JP3399907B2 - Display method of display 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 liquid crystal display device or a similar display device. The present invention particularly relates to an active matrix display device, a display method thereof, and a manufacturing method thereof. One of the objects of the present invention is a black-and-white display, and relates to a display which is required to be easy to see and to be low in price, in spite of not requiring high-level operation and high-speed operation such as gradation display. In particular, a display having such a function is used for a read-only display device such as various information displays.

[0002]

2. Description of the Related Art With the recent miniaturization and power saving of various office automation equipment, a display device is also equipped with a conventional cathode ray tube (CR).
T) to a flat panel display (FP) such as a liquid crystal display (LCD) or plasma display.
It is being replaced by D). In particular, LCDs have been used in portable devices because of their low power consumption.

However, the LCD still has many problems to be solved. The LCD that is often used at present is called a simple matrix LCD, and is sometimes called STNLCD after the name of liquid crystal material. S
Since TNLCD is easy to manufacture, it has low cost and is widely used.

However, the STN as a liquid crystal material has a problem that the response speed, which is a characteristic of the material, is extremely slow, and when an object moving at a high speed is displayed, it cannot follow the object and cannot be displayed. .

According to the operation method, the time during which one pixel is lit in one frame (usually 10 to 30 msec) is from several tens of μsec to several msec. This is inversely proportional to the number of rows in the matrix, and in a matrix of 200 rows, one frame is 30 msec and about 150 μsec.
Only lights up. For this reason, the screen has low contrast and is very difficult to see when the screen is viewed obliquely. Furthermore, if there is a very bright or dark part in a part of the screen, a phenomenon (crosstalk) that affects even the surroundings occurs.

On the other hand, in recent years, an LCD having a system in which each pixel has an active element to switch the pixel has been proposed and put on the market. These are generally called active matrix LCDs, but are called TFTLCDs or MIMLCDs depending on the types of active elements. The TFT is a thin film transistor, and the MIM is a diode having a structure of metal / insulator / metal.

In these LCDs, the lighting time of a pixel during one frame is approximately equal to one frame, so that the contrast is high and the viewing angle is wide. However, due to technical problems, the manufacturing yield is low, the cost and the selling price are high, and at present, it has been put to practical use only as a display for a high-class computer.

Further, the current demand for LCDs is such that they are mainly used in portable computers, but a wider range of applications are expected in the future. For example, there are applications such as cordless phones, displays attached to mobile phones, and information displays such as portable electronic dictionaries. In such a case, it is required to be easy to see and to be low-priced, and power saving is also required. However, conventional LCDs have not been satisfactory in that respect.

For example, the STN LCD is low in cost, but it is difficult to see because of the above problems. Further, there are two types of TFTLCDs, which are roughly classified into a TFTLCD that uses a TFT that uses amorphous silicon (hereinafter referred to as a-SiTFTLCD) and a TFTLCD that uses a TFT that uses polysilicon (hereinafter referred to as a polysilicon TFTLCD). , The former and the latter have no problem in viewability of images, but in terms of cost, ST
NLCD cannot compete with it.

Especially when an a-SiTFT LCD is used as a small read-only display, one of the factors that raises the cost most is that the driver circuit cannot be built in, so the driver IC must be connected by the TAB method or the like. The cost of this IC will be a large part of the cost increase.

FIG. 3 shows the number of pixels (dots) of the LCD.
And the cost relationship is shown. This relationship is conceptual and semi-quantitative. In the simple matrix method such as STNLCD, the matrix itself is relatively easy to manufacture, and the driver IC occupies most of the cost of the small-scale matrix. That is, the number of driver ICs is proportional to the number of terminals in the matrix, whereas the number of dots is proportional to the square of the number of terminals, and eventually the price of the driver IC is proportional to the square root of the number of dots. The cost is dominated by the price of. This is shown in the simple matrix: TAB in the figure.

In the a-SiTFT LCD, the production of the matrix is complicated and the yield of the matrix is low, and the matrix shifts upward as compared with the simple matrix. A-Si TFT in the figure:
This is shown in TAB. In the a-Si TFT LCD, the small-scale matrix and the large-scale matrix have different factors in the price. In the small-scale matrix, the price of the driver IC occupies a large part of the cost as in the STN LCD. On the other hand, in a large scale matrix, the cost is a major factor due to the reduction in the yield of the matrix.

