KR100945350B1 - Liquid crystal display device and fabrication method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display element and a method of manufacturing the same. In the reflective or semi-transmissive liquid crystal display element, the shape of the irregularities formed in the reflective portion is formed to have an asymmetric structure thicker than either one of the thicknesses, The reflection efficiency of external light is further improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a liquid crystal display device,

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exemplary sectional view showing a general reflection type liquid crystal display device. Fig.

FIGS. 2A to 2F are process flow charts showing a conventional method for manufacturing a reflective plate.

3 is a view showing a reflection type liquid crystal display device according to the present invention.

Fig. 4 is an enlarged view showing an enlarged view of the reflector region in Fig. 3; Fig.

Fig. 5A and Fig. 5B are plan views and cross-sectional views of the first uneven layer shown in Fig.

6A to 6F are process flow charts showing a method of manufacturing a liquid crystal display element according to the present invention.

DESCRIPTION OF THE REFERENCE SYMBOLS

210: substrate 220: gate electrode

230: gate insulating film 240: active layer

250: protective film 270: reflective electrode

280: first uneven layer 285: second uneven layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display element, and more particularly, to a liquid crystal display element capable of further improving reflection efficiency and a method of manufacturing the same.

In recent years, the expansion of communication infrastructure has rapidly expanded the use of computer networks, and an environment has been created in which the necessary information can be used anytime, anywhere, by anyone. As the market for information communication devices such as personal information communication devices, web terminals, and portable terminals requiring mobility explosively increases, the demand for displays that are light in weight and low in power consumption is increasing. Unlike the related art, a display device capable of expressing a variety of information including a still image beyond a level of performing only on / off of a number or a predetermined image is demanded. In response to such requests, demand for mobile devices capable of color image display is rapidly expanding. The characteristics required for a mobile device are as thin as possible, lightweight, and low power consumption for a long time.

Since a liquid crystal display device is light and thin and consumes a small amount of power, it is widely applied to such portable information communication devices. However, since a general transmissive liquid crystal display device requires a backlight device, when it is used as a display device of a portable information device, There is a problem that the use time of the portable device after a single charge is shortened due to power consumption, and the portability is degraded due to the weight and thickness of the backlight. In order to overcome these problems, a reflection type liquid crystal display device has been proposed recently.

Since the reflection type liquid crystal display device uses ambient light as a light source, there is no power consumption due to the backlight which occupies about 70% or more of power consumption, and there is no increase in thickness and weight due to the backlight. Therefore, it is possible to realize an information display device having excellent display quality with very little power. In the case of a mobile device, its adaptability to outdoor use is important due to its nature. However, in a conventional transmissive LCD, there is a problem in visibility that color contrast is lowered due to reflection of a panel surface under a bright external environment, There is a feature that looks rather clearer.

1 is an exemplary sectional view showing a general reflection type liquid crystal display device.

As shown in the drawing, a conventional reflective liquid crystal display device includes an upper substrate 10 on which a black matrix 11, a color filter 13, an overcoat film 15, and a common electrode 17 are formed and a reflective electrode 27 And a liquid crystal layer 30 filled therebetween. The liquid crystal layer 30 is divided into a plurality of pixel regions by gate wirings and data wirings formed on the lower substrate 30 (not shown) And one thin film transistor as a switching element is arranged for each pixel region. The thin film transistor includes a gate electrode 22, an active layer 24 composed of an ohmic contact layer 24a and a semiconductor layer 24b, and source / drain electrodes 26a / 26b. The gate electrode 22, A gate insulating film 23 formed for insulation with the active layer 24 and a protective film 25 for protecting the thin film transistor are additionally formed. The reflective electrode 27 is formed for each pixel region and is connected to the drain electrode 26b of the thin film transistor.

The reflective electrode 27 acts as a pixel electrode for adjusting the arrangement of liquid crystal molecules by applying an electric field to the liquid crystal layer 30 together with the common electrode 17 of the upper substrate in accordance with the applied pixel data voltage, And at the same time, serves as a mirror for reflecting the light incident through the upper substrate and the liquid crystal layer in the direction of the user's view. However, when the surface of the reflective electrode is flat, light incident from outside light in a specific direction is reflected in the specific direction, thereby narrowing the viewing angle range in which the user can see the reflected light. Therefore, although light scattering means may be provided on the upper substrate to widen the viewing angle, a method mainly used is to form the surface of the reflecting electrode in a concavo-convex shape.

