JPH0643434A - Electro-optical device and its image display method - Google Patents

Abstract

PURPOSE:To decrease a variance of a characteristic, and to execute control at a high speed by inputting a reference voltage value repeated in a prescribed period, as a signal, controlling its timing by a digital value, and controlling an applied voltage. CONSTITUTION:As a reference signal waveform, a half wave of a sine wave is used. Sine waves as shown in VDD1, VDD2 are applied to signal lines Y1 303, Y2 304 lying in the scanning line direction, and bipolar signals whose polarity is inverted, as shown in VGG1, VGG2 are applied to signal lines X1 301, X2 302 lying in the information line direction. By selecting a timing for applying this bipolar signal, a voltage applied to each picture element can be controlled arbitrarily. In such a way, by varying the timing of the bipolar signal, the charge quantity and the potential accumulated in four liquid crystal picture element electrodes A-D are determined, and also, by taking arbitrarily the potential of a counter electrode, magnitude of an electric field applied to a picture element and a liquid crystal is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active type electro-optical device, and more particularly to an active type liquid crystal electro-optical device, in which a clear gradation level can be set.

[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 because of their material properties. Therefore, liquid crystal compositions may be aligned horizontally or vertically with respect to an external electric field. It can be done easily. The liquid crystal electro-optical device uses the anisotropy of the dielectric constant to control the amount of transmitted light or the amount of dispersion of light to perform ON / OFF display.

FIG. 2 shows the electro-optical characteristics of nematic liquid crystal. When the applied voltage is Va (point A), the amount of transmitted light is almost 0%, and when Vb (point B) is about 20%,
It becomes about 70% in the case of c (point C) and about 100% in the case of Vd (point D). That is, if only points A and D are used, black and white two-gradation display can be performed, and if points at which the electro-optical characteristics rise such as points B and C are used, halftone display can be performed.

Conventionally, in the case of gradation display of a liquid crystal electro-optical device using a TFT, gradation display is performed by changing the voltage applied to the gate of the TFT or the voltage applied between the source and the drain to adjust the voltage in an analog manner. Was there.

[0005]

A description will be given of the gradation display method of the liquid crystal electro-optical device using the TFT. An N-channel type thin film transistor, which is conventionally used in a liquid crystal electro-optical device, has a voltage-current characteristic as shown in FIG. The voltage-current characteristics shown in FIG. 3 are the characteristics of the N-channel type thin film transistor using amorphous silicon and the characteristics of the N-channel type thin film transistor using polysilicon.

By controlling the voltage applied to the gate electrode in an analog manner, the drain current can be controlled and the magnitude of the electric field applied to the liquid crystal can be changed. Thereby, gradation display is possible.

However, when a liquid crystal electro-optical device having a pixel number of 640.times.400 dots is assumed, it is very difficult to manufacture the characteristics of all 256,000 TFTs in total without variations. In reality, 16-gradation display is considered to be the limit in consideration of mass productivity and yield.

Further, the gate voltage is set to a constant value, and O
A method of performing gradation display by controlling only N / OFF and controlling the source / drain voltage has been considered, but it is considered that about 16 gradations are the limit due to the instability of the characteristics. The analog gradation display control is greatly influenced by the characteristics of the TFT, and clear display is difficult.

As another method, a gradation display method using a plurality of frames has been proposed. As shown in FIG. 11, for example, when gradation display is performed using 10 frames, the pixel A makes 2 frames out of 10 frames transparent and the remaining 8 frames non-transparent so that the average is 20%. It can be displayed as transparent. Similarly, for pixel B, 70%, pixel C
Similarly, it can be displayed as 50% transmission.

However, when such a display is performed, the number of frames is substantially reduced, so that the occurrence of flicker and the display injury occur. In order to solve this, an increase in the frame frequency or the like has been devised, but it is a technology that has a limit because it is difficult to increase the power consumption accompanying the increase in the driving frequency or to speed up the IC.

[0011]

Therefore, in the present invention, in order to clarify the applied voltage level, not a completely uncertain analog value but a reference voltage value repeated at a constant cycle is input from the controller side as a signal. However, the present invention adopts a method of covering the characteristic variation of the TFT by controlling the voltage applied to the TFT by controlling the timing of connecting the reference signal to the TFT with a digital value. I am trying.

That is, a signal used for arbitrary pixel drive selection is gradation display of an electro-optical device using a display drive system having a display timing related by a time F for writing one screen and a time t for writing one pixel. The time t on one of the lines
A selection signal is applied to the reference signal and the other signal line having a voltage change whose period is, at an arbitrary timing within the time t,
The feature is that the gradation can be displayed without changing the time F by determining the voltage applied to the liquid crystal and actually applying the voltage to the pixel. In addition, the timing does not depend on the data transfer, but a high-speed clock is applied to the driver IC itself mounted in the liquid crystal electro-optical device to process in the signal processing portion, so that the conventional CMOS data transfer speed is used. It is characterized in that it enables high-speed control that is not limited to tens of MHz, which was the limit of.

FIG. 1 specifically shows drive waveforms of the electro-optical device according to the present invention. FIG. 1 shows an example in which the main drive waveform is put in the 2 × 2 active matrix circuit using the so-called transfer gate element shown in FIG. Here, a half wave of a sine wave is used as the reference signal waveform. Signal lines Y ₁ 303 and Y ₂ 304 corresponding to the scanning line direction
To the signal line X ₁ 301 corresponding to the information line direction by applying a sine wave as shown in V _DD1 and V _DD2 in FIG. , X ₂ 30
A signal having two polarities (hereinafter referred to as "bipolar") whose polarities are inverted is added to ₂ as shown by V _GG1 and V _GG2 in FIG. By selecting the timing of applying this bipolar signal, the voltage applied to each pixel can be arbitrarily controlled. That is, the pixel is charged with a sinusoidal voltage when a bipolar signal is applied. For example, when a bipolar signal is added when the sine wave signal is almost 0, the voltage stored in the pixel capacitor is almost 0, and when a bipolar signal is added when the sine wave signal has the maximum value. , The pixel voltage is the same as the maximum value of the sine wave signal. When the timing of applying the bipolar signal is set to an intermediate timing, an intermediate voltage is applied to the pixel. Then, by changing the timing of the bipolar signal and using an appropriate scanning technique for selecting each pixel in this way, the amount of charges accumulated in the four liquid crystal pixel electrodes A to D in FIG. The electric potential is determined, and the electric potential applied to the pixel and the liquid crystal is determined by arbitrarily setting the electric potential of the counter electrode.
If the potential of the counter electrode is set to 0V, the voltages applied to the pixels A to D can take arbitrary values as shown in FIG. 1, and gradation display can be performed. In FIG. 1, for the sake of simplification, an extremely simple matrix of 2 × 2 is used for description, but gradation display can be similarly performed even when the scale of the matrix becomes larger. Also, the positional relationship between PTFT and NTFT may be interchanged.

