KR100848558B1 - Transreflective liquid crystal display and fabrication method thereof - Google Patents

Abstract

The present invention relates to a transflective liquid crystal display device and a method for manufacturing the same, comprising the steps of: forming a concave groove in a transmission portion of a substrate; Forming a thin film transistor including a gate / source / drain electrode and an active layer on the substrate; Forming a passivation layer exposing a portion of the drain electrode on an upper surface of the substrate and an upper surface of the thin film transistor; Forming a pixel electrode and a reflector on the passivation layer.

Description

Reflective liquid crystal display device and manufacturing method therefor {TRANSREFLECTIVE LIQUID CRYSTAL DISPLAY AND FABRICATION METHOD THEREOF}

1 is a schematic view of a general transflective liquid crystal display device.

FIG. 2 is an enlarged view of a portion of a pixel area including an interface between a transmissive part and a reflective part of FIG. 1; FIG.

3 is a view showing a transflective liquid crystal display device of the present invention.

FIG. 4 is an enlarged view of a portion of a pixel area including an interface between a transmissive part and a reflective part of FIG. 3; FIG.

5A to 5E are process flowcharts illustrating a method of manufacturing a transflective liquid crystal display device of the present invention.

6 illustrates another embodiment of the present invention.

7 is a view comparing the interface shape between the transmission portion and the reflection portion according to the prior art and the present invention

*** Explanation of symbols for main parts of drawing ***

1: substrate 2a: gate electrode

3: gate insulating film 5a: semiconductor layer

5b: ohmic layer 6: data line                 

6a: source electrode 6b: drain electrode

8: pixel electrode 9: reflecting electrode

10: through hole 14: color filter

11: lower substrate 12: upper substrate

13: protective film 15: liquid crystal layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transflective liquid crystal display, and more particularly, to a transflective liquid crystal display and a method of manufacturing the same for reducing the misalignment region of the liquid crystal generated at the interface between the reflective portion and the transmissive portion and improving the step coverage of the interface.

In recent years, with the expansion of communication infrastructures, the use of computer networks has rapidly expanded, and an environment in which anyone can use necessary information anytime, anywhere has been created. Accordingly, as the market for information and communication devices such as personal information and communication devices, web terminals, and portable terminals that require mobility is exploding, demand for displays having light weight and low power consumption is increasing. Unlike the related art, there is a demand for a display device capable of expressing a variety of information including a still image beyond a level of performing only on / off of numbers or a predetermined image. In such a request, the demand for mobile devices capable of displaying color images is rapidly expanding. The characteristics required for a mobile device are that it can be used for a long time with a thin, light weight and low power consumption.

Liquid crystal displays have been widely applied to such portable information and communication devices because they are light, thin, and have low power consumption. However, since a general transmissive liquid crystal display device requires a backlight device, when it is used as a display element such as a portable information device, the power consumption of the backlight not only shortens the use time after one-time charging of the portable device, but also reduces the weight and thickness of the backlight. There is a problem of poor portability.

In order to overcome these problems, the reflective liquid crystal display device, which is recently proposed, uses ambient light as a light source, so that there is no power consumption by the backlight which occupies about 70% or more of power consumption, and no thickness and weight increase by the backlight. Thus, an information display element having excellent display quality with very little power can be realized. In addition, in mobile devices, the adaptability of outdoor use becomes important, but in the conventional transmissive LCD, there is a problem in visibility that the color contrast decreases due to reflection of the panel surface under a bright external environment. On the device there is an advantage that looks more clear.

However, since ambient light such as natural light or artificial light sources do not always exist, it may be used during daytime when natural light is present or inside offices and buildings where external artificial light exists, but it is not possible to use it at night when natural light does not exist. There is an impossible problem.

Accordingly, a semi-transmissive liquid crystal display device that can be used simultaneously and day and night while accepting the advantages of the transmissive liquid crystal display and the reflective display device has been developed.

In the transflective liquid crystal display, as shown in FIG. 1, the lower substrate 11 including the switching element 19 and the upper substrate 12 including the color filter 14 are disposed to face each other. The liquid crystal layer 15 into which the liquid crystal 15a is injected is formed between the substrate 11 and the upper substrate 12.