In the polysilicon TFT LCD, the driver IC can be manufactured at the same time as the matrix is manufactured by using polysilicon, so that it is not necessary to mount the IC, and therefore the driver IC does not become a factor of cost. In particular, the mounting of the driver IC is technically problematic, and the purpose of considering miniaturization is originally unsuitable. Therefore, the polysilicon TFT LCD is also characterized in that it can be miniaturized. However, polysilicon TFT
It is more difficult to fabricate the matrix of the LCD than the a-SiTFT LCD, and the cost increases significantly as the number of dots increases. However, since there is no cost factor for the driver IC in a small-scale matrix, as shown in the complete polysilicon TFT in the figure, a-Si
The cost is competitive with the TFT LCD.

Even in an a-Si TFT LCD, if the driver can be formed of a-Si, the dotted line (complete a-Si
Competing with STNLCD, as shown in (TFT).
However, it is impossible with the conventional TFT LCD method. That is, for example, when considering a relatively small matrix of 160 × 100, the frame frequency is 30 Hz in the normal operation, so that a 480 kHz signal is particularly input to the driver of the data line. However, the a-Si TFT cannot follow such high speed operation. The same applies to compound semiconductors such as cadmium-selenium (CdSe) -based semiconductors. The reason why these semiconductor materials are not positively used as an active element is their toxicity and resource problems, but their low response speed is also a serious problem.

To avoid this difficulty, the frame frequency may be lowered. In particular, when it is not necessary to display a moving image, it seems that there is no problem with the lowering of the frame frequency, but due to the technical problem of the current TFT LCD, the state of frame scanning is visible and the screen is extremely difficult. It becomes difficult to see.

T using TN liquid crystal as a conventional liquid crystal material
FIG. 2 shows a pixel circuit of the FTLCD and its operation example. TF
The gate electrode of T is connected to a selection line (also called a gate line), the drain is connected to a data line (also called a drain line), and the source is connected to a pixel electrode. The counter electrode of the pixel electrode is usually kept at a constant voltage as a common electrode. Generally grounded.

As shown in FIG. 2B, a pulse is periodically applied to the select line, and pixel information is applied as a voltage signal to the data line. The pulse period of the select line is
In normal operation, the period is 1 frame, typically 1
It is 0 to 30 msec. The pulse width is about the cycle divided by the number of rows in the matrix or less, and is 100 to 300 μsec in a relatively small matrix of 100 rows such as used for information displays.

The signal on the data line is in a voltage state when the pixel is in a lighted state, and is in a non-voltage state when the pixel is in a lighted state. Also, the polarities of the voltage states are switched periodically. This is because TN liquid crystal material
This is because when a direct current is applied, it causes electrolysis and deteriorates. This operation is called alternating current.

Now, a TFT to which such a signal is applied
The signal on the source side of is as shown by V ₁ . First, by applying the pulse of the select line, the TFT is turned on and the voltage of the source rises even if it becomes the same as the voltage of the drain. However, at the same time when the pulse is cut off, there is a voltage effect of ΔV due to the parasitic capacitance between the gate electrode of the TFT and the source region. After that, the TFT is turned off, so that the pixel electrode is in an electrically floating state and the TFT
The voltage gradually decreases due to the leakage current of.

Next, a pulse is applied to the selection line again,
When the TFT is turned on, the source voltage now approaches the negative drain voltage. After that, as the pulse is cut off, the voltage is negatively shifted by ΔV due to the influence of the parasitic capacitance, and the voltage is attenuated by the leak current. When the pulse of the last select line is applied, the voltage of the drain is 0, so the charge accumulated in the pixel electrode is discharged and V
₁ becomes 0.

If the frame frequency is lowered, such voltage fluctuation becomes visible at the frame frequency. The decrease in frame frequency is limited to 10 Hz.

Another solution is to manufacture only the driver IC from polysilicon, but since the type of glass substrate is not limited, annealing at a high temperature that is usually performed cannot be performed. Advanced technologies such as laser annealing must be adopted. However, laser annealing is a method that is not well established and its mass productivity is poor.

[0023]

DISCLOSURE OF THE INVENTION The present invention is a new active matrix system capable of competing with the simple matrix system in terms of cost and realizing an image quality equivalent to that of the active matrix system in a display device which does not particularly need to display a moving image. And a display device thereof.

In particular, the present invention eliminates the need for a driver IC by simultaneously forming the pixel matrix and the peripheral driver circuit with an a-Si TFT or a similar TFT that can be manufactured at a relatively low temperature, thereby improving the yield and reducing the cost. This is something that will be realized.

