JP2003315768A - Method for driving liquid crystal device and display system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving a liquid crystal device and a display system having high reliability and excellent a display characteristic. <P>SOLUTION: Analog switches TFT 20-11 to 20-nm are divided into (n) blocks with (m) pieces as one block. When the amplitudes of input signals to be supplied to source areas of the analog switches are made 5 volts or lower, and the potentials to be applied to the counter electrodes of the pixel electrodes connected with pixel transistors are made counter electrode potential, the polarity of the counter electrode potential to the input signals is inverted for each horizontal scanning period. In a horizontal blanking period, a period for turning off the analog switches TFT is arranged. In the horizontal blanking period, the polarity of the potential to be applied to the counter electrodes is inverted, and then the analog switches TFT are turned on and a period for applying a necessary potential to the signal lines is arranged. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device driving method and a display system.

[0002]

BACKGROUND ART As an example of an active matrix type liquid crystal device using a thin film transistor (hereinafter referred to as a TFT), there are conventional techniques disclosed in JP-B-6-5478 and JP-B-6-68673. In this conventional technique, the M signal lines to which the pixel TFTs are connected are
n blocks of analog switches, with m blocks as one block, are connected. Then, the on / off of the analog switch is controlled by a given control signal so that the number of terminals of the signal line drawn from the liquid crystal panel is reduced to 1 / n. By reducing the number of terminals, simplification of mounting and cost reduction can be achieved.

However, the above-mentioned prior art has the following problems.

First, the analog switch is connected to the pixel TF.
Similar to T, when formed by TFT, there is a problem that it is difficult to secure the reliability of this analog switch (hereinafter referred to as analog switch TFT). That is, various capacitances such as a liquid crystal capacitance, a storage capacitance, and a capacitance of a diffusion region of a pixel TFT are parasitic on the signal line of the liquid crystal device, and a large amount of current flows through the signal line to charge and discharge these capacitances. Especially n
In the configuration where the block analog switch TFT is provided,
The time allowed for charging / discharging the various capacitors is short, and it is necessary to charge / discharge to a given potential in a short time, so that the current flowing through the analog switch TFT is further increased. When a large amount of current flows through the TFT for a long period of time, the threshold voltage of the TFT shifts, and secondly, when the analog switch TFT is interposed between the data driver and the signal line,
Due to the on-resistance of the analog switch TFT and the parasitic wiring resistance generated by providing the analog switch TFT, the voltage applied to the pixel is lowered, or the voltage applied to the pixel varies. Decrease in applied voltage,
The variation is a factor that deteriorates the display quality and makes the design difficult.

Third, as described above, the analog switch T
There is also a problem of how to efficiently implement the data driver and the scan driver when the FT is provided.

The present invention has been made in view of the above problems, and an object thereof is to provide a driving method and a display system of a liquid crystal device having excellent display characteristics and high reliability. is there.

[0007]

In order to solve the above problems, a liquid crystal device according to the present invention includes a pixel transistor formed of thin film transistors and arranged in a matrix of N rows × M columns, and a gate electrode of the pixel transistor. N scanning lines connected to each other, and M (= m ×) intersecting the scanning lines and connected to the source region of the pixel transistor.
n) signal lines and thin film transistors and connected to the M signal lines.
M analog switch transistors divided into n blocks as a block, n first wirings commonly connecting gate electrodes of m adjacent analog switch transistors included in the same block, and included in different blocks And m second wirings that commonly connect the source regions of n adjacent analog switch transistors,
The amplitude of the input signal supplied to the source region of the analog switch transistor via the second wiring is set to 5 V or less.

According to the present invention, by using the analog switch transistor divided into n blocks, the number of data drivers and the number of terminals can be reduced, and the device can be made compact. By setting the amplitude of the input signal of the analog switch transistor to 5 V or less, the shift amount of the threshold voltage of the analog switch transistor can be optimized and the reliability can be improved.

Further, the present invention is characterized in that the pixel transistor and the analog switch transistor are formed of a polycrystalline silicon thin film transistor and are integrally formed on a glass substrate. According to the present invention, by using the polycrystalline silicon TFT, the ON resistance of the analog switch transistor can be lowered, and the pixel transistor and the analog switch transistor can be integrally formed practically.

Further, the present invention is characterized in that the wiring resistance from each output terminal of the data driver for supplying an input signal to the second wiring to the source region of the analog switch transistor is made substantially constant. By doing so, it is possible to effectively prevent the occurrence of line unevenness and brightness unevenness.

According to the present invention, half of the analog switch transistors are arranged above and below the active matrix area in which the pixel transistors are arranged,
The (2L-1) th signal line is connected to the analog switch transistor arranged on either the upper side or the lower side, and the 2Lth signal line is connected to the analog switch transistor arranged on the other side. To do. By using the comb-teeth wiring in this way, signal line inversion drive and dot inversion drive are facilitated and the operating frequency of the data driver can be reduced. Moreover, when the comb-shaped wiring is used, the external dimensions of the device are increased, and the circuit board wiring is complicated.
According to the configuration of the present invention, this can be solved.

According to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect with each other. And M signal lines connected to the source regions of the pixel transistors and above and below the active matrix area formed of thin film transistors and connected to the M signal lines, in which the pixel transistors are arranged. And (2L-1) th signal line is connected to the analog switch transistors arranged on either the upper side or the lower side of the active matrix area, and Connect the 2Lth signal line to the analog switch transistor arranged in At least one data driver for supplying a signal to the source region of the analog switch transistor and at least one scan driver for supplying a signal to the gate electrode of the pixel transistor are mounted on the same side of the liquid crystal panel. And

According to the present invention, the number of data drivers and the number of terminals can be reduced by using the analog switch transistors divided into n blocks, and the data driver and the scan driver are mounted on the same side of the liquid crystal panel. it can. This makes it possible to reduce the external dimensions of the device, reduce noise, and simplify circuit board wiring.

According to the present invention, the first data driver, the scan driver, and the second data driver are mounted in order from the upper side on either the left side or the right side of the liquid crystal panel,
A wiring pattern for connecting the analog switch transistor arranged above the active matrix area and the first data driver, and connecting an analog switch transistor arranged below the active matrix area and the second data driver It is characterized in that it is vertically symmetrical with the wiring pattern. By arranging the wiring patterns symmetrically in this manner, the layout pattern can be easily created and the display characteristics can be improved.

Further, according to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect. Together with M (= m ×) connected to the source region of the pixel transistor
n) signal lines and M analog switch transistors which are formed by thin film transistors and are connected to the M signal lines and are divided into n blocks with m blocks not adjacent to each other included in the same block N first wirings that commonly connect the gate electrodes of m non-adjacent analog switch transistors and m second second wirings that commonly connect the source regions of adjacent n analog switch transistors included in different blocks. And the amplitude of the input signal supplied to the source region of the analog switch transistor via the second wiring is 5V.
It is characterized by the following.

According to the present invention, by setting the amplitude of the input signal of the analog switch transistor to 5 V or less, the shift amount of the threshold voltage of the analog switch transistor can be optimized and the reliability can be improved. Further, it is possible to prevent the occurrence of stripes at the boundary of the active matrix area region corresponding to each block.

Further, according to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect the scanning lines. Together with M (= m ×) connected to the source region of the pixel transistor
n) signal lines and M analog switch transistors formed by thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. The analog switch transistor and the scan driver circuit for supplying a signal to the scan line are formed of a polycrystalline silicon thin film transistor and are integrally formed on a glass substrate.

Polycrystalline silicon TFT has high mobility,
It is most suitable for forming an analog switch transistor. Polycrystalline silicon TF having a low on-resistance required for analog switch transistors
If T is used, the scan driver circuit can be easily formed.

According to the present invention, the scan driver circuit is
It is characterized in that it is formed by a dynamic type or static type shift register composed of a thin film transistor having the same polarity as the pixel transistor and the analog switch transistor. In this way, T of the same polarity
Since the liquid crystal device can be formed using only FT, the manufacturing process can be simplified and the circuit scale can be reduced.

Further, according to the present invention, pixel transistors formed by thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect with each other. Together with M (= m ×) connected to the source region of the pixel transistor
n) signal lines and M analog switch transistors which are formed by thin film transistors and are connected to the M signal lines and are divided into n blocks with m as one block, and a liquid crystal material is enclosed. A dual structure seal part provided with a first enclosing area and at least one second enclosing area separated from the first enclosing area and enclosing a gas; and the analog switch transistor or the analog switch The transistor and its wiring are formed in the second enclosed area.

