JPS5853343B2 - exiyouhiyoujisouchinokudouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a liquid crystal display device which is a combination of a liquid crystal display element and a switching element.

Conventionally, in order to display a large number of selection points on a single liquid crystal display element by electrical drive, electrode terminals corresponding to the large number of selection points are guided to one end of the liquid crystal display element substrate. The desired electrical drive was only possible by connecting the required circuits with a large number of lead wires.

In such a method, a desired display is performed by configuring a circuit having arbitrary electrical characteristics on a portion of a printed circuit board or the like outside the liquid crystal display element, and adapting the circuit to the characteristics of the liquid crystal.

Unfortunately, in order to selectively electrically display a large number of selected points, it is often desirable to maintain some kind of common electrical function.

That is, there are cases where it is desired that the liquid crystal display element has a memory function or a time-division drive function.

Furthermore, conventionally, for a large number of resistors connected in series, the portion drawn out from the middle of each paper body and the display segment of a liquid crystal display element are connected, and a voltage is applied between the ends of the series resistors. A proposal has been made to connect one side and the voltage drawn from the intermediate portion of the resistor or between the lead portions between the terminals of a liquid crystal display element, thereby directly converting the applied signal voltage into an analog display.

However, with this method, it was difficult to sufficiently widen the input voltage because the liquid crystal itself has a high resistance and operates at low voltage and current.

In addition, there are other drawbacks, such as the threshold characteristics of the liquid crystal display panel itself being unclear, the use of a resistor specified for the display being difficult to use, and the position to be displayed being unclear.

Furthermore, the voltage applied to the liquid crystal becomes higher than necessary, which causes the liquid crystal display element to be destroyed.

Another proposal is to make the opposing electrodes of the liquid crystal display element non-parallel to make the threshold characteristics of the liquid crystal different and to display analog signals as position indicators, but in this case too, the threshold characteristics of the liquid crystal display element It has been extremely difficult to construct a liquid crystal display device that is sufficiently satisfactory for practical use because of the drawbacks such as variations in voltage and the inability to obtain a very large target voltage.

The present invention has been made in order to improve the above-mentioned problems, and it connects a liquid crystal display element, a threshold type switching element, and a resistor in series or in parallel, turns the switching element on by a pulse signal, and Although the switching element itself cannot change from the off state to the on state, once the on state is obtained, the on state of the switching element is continuously maintained by an alternating current signal that can maintain the on state. It is characterized in that the liquid crystal display element is driven in accordance with the operating state of the device.

The threshold type switching element used in the present invention has characteristics as shown in FIG. 1a.

This is the current-voltage characteristic due to the circuit in the same figure, and is the reading of a voltage-ammeter with a switching element S and a load resistor R connected in series, and a voltage applied from a constant-voltage power source connected in a prescribed manner. This is obtained by

As seen in FIG. 1a, when the voltage of this switching element exceeds a certain level, the resistance value decreases, and as a result, the current value increases rapidly.

The voltage at this time is called the threshold voltage. At this time, if the load resistance is sufficiently large compared to the resistance of the switching element, the current value will be regulated by the load resistance, and if the voltage is gradually lowered from this point, the load will change according to Ohm's law. It comes down as a current characteristic.

It can be seen that when the voltage drops to a certain level, the current value decreases rapidly and the element returns to a high resistance state.

Characteristics can be obtained through a similar path for the voltage rise and fall again.

The voltage at which the lower limit of the low resistance state changes to the high resistance state is defined as vb, and the current at this time is defined as Ib.

In other words, it is called the minimum sustaining current or voltage because it is the lower limit current or voltage that can maintain a low resistance state.

In the present invention, switching elements having such characteristics can be used in combination with a liquid crystal display element as shown in the circuit diagrams in FIGS. 2a" and 2d.

In FIG. 2, S is a switching element, L is a liquid crystal display element, and R is a resistor.

These can be arranged in large numbers on the same substrate as necessary, and the threshold values of the switching elements can be individually varied, the value of R can be gradually bounded, and the liquid crystal display elements can be arranged as necessary. It can be integrally constructed in various pattern shapes, numbers, letters, cement shapes, etc.

The switching function element that can be used in the present invention is one that is capable of switching from a high resistance state to a low resistance state with a single pulse and that can operate in both alternating current and direct current.

In addition, the rise time of these is sufficiently fast compared to that of liquid crystal, and the fall time is also short when the applied voltage is removed or VB
Alternatively, a device that switches off again to the high resistance state by a signal of Ib or lower may be used.

This device has such a switching function, and in a circuit connected as shown in FIG. 2, driving as the object of the present invention is performed by applying voltages as shown in FIG. 3.

An example of the operation of the present invention is shown using the circuit shown in FIG. 2 and the applied voltage shown in FIG.

In this case, the high resistance state R of the switching element S shown in FIG.
8, H is sufficiently large with respect to R connected in series, and resistance RL in the liquid crystal display element is also sufficiently large with respect to R.