[0025]

As described above, it is necessary to use a low-mobility semiconductor such as an a-Si TFT or a CdSe-based semiconductor to reduce the frame frequency particularly in a display that does not need to display a moving image. This is an important method for using the TFT in the driver circuit. However, the reduction in frame frequency should not cause any visible degradation of image quality such as flicker.

By the way, according to the conventional idea, the meaning of the alternating frequency and the rewriting frequency overlap in the frame frequency. Even if the two are separated, it is natural that the rewriting frequency is higher than the alternating frequency. Here, be careful about the word rewriting used in the text. In the text, rewriting does not only mean a change in display content, but it means that a signal is newly injected from the outside or there is an opportunity even if the display content is the same. Therefore, in the conventional TFT LCD, the pixel that was in the lighting state in one frame can be kept in the lighting state in the next frame, and therefore a pulse is applied to the selection line and a signal is sent to the data line at the same time. , And that it has been rewritten.

As described above, the rewriting frequency cannot be set to 10 Hz or less due to a visual problem.
In the present invention, it is attempted to solve the above-mentioned problems by clearly distinguishing between alternating and rewriting and controlling both independently. When these elements are separated, it will be clear that it is the alternating frequency, and not the rewriting frequency, that affects vision. For example,
In the segment type LCD, the rewriting operation is substantially different from the alternating operation. In fact, the rewriting frequency of the calculator LCD is quite slow. However, the frequency of alternating current is about 30 Hz. The flickering of the display on the LCD due to the consumption of the battery or the like is due to the lowering of the alternating frequency, not because the rewriting cycle is reduced.

Also in the present invention, in order to prevent flicker, the frequency of alternating current must be 10 Hz or higher. However, the rewriting frequency needs to be 1 Hz or less.

For example, if rewriting is 1 Hz, 160
The signal sent to the driver of the data line of the LCD of × 100 dots is 16 kHz, which is one-third that of the conventional one.
-It is a speed that can be sufficiently driven even by SiTFT.

In order to achieve such an object, the conventional TFT LCD system is extremely unsuitable. In the conventional TFT LCD, one TFT,
This is because it plays two roles of selecting a pixel and supplying a voltage to the pixel. Therefore, in the present invention, these two roles are separately assigned to the active elements. Here, an element that selects a pixel is a first element, and an element that receives an output of the first element and supplies a voltage to the pixel is a second element.

These elements are composed of active elements such as TFTs and various diodes, or passive elements such as resistors and capacitors. At the time of manufacturing these, a-Si or one which is manufactured under conditions equivalent to that is desired, and adoption of a high temperature process of 600 ° C. or higher is avoided.

In the simplest case, as shown in FIG.
Two TFTs are connected to the first element (Tr₁), The second
Element (Tr₂). In the present invention, the pixel book
Conventionally, in the sense that it will be exchanged regardless of replacement
It is necessary to have a voltage supply line which is not in the TFT LCD system of
There is a point. Regarding the connection with each wiring, as shown in the figure
Tr₁The drain of the as the data line and the gate electrode as the select line
Connect and source is Tr ₂Connect to the gate electrode of. Well
And Tr₂The drain is the voltage supply line and the source is the pixel
Connect to each pole.

The operation of this example will be described below with reference to FIG. Here, for the sake of simplicity, the conversion is 2
Rewriting shall be carried out once while being carried out. As a matter of course, the case where rewriting is performed once while the alternating operation is performed 10 times, and the case where the rewriting is performed once while the alternating operation is performed 30 times can be similarly expanded.

In this example, it is assumed that the pixel that was initially in the off state is turned on and then turned off again in the next rewriting. Pulses are regularly applied to the select line V _G as in the conventional case. On the other hand, the necessary signal is also applied to the data line. The signal applied to the data line is a binary value of positive and negative,
Alternatively, it is a binary value of a voltage state and a non-voltage state. Here, it is assumed that both Tr ₁ and Tr ₂ are NMOS. Further, the potential of the counter electrode of the pixel is set to zero.