According to the present invention, since the analog switch transistor and the like can be hermetically sealed with gas, the moisture resistance is improved,
It is possible to improve reliability and reduce parasitic capacitance. Further, there is an advantage that the gas can be easily supplied to the second enclosed area, and the addition of new steps is small.

According to the present invention, the second enclosing area is provided at least above and below the active matrix area in which the pixel transistor is arranged, and the liquid crystal material is enclosed on either the right or left side of the active matrix area. An inlet is provided, and half of the analog switch transistors are arranged in the second enclosed area above and below the active area. With this configuration, the analog switch transistor can be sealed even when the comb wiring is performed. Further, since the second enclosed area is provided above and below the active matrix area, the liquid crystal can be enclosed from the right side or the left side. At this time, it is desirable to mount a data driver, a scan driver, etc. on the side without the sealing port.

Further, according to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect the scanning lines. Together with M (= m ×) connected to the source region of the pixel transistor
The analog switch transistor includes n) signal lines and M analog switch transistors formed of thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. Alternatively, the analog switch transistor and its wiring are covered with an insulating film having a dielectric constant lower than that of at least a liquid crystal material.

By covering the analog switch transistor and the wiring with an insulating film, the protection and reliability of the analog switch transistor can be improved. By using an insulating film having a dielectric constant smaller than that of liquid crystal, parasitic capacitance can be reduced and display characteristics can be improved.

Further, the present invention is characterized in that the signal line is covered with an insulating film having a dielectric constant lower than that of at least a liquid crystal material. By doing so, the parasitic capacitance of the signal line can be reduced, and the display characteristics can be further improved.

Further, according to the present invention, pixel transistors formed by thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect with each other. Together with M (= m ×) connected to the source region of the pixel transistor
A liquid crystal device including n signal lines and M analog switch transistors formed by thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. In the driving method, the amplitude of the input signal supplied to the source region of the analog switch transistor is set to 5 V or less, and the potential applied to the counter electrode of the pixel electrode to which the pixel transistor is connected is set to the counter electrode potential. A driving method characterized in that the polarity of the electrode potential with respect to the input signal is inverted every horizontal scanning period.

By thus performing the 1H common swing inverting drive, the input signal of the analog switch transistor is changed to 5
Even if the voltage is V or less, a sufficiently large applied voltage can be applied to the liquid crystal, and reliability can be secured without degrading display characteristics. Further, the data driver can be formed by a low withstand voltage process, and the cost can be reduced.

According to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect the scanning lines. Together with M (= m ×) connected to the source region of the pixel transistor
A liquid crystal device including n signal lines and M analog switch transistors formed by thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. A driving method, wherein an amplitude of an input signal supplied to a source region of the analog switch transistor is set to 5 V or less, and a selection potential, a non-selection potential, and a first potential lower than the non-selection potential are applied to a signal supplied to a scan line. , A case in which a second potential having a higher potential than the non-selection potential is provided and the non-selection potential is maintained after the first potential is kept for a certain period, and a case where the second potential is changed from the selection potential It is characterized in that the case where the non-selection potential is applied after the holding is switched for each scanning line.

By thus performing the 1H 4-value gate inversion drive, the input signal of the analog switch transistor is changed to 5
Even if the voltage is V or less, a sufficiently large applied voltage can be applied to the liquid crystal, and the cost of the data driver can be reduced. Furthermore, since it is not necessary to reverse the polarity of the potential of the counter electrode, power consumption can be reduced.

Further, the present invention is characterized in that a period during which the analog switch transistor is turned off is provided in the horizontal blanking period. By doing so, it is possible to change the counter voltage and the potential of the scanning line during the off period.

Further, according to the present invention, in the horizontal blanking period, the analog switch transistor is turned on after inverting the polarity of the potential applied to the counter electrode or after changing to the first potential or the second potential. It is characterized in that a period for applying a given potential to the signal line is provided. In this way, the data remaining on the signal line can be reset and crosstalk can be prevented.

According to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect with each other. Together with M (= m ×) connected to the source region of the pixel transistor
A liquid crystal device including n signal lines and M analog switch transistors formed by thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. A driving method, wherein half of the analog transistors are arranged on the upper side and the lower side of the active matrix area in which the pixel transistors are arranged, and an analog switch is arranged on either the upper side or the lower side of the active matrix area. The (2L-1) th signal line is connected to the transistor, the 2Lth signal line is connected to the analog switch transistor arranged on the other side, and the amplitude of the input signal supplied to the source region of the analog switch transistor is set to 5
When the potential applied to the counter electrode of the pixel electrode to which the pixel transistor is connected is set to the counter electrode potential, the polarity of the potential applied to the adjacent signal line with respect to the counter electrode potential is inverted. To do.

By using the comb-teeth wiring and the signal line inversion drive as described above, the amplitude of the input signal of the analog switch transistor can be set to 5 V or less, the shift amount of the threshold voltage can be optimized, and the liquid crystal can be displayed. The DC voltage can be prevented from being applied.

Further, according to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect the scanning lines. Together with M (= m ×) connected to the source region of the pixel transistor
n) signal lines and M analog switch transistors which are formed by thin film transistors and are connected to the M signal lines and are divided into n blocks with m blocks not adjacent to each other included in the same block N first wirings that commonly connect the gate electrodes of m non-adjacent analog switch transistors and m second second wirings that commonly connect the source regions of adjacent n analog switch transistors included in different blocks. A driving method used for a liquid crystal device including a wiring, the data of the video signal is rearranged using a line memory, and the rearranged signal is not adjacent to the second wiring. It is characterized in that data is written to a signal line through m analog switch transistors.

According to the present invention, it is possible to properly write data to a signal line in a liquid crystal device having a structure using an analog switch transistor which is divided into n blocks with m blocks not adjacent to each other as one block.

Further, according to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect. Together with M (= m ×) connected to the source region of the pixel transistor
A liquid crystal device including n signal lines and M analog switch transistors formed by thin film transistors and connected to the M signal lines and divided into n blocks with m blocks as one block. A driving method, wherein an input signal corrected to compensate for a punch-through voltage that changes depending on the magnitude of the potential of an input signal supplied to the source region of the analog switch transistor is supplied to the source region of the analog switch transistor. And

According to the present invention, since the input signal corrected for compensating the punch-through voltage is supplied to the analog switch transistor, it is possible to prevent the application of the DC voltage to the liquid crystal and to maintain the proper gradation display. can do.

In the display system according to the present invention, pixel transistors formed of thin film transistors are arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning. M (= m × n) signal lines that intersect the lines and are connected to the source regions of the pixel transistors, and are formed by thin film transistors and are connected to the M signal lines,
M analog switch transistors that are divided into n blocks with m blocks that are not adjacent to each other as one block, and n first wires that commonly connect the gate electrodes of the m analog switch transistors that are not adjacent and are included in the same block , M second wirings commonly connected to the source regions of adjacent n analog switch transistors included in different blocks, and a digital signal from the video signal generator or an analog signal from the video signal generator. A digital signal that has been A / D converted is input, processing means for performing a rearrangement process for the data of the digital signal or a process for reducing the rearrangement process and the data transfer frequency, and a signal from the processing means is D / A converted. And a data driver that supplies the signal to the analog switch transistor.

According to the present invention, when an analog switch transistor that is divided into n blocks with m blocks not adjacent to each other as one block is used, data can be properly written to the signal line. Further, by lowering the data transfer frequency, it is possible to reduce the speed and cost of the data driver.

According to the present invention, pixel transistors formed of thin film transistors and arranged in a matrix of N rows × M columns, N scanning lines connected to the gate electrodes of the pixel transistors, and the scanning lines intersect each other. And M signal lines connected to the source regions of the pixel transistors and above and below the active matrix area formed of thin film transistors and connected to the M signal lines, in which the pixel transistors are arranged. M number of analog switch transistors arranged by half,
First connected to the upper analog switch transistor
Data driver, a second data driver connected to the lower analog switch transistor, and processing means for reducing the data transfer frequency of a signal given to the first and second data drivers, In the analog switch transistor arranged on either the upper side or the lower side of the active matrix area (2L-1)
The second signal line is connected, and the 2Lth signal line is connected to the analog switch transistor arranged on the other side, and the processing means halves the data transfer frequency.

