JPH0990420A - Active matrix liquid crystal display device - Google Patents

Abstract

An object of the present invention is to improve the aperture ratio of an active matrix substrate using TFTs, stabilize the storage capacitance, prevent display defects, and improve display quality. A width of a scanning line 30 is set as a minimum processing limit size, and a storage capacitance line 13 is provided close to the scanning line 30 with a gap 12 having a minimum processing limit size. A part is connected at the connecting portion 13a. Further, the pixel electrode 43 is patterned so that one side 43 a is located in the gap 12 above the storage capacitance line 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention holds a liquid crystal composition between an active matrix substrate provided with thin film transistors (hereinafter abbreviated as TFT) arranged in a matrix as driving elements and a counter substrate. And an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device which has a high density and a large capacity but has a high function and a high definition has been put into practical use.

Of these liquid crystal display devices, there is no crosstalk between adjacent pixels, a high contrast display can be obtained, a transmissive display is possible, and a large area can be easily obtained. Conventionally, an active matrix type liquid crystal display device including a TFT as a control element has been widely used.

Among the active matrix substrates used for the liquid crystal display device, the ones in which the storage capacitor lines are made of the same material as the scanning lines and the gate electrodes and are patterned together in the same forming process are not used. Conventionally, the structure is the same as that of the first conventional example shown in FIG.

That is, on the insulating substrate of the active matrix substrate 1, pixel electrodes 6 connected to the source electrodes 4a of the TFTs 4 provided at the intersections of the scanning lines 2 and the signal lines 3 are patterned in a matrix pattern, and further, Below the pixel electrode 6, a storage capacitor line 7 made of a light shielding member is patterned in the same process as the scanning line 2 is formed.
An auxiliary capacitance is formed between the pixel electrode 6 and the gate insulating film.

However, in such an active matrix substrate 1, the storage capacitance line 7 is formed so as to cross substantially the center of the pixel electrode 6, and the light storage area in the pixel electrode 6 is formed by the storage capacitance line 7. Since it is increased, the aperture ratio has been reduced. Therefore, when such an active matrix substrate is used in a liquid crystal display device, the displayed screen brightness is lowered, and in order to obtain the required brightness, the light amount of the backlight must be increased,
Therefore, there has been a problem that power consumption is increased and energy saving of the device is hindered.

Therefore, instead of providing a storage capacitance line independent of the scanning line, as in the second conventional example shown in FIG. 5, a part of the scanning line 8 is made to act as a storage capacitance line, and the gate insulating film is formed. The overlapping portion 10 with the scanning line 8 and the pixel electrode 9
The active matrix substrate 11 that forms the auxiliary capacitance is also developed.

[0008]

Conventionally, in a transmissive liquid crystal display device using an active matrix substrate having a TFT as a driving element, accumulation is made at a position which is independent of a scanning line and crosses substantially the center of a pixel electrode. A capacitance line is provided and an auxiliary capacitance is formed at the overlapping portion with the pixel electrode, or a part of the scanning line is used as a storage capacitance line, and the auxiliary capacitance is formed at the overlapping portion between the pixel electrode and the scanning line.

Therefore, in the former case, the light transmission area in the pixel electrode is reduced, the aperture ratio of the liquid crystal display device is reduced, the required screen brightness cannot be obtained, and the light amount of the backlight must be increased. Therefore, there was a problem that energy saving was hindered.

On the other hand, in the latter, since a part of the scanning line also serves as the storage capacitance line, the storage capacitance line which crosses the pixel electrode can be eliminated, and the aperture ratio of the active matrix substrate can be improved. Since the auxiliary capacitance is formed at the end portion of the pixel electrode that overlaps the scanning line, if there is a misalignment in the pattern of the scanning line and the pixel electrode during manufacturing, the overlapping area between the pixel electrode and the scanning line Because of the fluctuation of, the size of the storage capacity has changed greatly.

That is, for example, when the pixel electrode 9 is displaced from the scanning line 8 in the direction of the arrow s as shown in FIG. 6, the overlapping portion 10 of the scanning line 8 and the pixel electrode 9 is reduced as compared with FIG. However, in proportion to this, the storage capacity also becomes smaller than that shown in FIG. 5, and there is a problem in that display defects such as shot unevenness and image sticking occur and display quality is degraded.

