KR20170135555A - Method for improving afterimage of liquid crystal display device - Google Patents

Abstract

Disclosed is a method for alleviating an afterimage of a liquid crystal display device, which comprises the steps of: adjusting a gamma voltage in a white grayscale in an initial gamma curve of a liquid crystal display device; setting a reference common voltage at which a flicker level is minimized in the liquid crystal display device; generating a middle gamma curve by adjusting the gamma voltage in a black grayscale to allow the flicker level to be minimized in the liquid crystal display device; generating a flat gamma curve by adjusting the gamma voltage in each predetermined grayscale to allow the middle gamma curve to correspond to a normalized gamma curve; generating a first gamma curve by applying a first offset for each predetermined grayscale to the flat gamma curve to allow the flicker level to be minimized at each predetermined grayscale; evaluating a first afterimage of the liquid crystal display device on the basis of the first gamma curve; and generating a second gamma curve by applying a second offset for the white grayscale in the first gamma curve so as to allow the flicker level to be minimized in the liquid crystal display device when a predetermined afterimage level is not satisfied as a result of evaluating the first afterimage. Thus, according to the present invention, a flicker is reduced, and also, an afterimage in the liquid crystal display device having an alignment film made of a high resistance polyimide (PI) can be reduced.

Description

[0001] The present invention relates to a method for improving afterimage of a liquid crystal display device,

The present invention relates to a method for improving an afterimage of a liquid crystal display device, and more particularly, to a method for improving afterimage of a liquid crystal display device capable of effectively improving an afterimage in a liquid crystal display device.

Recently, as the information age has come to the age of information, a display field for visually expressing electrical information signals has been rapidly developed. In response to this, various display devices having excellent performance in thinning, light weighting, Is being developed.

Specific examples of such a display device include a liquid crystal display device (LCD), a plasma display panel (PDP), a field emission display device (FED), an organic light emitting display device Organic Light Emitting Display Device (OLED).

Here, the liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal using an electric field. Specifically, the liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix form, and a drive circuit for driving the liquid crystal display panel. Further, a liquid crystal layer for controlling the light transmittance in the liquid crystal display panel is formed. In such a liquid crystal layer, the liquid crystal molecules are arranged in a certain direction between the upper substrate and the lower substrate by the alignment film.

In general, one of the typical characteristics to be tuned in a liquid crystal display device is a flicker level. Here, the flicker is a phenomenon in which the intensity of the light emitted from the liquid crystal display panel is not constant and varies periodically with time, and a flicker of the screen is felt to the user. At this time, the flicker level can define the extent to which the flickering of the screen is perceived by the user. Such a flicker may cause inconvenience to the user, so it is necessary to minimize the flicker level. Thereby, the level of the common voltage Vcom that can minimize the flicker level is detected, and the optimum common voltage is recorded in the liquid crystal display panel to adjust the flicker level.

When a frequency of a signal applied to output one frame in such a liquid crystal display device is variable, a flicker phenomenon may occur. That is, a flicker occurs at a moment when a frequency of a signal applied to the liquid crystal display device is varied, and a flicker of the screen can be recognized to the user. In order to suppress the flicker phenomenon in such a liquid crystal display device, a method of using a high resistance polyimide (PI) as an alignment film has been studied.

On the other hand, when the alignment film is used as the high resistance PI in order to suppress the flicker phenomenon in the liquid crystal display device, the after-image in the liquid crystal display device may deteriorate the quality of the liquid crystal display device. The afterimage is a phenomenon in which the visual experience continues for a certain period of time even after the external stimulus disappears. In the liquid crystal display device, the light corresponding to the previous signal is transmitted or the image is outputted even after the signal such as the data voltage is removed .

Accordingly, the use of a high resistance PI as an alignment film for reducing flicker in a liquid crystal display device has caused a problem of residual image defects due to direct current (DC) applied to a liquid crystal display device. That is, there is a problem that the afterimage of the liquid crystal display device deteriorates the display quality due to the high resistance PI alignment film for reducing the flicker.

[Related Technical Literature]

One. Liquid crystal display and driving method thereof (Korean Patent Laid-Open No. 10-2007-0120280)

The inventors of the present invention have recognized a method of adjusting a common voltage and a gamma voltage in order to improve a residual image due to DC charging in a liquid crystal display panel. Accordingly, the present inventors have invented a method for improving afterimage of a liquid crystal display device capable of improving a residual image in a liquid crystal display device having a high resistance PI.

Accordingly, an object of the present invention is to provide a method for improving afterimage of a liquid crystal display device capable of reducing flicker while suppressing afterimage of a liquid crystal display device.

Another problem to be solved by the present invention is to provide a method for improving afterimage of a liquid crystal display device capable of reducing a DC charge amount in a liquid crystal display panel by adjusting a common voltage and a gamma voltage.

Another object of the present invention is to provide a method for improving afterimage of a liquid crystal display device capable of maximizing a recovery characteristic for discharging DC charging in a liquid crystal display panel by adjusting a common voltage and a gamma voltage .

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method for improving afterimage of a liquid crystal display (LCD) device, the method comprising: adjusting a gamma voltage in a white gamma curve in an initial gamma curve of a liquid crystal display device; Generating a middle gamma curve by adjusting a gamma voltage in a black gradation so that a flicker level is minimized in a liquid crystal display; generating a gamma curve corresponding to a normalized gamma curve; Adjusting a gamma voltage in each of the predetermined gradations to generate a flat gamma curve, calculating a first offset for each of the predetermined gradations so that the flicker level is minimized in each of the predetermined gradations, Generating a first gamma curve based on the first gamma curve, And a second offset for the white gradation in the first gamma curve is set so that the flicker level is minimized in the liquid crystal display device when the predetermined afterimage level is not satisfied as a result of evaluating the first afterimage To generate a second gamma curve. The afterimage improvement method of the liquid crystal display according to the embodiment of the present invention has the effect of remarkably reducing the afterimage in the liquid crystal display device having the alignment film made of the high resistance PI while reducing the flicker.

The details of other embodiments are included in the detailed description and drawings.

The present invention has the effect of reducing the afterimage in the liquid crystal display device having the alignment film made of the high resistance PI while reducing the flicker by adjusting the common voltage and the gamma voltage.

The present invention has the effect of reducing the flicker and the afterimage in the alignment film made of the high resistance PI and the liquid crystal display device having the variable frequency by adjusting the common voltage and the gamma voltage.

The present invention applies the offset of the optimum common voltage at which the flicker level is minimum before and after outputting the white gradation pattern to the gamma voltage in the white gradation as an offset so that the DC charge amount Can be reduced.

