JPH1062743A - Liquid crystal display device and driving circuit therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid display device and a driving circuit therefor permitting to remove crosstalk (an after-image extending from a line displayed) from screen. SOLUTION: V1 is applied to a common electrode selected during a positive frame period, while it is applied to a segment electrode in which ON is written, during a negative frame period. V2 is applied, during the positive frame period, to a segment electrode in which ON is written, and is supplied to the selected common electrode during the negative frame period. V3 is applied, during the negative frame period, to a segment electrode in which OFF is written. V4 is applied, during the positive frame period, to a segment electrode in which OFF is written. V5 is applied to an unselected common electrode during the positive frame period. V6 is applied to an unselected electrode during the negative frame period. Then, it is possible to remove crosstalk from a screen by adjusting a variable resister Rx for the voltages to be V1-V6>V6-V3 or V1-V6<V6-V3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for applying a common voltage and a segment voltage to a liquid crystal display panel (LCD panel) to drive the liquid crystal display panel, and a liquid crystal display device including the driving device.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing an example of a conventional liquid crystal display. In this figure, the voltages V1 to V6 generated by the bias power supply circuit 1 are applied to the LCD panel 3 at the timing generated by the timing circuit 2.

FIG. 11 is a circuit diagram showing a configuration example of a conventional bias power supply circuit. In this figure, the resistance value of each resistor is, for example, 1 [kΩ] for each of the resistors R1, R2, R4 and R5, and 11 [kΩ] for the resistor R3. The amplifier 4 is for preventing the voltages V3 to V6 from dropping when an overcurrent flows. As shown in the figure, the bias power supply circuit 1 divides a power supply voltage VEE (for example, 30 [V]) supplied from the outside (such as a personal computer) to generate voltages V1 to V6.

In this figure, when the voltage value of each voltage is calculated, V1 = 30 [V] V6 = (30/15) × 14 = 28 [V] V3 = (30/15) × 13 = 26 [V] V4 = (30/15) × 2 = 4 [V] V5 = (30/15) × 1 = 2 [V] V2 = 0 [V] Here, assuming that an intermediate voltage (15 [V]) between the power supply voltage VEE (30 [V]) and the ground voltage (0 [V]) is the center voltage, the voltages V1 and V2, the voltages V3 and V4, and the voltage V5 are V6
Have voltage values that are symmetric with respect to the center voltage. That is, a voltage obtained by inverting the voltage V1 around the center voltage is the voltage V2, and the voltage V3
Is the voltage V4, and the voltage obtained by inverting the voltage V5 is the voltage V6.

FIG. 12 is an explanatory diagram showing an example of wiring of common electrodes and segment electrodes of the LCD panel 3. As shown in this figure, the LCD panel 3 has, for example, 4
80 common electrodes and 640 segment electrodes
They are wired orthogonally to each other. Each intersection of the common electrode and the segment electrode constitutes one pixel of the LCD panel 3. As a result, a voltage of (voltage applied to the common electrode) − (voltage applied to the segment electrode) is applied to the liquid crystal layer of each pixel.

[0006] The voltage applied to the common electrode (hereinafter referred to as "common voltage") determines the selection state (selection period or non-selection period) of a pixel on the common electrode. In addition, the voltage applied to the segment electrodes (hereinafter, referred to as
The “segment voltage” determines the display state (ON display or OFF display) of the pixel on the segment electrode.

[0007] One screen of the liquid crystal display device (ie, one screen)
A period during which ON or OFF writing is performed on all pixels) is called one frame period. That is, in order to turn on a certain pixel in a certain frame period, as shown in FIG. 12, a voltage V1 is applied to a common electrode of the pixel and a voltage V2 is applied to a segment electrode of the pixel. In addition, in order to turn off a certain pixel in the same frame period, as shown in FIG. 12, a voltage V1 is applied to a common electrode of the pixel and a voltage V4 is applied to a segment electrode of the pixel. At this time, a voltage V5 is applied to the common electrode in order to set the pixels on the other common electrodes to a non-selected state.

Note that these applied voltages are inverted every frame period. As described above, the value obtained by inverting the voltage V1 is the voltage V2, and the value obtained by inverting the voltage V3 is the voltage V4.
And the value obtained by inverting the voltage V5 is the voltage V6. In addition,
Here, a frame period in which a positive voltage is applied to the liquid crystal layer at the time of writing ON or OFF is referred to as a “positive frame period”, and a frame period in which a negative voltage is applied to the liquid crystal layer is referred to as a “negative frame period”. I will call it. The applied voltages shown in FIG. 12 are for the positive frame period. on the other hand,
In order to turn on a certain pixel during the negative frame period, the voltage V2 (inversion of the voltage V1) is applied to the common electrode of the pixel, and the voltage V1 (inversion of the voltage V2) is applied to the segment electrode of the pixel. I do. In order to turn off a certain pixel in the negative frame period, a voltage V3 (inversion of the voltage V4) is applied to a segment electrode of the pixel. At this time, voltage V6 (inversion of voltage V5) is applied to the unselected common electrodes.

