JPS5925229B2 - Driving method of liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving method for a liquid crystal display element having a matrix-facing electrode structure or a display element in which segments are connected in a matrix-facing manner, and particularly relates to a driving method that speeds up the brightness rise response time. Regarding the method.

In a liquid crystal display element having a matrix facing electrode structure, a driving method using line sequential scanning is generally used. this is,
The scanning electrodes constituting one side of the matrix are sequentially selected one by one, and in synchronization with this, the necessary signal electrodes on the other side are selected in a time-division manner and voltage is applied to the picture elements located at the intersections of the matrix. Among them, those that are turned on are selected in a time-division manner, and the average voltage during this period is used to obtain a display. Also,
Elements in which segments are connected in a matrix are also used in liquid crystal display devices for displaying numbers, and in this case, the same driving method as described above is used.

Here, as an example, a driving method called the 1/3 bias voltage averaging method was applied to a liquid crystal display element for displaying 4-digit numbers in which one character is composed of 7 segments and each digit has a decimal point. explain something FIG. 1 is a block diagram of a numeric display element.

Digit electrode A9B9C9D and connection wires a, b9c,
d, e, f, g) and segment electrodes connected by D and P face each other with a liquid crystal layer in between, forming a matrix. For a 4-digit numeric display like this example, typically
Line sequential scanning is performed using digit electrodes A-D as scan electrodes and leader lines a-f, D, and P as signal electrodes. Second
The figure is a state diagram explaining the 1/3 bias voltage averaging method, where VX and VY are the voltages applied to the scanning electrode and signal electrode, respectively, and VX-VY is the voltage applied to the picture element at the intersection of the matrix. show.

As shown in this figure, the picture element in the selected state, that is, the state where it is selected from both the signal electrode and the scanning electrode, has a
o voltage is applied, and in other states, the applied voltage is ±1/3Vo. FIG. 3 is a waveform diagram of a voltage actually applied to a picture element, where a indicates a picture element that changes from a non-lighting state to a lighting state, and "a" indicates a picture element that remains in a non-lighting state.

In this way, in the lit state, the selected state is time-divided (
In this case, the liquid crystal is excited by the average voltage during this period (time division using four scanning lines) to obtain a display. The problem with the conventional driving method described above is that there is a delay in the response of the brightness characteristics of the liquid crystal to changes in display content, making it impossible to provide a sharp display.

In particular, the delay in brightness rise response time at low temperatures becomes a problem. Until now, the static 5 drive method was
A method has been proposed to shorten the response time by applying a DC voltage higher than usual until the brightness is saturated when lighting a picture element. However, if such a method of changing the voltage is applied to the time-division driving method using the voltage averaging method described above, it becomes impossible to average the crosstalk voltage, resulting in uneven display. An object of the present invention is to provide a new driving method that shortens the response time to the rise in brightness of a liquid crystal without sacrificing the advantages of the conventional time-division driving method.

A feature of the present invention is that in the first stage, all picture elements are set to a selected state during the liquid crystal response delay time by inputting a signal notifying the change of display content, and in the second stage, the signal electrodes are time-divided while scanning the scanning electrodes sequentially. This is a two-step driving method in which picture elements to be turned on are brought into a selected state in a time-division manner by driving. That is, in the present invention, the rise in brightness of picture elements that have not been lit and will be lit next is accelerated by continuous selection voltage application to all picture elements, and the lighting state of picture elements is maintained by line-sequential time-division driving. It will be held at Examples of the present invention will be described below.

FIG. 4 is an equivalent circuit diagram of a matrix type display element.

A 4X4 matrix is shown here, with 3-1,
3-2, 3-3, 3-4 are scanning electrodes, 4-1, 4-2,
4-3 and 4-4 indicate signal electrodes. A liquid crystal cell 5 is connected to each intersection of these electrodes, and each becomes a picture element of a liquid crystal display element. Even in a liquid crystal display element in which segments are connected in a matrix as shown in FIG. 1, the equivalent circuit is similar to that shown in FIG. 4. In the case of FIG. 1, it is a 4×8 matrix, but the following explanation will be based on a 4×4 matrix. FIG. 5 shows a block diagram of a system for driving the matrix display element shown in FIG. 4.

Reference numeral 9 in FIG. 5 is a scanning signal generating circuit that generates a signal to sequentially scan the scanning electrodes 3-1 to 3-4. Further, 8 is a display signal generation circuit for selecting which of the picture elements Cll to C44 shown in FIG. emanate. In addition, from 8 onwards, a signal S indicating a change in the content is sent.
P is output. Reference numeral 10 denotes a hold signal generating circuit that generates a hold signal TP that is output for a certain period of time only when a signal SP notifying a change in display content is input.

Further, when this hold signal TP is not input, 11 outputs the selection signal from the display signal generation circuit 8 as it is,
When the hold signal TP is input, all selection signals are set to 11.
12 is a scanning signal hold circuit that similarly holds the scanning signal by inputting the hold signal TP. 6-
1 to 6-8 are drive circuits that generate voltages for driving each scan electrode based on selection signals AP5 to AP8 obtained through 11 and 12 and scan signals AP1 to AP4.

