JP2000098334A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality display picture with a simple circuit constitution by making a dual scan system of a two pieces selection system realizable. SOLUTION: A common signal CU is imparted successively to a common electrode of a piece each of an upper picture of a liquid crystal panel 1 by a common driver 5U, and a common signal CL is imparted successively to the common electrode of a piece each of a lower picture by the common driver 5L. The display data for the upper picture are held by a first line latch 12a, and the display data for the lower picture are held by a second line latch 12b to be imparted to an operation circuit 13. In the operation circuit 13, exclusive OR is operated by both display data and normal orthogonal function codes of both common signals CU and CL, and a voltage level imparted to a segment electrode 3 is decided. Dual scan operation becomes possible with a simple drive circuit constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple matrix for sequentially selecting a common electrode, applying a segment voltage synchronized to the selection of the common electrode to a segment electrode, and applying a drive voltage to a liquid crystal material at the intersection of the two electrodes. In particular, the present invention relates to a liquid crystal display device in which a liquid crystal panel is divided into two screens and a common electrode is simultaneously selected on both screens.

[0002]

2. Description of the Related Art As a driving method of a liquid crystal display device, in a single scan system, a screen of a liquid crystal panel is taken as one screen, and a common electrode is sequentially selected in this one screen, and a segment voltage is applied to each segment electrode in synchronization with the selection. Is given.

In the dual scan system, the liquid crystal panel is divided into an upper half first screen and a lower half second screen, and a common electrode is simultaneously selected on the first screen and the second screen. In this case, a segment-side drive circuit for the first screen and a segment-side drive circuit for the second screen are provided. Then, the common electrode is sequentially selected in each screen, and in synchronization with this, the segment voltage is applied to each segment electrode in both screens from both segment side drive circuits.

As a selection method for applying a segment voltage in synchronization with selection of a common electrode, a single selection drive method and a multiple selection drive method (MLA: Multi Line Address) are used.
ing). In the single-selection driving method, one common electrode is selected in the screen, and a segment voltage is applied to the selected one common electrode from the segment-side drive circuit. In the multiple selection drive system, a plurality of common electrodes such as three or five are simultaneously selected in a screen, and the common electrodes are sequentially selected in units of three or five, and the segment electrodes are synchronized with the common electrodes. To the segment voltage.

In the multiple selection driving method, an operation of integrating an exclusive OR is performed based on a normal orthogonal function of a common signal applied to a common electrode and data applied to each pixel. Thus, the segment voltage level applied to each segment electrode is set.

[0006]

First, in the single scan system, the configuration of the segment side drive circuit can be simplified, and the cost of the entire apparatus can be reduced. But,
Since the driving duty is high and crosstalk between pixels easily occurs, the contrast is apt to deteriorate. In order to prevent the crosstalk, there is a method in which a correction voltage is applied to the segment side in accordance with a change in a signal applied to the segment electrode. However, there is a limit in improving the performance.

In the dual scan system, the driving duty can be realized by half of the single scan system.
Crosstalk can be improved and contrast can be improved.
However, since the segment-side drive circuits corresponding to the segment electrodes of both the first screen and the second screen are separately required, the circuit configuration is complicated and the cost is high.

On the other hand, the multiple selection method is superior in terms of contrast and response speed. However, the multiple selection method is calculated by using a normal orthogonal function of a common signal and data corresponding to each of the selected common electrodes. Since the segment voltage level is set, the number of common electrodes to be selected is three or five.
When the number is increased as in a book, more memory is required to hold the data on the segment side. Also, if the number of common electrodes to be selected at the same time is N, the number of common electrodes must be set to N + 1. If the number of common electrodes to be selected at the same time increases to three or more, the segment voltage level may be set finely. Will be needed.

The present invention solves the above-mentioned conventional problems. By applying a dual-selection drive system (MLA) to the dual scan system, the number of memories in the segment side drive circuit can be minimized. It is an object of the present invention to provide a liquid crystal display device capable of simplifying the configuration of a drive circuit and obtaining a high-quality display screen in which crosstalk is suppressed with a low drive duty.

Further, the present invention provides a conventional one-line selection method.
A liquid crystal display capable of obtaining a high-quality display screen with a simple circuit configuration by realizing a dual-selection dual-scan method using a segment-side drive circuit having a stage latch circuit. It is intended to provide a device.

