CN101029987A - Color sequential display device with back-light time delay control and its controlling method - Google Patents

Abstract

The invention discloses a color sequential display with backlight time delay control and a control method thereof. The color sequential display includes a liquid crystal panel, a backlight source, and a driving circuit for generating pixel voltages for driving the liquid crystal panel. And a backlight delay control unit, which is used to delay and adjust the turn-off time point of the backlight source, and the turn-off time point is in the next subframe. Using the delay turn-off function can make the liquid crystal display have better picture uniformity.

Description

Color sequential display with backlight time delay control and control method thereof

technical field

The present invention relates to a liquid crystal display, in particular to a color sequential display (Color Sequential Display) with backlight time delay control and a control method thereof.

Background technique

Generally, the color mixing method commonly used in liquid crystal displays can be divided into two categories. One is the spatial color mixing method such as color filter (Color Filter) technology, which is mainly used to make color mixing in space, because each pixel is composed of three primary colors (RGB) sub-pixel configuration. When the sub-pixels of the three primary colors are smaller than the range that can be distinguished by human eyes, by controlling the intensity of light passing through the sub-pixels of the three primary colors, the effect of color mixing can be obtained. For example, a conventional liquid crystal panel 10a shown in FIG. 1a uses color filter technology to form any frame 120 . Because the color filter has the filter films 102a, 103a, and 104a of the three primary colors of red, green, and blue respectively, after it is irradiated by a backlight source, the intensity of light passing through the sub-pixels of the three primary colors is controlled by the liquid crystal 100a to obtain the required The red light 110a, the green light 111a and the blue light 112a are used to obtain the effect of color mixing and addition. The other is the sequential color mixing method, such as color sequential technology, which mainly uses color mixing on the time axis, which is common in color sequential displays (Color Sequential Display), also known as field sequential displays (Field Sequential Display) or achromatic filter Light sheet display (Color Filter-less Display). The principle of the sequential color mixing method is to switch the three primary color (RGB) light sources in sequence to synthesize a color image or frame (Frame) during the time when the human eye will produce visual persistence, that is, to cut the chromaticity of the three primary colors in sequence In three different display periods or sub-frames (Sub-frame), but in the same pixel. By quickly switching the three primary colors sequentially, if the switching time is shorter than the time range that the human eye can distinguish, the human eye cannot see the three primary colors, but sees a color mixing effect. For example, for a display with an image frequency of 60 Hz, the switching time of the three primary colors needs to be within 1/180 second, which are sequentially divided into three different display periods or sub-frames to display in the same pixel. Due to the influence of the persistence of vision of the human eye, three primary colors with different light intensities overlap within 1/60 second, and a colorful display effect can be obtained.

Please refer to FIG. 1 b , which shows a liquid crystal panel 10 b using color sequential technology to form the frame 120 . Wherein the three-primary-color (RGB) backlight source further divides the time for forming the frame 120 into three display periods according to different color light sources, such as the first sub-frame 121, the second sub-frame 122 and the third sub-frame 123, which are sequentially emitted respectively. The red light source 107b, the green light source 108b and the blue light source 109b are quickly displayed in each pixel, and then the display degree of each pixel is determined by the reaction of the liquid crystal 100b, so as to form a mixed color by three primary colors (such as numbers 110b, 111b and 112b) superimposed images.

In addition, compared with traditional color filters, color sequential technology has the following advantages:

(1) High resolution: Because the color sequential technology does not have the problem of color resistance of color filters (ColorResisters), it can improve the spatial resolution of the panel pixels. Because there is no light loss caused by color resistance, the transmission efficiency (Transmittance) can be improved. For example, the original substrate transmittance of 27% can be increased by nearly 100%.

(2) Cost reduction: The color sequential technology eliminates the need for color filters, which simplifies the structure. In addition to saving component costs in manufacturing, the process of coating and making filters can be omitted, and man-hours and costs can be reduced. Improve yield.

(3) Reduce the drive integrated circuit: The drive integrated circuit uses the output voltage to change the arrangement of the liquid crystal molecules in the panel pixels, and then controls the light transmittance of each pixel to form a displayed picture. The color sequential technology can reduce the number of thin film transistors required in a single pixel, so it can simplify the complexity of the control circuit and help improve the spatial resolution of the panel pixels.

(4) Better color balance adjustment: Because independent light sources are used, color adjustment can be made for each independent light source to make the color balance on the entire panel more uniform.

However, it should be noted that the screen display frequency of the traditional twisted nematic TN (Twisted Nematic) LCD panel is 60Hz, and its LCD driving voltage is changed every 16.67ms, so the LCD only needs to reach the potential before the signal changes. . In contrast, the liquid crystal driving voltage of the color sequential liquid crystal display is changed every 5.56ms, which is equivalent to the time of each subframe, but the period of 5.56ms also includes the time when the backlight is turned on. Time, so the liquid crystal reaction time can be allowed to be shorter, because the liquid crystal must complete the reaction before the backlight is turned on.

