JPH0337622A - Driving method for liquid crystal panel - Google Patents

Abstract

PURPOSE:To prevent the occurrence of flicker accompanied with reduction of a frame frequency at the time of increasing the number of gradations by distributing a selected field to two or more time areas to display gradations. CONSTITUTION:One frame consists of plural fields, and the number of selected fields is changed to change the duty of the voltage impressed to a liquid crystal cell and the gradation is displayed. In this case, one frame consists of fields whose number (N+alpha) is larger than a number N of gradations except the black level, and all selected field in each gradation are not continuous with respect to time and are distributed to two or more time areas to display the gradation. Consequently, the number of fields is larger than the number of gradations, and two discontinuous fields are selected in one frame in the case of a gradation level 1 following the black level. Thus, the frequency of selected fields is prevented from being increased to coincide with the frequency of one frame, and the occurrence of flicker is reduced.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for driving a simple matrix type liquid crystal panel using a frame modulation method, the present invention aims to prevent the occurrence of flicker due to a decrease in frame frequency when the number of gradations is increased. One frame is composed of the number of fields N+α which is greater than the number of gradations N except for the black level, and the selected field at each gradation is divided into two or more time domains without making all the selected fields temporally consecutive. A method for driving a liquid crystal panel, characterized in that gradation is displayed in a dispersed manner.

[Industrial application field]

The present invention relates to a method for driving a liquid crystal panel, and more particularly to a method for driving a simple matrix type liquid crystal panel using a frame modulation method.

Display devices using simple matrix liquid crystal panels have a simple structure, low price, and low power consumption.
In recent years, they have come to be widely used as display devices for Japanese document creation devices (word processors), laptop-type personal computers, and the like. and,
Display panels with a large display capacity of 640 x 400 dots are beginning to be adopted. Also,
On the other hand, studies are underway to further improve functionality such as colorization and gradation display.

However, if the number of gradations of the liquid crystal panel is increased in a simple matrix type liquid crystal display device, flicker occurs due to a decrease in frame frequency, and a countermeasure against this problem is desired.

[Conventional technology]

Figure 5 shows a frame modulation method in which one frame is made up of multiple fields in a simple matrix type liquid crystal panel, and the duty of the voltage applied to the liquid crystal cell is changed by thinning out the number of selected fields to display gradation. FIG. This figure shows one frame (10 Fl
A conventional gradation display method is shown in which 8 levels of gradation are displayed by dividing z) into seven fields. Note that when all seven fields are selected ("gradation level 7"), the level is white, and when none of the seven fields are selected ("gradation level OJ"), the level is black.

As can be seen from Figure 5, conventionally all fields of one frame are selected when the gradation level is 7, and every time the gradation level decreases to 6.5, etc., the last field of one frame is selected. I canceled the selection of fields one by one and @ controlled the number of fields to be selected. Therefore, at "gradation level 3", control is performed such that only the first three fields out of seven fields in one frame are selected.

[Problem to be solved by the invention]

However, when displaying gradations on the liquid crystal panel of a simple matrix type liquid crystal display device using the conventional method as shown in FIG. There is a problem in that the frequency of the selected field matches the frequency of one frame, causing flicker. For example, as shown in Figure 5, the field frequency is 7.
In the case of 0 Hz, a 10 Hz flicker that matches the frame frequency will occur.

Further, as a result of research conducted by the present inventors, it has been found that the above-mentioned flicker becomes more visible on the liquid crystal panel when selection fields are arranged sequentially in time.

The purpose of the present invention is to solve the problems when performing gradation display on the conventional simple IJ type liquid crystal panel,
An object of the present invention is to provide a method for driving a liquid crystal panel that can reduce the generation of printing force visually recognized on the display panel and perform gradation display with excellent display quality.

[Means to solve the problem]

A method for driving a liquid crystal panel of the present invention that solves the above object is as follows:
One frame consists of multiple fields, and the black level is controlled by a frame modulation method that displays gradations by changing the duty of the voltage applied to the liquid crystal cell by changing the number of selected fields. The number of fields (N + α
) constitutes one frame, and the selected field at each gradation is displayed in gradation by distributing the selected field into two or more time regions, without making all the selected fields temporally continuous. It is characterized by:

[Effect]

According to the liquid crystal panel driving method of the present invention, the number of fields is greater than the number of gradations, and at "gradation level 1" which is the next gradation level after the black level, two non-consecutive fields are selected within one frame. Therefore, the frequency of the selected field increases and no longer matches the frequency of one frame, reducing the occurrence of flicker. Furthermore, at other gradation levels, the fields selected in one frame are not consecutive, so even if flicker occurs, it becomes difficult to see.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the configuration of a simple matrix type liquid crystal display device to which the liquid crystal panel driving method of the present invention is applied. In the figure, 1 is a simple matrix type liquid crystal display panel, 2
3 is a scan driver that drives a plurality of electrodes extending in the horizontal direction of the display panel 1; and 3 is a data driver that drives a plurality of electrodes that extend in the vertical direction of the display panel 1. Also,
Reference numeral 4 denotes a drive circuit that provides signals to the aforementioned scan driver 2 and data driver 3, and in this embodiment is divided into a gradation data generation section 41 and a timing generation section 42. A data signal from a host system 5 such as a personal computer is input to the gradation data generation section 41, and a horizontal synchronization signal, a vertical synchronization signal, and a clock signal from the host system 5 such as a personal computer are input to the timing generation circuit 42. etc., and control signals are input.