[0035] When a pulse is applied to the first select line, the signal of the data line is positive, the potential V ₁ of the source of the Tr ₁ becomes a positive value, as in the conventional TFTLCD The voltage increases and drops at the end of the pulse, after which it spontaneously discharges. The time required for this discharge is determined by the OFF resistance of Tr ₁ and the capacitance C between the gate electrode of Tr ₂ and the channel. For example, a-Si
In the TFT, since the OFF resistance is about 10 ¹³ Ω and the C is about 10 ^-13 F, the attenuation constant is about 1 second. That is, the voltage is about 40% after 1 second.
It has become. It is also possible to extend this time by making C larger.

On the other hand, a signal synchronized with the pulse of the selection line is sent to the voltage supply line, and an AC pulse is sent to this voltage supply line as shown in the figure for the purpose of making the pixel drive AC. Here, the signal polarity of the voltage supply line changes twice, positive and negative, per one selection pulse. Of course, the polarity may be changed more per one selection pulse.

[0037] Since the gate electrode of Tr ₂ already takes a positive voltage, Tr ₂ is turned ON, the voltage of the voltage supply line is directly applied to the pixel electrode, the voltage V ₂ of the pixel electrode, FIG. First, as shown in 1 (B), it takes a negative value,
After that, it takes a positive value as the voltage of the voltage supply line is inverted. It can be said that this is a characteristic of the present invention, but by such a two-stage operation, the pixel is supplied with a voltage substantially the same as the voltage of the voltage supply line, and this is due to natural discharge as in the conventional case. It never decreases. Therefore, black and white are clearly discriminated.

Next, a pulse is applied to the select line again. At this time, since the voltage of the data line is 0, the electric charge stored in C is discharged and V ₁ becomes 0. As a result, Tr _{2 is} also turned off and the voltage supply to the pixel is stopped.

In the prior art, the alternating period was the same as or longer than the rewriting period, so that the pulse shown by the dotted line had to be applied to the select line. However, the present invention eliminates that pulse and reduces the operating signal by one half.

Considering further the effect of the present invention, for example, if rewriting is performed once per second by the same method as in FIG. 1, this is 1/30 of the conventional speed. This means that both the pulse applied to the select line and the signal on the data line can be made 30 times longer. For example, in the case of the pulse of the selection line, it is about 100 μsec in the matrix of 200 rows in the related art, but it can be set to 3 msec which is 30 times that in the present invention. This means that even if the operation of the TFT is slow, it can respond reliably to charge and supply the required voltage. Conventionally, since the a-Si TFT has a response in a short time in which it is difficult to operate, there are pixels that are sufficiently charged and pixels that are not sufficiently charged due to variations in the characteristics of each TFT, which leads to deterioration in image quality.

In the present invention, a semi-analog voltage is not applied to the pixel by the operation of the two-stage TFT already. However, due to such a feature, defective TFTs can be reduced and the yield can be improved. Contribute.

In this description, the TFT is a-SiT.
It is desirable to use FT. And both are NM
Although an OS a-Si TFT may be used, an enhancement type TFT may be used for Tr ₁ and a depletion type TFT may be used for Tr ₂ . When using the a-Si TFT, the PMOS is not suitable for the purpose because its operating speed is extremely slow. However, since the mobility of holes is considerably large in a silicon semiconductor in an intermediate state between amorphous silicon and polysilicon, PMOS can be used. In that case, the peripheral circuits can also be CMOS.

An example of the overall configuration of the device of the present invention is shown in FIG. The number of dots on this LCD is, for example, 320 × 480.
(Half the screen of a normal laptop computer). However, the screen is roughly divided into four parts vertically and horizontally, and each screen is driven by a driver (401) of four selection lines and a voltage supply line arranged beside the LCD matrix (406). Furthermore, each of the four divided screens is further divided in half and driven by the data line drivers (402) provided above and below. Each driver has a wire bonding terminal (40
From 3), the wiring (405) connected by the wire bonding method is connected to an external circuit.

For example, paying attention to the lower left screen, the number of pixels here is 1600, which is 1/8 of the whole. if,
If the operation of rewriting only once per second is performed, the frequency of the signal sent from the wiring 405 to the data line driver 402 is 9.6 kHz. Also,
The signals sent to the select line and the voltage supply line must be at least 30 Hz signal for one row in the voltage supply line, and the number of rows is half of 240 (120 rows are the other 120 rows). The driver on the side is in charge)
A signal of 3.6 kHz is sent. In both cases, the frequency is extremely small, and the driver is a-Si.
Even if it is composed of TFTs, there is almost no problem.

Further, when the driver circuit is formed at the same time as the matrix as described above, the decrease in the yield due to that is almost negligible. In the present invention, the capacitance C between the gate electrode of Tr ₂ and the channel becomes a particular problem. As described above, in maintaining the potential of V ₁ , Tr
The OFF resistance of ₁ and C are the parameters. The OFF resistance of the TFT can be changed to some extent by changing the thickness and width of the channel. However, it is difficult to achieve a high resistance of 10 ¹³ Ω or more. On the other hand, C is determined by the size of the gate electrode of Tr ₂ . For example, 10 × 10
When the gate electrode has a thickness of 0 μm ² and the thickness of the insulating film is 100 nm, C is 10 ⁻¹³ to 10 ⁻¹² F. If silicon nitride having a high dielectric constant is used as the insulating film, C will increase.

It is not desirable to use an area of 10 × 100 μm for the gate electrode of Tr ₂ because the aperture ratio is lowered. In fact, it is unwise to devote more area to the TFT. Therefore, in order to solve this contradiction, it is advisable to overlap the source electrode / wiring of Tr _{1 on} the voltage supply line. In this way, a large capacitance can be obtained without reducing the aperture ratio. In that case, one of the methods is to use a material having a large dielectric constant for the interlayer insulator.

Since a large C is connected to Tr ₁ in this way, some people may be concerned about a decrease in the ON / OFF operating speed of Tr ₁ . However, in the present invention,
The signal on each data line also lasts significantly longer than the pulse of the select line, for example 30 times longer. On the other hand, conventional T
In FTLCD, the capacitance of the pixel electrode, which is the load, is 10 ^{-1 3}
It was about F. In the case of the present invention, a load capacity that is about the same as or larger than that of the conventional one is required, but since the response speed is reduced to 1/10 or less, there is no problem at all, and there is a margin more than the conventional one. It may be possible to respond and operate with.

According to the present invention, when rewriting (including maintaining) the display, there is a method of carrying out every suitable number of lines in accordance with the timing of alternating current. For example, a method as shown in FIG. For example, let's assume a matrix of 100 rows. And the 1st line, 21st line, 41st line and 6th line
It is assumed that the same signal is applied to the voltage supply lines of the five rows of the 1st row and the 81st row in synchronization. Similarly, line 2 and line 22
It is assumed that the row, the five rows of the 42nd row, the 62nd row and the 82nd row, and the other rows also form a set and operate in synchronization with each other.

At the first AC conversion (FIG. 5A),
Suppose that the rewriting of pixels from the 1st row to the 20th row is performed. At this time, a pulse is applied to the selection line and a positive voltage is applied to the voltage supply line for the pixels in the first row. On the other hand, the 21st
The voltage is applied to the voltage supply line and the pulse is not applied to the select line for other pixels that move in synchronization with the row and other first rows. Therefore, at this time, only the first row is rewritten among the rows that operate as a set of five. The same is true for the other sets, and in the end, only the first to twentieth lines are rewritten at this time.

Next, in the 21st row, assume that a negative voltage is applied to the voltage supply line at the same time as a pulse is applied to the selection line. However, at this time, no pulse is applied to the selection line in the first row and the other rows that operate in synchronization. A voltage is applied to the voltage supply line as in the 21st row. The same applies to the other row sets, as shown in FIG. 5B, from the 21st row to the 4th row.
Only line 0 can be rewritten.

Thereafter, the same operation is repeated. Figure 5 (C)
Then, the 41st to 60th lines are rewritten, but at this time, a positive voltage is applied to the voltage supply line. Figure 5
In (D), the 61st to 80th lines are rewritten, but at this time, a negative voltage is applied to the voltage supply line. In FIG. 5E, the 81st to 100th lines are rewritten, but at this time, a positive voltage is applied to the voltage supply line.

Thus, in FIG. 5F, the first to twentieth lines are rewritten again. At this time, the voltage applied to the voltage supply line is negative. Figure 5
Each pixel was rewritten once between (A) and (E), but the voltage of the pixel changed five times such as positive, negative, positive, negative, and positive. This is exactly what is the feature of the present invention. That is, the rewriting cycle is longer than the alternating cycle. Particularly, in the present invention, the load of the driver circuit is remarkably reduced by setting the ratio of this period to 30 times or more.

Now, according to the present invention, the power for driving the LCD can be reduced. Conventional TFT LCD or STNL
In CD, the frequency of the signal output to each data line is
(Number of rows × 30) Hz. However, in the present invention, for example, if rewriting is performed only once per second, the number of lines is (number of rows × 1) Hz.

