JP2011022587A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which is improved in reliability or expanded in the tolerance of design and a process by making a transistor high in breakdown voltage by devising a circuit. <P>SOLUTION: A single channel shift register is included. The single channel shift register includes n (n≥2) basic circuits which are connected in a multi-stage cascade. The basic circuit includes a first transistor in which a first electrode is connected to a power line to which a reference voltage of V1 is applied, and a second transistor in which a first electrode is connected to a second electrode of the first transistor, and a bias voltage of Vc is applied to a control electrode. When the first transistor is turned off, and a maximum voltage applied to a second electrode of the second transistor is V2, an expression of V1<Vc<V2 is satisfied. The control electrode of the basic circuit includes a transistor for setting which is connected to the second electrode of the second transistor, and a capacitor which is connected between the second electrode and the control electrode of the transistor for setting. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a technique effective when applied to an active matrix display device in which a display drive circuit is formed on a substrate surface thereof.

For example, an active matrix liquid crystal display device using a thin film transistor (TFT) as an active element extends in the x direction on the liquid crystal side surface of one of the substrates opposed to each other through the liquid crystal. The pixel region is surrounded by gate lines arranged in parallel in the y direction and drain lines extending in the y direction and arranged in parallel in the x direction.
The pixel region includes a thin film transistor (TFT) that operates by supplying a scanning signal from a gate line, and a pixel electrode to which a video signal from a drain line is supplied via the thin film transistor. Yes.
For example, an electric field is generated between the pixel electrode and the counter electrode formed on the other substrate side, and the light transmittance of the liquid crystal between the electrodes is controlled by the electric field.
The liquid crystal display device includes a scanning signal driving circuit that supplies a scanning signal to each of the gate lines and a video signal driving circuit that supplies a video signal to each of the drain lines. It has.

There is also known a polysilicon type liquid crystal display device in which the semiconductor layer of the thin film transistor constituting the active element is formed of polycrystalline silicon (polysilicon; p-Si).
In such a polysilicon type liquid crystal display device, the thin film transistor (for example, MIS transistor) constituting the scanning signal driving circuit and the video signal driving circuit is also formed in the same process as the thin film transistor constituting the active element in the above-mentioned one substrate. Formed on the surface.
Such a polysilicon type liquid crystal display device may require a high voltage for inversion driving of the liquid crystal.
Generally, a thin film transistor using polysilicon as a semiconductor layer forms a gate film by deposition, so that it is basically low in gate breakdown voltage and easily deteriorated with respect to a through current. It is unsuitable.
In the future, it is predicted that the recrystallization technique for producing polysilicon will be improved, but it is highly possible that high voltage processing becomes difficult as performance increases.
On the other hand, in the field of semiconductors, an LDD structure and a double gate structure are known as techniques for improving the breakdown voltage characteristics of transistors.

The LDD structure described above is intended to improve drain-source breakdown voltage (BVds) resistance such as a short channel effect by reducing the impurity concentration of the source / drain (so-called diffusion layer) around the gate.
However, the LDD structure is basically equivalent to adding a resistance to the gate end, and hinders high performance.
Further, the double gate structure can improve drain-source breakdown voltage (BVds) resistance such as a short channel effect, and can reduce leakage current.
However, although the double gate structure improves the BVds level, it may not be sufficient.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to increase the breakdown voltage of a transistor by a circuit in a display device, improve reliability, or design / process. The purpose is to provide a technology capable of expanding the margin.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
In order to achieve the above object, a display device of the present invention includes a plurality of pixels and a drive circuit that drives the plurality of pixels, and the drive circuit is connected to a power supply line to which a reference voltage of V1 is applied. The first transistor to which the first electrode is connected, the first electrode is connected to the second electrode of the first transistor, and a bias voltage of Vc is applied to the control electrode. V2 <Vc <V1 (or V1 <Vc) when the voltage applied to the second electrode of the second transistor is V2 when the first transistor is in the off state. <V2) is satisfied.
In one embodiment of the present invention, 0.9 × (V1−V2) /2≦Vc≦1.1× (V1−V2) / 2 (or 0.9 × (V2−V1) / 2 ≦ Vc. ≦ 1.1 × (V2−V1) / 2).