The present invention has the effect of improving the recovery characteristic by rapidly discharging the DC charge in the liquid crystal display panel by applying different offsets for every predetermined gradation so that the afterimage level can be minimized in the liquid crystal display panel.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

1 is a schematic block diagram illustrating a liquid crystal display according to an embodiment of the present invention.
2 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to an embodiment of the present invention.
FIGS. 3A to 3G are step-by-step gamma curves for explaining a residual image improvement method of a liquid crystal display according to an embodiment of the present invention.
4 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to another embodiment of the present invention.
FIGS. 5A and 5B are step-by-step gamma curves for explaining a residual image improvement method of a liquid crystal display according to another embodiment of the present invention.
6 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to another embodiment of the present invention.
FIGS. 7A and 7B are step-by-step gamma curves for explaining a residual image improving method of a liquid crystal display according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Where the terms "comprises", "having", "done", and the like are used in this specification, other portions may be added unless "only" is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions.

An element or layer is referred to as being another element or layer "on ", including both intervening layers or other elements directly on or in between.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical spirit of the present invention.

Like reference numerals refer to like elements throughout the specification.

The sizes and thicknesses of the individual components shown in the figures are shown for convenience of explanation and the present invention is not necessarily limited to the size and thickness of the components shown.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, technically various interlocking and driving, and that the embodiments may be practiced independently of each other, It is possible.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram illustrating a liquid crystal display according to an embodiment of the present invention.

1, a liquid crystal display 100 includes a liquid crystal display panel 110, a gate driver 120, a data driver 130, a timing controller 140, a common voltage generator 150, (160).

1, the liquid crystal display panel 110 includes a plurality of gate lines G1 to Gn and a plurality of data lines D1 to Dm, which display an image according to an input video signal. The liquid crystal display panel 110 includes a plurality of pixels PX formed in regions defined by intersecting the plurality of gate lines G1 to Gn and the plurality of data lines D1 to Dm.

In addition, the liquid crystal display panel 110 has a structure in which multiple layers are stacked. Specifically, a thin film transistor (TFT) as a switching element is disposed in each of the plurality of pixels PX in the liquid crystal display panel 110, and a pixel electrode, a common electrode, a liquid crystal layer, .

The pixel electrode and the common electrode can be formed on one substrate to form a transverse electric field. The liquid crystal layer may include a negative-type liquid crystal layer having a negative dielectric anisotropy or a positive-type liquid crystal layer having a positive dielectric anisotropy.

The orientation film is made of high resistance PI, and the high resistance can have a volume resistance of 1X10 ¹⁵ ? Cm. The alignment layer may be a photo alignment layer oriented by light such as ultraviolet (UV) light.

Referring to FIG. 1, the gate driver 120 is disposed on one side of the liquid crystal display panel 110. In some embodiments, the gate driver 120 may be mounted on one side of the liquid crystal display panel 110 and may be implemented as a GIP (Gate Drive In In Panel) circuit. The gate driver 120 supplies a gate voltage to each of the plurality of pixels PX through a plurality of gate lines G1 to Gn connected to the gate driver 120. [ Although the gate driver 120 is illustrated as being disposed on one side of the liquid crystal display panel 110 in FIG. 1, the gate driver 120 may be disposed on a plurality of sides of the liquid crystal display panel 110.

1, the data driver 130 is disposed on one side of the liquid crystal display panel 110 adjacent to the side of the liquid crystal display panel 110 in which the gate driver 120 is disposed. The data driver 130 supplies a data voltage to the liquid crystal display panel 110 through the plurality of data lines D1 to Dm. That is, the data driver 130 supplies a data voltage to each of the plurality of pixels PX connected to the plurality of data lines D1 to Dm. Here, the data voltage supplied to each of the plurality of pixels PX may be a gamma voltage generated by the gamma voltage generator 160.

Referring to FIG. 1, the timing controller 140 supplies various signals to the gate driver 120 and the data driver 130. Specifically, the timing controller 140 generates a data driver control signal (DDC) and supplies the data driver control signal to the data driver 130. The gate driver generates a gate driver control signal (GDC) (120). Here, the gate driver control signal GDC includes a gate start pulse (GSP), a gate shift clock (GSC), and a gate output enable signal (GOE). The data driver control signal DDC includes a source start pulse SSP, a source sampling clock SSC, and a source output enable signal SOE. The gate driving unit control signal GDC and the data driving unit control signal DDC may be supplied to the gate driving unit 120 and the data driving unit 130 based on the horizontal synchronizing signal Hsync and the vertical synchronizing signal Vsync, have. However, signal constructions of the data driver control signal DDC and the gate driver control signal GDC are not limited thereto. In particular, the timing controller 140 generates a voltage control signal (VCS) for changing the common voltage and the gamma voltage based on the driving time of the liquid crystal display device, and supplies the generated voltage control signal VCS to the gamma To the voltage generating unit 160 and the common voltage generating unit 150. The timing controller 140 receives the video signals R, G, and B and transmits the video data signals RGB together with the data driver control signal DDC to the data driver 130.

Referring to FIG. 1, the common voltage generator 150 is disposed on one side of the liquid crystal display panel 110. The common voltage generator 150 supplies a predetermined common voltage Vcom to the common electrodes disposed entirely on the liquid crystal display panel 110. [ When the liquid crystal display panel 110 outputs an image, the common voltage generator 150 can adjust the common voltage Vcom to suppress the flicker and the afterimage.

Referring to FIG. 1, the gamma voltage generator 160 is connected to the data driver 130. Also, the gamma voltage generator 160 includes a gamma curve formed of a positive gamma voltage and a negative gamma voltage, and a digital-analog converter (DAC) converting a gamma data into a gamma voltage based on the gamma curve. When the image is output from the liquid crystal display panel 110, the gamma voltage generator 160 may adjust the gamma voltage to suppress the flicker and the afterimage.

In FIG. 1, the common voltage generator 150 and the gamma voltage generator 160 are shown as separate modules. However, the common voltage generator 150 and the gamma voltage generator 160 may be implemented in one voltage generator according to an embodiment of the present invention.

The liquid crystal display 100 of the present invention includes a liquid crystal display panel 110 having a plurality of layers and includes a common voltage generator 150 for supplying a common voltage Vcom to the liquid crystal display panel 110, And a gamma voltage generator 160 for supplying a voltage. Accordingly, in the liquid crystal display panel 110, the common voltage Vcom is supplied from the common voltage generator 150 to the common electrode, and the data signal corresponding to the gamma voltage is supplied from the gamma voltage generator 160 to the pixel electrode do.

The display quality of the liquid crystal display device 100 is evaluated so that the liquid crystal display device 100 can be stably driven in various environments. Specifically, flicker and afterimages can be evaluated so that the liquid crystal display device 100 can be stably driven at various frequencies. Particularly, when a frequency of a signal applied to a liquid crystal display device including an orientation film made of a general high resistance PI is changed, a residual image defect may occur. The change of the frequency may include, for example, variable drive at 60 Hz to 30 Hz or variable drive at 24 Hz to 120 Hz, but is not limited thereto. When the variable driving is applied, the power consumption is reduced and the reaction speed can be increased at the time of touch. Therefore, it is required that the common voltage and the gamma voltage be efficiently determined so as to suppress flicker and afterimage on the liquid crystal display device 100. [ As described above, the common voltage and the gamma voltage supplied to the liquid crystal display panel 110 are adjusted to reduce the flicker and the afterimage. Specifically, a method of suppressing flicker and afterimages will be described below with reference to the drawings.

