JPH04371928A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the active matrix type liquid crystal display device having a good display grade having no crosstalks without changing production stages by substantially entirely eliminating the capacity coupling between data lines and transparent picture element electrodes. CONSTITUTION:This active matrix type liquid crystal display device has a 1st substrate 11 which has plural pieces of the gate lines on a transparent insulating substrate 12, thin-film transistors(TFTRs) 24 provided at the respective intersected points with plural pieces of the data lines intersecting therewith and the transparent picture element electrodes 18 connected to source electrodes 21 of these TFTRs 24. Further, this device is provided with a 1st substrate 11 formed with picture element accumulation capacitors constituted by laminating electrodes for forming the accumulation capacitors and the transparent picture element electrodes 18 via a insulation film, a 2nd substrate 31 formed with a transparent counter electrode, and a liquid crystal 41 which is clamped between the 1st substrate 11 and the 2nd substrate 31. The electrodes for forming the accumulation capacitors are constituted by extending to the regions formed of the pattern ends of the transparent picture element electrodes adjacent to the pattern ends of the data lines. The above-mentioned purposes are thus attained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display device using thin film transistors (hereinafter abbreviated as TFTs) as switching elements.

0002

2. Description of the Related Art Generally, liquid crystal display devices are used for television displays, graphic displays, etc., and active matrix type liquid crystal display devices with large capacity and high definition are being actively developed and put into practical use. In this type of liquid crystal display device, semiconductor switches are used as means for driving and controlling each pixel so that high contrast display without crosstalk can be achieved.

[0003] TFTs are often used as semiconductor switches because they are capable of transmissive display and are easy to increase in area. FIG. 4 is a cross-sectional view of a conventional active matrix liquid crystal display device using an array of TFTs. , III-I in Fig. 5
A cross section corresponding to part II is shown, and FIG. 5 is a plan view of a part of the first substrate in FIG. 4.

Reference numeral 11 in the figure is a first substrate, and this first substrate 11 has a gate line 13 on an insulating substrate 12 made of, for example, transparent glass, and a gate integrated with the gate line 13. −
A gate electrode 14 and an auxiliary storage capacitor forming electrode (hereinafter referred to as a capacitor electrode) 15 are formed, and these gate lines 1
3. An insulating film 16 is formed to cover the gate electrode 14 and the capacitor electrode 15. Furthermore, this insulating film 1
A semiconductor layer 17 made of, for example, amorphous silicon is formed at a predetermined position on 6, and at another predetermined position,
A transparent pixel electrode 18 is formed on the capacitor electrode 15.

A data line 19 made of aluminum, for example, intersects with the gate line 13 and the capacitor electrode 15 on the insulating film 16, and integrally with this data line 19, a semiconductor layer 1 is formed.
Drain electrode 20 located on 7, this drain electrode 2
A source electrode 21 made of, for example, aluminum is formed to connect the semiconductor layer 17 and the transparent pixel electrode 18 facing each other.

[0006] An insulating protective film 22 is formed at a predetermined position on the insulating substrate 12 on which each element is arranged as described above, and a liquid crystal alignment film 23 is further formed over the entire upper surface of this film.

In this way, the first substrate 11 is formed, and the gate electrode 14 is formed on the first substrate 11.
, a semiconductor layer 17, a drain electrode 20, and a source electrode 21.

On the other hand, the second substrate 31 includes a transparent counter electrode 33 and a liquid crystal alignment film 34 formed in this order on an insulating substrate 32 made of glass, for example. The peripheral portions of the first substrate 11 and the second substrate 31 are sealed with a gap of about 6 μm maintained, and a liquid crystal 41 is sealed and held in this gap.

FIG. 6 shows an equivalent circuit of the above liquid crystal display device. That is, a plurality of gate lines 13 parallel to each other,
A TFT 24 is arranged at each intersection with a plurality of data lines 19 that are perpendicular to this and parallel to each other, and each gate electrode 14 of this TFT 24 is connected to the gate line 13 for each row. Each drain electrode 20 is connected to the data line 19 for each column, and each source electrode 21 is connected to each transparent pixel electrode 18, and a liquid crystal 41 is connected between the transparent pixel electrode 18 and the transparent counter electrode 33. is being held. Then, each transparent pixel electrode 1
8 and the capacitor electrode 15 facing thereto form an insulating film 16.
By sandwiching them, an auxiliary storage capacitor C is formed.

