KR100906700B1 - Liquid crystal display - Google Patents

Abstract

In a predetermined period (one frame or one subframe), the backlight is turned on for each lighting region in which the backlight is divided into four between the intermediate time point in the first data write scan and the intermediate time point in the second data write scan. . When the time required for data recording scanning is set to 50% of a predetermined period, the ratio (panel on rate) of the time when the liquid crystal panel is in a transmissive state relative to the time when the backlight is turned on is high as 93.8%. In addition, the ratio of luminance gradient (luminance at the center of the display area / luminance at the end of the display area) is as small as 1.14 times. By dividing the backlight into 10 parts and lighting the panel, the panel temperature can be increased to 97.5%, and the ratio of the luminance gradient is also reduced to 1.05 times.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device for synchronizing data recording scan for a liquid crystal panel with lighting control of a light source for display.

In recent years, with the advancement of the so-called information society, electronic devices represented by personal computers, PDAs (Personal Digital Assistants), and the like are widely used. With the spread of such electronic devices, there is a demand for a portable type that can be used both in the office and outdoors, and their miniaturization and light weight are desired. As one of means for achieving such an objective, a liquid crystal display device is widely used. The liquid crystal display device is an indispensable technique not only for miniaturization and weight reduction, but also for lowering power consumption of a battery-powered portable electronic device.

The liquid crystal display device is classified into a reflection type and a transmission type if it is largely classified. The reflection type reflects the light incident from the front surface of the liquid crystal panel on the rear surface of the liquid crystal panel and visually recognizes the image by the reflected light. The transmission type visually recognizes the image by the transmitted light from the light source (backlight) provided on the rear surface of the liquid crystal panel. It is a structure to let. Since the reflection type is inferior in visibility because the amount of reflected light is not constant due to environmental conditions, in particular, as a display device such as a personal computer that performs multi-color or full-color display, a transmissive color liquid crystal display using a color filter is generally used. It is used.

In the color liquid crystal display device, the active drive type using switching elements, such as TFT (Thin Film Transistor), is currently widely used. This TFT drive liquid crystal display device has high display quality, but since the light transmittance of the liquid crystal panel is only about several percent in development, high brightness backlight is required to obtain high screen brightness. For this reason, power consumption by a backlight becomes large. Moreover, since it is a color display using a color filter, one pixel must be comprised with three subpixels, high definition is difficult, and the display color purity is also not enough.

In order to solve such a problem, the present inventors have developed a field sequential liquid crystal display device (for example, see Nonpatent Documents 1, 2, and 3). This field sequential liquid crystal display device does not require a subpixel as compared to the color filter liquid crystal display device, so that a more accurate display can be easily realized and a light source can be used without using a color filter. Since the light emission color can be used for display as it is, the display color purity is also excellent. Since the light utilization efficiency is also higher, it also has the advantage that the power consumption is reduced. However, in order to realize a field sequential liquid crystal display device, high-speed response (2 ms or less) of the liquid crystal is essential.

Therefore, the inventors of the present invention have a high speed of 100 to 1000 times as compared with the conventional one so as to achieve high-speed response of the field-sequential liquid crystal display device having the excellent advantages as described above, or the liquid crystal display device of the color filter method. Research and development of driving by switching elements, such as TFT, of liquid crystals, such as ferroelectric liquid crystal which have spontaneous polarization which can expect a response, are investigated (for example, refer patent document 1). The ferroelectric liquid crystal tilts in the longitudinal axis direction of the liquid crystal molecules by applying a voltage. The liquid crystal panel sandwiching the ferroelectric liquid crystal is sandwiched between two polarizing plates of which the polarization axes are perpendicular to each other, and the transmitted light intensity is changed by using birefringence due to the change in the longitudinal axis direction of the liquid crystal molecules.

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-119189

[Non-Patent Document 1] Toshiaki Yoshihara, et al. (T. Yoshihara, et.al.): International Labor Conference C98 (ILCC 98) P1-074 Published in 1998

[Non-Patent Document 2] Toshiaki Yoshihara, et al .: AM-LCD'99 Digest of Technical Papers, published in 1999, page 185

[Non-Patent Document 3] T.Yoshihara, et.al., published in 2000, SID'00 Digest of Technical Papers, page 1176:

Although the field sequential liquid crystal display device has the advantage that the light utilization efficiency is high and power consumption can be reduced, further reduction in power consumption is required for mounting to a portable device. The demand for such a reduction in power consumption is the same for not only the field sequential liquid crystal display but also the color filter liquid crystal display.

