JPH07281152A - Method and device for driving liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a driving method and device capable of performing a high contrast and multi-level display for a high speed responsiveness liquid crystal element. CONSTITUTION:Scanning signals led from an orthogonal normal matrix being held in selection periods t1, t2, t3, t4 and led from a non-orthogonal normal matrix consisting of a compensation period t' in each field period T and a data signal so as to compensate ununiformed portion of an effective voltage in a picture to the same gradation in the compensation period uniformly are impressed. Thus, a high speed response, high contrast and uniform gradation display is attained independently of a display pattern, and the multi-level display is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple matrix type liquid crystal driving method and driving device capable of high contrast and high speed response.

[0002]

2. Description of the Related Art A simple matrix liquid crystal display device has a plurality of data lines and scanning lines and liquid crystal pixels provided at intersections of the data lines and scanning lines, and a scanning signal is applied to the scanning lines. Then, the data signal is applied to the data line.
Typical high-multiplexable liquid crystal display modes used for such a simple matrix are STN and EC.
There is B (electric field control birefringence mode).

However, both of them have the drawback that the contrast and response speed are lowered when the number of divisions of the multiplex is increased. In particular, the contrast and the response speed are in a trade-off relationship, and improving one of them reduces the other. It has been clarified that this cause is due to "frame response". (Reference 1: Kaneko et al .. Proc.
EuroDisplay'90, p.100, 1990)

The conventional simple matrix method uses a single line scanning method, and the drawback of this method is that as the number of divisions increases, the electric energy applied to the liquid crystal pixels is concentrated in a short selection period. . Also STN
In such modes, the liquid crystal that basically responds with an effective voltage has the property of responding to a pulse. This property is further enhanced by using a liquid crystal material with a high response speed and selecting the cell formation conditions.

The "frame response" at issue here
Is energy concentration and ST by single line scanning
Due to the phenomenon based on the property of N, if an attempt is made to obtain a high-speed response with high division, the liquid crystal will respond to the selection pulse in which the energy is concentrated in each field, resulting in a significant loss of contrast. .

As a method of reducing this "frame response", "active driving method" (reference 2: TJ Sheffer et al.
al. SID 92 Digest, 228, 1992) and "Multiline scanning method (MLS method)" (Reference 3: S. Ihara et al. SID)
92 Digest, 232, 1992) has been proposed.

These methods are based on a similar principle already proposed, and have a period in which a plurality of scan lines are simultaneously selected in each field period, and a scan applied to a selected scan line. The signals have a selection potential, the scanning signals applied to the other scanning lines have a non-selection potential, and the data signals applied to the data lines are at the intersections with the scanning lines selected in each selection period. It has a potential based on pixel information of liquid crystal pixels.

The difference between Reference 2 and Reference 3 is that the former is for selecting all lines simultaneously, whereas the latter is for selecting partial lines. However, since the principles are the same, in the description of the present invention, they are collectively referred to as the MLS (multi-line scanning) method.

FIG. 2 shows an in-focus system (IF
It is a drive waveform of a conventional example of an MLS type matrix display device of all-row selection type manufactured by S). In FIG. 2, scanning signals r1, r2, r3, r4, r5, r6 applied to the row electrodes are shown.
And the data signal cm applied to the column signal is shown. In this conventional example, all the row electrodes R1, R2, R3, R
4, R5, R6 are selected and the scanning signals r1, r2, r
3, r4, r5, r6 are represented by a perfect non-diagonal orthogonal matrix.

PHM (Pulse Height Modulation) by IFS
The gradation display method of the method will be described with reference to FIG. The data signal is derived from the sum of the products of the scanning signal and the corresponding pixel information.

However, since an error in the effective voltage is generated by itself, the virtual scanning signal r7 supplied to the virtual row (R7) which does not actually exist is virtually considered and the virtual pixel (R
The virtual gradation information of 7) is calculated and the error on the effective voltage is compensated by adding this compensation signal to display the gradation. In this example, the calculated value of the virtual pixel information is 1.87 to compensate the error.

[0012]

As described above, there is a problem in the MLS driving method using the virtual row.

In the MLS driving method using the virtual row, it is necessary to calculate and continue to apply the signal within the field period in order to correct the error in the effective voltage. Therefore, it is necessary to continue calculating the correction signal using the virtual row.

