KR20060071700A - Method for controlling common voltage of liquid crystal display device - Google Patents

Abstract

The present invention relates to a method for adjusting a common voltage of a liquid crystal display and a voltage adjusting means used therefor, and particularly, to aim for preventing flicker by aiming at a common voltage.

The present invention includes generating a common voltage through a common voltage generator having a variable resistor terminal protruding outward of the liquid crystal display panel for the above purpose; A first shaft that rotates, a handle formed at one end of the first shaft, a second shaft that is engaged with the first shaft and rotates smaller than a rotation angle of the first shaft as the first shaft rotates, and the second Contacting the variable resistance terminal with an adjusting rod having one end of the shaft and having a tip contacting the variable resistance; Adjusting the resistance by rotating the knob to rotate the variable resistance terminal; It provides a common voltage control method comprising the step of determining the optimum common voltage value by adjusting the adjusting rod, the operator can finely adjust the common voltage is easy to remove the flicker phenomenon.

Flicker, common voltage, resistance control means

Description

Common voltage control method of liquid crystal display device {METHOD FOR CONTROLLING COMMON VOLTAGE OF LIQUID CRYSTAL DISPLAY DEVICE}

1 is a cross-sectional view of a general liquid crystal display panel.

2 is a plan view showing the configuration of a liquid crystal display panel and a driving circuit section.

3 is a partial circuit diagram of a common voltage generation unit of the present invention.

4 is a conceptual diagram showing a voltage adjusting method of the present invention.

5 is a cross-sectional view showing a voltage regulating means of the present invention.

******* Explanation of symbols on the main parts of the drawing ********

401: liquid crystal display panel 402: variable resistance terminal

403: adjustment bar 501: thimble

502: first gear 503: third gear

505: second gear 504: fourth gear

507: power transmission shaft 510: first axis

506: second axis

The present invention relates to a method of adjusting the common voltage of a liquid crystal display device, and more particularly, to a method of eliminating the flicker phenomenon by improving the method of adjusting the common voltage.

Liquid crystal display devices are a kind of display device, and are being actively developed due to their lightness, simplicity and portability.

The liquid crystal display device includes a liquid crystal display panel, wherein the liquid crystal display panel includes an upper color filter substrate, a lower array substrate, and a liquid crystal layer filled between the two substrates.

Hereinafter, the structure of the liquid crystal display panel will be described in more detail with reference to FIG. 1.

As shown in FIG. 1, the liquid crystal display panel is configured such that the upper color filter substrate 150 and the lower array substrate 101 face each other, and the liquid crystal layer 108 is filled therebetween.

A plurality of gate lines (not shown) and data lines (not shown) are vertically intersected with each other in the array substrate 101, and unit pixels are defined by intersections of the gate lines and the data lines. The thin film transistor 103, which is a switching element, and the storage capacitor 104 are formed in the intersection area of the gate line and the data line among the unit pixels to drive the unit pixel.

Meanwhile, each unit pixel further includes a pixel electrode 106 connected to the thin film transistor and applying an electric field to the liquid crystal, and the pixel electrode 106 includes a common electrode 152 formed on the curl filter substrate 150. In addition, the arrangement of the liquid crystals is controlled by applying an electric field to the liquid crystals.

On the other hand, the color filter substrate 150 is applied to the black matrix (not shown) to block the unnecessary light of the light from the array substrate, the color filter layer 151 for expressing the screen in a natural color, and an electric field to the liquid crystal The common electrode 152 is formed.

In addition, alignment layers 106 and 153 for initial alignment of liquid crystals are further formed on inner layers of the array substrate and the color filter substrate.

A sealant 109 is formed outside the pixel portion of the array substrate to bond the array substrate and the color filter substrate and to maintain the liquid crystal filled between the array substrate and the color filter substrate. In addition, a spacer 107 is distributed on the array substrate or the color filter substrate to maintain a cell gap between the array substrate and the color filter substrate.

Meanwhile, a driving circuit unit is formed outside the liquid crystal display panel to provide a gate signal and a data signal to a switching element formed on an array substrate, and provide a common voltage signal to the common electrode.

The driving circuit unit may be separately configured on the outer side of the liquid crystal display panel, or may be integrally formed on the array substrate.

In addition, polarizing plates 102 and 154 are formed outside the liquid crystal display panel to provide polarization to the liquid crystal.

The liquid crystal display panel may be further divided into a pixel unit and a driving circuit unit. Referring to FIG. 2, the relationship between the conventional driving circuit unit and the liquid crystal display panel will be described.