[0011]

According to the present invention, there is provided a liquid crystal display device having a plurality of common electrodes and a plurality of segment electrodes, wherein a drive voltage is applied to a liquid crystal material at an intersection of the common electrode and the segment electrodes. Panel and the liquid crystal panel are divided into a first screen and a second screen for each predetermined number of common electrodes, and the common electrode of the first screen and the common electrode of the second screen are simultaneously selected one by one. And a common electrode driving means for sequentially selecting a common electrode for each screen,
First data holding means for holding data to be given to the first screen, second data holding means for holding data to be given to the second screen, data to be given to the first screen, and second data holding means. A segment voltage level applied to each segment electrode based on data applied to the screen, a common signal applied to the common electrode selected on the first screen, and a common signal applied to the common electrode selected on the second screen. And a segment driver for applying a segment voltage to each segment electrode based on the operation result of the operation circuit.

In the present invention, the data for the first screen and the data for the second screen are held in each data holding means by using two data holding means such as two line latches. A drive voltage is applied to each segment electrode based on an operation of the common signal with a normal orthogonal function.

As described above, two lines are selected (two lines are selected) by selecting one common electrode on each of the first screen and the second screen.
Since the MLA driving method is used, the voltage level applied to the segment electrodes may be three levels, and low-power driving is possible. Further, since the dual scan method is used in which the common electrode is simultaneously selected on two screens, the drive duty is low, crosstalk can be improved, and a high quality display screen can be obtained.

Further, as the segment side driving circuit, 2
It can be composed of data holding means such as two line latches, an arithmetic circuit, and one segment driver. Separate segment drivers and the like are provided for each of the upper and lower screens as in the conventional dual scan drive There is no need, the structure can be simplified, and it can be manufactured at low cost. Further, as the first data holding means and the second data holding means, it is possible to use a line latch of a conventional segment-side drive circuit for a single-select driving system using a correction voltage.

In the above, the voltage level applied to the segment electrodes can be set as follows. The normal orthogonal functions of the common signal applied to the common electrode selected on the first screen and the common signal applied to the common electrode selected on the second screen are A1 and A2, respectively. When the data and the data for the second screen are D1 and D2, respectively, the segment voltage level VLx (x
= 1, 2, 3,...) Is represented by the above equation (1).

The arithmetic circuit at this time can be used as an arithmetic circuit for comparing the current data with the previous data and applying the correction voltage when the correction voltage is applied by the single-select driving method. .

That is, in the present invention, when the liquid crystal panel is driven as one screen, the common electrode driving means sequentially selects the common electrodes one by one over the entire area of the liquid crystal panel and gives a common signal. One data holding unit holds data corresponding to the selected common electrode, and the other data holding unit holds data corresponding to the common electrode before the data. Thus, a correction signal is given to the arithmetic circuit.

As described above, according to the present invention, the dual-selection driving method in which the common electrodes are simultaneously selected one by one on the upper and lower screens and the driving by the dual scan method, and the common electrodes are sequentially selected one by one as one screen. And the single-scan driving method and the single-scan driving method can be performed.
The liquid crystal display device of the present invention can be applied to both of the dual scan type interfaces.

In this case, the first data holding means and the second data holding means are provided in accordance with a switching signal indicating whether the liquid crystal panel is divided into two screens or the whole is used as one screen. If the latch control means for switching the data to be held is provided, it can be easily applied to any interface by a simple switching operation.

[0020]

FIG. 1 is a block diagram showing the structure of a liquid crystal display device according to the present invention. (Structure of Liquid Crystal Panel) The liquid crystal panel 1 used in this liquid crystal display device is of a simple matrix type, and an STN liquid crystal material is sealed between glass substrates. One of the glass substrates is provided with 480 common electrodes 2U and 2L arranged at a predetermined pitch in the vertical direction in FIG. 1, and the other glass substrate is provided with 480 common electrodes 2U and 2L arranged at a predetermined pitch in the horizontal direction.
Forty segment electrodes 3 are formed, and the common electrode 2
640 × 4 at the intersection of U, 2L and segment electrode 3
80 dots of pixels are formed.

The liquid crystal display device of the present invention is capable of dual scan driving. In this case, an area having an upper group of 240 common electrodes 2U is a first screen (upper screen), and a lower 240 common electrodes is provided. The area having the 2L group is the second screen (lower screen). The 640 segment electrodes 3 extend in common over the first screen and the second screen.

