KR20110061136A - In plane switching mode liquid crystal display device - Google Patents

Abstract

PURPOSE: An in-plane switching mode liquid crystal display device is provided to increase the luminance of a liquid crystal display device and to increase the aperture ratio. CONSTITUTION: A liquid crystal layer is formed between a first substrate and a second substrate. A gate line(110) and a dataline(130) are arranged in order to cross with each other on the first substrate. A thin film transistor is formed in the area in which the gate line and the data line cross. A pixel electrode(145) is connected to the thin film transistor. Common electrodes are parallel arranged with the pixel electrode.

Description

Transverse electric field type liquid crystal display device {In Plane Switching mode Liquid Crystal Display Device}

The present invention relates to a liquid crystal display device, and more particularly, to a transverse electric field type liquid crystal display device.

Liquid crystal display devices have a wide range of applications ranging from notebook computers, monitors, spacecrafts, aircrafts, etc. to the advantages of low power consumption and low power consumption.

The liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the two substrates, and the arrangement of the liquid crystal layers is adjusted according to whether an electric field is applied, and thus the light transmittance is adjusted to display an image. .

Such liquid crystal display devices have been developed in various ways such as twisted nematic (TN) mode, in plane switching (IPS) mode, and vertical alignment (VA) mode according to a method of controlling the arrangement of the liquid crystal layer.

The IPS mode is a method of controlling the arrangement of the liquid crystal layer through a horizontal electric field by arranging the electrodes forming the electric field in parallel on the same substrate. Also called.

Hereinafter, a conventional transverse electric field type liquid crystal display device will be described with reference to the drawings.

1A and 1B are schematic cross-sectional views of a conventional transverse electric field type liquid crystal display device. 1A and 1B are for explaining the principle of a transverse electric field type liquid crystal display device. FIG. 1A shows a state in which an electric field is not applied, and FIG. 1B shows a state in which an electric field is applied.

As shown in FIGS. 1A and 1B, a conventional transverse electric field type liquid crystal display device includes a lower substrate 10, an upper substrate 20, and a liquid crystal layer 30 formed between both substrates 10 and 20. Is done.

On one surface of the lower substrate 10, the common electrode 12 and the pixel electrode 14 are arranged in parallel with each other at predetermined intervals to form an electric field in the horizontal direction.

In addition, a lower alignment layer 16 and an upper alignment layer 26 are formed on one surface of the lower substrate 10 and one surface of the upper substrate 20 for initial alignment of the liquid crystal layer 30. The lower alignment layer 16 and the upper alignment layer 26 are aligned in a predetermined rubbing direction.

In addition, the lower polarizing plate 18 and the upper polarizing plate 28 are formed on the other surface of the lower substrate 10 and the other surface of the upper substrate 20, respectively. The lower polarizer 18 and the upper polarizer 28 are formed such that their optical axes are perpendicular to each other.

The principle of operation of such a transverse electric field type liquid crystal display device will be described below.

As shown in FIG. 1A, when no electric field is applied between the common electrode 12 and the pixel electrode 14, the liquid crystal layer 30 maintains an initial arrangement. In this case, the light incident from below passes through the lower polarizing plate 18 and then passes through the liquid crystal layer 30 so that rotation of the polarization direction is not performed. Accordingly, the lower polarizing plate 18 and the optical axis are perpendicular to each other. The upper polarizer 28 does not transmit. Thus, the image is in a black state.

As shown in FIG. 1B, when an electric field is applied between the common electrode 12 and the pixel electrode 14, the arrangement state of the liquid crystal layer 30 is changed. Specifically, the liquid crystal layer 30 rotates in the electric field direction between the common electrode 12 and the pixel electrode 14 in the vicinity of the lower substrate 10, but the influence of the electric field in the vicinity of the upper substrate 20. This decreases the liquid crystal layer 30 from rotating. In this case, the light incident from below passes through the lower polarizing plate 18 and passes through the liquid crystal layer 30 to be rotated in the polarization direction, whereby the upper polarizing plate having an optical axis perpendicular to the lower polarizing plate 18. It passes through (28). Thus, the image is in a white state.