As shown in FIG. 2, a liquid crystal display panel includes a pixel portion in which a plurality of gate lines GL parallel to each other and a plurality of data lines DL perpendicularly intersect the gate lines GL are formed, and the pixel portion A driving circuit portion for providing a driving signal is formed in the. In the driving circuit unit, a gate driver 206 for driving a gate line and a data driver 204 for driving a data line are formed.

In addition, the timing controller 208 for controlling the driving timing of the gate driver 206 and the data driver 204 and the common voltage supply unit 10 for controlling the common voltage Vcom of the common electrode applying the electric field to the liquid crystal layer. It is further provided.

The timing controller 208 receives a data clock DCLK, a horizontal synchronization signal Hsink, a vertical synchronization signal Vsink, a data enable data DE, and a data signal from an external system. Accordingly, the timing controller 208 receiving the data generates control signals such as timing signals and polarity inversion signals for controlling the drive timing of the gate and the data driver.

On the other hand, a thin film transistor for driving a unit pixel defined by a gate line formed on an array substrate and a data line perpendicular to the array substrate applies a signal to the unit pixel electrode by driver signals, and faces the pixel electrode and faces the pixel electrode. In addition to the common electrode formed on the color filter substrate, an electric field is applied to the liquid crystal to control the direction of the liquid crystal.

In this case, the element applying the common voltage to the common electrode is the common voltage generator 210.

The common voltage generator 210 is provided with a DC-DC converter to receive and process a DC voltage from an external system, and then apply the DC voltage to the common voltage.

In addition, the common constant voltage generation unit includes a plurality of resistors for dividing the common voltage, and a variable resistor formed between the fraudulent resistors. The common voltage may be adjusted by adjusting the variable resistor. The terminal for adjusting the variable resistor protrudes out of the liquid crystal display panel, and the operator adjusts the terminal to adjust the common voltage.

However, when the common voltage deviates from the reference value, especially in a liquid crystal display device driven in an inversion method, voltage imbalance occurs between the common electrode and the pixel electrode, and flicker occurs when the screen flickers every frame. do.

In addition, since the common voltage is manually adjusted using a driver or the like, the flicker is more frequently generated due to incorrect regulation of the common voltage.

Therefore, an object of the present invention is to improve the flicker phenomenon by improving the method of adjusting the common voltage of a liquid crystal display panel. In addition, it is an object to be able to finely adjust the common voltage by using a variable switching regulator to adjust the common voltage by adjusting the variable resistance by the operator's hand.

The common voltage control method of the liquid crystal display device of the present invention for achieving the above object comprises the steps of generating a common voltage through a common voltage generator having a variable resistor terminal protruding outward of the liquid crystal display panel; A first shaft that rotates, a handle formed at one end of the first shaft, a second shaft that is engaged with the first shaft and rotates smaller than a rotation angle of the first shaft as the first shaft rotates, and the second Contacting the variable resistance terminal with an adjusting rod having one end of the shaft and having a tip contacting the variable resistance; Adjusting the resistance by rotating the knob to rotate the variable resistance terminal; And determining an optimum common voltage value by adjusting the adjusting rod. In addition, the common voltage adjusting method of the liquid crystal display according to another embodiment of the present invention comprises the steps of generating a common voltage through a common voltage generating unit having a variable resistor terminal protruding outward of the liquid crystal display panel; Providing a polarizer on a surface of the pixel portion of the liquid crystal display panel; Rotating the variable resistance terminal to change a common voltage; And observing the flicker of the liquid crystal display panel generated according to the change of the common voltage through the polarizer to determine an optimum common voltage value.

In a liquid crystal display device configured in an inversion method, particularly in a liquid crystal display device driven in a dot inversion method, each pixel is flickered due to a luminance difference in each pixel when a deviation occurs in an effective voltage. The flicker phenomenon occurs because the deviation of the effective voltage causing the flicker is because the common voltage deviates from the reference value.

Therefore, after the liquid crystal display panel is completed, it is essential to adjust the common voltage to the reference value. In the conventional method of adjusting the common voltage, the operator manually adjusts the variable resistor in the common voltage generator to adjust the common voltage value to the reference value. It was.

However, this method often causes errors in common voltage regulation, and it is very difficult for an operator to finely control the variable resistor. In general, the variable resistance terminal protrudes from the outside of the liquid crystal display panel and rotates in the screw direction to change the size of the resistance.                     

Therefore, an object of the present invention is to provide a method for controlling the common voltage conveniently and accurately by providing a resistance control means for finely adjusting the variable resistor.

FIG. 3 illustrates a part of a common voltage control circuit in the common voltage generation unit of the present invention. As shown in FIG. 3, the common voltage generation unit includes a second voltage for dividing a voltage of the common voltage source Vc. A third resistor (R2, R3) and a variable resistor (R4) formed between the common voltage source (Vc) and the second resistor (R2), and the common voltage (Vcom) is the second and third resistors (R2, It is output from the output terminal between R3).

