JPH0423245B2 - - 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 with two common electrodes and a plurality of segment electrodes is formed.

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. In addition, the pulse group P ₅ causes the pixel A ₁ ,
Voltages V ₅ and V ₆ are respectively applied to A ₂ and both are displayed. Furthermore, the _pixel is
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] In the present invention, one of the two common electrodes is provided with first and second pulse groups each consisting of a scanning pulse with a pulse width t and a high-frequency pulse with the same voltage as the scanning pulse. The other common electrode is supplied with the first and second pulse groups with different phases, and the segment electrodes are supplied with the same voltage as the scanning pulse with a period of 4t and a pulse width of 4t. It is designed to selectively display pixels by selectively supplying one of four types of selective pulse groups consisting of 2t pulses and with a phase shift of 1/4 period. be.

[Example] In FIG. 1, a pulse group P ₇ and a pulse group P ₈ are constantly supplied to two common electrodes, respectively.
The pulse group P ₇ consists of a first pulse group E 1 consisting of a scanning pulse P ₇ with a pulse width t and a high-frequency pulse f ₁ that is generated for a time t before that, and a first pulse group E ₁ which is a level-inverted version of this first pulse group. It consists of two pulse groups _E2 .

Further, the pulse group P ₈ is obtained by shifting the phase of the pulse group P ₇ by a time t.

On the other hand, the segment electrodes are provided with four types of selected pulse groups P ₃ - 4 types of pulses with a period of 4t and a pulse width of 2t, whose phases are shifted by 1/4 period.
It selectively supplies either _P6 .
The voltage of this pulse group is the same as that of pulse groups P ₇ and P ₈ .

First, a voltage is applied to the pixel by supplying the pulse group _P3 .
V ₉ or V ₁₀ is applied and both become invisible.

Next, a voltage V ₁₁ or V ₁₂ is applied to each pixel by supplying the pulse group P ₄ to display and non-display, respectively.

Furthermore, by supplying the pulse group _P5 , a voltage _V13 or _V14 is applied to each pixel, and both display.

Then, by supplying the pulse group _P6 , a voltage _V15 or _V16 is applied to each pixel, and the pixel becomes non-display and display mode, respectively.

[Effects of the Invention] According to the present invention, the pulse voltage supplied to the common electrode and the segment electrode is one voltage, so a step-up circuit or a step-down circuit is not necessary, and an external capacitor is also not required, and the circuit configuration can be simplified. can be extremely simplified. 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 group, E ₂
... Second pulse group, P ₇ ... Scanning pulse, f ₁ ...
High frequency pulse, P ₃ to P ₆ ...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, one common electrode is supplied with a scanning pulse having a pulse width t and a time t before or after this scanning pulse.
A first pulse group consisting of a high frequency pulse of the same voltage as the scanning pulse generated during the scanning pulse, and a second pulse group formed by inverting the level of this first pulse group are alternately supplied, and the other common electrode is , the first pulse group and the second pulse group are supplied with a phase difference of time t from one of the common electrodes, and each segment electrode is supplied with the same voltage as the scanning pulse and for a time of 4t. By selectively supplying one of four types of selective pulse groups with a phase shift of 1/4 period and consisting of pulses with a pulse width of 2t and a pulse width of 2t, each pixel can be selectively displayed or hidden. A method for driving a matrix type liquid crystal display device, characterized in that: