JP2731985B2 - Driving method of electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of displaying an image in a liquid crystal electro-optical device using a thin film transistor (hereinafter referred to as a TFT) as a driving switching element, and particularly to a gradation display for obtaining an intermediate color tone or light and shade. It is about the method. The present invention particularly relates to a so-called full digital gradation display for performing gradation display without applying any analog signal to an active element from the outside.

[0002]

2. Description of the Related Art Liquid crystal compositions have different dielectric constants in the horizontal and vertical directions with respect to the molecular axis due to their material properties. Can be easily done. The liquid crystal electro-optical device displays ON / OFF, that is, displays light and dark, by controlling the amount of transmitted light or the amount of scattering of light using the anisotropic generation of the dielectric constant. As liquid crystal materials, TN (twisted nematic) liquid crystal, STN (super
Materials known as "twisted nematic" liquid crystal, ferroelectric liquid crystal, polymer liquid crystal or dispersion type liquid crystal are known.

It is known that a liquid crystal does not respond to an external voltage in an infinitely short time, but takes a certain time to respond. The value is specific to each liquid crystal material. In the case of a TN liquid crystal, the value is several tens of msec.
The time is several hundred msec for STN liquid crystal, several hundred μsec for ferroelectric liquid crystal, and several tens msec for dispersion or polymer liquid crystal.

[0004] Among electro-optical devices using liquid crystal, the one that can obtain the best image quality is the one using the active matrix system. In a conventional active matrix type liquid crystal electro-optical device, a thin film transistor (TFT) is used as an active element, an amorphous or polycrystalline semiconductor is used for the TFT, and P
In this case, a TFT of only one of the N-type and the N-type was used. That is, in general, an N-channel TFT
(Referred to as NTFT) is connected in series to the pixel. Then, a signal voltage is applied to the signal lines of the matrix, and when signals are applied from both sides to the TFTs provided at the orthogonal portions of the respective signal lines, the ON / OFF state of the liquid crystal pixels is utilized by utilizing the fact that the TFTs are turned ON. OFF was individually controlled. By controlling the pixels by such a method, a liquid crystal electro-optical device having a high contrast can be realized.

[0005]

However, in such an active matrix system, it is extremely difficult to perform gradation display such as light and dark and color tone. Conventionally, for gray scale display, a method has been studied which utilizes the fact that the light transmittance of a liquid crystal changes depending on the magnitude of an applied voltage. This is, for example, the source of the TFT in the matrix.
By supplying an appropriate voltage from the peripheral circuit between the drains and applying a signal voltage to the gate electrode in that state,
It is intended to apply a voltage of that magnitude to the liquid crystal pixels.

However, in such a method, for example, due to the inhomogeneity of the TFT and the inhomogeneity of the matrix wiring, the voltage actually applied to the liquid crystal pixels differs by at least several% depending on each pixel. Oops. On the other hand, for example, the voltage dependence of the light transmittance of the liquid crystal is extremely non-linear, and the light transmittance changes rapidly at a specific voltage. In some cases it was significantly different. Therefore, in practice, achieving 16 gradations has been the limit.

[0007] As described above, the difficulty of gradation display is extremely disadvantageous in that a liquid crystal display device competes with a CRT (cathode ray tube) which is a conventional general display device. An object of the present invention is to propose a completely new method for realizing a gray scale display which has been difficult in the past.

[0008]

[Means for Solving the Problem] As mentioned above, it is possible to control the light transmittance of the liquid crystal by controlling the voltage applied to the liquid crystal in an analog manner. It has been found that gradation can be visually obtained by controlling the time during which voltage is applied to the liquid crystal.

For example, when a TN (twisted nematic) liquid crystal, which is a typical liquid crystal material, is used,
For example, in FIG. 1A, when comparing a case where a rectangular pulse as shown by A is applied with a case where a rectangular pulse as shown by C is applied, it is found that A is brighter. . Here, the pulse period was 1 msec. As a result, A was the brightest, and then B, C, and D in that order. This is completely unexpected. This is because in the above-mentioned ordinary TN liquid crystal material, 1 ms
The time ec is too short, and the TN liquid crystal does not react in such a short time. Therefore, in any case, it is impossible to realize the ON state of the liquid crystal. However, in reality, the liquid crystal was able to realize an intermediate density.

The specific principle is not yet known in detail. However, the present inventors have found that gradation expression can be performed using this phenomenon. That is, by applying a pulse to the liquid crystal material at a period such that the liquid crystal material does not react, by controlling the pulse width, an intermediate brightness is realized by digital control, which is exactly the feature of the present invention. Things. As a result of the study of the present inventors, it has been found that the pulse period for obtaining such an intermediate density needs to be 10 msec or less in the case of a TN liquid crystal.

Here, the meaning of the term pulse period will be clarified. That is, in this case,
A plurality of pulses are continuously applied to the liquid crystal. In this case, the pulse cycle refers to the time from the start of one pulse to the start of the next pulse.
Therefore, it is the reciprocal of the pulse repetition frequency. The pulse width refers to a time during which a pulse is in a voltage state. Therefore, in FIG. 1, for example, in the case of a pulse train of C, T is the pulse period, and τ is the pulse width.

A similar effect was observed in the STN liquid crystal, the ferroelectric liquid crystal, and the polymer liquid crystal or the dispersion type liquid crystal. In each case, it became clear that an intermediate color tone can be obtained by applying a pulse having a period shorter than the response time. That is, S
100 msec or less, preferably 10 msec or less for a TN liquid crystal, and 100 μsec or less for a ferroelectric liquid crystal.
sec or less, preferably 10 μsec or less, and 10 msec or less for polymer liquid crystal or dispersion type liquid crystal.
Preferably, by applying a pulse having a cycle of 1 msec or less, a gradation display was obtained.

Normally, for an image of a television or the like, 30 times per second is required.
The still images are sequentially fed out to form a moving image. Therefore, the duration of one still image is about 30 msec.
It is. This time is too early for the human eye,
It is literally “not to be caught”, and as a result, still images cannot be visually identified one by one. In any case, in order to obtain a normal moving image, one still image cannot be continued for 100 msec or longer at the longest.