This invention is made | formed in view of such a situation, and an object of this invention is to provide the liquid crystal display device which can improve the utilization efficiency of the light from the light source for display, and can aim at reduction of power consumption.

Another object of the present invention is to provide a liquid crystal display device which can suppress the luminance gradient and increase the scanning time.

The liquid crystal display device according to the first invention is a liquid crystal display device which synchronizes lighting control of a light source that emits light incident on a liquid crystal panel in which a liquid crystal material is enclosed, and a plurality of data recording scans to the liquid crystal panel at predetermined intervals. And the light source is divided into a plurality of lighting areas and lights up, and one or a plurality of first data recording scans within the predetermined period corresponding to each of the lighting areas and a display darker than or substantially the same brightness as the first data recording scans. The light source is turned on between timings corresponding to the first scan in each of one or a plurality of second data recording scans for obtaining a display of?.

In the liquid crystal display device of the first invention, the first data recording scan in a predetermined period (one frame or one subframe) in correspondence with each of a plurality of divided lighting regions of the light source (backlight) for display. The light source (backlight) is turned on between any timing at the time of scanning of the pulse and the timing corresponding to the timing at the time of the first scanning in the second data recording scan within a predetermined period (one frame or one subframe). . Therefore, as described below, the light utilization efficiency is increased, and the power consumption of the light source (backlight) can be reduced. In addition, the luminance gradient can be suppressed, and the scanning time can also be lengthened.

Fig. 1 is a view showing an example of a driving sequence in the liquid crystal display device of the present invention. Fig. 1 (a) shows the scanning timing of each line of the liquid crystal panel, and Fig. 1 (b) shows the lighting timing of the backlight. have. In this example, the lighting region of the backlight is divided into four in the scanning direction, and in each of the divided lighting regions, an intermediate time point in the first data recording scan within a predetermined period (one frame or one subframe) and The backlight is turned on between the intermediate time points in the second data recording scan. In addition, as can be clearly understood the relationship between the timing of the data recording scan and the lighting timing in each lighting area, the data recording scanning is indicated by broken lines in FIG.

FIG. 2 is a diagram showing an example of a drive sequence in a liquid crystal display as a comparative example, FIG. 2 (a) shows the scanning timing of each line of the liquid crystal panel, and FIG. 2 (b) shows the lighting timing of the backlight. . In the example shown in FIG. 2, the backlight is turned on between an intermediate point in the first data write scan and an intermediate point in the second data write scan within a predetermined period (one frame or one subframe). However, the backlight is not divided into a plurality of lighting regions.

As in the comparative example shown in Fig. 2, when the time required for each data recording scan is set to 50% of one frame or one subframe, the ratio of the time that the liquid crystal panel is in a transmissive state with respect to the time that the backlight is turned on. (Hereinafter also referred to as panel temperature rate) is low as 87.5%, and light utilization efficiency is low. When the time required for each data recording scan is shortened to 25% of one frame or one subframe, the panel on rate can be increased to 67%, but this is not sufficient.

In addition, since the backlight is turned on between the midpoint of the first data recording scan and the midpoint of the second data recording scan, the luminance is different in the center region and the end region of the display area. The ratio of the luminance inclination (luminance at the center of the display area / luminance at the end of the display area) is twice as long as the time of data recording scan is 50% of one frame or one subframe. Even when the time is set to 25% of one frame or one subframe, the size is increased by 1.33 times.

As described above, when the ratio of the time of data recording scan to one frame or one subframe is reduced, it is advantageous in terms of light utilization efficiency and luminance gradient, but the burden on the driver IC and the control circuit is increased.

On the other hand, according to the first invention, even when the time required for data recording scan is set to 50% of one frame or one subframe, as shown in FIG. It becomes high as 93.8%. The ratio of luminance gradient at this time is as small as 1.14 times. In addition, by dividing the backlight into 10 parts and lighting the panel, the panel temperature can be increased to 97.5%, and the ratio of the luminance gradient is also reduced to 1.05 times.

As mentioned above, since a very high panel temperature rate can be implement | achieved in 1st invention, light utilization efficiency can be made high and power consumption can be reduced. In addition, the luminance gradient can be suppressed, and the scanning time can also be lengthened. In addition, when the scanning time is shorter, the light utilization efficiency can be made higher, and the luminance gradient can be further suppressed.

The liquid crystal display device according to the second aspect of the invention is characterized in that the corresponding timing is approximately an intermediate point in time of each first scan.

