KR100811642B1 - BM-free reflection type liquid crystal display device and the method for fabricating thereof - Google Patents

Abstract

The present invention relates to a reflective liquid crystal display device for improving luminance by removing a black matrix to achieve high magnification.

In the case of the transmissive liquid crystal display, since the backlight uses light, a black matrix is used for the upper substrate to reduce contrast ratio and disintegration caused by the liquid crystal in the non-driving region. Therefore, in the case of a transmissive liquid crystal display, it is inevitable to reduce the aperture ratio by the black matrix.

On the other hand, the reflective liquid crystal display device uses an external light source, and thus has a disadvantage in that luminance is lower than that of the transmissive liquid crystal display device. For this reason, in the case of a reflective liquid crystal display device, luminance improvement is a major problem.

The reflective liquid crystal display according to the present invention adopts a high opening ratio structure using an organic insulating layer to compensate for the shortcomings in luminance. The result is that no black matrix is used, resulting in a high opening rate.

Description

BM-free reflection type liquid crystal display device and the method for fabricating according to the present invention.

1 is a diagram showing the transmittance of each layer of light emitted from the backlight.

2 is a plan view showing a portion corresponding to one pixel of a conventional reflective liquid crystal display.

3 is a cross-sectional view showing a cross section corresponding to one pixel portion of a conventional reflective liquid crystal display device;

4 is a cross-sectional view showing the operation of a general transmissive liquid crystal display.

5 is a cross-sectional view showing the operation of a general reflective liquid crystal display device;

6 is a plan view showing a portion corresponding to one pixel portion of the array panel of the reflective liquid crystal display according to the first embodiment of the present invention;

FIG. 7 is a cross-sectional view illustrating a cross section taken along the line VII-VII of FIG. 6 and a color filter substrate corresponding thereto.

8 is a plan view of an array panel of a reflective liquid crystal display device according to a first embodiment of the present invention;

9 is a cross-sectional view illustrating a path of light traveling in a reflective liquid crystal display according to a first exemplary embodiment of the present invention.

10 is a cross-sectional view showing a cross section corresponding to one pixel portion of a reflective liquid crystal display device according to a second embodiment of the present invention;

FIG. 11 is a cross-sectional view illustrating a path of light traveling in a reflective liquid crystal display according to a second exemplary embodiment of the present invention. FIG.

<Explanation of symbols for main parts of drawing>

 101: substrate 102: gate wiring

 103: gate electrode 104: gate insulating film

 107: source electrode 108: drain electrode

 109: data wiring 110: protective layer

 111: contact hole 112: reflective electrode

115: common electrode 230: light absorbing layer

The present invention relates to a liquid crystal display device, and more particularly, to a reflective liquid crystal display device that does not employ a black matrix.

Recently, as the information society has progressed rapidly, a display field for processing and displaying a large amount of information has been developed.

Until modern times, cathode ray tube (CRT) has become the mainstream of display devices and has been developing.

However, in recent years, the need for a flat panel display has emerged in order to meet the era of thinning, light weight, and low power consumption. Accordingly, a thin film transistor-liquid crystal display (hereinafter referred to as TFT-LCD) having excellent color reproducibility has been developed.

Referring to the operation of the TFT-LCD, when any pixel is switched by the thin film transistor, the switched arbitrary pixel can transmit the light of the lower light source.

The switching element is mainly composed of an amorphous silicon thin film transistor (a-Si: H TFT) in which a semiconductor layer is formed of amorphous silicon. This is because the amorphous silicon thin film can be formed at a low temperature on a large insulating substrate such as a low-cost glass substrate.

TFT-LCDs, which are generally used, have been used to express an image by the light of a light source called a back light located at the bottom of a panel.

However, TFT-LCDs are very inefficient light modulators that transmit only 3-8% of the light incident by the backlight.