FIG. 13 is a graph showing the relationship between
FIG. 3 is an explanatory diagram illustrating a voltage waveform applied to an arbitrary pixel. As shown in this figure, one frame period includes a selection period and a non-selection period. The selection period is a period in which writing of ON or OFF is performed on the pixel, and the non-selection period is ON or OF of another pixel.
This is a period in which writing of F is performed. In the example shown in this figure, when the voltage V1 is applied to the common electrode, the pixels on the common electrode are in a selected state. During the selection period, the voltage (V1) is applied by applying the voltage V2 to the segment electrode. -V2) is applied to the liquid crystal layer of the pixel, and the pixel is turned on.

Next, when the voltage V5 is applied to the common electrode, the pixels on the common electrode are in a non-selected state. At this time, the other pixels are sequentially selected, and the voltage V2 (during ON display) or the voltage V4 is applied to the segment electrode.
(During OFF display) is applied. Therefore, (common voltage V5)-(segment voltage V2 or V4) appears in the waveform of FIG. Note that FIG. 13 shows a waveform example in a case where another pixel on the same segment electrode performs OFF display in the non-selection period.

[0011]

In the above-mentioned conventional liquid crystal display device, when a thin black bar is displayed on a white background on the screen of the LCD panel, the thin black bar is displayed on an extension of the black bar. Further, there is a problem that a white bar having a higher brightness (hereinafter, the white bar is referred to as “white crosstalk”) is displayed as an afterimage. Also, on the same screen,
When a thick black bar is displayed on a white background, on the extension of the black bar,
There is a problem that a black bar slightly lower in brightness than the white background (hereinafter, the black bar is referred to as “black crosstalk”) is displayed as an afterimage.

The present invention has been made under such a background, and provides a liquid crystal display device capable of eliminating the crosstalk from the screen of the liquid crystal display device, and a drive circuit for the liquid crystal display device. With the goal.

[0013]

According to the present invention, a liquid crystal display device is turned on or off during a normal frame period in which all pixels on one screen of the liquid crystal display device are written on or off.
Is applied to a common electrode provided with a pixel for writing ON, and a pixel for writing ON is provided in a negative frame period which is provided alternately with the positive frame period and is a period for writing ON or OFF for all pixels. The voltage V1 applied to the segment electrode is applied to the segment electrode provided with the pixel for writing ON during the positive frame period, and is turned ON or OFF during the negative frame period.
And a voltage V3 applied to a segment electrode provided with a pixel for writing OFF during the negative frame period.
A voltage V4 applied to a segment electrode provided with a pixel to which OFF is written in the positive frame period, and a common voltage excluding a common electrode provided with a pixel to which ON or OFF is provided in the positive frame period. A voltage V5 applied to the electrode and a voltage V6 applied to the common electrode except for a common electrode provided with a pixel for writing ON or OFF are generated in the negative frame period, and the voltages V1 to V6 are generated. In the case where V1>V6>V3>V4>V5> V2, V1-V6 ≒ V5-V2 and V6-V3 ≒ V4-V5, and V1-V6> V6-V3 or V1-V6 <V6 A bias power supply circuit having a relationship of -V3 is provided.
Further, according to the present invention, on the screen of the liquid crystal display device, white crosstalk generated when a thin black bar is displayed on a white background (higher brightness than the white background generated on an extension of the black bar) Black crosstalk that occurs when a thick black bar is displayed on a white background (a black bar slightly lower in brightness than the white background that occurs on an extension of the black bar).
Can be removed from the screen.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

§1. Overview The applicant has now noticed that by improving the bias power supply circuit, crosstalk can be eliminated from the screen. Hereinafter, the details of this improvement will be described.

First, in the present invention, as a measure against white crosstalk, the conventional circuit shown in FIG. 11 is improved as follows. That is, the voltages V1 and V2, the voltages V3 and V4, and the voltages V5 and V6 are respectively equal to the predetermined center voltage (15
[V]), the voltages (V1-V6) are made larger than the voltages (V6-V3) when the voltage values are symmetric with respect to each other. When this is expressed by an equation, when V1−V6 ≒ V5−V2 and V6−V3 ≒ V4−V5, V1−V6> V6−V3. Thereby, white crosstalk is removed from the screen.