In the liquid crystal display device of the second aspect of the invention, the timings of the start of lighting and the end of the lighting of the light source (backlight) in each lighting region are set to almost mid-points of the data recording scan. Therefore, the luminance inclination becomes substantially symmetric up and down in the data recording scanning direction of the liquid crystal panel, and the luminance inclination is also small and favorable as compared with the case where the timing of the start of the light source (backlight) and the end of the lighting is not an intermediate point in the data recording scan. The display becomes possible.

The liquid crystal display device according to the third aspect of the invention is provided with a switching element for controlling voltage application to the liquid crystal material corresponding to each of the plurality of pixels.

In the liquid crystal display device of the third aspect of the invention, a switching element for controlling voltage application to the liquid crystal material is provided in each pixel. Therefore, voltage control for each pixel becomes easy, and a clear display can be obtained as compared with a simple matrix type liquid crystal display device in which no switching element is provided.

In the liquid crystal display device according to the fourth aspect of the invention, the liquid crystal material is a liquid crystal material having spontaneous polarization.

In the liquid crystal display device of the fourth invention, a material having spontaneous polarization is used as the liquid crystal material. By using a liquid crystal material having spontaneous polarization, high-speed response becomes possible, so that high moving picture display characteristics can be realized, and field-sequential display can be easily realized. In particular, by using a ferroelectric liquid crystal having a small spontaneous polarization value as the liquid crystal material having spontaneous polarization, driving by switching elements such as TFTs becomes easy.

In the liquid crystal display device according to the fifth invention, the voltage applied to the liquid crystal material in the first data recording scan and the voltage applied to the liquid crystal material in the second data recording scan are the same in magnitude and different in polarity. It is characterized by.

In the liquid crystal display device of the fifth aspect, the first data write scan and the second data write scan in one frame or one subframe make the magnitude of the applied voltage to the liquid crystal material the same and different in polarity. Therefore, the slope of the voltage applied to the liquid crystal material is suppressed, and burning of the display is prevented.

A liquid crystal display device according to a sixth aspect of the invention is configured to perform the second data write scan after the first data write scan.

In the liquid crystal display device of the sixth invention, in one frame or one sub-frame, after the first data recording scan for obtaining a bright display, the second display for obtaining a display darker than the first data recording scan or a display of substantially the same brightness is obtained. Data recording scan is performed. As a result, particularly in the field sequential method, since dark display is performed after bright display in the sub-frame of each color, mixed color of the display can be suppressed. On the contrary, in the case where bright display is performed after dark display in each color subframe, mixed color occurs as the downstream of the scan occurs during the line scan, and a color different from the desired display color is displayed. In the invention, this can be prevented.

The liquid crystal display device according to the seventh invention performs color display by a field sequential method.

In the liquid crystal display device of the seventh invention, color display is performed by a field sequential method of switching a plurality of colors of light over time. Therefore, color display with high definition, high color purity, and high speed response is possible.

The liquid crystal display device according to the eighth invention performs color display by a color filter method.

In the liquid crystal display device of the eighth invention, color display is performed by a color filter method using a color filter. Therefore, color display can be performed easily.

In the liquid crystal display device according to the ninth invention, the light source is a light emitting diode.

In the liquid crystal display device of the ninth invention, a light emitting diode is used as a light source for display. Therefore, it is possible to easily switch between lighting and extinction, and it is easy to divide and illuminate the light source.

In the present invention, in each of the first data recording scan and the second data recording scan in a predetermined period (one frame or one subframe) in correspondence with each of the plurality of divided lighting regions of the light source (backlight) for display. Since the light source (backlight) was turned on between the corresponding timings at the time of the first scan of the light source, the light utilization efficiency of the liquid crystal display device of the field sequential method and the color filter method can be improved, and the power consumption can be reduced. One liquid crystal display device can be realized. In addition, suppression of luminance gradient and prolongation of scanning time can also be achieved.

1 is a diagram showing an example of a driving sequence in the liquid crystal display of the present invention.

2 is a diagram illustrating an example of a drive sequence in the liquid crystal display device of the comparative example.

3 is a block diagram showing the circuit configuration of the liquid crystal display device of the present invention.

It is typical sectional drawing of the liquid crystal panel and backlight in the liquid crystal display device of a field sequential system.

It is a schematic diagram which shows the structural example of the whole liquid crystal display device.

6 is a schematic diagram illustrating a configuration example of an LED array.

FIG. 7 is a diagram showing a drive sequence in the liquid crystal display device of the first embodiment. FIG.

8 is a diagram showing a driving sequence in the liquid crystal display device of the first comparative example.

9 is a diagram illustrating a drive sequence in the liquid crystal display device of the second embodiment.

FIG. 10 is a diagram showing a drive sequence in the liquid crystal display of the second comparative example. FIG.

It is a figure which shows the drive sequence in the liquid crystal display device of 3rd Embodiment.

It is typical sectional drawing of the liquid crystal panel and backlight in the liquid crystal display device of a color filter system.

It is a figure which shows an example of the drive sequence in the liquid crystal display device of a color filter system.

<Explanation of symbols for the main parts of the drawings>

7: LED array 13: liquid crystal layer

21: liquid crystal panel 22: backlight

32: Data Driver 33: Scan Driver

35: backlight control circuit 41: TFT

70: white light source 221, 222, 223, 224: lighting area

The present invention will be described in detail with reference to the drawings showing the embodiments thereof. In addition, this invention is not limited to the following embodiment.

Fig. 3 is a block diagram showing the circuit configuration of the liquid crystal display device of the present invention, Fig. 4 is a schematic cross-sectional view of a liquid crystal panel and a backlight, Fig. 5 is a schematic diagram showing an example of the overall configuration of a liquid crystal display device, and Fig. 6 is a backlight. It is a schematic diagram which shows the structural example of the LED (Laser Emitting Diode) array which is a light source.

In FIG. 3, 21 and 22 have shown the liquid crystal panel and backlight which the cross-sectional structure is shown in FIG. As shown in FIG. 4, the backlight 22 includes an LED array 7 and a light guide and a light diffusion plate 6. As shown to FIG. 4, FIG. 5, the liquid crystal panel 21 is a polarizing film 1, the glass substrate 2, the common electrode 3, and a glass substrate from the upper layer (surface) side to the lower layer (back surface) side. (4) and the polarizing film 5 are laminated | stacked in this order, and the pixel electrode 40, 40 ... arrange | positioned in matrix form is formed in the surface on the common electrode 3 side of the glass substrate 4, have.

The driver 50 which consists of the data driver 32, the scan driver 33, etc. is connected between these common electrodes 3 and the pixel electrodes 40, 40 .... The data driver 32 is connected to the TFT 41 via the signal line 42, and the scan driver 33 is connected to the TFT 41 via the scan line 43. The TFT 41 is controlled on / off by the scan driver 33. Further, the individual pixel electrodes 40, 40... Are connected to the TFT 41. Therefore, the transmitted light intensity of each pixel is controlled by the signal from the data driver 32 given through the signal line 42 and the TFT 41.

The alignment film 12 is disposed on the top surface of the pixel electrodes 40, 40... On the glass substrate 4, and the alignment film 11 is disposed on the bottom surface of the common electrode 3, respectively, and the liquid crystal between the alignment films 11, 12. The material is filled to form the liquid crystal layer 13. In addition, 14 is a space for maintaining the layer thickness of the liquid crystal layer 13.

The backlight 22 is disposed on the lower layer (back) side of the liquid crystal panel 21, and the LED array 7 is provided in a state of facing the end surface of the light guide and the light diffusion plate 6 constituting the light emitting region. have. As shown in FIG. 6, the LED array 7 has three primary colors, ie, red (R), green (G), and blue (B), on the surface opposite to the light guide and the light diffusion plate 6. Each LED has a plurality of LEDs each having one LED as a chip. In each of the subframes of red, green, and blue, the LED elements of red, green, and blue are turned on. The light guide and the light diffusion plate 6 function as light emitting regions by guiding the light from each LED of the LED array 7 to the entire surface thereof and simultaneously diffusing it to the upper surface.

In the present invention, the backlight 22 is divided into four lighting regions 221, 222, 223 and 224 along the line direction of the liquid crystal panel 21, and each of these lighting regions 221, 222, 223 and 224. Note that the light emission timing and the light emission color are controlled by the backlight control circuit 35 independently of each other.

The liquid crystal panel 21 and the backlight 22 capable of time-division light emission of red, green, and blue for each lighting region are superimposed. The lighting timing and emission color in each lighting area of the backlight 22 are controlled in synchronization with the data recording scan based on the display data for the liquid crystal panel 21.