The limitation of the liquid crystal reaction speed is the biggest problem in the current color sequential technology. If color-sequential technology is used, the response speed needs to be nearly three times faster to achieve the picture level of traditional liquid crystal displays, which also means that the response time of color-sequential displays should be shortened to one-third of that of traditional displays in theory. If the liquid crystal response speed of the color sequential display is not fast enough, the following problems will occur:

(1) The gamma curve drifts in the grayscale: the gamma curve is used to display the relationship between different grayscales and brightness, which will directly affect the gradient effect of the display screen. If the liquid crystal has different response speeds in different gray levels, it will cause the gamma curve to drift in the gray levels.

(2) Uneven brightness of the panel: as shown in FIG. 2 , it is a schematic diagram of the panel grid scanning time difference of a liquid crystal display. The panel includes an uppermost pixel area 202, a middle pixel area 203 and a lowermost pixel area 204, Because one of the gate scanning driving circuits 200 scans down column by column through its horizontal scanning lines in different timings, although the response time of the liquid crystal can match the driving frequency of 180 Hz, the gap between the uppermost pixel area 202 and the lowermost pixel area 204 The existing scanning time difference is roughly equal to the liquid crystal reaction time. Therefore, although the liquid crystal in the uppermost pixel region 202 has completely reacted, the liquid crystal in the lowermost pixel region 204 has not yet completely reacted, thus resulting in uneven brightness at the upper and lower positions of the panel. Phenomenon.

FIG. 3 is a schematic diagram of the coordinates of the grid scanning time difference in the conventional liquid crystal panel shown in FIG. 2 , wherein the horizontal axis of the coordinates is the time axis, and the vertical axis represents the transmittance. The display time 307 of each subframe includes three periods of time: the scan time 301 of the scan drive circuit, the waiting time 302 for liquid crystal response, and the backlight turn-on time 303 . From the scanning time 301, it can be found that there is a time difference between the initial scanning time points T1 and T2 of the first gate scanning line G001 and the 160th gate scanning line G160 of the panel. Time 302 waits for the liquid crystal to react gradually (that is, the curve rises), and then when the backlight is turned on at time 303, because the 160th grid scanning line G160 scans later, if the liquid crystal at the bottom of the panel has not completely reacted, it will appear as shown in Figure 3 The shown difference area A3 causes the upper and lower pixel regions of the panel to have different transmittances, that is, the transmittance corresponding to the gate scan line G001 is greater than the transmittance corresponding to the gate scan line G160 .

Please also refer to FIG. 4 , which illustrates a coordinate diagram of the relationship between the response time of each gate scan line to the liquid crystal and the transmittance in a known liquid crystal display using Black Data Insertion Technology (BDI). After 400 black insertion time (or RESET time) of the liquid crystal display, due to the scanning time difference of each grid and the liquid crystal reaction time is not fast enough, when the uppermost pixel area of the panel (such as the grid scanning line G001) has roughly completed the reaction , but the lower pixel area (such as the gate scanning line G160) has not yet completed the reaction, and the black insertion is already performed and the backlight is turned off, so the brightness of the upper and lower ends of the liquid crystal panel is uneven. Moreover, when black is inserted, the liquid crystal also needs time to respond to correspond to the scanning of the next sub-frame, so that after black is inserted, the response time of the liquid crystal is even more delayed when each grid is scanned in the next sub-frame. , causing the light transmittance of the upper and lower regions of the liquid crystal panel to become poor and inconsistent, resulting in uneven brightness.

Please also refer to FIG. 5 , which is a coordinate diagram of the liquid crystal time and transmittance of a known liquid crystal display using simultaneous black insertion. In the display time 507 of a sub-frame, the scan driving circuit scans sequentially in a scan time 501 (from the gate scan line G001 to G160), and after a waiting time 502, after the liquid crystal has completely reacted, it turns on the backlight in the backlight time 503 Afterwards, during a black insertion time 500, a black insertion signal is simultaneously input to all scanning lines of the gate scanning driving circuit. Please refer to FIG. 6 , which is a diagram showing the relationship between liquid crystal time and transmittance of another liquid crystal display using sequential black insertion. The difference between FIG. 6 and FIG. 5 lies in that when using the black insertion technology, a black insertion signal is sequentially input to the scanning lines. For the liquid crystal display shown in FIG. 5 and FIG. 6 mentioned above, if the liquid crystal response time of the panel is not fast enough, there will be a problem of uneven brightness in the upper and lower regions of the panel as mentioned in FIG. 4 .

