KR101338109B1 - Liuquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, comprising: a first substrate and a second substrate; Gate lines and data lines arranged vertically and horizontally on the first substrate to define a plurality of pixels; A thin film transistor formed at an intersection of the gate line and the data line of the first substrate; A sealing member formed at an outer portion of the first substrate and the second substrate to bond the first substrate and the second substrate to each other; A black matrix formed in an image non-display area of the first substrate, the matrix formed in a sealing area in which the gate line and the data line between the pixel and the pixel, the lower portion of the thin film transistor, and the sealing material are formed; And a ground connection connected to the black matrix to ground the black matrix.

LCD, Black Matrix, Ground, Voltage, Metal Layer

Description

Liquid crystal display device {LIUQUID CRYSTAL DISPLAY DEVICE}

1 is a plan view showing the structure of a conventional liquid crystal display device.

2 is a view showing a characteristic curve of a thin film transistor of a conventional liquid crystal display device.

3 is a plan view showing the structure of a liquid crystal display device according to the present invention;

4 is a cross-sectional view showing a pixel structure of a liquid crystal display device according to the present invention.

5 is a cross-sectional view taken along line II ′ of FIG. 3.

6 is a view showing a characteristic curve of a thin film transistor of a liquid crystal display according to the present invention.

Description of the Related Art [0002]

103,105 substrate 109 black matrix

131: gate electrode 136: source electrode

137: drain electrode 142,144,146 insulation layer

148 protective layer 150 liquid crystal layer

153: color filter layer 160: ground connection

162: metal layer 164: metal wiring

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of preventing the deterioration of characteristics of a thin film transistor by grounding a black matrix formed on a lower substrate.

Liquid crystal display devices are transmissive flat panel displays, and are widely applied to various electronic devices such as mobile phones, PDAs, and notebook computers. Such liquid crystal display devices are light and small in size, and can realize high image quality. Therefore, many practical use is being made compared to other flat panel display devices. In addition, as the demand for digital TVs, high-definition TVs, and wall-mounted TVs increases, studies on large-area liquid crystal display devices applicable to TVs are being actively conducted.

In general, the liquid crystal display device can be divided into several methods depending on the method of operating the liquid crystal molecules, but nowadays the thin film transistor liquid crystal display device is mainly used in view of the fast reaction speed and low afterimage. .

1 is a plan view showing the structure of such a liquid crystal display device. As shown in FIG. 1, the liquid crystal display device 1 is composed of a first substrate 3, a second substrate 5, and a liquid crystal layer 17 formed therebetween, and the first substrate 3. ), The gate line 11 and the data line 13 are arranged vertically and horizontally to define a plurality of pixels. Each gate line 11 and data line 13 is electrically connected to an external driving element (not shown) through pads 12 and 14 formed in the non-display area of the first substrate 3. In addition, as the scanning signal is applied through the gate line 11 in each pixel, the thin film transistor 15 is switched to apply an image signal input through the data line 13 to the liquid crystal layer 17. do.

In the outer portions of the first substrate 3 and the second substrate 5, a sealing region 7 coated with a sealing material 22 is formed, and the first substrate 3 and the first substrate 3 are formed by the sealing material 22. The substrate 5 is bonded. At this time, as shown in the figure, a black matrix 9 as a light blocking means is formed in the sealing region 7 to prevent light from being transmitted to the sealing region 7. The black matrix 9 is formed on the second substrate 5 and is formed in the image non-display area and the sealing area 7 between the pixels. In addition, although not shown in the drawing, the black matrix 9 is formed in the region of the thin film transistor 15 to block light from being transmitted to the non-display area of the liquid crystal display device.

Although not shown in the figure, a color filter layer is formed on the pixel. The color filter layer is an R (Red), G (Green), B (Blue) color filter layer to implement an image of the actual liquid crystal display device, and is formed between the black matrix (9).

In the liquid crystal display device configured as described above, when light is supplied from a light source provided outside the first substrate 3 to the liquid crystal panel, an image is realized by adjusting the transmittance of light passing through the liquid crystal layer by the liquid crystal molecules of the liquid crystal layer. In this case, the actual image is implemented while passing through the color filter layer.

However, the following problems occur in the liquid crystal display device having the above structure.

The black matrix 9 is for preventing light from leaking into the image non-display area and degrading the image quality. However, since the black matrix 9 is formed on the second substrate 5, the area of the black matrix 9 is set to completely block light transmitted through the liquid crystal layer through the first substrate 3 at an angle. It must be wider than the non-image display area. In addition, when the first substrate 3 and the second substrate 5 are bonded, the area of the black matrix 9 must be further widened because a bonding margin is required. However, when the area of the black matrix 9 increases as described above, there is a fatal weakness that the aperture ratio of the liquid crystal display device decreases.