If 256 gradations are to be displayed using the present invention, for example, if T = 3 msec,
It is necessary to adopt a pulse voltage application method capable of dividing the time of 3 msec by at least 256 as a method of applying a voltage to a pixel. That is, at least 3 msec /
It is necessary to form a circuit in which a pulse voltage of 256 = 11.7 μsec is applied to the pixel. Actually, as shown in FIG. 3, the duty ratio τ / T of the pulse and the light transmittance of the liquid crystal pixel are in a non-linear relationship. In order to obtain 256 gradations, the duty ratio of the pulse must be further reduced. Fine control is necessary.

In addition, when an actual image is displayed, other pixels must be considered. In an actual image display device, for example, there are as many as 400 rows. That is,
As will be described later, the number of active elements in the matrix is 10
An extremely short response of 0 nsec is required. Therefore, an example of a circuit having such a short-time response is shown in FIG.
Hereinafter, the description will be made.

FIG. 4 shows an example of an active matrix circuit of a liquid crystal display device necessary for carrying out the present invention. In the present invention, since the active element is required to respond in a short time of 100 nsec or less, it is necessary to form a circuit that operates at high speed. In order to do not perform the NTFT or PTFT only Death switching as in the prior art, the NTFT and PTFT as shown in FIG. 4 is configured to operate in a complementary manner, deformation Transfer
It is necessary to use a gate type circuit. Although this example shows an example of an N × M matrix, only the vicinity of n rows and m columns is shown to avoid complexity. If you expand the same thing up, down, left and right, you will get a complete one.

FIG. 4 shows four modified transfer gates. The source of each modified transfer gate is connected to _Ym or Ym _{+ 1} (hereinafter collectively referred to as Y line). The gate of the modified transfer gate is connected to _Xn or _{Xn + 1} (hereinafter collectively referred to as X-ray). In addition, each deformation transfer
The gate drain is the liquid crystal pixel Zn _{. m} , Zn _{. m + 1} ,
Zn _{+ 1. m} , Zn _{+ 1. m + 1} . NTFT and PTF in modified transfer gate
Since T is symmetric, its positions may be interchanged.

Next, an example of the operation of a circuit using such a circuit will be described with reference to FIGS. This matrix circuit needs to operate so as to apply a pulsed voltage as shown in FIG. 1A to the liquid crystal cell. FIG. 1B shows an outline of the signal voltages applied to the X-rays and the Y-lines to generate such a pulse. As an example, consider a 400 × 640 matrix.

The signal applied to the Y line is represented by V (Y _m ) in the case of the _Ym line, for example, which is actually 256 out of a group of pulses repeated in the cycle T. Pulse (hereinafter referred to as sub-pulse),
Further, each of the 256 sub-pulses is 400
It can be seen that the pulse train is composed of a pulse train including a number of elements. Here, the number 400 is the number of rows in the matrix. Therefore, if the minimum unit of the pulse applied to the Y line is T = 3 msec, it is 29 nsec.

On the other hand, during the time T / 256,
V (X ₁ ), V (X _n ), V (X _{n + 1} ), V (X
₄₀₀ ), a pulse whose polarity is inverted at least once (hereinafter referred to as a bipolar pulse) is applied with a staggered timing. The bipolar pulse needs to be shorter than the minimum unit pulse of the pulse applied to the Y line. Eventually, during time T, 256 bipolar pulses are applied to each X-ray.

Next, the operation of the actual circuit will be described with reference to FIG. First, a first sub-pulse is applied to each Y line. Of course, these sub-pulses are different for each Y line. On the other hand, as described above, the bipolar pulse is applied to the X-ray in order of X ₁ and then X ₂ . First, consider the case where the bipolar pulse is applied to the X _1. At this time, the pixel Z
_The active element connected to _1.1 is turned on. Then, the Y connected to this active element
Line because it is a state where a voltage is applied, pixel Z ₁₁ is charged. Then, since the bipolar pulse is cut off before the voltage of the Y line becomes zero, electric charge is left in the pixel _Z1.1 and the voltage state is maintained. Similarly, Z _{1.. m} is also Z
_{1. Both m + 1} and Z _1.400 are in a voltage state.

In this way, consider the case where bipolar pulses are applied one after the other and applied to _Xn .
Now, four pixels Zn _{. m} , Zn _{. m + 1} ,
Zn _{+ 1. m} , Zn _{+ 1.} if has focused on _{m + 1,} it may be of interest to the n-th and (n + 1) th first sub-pulse of _{Y m} and _{Y m + 1.} Y _{m is} also Y _{m + 1}
Also has an n-th pulse, so pixel Z _{n. m} , Z
_{n. m + 1} becomes a voltage state. Next, a bipolar pulse is applied to _{Xn + 1} . Both Y _m and Y _{m + 1} (n +
1) Since there is a pulse at the first position, the pixel Z
_{n + 1. m} , Zn _{+ 1. m + 1} is charged.

Next, although omitted in the figure, it is assumed that a second sub-pulse has arrived. At this time, Y _{m is} also Y _{m + 1}
Also, if there are n-th and (n + 1) -th pulses, the state of charge is not lost, and the four pixels continue to be in the voltage state. Thereafter, it is assumed that the voltage state of all four pixels continues until the (h-1) th sub-pulse.

Next, it is assumed that the sub-pulse advances and the h-th sub-pulse arrives. In the figure, to avoid complexity, n
Pulses other than the (th) and (n + 1) th pulses are omitted. At this time, since there are n-th pulses in both Y _m and Y _{m + 1} , the pixel Zn _{. m} , Zn _{. m + 1} continues the voltage state. However, since Y _{m + 1} did not have the (n + 1) th pulse, pixels Zn _{+ 1. m} indicates that the voltage state continues but the pixels Zn _{+ 1. m + 1} is a state in which the gate of the active element is ON, and since there is no external supply of voltage, the stored charge is released and the voltage state is interrupted.

Furthermore, when the sub-pulses of the i came, because the voltage of the (n + 1) th pulse of the _{Y m} is _{zero, Z n + 1.} The charge state of _m is released. Less than,
In the j-th and k-th sub-pulses, respectively,
_{m + 1} , Y _{m, since} the n-th signal was zero, the pixel Zn _{. m} , Zn _{. The} state of charge of _{m + 1} is k-th,
Interrupted during the j-th sub-pulse. Through such a process, the time of the voltage state can be digitally controlled for each pixel as shown by V (Z) in FIG.

