JPH0553141A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the active matrix type liquid crystal display device which compensates a DC voltage level shift by the compensation capacity of a small element area, and also, can suppress a crosstalk, can realize the manufacture yield at a low cost even in the case of a large screen, and moreover, can execute a beautiful full color display. CONSTITUTION:In the active matrix type liquid crystal display device of an opposed matrix format, plural scan bus lines 1, a thin film transistor 2, a display electrode 3, and a reference potential supply bus line 4 are formed on one of two pieces of substrates placed opposingly by interposing a liquid crystal between them, a gate of the thin film transistor 2, one of its source and drain, and the other are connected to the scan bus line 1, the display electrode 3, and the reference potential supply bus line 4, respectively, and in the other of two pieces of substrates, plural stripe-like data bus lines 5 opposed to the display electrode 3 are formed, and this device is constituted so as to add the compensation capacity 6 consisting of a ferroelectric thin film to each display electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device for writing and holding a voltage in a liquid crystal cell by a switching action of a thin film transistor (TFT) corresponding to each pixel. The present invention relates to a matrix type liquid crystal display device.

An active matrix type liquid crystal display device is
Since it is as thin as a simple matrix liquid crystal display device, it is widely used as various display devices for laptop personal computers, word processors, portable televisions and the like. That is, since the active matrix type liquid crystal display device drives each pixel independently by the thin film transistor provided corresponding to the pixel, even if the number of lines is increased as the display capacity is increased, the simple matrix type liquid crystal display device is used. Unlike the display device, there is no problem of a decrease in contrast and a decrease in viewing angle due to a decrease in drive duty. Therefore, the active matrix type liquid crystal display device is capable of color display with the same quality as that of a cathode ray tube (CRT), and its application as a flat display device is expanding.

However, in the active matrix type liquid crystal display device, it is necessary to provide a thin film transistor or the like as a switching element for each pixel, and therefore the manufacturing process becomes complicated, and when manufacturing a large screen display device, a large manufacturing device is required. Need. Further, the manufacturing equipment cost increases and the manufacturing yield decreases, so that the active matrix type liquid crystal display device becomes very expensive.
Therefore, the current active matrix type liquid crystal display device which has been put into practical use is limited to a relatively small one.

Further, in order to improve the reduction in manufacturing yield caused by the complexity of the structure of the active matrix type liquid crystal display device, the scan bus lines and the data bus lines are formed on different substrates, and the scan bus lines and the data bus lines are formed on the same substrate. There has been proposed an active matrix type liquid crystal display device of an opposed matrix type which eliminates the intersection of bus lines, and further improvement in display quality has been demanded.

[0005]

2. Description of the Related Art Conventionally, scan bus lines and data bus lines are formed on the same substrate so as to be orthogonal to each other,
There is provided an active matrix liquid crystal display device having a structure in which display electrodes are connected to the intersections via thin film transistors. However, in such an active matrix type liquid crystal display device, since scan bus lines and data bus lines are formed on the same substrate so as to intersect with each other, insulation failure, short circuit or the like may occur at the intersecting points, or
There may be a break in the upper bus line due to the step at the intersection. Further, since there is a limit to the formation of the lower bus line and the insulating layer thick, it is not easy to reduce the resistance of the lower bus line, and since the insulating layer cannot be formed thick, it is possible to avoid It was difficult to prevent short circuits completely.

Therefore, there has been proposed an active matrix type liquid crystal display device of the opposed matrix type in which the scan bus lines and the data bus lines are formed on one substrate and the other substrate made of glass or the like, which are opposed to each other with a liquid crystal interposed therebetween.
9 is an exploded perspective view showing a panel portion of a conventional opposed matrix type active matrix type liquid crystal display device, and FIG. 10 is a diagram showing an equivalent circuit of the active matrix type liquid crystal display device shown in FIG.