Further, during the field period, in order to generate the compensation signal, it is necessary to calculate the virtual pixel information before calculating the data signal. Therefore, calculation of virtual pixel information requires a circuit capable of high-speed processing, resulting in high cost.

In order to solve such a problem, it is an object of the present invention to provide a driving method and a driving apparatus of the MLS system capable of multi-gradation display without calculating and applying a compensation signal within a field period. .

[0016]

In order to achieve the above object, the present invention is characterized by adopting the following means.

The liquid crystal element driving method has a plurality of data lines and scanning lines and liquid crystal pixels provided corresponding to the intersections of the data lines and scanning lines, and scanning signals are applied to the scanning lines. In a driving method of a liquid crystal display element using a multi-line scanning method in which a data signal is applied to a data line and all scanning lines are simultaneously selected, in each field period, the scanning signal is a selection period derived from an orthogonal normal matrix. And a compensation period of at least one or more times, and a scanning method in which scanning signals to be applied to the scanning lines are not orthogonal to each other in each field period.

As a preferable method of generating the data signal, a liquid crystal element provided on the same data line is displayed so as to uniformly compensate the nonuniformity of the effective voltage for the same gradation in the screen during the compensation period. There is a method of making decisions based on the sum of squares of the pixel information to be squared.

Further, in the liquid crystal element driving device, a means for generating a plurality of scanning line selection type scanning signals for simultaneously selecting a plurality of scanning lines based on a non-diagonal type orthogonal function, and application during a scanning signal compensation period. The pixel information to be displayed on the liquid crystal element provided on the same data line so as to uniformly compensate the non-uniformity of the effective voltage for the same gray level in the screen during the compensation period of the signal and the data signal. Is a driving device having a means for generating a data signal determined based on the sum of squares.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a signal waveform diagram used in this embodiment. However, here, for simplification of description, it is assumed that the total number of scanning lines is four, and that four scanning lines are simultaneously driven.

In the field period T, t1, t2, t
A selection period of 3, t4 and a compensation period of t'are provided, and the lengths of the individual periods of t1, t2, t3, t4 and t'are equally divided within the field period. r1, r2,
It has a + F or -F selection potential in the r3 and r4 selection periods, and has a + F potential in the compensation period.

The scanning signal potential in the selection period t1 in FIG.
F, the scanning signal potential in the selection period t2 is + F, the selection period t3
The scan signal r1 having the scan signal potential of + F, the scan signal potential of the selection period t4 is + F, and the scan signal potential of the compensation period t ′ is + F is represented as follows. Similarly, the scan signals r2, r3, and r4 shown in FIG. 1 can be expressed in the following manner in the same format.

As described above, the characteristic of the scanning signal of this embodiment is that the selection periods t1, t2, t3, and t4 have a completely non-diagonal orthogonal function and a compensation period t '.

Further, as shown in FIG. 1, the scanning electrodes R1,
Pixel information to be displayed on the liquid crystal display element provided at the intersections of R2, R3, R4 and the data electrode Cm are −1, − in order.
It is assumed that they are 0.5, 0 and 1.

The value that can be taken as the pixel information is a value of -1 or more and 1 or less. Here, the pixel information of −1 indicates that the pixel is turned on, and the pixel information of 1 indicates that the pixel remains unlit, and the pixel information indicates −1. Intermediate values of 1 represent a halftone.

The data signal applied from the data electrode is obtained as follows. First, the data signal potential in the selection period can be obtained by multiplying the scanning signal potential by the pixel information in each selection period to obtain the sum.

Selection periods t1, t2, t3, t of this embodiment
If the data signal of No. 4 obtained by the above method is expressed in the format showing the scanning signal r1, it can be described as follows. (T1, t2, t3, t4) cm = a × (−0.5F, −2.5F, 0.5F, −2.5F) where a is a proportional constant for maximizing the contrast, and its value is If the number of all scanning lines is N, then a = 1 / (N)
It can be ^calculated by ^1/2 . In this embodiment, since N = 4, a = 1/2 = 0.5.

With respect to the data signal in the compensation period t ′, if the sum of squares of pixel information on the same data line is S, the data signal potential in the compensation period t ′ is cm = a × F × (N) ^1/2 × (( N−S) ^1/2 ) −F .. In the present embodiment, the data signal voltage in the compensation period t ′ is cm = 0.3229F when calculated using the formula. However, this value is rounded off to the fifth decimal place.

