JP4429335B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a color light source type liquid crystal display device that performs multi-color display by time-dividing light of a plurality of colors.

  With the progress of the information society in recent years, various electronic devices typified by personal computers, PDAs (Personal Digital assistants) and the like have been widely used. In particular, there is a high demand for portable electronic devices that can be used outdoors, and there is a demand for reduction in size and weight. As one of means for achieving such an object, a liquid crystal display device has been widely used. A liquid crystal display device is an indispensable technology for reducing power consumption of a battery-driven portable electronic device as well as reducing the size and weight.

  By the way, liquid crystal display devices are roughly classified into a reflection type and a transmission type. The reflective liquid crystal display device has a configuration in which light incident from the front surface of the liquid crystal panel is reflected by the back surface of the liquid crystal panel and an image is visually recognized by the reflected light. In recent years, a configuration has been developed in which a light source is provided on the viewing side, and light rays emitted from the light source are also reflected. The transmissive type is configured to visually recognize an image with transmitted light from a light source (backlight) provided on the back surface of the liquid crystal panel. The reflective type is inferior in visibility because the amount of reflected light is not constant depending on the environmental conditions, but is inexpensive, so it is widely used as a display device of a single color (for example, white / black display) such as a calculator, a clock, It is not suitable as a display device such as a personal computer for performing multi-color or full-color display. Therefore, a transmissive liquid crystal display device is generally used as a display device such as a personal computer that performs multi-color or full-color display.

  On the other hand, current color liquid crystal display devices are generally classified into STN (Super Twisted Nematic) type and TFT-TN (Thin Film Transistor-Twisted Nematic) type in terms of the liquid crystal material used. Although the STN type is relatively inexpensive to manufacture, there is a problem that it is not suitable for displaying moving images because crosstalk is likely to occur and the response speed is relatively slow. On the other hand, the TFT-TN type has higher display quality than the STN type. However, since the transmittance of the liquid crystal panel is currently only about 4%, a high-brightness backlight is required. For this reason, the TFT-TN type has a problem in use when carrying a battery power supply because power consumption by the backlight increases. The TFT-TN type also has problems such as a slow response speed, particularly a halftone response speed, a narrow viewing angle, and a difficulty in adjusting the color balance.

  In addition, a conventional liquid crystal display device has a color filter type configured to perform multi-color or full-color display by using a white light backlight and selectively transmitting white light with three primary color filters. It was general. However, in such a color filter type, the display pixel is configured with the range of the adjacent three color filters as one unit, so the resolution is substantially reduced to 1/3. Furthermore, since the transmittance of the liquid crystal panel is reduced by using the color filter, the luminance is also reduced as compared with the case where the color filter is not used.

  In order to solve such a problem, a color display is performed by using a ferroelectric liquid crystal element or an anti-ferroelectric liquid crystal element having a high response speed to an applied electric field as a liquid crystal element, and emitting the same pixel in three primary colors in a time-sharing manner. A liquid crystal display device has been proposed (see Patent Document 1 and the like).

  This liquid crystal display device can emit red, green and blue light in a time-sharing manner with a liquid crystal panel using a ferroelectric liquid crystal element or antiferroelectric liquid crystal element capable of high-speed response on the order of several hundred to several microseconds. In combination with a simple backlight, the color display is realized by synchronizing the switching of the liquid crystal element and the light emission of the backlight. Such a color display system is generally called a field sequential color system.

  In a field sequential color liquid crystal display device, when a ferroelectric liquid crystal element or an antiferroelectric liquid crystal element is used as the liquid crystal material, the liquid crystal molecules are applied to the substrate (glass substrate) regardless of the applied voltage. Since it is always parallel, the viewing angle becomes extremely wide, and there is no practical problem. Further, when a backlight using red, green, and blue light emitting diodes (LEDs) is used, it is possible to adjust the color balance by controlling the current that flows through each LED.

  FIG. 10 is a block diagram showing an example of the configuration of a conventional field sequential color liquid crystal display device. Display data DD to be displayed by the liquid crystal panel 53 is given to the image memory unit 52 of the display control means 51 from an external personal computer, for example. The image memory unit 52 temporarily stores the display data DD, and then transfers data in units of pixels (hereinafter referred to as pixel data PD) to the data driver 55. The data driver 55 transfers the transferred pixel data PD. Is output. The display control means 51 outputs a control signal to the scan driver 56, and the scan driver 56 controls on / off of the scanning lines provided in the liquid crystal panel 53 according to the control signal. Further, the display control unit 51 applies a driving voltage to the backlight 54 to cause the LED array included in the backlight 54 to emit light.

  FIG. 11 is a time chart showing an example of display control in such a liquid crystal display device. FIG. 11A shows the light emission timings of the red, green, and blue LEDs of the backlight 54, and FIG. Indicates the scanning timing of each line of the liquid crystal panel 53, respectively.

  As shown in FIG. 11A, the LEDs of the backlight 54 are made to emit light sequentially in the order of red, green, and blue every 1/180 seconds, for example, and each pixel of the liquid crystal panel 53 is switched in line units in synchronization therewith. Display. When displaying 60 frames per second, the period of one frame is 1/60 seconds, and this one-frame period is further divided into three subframes of 1/180 seconds each. For example, FIG. In the example shown in FIG. 5B, a red LED is emitted in the first subframe, a green LED is emitted in the second subframe, and a blue LED is emitted in the third subframe.

  On the other hand, as shown in FIG. 11B, the liquid crystal panel 53 is scanned twice in the red, green, and blue subframes. However, the start timing of the first scan (data write scan) (timing to the first line) coincides with the start timing of each subframe, and the end timing of the second scan (data erase scan) (final) The timing is adjusted so that (timing to line) coincides with the end timing of each subframe.

In the data writing scan, a voltage corresponding to the pixel data PD is supplied to each pixel of the liquid crystal panel 53, and the transmittance is adjusted. This enables full color display. In the data erasure scan, a voltage having the same voltage and reverse polarity as that in the data write scan is supplied to each pixel of the liquid crystal panel 53, the display of each pixel of the liquid crystal panel 53 is erased, and the direct current component to the liquid crystal is Application is prevented.
JP 7-281150 A

  By the way, when the display data is a single color (for example, white / black, red / black, green / black, blue / black, etc.), it may not be necessary to emit all colors of red, green, and blue. is there. However, in the above-described conventional field sequential color liquid crystal display device, as is clear from FIG. 11, all red, green, and blue colors are always emitted sequentially, so that the display data is monochromatic. Even in some cases, all the colors are emitted sequentially in the same manner, and there is a problem that a considerable amount of power is consumed.

  Further, as shown in FIG. 11, the above-described conventional field sequential color liquid crystal display device has to finish the response of the liquid crystal element within the subframe, so that it is different from the color filter liquid crystal display device. Therefore, high-speed response of the liquid crystal element is required. However, in general, since the viscosity of the liquid crystal element increases as the temperature decreases, the responsiveness decreases. Therefore, when the temperature of the liquid crystal panel is lowered, the responsiveness of the liquid crystal element is lowered. Therefore, there is a problem that it is difficult to perform display in the field sequential color system.

  The present invention has been made in view of such circumstances, and realizes power saving when the display data is monochromatic, and also has a wide temperature range when the temperature of the liquid crystal panel becomes a predetermined value or less. An object of the present invention is to provide a liquid crystal display device capable of realizing display in the above.

