JP3271484B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device represented by an active matrix type liquid crystal panel and the like, and more particularly, to a liquid crystal display device having an improved vertical driving circuit grounding system.

[0002]

2. Description of the Related Art In recent years, with the spread of devices with a liquid crystal display device typified by a camera-integrated VTR and a liquid crystal projector, demands for higher performance of the liquid crystal display device have increased, and higher resolution and higher image quality of the liquid crystal display device have been demanded. Is progressing. For example,
High Definition (High Definition Television) and VGA (V
Liquid crystal display devices compatible with ideo Graphics Array) have also been developed. In a liquid crystal display device, a driving level and a driving frequency increase with an increase in resolution, and noise generated in the liquid crystal display device tends to increase. The present invention relates to the display quality of an image related to the high resolution and high image quality, and will be described below with reference to specific examples.

A prior art liquid crystal display device will be described with reference to FIG. FIG. 2 is a schematic plan view showing a conventional liquid crystal display device.

First, the configuration of a conventional liquid crystal display device will be described. Driving substrate 1 in conventional liquid crystal display device
Is generally constituted by a pixel array section 2 and a peripheral section 3 as shown in the figure. The pixel array section 2 includes a pixel electrode 4 and a thin film transistor (TFT: Thin Film Tra) for switching driving thereof.
nsistor) (hereinafter simply referred to as “TFT”). The peripheral portion 3 includes vertical drive circuits 6 and 6 ′ for operating the pixel array portion 2, a horizontal drive circuit 7, external connection pads 8, and the like. The horizontal drive circuit 7
Are connected to the signal lines X, and the vertical drive circuits 6, 6 'are connected to the gate bus lines Y, and extend to the pixel array section 2, respectively. The signal line X and the gate bus line Y are formed orthogonal to each other, and the pixel electrode 4 and the TFT 5 are formed in the orthogonal part.

[0005] The external connection pad 8 comprises a vertical drive circuit 6,
The video signals and various control signals input to the horizontal drive circuit 6 'and the vertical drive circuits 6 and 6' are connected.
Further, a power supply terminal and a ground terminal used for the horizontal drive circuit 7 are provided. As an example, the ground terminal 9 in the external connection pad 8 is connected to the ground terminals of the vertical drive circuits 6, 6 'and the horizontal drive circuit 7.

An opposing substrate (not shown) on which a black matrix and a color filter (in the case of a color liquid crystal panel) are formed is opposed to the driving substrate 1 while maintaining a predetermined interval (several μm). A liquid crystal composition is sandwiched. The periphery is sealed and fixed by a sealing material (not shown). A conventional liquid crystal display device is constructed by integrally laminating polarizing plates on both surfaces of these substrates.

Subsequently, the operation of the conventional liquid crystal display device will be briefly described. Video signals and various control signals input from an external IC (not shown) via the external connection pads 8 are input to the vertical drive circuits 6, 6 'and the horizontal drive circuit 7. In the TFT 5, in response to a selection pulse supplied from the gate bus line Y connected to the vertical drive circuits 6, 6 ', a video signal is taken into the pixel electrode 4 via the signal line X connected to the horizontal drive circuit 7. . The liquid crystal molecules (not shown) are twisted and inverted by the pixel electrode 4 in the direction of the applied voltage, and information is displayed on the liquid crystal display device of the prior art by utilizing the optical rotation caused by the liquid crystal molecules and the polarizing plate.

The ground line 10 of the prior art liquid crystal display device
In order to prevent the driving noise of the signal line X and the gate bus line Y from entering the pixel array unit 2 via the ground line 10, it is necessary to reduce the impedance as a thick wiring pattern. Note that there is a 1H inversion driving method as a method for driving a high-resolution liquid crystal display device. In this method, after a video signal is written to a selected scanning line, a predetermined control pulse is applied to the next selected scanning line. In some cases, a precharge method for facilitating the writing of a video signal by applying a voltage is used. In this case, a control pulse may be mixed into the non-selected scanning line or the gate bus line Y to cause a deterioration in image quality.

[0009]

However, in the above-described prior art liquid crystal display device, noise generated in the liquid crystal display device increases due to an increase in driving frequency accompanying an increase in resolution of the liquid crystal display device. There is a problem that the noise tends to be mixed into the pixel electrodes of the liquid crystal display device to degrade the display image quality. In particular, in the liquid crystal display device using the precharge method together, there is a problem that a control pulse is mixed into a non-selected scanning line or a gate bus line to cause deterioration of image quality.