When expressed in the format used for the data signal scanning signal r1 of this embodiment, it can be expressed as follows. Further, when the data signal cm is illustrated, it can be shown as the data signal cm in FIG.

By applying the scanning signal and the data signal obtained by the above method, a high speed response and a high contrast can be obtained.
A uniform gradation can be obtained.

As another embodiment, an example in which the total number of scanning lines is 8 and 8 lines are simultaneously selected and there are a plurality of compensation periods,
Description will be made with reference to FIG. FIG. 3 is a signal waveform diagram used in this embodiment. Needless to say, the number of scanning lines and the number of lines to be simultaneously selected are not limited to those described in this embodiment, and a larger number can be used.

In this embodiment, the field period T is t1,
It is divided into a selection period of t2, t3, t4, t5, t6, t7 and t8 and a compensation period of 1t 'and 2t'. However, the sum of the compensation periods of 1t ′ and 2t ′ is equal to one period of the selection period. Then, r1, r2, r3, r4, r5,
In the selection period of r6, r7, and r8, either + F or -F is selected, and in the compensation period, + F is selected.

The scanning signal potential in the selection period t1 in FIG.
F, the scanning signal potential in the selection period t2 is + F, the selection period t3
Is + F, the scanning signal potential in the selection period t4 is + F, the scanning signal potential in the compensation period 1t 'is + F, the scanning signal potential in the selection period t5 is + F, the scanning signal potential in the selection period t6 is + F, and the selection period is + F. The scanning signal r1 in which the scanning signal potential in t7 is + F, the scanning signal potential in the selection period t8 is + F, and the scanning signal potential in the compensation period 2t ′ is + F is represented as follows. (T1, t2, t3, t4, 1t ', t5, t6, t7, t8, 2t') r1 = (+ F, + F, + F, + F, + F, + F, + F, + F, + F, + F) Similarly, Each scan signal in FIG. 3 can be expressed as follows in the same format as r1. (T1, t2, t3, t4, 1t ', t5, t6, t7, t8, 2t') r2 = (+ F, + F, + F, + F, + F, -F, -F, -F, -F, + F) r3 = (+ F, + F, -F, -F, + F, -F, -F, + F, + F, + F) r4 = (+ F, + F, -F, -F, + F, + F, + F, -F,-) F, + F) r5 = (+ F, -F, -F, + F, + F, + F, -F, -F, + F, + F) r6 = (+ F, -F, -F, + F, + F, -F, + F) , + F, -F, + F) r7 = (+ F, -F, + F, -F, + F, -F, + F, -F, + F, + F) r8 = (+ F, -F, + F, -F, + F, + F, -F, + F, -F, + F)

Further, as shown in FIG. 1, the scanning electrodes R1,
The pixel information to be displayed on the liquid crystal display element provided at the intersections of R2, R3, R4, R5, R6, R7, R8 and the data electrode Cm are -1, 0.5, 0, 1, -0. 5,
It is assumed that they are 0, 0.5, and 1.

Selection periods t1, t2, t3, t4, t5, t6, t7 of the data signal voltage applied from the data electrode,
The voltage at t8 can be calculated as follows. (T1, t2, t3, t4, t5, t6, t7, t8) cm = (1 / (8) ^1/2 ) × (1.5F, −0.5F, 0.5F, −3.5F, − 0.5F, -0.5F, -1.5F, -3.5F)

Next, the voltages of the data signal voltage applied from the data electrode in the compensation periods 1t 'and 2t' are obtained.
As in the present embodiment, when there are a plurality of compensation periods, the data signal potential of the compensation period is also obtained by multiplying the formula by the reciprocal of the root of the ratio of the sum of the compensation periods and one of the selection periods. You can Here, if the total sum of the compensation period is s ′ and one of the selection periods is t, the data signal potential in the compensation period can be written as follows. cm = a × (1 / (t / s ′) ^1/2 ) × F × (N) ^1/2 × ((N−S) ^1/2 ) −F ... Formula

Using the formula, the compensation period 1 of the present embodiment
The data signal potentials at t ′ and 2t ′ are the same in both periods and are cm = 1.0616F. However, the potentials during the compensation periods 1t ′ and 2t ′ are values obtained by rounding the fifth decimal place.