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the display device of the present invention, it is possible to increase the breakdown voltage of a transistor by using a circuit, thereby improving reliability or expanding design / process margin.

It is a circuit diagram showing a CMOS inverter to which the present invention is applied. FIG. 6 is a circuit diagram showing another example of a bias voltage application method in the CMOS inverter shown in FIG. 1. FIG. 6 is a circuit diagram showing another example of a bias voltage application method in the CMOS inverter shown in FIG. 1. It is a circuit diagram which shows the equivalent circuit of the active matrix type liquid crystal display device of the Example of this invention. It is a circuit diagram which shows the shift register applied to the active matrix type liquid crystal display device of the Example of this invention. 6 is a timing chart of the shift register shown in FIG. FIG. 6 is a circuit diagram illustrating a modification of the shift register illustrated in FIG. 5. It is a circuit diagram which shows the conventional CMOS inverter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
[Outline of the present invention]
FIG. 8 is a circuit diagram showing a conventional CMOS inverter.
As shown in FIG. 8, the conventional CMOS inverter has a p-type MOS transistor (hereinafter simply referred to as PMOS) (PM1) between a first power supply voltage (VDD) and a second power supply voltage (VSS). And an n-type MOS transistor (hereinafter simply referred to as NMOS) (NM1) are connected in series.
The gate of the PMOS (PM1) and the gate of the NMOS (NM1) are commonly connected to serve as a signal input terminal (VIN), and the connection between the drain of the PMOS (PM1) and the drain of the NMOS (NM1) The point is the signal output terminal (VOUT).
FIG. 1 is a circuit diagram showing a CMOS inverter to which the present invention is applied.
The CMOS inverter shown in FIG. 1 has a second PMOS (PM2) between the PMOS (PM1) and the output terminal (VOUT), and a second NMOS between the NMOS (NM1) and the output terminal (VOUT). It differs from the inverter shown in FIG. 8 in that (NM2) is connected.

Here, as shown in FIG. 1, a fixed bias voltage (VCBP) is applied to the gate of the PMOS (PM2), and a fixed bias voltage (VCBN) is applied to the gate of the NMOS (NM2). As shown, the same fixed bias voltage (VCB) is applied to the gate of the PMOS (PM2) and the gate of the NMOS (NM2).
The fixed bias voltages of these VCBP, VCBN, and VCB are lower than the first power supply voltage (VDD) and higher than the second power supply voltage (VSS) (that is, VSS <VCBP <VDD, VSS <VCBN <VDD, VSS <VCB <VDD) or a pulse described later.
In FIG. 2, a case is considered where VSS = 0V, VCB = VDD / 2, and VIN = VSS = 0V.
In the inverter shown in FIG. 8, since VIN = 0V, PMOS (PM1) is turned on and NMOS (NM1) is turned off, so that VOUT = VDD.
Therefore, a voltage of VDD-0 = VDD is applied between the source and the drain of the NMOS (NM1) and between the gate and the drain, and depending on the voltage of VDD, there is a high possibility that the transistor deteriorates.

On the other hand, in the inverter shown in FIG. 2, PMOS (PM1) and PMOS (PM2) are in an ON state, NMOS (NM1) and NMOS (NM2) are in an OFF state, and VOUT = VDD.
However, since the gate voltage of the NMOS (NM2) is VDD / 2, when the threshold voltage of the NMOS (NM2) is (Vth), the source voltage of the NMOS (NM2) (that is, the drain voltage of the NMOS (NM1)) is , VDD / 2−Vth.
Therefore, the source-drain voltage and the gate-drain voltage of the NMOS (NM1) are VDD / 2−Vth, which can have a high tolerance for the drain-source breakdown voltage (BVds).
Similarly, the source-drain voltage of the NMOS (NM2) is {VDD- (VDD / 2−Vth)} = VDD / 2 + Vth, and the gate-drain voltage is VDD−VDD / 2 = VDD / 2. For this reason, the operation has a higher drain voltage tolerance than the normal inverter configuration. As a result, even a transistor having the same voltage tolerance can be processed up to a higher voltage.