A method of forming a reflective electrode having a concave-convex shape will now be described with reference to FIGS. 2A to 2F.

First, as shown in Fig. 2A, a photosensitive resin film 33 is formed on a substrate 31. Then, as shown in Fig.

2B, the photosensitive resin film 33 is shielded by a mask 35, and ultraviolet rays (arrows) are irradiated on the entire surface of the photosensitive resin film 33. Then, as shown in Fig.

Thereafter, as shown in Fig. 2C, the photosensitive resin film 33 is dissolved in a developing solution to form a convex pattern 37 on the substrate 31. Then, as shown in Fig.

Then, as shown in Fig. 2D, the convex pattern 37 is subjected to heat treatment to form a dome-shaped surface.

Thereafter, as shown in FIG. 2E, the photosensitive resin pattern 37 having a tom shape and the overcoat film 39 are formed on the upper surface of the substrate 31 using spin gating to provide a continuous uneven surface.

Finally, as shown in FIG. 2F, opaque metal is deposited by a sputtering method to form a metal film 38. The metal film having a concavo-convex shape and a symmetrical structure serves to scatter incident light at various angles, thereby improving reflection efficiency and viewing angle.

However, the conventional concavo-convex shape having a symmetrical structure as described above has limitations in improving the reflection efficiency.

Accordingly, the present invention has been made in order to further improve the reflection efficiency of light incident from the outside. In order to improve the reflection efficiency of light incident from the outside, a primary pattern is formed to form irregularities, an organic film is coated on the pattern, To form a reflective concavo-convex layer having an asymmetric structure, thereby providing a liquid crystal display element having a highly efficient reflection plate.

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

In order to achieve the above object, a liquid crystal display device according to the present invention includes an upper substrate on which a color filter and a common electrode are formed, a thin film transistor, a reflector on which an asperity layer having an asymmetric structure is formed, and a liquid crystal layer filled therebetween.

The concavo-convex layer is formed such that each pattern is directed to one side, and the thickness of one of the opposed portions is relatively thicker than that of the other portion. A reflective electrode made of opaque metal is formed on the uneven layer.                     

The thin film transistor includes a gate electrode to which a scan signal is applied, an active layer adapted to transmit a data signal in response to the scan signal, a gate insulating film for electrically isolating the active layer from the gate electrode, A source electrode for applying a data signal, and a drain electrode for applying a data signal to the pixel electrode.

According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, including: forming a thin film transistor on a transparent substrate and forming a protective film thereon; Forming an organic layer or an inorganic layer on the passivation layer of the pixel region and patterning the organic layer or the inorganic layer to form a first rugged layer; Coating an organic film on the first irregular layer and the protective film and then tilting the substrate at a predetermined angle; Forming a second uneven layer by curing the organic film while tilting the substrate; And forming a reflective electrode on the second rugged layer.

In the step of tilting the substrate after coating the organic film, the organic film is tilted to one side and then, when the curing process is performed, the tilted side has an asymmetric structure with a thicker thickness. If the uneven layer has an asymmetric structure, the external light can be reflected more effectively than the symmetrical structure, and the light reflection efficiency can be further improved.

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

FIG. 3 shows a reflection type liquid crystal display device according to the present invention, and FIG. 4 is an enlarged view showing an enlarged view of a reflection plate area in FIG.

3, the reflection type liquid crystal display according to the present invention includes an upper substrate 100 including a color filter 130, a thin film transistor, an uneven layer 285 having an asymmetric structure, and a reflective electrode 270 And a liquid crystal layer 300 filled between the lower substrate 200 and the lower substrate 200.

A black matrix 110 formed in an upper region of the thin film transistor and an overcoat film 150 for planarizing the color filter 130 are formed on the upper substrate 100. A common electrode 150 for driving the liquid crystal (Not shown).