In this liquid crystal display device, a two-selection drive system (MLA) in which a common electrode is selected one by one on the upper and lower screens and a common electrode is sequentially selected on each of the upper and lower screens by the M / N switching signal S. Drive) and dual scan drive, and a single selection drive system (N drive) in which the entire screen is selected as one screen and the common electrodes are sequentially selected one by one from 2U side to 2L side and single scan drive. it can. In FIG. 1, the M / N switching signal S is provided from a switching control unit (not shown). (Configuration of Common-side Drive Circuit) The common-side drive circuit includes a common data processing unit 4. In the common data processing unit 4, a common signal is generated based on the frame data FD, a scanning clock CK is generated based on the load signal RD, and the common signal and the scanning clock CK are generated.
Are provided to the common drivers 5U and 5L.

When the M / N switching signal S is switched to the dual selection driving method (MLA driving), the common data processing section 4 supplies a common signal CU given to the common electrode 2U of the first screen, A common signal CL applied to the common electrode 2L of the second screen is formed, and a common driver 5U for the upper screen and a common driver 5U for the lower screen are respectively formed.
L. In the common driver 5U, in synchronization with the timing determined by the scanning clock CK,
The common signal CU is sequentially applied to the common electrodes 2U of the first screen one by one. Similarly, in the common driver 5L,
The common signal CL is applied to the common electrode 2L of the second screen in synchronization with the timing determined by the scanning clock CK.
The books are given in order.

As a result, one common electrode 2U of the first screen and one common electrode 2L of the second screen are selected at the same time, and the common electrode 2U of the first screen and the second screen are selected. 2U and 2L are sequentially selected one by one. The uppermost common electrode 2U of the first screen of the liquid crystal panel is the first common electrode, the lowermost common electrode of the first screen is the 240th common electrode, and the uppermost common electrode of the second screen is the 241st common electrode. The electrode and the lowermost common electrode of the second screen are referred to as a 480th common electrode. In the two-selection driving method, the common electrode is selected in such a manner that the first common electrode and the 241st common electrode are selected at the same time, and the common signals CU and CL are applied at the same time. The electrodes are simultaneously selected to provide common signals CU and CL. This selection is performed in order, and the 240th common electrode and the 48th common electrode
It is one frame period until the 0 common electrode is selected.

In the next frame period, the next common signals CU and CL generated by the common data processing unit 4
Are simultaneously applied to the first common electrode and the 241st common electrode, and the same common signal is sequentially applied to each common electrode.

When the liquid crystal display device is driven by the single-selection driving method (N driving) by the M / N switching signal S, the common data processing unit 4 causes the common signal processing unit 4 to output the common signal every frame period. Is generated. Then, the common drivers 5U and 5L sequentially apply a common signal to one common electrode from the first common electrode to the 480th common electrode. (Structure of the segment side drive circuit) The shift register 11 is provided in the segment side drive circuit. When this liquid crystal display device is driven by the dual selection drive system (MLA drive), the upper 4 bits are used as display data UD0 to UD3 for the first screen (upper screen) from the dual scan system interface, and The lower 4 bits are given to the shift register 11 as display data LD0 to LD3 for the second screen (lower screen).

The latch circuit 12 is provided with a first line latch 12a serving as first data holding means and a second line latch 12b serving as second data holding means. And 12b are controlled by a latch controller 16 which is a latch control means.

Display data is sequentially read into the shift register 11 and shifted. When 680 bits are read, the display data is sent to the latch circuit 12.

When the M / N switching signal S is switched to the M drive and driven by the two-select driving method, the 4-bit display data UD0 to UD3 for the first screen sent from the interface are shifted by the shift register. 11 is read 160 times, and the 4-bit display data LD0 to LD0 to
LD3 is also read into the shift register 11 160 times.
One-bit display data is data given to one segment electrode 3. The display data for the first screen of 4 bits × 160 = 640 bits is sent from the shift register 11 to the first line latch 12a, held therein,
, The display data for the second screen of 4 bits × 160 = 640 bits is sent and held.

When the M / N switching signal S is switched to N drive and driven by the single-line drive system, the display data ND0 to ND are output from the single scan system interface.
D7 is read into the shift register 11, the display data is read into the shift register 80 80 times, and the 640-bit display data is sent to the first line latch 12a. In this case, the second line latch 12b holds the previous display data for 640 bits.

The latch controller 16 has a load signal R
The display data held in the latch circuit 12 is applied to the arithmetic circuit 13 at the timing when D is applied and set by the load signal RD. In the case of the two-line selection driving, the upper screen 1D held in the first line latch 12a is used.
The 640-bit display data corresponding to the scanning line and the 640-bit display data corresponding to one scanning line for the lower screen held in the second line latch 12b are supplied to the arithmetic circuit 13 together.