2 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to an embodiment of the present invention. FIGS. 3A to 3G are step-by-step gamma curves for explaining a residual image improvement method of a liquid crystal display according to an embodiment of the present invention. Will be described with reference to Fig. 1 for convenience of explanation.

Referring to FIG. 2, the gamma voltage in the white gradation is adjusted in the initial gamma curve of the liquid crystal display 100 (S211).

Referring to FIG. 3A, the initial gamma curve 310 of the liquid crystal display 100 includes a positive gamma voltage curve 310a and a negative gamma voltage curve 310b. Here, the initial gamma curve 310 means the first gamma curve in which the common voltage and the gamma voltage are not adjusted in the liquid crystal display device. That is, the initial gamma curve 310 is a gamma curve that is produced and output for the first time. In the initial gamma curve 310, the positive gamma voltage curve 310a and the negative gamma voltage curve 310b are symmetrical with respect to the center gamma voltage Vcenter. That is, the positive gamma voltage and the negative gamma voltage at predetermined gradations, for example, 255 gradations, 233 gradations, 191 gradations, 127 gradations, 63 gradations, 15 gradations, and 0 gradation, Symmetric to each other. For example, when VDD is 8V and GND is 0V, the central gamma voltage Vcenter is 4V, the positive gamma voltage 311a in the white gradation is 7.5V and the negative gamma voltage 311b in the white gradation ) May be 0.5V. That is, the positive gamma voltage 311a in the white gradation and the negative gamma voltage 311b in the white gradation may differ by 3.5V from the center gamma voltage Vcenter. In this specification, seven gradations of 255 gradations, 233 gradations, 191 gradations, 127 gradations, 63 gradations, 15 gradations and 0 gradation are defined as predetermined gradations, but the predetermined gradation values and the number of gradations may vary Can be set.

Referring to FIG. 3A, the gamma voltage 311 in the white gradation is adjusted in the initial gamma curve 310. Specifically, the gamma voltage 311 in the white gradation is adjusted in the first direction (1) or the second direction (2) in consideration of the brightness saturation point and the occurrence of the touch blur in the white gradation. Here, the first direction (1) means a positive direction at a positive gamma voltage and the positive direction at a negative gamma voltage, the second direction (2) means a positive direction at a positive gamma voltage, In voltage, it means negative direction. That is, the first direction (1) is a direction in which the gamma voltage is adjusted so as to face the center gamma voltage (Vcenter), and the second direction (2) is a direction in which the gamma voltage is adjusted to be away from the center gamma voltage (Vcenter). Hereinafter, the first direction (1) and the second direction (2) can be understood as such.

Referring to FIGS. 2 and 3B, when the gamma voltage is adjusted in the first direction (1), the gamma voltage 321 in the adjusted white tones is adjusted by the positive gamma voltage 321a in the adjusted white tones, And a negative gamma voltage 321b in the white tones. That is, as the gamma voltage is adjusted in the first direction (1), the gamma curve 320 having the gamma voltage at the adjusted white gradation level is set to a positive gamma curve 320a having a positive gamma voltage in the adjusted white gradation And a negative gamma curve 320b having a negative gamma voltage in the adjusted white gradation. FIG. 3B shows the case where the gamma voltage is adjusted in the first direction (1), but the gamma voltage may be adjusted in the second direction (2) according to the embodiment.

Subsequently, a reference common voltage at which the flicker level becomes minimum in the liquid crystal display device is set (S212).

Referring to Figs. 2 and 3B, the liquid crystal display 100 is set to have a reference common voltage Vcom, r at which the flicker level becomes minimum. Specifically, the liquid crystal display device 100 having the gamma curve 320 having the gamma voltage 321 in the adjusted white gradation outputs the white gradation-black gradation pattern, so that the common voltage at which the flicker level becomes minimum becomes the reference Is set to the common voltage Vcom, r. Here, the reference common voltage Vcom, r may be a voltage that is lowered by the kick-back voltage due to parasitic capacitance in the liquid crystal display panel 110 at the center gamma voltage Vcenter. The white gradation-black gradation pattern means a mosaic pattern in which white gradation and black gradation are alternately output for each pixel PX.

Subsequently, the gamma voltage in the black gradation is adjusted so that the flicker level is minimized in the liquid crystal display device to generate the intermediate gamma curve (S213).

2 and 3C, when the liquid crystal display device 100 to which the reference common voltage Vcom, r is fixedly applied outputs the low gray level-black gray level pattern, the flicker level of the liquid crystal display device 100 The gamma voltage 331 in the black gradation is adjusted so as to be minimum. More specifically, the gamma voltage 331 in the black gradation is composed of the positive gamma voltage 331a in the black gradation and the negative gamma voltage 331b in the black gradation, Is adjusted in the first direction (1) or the second direction (2) so that the flicker level can be minimized in the display device (100). Here, the low gradation means the gradation adjacent to the black gradation, and may be, for example, five gradations.

Referring to FIGS. 2 and 3, the gamma voltage 311 in the white gradation is adjusted in the initial gamma curve 310 of the liquid crystal display 100, the reference common voltage Vcom, r is set, The gamma voltage 331 at the intermediate gamma curve 340 is adjusted so that the intermediate gamma curve 340 including the positive middle gamma curve 340a and the negative middle gamma curve 340b is generated. For example, the positive gamma voltage 331a in the black gradation and the negative gamma voltage 331b in the black gradation are adjusted in the first direction (1) to generate the intermediate gamma curve 340. The intermediate gamma curve 340 is adjusted such that the gamma voltage 341 in the black gradation adjusted in the first direction (1) is adjusted by the same voltage toward the center gamma voltage Vcenter to maintain a constant central gamma voltage Vcenter .

Subsequently, a gamma curve in each of the predetermined gradations is adjusted so that the intermediate gamma curve corresponds to the normalized gamma curve to generate a flat gamma curve (S214).

Referring to FIGS. 2 and 3, the intermediate gamma curve 340 is different from the normalized gamma curve so that the intermediate gamma curve 340 is tuned to correspond to the normalized gamma curve in order for the liquid crystal display device 100 to be normally driven tuning. Here, the normalized gamma curve is a gamma curve obtained by normalizing the transmittance or the brightness corresponding to the gradation, for example, a gamma curve of 2.2.

Thus, the gamma voltages in the predetermined gradations except the gamma voltage in the white gradation and the gamma voltage in the black gradation are adjusted so that the intermediate gamma curve 340 corresponds to the normalized gamma curve. The gamma voltages in the respective predetermined gradations are adjusted in the first direction (1) or the second direction (2) like the gamma voltage in the white gradation and the gamma voltage in the black gradation.

2 and 3E, by adjusting the gamma voltage in each of the predetermined gradations in the intermediate gamma curve 340 of the liquid crystal display 100, a flat gamma curve 350 (corresponding to the normalized gamma curve) ) Is generated. Here, the flat gamma curve 350 is a gamma curve in which the gamma voltages in the respective gradations are adjusted so as to correspond to the gamma curve normalized from the intermediate gamma curve 340 of the liquid crystal display 100, and the center gamma voltage Vcenter Means a gamma curve maintained constant. That is, the flat gamma curve 350 means a gamma curve in which the difference between the positive gamma voltage and the center gamma voltage Vcenter and the difference between the center gamma voltage Vcenter and the negative gamma voltage remain the same. For example, the gamma voltage in each of the predetermined gradations can be adjusted in the first direction (1), so that the difference between the positive gamma voltage and the central gamma voltage Vcenter in each of the predetermined gradations becomes the center gamma voltage Vcenter ) And the negative gamma voltage at each of the predetermined gradations.

Next, a first gamma curve is generated by applying a first offset to each of the predetermined gradations to the flat gamma curve so as to minimize the flicker level in each of the predetermined gradations (S220).

Referring to FIGS. 2 and 3E, in the flat gamma curve 350, the reference common voltage Vcom, r is applied to the liquid crystal display 100, The gamma voltages in each are adjusted. Specifically, one predetermined gradation-black gradation pattern is output in a state where the reference common voltage Vcom, r is applied to the liquid crystal display device 100, and a predetermined gamma -voltage level at which the flicker level of the liquid crystal display device 100 becomes minimum The gamma voltage at one of the predetermined gradations is adjusted by the voltage. The gamma voltages in all the predetermined gradations are adjusted such that the flicker level of the liquid crystal display device 100 is minimized through the same process for the remaining predetermined gradations.

The gamma voltage in each of the predetermined gradations is adjusted in the third direction (3) or the fourth direction (4). Here, the third direction (3) means a negative direction in both the positive gamma voltage and the negative gamma voltage, and the fourth direction (4) means positive direction in both the positive gamma voltage and the negative gamma voltage. do. Hereinafter, the third direction (3) and the fourth direction (4) can be understood as such. However, the third direction (③) and the fourth direction (④) indicate only the directional tendency, but are independent of the magnitude of the voltage adjusted in the corresponding direction.

The gamma voltage at one predetermined gradation is adjusted in the same direction so that the flicker level is minimized. Specifically, both the positive gamma voltage and the negative gamma voltage at one predetermined gradation are adjusted to the same magnitude of voltage in the same direction. For example, the positive gamma voltage 351a at the 233th gradation and the negative gamma voltage 351b at the 233th gradation can be adjusted by 10mV in the third direction (3), respectively.

Further, the gamma voltages at different predetermined gradations may be adjusted in different directions. For example, the gamma voltage 351 at the 233th gradation is adjusted to the third direction (3), while the positive gamma voltage 352a at the 127th gradation and the negative gamma voltage 352b at the 127th gradation are included The gamma voltage 352 at the 127th gradation can be adjusted in the fourth direction (4).

As such, the gamma voltages adjusted to minimize the flicker level in each of the predetermined gradations constitute a first offset 355 for each of the predetermined gradations. That is, the direction and magnitude in which the gamma voltage is adjusted in each of the predetermined gradations constitutes the first offset 355. [ This first offset 355 corresponds to a positive first offset 355a applied to the positive first gamma curve 350a and a negative first offset 355b applied to the negative first gamma curve 350b .

Referring to FIGS. 2 and 3F, a first offset 355 is applied to the flat gamma curve 350 to produce the first gamma curve 360. That is, the first gamma curve 360 is generated by applying a first offset 355 to each of the predetermined gradations in the flat gamma curve 350.

Then, the first afterimage of the liquid crystal display device is evaluated based on the first gamma curve (S230). If a predetermined afterimage level is not satisfied as a result of the first afterimage evaluation, a second offset for the white gradation in the first gamma curve is applied so as to minimize the flicker level in the liquid crystal display to generate the second gamma curve (S240).

Referring to FIGS. 2 and 3F, the first gamma curve 360 may have a first central gamma voltage Vcenter, 1, which is non-linear. Specifically, the positive gamma voltage and the negative gamma voltage in each of the gradations in the first gamma curve 360 are mutually symmetric with respect to the first central gamma voltage Vcenter, 1. The first center gamma voltage Vcenter, 1 may be nonlinear since the first offset 355 may be different in direction and magnitude in each of the predetermined gradations. That is, the first central gamma voltage (Vcenter, 1) connecting the center gamma voltages in each of the predetermined gradations may not be maintained in a straight line. In addition, since each of the first offsets 355 in each of the predetermined gradations is the same in direction and size, the positive gamma voltage in each of the predetermined gradations between the flat gamma curve 350 and the first gamma curve 360 The difference in the negative gamma voltage is kept the same.

The first gamma curve 360 thus generated is applied to the liquid crystal display device 100 and used to evaluate the afterimage of the liquid crystal display device. In the method of evaluating the residual image, a residual image evaluation pattern is output from the liquid crystal display device 100 for a predetermined period of time, and thereafter, the liquid crystal display device outputs a gradation pattern for judging the afterimage and compares the residual image evaluation pattern on the basis of the gradation pattern And judges whether or not a predetermined level of afterimage is output from the gradation, thereby evaluating the afterimage. Specifically, after the residual image evaluation pattern is output for 10 seconds, 3 minutes, 1 hour, or 6 hours while driving the liquid crystal display device at 30 Hz and 60 Hz, And judges whether a residual image level lower than the determined level appears.

Here, the afterimage evaluation pattern is a mosaic pattern in which a white gradation and a black gradation are alternately output in a sub region in which a plurality of sub regions divided from the active region of the liquid crystal display device are adjacent to each other. That is, the afterimage evaluation pattern may be a pattern output to the active area like a chess board. For example, the afterimage evaluation pattern may be a mosaic pattern that alternately outputs white gradation and black gradation with a matrix of 6X4 in the active area. In this specification, the evaluation of the afterimage of the liquid crystal display 100 based on the first gamma curve 360 is expressed as evaluating the first afterimage.

When the afterimage evaluation pattern is used to evaluate the first afterimage of the liquid crystal display device and the predetermined afterimage level is not satisfied, the second offset is determined.

Referring to FIG. 2 and FIG. 3F, first, the liquid crystal display 100 outputs a halftone-black gradation pattern, and a first initial optimum common voltage 127G Vcom, 1, at which the flicker level is minimized, (100). Specifically, in a state in which the 127 gradation and the black gradation corresponding to the halftone are alternately arranged on the basis of one pixel and the halftone-black gradation pattern is outputted, the flicker level of the liquid crystal display 100 becomes minimum The optimum common voltage is set to the first initial optimum common voltage 127G Vcom, 1.

Next, a gamma voltage for outputting a high gray level is applied to the pixel electrodes of the liquid crystal display device 100 for a predetermined time, so that the liquid crystal display device 100 is charged with DC. Here, the high gradation means a gradation close to white gradation and white gradation. Specifically, in a state in which the first initial optimum common voltage (127G Vcom, 1) is applied to the liquid crystal display device 100 as a common voltage of the liquid crystal display device 100, the liquid crystal display device 100 displays white And outputs the gradation pattern. For example, white light may be output for 6 hours in the liquid crystal display device 100. [ Thus, the gamma voltage in the white gradation having the greatest difference from the first initial optimum common voltage 127G Vcom, 1 is supplied to the liquid crystal display panel 110 of the liquid crystal display device 100. [ That is, since the gamma voltage in the white gradation is supplied for a long time, the DC charge amount can be maximized in the liquid crystal display panel 110.

Subsequently, the liquid crystal display device 100 outputs the halftone-black gradation pattern to obtain the first final optimum common voltage which minimizes the flicker level. Specifically, the common voltage can be adjusted so that the flicker level of the liquid crystal display device 100 is minimized in a state in which the halftone-black gradation pattern is output again to the liquid crystal display panel 100 in which the white gradation pattern is output for a long time have. That is, as the white gradation pattern is output for a long time, the amount of DC charging increases in the liquid crystal display panel 110, and the flicker level of the first initial optimum common voltage 127G Vcom, 1 can be raised. Therefore, the common voltage at which the flicker level of the liquid crystal display device 100 is minimized after the output of the white gradation pattern for a long time can be changed. Therefore, in the state in which the intermediate gradation-black gradation pattern is outputted, The first final optimum common voltage at which the flicker level of the pixel is minimized can be obtained.

By applying the difference of the optimum common voltage at which the flicker level is minimum before and after outputting the white gradation pattern as an offset to the gamma voltage in the white gradation, the DC charging amount due to the output of the white gradation pattern can be originally limited . Specifically, the second offset 365 is a difference between the first final optimum common voltage and the first initial optimum common voltage 127G Vcom, 1, and the gamma voltage 361 in the white gradation is equal to the second offset 365 A second gamma curve can be generated. Here, the gamma voltage 361 in the white gradation is adjusted to the third direction (3) or the fourth direction (4) by the second offset 365. For example, when the second offset 365 is -10 mV, the positive gamma voltage 361a in the white gradation and the negative gamma voltage 361b in the white gradation are both 10 mV in the third direction (3) Lt; / RTI >

Accordingly, the second gamma curve can reduce the DC charge amount due to the output of the long-time white gradation pattern having the maximum DC stress to the liquid crystal display panel 110 by the second offset 365. That is, by adjusting the gamma voltage 361 in the white gradation through the second offset 365, the DC charge amount that can be charged in the liquid crystal display panel 110 is limited due to the output of the white gradation pattern, The residual image can be remarkably reduced as well.

Referring to FIG. 3G, the second gamma curve 370 is generated by applying a second offset 365 to the white gradation in the first gamma curve 360. Since only the gamma voltage 361 in the white gradation is adjusted in the first gamma curve 360, the second gamma curve 370 may also have a second central gamma voltage Vcenter, 2, which is nonlinear. In addition, since the second offset 365 in the white gradation is the same in direction and size, the positive gamma voltage and the negative gamma voltage in the respective gradations between the first gamma curve 360 and the second gamma curve 370 The difference remains the same.

The second gamma curve 370 thus generated is applied to the liquid crystal display device 100 and used to evaluate the afterimage of the liquid crystal display device. That is, the second afterimage of the liquid crystal display device is evaluated based on the second gamma curve 370 (S250). In this specification, the evaluation of the afterimage of the liquid crystal display 100 based on the second gamma curve 370 is expressed as evaluating the second afterimage. The method of evaluating the second afterimage in this manner is substantially the same as the method of evaluating the first afterimage, so duplicate explanation is omitted.

When the second afterimage of the liquid crystal display device 100 is evaluated based on the second gamma curve 370 and the predetermined afterimage level is satisfied as a result of evaluating the second afterimage, the second gamma curve 370 is displayed on the liquid crystal display May be determined as a gamma curve that minimizes the afterimage of the apparatus 100 (S300).

The method of improving the afterimage of the liquid crystal display 100 according to an embodiment of the present invention allows the liquid crystal display 100 to have a minimum flicker level based on the flat gamma curve 350 corresponding to the normalized gamma curve The first gamma curve 360 to which the first offset 355 is applied is generated and when the first gamma curve 360 does not pass the first afterimage evaluation, the second offset 365, at which the flicker level becomes minimum again, The second gamma curve 370 is generated. Since the first offset 355 and the second offset 365 are set such that the gamma voltages in the respective gradations have the same tendency, the first center gamma voltage Vcenter, 1, The second central gamma voltage Vcenter 2 of the second gamma curve 370 is non-linear. In particular, since the gamma voltage 361 in the white gradation is adjusted by the second offset 365, the DC charge amount that can be charged in the liquid crystal display panel 110 is limited due to the output of the white gradation pattern, The residual image can be remarkably reduced as well.

4 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to another embodiment of the present invention. FIGS. 5A and 5B are step-by-step gamma curves for explaining a residual image improvement method of a liquid crystal display according to another embodiment of the present invention. The flowchart shown in FIG. 4 further includes a step of generating a third gamma curve and a step of evaluating a third afterimage in the flowchart shown in FIG. 2, and the remaining configurations are substantially the same, . Will be described with reference to Fig. 1 for convenience of explanation.

First, if a predetermined afterimage level is not satisfied as a result of evaluation of the second afterimage, a third offset for adjusting the gamma voltage in each of the predetermined gradations is applied to the second gamma curve so that the afterimage level of the liquid crystal display device is minimized Thereby generating a third gamma curve (S460).

Referring to FIGS. 4 and 5A, when the second afterimage evaluation is not passed to the second gamma curve 570, the gamma voltage in each of the predetermined gradations is adjusted so as to reduce the afterimage level. Specifically, the liquid crystal display 100 outputs the halftone-black gradation pattern to set the second initial optimum common voltage 127G Vcom, 2, which has the minimum flicker level, to the common voltage of the liquid crystal display 100 do. Specifically, in a state in which the 127 gradation and the black gradation corresponding to the halftone are alternately arranged on the basis of one pixel and the halftone-black gradation pattern is outputted, the flicker level of the liquid crystal display 100 becomes minimum The optimum common voltage is set to the second initial optimum common voltage 127G Vcom, 2.