The timing of applying the bipolar signal is not determined by the transfer rate of the information signal, but is limited by the basic clock input to the driver IC directly connected to the liquid crystal electro-optical device in the configuration according to the present invention. That is, when considering a liquid crystal electro-optical device of 640 × 400 dots, the driving frequency is 2 from the limit of CMOS.
It is about 0 MHz, and in order to calculate the gradation display number using this value, the driving frequency is determined by the product of the number of scanning lines, the number of frames, the bipolar pulse, and the gradation display number, and therefore 20 MHz ( It is only necessary to divide by 400 × 60 × 2), and therefore, it is possible to display up to 416 gradation levels. It goes without saying that the display screen can be divided into two to obtain 832 gradations. Examples will be given below, and further detailed description will be added.

[0015]

【Example】

[Embodiment 1] In this embodiment, a wall-mounted television is manufactured by using a liquid crystal display device having a circuit configuration as shown in FIG. 5, which will be described. Further, the TFT at that time was made of polycrystalline silicon using laser annealing.

FIG. 6 shows the actual arrangement of electrodes and the like corresponding to this circuit structure. For simplicity of description, only the portion corresponding to 2 × 2 (or less) is shown. The actual drive signal waveform is shown in FIG. In order to simplify the description, the description will be made with the signal waveform in the case of the 2 × 2 matrix configuration.

First, a method of manufacturing the liquid crystal panel used in this embodiment will be described with reference to FIG. In FIG. 7A, the blocking layer 5 is formed on the glass 50, such as quartz glass, which can withstand a heat treatment at 700 ° C. or less, for example, about 600 ° C., which is not expensive, by using a magnetron RF (radio frequency) sputtering method.
A silicon oxide film as No. 1 is formed to a thickness of 1000 to 3000Å. The process conditions were an atmosphere of 100% oxygen, a film forming temperature of 150 ° C., an output of 400 to 800 W, and a pressure of 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 Å / min.

A silicon film 52 was formed on this by a plasma CVD method. The film forming temperature is 250 ° C. to 35
The temperature is set to 0 ° C., and in this embodiment, the temperature is set to 320 ° C.
₄ ) was used. Not only monosilane (SiH ₄ ) but also disilane (Si ₂
H ₆ ) Alternatively, trisilane (Si ₃ H ₈ ) may be used. These were introduced into the PCVD device at a pressure of 3 Pa, and 13.56M
A high frequency power of Hz was applied to form a film. At this time, the high frequency power is suitably 0.02 to 0.10 W / cm ² , and in this example, 0.055 W / cm ² was used. The flow rate of monosilane (SiH ₄ ) was 20 SCCM, and the film formation rate at that time was about 120 Å / min. In order to control the threshold voltage (Vth) of the PTFT and the NTFT to be approximately the same, boron is used in an amount of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm by using diborane.
^-3 may be added during film formation. Further, not only the plasma CVD but also the sputtering method or the low pressure CVD method may be used for forming the silicon layer to be the channel region of the TFT. The method will be briefly described below.

When the sputtering method is used, the back pressure before the sputtering is set to 1 × 10 ^-5 Pa or less, the single crystal silicon is used as the target, and the atmosphere is mixed with 20% to 80% of hydrogen in argon. For example, argon is 20% and hydrogen is 80%.
The film forming temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

When formed by the reduced pressure vapor phase method, it is 450 to 550 ° C., which is 100 to 200 ° C. lower than the crystallization temperature, for example, 5
Disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) was supplied to a CVD apparatus at 30 ° C. to form a film. The reactor pressure is 30 ~
It was set to 300 Pa. The film forming rate was 50 to 250 Å / min. In order to control the threshold voltage (Vth) of the PTFT and the NTFT to be approximately the same, boron may be added during film formation using diborane at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ^-3. .

The film formed by these methods is
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. In order to promote crystallization, the oxygen concentration is 7 × 10 ¹⁹ cm ^-3 or less,
It is preferable that the size is 1 × 10 ¹⁹ cm ^-3 or less,
If the amount is too small, the leak current in the off state increases due to the backlight, so this concentration was selected. If the oxygen concentration is high, it is difficult to crystallize, and the laser annealing temperature must be high or the laser annealing time must be long. Hydrogen is 4 × 10 ²⁰ cm ^-3 and silicon is 4 × 10 ²²
It was 1 atom% when compared as cm ^-3 .

In order to further promote crystallization of the source and drain, the oxygen concentration is set to 7 × 10 ¹⁹ cm ^-3 or less, preferably 1 × 10 ¹⁹ cm ^-3 or less, and the TF for forming a pixel is set.
Oxygen may be added only to the channel forming region of T by the ion implantation method so as to have a concentration of 5 × 10 ^{20 to} 5 × 10 ²¹ cm ⁻³ .

By the above method, a silicon film in an amorphous state was formed to a thickness of 500 to 5000 Å, 1000 Å in this embodiment.

After that, as shown in FIG. 7B, a pattern was formed in which only the source / drain regions were opened in the photoresist 53 using the mask P1. A silicon film 54, which will be an n-type active layer, was formed thereon by a plasma CVD method. The film formation temperature is 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% were used. These are introduced into the PCVD apparatus at a pressure of 5 Pa, and 13.56
A high frequency power of MHz was applied to form a film. At this time, the high-frequency power is suitably 0.05~0.20W / cm ^2, in this embodiment using 0.120W / cm ^2.

The specific conductivity of the n-type silicon layer produced by this method was about 2 × 10 ^-1 [Ωcm ^-1 ]. The film thickness was 50Å. After that, the lift-off method is used to remove the resist 53, and the source / drain regions 5 are removed.
5, 56 were formed.