The present invention has been made in view of the above points, and the effect of noise accompanying a higher resolution of a liquid crystal display device and noise in a liquid crystal display device using a precharge system is mixed into pixel electrodes. An object of the present invention is to provide a liquid crystal display device that avoids deterioration of display image quality.

[0011]

In order to solve the above-mentioned problems of the prior art, the following measures have been taken. That is, in the liquid crystal display device according to the present invention, in a liquid crystal display device in which a pixel array portion is integrally formed with a drive circuit portion having a drive transistor, a first ground line connected to the drive circuit portion; And a second ground line connected to the second ground line. The drive circuit section and the pixel array section are separated by the first ground line and the second ground line so that noise generated by the drive circuit section is not mixed into the pixel array section and noise generated by the pixel array section is reduced. It is configured not to be mixed in the drive circuit section.

The driving transistor is formed of a P-channel transistor and an N-channel transistor, and the source electrode of the N-channel transistor is connected to a second electrode.
The above problem was solved by connecting to a ground line.

[0013]

According to the liquid crystal display device of the present invention, the first ground line connected to the drive circuit section and the second ground line connected to the drive transistor are separated, and the noise of the noise source is supplied to the pixel array section. While avoiding mixing
The impedance of the second ground line is reduced to suppress noise generated in the pixel array unit, and to prevent the noise from being mixed into the drive circuit unit. Accordingly, the noise generated in the driving circuit unit does not enter the pixel array unit via the driving transistor of the driving circuit unit, the noise generated in the pixel array unit is suppressed, and the noise is not mixed in the driving circuit unit. A high quality liquid crystal driving device can be configured.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. The same parts as those of the liquid crystal display device of the prior art are denoted by the same reference numerals,
Some of those descriptions are omitted.

First, the configuration of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 1A is a schematic plan view showing a liquid crystal display device of the present invention, and FIG. 1B is a circuit diagram showing a vertical drive circuit partially enlarged.

Referring to FIG. 1A, the driving substrate 11 of the liquid crystal display device according to the present invention is generally constituted by the pixel array section 2 and the peripheral section 3 as described above. The pixel array unit 2 is an area for controlling an input video signal and displaying an image or the like, and has the above-described TFTs and pixel electrodes formed in a matrix. The peripheral portion 3 includes vertical drive circuits 6 and 6 ′ for operating the pixel array portion 2, a horizontal drive circuit 7, and an external connection pad 8.
And so on. The gate bus lines Y are connected to the vertical drive circuits 6, 6 'via the drive transistor sections 12, 12'. Driving transistor section 12, 1
2 'are connected in the pixel array unit 2 respectively.

The first ground terminal 13 of the external connection pad 8 is connected to the vertical drive circuit 6 via the first ground line 14.
6 'and the horizontal drive circuit 7, and a level conversion means 15 for adjusting the ground level of the first ground line 14 as necessary. As a feature of the present invention, the source electrodes of the driving transistors 12 and 12 ′ are connected to a newly provided second ground line 16, and the second ground line 16 is connected to the second ground terminal 17 of the external connection pad 8. Connected and configured.

In FIG. 1B, the driving transistor 1
Numerals 2 and 12 'are configured as a series connection of a P-channel transistor 20 and an N-channel transistor 21, and their intersection is connected to the gate bus line Y. One end of the P-channel transistor 20 is, for example, 1
The power supply terminal Vcc is connected to 5.5 V, and one end of the N-channel transistor 21 is connected to the second ground line 16 of the present invention. The gate electrodes of the P-channel transistor 20 and the N-channel transistor 21 are connected to each other and connected to the vertical drive circuits 6, 6 '.

A counter substrate (not shown) is disposed opposite to the drive substrate 11 with a predetermined space between them. The liquid crystal composition is sandwiched in these spaces, and the periphery thereof is sealed with a sealing material (not shown). Fixed. Furthermore, the liquid crystal display device of the present invention is constituted by integrally laminating polarizing plates on both sides of these substrates.