Then, a gamma voltage for outputting a high gray-scale low-gray-level pattern is applied to the pixel electrodes of the liquid crystal display device 100 for a predetermined time to charge the liquid crystal display device 100 with DC. Here, the low gradation means a gradation close to black gradation and black gradation. Specifically, in a state in which the second initial optimal common voltage (127G Vcom, 2) is applied to the liquid crystal display device 100 as a common voltage of the liquid crystal display device 100, And outputs an evaluation pattern. For example, the afterimage evaluation pattern can be output in the liquid crystal display 100 for 6 hours. Here, the residual image evaluation pattern may be the same as the residual image evaluation pattern used in the method of evaluating the first residual image and the method of evaluating the second residual image. Thus, a gamma voltage having a white gradation and a black gradation having the same gradation difference from the intermediate gradation is supplied to the liquid crystal display panel 110 of the liquid crystal display device 100. [ This may be a condition set so as to confirm the recovered speed from the white gradation and the black gradation to each of the predetermined gradations.

Subsequently, the liquid crystal display 100 outputs a pattern corresponding to each of the predetermined gradations, and a second final optimum common voltage at which the afterimage level becomes minimum for each predetermined gradation is obtained. Specifically, when the liquid crystal display device 100 is changed from a state in which the residual image evaluation pattern is output for a long time to a state in which one predetermined gradation is output, a residual image which can not be recovered from the white gradation or the black gradation by one predetermined gradation Can be found. Thus, a second final optimum common voltage at which a residual image level becomes minimum can be obtained while adjusting the gamma voltage so that it can be quickly recovered from white gradation or black gradation to one predetermined gradation.

For example, when the afterimage evaluation pattern is output to the liquid crystal display device 100 for a predetermined time with respect to 233 gradations, 233 gradations are outputted. Since the 233 gradation is a gradation close to white gradation, The recovery can be performed quickly with 233 gradations, but since the gradation is far away from the black gradation, the area in which the black gradation is outputted can be recovered at 233 gradation and the afterimage can be found. Thus, a second final optimum common voltage at which a residual image level becomes minimum can be obtained by adjusting the gamma voltage at 233 gradations so as to be quickly recovered from the black gradation to the 233 gradation. Likewise, a second final optimum common voltage is obtained so that the afterimage level can be quickly minimized by quickly recovering for every other predetermined gradation.

The third offset 575 is a difference between the second final optimal common voltage and the second initial optimal common voltage 127G Vcom, 2, and the third offset 575 is adjusted by the third offset 575 for every predetermined gradation, Can be generated. Here, the gamma voltage in each of the predetermined gradations is adjusted to the third direction (3) or the fourth direction (4) by the third offset (575). For example, when the third offset 575 at 233 gradation is +10 mV, both the positive gamma voltage 571a at the 233th gradation and the negative gamma voltage 571b at the 233th gradation are all in the fourth direction (4) ) Can be adjusted by 10 mV. Thus, the third offset 365 is applied to the gamma voltage every predetermined gradation to generate the third gamma curve.

Accordingly, the third gamma curve may be generated by applying a third offset 575 different every predetermined gray level so that the afterimage level may be minimized in the liquid crystal display panel 110. [ That is, the rate of recovery to each of the predetermined gradations through the third offset 575 can be remarkably improved, and the afterimage can be remarkably reduced.

Referring to FIG. 5B, the third gamma curve 580 is generated by applying a third offset 575 in each of the predetermined gradations in the second gamma curve 570. The third gamma curve 580 may also have a third center gamma voltage Vcenter, 3, which is non-linear, since both gamma voltages at each predetermined gray level in the second gamma curve 570 can be adjusted. In addition, since the third offset 575 in each of the predetermined gradations is the same in direction and size, the positive gamma voltage and the negative gamma voltage in each of the gradations between the second gamma curve 570 and the third gamma curve 580 The difference in the gamma voltage is kept the same.

The third gamma curve 580 thus generated is applied to the liquid crystal display device 100 and used to evaluate the afterimage of the liquid crystal display device. That is, the third afterimage of the liquid crystal display device is evaluated based on the third gamma curve 580 (S470). In this specification, the evaluation of the afterimage of the liquid crystal display 100 based on the third gamma curve 580 is expressed as evaluating the third afterimage. Since the method of evaluating the third residual image is substantially the same as the method of evaluating the first residual image and the method of evaluating the second residual image, redundant description will be omitted.

When the third afterimage of the liquid crystal display apparatus 100 is evaluated based on the third gamma curve 580 and the predetermined afterimage level is satisfied as a result of evaluating the third afterimage, the third gamma curve 580 is displayed on the liquid crystal display May be determined as a gamma curve that minimizes the afterimage of the apparatus 100 (S300).

It is possible to improve the afterimage of the liquid crystal display device 100 according to another embodiment of the present invention so that the afterimage level of the liquid crystal display device 100, The voltage can be adjusted. That is, a third offset 575 for adjusting the gamma voltage in each of the predetermined gradations is determined so that the afterimage level is minimized for each predetermined gradation. Accordingly, a third offset 575 is applied to the second gamma curve 570 to generate a third gamma curve 580. [ Further, when the third gamma curve 580 passes the third afterimage evaluation, the recovery speed is improved and the recovery speed is improved in the liquid crystal display 100 to which the third gamma curve 580 is applied, .

6 is a flowchart illustrating a method of improving afterimage of a liquid crystal display according to another embodiment of the present invention. FIGS. 7A and 7B are step-by-step gamma curves for explaining a residual image improving method of a liquid crystal display according to another embodiment of the present invention. The flowchart shown in Fig. 6 further includes a step of generating a fourth gamma curve and a step of evaluating a fourth afterimage in the flowchart shown in Fig. 4, and the remaining configuration is substantially the same, and a duplicate description thereof will be omitted . Will be described with reference to Fig. 1 for convenience of explanation.

First, based on the tendency of the third offset in each of the predetermined gradations so that the afterimage level of the liquid crystal display device 100 is minimized when the predetermined afterimage level is not satisfied as a result of the evaluation of the third afterimage, Determines the offset. Then, a fourth offset is applied to the third gamma curve to generate a fourth gamma curve (S680), at least one of which is the minimum offset of the adjustment offset of the liquid crystal display device 100.

Referring to Figs. 6 and 7A, the adjustment offset is an offset having the same tendency as the third offset. Specifically, when the third offset has a tendency to adjust the gamma voltage in the gradation to the fourth direction (4), the adjustment offset is also determined to adjust the gamma voltage in the gradation in the fourth direction (4). For example, when the third offset is -10 mV at the 127th gradation, the first adjustment offset 785 at the 127th gradation can be determined to be 5 mV in the fourth direction (4), and the second adjustment offset 786 at the 127th gradation, May be determined to be 20 mV in the fourth direction (4). In FIG. 7A, only the first adjustment offset 785 and the second adjustment offset 786 at the 127th gradation are shown at the 127th gradation, but if the third adjustment offset 786 has the same tendency as the third offset, the number of adjustment offsets in one gradation, The size is not limited. Also, although the adjustment offsets 785 and 786 are shown only for 127 gradations in Fig. 7A, the adjustment offset can be determined for each of the remaining predetermined gradations.

Further, based on the determined adjustment offset, at least one of the adjustment offsets 785 and 786 and the offset at which the afterimage level becomes the smallest among the third offsets is determined as the fourth offset and applied to the third gamma curve 780. By applying the fourth offset, which is the offset that minimizes the afterimage level, to the third gamma curve based on the various adjustment offsets and the third offset, the fourth gamma curve that can minimize the afterimage level finally, Is generated.

Accordingly, the fourth gamma curve may be generated by applying a fourth offset different every predetermined gray level so that the afterimage level may be minimized in the liquid crystal display panel 110. [ That is, the afterimage level can be remarkably reduced through the fourth gamma curve to which the fourth offset is applied.

Referring to FIG. 7B, the fourth gamma curve 790 is generated in the third gamma curve 780 by applying a fourth offset of at least one of the adjustment offsets. The fourth gamma curve 790 may also have a non-linear fourth center gamma voltage Vcenter, 4, since the gamma voltages at each of the predetermined gradations in the fourth gamma curve 790 can all be adjusted. In addition, since the fourth offset in each of the predetermined gradations is the same in direction and size, the positive gamma voltage and the negative gamma voltage in each of the gradations between the third gamma curve 780 and the fourth gamma curve 790 The difference remains the same.

The fourth gamma curve 790 thus generated is applied to the liquid crystal display device 100 and used to evaluate the afterimage of the liquid crystal display device. That is, the fourth afterimage of the liquid crystal display device is evaluated based on the fourth gamma curve 790 (S690). In this specification, evaluation of the afterimage of the liquid crystal display device 100 based on the fourth gamma curve 790 is expressed as evaluating the fourth afterimage. The method of evaluating the fourth residual image is substantially the same as the method of evaluating the first residual image, the method of evaluating the second residual image, and the method of evaluating the third residual image.

When the fourth afterimage of the liquid crystal display apparatus 100 is evaluated based on the fourth gamma curve 790 and the predetermined afterimage level is satisfied as a result of evaluation of the fourth afterimage, the fourth gamma curve 790 is displayed on the liquid crystal display May be finally determined as a gamma curve that minimizes the afterimage of the apparatus 100 (S300).

The method of improving the afterimage of the liquid crystal display device 100 according to another embodiment of the present invention can reduce the afterimage level of the liquid crystal display device 100 that has not passed the third afterimage evaluation The gamma voltage can be adjusted to various levels. That is, the residual image evaluation of the liquid crystal display 100 is performed based on the various adjustment offsets 786, so that the gamma voltage that can minimize the afterimage level in each of the predetermined gradations can be examined in more detail. Accordingly, an optimum offset at which the afterimage can be minimized over all predetermined gradations of the liquid crystal display device 100 can be determined, and through the fourth gamma curve 790 to which such optimal offset is applied, The afterimage level of the light emitting device 100 can be remarkably reduced.

The organic light emitting display according to embodiments of the present invention can be described as follows.

According to an embodiment of the present invention, there is provided a method of improving afterimage of a liquid crystal display device, the method comprising: adjusting a gamma voltage in a white gradation in an initial gamma curve of a liquid crystal display device; setting a reference common voltage in which a flicker level is minimum in a liquid crystal display A step of adjusting the gamma voltage in the black gradation so as to minimize the flicker level in the liquid crystal display device to generate a middle gamma curve, a step of adjusting the gamma curve in each of the predetermined gradations so that the intermediate gamma curve corresponds to the normalized gamma curve Generating a first gamma curve by applying a first offset to each of the predetermined gradations to the flat gamma curve so as to minimize the flicker level in each of the predetermined gradations, Evaluating the first afterimage of the liquid crystal display device on the basis of the first gamma curve, And generating a second gamma curve by applying a second offset to the white gradation in the first gamma curve so that the flicker level is minimized in the liquid crystal display if the predetermined afterimage level is not satisfied . The afterimage improvement method of the liquid crystal display according to the embodiment of the present invention has the effect of remarkably reducing the afterimage in the liquid crystal display device having the alignment film made of the high resistance PI while reducing the flicker.

According to another aspect of the present invention, the step of setting the reference common voltage is a step of outputting a white gradation-black gradation pattern in the liquid crystal display device to set a reference common voltage that minimizes the flicker level, Is a step of generating a middle gamma curve by outputting a low gradation-black gradation pattern in the liquid crystal display device and adjusting a gamma voltage in the black gradation so that the flicker level is minimized, and generating a second gamma curve May include DC charging the liquid crystal display by applying a gamma voltage that outputs a high gray level to the pixel electrode of the liquid crystal display device for a predetermined time.

According to another aspect of the present invention, in the step of generating the second gamma curve, a liquid crystal display device outputs a halftone-black gradation pattern and outputs a first initial optimum common voltage, which has a minimum flicker level, Outputting a white gradation pattern in a liquid crystal display device for a predetermined period of time, and outputting an intermediate gradation-black gradation pattern in a liquid crystal display device to output a first final optimum common voltage And the second offset may be a difference between the first final optimum common voltage and the first initial optimum common voltage.

According to still another aspect of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal display device having a first gamma curve and a second gamma curve, wherein the second afterimage of the liquid crystal display device is evaluated based on a second gamma curve, And generating a third gamma curve by applying a third offset to the second gamma curve to adjust the gamma voltage in each of the predetermined gradations so that the afterimage level is minimized.

According to another aspect of the present invention, the step of generating the third gamma curve includes applying a gamma voltage to the pixel electrode of the liquid crystal display device for outputting a high gray-low gray-level pattern for a predetermined time, . ≪ / RTI >

According to another aspect of the present invention, in the step of generating the third gamma curve, the liquid crystal display device outputs the halftone-black gradation pattern, sets the second initial optimum common voltage at which the flicker level is minimum to the common voltage Outputting a residual image evaluation pattern in a liquid crystal display device for a predetermined time and outputting a pattern corresponding to each of the predetermined gradations in the liquid crystal display device to generate a second final optimum image having a minimum residual image level for each predetermined gradation, Obtaining a common voltage, and the third offset may be a difference between the second final optimum common voltage and the second initial optimum common voltage.

According to still another aspect of the present invention, the afterimage evaluation pattern is a mosaic-like pattern in which a white gradation and a black gradation are alternately outputted in a sub-area in which a plurality of sub areas divided from an active area of a liquid crystal display device are adjacent to each other have.

According to another aspect of the present invention, in the step of generating the first gamma curve, the step of generating the second gamma curve, and the step of generating the third gamma curve, the gamma voltage is set to a positive gamma voltage and a negative gamma voltage Wherein the positive gamma voltage and the negative gamma voltage are symmetrical to each other about a central gamma voltage and wherein in the first gamma curve, the second gamma curve, and the third gamma curve, a positive gamma voltage And the difference of the negative gamma voltages can be kept the same.

According to another aspect of the present invention, in generating the first gamma curve, generating the second gamma curve, and generating the third gamma curve, the center gamma voltage may be non-linear .

