KR100989346B1 - Liquid Crystal Display and Manufacturing Method Thereof - Google Patents

Abstract

Disclosed are a liquid crystal display device and a method of manufacturing the same, which can increase a response speed without reducing transmittance. A pixel electrode is formed on the first substrate on which the common electrode is formed, and a protective film is formed on the pixel electrode. On the passivation layer, a conductive electrode electrically connected to the common electrode and the pixel electrode through the contact and spaced apart between the common electrode and the pixel electrode is formed. The liquid crystal layer is formed between the second substrate and the first substrate facing the first substrate. Since the common electrode and the pixel electrode are located at a position higher by the height of the passivation layer, an electric field may be formed between the common electrode and the pixel electrode not only through the passivation layer but also through the lower part of the passivation layer. Therefore, since the liquid crystal interposed between the first substrate and the second substrate is affected by a larger electric field, the response time of the liquid crystal display device is shortened.

Protective film, common electrode, pixel electrode, conductive electrode

Description

Liquid crystal display device and its manufacturing method {LIQUID CRYSTAL DISPLAY AND METHOD FOR MANUFACTURING THE SAME}

1A is a cross-sectional view conceptually illustrating a shape of an electric field formed between a liquid crystal display device of a conventional transverse electric field system and a common electrode and a pixel electrode.

FIG. 1B is a graph illustrating a change in light transmittance with time in the liquid crystal display of FIG. 1A.

2 is a cross-sectional view illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

3A to 3E are views illustrating part of the manufacturing method of the liquid crystal display according to the first embodiment of the present invention in the order of process.

4A is a cross-sectional view conceptually illustrating a shape of an electric field formed between the liquid crystal display of FIG. 2, the common electrode, and the pixel electrode.

4B is a graph illustrating a change in light transmittance at time in the liquid crystal display of FIG. 4A.

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

20, 120: common electrode, 40, 140: pixel electrode

100: first substrate 110: thin film transistor

111: gate electrode 112: active layer                 

113: ohmic contact layer 114: source electrode

116: drain electrode 120: common electrode

125, 130: insulating film 140: pixel electrode

145, 147, 150: protective film 160: conductive electrode

170: photoresist film 175: photoresist pattern

190a: first contact hole 190b: second contact hole

195a: first contact 195b: second contact

200: second substrate 300: liquid crystal layer

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 that can increase the response speed without reducing the transmittance.

The liquid crystal display applies an electric field to the liquid crystal material injected between the liquid crystal display devices in which the switching element is formed, and adjusts the intensity of the electric field to adjust the amount of light transmitted to the substrate. It is a display device which obtains a desired image signal. Liquid crystal display devices are thinner and lighter than other display devices, and are widely used in various electronic devices because they have low power consumption and low driving voltage and can display images close to cathode ray tubes.                         

 Twisted Nematic (TN) type liquid crystal display devices have been mainly used. In the TN type, electrodes are installed on two substrates and the liquid crystal directors are arranged to be twisted by 90 °, and then a voltage is applied to the electrodes. It is a technique to drive the director.

However, the TN type liquid crystal display has a disadvantage that the viewing angle is narrow and the response speed is slow. Therefore, in order to increase the response speed and improve the viewing angle, an in-plane switching (IPS) type liquid crystal display device has been proposed. In a transverse electric field type liquid crystal display, two electrodes are formed on a substrate, and then a voltage is applied between the two electrodes to generate an electric field in a horizontal direction with respect to the substrate so that the directors of the liquid crystal are twisted in parallel planes of the alignment layer. Form.

1A is a cross-sectional view conceptually illustrating a shape of a conventional transverse electric field type liquid crystal display device and an electric field formed between a common electrode and a pixel electrode of the liquid crystal display device. Referring to FIG. 1A, the liquid crystal layer 300 is formed between the first substrate 100 and the second substrate 200, and the electric field (dotted line) applied to the liquid crystal layer 300 includes the common electrode 20 and It is mainly formed on the pixel electrode 40 and its shape is close to the semicircle shape.

FIG. 1B is a graph illustrating a change in light transmittance with time in the liquid crystal display of FIG. 1A. The graph of FIG. 1B was obtained through a simulation experiment using the liquid crystal display of FIG. 1A using light having a wavelength of 550 nm. As can be seen in FIG. 1B, the time from reaching the value T10 corresponding to 10% of the maximum value of transmittance to reaching the value T90 corresponding to 90% of the maximum value of transmittance Is about 31 ms.                         

