JP2590456B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tone liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device has attracted attention as a flat panel display, and a multi-gradation liquid crystal display device has been developed and put into practical use because of a tendency to improve image quality in both monochrome and color.

[0003] Figure 4 shows a schematic configuration of a multi-gradation liquid crystal display device of a conventional active matrix driving method, 1 X signal line X _1, X _2, X _3, · · · X _m and Y signal lines Y ₁ ,
Selecting one of the gradation signal based on Y _2, Y ₃ ··· Y _n and a liquid crystal panel including a thin film transistor (TFT) at the intersection position of the two image data signals to be displayed from a plurality of gradation signal A horizontal driver for outputting a gate signal as a scanning signal for scanning the liquid crystal panel 1 to a Y signal line of the liquid crystal panel 1; Is generated and the gradation signals V _{0 to} V
₇ (in the case of 8 gradations). The horizontal driver 2 receives, in addition to the gradation signals V _{0 to} V ₇ , a vertical synchronization signal S _v and a data signal S of an image to be displayed.
_d, is inputted start signal S _s, the vertical driver 3, a gate voltage V _G is applied, the horizontal sync signal S _h and the clock signal CLK is input.

[0004] When multiple gray-scale signal V ₀ ~V ₇ outputted from the gradation voltage generating circuit 4 is input to the horizontal driver 2, a horizontal driver 2 one gradation signal from the based on the data signal S _d stored as the gradation signal of one line select, and outputs the tone signals to the liquid crystal panel 1 by the vertical synchronizing signal S _v and the start signal S _s. This gradation signal is supplied to the drain terminal of the thin film transistor of the liquid crystal panel 1.

On the other hand, the Y signal line Y from the vertical driver 3
_{1, Y 2, Y 3,} ··· Y n is connected to the gate terminals of the liquid crystal panel 1 TFT, horizontal sync signal S _h in synchronization with the gate signal generated based on the clock signal the scanning signal Are sequentially supplied to the Y signal lines, and as a result, the thin film transistors connected to each Y signal line are sequentially turned on. One screen ends when the gate signal is supplied to all the Y signal lines.

FIG. 5 shows an example of a circuit configuration of the gradation voltage generating circuit 4 shown in FIG. This example 8 but outputs 8 kinds of gray-scale signal V ₀ ~V ₇ to represent a gray scale, to generate 16 different gray-scale voltage level since it is an AC drive.

The gradation voltage generating circuit 4 has 14 fixed resistors R ₁ , R ₂ , R ₃ ... R ₁₄ between two reference voltages V _H and V _L (V _H > V _L ). And one variable resistor VR ₁
Are connected in series and different voltages V _0H , V _1H , V _2H ... V _7H and V _0L , V _0L , V _7H obtained from a connection point between these fixed resistors and a connection point between the fixed resistor and the variable resistor.
_A switch 10 for switching voltages of the same potential and opposite polarities (for example, V _0H and V _0L ) from among _1L , V _2L ... V _7L ;
The buffer circuit 11 is connected in series corresponding to each switch 10. When the switch 10 is switched in synchronism with the horizontal synchronizing signal, whereby the tone signal V ₀ ~V ₇ of opposite polarity are obtained in the form of a square wave alternating. For example, the gradation signal V ₀ is a rectangular wave having voltage levels of V _0H and V _0L . The gradation expression is determined by the voltage level of the gradation signal.

[0008]

In the above-mentioned conventional liquid crystal display device, the voltage level of the gray scale signal for determining the gray scale characteristics is the voltage level for voltage division connected in series between the reference voltages _VH and _VL . Since it is determined by the resistance values of the fixed resistors R _{1 to} R ₁₄ , once the device is designed and assembled, the gradation characteristics cannot be arbitrarily changed thereafter.

However, in the display of a color television or a personal computer, the appearance of colors may change depending on the angle at which the user looks at the screen (called the viewing angle). There is a case where it is desired to adjust the color appearance to an optimum state by adjusting, but there is a problem that the conventional liquid crystal display device cannot do so. Also, in the final stage of manufacturing, it is not possible to correct variations in gradation due to variations in the product of the liquid crystal panel and manufacturing errors in the fixed resistance value for voltage division.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to make it possible to freely adjust the gradation characteristics of a liquid crystal display device at any time.

