 may be formed in a single mask process by using the half-tone mask 300 which is capable of differential exposure by controlling light transmittance for each region, thereby reducing manufacturing costs.

As mentioned above, although this invention was demonstrated with reference to the above-mentioned Example and an accompanying drawing, this invention is not limited to this, It is limited by the following claims. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the technical spirit of the following claims.

As described above, the present invention improves the viewing angle and the side visibility by driving the voltages of the main pixel and the sub pixel differently, and simultaneously adjusts the cell gap of the main pixel and the sub pixel through the insulating film of the multi-layer structure to lower the sub pixel. As the voltage is compensated, the white brightness is improved. In addition, the insulating film of the multi-layer structure can be formed in a single mask process using a half-tone mask that can be differentially exposed by controlling the transmittance of light for each region, it is possible to reduce the manufacturing cost.

Claims (13)

An upper substrate on which color filters are arranged in a matrix; The thin film transistor includes a lower substrate arranged in a matrix form, The lower substrate, An insulating film formed on the thin film transistor in a multilayer structure; And a main pixel electrode and a sub pixel electrode formed on different layers of the insulating layer. The method according to claim 1, And the sub pixel electrode is formed on an insulating layer of a higher layer than the main pixel electrode. The method according to claim 1, The insulating film includes a first layer having a first thickness T ₁ , a second layer having a second thickness T ₂ , and a third layer having a third thickness T ₃ , wherein each layer has a thickness T ₁ <T ₂ <Liquid crystal display device, characterized in that a relationship of T _3. The method according to claim 3, And the main pixel electrode is formed on a second layer of the insulating layer. The method according to claim 3, And the sub pixel electrode is formed on a third layer of the insulating layer. The method according to claim 3, The insulating film further includes a through region, And the main pixel electrode is electrically connected to a lower thin film transistor through the through region. The method according to claim 1, And a cutout pattern formed on at least one of the main pixel electrode and the sub pixel electrode. (a) forming an insulating film and a photosensitive film on the substrate having a predetermined structure; (b) forming the photosensitive film in a multilayered structure by differentially exposing the photosensitive film for each region and then developing the photosensitive film; (c) etching the entire surface of the photosensitive film and the insulating film to form the insulating film in a multilayer structure; (d) forming a main pixel electrode and a sub pixel electrode on different layers of the insulating film having a multilayer structure. The method according to claim 8, In step (b), The photosensitive film is exposed using a halftone mask in which light transmittance is controlled for each region. The method according to claim 9, The halftone mask includes a first region having a first transmittance P ₁ , a second region having a second transmittance P ₂ , a third region having a third transmittance P ₃ , and a fourth transmittance P _4. And a fourth region having (), wherein the transmittance of each region has a relation of P ₁ > P ₂ > P ₃ > P ₄ . The method according to claim 8, The insulating film of the multi-layer structure of step (c), A first layer having a first thickness T ₁ , a second layer having a second thickness T ₂ , a third layer having a third thickness T ₃ , wherein each layer has a thickness of T ₁ < T ₂ <Method of producing a liquid crystal display device characterized in that it formed to have a relationship of T _3. The method according to claim 8, In step (d), And forming a light-transmitting conductive film on the insulating film of the multi-layer structure, and patterning the light-transmitting conductive film to form the main pixel electrode and the sub-pixel electrode. The method according to claim 12, And the sub pixel electrode is formed on an insulating layer of a higher layer than the main pixel electrode.

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