JPS61128292A - Driver for active matrix type display panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a drive device for an active matrix type display panel, and particularly to a panel using a liquid crystal as a picture element, the ground motion circuit configuration of the panel is This invention relates to a device configuration that can simplify the process.

Matrix display devices using nematic liquid crystals are available as low-voltage drive, low power consumption, light-density, thin display devices, but flickering occurs due to the slow response characteristics of nematic liquid crystals and the lack of memory properties. However, about half of the voltage applied to the selected picture element is also applied to the half-selected picture element, resulting in a decrease in contrast.

The active matrix method is a method that overcomes these difficulties all at once. This means that there is one FET switch (source S, drain D, gate G) per pixel in Figure 6.
A liquid crystal cell LCD is provided. An active matrix type display panel is constructed by sealing liquid crystal between a substrate on which these FET switches are integrated and another glass substrate having a transparent electrode (common electrode C) provided on its entire surface. In order to apply a voltage to the picture element (i, j), for example, 6
A signal pulse may be applied to the electrode Yj in synchronization with the selection of the voltage +t&Xi by applying a scanning pulse for 0 μ8. Since the switch element attached to picture element (1, j) is in the on state, charge flows into the capacitor consisting of the liquid crystal and the upper and lower transparent electrodes. After 60 microseconds have elapsed, the capacitor is turned off, so the charge in the capacitor is held, and voltage continues to be applied to the liquid crystal for 50 microseconds until the next scanning pulse is applied. The FET switch is fabricated on a monocrystalline silicon substrate or on an L-reflection glass substrate using thin film transistor (TPT) technology, and the active 711x method, such as 6° or more, can improve the drawbacks of liquid crystal. However, the switch element (FET switch)
A good large panel with integrated
However, there are problems that need to be improved.

[Conventional technology]

FIG. 6 shows an example of a conventional TPT-LCD drive circuit configuration. In the figure, the TPT-LCD panel 1 includes electrodes D1 to DM on the data side and electrodes S1 to S1 on the scan side.
M is formed in the shape of a square IJ, and the intersection thereof is provided with an FET switch and a liquid crystal cell as in FIG. 6. A three-value switch group 2 is provided on the data side electrode, and this switch switches the voltage +vD*-vpl, for example +5"/
, -5vf: The voltage is supplied to the picture element by switching. A shift register 4 and a latch 6 are provided to supply data to the driver, and the data signal is passed through the serial-in-parallel-out shift register 4 and its output latch circuit 3 to the driver's 5. Normally, the bias voltage is set to a negative value by the power supply 13, for example, VG-=-10V, and only one selected scan side electrode has a bias voltage of, for example, vG+.
= +10V voltage is supplied. Therefore, only one of the binary changeover switches is selected, and the driver's power supply 1 is selected.
vG+=+10V is supplied to the scan electrode selected from 2. And a latch circuit 6 on the scan side. shift·
A register 7 is provided similarly to the data side. However, on the scan side, since the voltage at which the driver circuit operates is negative as described above, the level is not the same as that of the control circuit 9.

A level conversion circuit 8 (photocoupler or pulse transformer, etc.) is provided, and the data signal of the control circuit 9, the clock signal Δ,
The level of the strobe signal is converted.

However, this method requires a six-value changeover switch group 2, and has the disadvantage that the driver configuration is complicated.It is difficult to manufacture a highly integrated device, the cost is high, and the withstand voltage is low (±5V). ) Since it must be able to swing, there is a problem in that it requires sufficient pressure resistance.