In this embodiment, the data signals cm applied from the data electrodes are summarized in the format used for the scanning signal r1.
It can be described as follows. (T1, t2, t3, t4, 1t ', t5, t6, t7, t8, 2t') cm = (0.5303F, -0.1768F, 0.1768F, -1.2374F, 1.0616F, -0 .1768F, -0.1768F, -0.5303F, -1.2374F, 1.0616F) When this data signal cm is displayed, it can be shown as the data signal cm in FIG.

By applying the scanning signal and the data signal as described above, it is possible to display a uniform gradation with high contrast.

Further, in order to prevent the liquid crystal from being deteriorated by applying a DC voltage to the liquid crystal pixel, it is necessary to invert the polarities of the scanning signal potential and the data signal potential every compensation period and every field period.

FIG. 4 is a block diagram of a matrix liquid crystal display device using the present invention. The operation of the block diagram is controlled by the timing circuit 10, and when pixel information is input, it is stored in the buffer memory 5. The pixel information read from the buffer memory 5 and the scanning signal sent from the scanning signal generation circuit 4 are input to the data signal arithmetic circuit 6 to calculate the data signal. At the same time, the compensation signal calculation circuit 9 is used to calculate the compensation signal.

The calculation result is sent to the data signal buffer 7,
Next, the D / A converter 8 performs D / A conversion on the data signal.
Then, the scanning signal sent from the scanning signal generation circuit 4 is applied to the LCD panel 1 from the scanning line driver 2, and the data signal sent from the D / A converter 8 is applied to the LCD panel 1.

[0043]

EFFECT OF THE INVENTION While maintaining the effect of reducing the frame response, which is an advantage of the MLS method, by applying a data signal that eliminates the error in the effective voltage only during the compensation period, uniform gradation can be achieved without depending on the display pattern. Display is possible, and multi-gradation display is possible.

[Brief description of drawings]

FIG. 1 is a waveform diagram in an embodiment of a driving method of the present invention.

FIG. 2 is a waveform diagram in an example of a conventional MLS driving method.

FIG. 3 is a waveform chart in one embodiment of the driving method of the present invention.

FIG. 4 is a block diagram of an embodiment of a liquid crystal display device of the present invention.

[Explanation of symbols]

r1, r2, r3, r4, r5, r6, r7, r8
Scanning signal cm
Data signals t1, t2, t3, t4, t5, t6, t7, t8
Selection period t ', 1t', 2t '
Compensation period 1 LCD panel 2 Scan line driver 3 Data line driver 4 Scan signal generation circuit 5 Buffer memory 6 Data signal arithmetic circuit 7 Data signal buffer 8 D / A converter 9 Compensation signal arithmetic circuit 10 Timing circuit

Claims (3)

[Claims] 1. A plurality of data lines and scan lines, and liquid crystal pixels provided corresponding to the intersections of the data lines and scan lines, wherein a scan signal is applied to the scan lines and data is applied to the data lines. In a driving method of a matrix liquid crystal display device using a multi-line scanning method in which signals are applied and all scanning lines are simultaneously selected, a scanning signal is at least equal to a signal in a selection period derived from an orthogonal normal matrix in each field period. With one or more compensation periods, for each field period,
A method for driving a liquid crystal display device, wherein scanning signals to be applied to the respective scanning lines have scanning signals which are not orthogonal to each other. 2. In the compensation period, the nonuniformity of the effective voltage for the same gray level within the screen is uniformly compensated.
2. The method of driving a liquid crystal display element according to claim 1, further comprising a data signal determined based on a sum of squares of pixel information to be displayed on the liquid crystal element provided on the same data line. 3. A means for generating a plurality of scanning line selection type scanning signals for simultaneously selecting a plurality of scanning lines based on a non-diagonal type orthogonal function, and a means for generating a signal applied during a scanning signal compensation period. In order to evenly compensate for the non-uniformity of the effective voltage for the same gray level within the screen during the data signal compensation period, the sum of squares of the pixel information to be displayed on the liquid crystal elements provided on the same data line is also used. A driving device for a liquid crystal display element, comprising means for generating a data signal to be determined.