Further, in a large-area liquid crystal display device, when one screen is divided into a plurality of blocks and each block is exposed and etched to form a storage capacitor line or a pixel electrode, a pattern is formed for each block. There is also a problem that the value of the storage capacitance varies from block to block due to the deviation of the pattern of the scanning line and the pixel electrode, display defects occur due to burn-in and shot unevenness in each block, and the shot block is visually recognized and the display quality deteriorates. .

Therefore, the present invention eliminates the above-mentioned problems, and in an active matrix substrate using a TFT as a driving element, the auxiliary capacitance is stabilized and the screen brightness is improved without lowering the aperture ratio. It is an object of the present invention to provide an active matrix type liquid crystal display device which has a high display quality while preventing a display defect while saving energy required for a conventional backlight.

[0014]

According to a first aspect of the present invention for solving the above-mentioned problems, an active matrix substrate having pixel electrodes arranged in a matrix, and an opposite electrode facing the active matrix substrate are provided. In an active matrix type liquid crystal display device comprising a counter substrate having, and a liquid crystal composition enclosed between the active matrix substrate and the counter substrate, the active matrix substrate is formed on a transparent insulating substrate,
An active region provided above the gate electrode through the gate insulating film, and a plurality of thin film transistors arranged in a matrix, including a source electrode and a drain electrode sandwiching the active region, and formed on the insulating substrate, A plurality of thin line-shaped scanning lines for supplying a scanning signal to the gate electrode,
A plurality of signal lines for supplying a video signal to the drain electrode and a scanning line of the preceding stage are formed in proximity to each other on the insulating substrate with a thin line-shaped gap therebetween, and a part thereof is connected to the scanning line of the preceding stage. Storage capacitor lines and pixel electrodes arranged in a matrix and connected to the source electrodes are provided.

According to a second aspect of the invention, in the active matrix type liquid crystal display device according to the first aspect, the width of the scanning line is set as the minimum processing limit dimension.

According to a third aspect of the present invention, in the active matrix type liquid crystal display device according to the first or second aspect, one side of the pixel electrode is located in the thin line-shaped gap, and the preceding scanning is performed. It is formed so that it does not overlap the line.

According to a fourth aspect of the invention, in the active matrix type liquid crystal display device according to the first or second aspect, the fine line-shaped gap is 10 μm or less. The invention described in claim 5 is the same as claim 1 or claim 2.
In the active matrix type liquid crystal display device described in (1), the width of the scanning line is 10 μm or less.

[0018]

According to the present invention, the scanning line is processed into a fine line shape, and the storage capacitance line is close to the preceding scanning line so as to have a thin line-shaped gap, while the preceding scanning line and the storage capacitance line are partially formed. By connecting with, the area of the pixel electrode is increased,
The aperture ratio of the active matrix substrate and thus the screen brightness are improved to save the power required for the backlight, and even if the scan line is broken due to the thin line, it is electrically connected to the storage capacitor line side. The signal transmission function is not impaired because it is bypassed and conducted.

Further, according to the present invention, the pixel electrode is formed so that one side thereof is located in the thin line-shaped gap between the scanning line and the storage capacitor line, so that the pattern of the scanning line and the storage capacitor line and the pixel electrode are formed. Even if the overlay of the patterns is misaligned, the misalignment can be compensated for by the thin line-shaped gap, so the storage capacitor can always obtain the required constant value, prevent the occurrence of display defects due to burn-in and shot unevenness, and improve the display quality. It is intended to improve.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Reference numeral 20 denotes an active matrix type liquid crystal display device, which is a nematic type liquid crystal composition which is a liquid crystal composition with alignment films 24 and 26 made of polyimide interposed between an active matrix substrate 22 and a counter substrate 23 using a TFT 21 as a driving element. The liquid crystal 27 is held and also has polarizing plates 53 and 54.