A liquid crystal display device according to a first aspect of the present invention is a transmissive or transflective liquid crystal panel having a plurality of liquid crystal pixels and a switching element provided corresponding to each of the liquid crystal pixels, and disposed on the back surface of the liquid crystal panel. In a liquid crystal display device comprising: a light source that emits light of a plurality of colors; and a drive unit for changing the light transmittance of the liquid crystal pixels corresponding to display data, the drive unit displays display data In the first driving state in which data scanning and data erasing scanning are performed twice in each sub-frame period obtained by further dividing one frame period of a predetermined time for each period, and in each frame period A second drive that has two scans, a data write scan and a data erase scan, and performs the scan so that the end timing of the data erase scan comes before the next frame start timing Any one of the plurality of colors in the period of each subframe when the driving unit is in the first driving state. When the first light source control unit that controls the light source to emit light and the drive unit are in the second drive state, the start of the data erasure scan starts from the end timing of the data write scan within the period of one frame. second light source for controlling the light source to emit the remainder of the non-emitting period, in the same one or more colors of the light emission period of light of said plurality of colors of light as well as between the up timing and light emission period A control unit, and switching means for switching between control by the first light source control unit and control by the second light source control unit are provided.

In the liquid crystal display device according to the first aspect of the invention, the first light source control unit emits light of any one of a plurality of colors of the light source in each subframe, so that a transmissive or transflective liquid crystal panel is used. The control for performing the color display and the second light source control unit as the light emission period from the end timing of the data write scan to the start timing of the data erasure scan within the period of one frame, and the remaining period as the non-light emission period , it is switched and controlled to perform a monochromatic display by O Ri liquid crystal panel to emit light in a plurality of same one or more colors of the light emission period of light of the color of the light source.

The liquid crystal display device according to the second invention, Oite the liquid crystal display equipment according to the first shot bright, the second light source control unit to emit a small light emission intensity than that of the control by the first light source controller And the light source is controlled.

The liquid crystal display device according to the second invention, a liquid crystal Oite the display equipment, the time of control by the second light source controller than in the case of multicolor display during the control by the first light source control unit according to the first shot bright The light emission intensity of the light source in the case of monochromatic display is lowered .

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
1 is a block diagram illustrating a configuration of a liquid crystal display device according to Embodiment 1 of the present invention, FIG. 2 is a schematic cross-sectional view of the liquid crystal panel and a backlight, and FIG. 3 illustrates a configuration example of the liquid crystal display device. It is a schematic diagram.

  In FIG. 1, reference numerals 21 and 22 denote a transmissive liquid crystal panel and a backlight whose cross-sectional structure is shown in FIG. As shown in FIG. 2, the backlight 22 includes an LED array 7 that emits red, green, and blue light and a light guide and light diffusion plate 6.

  As shown in FIG. 2 and FIG. 3, the liquid crystal panel 21 includes a polarizing film 1, a glass substrate 2, a common electrode 3, a glass substrate 4, and a polarizing film 5 from the upper layer (front surface) side to the lower layer (back surface) side. The glass substrate 4 is formed by laminating in this order, and liquid crystal pixel electrodes (pixel electrodes) 40, 40... Arranged in a matrix are formed on the surface of the glass substrate 4 on the common electrode 3 side. The common electrode 3 and the pixel electrode 40 are connected to a driving unit 50 including a data driver 33 and a scan driver 34 described later. The data driver 33 is connected to the TFT 41 via the signal line 42, and the scan driver 34 is connected to the TFT 41 via the scanning line 43. The gate of the TFT 41 is on / off controlled by the scan driver 34. A voltage corresponding to display data is applied to each pixel electrode 40 through control of the data driver 34 and the TFT 41, and the transmitted light intensity of each pixel is controlled.

  An alignment film 12 is disposed on the upper surface of the pixel electrodes 40, 40... On the glass substrate 4, and an alignment film 11 is disposed on the lower surface of the common electrode 3, and a liquid crystal substance is filled between the alignment films 11 and 12. Thus, the liquid crystal layer 13 is formed. Reference numeral 14 denotes a spacer for maintaining the layer thickness of the liquid crystal layer 13.

  The backlight 22 is located on the lower layer (rear) side of the liquid crystal panel 21, and the LED array 7 is provided in a state where the backlight 22 faces the end face of the light guide and light diffusion plate 6 constituting the light emitting region. The light guide and light diffusing plate 6 functions as a light emitting region by guiding light emitted from each LED of the LED array 7 to its entire surface and diffusing it to the upper surface.

Here, a specific example of the liquid crystal display device according to the present invention will be described.
First, the liquid crystal panel 21 shown in FIGS. 2 and 3 was produced as follows. The individual pixel electrodes 40 were arranged in a matrix, and a TFT substrate having a pixel number of 640 × 480 and a diagonal size of 3.2 inches was manufactured. After such a TFT substrate and the glass substrate 2 having the common electrode 3 are washed, a polyimide is applied by a spin coater and baked at 200 ° C. for 1 hour, whereby a polyimide film of about 200 mm is formed as the alignment films 11 and 12. Filmed.

Furthermore, these alignment films 11 and 12 were rubbed with a cloth made of rayon and overlapped with a gap maintained by a silica spacer 14 having an average particle diameter of 1.6 μm between them to produce an empty panel. A ferroelectric liquid crystal mainly composed of naphthalene-based liquid crystal is sealed between the alignment films 11 and 12 of this empty panel to form a liquid crystal layer 13. The spontaneous polarization of this ferroelectric liquid crystal was 6 nC / cm ² . The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state so that the ferroelectric liquid crystal molecules of the liquid crystal layer 13 are in a dark state when tilted to one side to form a liquid crystal panel 21. .

  This liquid crystal panel 21 and a backlight 22 capable of time-division light emission of red, green, and blue were overlapped. The light emission timing and light emission color of the backlight 22 are controlled in synchronization with the data write / erase scan of the liquid crystal panel 21.

  In FIG. 1, display data DD to be displayed is supplied from an external personal computer or the like to a switching circuit 30 for switching between full color display or single color display. The switching circuit 30 outputs the display data DD to the image memory unit 31 and determines whether the display data DD is data related to full color or single color. When the display data DD given to is a single color, the display is changed from the full color display to the single color display, or when the display data DD given immediately before is full color, A switching signal SS indicating that switching is performed is generated, and the generated switching signal SS is output to the control signal generation circuit 32. The control signal generation circuit 32 generates the synchronization signal SYN at different timings according to the switching signal SS.

  The image memory unit 31 temporarily stores the display data DD, and then outputs data in units of pixels (hereinafter referred to as pixel data PD) in synchronization with a synchronization signal SYN generated by the control signal generation circuit 32. The pixel data PD output from the image memory unit 31 is given to the data conversion circuit 37.

  The data conversion circuit 37 passes the pixel data PD as it is when the data conversion control signal DCS output from the control signal generation circuit 32 is at L level, and is given to each pixel by the pixel data PD when it is at H level. Generate and output pixel data #PD for canceling the voltage. Pixel data PD or pixel data #PD output from the data conversion circuit 37 is supplied to the data driver 33. The data driver 33 controls on / off of the signal line 42 of the pixel electrode 40 according to the pixel data PD or the pixel data #PD output from the data conversion circuit 37.

  The synchronization signal SYN generated by the control signal generation circuit 32 is also supplied to the scan driver 34, the reference voltage generation circuit 35, the backlight control circuit and the drive power supply 36. The scan driver 34 controls on / off of the scanning line 43 of the pixel electrode 40 in synchronization with the synchronization signal SYN. The reference voltage generation circuit 35 generates reference voltages VR1 and VR2 in synchronization with the synchronization signal SYN, and supplies the generated reference voltage VR1 to the data driver 33 and the reference voltage VR2 to the scan driver 34, respectively. The backlight control circuit and drive power supply 36 applies a drive voltage to the backlight 22 in synchronization with the synchronization signal SYN to cause the LED array 7 of the backlight 22 to emit light.