FIG. 6 is a waveform diagram of each part showing the operation of FIG.
4 shows an example in which only picture elements C and l in FIG. 4 are to be lit.

The scanning signals AP1 to AP4 are normally set to level 11' sequentially at a fixed period, but are held at level 01' while the signal TP is output for a fixed time Tb from time Ta. Selection signals AP5 to AP8 are also level 8 at the same time.
It is held at 1, so that all the picture elements are continuously selected during this period. After time t, selection signal A
Only the pixel P5 is set to level 61'' in synchronization with the scanning signal APel, so that only the picture element Cll is time-divisionally selected and turned on.

FIG. 7 is a circuit diagram of the hold signal generation rotation indicated by reference numeral 10 in FIG.
It consists of a K flip-flop 14, an AND gate 15, a counter 16, and an inverting gate 17.

Further, FIG. 8 is a waveform diagram of each part showing the operation of the circuit of FIG. 7. Here, the signal PA is a pulse signal sent from the scanning signal generation circuit 9 in FIG. 5 every time a scanning signal is generated for each scanning electrode, and the hold signal TP is a pulse signal sent from the scanning signal generation circuit 9 in FIG. It rises in synchronization with the rise of signal AP after input. The duration Tb of the signal TP is set by the count value of the counter 16. FIG. 9 is a circuit diagram of the drive circuits 6-1 to 6-8 in FIG. 5, which are composed of transistors 18, 19, 20, N0R gates 21, 22, 23, an inverting gate 24, and each resistor.

This drive circuit is for applying the 1/3 bias voltage averaging method, and the signal CP or C is applied according to the input of the scanning signals APl to AP4 or the selection signals AP5 to AP8.
Based on the input clock of P, VO, 2/3V0, 1/3V0
The drive signal VOU for each electrode is a combination of
Emits a T. FIG. 10 shows the applied voltages applied to each picture element according to the embodiment described above, where a is a picture element that is already in the lighting state, b is a picture element that is still in the non-lighting state, and c is a picture element that is in the non-lighting state. It shows the voltage applied to a picture element that changes from a non-lit state to a lit state.

Furthermore, Fig. 11 shows the voltage waveform applied to the picture element and the response waveform of the luminance of the picture element as it changes from the non-lighting state to the lighting state when using the conventional time-division single driving method. teeth,
3 shows the applied voltage waveform and the response waveform of the luminance of the picture element in this example. In this way, according to this embodiment, the time T
During period b, a voltage of ±VO is continuously applied, which serves as a pre-bias and shortens the brightness rise time T of the liquid crystal. However, as shown in FIG. 10, during this pre-bias period, the voltage of VO is applied even to picture elements that are not turned on. Therefore, by making the duration Tb of the hold signal TP set by the counter 16 in FIG. 7 equal to or less than the response delay time of the liquid crystal indicated by T in FIG. 12, unnecessary picture elements can be instantly removed. It is desirable to prevent it from lighting up. Although the embodiment of the present invention using the 1/3 bias voltage averaging method has been described above, the present invention can also be applied to other driving methods. Since the element does not turn on instantly, the response time for rising the brightness of the liquid crystal can be shortened.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a numeric display element, Fig. 2 is a voltage state diagram of the bias voltage averaging method, Fig. 3 is a voltage waveform diagram applied to the liquid crystal segment to explain the conventional time division driving method, and Fig. 4 is a diagram of the voltage applied to the liquid crystal segment.
The figure is an equivalent circuit diagram of a matrix display element used in an embodiment of the present invention, FIG. 5 is a block diagram of a system according to an embodiment of the present invention, FIG. 6 is a waveform diagram of each part of FIG. 5, and FIG. 5 is a circuit diagram of block 10, FIG. 8 is a signal waveform diagram of FIG. 7, FIG. 9 is a circuit diagram of blocks 6-1 to 6-8 of FIG. 5, and FIG. FIG. 11 is a diagram of the voltage waveforms applied to each liquid crystal segment according to the embodiment. FIG. 11 is a diagram of response waveforms of the liquid crystal when driven by a conventional driving method. FIG. 12 is a diagram of response waveforms of the liquid crystal according to the embodiment of the present invention. Explanation of symbols, 3-1 to 3-4...Scanning electrode, 4
-1 to 4-4... Signal electrode, 5... Picture element, 6-1 to 6-8... Drive circuit, 8...
...Display signal generation circuit, 9...Scanning signal generation circuit, 10...Hold signal generation circuit, 11...
...Display signal hold circuit, 12...Scanning signal hold circuit.

Claims (1)

[Claims] 1. In a device that drives a liquid crystal display element in which a plurality of picture elements are formed at the intersections of scanning electrodes and signal electrodes, in the first step, all picture elements are controlled by a signal that notifies a change in display content to a time that is less than or equal to the response delay time of the liquid crystal. In the second step, necessary signal electrodes are driven in a time-division manner in synchronization with the line-sequential scanning of the scanning electrodes, thereby bringing the picture elements to be lit in a time-divisionally selected state. A method for driving a liquid crystal display element.