Further, in the present invention, as a measure against black crosstalk, the conventional circuit shown in FIG. 11 is improved as follows. That is, the voltages V1 and V2, the voltages V3 and V4, and the voltages V5 and V6 are respectively equal to the predetermined center voltage (15
[V]), the voltage (V1-V6) is made smaller than the voltage (V6-V3) when the voltage values are symmetric with respect to each other. When this is represented by an equation, when V1−V6 ≒ V5−V2 and V6−V3 ≒ V4−V5, V1−V6 <V6−V3. Thereby, black crosstalk is removed from the screen.

Next, specific circuit configurations (first to fifth embodiments) for realizing the above outline will be described. §2. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration example of a bias power supply circuit according to a first embodiment of the present invention.

In this figure, the resistance value of each resistor is, for example, 1 [kΩ] for resistors R1 and R3, and 2 kΩ for resistors R4 and R6.
[KΩ], resistance R2 is 13 [kΩ], resistance R5 is 10.9
[KΩ]. The resistor Rx is a variable resistor, and can be adjusted in a range of 0 to 200 [Ω], for example.
When the resistance value of the variable resistor Rx is 100 [Ω],
The series resistance value RS of the resistor R5 and the variable resistor Rx is 11 [k
Ω], which is an equivalent circuit to the conventional bias power supply circuit shown in FIG. That is, the variable resistance Rx is set to 0 to 200
[Ω], the series resistance RS of the resistor R5 and the variable resistor Rx becomes 10.9 to 11.1 [k
Ω]. In this figure, when the voltage value of each voltage is calculated, the voltages V1, V2, V5, and V6 are as follows.
The values are the same as the voltages V1, V2, V5, and V6 shown in FIG.

Next, the voltage value of the voltage V3 will be described. When the resistance value of the variable resistor Rx is 0 [Ω], V3 = (30 / 14.9) × 12.9 ≒ 25.973
[V], and when the resistance value of the variable resistor Rx is 200 [Ω], V3 = (30 / 15.1) × 13.1 ≒ 26.026
[V]. That is, by adjusting the variable resistance Rx in the range of 0 to 200 [Ω], the voltage V3 becomes 25.973.
２６26.026 [V].

Next, the voltage value of the voltage V4 will be described. When the resistance value of the variable resistor Rx is 0 [Ω], V4 = (30 / 14.9) × 2 ≒ 4.027 [V], and when the resistance value of the variable resistor Rx is 200 [Ω], V4 = (30 / 15.1) × 2 ≒ 3.974 [V]. That is, by adjusting the variable resistance Rx in the range of 0 to 200 [Ω], the voltage V4 becomes 4.027 to
It changes within the range of 3.974 [V].

As can be seen from the above formula, by adjusting the variable resistance Rx in the range of 0 to 200 [Ω],
The voltages V3 and V4 change symmetrically about the center voltage (15 [V]). Therefore, the resistance value of the variable resistor Rx is set to 1
If it is larger than 00 [Ω], V1−V6> V6−V3, and white crosstalk can be removed from the screen. At this time, the voltage V4 is different from the voltage V3.
Since the voltage changes symmetrically around the center voltage (15 [V]), V5−V2> V4−V5.

On the other hand, the resistance value of the variable resistor Rx is set to 100
If it is smaller than [Ω], V1−V6 <V6−V3, and black crosstalk can be eliminated from the screen. At this time, V5−V2 <V4−V5. Thereby, the user can adjust the resistance value of the variable resistor Rx to a value at which the crosstalk is removed from the screen while watching the screen. Further, in this circuit, the two voltages V3 and V4 can be changed simultaneously and symmetrically only by adjusting one variable resistor Rx.

§3. Second Embodiment Next, a second embodiment of the present invention will be described. FIG.
FIG. 7 is a circuit diagram showing a configuration example of a bias power supply circuit according to a second embodiment of the present invention.

In this figure, the resistance value of each resistor is, for example, 1 [kΩ] for the resistors R1 and R3, and 2 for the resistors R4 and R6.
[KΩ], resistance R2 is 12.9 [kΩ], resistance R5 is 11
[KΩ]. The resistor Rx is a variable resistor, and can be adjusted in a range of 0 to 200 [Ω], for example.
When the resistance value of the variable resistor Rx is 100 [Ω],
The series resistance value RS of the resistor R2 and the variable resistor Rx is 13 [k
Ω], which is an equivalent circuit to the conventional bias power supply circuit shown in FIG. That is, the variable resistance Rx is
By adjusting the resistance in the range of [Ω], the series resistance RS of the resistor R2 and the variable resistor Rx becomes 12.9 to 13.1 [k
Ω]. In this figure, when the voltage value of each voltage is calculated, for the voltages V1, V2, V3, and V4,
It has the same value as the voltages V1, V2, V3, V4 shown in FIG.