As shown in FIG. 9, an opposed matrix type active matrix liquid crystal display device is one in which one glass substrate 89 and the other glass substrate 80 are opposed to each other with a liquid crystal (not shown) interposed therebetween. On the one glass substrate (TFT substrate) 89, the scan bus line 81,
Thin film transistor 83, display electrode 84 constituting liquid crystal cell 84
a and a reference potential supply bus line 88 (shown as ground in FIG. 10) are formed, and a striped data bus line 82 is formed on the other glass substrate (counter substrate) 80. Here, a liquid crystal is sealed between the stripe-shaped data bus line 82 and the display electrode 84a, whereby a liquid crystal cell 84 is formed. The liquid crystal cell 84 is connected between the data bus line 82 and the drain (or source) 86 of the thin film transistor 83,
The gate 85 of 83 is connected to the scan bus line 81, and the source (or drain) of the thin film transistor 83.
87 is connected to the reference potential supply bus line 88.

With the above structure, the data bus line 82
The scan bus line 81 and the scan bus line 81 are arranged orthogonally through the liquid crystal, but since they do not intersect on the same substrate, it is not necessary to form an insulating layer at the intersection, and the configuration can be simplified. it can. In addition, the data bus line
Since a short circuit does not occur between the 82 and the scan bus line 81, the scan bus line and the data bus line are formed orthogonally on the same substrate, and the display electrode is connected to each intersection through the thin film transistor. It is possible to reduce display defects and improve the manufacturing yield, as compared with the conventional general type active matrix type liquid crystal display device having the configuration.

By the way, it is known that the crosstalk is larger in the counter matrix type active matrix type liquid crystal display device than in the conventional general type active matrix type liquid crystal display device. That is, in the opposed matrix type active matrix liquid crystal display device, even when the thin film transistor is in an off state, the data voltage sequentially applied to the data bus line is parallel to the liquid crystal cell (the thin film transistor gate capacitance). Between the scan bus line connected to the display electrode and the display electrode forming the liquid crystal cell, and between the display electrode and the data bus line, or between the display electrode and the reference potential supply bus line. Voltage, that is, the capacitance between the source and drain of the thin film transistor), the liquid crystal cell voltage fluctuates due to the data voltage for other cells, and as a result, the display quality deteriorates. was there.

Further, the conventional general type active matrix type liquid crystal display device can add a storage capacitor to reduce the capacitive coupling ratio, but the opposed matrix type active matrix type liquid crystal display device has this capacity. Since it is not possible to add such a storage capacitance, it is difficult to reduce the capacitive coupling ratio. Furthermore, since it is difficult to add storage capacitance, the thin film transistor (83)
There is a drawback that the afterimage phenomenon becomes large due to the DC voltage level shift immediately after selecting the scan bus line (81) connected to the gate (85) of It is also supposed to reduce the quality.

Therefore, the present inventors have proposed an active matrix type liquid crystal display device capable of reducing crosstalk and compensating for a DC voltage level shift (DC level shift) to improve display quality. (Patent application 2-
218966: see FIG. 11).

[0012]

FIG. 11 is a diagram showing an example of an active matrix type liquid crystal display device as a related technique. As shown in FIG. 11, Japanese Patent Application No. 2-218966
In the active matrix type liquid crystal display device proposed in No. 1, a thin film transistor (TFT) for compensation is used as a method capable of realizing a high manufacturing yield and a beautiful display without an afterimage in order to compensate for a DC voltage level shift that causes an afterimage.
Is provided. That is, one of the two substrates (TFT substrate 89) arranged to face each other with the liquid crystal interposed therebetween has a plurality of scan bus lines 11 ', 12', thin film transistors 21, 22, display electrodes 3, and a reference potential supply bus. Lines 4 are formed, and a plurality of stripe-shaped data bus lines 5 facing the display electrodes 3 are formed on the other of the two substrates (counter substrate 80). Where scan bus line 1
1'and 12 'are provided in parallel on both sides of the reference potential supply bus line 4.

The thin film transistor 21 is for selectively driving a predetermined liquid crystal cell, and the thin film transistor 22 is for compensating a DC voltage level shift. That is, the gate of the thin film transistor 21 'is connected to the (S _i), the gate of the thin film transistor 22, scan bus line 11 gates are connected to the thin film transistor 21' scan bus lines 11 on one of the (S _i) It is connected to the scan bus line 12 '(S _i-1 ) for driving the line. Further, the drains (or sources) of the thin film transistors 21 and 22 are connected to the display electrode 3 (liquid crystal cell P _i ).
And the sources (or drains) of the thin film transistors 21 and 22 are connected to the reference potential supply bus line 4. Then, the thin film transistor 22 is adapted to compensate for the fluctuation of the display electrode potential that occurs at the end of the gate selection of the thin film transistor 21, and by configuring the drive waveform of the scan bus line with an address pulse and a compensation pulse. It is designed to work. With such a structure, it is possible to realize a high display because there is no intersection of bus lines on the TFT substrate, and a beautiful display without afterimage because there is no compensation for the DC voltage level shift.