Furthermore, each capacitor electrode 15 is either grounded as shown in FIG. 6 or connected to the transparent counter electrode 33, so that all pixels have the same potential. During operation, the gate lines 13 are sequentially scanned and driven by address signals, and the TFTs 24 are sequentially rendered conductive row by row. On the other hand, in synchronization with the scanning of the gate line 13, pixel signals are supplied to the data line 19 in parallel to the selected number columns. As a result, the signal voltage is applied to the transparent pixel electrode 1 row by row.
8, the liquid crystal 41 held between the transparent counter electrode 33 is excited, and an image signal is generated to display an image.

[0011]

[Problems to be Solved by the Invention] In the conventional active matrix liquid crystal display device as described above, when the address signal voltage applied to the gate line 13 falls, the pixel potential decreases due to capacitive coupling of the device. Causes a level shift. It is desirable that this level shift be small from the viewpoint of display quality (for example, flicker) and reliability of the liquid crystal material, and for this reason, the auxiliary storage capacitor C is required.

By the way, the data line 19 and the transparent pixel electrode 1
8, there is a capacitive coupling Cx. The relevant part is
This is the part in FIG. 4B, and an enlarged view of the vicinity is shown in FIG. The numbers in the figure are the same as those in FIGS. 4 and 5, and the arrows represent capacitive coupling with respect to the data line 19 and the transparent pixel electrode 18. this house,
The direct coupling between the transparent pixel electrode 18 and the data line 19 is capacitive coupling Cx. Due to the existence of this capacitive coupling Cx, a variation ΔVsig in the data signal voltage causes the pixel potential to vary by ΔVp as shown in the following equation.

[0013]

[Math 1] Here, CLC is liquid crystal capacitance.

This phenomenon means that the pixel potential follows fluctuations in the signal voltage, resulting in crosstalk on the displayed image. This is particularly noticeable when the pixel is vertically long and the transparent pixel electrode and the data line face each other over a long distance, or when the pixel is small and the value of the denominator in the above equation is small.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an active matrix liquid crystal display device with no crosstalk and good display quality without increasing the number of manufacturing steps.

[0016]

[Means for Solving the Problems] The present invention provides a thin film transistor formed on an insulating substrate by a plurality of data lines and a plurality of gate lines intersecting with each other, and arranged at each intersection. a transparent pixel electrode connected to the source electrode of the thin film transistor, and a pixel storage capacitor is formed by laminating the storage capacitor forming electrode and the transparent pixel electrode with an insulating film interposed therebetween; An active matrix liquid crystal display device comprising a substrate, a second substrate on which a transparent counter electrode is formed, and a liquid crystal sandwiched between the first substrate and the second substrate, The storage capacitor forming electrode extends in a region formed by a pattern end of the transparent pixel electrode adjacent to a pattern end of the data line.

[0017]

[Operation] According to the present invention, since the storage capacitor forming electrode is extended in the area formed by the end of the data line pattern and the end of the transparent pixel electrode pattern adjacent to the end of the data line, Capacitive coupling with the transparent pixel electrode can be extremely small and virtually eliminated. As a result, without changing the manufacturing process,
An active matrix liquid crystal display device with good display quality and no crosstalk can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of an active matrix liquid crystal display device of the present invention, showing a cross section corresponding to the section I-I in FIG. 2, and FIG. 2 is a plan view of a part of the first substrate in FIG. It is.

[0020] This liquid crystal display device is basically as shown in Figs.
It has the same configuration as the conventional liquid crystal display device shown in FIG. 7, and corresponding parts are given the same reference numerals and will be explained according to the manufacturing process.

First, the first substrate 11 is formed by depositing molybdenum to a thickness of 150 nm on an insulating substrate 12 made of, for example, transparent glass by sputtering.
, a gate electrode 14 integrated with this gate line 13 and an auxiliary storage capacitor forming electrode (hereinafter referred to as a capacitor electrode) 1
Form a pattern of 5A. This capacitor electrode 15A is functionally the same whether it is a transparent electrode or an opaque electrode. At this time, a pattern is formed so as to extend to the capacitor electrode 15B.

Next, the gate wire 13 is placed on the insulating substrate 12.
An insulating film 16 made of silicon dioxide, for example, is formed to cover the gate electrode 14 and the capacitor electrodes 15A and 15B.
is deposited to a thickness of 300 nm by plasma CVD. Furthermore, amorphous silicon, for example, is deposited at a predetermined position on this insulating film 16 to a thickness of 300 nm by plasma CVD.
The semiconductor layer 17 is patterned by depositing the semiconductor layer 17 on the substrate. next,
At another predetermined position on the insulating film 16, a transparent pixel electrode 18 is formed by depositing, for example, ITO to a thickness of 150 nm by sputtering.