By repeating such an operation, the width of the voltage pulse applied to each pixel can be arbitrarily controlled as shown in FIG. As is apparent from the above description, in practicing the present invention, the sub-pulses as described above do not have to be in a pulse form that can be clearly defined. For the sake of simplicity, the concept of sub-pulses has been introduced. In particular, it is apparent that the present invention can be implemented even if the sub-pulses are not clear and the signals have almost no boundaries. is there.

Similarly, a large number of pulses included in the sub-pulses need not be independent pulses, and may be a series of ON / OFF signals. Furthermore, for simplicity of explanation, the zero level and voltage level of the signal have been clarified, but since this is only a matter of being below or above the threshold voltage of the liquid crystal, it is absolutely necessary. It does not need to be zero.

Replace the above with general expressions
When the present invention, signal a signal that lasts from the time _{T 0} until _{T 1}
While applying to at least one of the
Less positive and negative less than or equal to (T ₁ −T ₀ )
And two pulses, the N-channel transistor and
Process of applying to the gate of the P-channel transistor
And from time T ₂ to T ₃ (T ₁ <T ₂ <T ₃ )
No signal is applied to the Y line, during which the pulse width
_(T 3 -T ₂₎ positive and negative of the at least two or less
Is applied to the N-channel transistor and the P-channel transistor.
Applying a voltage to the gate of the channel transistor.
It can be expressed as a feature.

[0029] In addition, in the other expressions of the present invention, whether the time _{T 0}
At least one signal which lasts until Luo T ₁ of the signal lines Y line
, And during this time, the pulse width is less than (T ₁ −T ₀ ).
The lower bipolar pulse is applied to the X-ray 1
Comprising the steps of applying to the One, _T 3 from the time _{T 2 (T 1 <T 2} <
Until T ₃ ), no signal is applied to the Y line.
In addition , a bipolar transistor having a pulse width equal to or less than (T ₃ −T ₂ )
Applying a pulse to the X-rays.
It can also be expressed as a feature.

[0030]

[Embodiment 1] "Example 1" This embodiment using the liquid crystal display device using the circuit configuration as shown in FIG. 4, since to produce a wall-mounted television, intends Okona description thereof. The TFT at that time was made of polycrystalline silicon using laser annealing. FIG. 5 shows an actual arrangement of electrodes and the like corresponding to this circuit configuration for one pixel. First, a method for manufacturing a liquid crystal panel used in this embodiment using FIGS.

In FIG. 6A, a silicon oxide as a blocking layer 51 is formed on a glass 50 other than quartz glass which can withstand a heat treatment at an inexpensive temperature of 700 ° C. or less, for example, about 600 ° C. by using a magnetron RF (high frequency) sputtering method. The membrane is made to a thickness of 1000-3000 °. The process conditions are as follows: 100% oxygen atmosphere, film formation temperature 150 ° C, output 40
The pressure was set to 0 to 800 W and the pressure to 0.5 Pa. The deposition rate using quartz or single crystal silicon as the target is 30 to 100 °
/ Min.

[0032] was prepared silicon film 52 by the plasma CVD method a silicon film thereon. The film formation temperature is 250 ° C to 350 ° C
In have Okona, and 320 ° C. In this embodiment, a monosilane (SiH _4). Not only monosilane (SiH ₄ ) but also disilane (Si ₂ H ₆ ) and trisilane (Si ₃ H
₈ ) may be used. These are placed in a PCVD apparatus at 3 Pa.
And a high frequency power of 13.56 MHz was applied to form a film. At this time, the high frequency power is 0.02 to 0.10
W / cm ² is appropriate, and in this embodiment, 0.055 W / cm ²
cm ² was used. The flow rate of monosilane (SiH ₄ ) was set to 20 SCCM, and the deposition rate at that time was about 120 ° /
Minutes. In order to control the threshold voltage (Vth) between the PTFT and the NTFT to be substantially the same, boron is used in a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ by using diborane.
May be added during the film formation.

In addition to the plasma CVD, the silicon layer serving as the channel region of the TFT is formed by sputtering,
A low pressure CVD method may be used, and the method will be briefly described below. If the Hare Okona by sputtering, the back pressure of the pre-sputtered with 1 × ¹⁰ -5 Pa or less single-crystal silicon as a target, and Tsu Okona in an atmosphere mixed 20-80% of hydrogen into the argon. For example, argon was 20% and hydrogen was 80%. The deposition temperature is 150 ° C., the frequency is 13.56 MHz,
The sputter output was 400-800 W and the pressure was 0.5 Pa.

In the case of forming by a reduced pressure gas phase method, 450 to 550 ° C. lower by 100 to 200 ° C. than the crystallization temperature, for example, 5 to 50 ° C.
At 30 ° C., disilane (Si ₂ H ₆ ) or trisilane (S
i ₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. Film formation rate is 50-25
0 ° / min. In order to control the threshold voltage (Vth) of the PTFT and the NTFT to be substantially the same, boron is used to form 1 × 10 ¹⁵ to 1 × 10 ¹⁸ c using diborane.
It may be added during film formation as a concentration of m- ³ .

The coatings formed by these methods are:
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. In order to promote crystallization, the oxygen concentration should be 7 × 10
It is desirable to be ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less. However, if the amount is too small, the off-state leakage current increases due to the backlight.
This concentration was chosen. If the oxygen concentration is high, crystallization is difficult, and the laser annealing temperature must be increased or the laser annealing time must be lengthened. Hydrogen is 4 × 1
It was 0 ²⁰ cm ⁻³ , which was 1 atomic% as compared with silicon 4 × 10 ²² cm ⁻³ .

In order to further promote crystallization of the source and the drain, the oxygen concentration is set to 7 × 10 ¹⁹ cm ^−3.
Hereafter, preferably, it is set to 1 × 10 ¹⁹ cm ⁻³ or less, and oxygen is ion-implanted only in a channel formation region of a TFT forming a pixel to 5 × 10 ^{20 to} 5 × 10 ²¹ cm ^−3.
You may add so that it may become. By the above method, a silicon film in an amorphous state was formed to a thickness of 500 to 5000 °, in this example, 1000 °.