Subsequently, the operation of the liquid crystal display device of the present invention will be described. In FIG. 1A, a video signal and various control signals input from an external IC (not shown) via an external connection pad 8 are input to vertical driving circuits 6, 6 'and a horizontal driving circuit 7. In a TFT (not shown), in response to a selection pulse supplied from a gate bus line Y via drive transistors 12 and 12 'connected to vertical drive circuits 6 and 6', an image is transmitted from a horizontal drive circuit 7 via a signal line. Capture the signal. Thereafter, information display of the liquid crystal display device of the present invention is performed according to a conventional method. According to the liquid crystal driving device of the present invention, since the selection pulse is supplied to the vertical driving circuits 6, 6 'through the driving transistors 12, 12' having different ground lines, noise is mixed in the pixel array section 2. A stable image can be displayed without any trouble.

That is, the ground level of the drive transistors 12, 12 'supplied to the gate bus line Y is made of, for example, Al metal or the like so as to be in a low-impedance state, so that disturbance noise can be reduced. This is because it can be done. Accordingly, the vertical drive circuit 6,
It is not necessary to lower the impedance of the ground line 6 'and the horizontal drive circuit 7 as in the liquid crystal display device of the prior art, and a relatively thin wiring pattern is sufficient. Is born.

Further, the liquid crystal display device of the present invention is provided with level conversion means 15 , and the threshold level Vth of the level conversion means 15 is set to 1.5 to 2.5V. If the first ground line 14 and the second ground line 16 are the same, noise due to the precharge method rides on the ground line inside the level converting means 15, causing the level converting means 15 to malfunction. In the present invention, by separating the first ground line 14 and the second ground line 16, the malfunction of the level conversion means 15 is avoided.

In FIG. 1B, a P-channel transistor 20 and an N-channel transistor 21
While receiving power from the power supply terminal Vcc of the channel type transistor 20, it receives a selection pulse from the vertical drive circuits 6, 6 'and outputs its output to the gate bus line Y. The source electrode of the N-channel transistor 21 is
As shown in the figure, since it is connected to the second ground line 16, it is in a low impedance state to prevent the driving noise and the like from being mixed, and also prevent the noise generated in the pixel electrode from being mixed into the driving circuit by the precharge method or the like. be able to.

The present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example, in this embodiment, the vertical drive circuit is described as an example, but the present invention can be applied to a horizontal drive circuit. Needless to say, the present invention can be appropriately applied without departing from the gist of the present invention.

[0026]

As described above, according to the liquid crystal display device of the present invention, the ground line of the driving transistor is separately set to separate the vertical line from the vertical driving circuit, and the impedance of the ground line of the driving transistor is reduced. Was planned.
Therefore, noise due to an increase in the driving frequency due to an increase in the resolution of the liquid crystal display device is not mixed into the pixel electrode, and noise due to the precharge driving method is reduced from being mixed into the pixel electrode. It is possible to realize a liquid crystal driving device.

[Brief description of the drawings]

FIG. 1A is a schematic plan view showing a liquid crystal display device of the present invention, and FIG. 1B is a circuit diagram showing a vertical drive circuit partially enlarged.

FIG. 2 is a schematic plan view showing a conventional liquid crystal display device.

[Explanation of symbols]

 1, 11 drive substrate 2 pixel array section 3 peripheral section 4 pixel electrode 5 TFT 6, 6 'vertical drive circuit 7 horizontal drive circuit 8 external connection pad 9 ground terminal 12, 12' drive transistor 13 first ground terminal 14 first Ground line 15 Level conversion means 16 Second ground line 17 Second ground terminal 20 P-channel transistor 21 N-channel transistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 550 G09G 3/36

Claims (2)

(57) [Claims] 1. A liquid crystal display device in which a driving circuit portion having a driving transistor and a pixel array portion are integrally formed, a first ground line connected to the driving circuit portion, and a driving transistor connected to the driving transistor. A second ground line, wherein the first ground line and the second ground line separate the drive circuit unit and the pixel array unit, and noise generated in the drive circuit unit and the pixel array unit is mixed with each other A liquid crystal driving device characterized in that the driving is not performed. 2. The driving transistor according to claim 1, wherein the driving transistor is formed of a P-channel transistor and an N-channel transistor, and a source electrode of the N-channel transistor is connected to the second ground line. 3. The liquid crystal display device according to 1.