In order to prevent such a decrease in the aperture ratio, recently, a liquid crystal display device in which a black matrix 9 is formed on the first substrate 3 has been proposed. However, the liquid crystal display device having the structure in which the black matrix 9 is formed on the first substrate 3 has the following problems.

As shown in FIG. 1, the black matrix 9 has a matrix shape throughout the first substrate 3. In other words, the black matrix 9 is connected over the entire first substrate 3. Meanwhile, the black matrix 9 is made of an opaque metal under the gate line and the data line between the pixel and the lower part of the thin film transistor. Accordingly, the black matrix 9 functions as a matrix floating electrode in the first substrate 3, and a voltage is induced therein by signals applied to data lines and gate lines. However, since the black matrix 9 is located under the thin film transistor, the voltage induced in the black matrix 9 affects the channel layer of the thin film transistor. That is, as shown in FIG. 2, as the data voltage is applied, a voltage is induced in the black matrix 9, and the threshold voltage of the thin film transistor is shifted by the induced voltage, thereby causing a change in device characteristics. The change is a major cause of defective liquid crystal display elements.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described object, and an object of the present invention is to provide a liquid crystal display device capable of grounding the black matrix formed under the thin film transistor to prevent deterioration of characteristics of the thin film transistor due to an induced voltage.

In order to achieve the above object, the liquid crystal display device according to the present invention comprises a first substrate and a second substrate; Gate lines and data lines arranged vertically and horizontally on the first substrate to define a plurality of pixels; A thin film transistor formed at an intersection of the gate line and the data line of the first substrate; A sealing member formed at an outer portion of the first substrate and the second substrate to bond the first substrate and the second substrate to each other; A black matrix formed in an image non-display area of the first substrate, the matrix formed in a sealing area in which the gate line and the data line between the pixel and the pixel, the lower portion of the thin film transistor, and the sealing material are formed; And a ground connection connected to the black matrix to ground the black matrix.

The ground connection part may include a metal layer extending from the black matrix and a metal wiring connected to the metal layer, thereby preventing the induced voltage from occurring in the black matrix when a voltage is applied to the data line, thereby preventing the characteristics of the thin film transistor from being changed. Will be.

Hereinafter, a liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a plan view showing the structure of a liquid crystal display device according to the present invention. As shown in FIG. 3, the liquid crystal display device 101 according to the present invention includes a first substrate 103, a second substrate 105, and a liquid crystal layer 117 formed therebetween. The first substrate 103 is provided with a gate line 111 and a data line 113 arranged vertically and horizontally to define a plurality of pixels. Each gate line 111 and data line 113 is electrically connected to an external driving device through pads 112 and 114 formed in a non-display area of the first substrate 103. In addition, as the scan signal is applied to each pixel through the gate line 111, the thin film transistor 115 is switched to apply an image signal input through the data line 113 to the liquid crystal layer 117.

Sealing regions 7 coated with a sealing material 122 are formed at outer portions of the first substrate 103 and the second substrate 105, and the first substrate 103 and the first substrate 103 are formed by the sealing material 122. The substrate 105 is bonded.

The black matrix 109 is formed in the image non-display area of the first substrate 103. In this case, the image non-display area is formed between the pixel and the pixel, the region and the outer portion of the thin film transistor 115, and the black matrix 109 is formed in a matrix shape.

The ground connection part 160 is formed in the outer region of the first substrate 103. The ground connector 160 is for grounding the black matrix 109, and is for flowing a voltage induced in the black matrix 109 to the ground when a signal is applied to the data line 113. The ground connection unit 160 may include a metal layer 152 extending from the black matrix 109, a metal wire connecting the metal layer 152 and a printed circuit board or an external case to ground the voltage of the black matrix 109. 164).

The liquid crystal display device having the above structure will be described in more detail with reference to the cross-sectional views of FIGS. 4 and 5. In this case, although the liquid crystal display device is composed of a plurality of pixels, only one pixel is shown in the drawing for convenience of description.

As shown in FIG. 4, the black matrix 109 is formed on the first substrate 103, and the first insulating layer 142 is formed thereon, and the channel region 132 and the source region 133 are formed thereon. A semiconductor layer consisting of the drain region 134 is formed.

The black matrix 109 is a metal layer such as Cr, CrOx, Mo, and AlNd. The black matrix 109 is formed by laminating opaque metals such as Cr, CrOx, Mo, and AlNd on the first substrate 103, and then etching the same by photolithography. Is formed. The first insulating layer 142 is an inorganic layer, such as SiO ₂ or SiNx, and is formed by chemical vapor deposition. The semiconductor layer is formed by stacking and patterning polycrystalline silicon on the first insulating layer 142 as a polycrystalline silicon layer and then doping impurities into the source region 133 and the drain region 134. In the drawing, the black matrix 109 is formed only on the thin film transistor, but the black matrix 109 is substantially formed over the entire image non-display area on the first substrate 103.

 In addition, the polysilicon layer may be formed of polysilicon through a crystallization process of applying heat or irradiating ultraviolet rays after applying and patterning amorphous silicon on the first insulating layer 142. In this case, the source region 133 and the drain region 134 are doped with impurities to form an impurity region.

A second insulating layer 144 is formed on the semiconductor layer, and a gate electrode 131 is formed thereon. The second insulating layer 144 is an inorganic layer such as SiO ₂ or SiNx, and is formed by laminating the entire first substrate 103 by chemical vapor deposition. In addition, the gate electrode 131 is formed by laminating a metal having low resistance over the entire second insulating layer 144 and then etching the same by a photolithography method.

The third insulating layer 146 is formed on the gate electrode 131. The third insulating layer 146 is an inorganic layer such as SiO ₂ or SiNx and is formed by laminating the entire first substrate 103 by a chemical vapor deposition method. In this case, the third insulating layer 146 on the source region 133 and the drain region 134 is etched to form a contact hole, respectively, in the contact holes formed in the source region 133 and the drain region 134. The source electrode 136 and the drain electrode 137 are formed.

The source electrode 136 and the drain electrode 137 are formed by depositing a metal such as Al alloy, Cr, Mo, or the like having low resistance on the third insulating layer 145 by vapor deposition or sputtering, and then using a photolithography method using a mask. By etching.

A passivation layer 148 is formed on the source electrode 136 and the drain electrode 137, and the pixel electrode 150 is formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). Is formed. In this case, the pixel electrode 150 is electrically connected to the drain electrode 137 through a contact hole formed in the protective layer 148.

The protective layer 148 may be made of an inorganic material such as SiO ₂ or SiNx, or may be made of an organic material having a low dielectric constant such as photoacrylic or benzocyclobutene (BCB).

The color filter layer 153 is formed on the second substrate 105. The color filter layer 153 is composed of R (Red), G (Green), and B (Blue) color filter layers to realize an actual image. In addition, the first substrate 103 and the second substrate 105 are bonded to each other, and a liquid crystal layer 155 is formed therebetween.

 In addition, although not shown in the drawing, a common electrode made of a transparent conductive material is formed on the color filter layer 153, and an alignment film applied with an alignment control force is applied to the first substrate 103 and the second substrate 105 to form a liquid crystal layer. The liquid crystal of (155) is oriented in a desired direction.

As described above, in the present invention, since the black matrix 109 is formed in the image non-display area in which the thin film transistor of the first substrate 103 is formed, even when the light passing through the liquid crystal layer through the backlight is incident at a constant angle. It is possible to prevent light from passing through the image non-display area. Further, since the bonding margin of the first substrate 103 and the second substrate 105 is not taken into consideration, it is possible to effectively prevent the small area from penetrating into the image non-display area.

FIG. 5 is a cross-sectional view taken along line II ′ of FIG. 3 and illustrates the structure of the ground connection part 160. In this case, the structure of the second substrate 105 is omitted, and only the structure of the first substrate 103 is illustrated.

As shown in FIG. 5, contact holes 165 are formed in the first to third insulating layers 142, 144, and 148 formed on the metal layer 162 extending from the black matrix 109 on the first substrate 103. The matrix 109 is exposed to the outside, and the metal wiring 164 is formed in the exposed black matrix 109 and the contact hole 165. In this case, the metal layer 162 is made of the same material as the black matrix 109, that is, metal such as Cr, CrOx, Mo, and AlNd.

Although not shown in the drawing, the metal wiring 164 extends to a pad region in which the pads 112 and 114 of the first substrate 103 are formed and is connected to a printed circuit board or is connected to an outer case of the liquid crystal display by a separate connection means. Connected.