Next, the voltage value of the voltage V6 will be described. When the resistance value of the variable resistor Rx is 0 [Ω], V6 = (30 / 14.9) × 13.9 ≒ 27.987
[V], and when the resistance value of the variable resistor Rx is 200 [Ω], V6 = (30 / 15.1) × 14.1 ≒ 28.013
[V]. That is, by adjusting the variable resistance Rx in the range of 0 to 200 [Ω], the voltage V6 becomes 27.987.
~ 28.013 [V].

Next, the voltage value of the voltage V5 will be described. When the resistance value of the variable resistor Rx is 0 [Ω], V5 = (30 / 14.9) × 1 ≒ 2.013 [V], and when the resistance value of the variable resistor Rx is 200 [Ω], V5 = (30 / 15.1) × 1 ≒ 1.987 [V]. That is, by adjusting the variable resistance Rx in the range of 0 to 200 [Ω], the voltage V5 becomes 2.013 to
It changes within the range of 1.987 [V]. As can be seen from the above formula, by adjusting the variable resistor Rx in the range of 0 to 200 [Ω], the voltages V6 and V5 become the center voltage (1).
5 [V]), and changes symmetrically with each other.

Therefore, the resistance value of the variable resistor Rx is set to 100
When it is smaller than [Ω], V1−V6> V6−V3, and white crosstalk can be removed from the screen. At this time, the voltage V5 is different from the voltage V6.
Since the voltage changes symmetrically around the center voltage (15 [V]), V5−V2> V4−V5.

On the other hand, the resistance value of the variable resistor Rx is set to 100
If it is larger than [Ω], V1−V6 <V6−V3, and black crosstalk can be eliminated from the screen. At this time, V5−V2 <V4−V5.

§4. Third Embodiment Next, a third embodiment of the present invention will be described. FIG.
FIG. 9 is a circuit diagram showing a configuration example of a bias power supply circuit according to a third embodiment of the present invention. In this figure, the resistance value of each resistor is, for example, 1 [kΩ] for resistors R1 and R3, 2 [kΩ] for resistors R4 and R6, 13 [kΩ] for resistor R2, and 11.2 [kΩ] for resistor R5. ]. The resistor Rx is a variable resistor, and can be adjusted in a range of 407 to 1243 [kΩ], for example.

Here, the resistance value of the variable resistor Rx is set to 407
[KΩ], the parallel resistance value RP of the resistor R5 and the variable resistor Rx is: RP = 1 / {(1 / 11.2) + (1/407)} 1
0.9 [kΩ]. Therefore, in this case, the case where the resistance value of the variable resistor Rx is set to 0 [Ω] in the first embodiment (see FIG. 1),
It becomes an equivalent circuit.

On the other hand, the resistance value of the variable resistor Rx is
[KΩ], the parallel resistance value RP of the resistor R5 and the variable resistor Rx is RP = 1 / {(1 / 11.2) + (1/1243)}.
11.1 [kΩ]. Therefore, in this case, an equivalent circuit is obtained when the resistance value of the variable resistor Rx is set to 200 [Ω] in the first embodiment (see FIG. 1).

As described above, the variable resistor Rx is set to 407 to 12
By adjusting the resistance in the range of 43 [kΩ], the parallel resistance value RP of the resistor R5 and the variable resistor Rx becomes 10.9-11.1.
It changes within the range of [kΩ]. If the resistance value of the variable resistor Rx is 616 [kΩ], the parallel resistance value RP of the resistor R5 and the variable resistor Rx is RP = 1 / {(1 / 11.2) + (1/616)}. 1
1 [kΩ]. Therefore, in this case, the circuit is equivalent to the conventional bias power supply circuit shown in FIG.

Next, when the voltage values of the respective voltages are calculated in this figure, the voltages V1, V2, V5, V6 have the same values as the voltages V1, V2, V5, V6 shown in FIG. Next, the voltage V
The voltage value of 3 will be described. The resistance value of the variable resistor Rx is 4
In the case of 07 [kΩ], the resistance value of the variable resistor Rx is set to 0 [Ω] in the first embodiment (see FIG. 1) as described above.
And an equivalent circuit, V3 = (30 / 14.9) × 12.9 ≒ 25.973
[V].