Here, the active matrix substrate 22 is
On the insulating substrate 28 made of transparent glass, thallium (T
a), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), aluminum (Al),
It is composed of a single layer film or a laminated film made of a metal material such as copper (Cu), or an alloy thereof, and supplies a scanning signal and partly projects as a gate electrode 31 and has a width of 5 μm, which is about the minimum processing limit dimension. The N-th stage scanning line 30 and the (N + 1) -th stage storage capacitance line 13 that is separated from the scanning line 30 by a thin line-shaped gap 12 having a width of 5 μm and is connected to the scanning line 30 at the connection portion 13a are patterned. Has been formed.

On top of these, silicon oxide (S
A gate insulating film 32 made of iOx) is covered, and above the gate electrode 31 via the gate insulating film 32, i-type hydrogenated amorphous silicon (hereinafter, i-type a-Si: H) is formed.
Called. ) Semiconductor layer 34, a protective insulating film 35 made of silicon nitride (SiNx), and an ohmic film 40 made of n-type amorphous silicon (hereinafter referred to as n-type a-Si) for obtaining a good ohmic contact. Patterned, T with channel region (A), source region (B), drain region (C)
FT21 is formed.

Further, a pixel electrode 43 made of indium tin oxide (hereinafter referred to as ITO) is formed on the gate insulating film 32.
Are formed in a pattern, but the end portion 43a of the pixel electrode 43 on the side of the storage capacitance line 13 has the storage capacitance line 13 and the scanning line 30.
The pattern is formed so as to be located approximately in the center of the gap 12 and is larger than the end portion 13b of the storage capacitance line 13 by about 2 μm. The overlapping portion of the storage capacitance line 13 and the pixel electrode 43 forms a storage capacitance.

Furthermore, thallium (Ta), molybdenum (M
o), tungsten (W), titanium (Ti), chromium (Cr), aluminum (Al), copper (Cu), or other metal material, or a single layer film or a laminated film made of an alloy thereof. A source electrode 37, a signal line 38, and a drain electrode 39, which is branched from the signal line 38, are patterned.

The upper surfaces of these are covered with an insulating protective film 41 made of silicon nitride (SiNx).

On the other hand, the counter substrate 23 is made of a light-shielding material such as chromium (Cr) on an insulating substrate 46 made of transparent glass, and each region is colored with red (R), green (G), and blue (B). It has a black matrix 47 having layers and a counter electrode 48 made of ITO.

Next, a method of manufacturing the liquid crystal display device 20 will be described. First, the active matrix substrate 22 is formed by sputtering thallium (Ta), molybdenum (Mo), tungsten (W), titanium (Ti) on the insulating substrate 28.
Metal materials such as chromium (Cr) and aluminum (Al),
Alternatively, a patterning of the scanning line 30, the gate electrode 31, and the storage capacitance line 13 is performed by using a photolithography technique in which a single layer film or a laminated film made of the alloy is formed and etching is performed using a photoresist (not shown) as a mask. To do.

Next, the gate insulating film 32, (i-type a-Si: H) film, and silicon nitride (SiN) are formed by the plasma CVD method.
x) A negative resist is applied on the laminated film,
Exposure is performed from the back surface of the insulating substrate 28 using the gate electrode 31 as a mask, and a negative resist is patterned to leave an exposed portion. Then, using this negative resist as a mask, the silicon nitride (SiNx) film is shaped in a self-aligning manner with respect to the gate electrode 31 to form the protective insulating film 35. As a result, the protective insulating film 35 is formed to be smaller than the gate electrode 31 by 0 to 3 μm due to the diffraction of light during the back surface exposure.

Subsequently, the plasma CVD method is used (i-type a
A (n-type a-Si) film is formed on the -Si: H) film, and the (i-type a-Si: H) film and the (n-type a-Si) film are photoetched by a photolithography technique to form a semiconductor. The layer 34 and ohmic layer 40 are patterned.

Next, an ITO film is formed by a sputtering method, a resist is applied on the ITO film, and the resist is patterned by a photolithography technique.
The TO film is photo-etched to form the pixel electrode 43 in a pattern.