In FIG. 2, when VSS = 0V, VCB = VDD / 2, and VIN = VDD, in the inverter shown in FIG. 2, PMOS (PM1) and PMOS (PM2) are in an OFF state, NMOS (NM1) and NMOS (NM2). ) Is in an ON state, and VOUT = 0V.
Further, since the gate voltage of the PMOS (PM2) is VDD / 2, when the threshold voltage of the PMOS (PM2) is (Vth), the source voltage of the PMOS (PM2) (that is, the drain voltage of the PMOS (PM1)) is VDD / 2 + Vth.
Therefore, the source-drain and gate-drain voltages of the PMOS (PM1) are {VDD- (VDD / 2 + Vth)} = VDD / 2-Vth, and the source-drain voltage of the PMOS (PM2) is VDD / 2 + Vth, and the gate-drain voltage is (VDD / 2−0) = VDD / 2.
In this case, as shown in FIG. 1, the gate voltage of NMOS (NM2) and PMOS (PM2) can be set independently, so that a finer response can be achieved.
Further, as shown in FIG. 3, it is fixed in accordance with the high level (hereinafter simply referred to as H level) or the low level (hereinafter simply referred to as L level) of the signal input to the input terminal (VIN). By pulsing the bias voltage (VCB), both high breakdown voltage and high speed can be achieved.

For example, in FIGS. 2 and 3, when VIN = 0V and VOUT = VDD, since the NMOS (NM1) is in the OFF state, the bias voltage VCB of VSS <VCB <VDD is applied to the gate of the NMOS (NM2). The deterioration of the NMOS (NM1) can be prevented by applying.
However, when switching to VIN = VDD and VOUT = 0V, the NMOS (NM1) is turned on, and the VOUT is discharged from VDD to 0V. At this time, the gate of the NMOS (NM2) is as high as possible. Discharge is performed faster when voltage is applied.
Therefore, when the NMOS (NM1) is turned on, the speed can be increased by increasing the bias voltage VCB of the NMOS (NM2) than when the NMOS (NM1) is turned off.
The PMOS (PM1) and PMOS (PM2) may be reversed from those of the NMOS (NM1) and NMOS (NM2). That is, when the PMOS (PM1) is turned on, the speed can be increased by reducing the bias voltage VCB of the PMOS (PM2) than when the PMOS (PM1) is turned off.
Therefore, as shown in FIG. 3, the bias voltage (in FIG. 3) is synchronized with the change in the ON state and OFF state of the NMOS (NM1) and PMOS (PM1) (that is, the change in the level of the signal input to the input terminal (VIN)). VCB) is pulsed to change the size.
For example, VCB is changed by a combination of VDD / 3 and 2VDD / 3, or is changed by a combination of VDD / 4 and 3VDD / 4.
The numerical value such as VDD / 4 does not need to be a strict value and may be changed within a range of error of ± 10%. In the case of FIG. 1, it may be changed similarly.
For example, the bias voltage VCBP is set to VDD / 2 (or higher voltage) when the PMOS (PM1) is in the OFF state, and the bias voltage VCBP is lower than when the PMOS (PM1) is in the OFF state when the PMOS (PM1) is in the ON state. For example, it is changed to VDD / 3 or VDD / 4.
Similarly, the bias voltage VCBN is set to VDD / 2 (or a lower voltage) when the NMOS (NM1) is OFF, and the bias voltage VCBN is higher when the NMOS (NM1) is OFF than when the NMOS (NM1) is OFF. The voltage is changed to, for example, 2VDD / 3 or 3VDD / 4.
Note that the specific numerical values described here may also be changed within an error range of ± 10%.

[Outline of Active Matrix Type Liquid Crystal Display Device of the Present Invention]
FIG. 4 is a circuit diagram showing an equivalent circuit of the active matrix liquid crystal display device according to the embodiment of the present invention.
As shown in FIG. 4, the active matrix type liquid crystal display device of this embodiment is arranged in the y direction on the liquid crystal side surface of one of a pair of substrates disposed opposite to each other via liquid crystal. Gate lines (X1, X2,..., Xn) and m drain lines (Y1, Y2,..., Ym) provided side by side in the x direction and extending in the y direction.
A region surrounded by a gate line (also referred to as a scanning line) and a drain line (also referred to as a video line) is a pixel region. In one pixel region, a gate serves as a gate line and a drain (or source). Is provided on the drain line and the thin film transistor (Tnm) having the source (or drain) connected to the pixel electrode is provided. Further, a storage capacitor (Cnm) is provided between the pixel electrode and the common electrode (COM).
Each gate line (X1, X2,..., Xn) is connected to a scanning signal driving circuit (XDV), and the scanning signal driving circuit (XDV) sends a gate signal from X1 to the Xn gate line. Alternatively, Xn is sequentially supplied toward the gate line X1.

Each drain line (Y1, Y2, ..., Ym) is connected to the drain (or source) of the switch element (S1, S2, ..., Sm).
The sources (or drains) of the switch elements (S1, S2,..., Sm) are connected to the video signal line (DATA), and the gates are connected to the video signal drive circuit (YDV).
The video signal driving circuit (YDV) sequentially scans from S1 to Sm switch element or from Sm to S1 switch element.
In this embodiment, the thin film transistors of the scanning signal driving circuit (XDV) and the video signal driving circuit (YDV) are formed in the same process as the thin film transistors forming the active element, in which the semiconductor layer is formed of polycrystalline silicon (polysilicon). It is formed on one substrate surface.
Further, the scanning signal driving circuit (XDV) and the video signal driving circuit (YDV) have the CMOS circuits shown in FIGS.
In the above description, the case where the present invention is applied to a CMOS circuit has been described. However, the present invention can also be applied to a circuit including only NMOS or PMOS.
Hereinafter, an embodiment in which the present invention is applied to an NMOS single channel circuit shift register will be described.

FIG. 5 is a circuit diagram showing a single channel shift register applied to the active matrix type liquid crystal display device of the embodiment of the present invention.
The shift register shown in FIG. 5 includes n basic circuits connected in cascade.
Each basic circuit has a first NMOS (NMn1), and the shift output of the previous stage is applied to the gate of the NMOS (NMn1). For example, an input pulse (φIN) (also referred to as a start pulse) having an amplitude Vφ is applied to the gate of the first-stage NMOS (NM11). The first NMOS (NMn1) is a setting transistor (or drive transistor).
The source of the odd-numbered NMOS in the first NMOS (NMn1) is supplied to the first clock signal line to which the clock signal (φ1) is supplied, and the source of the even-numbered NMOS is supplied with the clock signal (φ2). Connected to the second clock signal line.
Here, the clock signal (φ1) and the clock signal (φ2) are opposite in phase to each other, and are signals having the same cycle and opposite phases. The amplitude of the clock signal (φ1, φ2) is Vφ.
The drain of the NMOS (NMn1) is connected to the external output terminal (OUTn) of each basic circuit. This is also the shift output of each stage. Furthermore, the second NMOS (NMn2) diode-connected is connected to the drain of the NMOS (NMn1), and the output of the NMOS (NMn2) is output to the next stage.

A capacitive element (Cbn) is connected between the drain and gate of the first NMOS (NMn1). This capacitive element (Cbn) functions as a bootstrap capacitor.
A third NMOS (NMn3) and a fourth NMOS (NMn4) are connected in series between the node (Nn) and the power supply line to which the VSS power supply voltage is supplied. A fixed bias voltage of VC is applied to the gate of the NMOS (NMn4). VSS is, for example, 0V.
The shift output of the subsequent stage is applied to the gate of the NMOS (NMn3) via a diode. Specifically, in the second and subsequent basic circuits, the shift output of each stage is transferred to the preceding stage NMOS (NMn6) via the diode-connected sixth NMOS (NMn6) connected to the drain of the NMOS (NMn1). Applied to the gate of NMn3). As a result, the NMOS (NMn3) functions as a reset transistor.
A fifth NMOS (NMn5) and a capacitor element (Cn) are connected between the gate of the NMOS (NMn3) and the power supply line to which the power supply voltage of VSS is supplied, and the gate of the NMOS (NMn5) is connected to the gate of the NMOS (NMn5). The drain voltage of the third NMOS (NMn3) in the previous stage is applied.
An input pulse (φIN) is applied to the gate of the first stage NMOS (NM15).