The lower substrate 11 is disposed at each pixel to form a switching element 19 for applying and blocking a signal voltage to the liquid crystal. The switching element is formed on a glass substrate or a plastic substrate to apply a scan signal. An active layer comprising a gate electrode 2a, a semiconductor layer 5a for transmitting a data signal in response to the scan signal, and an ohmic contact layer 5b doped with n + on both sides of the semiconductor layer 5b. A layer 5, a gate insulating film 3 that electrically isolates the active layer 5 and the gate electrode 2a, and a source electrode 6a formed on the active layer 5 to apply a data signal. ), A drain electrode 6b for applying a data signal to the pixel electrode, and a protective film 13 for protecting the source electrode 6a and the drain electrode 6b, and the drain electrode 6b has a contact hole. It is connected to the pixel electrode 8 through the pixel electrode 8. The protective film 13 is formed of an inorganic film such as SiO 2 or SiN, and may be formed of an organic film such as BCB for high opening ratio. In addition, although not shown in the figure, when the protective film is made of an organic film such as BCB, a SiN layer is further formed above and below.

In addition, in the pixel region of each pixel except the region where the switching element 19 is formed, a transmissive portion 9 is formed on the reflective electrode 9 and the reflective electrode 9 in a planar manner, through which backlight light incident from the backlight can pass. 10) and a pixel electrode 8 for applying a signal voltage applied through the switching element 19 to the liquid crystal cell.

In addition, the recessed groove is formed in the area | region in which the permeation | transmission part 10 was formed by removing the protective film 13. In this way, the concave groove is formed in the concave groove in order to match the on / off mode of the reflector and the transmissive part and to maximize the efficiency of the transmissive mode. Most preferably, it is 1.

The protective film formed in the transmissive part is etched so that the ratio of the cell gap between the transmissive part and the reflecting part is 2: 1, wherein the boundary surface of the protective film forms an inclined part having a constant slope. The liquid crystal oriented on the inclined portion is formed differently from the liquid crystal oriented on the flat surface, and affects the liquid crystal array formed on the flat surface adjacent to the inclined portion. This causes the contrast of the screen to decrease in the transmissive mode, and in order to prevent this, the reflector is formed up to a part of the flat transmissive region adjacent to the inclined portion. However, there is a problem that the aperture ratio decreases as the opaque reflector is formed up to a part of the transmission region.

In addition, due to the characteristics of dry etching that is commonly used to etch the gate insulating film and the protective film, there is a problem in that step coverage of an interface is difficult to come out properly.

Hereinafter, a conventional problem will be described in more detail with reference to the accompanying drawings.

FIG. 2 is an enlarged view of a part of the pixel area including the interface between the transmissive part and the reflecting part of FIG. 1 in the case of the high-aperture structure. After the gate insulating film 3 is formed on the entire upper surface of the substrate 11a, a silicon nitride film (SiN) is formed. ) / BCB / SiN are sequentially stacked to form the protective film 13, and then a part of the protective film 13 is removed by dry etching, thereby forming a step between the transmission part and the reflection part. Thereafter, an ITO material is deposited on the entire surface of the structure to form the pixel electrode 8, and the reflective plate 9 is formed on the pixel electrode 8 corresponding to the passivation layer 19. In this case, the reflective plate 9 is formed up to a part of the gate insulating film 3 including the upper portion of the protective film 13 and defined as the boundary surface and the transmissive region of the protective film 13.

Due to the characteristics of dry etching, the interface where the protective film is etched has an inclined portion having a constant slope, and the liquid crystal oriented in the inclined region is different from the liquid crystal oriented in the other flat surface, that is, the liquid crystal misaligned in this region. This affects the flat surface adjacent to the inclined surface to form the liquid crystal misalignment region D1, where the liquid crystal misalignment region causes defects on the screen in the transmission mode. In order to solve the above problems, the reflection plate is formed to a part of the flat surface which is affected by the liquid crystal in the inclined area, thereby eliminating defects in the screen that may occur in the transmissive mode. However, there is a problem that the aperture ratio decreases as the range of forming the reflector is widened.

In addition, since the etching rates of the organic layer 13b and the inorganic layers 13a and 13c are different from each other in the process of etching the passivation layer 13, the step coverage is applied to the interface between the organic layer and the inorganic layer due to the undercut. In this area, as shown in the enlarged view, the ITO and its upper layer are not formed properly, resulting in a poor opening of the pixel electrode 8 and its upper layers.

In addition, since the area for etching the protective film is large, there is a problem that the load of the equipment becomes large.

 Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a transflective liquid crystal display device having an improved aperture ratio in a transmissive mode by reducing the area of an inclined portion in which liquid crystals are misaligned by etching a substrate through a wet etching method. It is done.