However, such a transverse electric field type liquid crystal display has a problem that the aperture ratio decreases and thus the luminance decreases, which will be described in detail below.

FIG. 2A is a schematic plan view of a lower substrate of a conventional transverse electric field liquid crystal display device, and FIG. 2B is a cross-sectional view of a conventional transverse electric field liquid crystal display device corresponding to a cross section of the line I-I of FIG. 2A.

As shown in FIGS. 2A and 2B, a gate line 11, a data line 13, a common electrode 12, and a pixel electrode 14 are formed on the lower substrate 10.

The gate line 11 is arranged in a horizontal direction, the data line 13 is arranged in a vertical direction, and a thin film transistor as a switching element in a region where the gate line 11 and the data line 13 intersect. (T) is formed.

The common electrode 12 is branched from a common line 12a arranged in the horizontal direction, and the pixel electrode 14 is arranged to be parallel to the common electrode 12 while being connected to the thin film transistor T. .

Reference numeral 15, which is not explained, is an insulating layer for insulating the electrodes.

On the other hand, since the region where the image is displayed in the liquid crystal display device is a pixel region, light is transmitted to a region other than the pixel region, for example, the gate line 11, the data line 13, and the thin film transistor T forming region. It should be prevented from leaking, and the light shielding layer 22 is formed in the upper substrate 20 for that purpose.

However, although the light blocking layer 22 is formed on the upper substrate 20 as described above, light leakage is prevented. However, the aperture ratio of the liquid crystal display is reduced, resulting in a problem that the luminance is lowered.

In particular, in the conventional transverse electric field type liquid crystal display device, light leakage occurs severely in the vicinity of the data line 13, and thus the light blocking layer is extended to a region corresponding to a substantially wide width to the left and right of the data line 13 as shown in FIG. 2B. (22) is formed so that the opening ratio reduction width of the liquid crystal display device is increased.

In this regard, if the electric field is not applied between the common electrode 12 and the pixel electrode 14, the liquid crystal is maintained in the rubbing direction and thus the image becomes black. When an electric field is applied between 12) and the pixel electrode 14, the arrangement of the liquid crystal is changed in the electric field direction and thus the image becomes white.

On the other hand, since the data line 12 is arranged in the same direction as the common electrode 12 and the pixel electrode 14, a horizontal electric field is generated on the left and right sides of the data line 12 when an electric field is applied, and accordingly, the area is Also, the arrangement of the liquid crystals is changed so that the image becomes white and light leakage occurs severely. As described above, since the data line 12 formation region is not a pixel region, light leakage must be blocked to the region. Thus, since light leakage occurs severely on the left and right sides of the data line 12 to prevent light leakage. As shown in FIG. 2B, the width of the light shielding layer 22 should be large, thereby decreasing the aperture ratio of the liquid crystal display device, thereby lowering the luminance.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a transverse electric field type liquid crystal display device having improved luminance by increasing the aperture ratio.

The present invention, in order to achieve the above object, a first substrate and a second substrate; A liquid crystal layer formed between the first substrate and the second substrate; A gate line and a data line arranged to cross each other on the first substrate; A thin film transistor formed at an area where the gate line and the data line cross each other; A pixel electrode connected to the thin film transistor; A common electrode arranged in parallel with the pixel electrode; And a light leakage prevention layer formed to overlap the data line and preventing light leakage.

The light leakage preventing layer may be electrically connected to the data line. In this case, the light leakage prevention layer may include a protrusion at a predetermined area, and the data line may have a protrusion at a position corresponding to the protrusion of the light leakage prevention layer. The protrusion of the light leakage preventing layer and the protrusion of the data line may be connected to each other. In addition, a semiconductor layer may be formed between the light leakage preventing layer and the data line, and the semiconductor layer may be formed in a region other than a region in which a protrusion of the light leakage prevention layer and a protrusion of the data line are formed.

The light leakage preventing layer may extend in the same direction as the data line with a width greater than that of the data line.

The light leakage preventing layer may be formed on the same layer as the gate line.