Further, on the insulating film 16, a data line 19 made of aluminum, for example, intersects with the gate line 13 and the capacitor electrodes 15A, 15B, and is integrated with the data line 19 on one side of the semiconductor layer 17. Drain electrode 2 located above
0. A source electrode 21 made of aluminum, for example, is formed to face the drain electrode 20 and connect the other side of the semiconductor layer 17 to the transparent pixel electrode 18.

Next, after applying an insulating protective film 22 made of polyimide to a thickness of 1 μm over the entire surface of the insulating substrate 12 on which each element is arranged as described above, the transparent pixel electrode 1
The polymide on the upper surface at a predetermined position of 8 is removed, and a liquid crystal alignment film 23 made of polymide is further coated over the entire region of this upper surface.

In this manner, the first substrate 11 is formed, and the TFT 24 consisting of the gate electrode 14, the semiconductor layer 17, the drain electrode 20, and the source electrode 21 is formed on the first substrate 11. .

On the other hand, for the second substrate 31, a transparent counter electrode 33 made of ITO having a thickness of 100 nm and a liquid crystal alignment film 34 are sequentially formed on an insulating substrate 32 made of glass, for example. Then, the first substrate 11 and the second substrate 31 are sealed at their peripheries with a gap of about 6 μm maintained, and furthermore, the liquid crystal 41 is enclosed and held in this gap.

As shown in FIG. 6, a TFT 24 is placed at each intersection between a plurality of gate lines 13 parallel to each other and a plurality of data lines 19 perpendicular to these and parallel to each other. Each gate electrode 14 of the TFT 24 is connected to the gate line 13 for each row, and each drain electrode 20 is connected to the data line 1 for each column.
9 and connect each source electrode 21 to each transparent pixel electrode 1.
8, and the insulating film 16 is sandwiched between the transparent pixel electrode 18 and the capacitor electrode 15A facing the transparent pixel electrode 18, thereby forming an auxiliary storage capacitor C.

FIG. 3 shows A of FIG. 1 having the above-mentioned configuration.
This is an enlarged view of the section. The symbols in the figure are the same as those in FIGS. 1 and 2, and the arrows indicate the data line 19 and the transparent pixel electrode 1.
8 shows the capacitive coupling for 8. Direct contact between the data line 19 and the transparent pixel electrode 18 can be prevented by the extended capacitor electrode 15B, eliminating Cx in FIG. That is, due to the capacitor electrode 15B which is the extension part,
Since capacitive coupling between the data line 19 and the transparent pixel electrode 18 is substantially eliminated, a good image without crosstalk can be obtained on the display screen.

[0029]

According to the present invention, since the storage capacitor forming electrode is extended in the area formed by the data line pattern end and the adjacent transparent pixel electrode pattern end, the data Capacitive coupling between the line and the transparent pixel electrode can be extremely small and virtually eliminated. As a result, an active matrix liquid crystal display device with no crosstalk and good display quality can be obtained without changing the manufacturing process.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along line I-I in FIG. 2 showing an active matrix liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a part of FIG. 1;

FIG. 3 is an enlarged sectional view of FIG. 1 showing the effects of the present invention.

FIG. 4 is a sectional view taken along line III-III in FIG. 5 showing a conventional active matrix liquid crystal display device.

FIG. 5 is a plan view showing a part of FIG. 4;

FIG. 6 is an equivalent circuit diagram of the liquid crystal display device of FIGS. 4 and 5. FIG.

FIG. 7 is an enlarged cross-sectional view of FIG. 4 showing the drawbacks of the conventional active matrix liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11... First substrate, 13... Gate electrode, 15A... Capacitor electrode, 15B... Extended portion of capacitor electrode, 17... Semiconductor layer, 18... Transparent pixel electrode, 19... Data line, 20...
Drain electrode, 21... Source electrode, 24... TFT, 31
...Second substrate, 33...Transparent counter electrode, 41...Liquid crystal, C...
Auxiliary storage capacity.

Claims (1)

[Claims] 1. A plurality of data lines and a plurality of gate lines are formed on an insulating substrate to intersect with each other, and a thin film transistor is arranged at each intersection, and a sort of the thin film transistor is formed.
a first substrate having a transparent pixel electrode connected to the base electrode, and on which a pixel storage capacitor is formed by laminating a storage capacitor forming electrode and the transparent pixel electrode with an insulating film interposed therebetween; In an active matrix liquid crystal display device comprising: a second substrate on which electrodes are formed; and a liquid crystal sandwiched between the first substrate and the second substrate, An active matrix liquid crystal display device characterized in that the electrode extends in a region formed by a pattern end of the transparent pixel electrode adjacent to a pattern end of the data line.