FIG. 4 shows the drive waveform applied to the panel and the voltage waveform applied to the liquid crystal, which is a picture element, in accordance with the circuit configuration of FIG. 5. In the figure, 512 lines x 352
The TET-LCDCD waveform of the line is j6,
Data electrode D1 is selected at +5V in one frame.
, non-selection is Ov, and in the next 7 frames, the polarity is switched to 15V for selection and Ov for non-selection. The reason why it is necessary to switch the polarity in this way is because due to the characteristics of the mixed crystal, repeated application of the same polarity causes deterioration, and in general, the polarity is switched and driven to prevent deterioration. Therefore, a three-value switching type switch group 2 for switching three values (-5V, OV, 5V) is required. A constant potential, in this case the ground potential OV, is applied to the common electrode C. The scan electrodes 81 to 5352 normally have a bias voltage of -10V, and +10V is applied only when selected. As shown in the figure, the polarity of the voltage applied to each picture element is switched for each frame from the picture element on the S1 line to the picture element on the 5352 line, and the liquid crystal cell of each picture element is driven with alternating current.

The problems with the configuration shown in FIG. 3 shown above have been described above. The problem is that c5 does not have an appropriate three-value switching type switch f2, which is a data electrode side driver. This three-value switching type switch f2 is usually made into an IC, but it is very expensive and there is no highly integrated one.

What is shown in FIG. 5 is to make it possible to use a binary changeover switch group 52 on the data side in order to improve the drawbacks of the circuit configuration shown in FIG. 7B5. Switch the reference potential? By switching between positive and negative (the voltage supplied from the power supply 55) at 54, it is possible to apparently obtain a three-value output. However, in this method, the level conversion circuit 55 (photocoupler or pulse transformer) is required because the reference voltage of the binary switching circuit is changed between positive and negative. However, the photocoupler and pulse transformer have a limit in operating speed. This becomes an obstacle when trying to increase the number of data lines to create a larger panel.When increasing the number of lines and using a high-frequency level conversion circuit such as 10 megacycles or 20 megacycles, the cost increases. In addition, conversion circuits for even higher frequencies have not been realized, which limits the ability to increase the density and size of panels.

[Problem to be Solved by the Invention 3] As mentioned above, in the drive circuit of the conventional active matrix type display device, the structure of the driver becomes complicated,
There are drawbacks such as not being able to obtain a high degree of integration and high cost, and in order to simplify the configuration of driver 1, a level conversion circuit is required when a binary switching circuit is used for the driver on the data electrode side. There is a problem in that it is difficult to increase the number of display lines and increase the size or density of the panel due to the limit of the response speed of the circuit.

[Failure to solve the problem]

The present invention is a driving method for an active matrix type display panel that uses a binary switching type switch as a data electrode side driver in order to solve the above problems, and in which the reference voltage of the binary switching type switch is the ground potential. By using a binary switching type switch connected to the data electrode side, a level conversion circuit is not required on the data electrode side, and a common electrode is used as a common electrode to reverse the voltage level for each frame of the liquid crystal, which is a picture element. The voltage level applied to the sensor is changed from high to low.

[Function] Accordingly, a low-cost, highly integrated binary switching type SIN FT is used on the data electrode side, and the signal input section is directly connected to the control circuit, eliminating the need to use a level conversion circuit.

On the other hand, a certain frame (Fi frame) is placed on the data side electrode.
If we apply +VD voltage to the selected electrode and OV (ground level) to the non-selected electrode, then in the next frame (Fi+1 frame), we reverse the potential level supplied from the driver and restore the non-selected state. +VD, set the selection state to OV (ground degree level).

At the same time, the potential of the common electrode, which was set to the ground level in the i frame, is changed to a positive potential (+VD) in the i+1 frame.

On the other hand, the scanning side is almost the same as the conventional configuration.

In this case, a level conversion circuit is required, but since the frequency on the scan side is relatively low, there is no problem.

By controlling the voltages on the common electrode and the data electrode as described above, it is possible to apply a voltage waveform that is completely the same as the conventional voltage waveform to the display picture element, without deteriorating the display quality.

EXAMPLES Below, the present invention will be explained in detail by way of examples.

〔Example〕

In FIG. 1, parts corresponding to the circuits in FIG. 113 and FIG.

The scan side has the same configuration as the conventional one, and in this case, the level conversion circuit 8 has one frame 201TII, for example.
I, if the number of scan lines is 500, then the number of scan lines is 4
The frequency of No. N is 500/20 ms = 25 KHz
Since the frequency is relatively low, common low-cost products can be used.