FIG. 12 is a diagram showing an equivalent circuit of the active matrix type liquid crystal display device shown in FIG. As shown in the figure, a TFT that functions as a normal address
Assuming that the capacitance related to (thin film transistor 21) is C _GS ^A and the capacitance related to the TFT (thin film transistor 22) that functions for DC voltage level shift compensation is C _GS ^C , the compensation voltage V _C is V _C = (C _GS ^A * V _A ) / C _GS ^C

In the counter matrix, the magnitude of crosstalk due to data being written in another display cell during the accumulation period in which the TFT is in the OFF state is determined by the coupling constant α α = (C _GS ^C + C _GS ^A + C _RS ) / It will be proportional to (C _LC + C _GS ^C + C _GS ^A + C _RS ). For this reason, when the compensation capacitance is increased to reduce the compensation voltage, crosstalk increases accordingly, which causes a problem that a beautiful full-color display cannot be realized.

In view of the problems of the above-described conventional active matrix type liquid crystal display device, the present invention can compensate the DC voltage level shift by the compensation capacitance of a small element area and suppress the crosstalk, and can reduce the crosstalk even in a large screen. It is an object of the present invention to provide an active matrix type liquid crystal display device which can realize a high manufacturing yield at a cost and can perform beautiful full color display.

[0017]

FIG. 1 is a diagram showing the principle of an active matrix type liquid crystal display device according to the present invention. As shown in FIG. 1 (a), according to the present invention, a plurality of scan bus lines 1, thin film transistors 2, display electrodes 3, and a reference electrode are provided on one of two substrates which are opposed to each other with a liquid crystal interposed therebetween. A potential supply bus line 4 is formed, a gate of the thin film transistor 2 is connected to the scan bus line 1, one of a source and a drain is connected to the display electrode 3, and the other is connected to the reference potential supply bus line 4, respectively. A plurality of stripe-shaped data bus lines 5 facing the display electrodes 3 are provided on the other of the two substrates.
And a compensation capacitor 6 made of a ferroelectric thin film is added to each display electrode 3 in the opposed matrix type active matrix liquid crystal display device. A device is provided. Here, the compensation capacitance (6) is generated at the end of gate selection of the thin film transistor by inverting the spontaneous polarization in the ferroelectric thin film of the compensation capacitance at or immediately after the completion of gate selection of the thin film transistor. It is designed to compensate for potential fluctuations.

[0018]

According to the active matrix type liquid crystal display device of the present invention, the compensation capacitor 6 provided for each display electrode 3 is provided.
As a result, the fluctuation of the display electrode potential that occurs when the gate selection of the thin film transistor 2 is completed is compensated.
The compensation capacitor 6 inverts the spontaneous polarization in the ferroelectric thin film of the compensation capacitor 6 at the end of the gate selection of the thin film transistor 2 or immediately after the completion of the gate selection, so that the potential of the display electrode fluctuates at the end of the gate selection of the thin film transistor 2. To compensate.

That is, according to the active matrix type liquid crystal display device of the present invention, a compensation capacitor 6 made of a ferroelectric thin film is added to each display electrode 3, and the spontaneous polarization of the ferroelectric thin film is inverted to thereby obtain a DC voltage level. Shift compensation is performed. Here, when the magnitude of the spontaneous polarization per unit area of the spontaneous polarization of the ferroelectric thin film is P _S , the amount of charge induced by the inversion of the spontaneous polarization is 2P _S S (where S is the compensation capacitance 6 Area). Further, the DC voltage level shift that occurs at the end of gate selection is caused by effectively inducing the charge of −C _GS ^A * V _A in the display electrode, so that 2P _S S = C _GS ^A * V _A is established. By designing the compensation capacitor 6 as described above, the DC voltage level shift can be compensated. Here, in the ferroelectric thin film (ferroelectric material), the amount of electric charge induced by spontaneous polarization is large, so that it is possible to compensate the DC voltage level shift with a small element area.