[0011]

According to the present invention, in order to achieve the above object, a gradation voltage generating circuit of a liquid crystal display device is connected in series between a high potential reference voltage and a low potential reference voltage. A plurality of fixed resistors, and voltage changing means for changing a voltage at a connection point between the fixed resistors between the high-potential reference voltage and the low-potential reference voltage. The voltage at the point was used as a gradation signal.

[0012]

According to the present invention, the voltage between the fixed resistors can be changed to a value different from the voltage determined by the fixed resistor by adjusting the voltage variable means, so that the gradation voltage can be changed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

Although the schematic configuration of the liquid crystal display device according to the present invention is the same as that shown in FIG. 4, it is not shown, but the gradation voltage generating circuit of the liquid crystal display device according to the present invention is as shown in FIG. It is assumed that the gray scale voltage generation circuit shown in FIG. 1 generates gray scale signals V _{0 to} V ₇ for eight gray scale display. The gradation voltage generation circuit includes fixed resistors R _{1 to} R between reference voltages V _H and V _L.
14 and the variable resistor VR ₁ are connected in series, and the variable resistors VR ₂ , VR ₃ , VR ₄ and VR ₄ are connected in series,
An operational amplifier 12 is connected between the node between the fixed resistors R ₂ and R ₃ and the variable resistor VR _2, and an operational amplifier 13 is connected between a node between the fixed resistors R ₅ and R ₆ and the variable resistor VR _3. and connects the operational amplifier 14 between the connection point between the fixed resistor R ₁₀ R ₁₁ and a variable resistor VR _4, the operational amplifier 15 between the connection point and the variable resistor VR ₅ and the fixed resistor R ₁₃ and R ₁₄ And the connection point between the fixed resistors and the fixed resistor and the variable resistor V
Different voltages V _0H , V _1H , V obtained from the connection point with R _1
2H · · · V _7H and V _0L, V _1L, a switch 10 for switching the reverse polarity voltage (eg V _0H and V _0L) at the same potential among the V _2L ··· V _7L, corresponding to the switches 10 And a buffer circuit 11 connected in series.

In this gradation voltage generation circuit, the reference voltage V _H is output as it is as the gradation voltage V _0H , and the gradation voltage V _0H is output.
_The voltage divided by the fixed resistor R ₁ is output to _1H , but the gradation voltages V _2H , V _3H and V _4H depend on the output voltage of the operational amplifier 12 and are connected to the input side of the operational amplifier 12. output voltage is changed by the resistance value of the variable resistor VR _2. That is, the gradation voltages V _2H , V _3H , and V _4H can be adjusted by adjusting the resistance value of the variable resistor VR ₂ . Similarly, a variable gray scale voltage V _5H by adjusting the resistance values of the resistors VR _3, V _6H, can adjust the V _7H, gradation voltages V _4L by adjusting the resistance value of the variable resistor VR ₄ , can be adjusted V _3L, V _2L, it is possible to adjust the gradation voltages V _1L by adjusting the resistance value of the variable resistor VR _5. Gradation voltages V _7L, V _6L, V _5L can be adjusted by the variable resistor VR _1.

As described above, the variable resistors VR ₁ , VR ₂ , VR
By adjusting the resistance values of ₃ , VR ₄ and VR ₅ , the voltage level of the gray scale signal, that is, the gray scale voltage can be arbitrarily adjusted, and the gray scale characteristics can be freely changed.

As shown in FIG. 2, for example, when the gradation characteristic is γ
When (gamma) = 3, the gradation characteristic is set to γ =
To change to 4, the following adjustment is made to the gradation voltage when the gradation characteristic is γ = 3.

The gray scale voltage V _2H is reduced to 0 by the variable resistor VR ₂ .
Lower by 25V.

The gray scale voltage V _5H is reduced to 0 by the variable resistor VR ₃ .
Lower 125V.

The gray scale voltage V _7L is reduced to 0 by the variable resistor VR ₁ .
Increase 125V.

The gray scale voltage V _4L is reduced to 0 by the variable resistor VR ₄ .
Increase by 25V.

The result is as shown in FIG. 2 as "the present invention", and a gradation characteristic similar to the gradation characteristic set as γ = 4 from the beginning can be obtained.

