JPH0634938A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To drive an LCD with large display area with small power consumption by composing the output stage of a driving element of unidirectional transistors(TR) which output bias voltages having a selection potential and bidirectional TRs which output bias voltages having a nonselection potential. CONSTITUTION:The output stage of the driving element 2 which applies a specific bias voltage to a simple matrix type liquid crystal cell 1 which has orthogonal electrode groups consists of the unidirectional MOS TRs 21 and 22 which outputs the bias voltage with the selection potential and bidirectional MOS TRs 23 and 24 which output the bias voltage with the nonselection potential. Then the bias voltages are supplied from a bias circuit 3 of resistance division constitution, and the bias potentials as selection potentials and nonselection potentials which are a scanning-side and a data-side high selection potential VH, a scanning-side high nonselection potential VSNH, a data-side high nonselection potential VDNH and a low nonselection potential VDNL, a scanning- side low nonselection potential VSNL, a scanning-side and a data-side low selection potential VL are received through a buffer to outputs the bias voltages selectively according to an illumination signal or scanning signal.

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 using a selection potential and a non-selection potential.

[0002]

2. Description of the Related Art Conventionally, in a so-called simple matrix type liquid crystal display device, a liquid crystal cell is driven according to a voltage averaging method. It is provided with an electrode group orthogonal to the liquid crystal cell and selectively applies a selection voltage or a non-selection voltage according to a driving signal to the liquid crystal cell.
It is applied to the liquid crystal cell by a driving element composed of a C-MOS transistor as shown in Japanese Patent Publication No.

[0003]

However, in recent years, in the liquid crystal display device, the display capacitance is increased, but the driving element is arranged extremely in the peripheral portion of the liquid crystal cell. Therefore, when the driving element is large, the display area is larger than the display area. Surface area is increased. Therefore, the width of the driving element tends to be significantly narrowed. Further, since the display capacity has increased, the number of pixels driven by one drive terminal has increased, and it has become necessary to further reduce power consumption.

[0004]

SUMMARY OF THE INVENTION In consideration of the above points, the present invention has been made by paying attention to the difference in driving current flow between a selected voltage and a non-selected voltage.
It is configured by a unidirectional MOS transistor that outputs a bias voltage of a selection potential and a bidirectional MOS transistor that outputs a bias voltage of a non-selection potential.

[0005]

As a result, the element occupying area of the output stage at the selection voltage is reduced and the bias current and the like are reduced.

[0006]

FIG. 1 is a circuit diagram of a liquid crystal display device according to an embodiment of the present invention. Reference numeral 1 is a so-called simple matrix type liquid crystal cell.
It has a group of electrodes (not shown) orthogonal to each other so as to apply a voltage according to the voltage averaging method to the liquid crystal molecules twisted by ˜360 degrees. _{Reference numeral} 2 is a drive element for applying a predetermined bias voltage to the liquid crystal cell 1. The bias voltage is supplied from the bias circuit 3 by resistance division, and the high selection potential V _H on the scanning side / data side and the high non-selection potential V _SNH on the scanning side are provided. , High non-selection potential V _{DNH on} the data side, low non-selection potential V _DNL on the data side, low non-selection potential V _{SNL on} the scanning side, low selection potential _VL on the scanning side / data side Each bias potential is received through a buffer, and a bias voltage is selectively output according to a lighting signal or a scanning signal. In the output stage of the drive element 2, only one unit portion connected to one electrode is shown with the reference numeral 20. However, unidirectional MOS transistors 21 and 22 that output a bias voltage of a selection potential are used. , Bidirectional MOS transistors 23 and 24 that output a bias voltage of a non-selection potential.

Such an output stage is made because it has been found that the liquid crystal driving by the voltage averaging method is substantially unidirectional in the case of the selection voltage and bidirectional in the case of the non-selection voltage. For example, 640 × 200 for scanning 200 lines
In the dot matrix display of No. 3, when all lighting, all non-lighting, and grid display are performed, the selection current for the high selection potential V _H is 1.70 mA, 0.25 mA, 4.20 mA,
The selection current of the low selection potential V _L is -1.70 mA, -0.3.
It has the same polarity as 0 mA and -4.25 mA. On the other hand, the non-selection current on the scanning side is -0.70 mA, 0.90 mA, 0.30 mA for the high non-selection potential V _SNH , and 0.70 mA, -0 for the low non-selection potential V _SNL . .92 m
A, −0.30 mA, the current polarity differs depending on the display form, and similarly, even for the non-selection current on the data side, 0.05 mA, −0.60 mA, − for the high non-selection potential V _DNH .
3.20 mA, -0.05 mA, 0.60 mA, and 3.12 mA with respect to the low non-selection potential V _DNL on the data side.

Therefore, in each of the scanning side driving element and the data side driving element, a unidirectional element is used for the selection voltage and a bidirectional element is used for the non-selection voltage. Thus, taking a driving element having a thickness of 0.2 to 0.3 mm in which 80 output terminals are arranged along one side as an example, a conventional bidirectional element uses a length of 9 mm and a width of 2 mm. However, in the embodiment of the present invention, the width is 1.8 to 2.1 mm, and the power consumption is 5 to 20% depending on the displayed content in the display of 12 inches.
Reduced.

[0009]

As described above, the present invention is made by paying attention to the current characteristics of the selection voltage and the non-selection voltage, and the element occupying area of the output stage at the selection voltage is reduced and the transistor bias current is reduced. Therefore, the width of the frame required in the peripheral portion of the liquid crystal cell can be reduced, and a large display area can be driven with substantially the same power consumption as in the conventional case.

[Brief description of drawings]

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

[Explanation of symbols]

 1 liquid crystal cell 2 driving element 3 bias circuit

Claims (1)

[Claims] 1. A unidirectional MOS transistor having a liquid crystal cell having orthogonal electrode groups, and a drive element for applying a predetermined bias voltage to the liquid crystal cell, wherein the drive element outputs a bias voltage of a selection potential. A liquid crystal display device comprising an output stage including a bidirectional MOS transistor that outputs a bias voltage of a non-selection potential.