In the case of the double selection drive (M drive), the arithmetic circuit 13 is supplied with a normal orthogonal function code of the common signal CU for the first screen and the common signal CL for the second screen. In the circuit, an exclusive OR (EX-OR) is calculated with the normal orthogonal function codes of the common signals CU and CL, the display data for the upper screen, and the display data for the lower screen. This operation is performed for each of the 640 bits, that is, for each segment electrode 3, and the operation result is held in the final latch circuit 14. And load pulse LP
Is given to the segment driver 15 based on

The operation result sets the segment voltage level applied to each segment electrode 3.
The segment driver 15 is supplied with a three-stage voltage VLCD, and the segment voltage is simultaneously applied to the 640 segment electrodes 3 based on the calculation result.

In the case of one-line selection drive (N drive), 640-bit display data corresponding to one scanning line is held in the first line latch 12a, and the previous display data is stored in the second line latch 12b. When the display data of the line latches 12a and 12b is sent to the arithmetic circuit 13, the arithmetic circuit 13 compares the two display data. It is compared whether the display data corresponding to each segment electrode and the display data before it are the same or different. If both display data are the same, the arithmetic circuit 1
The display data is corrected by the correction signal given to the display device 3. When the corrected display data is supplied from the final latch circuit 14 to the segment driver 15, the corrected segment voltage is set in the segment driver 15, and is supplied to each segment electrode 3 at the same time. (Two-selection drive: M drive) In the two-selection drive, the common electrodes are simultaneously selected one by one in the first screen and the second screen, and the common electrodes are sequentially selected one by one in both screens. Go. When the common signal CU for the upper screen is given to the first common electrode, the common signal CL for the lower screen is given to the 241st common electrode. By sequential selection, common signal C
One frame period is from when U is applied to the 240th common electrode and the common signal CL is applied to the 480th common electrode.

The normal orthogonal function codes of the common signals CU and CL are the same during one frame period, and the same function code of the common signal CU is applied from the first common electrode to the 240th common electrode from the 241st common electrode to the 480th common electrode. The same function code of the common signal CL is given to the common electrode.
The common signals CU and CL are updated every frame period based on a predetermined normal orthogonal function code.

This normal orthogonal function code can be set arbitrarily. In FIG. 2, the normal orthogonal function code of the upper screen common electrode CU is represented by A1, and the normal orthogonal function code of the lower screen common electrode CL is represented by A2. ing. In FIG. 2, the normal orthogonal function code A1 is (1) (1) every frame period.
(1) (0) and normal orthogonal function code A2 are changed every frame period as (1) (0) (1) (1), and these normal orthogonal function codes A1 and A2 change in four frame periods. It is repeated every time. Note that (1) means that the voltage of the common signal applied to the common electrode is a predetermined high level, and (0) means that the voltage is a predetermined low level.

As shown in FIG. 2, the normal orthogonal function code A1
, 1 → 1 → 1 → 0 in 4 frames, and the normal orthogonal function code A2 in synchronization with 1 → 1 → 1 → 0 in 4 frames.
By changing from 0 → 1 → 1, it is possible to eliminate the frequency difference between the driving frequency of the upper screen and the driving frequency of the lower screen, and to prevent a decrease in display quality.

On the other hand, on the segment side, display data corresponding to the pixel on the common electrode selected on the upper side is held in the first line latch 12a for 640 segment electrodes, and the common line selected on the lower screen is held. Display data corresponding to pixels on the electrodes is held for 640 segment electrodes. These two display data are given to the arithmetic circuit 13, and the display data for the upper screen and the display data for the lower screen,
With the normal orthogonal function code of the common signals CU and CL,
The exclusive OR operation is performed for each segment electrode.

In FIG. 2, D1 represents display data for turning on, turning on, and turning off the pixels on the common electrode on the upper screen selected at a certain point in time from the left. The display data D1 is (1) in the order of the segment electrodes (i), (ii), and (iii).
(1) (0). At the same time, display data for setting the pixels on the common electrode of the lower screen to be non-lit, lit, and non-lit from the left is indicated by D2. This display data D2
Are (0), (1), and (0) in the order of the segment electrodes (i), (ii), and (iii).

The arithmetic circuit 13 performs the arithmetic operation shown in Expression 1. (+) In Expression 1 is exclusive OR (EX-OR)
It is.