The operation of the shift register shown in FIG. 5 is described below with reference to the timing chart shown in FIG.
At time t1, when the clock (φ1) changes from H level to L level and the clock (φ2) changes from L level to H level, the input pulse (φIN) is L level between time t0 and time t1. Since the NMOS (NM15) is turned on and the voltage (VP1) of the node (P1) is at the L level, the NMOS (NM13) is turned off and the node (N1) is floating. It is in a state.
At the same time, the voltage (VN1) of the node (N1) becomes the H level (strictly, VN1 = Vφ−Vth) by the diode-connected NMOS (NM00).
If VN1 (= Vφ−Vth)> Vth (NMOS (NM11)) is set, NMOS (NM11) is also turned on.
Furthermore, when VN1 (= Vφ−Vth)> Vth (NMOS (NM25)) is set, the NMOS (NM25) is turned on, and the voltage (VP2) of the node (P2) becomes L level. Therefore, the NMOS (NM23) is turned off, and the node (N2) is in a floating state.
At this time, among the NMOSs (NMn1) to which the clock signals (φ1, φ2) are applied to the drains, only the gates of the NMOS (NM11) and the NMOS (NM21) are in a floating state.

At time t2, the clock (φ1) changes from L level to H level, and the clock (φ2) changes from H level to L level.
At this time, since the NMOS (NM11) is in the ON state, the voltage of the node (M1) rises, and the voltage (VM1) of the node (M1) becomes Vφ due to the bootstrap effect of the capacitor (Cb1).
At this time, the node (N1) is boosted and the voltage (VN1) rises to VN1 = (Vφ−Vth) + Vφ (Cb / (Cb + Cs)), but the input pulse (φIN) is at the H level and the NMOS ( Since the gate of NM13) is VSS (= GND), the NMOS (NM13) is forcibly maintained in the OFF state.
Cb is a capacitance (bootstrap capacitance) of the capacitive element (Cb1), and Cs is a value obtained by subtracting the bootstrap capacitance (Cb) from all the capacitances of the node (N1), and so-called parasitic capacitance. It is.
The voltage (VN2) of the node (N2) becomes VN2 = Vφ−Vth by the diode-connected NMOS (NM12).
As a result, the NMOS (NM21) to which the voltage VN2 is applied to the gate is turned on, and the NMOS (NM35) to which the voltage VN2 is applied to the gate is turned on, so that the voltage of the node (P3) ( Since (VP3) becomes L level, the NMOS (NM33) is turned off and the node (N3) is in a floating state.

At time t3, the clock (φ1) changes from the H level to the L level, and the clock (φ2) changes from the L level to the H level.
When the clock (φ1) changes from the H level to the L level, the voltage (VM1) of the node (M1) becomes the L level, but the node (N2) maintains the H level.
Further, when the clock (φ2) changes from the L level to the H level, the voltage (VM2) of the node (M2) becomes Vφ via the NMOS (NM21) in the ON state.
Accordingly, the voltage (VN3) of the node (N3) becomes VN3 = Vφ−Vth by the diode-connected NMOS (NM22), and the NMOS (NM31) to which the voltage of VN3 is applied to the gate is turned on. At the same time, the NMOS (NM45) to which the voltage of VN3 is applied to the gate is turned ON, and the voltage (VP4) of the node (P4) becomes L level, so that the NMOS (NM43) is turned OFF and the node (N4 ) Enters a floating state.
At the same time, the voltage (VP1) of the node (P1) becomes VP1 = Vφ−Vth due to the diode-connected NMOS (NM26), and this voltage VP1 turns on the NMOS (NM13) applied to the gate.
As a result, the voltage (VN1) of the node (N1) becomes the VSS voltage, so that the NMOS (NM11) is forcibly turned off.
Since the voltage (VP1) of the node (P1) is held by the capacitor (C1), the node (P1) is in the H state even if the voltage (VN2) of the node (N2) becomes L level thereafter. To maintain.
That is, since the VSS voltage is applied to the NMOS (NM11) gate again until the input pulse (φIN) becomes the H level again, the NMOS (NM11) maintains the OFF state. Note that the capacitance element (C1) can be replaced with a parasitic capacitance.