According to the present invention, the speeds of the first and second data drivers can be reduced, and the first and second data drivers can be formed on the same side of the liquid crystal panel together with the scan driver.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows the configuration of Example 1. In the active matrix area 10, pixel TFTs 8 are arranged in N rows × M columns, N scanning lines connected to the gate electrodes of these pixel TFTs and M (m × n) lines connected to the source region. Signal line is formed. These M signal lines have analog switch TFTs (20-1
1 to 20-nm) are connected. Analog switch TFT
Is divided into n blocks with m adjacent blocks as one block, and analog switch TFTs (20-11, 20-
12 to 20-1m) is the first block, (20-21, 20-2)
2 to 20-2m) is the second block ... (20-n1, 2)
0-n2 to 20-nm) becomes the n-th block. And adjacent analog switch TFTs included in the same block
The gate electrodes (20-11, 20-12 to 20-1m) are commonly connected by the first wiring 22-1. Similarly, analog switch TFT (20-21, 20-22 to 20-2m) ... (2
The gate electrodes of 0-n1, 20-n2 to 20-nm) are commonly connected by the second wirings 22-2 ... 22-n.

Analog switch TFTs (20-11, 20-21 to 20-n1) which are included in different blocks and are not adjacent to each other
The source regions of are commonly connected by the second wiring 24-1. Similarly, analog switch TFT (20-12, 20-22
.About.20-n2) ... (20-1m, 20-2m to 20-nm) are commonly connected by the second wirings 24-2 ... 24-m.

In this way, the analog switch TFT is divided into n blocks by m, and the ON / OFF of the analog switch TFT is controlled by the control signal applied to the first wiring. Can be That is, when there are no analog switch TFTs, the number of terminals of the signal line that existed in M lines can be set to m (= M / n) lines. Then, the data driver is connected to the m second wirings 24-1 to 24-m, the number of data drivers and the number of terminals can be reduced, and the device can be made compact and the cost can be reduced.

The first feature of this embodiment is that the second wiring 24
-Analog switch TFT 20-11 through 1 to 24-m
The amplitude of the input signal supplied to the source region of 20-nm is 5V
There are the following points. By doing so, the shift amount of the threshold voltage of the analog switch TFT can be reduced, and reliability can be secured and display quality can be improved.

FIG. 2 shows the measurement results regarding the relationship between the threshold voltage shift amount of the analog switch TFT and the operating time. Vg = 20V, and the load capacitance C is set to about C = 10 pF so as to be the same as the load capacitance in a standard liquid crystal panel. The operating frequency f is 320 KHZ. In the present embodiment, since the analog switch TFT divided into n blocks is provided and the number of data drivers (or the number of terminals) is reduced (for example, reduced to 1 / n),
The time allowed for charging / discharging the pixel electrode is shorter than usual. Therefore, the operating frequency f is also increased. 1 corresponding to the input signal supplied to the analog switch TFT
When a rectangular wave signal of 0V amplitude (Vd = 10V) is added, the threshold shift characteristic becomes like G, and 5V amplitude (Vd
When a rectangular wave signal of (= 5V) is added, it becomes H.
When Vd = 10V, the threshold voltage shifts by 1V in about 200 hours. On the other hand, analog switch T
When the amplitude of the input signal applied to the source region of the FT is 5V, that is, when Vd = 5V, the shift amount of the threshold voltage can be kept at 1V or less until about 10,000 hours.

When the shift amount of the threshold voltage is larger than 1 V, the amount of data written to the pixel electrode becomes insufficient (the potential of the pixel electrode cannot be set to a desired potential) and the contrast ratio is lowered. . In particular, for example, when the threshold voltage of the analog switch TFT is about 1V, if the threshold voltage is shifted to the minus side by about 1V, the analog switch TFT will be in the depletion mode and the analog switch TFT will be turned off. Even in the state, current leaks, which leads to deterioration of display characteristics.

In order to make the reliability of the liquid crystal device sufficient, it is necessary to keep the shift amount of the threshold voltage at 1 V or less for at least about 1000 hours, and it may be 1 V or less for about several thousand hours. desirable. When Vd = 10V, the shift amount is 1 in about 200 hours as shown in FIG.
It becomes larger than V and shifts by about 2 V in 1000 hours, which is very problematic in ensuring reliability. In this embodiment, the electric field concentration at the end of the source region can be relaxed by setting the amplitude of the input signal of the analog switch TFT to 5 V or less. As a result, the shift amount of the threshold voltage can be kept at 1 V or less for about 10,000 hours, and the reliability can be secured while maintaining a sufficient margin. Further, by setting the amplitude of the input signal to 5 V or less, the difference between the punch-through voltages of the analog switch TFT (which will be described in detail later) can be reduced, and the DC voltage applied to the liquid crystal can be lowered.

In addition, in FIG. 2, in order to make a proper comparison with the case of Vd = 10V, Vg = 20 even when Vd = 5V.
V is measured. However, Vd = 5V
In the case of (amplitude of input signal is 5V), even if Vg = 15V, the same writing performance as in the case of Vd = 10V and Vg = 20V can be secured. In that case, the shift amount of the threshold voltage is further reduced than that shown in FIG. 2H, and the reliability is improved. Further, in order to further improve reliability, it is desirable that Vd = 3V or less. In addition, the measurement result in the case of Vd = 5V and operating frequency 32 KH is also shown in I of FIG. 2 for reference.

The second feature of this embodiment is that the pixel TFT and the analog switch TFT are formed of polycrystalline (poly) silicon and are integrally formed on the glass substrate. An input signal is added to the analog switch TFT,
If the charging / discharging of the pixel electrode is not completed within a given period, the display characteristics are deteriorated, and it is necessary to reduce the on resistance of the analog switch TFT. Especially analog switch TFT
Is divided into n blocks and the number of data drivers is reduced, the demand for reducing the ON resistance becomes more severe. However, an amorphous silicon TFT has a very low mobility, and even if it can be used as a pixel TFT, it cannot be practically used as an analog switch TFT due to the above-mentioned problem of ON resistance. In this embodiment, the pixel TFT and the analog switch TFT are formed of polycrystalline polysilicon having a mobility much higher than that of an amorphous TFT. This practically enables the pixel TFT and the analog switch TFT to be integrally formed on the glass substrate. By integrally forming the pixel TFT and the analog switch TFT on the glass substrate, the external dimensions of the liquid crystal device can be reduced, and the cost of the device can be reduced.

Next, the manufacturing method and device structure in the case of integrally forming the pixel TFT and the analog switch TFT will be described with reference to FIG. First, a base insulating film 32 for preventing diffusion of impurities from the glass substrate is deposited on the glass substrate 30, and then a polycrystalline silicon thin film 34 is deposited. It is necessary to improve the crystallinity of the polycrystalline silicon thin film 34 in order to increase the field effect mobility. Therefore, a polycrystalline silicon thin film is recrystallized by laser annealing or a solid phase growth method, or an amorphous silicon thin film is crystallized to be polycrystalline silicon. After patterning the polycrystalline silicon film 34 in an island shape, a gate insulating film 36 is deposited.

Next, a gate electrode (metal) 38 is formed,
After that, the entire surface is doped with impurities such as phosphorus ions.
Next, an interlayer insulating film (SiO ₂ ) 40 is formed, a signal line or the like is formed with a metal thin film (Al) 42, and a transparent conductive film (IT
By forming the pixel electrode with O) 44 and forming the passivation film 46, a substrate in which the pixel TFT and the analog switch TFT are integrally formed is completed. A liquid crystal device is completed by subjecting this substrate to an alignment treatment, facing opposite substrates subjected to the same alignment treatment with a gap of several μm therebetween, and enclosing a liquid crystal.

The third feature of this embodiment is that the wiring resistance from each output terminal of the data driver to the source region of the analog switch TFT is made substantially constant. FIG. 4 shows an example of the layout pattern of this embodiment. In FIG. 4, for example, output terminals 50-1, 50-2 of the data driver,
Analog switch TFTs 20-11, 20-1 from 50-3 etc.
The wiring resistance up to 2, 20-13, etc. is made almost constant. Specifically, as shown in FIG. 5A, the analog switch T
Lead lines 52-1, 52-2, 52-3 from the FT to the second wiring
Is changing the thickness of. That is, the long leader line is thick and the short leader line is thin so that the resistances of the leader lines are constant with each other. When forming a TFT in a low temperature process, these lead lines are likely to be formed of a metal (chrome, tantalum, etc.) having a higher resistance than aluminum, so the resistance of this lead line is a big problem. Becomes Further, in the portion indicated by D in FIG. 4, the thicknesses of the portions E, F, G and H are changed as shown in FIG. That is, in the layout pattern of FIG. 4, since the wiring pitch of the portion indicated by I in FIG. 5B (the pitch of the output terminals of the data driver) and the wiring pitch of the portion indicated by J are different, the wiring of the H portion The length L2 becomes longer than the wiring length L1 in the E portion. Therefore, the wiring in the H portion is made thicker than in the E portion, and the resistance in this portion is made constant.