Contents of the invention

Therefore, in order to improve the above problems, the present invention provides a color sequential display with controlled backlight time, which is used to improve the brightness uniformity of each distribution area on the panel. Adjust the time point when the backlight is turned off through the backlight delay control unit. For example, the time point when the backlight is turned off is about the addressing time of the next sub-image data address data, so as to improve the uneven brightness of the panel caused by the scanning time difference of the scanning line. The problem.

In order to achieve the aforementioned object of the invention, the present invention provides a color sequential display with backlight time delay control, through a liquid crystal panel, a backlight source, a source data drive circuit to provide a data line voltage, a grid scan drive The circuit provides a scanning line voltage, a backlight control circuit to drive the backlight, and a backlight delay control unit to adjust the time point when the backlight is turned off. According to the color sequential display with backlight time delay control of the present invention, the scanning line of the gate scanning driving circuit and the data line of the source data driving circuit are connected to a pixel electrode on the liquid crystal panel. The pixel electrode is composed of a thin film transistor which functions as a switch. When the gate scanning drive circuit and the source data drive circuit respectively output the scan line voltage (or gate signal) and the data line voltage to the thin film transistor of the pixel electrode through the scan line and the data line, the scan line voltage controls the thin film transistor The switch of the transistor, the voltage of the data line will be written into the liquid crystal capacitor on the liquid crystal panel to determine the turning angle of the liquid crystal molecules. When the thin film transistor is turned off, a high impedance is formed to prevent the voltage leakage of the data line. However, the liquid crystal capacitor cannot hold the voltage until the next update of the data line voltage, so the liquid crystal capacitor is connected in parallel with a storage capacitor to hold the signal voltage until the next update. Therefore, the gate scanning driving circuit and the source data driving circuit can generate pixel voltages for driving the liquid crystal panel, wherein the pixel voltages at least include a first voltage and a second voltage to switch pixels on and off, and make each of the aforementioned A subframe is divided into a first time zone and a second time zone, wherein the first voltage is driven in the first time zone, and the second voltage is driven in the second time zone. The backlight control circuit is used to drive the backlight to sequentially generate three primary color light sources in multiple sub-frames constituting one frame to form an image output. Use the backlight delay control unit to output a delay signal to the backlight control circuit to adjust the backlight off time point, such as between the beginning of the first time zone and the end of the second time zone in the first subframe time, to improve the scanning of the panel due to the scanning line The uneven brightness caused by time difference and liquid crystal reaction speed.

In addition, the present invention provides a control method for delayed control of the backlight time of a color sequential display, wherein each frame generated by the color sequential display is at least divided into a first subframe and a second subframe, and each of the aforementioned A subframe is divided into a first time zone and a second time zone according to time sequence, including:

Turn on a backlight at a time point in the first subframe;

According to a preset time period, a turn-off time point of the backlight is determined between the end of the second time zone of the first subframe and the end of the scanning of the first time zone of the second subframe; and

According to the turn-off time point of the backlight, delay outputting a backlight driving signal to the backlight, so as to delay the turn-off time of the backlight. Therefore, delaying the turn-off time point of the backlight to the next subframe can make the backlight have a longer turn-on time when the response speed of the liquid crystal is insufficient, so as to make up for the uniformity of the brightness of the panel.

Description of drawings

Figure 1a and Figure 1b are schematic diagrams of traditional color filter technology and color sequential technology;

2 is a schematic diagram of a panel grid scanning time difference of a liquid crystal display;

FIG. 3 is a schematic diagram of the coordinates of the grid scanning time difference in the liquid crystal panel of FIG. 2;

4 is a coordinate diagram of the relationship between each grid scanning line of the liquid crystal display and the liquid crystal reaction time and the transmittance;

Fig. 5 is a coordinate relationship diagram of liquid crystal display time and transmittance using simultaneous black insertion;

Fig. 6 is a coordinate relationship diagram of liquid crystal time and transmittance of a liquid crystal display using sequential black insertion;

Fig. 7 is a functional block diagram of the color sequential display of the present invention;

FIG. 8 is an overview view of the structure of the color sequential display of the present invention;

9a and 9b are graphs showing the relationship between liquid crystal response time and transmittance of the color sequential display of the present invention;

10 is a schematic diagram of the operation of each gate scanning line of the first embodiment of the color sequential display of the present invention;

11 is a coordinate diagram of liquid crystal response time corresponding to each gate scanning line of the color sequential display of the present invention shown in FIG. 10;

FIG. 12 is a schematic diagram of the detection of the selection point of the turn-on time of the backlight source of the color sequential display of the present invention shown in FIG. 10 .

13 is a schematic diagram of the operation of each gate scanning line of the second embodiment of the color sequential display of the present invention;

14 is a schematic diagram of the liquid crystal response time of the second embodiment of the color sequential display of the present invention shown in FIG. 13;

FIG. 15 is a schematic diagram of the detection of the selection point of the turn-on time of the backlight source of the second embodiment of the color sequential display of the present invention shown in FIG. 13;

FIG. 16 is a flow chart of the control method of the present invention, which delays the time of controlling the backlight of a color sequential display.

