JP2000206492A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dynamic image quality in a TV system using a liquid crystal display device. SOLUTION: In this liquid crystal display constituted of plural pixel electrodes arranged in matrix, switching elements connected to the pixel electrodes and scanning electrodes and signal electrodes connected to the switching elements, the means for inserting a non-display signal into a video signal inputted to the signal electrodes at a prescribed period is provided, and a display is made non-hold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device used as a display of a television receiver or the like.

[0002]

2. Description of the Related Art As a conventional liquid crystal display device, an active matrix type liquid crystal display device in which a switching element such as a thin film transistor (TFT) is disposed in each pixel by a twisted nematic (TN) type display method is generally used. As a display device with high contrast and multi-gradation,
It is widely used as a display for television receivers and video tape recorders.

FIG. 4 is a block diagram of such a conventional liquid crystal display device. As shown in FIG. 5, the liquid crystal display device 1 includes a display unit 3 in which a large number of pixel electrodes 2 are arranged in a matrix, and one terminal of a TFT 4 is connected to each pixel electrode 2. The other terminal of each TFT 4 is connected to the signal electrode 5, and the gate of the TFT 4 is connected to the scanning electrode 6. Each scanning electrode 6 is connected to a scanning circuit 7, and the signal electrode 5 is connected to a data signal circuit 8. The operations of these circuits 7 and 8 are controlled by a control circuit 9.

The scanning circuit 7 selects the scanning electrodes 6 in a line-sequential manner, and in synchronism therewith, a signal voltage corresponding to a desired display is applied to each signal electrode 5 from a data signal circuit 8 so as to correspond to one screen. The display ends. Such processing is, for example, 1/6
The image is displayed repeatedly every 0 or 1/30 seconds.

When such a liquid crystal display device 1 is used as a so-called liquid crystal television receiver, for example, an NTSC video signal is used as a display signal. In this case, the video signal is received by the antenna 10, a predetermined video signal is separated by a receiving circuit 11 including, for example, a detection circuit and an amplification circuit, and the analog / digital conversion circuit (hereinafter referred to as A / D converter) is used.
After being converted into a digital signal by a / D conversion circuit 12, various signal processing is performed by a signal processing circuit 13, and a digital / analog conversion circuit (hereinafter abbreviated as a D / A conversion circuit) 14 converts the analog signal into a digital signal. And supplied to the data signal circuit 8, and the reference signal Sy is supplied to the circuits 8, 9
And a predetermined display operation is performed.

[0006]

FIG. 6 is a timing chart showing a specific operation example. As an example, scanning signals G1 to G10 applied to ten scanning electrodes 6 and signal voltages corresponding thereto are shown. NTS mentioned above
In the C system, interlaced scanning is performed, and one frame is constituted by fields for scanning odd-numbered scanning electrodes and fields for scanning even-numbered scanning electrodes.
The polarity of the signal voltage is usually inverted for each frame, and the deterioration is prevented by canceling the DC component applied to the liquid crystal layer.

In order to prevent display flicker,
A method of converting interlaced scanning into non-interlaced scanning by image processing is also used. In this case, a method of complementing image data by applying a signal voltage of the previous field whose polarity has been inverted to a pixel electrode on a scanning electrode having no corresponding video signal in each field is used.

On the other hand, in recent years, the quality of moving images (moving image quality) has become a problem in the field of display devices. For example, see “IEICE Technical Report”, EID96-4 (1996), p. As described in No. 16, a continuous lighting type display device such as a conventional liquid crystal element (hold type display device) is in principle a moving picture compared to a pulse lighting type (impulse type display device) such as a CRT. Poor quality has been reported. As a method for improving moving image quality, for example, Japanese Patent Application Laid-Open No. 09-325
As described in 715, by controlling the lighting period of the backlight or the ON period of the display element,
A method of controlling the display period to a fixed period within one field has been proposed. However, in a television system such as the NTSC system, a technique for making such a non-hold has not been disclosed.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the quality of a moving image by holding a display in a television system using a liquid crystal display device.

[0010]

According to the present invention, there is provided a liquid crystal display device comprising: a plurality of pixel electrodes arranged in a matrix; a switching element connected to the pixel electrode; and a switching element connected to the switching element. A liquid crystal display device comprising a scanning electrode and a signal electrode, wherein a means for inserting a non-display signal at a predetermined period into a video signal input to the signal electrode is provided.