In Fig. 3, 31 is a control signal generation circuit for inputting a synchronization signal SYN from a personal computer to generate various control signals CS for display. The pixel data PD is output from the image memory unit 30 to the data driver 32. Based on the control signal CS for changing the polarity of the pixel data PD and the applied voltage, a voltage is applied to the liquid crystal panel 21 through the data driver 32.

The control signal CS is output from the control signal generating circuit 31 to the reference voltage generating circuit 34, the data driver 32, the scan driver 33 and the backlight control circuit 35, respectively. The reference voltage generator 34 generates the reference voltages VR1 and VR2, and outputs the generated reference voltage VR1 to the data driver 32 and the reference voltage VR2 to the scan driver 33, respectively. The data driver 32 applies the signal line 42 of the pixel electrode 40 based on the pixel data PD from the image memory unit 30 and the control signal CS from the control signal generation circuit 31. Output the signal. In synchronization with the output of this signal, the scan driver 33 sequentially scans the scanning line 43 of the pixel electrode 40 for each line. In addition, the backlight control circuit 35 applies a driving voltage to the backlight 22 to emit red light, green light, and blue light from the respective lighting regions 221, 222, 223, and 224 of the backlight 22, respectively.

Next, the operation of the liquid crystal display device will be described. The pixel data PD for display is input from the personal computer to the image memory unit 30, and the image memory unit 30 stores the pixel data PD once and then outputs it from the control signal generation circuit 31. When the control signal CS is received, this pixel data PD is output. The control signal CS generated by the control signal generating circuit 31 is applied to the data driver 32, the scan driver 33, the reference voltage generating circuit 34, and the backlight control circuit 35. The reference voltage generation circuit 34 scans the reference voltage VR2 and the reference voltage VR1 generated by generating the reference voltages VR1 and VR2 when the control signal CS is received, and scans the reference voltage VR2. Output each to (33).

When the data driver 32 receives the control signal CS, the data driver 32 outputs a signal to the signal line 42 of the pixel electrode 40 based on the pixel data PD output from the image memory unit 30. do. When the scan driver 33 receives the control signal CS, the scan driver 33 sequentially scans the scan line 43 of the pixel electrode 40 for each line. In response to the output of the signal from the data driver 32 and the scanning of the scan driver 33, the TFT 41 is driven to apply a voltage to the pixel electrode 40, thereby controlling the transmitted light intensity of the pixel. When the backlight control circuit 35 receives the control signal CS, the driving voltage is applied to the backlight 22 to supply LEDs of red, green, and blue colors of the LED array 7 of the backlight 22. Time-divided light is emitted for each lighting region, and red light, green light, and blue light are sequentially emitted over time. Thus, color display is performed by synchronizing the lighting control for each lighting area of the backlight 22 which emits incident light to the liquid crystal panel 21, and the data recording scan of the liquid crystal panel 21 several times.

(First embodiment)

After cleaning the TFT substrate having the pixel electrodes 40, 40... (Pixel number 640 x 480, 3.2 inches diagonal) and the glass substrate 2 having the common electrode 3, polyimide was applied to 1 to 200 占 폚. By baking for time, the polyimide film of about 200 GPa was formed into a film as the orientation films 11 and 12. These alignment films 11 and 12 were further rubbed with a rayon cloth, and these two substrates were superposed so that the rubbing direction became parallel, and the empty panel was produced. Here, the gap is maintained between the board | substrates of an empty panel in the space 14 made from silica with an average particle diameter of 1.6 micrometers. Between the alignment films 11 and 12 of this blank panel, a ferroelectric liquid crystal material having a naphthalene-based liquid crystal showing the half-member V-shaped electro-optic response characteristic as a main component [for example,

A. Mochizuki, et. Al .: Ferroelectrics, 133, 353 (1991)] was encapsulated to form a liquid crystal layer (13). The size of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 6 nC / cm 2. The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21 so that the ferroelectric liquid crystal molecules were in a dark state when the longitudinal axis direction of the ferroelectric liquid crystal molecules was tilted to one side.

The LED array 7 which consists of the liquid crystal panel 21 produced in this way, and 12 LED which used as one chip each LED element which emits each color of red (R), green (G), and blue (B). The backlight 22 using the light source was superimposed, and the color display by the field sequential system was performed according to the drive sequence as shown in FIG.

As the frame frequency is 60 Hz, one frame (period: 1 / 60s) is divided into three subframes (period: 1 / 180s), and as shown in FIG. Two recording scans of the red image data (first data recording scan and the second data recording scan) are performed in the subframe, and two recording scans of the green image data (first data) are performed in the next subframe. Recording scan and second data recording scan), and two recording scans (first data recording scan and second data recording scan) of blue image data were performed in the last third subframe.

In each subframe, the time required for each data recording scan was 50% (1 / 360s) of the subframe (1 / 180s). In each subframe, at the first (first half) first data recording scan, a voltage having a polarity capable of obtaining a bright display in accordance with the display data is applied to the liquid crystal of each pixel, and the second (second half) first At the time of the two data write scans, based on the same display data as the first data write scans, voltages having different polarities and the same magnitude as the first data write scans were applied to the liquid crystals of the respective pixels. As a result, at the time of the second data recording scan, a dark display that can be regarded as substantially black display was obtained as compared with the first data recording scanning time.

On the other hand, lighting of the red, green, and auditory colors of the backlight 22 was controlled as shown in Fig. 7B. In each subframe, each of the lighting regions 221, 222, 223, and 224 divided into three three LEDs of the backlight 22 in each subframe, the intermediate time point in the first data recording scan and the second data recording. Between the midpoints in the scan, the backlight 22 was turned on. Therefore, the lighting time of the backlight 22 in each subframe is 50% (1 / 360s) of the subframe 1 / 180s.

As a result, high definition, fast response and high color purity display have been realized. The screen luminance in the display area ranged from about 160 to 180 cd / m 2. At this time, the power consumption of the backlight 22 was 0.55W. Therefore, high brightness display and power consumption reduction are realized.

(First Comparative Example)

The liquid crystal panel produced similarly to 1st Embodiment and the same backlight as 1st Embodiment were superimposed, and the color display by the field sequential system was performed according to the drive sequence as shown in FIG.

The polarity and magnitude of the voltage in two data write scans in each subframe shown in Fig. 8A are the same as in the first embodiment (see Fig. 7A). However, in each subframe, the time required for the first data recording scan and the second data recording scan is 25% (1 / 720s) of the subframe (1 / 180s), and the time between adjacent data recording scans. Fig. 25 was set to 25% (1 / 720s) of the subframe (1 / 180s).

On the other hand, lighting of red, green, and auditory colors of the backlight was controlled as shown in Fig. 8B. In each subframe, the backlight was turned on between an intermediate time point in the first data write scan and an intermediate time point in the second data write scan. However, as in the first embodiment, the backlight is not divided into a plurality of lighting regions. Therefore, the lighting time of the backlight in each subframe is the same as that of 1st Embodiment, and is 50% (1 / 360s) of the subframe (1 / 180s).

As a result, similarly to the first embodiment, high definition, high speed response, and high color purity display were realized. The screen luminance in the display area ranges from about 135 to 180 cd / m 2, and the luminance inclination was larger than that in the first embodiment. In addition, a shorter scanning time was required than in the first embodiment. In addition, the power consumption of the backlight was 0.55W.

(2nd embodiment)

The liquid crystal panel 21 produced in the same manner as in the first embodiment and the same backlight 22 as in the first embodiment are superposed, and color display by the field sequential method is performed in accordance with the driving sequence as shown in FIG. 9. Done.

The frame frequency is 60 Hz, one frame (period: 1 / 60s) is divided into three sub-frames (period: 1 / 180s), and as shown in FIG. 9 (a), for example, the first one in one frame. Four recording scans of the red image data are performed in the subframe, four recording scans of the green image data are performed in the second subframe, and four of the blue image data are performed in the last third subframe. Meeting recording scans were performed. In each subframe, the time required for each data recording scan is 25% (1 / 720s) of the subframe (1 / 180s), and the end timing of the previous data recording scan coincides with the start timing of the next data recording scan. I made it.

Further, in four data write scans in each subframe, the voltage applied to the liquid crystal of each pixel during the first two data write scans (first data write scan) and the second two data write scans (first The voltage applied to the liquid crystal of each pixel at the time of two data recording scans) was made to have the same magnitude with the opposite polarity. As a result, at the time of two data recording scans in the second half, a dark display that can be regarded as substantially black display was obtained as compared with the two data recording scan times in the first half.

On the other hand, lighting of the red, green, and blue colors of the backlight 22 was controlled as shown in Fig. 9B. In each subframe, each of the lighting regions 221, 222, 223, and 224 divided into four of the 12 LEDs of the backlight 22 in each of the first two data recording scans (first data recording scan). The first data record scan (third data record scan) in the middle of the first data record scan (first data record scan) and the second two data record scans (second data record scan) The backlight 22 was turned on between the midpoints in time. Therefore, the lighting time of the backlight 22 in each subframe is 50% (1 / 360s) of the subframe 1 / 180s.