The thin film transistor formed on the lower substrate 200 includes a gate electrode 220 to which a scan signal is applied, an active layer 240 for transmitting a data signal in response to a scan signal, A gate insulator 230 for electrically isolating the source electrode 240 and the gate electrode 220 from each other and a source electrode 230 formed on both sides of the active layer 240, And a drain electrode 260b for applying a data signal to the reflective electrode 270. The protective layer 250 for protecting the thin film transistor including the source / drain electrodes 260a / 260b Respectively.

When a scanning signal having a high level is applied to the gate electrode 220, a channel through which electrons can move is formed in the active layer 240, so that the data signal of the source electrode 260a is applied to the active layer 240 to the drain electrode 260b. On the other hand, when a scan signal having a low level is applied to the gate electrode 220, the channel formed in the active layer 240 is cut off, thereby stopping the transmission of the data signal to the drain electrode 260b.

The active layer 240 includes a semiconductor layer 240b formed by depositing amorphous silicon (a-Si), an ohmic contact layer formed by depositing amorphous silicon on both sides of the semiconductor layer 240b, (240a).

The uneven layer 220 formed to efficiently reflect light incident from the outside has an asymmetric shape having different heights at left and right with respect to the center. This is because the light is reflected more efficiently than the symmetrical shape It plays a role.

An upper portion of the uneven layer 285 is formed with a reflective electrode 270 that substantially reflects external light and is electrically connected to the drain electrode 260b of the thin film transistor to drive the liquid crystal. At this time, the reflective electrode 270 is made of a metal material having excellent reflectivity such as Al, Al alloy, Ag, or the like.

FIG. 4 is an enlarged view of a part of the area of the reflective plate on which irregularities are formed. As shown in FIG. 4, the first irregular layer 280 is formed on the protective layer 250 in irregular or regular patterns. A second uneven layer 285 formed of an organic film is formed on the protective film 250 and the first uneven layer 280. The shape of the first uneven layer 280 formed between the protective film 250 and the second uneven layer 285 may have various shapes such as a circle or a square.

FIG. 5A shows an example of several forms that the first rugged layer 280 may have. It may have a circular shape, a square shape or a rhombus shape as shown in the drawing. At this time, the second uneven layer 285 formed on the upper part thereof is the same as the section of the first uneven layer 280 formed on the lower part thereof, as shown in FIG. 5B. In other words, the second uneven layer 285 formed on the upper portion of the first uneven layer 280 has an asymmetric structure in which one of the thicknesses is thicker than the other, and the width is about 3 탆 or more.

Hereinafter, a method of manufacturing a thin film transistor and a reflection plate of a reflection type liquid crystal display device according to the present invention having the structure as shown in FIG. 3 will be described in detail with reference to FIGS. 6A to 6E. FIG.

First, as shown in FIG. 6A, a metal material is sputtered on a transparent substrate 210 and patterned by a photo-etching method using a photo resist to form a gate electrode 220 are formed.

6B, the gate electrode 220 and the inorganic material such as SiNx or SiO2 of the transparent substrate 210 are deposited on the entire surface to form the gate insulating film 230. Then, as shown in FIG. Then, a semiconductor layer 240b made of amorphous-Si and an ohmic contact layer 240a made of n + amorphous silicon doped with phosphorous (P) are successively deposited on the gate insulating layer 230 and then patterned Thereby forming the active layer 240 of the thin film transistor.

Next, as shown in FIG. 6C, a metal material is entirely deposited on the ohmic contact layer 240a and the gate insulating film 230, and then patterned. The patterned metal material layer becomes the source electrode 260a and the drain electrode 260b of the thin film transistor.

Thereafter, the ohmic contact layer 240a exposed on the source electrode 260a and the drain electrode 260b is removed by etching and the source and drain electrodes 260a and 260b (including the exposed semiconductor layer 240b) A protective film 250 made of an inorganic material such as SiNx or SiO2 or an organic material such as BCB or acrylic is formed on the gate insulating film 230 and the protective film 250 on the drain electrode 260b of the thin film transistor Is removed by an etching operation using a mask pattern, and a contact hole 251 is formed.

6D, an inorganic material such as SiNx or SiO2, an organic material such as BCB or acrylic is formed on the protective film 250 formed in the pixel region, and then patterned to form a first So that the uneven layer 280 is formed. At this time, the first uneven layers 280 formed in the form of a pattern on the protective film 250 may be formed to have an irregular distribution or be distributed regularly.