Thereafter, as shown in FIG. 6B, a pattern was formed by opening only the source / drain regions of the photoresist 53 using the mask P1. A silicon film 54 serving as an n-type active layer was formed thereon by a plasma CVD method. The film formation temperature is from 250 ° C. to 350 ° C., and in this embodiment, it is 320 ° C., and monosilane (SiH ₄ ) and monosilane-based phosphine (PH ₃ ) having a concentration of 3% are used. These were introduced into the PCVD apparatus at a pressure of 5 Pa, and high-frequency power of 13.56 MHz was applied to form a film. At this time, the high frequency power is 0.05 to 0.20 W / cm.
² is appropriate, and in this example, 0.120 W / cm ² was used.

The specific conductivity of the n-type silicon layer formed by this method was about 2 × 10 ⁻¹ [Ωcm ⁻¹ ]. The film thickness was 50 °. Thereafter, the resist 53 is removed by a lift-off method, and the source / drain region 5 is removed.
5, 56 were formed. A p-type active layer was formed using a similar process. The gas introduced at that time is monosilane (SiH ₄ ) and monosilane-based diborane (B
Using ₂ H ₆₎ 5% strength ones. These introduced city at a pressure of 4Pa in PCVD apparatus, was formed by adding 13.56MHz high frequency power. At this time, the high frequency power is 0.0
5 to 0.20 W / cm ² is appropriate, and in this example, 0.120 W / cm ² was used. The specific conductivity of the p-type silicon layer completed by this method is 5 × 10 ⁻² [Ωcm
^-1 ]. The film thickness was 50 °. (FIG. 6
(C))

Thereafter, source / drain regions 59 and 60 were formed by the lift-off method in the same manner as in the N-type region. Thereafter, the silicon film 52 is etched away using the mask P3, and the island region 6 for the N-channel thin film transistor is removed.
3 and island region 6 for P-channel type thin film transistor
4 was formed.

[0040] Then using the XeCl excimer laser, and at the same time laser annealing the source, drain and channel regions, the active layer was Do Tsu <br/> to put the laser doping. At this time, the laser energy has a threshold energy of 130 mJ / cm ^2.
0 mJ / cm ² is required. However, from the beginning 220
When energy of mJ / cm ² or more is irradiated, hydrogen contained in the film is rapidly released, and the film is destroyed. For this purpose, it is necessary to first displace hydrogen and then melt it with low energy. In this embodiment, first 150 m
After purging hydrogen at J / cm ² , 230m
Crystallization was performed at J / cm ² . (FIG. 6 (D))

On this, a silicon oxide film was formed as a gate insulating film to a thickness of 500 to 2000 {for example, 1000}. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix the sodium ions.

Thereafter, 1 to 5 × 10
A silicon film having a concentration of ²¹ cm ⁻³ or a silicon film and molybdenum (Mo), tungsten (W), M
A multilayer film with oSi ₂ or WSi ₂ was formed. This is patterned by a fourth photomask P4 to obtain FIG.
(E) was obtained. Gate electrode 66 for NTFT, PTFT
A gate electrode 67 was formed. For example, channel length 7μ
m, as a gate electrode, phosphorus-doped silicon was formed to a thickness of 0.2 μm, and molybdenum was formed thereon to a thickness of 0.3 μm. (Figure
6 (E))

When aluminum (Al) is used as the gate electrode material, the aluminum is used as the fourth photomask 69.
After patterning in, by anodizing the surface,
Since the self-alignment method can be applied, the source and drain contact holes can be formed at positions closer to the gate, so that the mobility and threshold voltage can be further reduced, and the characteristics of the TFT can be further improved.

Thus, a C / TFT can be manufactured without applying a temperature to 400 ° C. or more in all steps. Therefore, it is not necessary to use an expensive substrate such as quartz as a substrate material, and it can be said that the process is very suitable for the large-screen liquid crystal display device of the present invention.

[0045] In FIG. 7 (A), was Tsu Okona <br/> as formation of a silicon oxide film by an interlayer insulator 68 sputtering as described above. This silicon oxide film is formed by LPCVD, optical CVD
Or a normal pressure CVD method. For example, 0.2-0.
6 μm thick, and then a fifth photomask P
5 was used to form an electrode window 79. Thereafter, further, aluminum was formed on the entire surface to a thickness of 0.3 μm by a sputtering method, and leads 74 and contacts 73 and 75 were formed using a sixth photomask P6 .
After 7 (B)), the planarizing organic resin 77 for example translucent polyimide resin surface formed by coating and Tsu Okona electrodes drilling again in a seventh photomask P7. (FIG. 7 (C))

Further, an ITO (indium tin oxide) was formed on the whole to a thickness of 0.1 μm by a sputtering method, and a pixel electrode 71 was formed using an eighth photomask P8. This ITO is deposited at room temperature to 150 ° C.
Fulfilled by annealing at 00 ° C. oxygen or air.
(FIG. 7D) The electrical characteristics of the obtained TFT are PTF
At T, the mobility is 40 (cm ² / Vs), and Vth is −5.9.
(V), the mobility of NTFT is 80 (cm ² / Vs),
Vth was 5.0 (V).

One substrate for a liquid crystal electro-optical device manufactured according to the above method was obtained. FIG. 5 shows the arrangement of the electrodes and the like of the liquid crystal display device.
An N-channel thin film transistor and a P-channel thin film transistor are provided at the intersection of the first signal line 3 and the second signal line 4. A matrix configuration using such a C / TFT is provided. By repeating such a structure left and right, up and down, 640 × 480, 1280 × 9
A liquid crystal display device having a large pixel such as 60 can be obtained. In this embodiment, the size is set to 1920 × 400. Thus, a first substrate was obtained.