Assuming that the transmittance of the two polarized light is 45%, the transmittance of the two glass sheets of the lower plate and the upper plate is 94%, the TFT array and pixel transmittance is about 65%, and the color filter transmittance is 27%. The light transmittance of the LCD is about 7.4%.

1 is a diagram schematically illustrating transmittance of each layer of light emitted from a backlight.

As described above, since the amount of light actually visible through the TFT-LCD is about 7% of the light generated by the backlight, the backlight of the high brightness TFT-LCD needs to be bright, so the power consumption of the backlight is large. .

Therefore, in order to supply sufficient backlight power, a battery having a large weight has been used by increasing the capacity of the power supply device. However, this too could not be used for a long time.

In order to solve the above-mentioned problem, a reflective type TFT-LCD that does not use backlight light has recently been studied. Since it operates using natural light, it can save the amount of power consumed by the backlight, so it can be used in a portable state for a long time, and the aperture ratio is also superior to that of the conventional backlight TFT-LCD.

Hereinafter, a reflective TFT-LCD will be described with reference to the accompanying drawings.

A general TFT-LCD is composed of a thin film transistor array substrate called a lower substrate, a color filter substrate called an upper substrate, and the like. The following description relates to a thin film transistor array substrate which is a lower substrate.

First, referring to FIG. 2, which is a plan view corresponding to one pixel of a conventional reflective TFT-LCD, the N-th gate wiring line 8 and the N-th th array arranged in rows on a substrate are described. The gate wiring 6 is located, and the N-th data wiring 2 and the N + 1-th data wiring 4 arranged in a column form a matrix.

In addition, the gate electrode 18 is positioned at a predetermined position of the N-th gate line 8, and the source electrode 12 extending from the N-th data line 2 has a predetermined length on the gate electrode 18. It is formed to overlap.

In addition, a drain electrode 14 is formed to correspond to the source electrode 12, and the reflective electrode 10 is drained through the drain contact hole 16 located on the drain electrode 14. It is in electrical contact with the electrode 14. In general, the reflective electrode 10 is made of a metal having excellent reflectance.

FIG. 3 is a cross sectional view taken along the cut line III-III of FIG. 2, and the cross-sectional structure of the conventional reflective TFT-LCD is well shown.

Looking at the cross-sectional structure of the reflective TFT-LCD, a gate electrode 18 is formed on the substrate 1 and the substrate 1. A gate insulating film 20 is formed on the gate electrode 18, a semiconductor layer 22 is formed on the gate insulating film 20 on the gate electrode 18, and a source in contact with the semiconductor layer 22; Drain electrodes 12 and 14 are formed.

In addition, a passivation layer 24 is formed on the entire surface of the substrate, where the source and drain electrodes 12 and 14 are exposed. A drain contact hole 16 is formed in the passivation layer 24 so that a portion of the drain electrode 14 is exposed, and a reflective electrode contacting the drain electrode 14 through the drain contact hole 16. 10) is formed on the protective film 24.

The reflective TFT-LCD as described above can be used for a long time because it is driven using natural light or an external artificial light source without using an internal light source such as a backlight.

In other words, the reflective TFT-LCD reflects the external natural light to the reflective electrode 10 and uses the reflected light.

4 illustrates the operation of the general transmissive liquid crystal display.

As the light source, light of the backlight 31 positioned under the lower substrate 25 is used. The light emitted from the backlight 31 enters the liquid crystal 33 through the transparent electrode 32, and is formed by the liquid crystal 33 arranged by the electric field of the transparent electrode 32 and the common electrode 34. The amount of light incident from the backlight 31 is adjusted to implement an image.

However, in order to prevent light from being incident to the channel of the thin film transistor T at a position corresponding to the thin film transistor T and the contact hole 30 of the array substrate 25, the array substrate ( 25, a black matrix 36 is formed on a lower portion of the upper substrate 26, which is spaced at a predetermined interval and formed of a transparent material.