Further, during the storage period in which the gate of the thin film transistor 2 is not selected, the capacitance of the compensation capacitance 6 induces a charge with respect to voltage fluctuation like a normal paraelectric material, but this charge amount is compensated. Since the element area of the capacitor 6 can be made small, it can be made much smaller than in the case of a normal capacitor which is a conventional compensating element, and crosstalk can be reduced.

Further, according to the active matrix type liquid crystal display device of the present invention, since compensation is similarly performed in the next frame, it is necessary to reset the direction of spontaneous polarization to the original state. This reset operation is shown in FIG.
As shown in (c), this is performed by applying a pulse in the direction opposite to that in the compensation operation immediately before the corresponding thin film transistor 2 is selected. Thus, if the thin film transistor 2 is reset just before being selected, the fluctuation of the spontaneous polarization in the ferroelectric thin film of the compensation capacitor 6 caused by the reset operation has almost no effect on the effective voltage applied to the liquid crystal. There will be no.

As described above, according to the active matrix type liquid crystal display device of the present invention, a compensation capacitor made of a ferroelectric thin film is added to each display electrode, the spontaneous polarization of the ferroelectric thin film is inverted, and a DC voltage level is obtained. By performing shift compensation, the value of the compensation capacitance is made large during the compensation operation period of the DC voltage level shift and is made small during the other period (accumulation period when the gate of the thin film transistor for address is not selected). It has become. As described above, in the active matrix type liquid crystal display device of the present invention, it is possible to compensate the DC voltage level shift and suppress the crosstalk by the compensation capacitor having a small DC element area, and to achieve a high manufacturing yield at a low cost even on a large screen. It ’s possible, and yet
It is possible to provide an active matrix type liquid crystal display device capable of beautiful full color display.

[0023]

Embodiments of the active matrix type liquid crystal display device according to the present invention will be described below with reference to the drawings. Figure 2
FIG. 3 is a diagram showing a basic configuration example of an active matrix type liquid crystal display device of the present invention, showing a pattern on one substrate of an opposed matrix type active matrix type liquid crystal display device.

As shown in FIG. 2, in the active matrix type liquid crystal display device of this embodiment, one of the two substrates (TFT substrate 89 in FIG. 9) which are opposed to each other with the liquid crystal interposed therebetween is A plurality of scan bus lines 11 and 12, a thin film transistor 2, a display electrode 3, a reference potential supply bus line 4,
And the compensation capacitance 6 is formed. A plurality of stripe-shaped data bus lines 5 facing the display electrodes 3 are formed on the other of the two substrates (counter substrate 80 in FIG. 9). Where scan bus lines 11 and 12
Are provided in parallel on both sides of the reference potential supply bus line 4. Further, the reference potential supply bus line 4 is commonly connected to all, and can be switched to one of two different levels for each horizontal scanning period, for example.

The thin film transistor 2 is for selectively driving a predetermined liquid crystal cell, and the compensation capacitor 6 is
This is for compensating for the DC voltage level shift. That is, the gate of the thin film transistor 2 is connected to the scan bus line 11 (S _i ), and one terminal of the compensation capacitor 6 is located above the scan bus line 11 (S _i ) to which the gate of the thin film transistor 2 is connected. Is connected to the scan bus line 12 (S _i-1 ) for driving the line.
Further, the drain (or source) of the thin film transistor 2 is connected to the display electrode 3 (liquid crystal cell P _i ), and
The source (or drain) of the thin film transistor 2 is connected to the reference potential supply bus line 4. The other terminal of the compensation capacitor 6 is connected to the display electrode 3 (liquid crystal cell P _i ).
It is connected to the. Here, the compensation capacitor 6 is formed such that the ferroelectric thin film is sandwiched by two electrodes.

FIG. 3 is a timing diagram in the active matrix type liquid crystal display device shown in FIG. 2, and the scan bus line S for driving the liquid crystal cell P _i-1 of the i-1 column.
_i-1 (compensation capacitance 6 connected to the display electrode 3 of the liquid crystal cell P _i
Voltage waveform of the scan bus line 12 to which one terminal is connected, and the scan bus line S _i for driving the liquid crystal cell P _i in the i-th column (thin film transistor connected to the display electrode 3 of the liquid crystal cell P _i ) The voltage waveform of the scan bus line 11) to which the second gate is connected is shown. FIG. 4 is a diagram for explaining the compensation capacitance in the active matrix type liquid crystal display device of the present invention.