On the other hand, the resistance value of the variable resistor Rx is 1243.
In the case of [kΩ], as described above, the first embodiment (FIG. 1)
In the case where the resistance value of the variable resistor Rx is set to 200 [Ω], an equivalent circuit is obtained, and V3 = (30 / 15.1) × 13.1 ≒ 26.026
[V]. That is, the variable resistor Rx is set to 407-1243.
By adjusting the voltage in the range of [kΩ], the voltage V3 becomes 2
It changes within the range of 5.973 to 26.026 [V].

Next, the voltage value of the voltage V4 will be described. Considering the same as the voltage V3, when the resistance value of the variable resistor Rx is 407 [kΩ], V4 = (30 / 14.9) × 2 ≒ 4.027 [V], and the resistance value of the variable resistor Rx is 1243. In the case of [kΩ], V4 = (30 / 15.1) × 2 ≒ 3.974 [V]. That is, the variable resistor Rx is set to 407-1243.
By adjusting in the range of [kΩ], the voltage V4 becomes
It changes within the range of 4.027 to 3.974 [V]. As can be seen from the above formula, the variable resistance Rx is set to 407 to 1
By adjusting within the range of 243 [kΩ], the voltage V3
And V4 change symmetrically about the center voltage (15 [V]).

Therefore, the resistance value of the variable resistor Rx is set to 616 [k
Ω], V1−V6> V6−V3, and white crosstalk can be eliminated from the screen. At this time, the voltage V4 is different from the voltage V3.
Since the voltage changes symmetrically around the center voltage (15 [V]), V5−V2> V4−V5.

On the other hand, the resistance value of the variable resistor Rx is set to 616 [k
Ω], V1−V6 <V6−V3, and black crosstalk can be removed from the screen. At this time, V5−V2 <V4−V5.

§5. Fourth Embodiment Next, a fourth embodiment of the present invention will be described. FIG.
FIG. 9 is a circuit diagram showing a configuration example of a bias power supply circuit according to a fourth embodiment of the present invention. In this figure, the resistance values of the resistors are, for example, 1 [kΩ] for the resistors R1 and R3, 2 [kΩ] for the resistors R4 and R6, and 13.2 [k] for the resistor R2.
Ω] and the resistance R5 is 11 [kΩ]. The resistor Rx is a variable resistor, for example, 568 to 1729 [k
Ω].

Here, the resistance value of the variable resistor Rx is 568.
[KΩ], the parallel resistance value RP of the resistor R2 and the variable resistor Rx is: RP = 1 / {(1 / 13.2) + (1/568)} 1
2.9 [kΩ]. Therefore, in this case, the case where the resistance value of the variable resistor Rx is set to 0 [Ω] in the second embodiment (see FIG. 2),
It becomes an equivalent circuit.

On the other hand, the resistance value of the variable resistor Rx is set to 1729.
[KΩ], the parallel resistance value RP of the resistor R2 and the variable resistor Rx is RP = 1 / {(1 / 13.2) + (1/1729)}.
13.1 [kΩ]. Therefore, in this case, an equivalent circuit is obtained when the resistance value of the variable resistor Rx is set to 200 [Ω] in the second embodiment (see FIG. 2).

As described above, the variable resistance Rx is set to 568 to 17
By adjusting the resistance in the range of 29 [kΩ], the parallel resistance value RP of the resistor R2 and the variable resistor Rx becomes 12.9 to 13.1.
It changes within the range of [kΩ]. When the resistance value of the variable resistor Rx is 858 [kΩ], the parallel resistance value RP of the resistor R2 and the variable resistor Rx is RP = 1 / {(1 / 13.2) + (1/858)}. 1
3 [kΩ]. Therefore, in this case, the circuit is equivalent to the conventional bias power supply circuit shown in FIG.

Next, in this figure, when the voltage values of the respective voltages are calculated, the voltages V1, V2, V3, V4 have the same values as the voltages V1, V2, V3, V4 shown in FIG. Next, the voltage V
The voltage value of 6 will be described. The resistance value of the variable resistor Rx is 5
In the case of 68 [kΩ], as described above, the resistance value of the variable resistor Rx is set to 0 [Ω] in the second embodiment (see FIG. 2).
And the equivalent circuit becomes: V6 = (30 / 14.9) × 13.9 ≒ 27.987
[V].

On the other hand, the resistance value of the variable resistor Rx is 1729.
In the case of [kΩ], as described above, the second embodiment (FIG. 2)
In the case where the resistance value of the variable resistor Rx is set to 200 [Ω], an equivalent circuit is obtained, and V6 = (30 / 15.1) × 14.1 ≒ 28.013
[V]. That is, the variable resistance Rx is set to 568 to 1729.
By adjusting the voltage in the range of [kΩ], the voltage V6 becomes 2
It changes within the range of 7.987 to 28.013 [V].