At the same time, in the area where the transparent electrode is not formed, that is, in the area where the liquid crystal does not drive, in the area of the color filter 37 located under the upper substrate for the purpose of eliminating defects such as color contrast and disclination due to light leakage. The black matrix 36 is formed. This causes the aperture ratio to decrease.

5 illustrates an operation of a general reflective liquid crystal display device.

As the light source, an external natural light or artificial light source is used, and the light incident on the upper substrate 51 of the liquid crystal display is reflected by the reflecting electrode 41 and arranged by the electric field of the reflecting electrode 41 and the common electrode 42. After passing through the liquid crystal 43, the amount of light passing through the liquid crystal 43 is adjusted according to the arrangement of the liquid crystal 43 to realize an image.

In the case of a reflective liquid crystal display device, a high opening ratio structure is generally adopted using the organic insulating layer 44 to improve luminance. When the organic insulating film 44 is used, the reflective electrode 41 can be overlapped on the data line 45 as compared with the general transmissive liquid crystal display device, thereby improving the aperture ratio.

However, in a portion where the reflective electrode 41 is patterned away from the data line 45, the black matrix (or black matrix) is still applied to the upper substrate 51 in order to eliminate the influence of light reflected by the source and drain electrodes 60 and 61. 48). The black matrix 48 has the effect of preventing the reduction of the contrast ratio, but the decrease of the aperture ratio and the loss of the luminance inevitably become a problem.

The present invention has been made to solve the conventional problems as described above, an object of the present invention is to provide a reflective liquid crystal display device that can improve the brightness.

Other objects and effects of the present invention will be understood from the preferred embodiments and the accompanying drawings.

According to an aspect of the present invention to achieve the above object, a substrate, first and second data wires arranged in a first direction on the substrate, and a second direction intersecting the first and second data wires. Covering the first and second gate wiring lines, a first switching device connected to the first data and second gate wirings, a second switching device connected to the second data and second gate wirings, and covering the switching devices. An insulating layer and first and second reflective electrodes connected to the switching elements and covering each switching element, wherein the boundaries of the first and second reflective electrodes are formed on the first and second data lines. An array panel for a reflective liquid crystal display device is provided.

According to another aspect of the invention, the substrate; A plurality of data and gate wirings crossing each other to define pixel regions; A plurality of switching elements connected to the data and gate wirings; An insulating layer covering the plurality of switching elements and the respective wirings; Each includes a plurality of reflective electrodes connected to the switching elements and covering the switching elements, and the boundary of the plurality of reflective electrodes provides an array panel for a reflective liquid crystal display device.

One of the edges close to the adjacent data line of the boundary of the reflective electrode covers the data line, and the other does not cover the data line.

It is also a feature of the present invention that the light absorbing layer is positioned between the substrate and the gate wiring at least at a position corresponding to the boundary of each reflective electrode.                     

Preferably, each switching element is a thin film transistor including a gate electrode, a source electrode and a drain electrode, and an active layer. In this case, each of the reflective electrodes is connected to the drain electrode through a contact hole formed in the insulating layer.

The insulating layer is preferably an organic insulating layer, for example BCB or acrylic.

It is advantageous for the reflection efficiency that the upper surface of the reflective electrode is uneven.

In addition, it is a main feature of the present invention that there is no black matrix in the color filter substrate bonded to the array panel.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

 First embodiment

       FIG. 6 is a plan view of an array substrate of a reflective liquid crystal display according to the present invention, and FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6 and a color filter substrate corresponding thereto.

The array panel for a reflective liquid crystal display device according to the present invention is composed of a substrate, each signal line, a switching element connected to each signal line, and a reflective electrode connected to the switching element, as in a typical array panel. Usually, the switching element uses a thin film transistor.

6 and 7, a gate wiring 102 and a gate electrode 103 made of a conductive material are formed on an insulating substrate 101 such as glass, and the gate wiring 102 is formed. Extends in the horizontal direction, and the gate electrode 103 extends from the gate wiring 102. In addition, the gate wiring 102 may be a single metal layer or a double metal layer.