FIG. 8 shows a method for manufacturing the other substrate. A polyimide resin obtained by mixing a black pigment with polyimide is formed on a glass substrate to a thickness of 1 μm using a spin coating method,
Black stripe 8 using ninth photomask P9
1 was produced. (FIG. 8A) Thereafter, a polyimide resin mixed with a red pigment was formed into a film having a thickness of 1 μm by spin coating, and a red filter 83 was manufactured using a tenth photomask P10. (FIG. 8 (B))

Similarly, a green filter 85 and a blue filter 86 were manufactured using the masks P11 and P12. During these fabrications, each filter was fired at 350 ° C. in nitrogen for 60 minutes. (FIG. 8 (C)) Thereafter, the leveling layer 89 is formed again by the spin coating method.
Was produced using transparent polyimide. (FIG. 8 (D))

Thereafter, ITO (indium tin oxide) was formed on the entire surface by sputtering to a thickness of 0.1 μm, and a common electrode 90 was formed using a fifth photomask P13. This ITO is deposited at room temperature to 150 ° C.
This was achieved by annealing in oxygen or air at ~ 300 ° C to obtain a second substrate. (FIG. 8 (E))

[0051] on the substrate, using the offset method, a polyimide precursor was printed, the 350 ° C. 1 hour calcination in a non-oxidizing atmosphere for example in nitrogen Tsu Okona. Thereafter, a known rubbing method was used to modify the surface of the polyimide, and at least initially, a means for aligning liquid crystal molecules in a certain direction was provided.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. A drive IC having a TAB shape and a PCB having a common signal and potential wiring were connected to leads on the substrate, and a polarizing plate was attached on the outside to obtain a transmissive liquid crystal electro-optical device. This was connected to a rear lighting device in which three cold cathode tubes were arranged, and a tuner for receiving TV radio waves to complete a wall-mounted TV. Compared to a conventional CRT system television, the device has a flat shape, so that it can be installed on a wall or the like. The operation of this liquid crystal television was confirmed by applying signals substantially equivalent to those shown in FIGS. 1 and 2 to the liquid crystal pixels.

Embodiment 2 In this embodiment, a viewfinder for a video camera using a liquid crystal electro-optical device having a diagonal width of 1 inch is manufactured and the present invention is implemented. In this embodiment, a viewfinder was formed by forming a device using a high mobility TFT by a low-temperature process with a configuration of 387 × 128 pixels. The arrangement of the active elements on the substrate of the liquid crystal display device used in this embodiment is shown in FIG.
FIG. 9 illustrates a fabrication process showing a B ′ cross section.

[0054] In FIG. 9 (A), the inexpensive, 700 ° C. or less, for example, a silicon oxide film as a blocking layer using magnetron RF (radio frequency) sputtering method on the glass 50 capable of withstanding heat treatment at about 600 ° C. 1000 to 3000Å
To a thickness of The process conditions are a 100% oxygen atmosphere, a film forming temperature of 15 ° C., an output of 400 to 800 W, and a pressure of 0.
5 Pa was set. The deposition rate using quartz or single crystal silicon as the target was 30 to 100 ° / min.

On this, a silicon film is formed by LPCVD (decompression gas phase).
It was formed by a sputtering method, a sputtering method or a plasma CVD method. When formed by the reduced pressure gas phase method, the crystallization temperature is 10
At a temperature of 450 to 550 ° C, for example 530 ° C, which is lower by 0 to 200 ° C, disilane (Si ₂ H ₆ ) or trisilane (Si
₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. The deposition rate is 50 to 250
Å / min. In order to control the threshold voltage (Vth) of the PTFT and the NTFT to be substantially the same, boron is used to diborane to 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm.
A concentration of ⁻³ may be added during film formation.

[0056] When performing the sputtering method, the back pressure of the pre-sputtered with 1 × ¹⁰ -5 Pa or less single-crystal silicon as a target, and Tsu Okona in an atmosphere mixed 20-80% of hydrogen into the argon. For example, argon 20%, hydrogen 80%
And The deposition temperature is 150 ° C. and the frequency is 13.56 MH.
z, sputter output 400-800W, pressure 0.5P
a.

When a silicon film is formed by the plasma CVD method, the temperature is set to, for example, 300 ° C., and monosilane (SiH
₄ ) or disilane (Si ₂ H ₆ ) was used. These were introduced into a PCVD apparatus, and a high-frequency power of 13.56 MHz was applied to form a film. According to the above method, the silicon film in the amorphous state is formed at 500 to 5000 °, for example, 1500 °.
After fabrication to a thickness of 12 to 12
The heat treatment was performed at a medium temperature in a non-oxide atmosphere for 70 hours, for example, at a temperature of 600 ° C. in a hydrogen atmosphere.

[0058] In FIG. 9 (A), the subjected to photo-etching silicon film at a first photomask, the A-A 'cross-sectional side region 13 (channel width 20 [mu] m) figures for NTFT, area for PTFT No. 22 was formed on the BB 'cross section side. On this, a silicon oxide film is used as a gate insulating film,
It was formed to a thickness of 2000 {for example, 1000}. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix the sodium ions.

Thereafter, 1 to 5 × 10
A silicon film having a concentration of ²¹ cm ⁻³ or a silicon film and molybdenum (Mo), tungsten (W), M
A multilayer film with oSi ₂ or WSi ₂ was formed. This is patterned using a second photomask, and FIG.
I got A gate electrode 9 for NTFT and a gate electrode 21 for PTFT were formed. In this embodiment, the channel length for NTFT is 10 μm, the channel length for PTFT is 7 μm,
As a gate electrode, phosphorus-doped silicon was formed to a thickness of 0.2 μm, and molybdenum was formed thereon to a thickness of 0.3 μm.

[0060] In FIG. 9 (C), the relative source 18 drain 20 for PTFT, boron 1 to 5 × ^{10 15} c
It was added by ion implantation at a dose of m- ² . Then as FIG. 9 (D), and the photoresist 61 is formed using a photomask. Phosphorus was added as a source 10 and a drain 12 for NTFT by an ion implantation method at a dose of 1 to 5 × 10 ¹⁵ cm ⁻² .

When aluminum (Al) is used as a gate electrode material, after patterning it with a second photomask and then anodizing the surface, the self-alignment method can be applied. Since the drain contact hole can be formed at a position closer to the gate, the characteristics of the TFT can be further improved from the reduction of the mobility and the threshold voltage.