Among them, reference signs:

10a Traditional LCD panel

10b Color sequential LCD panel

100a, 100b LCD

102a Red filter film

103a Green filter film

104a Blue filter film

107b Red backlight

108b Green Backlight

109b blue backlight

110a, 110b Red light

111a, 111b Green light

112a, 112b Blu-ray

120 one frame

121, 901, 1001, 1301 first subframe

122, 902, 1002, 1302 second subframe

123 The third subframe

200, 705 Gate scan drive circuit

706 Source data drive circuit

202 The pixel area at the top of the panel

203 The pixel area in the middle of the panel

204 The bottom pixel area of the panel

400, 500, 600, 1004, 1304 black time

301, 401, 501, 601, 1003, 1303 scan time of the scan drive circuit

302, 402, 502, 602 Waiting time for liquid crystal response

303, 403, 503, 603 Backlight on time

A3 Scan Time Difference Area

307, 407, 507, 607, 1100, 1400 One subframe time

T1 The first gate scan line starts to scan the starting point

T2 The 160th gate scan line starts to scan the starting point

G001 The first gate scan line

G080 The 80th gate scan line

G160 The 160th gate scan line

G001a The 1st scan line of the gate of the first time zone

G001b The first scan line of the gate of the second time zone

G080a The 80th scanning line of the gate of the first time zone

G080b The 80th scanning line of the gate of the second time zone

A1 First choice point

B2 Second choice point

C3 Third choice point

S001 Scanning starting point of the first scanning line of the gate

S080 Scanning starting point of the 80th scanning line of the gate

S160 Scanning starting point of the 160th scanning line of the gate

1101, 1401 LCD update time

T Backlight delay time

BFI Insertion time point

1201, 1501 Brightness difference curve

1202, 1502 Luminance Curve

1203, 1503 Higher brightness

1204, 1504 Better picture brightness consistency

701 Backlight delay control unit

702 Backlight control circuit

703 Backlight

704 LCD panel

801 drive circuit

804 Second Polarizing Film

805 LED array

806 Second glass substrate

807 Thin Film Transistor

808 common electrode

809 The first glass substrate

810 first polarizing film

811 data cable

812 scan lines

813 Light guide plate/diffuser plate

814 pixel electrode

BL_ON Backlight on time

S162, S164 and S166 are all method steps

Detailed ways

Please refer to FIG. 7 , which is a functional block diagram of a color sequential display with backlight time delay control according to a first preferred embodiment of the present invention. The color sequential display includes a liquid crystal panel 704 , a backlight source 703 , a source data driving circuit 705 , a gate scanning driving circuit 706 , a backlight control circuit 702 and a backlight delay control unit 701 . If the three-primary-color (RGB) backlight source 703 is a light-emitting diode array (LED Array), in the three sub-frames constituting each frame, the three-primary-color light sources are respectively switched on and off in order to inject light into the liquid crystal panel 704. The source data driving circuit 705 provides a data line voltage which determines the steering angle of the liquid crystal molecules. The gate scan driving circuit 706 sequentially provides scan line voltages to each scan line on the panel 704 . The backlight control circuit 702 provides a backlight driving voltage to the backlight 703 to generate three primary color light sources (ie, red light, green light, and blue light) respectively. The backlight delay control unit 701 provides a delay signal to the backlight control circuit 702 according to a predetermined timing, so as to delay the turn-off time of the backlight.

However, the application of the present invention is not limited to the three primary color light sources, that is, the number of additional light sources that can be used is not limited, and can actually be set according to needs. For example, white light can also be achieved by mixing five colors of RRGBB or four colors of RGGB, that is, using an array of LEDs with more than three colors. Because from the perspective of color display, the wider the color gamut of the display, the stronger its color display capability. In order to expand the color gamut, a light source with the same color as the three primary colors (RGB) light source but with a different dominant wavelength can be used as an additional light source. Here, the definition of the same color is the same as the cognition of general color science. However, the selection of the additional light source is not limited thereto, and light sources of other colors than the three primary colors can also be used, such as cyan light or yellow light (Y). Even with one of the three primary color (RGB) light sources having the same dominant wavelength can also be used, in terms of color, that is, the phenomenon of metamerism, that is, the same color light with the same dominant wavelength has a difference in the spectrum, resulting in color coordinates different. Regardless of whether a light source with a different dominant wavelength or the same light source is used as an additional light source, its color coordinates must be different from those of the three primary colors (RGB) light source. In addition, the color coordinates of the additional light source must fall outside the color gamut enclosed by the three primary color (RGB) light sources in the chromaticity space, in order to have the effect of expanding the color gamut.