In addition, the resistance state R8, L of the switching element S divides the voltage between terminals a and b by resistance division at the value of R,
It is set to a value that provides an appropriate operating voltage for the liquid crystal display element.

Various electro-optical effects can be considered for the liquid crystal display element, but in this example, one is used in which the transmittance increases when a voltage is applied, and the transmittance decreases when no voltage is applied.

An applied signal shown in FIG. 3 is applied between terminals a and b of the circuit shown in FIG. b, which are set to such individual characteristic values.

In FIG. 3, 1 is a write pulse and has a voltage value of Vs, and the switching element in FIG. 2 has a voltage value exceeding Vth in FIG. 1.

As a result, the switching element S changes from R8,H to R8,
It becomes L.

When R8 and H are selected, due to the above settings, almost all of the applied voltage is applied to S because R is sufficiently small compared to both of them, and the L side is substantially electrically charged. The voltage is so large that no optical effect can occur.

On the other hand, when R8,L is reached, the applied voltage of the liquid crystal vL=(R/
R+Rs, L) Only the magnitude of Vs is applied to L, and the electro-optic effect of the liquid crystal can occur.

Therefore, as shown in the graph of the amount of transmitted light in FIG. 3, at this time the liquid crystal display element changes from a low transmittance state to a high transmittance state.

Following this write pulse signal, AC voltage 2 is applied.

This voltage is smaller than Vth in the characteristics shown in Figure 1a.
A voltage greater than vb is applied to S, and the indication of L is also selected to be in the active state.

This voltage is not switched when S is in a high resistance state because only a voltage smaller than vth is applied to S, and therefore the voltage applied to the liquid crystal cannot produce an electro-optic effect.

When such a signal is applied, writing can be accomplished by Vs, and then the operating state of the switching element and the liquid crystal can be continuously maintained by the signal 2h.

Switching from the operating state to the non-operating state can be achieved by stopping these continuation signals or by applying an erase signal for a short time so that the voltage applied to S becomes equal to or less than vb.

At this time, the switching element becomes in a high resistance state again, so that even if the above-mentioned alternating current continuation signal is applied next time, the switching element does not operate, and at the same time, the display element also does not operate.

The transmittance at this time is low, resulting in the off state shown in FIG.

By continuously applying the sustain voltage in this way, the on or off state can be maintained arbitrarily and continuously in response to write and erase signals, thereby providing a memory effect.

Switching elements that can be used in the present invention include polymethyl acrylate as an organic thin film switching element;
Examples include polystyrene, polyethyl methacrylate, and polymethyl methacrylate.

Inorganic film switching elements include those known as amorphous semiconductors, such as chalcogen glass and metal oxide switching elements.

There are many examples of elements used for these, but so-called chalcogen-based substances include the three elements of sulfur/selenium/tellurium, three elements selected from two of these, and gallium arsenide, cadmium selenium sulfide, etc. There are also cadmium oxide, zinc sulfide, antimony silicide, etc.

As the metal oxide, silicon oxide, titanium oxide, niobium oxide, vanadium oxide, aluminum oxide, tantalum oxide, etc. are used, and combinations of these and doping agents for improving properties are used as necessary.

In addition, these materials are subjected to processes such as a forming process by temperature treatment and energization treatment, as necessary, in order to obtain the desired characteristics.

In addition, the electro-optical effects of the liquid crystal used in such driving include those displayed by optical scattering, changes in transmittance, changes in hue, etc., and various optical means such as reflection, transmission, and projection are used. be able to.

Various modes have been proposed for the electro-optic effect of liquid crystals, including dynamic scattering mode, twisted nematic mode, deformation off vertically aligned phase (DAP), guest host, and cholesteric nematic mode. It can be used in combination with the phase transition effect of mixed liquid crystals and other means of optically detecting the orientation of liquid crystals.

The present invention is extremely effective in that it enables a wide range of practical applications and the addition of a memory function to such various electro-optical effects.

[Brief explanation of the drawing]

Fig. 1a is a graph showing the voltage-current characteristics of the switching element used in the present invention, Fig. 1 is a circuit diagram for obtaining the graph of Fig. 1a, and Fig. 2 a = d is the basic circuit of the invention. 3 are diagrams showing the waveforms of the signals applied to the circuits of FIGS. 2a to 3d and the amount of light transmitted through the liquid crystal display element at that time.

Claims (1)

[Claims] 1. In a method for driving a liquid crystal display device having a liquid crystal display element, a threshold type switching element, and a resistor, the switching element is turned on by a pulse signal, and the switching element cannot be changed from an off state to an on state by itself. However, once the on state is obtained, the on state of the switching element is continuously maintained by an alternating current signal that can maintain the on state, and the liquid crystal display element is driven in accordance with the operating state of the switching element. A method for driving a liquid crystal display device characterized by: