JPH08320465A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To simplify a circuit design, to reduce a circuit scale and a parts cost and to improve reliability by constituting a scan electrode drive circuit of a capacity coupling drive system with only a scan electrode drive IC. CONSTITUTION: A controller and a liquid crystal drive power source 11 output a voltage driving the scan electrode drive IC 13 and a signal electrode drive IC 12, a control signal and a data signal, and apply a bias voltage deciding an operation point of a liquid crystal to a common electrode, and the scan electrode drive IC 13 outputs successively the drive voltage to scan electrodes X0 -C2n , and the signal electrode drive IC 12 outputs successively a signal voltage to signal electrodes Y1 -Y2n to drive a liquid crystal panel 14 and to display an image. In such a manner, since the scan electrode exclusive drive circuit of an initial stage or a final stage required usually is eliminated, the design of the scan electrode drive circuit is simplified, and a printed circuit board is reduced, and the designs of the controller and the liquid crystal drive power source circuit are simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device useful as a display for video equipment such as televisions and information equipment such as computers.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional liquid crystal display device. In FIG. 6, X _{0 to} X _2n are scan electrodes and Y _{1 to} Y _2m.
Is a signal electrode, 61 is a controller and liquid crystal drive power supply,
62 the signal electrode driving IC, 63 scanning electrodes X ₀ only drive IC, 64 for driving only the scanning electrodes X ₀ scan electrodes X ₁ to X _n, except the scanning electrodes X _0, drives the X _n + 1 ~X _2n The scan electrode drive IC 65 is a liquid crystal panel.

The number of electrodes of the liquid crystal panel 65 is the signal electrode Y.₁
~ Y_2m2m, scanning electrode X₀~ X _2nIs 2n + 1
It The equivalent circuit of the liquid crystal panel 65 is shown in FIG.
Is the same as. In FIG. 2, 23 is a common electrode and 24 is
TFT, 25 is auxiliary capacity, 26 is liquid crystal, 27 is TFT2
The gate 4 and the drain 28 of the TFT 24. this
The signal electrode driving circuit of the conventional liquid crystal display device uses two signals.
The scan electrode drive circuit is composed of an electrode drive IC 62.
Scan electrode X₀Dedicated drive IC 63 and two scan electrode drive I
It is composed of C64.

FIG. 7 is a block diagram of the scan electrode driving IC 64 of FIG. In FIG. 7, 71 is a liquid crystal drive voltage input terminal, 72 is an input terminal for data signals, control signals and logic signals, 73 is a drive voltage output circuit, 74 is a decoder, 75 is a shift register, 76 is a control circuit, and 77 is an input. A circuit, 78 is a drive voltage output terminal. The number of drive voltage output terminals 78 of this scan electrode drive IC 64 is n.

FIG. 8 is a diagram showing the drive waveforms and timings of the scanning electrodes of the liquid crystal panel 65 of FIG. In FIG.
Reference numeral 81 is a clock of the scan electrode driving IC 64, 82 is a first data signal of the scan electrode driving IC 64, 83 is a second data signal of the scan electrode driving IC 64, 84 is an output of the scan electrode X ₀ dedicated drive IC 63, and 85 is a scan. The output of the electrode drive IC 64 is shown. Further, 86 is a TFT (TFT2 shown in FIG.
4) ON drive voltage level, 87 is a first auxiliary capacitance drive voltage level, 88 is a TFT (TFT 24 shown in FIG. 2) OFF drive voltage level, and 89 is a second auxiliary capacitance drive voltage level. Note that 1V is one vertical scanning period.

The operation of this conventional liquid crystal driving device is explained.
Reveal The controller and the liquid crystal drive power supply 61 scan
Electrode drive circuit (scan electrode X₀Dedicated drive IC 63 and scanning
Drive the electrode drive IC 64) and the signal electrode drive IC 62
Output voltage, control signal, and data signal.
Vias that determine the operating point of the liquid crystal on the through electrodes 23 (see FIG. 2)
Scan voltage is applied, and the scan electrode drive circuit scans the scan electrode X. ₁~ X
_2nTo the signal electrode drive IC 62.
No. electrode Y₁~ Y_2mLCD panel that outputs signal voltage sequentially
65 is driven to display an image.