A gate insulating film 104 made of a silicon nitride film (SiNx) or a silicon oxide film (SiO ₂ ) is covered on the gate wiring 102.

An active layer 105 made of amorphous silicon is generally formed on the gate insulating film 104 on the gate electrode 103, and an ohmic contact layer made of amorphous silicon doped with impurities thereon ( 106 is formed.

On the ohmic contact layer 106, a data line 109 made of a conductive material such as metal and defining a pixel area orthogonal to the gate line 102, a source electrode 107 extending from the data line 109, and A drain electrode 108 facing the source electrode 107 is formed around the gate electrode 103, and the source and drain electrodes 107 and 108 form a thin film transistor T together with the gate electrode 103. .

Subsequently, a passivation layer 110 made of a silicon nitride film or a silicon oxide film, preferably a benzocyclobutene (BCB) or a photo acryl series organic insulating layer, is formed on the data line 109 and the source and drain electrodes 107 and 108. ) Is formed, and a contact hole 111 exposing the drain electrode 108 is formed in the protective layer 110. The reason why the organic insulating film is preferably used as the protective layer 110 in the present invention is to adopt an organic insulating film having a low dielectric constant to reduce parasitic capacitance that may occur between the wiring below and the reflective electrode 112 to be formed later. do.

In this case, after patterning the protective layer 110, the protective layer 110 by dry etching using SF ₆ + O ₂ for about 50 seconds or by oxygen ashing for 150 seconds. The surface may be treated very strongly to form embossing such as a plurality of small irregularities on the surface of the protective layer 110. The effect of the embossing treatment on the upper surface of the protective layer 110 will be described later.

Next, when an opaque conductive metal having excellent reflection characteristics is deposited on the surface of the protective layer 110 having irregularities formed on the surface, the opaque metal is applied in the shape of the surface of the protective layer 110 described above, so that the reflective electrode has an irregular shape. 112 can be formed. Preferably, aluminum is used as the reflective electrode 112. Because the aluminum is used as the reflective electrode 112, since the aluminum has excellent contact with the protective layer 110, the aluminum may be deposited on the curved protective layer without lifting. The reason for processing the surface of the reflective electrode 112 to be embossed is to increase the reflection efficiency but is not essential to the present invention.

Next, an upper substrate 116 formed of a transparent insulating material spaced apart from each other by a predetermined interval is disposed on the array substrate, and a common electrode 115 is formed on a lower front surface thereof. A color filter 120 is formed between the upper substrate 116 and the common electrode 115, and a black matrix is omitted between each color filter 120.

On the other hand, the reflective electrode 112 covers the thin film transistor T, and the boundary is located in the pixel area. This can be seen in FIG. 8, which shows a plurality of pixel regions. As a result, as shown in FIG. 9, the light I incident on the reflective electrode 112 is reflected, but the light II incident between the adjacent reflective electrodes 112 is absorbed in the pixel region and is not reflected again. In addition, the black matrix may be omitted in the color filter substrate bonded to the array substrate.

Second embodiment

10 is a cross-sectional view of a reflective liquid crystal display device according to still another embodiment of the present invention. The second embodiment of the present invention has the same structure as that of the first embodiment except for the lower substrate. Description of the description will be omitted.

As shown in FIG. 10, in the second embodiment of the present invention, a light absorbing body 230 is formed on a transparent glass substrate such as glass.

In the case of the first embodiment, when the light passing through the reflective electrode pattern reaches the lower substrate, due to the difference in refractive index between the protective layer 110 made of the organic layer and the lower substrate 101 which is usually glass. This is because 4% of light can be reflected.

FIG. 11 illustrates a light propagation path in a structure of a BM-free reflective liquid crystal display employing a light absorbing layer 230 to block reflected light due to a difference in refractive index between a glass substrate and other materials. By forming the light absorbing layer 230 on the lower substrate 101 before forming the), it is possible to minimize the reflection of light due to the difference in refractive index.