The magnitude of the resistance parasitic on the path from the output terminal of the data driver to the pixel electrode greatly affects the display characteristics. This is because if this resistance is high, charging / discharging of the pixel electrode may not be completed within a given period.
Particularly, in this embodiment, the on resistance of the analog switch TFT is added to the resistance of the path from the output terminal of the data driver to the pixel electrode, and the analog switch TF divided into n parts is used.
Since T is used, the allowable writing time to the pixel electrode is short. Therefore, the design condition for the resistance of this path becomes very strict. In this embodiment, FIG.
By taking various measures as shown in (B), the resistance from the output terminal of the data driver to the source region of the analog switch TFT is made substantially constant. This makes it possible to minimize the deterioration of the display characteristics due to the presence of the analog switch TFT. The conventional analog switch TF
In the liquid crystal device having no T, the signal lines are directly drawn out above the active matrix area 10 in FIG. 4, and the output terminals of the data drivers are evenly arranged above the active matrix area 10. Therefore, the difference in wiring resistance from each output terminal of the data driver to the active matrix area has not been a big problem.

As shown in FIG. 4, the fourth characteristic of the present embodiment is that half of the analog switch TFTs are arranged on the upper side and the lower side of the active matrix area 10, and odd-numbered signals are input to the upper analog switch TFTs. The line is connected and the even-numbered signal line is connected to the lower analog switch TFT (hereinafter, such wiring is referred to as comb wiring). The comb-teeth wiring can halve the operating frequency of the data driver. Also, by inverting the polarities of the outputs of the upper data driver and the lower data driver, signal line inversion drive and dot inversion drive can be easily realized. However, in the conventional configuration in which the analog switch TFT is not provided, the data driver is provided in the active matrix area 10 in order to realize the comb wiring.
Must be arranged above and below (see FIG. 6B, which will be described later), which causes problems such as an increase in external dimensions of the liquid crystal device and complication of circuit board wiring. According to this embodiment, the number of data drivers can be reduced by providing n blocks of analog switch TFTs. Therefore, even if the comb wiring is performed, the external dimensions of the liquid crystal device can be reduced, and the circuit board wiring can be simplified.

(Embodiment 2) Embodiment 2 is an embodiment relating to mounting of a data driver (IC) and a scan driver (IC), and the configuration thereof is shown in FIG. 6 (A). A portion indicated by a dotted line in FIG. 6A is an active matrix area (display screen) 60. The liquid crystal material is CF (color filter)
It is sandwiched between the substrate 62 and the TFT substrate 64. Area 6
An analog switch TFT and its wiring are arranged at 6. The data driver 70 is mounted using the TAB tape 68. The same applies to the data driver 72 and the scan driver 74. On the circuit board 76, wirings for supplying signals to the data drivers 70 and 72 and the scanning driver 74, capacitors, and the like are provided. In some cases, a control circuit for controlling the data driver and the scan driver is also provided.

The first characteristic of this embodiment is that half the analog switch TFTs are arranged on the upper side and the lower side of the active matrix area 60, and the comb-shaped wiring as shown in FIG. , The CF substrate 62 and the TFT substrate 64 are mounted on the same side of the liquid crystal panel.

For comparison, FIG. 6B shows a mounting example in the case where comb-shaped wiring is performed in a liquid crystal device having no analog switch TFT. When comb-shaped wiring is performed in such a liquid crystal device, the data driver 70 is provided above and below the active matrix area (display screen) 60.
And 72 need to be mounted, which increases the outer dimension L4 of the liquid crystal device.

Further, in this comparative example, since the analog switch TFT divided into n blocks is not provided,
The number of data drivers cannot be reduced, and a plurality of data drivers are mounted on the upper and lower sides of the liquid crystal panel. Therefore, the wiring of the circuit board becomes very complicated. In addition, the data driver usually operates at a very high frequency, so noise (electromagnetic radiation) from this data driver
However, it leaks to the outside of the liquid crystal device and adversely affects the display characteristics of the liquid crystal device. Further, in the configuration of FIG. 6B in which a plurality of data drivers are mounted above and below the liquid crystal panel, the area occupied by the data driver, which is a noise source, becomes large, so this noise is effectively shielded.
It is not easy to take measures against MI.

On the other hand, in the configuration of this embodiment shown in FIG. 6A, the data driver and the scan driver are mounted on the same side, and the data driver is not mounted above and below the liquid crystal panel. It is possible to provide a liquid crystal device that is smaller than L4 and is optimal for portable electronic devices and the like. Further, since the number of data drivers is small and the data driver is formed on the same side as the scan driver, the wiring of the circuit board can be greatly simplified. Furthermore, since the area occupied by the data driver, which is a noise source, is small, it is easy to shield the noise from the data driver and take EMI countermeasures, and it is possible to effectively prevent the adverse effects of noise from leaking to the outside.

The second feature of this embodiment is that a data driver 70, a scan driver 74, and a data driver 72 are mounted in this order from the upper side on the left side of the liquid crystal panel, for example, and the upper analog switch TFT and the data driver 70 are connected. That is, the wiring pattern to be connected and the wiring pattern for connecting the lower analog switch TFT and the data driver 74 are formed vertically symmetrically. Taking FIG. 4 as an example, the wiring pattern shown by P and the wiring pattern shown by Q are vertically symmetrical. Therefore, when the layout pattern is created, the upper wiring pattern P may be first created, and this may be vertically symmetrically converted to form the lower wiring pattern Q, which facilitates the creation of the layout pattern. See also FIG.
The wiring pattern of the circuit board 76 of (B) is also vertically symmetrical, which facilitates the design. Further, by forming the wiring patterns P and Q symmetrically in the vertical direction, the wiring resistance from the upper data driver to the upper analog switch TFT and the wiring resistance from the lower data driver to the lower analog switch TFT are the same. You can As a result, the driving conditions of the pixel electrodes connected to the upper and lower analog switch TFTs can be made the same, and the display characteristics can be improved. Further, the upper and lower data drivers having the same circuit configuration can be used, which facilitates the design. Further, in the present embodiment, by using the comb-teeth wiring, signal line inversion (source line inversion) drive, dot inversion drive, etc. can be easily performed, and the display characteristics can be further improved.

As described above, in this embodiment, various peculiar effects are obtained by providing the analog switch TFT, using the comb-teeth wiring, and devising the mounting position of the data driver. Note that in FIG. 6A, one data driver is mounted above and below the left side, but two or more data drivers may be mounted above and below the left side.

(Third Embodiment) FIG. 7 shows the configuration of the third embodiment. In the third embodiment, unlike the first embodiment, the analog switch TFT is divided into n blocks, with m blocks that are not adjacent to each other as one block.
1, 20-21 to 20-m1) is the first block, (20-1
2, 20-22 to 20-m2) is the second block ... (2
0-1n, 20-2n to 20-mn) becomes the n-th block. The gate electrodes of the analog switch TFTs (20-11, 20-21 to 20-m1) included in the same block and not adjacent to each other are commonly connected by the first wiring 22-1. Similarly, analog switch TFT (20-12, 20-22 to 20-m
2) ... (20-1n, 20-2n to 20-mn) gate electrodes are commonly connected by the second wirings 22-2 ... 22-n. Further, the source regions of adjacent analog switch TFTs (20-11, 20-12 to 20-1n) included in different blocks are commonly connected by the second wiring 24-1. Similarly, analog switch TFT (20-21, 20-22 to 20-2n)
The source regions of (20-m1, 20-m2 to 20-mn) are commonly connected to the second wirings 24-2 ... 24-m.
With this configuration, the number of data drivers and the number of terminals can be reduced, and the device can be made compact and the cost can be reduced.

The first feature of this embodiment is that the first embodiment
2, the amplitude of the input signal supplied to the source region of the analog switch TFT via the second wirings 24-1 to 24-m is set to 5 V or less. As a result, the shift amount of the threshold voltage of the analog switch TFT can be reduced, and reliability can be secured and display quality can be improved.