A p-type active layer 57 was formed on the resist 58 using the same process. The gas introduced at that time is
Monosilane (SiH ₄ ) and monosilane-based diborane (B ₂ H ₆ ).
A 5% concentration was used. Put these in the PCVD equipment.
It was introduced at a pressure of Pa and a film was formed by applying high frequency power of 13.56 MHz. At this time, the high frequency power is 0.05 to
0.20 W / cm ² is suitable, and is 0.1 in this embodiment.
20 W / cm ² was used. The specific conductivity of the p-type silicon layer produced by this method is 5 × 10 ^-2 [Ωcm ^-1 ]
It became a degree. The film thickness was 50Å. After that, the source / drain region 5 is formed by using the lift-off method similarly to the N-type region.
9 and 60 were formed. Then, the silicon film 52 was removed by etching using the mask P3 to form an N-channel type thin film transistor island region 63 and a P-channel type thin film transistor island region 64.

Then, using a XeCl excimer laser 61, the source / drain / channel regions were laser-annealed, and at the same time, the active layer was laser-doped. The laser energy at this time has a threshold energy of 130 mJ / cm ² and is 22 to melt the entire film thickness.
0 mJ / cm ² is required. But from the beginning 220
When the energy of mJ / cm ² or more is applied, hydrogen contained in the film is rapidly released, so that the film is broken. Therefore, it is necessary to first drive out hydrogen with low energy and then melt it. In this embodiment, first 150 m
After ejecting hydrogen at J / cm ² , 230mJ
Crystallization was performed at / cm ² .

The annealing causes the silicon film to shift from an amorphous structure to a highly ordered state, and a part thereof assumes a crystalline state. In particular, a region having a relatively high degree of ordering after the film formation of silicon tends to be crystallized and become a crystalline state. However, since silicon existing between these regions is bonded to each other, the silicon members pull each other. Peak 522 of single crystal silicon as measured by laser Raman spectroscopy
Peaks shifted to lower frequencies than cm ^-1 are observed. The apparent particle size is 50 to 5 when calculated from the full width at half maximum.
Although it is 00 Å, in reality there are many regions with high crystallinity and they have a cluster structure, and it was possible to form a film with a structure in which the clusters are mutually anchored (anchoring) between silicon clusters. .

As a result, the film exhibits a state in which it can be said that it is substantially free of grain boundaries (hereinafter referred to as GB). Since the carriers can easily move between the clusters through the anchored portions, the carrier mobility is higher than that of polycrystalline silicon in which so-called GB is clearly present. That is, hole mobility (μh) = 10 to ²⁰⁰ cm ² /
VSec, electron mobility (μe) = 15 to 300 cm ² / V
Sec is obtained.

A silicon oxide film 65 is formed thereon as a gate insulating film with a thickness of 500 to 2000 Å, for example 1000 Å. This was performed under the same conditions as the production of the silicon oxide film as the blocking layer. During this film formation, a small amount of fluorine may be added to immobilize sodium ions.

After this, 1 to 5 × 10 ²¹ cm of phosphorus is placed on the upper side.
^-3 concentration silicon film or this silicon film with molybdenum (Mo), tungsten (W), MoSi ₂ or
A multilayer film with WSi ₂ was formed. This was patterned with a fourth photomask P4 to obtain FIG. 7 (E). A gate electrode 66 for NTFT and a gate electrode 67 for PTFT were formed. For example, the channel length is 7 μm, the gate electrode is 0.2 μm of phosphorus-doped silicon, and 0.3 molybdenum is formed thereon.
It was formed to a thickness of μm.

When aluminum (Al) is used as the gate electrode material, the self-alignment method can be applied by patterning this with the fourth photomask P4 and then anodizing the surface. Since the source / drain contact holes can be formed at positions closer to the gate, the characteristics of the TFT can be further improved by reducing the mobility and the threshold voltage.

In this way, a C / TFT can be manufactured without applying a temperature above 400 ° C. in all steps. Therefore, an expensive substrate such as quartz does not have to be used as the substrate material, and it can be said that the process is extremely suitable for the large-screen liquid crystal display device of the present invention.

In FIG. 7F, the inter-layer insulator 68 was formed as a silicon oxide film by the above-mentioned sputtering method. This silicon oxide film is formed by LPCVD method, photo CVD method.
Method, atmospheric pressure CVD method may be used. For example, 0.2-0.
Formed to a thickness of 6 μm, and then a fifth photomask P
5 was used to form the window 79 for the electrode. After that, aluminum is further formed on the entire surface to a thickness of 0.3 μm by a sputtering method, and a lead 74 and contacts 73 and 75 are formed using a sixth photomask P6.
An organic resin 77 for flattening the surface, for example, a translucent polyimide resin was applied and formed, and the electrode hole was formed again using the seventh photomask P7. Further, ITO (Indium Tin Oxide) was formed on the whole of these by a sputtering method to a thickness of 0.1 μm, and the pixel electrode 71 was formed using the eighth photomask P8. This ITO film is formed at room temperature to 150 ° C.
Fulfilled by oxygen at 0-400 ° C or anneal in air.

The electric characteristics of the obtained TFT are PTFT.
The mobility is 40 (cm ² / Vs), Vth is -5.9 (V),
Mobility is 80 (cm ² / Vs) and Vth is 5.0 with NTFT
(V).

One substrate for a liquid crystal electro-optical device could be obtained by manufacturing according to the above method.

FIG. 6 shows the arrangement of electrodes and the like of this liquid crystal display device. N-channel thin film transistor and P
The channel type thin film transistor is connected to the first signal line 3 and the second signal line 3.
Are provided at the intersections of the signal lines 4 and. A matrix structure using such C / TFT is provided. NT
The FT 13 is connected to the second signal line 4 via the contact at the input end of the source 10, and the gate 9 is connected to the first signal line 3. The output end of the drain 12 is connected to the pixel electrode 17 via a contact.

On the other hand, in the PTFT 22, the input end of the source 20 is connected to the second signal line 4 via the contact, the gate 21 is connected to the signal line 3, and the output end of the drain 18 is connected via the contact in the same manner as the NTFT. It is connected to the electrode 17. By repeating this structure horizontally and vertically, 6
A liquid crystal display device having a large pixel size of 40 × 480 and 1280 × 960 can be used. In this embodiment, 1920 ×
It was set to 400. Thus, the first substrate was obtained.

A method for manufacturing the other substrate is shown in FIG. A polyimide resin in which a black pigment was mixed with polyimide was formed on a glass substrate with a thickness of 1 μm by a spin coating method, and a black stripe 81 was formed using a ninth photomask P9. After that, a polyimide resin mixed with a red pigment was formed into a film with a thickness of 1 μm by a spin coating method, and a red filter 83 was manufactured using a tenth photomask P10. Similarly, the masks P11 and P12 are used, and the green filter 85 and the blue filter 86 are used.
Was produced. During manufacture of these filters, each filter was baked at 350 ° C. in nitrogen for 60 minutes. After that, the leveling layer 89 was made of transparent polyimide by using the spin coating method.