At time t4, the clock (φ1) changes from L level to H level, and the clock (φ2) changes from H level to L level.
When the clock (φ2) changes from the H level to the L level, the voltage (VM2) of the node (M2) becomes the L level, but the node (N3) maintains the H level.
When the clock (φ1) becomes the H level, the voltage (VM3) of the node (M3) becomes Vφ via the NMOS (NM31) in the ON state, and the node (M32) connected by the diode connection causes the node (M32). The voltage (VN4) of (N4) becomes VN4 = Vφ−Vth.
As a result, the NMOS (NM41) to which the voltage of VN4 is applied to the gate is turned on, and the NMOS (NM55) to which the voltage of VN4 is applied to the gate is turned on, so that the voltage of the node (P5) ( Since VP5) becomes L level, the NMOS (NM53) is turned off and the node (N5) is in a floating state.
At the same time, the voltage (VP2) of the node (P2) becomes VP2 = Vφ−Vth by the diode-connected NMOS (NM36), and the NMOS (NM23) applied to the gate of this voltage VP2 is turned on.
Accordingly, the voltage (VN2) of the node (N2) becomes the voltage of VSS, so that the NMOS (NM21) is forcibly turned off.
Since the voltage VP2 of the node (P2) is held by the capacitor (C2), the node (P2) remains in the H state even when the voltage (VN3) of the node (N3) becomes L level thereafter. To do.
That is, since the VSS voltage is applied to the NMOS (NM21) gate again until the node (N1) becomes H level again, the NMOS (NM21) maintains the OFF state.
Thereafter, the above-described operations are sequentially repeated to operate the shift register.

In this embodiment, in each basic circuit, a third NMOS (NMn3) and a fourth NMOS (NMn4) are connected in series between the node (Nn) and the power supply line to which the power supply voltage of VSS is supplied. Connected to.
A fixed bias voltage of VC is applied to the gate of the NMOS (NMn4).
Therefore, when there is no NMOS (NMn4), for example, at time t2, the clock (φ1) changes from the L level to the H level, and the voltage (VN1) of the node (N1) becomes VN1 = (Vφ−Vth). ) + Vφ (Cb / (Cb + Cs)), the drain voltage of the NMOS (NMn3) becomes Vφ or more, which is disadvantageous in terms of resistance to the drain-source breakdown voltage (BVds).
However, in this embodiment, an NMOS (NMn4) is provided, and a fixed bias voltage of VC is applied to the gate of the NMOS (NMn4). For the reason described in the above [Summary of the invention], for example, The drain voltage of the NMOS (NMn3) can be made lower than the bias voltage of VC (VC-Vth).
As a result, it is possible to improve the drain-source breakdown voltage (BVds) tolerance of the entire circuit. Similarly, with respect to the NMOS (NMn5), the drain-source breakdown voltage (BVds) tolerance can be improved.
When the maximum voltage generated at the node (Nn) is VN (max) {VN (max) = (Vφ−Vth) + Vφ (Cb / (Cb + Cs))}, the bias voltage of VC is VN (max) Is a voltage lower than the voltage of VSS and higher than the voltage of VSS {ie, VSS <VC <VN (max)}, for example, VC = Vφ.
Further, in consideration of an error of ± 10%, 0.9 × Vφ ≦ VC ≦ 1.1 × Vφ may be satisfied, and 0.9 × (VN (max) −VSS) /2≦VC≦1.1×. It may be (VN (max) −VSS) / 2.
Note that the bias voltage of VC is a pulse operation similar to the above-mentioned [Outline of the present invention], and it is possible to improve the operation more finely.

FIG. 7 is a circuit diagram showing a modification of the shift register shown in FIG.
The shift register shown in FIG. 7 is the same as the shift register shown in FIG. 5 except that the input pulse signal (φIN) is sent to the nodes (P2, P3) via diode-connected NMOSs (NM47, NM57, NM67, NM77,...). , P4, P5,...).
These NMOSs (NM47, NM57, NM67, NM77,...) Are connected to the floating nodes (P2, P3, P4, P5,...) When the input pulse signal (φIN) becomes H level. The H level can be reinforced, and the forced OFF state of the non-selected input gate can be made more reliable.
In addition, there is an effect that the same initialization as the normal operation state can be performed at the start of scanning immediately after the power is turned on.