On the other hand, the frequency of the signal output to each selection line is 30 Hz in the conventional LCD, whereas it is 1 Hz in the present invention. However, in the present invention, since a signal of 30 Hz is output to the voltage supply line, this point is almost equal to the conventional one.

As a result, the power consumption can be reduced by reducing the signals on the data lines. Further, in the conventional STN LCD, since the operation is in the dynamic mode, it is necessary to illuminate the screen with a backlight in order to make the screen easy to see. However, in the present invention, since the operation is in the static mode, the backlight is It is possible to obtain good visibility even without it.

To implement the present invention, known thin film semiconductor manufacturing techniques may be applied. Although the details thereof will not be described one by one, examples will be shown and described below.

[0057]

EXAMPLE FIG. 6 shows an example of a pixel drive circuit for implementing the present invention and a manufacturing method thereof. This shows a state when the pixel circuit is viewed from above. The circuit of this embodiment has an inverted stagger type double TFT having triple metal wiring. To manufacture such a circuit, the following may be performed.

First, a select line (which will be the gate electrode / wiring of Tr ₁ ) 601 made of a metal material such as aluminum is patterned on a suitable substrate (mask 1). At this time, if a metal oxide film having a good insulating property is formed on the surface of the select line by a method such as anodic oxidation, the probability that a defect will occur in a later process becomes small. Then, a first insulating layer that functions as a gate insulating film and an interlayer insulating film is formed. Next, an amorphous silicon or polysilicon film is formed by the CVD method or the like and patterned (mask 2). Next, using the mask 1, an etching stopper such as a silicon nitride film is formed so as to overlap the selection line. Alternatively, light may be irradiated from the back surface of the substrate, and the etching stopper may be patterned in a self-aligned manner so as to overlap the selection line.

Next, an impurity-doped semiconductor film is formed and patterned (mask 3). In this way, the semiconductor region 602 of the first TFT is manufactured. FIG. 6 (A)
The situation is shown in.

Next, the data line 603 is formed of a metal material. The data line is formed so as to be connected to the source of the first TFT (mask 4). Also, at the same time, the same material
A wiring 604 extending from the drain electrode of the TFT is formed. At this time, the reason why the metal wiring 604 has such a complicated structure is that the metal wiring 604 overlaps with the voltage supply line later. This is shown in FIG. 6 (B).

Further, as in the case of manufacturing the first TFT, a second insulating film (which will be the gate insulating film of the second TFT) is formed and the activation semiconductor film of the second TFT is patterned. (Mask 5), then using mask 4,
An etching stopper is formed, and an impurity-doped semiconductor film is formed and patterned (mask 6). In this way, the semiconductor region 605 of the second TFT is formed.
Further, a voltage supply line 606 is formed with a metal material (mask 7), and a drain and a contact of the second TFT are formed. In this way, a circuit as shown in FIG. 6C is obtained. Finally, as shown in FIG. 6D, the transparent conductive film 607 is patterned (mask 8) to complete the circuit.

The above steps require a total of eight masks, and the mask process requires ten times. In order to actively reduce the mask process, it is desirable to introduce a self-aligned process. In addition, in order to form a TFT without using an etching stopper, first the source,
The impurity semiconductor to be the drain region may be formed by patterning, and then the activated semiconductor film may be formed.

In this circuit, the voltage supply line and the second TFT
The gate electrode wiring is designed to overlap intentionally. This is the capacity of both (corresponding to C in Fig. 1 (A)).
This is because it is intended to increase the holding time of the charge accumulated in the gate electrode of the second TFT and reduce the number of times of rewriting.

[0064]

According to the present invention, T is easy to see.
L, which is equivalent to the active matrix system such as FTLCD, and can be competitive in price with the STNLCD system
A CD can be provided.

An object of the present invention is to provide an LCD used for a display device that does not need to display moving images. For example, it is used as an accessory of an electric device and used for displaying a method of operating the device or an operating state of the device. In the past, such applications were extremely limited and the market was small. Conventionally, segment-type LCDs and SETNLCDs have been used as read-only displays.

However, the segment type has a limited display capacity. Further, in STNLCD, it was necessary to mount a driver IC. At present, the TAB method is generally used as a technology for mounting such an IC, but it becomes technically difficult to adopt the TAB method due to the reduction of pixels. In general, the TAB method cannot be used when one side of the pixel is 100 μm or less.