As shown in FIG. 3, the liquid crystal cell P in the i-th column is
_iScan bus line S for driving_iVoltage waveform
Is the liquid crystal cell P in the i-1 column_i-1For driving
Bus line S_i-1 With the same shape as the voltage waveform of
That the timing is delayed (according to the clock signal)
Is becoming That is, the active matrix type liquid crystal display
The drive signal for each column line in the device
It is selected sequentially according to the signal and changes to a predetermined level.
It has become. Here, the scan bus line S _i-1 Electric power
The pressure waveform is the liquid crystal cell P of the i-1th column._i-1To drive
And the liquid crystal cell P in the i-th column_iScan bus line to drive
S_iTurn on voltage Vg (V_ONJust before rising up to)
g (V_ON), And the scan bus line S_iIs off
Voltage V_OFFImmediately after falling to the negative voltage
It becomes Vcg. That is, the scan bus line S_i-1 Is
S canvas line S_iIs immediately raised to ON voltage Vg
The voltage becomes Vg before, which is the liquid crystal cell P of the i-1th column.
_i-1Not only to drive the
It is also used to reset the spontaneous polarization of an electric body. Well
And scan bus line S_iIs the off voltage V_OFFDown to
Immediately after the scan, the scan bus line S_i-1 Is the voltage-Vcg
Therefore, the ferroelectric substance that composes the compensation capacitor 6 becomes
Liquid crystal cell P which is generated at the end of gate selection by reversing polarization.
_iTo compensate for the DC voltage level shift of
It

Here, as shown in FIG. 4C, the voltage Vg is the positive coercive power V of the ferroelectric substance used for the compensation capacitor 6.
_The voltage is higher than _I ⁺ , and the voltage −Vcg is lower than the negative coercive power V _I ⁻ of the ferroelectric used for the compensation capacitor 6. Therefore, the compensation capacitor 6 has a voltage Vg
Every time the voltage -Vcg is applied, the polarization (spontaneous polarization) of the ferroelectric substance forming the compensation capacitor 6 is inverted.

That is, as shown in FIG. 4A, when the scan bus line S _i-1 has a voltage Vg higher than the positive coercive power V _I ^+, the compensation capacitance 6 connected to the liquid crystal cell P _i is used. The ferroelectric substance that composes the structure has a positive spontaneous polarization (residual polarization) Ps through AA in the hysteresis curve of FIG. 4 (c).
Is induced and held. In this state, when the scan bus line S _i becomes the voltage Vg, the thin film transistor 2 is turned on, the liquid crystal cell P _i is selected, and predetermined data is written.

Further, the scan bus line S_iIs falling
Voltage V_OFFThen, immediately after that, as shown in Fig. 4 (b).
Scan bus line S_i-1 Has negative anti-power
V_I ^-Lower voltage -Vcg, resulting in
For the ferroelectric material that composes the compensation capacitor 6, the hysteresis of Fig. 4 (c) is used.
Negative spontaneous polarization -Ps is induced via BB in the cis curve.
Raised and held. That is, the compensation capacitor 6 is configured.
The spontaneous polarization of the ferroelectric substance is inverted, and this spontaneous polarization is inverted.
2P_SThe amount of electric charge of S will be induced (where
(S is the area of the compensation capacitor 6.)

By the way, as described above, when the scan bus line S _i falls to the voltage V _{OF F} , the thin film transistor 2 is turned off (at the end of the gate selection), and at the end of the gate selection, the DC voltage level shift (−C) is performed. _GS ^A * V _A
Charge) is generated. Then, in the active matrix type liquid crystal display device of the present embodiment, this DC voltage level shift is compensated by the charge amount of 2P _S S induced by the inversion of the spontaneous polarization of the ferroelectric substance forming the compensation capacitor 6. It has become. Further, the spontaneous polarization of the ferroelectric substance of the compensation capacitor 6 shows that the scan bus line S _i-1 has the liquid crystal cell P.
_The voltage Vg is reset immediately before _i is driven, which is reset. However, if the reset is performed immediately before the thin film transistor 2 is selected, the spontaneous polarization of the ferroelectric thin film of the compensation capacitor 6 caused by the reset operation is generated. This is because it is possible to make the variation hardly affect the effective voltage applied to the liquid crystal.