After that, 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 91. This ITO film is formed at room temperature to 150 ° C.
Achieved by oxygen at 300 ° C or annealing in the atmosphere,
A second substrate was obtained.

A polyimide precursor was printed on the substrate by the offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. Then, a known rubbing method was used to modify the surface of the polyimide, and a means for orienting liquid crystal molecules in a certain direction was provided at least in the initial stage.

After that, 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 TAB-shaped drive IC, a PCB having a common signal and a potential wiring were connected to the leads on the substrate, and a polarizing plate was attached to the outside to obtain a transmissive liquid crystal electro-optical device.

8 and 9 are schematic structural views of the electro-optical device according to this embodiment. The rear illumination device 221 in which the liquid crystal panel 220 obtained in the above process is arranged with three cold cathode tubes
It was installed in combination with. After that, a tuner 223 for receiving television radio waves was connected to complete the electro-optical device. Compared with the conventional CRT type electro-optical device, the device has a planar shape, so that it can be installed on a wall or the like. Next, the peripheral circuit of the liquid crystal electro-optical device for completing the present invention will be described with reference to FIG.

A driving circuit 352 is connected to the information signal side wirings 350 and 351 connected to the matrix circuit of the liquid crystal electro-optical device.
It has a configuration in which is connected. The drive circuit 352 is composed of two parts when divided by the drive frequency system. One is a data latch circuit system 353 similar to the conventional drive system,
The main configuration of this is a basic clock CLK 355 for sequentially transferring the data 356, and 1-bit to 12-bit parallel processing is performed. The other one is a component according to the present invention, which is composed of a clock 357, a flip-flop circuit 358, and a counter 360 according to the ratio of division necessary for gradation display. The counter 360 makes a bipolar pulse generation timing according to the gradation display data sent from the data latch system 353. Furthermore, Δt is provided between the exit of the latch circuit and the data line 361.
It was found that the gradation display data can be controlled more finely by using the ROM table of → sin θ conversion. What is characteristic of the present invention is exactly these parts, and by adopting two kinds of drive frequencies, it is possible to perform clear digital gradation display without changing the number of frames for screen rewriting. is there. Furthermore, it is possible to avoid the occurrence of flicker due to the decrease in the number of frames.

On the other hand, the drive circuit 364 connected to the signal lines 363 and 362 on the scanning side controls the sine wave transmitted from the sine wave oscillating circuit 365 by the flip-flop circuit 366 of the clock CLK 367 and adds a selection signal.

In this manner, gradation display is enabled by digitally voltage-controlling the timing of cutting the sine wave on the scanning line side by the bipolar pulse on the information line side.

For example, 1920 × 400 dot 768,
When a normal analog gray scale display is performed on a liquid crystal electro-optical device in which 000 sets of TFTs are formed in a 300 mm square, 16 gray scale display is limited because there is about ± 10% variation in TFT characteristics. there were. However, when the digital gradation display according to the present invention is performed, since it is not easily affected by the characteristic variation of the TFT element, it is possible to display up to 64 gradations, and in the color display, there are 262,144 colorful and delicate colors. The display is realized.

[Embodiment 2] In this embodiment, a viewfinder for a video camera using a liquid crystal electro-optical device having a diagonal of 1 inch was manufactured and the present invention was carried out. In the description of the reference numerals of the drawings in this embodiment, the same parts as those in the embodiment are the same as those in the first embodiment.

In this embodiment, a viewfinder is constructed by forming a device using a high-mobility TFT by a low temperature process with a structure of 387 × 128 pixels. FIG. 13 shows the arrangement of the active elements on the substrate of the liquid crystal display device used in this example, and FIG. 14 shows the manufacturing process showing the AA ′ cross section and the BB ′ cross section of FIG.

In FIG. 14 (A), inexpensive, 700 ° C.
Hereinafter, for example, glass 50 that can withstand heat treatment at about 600 ° C.
A silicon oxide film as the blocking layer 51 is formed on the upper surface by a magnetron RF (radio frequency) sputtering method to a thickness of 1000 to 30.
Fabricate to a thickness of 00Å. Process conditions are 100% oxygen
The atmosphere, the film forming temperature was 150 ° C., the output was 400 to 800 W, and the pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 Å / min.

A silicon film was formed thereon by LPCVD (Low Pressure Vapor Phase) method, sputtering method or plasma CVD method. When forming by the reduced pressure vapor phase method, it is 1
450-550 ° C, which is low by 00-200 ° C, for example, 530 ° C
CVD of disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ )
The film was supplied to the apparatus to form a film. The reactor pressure is 30-300
It was Pa. The film forming rate was 50 to 250 Å / min.
Threshold voltage (Vt) between PTFT and NTFT
In order to control the concentration to be substantially the same as that of h), boron may be added during the film formation with diborane at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ .

When the sputtering method is used, the back pressure before the sputtering is set to 1 × 10 ^-5 Pa or less, the single crystal silicon is used as the target, and the atmosphere is mixed with 20% to 80% of hydrogen in argon. For example, argon is 20% and hydrogen is 80%.
The film forming temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

When a silicon film is formed by the plasma CVD method, the temperature is set to 300 ° C., and monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used. These were introduced into a PCVD apparatus, and high-frequency power of 13.56 MHz was applied to form a film.

The coatings formed by these methods are
It is preferable that oxygen is 5 × 10 ²¹ cm ⁻³ or less. If this oxygen concentration is high, it is difficult to crystallize and the thermal annealing temperature must be high or the thermal annealing time must be long.
If it is too small, the backlight will turn off the light.
The current will increase. Therefore 4 × 10 ¹⁹ to 4 × 10 ²¹
The range was cm ^-3 . Hydrogen is 4 × 10 ²⁰ cm ^-3 and silicon 4
When compared with ^{x10 22} cm ^-3 , it was 1 atom%.

By the above method, a silicon film in an amorphous state is formed to a thickness of 500 to 5000 Å, for example 1500 Å, and then a heat treatment of a medium temperature in a non-oxide atmosphere at a temperature of 450 to 700 ° C. for 12 to 70 hours, For example, it was held at a temperature of 600 ° C. in a hydrogen atmosphere. Since a silicon oxide film having an amorphous structure is formed on the surface of the substrate below the silicon film, no specific crystal nuclei are formed by this heat treatment, and the whole is annealed uniformly. That is, it has an amorphous structure at the time of film formation, and hydrogen is simply mixed therein.