 Thereafter, as shown in FIG. 6E, BCB, acrylic, PR resin, and the like are formed on the irregularly or regularly arranged first unevenness layer 280 and the protective layer 250 exposed between the first unevenness layers After coating the same organic film, the substrate is tilted at a predetermined angle before the organic film is cured, so that the organic film is moved to one side.

Next, the organic layer is cured in a state in which the substrate is tilted to form a second uneven layer 285 having a different thickness with respect to both sides. At this time, the baking temperature for curing the organic film is 100 to 300 占 폚, and the curing method may use UV curing or heat curing. At this time, the tilt angle [theta] of the substrate has an angle of not more than 90 [deg.] With reference to a flat surface.

Finally, as shown in FIG. 6F, an opaque metal layer such as Al or Al-Aluminum (AlNd) is deposited on the second unevenness layer 285, A reflective electrode 270 is formed to be connected to the electrode 260b.

As described above, the present invention improves the reflection efficiency by forming the asperities formed on the reflection plate in an asymmetrical form.

The present invention can be applied to a reflective portion of a transflective liquid crystal display element in which a transmissive region and a reflective region are formed together in one pixel in addition to the reflective liquid crystal display element shown in the embodiments.

In the case of the transflective liquid crystal display device, since the first uneven layer can be formed together when the transparent electrode is formed, it is possible to form the first uneven layer by performing the additional process for forming the first uneven layer such as the photoresist application, develop, etch, strip, It is possible to omit the patterning process, thereby reducing the manufacturing cost.

As described above, according to the present invention, the shape of the concavo-convex layer formed on the reflection plate is formed into a thick asymmetric structure as compared with the other one, so that the reflection brightness can be further improved as compared with the conventional one.

Claims (19)

delete delete delete delete A substrate on which a switching region and a pixel region are defined; A thin film transistor formed in the switching region and having a gate electrode, a source electrode, and a drain electrode; A protective film formed on the thin film transistor and the pixel region; A first rugged layer formed on the protective film of the pixel region; A second uneven layer formed on the first uneven layer and a protective film therebetween, the second uneven layer being thicker than the thickness of one of the first uneven layer and the other one; And a reflective electrode formed on the second uneven layer and connected to a drain electrode of the thin film transistor. The liquid crystal display element according to claim 5, wherein the first uneven layer is irregularly distributed. The liquid crystal display element according to claim 5, wherein the first uneven layer is regularly distributed. The liquid crystal display element according to claim 5, wherein the first rugged layer is an organic material such as BCB, acrylic or resin PR. The liquid crystal display element according to claim 5, wherein the first rugged layer is an inorganic material such as SiOx or SiNx. The liquid crystal display element according to claim 5, wherein the second uneven layer is an organic material such as BCB, acrylic, and resin PR. The liquid crystal display element according to claim 5, wherein the first uneven layer is a circular shape. The liquid crystal display element according to claim 5, wherein the first uneven layer is a quadrangular shape. The liquid crystal display element according to claim 5, wherein the width of the first uneven layer is 3 m or more. Preparing a substrate on which a switching region and a pixel region are defined; Forming a thin film transistor in the switching region; Forming a protective film on the thin film transistor and the pixel region; Forming a first uneven layer on the protective film of the pixel region; Applying an organic material on the first unevenness layer and a protective film therebetween; Tilting the substrate; Baking the organic material in an inclined state of the substrate, curing the organic material, and forming a second concavo-convex layer having a thickness greater than that of the other side; And forming a reflective electrode on the second unevenness layer. 15. The method of claim 14, wherein forming the thin film transistor comprises: forming a gate electrode on a transparent substrate; Depositing a gate insulating film on the gate electrode; Forming a semiconductor layer on the gate electrode and on the gate insulating layer; And forming source and drain electrodes on the upper side of the semiconductor layer. 15. The method of claim 14, wherein the inclination angle at which the substrate is tilted is less than 90 DEG with respect to a flat surface. delete 15. The method of claim 14, wherein the organic material has a baking temperature of 100 to 300 캜. 15. The method of claim 14, wherein the organic material is cured using heat or UV.

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