Here, in FIG. 2, each TFT 24 is
Is connected to the signal electrode, and the gate 27 is connected to the scan electrode.
The drain 28 is connected to one electrode of the liquid crystal 26 (pixel
Electrode), for example, the signal electrode Y_mSeo
Connected to the scanning electrode X _{n + 1}Gate 27 is connected to
The drain 24 of the TFT 24 that has been
X_nAnd the auxiliary capacitor 25. This is the content
It is called quantity combination. The signal electrode Y_mSource connected to
Scan electrode X_{n + 1}TFT2 with gate 27 connected to
The drain 28 of the No. 4 is the scanning electrode X of the latter stage_{n + 2}And auxiliary capacity
If they are coupled with each other, it is referred to as capacitive coupling in the subsequent stage. Figure
2 shows the case of capacitive coupling in the previous stage. Such capacitive coupling
Scanning electrode drive of liquid crystal panel
Let it be an expression.

In driving the scan electrodes of the liquid crystal panel 65 having the TFTs capacitively coupled as described above, as shown in FIG. 8, the TFT ON drive voltage level 86 is applied to the scan electrodes X _{n + 1.}
Within the same scanning timing that outputs the
The first or second auxiliary capacitance drive voltage level 87 or 89 is output to _n , a constant voltage is applied to the liquid crystal 26 via the auxiliary capacitance 25, and the signal voltage applied from the signal electrodes Y _{1 to} Y _2m As a result, an appropriate voltage is applied to the liquid crystal 26 and an image is displayed. That is, in the capacitive coupling driving method of the liquid crystal panel shown in FIG. 2, when the scanning electrodes are scanned to display an image, the scanning electrodes in the preceding stage are driven within the same scanning timing, and the liquid crystal is appropriately supplied to the liquid crystal via the auxiliary capacitance. This is a method of driving so that an image voltage is applied.

Therefore, the capacitive coupling driving method requires a scanning electrode composed of an auxiliary capacitance that does not contribute to image display. That is, the capacitive coupling in the preceding stage requires the scan electrode X _{0 in the} first stage shown in FIG. 2, and the capacitive coupling in the subsequent stage requires the scan electrode in the final stage. It is the scan electrode X ₀ dedicated drive IC 63 shown in FIG. 6 that drives the first-stage scan electrode X _{0 including the} auxiliary capacitance shown in FIG. Further, in the case of capacitive coupling in the latter stage, a final stage scan electrode dedicated drive IC is required.

[0010]

SUMMARY OF THE INVENTION In the above conventional configuration,
In order to drive the liquid crystal panel 65 to display an image, in addition to the scan electrode drive IC 64 and the signal electrode drive IC 62,
A drive circuit dedicated to driving one scan electrode in the first stage or the last stage (in FIG. 6, the drive electrode 6 dedicated to the scan electrode X ₀ is used).
3) is required, the scan electrode drive circuit and the controller are complicated, and there are problems that the circuit design is complicated, the circuit scale is increased, and the parts cost is increased.

An object of the present invention is to provide a liquid crystal display device capable of simplifying the circuit design, reducing the circuit scale, and reducing the component cost.

[0012]

According to a first aspect of the present invention, a liquid crystal display device has a plurality of signal electrodes and a plurality of scanning electrodes arranged in a matrix, and the plurality of signal electrodes and one of the first stage or the last stage. A liquid crystal panel in which a TFT whose drain is connected to a pixel is arranged at each intersection with a plurality of scanning electrodes except the liquid crystal panel in which the drain of the TFT and the scanning electrode in the previous stage or the subsequent stage are capacitively coupled, and a signal electrode drive circuit which drives the signal electrode A liquid crystal display device comprising a scan electrode drive circuit for driving the scan electrodes, wherein the scan electrode drive circuit comprises only a scan electrode drive IC for driving all scan electrodes.