In the above, the capacitance value of the compensation capacitor 6 is the same value as the normal capacitance (or the value that is small enough to make the device small) except when the spontaneous polarization is inverted, so that the crosstalk is suppressed. Hardly affected. In the active matrix type liquid crystal display device of the present embodiment, when the gate selection is completed, the DC voltage level shift in the liquid crystal cell P _i is 2P due to the inversion of the spontaneous polarization of the ferroelectric substance (ferroelectric thin film) forming the compensation capacitor 6. _{Since the} compensation is performed by the charge amount of _S S, the compensation capacitance 6 can be configured by a capacitance having a small element area. This also corresponds to the fact that the compensation voltage for compensating for the DC voltage level shift can be lowered.

The scan bus lines 11 and 12 are provided in parallel on both sides of the reference potential supply bus line 4, and the gate of the thin film transistor 2 of the liquid crystal cell P _i is connected to the scan bus line 11 (S _i ). , One terminal of the compensation capacitor 6 of the liquid crystal cell P _i is connected to the scan bus line 12 (S _i-1 ), but it goes without saying that these configurations can be variously modified. ..

5 to 8 are views for explaining an example of the manufacturing process of one embodiment of the active matrix type liquid crystal display device of the present invention. First, as shown in FIGS. 5A to 5C, ITO is formed as a transparent electrode to a thickness of 50 nm on the glass substrate 8 (TFT substrate) by a sputtering method. Next, FIG.
As shown in (c), the ohmic contact layer (source 21 and drain) of the thin film transistor 2 for addressing is used.
22) As a result, N ⁺ a-Si (amorphous silicon) is formed to a thickness of 30 nm by a plasma CVD method, and then a predetermined resist pattern (pre-resource / drain pattern) is formed by a resist.
Then, only N ⁺ a-Si is etched according to the resist pattern to form the source electrode 21 and the drain electrode 22 of the thin film transistor 2. Here, in the compensation capacitor 6, as shown in FIG. 5B, one electrode 61 of the compensation capacitor is formed by a transparent electrode (ITO) integrally with the display electrode 3 of the liquid crystal cell. At this stage, N ⁺ a-Si 62 is formed on the electrode 61.

Next, as shown in FIG. 6C, plasma CVD of a-Si is performed as the semiconductor layer 23 of the thin film transistor 2.
To a thickness of 30 nm by the CVD method, and SiN was used as the first insulating layer (gate insulating film layer) 24 by the plasma CVD method.
After forming 50 nm, patterning for element isolation is performed. Then, as shown in FIG. 7 (c), SiN is formed to a thickness of 250 nm as a second insulating layer (gate insulating film layer) 9 (24),
Contact hole patterning is performed. And FIG.
As shown in (c), after forming Al (aluminum) by the sputtering method, the scan bus line 11 and the reference potential supply bus line 4 are patterned. here,
Reference numeral 40 is formed of ITO and is a conductor portion for connecting the source 21 of the thin film transistor 2 and the reference potential supply bus line 4, and a part of the scan bus line 11 is used as the gate 25 of the thin film transistor 2. It is supposed to do.

On the other hand, as shown in FIGS. 6 (b) and 7 (b), the compensating capacitor 6 is first provided with an electrode 61 on the glass substrate 8.
8B, a thin film of a ferroelectric substance (ferroelectric thin film) 63 is formed, and the scan bus line 12 (64) is patterned. That is, for example, VDF (Vinylidene Fluoride) and TrFE (Trifl
A ferroelectric layer 63 is formed by applying a copolymer of uoroethylene and spin coat to a thickness of 150 nm, annealing at 145 ° C. and slowly cooling. Then, after removing the ferroelectric layer other than the compensation element (compensation capacitor 6) portion by patterning, Al (aluminum) is formed by the sputtering method, and the scan bus line 12 is patterned. As a result, the control bus line (64) for the compensation capacitor 6
Will be connected to the scan bus line in the previous stage. Here, a part of the scan bus line 12 is adapted to be used as the upper electrode 64 of the compensation capacitor 6, and the lower electrode 61 of the compensation capacitor 6 is connected to the display electrode 3.