The shift register described with reference to FIGS. 5 to 7 can be used as a shift register in the scanning signal drive circuit XDV of FIG. In this case, signals output to the external output terminals (OUT1 to OUTn) can be used as scanning signals applied to the gate lines (X1 to Xn).
Further, by setting the number of stages of the basic circuit to m, it can be used as a shift register in the video signal driving circuit YDV of FIG. In this case, signals output to the external output terminals (OUT1 to OUTm) can be used as signals (D1 to Dm) applied to the gates of the switch elements (S1 to Sm).
The number of stages of the basic circuit is not limited to n stages or m stages, and the number of stages may be further increased and the first or last one or more stages may be set as dummy.
In the above-described embodiment, the case where an n-type transistor is used as the thin film transistor that constitutes the shift register has been described. However, by using the H-level and L-level absolute potentials of each signal reversed, the shift register can be used. A p-type transistor can also be used as the thin film transistor to be formed.
In the embodiment described above, the gate insulating film is shown as a MOS transistor made of, for example, SiO 2 as the thin film transistor. However, the gate insulating film may be made of, for example, SiN. Needless to say.
Further, in the above-described embodiments, the shift register used in the liquid crystal display device has been described. However, the present invention is not limited to this, and the shift register used in other display devices such as an EL display device, for example. Needless to say, this also applies to registers.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

X1, X2, ..., Xn Gate lines (or scanning lines)
Y1, Y2, ..., Ym Drain line (or video line)
Tnm Thin film transistor Cnm Retention capacitance S1, S2, ..., Sm Switch element DATA Video signal line XDV Scan signal drive circuit YDV Video signal drive circuit COM Common electrode Cbn, Cn Capacitor element PMn P-type MOS transistor NMn, NMnm n-type MOS transistor Nn, Mn, Pn nodes

Claims (6)

A plurality of pixels;
A drive circuit for driving the plurality of pixels,
The drive circuit has a single channel shift register,
The single channel shift register has n (n ≧ 2) basic circuits cascaded in multiple stages,
The basic circuit includes: a first transistor having a first electrode connected to a power supply line to which a reference voltage of V1 is applied;
A first electrode connected to a second electrode of the first transistor, and a control electrode having a second transistor to which a bias voltage of Vc is applied;
When the maximum voltage applied to the second electrode of the second transistor is V2 when the first transistor is in an off state, V1 <Vc <V2 is satisfied,
The basic circuit includes a setting transistor in which a control electrode is connected to a second electrode of the second transistor;
A capacitive element connected between the second electrode and the control electrode of the setting transistor;
The shift output of each stage is output from the second electrode of the setting transistor,
The first electrode of the set transistor of the odd-numbered basic circuit is connected to a first clock signal line to which a first clock is applied,
The first electrode of the set transistor of the even-numbered basic circuit is connected to a second clock signal line to which a second clock is applied,
The first clock and the second clock have the same period and different phases,
A display device, wherein an input pulse or a previous shift output is applied via a diode to a connection point between a control electrode of the set transistor and a second electrode of the second transistor.   The display device according to claim 1, wherein 0.9 × (V2−V1) /2≦Vc≦1.1× (V2−V1) / 2.   The bias voltage of Vc applied to the control electrode of the second transistor takes a value of Vc1 when the first transistor is in an off state, and a value of Vc2 when the first transistor is in an on state. The display device according to claim 1, wherein V1 <Vc1 <Vc2 <V2 is satisfied.   4. The shift output of the basic circuit of the next stage is applied to the control electrode of the first transistor through a second diode. 5. Display device. A third transistor connected between a first electrode of the first transistor and a control electrode;
An input pulse or a voltage at a connection point between the second electrode of the first transistor and the first electrode of the second transistor is applied to the control electrode of the third transistor. The display device according to claim 4.   6. The device according to claim 1, wherein when the amplitude of the first clock and the second clock is Vφ, 0.9 × Vφ ≦ Vc ≦ 1.1 × Vφ. The display device described in 1.

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