  An example of the display operation by the liquid crystal display device of the present invention according to the first embodiment will be described below. When performing full-color display, the liquid crystal display device of the present invention according to Embodiment 1 operates according to the display control time chart in the conventional field sequential color liquid crystal display device described above with reference to FIG. In addition, when performing monochromatic display, the operation is as follows.

  FIG. 4 is a time chart of display control in the liquid crystal display device of the present invention according to Embodiment 1 when performing monochromatic display. 4, (a) -1 is an example of light emission timing of each color LED of the backlight 22, and (a) -2 is an example of light emission timing different from (a) -1 of each color LED of the backlight 22. In FIG. (B) shows the scanning timing of each line of the liquid crystal panel 21, respectively.

  When the display data DD is data for displaying only green, as shown in FIG. 4A, the green LED of the backlight 22 is caused to emit light in the second subframe and the liquid crystal is synchronized therewith. Green / black display is performed by switching each pixel of the panel 21 in units of lines. In this case, the backlight 22 does not emit light in the first and third subframes.

  When the display data DD is data for displaying only magenta color, red and green LEDs of the backlight 22 in the first and third subframes as shown in FIG. 4A-2. , And magenta / black display is performed by switching each pixel of the liquid crystal panel 21 in units of lines in synchronization therewith. In this case, the backlight 22 does not emit light in the second subframe.

  On the other hand, as shown in FIG. 4B, the liquid crystal panel 21 is scanned twice in each color sub-frame. However, the start timing of the first scan (data write scan) (timing to the first line) coincides with the start timing of each subframe, and the end timing of the second scan (data erase scan) (final) The timing is adjusted so that (timing to line) coincides with the end timing of each subframe.

  In the data writing scan, a voltage corresponding to the pixel data PD is supplied to each pixel of the liquid crystal panel 21 to adjust the transmittance. In the data erasure scan, a voltage having the same voltage and reverse polarity as that in the data write scan is supplied to each pixel of the liquid crystal panel 21, and the display of each pixel of the liquid crystal panel 21 is erased. Application is prevented.

The power consumption when green / black display is performed as described above is 0.8 W, and the power consumption when magenta / black display is performed is 1.3 W.
For comparison with these results, green / black display and magenta / black display using a conventional field sequential color liquid crystal display device including a liquid crystal panel manufactured in the same manner as in the first embodiment. Displayed. As a result, the power consumption when green / black display was performed was 1.8 W, and the power consumption when magenta / black display was performed was also 1.8 W.
As described above, the power consumption of the liquid crystal display device of the present invention is lower than that of the conventional liquid crystal display device in both cases of green / black display and magenta / black display.

(Embodiment 2)
An example of the liquid crystal display device of the present invention according to Embodiment 2 switches between full color display and single color display based on the temperature of the liquid crystal panel.
FIG. 5 is a block diagram showing a configuration of the liquid crystal display device according to the second embodiment of the present invention. In FIG. 5, reference numeral 40 denotes a temperature sensor that measures the temperature of the liquid crystal panel 21, and the temperature sensor 40 outputs a signal TS indicating the measured temperature to the switching circuit 38.

  The switching circuit 38 compares the previous temperature with the current temperature based on the signal TS output from the temperature sensor 40. When the immediately preceding temperature is higher than 0 ° C. and the current temperature falls below 0 ° C., the full color display is changed to the single color display, or when the immediately preceding temperature is lower than 0 ° C., the current temperature is When the temperature becomes 0 ° C. or higher, a switching signal SS indicating that switching from single color display to full color display is generated, and the generated switching signal SS is output to the control signal generation circuit 32.

  The switching circuit 38 outputs display data DD given from an external personal computer, for example, to the image memory unit 31 when full-color display is performed, and to the single-color data generation circuit 39 when single-color display is performed. .

  The single color data generation circuit 39 generates single color data MD that is display data for single color display such as white / black display or green / black based on the display data DD output from the switching circuit 38, and generates the generated single color. Data MD is output to the image memory unit 31.

  Since other configurations are the same as those in the first embodiment, the same reference numerals are given and description thereof is omitted.