The second feature of this embodiment is that the pixel TFT is
The analog switch TFT and the analog switch TFT are formed of polycrystalline silicon and are integrally formed on a glass substrate.
As a result, the external dimensions of the liquid crystal device can be reduced, and the cost of the device can be reduced. The manufacturing method and device configuration in this case are as already shown in FIG.

The third feature of this embodiment is that the wiring resistance from each output terminal of the data driver to the source region of the analog switch TFT is made substantially constant. This makes it possible to minimize the deterioration of the display characteristics due to the presence of the analog switch TFT. Note that FIG. 8 shows an example of the layout pattern of this embodiment.

The fourth characteristic of the present embodiment is that, as shown in FIG. 8, half of the analog switch TFTs are arranged on the upper side and the lower side of the active matrix area 10 to form comb-shaped wiring. By using the comb-like wiring, the operating frequency of the data driver can be halved, and the signal line inversion drive and the dot inversion drive can be easily realized. Further, in the present embodiment, even if the comb-teeth wiring is used, the number of data drivers can be reduced and the area occupied by the data drivers that are noise sources can be reduced. As a result, noise from the data driver can be shielded and EMI countermeasures can be easily taken, and the adverse effects of noise can be effectively prevented from leaking to the outside. Further, it becomes easy to design the circuit board on which the wiring to the data driver is formed.

The configuration of the third embodiment has the following advantages over the first embodiment. In the first embodiment, one block is composed of m adjacent analog switch TFTs. When data is written to the signal line corresponding to the first block, the first switch 22-1 is used to simultaneously turn on the analog switch TFTs (20-11, 20-12 to 20-1m). Write. When writing to the second block, analog switch TFTs (20-21, 20-22 to 20-20
-2m) are turned on at the same time to write data. For this reason,
Stripes may occur at the boundary R (see FIG. 1) of the areas of the active matrix area corresponding to the first and second blocks. Further, since the driving conditions are different between the area of the active matrix area corresponding to the block closer to the data driver and that of the block farther from the data driver, crosstalk in the horizontal direction may occur. On the other hand, in the third embodiment, since one block is composed of m analog switch TFTs that are not adjacent to each other, the above-mentioned problem does not occur.

Example 4 In Example 4, as shown in FIG. 9, an active matrix area 82 in which pixel TFTs are arranged, an analog switch TFT section 84, a scan driver circuit 86, and a polycrystalline silicon TFT. This is an example in which the glass substrate 80 and the glass substrate 80 are integrally formed. Here, in the analog switch TFT section 84, as shown in FIG.
As shown in FIG. 5, the analog switch TFT is connected to M (n × m) signal lines and is divided into n blocks with m blocks as one block. The manufacturing method and device structure in the case of integrally forming are as already described with reference to FIG. Since the polycrystalline silicon TFT has high mobility, it is most suitable for forming an analog switch TFT. Polycrystalline silicon TF having a low on-resistance required for analog switch TFT
If T is used, the scan driver circuit can be easily formed.
In this embodiment, focusing on this point, the analog switch TF
The T portion 84 and the scan driver circuit 86 are integrally formed. By forming the scan driver circuit on the glass substrate 80, it is possible to reduce the outer dimensions of the liquid crystal device and reduce the cost.

Particularly in the present embodiment, the scan driver circuit 86
Is preferably formed by a dynamic or static shift register composed of a TFT having the same polarity as the pixel TFT and the analog switch TFT. For example, when the pixel TFT and the analog switch TFT are N-channel, they are formed by a shift register composed of only N-channel TFTs, and when they are P-channel, they are formed by a shift register composed of only P-channel TFTs. By using only TFTs having the same polarity as described above, the manufacturing process can be simplified, the circuit scale can be reduced, and the cost can be reduced. Note that the N-channel TFT is excellent in high mobility, and the P-channel TFT is excellent in stable device characteristics.

FIG. 10A shows an example of the structure of a rheosis type dynamic shift register, and FIG. 10B shows a timing chart thereof. CLK1 and CLK2 are non-overlapping clocks and also serve as a substitute for the positive power supply. As shown in FIG. 10B, the input data DIN is captured and held at CLK1 = H level. Next, when CLK2 = H level, the held data is transferred to the node P and held. And then CLK1 = H
When the level is reached, the data held in the node P is output to the node Q. The data shift operation is performed as described above. The feature of this shift register is that the power source is G
There is no need for a positive power supply because only ND is required.

FIG. 11A shows another example of the rheosis type dynamic shift register, and FIG. 11B shows a timing chart thereof. When CLK1 = H level, the input data DIN is taken in and held at the node A. Next, when CLK2 = H level, the held data is transferred to the nodes B and C and held in the node C. Then, when CLK1 = H level next, the held data is transferred to the nodes D and E. The data shift operation is performed as described above. The features of this shift register are:
Unlike FIG. 10A, a positive power supply is necessary, but the number of capacitors can be reduced.

The dynamic shift register described above has the advantages that the circuit structure is simple and the circuit area can be reduced.

FIG. 12A shows a configuration example of a two-phase static shift register with bootstrapped load, and FIG. 12B shows a timing chart thereof. The input data DIN is read at CLK1 = H level and statically held in the nodes P and Q. Next, when CLK2 = H, the held data is output to the node R. The data shift operation is performed as described above. Although this shift register has a complicated circuit configuration, it has an advantage of being resistant to noise because it can hold data statically.

According to the shift register having the above structure, all the TFTs can be formed by N-channels. Therefore, when the N-channel analog switch TFTs and the pixel TFTs are integrally formed on the substrate, the manufacturing process can be simplified. The circuit scale can be reduced.

(Fifth Embodiment) FIG. 13A shows an example of the structure of the fifth embodiment, and FIG. 13B shows a sectional view taken along the CD plane.
The seal portion 90 for enclosing the liquid crystal material is the CF substrate 98.
And the TFT substrate 100. The liquid crystal material is sealed by the sealing port 102, and the sealing port 102 is the sealing material 1.
It is sealed by 04. Data driver 106, 10
8. The scan driver 110 is provided on the same side of the liquid crystal panel as in FIG. 6A, and the circuit board 112 is provided with wiring, capacitors and the like.

In this embodiment, the seal portion 90 has a double structure and the first enclosed area 9 in which the liquid crystal material is enclosed.
2 and a second enclosed area 94 which is separated from the first enclosed area 92 and in which a gas such as dry air is enclosed. The first feature of this embodiment is that the analog switch TF is used.
The point is that T or the analog switch TFT and its wiring are formed in the second enclosed area 94. By doing so, as shown in FIG. 13B, the analog switch TFT 102 and its wiring can be sealed with a gas such as dry air. As a result, the analog switch TF
T, the moisture resistance in the wiring region can be improved. The degree of corrosion due to moisture depends on the electric field strength.
As described above, there are many areas where a large amount of current flows and the electric field strength is high. Therefore, enclose the analog switch TFT with gas,
If the moisture resistance is improved, the reliability can be improved and the shift amount of the threshold voltage can be further reduced. Further, by encapsulating the analog switch TFT with gas, the circuit can be protected without using an insulating film. Then, as compared with the case where an insulating film having a high dielectric constant and a liquid crystal material are present above the analog switch TFT, the capacitance parasitic on the wiring can be reduced. This can improve the display characteristics.

The second feature of this embodiment is that, as shown in FIG. 13A, an active matrix area (display screen).
Second enclosing areas 94 are provided on the upper side and the lower side of 96, an enclosing port 102 of the liquid crystal material is provided on the right side (or the left side), and half the analog switch TFTs are provided in the second enclosing areas 94 on the upper side and the lower side. It is at the point where it is placed. By doing so, comb-teeth wiring is possible, and dot inversion drive and the like are easily realized. And the active matrix area 96
On the right side, the second enclosed area 94 also includes the data driver 10.
6, 108 and the scan driver 110 are not provided, the liquid crystal material can be sealed from the right side. In addition, in the present embodiment, the second enclosed area may be provided at least above and below the active matrix area 96, and for example, the enclosed area indicated by E in FIG. 13A is not necessarily required. However, if the second enclosed area is provided in the portion indicated by E, the parasitic capacitance in the wiring region as shown by D in FIG. 4 can be reduced, and the display characteristics can be expected to be improved.