The common electrode includes a first common electrode formed at an outermost position of one pixel adjacent to the data line and a second common electrode formed between the first common electrode, and the first common electrode and the second common electrode. The common electrode may be formed on different layers, and in this case, the first common electrode may be formed to overlap the light leakage preventing layer in a predetermined region. In addition, the first common electrode may be formed on the same layer as the pixel electrode, and the second common electrode may be formed on the same layer as the gate line. In addition, a light blocking layer may be formed on the second substrate, and the light blocking layer may be formed to overlap a portion of the first common electrode.

According to the present invention as described above has the following effects.

According to the present invention, light leakage is prevented in the vicinity of the data line by forming a light leakage prevention layer to overlap the data line. As described above, in the present invention, since light leakage can be prevented in the vicinity of the data line of the lower substrate, the width of the light shielding layer formed on the upper substrate can be reduced, and the aperture ratio is increased, and thus the brightness of the liquid crystal display device is improved. There is.

In addition, according to the present invention, by forming the light leakage preventing layer electrically connected to the data line, generation of parasitic capacitance by the data line and the light leakage preventing layer can be prevented and the resistance of the line can be reduced.

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

FIG. 3 is a schematic plan view of a lower substrate of a transverse electric field type liquid crystal display according to an exemplary embodiment of the present invention, showing only two pixels neighboring each other.

As can be seen in Figure 3, the lower substrate of the transverse electric field type liquid crystal display device according to an embodiment of the present invention, the first substrate 100, the gate line 110, the common line 120, the data line 130 , The thin film transistor T, the pixel electrode 145, the common electrodes 125a and 125b, and the light leakage preventing layer 118.

The gate line 110 and the common line 120 are arranged in a first direction, specifically, in a horizontal direction. The gate line 110 and the common line 120 may be formed of the same material in the same layer.

The data lines 130 are arranged in a second direction different from the first direction, specifically, in the vertical direction. Therefore, the data line 130 crosses the gate line 110 and the common line 120 which are arranged in the horizontal direction, respectively. The data line 130 may be configured in a straight line shape as shown, but is not necessarily limited thereto, and may be configured in a curved straight line shape.

The thin film transistor T is formed in an area where the gate line 110 and the data line 130 cross each other, and the gate electrode 112, the semiconductor layer 115, the source electrode 132, and the drain electrode ( 134).

The gate electrode 112 extends from the gate line 110.

The source electrode 132 extends from the data line 130, and the drain electrode 134 is spaced apart from the source electrode 132 at predetermined intervals.

The semiconductor layer 115 is disposed above the gate electrode 112 and below the source / drain electrodes 132 and 134, that is, between the gate electrode 112 and the source / drain electrodes 132 and 134. Is formed on the layer of.

The pixel electrode 145 is connected to the drain electrode 134 of the thin film transistor T. In detail, the pixel electrode 145 is formed on a passivation layer having a predetermined contact hole, and is connected to the drain electrode 134 through the contact hole.

The common electrodes 125a and 125b are connected to the common line 120 and arranged in parallel with the pixel electrode 145.

The pixel electrode 145 and the common electrodes 125a and 125b are arranged in parallel with each other in a second direction, that is, in a vertical direction, similarly to the data line 130 to generate a horizontal electric field, and such a horizontal electric field. By the arrangement of the liquid crystal layer is controlled.

The common electrodes 125a and 125b may include a first common electrode 125a and a second common electrode 125b. The first common electrode 125a is formed at a position closest to the data line 130, that is, at a position corresponding to the outermost portion of one pixel, and the second common electrode 125b is formed on the first common electrode. It is formed at a position between the 125a.

The first common electrode 125a is formed on a layer different from the common line 120, for example, the same layer as the pixel electrode 145, and one end of the first common electrode 125a is formed on the common line ( 120). That is, a gate insulating film and a passivation layer may be formed between the first common electrode 125a and the common line 120. Contact holes are formed in the gate insulating layer and the passivation layer, and the first hole is formed through the contact hole. The common electrode 125a and the common line 120 may be connected. The first common electrode 125a generates a horizontal electric field together with the pixel electrode 145 and prevents cross talk between the data line 130 and the pixel electrode 145. It plays a role. In addition, the first common electrode 125a may be formed to overlap the light leakage preventing layer 118 in a predetermined region.

The second common electrode 125b is formed on the same layer as the common line 120 and extends from the common line 120. The second common electrode 125b serves to generate a horizontal electric field together with the pixel electrode 145.

The light leakage preventing layer 118 is formed to overlap the data line 130 to prevent light leakage occurring near the data line 130. The light leakage prevention layer 118 has a width larger than that of the data line 130. It may be formed extending in the same direction as the data line 130.

The light leakage preventing layer 118 may be formed of the same material on the same layer as the gate line 110 and the common line 120. Thus, as shown, the light leakage prevention layer 118 may be formed on the data line. It is formed extending in the same direction as 130, but is discontinuously formed so as not to be connected to the gate line 110 and the common line 120.

The light leakage preventing layer 118 may be formed to be electrically connected to the data line 130. That is, a gate insulating layer may be formed between the light leakage preventing layer 118 and the data line 130. A contact hole is formed in the gate insulating layer, so that the light leakage preventing layer 118 and the data line are formed through the contact hole. 130 may be connected. As such, when the light leakage preventing layer 118 is electrically connected to the data line 130, generation of parasitic capacitance by the data line 130 and the light leakage prevention layer 118 may be prevented.

Hereinafter, a transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 4A and 4B.

4A is a schematic cross-sectional view of a transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention, which corresponds to a cross section of the A-A line of FIG. 3.

As can be seen in FIG. 4A, a transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention includes a first substrate 100, a second substrate 200, and the first substrate 100 and the second substrate 200. It comprises a liquid crystal layer 300 formed between.

The gate electrode 112 and the second common electrode 125b are formed on the first substrate 100.

A gate insulating layer 113 is formed on an entire surface of the first substrate 100 including the gate electrode 112 and the second common electrode 125b.

The semiconductor layer 115 is formed on the gate insulating layer 113, and the source electrode 132 and the drain electrode 134 are formed on the semiconductor layer 115.

The semiconductor layer 115 includes an ohmic contact layer doped with an impurity in a portion in contact with the source electrode 132 and the drain electrode 134, and the source electrode 132 and the drain electrode 134 are provided at predetermined intervals. Spaced apart.

A passivation layer 137 is formed on an entire surface of the first substrate 100 including the source electrode 132 and the drain electrode 134. The passivation layer 137 is provided with a contact hole 138 in a predetermined area so that the drain electrode 137 can be exposed.

The pixel electrode 145 is formed on the passivation layer 137. The pixel electrode 145 is connected to the drain electrode 134 through the contact hole 138 provided in the passivation layer 137.

The light blocking layer 210 is formed on the second substrate 200. The light blocking layer 210 serves to block leakage of light to a region other than the pixel region, and has a matrix structure.

The color filter layer 230 is formed between the light blocking layers 210. The color filter layer 230 includes a color filter layer of red (R), green (G), and blue (B).

An overcoat layer 250 is formed on the color filter layer 230 to planarize the substrate.

FIG. 4B is a schematic cross-sectional view of a transverse electric field type liquid crystal display device according to an exemplary embodiment corresponding to a cross section of the BB line of FIG. 3, near the data line 130 where the light leakage preventing layer 118 is formed. Corresponding cross section.

As shown in FIG. 4B, the light leakage preventing layer 118 is formed on the first substrate 100. The light leakage preventing layer 118 is formed of the same material on the same layer as the gate electrode 112 and the second common electrode 125b described with reference to FIG. 4A.

The gate insulating layer 113 is formed on the light leakage preventing layer 118. In the gate insulating layer 113, a contact hole 114 is formed in a predetermined region so that the light leakage preventing layer 118 is exposed.

The data line 130 is formed on the gate insulating layer 113. The data line 130 is connected to the light leakage preventing layer 118 through a contact hole 114 provided in the gate insulating layer 113.