  The display operation by the liquid crystal display device of the present invention according to the second embodiment will be described below. When performing full color display, the liquid crystal display device of the present invention according to Embodiment 2 operates according to the display control time chart in the conventional field sequential color liquid crystal display device described above with reference to FIG. In addition, when performing monochromatic display, the operation is as follows.

  FIG. 6 is a time chart of display control in the liquid crystal display device of the present invention according to Embodiment 2 when performing monochromatic display. 6, (a) shows the light emission timing of each color LED of the backlight 22, (b) -1 shows the scanning timing of each line of the liquid crystal panel 21, and (b) -2 shows (b) of the liquid crystal panel 21. Scan timings different from -1 are shown.

  As shown in FIG. 6A, the backlight 22 emits light in one frame without providing a subframe. Here, when white / black display is performed, red, green, and blue LEDs are caused to emit light at the same time, and each pixel of the liquid crystal panel 21 is switched in line units in synchronization therewith. For example, when green / black display is performed, only the green LED is caused to emit light, and the same switching is performed in synchronization therewith.

  On the other hand, as shown in FIGS. 6B-1 and 2B-2, the liquid crystal panel 21 is scanned twice in one frame. However, the timing is adjusted so that the start timing (timing to the first line) of the first scan (data writing scan) coincides with the start timing of the frame.

  In the data writing scan, a voltage corresponding to the pixel data PD is supplied to each pixel of the liquid crystal panel 21 to adjust the transmittance. In the data erasure scan, a voltage having the same voltage and reverse polarity as that in the data write scan is supplied to each pixel of the liquid crystal panel 21, and the display of each pixel of the liquid crystal panel 21 is erased. Application is prevented.

  By performing such a display operation, display can be performed without any problem even if the response of the liquid crystal element does not end within the subframe as in the case of a conventional field sequential color liquid crystal display device. Even at a low temperature at which the responsiveness of the liquid crystal element decreases, full color display is not possible, but good display can be obtained.

  FIG. 7 is a graph showing the temperature dependence of the transmittance of the liquid crystal panel. In FIG. 7, the vertical axis indicates the transmittance of the liquid crystal panel 21, the horizontal axis indicates the temperature of the liquid crystal panel 21, and (a) indicates the transmittance at the time of full-color display when a drive voltage of 5V is applied. Similarly, (b) shows the measurement results of the transmittance during monochromatic display.

  As shown in FIG. 7A, in the case of full color display, the transmittance required for obtaining a good display was obtained within the range of 0 to 60 ° C., but sufficient transmittance was obtained at 0 ° C. or less. Couldn't get. On the other hand, as shown in FIG. 7B, a sufficient transmittance could be obtained up to about −15 ° C. even at 0 ° C. or lower during monochromatic display. As a result, it was possible to obtain a good display in a wide temperature range as compared with the conventional field sequential color liquid crystal display device.

In addition to the display operation as described above, the liquid crystal display device of the present invention according to Embodiment 2 can perform a display operation according to a time chart as shown in FIG.
8, (a) shows the light emission timing of each color LED of the backlight 22, and (b) shows the scanning timing of each line of the liquid crystal panel 21, respectively.

  As shown in FIG. 8A, the backlight 22 emits light for a necessary time in one frame without providing a subframe. Here, when white / black display is performed, red, green, and blue LEDs are caused to emit light at the same time, and each pixel of the liquid crystal panel 21 is switched in line units in synchronization therewith. For example, when green / black display is performed, only the green LED is caused to emit light, and the same switching is performed in synchronization therewith.

  On the other hand, as shown in FIG. 8B, the liquid crystal panel 21 is scanned twice in one frame. However, the end timing of the first scan (data write scan) (timing to the final L line) coincides with the start time of the light emission time of the backlight 22, and the second scan (data erase scan). The timing is adjusted so that the start timing (timing to the first line) coincides with the end of the light emission time of the backlight 22.