Next, the voltage value of the voltage V5 will be described. Considering the same as the voltage V6, when the resistance value of the variable resistor Rx is 568 [kΩ], V5 = (30 / 14.9) × 1 ≒ 2.013 [V], and the resistance value of the variable resistor Rx is 1729. In the case of [kΩ], V5 = (30 / 15.1) × 1 ≒ 1.987 [V]. That is, the variable resistance Rx is set to 568 to 1729.
By adjusting in the range of [kΩ], the voltage V5 becomes
It changes within the range of 2.013 to 1.987 [V]. As can be seen from the above formula, the variable resistance Rx is set to 568 to 1
By adjusting within the range of 729 [kΩ], the voltage V6
And V5 change symmetrically about the center voltage (15 [V]).

Therefore, the resistance value of the variable resistor Rx is set to 858 [k
Ω], V1−V6> V6−V3, and white crosstalk can be eliminated from the screen. At this time, the voltage V5 is different from the voltage V6.
Since the voltage changes symmetrically around the center voltage (15 [V]), V5−V2> V4−V5.

On the other hand, the resistance value of the variable resistor Rx is 858 [k
Ω], V1−V6 <V6−V3, and black crosstalk can be eliminated from the screen. At this time, V5−V2 <V4−V5.

§6. Fifth Embodiment Next, a fifth embodiment of the present invention will be described. FIG.
FIG. 6 is a circuit diagram showing a configuration example of a bias power supply circuit according to a fifth embodiment of the present invention. The resistance value of each resistor shown in FIG. 5 is the same as the resistance value of each resistor shown in FIG. 1, and the resistance value of each resistor shown in FIG. 6 is the same as the resistance value of each resistor shown in FIG. is there. As shown in FIGS. 5 and 6, the first embodiment (FIG. 1) and the second embodiment (FIG. 2)
In this embodiment, the resistors R4 and R6 (= 2 [kΩ])
It is composed of two resistors R1 (= 1 [kΩ]). As a result, in the present embodiment, the types of components can be reduced, and component management during manufacturing is simplified. For the operation,
The operation of the circuit shown in FIG. 5 is the same as that of the circuit shown in FIG. 1, and the operation of the circuit shown in FIG. 6 is the same as that of the circuit shown in FIG. In the present embodiment, the first embodiment (FIG. 1) and the second embodiment (FIG. 2)
However, similarly, in the third embodiment (FIG. 3) and the fourth embodiment (FIG. 4), the resistors R4 and R6 may be constituted by a plurality of resistors R1.

§7. Supplement Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the embodiment, and there may be a design change or the like without departing from the gist of the present invention. Even this is included in the present invention. For example, FIGS.
Although not shown in the figure, in the present embodiment, it is conceivable that the voltages V1 to V6 are amplified by the amplifier similarly to the conventional circuit shown in FIG. The circuit diagrams shown in FIGS. 1 to 6 are merely examples, and any circuit may be used as long as it satisfies the conditions described in Ҥ1.

[0049]

Embodiments of the present invention will be described below with reference to the drawings. §1. First Embodiment FIG. 7A is a circuit diagram showing a configuration example of a bias power supply circuit according to a first embodiment of the present invention, and FIG. 7B is a table showing a voltage measurement example according to the first embodiment. It is. FIG.
FIG. 4 is an explanatory diagram showing a display example of the liquid crystal display device according to the embodiment. In FIG. 8A, the white crosstalk is represented by a broken line, but this is due to restrictions on the drawing with respect to this drawing, and in practice, the brightness is increased from the surroundings so as to extend a thin black bar. The line with a high level appears to be thin.

In FIG. 7A, the resistance of the resistors R2 and R4 is 1 [kΩ], and the resistance of the resistor R3 is 9 [kΩ].
Ω]. The resistors R1 and R5 are variable resistors, and the resistance value can be increased or decreased by 1 [Ω] with 1 [kΩ] as a center value. In FIG. 7B, the voltage ΔV is represented by the following equation. Here, the pixel A and the pixel B
Indicates a pixel A and a pixel B shown in FIG. 8, and the pixel B is a pixel adjacent to the pixel A. ΔV = (effective voltage applied to pixel A in one frame period) − (effective voltage applied to pixel B in one frame period) Here, voltage ΔV becomes larger than 0, that is,
The fact that the effective voltage of the pixel A becomes higher than the effective voltage of the pixel B is a cause of white crosstalk.