A liquid crystal display device according to a second aspect is the first aspect.
In the liquid crystal display device described above, the scan electrode driving IC is T
A shift register for sequentially selecting the scan electrodes connected to the gates of the FT is built in so that the output to the scan electrodes of the first stage or the last stage not connected to the gates of the TFTs can be made independent of the shift operation of the shift register. It is characterized by having done.

[0014]

According to the structure of the present invention, the scan electrode drive circuit is composed only of the scan electrode drive ICs for driving all the scan electrodes, and the drive circuit dedicated to the scan electrode of the first stage or the last stage, which has been conventionally required, is provided. It is unnecessary, and the circuit design can be simplified, the circuit scale can be reduced, and the component cost can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.
Reveal FIG. 1 shows the structure of a liquid crystal display device according to an embodiment of the present invention.
It is a diagram. In FIG. 1, X ₀~ X_2nIs the scan electrode, Y
₁~ Y_2mIs a signal electrode, 11 is a controller and a liquid crystal drive
Power source, 12 is signal electrode drive IC, 13 is scan electrode drive
ICs and 14 are liquid crystal panels.

The number of electrodes of the liquid crystal panel 14 is the signal electrode Y.₁
~ Y_2m2m, scanning electrode X₀~ X _2nIs 2n + 1
It An equivalent circuit of the liquid crystal panel 14 is shown in FIG.
, 23 is a common electrode, 24 is a TFT, and 25 is an auxiliary
Capacitance, 26 is liquid crystal, 27 is the gate of TFT 24, 28 is
It is the drain of the TFT 24. FIG. 3 shows the scanning electrode drive of FIG.
It is a block diagram of the dynamic IC13. In FIG. 3, 31 is
LCD drive voltage input terminal, 32 is data signal, control signal
And a logic signal input terminal, 33 is a drive voltage output circuit
, 34 is a decoder, 35 is a shift register, and 36 is a control.
Control circuit, 37 is an input circuit, and 38 is a drive voltage output terminal.
It The drive voltage output terminal 38 of the scan electrode drive IC 13
Is n + 2. The drive voltage output circuit 33 is a
The liquid crystal drive voltage input terminal 31
It is a circuit that selects and outputs the voltage applied to the. Decor
Is the control circuit 36 or the shift register 35?
These signals are decoded, and a predetermined value is output from the drive voltage output circuit 33.
It is a circuit for outputting the drive voltage of. Shift register 3
5, the drive voltage output circuit 33 has a drive voltage output terminal 38
From "1" to "n" or from "n" to "1"
Control signal to the decoder 34 so that it is driven corresponding to
It is a circuit to give. From the input circuit 37, the control circuit 36
Right shift, left shift or shift depending on the logic signal of
Control of the shift register 35 such as shift stop and drive power
A circuit for controlling ON / OFF of the pressure output circuit 33.
It The input circuit 37 includes a data signal, a control signal, and a logic.
Upon receiving an input signal such as a signal, the shift register 35 and the control register
It is a circuit that sends necessary signals to the control circuit 36.
A circuit for outputting the data output of the register 35 to the outside.
It

FIG. 4 is a diagram showing the drive waveforms and timings of the scan electrodes in this embodiment. In FIG. 4, 41
Is a clock of the scan electrode driving IC 13, 42 is a first data signal of the scan electrode driving IC 13, 43 is a scan electrode driving I
The second data signal of C13, 44 is the scan electrode driving IC 1
3 output is shown. Further, 45 is a TFT (TFT2 of FIG. 2
4) ON drive voltage level, 46 is the first auxiliary capacity drive voltage level, 47 is the TFT (TFT 24 in FIG. 2) OFF drive voltage level, and 48 is the second auxiliary capacity drive voltage level. Note that 1V is one vertical scanning period.