Further, thallium (Ta) is formed by the sputtering method.
Molybdenum (Mo), tungsten (W), titanium (T
i), a single layer film or a laminated film made of a metal material such as chromium (Cr), aluminum (Al), or an alloy thereof is formed, and the source electrode 37, the signal line 38, and the drain electrode 39 are patterned by the photolithography technique. After forming
An insulating protective film 41 made of silicon nitride (SiNx) is formed and patterned into a predetermined shape by a photolithography technique to form an active matrix substrate 22.

Next, in the counter substrate 23, the insulating substrate 4
A film of chromium (Cr) is formed on 6 by a sputtering method and etched into a predetermined shape by a photolithography technique.
The black matrix 47 is formed in a lattice shape. Then, after coating the layer in which the pigment is dispersed on the black matrix 47,
Repeat pattern exposure and development, and black matrix 4
After forming the stripe regions of three colors of red, green and blue on the counter electrode 7, the counter electrode 48 made of ITO is formed on the entire surface by the sputtering method to form the counter substrate 23.

Then, the alignment films 24 and 2 made of low temperature cure type polyimide are formed on the entire surfaces of the active matrix substrate 22 and the counter substrate 23 on the pixel electrode 43 side and the counter electrode 48 side.
6 is applied by printing, and when both substrates 22 and 23 face each other, a rubbing treatment is performed so that the orientation axis becomes 90 °, and then both substrates 2
2 and 23 are assembled to face each other to form a cell, and nematic liquid crystal 27 is injected into the gap and sealed. And both substrates 2
Polarizing plates 53 and 54 are attached to the insulating substrates 28 and 46 of Nos. 2 and 23 to complete the liquid crystal display device 20.

According to this structure, the width of the scanning line 30 is patterned to the minimum processing size, and the storage capacity line 13 is scanned so that the gap 12 between the scanning line 30 and the storage capacity line 13 becomes the minimum processing size. Since the area of the light transmitting portion of the pixel electrode 43 can be enlarged by forming the proximity pattern on the pixel 30, the aperture ratio of the active matrix substrate 22 can be improved and the screen brightness of the liquid crystal display device 20 can be improved. Therefore, the light amount of the backlight can be reduced, and energy saving of the device can be promoted.

Moreover, by setting the width of the scanning line 30 to the minimum processing size, even if a disconnection occurs, it is connected to the storage capacitance line 13 at the connection portion 13a and electrically connected,
The scanning signal supply function is not impaired, and the yield is not reduced due to the disconnection of the scanning line 30 during manufacturing.

Further, even if the pattern of the pixel electrode 43 overlaid on the storage capacitor line 13 is displaced during manufacturing, the amount of protrusion of the pixel electrode 43 into the gap 12 between the storage capacitor line 13 and the scanning line 30 is actually. Although it varies, the storage capacitance line 13
Since the area of the overlapping portion between the pixel electrode 43 and the pixel electrode 43 is the same, it is possible to prevent display defects due to shot unevenness and image sticking without changing the value of the storage capacitance, and obtain a high-quality display image.

The present invention is not limited to the above-mentioned embodiments, and modifications can be made without departing from the spirit of the invention.
For example, the material of the gate electrode, the scanning line or the signal line, the material of the gate insulating film or the insulating protective film, and the like are arbitrary.

The width of the scanning line and the width of the gap between the scanning line and the storage capacitor line are arbitrary, but in order to improve the aperture ratio, it is desirable to make them finer, more preferably 10 μm.
It is considered as follows.

However, regarding the width of the gap between the scanning lines and the storage capacitor lines, it is necessary to further consider the overlay accuracy of the patterns of the storage capacitor lines and the scanning lines and the pixel electrode pattern. If the accuracy is aμm,
If the width of the gap is set to hold at least 2a (μm), it is possible to reliably compensate for the deviation at the time of pattern formation and to more reliably prevent the variation in the storage capacitance.

Further, the storage capacitor line may have any shape as long as it is close to the scanning line so as to maintain a thin line-shaped gap. For example, as in another modification shown in FIG. It is also possible to form the storage capacitor line 60, which holds 58 and is close to it, in a π-type pattern instead of a linear shape and connect it to the scanning line 57 at the connection portion 60a.

With this structure, the storage capacitor line 60 can be used also as a part of the light shield, and light can also be transmitted to the hatched area (D) of the pixel electrode 61, so that the active matrix substrate 62 is formed. The aperture ratio can be further improved.