In addition, another object of the present invention is to etch the substrate or the plastic substrate itself to improve the step coverage on the interface between the reflecting portion and the transmitting portion to prevent defects caused by the short circuit of the ITO or its upper layers.

In addition, another object of the present invention to provide a method for manufacturing a liquid crystal display device that can reduce the load of the etching equipment through the wet etching of the substrate or plastic substrate.

Other objects and features of the present invention will be described in detail in the configuration and claims of the following invention.

According to one aspect of the present invention, there is provided a reflective liquid crystal display device comprising: a glass or plastic substrate having a plurality of pixels and grooves having a predetermined depth in a transmissive part region of each pixel; A thin film transistor disposed at each pixel to apply and block a signal voltage to the liquid crystal, the thin film transistor including a gate / source / drain electrode and an active layer; ITO electrically connected to the drain electrode of the thin film transistor; The pixel may include a reflective plate formed in the remaining area of the pixel, except for the transmissive part, and further include a passivation layer formed under the pixel electrode and over the source / drain electrode.                     

Since the groove formed in the substrate has a very gentle slope and is connected to the flat surface of the transmissive part, the area where the liquid crystal is misaligned becomes narrower than in the related art. Therefore, the area in which the reflector is formed can be reduced, and the aperture ratio can be improved, and the step coverage of the interface between the transmissive part and the reflecting part can be improved, thereby preventing the defective opening of the ITO and its upper films.

In addition, the method of manufacturing a reflective liquid crystal display device having the above structure includes the steps of forming a constant groove in the transmission region of the substrate through wet etching; Forming a thin film transistor including a gate / source / drain electrode and an active layer on the substrate; Forming a passivation layer over the thin film transistor and the pixel region; Forming ITO on the protective film; The reflective plate may be formed in the remaining area except for the transmissive part of the pixel area, and the reflective plate may be directly formed on a glass or plastic substrate, or may be formed on or under the ITO.

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

First, FIG. 3 is a cross-sectional view of a transflective liquid crystal display device according to an embodiment of the present invention. The substrate 11a includes a pixel having a reflective portion and a transmissive portion defined therein and a groove having a constant depth having an inclined portion having a gentle inclination into the transmissive portion. And the lower substrate 11 including the thin film transistor 19 formed on the substrate, the upper substrate 12 having the color filter 14 and the liquid crystal layer 15 interposed therebetween. The cell spacing of 1 is maintained. In addition, the backlight unit 40 is positioned under the lower substrate 11.

 The gate insulating layer 3 and the passivation layer 13 formed on the substrate 11a are stacked in the pixel region, and the contact hole in which the pixel electrode 8 made of a transparent material is formed on the passivation layer 13 is formed on the entire passivation layer 13. It is connected to the drain electrode 6b of the thin film transistor 19 through 8a, and the reflecting plate 9 is formed in the remaining area | region except a permeation | transmission part.

The passivation layer 13 may be formed of an inorganic material such as silicon nitride layer (SiNx) or silicon oxide layer (SiOx), or an organic material such as BCB. When the passivation layer is formed of an organic layer, upper and lower portions of SiNx and The same inorganic film is further formed.

In addition, the reflector 9 may be formed on the upper or lower portion of the pixel electrode 8 or on the substrate 11a, and may be formed between SiNx and BCB when the protective layer is stacked with SiNx / BCB / SiNx. have.

The thin film transistor 19 is formed on the substrate 11a and has a gate electrode 2a to which a scan signal is applied, an active layer 5 provided to transmit a data signal in response to the scan signal, and an active layer 5. A gate insulating film 3 that electrically isolates the gate electrode 2a, a source electrode 6a formed on the active layer 5 to apply a data signal, and a drain to apply the data signal to the ITO electrode. And a protective film 13 for protecting the electrode 6b, the source electrode 6a, and the drain electrode 6b. A contact hole 8a is formed in the protective film 13 to be transparent to the drain electrode 6b. It is connected to the pixel electrode 8 made of metal. The active layer 5 is composed of a semiconductor layer 5a formed by depositing amorphous silicon (a-Si) and an ohmic contact layer 5b doped with n + doped on both sides of the semiconductor layer 5a. do.