As a result, high definition, fast response and high color purity display have been realized. Compared with the first embodiment, the screen luminance in the display area was improved in the range of about 190 to 215 cd / m 2 by the improvement of the transmittance due to the effect of increasing the number of times of data recording scan. At this time, the power consumption of the backlight 22 was 0.55W. Therefore, high brightness display and power consumption reduction are realized.

(2nd comparative example)

The liquid crystal panel produced similarly to 1st Embodiment and the same backlight as 1st Embodiment were superimposed, and the color display by the field sequential system was performed according to the drive sequence as shown in FIG.

The four data recording scans in each subframe shown in Fig. 10A are completely the same as in the second embodiment (see Fig. 9A).

On the other hand, lighting of red, green, and auditory colors of the backlight was controlled as shown in Fig. 10B. In each subframe, an intermediate time point in the first data recording scan (first data recording scan) in the first two data recording scans (first data recording scan), and the second two data recording scans ( The backlight was turned on between the intermediate time points in the first data recording scan (third data recording scan) in the second data recording scan). However, as in the second embodiment, the backlight is not divided into a plurality of lighting regions. Therefore, the lighting time of the backlight in each subframe is the same as that of 2nd Embodiment, and is 50% (1 / 360s) of the subframe (1 / 180s).

As a result, similar to the second embodiment, high definition, high speed response, and high color purity display were realized. The screen luminance in the display area is in the range of about 160 to 215 cd / m 2, and the luminance gradient is larger than that in the second embodiment. In addition, the power consumption of the backlight was 0.55W.

(Third embodiment)

Monostable ferroelectric liquid crystal material (for example, R 2301 made by Clariant Japan) showing the half-member V-shaped electro-optic response characteristics between the alignment films 11 and 12 of the blank panel produced in the same process as in the first embodiment. Was sealed and it was set as the liquid crystal layer 13. The size of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 6 nC / cm 2. After the liquid crystal material was enclosed in the panel, the same liquid crystal alignment state was realized by applying a voltage of 10 V across the transition point from the cholesteric phase to the chiral metic C phase. The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21 so as to become a dark state when no voltage was applied.

The liquid crystal panel 21 produced in this way and the backlight 22 similar to 1st Embodiment were superimposed, and the color display by the field sequential system was performed according to the drive sequence as shown in FIG.

As the frame frequency is 60 Hz, one frame (period: 1 / 60s) is divided into three subframes (period: 1 / 180s), and as shown in FIG. Two recording scans of the red image data (first data recording scan and the second data recording scan) are performed in the subframe, and two recording scans of the green image data (first data recording) are performed in the next subframe. Scanning and second data recording scan), and two recording scans (first data recording scan and second data recording scan) of blue image data were performed in the last third subframe.

In each subframe, the time required for the first data recording scan and the second data recording scan is 25% (1 / 720s) of the subframe (1 / 180s), and the time between adjacent data recording scans is also used. 25% (1 / 720s) of the subframe (1 / 180s). In each subframe, at the first (first half) first data recording scan, a voltage having a polarity capable of obtaining bright display in accordance with the display data is applied to the liquid crystal of each pixel, and the second (second half). In the second data write scan, the first data write scan was applied to the liquid crystal of each pixel with different polarities and the same magnitude based on the same display data as the first data write scan. As a result, at the time of the second data recording scan, a dark display that can be regarded as a black display substantially compared with the first data recording scan time was obtained.

On the other hand, the lighting of the red, green, and blue colors of the backlight 22 was controlled as shown in Fig. 11B. In each subframe, each of the lighting regions 221, 222, 223, and 224 divided into three three LEDs of the backlight 22 in each subframe, the intermediate time point in the first data recording scan and the second data recording. The backlight 22 was turned on between the intermediate time points in the scan. Therefore, the lighting time of the backlight 22 in each subframe is 50% (1 / 360s) of the subframe 1 / 180s.

As a result, high definition, fast response and high color purity display have been realized. The screen brightness in the display area ranged from about 185 to 200 cd / m 2. At this time, the power consumption of the backlight 22 was 0.55W. Therefore, high brightness display and power consumption reduction are realized. In addition, compared with the first embodiment, the ratio of the luminance gradient can be reduced.