[0011]

According to the above arrangement, a non-display signal is inserted into the video signal input to the signal electrode at a predetermined cycle. A selection signal is applied to the scanning electrode. Since the signal applied to the signal electrode in synchronization with the selection signal is a non-display signal, a non-display state is written and display hold is prohibited there. That is, the display is prohibited from being held at the above-described predetermined cycle and is not held, so that the moving image quality is improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to one embodiment of the present invention. Although the basic configuration and functions are the same as those of the conventional example shown in FIG. 4, in this embodiment, a frame memory 15 is added.
As in the conventional example of FIG. 4, a video signal of the NTSC system is received by an antenna 10, a desired video signal is separated by a receiving circuit 11, converted into a digital signal by an A / D conversion circuit 12, and then processed by a signal processing circuit. Various signal processing is performed at 13,
The signal is converted into an analog signal by the D / A conversion circuit 14 and supplied to the data signal circuit 8, and the reference signal Sy is input to the circuits 8 and 9 to perform a predetermined display operation.
However, the A / D converted video data is temporarily stored in the frame memory 15. The signal processing circuit 13 fetches the video data from the frame memory 15 and, in each field, scan electrodes 6 not selected by interlace scanning.
As a non-display signal voltage is applied to the upper pixel electrode,
A process of inserting a non-display signal into each video data is performed. At this time, the control circuit 9 performs an operation of applying a scanning voltage to the selected scanning electrodes 6 and applying a selection voltage line-sequentially so that the non-display signal is also applied to the non-selected scanning electrodes.

FIG. 2 is a timing chart showing an example of such an operation. 6, scanning signals G1 to G10 applied to ten scanning electrodes 6 and signal voltages corresponding thereto are shown. In the first field, the odd-numbered scan electrodes G1, G3,..., G9 are selected, and the corresponding signal voltage is applied to the signal electrode 5. A non-display signal (in this case, a non-display signal (in this case, a state where the transmittance of each pixel is substantially lowest) is not displayed on the pixel electrodes on the scanning electrodes G2, G4,..., G10 not selected in this field. Is applied to the signal electrode 5. In the subsequent second field, the even-numbered scan electrodes are selected and the signal voltage is applied correspondingly, while the odd-numbered scan electrodes are not selected and the non-display signals are respectively correspondingly applied to the signal electrodes. Is applied to One frame for displaying one screen is constituted by these two fields. However, in this embodiment, since one field is set to 60 Hz, the selection time per one scanning electrode is １ ／ of the selection time in the conventional example shown in FIG. The same operation is performed in the next frame, but the polarity of the signal voltage is inverted, and an operation for preventing the deterioration of the liquid crystal layer is performed.

FIG. 3 is a timing chart of scanning signals and signal voltages according to the second embodiment of the present invention. FIG.
In this method, one field is written with a signal voltage of opposite polarity, and then the next field is set as a non-display period. Thereby, the flicker of the image is improved. By the above-described operation, each pixel enters a display state in one field and a non-display state in the other field in one frame, and as a result, non-hold display with a time aperture ratio of 50% is performed.

The liquid crystal used in the present invention needs to respond in one field. Therefore, the liquid crystal used is a ferroelectric liquid crystal, an antiferroelectric liquid crystal, or a nematic liquid crystal that responds at high speed. The same operation can be performed on a PAL video signal by performing a thinning operation, which is a known technique relating to the difference in the number of scanning lines. That is, the signal processing circuit 13 can display the video of the entire range of the display signal by decimating and outputting the video signal stored in the frame memory 15.

[0016]

As described above, according to the present invention,
In the liquid crystal display device, it is possible to display a television image with excellent moving image quality.

[Brief description of the drawings]

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

FIG. 2 is a timing chart for explaining the operation of the device of FIG.

FIG. 3 is a timing chart of a scanning signal and a signal voltage according to another embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a conventional liquid crystal display device.

5 is a circuit diagram showing a configuration of a display unit of the liquid crystal display device shown in FIG.

6 is a timing chart for explaining a television system using the liquid crystal display device shown in FIG.

[Explanation of symbols]

1: liquid crystal display device, 2: pixel electrode, 3: display portion, 4: T
FT, 5: signal electrode, 6: scanning electrode, 7: scanning circuit,
8: data signal circuit, 9: control circuit, 10: antenna,
11: receiving circuit, 12: analog / digital conversion circuit,
13: signal processing circuit, 14: digital / analog conversion circuit, 15: frame memory.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA11 NA16 NA33 NA43 NA53 NC21 NC24 NC29 NC34 ND10 NF19 NF20 5C006 AA01 AC24 AC26 AC29 AC30 BA12 BA13 BB16 5C080 AA10 BB05 DD01 DD07 EE19 EE29 EJ02 JJ02 JJ04 KK43

Claims (4)

[Claims] 1. A liquid crystal display device comprising a plurality of pixel electrodes arranged in a matrix, a switching element connected to the pixel electrode, and a scanning electrode and a signal electrode connected to the switching element. A liquid crystal display device comprising means for inserting a non-display signal at a predetermined period into a video signal input to the liquid crystal display device. 2. The method according to claim 1, wherein the video signal is NTSC or PA.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is an L-type video signal. 3. One frame is composed of two fields, and the scan electrodes are selected line-sequentially in each field, and in each field, a non-display signal is applied to at least every other pixel electrode on the scan electrodes. 3. The liquid crystal display device according to claim 1, wherein 4. The method according to claim 1, wherein the polarity of the signal voltage applied to the pixel electrode is inverted at a predetermined cycle.
Or the liquid crystal display device according to 3.