Please further refer to FIG. 7 and FIG. 8 . FIG. 8 is a structural schematic view of a color sequential display according to a preferred embodiment of the present invention. The aforementioned liquid crystal panel 704 further has a common electrode 808 disposed on a first glass substrate 809 , and at least one pixel electrode 814 disposed on a second glass substrate 806 for connecting a corresponding thin film transistor 807 . One of the storage capacitors (not shown) is coupled to the pixel electrode 814 and the common electrode 808, or each pixel electrode 814 itself has a capacitive effect, so as to maintain a potential state, and is used to sense the common electrode 808 to control its liquid crystal molecules twist. A light guide plate/diffusion plate 813 can be further provided between the panel 704 and the backlight 703 to guide the light source provided by the backlight 703 toward the same diffusion direction, so that the light source can be evenly distributed, and then use the first polarizing film 810 and The second polarizing film 804 polarizes the light source.

The driving circuit 801 includes a source data driving circuit 705 and a gate scanning driving circuit 706 , which are respectively connected to the aforementioned pixel electrode 814 and the common electrode 808 . Because the pixel electrode 814 is composed of a thin film transistor 807, and the function of the thin film transistor is like a switch, the source data driving circuit 705 is connected to the source of the thin film transistor 807 through the data line 811, and the gate scanning driving circuit 706 The scanning line 812 is connected to the gate of the thin film transistor 807 to control the opening and closing of the thin film transistor 807 .

When the gate scanning driving circuit 705 and the source data driving circuit 706 receive an instruction to drive the liquid crystal, they will respectively output a scanning line voltage and a data line voltage through their scanning line 812 and data line 811, wherein the scanning line A voltage (or a gate signal) can control the switch of the thin film transistor 807, and the source data drive circuit 705 controls the light intensity of each single pixel through its data line 811 and the thin film transistor 807. The data line voltage is written into a liquid crystal capacitor (the liquid crystal is sandwiched between the two glass plates 806, 809 to form a parallel plate capacitor) to determine the turning angle of the liquid crystal molecules. When the thin film transistor 807 is turned off, it will form a high impedance to prevent the leakage of the data line voltage. However, the liquid crystal capacitor cannot maintain the voltage until the next update of the data line voltage, so the liquid crystal capacitor is connected in parallel with the storage capacitor to maintain the voltage of the data line until the next update. After the above actions, a voltage difference (called a first voltage, to be described in detail later) will be generated between the pixel electrode 814 and the common electrode 808, and the turning action of the liquid crystal molecules can be changed to improve the backlight by using the voltage difference. Source 703 Light Pass Intensity. On the contrary, in a reset period such as the black insertion (BDI) period, the voltage difference modulation of the common electrode 808 is used to generate another voltage difference (namely called a second voltage, which will be described in detail later), and then change the liquid crystal molecule. Turn to reduce the light pass intensity of the backlight 703 .

Because the turn-on time point of the backlight 703 and the color of the light source need to be synchronously controlled by the data scanning of the liquid crystal panel 704 based on the generation of image data, so after the backlight control circuit 702 receives a synchronous control signal, it will drive the backlight 703 sequentially generates three primary color light sources within the frame time of an image to form an image output. Through the control of the backlight control circuit 702, the light of different colors of the three primary color light sources (such as light-emitting diode arrays) 805 of the backlight 703 are respectively switched to be respectively emitted into the respective display periods in which a frame (Frame) is divided into three sub-frames, to form mixed light images. In addition, the backlight delay control unit 701 is used to further control the turn-off time of the backlight source 703, so that the turn-off time point of the backlight source 703 spans between two subframes, and it is about when or after the next subframe data address data is addressed. The backlight source 703 is turned off as compensation for areas with insufficient brightness. The backlight delay control unit 701 can use a delay hardware circuit or software, according to the preset display period (such as 5.56ms) of each subframe or the preset turn-on time of the backlight 703 (such as 3.9ms after the first gate of the panel is turned on) ) to achieve the optimal turn-off time point of the backlight source 703 (for example, greater than 5.56 ms after the first gate of the panel is turned on), which can span between the display periods of two sub-frames.

Fig. 9a and Fig. 9b are the coordinate relationship diagrams between the liquid crystal time and the transmittance of a color sequential display in a preferred embodiment of the present invention, wherein Fig. 9a represents a kind of liquid crystal display using sequential black insertion, and Fig. 9b Represents another LCD display that uses simultaneous black insertion. Compared with the known FIG. 4 , the present invention can compensate each grid scan of the panel by extending the off time of the backlight source from a first subframe 901a, 901b to the display period of the next subframe 902a, 902b ( G001a to G160a or G001b to G160b) after a black insertion time, the problem of uneven brightness is caused by the insufficient response time of the liquid crystal.

