JPS6336648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving circuit for a liquid crystal matrix display in which signal electrodes and scanning electrodes are formed in a matrix.

Before explaining the present invention, the prior art will be explained first. Liquid crystal matrix displays basically use liquid crystal panels such as those shown in FIGS. 1a and 1b.

That is, a gap is provided by inserting a spacer 3 between the upper glass plate 1 and the lower glass plate 2, and liquid crystal 4 is sealed in the gap to form a thin layer of liquid crystal. Electrodes 5 are provided between the upper glass plate 1 and the lower glass plate 2, and the electrodes of the upper glass plate 1 are made of a transparent conductive film, and the electrodes of the lower glass plate 2 are made of a transparent conductive film depending on the purpose. A conductive film or metal film is used.

In addition, the liquid crystal to be sealed is a nematic liquid crystal,
The principles of display include dynamic scattering mode (DSM) and field effect mode (FEM).

In DSM, it is transparent when no electric field is applied, but when an electric field of a certain value or more is applied, it becomes cloudy and opaque, and a display is performed.

A state in which such a display is performed and is visible will be hereinafter referred to as a lighting state. On the other hand, FEM uses the property that liquid crystal molecules have birefringence or light-sharpening properties depending on their molecular arrangement, and that the molecular arrangement can be controlled by the strength of the electric field, and is used for color-selective display or black-and-white display. can.

In a liquid crystal matrix display, the electrodes 5 of the upper glass plate 1 and the lower glass plate 2 are crossed to form an X-Y matrix electrode, and the electrodes to which an electric field is applied are selected and applied to the liquid crystal at the intersection in the thickness direction. By applying an electric field, characters and images are displayed using the display principle described above.

The basic structure of the liquid crystal matrix display is the second
As shown in the figure, it consists of a liquid crystal panel 6, a row drive circuit 7, and a column drive circuit 8.

3 shows the row drive circuit 7 and column drive circuit 8 in FIG. 2 in some detail, and FIG. 4 shows the voltage waveforms applied to each signal line in FIG. The drive voltage waveform applied to one pixel is expressed with respect to the time axis.

In FIG. 3, 9 indicates an inverter, and 10 indicates a transmission gate.
In addition, the scanning line side bus line X and the scanning line side control lines X ₁ , X ₂ , X ₃ . . . Scanning line side control signals x ₁ , x ₂ , x ₃ . . . xn for sequentially scanning the lines are added, and similarly, the signal line side bus line Y
And signal line side control lines Y ₁ , Y ₂
...Ym includes the signal line side selection voltage waveform y, the signal line side non-selection voltage waveform, and the signal line side control signal _y1 corresponding to the display data shown in FIG. 4.

The scanning line side selection voltage waveform x or the non-selection voltage waveform is selected by the scanning line side control signal _X1 in FIG.
is obtained. Similarly, the signal line side selection voltage waveform y or the non-selection voltage waveform is selected by the signal line side control signal _Y1 , and the signal line side drive voltage waveform Vy is obtained.

A pixel where the scanning side electrode of the liquid crystal panel 6 to which the scanning line side driving voltage waveform Vx is applied and the signal side electrode to which the signal line side driving voltage waveform Vy is applied intersects,
A drive voltage waveform of Vx-Vy shown in FIG. 4 is applied to turn on or off.

The conventional driving method has been explained above, but as is clear from FIG. 4, the scanning line side selection voltage waveform x
The frequencies (hereinafter referred to as driving frequencies) of the signal line side selection voltage waveform y and the non-selection voltage waveform are the same. Also, the period is
The H level period or L level period of the signal line side control signal y ₁ (hereinafter referred to as the lighting period and non-lighting period, respectively) and the H level period of the scanning line side control signal x ₁ , x ₂ , x ₃ . . . xn (hereinafter referred to as the non-lighting period) , scanning period), and the phases are the same.

In liquid crystal matrix displays, the driving frequency increases in proportion to the number of scanning lines. In particular, when displaying images on a television or the like using a liquid crystal matrix display, the number of scanning lines increases because the display must be dense.
As the drive frequency increases, the power consumed by the drive circuit increases, which affects battery life in small portable devices.