FIG. 3 shows a gradation voltage generating circuit of a liquid crystal display device according to another embodiment of the present invention. The grayscale voltage generating circuit of this embodiment generates a grayscale signal of 16 grayscales and, like the grayscale voltage generating circuit shown in FIG. 1, separates between the reference voltages _VH and _VL. Fixed resistors R ₁ , R ₂ , R
_3, along with connecting the ···· R _27, R ₂₈ and the variable resistor VR ₁ in series, the variable resistor _{VR 2, VR 3, VR 4} , V
Connect R ₅ in series, and connected as shown to an operational amplifier 16, 17, 18, 19 between these two series circuits,
Different voltages V _0H , V _1H , V _2H ... Obtained from the connection point between the fixed resistors and the connection point between the fixed resistor and the variable resistor VR _1.
A switch 10 for switching the same potential and opposite polarity voltages (for example, V _0H and V _0L ) from V _15H and V _0L , V _1L , V _2L ... V _15L , and a buffer circuit corresponding to each switch 10 11 are connected in series.

According to this circuit, the voltage level of the gradation voltages V _{4H to} V _9H can be changed by adjusting the resistance value of the variable resistor VR ₂ , and the resistance value of the variable resistor VR ₃ can be adjusted. gray-scale voltage V _10H ~V voltage level of _15H can be changed, it is possible to change the voltage level of the gradation voltages V _{9 L} ~V _4L by adjusting the resistance value of the variable resistor VR _4, the variable it is possible to change the voltage level of the gradation voltages V _3L ~V _1L by adjusting the resistance value of the resistor VR _5. Gray-scale voltage V _15L ~V _10L can be adjusted by the variable resistor VR _1.

As described above, the variable resistors VR ₁ , VR ₂ , VR
By adjusting the resistance values of ₃ , VR ₄ and VR ₅ , the voltage level of the gray scale signal, that is, the gray scale voltage can be arbitrarily adjusted, and the gray scale characteristics can be freely changed as shown in FIG. This is the same as the embodiment.

In the above two embodiments, the operational amplifier is used to adjust the gradation voltage. However, the present invention is not limited to this, and a circuit or an element such as a DC / DC converter whose output voltage can be changed by external adjustment is used. be able to. Further, the present invention can be applied to any liquid crystal display device in monochrome or color, and the driving method is not limited to the active matrix driving method or the AC driving method.

[0027]

As described above, according to the present invention,
Since the gradation voltage can be freely changed even after the liquid crystal display device is assembled, variations in the gradation characteristics due to variations in the product of the liquid crystal panel and variations in the resistance value of the fixed resistor for voltage division are used during the final stage of manufacturing by the user. Can be arbitrarily corrected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a gradation voltage generation circuit of a liquid crystal display device as one embodiment of the present invention.

FIG. 2 shows the result of adjusting the gradation characteristics of the liquid crystal display device according to the present invention.

FIG. 3 is a circuit diagram of a gradation voltage generation circuit of a liquid crystal display device as another embodiment of the present invention.

FIG. 4 is a block diagram illustrating a schematic configuration of the present invention and a conventional liquid crystal display device.

FIG. 5 is a circuit diagram of an example of a gradation voltage generation circuit of a conventional liquid crystal display device.

[Explanation of symbols]

1 liquid crystal panel 2 horizontal driver 3 vertical driver 4 grayscale voltage generating circuit 10 switch 11 buffer circuits _{V 0, V 1, V 2} ··· V 7 gradation signals _{R 1, R 2, ··· R} 14 fixed resistor VR _{1, VR 2, VR 3,} VR 4, VR 5 variable resistor

Claims (1)

(57) [Claims] 1. A liquid crystal panel having an X signal line and a Y signal line, and one gradation signal based on a data signal of an image to be displayed from a plurality of gradation signals output from a gradation voltage generation circuit. In a liquid crystal display device provided with a horizontal driver for selecting and outputting an X signal line of the liquid crystal panel to an X signal line and a vertical driver for outputting a scanning signal of the liquid crystal panel to a Y signal line of the liquid crystal panel, the gradation voltage generation circuit is A plurality of fixed resistors connected in series between a high-potential reference voltage and a low-potential reference voltage; and a voltage at a connection point between the fixed resistors, the high-potential reference voltage and the low-potential reference voltage. And a voltage variable means that varies between the high-voltage reference and the high-potential reference.
Variable resistor connected between voltage and low potential reference voltage
And one input terminal is connected to the voltage variable terminal of the variable resistor
Output terminal at a predetermined connection point between the plurality of fixed resistors.
A liquid crystal display device comprising: a connected buffer circuit .