FIG. 10 is a schematic diagram of the first embodiment of the color sequential display of the present invention. Each gate is scanned and driven in each subframe, for example, the display period of the first subframe 1001 can be divided into a first time zone and a second time zone. In the first time zone, the gate scanning driving circuit sends a gate signal to drive the thin film transistor on the panel to turn on, so that a voltage difference is generated between the pixel electrode and the common electrode, which is the first voltage, which is used to twist the liquid crystal Molecules to allow the expected amount of light transmission, for example, for the first grid scan line, G001a is its first time zone, and for the 80th gate scan line, G080a is its first time zone; on the contrary, in the second time zone Inside, the voltage difference generated between the pixel electrode and the common electrode is the voltage of liquid crystal reset, that is, the second voltage, which is used to twist the liquid crystal molecules to prevent light transmission, wherein the second voltage is coupled to the pixel electrode and the common electrode The storage capacitance of the electrode is used to modulate the voltage difference of the common electrode, or the common electrode can be divided into a plurality of regions, and the voltage difference of the common electrode can be modulated. The polarities of the first voltage and the second voltage are opposite or in the same direction, and the polarity of the next frame is generally opposite to that of the previous frame, or reversed after 3 sub-frames, so if it is in Various polarity transformations can be designed in six consecutive subframes; as shown in Figure 10, G001a is the first time zone of the first gate scanning line, G001b is the second time zone of the first gate scanning line, and G080a is the first time zone of the 80th gate scan line, and G080b is the second time zone of the 80th gate scan line. Taking a scanning driving circuit with 160 scanning lines as an example, a gate scanning driving circuit sequentially drives the pixel electrode and the common electrode through the first scanning line to the 160th scanning line to generate a first voltage, thereby driving the liquid crystal The reaction turns to allow light from the backlight to pass through. In the respective first time zone of each grid scanning, there is a scanning time difference between the first scanning line G001 of the grid and the 160th scanning line G160, and this time difference causes the transmittance of the upper and lower ends of the panel to be inconsistent. That is, penetration rate (G001) > penetration rate (G160). However, at this time, if the backlight delay control unit is used to output a delay signal to the backlight control circuit, an effect of delaying the turning off of the backlight can be produced. This figure 10 further introduces the application of the following three different backlight turn-off times. One is that the backlight turn-off time point is located at the first selection point A1, that is, each gate scan of the first sub-frame time starts from the first time zone to the first between time zone ends to compensate for panel brightness. After the end of the first time zone, when it is desired to perform black insertion (that is, the second time zone), the gate scanning driving circuit drives the first to the 160th scanning line simultaneously, so that the driving pixel electrode and the common electrode are simultaneously generated The second voltage is used to prompt the liquid crystal to react and transition to output a black picture, and there is a time difference between the second time zone G001b of the first scanning line of the grid and the second time zone G080b of the 80th scanning line. Second, when the time point of turning off the backlight source is set at the second selection point B2, that is, between the start of the second time zone of the first subframe time and the start of scanning of the first time zone of the second subframe time, to compensate for the insufficient response speed of the liquid crystal , resulting in brightness differences. When the next sub-frame 1002 arrives after black insertion, the brightness is uneven due to the time difference between the front and rear scanning lines. Third, when the time point of turning off the backlight source is set at the third selection point C3, that is, between the first time zone scanning in the first subframe time and before the end of the first time zone scanning in the second subframe time, to compensate for the brightness of the panel . In order to ensure that the turn-off time point of the backlight falls on the third selection point C3 between the first subframe and the second subframe, various methods can be used. For example, adding a preset period to the start time point of the first time zone of each subframe is the backlight off time, and make the preset period longer than the display period of each subframe (for example, greater than 5.56 ms or more can be). The data of the preset period can be pre-stored in a memory storage for the backlight delay control unit to read.

Please refer to Figure 11, Figure 11 is a coordinate diagram of the liquid crystal response time corresponding to each gate scanning line of the color sequential display shown in Figure 10, the horizontal axis is the time axis, the unit is milliseconds, and the vertical axis is the transmittance , and its unit is a percentage. BL_ON represents the ON period of the backlight. S080 represents the scanning starting point of the 80th scanning line of the grid; S160 represents the scanning starting point of the 160th scanning line of the grid. The three curves drawn in Figure 11 respectively represent the relationship curves between the liquid crystal response time and the transmittance scanned by the scanning drive circuit at three different positions, wherein the first curve represents the gate scanning line G001, and the second curve represents the gate scanning line G080, and the third curve represents the gate scanning line G160. It can be seen from the figure 11 that although there is a difference between the scanning time and the liquid crystal reaction time between the gate scanning lines G001 and G160, and after the black insertion at the same time, each scanning line starts from the black insertion (BDI) period. The time sequence of re-scanning to the next sub-frame is also different, but because the light transmittance of the lowermost area of the panel (such as the gate scanning line G160) is affected by the aforementioned backlight delay control unit delaying the turn-off time point of the backlight Due to the influence of the backlight delay time T, it can wait for the response time of the liquid crystal to complete, thereby increasing the light transmittance and making the brightness of the panel more uniform.