For the active matrix type liquid crystal display device manufactured as described above, the scan bus lines S _i-1 (12) and S _i (11) are applied with a voltage having a waveform as shown in FIG.
To increase the capacitance value of the compensation capacitor 6 during the compensation operation period to compensate for the DC voltage level shift of the liquid crystal cell, and reduce the capacitance value of the compensation capacitor 6 during the accumulation period to reduce crosstalk. Can be suppressed.

[0038]

As described above in detail, according to the active matrix type liquid crystal display device of the present invention, a compensation capacitor made of a ferroelectric thin film is added to each display electrode to invert the spontaneous polarization of the ferroelectric thin film. Then, by compensating for the DC voltage level shift, it is possible to compensate the DC voltage level shift by the compensation capacitance of a small element area and suppress crosstalk, and realize a high manufacturing yield at a low cost even on a large screen. It is possible to provide an active matrix type liquid crystal display device capable of beautiful full color display.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of an active matrix type liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing a basic configuration example of an active matrix type liquid crystal display device of the present invention.

FIG. 3 is a timing diagram in the active matrix liquid crystal display device shown in FIG.

FIG. 4 is a diagram for explaining a compensation capacitance in the active matrix type liquid crystal display device of the present invention.

FIG. 5 is a diagram (No. 1) for explaining an example of the manufacturing process of the embodiment of the active matrix type liquid crystal display device of the present invention.
Is.

FIG. 6 is a view for explaining an example of the manufacturing process of the embodiment of the active matrix type liquid crystal display device of the present invention (Part 2).
Is.

FIG. 7 is a diagram (No. 3) for explaining an example of the manufacturing process of the embodiment of the active matrix liquid crystal display device of the present invention.
Is.

FIG. 8 is a view for explaining an example of the manufacturing process of the embodiment of the active matrix type liquid crystal display device of the present invention (Part 4).
Is.

FIG. 9 is an exploded perspective view showing a panel portion of a conventional opposed matrix type active matrix type liquid crystal display device.

10 is a diagram showing an equivalent circuit of the active matrix liquid crystal display device shown in FIG.

FIG. 11 is a diagram showing an example of an active matrix type liquid crystal display device as a related technique.

12 is a diagram showing an equivalent circuit of the active matrix liquid crystal display device shown in FIG.

[Explanation of symbols]

 1, 11, 12 ... Scan bus line 2 ... Thin film transistor (TFT) 3 ... Display electrode 4 ... Reference potential supply bus line 5 ... Data bus line 6 ... Compensation capacitance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ogata 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Kenichi Oki 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited Within

Claims (5)

[Claims] 1. A plurality of scan bus lines (1), thin film transistors (2), display electrodes (3), and a reference potential supply bus line (4 ) Is formed, the gate of the thin film transistor is connected to the scan bus line, one of the source and the drain is connected to the display electrode, and the other is connected to the reference potential supply bus line, and the other of the two substrates is connected. A counter-matrix active matrix liquid crystal display device in which a plurality of stripe-shaped data bus lines (5) opposed to the display electrodes are formed, and a compensation capacitor formed of a ferroelectric thin film for each of the display electrodes. An active matrix type liquid crystal display device characterized in that (6) is added. 2. The compensation capacitance (6) is generated at the end of gate selection of the thin film transistor by inverting the spontaneous polarization in the ferroelectric thin film of the compensation capacitance at or immediately after the end of gate selection of the thin film transistor. 2. The active matrix type liquid crystal display device according to claim 1, characterized in that a variation in the potential of the display electrode is compensated. 3. The gate selection voltage of the thin film transistor (2) is at least with respect to the voltage of the display electrode,
3. The active matrix type liquid crystal display device according to claim 2, wherein the compensation capacitor (6) is set to have a voltage larger than a voltage at which spontaneous polarization of the ferroelectric thin film is inverted. 4. The compensation capacitance (6) is reset by further inverting the spontaneous polarization in the ferroelectric thin film of the compensation capacitance immediately before the display electrode to which the compensation capacitance is connected is selected. The active matrix type liquid crystal display device according to claim 2. 5. One of the electrodes of the compensation capacitor (6) is connected to the display electrode, and the other electrode of the compensation capacitor (6) is connected to a scan bus line in front of the scan order. The active matrix liquid crystal display device according to claim 1.