In general, the rise time of the response speed of the transverse electric field type liquid crystal display device is proportional to the cell gap of the liquid crystal display device, the rotational viscosity of the liquid crystal, and the distance between the electrodes, and is inversely proportional to the dielectric constant and applied voltage of the liquid crystal. The fall time is proportional to the cell gap of the liquid crystal display and the viscosity of the liquid crystal and inversely proportional to the elastic constant ratio. In order to reduce the response time, reducing the distance between electrodes decreases the transmittance of the liquid crystal display. Accordingly, there is a need for a transverse electric field liquid crystal display device capable of shortening a response time without decreasing transmittance.

Accordingly, it is a first object of the present invention to provide a liquid crystal display device capable of shortening a response time without reducing transmittance.

Further, a second object of the present invention is to provide a method of manufacturing a liquid crystal display device suitable for manufacturing the liquid crystal display device.

In order to achieve the first object of the present invention described above, the present invention comprises a first substrate; A common electrode formed on the first substrate; A pixel electrode formed on the first substrate on which the common electrode is formed; A protective film formed on the pixel electrode; A conductive electrode formed on the passivation layer and electrically connected to the common electrode and the pixel electrode through a contact, and spaced apart between the common electrode and the pixel electrode; A second substrate facing the first substrate; And a liquid crystal layer formed between the first substrate and the second substrate.                     

In addition, to achieve the above-described second object of the present invention, the present invention comprises the steps of forming a common electrode on the first substrate; Forming a pixel electrode on the first substrate on which the common electrode is formed; Forming a protective film on the first substrate on which the pixel electrode is formed; Forming a conductive electrode on the first substrate on which the passivation layer is formed, the conductive electrode being electrically connected to the common electrode and the pixel electrode through a contact and spaced apart between the common electrode and the pixel electrode; Forming a second substrate opposite the first substrate; And forming a liquid crystal layer between the first substrate and the second substrate.

According to such a liquid crystal display and a manufacturing method thereof, the effect that the common electrode and the pixel electrode are present at a position higher by the height of the passivation layer than that of the conventional common electrode and the pixel electrode occurs. Therefore, since the liquid crystal interposed between the first substrate and the second substrate is affected by a larger electric field, the response time of the liquid crystal display device is shortened. In addition, since the gap between the common electrode and the pixel electrode is not shortened, the problem that the transmittance of the liquid crystal display is reduced does not occur. Therefore, the liquid crystal display according to the present invention can shorten the response time without reducing the transmittance.

Hereinafter, a liquid crystal display and a method of manufacturing the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the liquid crystal display according to the exemplary embodiment of the present invention may include a liquid crystal layer formed between the first substrate 100, the second substrate 200, and the first substrate 100 and the second substrate 200. 300).

The first substrate 100 is made of a material such as glass, quartz, or sapphire that can transmit light. Applying a common voltage to the thin film transistor (TFT) 110 and the first substrate 100 that are switching elements for applying and blocking a voltage to the liquid crystal layer 300 on the first substrate 100. The common electrode 120 and the pixel electrode 140 insulated from the common electrode 120 are formed.

The common electrode 120 is formed on the first substrate 100, and at the same time, the gate electrode 111 is formed in the region where the TFT 110 is to be formed. The common electrode 120 may include indium tin oxide (ITO) or indium zinc oxide (IZO) of a transparent conductive material. However, the material of the common electrode 120 is not limited thereto and may be made of an opaque material according to the characteristics of the liquid crystal display.

An insulating layer 130 for protecting the gate 111 and the common electrode 120 is formed on the first substrate 100 on which the common electrode 120 and the gate electrode 111 are formed. The insulating layer 130 is made of an inorganic insulating material such as silicon oxide or silicon nitride, which has good adhesion with a metal material and suppresses formation of an air layer at an interface. Subsequently, in the region where the TFT 110 is to be formed, an active layer 112 made of amorphous silicon and an ohmic contact layer 113 made of n + amorphous silicon are sequentially stacked at a position corresponding to the gate electrode 111. In this case, the ohmic contact layer 113 may be etched to form a channel region. A portion of the active layer 112 is exposed through the channel region.

A source electrode 114 and a drain electrode 115 are provided on the ohmic contact layer 113 separated into two around the channel region, and the insulating layer 130 is disposed between the upper region of the common electrode 120. The pixel electrode 140 is formed. One end of the source electrode 114 and the drain electrode 115 is in contact with the top surface of the ohmic contact layer 113, and the other end is in contact with the top surface of the insulating layer 130. The pixel electrode 140 is connected to the drain electrode 115 through a contact (not shown) to apply a signal voltage to the liquid crystal layer 300. The pixel electrode 140 may include indium tin oxide (ITO) or indium zinc oxide (IZO) made of a transparent conductive material. However, the material of the pixel electrode 120 is not limited thereto and may be made of an opaque material according to the characteristics of the liquid crystal display.

