JP4189115B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to an active matrix liquid crystal display device.
[0002]
[Prior art]
A display device using liquid crystal has characteristics not seen in conventional display devices, such as low power driving and light weight. In particular, an active matrix liquid crystal display device in which a thin film transistor (hereinafter referred to as “TFT”) is provided as a switching element in each pixel can provide a clear image display with little crosstalk. It is used as a display for car navigation, and in recent years, it has been rapidly used as a large display monitor.
[0003]
In general, an active matrix liquid crystal display device is configured by disposing an active matrix substrate having pixel electrodes and switching elements and a counter substrate having counter electrodes so as to face each other with a liquid crystal layer interposed therebetween. 4 is a partial plan view of an active matrix substrate 55 included in a conventional liquid crystal display device 80. FIGS. 5 and 6 are respectively DD ′ and AA ′ of the active matrix substrate 55 of FIG. 4 is a cross-sectional view of a corresponding liquid crystal display device 80. FIG. Hereinafter, a conventional liquid crystal display device 80 will be described with reference to FIGS. 4, 5, and 6.
[0004]
As shown in FIGS. 5 and 6, the liquid crystal display device 80 includes an active matrix substrate 55, a counter substrate 60, and a liquid crystal layer 70 sandwiched between these substrates.
[0005]
As shown in FIG. 4, the active matrix substrate 55 is connected to the scanning signal supply lines 2 arranged in the row direction, the video signal supply lines 5 arranged in the column direction, and these wirings 2 and 5 via the TFT 20. Pixel electrodes 10 arranged in a matrix, common electrodes 28 provided so as to correspond to the rows of the pixel electrodes 10, first and second common electrode signal supply lines 8 electrically connected to the common electrodes 28, and Twelve. The common electrode 28 faces the pixel electrode 10 in the corresponding row, and forms a storage capacitor between the pixel electrode 10. As shown in FIG. 6, the TFT 20 is electrically connected to the gate electrode 32 formed on the substrate 1, the semiconductor layer 4 formed on the gate electrode 32 via the insulating film 3, and the semiconductor layer 4. A source electrode 35 and a drain electrode 9 are provided.
[0006]
The scanning signal supply line 2 is supplied with an address signal, and the video signal supply line 5 is supplied with a video display signal whose polarity is inverted every frame scanning period. This video display signal is written into the capacitance of each pixel via the TFT 20 which is a switching element that is turned on / off by an address signal and controlled. The liquid crystal layer 70 on each pixel electrode is excited by the potential difference between the pixel electrode voltage and the voltage supplied to the counter electrode, and the orientation of the liquid crystal molecules contained in the liquid crystal layer 70 is arbitrarily changed to adjust the light transmittance. To produce the desired image. Writing to the pixel electrode is performed by line sequential driving in which signals simultaneously supplied to the video signal supply line 5 are sampled by an address signal sequentially supplied to the scanning signal supply line 2. The display signal written in the pixel electrode (capacitance) is accumulated by a storage capacitor formed between the pixel electrode 10 and the common electrode 28 until the next frame is scanned, and the potential is held. The liquid crystal display device 80 is driven as described above.
[0007]
Next, a method for manufacturing the active matrix substrate 55 will be briefly described. First, the scanning signal supply line 2, the first common electrode signal supply line 8, and the common electrode 28 that also function as the gate electrode 32 of the TFT 20 are formed on the substrate 1, and the insulating film 3 is deposited thereon (FIG. 4 and FIG. 4). (See FIG. 5). As shown in FIG. 5, the first common electrode signal supply line 8 and the common electrode 28 are small so that the distance L between the first common electrode signal supply line 8 and the common electrode 28 is about 4 μm to several tens of μm or less. Providing close proximity with a line space. Conventionally, the distance L between the first common electrode signal supply line 8 and the common electrode 28 is set to about 4 μm or more in consideration of the minimum resolution dimension of patterning by the photolithography technique. Further, the resistance (sheet resistance) of the common electrode 28 containing Al as a main component is 0.2Ω / □, whereas the connection portion 13 made of the same ITO as the pixel electrode 10 has a high resistance of 30Ω / □. Therefore, the distance L is set to several tens of μm or less so that the resistance at the connecting portion 13 does not become too large.