In this embodiment, in such a configuration,
After displaying a thin black bar on a white background on the screen of the liquid crystal display device, the resistance values of the variable resistors R1 and R5 were sequentially increased, and the display state of white crosstalk was evaluated by a visual test. As a result, when the resistance values of the resistors R1 and R5 are increased from 1 [kΩ] to 1.006 [kΩ], the voltage ΔV becomes almost 0 [mV] as shown in FIG.
As shown in (b), the white crosstalk is no longer displayed.

Further, in this embodiment, in the same configuration, a thick black bar is displayed on a white background on the screen of the liquid crystal display device, and then the resistance values of the variable resistors R1 and R5 are sequentially reduced to reduce black crosstalk. The display state was evaluated by a visual test. As a result, although not shown in the figure, when the resistance values of the resistors R1 and R5 are reduced to 0.994 [kΩ], the voltage ΔV
Became almost 0 [mV], and no black crosstalk was displayed.

§2. Second Embodiment FIG. 9A is a circuit diagram illustrating a configuration example of a bias power supply circuit according to a second embodiment of the present invention, and FIG. 9B is a table illustrating a voltage measurement example according to the second embodiment. It is. FIG. 9 (a)
, The resistance values of the resistors R1 and R5 are 1 [kΩ], and the resistance value of the resistor R3 is 9 [kΩ]. The resistors R2 and R4 are variable resistors, and the resistance value can be increased or decreased by 1 [Ω] with 1 [kΩ] as a center value. The voltage ΔV and the pixels A and B are the same as in the first embodiment.

In this embodiment, in such a configuration,
After displaying a thin black bar on a white background on the screen of the liquid crystal display device, the resistance values of the variable resistors R2 and R4 were sequentially reduced, and the display state of white crosstalk was evaluated by a visual test. As a result, when the resistance values of the resistors R2 and R4 are reduced from 1 [kΩ] to 0.994 [kΩ], the voltage ΔV becomes almost 0 [mV] as shown in FIG.
As shown in (b), the white crosstalk is no longer displayed.

Also, in this embodiment, in the same configuration, a thick black bar is displayed on a white background on the screen of the liquid crystal display device, and then the resistance values of the variable resistors R2 and R4 are sequentially increased to reduce black crosstalk. The display state was evaluated by a visual test. As a result, although not shown in the figure, when the resistance values of the resistors R2 and R4 are increased to 1.006 [kΩ], the voltage ΔV
Became almost 0 [mV], and no black crosstalk was displayed.

[0056]

As described above, according to the present invention, on the screen of the liquid crystal display device, white crosstalk which occurs when a thin black bar is displayed on a white background (which occurs on an extension of the black bar, A white bar that is even brighter than the white background),
And removing black crosstalk (a black bar slightly lower in brightness than the white background that occurs on an extension of the black bar) generated when a thick black bar is displayed on a white background from the screen. it can.

Further, according to the present invention, the user can adjust the resistance value of the variable resistor to a value at which the crosstalk is removed from the screen while watching the screen. Furthermore, the output voltage of each output terminal can be changed simultaneously and symmetrically only by adjusting one variable resistor, so that the adjustment is simple.

Further, according to the present invention, the number of types of parts can be reduced, and parts management during manufacturing can be simplified. Further, according to the present invention, even when an overcurrent flows from the output terminal, it is possible to prevent the output voltage of the output terminal from decreasing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a bias power supply circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a bias power supply circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a bias power supply circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration example of a bias power supply circuit according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration example of a bias power supply circuit according to a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration example of a bias power supply circuit according to a sixth embodiment of the present invention.

FIG. 7A is a circuit diagram showing a configuration example of a bias power supply circuit according to a first embodiment of the present invention, and FIG.
4 is a table showing a measurement example of a voltage according to the embodiment.

FIG. 8 is an explanatory diagram showing a display example of the liquid crystal display device according to the same embodiment.

FIG. 9A is a circuit diagram showing a configuration example of a bias power supply circuit according to a second embodiment of the present invention, and FIG.
4 is a table showing a measurement example of a voltage according to the embodiment.

FIG. 10 is a block diagram illustrating an example of a conventional liquid crystal display device.

FIG. 11 is a circuit diagram illustrating a configuration example of a conventional bias power supply circuit.

FIG. 12 is an explanatory diagram showing an example of wiring of common electrodes and segment electrodes of an LCD panel.

FIG. 13 is an explanatory diagram showing a voltage waveform applied to an arbitrary pixel.