The passivation layer 150 is formed on the first substrate 100 on which the source electrode 114, the drain electrode 115, and the pixel electrode 140 are formed. The protective film 150 is preferably made of an inorganic insulator such as silicon oxide or silicon nitride, which has good adhesion with a metal material and suppresses formation of an air layer at an interface.

The conductive electrode 150 is electrically connected to the common electrode 120, the pixel electrode 140, and the contacts 195a and 195b on the passivation layer 150, and is spaced apart between the common electrode 120 and the upper portion of the pixel electrode 140. 160 is formed.

In the liquid crystal display according to the present invention, the common electrode 120 and the pixel electrode 140 are electrically connected to the conductive electrode 160 on the passivation layer 150. Therefore, the common electrode 120 and the pixel electrode 140 are present at a position higher by the height of the passivation layer 150 than the positions of the conventional common electrode and the pixel electrode. That is, the conductive electrode connected to the common electrode 120 and the conductive electrode connected to the pixel electrode 140 are positioned at substantially the same height.

In the conventional transverse electric field type liquid crystal display, a semicircular electric field is formed between the common electrode and the pixel electrode. However, in the liquid crystal display according to the present invention, not only the upper portion of the passivation layer 150 but also the lower portion of the passivation layer 150. An electric field may be formed between the 120 and the pixel electrode 140. Therefore, since the liquid crystal layer 300 interposed between the first substrate 100 and the second substrate 200 is affected by a larger electric field, the response time of the liquid crystal display device is shortened.

 The passivation layer 150 may have protrusions on the common electrode 120 and the pixel electrode 140. In other words, the passivation layer 150 may have an etched shape between the common electrode 120 and the pixel electrode 140. Since a portion of the passivation layer 150 is not etched between the common electrode 120 and the upper portion of the pixel electrode 140, a larger electric field is formed in the liquid crystal than in the case where the passivation layer 150 exists, and the liquid crystal display device Can speed up the response.

An angle formed by a line perpendicular to the upper surface of the passivation layer 150 and a side surface of the protrusion of the passivation layer 150 may be 45 ° or less. 2 illustrates a case where an angle formed by a line perpendicular to the upper surface of the passivation layer 150 and a side surface of the protrusion of the passivation layer 150 is 0 °. When the angle formed by the line perpendicular to the upper surface of the passivation layer 150 and the side surface of the protrusion of the passivation layer 150 exceeds 45 °, the passivation layer 150 remains between the upper part of the common electrode 120 and the upper part of the pixel electrode 140. Since the amount is increased, the effect of etching may not be expressed, and thus, a range of improvement in response time is reduced.

The conductive electrode 160 is present on the protrusion 1 of the protective layer 150 as well as the contact 195b connected to the common electrode 120 and the contact 195a connected to the pixel electrode 140. Since the conductive electrode 160 is on the protrusion and does not exist between the upper portion of the common electrode 120 and the upper portion of the pixel electrode 140, the common electrode 120 and the pixel electrode 140 are shorted to each other on the passivation layer 150. The phenomenon does not occur.

On the other hand, although not shown, the conductive electrode 160 may exist on the side as well as the top surface of the protrusion of the protective film 150. That is, the conductive electrode 160 may exist while covering the entire protruding portion of the passivation layer 150. Since the surface area of the conductive electrode 160 is wider, the surface area of the electrodes serving as the common electrode 120 and the pixel electrode 140 is also increased to increase the electric field generated between the common electrode 120 and the pixel electrode 140. do.

The average maximum height of the protrusion of the protective film 150 is preferably 0.3 to 2 ㎛. Herein, the average maximum height of the protruding portion of the passivation layer 150 refers to an average value of the height from the bottom of the passivation layer 150 to the protruding upper surface. If the height is less than 0.3 μm, the amount of the protective film 150 is not sufficient to form a contact while protecting the pixel electrode 140. If the height is more than 2 μm, the height of the protective film 150 is too high. The layer structure may be stressed.

The protective film 150 is made of an inorganic insulator, and the dielectric constant is preferably 2 to 7 F / m.

A transparent second substrate 200 facing the first substrate is provided, and the liquid crystal layer 300 is formed between the first substrate 100 and the second substrate 200. The liquid crystal layer 300 is arranged in the same direction as the horizontal electric field by a horizontal electric field formed by applying a voltage between the common electrode and the pixel electrode.