Encapsulation of gas in the second encapsulation area 94 is realized as follows, for example. First, the seal portion 90 is printed on the substrate, the CF substrate 98 and the TFT substrate 100 are attached to each other, and a vacuum atmosphere is created. At this time, for example, in FIG.
A small sealing port is formed in the portion indicated by F in (A). Next, when the liquid crystal material is placed near the filling port 102 and returned to the atmosphere, the liquid crystal material is allowed to flow through the filling port 102 to the first position.
Flows into the enclosed area 92. At this time, gas flows into the second enclosed area 94 via the enclosed port formed in F or the like. If the atmospheric state when the vacuum state is released is set to the dry air state, the dry air flows into the second enclosed area 94. After that, the sealing port 102 is filled with the sealing material 10.
4, and the sealing port of the F portion is also sealed with a given sealing material. As a result, liquid crystal material can be enclosed in the first enclosed area 92, and dry air or the like can be enclosed in the second enclosed area 94.

As another method for protecting the analog switch TFT and improving the moisture resistance, as shown in FIG. 14, the analog switch TFT 102 or the analog switch TFT and its wiring are insulated with a dielectric constant lower than that of the liquid crystal material. A method of covering with the film 114 is possible. By covering with the insulating film 114, it is possible to prevent the wiring and the like that form the analog switch TFT 102 from being corroded and improve the reliability. In addition, by using an insulating film having a low dielectric constant, parasitic capacitance can be reduced and display characteristics can be improved.

In order to further reduce the parasitic capacitance,
It is desirable to cover not only the analog switch TFTs but also the signal lines formed in the active matrix area 96 with an insulating film having a dielectric constant lower than that of the liquid crystal material. Since the liquid crystal material 104 having a high dielectric constant exists on the signal line, the capacitance parasitic on the signal line becomes extremely large. By covering the signal line with an insulating film having a low dielectric constant, this problem can be solved, the charge / discharge current flowing through the analog switch TFT can be reduced, and the display characteristics and reliability can be improved.

Example 6 Example 6 is an example relating to a method of driving a liquid crystal device. As described in Embodiments 1 and 3, in order to make the shift amount of the threshold voltage of the analog switch TFT appropriate, the analog switch TFT
It is desirable to set the amplitude of the input signal supplied to the source region of 5 V or less. However, in this case, the following problems occur when the normal driving method is used.

FIG. 15 shows an example of drive waveforms when field inversion drive is performed. Since the liquid crystal needs to be driven by an alternating current, it is necessary to invert the polarity of the signal Vs applied to the signal line for each given period centered on a given potential Vc. Therefore, the amplitude of Vs becomes extremely wide as shown in FIG. Since it is necessary to apply a voltage of about ± 5 to a normal TN liquid crystal, the VS amplitude is also required to be about 10V. The potential Vcom applied to the counter electrode is the pixel TFT.
In order to compensate the punch-through voltage that occurs when is turned off, the potential is set to a potential lower than the central potential Vc of Vs by ΔV. Here, the relationship of the average value of ΔV = Vc−Vcom is established.

Thus, in the drive waveform shown in FIG. 15, V
It is necessary to widen the amplitude of s to about 10V. Therefore,
The amplitude of the input signal of the analog switch TFT also needs to be wide, and the amplitude of the input signal cannot be 5 V or less. Therefore, in this embodiment, as shown in FIG. 16, the polarity of the potential applied to the counter electrode with respect to the input signal is inverted every horizontal scanning period (hereinafter referred to as 1H common swing drive). In FIG. 15, the polarity of Vs is inverted for each field centering on Vc, but in 1H common swing drive, the polarity of Vcom is inverted for each horizontal scanning period, so it is necessary to invert the polarity of Vs. There is no. Therefore, the amplitude of Vs can be reduced. As a result, the input signal of the analog switch TFT can be set to 5 V or less while maintaining the display quality. Further, the data driver can be made to have a low operating voltage and can be formed by a manufacturing process having a withstand voltage of 5 V, so that the data driver can be downsized, the power consumption can be reduced, and the cost can be reduced. As described above, according to the 1H common swing drive, it is possible to improve the reliability of the analog switch TFT and reduce the operating voltage of the data driver.
Note that, in FIG. 16, in order to prevent the adverse effect due to the punch-through voltage, the relationship of the average value of ΔV = the average value of Vs−the average value of Vcom is established.

Next, another driving method of this embodiment will be described with reference to FIG. In FIG. 17, in order to set the input signal of the analog switch TFT to 5 V or less, 4-value gate drive for each scanning line (hereinafter referred to as 1H 4-value gate drive) is used. In the 1H four-value gate drive, as shown in FIG. 17, the signals Vgate1 and Vgate2 supplied to the scanning line have a selection potential, a non-selection potential, a first potential lower than the non-selection potential, and a potential higher than the non-selection potential. It has a second potential. Then, the case where the selection potential becomes the non-selection potential after the first potential is maintained for a certain period and the case where the selection potential becomes the non-selection potential after the second potential is maintained for the certain period are alternately switched for each scanning line. . Here, unlike FIG. 16, Vcom
The electric potential of is constant without switching. Further, in this 1H 4-value gate drive, a storage capacitor is formed between the pixel electrode and the preceding scanning line. As shown in FIG. 17, the selection period T
After one, for example, as T2, a potential different from the non-selection potential is applied to the scanning line for two horizontal scanning periods. After T2, the potential of the storage capacitor is increased by V1 on the scanning line of Vgate1, while the potential of the storage capacitor is decreased by V2 on the scanning line of Vgate2. As a result, the same effect as when the polarity of Vcom is inverted can be obtained. Therefore, it is not necessary to reverse the polarity of Vs, the amplitude of Vs can be reduced, and the input signal of the analog switch TFT can be set to 5 V or less. As a result, improved reliability,
The operating voltage of the data driver can be lowered.

The 1H common swing drive has an advantage that it can be easily realized because only the potential applied to the counter electrode needs to be changed. Further, in the 1H common swing drive, since the polarity of the potential of the counter electrode has to be inverted, there is a problem that power consumption increases. On the other hand, according to the 1H 4-value gate electrode driving, the electric potential of the counter electrode is constant, so that power consumption can be reduced. However, there is a problem that the scan driver circuit that controls the potential applied to the scan line becomes complicated.

Next, still another driving method of this embodiment will be described with reference to FIGS. 18 (A) and 18 (B). With this driving method,
As shown in FIGS. 4 and 8, half of the analog switch TFTs are arranged on the upper side and the lower side of the active matrix area, and the signal lines are comb-teeth wiring. Then, the amplitude of the input signal of the analog switch TFT is set to 5 V or less, and signal line inversion (source line inversion) driving is performed to invert the polarity of the potential applied to the adjacent signal line with respect to the counter electrode potential. For example, as shown in FIG. 18B, the range of the output signal of the upper analog switch TFT is set to the first
The field is 5V to 10V, and the second field is 0 to 5V. On the other hand, the lower analog switch TFT
The output signal range is set to 0V to 5V in the first field and 5 to 10V in the second field. Also Vco
m is a DC voltage of 5V. By doing this, 1
Within the field period, the amplitude of the output signal of the analog switch TFT is 5V or less, and the amplitude of the input signal is 5V.
You can: When the first field is switched to the second field, the output signal range of the upper analog switch TFT is switched from 5-10V to 0-5V and Vc
The polarity is inverted around om. On the other hand, the output signal range of the lower analog switch TFT is also switched from 0 to 5V to 5 to 10V, and the polarity is inverted around Vcom. Therefore, the DC voltage applied to the liquid crystal can be set to 0V. That is, according to this driving method, the amplitude of the input signal of the analog switch TFT can be set to 5 V or less, the shift amount of the threshold voltage can be optimized, and the DC voltage can be prevented from being applied to the liquid crystal.

Various driving methods for improving display quality will be described below.

In this embodiment, as shown in P of FIG.
In the horizontal blanking period, a period for turning off all the analog switch TFTs is provided. In FIG. 19, G1 to Gn are block selection signals, which are signals given to the first wirings 22-1 to 22-n in FIGS. For example, if the counter electrode Vcom is reversed in polarity during the off period indicated by P (1H common swing drive), low power consumption can be achieved. That is, when the analog switch TFT is turned off, the signal line and the like are in a floating state. Therefore, by reversing the polarity of Vcom at this time, it is possible to eliminate the charge / discharge current in the parasitic capacitance formed by the signal line and the counter electrode. Further, in the case of 1H 4-value gate driving, power consumption can be reduced by changing the potential applied to the scanning line during the off period indicated by P. Further, in this method, the analog switch TFT is turned off and the signal line is in the floating state during the horizontal blanking period, so that there is no problem that the display characteristic is deteriorated due to the floating state of the signal line. Further, by providing the off period of the analog switch TFT, it is possible to prevent noise or the like generated in the data driver from being transmitted to the signal line during this period.