The features of the liquid crystal drive device of this embodiment will be described. Here, the scan electrode drive circuit eliminates the drive circuit dedicated to the scan electrode of the first stage or the final stage (for example, the drive IC 63 dedicated to the scan electrode X _{0 in} FIG. 6) which is conventionally required,
It is composed of two scan electrode driving ICs 13, and these two scan electrode driving ICs 13 drive all the scan electrodes X _{0 to} X _2n by the capacitive coupling driving method. In addition to the configuration of the conventional scan electrode drive IC (see FIG. 7), the scan electrode drive IC 13 has “0” and “n + 1” as shown in FIG. 3 so as to drive the scan electrode at the first stage or the last stage. Drive voltage output terminal 38
The configuration includes a drive voltage output circuit 33 and a decoder 34 corresponding to.

This embodiment is a case of capacitive coupling in the previous stage, and the scan electrode drive IC 13 connected to the scan electrodes X _{0 to} X _n has the drive voltage output terminal 38 of "0" in the first stage scan. is connected to the electrode X _0, the scanning electrode X ₀ is 4
The output 44 (X ₀ ) of the scan electrode driving IC shown in FIG. The output 44 (X ₀ ) of this scan electrode drive IC is
First and second data signals 42 and 43 of the scan electrode driving IC
In a controlled, the TFT on-drive voltage level 45 in the output period to the scanning electrodes X _1, and outputs a first or second storage capacitor driving voltage level 46 or 48 to the scanning electrodes X ₀ of the first stage. Incidentally, in the case of the liquid crystal panel of the capacitive coupling of the latter stage in which the scanning electrode X ₀ of the first stage is not provided and the scanning electrode X _{2n + 1} of the last stage is provided, it is connected to the scanning electrodes X _{n + 1 to} X _2n . "N + 1" drive voltage output terminal 38 of the other scan electrode drive IC 13
To connect the scanning electrodes X _{2n + 1} of the final stage, the voltage applied to the scanning electrodes X _{2n + 1} of the final stage is controlled by the first and second data signal of the scanning electrode driving IC, the scan electrode X _2n During the output period of the TFT-on drive voltage level 45, the first or second auxiliary capacitance drive voltage level 46 is applied to the scan electrode X _{2n + 1} at the final stage.
Or 48 will be output.

With the above structure, the controller and the liquid crystal drive power supply 11 output the voltage, the control signal and the data signal for driving the scan electrode drive IC 13 and the signal electrode drive IC 12, and thereby the liquid crystal to the common electrode 23 (FIG. 2). Applying a bias voltage that determines the operating point, scan electrode drive IC1
3 sequentially outputs drive voltages to the scan electrodes X _{0 to} X _2n , and the signal electrode drive IC 12 sequentially outputs signal voltages to the signal electrodes Y _{1 to} Y _2m to drive the liquid crystal panel 14 to display an image.

As described above, according to this embodiment, the drive circuit dedicated to the first-stage or last-stage scan electrodes (for example, the drive electrode 63 dedicated to scan electrode X _{0 in} FIG. 6) which is conventionally required is not required, and the scan electrodes are eliminated. The design of the drive circuit is simplified, the printed circuit board can be downsized, and the design of the controller and the liquid crystal drive power supply circuit is simplified. In this way, simplification of the circuit design, reduction of the circuit scale, reduction of component cost and improvement of reliability can be realized, and its practical effect is great.

The influence on the cost when the scan electrode drive IC 13 includes the drive voltage output circuit 33 and the decoder 34 corresponding to the drive voltage output terminals 38 of "0" and "n + 1" shown in FIG. Conventional scan electrode driving IC 64
The number of output terminals of (FIG. 6) is 100 or more, and the chip size is slightly larger than that of the conventional configuration.
I can ignore it.