The annealing causes the silicon film to shift from an amorphous structure to a highly ordered state, and a part thereof assumes a crystalline state. In particular, a region having a relatively high degree of ordering after the film formation of silicon tends to be crystallized and become a crystalline state. However, since silicon existing between these regions is bonded to each other, the silicon members pull each other. Peak 522 of single crystal silicon as measured by laser Raman spectroscopy
Peaks shifted to lower frequencies than cm ^-1 are observed. The apparent particle size is 50 to 5 when calculated from the full width at half maximum.
Although it is a microcrystal like 00Å, in reality there are many highly crystalline regions with a cluster structure, and each cluster has a semi-amorphous structure in which silicon is bonded (anchoring) with each other. Could be formed.

As a result, the coating is in a state in which it can be said that there is substantially no grain boundary (hereinafter referred to as GB). Since the carriers can easily move between the clusters through the anchored portions, the carrier mobility is higher than that of polycrystalline silicon in which so-called GB is clearly present. That is, hole mobility (μh) = 10 to ²⁰⁰ cm ² /
VSec, electron mobility (μe) = 15 to 300 cm ² / V
Sec is obtained.

On the other hand, when the film is polycrystallized by a high temperature anneal of 900 to 1200 ° C. instead of the anneal at a medium temperature as described above, segregation of impurities in the film occurs due to solid phase growth from nuclei. , GB have a large amount of impurities such as oxygen, carbon, and nitrogen, and have a large mobility in the crystal, but they form a barrier in GB and hinder the movement of carriers there. As a result, it is difficult to obtain a mobility of 10 cm ² / Vsec or more. That is, in this embodiment, the silicon semiconductor having the semi-amorphous or semi-crystal structure is used for the reason as described above.

In FIG. 14A, the silicon film is photoetched using a first photomask, and an NTFT region 141 (channel width 20 μm) is formed on the AA ′ cross section side of the drawing, and a PTFT region. 142 was produced on the BB ′ cross section side.

A silicon oxide film was formed thereon as a gate insulating film to a thickness of 500 to 2000Å, for example, 1000Å. This was performed under the same conditions as the production of the silicon oxide film as the blocking layer. During this film formation, a small amount of fluorine may be added to immobilize sodium ions.

After this, 1-5 × 10 ²¹ cm of phosphorus is placed on the upper side.
^-3 concentration silicon film or this silicon film with molybdenum (Mo), tungsten (W), MoSi ₂ or
A multilayer film with WSi ₂ was formed. This was patterned with a second photomask to obtain FIG. 14 (B). A gate electrode 9 for NTFT and a gate electrode 21 for PTFT were formed. In this embodiment, the NTFT channel length is 10 μm.
m, the channel length for the PTFT is 7 μm, the gate electrode is made of 0.2 μm of phosphorus-doped silicon, and molybdenum is formed thereon to a thickness of 0.3 μm. In FIG. 14 (C), the source for the PTFT - to scan 18 drain 20, de of boron 1~5 × 10 ¹⁵ cm ^-2 - was added by ion implantation in amount's. Next, as shown in FIG. 14D, a photoresist 61 was formed using a photomask. Phosphorus 1-5 × 10 as source 10 and drain 12 for NTFT
^It was added by the ion implantation method at a dose amount of ¹⁵ cm ^-2 .

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

Next, heating anneal was performed again at 600 ° C. for 10 to 50 hours. The source 10 and the drain 12 of the NTFT, the source 18 and the drain 20 of the PTFT were produced as P ⁺ and N ⁺ by activating impurities. Channel forming regions 19 and 11 are formed as semi-amorphous semiconductors below the gate electrodes 21 and 9.

By doing so, it is possible to fabricate a C / TFT without applying a temperature above 700 ° C. in all steps even though it is a self-aligned method. Therefore, it is not necessary to use an expensive substrate such as quartz as the substrate material, and the process is very suitable for the large-pixel liquid crystal display device of the present invention.

In this embodiment, the thermal anneal is shown in FIG.
Done twice in (D). However, the anneal shown in FIG. 14 (A) is omitted depending on the desired characteristics, and both are omitted from the anneal shown in FIG. 14 (D).
The manufacturing time may be shortened depending on the requirements. 14
In (E), the interlayer insulator 65 was formed as a silicon oxide film by the above-described sputtering method. The silicon oxide film may be formed by using the LPCVD method, the photo CVD method, or the atmospheric pressure CVD method. For example, it is formed to a thickness of 0.2 to 0.6 μm, and then a window 79 for an electrode is formed using a photomask. Further, as shown in FIG. 14 (F), aluminum is formed on the whole by sputtering, and the lead 7
4 and the contact 75 were formed using a photomask, an organic resin 77 for flattening the surface was applied and formed on the surface, and another hole for the electrode was formed using the photomask.

ITO (indium tin oxide film) was formed by the sputtering method in order to connect two TFTs with a complementary structure and to connect the output terminal thereof to the electrode of one pixel of the liquid crystal device as a transparent electrode. . It was etched with a photomask to form the electrode 17. This I
The TO film was formed at room temperature to 150 ° C. and was accomplished by oxygen at 200 to 400 ° C. or anneal in the atmosphere. In this way, the NTFT 13, the PTFT 22, and the transparent conductive film electrode 17 were formed on the same glass substrate 50. Obtained T
The electrical characteristics of FT are PTFT and the mobility is 20 (cm ² / V
s), Vth is -5.9 (V), and the mobility is 4 with NTFT.
It was 0 (cm ² / Vs) and Vth was 5.0 (V).

One substrate for a liquid crystal device was manufactured according to the method as described above. FIG. 13 shows the arrangement of electrodes and the like of this liquid crystal display device. NTFT13 and PTF
T22 is provided at the intersection of the first signal line 3 and the second signal line 4. A matrix structure using such C / TFT is provided. The NTFT 13 is connected to the second signal line 4 via the contact at the input end of the drain 10, and the gate 9 is connected to the signal line 3 in which the multilayer wiring is formed. The output end of the source 12 is connected to the pixel electrode 17 via a contact.

On the other hand, in the PTFT 22, the input end of the drain 20 is connected to the second signal line 4 via a contact, the gate 21 is connected to the signal line 3, and the output end of the source 18 is connected via a contact like an NTFT. Is connected to the pixel electrode 17. This embodiment is constructed by repeating such a structure horizontally and vertically.