Referring to the operation of the liquid crystal display device configured as described above, in the reflective mode, the light incident from the outside is reflected by the reflector 9 to the upper substrate 12, in the transmissive mode the light generated from the backlight is It is transmitted to the upper substrate 12 through the pixel electrode (8). At this time, when a signal is applied to the reflector 9 to the pixel electrode 8 by the action of the thin film transistor 19, the phase of the liquid crystal layer 15 is changed, the light transmitted through the liquid crystal layer 15 or reflected Is colored by the color filter 14 formed on the upper substrate 12 to be seen as a color screen.

4 is an enlarged view of a portion of a pixel area including an interface between the transmissive part and the reflective part of FIG. 5, wherein the flat surface of the transmissive part and the interface 11a have a gentle slope; A gate insulating film 3 formed on the entire upper surface of the substrate; A protective film 13 formed on the gate insulating film 3; A pixel electrode 8 formed on the protective film; The reflective plate 9 is formed on the pixel electrode 8, and the reflective plate 9 is formed up to an inclined surface connected to the flat surface of the transmissive part.

Since the step between the transmissive part and the reflecting part is caused by the substrate itself, the step coverage is very good for the gate insulating film 3 and all the films formed thereon. Therefore, it is possible to prevent the opening failure caused in the upper layer of the protective film due to the poor step coverage on the etching interface of the conventional protective film.

5A to 5E are process flowcharts for explaining a method of manufacturing a transflective liquid crystal display device configured as described above.                     

First, as shown in FIG. 5A, after the glass or plastic substrate 11a is prepared, a portion of the substrate is removed by wet etching in the transmissive portion of the substrate 11a to form a step between the transmissive portion and the reflective portion. At this time, the interface between the transmissive part and the reflecting part has a very gentle inclined part due to the wet etching characteristics.

In the method of patterning the substrate 11a, a glass substrate may be a photoresist film, which is generally used for photolithography, as a mask, but the photoresist may be lost by an etching solution. After forming the metal pattern is used as a mask.

In the case of a plastic substrate, heat is applied to the plastic substrate to have a ductile, and then a stamp method of dipping a stamp formed with convex protrusions corresponding to the shape of the transmission part on the substrate, or forming a groove with a plastic solution. It uses a molding method that is poured into a plate prepared in advance so as to harden.

Next, as illustrated in FIG. 5B, a metal material is deposited on the substrate 11a and then patterned to form a gate electrode 2a of the thin film transistor.

Next, as shown in FIG. 5C, an insulating material is deposited on the entire upper surface of the substrate 11a including the gate electrode 2a to form a gate insulating film 3. As the material of the gate insulating film 3, an inorganic material such as SiNx or SiO2 is used. Subsequently, the semiconductor layer 5a made of amorphous silicon (amorphous-Si) and the ohmic contact layer 5b made of n + amorphous silicon doped with phosphorus (P) are successively deposited on the gate insulating film 3, and then patterned. The active layer 5 of the thin film transistor is formed.

As shown in FIG. 5D, a metal material is entirely deposited on the ohmic contact layer 5b and the gate insulating film 3 and then patterned to form a source electrode 6a and a drain electrode 6b of the thin film transistor. .

Thereafter, the ohmic contact layer 5b exposed on the source electrode 6a and the drain electrode 6b is removed by etching, and the source and drain electrodes 6b including the exposed semiconductor layer 5a are removed. After forming the protective film 13 on the formed gate insulating film 3, the protective film is patterned so that a part of the drain electrode 6b is exposed to form the contact hole 8a. The ITO material is deposited on the entire surface of the passivation layer 13 including the exposed drain electrode 6b and then patterned to form the pixel electrode 8. At this time, the pixel electrode 8 is connected to the drain electrode 6b of the thin film transistor through the contact hole 8a.

Subsequently, as shown in FIG. 5E, an opaque metal material is deposited on the remaining region except for the transmissive portion where the pixel electrode 8 is formed, and then patterned to include the upper surface of the protective film 13, including the boundary surface of the protective film 13. The reflector 9 is formed.

 The reflector 9 is capable of reflecting light incident from the outside well, and it is preferable to use a material having a high reflectance such as Al or AlNd.

In the forming of the reflector plate, the position is not limited and may be located below the pixel electrode ITO or on the substrate 11a, and in the case where the protective layer is formed of SiNx / BCB / SiNx, SiNx and It can also be formed between BCBs.

FIG. 6 shows that the reflector 9 is formed on the substrate 11a. The reflector 9 is formed when the gate electrode is formed using a reflective metal material such as Al and AlNd.