In the above-mentioned embodiment, although the ratio which occupies for each subframe of time required for one data recording scan was 50% or 25%, by making this ratio small and making time between adjacent data recording scans long, It goes without saying that the further improvement in light utilization efficiency and the suppression of luminance unevenness can be further achieved.

In addition, in the above-mentioned embodiment, although the number of divisions into the several lighting area | region of the backlight 22 was set to four, not only this but the division number is not limited to this, By further increasing the number of divisions, the further improvement of light utilization efficiency is further made. It goes without saying that the suppression of luminance uniformity can be further reduced.

In addition, in the above-mentioned example, although the case where the liquid crystal material which has the half-member V-shaped electro-optic response characteristic was used was demonstrated, this invention is similarly applied also when using the liquid crystal material which has the V-shaped electro-optic response characteristic. Of course you can. Even in such a case, in each subframe, the polarity is different from the voltage applied to the liquid crystal of each pixel in the first data write scan in the first half and the voltage applied to the liquid crystal of each pixel in the second data write scan in the second half. The opposite and substantially the same size, but using a liquid crystal material having a V-shaped electro-optic response characteristic, in the second half of the second data recording scan, the brightness almost the same as compared with the first data recording scan time of the first half Can be obtained.

In the above-mentioned embodiment, although the liquid crystal display device of the field sequential system was demonstrated as an example, the same effect can be acquired also in the liquid crystal display device of the color filter system which provided the color filter. This is because the present invention can be similarly applied by applying the drive sequence in the subframe in the field sequential method to the frame in the color filter method.

It is typical sectional drawing of the liquid crystal panel and backlight in the liquid crystal display device of a color filter system. In Fig. 12, the same parts as in Fig. 4 are denoted by the same reference numerals, and their description is omitted. In the common electrode 3, color filters 60 and 60 of three primary colors R, G, and B are disposed. The backlight 22 is composed of a white light source 70 having a plurality of white light source elements emitting white light, and a light guide and a light diffusion plate 6. In the liquid crystal display device of such a color filter method, color display is performed by selectively transmitting the white light from the white light source 70 by the color filter 60 of a plurality of colors. In addition, the backlight 22 (white light source 70) is divided into a plurality of lighting regions.

Then, the driving sequence as shown in Fig. 13 (in each frame, for each lit region divided by four of the backlight 22, an intermediate point in the first data write scan and an intermediate point in the second data write scan. By turning on the backlight 22 between the viewpoints], the use efficiency of the light from the backlight 22 can be improved in the same way as the above-described liquid crystal display device of the field sequential method in the liquid crystal display device of the color filter method. The effect of being able to improve and to reduce power consumption is shown. In addition, the luminance inclination can be reduced, so that the scanning time can be extended.

In the above-described embodiment, the case where a ferroelectric liquid crystal material having spontaneous polarization is used has been described. However, when another liquid crystal material having spontaneous polarization is used, for example, a semiferroelectric liquid crystal material, or a nematic liquid crystal material having no spontaneous polarization is used. Also in the case of using, if the drive display system is the same, the same effect can be obtained. In addition, the present invention can be applied not only to a transmissive liquid crystal display but also to a reflective liquid crystal display and a front / rear projector.

Claims (9)

In a liquid crystal display device which synchronizes lighting control of a light source that emits light incident on a liquid crystal panel in which a liquid crystal material is enclosed, and a plurality of data recording scans to the liquid crystal panel every predetermined period, the light source is divided into a plurality of lighting regions. The respective lighting areas are divided and lit, and are darker than the intermediate time point of the first data recording scan among the one or more first data recording scans of each of the lighting areas within the predetermined period and the first data recording scan. And the light source is turned on between an intermediate time point of the first data recording scan among one or more second data recording scans for obtaining a display or the same brightness display. delete The liquid crystal display device according to claim 1, wherein a switching element for controlling voltage application to the liquid crystal material is provided corresponding to each of the plurality of pixels. The liquid crystal display device according to claim 1, wherein the liquid crystal material is a liquid crystal material having spontaneous polarization. The voltage applied to the liquid crystal material in the first data write scan and the voltage applied to the liquid crystal material in the second data write scan are equal in magnitude and different in polarity. Liquid crystal display device. The liquid crystal display device according to claim 1, wherein the second data write scan is performed after the first data write scan. The liquid crystal display device according to claim 1, wherein color display is performed by a field sequential method. The liquid crystal display device according to claim 1, wherein color display is performed by a color filter method. The liquid crystal display of claim 1, wherein the light source is a light emitting diode.

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