Next, as a second substrate, ITO (injected) was also formed on the substrate in which a silicon oxide film was laminated in 2000 liters on a soda-lime glass by the sputtering method.
A tin oxide film) was formed. This ITO is room temperature ~ 15
The film was formed at 0 ° C. and was accomplished by oxygen at 200 to 400 ° C. or annealing in the atmosphere. A color filter was formed on this substrate using the same method as in "Example 1" to obtain a second substrate. A polyimide precursor was printed on the substrate using an offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. After that, a known rubbing method was used to modify the surface of the polyimide, and at least in the initial stage, a means for orienting liquid crystal molecules in a certain direction was provided to obtain first and second substrates.

Then, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. Since the pitch of the leads on the substrate was as fine as 46 μm, the COG method was used for connection. In this embodiment, the gold bumps provided on the IC chip are connected by an epoxy-based silver-palladium resin, and the IC chip and the substrate are embedded and fixed by epoxy modified acrylic resin for the purpose of fixing and sealing. I was there. After that, a polarizing plate was attached to the outside to obtain a transmissive liquid crystal display device.

FIG. 15A shows the drive waveform used in this embodiment. Instead of the sine wave used in Example 1, a ramp waveform was used. The ramp wave has an advantage in that the structure is simple and that the gradation data can be easily converted into Δt. Figure 15
In (a), as in FIG. 1, the analog voltage applied to the pixel can be digitally obtained. For example, in the pixel A, although the voltage is low, the time during which the voltage is applied to the pixel is long, and conversely, the pixel B is applied. However, although a high voltage is applied, the time is shorter than that of the pixel A. Therefore, visually, the difference in shade between the pixel A and the pixel B may be smaller than expected. In order to overcome the difficulty, as shown in FIG. 15B, the time when no voltage is applied to both V _DD1 and V _DD2 may be set larger than the time when a voltage is applied. For example, if you set the time to be the same as the voltage
Theoretically, the longest time that a voltage is applied to each pixel is three times the shortest time, and actually about twice. Furthermore, FIG.
As shown in (b), if the time during which no voltage is applied to V _DD1 or V _DD2 is set twice as long as the time during which voltage is applied, for example, pixel A is applied 40% longer than pixel B. It ’s just that. Therefore, apart from the pixel voltage,
The visual shading error due to the voltage applied to the pixel can be greatly improved.

FIG. 16 is a block diagram of the viewfinder according to this embodiment. In this example, the liquid crystal electro-optical device 370 manufactured by the above method was used.

For example, 49,15 of 384 × 128 dots
Two sets of TFT are 50mm square (36mm from 300mm square substrate)
When a normal analog gradation display is performed on a liquid crystal electro-optical device formed in a multi-layered manner, 16 gradation display is the limit because there is about ± 10% variation in TFT characteristics. . However, when the digital gray scale display according to the present invention is performed, it is possible to display up to 128 gray scales because it is not easily affected by the characteristic variation of the TFT element, and in the color display, 2,097,152 colors are various and delicate. Color display is realized.

[Embodiment 3] In this embodiment, a projection type image display device as shown in FIG. 17 was produced, and therefore, description will be added.

In this embodiment, three liquid crystal electro-optical devices 20 are used.
1 is used to assemble a projection type image display device projection unit. Each of them has a structure of 640 × 480 dots, and 307,200 in a diagonal of 4 inches.
Pixels were made. The size per pixel was 127 μm square.

As the configuration of the projection type image display device, the liquid crystal electro-optical device 201 is used as the three primary colors of light.
Separately installed for green and blue, red filter 2
02, green filter 203, blue filter 204
And reflector plate 205, prism mirrors 206, 207 and 1
It is composed of a 50 W metal halide light source 208 and a focusing optical system 209.

The substrate of the liquid crystal electro-optical device used in the electro-optical device of this example was a substrate having a matrix circuit of C / MOS structure, using the same steps as those manufactured in "Example 2". .

FIG. 18 shows a schematic structure. On the substrate 21
Fumaric acid-based polymer resin and nematic liquid crystal 65:
The mixture dissolved in xylene, which is a common solvent, in a ratio of 35 was formed into a thickness of 10 μm by a die casting method. After that, the solvent was removed in a nitrogen atmosphere at 120 ° C. for 180 minutes to form a liquid crystal dispersion layer 211. In this case, it was found that the takt time can be shortened by slightly reducing the pressure from the atmospheric pressure.

Then, ITO (indium tin oxide film) was formed by the sputtering method to obtain the counter electrode 212. This ITO was formed at room temperature to 150 ° C. Then, using a printing method, a translucent silicone resin was applied to a thickness of 30 μm and baked at 100 ° C. for 30 minutes to obtain a liquid crystal electro-optical device.

FIG. 19 shows the functional structure of the driving IC used in this embodiment. The configuration on the information electrode side is the same as in "Example 1". The drive circuit 400 connected to the scan side wirings 406 and 407 outputs the ramp wave transmitted from the ramp wave oscillation circuit 405 to the flip-flop circuit 4 of the clock CLK 408.
Control by 03 and 404, and a selection signal is added.

In this way, gradation display is enabled by digitally voltage-controlling the timing of cutting the ramp wave on the scanning line side by the bipolar pulse on the information line side.

For example, 307 × 2 of 640 × 480 dots
When normal analog gradation display is performed on a liquid crystal electro-optical device in which 00 sets of TFTs are formed in a 300 mm square,
Since there is about ± 10% variation in TFT characteristics, 1
6 gradation display was the limit. However, when the digital gray scale display according to the present invention is performed, it is possible to display up to 256 gray scales because it is hardly affected by the characteristic variation of the TFT element, and the color display is 16,777,2.
A wide variety of 16 colors and subtle colors can be displayed.

In the case of displaying software such as a television image, for example, even "rock" of the same color has a slightly different shade due to the adjustment of the light hitting the minute depressions. If an attempt is made to display a color that is close to the natural color, 16 gradations are difficult and it is not suitable for expressing these subtle depressions. The gradation display according to the present invention makes it possible to impart these minute color tone changes.

The liquid crystal electro-optics can be used not only for the front type projection television shown in FIG. 17 but also for the rear type projection television.