The common voltage is adjusted by adjusting the variable resistor R4. The variable resistor adjusting terminal is exposed to the outside of the liquid crystal display panel, and the common voltage is controlled by controlling the terminal through the voltage adjusting rod of the present invention. Adjust

Referring to FIG. 4, the common voltage may be adjusted by adjusting the variable resistance terminal 402 exposed to the outside of the liquid crystal display panel 401.

The common voltage generation unit providing the common voltage includes a plurality of resistors for dividing the voltage of the common voltage source and a variable resistor formed between the common voltage source and the resistors to change the common voltage value by adjusting the variable resistor. You can. In addition, since the terminal of the variable resistor is exposed to the outside of the liquid crystal display panel, the operator adjusts the variable resistor terminal to control the common voltage.

The variable resistor terminal is composed of a screw thread to change the resistance value according to the degree of rotation. Therefore, the present invention further provides a resistance adjusting means 403 capable of finely adjusting the rotation angle of the variable resistance terminal 402.

Hereinafter, the configuration of the resistance adjusting means 403 according to an embodiment of the present invention will be described with reference to FIG.

The resistance adjusting means of the present invention is characterized in that the operator can directly adjust the variable resistance terminal, the handle that is directly adjusted by the operator, that is, the rotation angle of the thimble (thimble) is reduced to a predetermined ratio and is transmitted to the tip. The tip is the end of the resistance adjusting means for contacting the variable resistance terminal to rotate the variable resistance terminal.

As an example, the resistance adjusting means of FIG. 5 includes a thimble 501 through which an operator adjusts a rotation angle, a first rotation shaft 510 transmitting a rotational power of the thimble 501, and the first The second rotary shaft 506 for receiving the rotational power from the rotary shaft 510 to rotate the resistance adjusting terminal and the first rotary shaft 510 and the second rotary shaft 506 can be adjusted to control the magnification of the rotation angle. A power transmission shaft 507, a first gear 502 formed at the end of the first rotation shaft 510, a second gear 505 formed at the end of the second rotation shaft 506, and The third cogwheel 503 formed at one end of the power transmission shaft 507 while engaging with the first cogwheel 502 and the other of the power transmission shaft 507 while engaging with the second cogwheel 505. And a fourth cog wheel 504 formed at one end thereof.

The resistance adjusting means 403 is configured to adjust the resistance control terminal at a reduced angle when the operator rotates the thimble 501 to enable the operator to finely adjust the resistance control terminal.                     

Therefore, the first cog wheel 502, the third cog wheel 503, the second cog wheel 505 and the fourth cog wheel 504 constituting the resistance adjusting means have a predetermined ratio, respectively.

Hereinafter, an operation relationship in which the second rotating shaft 506 is rotated by reducing the rotation angle of the thimble 501 will be described.

The tooth of the first gear 502 is five, the tooth of the third gear 503 meshing with it is 50, and the tooth of the fourth gear 504 formed at the other end of the power transmission shaft is five. If the number of teeth of the second gear 505 engaged with the dog is 50, the third gear 503 rotates one wheel while the first gear 502 rotates ten times, and the fourth gear 504 The second cogwheel 505 rotates one revolution while the cogwheel 10 rotates 10 times. Therefore, the second cogwheel 505 is reduced by 1/100 of the rotation of the first cogwheel 502 so that the second rotating shaft 506 rotates. That is, the control of the thimble 501 can be made 100 times more precise.

In addition, if the second gear 505 is configured to rotate with a ratio of 360: 1 with respect to the first gear 502 by adjusting the ratio of the cog wheels, one rotation (360 degree rotation) of the thimble is second. The rotation shaft 506 may be rotated by one degree.

As a result, the operator can precisely control the second rotation axis while roughly rotating the thimble 501, so that the operator can easily and precisely adjust the common voltage to find the reference common voltage value.

The above example merely shows an example in which an operator-controlled first rotational shaft and a second rotational shaft that transmits this power to the resistor operate, and the first rotational shaft and the second rotational shaft are directly engaged with each other to rotate at a predetermined rate. In addition, other configurations of rotating at a predetermined reduction ratio are possible.

Therefore, the generation of flicker due to the imbalance of the common voltage can be simply controlled by using the voltage adjusting means configured as described above.

Meanwhile, the present invention proposes another method for finding a common voltage value as a reference.

The flicker generated in the liquid crystal display device, in particular, the liquid crystal display device operating in the dot inversion method, is mainly focused on the DC bias Vcom by the inversion of the signal voltage applied to the TFT of the unit pixel ( When a difference occurs in the effective value rms of the voltage applied to the liquid crystal at +) (-), the difference in the effective value rms is a phenomenon that the screen is shaken while appearing as a difference in luminance on the screen of the liquid crystal display device.

