JPH0423246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a matrix type liquid crystal display device.

[Prior Art] Conventionally, matrix-type liquid crystal display devices in which a plurality of pixels are formed by the intersections of two common electrodes and a plurality of segment electrodes facing each other via a liquid crystal have been widely used. There is.

For example, in a digital watch or the like, display is performed using a Japanese character-shaped display pattern made up of seven pixels A ₁ to _{A 7} as shown in FIG.
In each pixel, for example, pixels A ₂ , A ₃ ,
A ₇ uses one common electrode C ₁ (not shown), and pixels A ₁ , A ₄ , A ₅ , A ₆ use the other common electrode C ₂
(not shown) is used. Furthermore, regarding segment electrodes, pixels A ₁ , A ₂ , pixels A ₃ , A ₄ , pixels
By connecting A ₆ and A ₇ and making the pixel A ₅ independent, a matrix type liquid crystal display device is formed with two common electrodes and a plurality of segment electrodes.

Each of the pixels described above is driven as follows. For example, in the case of driving pixels A ₁ and A ₂ whose segment electrodes are connected to each other, the pulse groups P ₁ and P ₂ shown in FIG. 3 are constantly supplied to the common electrodes C ₁ and C ₂ , respectively. On the other hand, a selection pulse group P _{3 whose} phase is shifted by 1/4 period is applied to the segment electrode.
Selectively feed one of ~ _P6 .

Voltages _V1 and _V2 are applied to pixels _A1 and _A2 , respectively, by pulse group _P3 , and both become non-displayable. Voltages V ₃ and V ₄ are applied to the pixels A ₁ and A ₂ , respectively, by the pulse group P ₄ , and the pixels become display and non-display, respectively. Furthermore, by the pulse group P ₅ , the pixels A ₁ ,
Voltages V ₅ and V ₆ are respectively applied to A ₂ and both are displayed. Furthermore, the pixel of pulse group _P6
Voltages V ₇ and V ₈ are applied to A ₁ and A ₂ so that they become non-display and display, respectively.

As described above, pixels A ₁ and A ₂ are selectively displayed.

[Problems to be Solved by the Invention] In the above driving method, the pulses supplied to the common electrode require two types of potential, which requires a step-up circuit or a step-down circuit. It was necessary to attach an external capacitor. As a result, the power supply circuit has become complicated, which has been an impediment to cost reduction.

The present invention aims at simplifying a power supply circuit.

[Means for Solving the Problems] The present invention provides a scanning pulse having a pulse width of 2t and a period of 4t to one of two common electrodes, and a scanning pulse having a period of 1/4 of the above scanning pulse to the other common electrode. Phase-shifted scanning pulses are supplied, and each segment electrode is supplied with a selection pulse having the same voltage as the scanning pulse and a pulse width of time t, and first and second high-frequency pulses having the same voltage as the selection pulse. The pixels are selectively displayed by selectively supplying either a selection pulse group consisting of a pulse train of It was designed to do so.

[Example] In FIG. 1, scanning pulses P ₇ and P ₈ each having a pulse width of 2t and a period of 4t are constantly supplied to two common electrodes. Pulses P ₇ and P ₈ are out of phase by 1/4 period.

On the other hand, the segment electrodes are provided with a first pulse train E 1 and a pulse train E 1 which has a pulse width of time t and is composed of a selection pulse P ₉ having the same voltage as the pulse P ₇ and a high-frequency pulse f that occurs for a time _t before this selection pulse. A selection pulse group B 1 consisting of a second pulse train E ₂ obtained by inverting the level of this first pulse train E ₁ and a selection pulse group B ₂ - which is obtained by shifting the phase of this selection pulse group B ₁ by 1/4 _period . B ₄ is selectively supplied.

First, voltages V ₉ and V ₁₀ are applied to each pixel by supplying the pulse group B ₁ , and both display.

Next, voltages V ₁₁ and V ₁₂ are applied to the pixels by supplying the pulse group B ₂ , respectively, and the pixels become display and non-display, respectively.

Furthermore, by supplying the pulse group _B3 , voltages _V13 and _V14 are applied to the pixels, respectively, and both become non-displayed.

Then, by supplying the pulse group _B4 , voltages _V15 and _V16 are applied to the pixels, respectively, and the pixels become non-display and display, respectively.

[Effects of the Invention] According to the present invention, only one pulse voltage is required to be supplied to the common electrode and the segment electrode.
A step-up circuit or a step-down circuit is not required, and an external capacitor is also not required, making it possible to extremely simplify the circuit configuration. Furthermore, pads for external capacitors are no longer required, which is effective in reducing the chip area of the integrated circuit.

[Brief explanation of drawings]

Figure 1 is a waveform diagram showing an example of the voltage waveform used in the driving method of the present invention, Figure 2 is a front view showing an example of a pixel, and Figure 3 is the voltage waveform used in the conventional driving method. FIG. A ₁ to _{A 7} ... Pixel, E ₁ ... First pulse train, E ₂
... second pulse train, P ₇ , P ₈ ... scanning pulse,
f...high frequency pulse, _B1 to _B4 ...selected pulse group.

Claims (1)

[Claims] 1. A matrix liquid crystal display device in which a liquid crystal is interposed between two common electrodes and a plurality of segment electrodes, and a plurality of pixels are formed by the intersections of each common electrode and each segment electrode. In the driving method, a scanning pulse with a pulse width of 2t and a period of 4t is supplied to one common electrode, and the above scanning pulse is supplied to the other common electrode with a phase shift of 1/4 cycle, and each of the above The segment electrode is provided with a first pulse consisting of a selection pulse having the same voltage as the scanning pulse and having a pulse width of time t, and a high-frequency pulse having the same voltage as the selection pulse that occurs before or after the selection pulse for a time t. A selection pulse group consisting of a pulse train and a second pulse train obtained by inverting the level of this first pulse train, and one of three types of selection pulse groups in which the phase of this selection pulse group is shifted by 1/4 period. 1. A method for driving a matrix liquid crystal display device, comprising selectively supplying the pixel and selectively displaying or non-displaying each pixel.