[Embodiment 4] In this embodiment, an electro-optical device for a portable computer is manufactured by using a reflection type liquid crystal dispersion type display device as shown in FIG. As the first substrate used in this example, the one prepared in the same process as in "Example 1" was used. On the substrate 210, a nematic liquid crystal prepared by mixing a fumaric acid-based polymer resin and a black dye in an amount of 15% was dissolved in xylene as a common solvent at a ratio of 65:35 to obtain a mixture of 10 μm by a die casting method.
m to a thickness of 18 and then at 120 ° C. in a nitrogen atmosphere for 18
The liquid crystal dispersion layer 211 was formed by removing the solvent for 0 minutes.

Here, since a black dye is used, a flat panel display, which has been difficult to display with a dispersion type liquid crystal display, appears black when light is scattered (when no electric field is applied) and white when transmitted (when an electric field is applied). It can be displayed, and it is possible to display it like the letters written on paper.

As an opposite structure, it is also possible to express a white color when scattering and a black color when transmitting without mixing a black dye. However, in this case, it is necessary to make the back side shown below black. This is also possible to display like letters written on paper.

After that, ITO (indium tin oxide film) was formed by a sputtering method to obtain a counter electrode 212. This ITO was formed at room temperature to 150 ° C. Then, using a printing method, a white silicone resin was applied in a thickness of 55 μm and baked at 100 ° C. for 90 minutes to obtain a liquid crystal electro-optical device.

[0089]

The present invention is characterized in that digital gradation display is performed in contrast to conventional analog gradation display. As an effect, if a liquid crystal electro-optical device having a number of pixels of 640 × 400 dots is assumed, it is very difficult to manufacture the characteristics of all 256,000 TFTs in total without variations. Considering mass productivity and yield, 16-gradation display is considered to be the limit, but in order to clarify the applied voltage level, not the analog value but the reference voltage value is input as a signal from the controller side. Then, by controlling the timing of connecting the reference signal to the TFT with a digital value, the voltage applied to the TFT is controlled, thereby
The present invention is characterized by adopting a method of covering the characteristic variation of the present invention, and therefore, clear digital gradation display is possible. Further, by using two kinds of drive frequencies, it is possible to perform clear digital gradation display without changing the number of frames for screen rewriting. It is possible to avoid the occurrence of flicker due to the decrease in the number of frames.

For example, 256,0 of 640 × 400 dots
When normal analog gradation display is performed on a liquid crystal electro-optical device in which 00 sets of TFTs are formed in a 300 mm square,
Since there is about ± 10% variation in TFT characteristics, 1
6 gradation display was the limit. However, when the digital gray scale display according to the present invention is performed, it is possible to display up to 256 gray scales because it is hardly affected by the characteristic variation of the TFT element, and the color display is 16,777,2.
A wide variety of 16 colors and subtle colors can be displayed. When displaying software such as a television image, for example, even "rocks" of the same color have slightly different shades due to their fine depressions. If you try to display something close to the natural color,
16 gradations are difficult. The gradation display according to the present invention makes it possible to impart these minute color tone changes.

The present invention is characterized in that 64 gray scales, 256 gray scales or higher gray scales can be displayed without changing the number of frames. This means that no frame count is currently used. It does not mean that it is limited to 30 to 60 frames. It will be apparent that increasing the number of frames to improve the image quality does not contradict the intention of the present invention. Furthermore, in the embodiments of the present invention, the description has been given centering on the TFT using silicon, but a 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 1800.
cm ² / Vs and the value of single crystal silicon (electron mobility is 1
350 cm ² / Vs, Hall mobility is 480 cm ² / V
Since it exceeds the characteristics of s), it is an extremely excellent material for carrying out 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.
Further, the nucleation rate during crystal growth is small, and therefore,
Generally, large crystals are obtained when polycrystal growth is performed. Thus, germanium has characteristics comparable to those of silicon.

[Brief description of drawings]

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

FIG. 2 shows electro-optical characteristics of nematic liquid crystal.

FIG. 3 shows current-voltage characteristics of TFTs made of polysilicon and amorphous silicon.

FIG. 4 shows a matrix configuration according to the present invention.

FIG. 5 shows a matrix circuit according to an embodiment.

FIG. 6 shows a planar structure of a device according to an example.

FIG. 7 shows a process of a TFT according to an example.

FIG. 8 shows a structure of a liquid crystal display device (TV) according to an example.

FIG. 9 shows a configuration of a liquid crystal display device (TV) according to an example.

FIG. 10 shows a system configuration of a drive circuit according to an embodiment.

FIG. 11 shows a frame gradation display according to a conventional example.

FIG. 12 shows a process of a color filter according to an example.

FIG. 13 shows a planar structure of a device according to an example.

FIG. 14 shows a process of a TFT according to an example.

15 (a) and 15 (b) show other drive waveforms according to the present invention.

FIG. 16 shows a viewfinder structure according to an embodiment.

FIG. 17 shows a structure of a front type projection television according to an embodiment.

FIG. 18 shows a liquid crystal electro-optical device according to an example.

FIG. 19 shows a system configuration of a drive circuit according to an example.

FIG. 20 shows a configuration of a portable personal computer according to an embodiment.

[Explanation of symbols]

 50 glass substrate 51 silicon oxide film 52 silicon film 53 resist 54 N-type silicon film 55 NTFT source region 56 NTFT drain region 57 P-type silicon film 58 resist 59 PTFT source region 60 PTFT drain region 65 silicon oxide film 66 Gate electrode of NTFT 67 Gate electrode of PTFT 68 Interlayer insulating film 79 Electrode window 74 Lead 73.75 Contact 77 Flattening organic resin 17,71 Pixel electrode 13 NTFT 22 PTFT 10 NTFT source 9 NTFT gate 12 NTFT Drain 20 PTFT source 21 PTFT gate 18 PTFT drain 141 NTFT region 142 PTFT region

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

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

FIG. 2 shows electro-optical characteristics of nematic liquid crystal.

FIG. 3 shows current-voltage characteristics of TFTs made of polysilicon and amorphous silicon.

FIG. 4 shows a matrix configuration according to the present invention.

FIG. 5 shows a matrix circuit according to an embodiment.

FIG. 6 shows a planar structure of a device according to an example.

FIG. 7 shows a process of a TFT according to an example.

FIG. 8 shows a process of a TFT according to an example.

FIG. 9 shows a structure of a liquid crystal display device (TV) according to an embodiment.

FIG. 10 shows a configuration of a liquid crystal display device (TV) according to an embodiment.

FIG. 11 shows a system configuration of a drive circuit according to an embodiment.

FIG. 12 shows a frame gradation display according to a conventional example.

FIG. 13 shows a process of a color filter according to an example.

FIG. 14 shows a planar structure of a device according to an example.

FIG. 15 shows a process of a TFT according to an example.

FIG. 16 shows another drive waveform according to the present invention.

FIG. 17 shows another drive waveform according to the present invention.

FIG. 18 shows a structure of a viewfinder according to an embodiment.

FIG. 19 shows a structure of a front projection television according to an embodiment.

FIG. 20 shows a liquid crystal electro-optical device according to an example.

FIG. 21 shows a system configuration of a drive circuit according to an example.

FIG. 22 shows a configuration of a portable personal computer according to an embodiment.

[Description of Reference Signs] 50 glass substrate 51 silicon oxide film 52 silicon film 53 resist 54 N-type silicon film 55 NTFT source region 56 NTFT drain region 57 P-type silicon film 58 resist 59 PTFT source region 60 PTFT drain Region 65 Silicon oxide film 66 Gate electrode of NTFT 67 Gate electrode of PTFT 68 Interlayer insulating film 79 Electrode window 74 Lead 73.75 Contact 77 Flattening organic resin 17,71 Pixel electrode 13 NTFT 22 PTFT 10 NTFT source 9 Gate 12 of NTFT 12 Drain of NTFT 20 Source of PTFT 21 Gate of PTFT 18 Drain of PTFT 141 NTFT area 142 PTFT area

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Fig. 2]

FIG. 20

[Figure 1]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 9]

[Figure 7]

[Figure 8]

[Figure 10]

[Fig. 13]

FIG. 11

[Fig. 12]

FIG. 14

FIG. 15

FIG. 16

FIG. 18

FIG. 17

FIG. 19

FIG. 21

FIG. 22

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01L 29/784 (72) Inventor Yasuhiko Takemura 398 Hase, Atsugi, Kanagawa Prefecture

Claims (8)

[Claims] 1. An electro-optical device having electric wirings and pixels each having a matrix structure on a substrate, wherein an N-channel type thin film transistor and a P-channel type thin film transistor are provided at an input side terminal and an output side terminal of each other at an intersection of each matrix. Connected to each other, the gates of the N-channel thin film transistor and the P-channel thin film transistor are commonly connected to the first signal line, and the source or drain is the input side of the N-channel thin film transistor and the P-channel thin film transistor. Is connected to the second signal line,
In addition, in the electro-optical device in which drains or sources on the output sides of the N-channel type thin film transistor and the P-channel type thin film transistor are connected to a common pixel electrode,
The gradation display of the electro-optical device using the display drive method having the display timing related to the time F for writing one screen and the time t for writing one pixel is displayed on one of the signal lines used for arbitrary pixel drive selection. By applying a reference signal having a voltage change having a cycle of time t, while applying a selection signal to another signal line at an arbitrary timing within the time t,
An electro-optical device characterized in that gradations can be displayed without changing the time F by determining the voltage to be applied to the liquid crystal and actually applying the voltage to the pixel. 2. The electro-optical device according to claim 1, wherein the reference signal is a sine wave. 3. The electro-optical device according to claim 1, wherein the reference signal is a cosine wave. 4. The electro-optical device according to claim 1, wherein the reference signal is a ramp wave. 5. The electro-optical device according to claim 1, wherein the reference signal is a triangular wave. 6. An electro-optical device having electric wirings and pixels each having a matrix structure on a substrate, wherein an N-channel type thin film transistor and a P-channel type thin film transistor are mutually input side terminals and output side terminals at intersections of each matrix. Connected to each other, the gates of the N-channel thin film transistor and the P-channel thin film transistor are commonly connected to the first signal line, and the source or drain is the input side of the N-channel thin film transistor and the P-channel thin film transistor. Is connected to the second signal line,
In addition, in the electro-optical device in which drains or sources on the output sides of the N-channel type thin film transistor and the P-channel type thin film transistor are connected to a common pixel electrode,
The gradation display of the electro-optical device using the display driving method having the display timing related to the time F for writing one screen and the time t for writing one pixel is displayed on one of the signal lines used for arbitrary pixel drive selection. A reference signal having a time having a voltage change as a function of and a time holding a constant value irrespective of time is applied, while the other signal line is applied at any timing within the time t at a previous time t. The voltage applied to the liquid crystal is determined by applying the selection signal having a smaller time width and the polarity inverted at least once, and the time F is changed by actually applying the voltage to the pixel. An electro-optical device characterized by being capable of displaying gradation without causing 7. A plurality of signal lines X _1, X _2, ..., X _N on a substrate.
And a plurality of other signal lines Y _1, Y _2, ... _, Y _M
Wirings formed in a matrix form by, and N-channel thin film transistors and P
At least one transfer gate element formed by a channel type thin film transistor and an output terminal of the transfer gate element are connected to one of electrodes of an electrostatic device forming a pixel provided in an intersection region of each signal line. The control electrode of the transfer gate element is the signal line X _n (1 ≦ n ≦ N), and the input terminal is the signal line Y _m.
In the electro-optical device connected to (1 ≦ m ≦ M), when the time t is 0 ≦ t ≦ T ₁ , the voltage shown as a function of time is applied only to the signal line Y _m , and the signal line X _1, X
_, ..., X _N are independently applied with a selection signal having a time width smaller than the time T ₁ and a polarity inverted at least once, at any timing, so that the signal line X ₁
And Y _m , X ₂ and Y _m , ..., X _N and Y _m , and an arbitrary voltage is supplied to the pixels provided in each intersection area, and thus, the density of the pixels in each intersection area is controlled arbitrarily. And T ₂ ≦
At t ≦ T ₃ (T ₁ ≦ T ₂ ), the signal line Y _{m + 1} (m =
In the case of M, the voltage shown as a function of time is applied only to Y ₁ ), and the signal lines X _1, X _2, ..., X _N are independently and independently of time T ₃ −T _2. Is applied to the signal lines X ₁ and Y _{m + 1} , X ₂ by applying a selection signal whose polarity is small and whose polarity is inverted at least once at arbitrary timing.
, Y _{m + 1} , ..., Supplying an arbitrary voltage to the pixels provided in each intersection region of X _N and Y _{m + 1} , and thus arbitrarily controlling the shading of the pixels in each intersection region. An image display method for an electro-optical device, comprising: 8. The image display method for an electro-optical device according to claim 7, wherein 2T ₁ <T ₂ .