[0062] Next, Tsu Okona 10 to 50 hours again heating annealing at 600 ℃. The source 10 and the drain 12 of the NTFT and the source 18 and the drain 20 of the PTFT were formed as P ⁺ and N ⁺ by activating impurities. Channel formation regions 19 and 11 are formed below the gate electrodes 21 and 9 as semi-amorphous semiconductors. In this way, a C / TFT can be manufactured without applying a temperature to 700 ° C. or more in all steps, although it is a self-aligned method. Therefore, it is not necessary to use an expensive substrate such as quartz as a substrate material, and this is a process very suitable for the large pixel liquid crystal display device of the present invention.

[0063] Thermal annealing in this embodiment FIG. 9 (A), the
(D) was performed twice. However omitted by annealing obtaining characteristics of FIG. 9 (A), the both may be shortened in doubles by annealing manufacturing time in FIG. 9 (D) a. FIG.
In (E), an interlayer insulator 65 was formed as a silicon oxide film by the sputtering method described above. This silicon oxide film may be formed by an LPCVD method, a photo CVD method, or a normal pressure CVD method. For example, it is formed to a thickness of 0.2 to 0.6 μm, and thereafter, a window 66 for an electrode is formed using a photomask.
Was formed. Further, as shown in FIG. 9 (F), aluminum was entirely formed on these by sputtering, and
1, and after preparing the contact 72 by using a photomask, a planarizing organic resin 69 for example translucent polyimide resin surface formed by coating and Tsu Okona electrodes drilling again in the photomask.

An ITO (indium tin oxide film) was formed by a sputtering method so that the two TFTs had a complementary structure, and their output terminals were connected to the electrodes of one pixel of the liquid crystal device as transparent electrodes. It was etched using a photomask to form the electrode 17. This I
TO was formed at room temperature to 150 ° C. and achieved by annealing at 200 to 400 ° C. in oxygen or atmosphere. In this way, the NTFT, PTFT 22 and transparent conductive electrode 17 are formed.
Were fabricated on the same glass substrate 50. (Fig. 9 (G))
The electrical characteristics of the obtained TFT are PTFT and the mobility is 2
0 (cm ² / Vs), Vth is -5.9 (V), NT
In FT, the mobility is 40 (cm ² / Vs) and Vth is 5.0.
(V).

One substrate for a liquid crystal device was manufactured according to the method described above. FIG. 5 shows the arrangement of the electrodes and the like of the liquid crystal display device. A matrix configuration using such a C / TFT is provided. Next, as a second substrate, an ITO (indium tin oxide film) was formed also by a sputtering method on a substrate in which a silicon oxide film was laminated by 2000 mm on a soda lime glass by a sputtering method. This ITO is formed at room temperature to 150 ° C.
This was achieved by annealing in oxygen or air. Also,
On this substrate, a color filter was formed using the same method as in "Example 1" to obtain a second substrate.

[0066] on the substrate, using the offset method, a polyimide precursor was printed, the 350 ° C. 1 hour calcination in a non-oxidizing atmosphere for example in nitrogen Tsu Okona. Thereafter, the surface of the polyimide was modified using a known rubbing method, and at least initially, means for aligning the liquid crystal molecules in a certain direction was provided to obtain first and second substrates.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. Because the lead on the substrate that pitch and fine 46 [mu] m, was Okona Tsu <br/> connections using COG method. In this embodiment, a method is used in which gold bumps provided on an IC chip are connected with an epoxy-based silver-palladium resin, and the IC chip and the substrate are filled and fixed with an epoxy-modified acrylic resin for the purpose of fixing and sealing. Was. Thereafter, a polarizing plate was attached on the outside to obtain a transmission type liquid crystal display device.

It was confirmed that the liquid crystal display device could display 128 gradations by a driving method substantially equivalent to that of the first embodiment. For example, 49,152 of 384 × 128 dots
When an ordinary analog gradation display was Tsu Okona to the liquid crystal electro-optical device that created a set of TFT to 50mm square (gang of 36 sheets from 300mm square substrate), variations in characteristics of the TFT of about ± 10% Due to its existence, 16 gradation display was the limit. However, when the digital gradation display according to the present invention is performed, since it is hard to be affected by the characteristic variation of the TFT element, it is possible to display up to 128 gradations, and in the color display, 2,097,152 colors are various and delicate. Color display has been realized.

In the case of displaying software such as a television image, for example, even a “rock” having the same color has a slightly different color tone due to the degree of light corresponding to a minute depression or the like. If you Okona vomiting display close to natural colors, requires difficult with 16 gradations, not suitable for expression of these subtle depression. With the gradation display according to the present invention, it is possible to impart these minute color changes.

[0070] In "Example 3" This embodiment using the liquid crystal display device using the circuit configuration as shown in FIG. 4, since to produce a wall-mounted television, intends Okona description thereof. The TFT at that time was made of polycrystalline silicon using laser annealing. The following describes in accordance with FIG. 10 a method for manufacturing a TFT section.

[0071] FIG. 10 in (A), 700 ° C. or less inexpensive than the quartz glass, for example, about 600 ° C. magnetron RF on the glass 100 that can withstand the heat treatment (high frequency)
A silicon oxide film as the blocking layer 101 is formed to a thickness of 1000 to 3000 ° by using a sputtering method. The process conditions were a 100% oxygen atmosphere, a film formation temperature of 15 ° C., an output of 400 to 800 W, and a pressure of 0.5 Pa. The deposition rate using quartz or single crystal silicon as the target is 30 to 10
0 ° / min.

[0072] was prepared silicon film 102 by a plasma CVD silicon film thereon. The deposition temperature is 250 ° C to 350
In this example, the temperature was set to 320 ° C., and monosilane (SiH ₄ ) was used. Not only monosilane (SiH ₄ ) but also disilane (Si ₂ H ₆ ) and trisilane (Si ₃ H
₈ ) may be used. These are placed in a PCVD apparatus at 3 Pa.
And a high frequency power of 13.56 MHz was applied to form a film.

At this time, the high frequency power is 0.02 to 0.10
W / cm ² is appropriate, and in this embodiment, 0.055 W / cm ²
cm ² was used. The flow rate of monosilane (SiH ₄ ) was set to 20 SCCM, and the deposition rate at that time was about 120 ° /
Minutes. In order to control the threshold voltage (Vth) between the PTFT and the NTFT to be substantially the same, boron is used in a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ by using diborane.
May be added during the film formation. The plasma CVD is used to form a silicon layer to be a channel region of a TFT.
In addition, a sputtering method or a low pressure CVD method may be used, and the method will be briefly described below.