The method of manufacturing the active matrix substrate is also arbitrary. For example, for a large area liquid crystal display device, one screen is divided into a plurality of blocks, and each block is exposed and etched to carry out storage capacitance line. Alternatively, the pixel electrodes and the like may be patterned. Even in such a manufacturing method, since the value of the storage capacity does not vary from block to block as in the conventional case, a shot block due to image sticking or shot unevenness is not visually recognized even if halftone display is performed. The display quality can be improved.

[0043]

As described above, according to the present invention, the area of the light transmitting portion of the pixel electrode can be increased by patterning the scanning line and the gap between the scanning line and the storage capacitance line in a thin line pattern. Since the aperture ratio of the active matrix substrate and thus the screen brightness of the liquid crystal display device can be improved, energy saving can be promoted by reducing the light amount of the backlight.

Moreover, even if a disconnection occurs due to the thinning of the scanning line, a part of the scanning line is connected to the storage capacitance line and the scanning signal is bypassed to the storage capacitance line, so that the signal transmission function is not impaired and scanning is performed. The yield will not be reduced due to the wire breakage.

Further, even if the pattern of the storage capacitor line and the pattern of the pixel electrode overlaid thereon are deviated at the time of manufacturing,
The gap is compensated for, and the area of the overlapping portion of the storage capacitance line and the pixel electrode is always kept constant. Therefore, it is possible to prevent display defects due to shot unevenness, burn-in, and visual recognition of shot blocks. A display image of quality can be obtained.

[Brief description of drawings]

FIG. 1 is a partial schematic explanatory view of an active matrix substrate of one embodiment of the present invention seen from above.

2 shows a liquid crystal display device according to an embodiment of the present invention, and FIG.
It is a schematic sectional drawing in the position corresponding to the AB line and BC line of FIG.

FIG. 3 is a partial schematic explanatory view of an active matrix substrate of another modified example of the present invention as viewed from above.

FIG. 4 is a partial schematic explanatory view of an active matrix substrate of a first conventional example as viewed from above.

FIG. 5 is a partial schematic explanatory view of an active matrix substrate of a second conventional example as viewed from above.

FIG. 6 is a partial schematic explanatory view of the case where the pattern of the storage capacitor electrode and the pattern of the pixel electrode of the active matrix substrate of the second conventional example are deviated from the top view.

[Explanation of symbols]

 12 ... Gap 13 ... Storage capacitance line 20 ... Liquid crystal display device 21 ... TFT 22 ... Active matrix substrate 30 ... Scan line 43 ... Pixel electrode

Claims (5)

[Claims] 1. An active matrix substrate having pixel electrodes arranged in a matrix, a counter substrate having a counter electrode facing the active matrix substrate, and a liquid crystal sealed between the active matrix substrate and the counter substrate. An active matrix type liquid crystal display device comprising a composition, wherein the active matrix substrate is formed on a transparent insulating substrate, and an active region is provided above the gate electrode via a gate insulating film, and the active region is sandwiched. A plurality of thin film transistors that are arranged in a matrix and include a source electrode and a drain electrode; a plurality of thin line-shaped scanning lines that are formed on the insulating substrate and supply a scanning signal to the gate electrode; and the drain electrode A plurality of signal lines for supplying video signals to the The scanning line includes a storage capacitor line that is formed in proximity to the scanning line with a thin line-shaped gap, a part of which is connected to the preceding scanning line, and a pixel electrode that is arranged in a matrix and connected to the source electrode. An active matrix type liquid crystal display device characterized by the above. 2. The active matrix type liquid crystal display device according to claim 1, wherein the width of the scanning line is a minimum processing limit dimension. 3. The active matrix liquid crystal according to claim 1 or 2, wherein one side of the pixel electrode is located in the thin line-shaped gap and is formed so as not to overlap the scanning line of the preceding stage. Display device. 4. The active matrix type liquid crystal display device according to claim 1, wherein the thin line-shaped gap is 10 μm or less. 5. The active matrix type liquid crystal display device according to claim 1, wherein the width of the scanning line is 10 μm or less.