On the other hand, the data electrode side is configured using a low-cost, highly integrated binary switch group 102, the signal input section is directly connected to the control circuit 9, and a shift register (serial in/out) is used.
parallel out) 4. Each data signal, RACK signal, latch signal, and strobe signal are directly input to the latch circuit 6 and the binary switch group 102.

Further, a switch circuit 105 for applying a voltage to the common electrode C is provided. This is a normal transistor,
This is a push-pull configuration using MOSFET.

FIG. 2 shows the drive waveform with the above configuration. Now, if it is the @F1th frame at a certain point in time, the potential of the common electrode C is set to GND, and to the data side electrodes, a potential of +VD level is applied to the selected line, and a potential of GND level is applied to the non-selected line. At the moment when this drive ends and the next F't++th frame is started, the common electrode potential '&N'p (+5V)
Set to level. At the same time, the reference potential of the data side electrode is also set from GND to VD level. Then, in synchronization with the scan side electrode voltage, G is applied to the selected data line.
A voltage of ND level and VD level is applied to the unselected data line (the polarity is opposite to that of the Ft frame).

By controlling the voltages on the common electrode and the data electrode as described above, the display picture element has 12 Figures 81 to 8N Li
As shown in ne and f, it is possible to apply a voltage waveform that is completely the same as the conventional one, without degrading the display quality.

Note that in the above embodiment, the data side electrode driver/
If there is a problem that the supply voltage VD of ＼ and the supply voltage to the common electrode increase, the common electrode ＼
It is possible to apply a compensation voltage of 0 to the device of the present invention as well.

The present invention is not limited to active matrix type display panels using liquid crystals as described above, but is also applicable to other materials used in similar active matrix type display configurations, such as: PLZT (a transparent ceramic material that converts information from electrical signals into patterns of light transmittance) and EPDCI tactrophoretic
DisplAy) or BCD (E#atroer
omia11spt&y), etc.

[Effects of the Invention] As described above, if the present invention is implemented, the voltage level applied to the common electrode, which is a common electrode, is changed from high to low, and the base r$ voltage is grounded to the data electrode side driver. It is possible to use a binary switch connected to a potential. As a result, a low-cost, W-integrated binary changeover switch is used on the data side electrode side, and the No. 8 input section is directly connected to the control circuit, eliminating the need for a level conversion circuit. This makes it possible to realize a low cost, compact drive circuit, and even a display unit. Furthermore, it is possible to apply voltage waveforms that are completely the same as those of the prior art to the display picture elements, without degrading the display quality at all.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the device of the present invention, Fig. 2 is a driving waveform diagram of the device of Fig. 1, Fig. 6 is a ground motion circuit diagram of a conventional TFT LCD, and Fig. 4 is a circuit diagram of the TFT I, CD of Fig. 1I43. Figure 5 is a drive circuit diagram of a conventional TPT LCD.
Figure W16 is an explanatory diagram of active matrix type I and CD. (Main symbols) 1...TPT-LCD panel 3...Latch circuit 4...Shift register 5...Binary switching type switch group 6...Latch circuit 7...Shift register 8 ... Level conversion circuit 9 ... Control # circuit 102 ... Binary switching type switch group 103 ... Switch circuit

Claims (1)

[Claims] It consists of a combination of a plurality of switching elements and a picture element, one electrode of the picture element is connected to the output electrode of the switching element, and the other electrode is connected to a common electrode common to the plurality of picture elements. In an active matrix type display panel, a binary switch that switches between two predetermined potentials is connected to a data electrode that is commonly connected to the input electrodes of multiple switching elements, and the multiple switching elements are controlled. The scan electrode and the common electrode, which are connected in common to the electrodes, each have two electrodes that can have arbitrary potentials.
1. A drive device for an active matrix display panel, characterized in that a value changeover type switch is connected and a display is performed by applying a predetermined potential.