A passivation layer 137 is formed on the data line 130, and a first common electrode 125a is formed on the passivation layer 137. The first common electrode 125a may be formed to overlap the light leakage preventing layer 118 in a predetermined region.

The light blocking layer 210, the color filter layer 230, and the overcoat layer 250 are sequentially formed on the second substrate 200.

Here, the light blocking layer 210 serves to prevent light leakage as described above. Since the light leakage preventing layer 118 is formed on the first substrate 100, the light blocking layer 210 is formed. It can be formed with a relatively small width. That is, the light blocking layer 210 may be formed to have a width slightly larger than the width of the light leakage preventing layer 118, and may be formed to overlap a part of the first common electrode 125a, for example.

Each of the configurations described above can be patterned through various methods known in the art to a variety of materials known in the art. Hereinafter, examples of the material and the pattern forming method of the respective components will be described, but are not necessarily limited thereto.

The gate line 110, the common line 120, the data line 130, the electrodes connected to the lines, and the light leakage preventing layer 118 are formed of molybdenum (Mo), aluminum (Al), and chromium (Cr). ), Gold (Au), titanium (Ti), nickel (Ni), neodium (Nd), copper (Cu), or alloys thereof, and may be composed of a single layer or two or more layers of the metal or alloy. Can be done.

The gate insulating layer 113 and the protective layer 137 may be formed of a silicon oxide layer (SiOx) or a silicon nitride layer (SiNx), and may be formed of a single layer or two or more layers of the oxide layer or nitride layer.

The semiconductor layer 115 may include amorphous silicon or crystalline silicon. In addition, the semiconductor layer 115 may include an ohmic contact layer doped with impurities in a region in contact with the source electrode 132 and the drain electrode 134.

The pixel electrode 145 may be made of a transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO), and the first common electrode 125a may also be the pixel electrode 145. Like) can be made of a transparent conductive material.

Each of these components may be patterned through a so-called photolithography process in which exposure, development, and etching are performed using photoresist (PR). Further, in addition to the photolithography process, screen printing, inkjet printing, gravure printing, gravure offset printing, reverse offset printing using reverse metal pastes The pattern may be formed through a printing process such as offset printing, flexo printing, or microcontact printing.

FIG. 5 is a schematic plan view of a lower substrate of a transverse electric field liquid crystal display according to another exemplary embodiment of the present invention, and FIG. 6A is a transverse electric field method according to another exemplary embodiment of the present invention corresponding to a cross section taken along line AA of FIG. FIG. 6B is a schematic cross-sectional view of a transverse electric field type liquid crystal display device according to another exemplary embodiment of the present invention, which corresponds to a cross section of the BB line of FIG. 5.

As described above, the transverse electric field type liquid crystal display device according to another exemplary embodiment of the present invention illustrated in FIGS. 5, 6A, and 6B includes a semiconductor layer 115 between the light leakage preventing layer 118 and the data line 130. This is further formed according to the embodiment of the present invention shown in FIGS. 3, 4A and 4B except that the electrical connection structure between the light leakage preventing layer 118 and the data line 130 is changed. It is the same as the transverse electric field type liquid crystal display device. Therefore, the same reference numerals are assigned to the same components, and detailed description of the same components will be omitted.

According to another embodiment of the present invention, the semiconductor layer 115 is formed in an area where the gate line 110 and the data line 130 cross each other to form a thin film transistor and to the area where the data line 130 is formed. It is formed to extend.

That is, as shown in FIG. 6A, the semiconductor layer 115 is formed between the gate insulating layer 113 and the source / drain electrodes 132 and 134 to form a thin film transistor, and as shown in FIG. 6B, the semiconductor The layer 115 is also formed between the gate insulating layer 113 and the data line 130.

As such, when the semiconductor layer 115 is formed between the gate insulating layer 113 and the data line 130, the light leakage preventing layer 118 formed under the gate insulating layer 113 may be formed with the data line 130. In order to make electrical connections, structural changes are necessary.

Thus, as shown in FIG. 5, the data line 130 has a protrusion 130a formed in a predetermined region, and the light leakage preventing layer 118 also corresponds to the protrusion 130a of the data line 130. A protrusion 118a is formed at an upper portion thereof, and an electrical connection is formed between the protrusion 118a of the light leakage preventing layer 118 and the protrusion 130a of the data line 130.