Accordingly, the light (III) incident between the reflective electrode patterns is absorbed by the light absorbing layer 230, so that even if the black matrix is completely removed from the upper side, there is no need to worry about lowering the contrast ratio or light leakage. .

As described above, when the reflective liquid crystal display device is manufactured according to the exemplary embodiments of the present invention, the following characteristics are present.

First, in the reflection type liquid crystal display device, the boundary of the reflective electrode is formed inside the pixel as well as the data line or the gate line, so that light from the outside is not directly absorbed and re-reflected by the lower layer, thereby not using the black matrix. The liquid crystal display device can be manufactured.

Second, in spite of the above effect, when the light passing through the reflecting plate reaches the lower glass, 4% of the light may be reflected due to the difference in refractive index between the organic film and the glass. Reflection may be minimized by first forming a light absorbing layer on the glass.

Claims (11)

Board; First and second data lines arranged in a first direction on the substrate; 1 and 2 gate lines arranged in a second direction crossing the first and second data lines; A first switching device connected to the first data and the second gate wiring; A second switching element connected to the second data and the second gate wiring; An insulating layer covering each switching element; A first and second reflective electrodes connected to the switching elements and covering the switching elements, wherein the boundary of the first and second reflective electrodes is positioned between the first and second data wires; Panel for LCD Liquid Crystal Display 2 substrates;        A plurality of data and gate wirings crossing each other to define pixel regions;  A plurality of switching elements connected to the data and gate wirings;        An insulating layer covering the plurality of switching elements and the respective wirings;       And a plurality of reflecting electrodes connected to the plurality of switching elements and covering the plurality of switching elements, respectively, wherein a boundary of the plurality of reflecting electrodes is in a pixel region, and one side of the reflecting electrode has a data line adjacent thereto. An array panel for covering the liquid crystal display device, wherein the other side of the reflective electrode facing one side of the reflective electrode does not cover the data line adjacent thereto;        The method according to any one of claims 1 and 2 An array panel for a reflective liquid crystal display device including a light absorption layer at a position corresponding to a boundary of each of the reflective electrodes between the substrate and the gate wiring.        The method according to any one of claims 1 and 2, Each switching element includes a thin film transistor including a gate electrode, a source electrode and a drain electrode, and an active layer.         The method according to any one of claims 1 and 2,        Each reflective electrode is connected to the drain electrode through a contact hole formed in the insulating layer.       The method according to any one of claims 1 and 2, The insulating layer is an array panel for a reflective liquid crystal display device, which is an organic insulating layer such as benzocyclobutene (BCB) or an acrylic resin (resin).        The method according to any one of claims 1 and 2, An upper surface of the reflective electrode is a concave-convex shape array panel for reflective liquid crystal display device       A first substrate, first and second data wirings arranged in a first direction on the first substrate, first and second gate wirings arranged in a second direction crossing the first and second data wirings, and A first switching device connected to first data and first gate wirings, a second switching device connected to the second data and first gate wirings, an insulating layer covering each of the switching devices, and an upper portion of the insulating layer An array panel for a liquid crystal display device connected to the switching elements and covering the switching elements, the first and second reflecting electrodes having a boundary between the first and second reflecting electrodes; A reflective liquid crystal display device including a color filter substrate bonded to the array panel and having a second substrate, a plurality of color filters formed on the second substrate, and a common electrode on the color filter, the common electrode facing the reflective electrode.      The method of claim 8,      The color filter substrate is a reflection type liquid crystal display device without a black matrix      The method of claim 8,      One side of the first reflective electrode overlaps the first data line, and the other side of the first reflective electrode facing one side of the first reflective electrode is spaced apart from the second data line.      The method of claim 1,      One side of the first reflective electrode overlaps the first data line, and the other side of the first reflective electrode facing one side of the first reflective electrode is spaced apart from the second data line. Array panel.

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