Hereinafter, a method of manufacturing a liquid crystal display device suitable for manufacturing the liquid crystal display device of the present invention will be described with reference to the drawings.

3A to 3E are views illustrating part of the manufacturing method of the liquid crystal display according to the first embodiment of the present invention in the order of process.

Referring to FIG. 3A, a common electrode 120 made of ITO is formed on the first substrate 100. Silicon nitride is coated on the first substrate on which the common electrode 120 is formed to form an insulating layer 125 to protect the common electrode 120. The insulating film 125 is patterned to have a contact in a later process and formed into the insulating film 130 of FIG. 2.

The pixel electrode 140 made of ITO is formed on the insulating film 125. The pixel electrode 140 is formed in the region between the common electrodes 120, not the upper region of the common electrode 120, on the insulating layer 125.

A passivation layer 145 made of silicon nitride is formed on the pixel electrode 140 to protect the pixel electrode 140. The passivation layer 145 is patterned in subsequent steps to form the passivation layer 150 of FIG. 2. The photoresist 170 is spin coated on the passivation layer 145 to pattern the insulating layer 125 and the passivation layer 145 to have a contact.                     

3B to 3C, the photoresist 170 is exposed to form a pattern for exposing the common electrode 120 and the pixel electrode 140. Next, the exposed photoresist 170 is developed to form a photoresist pattern 175. The protective layer 145 and the insulating layer 125 are etched using the photoresist pattern 175 as an etching mask to expose the common electrode 120 on the first substrate 100, and the protective layer 145 is etched to form an insulating layer ( The pixel electrode 140 on the 125 is exposed. When the etching selectivity of the insulating film 125 and the protective film 145 is large, the etching process of the protective film 145 and the etching process of the insulating film 125 may be simultaneously performed. However, when the etching selectivity of the insulating film 125 and the protective film 145 is not large, it may be performed in a separate process.

The patterned passivation layer 147 and the patterned insulating layer 130 are formed by the etching process. The first contact hole 190a exposes the pixel electrode 140 on the insulating layer 130 through the passivation layer 147, and the second contact hole 190b exposes the patterned passivation layer 147 and the patterned insulating layer 130. The common electrode 120 on the first substrate 100 is exposed.

After etching, the remaining photoresist pattern 175 is stripped by an ashing process.

3D to 3E, a conductive film 155 made of ITO is formed on the first substrate on which contact holes are formed. The conductive film 155 is formed on the patterned passivation film 147 while filling the contact holes.

Subsequently, the conductive layer 155 is patterned to separate the conductive layer 155 between the upper portion of the common electrode 120 and the upper portion of the pixel electrode 140. Accordingly, the conductive electrodes 160 are formed on the common electrode 120 and the pixel electrode 140. When the conductive film 155 is patterned, a photoresist film is formed on the conductive film 155 in the same manner as the process of forming contact holes in FIGS. 3B to 3C, followed by exposure, development, etching, and photoresist stripping. The conductive electrode 160 is formed. In this case, the passivation layer 147 may be etched together to form the passivation layer 150 having the protrusion. When the protective film 150 having the protrusion is formed, a mask having a slit is used on the portion to be etched instead of the upper portion of the protrusion. In this case, by adjusting the shape of the mask, the angle formed by the line perpendicular to the upper surface of the passivation layer 150 and the side surface of the protrusion of the passivation layer 150 may be adjusted. In addition, the shape of the mask may be adjusted so that the conductive electrode is present on the side surface of the protrusion of the protective layer.

Although not shown, after forming a second substrate facing the first substrate, a liquid crystal layer is formed between the first substrate and the second substrate to manufacture a liquid crystal display device.

In the liquid crystal display manufactured by the above method, the common electrode 120 and the pixel electrode 140 have an effect of being present at a position higher by the height of the passivation layer 150 than the positions of the conventional common electrode and the pixel electrode. . Therefore, since the liquid crystal layer interposed between the first substrate and the second substrate is affected by a larger electric field, the response time of the liquid crystal display device is shortened.

The improvement of the response speed of the liquid crystal display according to the present invention was confirmed through a simulation experiment.

4A is a cross-sectional view conceptually illustrating the liquid crystal display of FIG. 2 according to the first embodiment. In FIG. 4A, the shape of the electric field formed between the common electrode and the pixel electrode is conceptually represented, and the response speed of the liquid crystal display is calculated through simulation.