[0074] When the Hare Okona by sputtering, the back pressure of the pre-sputtered with 1 × ¹⁰ -5 Pa or less single-crystal silicon as a target was performed in an atmosphere mixed with hydrogen in argon 20-80%. For example, argon 20%, hydrogen 80%
And The deposition temperature is 150 ° C. and the frequency is 13.56 MH.
z, sputter output 400-800W, pressure 0.5P
a.

When the film is formed by the reduced pressure gas phase method, 450 to 550 ° C. lower than the crystallization temperature by 100 to 200 ° C., for example, 5 to 50 ° C.
At 30 ° C., disilane (Si ₂ H ₆ ) or trisilane (S
i ₃ H ₈ ) was supplied to a CVD apparatus to form a film. The pressure in the reactor was 30 to 300 Pa. Film formation rate is 50-25
0 ° / min. In order to control the threshold voltage (Vth) of the PTFT and the NTFT to be substantially the same, boron is used to form 1 × 10 ¹⁵ to 1 × 10 ¹⁸ c using diborane.
It may be added during film formation as a concentration of m- ³ .

The coatings formed by these methods are:
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. In order to promote crystallization, the oxygen concentration should be 7 × 10
It is desirable to be ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less. However, if the amount is too small, the off-state leakage current increases due to the backlight.
This concentration was chosen. If the oxygen concentration is high, crystallization is difficult, and the laser annealing temperature must be increased or the laser annealing time must be lengthened. Hydrogen is 4 × 1
It was 0 ²⁰ cm ⁻³ , which was 1 atomic% as compared with silicon 4 × 10 ²² cm ⁻³ .

In order to promote crystallization of the source and the drain, the oxygen concentration is set to 7 × 10 ¹⁹ cm ^−3.
Hereafter, preferably, it is set to 1 × 10 ¹⁹ cm ⁻³ or less, and oxygen is ion-implanted only in a channel formation region of a TFT forming a pixel to 5 × 10 ^{20 to} 5 × 10 ²¹ cm ^−3.
You may add so that it may become. By the above method, a silicon film in an amorphous state was formed to a thickness of 500 to 5000 °, in this example, 1000 °.

After that, the photoresist 103 is
Using No. 1, a pattern was formed in which only the region to be the source / drain region of the NTFT was opened. Using the resist 103 as a mask, phosphorus ions are implanted by ion implantation at a dose of 2 × 10 ^{14 to} 5 × 10 ¹⁶ cm ⁻² , preferably 2 × 10 ¹⁶ cm ⁻² to form the n-type impurity region 104. . (FIG. 10A) After that, the resist 103 was removed.

Similarly, a resist 105 was applied, and using the mask P3, a pattern was formed in which only the regions to be the source / drain regions of the PTFT were opened. Then, using the resist 105 as a mask, a p-type impurity region was formed. As an impurity, boron is used, and an ion implantation method is used, and 2 × 10 ^{14 to} 5 × 10 ¹⁶ cm ⁻² ,
Preferably, an impurity is introduced only by 2 × 10 ¹⁶ cm ⁻² . Like this. To give 10 a (B).

After that, a thickness of 50 to 3
00 nm, for example, 100 nm silicon oxide film 107
Was formed by the above-mentioned RF sputtering method. And
Using a XeC1 excimer laser, the source, drain and channel regions are crystallized by laser annealing.
Activated. At this time, the threshold energy of the laser energy is 130 mJ / cm ² , and 220 mJ / cm ² is required to melt the entire film thickness. However, when an energy of 220 mJ / cm ² or more is irradiated from the beginning, hydrogen contained in the film is rapidly released, and the film is destroyed. For this purpose, it is necessary to first displace hydrogen and then melt it with low energy. In this embodiment, first
After becoming Oko the eviction of hydrogen at 50mJ / cm ^{2, 2}
Crystallization was performed at 30 mJ / cm ² . (FIG. 10
(C))

After the completion of the laser annealing, the silicon oxide film 107 was removed. Thereafter, the island-shaped NTFT region 111 and the PTFT are
A region 112 was formed. On this, a silicon oxide film 108 is used as a gate insulating film to form 500 to 2000 {for example, 1000}.
It was formed in thickness. This was made under the same conditions as those for forming the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix the sodium ions.

After this, 1 to 5 × 10
²¹cm^-3Silicon film with a concentration of
Molybdenum (Mo), tungsten (W), M
oSi₂Or WSi₂Was formed. this
Patterned using a fourth photomask P410
(D) was obtained. Gate electrode 109 for NTFT, PTF
A gate electrode 110 for T was formed. For example, channel length
7 μm, phosphorus-doped silicon as gate electrode 0.2 μm
m, on which molybdenum is formed to a thickness of 0.3 μm
Was.(FIG. 10 (D))

In the case where aluminum (Al) is used as the gate electrode material, it is used as the fourth photomask P4.
After patterning in, by anodizing the surface,
Since the self-alignment method can be applied, the source and drain contact holes can be formed at positions closer to the gate, so that the mobility and threshold voltage can be further reduced, and the characteristics of the TFT can be further improved.

Thus, a C / TFT can be manufactured without applying a temperature to 400 ° C. or more in all steps. Therefore, it is not necessary to use an expensive substrate such as quartz as a substrate material, and it can be said that the process is very suitable for the large-screen liquid crystal display device of the present invention. In FIG. 10 (E), was performed as formation of a silicon oxide film by a sputtering method with the interlayer insulator 113. This silicon oxide film may be formed by an LPCVD method, a photo CVD method, or a normal pressure CVD method. For example, formed to a thickness of 0.2 to 0.6 μm,
Thereafter, the window 1 for the electrode is formed using the fifth photomask P5.
17 was formed.