Therefore, the DC bias Vcom is changed to minimize the flicker value at the time of inverting the signal voltage so that each rms value is equal to the rms value. To improve.

In the related art, the change of the DC bias, that is, the change of the common voltage, is merely performed by the operator's manual control of the variable resistor terminal and the change is made by observing the flicker with the naked eye. Difficult to find the DC bias value at the point of occurrence.

In the present invention, when the flicker occurs, the flicker is reduced by placing a polarizing plate on the liquid crystal display panel so that the flicker can be easily determined while changing the common voltage value to minimize the flicker. Easily find the minimum common voltage.                     

For example, if a polarizer is arranged to be black in a display panel having a liquid crystal array when the flicker is a minimum common voltage value, when the flicker occurs, that is, when a difference occurs in the effective voltage value of the common voltage, the arrangement of the liquid crystals may occur. Distorted, light leakage is observed through the polarizer. Therefore, while adjusting the variable resistance terminal through the adjusting means, it is possible to easily find the common voltage value that minimizes the flicker by observing the light leakage of the polarizer with the naked eye.

At this time, the common voltage can be finely adjusted by using the voltage adjusting means of the first embodiment as the adjusting means, and the common voltage can be easily adjusted by observing light leakage through the polarizer.

On the other hand, it is also possible to arrange the polarizing plate so as to be in a white state at the common voltage having the least flicker generation. That is, when the polarizers are arranged so that the polarization axis is parallel to the polarization proceeding from the liquid crystal display panel, and flickering is performed, the effective values at the inversion of the common voltage are the same, and the effective values at the inversion and the maximum brightness By comparing the contrast when the light becomes asymmetrical and dark through the polarizing plate, the common voltage value with the smallest flicker is found. That is, in this case, flicker is minimum when the light seen through the polarizer is maximum.

Therefore, in the present invention, when flicker occurs due to an asymmetry of the signal voltage value, the common voltage value for minimizing flicker generation can be found by finely adjusting the common voltage value through the first embodiment of the present invention. It can be easily found while visually checking the common voltage value to minimize the flicker through. The operator can conveniently adjust the common voltage value using the voltage adjusting means of the present invention.

Claims (7)

Generating a common voltage through a common voltage generator having a variable resistance terminal protruding outward of the liquid crystal display panel; A first shaft that rotates, a handle formed at one end of the first shaft, a second shaft that is engaged with the first shaft and rotates smaller than a rotation angle of the first shaft as the first shaft rotates, and the second Contacting the variable resistance terminal with an adjusting rod having one end of the shaft and having a tip contacting the variable resistance; Adjusting the resistance by rotating the knob to rotate the variable resistance terminal; And determining an optimum common voltage value by adjusting the adjusting rod. 2. The method of claim 1, wherein adjusting the resistance comprises: rotating a knob that constitutes one end of the first axis and is marked in the circumferential direction; Rotating a second axis that engages the first axis and rotates at a reduced rate by rotating the handle; And adjusting the size of the resistance by rotating the variable resistance terminal with a tip installed at one end of the second shaft. 3. The third gear according to claim 1, wherein the adjusting rod includes a first cog wheel at one end of the first shaft, a second cog wheel at one end of the second shaft, and a third tooth engaged with the first cog wheel. The wheel is provided at one end, and the other end is provided with a fourth cogwheel meshing with the second cogwheel to provide a power transmission shaft for transmitting the power of the first axis to the second axis. The method of controlling the voltage, characterized in that to finely control the size of the resistance by finely adjusting the variable resistance terminal through the tip rotates at a reduced rate than the rotation angle of the handle. The method of claim 1, further comprising: installing a polarizer on the liquid crystal display panel; Varying resistance by rotating a variable resistance terminal through the adjusting rod; And determining the common voltage value by detecting the flicker which is changed as the resistance is changed through the polarizer. Generating a common voltage through a common voltage generator having a variable resistance terminal protruding outward of the liquid crystal display panel; Providing a polarizer on a surface of the pixel portion of the liquid crystal display panel; Rotating the variable resistance terminal to change a common voltage; And observing the flicker of the liquid crystal display panel generated according to the change of the common voltage through the polarizing plate to determine an optimum common voltage value. The method of claim 5, wherein a black screen is observed through the polarizing plate at the optimum common voltage value, and light leakage is observed at a common voltage value at which flicker occurs. The method of claim 5, wherein a white screen is observed through the polarizer at the optimal common voltage value, and a screen darker than the white screen is observed at a common voltage value at which flicker occurs.

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