Further, as shown in FIG. 5, the scan electrode driving IC may be arranged in the left-right direction opposite to that in FIG. FIG. 5 is a block diagram of a liquid crystal display device according to another embodiment of the present invention. In FIG. 5, reference numeral 51 denotes a controller and a liquid crystal drive power source, 52
Is a signal electrode driving IC, 53 is a scanning electrode driving IC, and 54 is a liquid crystal panel, and these constituent elements are equivalent to the constituent elements shown in FIG. In FIG. 5, the arrangement of the scan electrode drive IC 53 is the left and right opposite to that of the scan electrode drive IC 13 of FIG. 1, so the scan is reversed.

The data signals 42 and 43 shown in FIG. 4 are merely examples, and any data signal having an arbitrary waveform may be used as long as the output waveform is the waveform 44 of this embodiment. Further, the configuration shown in the embodiment of the present invention is an example, and may be a flat-panel display device in which scanning electrodes and signal electrodes that are capacitively coupled are formed in a matrix.

[0025]

According to the present invention, the capacitive coupling drive type scan electrode drive circuit is composed of only the scan electrode drive ICs, and the drive circuit dedicated to the scan electrode of the first stage or the final stage, which has been conventionally required, is unnecessary. The circuit design can be simplified, the circuit scale can be reduced, the component cost can be reduced, and the reliability can be improved, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a liquid crystal panel.

FIG. 3 is a scan electrode driving IC according to an embodiment of the present invention.
Block diagram of.

FIG. 4 is a diagram showing scan electrode drive waveforms and timing in one embodiment of the present invention.

FIG. 5 is a configuration diagram of a liquid crystal display device according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional liquid crystal display device.

FIG. 7 is a block diagram of a scan electrode driving IC in a conventional example.

FIG. 8 is a diagram showing scan electrode drive waveforms and timing in a conventional example.

[Explanation of symbols]

Y _{1 to} Y _2n signal electrode X _{0 to} X _2n scan electrode 11 controller and liquid crystal drive power supply 12 signal electrode drive IC 13 scan electrode drive IC 14 liquid crystal panel 23 common electrode 24 TFT 25 auxiliary capacitance 26 liquid crystal 27 gate 28 drain 31 drive voltage Input terminal 32 Data signal, control signal and logic signal input terminal 33 Drive voltage output circuit 34 Decoder 35 Shift register 36 Control circuit 37 Input circuit 38 Drive voltage output terminal 41 Scan electrode drive IC clock 42 Scan electrode drive IC first Data signal 43 Second data signal of scan electrode drive IC 44 Output of scan electrode drive IC 45 TFT on drive voltage level 46 First auxiliary capacitance drive voltage level 47 TFT off drive voltage level 48 Second auxiliary capacitance drive voltage level 51 Controller and LCD Drive power supply 52 Signal electrode drive IC 53 Scan electrode drive IC 54 Liquid crystal panel

Claims (2)

[Claims] 1. A plurality of signal electrodes and a plurality of scan electrodes are arranged in a matrix, and a drain is provided at each intersection of the plurality of signal electrodes and the plurality of scan electrodes except one at the first stage or the last stage. The TFT connected to the pixel is arranged, and the T
A liquid crystal display device comprising: a liquid crystal panel in which a drain of an FT is capacitively coupled to a scan electrode at a front stage or a rear stage; a signal electrode drive circuit for driving the signal electrode; and a scan electrode drive circuit for driving the scan electrode. The liquid crystal display device is characterized in that the scan electrode driving circuit includes only scan electrode driving ICs for driving all the scan electrodes. 2. The scan electrode driving IC has a built-in shift register for sequentially selecting the scan electrodes connected to the gates of the TFTs, and connects the scan electrodes to the first stage or the last stage scan electrodes not connected to the gates of the TFTs. 2. The liquid crystal display device according to claim 1, wherein the output is made independent of the shift operation of the shift register.