In FIG. 2, the normal orthogonal function codes of the common signals simultaneously applied to the two common electrodes on the upper and lower screens in the first frame are A1 = 1 and A2 = 1, and the segment electrode (i) is selected. The display data corresponding to the pixel at the intersection with the common electrode is D1 = 1 and D2 = 0. Accordingly, in the first frame, the segment voltage level VL1 applied to the segment electrode (i) is the exclusive OR of A1 = 1 and D1 = 1, and A2 = 1 and D2 = 0.
VL1 =
It is one. FIG. 2 lists the segment electrode level VLx given to each segment electrode (i) (ii) (iii) for each frame. (Single selection drive: N drive) In the single selection drive, the display data for one scan held in the first line latch 12a and the previous display data held in the second line latch 12b are used. Are compared for equality. When the two display data are the same, the correction value is added by the arithmetic circuit 13 to correct the segment electrodes provided to each segment electrode 3.

[0042]

As described above, according to the present invention, only two rows of data holding means such as line latches are provided, and two-row selection drive can be performed by dual scanning. Therefore, the circuit configuration can be simplified. Further, the two columns of data holding means can also serve as a conventional two-stage line latch for selective driving of one line, and can constitute the liquid crystal display device of the present invention without largely changing a conventional driving circuit. It is also possible to connect and use both interfaces for dual scan and single scan.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a liquid crystal display device of the present invention;

FIG. 2 is an explanatory diagram of the operation of two-line selection driving,

[Explanation of symbols]

 Reference Signs List 1 liquid crystal panel 2U upper screen common electrode 2L lower screen common electrode 3 segment electrode 4 common data processing unit 5U upper screen common driver 5L lower screen common driver 11 shift register 12 latch circuit 12a first line latch (first 12b Second line latch (second data holding means) 13 Arithmetic circuit 14 Final latch circuit 15 Segment driver 16 Latch controller CU Common signal for upper screen CL Common signal for lower screen A1 Common signal CU Normal orthogonal function code of A2 Normal orthogonal function code of common signal CL UD0-UD3 Display data for upper screen LD0-LD3 Display data for lower screen

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Tokita 1-7 Yukitani Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Yoshifumi Masmoto 1-7 Yukitani-Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. F-term (reference) 2H093 NC18 NC22 NC26 NC28 ND04 ND15 ND49 ND54 NF13 5C006 AF44 AF46 BB12 BB14 BC03 BF03 BF04 BF05 BF16 BF26 BF28 FA41 FA51 FA54

Claims (4)

[Claims] A liquid crystal panel having a plurality of common electrodes and a plurality of segment electrodes, wherein a driving voltage is applied to a liquid crystal material at a crossing point of the common electrodes and the segment electrodes; Each of which is divided into a first screen and a second screen, the common electrode of the first screen and the common electrode of the second screen are simultaneously selected one by one, and the common electrode is sequentially selected for each screen. Common electrode driving means; first data holding means for holding data to be provided to the first screen; second data holding means for holding data to be provided to the second screen; Data to be provided, data to be provided to the second screen, a common signal to be provided to the common electrode selected in the first screen, and a common signal to be provided to the common electrode selected in the second screen. A liquid crystal comprising: a calculation circuit that calculates a segment voltage level to be applied to each segment electrode based on a signal; and a segment driver that applies a segment voltage to each segment electrode based on a calculation result of the calculation circuit. Display device. 2. The normal orthogonal functions of the common signal applied to the common electrode selected on the first screen and the common signal applied to the common electrode selected on the second screen are A1 and A2, respectively. When the data for the first screen and the data for the second screen are D1 and D2, respectively, the segment voltage levels VLx (x = 1, 2, 3,...) Given to the respective segment electrodes are as follows. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is represented by the following equation (1). (Equation 1) However, (+) in the expression 1 is an exclusive OR. 3. When the liquid crystal panel is driven as one screen, the common electrode driving means sequentially selects one common electrode at a time over the entire area of the liquid crystal panel and applies a common signal to the common electrode. The data corresponding to the selected common electrode is stored in the means, and the data corresponding to the common electrode before the data is stored in the other data holding means. 3. The liquid crystal display device according to claim 1, wherein a correction signal is provided. 4. The first data holding means and the second data holding means according to a switching signal for switching between using the liquid crystal panel on two screens or using the whole as one screen. 4. A liquid crystal display device according to claim 3, further comprising a latch control means for switching data to be held.