When such a display operation is performed, the light emission time of the backlight 22 is different because the light emission time of the backlight in one frame and the light use efficiency of the liquid crystal panel are different from those of the conventional field sequential color liquid crystal display device. The intensity was adjusted so that the luminance in white display was approximately the same as in the conventional case (70 cd / m ² ).

When white / black display was performed as described above, power consumption was 2.1 W. For comparison with this result, white / black display was performed using a conventional field-sequential color liquid crystal display device including a liquid crystal panel manufactured in the same manner as in the first embodiment. As a result, the power consumption was 4.8W.
Thus, the power consumption of the liquid crystal display device of the present invention was lower than that of the conventional liquid crystal display device.

(Embodiment 3)
An example of the liquid crystal display device according to the third embodiment of the present invention includes a liquid crystal panel and a front light as described later instead of the liquid crystal panel 21 and the backlight 22 in the first and second embodiments. . Other configurations are the same as those in the first and second embodiments, and the backlight control circuit and the drive power supply 36 function as a frontlight control circuit and a drive power supply.

  FIG. 9 is a schematic cross-sectional view of a liquid crystal panel and a front light used in the liquid crystal display device of the present invention according to Embodiment 3. In FIG. 9, reference numeral 62 denotes a reflective liquid crystal panel manufactured by a known technique. A front light 61 is disposed on the upper surface (front surface) side of the liquid crystal panel 62, and the front light 61 faces red, green, and red, facing the end surface of the light guide plate 8 constituting the light emitting region. An LED array 7 for emitting each color of blue is provided. The light guide plate 8 functions as a light emitting region by guiding light emitted from each LED of the LED array 7 to its entire surface.

  In the liquid crystal display device of the present invention according to the third embodiment, when performing full color display, according to the display control time chart in the conventional field sequential color liquid crystal display device described above with reference to FIG. Operate. Further, when performing monochromatic display, all the LEDs of red, green and blue of the front light 61 are turned off. As a result, the liquid crystal panel 62 reflects only natural light so that an image can be viewed with the reflected light.

  By controlling the light emission of the front light 61 in this way, a significant power saving can be achieved as compared with a conventional field sequential color liquid crystal display device. Further, when the control for switching between full color display and single color display is performed based on the temperature of the liquid crystal panel 62, it is possible to obtain a good display in a wider temperature range than in the past.

As described above, the liquid crystal display device of the present invention includes a transmissive liquid crystal panel in the first and second embodiments and a reflective liquid crystal panel in the third embodiment. Instead of these liquid crystal panels, a transflective liquid crystal panel may be provided.
In addition, although three colors of red, green, and blue are used as the light emission colors of the light source, it goes without saying that the same effect can be obtained even if the number of light emission colors of the light source is two or more.

  As described above in detail, the liquid crystal display device described in the present embodiment is configured to perform multicolor display on a transmissive or transflective liquid crystal panel by time-dividing light of a plurality of colors of a light source, By making the light emission time and timing of the light source substantially coincide with each other and switching the control to perform monochromatic display on the liquid crystal panel, it is possible to perform appropriate display according to the situation.

  In addition, the liquid crystal display device described in this embodiment is capable of performing multicolor display on a transmissive or transflective liquid crystal panel by time-dividing light of a plurality of colors from a light source, and a plurality of colors. By switching to control for performing monochromatic display on the liquid crystal panel by emitting light of at least one color of light, it is possible to perform appropriate display according to the situation.

  Further, the liquid crystal display device described in this embodiment includes a control for performing multicolor display on a reflective or transflective liquid crystal panel by time-dividing light of a plurality of colors of the light source, and a plurality of light sources of the light source. By switching off the color light and switching the control to perform the monochromatic display on the liquid crystal panel, it is possible to perform an appropriate display according to the situation.

  Furthermore, the liquid crystal display device described in this embodiment emits light from the light source at different emission intensities when performing multicolor display by time-dividing light of a plurality of colors and when performing monochromatic display. Thus, for example, it is possible to perform display with the same luminance in both multicolor display and single color display.