According to still another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display, comprising the steps of: generating a third gamma curve; evaluating a third afterimage of the liquid crystal display device based on a third gamma curve; Determining at least one adjustment offset based on the tendency of the third offset in each of the predetermined gradations if the pixel value of the at least one adjustment offset is not satisfactory, And generating the fourth gamma curve by applying the third gamma curve to the third gamma curve.

According to still another aspect of the present invention, the step of evaluating the first afterimage, the step of evaluating the second afterimage, and the step of evaluating the third afterimage include the steps of outputting the afterimage evaluation pattern on the liquid crystal display for a predetermined time, Outputting a gradation pattern for determining a residual image in the liquid crystal display device and comparing the residual image evaluation pattern based on the gradation pattern to determine whether a residual image of a predetermined level is output from the gradation.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those embodiments and various changes and modifications may be made without departing from the scope of the present invention. . Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: liquid crystal display
110: liquid crystal display panel
120: Gate driver
130: Data driver
140: Timing controller
150: common voltage generator
160: gamma voltage generator
310: initial gamma curve
311: Gamma voltage in white gradation
320: gamma curve with gamma voltage in adjusted white tones
321: Gamma voltage in the adjusted white gradation
331: Gamma voltage in black gradation
340: Medium gamma curve
341: Gamma voltage in adjusted black gradation
350: Flat gamma curve
351: Gamma voltage at 233 gray levels
352: Gamma voltage at 127 gray levels
355: first offset
360: 1st gamma curve
361: Gamma voltage in white tones
365: second offset
370, 570: the second gamma curve
571: Gamma voltage at 233 gray levels
575: Third offset
580, 780: Third gamma curve
785: First adjustment offset in 127 gradations
At 786: 127 gradations, the second adjustment offset
790: fourth gamma curve

Claims (11)

Adjusting a gamma voltage in a white gradation in an initial gamma curve of a liquid crystal display;
Setting a reference common voltage at which a flicker level is minimum in the liquid crystal display;
Adjusting a gamma voltage in a black gradation so as to minimize a flicker level in the liquid crystal display, thereby generating a middle gamma curve;
Adjusting a gamma voltage in each of the predetermined gradations to generate a flat gamma curve such that the intermediate gamma curve corresponds to a normalized gamma curve;
Generating a first gamma curve by applying a first offset to each of the predetermined gradations to the flat gamma curve such that a flicker level is minimized in each of the predetermined gradations;
Evaluating a first afterimage of the liquid crystal display device based on the first gamma curve; And
And applying a second offset to the white gradation in the first gamma curve so as to minimize the flicker level in the liquid crystal display if the predetermined afterimage level is not satisfied as a result of the evaluation of the first afterimage, And generating a curve for the afterimage of the liquid crystal display. The method according to claim 1,
The step of setting the reference common voltage is a step of outputting a white gradation-black gradation pattern in the liquid crystal display device and setting a reference common voltage at which the flicker level becomes minimum,
The step of generating the intermediate gamma curve is a step of generating a middle gamma curve by outputting a low gradation-black gradation pattern in the liquid crystal display and adjusting a gamma voltage in the black gradation so that the flicker level is minimized,
Wherein the step of generating the second gamma curve includes charging the liquid crystal display device with DC by applying a gamma voltage for outputting a high gray level to the pixel electrode of the liquid crystal display device for a predetermined period of time. A method for improving afterimage. The method according to claim 1,
Wherein generating the second gamma curve comprises:
Outputting an intermediate gradation-black gradation pattern in the liquid crystal display to set a first initial optimum common voltage at which a flicker level is minimized as a common voltage of the liquid crystal display;
Outputting a white gradation pattern in the liquid crystal display device for a predetermined time; And
And outputting the halftone-black gradation pattern in the liquid crystal display to obtain a first final optimum common voltage at which the flicker level becomes minimum,
Wherein the second offset is a difference between the first final optimum common voltage and the first initial optimal common voltage. The method according to claim 1,
Evaluating a second afterimage of the liquid crystal display device based on the second gamma curve; And
A third offset for adjusting the gamma voltage in each of the predetermined gradations so that the afterimage level of the liquid crystal display device is minimized when the predetermined afterimage level is not satisfied as a result of the evaluation of the second afterimage, And applying the second gamma curve to the curve to generate a third gamma curve. 5. The method of claim 4,
Wherein the step of generating the third gamma curve comprises the step of DC charging the liquid crystal display by applying a gamma voltage for outputting a high gray level low gray level pattern to the pixel electrode of the liquid crystal display for a predetermined time. (Method for improving afterimage of liquid crystal display). 5. The method of claim 4,
Wherein generating the third gamma curve comprises:
Outputting an intermediate gradation-black gradation pattern in the liquid crystal display device, and setting a second initial optimum common voltage at which a flicker level is minimized as a common voltage;
Outputting a residual image evaluation pattern in the liquid crystal display for a predetermined time; And
And outputting a pattern corresponding to each of the predetermined gradations in the liquid crystal display device to obtain a second final optimum common voltage at which the afterimage level becomes minimum for each of the predetermined gradations,
And the third offset is a difference between the second final optimal common voltage and the second initial optimum common voltage. The method according to claim 6,
Wherein the residual image evaluation pattern is a mosaic pattern in which a white gradation and a black gradation are alternately output in a sub region in which a plurality of sub regions divided from an active region of the liquid crystal display device are adjacent to each other, . 5. The method of claim 4,
Generating the first gamma curve, generating the second gamma curve, and generating the third gamma curve, wherein the gamma voltage comprises a positive gamma voltage and a negative gamma voltage, And the negative gamma voltage are symmetrical with respect to the center gamma voltage,
Wherein in the first gamma curve, the second gamma curve, and the third gamma curve, the difference between the positive gamma voltage and the negative gamma voltage in each of the predetermined gradations is kept the same, A method for improving afterimage. 9. The method of claim 8,
Generating the first gamma curve, generating the second gamma curve, and generating the third gamma curve, wherein the center gamma voltage is a non-linear, afterimage improvement of the liquid crystal display Way. 5. The method of claim 4,
After generating the third gamma curve,
Evaluating a third afterimage of the liquid crystal display device based on the third gamma curve;
Determining at least one adjustment offset based on the tendency of the third offset in each of the predetermined gradations when the third afterimage is evaluated and the predetermined afterimage level is not satisfied; And
Further comprising applying a fourth offset to the third gamma curve such that a residual image level of the liquid crystal display device is at least one of the at least one adjustment offset to generate a fourth gamma curve, . 11. The method of claim 10,
Evaluating the first afterimage, evaluating the second afterimage, and evaluating the third afterimage,
Outputting a residual image evaluation pattern in the liquid crystal display for a predetermined time;
Outputting a gradation pattern for determining a residual image in the liquid crystal display; And
And comparing the residual image evaluation pattern based on the gradation pattern to determine whether a residual image of a predetermined level is output from the gradation.

Images