FIG. 2 shows a schematic configuration of the gradation generating section 41 of FIG. 1 when 8 gradation display is performed in 9 fields. This gradation generation section 41 includes a gradation generation circuit 411 to which gradation data from the host system and the counter output of the number of fields (1 to 9), which are nine in one frame, are input; There is an AND circuit 412 in which the output and display data are input manually.

The gradation generation circuit 411 has built-in field selection data in the form of a table in a ROM or the like that determines which field to select and output in one frame according to the input gradation data. Then, the output of the gradation generation circuit 411 becomes a high level 6H'', and only at this time, the display data is outputted from the AND circuit 412 as display data with gradation.

FIG. 3 shows an example of data in the ROM built in the gradation generating circuit 411 when displaying 8 gradations in 9 fields. As shown in this figure, the ROM stores data on which field to select in one frame consisting of 9 fields according to the input 8-step gradation level. The part is at a high level "I(". Therefore, for example, when a signal indicating "grayscale level 7" is input to the grayscale generation circuit 411, all fields are selected and "grayscale level 3" is input. When a signal indicating "gradation level 1" is input, the 1st, 4th, 6th, and 7th fields are selected, and when "gradation level 1" is input, the 1st and 5th fields are selected,
The output of the gradation generating circuit 411 becomes high level "H" only for the time of the selected field.

FIG. 4 is a diagram illustrating control of an embodiment of the method of the present invention. When displaying 8 levels of gradation, 9 fields are taken as one frame, and "gradation level 6" and below are r gradation levels. The number of fields is "level + 1", and the fields selected for each gradation are distributed and arranged so as not to be temporally continuous as much as possible. Note that the method of dispersion is not limited to this embodiment. Therefore, 1
If the field frequency is 70Hz, which is the same as before, 9
In this example, where one frame is made up of fields,
The frequency of the l frame is 70/9Hz, which is the frequency of the field selected at "gradation level 1", i.e.
The flicker frequency is 2 x (70/9)Hz ('
+15.61 (z), which is about 1 of the 10Hz of the conventional technology.
．． It can be multiplied by 5 times. As a result, flicker can be reduced compared to the conventional method.

In this way, by increasing the number of fields in one frame more than the number of gradations, the degree of flicker reduction increases.

Furthermore, as mentioned above, "gradation level 6" and below are composed of the number of fields of r gradation level + 11, and the fields selected at each gradation are distributed and arranged so that they are not temporally consecutive. , since the selection fields are not arranged temporally consecutively, the flicker that occurs at "gradation level 1" is less noticeable.

In the above embodiment, the case of 8 gradations was explained, but in the case of higher gradations, for example, 166 gradations, the same effect can be obtained by configuring one frame with 17 fields or more. .

〔Effect of the invention〕

As explained above, according to the liquid crystal panel driving method of the present invention, it is possible to realize a gradation display with excellent display quality and less flicker. It has the advantage that gradation display can be easily realized, which greatly contributes to improving the usability.

[Brief explanation of drawings]

FIG. 1 shows the constituent countries of a liquid crystal display device to which the liquid crystal panel driving method of the present invention is applied, and FIG. 2 shows a schematic configuration diagram of the gradation generating section in FIG. 1 when 8 gradation display is performed in 9 fields. Figure 3 is a waveform diagram showing an example of data in the ROM built into the gradation generation circuit of Figure 2 when 8 gradations are displayed in 9 fields, and Figure 4 is a waveform diagram showing an example of data in the ROM built into the gradation generation circuit in Figure 2 when 8 gradations are displayed in 9 fields. Explanatory diagram illustrating the method of driving a liquid crystal panel of the present invention when performing
The figure is an explanatory diagram of control for conventional 8-gradation display. l...Liquid crystal display panel, 2...scan driver, 3.
... Data driver, 4... Drive circuit, 5... Host system, 41... Gradation data generation section, 42... Tying generation section, 411... Gradation generation circuit, 412.
...AND circuit.

Claims (1)

[Claims] Driving a simple matrix liquid crystal panel using a frame modulation method in which one frame is composed of a plurality of fields, and by changing the number of selected fields, the duty of the voltage applied to the liquid crystal cell is changed to display gradation. The number of fields (N) is greater than the number of tones (N) excluding the black level.
N+α) constitutes one frame, and the selected fields at each gradation are displayed in gradations by distributing the selected fields into two or more time regions, without making all the selected fields temporally continuous. A method for driving a liquid crystal panel characterized by the following.