In the present invention, since the driver IC is also formed integrally, there is no such problem. However, in the conventional a-SiTFT LCD, it was difficult to configure the driver IC with the a-SiTFT due to the difficulty of the operating method. The present invention successfully solved this point.

The present invention promises a whole new application for read-only LCDs. For example, in the present invention, an external I
Since C is not required, the size can be extremely reduced. Therefore, it can be used for a card type display device. For example,
It can be used for card-type pagers (registered trademark) and display devices for various credit cards. Although such applications are expected, they could not be put into practical use because there was no suitable display device or LCD. At present, the market size for such purposes is small, but it is expected that there is enormous potential demand, and it is expected to grow into a large market.

In the present invention, the material of the TFT is 600
It is desirable to use a material manufactured at a low temperature of ℃ or less. Although a-SiTFT is taken up in the embodiment, CdS
There is no particular problem even with a compound semiconductor such as CdSe or CdSe.

[Brief description of drawings]

FIG. 1 shows a circuit example of a pixel of a TFT LCD of the present invention and an operation example thereof.

FIG. 2 shows a circuit example of a pixel of a conventional TFT LCD and an operation example thereof.

FIG. 3 schematically shows the relationship between the number of pixels of various LCDs and cost.

FIG. 4 shows a configuration example of a panel of the TFT LCD of the present invention.

FIG. 5 shows an example of a display method of the TFT LCD of the present invention.

FIG. 6 shows an example of a pixel circuit of a TFT LCD of the present invention and an example of a manufacturing method thereof.

[Explanation of symbols]

401 ・ ・ ・ ・ Selection line ・ Voltage supply line driver circuit 402 ... Data line driver circuit 403 ... Bonding pad 405 ... Bonding wire 406 ... Matrix area

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G09F 9/30 G02F 1/1368 H01L 29/786

Claims (3)

(57) [Claims] Has a 1. A plurality arranged in a matrix on a substrate having an insulating surface pixels, formed on said substrate, and a driving circuit for driving the plurality of pixels, the plurality of pixels Is m rows, and each row of the plurality of pixels has a voltage supply line and a selection line.
A selection line is provided, and each of the plurality of pixels has amorphous silicon.
That has an N-type first and second thin film transistor, wherein the source or drain of the first thin film transistor second thin film transistor gate is connected, the selected line, a gate of the first thin film transistor
And the voltage supply line is connected to the saw of the second thin film transistor.
Display method connected to the drain or drain
A is, the plurality of pixels, I each first row to m / n-th row
Into the first to nth blocks, and the same rows of the first to nth blocks are
Apply a pulse to the selection line in order as one set
By rewriting the pixels in the row to which the pulse is applied
Was carried out simultaneously with rewriting of pixels in a row of applying the pulse, the
Provided in each row of the same set as the pulsed row
Voltage of the same polarity is applied to the voltage supply line,
Rewriting of one block among the 1st to nth blocks is completed.
The polarity of the voltage applied to the voltage supply line is changed each time
A display method for a display device, comprising: 2. A matrix is formed on a substrate having an insulating surface.
A plurality of arranged pixels and a driving device for driving the plurality of pixels formed on the substrate.
A plurality of pixels , and the plurality of pixels comprises 100 rows, and each row of the plurality of pixels has a voltage supply line and a selection line.
A selection line is provided, and each of the plurality of pixels has amorphous silicon.
And N-type first and second thin film transistors, which are connected to the source or drain of the first thin film transistor.
The gate of the second thin film transistor is connected, and the select line is connected to the gate of the first thin film transistor.
And the voltage supply line is connected to the saw of the second thin film transistor.
Display method connected to the drain or drain
And each of the plurality of pixels is in the first to twentieth rows.
It is divided into first to fifth blocks, and the same rows of the first to fifth blocks are respectively
Apply a pulse to the selection line in order as one set
By rewriting the pixels in the row to which the pulse is applied
Was carried out simultaneously with rewriting of pixels in a row of applying the pulse, the
Provided in each row of the same set as the pulsed row
Voltage of the same polarity is applied to the voltage supply line,
Rewriting of one block from the 1st to 5th blocks is completed.
The polarity of the voltage applied to the voltage supply line is changed each time
A display method for a display device, comprising: 3. The first and second thin film transistors,
The display method of the display device according to claim 1, wherein the display device is an inverted stagger type.