The metal wire 164 may be formed by a separate process, but it may be formed of the same metal by the same process as the source electrode 136 and the drain electrode 137 of the thin film transistor. However, the structure of the metal wire 164 is not limited to the illustrated structure. The illustrated structure represents an example of the ground connection 160 of the present invention, the present invention is not limited to this structure. That is, the metal wiring 164 of the present invention may be formed on the second insulating layer 144 by the same process as the gate electrode 131 and connected to the printed circuit board or the outer case. Of course, the metal wire 164 may be formed on the first insulating layer 142 or the protective layer 148.

As described above, when the data signal is applied to the data line 114 by being connected to the printed circuit board of the metal wiring 164 or connected to the external case, the induced voltage is induced in the lower black matrix 109. The metal wiring 164 may be grounded to a printed circuit board or an external case to remove an induced voltage formed on the black matrix 109.

6 is a view showing a characteristic curve of a thin film transistor of a liquid crystal display according to the present invention.

As shown in FIG. 6, in the liquid crystal display according to the present invention, there is almost no change in the characteristic curve when the data voltage is applied at 0.1V and when 10V is applied. This is because a voltage induced in the black matrix 109 is grounded through the ground connection unit 160 when a data voltage of 10V is applied, thereby removing the voltage in the black matrix 109. Accordingly, it is possible to prevent the induced voltage from being applied to the channel region 132 of the thin film transistor, thereby preventing the characteristic curve from changing.

Compared with the characteristic curve of the conventional liquid crystal display device shown in FIG. 2, the characteristic curve is severely shifted when a data voltage of 0.1 V is applied and a data voltage of 10 V is conventionally applied. We can see that there is no shift in these characteristic curves.

On the other hand, in the above description, the liquid crystal display device of the present invention is made of a polycrystalline semiconductor thin film transistor, but this is only one example for explaining the present invention. The thin film transistor of the present invention will be applied not only to a polycrystalline thin film transistor but also to an amorphous thin film transistor having an amorphous semiconductor layer. In this case, the black matrix formed under the amorphous thin film transistor is grounded to prevent the channel region from being affected by the voltage induced in the black matrix.

In the above description, only the TN (twisted nematic) mode liquid crystal display device in which the pixel electrode and the common electrode are formed with the liquid crystal layer interposed therebetween to apply an electric field in a direction perpendicular to the surface of the substrate, The present invention is not limited to the liquid crystal display device having such a structure, but an in-plane switching (IPS) mode liquid crystal display in which a pair of electrodes are disposed in parallel on each other on the same substrate to form an electric field substantially parallel to the surface of the substrate. It may be applied to the device or the VA (Vertical Alignment) mode liquid crystal display device.

Accordingly, the scope of the invention should be determined by the appended claims rather than by the foregoing description.

As described above, in the present invention, the black matrix formed under the thin film transistor is grounded to prevent the induced voltage from being formed in the black matrix, thereby preventing the deterioration of the characteristics of the thin film transistor of the liquid crystal display device d.

Claims (12)

A first substrate and a second substrate; Gate lines and data lines arranged vertically and horizontally on the first substrate to define a plurality of pixels; A thin film transistor formed at an intersection of the gate line and the data line of the first substrate; A sealing member formed at an outer portion of the first substrate and the second substrate to bond the first substrate and the second substrate to each other; A black matrix formed in an image non-display area of the first substrate, the matrix formed in a sealing area in which the gate line and the data line between the pixel and the pixel, the lower portion of the thin film transistor, and the sealing material are formed; And And a ground connection connected to the black matrix to ground the black matrix. The liquid crystal display device of claim 1, wherein the black matrix is made of a metal selected from the group consisting of Cr, CrOx, Mo, and AlNd. The liquid crystal display device of claim 1, wherein the thin film transistor is a polycrystalline thin film transistor. The method of claim 3, wherein the polycrystalline thin film transistor, A semiconductor layer formed on the first substrate; A gate electrode formed on the semiconductor layer; And And a source electrode and a drain electrode formed on the gate electrode and connected to the semiconductor layer. The liquid crystal display device of claim 1, wherein the thin film transistor is an amorphous thin film transistor. According to claim 1, The ground connection portion, A metal layer extending from the black matrix; And Liquid crystal display device comprising a metal wiring connected to the metal layer. The liquid crystal display device of claim 6, wherein the metal layer is formed of the same material as the black matrix. 7. The liquid crystal display device according to claim 6, wherein the metal wiring is connected to an outer case. The liquid crystal display device according to claim 6, wherein the metal wiring is connected to a printed circuit board. The display device of claim 1, further comprising: a color filter layer formed on the second substrate; And a liquid crystal layer formed between the first substrate and the second substrate. delete delete

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