Referring to FIG. 4A, the liquid crystal layer 300 is formed between the first substrate 100 and the second substrate 200, and the electric field (dotted line) applied to the liquid crystal layer 300 includes the common electrode 120 and It is formed not only on the pixel electrode 140 but also on the bottom thereof. In FIG. 4A, the common electrode 120 and the pixel electrode 140 are conceptually illustrated as being disposed on the passivation layer 150. In reality, however, as shown in FIG. 2, the common electrode 120 and the pixel electrode 140 exist below the passivation layer 150 and are connected through a contact.

4B is a graph illustrating a change in light transmittance with time in the liquid crystal display of FIG. 4A. The graph of FIG. 4B was obtained through a 2-DMOS simulation experiment using the liquid crystal display of FIG. 4A using light having a wavelength of 550 nm. As can be seen in FIG. 4B, the time from reaching the value T10 corresponding to 10% of the maximum value of the transmittance to reaching the value T90 corresponding to 90% of the maximum value of the transmittance. Is about 20.5 ms. Accordingly, it can be seen that the response time of the liquid crystal display of FIG. 1 is shortened compared to that of 31 ms.

As described above, according to the present invention, there is an effect that the common electrode and the pixel electrode exist at a position higher by the height of the passivation layer than the positions of the conventional common electrode and the pixel electrode. In the conventional transverse electric field type liquid crystal display device, a semicircular electric field is formed between the common electrode and the pixel electrode. However, in the liquid crystal display according to the present invention, the electric field is formed between the common electrode and the pixel electrode not only through the upper portion of the protective layer but also through the lower portion of the protective layer. This can be formed. Therefore, since the liquid crystal interposed between the first substrate and the second substrate is affected by a larger electric field, the response time of the liquid crystal display device is shortened.

In addition, since the gap between the common electrode and the pixel electrode is not reduced, the problem that the transmittance of the liquid crystal display is reduced does not occur. Therefore, the liquid crystal display according to the present invention can shorten the response time without reducing the transmittance.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (12)

A first substrate; A common electrode formed on the first substrate; An insulating film formed on the first substrate including the common electrode; A pixel electrode spaced apart from an area where the common electrode is formed on the insulating layer; A passivation layer formed on the first substrate including the common electrode and the pixel electrode and including contact holes exposing the common electrode and the pixel electrode, respectively; Conductive electrodes formed on the passivation layer and disposed on regions where the common electrode and the pixel electrode are formed, and electrically connected to the common electrode and the pixel electrode through the contact holes, and spaced apart from each other; A second substrate facing the first substrate; And And a liquid crystal layer formed between the first substrate and the second substrate. The liquid crystal display of claim 1, wherein the conductive electrode connected to the common electrode and the conductive electrode connected to the pixel electrode are positioned at substantially the same height. The liquid crystal display device of claim 1, wherein the passivation layer has protrusions on the common electrode and the pixel electrode. The liquid crystal display device according to claim 3, wherein an angle formed by a line perpendicular to the upper surface of the protective film and a side surface of the protrusion of the protective film is 45 degrees or less. The liquid crystal display of claim 3, wherein a conductive electrode is present on an upper surface of the protruding portion of the passivation layer. The liquid crystal display of claim 3, wherein conductive electrodes are present on upper and side surfaces of the protruding portion of the passivation layer. The liquid crystal display device according to claim 3, wherein the average maximum height of the protruding portion of the protective film is 0.3 to 2 m. The liquid crystal display device according to claim 1, wherein the dielectric constant of the protective film is 2 to 7 F / m. Forming a common electrode on the first substrate; Forming an insulating film on the first substrate including the common electrode; Forming a pixel electrode spaced apart from an area where the common electrode is formed on the first substrate on which the insulating film is formed; Forming a passivation layer including contact holes exposing the common electrode and the pixel electrode on the first substrate on which the pixel electrode is formed; Conductive electrodes disposed on the common substrate and the pixel electrodes on the first substrate on which the passivation layer is formed, electrically connected to the common electrode, the pixel electrode, and the contact holes, and spaced apart from each other. Forming; Forming a second substrate opposite the first substrate; And Forming a liquid crystal layer between the first substrate and the second substrate. delete The method of claim 9, wherein forming the conductive electrodes comprises: Forming a conductive layer on the passivation layer on which the contact holes are formed to form a conductive layer to electrically connect the common electrode and the pixel electrode; And Patterning the conductive film on which the contact is formed to form the conductive electrodes spaced apart from the upper portion of the common electrode and the upper portion of the pixel electrode. The method of claim 9, further comprising forming a protrusion on the passivation layer by patterning the passivation layer.

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