An object of the present invention is to provide a circuit that can drive a liquid crystal matrix display at half the conventional drive frequency while averaging crosstalk voltage.

An embodiment of the present invention is shown in FIG. 5, FIG. 6 is a timing chart of each part of FIG. 5, and FIG. 7 is a drive voltage waveform.

In FIG. 5, 11, 13, and 14 represent flip-flops L1, L3, and L4, and 12 represents a shift register L2. L1, L2, L
Assuming that both L3 and L4 have rising operation, the rising of the signal CL causes the Q output of L1 to output a signal at half the frequency of CL.

Further, a signal obtained by inverting CL by an inverter 9 is applied to the input of L2, and a shifted signal is output from L2 at the rising edge of the signal. Similarly, due to the rise of L3,
Display data DY ₁ and DY ₂ input to L4 are latched and output from L3 and L4.

In other words, the output signals of L2, L3, and L4 are output with a phase shift of 90° with respect to the Q output signal of L1.

The Q output signal of L1 is input to a selection circuit configured by a transmission gate 10, and by selecting one of the two transmission gates, the input signal of that transmission gate is input. Outputs the signal applied to the terminal. This applies to the scanning line side selection voltage waveform x, the scanning line side non-selection voltage waveform, the signal line side selection voltage waveform y and the signal line side non-selection voltage waveform in FIG. In addition, the output signals of L2 correspond to the scanning line side control signals x ₁ , x ₂ , x ₃ . . . xn in FIG.
The output signal of L3 corresponds to the signal line side control signal _y1 .

Looking at the drive voltage waveforms in FIG. 7, _we can see that the scanning line side control signals x ₁ , x ₂ , x ₃ . . . Line side selection voltage waveform y
It can be seen that by shifting the phase by 90 degrees with respect to the non-selected voltage waveforms, the x and y driving frequencies can be halved compared to the conventional ones while averaging the crosstalk voltage of the liquid crystal matrix display.

As described above, the present invention shifts the phase of the lighting and non-lighting periods of the signal electrodes and the scanning period of the scanning electrodes by 90 degrees with respect to the signal line side selection or non-selection voltage waveform or the scanning line side selection or non-selection voltage waveform. In particular, since the driving frequency can be reduced to half of the conventional driving frequency, it is possible to extend the battery life of small portable devices using liquid crystal matrix displays.

[Brief explanation of the drawing]

Figures 1a and b are a schematic cross-sectional view and a plan view, respectively, to explain a typical liquid crystal panel, Figure 2 is a basic configuration block diagram of a typical liquid crystal matrix display, and Figure 3 is a diagram of a typical liquid crystal matrix display. A circuit diagram showing an example of a drive circuit for obtaining a directly applied waveform, Fig. 4 is a time chart showing an example of a conventional drive voltage waveform, and Fig. 5 is a circuit diagram for obtaining a drive voltage waveform of the present invention. FIG. 6 is a circuit diagram showing one embodiment, FIG. 6 is a timing chart of each part of FIG. 5, and FIG. 7 is a time chart showing a specific example of the drive voltage waveform according to the present invention. 1... Upper glass plate, 2... Lower glass plate, 3...
Spacer, 4...Liquid crystal, 5...Electrode, 6...Liquid crystal panel, 7...Row drive circuit, 8...Column drive circuit,
9...Inverter, 10...Transmission gate, 11, 13, 14...Flip-flop, 12...Shift register.

Claims (1)

[Claims] 1. In a circuit that drives a liquid crystal matrix display in which signal electrodes and scanning electrodes are formed in a matrix, each scanning period in which scanning lines are sequentially scanned is
It is half of one cycle of the scanning line side selection voltage waveform and the scanning line side non-selection voltage waveform, and the phase of each scanning line side control signal is 90 degrees with respect to the scanning line side selection voltage waveform and the scanning line side non-selection voltage waveform. A drive circuit for a liquid crystal matrix display that is characterized by a shifted structure.