[0008]
Next, the semiconductor layer 4 for forming the source, drain and channel regions of the TFT 20 is formed (see FIG. 6). Further, the video signal supply line 5 and the source electrode 35, the drain electrode 9 and the second common electrode signal supply line 12 formed so as to extend therefrom are formed (see FIGS. 4 to 6).
[0009]
Further, an insulating film 6 that is a passivation film covering the TFT 20 is formed, and a portion corresponding to the contact hole 7 is removed (see FIGS. 5 and 6). A pixel electrode 10 connected to the drain electrode 9 through the contact hole 7 is formed on the insulating film 6. At the same time, a connecting portion 13 for electrically connecting the common electrode 28 and the first common electrode signal supply line 8 through the contact hole 7 is formed on the insulating film 6 (see FIGS. 4 and 5). ). The active matrix substrate 55 is produced as described above.
[0010]
[Problems to be solved by the invention]
In the manufacturing process of the liquid crystal display device, the substrate may be charged. In particular, when a substrate is exposed to an electric field in a sputtering process, a CVD (chemical vapor deposition) process, a photolithography process, and a dry etching process, which are general film forming methods, The substrate is likely to be charged.
[0011]
In the manufacturing process of the conventional liquid crystal display device 80 described above, if the substrate is charged when the insulating film 3 is formed, a discharge occurs between the common electrode 28 and the first common electrode signal supply line 8, and the common electrode 28. The first common electrode signal supply line 8 and the insulating film 3 may be partially thermally destroyed, resulting in pattern defects and dust.
[0012]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device that can be manufactured with high yield, in which dielectric breakdown due to electric discharge is suppressed in the manufacturing process. .
[0013]
[Means for Solving the Problems]
The liquid crystal display device of the present invention, the liquid crystal layer is sandwiched between a pair of substrates, one of the pair of substrates, and the picture element electrodes, the front Symbol pixel electrode opposing provided pairs toward the pixel electrode A liquid crystal display device having a common electrode forming a storage capacitor between the common electrode and a common electrode signal supply line, wherein the common electrode and the common electrode signal supply line are It is characterized by being spaced apart by 200 μm or more .
Thus, according to the present invention, Runode provided apart from the common electrode and the common electrode signal supply line is 200μm or more, causing no discharge between the common electrode and the common electrode signal supply line. Therefore, the insulating film, the common electrode, and the common electrode signal supply line are not thermally destroyed, and the liquid crystal display device can be manufactured with a high yield.
[0014]
Also, if the common electrode and said common electrode signal supply line formed in the same step, it is possible to easily prepare a common electrode and a common electrode signal supply line.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a plan view of an active matrix substrate 50 included in a liquid crystal display device 90 of the present invention. 2 is a cross-sectional view taken along the line BB ′ of FIG. A cross-sectional view taken along line AA ′ in FIG. 1 is the same as FIG. 6 shown as the conventional example. Members having substantially the same functions as those of the conventional liquid crystal display device 80 are denoted by the same reference numerals, and detailed description thereof is omitted. The liquid crystal display device 90 of the present invention is driven in the same manner as the conventional liquid crystal display device 80 described above. For the sake of simplicity, FIG. 1 shows that a pixel region (region contributing to display) has a 2 × 2 matrix of pixel electrodes 10 of 2 rows and 2 columns, but the present invention is limited to this. It is not a thing. Hereinafter, the liquid crystal display device 90 of the present invention will be described with reference to FIGS. 1, 2, and 6.
[0016]
As shown in FIG. 2, the liquid crystal display device 90 includes a pair of substrates, an active matrix substrate 50 and a counter substrate 60, and a liquid crystal layer 70 sandwiched between these substrates.
[0017]
As shown in FIG. 1, the active matrix substrate 50 includes a pixel electrode 10 arranged in a matrix, a common electrode 11 that forms a storage capacitor opposite to the pixel electrode 10, and a common electrode 11 formed by a connection portion 13. The first common electrode signal supply line 8 is electrically connected. The common electrode 11 is provided corresponding to each row of the pixel electrodes 10 and forms a storage capacitor so as to face each of the pixel electrodes 10 of each row. In particular, in the present invention, as shown in FIG. 2, the insulating film 3 is provided between the common electrode 11 and the common electrode signal supply line 8, and the common electrode 11 and the common electrode signal supply line 8 are electrically separated. The common electrode 11 and the common electrode signal so that the electric field strength generated in the insulating film 3 between the common electrode 11 and the common electrode signal supply line 8 is less than the electric field strength at the withstand voltage of the insulating film 3. It is characterized in that it is separated from the supply line 8.
[0018]
An example of a method for manufacturing the liquid crystal display device 90 of the present invention will be briefly described below with reference to FIG.
[0019]
First, an Al / Ti thin film is deposited on the entire surface of the substrate 1 made of glass, for example. In the photolithography process, the Al / Ti thin film is subjected to resist coating, exposure and development processes, and then subjected to dry etching to supply the scanning signal supply line 2 that also functions as the gate electrode 32 of the TFT, and the first common electrode signal supply. The line 8 and the common electrode 11 are formed (step 102). In this step 102, the common electrode 11 and the first common electrode signal supply line 8 are formed so as to be separated from each other by a distance S as shown in FIG. The separation distance S between the end 22 of the common electrode 11 and the common electrode signal supply line 8 is when the common electrode 11 and the first common electrode signal supply line 8 are electrically separated (the connection electrode 13 is formed). The electric field strength generated in the insulating film 3 (formed in the subsequent step 104) between the common electrode 11 and the first common electrode signal supply line 8 in the step before the step 112) is the withstand voltage of the insulating film 3. It is determined appropriately so as to be suppressed below the electric field strength. The separation distance S is preferably about 200 μm or more. The scanning signal supply line 2, the first common electrode signal supply line 8, and the common electrode 11 include, for example, Ta, Mo, MoW, Cr, (Si, Cu, Nd, Zr, Ta, etc.) in addition to Al / Ti. ) Can be formed from an Al alloy.
[0020]
Next, for example, a SiN _x thin film is deposited on the entire surface of the substrate 1 to form the insulating film 3 (see step 104, FIG. 2 and FIG. 6). In addition to SiN _x , the insulating film 3 can be formed of, for example, a mixture of SiN _x and SiO ₂ , AlO _x , and TaO _x . Further, a Si thin film is deposited on the insulating film 3. A photolithography step and an etching step (dry etching or wet etching) are performed to form the semiconductor layer 4 for forming the source, drain, and channel regions of the TFT 20 (step 106, see FIG. 6).
[0021]
Next, for example, an Al / Ti thin film is deposited, a photolithography process and a dry etching process are performed, and the video signal supply line 5 and the source electrode 35, the drain electrode 9 and the second common electrode signal supply line which are formed extending therefrom. 12 (see step 108, FIGS. 1, 2 and 6). The video signal supply line 5, the drain electrode 9, and the second common electrode signal supply line 12 are not limited to Al / Ti, for example, Ta, Mo, MoW, Cr, Al alloy (Si, Cu, Nd, Zr, Ta, etc.) Including).
[0022]
Further, for example, an SiNx thin film is deposited on the entire surface of the substrate to form the insulating film 6, and a photolithography process and a dry etching process are performed to remove portions corresponding to the contact holes 7 in the insulating films 3 and 6 (process 110, (See FIGS. 2 and 6). The insulating film 6 can be made of, for example, SiC ₂ , acrylic resin, polyimide, polyamide, and polycarbonate other than SiN _x .
[0023]
An indium tin oxide (ITO) thin film is deposited on the insulating film 6, and a photolithography process and a wet etching process are performed to form the pixel electrode 10 and the connection portion 13 (process 112). The pixel electrode 10 is connected to the drain electrode 9 of the TFT 20 through the contact hole 7 (see FIG. 6). The connecting portion 13 connects the common electrode 11 and the second common electrode signal supply line 12 through the contact hole 7. The active matrix substrate 50 is produced as described above.
[0024]
Further, the counter substrate 60 is manufactured by a method known to those skilled in the art, and the liquid crystal display device 90 is completed by sandwiching the liquid crystal layer 70 between the active matrix substrate 50 and the counter substrate 60.
[0025]
In the liquid crystal display device 90 of the present invention manufactured by the manufacturing method as described above, the common electrode 11 and the common electrode signal supply when the common electrode 11 and the first common electrode signal supply line 8 are electrically separated from each other. The common electrode 11 and the first common electrode signal supply line 8 are separated by a distance S so that the electric field strength generated in the insulating film 3 between the line 8 and the electric field strength at the withstand voltage of the insulating film 3 is suppressed below. Is formed. Therefore, when the insulating film 3 is deposited (step 104 in FIG. 5), the insulating film 3 provided between the common electrode 11 and the first common electrode signal supply line 8 even if the substrate 1 is charged. Is less than the electric field strength at the withstand voltage of the insulating film 3. Therefore, since no discharge is generated between the common electrode 11 and the first common electrode signal supply line 8, the insulating film 3, the common electrode 11, and the first common electrode signal supply line 8 are not thermally destroyed.
[0026]
Furthermore, it is more preferable to set the separation distance V between the common electrode 11 and the second common electrode signal supply line 12 in the same manner as the distance S. As a result, it is possible to further suppress the breakdown of the insulating film 3, the common electrode 11, and the second common electrode signal supply line 12 formed between the common electrode 11 and the second common electrode signal supply line 12. When the distance S between the common electrode 11 and the first common electrode signal supply line 8 and the distance V between the common electrode 11 and the second common electrode signal supply line 12 are formed as separated as described above, Resistance may be too high. In order to suppress the resistance at the connection portion 13 within an allowable range, the line width of the connection portion 13 may be increased as appropriate. In order to increase the line width of the connecting portion 13, for example, as shown in FIG. 7, at least two connecting portions 13 adjacent in the column direction may be integrally formed and connected. The number of connection parts 13 to be integrally formed is appropriately determined, preferably 3 or more, more preferably all.
[0027]
In the present embodiment, a potential signal is supplied from the first common electrode signal supply line 8 and the second common electrode signal supply line 12 to the common through electrode 11, but a common electrode signal that supplies a potential signal to the common electrode and the common electrode. The shape of the supply line is not limited to this. For example, the potential signal may be supplied to the common electrode 11 only from the first common electrode signal supply line 8 without forming the second common electrode signal supply line 12. Further, the switching element connected to the pixel electrode 10 is not limited to the TFT 20, and an MIM element and a varistor can be used.
[0028]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a liquid crystal display device capable of being manufactured with a high yield, in which dielectric breakdown due to electric discharge is suppressed in the manufacturing process.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of an active matrix substrate included in a liquid crystal display device of the present invention.
FIG. 2 is a cross-sectional view of the liquid crystal display device corresponding to the line BB ′ of FIG.
FIG. 3 is a diagram illustrating a method for manufacturing a liquid crystal display device of the present invention.
FIG. 4 is a plan view of an active matrix substrate included in a conventional liquid crystal display device.
FIG. 5 is a cross-sectional view of the liquid crystal display device corresponding to the line DD ′ in FIG.
6 is a cross-sectional view of the liquid crystal display device corresponding to the line AA ′ in FIGS. 1 and 4. FIG.
FIG. 7 is a plan view showing an example of an active matrix substrate included in the liquid crystal display device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Scan signal supply line 3 Insulating film 4 Semiconductor layer 5 Video signal supply line 6 Insulating film 7 Contact hole 8 First common electrode signal supply line 9 Drain electrode 10 Pixel electrodes 11 and 28 Common electrode 12 Second common electrode signal supply Line 13 Connection 20 TFT
22 End 32 Gate electrode 35 Source electrodes 50 and 55 Active matrix substrate 70 Liquid crystal layer 60 Counter substrate 80 and 90 Liquid crystal display device

Claims (2)

Liquid crystal layer is sandwiched between a pair of substrates, the common one of the pair of substrates, to form the picture element electrodes, a storage capacitor between the front Symbol pixel electrode opposing provided pairs toward the pixel electrode A liquid crystal display device, wherein the common electrode is electrically connected to a common electrode signal supply line,
A liquid crystal display device in which the common electrode and the common electrode signal supply line are spaced apart by 200 μm or more .   The liquid crystal display device according to claim 1, wherein the common electrode and the common electrode signal supply line are formed in the same process.

Images