  Furthermore, the liquid crystal display device described in this embodiment can obtain a good display when switching from multicolor display to single color display by converting display data by combining a plurality of colors into single color display data. it can.

  Furthermore, the liquid crystal display device described in the present embodiment switches between multicolor display and single color display based on the content of the display data, for example, when display data that can be displayed in a single color is generated during multicolor display. Since an operation such as switching to monochromatic display can be realized, power saving can be achieved.

  Further, the liquid crystal display device described in the present embodiment usually performs multicolor display by measuring the temperature of the liquid crystal panel and switching between multicolor display and single color display based on the measurement result. Since an operation such as switching to a monochromatic display can be realized at a low temperature at which the responsiveness of the element is lowered, a favorable display can be realized in a wide temperature range.

  Furthermore, the liquid crystal display device described in the present embodiment generates switching information indicating that switching between multicolor display and single color display has been performed, and displays display data including this switching information on the liquid crystal panel. For example, when the display is switched from the multicolor display to the single color display, the present invention has an excellent effect such that the user can confirm that it is not due to the failure of the apparatus.

1 is a block diagram showing a configuration of a liquid crystal display device of the present invention according to Embodiment 1. FIG. 2 is a schematic cross-sectional view of a liquid crystal panel and a backlight used in the liquid crystal display device of the present invention according to Embodiment 1. FIG. 1 is a schematic diagram illustrating a configuration example of a liquid crystal display device of the present invention according to Embodiment 1. FIG. 3 is a time chart of display control in the liquid crystal display device of the present invention according to Embodiment 1. FIG. 6 is a block diagram illustrating a configuration of a liquid crystal display device of the present invention according to Embodiment 2. 6 is a time chart of display control in the liquid crystal display device of the present invention according to Embodiment 2. It is a graph which shows the temperature dependence of the transmittance | permeability of a liquid crystal panel. 6 is a time chart of display control in the liquid crystal display device of the present invention according to Embodiment 2. 6 is a schematic cross-sectional view of a liquid crystal panel and a front light used in a liquid crystal display device of the present invention according to Embodiment 3. FIG. It is a block diagram which shows an example of a structure of the liquid crystal display device of the conventional field sequential color system. It is a time chart of the display control in the conventional field sequential color type liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Liquid crystal panel 22 Backlight 30 Switching circuit 31 Image memory part 32 Control signal generation circuit 33 Data driver 34 Scan driver 36 Backlight control circuit and drive power supply 40 Pixel electrode

Claims (2)

A transmissive or transflective liquid crystal panel having a plurality of liquid crystal pixels and switching elements provided corresponding to each of the liquid crystal pixels, and a light source that is disposed on the back surface of the liquid crystal panel and emits light of a plurality of colors And a driving unit for changing the light transmittance of the liquid crystal pixel corresponding to display data,
The driving unit performs a first driving for performing two scans of a data writing scan and a data erasing scan within each subframe obtained by further dividing one frame period of a predetermined time for displaying display data. Scanning is performed so that the end timing of the data erasure scan is before the start timing of the next frame. It is configured to be able to take one of the driving states of the second driving state,
A first light source control unit configured to control the light source to emit light of any one of the plurality of colors in a period of each subframe when the driving unit is in a first driving state;
When the driving unit is in the second driving state, the period from the end timing of the data writing scan to the start timing of the data erasing scan within the period of one frame is set as the light emission period and the remaining period is set as the non-light emission period. A second light source control unit that controls the light source so as to emit light of the same one or more of the plurality of colors in a light emission period ;
A liquid crystal display device comprising: switching means for switching between control by the first light source control unit and control by the second light source control unit.   2. The liquid crystal display device according to claim 1, wherein the second light source control unit is configured to control the light source so as to emit light with a light emission intensity smaller than in the case of control by the first light source control unit. .

Images