Further, in this embodiment, as shown in Q and R of FIG. 20, all analog switch TFTs are turned on after inverting the polarity of Vcom, and a reset period for applying a given reset potential to the signal line is set. It is provided. Thus, by providing the reset period before the data writing period and setting the potential of the signal line to a given reset potential, the problem that the previously written data remains in the signal line or the like and crosstalk occurs can be solved. . Further, in FIG. 20, the signal line is set to the reset potential after the polarity of Vcom is inverted. Therefore, the potential of the signal line can be precharged to the standard reset potential before data writing, and the subsequent data writing becomes easy.

Further, in this embodiment, as shown in FIG.
The line memory is used to sort the data of the video signal. That is, in the liquid crystal device having the configuration shown in FIG. 7, for example, when the first wiring 22-1 is selected, the analog switch TFTs (20-11, 20-21 to 20-m1) which are not adjacent to each other are connected to the signal line. On the other hand, the second wirings 24-1, 24-2 ...
Data is written simultaneously via 24-m. At this time,
Since the signal lines to which data is written are not adjacent to each other, the data of the video signal cannot be written as it is. In view of this, in this embodiment, as shown in FIG. 21, data rearrangement processing is performed using a line memory, and the rearranged processing signals are output to the second wiring and m non-adjacent analog switch TFTs. Writing to the signal line via. By doing so, appropriate data can be written in the signal line even with the configuration shown in FIG. 7. According to the configuration of FIG. 7, as compared with the configuration of FIG. 1, stripes do not occur at the boundaries between blocks, and driving conditions can be made substantially the same between blocks near and far from the data driver, and display characteristics can be improved. Can be improved.

(Embodiment 7) Embodiment 7 is an embodiment relating to the compensation of the punch-through voltage of the analog switch TFT.
FIG. 22A shows an equivalent circuit of the analog switch TFT. The punch-through voltage ΔV generated at the moment when the analog switch TFT is turned off can be expressed by the following equation. ΔV = ΔVg × Cgd / (Cgd + CO) (1) where ΔVg is the selection signal V of the analog switch TFT
It is the amount of voltage change of g. Cgd is the gate-drain capacitance of the analog switch TFT.

Gate-drain capacitance Cgd of TFT
22 is the sum of the overlapping capacitance Cgd0 and the channel capacitance Cgdc of the inversion layer 120, as shown in FIG. The overlap capacitance Cgd0 has no gate bias dependence, but the channel capacitance Cgdc has gate bias dependence. That is, as shown in FIG. 22C, the channel capacitance Cgdc increases when the gate-drain voltage Vgd exceeds the threshold voltage Vth.

On the other hand, the drive timing chart of the analog switch TFT is shown in FIG. Here, the input signal Vin to the analog switch TFT is + V
Consider the case of 1 (case 1) and the case of + V2 (case 2). At the moment when the analog switch TFT turns off,
In either case, the punch-through voltage according to the above equation (1) is generated, but since the gate bias is different between case 1 and case 2, the apparent gate-drain capacitance Cg
d is different. That is, as shown in FIG. 22C, since the case 1 uses more gate bias in the range in which the channel capacitance Cgdc of the inversion layer 120 contributes than the case 2, the case 1 has an apparent Cgd. The value of increases. Therefore, as is clear from the above equation (1), as shown in FIG.
The relationship of ΔVa> ΔVb (2) is established between ΔVa and ΔVb shown in 2 (D). That is, the value of the punch-through voltage changes depending on the magnitude of the input signal Vin of the analog switch TFT, which causes the following problem.

In FIG. 23A, P is the output characteristic of the analog switch TFT when there is no punch-through voltage, and Q is the actual output characteristic of the analog switch TFT. Originally, a positive / negative symmetrical signal of ± V1 to ± V2 should be applied to the liquid crystal, but a positive / negative asymmetrical signal of ± V1 ′ to ± V2 ′ is output when a punch-through voltage is generated. For this reason, a DC voltage is applied to the liquid crystal, and problems such as afterimage and image sticking occur. Moreover, since the punch-through voltage has a different magnitude depending on the bias condition as shown in the above equation (2), the voltage applied to the liquid crystal is also different between the white level and the black level. That is, the gradation display is different from the original one.

Therefore, in this embodiment, the analog switch T
An input signal corrected to compensate for a punch-through voltage that varies depending on the magnitude of the potential of the input signal supplied to the source region of the FT is supplied to the source region of the analog switch transistor. For example, in FIG. 23B, R is an input signal of the analog switch TFT that has been corrected,
S is the output characteristic of the analog switch TFT in that case. In this way, by using the input signal in which the punch-through voltage of the analog switch TFT is corrected in advance, the signal voltage-shifted by the punch-through voltage can be made a positive / negative symmetrical signal of ± V1 to ± V2. As a result, it is possible to avoid the problem of afterimage and image sticking, and it is possible to display an appropriate gradation.

Various correction methods for compensating the penetration voltage can be considered. For example, the penetration voltage or the like is actually measured in an actual liquid crystal device. Then, when the measured punch-through voltages are ΔVa and ΔVb, FIG.
A lookup table for performing conversion as shown by R is provided, and the input signal of the analog switch TFT is converted by this lookup table. More specifically, a digital video signal or an analog video signal A / D converted is corrected using the lookup table. Then, the corrected signal may be D / A converted and input to the analog switch TFT.

(Embodiment 8) This embodiment relates to a display system incorporating a liquid crystal device provided with an analog switch TFT. In FIG. 24, analog R, G, and B video signals generated from an analog video signal generator 130 such as a computer are A / D converters 13.
At 2, it is converted into a digital signal. When a video device or the like is used as a signal source, it is converted into analog R, G, B video signals and then input to the A / D converter 132. Of course, when the signal source generates a digital video signal, this A / D converter 132 is unnecessary. Next, data rearrangement processing is performed using the line memory 134. That is, in the liquid crystal device having the configuration shown in FIG. 7, since it is necessary to write data to signal lines that are not adjacent to each other at the same time, the data rearrangement process described above with reference to FIG. 21 is required. By performing the rearrangement processing, it is possible to write a plurality of data at the same time, and it is possible to reduce the data transfer frequency. In this case, the data transfer frequency conversion processing is performed by the frequency conversion circuit 136. The frequency-converted signal is input to the data driver 138 having a D / A converter. By lowering the data transfer frequency, the data driver 138 can also be operated at low speed, and the cost of the data driver 138 can be reduced and the circuit scale can be reduced. The output of the data driver 138 is input to the analog switch TFT section 140, whereby data is written in the signal line.

As shown in FIGS. 4 and 8, when half the analog switch TFTs are arranged on the upper side and the lower side of the active matrix area and the signal lines are comb-shaped wiring, the frequency conversion circuit 136 is used for data conversion. Double the transfer frequency. Then, the frequency-converted signal is supplied to the first and second data drivers connected to the upper and lower analog switch TFTs. As a result, the operating frequencies of the first and second data drivers can be halved,
The cost of the data driver can be reduced. The comb-teeth wiring enables signal line inversion drive and dot inversion drive. Further, by mounting the data driver as shown in FIG. 6A, the display system can be downsized, noise can be effectively removed, and the circuit board can be easily designed.

The present invention is not limited to those described in the first to eighth embodiments, and various modifications equivalent to these are possible. For example, as the layout configuration of the liquid crystal device according to the present invention, those shown in FIGS. 4 and 8 are particularly preferable, but various arrangements of analog switch TFTs, wiring methods and the like can be adopted. The liquid crystal device according to the present invention is preferably mounted as shown in FIG. 6A. However, the arrangement position, the number, the mounting method, the analog switch T of the data driver and the scan driver are preferable.
With respect to the arrangement position of the FT, various modifications different from this are possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration example of a liquid crystal device according to a first embodiment.

FIG. 2 is a diagram showing a relationship between a shift amount of a threshold voltage and an operation time.

FIG. 3 is a diagram for explaining a method of integrally forming a pixel TFT and an analog switch TFT on a glass substrate.

FIG. 4 is a diagram showing an example of a layout pattern according to the first embodiment.

5A and 5B are diagrams for explaining a method of equalizing wiring resistance.

FIG. 6 (A) is a diagram showing a configuration example of the second embodiment, and FIG. 6 (B) is a diagram showing a comparative example.