Specifically, as shown in FIG. 6B, protrusions 118a of the light leakage preventing layer 118 and protrusions 130a of the data line 130 are formed in regions where the semiconductor layer 115 is not formed. The protrusion 118a of the light leakage preventing layer 118 and the protrusion 130a of the data line 130 are electrically connected to each other through the contact hole 114 formed in the gate insulating layer 113.

However, when the width of the light leakage preventing layer 118 is formed to be large, the protrusion 130a is formed only on the data line 130 so that the protrusion 130a and the light leakage preventing layer 118 of the data line 130 are formed. Although electrically connected, in this case, the aperture ratio may decrease as the width of the light leakage preventing layer 118 increases.

1A and 1B are schematic cross-sectional views of a conventional transverse electric field type liquid crystal display device.

FIG. 2A is a schematic plan view of a lower substrate of a conventional transverse electric field liquid crystal display device, and FIG. 2B is a cross-sectional view of a conventional transverse electric field liquid crystal display device corresponding to a cross section of the line I-I of FIG. 2A.

3 is a schematic plan view of a lower substrate of a transverse electric field type liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 4a is a transverse electric field method according to an embodiment of the present invention corresponding to a cross section taken along line AA of FIG. 3. FIG. 4B is a schematic cross-sectional view of a transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention, which corresponds to a cross section of the BB line of FIG. 3.

FIG. 5 is a schematic plan view of a lower substrate of a transverse electric field liquid crystal display according to another exemplary embodiment of the present invention, and FIG. 6A is a transverse electric field method according to another exemplary embodiment of the present invention corresponding to a cross section taken along line AA of FIG. FIG. 6B is a schematic cross-sectional view of a transverse electric field type liquid crystal display device according to another exemplary embodiment of the present invention, which corresponds to a cross section of the BB line of FIG. 5.

<Description of the code | symbol about the structure of the principal part of drawing>

110: gate line 115: semiconductor layer

118: light leakage prevention layer 120: common line

125a and 125b: first and second common electrodes

130: data line 145: pixel electrode

Claims (10)

A first substrate and a second substrate; A liquid crystal layer formed between the first substrate and the second substrate; A gate line and a data line arranged to cross each other on the first substrate; A thin film transistor formed at an area where the gate line and the data line cross each other; A pixel electrode connected to the thin film transistor; A common electrode arranged in parallel with the pixel electrode; And And a light leakage prevention layer formed to overlap the data line to prevent light leakage. The method of claim 1, The light leakage preventing layer is electrically connected to the data line. The method of claim 2, The light leakage preventing layer is provided with a protrusion in a predetermined region, the data line is provided with a protrusion corresponding to the protrusion of the light leakage prevention layer, the protrusion of the light leakage prevention layer and the protrusion of the data line is connected to each other. Transverse electric field type liquid crystal display device. The method of claim 3, wherein And a semiconductor layer is formed between the light leakage preventing layer and the data line, wherein the semiconductor layer is formed in a region other than a region where a protrusion of the light leakage prevention layer and a protrusion of the data line are formed. The method of claim 1, And the light leakage preventing layer extends in the same direction as the data line with a width larger than the width of the data line. The method of claim 1, The light leakage preventing layer is formed on the same layer as the gate line. The method of claim 1, The common electrode includes a first common electrode formed at an outermost position of one pixel adjacent to the data line and a second common electrode formed between the first common electrode, and the first common electrode and the second common electrode. The common electrode is a transverse electric field type liquid crystal display device, characterized in that formed on different layers. The method of claim 7, wherein And the first common electrode is overlapped with the light leakage preventing layer in a predetermined region. The method of claim 7, wherein And the first common electrode is formed on the same layer as the pixel electrode, and the second common electrode is formed on the same layer as the gate line. The method of claim 7, wherein A light blocking layer is formed on the second substrate, and the light blocking layer is formed to overlap a part of the first common electrode.

Images