Thereafter, further, aluminum was formed on the whole of this to a thickness of 0.3 μm by sputtering, and leads 116 and contacts 114 and 115 were formed using a sixth photomask P6 (FIG. 10E ). Then, the surface was coated with an organic resin 119 for planarization, for example, a translucent polyimide resin, and an electrode hole was formed again using a seventh photomask P7. In addition, all of these
(Indium tin oxide) was formed to a thickness of 0.1 μm by a sputtering method, and a pixel electrode 118 was formed using an eighth photomask P8. This ITO film was formed at room temperature to 150 ° C. and achieved by annealing at 200 to 400 ° C. in oxygen or atmosphere. (FIG. 10 (F))

The electrical characteristics of the obtained TFT are PTFT
And the mobility is 35 (cm ² / Vs) and the Vth is −5.9.
(V), the mobility of NTFT is 90 (cm ² / Vs),
Vth was 4.8 (V). One substrate for a liquid crystal electro-optical device manufactured according to the above method was obtained. The method for fabricating the other substrate is the same as that in the first embodiment, and will not be described. Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive.

A drive IC in the form of a TAB and a PCB having a common signal and potential wiring were connected to leads on the substrate, and a polarizing plate was adhered on the outside to obtain a transmission type liquid crystal electro-optical device. This was connected to a rear lighting device in which three cold cathode tubes were arranged, and a tuner for receiving TV radio waves to complete a wall-mounted TV. Compared to a conventional CRT system television, the device has a flat shape, so that it can be installed on a wall or the like. The operation of this liquid crystal television was confirmed by applying signals substantially equivalent to those shown in FIGS. 1 and 2 to the liquid crystal pixels.

[0088]

In the present invention, with respect to gray scale display of a conventional analog method is characterized in Okona Ukoto gray scale display of the digital system. The effect is, for example, 640 × 40
Assuming a liquid crystal electro-optical device having a pixel number of 0 dots, it is extremely difficult to manufacture all the characteristics of all 256,000 TFTs without variation, and in reality, mass production and yield In consideration of the above, 16 gray scale display is considered to be the limit. On the other hand, as in the present invention, 256 gray scale display is performed by purely digital control only without adding any analog signal. It is possible to display more gradations than can be displayed. Since it is a complete digital display, there is no ambiguity of gradation due to variation in TFT characteristics. Therefore, even if there is little variation in TFT, extremely uniform gradation display was possible.

Therefore, conventionally, the TF with little variation
Although the yield was extremely poor in order to obtain T, the yield of the TFT was no longer a problem according to the present invention. Therefore, the yield of the liquid crystal device was improved, and the manufacturing cost was significantly reduced. For example, when a normal analog gray scale display is performed on a liquid crystal electro-optical device in which 256,000 sets of 640 × 400 dot 256,000 TFTs are formed in a 300 mm square, there is about ± 10% variation in TFT characteristics. , 16 gradation display was the limit.

However, when the digital gradation display according to the present invention is performed, it is hardly affected by the variation in the characteristics of the TFT elements, so that it is possible to display up to 256 gradations, and in the color display, a variety of 16,777,216 colors can be obtained. Thus, a subtle color display can be realized. In the case of displaying software such as television images, for example, even a “rock” made of the same color has a slightly different color due to its minute dents and the like. In the case where a display close to natural colors is to be performed, difficulties are required at 16 gradations. With the gradation display according to the present invention, it is possible to impart these minute color changes.

In the embodiment of the present invention, a TFT using silicon is used.
Has been mainly explained, but TFT using germanium
Can be used as well. In particular, single crystal germanium has an electron mobility of 3600 cm ² / Vs and a hole mobility of 18
00 cm ² / Vs and the value of single crystal silicon (1
350 cm ² / Vs, 480 cm ² / V in hole mobility
Since it exceeds the characteristic of s), it is a very excellent material for implementing the present invention that requires high-speed operation. Also,
Germanium has a lower transition temperature from an amorphous state to a crystalline state than silicon , and is suitable for a low-temperature process. In addition, the nucleation rate during crystal growth is low, and therefore, generally, large crystals are obtained when polycrystals are grown. Thus, germanium has characteristics comparable to those of silicon.

In order to explain the technical concept of the present invention, an electro-optical device using liquid crystal, particularly a display device has been mainly described as an example. However, in order to apply the idea of the present invention, no display device is required. It is not necessary to use a so-called projection type television, another optical switch, or an optical shutter. Further, it is apparent that the present invention can be applied to electro-optical materials that are not limited to liquid crystals, as long as optical characteristics change due to electric influences such as electric fields and voltages.

[Brief description of the drawings]

FIG. 1 shows a driving waveform according to the present invention.

FIG. 2 shows a driving waveform according to the present invention.

FIG. 3 shows an example of a gradation display characteristic according to the present invention.

FIG. 4 shows an example of a matrix configuration according to the invention.

FIG. 5 shows a planar structure of a device according to an example.

FIG. 6 shows a TFT process according to an embodiment.

FIG. 7 illustrates a TFT process according to an embodiment.

FIG. 8 shows a process of a color filter according to an example.

FIG. 9 shows a TFT process according to an embodiment.

FIG. 10 illustrates a TFT process according to an embodiment.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-50528 (JP, A)

Claims (3)

(57) [Claims] 1. A source over scan, one can signal Route drain, the other
And N-channel transistor connected to Gae-containing source, one said signal line of the drain drive of <br/> electro-optical device having a P-channel transistor and the other is connected to the pixel a method, by applying a signal that lasts from time _{T 0} to _{T 1 (T 0 <T 1} ) to the signal line, during the time _{T 0} to _{T 1,} the pulse width _(T 1 -T ₀₎ or less in a positive and negative of the at least two pulses, and the process to be applied to the gate of the said N-channel transistor P-channel transistor, from time T ₂ to _{T 3 (T 1 <T 2} <T 3) the any without applying a signal to the signal line, during the time T ₂ to T _3, the pulse width of the (T 3 _{-T 2)} or less is positive and negative at least two pulses, the N-channel transistor And the P The method of driving an electro-optical device characterized in that it comprises the steps of applying to the gate of the Yaneru type transistor. The pixel from wherein at least the time _{T 1} to _{T 2}
2. A state in which electric charges remain.
Driving method of the electro-optical device. 3. The method according to claim 1, wherein a rectangular pulse is applied to the signal line.