As such, when the gate electrode and the reflector are formed at the same time, a mask process added for forming the reflector may be omitted, and the gate electrode and the reflector may be electrically connected to each other to form the gate line and the gate line therebetween. Storage capacitors generated between the pixel electrodes or separate storage lines may be increased.

7 is a view comparing the interface between the transmissive portion and the reflective portion according to the prior art and the present invention, wherein the portion indicated by the dotted line in the boundary region is the conventional form, and the portion indicated by the solid line is the form of the present invention.

As shown in the related art, an inclined portion having a predetermined slope is formed by removing the protective layer through dry etching, and the liquid crystals oriented in the inclined portion region are different from those of liquid crystals oriented on other flat surfaces. The misaligned liquid crystal in the inclined portion region also affects the flat surface adjacent to the inclined surface to form the liquid crystal misalignment region D1. On the other hand, the present invention obtains a step on the substrate through wet etching so that the inclination of the flat surface and the boundary surface leading to the transmissive surface is very gentle and the liquid crystals oriented on the boundary surface do not affect the arrangement of the adjacent flat surfaces. That is, the present invention has liquid crystal misalignment (disclination) corresponding to D2. However, as described above, a reflection film is formed in the liquid crystal misaligned region in order to prevent defects in the screen caused by the liquid crystal misaligned region in the transmissive mode. The liquid crystal misaligned region D2 of the present invention is narrower than that of the conventional D1, so that the reflective plate is formed. It is possible to reduce the reduction of the aperture ratio due to.

As described above, according to the present invention, a substrate made of glass or plastic in the case where a step is formed in the transmissive part and the reflecting part so as to make the cell gap of the transmissive part double the cell gap of the reflective part in the transmissive reflection type liquid crystal display device. By forming a step between the transmissive portion and the reflective portion through wet etching, the semi-transmissive liquid crystal display device having an improved aperture ratio in the transmissive mode can be provided by reducing the area of the inclined portion where the liquid crystal is misaligned.

In addition, another object of the present invention is to etch the substrate or the plastic substrate itself to improve the step coverage on the interface between the reflective portion and the transmissive portion to prevent defects caused by the short circuit of the ITO or the reflective plate.

In addition, the present invention can reduce the load of the etching equipment because it is not necessary to etch a protective film of a large area.

In addition, by simultaneously forming the reflective plate and electrically connecting them when forming the gate electrode, a separate additional process for forming the reflective electrode can be omitted to increase productivity, and the storage capacitor can be increased without decreasing the aperture ratio.

Claims (11)

A substrate in which grooves having a predetermined depth are formed in the transmissive portion of the pixel region; A thin film transistor formed on the substrate and disposed for each pixel to apply and block a signal voltage to the liquid crystal, the thin film transistor including a gate / source / drain electrode and an active layer; A pixel electrode formed over the entire pixel area; And a reflecting plate formed in the remaining area of the pixel area except for the transmissive part. The transflective liquid crystal display of claim 1, wherein the substrate is made of glass or plastic. The semi-transmissive liquid crystal display device according to claim 1, wherein the boundary surface of the groove formed on the substrate is a curved surface concave inwardly of the groove. The transflective liquid crystal display device according to claim 1, wherein the reflecting plate is formed on the substrate. The transflective liquid crystal display of claim 1, wherein the reflector is formed above or below the pixel electrode. The transflective liquid crystal display device according to claim 1, wherein the reflecting plate is formed up to an interface of the groove. Forming a recess in the transmission portion of the substrate; Forming a thin film transistor including a gate / source / drain electrode and an active layer on the substrate; Forming a passivation layer exposing a portion of the drain electrode on an upper surface of the substrate and an upper surface of the thin film transistor; And forming a pixel electrode and a reflecting plate on the passivation layer. 8. The method of claim 7, wherein the substrate is a glass substrate, and the recess is formed by wet etching. 8. The method of claim 7, wherein the substrate is a plastic substrate, and the concave groove is formed by a stamp or molding method. The method of claim 7, wherein the protective film is formed of any one of a silicon nitride film, a silicon oxide film, and an organic insulating film. Forming a recess in the transmission portion of the substrate; Forming a gate electrode and a reflector of the thin film transistor on the substrate; Forming a gate insulating film on the entire upper surface of the gate electrode and the reflector, and sequentially forming an active layer and a source / drain electrode of the thin film transistor; Forming a passivation layer exposing a portion of the drain electrode on the gate insulating layer on which the source / drain electrode and the reflector are formed; And forming a pixel electrode electrically connected to the drain electrode on the passivation layer.

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