Please refer to FIG. 12 . FIG. 12 is a schematic diagram of the detection of the selection point of the turn-on time of the backlight of the color sequential display of the present invention shown in FIG. 10 . The horizontal axis represents the start point time of the backlight source of the liquid crystal display, and the vertical axis on the left represents luminance (brightness), and its unit is nit, which is defined as the luminosity value per unit area in a specific direction. The vertical axis on the right represents the brightness difference, and its unit is percentage, and the lower the value, the better. For example, the display period of each sub-frame of a color sequential display is about 5.56ms, and the turn-on period of the backlight is deducted for about 2ms, and the liquid crystal needs to complete the reaction before the backlight is turned on. A luminance curve 1202 at 3.7ms (this time is defined as 3.7ms after the grid scanning line G001 action, the backlight is on), the backlight response can reach a better panel brightness point 1203; and at 3.9ms, the liquid crystal response Complete, make a luminance difference curve 1201 obtain a lower luminance difference point (that is, the panel has better luminance uniformity).

It can be known from the above embodiments that the liquid crystal display of the present invention can improve panel transmittance and brightness uniformity by delaying the turn-off time of the backlight source, and after the brightness uniformity is improved, the gamma curve is also improved.

Please refer to FIG. 13 , which is a schematic diagram of a second embodiment of the color sequential display of the present invention. Compared with the first embodiment, each gate scanning of the second embodiment adopts sequential black insertion. Similarly, the second embodiment can also use the backlight delay control unit to control the turn-off time point of the backlight at the first selection point A1, that is, between the beginning of the first time zone and the end of the second time zone of the first sub-frame time, or at the first selection point A1. The second selection point B2, or the third selection point C3, that is, between the time scanning of the first subframe and the end of the time scanning of the second subframe, is used to compensate the problem of uneven brightness caused by insufficient liquid crystal response speed.

Please refer to FIG. 14 . FIG. 14 is a liquid crystal response time chart of the second embodiment of the color sequential display of the present invention. S160 represents the scanning starting point of the 160th scanning line of the gate. Because the second embodiment uses sequential black insertion, the liquid crystal response time is not as long as that of the first embodiment. However, since the black insertion time of each scanning line is consistent, the difference in the transmittance between the upper and lower ends of the panel is not as obvious as in the first embodiment. Similarly, in the delay time T of the backlight, the turn-off time of the backlight is delayed to compensate for the decrease of its transmittance, so that the brightness of the panel can be more uniform.

Please refer to FIG. 15 . FIG. 15 is a schematic diagram of the detection of each backlight turn-on time selection point of the second embodiment of the color sequential display of the present invention. The horizontal axis of the coordinates in Figure 15 represents the start point time of the backlight source of the liquid crystal display (this time is defined as the predetermined time point after the grid scanning line G001 is activated, and the backlight is turned on), and the vertical axis on the left represents the luminance (brightness), and its unit It is nit, which is defined as the luminosity value per unit area in a specific direction. The vertical axis on the right represents the brightness difference, and its unit is percentage, and the lower the value, the better. Compared with the first embodiment in FIG. 12 , the brightness uniformity of the second embodiment (see the brightness error point 1504 of a brightness difference curve 1501 ) is better than that of the first embodiment.

Fig. 16 is a control method according to the present invention, which is suitable for delaying the backlight time of a color sequential display, wherein the color sequential display, as shown in Fig. 7 and Fig. 8, has a liquid crystal panel for generating each frame of image And each frame is divided into a plurality of subframes (including a first subframe and a second subframe) and each subframe is divided into a first time zone and a second time zone in time sequence, and a backlight source is used to generate a light source 1. A backlight control circuit is used to control the turn-on and turn-off time of the backlight, and a backlight delay control unit is used to delay the turn-off time of the backlight. The flow of the control method includes the following steps:

Step S162: the backlight control circuit turns on the backlight at a time point (for example, in the first time zone) of a first subframe, so as to generate light to irradiate the liquid crystal panel;

Step S164: According to a preset time period, determine a turn-off time point of the backlight between the end of the second time zone of the first subframe and the end of scanning of the first time zone of the second subframe. In order to ensure that the turn-off time point of the backlight falls within the second subframe, various steps can be used, and are not limited to specific steps. For example, adding a preset period to the first time point of the first time zone of each subframe, wherein the preset period is greater than the display period of each subframe (for example, greater than 5.56ms), or adding each subframe An end time point of the second time zone of the frame plus a preset period, wherein the preset period is less than the first time zone of each sub-frame, or the preset period is a preset turn-on of the backlight Therefore, counting from the turn-on time point of the backlight to the preset time period can ensure that the turn-off time point of the backlight falls within the second subframe. The data of the preset period can be pre-stored in a memory storage for the backlight delay control unit to read; and

Step S166: The backlight delay control unit controls the backlight control circuit to delay outputting a backlight driving signal to the backlight according to the turn-off time point of the backlight source, so that the turn-off time point of the backlight source is delayed to the time point of the first subframe Between the end of the second time zone and the end of scanning the first time zone of the second subframe.

Although the present invention has been described above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (21)

1. A color sequential display, characterized in that it comprises: A liquid crystal panel having a plurality of pixels to generate each frame of image, wherein each frame is divided into a plurality of sub-frames: a backlight source, used to generate light incident on the liquid crystal panel; A drive circuit, electrically connected to at least one scan line and a data line, and generates a first voltage and a second voltage to switch the on and off of the pixel, and divide each sub-frame into a first time zone and a time zone according to time sequence a second time zone, wherein the first voltage is driven in the first time zone, and the second voltage is driven in the second time zone; A backlight control circuit, used to control the turn-on time of the aforementioned backlight; and A backlight delay control unit, used to control the turn-off time point of the backlight source, so that the turn-off time point of the backlight source is between the end of the second time zone of the first subframe and the end of scanning of the first time zone of the second subframe. 2 . The color sequential display according to claim 1 , wherein the backlight control circuit controls the backlight to correspondingly switch light sources of different colors in each subframe. 3. The color sequential display according to claim 1, wherein the liquid crystal panel further comprises a pixel electrode and a common electrode for controlling the pixel. 4. The color sequential display according to claim 1, wherein the driving circuit has a scanning driving circuit, wherein the scanning driving circuit outputs a gate signal to the gate of the thin film transistor through the scanning line. 5. The color sequential display according to claim 4, wherein the second voltage is sequentially generated according to the gate signal output by each scanning line to drive the liquid crystal. 6. The color sequential display according to claim 4, wherein the second voltage is generated simultaneously according to the gate signal output by each scanning line to drive the liquid crystal. 7. The color sequential display according to claim 4, wherein the driving circuit further has a data driving circuit, wherein the data driving circuit is connected to the source of the thin film transistor through the data line. 8. The color sequential display according to claim 3, wherein the driving circuit has a storage capacitor electrically coupled to the pixel electrode and the common electrode. 9. The color sequential display according to claim 8, wherein the second voltage is adjusted by the voltage difference of the common electrode. 10 . The color sequential display according to claim 8 , wherein the common electrode is divided into a plurality of regions, and the second voltage is modulated according to the voltage difference of the common electrode. 11 . 11. The color sequential display according to claim 1, wherein the backlight delay control unit is formed by a hardware circuit or software. 12 . The color sequential display according to claim 1 , wherein the backlight delay control unit controls the delayed turn-off time of the backlight according to the display time of each subframe. 13 . 13 . The color sequential display according to claim 1 , wherein the backlight delay control unit controls the delay turn-off time of the backlight according to the turn-on period of the backlight. 14 . 14. The color sequential display according to claim 1, wherein the polarities of the first voltage and the second voltage are opposite to each other. 15. The color sequential display according to claim 1, wherein the polarity of the first voltage and the second voltage are in the same direction. 16. A control method for delaying the backlight time of a color sequential display, characterized in that at least two frames displayed by the color sequential display are at least divided into a first subframe and a second subframe, and each of the aforementioned A subframe is divided into a first time zone and a second time zone according to time sequence, and the method includes the following steps: Turn on a backlight at a time point in the first subframe; According to a preset time period, a turn-off time point of the backlight is determined between the end of the second time zone of the first subframe and the end of the scanning of the first time zone of the second subframe; and According to the turn-off time point of the backlight, delay outputting a backlight driving signal to the backlight. 17. The control method according to claim 16, further comprising: adding a start time point of the first time zone of each sub-frame to the preset period of time to determine the turn-off time point of the backlight, wherein the The preset period is longer than the display period of each sub-frame. 18. The control method according to claim 16, further comprising: adding an end time point of the second time zone of each subframe to the preset time period to determine the turn-off time point of the backlight, the feature That is, the preset period is smaller than the first time zone of each subframe. 19. The control method according to claim 16, wherein the preset period is a preset turn-on period of the backlight. 20. The control method according to claim 16, further comprising: using a backlight delay control unit to control a backlight control circuit to delay outputting the backlight driving signal to the backlight according to the preset time period. 21. The control method according to claim 20, wherein the backlight delay control unit is formed by a hardware circuit or software.

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