FIG. 7 is a diagram showing a configuration example of a liquid crystal device of Example 3.

FIG. 8 is a diagram showing an example of a layout pattern of Example 3;

FIG. 9 is a diagram showing a configuration example of a liquid crystal device of Example 4.

10A and 10B are diagrams illustrating a circuit configuration example and a timing chart of a dynamic shift register.

11A and 11B are diagrams showing a circuit configuration example and a timing chart of a dynamic shift register.

12A and 12B are diagrams illustrating a circuit configuration example and a timing chart of a static shift register.

13A is a diagram showing a configuration example of a liquid crystal device of Example 5, and FIG. 13B is a sectional view thereof.

FIG. 14 is a diagram showing another example of the fifth embodiment.

FIG. 15 is a diagram showing drive waveforms in field inversion drive.

FIG. 16 is a diagram showing a drive waveform of 1H common swing inversion drive according to the sixth embodiment.

FIG. 17 is a diagram showing a drive waveform of 1H four-value gate drive according to the sixth embodiment.

18A and 18B are diagrams for explaining a method of performing signal line inversion driving with a comb-shaped wiring.

FIG. 19 is a diagram for explaining a method of providing an off period of the analog switch TFT.

FIG. 20 is a diagram for explaining a method of providing a reset period of the analog switch TFT.

FIG. 21 is a diagram for explaining a data rearrangement process using a line memory.

FIG. 22 (A), (B), (C), (D)
FIG. 6 is a diagram for explaining a punch-through voltage.

23A and 23B are diagrams for explaining a punch-through voltage correction method according to the seventh embodiment.

FIG. 24 is a diagram illustrating an example of a display system according to an eighth embodiment.

[Explanation of symbols]

8 pixel TFT, 10 active matrix area (display screen), 20-11 to 20-nm analog switch T
FT, 22-1 to 22-n First wiring 24-1 to 24-m
Second wiring, 30 glass substrate, 32 base insulating film, 34 polycrystalline silicon film, 36 gate insulating film,
38 gate electrode, 40 interlayer insulating film, 42 metal thin film, 44 transparent conductive film, 60 active matrix area, 62 CF substrate, 64 TFT substrate, 6
8 TAB tape, 70, 72 data driver,
74 scan driver, 76 circuit board, 80 glass substrate, 82 active matrix area, 84 analog switch TFT section, 86 scan driver circuit,
90 seal part, 92 first enclosed area, 94
Second enclosing area, 96 active matrix area, 98 CF substrate, 100 TFT substrate, 102
Sealing port, 104 sealing material, 106, 108 data driver, 110 scanning driver, 112 circuit board, 114 insulating film, 130 video signal generator,
132 A / D converter, 134 line memory,
136 frequency conversion circuit, 138 D / A built-in data driver, 140 analog TFT section

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 622 G09G 3/20 622C 622R 623 623C 623W 624 624D 641 641P 650 650J 3/36 3/36 F Terms (reference) 2H093 NA16 NA32 NA43 NB13 NB14 NB15 NB22 NC09 NC12 NC13 NC18 NC22 NC24 NC28 NC34 ND01 ND06 ND09 ND12 ND15 ND38 ND40 ND42 ND48 ND49 ND60 NE03 5C006 AC24 AC25 AC26 AF42 AF46 BC16 BC02 BC16 BC02 AF06 AF73 AF83 AF83 AF03 AF83 AF02 BF37 FA22 FA31 FA42 FA43 FA46 FA48 5C080 AA10 BB05 DD05 DD19 DD22 DD23 DD26 DD28 EE29 FF01 FF11 GG09 JJ02 JJ03 JJ04 JJ06

Claims (9)

[Claims] 1. A pixel transistor formed of a thin film transistor and arranged in a matrix of N rows × M columns, N scanning lines connected to a gate electrode of the pixel transistor, and the pixel intersecting the scanning line and the pixel. M (= m × n) signal lines connected to the source region of the transistor and M signal lines that are formed of thin film transistors and are connected to the M signal lines, and are divided into n blocks with m blocks as one block. A driving method used in a liquid crystal device including a plurality of analog switch transistors, wherein an amplitude of an input signal supplied to a source region of the analog switch transistor is set to 5 V or less, and a counter electrode of a pixel electrode to which the pixel transistor is connected. When the potential to be applied to the counter electrode is the counter electrode potential, the polarity of the counter electrode potential with respect to the input signal is 1 horizontal scan Driving method characterized by reversing between every. 2. The driving method according to claim 1, wherein a period for turning off the analog switch transistor is provided in a horizontal blanking period. 3. A horizontal blanking period according to claim 1, wherein the analog switch transistor is turned on after inverting the polarity of the potential applied to the counter electrode to apply a given potential to the signal line. A driving method characterized by providing a period. 4. A pixel transistor formed of a thin film transistor and arranged in a matrix of N rows × M columns, N scanning lines connected to a gate electrode of the pixel transistor, and the pixel intersecting the scanning line and the pixel. M (= m × n) signal lines connected to the source region of the transistor and M signal lines that are formed by thin film transistors and are connected to the M signal lines, and are divided into n blocks with m blocks as one block. A driving method used for a liquid crystal device including a plurality of analog switch transistors, wherein an amplitude of an input signal supplied to a source region of the analog switch transistor is set to 5 V or less, and a selection potential and a non-selection potential are applied to a signal given to a scanning line. , A first potential having a lower potential than the non-selection potential and a second potential having a higher potential than the non-selection potential, and a selection potential. It is characterized in that switching is performed for each scanning line between a case where a non-selection potential is obtained after the first potential is maintained for a certain period and a case where a non-selection potential is obtained after maintaining the second potential from the selection potential for a certain period. Driving method. 5. The driving method according to claim 4, wherein a period during which the analog switch transistor is turned off is provided in the horizontal blanking period. 6. The horizontal switching circuit according to claim 4, wherein in the horizontal blanking period, the analog switch transistor is turned on after changing to the first potential or the second potential. The driving method is characterized in that a period for giving is provided. 7. A pixel transistor formed of a thin film transistor and arranged in a matrix of N rows × M columns, N scanning lines connected to a gate electrode of the pixel transistor, and the pixel intersecting the scanning line and the pixel. M (= m × n) signal lines connected to the source region of the transistor and M signal lines that are formed by thin film transistors and are connected to the M signal lines, and are divided into n blocks with m blocks as one block. A driving method used for a liquid crystal device including a plurality of analog switch transistors, wherein half of the analog transistors are arranged above and below the active matrix area in which the pixel transistors are arranged, and the upper side of the active matrix area is arranged. And an analog switch transistor (2L-1 The second signal line is connected to the analog switch transistor arranged on the other side, and the amplitude of the input signal supplied to the source region of the analog switch transistor is set to 5 V or less, and the pixel transistor is connected to the pixel switch. When the potential applied to the counter electrode of the pixel electrode connected to is the counter electrode potential, the polarity of the potential applied to the adjacent signal line with respect to the counter electrode potential is inverted. 8. A pixel transistor formed of a thin film transistor and arranged in a matrix of N rows × M columns, N scanning lines connected to a gate electrode of the pixel transistor, and the pixel intersecting the scanning line and the pixel. M (= m × n) signal lines connected to the source region of the transistor and M signal lines that are formed by thin film transistors and are connected to the M signal lines, and are divided into n blocks with m blocks as one block. A driving method used in a liquid crystal device including individual analog switch transistors, wherein an input signal corrected to compensate for a punch-through voltage that changes depending on the magnitude of the potential of the input signal supplied to the source region of the analog switch transistor is A driving method comprising supplying to a source region of the analog switch transistor. 9. A pixel transistor formed of a thin film transistor and arranged in a matrix of N rows × M columns, N scanning lines connected to a gate electrode of the pixel transistor, and the pixel intersecting the scanning line and the pixel. Half the number of signal lines connected to the source region of the transistor, and half of the number of signal lines formed of thin film transistors and connected to the M number of signal lines above and below the active matrix area in which the pixel transistors are arranged. M analog switch transistors and a first analog switch transistor connected to the upper analog switch transistor
Second data driver and second analog switch transistor connected to the bottom
Data driver and processing means for performing processing for lowering the data transfer frequency of the signal given to the first and second data drivers, and are arranged on either the upper side or the lower side of the active matrix area. The (2L-1) th signal line is connected to the analog switch transistor, the 2Lth signal line is connected to the other analog switch transistor, and the processing means reduces the data transfer frequency to 1 /
Display system characterized by doubling.