[Explanation of symbols]

1 ... bias power supply circuit, 2 ... timing circuit, 3
…… LCD panel, 4 …… Amplifier, R1, R2, R3,
R4, R5, R6: resistance, Rx: variable resistance

Continued on the front page (72) Inventor Takehiko Sone 1-7 Yukiya Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd.

Claims (5)

[Claims] 1. A positive frame period in which ON or OFF is written to all pixels of one screen of a liquid crystal display device is applied to a common electrode provided with a pixel in which ON or OFF is written. In a negative frame period which is provided alternately with the frame period and in which ON or OFF is written to all the pixels, the voltage V1 applied to the segment electrode provided with the pixel in which ON is written is provided.
In the positive frame period, a voltage V2 applied to a segment electrode provided with a pixel for writing ON, and a voltage V2 applied to a common electrode provided with a pixel for writing ON or OFF in the negative frame period; In the negative frame period, a voltage V3 applied to a segment electrode provided with a pixel for writing OFF, and in the positive frame period, a voltage V4 applied to a segment electrode provided with a pixel for writing OFF, In the positive frame period, a voltage V5 applied to a common electrode excluding a common electrode provided with a pixel to which ON or OFF is provided; and in the negative frame period, a common voltage in which a pixel to which ON or OFF is provided is provided. A voltage V6 applied to the common electrode excluding the electrodes is generated. Between the voltages V1 to V6, V1>V6>V3>V4>V5> V In the case of 2, V1−V6 ≒ V5−V2 and V6−V3−V4−V5, and a bias power supply circuit having a relationship of V1−V6> V6−V3 or V1−V6 <V6−V3 is provided. Driving circuit of a liquid crystal display device. 2. The bias power supply circuit, comprising: a first resistor having one end connected to a power supply; and a first resistor having one end connected to the other end of the first resistor and having a resistance greater than the first resistor. A third resistor having one end connected to the other end of the second resistor, the other end connected to the ground point, and having a resistance value equal to the first resistance; A fourth resistor in which the first resistors are arranged in series, and a fourth resistor having one end connected to the other end of the fourth resistor and having a larger resistance value than the fourth resistor. A fifth resistor, one end of which is connected to the other end of the fifth resistor, and the other end of which is connected to the ground point, and a sixth resistor in which the two first resistors are arranged in series; A variable resistor connected in parallel with the fifth resistor; a first output terminal connected to the power supply and outputting the voltage V1 A second output terminal that is connected to the ground point and outputs the voltage V2; and a third output terminal that is connected to a connection point between the fourth resistor and the fifth resistor and outputs the voltage V3. An output terminal, a fourth output terminal connected to a connection point between the fifth resistor and the sixth resistor, and outputting the voltage V4, and a connection between the second resistor and the third resistor. A fifth output terminal that is connected to a point and outputs the voltage V5; and a sixth output terminal that is connected to a connection point between the first resistor and the second resistor and outputs the voltage V6. The driving circuit for a liquid crystal display device according to claim 1, wherein 3. A bias power supply circuit comprising: a first resistor having one end connected to a power supply; and a first resistor having one end connected to the other end of the first resistor and having a resistance value larger than the first resistor. A second resistor, one end of which is connected to the other end of the second resistor, and the other end of which is connected to the ground, and a third resistor having a resistance value equal to the first resistor; A variable resistor connected in parallel with the resistor, a fourth resistor having one end connected to the power supply and the two first resistors arranged in series, and one end connected to the other end of the fourth resistor. A fifth resistor having a resistance greater than the fourth resistor, one end connected to the other end of the fifth resistor, and the other end connected to the ground point, A sixth resistor formed by arranging two resistors in series, and a first output terminal connected to the power supply and outputting the voltage V1 A second output terminal that is connected to the ground point and outputs the voltage V2; and a third output terminal that is connected to a connection point between the fourth resistor and the fifth resistor and outputs the voltage V3. An output terminal, a fourth output terminal connected to a connection point between the fifth resistor and the sixth resistor, and outputting the voltage V4, and a connection between the second resistor and the third resistor. A fifth output terminal that is connected to a point and outputs the voltage V5; and a sixth output terminal that is connected to a connection point between the first resistor and the second resistor and outputs the voltage V6. The driving circuit for a liquid crystal display device according to claim 1, wherein 4. The apparatus according to claim 1, wherein the bias power supply circuit includes an amplifier connected to each of the output terminals and configured to prevent a decrease in an output voltage of the output terminal when an overcurrent flows from the output terminal. 4. A driving circuit for a liquid crystal display device according to claim 2, wherein 5. A liquid crystal display device comprising: the driving circuit according to claim 1; and a liquid crystal display panel driven by the driving circuit.